Note: Descriptions are shown in the official language in which they were submitted.
203~6~6
-1- (8CN-8429)
PROCESS FOR PRODUCING EXPA~DA~LE
T~R~O~ASTIC MICROPAR$ICL~S
The present invention relates to the
production of expandable thermoplastic microparticle~.
More particulariy it relates to a process for melt
compounding micropellets of a thermoplastic resin and
impregnating the micropellets with a blowing agent to
form expandable microparticles. As used hereinafter the
term microparticles is intended to comprise both
substantially cylindrical micropellets and substantially
spherical microbeads.
8AC~GROUND OF T~E INVENTION
:et.^^_s for the production of exoandable
thermoplasti_ ~esin beads for use in the manufacture of
foam moiaea _rt-cles are well known in the art. For
instance, traditional expanded polystyrene tecnnology
has existed since the early 1~5~'s.
The production of expandable beads can include
the incorporation of a blowlng agent by one of three
methods. ~ne method, known as the "one-step" ?rocess,
is to suspend styrene monomer, initiators ana nyarocarbon
blowing agent in water and polymerize at Aigh temperature.
This metnod is taught by Japanese Patent ?ublication No.
32623/70.
In a second process, called the "l~ step"
process, t~.e polymerization is brougnt to ~0 percent
completion before the blowing agent is introauced into
the system. ~e "two-step" process incorporates the
blowing agent into suspension polymerized beads (100%
converted) or melt compounaed pellets. llhe two-step
process is used in Japanese Patent Publication No.
36097/72 wAicn discloses neat-melting a polymer,
pelletizing the melt and incorporating t.~e formed
pellets wlth a blowinq agent.
Incorporation of the blowing agent into the
2030646
-2- (8C~-8429)
extruder has been disclosed in Collins, United States
~atent ~io. 3,250,~34. ~ollins compressed the heated
polystyrene prior to introduction of the blowing agent
and cooled the mixture thereafter extruding the mixture
into stranas wnich are later cut into pellets. The
problem in Collins is the cooling necessary to prevent
expansion of the mixture prlor to extrusion. Further,
the strands produced by the Collins process are taught
to have a diameter of about 0.06 inches.
~he ?roDlem of temperature control wnile
cooling the extrudate passing through the die, as
causing -locKa~e of t..e die, is dealt with in United
~ingdom 2~te~.r ~.o. 348,200 (Platz et al.) and Canadian
?atent o. ~o~,i64 (acnroeaer et al.). Platz et al.
make use o~ a -ie either made from or lined with
polytetrafluoroe~hylene having openings of ~ to 8 mm in
aiameter. Schroeder et al., on the other hana, deal
with this DroDlem by regulating the temperature of the
composition entering the die to assure free flow and
cooling t-e composition almost immediately as it exits
the die. achroeder e~ al. make no mention of a minimum
diameter of extrudate leaving the die.
~ther -rocesses for the productlon of
expandable resin compositions are disclosea in ~1nited
States Patent ~o. 3,026,273 (Engles), United States
Patent ~o. 3,026,272 (~ubens et al.), United States
Patent No. 3,121,132 (Bene) and United States Patent No.
3,u26,274 (~lactiillan et al.). These disclosures aeal
with the pre-expansion of the composition. The size of
the pellets proauced in these disclosures are limited,
in their minimum dimensions, to normal diameters, as no
mention of small or microdiameter particles is made.
The process of underwater pelletizin~ of
polymers wltn an adjustable blade for varying ^eilet
size is disclosed in Smith, United States Patent ~o.
20306~
_3_ (8CN-8~29)
~,500,271. Size restrictions of the extrusion die due
to flow of the polymer are limltea to a minimum of about
0.035 inches to proauce uniform beaa size distribution.
Sucn techniques are good for resins which process at low
temperatures, such as polyolefins, but not for
engineered thermoplastics. Allen et al., in commonly
assigned United States Patent Application, Serial ~o.
