Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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INJECTION-MOLDED ARTICLES MADE FROM LONG CHAIN BRANCHED
SYNDIOTACTIC MONOVINYLIDENE AROMATIC POLYMERS
The present invention relates to syndiotactic monovinylidene aromatic
polymers and injection-molded articles produced therefrom.
Syndiotactic monovinylidene aromatic polymers such as syndiotactic
polystyrene (SPS) are useful polymers having a high melting point and
crystallization
rate as well as excellent heat and chemical resistance. However, in some
applications such as in injection-molded articles for electronic connectors
and
automotive parts, the melt flow rate or crystallization rate is insufficient
when injection
molding to obtain desired properties.
Syndiotactic copolymers have also been developed having superior heat and
chemical resistance. US-A-5,202,402 issued to Funaki et al. utilizes a
difunctional
monomer to form a syndiotactic copolymer with styrene, however, the polymer
fully
crosslinks at high temperatures, forming a thermoset and cannot be melt
processed
to produce injection-molded articles.
Injection-molded articles have been produced from linear syndiotactic
monovinylidene aromatic polymers as described in US-A-5,034,441, 5,326,813;
5,444,126, 5,418,275, and EP-312976, EP-733675, and EP-736364. However, the
melt flow rates and crystallization rates of linear syndiotactic
monovinylidene aromatic
polymers are sometimes too low to produce injection-molded articles,
especially, thin-
wall injection-molded articles, with desirable properties such as low molded
in stress,
sufficient crystallinity, and uniform crystallinity.
Therefore, it would be useful to obtain injection molded articles from a
syndiotactic monovinylidene aromatic polymer having good heat and chemical
resistance, with high melt flow and crystallization rate.
The present invention is directed to injection-molded articles prepared from a
composition comprising a long chain branched syndiotactic monovinylidene
aromatic
polymer. Long chain branches can be produced during polymerization by
polymerizing in the presence of a small amount of a difunctional monomer.
The injection-molded articles of the present invention have less molded in
stress, require less pressure for filling and have a more uniform and higher
level of
crystallinity, which manifests itself in improved heat performance and
mechanical
properties such as high temperature creep when compared to those made of
linear
syndiotactic monovinylidene aromatic polymer.
-1-
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In one embodiment, the present invention is an injection-molded article
prepared from a composition comprising a long chain branched syndiotactic
monovinylidene aromatic (LCB-SVA) polymer.
As used herein, the term "syndiotactic" refers to polymers having a
stereoregular structure of greater than 90 percent syndiotactic, preferably
greater
than 95 percent syndiotactic, of a racemic triad as determined by 13C nuclear
magnetic resonance spectroscopy.
Syndiotactic monovinylidene aromatic polymers are homopolymers and
copolymers of vinyl aromatic monomers, that is, monomers whose chemical
structure
possess both an unsaturated moiety and an aromatic moiety. The preferred vinyl
aromatic monomers have the formula:
H2C=CR-Ar;
wherein R is hydrogen or an alkyl group having from 1 to 4 carbon atoms, and
Ar is
an aromatic radical of from 6 to 10 carbon atoms. Examples of such vinyl
aromatic
monomers are styrene, alpha-methylstyrene, ortho-methylstyrene, meta-
methylstyrene, para-methylstyrene, vinyl toluene, para-t-butylstyrene, and
vinyl
naphthalene; bromo- substituted styrenes, especially p-vinyltoluene and ring
brominated or dibrominated styrenes. Brominated styrenes are particularly
useful in
the preparation of ignition resistant syndiotactic monovinylidene aromatic
polymers.
Alternatively, ignition resistant LCB-SVA polymers can be produced by
brominating
LCB-SVA polymers. Representative syndiotactic copolymers include styrene-p-
methylstyrene, styrene-p-t-butylstyrene and styrene-toluene copolymers.
Syndiotactic monovinylidene aromatic polymers and monomers made therefrom are
known in the art having been previously disclosed in, for example, US-A-
4,680,353;
US-A-4,959,435; US-A-4,950,724; and US-A-4,774,301. Syndiotactic polystyrene
is
the currently preferred syndiotactic monovinylidene aromatic polymer.
