Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
This invention relates to making hollow biaxially
oriented heat set partlally crystalline articles and
particularly articles made of poly(ethylene) terephthalate.
Backqround and Summar~ of the Invention
It has heretofore been known that the thermalstability
and barrier properties of oriented blow molded containers of
poly(ethylene) terephthalate are significantly increased by
heat setting. Typical processes for heat setting are shown in
United States Patents 4,476,170, 4,512,948 and 4,522,779.
In United States patents 4,476,170 and 4,512,948,
there is disclosed an article and a process of making an oriented
and heat set blow molded container of poly(ethylene)
terephthalate. In the pro~ess, a preform preheated to a
temperature suitable for orientation is biaxially stretched in
a blow mold and then while the hollow container is still in
contact with the blow mold walls, the article is raised to a
higher heat setting temperature preferably in the range of 200-
250C. (except for the neck) thus heat setting the container,
and while the container is still at a shrinkage resisting
pressure exceeding atmospheric, it is cooled in the same mold to
a temperature at which is it maintains its shape when not
pressurized but not below 100C. It is also particularly
disclo~ed that this cooling step can be done in the air outside
the mold while maintaining internal pressure. According to
these patents, when the heat setting temperature of the hot
mold ranges from 220-250C and the quenching temperature is not
below 100C, higher onset-of-shrinkage temperatures are
obtained.
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il.288913
In United States Patent 4,52~,779, there are disclosed
improved plastic containers and a process for their production.
In the first embodiment, a container is blow molded in a first
hot blow mold, then reblown to a larger size in a second cold
mold of larger volume than the first hot mold. Such containers
are stated as having improved physical properties, particularly
very high hoop yield stresses. However, the utilization of a
larger volume cold mold substantially reduces the thermal
stability. In the second embodiment, a container is blow molded
in a hot blow mold, then reblown to a larger size in a second
hot blow mold where it is blown to the confines of of the second
mold and the container is then removed from the second hot mold
and transferred to a third cold mold and cooled to room
temperature while maintaining internal pressure. In a further
embodiment, the container is blow molded in a first hot mold,
reblown in a second hot mold, and thereafter the second mold
is cooled to cool the container.
United States Patent 4,385,089 (British Patent
Specification 1,604,203) is directed to heat set biaxially
oriented hollow articles and states that the preform or p~rison
should be heated at least to biaxially oriented temperature and
maintained in closed contact with a hot mold which is at a
temperature of up to 40C above the minimum oriented temperature.
In one embodi~ent, the resultant molded hollow article is
moderately cooled causing a temperature drop of 10-30C by
introducing cooling vapor or mist into the hollow article,
interrupting the cooling vapor, and opening the mold. In another
embodiment, the heat set article is allowed to shrink freely
and then reblown in the same hot mold or in a separate cooled
mold. The patent calls for a heat setting temperature of 40C
above the orientation temperture limits thermal stability and
barrier properties from heat setting.
According to this patent, the temperature of the hot
mold should be maintained between 30 and 50C above the minimum
orientation temperature of the plastic material. Otherwise,
it is stated there are numerous disadvantages including lowering
of the production rate, the danger of the appearance of major
distortion and major shrinkage on mold release, the disadvantage
inherent in heating metal molds to very high temperatures and
keeping them at such tempertures, and the danger of
crystallization which would cause a loss of transparency.
Further, in accordance with this prior patent, excessive
shrinkage is to be avoided and generally the temperature drop
of 10 to 30~C should be made. Accordingly, such a method
precludes obtaining a degree of heat setting which would produce
thermal stability at higher temperatures as may be required in
filling the container with various products. In addition, such
a method will preclude o~taining the higher degrees of
crystallinity and resultant high barrier properties which are
required for some products.
