FIELD OF THE INVENTION
One or more embodiments of the present invention relates
to sealing articles that include a thermoplastic vulcanizate.
BACKGROUND OF THE INVENTION
Containers for storing fluids such as liquids have been
closed or sealed by employing various devices. For example, bottles, such as wine
bottles, have been sealed by employing cylindrically shaped devices called corks.
These devices, which are typically fabricated from cellulosic material, are compressed
and placed into the opening of a bottle. Upon expansion of the cork, the bottle
can be sealed thereby preventing the escape of fluid contained within the bottle.
In certain instances, it may be important to minimize or
prevent the contamination of certain fluids stored within containers. For example,
it is important to prevent medical fluids (e.g., medications or bodily fluids) from
being contaminated or impacted by oxygen. Accordingly, it is highly advantageous
to seal these containers with devices that prevent oxygen permeation into the container.
As a result, corks or stoppers employed in conjunction with containers used in the
medical industry often include natural or synthetic rubbers that exhibit low oxygen
permeability.
Not only is contamination by oxygen is a concern, there
is also a need in the industry, particularly in the medical industry, to allow for
the addition and withdrawal of fluids from these containers. For example, as described
in
U.S. Patent Nos. 6,840,510
and
5,232,109
, a hypodermic needle or infusion spike is inserted through the stopper
in order to add or withdraw fluid from the container. Upon removal of the hypodermic
needle or infusion spike, the stopper advantageously reseals itself.
While both low oxygen permeability and curability (i.e.,
the ability to reseal after puncture) are important features for stopper devices,
the ability to manufacture stopper devices by efficient and economic processing
techniques is likewise important. Where natural or synthetic rubbers are employed
to manufacture these devices, the fabrication techniques are often limited to rubber
casting or thermosetting techniques. In other words, the rubber is cured within
a mold and released from the mold after the curing process.
Thermoplastic elastomers include materials that exhibit
many of the properties of thermoset elastomers yet are processable as thermoplastics.
One type of thermoplastic elastomer is a thermoplastic vulcanizate, which includes
fully cured or partially cured rubber within a thermoplastic matrix. Thermoplastic
vulcanizates are conventionally produced by dynamic vulcanization, which includes
a process whereby a rubber can be cured or vulcanized within a blend with thermoplastic
resin while the polymers are undergoing mixing or masticating at some elevated temperature,
preferably above the melt temperature of the thermoplastic resin. For example,
WO 01/10950
teaches thermoplastic vulcanizates that include a thermoplastic polyurethane
having one major glass transition temperature of less than 60°C and an a polar
rubber. The a polar rubber may include butadiene rubber, styrene-butadiene rubber,
isoprene rubber, natural rubber, butyl rubber, ethylene-propylene rubber, ethylene-propylene-diene
monomer rubber, or others. The thermoplastic vulcanizate may also include other
constituents commonly employed in the art including extender oils.
Despite the fact that thermoplastic elastomers, particularly
thermoplastic vulcanizates, have been known for many years, and the need for useful
stoppers, particularly for the medical industry, has existed for many years, technologically
useful stoppers prepared from thermoplastic vulcanizates do not exist in the prior
art. Inasmuch as thermoplastic vulcanizates provide an efficient and economical
route to the preparation of stoppers, the ability to fabricate stoppers from plastic
vulcanizate would be desirable.
SUMMARY OF THE INVENTION
The present invention includes an article for sealing the
contents of a container, the article comprising a member adapted for sealing the
container, where the member includes a thermoplastic vulcanizate including a dynamically
cured butyl rubber, a thermoplastic polyurethane having a glass transition temperature
of less than about 6o°C, and a synthetic oil.
The present invention also includes a thermoplastic vulcanizate
a dynamically cured butyl rubber, a thermoplastic polyurethane having a glass transition
temperature of less than about 60°C, and a synthetic oil.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view of an article for sealing
a container according to one or more embodiments of the present invention, where
the article is adapted to seal a particular container by insertion into the container.
Fig. 2 is a perspective view of a multi-layered article
for sealing a container according to one or more embodiments of the present invention.
Fig. 3 is a perspective view of an article for sealing
a container according to one or more embodiments of the present invention, where
the article seals a particular container by circumscribing the container.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
One or more embodiments of the present invention are directed
toward articles for sealing a container. In one or more embodiments, these articles
may be referred to as corks, stoppers, caps, or sealing devices. In one or more
embodiments, the articles include at least one member that includes a particular
thermoplastic vulcanizate, and as a result, the articles demonstrate technologically
useful coring properties, sealing properties, and low air permeability. In view
of these characteristics, the articles of one or more embodiments may advantageously
be employed in conjunction with containers that are useful for holding fluids, such
as medical fluids, which are desirably sealed within a container.
In one or more embodiments, the thermoplastic vulcanizates
include dynamically-cured butyl rubber, a thermoplastic polyurethane resin, a synthetic
oil, optionally a compatibilizer, and optionally other components or constituents
that are typically included in thermoplastic vulcanizates.
In one or more embodiments, butyl rubber includes copolymers
and terpolymers of isobutylene and at least one other comonomer. Useful comonomers
include isoprene, divinyl aromatic monomers, alkyl substituted vinyl aromatic monomers,
and mixtures thereof. Exemplary divinyl aromatic monomers include vinyl styrene.
Exemplary alkyl substituted vinyl aromatic monomers include &agr;-methyl styrene
and paramethyl styrene. These copolymers and terpolymers may also be halogenated
such as in the case of chlorinated and brominated butyl rubber. In one or more embodiments,
these halogenated polymers may derive from monomer such as parabromomethylstyrene.
In one or more embodiments, butyl rubber includes copolymers
of isobutylene and isoprene, copolymers of isobutylene and paramethyl styrene, as
described in
U.S. Patent No. 5,013,793
, which is incorporated herein by reference for purpose of U.S. patent
practice, terpolymers of isobutylene, isoprene, and divinyl styrene, as described
in
U.S. Patent No. 4,916,180
, which is incorporated herein by reference for purpose of U.S. patent
practice, and branched butyl rubber, as described in
U.S. Patent No. 6,255,389
, which is incorporated herein by reference for purpose of U.S. patent
practice, and brominated copolymers of isobutene and paramethylstyrene (yielding
copolymers with parabromomethylstyrenyl mer units) as described in
U.S. Patent No. 5,162,445
, which is incorporated herein by reference for purpose of U.S. patent
practice. These copolymers and terpolymers may be halogenated.
In one embodiment, where butyl rubber includes the isobutylene-isoprene
copolymer, the copolymer may include from about 0.5 to about 30, or from about 0.8
to about 5, percent by weight isoprene based on the entire weight of the copolymer
with the remainder being isobutylene.
In another embodiment, where butyl rubber includes isobutylene-paramethyl
styrene copolymer, the copolymer may include from about 0.5 to about 25, and from
about 2 to about 20, percent by weight paramethyl styrene based on the entire weight
of the copolymer with the remainder being isobutylene. In one embodiment, isobutylene-paramethyl
styrene copolymers can be halogenated, such as with bromine, and these halogenated
copolymers can contain from about o to about 10 percent by weight, or from about
0.3 to about 7 percent by weight halogenation.
In other embodiments, where butyl rubber includes isobutylene-isoprene-divinyl
styrene, the terpolymer may include from about 95 to about 99, or from about 96
to about 98.5, percent by weight isobutylene, and from about 0.5 to about 5, or
from about 0.8 to about 2.5, percent by weight isoprene based on the entire weight
of the terpolymer, with the balance being divinyl styrene.
In the case of halogenated butyl rubbers, the butyl rubber
may include from about 0.1 to about 10, or from about 0.3 to about 7, or from about
0.5 to about 3 percent by weight halogen based upon the entire weight of the copolymer
or terpolymer.
In one or more embodiments, the glass transition temperature
(Tg) of useful butyl rubber can be less than about -55°C, or less than about
-58°C, or less than about -60°C, or less than about -63°C.
In one or more embodiments, the Mooney viscosity (ML1+8@125°C)
of useful butyl rubber can be from about 25 to about 75, or from about 30 to about
60, or from about 40 to about 55.
