U.S. patent application number 13/723963 was filed with the patent office on 2013-05-23 for adhesive composition.
This patent application is currently assigned to EXXONMOBIL CHEMICAL PATENTS INC.. The applicant listed for this patent is EXXONMOBIL CHEMICAL PATENTS INC.. Invention is credited to Christopher Lewis Curry, Jurgen Jan Martha Schroeyers.
Application Number | 20130130027 13/723963 |
Document ID | / |
Family ID | 42938293 |
Filed Date | 2013-05-23 |
United States Patent
Application |
20130130027 |
Kind Code |
A1 |
Curry; Christopher Lewis ;
et al. |
May 23, 2013 |
Adhesive Composition
Abstract
A composition comprising a hot melt pressure-sensitive adhesive
comprising a propylene-based polymer component having a melting
point less than or equal to about 130.degree. C. and a triad
tacticity greater than about 75%, and free of or having a low block
copolymer content. Also, an adhesive article comprising the
composition.
Inventors: |
Curry; Christopher Lewis;
(Dayton, TX) ; Schroeyers; Jurgen Jan Martha;
(Helchteren, BE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EXXONMOBIL CHEMICAL PATENTS INC.; |
Baytown |
TX |
US |
|
|
Assignee: |
EXXONMOBIL CHEMICAL PATENTS
INC.
Baytown
TX
|
Family ID: |
42938293 |
Appl. No.: |
13/723963 |
Filed: |
December 21, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12880762 |
Sep 13, 2010 |
|
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|
13723963 |
|
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|
61256124 |
Oct 29, 2009 |
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Current U.S.
Class: |
428/355EN ;
524/505 |
Current CPC
Class: |
C09J 4/06 20130101; C09J
123/10 20130101; C08L 57/00 20130101; C09J 2453/00 20130101; C09J
2423/00 20130101; C08L 2666/04 20130101; C09J 123/10 20130101; C09J
153/02 20130101; C09J 7/381 20180101; C09J 2453/00 20130101; C09J
123/14 20130101; Y10T 428/2883 20150115; C08L 23/14 20130101; C08L
2666/04 20130101; C09J 2423/00 20130101; C09J 2453/00 20130101;
C08L 2666/06 20130101; C09J 2423/00 20130101; Y10T 428/2878
20150115; C09J 153/02 20130101; C08L 2666/06 20130101 |
Class at
Publication: |
428/355EN ;
524/505 |
International
Class: |
C09J 123/14 20060101
C09J123/14 |
Claims
1. A hot melt pressure-sensitive adhesive composition comprising a
propylene-based polymer component comprising from about 60 to about
98 wt % propylene and from about 2 to about 40 wt % of one or more
of ethylene and C.sub.4-C.sub.10 alpha-olefins, based on the weight
of the propylene-based polymer component, the propylene-based
polymer component having a melting point less than or equal to
about 130.degree. C. and a triad tacticity greater than about 75%;
the hot melt pressure-sensitive adhesive composition free of or
comprising not more than about 30 wt % of a block copolymer based
on the weight of the hot melt pressure sensitive adhesive
composition.
2. The hot melt pressure-sensitive adhesive composition of claim 1,
wherein the propylene-based polymer component comprises from about
75 to about 98 wt % propylene and from about 2 to about 25 wt % of
one or more of ethylene and C.sub.4-C.sub.10 alpha-olefins, and
wherein the propylene-based polymer component has a melting point
less than or equal to about 120.degree. C.
3. The hot melt pressure-sensitive adhesive composition of claim 1,
wherein the propylene-based polymer component further has a heat of
fusion less than about 90 J/g.
4. The hot melt pressure-sensitive adhesive composition of claim 1,
wherein the propylene-based polymer component has a melt flow rate
(MFR) of from about 1 to about 900 g/10 min, as measured according
to ASTM D-1238 at 230.degree. C., 2.16 kg.
5. The hot melt pressure-sensitive adhesive composition of claim 1,
having a viscosity of less than or equal to about 150,000 mPa-s at
175.degree. C. determined according to ASTM D 3236, or an
equivalent thereof.
6. The hot melt pressure-sensitive adhesive composition of claim 1,
comprising less than 0.01 wt % of the block copolymer.
7. The hot melt pressure-sensitive adhesive composition of claim 1,
comprising less than 0.01 wt % of a block copolymer comprising
styrene.
8. The hot melt pressure-sensitive adhesive composition of claim 1,
comprising from about 1, to about 60 wt % of a hydrocarbon
tackifier resin based on the weight of the hot melt pressure
sensitive adhesive.
9. The hot melt pressure-sensitive adhesive composition of claim 8,
wherein the hydrocarbon tackifier resin has a ring-and-ball
softening point of from about 50 to about 150.degree. C.
10. The hot melt pressure-sensitive adhesive composition of claim
1, comprising from about 1 to about 30 wt % of a process oil based
on the weight of the hot melt pressure-sensitive adhesive.
11. The hot melt pressure-sensitive adhesive composition of claim
1, wherein the hot melt pressure-sensitive adhesive composition is
a removable hot melt pressure-sensitive adhesive and wherein the
hot melt pressure-sensitive adhesive composition comprises less
than 0.01 wt % total of silicon oils and waxes.
12. The hot melt pressure-sensitive adhesive composition of claim
1, having a clear visual determination, wherein the visual
determination consists of providing a testing square consisting of
a piece of white 20 pound weight paper having a brightness of 90%,
the testing square having a printed portion comprising the capital
letters "O" and "Q" printed with a laser printer to be visually
distinguishable at 1 space apart from each other thereon in black
text using 10-point Helvetica font; depositing a sample of the hot
melt pressure-sensitive adhesive composition at a temperature above
the melting point of the hot melt pressure-sensitive adhesive
composition onto the testing square using a flat applicator to
cover the printed portion of the testing square with a film of the
hot melt pressure-sensitive adhesive composition having a thickness
of 1 mm, followed by allowing the hot melt pressure-sensitive
adhesive composition to cool to a temperature of 25.degree. C. to
produce a prepared test sample; and visually determining the
clarity of the prepared test sample wherein the prepared test
sample has a clear visual determination when an observer having
essentially 20:20 vision is able to visually distinguish the letter
"O" from the letter "Q" in the printed portion of the testing
square at a distance of about 30 cm from the prepared test sample
at an illumination of 1000 lux.
13. The hot melt pressure-sensitive adhesive composition of claim
1, wherein the propylene-based polymer component has a solubility
in toluene of less than 10 wt % at 25.degree. C.
14. An adhesive article comprising a substrate and a hot melt
pressure-sensitive adhesive composition comprising a
propylene-based polymer component comprising from about 60 to about
98 wt % propylene and from about 2 to about 40 wt % ethylene and/or
C.sub.4-C.sub.10 alpha-olefins, based on the weight of the
propylene-based polymer component, the propylene-based polymer
component having a melting point less than or equal to about
130.degree. C. and a triad tacticity greater than about 75%; the
adhesive composition free of or comprising less than about 30 wt %
of a block copolymer based on the weight of the hot melt
pressure-sensitive adhesive.
15. The adhesive article of claim 14, wherein the hot melt
pressure-sensitive adhesive composition comprises from about 1 to
about 60 wt % of a hydrocarbon tackifier resin based on the weight
of the hot melt pressure-sensitive adhesive.
16. The adhesive article of claim 15, wherein the hydrocarbon
tackifier resin has a ring-and-ball softening point of from about
50 to about 150.degree. C.
17. The adhesive article of claim 14, wherein the hot melt
pressure-sensitive adhesive composition comprises less than about
0.01 wt % of the block copolymer.
18. The adhesive article of claim 14, wherein the adhesive
composition has a clear visual determination, wherein the visual
determination consists of providing a testing square consisting of
a piece of white 20 pound weight paper having a brightness of 90%,
the testing square having a printed portion comprising the capital
letters "O" and "Q" printed with a laser printer to be visually
distinguishable at 1 space apart from each other thereon in black
text using 10-point Helvetica font; depositing a sample of the
composition at a temperature above the melting point of the
composition onto the testing square using a flat applicator to
cover the printed portion of the testing square with a film of the
composition having a thickness of 1 mm, followed by allowing the
composition to cool to a temperature of 25.degree. C. to produce a
prepared test sample; and visually determining the clarity of the
prepared test sample wherein the prepared test sample has a clear
visual determination when an observer having essentially 20:20
vision is able to visually distinguish the letter "O" from the
letter "Q" in the printed portion of the testing square at a
distance of about 30 cm from the prepared test sample at an
illumination of 1000 lux.
19. The adhesive article of claim 14, wherein the adhesive article
is an adhesive tape having an initial 180.degree. peel strength of
the tape on glass of from 0.1 to about 10 N/25 mm at a coating
weight of 20 g/m.sup.2.
20. The adhesive article of claim 14, wherein the adhesive article
is an adhesive tape having an initial 180.degree. peel strength of
the tape on polyethylene film of from 0.1 to about 10 N/25 mm at a
coating weight of 20 g/m2.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of co-pending
U.S. patent application Ser. No. 12/880,762, filed Sep. 13, 2010,
which claims priority to U.S. Provisional Application Ser. No.
61/256,124, filed Oct. 29, 2009, the disclosures of which are fully
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The instant disclosure is related to hot melt
pressure-sensitive adhesive compositions and their applications. In
particular, the adhesive compositions described herein comprise a
propylene-based polymer component.
BACKGROUND
[0003] Pressure-sensitive adhesives are well known, and are used in
a wide variety of applications, the largest among them being label
and tape. Such adhesives may be applied to, for example, paper,
plastic films, metal, etc., to form the aforementioned labels or
tapes.
[0004] These labels and tapes may be affixed to a wide variety of
substrates, and in many cases are removable or repositionable.
[0005] "No-label look" labels, also referred to as
"super-transparent" labels, are obtaining popularity and are of
significant commercial interest. Adhesives for no-label look labels
require a high level of transparency or clarity, along with other
properties typical of such adhesives.
[0006] Hot melt pressure-sensitive adhesive systems are known in
the art and consist of tackified thermoplastic elastomers such as
styrenic block copolymers together with tackifying resin(s) and
generally some plasticizing oil, an antioxidant, and optional
fillers. Styrenic block copolymers containing polystyrene and
polybutadiene blocks and/or polyisoprene blocks are particularly
useful. These materials are generally available as pure triblocks,
sometimes referred to as SIS and SBS copolymers, and diblocks,
sometimes referred to as SI and SB copolymers or SIB copolymers.
