U.S. patent application number 10/029697 was filed with the patent office on 2003-06-26 for compositions comprising a substantially random interpolymer of at least one alpha-olefin and at least one vinylidene aromatic monomer or hindered aliphatic vinylidene monomer.
Invention is credited to Guest, Martin J., Parikh, Deepak R., Speth, David A..
Application Number | 20030119974 10/029697 |
Document ID | / |
Family ID | 21827132 |
Filed Date | 2003-06-26 |
United States Patent
Application |
20030119974 |
Kind Code |
A1 |
Parikh, Deepak R. ; et
al. |
June 26, 2003 |
Compositions comprising a substantially random interpolymer of at
least one alpha-olefin and at least one vinylidene aromatic monomer
or hindered aliphatic vinylidene monomer
Abstract
Disclosed are compositions comprising at least one substantially
random interpolymer of ethylene and a vinylidene aromatic monomer
or a hindered aliphatic vinylidene monomer and optionally at least
one C.sub.3-C.sub.20 .alpha.-olefin monomer, and at least one
tackifier. The claimed compositions are useful in adhesives, such
as are employed in various applications, such as in packaging and
carton sealing, bookbinding, masking tape, clear office tape,
labels, decals, bandages, decorative and protective sheets (such as
shelf and drawer liners), floor tiles, sanitary napkin/incontinence
device placement strips, sun control films, and the joining of
gaskets to automobile windows. The claimed compositions further
find use in a variety of applications, such as sealants, coatings,
molded articles, and multilayered structures.
Inventors: |
Parikh, Deepak R.; (Lake
Jackson, TX) ; Guest, Martin J.; (Lake Jackson,
TX) ; Speth, David A.; (Midland, MI) |
Correspondence
Address: |
J. Benjamin Bai
Jenkens & Gilchrist
1100 Louisiana, Suite 1800
Houston
TX
77002
US
|
Family ID: |
21827132 |
Appl. No.: |
10/029697 |
Filed: |
December 18, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10029697 |
Dec 18, 2001 |
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08923191 |
Sep 4, 1997 |
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6344515 |
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60025622 |
Sep 4, 1996 |
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Current U.S.
Class: |
524/578 ;
156/334; 524/274; 524/296; 524/553; 524/577; 526/347 |
Current CPC
Class: |
B32B 7/12 20130101; C09J
125/02 20130101; C08L 2666/02 20130101; C09J 125/08 20130101; C08L
91/08 20130101; C08L 23/0823 20130101; C09J 123/08 20130101; B32B
27/28 20130101; C08L 23/08 20130101; C08L 2666/04 20130101; C09J
123/0823 20130101; C08L 23/0838 20130101; C08L 91/00 20130101; C08L
2205/02 20130101; B32B 15/04 20130101; C08L 25/06 20130101; C08L
25/08 20130101; C08L 23/0823 20130101; C08L 2666/02 20130101; C08L
25/08 20130101; C08L 2666/02 20130101; C08L 23/08 20130101; C08L
2666/02 20130101; C09J 123/0823 20130101; C08L 2666/02 20130101;
C09J 125/02 20130101; C08L 2666/02 20130101; C09J 125/02 20130101;
C08L 2666/04 20130101; C09J 125/08 20130101; C08L 2666/02 20130101;
C09J 125/08 20130101; C08L 2666/04 20130101; C09J 123/08 20130101;
C08L 2666/02 20130101 |
Class at
Publication: |
524/578 ;
524/274; 524/296; 524/553; 524/577; 156/334; 526/347 |
International
Class: |
C08L 023/08 |
Claims
1. A composition comprising from 5 to 95 weight percent of at least
one substantially random interpolymer of ethylene and a vinylidene
aromatic monomer or a hindered aliphatic vinylidene monomer and
optionally at least one C.sub.3-C.sub.20 .alpha.-olefin monomer,
wherein the substantially random interpolymer comprises from 1-65
mole percent of the vinylidene aromatic monomer or hindered
aliphatic vinylidene monomer, and from 5 to 95 weight percent of at
least one tackifier.
2. The composition of claim 1, wherein the at least one
substantially random interpolymer is an interpolymer of ethylene
and a vinylidene aromatic monomer represented by the following
formula: 6wherein R.sub.1 is selected from the group of radicals
consisting of hydrogen and alkyl radicals containing three carbons
or less, and Ar is a phenyl group or a phenyl group substituted
with from 1 to 5 substituents selected from the group consisting of
halo, C.sub.1-4 alky, and C.sub.1-4 haloalkyl.
3. The composition of claim 1, wherein the substantially random
interpolymer is an interpolymer of ethylene, a vinylidene aromatic
monomer or a hindered aliphatic vinylidene monomer, and at least
one third monomer selected from the group consisting of
C.sub.3-C.sub.20 .alpha.-olefins and norbornene.
4. The compositions of claim 1, wherein the substantially random
interpolymer is an interpolymer of ethylene, a vinylidene aromatic
monomer, and optionally at least one third monomer selected from
the group consisting of C.sub.3-C.sub.20 .alpha.-olefins and
norbornene.
5. The composition of claim 1, wherein the composition comprises
from 25 to 95 weight percent of the substantially random
interpolymer and from 5 to 75 weight percent of at least one
tackifier.
6. The composition of claim 1, wherein the at least one tackifier
is selected from the group consisting of wood rosin, tall oil
derivatives, cyclopentadiene derivatives, natural and synthetic
terpenes, terpene-phenolics, styrene/.alpha.-methyl styrene resins,
and mixed aliphatic-aromatic tackifying resins.
7. The composition of claim 1, wherein the composition further
comprises from 5 to 75 weight percent of at least one modifying or
extending composition selected from the group consisting of
paraffinic waxes, crystalline polyethylene waxes, ultralow
molecular weight ethylene polymers, homogeneous linear or
substantially linear ethylene/.alpha.-olefin interpolymers,
polystyrene, styrene block copolymers, ethylene vinyl acetate, and
amorphous polyolefins.
8. The composition of claim 1, wherein the composition comprises
from 1 to 60 weight percent of one or more processing aids selected
from the group consisting of phthalate esters, natural oils,
paraffinic oils, naphthenic oils, and aromatic oils.
9. The composition of claim 1, in the form of an adhesive, layer of
a multilayer food packaging structure, coating, sealant or molded
article, calendared article, or extruded article.
10. An adhesive which comprises from 5 to 95 weight percent of at
least one substantially random interpolymer of ethylene and a
vinylidene aromatic monomer or a hindered aliphatic vinylidene
monomer and optionally at least one C.sub.3-C.sub.20 .alpha.-olefin
monomer, wherein the substantially random interpolymer comprises
from 1-65 mole percent of the vinylidene aromatic monomer or
hindered aliphatic vinylidene monomer, and wherein the adhesive
further comprises from 95 to 5 weight percent of at least one
second component selected from the group consisting of tackifiers,
waxes, homogeneous linear or substantially linear
ethylene/.alpha.-olefin interpolymers, ultra-low molecular weight
ethylene polymers, processing aids, and mixtures thereof.
11. The adhesive of claim 10, wherein the substantially random
interpolymer comprises from 25 to 65 weight percent of the
vinylidene aromatic monomer or hindered aliphatic vinylidene
monomer.
12. The adhesive of claim 10, wherein the adhesive comprises a
plurality of substantially random interpolymer components which
differ in the amount of vinylidene aromatic monomer or hindered
aliphatic vinylidene monomer content, which differ in molecular
weight, or which differ in both the amount of vinylidene aromatic
monomer or hindered aliphatic vinylidene monomer content and in
molecular weight.
13. The adhesive of claim 12, which comprises: (a) 5 to 75 weight
percent of a substantially random interpolymer of ethylene and at
least one vinylidene aromatic comonomer or hindered aliphatic
vinylidene comonomer, which interpolymer has an Mn of greater than
about 10,000 and comprises from 5 to less than 25 mole percent of
the at least one vinylidene aromatic comonomer or hindered
aliphatic vinylidene comonomer; (b) from 5 to 75 weight percent of
a substantially random interpolymer of ethylene and at least one
vinylidene aromatic comonomer or hindered aliphatic vinylidene
comonomer, which interpolymer has an Mn of less than about 8,200
and comprises from 1 to less than 5 mole percent of the at least
one vinylidene aromatic comonomer or hindered aliphatic vinylidene
comonomer; and (c) from 5 to 75 weight percent of a substantially
random interpolymer of ethylene and at least one vinylidene
aromatic comonomer or hindered aliphatic vinylidene comonomer,
which interpolymer has an Mn of less than about 8,200 and comprises
at least 25 mole percent of the at least one vinylidene aromatic
comonomer or hindered aliphatic vinylidene comonomer.
14. The adhesive of claim 10, wherein the substantially random
interpolymer is an interpolymer of ethylene, at least one
vinylidene aromatic monomer, and optionally at least one
.alpha.-olefin monomer.
15. The adhesive of claim 10, as applied to a substrate selected
from the group consisting of a package, carton, bookbinding, tape,
label, decal, bandage, decorative sheet, protective sheet, ceramic
tile, vinyl tile, vinyl flooring, carpet backing, nonwoven fabric,
woven fabric, personal hygiene device placement strip, sun control
film, gasket, caulk, wood, or veneer.
15. A coextruded or laminated multilayer film, in which at least
one layer comprises an adhesive comprising at least one
substantially random interpolymer of ethylene and a vinylidene
aromatic monomer or a hindered aliphatic vinylidene monomer and
optionally at least one C.sub.3-C.sub.20 .alpha.-olefin
monomer.
17. The coextruded or laminated multilayer film of claim 16 in
which the adhesive is adhered to a metal foil.
18. A tape comprising a substrate to which has been applied an
adhesive comprising: a. from 40 to 60 weight percent of a
substantially random interpolymer of ethylene and a vinylidene
aromatic monomer or a hindered vinylidene aromatic monomer and
optionally at least one C.sub.3-C.sub.20 .alpha.-olefin monomer,
said substantially random interpolymer comprising from 25 to 65
weight percent of the vinylidene aromatic monomer or hindered
aliphatic vinylidene monomer, b. from 40 to 60 weight percent of a
tackifier, and c. from 0 to 10 weight percent of a processing aid,
wherein the adhesive is characterized as having a storage modulus
(G') at 25.degree. C. of from 2.times.10.sup.5 to 5.times.10.sup.6
dynes/cm.sup.2 (0.2 to 5 MPa).
Description
[0001] The subject invention pertains to olefin-based compositions.
In particular, the subject invention pertains to compositions
comprising at least one substantially random interpolymer of at
least one .alpha.-olefin and a vinylidene aromatic monomer or a
hindered aliphatic vinylidene monomer, preferably at least one
substantially random interpolymer of ethylene, optionally at least
one .alpha.-olefin and a vinylidene aromatic monomer, in
conjunction with at least one tackifier, and optionally at least
one extending or modifying composition or processing aid.
[0002] Substantially random interpolymers of at least one
.alpha.-olefin and a vinylidene aromatic monomer or a hindered
aliphatic vinylidene monomer, including materials such as
.alpha.-olefin/vinyl aromatic monomer interpolymers, are known in
the art and offer a range of material structures and properties
which makes them useful for varied applications, such as
compatibilizers for blends of polyethylene and polystyrene as
described in U.S. Pat. No. 5,460,818.
[0003] One particular aspect described by D'Anniello et al.
(Journal of Applied Polymer Science, Volume 58, pages 1701-1706
[1995]) is that such interpolymers can show good elastic properties
and energy dissipation characteristics. In another aspect, selected
interpolymers can find utility in adhesive systems, as illustrated
in U.S. Pat. No. 5,244,996, issued to Mitsui Petrochemical
Industries Ltd.
[0004] Although of utility in their own right, the industry seeks
to improve the applicability of these substantially random
interpolymers. For example, it may be desirable in certain
instances to manipulate the glass transition temperature of the
substantially random interpolymer, and thus allow materials based
on substantially random interpolymers to find application, for
example, in molded articles and as sealants and adhesives.
[0005] The glass transition temperature of a polymer is one of the
major physical parameters that determines its mechanical
properties. Below the glass transition temperature, polymers are
commonly stiff load bearing rigid plastics. Above the glass
transition temperature, materials exhibit more rubbery behavior.
When the glass transition temperature is in the range of room
temperature, the properties observed for the polymer may change
depending on the ambient conditions. It is therefore advantageous
to be able to control the glass transition temperature of a polymer
to achieve the desired property profile.
[0006] For instance, in the case of substantially random
interpolymers which have a glass transition temperature of about
-25 to about 25.degree. C., it would be desirable in certain
instances to raise the glass transition temperature. For instance,
substantially random interpolymers having a glass transition
temperature at about ambient temperature are susceptible to
detrimental blocking. Further, when the glass transition
temperature is about ambient temperature, the product properties
will vary, depending on the actual temperature, which leads to an
undesired product variance. Further, when the glass transition
temperature is at ambient temperature, optimized utility in certain
applications, such as in pressure sensitive adhesives, is
desired.
[0007] One way to control the glass transition temperature of a
copolymer is to change the type of comonomer and the amount of it
present in the copolymer. For instance, this approach is employed
for controlling the glass transition temperature of acrylic
copolymers.
[0008] An alternative to varying comonomer content is to add to a
base material another material having a different glass transition
temperature. However, it is known that the addition of a low
molecular weight brittle diluent, while it may increase the glass
transition temperature, will typically lead to a degradation in
mechanical properties, such as tensile strength. It was expected
that the addition of the class of materials commonly decribed as
tackifiers to substantially random interpolymers, particularly
those interpolymers which are elastomeric, would dilute the polymer
network and lead to tensile properties, that is, tensile strength
at break and elongation at break, which are less than the
substantially random interpolymer alone.
