ARTICLES ELASTOMERES FABRIQUES A PARTIR D'UN MELANGE DE CHLOROPRENE ET D'ACRYLONITRILE

ELASTOMERIC ARTICLES FROM A BLEND OF POLYCHLOROPRENE AND ACRYLONITRILE

Abrégé français

L'invention concerne des articles élastomères profilés, par exemple des gants, des préservatifs, et des sacs respiratoires, préparés à partir d'une composition mélangée de polymères. Cette composition renferment environ entre 10 et 90 parties en poids d'un polymère de chloroprène, et environ entre 10 et 90 parties en poids d'un polymère de nitrile, sur la base de 100 parties en poids du polymère total. Une fois durci, cet article présente une épaisseur variant entre 0,05 et 50 mils, une résistance à la traction d'au moins 9 MPA, et une élongation atteignant au moins 300 %. Lorsque cet article est étiré pour venir s'ajuster sur un membre du corps humain, par exemple la main, il exerce une pression initiale avant de se relâcher de manière à exercer une pression réduite, qui atteint au moins 50 % de ladite pression initiale. Cette invention concerne également un mélange de chloroprène et de nitrile, permettant de produire des articles provoquant une sensation et une fonctionnalité équivalente ou similaire à celles d'un gant classique en latex de caoutchouc naturel. Ces articles donnent donc une sensation équivalente ou meilleure que les gants en vinyle ou en nitrile actuellement disponibles.

Abrégé anglais

Shaped elastomeric articles such as gloves, condoms and breather bags, are
prepared from a polymer blend composition comprising about 10 to about 90
parts by weight of a chloroprene polymer and about 10 to about 90 parts by
weight of a nitrile polymer, based on 100 parts by weight of total polymer.
The cured article has a thickness of 0.05 to 50 mils, a tensile strength of at
least 9 MPA and an elongation of at least 300 %. The article, when stretched
to fit over a human body member such as a hand, exerts an initial pressure,
but thereafter relaxes to exert a reduced pressure which is no less than 50 %
of the initial pressure. This invention provides a blend of a polychloroprene
and a nitrile polymer that yields products of equivalent or similar feel and
functionality compared to the common natural rubber latex glove. These
products provide equal or better feel than nitrile or vinyl gloves currently
available.

Revendications

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What is Claimed is:
1. A polymer blend composition comprising:
(I) about 10 to about 90 parts by weight of a chloroprene polymer and
(II) about 10 to about 90 parts by weight of an acrylonitrile copolymer
wherein
said acrylonitrile copolymer is a carboxylated copolymer of acrylonitrile and
butadiene;
said blend further comprising at least one crosslinking agent and at least
one vulcanization accelerator;
said blend being curable to an elastomer in film form having a tensile
strength of at least 9 MPA and an elongation of at least 300%.
2. A polymer blend composition according to claim 1, wherein
said composition comprises about 25 to about 75 parts by weight of said
chloroprene polymer and about 25 to about 75 parts by weight of said
acrylonitrile polymer.
3. A polymer blend according to claim 1, wherein said composition
comprises about 40 to about 75 parts by weight of said chloroprene polymer and
about 25 to about 60 parts by weight of said acrylonitrile polymer.
4. A polymer blend composition according to claim 1, wherein
said chloroprene polymer is polychloroprene or a copolymer of monomers
comprising
(a) 2-chloro-1,3-butadiene and
(b) at least one monomer selected from the group consisting of
2,3-dichloro-1,3-butadiene, 2,3-dibromo-1,3-butadiene,
2-chloro-3-bromo-1,3-butadiene, 2-bromo-3-chloro-1,3-butadiene and
1,3-butadiene.
5. A polymer blend composition according to claim 1, wherein said
chloroprene polymer is polychloroprene or a copolymer of monomers comprising
(a) 2-chloro-1,3-butadiene and
(b) at least one monomer selected from the group consisting of
2,3-dichloro-1,3-butadiene, 2,3-dibromo-1,3-butadiene,
2-chloro-3-bromo-1,3-butadiene, 2-bromo-3-chloro-1,3-butadiene, and 1,3-

