U.S. patent application number 11/094959 was filed with the patent office on 2006-10-05 for gloves with enhanced anti-cuff-slip surface.
This patent application is currently assigned to Kimberly-Clark Worldwide, Inc.. Invention is credited to Shantilal H. Modha, Lin-Sun Woon.
Application Number | 20060218697 11/094959 |
Document ID | / |
Family ID | 36178013 |
Filed Date | 2006-10-05 |
United States Patent
Application |
20060218697 |
Kind Code |
A1 |
Modha; Shantilal H. ; et
al. |
October 5, 2006 |
Gloves with enhanced anti-cuff-slip surface
Abstract
An elastomeric article encompassing an enclosure with an
interior surface having at least two regions or zones is described.
The first region has a higher coefficient of friction than the
second region, in which an average coefficient of friction (COF)
ratio between the first and second regions of the wearer-contact
surface ranges from about 1:1.2 to about 1:3.8 or 4.0. The first
region has either the same or smaller surface area than the second
region, and is situated at or near an opening to the enclosure. The
second region is coated with a hydrogel-based donning layer. A
process of making the elastomeric article is also provided.
Examples of elastomeric articles according to the invention include
surgeons' gloves that exhibit good lubricity and donning
characteristics, and have an improved cuff-slippage control.
Inventors: |
Modha; Shantilal H.;
(Alpharetta, GA) ; Woon; Lin-Sun; (Alpharetta,
GA) |
Correspondence
Address: |
KIMBERLY-CLARK WORLDWIDE, INC.
401 NORTH LAKE STREET
NEENAH
WI
54956
US
|
Assignee: |
Kimberly-Clark Worldwide,
Inc.
|
Family ID: |
36178013 |
Appl. No.: |
11/094959 |
Filed: |
March 31, 2005 |
Current U.S.
Class: |
2/161.7 |
Current CPC
Class: |
A41D 19/0089 20130101;
A41D 2400/44 20130101; A61B 42/00 20160201; A41D 19/0055
20130101 |
Class at
Publication: |
002/161.7 |
International
Class: |
A41D 19/00 20060101
A41D019/00 |
Claims
1. A flexible article comprising: a substrate body formed largely
from an elastomeric material, said substrate body having a first
surface and a second surface; said first surface is differentiated
into at least a first and a second zone, each zone having a
coefficient of friction, such that the coefficient of friction for
said first zone is greater than the coefficient for said second
zone, according to an average ratio in a range from about 1.2:1 to
about 4.5:1 said first zone is absent a donning layer, and said
second zone has said donning layer.
2. The elastomeric article according to claim 1, wherein said
average coefficient of friction ratio is about 1.4:1 to about 3.8:1
for said first zone to said second zone.
3. The elastomeric article according to claim 2, wherein said
average coefficient of friction ratio is about 1:5 to about 2.8:1
for said first zone to said second zone.
4. The elastomeric article according to claim 2, wherein said
average coefficient of friction ratio is about 1.6:1 to about 2.5:1
for said first zone to said second zone.
5. The elastomeric article according to claim 1, wherein said first
zone has a surface that is a bare elastomeric material or coated
with a tackifying material.
6. The elastomeric article according to claim 1, wherein said first
region is part of a surface adapted to prevent slippage of said
article when in contact with either human skin, or a fabric
material.
7. The elastomeric article according to claim 1, wherein aid
article is made from either a natural rubber latex or synthetic
polymer latex material.
8. An glove comprising: an elastomeric substrate body with an inner
surface having a first and a second region, said first region
having a higher coefficient of friction relative to said second
region, according to a ratio in a range from about 1.2:1 to about
3.5:1, and said second region being either substantially larger or
about equal in surface area than said first region, and having at
least a partially coating of a donning material layer.
9. The glove according to claim 8, wherein said first zone forms
part of a glove cuff.
10. The glove according to claim 8, wherein said second zone forms
at least part of a hand-donning portion of said glove.
11. The glove according to claim 8, wherein said inner surface is
subject to an oxidizing agent.
12. The glove according to claim 8, wherein said inner surface is
subject to a partial halogenation, such that said first region is
un-chlorinated and said second regions is chlorinated.
13. The glove according to claim 8, wherein said donning material
includes at least one of the following polymeric materials:
hydrogel-based polymer, polyurethanes, polyacrylates, polyvinyl
alcohol condensation product, poly(styrene-butadiene-styrene)
(SBS), or poly(styrene-ethylene-butadiene-styrene) (SEBS).
14. The glove according to claim 8, wherein said first region forms
at least part of an inner surface at or about a cuff portion of
said glove.
15. The glove according to claim 10, wherein said first region is
adapted to exhibit a tendency to retard cuff slippage off of a
wearer's wrist or forearm.
16. The glove according to claim 10, wherein said inner surface
contacts an article of protective clothing and tends to engage with
a material of said protective clothing.
17. The glove according to claim 8, wherein said second region
forms at least part of a surface that contacts a wearer's skin.
