Note: Descriptions are shown in the official language in which they were submitted.
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POLYPHENYLENE COMPOSITIONS
HAVING IMPROVED MELT BEHAVIOR
Field of the Invention
The melt behavior of polyphenylene ether
compositions can be improved or controlled without
reducing the inherent thermal properties of such
compositions. The improvement is achieved by a combination
of polyphenylene ether resin and an alkyl or aralkyl
sulfonate compound.
Background of the Invention
Polyphenylene ether resin compositions have long
been utilized as thermoplastics because they exhibit a
variety of beneficial physical and chemical properties
which are useful in many applications. E`xcellent
electrical properties, high DTUL as well as inherent flame
retardance are three of the prime advan-tages of polyphenylene
ether resins. Despite these advantages, polyphenylene
ether resins are not necessarily suitable as molding
compositions or many applications without further
modification. One of the primary reasons for this is -the
relatively high melt viscosity of polyphenylene ether
resins. A result of this property is relatively poor flow
channel exhibited in a typical molding process. Poor flow
results in difficulties in molding, losses in manufacturing
efficiency as well as poor material performance. For
example, in a typical molding process, polyphenylene ethers
might have a flow channel of less than twelve inches even
at very high temperatures. A glass transition temperature
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of 210C for polyphenylene ethers also indicates that
these polymers have characteristically superior thermal
properties which may require an element of control in
order to provide certain useful products.
A very successful fami]y of thermoplastic
products are the modified-polyphenylene ether products
wherein the polyphenylene ether base resin is modified
or plasticized with another compound in order to provide
useful plastic compositions. Typically, modified poly-
phenylene ethers are comprised of PPE and an alkenyl
aromatic compound such as high impact polystyrene. These
materials are alloyable in all proportions and provide a
variety of products exhibiting advantages of both classes
of compounds while minimizing the disadvantages of each.
Other plasticization methods are also useful for poly-
phenylene ether compounds and many conventional plasticizers
have been tried. One successful category of such
plasticizers has been the triaryl phosphates which are
low molecular weight materials which not only tend to
plasticize the polyphenylene ethers but also impart an
additional degree of flame retardance for these
compounds.
Such plasticized modi~ied polyphenylene ether
compositions have provided use~ul products whi.ch, however,
do not necessarily exhibit the extraordinary thermal
properties oE unmodlfied polyphenylene ether.
Additionally, some plasticized modiEied-polyphenylene ether
compositions tend to experience environmental stress
cracking under certain conditions when exposed to stress
cracking agents.
In U.S. Patent 4,529,761, which issued
July 16, 1985, Lohmeijer described polyphenylene ether
resin compositions which exhibited improved environmental
stress crack resistance and which were comprised of
polyphenylene ether resins or such resins modified with
alkenyl aromatic resins and effective amounts an
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environmental stress crack resistance agent which was
an alkyl or aralkyl sulfonate compound. Lohmeijer did
not recognize, however, that such environmental stress
crack resistance agents could be utilized in unmodified
polyphenylene ether resin compositions (i.e. those which
do not contain alkenyl aromatic compounds) and which would
thereby provide extraordinarily beneficial thermal properties
not otherwise available in modified-PPE systems.
It has now been discovered that the melt behavior
of polyphenylene ether resin compositions can be controlled
or improved without significantly reducing the inherent
thermal properties of such materials and without having to
incorporate conventional plasticizers in the compositions.
Although conventional plasticizers can improve the melt
behavior of polyphenylene ether resins as, for instance,
by making them easier to flow in a molding process, they
traditionally degrade the other thermal properties of
the base resin due to their plasticizing effect. For
example, when plasticizers are added to polyphenylene
ethers, the flow channel of the resin may increase but
the heat distortion temperature of the plastic wll]
generally decrease.
The present invention improves the melt
behavior of the polyphenylene ether without conventional
plasticizer~, thereore, while the Elow channel in a
molding process will be improved, the heat distortion
temperature and thermal stability will not be degraded.
The polyphenylene ether resin compositions of the present
invention will thereby exhibit good low temperature and
high temperature ductility, as well as, excellent
hydrolytic stability and the aforementioned excellent
electrical properties.
Unmodified polyphenylene ether resin
compositions were former non-processable or difficult to
process materials. The compositions of the present
invention, which exhibit improved flow and melt
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characteristics while not tending plasticizing the base
resin can form the basis of new resin systems which take
advantage of these properties.
It is therefore an object of the present
invention to provide polyphenylene ether resin compositions
which exhibit improved or at least controlled melt
characteristics while no generally degrading the inherent
advantageous thermal properties of the base resin.