Useful butyl rubber includes that prepared by polymerization
at low temperature in the presence of a Friedel-Crafts catalyst as disclosed within
U.S. Pat. Nos. 2,356,128
and
2,944,576
. Other methods may also be employed.
Butyl rubber can be obtained from a number of commercial
sources as disclosed in the Rubber World Blue Book. For example, both halogenated
and un-halogenated copolymers of isobutylene and isoprene are available under the
tradename Exxon Butyl™ (ExxonMobil Chemical Co.), halogenated and un-halogenated
copolymers of isobutylene and paramethyl styrene are available under the tradename
EXXPRO™ (ExxonMobil Chemical Co.), star branched butyl rubbers are available
under the tradename STAR BRANCHED BUTYL™ (ExxonMobil Chemical Co.), and copolymers
containing parabromomethylstyrenyl mer units are available under the tradename EXXPRO
3745 (ExxonMobil Chemical Co.). Halogenated and non-halogenated terpolymers of isobutylene,
isoprene, and divinyl styrene are available under the tradename Polysar Butyl™
(Bayer; Germany).
The butyl rubber may be partially of fully cured or crosslinked.
In one embodiment, the butyl rubber is advantageously completely or fully cured.
The degree of cure can be measured by determining the amount of rubber that is extractable
from the thermoplastic vulcanizate by using cyclohexane or boiling xylene as an
extractant. This method is disclosed in
U.S. Pat. No. 4,311,628
, which is incorporated herein by reference for purpose of U.S. patent
practice. In one embodiment, the rubber has a degree of cure where not more than
15 weight percent, in other embodiments not more than 10 weight percent, in other
embodiments not more than 5 weight percent, and in other embodiments not more than
3 weight percent is extractable by cyclohexane at 23°C as described in U.S
Patent Nos. 5,100,947 and 5,157,081, which are incorporated herein by reference
for purpose of U.S. patent practice. Alternatively, in one or more embodiments,
the rubber has a degree of cure such that the crosslink density is preferably at
least 4 x 10-5, in other embodiments at least 7 x 10-5, and
in other embodiments at least 10 x 10-5 moles per milliliter of rubber.
See also "
Crosslink Densities and Phase Morphologies in Dynamically Vulcanized TPEs,"
by Ellul et al., RUBBER CHEMISTRY AND TECHNOLOGY, Vol 68, pp. 573-584 (1995)
.
In one or more embodiments, thermoplastic polyurethane
(TPU) includes thermoplastic elastomer copolymers including one or more polyurethane
hard blocks or segments and one or more soft blocks. In one or more embodiments,
these copolymers include those compositions obtained by reacting multi-functional
isocyanate(s) with chain extender(s) and optionally macroglycol(s). In one or more
embodiments, these reactions occur an isocyanate index of at least 95 and in other
embodiments at least 98; in these or other embodiments, these reactions occur at
an isocyanate index of 105 or less, and in other embodiments 102 or less.
In one or more embodiments, thermoplastic polyurethane
includes a blend of different thermoplastic polyurethanes in such amounts that the
blend has at least one major Tg of less than 60°C.
Isocyanate index includes the ratio of isocyanate-groups
over isocyanate-reactive hydrogen atoms present in a formulation, given as a percentage.
In other words, the isocyanate index expresses the percentage of isocyanate actually
used in a formulation with respect to the amount of isocyanate theoretically required
for reacting with the amount of isocyanate-reactive hydrogen used in a formulation.
In one or more embodiments, isocyanate index is considered from the point of view
of the actual polymer forming process involving the isocyanate ingredient and the
isocyanate-reactive ingredients. Any isocyanate groups consumed in a preliminary
step to produce modified polyisocyanates (including isocyanate-derivatives referred
to in the art as quasi- or semi-prepolymers) or any active hydrogens reacted with
isocyanate to produce modified polyols or polyamines, are not taken into account
in the calculation of the isocyanate index; only the free isocyanate groups and
the free isocyanate-reactive hydrogens present at the actual elastomer forming stage
are taken into account.
TPU can be produced in the so-called one-shot, semi-prepolymer
or prepolymer method, by casting, extrusion, or any other process known to the person
skilled in the art.
In one or more embodiments, useful multi-functional isocyanates
include organic diisocyanates and polyisocyanates such as aliphatic, cycloaliphatic
and araliphatic polyisocyanates. Examples of diisocyanates include hexamethylene
diisocyanate, isophorone diisocyanate, cyclohexane-1,4-diisocyanate, 4,4'-dicyclohexylmethane
diisocyanate and m- and p-tetramethylxylylene diisocyanate. Examples of aromatic
polyisocyanates include tolylene diisocyanates (TDI), phenylene diisocyanates, diphenylmethane
diisocyanates (MDI), and MDI comprising 4,4'-diphenylmethane diisocyanate.
In one or more embodiments, the diphenylmethane diisocyanates
may consist essentially of pure 4,4'-diphenylmethane diisocyanate or mixtures of
that diisocyanate with one or more other organic polyisocyanates including other
diphenylmethane diisocyanate isomers such as the 2,4'-isomer optionally in conjunction
with the 2,2'-isomer. The polyisocyanate may also be an MDI-variant derived from
a polyisocyanate composition containing at least 85% by weight of 4,4'-diphenylmethane
diisocyanate. MDI variants include liquid products obtained by introducing carbodiimide
groups into said polyisocyanate composition and/or by reacting with one or more
polyols.
In one or more embodiments, the polyisocyanate includes
at least 90% by weight of 4,4'-diphenylmethane diisocyanate, and in other embodiments
at least 95% by weight of 4,4'-diphenylmethane diisocyanate.
In one or more embodiments, chain extenders include di-functional
isocyanate-reactive species. In these or other embodiments, these di-functional
compounds are characterized by a molecular weight of less than 500. In one or more
embodiments, the chain extender includes a diol, and in certain embodiments a branched
diol. In one or more embodiments, blends of different types of diols are employed.
Examples of chain extenders include aliphatic diols, such
as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,2-propanediol,
1,3-butanediol, 2,3-butanediol, 1,3-pentanediol, 1,2-hexanediol, 3-methyl-1,5-pentanediol,
diethylene glycol, dipropylene glycol and tripropylene glycol. In one or more embodiments,
the chain extenders include an odd-number of carbon atoms between the hydroxyl groups.
In these or other embodiments, the chain extenders with a branched chain structure
such as 2-methyl-1,3-propanediol, 2,2-dimethyl-2,3-propanediol, 1,3-propanediol,
1,5-pentanediol are employed. In one or more embodiments, cycloaliphatic diols such
as 1,4-cyclohexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanedimethanol or 1,2-cyclohexanedimethanol,
and aromatic diols such as hydroquinone bis(hydroxyethylether) and the like can
also be used. Other examples include neopentylglycol, 1,3-propanediol and 2-methyl-1,3-propanediol.
In certain embodiments, other diols having a molecular weight of less than 500 containing
an alkylene group with an odd number of carbon atoms between the two hydroxyl groups
can be employed.
In one or more embodiments, the macroglycols include compounds
having a molecular weight of between 500 and 20,000. In these or other embodiments,
macroglycols can be used in an amount such that the TPU has at least one major Tg
of less than 60 C. In these or other embodiments, the macroglycol is employed in
an amount of from about 25 to about 75 parts by weight based upon the total weight
of the TPU. The amount of macroglycols as a percentage of the total composition
of the TPU may define the softblock content of the TPU.
In one or more embodiments, macroglycols include polyesters,
polyethers, polyesteramides, polythioethers, polycarbonates, polyacetals, polyolefins,
polysiloxanes, or mixtures two or more thereof.
Polyethers, which may be referred to as polyether glycols,
may include products obtained by the polymerization of a cyclic oxide, for example
ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, or mixtures of
two or more thereof, in the optional presence of an initiator such as a di-functional
initiator. In one or more embodiments, suitable initiator compounds include 2 active
hydrogen atoms. Examples of initiators include water, butanediol, ethylene glycol,
propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, and
mixtures thereof. Mixtures of initiators and/or cyclic oxides may also be used.