18. A method of fabricating an elastomeric article having a surface
with at least two regions with differentiated coefficients of
friction, the method comprises: providing a natural rubber or
synthetic polymer latex substrate on a mould; subjecting said latex
substrate to a first water leach; applying an aqueous
AlSO.sub.4-containing solution to a surface of said latex
substrate; applying a donning coating over a part of said
AlSO.sub.4-coated surface, leaving a zone of about at least 1 inch
(.about.2.2 cm) from a terminal edge of said latex substrate
uncoated with said donning coating; drying and curing said donning
coating; subjecting said latex substrate to a second water leach;
applying a second layer of AlSO.sub.4 over said donning coating;
and exposing said latex substrate to a dilute solution of an
oxidizing agent under alkaline conditions of about pH
.gtoreq.8.
19. The method according to claim 18, wherein said pH is about
9-11.
20. The method according to claim 18, wherein said donning coating
includes a hydrogel material.
21. The method according to claim 18, wherein said oxidizing agent
is a hypochlorite (NaOCl) solution.
22. The method according to claim 18, wherein said hypochlorite
solution is adapted to impart a sleek finish to said hydrogel
material.
23. The method according to claim 18, further comprises applying a
coating of powdered release agent to reduce self-blocking of said
region absent the donning coating.
24. The method according to claim 18, further comprising stripping
said latex substrate from said mould, inverting said latex
substrate, and applying a lubricating layer formed from a silicone
emulsion.
25. The method according to claim 18, wherein said silicone
emulsion imparts either a tackifying effect to said zone absent
said donning coating or a slickening effect to said donning
coating.
26. The method according to claim 18, further comprising treating
said latex substrate to a first and second consecutive rinse with
water, and a chlorine-containing water at .about.30-75 ppm vol.,
and a dilute hydrochloric (HCl) solution of about 0.1-0.85% by
volume to remove any remaining powdered release agent after said
first and second water rinses.
27. The method according to claim 18, further comprising subjecting
said latex substrate to a medium including a combination of
HCl+chlorine+silicone emulsion in one process step to achieve tacky
a surface on non-donning-material coated surface and a sleek
surface on donning material-coated surface.
28. The method according to claim 18, further comprising applying
another layer of silicone emulsion treatment.
29. The method according to claim 18, wherein said elastomeric
article has at least a first and a second zone on an inner surface,
in which said first zone has a relative higher coefficient of
friction, according to an average ratio in the range of about 1.4:1
to about 3.5:1.
30. The method according to claim 29, wherein said average ratio of
coefficient of friction between first and second regions is about
1.8:1 to about 3.0:1.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to elastomeric articles. In
particular, the invention relates to certain work, medical, or
surgical gloves that have a modified surface, which reduces
cuff-slip down, for enhanced protection of wearers.
BACKGROUND
[0002] Tight-fitting elastomeric articles, such as examination,
medical, or surgical gloves, are usually made from either natural
rubber or synthetic latex materials. Typically, such natural or
synthetic latex materials are tacky and have a high coefficient of
friction. This does not allow for easy introduction of a hand into
the glove. Hence, some sort of surface treatment is required on the
inner surface of the glove to facilitate donning, which may also
involve lubricating the interior surface to enable ease of donning
by a wearer because of undue clinging or friction between the
surface of the article and that of the wear's skin. Traditionally,
powdered lubricants have been applied to the inside surface of the
glove to reduce friction between the skin and the glove.
Unfortunately, the use of powdered lubricants may not be
appropriate for specific situations, such as the case of surgical
gloves. Specifically, if some of the powder escapes from the inside
of the glove into the surgical environment, as for example if the
glove is torn during the surgery, the powder may enter the surgical
wound and cause further complications for the patient.
[0003] As a result, other solutions have been developed to aid in
the donning of elastomeric gloves. Polymeric lubricant coatings
have been developed to modify the interior surface of the gloves in
an effort to provide a safe and effective donning for medical
practitioners. To date, the surface modification coating that has
had the best success and that is most accepted is a hydrogel
polymeric coating.
[0004] Several kinds and ways of applying lubricating coatings,
such as silicones or hydrogels, have been developed in the past;
many with great success at alleviating the problem of donning.
Coating the inner surface of elastomeric gloves with lubricant or
donning layers, however, is believed to have unintentionally
aggravated the tendency of the cuff regions of gloves to slip or
roll down along the wrist during use. The problem is particularly
burdensome with surgical gloves, in view of the critical nature of
the surgeon's activities, and also in view of the danger that
sterile field on the gloves may be compromised by attempts to
re-roll the glove backup along the surgeon's arm. Surgical gloves
currently on the market experience significant cuff slippage during
use.
