This application is a continuation-in-part of copending U.S. application
S.N. 08/906,870, filed August 6, 1997, which is in turn based on provisional application
60/0022432 filed August 6, 1996.
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to thermoplastic elastomer compositions based
on a blend of a thermoplastic material and a cured or non-cured elastomer, and
to the processing of such compositions.
Description of Related Art
A thermoplastic elastomer is generally defined as a polymer or blend
of polymers that can be processed and recycled in the same way as a conventional
thermoplastic material, yet has properties and performance similar to that of
vulcanized rubber at service temperatures. Blends or alloys of plastic and elastomeric
rubber have become increasingly important in the production of high performance
thermoplastic elastomers, particularly for the replacement of thermoset rubber
in various applications.
Polymer blends which have a combination of both thermoplastic and
elastic properties are generally obtained by combining a thermoplastic polymer
with an elastomeric composition in a way such that the elastomer is intimately
and uniformly dispersed as a discrete particulate phase within a continuous phase
of the thermoplastic. Early work with vulcanized compositions is found in U.S.
Pat. No. 3,037,954 which discloses static vulcanization as well as the technique
of dynamic vulcanization wherein a vulcanizable elastomer is dispersed into a resinous
thermoplastic polymer and the elastomer is cured while continuously mixing and
shearing the polymer blend. The resulting composition is a microgel dispersion
of cured elastomer, such as butyl rubber, chlorinated butyl rubber, polybutadiene
or polyisoprene in an uncured matrix of thermoplastic polymer such as polypropylene.
Depending on the ultimate application, such thermoplastic elastomer
(TPE) compositions may comprise one or a mixture of thermoplastic materials such
as propylene homopolymers and propylene copolymers and like thermoplastics used
in combination with one or a mixture of cured or non-cured elastomers such as
ethylene/propylene rubber, EPDM rubber, diolefin rubber, butyl rubber or similar
elastomers. TPE compositions may also be prepared where the thermoplastic material
used is an engineering resin having good high temperature properties, such as a
polyamide or a polyester, used in combination with a cured or non-cured elastomer.
Examples of such TPE compositions and methods of processing such compositions,
including methods of dynamic vulcanization, may be found in U.S. Patents 4,130,534,
4,130,535, 4,594,390, 5,177,147 and 5,290,886, as well as in WO 92/02582.
TPE compositions are normally melt processed using conventional thermoplastic
molding equipment such as by injection molding, compression molding, extrusion,
blow molding or other thermoforming techniques. In such TPE compositions, the presence
of the elastomeric component does not necessarily improve the processability of
the composition. In fact, where the elastomeric component is partially or fully
cured (cross-linked) in-situ during the mixing of the TPE polymer components (dynamically
vulcanized), or where a dynamically vulcanized TPE composition is further processed,
there are heavier demands placed upon processing machinery as compared with the
processing of a thermoplastic composition which is free of cured elastomer. Increases
such as higher motor load, head pressure and/or torque can place undesirable, unacceptable,
or unattainable requirements on specific machinery. For instance, a specific extruder
having a specific motor power and gearing, will reach a maximum of motor load,
or head pressure, under certain melt temperature conditions for a given polymer
being processed. If a polymer or polymer blend is introduced to such an extruder
which has such a higher requirement for power to process at least one component,
such as a polymer having higher molecular weight and/or narrower molecular weight
distribution and/or lower shear sensitivity, the extruder will reach a maximum
of one or several of these parameters, and be therefore limited in its ability
to pump/perform at a similar level to the performance expected with a more easily
processable polymer. In the alternative, if melt blending or processing machinery
is to be used for certain production/extrusion, and it is not so limited, the prospect
of using more power or increasing head pressure for a more difficult to extrude
material would be achievable, but the user of the machinery would still nonetheless
desire to conserve power.
Additionally, TPE compositions may exhibit other imperfections during
extrusion, specifically film extrusion, that may be undesirable, such as melt
fracture. These imperfections are undesirable from a quality standpoint. For example,
melt fracture also known as "shark skin" or "orange peel", can lead to poorer optical
properties and/or diminished film physical properties that are generally unacceptable.
