Note: Descriptions are shown in the official language in which they were submitted.
FIFLO OF THE INVENTION
This invention releases to a process for producing
polystyrene compositions having improved stability, and
their use in making foamed products.
BACKGROUND OF THE INVENTION
.
Polystyrene is a homopolymer of styrenes which
contains no reinforcing polymeric rubbery additives and is
frequently used for making injection molded articles and
extruded films and for making expanded foams. For tube
production of expanded foams, tube polystyrene is mixed
wit a blowing agent, e.g. butane, pontoon or fluorocarbon
compounds, under conditions suck that tube blowing agent
is vaporized wile ye polystyrene is fluid. In
manufacturing operations for toe production of expanded
foam polystyrene as finished articles, including
tbermoforming processes, where is considerable degradation
of the expanded polystyrene due to the bib temperatures,
swear stresses and oxidation involved and recycling of
scrap foam and trimmings is necessary to avoid excess
JO wastage.
The stabilization of polymers against degradation
is an extensive field. However, the stabilization of
polystyrene against degradation is a more limited field
because polystyrene bus generally been regarded as having
sufficient stability. Toe stabilization of impact
polystyrene was been extensively studied, the presence in
the impact polystyrene of the reinforcing polymer which
contains ~arbon-carbon unsatura~ion being mainly
responsible for tube need for stabilization. Because
polystyrene does not contain a reinforcing polymer, such
stability problems are normally not encountered.
When polystyrene is used in a foam extrusion
operation with or without repelletizing of recycled
polymer it is exposed to relatively sigh temperatures,
- 2 -
- 12~ 4~5
big shear stresses and degradative conditions in the
presence of absorbed or entrained oxygen.
BRIEF DESCRIPTION OF THE PRIOR ART
Altbougb muck work is reported identifying
stabilizers or antioxidant for use wit many polymers,
few references exist describing the use of stabilizers
with polystyrene. US. Patent 4,136,142 teaches that a
mixture of 1,1,3-tris(2-methyl-4-bydroxy-5-~ert.butyl
phenol) butane and iris (mixed moo- and di-nonylpbenyl)
pbospbite wren added to polystyrene stabilizes toe
polystyrene against degradation. US. Patent 3,637,587
teaches toe stabilization of polymers including
polystyrene by the addition of N,N-disubstituted-aminoalkyl
pbospbites. US. 3,530,091 teaches tube stabilization of
polymers including polystyrene by the addition of
bis-pbenol ornate derivatives.
SUMMARY OF THE INVENTION
It is an object of the present invention to
provide a novel process for tube production of polystyrene
and poly(p-metbylstyrene) compositions braving improved
stability against degradation.
It is a further object of tube present invention
to provide a novel process for tube production of a foam
polystyrene or poly(p-metbylstyrene) product utilizing a
polystyrene or poly~p-metbylstyrene) composition braving
improved stability against degradation.
Further reference to polystyrene is intended to
mean polystyrene and poly(p-metbylstyrene3.
According to the present invention, there is
provided a process for tube production of polymer
compositions selected from polystyrene and
poly(p-metbylstyrene3 having improved stability against
degradation, said process comprising subjecting styrenes or
p-me~bylstyrene monomer to thermal polymerization wit or
-- 3
us
without tube addition of free radical polymerization
initiators to achieve a conversion of monomer to polymer
of at least about 65 per cent by weight and recovering the
so-formed polymer, wherein a solution or suspension of
polymer stabilizer is added to the monomer or to the
polymerizing mixture at a point in the process where there
is still to occur a further conversion of monomer to
polymer of not less than about 3 per cent, said polymer
stabilizer being a mixture of a hindered phenol compound
and a polypbosphite compound in a weigh ratio of hindered
phenol compound to polyphospbite compound of from about
1:2 to about 1:4, tube amount of polymer stabilizer being
such as to provide from about 0.1 to about 6 weight per
cent based on polystyrene or poly(p-methylstyrene)~ said
hindered phenol compound being selected from toe group
comprising 2,6-di-tert.butyl-4 methyl phenol and phenol
compounds waving at least 2 and not more than 4 phenol
groups, each phenol group being linked directly or through
an alkaline, alkoxy or aureole group from a carbon atom of
the aromatic ring to a carbon atom of toe aromatic ring of
at least one otter phenol group, and each phenol group
waving in tube aromatic ring at least one alkyd substituent
comprising at least one tertiary bottle group ortho to the
hydroxy group, and said polypbospbite compound being
selected from the group consisting of compounds waving
from 2 to 8 p~ospbite groups, each compound having each
pbospborus atom bonded directly to tree separate oxygen
atoms which oxygen atoms are also bonded directly to a
carbon atom of an alkyd, aureole, alkoxy or airlocks group.