[0005] Attempts that solving the glove-cuff slippage problem have
traditionally focused on changing the physical shape or design of
the glove. For instance, some commercially available gloves are
provided with relatively thick, circumferential or longitudinal
bands, ribs, fluting, or beaded cuffs, in an attempt to minimize
cuff roll-down. Alternatively, others have suggested applying an
adhesive strip to inside of the cuff, and still others have
suggested employing rather cumbersome straps and pegs to secure the
cuff tightly to the wear's wrist and forearm. Some manufactures
have remedied this issue by narrowing the diameter of gloves at the
cuff opening or its immediate area, which has resulted in more
constrictive force on the arms producing discomfort and often a
compression band on the skin. Hence, these efforts have not been
very successful.
[0006] A need exists for a better alternative that does not
constrict the glove cuff, nor substantially change the gross
physical configuration of the glove from designs which medical,
surgical, or laboratory workers have become accustomed. The present
invention satisfies this need and can provide such an
alternative.
SUMMARY OF THE INVENTION
[0007] The present invention pertains to the development of
elastomeric articles, such as medical, surgical, or work gloves,
that have a natural rubber latex or synthetic polymer latex
substrate with a final interior surface that is differentiated into
at least two major zones or regions, each with a different surface
characteristic. At least one zone, a first region, of the
elastomeric article is directed to achieving improved anti-slip or
anti-roll-down characteristics when worn by a user against fabric
or skin. To the extent that this first region of a glove has
anti-slip properties, the surface of the glove is modified to have
a higher coefficient of friction (COF) relative to the other,
second region. In some embodiments, the higher COF may be achieved
by either providing a more tacky surface in the first region or
generating a slicker surface in the second region, each of which
may involve the application or removal of a coating, such as of a
hydrogel or other lubricating cover, to the respective zone.
According to certain embodiments, the surface of the first region
can be left substantially bare of any coating. That is, the
elastomeric material (e.g., natural rubber or synthetic polymer)
surface is exposed, or the region can be coated with a layer of
adhesive or tackifying material (e.g., rubber cement). The
difference in relative coefficient of friction helps prevent the
glove from slipping down off of a sleeve of a surgical gown or
other garment surface. Hence, the anti-slip first region preferably
should be situated at or near the cuff portion of the glove. The
difference in relative coefficients of friction between the two
regions or zones of the inner, wearer-contacting surface can be
expresses as a ratio in a range of at least about 1:1.2, up to
about 4.5, more typically about 1:1.3 to about 1:3.8, preferably,
about 1:1.4 to about 1:3.35. The first region, depending on the
physical dimensions or size of the glove, can cover a distance or
width that extends inwardly, from the terminal edge of the glove
cuff, about 1 inch (2 cm) to about 5 or 6 inches (.about.12-13 cm),
and around laterally over a surface area that encompasses the
entire periphery of the cuff area.
[0008] Just as the first region of the glove, absent a slick
coating, will exhibit a relatively more tacky surface, it is
envisioned that the second region of the glove includes a donning
layer, such as a hydrogel or lubricating silicone layer, which will
exhibit a low friction, sleek surface. This may be accomplish in
the second region through application of a variety of different
kinds of donning coatings that, for example, may either completely
or partially cover the surface to assist donning requirements.
[0009] In another aspect, the present invention also pertains to an
online method of fabricating an elastomeric article having a
surface with differentiated coefficients of friction. That is, one
can create the different surfaces while the elastomeric article is
still on its mould, according to a dipped-goods technique. The
method encompasses: forming or providing a natural or synthetic
rubber latex substrate; subjecting the latex substrate to a first
water leach; applying an aqueous AlSO.sub.4-containing solution to
a surface of the latex substrate; applying a donning coating over a
part of the AlSO.sub.4-coated surface, such that a region of about
at least 1 inch (.about.2.5 cm) from a terminal edge of the latex
substrate remains uncoated with the donning coating. After the
donning coating is dried and cured, second layer of AlSO.sub.4 is
applied over the donning coating, followed by at least a second
water leach. This application seals the donning coating, and
prepared the coated latex substrate surface for exposure to a
dilute solution of an oxidizing agent under alkaline conditions of
about pH 9-11. The oxidizing agent can be a hypochlorite (e.g.,
NaOCl) solution, which is adapted to impart a sleek or smooth
finish to the donning coating.
[0010] Additional features and advantageous of the present
invention will be revealed in the following detailed description.
Both the foregoing summary and the following detailed description
and examples are merely representative of the invention, and are
intended to provide an overview for understanding the invention as
claimed.
BRIEF DESCRIPTION OF FIGURES
[0011] FIG. 1 is a representation of a glove according to the
present invention, as worn on the hand.
[0012] FIG. 2 shows the cuff region of the glove depicted in FIG.
1, partially rolled back over the hand portion of the glove.
[0013] FIG. 3 is a stylized depiction of the glove depicted in
FIGS. 1 and 2, showing differentiated surface regions or zone on
the donning side of the glove. In one zone, near the cuff, the
article has an anti-slip surface that has a higher relative
coefficient of friction than the other zone.
