Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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POLYESTER RESIN BLENDS
Keith N. Gray
This invention relates to thermoplastic molding
compositions that have improved physical properties.
More particularly, the invention pertains to reinforced
compositions, preferably glass reinforced compositions,
containing a poly(arylene sulfide) resin, preferably
polyphenylene sulfide (PPS) resin; and (b) a polyester
resin derived from a cyclohexane dimethanol and a
carbocylic dicarboxylic acid or ester.
8ACKGROUND OF THE INVF~TION
High molecular weight polyesters and particularly
linear polyesters derived from 1,4-cyclohexanedi-
methanol have been available for a number of years.
These are described inter a_ in Kilber et al~
U.S. Pat. No. 2,901,466. This patent discloses that
such polyesters are particularly advantageous as film
and fiber-formers. The compositions disclosed herein
are also used for injection molding, extrusion and
other plastic forming operations.
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Poly(arylene sulfide) resins, e.g., poly(phenylene
sulfide)(PPS), have become well known in the art for
their thermal resistance, chemical resistance and an
excellent balance of physical properties for use in
preparing a variety of compositions useful in
preparing articles by injection molding or compression
molding techniques.
It has now been unexpectedly discovered that
reinforced mixtures, preferably glass reinforced
mixtures, of poly(cyclohéxane-dimethylene arylates) and
poly(arylene sulfide) resin, particularly a PPS resin,
exhibit an improvement in impact strength and other
improved physical properties.
DETAILED DESCRIPTION OF THE INVENTION
The polyesters utilized in the process of
the present invention are derived from
cyclohexanedimethanol and are prepared by condensing
either the cis- or trans-isomer (or a mixture thereof)
of, for example, 1,4-cyclohexanedimethanol with a
carbocyclic dicarboxylic acid or ester so as to produce
a polyester having recurring units having the following
formula I:
~CH2-CH2 R 1l
-O-CH2-CH CH-CH2-0-C-R-C-
CH2 - CH2
wherein the substituted cyclohexane ring is selected
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from the group consisting of the cis- and trans-isomers
thereof and R represents an organic radical containing
from 6 to 20 carbon atoms which is the decarboxylated
residue derived from a carbocyclic d;carboxylic acid or
ester.
The preferred polyester resins may be
derived from the reaction of a mixture of the cis-
and trans-isomers of 1,4-cyclohexanedimethanol with a
mixture of iso- and terephthalic acids. These
polyesters have recurring units of the formula II:
CH2 - CH2 l
O-CH2-CH CH-CH2-0-C~C-
CH2-CH2
These polyesters can be produced by well
known methods in the art such as those set forth in
U.S. 2,901,466. The poly (1,4-cyclohexanedimethanol
terephthalate) is commercially available. Of course,
it is understood that the polyester resins of this
invention can be prepared by condensing
1,4-cyclohexanedimethanol and minor amounts of other
bifunctional glycols with the carbocyclic dicarboxylic
acid. These other bifunctional glycols include the
polymethylene glycols containing from 2 to 10 or more
carbon atoms such as ethylene glycol, butylene glycol,
etc. Preferred polyesters will contain cyclohexane
dimethanol units in which the ratio of the trans-/cis-
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isomer moities is greater than approximately 70%.
The term "carbocyclic" is used herein in
its art recognized sense, that is, it refers to any
organic compound whose carbon skeleton is in the form
of a closed ring. Obviously, not all the atoms in the
closed ring have to be carbon, although the term
incorporates both aliphatic and aromatic compounds in
which all the atoms are carbon. The preferred number
of carbon atoms in the carbocyclic functionality
employed in the present invention will generally range
between 3 and about 15, with the more preferred number
of carbon atoms being 6. In the most preferred
embodiment of this invention, the carbocyclic
dicarboxylic acid or ester is a hexacarbocyclic
dicarboxylic acid or ester.