10
butadiene and said acrylonitrile copolymer is a carboxylated copolymer of
acrylonitrile and butadiene.
6. A vulcanizate of a composition according to claim 1.
7. A vulcanizate according to claim 8, said vulcanizate being in the form of a
film.
8. A vulcanizate according to claim 9, wherein said film has a thickness from
0.05 to 50 mils.
9. A vulcanizate according to claim 10, wherein said film has a thickness
from 0.1 to 20 mils.
10. A vulcanizate according to claim 10, wherein said film has a tensile
strength of at least 9 MPA and an elongation of at least 300%.
11. A vulcanizate according to claim 12, wherein said film has a tensile
strength of at least 12.5 MPA and an elongation of at least 500%.
12. A shaped elastomeric article comprising a layer of elastomeric material
(a)
comprising a cured polymer blend composition, wherein said polymer blend
composition prior to curing comprises about 10 to about 90 parts by weight of
a
chloroprene polymer and about 10 to about 90 parts by weight of a
acrylonitrile
copolymer polymer, based on 100 parts by weight of polymer, and (b) has a
tensile strength greater than 9 MPA and an elongation greater than 300%.
Wherein said acrylonitrile copolymer is a carboxylated acrylontirle-butadene
copolymer.
13. A shaped elastomeric article according to claim 14, wherein said polymer
blend composition prior to curing comprises about 20 to about 85 parts by
weight
of said chloroprene polymer and about 15 to about 80 parts by weight of said
acrylonitrile polymer.
14. A shaped elastomeric article according to claim 14, wherein said polymer
blend comprises about 40 to about 75 parts by weight of said chloroprene
polymer and about 25 to about 60 parts by weight of said acrylonitrile
polymer.
15. A shaped elastomeric article according to claim 14, wherein said tensile
strength is greater than 12.5 MPA and said elongation is greater than 500%.

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16. A shaped elastomeric article according to claim 14, wherein further said
layer of elastomeric material (c) is substantially impermeable to water and
water
vapor, (d) has a thickness such that it is capable of being stretched to fit
securely
about a human body member and to conform to the configuration of said human
body member, thereby exerting an initial pressure on said human body member,
and then relaxing to exert on said body member a reduced pressure, greater
than 60% of said initial pressure one minute, after being stretched and
greater
than 50% of said initial pressure ten minutes after being stretched.
17. A shaped elastomeric article according to claim 20, said layer having a
thickness from about 0.05 to about 50 mils.
18. A shaped elastomeric article according to claim 20, said layer having a
thickness from about 0.1 to about 20 mils.
19. A shaped article according to claim 20, said article being a glove.
20. A shaped article according to claim 20, said article being a condom.
21. A shaped article according to claim 20, said article being a breather bag.

Description

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ELASTOMERIC ARTICLES FROM A BLEND
OF POLYCHLOROPRENE AND ACRYLONITRILE
Field of the Invention
This invention relates to shaped elastomeric articles, in particular to
gloves, condoms and breather bags, and to polymer blends and polymer blend
compositions usefull in the preparation of such articles.
Background of the Invention
Elastomeric examination and surgeon's gloves as well as condoms and
breather bags, dipped products (i.e., finger cots, catheters, balloons) and
cast
products (i.e., tourniquets, sheeting) are currently made from several
different
polymers. Non-natural rubber latex products have been developed to address
the issues related to natural rubber latex allergy. These current materials
lack
the appropriate properties necessary to serve as a suitable substitute for
natural
rubber latex. In addition, individual polymers have specific chemical
compatibility
problems that limit l:heir application in broad markets including health care,
laboratory, emergency medical services and food handling.
One such surgical glove is that described in U.S. Patent No. 5,014,362 to
Tillotson et al. and 'in Re. 3.5,616, which is a reissue of U.S. Patent No.
5,014,362. The glove described therein is a nitrite elastomer glove. More
precisely, "nitrite elastomer" is a carboxylated nitrite-butadiene elastomer.
The
material of the Tillotson glove has a relatively low resilience; when a glove
made
of such material is stretched, the stress (i.e., pressure or force per unit
area)
exerted by the material quickly drops from its initial value. In other words,
the
material has a high permanent set.
a
This invention provides a blend of a polychloroprene and a nitrite polymer
that yields products of equivalent or similar feel and functionality compared
to the
common natural n:bber latex glove. These products provide equal or better
feel,
comfort and fit than nitrite or vinyl gloves currently available.

