~Q~J~~~~
POLYMER BLENDS WTTH ENHANCED PROPERTIES
This invention relates to polymer blends of (meth)acrylate
polymers, or glutarimides derived from such polymers, with polymers
containing vinyl alcohol mers which are either miscible with, or form
a discontinuous phase in, the poly(lower alkyl (iineth)acrylate),
glutarimide polymer, or other polymers which may be present. It
further relates to such blends in the farm of film, sheet; bottles, or
other packaging articles.
Bac ,g,~,~a~nd of the Invention
The packaging industry has long sought to develop plastic film,
sheet, bottles, wrappings, and containers which are impervious to
1
~Q~~J~4
oxygen for preserving oxidizable materials and oxygen-sensitive foods
and beverages. That industry has further sought to develop similar
materials resistant to the passage of carbon dioxide for use in
maintaining the carbonation of carbonated beverages. Resistance to
passage of water vapor is also important to the packaging industry. No
organic polymeric materials are truly impervious to gases; they all
show some degree of permeability. Those which have low
permeability to a particular gas are considered to be good barriers for
that gas, while those which have high permeability are considered to
l0 be non-barrier materials with respect to that particular gas. The most
useful polymers which exhibit very low values for oxygen
permeability, i.e., are good barriers to oxygen, are poly(vinylidene
chloride) and polymers containing vinyl alcohol mers, such as
ethylene-vinyl almhol copolymers containing less than about 50 mol
percent ethylene units, or the homopolymers of hydrolyzed polyvinyl
acetate) known as polyvinyl alcohol)s.
Although each of these types of polymers is utilized in
commerce, they have deficiencies which limit their broader use.
Poly(vinylidene chloride) is thermally less stable 'than most polymers
2 0 and is difficult to process; polyvinyl alcohol)s are difficult to process,
and their barrier properties are greatly affected by high relative
humidity, and the ethylene-vinyl alcohol polymers, which are more
easily processed than polyvinyl alcohols not containing ethylene, axe
also sensitive to moisture, and are not optically clear. Further, the
2 5 structural properties required for many applications are difficult to
achieve with these polymers.
2
~:~7~~5~4
The packaging industry has also sought to prepare containers
exhibiting enhanced service temperature for the hot-fill packaging of
foods, sterilization prior to packaging, autoclaving to sterilize contents,
and the like. Materials attractive for such heat-sensitive uses tend to
have poor barrier properties.
Polymers based on lower alkyl methacrylates, such as
poly(methyl methacrylate) exhibit clarity, have some degree of
toughness, and can be compounded with impact modifiers to improve
toughness, but do not exhibit satisfactory barrier properties.
Conversion by reaction with lower alkyl amines or ammonia to
polymers with mers of glutarimide improves the barrier properties
significantly, but they still do not meet the requirements of the most
demanding barrier applications. Kopchik, U. S. Patent No. 4,246, 374,
discloses such polymers in thermally stable form, and discloses that
their barrier properties are superior to most clear thermoplastics.
Hallden-Abberton et al., in U.S. Patent No. 4,727,117, describe a
means of reducing the content of unreacted acid and anhydride groups
of glutarimide polymers to prepare novel polymers of even higher
thermal stability. In that patent, an extensive list of polymers with
2 o which such acid-content reduced glutarimides may be blended is given.
Among these polymers are listed ethylene-vinyl acetate polymers and
polyvinyl alcohol. Ethylene-vinyl alcohol polymers have not been
disclosed for this use, and there is no suggestion in the prior art that
the permeability behavior of such blends would differ in any way from
2 5 an expected average performance, nor that the resulting blend would
be particularly useful in barrier packaging applications. There is
3
~t3~!~~~4
further no suggestion that blends of a second polymer with the acid-
reduced polyglutarimides could be admixed with the polymers
containing vinyl alcohol mers to obtain the barrier properties of the
present invention.
Blends of ethylene-vinyl alcohol polymers with vinyl alcohol
contents greater than about 50 mol percent have been noted in the
patent literature as components of blends with certain matrix
polymers, such blends having attractive barrier properties. Particularly
noted as matrices are polyvinyl chloride) in U.S. Patent No. 4,003,963,
1 o polyethylene terephthalate) in US Patent No. 4,284,671, and
polypropylene in U.S. Patent No. 4,362,844. These patents do not
suggest the use of ethylene-vinyl alcohol copolymers with acrylic or
glutarimide polymers for such purposes, nor do they disclose
unexpected improvement in barrier properties at low levels of the
ethylene-vinyl alcohol copolymer in the blend.
Particularly noted is the intensive study of polyamide blends
with ethylene-vinyl alcohol resins. U.S. Patent No. 4,427,825 teaches
such blends, wherein there are regions of the ethylene-vinyl alcohol
copolymer having an average diameter of less than 50. nanometers in
2 o the polyamide. These compositions, as do those of the blends noted in
the previous paragraph, exhibit a linear relationship for permeability
behavior which is expected for such blends and which is demonstrated
by a straight-line plot when the permeability is plotted as the ordinate
on semi-logarithmic paper with ethylene-vinyl alcohol content as the
2 5 abscissa.
4
~~~.'~~~ :~
One known exception to this additive relationship of the linear
logarithm of permeability is the disclosure in U.S. Patent No. 4,410,452
of blends of a polyolefin matrix and a modified or dispersed nylon
polymer, in which the nylon is processed to form laminar domains in
the matrix. Such blends exhibit barrier properties against hydrocarbon
liquids and gases substantially improved over that predicted for a
homogeneous blend. Processes are also taught for the incorporation
into the polyolefin matrix of dispersed similar platelets of other
polymers, such as polycarbonate and poly(butylene terephthalate).
'This patent does not teach or suggest the utility of ethylene-vinyl
alrnhol to form laminar structures in poly(glutarimides); indeed, it
requires a solvent or a dispersant polymer to obtain the laminar
structures, whereas the present invention aehieves the desired
structure by a conventional thermal/ mechanical history of mixing.
This patent also does not teach or suggest that the combination of
ethylene-vinyl alcohol or polyvinyl alcohol) polymers within a
polyglutarimide matrix will produce unexpectedly good resistance to
the passage of gases. Further, the platelet or laminar morphology
shown by this patent does not necessarily correspond with the
2 o morphology of the present blends; in some exatriples of improved
barrier propeaies exemplified herein, the vinyl alcohol (co)polymer is
finely dispersed in very small particles uniformly throughout the
glutarimide matrix, and in others, the vinyl alcohol (co)polymer blend
with the glutarimide or poly(lower alkyl) methacrylate matrix polymer
shows optical clarity, a single glass-transition temperature, and/or
other indicators of blend compatibility. Certain blends at relatively
high levels of certain ethylene-vinyl alcohol copolymers do produce a
laminar struchue with excellent barrier performance.
5
~0~'~~~~
European Patent Application No. 273,897 discloses blends of
polyethylene terephthalate with styrene-malefic anhydride as
blow-molded containers having an oriented crystalline continuous
phase of polyethylene terephthalate containing dispersed ovoid
particles of the styrene copolymer, the ovoids having a diameter of 0.1
to 0.8 N.m and a length of 0.3 to 2 Eun. The microstructure is reported to
impart physical properties suitable for containment or protection
against permeation of gases or organic fuels.
A publication in Research Disclosure, October, 1988, page 726,
discusses the barrier properties of blends of polyethylene naphthalene
carboxylate) with relatively low levels of ethylene-vinyl alcohol
copolymers. This publication states that the actual values for oxygen
permeability in such blends are four to five times lower than predicted
from calculations of the effective permeability of the ethylene-vinyl
alcohol rnpolymer from PET data. These data, while not calculated
against a pure ethylene-vinyl alcohol polymer standard and thus not
directly comparable with the data of the present invention, do show an
unexpected improvement in a manner also demonstrated herein. The
composite materials of the reference are opaque; the domains which
2 o are necessary to lower the oxygen permeability must be large enough to
eliminate the clarify of the blends and thus destroy one of the
particularly useful properties of the matrix polymers.
It is thus an object of the present invention to prepare a blend of
polymers having outstanding barrier properties to oxygen, carbon
2 5 dioxide and moisture from one or more polymers having certain
desirable physical properties but inadequate gas barrier properties of
6
0~0~~5~,'4
their own, and a polymer with vinyl alcohol mers which has excellent
barrier properties. .Another object is to prepare such a barrier blend
structure further having excellent optical properties, resistance to
impact, a service temperature sufficient for hot-fill and sterilization,
and/or other desirable physical properties. Further objects and
advantages will be apparent from the following description of the
present invention.
