Note: Descriptions are shown in the official language in which they were submitted.
CA 02089267 2000-11-17
WO 92/03274 PCT/US91/05591
-1-
TITLE
DIRECT FABRICATION
Field of Invention
This invention relates to the direct fabrication of incompatible
thermoplastic resins which is applicable to upgrading the properties and thus
the utility of
recycle plastics.
Barck~round of the Invention
Post consumer plastics, such as polyester resins, can be recycled by melt
fabrication to produce articles which can serve in utilities usually less
demanding than the
same articles molded from virgin resin. The reason for this less demanding
utility may
arise from the presence of contaminants accompanying the post consumer
plastic. Efforts
are made to remove all contaminants, but this is an elusive goal under the
current state of
recycle technology.
It thus becomes desirable to incorporate resin modifiers in the recycle
resin which will upgrade its properties. For recycle polyester resins, a
highly desirable
group of modifiers are the ethylene random copolymer tougheners such as
disclosed in
U.S. Pat. 4,172,859 (Epstein I). In most cases, these modifies are
incompatible with the
polyester matrix resin making it difficult to get the fine dispersion of
modifier into the
matrix resin that is necessary for the modifier to upgrade the properties of
the matrix
resin rather than detract therefrom or affect them so modestly that the
modification is
economically impractical. The same situation exists for virgin
WU 92/Q3274 PCT/US91/t~559~
2Q~~~Jr~ - ~ -
resins when the modifier resin is incompatible
therewith.
._._v.S~ Fats. 4,1?2,859 (Epstein I) and
4,1?4,358 (Epstein II) disclose the toughening of
polyester and polyamide resins, respectively, by the
incorporation of relatively low modulus random
copolymers in the polyester or polyamide matrix. The
methods of incorporation disclosed are (i) melt
l0 blending ire a twin screw extruder or other
conventional plasticating device, such ae a Brabender
or Banbury mill, (ii) blending by coprecipitation from
solution, and (iii) blending or dry mixing of the
components, follawed by melt fabrication of the dry
1~ mixture by extrusion (Epstein I, col. 10, 1. 3?-4?).
In the case of,melt blending, further details on the
use of the twin screw extruder are disclosed, ending
with the extruder producing an extrudate which is
cooled in a water bath, cut, dried, and molded into
0 test pieces (Epstein I, col. 10, 1. 48-~?). The
cutting step produces molding pellets, generally
having at least one dimension which is at least 2 mm.
The molding step involeres the use of an injection
molding machine (Epstein I, col. 12, 1. 19-22), i.e.,
~ the molding pellets are fed to the injection molding
machine for fabrication into the test bars. Epstein II
sometimes uses other plasticating apparatus
(Hrabender, roll mill) in place of the twin screw
extruder.
30 In both Epstein I and EpsteinW T, the
injection molded test bars were prepared in two steps,
first, compounding of the random copolymer into the
matrix resin to form molding pellets (hereinafter
referred to as pre-compounding), followed by injection
~ molding to form articles as the second step. This
sequence. of steps was selected in the Epstein patents
w~ ~~ia~a7~ r~rius~nassm
~- 3
because of the need to achieve a very fine dispersion
of the random copolymer within the resin matrix in
order to realize optimum toughening in the molded
articles, , e.g. , impact test bars; .. ~,h~ ~pa:~ents
disclose the fineness of this dispersion desired,
e.g., random copolymer particle s~.ze of 0.01 to 3
macrons, but preferably 0.02 to 1 micron, within the
matrix (Epstein I, col. 5, 1. 14-15). The second
step, injection molding, takes the molding pellets,
melts them and injects the molten resin into the test
bar mold. The dispersion is accomplished in the
pre-compounding step and the fabrication is
accomplished in the injection molding step. Example
168 of Epstein II departs from this combination of
operations by extruding a film from a blend of 66
nylon with a fumaric acid-grafted EPDM and subjecting
the extruded film to stretching or thermoforming.
This has been the commercial practice for
toughening polyester and polyamide resins with other
. more flexible resins which are relatively incompatible
with these matrix resins. This is the present
commercial practice which offers itself for use to
upgrade post consumer plastics. Unfortunately, this
two step preparation process has the disadvantage~of
raising the cost of the molded articles.
It would be desirable if the pre-compounding
step could be eliminated and the matrix resin and
toughening resin be brought together for the first
time as~the feed to the injection molding machine, so
that articles could be directly fabricated from the
blend components.
Unfortunately, injection molding, such as
' that used in common single-stage injection molding
5 machines does not lend itself to making a fine
dispersion of incompatible resins within a matrix
iVt3 92/a3274 PCT/CJS91/05541
-
resin, hence the need heretofore for the
pre-compounding step. Such injection molding machines
use a single screw which both. reciprocates and rotates
~ within a barrel in the following sequence of steps
which constitute the molding cycle:
(i) screw forward or injection (fill) tame
(ii) hold time
(iii) mold open (eject) time.
During the screw forward time, the screw rams
towt~rds the injection port (nozzle) ag the machine to
force molten resin unto the mold. Also included in
this step is the time the screw is held in the for~rard
position to keep the mold full of molten resin as the
Z5 molded article starts to solidify.
During the hold time, the screw rotates and
retracts under the pressure of the molten resin being
forced by the screw into the forward end of the
barrel, i.e., adjacent the injection port of the
barrel. During dais rotation, the resin feed to the
injection molding machine becomes melted and
transported into this injection position. Normally,
when the screw retracts to a certain point, this means
the forward end of the barrel is filled with the
desired amount of molten resin and the screw stops
rotating. Additional hold time is typically taken up
with the screw positioned stationary in the retracted
position until the molded article has cooled
sufficiently.
During the mold opening step-of the cycle,
the screw remains stationary and retracted whiles the
mold opens and the molded article is removed from the
mold.
A typical molding cycle might take 43
seconds, consisting of 20 seconds screw forward time,
20 seconds hold time, and 3 seconds mold open time. Of
WO 9~J032id t~ ~ ~ d PCT/IJ~91/~5591
- 5 -
the 20 seconds hold time, typically only a portion of
it is screw rotation time, e.g., 5 seconds whereby it
is apparent that the screw rotates for only a small
fraction of the time of molding cycle.
Faced with this fact, pre-compounding has
served as the standard for resin feed of incompatible
resins to injection molding machines.
C.P.J.M.Verbraak and H. E. H. Meijer, °°Screw
Design in Injection Molding", _~olymer ~na~.neerina and
ence, Vol. 29, No. 7, pp. 479-487 (April, 1989)
discloses the insufficient plasticating capacity of
injection molding with high capacity (p. 479) and the
testing of screw designs in injection molding using
screw sections taken from cantinuous extrusion
practice (sentence beginning p. 479-480). ~'he article
reports the testing of both distributive mixing and
dispersive mixing capability. In distributive mixing,
polyethylene is blended with color xnasterbatch to
determine color distribution within the resultant
blend obtained with various screw designs. Color
masterbatch is normally made from colorant dispersed
in polymer which is the same or is at least miscible
with the resin being colored, so that uniform coloring
of the resin can occur in injection molding. In
dispersive mixing, ethylene-propylene-diene (EpDM)
elastomer is blended with polypropylene (Pia) using
various screw designs in an injection molding machine.
In dispersive mixing, the elastomer~may remain a
separate dispersed phase within the polymer matrix or
become dissolved in the polymer matrix if sufficient
compatibility (miscibility) exists.
Verbraak et al, reports testing eight
different screws for dispersive mixing and summarizes
the results of this testing as follows:
WQ 92/03274 ~'~.'f/US91/U559y
~'A reasonable morphology was achieved only
with a combination of Ingen Hausz, Maddock
and pineapple sections and,a high back
pressure. However, the thermal load on the
polymer (the resulting melt temperature
exceeded the barrel temperature over~80')
caused degradation of the PP, resulting in
slightly poorer mechanical properties than
those of the commercial blend."
(p. X81).
This °'reasonable morphology" is based on examinations
at only 40X and 160X magnification. While "globs" of
EPDM are visible at these low magnifications, the
degree of dispersion necessary to obtain optimum
toughening is not visible at these magnifications.
Even with the degree of dispersion or
miscibility of the EPDM in the polypropylene obtained,
this was at the expense of polymer degradation because
of overheating of the polymer within the barrel. This
result required greatly increased back pressure on the
screw, i.e., pressure applied to retard the retraction
of a screw during the hold time portion of the overall
.infection molding cycle. As indicated in Table 3, for
the particular screw in question, 1H6M5PA, the back
pressure was increased from A bar to 150 bar, which
increased plasticating time from 8.3 to 17.7 seconds.
The result of the dispersive mixing reported
in terms of IZOD impact strength at' ~40°C in kJ/m2 in
Table 3 is rather uninspiring. The maximum impact
strength acha.eved was 8.6 kJ/m2 for the
polypropylene/EPDM blend, which corresponds to
87.4 J/m when converting the test result to the
procedure to ASTM D-256. D'Orazio et al., Polymer
Encineering and Science, June, 1982 reports the room
temperature impact strength of polypropylene/EPDM in _.
WO 9'~~U32'7~l ~ ~ U ~ ~r ~ ~ p~l'~U591~05~91
- 7 -
an 85j15 wt. ratio to be only 2.6 J/cm2 which
corresponds to 117.4 Jjm when converting the test
result to~the procedure of ASTM D~256. zn'other
~ 5 words, the blend of polypropylenejEPDM is~not very
tough to begin with, especially from the point of view
of applications demanding room temperature impact
toughness of 300 Jjm and higher. Verbraak et al. does
not disclose his dispersive mixing to achieve this
desired toughness result.
Tn .Infection '~,oldincr 3~achines, .by A. whelan,
published by ElseVier Applied Science Publishers,
Ltd., Essex, England (1984) the use of back pressure
in injection molding machines is generally described
on pages 398-401. Back pressure is the pressure the
screw must overcame in order to retract (p. 398).
Back pressure is usually adjusted as low as possible
which yields the result of a well-compacted melt which
is free from bubbles or voids (p. 399). The use of
a0 increased, back pressure will result in improved
mixing; but accompanied by disadvantages of long screw
recovery times, high pressures on the resin melt which
may result in nozzle drooling, and increased wear of
the injection molding machine (p. 399).
Du Pont Information Bulletin A-88012 (1973)
provides information on the use of back pressure in
injectian molding. Back pressure is disclosed to be
helpful for acrylic resins as a way of preventing air
pick-up in the screw which cause black streaks in the
30 molded part. For polyamide (~ytel~) and
polyoxymethylene (Delrin~), back pressure may help
produce a more uniform melt temperature and in color
mixing, but is riot needed for most molding and could
~ cause nozzle leakage.
35 EPO 0 340 873 A1 discloses a. mixing device
with distributive mixing action for an extruder and
BYO 92/0327~b PCT/iJS91/0559i
- 8
injection molding machine, which is useful for mixing
viscous materials such as melted plastics and rubber,
materials such as soap and clay in addition to
foodstuffs such as dough and margarine. Product
literature on the mixing device of this publication,
entitled "'Twente Mixing Rang", published by the
University of Twente, and understood to have been
printed in November, 1989, discloses various mixing
In applications and test results including the disclosure
of "fewer unmelted particles'°. The existence of
unmelted particles indicates that this device is
intended for distributive mixing.
U.8. Pat. x,912,167 discloses an improvement
in melt blends of polyester resin with an epoxide
copolymer, the improvement involving the incorporation
of metal salts of certain acids or certain
carboxyl-containing polymers, the metal. salts being
selected from the group consisting of Al+'~'~, Cd+'~,
20 C~~~a CLl't"~', FE:'f"~'r In'f'-1-+f Mn'i"'~.'I PId'~'-1'~',
Sb'~'°f'-!., Sn'~'"'E'~ and
Zn'~+. The nature of this improvement is disclosed to
be increased melt strength and increased melt
viscosity for the blends, anhanaing the blow
moldability of the blends. lThe blow molding
25 fabrication is disclosed to be carried out in two
steps, first the ingredients are melt blended and
palletized and these pellets are then fed to an
extrusion blow molding machine (Col. 4, 1. 36-45).
