Latex gloves abstract
A polymer latex for making gloves having excellent donning and
doffing characteristics comprises a carboxylated open chain aliphatic
diene/acrylonitrile/(meth)acrylate terpolymer. A process for making
latex gloves using the polymer latex prepared in accordance with
the invention is also disclosed.
Latex gloves claims
What is claimed is:
1. A latex glove with improved doffing and donning characteristics,
wherein said glove is formed from a carboxylated open chain aliphatic
diene/acrylonitrile/(meth)acrylate latex polymer comprising about
40 to 80 weight % butadiene, about 15 to 45 weight % acrylonitrile,
about 2 to 12 weight (meth)acrylate, and about 2 to 10 weight %
of a carboxylic acid or a half ester of a dicarboxylic acid.
2. The glove of claim 1, wherein the open chain aliphatic diene
is butadiene.
3. The glove of claim 2, wherein the dryness coefficient of the
neat glove varies from about 8 to 10.
4. The glove of claim 2 wherein the (meth)acrylate component is
a monomer selected from the group consisting of methyl acrylate,
methyl methacrylate, butyl acrylate, ethyl acrylate, 2-ethyl hexyl
acrylate and mixtures thereof.
5. The glove of claim 1, wherein at least one other latex polymer
component selected from the group consisting of acrylics, butyl
latex, ethylene-vinyl acetate, carboxylated butadiene styrene, polyurethane,
neoprene, and natural rubber is blended with the carboxylated open
chain aliphatic diene/acrylonitrile/(meth)acrylate latex polymer,
and wherein the other latex components comprise up to about 25%
by weight of the total composition.
6. In a method for preparing a latex glove comprising:
(a) contacting a mold resembling a hand with a coagulant;
(b) removing the mold from the coagulant;
(c) contacting the coagulant coated mold with a latex for a sufficient
period of time to form a gelled latex coating of a desired thickness
on the mold;
(d) drying the latex coated old;
(e) curing the dried latex coated mold;
(f) removing the finished cured glove from the mold; the improvement
which comprises using a latex comprising a carboxylated open chain
aliphatic diene/acrylonitrile/(meth)acrylate polymer comprising
about 40 to 80 weight % butadiene, about 15 to 45 weight % acrylonitrile,
about 2 to 12 weight % (meth)acrylate, and about 2 to 10 weight
% of a carboxylic acid.
7. The method of claim 6, wherein the open chain aliphatic diene
is butadiene.
8. The method of claim 7, wherein the dryness coefficient of the
neat glove varies from about 8 to 10.
9. The method of claim 7, wherein the (meth)acrylate component
is a monomer selected from the group consisting of methyl acrylate,
methyl methacrylate, butyl acrylate, ethyl acrylate, 2-ethyl hexyl
acrylate and mixtures thereof.
10. The method of claim 6, wherein at least one other latex polymer
component selected from the group consisting of acrylics, butyl
latex, ethylene-vinyl acetate, carboxylated butadiene styrene, polyurethane,
neoprene, and natural rubber is blended with the carboxylated open
chain aliphatic diene/acrylonitrile/(meth)acrylate latex polymer,
and wherein the other latex components comprise up to about 25%
by weight of the total composition.
11. A method for imparting improved donning and doffing characteristics
to a latex glove, comprising forming the glove from a latex composition
comprising a carboxylated open chain aliphatic diene/acrylonitrile/(meth)acrylate
polymer comprising about 40 to 80 weight % butadiene, about 15 to
45 weight % acrylonitrile, about 2 to 12 weight % (meth)acrylate,
and about 2 to 10 weight % of a carboxylic acid or a half ester
of a dicarboxylic acid.
12. The method of claim 11, wherein the open chain aliphatic diene
is butadiene.
13. The method of claim 11, wherein the (meth)acrylate component
is a monomer selected from the group consisting of methyl acrylate,
methyl methacrylate, butyl acrylate, ethyl acrylate, 2-ethyl hexyl
acrylate and mixtures thereof.
