U.S. patent application number 09/209310 was filed with the patent office on 2001-07-19 for clear, high-barrier polymer - platelet composite multilayer structures.
Invention is credited to BAGRODIA, SHRIRAM, GERMINARIO, LOUIS THOMAS, PINER, RODNEY LAYNE, TREXLER, JACK WESLEY JR..
Application Number | 20010008699 09/209310 |
Document ID | / |
Family ID | 26758135 |
Filed Date | 2001-07-19 |
United States Patent
Application |
20010008699 |
Kind Code |
A1 |
BAGRODIA, SHRIRAM ; et
al. |
July 19, 2001 |
CLEAR, HIGH-BARRIER POLYMER - PLATELET COMPOSITE MULTILAYER
STRUCTURES
Abstract
This invention relates to novel multilayer formed articles
including, but not limited to containers such as bottles, tubes,
pipes, preforms and films (including oriented films such as
biaxially oriented) comprising a melt processible resin having
dispersed therein a platelet filler. The multilayer formed articles
have improved barrier while maintaining excellent clarity. More
particularly, the multilayer structures of the present invention
display haze values of less than about 2% and carrier resins which
are substantially free from platelet particles having a diameter
greater than about 15 microns.
Inventors: |
BAGRODIA, SHRIRAM;
(KINGSPORT, TN) ; GERMINARIO, LOUIS THOMAS;
(KINGSPORT, TN) ; PINER, RODNEY LAYNE; (KINGSPORT,
TN) ; TREXLER, JACK WESLEY JR.; (KINGSPORT,
TN) |
Correspondence
Address: |
NEEDLE & ROSENBERG P.C.
SUITE 1200
THE CANDLER BUILDING
127 PEACHTREE STREET N.E.
ATLANTA
GA
303031811
|
Family ID: |
26758135 |
Appl. No.: |
09/209310 |
Filed: |
December 11, 1998 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60076458 |
Mar 2, 1998 |
|
|
|
Current U.S.
Class: |
428/475.2 ;
428/324; 428/331; 428/476.9; 428/483; 428/522 |
Current CPC
Class: |
Y10T 428/251 20150115;
Y10T 428/31725 20150401; Y10T 428/31757 20150401; Y10T 428/31913
20150401; Y10T 428/31721 20150401; Y10T 428/25 20150115; Y10T
428/31935 20150401; B32B 27/20 20130101; Y10T 428/31928 20150401;
Y10T 428/31786 20150401; Y10T 428/31938 20150401; Y10T 428/31736
20150401; Y10T 428/31855 20150401; Y10T 428/3175 20150401; Y10T
428/31797 20150401; Y10T 428/259 20150115; Y10S 428/91 20130101;
Y10T 428/31728 20150401; Y10T 428/31507 20150401; Y10T 428/3192
20150401 |
Class at
Publication: |
428/475.2 ;
428/324; 428/331; 428/476.9; 428/483; 428/522 |
International
Class: |
B32B 027/36; B32B
027/06; B32B 005/16 |
Claims
We claim:
1. Multilayer, oriented structures comprising at least one inner
layer comprising a carrier resin and at least about 0.01 weight %
platelet particles and at least one outer layer comprising a
thermoplastic polymer, wherein said multilayer structures display
haze values of less than about 2% and said carrier resin is
substantially free from platelet particles having a diameter
greater than about 15 microns.
2. The multilayer structures of claim 1 wherein said structures
comprise at least three layers, and said inner layer is disposed
between at least two outer layers.
3. The multilayer structures of claim 1 wherein said structures
display a permeability to oxygen which is at least about 10% lower
than permeability to oxygen of a film of said thermoplastic polymer
alone.
4. The multilayer structures of claim 1 wherein said platelet
particles have a mean platelet particle of less than about 10
microns.
5. The multilayer structures of claim 1 wherein said platelet
particles have a mean platelet particle of less than about 7
microns.
6. The multilayer structures of claim 2 wherein said at least two
outer layers are independently selected from the group consisting
of melt processible synthetic polymeric materials.
7. The multilayer structures of claim 6 wherein said at least two
outer layers are independently selected from the group consisting
of polyesters, wholly aromatic polyesters, water dispersible
polyesters, polyamides, copolymers of ethylene and vinyl alcohol,
ethyl-vinyl acetate copolymer, polyimides, polycarbonate,
polystyrene, polyvinylchloride (PVC), polyacrylates, polyolefins,
recycled polymers and mixtures thereof.
8. The multilayer structures of claim 6 wherein said at least two
outer layers are independently selected from the group consisting
of polyesters, copolymers of ethylene vinyl acetate copolymer,
copolymers of ethylene and vinyl alcohol, polyamides and mixtures
thereof.
10. The multilayer structure of claim 1 wherein said carrier resin
is selected from the group consisting of polyesters, wholly
aromatic polyesters, water dispersible polyesters, polyamides,
copolymers of ethylene and vinyl alcohol, ethyl-vinyl acetate
copolymer, polyimides, polycarbonate, polystyrene,
polyvinylchloride (PVC), polyacrylates, polyolefins, recycled
polymers and mixtures thereof.
11. The multilayer structure of claim 1 wherein said carrier resin
is selected from the group consisting of polyesters, copolymers of
ethylene vinyl acetate copolymer, copolymers of ethylene and vinyl
alcohol, polyamides and mixtures thereof.
12. The multilayer structure of claim 1 wherein said platelet
particles are present in said carrier resin in an amount between
about 0.01 weight % and 50 weight %.
13. The multilayer structure of claim 1 wherein said carrier resin
is selected from the group consisting of polyesters, copolymers of
ethylene vinyl acetate copolymer, copolymers of ethylene and vinyl
alcohol, polyamides and mixtures thereof and said at least two
outer layers are selected from the group consisting of
polyesters.
16. The multilayer structures of claim 1 wherein said carrier resin
comprises less than about 100 visible platelet particles/mm.sup.2
at a magnification of 40X.
17. The multilayer structures of claim 1 wherein said carrier resin
comprises less than about 50 visible platelet particles/mm.sup.2 at
a magnification of 40X.
18. The multilayer structures of claim 1 wherein said carrier resin
comprises less than about 30 visible platelet particles/mm.sup.2 at
a magnification of 40X.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. provisional
application Ser. No. 60/076,458 filed Mar. 2, 1998.
