Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS TO PREPARE A
POLYMER NANOCOMPOSITE COMPOSITION
FIELD OF THE INVENTION
This invention relates to a process to prepare a nanocomposite material
comprising a
s polymer matrix having dispersed therein a silicate. More particularly, this
invention relates to a
process to prepare a nanocomposite material comprising forming a flowable
mixture of a
polyamide and a silicate material, dissociating the silicate, and subjecting
the dissociated
flowable mixture to a solid state polymerization step to produce the
nanocomposite material.
CROSS-REFERENCE TO RELATED APPLICATIONS
~o The present application claims the benefit of U.S. Provisional Application
Serial No.
60/074,639, filed February 13, 1998.
BACKGROUND OF THE INVENTION
International Application WO 93/04118 discloses a process of preparing a
polymer
nanocomposite having platelet particles dispersed therein. The process
involves melt-processing
is the polymer with a swellable and polymer-compatible intercalated layered
material and
subjecting it to a shear rate sufficient to dissociate the layers. The layered
material is
compatibilized with one or more "effective swelling/compatibilizing agents"
having a silane
function or an onium cation function.
International Application WO 93/04117 discloses a process of preparing a
polymer
2o nanocomposite. having platelet particles dispersed therein, where the
polymer and the swellable
and polymer-compatible intercalated layered material are melt-processed; The
layered material is
compatibilized with one or more "effective swelling/compatibilizing agents"
selected from
primary ammonium, secondary ammonium and quaternary phosphonium ions. The
selected
swelling/compatibilizing agents "...render their surfaces more organophilic
than those
2s compatibilized by tertiary and quaternary ammonium ion complexes...",
facilitate exfoliation,
resulting in less shear in mixing and less decomposition of the polymer, and
heat stabilize the
composite more than other nations (such as quaternary ammonium cation)
swelling/compatibilizing agents.
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International Patent Application WO 94/22430 discloses a nanocomposite
composition
having a polymer matrix comprising at least one gamma phase polyamide, and
dispersed in the
polyamide is a matrix of a manometer-scale particulate material. The addition
of the particulate
material to nylon 6 resulted in an improvement of flexural modulus and
flexural strength (from 7
to 35%), when compared to unfilled nylon 6. The addition of the particulate
material to nylon
6,6 resulted in very little improvement (1 to 3%) of flexural modulus and
flexural strength when
compared to unfilled nylon 6,6.
International Patent Application WO 93/10098 discloses a polymer composite
made by
melt-processing a polymer with swellable and polymer-compatible intercalated
layered material
~o comprising layers having reactive organo- silane species covalently bonded
to their surfaces.
International Patent Application WO 95/14733 discloses a method of producing a
polymer composite that does not demonstrate melting or glass transition by
melt-processing a
polymer with a layered gallery-containing crystalline silicate. The examples
include intercalated
sodium silicate and a crystalline polyethylene oxide), montmorillonite
intercalated with a
~s quaternary ammonium and polystyrene, and montmorillonite intercalated with
a quaternary
ammonium and nylon 6.
International Patent Application WO 98/29499 discloses polyester nanocomposite
compositions containing clay particles. The clay particles are preferably
synthetic or chemically
modified.
2o U.S. Patent No. 4,889,885 (issued December 26, 1989) describes a composite
of a non-
polyamide resin and a dispersed layered silicate. The silicate is treated with
an opium salt ion
exchange, and added to a monomer or oligomer.
U.S. Patent No. 5,514,734 (issued May 7, 1996) describes polymer composites
containing layered or fibrillar particles derivatized with organosilanes,
organotitanates, or
2s organozirconates. Composite materials are characterized by thickness,
diameter, and interlayer
distances.
International Patent Application WO 93/11190 describes a polymer composite
containing
an exfoliated material derivatized with a reactive organosilane. Polymers are
added prior to
mixing in an extruder.
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International Patent Application WO 94/11430 describes gamma crystalline phase
polyamides containing dispersed layered inorganic materials.
EPO application 0 358 415 A1 describes a polyamide resin containing a
dispersed
layered silicate which has been treated with an organic cation of a lactam as
a swelling agent.
Japanese Kokai Patent No. SHO 62[1987]-252426 describes polymerization of a
nylon 6
monomer in the presence of a silicate. The cooling rate of the polymer is
controlled to achieve
particular crystalline structures in the resulting composite.
None of the above references, alone or in combination, disclose the present
invention, as
claimed.
SUMMARY OF THE INVENTION
This invention relates to a process to prepare a polymer nanocomposite
composition
suitable for automotive, electronic, film and fiber applications, where a
combination of tensile
strength, tensile modulus and flexural modulus are required. Additionally, the
claimed polymer
nanocomposite composition has a desirable surface appearance, toughness,
ductility and
is dimensional stability. The composition processes well and tolerates a wide
range of molding
conditions.
The present invention relates to a process to prepare the above polymer
nanocomposite
composition comprising forming a flowable mixture of a polyamide and a
silicate material and
dissociating (as that term is described in more detail below) at least about
50% but not all of the
2o silicate, and subjecting the polyamide in the dissociated flowable mixture
to a solid state
polymerization step. Optionally, the silicate is a silicate material treated
with at least one
ammonium ion of the formula:
~'NR, R2R3R4
wherein:
2s R,, R2, R3 and R4 are independently selected from a group consisting of a
saturated or
unsaturated C, to C22 hydrocarbon, substituted hydrocarbon and branched
hydrocarbon, or where
Rl and R2 form a N,N-cyclic ether. Examples include saturated or unsaturated
alkyls, including
alkylenes; substituted alkyls such as hydroxyalkyls, alkoxyalkyls, alkoxys,
amino alkyls, acid
alkyls, halogenated alkyls, sulfonated alkyls, nitrated alkyls and the like;
branched alkyls; aryls
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and substituted aryls, such as alkylaryls, alkyoxyaryls, alkylhydroxyaryls,
alkylalkoxyaryls and
the like. Optionally, one of Ri, R2, R3 and R4 is hydrogen. The milligrams of
treatment per 100
grams of silicate (MER) of the treated silicate, described in more detail
below, is preferably from
about 10 milliequivalents/100 g below the cation exchange capacity of the
untreated silicate to
s about 30 milliequivalents/100 g above the cation exchange capacity of the
untreated silicate.
An additional embodiment of the invention relates to nanocomposite
compositions
comprising a polyamide and a silicate. The polyamide may have a concentration
of amine
groups at least 10 mole % greater than the concentration of the carboxylic
acid end groups.
Preferably the polyamide has a weight average molecular weight in the range of
about 30,000 D
io to about 40,000 D. Alternatively, the polyamide may have a weight average
molecular weight of
at least 40,000 D.
A further embodiment is directed towards a nanocomposite composition
comprising a
polyamide and a silicate, wherein the silicate is treated with an ammonium ion
of the formula:
+NReRbR~IZd; wherein Re, Rb and R~ is hydrogen (H) and and Rd includes a
carboxylic acid
~ s moiety.
The composite polymer matrix material of the present invention demonstrates,
when
tested, an improvement in tensile modulus and flexural modulus, without a
substantial decrease
in tensile strength or toughness when compared to that of the polymer without
the silicate.
DESCRIPTION OF THE FIGURES
2o The following figures form part of the present specif cation and are
included to further
demonstrate certain aspects of the present invention. The invention may be
better understood by
reference to one or more of these drawings in combination with the detailed
description of
specific embodiments presented herein.
