Note: Descriptions are shown in the official language in which they were submitted.
CA 02314871 2000-06-20
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PROCESS FOR PRODUCING CONTAINERS FROM
POLYMER/PLATELET PARTICLE COMPOST'TIONS
Background of Invention
Polyesters such as polyethylene terephthalate) (PET) are widely used in
bottles
and containers for carbonated beverages, fruit juices, and certain foods.
Because of
the limited barrier properties of polyesters with regard to oxygen and other
gases,
polyester nanocomposites have been developed which contain chemically modified
organoclay materials. Due to the high aspect ratio of the organoclays selected
for
the formation of polyester nanocomposites, frequently a tortuous path is
created
which the penetrating gas must follow to diffuse through this material, thus
markedly increasing the barrier of the polyester material.
One of the primary processes which has been used to form bottles and
containers from polyester nanocomposites is stretch blow molding (SBM). With
this blow molding process, usually the preform is molded at a temperature
about 20--
to 50 degrees Celsius above the glass transition temperature of the polyester.
Molding in this range of temperature, it has been very difficult to form a
bottle or
container which did not exhibit substantial opacity or cloudiness in the
sidewall. It
is very desirable to have processing methods available which allow the
formation
of polyester nanocomposite containers possessing both high clarity and
barrier.
There are many examples in the patent literature of the formation of
i
polymer/clay nanocomposites containing, for example, Nylon-6 and alkyl
ammonium treated montmorillonite. Some patents describe the blending of up to
60 weight percent of intercalated clay materials with a wide range of polymers
including polyamides, polyesters, polyurethanes, polycarbonates, polyolefins,
vinyl
polymers, thermosetting resins and the like. WO 93/04117 discloses a wide
range
of polymers melt blended with up to 60 weight percent of dispersed platelet
particles. Although the use of polyesters is disclosed, polyester/platelet
compositions of a specific molecular weight are not disclosed. WO 93/04118
discloses composite material of a melt processable polymer and up to 60 weight
percent of dispersed platelet particles. Among a wide range of thermoplastic
polymers indicated, polyesters are included. U.S. Patent 5,552,469 describes
the
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preparation of intercalates derived from certain clays and water soluble
polymers
such as polyvinyl pyrrolidone, polyvinyl alcohol, and polyacrylic acid. The
specification describes a wide range of thermoplastic resins including
polyesters
and rubbers which can be used in blends with these intercalates. U.S. Patent
4,889,885 describes the polymerization of various vinyl monomers such as
methyl
methacrylate and isoprene in the presence of sodium montmorillonite. In
Example
11, it describes the polycondensation of dimethyl terephthalate and ethylene
glycol
in the presence of 33 weight percent of a montmorillonite clay in water (for
6.2
final weight percent of clay in the polyester resin).
1
JP Kokai patent no. 9-176461 discloses polyester bottles wherein the
polyester contains swellable laminar silicate. WO 97/31057 discloses polymer
composite having dispersed therein inorganic material such as clay which is
separated with an inorganic intercalant. WO 97131973 discloses producing a
composite material by mixing a potassium ionomer in which ethylene
methacrylate
copolymer is either partially or completely neutralized with an organic
polymer.
However, the foregoing references produce materials comprising very large
tactoids and little if any dispersion of individual platelet particles. Nor do
any of
the references disclose nanocomposite compositions having other specific
properties such as melt strength and viscosity and high LV. which are
necessary to
produce containers by any method.
i
For the formation of molded articles from polyester nanocomposites, little
specific prior art was found to be in existence. In U.S. patent 5,102,948, a
polyamide/clay composite was formulated in such a manner that the material was
resistant to whitening during stretching. With polyester resins, no such prior
art has
been found.
As an initial attempt to process polyester based nanocomposites, variations
of conventional techniques for polyester processing have been utilized in our
laboratory to form the objects desired. For blow molding polyester resins into
bottles, jars and other containers, several processes are well established:
SBM,
extrusion blow molding (EBM), and injection blow molding (IBM). Polyester/clay
nanocomposites contain dispersed clay particles which frequently also act as
CA 02314871 2000-06-20
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5 nucleation agents for the polyester material. Using SBM to mold bottles of
polyester/clay composites frequently imparts sufficient orientation to the
wall of
the bottle to prevent creep when the contents of the bottle is under pressure.
However, initial attempts to employ SBM with these materials consistently
yielded
bottles which exhibited a hazy or turbid sidewall. Only when high melt
strength
polyester/clay composite resins were prepared which were processable at high
melt
temperatures, have containers with clear sidewalls been obtained from these
materials.
Figure 2 is a plot showing the melt viscosity at 280°C as a function
of LV.
15 for polyester-platelet composites and polyesters without any platelet
particles.
Figure 1 is a plot showing the melt strength at 265°C as a function
of LV.
for polyester-platelet composites and polyesters without any platelet
particles.