Adjustments to the extrusion process which are made to avoid the development of
melt fracture generally involve a slowing down of the process which leads to a
reduced rate of extrudate output.
Various prior art references generally disclose the addition of various
additives to olefin polymer compositions to improve the extrusion or other properties
ofthe polymer. For example, GB 1,104,662 teaches addition of the salt of alkyl
benzene sulfonic acids to polyolefins that purportedly gives a beneficial effect
on melt extrusion behavior of the polyolefin. The purported effect is the reduction
of the occurrence of "shark skin" or "orange peel". Both alkali and alkaline earth
metal salts of alkyl benzene sulfonic acids are said to be effective.
GB 1,078,738 discloses that addition of an "external lubricant" to
high molecular weight polyolefins can, purportedly, reduce occurrence of melt fracture.
Suggested as external lubricants are salts of monovalent to tetravalent metals,
and saturated or unsaturated carboxylic acids containing 10 to 50 carbon atoms.
Sulfonates corresponding to the fatty acid salts are also said to be suitable.
JP A 59-176339 discloses that when polyolefins are narrowed in MWD
or given higher molecular weight, poor fluidity results which in turn gives rise
to melt fracture. The solution suggested is addition of fluorinated compounds including
potassium salts of fluoroalkylsulfonic acids. These potassium salts are said to
exhibit preferable temperature dependence when compared to other cations such as
sodium, calcium, lithium and ammonium. The polyolefin/salt combination is said
to be effective at 230° C or higher.
DE 2,823,507 discloses calendered ethylene polymers and propylene
polymers containing alkali or alkaline earth mono sulfonates such as alkyl sulfonates,
alenyl sulfonates, alkylaryl sulfonates and succinic acid dialkyl ester sulfonates.
Sodium or calcium mono sulfonates are preferred. A suggested benefit is purported
to be outstanding separation ofthe polymer from calendering rolls.
Canadian Patent 731,225 discloses the use of alkali metal salts of
certain monosulfonic acids as additives to crystallizable polypropylene compositions
to modify the crystallization properties of the polymer. Although these compositions
may also include an elastomeric polymer as an impact modifier, the reference does
not indicate that the additives improve polymer processability.
There is a need therefore for a relatively inexpensive, easily implemented
solution to the processing problems outlined above. Such a solution should also
include a material that will readily melt or incorporate into the melted TPE and
not adversely affect physical properties, not interfere with crosslinking chemistry
or structure produced by that chemistry, not be extractable, or negatively impact
organolleptics of shaped TPE articles. Specifically, there is a commercial need
for a material that may be easily incorporated into TPE compositions, that will
reduce or eliminate the increased power requirement (e.g., motor load and or torque)
and increased head pressure.
SUMMARY OF THE INVENTION
This invention provides a thermoplastic elastomer composition comprising
a blend of: a) a thermoplastic polymer; b) an olefinic rubber; and c) from 0.005
to 5 wt%, based on the polymeric content of said blend, of at least one sulfate
or sulfonate salt having the formula (R-SOx)M where X is 3 or 4, R is
an organic aliphatic radical containing from 6 to 30 carbon atoms and M is a cation
selected from the group consisting of alkali metals, alkaline earth metals and
The invention also provides a process for forming a composition or
an extruded article comprising melt blending a thermoplastic elastomer composition
comprising a blend of: a) a thermoplastic polymer; b) an olefinic rubber; and c)
from 0.005 to 5 wt%, based on the polymeric content of said blend, of at least
one sulfate or sulfonate salt having the formula (R-SOx)M where X is
3 or 4, R is an organic aliphatic radical containing from 6 to 30 carbon atoms
and M is a cation selected from the group consisting of alkali metals, alkaline
earth metals and ammonium.
The invention is based on the discovery that inclusion of the above-described
sulfate or sulfonate salts in TPE molding compositions results in a marked reduction
of the energy requirements for melt processing and extrusion of conventional TPE
compositions. In addition, injection mold spiral flow lengths are increased and
fill times are significantly lowered which leads to reduced cycle times in injection
DETAILED DESCRIPTION OF THE INVENTION
Following is a description of the various ingredients which may be
used to formulate the TPE compositions of this invention.