BACKGROUND OF THE INVENTION
[0002] There are many bottle and film applications for melt
processible plastics with improved barrier properties. Dispersion
of platelet like fillers has the potential to improve the oxygen
barrier of polymers while maintaining clarity in amorphous film;
however, these materials are not suited to processes that involve
orientation between the melting point and glass transition
temperatures, including stretch blow molding of bottles and biaxial
orientation of film, due to the formation of translucent to opaque
materials It would therefore be desirable to provide improved
barrier properties by use of platelet fillers while retaining the
ability to form clear material upon orientation below the melting
point temperature.
[0003] Many processes to form multilayer stretch blow molded
bottles having 2 to 7 layers are known in the art. For example,
U.S. Pat. No. 4,646,925 discloses the production of multilayer
stretch blow molded bottles comprising an internal layer of
unfilled polyethylene-co-vinyl alcohol.
[0004] Researchers have attempted to incorporate fillers, including
platelet fillers, in an effort to improve the barrier of
polyethylene-co-vinyl alcohol used in multilayer bottles; however,
the bottles are opaque or have poor appearance due to the large
size of the filler particles and have only a minor improvement in
barrier compared to bottles prepared using unfilled
polyethylene-co-vinyl alcohol due to the low aspect ratios of the
filler particles. Japanese Kokai patent No. Hei 9-176461 discloses
multilayer polyester bottles having an inner layer containing
swellable laminar silicate. However, the laminar silicates are not
well dispersed, and therefore provide little or no improvement in
barrier of the resulting multilayer structure. U.S. Pat. No.
4,680,208 discloses trilayer stretch blow molded bottles comprising
an internal layer of a 0.5 to 30 weight percent glass fiber
reinforced composite with either polyethylene-co-vinyl alcohol,
meta-xylene type polyamide, or polyethylene terephthalate. U.S.
Pat. No. 4,983,432 discloses multilayer structures, including
bottles, comprising a layer of a composite of polyethylene-co-vinyl
alcohol and mica that has a particle size of less than about 74
microns and an aspect ratio less than 50. PCT Application WO
97/44384 is concerned with multilayer toothpaste tube bodies
comprising a white, opaque layer of polyethylene-co-vinyl alcohol
containing talc particles that have been delaminated by shearing to
provide reduced particles size, thickness of less than 1 micron,
and increased aspect ratio of less than 35. Similar efforts to
delaminate mica particles have provided a reduction in particle
size at the expense of a reduction in particle aspect ratio due to
breakage of the mica platelets.
[0005] European Patent Applications EP 0 590 263 A2, EP 0 691 212
A1 (1996), EP 0 691 376 A1 (1996), and EP 0 761 739 A1 (1997) are
concerned with water or solvent cast laminates of a composite
comprised of a high hydrogen-bonding resin, such as polyvinyl
alcohol and polyethylene-co-vinyl alcohol, and an inorganic laminar
compound, such as sodium montmorillonite. European Patent
Application EP 0 761 739 A1 (1997) further refines the above
applications and is concerned with water cast films of a composite
comprising either polyvinyl alcohol and polyethylene-co-vinyl
alcohol and an inorganic laminar compound, such as sodium
montmorillonite, that has been delaminated to provide particles
with high aspect ratio by aggregating the particles by treatment of
the aqueous dispersion with either acid or alumina sol prior to
evaporating the solvent. However, the preparation of bottles is not
contemplated, as the processes of these inventions and the films
coating thereby formed are not suitable or practical for use in the
manufacture of stretch blow molded bottles comprising an internal
layer of the barrier substrate.
[0006] U.S. Pat. No. 5,552,469, incorporated herein by reference,
describes the preparation of intercalates derived from certain
phyllosilicates and water-soluble polymers such as polyvinyl
pyrrolidone, polyvinyl alcohol, polyethylene-co-vinyl alcohol, and
polyacrylic acid and composite blends prepared from these
intercalates. European Patent Application EP 0 846 723 A1 (1998),
incorporated herein by reference, is concerned with composites
comprising a matrix of polyethylene-co-vinyl alcohol and a
phyllosilicate which has been intercalated with a material other
than polyethylene-co-vinyl alcohol or its monomers.
[0007] There are many examples in the patent literature of
polyamide/organoclay composites containing, for example, Nylon-6
and alkyl ammonium treated montmorillonite. Some patents describe
the blending of up to 60 weight percent of organoclay materials
with a wide range of polymers including polyamides, polyesters,
polyurethanes, polycarbonates, polyolefins, vinyl polymers,
thermosetting resins and the like. Such high loadings with
organoclays are impractical and useless with most polymers because
the melt viscosity of the blends increases so much that they cannot
be molded. This is especially true with polyesters. Also, clays
tend to absorb large quantities of water and attempts to blend them
with preformed polyesters at elevated temperatures cause sever
degradation of the molecular weight of the polyester.
[0008] 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 Pat.
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).
[0009] Among the numerous patents that describe the preparation of
organoclays containing ammonium salts are U.S. Pat. Nos. 2,531,427;
2,966,506; 4,081,496, 4,105,578; 4,116,866, 4,208,218; 4,391,637;
4,410,364; 4,412,018; 4,434,075; 4,434,076, 4,450,095; 4,517,112,
4,677,158; 4,769,078; 5,110,501; and 5,334,241.
[0010] U.S. Pat. No. 4,810,734 describes a process for the
preparation of a mixture of organoclay, monomer, and a dispersing
medium and subsequent polymerization to obtain a polymer/organoclay
composite. The dispersing medium, such as water or alcohol, is
required to improve intercalation of the monomer into the
organoclay and resulted in reduced process time and formation of
composites with improved properties compared to the process using
dry organoclay. Although polyesters are disclosed, no working
example demonstrates the use of polyesters.
[0011] Example II of U.S. Pat. No. 4,889,885 describes the
polycondensation of a mixture of dimethyl terephthalate, ethylene
glycol, and an organoclay in water to achieve 6.2 weight percent
clay in the final PET/organoclay composite. It is known that the
addition of water to the preparation of Nylon-6 from caprolactam
increases polymerization rate. However, addition of water and
alcohols to preparations of PET will have adverse effects on
reaction rate, catalyst activity, final IV, and haze in molded
articles. Therefore, it is desirable to have a process that does
not require the use of water or alcohol as a dispersing aid.