Examples of polyether glycols include polyoxypropylene
glycols and poly(oxyethylene-oxypropylene) glycols obtained by the simultaneous
or sequential addition of ethylene or propylene oxides to di-functional initiators.
Random copolymers having oxyethylene contents of 10-80%, block copolymers having
oxyethylene contents of up to 25% and random/block copolymers having oxyethylene
contents of up to 50%, based on the total weight of oxyalkylene units, can be employed.
In one or more embodiments, those having at least part of the oxyethylene groups
at the end of the polymer chain are employed. Other useful polyether glycols include
polytetramethylene glycols obtained by the polymerization of tetrahydrofuran.
Polyesters, which may be referred to as polyester glycols,
include hydroxyl-terminated reaction products of dihydric alcohols such as ethylene
glycol, propylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol or
1,6-hexanediol, or mixtures of dihydric alcohols, and dicarboxylic acids and their
ester-forming derivatives such as succinic, glutaric and adipic acids or their dimethyl
esters, sebacic acid, phthalic anhydride, tetrachlorophthalic anhydride or dimethyl
terephthalate or mixtures thereof.
Polythioether glycols include products obtained by condensing
thiodiglycol either alone or with other glycols, alkylene oxides or dicarboxylic
acids.
Polycarbonate glycols include products obtained by reacting
diols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol
or tetraethylene glycol with diaryl carbonates, for example diphenyl carbonate,
or with phosgene.
Polyacetal glycols include products prepared by reacting
glycols such as diethylene glycol, triethylene glycol or hexanediol with formaldehyde.
Suitable polyacetals may also be prepared by polymerizing cyclic acetals.
Suitable polyolefin glycols include hydroxy-terminated
butadiene homo- and copolymers and suitable polysiloxane glycols include polydimethylsiloxane
diols.
Thermoplastic polyurethane resins are commercially available.
For example, they can be obtained under the trademark TEXIN™ (Bayer); TEXIN™
285 is a polyester-based thermoplastic polyurethane having a Shore A of about 85,
TEXIN™ 985 is a polyether-based thermoplastic polyurethane having a Shore
A of about 86, and TEXIN™ 945 is a polyether-based thermoplastic polyurethane
having a Shore D of about 50. Other commercial products include PELLTHANE (Dow)
and ESTANE (Noveon).
In one or more embodiments, synthetic oils include polymers
and oligomers of butenes including isobutene, 1-butene, 2-butene, butadiene, and
mixtures thereof. In one or more embodiments, these oligomers include isobutenyl
mer units. Exemplary synthetic oils include polyisobutylene, poly(isobutylene-co-butene),
polybutadiene, poly(butadiene-co-butene), and mixtures thereof.
In one or more embodiments, the synthetic oils include
synthetic polymers or copolymers having a viscosity in excess of about 20 cp, in
other embodiments in excess of about 100 cp, and in other embodiments in excess
of about 190 cp, where the viscosity is measured by a Brookfield viscometer according
to ASTM D-4402 at 38°C; in these or other embodiments, the viscosity of these
oils can be less than 4,000 cp and in other embodiments less than 1,000 cp.
In one or more embodiments, these oligomers can be characterized
by a number average molecular weight (Mn) of from about 300 to about
9,000 g/mole, and in other embodiments from about 700 to about 1,300 g/mole.
Useful synthetic oils can be commercially obtained under
the tradenames Polybutene™ (Soltex; Houston, Texas), Indopol™ (BP;
Great Britain), and Parapol™ (ExxonMobil).
In one or more embodiments, the thermoplastic vulcanizates
of this invention are substantially devoid of mineral oils. By substantially devoid,
it is meant that the thermoplastic vulcanizates include less mineral oil than would
otherwise have an appreciable impact on the technological features of the thermoplastic
vulcanizate. In one or more embodiments, the thermoplastic vulcanizates includes
less than 5% by weight, and in other embodiments less than 3% by weight, in other
embodiments less than 2% by weight, and in other embodiments less than 1% by weight
mineral oil, where the weight percent is based on the total weight of the thermoplastic
vulcanizate. In one embodiment, the thermoplastic vulcanizates are devoid of mineral
oil. In one or more embodiments, mineral oils include petroleum derived oils such
as saturated and unsaturated aliphatic oils, aromatic oils, and naphthenic oils.
In one or more embodiments, useful compatibilizers include
maleated thermoplastics, thermoplastic elastomer block copolymers, crystallizable
copolymers of propylene with ethylene or other higher &agr;-olefins, chlorinated
thermoplastics, ionomers, maleated elastomeric copolymers, and mixtures thereof.
Modified polyolefins include modified thermoplastics and
modified rubbers. In one or more embodiments, these modified polyolefins include
at least one functional group attached thereto. In one or more embodiments, these
functional groups can include carboxylic acid; C1 to C8 carboxylate
ester such as carbomethoxy, carboethoxy, carbopropoxy, carbobutoxy, carbopentoxy,
carbohexoxy, carboheptoxy, carboctoxy, and isomeric forms thereof; carboxylic acid
anhydride; carboxylate salts formed from the neutralization of carboxylic acid group(s)
with metal ions from Groups I, II, III, IV-A and VII of the periodic table, illustratively
including sodium, potassium, lithium, magnesium, calcium, iron, nickel, zinc, and
aluminum, and mixtures thereof; amide; epoxy; hydroxy; amino; and C2
to C6 acyloxy such as acetoxy, propionyloxy, or butyryloxy. In one or
more embodiments, these functional groups may be part of an unsaturated monomer
precursor that can be copolymerized with an olefin monomer or grafted onto a polyolefin
to form the modified polyolefin.
Useful functionalizing monomers or agents include acrylic
acid, methacrylic acid, maleic acid, maleic anhydride, acrylamide, methacrylamide,
glycidyl acrylate, glycidyl methacrylate, vinyl acetate, vinyl butyrate, methyl
acrylate, ethyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate, sodium acrylate,
zinc acrylate, the ionic hydrocarbon polymers from the polymerization of &agr;-olefins
with &agr;,&bgr;-ethylenically unsaturated carboxylic acids.
Useful modified polyolefins include those disclosed in
U.S. Patent Nos. 6,001,484
,
6,072,003
,
3,264,272
, and
3,939,242
, which are incorporated herein by reference.
In one or more embodiments, the mer units of the polyolefin
containing the functional groups can be present in the polyolefin in an amount from
about 0.05 to about 5 mole percent. For example, in the case of maleated polyethylene,
from about 0.005 to about 5 mole percent of the mer units include the residue of
maleic acid pendent to the backbone.
In one or more embodiments, useful modified polyolefins
can be obtained under the tradename OPTEMA™ TC130 (ExxonMobil),
which is an ethylmethacrylate copolymer, and POLYBOND™ (Crompton Uniroyal),
or FUSABOND™ (DuPont), which are maleated polypropylenes.
Maleated elastomeric copolymers include copolymers of ethylene,
an alpha-olefin, and one or more dienes, where the copolymer is reacted with maleic
anhydride to provide further functionality. These copolymers are commercially available
under the tradename EXXELOR (ExxonMobil).
In one or more embodiments, useful thermoplastic elastomer
block copolymers include at least one hard block or segment and at least one soft
block or segment. In certain embodiments, the block copolymer include two hard blocks
with a soft block positioned therebetween (i.e., ABA bock copolymer). In
other embodiments, the block copolymer includes two soft blocks with a hard block
positioned therebetween (i.e., BAB block copolymer).
In one or more embodiments, the soft blocks can be characterized
by a glass transition temperature (Tg) of less than 25°C, in other embodiments
less than o°C, and in other embodiments less than - 20°C.
In one or more embodiments, the soft block can include
a unit deriving from conjugated diene monomers and optionally vinyl aromatic monomers.
Suitable diene monomers include 1,3-butadiene, isoprene, piperylene, phenylbutadiene,
and mixtures thereof. Those units deriving from conjugated diene monomers can optionally
be hydrogenated. Suitable vinyl aromatic monomers include styrene, alkyl-substituted
styrenes such as paramethyl styrene, and &agr;-methyl styrene, as well as mixtures
thereof.