In summary, injection molding has been used
30 to obtain distributive mixing of colorant within
polymer, while preparing the polymer for,injection
molding. Verbraak et al. discloses an unsuccessful
attempt to perform dispersive mixing in an injection
molding machine. The polymers used in Verbraak et
al., polypropylene and ethylene-propylene-dime
elastomer, axe fairly compatible as indicated by the
dVn 92/0327~d ~ ~ ~ ~ ? ~ ~ fCfi/U~911055
similarity of their solubility parameters of
16.0 (J/cm3)1/2 and 16.5 (J/cm3)1/2, respectively.
There still exists the need to be able to
more economically injection mold a blend of
incompatible thermoplastic resins, which would be
especially useful for upgrading post consumer
plastics, by eliminating the need for pre--compounding
of the resins.
Zo Summaxv of t~aE ~nVgntxon
The present invention satisfies this need by
providing a process for the direct fabrication of
incompatible resins, i.e., the pre-compounding step
can be eliminated, and the incompatible resins can be
15 compounded sufficiently within the injection molding
machine and then directly molded to produce articles
of modified resins all without causing degradation of
any of the resins used.
The process for the direct fabrication of
20 articles from incompatible resins comprises
a) combining particles of a first
thermoplastic resin with particles of a second
thermoplastic resin which is incompatible with said
first resin, this incompatibility being characterized
25 by a difference of at least 2 (J/cm3)1/2 between the
solubility parameters of the first and second resins,
said particles having at least one dimension of at
least 2 mm, said first resin being present in a major
proportion and said second resin being present in a
3o minor proportion. .
b) melting this combination of particles
while mixing them together
c) periodically shearing the resultant melt
without degrading the resins therein to disperse the
35 melt of the second resin within the melt of the first
resin, the shear rate and shear time of this periodic
~Y~ ~~~'~~ ~ ~CIT'/US91/OS597
shearing step being effective to result in a number
average particle sire of the second resin in articles
fabricated, from the resultant melt of less than about
5 1 micron,
d) periodically forcing an amount of the
resultant Sheared melt into a pre--determined shape to
obtain as a result thereof said article o~ said
pre-determined shape directly fabricated from said
10 Combined particles.
This process is adaptable to being carried
out in the typical single-stage injection molding
machine which uses a single screw rotating and
reciprocating within a barrel to melt, shear and
inject molten resin into the mold of the~machine. In
the process conducted in this type of machine, the
periodic shearing and periodic-forcing steps are
alternating, i.e., while the molten resin is being
forced into the pre-deteranined shape in the mold, the
screw is not rotating and therefore the melt within
the barrel is not being subjected to shear.
The process of the present invention is also
applicable to injection blow molding wherein the same
alternating relationship between the sheering and
forcing steps is observed. In a machine carrying out
this particular process, the pre-determined shape is
subsealuently also subjected to blow molding within a
second mold to produce the article desired.
The process of the present'invention is also
applicable to injection molding in a two~stage machine
wherein a single screw is used to melt resin and force
it through a check valve into an injection cylinder.
A ram then forces this molten resin into the mold. Tn
one type of two-stage injection molding machine, the
screw does not reciprocate, but it does stop rotation
during the times the injection cylinder is filled with
~O 92103274 ~ ~ ~ ,~ ~ ~ PCd'/LJS91/05591
~ 11
molten resin, and the ram injects the molten resin
into the mold and the ram remains in the forward
- position to maintain pressure on the resin in the mold
until it solidifies.
In another type of two-stage injection
molding machine, the screw reciprocates similarly to
the operation of a single-stage injection molding
machine. In the two-stage machine, however, the
to fo~ard thrust of the screw injects molten resin into
the.injection cylinder rather than the mold, and the
ram then forces the molten resin into the mold.
During the remaining step, the screw can rotate to
melt resin, until the screw reciprocates to its back
15 position, which gives a faster cycle time as compared
to a single-stage machine. In this type of two-stage
machine, the shearing and forcing steps are
simultaneous.
The process of the present invention is also
applicable to extrusion blow molding, wherein the
forcing of the sheared melt into the pre-determined
shape is done by extrusion of a tube. A mold closes
around the tube. The mold is then transferred to a
blow molding station for blow molding into the article
~5 desired. During the mold closure and transfer, the
extruder screw is stopped, during which time the melt
within the extruder is not being subjected to shear.
Thus in the application of the present invention to
extrusion blow molding, the periodic shearing and
3D forcing steps are simultaneous.
In all cases, the process of the present
invention produces either a finished article having
generally the final shape desired or an intermediate
article which is blow molded to the finished article.
35 The process of the present invention is also
continuous in that the first resin particles and
WO 92/i13.'~.74 PC."T/US91/05591
12 -
~~~,~~6'~ _
second resin particles are fed into the process the
. step of combining) and are then subjected to
continuous processing until the articles, intermediate
or finished, are melt fabricated therefrom.
The process of the present invention is
accomplished by fitting the screw used in the
injection molding, injection blow molding, or
extrusion blow molding machine with an appropriate
to dispersion section and then operating the machine
under conditions of shear which gives the fine
dispersion result desired without degrading any of the
resins.
The_present process may also be described as
: being applicable to modifying polyamide and polyester
resins as the matrix. resins with incompatible resins
which impart greater utility, notably toughness, to
the matrix resins. Polyester resin is becoming
increasingly available as post consumer plastic, and
the process of the present invention is especially
applicable to upgrading the properties of such resin.
i~hen the direct fabrication process is
practiced on the dispersion of epoxide copolymer
sleetomer into polyester resin, particularly when the
polyester resin is flaDce derived from post consumer
use, the result of the process does not consistently
yield products of optimum toughness, i.e., the
toughness obtained on one occasion may not be
reproducible on other occasions. 'Another embodiment
3~ of the present invention salves this problem by
providing much more consistently high toughness
results when these resins are used. This embodiment
may be described as a process for the direct
fabrication of articles from a major proportion of
polyester resin and a minor proportion of
ethylenejepoxide copolymer elastomer, said copolymer
''
'~~~0 92103274 ~ ~ '~ '' d ~ P~C1'/U591/05591
13 -
elastomer in combination with said polyester resin
providing substantial toughening of said articles,
comprising
(a) combining particles of said polyester
resin with particles of said copolymer elastomer, said
particles having at least one dimension of at least
2 mm,
(b) melting this combination of particles
lp while mixing them together,
(c) periodically shearing the resultant
melt without degrading the polyester resin or
copolymer elastomer to finely disperse the melt of the
copolymer elastomer within the melt of the polyester
15 resin, said shearing being carried out in the presence
of adjuvant for said toughening of said articles
incorporated into said melt, and
(d) periodically foreing an amount of the
resultant sheared melt into a pre-determined shape and
0 obtaining as a result thereof said toughened articles
of pre-determined shape directly fabricated from said
combined particles.
The fine dispersion of the copolymer
elastomer within the melt of polyester resin is
g preferably the same as in the other embodiments
described hereinbefore, namely, the shear rate and
shear time of the periodic shearing step being
effective to result in a number average particle size
of the copolymer elastomer in articles fabricated from
the resultant melt of less than about 1 micron.
Description of Drawinq~
Fig. 1 is a schematic side elevation in
cross-section of an injection molding machine useful
for carrying out a process of the present invention,
with the embodiment of the screw shown in the
retracted position.
wo ~zr~~sz~a ~criu~gmossm
2~~u~~~~~ - ~a -
Fig. 2 shows the injection molding machine
of Fig. 1 with the screw in the rammed or forward
position.
'Fig. 3 is a side view, in enlargement and
indeterminate length, of the-embodiment of screw shown
in Figs. 1 and Z useful for carrying out the process
of the present invention.
Fig. 4 shows in enlargement as compared to
:LO Fig. 3 one of the plurality of shearing sections
making up the dispersion section of the screw of Fig.
3.
Fig. 5 is a cross section taken along line
5-5 of Fig. 4.
Fig. 6 shows in enlargement one embodiment
of barrier flight for use in the shearing sections of
the screw.
Fig. 7 shows in side elevation another
embodiment of dispersive mixing section for a screw
a0 which can be used in an injection molding machine far
carrying out the process of the present invention.
Fig. 8 shows a cross section of the
dispersive mixing section of Fig. 7 taken along line
~-s of Fig. a.
Fig. 9 shows a graph of impact strength mss.
~ shearing time for articles melded in accordance with
the process of the present in~rention as compared to
articles molded of the same resin by a conventional
distributive mixing screw.
30 ~esCrix~tion of Preferred Embodiments
The resin feed to the process of the present
invention comprises a major ~ropartion of a first
thermoplastic resin and a minor proportion of a second
thermoplastic resin which is incompatible with the
35 first resin. With respect to the total weight of
these resins, about 55 to 95~ can be the first resin
2~~~~~~
.,'~O 92/03274 PCT/US91/a5591
- 15 -
and correspondingly, about 5 to 45% can be the second
resin. Preferably, the weight proportions of these
resins are about 10 to 40% second resin and more
preferably about 10 to 25% second resin; and even more
preferably, about l0 to 20% secand resin with the
remainder being first resin. Since the second resin
component will usually be the more expensive resin as
compared to the cost of the first resin, it is desired
to use as small a proport3.on~of the second resin as is
possible to accomplish the modification desired, which
will generally be no greater than about 20 wt. % of
the combined weight of the first and second resins.
Tha desire to minimize the proportion of more
1~ expensive second resin increases the need for fineness
in the particle size of the second resin dispersed in
the first resin in articles directly fabricated from
the resin feed, so that the second resin present in
its limited amount can provide the modification effect
desired.
The first resin is provided in the form of
particles and the second resin is provided in the form
of particles essentially separate from the particles
of first resin, i.e., the resins are in different
particles. The particles have bulk aslindicated by
their having at least one dimension which is at least
about 2 mm. The particles are melt derived, either
from virgin or recycle polymer. As such they will
typically be in the form of pellets melt cut or cut
from a previously extruded strand from the original
manufacture of the resin. f3ry flake of the resin is
another particle form, but pellets are normally
preferred for use of handling. Nevertheless, for post
consumer plastics, the recycle form of the resin will
typically be flakes obtained by chopping up the
recycle articles such as bottles.
5f~ 9~/03~74 PCIf'/L159y105591
-m-
The first and second resins are also
incompatible with one another in the molten state.
one indication of this incompatibility is that
although the second resin is reduced to very fine
particle sizes within the first resin matrix by the
process of the present invention, the second resin
nevertheless remains as particles, and does not
dissolve, within the matrix, indicating immiscibility
ZO of the second. resin in the first resin. These micron
and smaller size particles of second resin can be seen
under high magnification, e.g., 5,000X or greater.
The incompatibility between the resins~in the molten
state is manifested by the high interfacial tension of
the molten particles of the second resin in the melt
of the first resin. This high interfacial tension
makes it difficult to break up the second resin
particles into fine particles, i.e., the molten
particles of the second resin want to retain their
particle size rather than break up into much smaller
particles.
The incompatibility between the first and
second resins used in the present invention cars be
also characterized by. difference between solubility
~5 parameters. Solubility parameter is a measure of the
cohesive energy density of the resin. Thus, the
solubility parameter is proportional to the strength
of attraction between the molecules making up the
resin. The closer the solubility parameters of two
different~resins, the more miscible they are with one
another. The converse is true as the difference
between solubility parameters increases. Solubility
parameter of resins can be measured by determination
of maximum swelling of the resin in a series of
~5 solvents having different solvent action on the resin,
with the solubility parameter of the solvent giving
.r l.T U tN t
WO 92/0327~i ~ ~ ~ ~ ? ~' ~~ PGT/US91/~i5591
_ 17
the maximum swelling action being the solubility
parameter of the resin. Solubility parameters for
many polymers are disclosed in the literature, see for
example Table 4, PP. 362-367 of the Polymer lia~dbook
by ~. brandrup and E. H. lmmergut, antersciencs
Publishers (1966) wherein the solubility parameters
ar$ reported in (cal/cm3)1/2.