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1 Molecular weight effects with 7 w/0 lonite
2M2HT-montmoril
2 Molecular weight effec on nanocomposite
stiffness 7 w/o 2M2HT-
montmorillonite
3 Stress vs. strain graph, without SSP
4 Stress vs. strain graph, with SSP
__ Intrinsic viscosity vs. solid state
~~ polymerization time graph
6 Intrinsic_viscosity vs. time at 220C
graph
7 UTS vs. % ash vs. SSP graph
8 eu vs. SSP vs. % ash graph
9 Notched Izod vs. Mw vs. SSP graph
Un-notched Izod vs. Amine/Acid vs. SSP
graph
11 E vs. SSP vs. % ash graph
DETAILED DESCRIPTION OF THE INVENTION
Polyamides of the present invention are synthetic linear polycarbonamides
characterized
by the presence of recurring carbonamide groups as an integral part of the
polymer chain which
are separated from one another by at least two carbon atoms. Polyamides of
this type include
polymers, generally known in the art as nylons, which can be obtained from
diamines and
dibasic acids having the recurring unit represented by the general formula:
-NHCORSCOHNR6 -
in which R; is an alkylene group of at least 2 carbon atoms, preferably from
about 2 to about 11
or arylene having at least about 6 carbon atoms, preferably about 6 to about
17 carbon atoms;
~o and Rb is selected from RS and aryl groups. Also, included are
copolyamides, terpolyamides and
the like obtained by known methods, for example, by condensation of
hexamethylene diamine
and a mixture of dibasic acids consisting of terephthalic acid and adipic
acid. Polyamides of the
above description are well-known in the art and include, for example,
poly(hexamethylene
adipamide) (nylon 6,6), poly(hexamethylene sebacamide) (nylon 6,10),
poly(hexamethylene
is isophthalamide), poly(hexamethylerie terephthalamide), poly(heptamethylene
pimelamide)
(nylon 7,7), poly(octamethylene suberamide) (nylon 8,8), poly(nonamethylene
azelamide)
(nylon 9,9), poly (decamethylene sebacamide) (nylon 10,9), poly(decamethylene
sebacamide)
(nylon 10,10), poly[bis(4-amino cyclohexyl)methane-1,10-decanecarboxamide)),
poly(m-xylene
adipamide), polyp-xylene sebacamide), poly(2,2,2-trimethyl hexamethylene
terephthalamide),
2o poly(piperazine sebacamide), polyp-phenylene terephthalamide),
poly(metaphenylene
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isophthalamide), and copolymers and terpolymers of the above polymers.
Additional
polyamides include nylon 4,6, nylon 6,9, nylon 6,10, nylon 6,12, nylon 11,
nylon 12, amorphous
nylons, aromatic nylons and their copolymers.
Other useful polyamides are those formed by polymerization of amino acids and
s derivatives thereof, as for example, lactams. Illustrative of these useful
polyamides are
poly(caprolactam) (nylon 6), poly(4-aminobutyric acid) (nylon 4), poly(7-
aminoheptanoic acid)
(nylon 7), poly(8-aminooctanoic acid) (nylon 8), poly(9-aminononanoic acid)
(nylon 9),
poly(10-aminodecanoic acid) (nylon 10), poly(11-aminoundecanoic acid) (nylon
11), poly(12-
aminodocecanoic acid) (nylon 12) and the like.
~o The preferred polyamide is Vydyne nylon, which is poly(hexamethylene
adipamide)
(nylon 6,6), which gives a composite with the desired combination of tensile
strength, tensile
modulus and flexural modulus for the applications contemplated herein (Vydyne
is a registered
trademark of Solutia Inc.).
The preferred molecular weight of the polyamide is in the range of about
30,000 to about
~ s 80,000 D (weight average) with a more preferred molecular weight in the
range of about 30,000
to about 40,000 D. The most preferred molecular weight of the polyamide is at
least about
40,000 D (weight average). Increasing the weight average molecular weight of
the polyamide
from about 35,000 to about 55,000 D results in an unexpected increase in
toughness as indicated
by the notched Izod impact test. Whereas an increase in the weight average
molecular weight of
2o from about 35,000 to about 55,000 D in the polyamide neat results in a
small increase in
toughness, the same increase in molecular weight in the nanocomposite results
about twice the
increase in toughness. Therefore, the increase in toughness is enhanced in the
nanocomposite
when compared to that of the polyamide neat.
In a preferred embodiment, the polyamide has an amine end group/acid end group
ratio
2s greater than one ( 1 ). More preferably, the concentration of amine end
groups is at least 10 mole
greater than the concentration of the carboxylic acid end groups. In an even
more preferred
embodiment, the polyamide has a concentration of amine end groups at least 20
mole % greater
than the concentration of the carboxylic acid end groups, and in a most
preferred embodiment,
the polyamide has a concentration of amine end groups at least 30 mole %
greater than the
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concentration of the carboxylic acid end groups. In another embodiment, the
concentration of
amine end groups is essentially equal to the concentration of carboxylic acid
end groups.
Among the preferred embodiments is nylon 6, nylon 6,6, blends thereof and
copolymers
thereof. The range of ratios of the nylon 6/nylon 6,6 in the blends is from
about 1/100 to 100/1.
s Preferably, the range is from about I/10 to 10/1. The range of ratios of the
nylon 6/nylon 6,6 in
the copolymers is about 1/100 to 100/1. Preferably, the range is from about
1/10 to 10/1.
Optionally, the nanocomposite composition comprises at least one additional
polymer.
Examples of suitable polymers include polyethyleneoxide, polycarbonate,
polyethylene,
polypropylene, polystyrene-acrylonitrile), poly(acrylonitrile-butadiene-
styrene), polyethylene
~o terephthalate), poly(butylene terephthalate), poly(trimethylene
terephthalate), polyethylene
naphthalate), polyethylene terephthalate-co-cyclohexane dimethanol
terephthalate),
polysulphone, poly(phenylene oxide) or poly(phenylene ether),
poly(hydroxybenzoic acid-co-
ethylene terephthalate), poly(hydroxybenzoic acid-co-hydroxynaphthenic acid),
poly(esteramide), poly(etherimide), poly(phenylene sulfide), poly(phenylene
terephthalamide).
v s The mixture may include various optional components which are additives
commonly
employed with polymers. Such optional components include surfactants,
nucleating agents,
coupling agents, fillers, impact modifiers, chain extenders, plasticizers,
compatibilizers,
colorants, mold release lubricants, antistatic agents, pigments, fire
retardants, and the like.
Suitable examples of fillers include carbon fiber, glass fiber, kaolin clay,
wollastonite,
2o mica and talc. Suitable examples of compatibilizers include acid-modified
hydrocarbon
polymer, such as malefic anhydride-grafted propylethylene, malefic anhydride-
grafted
polypropylene, malefic anhydride-grafted ethylenebutylene-styrene block
copolymer. Suitable
examples of mold release lubricant includes alkyl amine, stearamide, and di-or
tri- aluminum
stearate.
2s Suitable examples of impact modifiers include ethylene-propylene rubber,
ethylene-
propylene diene rubber, methacrylate-butadiene-styrene (with core-shell
morphology),
poly(butylacrylate) with or without carboxyl modification, polyethylene
acrylate),
polyethylene methylacrylate), polyethylene acrylic acid), polyethylene
acrylate) ionomers,
polyethylene methacrylate acrylic acid) terpolymer, polystyrene-
butadiene)block copolymers,
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poly(styrene-butadiene-styrene)block terpolymers, poly(styrene-
ethylene/butylene-styrene)
block terpolymers and poly(styrene-ethylene/butylene-styrene carboxylate}
block terpolymers.
Suitable coupling agents include silane, titanate and zirconate coupling
agents. Silane
coupling agents are well-known in the art and are useful in the present
invention. Examples of
s suitable coupling agents include octadecyltrimethoxysilane, gamma-
aminopropyltriethoxysilane,
gamma-aminopropyltrimethoxysilane, gamma-aminopropylphenyldimethoxysilane,
gamma-
glycidoxypropyl tripropoxysilane, 3,3-epoxycyclohexylethyl trimethoxysilane,
gamma-
proprionamido trithoxysilane, N-trimethoxysilylpropyl-N(beta-aminoethyl)
amine,
trimethoxysilylundecylamine, trimethoxysilyl-2-chloromethylphenylethane,
~o trimethoxysilylethylphenylsulfonylazide, N-trimethoxysilylpropyl N,N,N-
trimethylammonium
chloride, N-(trimethoxysilylpropyl)-N-methyl-N,N-diallylammonium chloride,
trimethoxysilylpropylcinnamate, 3-mercaptopropyl trimethoxysilane, 3-
isocyanatopropyltriethoxysilane, and the like. The preferred silane is gamma-
aminopropyltriothexysilane. The silane coupling agent is optionally added to
the polymer
~ s composite in the range of about 0.5 to about 5 weight % of the layered
silicate. The preferred
concentration range of silane coupling agent is about 1 to about 3 weight % of
the layered
silicate in the composite.
In one embodiment, the nanocomposite composition further comprises a
composition
wherein an end group of the polyamide is bonded to a surface of the treated
silicate by a silane
2o coupling agent.
The silicate materials of the present invention are selected from the group
consisting of
layered silicates and fibrous, chain-like silicates, and include
phyllosilicates. Examples of
fibrous, chain-like silicates include chain-like minerals, for example
sepiolite and attapulgite,
with sepiolite being preferred. Such silicates are described, for example, in
Japanese Patent
2s Application Kokoku 6-84435 published October 26, 1994.