In one or more embodiments, the hard blocks can be characterized
by a glass transition temperature (Tg) of greater than 25°C, in other embodiments
greater than 50°C, and in other embodiments greater than 75°C.
In one or more embodiments, the hard blocks can include
polymeric units deriving from vinyl aromatic monomers. Useful vinyl aromatics include
styrene, alkyl-substituted styrenes such as paramethyl styrene, and &agr;-methyl
styrene, as well as mixtures thereof.
In one or more embodiments, useful thermoplastic elastomer
copolymers include, but are not limited to, styrene/butadiene rubber (SBR), styrene/isoprene
rubber (SIR), styrene/isoprene/butadiene rubber (SIBR), styrene-butadiene-styrene
block copolymer (SBS), hydrogenated styrene-butadiene-styrene block copolymer (SEBS),
hydrogenated styrene-butadiene block copolymer (SEB), styrene-isoprene-styrene block
copolymer (SIS), styrene-isoprene block copolymer (SI), hydrogenated styrene-isoprene
block copolymer (SEP), hydrogenated styrene-isoprene-styrene block copolymer (SEPS),
styrene-ethylene/butylene-ethylene block copolymer (SEBE), styrene-ethylene-styrene
block copolymer (SES), ethylene-ethylene/butylene block copolymer (EEB), ethylene-ethylene/butylene/styrene
block copolymer (hydrogenated BR-SBR block copolymer), styrene-ethylene/butylene-ethylene
block copolymer (SEBE), ethylene-ethylene/butylene-ethylene block copolymer (EEBE)
and mixtures thereof. Preferred copolymers include hydrogenated styrene-butadiene-styrene
block copolymer (SEBS), and hydrogenated styrene-isoprene-styrene block copolymer
(SEPS).
In one ore more embodiments, the block copolymers include
those disclosed in
U.S. Patent Nos. 6,177,517
Bi, and
6,369,160
Bi, which are incorporated herein by reference, as well as
International Patent Applications WO 96/20249
and
WO 96/23823
, which is incorporated herein by reference.
Other thermoplastic elastomer block copolymers include
block copolymers of a hydrogenated styrene block copolymer (e.g., SEPS or SEBS)
and thermoplastic polyurethane. These copolymers are commercially available under
the tradename S 5865 (Septon).
In one or more embodiments, the crystallizable propylene
copolymers include copolymers of propylene and at least one alpha-olefin. The copolymers
include from about 5 to about 35, in other embodiments from about 10 to about 30,
and in other embodiments from about 12 to about 20 mole percent units deriving from
the comonomer (ethylene). In one or more embodiments, these crystallizable propylene
copolymers can be characterized by propylene crystallinity.
Useful propylene copolymers are disclosed in
U.S. Patent Nos. 6,268,438
,
6,288,171
, and
6,245,856
, which are incorporated herein by reference. Useful propylene copolymers
are available under the tradename VISTAMAXX™ 1000, 2000, and 3000(Exxon Mobil).
In one or more embodiments, chlorinated polyolefins include
chlorinated poly-alpha-olefins. These poly-alpha-olefins may include from about
25 to about 45, and in other embodiments from about 30 to about 40 percent by weight
chlorine, where the weight percent includes the weight of the chlorine atoms attached
to the polymer backbone with respect to the overall weight of the polymer.
Chlorinated polyolefins are commercially available under
the tradename TYRIN™ (DuPont).
In one or more embodiments, ionomers include polymers having
a backbone composed of a thermoplastic resin and having side chains or groups pendent
to that backbone that are sufficiently polar so as to have the capability of forming
ionic domains (i.e., the capability to associate with one another so as to form
"physical crosslinks").
Ionomeric polymers can be prepared by attaching acid groups
to the polymer and then neutralizing the acid moiety with basic metal compounds
(e.g., metal hydroxides, metal salts, etc.) or basic nitrogen compounds (i.e., ammonia,
amines, etc.) to ionically link the polymers. The metal ions employed can include
alkali metals or alkaline earth metals. The acid group may be introduced into the
polymer chain in a variety of ways. One way is by introducing acid groups on the
predominant polymer, e.g., sulfonating polystyrene or by copolymerising an alpha,
beta-ethylenically unsaturated acid monomer with the predominant monomer, or by
graft-polymerizing an alpha, beta-ethylenically unsaturated acid moiety on the predominant
polymer.
Typical examples of ionomers employing salts of carboxylic
acid type pendent groups are disclosed in
British Patent No. 1,011,981
;
U.S. Pat. Nos. 3,264,272
;
3,322,734
;
3,338,734
;
3,355,319
;
3,522,222
; and
3,522,223
, which are incorporated herein by reference. Examples of ionomers employing
phosphonate-type pendent groups include those disclosed in
U.S. Pat. Nos. 3,094,144
;
2,764,563
,
3,097,194
; and
3,255,130
, which are incorporated herein by reference. Examples of ionomers employing
sulfonate-type pendent groups include those disclosed in
U.S. Pat. Nos. 2,714,605
;
3,072,618
; and
3,205,285
, which are incorporated herein by reference. The polar groups pendent
to the thermoplastic backbone can be present in from at least about 0.2 to about
as high as 15 mole % (i.e., 0.2-15 moles per mole of monomer repeating unit), or
in other embodiments 0.5 to 10 mole % of the total polymer.
Examples of thermoplastic ionomers include sulfonated polystyrene,
sulfonated poly-tertiary butylstyrene, sulfonated polymethylstyrene, sulfonated
polyethylene, sulfonated polypropylene, sulfonated polybutene-1, sulfonated styrene/methyl
methacrylate copolymers, sulfonated styrene/acrylonitrile copolymers, methacrylonitrile
copolymers, sulfonated polyformaldehyde and copolymers, sulfonated polyvinylchloride,
sulfonated block copolymers of polyethylene oxide and polystyrene, acrylic acid
copolymers with styrene, acrylic acid copolymers with methyl methacrylate. In one
or more embodiments, the thermoplastic ionomer can be sulfonated polystyrene or
sulfonated polyethylene and its copolymers. In addition to direct sulfonation of
these polymers or copolymers, a technique for incorporating a proper amount of sulfonate
salt in these polymers includes copolymerizing a suitable diene or di-functional
molecule at a low level (e.g., 0.5 to 10%) with the desired monomer. For
example, the copolymerization of 2 to 5 weight percent of ethylidene norbornene
with ethylene using coordination catalysts provides a polyethylene with a small
amount of unsaturation, yet the high crystallinity of polyethylene can still be
maintained.
Useful ionomers are commercially available under the tradename
SURLYN™ (DuPont) and IOTEK™ (Exxon Mobil).
In addition to the rubber, thermoplastic resin, and synthetic
oil, the thermoplastic vulcanizates of the invention may optionally include reinforcing
and non-reinforcing fillers, antioxidants, stabilizers, antiblocking agents, anti-static
agents, foaming agents, pigments, flame retardants and other processing aids known
in the rubber compounding art. These additives can comprise up to about 50 weight
percent of the total composition. Fillers that can be utilized include conventional
inorganics such as calcium carbonate, clays, silica, talc, titanium dioxide, carbon
black and the like.
In one or more embodiments, the thermoplastic vulcanizates
of this invention contain a sufficient amount of the butyl rubber to form rubbery
compositions of matter. The skilled artisan will understand that rubbery compositions
of matter include those that have ultimate elongations greater than 100 percent,
and that quickly retract to 150 percent or less of their original length within
about 10 minutes after being stretched to 200 percent of their original length and
held at 200 percent of their original length for about 10 minutes.
Thus, in one or more embodiments, the thermoplastic vulcanizates
can include at least about 25 percent by weight, in other embodiments at least about
40 percent by weight, and in other embodiments at least about 50 percent by weight
butyl rubber. In one or more embodiments, the amount of butyl rubber within the
thermoplastic vulcanizates can be from about 25 to about 90 percent by weight, in
other embodiments from about 45 to about 85 percent by weight, and in other embodiments
from about 60 to about 80 percent by weight, based on the entire weight of the butyl
rubber and thermoplastic polyurethane component combined.