We have discovered polymer blends comprising from about 20
to about 95% by weight of a first polymer containing at least 50 mole
percent mers of one or more of lower alkyl (meth)acrylates and
glutarimides and forming a continuous phase, from about 2.5% to
about 40~ by weight of a second polymer having at least 50 mole
percent vinyl alcohol mers which is either miscible with, or forms a
discontinuous phase in, the continuous phase, and up to about 75% by
weight of one or more additional thermoplastic polymers compatible
with the continuous phase. These blends have good barrier properties
to gases, and other useful physical and optical properties. We have
further discovered a process for improving the gas-barrier properties of
2 0 polymers containing at least 50 mole percent mers of lower alkyl
(meth)acrylate, glutarimide or a mixture of the two, which polymers
may have only moderate gas barrier properties themselves, which
comprises blending these polymers with tlhe second polymer having at
least 50 mol percent vinyl alcohol mers. The polymer blends may be
2 5 formed into a film, sheet, molded article, container or packaging
material.
7
~QO~ ~?~
The teen "mar" as used herein means a combination of
elements which, when polymerized by addition polymerization, forms
a single repeating unit in a polymer. Thus the monomer ethylene
(CH2=CHI becomes the mar ethylene (-CH2-CH2-) in polyethylene,
even though the ethyleruc double bond is no longer present in the
polymer. The mar may be hypothetical, as in a vinyl alcohol mar
present in hydrolyzed polyvinyl acetate). More than one mar is
present in a copolymer. Mars may be formed by post-reaction on a
polymer, such as in a N-methyl dimethylglutarimide mar formed by
the addition of methylamine to two neighboring mars of methyl
methacrylate accompanied by the loss of two molecules of methanol.
The term (meth)acrylate, as used herein refers to an acrylate
ester, a methacrylate ester, a mixture of the two, or mars of an acrylate
ester, a methacrylate ester or a mixture of the two. Similarly,
(meth)acrylamide refers to acrylamide, methacrylamide, a mixture of
the two, or mars of acrylamide, methacrylamide or a mixture of the
two.
In the present specification, the term "glutarimide" or
2 0 "glutarimide polymer" refers broadly to polymers containing the cyclic
group or mar of formula I,
8
2~~~~~4
R2
~cH~ C/'
c~I2 ~ I
o~co c~o
R
(I)
where R1 and R2 may be H or lower alkyl, preferably both R1 and R2
being methyl, and R3 is hydrogen, alkyl, aryl, alkaryl, or aralkyl. The
term "lower alkyl", as used herein, means alkyl groups having from
one to six carbon atoms, such as methyl, ethyl, n- propyl, sec-propyl,
n-butyl, isobutyl, pentyl, hexyl, cyclohexyl and the like. Substituents
may be present on the R3 groups, such as hydroxy, halogen, such as
chlorine or fluorine, and the like. Preferably, R3 is lower alkyl of from
one to four carbon atoms, and more preferably methyl. The
glutarimide group may be the sole repeating unit or mer in the
polymer, or the polymer may contain other mers, preferably those of
an alkyl (meth)acrylate, and more preferably methyl methacrylate.
Other mers, such as those from styrene, a-methyl'styrene, vinyl
chloride, (meth)acrylic acid, (meth)acryli~ anhydride,
(meth)acrylamides, such as (meth)acrylamide, N-methyl
(meth)acrylamide, N,N-dimethyl (meth)acrylamide, and the like, other
(meth)acrylic esters, (meth)acrylonitrile, N-substituted maleimides
where the substituted group is R3, and the like may also be present.
While the glutarimide polymer may contain smaller proportions of
glutarimide mers and still be within the invention as contemplated, a
preferred glutarimide polymer contains at least about 50% mers of
9
~~'~5~~
glutarimide, and a more preferred glutarimide polymer contains at
least about 80% mers of glutarimide.
The glutarimide polymer may be prepared by any of the methods
known to those skilled in the art, such as by the reaction at elevated
temperature of (meth)acrylic ester polymers or (meth)acrylic
acid-(meth)acrylic ester copolymers with ammonia, an amine, urea, or
a substituted urea, by reaction of poly((meth)acrylic anhydride) with
ammonia or an amine, by thermal reaction of a (meth)acrylic
ester-(meth)acrylamide copolymer to form the imide ring, or by
l0 reaction in solution or in the melt of a polymer containing a high
proportion of (meth)acrylic ester groups with ammonia or an amine.
Preferred glutarimides are prepared by the method taught in U.S.
Patent No. 4,246,374, in which a (meth)acrylic-ester-containing polymer
is reacted with an amine at elevated temperatures in a devolatilizing
15 extruder. The glutarimide polymer may be of weight-average
molecular weight from about 10,000 to about 10,000,000. A preferred
molecular-weight range for retention of properties and ease of
processing is from about 50,000 to about 200,000.
Polymers containing mers of formula I which have limited
2 0 thermal stability resulting from the presence of relatively large
amounts of acid, anhydride or other de-stabilizing components may be
used in the present invention, but they will be less desirable because of
deficiencies in processing and use.
The poly(glutarimide) may be further post-treated to reduce or
2 5 remove acid and/or anhydride groups by treating it with reagents that
' ~:Q~'Of'~~~~
eliminate such groups, such as, for example, dimethyl carbonate; these
reduced-acid polymers are preferred, but polyglutarimides containing
acids and/or anhydrides are also useful in the present invention.
Also useful in the present invention as the first polymer are
polymers containing at least about 50 mole percent of mers of a lower
alkyl (meth)acrylate, preferably methyl methacrylate, but including
mers such as methyl acrylate, ethyl acrylate or methacrylate, butyl
acaylate or methacrylate, hexyl methacrylate or methacrylate,
cyrlohexyl acrylate or methacrylate, and the like. The first polymer
may also include mers of such monomers as substituted alkyl acrylates
and methacrylates, such as [3-hydroxyethyl methacrylate,
~-hydroxypropyl acrylate, and the like, vinyl heterocyclic monomers,
such as 4-vinylpyridine, 2-vinylpyridine, N-vinylpyrrolidone,
N-vinylimidazole, 2-vinylthiophene and the like, unsaturated
carboxylic acids, such as methacrylic and, acrylic acid, acryloxypropioruc
acid, and the like, vinyl aromatic.monomers, such as
a-methylstyrene, styrene, p-hydroxystyrene, and the like, malefic
anhydride, maleimide, N-alkyl maleimides, N-aryl maleimides, vinyl
acetate, acrylonitrile, and other vinyl, vinylidene or malefic monomers.
2 0 Preferred are polymers with at least 80 mol % (meth)acrylate mers.
Especially preferred are polymers containing at least 90%
(meth)acrylate mers. As used herein with respect to mers, the terms "a
preponderance" and "predominantly" are used to mean a mol
percentage greater than 50%.
11
~~~~~~.;~~
The lower alkyl (meth)acrylate polymer useful for preparing the
glutarimide, for incorporating (meth)acrylate mers into the
glutarimide-containing polymer, and as the first polymer containing at
least al»ut 50 mole percent of lower alkyl (meth)acrylate mers, may be
prepared, using various ionic or free-radical methods, to a
weight-average molecular weight from about 10,000 to about
10,000,000. A preferred range for retention of properties and ease of
processing is from about 50,000 to about 200,000. A preferred process
for manufacture uses a continuous-flow, stirred-tank reactor, but other
l0 polymerization processes which will be readily apparent to those
skilled in the art, including suspension, bulk, or emulsion may be
employed. The polymer may contain stabilizers, such as against
ultraviolet light or heat degradation, and other additives such as
processing aids, dyes and the like which are well known to those
skilled in the art.
.Another preferred embodiment of the first polymer is a copolymer of
methyl methacrylate with up to about 30 mole percent, and more
preferably from about 20 to about 30 mole percent, of one or more of
styrene, a-methylstyrene, p-hydroxystyrene,. (meth)acrylic acid,
2 0 (meth)acrylic anhydride, (meth)acrylamide, malefic anhydride,
maleimide, cyclohexyl (meth)acrylate, N-alkylmaleimides,
N-arylmaleimides, 4-vinylpyridine, or N-vinylpyrrolidone.
A polymer containing at least 60% of mers of the glutarimide of
formula I where Rl = R2 = R3 = methyl is one preferred embodiment of
2 5 the first polymer. Such a polymer, either acid-reduced or non-acid
12
~0.'~5~~~
reduced, will exhibit a Vicat softening temperature greater than about
140°C.
