U.S. patent application number 11/444704 was filed with the patent office on 2006-10-26 for free-flowing polymer composition.
This patent application is currently assigned to The Dow Chemical Company. Invention is credited to Friedheim Bunge, Shirkant V. Dhodapkar, James W. McMichael, Jeffrey Richard Montayne.
Application Number | 20060241233 11/444704 |
Document ID | / |
Family ID | 23482652 |
Filed Date | 2006-10-26 |
United States Patent
Application |
20060241233 |
Kind Code |
A1 |
McMichael; James W. ; et
al. |
October 26, 2006 |
Free-flowing polymer composition
Abstract
The present invention relates to substantially free-flowing
polymer particles. The polymer particles are those which have a one
millimeter penetration temperature of less than about 75.degree. C.
as determined by thermal mechanical analysis or an unconfined yield
strength of greater than about 15 pounds per square foot (73
kilograms per square meter). The composition also comprises an
effective amount of an anti-blocking agent in the presence or
absence of a binding agent.
Inventors: |
McMichael; James W.; (Lake
Jackson, TX) ; Montayne; Jeffrey Richard; (Clarkston,
MI) ; Dhodapkar; Shirkant V.; (Lake Jackson, TX)
; Bunge; Friedheim; (Somerset, DE) |
Correspondence
Address: |
BAKER & MCKENZIE LLP
Pennzoil Place, South Tower
711 Louisiana, Suite 3400
HOUSTON
TX
77002-2716
US
|
Assignee: |
The Dow Chemical Company
Midland
MI
|
Family ID: |
23482652 |
Appl. No.: |
11/444704 |
Filed: |
June 1, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10961294 |
Oct 8, 2004 |
7101926 |
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11444704 |
Jun 1, 2006 |
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10049395 |
Feb 12, 2002 |
6852787 |
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PCT/US00/22424 |
Aug 16, 2000 |
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10961294 |
Oct 8, 2004 |
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09375856 |
Aug 17, 1999 |
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10049395 |
Feb 12, 2002 |
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Current U.S.
Class: |
524/451 |
Current CPC
Class: |
C08K 3/34 20130101; C08J
3/124 20130101; C08J 2325/08 20130101; Y10T 428/2993 20150115; C08L
2666/02 20130101; C08L 23/0838 20130101; C08L 2666/04 20130101;
C08L 2666/02 20130101; C08L 83/00 20130101; C08J 2323/08 20130101;
C08L 23/16 20130101; C08K 3/34 20130101; C08J 3/203 20130101; C08L
23/0838 20130101; C08L 23/16 20130101; C08L 23/16 20130101; C08L
23/0838 20130101; C08L 83/04 20130101; C08L 23/0838 20130101; C08L
25/06 20130101 |
Class at
Publication: |
524/451 |
International
Class: |
C08K 3/34 20060101
C08K003/34 |
Claims
1. A composition comprising: (a) polymer particles having one or
more of the following properties: (1) a one millimeter penetration
temperature of less than about 75.degree. C. as determined by
thermal mechanical analysis; or (2) an unconfined yield strength of
greater than about 15 pounds per square foot (73 kilograms per
square meter); (3) (b) an effective amount of an anti-blocking
agent; and (c) an effective amount of a binding agent capable of
binding the anti-blocking agent to the polymer particles.
2. The composition of claim 1 wherein the polymer comprises a
substantially random interpolymer comprising: (a) polymer units
derived from: (i) at least one vinyl or vinylidene aromatic
monomer; or (ii) a combination of at least one vinyl or vinylidene
aromatic monomer and at least one sterically hindered aliphatic or
cycloaliphatic vinyl or vinylidene monomer; and (b) polymer units
derived from at least one (i) ethylene; or (ii) aliphatic
alpha-olefin monomer having from 3 to 20 carbon atoms.
3. The composition of claim 1 wherein the polymer comprises at
least one substantially random interpolymer comprising: (a) polymer
units derived from: (i) at least one vinyl or vinylidene aromatic
monomer; and/or (ii) a combination of at least one vinyl or
vinylidene aromatic monomer and at least one sterically hindered
aliphatic or cycloaliphatic vinyl or vinylidene monomer; and (b)
polymer units derived from at least one aliphatic olefin monomer
having from 2 to 20 carbon atoms.
4. The composition of claim 2 wherein the interpolymer comprises:
(a) polymer units derived from one or more vinyl aromatic monomers
and polymer units derived from ethylene; (b) polymer units derived
from one or more vinyl aromatic monomers and polymer units derived
from ethylene and one or more C.sub.3 or C.sub.20 alpha-olefins; or
(c) polymer units derived from one or more vinyl aromatic monomers
and polymer units derived from a combination of ethylene and
norbornene.
5. The composition of claim 2 wherein the vinyl aromatic monomer is
styrene.
6. The composition of claim 2 wherein the interpolymer is selected
from the group consisting of polymer units derived from: (a)
ethylene and styrene; (b) ethylene and propylene and styrene; (c)
ethylene and butene and styrene; (d) ethylene and pentene and
styrene; (e) ethylene and hexene and styrene; and (f) ethylene and
octene and styrene.
7. The composition of claim 2 wherein the interpolymer comprises
from 50 to 97 mole percent of polymer units derived from ethylene
based on the total moles of monomer.
8. The composition of claim 2 wherein the interpolymer comprises
from 50 to 97 mole percent of polymer units derived from ethylene
based on the total moles of monomer and polymer units derived from
styrene.
9. The composition of claim 1 wherein the polymer is a polymer
comprising polymer units derived from ethylene.
10. The composition of claim 9 which further comprises polymer
units derived from a C.sub.3-C.sub.8 alpha-olefin.
11. The composition of claim 10 wherein the alpha-olefin is
selected from the group consisting of propylene, 1-butene,
1-pentene, 1-hexene, 1-heptene, and 1-octene.
12. The composition of claim 9 which further comprises polymer
units derived from vinyl acetates.
13. The composition of claim 1 wherein the polymer is a styrenic
block copolymer.
14. The composition of claim 13 wherein the styrenic block
copolymer is selected from the group consisting of
styrene-butadiene copolymer and styrene-butadiene-styrene
copolymer.
15. The composition of claim 1 wherein the polymer is a polyvinyl
chloride polymer.
16. The composition of claim 1 wherein the polymer comprises
polymer units derived from propylene.
17. The composition of claim 1 wherein the anti-blocking agent
comprises from 0.5 to 3 weight percent anti-blocking agent based on
the total composition.
18. The composition of claim 1 wherein the anti-blocking agent is
selected from the group consisting of talc, mica, calcium
carbonate, finely divided silica, fumed silica, organic acids,
metal organic esters, and powdered polymers.
19. The composition of claim 1 wherein the anti-blocking agent is
talc.
20. The composition of claim 1 wherein the anti-blocking agent is
calcium stearate.
21. The composition of claim 1 wherein the binding agent comprises
from 0.05 to 1 weight percent binding agent based on the total
composition.
22. The composition of claim 1 wherein the binding agent is
selected from the group consisting of polyether polyols, aliphatic
hydrocarbon oils, alkanes having between seven and 18 carbon atoms
optionally substituted with OH, CO.sub.2H, or esters, alkenes
having between seven and 18 carbon atoms optionally substituted
with OH, CO.sub.2H, or esters, natural oils, naphthenic oils,
paraffinic oils, aromatic oils, silicon oils, plasticizers,
tackifiers, and esters, alcohols, and acids of said oils,
plasticizers, and tackifiers.
23. The composition of claim 22 wherein the silicon oil is a
siloxane polymer having the structural formula
--Si(R.sup.1R.sup.1)--O-- wherein the R.sup.1 groups are
C.sub.1-C.sub.18 hydrocarbyl groups.