14. The method of claim 11, wherein the dryness coefficient of
the neat glove varies from about 8 to 10.
15. The method of claim 11, wherein at least one other latex polymer
component selected from the group consisting of acrylics, butyl
latex, ethylene-vinyl acetate, carboxylated butadiene styrene, polyurethane,
neoprene, and natural rubber is blended with the carboxylated open
chain aliphatic diene/acrylonitrile/(meth)acrylate latex polymer,
wherein the other latex components comprise up to about 25% by weight
of the total composition.
Latex gloves description
BACKGROUND OF THE INVENTION
1. Field of the Invention doffing and donning characteristics.
2. Description of the Prior Art
Latex gloves are generally manufactured by using molds shaped like
hands. The molds are dipped with the fingers pointing downward into
a latex polymer. The dipped mold is withdrawn from the polymer after
a predetermined time has elapsed, and a portion of the latex polymer
forms a coating on the mold. The latex polymer coating on the mold
is cured and then removed from the mold on an inside-out basis so
that the outer latex surface becomes the inside of the glove.
Removing the cured latex glove from the mold is referred to as
"doffing". Doffing is often a difficult procedure because
the cured latex glove tends to be tacky and adhere to the mold.
Another problem that must be dealt with after the gloves have been
removed from the mold, is that they are often difficult to put on
a human hand because of the same tacky quality of the latex. Putting
the glove on one's hand is referred to as "donnability"
or "donning" the glove. Numerous proposals have also been
made for improving the doffing and donning characteristics of latex
gloves.
U.S. Pat. No. 2,310,889 to Becker discloses vinyl resin compositions
that are used to make gloves. The vinyl resins are made by conjointly
polymerizing two or more vinyl derivatives such as vinyl halides,
especially vinyl chloride, with vinyl esters of aliphatic acids
such as vinyl acetate, propionate and butyrate. An acrylate resin
such as methyl methacrylate is used to give increased strength and
coherence to the composition.
U.S Pat. No. 3,411,982 to Kavalir et al, which is a division of
U.S. Pat. No. 3,286,011 to Kavalir et al, relates to a method of
making elastomeric articles by using a dipping form with a slippery
surface to facilitate donning and doffing. The slippery surface
is prepared from an elastomer latex mixed with a latex or aqueous
dispersion of a resin. The mixed latex composition contains rubber
solids and resin solids. The rubber comprises copolymers of butadiene
with acrylonitrile, methyl methacrylate and the like. The resins
include acrylic ester polymer resins such as methyl acrylate and
methacrylate, ethyl acrylate or methacrylate, butyl acrylate and
the like or copolymers of these acrylates with each other or with
other monomers such as styrene, acrylonitrile, acrylic acid, methacrylic
acid and mixtures of these resins.
U.S. Pat. No. 4,575,476 to Podell et al, discloses a dipped rubber
article having a skin contacting surface layer formed of a hydrogel
polymer, such as polyvinyl pyrrolidone, polyhydroxyethyl acrylate
or methacrylate, polyhydroxypropyl acrylate or methacrylate, and
copolymers of these with each other or with acrylic or methacrylic
acid, acrylic or methacrylic esters or vinyl pyridine. The preferred
hydrogel polymer is a copolymer of a 2-hydroxyethyl methacrylate
with methacrylic acid or with 2-ethylhexyl acrylate or a ternary
copolymer of 2-hydroxyethyl methacrylate, methacrylic acid and 2-ethylhexyl
acrylate.
U.S. Pat. No. 4,482,577 to Goldstein et al, discloses a process
of coating a flexible vulcanized surgeon's glove by forming a lamination
of a hydrophilic polymer so that the external lamination of the
coating of the polymer eliminates the need for lubricating powder
on the glove. The copolymer is produced from a mixture of 2-hydroxyethyl
methacrylate and 2-ethylhexyl acrylate.
