U.S. patent application number 14/886143 was filed with the patent office on 2016-02-11 for composition for maintaining good color when thermally treating polyester-polyamide blends.
This patent application is currently assigned to M&G USA Corporation. The applicant listed for this patent is M&G USA Corporation. Invention is credited to Paul HEATER.
Application Number | 20160040007 14/886143 |
Document ID | / |
Family ID | 37734274 |
Filed Date | 2016-02-11 |
United States Patent
Application |
20160040007 |
Kind Code |
A1 |
HEATER; Paul |
February 11, 2016 |
COMPOSITION FOR MAINTAINING GOOD COLOR WHEN THERMALLY TREATING
POLYESTER-POLYAMIDE BLENDS
Abstract
A polymer composition and wall of a container made from such
composition is set forth comprising a polyamide and polyester and a
sufficient amount of an interfacial tension reducing agent such
that the polyamide domains stretch disproportionately to the amount
of stretch experienced by the polyester both with and without a
cobalt salt.
Inventors: |
HEATER; Paul; (Navarre,
OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
M&G USA Corporation |
Apple Grove |
WV |
US |
|
|
Assignee: |
M&G USA Corporation
Apple Grove
WV
|
Family ID: |
37734274 |
Appl. No.: |
14/886143 |
Filed: |
October 19, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13919422 |
Jun 17, 2013 |
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14886143 |
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Current U.S.
Class: |
264/328.17 |
Current CPC
Class: |
C08K 5/42 20130101; B32B
2439/00 20130101; Y10T 428/1352 20150115; C08J 3/005 20130101; C08L
67/02 20130101; Y10T 428/1355 20150115; C08G 63/916 20130101; Y10T
428/13 20150115; C08L 67/00 20130101; Y10T 428/139 20150115; C08L
77/00 20130101; B32B 27/06 20130101; C08L 67/00 20130101; B32B
2553/00 20130101; B32B 2367/00 20130101; Y10T 428/1397 20150115;
C08L 2205/18 20130101; C08K 5/42 20130101; B32B 2377/00 20130101;
C08L 77/06 20130101; C08L 77/10 20130101; C08L 2666/18 20130101;
C08L 2666/18 20130101; Y10T 428/1393 20150115; C08K 5/42 20130101;
B32B 1/02 20130101; C08G 63/78 20130101; C08L 77/00 20130101; C08K
3/24 20130101; C08L 2666/20 20130101; C08L 77/00 20130101; B32B
27/34 20130101; C08L 67/00 20130101; B32B 27/36 20130101; C08L
77/00 20130101; C08L 77/06 20130101; B32B 27/18 20130101; Y10T
428/1334 20150115; C08L 67/02 20130101 |
International
Class: |
C08L 67/02 20060101
C08L067/02; C08L 77/00 20060101 C08L077/00 |
Claims
1. A process for making a wall of a container comprising the steps
of: A) making a crystallizable polyester in the presence of a
di-ethylene glycol suppressant in the absence of a cobalt salt
wherein the crystallizable polyester comprises acid units and
glycol units; at least 85% of the polyester acid units of the
crystallizable polyester are derived from terephthalic acid or the
dimethyl ester of terephthalic acid; and at least a portion of the
acid units, at least a portion of the glycol units, or at least a
portion of both the acid units and the glycol units of the
crystallizable polyester are an interfacial tension reducing agent
consisting of a metal sulfonate; B) forming a compartmentalized
pellet having a sheath comprising the crystallizable polyester and
a core comprising a polyamide; C) subjecting the compartmentalized
pellet to a solid state polymerization; D) injection molding the
compartmentalized pellet to form a preform comprising dispersed
particles of the polyamide wherein the dispersed particles of the
polyamide have an average particle diameter less than 100 nm; and
E) forming the wall of the container from the preform.
2. The process of claim 1, wherein the di-ethylene glycol
suppressant is selected from the group consisting of sodium acetate
and lithium acetate.
3. The process of claim 1, wherein the polyamide comprises at least
one reaction product selected from the group consisting of the
reaction of amino caproic acid with itself, and the reaction
product of A-D where A is a residue of dicarboxylic acid comprising
adipic acid, isophthalic acid, terephthalic acid, 1,4
cyclohexanedicarboxylic acid, resorcinol dicarboxylic acid, or
naphthalenedicarboxylic acid, or a mixture thereof, and D is a
residue of a diamine comprising m-xylylene diamine, p-xylylene
diamine, hexamethylene diamine, ethylene diamine, or 1,4
cyclohexanedimethylamine, or a mixture thereof.
4. The process of claim 2, wherein the polyamide comprises at least
one reaction product selected from the group consisting of the
reaction of amino caproic acid with itself, and the reaction
product of A-D where A is a residue of dicarboxylic acid comprising
adipic acid, isophthalic acid, terephthalic acid, 1,4
cyclohexanedicarboxylic acid, resorcinol dicarboxylic acid, or
naphthalenedicarboxylic acid, or a mixture thereof, and D is a
residue of a diamine comprising m-xylylene diamine, p-xylylene
diamine, hexamethylene diamine, ethylene diamine, or 1,4
cyclohexanedimethylamine, or a mixture thereof.
5. The process of claim 1, wherein the interfacial tension reducing
agent is lithium sulfoisophthalate or sodium sulfoisophthalate.
6. The process of claim 5, wherein the interfacial tension reducing
agent is present at a level within the range of 0.1 and 2.0 mole
percent based upon the moles of acid units or glycol units in the
polyester.
7. The process of claim 6, wherein the interfacial tension reducing
agent is selected from the group consisting of functionalized
lithium sulfonates, non-functionalized lithium sulfonates,
functionalized sodium sulfonates and non-functionalized sodium
sulfonates.
8. The process of claim 2, wherein the interfacial tension reducing
agent is lithium sulfoisophthalate or sodium sulfoisophthalate.
9. The process of claim 8, wherein the interfacial tension reducing
agent is present at a level within the range of 0.1 and 2.0 mole
percent based upon the moles of acid units or glycol units in the
polyester.
10. The process of claim 9, wherein the interfacial tension
reducing agent is selected from the group consisting of
functionalized lithium sulfonates, non-functionalized lithium
sulfonates, functionalized sodium sulfonates and non-functionalized
sodium sulfonates.
11. The process of claim 3, wherein the interfacial tension
reducing agent is lithium sulfoisophthalate or sodium
sulfoisophthalate.
12. The process of claim 11, wherein the interfacial tension
reducing agent is present at a level within the range of 0.1 and
2.0 mole percent based upon the moles of acid units or glycol units
in the polyester.
13. The process of claim 12, wherein the interfacial tension
reducing agent is selected from the group consisting of
functionalized lithium sulfonates, non-functionalized lithium
sulfonates, functionalized sodium sulfonates and non-functionalized
sodium sulfonates.
14. The process of claim 4, wherein the interfacial tension
reducing agent is lithium sulfoisophthalate or sodium
sulfoisophthalate.
15. The process of claim 14, wherein the interfacial tension
reducing agent is present at a level within the range of 0.1 and
2.0 mole percent based upon the moles of acid units or glycol units
in the polyester.
16. The process of claim 15, wherein the interfacial tension
reducing agent is selected from the group consisting of
functionalized lithium sulfonates, non-functionalized lithium
sulfonates, functionalized sodium sulfonates and non-functionalized
sodium sulfonates.
Description
PRIORITY AND CROSS REFERENCES
[0001] This patent application claims the benefit of the priority
of U.S. Provisional Patent Application Ser. No. 60/725,085 filed
Oct. 7, 2005 and U.S. Provisional Patent Application Ser. No.
60/827,147 filed Sep. 27, 2006. The teachings of these provisional
patent applications are incorporated herein by reference.
FIELD OF INVENTION
[0002] This invention relates to the stretched wall of a container
for packaging.
BACKGROUND OF THE INVENTION
[0003] United States Patent Applications 2002/0001684 (Jan. 3,
2002), 20030134966 (Jul. 13, 2003) and 20050106343 (May 19, 2005),
all of which have a common inventor Kim, teach a composition of PET
(A), a polyamide, MXD6 nylon (B), with cobalt octoate. The Kim
series of applications teach that when the PET/MXD6/Cobalt octoate
composition is injected molded into a preform (parison) and then
oriented (stretched) into a blown bottle, the resultant bottle is
hazy. The Kim applications also identify the cause of the haze.
According to Kim, the haze is caused by the MXD6 domains dispersed
into the PET which upon orientation have been stretched to the
point where the size of the domains are greater than the wavelength
of light.
[0004] Kim et al teaches that smaller domains reduce the haze
caused by the previously large domains. One of ordinary skill knows
there are two ways to have smaller domains in the stretched bottle.
One is to reduce the size of the starting domains in the preform or
parison, the other is to not orient or stretch the bottle as much.
The solution selected in the Kim series of applications to replace
the injection blow process of making the preform/parison and
subsequently orienting (stretching) the preform into a blown bottle
with a much lower stretch process called extrusion blow.
[0005] The Kim applications also teach that a container made with
PET/MXD6/Cobalt octoate exhibits higher oxygen barrier (lower
permeation rate) presumably due to the well known ability of the
cobalt octoate to catalyze the reaction of MXD6 nylon with oxygen.
While Kim et al, therefore teaches that reducing the size of the
MXD6 domains as a way to reduce the haze in stretched containers,
it does not teach how to solve the haze in an injection blown
container or how to reduce the size of the domains in an injection
blown container, presumably because this was already known in the
art prior to the invention of Kim.
[0006] JP-2663578-B2 (Oct. 15, 1997) to Yamamoto et al identifies
the same problem as the Kim applications with the same composition.
Yamamoto et al discloses that a hazy stretch blown bottle is
created when a composition of polyester (A) and MXD6 nylon (B) is
injection molded into a parison (preform) and oriented (stretched)
into a bottle. Recall that Kim et al teach that this haze is cause
by large domains and the only difference being that the bottle of
Kim et al contains cobalt octoate.
[0007] Yamamoto et al, then teaches that the haze in the PET/MXD6
injection blown bottle may be eliminated by incorporating a third
polyester component (C) wherein the third polyester component has
5-sodium sulfoisophthalate derived from 5-sodium sulfoisophthalic
acid in its polymer chain. The copolymerization of the 5-sodium
sulfoisophthalic acid is taught in Table 3 of Yamamoto with the
conclusion being: when polyester copolymerized with 5-sodium
sulfoisophthalate is used as the component (C), the transparency is
improved and the haze is notably reduced. One of ordinary skill
would therefore solve the haze of Kim's injection molded/stretch
blown bottle containing PET/MXD6/cobalt octoate by adding the
polyester (C) copolymerized with 5-sodium sulfoisophthalate taught
by Yamamoto et al. One would not eliminate the cobalt octoate found
in the Kim applications because that would reduce the oxygen
barrier of the container.
[0008] U.S. Pat. No. 5,300,572 (Apr. 5, 1994) to Tajima et al
teaches how to reduce the domain size of a polyamide dispersed into
a polyester. Tajima et al reduces the domain size of the polyamide
by adding sodium sulfoisophthalic acid, either copolymerized into
the backbone of polyester (A) or as a third component (C) which is
a polyester copolymerized with the sodium sulfoisophthalic acid.
Since the Kim applications teaches that reducing the size of the
polyamide domains solves the haze one of ordinary skill wishing to
make an injection molded/stretch blown bottle containing
PET/MXD6/Cobalt octoate would either use a PET copolymerized with
sodium sulfoisophthalate derived from sodium sulfoisophthalic acid
for the A component as taught by Tajima et al or add a polyester
(C) copolymerized with sodium isophthalate as taught by Yamamoto et
al. Again, one would not eliminate the cobalt octoate of Kim et al
because that would reduce the increased oxygen barrier of Kim et
al.
