U.S. patent application number 09/452821 was filed with the patent office on 2002-02-21 for polymer/clay intercalates, exfoliates, and nanocomposites comprising a clay mixture and a process for making same.
Invention is credited to BARBEE, ROBERT BOYD, GILMER, JOHN WALKER, LAN, TIE, MATAYABAS, JAMES CHRISTOPHER JR., PSHIHOGIOS, VASILIKI.
Application Number | 20020022678 09/452821 |
Document ID | / |
Family ID | 22336464 |
Filed Date | 2002-02-21 |
United States Patent
Application |
20020022678 |
Kind Code |
A1 |
LAN, TIE ; et al. |
February 21, 2002 |
POLYMER/CLAY INTERCALATES, EXFOLIATES, AND NANOCOMPOSITES
COMPRISING A CLAY MIXTURE AND A PROCESS FOR MAKING SAME
Abstract
This invention relates to a polymer-clay intercalates,
exfoliates, nanocomposites and methods of manufacturing comprising
(i) a melt-processible matrix polymer, and incorporated therein
(ii) a mixture of at least two layered clay materials. The
invention also relates to articles produced from a nanocomposite
and a process for preparing a nanocomposite.
Inventors: |
LAN, TIE; (LAKE ZURICH,
IL) ; PSHIHOGIOS, VASILIKI; (PALATINE, IL) ;
BARBEE, ROBERT BOYD; (KINGSPORT, TN) ; MATAYABAS,
JAMES CHRISTOPHER JR.; (CHANDLER, AZ) ; GILMER, JOHN
WALKER; (KINGSPORT, TN) |
Correspondence
Address: |
MARSHALL O'TOOLE GERSTEIN
MURRAY & BORUN
6300 SEARS TOWER
233 SOUTH WACKER DRIVE
CHICAGO
IL
606066402
|
Family ID: |
22336464 |
Appl. No.: |
09/452821 |
Filed: |
December 1, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60111074 |
Dec 7, 1998 |
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Current U.S.
Class: |
523/202 ;
428/402; 428/411.1; 523/203; 523/205; 524/442; 524/445; 524/446;
524/447; 524/448; 524/450; 524/709; 524/714; 524/789; 524/791;
524/839; 524/841; 524/845; 524/849 |
Current CPC
Class: |
Y10T 428/2982 20150115;
Y10T 428/31504 20150401; C08K 3/346 20130101; C08K 2201/014
20130101; C08K 9/04 20130101; C08K 7/00 20130101 |
Class at
Publication: |
523/202 ;
523/203; 523/205; 524/442; 524/445; 524/446; 524/447; 524/448;
524/450; 524/709; 524/714; 524/789; 524/791; 524/839; 524/841;
524/845; 524/849; 428/402; 428/411.1 |
International
Class: |
C08F 002/00; B32B
015/02; C08K 011/00 |
Claims
What is claimed is:
1. An intercalant comprising a mixture of at least two swellable
layered clay materials intercalated with a melt-processible
polymer.
2. The intercalate of claim 1, wherein the melt-processible polymer
comprises a polyester, polyetherester, polyamide, polyesteramide,
polyurethane, polyimide, polyetherimide, polyurea, polyamideimide,
polyphenyleneoxide, phenoxy resin, epoxy resin, polyolefin,
polyacrylate, polystyrene, polyethylene-co-vinyl alcohol, or a
copolymer thereof, or a mixture thereof.
3. The intercalate of claim 1, wherein the melt-processible polymer
comprises poly(m-xylylene adipamide), EVOH, or a copolymer thereof,
or a mixture thereof.
4. The intercalate of claim 1, wherein the melt-processible polymer
comprises poly(ethylene terephthalate) or a copolymer thereof, or a
mixture thereof.
5. The intercalate of claim 1, comprising greater than zero to
about 25 weight percent of layered clay material.
6. The intercalate of claim 1, comprising from about 0.5 to about
15 weight percent of layered clay material.
7. The intercalate of claim 1, comprising from about 0.5 to about
10 weight percent of layered clay material.
8. The intercalate of claim 1, wherein the mixture of layered clay
materials comprises natural, synthetic or modified
phyllosilicates.
9. The intercalate of claim 1, wherein the mixture of layered clay
materials comprises natural, synthetic or modified
montmorillonites, saponites, hectorites, micas, vermiculites,
bentonites, nontronites, beidellites, volkonskoites, magadites,
kenyaites, or mixtures thereof.
10. The intercalate of claim 1, wherein the mixture of layered clay
materials includes bis(2-hydroxyethyl) octadecyl methyl ammonium
montmorillonite and dodecyl ammonium montmorillonite, octadecyl
trimethyl ammonium montmorillonite and tetramethyl ammonium
montmorillonite, dodecyl ammonium montmorillonite and tetramethyl
ammonium montmorillonite, or dodecyl ammonium montmorillonite and
sodium montmorillonite.
11. The intercalate of claim 1, wherein the layered clay materials
are free flowing powders having a cation exchange capacity from
about 0.9 to about 1.5 meq/g.
12. The intercalate of claim 1, wherein at least 50 percent of the
layered clay materials are exfoliated in the form of individual
platelet particles and tactoids to form an exfoliate.
13. The exfoliated intercalate of claim 12, wherein the tactoids
have a thickness of less than about 20 nm.
14. The intercalate of claim 1, wherein the mixture of layered clay
materials is intercalated with an organic cation or a mixture of
organic cations.
15. The intercalate of claim 14, wherein the organic cation is
represented by the formula (I): 2wherein M is either nitrogen or
phosphorous; X.sup.- is a halide, hydroxide, or acetate anion,
preferably chloride and bromide; and R.sub.1, R.sub.2, R.sub.3, and
R.sub.4 are independently organic and/or oligomeric ligands or may
be hydrogen.
16. The intercalate of claim 14, wherein the organic cation is
derived from an onium salt compound comprising an ammonium or
phosphonium salt compound.
17. The intercalate of claim 14, wherein the organic cation
comprises an alkyl ammonium ion, an alkyl phosphonium ion, a
polyalkoxylated ammonium ion, or a mixture thereof.
18. The intercalate of claim 17, wherein the alkyl ammonium ion
comprises tetramethyl ammonium, hexyl ammonium, butyl ammonium,
bis(2-hydroxyethyl dimethyl ammonium, hexyl benzyl dimethyl
ammonium, benzyl trimethyl ammonium, butyl benzyl dimethyl
ammonium, tetrabutyl ammonium di(2-hyrdoxyethyl) ammonium, dodecyl
ammonium, octadecyl ammonium, octadecyl trimethyl ammonium,
bis(2-hydroxyethyl) octadecyl methyl ammonium, or octadecyl benzyl
dimethyl ammonium.
19. The intercalate of claim 17, wherein the alkyl phosphonium ion
comprises tetrabutyl phosphonium, trioctyl octadecyl phosphonium,
tetraoctyl phosphonium, or octadecyl triphenyl phosphonium.
20. The intercalate of claim 17, wherein the polyalkoxylated
ammonium ion is derived from a hydrochloride salt of
oligooxyethylene amine with a number average molecular weight of
about 1100 g/mol, a hydrochloride salt of oligooxypropylene amine
with a number average molecular weight of about 640 g/mol, a
hydrochloride salt of octadecyl bis(polyoxyethylene[15])amine or
octadecyl bis(polyoxyethylene[15]) ammonium chloride, wherein the
numbers in brackets are the total number of ethylene oxide
units.