Long chain branching can be achieved by polymerizing a vinyl aromatic
monomer in the presence of a small amount of a multifunctional monomer under
conditions sufficient to produce a syndiotactic monovinylidene aromatic
polymer. A
multifunctional monomer is any compound having more than one olefinic
functionality
which can react with a vinyl aromatic monomer under polymerization conditions.
Typically, the multifunctional monomer will contain 2-4 olefinic
functionalities and is
represented by formula (I):
-2-
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(R.)n
wherein R is a vinyl group or a group containing from 2 to 20 carbon atoms
including
a terminal vinyl group, wherein the groups containing 2 to 20 carbon atoms may
be
alkyl, alkenyl, cycloalkyl, or aromatic, wherein cycloalkyl groups contain at
least 5
carbon atoms and aromatic groups contain at least 6 carbon atoms, n is an
integer
from 1 to 3 wherein the R groups are meta or para in relation to the vinyl
group of
formula (I), and when n is greater than 1, R may be the same or different.
Preferably
R is a vinyl group.
Preferably the multifunctional monomer contains two terminal vinyl groups
wherein n would equal 1. Typically, such monomers include difunctional vinyl
aromatic monomers such as di-vinyl-benzene or di-styryl-ethane.
The amount of multifunctional monomer will depend upon the weight average
molecular weight (Mw) of the polymer to be produced, but typically is from 10,
preferably from 50, more preferably from 75, and most preferably from 100 ppm
to
1000, preferably to 800, more preferably to 500, and most preferably to 650
ppm,
based on the amount of vinyl aromatic monomer.
The multifunctional monomer can be introduced into the polymerization by any
method which will allow the multifunctional monomer to react with the vinyl
aromatic
monomer during polymerization to produce a LCB-SVA polymer. For example, the
multifunctional monomer can be first dissolved in the vinyl aromatic monomer
prior to
polymerization or introduced separately into the polymerization reactor before
or
during the polymerization. Additionally, the multifunctional monomer can be
dissolved in an inert solvent used in the polymerization such as toluene or
ethyl
benzene.
Any polymerization process which produces syndiotactic monovinylidene
aromatic polymers can be used to produce the LCB-SVA polymers of the present
invention as long as a multifunctional monomer is additionally present during
polymerization. Typical polymerization processes for producing syndiotactic
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WO 99/20449
monovinylidene aromatic polymers are well known in the art and are described
in
US-A-4,680,353, US-A-5,066,741, US-A-5,206,197 and US-A-5,294,685.
Typically, the weight average molecular weight (Mw) of the LCB-SVA polymer
is from 50,000, preferably from 100,000, more preferably from 125,000, and
most
preferably from 150,000 to 3,000,000, preferably to 1,000,000, more preferably
to
500,000 and most preferably to 350,000.
A branched syndiotactic monovinylidene aromatic polymer contains
extensions of syndiotactic monovinylidene aromatic polymer chain attached to
the
polymer backbone. A long chain branched syndiotactic monovinylidene aromatic
polymer typically contains chain extensions of at least 10 monomer repeating
units,
preferably at least 100, more preferably at least 300, and most preferably at
least 500
monomer repeating units.
Typically, the injection-molded articles of the present invention are produced
from a composition of a LCB-SVA polymer without the presence of other
polymers.
However, injection-molded articles may be produced from compositions
comprising a
LCB-SVA polymer and other components including other polymers. The amount of
LCB-SVA polymer contained within a composition for producing injection-molded
articles is dependent upon the final application wherein advantages may be
obtained
with only small amounts in some instances. Generally, at least 5 percent by
weight of
a LCB-SVA polymer is used in a composition for producing injection-molded
articles,
typically at least 20 percent, preferably at least 40 percent, more preferably
at least
70 percent and most preferably 100 percent. Other polymers which may be
included
in such compositions include but are not limited to linear SPS, polystyrene,
polyphenylene oxide, polyolefins, such as polypropylene, polyethylene, poly(4-
methylpentene), ethylene-propylene copolymers, ethyene-butene-propylene
copolymers, nylons, for example nylon-6, nylon-6,6; polyesters, such as
polyethylene
terephthalate), poly(butylene terephthalate); and copolymers or blends
thereof. Other
materials or additives, including antioxidants, impact modifiers, ignition
resistant
agents, coupling agents, for example maleated polymers, including malefic
anhydride
modified polyphenylene oxide, or malefic anhydride modified syndiotactic
monovinylidene aromatic polymers, binders to improve the wet strength of a
base
fabric, flame retardants including brominated polystyrene, brominated
syndiotactic
monovinylidene aromatic polymers, brominated aromatic compounds, antimony
trioxide, and polytetrafluoroethylene may be added to the LCB-SVA polymer
composition, or the injection-molded articles made therefrom.