Greater relative precision is available by
lp calculating the solubility parameter from the formula
.~~F~,/M wherein ~p is the density of the resin, ~F1 is
the sum of the molar attraction constants of all the
chemical groups in the polymer repeat unit, and M is
tha molecular weight of the repeat unit in the
polymer, as described in Pol~!mer blends, by D. R. Paul
and 8. IVewman, Academic Press, p. 4G (1978). Molar
attraction constants are disclosed on p. 47 of
vm~rBlends. To illustrate the application of this
formula as applicable to copolymers, solubility
2~ Parameter for the ethylene/n--butyl acrylate/glycidyl
methacrylate copolymer used in Examples 1-6, 23 and 24
and having the following mole %°s of each comonomer
X0.3, 8.3, and 1.~, respectively is calculated as
follows
The molecular weights of the 3 monomers are:
ethylene 28.
butyl acrylate 128.
glycidyl methacrylate 1~2s
The molar attraction constants in
3~ (cal/cm3)1/2/mole from Polymer Blends are:
CH3- 147.3
'cH2' 131.5
~~o~~
°COO- 326.58
°'O~ (EPOJCf) 176.2
0 0 ~zio~a7a pcrius9moss~l
The sum of the molar attraction constants
are
for ethylene 263.0
for bcttyl acrylate ~ ~ , 1085.87
for glycidyl methacrylate 1162.5
The sum of the molar attraction constants of
the chemical groups divided by the mole weight of the
repeat unit is as follows:
~ for: ethylene 263/28 a 9.39
for butyl acrylate 1085.87/128 = 8.48
for glycidyl methacrylate 1162.6/142 = 8.19
The solubility parameter for the resin is
the sum of these values in proportion to the mole % of
the comonomer present X resin density, as follows:
for ethylene .903 X 9.39=8>429
for butyl acrylats .083 X 8.48=0.703
for glycidyl methacrylate ~t314 X 8 i9=0 ,15
TOTAL 9>297
X .940 (polymer density at room
temperature) ~ 8.739 (cal/cm3)1/2
or in &1 unite 8.739 X 2.0455 - 17.88 (J/cm3)1/2
The calculated solubility parameters of a
number of resins useful in the practice of the present
invention are as follows:
3b
iV(a 92/032?4 ~'~LT/dJSl3/05591
- 19 -
Solubilit Parameter
~tesin t~ am~! Z/2
nylon 66 . 22.6
2. PET - 22.5
polypr~pylene 16.0
4. ethylene/n-butyl acrylate/ ~,?,g'
glycidyl methacrylate copalymer
from abave calculation
1~ 5. 6?.4 ~ by Wt. ethylene/20s9~ by 16.5
wt. prapylene/3.?~ by Wt.
l,4-hexadiene capalymer (EPDM)
Examples 14 and 15
~. EPDM grated With malefic l,~ o
anhydride '
Examples 14 and 15
?. Ianomer of Examples 16-22 (acid 1?.6
copolymer basis)
The sensitivity of the compatibility
relationship between resins is illustrated by the
attempt of Verbraak et al. to disperse EPDM in
polypropylene, the solubility parameters of these
resins differing from another by D.S (J/cm3)1/2. With
normal injection molding machine operation using a
special screw, dispersion Was poor. When back
pressure on the screw Was used, the "glabs~ of EPDM
disappeared but at the expense of resin degradation.
The process of the pxesent invention can obtain fine
dispersion of resins having even greater
incompatibility, far example characterized by a
3~ difference between solubility parameters of at least 2
(J/cm3)1/2 and more preferably at least 3 (~/cm3)1/2.
The above calculation of 0.5 (J/cm3)ll2
difference is based an the assumption that the EPDM
used by Verbraak et al. Was the same as resin 5
1V0 92~U327A PCT~US91~~5591
-
20 -
described above. If the EPDM was the other popular
EPDM, namely ethylene/propylene/5-ethylidene-2-
norbornene, the solubility parameters are~nevertheless
very close to the above reported value fear EPDM (and
to palypropylene). For two norbornene-based EPDNI
copolymers representing the approximate extremes of
compositions commercially available, the solubility
parameters ara as follows: For 69% by wt.
ethylene/29% by wt, propylene/2% by wt.
5-ethylidene-2-norbornena copolymer, the solubility
parameter is 16.2 (J/cm3)1/2, and for 68% by wt.
ethylene/28% by wt. propylene/4% by wt.
5-ethylidene-2-norbornene copolymer, the solubility
Parameter is 1.6.4 (cal/cm3)1/2, Prior to rounding
off, the spread between the solubility parameters for
all these EPDM polymer, including the 1,4-hexadiene
EPDP3 described above, is 0.22 (3/cm3)1/2.
The dispersion obtained by the process of
the present invention can be characterized by the
second resin present as a discrete phase within the
matrix of first resin, with the particles (areas of
discrete phase) of second resin preferably being
smaller than about 5 microns, which corresponds to a
5000X reduction in the size of the second resin
particles fed to the process. The second resin also
preferably has a number average particle size within
the~matrix of less than about 1 micron. Number average
particle size as measured by the procedure disclosed
in ~.~. Pat. 4,753,980 in col. 6, lines~l0-44.
Preferred first resins used in the process
of the present invention are polyesters, polyamides,
polyacetals, and polyarylates. Examples of polyesters
include polyethylene terephthalate (PET), copolymers
of PET and polyethylene isophthalate, cyclohexyl
dimethanol/terephthalic acid copolymer, cyclohexyl
i~ia 92/03274 ~ v ~ ~ ~~ F'CT/U~91/~5591
- 21 -
dimethanol/ethylene glycol/terephthalic acid
copolymers, polyethylene 1,4-dicarboxynaphthenate,
polybutylene terephthalate, and polycarbonates.
Examples of polyacetals are the oxymethylene
homapolymer and copolymers. Examples of polyarylates
include the polymers derived from polymerization of
bisphenol A with'isophthalic and terephthalic acids,
preferably a mixture of about 50% of each acid (wt.
basis). Examples of polyamides include conventional
semicrystalline nylons such as nylon 6, nylon 66,
nylon 69, nylon 6/10, nylon 6/12, nylon 11, nylon 12,
nylon copolymers such as 6/66, 66/6, 6/610, 6/612, and
recently introduced nylon 4/6, and nylon 12/12.
~°rphous nylons such as the copolymers of
hexamethylene diamine and isophthalic and terephthalic
acids, copolymers of 2,4,4- and 2,2,4-trimethyihexa-
methylene diamine and terephthalic acid, and p-amino
cyclohexyl methane and azelaic acid can also be used
in this invention. The first resin can be a single
resin or a blend of compatible resins.
The selection of second resin and its amount
will depend on the first resin used and the effect
desired from the modification of the first resin.
Preferably the second resin is an elastomer which when
finely dispersed within the first resin, significantly
improves toughness of the first resin by a factor of
at least 3X and preferably at least 5X. Toughness
improvements of 10X and higher are abtainable by the
process of the present invention. In this case, the
molecular weight of the first resin should be
sufficiently high to provide some toughness to
articles molded solely from the first resin, e.g., to
provide a toughness of at least about 15 J/m and
preferably at least about 30 J/m. Preferably, the
toughness of articles molded from the blend of resins
~1'~ 92/O~i274i 1PCT/US91/05591
-
22 -
exceeds 300 J/m. The toughness comparisons and the
toughness values reported herein are obtained by
notched Izod impact test conducted at room temperature
in accordance with ~IST~I D-256, unless otherwise
indicated. Elastomers are those thermoplastic resins
which at room temperature exhibit substantial
deformabil3ty, e.g., stretchability and substantially
immediate complete recovery of original dimension upon
release of the force causing the deformation. They
also typically exhibit a glass transition temperature
(Tg) below ambient temperature (20°C). Examples of
second resins include ethylene copolymers wherein
ethylene is copolymerized with one or more of such
l~ monomers as vinyl acetate, alkyl (math)acrylate, 6uch
as methyl,, ethyl, or butyl(meth)acrylates
(meth)acrylic acid, (meth)acrylamide, carbon monoxide,
or glycidyl (meth)acrylate. Examples of such ethylene
copolymers include ethylene/n-butyl acrylate/carbon
~0 monoxide, ethylene/n-butyl. acryiate/glycidyl
methacrylate, and ethylene/vinyl acetate/carbon
monoxide. Tha ethylene-vinyl acetate and
ethylene/(meth)acrylate copolymer may include grafted
acid, anhydride or glycidyl groups. d~dditional
~S ethylene copolymers include ionomers and
ethylene/propylene and ethylene/propylene/diene
elastomers'with or without grafted acid or anhydride
groups. Examples of additional second resins include
styrene copolymer-based elastomers such as
30 styrene-ethylenebutene block copolymers~with or
without grafted acid anhydride, or glycidyl groups,
styrene/butadiene block copolymer, styrene/acrylic
ester/acrylonitrile copolymer. Examples of additional
second resins include the block copolyetherester
35 elastomers such as those derived from polymerization
of 1,~-butylene terephthalate with poly(tetramethylene
WO 9210327! POI'/US911055~1
m ~3 r
ether) glycol terephthala~te, such as the copolymers
made from 25:75 weight proportion of these monomers.
The second resins can also be a blend of compatible
resins.
Preferred elastomers are the
ethylene/glycidyl ~meth)acrylate copolymers which also
contain Cl-CS alkyl (meth)acrylate, preferably n-butyl
acrylate, wherein the amount of glycidyl
(m8th)acr~rlate constitutes about 2 to 10 wt. % of the
copolymer, preferably about 2.5 to 7 wt. %, and the
alkyl (meth)acrylate constitutes about 15 to 35 wt. %
of the copolymer, and the ethylene constitutes about
55 to f34 wt. % of the copolymer to tatal 100%.
Preferably the relationship of the first and
second resin to one another is such that the
dispersion of the extremely fine particles of second
resin within the matrix of first resin in articles
fabricated by the process of the present invention is
~0 also accompanied by the particles adhering to the
matrix, despite the incompatibility of the resins.
This adhesion promotes the toughening of the
fabricated article and may be detected by exposing the
article to solvent, which reveals the presence of gel
a5 rather than the article completely dissolving in the
solvent. When the first and second resins are
polyester and epoxide copolymer elastomers,
respectively, this gelation is believed to be a
manifestation of reaction between the polyester resin
30 matrix and the dispersed fine particles of the
copolymer elastomer.
The first and/or second resins can contain
the usual compounding ingredients, e.g. antioxidants,
stabilizers,. colorants, and fine particulate inorganic
35 extenders and fillers.
w~ ~zio~z~~ Pc:rius9moss9~
a
24 -
The operation of the process of the present
invention'will be described with reference to the
drawings.
The first step is to combine the particles
of first and second'resin. This can be done by
simultaneously.feeding the particles as individual
streams or a dry mixed blend to the feed hopper 4 of
an injection molding machine 2 tFigs. Z arid 2). The
resins present in the particles are pre-conditioned,
e.g, dried, as may be required, depending on the
resins being used. .~ typical dry condition is such
that the dried resin has a moisture content of less
than about 0.02 wt. ~ when the resin is polyester and
~,5 less than about 0.0~ wt. ~ when the resin is
palyamide.