[0012] WO 93/04117 discloses a wide range of polymers melt blended
with up to 60 weight percent of organoclay. Although use of
polyesters is disclosed, specific polyester/organoclay compositions
of any molecular weight are not disclosed.
[0013] WO 93/04118 discloses a composite material of a melt
processible polymer and up to 60 weight percent of organoclay.
Among a wide range of thermoplastic polymers, polyesters are listed
as operable. Example 6 shows the melt compounding of PET and
polypropylene with Claytone APA (a commercial organoclay from
Southern Clay Products) in a twin screw extruder. There is no
identification of the PET with regard to I.V., and the I.V. is
believed to be relatively low (less than about 0.5 dl/g). There is
no disclosure which would suggest how to increase the I.V. of the
materials disclosed. WO 93/11190 describes similar polymer blends.
All examples include polyamides as a polymer component.
[0014] 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. Although the specification describes a wide range of
thermoplastic resins including polyesters and rubbers which can be
used in blends with these intercalates, there are no examples
teaching how to make such blends.
[0015] U.S. Pat. No. 5,578,672 discloses the melt extrusion of a
natural clay (not an organoclay), a polymer, and a liquid carrier
to prepare an intercalate that is capable of exfoliating into a
polymer in the melt. The preparation of intercalates with PET or
its monomers with sodium montmorillonite are demonstrated; however,
there are no examples teaching how to make the exfoliated composite
blends.
[0016] U.S. Ser. No. 995,670 discloses a process for the
preparation of clear bottles from a polyester-platelet composite by
blow molding a molten parison which avoids the opacity formed
during a stretch blow molding process.
DESCRIPTION OF THE FIGURES
[0017] FIG. 1 is a photomicrograph of a trilayer film of the
present invention at 40X.
[0018] FIG. 2 is a photomicrograph of a trilayer film of the prior
art at 40X.
DESCRIPTION OF THE INVENTION
[0019] This invention relates to novel multilayer formed articles
including, but not limited to containers such as bottles, tubes,
pipes, preforms and films (including oriented films such as
biaxially oriented) comprising a melt processible resin having
dispersed therein a platelet filler. The multilayer formed articles
have improved barrier while maintaining excellent clarity. It is
particularly surprising that the multilayer structures of the
present invention display both good dispersibility of the platelet
particles and good clarity, even upon orientation.
[0020] More specifically, the present invention relates to
multilayer, oriented structures comprising at least one inner layer
comprising a carrier resin and at least about 0.01 weight %
platelet particles and at least one outer layer comprising a
thermoplastic polymer, wherein said multilayer structures display
haze values of less than about 2% and said carrier resin is
substantially free from platelet particles having a diameter
greater than about 15 .mu.m.
[0021] It has been found that multilayer structures such as a film
comprising an internal layer of a carrier polymer-platelet
composite and two external layers of the unfilled polymer can be
oriented at temperatures between the glass transition and the
melting point to produce oriented articles with improved barrier
and excellent clarity. It was surprising that particles which are
small as those formed in the present invention would create
substantial haze upon orientation. Without being bound by any
particular theory, it is believed that the external polymer layers
heal the surface defects caused by the presence of filler particles
that would otherwise form upon orientation.
[0022] This approach can be used to take advantage of the improved
barrier properties of the polymer-platelet composites in a wide
variety of applications requiring clear, oriented products
including film and bottles. Many processes to form oriented
multilayer structures in films and bottles are known, and any of
these processes may be used in this invention. Formation of
multilayer structures having at least two layers and preferably
from about 2 to up to about 7 layers are known in the art. This
invention includes all multilayer structures, such as films and
bottles, having at least one layer comprising a melt processible
polymer-platelet composite. An alternate embodiment of the present
invention further comprises at least one layer comprising a melt
processible polymer which is substantially free of platelet
particles. In yet another embodiment the multilayer structure
includes at least one additional layer comprising a melt
processible polymer having platelet particles in a concentration
which may be the same or different than the first layer.
[0023] Carrier Polymers
[0024] Carrier polymers must be melt processible polymers which are
capable of having barrier enhancing platelet particles dispersed
therein. Suitable carrier polymers include, but are not limited to,
melt processible synthetic polymeric materials, such as polyesters
(including, but not limited to wholly aromatic polyesters and water
dispersible polyesters), polyamides, copolymers of ethylene and
vinyl alcohol, ethyl-vinyl acetate copolymer, polyimides,
polycarbonate, polystyrene, polyvinylchloride (PVC), polyacrylates,
polyolefins, recycled polymers and mixtures thereof. The preferred
carrier polymers are those comprising polyesters, copolymers of
ethylene vinyl acetate copolymer, copolymers of ethylene and vinyl
alcohol and polyamides. The carrier polymer is present in amounts
up to about 99.99 wt %, preferably from about 50 to about 99.99
weight %.
[0025] 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.
[0026] The dicarboxylic acid component of the polyester may
optionally be modified with up to about 50 mole percent of one or
more different dicarboxylic acids. Such additional dicarboxylic
acids include dicarboxylic acids having from 6 to about 40 carbon
atoms, and more preferably dicarboxylic acids selected from
aromatic dicarboxylic acids preferably having 8 to 14 carbon atoms,
aliphatic dicarboxylic acids preferably having 4 to 12 carbon
atoms, or cycloaliphatic dicarboxylic acids preferably having 7 to
12 carbon atoms. Examples of suitable dicarboxylic acids include
phthalic acid, isophthalic acid, naphthalene- 2,6-dicarboxylic
acid, cyclohexanedicarboxylic acid, cyclohexanediacetic acid,
diphenyl-4,4'-dicarboxylic acid, succinic acid, glutaric acid,
adipic acid, azelaic acid, sebacic acid, and the like. Polyesters
may be prepared from one or more of the above dicarboxylic
acids.
[0027] Typical glycols used in the polyester include aliphatic
glycols containing from two to about ten carbon atoms, aromatic
glycols containing from 6 to 15 carbon atoms and cycloaliphatic
glycols containing 7 to 14 carbon atoms Preferred glycols include
ethylene glycol, 1,4-butanediol, 1,6-hexanediol,
1,4-cyclohexanedimethanol, diethylene glycol and the like.