[0009] There is a need to provide compositions comprising
substantially random interpolymers of at least one .alpha.-olefin
and at least one vinylidene aromatic or hindered aliphatic monomer
which have an increased glass transition temperature over
unmodified substantially random interpolymers, particularly which
have a glass transition temperature greater than room temperature.
There is a need for such a composition which is attained without a
corresponding loss in tensile properties. There is a need to
provide improved hot melt adhesive formulations comprising
substantially random interpolymers of at least one .alpha.-olefin
and at least one vinylidene aromatic or hindered aliphatic monomer
which accords superior performance characteristics to the
unmodified polymers, which will further expand the utility of this
interesting class of materials.
[0010] Hot melt adhesives generally comprise three components: a
polymer, a tackifier, and a wax. Each component may comprise a
blend of two or more components, that is, the polymer component may
comprise a blend of two different polymers. The polymer provides
cohesive strength to the adhesive bond. The tackifier provides tack
to the adhesive which serves to secure the items to be bonded while
the adhesive sets, and reduces the viscosity of the system making
the adhesive easier to apply to the substrate. The tackifier may be
further used to control the glass transition temperature of the
formulation. The wax shortens the open/close times and reduces the
viscosity of the system. Hot melt adhesives may further typically
comprise oil as a filler and/or to reduce the viscosity of the
system.
[0011] Hot melt adhesives based on previously used polymers include
ethylene vinyl acetate copolymers (EVA), atactic polypropylene
(APP), amorphous polyolefins, low density polyethylene (LDPE), and
homogeneous linear ethylene/.alpha.-olefin copolymers. Prior art
hot melt adhesives typically employed large levels of tackifier to
reduce the viscosity of the system to levels which enabled its
facile application to the substrate, for instance, to viscosities
less than about 5000 centipoise.
[0012] Pressure sensitive adhesives are materials which are
aggressively and permanently tacky at room temperature at the time
of application, and which firmly adhere to a variety of dissimilar
surfaces with the application of light pressure, such as pressing
with a finger. Despite their aggressive tackiness, pressure
sensitive adhesives may be removed from smooth surfaces without
leaving significant residue. Pressure sensitive adhesives are
widely used in everyday applications, such as masking tape, clear
office tape, labels, decals, bandages, decorative and protective
sheets (such as shelf and drawer liners), floor tiles, sanitary
napkin/incontinence device placement strips, sun control films, and
the joining of gaskets to automobile windows.
[0013] Historically, pressure sensitive adhesives were based on
natural rubber and wood rosins, which were carried by a solvent.
Articles bearing such adhesives were manufactured by applying a
solution of the adhesive on a suitable backing, and removing the
solvent by a devolatilizing process. However, in response to cost
increases in solvents and regulatory restrictions regarding
emissions, water-based adhesives and solid-form hot melt adhesives
(HMA's) have been developed.
[0014] Historically, adhesives have been based on one of four types
of polymers: elastomers (such as natural rubber,
styrene-isoprene-styrene block copolymers,
styrene-butadiene-styrene block copolymers, and styrene-butadiene
random copolymers); acrylics (such as interpolymers of butyl
acrylate, 2-ethyl hexyl acrylate, and methyl methacrylate);
hydrocarbons (such as atactic polypropylene, amorphous
polypropylene, poly-1-butene, and low density polyethylene); and
ethylene vinyl acetate. More recently, hot melt adhesives based on
homogeneous linear and substantially linear ethylene polymers have
been disclosed and claimed.
[0015] Diene-based elastomers may be utilized in solvent-based,
water-born, and hot melt adhesives. However, adhesive systems based
on such elastomers are disadvantageous in that the sites of
unsaturation in the block copolymer backbone make the hot melt
adhesive susceptible to degradation by the action of oxygen and
ultraviolet light.
[0016] Acrylic systems, while stable to oxygen and ultraviolet
light, are inferior to diene-based elastomer systems in terms of
the balance of tack, peel and creep resistance which is preferred
for pressure sensitive adhesive applications. Further, such systems
are typically available only in the solvent-based and water-borne
systems, making them further disadvantageous for the reasons set
forth above.
[0017] Hydrocarbon-based systems were developed at least in part to
provide improved stability to oxygen and ultraviolet light, as
compared to diene-based elastomer systems, as well as the ability
to be utilized in hot melt adhesive systems. Hydrocarbon-based
systems which comprise, atactic polypropylene, interpolymers of
propylene with higher order .alpha.-olefins, or
poly-.alpha.-olefins, such systems exhibit a poor balance of
properties. In particular, poly-1-butene has a tendency to slowly
crystallize after application to the substrate, leading to a
profound loss of tack. When oil is added to increase tack, the oil
tends to migrate out of the adhesive into the backing layer or the
substrate. Atactic polypropylene and poly-.alpha.-olefins suffer
from low tensile strength, which leads to low cohesive strength on
peel and to the leaving of a residue on the substrate surface after
peeling. Hydrocarbon-based systems are typically not preferred due
to the limited ability of low density polyethylene to accept the
formulation ingredients required to produce a hot melt adhesive
with suitable mechanical properties.
[0018] Ethylene vinyl acetate based systems are limited in that as
higher vinyl acetate levels are selected, elastic performance
increases, but compatibility with formulation ingredients
decreases.
[0019] Hot melt adhesives based on homogeneous linear
ethylene/.alpha.-olefin copolymers are disclosed in U.S. Pat. No.
5,530,054. Preferred hot melt adhesives based on homogeneous linear
and substantially linear ethylene/.alpha.-olefin interpolymers are
disclosed in U.S. Ser. No. 08/616,406, entitled "Olefm Polymer
Blends for Hot Melt Adhesives", filed on Mar. 15, 1996 in the names
of Parikh et al., and U.S. Ser. No. 08/615,750, entitled "Adhesives
Comprising Olefin Polymers", filed on Mar. 14, 1996, in the names
of Simmons, et. al., the disclosures of which are incorporated
herein by reference. While these preferred hot melt adhesives are
advantageous, industry is continually in need of alternate adhesive
systems.
[0020] The subject invention pertains to a composition comprising
at least one substantially random interpolymer of ethylene and a
vinylidene aromatic comonomer or a hindered aliphatic vinylidene
comonomer and optionally at least one third comonomer selected from
the group consisting of C.sub.3-C.sub.20 .alpha.-olefins, and at
least one tackifier. The subject invention further pertains to a
composition comprising at least one substantially random
interpolymer of ethylene and a vinylidene aromatic comonomer or a
hindered aliphatic vinylidene comonomer and optionally at least one
third comonomer selected from the group consisting of
C.sub.3-C.sub.20 .alpha.-olefins, and at least one tackifier, and
at least one extending or modifying composition or processing aid.
The subject invention further pertains to such a composition,
wherein the extending or modifying composition is selected from the
group consisting of the following: paraffinic waxes, crystalline
polyethylene waxes, styrene block copolymers, ethylene vinyl
acetate, polymers or interpolymers of styrene and/or
alkyl-substituted styrene, such as .alpha.-methyl styrene, and
homogeneous linear or substantially linear interpolymers of
ethylene and one or more C.sub.3-C.sub.20 .alpha.-olefins. The
subject invention further pertains to such a composition in the
form of an adhesive, a layer of a multilayer food packaging
structure, a coating, a sealant, a molded article, or a sound
attenuating device.
[0021] Unless indicated otherwise, the following testing procedures
are to be employed:
[0022] Density is measured in accordance with ASTM D-792. The
samples are annealed at ambient conditions for 24 hours before the
measurement is taken.
[0023] Melt index (I.sub.2), is measured in accordance with ASTM
D-1238, condition 190.degree. C./2.16 kg (formally known as
"Condition (E)").
[0024] Molecular weight is determined using gel permeation
chromatography (GPC) on a Waters 150.degree. C. high temperature
chromatographic unit equipped with three mixed porosity columns
(Polymer Laboratories 103, 104, 105, and 106), operating at a
system temperature of 140.degree. C. The solvent is
1,2,4-trichlorobenzene, from which 0.3 percent by weight solutions
of the samples are prepared for injection. The flow rate is 1.0
mL/min. and the injection size is 100 microliters.
[0025] The molecular weight determination is deduced by using
narrow molecular weight distribution polystyrene standards (from
Polymer Laboratories) in conjunction with their elution volumes.
The equivalent polyethylene molecular weights are determined by
using appropriate Mark-Houwink coefficients for polyethylene and
polystyrene (as described by Williams and Word in Journal of
Polymer Science, Polymer Letters, Vol. 6, (621) 1968, incorporated
herein by reference) to derive the following equation:
M.sub.polyethylene=a*(M.sub.polystyrene)b.
[0026] In this equation, a=0.4316 and b=1.0. Weight average
molecular weight, M.sub.w, is calculated in the usual manner
according to the following formula: M.sub.w=.SIGMA.w.sub.i*M.sub.i,
where w.sub.i and M.sub.i are the weight fraction and molecular
weight, respectively, of the ith fraction eluting from the GPC
column.
[0027] Melt viscosity is determined in accordance with the
following procedure using a Brookfield Laboratories DVII+
Viscometer in disposable aluminum sample chambers. The spindle used
is a SC-31 hot-melt spindle, suitable for measuring viscosities in
the range of from 10 to 100,000 centipoise. A cutting blade is
employed to cut samples into pieces small enough to fit into the 1
inch wide, 5 inches long sample chamber. The sample is placed in
the chamber, which is in turn inserted into a Brookfield Thermosel
and locked into place with bent needle-nose pliers. The sample
chamber has a notch on the bottom that fits the bottom of the
Brookfield Thermosel to ensure that the chamber is not allowed to
turn when the spindle is inserted and spinning. The sample is
heated to 350.degree. F., with additional sample being added until
the melted sample is about 1 inch (2.54 cm) below the top of the
sample chamber. The viscometer apparatus is lowered and the spindle
submerged into the sample chamber. Lowering is continued until
brackets on the viscometer align on the Thermosel. The viscometer
is turned on, and set to a shear rate which leads to a torque
reading in the range of 30 to 60 percent. Readings are taken every
minute for about 15 minutes, or until the values stabilize, which
final reading is recorded.
[0028] G', G", and peak tan delta are determined as follows. The
samples are examined using melt rheology techniques on a
Rheometrics RDA-II Dynamic Analyzer. The Temperature-Step mode is
used utilizing the 7.9 mm diameter parallel plates geometry. The
sweep is run from approximately -70.degree. C. to 250.degree. C. at
5.degree. C. per step with 30 seconds equilibration delay at each
step. The oscillatory frequency is 1 radian/second with an
autostrain function of 0.1 percent strain initially, increasing in
positive 100 percent adjustments whenever the torque decreased to
10 gram-centimeters. The plates are used with an initial gap of 1.5
mm at 160.degree. C. The samples are maintained in a nitrogen
environment throughout the analyses to minimize oxidative
degradation. A plot of G' (the dynamic storage modulus of the
sample), G" (the dynamic loss modulus of the sample), tan delta
(G'/G"), and peak tan delta (a representation of the glass
transition temperature, are plotted.
[0029] Glass transition temperature (DSC) is determined using
differential scanning calorimetry, with a scan rate of 10.degree.
C./minute from -75 to 1 50.degree. C.
[0030] Probe tack is determined using a Digital Polyken Probe Tack
Tester TMI 80-02-01 (available from Testing Machines, Inc., (New
York)), in accordance with ASTM-D2979-71.
[0031] The term "interpolymer" is used herein to indicate a
copolymer, or a terpolymer, or the like. That is, at least one
other comonomer is polymerized with ethylene to make the
interpolymer.
[0032] The term "hydrocarbyl" means any aliphatic, cycloaliphatic,
aromatic, aryl substituted aliphatic, aryl substituted
cycloaliphatic, aliphatic substituted aromatic, or cycloaliphatic
substituted aromatic groups. The aliphatic or cycloaliphatic groups
are preferably saturated. Likewise, the term "hydrocarbyloxy" means
a hydrocarbyl group having an oxygen linkage between it and the
carbon atom to which it is attached.
[0033] The term "substantially random" in the substantially random
interpolymer comprising an .alpha.-olefin and a vinylidene aromatic
monomer or hindered aliphatic vinylidene monomer as used herein
means that the distribution of the monomers of said interpolymer
can be described by the Bernoulli statistical model or by a first
or second order Markovian statistical model, as described by J. C.
Randall in Polymer Sequence Determination, Carbon-13 NMR Method,
Academic Press New York, 1977, pp. 71-78. Preferably, the
substantially random interpolymer comprising an .alpha.-olefin and
a vinylidene aromatic monomer does not contain more than 15 percent
of the total amount of vinylidene aromatic monomer in blocks of
vinylidene aromatic monomer of more than 3 units. More preferably,
the interpolymer is not characterized by a high degree of either
isotacticity or syndiotacticity. This means that in the 13C-NMR
spectrum of the substantially random interpolymer the peak areas
corresponding to the main chain methylene and methine carbons
representing either meso diad sequences or racemic diad sequences
should not exceed 75 percent of the total peak area of the main
chain methylene and methine carbons.
[0034] Any numerical values recited herein include all values from
the lower value to the upper value in increments of one unit
provided that there is a separation of at least 2 units between any
lower value and any higher value. As an example, if it is stated
that the amount of a component or a value of a process variable
such as, for example, temperature, pressure and time is, for
example, from 1 to 90, preferably from 20 to 80, more preferably
from 30 to 70, it is intended that values such as 15 to 85, 22 to
68, 43 to 51, 30 to 32 etc. are expressly enumerated in this
specification. For values which are less than one, one unit is
considered to be 0.0001, 0.001, 0.01 or 0.1 as appropriate. These
are only examples of what is specifically intended and all possible
combinations of numerical values between the lowest value and the
highest value enumerated are to be considered to be expressly
stated in this application in a similar manner.