093,317, filed September 4, 19~7, attorney's docket
335-2051 (8C~-8335) discloses a one-step process for the
?roduction of small spnerical expandable beads employing
a heated die and unàerwater ?elletizer. Allen et al.
claim small expanàaDle Deaas naving aiameters ranging
from aoout ~.ûlC to aDout 0.~50 incnes and more
referaDiy -om aDout 0.ul~ ~o about 0.025 incnes.
1~ ~urrently, expandable polystyrene beaas are
generally ?roduced from so-called raw polystyrene Deads
which are made Dy a relatively inexpensive batch
emulsion polymerlzation process. As a consequence,
modification of the expandable polystyrene beads through
either coooli~,erlzation or Dlending is ,~ade airficult
~ecause of deleterious effects of additives on both the
?olymerization ~inetics and emulsion sta~ility.
It would therefore be a notable advance in the
state or the art i~ expanaable t-.ermoplastic resin ~eads
could be made from a resin produced througn a continuous
method of ~olymerization other tnan oatch emulslon
polymerization and/or modified with a variety of
additives sucn as plasticizers, lubricants, -lame
retardants, anti-static agents, ?igments and the like
~or improved ?roperties.
Allen et al., United States Patent No.
~,72/,093 teacn producing oolypnenylene etherJpOly-
styrene beads rangin~ in size from 0.0212 to 0.0661
inches (10 - 30 mesn, J.S. stanaard sieve size) :n
diameter and then imbibing tO produce expandable beads.
20306~6
_~_ (8CN-8429)
It has now unexpectedly been discovered that
?roducing micropellets, less than 0.02 inches in
diameter, facilitates ~he imbibing of a blowing agent
into the resin and that such microparticles suDse~uently
expand and fuse Detter when placed in a mold.
Surprisingly, tnese micropellets are also nighly
amenable to tne addition of a wide variety of additives
and copolymerizations thus enabling the producer to
obtain a resin with a wide variety of desired improved
properties.
This is especially significant in the
instances -~nere ~he resins sougnt tO be micropeiletized
~re Drl..ie, _ucn as .or principally atactic polystyrene
ana styrene-~aieic anhyaride copolymers. ?rocesses
employing stranas of tnese Drittle materials having very
small iiameters suffer from poor productivity aue to
strand breakage. Consequently, micropelletization is
not currently used in the production of expandable
polystyrene beaas.
~0 It has now been found, however, that
microparticles of these brittle resins ;nay be produced
accordin~ to the present invention by the addition of a
auctiii~y ennancing resin such as polypnenyiene ether~
; SUMMARY OF T~ PR~SENT INVENTION
Accorain~ to the present invention there is
providea a process for the production of expandable
microparticles of a thermoplastic resln, comprlsing the
following steps: (a) plasticating a substantially
nomo~eneous thermoplastic resin or a blena of at l~ast
two substantially miscible thermoplastic resins capable
of becomins substantiaily homogençous after said
plastication (b) extruding the plasticated material
formed in step (a) throush a multi-strana ;icrodie tO
form strands having an average diameter of less t~an
about 0.02 inches; (c) cooling the strands; (a)
20306~6
_5_ (8CN-0429)
comminuting the cooled strands to form substantially
cylindrical micropellets having a length to diameter
ratio of about 1:1; and either (e)(i) impregnating the
substantially c lindrical expandable micropellets with
S an effective amount of a blowing agent to form
substantially cylindrical expandable microparticles or
(e)(ii) impregnating the substantially cylindrical
micropellets with an effective amount of a blowing agent
at a temperature above the glass transition temperature
of the thermoplastic resin to form substantially
sphericai exDandable microparticles.