DETAILED DESCRIPTION OF THE INVENTION
Section I--Article
[0014] In general the present invention is directed to an
elastomeric article. As used herein, the term "elastomeric article"
refers to an article formed predominantly from an elastic or
elastomeric polymer latex. An "elastomeric polymer" refers to a
polymeric or rubber latex material that is capable of being
stretched or expanded, and upon release of the stretching or
expanding force, will return to substantially (e.g., .+-.5%) its
previous size and configuration. An article according to the
present invention, for example, may include clean-room, surgical,
work, and/or industrial gloves, that general exhibit a tendency to
slip down over time when worn or used. Hence, the present invention
is adapted to combat this problem, by providing, in part, a glove
with at least two zones on its inner surface with differentiated
surface characteristics. One of the zones is adapted to prevent
slippage of the article when in contact with either human skin, or
a fabric material by engaging with the skin or fabric material.
[0015] FIG. 1 depicts a glove 10 that has a flexible, substrate
body formed largely from an elastic, natural or synthetic latex
material. The substrate body has a first surface and a second
surface. For purposes of description, the first surface refers to
the inner surface of the glove substrate body which when worn by a
user in use is proximal or near to the body or skin of the wearer.
The second surface refers to the outer surface of the article,
which is remote from the body and skin of the wearer. The inner
first surface is differentiated into at least a first and a second
zone or region. FIG. 2 shows a partially inverted view of the glove
10 of FIG. 1, according to the present invention, which includes an
elastomeric substrate body 12 with an donning side inner surface 14
made up of at least a first 16 and a second region 18. Each zone or
region has a coefficient of friction, such that the coefficient of
friction for the first zone or region 16 is greater than the
coefficient for the second zone or region 18, according to a ratio
in a range from about 1.2:1 to about 4.5:1. More typically, an
average coefficient of friction ratio of the first zone to the
second zone is about 1.3:1 to about 3.5 or 3.8:1. Desirably, the
ratio is about 1.4:1 to about 2.75:1. More desirably, the
coefficient of friction ratio is about 1.5:1 to about 2.5:1.
[0016] In the present invention, as a general observation an inner
surface of a glove that has a higher coefficient of friction is
more desirable because of friction to retain the glove against the
material of a garment. Yet, this observation has caveats that were
surprisingly unexpected. Gloves, especially surgeon's gloves,
should not restrict the natural movement and flex of a wearer's
hands and wrist. Hence, the glove should not be too stiff and the
coefficient of friction ratio should not be too large. In our
experience, generally, a COF ratio that exceeds about 1:4.0 or 4.1
can overly restrict the ability of the user to freely move and flex
the user's hands and wrists. Further, a high COF will hinder the
ability of the wearer to easily don the glove, especially under
damp-skin conditions. The wear's hand will catch against the high
friction surface of the cuff region. To strike a balance between
maintaining a natural feel, without binding the movement of hands
and wrists, and better donning, while preventing the glove-cuff
from slipping down, an optimized range for the COF ratio is between
about 1:1.4 up to about 1:3.4 or 3.5, preferably about
1:2.0-3.0.
[0017] As depicted in FIG. 2, the first region 16 is at least part
of the inner surface 14 at or about a cuff portion 11 of the glove,
and is adapted to exhibit a tendency to retard the tendency of the
glove cuff slipping down from a wearer's wrist 2 or forearm 4 when
in use. The glove may have a bead 6 at the terminal edge of the
cuff, which further retards slippage. The first region 16,
according to an embodiment, is absent the donning coat layer. The
surface of the first region 16 may be either a bare, uncoated
elastomeric material; or alternatively, may be covered with at
least a layer of a tackifying material. In other words, the surface
characteristics of the first zone can be modified to create a
higher relative coefficient of friction than the second zone, by
means of either taking away or adding coating layers. The inner
surface at the first region 14a can contact an article of
protective clothing, such as a surgical gown, coverall, smock, or
other garment, and engage with the garment because of the first
region's relatively higher coefficient of friction. The higher
coefficient of friction can, in some embodiments, be derived from a
greater tackiness on the first zone. Since the second region 18
forms at least part of a surface that contacts the wearer's skin,
typically the hand 1 and wrist 2 portions of the glove, the second
region 18 can be either substantially larger or about equal in
surface area than the first region 16, and include at least a
partial coating of a donning material, such as a hydrogel-based
polymer. Alternate donning layer materials may include or be
selected from, for example, polyurethanes, polymers from the
poly-acrylate family, polyvinyl alcohol (PVA) condensation
products, poly(styrene-butadiene-styrene) (SBS), or
poly(styrene-ethylene-butadiene-styrene) (SEBS).