24. The composition of claim 23 wherein R.sup.1 is selected from an
aliphatic group and an aromatic group.
25. The composition of claim 24 wherein R.sup.1 is methyl.
26. The composition of claim 1 wherein the unconfined yield
strength of the composition is at least about 20 percent less than
the strength of the same composition without an anti-blocking
agent.
27. The composition of claim 2 which further comprises up to 50
percent of at least one other thermoplastic polymer.
28. The composition of claim 27 wherein the at least one other
thermoplastic polymer is selected from the group consisting of
homopolymers and copolymers of polystyrene, polyethylene and
polypropylene.
29. A composition comprising: (a) a substantially random
interpolymer comprised of polymer units derived from ethylene and
polymer units derived from styrene; (b) from 0.5 to 3 weight
percent of anti-blocking agent selected from the group consisting
of talc and calcium stearate; and (c) from 0.05 to 1 weight percent
of a silicone oil binding agent.
30. A process for making a polymer composition said process
comprising: contacting polymer particles with an effective amount
of: (a) an anti-blocking agent; and (b) a binding agent capable of
binding the anti-blocking agent to the polymer particles, wherein
the polymer particles have one or more of the following properties:
a one millimeter penetration temperature of less than about
75.degree. C. as determined by thermal mechanical analysis or an
unconfined yield strength of greater than 15 pounds per square foot
(73 kilograms per square meter).
31. The process of claim 30 wherein the binding agent and
anti-blocking agent are simultaneously contacted with the polymer
particles.
32. The process of claim 30 wherein the polymer particles are first
contacted with the binding agent and then contacted with the
anti-blocking agent.
33. The process of claim 30 wherein the polymer particles are first
contacted with the binding agent and then contacted with the
anti-blocking agent and then further contacted with binding agent,
anti-blocking agent, or both.
34. The process of claim 30 wherein the polymer is a substantially
random interpolymer comprising: (a) polymer units derived from: (i)
at least one vinyl or vinylidene aromatic monomer; or (ii) a
combination of at least one vinyl or vinylidene aromatic monomer
and at least one sterically hindered aliphatic or cycloaliphatic
vinyl or vinylidene monomer; and (b) polymer units derived from at
least one aliphatic olefin monomer having from 2 to 20 carbon
atoms.
35. The process of claim 30 wherein the interpolymer is selected
from the group consisting of polymer units derived from: (a)
ethylene and styrene; (b) ethylene and propylene and styrene; (c)
ethylene and butene and styrene; (d) ethylene and pentene and
styrene; (e) ethylene and hexene and styrene; or (f) ethylene and
octene and styrene.
36. The process of claim 30 wherein the polymer is selected from
the group consisting of an ethylene-alpha-olefin copolymer, an
ethylene-vinyl acetate copolymer, a styrenic block copolymer, a
polyvinyl chloride polymer, polypropylene, and propylene
copolymers.
37. The process of claim 30 wherein the anti-blocking agent
comprises from 0.5 to 3 weight percent anti-blocking agent based on
the total composition and wherein the anti-blocking agent is
selected from the group consisting of talc, mica, calcium
carbonate, finely divided silica, fumed silica, organic acids,
metal organic esters, and powdered polymers.
38. The process of claim 30 wherein the binding agent comprises
from 0.05 to 1 weight percent binding agent based on the total
composition and wherein the binding agent is selected from the
group consisting of polyether polyols, aliphatic hydrocarbon oils,
alkanes having between seven and 18 carbon atoms optionally
substituted with OH, CO.sub.2H, or esters, alkenes having between
seven and 18 carbon atoms optionally substituted with OH,
CO.sub.2H, or esters, natural oils, naphthenic oils, paraffinic
oils, aromatic oils, silicon oils, plasticizers, tackifiers, and
esters, alcohols, and acids of said oils, plasticizers, and
tackifiers.
39. The process of claim 30 wherein the binding agent is a siloxane
polymer having the structural formula --Si(R.sup.1R.sup.1)--O--
wherein the R.sup.1 groups are C.sub.1-C.sub.18 hydrocarbyl groups
and wherein the anti-blocking agent is selected from the group
consisting of talc and calcium carbonate.
40. The process of claim 39 wherein R.sup.1 is methyl.
41-72. (canceled)
73. A process for making a polymer composition, comprising:
softening polymer particles having a one millimeter penetration
temperature of less than about 75.degree. C. as determined by
thermal mechanical analysis or an unconfined yield strength of
greater than 15 pounds per square foot (73 kilograms per square
meter) or both; and then contacting said polymer particles with an
effective amount of anti-blocking agent such that said
anti-blocking agent is mechanically adhered to polymer particles,
wherein the polymer particles have one or more of the following
properties: a one millimeter penetration temperature of less than
about 75.degree. C. as determined by thermal mechanical analysis or
an unconfined yield strength of greater than 15 pounds per square
foot (73 kilograms per square meter).
74. The process of claim 73 wherein said anti-blocking agent is
adhered to the surface of at least about 50 percent of the polymer
particles and wherein at least about 10 percent of the diameter of
an individual anti-blocking particle is embedded into an individual
polymer particle.
75. The process of claim 73 wherein the anti-blocking agent is
talc.
76. The process of claim 73 wherein the anti-blocking agent
comprises from 0.15 to 0.3 weight percent anti-blocking agent based
on the total composition.
77. The process of claim 73 wherein the polymer is a substantially
random interpolymer comprising: (a) polymer units derived from: (i)
at least one vinyl or vinylidene aromatic monomer; or (ii) a
combination of at least one vinyl or vinylidene aromatic monomer
and at least one sterically hindered aliphatic or cycloaliphatic
vinyl or vinylidene monomer; and (b) polymer units derived from at
least one aliphatic olefin monomer having from 2 to 20 carbon
atoms.
78. The process of claim 73 wherein the interpolymer is selected
from the group consisting of polymer units derived from: (a)
ethylene and styrene; (b) ethylene and propylene and styrene; (c)
ethylene and butene and styrene; (d) ethylene and pentene and
styrene; (e) ethylene and hexene and styrene; or (f) ethylene and
octene and styrene.
79. The process of claim 73 wherein the polymer is selected from
the group consisting of an ethylene-alpha-olefin copolymer, an
ethylene-vinyl acetate copolymer, a styrenic block copolymer, a
polyvinyl chloride polymer, polypropylene, and propylene
copolymers.
80. The process of claim 73 wherein the anti-blocking agent
comprises from 0.5 to 3 weight percent anti-blocking agent based on
the total composition and wherein the anti-blocking agent is
selected from the group consisting of talc, mica, calcium
carbonate, finely divided silica, fumed silica, organic acids,
metal organic esters, and powdered polymers.
81. The process of claim 73 wherein the surface of the particles is
melted by hot air, radiation, contact heating, or a combination
thereof.
82. The process of claim 73 wherein the surface of the particles is
melted to a depth sufficient to bind an effective amount of
anti-blocking agent.
83. The process of claim 73 wherein the surface of the particles
are melted by hot air, radiation, contact heating, or a combination
thereof; (a) the interpolymer has polymer units derived from
ethylene and styrene; (b) the anti-blocking agent is talc and is
present from 0.15 to 0.3 weight percent of the composition; and (c)
the anti-blocking agent is in a substantially homogenous thick
layer having a thickness of from the diameter of the agent to about
5 times the diameter of the agent.
Description
[0001] The present invention pertains to a free-flowing polymer
composition and process therefor. More particularly, the present
invention pertains to a free-flowing polymer composition comprising
polymer and an anti-blocking agent and processes for producing such
a composition.
[0002] Many polymers are often prepared by a polymerization of a
mixture of monomers in, for example, a solution or slurry process.