[0009] WO 2005/023530 (Mar. 17, 2005) to Mehta et al teaches that a
cobalt salt is essential when injection molding a preform (parison)
comprising the composition of Kim et al [a polyester (A), a
polyamide such as MXD6 (B)], and in the presence of an ionic
compatibilizer such as 5-sodium sulfoisophthalic acid or 5-sodium
sulfoisophthalate. Mehta et al and Kim et al even use the same
cobalt salt--cobalt octoate. According to Mehta et al, a large
amount of yellow colour is created when combining the polyester
(A), with polyamide (B) in the presence of an ionic compatibilizer
(C) and the use of the cobalt octoate also taught in the Kim
applications prevents that colour formation.
[0010] While the use of cobalt may alleviate colour, it inherently
creates an active barrier package. There are other active barrier
mechanisms, such as oxidizing an elemental metal in the wall of the
container. Since there are packaging applications which do not
benefit and are in fact harmed by an organic scavenger or need a
less powerful active package; there exists, therefore, the need for
an MXD6/polyester ionic compatibilizer where cobalt is not
necessary to prevent the detrimental colour formation noted in
Mehta et al.
SUMMARY OF INVENTION
[0011] This invention discloses a composition and a container wall
made from that composition wherein the container wall comprises a
stretched layer, which could be a single layer (mono-layer),
wherein the layer is comprised of a crystallizable polyester with
at least 85% of the polyester's acid units derived from
terephthalic acid or the dimethyl ester of terephthalic acid or 2,6
naphthalate dicarboxylic acid or its dimethyl ester, a polyamide
with at least 85% the polyamide's polymer chain being the reaction
of amino caproic acid with itself, or the reaction product of A-D
where A is a residue of dicarboxylic acid comprising adipic acid,
isophthalic acid, terephthalic acid, 1,4 cyclohexanedicarboxylic
acid, resorcinol dicarboxylic acid, or naphthalenedicarboxylic
acid, or a mixture thereof and D, where D is a residue of a diamine
comprising m-xylylene diamine, p-xylylene diamine, hexamethylene
diamine, ethylene diamine, or 1,4 cyclohexanedimethylamine, or a
mixture thereof, and an interfacial tension reducing agent wherein
the polyamide is dispersed into the polyester and the interfacial
tension between the polyester and the polyamide is such that the
average diameter of the particles of the polyamide dispersed in the
polyester is less than 150 nm and the particle size measurement is
conducted on the layer at the region selected from the group
consisting of an unstretched portion of the layer and a portion of
the layer prior to stretching.
[0012] The invention further discloses that the interfacial
reducing agent is selected from the group consisting of
functionalized and non-functionalized lithium sulfonates, hydroxyl
terminated polyethers, cyclic amides and polyethers, with lithium
sulfoisophthalate being a particularly useful lithium interfacial
tension reducing agent.
[0013] An effective amount of lithium sulfonate, in particular,
lithium sulfoisophthalate (derived from 5-sulfoisophthalic acid
monolithium salt), is about 0.05 to 0.1 mole percent, with an
optimal amount being with the range of about 0.1 to about 2.0 mole
percent, with the range of about 0.1 to about 1.1 mole percent
being more optimal, and about 0.18 to about 0.74 being even better
yet, with the range of about 0.18 to about 0.6 mole percent being
the most optimal range.
[0014] The invention further discloses that MXD6 and PA 6 are
particularly suited polyamides and that the composition or wall of
the container can be free of cobalt compounds.
DESCRIPTION OF THE FIGURES
[0015] FIG. 1 depicts a scanning electron microscope
photomicrograph (SEM) of polyamide domains dispersed in a polyester
matrix in the absence of the interfacial tension reducing agent,
such as lithium sulfoisophthalate derived from lithium
sulfoisophthalic acid (LiSIPA). As detailed in the test method
section, the sample was prepared by removing the polyamide with
cold formic acid and exposing the sample to a scanning electron
microscope.
[0016] FIG. 2 depicts the graphical representation of the
distribution of the domains corresponding to the
polyester-polyamide system of FIG. 1.
[0017] FIG. 3 depicts a scanning electron microscope
photomicrograph of polyamide domains dispersed into a polyester
matrix in the presence of an interfacial tension reducing
agent--lithium sulfoisophthalate derived from lithium
sulfoisophthalic acid (LiSIPA). As detailed below, the sample was
prepared by removing the polyamide with cold formic acid.
[0018] FIG. 4 depicts the graphical representation of the
distribution of the domains corresponding to the
polyester-polyamide system of FIG. 3.
[0019] FIG. 5 depicts a photograph of the pellets of a
crystallizable polyethylene terephthalate blended with polyamide 6,
also known as PA6 or nylon 6 with and without the interfacial
tension reducing agent derived from lithium sulfoisophthalic acid
(LiSIPA). The impact of the interfacial tension reducing agent is
readily seen in the immediate clarity of the composition containing
the lithium sulfoisophthalate.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The deficiencies of colour formation when blending
polyamides, polyesters and interfacial tension reducing agents can
be overcome according to the invention by the use of lithium as the
metal ion in the interfacial tension reducing agent. Additionally
the deficiency of the large polyamide domains found in stretched
composition of polyamide, polyester and interfacial tension
reducing agents can be overcome when the interfacial reducing agent
is a lithium salt.
[0021] The polyamide domains of this invention exhibit a unique
behaviour when the article is stretched. In the prior art systems,
the relative increase in domain size very close to the overall
amount the article was stretched in the same direction. If the
article was stretched 5 times in one direction, the domain would
also be stretched approximately 5 times in that direction. The
domains of this composition do not stretch the same amount as the
article. In fact, the domains exhibit a very small amount of
stretch relative to the amount of stretch experienced by the
article.
[0022] While not to be bound by any theory it is hypothesized that
the lithium salt does not nucleate the crystallization of the
polyester like the other metals (e.g. sodium) and thus the domains
shrink while the stretched article is cooling. The reduced
interfacial tension between the polyamide and polyester coupled
with the stretch characteristics increases the dispersion of the
polyamide in the polyester and the average domain size of the
dispersed polymer in an unstretched portion of an article
comprising the composition is less than 125 nm, with better results
at less than 100 nm, even better results with the average domain
size being less than 75 nm, and with domains less than 60 nm being
the most optimal average domain size in the unstretched portion of
the container wall.
[0023] The stretch phenomenon can be characterised by the percent
stretch which is defined as the stretch ratio of the polyamide
domains divided by the stretch ratio of the matrix (polyester) in
the same direction. Theoretically this should be 100%, in that the
domains stretch the same amount as the polyester. However, when the
lithium salt is used, the percent stretch is often less than 75%,
with many observations less than 50%, and in one instance less than
30%. It is believed that the lower the percent stretch, the
better.
[0024] This invention also provides for a blend of a crystallizable
polyethylene terephthalate or its copolymers, a polyamide (in
particular MXD6 or nylon-6) and a separate interfacial tension
reducing agent to form the stretched wall of a container. The
separate interfacial tension reducing agent could be a metal salt
of sulfonated polystyrene or a metal salt of sulfonated
polyester.
[0025] This invention provides for a modified polyester, in
particular a crystallizable polyethylene terephthalate or its
copolymers, blended with a polyamide, in particular MXD6 or
nylon-6; or a polyester, in particular polyethylene terephthalate
or its copolymers, blended with a modified polyamide, in particular
MXD6 to form the stretched wall of a container.
[0026] Any polyester or polyamide suitable for making the desired
container is suitable for the current invention provided the
composition comprising the polyester and polyamide has a sufficient
amount of interfacial tension reducing agent either as a third
component or incorporated into the polyester chain, the polyamide
chain. A combination of the separate interfacial tension reducing
agent and a polyester or polyamide, or both being modified with an
interfacial tension reducing agent are contemplated. The
interfacial tension reducing agents need not be the same.
[0027] Polyesters of this invention can be prepared by
polymerization procedures well-known in the art. The polyester
polymers and copolymers may be prepared by melt phase
polymerization involving the reaction of a diol with a dicarboxylic
acid, or its corresponding ester. Various copolymers of multiple
diols and diacids may also be used.
[0028] In general, the polyester polymers and copolymers may be
prepared, for example, by melt phase polymerization involving the
reaction of a diol with a dicarboxylic acid, or its corresponding
diester. Various copolymers resulting from use of multiple diols
and diacids may also be used. Polymers containing repeating units
of only one chemical composition are homopolymers. Polymers with
two or more chemically different repeat units in the same
macromolecule are termed copolymers. The diversity of the repeat
units depends on the number of different types of monomers present
in the initial polymerization reaction. In the case of polyesters,
copolymers include reacting one or more diols with a diacid or
multiple diacids, and are sometimes referred to as terpolymers. For
example, in one embodiment of this invention, m-xylylene diamine
polyamide (MXD6 Grade 6007 from Mitsubishi Gas Chemical, Japan) is
dispersed into a polyethylene terephthalate copolymer comprised of
terephthalic acid, isophthalic acid and the lithium salt of
sulfoisophthalic acid.
[0029] As noted hereinabove, suitable dicarboxylic acids include
those comprising from about 4 to about 40 carbon atoms. Specific
dicarboxylic acids include, but are not limited to, terephthalic
acid, isophthalic acid, naphthalene 2,6-dicarboxylic acid,
cyclohexanedicarboxylic acid, cyclohexanediacetic acid,
diphenyl-4,4'-dicarboxylic acid, 1,3-phenylenedioxydiacetic acid,
1,2-phenylenedioxydiacetic acid, 1,4-phenylenedioxydiacetic acid,
succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic
acid, and the like. Specific esters include, but are not limited
to, phthalic esters and naphthalic diesters.
[0030] These acids or esters may be reacted with an aliphatic diol
preferably having from about 2 to about 24 carbon atoms, a
cycloaliphatic diol having from about 7 to about 24 carbon atoms,
an aromatic diol having from about 6 to about 24 carbon atoms, or a
glycol ether having from 4 to 24 carbon atoms. Suitable diols
include, but are not limited to, ethylene glycol, 1,4-butanediol,
trimethylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol,
diethylene glycol, resorcinol, 1,3-propanediol and
hydroquinone.
[0031] A useful polyester is a crystallizable polyester with more
than 85% of its acid units being derived from terephthalic acid. It
is generally accepted that polyesters with greater than 15%
comonomer modification are difficult to crystallize. However, this
invention includes polyesters which would crystallize and have more
than 15% comonomer content.
[0032] Polyfunctional comonomers can also be used, typically in
amounts of from about 0.01 to about 3 mole percent. Suitable
comonomers include, but are not limited to, trimellitic anhydride,
trimethylolpropane, pyromellitic dianhydride (PMDA), and
pentaerythritol. Polyester-forming polyacids or polyols can also be
used. Blends of polyesters and copolyesters may also be useful in
the present invention.
[0033] One suitable crystallizable polyester is polyethylene
terephthalate (PET) or a copolymer modified with lithium
sulfoisophthalate formed from the di-ester or di-carboxylic acid of
lithium sulfoisophthalate in the approximately 1:1 stoichiometric
reaction of acids, or their di-esters, with ethylene glycol.
Copolymers are also suitable. Specific copolymers and terpolymers
of interest are crystallizable polyesters comprising lithium
sulfoisophthalate in combinations of isophthalic acid or its
diester, 2,6 naphthalate dicarboxylic acid or its diester, and/or
cyclohexane dimethanol. The optimal levels of lithium
sulfoisophthalate are within the range of 0.1 and 2.0 mole percent
based upon the acid moieties in the polymer. While greater than 2.0
mole percent is not deleterious to the intended effect, greater
than 2.0 mole percent achieves little or no additional
improvement.
[0034] The amount of lithium sulfonate, in particular, lithium
sulfoisophthalate (derived from 5-sulfoisophthalic acid monolithium
salt), is about 0.05 to 10.0 mole percent, with an optimal amount
being with the range of about 0.1 to about 2.0 mole percent, with
the range of about 0.1 to about 1.1 mole percent being more
optimal, and about 0.18 to about 0.74 being even better yet, with
the range of about 0.18 to about 0.6 mole percent being the most
optimal range.