[0018] According to the present invention, the donning coat covers
only partially the interior surface of a glove. That is, in an
embodiment, a region of one to several inches (e.g., 1-5 or 6
inches) at or about the cuff portion of a glove is left free of a
hydrogel coating, which covers the hand-donning portion around
and/or below the wrist to the finger tips. The area of rubber film
without hydrogel coating provides a tacky surface to adhere to gown
fabric and this prevents the glove from slipping under normal use
by the wearer. The tacky surface may also provide a seal against
fluids draining under and into the glove, and afford more
protection to the user. This is more easily illustrated, as shown
in FIG. 3, with a glove 10 that is prepared just before being
stripped from its mould 20 and inverted, with what will become in
the inner surface 14 on the outside, away from the mould.
Section II--Process
[0019] In another aspect, the present invention pertains in part to
fabrication of elastomeric gloves according to either a post
formation tumbling process or an online process for increasing the
relative difference in coefficient of friction of the cuff portion
and hand-donning portion of an elastomeric glove. The term "online
process" refers to a mechanically automatable or
automation-friendly course of production, in which gloves do not
need to be removed from their moulds during the manufacture and
treatment steps. An elastic glove, is customarily fabricated by
dipping processes, which, typically, involve the use of a
hand-shaped mould, also known as a former. According to either
approach of the method, a hand-shaped former, is first dipped in a
coagulant solution bath to coat the mould. The mould can be
composed of a variety of materials, such as either metal or
ceramics, and can have a roughened or textured surface, or a smooth
surface. The coagulant is allowed to dry before dipping the mould
into an emulsion of a natural rubber or synthetic polymer latex,
which is applied to cover the mould. The mould dwells in the latex
for a short time period, about 1-5 minutes, to deposit a film layer
of predetermined thickness. The latex film is allowed to partially
dry. A bead may be formed at the terminal edge of the latex film.
The latex film is soaked in hot water at about 40-80.degree. C. to
leach out impurities. The leached latex film, while still on the
former, is then either sprayed with or dipped into a dilute
solution of AlSO.sub.4 (e.g., ActiveBond.TM. by Delta Polymer,
Inc.) with a total solids content of about 0.2-3.5%, desirably
about 2-3%, to apply a uniform layer to the latex substrate
surface. Afterwards, the glove is dried at a temperature in a range
of about 60-150.degree. C., preferably about 100-140.degree. C.
[0020] In some embodiments, a hydrogel-based donning coat is
applied to the dried latex film to cover the portion of the glove
that will be in contact with the hand. AlSO.sub.4, it is believed,
acts as a gelling coagulant for the hydrogel polymer and to enhance
its attachment to the rubber substrate of the glove. Examples of
possible suitable hydrogel polymer coatings are described in
various references, such as U.S. Pat. Nos. 4,548,844 and 4,575,476.
both to Podell et al., and U.S. Pat. No. 4,499,154 to James et al.
all disclose gloves with a continuous inner layer of such hydrogel
polymers; or U.S. patent application Ser. Nos. 10/978,343, and
11/023,743. The hydrogel solution can be about 1-5% total solids
contect (TSC). The hydrogel layer is allowed only to cover part of
the original latex surface. The hydrogel dip is maintained at a
level that is at least 1-2 inches below the upper terminal edge or
bead of the glove cuff. Preferably, the dip-level is lower by about
3-6 inches, depending on the overall length and configuration of
the glove. That is, a glove with a longer cuff region desirably
will have a proportionately larger area that is left uncoated with
the hydrogel polymer. After the hydrogel coating is applied to the
glove surface, a second layer of AlSO.sub.4 is applied over the
hydrogel layer. It is believed that this second layer provides an
acidic surface to the hydrogel layer.
[0021] To control self-blocking or sticking of the latex substrate
to itself and to facilitate stripping of the glove from its mould,
one applies a layer or coating of a fine powdered release agent,
such as calcium or magnesium carbonate (CaCO.sub.3, MgCO.sub.3)),
magnesium or zinc stearate (Mg(C.sub.18H.sub.35O.sub.2).sub.2,
Zn(C.sub.18H.sub.35O.sub.2).sub.2), from a slurry dip over the
entire glove to serve as an inorganic release agent.
[0022] Another way to obtain differentiation on a rubber surface
(i.e., to achieve a two-zone effect without hydrogel coating)
involves treating only part of the inner surface. That is, to
partially chlorinate part of the donning side, and the area of the
inner surface that is left un-chlorinated is treated with a
silicone lubricant to generate a higher COF than the chlorinated
surface.
[0023] In contrast to current, conventional processes that use
gaseous chlorine at acidic pH levels to halogenate the hydrogel
layer, an attribute of the present invention involves exposing the
gloves, while still on the former, to bath of an alkaline solution
of an oxidizing agent, such as sodium hypochlorite bleach. The
solution will have a pH .gtoreq.8 or 9. It is believed that the
hypochlorite works as a dilute chlorinating agent for the hydrogel
coating and uncoated rubber surface, and imparts a sleek finish to
the hydrogel coating for improved donning properties. In other
words, sodium hypochlorite is used as a processing aid to create a
smoother and sleeker hydrogel coating for easier donning
characteristics. This process step involves no chlorine gas to
enhance the relative smoothness of the coated surface for better
donning characteristics and relatively lower coefficient of
friction. Further, when processing online, with the donning layer
exposed to out side, the sodium hypochlorite modifies only the
donning side and one can avoid exposing the gripping region or
outer surface of the glove. In other words, as the glove is still
on the former, one can easily control the area and size of glove
surface that is exposed to chlorine by controlling to what level or
how far the glove substrate is submerged into the bleach solution.