The polymerization product may then be recovered in a form suitable
for subsequent handling and part manufacturing. This recovery
operation produces materials in the form of particles, flakes or
powders. Unfortunately, many such materials have a tendency to
stick together, that is, block, agglomerate or cake, and/or adhere
to processing equipment. Factors such as temperature, storage time,
and/or compression often faciliate, contribute to, or exacerbate
the aforementioned stickiness. Thus, the polymer materials are
often not substantially free-flowing.
[0003] If the polymer particles are not free-flowing, then they
present a few problems. One problem is that the particles may be
difficult to package, ship, and incorporate into subsequent
articles because the reduced flowability hinders the uniform
distribution of said particles. Another problem stems from the
tendency of the particles to stick to the manufacturing and
processing equipment, for example, screens, dryers, meters,
extruding equipment and other fabricating machinery. Thus,
production is often hindered because the equipment must be cleaned
periodically to remove the agglomerated particles.
[0004] One way in which the caking tendencies of polymers have been
reduced is by blending finely divided silica or fumed silica with
the polymer particles. Unfortunately, even though the caking
tendency of the polymer particles may be reduced, the silica is a
low bulk density solid and tends to make the working environment
unpleasant due to silica dust.
[0005] In order to reduce dust associated with finely divided or
fumed silica, U.S. Pat. No. 5,366,645 suggests that a porous,
amorphous silica be imbibed with a liquid oil and employed with
polymers. Unfortunately, the porous, amorphous silicas required for
such a composition are relatively expensive and difficult with
which to work.
[0006] For the aforementioned reasons, it would be desirable to
discover a new polymer particle composition which is substantially
free flowing and relatively dust-free. It would further be
desirable if such a composition employs readily available
components that are not difficult with which to work. It would
still further be desirable to discover a process for readily making
such a composition.
[0007] Advantageously, a new polymer particle composition has been
discovered which is substantially free flowing and relatively
dust-free. The composition comprises: [0008] (a) polymer particles
having (1) a one millimeter penetration temperature of less than
about 75.degree. C. as determined by thermal mechanical analysis or
(2) an unconfined yield strength of greater than about 15 pounds
per square foot (73 kilograms per square meter) or (3) both; [0009]
(b) an effective amount of an anti-blocking agent; and [0010] (c)
an effective amount of a binding agent capable of binding the
anti-blocking agent to the polymer particles.
[0011] Advantageously, a process for readily making the
aforementioned inventive composition has also been discovered. The
process comprises contacting polymer particles having (1) a one
millimeter penetration temperature of less than about 75.degree. C.
as determined by thermal mechanical analysis or (2) an unconfined
yield strength of greater than about 15 pounds per square foot (73
kilograms per square meter), with an effective amount of: [0012]
(1) a binding agent capable of binding the anti-blocking agent to
the polymer particles; and [0013] (2) an anti-blocking agent.
[0014] Another composition has also been discovered which does not
require a binding agent. The composition comprises: [0015] (a)
polymer particles having (1) a one millimeter penetration
temperature of less than about 75.degree. C. as determined by
thermal mechanical analysis or (2) an unconfined yield strength of
greater than about 15 pounds per square foot (73 kilograms per
square meter) or (3) both; and [0016] (b) an effective amount of an
anti-blocking agent mechanically adhered to the polymer
particles.
[0017] Advantageously, a process for readily making the
aforementioned composition has also been discovered. The process
comprises mechanically adhering an effective amount of an
anti-blocking agent to polymer particles having (1) a one
millimeter penetration temperature of less than about 75.degree. C.
as determined by thermal mechanical analysis or (2) an unconfined
yield strength of greater than 15 pounds per square foot (73
kilograms per square meter) or (3) both.
[0018] FIG. 1 is a cross section of ESI at 1000.times. (Sample 18
of Example 4) with 1500 ppm talc thermally bonded thereon.
[0019] FIG. 2 is an increased magnification (2500.times.) cross
section of ESI (Sample 18 of Example 4) with 1500 ppm talc
thermally bonded thereon.
[0020] FIG. 3 is a view of ESI pellet coated with talc using a
siloxane binder at 20.times. magnification (Sample 1 of Example 1
(Table 1)) with 9000 ppm talc and 2000 ppm siloxane.
[0021] FIG. 4 is an overview of ESI pellet (Sample 18 of Example 4)
at 20.times. with 1500 ppm talc thermally bonded thereon.
I. DEFINITIONS
[0022] All references herein to elements or metals belonging to a
certain Group refer to the Periodic Table of the Elements published
and copyrighted by CRC Press, Inc., 1989. Also any reference to the
Group or Groups shall be to the Group or Groups as reflected in
this Periodic Table of the Elements using the IUPAC system for
numbering groups.
[0023] As used herein "polymer particle" means a group of polymer
molecules that are intended to be associated together. A typical
polymer particle is a powder, flake, pellet or bead in a generally
substantially platelet, spherical, cylindrical, or rod shape. When
in the form of a pellet or bead, the size of the pellet or bead is
generally not so small as to be a powder and not so large that the
pellets or beads cannot be handled in conventional air conveying
and extruding equipment. While the cross-sectional area may vary
depending upon the polymer, preferably, the cross-sectional area of
a polymer particle employed in the present invention is from
3.times.10.sup.-3 (1.93.times.10.sup.-2 square centimeters) to 0.2
square inches (1.29 square centimeters), that is from 1/16 inch
(0.15875 cm) to 1/2 inch (1.27 cm) in diameter if the cross-section
is, for example, circular. Preferable particles include those with
a cross-sectional area of from 0.01 square inches
(6.45.times.10.sup.-2 square centimeters) to 0.05 square inches
(0.322 square centimeters), that is from 0.125 inches (0.3175 cm)
to 0.375 inches (0.9525cm) in diameter if, for example, the
cross-section is circular. Most preferred are particles from 0.25
cm to 0.3 cm in diameter.
[0024] As used herein "composition" includes a mixture of the
materials that comprise the composition, as well as, products
formed by the reaction or the decomposition of the materials that
comprise the composition.
[0025] As used herein "interpolymer" means a polymer wherein at
least two different monomers are polymerized to make the
interpolymer.
[0026] As used herein "derived from" means made or mixed from the
specified materials, but not necessarily composed of a simple
mixture of those materials. Compositions "derived from" specified
materials may be simple mixtures of the original materials, and may
also include the reaction products of those materials, or may even
be wholly composed of reaction or decomposition products of the
original materials. As used herein "substantially random" in the
substantially random interpolymer resulting from polymerizing one
or more .alpha.-olefin monomers and one or more vinylidene aromatic
monomers and optionally with other polymerizable ethylenically
unsaturated monomer(s) preferably 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 resulting from polymerizing one or more .alpha.-olefin
monomers and one or more vinylidene aromatic monomer, and
optionally, with other polymerizable ethylenically unsaturated
monomer(s) 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 was not characterized by a high degree of either
isotacticity or syndiotacticity. This means that in the
carbon.sup.-13 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.
[0027] As used herein "physical coating" means that a coating of
the agent is in physical contact with a substantial portion, for
example, greater than 50 percent, preferably greater than 75
percent, of the surface of the polymer particle and the agent is
preferably not chemically reacted with the polymer, that is, no
substantial covalent surface crosslinking reaction occurs.
[0028] As used herein "mechanically adhere" means physically bound
via adhesive means such as a particle embedded into the surface of
another particle. In this invention, an anti-blocking agent is
embedded into a polymer particle and thereby adhering.
[0029] 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, and 30 to 32 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.