United States Patent 4,039,641 discloses a process
for producinq a heat set biaxially oriented poly(ethylene)
terephthalate bottle filled with a li~uid wherein a parison is
expanded in a mold which is at a temperature in the range of 130
to 220C and maintained in contact with the mold by a gas such
as pressurized carbon dioxide and the crystallized bottle is
cooled by displacing the pressurizing gas with a cooling liquid
which is cooled to about 0 to 5DC. The liquid may be liquid to
be packaged in the container. Such a method substantially
reduces the cycle time because of the need to introduce the
89~3
liquid and thereafter remove the liquid, in the case where the
liquid is not that to be packaged in the container. Moreover,
utilizing a liquid within the container to cool the container
limits the amount o heat that can beextracted fromthe container
because it has a low coefficient of heat transfer. Furthermore,
the low coefficient of heat transfer takes a longer time to
extract the heat. In addition, filliDg the container with a
finite amount of liquid equal to the volume of the container
limits the amount of heat which can be extracted from the
container to the amount of heat that can be transferred to this
finite amount of liquid.
United States Patent RE. 28,497 discloses a method
and apparatus for reducing mold cycle time in a conventional
blow molding method wherein a heated parison is expanded by a
gas such as gaseous carbon dioxide in a blow mold and thereafter
subsequently internally chilled by a liquid carbon dioxide.
The article is cooled until it is self-sustaining, the article
is vented to atmospheric pressure, the mold is opened, and the
article is removed from the mold. ~he patent does not relate
to biaxially oriented articles or heat setting of biaxially
oriented articles.
None of the prior art recognizes or teaches that it
is necessary to continue the cooling by circulating liquid
carbon dioxide after the mold is opened in order to obtain self-
sustaining ~iaxially oriented heat set containers, as in the
present invention.
Accordingly, among the objectives of the present
invention are to provide a method and apparatus for making
partially crystalline, biaxially oriented heat set hollow
plastic containers which has a significantly lower cycle time;
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~ 2~31!3913
which permits heat set containers to be made that have complex
configurations including oval containers; which involves low
capital investment; which is easy to maintain; and which involves
the use of lower cost tooling.
In accordance with the invention, the method and
apparatus for making a partially crystalline, biaxially oriented
heat set hollow plastic container from a hollow parison having
an open end and a closed end comprising engaging the open end of
a plastic parison which is at a temperature within its molecular
orientation temperature range, enclosing the hot parison in a
hot mold, the mold being at heat setting temperature, expanding
the plastic parison within the hot mold by internal pressur-
ization to induce biaxial orientation of the plastic parison
and force the plastic parison into intimate contact and
conformance with the hot mold and to maintain contact by such
internal pres~urization between the mold and the biaxially
oriented container for a time sufficient to induce partial
crystallization in the biaxially oriented container, exhausting
the blow molding fluid while continuously introducing a cooling
fluid such as liquid carbon dioxide into the biaxially oriented
container and continuously removing the cooling fluid from the
container while the hot mold is closed for a period of time,
opening the hot mold while continuing to introduce, circulate
and remove coolant `fluid for a predetermined period of time
until thecontainer is cooled sufficiently topreventsignificant
shrinkage and finally releasing the container.
~Z~8913
Description of the Drawinqs
Fig, 1 is a diagrammatic view showing of thesuccessive
steps in the method embodying the invention.
Fig. 2 is a partly schematic view of a portion of an
apparatus utilized with the method.
Fig. 3 is an enlarged sectional view of a nozzle
utilized in the apparatus.
Fig. 4 is a séctional view taken along the line 4-4
in Fig. 3.
Fig. 5 is an elevational view of a container which
may be made in accordance with the invention.
FigO6 is abottomview of the containershownin Fig. 5.
Fig. 7 is a diagrammatic view of the successive steps
in a modified met~od embodying the invention.
i2~38913
According to o~e broad aspect the invention relates
to a method for making a partially crystalline, biaxially
oriented, heat set plastic container from a hollow
polyethylene terephthalate parison having an open end and
a clo~ed end, comprising engaging the open end of the
parison which is at a temperature within its molecular
orientation temperature range, enclosing the parison in a
hot mold, the mold being at heat-setting temperature of
180C to 230~C, expanding the parison to form the
lo container within the blow mold by introducing a blow
molding fluid within the parison, to induce biaxial
orientation of the parison and force the parison into
intimate contact with the blow mold, and to maintain
contact of the parison with the blow mold by the internal
pressure of the blow molding fluid for a time sufficient
to induce partial crystallization of the plastic
material, and further comprising the steps of: cooling
the container with a cooling fluid that changes its
state to cool by the latent heat of vaporization, the
cooling fluid being selected from the group consisting of
liquid carbon dioxide, liquid nitrogen, and a combined
mixture of water vapor and sub-zero temperature air, the
cooling fluid having a positive pressure sufficient to
allow the cooling fluid to change its state and to keep
the container in contact with the heated mold, while at
the same time exhausting the blow molding fluid with the
hot mold closed, the cooling within the mold being for a
time of 0.5 to 9.5 seconds until the average temperature
of the container is reduced to a condition such that it
will not expand under the positive pressure of the
cooling fluid but would collapse in the absence of the
positive pressure of the cooling fluid so that the
positive pressure of the cooling fluid prevents the
container from collapsing when the hot mold is opened,
and continuing to cool the container while preventing the
container from collapsing when the hot mold is opened
with positive pressure of the cooling fluid until the
container is self-sustaining.