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The invention further provides elastomeric films and shaped articles in film
form, which are obtainable from the foregoing polymer blends on vulcanization
or
curing. Preferred shaped articles include gloves, condoms and breather bags
and other dipped products.
The polychloroprene and nitrite blended gloves, condoms and breathing
bags of the invention are made from synthetic elastomers and are free of
allergenic latex proteins. They are made using processes similar to current
manufacturing processes and techniques. The products are resistant to oxygen
and ozone. Such blends yield films that have greater elongation and quicker
film
rebound compared to the current nitrite or vinyl products available. The blend
is
also softer at lower temperatures compared to current nitrite products
available.
The blend is more gasoline and oil resistant than current polychloroprene
products available. It is also less permeable to gases than current natural
rubber
latex products available.
Tactile and physical properties of elastomers and gloves of this invention
are similar to those: of natural rubber latex and are better than those of
other
latex derived synthetic elastomers. Materials and articles of this invention
have
good chemical and puncture resistance, similar to those of other synthetic
materials and bettE:r than those of natural rubber latex. In essence,
materials
and articles of this invention have all of the benefits of synthetic
materials, and
articles, e.g., good chemical resistance, good puncture resistance and no
known
allergens, and yet feel like natural rubber latex. Materials and articles such
as
gloves of this invention maintain a greater percentage of initial stress over
time
than do nitrite elastomers and articles made therefrom. In other words, they
undergo less relaxation. Nitrite elastomers have a high modulus and lower
elasticity so that gloves made therefrom may cause hand fatigue, in contrast,
gloves made from elastomers of this invention minimize hand fatigue. Nitrite
elastomers also have a permanent set, so that the materials loses resiliency
and
elasticity the longer it is stretched. Materials of this invention are more
like
natural rubber latex than nitrite elastomers in this regard. Another advantage
is

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that materials and gloves of this invention have no unpleasant odor, while
nitrite
gloves have an unpleasant odor which may bother both users and patients (e.g.,
dental patients).
Brief jZescri tion of the Drawinos
The objects and advantages of the invention will become apparent upon a
further reading of the detailed description of the preferred embodiments in
conjunction with the figures, wherein:
Fig. 1 is a graph comparing relaxation of stress over time in an elastomer
latex material of this invention with prior art elastomer latex materials.
Fig. 2 is a bar graph showing puncture resistance in an elastomer latex
material of this invention and in prior art elastomer latex materials.
The invention comprises elastomeric articles, in particular gloves,
condoms and breathing bags constructed from a polychloroprene (or chloroprene
polymer) and an ac;rylonitrile copolymer. The terms "polychloroprene" and
"chloroprene polymer" are used herein to denote both poly(2-chloro-1,3-
butadiene) homopolymer and copolymers of said 2-chloro-1;3-butadiene with one
or more additional halogenated monomers. Thus, 2-chloro-1,3-butadiene, which
is also known as chloroprene, may be copolymerized with one or more
monomers selected from the group consisting of 2,3-dichloro-1,3-butadiene or
2,3-dibromo-1,3-butadiene, 2-chloro-3-bromo-3,3-butadiene, 2-bromo-3-chloro-
1,3-butadiene and butadiene. The acrylonitrile copolymer is preferably a
carboxylated copolymer of acrylonitrile and butadiene. However, acrylonitrile-
butadiene copolymers which are not carboxylated are also useful. Carboxylation
is obtained by copolymerization of acrylonitrile and butadiene with a small
amount (typically IE;ss than 10%) of a monomer such as acrylic acid, or
methacrylic acid, or an ester thereof, such as methyl methacrylate.
A polymer blend as herein described, together with additional ingredients
will be described below, is vulcanized or cured to yield an elastomer in film
form.
The total blended, film thickness is about 0.05 - 50 mils., preferably about
0.1-20