II. POLYMERIC MATERIALS
[0030] The polymeric materials that are useful in the instant
invention are those based on polymers which have a tendency to
block, that is, aggregate or cake. Typical polymers that exhibit
such a tendency and are useful in the present invention have one of
the following two characteristics or both characteristics when the
polymer is unmodified, that is, the polymer is not mixed with a
filler or anti-blocking agent: [0031] 1) a one millimeter
penetration temperature of less than about 75, preferably less than
about 65, and more preferably less than about 60.degree. C. as
determined by thermal mechanical analysis (TMA); or [0032] 2) an
unconfined yield strength of greater than 15 pounds per square foot
(73 kilograms per square meter).
[0033] As used herein, TMA is measured according to the following
test:
[0034] A. Thermal Mechanical Analysis Test
[0035] The upper service temperature was determined from thermal
mechanical analysis (Perkin Elmer TMA 7 Series) scanned at
5.degree. C./min and a load of one Newton and defined as the point
at which the probe penetrates 1 mm into the sample.
[0036] As used herein, "unconfined yield strength" is measured
according to the following test:
[0037] B. Unconfined Yield Strength Test
[0038] The following test is a modified test from the yield
strength test described in Andrew W. Jenike, "Storage and Flow of
Solids", Bulletin No. 123 of the Utah Engineering Experiments
Station 1964 and the uniaxial compression test described by
William's, Powder Technology, 4, 1970/71, pp. 328-337. The test can
be carried out by first filling the polymeric material to be tested
into a split steel cylinder having a diameter of two inches and a
height of four inches. The material is subjected to a consolidation
pressure of 264 pounds per square foot (1289 kg/m.sup.2) for three
days at a temperature of 37.degree. C. at a controlled moisture,
that is, relative humidity. After consolidation, the resulting
polymer cylinder, comprised of individual particles, is compressed
between two parallel plates oriented on the top and bottom of the
cylinder at a rate of 1 millimeter per minute at ambient
conditions. The compressive force required to achieve the failure,
that is, falling apart, of the cylinder comprised of individual
particles corresponds to the unconfined yield strength of the bulk
material for the respective test conditions.
[0039] Polymers useful in the present invention, in addition to the
TMA and/or yield strength characteristic previously described,
often have a low level of crystallinity and/or are amorphous. Such
polymers are often exemplified by features such as low modulus,
that is, below about 50,000 psi (345 MPa) measured at 25.degree.
C., glass transition temperatures below about room temperature,
and/or a tacky nature.
[0040] One polymer which is particularly useful in the present
invention is a substantially random interpolymer comprising
[0041] a) polymer units derived from [0042] i) at least one vinyl
or vinylidene aromatic monomer, or [0043] ii) a combination of at
least one vinyl or vinylidene aromatic monomer and at least one
sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene
monomer; and
[0044] b) polymer units derived from at least one [0045] i)
ethylene; or [0046] ii) C.sub.3-20 .alpha.-olefin.
[0047] Other polymers which are useful in the present invention
include those comprising ethylene such as ethylene-alpha-olefin
co-polymers. Preferable alpha-olefins are those having from 3 to 8
carbon atoms such as propylene, 1-butene, 1-pentene, 1-hexene,
1-heptene, and 1-octene.
[0048] Yet other polymers which are useful in the present invention
include ethylene-vinyl acetate polymers (EVA) and styrenic block
co-polymers such as styrene-butadiene and
styrene-butadiene-styrene, as well as, plasticized polyvinyl
chloride (PVC) polymer, homopolymers and copolymers of propylene,
unvulcanized elastomers such as EPDM and EBDM.
[0049] Also within the scope of this invention are blended
compositions. Any two or more polymers may be blended together so
long as the polymer particles of the blend are desired to be
substantially free-flowing and relatively dust-free. Typically, the
blends useful in the present invention will exhibit a TMA,
unconfined yield strength, and/or other characteristics described
above. A particularly preferable blend comprises the substantially
random interpolymer described above and up to about 50 percent of
at least one thermoplastic polymer selected from the group
consisting of homopolymers and copolymers of polystyrene,
polyethylene, and polypropylene.
[0050] Types of blends that are useful in the compositions
disclosed herein include mechanical blends, in which the polymers
are mixed at temperatures above the T.sub.g or T.sub.m for the
amorphous or crystalline polymers respectively. Also included are
mechanochemical blends in which the polymers are mixed at shear
rates high enough to cause degradation. When using mechanochemical
blends, care must be taken to control combination of resultant free
radicals which form complex mixtures including graft and block
compositions. Solution-cast blends and latex blends are also useful
according to the present invention; as are a variety of
interpenetrating polymer network blends.
[0051] The polymer blends can be prepared by any conventional
compounding operation, such as for example single and twin screw
extruders, Banbury mixers, Brabender mixers, Farrel continuous
mixers, and two roll mills. The order of mixing and the form of the
blend components to be mixed is not critical; but rather, it may
vary depending on the particular requirements or needs of the
individual compounder. The mixing temperatures are preferably such
that an intimate blend is obtained of the components. Typical
temperatures are above the softening or melting points of at least
one of the components, and more preferably above the softening or
melting points of all the components.
[0052] C. Preferred Polymers and Processes for Preparing Such
Polymers
[0053] Particularly preferable polymers of the present invention
include interpolymers derived from .alpha.-olefin monomers and
vinyl or vinylidene monomers. Ideally, the interpolymers are at
least co-monomers, with the constituents of the comonomers
distributed substantially randomly to form a substantially random
interpolymer. Also specifically contemplated by the present
invention are substantially random interpolymers made by
polymerizing more than two monomeric species. The monomers that are
polymerized to form the interpolymers of the disclosed compositions
may remain substantially intact during the polymerization process,
or may be substantially transformed or inter-react during the
polymerization process.
[0054] Monomers that are acceptable for use in the interpolymers of
the present invention include, for example, ethylene and any
.alpha.-olefin and any vinyl or vinylidene monomer. Suitable
monomers include, for example, ethylene and .alpha.-olefins
containing from 3 to 20, preferably from 3 to 12, more preferably
from 3 to 8 carbon atoms. Particularly suitable are ethylene or one
or more .alpha.-olefins selected from propylene, butene-1,
4-methyl-1-pentene, hexene-1 and octene-1. These .alpha.-olefins do
not contain an aromatic moiety.
[0055] Examples of useable vinyl or vinylidene monomers include
vinyl or vinylidene aromatic monomers, cycloaliphatic monomers, and
any sterically hindered vinyl or vinylidene monomers. The
interpolymers of the present invention may also include one or more
additional polymerizable ethylenically unsaturated monomers.
[0056] Suitable vinyl or vinylidene aromatic monomers, which can be
employed to prepare the interpolymers, include, for example, those
represented by the following formula: ##STR1## wherein R.sup.1 is
selected from the group of radicals consisting of hydrogen and
alkyl radicals containing from 1 to 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 4 carbon atoms, preferably hydrogen or methyl;
Ar is a phenyl group or a phenyl group substituted with from I 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 4, preferably from zero to 2, most preferably zero.
Exemplary vinyl or vinylidene 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-
(C.sub.1-C.sub.4) or phenyl-ring substituted derivatives of
styrene, such as for example, ortho-, meta-, and
para-methylstyrene, the ring halogenated styrenes, para-vinyl
toluene or mixtures thereof. A more preferred aromatic vinyl
monomer is styrene.
[0057] By the term "sterically hindered aliphatic or cycloaliphatic
vinyl or vinylidene compounds", it is meant addition polymerizable
vinyl or vinylidene monomers corresponding to the formula: ##STR2##
wherein A.sup.1 is a sterically bulky, aliphatic or cycloaliphatic
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 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 4
carbon atoms, preferably hydrogen or methyl; or alternatively
R.sup.1 and A.sup.1 together form a ring system. Preferred
aliphatic or cycloaliphatic vinyl or vinylidene compounds are
monomers 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 aliphatic or cycloaliphatic vinyl or 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 and 5-ethylidene-2-norbornene. Simple linear
non-branched .alpha.-olefins including for example, .alpha.-olefins
containing from 3 to 20 carbon atoms such as propylene, butene-1,
4-methyl-1-pentene, hexene-1 or octene-1 are not examples of
sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene
compounds.