Description of the Invention
20 This invention relates to new polyester compositions, novel processes to
prepare molded articles from these new polyester compositions, and novel
containers fabricated from polyesterlclay composites for food and beverages.
The
processing methods employed in this invention enable containers to be formed
which exhibit excellent clarity.
25 Specifically, the present invention relates to a process comprising forming
a
parison or a preform from a composite composition comprising about 0.01 to
about
25 weight % platelet particles dispersed in at least one polyester at a
processing
temperature which is at least 50°C above the Tg of said polyester; and
molding said
parison or preform into a clear, thin walled article. To reach the optimum
blowing
30 temperature, frequently the processing temperature for the blowing of the
resin was
reached by starting in the melt (especially with crystallizable polyesters)
and then
lowering the resin to the desired processing temperature. For all
polyester/clay
composite resins, the processing temperature should be at least 50°C
above and
preferably more than 100°C above the glass transition of the polyester
component.
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Generally the compositions which are useful in the present invention
comprise about 0.01 to about 25 weight percent platelet particles, dispersed
in at
least one polyester. A variety of methods are useful for the preparation of
these
resins including, synthesis, extrusion formulation and compounding, and solid
state
advancing of the polyester resin to achieve the desired molecular weight for
the
polyester component.
Platelet Particles
The compositions of the present invention comprise between about 0.01 and
i about 25 wt%, preferably between 0.5 and 25 wt%, more preferably between 0.5
and 15 wt% and most preferably between 0.5 and 10 wt% of certain platelet
particles derived from organic and inorganic clay materials. The amount of
platelet
particles is determined by measuring the amount of ash of the polyester-
platelet
compositions when treated in accordance with ASTM D5630-94, which is
incorporated herein by reference.
The platelet particles of the present invention have a thickness of less than
about 2 nm and a diameter in the range of about 10 to about 1000 nm. For the
purposes of this invention measurements refer only to the platelet particle
and not
any dispersing aids or pretreatment compounds which might be used. Suitable
platelet particles are derived from clay materials which are free flowing
powders
having a cation exchange capacity between about 0.3 and about 3 meq/g and
preferably between about 0.8 and about 1.5 meq/g. Examples of suitable clay
materials include mica-type layered phyllosilicates, including clays, smectite
clays,
sodium montmorillonite, sodium hectorite, bentonites, nontronite, beidelite,
volonsloite, saponite, sauconite, magadiite, kenyaite, synthetic sodium
hecotorites,
and the like. Clays of this nature are available from various companies
including
Southern Clay Products and Nanocor, Inc. Generally the clay materials are a
dense
agglomeration of platelet particles which are closely stacked together like
cards.
Other non-clay materials having the above described ion exchange capacity
and size, such as chalcogens may also be used as the source of platelet
particles
under the present invention. These materials are known in the art and need not
be
described in detail here.
CA 02314871 2000-06-20
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5 The prior art has defined the degree of separation of the platelet particles
based on peak intensity and basal spacing, or lack thereof, as determined by X-
ray
analyses of polymer-platelet composites. However, in polyester composites X-
ray
analysis alone does not accurately predict the dispersion of the platelet
particles in
the polyester nor the resultant barrier improvement. TEM images of polyester-
10 platelet composites show that platelet particles which are incorporated
into at least
one polyester exist in a variety of forms, including, but not limited to
iavdividual
platelets (the exfoliated state), disordered agglomerates of platelets, well
ordered or
stacked aggregates of platelets (tactoids) and aggregates of tactoids. X-ray
analysis
only provides information related to the well ordered aggregates, which are
only a
small portion of the platelet particles which are present.
Without being bound by any particular theory, it is believed that the degree
of improved barrier depends upon the aspect ratio of the resulting particle
platelets
and aggregates, the degree to which they are dispersed or uniformly
distributed and
the degree to which they are ordered perpendicular to the flux of the
permeant. To
obtain the improvements in gas permeability and the enhanced melt visocity
disclosed in the present invention it is necessary that the platelet particles
be
dispersed in the polyester such that the majority, preferably at least about
75% and
perhaps as much as at least about 90 or more of the platelet particles have a
thickness in the shortest dimension of less than about 20 nm and preferably
less
than about 10 mn as estimated from TEM images representative of the bulk of
the
composite. Polyester-platelet composites containing more individual platelets
and
fewer aggregates, ordered or disordered are most preferred.
Dispersions containing a high level of individual platelet particles have not
been previously disclosed. Previous patents and applications have claimed to
produce polyesters containing intercalated or exfoliated platelet particles,
as
indicated by large basal spacings or the lack of a detectable basal spacing by
X-ray,
however, the results could not be reproduced. With the exception of WO
93/04118
(which does not posses suitable LV. and melt viscosity), the
polyester/platelet
compositions of the prior art are believed to be dispersions of aggregates
with large
thickness, typically greater than about 20 nm. While the aggregates were well
CA 02314871 2000-06-20
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5 spaced, very few individual platelets and tactoids or particles with
thicknesses less
than about 20 nm could be found. Without achieving a good dispersion and small
particle size improved barrier and visual properties cannot be achieved.