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mils. The blended fiilm is characterized as having a tensile strength of at
least
(i.e:, equal to or greater than) 9 MPA, preferably at least 12.5 MPA, and an
elongation equal to or greater than 300%, preferably at least 500%. The
products are further' characterized as having no latex protein allergens, low
modulus, high efon<~ation, good tensile strength, high puncture resistance,
good
UV (ultra-violet) resistance, good chemical resistance, and good film rebound.
The invention also comprises compositions and blending steps useful in
producing blended elastomeric products of the types described above.
A general formula of an unvulcanized or uncured polymer blend
composition according to this invention is set forth in Table 1. Ingredients
other
than the polymer blend shown in Table 1 may be conventional.
TABLE 1
Ingredients Parts per Hundred Rubber
Polymer Blend . 100
Crosslinker ~ 0.05 to 2
Vulcanization Accelerator (primary)0.10 to 10
Vulcanization Accelerator (secondary)0.10 to 10
Antidegradant 0.10 to 15
Pigment 0.01 to 5
pH Stabilizer 0.05 to 5
Surfactant Stabilizer 0.00 to 5
Emulsifying Agent 0.01 to 15
Reinforcing Filler 0.00 to 40
Softener 0.00 to 50
Defoamer 0.00 to 5
Polymer blending takes. place prior to vulcanization.
In the practice of this invention, a dipping form of desired shape is dipped
into either a single polymer blend latex bath containing a polymer blend
composition as shown in Table 1, or into two separate polymer latex dipping
baths, the first containing one of the polymers of the blend (say
pofychloroprene

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copolymer), the second containing the other polymer (say the acrylonitrile
copolymer). The dEaired polymer blend is formed on the dipping form in the
latter case. A single bath is preferred. The dipping form is dipped into a
coagulant bath and dried before it is dipped into a latex bath, whether a
single
5 latex bath or two latex baths are used. The latex coated dipping form may be
dipped into a warm water leach bath if desired. The latex coated dipping form
(or
former) is then heated in an oven to cure the polymer blend latex.
The shape of the dipping form governs the shape of the article obtained.
A glove-shaped dipping form is used to obtain a polymer blend latex glove.
Similarly, a condom-shaped dipping form is used to obtain a condom, and a
breather bag-shapE;d dipping form is used to obtain a breather bag.
Alternatively, films of this invention can be made by casting. Known casting
techniques can be used. -
A polymer blend as shown in Table 1 above may comprise about 10 to
about 90 parts by weight of polychloroprene (homopolymer or copolymer) and
about 10 to 90 parta by weight of acrylonitrile copolymer as described above.
The invention is summarized as an elastomeric film article (such as a
glove) comprising a layer of elastomeric material which is constructed of a
blend
of about 10-90 parts by weight polychloroprene (homopolymer or copolymer) and
about 10-90 parts by weight acrylonitrile copolymer with a tensile strength
greater
than 9 MPA and an elongation greater than 300%. Preferred tensile strength is
at least 12.5 MPA, and preferred elongation is at least 500%.
This layer of elastomeric material is substantially impermeable to water
and water vapor, has a thickness such that it is capable of being stretched to
fit
securely about a human bady member and to conform to the configuration of
said human body member, thereby exerting an initial pressure on said human
body member, and then relaxing to exert on said body member a reduced
pressure, greater than 60°/a of said initial pressure one minute after
being
stretched and greater than 50% of said initial pressure ten minutes after
being
stretched. More particularly, this layer has a thickness from about 0.05 to
about
50 mils., preferably from about 0.1 to 20 mils., and constitutes the entire
thickness of the article.