[0058] Other optional polymerizable ethylenically unsaturated
monomer(s) include norbornene and C.sub.1-10 alkyl or C.sub.6-10
aryl substituted norbornenes, with an exemplary interpolymer being
ethylene/styrene/norbornene.
[0059] The most preferred substantially random interpolymers are
the ethylene/styrene, ethylene/propylene/styrene,
ethylene/styrene/norbornene, and
ethylene/propylene/styrene/norbornene interpolymers.
[0060] The substantially random interpolymers include the
pseudo-random interpolymers as described in EP-A-0,416,815 by James
C. Stevens et al. and U.S. Pat. No. 5,703,187 by Francis J.
Timmers. The substantially random interpolymers can be prepared by
polymerizing a mixture of polymerizable monomers in the presence of
one or more metallocene or constrained geometry catalysts in
combination with various cocatalysts. Preferred operating
conditions for such polymerization reactions are pressures from
atmospheric (101 kPa) up to 3000 atmospheres (303MPa) and
temperatures from -30.degree. C. to 200.degree. C. Polymerizations
and unreacted monomer removal at temperatures above the
autopolymerization temperature of the respective monomers may
result in formation of some amounts of homopolymer polymerization
products resulting from free radical polymerization.
[0061] Examples of suitable catalysts and methods for preparing the
substantially random interpolymers are disclosed in U.S.
application Ser. No. 702,475, filed May 20, 1991 (EP-A-514,828); 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;
5,399,635; 5,470,993; 5,703,187; and 5,721,185.
[0062] The substantially random .alpha.-olefin/vinyl aromatic
interpolymers can also be prepared by the methods described in JP
07/278230 employing compounds shown by the general formula ##STR3##
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.
[0063] The substantially random .alpha.-olefin/vinyl 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 Technolog, p. 25 (September 1992).
[0064] Also suitable are the substantially random interpolymers
which comprise at least one .alpha.-olefin/vinyl aromatic/vinyl
aromatic/.alpha.-olefin tetrad disclosed in U.S. application Ser.
No. 08/708,869 filed Sep. 4, 1996 and WO 98/09999 both by Francis
J. Timmers et al. These interpolymers contain additional signals in
their carbon-13 NMR spectra with intensities greater than three
times the peak to peak noise. These signals appear in the chemical
shift range 43.70-44.25 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
43.70-44.25 ppm are methine carbons and the signals in the region
38.0-38.5 ppm are methylene carbons.
[0065] Further preparative methods for the interpolymers used in
the present invention 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
MgCl.sub.2/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. Sernetz
and Mulhaupt, (Macromol. Chem. Phys., v. 197, pp. 1071-1083, 1997)
have described the influence of polymerization conditions on the
copolymerization of styrene with ethylene using
Me.sub.2Si(Me.sub.4Cp)(N-tert-butyl)TiCl.sub.2/methylaluminoxane
Ziegler-Natta catalysts. Copolymers of ethylene and styrene
produced by bridged metallocene catalysts have been described by
Arai, Toshiaki and Suzuki (Polymer Preprints, Am. Chem. Soc., Div.
Polym. Chem.) Volume 38, pages 349, 350 [1997]) and in U.S. Pat.
No. 5,652,315, issued to Mitsui Toatsu Chemicals, Inc. 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
or U.S. Pat. No. 5,652,315 also issued to Mitsui Petrochemical
Industries Ltd or as disclosed in DE 197 11 339 A1 and U.S. Pat.
No. 5,883,213 to Denki Kagaku Kogyo KK. Also, although of high
isotacticity and therefore not "substantially random", the random
copolymers of ethylene and styrene as disclosed in Polymer
Preprints Vol 39, No. 1, March 1998 by Toru Aria et al. can also be
employed as blend components for the foams of the present
invention.
[0066] While preparing the substantially random interpolymer, an
amount of atactic vinyl aromatic homopolymer may be formed due to
homopolymerization of the vinyl aromatic monomer at elevated
temperatures. The presence of vinyl aromatic homopolymer is in
general not detrimental for the purposes of the present invention
and can be tolerated. The vinyl 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 vinyl aromatic
homopolymer. For the purpose of the present invention it is
preferred that no more than 30 weight percent, preferably less than
20 weight percent based on the total weight of the interpolymers of
atactic vinyl aromatic homopolymer is present.
[0067] The number average molecular weight (Mn) of the polymers and
interpolymers is usually greater than about 10,000, preferably from
20,000 to 1,000,000, more preferably from 50,000 to 500,000.
[0068] While preparing the substantially random interpolymers an
amount of atactic vinyl or vinylidene aromatic homopolymer may be
formed due to homopolymerization of the vinyl or vinylidene
aromatic monomer at elevated temperatures. In general, the higher
the polymerization temperature, the higher the amount of
homopolymer formed. The presence of vinyl or vinylidene aromatic
homopolymer is in general not detrimental for the purposes of the
present invention and may be tolerated. The vinyl or 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
vinyl or vinylidene aromatic homopolymer. For the purpose of the
present invention it is preferred that the level of the vinyl or
vinylidene aromatic homopolymer be no more than 20 weight percent,
preferably less than 15 weight percent, more preferably less than
10 weight percent, of the total weight of the polymer component of
the composition.
[0069] The substantially random interpolymers may be modified by
typical grafting, hydrogenation, functionalizing, crosslinking or
other reactions well known to those skilled in the art. The
polymers may also be readily sulfonated or chlorinated to provide
functionalized derivatives according to established techniques.
[0070] 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, vinyl or vinylidene
aromatic monomer or hindered aliphatic vinyl or 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.
[0071] 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 (355 MPa). The reactor temperature
will typically be from -30.degree. C. to 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 tempe at the higher end
of the range, that is, temperatures greater than 100.degree. C.
favoring the formation of lower molecular weight polymers.
Polymerizations and unreacted monomer removal 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.
[0072] 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 a major part, the monomer or
monomers to be polymerized.
II. THE INVENTION RELATED TO TWO COMPOSITIONS AND PROCESSES
EMPLOYING THE AFOREMENTIONED POLYMER PARTICLES
[0073] The present invention relates to at least two different
types of compositions employing the aforementioned polymer
particles. The first type of compositions are those which employ a
binding agent to bind the anti-blocking agent to the polymer
particles. The second type of compositions are those which do not
require employing a binding agent, but instead, have an
anti-blocking agent mechanically adhered to the polymer particles.
Those compositions requiring a binding agent will be discussed
first.
[0074] A. Compositions Comprising Polymer Particles, Anti-Blocking
Agent, and Binding Agent
[0075] Compositions comprising polymer particles, anti-blocking
agent, and binding agents are made with polymer particles such as
those described above. The process of forming the compositions of
the instant invention comprises contacting the polymer particles
with an effective amount of a binding agent and an anti-blocking
agent. The polymer particles may be contacted with the
anti-blocking agent either before, after, or simultaneously as the
contact with the binding agent. In any event, both the binding
agent and anti-blocking agent should be contacted with the polymer
particles under conditions such that the polymer particles can be
sufficiently physically coated with the desired agent or
agents.