[0035] The esterification or polycondensation reaction of the
carboxylic acids or esters with glycol typically takes place in the
presence of a catalyst. Suitable catalysts include, but are not
limited to, antimony oxide, antimony triacetate, antimony ethylene
glycolate, organomagnesium, tin oxide, titanium alkoxides, dibutyl
tin dilaurate, and germanium oxide. These catalysts may be used in
combination with zinc, manganese, or magnesium acetates or
benzoates. Catalysts comprising antimony are preferred. Another
preferred base polyester is polytrimethylene terephthalate (PTT).
It can be prepared by, for example, reacting 1,3-propanediol with
at least one aromatic diacid or alkyl ester thereof. Preferred
diacids and alkyl esters include terephthalic acid (TPA) or
dimethyl terephthalate (DMT). Accordingly, the PTT preferably
comprises at least about 80 mole percent of either TPA or DMT.
Other diols which may be copolymerized in such a polyester include,
for example, ethylene glycol, diethylene glycol, 1,4-cyclohexane
dimethanol, and 1,4-butanediol. In addition to the interfacial
tension reducing agent such as sulfoisophthalic acid, other
aromatic and aliphatic acids which may be used simultaneously to
make a copolymer include, for example, isophthalic acid and sebacic
acid.
[0036] Preferred catalysts for preparing PTT include titanium and
zirconium compounds. Suitable catalytic titanium compounds include,
but are not limited to, titanium alkylates and their derivatives,
titanium complex salts, titanium complexes with hydroxycarboxylic
acids, titanium dioxide-silicon dioxide-co-precipitates, and
hydrated alkaline-containing titanium dioxide. Specific examples
include tetra-(2-ethylhexyl)-titanate, tetrastearyl titanate,
diisopropoxy-bis(acetyl-acetonato)-titanium,
di-n-butoxy-bis(triethanolaminato)-titanium,
tributylmonoacetyltitanate, triisopropyl monoacetyltitanate,
tetrabenzoic acid titanate, alkali titanium oxalates and malonates,
potassium hexafluorotitanate, and titanium complexes with tartaric
acid, citric acid or lactic acid. Preferred catalytic titanium
compounds are titanium tetrabutylate and titanium
tetraisopropylate. The corresponding zirconium compounds may also
be used.
[0037] The polyesters of this invention may also contain small
amounts of phosphorous compounds, such as phosphates, and a
catalyst such as a cobalt compound, that tends to impart a blue
hue. Also, small amounts of other polymers such as polyolefins can
be tolerated in the continuous matrix. While WO 2005/023530 A1
teaches the use of cobalt salts as essential to prevent colour
formation, the use of cobalt salts is not necessary to reduce the
colour formation when the interfacial tension reducing agent is the
lithium salt, in particular lithium sulfoisophthalate derived from
Lithium SulfolsoPhthalic Acid (LiSIPA).
[0038] The molecular structure of lithium sulfoisophthalic acid
is:
##STR00001##
[0039] Lithium sulfoisophthalic acid (LiSIPA) or sulfonic acid
lithium salt modified isophthalic acid.
[0040] As is evident from the above diagram, the lithium
sulfoisophthalic acid comprises is a lithium sulfonate and
comprises lithium sulfoisophthalate. The lithium sulfoisophthalate
refers to the compound as it is appears incorporated into the
polymer chain. This is also known as the repeating unit of lithium
sulfoisophthalic acid. Lithium sulfoisophthalate therefore is the
lithium sulfoisophthalic acid less one water molecule, with one
hydroxyl group removed from one of the carboxyl end groups and a
hydrogen removed from the other carboxyl end group. This molecule
is then attached to one or more monomers (R.sub.1 and R.sub.2) in
the polymer backbone.
##STR00002##
[0041] The sulfonate, in this case lithium sulfoisophthalate, is
the molecule between the two R groups. Again, R could be the same
monomer, in the case of PET, the R's are likely the same being the
ethylene glycol moiety as reacted into the polymer chain.
[0042] After completion of the melt phase polymerization, the
polymer is either made into a form such as a film or part or
stranded and cut into smaller chips, such as pellets. The polymer
is usually then crystallized and subjected to a solid phase (solid
state) polymerization (SSP) step to achieve the intrinsic viscosity
necessary for the manufacture of certain articles such as bottles.
The crystallization and polymerization can be performed in a
tumbler dryer reactor in a batch-type system. The solid phase
polymerization can continue in the same tumble dryer where the
polymer is subjected to high vacuum to extract the polymerization
by-products
[0043] Alternatively, the crystallization and polymerization can be
accomplished in a continuous solid state polymerization process
whereby the polymer flows from one vessel to another after its
predetermined treatment in each vessel. The crystallization
conditions are relative to the polymer's crystallization and
sticking tendencies. However, preferable temperatures are from
about 100.degree. C. to about 235.degree. C. In the case of
crystallisable polyesters, the solid phase polymerization
conditions are generally 10.degree. C. below the melt point of the
polymer. In the case of non-crystallisable polyesters, the solid
phase polymerization temperature is generally about 10.degree. C.
below temperature where the polymer begins sticking to itself.
While traditional solid phase polymerization temperatures for
crystallisable polymers range from about 200.degree. C. to about
232.degree. C., many operations are from about 215.degree. C. to
about 232.degree. C. Those skilled in the art will realize that the
optimum solid phase polymerization temperature is polymer specific
and depends upon the type and amount of copolymers in the product.
However, determination of the optimum solid phase polymerization
conditions is frequently done in industry and can be easily done
without undue experimentation.
[0044] The solid phase polymerization may be carried out for a time
sufficient to raise the intrinsic viscosity to the desired level,
which will depend upon the application. For a typical bottle
application, the preferred intrinsic viscosity (I.V.) is from about
0.65 to about 1.0 deciliter/gram, as determined by the method
described in the methods section. The time required to reach this
I.V. from about 8 to about 21 hours.
[0045] In one embodiment of the invention, the crystallizable
polyester of the present invention may comprise recycled polyester
or materials derived from recycled polyester, such as polyester
monomers, catalysts, and oligomers.
[0046] The term crystallizable means that the polyethylene
terephthalate can be become semi-crystalline, either through
orientation or heat induced crystallinity. It is well known that no
plastic is completely crystalline and that the crystalline forms
are more accurately described as semi-crystalline. The term
semi-crystalline is well known in the prior art and is meant to
describe a polymer that exhibits X-ray patterns that have sharp
features of crystalline regions and diffuse features characteristic
of amorphous regions. It is also well known in the art that
semi-crystalline should be distinguished from the pure crystalline
and amorphous states.
[0047] The polyamides which could be modified or unmodified that
are suitable for this invention can be described as comprising the
repeating unit amino caproic acid or A-D, wherein A is the residue
of a dicarboxylic acid comprising adipic acid, isophthalic acid,
terephthalic acid, 1,4-cyclohexanedicarboxylic acid, resorcinol
dicarboxylic acid, or naphthalenedicarboxylic acid, or a mixture
thereof, and D is a residue of a diamine comprising m-xylylene
diamine, p-xylylene diamine, hexamethylene diamine, ethylene
diamine, or 1,4 cyclohexanedimethylamine, or a mixture thereof.
[0048] These polyamides can range in number average molecular
weight from 2000 to 60,000 as measured by end-group titration.
These polyamides can also be described as the reaction product of
amino caproic acid with itself and/or the reaction product of a
residue of dicarboxylic acid comprising adipic acid, isophthalic
acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid,
resorcinol dicarboxylic acid, or naphthalenedicarboxylic acid, or a
mixture thereof with a residue of a diamine comprising m-xylylene
diamine, p-xylylene diamine, hexamethylene diamine, ethylene
diamine, or 1,4 cyclohexanedimethylamine, or a mixture thereof.
[0049] Those skilled in the art will recognize many of the
combinations as well known commercially available polyamides. The
reaction product of the residue of sebacic acid with hexamethylene
diamine is nylon 6, 10 and the reaction product of the residue of
adipic acid and hexamethylene diamine is nylon 6, 6. Nylon 6, 12 is
another nylon which benefits from the invention. Nylon 6 is a
special type of polyamide which is made by the opening of
caprolactam and then polymerizing the resulting amino caproic acid
which has a formula of H.sub.2N--(CH.sub.2).sub.5--COOH. One useful
polyamide is the reaction product of the residues of adipic acid
and m-xylylene diamine, known as poly-m-xylylene adipamide. This
product is commercially known as MXD6 or nylon MXD6 and can be
purchased from Mitsubishi Gas Chemical Company, Japan.
[0050] The modified polyamide would have a 0.01-15 mole percent of
the respective acid or diamine replaced with an interfacial tension
modifying compound such as sulfonated isophthalic acid. U.S. Pat.
No. 3,328,484 the teachings of which are incorporated by reference,
herein, describes such modified co-polyamides.
[0051] The preferred amount of polyamide is between 1 and 15 parts
per 100 parts of the polyester plus polyamide, preferably between 3
and 8 parts per 100 parts of the polyester plus polyamide, with the
most utility occurring between 4 and 7 parts of polyamide per 100
parts of polyester plus polyamide.
[0052] The preferred composition contains at least one interfacial
tension reducing agent which reduces the interfacial tension
between the polyester and the polyamide. In order to understand the
role of the interfacial tension reducing agent, it is necessary to
understand the role of the interfacial tension reducing agent plays
in the polyester-polyamide dispersion.
[0053] The polyester-polyamide dispersion can be described as a
multi-phase system consisting of a dispersed polymer and a matrix
phase. The dispersed polymer is discontinuous, with many small
particles scattered throughout the matrix polymer. The matrix
polymer is a continuous phase, where the polymer is not broken up
into discrete units, but is constantly in contact with itself. In
other words, there is usually only one matrix phase, but many
particles of the dispersed polymer. Technically, therefore, the
dispersed component may be considered many phases, as each particle
is its own phase. However, in that description, each particle has
the same equilibrium properties of the other particle. For the
purposes of this invention, the term dispersed phase or dispersed
polymer refers to the totality of discrete particles of the
discontinuous component present in the continuous phase.
[0054] It is believed that the polyamide is dispersed into the
polyester matrix forming discrete particles in the polyester. And,
while not to be bound by any theory, it is also believed that the
inferior dispersion of polyester/polyamide system is due to the
high interfacial tension (IFT) existing between the two
polymers.
[0055] For a closed system (see An Introduction to the Principles
of Surface Chemistry, Aveyard, R. and Haydon, D. A. 1973), the
differential expression for the internal energy U of the system has
been described as
dU=dQ+dW
where dQ is the heat taken up by the system and dW is the change in
work. The relation is then isolated for dW which reduces the
equation to
dW=-pdV+.gamma.dA
where dV is the change in volume and .gamma. is the interfacial
tension, and dA is the change in interfacial area (the area of the
interface between the two components). In the liquid-liquid system,
such as exists with the mixture of melted polyester/polyamide,
there is no volume change (dV=0), and the equation reduces to the
change in work as a function of the interfacial tension and the
change in interfacial area.
dW=.gamma.dA
[0056] The lower the interfacial tension, therefore, the higher the
area of contact between the two materials. A higher area of
interfacial contact for a given amount of material is only achieved
by creating smaller particles of the dispersed material into the
matrix material. A higher interfacial contact area requires a
smaller diameter, and consequently a greater number of particles.
The effectiveness of the interfacial tension reducing agent can be
directly established by the average particle size. The lower the
average dispersed particle size, the lower the interfacial tension
and the more effective the interfacial tension reducing agent.
