Note: Descriptions are shown in the official language in which they were submitted.
D-16899
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DISPERSIONS OF POLYMER ADDITIVES
IN F~TT~ ~CI~ ESTE~$ _
Field of the Invention
The present invention relates to dispersions
of polymer additives in a continuous liquid phase.
More particularly, the present invention relates to
the distribution of a dispersion of solid additives
throughout polymeric compositions, especially
thermoplastic polymers.
Bakqround of the Invention
Stabilizers are commonly combined with
polymers for various purposes including the
prevention of thermal, oxidative and/or
photo-degradation of the polyrner during fabrication,
processing, storage and end use. The effectiveness
of the stabilizer in performing its intended purpose
is a function of how uniformly mixed or dispersed the
stabilizer is within the polymer. Areas containing
low levels of stabilizer can degrade more rapidly
than ar~as containing higher levels of the
stabilizer. In many instances the stabilizers are
solids which melt at high temperatures and are
difficult to disperse throughout the polymer. This
inability to disperse the stabilizer often reduces
the overall performance of the polymer.
A number of procedures well known to the art
have been used to incorporate stabilizers and other
additives into polymer systems. For example, high
shear mixing is frequently employed. To obtain
acceptable dispersion, this method requires
application of high shear forces for extended periods
D-16899
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of time to raise the temperature of the polymer to
form a molten material. Since many stabilizers have
significantly higher melting temperatures than the
polymer, the additives do not melt and are often
distributed non-uniformly in the polymer.~ E~posure
of the polymer to high temperatures during high shear
mi~ing can result in polymer degradation.
Another method is melt e~trusion by which
the stabilizer is distributed in the polymer as it is
being e~truded through a die. While this method
operates at lower temperatures and therefore does not
cause polymer degradation to the same extent as high
shear mi~ing, this technique does not adequately
distribute small levels of stabilizers uniformly in
the resin. Melt e~trusion tends to be useful
primarily for mi~ing large quantities of materials
homogeneously.
Accordingly, a need exists to distribute
stabilizers uniformly throughout a polymer without
subjecting the polymer to conditions which might
induce polymer degradation.
Summary nf ~he Inventio~
The present invention provides particular
stable dispersions of polymer stabilizers. The
dispersions comprise a normally liquid fatty acid
ester of a polyhydric organic compound as the liquid
or continuous phase. The discrete phase of the
dispersion is a stabilizer. The present invention
also provides a method for uniformly distributing
polymer stabilizers throughout polymeric
compositions, such as polyolefins.
D-16899
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Petailed pe~ription of the Invention
By the teachings of this present invention,
stable dispersions of polymer stabilizers are
provided using normally li~uid fatty acid esters of
polyhydric organic compounds as the liquid or
continuous phase of the dispersion. The stable
dispersions of the invention can be distributed
uniformly in various polymers, and with particular
advantage in thermoplastics, by blending the
dispersion and polymer by a variety of mixing
techniques known in the art including melt extrusion.
The liquid or continuous phase of the
dispersions of this invention comprises a normally
liquid, at ambient conditions, fatty acid ester of a
polyhydric organic compound. The fatty acids from
which the esters are derivable can be saturated or
ethylenically unsaturated and usually have from 12 to
18 carbon atoms. The preferred class of polyhydric
compounds, in turn, from which the fatty acid esters
are derivable consist of carbon, hydrogen and oxygen
and contain from three to six hydroxyl groups which
can be the terminal hydroxyl groups of etho~ylated
moieties. Oxygen can also be present as the cyclic
ether group,
I
H-C~
¦ O, in which event the polyhydric
H-C/
I
alcohol has no more than four hydroxyl groups.
Oxygen can also be present in the polyhydric alcohol
as acyclic ether linkages such as in the
D-16899
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aforementioned hydroxyl-terminated ethogylated or
poly(o~yethylene) moieties. It is to be understood
that the fatty acid ester can contain zero or from
one to si~ hydro~yl-terminated poly(ogyethylene)
chains. When the ester does contain such chains,
i.e., -(OC2H4)n-OH, the total average number (n) Of
o~yethylene units in the ester is a positive number,
usually ranging from about 1 to about 100. The
continuous phase of the dispersions of this invention
may comprise any combination of the aforesaid types
of fatty acid esters.