:-~efsraDly, the suDstantially homoaeneous
ther~opl-at - -esin ;s selected from the group
consistlng o, ~ ?oiypnenylene etner, a polyester, a
polystyrene, -n amorphous polyamide, a polycar~onate, a
polyether sul~one, a polyetherimide and substantially
nomogeneous mixtures and copolymers thereof. The
preferrea polyphenylene ethers are poly(2,~-dimethyl-
1,4-phenylene)ether and poly(2,6-dimethyl-co-2,3,6-tri-
methyl~ -pnenylene)ether. ~he preferred polystyrenes
are prlnci?aily atactic polystyrene, ooly(alpha-methyl-
styrene~, poly(nuclear-methylstyrene), poly(para-methyl-
styrene)~ poly(para-tert-butyl styrene), ..alogenated poly-
styrene, a styrene-maleic anhydride copolymer, styrene-
butadiene co?olymer, atyrene-acrylonitrlle copolymer,
styrene-acrylonitrile-butadiene terpolymer, styrene-di-
vinyl ~enzene copolymer and high i.mpact poiystyrene.
Also preferrea is a polyphenylene ether/polystyrene blend.
,he preferred blowing agents are selected from
tne grouD consisting of n-pentane, isopentane,
neopentane, _yclopentane, butane, sobutane, ~en~ene,
hexane, heptane, octane, propane, methylene chlorlde,
cnloroform, CarDOn tetracnloride, tric~lororluoromethane,
dichlorodifluoromethane, chlorodifluoromethane,
CClF2-CClF2, dichlorotrifluoroethane (CHCl~C~3),
203064~
-6- (8CN-a429)
dichlorotr1fluoroethane (CHFClCClF2), chlorotetrafluoro-
ethane, tetrafluoroethane, dichlorofluoroethane, chloro-
difluoroethane, difluoroethane, acetone, alcohols having
from 1 to 5 car~on atoms, halogenated alcohols such as
i fluoroisopropanol, carbon dioxide, nitrogen, water,
methylethyl ketone, ethyl acetate and mixtures or any of
the foregoing.
DETAIL~D D~SCRIPTION O~ T~ INVENTION
As used hereinabove and throughout the
application, the term plasticating is defined as a
process of heatlng and shearing a thermoplastic resin at
a temperature of at least the glass transition
~emper~tur~ --e case or amorpnous resins ana of at
least ~ne ~el~ temperature in the case of crystalline
resins. ~::.e -erm nomogeneous is aefinea as a resin or
blend of resins uniformly dispersed in each other having
a single onase tnermodynamically. The term "suostantially
miscible" is defined a~ substantially soluble or
substantially tnermoaynamlcally compatible, i.e. the
materials exist primarily as a single phase. However,
those of orainary skill in the art will understand that
such polymer systems may include minor amounts of phase
separatea or icropnase separated materials wnich exist
without detracting from the overall performance or the
oolymer system.
.Ae present invention relates to a process for
the proauction of expanaaDle thermoplastic microparticles.
~he invention may be practiced with the use of a wide
variety of materials encompassed within tne broader
description given above. In the typical case nowever,
use is maae or certain preferrea materials whic" are
described below.
.he oolyphenylene ether (PPE) is normaily a
nomo- or coDolymer inaving units of tne rcrmuia
20306~6
- ,- ( 8CN-8429 )
~ O ~ O ~
Q Q
. - . . .
wherein Q, ~ , 2 , Q are independently selected from
the group consisting of hydrogen, halogen, hydrocarbon,
halohydrocar~on, hydrocarDonoxy, and halohydrocarbonoxy;
and n represents the total ~umber of monomer units and
is an integer of at least about 20, and more usuaily at
leas t _ O .
The ?oiypnenylene ether can be prepareà in
~ccordance ;ilt.. ~nown ?rocedures such as those aescribed
in Hay, Unitea States Patent Nos. 3,306,874 and 3,306,875;
ana ~tamatoff, ~nlted States ~atent Nos. 3,2S7,357 and
O,257,35a, from the reaction of phenols including but
not limited to: 2,6-dimethylphenol; 2,6-diethylphenol;
2,6-dibutylphenol; 2,6-dilaurylphenol; 2,6-dipropylphenol;
2,6-diphenyi?henol; .-methyl-6-tolylphenol; 2-.~ethyl-6-
~ethoxyphenol; 2,3,6-trimetnylphenol; 2,3,5,6-tetramethyl-
?nenol; and 2~o-aietnyoxyphenol.