Examples of layered silicates include layered smectite clay minerals such as
montmorillonite, nontronite, beidellite, volkonskoite, Laponite~ synthetic
hectorite, natural
hectorite, saponite, sauconite, magadiite, and kenyaite; vermiculite; and the
like. Other useful
materials include layered illite minerals such as ledikite and admixtures of
illites with one or
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more of the clay minerals named above. The preferred layered silicates are the
smectite clay
minerals such as montmorillonite, nontronite, beidellite, volkonskoite,
Laponite synthetic
hectorite, natural hectorite, saponite, sauconite, magadite, and kenyaite.
The layered silicate materials suitable for use in the present invention are
well-known in
the art, and are sometimes referred to as "swellable layered material". A
further description of
the claimed layered silicates and the platelets formed when melt processed
with the polyamide is
found in International Patent Application WO 93/04117, which is hereby
incorporated by
reference. The layered silicate materials typically have planar layers arrayed
in a coherent,
coplanar structure, where the bonding within the layers is stronger than the
bonding between the
io layers such that the materials exhibit increased interlayer spacing when
treated.
The layered silicate materials may be treated as described in more detail
below with the
subject ammonium ion to enhance the interlayer swelling and/or spacing useful
for the
performance of the treated silicate of the present invention. As used herein
the "inter layer
spacing" refers to the distance between the faces of the layers as they are
assembled in the
~s treated material before any delamination (or exfoliation) takes place. The
preferred clay
materials generally include interlayer or exchangeable cations such as Li+,
Na+, Ca2+, K+, Mg2+
and the like. In this state, these materials have interlayer spacings usually
equal to or less than
about 4 ~ and only delaminate to a low extent in host polymer melts regardless
of mixing. In
the claimed embodiments, the cationic treatment is a ammonium species which is
capable of
2o exchanging with the interlayer cations such as Li+, Na+, Ca2+, K+, Mg2+ and
the like in order to
improve delamination of the layered silicate.
The treated silicate of the present invention is a silicate material as
described above
which is treated with at least one ammonium ion of the formula
NR,R2R3R4
2s wherein:
R,, R2, R3 and R4 are independently selected from a group consisting of a
saturated or
unsaturated C, to C22 hydrocarbon, substituted hydrocarbon and branched
hydrocarbon, or where
R, and R2 form a N,N-cyclic ether. Examples include saturated or unsaturated
alkyls, including
alkylenes; substituted alkyls such as hydroxyalkyls, alkoxyalkyis, alkoxys,
amino alkyls, acid
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alkyls, halogenated alkyls, sulfonated alkyls, nitrated alkyls and the like;
branched alkyls; aryls
and substituted aryls, such as alkylaryls, alkyoxyaryls, alkylhydroxyaryls,
alkylalkoxyaryls and
the like. Optionally, one of R~, R2, R3 and R4 is hydrogen. A mixture of two
or more
ammonium ions is contemplated by the present invention.
In an embodiment of the present invention, R~ is selected from the group
consisting of
hydrogenated tallow, unsaturated tallow or a hydrocarbon having at least 6
carbons, and R2, R3
and R4 independently have from one to eighteen carbons. Tallow is composed
predominantly of
octadecyl chains with small amounts of lower homologues, with an average of
from 1 to 2
degrees of unsaturation. The approximate composition is 70% C,g, 25% C16, 4%
C~4 and 1%
~o C,2. In another preferred embodiment of the present invention, R, and R2
are independently
selected from the group consisting of hydrogenated tallow, unsaturated tallow
or a hydrocarbon
having at least 6 carbons and R3 and R4 independently have from one to twelve
carbons.
Examples of suitable R~, R2, R3 and R4 groups are alkyl such as methyl, ethyl,
octyl,
nonyl, tent-butyl, ethylhexyl, neopentyl, isopropyl, sec-butyl, dodecyl and
the like; alkenyl such
~ s as 1-propenyl, 1-butenyl, 1-pentenyl, 1-hexenyl, 1-heptenyl, 1-octenyl and
the like; cycloalkyl
such as cyclohexyl, cyclopentyl, cyclooctyl, cycloheptyl and the like; alkoxy
such as ethoxy;
hydroxyalkyl; alkoxyalkyl such as methoxymethyl, ethoxymethyl, butoxymethyl,
propoxyethyl,
pentoxybutyl and the like; aryloxyalkyl and aryloxyaryl such as phenoxyphenyl,
phenoxymethyl,
phenoxydecyl, phenoxyoctyl and the like; arylalkyl such as benzyl,
phenylethyl, 8-phenyloctyl,
20 10-phenyIdecyl and the like, alkylaryl such as 3-decylphenyl, 4-
octylphenyl, nonylphenyl and
the like.
Suitable ammoniums used in treating the silicate materials include oniums such
as
dimethyldi(hydrogenated tallow) ammonium, dimethylbenzyl hydrogenated tallow
ammonium,
dimethyl(ethylhexyl) hydrogenated tallow ammonium, trimethyl hydrogenated
tallow
is ammonium, methylbenzyldi(hydrogenated tallow} ammonium, N,N-2-
cyclobutoxydi(hydrogenated tallow) ammonium, trimethyl tallow ammonium,
methyldihydroxyethyl tallow ammonium, octadecylmethyldihydroxyethyl ammonium,
dimethyl(ethylhexyl) hydrogenated tallow ammonium and mixtures thereof.
Particularly
preferred ammoniums include quaternary ammoniums, for example,
dimethyldi(hydrogenated
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tallow) ammonium, dimethylbenzyl hydrogenated tallow ammonium,
methyldihydroxyethyl
tallow ammonium, octadecylmethyldihydroxyethyl ammonium, dimethyl(ethylhexyl)
hydrogenated tallow ammonium and mixtures thereof.
The treatment with the ammonium ion(s), also called "cationic treatments",
includes
s introduction of the ions into the silicate material by ion exchange. In the
embodiment where the
silicate material is a layered silicate, the cationic treatments may be
introduced into the spaces
between every layer, nearly every layer, or a large fraction of the layers of
the layered material
such that the resulting platelet layers comprise less than about 20 particles
in thickness. The
platelet layers are preferably Less than about 8 particles in thickness, more
preferably less than
~o about 5 particles in thickness, and most preferably, about 1 or about 2
particles in thickness.
The treated silicate has a MER of from about 10 milliequivalents/100 g below
the cation
exchange capacity of the untreated silicate to about 30 milliequivalents/100 g
above the cation
exchange capacity of the untreated silicate. The MER is the milliequivalents
of treatment per
100 g of silicate. Each untreated silicate has a cation exchange capacity,
which is the
~s milliequivalents of cations available for exchange per 100 g of silicate.
For example, the cation
exchange capacity of the layered silicate montmorillonite can be about 95, and
the exchange
capacity of sepiolite is in the range of about 10 to about 20. When the MER of
the treated
silicate substantially exceeds the cation exchange capacity, there is an
excess of cationic
treatment which may be available to react with the polyamide. This excess may
cause
zo degradation of the properties of the polyamide.
The higher the MER, the lower the concentration of silicate in the treated
silicate.
Therefore, a first nanocomposite sample may have a higher concentration of
treated silicate but a
lower concentration of silicate, than a second nanocomposite sample, because
the first sample
has a higher MER than the second sample.
2s If the MER value of the treated silicate is substantially less than its
exchange capacity,
for example about 85 MER for the preferred montmorillonite, there is too
little of the cationic
treatment to have a beneficial effect. If the MER exceeds about 125, the
excess ammonium may
be detrimental to the properties of the nylon. Preferably, when the untreated
montmorillonite
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has an exchange capacity of about 95, the treated layered silicate has a
cation exchange capacity
of from about 85 to about 125.
The amount of silicate included in the composition is in the range of about
0.1 to about
12 weight % of the composite. The concentration is adjusted to provide a
composite polymer
matrix material which demonstrates, when tested, an increase in tensile
modulus and flexural
modulus, without a substantial decrease in tensile strength. Preferably, the
increase in tensile
modulus and flexural modulus is at least about 10%. More preferably, the
increase in tensile
modulus and flexural modulus is at least about 20%. Too little silicate fails
to provide the
desired increase in tensile modulus and flexural modulus. Too much silicate
provides a
~o polyamide composite with a decreased tensile strength. Further, it may be
desirable to have the
crystalline regions of the polyamide in the nanocomposite composition be less
than about 1.0
hem.
The particle size of the silicate is such that optimal contact between the
polymer and the
silicate is facilitated. The range of particle size can vary from about 10
microns to about 100
~s microns. Preferably, the particle size is in the range of from about 20 to
about 80 microns. Most
preferably, the particle size is below about 30 microns, such as those that
pass through 450 mesh
screens, in that the resulting polymer nanocomposite has improved performance
properties.