The materials are also available as mixtures of diblock and
triblock materials, sometimes referred to as SIS+SI or SIS+SB.
Styrenic block copolymers could also have a radial structure
generally identified as (SI)n or (SB)n where n for most commercial
available polymers equals, but is not limited to 4. In (for label)
a preferred case, those radial block copolymers are blended with
other styrenic block copolymers like diblock and triblock
structures.
[0007] Adhesive properties and viscosity can be controlled by
varying the diblock-to-triblock ratio, varying the styrene content,
varying the polymer molecular weight, and/or varying the block
molecular weights within the polymers. The melt viscosity can also
be controlled by the addition of tackifier resins and/or
plasticizers like oils.
[0008] One drawback of such adhesive formulations is that, in order
to achieve the desired processability and removability of a
product, many additives such as silicone oils, waxes, and other
fillers must be added. Incorporation of such additives leads to
increased expense, and by number of ingredients used also limits
the equipment that may be used to manufacture the adhesive
compositions.
[0009] In addition, hot melt pressure-sensitive adhesive systems
suitable for use in a no-label look label must have clarity in
combination with other properties. It would be useful, therefore,
to develop an adhesive composition for use with labels and/or tapes
having the properties of a typical block copolymer-based adhesive
at a lower cost and with increased processability, and which may be
suitable for use in no-label look labels.
SUMMARY
[0010] The instant disclosure is directed to adhesive compositions
which function as hot melt pressure-sensitive adhesive compositions
and their commercial applications. In one or more embodiments, the
adhesive compositions comprise at least one propylene-based polymer
component. In some embodiments, the adhesive compositions may be
free of, or further comprise, less than or equal to about 30 wt %
of a block copolymer.
[0011] In an embodiment, an adhesive article comprises a substrate
and a hot melt pressure-sensitive adhesive composition comprising a
propylene-based polymer component %. In an embodiment, the adhesive
composition may be free of, or further comprise less than about 30
wt % of a block copolymer.
[0012] The compositions described herein in some embodiments
combine excellent viscosity and/or shear properties while improving
the performance of tapes, labels, and other applications in which
the adhesives are employed, and may have clarity suitable for use
in no-label look labels. In further embodiments, adhesive articles
such as adhesive tapes and labels comprise a substrate and one or
more hot melt pressure-sensitive adhesive compositions according to
one or more embodiments described herein. Embodiments of the
resulting adhesive tapes may demonstrate good removability and/or
repositionability, along with exceptional peel strength on one or
more of various surfaces.
DETAILED DESCRIPTION
[0013] In an embodiment, a hot melt pressure-sensitive adhesive
composition comprising a propylene-based polymer component
comprising from about 60 to about 98 wt % propylene and from about
2 to about 40 wt % of one or more of ethylene and C.sub.4-C.sub.10
alpha-olefins, based on the weight of the propylene-based polymer
component, the propylene-based polymer component having a melting
point less than or equal to about 130.degree. C. and a triad
tacticity greater than about 75%; the composition free of or
comprising not more than about 30 wt % of a block copolymer based
on the weight of the hot melt pressure-sensitive adhesive
composition.
[0014] In an embodiment, the propylene-based polymer component may
comprise from about 75 to about 98 wt % propylene and from about 2
to about 25 wt % of one or more of ethylene and C.sub.4-C.sub.10
alpha-olefins, and wherein the propylene-based elastomer component
has a melting point less than or equal to about 120.degree. C.;
and/or
[0015] the propylene-based polymer component may further have a
heat of fusion less than about 90 J/g; and/or
[0016] the propylene-based polymer component may have a melt flow
rate (MFR) of from about 1 to about 900 g/10 min, as measured
according to ASTM D-1238 at 230.degree. C., 2.16 kg; and/or
[0017] the composition may have a viscosity of less than or equal
to about 150,000 mPa-s at 175.degree. C. determined according to
ASTM D 3236, for label application more preferably less than 40,000
mPa-s; and/or
[0018] the composition may be free of or comprises less than about
0.01 wt % of the block copolymer and/or;
[0019] the composition may be free of or comprise less than about
0.01 wt % of a block copolymer comprising styrene; and/or
[0020] the composition may comprise from about 1 to about 60 wt %
of a hydrocarbon tackifier resin; and/or
[0021] when present, the hydrocarbon tackifier resin may have a
ring-and-ball softening point of from about 50.degree. to about
140.degree. C. and/or;
[0022] the composition may comprise from about 1 to about 30 wt %
of a process oil; and/or
[0023] the composition may be a removable adhesive, and comprise
less than 0.01 wt % of a silicon oil and/or a silicon wax;
and/or
[0024] the composition may have a clear visual determination,
wherein the visual determination consists of providing a testing
square consisting of a piece of white 20 pound weight paper having
a brightness of 90%, the testing square having a printed portion
comprising the capital letters "O" and "Q" printed with a laser
printer to be visually distinguishable at 1 space apart from each
other thereon in black text using 10-point Helvetica font;
[0025] depositing a sample of the composition at a temperature
above the melting point of the composition onto the testing square
using a flat applicator to cover the printed portion of the testing
square with a film of the composition having a thickness of 1 mm,
followed by allowing the composition to cool to a temperature of
25.degree. C. to produce a prepared test sample; and
[0026] visually determining the clarity of the prepared test sample
wherein the prepared test sample has a clear visual determination
when an observer having essentially 20:20 vision is able to
visually distinguish the letter "O" from the letter "Q" in the
printed portion of the testing square at a distance of about 30 cm
from the prepared test sample at an illumination of 1000 lux;
and/or
[0027] the propylene-based polymer component of the composition may
have a solubility in toluene of less than 10 wt % at 25.degree. C.;
and/or any combination thereof.
[0028] In an embodiment, an adhesive article comprises a substrate
and a hot melt pressure-sensitive adhesive composition comprising a
propylene-based polymer component comprising from about 60 to about
98 wt % propylene and from about 2 to about 40 wt % ethylene and/or
C4-C10 alpha-olefins, the propylene-based elastomer component
having a melting point less than or equal to about 130.degree. C.
and a triad tacticity greater than about 75%; the adhesive
composition comprising less than or equal to about 30 wt % of a
block copolymer.
[0029] In an embodiment, the adhesive article may comprise an
adhesive composition comprising from about 1 to about 60 wt % of a
hydrocarbon tackifier resin; and/or
[0030] when present the hydrocarbon tackifier resin may have a
ring-and-ball softening point of from about 50 to about 140.degree.
C.; and/or
[0031] the adhesive composition has a clear visual determination as
described herein; and/or
[0032] the adhesive article may be an adhesive tape having an
initial 180.degree. peel strength of the tape on glass of less than
or equal to about 10 N/25 mm at a coating weight of about 20 g/m2;
and/or
[0033] the adhesive article may be an adhesive tape having an
initial 180.degree. peel strength of the tape on polyethylene film
of less than or equal to about 10 N/25 mm at a coating weight of
about 20 g/m.sup.2; and/or any combination thereof.
[0034] For purposes herein, a pressure sensitive adhesive (PSA)
forms a bond by the application of light pressure to many the
adhesive with the adherend. The bond forms because the adhesive is
soft enough to flow (i.e."wet") to the adherend. The bond has
strength because the adhesive is hard enough to resist flow when
stress is applied to the bond. Once the adhesive and the adherend
are in close proximity, molecular interactions, such as van der
Waals forces, become involved in the bond, contributing
significantly to its ultimate strength.
[0035] The compositions according to the instant disclosure possess
a glass transition temperature (Tg), at which the molecular chain
exhibits the greatest free volume or maximum flow character. When a
material is heated from its glassy state to either a rubbery or a
fluid state; if Tg appears in the vicinity of room temperature and
the value of Tangent delta (damping factor, the ratio of loss
modulus-G'' to storage modulus-G') is greater than one (1); the
material cold flows and is considered to be pressure sensitive.
[0036] PSAs, according to embodiments disclosed herein, may be
either permanent or removable applications. For purposes herein
removable adhesives, including PSA and articles comprising PSAs are
compositions which form a temporary bond, and ideally can be
removed after months or years without leaving residue on the
adherend. Removable adhesives are used in applications such as
surface protection films, masking tapes, bookmark and note papers,
price marking labels, promotional graphics materials, and the like,
whereas a permanent PSA refers to a PSA film which may be initially
removable (for example to recover mislabeled goods) and, which
builds adhesion to a permanent bond after several hours or
days.
[0037] Examples of permanent applications include safety labels for
power equipment, foil tape for HVAC duct work, automotive interior
trim assembly, and sound/vibration damping films. Embodiments
include so-called high performance permanent PSAs which exhibit
high adhesion values and can support kilograms of weight per square
centimeter of contact area, even at elevated temperature. Permanent
PSAs may be initially removable (for example to recover mislabeled
goods) and build adhesion to a permanent bond after several hours
or days.
[0038] For purposes herein removable adhesives and articles
comprising the same refer to compositions which form a temporary
bond, and ideally can be removed after months or years without
leaving residue on the adherend. Removable adhesives are used in
applications such as surface protection films, masking tapes,
bookmark and note papers, price marking labels, promotional
graphics materials. Some removable adhesives are designed to
repeatedly stick and unstick.
[0039] In addition to being pressure sensitive adhesives, the
instant disclosure is directed to PSA which are also hot melt
adhesives, which are generally defined as thermoplastic
compositions applied in molten form, which solidify on cooling to
form strong bonds between a wide range of materials. Accordingly,
in an embodiment, the compositions disclosed herein include hot
melt pressure-sensitive adhesives (HMPSA).
Propylene-Based Polymer Component
[0040] In one or more embodiments, the adhesive compositions
described herein comprise a propylene-based polymer component,
which in turn comprises one or more propylene-based polymers. In
some embodiments, the propylene-based polymers comprises propylene
and from about 2 to about 40 wt % units derived from ethylene
and/or a C4-C10 alpha-olefin. In one or more embodiments, the
alpha-olefin comonomer units may derive from ethylene, 1-butene,
1-hexene, 4-methyl-1-pentene, 1-octene, and/or 1-decene. The
embodiments described below are discussed with reference to
ethylene as the alpha-olefin comonomer, but the embodiments are
equally applicable to other propylene copolymers with other
alpha-olefin comonomers, or to propylene terpolymers with ethylene
and another alpha-olefin comonomer. In this regard, the copolymer
may simply be referred to as propylene-based polymers with
reference to ethylene as the alpha-olefin.