Still further in accordance With tube present
invention, there is provided a process for the production
of foam polymer selected from polystyrene and
poly(p-met~ylstyrene) comprising the steps of feeding to a
first stage of an extrude operation a feed material
4 --
Zigs
comprising a mixture of recycled foam polymer and or
virgin polymer, said first stage of said extrude
operation being at a temperature ox from about 200 to
about 290C to melt and homogenize said feed material,
adding blowing agent Jo toe molten feed material and
dispersing said blowing agent within said molten feed
material, feeding tube materiel prom said first stage to a
second stage of said extrude operation, whlcb is a second
section of a single extrude or a second extrude,
operated at a lower temperature to cool tube molten feed
material to a temperature of from ablate 110 to about
155C, and extruding the material from said second stage
through a die maintained at a temperature of from about
110 to about 155C and foaming tube extradite, said
feed material containing sufficient polymer produced by
the aforesaid process for tube production of polymer
compositions having improved stability against degradation
to provide from about 0.1 to about 0.6 weight per cent,
based on said feed material, of polymer stabilizer.
DESCRIPTION OX THE PREFERRED EMBODIMENTS
Styrenes and p-metbylstyrene monomers may be
polymerized to polystyrene or poly(p-met~ylstyrene) by
processes well known in tube art. The polymerization is a
thermal polymerization and may be undertaken with or
without free radical polymerization initiators present
The polymerization may be undertaken in a single reactor
or a series of reactors. The reactor or reactors may be
temperature controlled stirred tank reactors, temperature
controlled plug flow-type reactors equipped wit impellers
or a tower-type reactor having plug flow tberetbrough, or
combinations thereof. Preferably, the polymerization is
undertaken in either a series of two or three reactors
equipped with impellers to assist the flow of the
polymerizing mixture or a stirred tank reactor supplying a
-- 5 --
I ~95
tower reactor with the polymerizing mixture flowing
downward trough tube tower. Preferably, tube product from
the reactors is passed to a devolatilizing means to remove
residual styrenes monomer and then to a poulticing means.
Suitably the temperature of the polymerization may be from
about 85C to about 200C and may, wren more than one
reactor is used, be varied from about 85 to about
130C for a first reactor, from about 115 to about
135C for a second reactor, if used, and from about
120 to about 200C for a final reactor. Suitably,
tube conversion of styrenes monomer to polystyrene is at
least about 65 per cent my weight and preferably at least
about 70 up to about 95 per cent by weight. The
polystyrene recovered from the poulticing means will
desirably contain less than about 1000 parts per million
by weight of residual styrenes monomer.
When tube polymer stabilizer is added to the
styrenes monomer it becomes intimately intermixed with the
polystyrene as it is formed. Ibsen tube polymer stabilizer
is added to tube polymerizing mixture, it is added at a
point in toe process where there is still to occur a
further conversion of styrenes monomer to polystyrene of
not less than about 3 per gene and tube polymer stabilizer
becomes intimately intermixed with the polystyrene. Thus
cue polymer stabilizer may be added to toe feed to any of
tube reactors and even to the preheater wbic~ serves to
beat the polymerizing mixture before it is fed to tube
devolatilization clamber provided that there is further
conversion ox tube sturdy monomer to polystyrene of not
less than about 3 per cent. Tube polymer stabilizer is
added as a solution or suspension preferably in styrenes
and optionally in a compatible hydrocarbon suck as
ethylbenzene or mineral oil depending solely on the
~L2~l2~
volubility of the components of the polymer stabilizer in
styrenes monomer.