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~Z~ 3
~ ccording to a further broad aspect the invention
provides a method for making a partially crystalline,
biaxially oriented, heat-set plastic container from a
hollow parison having an open end and a closed end,
comprising engaging the open end of the parison which is
at a temperature within its molecular orientation
temperature range,
enclosing the parison in a hot mold, the mold being
at heat-setting temperature,
expanding the parison within the blow mold by a
blow-molding fluid to said container, to induce biaxial
orientation of the parison and force the parison into
intimate contact with the blow mold and to maintain
contact by the internal pressure of the blow-molding
fluid for a time sufficient to induce partial
crystallization of the plastic material,
exhausting the blow-molding fluid while at the same
time a cooling fluid is introduced, cooling the
container, removing it from the b~ow mold and cooling it
further external of the blow mold by means of the cooling
fluid,
characterized in that:
the cooling is obtained by a cooling fluid being of
a type which changes state when introduced into the blow
mold, the cooling fluid continuously circulating through
the container,
that the container is removed from the blow mold at
a time in which collapsing of the container is prevented
by the pressure of the cooling fluid,
and that circulating the cooling fluid is continued
for a period of time until the container achieves a self-
sustaining condition.
According to a still further broad aspect the
invention relates to an apparatus for making a partially
crystalline, biaxially oriented heat set hollow plastic
container from a hollow parison having an open end and a
-closed end comprising:
means for engaging and disengaging the open end of a
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.
~28~
plastic parison which is at a temperature within its
molecular orientation temperature range,
a hot mold having mold sections which can be opened
and closed enclosing the hot parison in said hot mold,
the mold being at heat setting temperature,
means for expanding the plastic parison within the
hot mold by internal pressurization to induce biaxial
orientation of the plastic parison and force the plastic
parison into intimate contact and conformance with the
hot mold and to maintain contact by such internal
pressurization between the mold and the biaxially
oriented container for a time sufficient to induce
partial crystallization in the biaxially oriented
container,
means for thereafter exhausting the blow molding
fluid while continuously introducing a cooling fluid
which changes state when introduced into the mold such as
liquid carbon dioxide into the biaxially oriented
container and continuously exhausting cooling fluid from
the container while the hot mold is closed for a period
of time,
means for continuing to introduce coolant fluid for
a predetermined period of time after the mold is opened
until the container is cooled sufficiently to prevent
significant shrinkage.
-6
~.~
,~.
,~,.. ..
~ ~8l~
Description
Referring to Fig. 1, the method for making a partially
crystalline, biaxially oriented heat set hollow plastic
container from a hollow parison having an open end and a closed
end comprises
engaging the open end of a plastic
parison P by a neck clamp which has been
heated (step A) at a temperature within its
molecular orientation temperature range,
enclosing the hot parison in a hot
mold M, the mold being at heat setting
temperature,
expanding the plastic parison within
the hot mold M by internal pressurization
to induce biaxialorientation of theplastic
parison and force the plastic parison into
intimate contact and conformance with the
hot mold M and to maintain contact by such
internal pressurization between the mold M
and the biaxially oriented container for a
time sufficient to induce partial
crystallization in the biaxially oriented
container tstep B),
exhausting the blow molding fluid
while continuously introducing a cooling
fluid such as liquid carbon dioxide into
the biaxially oriented container while
continuously circulating and continuously
removing the cooling fluid from the
~ ;28~ 3
container, while the hot mold is closed for
a period of time (step C),
opening the hot mold while continuing
to introduce coolant fluid and while
continuously circulating and continuously
removing tha cooling fluid from the
container for a predetermined period of
time until the container is cooled
sufficiently to prevent significant
shrinkage (step D) and
finally releasing the container.