In one or more embodiments, the thermoplastic vulcanizates
may include from about 10 to about 75 percent by weight, in other embodiments from
about 15 to about 70 percent by weight, in other embodiments from about 20 to about
50 percent by weight thermoplastic polyurethane resin based upon the entire weight
of the butyl rubber and thermoplastic polyurethane resin combined. The amount of
the thermoplastic polyurethane resin can also be expressed with respect to the amount
of the butyl rubber component. In one embodiment, the thermoplastic vulcanizates
may comprise from about 5 to about 100, in other embodiments from about 10 to about
80, and in other embodiments from about 20 to about 60 parts by weight thermoplastic
polyurethane resin per 100 parts by weight butyl rubber.
In one or more embodiments, the thermoplastic vulcanizates
may include from about 1 to about 60 parts by weight synthetic oil, in other embodiments
from about 5 to about 50 parts by weight synthetic oil, in other embodiments from
about 20 to about 45 parts by weight synthetic oil, and in other embodiments from
about 30 to about 40 parts by weight mineral oil per 100 parts by weight butyl rubber.
In one or more embodiments, the thermoplastic vulcanizates
may include from about 1 to about 20 parts by weight, in other embodiments from
about 5 to about 18 parts by weight, and in other embodiments from about 10 to about
15 parts by weight compatibilizer per 100 parts by weight butyl rubber. In one or
more embodiments, where the butyl rubber includes one or more parabromomethylstyrenyl
mer units, technologically useful thermoplastic vulcanizates according to the present
invention can be prepared in the substantial absence of a compatibilizer. In other
words, the thermoplastic vulcanizates can be prepared in the absence of that amount
of compatibilizer that would otherwise have an appreciable impact on the thermoplastic
vulcanizate. In one or more embodiments, the thermoplastic vulcanizates include
less than 1 part by weight, in other embodiments less than 0.5 parts by weight,
and in other embodiments less than 0.1 parts by weight compatibilizer per 100 parts
by weight butyl rubber. In one or more embodiments, the thermoplastic vulcanizates
are devoid of a compatibilizer.
Fillers, such as carbon black or clay, may be added in
amount from about 3 to about 50 parts by weight or in other embodiments from about
5 to about 30 parts by weight, per 100 parts by weight of rubber. The amount of
carbon black that can be used may depend, at least in part, upon the type of carbon
black.
In one or more embodiments, the butyl rubber is cured or
crosslinked by dynamic vulcanization. The term dynamic vulcanization refers to a
vulcanization or curing process for a rubber (e.g., butyl rubber) contained in a
blend with a thermoplastic resin (e.g., thermoplastic polyurethane), wherein the
rubber is crosslinked or vulcanized under conditions of high shear at a temperature
above the melting point of the thermoplastic. Dynamic vulcanization can occur in
the presence of the synthetic oil, or the synthetic oil can be added after dynamic
vulcanization (i.e., post added), or both (i.e., some can be added
prior to dynamic vulcanization and some can be added after dynamic vulcanization).
In certain embodiments, it may be advantageous to add compatibilizer prior to cure;
this may advantageously result in better dispersion of the rubber within the thermoplastic
phase, thereby leading to improved mechanical properties. In the event that certain
compatibilizers are employed, care should be taken to employ cure systems that are
less sensitive to interference (e.g. butyl zimate and zinc oxide). In other embodiments,
especially where sensitive cure systems are employed, certain ingredients, particularly
the compatibilizers (e.g., maleated plastics or chlorinated plastics), can be added
after dynamic vulcanization. In one or more embodiments, interference with the cure
may be minimized by adding these ingredients after dynamic vulcanization. Those
skilled in the art will be able to readily identify those ingredients that may be
better suited to addition after dynamic vulcanization.
In one embodiment, the butyl rubber can be simultaneously
crosslinked and dispersed as fine particles within the thermoplastic matrix, although
other morphologies may also exist. Dynamic vulcanization can be effected by mixing
the thermoplastic elastomer components at elevated temperature in conventional mixing
equipment such as roll mills, stabilizers, Banbury mixers, Brabender mixers, continuous
mixers, mixing extruders and the like. Methods for preparing thermoplastic vulcanizates
are described in
U.S. Patent Nos. 4,311,628
and
4,594,390
, which are incorporated herein by reference for purpose of U.S. patent
practice, although methods employing low shear rates can also be used. Multiple
step processes can also be employed whereby ingredients such as plastics, oils,
and scavengers can be added after dynamic vulcanization has been achieved as disclosed
in
International Application No. PCT/US04/30517
, which is incorporated herein by reference for purpose of U.S. patent
practice
Any cure system that is capable of curing or crosslinking
butyl rubber can be employed in practicing this invention. For example, where the
butyl rubber is either halogenated or non-halogenated, a phenolic cure system may
be employed. In one or more embodiments, these phenolic cure systems include halogenated
and non-halogenated phenolic resins that may be employed in conjunction with a catalyst
or accelerator such as stannous chloride and a metal activator. Useful phenolic
cure systems are disclosed in
U.S. Pat. Nos. 2,972,600
,
3,287,440
,
5,952,425
and
6,437,030
, which are incorporated herein by reference.
In one or more embodiments, phenolic resin curatives include
resole resins, which can be made by the condensation of alkyl substituted phenols
or unsubstituted phenols with aldehydes, preferably formaldehydes, in an alkaline
medium or by condensation of bi-functional phenoldialcohols. The alkyl substituents
of the alkyl substituted phenols may contain 1 to about 10 carbon atoms. Dimethylolphenols
or phenolic resins, substituted in para-positions with alkyl groups containing 1
to about 10 carbon atoms are preferred. In one embodiment, a blend of octyl phenol
and nonylphenol-formaldehyde resins are employed. The blend includes from about
25 to about 40% by weight octyl phenol and from about 75 to about 60% by weight
nonylphenol, more preferably, the blend includes from about 30 to about 35 weight
percent octyl phenol and from about 70 to about 65 weight percent nonylphenol. In
one embodiment, the blend includes about 33% by weight octylphenol-formaldehyde
and about 67% by weight nonylphenol formaldehyde resin, where each of the octylphenol
and nonylphenol include methylol groups. This blend can be solubilized in paraffinic
oil at about 30% solids.
Useful phenolic resins may be obtained under the tradenames
SP-1044, SP-1045 (Schenectady International; Schenectady, N.Y.), which may be referred
to as alkylphenol-formaldehyde resins. SP-1045 is believed to be an octylphenol-formaldehyde
resin that contains methylol groups. The SP-1044 and SP-1045 resins are believed
to be essentially free of halogen substituents or residual halogen compounds. By
essentially free of halogen substituents, it is meant that the synthesis of the
resin provides for a non-halogenated resin that may only contain trace amounts of
halogen containing compounds.
An example of a phenolic resin curative includes that defined
according to the general formula:
where Q is a divalent radical selected from the group consisting
of --CH2--, --CH2--O--CH2--; m is zero or a positive
integer from 1 to 20 and R' is an organic group. In one embodiment, Q is the divalent
radical-CH2--O--CH2--, m is zero or a positive integer from
1 to 10, and R' is an organic group having less than 20 carbon atoms. In other embodiments,
m is zero or a positive integer from 1 to 5 and R' is an organic radical having
between 4 and 12 carbon atoms.
The stannous chloride can be used in its hydrous (SnCl2·H2O)
or anhydrous (SnCl2) form. The stannous chloride can be used in a powdered,
granulated, or flake form. In one embodiment, metal oxide or acid reducing compound
includes zinc oxide.
Where the butyl rubber includes a vinyl, carboxyl, or carbonyl
functional group, a silicon-hydride containing cure system may be employed. For
example, polysiloxanes including active silicon hydride groups can be employed in
conjunction with a catalyst system such as a platinum catalyst system.