It is a further object of the present invention
to provide a process for advantageously controlling the
melt behavior of the otherwise difficult to process
polyphenylene ether resin compositions.
Summary of the Invention
There is provided a thermoplastic resin
composition exhibiting controlled melt behavior without
degradation of the inherent thermal properties of the
base resin, which consists essentially of:
a) a polyphenylene ether resin or copolymers
thereof, and which typically will be
poly(2,6-dimethyl-1,4-phenylene ether), and
b) a property improving amount of a compound of
the formula ~-SO3X wherein R represents an
alkyl or aralkyl radical having S to 25 carbon
atoms and X represents an alkali metal ion.
Typically radical ~ will have approximately
12 to 20 carbon atoms and is preferably an alkyl
radical, X is preferably a sodium ion. The
polyphenylene ether base resin will generally
have an intrinsic viscosity less than,
approximately, 0.42 and preferably between
0.38 to 0.42 deciliters per gram as measured in
chloroform at 25C. Conventional polyphenylene
ether resins have intrinsic typically in excess
of 0.~5 deciliters per gram and often in excess
of 0.50 deciliters per gram and this is felt to
substantially contribute to the poor melt
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behavior of such conventiona, unmodified
polyphenylene ether resins. On the other hand,
there is a practical limit as to how low the
intrinsic viscosity of such polyphenylene ether
resins can be and those acquainted with polymer
physics will recognize that intrinsic viscosities
for PPE much lower than the 0.38 deciliters per
gram required by compositions of the present
invention will yield polymer products having
poor physical properties. When the intrinsic
viscosity of the PPE utilized in compositions
of the present invention rises much above the
0.42 deciliters per gram mentioned above, the
compositions begin to behave more like
relatively unprocessable conventional poly-
phenylene ether resin compositions despite the
addition of the melt behavior improving agents
utilized by the present invention.
Polyphenylene ethers are a well known class of
compounds cometimes referred to as polyphenylene oxides.
Examples of suitable polyphenylene ethers and processes
for their peparation can be found in U.S. Patent
Nos. 3,306,874, issued February 28, lg67 to llay;
3,306,875, issued February 28, 1967 to Hay; 3,257,357,
is~ued June 21, 1966 to Stamato~f; and 3,257,358,
issued June 21, l9h6 to Stamatoff. Compositions of the
present invention will encompass homopolymers, copolymers
and graft copolymers obtained by the oxidative coupling
of phenolic compounds. The preferred polyphenylene
ethers used as base resins in compositions of the present
invention will be comprised of units derived from
2,6-dimethyl phenol. Also contemplated are PPE copolymers
comprised of units derived from 2,6-dimethyl phenol and
2,3,6-trimethyl phenol.
The polymer compositions of the present
invention will consists essentially of 0.5 to 10 parts
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by weight of the melt behavior improving compound based
upon 100 parts of the polyphenylene ether base resin.
Preferably about 1 to 5 parts by weight of the additive
will be used per 100 parts of the PPE base resin. When
less than about 0.5 parts additive are utilized,
insufficient beneficial effect will be achieved for
typical applications. When greater than approximately
5 to 10 parts of additives are utilized, little additional
benefit is achieved while other advantageous properties
of PPE may be diminished. This additive compound is an
alkyl or aralkyl sulfonate having a formula R-SO3X in
which R represents an alkyl or aralkyl radical with
5-25 carbon atoms and preferably and 12 to 20 carbon atoms
and X represents an alkali metal ion which is preferably
a sodium ion. It is also possible to utilize a mixture
of such SUlfOllateS.
Suitable sulfonates include the following
products which may be obtained commercially.
Cl~ 20H25 40SO3Na are compounds sold uner the
trademark HOSl'ASTAT. Compounds sold uner the -trademar]c
ATMER 190 have the general Eormula Cx~2x~lSO3Na. Others
are sold under the trademarlc MARANIL A and have the
C12H25 C6H4-SO3Na. It will be recogni~ed
by those skilled in the art that these formulas represent
sulonate salts o hydrocarbon compounds having varying
chain lengths.
The improved composi-tions of the present
invention are provded by combining the polyphenylene
ether based resin and the property improving melt behavior
additive by conventional means as will be demonstrated in
the examples below. Blended or extruded compositions
may be molded and tested by conventional means.
The following examples illustrate the invention
without limitation.
Examples 1-3
Compositions of the present invention exhibiting
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improved melt behavior were provided in the following
manner. The four experimental blends described in Table 1
were compounded using a 28 mm Werner & Pfleiderer twin
screw extruder having this temperature profile through
several stages (set temperatures)~ 500F (Feed Section),
550F, 590F, 590F, 590F, 600F (die Temperature).