U.S. Pat. No. 3,919,442 to Esemplare et al, discloses a slip coating
that is rubber free, extensible and adheres to the rubber surface
of a glove. The coating comprises about 5 to 95% by weight of a
first resin such as a vinyl chloride/alkyl acrylate copolymer, a
vinylidene chloride/alkyl acrylate copolymer or a vinyl acetate/alkyl
acrylate copolymer, and about 10 to 95% by weight of a second resin
such as a vinyl chloride-vinyl ester copolymer, or a vinylidene
chloride-vinyl ester copolymer.
U.S. Pat. No. 3,856,561 to Esemplare et al, discloses chloride/alkyl
acrylate copolymer slip coatings for rubber surfaces such as gloves.
U.S. Pat. No. 4,082,862 to Esemplare et al, relates to slip coatings
provided on the surface of rubber articles and defines the slip
coating composition and resins in terms of the percent elongation.
U.S. Pat. No. 3,268,647 to Hayes et al, discloses a dipping form
and method for manufacturing rubber gloves with strengthened cuff
portions. Hayes discloses a glove mold or form that uses generally
parallel flutes extending longitudinally from the wrist area to
the base of the glove form to strengthen the cuff portion of the
glove.
U.S. Pat. No. 3,852,826 to Shindler discloses surgical gloves provided
with a colored circumferential band overlying the cuff portion to
impart visual identification of the glove size and further strengthen
the cuff. The rate of deposition of the latex is accelerated by
dipping the form into a conventional coagulant such as a calcium
nitrate solution, a hydrated magnesium acetate solution or the like
prior to dipping the form into the latex. The thickness of the latex
coating varies with the type and concentration of the coagulant
and the immersion time.
U.S. Pat. No. 2,941,257 to Davis discloses a secondary coating
of synthetic rubber on gloves formed of natural rubber.
U.S. Pat. No. 3,859,410 to Sidley discloses a method of producing
gloves with a relatively thin wall thickness in the finger and palm
portions and a relatively thick wall thickness in the cuff portion.
U.S. Pat. No. 4,304,008 to Joung discloses a powder-free surgeon's
glove with a halogen resistant layer such as silicone covalently
bonded to an outer surface. The inner surface is halogen treated
for smooth, non-tacky donning characteristics.
U.S. Pat. No. 4,340,348 to Kurtz, which is a divisional patent
of U.S. Pat. No. 4,390,492 to Kurtz, discloses a molding device
for gloves with at least 300% elongation including a tank containing
a polymer and a pair of glove molds.
U.S. Pat. No. 4,521,365 to Kurtz discloses an apparatus for preventing
web formation during the dip molding of gloves by using small objects
having a diameter of about one-eighth inch that float on the surface
of the polymer and move along the surface of the polymer as the
mold is withdrawn.
SUMMARY OF THE INVENTION
A latex comprising a carboxylated butadiene/acrylonitrile/(meth)acrylate
terpolymer is useful for making latex gloves with improved doffing
and donning characteristics. The improved latex glove can be stripped
or removed from a mold without the use of powder to assist its release.
The glove has an extremely "dry feel", which improves
donnability.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In accordance with the present invention a carboxylated latex terpolymer
of butadiene/acrylonitrile/(meth)acrylate is used to make latex
gloves with improved doffing and donning characteristics. The term
"(meth)acrylate" is used herein to designate an acrylate
and/or methacrylate monomer.
The terpolymer is prepared by polymerizing all monomers, that is,
the butadiene, acrylonitrile, (meth)acrylate, and carboxylic acid
components together via standard emulsion polymerization techniques
in the presence of surfactants, water and initiator.
The butadiene component is the preferred embodiment of an open
chain aliphatic conjugated diene containing about 4 to 9 carbon
atoms and can vary from about 40 to 80 weight %, preferably about
50 to 70 weight % and most preferably about 55 to 65 weight % of
the total latex terpolymer composition. The butadiene is more precisely
1,3-butadiene.