21. The intercalate of claim 17, wherein the alkyl ammonium ion
comprises tetramethyl ammonium, hexyl ammonium, butyl ammonium,
bis(2-hydroxyethyl dimethyl ammonium, hexyl benzyl dimethyl
ammonium, benzyl trimethyl ammonium, butyl benzyl dimethyl
ammonium, tetrabutyl ammonium di(2-hyrdoxyethyl) ammonium, dodecyl
ammonium, octadecyl ammonium, octadecyl trimethyl ammonium,
bis(2-hydroxyethyl) octadecyl methyl ammonium, or octadecyl benzyl
dimethyl ammonium; and wherein the alkyl phosphonium ion comprises
tetrabutyl phosphonium, trioctyl octadecyl phosphonium, tetraoctyl
phosphonium, or octadecyl triphenyl phosphonium; wherein the
polyalkoxylated ammonium ion is derived from a hydrochloride salt
of oligooxyethylene amine with a number average molecular weight of
about 1100 g/mol, a hydrochloride salt of oligooxypropylene amine
with a number average molecular weight of about 640 g/mol, a
hydrochloride salt of octadecyl bis(polyoxyethylene[15])amine or
octadecyl methyl bis(polyoxyethylene[15]) ammonium chloride,
wherein the numbers in brackets are the total number of ethylene
oxide units.
22. The intercalate of claim 14, wherein the organic cation
comprises tetramethyl ammonium, octadecyl trimethyl ammonium or a
mixture thereof.
23. The intercalate of claim 1, wherein the melt-processible
polymer comprises poly(ethylene terephthalate) or a copolymer
thereof and the mixture of layered clay materials comprises dodecyl
ammonium montmorillonite, sodium beutonite, calcium
montmorillonite, calcium beutonite, or synthetic
phyllosilicates.
24. An exfoliate manufactured by shearing the intercalate of claim
1 to form a plurality of delaminated clay layers and clay tactoids
of said swellable layered clay materials.
25. A process for preparing an intercalate comprising: (i)
preparing a mixture of at least two swellable layered clay
materials; and (ii) incorporating the mixture with a matrix polymer
by melt processing a sufficient amount of a matrix polymer with the
mixture to form an intercalate wherein the matrix polymer
intercalate between adjacent layers of said swellable layered clay
materials.
36. The process of claim 25, wherein step (i) is conducted by
intimately mixing at least two swellable layered clay materials in
a solvent.
27. The process of claim 26, wherein the solvent is water, an
alcohol, a chlorinated solvent, a ketone, an ester, an ether or a
mixture thereof.
28. The process of claim 25, wherein step (ii) is conducted by a
melt compounding extrusion process.
29. A polymer-clay intercalate made by the process of claim 25.
30. A polymer-clay exfoliated made by shearing the intercalate made
by the process of claim 25.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. provisional patent
application Serial No. 60/111,074, filed Dec. 7, 1998, which is
incorporated herein by this reference in its entirety.
FIELD OF THE INVENTION
[0002] This invention relates generally to polymer-clay
nanocomposites comprising a mixture of clay materials. This
invention further relates to intercalates, exfoliates,
nanocomposites, and articles produced from the intercalates,
exfoliates and nanocomposites; and processes for preparing the
intercalates, exfoliates, nanocomposites, and articles.
BACKGROUND OF THE INVENTION
[0003] There is much interest in layered, clay-based polymer
nanocomposites because of the improved properties exhibited by the
nanocomposites. It is desirable to maximize delamination of the
clay into individual platelet particles in order to maximize some
property improvements, including barrier improvements, and to
minimize deleterious effects on some properties including
elongation-at-break. Ideally, the clay is exfoliated into particles
with size less than about 100 nm in order to achieve clarity that
is comparable to the clay-free polymer. To date, the only
polymer/clay nanocomposites that meet this expectation are prepared
by incorporation of organically treated clays during synthesis of
the polymer from monomer.
[0004] It is also widely known that the amount of clay that can be
admixed in a polymer and still exhibit exfoliation of the layered
clay is limited and some mechanical properties, such as
elongation-at-break, are often reduced considerably upon the
addition of the clay. Researchers recognized the value of inventing
melt compounding processes that provide exfoliated polymer/platelet
particle composites, namely more versatility of polymer choice and
clay loading, and the potential for cost savings. However, with
polymer/clay mixtures, the melt compounding processes explored to
date do not provide sufficient exfoliation of the platelet
particles.
[0005] Polyesters such as poly(ethylene terephthalate) (PET) are
widely used in bottles and containers which are used for carbonated
beverages, fruit juices, and certain foods. Useful polyesters have
high molecular weight values (high inherent viscosities (I.V.s)) as
determined by solution viscometry, which allow polyesters to be
formed into parisons and subsequently molded into containers.
Because of the limited barrier properties with regard to oxygen,
carbon dioxide and the like, PET containers are not generally used
for products requiring long shelf life. For example, oxygen
transmission into PET bottles which contain beer, wine and certain
food products causes these products to spoil. There have been
attempts to improve the barrier properties of PET containers by the
use of multilayer structures comprising one or more barrier layers
and one or more structural layers of PET. However, multilayer
structures have not found wide use and are not suitable for use as
a container for beer due to the high cost, the large thickness of
the barrier layer required and poor adhesion of the barrier layer
with the structural layer.
[0006] There are many examples in the patent literature of
polymer/clay nanocomposites prepared from monomers and treated
clays. For example, U.S. Pat. No. 4,739,007 discloses the
preparation of Nylon-6/clay nanocomposites from caprolactam and
alkyl ammonium-treated montmorillonite. U.S. Pat. No. 4,889,885
describes the polymerization of various vinyl monomers such as
methyl methacrylate and isoprene in the presence of sodium
montmorillonite.
[0007] Some patents describe the blending of up to 60 weight
percent of intercalated clay materials with a wide range of
polymers including polyamides, polyesters, polyurethanes,
polycarbonates, polyolefins, vinyl polymers, thermosetting resins
and the like. Such high loadings with modified clays are
impractical and useless with most polymers because the melt
viscosity of the blends increases so much that they cannot be
molded.
[0008] WO 93/04117 discloses a wide range of polymers melt blended
with up to 60 weight percent of dispersed platelet particles. WO
93/04118 discloses nanocomposite materials of a melt processable
polymer and up to 60 weight percent of a clay that is intercalated
with organic onium salts. The use of a mixture of swellable layered
clays or a clay mixture intercalated with an onium ion is not
contemplated nor disclosed.
[0009] U.S. Pat. No. 5,552,469 describes the preparation of
intercalates derived from certain clays and water soluble polymers
such as polyvinyl pyrrolidone, polyvinyl alcohol, and polyacrylic
acid. The use of clay mixtures or mixtures intercalated with onium
ions is specifically excluded.
[0010] JP Kokai patent no. 9-176461 discloses polyester bottles
wherein the polyester contains unmodified sodium montmorillonite.
Incorporation of the clay into the polyester by melt compounding is
disclosed; however the use of clay mixtures or clays intercalated
with onium ions was neither contemplated nor disclosed.
[0011] Clays intercalated with a mixture of onium ions are used as
rheology modifiers for certain coating applications; however, their
use in polymer/clay nanocomposites has been neither contemplated
nor disclosed. The following references are of interest with regard
to chemically modified organoclay materials: U.S. Pat. Nos.
4,472,538; 4,546,126; 4,676,929; 4,739,007; 4,777,206; 4,810,734;
4,889,885; 4,894,411; 5,091,462; 5,102,948; 5,153,062; 5,164,440;
5,164,460; 5,248,720; 5,382,650; 5,385,776; 5,414,042; 5,552,469;
WO Patent Application Nos. 93/04117; 93/04118; 93/11190; 94/11430;
95/06090; 95/14733; D. J. Greenland, J. Colloid Sci. 18, 647
(1963); Y. Sugahara et al., J. Ceramic Society of Japan 100, 413
(1992); P. B. Massersmith et al., J. Polymer Sci. Polymer Chem.,
33, 1047 (1995); C. O. Sriakhi et al., J. Mater. Chem. 6,
103(1996).
[0012] Therefore, as shown above, a need exists for polymer
nanocomposites having improved properties. This invention provides
a novel polymer nanocomposite comprising a mixture of clay
materials. This invention also provides articles produced from this
polymer nanocomposite that have improved properties.
