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Патент USA US2404406

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July 23, ‘1946.
-
- F, M RQDDY
‘2,404,406
_ PROCESS FOR PLASTICIZING OR PLASTICATING PLASTIC MATERIALS
Filed March 5, 1942
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I
‘
~
'
INVENTOR
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‘
BY
L‘ E“
V
FRED M/PODDY
' 2 ATTORNEY
,
Patented July 23, 1946
' 2,404,406
l UNITED ‘STATE s.‘
PATENT OFFICE
2,404,406 ,
PROCESS FOR PLASTICIZING 0R PLAs- '
'
TICATING PLASTIC’MATEBIALS
Fred M.. Roddy, ‘Providence, R. I.
Application March 3, 1942, Serial No. 433,118 '
1 Claim. (Cl. 18-48)
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1
2
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This invention, relates 'to a method for plasti?
cizing or plasticating plastic compounds, and
more particularly to plasticizing various kinds‘ of
thermoplastic molding materials‘ that‘ are/em
ployed in the plastics industry. By thermoplastic j,
molding materials is meant those materials which "
soften and can be 'made to ?owv under the action
of heat and pressure without: regard‘ to, any sub
sequent reaction which may alter its plastic prop
erties.
:
with a liquid'plasticizer but the solid cellulose
acetate material will predominate and the re
sulting mixturewill merely be moist or damp and
therefore capable of being fed into the plasticat
ing system by the type of injector mechanism
hereinafter
disclosed.
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,
‘
A further object of my invention is to provide
a method whereby a portion of the heat re
quired to plasticate the material is added to the
It is accordingly'one object of my inven- v 10 ‘material by means of the friction generated with
tion to‘ provide a process which will be capable of
plasticizing the above-mentioned materials at a
in the turbulently ?owing material as it passes
through various conduits and strictures in the
much more rapid rate than is the case with pres
mechanism of the system.
I
'
The more fundamental aspect of the'invention
ing in a shorter time with less consequent injury .15 is the method of injecting the cold powdered or
granular material into a ?owing stream of plas
to the materialbeing processed. "
tic material which has previously been plasti
‘Another ‘object of the invention is to provide a
cized, and thereafter pumping and circulating
continuous process thereby insuring a more'uni
this material through certain heated paths and
for-m quality of ‘product and also lessening the
20 .passages wherein the particles of the powdered
'cost of the manufacturing operation.
or granular material become thoroughly mixed
It is to be pointed out that'plastic materials ‘of
this class in either the powdered or granular form a with the plastic mass in the ?owing stream, and
themselves become quickly plasticated. Once the
are poor conductors of heat and because of this
cold powdered or granular material has been in
it is di?'lcult to bring these materialsto a plastic
state by contact heating as isv carried out in the 25 jected into ‘the stream of ?owing plastic material
there will obviously he numerous embodiments
present‘ types of rubber-type mills and other
ent equipment and also to accomplish the heat
kneading machines usedvfor plasticating plastic
and rami?cations that the mechanism employed
Once the material ‘has become sof
tened or slightly plastic, however, its heat con
in the process may take.
ductivity increases and‘it‘is less dif?cult to add
out my invention,‘ the powdered or granular ma
‘further heat to the material by the contact
terial is stored in the hopper of a plunger type
injector mechanism. Two plungers are provided
and it is intended that they be operated alter:
' compounds.
method;
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‘
'
'
f
.
a
‘ With, the foregoing principle in mind, another
object of the invention is to provide a means of
injecting vthe cold plastic compounds in'powdered
In the apparatus which I employ for carrying
nately in such a manner that at all times one of
35 the plungers tends to force cold granular mate
or‘ granular form into a moving stream of. pre
rial into the 'plasticating system. The injector
‘viously plasticized material, and then causing
plungers force the said cold powdered or granular '
this stream of material, consisting partially of ' material into the circuit of a ?owing plastic
stream which picks up these injected particles
plastic material and partially of the powdered or
granular material which has been injected into 40 and carries them along with the stream of flow
ing material. This stream then is led tola pump,
the stream, to flow through passages of the sys
preferably of the high pressure streamline ?ow
tem wherein additional heat is added to the ma
type capable of producing ?ow pressures of the
terial so that the aforesaid particles of powdered
' order of from ten thousand to thirty thousand
or, granular material will become thoroughly
pounds, per square inch. Such a pump is de
mixed and plasticized in the turbulently‘?owing
scribed in my'co-pending application Serial No.
stream and form' a' homogeneous mass of plasti
439,634, filed April"20,'1942. The material is
'cized
‘ It ismaterial.