The second polymer containing at least about 50 mole percent
vinyl alcohol mars is preferably a polyvinyl alcohol), an ethylene-
vinyl alcohol copolymer, or a copolymer of vinyl alcohol mars with
long-chain alkenoxy methacrylate mars. The polyvinyl alcohols) may
be made by hydrolysis of polyvinyl acetate), and can be obtained
commereially with varying degrees of hydrolysis. The resulting
polymers are copolymers containing mars of vinyl alcohol and vinyl
Z o acetate. The preferred polyvinyl alcohols) contain at least about 80
mole percent mars of vinyl alcohol. The preferred alkenoxy
methacrylate mars are those which terminate in hydrogen, Cl-Czo
alkyl, C6 aryl orC~-CC3o alkaryl groups.
Because polymers of vinyl acetate which have been extensively
or completely hydrolyzed to polyvinyl alcohol) are quite sensitive to
water and exhibit barrier properties influenced by the equilibrium
moisture content, it is preferred in the present invention, as it is
generally in the known art of barrier resins, to utilize copolymers
wherein the vinyl alcohol group is present along with some less
2 o hydrophilic mars. Such mars may be (meth)acrylic esters, olefins, and
the like, and mars of styrene and substituted styrenes grafted to the
polymer. Preferred because of ease of synthesis and control of the
extent of vinyl alcohol mars are hydrolyzed copolymers of ethylene.
The ethylene-vinyl alcohol rnpolymers may be made by hydrolysis of
2 5 an ethylene-vinyl acetate copolymer, or can be obtained commercially.
They contain from about 15 to about 50 mole percent ethylene mars,
13
~~'~~~4
and more preferably from about 25 to about 50 mole percent ethylene
mars, at least about 50 mole percent vinyl alcohol mars, and may
contain additional vinyl mars, as for example residual vinyl acetate
mars.
The second polymer may be present at amounts up to about 40%
by weight of the blend, more preferably from about 5% to about 40% by
weight, and still more preferably from about 5% to about 35% by
weight. At levels below about 5% the enhanced barrier properties are
difficult to discern, and above about 40% the undesirable physical
1 o properties of the vinyl alcohol polymer may degrade the physical
properties of the blend.
The blend of glutarimide or (meth)acrylate first polymer and
second polymer containing at least 50 mole percent vinyl alcohol mars
may further contain one or more other thermoplastic polymers with
15 which the first polymer is known to be compatible, to form a multi-
polymer blend. The other thermoplastic polymers include polymers
such as butadiene/styrene/(meth)acrylic, styrene/(meth)acrylic, and
(meth)acrylie multistage polymers (as used herein ' =" indicates blended
polymers, "/" statistical or random rnpolymers, and "/ /" graft or block
2o polymers); butadiene/styrene rubbers, ethylene/propylene/diene
rubbers, polyamides, polyamide-multistage polymer blends (as used
herein the mufti-stage polymer may be a rubber grafted with a
compatibilizing polymer and useful, for example, for imparting
improved impact resistance to polymers), ethylene/vinyl acetate,
2 5 styrene / acrylonitrile, styrene/ acrylonitrile-multistage polymer blends,
styrene/acrylonitrile-ethylene/propylene/diene rubber blends, oc-
14
~U~~J'~~.~~
methylstyrene/acrylonitrile, a-methylstyrene/styrene/acrylonitrile, a-
methylstyrene/methyl methacrylate/ethyl acrylate,
butadiene//acrylonitrile/styrene, polycarbonate, polycarbonate-
multistage polymer blends, polybutylene terephthalate, polybutylene
terephthalate-polycarbonate blends, polybutylene terephthalate-
multistage polymer blends, polybutylene
terephthalate/polytetrahydrofuran, polyvinyl chloride, polyvinyl
chloride-multistage polymer blends, polyvinyl chloride-(meth)acrylate
blends, chlorinated polyvinyl chloride,
to acrylonitrile/(meth)acrylate/sfyrene, epichlorohydrin/bisphenol-A,
polyethylene terephthalate or other polyalkylene terephthalate,
polyethylene terephthalate-glycol modified, polyethylene terephthalate-
acid modified, polyethylene terephthalate-polycarbonate blends,
polycaprolactone, polyarylate, copolyester of bisphenol-A with
15 isophthalic and/or terephthalic acids, poly(meth)acrylates, polyacetal,
polystyrene, polyp-hydroxystyrene), high-impact polystyrene,
styrene/maleic anhydride, styrene/maleimide, polyolefins,
polyvinylidene fluoride, polyvinylidene fluoride-multistage polymer
blends, cellulosics, polyethylene oxide, polyamideimide,
2 o polyetherester, polyetheresteramide and polyetheramide. The amount
of blended other polymers may be up to about 75% by weight of the
total m~lti-polymer blend; above that level the improved barrier
properties may be seriously degraded, and below about 5% little effect is
seen. A preferred range for the blended other polymers is from about 5
2 5 to about 50% by weight, and more preferred is from about 5 to about
30% by weight of the total mufti-polymer blend. The blended other
polymers may have moderately good barrier properties, such as
polyethylene terephthalate) or polyp-hydroxystyrene), or may be
~00'~~~~''."4
relatively poor in barrier properties, such as polyearbonate. The
blended other polymers may chemically combine with the first
polymer, as occurs under certain melt conditions with polymers of
caprolactam and poly(N-methyl)dimethylglutarimide containing
residual acid and anhydride groups.
In most cases the blended other polymers may exhibit good, but
not unexpectedly good, barrier performance when blended only with
the second polymer containing at least about 50 mole percent vinyl
alcohol mers. At levels of the blended other polymers above 75%, the
blend may lose the beneficial effects on barrier properties contributed
by the binary blend of acrylic or glutarimide polymer with the polymer
having vinyl alcohol mers, while below about 5%, the blended other
polymers contribute little useful in non-barrier, physical properties,
such as toughness, reinforcement, and the like.
Thus, mufti-polymer blends of the present invention preferably
contain from about 20 to about 95% by weight of (A) the first polymer
containing at least about 50 mole percent of mers of one or both of
lower alkyl (meth)acrylate and N(lower-alkyl)glutarimide and forming
a continuous phase, from about 2.5 to about 40% by weight of (B) the
2 0 second polymer containing at least about 50 mole percent of vinyl
alcohol mers and miscible with, or forming a discontinuous phase in,
the continuous phase, and up to about 75% by weight of (C) the
blended other polymers. A mare preferred blend is from about 30 to
about 95% of (A), from about 5 to about 40% of (B), and up to about
2 5 30% of (C), and a still more preferred blend is from about 40 to about
16
~Q~'~;;~~
70% by weight of (A), from about 10 to about 20% by weight of (B), and
from about 20 to about 30% by weight of (C).
Preferred mufti-polymer blends are those containing the
following polymers as components (A), (B) and (C): (A) poly(methyl
methacrylate) (PMMA~(B) ethylene/vinyl alcohol-(C)
polyp-hydroxystyrene); (A) copolymer(80% methyl methacrylate/20%
cyclohexyl methacrylate~(B) ethylene/vinyl alcohol-(C)
polycarbonate; (A) poly(N-methyldimethylglutarimide-(B)
ethylene/vinyl alcohol-(C) poly(caprolactam); and (A)
poly(N-methyldimethylglutarimide--(B) ethylene/vinyl alcohol-(C)
polyethylene terephthalate).
The poly(glutarimide) or poly(meth)acrylate may contain
additives, such as lubricants, ultraviolet stabilizers, antioxidants,
thermal stabilizers, and the like. It may also contain low levels of
inorganic fillers and/or fibers, such as mica, glass fibers, and the like.
The blend may be stabilized against interaction, e.g.
transesterification and the like, between the alcohol groups of the
polyvinyl alcohol) polymer and the amide or ester groups of the
glutarimide polymer; such stabilizers may be present in amounts from
2 o about 0.196 to about 2%. Preferred as stabilizers are phosphate or
phosphinate esters, such as tris(nonylphenyl) phosphate at levels from
about 0.1 to about 0.25 parts per 100 parts of total polymer.
17
~~~~~J~~
Other polymeric additives such as processing aids, fillers,
lubricants, flame retardants, dyes, impact modifiers, surface altering
agents, and the like may be present in the glutarimide or
(meth)acrylate polymer blend. Such impact modifiers may include
core/shell modifiers, such as those commonly called MBS modifiers,
acrylate rubber/ /rnethacrylate outer stage, acrylate
rubber//styrene/acrylorutrile outer stage, and the like.
An especially useful blend of the present invention containing
1 o the impact modifiers is a blend of the first polymer, the second
polymer, and impact-modified polyvinyl chloride); this blend is
tough, and exhibits barrier properties improved over the
impact-modified PVC blend and a service temperature suffieient for
hot-fill applications.