Improvements in gas barrier also increase as the amount of platelet
particles in the polyester increases. While amounts of platelet particles as
low as
0.01% provide improved barrier (especially when well dispersed and ordered),
compositions having at least about 0.5 wt% of the platelet particles are
preferred
because they display the desired improvements in gas permeability.
Generally, it is desirable to treat the selected clay material to separate the
agglomerates of platelet particles to individual platelet particles and small
tactoids
prior to introducing the platelet particles to the polyester. Predispersing or
separating the platelet particles also improves the polyester/platelet
interface. Any
treatment that achieves the above goals may be used. Examples of useful
treatments include intercalation with water soluble or water insoluble
polymers,
organic reagents or monomers, silane compounds, metals or organometallics,
organic cations to efFect cation exchange, and their combinations.
Examples of useful pretreatment with polymers and oligomers include those
disclosed in U.S. 5,552,469 and 5,578,672, incorporated herein by reference.
Examples of useful polymers for intercalating the platelet particles include
polyvinyl pyrrolidone, polyvinyl alcohol, polyethylene glycol,
polytetrahydrofuran,
polystyrene, polycaprolactone, certain water dispersable polyesters, Nylon-6
and
the like.
Examples of useful pretreatment with organic reagents and monomers
include those disclosed in EP 780,340 A1, incorporated herein by reference.
Examples of useful organic reagents and monomers for intercalating the
platelet
30 particles include dodecylpyrrolidone, caprolactone, caprolactam, ethylene
carbonate, ethylene glycol, bishydroxyethyl terephthalate, dimethyl
terephthalate,
and the like or mixtures thereof.
Examples of useful pretreatment with silane compounds include those
treatements disclosed in WO 93/I 1190, incorporated herein by reference.
Examples of useful silane compounds includes (3-
CA 02314871 2000-06-20
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glycidoxypropyl)trimethoxysilane, 2-methoxy (polyethyleneoxy)propyl
heptamethyl trisiloxane, octadecyl dimethyl (3-trimethoxysilylpropyl) ammonium
chloride and the like.
Numerous methods to modify layered particles with organic cations are
known, and any of these may be used in the process of this invention. One
embodiment of this invention is the modification of a layered particle with an
organic cation by the process of dispersing a layered particle material in hot
water,
most preferably from 50 to 80°C, adding an organic cation salt or
combinations of
organic cation salts (neat or dissolved in water or alcohol) with agitation,
then
blending for a period of time sufficient for the organic cations to exchange
most of
the metal cations present in the galleries between the layers of the clay
material.
Then, the organically modified layered particle material is isolated by
methods
known in the art including, but not limited to, filtration, centrifugation,
spray
drying, and their combinations. It is desirable to use a sufficient amount of
the
organic canon salt to permit exchange of most of the metal cations in the
galleries
of the layered particle for organic cations; therefore, at least about 1
equivalent of
organic cation salt is used and up to about 3 equivalents of organic cation
salt can
be used. It is preferred that about 1.1 to 2 equivalents of organic cation
salt be
used, more preferable about 1.1 to 1.5 equivalents. It is desirable, but not
required,
to remove most of the metal cation salt and most of the excess organic cation
salt
by washing and other techniques known in the art. The particle size of the
organoclay is reduced in size by methods known in the art, including, but not
limited to, grinding, pulverizing, hammer milling, jet milling, and their
combinations. It is preferred that the average particle size be reduced to
less than
100 micron in diameter, more preferably less than 50 micron in diameter, and
most
preferably less than 20 micron in diameter.
Useful organic cation salts for the process of this invention can be
represented as follows:
CA 02314871 2000-06-20
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R2 M R3 X-
R4
Wherein M represents either nitrogen or phosphourous; X-represents an anion
selected from the group consisting of halogen, hydroxide, or acetate anions,
preferably chloride and bromide; R~, RZ, R3 and R4 are independently selected
from
organic and oligomeric ligands or may be hydrogen. Examples of useful organic
10 ligands include, but are not limited to, linear or branched alkyl groups
having I to
22 carbon atoms, aralkyl groups which are benzyl and substituted benzyl
moieties
including fused ring moieties having linear chains or branches of I to 22
carbon
atoms in the alkyl portion of the structure, aryl groups such as phenyl and
substituted phenyl including fused ring aromatic substituents, beta, gamma
15 unsaturated groups having six or less carbon atoms, and alkyleneoxide
groups
having 2 to 6 carbon atoms. Examples of useful oligomeric ligands include, but
are
not limited to, poly(alkylene oxide), polystyrene, polyacrylate,
polycaprolactone,
and the like.