Selection ox the polymer stabilizer is
important. The polymer stabilizer should have a minimal
effect on tube polymerization of styrenes suck as not to
cause the rate of polymerization to be reduced to an
impracticably low value and should have toe desired
stabilizing effect on the polystyrene suck that when the
polystyrene is subjected to big temperatures, swearing
and possibly absorbed or entrained oxygen the molecular
weight of toe polystyrene is not drastically reduced.
The polymer stabilizer is a mixture of a hindered
phenol compound and a polyp~osphite compound in a weight
ratio of hindered phenol compound Jo polypbosphite
compound of from about 1:2 to about 1:4, preferably from
about 1:2 Lo about 1:3.5 and most preferably about 1:3.
Tube hindered phenol compound is selected from tube group
consisting of 2,6-di-ter~.butyl-4-metbyl phenol and phenol
compounds braving at least 2 and not more Han 4 phenol
groups, each phenol group being linked directly or tbroug~
an alkaline group, such as ethylene, an alkoxy group or
an aureole group from a carbon atom of tube aromatic ring to a
carbon atom of toe aromatic ring of at least one otter
phenol group, and each phenol group braving in tube aromatic
ring at least one alkyd ~ubstituen~ comprising at least
one tertiary bottle group ortbo to toe bydroxy group.
Otter substituents may include methyl, ethyl, propel or
tertiary bottle groups substituted at the second ortbo
position, if it is available, or at tube mote or pane
I positions. Examples of such hindered phenol compounds in
addition to 2~6-di-tert.butyl-4-methyl phenol include
4,4'-bis-(2,6-di-tert.butyl phenol), 4~4l-methylene-bi
(2 3 6-di-tert.butyl phenol 2J2l-metbylene-bis-(4-metb
6-tert.butyl phenol 2~2~-metbylene-bis-(4-ethyl-6-tert.
-- 7 --
I US
bottle phenol), 2~2l-methylene~bis-(4~6-di-tert.but
phenol), 1,1,3-tris-(2-metbyl-4-bydroxy-5-tert.butyl
phenol) butane, 2,6-bis-[(3,5-di-tert.butyl-2 bydroxy
phenol) metbylene]-4-tert.butyl phenol, 4,4'-methylene-bis
(2-methyl-6-tert.butyl phenol), 1,4-bis-(3,5-di-tert.butyl-
4 hydroxy-benzyl) te~rametbyl Bunsen, 1,3,5-trimethyl-
2,4,6-tris~3,5-di-tert.butyl-4-bydroxy bouncily) Bunsen
andtetrakis-[methylene-3-(3,5-di-tert.butyl-4-hydroxyy
pbenyl) preappoint] methane. Preferred hindered phenol
compounds include the dip and tri-pbenols and especially
the tri-pbenols such as 1,1,3-tris-(2-metbyl-4-~ydroxy-5
tert.butyl pbenyl) butane. The polypbosphite compound is
selected from tube group consisting of compounds having
from 2 to 8 pbospbite groups, each compound having each
phosphorus atom bonded directly to cbree separate oxygen
atoms wbicb oxygen atoms are also bonded directly to a
carbon atom of an alkyd, aureole, alkoxy or airlocks group.
Examples of such polypbospbi~e compounds include
deciduously pentaerytbritol diphosphite, di-stearyl
pentaerytbritol diphospbite, di-~2,4-ditert.butyl-phenyl)
pent~erytbritol diphospbite, tetra-pbenyl
dipropylene-glycol dipbospnice, dipbenyl di-decyl
(2~2~4-erimetbyl-l~3-pentane Doyle dipbosphite~
beptakis(dipropylene glycol) tripbosphite and
poly(dipropylene glycol) phenol phospbite wherein there is
up to a total of eight phosphorus atoms. Preferred among
the polypbospbite compounds are tube diphosphite compounds
suck as di-stearyl pentaerythritol diphosp~ite and
deciduously pentaerytbritol diphospbite. Certain of sun
polyp~osphite compounds are also supplied as containing
small amounts, about 0.5 to about 5 weight per cent, of
additives suck as amine or Stewart salts and as such are
also suitable for use.