Because the glutarimide polymers are relatively resistant to gas
permeation, addition of other polymers, either as blends into the
matrix or as impact modifiers, may lower the resistance to oxygen and
moisture, and more of the other polymer containing vinyl alcohol
mers may be required to achieve the desired balance of barrier and
2 0 other properties.
Without wishing to be bound by theory, in the binary blends the
polymer containing vinyl alcohol mers may be dispersed in relatively
fine particles, in laminar form, or even in such a fine dispersion that
the blend acts like a compatible mixture, i.e., it exhibits a single
2 5 glass-transition temperature. In many of the examples below, the
dispersion of the ethylene/vinyl alcohol copolymer in the glutarimide
18
~0~!~SM4
eontinuous phase results in a fine and relatively uniform dispersion of
the polymer with vinyl alcohol mers, with particle size averaging
below 50-100 nm, which is difficult to distinguish from a miscible
blend. 'There is little or no laminar structure noted. In other examples,
ethylene/vinyl alcohol polymer of higher ethylene content (44%
versus 32%) produces a laminar structure in the glutarimide
continuous phase; the barrier properties are comparable to those of the
non-laminar blend. Thus, no specific morphology of the polymer
causes the improvement in barrier properties, except that the polymer
l0 containing vinyl alcohol mers cannot be the continuous phase; when
it is, the physical properties of the resulting blend are degraded, and the
gas-barrier properties become sensitive to the presence of maisture.
Some end uses require good clarity. This can be obtained by
methods known in the art, i.e., by matching the refractive index of the
matrix polymer or matrix polymers to that of the vinyl alcohol
copolymer. This match must occur within the limits set forth herein
for component-polymer levels, nature of the continuous phase, and
compatibility of the polymers comprising the matrix blend. In other
cases, particularly with mufti-component blends~containing reactive
2 0 other polymers such as polyamides (nylons), clarity is observed where
one skilled in the art would expect hazy or translucent blends.
Many of the blends of the first polymer containing mers of
(meth)acrylate or glutarimide with the second polymer containing at
least 50 mol percent vinyl alrnhol mers exhibit surprisingly good gas-
2 5 barrier properties when compared with the barrier properties of the
first polymer alone, or when compared with the expected
19
CA 02004524 1999-12-23
improvement in barrier properties that should result from
incorporating a relatively small amount of the polymer containing the
vinyl alcohol mars. The improvement in gas-barrier properties of the
first polymer is not a linear function of the amount of the second,
vinyl-alcohol-containing polymer added, but instead increases sharply
with the addition of only a small amount of second polymer, and
shows little additional improvement at levels of second polymer
beyond 40°~ by weight. As little as 10% by weight, and preferably from
about IO to about 40% by weight, of second polymer blended with the
first polymer may produce a blend having oxygen permeability reduced
by approximately an order of magnitude or more when compared to
those of the first polymer alone.
For example, which is not to be considered limiting, the polymer blends are
characterized in that the permeability to oxygen of the blend is 10% or less
of the
permeability of the first polymer alone, preferably the permeability of oxygen
to
the blend is 1 % or less. More preferably, the permeability to oxygen of the
blend
is 0.1 % or less of the permeability of the first polymer alone.
In the data reported herein, the theoretical or calculated
permeability is based on what is essentially an averaging effect. This is
the expected behavior for compatible or well-dispersed mixtures, and is
2 0 represented by a straight-line plot of the natural logarithm of
permeability versus concentration of the blend components. Where
the dispersion is poor, another response to varying the concentration
of the polymer having better barrier properties may occur: the S-shaped
curve. In this case the barrier properties remain essentially those of the
poorer barrier continuous phase as the concentration of the second
phase is increased, until a concentration of the second phase is reached
where phase inversion occurs, and the second phase undergoes a
transition to the continuous phase as the poorer barrier polymer
becomes the discontinuous phase. Through that transition, the barrier
properties rapidly improve until they are essentially those of the
second polymer, which has now become the continuous phase.
2U~'~~~;.~
Although the specific polymer combinations of the present invention
exhibit essentially an S-shaped curve as the blend composition is
varied, the marked improvement in barner properties occurs in the
absence of phase inversion, and at an unexpectedly low level of the
second (good) barrier component.
Blending conditions are not thought to be critical, so long as
temperatures which eause significant loss of hydroxyl functionality
from the vinyl alcahol mers, through either infra- or intermolecular
reactions, are avoided. A reasonable range of processing temperatures
is from about 200°C to about 260°C; below this range the mixture
is
highly viscous and thus difficult to process, while above this range the
polymer tends to thermally degrade at an excessive rate, and
discoloration or bubbles may occur in the polymer if it is held at
temperatures above this range for extended periods. A temperature
range of from about 230° to about 240°C is preferred for the
polyglutarimides.
The polymers may be admixed and blended in a number of ways
known to the polymer processing art. The polymers, along with any
desired adjuvants and/or other polymers to be combined, may be
2 0 mixed on a heated mill roll or other compounding equipment, and the
mixture cooled, granulated and extruded into film. The polymers may
be admixed in extruders, such as single-screw or double-screw
extruders, compounded and extruded into pellets which may be then
re-fabricated. The extruder may also be used to extrude the blend as
2 5 pipe, sheet, film, or profile. Pelletized or granulated polymer may be
injection or compression molded into sheet, film, or shaped articles.
21
2~~~ ;~4
Thorough mixing and dispersion of the additive polymer is
important, but otherwise processing conditions are similar to those of
the unmodified matrix polymer and may be readily determined by
appropriate experimentation and adjustment of processing conditions
by one familiar with processing of the unmodified polymers.
Films or sheets may be uniaxially or biaxially oriented either
during extrusion or after such processing, by reheating and stretching.
The polymer granules may be injection molded or extruded into
appropriate parisons which are then treated by conventional molding
1 o and blowing techniques into bottles or other containers, which
containers may be stretch oriented uruaxially or biaxially, or may be left
unoriented. It is known in the art for such containers to have closures
that allow them to be sealed or capped.
Film or sheet may be treated with additives after forming, such
as appropriate heat-seal adhesives, coatings for ink adhesions, printing,
labels, and the like.
Films or sheets of the blends of the present invention may be
utilized in co-laminar structures, such as multilayered films,
co-extrusion into bottles, and the like. In such operations, the blends
2 o have excellent adhesion to a variety of substrates, and separate
adhesive layers, or "tie layers", are generally not required, although
they may be used. The other polymer of the co-laminate may have
specialized barrier properties, such as poly(vinylidene chloride)
22
~oo~~~~
imparts. Preferred is a co-laminate which is tough or inexpensive, such
as nylon, impact-modified nylon, polyvinyl chloride), polycarbonate,
polyethylene terephthalate), or a polyolefin such as polypropylene.
Such co-laminar structure may involve more than one species of
co-laminate and may also involve more than one layer of the blend
polymer. The total number of layers is limited only by the capability of
the equipment used to produce the mufti-layer film or sheet.
The films or sheets, as either monolithic or composite
structures, and including articles formed from the films or sheets, may
be biaxially oriented, uniaxially oriented or unoriented.
The uses to which the gas-barrier polymers of the present
invention may be put are many. Films or wrappings may be used in
the packaging of many foodstuffs, such as meat, snacks, boil-in-the-bag
items such as frozen vegetables, and the like. Containers suitable for
the packaging of carbonated or oxygen-sensitive beverages, such as
colas, ginger ale, fruit juice, and the like, may be prepared. Containers
suitable for hot-fill or sterilization may be molded from suitable
injection-molded or extruded parisons.
Such rnntainers or bottles may be used for packaging of
2 0 condiments, ketchup, maple syrup, and the like. They may also be
used for heat-sterilized containers, such as for intravenously
administered fluids, serum vials, medical specimen vials and the like,
and to package oxygen-sensitive chemicals.
23
~~!~5~~
Other uses for transparent barrier compositions include
protecting fragile artifacts, such as books and archaeological specimens,
from oxidation while permitting them to be viewed readily. They may
provide protective coatings for easily oxidized metals or oxygen-
sensitive conductive polymers, as for example in solar-energy
collection devices. They may also be used in devices where a specific
concentration of gases must be maintained, such as so-called high-
temperature metal oxide superconductors, which must be maintained
in an oxidizing atmosphere, and controlled-atmosphere chambers used
for handling sensitive chemical and biological materials, i.e. "dry
boxes" and the like.
The following examples are intended to illustrate the present
invention and not to limit it except as it is limited by the claims. All
percentages are by weight unless otherwise specified and all reagents
are of good commercial quality unless otherwise specified.