Examples of hexacarbocyclic dicarboxylic
acids or esters wherein the carboxy radicals are
attached in para relationship to a hexacarbocyclic
residue indicated by R in formula (I) include
terephthalic acid, trans-hexahydroterephthalic acid,
4,4'-sulfonyldibenzoic acid, 4,4' diphenic acid,
4,4'-benzophenone dicarboxylic acid,
1,2-di(p-carboxyphenyl)ethane,
1,2-di(p-carboxyphenyl)ethene,
1,2-di(p-carboxyphenoxy)-ethane, 4,4'-dicarboxydiphenyl
ether, etc. and mixtures of these. All of these acids
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contain at least one hexacarbocyclic nucleus. Fused
rings can also be present such as in 1,4-, 1,5 or 2,6-
napthalenedicarboxylic acid. The hexacarbocyclic
dicarboxylic acids or esters are preferably those
containing a trans cyclohexane nucleus or an aromatic
nucleus containing from one to two benzene rings of
which at least one has the usual benzenoid
unsaturation. Of course, either fused or attached
rings can be present. All of the compounds named in
this paragraph come within the scope of this preferred
group. The preferred dicarboxylic acid is terephthalic
acld.
These polyesters, which are alternatively
refered to herein as "PCT Resins" should have an
intrinsic viscosity between 0.40 and 2.0 dl./g.
measured in a 60/40 phenoltetrachloroethane solution or
a similar solvent at 25-30C. Especially preferred
polyesters will have an intrinsic viscosity in the
range of 0.5 and 1.2 dl./g.
Any crystallizable poly(arylene
sulfide)(PAS) can be employed in this invention,
including copolymers, mixtures and blends. Usually,
the PAS will contain repeat units of the formula [Ar-S]
wherein Ar is a divalent aromatic radical. Preferred
divalent aromatic radicals can be independently
selected from the group consisting of phenylene,
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biphenylene or naphthylene. Usually the poly(arylene
sulfide) will comprise a poly(phenylene sulfide~ which
has at least about 90 percent by weight of the repeat
units with the formula
~ S _
Examples of methods for obtaining this polymer
include a method which comprises polymerizing
p dichlorobenzene in the presence of sulfur and sodium
carbonate, a method which comprises polymerizing p-
dichlorobenzene in a basic solvent in the presence ofsodium sulfide, or sodium hydrosulfide and sodium
hydroxide or hydrogen sulfide and sodium hydroxide,
and a method comprising self-condensation of
p-chlorothiophenol.
PPS may also be prepared by reacting
p-dichlorobenzene with sodium sulfide in a polar
organic solvent to produce PPS and sodium chloride as a
by-product.
The invention encompasses the use of either or
both of linear and branched poly (arylene sulfides).
Virgin PPS is isolated as an off-white powder and
is a linear material of modest molecular weight, ie.
approximately 15,000 - 20,000. This material is
produced by the Toso Susteel Company under the
tradename SUSTEEL 160.
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The composition of the present invention will also
optionally include, as a third component of the com-
posisition, at least one a mineral reinforcing agent,
preferably a glass reinforcing agent. Suitable mineral
reinforcing agents for use in the present invention
include fillers such as talc, mica, wollastinite,
asbestos and clay. Other suitable mineral reinforcing
agents include fibrous materials such as ceramic fila-
ments, carbon fibers, glass flake and milled glass.
The preferred mineral reinforcing agent is fibrous
(filamentous) glass. Filamentous glass, is well known
to those skilled in the art and is widely available
from a number of manufacturers. For compositions
ultimately to be employed for electrical uses, it is
preferred to use fibrous glass filaments comprised of
lime-aluminum borosilicate glass that is relatively
soda free. This is known as "E" glass. However, other
glasses are userul where electrical properties are not
so important, e.g., the low soda glass known as "C"
glass. The filaments are made by standard processes,
e.g., by steam or air blowing, flame blowing and
mechanical pulling. The preferred filaments for
plastic reinforcements are made by mechanical pulling.
The filament diameters range from about 0.00012 to
0.00075 inch, but this is not critical to the present
invention. The length of the glass filaments is also
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not critical to the invention. However, in preparing
the molding compositions, it is convenient to use the
filamentous glass in the form of chopped strands of
from about one-eighth to about two inches long. In
articles molded from the compositions, on the other
hand, even shorter lengths will be encountered because,
during compounding considerable fragmentation will
occur. This is desirable, however, because the best
properties are exhibited by thermoplastic injection
molded articles in which the filament lengths lie
between about 0.0005 to 0.250 inch.