~212~
Tube styrenes or p-metbylstyrene monomer may
Contain small amounts of one or more other stabilizers at
concentrations of from about 0.02 to about 0.05 weight per
cent eased on monomer, which other stabilizers may be
selected especially from the various hindered mono-pbenol
compounds such as n-octadecyl-3,5-di-tert.-butyl-
4-bydroxy-pbenyl-propiona~e and 2,6-di-tert.-butyl-
para-cresol.
Additional materials may also be present in tube
monomer including inert delineates suck as ethyl Bunsen,
lubricants such as Starkey acid or zinc Stewart at
concentrations of from about 0.05 to about 0.2 weight per
cent based on styrenes and tube mineral oils used in the
polystyrene industry wbicb, if present, may be at
Concentrations of from about 0.5 to about 5 weight per
cent based on styrenes For tube process of ibis invention,
it is preferred to brave zinc Stewart present in tbè
monomer at preferred concentrations of from about 0.1 to
about 0.2 weight per cent based on styrenes
The polymer stabilizer may be added to tube
styrPne or p-me~bylstyrene monomer fed co Abe
polymerization system or it may be added as a solution or
suspension preferably in monomer and optionally in a
compatible hydrocarbon suck as etbylbenæene or mineral oil
as a separate stream to tube first reactor in the
polymerization system or it may be added to the
polymerizing mixture at a point in the process Burr there
is still to occur a further conversion of monomer to
polymer of no less than about 3 per cent. Wren tube
polymer stabilizer is added to tube polymerizing mixture,
toe conversion of monomer to polymer will preferably be
not less than about 15 per cent and no more than about 90
per cent by weight. Tube amount of polymer stabilizer bat
is added is suck as to provide from about 0.1 to about 6
_ g _
Liz
weight per cent based on polymer. In one preferred
embodiment, tube amount of polymer stabilizer is from about
0.1 to about 0.6 weight per cent based on polymer and the
stabilized polymer may be used in a process for the
production of foam polymer directly without mixing with
regular polymer or may be mixed with up to two or more
times the weight of regular polymer suck that tube mixture
of stabilized polystyrene and polystyrene contains not
1PSS than about 0.1 weight per cent of polymer stabilizer
based on toe mixture. In a second preferred embodiment,
toe amount of polymer stabilizer is from about 0.7 to
about 6 weight per cent based on polymer and tube
stabilized polymer may be used in a process for the
production of foam polymer as a mixture wit regular
polymer in suck proportions that the mixture of stabilized
polymer and regular polymer contains not less than about
0.1 weight per cent of polymer stabilizer based on the
mixture and generally not more than about 0.6, preferably
no more than about 0.4, weight per cent of polymer
stabilizer based on tbe-mixture.
Polystyrene and poly~p~metbylstyrene) containing
Abe polymer stabilizer as described herein is suitable for
use in tube production of foam polymer and particularly for
operations in wbic~ excess or scrap foam polymer is
recycled. Tube economics of many tbermoforming processes
rely on being able to recycle tube excess or scrap material
from Sue and tbermoforming processes. In order to
recycle foam polystyrene tube excess or scrap material may
be recycled to tube feed point of tube mixing and
homogenizing extrude where it will be fed together wit
virgin polystyrene into the extrude or it may be
converted back to a non-expanded form, which is usually
undertaken by feeding the excess or scrap material to a
recycle extrude, suck as a repelletizing extrude, in
-- 10 -
:12~ 5
which it is processed at elevated temperatures, suck as in
tube range of about 185 to about 290C. Tune product
from the recycle extrude in pellet form is then reused
by mixing wit virgin polystyrene. During toe recycle
process, the polystyrene is subject to oxidative, thermal
and shearing degradation and tube extent of suck
degradation affects tube quantity of recycle material which
may be mixed wit virgin polystyrene because toe recycle
material was reduced strength properties due Jo the
degradation and contains a smaller amount of big
molecular weight polymer than the virgin polystyrene.