Resourcinol and hydroquinone are preferred glycols for producing
fully aromatic polyesters. The glycol component may optionally be
modified with up to about 50 mole percent, preferably up to about
25 mole % and most preferably up to about 15 mole % of one or more
different diols. Such additional diols include cycloaliphatic diols
preferably having 6 to 20 carbon atoms or aliphatic diols
preferably having 3 to 20 carbon atoms. Examples of such diols
include: diethylene glycol, triethylene glycol,
1,4-cyclohexanedimethanol- , propane-1,3-diol, butane-1,4-diol,
pentane-1,5-diol, hexane-1,6-diol, 3-methylpentanediol-(2,4),
2-methylpentanediol-(1,4), 2,2,4-trimethylpentane-diol-( 1,3),
2-ethylhexanediol-( 1,3), 2,2-diethylpropane-diol-( 1,3),
hexanediol-( 1,3), 1,4-di-(2-hydroxyethoxy)-benzene,
2,2-bis-(4-hydroxycyclohexyl)-propane,
2,4-dihydroxy-1,1,3,3-tetramethyl-cyclobutane,
2,2-bis-(3-hydroxyethoxyph- enyl)-propane,
2,2-bis-(4-hydroxypropoxyphenyl)-propane and the like. Polyesters
may be prepared from one or more of the above diols.
[0028] Difunctional components such as hydroxybenzoic acid may also
be used.
[0029] Also small amounts of multifunctional polyols such as
trimethylolpropane, pentaerythritol, glycerol and the like may be
used if desired When using 1,4-cyclohexanedimethanol, it may be the
cis, trans or cis/trans mixtures.
[0030] The resin 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.
[0031] The polyesters of the present invention may be made by any
process which is known in the art. Typically polyesters are made
via known polycondensation processes. The platelet particles may be
added to the polyester at any time, including during melt phase
polymerization, after polymerization but prior to solid stating and
after polymerization via melt blending.
[0032] Suitable polyamides include partially aromatic polyamides,
aliphatic polyamides, wholly aromatic polyamides and 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.
[0033] Suitable polyamides have a film forming molecular weight and
preferably an I.V, of greater than about 0.4. 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 .alpha..SIGMA.-aliphatic dicarboxylic
acid having 6 to 10 carbon atoms, which are further discribed 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.
[0034] 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.
[0035] Preferred partially aromatic polyamides include:
poly(m-xylylene adipamide), poly(hexamethylene isophthalamide),
poly(hexamethylene adipamide-co-isophthalamide), poly(hexamethylene
adipamide-co-terephthala- mide), and poly(hexamethylene
isophthalamide-co-terephthalamide). The most preferred partially
aromatic polyamide is poly(m-xylylene adipamide).
[0036] Preferred aliphatic polyamides include 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
[0037] Preferred aliphatic polyamides include polycapramide (nylon
6), poly-aminoheptanoic acid (nylon 7), poly-aminonanoic acid
(nylon 9), polyundecane-amide (nylon 11), polyaurylactam (nylon
12), polyethylene-adipamide (nylon 2,6),
polytetramethylene-adipamide (nylon 4,6),
polyhexamethylene-adipamide (nylon 6,6),
polyhexamethylene-sebacami- de (nylon 6,10),
polyhexamethylene-dodecamide (nylon 6,12),
polyoctamethylene-adipamide (nylon 8,6),
polydecamethylene-adipamide (nylon 10,6),
polydodecamethylene-adipamide (nylon 12,6) and
polydodecamethylene-sebacamide (nylon 12,8).
[0038] The most preferred polyamides include poly(m -xylylene
adipamide), polycapramide (nylon 6), polyhexamethylene-adipamide
(nylon 6,6), and amorphous polyamides.
[0039] The polyamides are generally prepared by processes which are
known in the art.
[0040] Suitable saponified ethylene-vinyl acetate copolymer
(hereinafter referred to as "EVOH") include polymer prepared by
saponifying an ethylene-vinyl acetate copolymer having an ethylene
content of about 15 to about 60 mole % up to a degree of
saponification of about 90 to about 100%. The EVOH copolymer should
have a molecular weight sufficient for film formation, and a
viscosity of generally at least about 0.01 dl/g, especially at
least about 0.05 dl/g, when measured at 30.degree. C. in a
phenol/water solvent (85:15). Suitable EVOH is available from Eval
Company of America. Copolymers having greater than about 30%
ethylene content are preferred. Eval-F and Eval-H (about 32 and 38%
ethylene content respectively) are commercially available from Eval
Company of America and provide particularly desirable gas barrier
properties.
[0041] Suitable polyimides include condensation polymer derived
from bifunctional carboxylic acid anhydrides and primary diamines,
such as those disclosed in Encyclopedia of Polymer Science and
Engineering, 2.sup.nd Edition, vol 12, 1988, p. 364-383. Aromatic
polyetherimides, processable in the melt are preferred. An example
of a suitable polyimide is ULTEM 1000, which is available from
General Electric Co.
[0042] Suitable polycarbonates include bis-phenol A based
polycarbonates, which are commercially available from General
Electric and prepared by reacting 2,2-bis(4-hydroxyphenyl)propane
(bisphenol A) and phosgene or a diphenyl carbonate.
[0043] Suitable polystyrenes have a melt flow rate (g/10 min., ASTM
D-1238) of about 1.4 to about 14 and those that can be extruded
into films. Suitable polystyrenes are available from a number of
sources, including Dow Chemical Company.
[0044] Suitable polyvinylchloride (PVC) includes injection
moldable/extrudable grades of PVC. Various additives, such as
plasticizers, anti-oxidants, colorants, etc. may also be added. The
melt viscosity is adjusted to be able to blow mold. Typically,
medium to high molecular weight grades of PVC are used. Melt
viscosity is in the range of 1000 to 50,000 poise at processing
temperatures. These can be obtained from Geon, Georgia-Gulf and
many other PVC suppliers.
[0045] Suitable polyolefins, include injection moldable/extrudable
grades of polyolefins such as polypropylene, polyethylene, etc.
with a wide range of Melt Index of about 0.1 to about 20. Suitable
polypropylenes are available from Exxon Chemical Co., Himont, and
suitable polyethylenes are available from Eastman Chemical
Company.