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Impact modifiers which can be used in the LCB-SVA polymer composition
include block or graft copolymers of vinyl aromatic and butadiene or isoprene
monomers, substantially random interpolymers of an alpha-olefin and a vinyl
aromatic
monomer, and polyolefin eiastomers. The term "interpolymer" as used herein
refers
to polymers prepared by the polymerization of at least two different monomers.
The
generic term interpolymer thus embraces copolymers, usually employed to refer
to
polymers prepared from two different monomers, and polymers prepared from more
than two different monomers.
While describing in the present invention a polymer or interpolymer as
comprising or containing certain monomers, it is meant that such polymer or
interpolymer comprises or contains polymerized therein, units derived from
such a
monomer. For example, if the monomer is ethylene CH2=CH2, the derivative of
this
unit as incorporated in the polymer is -CH2-CH2-.
The vinyl aromatic monomers contained in the substantially random
interpolymers of an alpha-olefin and a vinyl aromatic monomer interpolymers
include
those vinyl aromatic monomers described previously as monomers useful for
preparing the syndiotactic monovinylidene aromatic polymers.
The aliphatic alpha-olefin monomers contained in the interpolymers include
aliphatic and cycloaliphatic alpha-olefins having from 2 to 18 carbon atoms,
and
preferably alpha-olefins having from 2 to 8 carbon atoms. Most preferably, the
aliphatic alpha-olefin comprises ethylene or propylene, preferably ethylene,
optionally
together with one or more other alpha-olefins having from 3 to 8 carbon atoms,
such
as for example ethylene and propylene, or ethylene and octane, or ethylene and
propylene and octane.
The interpolymers are preferably a pseudo-random linear or substantially
linear, more preferably a linear interpolymer comprising an aliphatic alpha-
olefin and
a vinyl aromatic monomer. These pseudo-random linear interpolymers are
described
in EP-A-0,416,815.
The substantially random interpolymers may be modified by typical grafting,
hydrogenation, functionalizing, or other reactions well known to those skilled
in the art,
provided their impact or ductility modification function will not be
substantially affected.
The polymers may be readily sulfonated or chlorinated to provide
functionalized
derivatives according to established techniques.
The pseudo-random interpolymers can be prepared as described in EP-A-
0,416,815. Preferred operating conditions for such polymerization reactions
are
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pressures from atmospheric up to 3000 atmospheres and temperatures from
30°C to
200°C.
Examples of suitable catalysts and methods for preparing the pseudo-random
interpolymers are disclosed in EP-A-416,815; EP-A-468,651; EP-A-514,828; EP-A-
520,732, WO 93/23412, US-A-5,347,024, US-A-5,470,993, US-A-5,624,878,
US-A-5,556,928" as well as US-A-5,055,438, US-A-5,057,475, US-A-5,096,867,
US-A-5,064,802, US-A-5,132,380, and US-A-5,189,192.
Elastomeric polyolefin impact modifiers can be any elastomeric polyolefin
such as those described in US-A-5,460,818. Elastomeric polyolefins include any
polymer comprising one or more C2_2o a-olefins in polymerized form, having Tg
less
than 25°C, preferably less than 0°C. Examples of the types of
polymers from which
the present elastomeric polyolefins are selected include homopolymers and
copolymers of a-olefins, such as ethylene/propylene, ethylene/1-butane,
ethylene/1-
hexene or ethylene/1-octane copolymers, and terpolymers of ethylene, propylene
and
a comonomer such as hexadiene or ethylidenenorbornene. Grafted derivatives of
the
foregoing rubbery polymers such as polystyrene-, malefic anhydride-,
polymethylmethacrylate- or styrene/methyl methacrylate copolymer-grafted
elastomeric polyolefins may also be used.