It has been found to be important to introduce the
cooling fluid medium such that it is applied over the entire
inner surface of the container, except possibly for the finish,
and preferably uniformly so that adequate cooling is achieved.
Thus, the position of the nozzle through which the cooling
medium is introduced is important as well as the construction
of the nozzle.
Referring to Figs. 2, 3, 4, a preferred nozzle N
comprises a first plurality of circumferentially spaced orifices
10 that extend radially, a second set of circumferentially
spaced orifices 11 that extend downwardly radially and axially
toward the neck of the container C and a third set of circum-
ferentially spaced orifices 12 that extend radially and axially
in an axial direction toward the base of the container.
Referring to Fig. 2, the nozzle N is positioned on a
hollow stretch rod 13 which is adapted to be moved within the
mold through the neck forming portion of the mold by operation of
a cylinder 14 cooperating with a piston 15 on the rod 13.
Blowing pressure is provided through a three way valve 16 for
--8--
supplying ~lowing fluid such as air or nitrogen through passage
17 to the space ~8 about the hollow rod 13 and nozzle N to blow
the parison P and form the container C. At this time, the nozzle
N is moved to the desired position within the container C.
Alternatively, the nozzle N may be used at the end of rod 13 as
a stretch rod to stretch the parison axially prior to introducing
the blowing fluid or simultaneously with introducing the blowing
fluid after which the rod is retracted to bring the nozzle N to
the desired position within the container C for cooling the
container C. The blowing fluid is first applied at a lower
pressure, for example, 70 to 200 p.s.i, and then the blowing
fluid is applied at a higher pressure, for example, 150 to 350
p.s.i,, to maintain contact of the container with the surface
of the mold. After the completion of the crystallization or
heat setting time, the valve 16 is activated to exhaust the
blowing fluid through passage 17 to the atmosphere. The cooling
fluid such as carbon dioxide is provided from a source S through
a line 19 and solenoid operated valve 20 to the passage in the
hollow rod 13 and nozzle into the blown container C and is
exhausted continuously about the periphery of the nozzle N
through passage 17. A plastic tube 21 of nylon or the like is
provided on the interior of rod 13 to minimize the freezing or
blockage of the passage in the hollow rod 13.
As used herein, cooling medium comprises liquid c~rbon
dioxide, liquid nitrogen, or combined mixture of water vapor
and sub-zero temperature air. A preferred cooling medium
comprises liquid carbon dixoide which is introduced at super
atmospheric pressures and expands from the openings or orifices
in the nozzle N, utilizes the combination of the temperature
differential between the container and the carbon dioxide and
9~3
the latent heat of evaporation of carbon dioxide from either
its liquid or solid state to its gaseous state in the lower
pressure existing in the container. During the cooling, the
pressure within the container is slightly greater than
atmospheric.
If the cooling medium is combined water mist and sub-
zero air, passage through the openings of a nozzle N will also
result in expansion and facilitate cooling by first forming a
solid state of snow or ice followed by evaporation to the gaseous
state. If the cooiing medium is liquid nitrogen, the heat
transfer or cooling action is by heat transfer due to latent
heat evaporation from the liquid to the gaseous state followed
by temperature differential between the gaseous state and the
container.
In operation, the steps comprise:
engaging the open end of a plastic
parison P which has been heated (step A) at
a temperature within its molecular
orientation temperature range,
enclosing the hot parison in a hot
mold M, the mold being at heat setting
temperature,
expanding the plastic parison within
the hot mold M by internal pressurization
to inducebiaxialorientation of the plastic
parison and force the plastic parison into
intimate contact and conformance with the
hot mold M and to maintain contact by such
internal pressurization between the mold M
and the biaxially oriented container for a
--10--
iL2~38~3
time sufficient to induce partial
crystallization in the biaxially oriented
container ~step B~,
exhausting the blow molding fluid
while continuously introducing a cooling
fluid such as liquid carbon dioxide into
the biaxially oriented container while
continuously circulating and continuously
removing the cooling fluid from the
container, while the hot mold is closed for
a period of time (step C),
opening the hot mold while continuing
to introduce coolant fluid while
continuously circulating and continuously
removing the cooling fluid from the
container for a predetermined period of
time until the container is cooled
sufficiently to prevent significant
shrin~age (step D) and
finally releasing the container (step
D).