[0035] The interpolymers suitable for use as, or as components in,
the compositions of the invention, include, but are not limited to,
interpolymers prepared by polymerizing one or more .alpha.-olefins
with one or more vinylidene aromatic monomers and/or one or more
hindered aliphatic vinylidene monomers, with interpolymers of
ethylene, one or more vinylidene aromatic monomers, and optionally
one or more .alpha.-olefins, being preferred.
[0036] Suitable .alpha.-olefins include for example, those
containing from 2 to about 20, preferably from 2 to about 12, more
preferably from 2 to about 8 carbon atoms. Particularly suitable
are ethylene, propylene, butene- 1, 4-methyl-1-pentene, hexene-1
and octene-1. Other suitable .alpha.-olefin monomers include
norbornenes.
[0037] Suitable vinylidene aromatic monomers include, for example,
those represented by the following formula: 1
[0038] wherein R.sup.1 is selected from the group of radicals
consisting of hydrogen and alkyl radicals containing from 1 to
about 4 carbon atoms, preferably hydrogen or methyl; each R.sup.2
is independently selected from the group of radicals consisting of
hydrogen and alkyl radicals containing from 1 to about 4 carbon
atoms, preferably hydrogen or methyl; Ar is a phenyl group or a
phenyl group substituted with from 1 to 5 substituents selected
from the group consisting of halo, C.sub.1-4-alkyl, and
C.sub.1-4-haloalkyl; and n has a value from zero to about 6,
preferably from zero to about 2, more preferably zero. Exemplary
monovinylidene aromatic monomers include styrene, vinyl toluene,
.alpha.-methylstyrene, t-butyl styrene, chlorostyrene, including
all isomers of these compounds. Particularly suitable such monomers
include styrene and lower alkyl- or halogen-substituted derivatives
thereof. Preferred monomers include styrene, .alpha.-methyl
styrene, the lower alkyl- or phenyl-ring substituted derivatives of
styrene, such as ortho-, meta-, and para-methylstyrene, the ring
halogenated styrenes, para-vinyl toluene or mixtures thereof A more
preferred monovinylidene aromatic monomer is styrene.
[0039] The term "hindered aliphatic or cycloaliphatic vinylidene
monomers" means addition polymerizable vinylidene monomers
corresponding to the following formula: 2
[0040] wherein and A.sup.1 is a sterically bulky, aliphatic
substituent of up to 20 carbons, R.sup.1 is selected from the group
of radicals consisting of hydrogen and alkyl radicals containing
from 1 to about 4 carbon atoms, preferably hydrogen or methyl; each
R.sup.2 is independently selected from the group of radicals
consisting of hydrogen and alkyl radicals containing from 1 to
about 4 carbon atoms, preferably hydrogen or methyl; or
alternatively R.sup.1 and A1 together form a ring system. By the
term "sterically bulky" is meant that the monomer bearing this
substituent is normally incapable of addition polymerization by
standard Ziegler-Natta polymerization catalysts at a rate
comparable with ethylene polymerizations. Preferred hindered
aliphatic or cycloaliphatic vinylidene monomers are those in which
one of the carbon atoms bearing ethylenic unsaturation is tertiary
or quaternary substituted. Examples of such substituents include
cyclic aliphatic groups such as cyclohexyl, cyclohexenyl,
cyclooctenyl, or ring alkyl or aryl substituted derivatives
thereof, tert-butyl, and norbornyl. Most preferred hindered
aliphatic vinylidene compounds are the various isomeric vinyl-ring
substituted derivatives of cyclohexene and substituted
cyclohexenes, and 5-ethylidene-2-norbornene. Especially suitable
are 1-, 3-, and 4-vinylcyclohexene.
[0041] The interpolymers of one or more .alpha.-olefins and one or
more monovinylidene aromatic monomers and/or one or more hindered
aliphatic or cycloaliphatic vinylidene monomers employed in the
present invention are substantially random polymers. These
interpolymers usually contain from about 1 to about 65 mole percent
of at least one vinylidene aromatic monomer and/or hindered
aliphatic or cycloaliphatic vinylidene monomer and from about 35 to
about 99 mole percent of at least one aliphatic .alpha.-olefin
having from 2 to about 20 carbon atoms. When the substantially
random interpolymer has from 1 to less than 5 mole percent of the
at least one vinylidene aromatic monomer and/or hindered aliphatic
or cycloaliphatic vinylidene monomer, the substantially random
interpolymer will impart a crystalline character to the adhesive
system. When the substantially random interpolymer has from 5 to
less than 25 mole percent of the at least one vinylidene aromatic
monomer and/or hindered aliphatic or cycloaliphatic vinylidene
monomer, the substantially random interpolymer will impart an
elastomeric character to the adhesive system. When the
substantially random interpolymer has from 25 to 50 mole percent of
the at least one vinylidene aromatic monomer and/or hindered
aliphatic or cycloaliphatic vinylidene monomer, the substantially
random interpolymer will impart an amorphous character to the
adhesive system.
[0042] When the substantially random interpolymer is used as the
strength imparting component of an adhesive, the number average
molecular weight (Mn) of these interpolymers is usually greater
than about 1,000, preferably from about 5,000 to about 1,000,000,
more preferably from about 10,000 to about 500,000, and most
preferably from about 50,000 to about 300,000. As described below,
ultra-low molecular weight ethylene polymers, one class of which
includes ultra-low molecular weight interpolymers of ethylene and
at least one vinylidene aromatic monomer and/or hindered aliphatic
or cycloaliphatic vinylidene monomer, may suitably be employed in
the practice of this invention, if not as the strength-imparting
component of the formulation, then as tackifiers or modifiers.
[0043] While preparing the substantially random interpolymers, as
will be described hereinafter, an amount of atactic vinylidene
aromatic homopolymer may be formed due to homopolymerization of the
vinylidene aromatic monomer at elevated temperatures. In general,
the higher the polymerization temperature was, the higher is the
amount of homopolymer formed. The presence of vinylidene aromatic
homopolymer is in general not detrimental for the purposes of the
present invention and may be tolerated. The vinylidene aromatic
homopolymer may be separated from the interpolymer, if desired, by
extraction techniques such as selective precipitation from solution
with a non solvent for either the interpolymer or the vinylidene
aromatic homopolymer. For the purpose of the present invention it
is preferred that no more than 20 weight percent, preferably less
than 15 weight percent, more preferably less than 10 weight
percent, based on the total weight of the interpolymers of
vinylidene aromatic homopolymer is present.
[0044] The substantially random interpolymers may be modified by
typical grafting, hydrogenation, functionalizing, or other
reactions well known to those skilled in the art. The polymers may
be readily sulfonated or chlorinated to provide functionalized
derivatives according to established techniques.
[0045] The substantially random interpolymers are prepared by
polymerizing a mixture of polymerizable monomers in the presence of
metallocene or constrained geometry catalysts.
[0046] The substantially random interpolymers can be prepared as
described in U.S. application Ser. No. 545,403 filed Jul. 3, 1990
(corresponding to EP-A-0,416,815) by James C. Stevens et al., both
of which are incorporated herein by reference. Preferred operating
conditions for such polymerization reactions are pressures from
atmospheric up to 3000 atmospheres (300 MPa) and temperatures from
-30.degree. C. to 200.degree. C.
[0047] Examples of suitable catalysts and methods for preparing the
substantially random interpolymers are disclosed in EP-A-416,815;
EP-A-514,828; EP-A-520,732; U.S. application Ser. No. 241,523,
filed May 12, 1994; as well as U.S. Pat. Nos. 5,055,438; 5,057,475;
5,096,867; 5,064,802; 5,132,380; 5,189,192; 5,321,106; 5,347,024;
5,350,723; 5,374,696; and 5,399,635, all of which are incorporated
herein by reference.
[0048] The substantially random .alpha.-olefin/vinylidene aromatic
interpolymers can also be prepared by the methods described by John
G. Bradfute et al. (W. R. Grace & Co.) in WO 95/32095; by R. B.
Pannell (Exxon Chemical Patents, Inc.) in WO 94/00500; and in
Plastics Technology, p. 25 (September 1992), all of which are
incorporated by reference in their entirety.
[0049] The substantially random .alpha.-olefin/vinylidene aromatic
interpolymers can also be prepared by the methods described in JP
07/278230 employing compounds shown by the general formula 3
[0050] where (Cp.sup.1 and Cp.sup.2 are cyclopentadienyl groups,
indenyl groups, fluorenyl groups, or substituents of these,
independently of each other; R.sup.1 and R.sup.2 are hydrogen
atoms, halogen atoms, hydrocarbon groups with carbon numbers of
1-12, alkoxyl groups, or aryloxyl groups, independently of each
other; M is a group IV metal, preferably Zr or Hf, most preferably
Zr; and R.sup.3 is an alkylene group or silanediyl group used to
cross-link Cp.sup.1 and Cp.sup.2).
[0051] Also suitable are the substantially random interpolymers
which possess at least one .alpha.-olefin/vinyl aromatic/vinyl
aromatic/.alpha.-olefin tetrad disclosed in a copending application
by Jasson T. Pafton et al., entitled "New .alpha.-olefin/Vinylidene
Aromatic Monomer and/or Hindered Aliphatic or Cycloaliphatic
Vinylidene Monomer Interpolymers, filed on Sep. 4, 1996,
incorporated herein by reference. These interpolymers contain
additional signals with intensities greater than three times the
peak to peak noise. These signals appear in the chemical shift
range 43.75-44.25 ppm and 38.0-38.5 ppm. Specifically, major peaks
are observed at 44.1, 43.9 and 38.2 ppm. A proton test NMR
experiment indicates that the signals in the chemical shift region
43.75-44.25 ppm are methine carbons and the signals in the region
38.0-38.5 ppm are methylene carbons.
[0052] In order to determine the carbon-13 NMR chemical shifts of
these interpolymers, the following procedures and conditions are
employed. A five to ten weight percent polymer solution is prepared
in a mixture consisting of 50 volume percent
1,1,2,2-tetrachloroethane-d.sub.2 and 50 volume percent 0.10 molar
chromium tris(acetylacetonate) in 1,2,4-trichlorobenzene. NMR
spectra are acquired at 130.degree. C. using an inverse gated
decoupling sequence, a 90.degree. pulse width and a pulse delay of
five seconds or more. The spectra are referenced to the isolated
methylene signal of the polymer assigned at 30.000 ppm.
[0053] It is believed that these new signals are due to sequences
involving two head-to-tail vinyl aromatic monomer preceded and
followed by at least one .alpha.-olefininsertion, for example an
ethylene/styrene/styrene/ethylene tetradwherein the styrene monomer
insertions of said tetrads occur exclusively in a 1,2 (head to
tail) manner. It is understood by one skilled in the art that for
such tetrads involving a vinyl aromatic monomer other than styrene
and an .alpha.-olefin other than ethylene that the ethylene/vinyl
aromatic monomer/vinyl aromatic monomer/ethylene tetrad will give
rise to similar carbon-13 NMR peaks but with slightly different
chemical shifts.
[0054] These interpolymers are prepared by conducting the
polymerization at temperatures of from about -30.degree. C. to
about 250.degree. C. in the presence of such catalysts as those
represented by the formula 4
[0055] wherein: each Cp is independently, each occurrence, a
substituted cyclopentadienyl group .pi.-bound to M; E is C or Si; M
is a group IV metal, preferably Zr or Hf, most preferably Zr; each
R is independently, each occurrence, H, hydrocarbyl,
silahydrocarbyl, or hydrocarbylsilyl, containing up to about 30
preferably from 1 to about 20 more preferably from 1 to about 10
carbon or silicon atoms; each R' is independently, each occurrence,
H, halo, hydrocarbyl, hyrocarbyloxy, silahydrocarbyl,
hydrocarbylsilyl containing up to about 30 preferably from 1 to
about 20 more preferably from 1 to about 10 carbon or silicon atoms
or two R' groups together can be a C.sub.1-10 hydrocarbyl
substituted 1,3-butadiene; m is 1 or 2; and optionally, but
preferably in the presence of an activating cocatalyst.
Particularly, suitable substituted cyclopentadienyl groups include
those illustrated by the formula: 5
[0056] wherein each R is independently, each occurrence, H,
hydrocarbyl, silahydrocarbyl, or hydrocarbylsilyl, containing up to
about 30 preferably from 1 to about 20 more preferably from 1 to
about 10 carbon or silicon atoms or two R groups together form a
divalent derivative of such group. Preferably, R independently each
occurrence is (including where appropriate all isomers) hydrogen,
methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, phenyl or
silyl or (where appropriate) two such R groups are linked together
forming a fused ring system such as indenyl, fluorenyl,
tetrahydroindenyl, tetrahydrofluorenyl, or octahydrofluorenyl.
[0057] Particularly preferred catalysts include, for example,
racemic-(dimethylsilanediyl(2-methyl-4-phenylindenyl))zirconium
dichloride,
racemic-(dimethylsilanediyl(2-methyl-4-phenyl-indenyl))zircon- ium
1,4-diphenyl-1,3-butadiene,
racemic-(dimethylsilanediyl(2-methyl-4-phe- nylindenyl))zirconium
di-C.sub.1-4 alkyl, racemic-(dimethylsilanediyl(2-me-
thyl-4-phenylindenyl))zirconium di-C.sub.1-4 alkoxide, or any
combination thereof.
[0058] Further preparative methods for the substantially random
interpolymer have been described in the literature. Longo and
Grassi (Makromol, Chem., Volume 191, pages 2387 to 2396 [1990]) and
D'Anniello et al. (Journal of Applied Polymer Science, Volume 58,
pages 1701-1706 [1995]) reported the use of a catalytic system
based on methylalumoxane (MAO) and cyclopentadienyltitanium
trichloride (CpTiCl.sub.3) to prepare an ethylene-styrene
copolymer. Xu and Lin (Polymer Preprints, Am.Chem.Soc.,Div.Polym.