The injection molding machine includes a
barrel portion 6, defining a heated cylindrical
chamber 8 and a hydraulic cylinder portion 10. .~
Plasticating screw 12 is positioned axially within the
chamber ~ and extends into the hydraulic cylinder
portion l0 of the machine, where the screw terminates
with a cylinder head 14. w
The screw has a helical flight l~ for
2~ advancing the particle feed from hopper 4 along the
length of chamber ~ towards the forward end of the
barrel portion 6 which is equipped with an injection
nozzle 17. During this advancement the resin
particles become mixed together, compacted, and melted
from the heat supplied by the barrel portion and
internally generated heat from the misting and
compaction. For amorphous resins, the melt condition
means that the resin is heated above its softening
point. For crystalline resin, the melt condition
means that the resin is heated above its melt
temperature.
~~~~?~~"~
wo 9iiosz~a ~~rius~~ioss~~
_ ~5 _
The molten combination of resins is next
received by the dispersion section 1s of the screw
which consists of three shear sections 2U separated by
intervening transverse mixing channels 22. Further
details of the screw will be described later herein
with reference to Figs. 3 to 6.
The dispersion section la which may be
called the dispersion head of the screw 12 reduces the
sire of the molten particles of second resin and
finely disperses them within the molten first resin.
The forward position of the screw 12 is
shown in Fig. 2. This position is representative of
the forward tame of the injection molding cycle, in
which the screw 12 forces an amount of molten resin
through the nozzle 17 into the mold 2~ which is merely
shown as a box because of the conventionality of this
aspect. During this time~ including the time the
screw is maintained in the forward position to
maintain pressure on the contents of the mold, the
screw is not rotating, and accordingly, the resin melt
is not being subjected to shear. The forward position
of the screw 12 is obtained by applying hydraulic
pressure by conventional means against the face 15 of
2~ the cylinder head 14 of the screw. The nose 26 of the
screw generally conforms to the iwterior shape of the
nozzle so as to minimize the amount of molten resin
remaining in the cylindrical chamber. The nose 25 may
also be equipped with a conventional check valve (not
shown) to prevent molten resin from back flow within
the cylindrical.chamber when the screw rams i~orward
and is held in the forward position. .
Upon completion of the screw forward time,
the screw commences rotation, for example via gear 28
3~ mounted on the screw 12 and engaged with conventional
gear driving means (not shown). During this rotation,
pcrius9aioss9a
w~~~s°~ ;~'~
the particle feed is subjected to additional melting
as it advances along the screw 12 and to shear as the
resultant melt traverses the dispersion section 18 of
the screw.
During the rotation of the screw, the
pressure against the cylinder head l4 of the screw is
reduced and the screw 12 retracts within the chamber 8
as the molten, sheared resin fills up the forward end
~Q of the chamber. Fig. ~. shows the screw Z2 in the
retracted position and the presence of molten resin 30
in the forward end of the chamber. When the screw
reaches this position, the amount of the molten resin
30 present in the forward end of the chamber is the
1~ amount necessary to fill the pre~deterr~ined shape
provided by the mold. The screw rotates during the
retraction and when it reaches the retracted position,
the rotation of the screw is stopped. This retraction
time and the time spent in the retracted position to
2o permit the molded article to cool to solidification is
the hold time of the injection molding cycle. The
screw rotates only during its retraction during the
hold time. The screw is also standing still. while the
mold is opened and the molded article removed
the refroms' .
Accordingly, it is apparent that the
shearing of the resin melt is only periodic during the
injection molding cycle and the forcing of the sheared
melt into the shapes (articles) desired is periodic,
gp ~ with these actions alternating with one another, and
with considerable additional portion of the injection
molding cycle being taken up with the screw standing
still, i.e., not rotating and therefore not shearing
the melt.
In accordance with the present invention,
the retraction of the screw is retarded so as to
!a't~ 92/03274 PCT/US91/OsS91
- 27 -
extend the rotation time of the screw. This is
accomplished by applying pressure to the face 15 of
cylinder head 1A of the screw during the hold time of
the molding cycle. The effect of this retardation is
to extend the shearing time for the molten resin.
This is applicable to single-stage injection molding,
two-stage injection molding wherein the screw
retracts, and injection blow molding. for typical
Injection molding operations, the back pressure on the
screw is about 0.3 MPa (50 psij. In operation of the
process of the present invention, the back pressure
will generally be at least 1.5 Mpa.
for two-stage injection molding wherein the
screw does not retract and extrusion blow molding, the
high degree of shear necessary to accomplish the fine
dispersion desired is obtained by the use of the
dispersion section on tlae~screw at the rotation speed
and spill clearance which provides this shear. The
check valve present in the two-stage injection molding
anachine between the screw barrel and the injection
chamber shears the molten resin as it is forced by the
screw into the injection cylinder, to supplement the
shear and thus the dispersion provided by the
dispersion'section of the screw.
Preferably, the shear time in the molding
operation comprises at least about 15~ and more
preferably at least about 20~ or at least about 25~ of
the molding cycle, with the choice of minimum shear
time depending on the particular molding~operation.
Most preferably the shear time is at least 30% of the
cycle time.
In combination with the extended shearing
time is the intensity of the shear to which the molten
3r resin is subjected by the dispersion section of the
«
'O 92/ti3274 PCT/US91/iD5~91
-2~-
screw. Figs. 3 to ~ show details of one embodiment of
screw design for accomplishing the necessary shear.
Screw 12;,has a helical bearing flight 1t and
a,root 32 which forms in sequence extending in the
direction of resin movement along the chamber 8, a
feed section 34, a transition section 36, and a
metering section 38 which are designed to deliver a
steady flow of malten resin to the dispersion section
18 of the screw.
~'he feed, transition, and metering sections
era conventional screw features and can have many
different designs to accomplish this delivery. In the
embodiment shown in Fig. 3, the r~ot 32 has a constant
1S diameter over several turns of flight 3.6 for receiving
the resin particles. In the transition section 36, it
has a root of increasing diameter, and in the metering
section 38, the root returns to a constant diameter
corresponding to the largest root diameter of the
transition zone., Tn accordance with this
configuration, the channel 40 formed by the helical
flight ~.6 and root 32 coupled with the interior wall
of chamber 8 decreases in volume within the transition
section 36.. Rotation of the screw in the direction
2g causing the resin particles to advance from the feed
section 34 through the transition section 36 causes
the resin particles to become compacted to provide
heating of the particles from several sources, the
heat from barrel f and the heat generated within the
chamber by compaction of particles within channel 40
and movement within these compacted particles caused
by the relative movement of the particles as they are
wiped along the wall of the heated barrel S by the
helical bearing flight 16. Substantial melting of the
3~ resin particles is desired by the time the resins
reach the metering section 38, where the resins may be
-eV0 9~10~27~1 ~ ~ ~ ;~ ~ ~ PCT/I1S91/05591
29
exposed to additional heating from the barrel and
motion of the resins within the shallow channel 40
present in this section.
r The dispersion section 18 is designed to
intensify the shear of the polymer during the next
portion of its advancement along the chamber. In fig.
3, the dispersion section 28 consists of three
shearing sections 20 spaced apart from one anather
along the length of the screw to form transverse
mixing channels 22 between adjacent sections 20.
~1s best shown in Fig. 4, each shearing
section 20 comprises a g~lurality of bearing flights 42
and a plurality of barrier flights 44 interleaved with
one another, each extending from the screw 12 and in
the embodiment shown, each forming a helix angle with
respect to the axis of the screw at 60°. The length
of each shearing section is about the same as the
diameter of the flight 42, which is the same as tine
diameter of the helical flight 16.
The spacing between the bearing flights and
barrier flights form a corresponding plurality of
interlea~red entrance channels 46 and exit channels 48
extending along the axis of the screw and having the
same helix angle as the bearing and barrier flights.
Means are provided for closing the entrance
or upstream end 50 of each exit channel, and means are
pravided for closing the exit end or d~wnstream end 52
of each entrance channel. In this~~embodiment, the
gp closure means consists of a web extending from the
corresponding ends of the bearing flights and having
the same diameter thereas sa that the resins being
plasticated do not pass over the closed ends 50 and 52
of channels 46 and 48. Instead, the resins are forced
g5 by the metering section 38 of the screw l2 into the
entrance or upstream ends 54 of the entrance channels
iVO 92/0327d Pf:T/U~91/OS591
i,~r~ ° 30 °
46. In this way, the metered resins are divided into
a plurality of streams of resin corresponding to the
number of entrance channels present.
Spurred by the metering section 38, the
resins are forced along the length of the entrance
channels 46, filling their volume with resin until the
resin reaches the closed downstream ends 52 of these
channels.
The bearing flights 42 form the force or
leading side of the entrance channels 46, and the
barrier flights 44 form the aft or trailing side of
the entrance channels, with reference to the direction
of rotation of screw 1.2. As shown best in fig. 5, the
barrier flights 44 are spaced further from the
interior wall of barrel 6 as compared to the bearing
flights, to form a small clearance 56 between the
barrier flights and the interior wall of the barrel.
The entrance channels 46 in effect overflow
2~ with resin over the barrier flights 44 through the
clearances 56 (spill clearance) to enter the trailing
exit channels. In the course of passing through these
clearances 56, any particles of resin present are
subjected to shear and heating to cause the particles
to melt and break down into small particles. The
width of the clearance 56 (spill clearance) between
the barrier flight and wall of the barrel 6 is
established such that sufficient shear is present to
cause this break down into smaller"particles and the
smaller particles to break down into even smaller
particles. In the embodiment shown in Fig. 4, the
entrance channels are wider and therefore have greater
volume than the eacit channels, which provides greater
residence time of the resins in the entrance channels
to promote the softening and melting of the resins
41 ~ ,J
1V(D 92/8327=i PCT/US91/OSS91
31
prior to shearing within clearance 56 in case there
are non-melted particles.
Fig. 6 shows one embodiment for shaping sects
barrier flight 44 so as to promote attenuation and
thus break down of polymer particles. In this
embodiment, the entry side of the clearance 56 from
the entrance channel 46 is tapered away from the wall
of the barrel 6 to form a wedge shaped opening 58 to
1~ the clearance 55. As the resin melt moves into the
clearance 56, it becomes subjected to greater and
greater shear arising fram compression between the
decreasing space within the wedge-shaped opening 58
and the wall of the barrel.
The resins entering the exit channels 48 via
their respective barrier flights 44 and clearances 56
eventually fill up the exit channels to eventually
leave these channels at the open downstream end 60 of
each such channel.
2p Upon leaving the exit channels of shearing
section 2~, the resins enter the adjacent transverse
mixing channel 22, where the streams of resin from the
preceding exit channels 48 become united by the
rotation of screw 12.
~5 Further advancement of the resin causes it
to be redivided into different streams of resin, as
compared to the streams leaving the preceding exit
channels 48, for entering the entrance channels 46 of
the succeeding shearing section 2d;~to be subjected to
3~ additional shearing in the same way as described for
the preceding shearing section 2~. The mixing
occurring in the transverse mixing channels and in the
entrance and exit channels causes the second resin t~
become finely dispersed with the molten first resin.
35 This is repeated for each transverse mixing
channel 2~ and succeeding shearing section 20 to
wc~ ~iio~z~~ ~eri~us9nosssl
provide a dispersion of increasing fineness and
uniform distribution, until the. thoroughly plasticated
resin reaches the nose ~6 of the screw 12 and forward
end of chamber 8, ready for melt fabrication. The
number of shearing sections 20 is preferably at least
2 and, more preferably at least 3, the number of such
sections depending on the amount of shear that can be
built into each dispersion section and the particular
dispersion tas3c to be accomplished within the
cylindrical chamber housing the screw. The number of
bearing and barrier flights per shearing section 20
will generally be from four to eight of each.
Some shear is accomplished in the feed,
transition and metering sections of the screw, but
this shear is minor and insufficient for dispersion as
compared to the shear provided by the dispersion
section 18. The dispersion section 28 accomplishes
both shear and mixing of the resultant fine particles
p of second resin within the first resin.