~ n the form of method shown i~ Fig. 7, the mold Ml is
a three sectional mold comprising mold sections 40 which close
about a mold base section 41. The mold base section 41 is
configured to form the bottom of the container. In this method,
the mold base is movable axially by a fluid cylinder 42 through
a piston rod 43 so that when the mold Ml is opened and the
cooling fluid is continuously introduced into the container,
circulated and continuously removed or exhausted, the base of
the container is held in position by the mold base section 41
of the mold as shown at station D in Fig. 7. After the completion
of the introduction of the coolant fluid, the mold base section
41 is retracted axially outwardly and the container is released
by opening the neck clamp 22.
This method of using a movable base section has
particular utility where the container base has a configuration
such that the resultant container is free standing.
It can thus be seen that the introduction of carbon
dioxide or similar cooling fluid functions to reduce the average
temperature of the container while the mold is closed. When
the mold is opened, the positive pressure of the continuously
flowing car~on dioxide not o~ly prevents the container from
collapsing but, in addition, continues the cooling of the
container from the interior and thereby continues to reduce the
average temperature of the container until it achieves a self-
sustaining condition. Where the heat setting temperature, on
the order of 200C or higher, the average temperature of the
container upon opening of the mold is necessarily higher, and
if the positive pressure of the carbon dioxide and the time of
cooling continues for an excessive period of time, there is a
possibility that the container may slightly grow in volume. In
order to obviate such growth, if it is necessary, the time of
application of the carbon dioxide after opening of the mold may
need to be reduced and controlled so that the cooling continues
until the container is self-sustaining and is terminated before
any undesirable growth is achieved. A further reason for
minimizing the cooling time is that otherwise the cycle time
is increased and the consumption of cooling fluid is
substantially increased, thereby adversely affecting
productivity and costs. It should be understood that the growth
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~2t~ 3
or expansion in volume in any event is minimal and the above
considerations are applicable only where it is desired that the
container have substantially no change in volume from that of
the blown container.
The process of the present invention is applicable
to polymers which are capable of being biaxially oriented when
blown at orientation temperatures and subsequently heat set at
higher heat setting temperatures to make the resultant hollow
article thermally stable and provide improved barrier
properties.
The process of the present invention, as well as the
product, is especially concerned with polymers of poly(ethylene)
terephthalate having an inherent viscosity of at least Q.6.
Poly(ethylene) terephthalate polymers useful in the present
invention include repeating ethylene terephthalate units with
the remainder being minor amounts of ester-forming components
and copolymers of ethylene terephthalate wherein up to about
10 mole percent of the copolymer is prepared from the monomer
units selected from butane-1,4-dicl;diethylene glycol; propane-
1,3-diol; poly tetramethylene glycol~; poly ethylene glycol~:
poly~propylene glycol~; 1,4-hydroxymethylcyclohexane and the
like, substituted for the glycol moiety in the preparation of
the copolymer, or isophthalic; naphthalene 1,4- or 2,6-
dicarboxylic; adipic, sebacic; decane-l,10-dicarboxylic acids,
and the like, substituted for up to 10 mole percent of the acid
moiety (terephthalic acid) in the preparation of the copolymer.
Of course, the poly(ethylene) terephthalate polymer
can include various additives that do not adversely affect the
polymer. For instance, some such additives are stabilizers,
e.g., antioxidants or ultraviolet light screening agents,
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~288~
extrusion aids, additives designed to make the polymer more
degradable or combustible, and dyes or pigments. Moreover,
cross-linking or branching agents such as are disclosed in
United States Patent No. 4,188,357 can be included in small
amounts in order to increase the melt strength of the
polytethylene) terephthalate.
The process is also applicable to multilayer parisons
comprising an orientable heatsettable polymer and other polymers
which provide desirable barrier properties wherein the
orientable heat settable polymer comprises a major portion of
the total weight, preferably at least 70%. Typical examples
are multilayer parisons of poly~ethylene) terephthalate and
copa~yester; po~y~et~ylene~ terepht~a~ate, nylon and
copolyester: poly(ethylene) terephthalate, adhesive, nylon,
glue and poly(ethylene) terephthalate.