The resins used in the following examples are described below:
Polyglutarimide as used in the following examples refers to
polymers made by reacting poly(alkyl rnethacrylate) homo- or
copolymers with amines or ammonia at elevated temperatures in a
2 o devolatilizing extruder. Poly(N-methylglutarimide) (PMG) refers to a
commercial polymer made from poly(methyl methacrylate) and
methyl amine. Acid-content-reduced poly(N-methylglutarimide) refers
to a similar polymer further reacted with agents that eliminate acid
and/or anhydride groups, as for example dimethyl carbonate, as taught
24
200~r~~~
in U.S. Patent No. 4,727,117. In both cases, the Vicat softening
temperature was related to the degree of imidization.
Poly(methyl methacrylate) (PMMA) in these examples refers to
polymers with a preponderance of methyl methacrylate mers, and
particularly those with greater than 85% methyl methacrylate mers,
with the other mers being lower alkyl esters of acrylic or methacrylic
acid. PMMA homopolymer refers to a polymer with mers at least
about 99% methyl methacrylate. Such polymers are made by
free-radical polymerization in a continuous stirred tank reactor to a
1 o range of from about 30 to about 65% conversion at temperatures from
about 120° to about 200°C, usually contain a mercaptan chain
transfer
agent, are separated from residual monomer in a devolatilizing
extruder, extruded through a die and the extruded strands cut into
pellets. Such polymers are the starting materials for the imidization
15 reactions with ammonia or lower alkyl amines. It should be noted that
the process for preparing the PMMA is not restricted to the continuous
process described aboWe; well-known methods such as bulk casting,
suspension polymerization, and emulsion polymerization may also be
used. In the mufti-polymer blends, the polycarbor<ate was a
2 o commercial bis-phenol A polycarbonate obtained from Mobay
Chemical Company, having a melt flow rate of 550 grams/10
minutes at 300°C, measured according to ASTM Method D 1238. The
polyp-hydroxystyrene), of 32,000 weight-average molecular weight,
was purchased from Hoechst-Celanese, and was reported to have a
25 barrier value against oxygen of 7.88 cm3~mm/(m2~atm~day).
2Q~!~5~~
The polyethylene-vinyl alcohol) copolymers and the polyvinyl
alcohol) polymers were commercially available; both are believed to be
prepared by the hydrolysis or saponification of the corresponding vinyl
acetate co- or homopolymers. For the copolymers used, the molar
percentage of ethylene in the copolymer and the melt index, as a
correlation with weight-average molecular weight, are given in Table I,
below.
26
CA 02004524 1999-12-23
Table I
Vinyl Alcohol Homo- and Copolymers
Desig- Polymer Type Mol% Melt M W
nation Ethylene Index
CoP-1 Ethylene-vinyl alcohol 32 I.3 -
CoP-2 Ethylene-vinyl alcohol 44 5.5 -
CoP-3 Ethylene-vinyl alcohol 27 - -
CoP-4 Ethylene-vinyl alcohol 38 3.5 -
HP-1 Polyvinyl alcohol) - . - 14000
HP-2 Polyvinyl alcohol) - - 85000
HP-3 Polyvinyl alcohol) - - 115000
HP-4 Polyvinyl alcohol)
Melt index was in grams/10 minutes, measured at 190°C for CoP-1
and CoP-2 and 2I0°C for CoP-4.
The commercial designations are: CoP-I: Eval F-lOlATM; CoP-2 =
Eval E lOSATM; CoP-3 = Eval LTM (all supplied by Evalco); CoP4 - SoarnolTM
ET, supplied by Nichimen America, Inc. New York, NY (U. S. agents
for Nippon Gohsei of Japan); HP-I, HP-2, and HP-3 supplied by
Polysciences Inc. Warrington, PA 18976; HP-4 = Hitech Polyvinyl
alcohol containing an unspecsfied plasticizer, made according to U. S.
27
' ~t~~~'~;~~~
Patent No. 4,536,532 , and supplied by Hitech Polymers, Inc., P. O. hox
30041, Cincinnati, OH 45230.
Blending of polymers: Polymer blends were prepared by
tumble-blending pellets, usually with addition of a small amount of
thermal stabilizer (0.25 wt. % tris(nonylphenyl phosphite) based on
total resin content). The pellets were fed to a twin-screw,
counter-rotating, intermeshing extruder, length 870 mm, equipped
with a vacuum vent, a single-hole strand die of approximately 6 mm.
diameter, a water bath for cooling the extruded strand, and a strand
l0 pelletizer. The feed zone was set at 230°C, and the barrel and die
zones
at 235°C. The melt temperature was between 226° and
238°C; a screw
speed of 100 rpm was employed.
Alternatively, for smaller samples, blends were prepared from
blends of polymer powders and granulated pellets or bulk castings.
fey were milled on a two-roll electric mill for three minutes at
205-215°C, then removed from the mill rolls, cooled, granulated and
compression molded using a Carver press. The samples were molded
at 138 megapascals (MPa) and 215°C into 127-mm-square plaques 0.13
mm thick.
2 0 Preparation of films: A single-screw extruder, 25.4 mm in
diameter, 24/1 length/diameter ratio was equipped with a two-stage
vacuum vent, a 152.4 mm "coat-hanger" adjustable-thickness film die,
a three-roll, heated film stack immediately adjacent to the die lips for
receiving the film on extrusion, and a film puller and film wind-up
28
~~0~.'~5~4
apparatus. The puller speed was set to avoid any drawdown of the
film. The extruder was operated at 75 rpm; melt temperatures were
usually 232° to 237°C, but may be adjusted depending on
recommendations from the resin supplier to achieve acceptable
extrusion rates. The roll temperatures of the stack were: top and
middle: 132°C, bottom 100°C. Film of thickness 76 to 635 Etm
were
prepared by this method.
Injection Molding: Blended pellets were molded in an injection-
molding apparatus equipped with a. heated, ASTM family mold.
l0 ~j~on pressures were 5.17 to 7.58 megaPascals (MPA), with back
pressure of 0.69 MPa; the melt temperature was 232° to 260°C,
depending upon the viscosity of the polymer melt. The mold
temperature was 110°C.
Morphology: Polymeric blends were sectioned by microtoming at
room temperature to sections about 100 nm thick, and stained with
ruthenium tetroxide by the method of Trent et al., Macromolecules, 16,
589 (1983). Exposure to vapors from a 0.5% aqueous solution of Ru04
was about one hour at room temperature. Transmission electron
microscopy at a magnification of up to 25000X was carried out on a
2 0 Zeiss EM-10 instrument.
Oxygen permeability values: Permeabffity was tested on a Mocon
Ox-Tran 1000 unit, manufactured by Modern Controls, Minneapolis,
MN. Films of measured dimensions were mounted in the unit,
equilibrated with nitrogen to determine any leakage factor or edge
2 5 effect, and then exposed to pure oxygen test gas until the carrier gas on
29
~~~~:;~4
the opposite side of the film reached equilibrium. Oxygen was detected
by a nickel-cadmium fuel cell known as a Coulox Detector. The unit
was equipped to record the oxygen content which was calculated in
units of cm3~mi1/100 in2~atm~day; these units were converted to
cm3~mm/mZ~atm~day by multiplying by 0.3937. The resulting values
were compared with values measured or reported for the single
component (non-blend) film. Measurements were at 23°C and 0%
relative humidity unless otherwise noted.
EXAMPLE 1
1 o This example illustrates preparation of a blend of a .
poly(glutarimide) and an ethylene-vinyl alcohol copolymer. The
values for the ethylene-vinyl alcohol polymer were from the
manufacturer's literature, and were conducted on the dry polymer
molding or film unless otherwise noted. Film thickness was
approximately 0.178 mm. The properties of the resulting blend are
shown in Table II below.
i~~~~JM~
Table II
Properties of a Po~glutarimide-Ethylene-Vinyl Alcohol Blend
Pol~~xner or Blend
Glutarimide containing
Ph3~sical Fropertv Glutarimidel CoP-12 10 wt. percent CoP-1
Oz Perm., 0% RH 1.0 >0.002 0.055
~ Perm., 100% RH 1.0 3.7 0.16
Tensile Modulus, MPa 4595 3686 4134
Glass temperature, C 1703 65 169, 694
Visual clarity excellent poor . good
1 N-methylglutarimide, no acid reduction
treatment, Vicat 170C
2 see Table describing composition and MW
of ethylene-vinyl alcohol copolymers.
3 from Vicat penetration or softening temperature
4 two peaks, from differential scanning
calorimetry .
EXAMPLES 2 - 6
These examples illustrate the oxygen permeability of glutarimide
blends with 10 to 25 weight percent of several polymers containing
vinyl alcohol mers. Blends were prepared with the same glutarimide
matrix as in Example 1. Values were at 0% relative humidity. The
31
~(~~~~~~
oxygen
permeability
for the
blends
at the
specified
levels
of polymers
containing
the vinyl
alcohol
mers are
shown
in Table
III below.