Optionally, the silicate can be treated with one or more ammonium ions of the
formula
+N~Rn~Ra
2o wherein at least one of Re, Re and R~ is hydrogen (H) and Rd is selected
from a group consisting
of a saturated or unsaturated C~ to C22 hydrocarbon, substituted hydrocarbon
and branched
hydrocarbon. Examples include saturated or unsaturated alkyls, including
alkylenes; substituted
alkyls such as hydroxyalkyls, alkoxyalkyls, alkoxys, amino alkyls, acid
alkyls, halogenated
alkyls, sulfonated alkyls, nitrated alkyls and the like; branched alkyls;
aryls and substituted aryls,
2s such as alkylaryls, alkyoxyaryls, alkylhydroxyaryls, alkylalkoxyaryls and
the like. As the
definition of the Rd group for the ammonium ion above is generally the same as
the definition
for the R4 group in the ammonium ion, the Examples set forth above for the R.~
group are also
exemplary of the Ra group.
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In a separate embodiment, Ra, Rb and R~ are hydrogen (H), and the Rd group
contains a
carboxylic acid moiety such that the ammonium ion
NRaRbR~Rd
is an amino acid, for example 12-aminolauric acid ammonium. In this
embodiment, it is
s particularly preferred that the amine end groups/acid end groups ratio of
the polyamide is greater
than one ( 1 ) .
Optionally, the above ammonium ions may be mixed with at least one quaternary
ammonium ion, said mixture used to treat the silicate. The quaternary ammonium
ion preferably
has a hydrocarbon chain. The hydrocarbon chain may be saturated or
unsaturated. The
io hydrocarbon chain may be obtained from a natural source such as tallow, or
from a synthetic
source such as a synthesized or purified C, 2, C 14, C ~ 6, or C ~ 8 chain. A
preferred mixture includes
at least one of dimethyldi(hydrogenated tallow) ammonium, methyl
dihydroxyethyl tallow
ammonium, dimethylbenzyl hydrogenated tallow ammonium and/or
dimethyl(ethylhexyl)
hydrogenated tallow ammonium, either alone or in combination with 12-
aminolauric acid
i s ammonium.
Optionally, the silicate can be further treated with azine cationic dyes, such
as nigrosines
or anthracines. Said cationic dyes would impart color-fastness and uniformity
of color in
addition to increasing the intercalation of the polymer molecules.
It is further desirable to have a polymer composite that provides both the
desired strength
2o and flexibility, and yet is lightweight. This is accomplished by minimizing
the concentration of
silicate in the nanocomposite. The preferred nanocomposite contains a
concentration of silicate
of from about 0.1 to about 12.0 weight % of the composite. The most preferred
nanocomposite
contains a concentration of silicate of from about 0.5 to about 6.0 weight %
of the composite.
In a first embodiment of the present invention, the nanocomposite composition
is
zs prepared using a three step process. One step includes forming a flowable
mixture of the
polyamide as a polymer melt and the silicate material. The second step
includes dissociating at
least 50% but not all of the silicate material. The term "dissociating", as
utilized herein, means
delaminating or separating the silicate material into submicron-scale
structures comprising
individual or small multiple units. For the embodiment wherein layered
silicates are utilized this
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dissociating step includes delaminating the silicate material into submicron
scale platelets
comprising individual or small multiple layers. For the embodiment wherein
fibrous, chain-like
silicates are utilized, this dissociating step includes separating the
silicate material into sub-
micron scale fibrous structures comprising individual or small multiple units.
As referred to in the mixture forming step, a flowable mixture is a mixture
which is
capable of dispersing dissociated silicate material at the submicron scale. A
polymer melt is a
melt processable polymer or mixture of polymers which has been heated to a
temperature
sufficiently high to produce a viscosity low enough for submicron scale mixing
to occur. The
process temperature should be at least as high as the melting point of the
polyamide employed
~o and below the degradation temperature of the polyamide and of the organic
treatment of the
silicate. The actual extruder temperature may be below the melting point of
the polyamide
employed, because heat is generated by the flow. The process temperature is
high enough that
the polymer will remain in the polymer melt during the conduct of the process.
In the case of a
crystalline polyamide, that temperature is above the polymer's melting
temperature. For
is example, a typical nylon 6, having a melting point of about 225°C,
can be melted in an extruder
at any temperature equal to or greater than about 225°C, as for example
between about 225°C
and about 260°C. For nylon 6,6 a temperature of preferably from about
260°C to about 320°C is
normally employed.
Conventional methods can be employed to form the flowable mixture. For
example, the
2o flowable mixture can be prepared through use of conventional polymer and
additive blending
means, in which the polymer is heated to a temperature sufficient to form a
polymer melt and
combined with the desired amount of the silicate material in a granulated or
powdered form in a
suitable mixer, as for example an extruder, a Banbury type mixer, a Brabender
type mixer,
Farrell continuous mixers, and the like.
2s In one embodiment, the flowable mixture may be formed by mixing the
polyamide with
a previously formed silicate-containing concentrate. The concentrate includes
the silicate and a
polymer carrier. The concentration of the silicate material in the
concentrate, and the amount of
concentrate are selected to provide the desired silicate concentration for the
final nanocomposite
composition. Examples of suitable polymers for the carrier polymer of the
concentrate include
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polyamide, ethylene propylene rubber, ethylene propylene diene rubber,
ethylene-ethylacrylate,
ethylene-ethylmethacrylate or ethylene methacrylate. Examples include Iotek~
ionomer and
Escor ATX acid terpolymer, both available from Exxon. The polyamide polymers
suitable for
the carrier polymer include nylons such as nylon 6, nylon 6,6, nylon 4,6,
nylon 6,9, nylon 6,10,
s nylon 6,12, nylon 11, nylon 12, amorphous nylons, aromatic nylons and their
copolymers. The
polymer of the carrier may be the same as or different from the polyamide of
the flowable
mixture. For example, both polymers may be a polyamide, particularly nylon
6,6, but may have
the same or different molecular weight. The preferred weight average molecular
weight of the
carrier polymer of the concentrate is in the range of about 5,000 D to about
60,000 D. The most
~o preferred range of the weight average molecular weight for the carrier
polymer is in the range of
about 10,000 to about 40,000 D. In this embodiment, the dissociation step of
the present
process, as described below, may occur at least in part via the forming of the
concentrate such
that the dissociation step may precede the step of forming the flowable
mixture. It is therefore
understood that the process steps (e.g., forming and dissociating) may occur
sequentially without
is regard to order, simultaneously or a combination thereof. In the second
step, the flowable
mixture is sufficiently mixed to form the dispersed nanocomposite structure of
dissociated
silicate in the polymer melt, and it is thereafter cooled. The silicate can be
dissociated by being
subjected to a shear having an effective shear rate. As used herein, an
effective shear rate is a
shear rate which is effective to aid in dissociation of the silicate and
provide a composition
2o comprising a polyamide matrix having silicate substantially homogeneously
dispersed therein
without substantially breaking the individual units (e.g., platelets or
fibrous chains).
Any method which can be used to apply a shear to a flowable mixture or any
polymer
melt can be used. The shearing action can be provided by any appropriate
method, such as by
mechanical means, by thermal shock, by pressure alteration, or by ultrasonics.
Preferably, the
2s flowable polymer mixture is sheared by mechanical methods in which portions
of the melt are
caused to flow past other portions of the mixture by use of mechanical means
such as stirrers,
Banbury type mixers, Brabender~ type mixers, Farrel~ continuous mixers, and
extruders. Most
preferably, the mixture is subjected to multiple shearings. In addition to the
increased shear
provided by multiple shearing, increased residence time is also provided,
which results in
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improved performance properties. Another procedure employs thermal shock in
which shearing
is achieved by alternatively raising or lowering the temperature of the
mixture causing thermal
expansions and resulting in internal stresses which cause the shear. In still
other procedures,
shear is achieved by sudden pressure changes in pressure alteration methods;
by ultrasonic
s techniques in which cavitation or resonant vibrations which cause portions
of the mixture to
vibrate or to be excited at different phases and thus subjected to shear.
These methods of
shearing flowable polymer mixtures and polymer melts are merely representative
of useful
methods, and any method known in the art for shearing flowable polymer
mixtures and polymer
melts may be used.
io Shearing can be achieved by introducing the polymer pellets at one end of
the extruder
(single or twin screw) and receiving the sheared polymer at the other end of
the extruder. A
preferred twin screw extruder is a co-rotating fully intermeshing type, such
as the ZSK series
manufactured by Werner and Pfleiderer Company. The silicate can be fed into
the twin screw
extruder at the feed throat or at the downstream vent. The preferred method is
to feed the silicate
~ s at the downstream vent, which produces a composite polymer with improved
performance
properties.