[0041] In one or more embodiments, the propylene-based polymers may
include at least about 2 wt %, at least about 3 wt %, at least
about 5 wt %, at least about 6 wt %, at least about 8 wt %, or at
least about 10 wt % ethylene-derived units. In those or other
embodiments, the propylene-based polymers may include up to about
40 wt %, or up to about 30 wt %, or up to about 25 wt %, or up to
about 20 wt %, or up to about 18 wt %, or up to about 16 wt %, or
up to about 12 wt % ethylene-derived units, where the percentage by
weight is based upon the total weight of the propylene-derived and
alpha-olefin derived units. Stated another way, the propylene-based
polymers may include at least about 60 wt %, or at least about 70
wt %, or at least about 75 wt %, or at least about 80 wt %, or at
least about 82 wt % propylene-derived units; and in these or other
embodiments, the copolymers may include up to about 98 wt %, or up
to about 97 wt %, or up to about 95 wt %, or up to about 94 wt %,
or up to about 92 wt %, or up to about 90 wt % propylene-derived
units, where the percentage by weight is based upon the total
weight of the propylene-derived and alpha-olefin derived units.
[0042] The propylene-based polymers of one or more embodiments are
characterized by having a single melting temperature as determined
by differential scanning calorimetry (DSC). The melting point is
defined as the temperature of the greatest heat absorption within
the range of melting of the sample. The propylene-based polymer may
show secondary melting peaks adjacent to the principal peak, but
for purposes herein, these secondary melting peaks are considered
together as a single melting point, with the highest of these peaks
being considered the melting point (Tm) of the propylene-based
polymer.
[0043] In one or more embodiments, the Tm of the propylene-based
polymer (as determined by DSC) is less than about 130.degree. C.,
or less than about 120.degree. C., or less than about 110.degree.
C., or less than about 105.degree. C., or less than about
100.degree. C., or less than about 95.degree. C., or less than
about 90.degree. C., or less than about 80.degree. C., or less than
about 70.degree. C.
[0044] In one or more embodiments, the propylene-based polymer may
be characterized by a heat of fusion (Hf) of at least about 0.5 J/g
as determined by DSC. In one or more embodiments, the
propylene-based copolymer may be characterized by a heat of fusion
that is at least about 0.75 J/g, or at least about 1.0 J/g, or at
least about 1.5 J/g, or at least about 3.0 J/g, or at least about
4.0 J/g, or at least about 6.0 J/g, or at least about 7.0 J/g. In
these or other embodiments, the propylene-based copolymer may be
characterized by a heat of fusion of less than about 90 J/g, or
less than about 70 J/g, or less than about 60 J/g, or less than
about 50 J/g, or less than about 45 J/g, or less than about 40 J/g,
or less than about 30 J/g. The heat of fusion may be reduced by
using additional comonomer, operating at higher polymerization
temperatures, and/or using a different catalyst that provides
reduced levels of steric constraints and favors more propagation
errors for propylene insertion.
[0045] As used within this specification, DSC procedures for
determining Tm and Hf include the following. The polymer is pressed
at a temperature of from about 200.degree. C. to about 230.degree.
C. in a heated press, and the resulting polymer sheet is hung,
under ambient conditions, in the air to cool. About 6 to 10 mg of
the polymer sheet is removed with a punch die. This 6 to 10 mg
sample is annealed at room temperature for about 80 to 100 hours.
At the end of this period, the sample is placed in a Differential
Scanning calorimeter (Perkin Elmer Pyris One Thermal Analysis
System) and cooled to about -50.degree. C. to about -70.degree. C.
The sample is heated at 10.degree. C./min to attain a final
temperature of about 200.degree. C. The sample is kept at
200.degree. C. for 5 minutes and a second cool-heat cycle is
performed. Events from both cycles are recorded. The thermal output
is recorded as the area under the melting peak of the sample, which
typically occurs between about 0.degree. C. and about 200.degree.
C.; it is measured in Joules and is a measure of the heat of fusion
(Hf) of the polymer. The melting point is recorded as the
temperature of the greatest heat absorption with respect to a
baseline within the range of melting of the sample.
[0046] The propylene-based polymer can have a triad tacticity of
three propylene units, as measured by .sup.13C NMR, of 75% or
greater, 80% or greater, 82% or greater, 85% or greater, or 90% or
greater. In one or more embodiments, ranges include from about 50
to about 99%, in other embodiments from about 60 to about 99%, in
other embodiments from about 75 to about 99%, in other embodiments
from about 80 to about 99%, and in other embodiments from about 60
to about 97%. Triad tacticity is determined by the methods
described in U.S. Patent Application Publication No. 2004/0236042.
If the triad tacticity of the copolymer is too high, the level of
stereo-irregular disruption of the chain is too low and the
material may not be compatible and sufficiently flexible for its
purpose in a coating or tie layer. If the triad tacticity is too
low, the bonding strength may be too low.
[0047] In one or more embodiments, the propylene-based polymer may
have a crystallinity of from about 0.5% to about 40%, or from about
1% to about 30%, or from about 5% to about 25%, determined
according to DSC procedures. Crystallinity may be determined by
dividing the heat of fusion of a sample by the heat of fusion of a
100% crystalline polymer, which is assumed to be 189 joules/gram
for isotactic polypropylene or 350 joules/gram for
polyethylene.
[0048] In one or more embodiments, the propylene-based polymer may
have a density of from about 0.85 g/cm3 to about 0.92 g/cm3, or
from about 0.87 g/cm3 to about 0.90 g/cm3, or from about 0.88 g/cm3
to about 0.89 g/cm3 at room temperature as measured per the ASTM
D-792 test method.
[0049] In one or more embodiments, the propylene-based polymer can
have an melt index (MI) (ASTM D-1238, 2.16 kg @ 190.degree. C.), of
less than or equal to about 10 dg/min, or less than or equal to
about 7.5 dg/min, or less than or equal to about 6.5 dg/min, or
less than or equal to about 5.5 dg/min, or less than or equal to
about 5 dg/min.
[0050] In an embodiment, the propylene-based polymer component has
a melt flow rate (MFR) of from about 1 to about 900 g/10 min (90
dg/min), as measured according to ASTM D-1238 at 230.degree. C.,
2.16 kg.
[0051] In one or more embodiments, the propylene-based polymer may
have a melt flow rate (MFR), as measured according to the ASTM
D-1238, 2.16 kg weight @ 230.degree. C., greater than or equal to
about 0.3 dg/min, or at least about 0.5 dg/min, or at least about
0.8 dg/min, or at least about 1.0 dg/min. In these or other
embodiments, the melt flow rate may be equal to or less than about
2000 dg/min, or less than about 1000 dg/min, or less than about 900
dg/min, or less than about 700 dg/min, or less than about 500
dg/min, 350 dg/min, or less than about 250 dg/min, or less than
about 100 dg/min.
[0052] In one or more embodiments, the propylene-based polymer can
have a weight average molecular weight (Mw) of from about 5,000 to
about 5,000,000 g/mole, or from about 10,000 to about 1,000,000
g/mole, or from about 20,000 to about 500,000 g/mole, or from about
50,000 to about 400,000 g/mole.
[0053] In one or more embodiments, the propylene-based polymer can
have a number average molecular weight (Mn) of from about 2,500 to
about 2,500,000 g/mole, or from about 5,000 to about 500,000
g/mole, or from about 10,000 to about 250,000 g/mole, or from about
25,000 to about 200,000 g/mole.
[0054] In one or more embodiments, the propylene-based polymer can
have a Z-average molecular weight (Mz) of from about 10,000 to
about 7,000,000 g/mole, or from about 50,000 to about 1,000,000
g/mole, or from about 80,000 to about 700,000 g/mole, or from about
100,000 to about 500,000 g/mole.
[0055] In one or more embodiments, the molecular weight
distribution (MWD=(Mw/Mn)) of the propylene-based polymer may be
from about 1 to about 40, or from about 1 to about 15, or from
about 1.8 to about 5, or from about 1.8 to about 3.
[0056] Techniques for determining the molecular weight (Mn, Mw and
Mz) and molecular weight distribution (MWD) may be found in U.S.
Pat. No. 4,540,753, which is incorporated by reference herein for
purposes of U.S. practices, and references cited therein, and in
Macromolecules, 1988, Volume 21, p. 3360-3371 (Verstrate et al.),
which is herein incorporated by reference for purposes of U.S.
practices, and references cited therein. For example, molecular
weight may be determined by size exclusion chromatography (SEC) by
using a Waters 150 gel permeation chromatograph equipped with the
differential refractive index detector and calibrated using
polystyrene standards.
Preparation of the Propylene-Based Polymer
[0057] The triad tacticity and tacticity index of the propylene
based polymer may be controlled by a catalyst which influences the
stereoregularity of propylene placement, the polymerization
temperature, according to which stereoregularity can be reduced by
increasing the temperature, and by the type and amount of a
comonomer which tends to disrupt reduce the level of longer
propylene derived sequences.
[0058] An excess of comonomer will reduce the crystallinity
provided by the crystallization of stereoregular propylene derived
sequences to the point where the material lacks strength; too
little and the material will be too crystalline. The comonomer
content and sequence distribution of the polymers can be measured
using 13C nuclear magnetic resonance (NMR) by methods well known to
those skilled in the art. Comonomer content of discrete molecular
weight ranges can be measured using methods well known to those
skilled in the art, including Fourier Transform Infrared
Spectroscopy (FTIR) in conjunction with samples by GPC, as
described in Wheeler and Willis, Applied Spectroscopy, 1993, Vol.
47, pp. 1128-1130. For a propylene ethylene copolymer containing
greater than 75 wt % propylene, the comonomer content (ethylene
content) of such a polymer can be measured as follows: A thin
homogeneous film is pressed at a temperature of about 150.degree.
C. or greater, and mounted on a Perkin Elmer PE 1760 infrared
spectrophotometer. A full spectrum of the sample from 600 cm.sup.-1
to 4000 cm.sup.-1 is recorded and the monomer weight percent of
ethylene can be calculated according to the following equation:
Ethylene wt %=82.585-111.987X+30.045X2, where X is the ratio of the
peak height at 1155 cm.sup.-1 and peak height at either 722
cm.sup.-1 or 732 cm.sup.-1, whichever is higher. For propylene
ethylene copolymers having 75 wt % or less propylene content, the
comonomer (ethylene) content can be measured using the procedure
described in Wheeler and Willis.