It should be unders~ood that the composition
obtained according to this invention may contain one
or more conventional additives such as, for example,
antioxidants, carbon black, agents, plasticizers,
rubbery impact modifiers, lubricity promoters, color
stabilizers, ultraviolet absorbers, X-ray opacifiers,
dyes, pigments, fillers, mold release agents,
nucleants, and the like. The composition of the
present invention can also contain standard halogenated
flame retardant compounds, particularly brominated
flame retardant compounds, with or without sodium
antimonate. Examples of suitable flame retardant
compounds for use in the present invention include
brominated polystyrene, brominated epoxides,
tetra-bromo bisphenol-A based polymers and the like.
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When such flame retardant additives are utilized, the
composition may also optionally contain an effec~ive
amount of a drip inhibitor. Suitable non-dripping
agents are well known and widely available. They
include fumed and collidal silicas and
polytetrafluoroethylene resins. Especially preferred
are the polytetrafluoroethylene resins, most preferably
TEFLON~6 from E.I. DuPont.
Representative phenol derivatives useful as
stabilizers include 3,5-di-tert-butyl-hydroxy hydro-
cinnamic triester with 1~3, 5-tris-(2-hydroxyethyl-s-
-triazine-2,4,6-(lH, 3H, 5H) trione; 4,4'-bis-
-(2,6-ditertiary-butylphenol); 1,3,5-trimethyl-2,4,6-
-tris-(3,5-ditertiary-butyl-4-hydroxylbenzyl)benzene
and 4,4'-butylidene-bis (6-tertiary-butyl-m-cresol).
Mixtures of hindered phenols with esters or
thiodipropionic, mercaptides and phosphite esters are
particularly useful. Additional stabilization to
ultraviolet light can be obtained by compounding with
various UV absorbers such as substituted benzophenones
and/or benzotriazoles.
Particularly useful stabilizers are hindered
phenols which include phenols of the formula
R4 OH
~ R3
R5
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wherein R3 and R4 are hydrocarbon groups having from one
to about 20 carbon atoms, and Rs is a hydrogen atom or a
hydrocarbon group having from one to about 20 carbon
atoms, and bisphenol of the formula
R6 A A R6
A ~ (CH2)n ~ A
R7 R8 R8 R7
wherein R6, R7 and R8 are each a hydrogen atom or a
hydrocarbon group having from one to about 20 carbon
atoms, one of the two A's on each ring is a hydroxyl
group and the other A on each ring is a hydrogen atom
or a hydrocarbon group having from one to about 20
carbon atoms; and n is an integer of from 0 to about 20.
The compositions of the present invention will
preferably contain (a) from about 5% to about 95%
by weight, and prefereably from about 40% to about 80%
by weight of a resin derived from a cyclohexane-
-dimethanol and a carbocylic dicarboxylic acid and
(b) from about 5 % to about 95% by weight and
preferably from about 20% to about 60% by weight of a
poly(arylene sulfide) resin, said weight percentages
being based on the total weight of (a) and (b).
Optionally, the composition of the present invention
may also contain from about 2% to about 100% by weight
add-on and preferably from about 10% to about 70% by
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weight add-on of a mineral reinforcing agen~, based on
the total weight of the polyester resin and the
poly(arylene sulfide) resin.
The components of the composition of the present
invention can be intimately blended in a number of
procedures. In one way, the various additives to the
polyester resin are put into an extrusion compounder
with the dry polyester resin and the blend is heated
at an elevated temperature, e.g., 560-600F., and
extruded to produce molding pellets. The additives are
mixed with the powdered or granular polyester and the
mixture can be heated and directly formed into molded
items using machines which compound and mold.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The following examples are presented to more
fully and clearly illus~rate the present invention.
They are presented as illustrative of the invention
and are not to be construed as limiting the invention
thereto. In the examples all parts and percentages
are on a weight basis unless otherwise specified.