In a process for toe production of Foam
polystyrene a feed material is fed to a first stage of an
extrude operation operated at a temperature of from about
200 to about 290C to melt and homogenize said feed
material, toe feed material comprising a mixture of
recycled foam polystyrene and of virgin polystyrene,
blowing agent suck as pontoon or a fluorocarbon compound
it added to and dispersed within tune molten feed material,
the molten feed material from tube first stage is fed to a
second stage of tube extrude operation, Waco may be a
second section of the same extrude or a second ex~ruder,
in which the molten feed material is cooled to a
temperature of from about 110 to about 155C,
following which Cue cooled material prom Abe second stage
is extruded through a die maintained at 110 to 155C
and the exudate is allowed to expand as a result of
volatilization of toe blowing agent to produce foam
polystyrene, said feed material containing sufficient
polystyrene produced by tube aforesaid process for one
production of polystyrene compositions waving improved
stability against degradation to provide from about 0.1 to
about 0.6, preferably from about 0.1 to about 0.4 weight
per cent, based on the feed material, of polymer
- 11 -
4~5
stabilizer. Tube recycled foam polystyrene may be
recovered from the expanded foam condition by compaction
and extrusion at elevated temperatures, such as from about
185 to about 290C, and by repelletizing. The amount
of recycled foam polystyrene in tube feed material may be
from about 2 to 100 weight per cent of the feed material
and correspondingly the amount of virgin polystyrene in
tube feed material may be from 0 to about 98 weight per
cent of tube feed material. ID one preferred embodiment,
cue amount of recycled foam polystyrene in the feed
material will be from about lo to about 75, most
preferably from about 30 to about 70, weight per cent. In
a second preferred embodiment, the amount of recycled foam
polystyrene in tube feed material will be from about 80 to
100 weight per cent. Tube polystyrene composition braving
improved stability against degradation Jay be in either or
both of tube recycled foam polystyrene or Abe virgin
polystyrene. In one embodiment, the polystyrene
composition braving improved stability against degradation
will form tube recycled foam polystyrene, braving already
been used as virgin polystyrene feed to tube exterior
operation. In a second embodiment, the polystyrene
composition having improved stability against degradation
will form the virgin polystyrene. And in a third
embodiment, the polystyrene composition braving improved
stability against degradation will form both toe recycled
polystyrene and tube virgin polystyrene. Exactly which
stream forms tube polystyrene composition braving improved
stability against degradation is not critical and will
generally depend on the economics of tube process and
product and Cue quality requirements of tube product
In one embodiment of tube process for the
production of foam polystyrene, tube polystyrene is a
stabilized polystyrene according to the present invention
_ 12 -
I s
and containing from about 0.1 to about 0.6 weight per cent
of polymer stabilizer mixed wit regular polystyrene such
that the concentration of polymer stabilizer in tune
mixture is from about Owl to about 0.6, preferably from
about Owl to about 0.4, weight per cent based on tube
mixture. In a second embodiment of the process for the
production of foam polystyrene, tube polystyrene is a
stabilized polystyrene according to tube present invention
containing from about Owl to about 0.6, preferably from
lo about Owl to about 0.4, weight per cent of polymer
stabilizer. In a third embodiment of the process for the
production of foam polystyrene, tune polystyrene is a
stabilized polystyrene according to the present invention
containing from about 0.7 to about 6 weight per cent of
polymer stabilizer based on stabilized polystyrene mixed
wit regular polystyrene in such a ratio to provide from
about Owl to about 0.6, preferably from about Owl to about
0.4, weight per cent of polymer stabilizer.