In one or more embodiments, useful silicon-containing cure
systems include silicon hydride compounds having at least two SiH groups. Silicon
hydride compounds that are useful in practicing the present invention include, but
are not limited to, methylhydrogen polysiloxanes, methylhydrogen dimethyl-siloxane
copolymers, alkyl methyl polysiloxanes, bis(dimethylsilyl)alkanes, bis(dimethylsilyl)benzene,
and mixtures thereof.
Useful catalysts for hydrosilation include, but are not
limited to, peroxide catalysts and catalysts including transition metals of Group
VIII. These metals include, but are not limited to, palladium, rhodium, and platinum,
as well as complexes of these metals. Useful silicon-containing curatives and cure
systems are disclosed in
U.S. Pat. No. 5,936,028
, which is incorporated herein by reference for purpose of U.S. patent
practice.
Where a halogenated butyl rubber is used, useful cure systems
include (i) zinc oxide, which may be used with an optional accelerator or (ii) an
amine, which may be used with an optional catalyst. These cure systems are described
in
U.S. Pat. Nos. 5,013,793
,
5,100,947
,
5,021,500
,
5,100,947
,
4,978,714
, and
4,810,752
, which are incorporated herein by reference.
Useful accelerators that may be used in conjunction with
the zinc oxide include carboxylic acids, carboxylates, maleimides, dithiocarbamates,
thiurams, thioureas, and mixtures thereof. Exemplary carboxylic acids include fatty
acids such as stearic acid. Exemplary carboxylates include salts of fatty acids
such as zinc stearate. Exemplary maleimides include bismaleimides such m-phenylene
bismaleimide (4,4'-m-phenylene bismaleimide), 4,4'-vinylenediphenyl bismaleimide,
p-phenylene bismaleimide, 4,4'-sulfonyldiphenyl bismaleimide, 2,2'-dithiodiphenyl
bismaleimide, 4,4'-ethylene-bis-oxophenyl bismaleimide, 3,3'-dichloro-4, 4'-biphenyl
bismaleimide, o-phenylene bismaleimide, m-phenylene bismaleimide (HVA-2), hexamethylene
bismaleimide, and 3,6-durine bismaleimides. Exemplary dithiocarbamates, thiurams,
and thioureas include 2,6-di-tert-butyl-para-cresol; N,N'-diethylthiourea; di-ortho-tolylguanidine;
dipentamethylene thiuram tetrasulfide; ethylene trithiocarbonate; 2-mercaptobenzothiazole;
benzothiazole disulfide; N-phenyl -beta-naphthylamine; tetramethyl thiuram disulfide,
zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, and zinc dimethyldithiocarbamate.
Useful amines include multi-functional amines, especially
blocked or hindered diamines. Exemplary hindered amines include hexamethylene diamine
carbamate, which is a blocked diamine having carbon dioxide blocking the amine function
to form a carbamate. This diamine is commercially available under the tradename
DIAK (DuPont Company). Useful catalysts that may be used in conjunction with the
amines include organic acids and salts thereof as well as metal hydroxides, especially
Group I and Group II hydroxides. The organic acids include dicarboxylic acids. Exemplary
carboxylic acids include stearic acid. Preferred salts of organic acids include
zinc stearate. In one embodiment metal hydroxides include Mg(OH)2.
The skilled artisan will be able to readily determine a
sufficient or effective amount of vulcanizing agent to be employed without undue
calculation or experimentation.
Despite the fact that the rubber may be partially or fully
cured, thermoplastic vulcanizates can be processed and reprocessed by conventional
plastic processing techniques such as extrusion, injection molding, blow molding,
and compression molding. In one or more embodiments, the butyl rubber within these
thermoplastic elastomers can be in the form of finely-divided and well-dispersed
particles of vulcanized or butyl rubber within a continuous thermoplastic phase
or matrix. In other embodiments, a co-continuous morphology or a phase inversion
can be achieved. In those embodiments where the cured rubber is in the form of finely-divided
and well-dispersed particles within the thermoplastic medium, the rubber particles
can have an average diameter that is less than 50 µm, optionally less than
30 µm, optionally less than 10 µm, optionally less than 5 µm, and
optionally less than 1 µm. In certain embodiments, at least 50%, optionally
at least 60%, and optionally at least 75% of the particles have an average diameter
of less than 5 µm, optionally less than 2 µm, and optionally less than
1 µm.
The present invention is not limited to the selection or
fabrication of any particular configuration for the article for sealing a container,
or by the container with which the article is employed. In one or more embodiments,
the sealing article may include a single component, solid structure including the
thermoplastic vulcanizate. In other embodiments, the article may include a multicomponent
structure where at least one of the components includes the thermoplastic vulcanizate.
In one or more embodiments, the shape of the article according to the present invention
can be generally cylindrical in nature including conical and frustoconical (i.e.,
frustums) shapes.
One embodiment of a stopper according to the present invention
can be described with reference to Fig. 1. Stopper 10, which may also be referred
to as sealing article 10, includes top surface 12, bottom surface 14, and frustoconical
side wall 16. In one or more embodiments, the stopper can be employed in conjunction
with container 20, which may include cylindrical side wall 22. Stopper 10 can seal
container 20 by inserting stopper 10 into opening 24 of container 20. Inasmuch as
the contact surface 18 of frustoconical side wall 16 may include the thermoplastic
vulcanizates of this invention, application of pressure to top surface 12 in a direction
perpendicular to opening 24 of container 20 will cause frustoconical side wall 16
to contact the inner wall 26 of container 20, which will in turn cause frustoconical
surface 16 to compress and thereby secure stopper 10 into container 20 and seal
the contents thereof. Inasmuch as the physical and dynamic properties of the thermoplastic
vulcanizate employed to fabricate stopper 10 are advantageous in this application
or use, in one or more embodiments, stopper 10 can be removed from container 20
and be reused.
In one or more embodiments, the physical characteristics
of the thermoplastic vulcanizates employed to fabricate stopper 10 advantageously
allow for the removal of at least a portion of the contents of container 20 by penetrating
through stopper 10. For example, a conventional hypodermic needle 30 can be employed
by inserting needle 32 into top surface 12 and through lower surface 14 to access
the contents (e.g., fluids) within container 20. The contents of container 20 can
be drawn into hypodermic needle 30 using conventional procedures, and the needle
can be withdrawn from stopper 10. Advantageously, the use of the thermoplastic vulcanizates
of one or more embodiments of this invention in the fabrication of stopper 10 will
allow for the resealing or closure of the hole caused by insertion of needle 32
into stopper 10 upon removal of needle 32.
Another embodiment of the present invention can be described
with reference to Fig. 2. Multi-component stopper 40, which may also be referred
to as sealing article 40, includes top surface 42, bottom surface 44, and frustoconical
sidewall 46. Stopper 40 includes a layered structure including first layer or top
layer 48, second or middle layer 50, and third or bottom layer 52. In one or more
embodiments, at least one of top layer 48, bottom layer 52, or in certain embodiments
both top layer 48 and bottom layer 52, include the thermoplastic vulcanizates described
herein, which include butyl rubber, thermoplastic polyurethane, and synthetic oil.
Second or middle layer 50 includes a thermoset rubber or thermoplastic vulcanizate
that may have characteristics that are distinct from the thermoplastic vulcanizate
of the top layer 48 or bottom layer 52. In one or more embodiments, the characteristics
of middle layer 50 may be characterized by one or more properties that are not as
advantageous as the properties of the thermoplastic vulcanizate of the top layer
48 or bottom layer 52. In other embodiments, certain properties of the middle layer
50 may be superior to the properties of the top layer 48 or bottom layer 52 (e.g.,
superior compression set).
In one or more embodiments, top layer 48 can be at least
0.05 mm thick, in other embodiments at least 0.1 mm thick, and in other embodiments
from about 1 to about 5 mm thick. In one or more embodiments, middle layer 50 can
be at least 0.05 mm thick, in other embodiments at least 0.1 mm thick, and in other
embodiments from about 1 to about 5 mm thick. In one or more embodiments, bottom
layer 52 can be at least 0.05 mm thick, in other embodiments at least 0.1 mm thick,
and in other embodiments from about 1 to about 5 mm thick.