to be explained
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r that the cold
V powdered
» ‘
or
pumpedv through ‘a conduit which branches into ‘V
two circuits, the one circuit leading to a second
granular material above referred to is either of
"the inherently thermoplastic type as methyl 50 pump preferably of the type just described, and
the other conduit serving as a ‘by-pass which leads '
methacrylate or of materials, such as cellulose
a portion of the'material past the connections
acetate, that are made thermoplastic by ‘the ad
dition of suitable liquid plasticizers} When cellu
lose acetate is used in this application, the dry
» with the injector mechanism wherethe?owifig
stream’ from the said by-pass circuit ‘again picks
cellulose acetate will have been prevlouslyi'mixed 55
1 up additional cold powdered or granular mate;
2,404,406
3
4
V
' rial which is again carried along by the stream
able for extrusion may be located either before
to the ?rst mentioned pump. The ?rst pump unit
.of the system will be hereinafter referred to‘as
the circulating pump and the second pump unit
or after the metering pump. The desirable loca
tion that would be selected in practice, however,
would depend on thenature and viscosity of the
hereinafter referred to as‘ the metering pump.
materials being processed.
,
While the apparatus above-described in general
illustrates the manufacture of thermoplastic
V The ?owing material which by the time it has
reached the ‘metering pump has become quite hot
and soft. is pumped from themetering pump ’ ‘molding materials, it is pointed out, that the ma
' through a ‘suitable, cooling unit wherein it'is
terial drawn from the plasticating‘ system may
cooled to a state of plasticity suitable for extrud l0 be taken directly to and employed in a fashioning
ing and thence the material is led to an extruding
: or fabricating operation, such as the extrusion of'
die located in the top of a vertical stack or cab
. strands, rods, sheets, or a molding operation for
inet. At the extrusion die, the material is formed’ ' ‘producingjmolded articles. The operations are
into strandswhich are cooled and becomehard- ' ‘ ‘simpli?ed if‘ the material is led directly from the V
ened as they are led downwardly throughthe.
plasticating system to the fashioning orrfabricat
' stack or cabinet which is cooled by circulating air, _ ,ing means. vIn practice, however, it is often'ad
or other means.
"vantageous‘ to miX the plastic compounds with
suitable plasticizers and dyes, subject this mix- j
ture of material to theplasticating process and
From the cooling cabinet, the
hardened strands are shown being led into}; a;
chopping device which cuts the strands into short
lengths providing a material in the form of pellets 20 “afterwards form the materialintopellets or gran- ~
'vwhijchmayybe used as a molding compound. _
_ “In the apparatus'just described the circulating
System is heated, by jacketing or by other heating’
rules which'arelatento be: replasticized and used
in fashioning operationsras extrusion or injec
tion molding. ' Whenyery large ,vomme of mate
,means. 'The injector mechanism'is cooled by ..
I
circulating a cooling medium through jackets’on
V
p
'25
{the injector cylinders. . Cooling 5 of the injector
vessfito thefashioning operation thereby eliminat- '
V 'Ving thenecessity for replasticizing the material.
_ ,Beferring to-the drawing which illustrates sev
‘mechanism is provided to prevent this mechanism
from'becoming hotby' heat conductedfrom the
.
rialisfinvolved, it may be'to advantage to take
the" material. directly from the. plasticating proc- ‘
‘fre'stlof. the‘ system. "ShouldTthe injector mech-yv _ eralforms of the invention, ‘
'
anism become hot, the‘p'owdered or granular ma
‘30
'
V Figllis ‘a diagrammatic view of one form of
}terial contacting this mechanism would plasticize
vpracticing the invention; and
'and'stick to the metallic parts of the mechanism
;_ Fig. 2 is a schematic 'view of a slightly different
arrangement. which may be substituted for a part
of the‘ system‘show'n inVVFi'g.» 1 and forming an,
l causing choking and interference With the feed
lingVofVthe injector mechanism.
V
I, The passages ofv the system particularly the by
,pa'ss 'should .be of such cross-section that the
{speed of'V?ow' of material through these said. pas
“s’agés will be comparatively: high'so as to cause
turbulence and mixing of the ‘material.
7 '
i flit. is desirable also that the volume of material
‘passing; through the by-pass system should be
‘large in proportion to the amount of powdered or
' V ?granularm‘aterial that is" forced into the system
‘by, means of the injector device; If only a small,
gpeitcjentageiof ‘coldlpowdered or granular material
is‘, picked up by the. stream as it ‘passes thein
‘j'ector'niechanis’m', the plastici'zing' off these par
,ticles will be made easy; ‘ Also,'the fact that only
‘a small“ percentage'of cold powdered'or granular
.