Most preferably the continuous phase of the
dispersions contain fatty acid esters of sorbitan,
glycerol or mixtures thereof. Illustrative of
suitable sorbitan and glyceryl esters are sorbitan
monooleate, sorbitan monolaurate, sorbitan trioleate,
glyceryl trioleate, glyceryl monooleate, and the
like. Various sorbitan esters, such as sorbitan
monooleate and sorbitan monolaurate, are available
commercially as Span 80 a~d Span 20 respectively from
Imperial Chemical Industries Ltd. (ICl). Similarly,
various glyceryl esters are commercially available
from Witco Corporation. Poly(o~yethylene)-containing
or ethoxylated derivatives of the sorbitan or
glyceryl esters can also be used in the present
invention. The latter materials are also
commercially available from ICI, such as for e~ample,
Tween 20. Of the above ester compositions,
especially preferred as the continuous phase of the
dispersions of this invention are sorbitan
monooleate, sorbitan monolaurate and glyceryl
trioleate.
D-16899
2~9~ ~i2
The continuous phase of the dispersion may
also contain other liquids which are miscible in the
fatty acid esters of the polyhydric organic
compound. Preferably, the second liqui~ of the
continuous phase also improves the properties of the
polymer. Illustrative liquids include, but are not
limited to, processing aids, liquid stabilizers and
lubricants. Liquid stabilizers include
organomodified silicones such as hindered amine
silicones, including W SIL~ 299 (Enichem Co.).
Especially preferred organomodified silicones are
polyether silicone processing aids such as VCARSIL~
PA-l (Union Carbide Chemicals and Plastics Company
Inc.)
The above-described fatty acid esters of
polyhydric coumpounds are known to be useful as
lubricants and surface active agents. Therefore,
their use as the continuous phase of the dispersions
of this invention allows for the elimination or
reduction in the concentration of other additives for
such purposes.
Improved performance of a polymer is noted
as the stabilizers become more uniformly distributed
within the polymer becomes more uniform. In
particular, color and resistance to thermal
degradation improve as stabilizers, such as
antio~idants are more uniformly dispersed within the
polymer. Illustrative of but not limited to then
types of stabilizers which can be used in the present
invention are ultraviolet light stabilizers,
thermostabilizers, antioxidants, catalyst
deactivators and acid neutralizers. Stabilizers are
D-16~99
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important additives because of their ability to
modify overall polymer performance. Because of their
high cost relative to the cost of most polymers, it
is essential that staoilizers are uniformly
distributed throughout the polymer to realize ma~imum
benefit.
As used herein, the term "stabilizer" is
meant to include all materials which can be added to
polymer compositions for the purpose of improving or
retaining the polymer's properties under various
conditions of exposure and use. Although many
stabilizers are solids, liquid stabilizers can also
be employed in the present invention. The better the
dispersion of the stabilizer in the polymer, the
better the stabilizer efficiency. Stabilizers
contain polar moieties and often are particularly
troublesome to disperse into relatively non-polar
polymer resins, particularly polyolefin resins. For
e~ample, the use of ETHANOX~ 330, a relatively high
molecular weight and high melting (244C)
antioxidant, in polypropylene and nylon theoretically
offers high performance, but has been excluded from
many applications because of the difficulty in
obtaining uniform additive-resin dispersions. For
similar reasons, relatively polar zinc oxide, a
low-cost acid scavenger, also is not used routinely
for stabilizing polyolefins because it is difficult
to disperse uniformly. ~ore particularly, the
present invention provides a solution to the problems
associated with attempts to disperse polar additives
into non-polar polymers.