The hypochlorite coated area can be coterminous with the hydrogel
coated region Further the present process will provide precise
control at level of chlorination needed to facilitate the donning
requiring. The present online process will improve, batch to batch,
the consistency of the halogenation process compared to current
process using gas and off line process. After at least a second
aqueous leaching, which removes most of the second AlSO.sub.4
application and powdered release agents, the glove is dried and
cured at temperatures in a range of about 90-150.degree. C. for
about 20-40 minutes.
[0024] Afterwards, the method may further comprising stripping the
latex substrate from a mould, inverting the latex substrate, and
applying a lubricating layer over the outside of the glove in an
off-line processing. A lubricating layer formed from a silicone,
such as a polydimethyl siloxane emulsion, can be applied at about
0.1-1.3 or 1.5 weight percent in an aqueous tumble inversion-rinse.
Desirably, the silicone emulsion is applied to the glove in an
amount of about 0.2-0.25% by vol. (.about.0.080-0.150% by wt.). In
some embodiments, the silicone emulsion may have a total solids
content (TSC) of not less than about 20% and up to about 60%. An
example of a desirable silicone emulsion is a pre-emulsified
formulation known as DC 365 (35% TSC), available commercially from
Dow Corning Corporation (Midland, Mich.). DC 365 is believed to
contain about 40-70 mass % water, about 30-60 mass %
methyl-modified polydimethylsiloxane, and about 1-5 mass %
octylphenoxy polyethoxy ethanol. Other examples of pre-emulsified
silicone formulations that may be suitable for use with the present
invention are available commercially from GE silicones (Waterford,
N.Y.) under the trade names SM 2140 (50% TSC), SM 2169, and AF-60.
SM 2140 is believed to contain about 30-60 mass % water, about
30-60 mass % amino-modified polydimethylsiloxane, about 1-5% mass %
trimethyl-4-nonyloxypolyethyleneoxy ethanol, and minor percentages
of acetaldehyde, formaldehyde, and 1,4 dioxane. SM 2169 is believed
to contain about 30-60 mass % water, about 60-80 mass %
polydimethylsiloxane, about 1-5 mass % polyoxyethylene lauryl
ether, and a small amount of formaldehyde. AF-60 is believed to
contain polydimethylsiloxane, acetylaldehyde, and small percentages
of emulsifiers. If desired, these pre-emulsified silicones may be
diluted with water or other solvents prior to use.
[0025] Silicone emulsions function as a lubricant on polymer-coated
surfaces, but on surfaces not coated with polymer, the silicone
emulsion enhances overall tackiness. Hence, the polymer-coated
sections of the glove become even more slick, which is good for
donning, while the areas of the substrate where there is no polymer
coating the silicone emulsion provides a desired grip level, such
that the inner surface of the glove will adhere to a gown material
when worn. The silicone emulsion is applied to both hydrogel-coated
and non-coated areas of the glove substrate.
[0026] After the glove has been stripped from its mould, the latex
substrate may be further subject to a series of at least two
consecutive rinses with heated water (.about.27.degree. C. or
30-40-88.degree. C.). In so-called backend processing operations,
the glove is treated with an effective amount of chlorine to
halogenated the gripping side. A chlorine-containing aqueous
solution (at .about.30-75 ppm) can be used to process the grip side
of the glove, followed with wash in a dilute hydrochloric acid
(HCl) solution (about 0.1-0.85% by volume, desirable about 0.2 or
0.25-0.37%) to remove any release agent power that may remain after
the water rinses. HCl dissolves the CaCO.sub.3 to produce a salt,
which is then washed away by water to produce a powder-free
product.
[0027] Alternatively, a batch of gloves can be tumbled in softened
or deionized water as a pre-rinse. We envision, according to
another aspect of the invention, a one-step treatment involving
exposing the gloves to a combined mixture containing
HCl+chlorine+silicone emulsion in either a bath or atomizing stray
in a tumble process. The combined HCl-chlorine-silicone treatment
can produce in one step several different surface effects, which
ordinarily would require several different process steps. The
silicone attaches to the non-polymer coated surface and the
chlorine attaches to the partial polymer-coated areas of the glove,
and the HCl helps remove excess CaCO.sub.3 powder that may be
present. Then, the gloves are again rinsed two times in softened
water, followed by rinse four times in deionized water. The batch
of gloves is then dried at about 70.degree. C. to about 80.degree.
C.