The process is also applicable to blends of
poly(ethylene) terephthalate with polymers which provide
desirable barrier properties wherein the poly(ethylene)
terephthalate comprises a major portion of the total weight,
preferably at least 70% of the total wei~ht.
Thus, as used herein in the specification and claims,
the term poly(ethylene) terephthalate is intended to include
the above poly(ethylene) terephthalate containin~ materials.
The followln~ parameters produce satisfactory results
for poly(ethylene) terephthalate:
~28~
Orientation temperature 80 - 110C
Heat setting temperature 120 - 250C
Heat setting time 0.5 - 10 sec.
Cooling time 1.0 - 10 sec.
Mold open delay 0.5 - 9.5 sec.
A preferred range of parameters comprises a heat
setting temperature which ranges between 180 to 230C, a heat
setting time ranging between 1 and 5 seconds, mold open delay
ranging between 0.5 to 5 seconds, and cooling after mold opening
ranging between 0.8 and 1.2 seconds.
The present in~entlon has particular utility for
making complex containers such as containers that are non-
cylindrical, for example, oval in cross section, which may
comprise two or more cylindrical portions of different cross
sectional dimensions, and which incorporate combinations of
cylindrical portions, inclined portions, flutes, ribs and the
like.
Referring to Fig~. 5 and 6, for example, such
containers 30 comprise eightvertical flutes 31, threehorizontal
frustoconical ribs 32, and a reverse frusto-concial shoulder
portion 33.
In the following test results, the containers had the
configuration shown in Figs. 5 and 6 and exhausting of blowing
fluid and introduction of cooling were initiated simultaneously.
The mold opening delay time was measured from the beginning of
the exhaust and introduction of cooling fluid. The bottom
temperatures of the molds were lower in order that there would
be less heat setting of the thicker bottom of the container.
In the following test results, the containers were
made from poly(ethylene) terephthalate having an I.V. of 0.80.
The axial stretch ratio was 1.6X and hoop stretch ratio ranged
from 4.8X to 5.3X in the area of flutes 31; ranged from 3.4X to
5.3X in the area of ribs 32; ranged from 3.4X to 3.66X in
shoulder portion 33.
In connection with showing how the importance of
positioning of the nozzle is in making complex containers, tests
were conducted by making containers shown in Figs. 5 and 6 having
a height of 9~ inches and a satisfactory overflow container
volume without shrinkage being about 1490 cc.
~ ~8l~9~3
The following TABLE A summarizes the results:
TABLE A
Nozzle Location
Bottle Number lA 2A 3A 4A
Crystallization
Temp, C 224 224 224 224
Time, Sec. 6 6 6 6
Bottom Temp, QC. 122 122 122 122
Mold Open
Delay, Sec. 4 4 4 4
C2 On Time,
Sec. 5 5 5 5
Nozzle Location,
Distance From
Bottom, Inch 2 2~ 3 3
Overflow
Vol., CC 1475.7 1481.0 1476.0 1478.5
It can be seen that when the nozzle location is between
2 and 3~ inches from the battom, satisfactory containers with
good definition and reduced post mold shrinkage~overflow volume)
were obtained. Thus, it is necessary to construct and position
the nozzle so that the cooling medium cools all portions of the
containers.
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~ 43
TABLE B summarizes a series of tests of containers
made with varying mold open delay and carbon dioxide cooling
times.