Preferably, the dispersion section 18, under
the conditions of plastication, achieves a shear rate
of at least about 300 sec°1 within the molten resin,
more preferably at least about 450 sec"'1, and even
more preferably at least about 900 sec°1 for thorough
dispersion of the second resin within the first resin.
Shear rate is the circumferential speed of
the screw divided by the spill clearance (clearance
56). The circumferential speed of'the screw is the
screw diameter X 3.3.4159 X rpm. The spill clearance
is the difference between the radius of the barrel or
cylindrical chamber and the barrier flight radius. By
way of sample calculation, far a barrel having an
inner diameter of 44.5 mm, the circumference of the
screw will be 139.7 mm. When the screw rotates at 100
rpm, the circumferential speed is 13970 mmjmin or
7n
!~'iD 12!03274 ~ ~ ~ ~ "'' ~ ~ PCT/US91/05591
33 --
232.8 mm/sec. For a spill clearance of 0.1524 mm, the
shear rate is 232.8 mm/sec 0.1524 mm a 1528 sec'1.
9ne limitation on the amount of shear
applied to the molten resin being plasticated by the
.dispersion section Z8 is that overheating of the
resins to cause resin discoloration which is
indicative of degradation and a deterioration of
properties must be avoided. The present invention
achieves this result by judicious choice of shear time
and shear intensity conditions for the particular
combination of first and second resin being processed.
Shear intensity will depend an the melt viscosity of
the rssins being sheared, the screw rotation speed,
the clearance 56 and the number of such clearances.
Typically, the clearance 55 will be selected from the
range of about 0.15 to 0.7 mm to obtain the result
desired. Osually, the lower spill clearance will be
no greater than about 0.35 mm.
The relative melt viscosities of the first
and second resins under plasticating conditions in the
dispersion section also contribute to the shear
present in the dispersion section 18 to cause the
molten particles of ascend resin to break down inter
smaller particles, and these smaller particles to
break down into even smaller particles.within the
dispersion section. When the first resin is
non-~elastameric, its viscosity usually,ciecreases
rapidly with increasing temperature. When the second
resin is an elastomer, its viscosity usually decreases
mare slowly with increasing temperature. Preferably,
' the first and second resins are selected so that their
melt viscosities at plasticating temperature produces
the shear between resins described above, so as to
achieve the best dispersion result possible for the
plasticating conditions used. Preferably, the melt
~V~O 9~10327~i P(_°fJU591/05591
- 3d -
viscosities of the first resins will be within the
range of about 5:1 to 1:5 of one another, i.e.,
the
melt viscosity of the first resin can be from five
times greater to 1/5 of the melt ~riscosity of the
second resin. More preferably, the range of relative
malt viscos~.ties is about 2:1 to 1:2 and even more
preferably about 1:1.
The foregoing detailed discussion is
1~ applicable to carrying out the grocess of the present
invention in both injection and injection blew molding
of articles. This discussion is applicable to
injection molding in a two-stage machine whether
or
not thf! screw recl.procates . ~ f the Screw
reciprocates, the opportunity is offered for
increasing shear time by increasing back pressure
on
the screw to retard its retraction. zf the screw
does
not reciprocate, the necessary shear is accomplished
during the screw rotation time in the molding cycle.
2a In both types of two-stage machines, the forcing
of
the molten resin through the check valve between
the
screw barrel and the injection chambers subjects
the
molten resin to high shear to augment the shear
achieved by the dispersion head of the screw. The
IProcess of the present inventian can also be carried
out in extrusion blow molding wherein that the screw
does not reciprocate. instead it is the periodic
rotation of the screw that forces an amount of molten
resin into the shape desired. In extrusion blow
~ molding, a blow-mold is then closed about the extruded
shape (parison), and the mold is next transferred
to
a
blowing station. During this mold closing and mold
transfer, the screw does not rotate. in this
embodiment, the fine dispersion of second resin
within
~5 first resin is achieved by shear rate and shear
time
W~O 92/0324 ~ c~ ~ PCT/US91/0_>"591
- 35
but without the possibility of extending the shear
time by retarding retraction of the screw.
_. The screw design of lFig. 3 insofar as the
design of the dispersion section 18 is cancerned is a
preferred design for shearing the melt~of the
combination of first and second resins in the process
of the present invention>. In view of the results
abtained with this design, other designs for
accomplishing this result will be suggested to those
skilled in the art.
1~igs. 7 and 8 show another design of a
dispersion head that can be used in the present
invention. This head ?O forms the forward end of a
screw °72 having a helical bearing flight 74 only
partially shown, which can be the same as screw 12,
with head,70 forming the dispersion section to take
the plane of dispersion section 18. Head 70 is
cammonly available as a Maddock head for use in mixing
colorant into thermoplastic resin. ~t lass a plurality
~f bearing flights 76 and barrier flights 78
interleaved with one another and separated by entrance
channels 80 and exit channels 82. Tta~ss function
similar to the corresponding elements of dispersion
section 1.8, except that in dispersion head ?0, they
are parallel to the axis of the screw 72 and therefore
do not participate in the pumping action of the screw
and each shear section 20 of dispersion section 18 has
a greater number of flights and channels. In the
embodiment shown in figs. 7 and 8, the spill clearance
B6 is defined by the smaller radius of the barrier
flights 78 as compared to the bearing flights 76 and
the distance between the barrier flights and the
interior wall of the barrel. Webs 8~ extend from the
bearing flights to close the exit end of the entrance
channels and the entrance end of the exit channels and
W~O 92/0327~i PCT/US91/05591
° 36
to define the sides of the spill clearance. The
nose
88 of the disgarsion head 70 can be equipped with
a
conventional check valve (not shown) so that the
scre~ri
using,this head can be used in infection molding
involving reciprocation of the screw.
The.foregoing description of apparatus for
conducting the direct fabrication process of the
present invention works admirably well for combining
a
: wide variety of first and second resins which are
incompatible with one another and of course is also
operable for use on compatible resins.
Tn the case of the direct fabrication of
polyester resin as the mayor component and
ethylene/epoxide copolymer elastomer, the toughness
result for the directly fabricated articles is not
consistently optimum. Polyester resins, particularly
polyethylene terephthalate, are moisture sensitive
such that the presence of moisture during melt
processing can cause molecular weight degradation,
which adversely affects toughness, when the resin
is
post consumer waste obtained, e.g., from chopped-up
bottles, whereby the resin is in the form of flakes,
such flakes can be contaminated with impurities
despite cleaning and separation treatment, which
can
also cause polymer degradation. F'or these or perhaps
other causes, the practice of the direct fabrication
process on polyester resin and epoxide copolymer
elastomer can give inconsistent results.
0 one embodiment of the present invention
solves this problem by providing much more
consistently high toughness results for the directly
fabricated articles from these polymers. It has
been
discovered that the toughening effect of the copolymer
elastomer on the polyester resin can be enhanced
by
incorparation of adjuvant into the melt blend of
these
2~~~~~r~
,e~'O 92/03274 PC1'/US91/05591
- 37 -
polymers. This incorporation can be carried out by
adding the adjuvant to the melt blend, whereby the
shearing of the melt blend disperses the adjuvant
therein. Alternatively, the incorporation can be
carried out by adding the adjuvant to the feed of
polymer particles to the direct fabrication process.
The adjuvant can be in the form of finely divided
particulate material which can be dry mired with the
Polymer particle feed. The adjuvant can also be
normally liquid (at room temperature), which state
lends itself to either miring with the polymer
particle or injection inta the melt blend of the
polymer. Preferably the adjuvant does not contain any
~,5 water. When added in the dry form, the adjuvant needs
to be dispersible in the polymer melt. Preferably,
the adjuvant in the dry form has a melting point which
is less than the temperature of the melt blend of
polymers. The temperature of the melt blend will
generally be at least 24o'C. In any event, the
adjuvant is preferably neat, i.e., without dilution in
a licruid solvent or dispersant, so that such diluents
do not have t~ be disposed of and will not interfere
with the direct fabrication process. The shearing of
~5 the melt blend disperses the adjuvant therein so that
preferably, it is no longer visible in the blend or in
the articles fabricated therefrom, even under
magnification of loon ~c.
A number of compounds incorporated into the
~ melt blend provides the adjuvant effect, i.e., the
toughness of articles molded from the melt blend is
high ~-~.~.th much greater consistency than wtaen the
adjuvant is not present. Preferably the toughness of
the articles molded in accordance with the embodiment
35 of the present invention is at least 50o J/m and more
preferably at least 70o J/m.
CVO 92/fl3274 P'CT/US91105591
- 3~
Examples of adjuvants include zinc salts and
zinc complexes. Examples of zinc salts inelude the
zinc salts of fatty acids which are saturated and
have
the general formula CH3 (CH2,n COON wherein n is
4 to
2'J, preferably 7 to 1~. Examples of such zinc salts
are zinc valerate, zinc octanoate, zinc laurate,
and
zinc stearate, with zinc stearate being preferred.
Zinc octanoate is an example of normally liquid
adjuvant, while zinc stearate is a solid at room
temperature but melts at about 130'C. Examples of
zinc complexes axe zinc acetyl acetana~te and zinc
diethyldithiocarbonate.
Additional adjuvants include certain salts
of certain other metals, including tin stearate,
copper stearate and cerium stearate.
Just as a number of compounds provide the
adjuvant effect, a number of compounds do not as
will
be detailed in the Examples. Stearic acid is not
an
a0 adjuvant. The same is true for the 3Ja, K, hi, Ca,
R3g,
Al, Co, and rti stearates.
Zn salicylate is an adjuvant but zinc
benzaate and zinc citrate are not. Znco3 is an
adjuvant but Zno is not.
Zinc acetate is not an adjuvant apparently
because it is not dispersible in the melt blend,
i.e.,
the zinc acetate end up as 'clumps' thereof in
articles molded from the melt blend.
'The effect of the adjuvant on the toughness
0 of artic3es molded from the melt blend of polyester
resin and copolymer elastomer, as previously described
is to provide more consistently high toughness results
than without the adjuvant being present. Apparently,
the adjuvant makes the direct fabrication process
more
~fargiving' insofar as being able to tolerate polymer
degration, presence of impurities, and other
WO 92/03274
'~ PCT/i1591/95591
-- 3 9
variabilities in feed composition and processing
conditions that would otherwise only give occasionally
high toughness results.- The reason for the adjuvant
effect of more consistently high toughness ,is unknown,
as is the reason why seemingly clasely related
compounds are not adjuvants. Apparently, however, the
adjuvant aids in the reaction between the polyester
resin and the copolymer elastomer.
The..adjuvant effect for particular compounds
may also depend on the amount of shear to~which the
melt blend incorporating the adjuvant is subjected.
~1t low shear, characterized by a screw back pressure
of only about 0.3 MPa, the adjuvant effect.may not be
lr ~btained, but is obtained when screw back pressure is
increased to increase shear time, or other measures to
increase shear intensity are taken. Several
adjuvants, especially zinc stearate provides good
results even at low screw back pressure. In this
case, the adjuvant provides a two fold effect to the
direct fabrication process. First, the adjuvant
increases the consistency of the direct fabrication
result of high toughness for the polyester
resin/epoxide copolymer eiastomer combination.
aecond, the adjuvant also reduces the'amount of shear
that is necessary to achieve the fine dispersion of
the copolymer elastomer within the polyester resin,
and promotes interaction therebetween which produces
adhesion between these polymers. This means, e.g.,
that the shear time may be reduced and fine dispersion
and superior toughness results still obtained. nne
manner of reducing shear time is to reduce the back
pressure on the melt processing screw, which is used
in direct fabrication molding to increase shear time.
This may also lead to shorter molding cycles.
6V0 9210274 PCT/US91/05591
ao -
2~~~~5'~
"_ The amount of adjuvant used will generally
be about 0.05 to 2.0~ based on the weight of the
\, _ polyester resin plus the copolymer elastomer, and is
preferably._about 0.lto 0.5 wt. ~ thereof.