The LCB-SVA polymer compositions may also contain inorganic reinforcing
agents. Suitable reinforcing agents include any mineral, glass, ceramic,
polymeric or
carbon reinforcing agent fillers such as glass fibers, micas, tales, carbon
fibers,
wollastonite, graphite, silica, magnesium carbonate, alumina, metal fibers,
kaolin,
silicon carbide, and glass flake. Such material may be in the shape of fibers
having a
length to diameter ratio (UD) of greater than 5. Preferred particle diameters
are from
0.1 micrometers to 1 millimeter. Preferred reinforcing agents are glass
fibers, glass
roving or chopped glass fibers having lengths from 0.1 to 10 millimeters and
UD from
5 to 100. Three such suitable glass fibers are available from Owens Coming
Fiberglas under the designation OCF-187A or 497 or from PPG under the
designation 3540. Suitable fillers include nonpolymeric materials designed to
reduce
the coefficient of linear thermal expansion of the resulting material, to
provide color or
pigment thereto, to reduce the flame propagation properties of the
composition, or to
otherwise modify the composition's physical properties. Suitable fillers
include mica,
talc, chalk, titanium dioxide, clay, alumina, silica, glass microspheres,
wollastonite,
calcium carbonate, magnesium sulfate, barium sulfate, calcium oxysulfate, tin
oxide,
metal powder, glass powder, and various pigments. Preferred fillers are in the
shape
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WO 99/20449
of particulates having (UD) less than 5. The amount of reinforcing agent or
filler
employed is preferably from 10 to 50 parts by weight. Preferred fillers are
talcs with
number average diameter less than 1 micron such as MP 10-52 available form
Mineral Technologies and wollastonite with number average diameter less than 5
such as Jilin 2000 available from GLS.
The reinforcing agent may include a surface coating of a sizing agent or
similar coating which, among other functions, may promote adhesion between the
reinforcing agent and the remaining Components, especially the matrix, of the
composition. Suitable sizing agents may contain amine, aminosiiane, epoxy, and
aminophosphine functional groups and contain up to 30 nonhydrogen atoms.
Preferred are aminosilane coupling agents and C,~ alkoxy substituted
derivatives
thereof, especially 3-aminopropyltrimethoxysilane.
The LCB-SVA polymer compositions may also contain other additives
including lubricants such as stearic acid, behenic acid, zinc stearate,
calcium
stearate, magnesium stearate, ethylene bis-stearamide, pentaerythritol
tetrastearate,
organo phosphate, mineral oil, trimellitate, polyethylene glycol, silicone
oil, epoxidized
soy bean oil, tricresyl phosphate, polyethylene glycol dimethyl ether, dioctyl
adipate,
di-n-butyl phthalate, butylene glycol montanate (Wax OP), pentaerythritol
tetramontanate (TPET 141 ), aluminum mono-stearate, aluminum di-stearate,
montanic acid wax, montanic acid ester wax, polar polyethylene waxes, and non-
polar polyethylene waxes. Other additives include polyarylene ethers such as
those
described in US-A-3,306,874, US-A-3,306,875, US-A-3,257,357, and
US-A-3,257,358. A preferred polyarylene ether is poly(2,6-dimethyl-1,4-
phenylene)ether. The polyphenylene ethers are normally prepared by an
oxidative
coupling reaction of the corresponding bisphenol compound. Preferred
polyarylene
ethers are polar group functionalized polyarylene ethers, which are a known
class of
compounds prepared by contacting polar group containing reactants with
polyarylene
ethers. The reaction is normally conducted at an elevated temperature,
preferably in
a melt of the polyarylene ether, under conditions to obtain homogeneous
incorporation of the functionalizing reagent. Suitable temperatures are from
150°C to
300°C.