[0057] This increase in surface area and corresponding decrease in
domain size and subsequent increase in the number of domains is
believed to increase the barrier, improve the aesthetics (reduced
haze) and also increase the amount of oxygen scavenging ability
when the polyamide has been activated to react with oxygen. This
activation is often done by exposing the polyamide to a transition
metal catalyst, usually in its positive valence state.
[0058] Other ways to increase the surface area exist. These include
increasing the amount of shear during the melt blending process,
varying the viscosity ratios, attempting to cross link or graft the
materials. While the inventors are familiar with all of the above
techniques, no technique has been as successful as directly
modifying at least one of the polymers to reduce the interfacial
tension between the two polymers.
[0059] The interfacial tension between two polymers in their liquid
state is difficult to determine due to the high temperatures
involved. One technique is to use a spin tensiometer. However, in
the absence of sophisticated equipment it is much easier to make
two separate polymer dispersions, one modified, the other
unmodified, using the same amount of work (torque, screw design,
temperatures) and compare the difference in average particle size
of the dispersed material.
[0060] The immediate effect of the reduction in interfacial tension
can be seen by reduced haze in the stretched article or by
comparing the average polyamide particle size of an unmodified
polyester-polyamide dispersion with a modified polyester-polyamide
system. This test easily determines whether the interfacial tension
has been reduced.
[0061] The composition should have a sufficient amount of
interfacial tension reducing agent added either separately or
reacted into the backbone of the polyester, polyamide or both. A
combination of the separate interfacial tension reducing agent and
a polyester or polyamide, or both being modified with an
interfacial tension reducing agent are contemplated. The
interfacial tension reducing agents need not be the same.
[0062] Preferably, the interfacial tension reducing agent is a
co-monomer reacted with the polymer. To be a co-monomer, the
interfacial tension reducing agent is functionalized with at least
one end group which allows the interfacial tension reducing agent
to react with at least one of the other polymers or polymer
co-monomers in the composition.
[0063] In the case of polyesters, these can be the polar
co-monomers used to create PET ionomers. In the case of polyamides,
the interfacial tension reducing agent can be the polar co-monomers
used to create polyamide ionomers. Examples of these co-monomers
are the monovalent and/or divalent salt of the respective sulfonate
described in U.S. Pat. No. 6,500,895 (B1) the teachings of which
are incorporated herein. Also included are the monovalent and
bivalent metal salts described in the following formulas found in
Japanese Patent Application 0 3281246 A, the teachings of which are
incorporated herein.
[0064] In general, the interfacial tension reducing agent exists in
functionalized form of the form X--R, where X is an alcohol,
carboxylic acid or epoxy, most preferably a dicarboxylic acid or
diol and R is R is --SO.sub.3Li, --COOLi, --OLi,
--PO.sub.3(Li).sub.2, and X--R is copolymerized into the polyester
polymer to modify the interfacial tension. The amount of X--R
needed will exceed 0.01 mole percent with respect to the total
number of respective dicarboxylic acid or diol moles in the
polymer. It is possible for X--R to include both a diol or
dicarboxylic acid. In that case, the mole percent is based upon the
total number of moles of respective diols, dicarboxylic acids, or
polymer repeating units.
[0065] The functionalized interfacial tension reducing agent may
contain 2 or more R groups. R may also be combined directly to the
aromatic ring of X, which could be a diol, a dicarboxylic acid, or
a side chain such as a methylene group.
##STR00003##
[0066] Where R is --SO.sub.3Li, --COOLi, --OLi,
--PO.sub.3(Li).sub.2
[0067] Here, the dicarboxylic acids represented by X may be in the
ortho, meta, or para structures. They comprise for instance
aromatic dicarboxylic acids such as terephthalic acid, isophthalic
acid, orthophthalic acid, naphthalene dicarboxylic acid,
diphenylether dicarboxylic acid, diphenyl-4,4-dicarboxylic acid
etc.
[0068] Aliphatic dicarboxylic acids such as oxalic acid, malonic
acid succinic acid, glutaric acid, adipic acid, pimelic acid,
suberic acid, azelaic acid, sebacic acid, etc. Cycloaliphatic
dicarboxylic acids such as cyclohexanedicarboxylic acid and one or
more species of these can be used. Specifically contemplated are
mixtures of the dicarboxylic acids as well.
[0069] X can also represent an alcohol, preferably a diol of the
structure:
##STR00004##
[0070] Where R is --SO.sub.3Li, --COOLi, --OLi,
--PO.sub.3(Lli).sub.2
[0071] The diols represented by X may be for instance aliphatic
glycols such as ethylene glycol, 1,3 propanediol, 1,4-butanediol,
1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, diethylene glycol,
trimethylene glycol and cycloaliphatic diols such as
cycloheaxanediol, cycloheaxanedimethanol and one or more species in
combination can be used. Among these, ethylene glycol, diethylene
glycol and cyclohexanediol are preferred.
[0072] Other functionalized interfacial tension reducing agents
which can be used to decrease the interfacial tension include
hydroxyl terminated polyethers, such as polyethylene glycol
(Carbowax) and cyclic amides such as ethoxylated dimethyl
hydantoin. In addition, polyesters can be reacted with epoxy
terminated compounds, including epoxy terminated polyethers, to
produce a polyether side chain attached to the polymer.
[0073] As used in this specification, the term interfacial tension
reducing agent refers to the agent as it is exists without being
incorporated into the backbone of a polymer and as it has been
incorporated into the backbone of the polymer,
[0074] Of the metal salts, it has been found that lithium, a
monovalent metal, performs much better than sodium. In fact, the
lithium salt imparts very little, if any, haze in the polyester
matrix when blended with MXD6 and produces a dispersion with
average domains lower than levels previously measured. Unlike other
systems presented in the art, the lithium salt exhibits a very
little increase in haze with increased levels of MXD6, and in fact
at some levels no increase in haze was measured. Also, lithium
shows dramatically lower yellow colour when melt blended with the
polyamide thus eliminating the need for cobalt salt or zinc as
described in WO 2005/023530 A1, the teachings of which are
incorporated herein. In fact, as described below, the lithium
sulfoisophthalate without a cobalt compound has better colour than
the sodium isophthalate blended with the same amount of MXD6 in the
presence of a cobalt salt.
[0075] Of the salt forms, the di-carboxylic acid, di-ester, or
pre-reacted low molecular weight oligomers and other building
blocks such as the bis-hydroxyethyl ester of lithium
sulfoisophthalate are preferred. It is also possible that the
interfacial tension reducing agent, in this case the lithium
sulfonate, occur in the diol form as well. Possible alternatives
are isethionic acid. It has even been proposed to place the
sulfonate at the end of the polyester molecule. This could be
accomplished by reacting or copolymerizing the polyester with the
sulfonated salt of benzoic acid or other monofunctional species
either in the melt reactor or in an extruder. In this instance the
interfacial tension reducing agent reacted with the backbone of the
polymer would be lithium sulfobenzoate. One way to describe the
various lithium salts is to use the term functionalized lithium
sulfonate to describe a compound of the form R--SO.sub.3Li, where R
is an aliphatic, aromatic, or cyclic compound with at least one
functional group that allows the functionalized lithium salt to
react with the polyester or polyamide, or their respective monomers
or oligomers. Functionalized lithium sulfonates included in this
invention are the lithium salts of sulfonated comonomers, including
aliphatic and aromatic alcohols, carboxylic acids, diols,
dicarboxylic acids, and multifunctional alcohols, carboxylic acids,
amines and diamines. Lithium sulfoisophthalic acid is a
functionalized lithium sulfonate as is lithium sulfobenzoic
acid.
[0076] In order to be reacted into either polymer, the modifying
agent must have at least one functional group. These functional
groups are carboxylic acid (--COOH), alcohol (--OH), the ester of
the carboxylic acid, epoxy termination, the diamine, or amine end
groups.
[0077] Because a high I.V. polyester would have two functional end
groups per polymer chain, a high I.V. polyester containing lithium
sulfoisophthalate in its backbone is an interfacial reducing agent
when blended with a polyamide and polyester without lithium
sulfoisophthalate. Should the high I.V. polyester have both polymer
chain ends terminated with non-functional groups, then the
polyester would be considered a non-functionalized or
non-functional interfacial tension reducing agent.
[0078] The non-functionalized interfacial tension reducing agents
are those compounds which contain a polar group, in particular the
lithium salt, but do not have any functional end groups which allow
the interfacial tension reducing agent to react with the polyester
or polyamide. The lithium salt of sulfonated polystyrene is an
example.
[0079] As taught below, the polymer is preferably modified with the
interfacial tension reducing agent. This modification is done by
copolymerizing the interfacial tension reducing agent into the
polymer chain. As taught in Example 6, the compartmentalized
pellet, the interfacial tension reducing agent can be incorporated
into the polyester and then blended with an unmodified polyester
and polyamide to produce the composition.
[0080] Levels of the interfacial tension reducing agent needed to
decrease the interfacial tension range from 0.01 mole percent to 15
mole percent with respect to the total number of moles of the
respective acid or diol moiety. For example, a typical homopolymer
polyester has 100 mole percent terephthalic acid and 100 mole
percent ethylene glycol. A polyester containing 5 mole percent of
the ionic dicarboxylic acid co-monomer would be derived from 95
moles of terephthalic acid, 5 moles of lithium sulfonate (such as
lithium sulfoisophthalic acid) and 100 moles of ethylene glycol.
Similarly, it may be advantageous to add another comonomer such as
isophthalic acid. For example, a 2 mole percent isophthalate
polymer would contain 93 moles terephthalic acid, 2 moles of
isophthalic acid, 5 moles of functionalized lithium sulfonate and
100 moles ethylene glycol to make 100 moles of polymer repeat
unit.
[0081] In the three component blend system, the moles of acid are
the moles of acid in the modified polymer plus the moles of acid in
the unmodified polymer.
[0082] It is also well known that di-ethylene glycol is formed
in-situ in the manufacture of polyester and about 2-3 percent of
the total moles of glycol will be diethylene glycol. Therefore, the
composition is 97 mole percent ethylene glycol and 3 mole percent
di-ethylene glycol.
[0083] The amount of interfacial tension reducing agent is
determined empirically. Generally, a small amount is needed and
approaches a critical amount beyond which additional amounts have
no effect. In the surface science field, this amount is referred to
as the Critical Micelle Concentration (CMC). As seen in the
examples, a small amount of sulfonated material has a significant
effect, but at a certain point, around 0.4 or 0.5 mole percent in
the case of lithium sulfoisophthalic acid, no increase in
effectiveness is seen. Levels above the CMC would be the functional
equivalent of the CMC as it pertains to reducing the interfacial
tension of the polyester-polyamide. Unlike other salts, the lithium
salt, in particular shows an optimum level at approximately between
0.3 and 1.0 moles per 100 moles polymer repeat unit. This can also
be expressed as 0.4 to 1.0 mole percent of the acid or glycol
moiety to which the lithium salt is attached.
[0084] Examples of modified polyesters employed in the present
invention are those prepared by virtually any polycondensation
polymerization procedure. The traditional techniques can be divided
into the ester, acid, and modified processes. In the ester process,
the dimethyl ester of the carboxylic acid or acids is reacted with
the glycol or glycols in the presence of heat and the methanol
removed yielding the bis-hydroxyethyl ester of the acids. The
bis-hydroxyethyl ester is then polymerized in its liquid form by
subjecting the material to vacuum and heat to remove the glycols
and increase the molecular weight. A typical process for the object
polymer would start with these ratios: 98 moles of dimethyl
terephthalate, 2 moles of dimethyl sodium salt of sulfoisophthalate
and 220 moles of glycol, typically ethylene glycol. Of the 220
moles of glycol, 120 are excess which are removed during
processing. It should be noted that it is possible to obtain the
sulfonated co-monomer in either its bis-(hydroxyethyl) or dimethyl
ester form.