Examples of useful organic cations include, but are not limited to, alkyl
20 ammonium ions, such as dodecyl ammonium, octadecyl ammonium, bis(2-
hydroxyethyl) octadecyl methyl ammonium, octadecyl benzyl dimethyl
ammonium, tetramethyl ammonium, and the like or mixtures thereof, and alkyl
phosphonium ions such as tetrabutyl phosphonium, trioctyl octadecyl
phosphonium, tetraoctyl phosphonium, octadecyl triphenyl phosphonium, and the
25 like or mixtures thereof. Illustrative examples of suitable polyalkoxylated
ammoniium compounds include those available under the trade name Ethoquad or
Ethomeen from Akzo Chemie America, namely, Ethoquad 18/25 which is
octadecyl methyl bis(polyoxyethylene[ I S]) ammonium chloride and Ethomeen
18/25 which is octadecyl bis(polyoxyethylene[ I 5])amine, wherein the numbers
in
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brackets refer to the total number of ethylene oxide units. The most preferred
organic cation is octadecyl methyl bis(polyoxyethylene{ 15 }) ammonium
chloride.
If desired, the treated or untreated platelet particles may be further
separated
into a dispersing medium prior to or during contact with polyester monomers.
Many such dispersing aids are known, covering a wide range of materials
including
water, alcohols, ketones, aldehydes, chlorinated solvents, hydrocarbon
solvents,
aromatic solvents, and the like or combinations thereof. One especially useful
embodiment is exfoliation or dispersion of treated or untreated platelet
particles
into ethylene glycol with the addition of one or more of the above swelling
aids or
i
intercalating compounds. The particles are dispersed as individual platelet
particles
and tactoids. The ethylene glycol/platelet particle blends are usually high
viscosity
gels at zero shear, but they undergo shear thinning and flow under shear
stresses
caused by stirring and pumping. Other examples of predispersion of modified or
unmodified particles include, but are not limited to, those disclosed in EP
747,451
A2 and U.S. 4,889,885, which are incorporated herein by reference.
It should be appreciated that on a total composition basis dispersing aids
and/or pretreatment compounds which are used may account for significant
amount
of the total composition, in some cases up to about 30 weight%. While it is
preferred to use as little dispersing aid/pretreatment compounds as possible,
the
amounts of dispersing aids and/or pretreatment compounds may be as much as
about 8 times the amount of the platelet particles.
Polyesters
The polyester component of the compound of the present invention is
present in amounts between about 99.99 weight percent to about 75 weight
percent,
preferably between 99.5 and about 75 wt%, more preferably 99.5 to about 85 wt%
and most preferably between 99.5 and about 90 wt%..
Suitable polyesters include at least one dibasic acid and at least one glycol.
The primary dibasic acids are terephthalic, isophthalic,
naphthalenedicarboxylic,
1,4-cyclohexanedicarboxylic acid and the like. The various isomers of
naphthalenedicarboxylic acid or mixtures of isomers may be used but the 1,4-,
1,5-,
2,6-, and 2,7-isomers are preferred. The 1,4-cyclohexanedicarboxylic acid may
be
CA 02314871 2000-06-20
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5 in the form of cis, traps, or cis/trans mixtures. In addition to the acid
forms, the
lower alkyl esters or acid chlorides may be also be used.
The dicarboxylic acid component of the polyester may optionally be
modified with up to about 50 mole percent of one or more different
dicarboxylic
acids. Such additional dicarboxylic acids include dicarboxylic acids having
from 6
10 to about 40 carbon atoms, and more preferably dicarboxylic acids selected
from
aromatic dicarboxylic acids preferably having 8 to 14 carbon atoms, aliphatic
dicarboxylic acids preferably having 4 to 12 carbon atoms, or cycloaliphatic
dicarboxylic acids preferably having 7 to 12 carbon atoms. Examples of
suitable
dicarboxylic acids include phthalic acid, isophthalic acid, naphthalene- 2,6-
dicarboxylic acid, cyclohexanedicarboxylic acid, cyclohexanediacetic acid,
diphenyl-4,4'-dicarboxylic acid, succinic acid, glutaric acid, adipic acid,
azelaic
acid, sebacic acid, and the like. Polyesters may be prepared from one or more
of
the above dicarboxylic acids.