The acrylonitrile component can vary from about 15 to 45 weight
%, preferably about 20 to 40 weight %, and most preferably about
25 to 35 weight % of the total latex terpolymer composition.
The acrylate/methacrylate component is preferably an acrylate monomer,
such as methyl acrylate, methyl methacrylate, butyl acrylate, ethyl
acrylate, 2-ethyl hexyl acrylate and the like. This acrylate/methacrylate
component can vary from about 2 to 12 weight %, preferably about
4 to 10 weight %, and most preferably about 5 to 7 weight % of the
total terpolymer composition.
The acid component used to carboxylate the terpolymer is a carboxylic
acid, such as acrylic acid, methacrylic acid, maleic acid, itaconic
acid, fumaric acid and the like, or a half ester of a dicarboxylic
acid such as itaconic acid, maleic acid, or fumaric acid. The acid
component can vary from about 2 to 10 weight %, preferably from
about 5 to 7 weight % of the total terpolymer composition.
Latex gloves are manufactured using the liquid carboxylated butadiene/acrylonitrile/(meth)acrylate
latex terpolymer as a dipping medium for the glove form or mold,
which resembles a hand. Other latexes, such as acrylics, butyl latex,
ethylenevinyl acetate, carboxylated butadiene styrene, polyurethane,
neoprene, natural rubber and the like can be blended with the carboxylated
butadiene/acrylonitrile/(meth)acrylate latex terpolymer, in amounts
up to about 25% by weight.
Separate glove forms or molds, are provided for the right and left
hand. The molds are made in a variety of sizes and shapes corresponding
to the various hand sizes for which the gloves are intended. The
mold substrate is preferably porcelain, bisque or glazed, but other
substrates such as stainless steel, glass, hard woods, and plastic
can also be used.
The form or mold is dipped or immersed into a gelling agent or
coagulant for the latex polymer, and then withdrawn. The coagulant
is maintained at temperatures of about 65.degree. F. to 150.degree.
F., preferably about 70.degree. F. to 90.degree. F. for alcohol
based coagulants, and about 110.degree. F. to 140.degree. F. for
water based coagulants.
Suitable coagulants include, but are not limited to, calcium nitrate,
calcium chloride, acetic acid, magnesium acetate, and the like.
A 25 to 50% solution of calcium nitrate in water or ethyl alcohol
is preferred, and a 30 to 40% calcium nitrate concentration is particularly
preferred.
After the mold is removed from the coagulant, any excess liquid
is permitted to flash off or dry, leaving a residual coating of
the coagulant on the mold.
The mold coated with coagulant is then dipped into the liquid carboxylated
butadiene/acrylonitrile/(meth)acrylate latex terpolymer, at a temperature
of about 65.degree. F. to 100.degree. F., and preferably about 70.degree.
F. to 90.degree. F. The amount of time that the mold is immersed
in the latex determines the wall thickness of the glove that is
produced. The shorter the dwell time period, the thinner the wall
thickness of the glove, and vice-versa.
The following table shows a typical variation in coating thickness
of the latex as a function of dwell time:
TABLE 1 ______________________________________ Dwell Time (seconds)
Coating Thickness (mils) ______________________________________
0 (in and out) 5-6 30 9-10 60 11-13 ______________________________________
The mold is removed from the latex with a coating of gelled latex
adhering to the mold. The mold is then placed in a water bath to
leach out the gelling agent at a temperature of about 80.degree.
F. to 140.degree. F., and preferably about 85.degree. F. to 115.degree.
F. for about 1 to 10 minutes.
The latex coated mold is then removed from the leach bath and placed
into a drier. The drier temperature can vary from about 120.degree.
to 200.degree. F. In one embodiment, the mold with the gelled latex
can be placed into the dryer at 120.degree. F. and the temperature
gradually increased to 200.degree. F.
The latex coated mold is generally maintained in the dryer for
a period for about 40 to 120 minutes, and preferably about 60 to
75 minutes. A drying time of about sixty minutes is preferred when
the dryer is maintained at a temperature of about 160.degree. F.
for the entire drying cycle.