The process of the present invention in its
many embodiments is useful to directly fabricate a
wide variety of articles such as containers for many
different utilities. iNormally the process of the
1~ present invention will bs practiced by combining the
first and second resins for the first time at the
start~of the practice of the process which ends up
with directly fabricated articles of predetermined
shape, either finished articles as in the case of
injection molded articles or intermediates such as a
tubular parison for subsequent blow molding into the
finished akticle. This saves the fabricator the need
and expense to undertake precompounding. Tt is
contemplated, however, that the resin supplier may
0 wish to provide the second resin, ordinarily the minor
resin compcanent, to the fabricator in the form of a
concentrate in a first resin, within which the second
resin may be the major or minor resin component,
ultimately to end up as the minor resin component in
the fabricated article. When the second resin is low
melting and moisture sensitive, the concentrate with
the higher melting first resin gives a more
conveniently dryable combination of resins. The
,concentrate will generally be supplied as pellets
0 containing both the first and second resin for
combination with additional similar or identical first
resin for feed to the direct fabrication process of
the present invention. Typically, when this embodiment
is used, the pellets containing both the first and
second resins will constitute a minor proportion of
the feed to the direct fabrication process, and more
CA 02089267 2001-03-26
PCT/US91 /05591
WO 92/03274
- 41 -
often; no greater than about 40% of the weight of the
resin components of such feed. In accordance with the
present invention, the fabricator then subjects the
combination of concentrate particles with first resin
particles to the melting/shearing process to produce
the fine dispersion of second resin particles within
the matrix of first resin hereinbefore described.
Examples of the present invention'are
presented hereinafter (parts and percents nre by
weight unless otherwise indicated).
plea 1-6
The polyester compositions used in these
Examples were as follows: (a), 42 lbs. (19:i kg)°of PET
recycle soda bottle flake (about 6 to 9 mm in lateral
dimension and .05 to l mm thick) which was vacuum
dried 18 hours at 100'C; and (b) 8.3 lbs. (3.8 kg) of
pellets (3.5 mm diameter, 3.5 mm long) of 76.75% by
wt~ ethylene/28% by wt. n-butyl acrylate/5.25% by wt.
glycidyl methacrylate copolymer elastomer which was
vacuum dried 18 hours at 40'C. These two components
and l00 grams of tetra bismethylene-(3,5-dibutyl-4-
hydroxyhydrocinnamate) methane, a hindered phenol
antioxidant available as Irganox' 1010, were then drum
tumbled in a 132.5 L. drum lined with a polyethylene
bag and blanketed with nitrogen gas atmosphere for 20
minutes and. then fed directly to a single-stage
infection molding machine. The hopper of the
injection molding machine:was continuously blanketed
with nitrogen.
The injection molding machine was a 6 ounce
(0.17 kg), 125 ton (1.11 MN) machine containing a 4.44
cm diameter screw. The screw was the screw described
in Fig. 3, except that the screw had four shearing
sections 20, in which the clearance 56 was 0.15 mm
~3'O 92/3274 PCT/ZJS91/05591
42
(0>006 in.) and each dispersion section 18 had 6
barrier flights. The,temperatures used were as
follows> Sarrel rear, 175'C; barrel center, 260'C;
barrel front, 260'C; nozzle, 260'C;,mold, 40'C. The
screw speed was 100 rpm resulting in a shear rate of
1528 secW, and the time for the screw retraction
(rotation) was varied from about 10 seconds to 28
seconds by application of bank pressure to the screw
as campared to the usual back pressure 0.3 MPa..used
for molding PET resin. Each shot produced two 3.18 rnm
X 1.27 mm x 127 mm flex bars and one 3.18 mm X 76.2 mm
X 127 mm plaque.
Table I shows further details of the
1S operating conditions for each Example. The Notched
Izod impact strength was measured for each Example on
the flex bars produced by the 10th, 20th, 30th, 40th
and 50th infection molding shots. The flex bars were
cut in half, one half representing the gate end and
the other half representing the far end of the
infection molded flex bar. The test results were
averaged to represent the result for each Example.
These results are shown in Table I and are plotted as
curve 90 in the graph of Fig. 9.
These results show in general the increase
in toughness with increasing screw rotation time
obtained by retarding the retraction of the screw.
There was no discoloration present in the molded
articles, indicating the absence of'degradation. Such
a small proportion of screw rgtation time as compared-
to total cycle time was used for Example 1 that
improved impact strength over.the PET by itself was
minimal. _The impact strength of the PET resin by
itself is generally less than 25 J/m. The number
average particle size of the second resin within the
i'V~ 92/03274 ~ ~ ~ ~ ~ ~ ~~ Pt,°T/LJS91/~D5591
- d3 -
PET resin matrix for the toughened molded samples was
less than 1 micron.
~o~parative Examples 7-~3
S The general molding procedure of Examples 1
to s Was repeated, using the molding machine and same
Composition, except that the screw was a distributive
mixing sCreW disclosed in U.S. Pat. 3,006,29, whiC:h
had bearing flights in the mixing section, but no
barrier flights. Further details of operation are
reported in Table Tx and the impact~test results
obtained in the same manner as for Examples 1-6,
except that for Example ~, flex bars molded only at
the lath shot were tested, and are reported in Table
S I7: and plotted as curve 92 in Fig. 7.
0
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WO 92/03274 ~C T/US91 /05591_
_4s_
Comparison of curves 90 and 92 shows that as
the % of screw rotation time increases, so does
toughness, but the increase becomes much greater for a
given screw rotation time using the screw with the
dispersion section. The high average impact strength
obtained for Example 7 is believed to be spurious,
resulting from an almost 3% difference between impact
strength of flex bars molded at the 10th shot vs. the
.10 20th shot. The screw of,U.B. lPat. 3,006,029 used.for
Comparative Examples 7w13 had no dispersion section.
For the curve 90, the increased screw rotation time
represents increasing shear time, while for curve 92,
the increased screw rotation represents increased
mixing time, with insufficient shear to obtain the
fine dispersion of second resin within the first resin
necessary to achieve high toughening.
examples 1~4 and 15
The polyamide composition used in these
20 Examples was as follows: 81% by wt. nylon 66 which was
vacuum dried: 10% by wt. ethylene/propylene/diene
copolymer elastomer grafted with 1.8% malefic anhydride
groupsr and 9% by wt. ethylene/propylene/1,A-hexadiene
copolymer elastom~r. These components are available
25 from 10u Pont as Zytel~ 101, anhydride grafted E/P
rubber and ~tordel~ 3781, respectively. The three
components were each in the form of pellets of about
3.5 mm in diameter ~C 3.5 mm in length and they were
drum tumbled for 10 minutes under a nitrogen
30 atmosphere and fed directly to the hopper of the
injection molding machine used far Examples 1~6.
Moldings were produced on the injection
molding machine using the following molding machine
temperatures; barrel rear, 261°C, barrel center 281°C,
35 barrel front 281°C, nozzle, 280°C, mold temperature
90°C. The screw used for this direct molding
a~'~O 92/0327 ~ ~ b ~ ~ ~ ~ PC,'T/US91/05593
operation wa.s the screw of Fig. 3, except that there
were four shearing sections 2~, used in Examples 1~6
operating at la0 rpm to produce a shear rate of 1528
sec'1. The results are shown in Fable III.
15
25
35
i~'O 92/03Z'~ PCi'/US9i/m559i,
~ 48 -
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W~ 92/03274 ~ ~ ~ '~-~' ~ ~ ~ PCT/US91/05591
4g
These results show that as screw rotation
time increases, so does toughness of the molded
article without causing discoloration to be present in
the molded articles. The back pressure used in these
Examples can be compared to the usual bacJc pressure of
0.3 MPs used for injection molding nylon 66, and the
notched Izod impact strength for nylan 66 by itself is
g~nerally no greater than 112.1 JJm even after
.10 conditioning to, 50% R. tI. The number average, particle
size of the second resins in the nylon was less than 1
micron.
When this experiment was repeated but using
the distributive misting screw of U.S. Pat. 3,006,029,
15 and back pressures of 2.07 and 2.41 MPs were used to
give screw rotation times of 11 and 25 sacs, the
impact strengths obtained were only 203.and 165 Jfm,
respectively.
~atampi es ~L6-22
20 ~ blend of 85% by wt. of PET recycle soda
bottle flake with 15% by wt. of 3.5 mm pellets of
Surlyn~ 8270 were drum tumbled as described for
Examples 1-6, along with the antioxidant used in those
Examples after vacuum drying of the PET flake.
25 Surlyn~ 8270 is a zinc neutralized copolymer of
ethylene/23.5% by wt. n-butyl acrylate/9% by wt.
methacrylic acid and as an elastomer. The same
injection molding machine and screw (Fig. 3, except
there were four shearing sections 20,j as Examples 1-6
30 was used to mold samples from this dry blend of flake
and pellets. The molding conditions used were as
follows Temperatures; barrel rear, 175'C; barrel.
center, 260°C; barrel front, 260'C; nozzle, 260°C;
screw speed, 100 rpm; ram speed, fast; mold
35 temperature, 40'C. The shear rate was 1528 sec°1.
Total injection molding cycle times of 43 seconds and
\i'O 92/0327=1 ~'~T/US91/a5591
53 seconds were used with injection/hold times of
20/20 seconds and 20,/30 second, respectively.
Injection pressures of 3. 55.5 MPa and a fast Ram
5 speed were used to produce two 3.18 mm flex bars and
one 3.18 mm plaque. Table TV shows the further
operating conditions used and the toughness results.
The notched Izod impact data is the average of 24
individual determinations. The different screw
10 ~'otation times reported in Table IV were obtained by
increasing back pressure on the rotating screw.
20
30
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CVO 92/03274 ~'t.'T/'11591/05591_
-° 52 -
~~~~ F ~r~
Since PET has a notched Izod impact strength
of about 25 J/m, it is apparent from Tables 2V that
considerable toughening of PET resin is obtained by
the incorporation of this ionomer.into the resin, with
this toughening increasing with increasing shear time.
In these Examples, the number average particle size of
the ionomer in the PET matrix was about 1 micron.
l~xample 23
to ~, two-stage injection molding machine,
equipped with a reciprocating screw having the Maddock
dispersion head of Fig. 7 and 8 was used to injection
mold one liter flower pot type containers using a
4-cavity hot runner mold. The flower pot taad~a 1.2 mm
thick wall and a 1.4 mm thick base. The feed to the
injection molding machine consisted of a dry tumbled
(under N2 blanket) mixture of the following
campasitian:
24.2 kg PET recycle soda bottle flake which
2p had been vacuum dried for
16 hears at 10o'C
4.3 kg of 3.5 mm pellets ethylene/28% by wt.
n-butyl acrylate/5.25% by wt. glycidyl
methacrylate copolymer elastamer which
had been vacuum dried for l~ hours at
40'C.
85 g of hindered phenol antioxidant
(Irganox~ 1010)
The machine operating conditions were as follows:
3Q temperatures from rear to the forward of. the extrusion
barrel were 232°C, 24S'C, 277°C and 278°C, and
279°C
at the nozzle. The mold temperatures were 38'C for
the core and 51.7'C for the cavity. The extruder was
a 7o mm diameter 24/1 length to diameter ratio,
equipped with a screw having a 3/1 c~mpression ratio
and the Maddock head. The Maddack head had a spill
1V0 92/03274 ~ ~ ~ ~ ~ ~ ~ ~'~1'1US9110559y
,,
53 -
clearance of 0.635 mm and the screw operated at 7.25
rpm to give a shear rate of 651 sec-1. The molding
cycle was 7.8 sec.; the screw rotation time was only 3
sec.; giving a shear time of only 17~ of the total
cycle time.