Suitable polar groups include the acid anhydrides, acid halides, acid amides,
sulfones, oxazolines, epoxies, isocyanates, and amino groups. Preferred polar
group
containing reactants are compounds having up to 20 carbons containing reactive
unsaturation, such as ethylenic or aliphatic ring unsaturation, along with the
desired
polar group functionality. Particularly preferred polar group containing
reactants are
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WO 99/20449 PCT/US98/I8666
dicarboxyiic acid anhydrides, most preferably malefic anhydride. Typically the
amount
of polar group functionalizing reagent employed is from 0.01 percent to 20
percent,
preferably from 0.5 to 15 percent, most preferably from 1 to 10 percent by
weight
based on the weight of polyarylene ether. The reaction may be conducted in the
presence of a free radical generator such as an organic peroxide or
hydroperoxide
agent if desired. Preparation of polar group functionalized polyarylene ethers
have
been previously described in US-A-3,375,228, US-A-4,771,096 and US-A-
4,654,405.
The polar group modified polyaryiene ethers beneficially act as
compatibilizers
to improve adhesion between the reinforcing agent and the syndiotactic
i 0 monovinylidene aromatic polymer. Thus, their use is particularly desirable
when a
filler or reinforcing agent is additionally utilized. The amount of
polyarylene ether
employed in the present resin blend is beneficially from 0.1 to 50 parts by
weight,
preferably from 0.2 to 10 parts by weight based on 100 parts glass and
polyarylene
ether.
The polar group modified polyarylene ether may be in the form of a coating
applied to the outer surface of the reinforcing agent to impart added
compatibility
between the reinforcing agent and the polymer matrix. The polar group modified
polyarylene ether so utilized may be in addition to further amounts of
polyarylene
ether or polar group modified polyarylene ether also incorporated in the
blend. The
surface coating is suitably applied to the reinforcing agent by contacting the
same
with a solution or emulsion of the polar group functionalized polyarylene
ether.
Suitable solvents for dissolving the polar group functionalized polyarylene
ether to
form a solution or for use in preparing an emulsion of a water-in-oil or oil-
in-water
type include methylene chloride, trichloromethane, trichloroethylene and
trichloroethane. Preferably the concentration of polar group functionalized
polyarylene ether in the solution or emulsion is from 0.1 weight percent to 20
weight
percent, preferably 0.5 to 5 percent by weight. After coating of the
reinforcing agent
using either a solution or emulsion, the liquid vehicle is removed by, for
example,
evaporation, devolatilization or vacuum drying. The resulting surface coating
is
desirably from 0.001 to 10 weight percent of the uncoated reinforcing agent
weight.
Other additives useful in the LCB-SVA polymer compositions include
nucleators capable of reducing the time required for the onset of
crystallization of the
syndiotactic monovinylidene aromatic polymer upon cooling from the melt.
Nucleators provide a greater degree of crystallinity in a molding resin and
more
consistent distribution of crystallinity under a variety of molding
conditions. Higher
levels of crystallinity are desired in order to achieve increased chemical
resistance
_g_
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WO 99/20449 PCT/US98/18666
and improved heat performance. In addition crystal morphology may be desirably
altered. Examples of suitable nucleators for use herein are monolayer of
magnesium
aluminum hydroxide, calcium carbonate, mica, wollastonite, titanium dioxide,
silica,
sodium sulfate, lithium chloride, sodium benzoate, aluminum benzoate, talc,
and
metal salts, especially aluminum salts or sodium salts of organic acids or
phosphoric
acids. Especially preferred compounds are aluminum and sodium salts of benzoic
acid and C,_,o alkyl substituted benzoic acid derivatives. A most highly
preferred
nucleator is aluminum tris(p-tert-butyl)benzoate. The amount of nucleator used
should be sufficient to cause nucleation and the onset of crystallization in
the
syndiotactic vinylaromatic polymer in a reduced time compared to compositions
lacking in such nucleator. Preferred amounts are from 0.5 to 5 parts by
weight.