Typical glycols used in the polyester include those containing from two to
about ten carbon atoms. Preferred glycols include ethylene glycol, 1,4-
butanediol,
1,6-hexanediol, 1,4-cyclohexanedimethanol, diethylene glycol and the like. The
glycol component may optionally be modified with up to about 50 mole percent,
of
one or more different diols. Such additional diols include cycloaliphatic
diols
preferably having 6 to 20 carbon atoms or aliphatic diols preferably having 3
to 20
carbon atoms. Examples of such diols include: diethylene glycol, triethylene
glycol, 1,4-cyclohexanedimethanol, propane-1,3-diol, butane-1,4-diol, pentane-
1,5-
diol, hexane-1,6-diol, 3-methylpentanediol-(2,4), 2-methylpentanediol-(1,4),
2,2,4-
trimethylpentane-diol-(1,3), 2-ethylhexanediol-(1,3), 2,2-diethylpropane-diol-
(1,3),
hexanediol-(1,3), 1,4-di-(2-hydroxyethoxy)-benzene, 2,2-bis-(4-
hydroxycyclohexyl)-propane, 2,4-dihydroxy-1,1,3,3-tetramethyl-cyclobutane, 2,2-
bis-(3-hydroxyethoxyphenyl)-propane, 2,2-bis-(4-hydroxypropoxyphenyl)-propane
and the like. Polyesters may be prepared from one or more of the above diols.
The resin may also contain small amounts oftrifunctional ortetrafunctional
comonomers to provide controlled branching in the polymers. These monomers
can be extremely beneficial for imparting enhanced melt strength to a
polyester at a
CA 02314871 2000-06-20
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lower average molecular weight. Such comonomers include trimellitic anhydride,
trimethylolpropane, pyromellitic dianhydride, pentaerythritol, trimellitic
acid,
pyromellitic acid and other polyester forming polyacids or polyols generally
known
in the art.
Also small amounts of multifunctional polyols such as trimethylolpropane,
pentaerythritol, glycerol and the like may be used if desired. When using 1,4-
cyclohexanedimethanol, it may be the cis, trans or cis/trans mixtures.
Also, although not required, additives normally used in polyesters may be
used if desired. Such additives include colorants, pigments, carbon black,
glass
fibers, fillers, impact modifiers, antioxidants, stabilizers, flame
retardants, reheat
aids, acetaldehyde reducing compounds and the like.
The polyester/dispersed platelet compositions should be crystallizable to an
extent that is sufficient to prevent sticking during subsequent treatment such
as
solid stating.
The polyesters of the present invention may be made by any process which
is known in the art. Typically polyesters are made via well known
polycondensation processes.
The polyester-platelet particle composite compositions of the present
invention may be made by a wide variety of the process steps which are
disclosed
herein. For example, the platelet particles may be added to the polyester
before
(mixed in with one of the monomer components, such as ethylene glycol) melt
polymerization, during melt polymerization or after (such as via compounding.
The polyester-platelet particle composite material may be polymerized from the
melt and used with or without further treatment such as, but not limited to
solid
stating. Alternatively the polyester-platelet composite materials may be
molded
directly from melt polymerization as disclosed in U.S. Patent (EMS patent).or
U.S.
Serial No. (D70161), which are incorporated herein by reference. In fact, due
to
the higher melt strength of the polyester-platelet particle composites,
molding
directly from melt polymerization is even more beneficial than with polyesters
which do not contain platelet particles because less thermal history is
required to
achieve the desired melt strength. The reduced thermal history provides
bottles
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with better color (less yellow hugs) and lower coa~xntratio~ss of n~dG~itablc
side
products, such as acctald~'dc.
The prods of five present invention co>tuplrises the step of ~Omuag a parison
from a golynaorJplatelet particle composition at a ~cap~ature wl~ch is at
least ~0°C
higher thaai the Tg of said polymerlplatclet particle composiHon;vaod
as,olding said
parisoa into a shapod article.
When a high tomperature blowing process such as F8M i>; a~ployed for
g the desired vessel, the melt strength. and thus the'anoloqular weight, of
the
txtoldin$ resin must be sutflclently high for a suitable pariron to ~e
foJ:med.. The
polyester/clay composite must, first of all, be ready melt procee~sab'io. In
addition,
the welt must ps~~~ ~B~ ~ the perison to s>sppprt its owti weight.
With the dispersion of an orgaxfoclay in a polyes~t~'resiri, the del5ired
117e1t sb'~$~ c~
usually be obtained esra~n whoa. the moler~ular weight of the polyester is at
a
on of the clay
2D lower vaiuc than with the neat material (Fig, l). Since the dispp~
layers into the polyester melt often improves the melt viscosity; and the
other
properties of the resin. 'the clay can be considered as aid for high
icaspcrature
processing methods such as EBM. In addition, branching agents, such as glycois
or
acids possessing a tonality of three or greater, can be rr,~cd into the
polyester
ZS contpaneat of the »anoeompositc for the optimum balance of~rocessability
arid melt
strength. The various components of the present invention ark disclosed itl
detail,
below.
f,....~.~~ZX 'Z
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BNSDOCID: <E2 972410206
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Blow Molding from Polyester Melts
Many procedures have been established for molding a thermoplastic
material into a bottle, jar or other container. With polyesters, some of the
more
common processing methods include stretch blow molding, SBM; injection blow
molding, IBM and extrusion blow molding, EBM. Other processing methods such
as rotomolding might also be employed. Each of these processing methods allows
a polyester of the proper composition and molecular weight to be formed into a
clear, durable containers which are valuable for a variety of uses. When a
polyester/clay nanocomposite is molded into a vessel such as a bottle or a
jar,
turbidity is commonly present in the sidewaIl of the container. Though this
turbidity may have several different causes, with stretch blow molding in the
conventional manner, it is frequently difficult to avoid the presence of some
haze in
the molded object.