Chem.) Volume 35, pages 686,687 [1994]) have reported
copolymerization using a TiCl.sub.4/NdCl.sub.3/Al(iBu).sub.3
catalyst to give random copolymers of styrene and propylene. Lu et
al (Journal of Applied Polymer Science, Volume 53, pages 1453 to
1460 [1994]) have described the copolymerization of ethylene and
styrene using a TiCl.sub.4/NdCl.sub.3/MgCl.sub.2/Al(Et).sub.3
catalyst. The manufacture of .alpha.-olefin/vinyl aromatic monomer
interpolymers such as propylene/styrene and butene/styrene are
described in U.S. Pat. No. 5,244,996, issued to Mitsui
Petrochemical Industries Ltd. All of the above methods disclosed
for preparing the substantially random interpolymer are
incorporated herein by reference.
[0059] The polymerization may be carried out in solution, slurry,
or gas phase polymerization reactions. Further, the polymerization
may be carried out as a batchwise or a continuous polymerization
process. In a continuous process, ethylene, vinylidene aromatic
monomer or hindered aliphatic vinylidene monomer, and solvent and
the optional propylene or alternate third monomer are continuously
supplied to the reaction zone and polymer product continuously
removed therefrom.
[0060] In general, the substantially random interpolymer may be
polymerized at conditions for Ziegler-Natta or Kaminsky-Sinn type
polymerization reactions, that is, reactor pressures ranging from
atmospheric to 3500 atmospheres (350 MPa). The reactor temperature
will typically be from -30.degree. C.-200.degree. C. Preferably,
the reactor temperature will be greater than 80.degree. C.,
typically from 100.degree. C. to 200.degree. C., and preferably
from 100.degree. C. to 150.degree. C., with temperatures at the
higher end of the range, that is, temperatures greater than
100.degree. C. favoring the formation of lower molecular weight
polymers. Polymerizations at temperatures above the
autopolymerization temperature of the respective monomers may
result in the formation of some amounts of homopolymer
polymerization products resulting from free radical
polymerization.
[0061] In the case of a slurry polymerization process, the
substantially random interpolymer may use the catalysts as
described above as supported in an inert support, such as silica.
As a practical limitation, slurry polymerizations take place in
liquid diluents in which the polymer product is substantially
insoluble. Preferably, the diluent for slurry polymerization is one
or more hydrocarbons with less than 5 carbon atoms. If desired,
saturated hydrocarbons such as ethane, propane or butane may be
used in whole or part as the diluent. Likewise the .alpha.-olefin
monomer or a mixture of different .alpha.-olefin monomers may be
used in whole or in part as the diluent. Most preferably the
diluent comprises in at least major part the monomer or monomers to
be polymerized.
[0062] The glass transition temperature of substantially random
interpolymers increases as the mole percent of the vinylidene
aromatic comonomer or hindered aliphatic vinylidene comonomer
increases. This suggests that by controlling the content of the
vinylidene aromatic comonomer or hindered aliphatic vinylidene
comonomer, one can control the tack of the adhesive system. In
particular, substantially random ethylene/styrene interpolymers,
comprising from 1 to less than 5 mole percent styrene will have a
Tg of from approximately -15 to -20.degree. C.; substantially
random ethylene/styrene interpolymers comprising from 5 to less
than 25 mole percent styrene will have a Tg of from approximately
-15 to 0.degree. C.; and substantially random ethyelen/styrene
interpolymers at least 25 mole percent styrene will have a Tg of
approximately 0 to 30.degree. C., with Tg being determined by
differential scanning calorimetry. Accordingly, ultra-low molecular
weight interpolymers of ethylene and at least one vinylidene
aromatic comonomer or hindered aliphatic vinylidene comonomer, may
be used as an optional tackifier component of the adhesive system.
Those skilled in the art will recognize that the incorporation of
termonomers, such as other .alpha.-olefins, will give rise to
different glass transition temperatures than those set forth
above.
[0063] In addition or as an alternative to adjusting the styrene
content of the substantially random interpolymer, when a
composition having a glass transition temperature of at least
-10.degree. C. is desired, particularly when it is desired that the
composition maintain elastomeric properties, it will be preferred
that such composition comprise at least one substantially random
interpolymer and at least one tackifier.
[0064] As used herein, the term "tackifier" means any of several
hydrocarbon based compositions useful to raise the glass transition
temperature of the substantially random polymer by at least
5.degree. C. and/or to impart tack to a hot melt adhesive which
comprises the substantially random interpolymer. ASTM D-1878-61T
defines tack as "the property of a material which enables it to
form a bond of measurable strength immediately on contact with
another surface."
[0065] Tackifying resins are obtained by the polymerization of
petroleum and terpene feedstreams and from the derivatization of
wood, gum, and tall oil rosin. Several classes of tackifiers
include wood rosin, tall oil and tall oil derivatives,
cyclopentadiene derivatives, such as are described in United
Kingdom patent application GB 2,032,439A. Other classes of
tackifiers include aliphatic C.sub.5 resins, polyterpene resins,
hydrogenated resins, mixed aliphatic-aromatic resins, rosin esters,
natural and synthetic terpenes, terpene-phenolics, and hydrogenated
rosin esters.
[0066] Rosin is a sold material that occurs naturally in the oleo
rosin of pine trees and typically is derived from the oleo resinous
exudate of the living tree, from aged stumps and from tall oil
produced as a by-product of kraft paper manufacture. After it is
obtained rosin can be treated by hydrogenation, dehydrogenation,
polymerization, esterification, and other post treatment processes.
Rosin is typically classed as a gum rosin, a wood rosin, or as a
tall oil rosin which indicate its source. The materials can be used
unmodified, in the form of esters of polyhydric alcohols, and can
be polymerized through the inherent unsaturation of the molecules.
These materials are commercially available and can be blended into
the adhesive compositions using standard blending techniques.
Representative examples of such rosin derivatives include
pentaerythritol esters of tall oil, gum rosin, wood rosin, or
mixtures thereof.
[0067] Exemplary aliphatic resins include those available under the
trade designations Escorez.TM., Piccotac.TM., Mercures.TM.,
Wingtack.TM., Hi-Rez.TM., Quintone.TM., Tackirol.TM., etc.
Exemplary polyterpene resins include those available under the
trade designations Nirez.TM., Piccolyte.TM., Wingtack.TM.,
Zonarez.TM., etc. Exemplary hydrogenated resins include those
available under the trade designations Escorez.TM., Arkon.TM.,
Clearon.TM., etc. Exemplary mixed aliphatic-aromatic resins include
those available under the trade designations Escorez.TM.,
Regalite.TM., Hercures.TM., AR.TM., Imprez.TM., Norsolene.TM. M,
Marukarez.TM., Arkonm.TM. M, Quintone.TM., Wingtack.TM., etc. One
particularly preferred class of tackifiers includes the
styrene/.alpha.-methylene stryene tackifiers available from
Hercules. Other tackifiers may be employed, provided they are
compatible with the homogeneous linear or substantially linear
ethylene/.alpha.-olefin interpolymer and the optional
plasticizer.
[0068] A suitable tackifier may be selected on the basis of the
criteria outlined by Hercules in J. Simons, Adhesives Age, "The
HMDA Concept: A New Method for Selection of Resins", November 1996.
This reference discusses the importance of the polarity and
molecular weight of the resin in determining compatibility with the
polymer. For the substantially random interpolymers useful in the
practice of the claimed invention, low molecular weight polar
resins are indicated to be preferred.
[0069] The tackifier(s) will typically be present in the
composition of the invention in an amount of at least 10, typically
at least 20 weight percent. The tackifier(s) will be present in an
amount of no more than 90, preferably no more than 75, and most
preferably no more than 70 weight percent.
[0070] In the case of substantially random interpolymers of at
least one .alpha.-olefin and a monovinylidene aromatic monomer,
preferred tackifiers will have some degree of aromatic character to
promote compatibility, particularly in the case of substantially
random interpolymers having a high content of the monovinylidene
aromatic monomer. As an initial indicator, compatible tackifiers
are those which are also known to be compatible with ethylene/vinyl
acetate having 28 weight percent vinyl acetate. Particularly
suitable classes of tackifiers include Wingtack.TM. 86 and
Hercotac.TM. 1149 Eastman H-130, and styrene/.alpha.-methyl styrene
tackifiers. Another preferred tackifier is Piccotex 75, a pure
monomer hydrocarbon resin having a glass transition temperature of
33.degree. C., available from Hercules.
[0071] It is noted that there is an unexpected benefit associated
with raising the glass transition temperature of a substantially
random interpolymer by addition of a compatible tackifier, in that
when a compatible tackifier is utilized, not only does the glass
transition temperature increase, but the tensile strength increases
without a corresponding decrease in elongation at break, relative
to the unmodified substantially random interpolymer. Although this
effect holds true for substantially random interpolymers having
both a higher and lower comonomer content, the effect is most
pronounced for substantially random interpolymers having from 45-65
weight percent of the monovinylidene aromatic or hindered aliphatic
comonomer, which are the most elastomeric of the substantially
random interpolymers. This is contrary to what is expected, for
typically, when a low molecular weight brittle solid is added to an
elastomeric solid, the low molecular weight material dilutes the
polymer network which leads to tensile strength and elongation at
break which are less than those of the polymer alone.
[0072] Improved tensile strength has value in a number of
applications, such as adhesives, elastomeric film applications,
automotive parts, wire and cable jacketing, durable goods (such as
appliances), gaskets, and shoe soles.
[0073] For instance, in the case of adhesive formulations, it has
been found that when the glass transition temperature of the
substantially random interpolymer is less than -20.degree. C., the
composition exhibits poor peel strength and tack. However, by
raising the glass transition temperature to 0.degree. C. by
addition of a tackifier increases the peel strength of the
formulation.
[0074] In the case of improved resistance to blocking, it is
desirable to avoid bonding together or blocking of polymer pellets
during transportation and storage. Thus, utilizing the compositions
of the invention which comprise a substantially random interpolymer
and a tackifier, such that the glass transition temperature is
above the temperature during transportation and storage, will
increase the stiffness of the polymer pellets, and will lead to a
resistance to deformation during transportation and storage. In
another embodiment, pellets of a substantially random interpolymer
may be coated with a tackifier to create a surface composition
which comprises the substantially random interpolymer and tackifier
which minimizes blocking.
[0075] The compositions of the invention which comprise a tackifier
will find further utility in sound attenuation applications. For
instance, to attenuate sound, a material must be able to dissipate
high levels of energy over the broad frequency range of normal
sound under ambient conditions. This occurs when the glass
transition temperature is from about -20 to about 10.degree. C.
Compositions of the invention which exhibit a glass transition
temperature in this range, will attenuate sound in a variety of
structures, such as automobiles.
[0076] Processing aids, which are also referred to herein as
plasticizers, are optionally provided to reduce the viscosity of a
composition, such as an adhesive, and include the phthalates, such
as dioctyl phthalate and diisobutyl phthalate, natural oils such as
lanolin, and paraffin, naphthenic and aromatic oils obtained from
petroleum refining, and liquid resins from rosin or petroleum
feedstocks.
[0077] Exemplary classes of oils useful as processing aids include
white mineral oil (such as Kaydol.TM. oil (available from Witco),
and Shellflex.TM. 371 naphthenic oil (available from Shell Oil
Company). Another suitable oil is Tuflo.multidot. oil (available
from Lyondell).
[0078] When a processing aid is employed, it will be present in the
composition of the invention in an amount of at least 5 percent.
The processing aid will typically be present in an amount of no
more than 60, preferably no more than 30, and most preferably no
more than 20 weight percent.
[0079] The composition comprising the substantially random
interpolymer of ethylene and at least one vinylidene aromatic
monomer or hindered aliphatic vinylidene monomer, and optional
C.sub.3-C.sub.20 .alpha.-olefin, may be optionally modified by the
inclusion of an extending or modifying composition. Exemplary
extending or modifying compositions include paraffinic wax,
crystalline polyethylene wax, and/or a homogeneous linear or
substantially linear ethylene/.alpha.-olefin interpolymer.
[0080] Likewise, the composition of the invention may further
comprise a homogeneous linear or substantially linear
ethylene/.alpha.-olefin interpolymer as an extending or modifying
composition. Modification of the composition with a homogeneous
linear or substantially linear ethylene/.alpha.-olefin
interpolymer, particularly when such interpolymer is an elastomer,
will tend to extend the composition when the composition comprises
a substantially random interpolymer which has a high styrene
content, and to improve the tack and modulus of the adhesive when
the adhesive comprises a substantially random interpolymer which
has a low styrene content.
[0081] The homogeneous linear or substantially linear
ethylene/.alpha.-olefin interpolymer is an ethylene polymer
prepared using a single site, single site metallocene, or single
site constrained geometry catalyst. By the term homogenous, it is
meant that any comonomer is randomly distributed within a given
interpolymer molecule and substantially all of the interpolymer
molecules have the same ethylene/comonomer ratio within that
interpolymer. The DSC melting peak of homogeneous linear and
substantially linear ethylene polymers will broaden as the density
decreases and/or as the number average molecular weight decreases.
However, unlike heterogeneous polymers, when a homogeneous polymer
has a melting peak greater than 115.degree. C. (such as is the case
of polymers having a density greater than 0.940 g/cm.sup.3), such
polymers typically do not additionally have a distinct lower
temperature melting peak.
[0082] Homogeneous linear and substantially linear interpolymers
useful in the invention further differ from low density
polyethylene prepared in a high pressure process. In one regard,
whereas low density polyethylene is an ethylene homopolymer having
a density of from 0.900 to 0.935 g/cm.sup.3, the homogeneous linear
and substantially linear interpolymers useful in the invention
require the presence of a comonomer to reduce the density to the
range of from 0.900 to 0.935 g/cm.sup.3.