[0059] Reference is made to U.S. Pat. No. 6,525,157, which
describes test methods that are fully applicable for the various
measurements referred to in this specification and claims and which
contains more details on GPC measurements, the determination of
ethylene content by NMR and the DSC measurements.
[0060] The catalyst may also control the stereoregularity in
combination with the comonomer and the polymerization temperature.
The catalyst should, however, be capable of a level of
stereoregular placement, generally by suitable chirality of the
catalyst.
[0061] In one embodiment, the polymer can be prepared using any
single sited metallocene catalyst. Such a catalyst may be a
transition metal complex generally containing a transition metal
Groups 3 to 10 of the Periodic Table and at least one ancillary
ligand that remains bonded to the transition metal during
polymerization. Preferably the transition metal is used in a
reduced cationic state and stabilized by a cocatalyst or
activator.
[0062] The ancillary ligand may be a structure capable of forming a
bond such a cyclopentadienyl type ring structure (See EP129368,
EP284708, Rieger EP1070087 and U.S. Pat. No. 6,559,262). The
ancillary ligand may also be a pyridinyl or amide ligand (See
International Patent Application No. WO2003/040201). The transition
metal is preferably of Group 4 of the Periodic table such as
titanium, hafnium or zirconium, which is used in polymerization in
the dO mono-valent cationic state and has one or two ancillary
ligands as described in more detail hereafter. The important
features of such catalysts for coordination polymerization are the
ligand capable of abstraction and that ligand into which the
ethylene (olefinic) group can be inserted.
[0063] The manner of activation of the single site catalyst can
vary. Alumoxane and preferably methyl alumoxane can be used
suitably in an amount to provide a molar aluminum to metallocene
ratio of from 1:1 to 20,000:1. Higher molecular weights can be
obtained using non- or weakly coordinating anion activators (NCA)
derived and generated in any of the ways amply described in
published patent art such as EP 277004, EP 426637, EP 426638, and
many others. The non-coordinating anion can be a Group 10-14
complex wherein boron or aluminum is the charge-bearing atom
shielded by ligands, which may be halogenated, and especially
perfluorinated. Preferably tetra-aryl-substituted Group 10-14
non-carbon element-based anion, especially those that are have
fluorine groups substituted for hydrogen atoms on the aryl groups,
or on alkyl substituents on those aryl groups. The non-coordinating
anion may be used in approximately equimolar amounts relative to
the transition metal complex, such as at least 0.25, preferably
0.5, and especially 0.8 and such as no more than 4, preferably 2,
and especially 1.5. Further options are described in U.S. Pat. Nos.
6,048,950; 6,448,358; 6,265,212; 5,198,401; and 5,391,629, and
International Patent Application No. WO 1998/27154.
[0064] The polymerization reaction is conducted by reacting
monomers in the presence of a metallocene catalyst system described
herein at a temperature of from 0.degree. C. to 200.degree. C. for
a time of from 1 second to 10 hours. Preferably homogeneous
conditions are used, such as a continuous solution process or a
bulk polymerization process with excess monomer used as diluent.
The continuous process may use some form of agitation to reduce
concentration differences in the reactor and maintain steady state
polymerization conditions. The heat of the polymerization reaction
is preferably removed by cooling of the polymerization feed and
allowing the polymerization to heat up to the polymerization,
although internal cooling systems may be used.
Block Copolymer Component
[0065] In an embodiment, the compositions described herein
comprises less than or equal to about 30 wt % of a block copolymer
component. In an embodiment, the composition comprises less than or
equal to about 20 wt %, or 15 wt %, or 10 wt %, or 5 wt %, or 2 wt
%, or 1 wt %, or 0.1 wt % of a block copolymer. In an embodiment,
the composition may be free of, or comprise less than 0.01 wt % of
a block copolymer. As used herein, a composition is free of a
particular ingredient if it contains less than 0.1 wt % of the
particular ingredient by total weight of the composition. As used
herein in one embodiment, a composition is essentially free of
block copolymer if the block copolymer is present in such minor
amounts that the clear visual determination described below is
still obtained. The composition in one embodiment consists
essentially of the propylene-based polymer component and
optionally, other ingredients and additives, such that the clear
visual determination is not adversely impacted. In an embodiment,
the composition may be free of, or comprise less than 1 wt % of a
block copolymer comprising styrene, also referred to in the art as
a styrenic block copolymer. For purposes herein, the phrase "block
copolymer" includes any manner of block copolymer having two or
more polymer chains attached at their ends, including but not
limited to diblock, triblock, and tetrablock copolymers. "Block
copolymer" is further meant to include copolymers having any
structure known to those of skill in the art, including but not
limited to linear, radial or multi-arm star, multi-branched block
copolymers, and random block copolymers. "Linear block copolymers"
comprise two or more polymer chains in sequence. "Radial block
copolymers" (or "star block copolymers") comprise more than two
linear block copolymers attached at a common branch point.
"Styrenic block copolymers" comprise a block copolymer having at
least one block that is greater than 50% styrene. For purposes
herein, block copolymers may be linear or radial, or combinations
of linear and radial block copolymers. The block copolymers may or
may not be hydrogenated.
[0066] Block copolymers comprising styrene include linear block
copolymers of styrene and one or more conjugated dienes such as SI
(styrene-isoprene), SIS (styrene-isoprene-styrene), SB
(styrene-butadiene), SBS (styrene-butadiene-styrene), SIB
(styrene-isoprene-butadiene), or combination thereof.
[0067] Block copolymers also include tetrablock or pentablock
copolymers selected from A-B-A-B tetrablock copolymers or A-B-A-B-A
pentablock copolymers and the like are also suitable such as SISI
(styrene-isoprene-styrene-isoprene), SISB, SBSB, SBSI, SIBS, ISISI,
ISISB, BSISB, ISBSI, BSBSB, and BSBSI block copolymers.
[0068] In one or more embodiments, the composition may include less
than 30 wt %, or may be free of, or comprise less than about 0.01
wt % of linear block copolymer includes a linear polymer of the
formula S-I-S or S-B-S, wherein S is substantially a polystyrene
block, I is substantially a polyisoprene block, and B is
substantially a polybutadiene block. The styrene content of the SBS
block copolymer is typically from about 10 to about 45 wt %, or
from about 15 to about 35 wt %, or from about 20 to 30 wt %. The
SIS block copolymers may be prepared by well-known anionic solution
polymerization techniques using lithium-type initiators such as
disclosed in U.S. Pat. Nos. 3,251,905 and 3,239,478, which are
hereby incorporated by reference in their entireties. The SIS and
the SBS copolymer may be a pure triblock (one having less than 0.1
wt % of diblock polymer, preferably 0% diblock polymer), or may
contain from about 0.1 to about 85 wt %, or from about 0.1 to about
75 wt %, or from about 1 to about 65 wt %, or from about 5 to about
50 wt %, or from 5 to 25 wt %, or from 10 to 20 wt % diblock
copolymer having the structure S-I or SB, respectively. The SI or
SB diblock may be present as a residue from the manufacture of the
triblock copolymer or may be separately blended with the triblock
as a further technique for achieving target polystyrene content or
modifying the cohesive properties of the composition. In one or
more embodiments, the number average molecular weight of the
diblock SI copolymers may range from about 100,000 to about
250,000.
Hydrocarbon Tackifier Component
[0069] In one or more embodiments the adhesive compositions
described herein comprise a hydrocarbon tackifier resin component,
which may in turn comprise one or more hydrocarbon tackifier
resins.
[0070] Hydrocarbon tackifier resins suitable for use according to
one or more embodiments of the instant disclosure include, but are
not limited to, aliphatic hydrocarbon resins, at least partially
hydrogenated aliphatic hydrocarbon resins, aliphatic/aromatic
hydrocarbon resins, at least partially hydrogenated aliphatic
aromatic hydrocarbon resins, aromatic resins, at least partially
hydrogenated aromatic hydrocarbon resins, cycloaliphatic
hydrocarbon resins, at least partially hydrogenated cycloaliphatic
resins, cycloaliphatic/aromatic hydrocarbon resins,
cycloaliphatic/aromatic at least partially hydrogenated hydrocarbon
resins, polyterpene resins, terpene-phenol resins, rosin esters,
rosin acids, grafted resins, and mixtures of two or more of the
foregoing. The hydrocarbon tackifiers may be polar or apolar.
[0071] In one embodiment, the tackifier component may comprise one
or more hydrocarbon resins produced by the thermal polymerization
of cyclopentadiene (CPD) or substituted CPD, which may further
include aliphatic or aromatic monomers as described later. The
hydrocarbon resin may be a non-aromatic resin or an aromatic resin.
The hydrocarbon resin may have an aromatic content between 0 wt %
and 60 wt %, preferably between 1% and 60%, or between 1% and 40%,
or between 1% and 20%, or between 10% and 20%. In further
embodiments, the hydrocarbon resin may have an aromatic content
between 15% and 20%, or between 1% and 10%, or between 5% and
10%.
[0072] In another embodiment, the tackifier component may comprise
hydrocarbon resins produced by the catalytic (cationic)
polymerization of linear dienes. Such monomers are primarily
derived from Steam Cracked Naptha (SCN) and include C5 dienes such
as piperylene (also known as 1,3-pentadiene). Polymerizable
aromatic monomers can also be used to produce resins and may be
relatively pure, e.g., styrene, -methyl styrene, or from a
C9-aromatic SCN stream. Such aromatic monomers can be used alone or
in combination with the linear dienes previously described.
"Natural" monomers can also be used to produce resins, e.g.,
terpenes such as alpha-pinene or beta-carene, either used alone or
in high or low concentrations with other polymerizable monomers.
Typical catalysts used to make these resins are AlCl3 and BF3,
either alone or complexed. Mono-olefin modifiers such as 2-methyl,
2-butene may also be used to control the molecular weight
distribution (MWD) of the final resin. The final resin may be
partially or totally hydrogenated as described in further detail
herein.
[0073] As used herein, aromatic content and olefin content are
measured by .sup.1H-NMR, as measured directly from the .sup.1H NMR
spectrum from a spectrometer with a field strength greater than 300
MHz, preferably 400 MHz. Aromatic content is the integration of
aromatic protons versus the total number of protons. Olefin proton
or olefinic proton content is the integration of olefinic protons
versus the total number of protons.