V
other form of practicing: my invention.
Referring nowfito the drawing,and morepar
lrticularly to Fig. 1,, asupply hopper i0 is shown
in which powdered or granular material is stored.
From the hopper, liland'via conduits] ‘I. the ma
terialis fed into an injector mechanism whieh'is
' VrepresentedVschematically in this'?gure and com
fpri'ses a pair of- lacketed cylinders I2, cooled by '
the circulationofa suitable cooling medium, and
the material to'lbe processed is fed alternately to
‘the heated conduit I8,I_heated_by suitable jacket
{in'g (not shown), by‘ the plungers l3 which .force
V the material througl'ithexbores M of the cylinders.
:valvesfli are provided in. the bores 14, and suit
able mechanism‘ (notshown) associated with the
V material" is picked’ up by the flowing stream as
v‘plunger actuating apparatus eifects' the opening
‘it passes the injectorm'echanism. means that on
of'thes'e'valves' during ‘the forward or injecting
stroke ,of-a plunger and the’ closing of the. valves
‘the average each particleof material that‘ is with- V
ldrawn‘from the system in the ?nal product has
"been circulated through, ‘the by-pa'ss system a
' large number of times. 'This rapid circulation of
‘the. plastic material ‘through the by-pass system
provides an efficient meansof applying heat to
the plastic material; ?rst, because the heat trans
‘fe'rhfrom metallic surfaces to plastic material is
t Y "greater if the material is moving or ?owing rap
idly than is the case when slow movement or no
movement at all takes place between?the plastic
~material. and its ‘contacting surface; second, be
cause'heat is generated [by thqfriction , of‘ the '
‘ii-owing; material/as it’ moyesthrough the passages,
andjthird‘tbecause each small vparticle ofthe cold
i V material injected into the stream of‘plastic'ma
terialvbecome's ‘surrounded’by .thev hot plastic ma; j
renal and intimately mixed with it.’ j'The third ,
reason abovementioned covers a. principle which
to my knowledgehas. not'heretofore been ap
ind,
V plasticating systems‘, used to . plasticate
pl tic compounds. 1 ; '
‘ ‘
stealing
emptied-treatmentpas
tici'zed material to astate of viscosity’moresuit
V
,during‘the rearward'or' charging stroke of "the
‘plungers. From ‘the bores’ M" the powdered: or
granulated material‘ is forced thence through the
1 conduits: [Tinto the lines ‘ l8 and I9, leading to’ '
the pump 29. VFromltheV exit of the pump 20' the
pumped material passes via pipe Z] .to a junction
point indicated at 22 where the pumped stréamV
of‘mat'erial becomes divided with part'of the
pumped materiah?owing' throughthe by-pass
‘conduit 23 which communicates ‘with thej'line I8 V
eatapoint near .the'exit from onefof the injector
mechanisms; and with the remainder , of the
pumpedmaterialj being forced through‘conduit 24
to ‘the pump‘25'. Pump :25 forces,v the rmat'erial
7 through conduit '26 to the cooling'unit 2s and
thence ' through‘ "conduit V 29 :to the extrusion ‘die
.31 pat'wwhich point thejmaterial i's'lextruded'into
strands 'whichare cooled‘ in the vertical stack or
cabinet 30. Vli‘r'om' this _cabinetj-the. hardened V
strandsv are. then led to itheffcutting ,inachine" 3-5
V which §chops thejstralflds- ir'itolboVd'ie'sV'll'?i of suitable ' '
length .or; or practical siZe.__ .The'V cooling. unit 1.3
may be'located' either before'or ‘after ‘the meter-3
\
. '
2,404,406
5
6
ing pump 25 or in certain instances the cooling
material the plasticized and colored material in
unit 28 may be dispensed with. The purpose of
the cooling unit 28 is to cool the material to a
state of viscosity where it will be about as viscous
the form of pellets which come from the material
as it is possible to extrude or fashion the material.
It is to be explained that the pump 20 should
supplier’s cutting machine at the end of his proc
ess.