The molded flower pot containers wero tested
for toughness by being filled with water and sapped at
roam temperature and were dropped against a solid
ZO surface from a height of 122 cm.~ When the drop angle
was 45'C, i.e., the filled container struck the
surface at the corner between its wall and bottom,
none of five containers tested failed (none brokej.
This test was repeated for the same containers molded
1S the same way from the same composition, except the
composition was pre-compounded, so that pellets of the
mixed composition were fed to the 2-stagy infection
molding machine. Five of the containers were tested
by the same drop test and all survived.
20 The drop test was repeated except that the
drop angle was zero, i.e., the impact of the container
on the solid surface was between the bottom of the
container and the solid surface. In this test, none
of the pre-compounded containers failed, while one of
25 the~five directly fabricated containers failed. This
same result occurred when the room temperature water
content of the containers was replaced by a
glyeol/water mixture at -18'C and the containers were
dropped at a 45' angle: When the containers with the
30 cold glycol/water mixture were dropped flat (zero
anglej, one of the pre-compounded containers failed
and two of the directly fabricated containers failed,
These results show that direct fabrication produced a
product which was about as Laugh as the same product
35 produced by the more expensive route of
pre-compounding.
db'O 9x~03x7~i PCT/U59i/05591_
- 54 -
example 24
Example 23 was repeated except that the
containers molded were:a 2 gallon pail liner about
22.9 cm in diameter and 27.9 cm tall, having~a 2.3 mm
wall thickness and each weighing about 0.9 kg. The
barrel temperatures were as follows: rear, 230°C;
center, 260°C; and forward 260°C. The nozzle
temperature was 250°C, and the mold cavity and core
temperature was 13°C." The total molding,cycle was
35.4 sec, of which the screw rotation time was 16 sec.
The impact strength of the wall of the container was
tested by the Gardner impact test (ASTP3 b°3029). ~t
room temperature, the directly fabricated containers
had a toughness of 55.1 J as compared to greater than
59.0 J for pre-compounded containers. At -20°C, the
directly fabricated containers exhibited an impact
strength of 24.4 J as compared to 35.3 J for the
pre-compounded containers. Measurement of the
particle size (of the ethylene elastomer) in the
bottom o~ the pails revealed that for the directly
fabricated pails the particle size range was 0.1 to
6.0 microns and the number average particle size was
0.6 micron. For the pre-compounded parts, the
particle size range was 0.08 to 3.0 microns, and the
number average particle size was 0.3 microns. From
these results, it is apparent that direct fabrication
produces a very fine dispersion of elastomer particles
within the resin (PET) matrix, almost as fine as
obtained through pre-compounding. Tt is believed that
further experimentation, involving e.g., decreasing
the spill clearance, will provide egually as good
results as obtained by pre-compounding.
N i) r~
_ 1i'CD 92103271 PCI°lLIS91105591
y
- 55 -
~xamx~ ~e 2 5
In the experiments described under this
Example, the procedure of Examples z-6 was essentially
repeated to prepare by direct fabrication and test the
infection molded flex bars so fabricated. The same
PET recycle flakes and ethylene/n-butyl
acrylate/glycidyl copolymer elastomer in the same
proportion were used in these experiments. These
1~ experiments, however, address the variability in
toughness results obtained when the first and second
resins are polyester, especially PET recycle flake,
and the ethylene-glycidyl methacrylate copolymer
elastomer, respectively. While fine dispersion of the
second resin iota the first resin is obtained by the
direct fabrication process of the present invention,
the toughness of the molded article is often deficient
in comparison with the high toughness results obtained
in same of the experiments, e.g., Examples 2-C. The
p cause of this variability may be due to impurities in
the recycle PET coming from the post-consumer source
_ of these flakes, v~~iability in the PET flake itself
because of the different sources of the PET resin from
which the consumer plastic was originally made,
~5 insufficient drying of the PET flake before feeding to
the direct fabrication process and/or a combination of
these phenomena.
The embodiment of the present invention
involving the use of ad~uvants to improve the
toughness result is shown in the series of experiments
constituting this Example 25. The procedure for
incorporating the ad~uvant ar comparison compounds
into the molten blend of first and sec~nd resin was t~
add the adjuvant or comparison compound gcollectively
~5 referred to herein as additive) in powder form unless
otherwise indicated to the drum used for dry blending
'~a 9zio~z~~ ~crius~m~s~n
°- 56
the resins together, whereby the additive was blended
with the resins at the same tame. The following
experiments show the improved toughness result. In
these experiments, the Izod impact test results
reported represent the average of 12 to 20 impact
tests, one half of which were done on gate ends of the
molded flex bars and the other half of which were done
on far ends of the flex bars. The notched Izod impact
test. results were all obtained a~ room temperature.
The wt. % of ad~uvant or comparison compound used is
based on the weight of the PET flake plus copolymer
elastomer.
(a) In this experiment, 0.25 wt. % of zinc
stearate as the ad~uvant was added to these resins.
When the back pressure on the screw was 4.07 MPa to
give a screw rotation time of 38.7% of the total cycle
time (53 sec.), the notched Izod impact strength was
682.6 J/m. When the pressure was increased to
4.34 MPa to give a screw rotation time of 39.8% of the
total cycle time (43 sec.), the notched Izod impact
strength was 695.9 J/m. By way of comparison, in
experiments done the same time and the same way, but
in which the zinc compound was omitted, the following
results were obtainedc (1) back pressure of 2.07 MPa
to give a screw rotation time of 39.3% of total cycle
time of 43 sec., the notched Izod impact strength was
only 87.0 J/m and (ii) back pressure of 2.97 MPa to
give a screw rotation time of 49.8% of total cycle
time of 53 sec., the notched Izod impact strength was
only 77.4 J/m.
(b) In additional experiments, the effect
of zinc stearate vs. calcium stearate, potassium
stearate, and stearic acid as additives to the resin
blend can be compared, as follows
'i~~O 92/D3274 fCT/US91/OSS91
_ 57 -
TASIaE v _ EFFECT OF ~AI~IpUS
OOM~OUNDS ~N HLER1D TOUGHNESS
Screw
RotationAverage
Time Notched
As
Screw ~ of Izod
Back Molding Total Impact
Pressure Cycle Cycle Strength
As3 itive Wt. ~ iM~a) Sec _~,~me _/m)
None 2.28 20/20/3 37.9 106.7
None 0.34 20/20/3 IB.~ 85.4
None ' 3.24 20/30/3 50.5 74.2
~n Stearate 0.25 3,10 20/20/3 37.0 9?1.3
Zn Stearate 0.25 0.62 20/20/3 21.2 800.0
Zn Stearate 0.25 4.83 20/30/3 50.9 613.8
Ca Stearate 0.25 2.34 20/20/3 38.6 90,7
Ca Stearate 0.25 0.34 20/20/3 1.9.1 85.4
Ca Stearate 0.25 3.19 20/30/3 53.5 69.4
gC Stearats 0 .25 2.97 20/30/3 51.9 80.1
K Stearate 0 .25 0.34 20/20/3 20.5 90.7
~ Stearate .25 2.03 20/20/3 40.0 74.7
0
Stearic Acid 0.25 0.34 20/20/3 20.8 88.x.
Stearic Acid 0.25 2.00 20/20/3 39.8 80.1
Stearic Acid 0.25 3.03 20/30/3 51.4 10.35
These experiments were~conducted at the same
time and in the same way. The directly fabricated
articles containing the zinc stearate additive gave
mach improved toughness results as compared to when
the other additives were used and r)o additive was
used.
(c) In additional experiments, varying
amounts of zinc stearate was used in the resin blends
for comparison with blends made and tested at the same
time in which no additive was present or when zinc
acetate was the additive. Although these results
reported in Table VI include some variability with the
'~'d~ 92/03274 P~i'/1JS91/05591_
- 58 -
results when zinc stearate was used, the trend of
clear superiority of the zinc--stearate containing
blends is evident.
.5
xA~sr~ vz
screw
Rotation
Average
~'ime Notched
As
screw ~ Of Izod
Hack Molding ~ota~l Impart
Pressure Cycle Cycle Strength
Additive Wt. % ~~IPay Sec M'~.me
f~/m)
None 2.07 20/20/3 41.3 95.0
None 0.41 20/20/3 20.2 89.1
None 1.38 '20/20/329.1 ~ 8745
None 3.10 20/30/3 51.9 87.5
Zri Stearate 0.504.83 25/30/3 42.2 1010.8
Zn Stearate 0.25 3.51 20/20/3 41.9 995.4
Zn Stearate 0.25 0.34 20/20/3 19.5 624.4
~Zri Stearate 1.93 20/20/3 28.8 717.8
0.25
Zri Stearate 0.254.28 20/30/3 44.1 130.8
~n Stearate 0.10 2.72 20/20/3 38.6 514.8
Zn Stearate 0.10 0.34 20/20/3 21.6 116.9
Zn Btearate 0.10 1.86 20/20/3 3Ø95 139.8
Zn Stearate 0.10 4.00 20/30/3 46.2 547.0
Zit Acetate 0.07 2.83 20/20/3 42.8 79,5
Zri Acetate 0.07 0.34 20/20/3 23.5 112.6
Zri Acetate 0.07 1.45 20/20/3 29.1 1.09.9
Zri Acetate 0.07 3.31 20/30/3 48.9 389.1
Greater amounts f zinc
o acetate
could
not
be
used because evenat the 07 wt. level,
0. ~ the
zinc
acetate could be uniformly the melt
not dispersed
in
blend, as evidenced molded exhibited
by the flex
bars
SpOt6 O the aCBtate tive, ar7.siT3g
addi dppared'atly
from the non-dispersibi~.ity of the with the
additive
~'~ X2/03274 ~ ~ U ~ ~ ~ ~~ 1'LT/US91/05591
59 m
blend, despite the shearing of the blend in accordance
with the present invention. __.
(dy Tn another series og experiments done
at the same time, and in the same'way, the
ef~ectivenass of zinc stearate is compared with other
stearates in Ta?ale VxI.
,~,BL
Screw
RotationAverage
Time Notched
As
Screw ~ ~~ Izod
Back Molding Total Impact
Pressure Cycle Cyc~,e strength
~lclditi
v~ 1yt (M1'~ S
~
(Jlm1
ec T me
~
None 2.28 25/20/3 37.5 98.7
None 0.34 25/20/3 17.5 99.3
No ne 3.10 25/30/3 45.2 101.9
n Stsarate0.25 3.24 25/20/3 36.0 989.5
~n Stearate0.25 0.34 25/20/3 17.7 547.6
Zn Stgarate0.25 4.48 25/30/3 47.8 968.7
Mg Stearate0.25 2.83 25/20/3 37.3 594.5
P'igStea~ate0.25 0.34 25/20,3 16.5 112.6
Mg Stearate0.25 3.45 25/30/3 44
5
. 525.7
Ca Stearate0.25 2.59 25/20/3 36
9
. 92.9
Ca Stearate0.25 0.34 25/20/3 15
4
. 90.7
Ca Stearate0.25 4.00 25/30/3 47.4 135.0
A3 Stearate0.25 2.76 25/20/3 36.5 567.3
A1 Stearate0.25 0.34 25/20/3 16.0 103.5
~1 Stearate0.25 4.00 25/30/3 44.0 587>1
Li Stearate0.25 1.97 25/20/3.36.9 146,2
Li Stearate0.25 0.34 25/20/3 16.3 90.7
i~i Stsarate0.25 2.90 25/30/3 44.7 132.7
Na Stearate0.25 2.59 25/20/3 37.1 86.5
Na Stearate0.25 0.34 25/20/3 15.6 88.8
Na Stearate0.25 3.45 25/30/3 44.8 108.9
4fO 92/327:1 PC.T/US91/Q5591._.