SUMMARY OF THE INVENTION
[0013] It has been discovered that a mixture of clays is useful for
the preparation of a polymer/clay nanocomposite with sufficient
exfoliation for improved properties and clarity for commercial
applications, including film, bottles, and containers. The polymer
nanocomposite materials of this invention are useful for forming
articles or packages that have improved gas barrier properties over
neat PET, for example. Containers made from these polymer composite
materials are ideally suited for protecting consumable products,
such as foodstuffs, soft drinks, and medicines.
[0014] This invention also seeks to provide a cost-effective method
for producing nanocomposite compositions, and articles made
therefrom, having sufficient barrier and clarity for wide spread
applications as multilayer bottles and containers, including beer
bottles. The polymer/clay nanocomposite composition and process of
this invention are especially suited for use in applications
requiring crystalline, molded or thermoformed parts.
[0015] In accordance with the purpose(s) of this invention, as
embodied and broadly described herein, this invention, in one
embodiment, relates to a polymer-clay nanocomposite comprising (i)
a melt-processible matrix polymer, and incorporated therein (ii) a
mixture of at least two swellable layered clay materials.
[0016] In another embodiment, this invention relates to a process
for preparing a polymer-clay nanocomposite comprising (i) preparing
a mixture of at least two swellable layered clay materials, and
(ii) incorporating the mixture with a matrix polymer by melt
processing the matrix polymer with the mixture.
[0017] Additional advantages of the invention will be set forth in
part in the detailed description, which follows, and in part will
be obvious from the description, or may be learned by practice of
the invention. The advantages of the invention will be realized and
attained by means of the elements and combinations particularly
pointed out in the appended claims. It is to be understood that
both the foregoing general description and the following detailed
description are exemplary and explanatory of preferred embodiments
of the invention, and are not restrictive of the invention, as
claimed.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The present invention may be understood more readily by
reference to the following detailed description of the invention
and the examples provided therein. It is to be understood that this
invention is not limited to the specific processes and conditions
described, as specific processes and/or process conditions for
processing polymer articles as such may, of course, vary. It is
also understood that the terminology used herein is for the purpose
of describing particular embodiments only and is not intended to be
limiting.
[0019] It must also be noted that, as used in the specification and
the appended claims, the singular forms "a," "an" and "the"
included plural references unless the context clearly dictates
otherwise.
[0020] Ranges may be expressed herein as from "about" or
"approximately" one particular value and/or to "about" or
"approximately" another particular value. When such a range is
expressed, another embodiment includes from the one particular
and/or to the other particular value. Similarly, when values are
expressed as approximations, by use of the antecedent "about," it
will be understood that the particular value forms another
embodiment.
Definitions
[0021] Whenever used in this specification or claims, the terms set
forth shall have the following meanings:
[0022] "Clay material," "layered clay" or "layered clay material"
shall mean any organic or inorganic material or mixtures thereof,
such as a smectite clay mineral, which is in the form of a
plurality of adjacent, bound layers. The layered clay comprises
platelet particles and is typically swellable.
[0023] "Platelet particles," "platelets" or "particles" shall mean
individual or aggregate unbound layers of the layered clay
material. These layers may be in the form of individual platelet
particles, ordered or disordered small aggregates of platelet
particles (tactoids), and small aggregates of tactoids.
[0024] "Dispersion" or "dispersed" is a general term that refers to
a variety of levels or degrees of separation of the platelet
particles. The higher levels of dispersion include, but are not
limited to, "intercalated" and "exfoliated."
[0025] "Intercalated" or "intercalate" shall mean a layered clay
material that includes an intercalant disposed between adjacent
platelet particles or tactoids of the layered material to increase
the interlayer spacing between the adjacent platelets and tactoids.
In this invention, the intercalant is preferably an organic cation
and may also be a matrix polymer.
[0026] "Exfoliate" or "exfoliated" shall mean platelets dispersed
predominantly in an individual state throughout a carrier material,
such as a matrix polymer. Typically, "exfoliated" is used to denote
the highest degree of separation of platelet particles.
[0027] "Exfoliation" shall mean a process for forming an exfoliate
from an intercalated or otherwise less dispersed state of
separation.
[0028] "Nanocomposite(s)" or "nanocomposite composition(s)" shall
mean a polymer or copolymer having dispersed therein a plurality of
individual platelets obtained from an exfoliated, layered clay
material.
[0029] "Matrix polymer" shall mean a thermoplastic or
melt-processible polymer in which the platelet particles are
dispersed to form a nanocomposite. In this invention, however, the
platelet particles are predominantly exfoliated in the matrix
polymer to form a nanocomposite.
DESCRIPTION OF THE EMBODIMENTS
[0030] The present invention relates to clay mixtures, polymer/clay
nanocomposite compositions comprising clay mixtures, a process for
preparing a polymer/clay nanocomposite, and to molded articles,
films, fiber, etc. prepared from the polymer/clay nanocomposites of
this invention. The process of this invention may be used to
prepare a wide variety of polymer/clay nanocomposite compositions,
the most preferred being polyester/clay nanocomposites.
[0031] Without being bound by any particular theory, it is believed
that the degree of improved gas barrier (permeability) depends upon
the embodiment ratio of the resulting particle platelets and
aggregates, the degree to which they are dispersed or uniformly
distributed, and the degree to which they are ordered perpendicular
to the flux of the permeant.
[0032] To obtain the improvements in gas permeability according to
the present invention, it is preferable that the platelet particles
representative of the bulk of the composite be exfoliated, and
preferably be highly exfoliated, in the matrix polymer such that
the majority, preferably at least about 75 percent and perhaps as
much as at least about 90 percent or more of the platelet
particles, be dispersed in the form of individual platelets and
small aggregates having a thickness in the shortest dimension of
less than about 20 nm and preferably less than about 10 nm, as
estimated from TEM images. Polymer-platelet nanocomposites
containing more individual platelets and fewer aggregates, ordered
or disordered, are most preferred.
[0033] Significant levels of incomplete dispersion (i.e., the
presence of large agglomerates and tactoids greater than about 20
nm) not only lead to an exponential reduction in the potential
barrier improvements attributable to the platelet particles, but
also can lead to deleterious affects to other properties inherent
to polymer resins such as strength, toughness, and heat resistance,
and processability.
[0034] Again, without being bound by a particular theory, it is
believed that delamination of platelet particles upon melt
processing or mixing with a polymer requires favorable free energy
of mixing, which has contributions from the enthalpy of mixing and
the entropy of mixing. Melt processing clay with polymers results
in a negative entropy of mixing due to the reduced number of
conformations, which are accessible to a polymer chain when it
resides in the region between two layers of clay. It is believed
that poor dispersion is obtained using melt-processible polyesters,
for example, because the enthalpy of mixing is not sufficient to
overcome the negative entropy of mixing. In contrast, generally
good dispersions are obtained with polyamides due to their hydrogen
bonding character. However, the extent of this dispersion is
frequently lessened because of the negative entropy of mixing.
Heretofore, efforts to achieve a favorable enthalpy of mixing of
platelet particles with melt processible polymers by pretreating
the platelet particles (e.g., by cation exchange with alkyl
ammonium ions) have been unsuccessful.
[0035] The prior art has defined the degree of separation of
platelet particles based on peak intensity and basal spacing value,
or lack of predominant basal spacing, as determined by X-ray
analyses of polymer-platelet composites. Even though X-ray analysis
alone often does not unambiguously predict whether the platelet
particles are individually dispersed in the polymer, it can often
allow quantification of the level of dispersion achieved. Basal
spacing by X-ray diffraction indicates the separation distance of a
platelet in a tactoid rather than single platelets. X-ray
diffraction intensity (basal spacing peak height) may correlate to
barrier in an article resulting from a nanocomposite including a
clay material mixture as described above. For example, a low basal
spacing peak height indicates few tactoids; therefore, the
remainder must be either individual platelets or tactoids that are
disordered. Moreover, if one organoclay (a clay treated with an
organic cation) that has a high basal spacing, as shown by X-ray,
is mixed with another organoclay that has a low basal spacing, as
shown by X-ray, two individual X-ray spacings are expected.