Ta le III
C~xvgen Permeability 2f PolXglutarimide Blends
Example Vinyl Alcohol Level of Copolymer in Glutarimide
~Co)polymer of Example 1, wt. %
10% 15% 20% 25%
1 CoP-1, Ex. 4.92 0.057 - 0.083 -
2 CoP-4 - <0.31 - <0.002 -
3 HP-1 - 1.0 - <0.002 --
4 HP-2 - 0.91 - <0.002 --
HP-3 - 1.06 -- 0.71 --
6a HP-4, Lot 1 - 0.055 -- 0.083 --
6b HP-4, Lot 2 - 0.71 0.79 -- 0.13
1 In separate measurement, <0.005 was value.
EXAMPLE 7
This example illustrates rapid decrease of oxygen permeability at
increasing but still low levels of an ethylene-vinyl alcohol copolymer.
The polymers and processing were that of Example 1. The predicted
values were those read from a line drawn on semi-log paper between
32
r
2~D~~;~~~
the 0 and 100 CoP-1 levels. Film thiclcnesses were about 0.177 mm. The
observed and predicted values for oxygen permeability of the blends
are shown in Table IV below.
Table N
Oxygen Permeabili , of Pol3~,~glutarimide-Ethylene-Vimtl Alcohol Blends
% CoP-1 Predicted Found
Q --- L'L2
1 1.18 0.81
2.9 1.10 0.8$
6.5 0.97 0.81
9.1 0.88 0.34
11.1 0.82 0.24
12.6 0.78 0.13
15 0.71 0.078
100 --- 0.033
The onset of substantial lessening of oxygen permeability in the
present system was seen at about 9 wt. % of the CoP-1 additive, but
values below the theoretical were seen at lower concentrations in the
blend. Examination of the blends with above 9.1 % CoP-1 showed little
evidence of a laminar morphology fox the dispersed CoP-1 phase.
33
2~~!~5~,~
EXAMPLE ~
This example illustrates rapid decrease of oxygen permeability at
increasing but still low levels of a second ethylene-vinyl almhol
copolymer (CoP-3, containing 27 mol-% ethylene). The PMG was that
of Example 1. The predicted values were those read from a line drawn
on semi-log paper between the 0 and 100 CoP-3 levels. Film thiclcnesses -
were about 0.177 mm. The predicted and observed values for oxygen
permeability of the blends are shown in Table V below.
Table V
Oxygen Permeability of Polyp,;lutarimide-Ethylene-Vinyl Alcohol Blends
% CoP-3 Predicted Found
0 --- 1.22
3 1.15 1.32
6.5 0.79 1.15
9 0.69 0.67
11 0.61 0.17 *
0.45 0.07
17.5 0.38 0.026
0.32 0.086
23.6 0.25 0.0016
100 - 0.0016
* From a separate series of experiments.
34
' i~(~~~~ii~~
EXAMPLE 9
This example illustrates rapid decrease of oxygen permeability
at increasing but still low levels of a third ethylene-vinyl alcohol
copolymer (CoP-2, containing 44 mol-% ethylene). The PMG was that
of Example 1. The predicted values were those read from a line drawn
on semi-log paper between the 0 and 100 CoP-2 levels. Film thiclcnesses
were about 0.177 mm. The predicted and observed values for oxygen
permeability of the blends are shown in Table VI below.
Table VI
OxXgen Permeabilit;rof PQlvelutarimide-Ethylene-Vin3r1
Alcohol Blends
Oxyg en Permeability
% oP-2 Pre ict Found
0 ---- 1.22
6 0.96 1.24
9 0.84 0.70
12 0.74 0.58
13.4 0.70 0.43
14.3 0.68 0.54
0.66 O.IO
0.54 0.20
0.44 0.002
27.3 0.40 0.0015
0.29 0.18
0.24 0.24
100 ----- 0.001
. ~0~1'~;:~~~
Microscopic examination of the blend containing 20% of the
CoP-2 additive showed a laminar morphology for the dispersed CoP-I
phase.
EXAMPLES 10 - 26
These examples show the effect of relative humidity on blends of
a polyvinyl alcohol) homopolymer with various glutarimide
matrices. The polyvinyl alcohol) was that used in Example 1 (HP-4).
The polyglutarimides were imidized in a devolatilizing extruder to
degrees of imidization measured by the Vicat softening temperature of
the resulting resin. Portions of these polymers were then reduced in
acid content by treatment by the method of Hallden-Abberton et al.
The polymers used in the examples are shown in Table VII below.
Table VII
Pol3~ners Used in Relative Humidity Effects Study
ExamplePoly(glutarimide) Vicat softening
Aad-reduced?
____ Source ____ _______ temperature,
C
10 PMG (from Example N 170
1)
11 PMG N 150
12 PMG-T Y (Ex.10)160
13 PMG-T Y (Ex.11)145
36
~0~!~~~4
Blends of these polymers were then made as in previous
examples, with the polyvinyl alcohol) at 10 and 20% use levels, and
oxygen permeability measured at 0 and 100% relative humidifies on
films of similar thicknesses. The results of these measurements are
shown in Table VIII below.
Table VIII
Effects of R~lativg Humidit~r on Oxygen Permeabilit;~r of Blends
Source of Wt. % Relative Oxygen
Example Glutarimide PVOH(HP-4) Humidi Permeability
1 Ex.lO -- 0 0.98
1 Ex.lO - 100 0.98
14 Ex.10 10 0 0.71
I5 Ex.10 10 100 1.3
16 Ex.11 - 0 1.2
17 Ex.11 IO 0 1.2
18 Ex.11 10 100 1.5
19 Ex. l1 20 n 1.1
20 Ex.12 10 0 1.2
21 Ex.12 10 100 1.9
22 Ex. l2 20 0 0.002
23 Ex. l3 - 0 2.2
24 Ex.13 10 0 1.5
25 Ex. l3 10 100 2.2
26 Ex. l3 20 0 0.94
37
~(l'~!~~~4
These data show that a) high relative humidity is deleterious to
permeability behavior, even at the relatively low levels of polyvinyl
alcohol) homopolymer employed, and b) IO% of polyvinyl alcohol) .
additive is not enough to produce a drastic decrease in the permeability
value.
EXAMPLES 27 - 36
These examples illustrate that substantial improvements in
barrier performance can be achieved by blending relatively low levels
of an ethylene-vinyl alcohol copolymer with an acid-reduced poly-
1 o N-methylglutarimide. The polyglutarimide was that of Example I2
except for one example where a polymer of lower imide content (Ex.
13) was used; the vinyl alcohol copolymer was CoP-I. The oxygen
permeability of the blends is shown in Table IX below.
38
~a'C1~5~4
Table IX
Oxygen Permeabilit<~of Blends of Acid-Reduced Pol~rglutarimide with Eth3rlene
Vin~l Alcohol Polymer
Source of Wt. % Relative Oxygen
Ex, Glutarimide CoP-1 Humidity Permeability
ample
27 Ex. l2 0 0 2.42
28 Ex. l2 3 0 3.40
29 Ex. l2 6 0 2.15
30 Ex. l2 9 0 0.721
31 Ex.12 10 0 1.2
32 Ex. l3 11.1 0 0.33
33 Ex.12 12 0 0.131
34 Ex. l2 15 0 0.0004
35 Ex. l2 20 0 0.0004
36 Ex. I2 25 . 0 0.079
* sample palletized poorly and film may not have been uniform.
EXAMPLE 37
This example illustrates that blends of non-imidized
poly(methyl methacrylate) will also exhibit unexpectedly good barrier
39
~d~~4»~
properties when blended with an ethylene-vinyl alcohol copolymer.
The polymer used is a poly(methyl methacrylate) homopolymer of
molecular weight ca. 150,000. The unmodified PMMA has an oxygen
permeability value of 3.9 cm3~mrn/m2~atm~day; the value for the blend
with 20% CoP-1 was 0.004. The blend had excellent contact clarity and
was only slightly hazy.
EXAMPLES 38 - 40
These examples illustrate that a glutarimide prepared from
ammonia does not exhibit the improvement in barrier properties at
low levels of blending with a ethylene-vinyl alcohol; copolymer. The
ammonia imide had a Vicat temperature of 205°C, was >90% imidized,
and about 48% percent of the irnide groups were N-methylimide
(during imidization with ammonia, monomethylamine is formed,
which then competes for the sites of imidization). The samples at 5
1 ~ and 10% ethylene-vinyl alcohol polymer were hazy; the sample at 20%
could not be processed, possibly due to chemical interactions leading to
crosslinlcing. Results of these tests are shown in Table X, below.