[0076] Preferably, such contacting is conducted by first liquid
feeding part or all of the binding agent onto the polymer particles
or immersing the polymer particles in part or all of the binding
agent. The anti-blocking agent is then distributed onto the polymer
particles that are coated with the binding agent. If only part of
the amount of binding agent was employed, then the rest of the
binding agent is distributed onto the polymer particles. The means
of contacting and distributing may vary so long as the polymer
particles become sufficiently coated with the anti-blocking agent
such that the anti-blocking agent is adhered to the surface of the
particle and particles with the desired unconfined yield strength
are obtained.
[0077] While not wishing to be bound by any theory, it is believed
that the homogeneity of the thickness of the binding agent coating
and anti-blocking agent coating around the polymer particles
contributes to ability of the polymer compositions of the present
invention to have the desired unconfined yield strengths. It is
believed that such homogeneity of thickness is often determined by
the process of contacting the binding and anti-blocking agents with
the polymer particles. Therefore, it is preferable to employ a
process in which the resulting thickness of the anti-blocking agent
is substantially homogeneous, that is, the layer thickness is
generally uniform around the particle. However, it is not necessary
that each particle or pellet be totally covered with anti-blocking
agent. In addition, it is not necessary that every particle be
covered with any anti-blocking agent. Usually, the process is
sufficient so long as the average amount of surface coating is
above about 50 percent, preferably above about 60 percent.
[0078] Generally, preferable methods include those that create the
thickest anti-block layer at the lowest apparent density. By this
it is meant that if a coating comprised of a given composition
results in a thicker coating than one of the same weight percent,
then the thicker coating will often be more effective in reducing
blocking behavior. For many of the polymers described herein, the
preferred thickness of the anti-block coating is between 1.0
microns and 150 microns. This value may also be expressed in terms
of percent increase in the average size of the pellets or group of
pellets. This is generally between 0.01 percent to 15 percent
depending on amount of anti-block material and type of method used
to apply and process the coating.
[0079] Examples of blending equipment/processes include any
mechanical means of moving the pellets such as a simple tumbling of
ajar, or blending in a conical rotating vessel, ribbon blender,
drum tumbler, paddle blender, agglomeration pan and fluidized bed
operations, etc. A particularly preferable method includes the use
of a pneumatic conveyor under air or inert gas. Moderate stirring,
shaking or even a short distance of conveying in a screw conveyor
can be sufficient for such adequate distribution of the agent or
agents. The type of contacting employed may be the same or
different for the binding agent and anti-blocking agent if the
polymer particles are contacted with the binding agent and
anti-blocking agent at separate times.
[0080] The contacting of the agents and particles can be conducted
at any temperature at which the agent does not evaporate, solidify,
become too viscous or significantly react with the polymer
particles. Such temperatures often vary depending upon the
components of the composition but typically are from -10 to 150,
preferably from 0 to 60, more preferably from 5 to 35.degree.
C.
[0081] 1. Anti-Blocking Agent
[0082] Anti-blocking agents are those agents that inhibit polymer
particle blocking i.e, caking, agglomerating, aggregating and/or
sticking, when physically coated on the surface of the polymer
particles in a sufficient amount. Thus, polymer particles remain
substantially free-flowing even under temperatures, storage times
and compression which might otherwise facilitate caking or
agglomeration.
[0083] The anti-blocking agents of the present invention are
typically not colorants, that is, the anti-blocking agent does not
substantially modify the visual appearance of the polymer to the
naked eye. Compositions of the present invention comprising an
anti-blocking agent appear somewhat similar in color to
compositions lacking an anti-blocking agent. For example, if a
polymer composition is transparent to the naked eye, then the
polymer composition, while slightly cloudy, will also be
substantially transparent to the naked eye after adding the
anti-blocking agent to form a composition of the present
invention.
[0084] While not wishing to be bound by any particular theory, it
is believed that the anti-blocking agents function by inhibiting
the polymers' blocking process. Particularly effective
anti-blocking agents include organic or inorganic compounds such as
those selected from the group consisting of talc, mica, calcium
carbonate, finely divided or fumed silica, organic acids, metal
organic esters, cellulose derivatives, as well as, powdered
polymers which exhibit a TMA of greater than 75.degree. C., such as
powdered polyethylene, polystyrene and polypropylene. Also, some
fillers may also be employed such as those described by The Dow
Chemical Company in WO 99/00449 published on Jan. 7, 1999. Such
fillers include alumina trihydrate, marble dust, cement dust, clay,
feldspar, alumina, magnesium oxide, magnesium hydroxide, antimony
oxide, zinc oxide, barium sulfate, aluminum silicate, calcium
silicate, titanium dioxide, titanates, and chalk. The
aforementioned anti-blocking agents may be employed in purified
form or in mixtures.
[0085] The anti-blocking agent may be employed in any form,
however, powders are generally preferable. While the particle size
of the powder may vary depending upon the polymer and the
anti-blocking agent, preferred powders generally have a mean
particle size of less than about 100, preferably less than about
10, and more preferably less than about 5 microns. Correspondingly,
the powders should generally have a mean particle size greater than
about 0.5 microns.
[0086] The anti-blocking agent is typically employed in an
effective amount. Effective amounts often vary depending upon the
anti-blocking agent, polymer, application process and other
ingredients of the composition. Typically, an effective amount of
anti-blocking agent is that amount which decreases the unconfined
yield strength of the composition by at least about 20, preferably
by at least about 30 percent. In many instances, the unconfined
yield strength may be decreased by over 100, or even 1000 percent
or more.
[0087] Generally, the minimum effective amount of anti-blocking
agent is at least the amount of agent at which the desired
unconfined yield strength is achieved. Generally, the amount of
anti-blocking agent is at least about 0.05, preferably at least
about 0.1, more preferably at least about 0.2 weight percent based
on the total composition.
[0088] Generally, the maximum effective amount of anti-blocking
agent is the greatest amount of anti-blocking agent at which the
physical properties of the polymer are not adversely affected in
the polymer's desired end-use application. Generally, the amount of
anti-blocking agent is less than about 5, preferably less than
about 4, more preferably less than about 1.5 weight percent based
on the total composition.
[0089] 2. Binding Agent
[0090] Binding agents are those agents that hold or fix the
anti-blocking agent to the polymeric particles such that at normal
handling and shipping conditions the anti-blocking agent remains on
the particle. While some anti-blocking agents may also serve as
binding agents themselves, in most instances, the binding agent is
different from the anti-blocking agent.
[0091] The type of binding agent and effective amount will vary
depending upon the anti-blocking agent, polymer, and other
components of the composition. The preferred binding agents are
those in which the viscosity is not so high such that the binding
agent is difficult to apply. On the other hand, the viscosity
should not be so low that excessive dust from the anti-blocking
agent results. Generally, non-penetrating liquids with a viscosity
in the range of 50 to 60,000 centistokes are useful.
[0092] Generally, the binding agent is selected from the group
consisting of polyether polyols, aliphatic hydrocarbon oils such as
mineral oil, and alkanes or alkenes having between seven and 18
carbon atoms optionally substituted with OH, CO.sub.2H, or esters.
Other binding agents include natural oils such as castor, corn,
cottonseed, olive, rapeseed, soybean, sunflower, other vegetable
and animal oils, as well as, naphthenic, paraffinic, aromatic, and
silicon oils, and esters, alcohols, and acids of said oils or their
emulsions. Substances which are often employed as plasticizers or
tackifiers may also be useful as the binding agent. Most preferable
are binding agents which are not thermoplastic in nature.
[0093] A particularly preferable binding agent is a siloxane
polymer having the structural formula -Si(R.sup.1R.sup.-)-0-
wherein the R.sup.1 groups are C.sub.1-C.sub.18 hydrocarbyl groups.