[0046] Suitable recycled polymer includes any recycled carrier
polymer having properties suitable for molding.
[0047] Also, although not required, additives normally used in any
of the above polymers may be used if desired. Such additives
include, but are not limited to colorants, pigments, carbon black,
glass fibers, fillers, impact modifiers, antioxidants, stabilizers,
flame retardants, reheat aids, acetaldehyde reducing compounds,
oxygen scavaging compounds and the like.
[0048] Unfilled Resin
[0049] The exterior layer of the multilayer structure may be
independently selected from any of the polymers which are disclosed
as suitable for the carrier resin. When the multilayer structure is
a container it is preferable that the inner layer which will be in
contact with the contents of the container be a material which will
not deleteriously effect the contents, either by reaction with the
contents or via migration of undesirable compounds from the
unfilled resin to the contents. The unfilled resin must also
possess adequate stretch and molding characteristics to permit
formation of the desired multilayer structure. Finally, the
unfilled resin must have compatible molding characteristics with
each adjacent polymer layer, including the carrier resin/platelet
particle interlayer. It should be appreciated that the unfilled
resin may be the same as or different from the carrier resin and
that each layer of unfilled resin may also be the same or
different. However, in many embodiments it will be preferable to
use no more than three different resins, and perhaps no more than
two (carrier resin and one unfilled resin in the exterior layers).
For many container applications, polyesters, and particularly homo
and compolymers of PET will be the preferred unfilled resin.
[0050] Also, as above, additives normally used in any of the above
polymers may be used if desired. Such additives include, but are
not limited to colorants, pigments, carbon black, glass fibers,
fillers, impact modifiers, antioxidants, stabilizers, flame
retardants, reheat aids, acetaldehyde reducing compounds, oxygen
scavaging compounds and the like.
[0051] Platelet Particles
[0052] Suitable platelet particles of the present invention have a
thickness of less than about 2 nm and a diameter in the range of
about 10 to about 1000 nm. For the purposes of this invention
measurements refer only to the platelet particle and not to any
dispersing aids or pretreatment compounds which might be used.
Suitable platelet particles are derived from clay materials which
are free flowing powders having a cation exchange capacity between
about 0.3 and about 3 meq/g and preferably between about 0.8 and
about 1.5 meq/g. Examples of suitable clay materials include
mica-type layered phyllosilicates, including clays, smectite clays,
sodium montmorillonite, sodium hectorite, bentonites, nontronite,
beidellite, volkonskoite, saponite, sauconite, magadiite, kenyaite,
synthetic sodium hecotorites, and the like. A preferred clay
material comprises a montmorillonite-based platelet particle.
[0053] Clays of this nature are available from various companies
including Southern Clay Products, Kunimine Ind. Co. and Nanocor,
Inc. Generally the clay materials are a dense agglomeration of
platelet particles which are closely stacked together like
cards.
[0054] Other non-clay materials having the above described ion
exchange capacity and size, such as chalcogens may also be used as
the source of platelet particles under the present invention. These
materials are known in the art and need not be described in detail
here.
[0055] Generally, it is desirable to treat the selected clay
material to separate the agglomerates of platelet particles to
individual platelet particles and small tactoids prior to
introducing the platelet particles to the polyester. Separating the
platelet particles prior to incorporation into the polyester also
improves the polyester/platelet interface. Any treatment that
achieves the above goals may be used. Examples of useful treatments
include intercalation with water soluble or water insoluble
polymers, organic reagents or monomers, silane compounds, metals or
organometallics, organic cations to effect cation exchange,
surfactants and their combinations. Multilayer structures of the
present invention are unique in that the carrier layer is
substantially free from platelet particles having a diameter
greater than about 15 .mu.m. Preferably the multilayer structures
of the present invention comprise platelet particles having a mean
platelet particle of less than about 10 microns, and preferably
less than about 7 microns. Particle size analysis can be performed
by making a micrograph of the multilayer structure and analyzing
using Visilog 5 software by Noesis Vision Inc.
[0056] 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
intercalating the platelet particles include polyvinyl pyrrolidone,
polyvinyl alcohol, polyethylene glycol, polytetrahydrofuran,
polystyrene, polycaprolactone, certain water dispersable
polyesters, Nylon-6 and the like.
[0057] Examples of useful pretreatment with organic reagents and
monomers include those disclosed in EP 780,340 A1, incorporated
herein by reference. Examples of useful organic reagents and
monomers for intercalating the platelet particles include
dodecylpyrrolidone, caprolactone, aprolactam, ethylene carbonate,
ethylene glycol, bishydroxyethyl terephthalate, dimethyl
terephthalate, and the like or mixtures thereof.
[0058] Examples of useful pretreatment with silane compounds
include those treatements 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.
[0059] Numerous methods to modify layered particles with organic
cations are known, and any of these may be used in the process of
this invention. One embodiment of this invention is the
modification of a layered particle with an organic cation by the
process of dispersing a layered particle material in hot water,
most preferably from 50 to 80.degree. C., adding an organic cation
salt or combinations of organic cation salts (neat or dissolved in
water or alcohol) with agitation, then blending for a period of
time sufficient for the organic cations to exchange most of the
metal cations present in the galleries between the layers of the
clay material. Then, the organically modified layered particle
material is isolated by methods known in the art including, but not
limited to, filtration, centrifugation, spray drying, and their
combinations. It is desirable to use a sufficient amount of the
organic cation salt to permit exchange of most of the metal cations
in the galleries of the layered particle for organic cations;
therefore, at least about 1 equivalent of organic cation salt is
used and up to about 3 equivalents of organic cation salt can be
used. It is preferred that about 1.1 to 2 equivalents of organic
cation salt be used, more preferable about 1.1 to 1.5 equivalents.
It is desirable, but not required, to remove most of the metal
cation salt and most of the excess organic cation salt by washing
and other techniques known in the art. The particle size of the
organoclay is reduced in size by methods known in the art,
including, but not limited to, grinding, pulverizing, hammer
milling, jet milling, and their combinations. It is preferred that
the average particle size be reduced to less than 100 micron in
diameter, more preferably less than 50 micron in diameter, and most
preferably less than 20 micron in diameter.