[0036] Moreover, in polymer nanocomposites, X-ray analysis alone
does not accurately predict either the dispersion of the platelet
particles in the polymer or the resultant gas barrier improvement.
TEM images of polymer-platelet composites show that platelet
particles which are incorporated into at least one polymer exist in
a variety of forms, including, but not limited to, individual
platelets (the exfoliated state), disordered agglomerates of
platelets, well ordered or stacked aggregates of platelets
(tactoids), swollen aggregates of stacked platelets (intercalated
tactoids), and aggregates of tactoids.
[0037] It has been discovered that intimately mixing two individual
clays, for example, does not produce the expected two individual
X-ray spacings. Rather, only an intermediate X-ray basal spacing is
observed when at least two different clay materials are intimately
mixed. Intimate mixing of a clay blend (e.g., sodium
montmorillonite and sodium Laponite RD) can be achieved by
delaminating the stacked silicate layered structure of each clay or
organoclay, usually from a solvent. The clay (silicate) layers may
be recombined upon removal of the solvent to provide a uniform
dispersion of silicate layers within the clay blend. Solvents
useful for obtaining an intimate mixture of clays include, but are
not limited to water, alcohols (e.g., methanol), chlorinated
solvents (e.g., methylene chloride), ketones (e.g., acetone),
esters (e.g., ethyl acetate), and/or ethers (e.g., tetrahydrofuran
or dioxane). After intimately mixing the clays, the solvents are
removed, and as such, low boiling point solvents are preferred.
[0038] Without being bound by any particular theory, it is believed
that intimately mixed clay mixtures are less ordered and are
therefore more easily separated and delaminated into the preferred
small tactoid and individual platelet structures. As such, the
polymer/clay nanocomposites of this invention exhibit an
unexpectedly lower gas permeability, particularly oxygen
permeability, than clay-free polymers.
[0039] Therefore, regarding the present invention, it has been
found that using a mixture of layered clay materials while melt
processing with a polymer gives a good dispersion of platelet
particles in a resulting nanocomposite, creating mostly individual
platelet particles. The resulting nanocomposite has improved
barrier to gas when formed into a wall or article compared to a
neat polymer formed into the same or similar structure.
[0040] In one embodiment, this invention relates to a polymer
nanocomposite comprising a melt-processible polymer and up to about
25 weight percent of a mixture of swellable layered clay materials,
which may be intercalated with an organic cation, preferably an
onium ion. The intercalated clay material mixture has platelet
particles, which are dispersed in the polymer. The polymer
nanocomposite is preferably a polyester polymer or copolymer
nanocomposite having an I.V. of at least 0.5 dL/g as measured in 60
wt. %/40 wt. % phenol/tetrachloroethane at 25.degree. C.
[0041] In another embodiment, a process for manufacturing the
polymer nanocomposite of this invention comprises (1) preparing the
layered clay material mixture and (2) incorporating the layered
clay material mixture with a polymer by melt processing the polymer
and the layered clay material mixture. Melt processing includes
melt and extrusion compounding. Use of extrusion compounding to mix
the clay mixture and the polymer presents advantages. Chiefly, the
extruder is able to handle the high viscosity exhibited by the
nanocomposite material. In addition, in a melt mixing approach for
producing nanocomposite materials, the use of solvents can be
avoided. Low molecular weight liquids can often be costly to remove
from the nanocomposite resin.
[0042] The nanocomposite composition of the present invention
comprises less than about 25 weight percent, preferably from about
0.5 to about 20 weight percent, more preferably from about 0.5 to
about 15 weight percent, and most preferably from about 0.5 to
about 10 weight percent of clay mixtures. The amount of platelet
particles is determined by measuring the amount of silicate residue
in the ash of the polymer/platelet composition when treated in
accordance with ASTM D5630-94.
[0043] Useful clay materials include natural, synthetic, and
modified phyllosilicates. Natural clays include smectite clays,
such as montmorillonite, hectorite, mica, vermiculite, bentonite,
nontronite, beidellite, volkonskoite, saponite, magadite, kenyaite,
and the like. Synthetic clays include synthetic mica, synthetic
saponite, synthetic hectorite, and the like. Modified clays include
fluoronated montmorillonite, fluoronated mica, and the like.
Suitable clays are available from various companies including
Nanocor, Inc., Southern Clay Products, Kunimine Industries, Ltd.,
and Rheox.
[0044] Generally, the layered clay materials useful in this
invention are an agglomeration of individual platelet particles
that are closely stacked together like cards, in domains called
tactoids. The individual platelet particles of the clays preferably
have thickness of less than about 2 nm and diameter in the range of
about 10 to about 3000 nm. Preferably, the clays are dispersed in
the polymer so that most of the clay material exists as individual
platelet particles, small tactoids, and small aggregates of
tactoids. Preferably, a majority of the tactoids and aggregates in
the polymer/clay nanocomposites of the present invention will have
thickness in its smallest dimension of less than about 20 nm.
Polymer/clay nanocomposite compositions with the higher
concentration of individual platelet particles and fewer tactoids
or aggregates are preferred.
[0045] Moreover, the layered clay materials are typically swellable
free flowing powders having a cation exchange capacity from about
0.3 to about 3.0 milliequivalents per gram of mineral (meq/g),
preferably from about 0.9 to about 1.5 meq/g. The clay may have a
wide variety of exchangeable cations present in the galleries
between the layers of the clay, including, but not limited to,
cations comprising the alkaline metals (group IA), the alkaline
earth metals (group IIA), and their mixtures. The most preferred
cation is sodium; however, any cation or combination of cations may
be used provided that most of the cations may be exchanged for
organic cations (onium ions). The exchange may occur by treating a
individual clay for a mixture or a mixture of clays with organic
cations.
[0046] Preferred clay materials, for at least one of the components
of the clay mixture, are phyllosilicates of the 2:1 type having a
cation exchange capacity of 0.5 to 2.0 meq/g. The most preferred
clay materials, for at least one of the components of the clay
mixture, are smectite clay minerals, particularly bentonite or
montmorillonite, more particularly Wyoming-type sodium
montmorillonite or Wyoming-type sodium bentonite.
[0047] Although any mixture of clays in any ratio and/or weight
percentage is contemplated by this invention, preferred clay
mixtures include mixtures in which at least one the clay components
has an alkyl group containing at least 12 carbon atoms and the
other clay component has an alkyl group containing less than 12
carbon atoms. Preferred mixtures would be a mixture of dodecyl
ammonium montmorillonite with tetramethyl ammonium montmorillonite
or dodecyl ammonium montmorillonite with sodium montmorillonite.
The most preferred mixtures include mixtures in which at least one
clay component has an alkyl group containing 18 carbons and the
other component has an alkyl group containing less than 18 carbons.
Most preferred mixtures would be mixtures of bis(2-hydroxyethyl)
octadecyl methyl ammonium montmorillonite with dodecyl ammonium
montmorillonite and octadecyl trimethyl ammonium montmorillonite
with tetramethyl ammonium montmorillonite.
[0048] Further, the preferred ratios of the clay mixtures include
any ratio from about 75/25 to about 25/75, and more preferably from
about 60/40 to about 40/60. The preferred ratios apply to mixtures
containing two clay materials. However, mixtures and ratios of
mixtures of clay materials of more than two clays are also
contemplated by this invention.
[0049] Other non-clay materials having the above-described
ion-exchange capacity and size, such as chalcogens, may also be
used as a source of platelet particles under the present invention.
Chalcogens are salts of a heavy metal and group VIA (O, S, Se, and
Te). These materials are known in the art and do not need to be
described in detail here.
[0050] The clay mixtures of this invention may comprise refined but
unmodified clays, modified clays or mixtures of modified and
unmodified clays. Many clay treatments used to modify the clay for
the purpose of improving dispersion of clay materials are known and
may be used in the practice of this invention. The clay treatments
may be conducted prior to, during, or after mixing the clay
materials. When the treatments are made prior to mixing, the
modifications may be the same or different.