[0028] The chlorine and HCl treatment is believed to impart a
smooth and sleek finish, enhancing the donning properties of the
hydrogel-coated rubber surface. Generally, the higher the
percentage chlorine content, the slicker the finished rubber
surface becomes with an attending reduction in COF. Subsequently,
one may further immerse and tumble rinse the glove for an
additional third or fourth time to remove either powder residues or
latex proteins in natural rubber-based gloves. Further, one may
rinse up to an additional two more times in deionized water baths.
Finally, another layer of silicone emulsion (e.g., DC 365) is
applied in aqueous treatment via a tumble inversion-rinse, and the
glove is dried.
[0029] When comparing the two versions of the present process
treatment, the online approach tends to produce more consistent
results, hence it is a more cost-effective and desirable process
than the tumble approach.
EXAMPLES
Example 1
[0030] According to the online process the hand-shaped former is
dipped in a coagulant bath to coat the mould. A natural or
synthetic rubber latex is applied by dipping into a bath and
partial dried on the mould. A bead may be formed at the cuff. While
the latex substrate is on the former, the glove is subject to a
first water leach. An AlSO.sub.4 (e.g., Active Bond.TM.) solution
(.about.1%) is applied by either spraying or dipping of the glove
into an aqueous bath for about 1-3 minutes, over the entire surface
of the glove, up to and including the glove cuff. AlSO.sub.4
functions as a primer that helps enhance subsequent surface
modifications. A donning coat, such as a hydrogel or polyurethane
layer, is applied over part of the AlSO.sub.4-coated surface. The
AlSO.sub.4 on the surface of the hydrogel layer is unreacted with
the hydrogel. Typically, an area with a width of about 1 or 2
inches to up to about 5 or 7 inches (.about.2.5-13 or 16 cm), down
from the end of the glove cuff or bead, if present, is left
uncoated with the donning coat. Preferably, the region left
uncoated is about 1-2 inches (.about.2.5-5 cm). The donning coated
is dried and cured. The glove is subject to a second water leach
and dried. The entire glove can then be either immersed in a bath
or sprayed with a hypochlorite (NaOCl) solution and dried. Online
treatment with NaOCl can simplify the post processing, by removing
the chlorination process conventionally performed in tumblers. The
water rinse removes the AlSO.sub.4 treatment, hence the AlSO.sub.4
does not react with the hypochlorite.
[0031] According to the present invention, chlorination process
takes place under alkaline conditions of pH .about.9-10 or 11,
which are gentler and more conducive for online fabrication. Under
acidic conditions, the hydrochlorous acid (HOCl) will tend to
dissociate and release chlorine gas, which can be quite caustic and
harsh, hence not useful in an online process. In our process, it is
believed that the NaOCl affects the hydrogel or polyurethane
coating only to make it slick for donning. This is done in a dip
tank with the online process. The percentage chlorine is present in
a range of about 0.2-1.0%. Typically, chlorine is at about 0.3%
(3000 ppm of Cl.sub.2). The available amount of chlorine in NaOCl
is about 6%. According to some embodiments, the effective amount of
chlorine is about 6% of 0.3%, or about 0.018%.
[0032] The hydrogel coating can be slickened with exposure to an
oxidizing agent, such as a solution of sodium hypochlorate, which
is desirably applied co-terminus with the hydrogel donning coated
region. Afterwards, the cured glove is soaked in hot water at about
40-80.degree. C. for about 0.5 to 3 or 4 minutes. After drying for
a few minutes 3-6 minutes, the glove can be dipped in a slurry of
calcium carbonate (2-5%) suspended in water. When the slurry is
dried, the glove can be removed from the ceramic mould. The
stripping and inversion of the glove will make the
partial-hydrogel-coated surface to become the interior surface of
the glove to facilitate donning.
[0033] A suitable silicone emulsion, such as commercially available
formulations from Dow Corning (DC 365) or General Electric (AF60)
can be applied to increase the coefficient of friction on the
uncoated latex surface.
Example 2
[0034] In an alternate tumbling process, a surgical glove made from
an elastic latex can be manufactured by dipping the former into a
coagulant solution. As with the previously described steps, a
former is coated with a layer of either natural rubber or synthetic
latex and allowed to partial dry. A bead may be formed at the end
of the latex substrate. A first water leach is applied, followed
with a coating of AlSO.sub.4 over the entire exposed surface of the
latex substrate on the former. A partial hydrogel coating is
applied only over the hand and wrist regions of the mould, dried
and cured. A band or region of latex is left uncoated. This band
can have a width of about 1-6 inches, preferably about 1-2 inches
(2.5-5 cm), from the terminal edge or bead, if present. The glove
is subjected to a second water leach and dried. The entire glove is
then dipped into a CaCO.sub.3 slurry, and dried. Afterwards, the
glove is stripped from the mould and inverted. The subsequent
process steps and chemical treatments are conducted in a tumbling
drum, such as in a washing machine. Another coating of AlSO.sub.4
is applied in a tumble inversion-rinse over the entire glove and
dried. A first treatment with silicone emulsion in water is then
applied. After at least two rinses in water, the glove is subject
to a rinse in HCL solution, followed by another at least two rinses
in softened water, and two more rinses in deionized water. Finally,
a second treatment with silicone emulsion is applied and the glove
is dried.