Eacn of tnese may be reacted alone to produce
the corresponaing homopolymer, or in palrs or ~ltn still
other ?nenols to produce the corresponaing copolymer.
Examples of the homopolymer include poly(2,6-dimethyl-l,
4-phenylene)ether, poly(2,6-diethyl-l,4-pnenylene~ether,
?oly('~,~-aibutyi-i,~-pnenylene)ether, poly(2~6-dilauryl-i~
~-phenylene)ether, ?oly(2,6-dipropyl-l,4-phenylene3ether,
?oly(2,6-aiphenyl-l,4-phenylene)ether, poly(2-.~ethyl-6-
outyl-l,~-phenylene)ether, poly(2,6-dimethoxy-l,'-Dneny-
lene)ether, ~oly(2,~,6-trimethyl-l,s-pnenylene)ether,
?oly(2,3,5,6-tetramethyl-l,4-pnenylene)ether, and poly
(2,6-diethyoxy-l,4-pnenylene)ether. Examples of ~he
copolymer include, especially those of 2,6-dimetnylphenol
2030646
-a- ( scN-a~2s
~ith other phenols, such as poly(2,6-~imethyl-co-2,3,6-
trimethyl-1,4-onenylene~et~er ana poly(2,6-dimethyl-co-
2-methyl-6-butyl-1,4-phenylene)ether.
For purposes of the present inven~ion, an
especially preferred family of polyphenylene ethers
include those naving alkyl substitution in the two
positions ortho to the oxygen ether atom, i.e., those of
the above formula wherein Q and Q are alkyl, most
preferaDly having from 1 to 4 carbon atoms. Illustrative
members of this class are: poly(2,6-dimethyl-1,4-pheny-
lene~ether: ~olv(2,6-diethyl-1,4-ohenylene)ether: poly
(2-methyl-6-etnvl-1,4-phenylene)echer poly(2-methyl-6-
~ropyl~ onenviene~ether: ?oly(2~6-dipropy~ -ohen
lene)etr.er; _oly(2-ethyl-6-propyl-1,4-pnenylene) ether;
anà t~.e l~e.
The most preferred polyphenylene ether resin
for purposes or the present invention is poly(2,6-ai-
methyl-l,~-phenylene)ether.
The term "alkenyl aromatic polymer" as it is
employed in t.his disclosure is intended to encompass
homopolymers, as well as rubber modified high impact
Jarieties, and also copolymers ana terpoiymers of
alkenyl aroma~ic compounds with one or more other
materials. ?refera~ly, the alkenyl aromatic polymer is
based at least in part on units of the formula
R5 CRl = CHR2
R6 ~ R3
wherein Rl and R2 are selected from the group consisting
of lower a!kyl or alkenyl ~roups of from 1 to 6 carDOn
203~646
_9_ (8CN-8429)
atoms and hydrogen R3 and R4 are selected from the
group consisting of chloro, bromo, hydrogen and low-r
alkyl of from 1 to 6 c~rbon atoms; R5 and R6 are
selected from the ~roup consisting of hydrogen and lower
alkyl and alkenyl groups of from 1 to 6 carbon atomnS or
R5 and R6 may be concatenated together with hydrocarbyl
groups to form a naphthyl group.
The aDove will encompass styrene, as well as
homologs and analogs of styrene. Specific example~
include in addition to styrene, chlorostyrene, dichloro-
styrene, ~romostyrene, dibromostyrene, alpha-methyl
styrene, auciear-metnyl styrene, para-methyl stvrene,
?ara--er--e~t l styrene, vinyl styrene, divinyi ~enzene
and vinyl napnthalene. Styrene is especlally preferred.