[0060] Also, it is preferred that the platelet particles be well
dispersed in the carrier resin. Small particles, when aggregated
become more easily visible under magnification. Thus, another
measure of good dispersibility is the number of particles in a
given area at a given magnification. The carrier resin of the
present invention comprises less than about 100 visible platelet
particles/mm.sup.2, preferably less than about 50 visible platelet
particles/mm.sup.2 and more preferably less than about 30 visible
platelet particles/mm.sup.2 at a magnification of 40X.
[0061] The process to modify layered particles with organic cations
may be conducted in a batch, semi-batch or continuous manner.
[0062] Useful organic cation salts for the process of this
invention can be represented as follows: 1
[0063] Wherein M represents either nitrogen or phosphorous;
X.sup.-represents an anion selected from the group consisting of
halogen, hydroxide, or acetate anions, preferably chloride and
bromide, R, R.sub.2, R.sub.3 and R.sub.4 are independently selected
from organic and oligomeric ligands or may be hydrogen. 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 22 carbon
atoms in the alkyl portion of the structure, aryl groups such as
phenyl and substituted phenyl including fused ring aromatic
substituents, beta, gamma unsaturated groups having six or less
carbon atoms, and alkyleneoxide groups having 2 to 6 carbon atoms.
Examples of useful oligomeric ligands include, but are not limited
to, poly(alkylene oxide), polystyrene, polyacrylate,
polycaprolactone, and the like.
[0064] Examples of useful organic cations include, but are not
limited to, alkyl ammonium ions, such as dodecyl ammonium,
octadecyl ammonium, bis(2-hydroxyethyl) octadecyl methyl ammonium,
octadecyl benzyl dimethyl ammonium, tetramethyl ammonium, and the
like or mixtures thereof, and alkyl phosphonium ions such as
tetrabutyl phosphonium, trioctyl octadecyl phosphonium, tetraoctyl
phosphonium, octadecyl triphenyl phosphonium, and the like or
mixtures thereof. Illustrative examples of suitable polyalkoxylated
ammonium compounds include those available under the trade name
Ethoquad or Ethomeen from Akzo Chemie America, namely, Ethoquad
18/25 which is octadecyl methyl bis(polyoxyethylene[15]) ammonium
chloride and Ethomeen 18/25 which is octadecyl
bis(polyoxyethylene[15])amine, wherein the numbers in brackets
refer to the total number of ethylene oxide units. The most
preferred organic cation is octadecyl methyl
bis(polyoxyethylene[15]) ammonium chloride.
[0065] If desired, the treated or untreated platelet particles may
be further separated into a dispersing medium prior to or during
contact with the polymer or polymer precursors. Many such
dispersing aids are known, covering a wide range of materials
including water, alcohols, ketones, aldehydes, chlorinated
solvents, hydrocarbon solvents, aromatic solvents, water
dissipatible or dispersible polymers, such as those disclosed in
U.S. Ser. No. 995,789, and incorporated herein by reference, and
the like or combinations thereof. Useful embodiments include
exfoliation or dispersion of treated or untreated platelet
particles into ethylene glycol or water with the addition of one or
more of the above swelling aids or intercalating compounds.
[0066] It should be appreciated that on a total composition basis,
dispersing aids and/or pretreatment compounds which are used may
account for a significant amount of the total composition, in some
cases up to about 30 weight %. For the purposes of this invention
the amount of dispersing aids and pretreatment compounds used (if
any) in the polymer platelet composite are a part of the amount of
polymer specified above. While it is preferred to use as little
dispersing aid/pretreatment compounds as possible, the amounts of
dispersing aids and/or pretreatment compounds may be as much as
about 8 times the amount of the platelet particles.
[0067] Methods for Forming Multilayer Structures
[0068] Methods for forming multilayer structures are known.
Suitable methods include, either singly or in combination,
coextrusion, coinjection, injection blow molding, injection
overmolding, and the like. U.S. Pat. Nos. 5,221,507; 5,037,285,
4,946,365; 5,523,045 discloses process and a method for coinjection
molding of preforms for multilayer containers. Recently, several
new technologies have been invented for co-injection molding
preforms. Japanese Kokai patent no Hei 9-176461 disclose multilayer
bottles containing polyester based nanocomposites. However, the
size of the particles in the nanocomposite layer are very large and
this results in lower barrier properties. WO 98/01346 discloses
containers containing nanocomposites that are limited to polyesters
or copolyesters only.
[0069] The following examples further illustrate the invention.
EXAMPLES
[0070] Percent haze measurements were obtained according to ASTM
D-1003 using a Hunter Lab Ultrascan Colorimeter. Oxygen
permeability measurements were obtained according to ASTM D-3985
using a MOCON Oxtran-1000 instrument at 30.degree. C. and 68%
relative humidity with a pure oxygen permeant and a nitrogen gas
carrier.
[0071] Two, 1" Killion extruders with the screw L:D of 24 1 were
used along with a Killion co-extrusion block for 1"system to
produce the 6" wide trilayer coextruded films of the A/B/A type.
The films were extruded through a film die and wound using the
take-up system. The "B" layer was the carrier resin/platelet
particle resin. Polymers "A" and "B" were dried in dryers at
appropriate temperatures before extrusion.
Comparative Example 1
[0072] PET-9921 pellets (Eastman Chemical Company, I.V. 0.80) were
dried at 150 C. for 6 hours then extruded through a 1 inch Killion
extruder and a 6" film die into film having a total thickness of
about 530 microns. The melt processing temperature was 286 C. and
the extruder RPM was 98. The film was biaxially oriented 4.times.4
at 100.degree. C. using a T. M. Long instrument. The oriented film
exhibited about 0.3% haze and an oxygen permeability of about 7.1
cc-mil/100sq.in.-day-atm.