In the present invention, it was discovered that polyester-platelet particle
20 composite bottles which exhibit high clarity can be formed by employing a
process
comprised of blow molding or processing at a temperature well above the glass
transition temperature, generally by more than 50°C and preferably by
more than
100°C. Moreover, the blowing temperature is frequently selected so that
the
occurrence of crystallization does not complicate the blowing process. The
enhanced melt strength (and rheology) of the polyester-platelet particle
composite
materials should allow the blow molding in a wider range of processing
temperature.
Suitable molding equipment is well known in the art. IBM equipment is
available from UNJZ,OY, WHEATON and JOMAR, EBM equipment is available
from Bekum, Battenfield Fisher and UNB,OY and stretch blow molding equipment
is available from companies such as Husky, Sidel, Aoki and Nissei.
CA 02314871 2000-06-20
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Examales
Example 1
A copolyester of polyethylene terephthalate (PETG) (derived from 100 m
terephthalic acid, 88 m% ethylene glycol and 12 m % 1,4-cyclohexane dimethanol
(CHDM), amorphous K-2000, without mold release agents, available from
Eastman Chemical Company, upon specific request) was dried for 72 hours at
60°C
in a desiccating oven. The PETG and Claytone APA clay from Southern Clay
Products, Inc (3.3 weight % of the composite) were introduced into a Werner-
Pfleiderer 30mm twin screw extruder (ZSK-30) with an L/D of approximately 34
and a general compounding screw design. The PETG and clay were compounded
at a melt processing temperature of 255°C and a screw speed of 200 rpm.
A$er
extrusion, the inherent viscosity (IV) for the nanocomposite material was
determined to be 0.59 dL/g in a 60/40 (w/w) phenoUl,1,2,2,-tetrachloroethane
solution at 25°C.
Example 2
PETG composite from example 1 was crystallized in a stainless steel double
cone rotating dryer. This unit is heated by a Marlotherm S (heat transfer
fluid)
y system and is equipped with a water cooled heat exchanger. The unit was
purged
with a 10 scfh (standard ft3/hr). nitrogen flow. The polyester-platelet
particle
composite was added and the unit was heated to 150°C and held for 6
hours. The
unit was then cooled and the polymer discharged. After crystallization was
complete the material was solid state polymerized to increase the molecular
weight
of the PETG component.
Solid-state polymerization was carried out in a static bed reactor at
198°C
for 300 hours. The reactor has a stainless steel basket with a sintered metal,
fritted
disk in the bottom of the basket for a uniform distribution of heated
nitrogen. The
reactor was heated to the desired temperature by a Marlotherm heating system
equipped with a heat exchanger for cooling. The nitrogen was heated to the
desired
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5 temperature by an electric heater. After 300 hours at 198°C, the unit
was cooled
and the polymer discharged. The resulting material had an I. V. of 0.82 dL/g.
The dried resins were extrusion blow molded on a Bekum EBM-unit. The
extruder contains an 80 millimeter diameter, New Castle feed screw. The
materials
were e,Ytruded at 235°C and a mold was utilized for a 12 ounce syrup
bottle with no
10 handle. A mold temperature of 49°C and a total cycle time of 10.78
seconds were
employed. Several bottles were made from this material. The 12 ounce bottles
made from the nanocomposite resin exhibited a high degree of clarity. These
bottles also exhibited an amber color due to the presence of impurities in the
clay.
The characterization of their visual appearance is given in Table 1.
15 The oxygen permeability of the sidewall of each of these bottles was
determined. The sidewall of the nanocomposite bottle exhibited an oxygen
permeability of 7.9 cc-miI/100 in2 day atm.
Comparative Example 1
PETG copolyester used in Example 1 without any clay material was
crystallized in the stainless steel double cone rotating dryer described in
Example 2.
Initially, 20 pounds of the PETG copolyester was charged to the unit. The unit
was
heated to 150°C and held for 45 minutes. The unit was then cooled to
50°C. An
additional 80 pounds of polymeric material was charged to the unit. The unit
was
again heated to 150°C and held for 6 hours. After 6 hours it was cooled
and the
polymer discharged. After crystallization was complete the resulting inherent
viscosity (IV) of the PETG copolymer was 0.70 dL/g in a 60/40 weight percent
mixture of phenol/1,1,2,2-tetrachloroethane. Extrusion blow molding was
employed as described in Example 2 to form bottles. The characterization of
the
visual appearance of the bottles is given in Table 1. The oxygen permeability
of
the sidewall of each of these bottles was determined to be I 0.9 cc-mil/100
in2 day
atm. Thus bottles which are extrusion blow molded in accordance with the
process
of the present invention (Example 2) display good visual properties and a 27%
improvement in the barrier over that of the neat copolyester.