Another preferred continuous compounder is the Farrel Continuous Mixer (FCM).
For
composites using Vydyne 21 nylon, the preferred temperature of the melt is in
the range from
about 275 to 315°C, with the most preferred range being from about 275
to 295°C.
2o The polymer melt containing nano-dispersed dissociated silicate material
may also be
formed by reactive extrusion in which the silicate material is initially
dispersed as aggregates or
at the nanoscale in a liquid or solid monomer and this monomer is subsequently
polymerized in
an extruder or the like. Alternatively, the polymer may be granulated and dry
mixed with the
treated silicate material, and thereafter, the composition may be heated in a
mixer until the
2s polymer is melted forming the flowable mixture.
The third process step is a solid state polymerization step, wherein the
compounded
pellets are held for several hours at a high temperature at least about
20°C below the melting or
softening point of the polymer. For example, for nylon 6 and nylon 6,6,
typical solid state
polymerization conditions are heating the solid polymer in the range of about
200°C to about
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240°C for a period of from about 2 to about 5 hours. It is desirable to
remove water produced
during polymerization, e.g. by a dry nitrogen stream. Said additional process
step results in an
increase in molecular weight and an improvement in toughness, ductility and
tensile strength of
the nanocomposite.
The solid state polymerization step can be further effected with a catalyst
that increases
the molecular weight of the polyamide, e.g., a phosphorous-containing catalyst
such as
monosodium phosphate. Such phosphorous-containing catalysts are disclosed in
U.S. Patent No.
4,966,949. For the composites that include a catalyst, milder treatment
conditions are needed to
effect the desired polymerization. For example, the treatment temperature can
be below the
~o temperature used in solid state polymerization absent the catalyst using
the same polyamide, i.e.,
more than 20°C below the melting or softening point of the polyamide.
The treatment time can
be lowered to the range of about 0.5 hours to about 5 hours.
An optional processing step is a heat treatment step, where the composition is
heated to
improve intercalation of the nylon molecules into the silicate structure. Said
heat treatment step
~s is performed by heating the composition at a temperature in the range of
about 200°C to about
240°C for a period of about 2 to about 5 hours. The heat treatment step
can optionally be
incorporated into the dissociating step by increasing the residence time of
the mixture in the
mixer or extruder, thereby heat treating under melt conditions.
The process to form the nanocomposite is preferably carried out in the absence
of air, as
2o for example in the presence of an inert gas, such as argon, neon~or
nitrogen. The process can be
carried out in a batchwise or discontinuous fashion, as for example, carrying
out the process in a
sealed container. Alternatively, the process can be carried out in a
continuous fashion in a single
processing zone, as for example, by use of an extruder, from which air is
largely excluded, or in
a plurality of such reaction zones in series or in parallel.
2s In another embodiment of the present invention, the process to prepare a
polymer
nanocomposite composition comprises forming a first flowable mixture of a
polyamide, at least
one monomer and a silicate material; dissociating at least 50% but not all of
the silicate material;
polymerizing the monomer; and subjecting the polyamide in the mixture to solid
state
polymerization. It is to be understood that the polymerization of the monomer
step can occur
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simultaneously or sequentially with one or more other steps in the process of
this embodiment.
Preferably, at least one monomer of the this embodiment includes monomers such
as s-
caprolactam, lauryllactam, and their corresponding lactones.
In yet another embodiment of the present invention, the process to prepare a
polymer
s nanocomposite composition comprises forming a flowable mixture of a
polyamide and a treated
silicate material; dissociating the at least about 50% but not all of the
treated silicate material;
adding an additional amount of said polyamide, most preferably during said
dissociating step;
and subjecting the polyamide in the mixture to solid state polymerization.
Each of the above embodiments of the process to prepare the polymer
nanocomposite
~o composition can be followed by additional steps or treatments, or
additional melt polymerization
of the composition by increasing the residence time in the mixer with the
removal of water
condensation product. The increased residence time can also improve the
intercalation of the
polyamide into the silicate, as discussed above.
The composition of the present invention may be made into, but is not limited
to, the
~s form of a fiber, film or a molded article.
Solid state polymerization increases toughness, strength, and ductility of the
produced
polymer, while generally maintaining processability and modulus. Solid-state
polymerization
may improve properties such as elongation at yield, tensile elongation at
break, flexural
modulus, elastic modulus and both notched and unnotched Izod impact strength.
Additional
2o catalysts may be added, but are not required. Acid-functional clay
treatments are particularly
amenable to SSP (e.g., SCPX 1016 and SCPX 1255}. They may serve to build
polymer-clay
linkages by tethering nylon molecules to the adsorbed acid moieties. The
stoichiometric balance
of amine and acid groups can impact the properties of the resulting polymer. A
higher
amine:acid ratio in the nylon is desirable, especially in the case of
aminoacid-treated silicates.
zs The use of solid state polymerization to finish the nanocomposite would
allow starting with a
lower RV nylon that would enhance intercalation, leading to greater
exfoliation of the clay
layers. The inherent brittleness of nanocomposites compounded on the FCM may
be overcome
with SSP finishing, to make the FCM a viable low cost process alternative.
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The following examples are included to demonstrate preferred embodiments of
the
invention. It should be appreciated by those of skill in the art that the
techniques disclosed in the
examples which follow represent techniques discovered by the inventors to
function well in the
practice of the invention, and thus can be considered to constitute preferred
modes for its
s practice. However, those of skill in the art should, in light of the present
disclosure, appreciate
that many changes can be made in the specific embodiments which are disclosed
and still obtain
a like or similar result without departing from the spirit and scope of the
invention.
EXAMPLES
Materials:
~o The following types of nylon 6,6 polymers have been employed in
nanocomposites
described herein.
NYLON MATRIX RESINS
'.,'", iy:: L:: :v4'i.:::::Y::. ~v :::: . .... . . ..
:'.::;~n?. :4:: ~ ~?::::.v.:::::. v:'v... . .. .............
:ya:,'.r:' : Y?:. . . . . .. .
i::. u.~... .L..,:~,...:~Gv
.?:r.l li ::> ''"r',:.! v .
r::G:'.??:.'.' ;.;<
.. .: .. .....
'' a . n
:..:. iv
J . ~ifi'.;~f
~ ' f . 0f
~ ! ~
>?
~
u
:: ;
.
i2'i.? ;.
........ % ~ t 3
..f :
v::tv:?:T:: . . y, ..:
%'4 .. ~ ...;av:fv :..'..:
..:. A.. l .' :.T':?. .
!>: ... ~~ :iGi:ri2?::
::::':':::::::'?v:?i.',~?:::'.'vi:.'i::4a....:.'i::?
.Gnn...::?.:n:vsv:n.v:::'i''.:$'.:::J::x ..:. .
.. .f.. .. Y.:. gt : . o:::: : :::::::::::
:~ ...: /: . ... ... .;:< a
: .:..................../: . . . ..:. '
> .:...........:.:~.::...........J.. .; ...; ::. ~
: :.:
.: .:.:
.:: :::::
:' ~::
.::: :
: >
::f::::
~'....;".
....,.. . .
:: ;. . .... .
'pry f.::!h:.l..:. ' .; .
:t >:.::.:::.::~ . ..:. .
...::::::::::.x.::x ,::?:...
?.,:.: ,.: . : .?. . .
:.;,:%:,%%:;:;. .: . .
::~ r::.G.,..;.
.:.,: >::?::.. .:
~: .:: ?.::.:?: .
.?. . :
.:::;.:.::.::w .> . f :.,?:.:.~:...::::'
fr?:. ~ ? : ~
:.o..: : :.,.>:;?.:Kn
.;..,:; ~ .::
.. :. :: . '
: . ,.... ,
c ~. : . .
. :?:::::::::..::
:?:.y: ,....
'', ,
:
:? :. . . .
:.:: >:;:: r::;:
. .. ..: , . .
. ... .. , .... . . .. .
. . .. ~~:. ......:: . ............
.:......................................... :, .:..:... ....: . ;$ .
. : 7::x:.:.::::4::
......:...........;..;.,.;::::i~':'.:.::?~.... .: .. . ..ff~x~~:G f v..
.,.,v.:.,.:
:.. ... ...::V::i:::;.:.:... ..., :.:.9:;~ ::;:in,:
n..i...< . ;;.v : :: :;
: .;.:v.v:y
.t: ~
a 35 55 60
b 35 45 70
c 50 40 40
d 21 125 70
The montmorillonite clay used has an exchange capacity of about 95
millieqivalents per
~ s 100 g of silicate.