Specific e~amples of the stabilizers
component of the dispersions of this invention
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include: fatty amine, fatty amide antistatic agents
and catalyst deactivators such as KEMAMINE~ and
XEMAMIDE~ and ATMER~ 163 (witco Chemical Co.);
stabilizers including organic phosphites, and other
organic phosphorus compounds, such as
tri-n-dodecylphosphite, the bis-substituted
pentaerythritol diphosphites such as bis~2,4-di-t-
butylphenyl) pentaerythritol diphosphite, tris(mono-
and di-nonylphenyl)phosphite IRGAFOS~ 168 (Ciba -
Geigy); phosphonites including fluorophosphonites
such as ETHANOX~ 398 (Ethyl Corp) and SANDOSTAB~
P-EPQ ~Sandoz); hindered phenols, such as octadecyl
3-(3',5'-di-t-butyl-4-hydro~yphenyl)- propionate,
IONOL~ (Shell), TOPANOL~CA (ICI); IRGANOX~
antio~idants such as IRGANOX~ 1076, 1093, 1098 and
IRGANOX~ 1010 (tetrakis[methylene-3(3'-5'-
di-tert-butyl-4'hydro~yphenyl)propionate] methane)
(Ciba-Geigy); and the ETHANOX~ antio~idants such as
ETHANOX~ 330 (1,3,5-tri-methyl-2,4,6-tris-
(3,5-di-tert-butyl-4-hydroxybenzyl) benzene) and
ETHANOX~ 702 (Ethyl Corp.); and ISONOX~ 129
(2,2'-ethylidene-bis(4,6-di-t-butyl)phenol)
(Schenectady Chemical); the CYANOX~ antioxidants
including CYANOX~ 1790 (American Cyanamid); the
GOOD-RITE~ antioxidants including GOODRITE~ 3114
(B.F. Goodrich Chemical Co.); antio~idants/metal
deactivators, such as the NAUGARD9 products such as
NAUGARD~ XLl (Uniroyal Inc.) and IRGANOX~ MD 1024
(Ciba-Geigy); thiodipropionate stabilizers such as
dilauryl thiodipropionate; hindered amine compounds
such as those containing tetra alkyl-piperidinyl
functionality, including the light stabilizers and W
D-16899
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absorbers such as TIN W IN~ 149, TIN WIN~ 326 and 327,
TIN W IN~ P, TIN W IN~ 622LD (Ciba-Geigy), CYANOX~ 3346
(American Cyanamid), GOO~RITE~ 304~ (B.F. Goodrich
Chemical Co.); benzophenone stabilizers, such as
CYASORB~- W 2098 (American Cyanamid), W INUL~M 90 and
W INUL~ 490 (BASF); blends of organic phosphorus
compounds and hindered phenol antioxidants including
IRGANOX~ 1411, 1412, 501W, 712FF, B-225, B-215, and
900 (Ciba-Geigy); nucleating agents such as
dibenzilydene sorbitol; acid neutralizers including
metal o~ides such as zinc oxide; hydrotalcites; metal
stearates; calcium lactate and the like.
The concentration of the dispersion, i.e.,
the weight of the discrete phase (stabilizer) in the
liquid phase, is usually about 0.1 to about 80
percent by weight, generally about 1 to about 60
percent by weight and usually about 10 to about 50
percent by weight.
The dispersions of this invention are
prepared by admixing the stabilizer with the normally
liquid fatty ester of a polyhydric organic compound
by using a high shear mi~er such as a COWLES~ mi~er.
Also within the scope of this invention are mi~tures
of solid and liquid stabilizers as the discrete phase
of the dispersion.
The process of the present invention can be
used for dispersing the various polymer stabilizers
in a wide variety of thermoplastic systems. The
process can be advantageously employed with
homopolymers, copolymers and polymer blends.
Illustrative of, but not limited to the polymers
include polyolefins, such as high density
2 ~ r,; ~j ~
polyethylene, low density polyethylene (LDPE), linear
low density polyethylene (LLDPE), polypropylene,
polyesters, polyvinyl chloride, polyacrylates,
polystyrene, styrene-butadiene copolymers, polyvinyl
chloride/polyvinylacetate copolymers, ethylene/
acrylic acid copolymers, ethylene/acrylic acid/vinyl
acetate terpolymers and the like.
Stabilizers which are used to formulate the
dispersions of this invention generally have the
following particle size distribution: at least about
95% by weight of the particles have a diameter of
less than 150 microns and about 20 percent by weight
have a particle size of less than about 20 microns.
Preferably at least about 95~ by weight of the
particles have a diameter of less than 100 microns
and at least 35% by weight have a particle size of
less than 10 microns. Even more preferable are
stabilizers having an average particle size of less
than 20 microns and more than 50% by weight less than
10 microns.
Particularly desirable for purposes of this
invention are stabilizers having the particle size
described above which are comprised of a bimodal size
distribution. A bimodal distribution has two
separate peaks around which the particles are
clustered. Especially advantageous are those bimodal
distributions where the weight fraction of the larger
particles, relative to the smaller particles, is from
about 30 to about 90 percent of the total weight of
the particles and the ratio of the average particle
size of the larger particle size is at least two and
preferably from about 2 to about 100. The
D-16B99
_ lo - 2~ 3~
dispersions having this particle size and weight
distributions have been found to be not only
e~tremely stable but also have a lower viscosity
compared to dispersions only containing smal~er
particles.
While not wishing to be bound by any
specific theory, it is believed that the stability of
the dispersions of this invention is due to the
occurrence of controlled agglomeration. Controlled
agglomeration is believed to result in a structure
which extends through the whole li~uid volume and
supports the individual particles, preventing the
particles from settling. Consequently, there is no
need to incorporate e~traneous ingredients in the
dispersion, such as surfactants and the like, whose
sole purpose is to ensure the stability of the
dispersion.