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S Comparative Example 2
PETG composite of Example 1 was dried by annealing in a vacuum oven
overnight at 60°C and then crystallized by stepping up over seven hours
to a final
temperature of 180°C. Bottles were stretch blow molded as follows.
Preforms for
half liter bottles were formed by injection molding on a Boy 22D at
approximately
280°C. Half liter bottles were then formed by stretch blow molding at a
temperature of approximately 120° to 130°C. The stretch blow
molded bottles of
this Example were very hazy. The characterization of their visual appearance
is
given in Table 1.
i
Assessment of Clarity:
The haze and opacity of the Example 2 EBM bottles were characterized and
compared both to the copolyester control (Comparative Example 1) and to
nanocomposite materials which were blown at a temperature approximately
40°C
above the glass transition temperature of the copolyester (Comparative Example
2).
The haze was determined examining the total transmission by ASTM D-1003.
The opacity of these materials was analyzed comparing the ratios of the
dii~use
reflectance first with a white reflective tile and then with a flat black tile
backing
the sample. These results are presented in Table 1. The bottles formed by EBM
at
230 to 240°C (Example 2) clearly exhibited superior clarity to the
samples blow
molded at 120 to 130°C (Comparative Example 2). Thus, by utilizing a
high
temperature blow molding process, for the first time high clarity bottles have
been
obtained with clay/polyester nanocomposites.
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Table 1. Haze Characterization in Polyester Nanocomposite Bottles
Example molding % Haze % Opacity oxygen
#
method platelet permeability*
Example EBM 3.3 8.8 12.5 7.9
2
Comp. EBM 0 1.8 10.8 10.9
Example
i I
Comp. SBM 3.3 62.1 52.2 na
Example
2
~' cc-m~l/100 W ' day atm
Bottles formed by the present invention (Example 2) display
surprisingly good clarity (low haze and opacity). This is clearly shown by
comparision with Comparative Example 2, which was blown by stretch blow
molding at temperatures which were less than 50°C above the Tg of the
polyester.
The bottle blown according to the process of the present invention was
approximately 7 times less hazy (8.8 vs. 62.I) than the bottle of Comparative
Example 2. While the haze values for the bottles of the present invention are
not as
i 15 good as those for polyester which does not contain platelet particles,
they are still
transparent to the human eye. Haze values of less than 20 are desireable, less
than
IS more desirable and less than about 10 are most desirable. Moreover, some of
the haze observed in the bottle of Example 2 are to impurities which were
present
in the clay.
Examples 3 - 7
PETG composite of Example 1 was crystallized by annealing in a
convection oven at 1 SO°C for 25 minutes and at 180°C for 15
minutes. This
material was then solid state polymerized at 198°C in a Glass column
heated with
refluxing ethylene glycol. During the solid stating process, which totaled
about 300
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hours, five samples were taken at different times to span a range of molecular
weights.
The melt strength of each sample was determined at 265°C using an
Instron
Capillary Rheometer. A strand of polymer was extruded through a capillary of
0.1
inch diameter and 0.25 inch length. A plunger speed of 2 cm/minute was
employed. The diameter of the strand was measured 6 inches from the thicker
end.
Generally, there is attenuation in the diameter of the strand due to
gravitational
forces acting on the molten extrudate. Greater attenuation of the diameter of
the
strand implies a lower melt strength. The melt strength is defined as follows:
melt strength = (strand diameter at 6 inch - capillary diameter)/ capillary
IS diameter * 100
The LV was measured in a 60/40 weight percent mixture ofphenol/1,1,2,2-
tetrachloroethane.. Figure 1 shows the melt strength as a function of I. V.
for
Examples 3-7.
Comparative Examples 3-7
PETG copolymer (12% CHD1V1) was crystallized by annealing in a
convection oven at 150°C for 2.5 hours. This material was then solid
state
annealed starting at 180°C and increasing stepwise to 198°C.
During the solid
stating process, which totaled about 100 hours, five samples were taken at
different
)
times to span a range of molecular weights. The melt strength was determined
using an Instron Capillary Rheometer in the same manner employed for Examples
3-7. In Figure 1, the melt strength values for Examples 3-7 and Comparative
Examples 3-7 are shown as a function of IV. Table 2 reports the LV. and melt
strength for each sample measured.