[0051] In another embodiment of this invention, an intercalated
layered clay material mixture is prepared by the reaction of a
swellable layered clay with an organic cation, preferably an
ammonium compound (to effect partial or complete cation exchange).
If desired, two or more organic cations may be used to treat a
clay. Moreover, mixtures of organic cations may also be used to
prepare an intercalated layered clay material, wherein the
intercalated layered clay material in a polymer nanocomposite
comprises a mixture of intercalated clays. The process to prepare
the organoclays (intercalated clays) may be conducted in a batch,
semi-batch, or continuous manner.
[0052] There is a good chance for different kinds of
montmorillonite clays to mix their basic platelets from different
tactoids in the clay dispersion, especially in water. Once the
water is removed, or the tactoids are intercalated with onium ions
(nanomers), the exfoliated platelets will collapse, or precipitate
out of the onium ion-containing intercalating composition, forming
new tactoids from the clay mixture. The tactoids in the mixed
montmorillonite clays will be "inter-exchanged", which means that
the clay tactoids will re-arrange to comprise individual layers in
a tactoid and can: (1) introduce mis-matched cation exchange
capacities, (2) introduce mismatched platelet particle sizes and
(3) change the color of the individual base clays. The mismatching
of charge density and dimensions of tactoid platelets will greatly
help the Nanomer to exfoliate and remain dispersed in a matrix
polymer.
[0053] Organic cations used to intercalate a clay material or a
mixture of clay materials of a nanocomposite of this invention are
derived from organic cation salts, preferably onium salt compounds.
Organic cation salts useful for the nanocomposite and process of
this invention may generally be represented by the following
formula (I): 1
[0054] wherein M is either nitrogen or phosphorous; X.sup.- is a
halide, hydroxide, or acetate anion, preferably chloride and
bromide; and R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are
independently organic and/or oligomeric ligands or may be
hydrogen.
[0055] Examples of useful organic ligands include, but are not
limited to, linear or branched alkyl groups having 1 to 22 carbon
atoms, aralkyl groups which are benzyl and substituted benzyl
moieties including fused-ring moieties having linear chains or
branches of 1 to 100 carbon atoms in the alkyl portion of the
structure, aryl groups such as phenyl and substituted phenyl
including fused-ring aromatic substituents, beta, gamma unsaturated
groups having six or less carbon atoms, and alkyleneoxide groups
having repeating units comprising 2 to 6 carbon atoms. Examples of
useful oligomeric ligands include, but are not limited to,
poly(alkylene oxide), polystyrene, polyacrylate, polycaprolactone,
and the like.
[0056] Examples of useful organic cations include, but are not
limited to, alkyl ammonium ions, such as tetramethyl ammonium,
hexyl ammonium, butyl ammonium, bis(2-hydroxyethyl) dimethyl
ammonium, hexyl benzyl dimethyl ammonium, benzyl trimethyl
ammonium, butyl benzyl dimethyl ammonium, tetrabutyl ammonium,
di(2-hydroxyethyl) ammonium, and the like, and alkyl phosphonium
ions such as tetrabutyl phosphonium, trioctyl octadecyl
phosphonium, tetraoctyl phosphonium, octadecyl triphenyl
phosphonium, and the like or mixtures thereof.
[0057] Other particularly useful organic cations for this invention
include, but are not limited to, alkyl ammonium ions such as
dodecyl ammonium, octadecyl trimethyl ammonium, bis(2-hydroxyethyl)
octadecyl methyl ammonium, octadecyl benzyl dimethyl ammonium, and
the like or mixtures thereof.
[0058] Illustrative examples of suitable polyalkoxylated ammonium
compounds include the hydrochloride salts of polyalkoxylated amines
such as JEFFAMINE (of Huntsman Chemical), namely, JEFFAMINE-506 and
JEFFAMINE 505, and an amine available under the trade name ETHOMEEN
(of Akzo Chemie America), namely, ETHOMEEN 18/25, which is
octadecyl bis(polyoxyethylene[15])amine, wherein the numbers in
brackets refer to the total number of ethylene oxide units. A
further illustrative example of a suitable polyalkoxylated ammonium
compound is ETHOQUAD 18/25 (of Akzo Chemie America), which is
octadecyl methyl bis(polyoxyethylene[15]) ammonium chloride,
wherein the numbers in brackets refer to the total number of
ethylene oxide units. The preferred organic cation for use in
polyesters, such as polyethylene terephthalates, is a
polyalkoxylated ammonium compound, preferably ETHOQUAD 18/25.
[0059] Numerous methods to modify layered clays with organic
cations are known, and any of these may be used in the practice of
this invention.
[0060] One embodiment of this invention is the modification of a
layered clay with an organic cation salt by the process of
dispersing a layered clay or mixture of clays into hot water, most
preferably from 50 to 80.degree. C., adding the organic cation salt
separately or adding a mixture of the organic cation salts (neat or
dissolved in water or alcohol) with agitation, then blending for a
period of time sufficient for the organic cations to exchange most
of the metal cations present in the galleries between the layers of
the clay material(s). Then, the organically modified layered clay
material(s) is isolated by methods known in the art including, but
not limited to, filtration, centrifugation, spray drying, and their
combinations.
[0061] It is desirable to use a sufficient amount of the organic
cation salt(s) to permit exchange of most of the metal cations in
the galleries of the layered particle for the organic cation(s);
therefore, at least about 0.5 equivalent of total organic cation
salts is used and up to about 3 equivalents of organic cation salts
can be used. It is preferred that about 0.5 to 2 equivalents of
organic cation salts be used, more preferably about 0.9 to 1.5
equivalents. It is desirable, but not required, to remove most of
the metal cation salts and most of the excess organic cation salts
by washing and other techniques known in the art.
[0062] Prior to incorporation into a polymer, the particle size of
the clay material is reduced in size by methods known in the art,
including, but not limited to, grinding, pulverizing, hammer
milling, jet milling, and their combinations. It is preferred that
the average particle size be reduced to less than 100 micron in
diameter, more preferably less than 50 micron in diameter, and most
preferably less than 20 micron in diameter.
[0063] The clay mixtures may be further treated for the purposes of
aiding exfoliation in the composite and/or improving the strength
of the polymer/clay interface. Any treatment that achieves the
above goals may be used. Examples of useful treatments include
intercalation with water-soluble or water-insoluble polymers,
organic reagents or monomers, silane compounds, metals or
organometallics, and/or their combinations. Treatment of the clay
can be accomplished prior to the addition of a polymer to the clay
material mixture, during the dispersion of the clay mixture with a
polymer or during a subsequent melt blending or melt fabrication
step.
[0064] Examples of useful pretreatment with polymers and oligomers
include those disclosed in U.S. Pat. Nos. 5,552,469 and 5,578,672,
incorporated herein by reference. Examples of useful polymers for
treating the clay mixtures include polyvinyl pyrrolidone, polyvinyl
alcohol, polyethylene glycol, polytetrahydrofuran, polystyrene,
polycaprolactone, certain water-dispersible polyesters, Nylon-6 and
the like.
[0065] Examples of useful pretreatment with organic reagents and
monomers include those disclosed in EP 780,340 A1, incorporated
herein by reference. Examples of useful organic reagents and
monomers for intercalating the swellable layered clay include
dodecylpyrrolidone, caprolactone, caprolactam, ethylene carbonate,
ethylene glycol, bishydroxyethyl terephthalate, dimethyl
terephthalate, and the like or mixtures thereof.
[0066] Examples of useful pretreatment with silane compounds
include those treatments disclosed in WO 93/11190, incorporated
herein by reference. Examples of useful silane compounds includes
(3-glycidoxypropyl)trimethox- ysilane, 2-methoxy
(polyethyleneoxy)propyl heptamethyl trisiloxane, octadecyl dimethyl
(3-trimethoxysilylpropyl) ammonium chloride and the like.
[0067] If desired, a dispersing aid may be present during or prior
to the formation of the composite by melt mixing for the purposes
of aiding exfoliation of the treated or untreated swellable layered
particles into the polymer. Many such dispersing aids are known,
covering a wide range of materials including water, alcohols,
ketones, aldehydes, chlorinated solvents, hydrocarbon solvents,
aromatic solvents, and the like or combinations thereof.