[0085] For clarification, the phrase copolymerized with at least X
percent of a specific acid means that the compound is considered as
part of the acid group of the polymer, such as terephthalic or
isophthalic acid. It provides the reference to determine how many
moles of the compound to use. The phrase does not mean that the
compound must be added to the process as an acid. For example,
lithium sulfoisophthalic acid could be copolymerized into
polyethylene terephthalate as the acid, with two carboxylic end
groups, the dimethyl ester of the carboxylic acid, or the
bishydroxy ester of the dimethyl ester or even very low molecular
weight oligomers of a glycol acid polymer where the acid moieties
are at least in part, the sulfoisophthalate salt.
[0086] The phrase "copolymerized salt of the acid" should not limit
the claim to only using the acid form, but should be read to mean
the compound is one of the acid groups in the polymer.
[0087] The phrase "copolymerized with" means that the compound has
been chemically reacted with the polymer, such as in the polymer
chain or as a pendant group. For example, a polyester copolymerized
with lithium sulfoisophthalate, or modified by copolymerizing at
least 0.01 mole percent lithium sulfoisophthalic acid into the
polyester, means that the lithium sulfoisophthalate is bonded to
the polymer, including bound into the polymer chain, with at least
one chemical bond. The phrases are indifferent to how the material
is incorporated into the polymer. A polyester copolymerized with
lithium sulfoisophthalate, or modified by copolymerizing at least
0.01 mole percent lithium sulfoisophthalate into polyester refers
to a polyester containing the lithium sulfoisophthalate whether
that lithium sulfoisophthalate was incorporated using but not to
limited to lithium sulfoisophthalic acid, lithium sulfobenzoic
acid, the dimethyl ester of lithium sulfoisophthalic acid, the
methyl ester of lithium sulfobenzoic acid, the di-alcohol of
lithium sulfoisophthalate, the lithium sulfohydroxy benzene, the
lithium salt of hydroxy benzene sulfonic acid, or oligomers or
polymers containing the lithium sulfoisophthalate.
[0088] The phrases "and derivatives" and "and its derivatives"
refer to the various functionalized forms of the interfacial
reducing agent which can be copolymerized into the polymer. For
example, lithium sulfoisophthalate "and its derivatives" refers
collectively and is not limited to lithium sulfoisophthalic acid,
the dimethyl ester of lithium sulfoisophthalic acid, the
bis-hydroxyethyl ester of lithium sulfoisophthalic acid, the
di-alcohol of lithium sulfoisophthalate, low molecular weight
oligomers, and high I.V. polymers containing lithium
sulfoisophthalate in the polymer chain.
[0089] The same nomenclature applies to the glycol or alcohol.
[0090] In the acid process, the starting materials are the
di-carboxylic acids, with water being the primary by-product. The
charge ratio in a typical acid process is 98 moles terephthalic
acid, 2 moles of a metal salt of sulfoisophthalic acid (e.g.
lithium sulfoisophthalic acid--LiSIPA), and 120 moles of glycols,
typical ethylene glycol. After reaction of the glycols with the
acids, the material is subjected to the same polymerization process
conditions as the ester process.
[0091] The modified processes are variations of either process:
combining the intermediary product at certain steps. One example is
to pre-polymerize the raw materials without the interfacial tension
reducing agent to a low molecular weight. In the case of the
examples described below, the molecular weight of the low molecular
weight polyester was typically in the range 0.096 to 0.103 dl/g
having a carboxyl end group number ranging from 586 to 1740
equivalents per 1,000,000 grams of polymer. Obviously, the
molecular weight could be easily varied without undue
experimentation as it has been for many years by those of ordinary
skill in the art when optimizing the addition point for their
additives.
[0092] Another example of a variation of is to use the acid process
with just terephthalic acid to produce its low molecular weight
intermediate and the ester process used to produce the
bis-hydroxyethyl ester of the homopolymer sulfonated polyester.
These two intermediates are then combined and polymerized to a
copolymer. Another variation is to add the finished modified
polymer to the melt reactor and let the melt process depolymerise
the modified polymer and then form a copolymer. While the three
component system, of PET, PET--ionomer, and polyamide is not nearly
as effective as the random copolymer the three component system is
considered a part of this invention. The copolymer is a preferred
embodiment of the invention.
[0093] Another technique for manufacturing the modified polymer is
to completely trans-esterify a modified polyester with a large
amount of interfacial tension reducing moieties into a unmodified
polyester to create a randomly structured modified copolymer. This
can be done using traditional techniques using a long residence
time and/or high temperature extrusion.
[0094] This same effect can be accomplished using the
multi-compartment pellet technique as described in WO 2005/110694
titled "Compartmentalized Resin Pellets", the teachings of which
are incorporated herein. This would involve using the core-sheath
design wherein the core is the hydrophilic polymer and the sheath
is the unmodified, more hydrophobic, polyester. The products are
then combined into the composition during melt fabrication of the
article. This was the procedure used in Example 6.
[0095] WO 2005/110694 titled "Compartmentalized Resin Pellets", the
teachings of which are incorporated herein, describes the zoned or
compartmentalized pellet as the preferred structure for the
polyamide/polyester pellet. The preferred pellet structure is
either a polyamide core with a sheath of the reduced interfacial
tension modified polyester, or a modified polyamide core with a
sheath of polyester, or both the polyamide and polyester have been
modified. It is recognized that the core or sheath could contain
some amount of the other ingredient as well.
[0096] As taught in the examples of the U.S. patent application
Ser. No. 11/130,961, this pellet can then be solid phased
polymerized without the attendant colour shift. The polyamide is
then melt blended with the polyester when the article is made, thus
taking advantage of the invention in the article. In fact, the
lowest average dispersed particle size of 57 nm was obtained using
a compartmentalized pellet structure.
[0097] Other methods of incorporating similar co-monomers are
listed in U.S. Pat. Nos. 3,936,389, 3,899,470, 5,178,950, and
United States Statutory Invention Registration H1760, the teachings
of all of which are incorporated herein.
[0098] The polyester and polyamide are melt blended and then
injection molded, pelletized or formed into a film. Analysis of the
dispersion at this point shows the polyamide dispersed into the
polyester matrix phase. There are many techniques to analyse the
dispersion properties.
[0099] The domain size of the dispersed polymer is measured in the
unstretched area. The unstretched area can exist in an unstretched
area of the wall, such as the thread, neck, and sealing portions or
it can be measured on the article before stretching. Measuring the
size of the dispersed particles in the article before stretching
the article yields the same value as measuring the size in the
unstretched portion after stretching. Therefore, if the stretched
wall does not have an unstretched portion, the size of the
dispersed particles prior to stretching can be used. In many
instances, the measurement was made on the preform or parison prior
to stretching.
[0100] In one example, a fractured sample is treated with cold
formic acid to remove the polyamide from the PET and the sample
subjected to scanning electron microscopy (SEM).
[0101] Based upon contrast, the domains where the polyamide once
was can be readily determined and measured. (See FIGS. 1 and
3).
[0102] Since the molded sample is unstretched, the particles are
present as spheres. The SEM picture can be analyzed either manually
or with various computer programs. The average particle size can
then be easily calculated from the picture. The average can be
determined by summing the diameters of all the particles in the
picture and dividing by the number of particles in the picture.
Alternatively, a statistically significant sample size could be
used instead of all the domains in the populations.
[0103] Similarly, a distribution analysis can be done (FIGS. 2 and
4), by making a histogram of the number of particles corresponding
to a given diameter. The data can also be normalized to a make a
particle density function. Such normalization would be done by
taking the number of particles per area observed and then
multiplying or dividing by the factor desired to normalize the
results.
[0104] For example, if one wanted to normalize the observation of
250 particles per 100 square nano-meters to the number of particles
for 1000 square nano-meters, one would multiply 250 by 10, which is
the factor of 1000 square nano-meters divided by 100 square
nano-meters.
[0105] The interfacial tension between two polymers in their liquid
state is difficult to determine due to the high temperatures
involved. One technique is to use a spin tensiometer. However, in
the absence of sophisticated equipment it is much easier to make
two separate polymer dispersions, one modified, the other
unmodified, using the same amount of work (torque, screw design,
temperatures) and compare the difference in average particle size
of the dispersed material.
[0106] The immediate effect of the reduction in interfacial tension
can be seen by comparing the average polyamide particle size of an
unmodified polyester-polyamide dispersion with a modified
polyester-polyamide system. This test easily determines whether the
interfacial tension has been reduced.
[0107] The viscosity difference between the modified and unmodified
materials has not been found to be a significant factor. However,
this difference can be accounted for by making sure that the
modified and unmodified polyester have the same melt viscosities.
Given the dramatic shift in particle size, the effectiveness of a
particular lithium compound to reduce the interfacial tension will
be readily determined.
[0108] Regardless of whether the interfacial tension has been
reduced, the molded part is generally not hazy. However, once the
article is stretched, the spherical domains will elongate, become
ellipsoidal, and at least one diameter of the ellipse will become
large enough to interfere with the visible light. Mathematically
expressed, one of the diameters of the ellipse will be greater than
approximately 400 nm but less than approximately 720 nm;
corresponding to the wavelength range of visible light.
[0109] Stretching occurs when the molded article, film or fiber is
subjected to a force and pulled or elongated. Generally, the
article is heated to a temperature below the melting point of the
matrix polymer and then pulled in one or two, or in the case of a
bubble, three directions. A fiber or a type of film is an example
of uni-axial stretching. A fiber is pulled in the direction of its
length to build strength. A film will be placed in a machine which
has a sequence of gears that move progressively faster, thus
stretching the film between each gear or other attaching
mechanism.
[0110] In the case of bottles, biaxially oriented films, or blown
films, the article is pulled in at least two directions. In the
case of a blown bottle or reheat blow or reheat stretch blow
bottle, pressure such as compressed air is introduced into the
article, also known as a preform or parison. The air will then
expand the article to take on the shape of the blow mold
surrounding the article. Depending upon the design of the article
and the mold, the article will have varying degrees of stretch in
the two directions.
[0111] In films, there are some techniques which simultaneously
stretch the article in the machine and transverse directions.
However, in industrial practice it is more common to stretch the
film first one way, then the other.
[0112] It is this stretched article where the object of this
invention has utility. By lowering the interfacial tension so that
the particles of the dispersed polymer are extremely small, the
article can be stretched to higher levels, and still maintain a
reduced haze appearance because many of the stretched particles are
still below 400 nm (the wavelength of light).
[0113] The amount of stretch, also known as draw, is described as
the stretch ratio. In the case of a uniaxial stretch, the ratio is
the length of the stretched article divided by the length of the
unstretched article, where both lengths are measured in the
direction of stretch. A 2 inch specimen stretched to 8 inches would
have a stretch ratio of 4.
[0114] For a bi-axially stretched article, the ratio is often
described as the stretch ratio of direction one multiplied by the
stretch ratio of direction two. Thus an article stretched 3 times
in one direction and 3 times in the other direction (usually
perpendicular to the first direction) has a stretch ratio of
3.times.3 or 9. However, an article with a stretch ratio of 2 in
one direction and 4.5 in the perpendicular direction also has a
stretch ratio of 9.
[0115] Another technique to measure stretch ratio, draw ratio, or
drawdown ratio is to trace or scribe a circle onto a plane of the
article, measure the area of the circle, stretch the article, then
measure the new area circumscribed by the enlarged circumference of
the old circle. The stretch ratio is then the area of the new
stretched circle divided by the area of the unstretched old circle.
That stretch ratio can also be determined by using the ratio of the
diameters or radii.
[0116] In the case of the three dimensional stretch, the change in
volume or area of a sphere could be used to approximate the stretch
ratio.
[0117] Regardless of the technique used to measure the stretch
ratio, stretching the molded article causes the dispersed component
to stretch as well. Even if the dispersed component does not
stretch, the domain surrounding the dispersed component will
elongate. If the elongation of the domain whether it is completely
filled with the dispersed material or not is greater than
approximately 400 nm but less that about 720 nm, then the stretched
article will have an increased Hunter Haze value, where haze is the
measure of the amount of light deviation from the direction of
transmittance by at least 2.5 degrees.