~~~!~~~~
Table X
Oxygen Permeability of Ammonia Polyglutarimides Blended with Poly(Ethylene
yinyl Alcohol)
Glutarimide % Relative Oxygen
Ex_ ambleGlutarimide CoP-I Humidity Permeability
38 Ammonia - 0 ~ 0.4
39 Ammonia 5 0 1.3
40 Ammonia 10 0 1.8
EXAMPLE 41
This example illustrates that a styrene copolymer containing
imide units does not exhibit outstanding barrier properties. A
commercial styrene-malefic anhydride copolymer containing about
20%a anhydride by weight was treated with methjrlamine to yield the
N-methylsuccinimide functionality. The permeability value for the
polymer was greater than 200. Blending with 20% CoP-1 did not
substantially decrease the permeability value.
41
~~~~~»~
EXAMPLE 42
This example demonstrates that the blends of glutarimide
polymer and ethylene-vinyl alcohol polymer may be further combined
with polyvinyl chloride) and a methacrylate-butadiene-styrene impact
modifier to produce a blend with good barrier performance and
improved service temperature.
Polyvinyl chloride) formulations were prepared as follows:
Polyvinyl chloride), K= t9 .100 parts
Organotin stabilizer . . . . . .1.0 phr
Polyglutarimide, (Ex. 11) . . . 0 or 40 phr
Ethylene-vinyl alcohol . . . . 0 or 4.4 phr
copolymer, (CoP-1)
MBS modifier . . . . . . . . . . 0 or 24 phr
The materials were intensively blended while dry, milled for 5
minutes on a two-mill roll at 190°C, and the .resulting polymer
blend
pressed into a film which was 0.2 mm thick. Results of oxygen
permeability tests on these materials are shown in Table XI, below.
42
~fJ~~S~ 4
Ta 1 XI
Blends of P~lyglutarimide-Ethylene Vinyl Alcohol with Pol,)r Vin~rl Chloride)
and
MBS
Glutarimide,~hrCoP-1, phr MBS, t?hr Oxygen Permeability
0 0 0 3.1
40 0 0 3.7
40 0 24 8.23
40 4.4 0 2.5
40 4.4 24 3.5
EXAMPLES 43 - 52
These examples illustrate that copolymers of methyl ,
methacrylate with acrylic monomers' bearing functional groups, which
are expected to improve compatibility with the vinyl alcohol moieties
of an ethylene-vinyl almhol copolymer, exhibit an unexpected
improvement in barrier properties. All blends contain 80%
methacrylic copolymer and 20% of the ethylene-vinyl alcohol
designated CoP-1. Controls with no CoP-1 are noted. The copolymers
are prepared by emulsion polymerization, as follows:
Five monomer mixtures were prepared, having respective
methyl methacrylate:hydroxyethyl methacrylate ratios of 100:0, 95:5,
90:10, 85:15 and 80:20. Each mixture contained 1320 parts of methyl
methacrylate:hydroxyethyl methacrylate monomer, 3.96 parts
43
~Qa~~~~
n-dodecyl mercaptan, 778.24 parts water and 19.8 parts 10% aqueous
sodium dodecylbenzene sulfonate solution (a total of 2122 parts).
Each monomer mixture was polymerized according to the
following procedure. To an appropriate glass vessel equipped with
stirrer, heater, a reflux condenser, and nitrogen sparge tube, was added
1992 parts of deionized water, 59.4 parts of a 10% aqueous solution of
sodium dodecylbenzene sulfonate, and 1 part of sodium carbonate.
The mixture was sparged for one hour with nitrogen while heating to
70°C. Ten percent of the monomer mixture (212.2 parts) was added at
70°C and the mixture was heated to 85°C. Then 14.89 parts of a
solution of sodium persulfate (2.24 parts) in 146.63 parts of deionized
water was added. The reaction was monitored until a color change and
exotherm were observed, signalling the onset of polymerization. Sixty
minutes after onset, gradual addition of the remainder of the
15 monomer mix was begun and continued over three hours. During
that time, the remainder of the initiator solution was added in 14.89-
part portions every 15 minutes. At the completion of the monomer
addition the mixture was held at 85°C for one hour. The mixture was
then cooled, filtered, and the polymer isolated by freeze-drying.
2 o Blends with and without the ethylene-vinyl alcohol copolymer
were prepared for testing by milling and compression molding films,
and the oxygen permeability was determined as described above. Table
XII shows the results for these films.
44
~(~a'-'~~~"4
TABLE xzz
Ox3~gen P~rmeabilstv~_og9lym~_r~ and Bjnarx B1_ends of MrLA/HEMA//GoP-1
Example Polymer/Blend ~ Composition Calculated Observed
(w//w) Perm.l Perm.l
43 (MMA/HEMA=100/0) 100//0 2.96
44 (M1HA/HEMA=95/5) 100//0 2.90
45 (1~~IA/HEMA=90/10) 100//0 2.93
46 (MMA/HEMA=85/15) 100//0 2.67
47 (Na~A/HEMA=80/20) 100//0 2.15
48 (N~iA/HEMA=100/0)//CoP-1 80//20 8.272
49 (I~iA/HEMA=95/5) CoP-1 80//20 0.77 0.39 '
// .
50 (1~IA/HEMA=90/10)//CoP-1 80//20 0.78 0.35
51 (I~1A/HEMA=85/15)//CoP-1 80//20 0.72 0.34
52 (MMA/HEMA=80/20)//CoP-1 80//20 0.61 0.37
1 indicates units of cm3~mm/m2~atm~day
2 This value is anomalously high; compare with Example 37. In no
other instance has a value for the methacrylate polymer blend with a
vinyl alcohol polymer given a higher value for oxygen permeability
than the unmodified control.
EXAMPLES 53 - 65
These examples illustrate that copolymers of cyclohexyl
methacrylate with methyl methacrylate may be blended with another
resin plus the ethylene-vinyl almhol polymer identified herein as
~; Q~.'~~~~4
CoP-1, to form tough blends having light transmission properties
ranging from translucent to transparent .
Samples of the methyl methacrylate/cyclohexyl methacrylate
copolymer were prepared as follows: Bags of polyvinyl alcohol) film
were prepared with tightly sealed edges, except for an opening to allow
addition of liquids. A monomer mixture of methyl methacrylate
(MMA) / cyclohexyl methacrylate (CHMA) was prepared from 2700
parts MMA and 800 parts of CHMA. A separate initiator solution was
prepared from 2200 parts MMA, 2.464 parts azobis(isobutyronitrile),
4.928 parts t-butyl peroxyacetate, and 70.4 parts n-dodecyl mercaptan.
To the MMA/CI~MA mixture was added 517.7 parts of the initiator
solution. The resulting monomer-initiator mixture was degassed by
sparging with nitrogen and transferred to a polyvinyl alcohol) bag.
The bag was degassed under mild vacuum. The bag was then
heated to 45°C and held at that temperature for at least 24 hours, then
slowly heated to 120°C and held there for six hours. The polyvinyl
alcohol)-film bag was removed from the resulting polymer, which was
then washed with water, dried, and granulated.
2 0 ~ ~e following blends of Table XIII, the aaylic copolymer was
blended with the polycarbonate (a commercial molding grade of
bis(phenol-A) polycarbonate) at various ratios, then that blend was
blended further with the ethylene-vinyl alcohol copolymer.
The blends were prepared as described above for "Blending of
2 5 polymers." Extrusion or the alternative milling procedure were used
depending upon the amount of polymer made.
46
~(~~!Wi~4
Table X>TI
ExamplePolymer//Blend ~ CompositionCalculatedObserved
(w//wl Perm.* Perm.*
53 (I~IA/CHMA=80/20) 100//0 9.88
54 (L~IA/CHMA=80/20)//PC75//25 18.04 15.46
55 (I9HiA/CHMA=80/20) 50//50 32 .84 28. 99
//PC
56 (N~IA/CHMA=80/20) 76//24 1 .51
//CoP-1
57 (~IA/CHMA=80/20)//CoP-154//46 0.27 0.03
58 (I9rIA/CHMA=80/20)//CoP-168//32 0.81 0.51
59 (1~~IA/CFiMA=80/20) 49//56 0 .12 0.03 ,
//COP-1
60 (I~IA/CHMA=80/20)//PC-81//19 3.61 0.26
{75//25}//CoP-1
61 (MMA/CHMA=80/20)//PC-61//39 0.97 0.2.3
(50//50}//CoP-1
62 PC//CoP-1 28//72 0.07 0.03
63 PC//CoP-1 44//56 0.33 0.04
64 PC 100//0 109.66
65 CoP-1 100//0 0.004
* indicates units of cm3~mm/m2~atm~day
EXAMPLES 66 - 72
The following examples illustrate that when the level of the
third polymer, whose burner properties are not decreased dramatically
by the vinyl alrnhol polymer blends, is raised above a critical level of
about 25% of the barrier polymer, the advantage of surprising barrier
properties of the ternary blend with an acrylic polymer is lost.