[0083] The homogeneous linear and substantially linear
interpolymers useful in the invention are typically characterized
as having a narrow molecular weight distribution (M.sub.w/M.sub.n).
For the linear and substantially linear interpolymers, the
M.sub.w/M.sub.n is typically from 1.5 to 2.5, preferably from 1.8
to 2.2.
[0084] In addition or in the alternative, the homogeneity of the
polymer may be described by the SCBDI (Short Chain Branching
Distribution Index) or CDBI (Composition Distribution Breadth
Index), which are defined as the weight percent of the polymer
molecules having a conomomer content within 50 percent of the
median total molar comonomer content. The SCBDI of a polymer is
readily calculated from data obtained from techniques known in the
art, such as, for example, temperature rising elution fractionation
(abbreviated herein as "TREF"), which is described, for example, in
Wild et al., Journal of Polymer Science, Poly. Phys. Ed., Vol. 20,
p. 441 (1982), in U.S. Pat. No. 4,798,081 (Hazlitt et al.), or in
U.S. Pat. No. 5,089,321 (Chum et al.), the disclosures of all of
which are incorporated herein by reference. The SCBDI or CDBI for
the homogeneous linear and substantially linear interpolymers
useful in the invention is preferably greater than 50 percent, more
preferably greater than 70 percent, with SCBDI's and CDBI of
greater than 90 percent being easily attained.
[0085] Substantially linear ethylene interpolymers are homogeneous
interpolymers having long chain branching. Due to the presence of
such long chain branching, substantially linear ethylene
interpolymers are further characterized as having a melt flow ratio
(I.sub.10/I.sub.2) which may be varied independently of the
polydispersity index, also referred to as the molecular weight
distribution M.sub.w/M.sub.n. This feature accords substantially
linear ethylene polymers with a high degree of processability
despite a narrow molecular weight distribution. When a
substantially linear ethylene interpolymer is employed in the
practice of the invention, such interpolymer will be characterized
as having an interpolymer backbone substituted with from 0.1 to 3
long chain branches per 1000 carbons.
[0086] Methods for determining the amount of long chain branching
present, both qualitatively and quantitatively, are known in the
art. For qualitative methods for determining the presence of long
chain branching, see, for example, U.S. Pat. Nos. 5,272,236 and
5,278,272, the disclosures of both of which are incorporated herein
by reference. As set forth therein, a gas extrusion rheometer (GER)
may be used to determine the rheological processing index (PI), the
critical shear rate at the onset of surface melt fracture, and the
critical shear stress at the onset of gross melt fracture, which in
turn indicate the presence or absence of long chain branching as
set forth below.
[0087] For quantitative methods for determining the presence of
long chain branching, see, for example, U.S. Pat. Nos. 5,272,236
and 5,278,272; Randall (Rev. Macromol. Chem. Phys., C29 (2&3),
p. 285-297), which discusses the measurement of long chain
branching using 13C nuclear magnetic resonance spectroscopy, Zimm,
G. H. and Stockmayer, W. H., J. Chem. Phys., 17, 1301 (1949); and
Rudin, A., Modern Methods of Polymer Characterization, John Wiley
& Sons, New York (1991) pp. 103-112, which discuss the use of
gel permeation chromatography coupled with a low angle laser light
scattering detector (GPC-LALLS) and gel permeation chromatography
coupled with a differential viscometer detector (GPC-DV). Each of
these references is incorporated herein by reference. Further, A.
Willem deGroot and P. Steve Chum, both of The Dow Chemical Company,
at the Oct. 4, 1994 conference of the Federation of Analytical
Chemistry and Sepctroscopy Society (FACSS) in St. Louis, Mo.,
presented data demonstrating that GPC-DV is a useful technique for
quantifying the presence of long chain branches in substantially
linear ethylene polymers. In particular, deGroot and Chum found
that the presence of long chain branches in substantially linear
ethylene polymers correlated well with the level of long chain
branches measured using .sup.13C NMR.
[0088] The homogeneous linear or substantially linear extending
polmer will be an interpolymer of ethylene with at least one
C.sub.3-C.sub.20 .alpha.-olefin. Exemplary C.sub.3-C.sub.20
.alpha.-olefins include propylene, isobutylene, 1-butene, 1-hexene,
4-methyl-1-pentene, 1-heptene, and 1-octene. Preferred
C.sub.3-C.sub.20 .alpha.-olefins include 1-butene, 1-hexene,
4-methyl-1-pentene, 1-heptene, and 1-octene, more preferably
1-hexene and 1-octene.
[0089] The homogeneous linear or substantially linear extending
polymer may further be an interpolymer of ethylene, the at least
one C.sub.3-C.sub.20 .alpha.-olefin, and a non-conjugated diene
having from 6 to 15 carbon atoms. Representative examples of
suitable non-conjugated dienes include:
[0090] (a) Straight chain acyclic dienes such as 1,4-hexadiene;
1,5-heptadiene; and 1,6-octadiene;
[0091] (b) Branched chain acyclic dienes such as
5-methyl-1,4-hexadiene; 3,7-dimethyl-1,6-octadiene; and
3,7-dimethyl-1,7-octadiene;
[0092] (c) Single ring alicyclic dienes such as 4-vinylcyclohexene;
1-allyl-4-isopropylidene cyclohexane; 3-allylcyclopentene;
4-allylcyclohexene; and 1-isopropenyl-4-butenylcyclohexene;
[0093] (d) Multi-ring alicyclic fused and bridged ring dienes such
as dicyclopentadiene; alkenyl, alkylidene, cycloalkenyl, and
cycloalkylidene norbornenes, such as 5-methylene-2-norbornene;
5-methylene-6-methyl-2-nor- bornene;
5-methylene-6,6-dimethyl-2-norbornene; 5-propenyl-2-norbornene;
5-(3-cyclopentenyl)-2-norbornene; 5-ethylidene-2-norbornene;
5-cyclohexylidene-2-norbornene; etc.
[0094] The preferred non-conjugated dienes are selected from the
group consisting of 1,4-hexadiene; dicyclopentadiene;
5-ethylidene-2-norbornene- ; 5-methylene-2-norbornene; 7-methyl-1,6
octadiene; piperylene; and 4-vinylcyclohexene. One suitable
conjugated diene is piperylene.
[0095] The ethylene/.alpha.-olefin interpolymer will have a density
of from 0.850 to 0.965 g/cm.sup.3, preferably from 0.850 to 0.900
g/cm.sup.3, and most preferably from 0.870 to 0.890 g/cm.sup.3.
[0096] The ethylene/.alpha.-olefin interpolymer may be of high or
low molecular weight. Suitable number average molecular weights
range from 3,000 to over 100,000, preferably from 3,000 to 60,000.
In certain applications, the use of ethylene/.alpha.-olefin
interpolymers having a number average molecular weight less than
20,000, preferably less than 12,000, will be preferred.
[0097] Homogeneously branched linear ethylene/.alpha.-olefin
interpolymers may be prepared using polymerization processes (such,
as described by Elston in U.S. Pat. No. 3,645,992) which provide a
homogeneous short chain branching distribution. In his
polymerization process, Elston uses soluble vanadium catalyst
systems to make such polymers. However, others such as Mitsui
Petrochemical Company and Exxon Chemical Company have used
so-called single site catalyst systems to make polymers having a
homogeneous linear structure. Homogeneous linear
ethylene/.alpha.-olefin interpolymers are currently available from
Mitsui Petrochemical Company under the tradename "Tafmer" and from
Exxon Chemical Company under the tradename "Exact".
[0098] Substantially linear ethylene/.alpha.-olefin interpolymers
are available from The Dow Chemical Company as Affinity.TM.
polyolefin plastomers. Substantially linear ethylene/.alpha.-olefin
interpolymers may be prepared in accordance with the techniques
described in U.S. Pat. No. 5,272,236 and in U.S. Pat. No.
5,278,272, each of which is incorporated herein by reference.
[0099] In another embodiment, ultra-low molecular weight ethylene
polymers may be employed as an extending or modifying composition.
Ultra-low molecular weight ethylene polymers are disclosed and
claimed in the patent application entitled Ultra-Low Molecular
Weight Polymers, filed provisionally on Jan. 22, 1996 in the names
of M. L. Finlayson, C. C. Garrison, R. E. Guerra, M. J. Guest, B.
W. S. Kolthammer, D. R. Parikh, and S. M. Ueligger, which is
incorporated herein by reference.
[0100] Ultra-low molecular weight polymers employed will be either
ethylene homopolymers or interpolymers of ethylene and a comonomer
selected from the group consisting of C.sub.3-C.sub.20
.alpha.-olefins, styrene, alkyl-substituted styrene,
tetrafluoroethylene, vinylbenzocyclobutane, non-conjugated dienes,
and cycloalkenes.
[0101] The ultra-low molecular weight polymer will have a number
average molecular weight less than 8200, preferably less than 6000,
and more preferably less than 5000. Such ultra-low molecular weight
polymer will typically have a number average molecular weight of at
least 800, preferably at least 1300.
[0102] Ultra-low molecular weight polymers, in contrast to
paraffinic waxes and crystalline ethylene homopolymer or
interpolymer waxes, will have a M.sub.w/M.sub.n of from 1.5 to 2.5,
preferably from 1.8 to 2.2.
[0103] Ultra-low molecular weight ethylene polymers lead to a low
polymer and formulation viscosity, but are characterized by peak
crystallization temperatures which are greater than the peak
crystallization temperatures of corresponding higher molecular
weight materials of the same density. In adhesive applications, the
increase in peak crystallization temperature translates to an
increased heat resistance, for instance, an improved creep
resistance in pressure sensitive adhesives, and improved shear
adhesion failure temperature (SAFT) in hot melt adhesives.
[0104] When the ultra-low molecular weight ethylene polymer is an
interpolymer of ethylene and at least one vinylidene aromatic
comonomer or hindered aliphatic vinylidene comonomer, it may be
employed as a tackifier (as described above). Further, as the mole
percent of ethylene increases, the crystallinity of the
interpolymer will likewise increase. Accordingly, ultra-low
molecular weight interpolymers of ethylene and less than 10 mole
percent of the least one vinylidene aromatic comonomer or hindered
aliphatic vinylidene comonomer, which interpolymers, such
interpolymers may be useful as waxes to control the open and close
time of the adhesive system.
[0105] In another embodiment, a traditional wax may be used as an
extending or modifying composition. Modification of the adhesive
with a paraffinic wax or a crystalline polyethylene wax, will tend
to improve the high temperature performance, such as creep
resistance and SAFT, and reduce the open and close times of
adhesives comprising substantially random interpolymers which have
a high styrene content.
[0106] Exemplary traditional waxes include ethylene homopolymers
available from Petrolite, Inc. (Tulsa, Okla.) as Polywax.TM. 500,
Polywax.TM. 1500, Polywax.TM. 1000, and Polywax.TM. 2000; and
paraffinic waxes available from CP Hall under the product
designations 1230, 1236, 1240, 1245, 1246, 1255, 1260, and
1262.
[0107] Polywax.TM. 2000 has a molecular weight of approximately
2000, an M.sub.w/M.sub.n of approximately 1.0, a density at
16.degree. C. of about 0.97 g/cm.sup.3, and a melting point of
approximately 126.degree. C.
[0108] CP Hall 1246 paraffinic wax is available from CP Hall (Stow,
Ohio). CP Hall 1246 paraffinic wax has a melting point of
143.degree. F. (62.degree. C.), a viscosity at 210.degree. F.
(99.degree. C.) of 4.2 centipoise, and a specific gravity at
73.degree. F. (23.degree. C.) of 0.915.
[0109] Traditional waxes useful in the adhesives of the invention
will typically have a density of at least 0.910 g/cm.sup.3. Such
waxes will have a density of no more than 0.970 g/cm.sup.3,
preferably no more than 0.965 g/cm.sup.3.
[0110] Additives such as antioxidants (such as hindered phenols,
for example, Irganox.RTM. 1010, Irganox.RTM. B900, and Irganox.RTM.
1076), phosphites (such as Irgafos.RTM. 168)), ultraviolet
stabilizers, cling additives (such as polyisobutylene), antiblock
additives, colorants, pigments, and fillers can also be included in
the compositions of the present invention, to the extent that they
do not interfere with the enhanced properties discovered by
Applicants.
[0111] The additives are employed in functionally equivalent
amounts known to those skilled in the art. For example, the amount
of antioxidant employed is that amount which prevents the polymer
or composition from undergoing oxidation at the temperatures and
environment employed during manufacture, storage and ultimate use
of the polymers. Such amounts of antioxidants is usually in the
range of from 0.05 to 10, preferably from 0.1 to 5, more preferably
from 0.1 to 2 percent by weight based upon the weight of the
composition. When employed, the antioxidant is most typically
present in an amount less than 0.5 weight percent, based on the
total weight of the composition.
[0112] Similarly, the amounts of any of the other enumerated
additives are the functionally equivalent amounts such as the
amount to render the polymer or polymer blend antiblocking, to
produce the desired amount of filler loading to produce the desired
result, to provide the desired color from the colorant or pigment.
Such additives can typically be employed in the range of from about
0.05 to about 50, preferably from about 0.1 to about 35, more
preferably from about 0.2 to about 20 percent by weight based upon
the weight of the substantially random interpolymer, although
filler may be employed in amount up to 90 weight percent, based on
the weight of the substantially random interpolymer.
[0113] The compositions of the invention may be prepared by
standard melt blending procedures. In particular, the substantially
random interpolymer(s), tackifier(s), and optional processing
aid(s) may be melt blended at a temperature suitable to achieve the
formation of a homogeneous melt blend, typically at temperatures of
from 100-200.degree. C., and under an inert gas blanket until a
homogeneous mix is obtained. Any mixing method producing a
homogeneous blend without degrading the hot melt components is
satisfactory, such as through the use of a heated vessel equipped
with a stirrer.