Particularly preferable hydrocarbyl groups include aliphatic and
aromatic groups. A particularly preferable group for R.sup.1 is a
methyl group. These materials are commercial available from Dow
Corning. The aforementioned binding agents may be employed in
purified form, in solutions, emulsions or in mixtures. If the
polymer is to be employed, for example, in a food application, it
may also be desirable that the binding agent be FDA approved. FDA
approved siloxanes having a viscosity of about 350 centistokes are
commercially available and often useful for this purpose. Mixing of
the anti-blocking agent and the polymer particles should be kept to
a minimum, especially when using non-thermoplastic binding agents.
Too much mixing may result in surface segregation, resulting in
non-homogeneous layers.
[0094] B. Compositions Comprising Polymer Particles and an
Anti-blocking Agent Mechanically Adhered to the Particles
[0095] In some situations it may not be desirable to employ a
binding agent. Such situations include, for example, when the
binding agent will interfere with the end-use application of the
polymer. Also, in some situations it may be desirable to minimize
the amount of anti-blocking agent. In this manner, the unassociated
environmental dust can be minimized. It also advantageous to reduce
the amount of anti-blocking agent if, for example, films are being
made from the composition and optical properties are important.
[0096] The compositions that do not require a binder employ the
same types of polymer particles and anti-blocking agents as
discussed above. However, the amount of anti-blocking agent can be
reduced to less than about 3, preferably less than about 1.5, more
preferably less than about 0.5, most preferably less than about 0.3
percent by weight of the composition. Correspondingly, the
effective amount of anti-blocking agent is typically at least about
0.08, preferably at least about 0. 1, more preferably at least
about 0.15 percent by weight of the composition.
[0097] As stated above, the unassociated environmental dust can be
minimized. While this can be directly observed, it can also be
empirically measured by the following method:
[0098] Attrition Test
[0099] The attrition test is performed by using a commercially
available vacuum cleaner having a 1.5 horsepower (1.119 kilowatts)
motor, with the filter removed. On kilogram of coated pellets is
loaded into a container, such as a bucket and the pellets are
vacuumed through a 1.25 inch (3.125 cm) diameter vacuum hose and
the pellets then exit into the vacuum receiver. The pellets are
then re-weighed to establish the amount of coating which was lost.
The attrited coating exits the vacuum through the air vent in the
absence of the filter. The pellets are removed from the receiver
and placed back into the bucket and the vacuum step is repeated for
sufficient repetitions until little to no weight loss is
measurable.
[0100] When a binding agent is not employed, the process varies
slightly from that described above. The process comprises
mechanically adhering an effective amount of anti-blocking agent to
more than about 40, preferably more than about 50 percent, most
preferably more than about 60 percent of individual polymer
particles. In this manner, polymer particles that have an effective
amount of anti-blocking agent adhered will serve as a barrier to
prevent large numbers of polymer particles that do not have an
effective amount of anti-blocking agent from agglomerating or
blocking.
[0101] The polymer particles that have an effective amount of
anti-blocking agent adhered will often resemble those particles
depicted in FIGS. 1, 2, and 4. That is, an individual polymer
particle will have an anti-blocking agent embedded into the polymer
particle. The depth to which the particle is embedded and the
amount of anti-blocking agent will determine the thickness of the
anti-blocking layer on the polymer particles. This thickness will,
of course, also vary depending upon the type of polymer, the size
of the particles, the type of anti-blocking agent, and the desired
anti-blocking.
[0102] Generally, it is desirable to employ conditions to obtain a
substantially homogeneous thickness wherein the diameter of the
anti-blocking particle determines the minimum thickness of the
coating. The maximum thickness is generally about 5 times the
diameter of the anti-blocking particle used. If, for example, talc
is employed which is generally spherical and has a particle
diameter of 0.5 to 10 micrometers and a polymer particle is
employed which is generally spherical and has a particle diameter
of 3 mm, then it is preferable to mechanically adhere the talc such
that at least 10 percent, and up to about 90 percent, of the
diameter is embedded into a given polymer particle. This can be
measured by, for example, scanning electron microscopy (SEM).
[0103] The anti-blocking agent can be mechanically adhered to the
polymer particles in any way. This may be accomplished
simultaneously with or subsequent to the particle formation. One
way in which this can be accomplished is, for example, by impact
coating the polymer particles such that the desired amount of
anti-blocking agent is adhered to the desired amount of polymer
particles. This can be facilitated by the use of steam.
[0104] Another way to mechanically adhere anti-blocking agent is to
soften the polymer particles either before, simultaneously with, or
after contacting the polymer particles with the anti-blocking
agents. The softening may be done in any manner so long as the
surface is softened sufficiently to adhere an effective amount of
the anti-blocking agent to the exterior surface of the polymer
particles. However, the polymer particles must not be softened so
much that there are no longer discrete particles, that is, the
polymer particles should not become melted or adhered together. In
general, one can usually observe the surface of the polymer
particles becoming slightly tacky and ready for coating. The point
at which this occurs will vary by polymer and the type of
anti-blocking agent employed.
[0105] If the softening is done subsequent to particle formation
then a variety of methods can be employed. The choice of method
will vary depending upon the type of polymer, type of anti-blocking
agent, and the desired results. Generally, heating by hot air,
radiation (UV, IR, visible), contact heating, or a combination
thereof may be employed. In general, one can usually observe when
the particles have been heated sufficiently because the surface of
the polymer particles will become slightly tacky and ready for
coating. The point at which this occurs will vary by the type of
polymer, the size of the particles, and the type of anti-blocking
agent employed.
EXAMPLE ONE
[0106] Samples were prepared by placing a predetermined amount of
polymer pellets into a drum (with revolving capabilities) or a
plow-share mixer. In some samples, a polystyrene or polyethylene is
blended into the core material. The addition of the blend component
decreases the pellets ability to deform, thus decreasing the
ability to self-weld. This significantly improved anti-blocking
characteristics. A predetermined amount of a binding agent was then
introduced by spraying directly onto the pellets via a spritzer
bottle or an air brush. The sprayed pellets were tumbled until the
pellets were substantially coated with the binding agent. A dusting
agent was directly applied to the mixer and tumbled for 0.5 to 2
minutes until free dust is no longer visible.
[0107] The pellets were removed and, if an emulsion was used,
allowed to dry. The pellets were then subjected to a predetermined
force at an elevated temperatures for various times. The pellets
were then evaluated based on the force required to break the
pellets apart. Specific parameters and results are shown in the
text and tables below.
[0108] Samples 1-6
[0109] Polymer particles of an ethylene-styrene interpolymer (ESI)
having 69 percent incorporated Styrene and a 1.0 g/10 min melt
index measured by ASTM D-1238, condition 190/2.16 having a typical
diameter of 3 mm (about 32 particles per gram) were employed in the
aforementioned method with a type and amount of binding agent and
anti-blocking agent as specified below. The yield strength was
determined after 3 days at 37.degree. C., 236 pounds per square
inch (psi) (165,932 kg/m.sup.2) load. Samples 5 and 6 also include
20 weight percent of general purpose polystyrene (Mw=192,000).
Results are shown in Table 1.