Other additives may also be included in the composition of the present
invention including additives such as flame retardants, pigments, and
antioxidants,
including IRGANOXTM 1010, 555, 1425 and 1076, IRGAFOSTM 168, CGL-415, and
GALVINOXYLTM available from Ciba Geigy Corporation, SEENOXTM 412S available
from Witco, ULTRANOXTM 626 and 815 available from GE Specialty Chemicals,
MARK PEPTM 36 available from Adeka Argus, AGERITETM WHITE, MA and DPPD,
METHYL ZIMATE, VANOXTM MTI and 12 available from R.T. Vanderbilt,
NAUGARDTM 445 and XL-1 available from Uniroyal Chemical, CYANOXTM STDP and
2777 available from American Cyanamid, RONOTECTM 201 (Vitamin E) available
from Roche, MIXXIM CD-12 and CD-16 available from Fairmount, EthanoxTM 398,
DHT-4a, SAYTEXTM 8010, 120, BT93 and 102 available from Ethyl, HostanoxTM PAR
24, 03, and ZnCSi available from Hoechst Celanese, cesium benzoate, sodium
hydroxide, SANDOSTABTM PEPQ available from Sandoz, t-butyl hydroquinone, and
SANTOVARTM A available from Monsanto, phenothiazine, pyridoxine, copper
stearate, cobalt stearate, MOLYBDENUM TENCEM available from Mooney
Chemicals, ruthenium (III) acetylacentonate, boric acid, citric acid, MARK
6000
available from Adeka Argus, antimony oxide, 2,6-di-t-butyl-4-methylphenol,
stearyl-(3-
(3,5-di-tert-butyl-4-hydroxyphenol)propionate, and triethylene glycol-bis-3-(3-
tert-
butyl-4-hydroxy-5-methylphenyl)propionate, tris(2,4-tert-butylphenyl)phosphite
and
4,4'-butylidenebis(3-methyl-6-tert-butylphenyl-di-tridecyl)-phosphite; tris
nonyl phenyl
phosphite, carbon black, PYROCHEK PB68 available from Ferro Corporation,
decabromodiphenyl oxide, antiblock agents such as fine particles composed of
alumina, silica, aluminosilicate, calcium carbonate, calcium phosphate, and
silicon
resins; light stabilizers, such as a hindered amine-based compounds or
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WO 99/20449 PCT/US98/18666
benzotriazole-based compounds; plasticizers such as an organopolysiloxane or
mineral oil; blowing agents, extrusion aids, stabilizers such as bis(2,4-di-
tertbutylphenyl)pentaerythritol and tris nonyl phenyl phosphite.
The injection-molded articles of the present invention can be made by various
processes including direct injection molding, gas-assist injection molding, co-
injection
molding, reciprocating screw injection molding, multi-station reciprocating
screw
injection molding, multi-station screw/RAM injection molding, and blow
molding.
Typically, the injection-molded articles of the present invention are from
approximately 0.1 to 10 mm. thick, more preferably 0.5 to 5 mm. thick.
The injection-molded articles of the present invention can also be coated or
laminated with other material to add additional properties to the injection-
molded
articles.
The injection-molded articles of the present invention can be used in
electronic
connectors, electric connectors, electrical components, automotive under-the-
hood
parts, lighting parts, automotive air induction parts, automotive coolant
system parts,
and battery seals.
The following examples are provided to illustrate the present invention. The
examples are not intended to limit the scope of the present invention and they
should
not be so interpreted. Amounts are in weight parts or weight percentages
unless
otherwise indicated.
EXAMPLES
PRODUCTION OF LCB-SVA
All reactions are conducted under inert atmosphere in a dry box. The
reagents, toluene and styrene monomer are purified and handled using standard
inert
atmosphere techniques. Di-styryl-ethane (DSE) is prepared following the
procedure
described in J. Polymer Sci., Part A, Polymer Chem., 32 (1994) 2023 by W.H.
Li, et
al.
A 10 percent methylalumoxane in toluene solution, 1 Molar
triisobutylaluminum in toluene and a 0.03 Molar solution of
pentamethylcyclopentadienyl-titanium trimethoxide in toluene are mixed in a
dry box
in volumetric flasks in ratios of 75:25:1 with a final concentration of the
catalyst
solution, based on titanium, of 0.003 Molar.