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More preferably the blend contains about 25-75 parts by weight
polychforoprene and about 25-75 parts by weight acrylonitrile butadiene. More
preferably the polychloroprene may comprise poly(2-chloro-1,3-butadiene) or a
copolymer comprising 2-chloro-1,3-butadiene and one or more of 2,3-dichloro-1,
3-butadiene, 2,3-dibromo-1,3-butadiene, 2-chloro-3-bromo-1,3-butadiene or 2-
bromo-3-chloro-1,3-butadiene, or 1,3-butadiene. The acrylonitrile copolymer
comprises a carboxylated copolymer of acrylonitrile and butadiene.
An elastomeric glove of this invention is characterized as having no latex
protein allergens, law modulus, high elongation, high puncture resistance,
high
cut resistance, good UV (ultra-violet) resistance, good chemical resistance,
and
good film rebound. Elastomeric films, condoms and breather bags possess
these same properties.
Polymer blend elastomers of this invention also exhibit greater oil and
chemical resistance (especially to oils and non-polar hydrocarbons) than
natural
rubber latex and better dexterity compared to nitrite.
An importanir characteristic of elastomeric polymer blend films of this
invention and articles (such as gloves) made therefrom is high stress
retention
{or low relaxation) when subjected to a strain (or deformation) which remains
constant over time. A polymer blend film or article of this invention
maintains
greater than 60% of its initial stress after one minute and greater than 50%
after
10 minutes.
Fig. 1 shows stress retention (as the percentage of initial stress) as a
function of time (in minutes) for a polymer blend elastomer of this invention
(denoted "NeoPro" in Fig. 1 ) and prior art elastomers, i.e., nitrite, vinyl
and natural
rubber latex. As Fig. 1 shows, the elastomer of this invention (NeoPro) had
better stress retention than either of the other synthetic polymers. Only
natural
rubber latex exhibii:ed better stress retention. Disadvantages of natural
rubber
latex, including allergenic tendencies, lower puncture resistance and lower
oil
resistance are well known.
Fig. 2 shows puncture resistance in polymer blend elastomers of this
invention (denoted "NeoPro") and in selected prior art elastomers, i.e.,
vinyl,
natural rubber late;~c and nitrite. Puncture resistance of polymer blend
elastomers

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of this invention and of nitrite elastomers are nearly equal. Both have far
better
puncture resistance than either vinyl or natural rubber latex.
Exa~paple of Best Mode Known to Anolicant
Gloves can be made as follows. A latex material having the formula set
forth in Table 2 is prepared. The referenced Parts Per Hundred Rubber (phr)
are
by weight and are based on dry material. Often, the material is in liquid form
at
various solid percentages by weight. The sulfur is a crosslinker, the zinc
dibutyl
dithiocarbamate is an accelerator, the zinc oxide is an accelerator and cure
agent, the phenolic antioxidant is an antidegradant, the potassium hydroxide
is a
pH stabilizer, the stabilizing surfactant is a stabilizer and wetting agent,
and the
paraffin wax is a softener.
Clean porcelain formers are dipped into a coagulant comprising a mixture
of calcium salts (i.e.., calcium nitrate, calcium chloride), water and non-
ionic
surfactant and driecd. Then the formers are dipped into the latex blend (Table
2).
The latex coated formers are then leached dried and cured in an oven for 20
minutes at 235 degrees Fahrenheit. After curing, the coated formers may be
leached once again in hot water and then dipped in a slurry containing water
and
slip agent and driecl. The gloves are then stripped from the formers.
If a powder-free product is desired, further processing is required off line.
TAB LE 2
Ingredients Parts per Hundred Rubber
Polychloroprene Polymer (Neoprene60.0
750)
Acrylonitrile Polymer (Tylac 40.0
58073)
Sulfur 1.0
Zinc Dibutyl Dithioc~~rbamate 1.5
Zinc Oxide 5.0
Phenolic Antioxidant 1.0
Potassium Hydroxide 0.5
Stabilizing Surfacant(s) 3.0
Paraffin Wax 2.0

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Neoprene 750 was obtained from DuPont Dow Elastomers L.L.C.,
Wilmington, Delaware. Tylac 68073 was obtained from Reichold Chemicals, Inc.,
Reserch Triangle Park, North Carolina.
This invention has been described with reference to the preferred
embodiments including a best mode and preferred embodiment. It shall be
understood that they foregoing description is by way of illustration and not
by
limitation.