60 -
-
Again the molded bars containing zinc
stearate were far tougher than the bars containing no
additive, about sX tougher based on the average of the
three toughness values X835 J/m} reported for the zinc
stearate-containing bars. Averaging the results for
the other additive-containing molded bars compares
with the zinc stearate-containing bars as follows:
,0 Average. Of..The~..Three
Notched Izad Impact
Strength Values from
Add tiye Table V'~1'
(J/m)
~~n stearate s3~
Mg Stearate ~ 410
1~
ca Stearate 106
A1 stearate 4i9
Li Stearate Z20
r1a Stearate 9q m
a0 This comparison reveals that the zinc
additive gave about ~X improvement in toughness than
the magnesium and aluminum additive and about sX
improvement than the remaining additives. The
improvement of the zinc additive over the magnesium
~5 and aluminum additives was more pronounced at low
screw back pressures (0.34 MPa), i.e., about 5X
greater toughness.
(e) In still another series of experiments
done at the same time, and in the same way, the
30 effectiveness of zinc stearate is compared to metal
salts of other fatty acids in Table VIII.
3~
2~~~~~~~
W ai m
iV0 9'x/03274 ~'C.°I'/iJS91/05591
- 61 -
~°ABLL VIII
$Cr'gio7
RotatirsnAverage
'.L'j.m~ NOtChed
X1:3
Screw ~ 0f Tzod
Back Molding Total Tmpact
Pressur~Cycle Cycle Strenr~th
Additive % ~M~a Sec Time fJ ml
Wt.
None 2.28 20/20/3 39.3 65.7.
None 0.34 20/20/ 19.1 68.3
,
Nonce 3.03 25/25/3 45.9 66,2
Zn Stearate 0.25 2.90 20/20/3 40.2 700.2
Zn Stearate 0.25 0.34 20/20/3 19.3 221.3
Zn Stearate 0.25 4.07 20/30/3 45.3 602.5
Zn MOntanate0.25 2.62 20/20/3 40.7 87.5
Zn Moritanate0.25 0.34 20/20/3 18.8 88.1
Zn Montanate0.25 4.00 25/30/3 43.6 353.3
Ca Montanate0.25 2.45 20/20/3 40,9 67.2
Ca Montanate0.25 0.34 20/20/3 17.0 73,7
Ca Montanate0.25 3.10 25/30/3 45.0 73,1
Na Montanate0.25 2.38 20/20/3 39.3 72.6
Na Montanate0.25 0.34 20/20/3 16.3 65,1
Na Montanate0.25 3.03 25/30/3 46.0 134.4
Zn Ibaurate .25 2.76 20/20/3 42.1 818.7
0
Zn haurate 0.34 20/20/3 20.9 321.3
0.25
Zn Laurate 3.59 25/20/3 49.1 336.2
0.25
Both the additive-free and the zinc stearate
- containing molded bars exhibitedw lower toughness
than shown in Table V, which is typical of results
obtained for experiments done at different times. The
significant feature is the fact that the zinc
stearate-containing bars were about 7.6X tougher than
the additive-free bars. The higher screw back
pressure experiments gave about 9.7X improvement in
toughness.
e~O 92/0327d pALTlUS91/~15591.
N- '
The average toughness for the zinc
montanate-containing bars was 176.3 J/m which although
less than the 535 J/m average for the zinc
steag°ate-containing test bars still produced more than
2X improvement when no additive was present. Thus the
3o carbon atoms fatty acid zinc salt is not preferred.
The 12 carbon atom-cantaining zinc salt (zinc lauratej
gave great improvement, averaging 492 J/m. The
1o calcium and sodium montanate additive-containing bars
gave little to no improvement as compared to when no
additive was present.
(fj Tn still mother series of experiments
done at the same time, and in the same way, the
15 effectiveness of zinc stearate is compared to other
zinc compounds in Table JCX.
~o
30
2~c~~ w~'~
e~~ ~zio3~~a Pcrius9vossm
° 63 --
TABS ax
scrs~r
. ~totation Average
~ Time Notched
As
Screw ~ Of Izod
..
Sacl~ NdoldingTotal Impact
Pressure Cycle Cycle Strength
~d~~
ti
, ( tPa) Sec _Ti.me
ve Wt. % ~ lLT/m1
None 2.38 20/20/3 38.4 88.1
Wone 0.34 20/20/3 18.6 81.1
Non~ 3.28 25/30/3 48.4 98.7
Zn Stearat$ 0.25 3.52 20/20/3 38.4 968.'7
Zn Stearate 0.25 0.34 2p/20/3 18.6 655.9
Zn Stearate 0.25 5.24 25/30/3 48.4 889.1
Zn Citrat~e 0.25 2.17 20/20/3 38.8 93.4
Zn Citrate 0.25 0.34 20/20/3 19.3 79,p
Zn Citrate 0.25 3.45 25/20/3 46.9 83.3
Zn Acetyl-
Acetonate 0.25 2.66 20/20/3 41.4 940.9
Zn Acetyl-
Acatonate,0.25 0.34 20/20/3 21.3 837.4
Zn Acetyl-
Acetona~te 0.25 4.24 25/30/3 41.0 920.1
Zn Diethyldithio-
Carbonate 0.25 2.90 20/20/3 38.4 823
5
.
Zn Diethyldithio-
Carbonate 0.25 0.34 20/20/3 19.3 617.5
Zn Diethyldithio-
Carbonate 0,25 4.38 25j30/.341.~ 916.4
The zinc stearate-containing bars taere
test
about 9X tougher
than the bars
containing no
additive
. and the zinc citrate citrateadditive
additive. The
contains 6 carbon atoms,
The remaining 'tt~o zinc
compounds
reported
in
Table IX are zinc complexes.The to ughnessof the
bars containing xes compared. orably
these comple fav
W~ 92J~~74 PCT/US91/05591
2~~~2~n ( _
s~ -
with the results obtained for the zinc
stearate-containing bars.
ample 2s
. ~ In this Example, Zn stearate is compared to
articles molded from melt blends in which no adjuvant
is present,and with other compounds incorporated into
the melt.blends, some of-which compounds- act as
adjuvants and soma of which do not. The melt bland
used in this series of experiments was derived from
85% by wt, of PET recycle soda bottle flake and 15% by
wt, of the copolymer elastomer plus 0.5% Irganox~ 1010
antioxidant (based on the weight of the polymers).
Ths adjuvant or camparison compound was mixed with the
Z5 polymer feed to the injection molding machine. The
injection molding of these specimens was essentially
the same as in Examples 1-5 except that the flex bars
used for testing were taken at the 5th, 10th, 15th,
20th and 25th injection molding "shotsn, each shot
producing two flex bars. Impact testing was carried
out on the gate end and far end of each bar, and the
impact toughness results reported in Tables X and XI
each represent the average of 20 impact tests.
Further details of these experiments are reported in
Tables X and 7tI. In these Tables, the variation in
back~pressure on the injection molding screw (same
screw as used in Examples 1-6) is expressed in terms
of.% shear time, which is the % of the injection
m~lding cycle during which the screw is rotating to
~0 shear the malt bland.
~ ~ ~ ~ ~ ~ r~ '
~'f.3 92/U327:3 PCI
/US9Il~ISS91
- 65 --
~'~H
AVERAGE
NOTCHED
IZOD
~ IMPACT
~T~ SHEAR STRENGTH
~DI2T',~IVE .w.~. ~ :f,~ /m
NONE -_~-_ 20.9 98.2
32.~ 9304
40.2 172.9
50 . 7 , 25d4 0 4
ZN sTEARATE 0.25 2~.2 ~4~,.Z
37.~ i0a2.3
43.6 1010.
ZN OCTOATE 0.14 19.5 765.9
37'. 7 972 a 4
42.5 999.1
ZN CARBONATE 0.125 23.3 243.4
4 V 0 7 6 7 3 0 0
5V a V ~21.9
Z.bNC O~~DE V . 05 23 .:J 911. 7
40e9 ~4.3
5 0 a 6 7 3 .
ZINC EENZOATE 0.22 19.3 111.0
39.5 345.
a 2 0 3
~A~TE . Oel9 20.2 149
4
37.0 e
104606
47.7 57207
ZN SALICS(LATE 0.20 21.2 47.2
40.5 1064.7
47 s 6 134 .
These results show that Zri
stedrdte, Zn
octodte, Zn carbonate, Zn valerdte, Zn sdlicyldte
and
are effective ddjuvdnts, i.e., the ticles molded
ds ar
from the melt ends incorporating compounds
bl these
gave high impacttoughness results as
compared to the
WO 92/~327d P~1'/US91/05591 ..
66
situation when no additive was present. Ths mix
time
of about 20~ represents a screw back pressure of
about
0.3 MPa. For some of the adjuvants, the toughness
result was minimal impro~rement at this minimum
amount
of shear time. For these adjuvants and others shown
in Table X, the toughness generally increased with
increasing shear time. Zn stearate produces a high
level of toughness even at minimum shear time,
with ~n
~ctoate which is normally liquid, producing similar
results. ZnO seems to have made the molded article
weaker while Zn benzoate provides some improvement,
but less than desired. In this experiment, the
zinc
octoate liquid was poured over the flake of PET
and
l~ copolymer elastomer pellets in the wt. ~ indicated
and
then the zinc octoate was drum tumbled with these
resins to obtain the blend, including antioxidant,
for
feed to the injection molding machine.
Table XI represents a second series of
experiments which includes moldings with no additive
and with zn stearate for purposes of comparison with
the other~compounds tested as additives.
2~
3~
iVU 92Ji~3Z'74
fCT/U591/05591
-,.,
&7
TASK x ~
AvEFZAGE
pdOTCiiiED
~ZOD
~ IMPACT
I4T. sFiEAFt :TkiENGTfi
,~DD:~TIVE ~ TY.
TdDI~TE _ ~--~-- 2 0 . 14 0 . 4
9
.39.1 132.8
51.1 88.1
'
ZF1 STEAI3ATE 0.25 21.2 504.9
37.9 801.9
41m5 590.8
aaT.Ci.111OUS ~ m 16 17 . 93 a 9
4
oCT~A~E 36 m 116 a 9
5
35.9 80.6
STA3dDTOUS 0 s 27 18 m 111 a 0
6
S~'ETE 38. 4 548 m 1
42.9 715.7
CCSAI~T Om25 18.1 91e3
ST~'E 3 9 . 14 6 . 8
3
50.0 106m7
MgCEE~ 0.2a 18.6 72.0
STEARATE 39m8 78m5
48m1 81.1
CEFta~T~i 0 m 3 9 19 . 12 ~. .1
3
S1''~'E 40.0 577.5
45.7 441.9
~O~~E~ V 25 18 . 9 V P 1
6
STEAItATE 3 8 . 82 3 . 9
8
47.9 692,2
This Table shows that Zn st~arate, stannous
stearate,.cerium stearate, and copper stearate all act
as adjuvants at certain shear tames used to produce
the molded articles. Stannous cobalt, and nickel
stearate do not have the adjuvant effect. The level
of toughness improvement for the experiments reported
in tha.s Table is less than for Table X, which is
WO 92/03274 1'CT/US91/fl559_1...
- 6~ -
typical of carrying out injection molding experiments
in experimental equipment at different times and
on
feed polymers Pram different sources. Some
degradation of just the polyester flake component,
either present in the flake feed or caused by moisture
present in the melt blend will typically lead to
lower
toughness values. Nevertheless, impact toughnesses
greater than 50o Jim are attainable by all of the
adjuvant-containing molded articles.
In all the experiments of Examples 25 and
26, experience indicates that the number average
particle size of the copolymer elastomer in the
polyester resin of the flex bars was less than one
micron when the adjuvant which produced substantially
increased toughness was used. The toughness
improvement obtained when the screw back pressure
was
only about o.3 MPa indicates this to be true even
under these shear conditions.
As many widely different embodiments of this
invention may be made without departing from the
spirit and scope thereof, it is to be understood
that
this invention is not limited to the specific
embodiments thereof except as defined in the appended
Claims.
35