[0068] It should be appreciated that on a total composition basis,
dispersing aids and/or pretreatment compounds may account for
significant amount of the total composition, in some cases up to
about 30 weight percent. While it is preferred to use as little
dispersing aid/pretreatment compound as possible, the amounts of
dispersing aids and/or pretreatment compounds may be as much as
about 8 times the amount of the platelet particles.
[0069] Any melt-processible polymer or oligomer may be used in this
invention. Illustrative of melt-processible polymers are
polyesters, polyetheresters, polyamides, polyesteramides,
polyurethanes, polyimides, polyetherimides, polyureas,
polyamideimides, polyphenyleneoxides, phenoxy resins, epoxy resins,
polyolefins, polyacrylates, polystyrenes, polyethylene-co-vinyl
alcohols (EVOH), and the like or their combinations and blends.
Although the preferred polymers are linear or nearly linear,
polymers with other architectures, including branched, star,
cross-linked and dendritic structures, may be used if desired.
[0070] The preferred polymers include those materials that are
suitable for use in the formation of multilayer structures with
polyesters, and include polyesters (such as poly(ethylene
terephthalate)), polyamides (such as poly(m-xylylene adipamide)),
polyethylene-co-vinyl alcohols (such as EVOH), and similar or
related polymers and/or copolymers. The most preferred polyester is
poly(ethylene terephthalate) and/or its copolymers. The most
preferred polyamide is poly(m-xylylene adipamide) and/or its
copolymers.
[0071] Suitable polyesters include at least one dibasic acid and at
least one glycol. The primary dibasic acids are terephthalic,
isophthalic, naphthalenedicarboxylic, 1,4-cyclohexanedicarboxylic
acid and the like. The various isomers of naphthalenedicarboxylic
acid or mixtures of isomers may be used, but the 1,4-, 1,5-, 2,6-,
and 2,7-isomers are preferred. The 1,4-cyclohexanedicarboxylic acid
may be in the form of cis, trans, or cis/trans mixtures. In
addition to the acid forms, the lower alkyl esters or acid
chlorides may be also be used.
[0072] The preferred polyester is poly(ethylene terephthalate)
(PET) or a copolymer thereof. The polyester may be prepared from
one or more of the following dicarboxylic acids and one or more of
the following glycols.
[0073] The dicarboxylic acid component of the polyester may
optionally be modified with up to about 50 mole percent of one or
more different dicarboxylic acids. Such additional dicarboxylic
acids include dicarboxylic acids having from 3 to about 40 carbon
atoms, and more preferably dicarboxylic acids selected from
aromatic dicarboxylic acids preferably having 8 to 14 carbon atoms
aliphatic dicarboxylic acids preferably having 4 to 12 carbon
atoms, or cycloaliphatic dicarboxylic acids preferably having 8 to
12 carbon atoms. Examples of suitable dicarboxylic acids include
phthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid,
cyclohexanedicarboxylic acid, cyclohexanediacetic acid,
diphenyl-4,4'-dicarboxylic acid, phenylene (oxyacetic acid)
succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic
acid, and the like. Polyesters may also be prepared from two or
more of the above dicarboxylic acids.
[0074] Typical glycols used in the polyester include those
containing from two to about ten carbon atoms. Preferred glycols
include ethylene glycol, propanediol, 1,4-butanediol,
1,6-hexanediol, 1,4-cyclohexanedimethanol, diethylene glycol and
the like. The glycol component may optionally be modified with up
to about 50 mole percent, preferably up to about 25 mole percent,
and more preferably up to about 15 mole percent of one or more
different diols. Such additional diols include cycloaliphatic diols
preferably having 3 to 20 carbon atoms or aliphatic diols
preferably having 3 to 20 carbon atoms. Examples of such diols
include: diethylene glycol, triethylene glycol,
1,4-cyclohexanedimethanol, propane-1,3-diol, butane-1,4-diol,
pentane-1,5-diol, hexane-1,6-diol, 3-methylpentanediol-(2,4),
2-methylpentanediol-(1,4), 2,2,4-trimethylpentane-diol-(1,3),
2-ethylhexanediol-(1,3), 2,2-diethylpropane-diol-(1,3),
hexanediol-(1,3), 1,4-di-(2-hydroxyethoxy)- -benzene,
2,2b-is-(4-hydroxycyclohexyl)-propane, 2,4-dihydroxy-1,1,3,3-tet-
ramethyl-cyclobutane, 2,2-bis-(3-hydroxyethoxyphenyl)-propane,
2,2-bis-(4-hydroxypropoxyphenyl)-propane and the like. Polyesters
may also be prepared from two or more of the above diols.
[0075] Small amounts of multifunctional polyols such as
trimethylolpropane, pentaerythritol, glycerol and the like may be
used, if desired. When using 1,4-cyclohexanedimethanol, it may be
the cis, trans or cis/trans mixtures. When using
phenylenedi(oxyacetic acid), it may be used as 1,2; 1,3; 1,4
isomers, or mixtures thereof.
[0076] The polymer may also contain small amounts of trifunctional
or tetrafunctional comonomers to provide controlled branching in
the polymers. Such comonomers include trimellitic anhydride,
trimethylolpropane, pyromellitic dianhydride, pentaerythritol,
trimellitic acid, trimellitic acid, pyromellitic acid and other
polyester forming polyacids or polyols generally known in the
art.
[0077] Suitable polyamides include partially aromatic polyamides,
aliphatic polyamides, wholly aromatic polyamides and/or mixtures
thereof. By "partially aromatic polyamide," it is meant that the
amide linkage of the partially aromatic polyamide contains at least
one aromatic ring and a nonaromatic species. Suitable polyamides
have an article forming molecular weight and preferably an I.V. of
greater than 0.4.
[0078] Preferred wholly aromatic polyamides comprise in the
molecule chain at least 70 mole % of structural units derived from
m-xylylene diamine or a xylylene diamine mixture comprising
m-xylylene diamine and up to 30% of p-xylylene diamine and an
aliphatic dicarboxylic acid having 6 to 10 carbon atoms, which are
further described in Japanese Patent Publications No. 1156/75, No.
5751/75, No. 5735/75 and No. 10196/75 and Japanese Patent
Application Laid-Open Specification No. 29697/75.
[0079] Polyamides formed from isophthalic acid, terephthalic acid,
cyclohexanedicarboxylic acid, meta- or para-xylylene diamine, 1,3-
or 1,4-cyclohexane(bis)methylamine, aliphatic diacids with 6 to 12
carbon atoms, aliphatic amino acids or lactams with 6 to 12 carbon
atoms, aliphatic diamines with 4 to 12 carbon atoms, and other
generally known polyamide forming diacids and diamines can be used.
The low molecular weight polyamides may also contain small amounts
of trifunctional or tetrafunctional comonomers such as trimellitic
anhydride, pyromellitic dianhydride, or other polyamide forming
polyacids and polyamines known in the art.
[0080] Preferred partially aromatic polyamides include, but are not
limited to poly(m-xylylene adipamide), poly(m-xylylene
adipamide-co-isophthalamide), poly(hexamethylene isophthalamide),
poly(hexamethylene isophthalamide-co-terephthalamide),
poly(hexamethylene adipamide-co-isophthalamide), poly(hexamethylene
adipamide-co-terephthala- mide), poly(hexamethylene
isophthalamide-co-terephthalamide) and the like or mixtures
thereof. More preferred partially aromatic polyamides include
poly(m-xylylene adipamide), poly(hexamethylene
isophthalamide-co-terephth- alamide), poly(m-xylylene
adipamide-co-isophthalamide), and/or mixtures thereof. The most
preferred partially aromatic polyamide is poly(m-xylylene
adipamide).
[0081] Preferred aliphatic polyamides include, but are not limited
to poly(hexamethylene adipamide) and poly(caprolactam). The most
preferred aliphatic polyamide is poly(hexamethylene adipamide).