Comparative Example 2
[0073] A dispersion was formed comprising 80 parts of AQ-55 (a
water dispersible polyester available from Eastman Chemical
Company), 30 parts of an organoclay that was cation exchanged with
octadecyl,trimethyl ammonium, and 700 parts of purified water. The
dispersion was poured over 1000 parts of PET-9921 pellets and
evaporated by heating at 85.degree. C. under a dynamic nitrogen
atmosphere. The coated pellets were further dried in a convection
oven at 110.degree. C. overnight then extruded at 280.degree. C.
using a Leistritz Micro-18 twin-screw extruder with a screw speed
of 200 rpm and feed rate of 2.5 kg/hr. The molten strand was
quenched in chilled water and chopped immediately. The
polyester-platelet composite pellets were dried at 100.degree. C.
overnight in a force air oven then extruded into 4 inch wide film
having a thickness of about 430 microns. The film was biaxialy
oriented 4.times.4 at 100.degree. C. using a T. M. Long instrument.
The oriented film exhibited about 20% haze and an oxygen
permeability of about 5.3 cc-mil/100 sq.in.-day-atm. The film
sample had about 2% clay (ash).
[0074] Although oriented film of polymer-platelet composites of
this example have improved barrier to oxygen, they also have an
unacceptably high percent haze (20%). Haze levels greater than 2%
are unacceptable for most food and beverage packaging.
Unfortunately the haze levels observed in this example are typical
for oriented polymer-platelet monolayer film, when orientation is
conducted at temperatures between the glass transition and melting
point temperatures.
Examples 1-3
[0075] PET-9921 pellets and polyester-platelet pellets formed as
described in Comparative Examples 1 and 2 were dried separately
then coextruded to form a trilayer film having the total
thicknesses and layer thicknesses listed in Table 1, below. The
tri-layered films were biaxialy oriented 4.times.4 at 100.degree.
C. using a T. M. Long. The haze and oxygen permeability of each
film was measured as described above. The results are shown in
Table 1, below
1TABLE 1 Oxygen permeability center total (cc- layer 1 layer layer
3 thick mil/100 sq.in.- Ex. # thick (.mu.) thick (.mu.) thick
(.mu.) (.mu.) haze day-atm.) 1 188 37 208 434 0.6% 6.0 2 228 64 158
450 0.9% 6.7 3 74 188 114 376 1.7% 5.7
[0076] The multilayer oriented film of the present invention
display significantly improved barrier compared to the PET-9921
control (Comparative Example 1, 7 1 cc-mil/100 sq.in.-day-atm) and
significantly improved haze compared to the orienting
polymer-platelet monolayer film (Comparative Example 2).
[0077] These examples also show that multilayer structures
comprising substantial carrier resin/platelet particle layers (at
least 50% of a polymer-platelet composite layer) can be used in
this invention to achieve significantly improved barrier compared
to the PET-9921 control (Comparative Example 1) and significantly
improved haze (decrease from 20% to 1.7%) compared to the orienting
polymer-platelet monolayer film (Comparative Example 2).
Comparative Example 3
[0078] This example illustrates the poor dispersion and
permeability results obtained when sodium montmorillonite without
additional treatement is melt compounded with PET. 9.27 grams (2
weight percent) and 23.89 grams (5 weight percent) of Kunipia F,
which is a commercial sodium montmorillonite with cation exchange
capacity of 119 milliequivalents per 100 grams available from
Kunimine Ind. Co., were dry mixed with PET-9921 (Eastman Chemical
Company. I.V. of about 0.72 dL/g, terephthalate residues and glycol
residues of about 3.5 mole % 1,4-cyclohexane dimethanol, about 1.5
mole % diethylene glycol, and about 95 mole % ethylene glycol). The
mixture was dried in a vacuum oven for 24 hours at 120.degree. C.
then extruded at a melt temperature of 280.degree. C. on a
Leistritz Micro 18 mm twin screw extruder using general purpose
screws. The extrudate was quenched in water and chopped into
pellets as it exited the die. The composites were found to have
inherent viscositites of 0.60 dL/g and 0.56 dL/g for the 2 and 5
weight percent Kunipia F composites, respectively.
[0079] The above composite materials were crystallized at
150.degree. C. in a forced air oven and dried overnight in a vacuum
oven at 120.degree. C. with a slight nitrogen purge. The dried
materials were placed into a glass solid state polymerization units
with a nitrogen purge of 14 scfh and heated by boiling diethyl
succinate which has a boiling point of 218.degree. C. After a
period of 24 hours, heating was discontinued and the solid state
polymerization units were allowed to cool. After cooling, the
composite materials was removed. Analytical results showed that the
composites had IV values of 0.88 dL/g and 0.85 dL/g for the 2 and 5
weight percent Kunipia F composites, respectively TEM imaging of
these composites showed the presence of mostly large aggregrates of
tactoids with average thickness greater than about 100 nm and very
few individual tactoids with thickness less than about 50-100 nm.
WAXS analyses of the composites shows a distinct basal spacing of
about 1.25 nm and 1.20 mn for the 2 and 5 weight percent Kunipia F
composites, respectively.
[0080] The above polyester-platelet composites were dried overnight
in a vacuum oven at 120.degree. C. with a slight nitrogen purge.
The dried materials were compression molded at 280.degree. C. then
quenched in ice-water to provide films with thickness of about 13
mil. Testing conducted on the films showed the oxygen
permeabilities were 13.5 cc-mil/100 in.sup.2-24 hr-atm and 12.4
cc-mil/100 in.sup.2-24 hr-atm for the 2 and 5 weight percent
Kunipia F composites, respectively. Thus, these polyester-particle
composites do not have significantly improved barrier properties
compared to clay free PET. The compression molded films were clear
but contained visible particles. Haze measurements on the films
produced percent haze values of 11 percent and 36 percent for the 2
and 5 weight percent Kunipia F composites, respectively.
[0081] The compression films were biaxially stretched 4.times.4 at
about 100.degree. C. in a T.M. Long instrument. The resulting
oriented films were clear but had increased haze related to the
visible particles. The measured percent haze values were found to
be 18% and 40% for the 2 and 5 weight percent Kunipia F composites,
respectively.
Comparative Examples 4 and 5
[0082] These examples illustrate the poor dispersion and
permeability results obtained when sodium montmorillonite without
additional treatement is added during polymerization of PET.