Thermoplastic polymers suitable for use in the present invention include
amorphous, partially crystalline or essentially totally crystalline polymers selected
from the group consisting of polyolefins, polyamides, polyimides, polyesters,
polycarbonates, polysulfones, polylactones, polyacetals, acrylonitrile/butadiene/
styrene copolymer resins, polyphenylene oxides, ethylene-carbon monoxide copolymers,
polyphenylene sulfides, polystyrene, styrene/ acrylonitrile copolymer resins, styrene/maleic
anhydride copolymer resins, aromatic polyketones and mixtures thereof
Polyolefins suitable for use in the compositions of the invention
include thermoplastic, at least partially crystalline polyolefin homopolymers and
copolymers, including polymers prepared using Ziegler/Natta type catalysts or
metallocene catalysts. They are desirably prepared from monoolefin monomers having
2 to 6 carbon atoms, such as ethylene, propylene, 1-butene, isobutylene, 1-pentene,
copolymers containing these monomers, and the like, with propylene being the preferred
monomer. As used in the specification and claims, the term polypropylene includes
homopolymers of propylene as well as reactor copolymers of propylene which can
contain 1 to 20 wt% of ethylene or an alpha-olefin comonomer of 4 to 16 carbon
atoms or mixtures thereof. The polypropylene can be highly crystalline isotactic
or syndiotactic polypropylene, usually having a narrow range of glass transition
temperature (Tg). Commercially available polyolefins may be used in
the practice of the invention.
Suitable theromplastic polyamides (nylons) comprise crystalline or
resinous, high molecular weight solid polymers including copolymers and terpolymers
having recurring amide units within the polymer chat Polyamides may be prepared
by polymerization of one or more epsilon lactams such as caprolactam, pyrrolidione,
lauryllactam and aminoundecanoic lactam, or amino acid, or by condensation of
dibasic acids and diamines. Both fiber-forming and molding grade nylons are suitable.
Examples of such polyamides are polycaprolactam (nylon 6), polylauryllactam (nylon
12), polyhexamethyl-eneadipamide(nylon-6,6), polyhexamethyleneazelamide(nylon -6,9),polyhexamethylenesebacamide(nylon
6,10), polyhexa-methyleneisophthalamide(nylon-6,IP) and the condensation product
of 11-amino-undecanoic acid (nylon 11). Commercially available thermoplastic polyamides
may be advantageously used in the practice of this invention, with linear crystalline
polyamides having a softening point or melting point between 160°C-230°C being
Suitable thermoplastic polyesters which may be employed include the
polymer reaction products of one or a mixture of alphatic or aromatic polycarboxylic
acids esters of anhydrides and one or a mixture of diols. Examples of satisfactory
polyesters include poly (trans-1,4-cyclohexylene C2-6 alkane discarboxylates
such as poly(trans-1,4-cyclohexylene succinate) and poly (trans-1,4-cyclohexylene
adipate); poly (cis or trans- 1,4-cyclohexanedimethylene) alkanedicarboxylates
such as poly(cis 1,4-cyclohexane-di-methylene) oxlate and poly-(cis 1,4-cyclohexane-di-
methylene) succinate, poly (C2-4 alkylene terephthalates) such as polyethyl-eneterephthalate
and polytetrametylene-terephthalate, poly (C2-4 alkylene isophthalates
such as polyethyleneisophthalate and polytetramethylene-isophthalate and like materials.
Preferred polyester are derived from aromatic dicarboxylic acids such as naphthalenic
or phthalic acids and C2 to C4 diols, such as polyethylene
terephthalate and polybutylene terephthalate. Preferred polyesters will have a
melting point in the range of 160°C to 260°C.
Poly(phenylene ether) (PPE) thermoplastic engineering resins which
may be used in accordance with this invention are well known, commercially available
materials produced by the oxidative coupling polymerization of alkyl substituted
phenols. They are generally linear polymers having a glass transition temperature
in the range of 190°C to 235°C. Examples of preferred PPE polymers include poly(2,6-dialkyl-1,4
phenylene ethers) such as poly(2,6 dimethyl-1,4-phenylenether), poly 2-methyl-6-ethyl-1,
4 phenylene ether), poly-(2,6-dipropyl-1,4-phenylene ether) and poly (2-ethyl-6-propyl-1,4-phenylene
ether). These polymers, their method of preparation and blends with polystyrene
are further described in U.S. Patent 3,383,435, the complete disclosure of which
is incorporated herein by reference.