[0114] Further, the substantially random interpolymer(s),
tackifier(s) and optional extending or modifying composition(s) may
be provided to an extrusion coater for application to the
substrate. The compositions may further be prepared in a
multi-reactor process, for example producing the substantially
random interpolymer in one reactor and further polymer component
(such as an ultra-low molecular weight polymer or wax) in a second
reactor, with other components optionally being introduced into the
second reactor or at a point downstream of the second reactor, such
as via a sidearm extruder.
[0115] In one preferred embodiment, the composition of the
invention will be provided in the form of an adhesive which
comprises at least one substantially random interpolymer.
Typically, the adhesive will comprise from 5 to 75 weight percent
of at least one tackifier, more preferably from 10 to 70 weight
percent of at least one tackifier. As set forth above, the
tackifier will preferably have an aromatic character. In some
instances, the tackifier will be an ultra-low molecular weight
interpolymer of ethylene and at least one vinylidene aromatic
comonomer or hindered aliphatic vinylidene comonomer, which
interpolymer comprises at least 25 mole percent of the at least one
vinylidene aromatic comonomer or hindered aliphatic vinylidene
comonomer.
[0116] The adhesive of the invention may further comprise at least
one modifying composition, as described above. When such a
modifying composition is employed, it will typically be present in
the adhesive system in an amount of from 5 to 75 weight percent.
One such modifying composition is a traditional wax or an ultra-low
molecular weight ethylene polymer. In some instances, the ultra-low
molecular weight ethylene polymer will be an interpolymer of
ethylene and at least one vinylidene aromatic comonomer or hindered
aliphatic vinylidene comonomer, which interpolymer comprises less
than 10 mole percent of the at least one vinylidene aromatic
comonomer or hindered aliphatic vinylidene comonomer.
[0117] Moreover, the adhesive of the invention may comprise a
plurality of substantially random interpolymer components which
differ in the amount of vinylidene aromatic monomer or hindered
aliphatic vinylidene monomer content, which differ in molecular
weight, or which differ in both the amount of vinylidene aromatic
monomer or hindered aliphatic vinylidene monomer content and in
molecular weight.
[0118] It will be clear that an adhesive containing a very high
content of the substantially random interpolymer may be designed.
For instance, one such adhesive may comprise as the strength
imparting component of the adhesive, from 5 to 75 weight percent of
a substantially random interpolymer of ethylene and at least one
vinylidene aromatic comonomer or hindered aliphatic vinylidene
comonomer, which interpolymer has an Mn of greater than about
10,000 and comprises from 10 to less than 25 mole percent of the at
least one vinylidene aromatic comonomer or hindered aliphatic
vinylidene comonomer; as a wax, from 5 to 75 weight percent of a
substantially random interpolymer of ethylene and at least one
vinylidene aromatic comonomer or hindered aliphatic vinylidene
comonomer, which interpolymer has an Mn of less than about 8,200
and comprises from 1 to less than 10 mole percent of the at least
one vinylidene aromatic comonomer or hindered aliphatic vinylidene
comonomer; and as a tackifier, from 5 to 75 weight percent of a
substantially random interpolymer of ethylene and at least one
vinylidene aromatic comonomer or hindered aliphatic vinylidene
comonomer, which interpolymer has an Mn of less than about 8,200
and comprises at least 25 mole percent of the at least one
vinylidene aromatic comonomer or hindered aliphatic vinylidene
comonomer.
[0119] As set forth in J. Class and S. Chu, Handbook of Pressure
Sensitive Adhesive Technology, Second Edition, D. Satas, e., 1989,
pp 158-204, incorporated herein by reference, the requirements for
pressure sensitive adhesive behavior may be defined by temperature
and rate dependent viscoelastic properties of the materials and
formulations.
[0120] Broadly speaking, to be a suitable pressure sensitive, the
formulations must have a glass transition temperature of from -20
to 25.degree. C., preferably from -10 to 10.degree. C., as
reflected by the tan .delta. peak temperature at 1 radian per
second, as determined by dynamic mechanical spectroscopy. Broad
glass transition peaks are favored, in that when the peak is broad,
the adhesive will perform over a wider temperature range, thereby
increasing its utility. Further, adhesives having a broad glass
transition peak typically be characterized as having increased tack
and peel strength.
[0121] According to what has come to be known as the Dahlquist
criteria, broadly speaking, to be a suitable pressure sensitive,
the formulation must have a plateau shear modulus at 25.degree. C.
at 1 radian per second which is between 1.times.10.sup.5 and
6.times.10.sup.6 dynes/cm.sup.2, preferably from 1.times.10.sup.5
and 3.times.10.sup.5 dynes/cm.sup.2, as determined by dynamic
mechanical spectroscopy. A material stiffer than this, that is, a
material which has a plateau shear modulus at 25.degree. C. of
1.times.10.sup.7 dynes/cm.sup.2, will not exhibit surface tack at
room temperature. A material less stiff than this, that is, a
material which has a plateau shear modulus at 25.degree. C. of
1.times.10.sup.4 dynes/cm.sup.2, will lack sufficient cohesive
strength to be useful.
[0122] In particular, preferred pressure sensitive adhesives for
use in low peel labels will have a G' of from 3.times.10.sup.5 to
1.times.10.sup.6 dynes/cm.sup.2 (0.3 to 1 MPa) and a glass
transition temperature of from -50 to -30.degree. C. Preferred
pressure sensitive adhesives for use in freezer labels will have a
G' of from 8.times.10.sup.4 to 2.times.10.sup.5 dynes/cm.sup.2
(0.08 to 0.2 MPa) and a glass transition temperature of from -45 to
-30.degree. C. Preferred pressure sensitive adhesives for use in
cold temperature labels will have a G' of from 2.times.10.sup.5 to
1.times.10.sup.6 dynes/cm.sup.2 (0.2 to 1 MPa) and a glass
transition temperature of from -25 to -10.degree. C. Preferred
pressure sensitive adhesives for use in pressure sensitive adhesive
tapes will have a G' of from 7.times.10.sup.5 to 5.times.10.sup.6
dynes/cm.sup.2 (0.7 to 5 MPa) and a glass transition temperature of
from -10 to 10.degree. C. Preferred pressure sensitive adhesives
for use in high peel labels will have a G' of from 2.times.10.sup.5
to 6.times.10.sup.5 dynes/cm.sup.2 (0.2 to 0.6 MPa) and a glass
transition temperature of from 0 to 10.degree. C. Preferred
pressure sensitive adhesives for use in disposables will have a G'
of from 4.times.10.sup.5 to 2.times.10.sup.6 dynes/cm.sup.2 (0.4 to
2 MPa) and a glass transition temperature of from 10 to 30.degree.
C.
[0123] Glass transition temperature is a function of tackifier
content, the presence and amount of processing aid, and the styrene
content and molecular weight of the substantially random
interpolymer. Accordingly, to raise the glass transition
temperature of the composition of the invention, one may increase
the amount of or glass transition temperature of the tackifier,
decrease the amount of processing aid, or increase the amount of
vinylidene aromatic monomer or hindered aliphatic vinylidene
monomer in the substantially random interpolymer. The plateau shear
modulus is a function of the presence and amount of processing aid
and the styrene content and molecular weight of the substantially
random interpolymer. To decrease the G', one may increase the
amount of processing aid in the composition or increase the amount
of vinylidene aromatic monomer or hindered aliphatic vinylidene
monomer in the substantially random interpolymer.
[0124] The compositions of the invention will have utility in
applications in which adhesives, particularly hot melt adhesives
are typically employed. Some representative examples include
packaging, box and carton sealing, bookbinding, lamination of
veneers to a substrate, tapes, and labels. The compositions may
further be utilized in multilayer food packaging structures wherein
at least one layer of the structure is aluminum. The compositions
may be readily extruded onto a variety of substrates, including but
not limited to carpet backing, flooring tiles and sheets, and woven
and nonwoven fabric. The compositions may similarly be molded into
a variety of shapes, including but not limited to shoe soles,
seals, toys, durable goods, wire and cable, and gaskets.
[0125] The following Examples are provided to illustrate particular
embodiments of the claimed invention, rather than to limit the
scope of the invention thereto.
EXAMPLE ONE
[0126] Preparation of Adhesives Based on Substantially Random
Interpolymers of Ethylene and a Monovinylidene Aromatic
Comonomer
[0127] Polymerization of Substantially Random Interpolymers of
Ethylene and a Monovinylidene Aromatic Comonomer
[0128] Polymer A was prepared in a one gallon (3.8 L) agitated
semi-continuous batch reactor. The reaction mixture consisted of
approximately 1100 grams cyclohexane and 818 grams styrene. Prior
to addition to the reactor, solvent, styrene and ethylene were
purified to remove water and oxygen. The inhibitor in the styrene
was also removed. Temperature in the vessel was controlled to a
set-point of 60.degree. C. by varying the coolant flow in the
cooling coils of the reactor. The vessel was then pressure
controlled to a set point of 100 psig (4.8 kPa) with ethylene.
Hydrogen was added in a controlled fashion to control molecular
weight. The catalyst components, which comprise a
monocyclopentadienyl titanium-containing catalyst, such as
titanium:
(N-1,1-dimethylethyl)dimethyl(1-(1,2,3,4,5-eta)-2,3,4,5-tetramethyl-2,4-c-
yclopentadien-1-yl)silanaminato))(2-)N)-dimethyl, CAS# 135072-62-7,
Tris(pentafluorophenyl)boron, CAS# 001109-15-5, modified
methylaluminoxane Type 3A, CAS# 146905-79-5, were flow controlled,
on a mole ratio basis of 1/1.5/20 respectively, and were combined
and added to the vessel. After starting, the polymerization was
allowed to proceed with ethylene supplied to the reactor as
required to maintain vessel pressure. In this case, approximately
50 grams of ethylene were loaded in the reactor, ethylene flowed
into the reactor at a maximum rate of 5.6 grams/minute, and the
total amount of ethylene added was 87 grams. The run continued for
30 minutes. At the end of the run, the catalyst flow was stopped,
ethylene was removed from the reactor, about 1000 ppm of
Irganox.TM. 1010 antioxidant on a polymer basis was then added to
the solution and the polymer was isolated from the solution. The
resulting polymers may be isolated from solution by either
stripping by use of a devolatilizing extruder.
[0129] Preparation of Adhesive Formulations
[0130] The indicated substantially random interpolymer, tackifier,
plasticizer, styrene block copolymer, and antioxidant were
simultaneously added in the indicated amounts to a Haake Rheocord
40 mixer using a 200 gram mixing bowl maintained at about
130.degree. C. at 95 revolutions per minute. The ingredients were
mixed for about 5 minutes, until they became molten.
[0131] Escorez.TM. 5300 petroleum hydrocarbon resin is a tackifier
available from Exxon Chemical Company (Houston, Tex.).
[0132] Irganox.TM. B900 hindered phenolic antioxidant is available
from Ciba-Geigy.
[0133] Primoil 355 is a mineral oil.
[0134] Example 1 was tested for initial viscosity and viscosity
after three days, using a Brookfield viscometer at 350.degree. F.
(177.degree. C.), probe tack, modulus (G'), and peak tan delta. The
formulations and the measured properties are set forth in Table
One. Note that in the case of modulus and peak tan delta, the
reported values were extracted from a computer-generated plot of
the results.
1 TABLE ONE Example 1 Polymer A 100/45.2 Escorez .TM. 5300
Tackifier 100/45.2 Primoil 355 20/9.0 Irganox .TM. B900 Antioxidant
1/0.5 Probe tack 94 G' at 0.degree. C. (dynes/cm.sup.2 (MPa)) 1.58
.times. 10.sup.8 (158) G' at 25.degree. C. (dynes/cm.sup.2 (MPa))
7.94 .times. 10.sup.5 (0.794) G' at 50.degree. C. (dynes/cm.sup.2
(MPa)) 1.58 .times. 10.sup.5 (0.158) G' at 75.degree. C.
(dynes/cm.sup.2 (MPa)) 2.51 .times. 10.sup.4 (0.0251) Temp. at
which G' = 10.sup.4 dynes/cm.sup.2 89 (10 kPa) (.degree. C.) Temp.
at which G' = 10.sup.5 dynes/cm.sup.2 57 (100 kPa)(.degree. C.)
Peak tan delta (.degree. C.) 4
[0135] As illustrated in Table One, the adhesive of Example 1 meets
the Dahlquist criteria, indicating its suitability as a traditional
pressure sensitive adhesive. The adhesive of Example 1 is further
preferred in that it has a glass transition temperature in the
range of -45 to 30.degree. C. The data regarding Example 1, taken
in conjunction with the Dahlquist criteria, suggest that the
adhesive of Example 1 may be suitably employed as a high peel label
and/or as a pressure sensitive adhesive tape.