As used throughout this specification, which
includes the claims, ~stable dispersions" are those
wherein there is less than about 5 percent by volume
separation of the liguid phase, evidenced by the
formation of a two-phase system, after centrifugation
of the dispersions under a force of one-hundred times
the force of gravity (lOOG) for one hour.
Particularly desirable are those dispersions which
exhibit less than about 5 percent by volume
separation after centrifugation under a force of
1400G for 9 hours. Dispersions which exhibit less
than about 5 percent by volume separation after
centrifugation under a force of 1400G for 4 hours are
considered as stable, under ambient conditions, for
at least 6 months. As used herein the phrase
dispersion also encompasses suspensions and emulsions.
D-16899
11
2 ~ J
The dispersion containing the desired
stabilizer in dispersed form is added directly to the
thermoplastic resin which can be in either the form
of solid particles (in pellet, granule, powder, etc.,
form) or in the molten state. In other words, the
stable dispersions of the present invention can be
pre-blended with polymer particles before polymer
processing operations such as melt e~trusion,
injection molding and the like, or the dispersion can
be added directly to a molten polymer during its
processing. The compounding of the dispersion and
thermoplastic resin may be done by spraying or by
mixing or tumbling the resin and suspension in a
ribbon blender, utilizing a two-roll mill, an
e~truder, including single screw and multiple screw
e~truders, a Banbury (Farrel Corp.) or Brabender
mixer. Suitable procedures and equipment will
readily occur to those skilled in the art of polymer
processing. Concentrates or master batches of the
dispersion and resin may be produced and blended with
virgin resin such as on a mill before final
processing. The rolls on a two-roll mill may operate
at different speeds and temperatures. In spite of
the simplicity of the milling operation, extrusion is
usually preferred for blending the suspension and
resin since an e~truder can operate continuously, for
example to produce strands that may be cut by a
rotating knife to produce pellets.
The stable dispersion can be added to the
synthetic resin at the end of the resin manufacturing
process, such as directly after resin polymerization
or polycondensation, for example while it is still
D-16899
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~ ~3 ~ 2 t~
molten or to powdered or pelleted polymer particles.
However, it also is possible, and often more
convenient, to admix the dispersion with the
synthetic resin subsequently during one of its myriad
processing stages, for e~ample prior to or during
extrusion. Using a fluid dispersion not only
facilitates the mixing/dispersing of the additive
with the polymer, but also makes it easier to control
the amount of stabilizer mixed with the resin
polymer. The dispersion can be mi~ed with polymer by
high shear mixing, tumbling in a drum or directly
metering through an extruder.
In any event, a homogeneous distribution of
the stabilizer with the polymer is achieved without
the danger of thermally degrading the polymer or
additive and without agglomerating the stabilizer.
The advantage of having uniformly dispersed
stabilizer is reflected in the aging characteristics
of the finished product. When the additives are
adequately dispersed, there are no localized areas
starved of stabilizer which can fail due to polymer
ogidation .
The amount of dispersion added to a
thermoplastic resin will vary and depend, in part,
upon the concentration of the dispersion, the actual
thermoplastic resin and the effect desired. Usually,
this is on the order of about 0.01 to about 2 percent
by weight, preferably about 0.02 to about 1 percent
by weight, based on the weight of the resin.
Whereas the exact scope of the instant
invention is set forth in the appended claims, the
following specific examples illustrate certain
D-16899
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aspects of the present invention and more
particularly, point out methods of evaluating the
same. All parts and percentages are by weight unless
otherwise specified. Particle size in microns, as
reported herein, was determined using a MICROTRAC~
particle size analyzer.
~efinitions
The following designations used in the
E~amples and elsewhere herein have the following
meaning:
Oxidative Induction Time (OLT) was
determined at a temperature of 200C under an oxygen
feed of 50 ml per minute. The test is a
determination of o~idative degradation stability.
Average oxidative induction time is reported in
minutes and described in chapter 9 of the following
publication:
H. E. Bair
Thermal Analysis of Additives in Polymers
Thermal Characteri~ation of Polymer Materials
E. A. Turi Ed.
Academic Press, 1981
New York
ellowness Index (YI) was determined in
accordance with ASTM D-1925-70, before and after
aging at 80C for a certain time period. A Pacific
Scientific Colorgard System/OS instrument was used in
determination of the color.
D-16899
2 ~ s~ ~i 2
SPAN 80: Sorbitan monooleate supplied by Imperial
Chemical Industries Ltd.
SPAN 20: Sorbitan monolaurate supplied by Imperial
Chemical In~dustries Ltd.
Ethanox~ 330:
(1,3,5-trimethyl)-2,9,6-tri(3,5-di-tert-butyl-4
hydro~ybenzyl)benzene, manufactured by Ethyl
Corporation.