[0118] If enough of the particles have diameters between 400 and
720 nanometers, then the haze will be detectable by the human eye.
As discussed below, the standard deviation becomes equally as
important as the average domain size.
[0119] It is apparent that the diameter of the dispersed particle
be small enough so that when stretched, the longest dimension of
the dispersed particle and the domain encompassing the particle be
less than 400 nm. For an article which stretches 3 in one direction
and 3 in another, the maximum particle size in the unstretched
article should be 400 nm divided by 3, or 133 nm. For the article
stretched 2.times.4.5, the particle size should be less than or
equal to 400 divided by 4.5, or 89 nm. The target average diameter
of the dispersed particles in the unstretched matrix phase could
then be easily expressed as 400 divided by longest dimension of
stretch. For example, if the final stretch dimension was 7.times.2,
then the goal would be to modify the interfacial tension so that
the average particle diameter in the unstretched article would be
400 divided by 7, or 57 nm. It is not only important that the
average diameter be below a certain size, but that the distribution
be narrow enough to reduce the number of dispersed particles which
will exist between 400-700 nm after stretching. While reducing the
average domain size is important to minimize the number of domains
in the visible region, narrowing the wide distribution is also
important.
[0120] Because the particles occur in a distribution, the average
particle diameter is used. Given the ranges of stretch ratios, the
average diameter of the dispersed particles in the unstretched
container should be less than 125 nm, more preferably less than 100
nm, even more preferably less than 80 nm. For articles to be
stretched into high stretch, high strength materials, average
particle diameters of less than 90 nm should be used, with particle
size less than 70 nm preferred, and particle size less then 60 nm
even more preferred, with the best appearance occurring with an
average particle diameter less than 50 nm.
[0121] What has been discovered is that when the lithium salt is
used, the domains do not follow the expected behaviour. Examination
of series 9 demonstrates this. The percent stretch which is defined
earlier as the stretch ratio of the polyamide domains divided by
the stretch ratio of the polyester matrix in the same direction can
be determined as follows:
[0122] The domain stretch ratio, or stretch ratio of the domain, is
the average length of the domains after stretching in the measured
direction of stretch divided by the average length of the domains
prior to stretching. Since the unstretched domain is spherical, any
radius or direction can be used.
[0123] The stretch ratio of the polyester or matrix is the change
in amount the polyester has been stretched coincident with the
approximate area where the domain is measured. The easiest way to
measure the stretch ratio of the polyester for the percent stretch
calculation is to place a line of known length on the article in
the approximate area where the stretch ratio where the domains were
measured. The article is then stretched, presumably in the
direction of the line and the new length of line is then measured.
The stretch ratio of the polyester is the length of the stretched
line divided by the length of the line before stretching. Of
course, the measurements must be in same direction of stretch.
[0124] Theoretically the percent stretch should be 100% (1.0), in
that the domains stretch the same amount as the polyester. However,
when the lithium salt is used, the percent stretch is often less
than 75%, with many observations less than 50%, and in one instance
less than 30%. It is believed that the lower the percent stretch,
the better. As shown in Series 9, the percent of stretch of the
traditional sodium sulfoisophthalate interfacial tension reducing
agent was 0.91 (91%) while the percent stretch using the lithium
salt was 0.71 (71%).
[0125] The thickness of the wall of the container of this invention
can range from 0.01 mm in the case of a film to the thickness of a
preform which is usually less than 6.5 mm. In the case of the
bottle, the stretched wall usually has a thickness of 0.2 to 0.9
mm. A container wall can also consist of layers of varying
thickness, the thickness of the layers is usually between 0.02 and
0.2 mm. A monolayer, which is the preferred wall of the container,
consists of one layer. A monolayer of the polyester-polyamide
dispersion would consist of one layer. This does not mean that
monolayer could not have a label wrapped around it. It would still
be a mono-layer bottle. In contrast, the multilayer bottle would
contain a least one layer of the composition.
[0126] References to the container sidewall and container wall of
this invention also refer to the lid, bottom and top sides of the
container, and a film that may be wrapped around the product such
as meat wraps. The container wall may be completely stretched or
have stretched and unstretched portions. For example, a reheat
blown or injection stretch blown bottle is a container with a
highly stretched portion in the middle of the wall, with the wall
having successfully lower stretch until the wall is unstretched in
the neck and thread areas. For clarity, the thread, neck, and
sealing portions where the cap is applied are considered part of
the wall of a container. In a reheat blown bottle the threads and
neck area are generally unstretched. A preform or parison is also a
container with at least one wall. Although an intermediate product,
the preform is capable of containing a packaged content as it is
closed on one end and open on the other.
[0127] A water activated oxygen scavenger may also be compounded
into the composition. These oxygen scavenging compositions are well
known in the literature and usually comprise oxidizable metal
particles, particularly elemental iron or aluminum, and an
activating component such as a water soluble salt, electrolytic,
acidic, non-electrolytic/acidic or water hydrolysable Lewis acids.
The activating component can either be blended or deposited upon
the oxidizable metal particles. The polymer composition may also
contain polyamide, in particular, poly-m-xylylene adipamide (MXD6).
If one wants to just increase the passive barrier, the polyamide
may be blended without the oxygen scavenging composition.
[0128] The oxygen-scavenging compositions can be added directly to
the polyester or polyamide, whether modified or not, at any step
where one of the polymer streams is in its liquid state such as
melt polymerization, pelletizing, separate compounding or
melt-fabrication operation, such as the extrusion section thereof,
after which the molten mixture can be advanced directly to the
article-fabrication line.
[0129] Typical values of the oxidizable metal will be from 300 to
3000 ppm by weight of the polymers in the composition.
[0130] The colour and brightness of a thermoplastic article can be
observed visually, and can also be quantitatively determined by a
HunterLab ColorQuest Spectrometer. This instrument uses the 1976
CIE, a*, b* and L* designation of colour and brightness. An a*
coordinate defines a colour axis wherein plus values are toward the
red end of the colour spectrum and minus values are toward the
green end.
[0131] The b* coordinate defines a second colour axis, wherein plus
values are toward the yellow end of the visible spectra and minus
values are toward the blue end of the visible spectra.
[0132] Higher L* values indicate enhanced brightness of the
material.
[0133] The following examples are provided for purpose of
illustrating the manufacture of the composition and the composition
properties and are not intended to limit the scope of the
invention.
[0134] The polyester polymers used in this invention were made via
extrusion and melt polymerization.
Example 1
Manufacture of Interfacially Modified Sodium Sulfonate Polymer Via
Melt Polymerization
[0135] A two vessel reactor train was used to manufacture the
intermediate molecular weight polymer at 0.5 and 2.0 mole percent
sodium sulfoisophthalate. The following example demonstrates how
the polymer containing 0.5 mole percent sodium isophthalate was
made. The same procedure was used for the 2.0 mole percent and
higher concentrations used in the extrusion manufacture
technique.
[0136] 8933.0 gms of dimethyl terephthalate, 69.7 gms di-methyl
sodium sulfoisophthalate, 7175 gms ethylene glycol and 261 g
manganese acetate were added to the first vessel. The ingredients
were heated to 214.degree. C. at a rate of 0.4.degree. C. per
minutes and the methanol removed. After the removal of 3660 ml of
methanol, the ingredients were transferred to the second vessel and
the batch temperature increased to 226.degree. C. 67 gms of
phosphite stabilizer were added and mixed for 5 minutes. 140 gms of
isophthalic acid were then added to the batch. After stirring for
15 minutes, 77 gms of Cobalt Acetate, and 173 gms of glycolated
antimony oxide were added and the vessel placed under a vacuum of
0.13 millibar. The batch was continually agitated and the
temperature increased to 256.degree. C. The resulting polymer was
discharged and pelletized after reaching the desired intrinsic
viscosity. The polymer produced in this particular batch had an
I.V. of 0.53 dl/gm, 14 carboxyl end group number (equivalent
milligrams per gram of polymer) and a melt point of 246.9.degree.
C.
[0137] The molecular weight of the material was increased by solid
phase polymerizing several melt batches in a rotating vacuum
vessel. The solid phase polymerization was accomplished by placing
5 melt batches of the same molecular constituency into the vessel.
The vessel pressure was reduced to 0.13 millibar, the temperature
set at 225.degree. C., and the vessel slowly rotated so the
material tumbled on itself. After 12 hours of tumbling, the
temperature was increased to 230.degree. C. for 6 hours, and then
increased to 235.degree. C. for 2 hours. The pellets were then
cooled and discharged. The final Intrinsic Viscosity was 0.82
dl/gm.
[0138] The following batches were made according to the process of
Example I and used in the experiments.
TABLE-US-00001 TABLE I Properties of Melt Produced Material Mole %
of Acid Moieties Melt Intrinsic NaSIPA* IPA* PTA* Point .degree. C.
Viscosity 0.5 1.79 97.71 247 0.82 0.5 1.79 97.71 254 0.83 2.0 2.45
95.55 243 0.82 Note: 19 gms of sodium acetate were added to the
melt reactions yielding the higher melt point. The sodium acetate
suppresses the formation of di-ethylene glycol as reflected in the
increased melt point. *Although the abbreviation is to the Acid, it
refers to the acid moiety, for instance, NaSIPA refers to the
sodium sulfoisophthalic acid moiety which occurs as sodium
sulfoisophthlate in the polymer chain.
Example 2
Manufacture of Modified Polymer Via Extrusion
[0139] 25 mole percent sodium sulfoisophthalate and 75 mole percent
terephthalate modified polymer was made using the melt production
techniques of Example 1. The polymer was then dried and melt
blended with a twin screw extruder into Cleartuf.RTM. 8006S
Polyester Resin from M&G Polymers, LLC, USA to achieve a
polymer with 2 mole percent SIPA. Cleartuf.RTM. 8006S Polyester
Resin is a 98.5 mole percent terephthalic acid, 1.5 mole percent
isophthalic copolymer of polyethylene terephthalate resin. The
polymer was then solid phase polymerized under vacuum to 0.862
dl/gm IV.
[0140] Other series were made in the same manner. In one case the
25% sodium sulfoisophthalate compound with 8006S to achieve a 0.5
mole percent final sodium sulfoisophthalate content and then
blended with 5% MXD6 Grade 6007 in a single screw Arburg Injection
machine with low shear conditions.
[0141] The 25% SIPA compound was blended with Turbo.RTM. II from
M&G Polymers USA, LLC, a 5% IPA, 95% TPA copolymer, to achieve
a 0.5 mole percent final sulfoisophthalate content and further
blended and 5% MXD6 Grade 6007 in a single screw Arburg Injection
machine with low shear conditions.
[0142] The 25% sulfoisophthalate compound was melt blended with
Cleartuf 8006S.RTM. polyester, 2500 ppm of Freshblend.RTM. iron
particle oxygen scavenger (Multisorb Technologies, Incorporated,
Buffalo, N.Y.) with 5% MXD6 Grade 6007 in a single screw Arburg
Injection machine with low shear conditions to achieve a 2 mole
percent final sulfoisophthalate content.
[0143] The results are presented in Table II. As can be seen,
changing the PET type or the amount of sodium sulfoisophthalate had
little affect on the domain size. Copolymerization yielded better
results in all cases.
TABLE-US-00002 TABLE II Diameter of Dispersed Particles in
Nanometers PET Control Reactive Extrusion Melt Polymerized 8006
(Example 2) Random Copolymer Diam. Std. Diam. Std. Diameter Std.