EXAMPLES 2-8
[0136] and
Comparative Examples A and B
[0137] Hot Melt Adhesives for Bonding Aluminum
[0138] Preparation of Ethylene Styrene Interpolymers B and C
[0139] Polymer is prepared in a 400 gallon (1500 L) agitated
semi-continuous batch reactor, utilizing the process conditions set
forth in the following Table Two. The reaction mixture consisted of
approximately 250 gallons (950 L) of a solvent comprising a mixture
of cyclohexane (85 weight percent) and isopentane (15 weight
percent), and styrene. Prior to addition, solvent, styrene and
ethylene are purified to remove water and oxygen. The inhibitor in
the styrene is also removed. Inerts are removed by purging the
vessel with ethylene. The vessel is then pressure controlled to a
set point with ethylene. Hydrogen is added to control molecular
weight. Temperature in the vessel is controlled to set-point by
varying the jacket water temperature on the vessel. Prior to
polymerization, the vessel is heated to the desired run temperature
and the catalyst components: Titanium:
(N-1,1-dimethylethyl)dimethyl(1-(1,2,3-
,4,5-eta)-2,3,4,5-tetramethyl-2,4-cyclopentadien-1-yl)silanaminato))(2-)N)-
-dimethyl, CAS# 135072-62-7, Tris(pentafluorophenyl)boron, CAS#
001109-15-5, Modified methylaluminoxane Type 3A, CAS# 146905-79-5,
are flow controlled, on a mole ratio basis of 1/3/5 respectively,
combined and added to the vessel. After starting, the
polymerization is allowed to proceed with ethylene supplied to the
reactor as required to maintain vessel pressure. In some cases,
hydrogen is added to the headspace of the reactor to maintain a
mole ratio with respect to the ethylene concentration. At the end
of the run, the catalyst flow is stopped, ethylene is removed from
the reactor, about 1000 ppm of Irganox* 1010 antioxidant is then
added to the solution and the polymer is isolated from the
solution. The resulting polymers are isolated from solution by
either stripping by use of a devolatilizing extruder.
2TABLE TWO Polymer Total in Solvent Styrene H.sub.2 Run Solution
Total Weight Talc Level Sample loaded loaded Pressure Temp. Added
Time Weight Melt Index Percent Styrene (Weight Isolation Number lbs
kg lbs kg Psig kPa .degree. C. Grams Hrs. Percent (I.sub.2 at
190.degree. C.) in Polymer* Percent) Method (B) 839 381 661 300 105
724 60 53.1 4.8 11.6 2.6 45.5 0 Extruder (C) 1196 542 225 102 70
483 60 7.5 6.1 7.2 0.03 29.8 0 Extruder *Total weight percent
styrene measured via Fourier Transform Infrared (FTIR)
technique
[0140] The interpolymer and vinyl aromatic polymer characteristics
are given in Table Three. The unblended polymers provide the
comparative examples of this invention.
[0141] Test parts and characterization data for the interpolymers
were generated according to the following procedures:
[0142] Plaques are compression molded as follows. Samples are
melted at 190.degree. C. for 3 minutes and compression molded at
190.degree. C. under 20,000 lb of pressure for another 2 minutes.
Subsequently, the molten materials are quenched in a press
equilibrated at room temperature.
[0143] Differential scanning calorimetry (DSC) determinations are
made as follows. A DuPont DSC-2920 is used to measure the thermal
transition temperatures and heat of transition for the
interpolymers. In order to eliminate previous thermal history,
samples are first heated to 200.degree. C. Heating and cooling
curves are recorded at 10.degree. C./min. Melting (from second
heat) and crystallization temperatures are recorded from the peak
temperatures of the endotherm and exotherm, respectively.
[0144] Melt shear rheology determinations are made as follows.
Oscillatory shear rheology measurements are performed with a
Rheometrics RMS-800 rheometer Rheological properties are monitored
at an isothermal set temperature of 190.degree. C. in a frequency
sweep mode. In tabulated data, .eta. is the viscosity and
.eta.(100/0.1) is the viscosity ratio of values recorded at 100/0.1
rad/sec frequencies.
[0145] Shore A hardness is measured at 23.degree. C. following
ASTM-D240.
[0146] Flexural modulus is evaluated according to ASTM-D790.
[0147] Tensile properties of the compression molded samples are
measured using an Instron 1145 tensile machine equipped with an
extensiometer. ASTM-D638 samples are tested at a strain rate of 5
min.sup.-1. The average of four tensile measurements is given. The
yield stress and yield strain are recorded at the inflection point
in the stress/strain curve. The Energy at break is the area under
the stress/strain curve.
[0148] Tensile stress relaxation is determined as follows. Uniaxial
tensile stress relaxation is evaluated using an Instron 1145
tensile machine. Compression molded film (approximately 20 mil,
0.0508 cm., thick) with a 1" (2.54 cm) gauge length is deformed to
a strain level of 50 percent at a strain rate of 20 min.sup.-1. The
force required to maintain 50 percent elongation is monitored for
10 minutes. The magnitude of the stress relaxation is defined as
(f.sub.i-f.sub.f/f.sub.i) where f.sub.i is the initial force and
f.sub.f is the final force.
[0149] Thermomechanical analysis (TMA) data are generated using a
Perkin Elmer TMA 7 series instrument. Probe penetration to 1 mm is
measured on 2 mm thick compression molded parts using a heating
rate of 5.degree. C./min and a load of 1 Newton.
3TABLE THREE Interpolymer and vinylidene aromatic polymer blend
components (C) (D) Composition weight percent atactic 10.3 1
Polystyrene in Interpolymer.sup.1 weight percent Styrene.sup.1 43.4
29.3 weight percent Ethylene 56.6 70.7 mole percent Styrene 17.1 10
mole percent Ethylene 82.9 90 Molecular Weight Melt flow rate,
I.sub.2 (g/10 min) 2.62 0.03 M.sub.n .times. 10.sup.-3 66.8 118.1
M.sub.w/M.sub.n 1.89 2.04 Physical Properties Density. g/cc 0.9626
0.943 Tm, .degree. C. 49.6 71.3 Percent Crystallinity 4.8 14.7 Tc,
.degree. C. 22.1 58.1 Tg(DSC) approximately -12 -17.2 Mechanical
Properties Shore A 75 88 Tensile Modulus, MPa 6.5 20 Flexural
Modulus, MPa 68.8 62.1 Yield Stress, MPa 1.3 2.4 Percent Strain at
Break 475.3 377.5 Stress at Break, MPa 22.6 34.3 Energy at Break,
Nm 102.2 145.5 Percent Stress Relaxation (50 38 30.2 percent/10
min) Melt Rheology .eta. .times. 10.sup.-5(0.1 rad/sec), Poise 1.05
16.6 .eta.(100/0.1) 0.15 0.16.sup.2 Tan .delta. (0.1 rad/sec) 4.2
2.37 .sup.1Measured by NMR technique. .sup.2Ratio of
.eta.(1.6)/.eta.(0.1).
[0150] The formulations described in Table Four were prepared in a
60 mL Brabender mixer using roller blades. The bowl was heated to
130.degree. C. prior to polymer introduction. The blade speed was
30 revolutions/minute. After the polymer was fused (approximately 5
minutes) the other ingredients were added in small portions over a
period of 10 to 30 minutes. The rate of addition depended on the
rate at which the mixing incorporated the material into the
mixture. Where there was a large mismatch in the melt viscosity of
the materials being mixed, higher temperatures and longer mixing
times were used. After the addition was complete, mixing was
continued for 10 minutes or until the sample was visually
homogeneous.
[0151] Adhesion samples were prepared from 3.17.times.15 cm strips
of aluminum foil 0.002 cm thick. The surface was wiped with methyl
ethyl ketone prior to bonding to remove any surface contamination.
Samples were prepared in a tetrahedron press with the platens set
at 177.degree. C. The samples were compression molded between
layers of silicone release paper using the following cycle: (1)
equilibrate 30 seconds at 177.degree. C. under contact pressure,
(2) ramp ram pressure to 11.2 kg/cm.sup.2, (3) maintain pressure
for 2 minutes and release. The pressure corresponds to
approximately 1.4 kg/cm.sup.2 on the samples.
[0152] Samples were tested in the T-peel geometry (ASTM-1876) using
an Instron tensile tester. Crosshead speed was 2.5 cm/min. Sample
composition and performance are set forth in Table Four.
4 TABLE FOUR Polymer type and amount Tackifier Wax Peel (weight
(weight (weight strength percent) percent) percent) (g/cm) Example
2 Polymer B-100 98 Example 3 Polymer B-50 Wingtack .TM. 1532 86 -
50 Example 4 Polymer B-50 Hercotac .TM. 672 1149 - 50 Example 5
Polymer B-50 Eastotac .TM. 870 H130 - 50 Example 6 Polymer C-50
Wingtack .TM. 1180 86 - 50 Example 7 Polymer C-50 Wingtack .TM. 127
95 - 50 Example 8 Polymer B-40 Wingtack .TM. Polywax .TM. 329 86 -
40 1000 - 20 Comparative Polymer D-33 Wingtack .TM. Polywax .TM. 77
Example A 95 - 33 1000 - 33 Comparative Polymer E-50 Wingtack .TM.
Polywax .TM. 257 Example B 95 - 50 1000 - 33
[0153] Wingtack is a trademark of Goodyear. Hercotac is a trademark
of Hercules. Eastotac is a trademark of Eastman Chemical. Polywax
is a trademark of Petrolite.
[0154] A comparison of Examples 3 to 6 of Table Four illustrates
the fact that formulations including an appropriate tackifier
exhibit peel strengths which are improved over that of the
uncompounded ethylene/styrene interpolymer. Formulation 7
illustrates the negative effect of an incompatible or only
partially compatible tackifier. As illustrated by Example 8, the
addition of wax to the high peel strength adhesive of Example 3
decreases the peel strength as compared to that of the adhesive of
Example 3, but results in a peel strength which is superior to that
of the comparative ethylene/octene interpolymer based formulations
of Comparative Examples A and B.
EXAMPLES 9-21
[0155] and
Comparative Examples C, D, and E
[0156] The formulations utilized in the following examples were
prepared in the manner set forth above. In the case of Examples
9-12, the polymer utilized was Polymer D, a substantially random
ethylene/styrene interpolymer having 42 weight percent styrene and
a melt index (I.sub.2) of 1 g/10 min. In the case of Examples
13-16, the polymer utilized was Polymer E, a substantially random
ethylene/styrene interpolymer having 57 weight percent styrene. In
the case of Examples 17-21, the polymer utilized was Polymer F, a
substantially random ethylene/styrene interpolymer having 65 weight
percent styrene. The tackifier utilized was Piccotex 75, which is a
pure monomer resin having a glass transition temperature, as
determined by DSC, of 31.degree. C., and which is available from
Hercules. The extending or modifying composition utilized was Tuflo
6056, which is a mineral oil available from Lyondell
Petrochemical.
[0157] The resultant formulations were evaluated for glass
transition temperature, tensile at break, elongation at break, bond
strength, G', 100 percent modulus, 200 percent modulus, and
toughness.
[0158] In the case of tensile determinations, samples were molded
at 115.degree. C. for 5 minutes at 10 tons ram pressure. Samples
which were 1 inch (2.54 cm) by 0.125 inches (0.318 cm) are
utilized. The Instron tensiometer was set at a crosshead speed of
50 cm/min. Modulus was taken as the slope of the stress-strain
curve at 100 and 200 percent extension (as measured by crosshead
displacement). Toughness was the area under the stress-strain
curve.
[0159] In the case of G' determinations, a Rheometrics RDSII Solids
Analyzer was used with 8 mm diameter parallel plates, operated in
the shear mode. The test rate was 1 radian/second. The temperature
was stepped from 5 to 10.degree. C., and was allowed to equilibrate
for 2 minutes before data collection.
[0160] The formulations and the resultant properties are set forth
in the following Table Five.
5TABLE FIVE A Glass Transition Elonga- Polymer Tackifier Processing
Temper- G' Tensile tion Polymer (wt (wt aid (wt ature
(dynes/cm.sup.2) strength at break Example Sample percent) percent)
percent) (.degree. C.) (Pa) (psi (MPa)) (percent) Comp. D (42 100 0
0 -22 1.36 .times. 10.sup.7 1879 930 Ex. C percent) (1.36 .times.
10.sup.6) (12.9) 9 D 40 47.5 12.5 -29.7 2.62 .times. 10.sup.6 882
1907 (2.62 .times. 10.sup.5) (6.08) 10 D 40 60 0 -8.2 1.06 .times.
10.sup.7 3280 766 (1.06 .times. 10.sup.6) (22.6) 11 D 55 45 0 -12.2
6.03 .times. 10.sup.6 3689 1235 (6.03 .times. 10.sup.5) (22.5) 12 D
70 30 0 -13.4 7.78 .times. 10.sup.6 3260 1382 (7.78 .times.
10.sup.5) (25.4) Comp. E (57 100 0 0 -10 1.21 .times. 10.sup.7 543
1030 Ex. D percent) (1.21 .times. 10.sup.6) (3.74) 13 E 40 47.5
12.5 -15.2 2.91 .times. 10.sup.6 275 1889 (2.91 .times. 10.sup.5)
(1.90) 14 E 40 60 0 7.5 7.30 .times. 10.sup.6 1867 565 (7.30
.times. 10.sup.5) (12.9) 100 200 Average percent percent Tough-
Coating strength modulus modulus ness thickness (lbs/in Example
(psi (MPa) (psi (MPa)) (psi (MPa)) (inches (cm)) (N/25.4 mm)) Comp.
295 .sup. 361 7507 .sup. N/D .sup. N/D Ex. C (2.0) (2.5) (51.8) 9
.sup. 68.9 77.4 6637 .sup. 0.0165 7.59 .sup. (0.48) (0.53) (45.8)
(0.04) (33.8).sup. 10 368 .sup. 578 10510 .sup. 0.0245 8.95 .sup.
(2.53) (1.68) (72.5) (0.062) (39.8).sup. 11 176 .sup. 239 14121
.sup. 0.024 10.3.sup. .sup. (1.34) (1.65) (97.6) (0.061)
(17.9).sup. 12 195 .sup. 243 14155 .sup. 0.0235 4.02 .sup. (1.21)
(0.18) (97.4) (0.060) (44.6).sup. Comp. 261 .sup. 294 3361 .sup.
N/D .sup. N/D Ex. D (1.8) (2.03) (23.2) 13 .sup. 14.3 25.6 2240
.sup. 0.0165 6.83 (0.099) (0.18) (15.4) (0.042) (30.4).sup. 14 418
.sup. 583 5666 .sup. 0.0155 .sup. 11.22 (2.9) (4.02) (39.1) (0.039)
(49.9).sup.