Partially aromatic polyamides are preferred over the aliphatic
polyamides where good thermal properties are crucial.
[0082] Preferred aliphatic polyamides include, but are not limited
to polycapramide (nylon 6), poly-aminoheptanoic acid (nylon 7),
poly-aminonanoic acid (nylon 9), polyundecane-amide (nylon 11),
polyaurylactam (nylon 12), poly(ethylene-adipamide) (nylon 2,6),
poly(tetramethylene-adipamide) (nylon 4,6),
poly(hexamethylene-adipamide) (nylon 6,6),
poly(hexamethylene-sebacamide) (nylon 6,10),
poly(hexamethylene-dodecamide) (nylon 6,12),
poly(octamethylene-adipamide- ) (nylon 8,6),
poly(decamethylene-adipamide) (nylon 10,6),
poly(dodecamethylene-adipamide) (nylon 12,6) and
poly(dodecamethylene-seb- acamide) (nylon 12,8).
[0083] The most preferred polyamides include poly(m-xylylene
adipamide), polycapramide (nylon 6) and polyhexamethylene-adipamide
(nylon 6,6). Poly(m-xylylene adipamide) is a preferred polyamide
due to its availability, high barrier, and processability.
[0084] The polyamides are generally prepared by processes that are
well known in the art.
[0085] Although not necessarily preferred, the polymers of the
present invention may also include additives normally used in
polymers. Illustrative of such additives known in the art are
colorants, pigments, carbon black, glass fibers, fillers, impact
modifiers, antioxidants, stabilizers, flame retardants, reheat
aids, crystallization aids, acetaldehyde reducing compounds,
recycling release aids, oxygen scavengers, plasticizers,
nucleators, mold release agents, compatibilizers, and the like, or
their combinations.
[0086] All of these additives and many others and their use are
known in the art and do not require extensive discussion.
Therefore, only a limited number will be referred to, it being
understood that any of these compounds can be used in any
combination so long as they do not hinder the present invention
from accomplishing its objects.
[0087] This invention also relates to monolayer and multilayer
articles prepared from the nanocomposite material of this
invention, including, but not limited to, film, sheet, pipes,
tubes, profiles, molded articles, preforms, stretch blow molded
films and containers, injection blow molded containers, extrusion
blow molded films and containers, thermoformed articles and the
like. The containers are preferably bottles.
[0088] The bottles and containers of this invention provide
increased shelf storage life for contents, including beverages and
food that are sensitive to the permeation of gases. Articles, more
preferably containers, of the present invention often display a gas
transmission or permeability rate (oxygen, carbon dioxide, water
vapor) of at least 10% lower (depending on clay concentration) than
that of similar containers made from clay-free polymer, resulting
in correspondingly longer product shelf life provided by the
container. Desirable values for the sidewall modulus and tensile
strength may also be maintained.
[0089] The articles may also be multilayered. Preferably, the
multilayered articles have a nanocomposite material disposed
intermediate to other layers, although the nanocomposite may also
be one layer of a two-layered article. In embodiments where the
nanocomposite and its components are approved for food contact, the
nanocomposite may form the food contact layer of the desired
articles. In other embodiments it is preferred that the
nanocomposite be in a layer other than the food contact layer.
[0090] The multilayer articles may also contain one or more layers
of the nanocomposite composition of this invention and one or more
layers of a structural polymer. A wide variety of structural
polymers may be used. Illustrative of structural polymers are
polyesters, polyetheresters, polyamides, polyesteramides,
polyurethanes, polyimides, polyetherimides, polyureas,
polyamideimides, polyphenyleneoxides, phenoxy resins, epoxy resins,
polyolefins, polyacrylates, polystyrene, polyethylene-co-vinyl
alcohols (EVOH), and the like or their combinations and blends. The
preferred structural polymers are polyesters, such as poly(ethylene
terephthalate) and its copolymers.
[0091] In another embodiment of this invention, the polymer-clay
nanocomposite and the molded article or extruded sheet may be
formed at the same time by co-injection molding or
co-extruding.
[0092] Another embodiment of this invention is the combined use of
silicate layers uniformly dispersed in the matrix of a high barrier
thermoplastic together with the multilayer approach to packaging
materials. By using a layered clay mixture to decrease the gas
permeability in the high barrier layer, the amount of this material
that is needed to generate a specific barrier level in the end
application is greatly reduced.
[0093] Since the high barrier material is often the most expensive
component in multilayer packaging, a reduction in the amount of
this material used can be quite beneficial. With the nanocomposite
layer being sandwiched between two outer polymer layers, the
surface roughness is often considerably less than for a monolayer
nanocomposite material. Thus, with a multilayer approach, the level
of haze is reduced.
EXAMPLES
[0094] The following examples are put forth to further illustrate
this invention and so as to provide those of ordinary skill in the
art with a more complete disclosure and description of how the
nanocomposite compositions claimed herein are made and evaluated.
They are not intended to limit the scope of what the inventors
regard as their invention. Efforts have been made to insure
accuracy with respect to numbers (e.g., amounts, temperature, etc.)
but some errors and deviations should be accounted for. Unless
indicated otherwise, parts are by weight, temperature is in .sup.BC
or is at room temperature and pressure is at or near
atmospheric.
EXAMPLE 1
[0095] This example illustrates a method for preparing a blend of
organoclays fabricated from different clays but containing the same
alkylammonium tether.
[0096] Sodium montmorillonite (7.50 grams, 7.12 milliequivalents)
supplied by Southern Clay Products and reported to have a cation
exchange capacity of 95 milliequivalents/100 grams and Laponite RD
(2.5 grams, 1.37 milliequivalents) were mixed in 490 ml of water at
60.degree. C. in a Vitamix blender to form a 2% by weight slurry of
clay in water. Octadecyltrimethylammonium chloride (5.9 grams, 8.49
milliequivalents), commercially available as a 50% solution in
isopropanol as ARQUAD 18/50, was dissolved in 25 ml of water then
added to the Vitamix blender containing the clay suspension. This
mixture was blended at high speed for one minute and the solids
formed were removed by filtration on a Buchner funnel. The product
was reslurried in 250 ml of water in a Vitamix blender, filtered
again, and dried in a circulating air oven at 60.degree. C. for 16
hours. The product exhibited a basal spacing by X-ray diffraction
of 1.86 nanometers.
EXAMPLE 2
[0097] This example illustrates a method for blending two
organoclays in solvents and the melt compounding of this blend into
PET.
[0098] Octadecyl methyl di(2-hydroxyethyl)ammonium montmorillonite
(20.7 grams) and dodecylammonium montmorillonite (19.2 grams) were
suspended in 1000 ml of a solution of 85 wt % toluene and 15 wt %
methanol. The mixture was thoroughly blended with an Ultra Turrax
T50 blender. The solvent was evaporated from the mixture and the
solid remaining was dried in an oven at 60.degree. C. for 24 hours.
The product exhibited a basal spacing by X-ray diffraction of 1.5
nanometers.
[0099] Polyethylene terephthalate (375 grams) (or PET 9921 of
Eastman Chemical Company) was dry blended with the mixed
organoclays (25 grams) described above and the blend dried in a
vacuum oven at 110.degree. C. for 16 hours. The blend was extruded
on a Leistritz Micro-18 double screw extruder at 275 .degree. C.
and 200 rpm. The molten strand was quenched in chilled water and
pelletized. The polyester composite had an inherent viscosity of
0.56 dl/g and an ash content of 4.5 wt %.
[0100] The pellets are dried at 115 .degree. C. in a vacuum oven
for about 16 hours then compression molded into about 10 mil film
by pressing the sample between layers of polyimide film at 285
.degree. C. The oxygen permeability of the polyester/composite is
then determined by correcting for the permeability of the polyimide
film and converting to a one-mil basis using conventional
calculations. The oxygen permeability rate is 5.48 cc-mil/100
in.sup.2-24 hour-atmosphere.