As to the purpose of the cooling unit 28, it
ume as compared with the amount of material
will often be necessary to heat the material quite
hot in order to thoroughly plasticize it and the
material may reach a state of plasticity too soft
that is actually taken off from the system through
to extrude well.
preferably have capacity for pumping a large vol
Thus, the material ?owing
the line 24 into the pump 25. It will be seen, 10 through the line 26 might need subsequent cool
ing to bring it to the desired state of plasticity
then, that much more material will pass through
for extrusion. Also, if the material is extruded
the by-pass conduit 23 and the conduits l8 and I9
in too hot :3. form too much plasticiZer might be
than is actually delivered from the system itself
lost at the point of extrusion.
through the line 24, and the subsequent pieces of
As another embodiment of this invention the
apparatus. From this it will be observed that 15
pressure dissipation valve 45, shown in the dot
the percentage of powdered or granular material
and dash quadrilateral in Fig. 2, might be intro
that is forced into the ?owing mass of material
duced into the conduit 2| of the plasticating
in the conduits I8 and 19 by means of the plunger
system in the position depicted in Fig. 2 when
iii of the injector mechanisms is small in pro
portion to the total mass of material that is 20 this alternative arrangement is substituted for
the flow circuit of the plasticating system bound
being recirculated by means of the pump 20.
ed by the dot and dash quadrilateral shown in
This will permit the plastic stream of material
Fig. 1. The constructionand function of this
to quickly plasticize the relatively small percent
pressure dissipation valve is more fully described
age of unplasticized material that is injected into
it. Also mixing of the material will be quite com 25 in my co-pending application, Serial No. 431,972,
?led February 23, 1942, entitled “Method for dis
plete as on the average each particle of material
solving organic solids with an organic liquid.”
that is led 01f through the line 24 will have Passed
In brief, the pressure dissipation valve 45 will
through the by-pass conduits 23, I8 and I9 and
serve the purpose of effecting disintegration and
through the pump 29 several times.
It is to be explained that the conduit lines I8, 30 complete solution of all undissolved solid particles
of thermoplastic material with the plasticizer by
I53, 2| and 23 are provided with suitable jacket
means of the combined effect of the violent tur
ing (not shown) and heat will be applied to such
bulence produced and the great heat generated
jacketed elements through which the material
within the material as terri?c pressure is dissi
flows and to the various items of equipment as
the material leaves the cylinders l2 of the in 35 pated in a restricted region, ori?ce or stricture »
in the said valve as the material is forced there;
jection units. These various pieces of equipment
through while the amount of pressure dissipated
preferably should be so designed that they hold
is controlled in a suitable manner.
a comparatively small volume of material. This
From the foregoing it will be seen that I have
will mean that after the material leaves both in
provided a new and efficient means of plasticat
jection mechanisms it will become quickly plas
ing plastic compounds, that this process makes
ticized and will not remain in the system long
it necessary to subject the materials to high tem
before it is taken from the system either in the
perature for a much shorter period of time than
fashioned form or in strands which are hardened
has been required by previously known methods
by cooling and chopped into particles which will
subsequently be used in a fashioning operation 45 of plasticating such materials, thereby being less
“heat rough” on the material, and it is to be noted
such as injection molding into objects or extru
also that the process is continuous affording
sion into strands or rods.
greater uniformity of the product.
i
‘i
An illustrative example of when it might be
I claim:
desirable to chop the material into small particles
Acontinuous process for plasticizing discrete,
as it leaves the process rather than carry out the
dry, solid particles of a thermoplastic material
fashioning operation at this time would be that
having poor heat conductivity when in a dry solid
of a materials manufacturer who supplies ther
state and having increased heat conductivity
moplastic molding materials to various fabrica
when in a highly heated plastic state, whichcproc
tors throughout the country. To take a speci?c
example, consider that the material involved is 55 ess comprises continuously circulating a stream
cellulose acetate. The materials manufacturer
will mix cellulose acetate ?ake or powdered ma
terial with a suitable liquid plasticizer and also
of the said thermoplastic material in a highly
heated, semi-molten, plastic condition through a
restricted passageway at a velocity sufficient to
produce turbulent ?ow, continuously adding heat
with suitable dyes for coloring the material, and
introduce this material into the supply hopper 60 to said stream, continuously withdrawing a minor
quantity‘ of material from said stream at one
l0 of the injector apparatus illustrated. Con
point, maintaining said quantity substantially
ceivably the cellulose acetate mixed with the
constant irrespective of variations in the viscosity
plasticizer and coloring material might be shipped
of the material which may occur due to variations
to the various fabricators in this form. How
ever, the material is bulky and shipping it is both 65 in the temperature of the material, and continu
ously forcing into said stream, at a point remote
inconvenient and costly. Also, the material would
from said point of withdrawal, a quantity of un
be more di?icult to handle at the fabricator’s
heated, discrete, dry, solid particles of said ther
plant and would be more subject to becoming
moplastic material equal in volume to the said
contaminated with dirt or foreign matter. The
fabricator might again use the process of my in 70 quantity of material withdrawn from the stream.
"
'
FRED M. RODDY,‘
vention for the fashioning operation using as raw
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