Tune presence of the polymer stabilizer inhibits
degradation of tune polystyrene during tube processing
thereof. It is desirable to use, for making foam
polystyrene articles, a polystyrene having a bin
molecular weight and a relatively narrow molecular eight
distribution in order to achieve tube desired strength
properties in tube foam polystyrene article. Toe presence
in tube polystyrene of the polymer stabilizer defined
herein inhibits the degradation of the polystyrene during
tune process of producing foamed articles and permits Abe
use of recycled polystyrene in admixture wit virgin
polystyrene without causing a large reduction of the
average molecular weight of tube mixture of recycled and
virgin polystyrene.
It is surprising that the polymer stabilizers
defined herein do not significantly affect tub
_ 13 -
lZ~249S
polymerization of tube styrenes monomer and also provide for
tube polystyrene so produced tube stability against
degradation. Other polymer stabilizers wren added in the
process of ibis invention alone or in combinations, have
been wound no to provide tube required stability against
degradation and tube polymer stabilizers defined Berlin
appear to be a unique system providing tube properties
needed.
The invention is further described with reference
to tube following specific examples.
EXAMPLE 1
To a quantity of styrenes monomer containing about
.2.5 weight per cent of etbylbenzene and about 0.035 weight
per cent of n-octadecyl-3,5-di-tert.butyl-4-hydroxy--
pbenyl-propionate at about 22 to 25C was added, per
100 parts by weight of styrenes 0.07 parts by weight ox
zinc Stewart and 0.1 parts by weight of Tracy-
met~yl-4-~ydroxy-5-tert.butyl phenol) butane and 0.3 parts
by weight of distearyl pentaerytbritol dipbosphite. This
styrenes was fed to a polymerization system which comprised
a series of tree reactors, each reactor being equipped
with heat transfer elements and impeller blades mounter on
a horizontal shaft located along the center of earn
reactor and wit means Jo permit control of tune
temperature within and along each reactor. Toe first
reactor was controlled at a temperature of about 125C:
toe polymerizing mixture from the exit of this reactor
contained about 15 to about 25 weight per cent of
polystyrene and from about 75 to about 85 weight per cent
of styrenes monomer and was fed directly to tube second
reactor. Tube second reactor was controlled at a
temperature of about 130C: tube polymerizing mixture
from tube exit of ibis reactor contained about 57 to about
61 weight per cent of polystyrene and from about 39 to
- 14
~2~2~
about 43 weight per cent of styrenes monomer and was fed
directly to toe third reactor. The bird reactor
was controlled at a temperature of about 140C:
the polymerizing mixture from tube third reactor
contained about 85 to about 92 weight per cent of
polystyrene and from about 8 to about 15 weight
per cent of styrenes monomer and was fed through a
preheater to a devolatilization means, maintained at a
temperature of about 230C and a pressure of about OHS
to about 1 cm of mercury, for tube removal of styrenes
monomer. Toe polystyrene from the devolatilizer contained
essentially no styrenes monomer and was fed to an extrude
equipped wit a multi-orifice die to produce small
diameter strands of polystyrene which were cooled and then
cropped into pellets.
The stabilized polystyrene so produced was
evaluated in toe laboratory in a Bra bender Plastic order
(Trade Mark) torque rbeometer by measurement over time of
tube torque on tube rotor shaft wren operated at 230C
20 wit the rotor at 100 rum. Samples of tub polymer, before
and after such evaluation, were used to measure molecular
weight, using gel permeation cbromatograpby. Tube results
of Casey evaluations are given in Table 1. It is readily
apparent that the molecular weigbC ox tune stabilized
polymer is not significantly affected by the treatment it
tic torque rneometer. A sample of toe stabilized polymer
was evaluated for the production of foam polystyrene egg
cartons and found to be suitable. Eve after recycling
five times in a foam extrusion process, tune properties of
tube stabilized polystyrene were still acceptable.
2~5
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- 17 -
I 5
EXAMPLE 2
For comparison purposes, a polystyrene was
produced using tube process of Example 1, the styrenes
monomer containing about 0.035 weight per cent of
n-octadecyl-3,5-di-ter~.butyl-4-hydroxy-phenyl_proopionate,
and was similarly evaluated. Tube results are given in
Table 2, from which it can be seen that, in comparison
with tube results of Example 1, tube polystyrene is readily
degraded and cannot be recycled as many times as tube
stabilized polymer.