The latex glove is then cured on the mold. Curing is carried out
at a temperature of about 250.degree. F. to 310.degree. F., for
about 15 to 30 minutes.
The latex glove is removed from the mold by turning it inside out
so that the inner latex surface contacting the mold becomes the
outside surface of the glove. The carboxylated butadiene/acrylonitrile/(meth)acrylate
terpolymer provided in accordance with the present invention enables
the glove to be removed easily from the mold without further treatment
or additives. The stripping process does not require any powder
to release the latex glove from the mold. The end product has an
extremely "dry feel" surface, which greatly improves donnability.
The evaluation of the donning and doffing characteristics of the
latex glove is essentially a qualitative exercise based on the ease
of removing the glove from the mold, and placing it on one's hand.
Since the ease of donning and doffing the latex glove is directly
related to its "reduced friction dry feel" or slipperiness,
a numerical dryness coefficient has been established to rate this
characteristic. The ratings scale varies from 1 to 10. The higher
the coefficient, the greater the non-tacky feel of the glove and
corresponding ease in donning and doffing the glove.
In practice, the dryness coefficient is obtained for latex gloves
prepared from a particular formulation by having a group of individuals
skilled in the art doff and don the gloves, and then rate them in
accordance with the ratings scale. An average dryness coefficient
of about 8 to 10 is indicative of a glove that has excellent donning
and doffing properties.
Generally, dryness coefficients of less than 8 are indicative of
gloves which require additives to improve slipperiness such as talc
or starch powder, halogenation treatment (chlorination, bromination),
or other slip coatings or detackifier treatments known in the art.
However, the present invention can achieve dryness coefficients
of about 8 to 10 in a neat state, without such slipperiness additives.
Thus, gloves prepared from the carboxylated butadiene/acrylonitrile/(meth)acrylate
terpolymer in accordance with the invention can be used without
powder, halogenation or secondary coatings. The gloves have an extremely
dry feel and excellent donning and doffing characteristics. This
is especially important with gloves used for medical applications,
for example, by physicians performing surgery.
Latex gloves that are presently available commercially generally
fall into 3 categories, high powder, low powder and no powder. Gloves
with powder in an operating or sterile environment can create a
danger of contamination. The "no powder" gloves are usually
halogenated or have special slip coatings or detackifiers, and are
extremely expensive.
In contrast, the inventive latex gloves can be easily doffed or
donned without powder, additives or secondary coatings, and are
a tremendous advantage in both a practical and economic sense.
In compounding the latex glove formulation, a blend of surfactants,
stabilizers, accelerators, cross-linkers, and activators can be
added to the liquid terpolymer formulation to optimize the polymerization
of the latex and formation of the glove.
Thus, for example, stabilizers such as potassium hydroxide, ammonia,
sodium hydroxide and the like can be added on the order of about
0.001 to 0.7 dry parts per 100 dry parts of the latex. Accelerators,
such as various zinc dithiocarbamates sold under the trade names
Butyl Zimate.TM., Ethyl Zimate.TM., and Methyl Zimate.TM. by R.
T. Vanderbilt Company, the sodium salt of dithiocarbamate, and the
like can be used on the order of about 0.1 to 1.5 parts per 100
dry parts of the latex.
Crosslinkers such as sulfur and sulfur equivalents such as tetramethylthiuram
disulfide sold under the tradename "Methyl Tuads" by R.
T. Vanderbilt Co., tetramethylthiuram disulfide sold under the tradename
"Ethyl Tuads" by R. T. Vanderbilt Co. and polysulfide
thiuram sold under the tradename "Sulfads" by R. T. Vanderbilt
Co. can be used on the order of about 0.01 to 2 dry parts per 100
dry parts of latex. Crosslinkers such as zinc oxide, can also be
used on the order of about 1 to 7 dry parts per 100 dry parts of
the latex. Generally, these additives are employed in solution or
as finally divided dispersions in water. |