Ry way of illustration, the polystyrene (PS)
component can se a homopolystyrene ~principally atactic)
or other alkenyl aromatic homopolymer which has been
modifiea by admixture or interreaction with a natural or
synthetic rubDer, for example, polybutadiene, polyiso-
2U prene, EPDM rubber or silicone rubber: or it can be a
copolymer or terpolymer of styrene or other alkenyl
aromatic compound with an elastomeric or other material,
such as ~lock copolymers of styrene ana Dutadiene (for
example, AB, ABA, A~AB or ABABA type), including hydro-
genated forms of t~e foregoin~, a raaial teleblockcopolymer of styrene, butadiene ana a coupling agent,
inclualng nyarogenated forms, ter?olymers of
acrylonitrile, styrene and butadiene (ABS~, styrene-
acrylonitrile copolymers (SA;~), and a copolymer of
styrene and maleic anhydride (SMA); or it can also be an
alkenvl aromatic copolymer or teroolymer ~nich has been
modified with rubber, for example, rubber modified
styrene-maleic anhydride copolymer. ~any of these are
described in the patent literature, such as Cizek,
United States Patent No. 3,383,435.
20306~6
-10- ( scN-a42s )
The polyphenylene ether (PPE) and polystyrene
resins may be comolneà in a conventional manner. PPE
resin will typically be in powder or pellet form and the
polystyrene will typicaily be in pellet form. The
resins may De combined by dry blending in a blender
which proviaes a relatively uniform mixture of the
resins or by other conventional means. This mixture is
typically airectea to a thermoplastic extruder, usually
of the single or twin screw type, wnere in the case of a
blend the resin is compounded with sufficient temperature
and shear tO ?rovlde an intimate PPE/PS blend.
Ihe product of the conventional extruder is an
extruaare :. -e ~orm of stranas wnicn may oe quenched
with a coolant âuch as cooling water. The cooled
,tranas are _ rected .o a pelletizer aevice whicn
provides the PPE/PS resin pellets in a conventional form
for use ln tne present invention.
Durlng the blending step it is contemplated
that convent.onal additives may be incorporated in the
resin mixture if desired. These lnclude rubbery impact
modifiers, Clame retarding agents, stabilizers ror
thermal and color stability, antioxidants, ?rocessing
aids, plasticizers, reinforcing and extenaing fillers,
pigments, antistatic agents, lubricants, mixtures of any
o~ ~he roregoing ana the like. Eacn of tnese may be
utilized to a greater or lesser degree depending on the
final requlrea proDerties desired in the foamea ?roauct.
Conventional surfactants and nucleants used in
expanaed polystyrene foams may also be utilized.
Examples of these include zinc or tin stearates,
,~aleates, fumarates, .alc, a citric acid and sodium
oicarbonate mixture (Hydrocerol-) and the like.
~ ther vrererred resins contemplatea for use
in the present invention are polyamides, e.~. nylon-6
and nylon-6,6; ana oreferably amorpnous nylons, e.~.
2~3~6~6
-ll- (8CN-8429)
Selar- PA (DuPont), 3exloy- C (DuPont), Zytel- 330
(DuPont), Trogamid- ~ (Dynamit Nobel), Grilamid T~55
(Emerson Industries) and MXD6 (Mitsubishi Gas Chemical);
Dolycarbonates such as poly(bisphenol-A) carbonate; poly-
ethersulfones and polyetherimides. These are available
commercially and are described in the literature.
The substantially homogeneous thermoplastic
resin is generally plasticated in a melt compounder.
This typically comprises an extruder although any melt
compounding apparati ~nown to those skilled in the art
~ may be employed. (See Modern Plastics Encyclopedia '89,
~cGraw Hill, ctooer 1988, ~ol. 65, ~o. ll, Dage 345 -
346). ; wlde iariety of extruders may ~e e.mploved, sucn
as those aescribed in Modern Plastics Encyclopeaia '89,
15 .~cGraw ~ill, ~ctoDer 1988, ~ol. 65, ~o. ll, ?P. 242 - 244.
~ he plasticated resins are then extrlded
through a multi-strand microdie. The microdie is
construc~ed to comprise a olurality of holes having a
diameter of up to about 0.02 inches. The strands
exiting ~ne ~icrodie have an average diameter of less
than about 0.02 inches.