Other thermoplastic resins which may be used include the polycarbonate
analogs of the polyesters described above such as segmented poly(ether co-phthalates);
polycaprolactone polymers; styrene resins such as copolymers of styrene with less
than 50 mole% of acrylonitrile (SAN) and resinous copolymers of styrene, acrylonitrile
and butadiene (ABS); sulfone polymers such as polyphenyl sulfone, and like engineering
resins as are known in the art.
Suitable rubbery materials which may be used include monoolefin copolymeric
rubbers, isobutylene copolymers and diolefin rubbers, as well as mixtures thereof.
Suitable monoolefin copolymer rubbers comprise non-polar, essentially
non-crystalline, rubbery copolymers of two or more alpha-monoolefins, preferably
copolymerized with at least one polyene, usually a diene. Saturated monoolefin
copolymer rubber, for example ethylene-propylene copolymer rubber (EPM) can be
used. However, unsaturated monoolefin rubber such as EPDM rubber is more suitable.
EPDM is a terpolymer of ethylene, propylene and a non-conjugated diene. Satisfactory
non-conjugated dienes include 5-ethylidene-2-norbornene (ENB); vinylnorbornene
(VNB) 1,4-hexadiene; 5-methylene-2-norbornene (MNB); 1,6-octadiene, 5-methyl-1,4-hexadiene;
3,7-dimethyl-1,6-octadiene; 1,3-cyclopentadiene; 1,4-cyclohexadiene; dicyclopentadiene
(DCPD); and the like.
Butyl rubbers are also useful in the compositions of the invention.
As used in the specification and claims, the term "butyl rubber" includes copolymers
of an isoolefin and a conjugated monoolefin, terpolymers of an isoolefin, a conjugated
monoolefin and divinyl aromatic monomers, and the halogenated derivatives of such
copolymers and terpolymers. The useful butyl rubber copolymers comprise a major
portion of isoolefin and a minor amount, usually less than 30 wt%, of a conjugated
multiolefin, and are preferably halogenated, e.g., brominated, to faciliate curing.
The preferred copolymers comprise 85-99.5 wt% of a C4-7
as isobutylene and 15-0.5 wt% of a multiolefin of 4-14 carbon atoms, such as isoprene,
butadiene, dimethyl butadiene and piperylene. Commercial butyl rubber, useful in
the invention, is a copolymer of isobutylene and minor amounts of isoprene. Other
butyl co- and terpolymer rubbers are illustrated by the description in U.S. Patent
No. 4,916,180, which is fully incorporated herein by this reference.
Another suitable copolymer within the scope of the olefinic rubber
of the present invention is a copolymer of a C4-7 isomonoolefin and
a para-alkylstyrene, and preferably a halogenated derivative thereof. The amount
of halogen in the copolymer, predominantly present as benzylic halogen, is from
0.1 to 10 wt%. A preferred example is the brominated copolymer of isobutylene and
para-methylstyrene. These copolymers are more fully described in U.S. Patent No.
5,162,445, which is fully incorporated herein by reference.
Another olefinic rubber class which may be used are diolefins such
as polybutadiene as well as elastomeric random copolymers of butadiene with less
than 50 wt% of styrene or acrylonitrile. Other suitable diolefin materials include
natural rubber or synthetic polyisoprene. Mixtures comprising two or more of the
olefinic rubbers may also be used.
Depending upon the desired applications, the amount of olefinic rubber
present in the composition may range from 10 to 90 wt% of the total polymer content
of the composition. In most applications and particularly where the rubber component
is dynamically vulcanized, the rubber component will constitute less than 70 wt%,
more preferably less than 50 wt%, and most preferably 10-40 wt% of the total polymer
content of the composition.
The surfactants useful in the present invention include one or a mixture
of sulfate and sulfonate salts having the generic formula (RSOx)M wherein
X is 3 or 4, R is an organic radical containing from 6 to 30 carbon atoms and M
is a cation selected from the group consisting of alkali metals, alkaline earth
metals and ammonium. Materials of this type are well known in the detergent art
and are commercially available.