[0074] In one or more embodiments, the resin may be at least
partially hydrogenated or substantially hydrogenated. As used
herein, "at least partially hydrogenated" means that the material
contains less than 90% olefinic protons, or less than 75% olefinic
protons, or less than 50% olefinic protons, or less than 40%
olefinic protons, or less than 25% olefinic protons. As used
herein, "substantially hydrogenated" means that the material
contains less than 5% olefinic protons, or less than 4% olefinic
protons, or less than 3% olefinic protons, or less than 2% olefinic
protons. The degree of hydrogenation is typically conducted so as
to minimize and preferably avoid hydrogenation of the aromatic
bonds.
[0075] In one or more embodiments, hydrocarbon tackifier resins
described herein may be uniquely characterized as totally or
substantially amorphous in nature. This means that a glass
transition temperature (Tg) is detectable, e.g., by Differential
Scanning calorimetry (DSC), but they have no melting point (Tm). To
characterize these resins, it is generally accepted to use a test
that roughly correlates with Tg, such as softening point (SP),
which provides approximate, but not exact, values. The softening
point (SP) of the resins is measured by a ring-and-ball softening
point test according to ASTM E-28.
[0076] In some embodiments, the hydrocarbon resin may have a ring
and ball softening point of from about 50.degree. C. to about
150.degree. C., or from about 60.degree. C. to about 130.degree.
C., or from about 70.degree. C. to about 120.degree. C., or from
about 80.degree. C. to about 110.degree. C., determined according
to ASTM E-28 or an equivalent thereof.
[0077] In one or more embodiments of the invention, the hydrocarbon
resin has a number average molecular weight (Mn) from about 400 to
about 3000, a weight average molecular weight (Mw) from about 500
to about 6000, a z-average molecular weight (Mz) from about 700 to
about 30,000 and a polydispersity (PD), defined as Mw/Mn, between
about 1.5 and about 4. As used herein, molecular weights (number
average molecular weight (Mn), weight average molecular weight
(Mw), and z-average molecular weight (Mz)) are measured by size
exclusion chromatography using a Waters 150 Gel Permeation
Chromatograph equipped with a differential refractive index
detector and calibrated using polystyrene standards. Samples are
run in tetrahydrofuran (THF) (45.degree. C.). Molecular weights are
reported as polystyrene-equivalent molecular weights and are
generally measured in g/mol.
[0078] In an embodiment, the hydrocarbon tackifier resin component
may comprise one or more oligomers such as dimers, trimers,
tetramers, pentamers, and hexamers. The oligomers may be derived
from a petroleum distillate boiling in the range of 30-210.degree.
C. The oligomers may be derived from any suitable process and are
often derived as a byproduct of resin polymerization. Suitable
oligomer streams may have molecular weights (Mn) between 130-500,
more preferably between 130-410, more preferably between 130-350,
or between 130-270, or between 200-350, or between 200-320.
Examples of suitable oligomer streams include, but are not limited
to, oligomers of cyclopentadiene and substituted cyclopentadiene,
oligomers of C4-C6 conjugated diolefins, oligomers of C8-C10
aromatic olefins, and combinations thereof. Other monomers may be
present. These include C4-C6 mono-olefins and terpenes. The
oligomers may comprise one or more aromatic monomers and may be at
least partially hydrogenated or substantially hydrogenated.
[0079] In an embodiment, the oligomers may be stripped from the
resin before hydrogenation. The oligomers may also be hydrogenated
with the resin and then stripped from the resin, yielding a
hydrogenated resin and hydrogenated oligomers. In another
embodiment, at least some of the oligomers are stripped before
hydrogenation and at least some hydrogenated oligomers are stripped
after hydrogenation. In yet another embodiment, the hydrogenated
resin/oligomers product may be further processed together as a
single mixture as described below. In yet another embodiment, the
oligomers can be derived from any suitable source and hydrogenated
(if necessary) before grafting so that the oligomers before
grafting are typically at least partially hydrogenated and
preferably substantially hydrogenated.
[0080] The hydrocarbon tackifier resin component may comprise one
or more hydrocarbon tackifier resins. When the composition
comprises a finite amount of a block copolymer, these resins may be
chosen based upon their compatibility with the one or more block
copolymers which comprise the block copolymer component of the
adhesive composition. For example, certain tackifier resins may be
better suited for use with SIS block copolymers, while other
tackifier resins may be more compatible with SBS block
copolymers.
[0081] Examples of commercially available SIS compatible tackifier
resins include, but are not limited to, ESCOREZ 2203LC, ESCOREZ
1310LC, ESCOREZ 1304, ESCOREZ 5380, and ESCOREZ 5600, manufactured
by ExxonMobil Chemical Company; Piccotac 1905 and EASTOTAC H-100,
manufactured by Eastman Chemicals; QUINTONE D and QUINTONE U 185,
manufactured by Nippon Zeon; MARUKARES R100, manufactured by
Maruzen; and WINGTACK EXTRA and WINGTACK PLUS, manufactured by Cray
Valley.
[0082] Examples of commercially available SBS compatible tackifier
resins include, but are not limited to, ESCOREZ 2101, ESCOREZ 5690,
and ESCOREZ 2173, manufactured by ExxonMobil Chemical Company;
Regalrez 5095, Regalrez 3102, Staybelite Ester 3, and Pentalyn H,
manufactured by Eastman Chemicals; Quintone U 190, manufactured by
Nippon Zeon; Wingtack 86, manufactured by Cray Valley; and
Sylvalite RE 885 and Sylvatac RE 85, available from Arizona
Chemical.
[0083] In one or more embodiments, the hot melt pressure-sensitive
adhesive compositions described herein may comprise from about 1 to
about 50 wt %, or from about 5 to about 45%, or from about 10 to
about 40 wt %, or from about 15 to about 35 wt % of the hydrocarbon
tackifier resin component, based on the total weight of the
composition.
Process Oil Component
[0084] In one or more embodiments according to the instant
disclosure, one or more process oils may be added to the hot melt
pressure-sensitive adhesive compositions described herein. As used
herein, the term "process oil" means both petroleum derived process
oils and synthetic plasticizers.
[0085] Examples of process oils suitable for use herein include,
but are not limited to, paraffinic or naphthenic oils such as
Primol 352 or Core 600 fluid, produced by ExxonMobil Chemical
France; and Nyflex 222B, available from Nynas AB.
[0086] Further process oils suitable for use herein include
aliphatic naphthenic oils, white oils, and the like. Exemplary
plasticizers and/or adjuvants include mineral oils, polybutenes,
phthalates and the like. In one or more embodiments, the
plasticizers may include phthalates such as diisoundecyl phthalate
(DIUP), diisononylphthalate (DINP), dioctylphthalates (DOP), and
polybutenes, such as Parapol 950 and Parapol 1300 available from
ExxonMobil Chemical Company in Houston, Tex. Further useful
plasticizers include those described in International Patent
Application No. WO01/18109A1 and U.S. Application Publication No.
2004/0106723, which are incorporated by reference herein.
[0087] In one or more embodiments, the hot melt pressure-sensitive
adhesive compositions described herein may comprise from about 1 to
about 50 wt %, or from about 5 to about 40 wt %, or from about 10
to about 35 wt %, or from about 15 to about 30 wt % of the optional
process oil component.
Other Additives and Fillers
[0088] In some embodiments, one or more additional fillers or
additives may be employed to achieve the properties and
characteristics desired in the final adhesive formulation. Such
additive and fillers are known in the art and may include, but are
not limited to fillers, cavitating agents, antioxidants,
surfactants, adjuvants, plasticizers, block, antiblock, colorants,
color masterbatches, pigments, dyes, processing aids, UV
stabilizers, neutralizers, lubricants, waxes, and/or nucleating
agents. The additives may be present in any amount determined to be
effective by those skilled in the art, such as for example from
about 0.001 wt % to about 10 wt %.
[0089] Examples of suitable antioxidants include, but are not
limited to, quinolein, e.g., trimethylhydroxyquinolein (TMQ);
imidazole, e.g., zincmercapto toluoyl imidazole (ZMTI); and
conventional antioxidants, such as hindered phenols, lactones,
phosphates, and hindered amines. Further suitable anti-oxidants are
commercially available from, for example, Ciba Geigy Corp. under
the trade names Irgafos 168, Irganox 1010, Irganox 3790, Irganox
B225, Irganox 1035, Irgafos 126, Irgastab 410, and Chimassorb
944.
[0090] Fillers, cavitating agents, and/or nucleating agents
suitable for use herein may comprise granular, fibrous, and
powder-like materials, and may include, but are not limited to,
titanium dioxide, calcium carbonate, barium sulfate, silica,
silicon dioxide, carbon black, sand, glass beads, mineral
aggregates, talc, natural and synthetic clays, diatomaceous earth,
and the like.
[0091] Processing aids, lubricants, waxes, and/or oils (e.g., oils
described above) which may be employed in embodiments of the
adhesive compositions disclosed herein include low molecular weight
products such as wax, oil, or low Mn polymer (low meaning having an
Mn less than 5000, preferably below 4000, or below 3000, or below
2500). Waxes may include polar or non-polar waxes, functionalized
waxes, polypropylene waxes, polyethylene waxes, and wax
modifiers.
[0092] The additives described herein can be added to the blend in
pure form or in master batches.
[0093] In one or more embodiments, the adhesive compositions
described herein may comprise one or more process oils as described
above, but are otherwise substantially free of silicon oils or
waxes. In an embodiment, the composition is removable and free of
silicon oils and waxes, or in an embodiment comprises less than
0.01 wt % of a silicon oil and wax. By "substantially free of" is
meant that any silicon oils or waxes in the adhesive composition
are present as impurities only; no silicon oils or waxes are
deliberately added to the adhesive formulation. In an embodiment,
the composition is removable and comprises less than 0.01 wt % of a
silicon oil and/or a silicon wax.
[0094] For purposes herein, an adhesive composition or an article
comprising an adhesive composition is removable wherein the
adhesive or the article comprising the adhesive can be applied to a
surface and easily removed without leaving a substantial amount or
without leaving any, or a substantial amount of residue as is
commonly understood by one having minimal skill in the art. In an
embodiment, the adhesive or the article comprising the adhesive is
removable when it can be applied to a surface and easily removed
leaving less than 0.1% of the adhesive originally present on the
surface, based on the total amount of adhesive originally
applied.
Preparation of the Hot Melt Pressure-Sensitive Adhesive
Composition
[0095] In one or more embodiments, the components of the hot melt
pressure-sensitive adhesive compositions described herein may be
blended by mixing, using any suitable mixing device at a
temperature above the melting point of the components, e.g., at 130
to 180.degree. C., for a period of time sufficient to form a
homogeneous mixture, normally from about 1 to about 120 minutes
depending on the type of mixing device.