Example 1: Conventional compounding without SSP
A high molecular weight in the nylon matrix of nanocomposites has been found
to be
even more beneficial for the ductility and toughness of the nanocomposites
than for the neat
nylon polymer. The smectic silicates reduce nylon molecular weight during the
compounding
zo operation, especially in the first pass, resulting in a loss of ductility
and toughness. For example,
the molecular weight of nylon b was observed to drop from 36,500 to 31,500 D
in a single pass
of 7% montmorillonite treated with dimethyl di(hydrogenated tallow) ammonium
cation
(2M2HT-montmorillonite) through a 40 mm ZSK twin screw extruder manufactured
by Krup
Werner & Pfleiderer Company. A second pass reduced the MW further to only
21,000 D. The
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-20-
second pass under dry conditions could instead improve mechanical performance
both due to
molecular weight building as well as enhanced exfoliation and dispersion of
the nano-platelets.
Solid state polymerization (SSP) can be implemented in compounded
nanocomposites
under similar conditions used for the neat polymer as a more efficient method
for building
s molecular weight. Improvements are obtained in tensile strength and
elongation, as well as
notched and un-notched Izod impact strength. Slight losses in modulus
sometimes occur,
perhaps due to breakage of the thin delaminated platelets during flow of the
higher viscosity
nylon matrix.
Effects of molecular weight
~o The effects ofthe nylon 6,6 molecular weight or its equivalent relative
solution viscosity
(RV) on mechanical properties are shown in Figures l and 2 for nanocomposites
prepared by
conventional compounding in a twin screw extruder without subsequent SSP. The
nylon RV is
that of the raw material fed to the extruder. P 1 and P2 in Figure 2 refer to
the first and second
passes through the compounder.
~s A higher amine/ carboxyl end group ratio on the nylon is preferable for
nanocomposites,
including those that are later subjected to SSP. The inherent Lewis acidity of
the clay surface in
combination with any acidity introduced from clay treatment, either in the
form of an aminoacid
cation or the polyacrylate peptizer used on some clay grades, could alter the
end group balance
of the nylon, resulting in some degree of depolymerization. For example, an
acidity of 40
2o pequiv/g (4.0 mequiv/100g clay) -COOH was measured for both acrylate-coated
Na-
montmorillonite and the 2M2HT-montmorillonite. Amino acid exchanged grades
would have
higher acid levels according to the degree of substitution, as measured by the
milliequivalenet
exchange ratio (MER) in milliequivalents of cation per 100 g of silicate.
Thus, nylons a, and c
are preferred to nylon b. The higher amine end group concentration of nylon d
would be
zs especially important in the case of silicates treated with amino acid
cations, which can react with
the amine end groups of the nylon. These treated silicates show a stronger
response to the
effects of SSP, resulting in larger increases in the above properties than
nanocomposites
containing pristine silicates or those treated with unreactive moieties.
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The molecular weight changes to the high amine nylon d due to compounding with
4%
montmorillonite exchanged with 12-aminolauric acid (ALA-montmorillonite) and
subsequent
solid state polymerized have been analyzed via GPC.
::>::.-..::~:::::::,......:....;>.:.>.::.:.,:::::::...............
a .~ . :..,..::,;::::.:.,::.::...:::.:::::..::............... ..............
......... ...
........ . .~......:......:............,.,.:.:.................. .........
............... . ...:;::,::::::::::::::;. ........... .............
. .... :... ...... > . ............ . .., ..
........ . .. . -:-__...-.-.-.:-...: . ........
..................,.. .......... ....................: :.
. ... .,.,.......,............ .::::::... ..:.
.:~: :.::::: :..; ..:... .: ,.::.>.... ::.~:.:
:.::.~.::~ ,:::.::n.::.,.: ..,::~ ::::::.:::. ..~:::::;:h---...
,.:.:.::::...V :: .: .::..:.::::,:.::. ::: . ::
......... .......:,:.:..:::::.<.:,.:...::...,:::.~:.:..:.... . .::.~....:a.
.
......... ................::....:.::.~.lt~t:.~.r,~.:..:.....:...:::
.::::~::...
::.::.::. .: ::::::::. .: .::
:...::.:..~:::::::1~::.::::.:3:::. :....:~:::
:.::..::._::: ..........~: .::::::..
:.............:.....k ...~~.::.~:::.....:::..:::~.::::.
. ................... .:.....::.
Nylon d flake 28.4 I 9 1.59 1.33 ~
.
,
99.2
Nylon d extruded30.3 19.7 1.54 1.38 100.
Nylon d + 4% 31.3 19.6 1.60 1.27 92.3
ALA-
montmorillonite
above + SSP 3 84.2 37.2 2.26 2.7s 70
hr @
220C
Nylon d + SSP highly gelled
3 hr @ - could
220C not be run
The symbols used in this table have the following meaning:
Mw: weight-average molecular weight
Mn: number-average molecular weight
IV: intrinsic viscosity measured in formic acid
Example 2: Solid state polymerization (SSP)
The extrusion process is seen in the above table to not change the molecular
weight or its
io distribution in the nylon signifcantly. While a large increase in molecular
weight of the
nanocomposite does occur during SSP, it is reduced from that of the neat resin
(which gels) by
the presence of the acid moieties on the clay. There is, furthermore, evidence
that the nylon
matrix is being bound to the clay even during the compounding operation.
During solid state
polymerization, the nylon either branches or couples further with the
organosilicate to form very
~ s high molecular weight species that become insoluble.
Solid state polymerization was practiced by heating the plastic pellets to 200-
240°C
(typically 220°C) with a dry nitrogen sweep to remove the water of
condensation for a period of
2-4 hours (typically 4 hours). It was not necessary t~o add additional
catalysts above those
present from the initial melt polymerization, although mono- or di- sodium
phosphate could have
2o been added at 100-500 ppm. In one instance, adding 1,000 ppm monosodium
phosphate resulted
in an increase of compounded molecular weight from 27,400 to 30,600 D (SSP was
not
performed).
CA 02320909 2000-08-11
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Typically, the SSP dryer is set to 470°F (243°C) oil temperature
and the nylon
nanocomposite is heated for four hours at 220°C (230°C shell
temperature} following an
approximately 2-hour heat-up period. The resulting time-temperature profiles
are shown below
for representative nanocomposite solid state polymerization runs.
6.6% wt. 2M2HT-montmorillontie in nylon a solid-state polymerized for five
hours
::~::::::;:::::.::::: .:::::::.;.. ............ . ..
:::.:.:::::.:~.,:.:.:;::..:.,~.: .; :..~::.:.:.:..a...;:. , r.:::r.
..:..,r:.t..s...:::::.~:. .. ~p x.:
:: : :y:. ;' .,...:::....:W :: - ::n
::..~:.::::::::::::::.. , i '.>:;::p.. . . :q::: :'. ~,
:;::;; . . . ... . : ..:.s. 4.
. .:::> v "n. ~:::.~. M
:...i :.: v~ :'~. . : .,_.,~,',.. ~ :. ~~~
.. ' . . ~~.;.~ , : :>::'
::::::::.,.;::::'. . : 'v . S ~~:~~:
:;_:...; ~~, 1:. .;; n
;;..;.t:..;.;~n:::::::::.:4 Sr.. ,
7:15 0 _ 0 ...
~~ .
520(271)
8:15 140 150 480 (249)
9:15 210 225 480 (249)
10:00 223 227 480(249)
11:00 220 226 470(243)
12:00 220 226 470(243)
13:00 220 226 470(243)
14:00 220 226 470(243)
15:00 220 226 470(243)
3.7% wt. 2M2HT-montmorillonite in nylon a solid-state polymerized for four
hours
....., . .; x::.:
wt: :,~: .
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11:10 192 200 470 (243)
12:15 217 225 470(243)
12:20 220 225 470(243)
13:20 220 225 470(243)
14:20 220 225 470 (243)
15:20 220 225 470(243)
16:20 220 225 470 (243)
3.7% wt. 2M2HT-montmorillonite in nylon a solid-state polymerized for five
hours
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CA 02320909 2000-08-11
WO 99/41060 PCT/US99/03097
- 23 -
4.0% wt. ALA-montmorillonite in nylon a solid-state polymerized for three
hours
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12:40 220 226 470(243)
13:40 ~ 220 ~ 226 470 (243)
12.2% wt. montmorillonite treated with dimethyl benzyl hydrogenated tallow
ammonium cation
(2MBHT-montmorillonite) in nylon c, solid-state polymerized for four hours
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I3:00 220 226 470(243)
14:00 220 226 470(243)
1$:00 220 226 470(243)
8.4% wt. 2MBHT-montmorillonite in nylon c solid-state polymerized for two
hours
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10:00 220 226 470 (243)
11:00 220 226 470(243)
12:00 220 226 470 (243).