[0110] Samples 7-8
[0111] Polymer particles described in Table 1 below were employed
in the aforementioned method with a type and amount of binding
agent and anti-blocking agent specified below in Table 1. The yield
strength was determined in the same manner as for Samples 1-6 and
the results are shown in Table 1. TABLE-US-00001 TABLE 1 One mm
Binding agent and Anti-blocking agent and Yield Strength
penetration amount amount Before, pounds per Yield Strength After,
temperature Sample (weight percent) (weight percent) square foot
pounds per square foot (.degree. C.) 1 ESI 0.2 percent Siloxane 1
percent ULTRA-TALC* >7000 67 (327 kg/m.sup.2) 70.9 609
(>34174 kg/m.sup.2) 2 ESI 0.2 percent Siloxane 2 percent
ULTRA-TALC* >7000 48 (234 kg/m.sup.2) 70.9 609 (>34174
kg/m.sup.2) 3 ESI 0.2 percent Siloxane 3 percent ULTRA-TALC*
>7000 10 (49 kg/m.sup.2) 70.9 609 (>34174 kg/m.sup.2) 4 ESI
0.2 percent Siloxane 2 percent calcium stearate >7000 14 (68
kg/m.sup.2) 70.9 (>34174 kg/m.sup.2) 5 ESI 0.2 percent Siloxane
2 percent calcium stearate >7000 0 (freely flows from 70.9
(>34174 kg/m.sup.2) cylinder) 6 ESI 0.2 percent Siloxane 2
percent ULTRA-TALC* >7000 0 (freely flows from 70.9 609
(>34174 kg/m.sup.2) cylinder) 7 Ethylene/ 0.15 percent 0.5
percent ULTRA- >7000 0 (free flowing) NA Butene Siloxane TALC*
609 (>34174 kg/m.sup.2) Grade # 8100 8 ITP** 0.15 percent 0.5
percent ULTRA- 200 (976 kg/m.sup.2) 0 (free flowing) NA Polymeric
Siloxane TALC* 609 adhesive *Trademark of Specialty Minerals Inc.
**ITP = single site catalyzed ethylene/1-octene copolymer having a
melt index greater than 400 g/10 minutes and density of 0.87
g/cm.sup.3. NA = Not available
EXAMPLE TWO
[0112] Three 1000 gram samples of the same ethylene-styrene
interpolymer were coated via the method described in Example One
with the type and amount of binding agent and antiblocking agent
specified in Table 2 below. The siloxane employed was a Dow Corning
1664.TM. emulsion which contains 50 percent polydimethyl siloxane.
Polydimethyl siloxane in the pure state exhibits a measurable
viscosity at 20 C of 60,000 centistokes. The yield strength was
determined in the same manner as for Samples 1-6 and the results
are shown in Table 2. The 1 mm penetration temperature of the
polymer of samples 9, 10 and 11 was 70.9.degree. C. TABLE-US-00002
TABLE 2 Binding agent and Yield Strength amount Anti-blocking agent
and amount Yield Strength Before, After, pounds per Sample (weight
percent) (weight percent) pounds per square foot square foot 9 ESI
0.25 percent 1 percent Ultra-talc >7000 27.5 Siloxane (>34174
kg/m.sup.2) (134 kg/m.sup.2) 10 ESI 0.15 percent 2 percent calcium
stearate >7000 88.0 Siloxane (>34174 kg/m.sup.2) (430
kg/m.sup.2) 11 ESI 0.09 percent 0.5 percent calcium stearate
>7000 15 Siloxane (>34174 kg/m.sup.2) (73 kg/m.sup.2)
EXAMPLE THREE
[0113] Two 1000 gram samples of ethylene/styrene interpolymers were
coated via the method described in Example One with the type and
amount of binding agent and antiblocking agent specified in Table 3
below except that the binding agent was sprayed onto the pellets
using an aspirating siphon feed and atomizing gas system. The
binding agent is a halocarbon/ fluorocarbon fluid, Flurolube.TM. LG
160, which is a product of the Hooker Chemical Company. The yield
strength was determined in the same manner as for Samples 1-6 and
the results are shown in Table 3. The 1 mm penetration temperature
of the polymer of samples 12 and 13 was 70.9.degree. C.
TABLE-US-00003 TABLE 3 Binding agent and Anti-blocking agent amount
and amount Yield Strength Before, Yield Strength After, Sample
(weight percent) (weight percent) pounds per square foot pounds per
square foot 12 ESI 0.115 percent halocarbon/ 0.5 percent Ultra-talc
>7000 288 fluorocarbon fluid (>34174 kg/m.sup.2) (1406
kg/m.sup.2) 13 ESI 0.115 percent halocarbon/ 1.0 percent Ultra-talc
>7000 12 fluorocarbon fluid (>34174 kg/m.sup.2) (59
kg/m.sup.2)
EXAMPLE FOUR
[0114] 1000 gram samples of the polymer particle compositions
listed in Table 4 were obtained. The sample particles were softened
by applying heat as described in Table 4 until the bulk temperature
reached the temperature of Table 4. The polymer particles were then
contacted with the amount of talc described in Table 4 such that
the talc was mechanically adhered to sample particles. The yield
strength was determined in the same manner as samples 1-13 and the
results are shown in Table 4. TABLE-US-00004 TABLE 4 Bulk
temperature of Yield Strength Yield Strength Amount of Talc
particles during Before, pounds After, pounds Sample (ppm by
weight) heating Type of Heat per square foot per square foot 14
DS201.sup.1 10,000 60.degree. C. Visible Infrared >7000 0
(>34174 kg/m.sup.2) 15 DS201.sup.1 10,000 148.degree. C. Hot Air
>7000 0 (>34174 kg/m.sup.2) 16 Blend of 90 percent 2000
100.degree. C. Hot Air >7000 0 DS201.sup.1 and 10 percent
PS.sup.2 (>34174 kg/m.sup.2) 17 DS201.sup.1 2000 100.degree. C.
Hot Air >7000 0 (>34174 kg/m.sup.2) 18 DS201.sup.1 1500
75.degree. C. Hot Air >7000 0 (>34174 kg/m.sup.2) 19 Blend of
90 percent 1500 65.degree. C. Hot Air >7000 0 DS201.sup.1 and 10
percent PS.sup.2 (>34174 kg/m.sup.2) 20 Blend of 90 percent 1000
50.degree. C. Hot Air >7000 18 (88 kg per DS201.sup.1 and 10
percent PS (>34174 kg/m.sup.2) square meter) 21 DS201.sup.1 2000
52.degree. C. Hot Air >7000 1035 (5053 kg (>34174 kg/m.sup.2)
per square meter) 22 DS201.sup.1 2000 40.degree. C. Invisible
>7000 0 Infrared (>34174 kg/m.sup.2) .sup.1DS201 is an
ethylene/styrene interpolymer comprising polymer units derived from
69 weight percent styrene, and ethylene, having a melt index of
about 1 g/10 minutes. .sup.2PS = homopolymer polystyrene having a
melt flow rate (condition 200/2.16) of about 7 g/10 minutes and a
molecular weight of about 158,000.
EXAMPLE FIVE
[0115] The attrition test described earlier was used to test
attrition of the antiblocking agent (talc) on an ESI having been
blended with 1 percent talc was the control. After 6 passes through
the vacuum, about 95 percent of the talc had been removed. In
comparison, a similar polymer having been coated using 0.2 percent
siloxane and 1 percent talc lost only about 10 percent after 12
passes through the vacuum. Finally, adhering the talc to the
surface of the particles (without use of a separate binding agent)
at a level of 2000 ppm of talc retained about 95 percent of the
talc after 6 passes through the vacuum (about 5 percent talc was
lost).
EXAMPLE SIX
[0116] Ethylene/propylene/diene polymer particles (EPDM) having a
Mooney viscosity of 30-40 (tested in accordance with ASTM D
1646-89, using a shear rheometer at 125.degree. C.) and a
crystallinity of less than 10 percent at 20.degree. C. were also
coated with 1 percent ULTRA-TALC.TM. 609 at a temperature of
110.degree. C. using hot air. The sample was consolidated at a
force equivalent to 160 pounds/square foot (781 kg/m.sup.2) force
at 35.degree. C. for 3 days. The unconfined yield strength at 20
mm/minute plunger rate was about 650 pounds/square foot (3173
kg/M.sup.2). Untreated EPDM has an unconfined yield strength of
greater than 7000 pounds/square foot (>34174 kg/M.sup.2).
* * * * *