EXAMPLE 3
Two further polymerizations of styrenes monomer
containing about 0.07 weight per cent of zinc Stewart,
about 2.5 weight per cent of etbylben~ene and about 0.035
weight per cent of n-octadecyl-3,5-di-Cert.butyl-4-hydroxy-
phenol preappoint were undertaken, using tube process of
Example 1. Tube first polymerization (Experiment No. 1)
used styrenes monomer containing, per 100 parts by weight
of styrenes 0.1 parts by weigbC of 1,1,3-cris(2-mecbyl-4-
bydroxy-5-tert.butyl phenol) butane and 0.3 parts by
weight of iris (mixed moo- and di-nonylphenyl)
pbosphite. Tube second polymerization (Experiment No. 2)
used styrenes monomer containing, per 100 parts by weight
of styrenes 0.1 parts by weight of 1,1,3-tris(2-metbyl-4-
bydroxy-5-tert.butyl pbenyl) butane and 0~1 parts by
weight ox distearyl pentaerythricol dipbospbite. Tube
polymers produced were evaluated wit tube results sown in
Table 3 from wbicb it is clear that tube polymer of
Experiment No. 1 showed less stability than the polymer of
Experiment No. 2.
~2~24~S
TABLE 2
Bra bender torque:
(230C, 100 rum)- at 5 minutes (mug) 680
- at 10 minutes (mug) 520
- at 15 minutes (mug) 410
- at 20 minutes (mug) 325
Before Bra bender After Bra bender
Molecular Weight Data Treatment Treatment _
My 126700 78140
My 336400 173900
10 My 581900 339200
Men 2.7 2.2
Calculated [I ] dug a . 82 0.51
Fraction ~lx105 Wit .% 18.6 40
Fraction ~6x105 wt.% 18.3 3.5
Recycled expanded polystyrene:
sty end 3rd
yokel Recycle yokel
My 101600 ~1450 84740
IT 255600 208~00 192000
20 My 474700 379500 355300
My n 2.5 2.3 2.3
Calculated [I ] dug 0.67 0.58 0.55
Fraction Clucks wt.% I 32 36
Fraction ~6x105 White 8.5 5 4
Bra bender torque of recycled polymer:
- 5 minutes mug 535 400 340
- 10 minutes mug 410 300 270
- 15 minutes mug 330 240 220
- 20 minutes mug 280 195 180
- 19 -
I 5
TABLE 3
Experiment No. 1 2
molecular weight data:
My 114000 123000
My 314000 318000
My 555000 545000
Mom 2.8 2.6
Bra bender torque:
(230C, 100 rum)
- at 5 minutes mug 770 800
- at 10 minutes mug 610 700
- at 15 minutes mug 520 630
- at 20 minutes mug 440 560
Molecular weight data after Bra bender treatment:
My . 86000 108000
My 197000 234000
I 364000 420000
MwjMn 2.3 2.2
- 20 -
~12~
EXAMPLE
Syrian monomer containing about 0.035 weight per
cent of octadecyl-3,5-di-tert.butyl-4-hydroxy phenol-
preappoint was mixed with various amounts of
3-tris(5-tert.butyl-4-hydroxy-2-met~yl pinwheel) butane
and di-stearyl pentaeryt~ritol diphosphite in a weight
range of about 1:3 and polymerized. About 35 ml of
styrenes containing the polymer stabilizer Wow transferred
Jo a capped glass vial and Abe vials were immersed in a
constant temperature bat at 135C for up to 12 hours.
Conversions of styrenes to polystyrene were determined at
various periods tbroug~ouc the 12 hours by removal of a
vial or such purpose. At the end of 12 yours, the
contents of a vial were removed formed into sweets of
about OHS em thickness and placed in an oven at about
15GC in a stream of nitrogen for about 12 bouts to
remove residual styrenes monomer to less than about 0.02
weight per cent.