(nm) Dev. (nm) Dev. (nm) Dev. 0% SIPA, 200 76.2 5% MXD6 0.5 mole %
97 36.3 78 27.5 NaSIPA, 5% MXD6 0.5 mole % 97 34.1 74 22.7 NaSIPA
5% MXD6 2 Mole % 100 29.1 81 26.2 NaSIPA 5% MXD6 0.18 Mole % 76.93
37.28 LiSIPA 7% MXD6 0.37 Mole % 67.85 34.44 LiSIPA 7% MXD6 0.74
Mole % 69.73 31.37 LiSIPA 7% MXD6 1.11 Mole % 77.98 39.89 LiSIPA 7%
MXD6 2.0 Mole % 90.6 37.46 LiSIPA 7% MXD6 The SIPA refers again to
the acid moieties in this table.
Example 3
Lithium Sulfonate with Cobalt Salt
[0144] A copolyethylene terephthalate was made which contained
various amounts lithium sulfonate in the form of lithium
sulfoisophthalate derived from lithium sulfoisophthalic acid
(LiSIPA). The lithium sulfoisophthalate modified copolymer was
manufactured by placing 7567 gms of terephthalic acid, 157 gms of
isophthalic acid, and 2974 gms of ethylene glycol into a vessel of
pre-reacted oligomers from the previous batch. The contents were
held under 35 psig pressure at 262.degree. C. After 35 minutes,
45.4 gms of 1% lithium by weight mixture of lithium acetate in
ethylene glycol and 18.1 gms of 1% phosphorous by weight mixture of
phosphoric acid diluted in ethylene glycol was charged to the
reactor. The contents were held in this vessel under agitation for
3 hours with an oil temperature of 271.degree. C., content
temperature increasing from 248.degree. C. to 263.degree. C., and
35 psig. During the time water was removed from the vessel.
[0145] After reacting for 3 hours, a portion of the contents were
transferred to a second vessel. The amount remaining in the first
vessel was approximately the same amount as was in the vessel when
the raw materials were first charged. Once in the second vessel,
146 gms of a 5% bis-hydroxyethyl ester of lithium sulfoisophthalic
acid -95% ethylene glycol solution and 1044 gms of ethylene glycol
were added to the material transferred from the first vessel to the
second vessel. The contents of the second vessel were agitated at
atmospheric pressure and 244.degree. C. After 30 minutes another
146 gms of the bis-hydroxy ester of lithium sulfoisophthalic acid,
1044 gms of ethylene glycol were added to the second vessel. After
30 minutes of mixing, 38.6 gms of 0.47% by weight cobalt mixture of
cobalt acetate and ethylene glycol were added to the second vessel.
After 3 minutes of mixing 206 gms of a 1% antimony by weight
mixture of Antimony oxide in ethylene glycol was added to the
vessel. After 45 minutes the pressure was reduced to 100 mm Hg, and
after another 26 minutes, the pressure reduced to 1.0 mm Hg. 40
minutes later the pressure was 0.2 mm Hg and held for 20 minutes
before discharging the ingredients and pelletizing the
material.
[0146] This amorphous material was combined with several other
similarly produced batches and then solid phase polymerized in a
batch rotating vacuum vessel at 0.1 mmHg and 232.degree. C. until a
0.802 I.V. (dl/gm) was reached. The amount of lithium
sulfoisophthalate was varied for the resulting mole percentages.
The amount of lithium sulfoisophthalate reported in the tables is
based upon measuring the amount of sulfur in the polymer and not
upon the amount charged.
[0147] This material was combined with 7% by weight MXD6 nylon
(Grade 6007 from Mitsubishi Gas Chemical, Japan) and injection
molded into a preform. The preform was subjected to SEM analysis
(FIG. 3) and compared to a similar preform with unmodified
polyester (FIG. 1). As can be readily seen from the
photomicrographs, the average polyamide particle size of the
unmodified system is much larger than the particle size of the
modified system. The larger particle size of the unmodified system
indicates the higher interfacial surface tension. The analysis of
the domains (FIGS. 2 and 4) show a much broader distribution for
the unmodified system as well. The superiority of the lithium
sulfoisophthalate is also demonstrated in Table III which compares
the change in Haze per mil. The 2 mole percent lithium
sulfoisophthalate showed almost no change in haze due to increasing
nylon contents, while the 2 mole percent sodium sulfoisophthalate
still shows a significant affect.
[0148] It is noteworthy that the sodium sulfoisophthalate is not
preferred for the stretched application, despite what the prior art
claims. The prior art states that sodium sulfoisophthalate is the
preferred material for the three component system. What has been
discovered is that the sodium sulfoisophthalate gave an
unacceptable haze, regardless of whether the stretched sample
contained nylon. Unlike sodium sulfoisophthalate in these examples,
lithium sulfoisophthalate did not exhibit a relatively high
inherent haze, thus making it the best commercially acceptable
material.
[0149] The optimum concentration and superiority of the low level
of lithium sulfoisophthalate is demonstrated in Tables III and IV.
In all cases, 7% MXD6 Grade 6007 from Mistubishi Gas Chemical Co,
Japan, was melt blended with PET--lithium sulfoisophthalate and
made into parisons or preforms and subsequently blown into bottles.
The mean particle diameter in nanometers was measured using the
cold formic acid technique followed by SEM analysis as described in
the test method section.
TABLE-US-00003 TABLE III Lithium Sulfoisophthalate Characterization
0.18% 0.37% 0.5% 0.74% 1.11% 2% LiSIPA LiSIPA LiSIPA LiSIPA LiSIPA
LiSIPA 0% With With without With With With LiSIPA Cobalt Cobalt
Cobalt Cobalt Cobalt Cobalt Mean Preform Particle Diameter (nm) 200
76.93 67.85 69.73 77.98 90.60 Standard Deviation of Particle
Distribution 76.2 37.28 34.44 31.37 39.89 37.46 Average Increase in
I.V. Loss During 0.005 0.013 0.014 0.018 0.043 Injection molding
from (no SIPA) control Increase in Preform Acetaldehyde (ppm) 2.0
3.2 6.7 5.7 from Control Increase (+) or decrease (-) in b* -1.06
-0.50 -0.32 Color after 7 hrs drying in N2 bed at 150.degree. C.
vs. control with no SIPA of -0.13 b* incr/decr when converting
pellets -0.093 -4.50 +0.16 +1.69 +3.18 to bottle vs. control with
no SIPA of +4.5 Change in Hunter Haze per mil (%) -0.34 -0.39 -0.44
+0.49 -0.46 versus control with no SIPA of 0.46 Change in b* when
converting pellets 1.97 1.81 1.32 0.69 1.72 to bottle divided by
percent MXD6 6007 *The 1.11% LiSIPA was analyzed for the nylon
content and 9.5% was found as opposed to 7%. This variability
happens during the extrusion process. The others were analysed for
nylon content as well with far less deviations from the 7% target.
** Again, the LiSIPA in this table refers to the acid moieties of
lithium sulfoisophthalate.
Example 4
Comparative Examples
[0150] Tables IV and V demonstrate the ability of the polyester
polymer modified with a small amount of the co-monomer to virtually
eliminate the haze brought on by blending nylon into the polymer. 3
and 5 weight percent of two polyamides (MXD6--Grades 6001 and 6007
from Mitsubishi Gas Chemical, Japan) were melt blended into
preforms with Cleartuf.RTM. Polyester Resin 8006S and
Turbo.RTM..RTM. II (both available from M&G Polymers USA) and
the three modified materials listed in Table I. While 8006S and
Turbo.RTM. II were the controls, Turbo.RTM. II is modified with
approximately 5 mole percent isophthalic acid. 0.5 L Bottles were
blown from the preforms and haze measured on each bottle (as
opposed to the sidewall). The haze is reported Table IV and the
change in haze per mil of the stretched wall from the control with
no polyamide are reported in Table V. The change is haze per mil
from the control is calculated by subtracting the haze per mil of
the wall without the nylon from the haze per mil of the wall with
the nylon. The more effective the material in reducing the
interfacial tension, the less the change in haze as more nylon is
added. In each case, the modified polymers suppressed the haze
caused by the addition of the nylon.
[0151] The particle dispersion analysis was also conducted on the
various unstretched preforms. The results for the dispersion of 5%
nylon (MXD6 Grade 6001) are shown when added to the unmodified
materials, the reactive extrusion method and the melt
polymerization method. The results in Table IV indicate that the
reactive extrusion achieves some advantages, but that complete
randomization has not occurred. The superiority of the random
copolymer is demonstrated by the fact that in each and every case,
the diameter of the particle is significantly smaller than the
particle of the others.
TABLE-US-00004 TABLE IV Hunter Haze per mil of sidewall % MXD6, 2
mole % 0.5 mole % 0.5 mole % 0.18 mole Grade Turbo .RTM. Cleartuf
NaSIPA NaSIPA NaSIPA % LiSIPA MXD6 II 8006S (MP 243.degree. C.) (MP
247.degree. C.) (MP 254.degree. C.) w/Cobalt 0%, 6001 0.08 0.15
0.34 0.12 3%, 6001 0.36 0.19 0.29 0.26 5%, 6001 0.46 0.22 0.33 0.31
0%, 6007 0.12 0.11 0.15 0.33 3%, 6007 0.23 0.17 0.38 5% 6007 0.46
0.99 0.22 7% 6007 0.45 % MXD6, 0.37 mole % 0.50 mole % 0.74 mole %
1.11 mole % 2.00 mole % Grade LiSIPA LiSIPA LiSPA LiSIPA LiSIPA
MXD6 w/Cobalt No Cobalt w/Cobalt w/Cobalt w/Cobalt 0%, 6001 3%,
6001 5%, 6001 0%, 6007 0.25 0.18 0.50 0.80 0.40 3%, 6007 0.28 0.22
0.47 0.82 0.40 5% 6007 0.24 7% 6007 0.32 0.27 0.51 0.77 0.40 * The
nomenclature NaSIPA or LiSIPA in this table means the mole percent
of the acid moietites of lithium sulfoisophthalate. However, one
skilled in the art knows that mole percent of lithium
sulfoisophthalate is equal to the mole percent of the starting
monomer.
TABLE-US-00005 TABLE V Change in Haze per mil from 0% Nylon Control
Bottle 2 mole % 0.5 mole % 0.5 mole % 0.18 Turbo .RTM. Cleartuf
NaSIPA NaSIPA NaSIPA mole % II 8006S (MP 243.degree. C.) (MP
247.degree. C.) (MP 254.degree. C.) LiSIPA 3% 6001 0.27 0.04 -0.06
0.15 5% 6001 0.38 0.08 -0.01 0.20 3% 6007 0.23 0.03 0.05 5% 6007
0.46 0.88 0.07 7% 6007 0.12 0.50 mole % 0.37 mole % LiSIPA 0.74
mole % 1.11 mole % 2.00 mole % LiSIPA No Cobalt LiSPA LiSIPA LiSIPA
3% 6001 5% 6001 3% 6007 0.03 0.04 0.01 0.02 0.00 5% 6007 0.06 7%
6007 0.07 0.09 0.03 -0.03 0.00 * The nomenclature NaSIPA or LiSIPA
in this table means the mole percent of the acid moietites of
lithium sulfoisophthalate. However, one skilled in the art knows
that mole percent of lithium sulfoisophthalate is equal to the mole
percent of the starting monomer.
Example 5
Lithium Sulfonate without Cobalt Salt
[0152] A copolymer of polyethylene terephthalate containing 0.5
mole percent lithium sulfonate (lithium sulfoisophthalate) was made
in the same manner as Example 3, except that the cobalt acetate was
replaced with a non-cobalt colour package. The colour package was
added at the beginning of the reaction and consisted of 3.03 ppm on
the basis of the final polymer yield SB138 (Solvent Blue 138) and
1.60 ppm on the basis of the final polymer yield SV50 (Solvent
Violet 50). Both colorants are available from Colorchem
International as Amaplast Violet PC and Amaplast Blue HB. These
colorant levels were selected to yield the similar L*, a*, b* as
the cobalt acetate.