TABLE B
Bottle Number lB 2B 3B 4B
Crystallization
Temp, C 228 228 228 228
Time, Sec. 5 5 5 5
Bottom Temp, C 122 122 122 122
Mold Open
Delay, Sec. 3 3 3 2
C2 On Time,
Sec. 4.2 3.8 3.5 2
Uozzle Locatio~,
Distance From
Bottom, Inch 3 3 3 3
Overflow
Vol., CC 1509.6 1486.2 1477.2 1385.6
TABLE B tcont'd)
Bottle Number 5B 6B 7B ~B
Crystallization
Temp, C 228 228 228 228
Time, Sec. 5 5 5 5
Bottom Temp, C 122 122 122 122
Mold Open
Delay, Sec. 2 2 2 1.5
C2 On Time,
Sec. 3 2.8 2.5 2.5
Nozzle Location,
Distance From
Bottom, Inch 3 3 3 3
Overflow
Vol., CC 1476.4 1478.5 1436.1 1480.1
-18-
TABLE B (cont'd)
Bottle Number 9B lOB llB 12B
Crystallization
Temp, C 228 228 228 2;28
Time, Sec. 5 5 5 S
Bottom Temp, C 122 122 122 122
Mold Open
Delay, Sec. 1.5 1.5 1.0 1.0
C2 On Time,
Sec. 2~3 2~0 2.0 1.8
Nozzle Location,
Distance From
Bottom, Inch 3 3 3 3
Overflow
Vol., CC 1475.1 1445.6 1491.1 1476.3
TABLE B tcont'd)
Bottle Number 13B 14B 15B 16B
Crystallization
Temp, C 2:28 228 228 228
Time~ Sec. 5 5 5 5
Bottom Temp, C 122 122 122 122
Mold Open
Delay, Sec. 1.0 0.8 0.8 0.8
C2 On Time,
Sec, 1.6 1.6 1.4 1.8
Nozzle Location,
Distance From
Bottom, Inch 3 3 3 3
Overflow
Vol., CC 1463.0 1473.2 1~32.1 1490.4
--19--
~.~889~3
It can be seen from TABLE B, bottle number 4B, that
where the mold opening delay and cooling times are the same,
the resultant container is grossly collapsed. Moreover, where
the difference between mold opening delay time and carbon dioxide
application time is less than 0.5 second, collapsing or
definition loss occurs, as shown in bottle numbers 4B, 7B, lOB.
In the case of bottle 15B, the combination of the mold opening
delay and cooling times was not adequate to cool the container
to the self-supporting condition. ~his can be remedied by
decreasing the mold opening delay time, as shown in bottle
number llB, compared with bottle number lOB, or bottle number
8B as compared to bottle number 7B. Alternatively, the cooling
time can be increased as shown in bottle numbers 14B and 16B
compared with bottle number 15B. The remaining containers were
satisfactory within the definition of desired overflow volume
and general appearance.
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~Zl38~L3
TABLE C represents a series of tests wherein mold
opening delay and CO2 application time are the same at variou~
heat setting or crystallization temperatures.
TABLE C
Bottle Number lC 2C 3C 4C
Crystallization
Temp, C 149 149 149 177
Time, Sec. 2.5 2.5 2.5 2.5
Bottom Temp, C 122 122 122 122
Mold Open
Delay, Sec. 2 3 4 2
C2 On Time,
Sec. 2 3 4 2
Nozzle Location,
Distance From
Bottom, Inch 3 3 3 3
Overflow
Vol., CC 1366.3 1408.0 14Q8.0 1362.6
TABLE C (cont'd)
Bottle Number 5C 6C 7C 8C 9C
Crystallization
Temp, C 177 177 205 205 205
Time, Sec. 2.5 2.5 2.5 2.5 2.5
Bottom Temp, C 122 122 122 122 122
Mold Open
Delay, Sec. 3 4 2 3 4
C2 On Time,
Sec. 3 4 2 3 4
Nozzle Location,
Distance From
Bottom, Inch 3 3 3 3 3
Overflow
Vol., CC 1391.9 1391.4 1340.9 1329.0 1355.2
-21-
~ ~8~3
All containers were grossly deformed and collapsed
and were not acceptable.
It can be seen that in each instance the resultant
container is grossly deformed and collapsed and would not be
acceptable commercially. Additional tests have shown that
comparable containers with substantial loss of definition occurs
at lower heat setting temperatures where the mold opening delay
and cooling time are the same.
It can thus be seen that it is essential that the
application of carbon dioxide be continued after the mold has
been opened in order to obtain satisfactory results.
815 ~
The following TABLE D summarizes the properties
obtained in typical examples of the container shown in Figs. 5
and 6:
TABLE D
PROPERTIES OF INTERNALLY COOLED CONTAINERS
Heatset Temperature = 228C
Heatset Time = 5 sec.
C2 Time = 5 sec.