6.2% wt. 2M2HT-montmorillonite in nylon b solid-state polymerized for three
hours
650 ppm of monosodium phosphate, monobasic, as catalyst
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10:1$ 18$ 190 400(204)
11:1$ 18$ '190 400 (204)
12:1$ 190 190 400(204)
13:1$ ~ 190 ~ 190 400 (204)
CA 02320909 2000-08-11
WO 99/41060 PCT/US99/03097
-24-
Example 3: Introduction of ductility
An example of the introduction of ductility through SSP is shown by the stress-
strain
curves (Figures 3 and 4) for 4.0 w/o ALA-montmorillonite in nylon a.
Example 4: Increase in molecular weieht
Increasing molecular weight of the nylon matrix is indicated by the intrinsic
viscosity
measurements shown in the table below.
Intrinsic viscosity vs. SSP Time
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~'4% sepiolite ~in~nylon d ~ ~ 2.04
Intrinsic viscosity builds linearly with time in the SSP dryer, as for example
shown by
the following data and graph (Figure 5).
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..................
.. . I. n .. .........;..:: ::::::::::::.n . ..
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a : v:::::::::::::x:::;. 4: .......::! ....................46.3
..............n.: :..
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. ....:........;. :;:..::........... .. :,:..
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.::.
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:.. . ,........:
: .:f: ... 3. .. ..... ..: .:
..: ........ .::::...:.:!??..;r;r~:~..:...
. s ..
:::..r..::.~....:.:r:::. .....:..:..............
~20,243~: .
: r.::..:....:.r:..., ...............::::.~:::.~:::.~::::::::.
,
: .... r
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r:;
0 .....;',~,..;
2M2H'1- ::~/.:..:..,
~ f:..
montmorillontie 40,373
I f.85
2 2.03
3 2.21
4 2.50 50.8 34.4 23,47446,835
-
-~~~
Nylon 2M2HT- 3.7 0 1.67 52.5 46.3 20,24340,373
a montmorillontie
I 1.89
2 2.14
3 2.34 51.9 36.3 22,67645,238
I
4 2.52 50.6 35.0 23>36446>616
5 2.73 50.5 33.0 23,95247,791
Nylon ALA- 4.0 0 1.63 50.5 28.5 n.a. n.a.
a montmorillonite
I 1.82
2 2.05
CA 02320909 2000-08-11
WO 99/41060 PCT/US99/03097
- 25 -
' 3 2.27
Nylon 2M2HT- 6.6 0 1.60 68.1 55.416.19432,276
a montmorilonite
1 1.78
2 1.91
3 2.10 67.8 46.017.57535.036
4 2.23
5 2.35 65.0 44.818,21536,317
Nylon sepiolite 4.0 0 1.05
d
3 2.04
L 1 I I I I I I I
The rate of increase is faster for acid-terminated ammonium cations at long
residence
times in a high-amine nylon matrix, as shown by the ALA-montmorillonite data
in the graph
below (Figure 6).
Example: 5: Infection molding of solid state polymerized nanocomposites
Solid-state polymerized nanocomposites based on nylons c and d mold easier
with higher
temperature setpoints than at lower temperature. Among these two nylons, the
nylon d-based
nanocomposites mold more easily than those based on the nylon c, perhaps
because the nylon c
matrix reaches a higher viscosity level than the nylon d. Lower pack and hold
pressures can also
be used.
to In both cases, however, higher pack pressures and hold pressures than
conventionally
used to injection mold nylon 6,6 are preferred to better pack out the mold.
CA 02320909 2000-08-11
WO 99/41060 PCT/US99/03097
-26-
Molding Comparisons
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. ....'~r..~...r~.,.r/..:.:::::::
~ ..... ...........:
Pressures (psig)
Injection Pressure:2000 2000 2000
Injection Xfer 2000 2000 2000
Press.
Pack Inj. Position0.60 0.60 0.60
Pack Pressure 700-800 900 900
Hold Pressure 700-800 900 900
Back Pressure 100 100 100
Screw Speed (%) 30 30 30
Extrude Position2.1 2.1 2.1
Cycle Times:
(sec)
Inject 1.0 - 2.0 1.0 1.0
Hold 15 15 15
Cure 15 15 1 S
Heaters: (C)
Rear 255 255 250
Middle 290 290 289
Front 295 295 290
Nozzle 295 295 290
Mold Temp. (C) 93 93 93
Lube Type None None None
Lube Level None None None
Comments: Molded Molded
Well Well
Such higher pack and hold pressures usually also tend to increase tensile
modulus and
strength. Without SSP, lower molding temperatures are preferred for higher
ductility in the
molded parts due to less thermal degradation of the polymer. However, the
higher ductility with
a SSP is instead achieved by higher molecular weight, thus allowing the use of
the higher
CA 02320909 2000-08-11
WO 99/41060 PCT/ITS99/03097
-27-
temperatures that are known to benefit the stiffness of the molded
nanocomposite. In this way,
an additional degree of processing freedom is introduced via the SSP process
by which injection
molding parameters can be adjusted to optimize the overall molding process and
property
spectrum.
s Example 6: Mechanical properties for concentrate route usinghi~h amine nylon
matrix
The use of a high amine end carrier nylon in a concentrate to enhance the
properties
induced by solid state polymerization of the final nanocomposite composition
was evaluated. A
high amine nylon concentrate comprising 17% ALA-montmorillonite in nylon d was
then let
down into three different resins having a range in molecular weight and
amine/acid end group
to concentration, with and without subsequent solid-state polymerization prior
to molding. A fairly
intense screw design was used in the ZSK 40mm twin screw extruder with a feed
rate of 100
lbs/hr (43.5 kg/hr) and screw speed of 250 rpm. The barrel zone temperatures
were set at 270°C.
For the solid-state polymerization the polymerization dryer was set to
470°F (243°C) oil
temperature from start to finish, giving a residence time of up to four hours
at a 220°C resin
is temperature and 230°C shell temperature. Sample descriptions and
mechanical properties are
given in the table below.
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f. ii.: f ~~ro-:: ..
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y'y::
~ .'~
..H i..
:.a.
. :.
16.0
0.79
~ 39.6
Nylon 3.794.770 11.85 592 2.5 56219.12 0.453.8 10.7
b
Nylon 3.995.020 13.29 570 15.7 55418.98 0.605.4 10.5
c
Nylon 3.985.010 L2.I2 622 2.4 57019.55 0.444.0 7
d 9
Mean 3.92 0 12.42 595 6.9 56219.22 0.504.4 .
9.7
Nylon 3.794.774 13.63 603 22.6 56018.6 0.8719.1 9.8
b
Nylon 3.995.024 13.64 605 20.4 54818.5 0.9250.3 10.6
c
Nylon 3.985.014 14.27 661 18.1 57719.3 0.7942.2 7
d 4
Mean 3.92 4 13.84 623 20.4 56218.79 0.8637.2 .
9.3
.W .iCSS meaSLLTeQ ai J% Siraln.
The previous table shows the beneficial effect of solid state polymerization
in improving
the ultimate mechanical properties of tensile strength and elongation, as well
as both notched and
2o un-notched Izod impact strength. Its strong effect on nanocomposites
comprising the ALA-
CA 02320909 2000-08-11
WO 99/41060 PCT/US99/03097
-28-
montmorillonite compensates any molecular weight degradation of the nylon that
might have
occurred during compounding.
The effects of the parameters can be analyzed more quantitatively by use of
the neural
network CAD/Chem software (AIWare, Cleveland, OH). In this approach, the
nylons are
s described by their nominal weight-average molecular weight and the nominal
ratio of amine/acid
end groups. The mineral content of the nanocomposite is retained as a
correlating variable to
account for the minor differences between samples. On this basis, the
following linear
correlation coefficients are obtained. SSP refers to the solid state
polymerization time, in hours.
..........
...........,... :: .. ..:...;, . . . . ..
......... .. .:::..::: .. .. ..... ~i %f,,::.:.
... .. :...::. .; . ... s'
. .. . ~...::::.. .:.::. f. .. .. " rr~r,~.
. .... .:.:.. . . . >: .. ~ ~%'>
. _ . ,T.;! %: ,. 7 ! : ~'ii fr.
:.:,'.,'.,'.:n~ , m ~~
ii:,:;~:1~:::"::': .C. .tS. ~ ~ . ,. ~~~ ~
i:..~ .: s ' ry:! ~ ~
:: :!:vbf' i ~W~'i. ~~ ~~! :r~'
. .i4<. ..r3~':'Wyi R:4~J,, i , i
. 7 .. ,~ .I:'S'~,. . ~ .