As a result of this configuration, the stopper of one or
more embodiments may advantageously demonstrate low oxygen permeability and good
coring properties deriving from the thermoplastic vulcanizates of the top and/or
bottom layers 48 and 52, and may advantageously exhibit technologically useful sealability
to containers or the like deriving at least in part from the optional low compression
set of middle layer 50. In one or more embodiments, technologically useful seal
or sealability includes advantageous oxygen permeability or lack thereof advantageous
liquid permeability or lack thereof, a combination thereof, or in certain embodiments
a hermetic seal.
Yet another embodiment of a stopper according to the present
invention can be described with reference to Fig. 3. Sealing article 60, which may
also be referred to as cap 60, includes a sheet 62 fastened over opening 24 of container
20. Sheet 62, which includes the thermoplastic vulcanizate employed in the previous
embodiments, can be fastened or secured to container 20 by employing a variety of
fastening devices. For example, as shown in Fig. 3, a fastening band 64 secures
sheet 62 to container 20, thereby sealing the contents thereof. In one embodiment,
fastening band 64 includes a metal band that is crimped to secure sheet 62 to container
20.
In one or more embodiments, sheet 62 includes a die-cut
sheet of thermoplastic vulcanizate having a thickness of from about 1 to about 10
mm, in other embodiments from about 1.5 to about 7 mm, and in other embodiments
from about 2 to about 5 mm. In one or more embodiments, the die-cut sheet is circular
in configuration, thereby allowing the sheet to be easily secured over a container
opening that is generally round in configuration. As those skilled in the art will
appreciate, other configurations can be die cut, thereby allowing for facile application
to a variety of container opening.
In one or more embodiments, the sealing articles of this
invention, or a member thereof, can advantageously be fabricated by employing injection
molding processes. In general, these processes include heating the thermoplastic
vulcanizate to a temperature that is equal to or in excess of the melt temperature
of the thermoplastic polyurethane resin to form a pre-form, forming the pre-form
within a mold to form a molded part, cooling the molded part to a temperature at
or below the crystallization temperature of the thermoplastic vulcanizate, and releasing
the molded part from a mold. In one or more embodiments, a melt of thermoplastic
vulcanizate is injected from a reservoir through a runner into a cavity within a
closed split mold. The mold cavity defines the shape of the molded part (e.g., stopper).
The molded part is cooled within the mold at a temperature at or below the crystallization
temperature of the thermoplastic vulcanizate, and the molded part can subsequently
be injected from the mold.
In other embodiments, particularly where the sealing articles
are configured as a sheet that can be fastened to a container, the sheet can be
fabricated by extruding a sheet of desired thickness and subsequently die cutting
a seal or cap of desired configuration. The seal can then be positioned over an
opening of a container, and fastened thereto. For example, a metal band can be positioned
circumferentially around the outside of a circular opening in a container while
maintaining at least a portion of the sheet between the container and the band.
The metal band can then be secured to the container by employing techniques such
as crimping. Other methods of securing a fastening article can be used such as an
adjustable ring clamp or a crimped aluminum ring.
In certain embodiments, more than one type of sealing device
can be employed to seal a container. For example, a stopper device 10 can be inserted
into an opening of a container 20, and then a seal 62 can be placed over the container
and fastened thereto.
The thermoplastic vulcanizates employed in the fabrication
of sealing articles according to the present invention are advantageous in several
respects. In one respect, the thermoplastic vulcanizates of one or more embodiments
exhibit sufficient flow properties so that the thermoplastic vulcanizates are technologically
useful in injection molding processes. For example, the thermoplastic vulcanizates
of one or more embodiments of this invention are characterized by LCR viscosity
of less than 200 Pa@1,200s-1, and in other embodiments less than 150
Pa@1,200s-1, and in other embodiments less than 100 Pa@1,200s-1,
where LCR viscosity is measured by with a Dynisco™ capillary rheometer at
30:1 aspect ratio at 1,200 S-1 @204°C. In these or other embodiments,
the thermoplastic vulcanizates of one or more embodiments can also be characterized
by an ACR viscosity of less than 4,500 poise, in other embodiments less than 4,000
poise, and in other embodiments less than 3,000 poise, where the ACR viscosity measured
by using an automated capillary rheometer that was equipped with a number AX150
33/1 L/D ratio, 0.031 diameter orifice, at 204°C and 118 KPa.
The thermoplastic vulcanizates of one or more embodiments
are also advantageous inasmuch as they are characterized by low oxygen permeability.
In one or more embodiments, the thermoplastic vulcanizates are characterized by
an oxygen permeability of less than 600 cc/m·m·day, in other embodiments
less than 550 cc/m.m.day, and in other embodiments less than 500 cc/m·m·day
when measured according to ASTM D1434.
The thermoplastic vulcanizates of one or more embodiments
are also characterized by an advantageously low compression set. In one or more
embodiments, the thermoplastic vulcanizates exhibit a compression set of less than
40%, in other embodiments less than 30%, and in other embodiments less than 20%
where the compression set is measured by ASTM D-395B
Furthermore, the thermoplastic vulcanizates of one or more
embodiments are also characterized by an advantageous coreability. In one or more
embodiments, this coreability is characterized by less than 5, in other embodiments
less than 3, and in other embodiments less than 2 cores per 100 punctures when a
disk of thermoplastic vulcanizate measuring about 2 millimeters thick is crimped
to a 10 cc vile and subject to puncture by a 20 gage hypodermic syringe needle at
a 90° angle to displace about 1-2 ml of water into the vile followed by removal
of the needle from the stopper; this step is repeated five times on each of 20 files
using care not to insert the needle at the same point more than once; after each
of the stoppers is punctured five times, the total number of cores are counted.
The needles were replaced after 25 punctures. For purposes of this specification,
this test will refer to the "coreability" of the thermoplastic vulcanizate or sealing
device.
The articles for sealing containers according to the present
invention can be used in conjunction with a multitude of containers. These containers
may include, but are not limited to, bottles, vials, test tubes, beakers, medical
containers, and blood sampling containers. These containers include those conventional
in the art including those fabricated of glass, polyethylene terephthalate, polycarbonate,
various multi-layered or laminate composites, and the like.
Articles of the present invention are particularly advantageous
when employed in combination with containers whose contents are oxygen sensitive.
In these or other embodiments, the articles of this invention are advantageous with
containers whose contents are desirably accessed by precision metering devices such
as syringes or hypodermic needles. In one or more embodiments, the contents of these
containers include medical fluids including, but not limited to, blood, other bodily
fluids, saline, and medications.
In order to demonstrate the practice of the present invention,
the following examples have been prepared and tested. The examples should not, however,
be viewed as limiting the scope of the invention. The claims will serve to define
the invention.
EXAMPLES
Samples 1-4
Four thermoplastic vulcanizates were prepared and tested
for various properties. These thermoplastic vulcanizates were prepared by employing
conventional techniques within a Brabender mixer. The following ingredients were
used in each sample. The ingredients optionally included 100 parts by weight butyl
rubber, 10 parts by weight clay, 6 parts by weight silicon hydride, and 10 parts
by weight platinum catalyst mixture. The ingredients also included, as specified
in Table I, polypropylene, thermoplastic polyurethane, compatibilizer, and synthetic
oil. The polypropylene was characterized by a melt flow index of 750. Thermoplastic
polyurethane I was a polyester-based TPU having a Shore A of about 85, and was obtained
under the tradename TEXIN™ 285. Thermoplastic polyurethane II was characterized
as a polyether-based resin having a Shore A of about 86 and was obtained under the
tradename TEXIN™ 985. The maleated polypropylene had an MFR of about 5, and
was obtained under the tradename FUSABOND™ 353D (DuPont). The SEPS copolymer
was a hydrogenated styrene-isoprene-styrene block copolymer and was obtained under
the tradename SEPTON™ 2002 (Kurraray). The synthetic oil was characterized
by a molecular weight of 950, and was obtained under the tradename PARAPOL™
950 (ExxonMobil). The butyl rubber was characterized by a Mooney Viscosity (ML1+4@100°C)
of about 51, and was obtained under the tradename BUTYL XL™ 10,000 (Polysar).