It is also contemplatea herein that tne
olasticated tnermoplastic resin is directed through a
spinning aoparatus c~ntaining a multi-fiber s?innerette
die to form fibers having an average diameter of less
than about O.C2 inches. Any spinning appa ~tus known to
those skilled in the art is contemplatea.
The strands or fibers are then cooled. It is
contemplated to effect the cooling by quenching the
stranas or fibers with a coolant. Typical coolants may
comprise water, air, aitrogen, helium, alcohols,
polyols, glycols or mixtures of any of them. Preferred
is a waterbath or air coolins.
The cooled strands or fibers are then directed
to a comminuting device, typically a high speed chopper
20306~6
-12- (8CN-8429)
or an impeller. See Modern Plastics Encyclopedia '89,
.~cGraw ~ill, Octobe l9a8, Yol. 65, No. 11, pp. 352 -
353. The strands or fibers are co~minuted to form ~
substantially cylindrical micropellets having an average
diameter of less than about 0.02 inches. Preferably
the micropellets have a length to diameter ratio of
about 1:1.
The micropellets are then impregnated with a
blowing agent. Preferably the blowing agent comprises a
volatile liquid or gas capable of being absorbed by the
thermoplastic resin and which will vaporize at or below
~he glass transition temperature of the thermoplastic
resin.
The clowing agents may include conventional
hydrocarbon or 'luorocarbon blowing agents. The
?referred h~drocarbon blowing agents will include
aliphatic hvdrocarbons. Examples include propane,
butane, isobutane, n-pentane, isopentane, neopentane,
pentene, cyclopentane, cyclohexane, hexane, heptane,
octane, .~ixtures thereof and the like. FluorocarDon
blowing agents incluae trichlorofluoromethane (CC13F),
dichlorodifluoromethane (CC12F2) ana CClF -_ClF_. These
are commercially available as FREON- 11, FREON- 12, and
FREON- 114. ~ther halogenated hyarocarbon ~lowing
2S agents include methylene chloride, chloroform, carbon
tetrachloride (CC14), HCFC's such as difluorochloro-
~ethane (CHClF~) (HCFC-22) (FCRCMACEL- S), dichlorotri-
fluoroethane (HCFC-123) (CHCl~CF3), dichlorotrifluoro-
ethane (HCFC-123A) (CHFClCClF2), chlorotetrafluoroethane
(HCFC-124) (CHClFCF3), tetrafluoroethane (HFC-134A)
(CH2FCF3), dicnlorofluoroethane (~CFC-141B) (CCl~cCH3),
chlorodifluoroethane (HCFC-142B) (CH3CClF2), difluoro-
ethane (HFC-152A) (CH3CHF2) the like. Other blowing
agents contemplated for use in the present invention
are: acetone, alcohols having ~rom 1 to 5 carbon atoms
20306~6
-13- (8CN-a~29)
such as isopropanol, halogenated alcohols such as
fluoro- isoproDanol, carbon dioxide, nitrogen, water,
mathy~ethyl ketone, ethy~ acetate or mixtures of any of
the foregoing.
The blowing agent may be impregnated into
the microparticles in any manner known to those skilled
in the art.
In one preferred embodiment the substantially
cylindrical thermoplastic resin micropellets and desired
amount of blowing agent are placed in a vessel, the
- mixture is agitated until tne blowing agent and
thermoDiastic resin micropellets are thoroughly mixed.
,e 1xture is then allowed to age at or near
ambient conaitlons for a period of time sufficient to
- 15 impregnate t.~e thermoplastic resin micropellets with the
blowing agent. Substantially cylindrical expandable
microparticles are produced by this method.
In another preferred embodiment the
substantlally cylinarical thermoplastic resin micropellets
are impregnated with an effective amount of blowing
agent at a temperature above the glass transition
temperature o~ the _olymer and blowing agent composition.
.ypicall~ the tnermopiastic resin micropellets are
supported in a wire mesh screen and placed in an
autoclave. The micropellets are dispersed on the screen
support in order to expose a maximum surface area to the
blowing agent vapors.