Preferred surfactants are those where R is a branched or straight
chain aliphatic group including alkyl, mono or di unsaturated alkenyl, alkoxy,
hydroxy substituted alkyl or alkoxy alkyl. M is preferably selected from lithium,
sodium, potassium, calcium or magnesium, with sodium most preferred. M may also
be an ammonium cation or a quaternary ammonium cation. Suitable surfactants include
sodium lauryl sulfate or sulfonate, sodium alpha olefin sulfonate, ammonium lauryl
sulfate, ammonium lauryl sulfonate, sodium myristyl sulfate or sulfonate, sodium
octyl sulfate, and like materials. Preferred surfactants are those where R contains
8 to 20 carbon atoms, more preferably 12 to 18 carbon atoms and where R is free
of halogen, e.g., fluorine substituent groups and does not contain aromatic groups.
The selection of particular surfactant is dictated by the fact that
the melting point of the surfactant should be lower than the temperature at which
the polymer compositions is processed, and preferably be lower than the softening
or melting point of the thermoplastic polymer component (and the rubber component)
present in the blend, preferably at least 10°C lower. Since the surfactant appears
to function as an external lubricant during processing, it is important that it
be in the melt state along with the molten polymers being processed. Thus preferred
surfacants are those with a melting point below 240°C, more preferably below 230°C
and most preferably below 210°C, e.g., sodium lauryl sulfate or sulfonate or sodium
alpha olefin sulfonates. On the other hand where the thermoplastic polymer being
processed is of relatively high melting point, e.g., polyamides, then higher melting
point surfactants may be used, e.g., the alkaline earth metal sulfate or sulfonate
Another factor dictating the choice of surfactant is that it should
be insoluble or only sparingly soluble in liquid or semi-liquid additive materials
included in the composition, such as processing oils. Severe dilution of the surfactant
by such additives will result in a diminution or loss of the enhanced melt processing
characteristics of the surfactant.
The surfactant may be incorporated into the composition at a level
of from 0.005 to 5 wt%, more preferably from 0.01 to 0.5 wt% and most preferably
from 0.03 to 0.35 wt%, based on the polymeric content of the blend.
The compositions of the invention may include plasticizers, curatives
and may also include reinforcing and non-reinforcing fillers, antioxidants, stabilizers,
rubber processing oil, plasticizers, extender oils, lubricants, antiblocking agents,
anti-static agents, waxes, foaming agents, pigments, flame retardants and other
processing aids known in the rubber compounding art. Such additives can comprise
up to 50 wt% of the total composition. Fillers and extenders which can be utilized
include conventional inorganics such as calcium carbonate, clays, silica, talc,
titanium dioxide, carbon black and the like. The rubber processing oils generally
are paraffinic, naphthenic or aromatic oils derived from petroleum fractions, but
are preferably paraffinic. The type will be that ordinarily used in conjunction
with the specific rubber or rubbers present in the composition, and the quantity
based on the total rubber content may range from zero up to 1-200 parts by weight
per hundred rubber (phr). Plasticizers such as trimellitate esters may also be
present in the composition.
The olefin rubber component of the thermoplastic elastomer is generally
present as small, i.e., micro-size, particles within a continuous plastic matrix,
although a co-continuous morphology or a phase inversion is also possible depending
on the amount of rubber relative to plastic, and the cure system or degree of cure
of the rubber. The rubber is desirably at least partially crosslinked, and preferably
is completely or fully cross-linked. The partial or complete crosslinking can be
achieved by adding an appropriate rubber curative to the blend of thermoplastic
polymer and rubber and vulcanizing the rubber to the desired degree under conventional
vulcanizing conditions. However, it is preferred that the rubber be crosslinked
by the process of dynamic vulcanization. As used in the specification and claims,
the term "dynamic vulcanization" means a vulcanization or curing process for a
rubber contained in a thermoplastic elastomer composition, wherein the rubber is
vulcanized under conditions of high shear at a temperature above the melting point
of the component thermoplastic. The rubber is thus simultaneously crosslinked and
dispersed as fine particles within the matrix thermoplastic, although as noted
above other morphologies may also exist. Dynamic vulcanization is effected by mixing
the thermoplastic elastomer components at elevated temperature in conventional
mixing equipment such as roll mills, Banbury mixers, Brabender mixers, continuous
mixers, mixing extruders and the like. The unique characteristic of dynamically
cured compositions is that, notwithstanding the fact that the rubber component
is partially or fully cured, the compositions can be processed and reprocessed
by conventional plastic processing techniques such as extrusion, injection molding,
blow molding and compression molding. Scrap or flashing can be salvaged and reprocessed.