During compounding, a vacuum of 5 inches were maintained
for all four samples, while the screw RPM's were a
constant 272. Table 1 also describes the extrusion
conditions which were observed to change among the
materials due to the compositional differences and which
demonstrate some of the advantages of the present
invention. The polyphenylene ether resin, having the
intrinsic viscosity indicated in Table 1, was the
oxidative coupling product of 2,6-dimethyl phenol.
Table 1
Composition (parts by weight) A*1 2 3
poly(2,6-dimethyl-1,4-
phenylene ether)(a) 100 100 100 100
12-20 25-41 3 --- 1 2 3
Extrusion Conditions A 1 2 3
Torque (in-lbs) 780 640 600 500
Power/Current (amp) 15 13 12,5 10
Melt ~emp. (E) 705 598 690 680
25 Extrusion Rate (g/hr) 2400 3400 4000 4000
Observations -Very Smooth -Very Smooth -Smooth -Rough
Strand Strand StrandStrand
-Uniform -Uniform -Uniform-Gassy,
Extrusion Extrusion Extrusion Surging
Extrudate
* Comparative Example
(a) polyphenylene ether having as intrinsic viscosity of 0.40 dl/g
as measured in chloroform at 25C.
(b) HOSTASTAT HS-l sodium salt of lauryl sulfonate (A.G. Hoechst Co.)
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Table 1 demonstrates that the sodium salt
additive clearly improved the compounding process for a
polyphenylene ether polymer. The reduction of extruder
torque and power requirements (amperes) are noteworthy
improvements in the processability of polyphenylene ether.
Furthermore, the lowering of the melt temperatures while
extrusion rates were increased are two additional benefits
achieved in compositions of the present invention. Lower
melt temperatures save energy and are less abusive to the
polymer. Increased extrusion rates are a productivity
improvement indicative of the efficiencies gained by the
present invention.
Pellets of each of the aforementioned composi-
tions were molded into ASTM test specimens using a 4
ounce Newbury injection molding machine. Prior to
molding the pellets were dried for four hours at 115C.
The followin~ molding conditions were present and
remained constant during the molding process of all four
samples:
Barrel Temperature (F) 630
Mold Temperature (F) 220
Cycle Time, Total (Sec) 40
Back Pressure (Psi) 50
Injection Speed Slow
As observed during the compounding process, certain
conditions changed during the molding process for each
of the four sample materials. Table 2 describes these
changes in molding conditions which are attributable to
the inherent advantages of the present invention.
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It is apparent that the sulfonate salt additive
lowers the melt temperature of the polyphenylene ether
required to mold parts. Furthermore there is a concurrent
lowering of the pressure required to fill the cavities of
the AST~ test speclmen mold. The channel flow increased
even though the molding temperature decreased.
It is evident from the foregoing that the
sulfonate salt additive for polyphenylene ether improves
not only the extrusion and compounding process for such
materials but also is beneficial for the polyphenylene
ether molding process.
The foregoing experimental materials were tested
to compare important physical properties of the resultant
thermoplastic products. The me]t viscosities of the
materials were tested using an Instron melt rheometer at
600F and 1500 sec l shear rate. Table 3 describes the other
physical properties which were tested hy ASTM test methods
and other accepted test practices.
Table 3
COM~OSITION NO. A* 1 2 _ 3
Tenslle (psi) 12,700 10,700 10,500 10,100
Elongation ~percent) 27 31 30 13
Flexur~l Str. tpsi) 15,200 15,200 15,200 14,700
Flexural Mod. (p8i) 344,000 356,000 349,000 343,000
rmpact Resistance
Notch. I~od @ 73P (ft-lb/in.ll) 1.4 1.7 1.9 2.0
Notch. I~od @ -40F (ft-lb/in.n) 1.2 1.7 1.9 l.S
Dynaptup Imp. St. ~ 73F (in-lbs) 63 156 205 61
Dynatup Imp. St. @ -40F (in-lbs) 32 55 64 39
Melt Viscosity ~ 600F (poise) 3168 2761 2440 2105
and 1500 sec
D~L @ 264 psi (F) 368F 368F 367F
*Comparative Example
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The sulfonate salt modified polyphenylene
ether especially at the 2 or 3 weight percent level has
greatly improved physical properties except for lower
tensile strength values. The most beneficial increase
are those of impact resistance and melt flow. The latter
benefit is achieved with a very slight sacrifices in
deflection temperature under load.