The autoclave is sealed and evacuated. Once
; tne autoclave is evacuated, a quantity o~ blowing agent
is drawn into tne autoclave. The amount of blowing
agent charged is aetermined by the amount of absorption
-~ desired and the amount of blowing agent required to
m~intaln a saturated atmosphere.
The autoclave is slowly heated to about a
temperature at or sligntly above the glass transition
2030646
-14- (8CN-~q29)
temperature (Tg) of the polymer and blowing agent
composition and maintained thereat for an extended
period of time. Higher temperature~ would result in
~icropellets that nave fused together. The temperature
and time is determlned by the Tg of the composition and
the rate at which the blowing agent is absorbed by the
pellets.
The autoclave is allowea to cool to room
temperature, opened and substantially spherical
expandable microparticles are removed.
Alternatively, the blowing agent may be
absorDed into tne micropellets through exposure of a
water/^eile- _uspenslon to the blowing agent as follows.
Substantially cylindrical micropellets, e.g.
125 9, ~re _~spended in an aqueous solution of
polyvinylalcohol (about l percent PVA by weight). Other
suspending agents or surfactants may be employed, e.g.
tricalcium pnosphate. ~his suspension is charged to an
autoclave (~0 ml) and is sufficient to fill this size
autoclave to 75 percent of capacity.
A quantity of blowing agent is cnargea to the
autoclave. .he autoclave is sealed, agitation is
initiate~, and the temperature is slowly increasea.
Agitat1on is required in order to prevent clumping of
the mlcropellets and to improve contact of the mlCrO-
pellets with the blowing agent. This is especially useful
for systems whicn consist of more than one liquid phase.
The system is heated to a temperature of about the Tg of
the blend and maintained thereat for a period of .ime.
The elevatea temperature increases the rate at wnich the
blowing agent evenly disperses through the micropellets
and determines the necessary absorption ~ime.
lhe system is then all^wea to cool ~nd ;he
micropellets are removed from the autoclave. ~he
micropeLlets are separated from the suspension solution
;
203064~
-15- (8CN-8~29)
with a sieve, rinsea with water and allowed to dry at
ambient conditions. Substantially spherical expandable
microparticles are thus produced.
DBSCRiPTIO~ OF Tn~ PR8PERReD E~BODIN~TS
The following spec~fic examples illustrate the
present invention. However, they are not to be
construed to limit the claims in any manner whatsoever.
ESA~PLE 1
A mixture of 10 weight percent of poly(2,6-di-
methyl-1,4-phenylene)ether and 90 weight percent of
principally atactic polystyrene are fed into a 30 mm
~erner Pfleiderer extruder equipped with a multiple
strand microaie. ~ultiple strands having a diameter of
less tnan 0.~2 inches are then cooled in a water bath
and fed tO a nigh speed chopper to produce micropellets
having a length to diameter ratio of about l:l. The
micropellets are then exposed to a saturated atmosphere
of blowing agent at a temperature of about 100C in an
autoclave for about 4 hours. The autoclave is allowed
to cool ana expanaable micropartlcles are produced in
accordance with the present invention.
EXA~PLES 2 - 5
The proceaure of Example 1 is followed except
blenas containing 20, 30, 40 and 50 weight percent of
polyphenylene ether are employed. The tempereature is
accordingly increased about 1C aoove 90C for each
adaitionai 1 weight percent of polyphenylene ether in
the composition. Expandable microparticles are produced
in accordance with the present invention.
EXAHPLE 6
The proceaure of Example 1 is followed except
a Dlena of 10 welght percent of Drominatea polys~yrene,
;0 weight percent polyphenylene ether and 40 weight
pPrcent of prlncipally atactic po~ystyrene is employea.
Expandable flame retardant microparticles are produced
2030~46
-16- (8CN-~429)
in accordance with the present invention~
~LB 7
The procedure of Example 1 is followed e~cept
3 weight percent of carbon black pigment is added to the
resin blend. Black expandable microparticles are
produced in accordance with the present invention.