Those ordinarily skilled in the art will appreciate the appropriate
quantities, types of cure systems and vulcanization conditions required to carry
out the vulcanization of the rubber. The rubber can be vulcanized using varying
amounts of curative, varying temperatures and varying time of cure in order to
obtain the optimum crosslinking desired. Any known cure system for the rubber can
be used, so long as it is suitable under the vulcanization conditions with the
specific olefinic rubber or combination of rubbers being used and with the thermoplastic
component. These curatives include sulfur, sulfur donors, metal oxides, resin
systems, peroxide-based systems, hydrosilation curatives, containing platinum or
peroxide catalysts, and the like, both with and without accelerators and co-agents.
Such cure systems are well known in the art and literature of vulcanization of
The terms "fully vulcanized" and "completely vulcanized" as used in
the specification and claims mean that the rubber component to be vulcanized has
been cured to a state in which the elastomeric properties of the crosslinked rubber
are similar to those of the rubber in its conventional vulcanized state, apart
from the thermoplastic elastomer composition. The degree of cure can be described
in terms of gel content or, conversely, extractable components. Alternatively the
degree of cure may be expressed in terms of crosslink density. All of these descriptions
are well known in the art, for example in U.S. Patent Nos. 5,100,947 and 5,157,081,
both of which are fully incorporated herein by reference.
The processing surfactants may be included in the composition during
the manufacture of the TPE composition by processes as described above, or may
be later combined with pelletized TPE compositions used by a processor to manufacture
shaped articles. For example, TPE extruded pellets may be thoroughly mixed with
the surfactant in finely divided powder or liquid form to thoroughly coat each
pellet, and the -coated pellets introduced into an extruder along with any other
additives used by the processor to produce extruded shaped articles by such process
as injection molding, compression molding, blow molding and similar extrusion processes.
Melt processing temperatures will generally range from above the melting
point of the highest melting polymer present in the TPE composition up to 300°C.
Preferred processing temperatures will range from 140°C up to 250°C, more preferably
from 150°C up to 225°C.
The following examples are illustrative of the invention.
TPE compositions used in the following examples are as follows:
- TPE-U A
- thermoplastic elastomer comprising a mixture of 100 parts by weight of EPDM
rubber (VISTALON® 7500 supplied by Exxon Chemical Co.) and 50 parts by weight
of isotactic polypropylene.
- A dynamically vulcanized version of TPE-U cured using a phenolic resin curing
system and containing 107 parts by weight of paraffin oil per 100 parts by weight
- A dynamically vulcanized thermoplastic elastomer cured using a phenolic resin
curing system and based on a mixture of 100 parts by weight of an elastomeric copolymer
of butadiene and acrylonitrile, 35 parts by weight of isotactic polypropylene,
and 50 parts by weight of a trimellitate ester plasticizer.
- A dynamically vulcanized blend of 100 parts by weight EPDM rubber, 41 parts
by weight of isotactic polypropylene and 130 parts by weight of paraffin oil cured
using a phenolic resin curing system
- Same as TPE-DS but containing 220 parts by weight isotatic polypropylene and
100 parts by weight EPDM rubber.
- A dynamically vulcanized blend of 100 parts by weight EPDM rubber, 50 parts
by weight isotactic polypropylene, 176 parts by weight processing oil and cured
using a hydrosilation cure system.
- A dynamically vulcanized blend of EPDM rubber and polyolefin, containing low
amounts of hydrocarbon oil and cured with a peroxide cure system.