[0101] A film of poly(ethylene terephthalate) molded under
conditions similar to those used above has an oxygen permeability
of 14.0 cc-mil/100 in.sup.2-24 hour-atmosphere.
EXAMPLE 3
[0102] This example illustrates a method for blending an organoclay
and sodium montmorillonite in solvents and the melt compounding of
this blend into PET.
[0103] Octadecyl methyl di(2-hydroxyethyl)ammonium montmorillonite
(39.9 grams) and sodium montmorillonite (20 grams) were suspended
in 1000 ml of a solution of 85 wt % toluene and 15 wt % methanol.
The mixture was thoroughly blended with an Ultra Turrax T50
blender. The solvent was evaporated from the mixture and the solid
remaining was dried in an oven at 60.degree. C. for 24 hours. The
product exhibited a basal spacing by X-ray diffraction of 1.4
nanometers.
[0104] Polyethylene terephthalate (375 grams) (or PET 9921 of
Eastman Chemical Company) was dry blended with the mixed clays (25
grams) described above and the blend dried in a vacuum oven at
110.degree. C. for 16 hours. The blend was extruded on a Leistritz
Micro-18 double screw extruder at 275.degree. C. and 200 rpm. The
molten strand was quenched in chilled water and pelletized. The
polyester composite had an inherent viscosity of 0.57 dl/g and an
ash content of 4.8wt %.
[0105] The pellets are dried at 115 .degree. C. in a vacuum oven
for about 16 hours then compression molded into about 10 mil film
by pressing the sample between layers of polyimide film at
285.degree. C. The oxygen permeability of the polyester/composite
is then determined by correcting for the permeability of the
polyimide film and converting to a one-mil basis using conventional
calculations. The oxygen permeability rate is 5.76 cc-mil/100
in.sup.2-24 hour-atmosphere.
EXAMPLE 4
[0106] This example illustrates a method for blending an organoclay
and the synthetic clay Laponite RD in solvents and the melt
compounding of this blend into PET.
[0107] Octadecyl methyl di(2-hydroxyethyl)ammonium montmorillonite
(39.9 grams) and Laponite RD (20 grams) were suspended in 1000 ml
of a solution of 85 wt % toluene and 15 wt % methanol. The mixture
was thoroughly blended with an Ultra Turrax T50 blender. The
solvent was evaporated from the mixture and the solid remaining was
dried in an oven at 60.degree. C. for 24 hours. The product
exhibited a basal spacing by X-ray diffraction of 1.4
nanometers.
[0108] Polyethylene terephthalate (375 grams) (or PET 9921 of
Eastman Chemical Company) was dry blended with the mixed clays (25
grams) described above and the blend dried in a vacuum oven at
110.degree. C. for 16 hours. The blend was extruded on a Leistritz
Micro- 18 double screw extruder at 275.degree. C. and 200 rpm. The
molten strand was quenched in chilled water and pelletized. The
polyester composite had an inherent viscosity of 0.63 dl/g and an
ash content of 4.1 wt %.
[0109] The pellets are dried at 115 .degree. C. in a vacuum oven
for about 16 hours then compression molded into about 10 mil film
by pressing the sample between layers of polyimide film at
285.degree. C. The oxygen permeability of the polyester/composite
is then determined by correcting for the permeability of the
polyimide film and converting to a one-mil basis using conventional
calculations. The oxygen permeability rate is 5.52 cc-mil/100
in.sup.2-24 hour-atmosphere.
EXAMPLE 5
[0110] The procedure of Example 1 was repeated using different
weight percent combinations of sodium montmorillonite and Laponite
RD. Sodium montmorillonite and Laponite RD were also tested
individually. The results are shown in Table 1.
[0111] The resulting clay mixtures, as shown in Table 1, display
X-ray diffraction basal spacings that are intermediate between that
of the two clays individually. Intermediate basal spacings indicate
that intimate mixing was achieved in the mixture and also indicates
a transformation of the order of the clay materials from two basal
spacings to one intermediate basal spacing. In other words, the
spacing of each individual organoclay has been disordered from one
basal spacing order to another.
1 TABLE 1 Weight Ratio of sodium montmorillonite to Laponite RD
X-ray Basal Spacing (nm) 100:0 2.0 75:25 1.86 50:50 1.78 25:75 1.49
0:100 1.43
EXAMPLE 6
[0112] This example demonstrates the formation of onium
ion-intercalated clay with mixed montmorillonite clays. Nanocor,
Inc. provides several kinds of Na-montmorillonite clays. These
clays originate from different geographic locations. For example,
one Na-montmorillonite is called Na-CWC, which has a cation
exchange capacity of about 1.4 meq per gram. Another
Na-montmorillonite, called Na-Belle Yellow (Na-BY), has a cation
exchange capacity of 1.2 meq per gram. Na-CWC and Na-BY also have
different particle sizes and particle size distributions. Na-CWC is
white-like, but with tint color when dispersed into water. Na-BY
has yellow color in dry and slurry form. They are not preferred to
use as a single clay source in the nanocomposite formation.
However, the combination of Na-CWC and Na-BY will alter the color
of the final clay. The CEC difference will allow the clay mixture
to create a disordered and more easily dispersed system of
platelets in a matrix polymer. They are good candidates for the
formation of onium ion-exchanged clays. 50 g of Na-CWC and 50 g of
Na-BY were slurried in 4000 g of distilled water, and mixed
thoroughly and heated to 80-85.degree. C. 0.13 moles of
octadecylamine and 0.13 moles of HCl were added to 2000 g of water
and heated to 80-85.degree. C. The ODA solution was mixed with the
mixed clay slurry. Onium ion-intercalated clay precipitated from
the slurry upon mixing. The treated clay was filtered, washed, and
dried according to procedures stated in the early text. X-ray
diffraction XRD results of the ODA-CWC/BY (1:1) and ODA-CWC, and
ODA-BY clays are given in the following table. The poor intensity
and broad half-height weight indicated the onium ion-intercalated
clays prepared with mixed montmorillonite clays had lower ordering
than their analogues.
2 Na-CWC to Na-BY X-ray Basal Spacing XRD d001 peak density
(weight) (nm) and half height width 0:100 19.2 Good intensity,
narrow width 50:50 20.3 Poor intensity, broad width 100:0 22.0 Good
intensity, narrow width
[0113] The milled clay was compounded into PET to form a
nanocomposite and the compounded nanocomposite showed improved
color compared to the nanocomposite prepared from single CWC or BY
clays. The nanocomposite demonstrated improved O.sub.2 barrier
properties compared with the PET-9921 (of Eastman Chemical) resin
and nanocomposites prepared from single clays. The nanocomposites
prepared from the mixed clays are suitable for use in PET contained
applications, such as bottled water, beer and soft drinks, as well
as for incorporation into all other polymers.
COMPARATIVE EXAMPLE 1
[0114] Equal portions of octadecyltrimethylammonium-intercalated
sodium montmorillonite and octadecylammonium-intercalated Laponite
RD were dry mixed (in contrast to intimately mixed) and then
evaluated by X-ray diffraction, which showed two basal spacings of
1.86 nm and 1.34 nm. These spacings are about the same as that of
the individual clay materials, indicating that the order within
each of the clay tactoids is preserved.
[0115] In other words, the dry mixed clay mixture did not transform
the order from two basal spacings to one intermediate basal
spacing. This lack of order transformation may result in less
dispersion when the clay mixture is intercalated with a matrix
polymer to form a polymer-clay nanocomposite.
[0116] Throughout this application, various publications are
referenced. The disclosures of these publications in their
entireties are hereby incorporated by reference into this
application in order to more fully describe the state of the art to
which this invention pertains.
[0117] It will be apparent to those skilled in the art that various
modifications and variations can be made in the present invention
without departing from the scope or spirit of the invention. Other
embodiments of the invention will be apparent to those skilled in
the art from consideration of the specification and practice of the
invention disclosed herein. It is intended that the specification
and examples be considered as exemplary only, with a true scope and
spirit of the invention being indicated by the following
claims.
* * * * *