The following Example 1 illustrates a compo-
sition following outside the scope of the instant
invention in that it does not contain any poly(arylene
sulfide) resin. Example 6 is also outside of the scope
of the present invention in that it doesn't contain any
of the specified polyester resin. These examples are
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presented for comparative purposes only.
In all the examples, the compositions were pre-
pared by melt blending the polyester resins and the
indicated additional components as set forth in Table I
below using a 2.5 inch single screw extruder at
approximately 570F. The resulting polymeric
composition was formed, by injection molding, into test
specimens of the size described in the corresponding
ASTM methods. The notched izod and other properties of
the compositions were tested with the results of these
tests set forth in Table II below.
The following ASTM methods were used in
determining the physical characteristics of the com-
positions:
Flexural Strength ASTM D790
Tensile Properties ASTM D638
Izod Impact Strength ASTM D256
Shrinkage ASTM D955
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TABLE I
FORMULATIONS
COMPONENTS 1 2 3 4 5 6
PCT 69.00 55.20 41.40 27.60 13.80 ---
PPS --- 13.80 27.60 41.40 55.20 69.00
STAB 1 0.5 0.5 0.5 0.5 0.5 0.5
STAB 2 0.5 0.5 0.5 0.5 0.5 0.5
GLASS 30.00 30.00 30.00 30.00 30.00 30.00
TABLE 2
PROPERTIES
EXAMPLE 1 2 3 4 5 6
MELT VISCOSITY 4,481 5,605 6,319 7,645 9,498 11,373
(POISE)@ 295C
HDT (F) 454 476 478 490 498 496
@ 264 psi
NOTCHED IMPACT
(FT. LBS./IN.) 1.5 1.4 1.3 1.2 1.1 1.3
UNNOTCHED IMPACT
(FT. LBS./IN.) 9.616.2 14.1 10.2 6.9 9.5
TENSILE
ELONGATION (%) 7.7 8.7 9.0 8.8 7.7 8.6
STRENGTH (kpsi) 14.7 15.9 17.2 18.0 18.6 20.1
FLEXURAL
STRENGTH (kpsi) 23.1 22.9 25.0 25.3 26.7 27.3
MODULUS (kpsi) 897 996 975 1080 1110 1320
SHRINK (WITH/AGAINST FLOW)
(MILS/IN.) 2 5/ 2 4/ 1 6/ 1 5 1 3 1 2
SPIRAL FLOW(IN.)8.69.2 9.6 10.7 NM NM
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Tensile elongation was measured by cross head
displacement on 2.5 by 0.5 inch Type 5 tensile bars.
Spiral flow was measured at 90 mil channel thickness
for the spiral flow, at a melt temperature of 305 C.
PCT stands for poly(l,4-cyclohexane dimethanol),
which is sold under the trademmark Eastman 3879 by the
Eastman Kodak Company.
PPS stands for poly(phenylen~ sulfide, SUSTEEL 160,
manufactured by Toso Susteel.
STAB 1 stands for tetrakis methylene (3,5-
di-t-butyl-4-hydroxyhydrocinnamate) which is
manufactured by Geigy Chemical Corporation under the
trademark Irganox~ 1010.
STAB 2 stands for bis(2,4-di-t-butylphenyl)
pentaerythritol diphosphate which is manufactured by
G.E. Specialty Chemicals under the trademark ULTRANOX
626.
The glass utilized was 1/8" chopped strand glass
fibers.
NM indicates not measured for those particular
formulations.
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The above data indicates that physical properties
of glass reinforced PCT/PPS blends are improved over
glass filled blends of PCT or PPS alone. For example,
it is surprising that the unnotched impact strength of
various PCT/PPS blends is improved over the glass
reinforced PCT or PPS compositions. The improvement in
spiral flow upon addition of PPS to the glass filled
PCT is especially surprising in view of the increased
melt viscosity. Such improvement is clearly unexpected
and is synergistic in nature.
Obviously, other modifications and variations of
the present invention are possible in light of the
above teachings. It is therefore to be understood
that changes may be made in the particular embodi-
ments of the invention described which are within thefull intended scope of the invention as defined by the
appended claims.