E~a~PLeS 8 - 21
The procedure of Example 1 is followed except
that poly(alpha-methylstyrene), poly(nuclear-methyl-
styrene~, poly(para-methylstyrene~, poly(para-tert-butyl-
styrene~, polymonochlorostyrene, polydichlorostyrene,
polybromostyrene, polydibromostyrene, styrene-maleic
annydride copolymer, styrene-butadiene copolymer,
styrene-acrylonitrile copolymer, styrene-acrylonitrile-
butadiene terpolymer, styrene-divinylbenzene copolymer
and rubber modified high impact polystyrene are
substituted for the principally atactic polystyrene.
ExpanaaDle ~icroparticles are produced in accordance
with the present invention.
EXAffPL~S 22 - 3~
lhe procedure of ~xample 1 is followed except
that instead of the polyphenylene ether~polystyrene
resin ~lend an amorphous polyamiae, a polycarDonate, a
polyphenylene ether~polyethylene blend, a polycarbonate/
polyetr,erimlde Dlend, a polycarDonate/amorphous polya~ide
blend, a polystyrene, a polysulphone, a polyphenylene
ether, a functionalized polyphenylene ether/amorphouS
polyamide blend, a polycarbonate/polyester blend, a
polyester/amorphous polyamide blend, a polyester~poly-
3~ etherimide blend, a polyetherimide/amorphous polyamideblend and a polyetherimide/polycarDonate/poiyester blend
are employed as the substan~ially homogeneous
thermoplastic resin. Expancable microparticles are
prod~ced in accordance with the present invention.
203~6~6
-17- (8CN-a~29)
ESA~PLeS 35 - 73
The procedure of Example 1 is followed exceet
~tXat inQtead of n-pentane, isopentane, neopentane, - -
cyclopentane, butane, isobutane, pentane, hexane,
S cyclohexane, heptane, octane, propane, methylene
chloride, chloroform, carbon tetrachloride, trichloro-
fluoromethane, dichlorodifluoromethane, difluorochloro-
methane, CClF2 - CClF2, HCFC - 123, HCFC - 123A, ~CFC -
124, HFC - 134A, HCFC - 141B, HCFC - 142B, HFC - 152A,
acetone, butanol, isopropanol, methanol, ethanol,
~ propanol, fluoroisopropanol, carbon dioxide, nitrogen,
air, methyl ethyl ketone, ethyl acetate and water are
employed as the blowing agent. Expandable microparticles
are producea in accordance with the present invention~
E~A~PLES 7~ - 8~
The procedure of Example 1 is followed except
that a plasticizer, a flame retardant, a thermal
stabilizer, a U-V stabilizer, a lubricant, an antistatic
agent, a nucleating agent, a pigment, a reinforcing
filler, a non-reinforcing filler and a mixture of the~e
are added to the extruder with the resin blend.
Fxpandable microparticles are produced in accoraance
with the present invention.
EXAMPLE 85
lhe procedure of Example 1 is followed except
that the resin blend is fed to a spinning apparatus
equipped with a multi-fiber spinnerette aie to rorm
multiple fibers having an average diameter of less than
0.02 incnes, air cooling the fibers and directing the
fibers to a high speed chopper to form substantially
cylindrical micropellets having a length to diameter
ratio of 1:1. The micropellets are then imbibed with
n-pentane. Expandable microparticles are produced in
accordance with the appended claims.
The above-mentioned patents, patent applications
203064~
-}8- t8CN-8429)
and publications are incorporated herein by reference.
^- Many variatio~ of the present invention will
~uggest themselves to those skilled in the art in light
of the above-detailed description. For example instead
of poly(2,6-dimethyl-1,4-phenylene)ether, a poly(2,6-
dimethyl-co-2,3,6-trimethyl-1,4-phenylene)ether resin
may be employed. It is also contemplated to use any
type of melt compounding apparatus instead of an
extruder, and an impeller or other comminuting device
may be used to form the substantially cylindrical
micropellets. Further, any imbibing process known to
those sKilled in the art is contemplated to impregnate
the microp~llets with blowing agents. All such obvious
modificatlons are with the full intended scope of the
appended claims.