4.54 gm of styrene are charged into 4 ampoules. A 1 percent solution of di-
styryl-ethane (DSE) in toluene, is added at the ppm level indicated below. The
-10-
;~~,;~y,~rr.~-W~::m.lll.. m.~ 1 -1 ~-J:p vCA~02304680 2000-03-27"ti =~7:~1-
+.~cJ. ~3cJ 'i3cJ,y.t..~.6u:p--3;_.
i2A
ampoules are then sealed and equilibrated at the polymerization temperature of
70°C for 10 minutes. Polymerization is initiated by addition of
catalyst solution in
mote ratio of styrene to titanium of 175,000:1. The polymerization is quenched
by
the addition of an 9xcess of methanol after one hour. The polymer is isolated
and
dried and molecular weight is determined via high temperature size exclusion
chromatography. The results are shown below.
ppm ~~ Cc~nv~sionbtn M.w i'vLz Mva~Nln
DSE ,
0 82 9>3.70U345.000 684,600 3.50
'?00 86 .~7.SOU4sJ6,9001.136.1007.'36
~t00 85 12,800 efi',4U(11,768,000S.17
80Q ?9 1(14.90069,300 1,703,7000.28
with cation
di-styryl-ethane of long
is .
an
indi
The
significant
increase
in
fuiz
chain branching in the SPS polymer.
U Larger scale reactions are conducted in a 5" (12.7 cm} Teledyne kneader-
mixer which is described in US-A-5,254,647. ?, solution of 1.3 wt. percent di-
styryi-
ethane in toluene is added to styrene monomer in the amounts listed in Table 1
and
fed to the reactor at 17.5 kg,'hr giving a mean residence time of 18 minutes.
The .
polymerization is conducted at temperatures of 55 to 67.5 °C. A
catalyst solution of
methyialuminoxane, triiscbutyfatuminum and octahydrcfiuorenyl titanium
trimethoxide catalyst is fed to the reactor at styrene to titanium mole ratios
of
80,000:1 to 100,000:1. The product is a fine, white-powder ranging in
conversion
from 36 to 50 percent. The samples are collected under nitrogan and quenched
by
the addition of an excess of methanci. The samples are then dried in a
nitrogen-
s~nrept, 220 °C, 5mm Hg vacuum oven for two hours. The weight average
molecular
weight (Mw} of the polymer is determined by high temperature size exclusion
chromatography. The results are shown in Table 1:
Table I
Sample m DSE Mw Mn Mz Mw/Mn
1 400 294,900 82,100 1,151,9003.59
2 400 334,800 86,500 1,377,3003.87
3 250 420,000 92,300 2,418,3004.55
4 250 3fi8 71 600 't 962.0005.15
900
The slgnfficant incr ease in Mz with di-styryl-ethane is an indication of long
chain branching. The above samples, in the form of powders, are :.onverted to
pellets using a 0.5° (1.27 cm} single-screw extn:der. The molecular
weight i~f the
pellets are sur nmarized below: .
11
AMENDED SW'ET
CA 02304680 2000-03-27
12A.
Sarn le Mw Mn Mz Mw/Mn _
_
1 279 900 75 600 1,137 400 3.73
2 304 900 82.600 1,1 fi 1,1 3.72
Oa
3 313 000 74 900 1 294 900 4.18
4 301 000 05 000 1 204 900 4.63
Melt strength is measured according to the tecnnfque described in Plastics
Engineering, 51, (2), 25, 1995 by S. K. Goyal with the test conditions of 1
in./min.
(2.54 cmlmin.) plunger speed, 50 ftJmin. winder rate and 279°C. Melt
flow rate is
measurad according to ASTM method D1238 with the test conditions of 1.2 Kg
Load
and 300°C. A 300,000 Mw linear SPS polymer is used as the control. The
results
are summarized below:
Sam le Melt stren th MFR /10 min.
1 4.0 19.1
2 5.4 14.4
3 5.5 15.5
4 I 4.5 ~ 17.1
', Control ~ i .9 3.6
The LCB-SPS samples have higher melt strengths and higher melt flow rates
than the linear SPS control sample.
EXAMPLE 1 PREPARATION OF LC8-SPS AND INJECTION-MOLDED ARTICLES
THE EPROM
Polymerization reactions ara carried out in a 5' (12.7 cm) Teledyne
kneader-mixer, with mean residence time of 18 minutes, followed by a 500
liter, tank
reactor, with mean residence time of t 0 hours_ Operation of these devices are
described in US-A-5,254,647. Styrene monomer is mixed with 250 ppm of a 3.3
percent solution of di-siyryl-ethane in toluene and fed to the reactor at 17.5
kg.lhr.