Details are sown in Table 4 in which the weight
per cent of polymer stabilizer is sown together with tie
molecular weight data for the polymers, Experiment #6
being a regular commercial polystyrene. Table 5 shows the
evaluation of the polymers, following the procedure
described in Example 1, using mixtures of the polymers
containing toe polymer stabilizer wit the commercial
polystyrene, toe improved polymer stability being readily
apparent even wren tube concentration of tube polymer
stabilizer in tube mixture is as low as 0.1 weight per cent.
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- 23 -
-
l~lZ~95
_ EXAMPLE 5
Tube polymer of Example 1 was compared wit a
commercial polystyrene to illustrate use in a foam
polystyrene production line. For recycling toe scrap
product, tube scrap material was no put tbrougb an
extrude system to compress the material to a non-expanded
form but ratter was fed directly to tube feed, together
wit the virgin polystyrene, of an extrude for melting
and homogenization. To illustrate tube characteristics of
I tube polystyrene used, tube polymer of Example 1 and toe
commercial polystyrene were separately subjected to tube
evaluation described in Example 1, tube results of wbicb
are sown in Table 6, from which it is readily apparent
that toe polymer of Example 1 retained acceptable
molecular weight characteristics whereas eye commercial
polystyrene did not retain acceptable molecular weight
characteristics. Evaluation of tube recycled scrap
commercial polystyrene showed that its molecular weight
properties were intermediate between those of tube virgin
polystyrene and those of tube Bra bender treated polymer.
I
- 24 -
12~L2~5
TABLE 6
Polymer type Polymer of Commercial
Example 1 polystyrene
Molecular weight data
My x 10-3 126 142
x 10-3 317 348
My x 10-3 567 708
Mom 2.5 2.5
Viscosity (caulked) dug 0.79 0.83
Fraction I x 105 wt.% lg.5 19
Fraction I x 105 it.% 15.5 18
Bra bender treatment (230C, 100 rum)
Torque at 5 minutes mug. 800 625
10 minutes mug. 760 455
15 minutes mug. 730 350
20 minutes mug. 700 280
Molecular weight data after Bra bender treatment
My x 10-3 114 83
My x 10-3 277 165
My x 10-3 499 298
Mom 2.4 2
Viscosity (caulked) dug 0.71 0.49
Fraction owl x 105 Wit .% 22.5 41
Fraction I x 105 wt.% 11.0 2
I
- 25 -
4~5
EXAMPLE _
Following the procedure described in Example 4,
samples of poly(p-metnyL styrenes were prepared using an
o'er polymerization time and then evaluated. Tube
p-methyl Syrian monomer contained about 0.035 weight per
cent of octadecyl-3,5-di-tert.butyl-4-bydroxy
pbenyl-propionate (Antioxidant in Table 7). The
quantities of di-stearyl pentaerytbritol diphosphite
(Stabilizer A in Table 7) and of 1,1,3-tris(5tert.
butyl-4-hydroxy-2-methyl pnenyl) butane stabilizer B in
Table 7) as sown in Table 7 were added and tube monomer
polymerized at 135C. Recovered poly(p-metbyl styrenes
samples were mixed as shown in Table 7 and tube polymer
stability was evaluated using the Bra bender wick tune
results sown in Table 7. Tube improved polymer stability,
as evidenced by tube smaller change in torque, is readily
seen for Mixtures B, C, D and E compared to tune control
Mixture A.
- 26 -
~Z~2~5
TABLE 7
Experiment # 1 2 3
p-Metbyl styrenes 99.965 99.165 97.565
Antioxidant 0.035 0.035 0.035
Stabilizer A - 0~6 1.8
Stabilizer B - 0.2 0.6
Mixture Compositions A B C D E
Polymer #1 100 7550 92 84
Polymer #2 - 2550
Polymer #3 - - - 8 16
Calculated Stabilizer content wt.% 0.04 0.27 0.51 0.39 0.75
Brabend~r treatment (230C, 100 rum)
20 Torque at 5 miss. mug. 485 465 478 450 413
10 miss. mug. 440 422 430 410 375
15 miss. mug. 420 420 422 400 362
20 miss. mar 400 410 418 385 358