Irganox~ 1010:
~tetrakis [methylene-3(3',5'-di-tert-butyl-4'
hydroxyphenyl)propionate~ methane, marketed by
Ciba-Geigy Corporation.
PA-l: VCARSIL~ PA-l is a polyether silicone
processing aid from Vnion Carbide Chemicals and
Plastics Company Inc., Danbury, CT.
Vano~ 1001: ~ substituted aromatic amine sold by
R. T. Vanderbilt Company, Inc. as a general purpose
antioxidant.
Cynox 711: Ditridecylthiodiproprionate made by
American Cyanamid Company.
Weston 399B: Tris(nonylphenyl)phosphite available
from Borg-Warner Chemical Co.
1 ~I LLDPE: Copolymer of ethylene/l-butene having a
melt index of 1 and density of 918 Kg/m3
D-16899
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2~9~ rj~
g - gram or grams.
Example 1
309 Ethanox~ 330 (50% by weight of the particles had
a particle size less than 75.5 microns) 309
micronized Ethano~ 330 (50% by weight of the
particles had a particle size less than 3.9 microns),
and 60g SPAN 80 were blended in a Cowles mixer at
1500 RPM for 5 minutes. The resulting dispersion was
sufficiently stable to withstand 4 hours of
centrifugation at a force of 1400G's.
Example 2
40g micronized Irganox~ 1010 (50% by weight of the
particles had a particle size less than about 3.2
microns) 60g of Span 80 were blended in a Cowles
mixer at 1500 RPM for 5 minutes. The resulting
dispersion was sufficiently stable to withstand 1
hour of centrifugation at a force of 1400G's.
Egample 3
40g micronized Irganox 1010 (50% by weight of the
particles had a particle size less than about 3.2
microns) and 60g of Span 20 were blended in a Cowles
mi~er at 1500 RPM for 5 minutes. The resulting
dispersion was sufficiently stable to withstand 1
hour of centrifugation at a force of 1400G's.
E~m~
lg PA-l and lg Weston 399B were mixed. They were not
mlsclle.
D-16899
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E~ample 5
E~ample 4 was repeated except that 2g of Span 20 was
added. The solution was mi~ed and was miscible.
This Example demonstrates the improved miscibility of
liquids when Span 20 was added to the formulation.
E~amPle 6
lg PA-l and lg SPAN 80 were mixed. They formed a
miscible solution.
~ample 7
lg Weston 399B and lg SPAN 80 were mi~ed. They
formed a miscible solution.
E~am~le 8
lg glyceryl trioleate and lg Weston 399B were mi~ed.
They formed a miscible solution.
E~ample 9
lg Cyanox 711, 19 Vanox 1001 and lg glyceryl
trioleate were mixed~ They formed a miscible
solution.
Example 10
lg Vanox 1001, lg mineral oil and lg glycerol
trioleate were mixed. They formed a miscible
solution.
Example 11
72g micronized Ethanox 330 (50% by weight of the
particles had a particle size less than about 3.9
microns) and 60g glyceryl trioleate were blended in a
D-16899
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Cowles mixer at 1500 RPM for 5 minutes. The
resulting dispersion was sufficiently stable to
withstand 4 hours of centrifugation at a force of
140OG's.
Example 12
40g PA-l and 90g SPAN 80 were mixed. They formed a
miscible solution. To the above solution 40g
micronized Ethanox 330 (50~ by weight of the
particles had a particle size less than about 3.g
microns) and 40g unground Ethanox 330 ~50% by weight
of the particles had a particle size less than about
75.5 microns) were blended in a Cowles mixer at 1500
RPM for 5 minutes. The resulting dispersion was
sufficiently stable to withstand 4 hours of
centrifugation at a force of 1400G's.
~xample 13
Respective compositions, the formulations of which
are described in Table 1 hereunder, were compounded
in a Henschel mixer and extruded at 218C through a
strand die fitted to a Brabender extruder and
pelletized.
D-16899
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Formulation Z YI lday 80~C YI 7day6 80-C OIT(min)
99.95% LLDPE
0.052 Micronized
Irganox 10l0 20 20 28.2
99.85~ LLDPE 12 12 30.3
0.05% Micronized
Irganox 1010
0.1% SPAN 80
(The Irganox l010 and
SPAN 80 were added to
the LLDPE a6 a di6per6ion.
Ihe di6per6ion6 was formed by
blending the component6
together in a Cowle6 mixer
at 1500 rpm for 5 minutes.)
The above results demonstrate the
improvement in the stabilization of the polymer when
the dispersion of the invention was employed.