47
~~~~J~4
TABLE XIV:
Oxygen Permeability of Transparent Ternary Blends of
(MMA/GHMjL 80/!20) /PG//GnP-1
Example Polymer/Blend ~ Composition Calculated Observed
(w/w) Perm.* Perm.*
66 (MMA/CHMA=80//20)//PC-80//20 5.41 19.6
50/50)//CoP-1
67 (MMA/CHMA=80//20)//PC-80//20 5.10 20.1
53/47)//CoP-1
68 (MMA/CHMA=80//20)//PC-80//20 4.91 16.3
55/45)//CoP-1
69 (MMA/CHMA=80//20)//PC-80//20 4.73 18.0
57/43)//CoP-1
70 (MMA/CHMA=80//20)//PC-80//20 4.46 15.1
60/40)//CoP-1
71 (MMA/CHMA=80//20)//PC-80//20 4.21 15.7
63/47)//CoP-1
72 (MMA/CHMA=80//20)//PC-80//20 4.05 16.9
65/35)//CoP-1
* indicates units of cm3~mm/m2~atm~day.
EXAMPLES 73 - 76
The following examples illustrate that a blend of
polyp-hydroxystyrene), which is compatible with methyl
methacrylate, and which has barrier properties somewhat similar to
those of poly(methyl methacrylate), may be used in conjunction with
an ethylene-vinyl alcohol copolymer to produce the unexpected
48
- ~~~!~5~~
improvement in barrier properties. Polyp-hydroxystyrene) of 32,000
weight-average molecular weight was purchased from Hoechst-
Celanese. The barrier value for this material is reported to be 7.88
cm~mm/m2~at~.n~day.
Three-component blends were prepared as described above for
"Blending of polymers." Extrusion ar the alternative milling
procedure were used depending upon the amount of polymer made.
The oxygen permeability of the samples was determined, and is shown
in Table XV. The reduction in permeability over expected values is
not discernible at low percentages of the ethylene-vinyl alcohol
polymer, but it is quite apparent that permeability has been
substantially decreased when the level of that copolymer in the blend
reaches about 20% .
49
~~~~JM
TABLE XV:
Oxygen Permeability of Ternary Blends of Pt~lA// Poly (p- ~Igdroxv,~S~rene
(PrHE)
//Ethylene-V~ny1_ Alcohol (CoP-1)
Example Polymer/Blend ~ Composition Calculated Observed
(w/w) Perm.* Perm.*
73 PI4rIA//PpHS//CoP-189.9/6.7/3.4 5.54 6.46
74 P~IA//PpHS//CoP-187.0/8.7/4.3 5.19 7.30
75 PMMA//PpHS//CoP-183.4/8.3/8.3 3.84 4.37
76 PI~IA//PpHS//CoP-154.0/26.0/20.0 1.63 0.120
EXAMPLES T7 - 8~
These examples illustrate blends of the first copolymer
containing mers of heterocyclic monomers. Copolymers of these
examples were prepared in emulsion using a polymerization
procedure similar to that of Example 43. N-vinylpyrrolidone (N-VP),
4-vinylpyridine (4-VP) and p-acetoxystyrene are commeroally
available monomers. The polymer containing units of
p-hydroxystyrene was prepared as follows: In a flask fitted with a reflex
condenser and stirrer, 100 g of p-acetoxystyrene copolymer with methyl
1 p methacrylate was dissolved in 1000 ml tetrahydrofuran. To this
solution was added 25 g sodium hydroxide dissolved in 100 ml water.
The mixture was refluxed for two hours, then cooled to 50°C; 500 ml
water was then added, followed by glacial acetic acid until the flask
contents were slightly acidic. Water (500 -1000 ml) was added to fully
precipitate the polymer, which was then filtered and dried under
~~~'~J~4
vacuum and blended as in Example 43 with various polymers
containing vinyl alcohol units. CoP-5 and CoP-6 are copolymers which
are primarily vinyl alcohol having long-chain (up to C2o) alkenoxy
methacrylate ester mers grafted onto the polymer, and were obtained
from Air Products Company. CoP-5 has a melt index of 4.5 g/10 '
minutes, a glass transition temperature (Tg) of 46°C, and a melt
viscosity of 9408 poise at 19°C. CoP~~6 has a melt index of 14 g/10
minutes, a Tg of 24°C, and a melt viscosity of 2970 at 195°C.
The melt
indices are measured at 230°C and 2160 g, and the melt viscosities are
at
l0 zero shear. Most of the polymer blends shown in Table XVI show
better resistance to oxygen permeability than predicted by plotting
either a linear or an S-shaped curve of the natural logarithm of
permeability versus polymer composition, based on the barrier
properties of the individual components.
51
~:QU.!~ i~~'"4
TABLE XVI
Oxygen Permeability of Binary Blends of MMA Copolymers
with Polar Monomers //Ethv~ene-Vinyl Alcohol Copolymer
Example Polymer/Blend ~ Composition Calculated Observed
(w/w) Perm.* Perm.*
77 (MMA/4VP=90/10)//CoP-180//20 2.27 0.131
78 (IrffrlA/4VP=80/20) 80//20 2 .27 0.43
//CoP-1
79 (MMA/NVP=75/25) 100//0 3.45
80 (I~IA/NVP=75/25)//CoP-180//20 0.89 0.019
81 (MMA/NVP=75/25)//CoP-175//25 0.63 0.013
82 (MMA/NVP=75/25)//CoP-580//20 0.89 0.057
83 (MMA/NVP=75/25)//CoP-575//25 0.63 0.056
84 (MMA/NVP=75/25)//CoP-566//34 0.34 0.004
85 (MMA/NVP=75/25)//CoP-680//20 0.89 0.030
86 (MMA/NVP=75/25)//CoP-675//25 0.63 0.033
87 (MMA/NVP=75/25)//PVOH 80//20 0.64 1.819
88 (MMA/NVP=75/25)//PVOH 75//25 0.64 2.226
* indicates units of cm3~mm/m2~atm~day.
EXAMPILES 89 -100
In the following examples, blends were prepared from CoP-1, N-
methyldimethylglutarimide of Vicat softening temperature 170°C and
made without acid reduction treatment, and nylon 6
(poly(caprolactam)) manufactured by Allied -Signal Inc. as Capron
8202. Sodium hydroxide was added at a level of 500 parts per million
parts of the total polymer blend to those blends indicated "NaOH - yes"
52
~Q~.!~5~~
below. 'These polymers were blended in a 2.5-cm Killion extruder
equipped with a barrier screw operating at 100 rpm and a 4.8-rnm die, ,
and having the following temperature profile: feed zone - 250°C; zone
2 - 300°C; zone 3 - 300°C; die 1- 275°C; die 2 -
275°C. Blended samples
were compression molded into 100-mm square films for permeability
testing. The blend rnrnpositions and testing results are shown in Table
XVII below. Upon visual examination, all samples were transparent
and free from haze.
TABLIr XVII
Imide-Poly(Vinyl Alcohol-Polramide Blends
Exam Glutar Nylon CoP-1NaOH Clarity
Film
Thick-
Permeability
_ple imide% 6 % % ness, *
~m
89 80.75 5.0 14.25N 307 0.705 Haze-free
o
90 80.75 5.0 14.25No 279 0.669 Haze-free
9I 72.25 15.0 12.75N 376 0.657 Haze-free
o
92 72.25 15.0 12.75N 269 0.677 Haze-free
o
93 72.25 15.0 12.75Yes 315 0.516 Haze-free
94 63.75 25.0 11.25No 345 0.508 Haze--free
95 63.75 25.0 11.25No 295 0.748 Haze-free
96 63.75 25.0 11.25Yes 340 0.776 Haze-free
97 63.75 25.0 11.25Yes 325 0.929 Haze-free
98 47.5 47.5 5.0 Yes 246 L14 Haze-free
99 45.0 45.0 10.0 Yes 170 0.921 Haze-free
100 42.5 42.5 15.0 Yes 216 0.638 Haze-free
* indicates units of cm3~mm/m2~atm~day.
53
While the invention has been described with reference to
specific examples and applications, other modifications and uses for
the invention will be apparent to those skilled in the art without
departing from the spirit and scope of the invention defined in the
claims below.
54