[0096] In the case of continuous mixing as practiced by most
commercial manufacturers, a twin screw extruder may be used to mix
the adhesive components. First the propylene-based polymer
components and block copolymers when present are introduced into
the extruder and mixed until the polymers have melted and are well
mixed. Then the tackifiers are added, followed by any process oils
which may be desired. To the extent pigments, antioxidants,
fillers, or other additives are used, they are normally blended in
with the propylene-based polymer components. The total mixing time
is typically on the order of from about 1 to 5 minutes.
[0097] In the case of batch mixing, the propylene-based polymer
component or components are added along with about 20% of the
tackifier component. When the polymers and tackifier reach a
homogeneous state, the remaining tackifier component is gradually
added to the mix. Once all of the tackifier components have been
added and homogeneous mix is achieved, the balance of the process
oil, antioxidants, fillers, and any other additives are added. The
total mixing time may run for up to 120 minutes.
Adhesive Articles
[0098] In one or more embodiments adhesive tapes may be formed
which comprise a substrate coated with one or more adhesive
compositions as described herein. As used herein, the term "tape"
is meant generically to encompass any manner of adhesive
application, including but not limited to tapes, labels, stickers,
decals, packaging applications, and the like. In an embodiment, the
adhesive tape is removable as described herein.
[0099] The adhesive compositions described herein may be applied to
any substrate. Suitable substrates may include, but are not limited
to, wood, paper, cardboard, plastic, plastic film, thermoplastic,
rubber, metal, metal film, metal foil (such as aluminum foil and
tin foil), metallized surfaces, cloth, non-wovens (particularly
polypropylene spun bonded fibers or non-wovens), spunbonded fibers,
cardboard, stone, plaster, glass (including silicon oxide (SiOx)
coatings applied by evaporating silicon oxide onto a film surface),
foam, rock, ceramics, films, polymer foams (such as polyurethane
foam), substrates coated with inks, dyes, pigments, PVDC and the
like or combinations thereof. Additional substrates may include
polyethylene, polypropylene, polyacrylates, acrylics, polyethylene
terephthalate, or blends thereof. Corona treatment, electron beam
irradiation, gamma irradiation, microwave or silanization may
modify any of the above substrates.
[0100] The adhesive compositions of this invention may be applied
to a substrate as a melt and then cooled. The adhesive composition
may be applied to a substrate using conventional coating techniques
such as spraying, roller coaters, die coaters and/or blade coaters,
generally at a temperature of from about 150.degree. C. to about
200.degree. C. In one or more embodiments, the adhesive composition
is applied to a substrate using a slot die.
[0101] A slot die is a closed system where an adhesive composition
is pumped through the system via a positive displacement pump. The
slot die usually includes a rotating bar at the point of the outlet
of the adhesive in order to maintain a smooth surface.
[0102] The substrate should be coated with sufficient adhesive
composition to provide a dry coating weight of from about 10 to
about 100, or from about 10 to about 50, or from about 15 to about
25 grams per square meter (g/m2).
[0103] After coating, the coated substrate is cut to the required
dimension. In the manufacture of tape, the substrate is slit into
strips and rolled into a finished product. The substrate may also
be cut into shaped items to provide labels. In one or more
embodiments, a release liner may also be employed if desired.
Properties of the Adhesive Composition
[0104] In one or more embodiments, the hot melt pressure-sensitive
adhesive compositions described herein may comprise from 5 wt % to
99 wt %, or greater than or equal to about 10 wt %, or 15 wt %, or
20 wt %, or 30 wt %, or 40 wt %, or 50 wt %, or 60 wt %, or 70 wt
%, or 80 wt %, or 90 wt % or 95 wt % of the propylene-based polymer
component. In embodiments, the hot melt pressure-sensitive adhesive
compositions described herein consist essentially of the
propylene-based polymer component, or consist essentially of the
propylene-based polymer component and the hydrocarbon tackifier
resin, or consist essentially of the propylene-based polymer
component, the hydrocarbon tackifier resin, and the process oil, or
consist essentially of the propylene-based polymer component, and
one or more of the hydrocarbon tackifier resin component, the
process oil component, and one or more additional fillers and/or
additives including, but are not limited to fillers, cavitating
agents, antioxidants, surfactants, adjuvants, plasticizers, block,
antiblock, colorants, color masterbatches, pigments, dyes,
processing aids, UV stabilizers, neutralizers, lubricants, waxes,
and/or nucleating agents as described herein.
[0105] In one or more embodiments, the compositions disclosed
herein comprise a hot melt pressure-sensitive adhesive comprising a
propylene-based polymer component. In an embodiment, the hot melt
pressure-sensitive adhesive comprises greater than or equal to
about 20 wt %, or 30 wt %, or 40 wt %, or 50 wt %, or 60 wt %, or
70 wt %, or 80 wt %, or 90 wt % or 95 wt % of the propylene-based
polymer component. In an embodiment, the compositions may comprise
a hot melt pressure-sensitive adhesive comprising less than or
equal to about 30 wt %, or 25 wt %, or 20 wt %, or 15 wt %, or 10
wt %, or 5 wt %, or 2 wt %, or 1 wt %, or 0.1 wt % of a block
copolymer component. In an embodiment, the compositions comprise a
hot melt pressure-sensitive adhesive which is free of a block
copolymer component, or which comprises less than about 0.01 wt %
of a block copolymer.
[0106] In an embodiment, the compositions comprise a hot melt
pressure-sensitive adhesive comprising from about 1 to about 60 wt
% of the hydrocarbon tackifier component. In an embodiment, the
compositions comprise a hot melt pressure-sensitive adhesive
comprising from about 1 to 30 wt % of a process oil.
[0107] In one or more embodiments, the adhesive composition has a
viscosity greater than about 500 mPa-s, or greater than about 1,000
mPa-s, or greater than about 5,000 mPa-s, or greater than about
10,000 mPa-s, and/or less than about 40,000 mPa-s, or less than
about 30,000 mPa-s, or less than about 20,000 mPa-s, or less than
about 15,000 mPa-s (measured at 175.degree. C.), determined
according to ASTM D 3236, or an equivalent thereof.
[0108] In an embodiment, the compositions comprise a hot melt
pressure-sensitive adhesive wherein the propylene-based polymer
component has a melt flow rate (MFR) of from about 1 to about 900
g/10 min, as measured according to ASTM D-1238 at 230.degree. C.,
2.16 kg.
[0109] In one or more embodiments, the initial 180.degree. peel
strength of the adhesive tape compositions described herein when
adhered to steel is less than or equal to about 10, or less than or
equal to about 8, or less than or equal to about 6, or less than or
equal to about 4 N/25 mm (at a coating weight of about 20 g/m2). In
an embodiment, the initial 180.degree. peel strength of an adhesive
tape on glass of from 0.1 to about 10 N/25 mm at a coating weight
of 20 g/m2. In an embodiment, an initial 180.degree. peel strength
of an adhesive tape on polyethylene film of from 0.1 to about 10
N/25 mm at a coating weight of 20 g/m2. In the same or other
embodiments, the initial 180.degree. peel strength of the adhesive
tape compositions described herein when adhered to glass is less
than or equal to about 10, or less than or equal to about 5, or
less than or equal to about 4, or less than or equal to about 3
N/25 mm (at a coating weight of about 20 g/m2). In the same or
other embodiments, the initial 180.degree. peel strength of the
adhesive tape compositions described herein when adhered to
polyethylene film is less than or equal to about 10, or less than
or equal to about 5, or less than or equal to about 3, or less than
or equal to about 2 N/25 mm (at a coating weight of about 20
g/m2).
[0110] In one or more embodiments, the 180.degree. peel strength of
the adhesive tape compositions described herein after one week
incubation at 60.degree. C. when adhered to steel is less than or
equal to about 35, or less than or equal to about 30, or less than
or equal to about 25, or less than or equal to about 20 N/25 mm (at
a coating weight of about 20 g/m2). In the same or other
embodiments, the 180.degree. peel strength of the adhesive tape
compositions described herein after one week incubation at
60.degree. C. when adhered to glass is less than or equal to about
30, or less than or equal to about 25, or less than or equal to
about 20, or less than or equal to about 15 N/25 mm (at a coating
weight of about 20 g/m2). In the same or other embodiments, the
180.degree. peel strength of the adhesive tape compositions
described herein after one week incubation at 60.degree. C. when
adhered to polyethylene film is less than or equal to about 15, or
less than or equal to about 10, or less than or equal to about 8,
or less than or equal to about 6 N/25 mm (at a coating weight of
about 20 g/m2).
[0111] As used herein, the 180.degree. peel strength of a sample is
determined according to FINAT testing method 1 (FTM 1).
[0112] In one or more embodiments, the shear of the adhesive tapes
described herein when adhered to steel (25 mm*25 mm, 1 kg) at room
temperature (23.degree. C.+-. 2.degree. C., 50%.+-0.5% RH) is
greater than or equal to about 10 hours, or greater than or equal
to about 15 hours, or greater than or equal to about 20 hours. As
used herein, shear is determined by FINAT testing method 8 (FTM
8).
[0113] In an embodiment, the compositions comprise a hot melt
pressure-sensitive adhesive having a clear visual determination
such that the compositions are suitable for use in no-label look
labels. While a number of determinations are suitable for
determining a visually clear composition, the instant compositions
do not lend themselves to standard testing methods directed to
clarity due to the difficulty in providing a sample with a uniform
thickness for spectroscopic testing. Accordingly, the following
test is used to determine the visual clarity of the instant
compositions, which allows for an objective determination of visual
clarity sufficient for use as a no-label look label, or the like.
In an embodiment, the composition has a clear visual determination,
wherein the visual determination consists of providing a testing
square consisting of a piece of white 20 weight paper having a
brightness of 90%. The paper may have a higher weight, and 20 pound
weight paper should be considered the minimum for use. Likewise,
the paper may have a higher brightness, and 90% brightness should
be considered the minimum brightness. The testing square having a
printed portion comprising the capital letters "O" and "Q" printed
with a laser printer to be visually distinguishable at 1 space
apart from each other thereon in black print using Helvetica number
10 font; depositing a sample of the composition at a temperature
above the melting point of the composition onto the testing square
using a flat applicator to cover the printed portion of the testing
square with a film of the composition having a thickness of 1 mm,
followed by allowing the composition to cool to a temperature of
25.degree. C. to produce a prepared test sample. The thickness may
be greater than 1 mm, and should be at least 1 mm. Accordingly, a
thickness of 1 mm to 5 mm may be acceptable, since clarity at
greater than 1 mm, e.g., 5 mm, would indicate clarity at 1 mm. The
method then includes visually determining the clarity of the
prepared test sample wherein the prepared test sample has a clear
visual determination when an observer having essentially 20:20
vision is able to visually distinguish the letter "O" from the
letter "Q" in the printed portion of the testing square at a
distance of about 30 cm from the prepared test sample at an
illumination of at least 1000 lux, which should be considered the
minimum, with an illumination from 1000 lux to 2000 lux being
acceptable.