The clay was obtained under the tradename ICECAP™ K. The silicon hydride
was a polysiloxane with silicon hydride functionality. The catalyst mixture included
0.0055 parts by weight platinum catalyst and 2.49 parts by weight mineral oil.
TABLE I
AES
#
322-1
322- 2
322- 4
322-5
Sample
1
2
3
4
Polypropylene
40
---
---
---
Thermoplastic
Polyurethane I
---
25
---
---
Thermoplastic
Polyurethane II
---
---
25
25
Maleated
Polypropylene
---
15
15
15
SEPS
Copolymer
---
---
---
20
Synthetic
Oil
40
40
40
40
Properties
Shore A Hardness
63
42
32
35
Ultimate Tensile Strength
(psi)
709
541
296
274
Modulus @100 (psi)
375
237
158
149
Elongation @ Break
(%)
275
255
234
345
Tension Set (%)
11
8
8
7
Compression Set @
22hr., 100°C
33.8
38.8
44.3
35.8
Shore hardness was determined according to ASTM ISO 868.
Ultimate tensile strength, ultimate elongation, and 100% modulus were determined
according to ASTM D-412 at 23EC by using an Instron testing machine. Tension set
was determined according to ASTM D-142. Compression Set was determined according
to ASTM D-395B. LCR Viscosity is measured with a Dynisco™ Capillary rheometer
at 30:1 L/D (length/diameter) at 1200s-1 at 204°C.
The data in Table I demonstrates that the use of a thermoplastic
polyurethane in lieu of a thermoplastic resin such as polypropylene allows for the
formation of softer thermoplastic vulcanizates, which is advantageous because softer
thermoplastic vulcanizates allow for the manufacture of flexible stoppers with good
sealability.
Samples 5-9
Five additional thermoplastic vulcanizates were prepared
and tested in a similar fashion to Samples 1-4, except that a different butyl rubber
was employed, as well as a distinct cure system. Specifically, the ingredients employed
included 100 parts by weight butyl rubber, 10 parts by weight clay, 4 parts by weight
zinc oxide, and 2 parts by weight zinc dibutyldithiocarbamate. Additionally, the
ingredients optionally included, as set forth in Table II, polypropylene, thermoplastic
polyurethane, a compatibilizer (maleated polypropylene or SEPS copolymer), and synthetic
oil. The chlorobutyl rubber was characterized by a Mooney viscosity (ML1+4@100°C)
of about 50, and was obtained under the tradename CHLOROBUTYL™ 168. The zinc
dibutyldithiocarbamate was obtained under the tradename BUTYL ZIMATE (Vanderbilt).
All other ingredients were similar to those employed in Samples 1-4.
TABLE II
AES #
326-1
326-2
326-3
326-4
326-5
Sample
5
6
7
8
9
Polypropylene
40
20
---
---
---
Thermoplastic
Polyurethane II
---
25
25
25
25
Maleated
Polypropylene
---
15
15
15
15
SEPS
Copolymer
---
---
---
---
20
Synthetic
Oil
40
---
40
---
---
Properties
Shore A Hardness
56.5
67
29.5
35
42
Ultimate Tensile Strength
(psi)
600
616
220
308
455
Modulus @100 (psi)
220
496
130
170
230
Elongation @ Break
(%)
327
170
227
230
240
Tension Set (%)
10
12
7
8
6
Compression Set @
22hr., 100°C
35
39.4
27
41.4
30.2
The data in Table II shows that thermoplastic vulcanizates
according to the present invention can be fabricated using different forms of butyl
rubber. Namely, the results obtained using chlorobutyl rubber were as advantageous
as Samples 1-4.
Samples 10-19
In a similar fashion to the previous samples, ten thermoplastic
vulcanizates were prepared by employing yet another butyl rubber. Specifically,
the ingredients included 100 parts by weight butyl rubber, 10 parts by weight clay,
4 parts by weight zinc oxide, and 2 parts by weight butyl Zimate. Additionally,
the ingredients optionally included, as set forth in Table III, thermoplastic polyurethane,
polypropylene, and an SEPS copolymer. The butyl rubber was characterized by a Mooney
Viscosity (ML1+8@125°C) of 50 and included about 2% bromine and
about 7.5% mer units deriving from paramethylstyrene, and was obtained under the
tradename EXXPRO™ 3745. Thermoplastic polyurethane III was a polyether based
TPU having a Shore D of about 50, and was obtained under the tradename TEXIN™
945.
TABLE III
AES#
336-1
336- 2
336- 3
336- 4
336-5
336- 6
336-7
336- 8
336- 9
336-10
Sample
10
11
12
13
14
15
16
17
18
19
Polypropylene
---
---
---
---
---
---
20
20
---
---
Thermoplastic
Polyurethane I
---
40
---
60
---
80
---
40
---
---
Thermoplastic
Polyurethane II
40
---
60
---
80
---
40
---
40
---
Thermoplastic
Polyurethane III
---
---
---
---
---
---
---
---
---
60
---
---
---
---
---
---
---
---
20
---
Properties
Shore A Hardness
38
34
49.5
47
51.5
57
59
59
51
63
Ultimate Tensile Strength
(psi)
250
352
623
637
362
520
800
827
396
796
Modulus @100 (psi)
115
181
190
228
158
205
223
252
284
188
Elongation @ Break
(%)
200
225
359
316
291
357
421
418
216
577
Tension Set (%)
Broke
6
8
8
Broke
14
8
9
8
9
Compression Set @
22hr., 100°C
42.6
21.5
53.6
54.5
81.3
55.8
62.2
61.6
60.6
61.8
As with the previous samples, the data in Table III shows
that useful thermoplastic vulcanizates can be prepared with the use of yet another
butyl rubber. Also, the data shows that this particular butyl rubber can advantageously
be employed in the absence of a compatibilizer.
Samples 20 and 21
As with the previous sample, two additional thermoplastic
vulcanizates were prepared and tested. The butyl rubber was similar to that employed
in Samples 1-4 (i.e., BUTYL™ XL 10,000). The ingredients include 100
parts by weight butyl rubber, 10 parts by weight clay, 10 parts by weight catalyst
mixture, 3 parts by weight silicon hydride, 20 parts by weight SEPS copolymer, and
35 parts by weight synthetic oil. The catalyst mixture, silicon hydride, and SEPS
copolymer were similar to those employed in the previous samples. The synthetic
oil was obtained under the tradename INDOPOL™ H100.
TABLE IV
AES#
3163
3165
Samples
20
21
Polypropylene
30
0
Thermoplastic
Polyurethane II
---
35
Maleated
Polypropylene
---
15
Properties
Shore A Hardness
60
43.5
Ultimate Tensile Strength
(psi)
454
226
Ultimate Elongation
329
283
Modulus @100 (psi)
242
137
LCR
97
---
Compression Set, 22hr
@ 23°C
28.3
19.6
Moisture Vapor Transmission,
(g/m*m*day)
0.56
1.4
Oxygen Permeability
(cc/ m*m*day)
424
504
Core Test (cores/100)
7
2
JP Pharma. Testing
Foaming visual
Pass
Pass
UV-22
0.049
0.003
UV-23 @ 430 nm
99.7
99.9
UV-23 @ 650 nm
100
99.9
Titrate 11
1.1
1.2
pH 14
-0.1
-0.4
Total Solids
0.5
0.2
The Moisture Vapor Transmission test was performed according
to ASTM F1249, and the Oxygen Permeability Test was performed according to ASTM
D-1434. The Japan Pharmacopoeia Testing which analyzes the degree of migration from
the thermoplastic vulcanizate.
The data in Table IV demonstrates that thermoplastic vulcanizates
prepared according to the present invention (i.e., Sample 21) exhibit superior
coring and mechanical properties over those thermoplastic vulcanizates prepared
using polypropylene while the oxygen permeability and migration of constituents
from the thermoplastic vulcanizate are comparable to those of polypropylene.
Various modifications and alterations that do not depart
from the scope and spirit of this invention will become apparent to those skilled
in the art. This invention is not to be duly limited to the illustrative embodiments
set forth herein.