[0083] 115 grams of oligo(ethylene terephthalate) (number average
molecular weight of about 867 g/mole), 4.59 grams of
1,4-cyclohexane dimethanol, and either 2.99 grams or 7.72 grams of
Kunipia F, which is a commercial sodium montmorillonite with cation
exchange capacity of 119 milliequivalents per 100 grams available
from Kunimine Ind Co., were charged to a single-neck, 1-L
round-bottom flask. The appropriate amounts of metal catalyst
solutions were added to provide 20 ppm titanium, 40 ppm phosphorus,
80 ppm cobalt, and 230 ppm of antimony in the final composite. The
flask was fitted with a stainless steel stirring rod and a polymer
head, consisting of a short distillation column and nitrogen inlet.
The flask was purged with nitrogen by alternating vacuum to 100
torr and nitrogen. The flask was given a dynamic nitrogen
atmosphere by passing nitrogen through the nitrogen inlet at a rate
of about 0.3 standard cubic feet per hour (scfh). A metal bath,
which was preheated to 220.degree. C., was raised until it covered
the flask. After the solid monomers melted, stirring at 150
rotations per minute (rpm) was begun. The temperature was held at
220.degree. C. for 15 minutes to allow the 1,4-cyclohexane
dimethanol to react. The metal bath temperature was increased to
280.degree. C. over a period of about 15 minutes. With stirring at
150 rpm at 280.degree. C., vacuum of less than 0.3 torr was applied
to the melt gradually over a period of 15 minutes to prevent
foaming. Vacuum of less than 0.3 torr, temperature of 280.degree.
C., stirring at 150 rpm was maintained for 15 minutes, during which
time ethylene glycol condensate collected in a receiving flask and
the viscosity of the melt increased. Then, the metal bath was
lowered, the vacuum was released with nitrogen, stirring was
stopped, and the composite cools to a semicrystalline solid. The
composite was released from the glass flask by melting the outer
edges of the polymer by immersing the flask into the metal bath,
which was preheated to 290.degree. C., and applying enough torque
on the stirring rod to allow the composite to release from the
flask wall. After cooling to room temperature, the flask was
broken, and the composite was then broken from the stirrer using a
hydraulic cutter. The composite pieces were ground to pass a 4 mm
mesh screen then fine particles were removed using a 0.85 mm mesh
screen to give about 160 g of a polyester-platelet precursor
material. Analytical analyses showed the composite materials have
an IV values of 0.50 dL/g and 0.41 dL/g for the 2 and 5 weight
percent Kunipia F composites, respectively.
[0084] The above composite materials were crystallized at
150.degree. C. in a forced air oven and dried overnight in a vacuum
oven at 120.degree. C. with a slight nitrogen purge. The dried
materials were placed into a glass solid state polymerization units
with a nitrogen purge of 14 scfh and heated by boiling diethyl
succinate which has a boiling point of 218.degree. C. After a
period of 48 hours, heating was discontinued and the solid state
polymerization units were allowed to cool. After cooling, the
composite materials was removed. Analytical results showed that the
composites had IV values of 1.12 dL/g and 1.27 dL/g for the 2 and 5
weight percent Kunipia F composites, respectively. TEM imaging of
these composites showed the presence of mostly large aggregrates of
tactoids with average thickness greater than about 100 nm and very
few individual tactoids with thickness less than about 50-100 nm.
WAXS analyses of the composites shows a distinct basal spacing of
about 1.45 nm and 1.46 mn for the 2 and 5 weight percent Kunipia F
composites, respectively.
[0085] The above polyester-platelet composites were dried overnight
in a vacuum oven at 120.degree. C. with a slight nitrogen purge.
The dried materials were compression molded at 280.degree. C. then
quenched in ice-water to provide a clear films with thickness of
about 13 mil. Testing conducted on the films showed the oxygen
permeabilities were 11.9 cc-mil/100 in.sup.2-24 hr-atm and 10.8
cc-mil/100 in.sup.2-24 hr-atm for the 2 and 5 weight percent
Kunipia F composites, respectively. Thus, these polyester-particle
composites do not have significantly improved barrier properties
compared to clay free PET. The compression molded films are clear
but contain visible particles. Haze measurements on the films
produced percent haze values of 12 percent and 16 percent for the 2
and 5 weight percent Kunipia F composites, respectively.
[0086] The compression films were biaxially stretched 4.times.4 at
about 100.degree. C. in a T.M. Long instrument. The resulting
oriented films were clear but had increased haze related to the
visible particles. The measured percent haze values were found to
be 51% and 59% for the 2 and 5 weight percent Kunipia F composites,
respectively.
[0087] Trilayer films with PET (9921, from Eastman Chemical
Company) as the outer layers and materials made in the present
Comparative Examples was formed. The total thickness of the film
was 1.63 mils and the thickness of the center layer was 0 32 mils.
The oxygen permeability was 9.6 cc-mil/100 in.sup.2-24 hr-atm and
11 0 cc-mil/100 in.sup.2-24 hr-atm for the 2 and 5 weight percent
Kunipia F composites, respectively. The films were cast, biaxially
oriented as above and analyzed for optical properties. Both films
were clear, but had visible particles throughout. The presence of
visible particles clearly indicates that the platelet particles are
not well dispersed in the films of the prior art. This observation
is confirmed by the lack of barrier improvement in the prior art
film.
[0088] FIGS. 1 and 2 clearly show the difference between the
trilayer films of the present invention and the prior art. FIG. 1
is a micrograph at 40X of the trilayer film prepared in Example 3.
The platelet particles appear as barely visible, well spaced dots.
Platelet particles visible at 40X magnification are >5 microns
in diameter and total 250 visible particles or 33 visible
particles/mm.sup.2. At 40X, only particles which are above about 5
microns can be seen. The mean platelet particle size, computed as
circular equivalent diameter is 7.2 (std. Dev. 3 3) microns.
Particle size analysis was performed using Visilog 5 software by
Noesis Vision Inc. It was surprising that particles which are small
as those in the film of Comparative Example 2 would create
substantial haze upon orientation.
[0089] FIG. 2 shows the trilayer film prepared from the material
produced in Comparative Example 4. The platelet particles are
clearly agglomerated in large clumps, which exceed about 15 microns
in diameter. The average particle size is 15.0 microns, ranging
from 5 microns to 402 microns. The total visible particles in this
analysis were 918, and there are 122 visible particles/mm.sup.2
area. Clearly, the films of comparative example 4 have over 400%
more particles greater than 15 microns and about 400% more
particles/mm.sup.2 compared to films of the present invention.
* * * * *