- A dynamically vulcanized blend of butyl rubber, isotactic polypropylene, oil
This example demonstrates a reduction in torque (as measured by changes
in amperage) of compositions of this invention when melt processed. A pelletized
form of the TPE compositions listed in Table 1 were each introduced into a Brabender™
Plasti-Corder melt mixer which was heated at 200°C. Typically, 50-60 g. of material
is introduced at a rotation speed of 40 RPM. Upon complete melting, the torque
remains essentially invariant with time and is used as the base value. Subsequently,
measured amounts of sodium alpha-olefin sulfonate surfactant (Bio Terge® AS-90
marketed by Stepan Co., Northfield, Ill.) were added to each sample in the amounts
listed in Table 1. After several minutes of mixing, the torque was again measured
at 40 RPM and compared with the base value for each sample. As shown in Table 1,
torque reductions ranging from 7.9 to 16.0% were achieved.
Surfactant CONC, (ppm)
Torque Reduction (%)
This example illustrates the effect of surfactants of this invention
on extrusion properties. TPE-DS thermoplastic elastomer identified above in pellet
form was tumbled in a drum with 1.14 g. HT100 mineral oil per pound of TPE-DS.
The surfactant in powder form was then added at the levels shown in Table 2 and
the material was tumbled another S hour to uniformly coat the pellets. Comparative
samples of TPE-DS coated with a known processing aid (Dow Corning MB50-001 silicone
rubber concentrate) were also prepared. The material identified in Table 2 as "AOK"
is also a sodium salt of an alpha-olefin sulfonate available from Witco Chemical
Co., Greenwich, CT. Prior to extrusion, the coated materials were run into a Berstorff
ZE-43 extruder at 350 rpm and at 234°C to homogenize the dispersion. The torque
for each sample processed in the extruder was measured in Amps and results are
shown in Table 2.
% Reduction Torque
Samples as shown in Table 2 were then fed into a Killion 3 horsepower
extruder heated to a 3 zone temperature ranging from 190°C to 200°C and extruded
into ribbon through a 0.020 inch slit die at a melt temperature of 215°C. Extruder
parameters for each sample processed are shown in Table 3.
* Output measured after 3 min run. Between runs the material was
extruded for 15 mins before any readings or output measurements were taken. Between
materials a purge was made.
**Duplicated 3 times.
Head Pressure psi
% Reduction Amps
% Change Ib/hr
The parameters as measured in Table 3 demonstrate a general reduction
in extruder head pressure and torque as measured by the Amps Output rate as measured
in Ib/hour was also not compromised and in most cases increased as compared with
the control containing no processing aid. In contrast, the comparative samples
containing 5% silicone polymer showed significant slippage and therefore a loss
The same materials as described in Example 2 were injection molded
using a Cincinnati Millacron 250 ton injection molder operating under the following
Machine Heat Settings
- Rear 182°C, Center 188°C,
Front 194°C, Nozzle 200°C.
- 0.85 inch
- 0.19 inch
- 100 rpm
- 3.0 inch/sec.
Injection molding results using an 1S0 standard mold to make plaques
of 2 mm thickness are shown in Table 4.
Fill time (sec)
Press. 1st Stage psi
Press Back Psi
Press. Hold Psi
Press. Back Psi
As shown in Table 4, the general effect of the use of the surfactants
of this invention is to lower the fill time up to a factor of three, which thereby
represents a potential of lowering the overall cycle time. It was also observed
that at all pressures there was a significant improvement in spiral flow for additives
used at the 5% by weight leveL Also, mold sticking was observed in all samples
containing the silicone polymer, but no mold sticking took place in samples containing
the surfactants of this invention.
Compositions as identified in Table 5 were coated with the identified
additive in the levels indicated and processed through a Berstorff extruder as
described in Example 2. Viscosity measurements and torque reductions for each
processed TPE sample were compared with TPE controls containing no added processing
aid. ACR viscosity is shear viscosity measured using a Monsanto automatic capillary
rheometer; extensional viscosity is measured using a Goettfert Rheotens rheometer.
% Reduc. Torque
Ext. Visc. at 190°C kPa s
% Reduc. Ext. Vise.
ACR Visc. at 204°C Poise
% Reduc. ACR Visc.
Results in Table 5 show a general reduction in torque for samples
containing additive vs control samples free of additive and also a general reduction
in extruder melt pressure, indicating improved flow. Reductions in extensional
viscosity and ACR viscosities are also demonstrated as compared with the controls.