Section III--Coefficient of Friction
[0035] It is believed that the modification of the inner surface of
a glove, according to the present invention can greatly reduce the
tendency for elastomeric gloves to slip when worn, especially when
in contact with an article of protective clothing. A portion of the
glove, not coated with donning layer, but a tacky surface engages
with the material of the protective clothing. As such, one creates
a good glove-gown interface region. In other words, due to the
combination the silicone emulsion over the latex substrate which
generates a higher COF at the cuff region than over the
hand-donning region of the glove. The cuff sticks to gown surface
and reduces slip down.
[0036] Two different tests were utilized in the determination of
the coefficient of friction:
[0037] (1) Classical Inclined Plane and Weight Method: This test
measures coefficient of friction via a determination of the angle
at which the test sample, weighted down in a standard manner,
slides down an inclined plane. The test is generally described in
Principles of Physics, by J. B. Marion et al., chapter 7-1,
Saunders College Publishing, New York, N.Y., 1984.
[0038] (2) Kawabata Method: This test is described in
Standardization Analysis of Hand Evaluation, by Sueo Kawabata;
July, 1980, 2nd Edition, pp 31-35, 48-50. As compared to the
Classical Method, the Kawabata test is more reliable for measuring
the coefficient of friction on rough surfaces or surfaces with
small areas. In this method, the test material is moved from left
to right while a contacting element (of specific dimensions, and
under constant force) touches the surface of the material. A
transducer connected to the detector is used to measure frictional
force as the test material is moved.
[0039] Tests using the Classical Method were repeated five times on
each sample to determine mean value. Tests using the Kawabata
method were repeated six times: two times for each sample. The
Kawabata COF data for two sizes (i.e., 6.5 & 7.5 inches) and 3
measurements of each size for each product sample were taken. The
coefficient of friction is determined on the cuff and palm areas of
the samples. In the test zone A is defined as the surface of the
glove within 1.25 to 2 inches from the cuff edge or bead, and zone
B is the surface of the donning areas of the glove, in particular
the palm region. Table 1 summaries the mean average values of the
Kawabata test results. TABLE-US-00001 TABLE 1 Sample No. zone A
zone B Ratio (C.O.F. of zone A v. zone B) 1 4.01 0.93 4.3:1.0 2
1.67 0.72 2.3:1.0 3 0.74 0.52 1.4:1.0 4 2.38 0.68 3.5:1.0 5 1.54
0.55 2.8:1.0 6 0.91 0.57 1.6:1.0 7 2.43 0.64 3.8:1.0 8 1.85 0.75
2.5:1.0 9 1.34 0.61 2.2:1.0 10 2.36 0.76 3.1:1.0 11 3.16 0.79
4.0:1.0 12 0.73 0.52 1.4:1.0
The above results clearly demonstrate that gloves produced
according to the present processing method exhibit an enhanced
friction characteristics as compared to the untreated counterparts.
The Kawabata test demonstrated enhanced friction for samples 1, 4,
5, 7, 10, and 11. Since low friction is the fundamental cause of
slippage at the cuff-sleeve interface, it appears clear that the
increases in the relative COF set forth in Table 1 will provide a
reduction in slippage without associated discomfort, such as
over-constriction on the forearm, which tend to be associated with
anti-slippage schemes that employ compression.
[0040] Table 1 also demonstrates that in some instances, relatively
low levels of the treatment agent (e.g., samples 3, 12) were
effective in significantly reducing the COF. As mentioned above,
the use of lower levels is often desirable in view of costs, and in
view of the tendency for gloves with high levels of the tackifying
agent to sometimes become stiff. As mentioned before for gloves,
COF ratios of over about 4.0:1 tend to hinder donning, and overly
tether the glove cuff to the user's forearm area and can restrict
the free movement or flex of the hands during use. This, however,
is not to disclaim the potential advantages of a high COF
differential for other applications which may appreciate a surface
with a higher coefficient or more tacky grip.
[0041] The present invention can be adapted to any base rubber
latex material formulation or dipping process. Hence, a variety of
products may employ the present technique. Such products may
include medical exam, surgical, or work gloves, condoms, as well as
any article that may require at least a two zone differentiated
surface having a contrast in coefficient of friction, such as for
better wearability.
[0042] The present invention has been described both in general and
in detail by way of examples. Persons skilled in the art will
understand that the invention is not limited necessarily to the
specific embodiments disclosed. Modifications and variations may be
made without departing from the scope of the invention as defined
by the following claims or their equivalents, including equivalent
components presently known, or to be developed, which may be used
within the scope of the present invention. Hence, unless changes
otherwise depart from the scope of the invention, the changes
should be construed as being included herein.
* * * * *