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Table 2
Example LV. (dL/g) Melt Strength
(%)
3 0.65 -36
4 0.69 -34
5 0.75 -28
6 0.79 -24
7 0.81 -22
CE 3 0.70 -72
CE 4 0.71 -63
CE 5 0.93 -20
CE 6 1.04 -8
CE 7 1.12 8
It was very surprising to find such a large increase in melt strength at
similar I. V. For example, the melt strength of the composite of the present
invention at 0.69 I. V. is twice as good (-34) as the melt strength (-72) of
the same
polyester without the clay platelets at a nearly identical LV. (Comparative
Example
y 3, I. V. of 0.7). The magnitude of this difference is very surprising and
extremely
significant. Generally EBM for polymers is conducted at I. V.s which are in
excess
of 0.9 dL/g. However, polyester-platelet composites of that LV. are difficult
to
produce because the melt viscosities of the composites of the present
invention are
very high, severely limiting the LV. which can be attained through melt
polymerization. Thus, the discovery that clear bottles could be extrusion blow
molded from polyester-platelet composites at LV.s far lower than generally
used
for non-modified polyesters was quite surprising.
Example 8
To a 18 gallon (68 liter) stainless steel batch reactor, with
intermeshing spiral agitators, was added 13.29 kilograms (68.59 moles) of
dimethyl
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5 terephthalate, 3.53 kilograms (57.04 moles) of ethylene glycol, 0.79
kilograms
(5.49 moles) of 1,4-cyclohexanedimethanol, 10.95 grams of a butanol solution
containing the titanium catalyst and 227.0 grams of an ethylene glycol
solution
containing the manganese catalyst. Added to this mixture was 2.50 kilograms of
an
experimental gel from Nanocor, Inc. designated #75 containing 10.9% sodium
10 montmorillonite, 82.36% ethylene glycol, 2.7% water, and 4.04%
polyvinylpyrollidone Nanomer PVP-B gel, available from Nanocor, Inc. The
reactor was heated to 200°C and held for 2 hours with agitation. The
temperature
was increased to 220°C and held for 1 hour. The phosphorus catalyst was
added
a
and the temperature was maintained at 220°C for 10 minutes_ 805 grams
were then
15 added of an ethylene glycol solution containing the cobalt and antimony
catalyst
and the temperature was increased to 285°C. When the melt temperature
reached
270°C, vacuum was applied at a rate of 13 mm per minute. When the
pressure had
dropped to lrnm and the melt temperature was 285°C, the polymer was let
down to
a nitrogen purge. The polymer was extruded into metal pans and ground to pass
a
20 3mm screen. The polymer had an inherent viscosity of 0.25 dL/g, a zero
shear melt
viscosity of 6600 P, and GPC MW = 11400, M" = 5700, MZ = 18000. The polymer
contained 1.6 mole % diethylene glycol, 8.1 mole % CHDM, 20 ppm of Ti, 55 ppm
of Mn, 80 ppm of Co, 230 ppm of Sb and 110 ppm of P.
The PETG composite was solid state polymerized in a fluidized bed reactor
at 215°C for 60 hours to an inherent viscosity of 0.93 dL/g, a zero
shear melt
viscosity of 270,000 P and a melt strength at 250°C of +2.8%.
The PETG composite was extrusion blow molded on a Bekum EBM-unit at
248°C and to form a 12 ounce Syrup bottle with no handle. The extruder
had an
80-mm diameter, New Castle feed screw. Total cycle time of 10.5 seconds was
utilized and the mold was cooled using tap water at 23°C. The 12 ounce
bottle was
clear with an amber color due to impurities present in the clay. The
crystallinity of
polyester composite was less than 5%. The bottle sidewall was tested for
oxygen
permeability at 23°C using a Modern Control (MOCON) Oxtran 10/SOA-
permeability tester. Test gases were passed through water bubblers, resulting
in
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about 75% relative humidity. The haze was determined for the total
transmission
by test method ASTM D-1003. The opacity of these materials was analyzed in
which the ratio of the diffuse reflectance of the sample is determined, first
with a
white reflective tile backing the sample and then a black one. The oxygen
permeability, haze and opacity are listed in the second column of Table 3,
below.
Comparative Example 8
A sample of polyethylene terephthalate) as produced in Example 8 with no
sodium montmorillonite was solid stated for 24 hours (control sample). It
exhibited
i
an LV. of 0.85 dL/g and a melt strength at 250°C of-27.2%. Bottles were
molded
as in Example 8. The bottles were clear and colorless. The crystallinity of
polyester composite was less than 5%. The oxygen permeability, haze and
opacity
of the control were measured as in Example 8. The results are shown in the
third
column of Table 3, below.
Table 3
Property Ex. 8 Comp. Ex.
8 '
melt strength @ 250C 2.8 -27.2
oxygen permeability (cc-mils/100inz-day-atm)10.1 11.6
haze 15.31 6.27
opacity (%) 12.23 11.78
As in the above Examples, the haze for bottles of the present invention
(Example 8) is far better than that achieved by conventional SBM methods.
Moreover the melt strength of the polyester-platelet particle composite
(Example 8)
was nearly I 0 times better than the Example without clay (Comparative Example
8). Thus, the Examples included herewith clearly show that clear bottles can
be
extrusion blow molded from different polyesters, containing different platelet
particles.