[0153] As demonstrated in Table VI, the 0.5 mole percent lithium
sulfonate material had much better colour with 5% MXD6 than did the
equivalent 0.5 mole percent sodium sulfonate with cobalt acetate.
In fact, it had better colour than the sodium sulfonate at 2 mole %
when combined with MXD6 in the presence of a cobalt salt. This
proves the superiority of the lithium sulfonate over sodium
sulfonate as a cobalt salt is not needed to control colour when the
material is melt mixed with MXD6 Nylon.
TABLE-US-00006 TABLE VI Cobalt versus No Cobalt Nylon Weight
Percent Bottle Grade Polymer Type Nylon b* 6001 0% SIPA, Cleartuf
.RTM. 0 8006S 5 0.5% NaSIPA, Cobalt 0 3 13.78 7 14.91 6007 0% SIPA,
Cleartuf .RTM. 0 1.51 8006S 5 15.5 Turbo II, High IPA, High 0 1.12
Clarity, Bottle Grade PET, 3 10.6 No SIPA 6 15.38 0.5% LiSIPA, No
Cobalt 0 4.81 3 8.78 5 11.01 7 12.49 2.0% NaSIPA, Cobalt 0 3 13.34
7 15.18 *The nomenclature NaSIPA or LiSIPA in this table means the
mole percent of the acid moietites of lithium sulfoisophthalate.
However, one skilled in the art knows that mole percent of lithium
sulfoisophthalate is equal to the mole percent of the starting
monomer.
[0154] The bottle Hunter b* is measured on a 0.5 Liter bottle with
nominal wall thicknesses of 0.36 mm to 0.42 mm, where the bottle
itself is placed into a properly adapted machine and the light
passes through both bottle sidewalls. Thus a bottle having a Hunter
b* colour as measured on the bottle through both sidewalls of less
than 20 units without Cobalt is easily achievable through the
teachings of this specifications. Also taught is a bottle with a
Hunter b* colour of less than 15 units. Also present in the bottle
may be a colorant or colorant system such as a pigment or dye which
reduces the Hunter b*. It is also noted that these bottles had less
than 0.5% haze per mil
Example 6
Lithium Sulfonate with Aliphatic Polyamide (Nylon 6)
[0155] Three blends were made demonstrating the effect of LiSIPA on
nylon 6 and MXD6 blended with nylon 6. The first blend was 5% by
weight PA6 with 95% by weight Cleartuf.RTM. 8006 polyethylene
terephthalate from M&G Polymers, USA. The blend was made into
preforms and blown into a bottle. As shown in FIG. 5, the
unmodified PET when blended with PA6 is very milky white and when
blown into a bottle has approximately 3% haze per mil thickness.
The resulting blend is clear as shown in FIG. 5 when the PA6 is
blended with 0.5 mole percent lithium sulfoisophthalate modified
polyethylene terephthalate and the bottle haze is 0.5% per mil. For
comparison, the bottle haze of the lithium sulfoisophthalate
modified polyethylene terephthalate and unmodified polyethylene
terephthalate are each approximately 0.2 percent haze per mil
without any nylon. A blend of 1.5% by weight PA6, 3.5% MXD6 and 95%
polyethylene terephthalate was also made with similar results. The
haze for the unmodified polyethylene terephthalate was
approximately 1.15 percent per mil, while the haze for the
polyethylene terephthalate modified with lithium sulfoisophthalate
was 0.3 percent per mil.
Example 7
Lithium Sulfoisophthalate in the Core-Shell Structure
[0156] In this series of experiments, various core-shell
configurations were evaluated as shown in Table V. The PET was
Cleartuf 8006 and the MXD6 was grade 6007. The modified polyester
contained 2.5 mole percent lithium sulfoisophthalate of sodium
sulfoisophthalate. The superiority of the lithium is again
demonstrated by comparing B with D and C with E. In both
comparisons, the lithium sulfoisophthalate had much lower haze. The
average domain size of the unmodified system was 200+/-61
nanometers, while the average domain size for the polymer modified
with lithium sulfoisophthalate (D) was 57+/-27 nanometers, a
reduction of almost 72%. Also noted is the superiority of placing
the PET and the modified polyester in the same compartment as
opposed to placing the nylon and modified polyester in the same
compartment.
TABLE-US-00007 TABLE VII Core-Sheath Comparisons of Sodium and
Lithium Sulfoisophthalate Haze Core Shell L* a* b* (%) A Control,
no core 5% MXD6, 78.46 -0.15 14.34 12.99 95% PET B 5% MXD6 19% of
2.5 79.98 -0.19 12.20 10.37 mole % NaSIPA, 76% PET C 5% MXD6, 5%
2.5 90% PET 76.05 0.01 12.93 23.36 mole % NaSIPA D 5% MXD6 19% of
2.5 85.25 -0.55 7.38 4.37 mole % LiSIPA, 76% PET E 5% MXD6, 5% 2.5
90% PET 76.85 -0.05 14.83 12.39 mole % LiSIPA F 5% MXD6 5% of 10
68.71 0.89 16.42 23.64 mole % NaSIPA, 90% PET G 5% MXD6, 5% 10 90%
PET 70.46 0.52 15.41 37.79 mole % NaSIPA The NaSIPA and LiSIPA,
refer to the acid moities as incorporated into the polyester
backbone.
Example Series 9
Demonstration of Lithium's Unique Stretch Characteristics
[0157] The following examples demonstrate the functionality of this
invention. In examples 1 through 3, 100 grams of polyamide pellets
with the end group and molecular weights provided in Table I were
dried separately and melt blended with 1900 grams of polyester
having the characteristics demonstrated in Table VI. Note that the
polyester in Examples 9B and 9C contained the interfacial tension
reducing agent with sodium and lithium respectively at the mole
percents indicated polymerized into the backbone of the polymer.
Example 9B is Crystar 3919/089 available from E.I. Dupont Nemours.
The polyester with interfacial reducing agent, lithium
sulfoisophthalate, copolymerized into the backbone used in Example
9C were prepared as disclosed earlier.
TABLE-US-00008 TABLE VIII 9C 9B Li SIPA 9A Na SIPA MXD6 MXD6
Example PET MXD6 6007 6007 6007 Polyamide (wt % of 5 5 5 polymer
components) R.V. 2.7 2.7 eg meas 2.7 AEG (mmol/kg) 16 16 16 CEG
(mmol/kg) 68 68 68 AEG/CEG (Amino/Acid End Group Ratio) Mn based on
TEG 23810 23810 23810 Polyester and 95 95 95 Interfacial Tension
Reducing Agent (wt % of polymer components) PTA mole % 97.5 98.2
98.3 IPA mole % 2.5 1.2 LiSIPA mole % 0.5 NaSIPA mole % 1.72 Cobalt
(ppm) 40 25 Preform Domain Size (nm) 71.9 47.6 Stretch Ratio of
2.91 3.36 2.73 Axis Measured Hunter b* 11.83 10.59 8.3 Thickness
(mm) 0.3 0.28 0.29 Domain Size (nm) 220 93.2 Domain Stretch 3.06
1.96 Ratio in hoop direction Stretch Ratio of 2.91 3.36 2.73 Axis
Measured Percent of Stretch 92 71 Haze (%) 12.09 5.7 6.1 Haze/mm 40
20 21
Test Methods
Intrinsic Viscosity
[0158] The intrinsic viscosity of intermediate molecular weight and
low crystalline poly(ethylene terephthalate) and related polymers
which are soluble in 60/40 phenol/tetrachloroethane can be
determined by dissolving 0.1 gms of polymer or ground pellet into
25 ml of 60/40 phenol/tetrachloroethane solution and determining
the viscosity of the solution at 30.degree. C.+/-0.05 relative to
the solvent at the same temperature using a Ubbelohde 1B
viscometer. The intrinsic viscosity is calculated using the
Billmeyer equation based upon the relative viscosity.
[0159] The intrinsic viscosity of high molecular weight or highly
crystalline poly(ethylene terephthalate) and related polymers which
are not soluble in phenol/tetrachloroethane was determined by
dissolving 0.1 gms of polymer or ground pellet into 25 ml of 50/50
trifluoroacetic Acid/Dichloromethane and determining the viscosity
of the solution at 30.degree. C.+/-0.05 relative to the solvent at
the same temperature using a Type OC Ubbelohde viscometer. The
intrinsic viscosity is calculated using the Billmeyer equation and
converted using a linear regression to obtain results which are
consistent with those obtained using 60/40 phenol/tetrachloroethane
solvent. The linear regression is IV in 60/40
phenol/tetrachloroethane=0.8229.times.IV in 50/50 trifluoroacetic
Acid/Dichloromethane+0.0124
The Hunter Haze Measurement
[0160] The measurements were taken through the bottle side-walls. A
HunterLab ColorQUEST Sphere Spectrophotometer System, assorted
specimen holders, and green, gray and white calibration tiles, and
light trap was used. The HunterLab Spectrocolorimeter integrating
sphere sensor is a colour and appearance measurement instrument.
Light from the lamp is diffused by the integrating sphere and
passed either through (transmitted) or reflected (reflectance) off
an object to a lens. The lens collects the light and directs it to
a diffraction grating that disperses it into its component wave
lengths. The dispersed light is reflected onto a silicon diode
array. Signals from the diodes pass through an amplifier to a
converter and are manipulated to produce the data. Haze data is
provided by the software. It is the calculated ratio of the diffuse
light transmittance to the total light transmittance multiplied by
100 to yield a "Haze %" (0% being a transparent material, and 100%
being an opaque material). Samples prepared for either
transmittance or reflectance must be clean and free of any surface
scratches or abrasion. The size of the sample must be consistent
with the geometry of the sphere opening and in the case of
transmittance; the sample size is limited by the compartment
dimension. Each sample is tested in four different places, for
example on the bottle sidewall or representative film area.
[0161] A Panametrics Magna-Mike 8000 Hall Effect Thickness Gauge
was employed to measure the bottle sidewall thickness.
Dispersed Domain Analysis.
Scanning Electron Microscopy
[0162] The sample is prepared by cutting the preform or wall of the
container and putting the cut pieces in liquid nitrogen for five
minutes. The pieces are then broken with a sharp blow. One piece of
the perform or wall is cut into a slice at the specified angle. The
slice is placed into a 50 cc. beaker and covered with approximately
25 cc of .gtoreq.96% formic acid (available as ACS reagent
[64-18-6] from Fluka, Aldrich or Merck) and stirred at room
temperature. The sample is removed after one hour take the slice
and washed with water until the water is a neutral pH. The sample
is then washed with acetone.
[0163] After washing in acetone, the specimen is placed into an
agar auto sputter coater (model 108 A, s.n. A10S) and plated with
gold in order to make it conductive. Typical conditions for the
agar auto sputter coater are to use an Argon flow, at 20 mA current
for 30 seconds using gold metal.
[0164] The coated specimen is then placed into the SEM holder and
photo taken. A typical SEM machine is SEM Leo Electronic Microscopy
Ltd, model LEO 1450 VP, s.n. 01-22 used in vacuum chamber modality
with Secondary Electron Detection 1 acquiring system. Other
settings are
[0165] Tension EHT: 20 KV
[0166] Focal distance, also known as working distance or WD: 10-11
mm
[0167] Spot size (dimensionless): 200-300 decreasing to 80 at large
magnifications
[0168] Filament current: 3-3.5 A depending upon filament age.
[0169] The dimensions and distribution of polyamide domains are
measured using Lucia M software (available from Laboratory Imaging
and may come as a package with a SEM machine provided by Nikon
Japan) in automatic or manual mode. Typically, more than 250
domains are measured over 10 different pictures, with the number of
domains analyzed per picture increasing with better dispersions. A
statistical analysis on the domains is then carried out to
determine the mean, the median and the distribution of the domains
as in FIG. 4, and frequency of domains at a given size interval per
unit area for each sample.
* * * * *