MECHANICAL PROPERTIES AXIAL HOOP
Elastic Modulus, kpsi x 394 644
~ 38 86
Yield Stress, kpsi x 14.9 27.3
~ 0.5 0.9
Yield Strain, % x 6.3 6.0
a 0.2 ---
Ultimate Strength, kpsi x 16.9 46.
~ 1.2 4.1
Ultimate Elongation ~ x 51 19
a 16 3
DENSITY
Density at 25C, g/c.c. 1.3960
~2~8~ `3
It can thus be seen that the mechanical properties
and improved density are satisfactory.
When inherent viscosity is referred to herein, it is
the viscosity as measured in a 60/40 weight ratio phenol/-
tetrachloroethane solution at 25C. Density was determined by
the method described by ASTM 1505, entitled "Density Gradient
Technique n.
The mechanical properties were measured as defined
in ASTM standard D-638.
The following TABLE E shows the onset-of-shrinkage
results. It can be seen thatonset-of-shrinkage is substantially
increased by the method for making the container shown in Figs.
5 and 6 over t~e same container made without heat settin~:
TA~LE E
ONSET OF SHRINKAGE
Heatset Temperature = 228C
Heatset Time = 5 sec.
C2 Time - S sec.
CONTAINER ONSET OF SHRINKAGE, C
Heatset 110C
Non-Heatset 50C
The onset-of-shrinkage temperature referred to herein
was determined as described in Brady and Jabarin "Thermal
Treatment of Cold-Formed Poly(Vinyl Chloride~ Polymer
Engineering and Science", pp. 686-90 of Vol. 17, No. 9, September
1977, except that the samples were cut from the sidewalls of
the bottles. No thermal treatment was effected on the cut
samples prior to the tests.
~L2~ !.3
TABLE F shows the results of tests conducted at lower
heat setting time.
TABLE F
Bottle Number lF
Crystallization
Temp, C 225
Time, Sec. 3
Bottom Temp, C 132
Mold Open
Delay, Sec. 2.5
C2 On Time,
Sec. 3-5
Nozzle Location,
Distance From
Bottom, Inch 3
Overflow
Vol., CC 1490.0
It can be seen that satisfactory containers are
obtained in accordance with the method at lower heat setting
times .
It can be seen that there has been provided a method
for making biaxially oriented heat set containers having a high
onset-of-shrinkage temperature.
In various tests of the heat setting method embodying
the invention, it has been found that the resultant container
can be readily cooled to substantially below 100~C and can be
handled easily and touched by operators performing the method.
Observations made in accordance with the well known
lightscattering test indicate that containers made in accordance
with the method appear to have more uniform crystalline size
distribution in the body of the container than is obtained by
prior known heat setting methods that require long periods of
-" ~28891;~
time to cool the container after heat setting. It is believed
that this more uni~orm crystalline size distri~ution is due to
rapid quenching or cooling achieved in accordance with the
method.
The sequence of operation utilized in accordance with
the method may be summarized as follows:
1. The parison is heated to theorientation temperature
(90 - 100C).
2. Parison is allowed to soak for a given period of
time in order to equilibrate the inside and outside temperature.
3. The parison is transferred to the blow station.
4. The mold is closed.
5. The parison is blown and heat set for a given
period of time.
6. The container is exhausted.
7. While the container is exhausting, the liquid CO2
is introduced.
- 8. The mold is opened and C02 injection is continuing.
- 9- C2 injection completed.
lO. The container is unclamped and released.
In the case of containers having complex or free
standing bottoms, a mold base is provided which remains in
contact with the base of the container when the mold is opened
and cooling fluid continues to be applied to the interior of
the container while the base mold is in engagement with the base
of the container. The movable mold base can be applied also to
a hemispherical bottom container to stabilize the container
while the mold is open and cooling fluid is being applied.
Accordingly, it can be seen that there has been
provided a method and apparatus for making partially crystalline,
-26-
~89~3
biaxially oriented heat set hollow plastic containers wherein
the containers have reduced post mold shrinkage, increased
density,increased onset-of-shrinkage temperature, satisfactory
mechanical properties, which has a significantly lower cycle
time; which permits heat set containers to be made that have
complexconfigurations including oval containers; which involves
low capital investment; which is easily to maintain; and which
involves the use of lower cost tooling and which can be adapted
readily to conventional machine for making biaxially oriented
containers.
-27-