[0161]
6TABLE FIVE B Glass Tensile Polymer Tackifier Processing Transition
G' strength Elongation Polymer (wt (wt aid (wt Temper-
(dynes/cm.sup.2) (psi at break Example Sample percent) percent)
percent) ature (.degree. C.) (Pa) (MPa)) (percent) 15 E 55 45 0 2.9
4.96 .times. 10.sup.6 2009 917 (4.96 .times. 10.sup.5) (15.0) 16 E
70 30 0 -0.2 5.63 .times. 10.sup.6 2172 1077 (5.63 .times.
10.sup.5) (13.9) Comp. F (65 100 0 0 -3.2 1.36 .times. 10.sup.7
1077 684 Ex. E percent) (1.36 .times. 10.sup.6) (7.43) 17 F 40 47.5
12.5 0.1 1.90 .times. 10.sup.6 735.8 1514 (1.90 .times. 10.sup.5)
(5.07) 18 F 40 60 0 19.9 1.63 .times. 10.sup.6 1725 368 (1.63
.times. 10.sup.5) (11.9) 19 F 55 45 0 13.2 6.59 .times. 10.sup.6
2996 607 (6.59 .times. 10.sup.5) (20.0) 20 F 70 30 0 8.9 6.11
.times. 10.sup.6 2896 822 (6.11 .times. 10.sup.5) (20.7) 100 200
percent percent Tough- Coating Average modulus modulus ness
thickness strength Exam- (psi (psi (psi (inches (lbs/in ple (MPa)
(MPa)) (MPa)) (cm)) (N/25.4 15 202 .sup. 271 .sup. 6683 0.023.sup.
.sup. 12.65 (1.5) .sup. (2.07) (65.8) (0.058).sup. (29.6).sup. 16
211 .sup. 300 .sup. 9539 0.023.sup. 6.65 (1.4) .sup. (1.87) (46.1)
(0.058).sup. (56.3).sup. Comp. 302 .sup. 413 .sup. 3963 N/D.sup.
.sup. N/D Ex. E (2.1) .sup. (2.84) (27.3) 17 .sup. 64.2 .sup. 77.5
3832 .sup. 0.0205 7.73 .sup. (0.44) .sup. (0.53) (26.4)
(0.052).sup. (34.4).sup. 18 899 .sup. 1146 .sup. 4519 .sup. 0.0235
6.88 (6.2) (7.9) (31.2) (0.06) (30.6).sup. 19 .sup. 0.24 592 .sup.
7739 0.025.sup. 2.25 .sup. (1.21) .sup. (2.06) (55.8) (0.064).sup.
(41.4).sup. 20 176 .sup. 299 .sup. 8086 .sup. 0.0245 9.31 (0.002)
.sup. (4.08) (53.4) (0.062).sup. (10.0).sup.
[0162] Table Five shows that the addition of tackifier to a
substantially random ethylene/styrene interpolymer increases the
tensile toughness of the interpolymer. This increase in toughness
(the result of the increased strain-hardening of the formulation)
contributes to an increase in the peel strength of a bonded
aluminum specimen. The aluminum-aluminum bonds are made at
177.degree. C. for 120 seconds under 8 pounds/square inch (0.055
Mpa) pressure. As illustrated by Table Six, the addition of
tackifier to a substantially random ethylene/styrene interpolymer
has the ability to increase the toughness of a substantially random
ethylene/styrene interpolymer which has less than 5 percent
crystallinity by DSC, that is, which is predominantly amorphous in
character.
EXAMPLES 21-23
[0163] and
Comparative Examples F and G
[0164] PSA Tapes
[0165] Samples of pressure sensitive adhesive tapes were prepared
by coating from the melt onto a 0.051 mm thick polyester backing,
and were covered with silicone release paper for storage and
transportation. The coater was a commercial unit available from
Chemsultants International. The adhesive layers were in the range
of 0.09 to 0.115 mm thick. Tests were performed in accordance with
the Pressure Sensitive Tape Council (PSTC) standards. A 180.degree.
peel test on stainless steel was done at 30 cm/min, at both 5
minute and 24 hour dwell times. Shear tests (Holding Power) were
performed at room temperature with a 1000 gram load and an overlay
of 12.7.times.25.4 mm on mirror polished stainless steel.
[0166] In the case of Comparative Example F, the polymer was Vector
4113 styrene/isoprene/styrene block copolymer, available from Dexco
Company. In the case of Comparative Example G, the polymer was
Vector 4114 styrene/isoprene/styrene block copolymer, available
from Dexco Company. In the case of Examples 21-23, the polymer was
the substantially random interpolymer of Polymer E.
[0167] The formulations employed and the resultant adhesive
properties are set forth in the following Tables Six and Seven:
7 TABLE SIX Comp. Ex. F Comp. Ex. G 21 22 23 Vector 4113 41.7 0 0 0
0 Vector 4114 0 35.7 0 0 0 Polymer E 0 0 48.75 57.6 42.5 Wingtack
95 52.1 50.0 0 0 0 Piccotex 75 0 0 38.75 30.0 32.5 Tuflo 6056 6.3
14.3 12.5 12.5 25.0
[0168]
8 TABLE SEVEN Comp. Comp. 21 22 23 Thickness 4.65 4.25 4.7 4.2 3.7
(mils (cm)) (0.12) (0.11) (0.12).sup. (0.11) (0.09) Peel (lbs/in
12.69 5.97 1.85.sup. 0.48 0.17 (N/25.4 mm)) (56.4) (26.6)
(8.22).sup. (2.13) (0.76) 24 hour peel N/D N/D 3.29.sup. 1.53 0.817
(lbs/in (14.6) .sup. (6.81) (3.63) (N/25.4 mm)) Shear (min) 259 22
1242 1796 40 Tg (.degree. C.) N/D -19.8 -15.7 .sup. -16.5 -20 G'
.sup. 6.13 .times. 10.sup.5 1.71 .times. 10.sup.5 .sup. 1.92
.times. 10.sup.6.sup. 3.96 .times. 10.sup.6 9.32 .times. 10.sup.5
(dynes/cm.sup.2 .sup. (6.13 .times. 10.sup.4) (1.71 .times.
10.sup.4) .sup. (1.92 .times. 10.sup.5).sup. (3.96 .times.
10.sup.5) (9.32 .times. 10.sup.4) (Pa)) Tensile (psi N/D N/D 192
.sup. 79 24 (MPa) (1.32).sup. (0.54) (0.17)
[0169] Tables Six and Seven show that substantially random
ethylene/styrene interpolymers having from 39 to 65, preferably
from 45 to 55 weight percent styrene can be formulated to give low
tack pressure sensitive adhesive formulations with improved creep
resistance when compared to styrene block copolymer
formulations.
[0170] Tackifier Screening Study
[0171] The tackifiers evaluated in the study, as well as properties
obtained from trade literature, are set forth in the following
Table Eight:
9TABLE EIGHT DACP MMAP Tackifier Manufacturer Feedstock Mn Tg Cloud
Cloud ECR 165 Exxon Aromatic/Cycloaliphatic 59 Escorez 5380 Exxon
Cycloaliphatic 160 35 ECR 149B Exxon Hydrogenated C5-C6 48 ECR 179
Exxon Hydrogenated Cycloaliphatic 57 Wingtack 86 Goodyear Aromatic
Modified C5 37 Wingtack 95 Goodyear C5 Hydrocarbon 59 Hercotac 1149
Hercules Aliphatic/Aromatic (C5-C9) 850 45 24 68 Piccotex 75
Hercules Copolymer Modified Styrene 680 29 <-50 1 Piccotex 100
Hercules Copolymer Modified Styrene 1200 42 -50 6 Regalrez 3102
Hercules Hydrogenated Styrenic 875 51 -30 24 Kristalex 3070
Hercules Copolymer of pure monomer 580 27 <-50 0.4 Piccolastic
A5 Hercules Styrenic Monomers 360 -28 <-50 -4 Piccolastic A75
Hercules Styrenic Monomers 670 28 <-50 6 Regalite R101 Hercules
Hydrogenated Hydrocarbon 44 Foral 85 Hercules Rosin Ester 35
Staybelite Ester 10 Hercules Hydrogenated Wood Rosin 29 Eastotac
H100E Eastman Modified C5 49 Piccotac 95 Hercules C5 Hydrocarbon
800 43 49 95 * DACP Cloud point reflects polarity of the resin,
with lower values indicating a higher degree of polarity. MMAP
cloud point is a value which reflects resin aromatic compatibility,
with lower values indicating a greater degree of aromaticity.
[0172] Formulations were prepared and evaluated, with the
formulations employed and the resultant properties being set forth
in the following Table Nine.
10TABLE NINE DMS G' Elongation 100 percent Tackifier DSC Tg at 20
C. Tensile Max at Break Modulus (psi 200 percent Toughness
Tackifier ID Phr (.degree. C.) (dynes/cm.sup.2) (psi (MPa))
(percent) (MPa)) Modulus (psi (MPa)) (psi (MPa)) -10.00 1.21E+07
543 (3.74) 1030 261 (1.8) 294 (2.0) 3361 (23.2) ECR165 100 6.40
8.32E+07 2418 (16.7) 587 598 (4.1) 911 (6.3) 8083 (55.7) Escorez
5380 100 7.80 1.62E+08 1543 (10.6) 1003 177 (1.2) 231 (1.6) 5732
(39.5) ECR 149B 100 6.40 9.49E+07 1654 (11.4) 622 426 (2.9) 565
(3.9) 5628 (38.8) ECR 179 100 7.60 8.55E+06 2286 (15.8) 544 587
(4.0) 839 (5.8) 6856 (47.3) ECR 179 100 5.50 8.59E+06 3047 (21.0)
1012 171 (1.2) 226 (1.6) 8100 (55.9) Escorez 5380 100 11.00
5.73E+06 1630 (11.2) 1288 116 (0.8) 146 (1.0) 6220 (42.9) Wingtack
86 100 0.20 2.59E+07 1862 (12.8) 627 362 (2.5) 609 (4.2) 5813
(40.1) Wingtack 95 100 6.50 3.29E+08 Hercotac 1149 100 7.70
2.45E+07 2205 (15.2) 538 601 (4.1) 970 (6.7) 6573 (45.3) Piccotex
75 100 2.8 3070 (21.2) 864 220 (1.5) 301 (2.1) 7957 (54.9) Piccotex
100 100 2.4 3520 (24.3) 527 1160 (8) 1537 (10.8) 10152 (70.0)
Regalrez 3102 100 -7.8 2194 (15.1) 550 618 (4.3) 864 (6.0) 6939
(47.9) Kristalex 3070 100 1.7 2334 (16.1) 924 193 (1.3) 262 (1.8)
6944 (47.9) Piccolastic A5 81.8 -20.2 2.47E+06 .sup. 66.3
(0.46).sup. 2500 .sup. 62.7 (0.43).sup. .sup. 65.6 (0.45).sup.
111.1 (0.77) Piccolastic A75 81.8 -4.8 6.19E+06 2924 (20.2) 723 352
(2.4) 566 (3.9) 9165 (63.2) Regalite R101 100 1.9 2111 (14.6) 640
378 (2.6) 585 (4.0) 6358 (43.8) Regalrez 3102 100 5.1 2389 (16.5)
528 664 (4.6) 903 (6.2) 7078 (48.8) Foral 85 100 5.2 1586 (10.9)
853 137 (0.94) 180 (1.2) 4505 (31.1) Kristalex 3070 100 1.4 2168
(15.0) 800 179 (1.2) 235 (1.6) 5683 (39.2) Foral 105 100 7.4 2028
(14.0) 632 424 (2.9) 545 (3.8) 6724 (46.4) Staybelite Ester 10 100
4.5 2080 (14.3) 995 113 (0.78) 150 (1.0) 5968 (41.2) Eastotac H100E
100 4.5 1949 (13.4) 583 460 (3.2) 610 (4.2) 6076 (41.9)
[0173] Table Nine shows that a wide variety of tackifier structures
can improve the tensile properties of substantially random
interpolymers. Tackifiers from the rosin ester, wood rosin, pure
monomer, C.sub.5-C.sub.9, aromatic modified C.sub.5, partially
hydrogenated C.sub.5-C.sub.9, and cycloaliphatic families have been
shown to be effective. Of particular and unexpected note in Table
Nine is that the combination of, for instance, 100 parts of
tackifier with 100 parts of the substantially random interpolymer
components results in materials having much higher tensile
strengths than the substantially random interpolymer alone,
preferably a maximum tensile strength of at least twice, more
preferably at least three times as great as that of the
substantially random interpolymer alone.
[0174] Glass Transition Temperature Adjustment for High Styrene
Content Polymers
[0175] A substantially random interpolymer of ethylene and styrene
having from 73.7 to 74.9 weight percent styrene and a melt index
(I.sub.2) of 1 g/10 minutes, is melt blended with the indicated
amount of Endex.TM. pure monomer resin, available from Hercules.
The formulations tested, and the glass transition temperature of
the resultant formulations, are set forth in the following Table
Ten.
11TABLE TEN Weight percent Weight Substantially percent Glass
Transition Sample No. Random Interpolymer Tackifier Temperature
(.degree. C.) Comparative 100 0 22.1 Ex. D Ex. 24 90 10 23.6 Ex. 25
80 20 25.6 Ex. 26 70 30 27.7
[0176] The data set forth in Table Ten illustrates the use of a
tackifier to raise the glass transition temperature of a high
styrene containing interpolymer to levels above ambient
temperature.
[0177] These and other embodiments will be readily ascertained by
one skilled in the art. Accordingly, the subject invention is to be
limited only by the following Claims.
* * * * *