[0114] For purposes herein, a piece of white 20 pound or higher
weight paper having a brightness of greater than 90% is exemplified
by standard copier or printer paper as generally known in the art
and which is readily available. For purposes herein the testing
square having a printed portion comprising the capital letters "O"
and "Q" printed with a laser printer to be visually distinguishable
at 1 space apart from each other thereon in black ink using
Helvetica number 10 font refers to a printing utilizing a typical
laser printer e.g., an HP LaserJet.TM. or the like, utilizing black
toner or ink (black print) to produce a black image on a white
background in which the letters O and Q are printed such that the
letters are readily distinguishable by an observer having about
20/20 vision at a distance of about 30 cm between the observer and
the testing sample. Accordingly, the test involves the ability for
an observer having 20/20 vision, or vision corrected to be
essentially 20/20 being able to discern the letter O from the
letter Q at a typical reading distance in an environment having an
amount of illumination suitable for reading (i.e., at an
illumination of from 1000 lux to 2000 lux).
[0115] The Helvetica font refers to the font developed in 1957 by
Max Miedinger with Eduard Hoffmann at the Haas'sche
Schriftgiesserei (Haas Type Foundry) of Munchenstein, Switzerland,
a new sans-serif typeface originally referred to as Neue Haas
Grotesk, and based on the Normal Grotesk of Schelter-Grotesk and
Haas. In 1960, the name of the typeface was changed to Helvetica.
For purposes herein, the capital letters "O" and "Q" printed using
10-point Helvetica font are defined as the same printed using a
common laser printer on plain copier paper as described herein, as
is readily understood by one having minimal skill in the art.
[0116] The deposit of the sample of the composition is conducted at
a temperature above the melting point of the composition, typically
between about 60 and 180.degree. C. onto the testing square using a
flat applicator to cover the printed portion of the testing square
with a film of the composition having a thickness of 1 mm to 5 mm,
followed by allowing the composition to cool to a temperature of
25.degree. C. to produce a prepared test sample. By specifying a
minimum thickness of 1 mm (i.e., a thickness of 1 mm to 5 mm), the
difficulty in producing a sample for observation is overcome since
a clear visual determination at a greater thickness implies that a
clear visual determination would be obtained at a thickness of 1
mm. The flat applicator may be a spatula or the like, and the
molten composition is simply spread over the letters on the testing
square and allowed to cool to determine the clarity of the
composition. A clear visual determination represents the ability of
an observer having essentially 20:20 vision is able to visually
distinguish the letter "O" from the letter "Q" in the printed
portion of the testing square at a distance of about 30 cm from the
prepared test sample at an illumination of from 1000 lux to 2000
lux. A hazy or not clear determination occurs when the letter "O"
cannot be distinguished from the letter "Q" in the printed portion
of the testing square at a distance of about 30 cm from the
prepared test sample at an illumination of from 1000 lux to 2000
lux.
[0117] Inherent in the above test is a sample essentially free of
bubbles and which is fully mixed and homogeneous over the printed
test area.
[0118] In an embodiment, the instant adhesive compositions show
improved solvent resistance in label applications. Typical adhesive
compositions are readily soluble in aromatic organic solvents, and
are typically dissolved at 50 wt % in toluene for color
determination and the like. In contrast, the adhesive compositions
disclosed herein, comprising the propylene-based polymer component
and less than 30 wt % of a block copolymer, are not readily soluble
in toluene. In an embodiment, the propylene-based polymer component
has a solubility in toluene of less than 50 wt %, or 40 wt %, or 30
wt %, or wt %, or 10 wt % at 25.degree. C. The propylene-based
polymer component simply "gels" in toluene, and is not readily
soluble therein. This attribute of the adhesive results in an
adhesive having improved solvent resistance as compared to
adhesives which are soluble in toluene at 50 wt % or above at
25.degree. C.
[0119] In an embodiment, the adhesive composition is clear
colorless, having an APHA of less than 10, determined according to
ASTM D1209 or an equivalent thereof, wherein APHA is a single
number yellowness index where each APHA unit is based on a dilution
of the 500 ppm stock solution of PtCo. Distilled water has an APHA
value of zero. The stock solution has an APHA value of 500. The
PtCo scale and Hazen scale are also based on this sample reagent
dilution and have units equivalent to APHA units.
[0120] Further embodiments according to the instant disclosure are
described with reference to the following lettered paragraphs:
A. A composition comprising a hot melt pressure-sensitive adhesive
comprising a propylene-based polymer component comprising from
about 60 to about 98 wt % propylene and from about 2 to about 40 wt
% of one or more of ethylene and C.sub.4-C.sub.10 alpha-olefins,
the propylene-based elastomer component having a melting point less
than or equal to about 130.degree. C. and a triad tacticity greater
than about 75%; the composition free of or comprising less than or
equal to about 30 wt % of a block copolymer. B. The composition
according to embodiment A, wherein the propylene-based polymer
component comprises from about 75 to about 98 wt % propylene and
from about 2 to about 25 wt % of one or more of ethylene and
C.sub.4-C.sub.10 alpha-olefins, and wherein the propylene-based
elastomer component has a melting point less than or equal to about
120.degree. C. C. The composition according to embodiment A or B,
wherein the propylene-based polymer component further has a heat of
fusion less than about 90 J/g. D. The composition according to any
one of embodiments A-C, wherein the propylene-based polymer
component has a melt flow rate (MFR) of from about 1 to about 900
g/10 min, as measured according to ASTM D-1238 at 230.degree. C.,
2.16 kg. E. The composition according to any one of embodiments
A-D, having a viscosity of less than or equal to about 150,000
mPa-s at 175.degree. C. determined according to ASTM D 3236, or an
equivalent thereof. F. The composition according to any one of
embodiments A-E free of or comprising less than about 0.01 wt % of
a block copolymer. G. The composition according to any one of
embodiments A-F free of or comprising less than about 0.01 wt % of
a block copolymer comprising styrene. H. The composition according
to any one of embodiments A-G, comprising from about 1 to about 60
wt % of a hydrocarbon tackifier resin. I. The composition according
to any one of embodiments A-H, wherein the hydrocarbon tackifier
resin has a ring-and-ball softening point of from about 50 to about
150.degree. C. J. The composition according to any one of
embodiments A-I, comprising from about 1 to about 30 wt % of a
process oil. K. The composition according to any one of embodiments
A-J, wherein the composition is removable and wherein the
composition comprises less than 0.01 wt % of a silicon oil, and/or
a silicon wax. L. The composition according to any one of
embodiments A-K, having a clear visual determination, wherein the
visual determination consists of providing a testing square
consisting of a piece of white 20 pound paper having a brightness
of 90%, the testing square having a printed portion comprising the
capital letters "O" and "Q" printed with a laser printer to be
visually distinguishable at 1 space apart from each other thereon
in black ink using Helvetica number 10 font; depositing a sample of
the composition at a temperature above the melting point of the
composition onto the testing square using a flat applicator to
cover the printed portion of the testing square with a film of the
composition having a thickness of 1 mm, followed by allowing the
composition to cool to a temperature of 25.degree. C. to produce a
prepared test sample; and visually determining the clarity of the
prepared test sample wherein the prepared test sample has a clear
visual determination when an observer having essentially 20:20
vision is able to visually distinguish the letter "O" from the
letter "Q" in the printed portion of the testing square at a
distance of about 30 cm from the prepared test sample at an
illumination of 1000 lux. M. The composition according to any one
of embodiments A-L, wherein the propylene-based polymer component
has a solubility in toluene of less than 10 wt % at 25.degree. C.
N. An adhesive article comprising a substrate and a hot melt
pressure-sensitive adhesive composition according to any one of
embodiments A-M. O. The adhesive article according to embodiment N,
comprising a substrate and a hot melt pressure-sensitive adhesive
composition comprising a propylene-based polymer component
comprising from about 60 to about 98 wt % propylene and from about
2 to about 40 wt % ethylene and/or C.sub.4-C.sub.10 alpha-olefins,
the propylene-based elastomer component having a melting point less
than or equal to about 130.degree. C. and a triad tacticity greater
than about 75%; the adhesive composition comprising less than about
0.01 wt % of a block copolymer. P. The adhesive article according
to embodiment N or O, wherein the adhesive composition comprises
from about 1 to about 50 wt % of a hydrocarbon tackifier resin. Q.
The adhesive article according to any one of embodiments N-P,
wherein the hydrocarbon tackifier resin has a ring-and-ball
softening point of from about 50 to about 140.degree. C. R. The
adhesive article according to any one of embodiments N-Q, wherein
the adhesive composition has a clear visual determination, wherein
the visual determination consists of providing a testing square
consisting of a piece of white copier paper having a printed
portion comprising the capital letters "O" and "Q" printed 1 space
apart from each other thereon in black ink using Helvetica number
10 font; depositing a sample of the composition at a temperature
above the melting point of the composition onto the testing square
using a flat applicator to cover the printed portion of the testing
square with a film of the composition having a thickness from about
1 to 5 mm, followed by allowing the composition to cool to a
temperature of 25.degree. C. to produce a prepared test sample; and
visually determining the clarity of the prepared test sample
wherein the prepared test sample has a clear visual determination
when an observer having essentially 20:20 vision is able to
visually distinguish the letter "O" from the letter "Q" in the
printed portion of the testing square at a distance of about 30 cm
from the prepared test sample at an illumination of from 1000 lux.
S. The adhesive article according to any one of embodiments N-R,
wherein the adhesive article is an adhesive tape having an initial
180.degree. peel strength of the tape on glass of less than or
equal to about 10 N/25 mm at a coating weight of about 20
g/m.sup.2. T. The adhesive article according to any one of
embodiments N--S, wherein the adhesive article is an adhesive tape
having an initial 180.degree. peel strength of the tape on
polyethylene film of less than or equal to about 10 N/25 mm at a
coating weight of about 20 g/m.sup.2.