Polymerization is carried out at a temperature of 55°G. A catalyst
solution of
methyalurninoxane, triisobutyfaluminurn and octahydrofluorenyititanium
trimethoxide
is also fed to the reactor at styrene to titanium mole ratios of 80,000:1.
After
polymerization, the pclymer is devolatilized and palletized as described
previously.
The molecular weight of the polymer is determined via high temperature size
exclusion chromatography and the results are shown below:
Mw Mn Mz Mz+1 Mw/Mn
313,900 86,100 1,227,500 2,729,300 3.65
A 300,OC0 Mw linear SPS polymer is used as a control.
12
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The LCB-SPS and Control polymers are formulated with 30 percent glass . -_
fibers, antioxidants, nucleating agent, and mold release agent. The
compositions
are extruded on a 4.0 mm co-rotating twin-scrsw extruder using the following
conditions.
The resulting pellets era injection molded into standard tensile bar specimens
with a 100 ton (91 metric ten) injection molder. The machine set points used
for
molding tensile bars are the following:
Cycle Time BO sec
Caalinr Time 38 sec
injection Speed 22 mm/sec
Hold Pressure 250 psi (1.72
Mpa)
Held Pressure Time 16 sec
Screw Speed 40
i3arrel Temperatures:
Feed Zone 45G
Bo~,rrei Zones 310, 310, 310C
Nozxie 315C
Mold Temperature 95C
The glass-filled LCB-SPS composition has a higher heat distortion
temperature l,4E1 °i= (238°C)) than the corresponding glass-
filled linear SPS
composition (373°F (189°G)).
Another lot of LCB-SPS polymer i5 prepared in tile same way as described
above. The molecular weight of the polymer is determined via high temperature
size
exclusion chromatography and the results are shown below:
Mw Mn Mz Mz+1 Mw/Mn
366,200 86,300 1,635,100 3,552,000 4_2~.
A 300,000 Mw linear SPS polymer is used as a control
The LCB-SPS and Control polymers are formulated with 30 percent glass
fibers, antioxidants, nucleating agent, mold release agent, and a flame
retardant
package. The compounds are extruded on a 40 mm co-rotating twin-screw extruder
- using the same conditions as described above. The resulting pellets are
injection
13
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rolded into standard tensile bar specimens with a 100 ton (91 metric tonl
injection
holder using the same injection molding conditions described above.
The formulated pellets are than melted and viscosities measured using the
:apillary tube method.
LCB-SP S 300 000 Mw Linear SPS 0 Mw
(300 00
Shsar Rate Viscosi Shear Rate Viscosit
sec c sl (sec ~) (c s
I 3U0C 81.92 7712 100.9 9200
252.5 3515 293_9 455
_
869.6 1481 950.7 ~ 701
2695 653.4 2780 752.4
9339 258.1 9029 323.9
320C 84.08 5849 99.68 7502
253.7 2655 295.2 3217
851 1186 970.6 1323
2568 553.5 2876 58C.9
8617 230.1 9485 236.7
The glass-filled, ignition-resistant LC13-SPS composition >~as 12 to 20
percent
', lower viscosity than the corresponding linear 5PS cornpaund over a~ range
of shear
rates frarn 100 to 10000 sec'.
Flexural creap is determined using a Rheometrics RSA II solids
analyzer fitted with a high temperature oven under a dry N2 environment.
Samples are fabricated from injection molded bars with final dimensions of
12.7 mm wide by 3.2 mm thick and at least 60 mm long. Three-point bend
fixtures are used with a constant 48 mm span. The oven is set. at the
250°C
and equilibrated for 10 min. A 1 g compression force is placed on the sample
to insure contact followed by 1 ~58 x 10B r a. The resulting creep strain is
recorded for over 600 s resulting in 500 measurements of strain during the
run.
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CA 02304680 2000-03-27
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LCB-SPS ~~ '."~.~~.,~_,~__ Linear SPS
_
Cree ~ 250_C after 10 min. Cree ~ 250C after 10 min.
~~ ~~
0.39 ercent 0.45 ercent
The LCB-SPS composition also has improved resistance to creep at
elevated temperatures.
-15-