.: x!$ '. ~ .~ k%'.,C!.. L:7i:!'-. ~ r
;~.:!.::ly:u/Y ry' I
~ 'n ftu /~.' .iM7YIlf /. y~ '
.y. . S r..'~,...,x~,.oil:..e:'ry~/.~.~.,T/Y:n..,
iix . ~f.: ,i , !. . r~ ''~....:::.'r.!!
t',/.;:.! /......:~.....;x..:.,, ~: %'. ~ ~" '.
. .. ..: .:~..~;~s....' ~;~~~:
.:, y ?~'...
,/y:.Y.F.,; v"U.17 ~~ x.39 ..~
yy . C
;; ~'~ 0.68
.:~yr'~'.:..
x:<:.:...~
. ,r...
.. s 9,
.
:',r..
y.:::;Ti
.::' v.
:.. :f:~
. ~ rv'.'i!::.
.: .'I
~ ~
:p;v~ yiixyaexe':
~,E _
::!:,.v
. ! "
Rb/...!G.....:...:.........!~
.. :,'.~:..:fG...xw
. .. eN........
Max TS 0.11
E tensile -0.14 -0.02 0.45 0.35
Ult Elong. 0.14 0.26 -0.39 0.41
E flex -0.19 0.05 0.25 0.09
E 5% flex -0.16 0.12 0.29 -0.03
Notched 0.45 0.02 -0.22 0.65
Izod
Un-not Izod0.00 0.37 -0.15 0.77
Shrinkage 0.22 0.07 -0.08 -0.02
These results show that solid state polymerization generally increases tensile
properties
io along with both types of Izod impact strength, while having a negligible
overall effect on flex
properties. A higher initial molecular weight in the nylon (prior to
compounding) could also be
somewhat beneficial for notched Izod impact strength, but does not positively
affect properties.
A higher amine/acid end group ratio is seen to be generally advantageous for
ductility
(elongation) and toughness (un-notched Izod impact strength) as it helps to
maintain nylon
~ s molecular weight by counteracting the additional acidity introduced by the
clay treatment.
However, strong parameter interactions not apparent in the above table do
occur and can
be seen in the following response surfaces. With 4 hours solid state
polymerization time, a
nanocomposite comprising 4.9% by weight ALA-montmorillonite (3.9% mineral ash)
in a
40,000 Mw nylon having balanced end groups is predicted to have the following
properties:
20 14.00 Kpsi tensile strength, 612 Kpsi Young's modulus, 21.6% ultimate
elongation, 558 Kpsi
CA 02320909 2000-08-11
WO 99/41060 PGT/US99/03097
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flex modulus, 18.68 Kpsi flex stress at 5% strain (below breaking strain),
0.91 ft-lb/in notched
Izod, 43.9 ft-Ib/in un-notched Izod and 9.5 mil/in shrinkage.
Figure 7 shows increasing tensile strength with SSP time when nanoclay is
present, but
not in the neat nylon.
s The ductility and toughness of nanocomposites, however, are increased
significantly by
solid state polymerization and to a lesser extent by higher amine/acid ratio
and initial molecular
weight of the nylon (Figures 8, 9 and 10). The ALA-montmorillonite
concentration in the last
two figures is 4.9%.
Stiffness (tensile modulus) is slightly increased by solid state
polymerization, perhaps
)o through network formation between the high MW nylon and the clay by
reactive tethering of the
nylon polymer molecules to the ammonium ions adsorbed on the clay surface
(Figure 11 ).
Example 7: Data Tabulation
A comprehensive listing of composition, SSP time and mechanical property data
is given
in the table below for all of the ALA-montmorillonite, 2M2HT-montmorillonite,
2MBHT-
) s montmorillonite and sepiolite nanocomposite preparations involving solid
state polymerization.
MineralTotalSilaneS.S.P. FlexuralFNxwalIZODIZODBreaksMold
Mex
Tsns
Tens
Brk
Tensile
NylwiClay Ash Clay(wtliTimeStrengthElonpat. ModulusStrerplhNot.Unnot.I
Shrinkage
on Modulus
k~s~iLk ~kp~tt tf Non-Bnaksmilslin
nil IWinIWin
a 2M2HT-moot.4.1 6.80.0 0 12.124.4 590 531 17.80.5216.2(5/0)
a 2M2HT-monl.4.1 6.60.0 5 11.7119.5548 549 17.70.8063
0
a 2M2HT-moot.2.3 3.70.0 0 11.8717.1522 494 17.30.69. (411
31.6)
a 2M2HT-moot.2.3 3.70.0 4 11.9696.6481 507 17.10.9650
6
a 2M2HT-moot.2.3 3.70.0 5 11.6073.3513 541 17.70.84.
83
1
a ALA~nont.3.2 4.00.0 0 12.814.6 548 507 17.90.37. (5/0)
3.4
a ALA-moot.3.2 4.00.0 3 12.0224.3528 515 17.30.7645.1
c ZMBHT-moot.5.1 8.42.0 0 13.975.9 687 701 20.60.5211.5(5l0)
'
c 2MBHT-moot.S.1 8.42.0 2 13.5311.7653 B95 21.10.5910.9
c 2MBHT-moot.7.5 12.22.0 0 12.862.0 754 626 20.40.6914.5(5/0)
c 2MBHT-moot.7.5 12.22.0 4 13.2422 734 615 19.70.7138.3
b 2M2HT-most.3.9 6.20Ø0 11.165.4 544 524 18.40.5012.9(510)
b 2M2HT-moot.3.9 6.20.0 3 11.917.4 537 540 17.60.5722.9
b 0.0 0.0 0 11.3847.7455 450 16.00.7939.6(113) 19
4
b AI.A-moot.3.8 4.82.0 0 11.852.5 592 562 19.10.453 (510) .
B 10
7
b ALA-moot.3.8 4.82.0 4 13.8322.6587 560 18.60.87. (3!0) .
19 9
1 8
c ALA-moM.4.0 5.02.0 D 13.2915.7570 554 19.00.60. (5/0) .
5 10
4 5
c AI.A-moot.4.0 5.02.0 4 13.6420.4587 548 18.50.92. (0l4) .
50 10
3 6
d ALA-moot.4.0 5.02.0 0 12.122.4 622 570 19.60.44. (5/0) .
4 7
0 9
d ALA-moot.4.0 5.02.0 4 14.2718.1647 577 19 0 . 2l3 .
3 79 42
2
. . . ( 7.4
)
d Sepiolite3.5 4.t0.0 0 12.943.3 543 504 17.90.585.5(510) n
a
.
d Sepiolite3.5 4.10.0 4 12.6810.6473 466 16.90.9542.3(1/4) .
13
7
c Sepiolite2.5 2.92.0 0 t1.8128.3467 446 15.80.9142 (1l4) .
6 16
8
c Sepiolite2.5 2.92.0 4 11.5636 413 401 14 1 . .
2 8 22
, . . 45.3(0/5) 16.5
CA 02320909 2000-08-11
WO 99/41060 PGT/US99/03097
-30-
Aminoacid organoclay is seen to provide the most favorable combination of
nanocomposite properties following SSP. However, it may cause more
embrittlement than other
clay types if SSP is not practiced. The acid functionalization is believed to
compete for the
amine end groups on the nylon chains, thus upsetting the end group balance and
degrading nylon
s molecular weight during compounding. Higher initial molecular weight or
amine/acid end
group ratio in the selected nylon would help to counteract this effect, but
SSP preferably would
be performed following compounding to restore or even further increase the
nylon molecular
weight. Pristine sepiolite is observed to be less destructive to ductility and
toughness than is the
montmorillonite.
~o Nanocomposite material compounded with a single pass through the Farrell
Continuous
Mixer, which tends to impart high modulus but embrittlement in nanocomposites,
could be
solid-state polymerized to restore ductility and toughness along with possible
increase in tensile
strength. The combination of FCM compounding with SSP would represent a low
cost process
to a ductile and tough, yet stiff, nanocomposite.
is All of the compositions, processes, and apparatus disclosed and claimed
herein can be
made and executed without undue experimentation in light of the present
disclosure. While the
compositions and processes of this invention have been described in terms of
preferred
embodiments, it will be apparent to those of skill in the art that variations
may be applied to the
compositions, processes, and apparatus and in the steps or in the sequence of
steps of the
2o processes described herein without departing from the concept, spirit and
scope of the invention.
More specifically, it will be apparent that certain agents which are
chemically related may be
substituted for the agents described herein while the same or similar results
would be achieved.
All such similar substitutes and modifications apparent to those skilled in
the art are deemed to
be within the spirit, scope and concept of the invention.