EXAMPLES
[0121] The following examples are illustrative of the invention.
Materials used in the preparation of the adhesive compositions as
identified in the examples are as follows:
TABLE-US-00001 V4186 Vector 4186A Styrenic Block Copolymer (Dexco
Polymers) E-5400 Escorez 5400 tackifier (ExxonMobil) Flexon 876
paraffinic processing oil IRG 1010 Irganox 1010 antioxidant VMX
6202 VISTAMAXX 6202 propylene-based polymer ExxonMobil VMX 2320
VISTAMAXX 2320 propylene-based polymer ExxonMobil VISTAMAXX 6202 is
a propylene-ethylene elastomeric copolymer having an ethylene
content of approximately 15 wt % and a Melt Flow Rate (MFR)
(230.degree. C., 2.16 kg) of approximately 18 g/10 min as
determined by ASTM D-1238. Irganox 1010 is a phenolic antioxidant
having a melting point from about 110.degree. C. to about
125.degree. C. and a density (at 20.degree. C.) of about 1.15
g/cm3. Irganox 1010 is available from Ciba Specialty Chemicals,
Switzerland.
[0122] The adhesive properties reported herein were evaluated
according to FINAT testing methods (FINAT, P.O. Box 85612, 2508 CH,
The Hague, The Netherlands; www.finat.com).
[0123] LAB 1.1: 180.degree. peel on different substrates (PE &
Glass) @ Room temperature. This method is based on Finat Test
Method no. 1--Peel adhesion (180.degree.). The test method is
designed to quantify the permanence of adhesion or peelability of
self-adhesive pressure sensitive materials. It is the force
required to peel off a pressure sensitive adhesive from a standard
test plate at a specified angle (180.degree.) and speed.
[0124] LAB 1.2: 180.degree. peel on different substrates (PE &
Glass) @ fridge or lower temperature is the same as LAB 1.1, but
applied at lower temperature (3.degree. C.).
[0125] LAB 2.1: Looptack on different substrates (PE & Glass) @
Room temperature, is a method based on Finat Test Method no.
9--`Loop` tack measurement. This test method describes the
evaluation of the loop tack developed by a label adhesive onto a
standard test plate at room temperature. The loop tack is expressed
as the force required separating a loop of adhesive from a standard
test plate. The contact between the loop of adhesive film and the
test plate is realized without any additional force.
[0126] LAB 2.2: Looptack on different substrates (PE & Glass) @
fridge or lower temperature is the same as LAB 2.1, but applied at
lower temperature (3.degree. C.).
[0127] HMA 1: T-peel of laminate is an ExxonMobil Internal method,
indicates low speed release force. LAB 4: Shear resistance is based
on Finat Test Method no. 8--Resistance to shear from a standard
surface. This procedure describes the evaluation of the resistance
to shear, under specified stress and temperature, of a label
pressure sensitive adhesive adhered onto a reference substrate, in
this case stainless steel.
[0128] ETM-e 31 Brookfield viscosity is based on ASTM D-3236. This
testing method describes the determination of the melt viscosity of
hotmelt adhesives by means of a Brookfield rotoviscometer.
[0129] LAB 13: Mandrel hold is a method based on Finat Test Method
no. 19--Mandrel hold. This test is used to determine the resistance
of a self-adhesive label to lift from an external curved surface.
This surfaces as used in PM are PE and glass.
[0130] Hot melt pressure-sensitive adhesive blend compositions were
prepared according to the formulations shown in Table 1. All
amounts are reported in weight percent based on the total weight of
block copolymer, hydrocarbon tackifier resin, propylene-based
polymer, and other components in the adhesive blend.
TABLE-US-00002 TABLE 1 Component Comp. 1 Sample 2 Sample 3 Sample 4
Sample 5 Sample 6 Nominal 32% BCP 29% BCP 27% BCP 26% BCP 22% BCP
0% BCP proportions 0% VMX 10% VMX 15% VMX 20% VMX 30% VMX 32% VMX
V4186 32 28.8 27.2 25.6 22.4 0 VMX 6202 0 3.2 4.8 6.4 9.6 32 ES400
50 50 50 50 50 50 FLEXON 876 18 18 18 18 18 IRG 1010 0.3 0.3 0.3
0.3 0.3 0.3
[0131] A series of adhesive labels were prepared by mixing the
blend compositions as set forth in Table 1 in a two blade mixer at
145.degree. C. for a period of 70 minutes. The composition was then
heated to a temperature of 175.degree. C. and then pumped through a
coating die onto a label paper substrate. The weight of the applied
coating layer ranged from about 19 to 21 g/m2. After coating, the
paper was laminated to a release liner and the resulting adhesive
tape was wound and cut.
[0132] Performance of the adhesive tapes on a variety of substrates
is reported in Table 2. As used in Table 2, "af" means that the
experimental tapes exhibited adhesive failure, and "cf" means that
the experimental tapes exhibited a clean break in the adhesive
layer, while some adhesive remained on the surface of the substrate
after the adhesive tape was removed (cohesive failure). "Fogging"
means that visible adhesive residue is left behind on the
substrate. The polyethylene film used was LK151 BW
(ExxonMobil).
TABLE-US-00003 TABLE 2 Test Comp. 1 Sample 2 Sample 3 Sample 4
Sample 5 Sample 6 Visual Test Hazy- Not Not Not Not Clear- not
clear- clear- clear- clear - clear- Pass Fail Fail Fail Fail Fail
Blend viscosity @ 8600 8000 8500 9650 1160 38000 175.degree. C.
(mPa s) Adhesive properties at 25.degree. C., 20 days after sample
preparation 180.degree. Peel on Glass pt pt pt pt pt pt (N/25 mm)
180.degree. Peel on PE pt pt pt pt pt pt (N/25 mm) Loop tack Glass
(N) 12.3 14.7 14.1 13.1 16.5 9.0 af af af af af jerking pt Loop
tack PEs (N) 10.7 12.9 13.61 13.9 13.7 pt af af af af af Loop tack
humid PE 10.8 4.0 6.7 3.6 5.5 0.1 (N) af af af af af af T-Peel on
label samples 2.5 4.2 4.2 4.7 5.1 6.3 @1000 mm/min Shear at
25.degree. C. Steel >300 >300 >300 >300 >260 76
25*25 mm-1 kg cf cf Adhesive properties at 3.degree. C., 20 days
after sample preparation 180.degree. Peel on Glass pt pt pt pt pt
pt (N/25 mm) 180.degree. Peel on PE pt pt pt pt pt pt (N/25 mm)
Loop tack Glass (N) pt pt pt pt pt pt Loop tack PEs (N) 14.9 pt pt
pt pt 2.0 af Mandrel Test (mm) 24 hrs on glass 1.0 0.6 0.4 0.4 0.4
1.0 24 hrs on PE 0 0 0 0 0 0 1 week on glass 1.8 0.9 0.6 0.8 0.9
2.0 1 week on PE 0 0 0 0 0 0.1 2 weeks on glass 1.9 0.9 0.9 0.8 0.9
2.4 2 weeks on PE 0.6 0 0 0 0 0.1 Notes for Table 2: af--adhesion
failure; cf--cohesion failure; pt--paper tear; Humid
PE--conditioned at 5.degree. C. for 1 hr, samples labeled at room
temperature
[0133] As shown in Table 2, the adhesive compositions according to
the invention demonstrate comparative properties to those
comprising block copolymer, with improved clarity over the
comparative example when the composition is free of the block
copolymer.
[0134] The hot melt PSA (HMPSA) formulations according to the
instant disclosure produced a very clear adhesive when no SIS
(block copolymer) was added to formulation. Blending of the
propylene copolymer also resulted in less entrapped atmospheric
gas. Besides good optical properties, it was also noticed that the
adhesives according to the instant disclosure showed good solvent
resistance. This was exemplified in failed attempts to characterize
the color of the compositions. The method for measuring adhesive
color involved dissolution in a suitable hydrocarbon solvent such
as xylene or toluene. The instant adhesive systems swelled in such
solvents; however, they did not completely dissolve. Although this
presented a problem in measuring color, it did suggest that such
adhesive systems are resistant to solvents that easily dissolve
other typical HMPSA systems used in the industry. Such behavior
results in adhesive compositions or systems suitable for specialty
label applications where enhanced solvent resistance is
necessary.
[0135] Additionally, the adhesive compositions disclosed herein
also exhibited reduced skinning during accelerated heat aging when
compared to traditional SIS-based adhesives, and when properly
tackified, the inventive adhesives demonstrated superior shear
properties, good removability and excellent wetting of standard
substrates. Skinning refers to a layer of mainly oxidative or
otherwise degraded material, visually different from bulk of molten
adhesive. Skinning can take part on a section of the top layer of
the molten adhesive and in extreme cases can grow over the entire
surface while thickening to several mm. The adhesive compositions
of the instant disclosure also provided improved wetting of low
energy surfaces (LDPE, for example). The data further show that
addition of the propylene-based polymer in the inventive
compositions described herein improved internal cohesive strength
of the adhesive and thereby reduced the occurrence of cohesive
failure or fogging.
[0136] For purposes of convenience, various specific test
procedures are identified above for determining certain properties.
However, when a person of ordinary skill reads this patent and
wishes to determine whether a composition or polymer has a
particular property identified in a claim, then any published or
well-recognized method or test procedure can be followed to
determine that property, although the specifically identified
procedure is preferred. Each claim should be construed to cover the
results of any of such procedures, even to the extent different
procedures can yield different results or measurements. Thus, a
person of ordinary skill in the art is to expect experimental
variations in measured properties that are reflected in the
claims.
[0137] Certain embodiments and features have been described using a
set of numerical upper limits and a set of numerical lower limits.
It should be appreciated that ranges from any lower limit to any
upper limit are contemplated unless otherwise indicated. Certain
lower limits, upper limits and ranges appear in one or more claims
below. All numerical values are "about" or "approximately" the
indicated value, and take into account experimental error and
variations that would be expected by a person having ordinary skill
in the art.
[0138] To the extent a term used in a claim is not defined above,
it should be given the broadest definition persons in the pertinent
art have given that term as reflected in at least one printed
publication or issued patent. Furthermore, all patents, test
procedures, and other documents cited in this application are fully
incorporated by reference to the extent such disclosure is not
inconsistent with this application and for all jurisdictions in
which such incorporation is permitted.
[0139] While the foregoing is directed to various embodiments,
other and further embodiments may be devised without departing from
the basic scope thereof, and the scope thereof is determined by the
claims that follow.
* * * * *
References