U.S. patent number 3,902,484 [Application Number 05/458,315] was granted by the patent office on 1975-09-02 for disposable surgical drape.
This patent grant is currently assigned to Kimberly-Clark Corporation. Invention is credited to Terry L. Winters.
United States Patent |
3,902,484 |
Winters |
September 2, 1975 |
Disposable surgical drape
Abstract
An improved disposable surgical drape comprising a fibrous base
sheet, a fluid impervious plastic layer covering at least a portion
of the base sheet, the improvement comprising a sheet of flexible,
normally hydrophobic, open celled foam material bonded to the outer
surface of the plastic layer, the foam material being treated with
the reaction product of a mineral acid and a fatty acid tertiary
amine wherein the amine is partially neutralized to a fatty acid
tertiary ammonium salt which renders the foam material antistatic,
while providing increased rates of fluid absorption and reduced
tendency for lathering when the foam material is rubbed with water
present on the foam material.
Inventors: |
Winters; Terry L. (Neenah,
WI) |
Assignee: |
Kimberly-Clark Corporation
(Neenah, WI)
|
Family
ID: |
26918324 |
Appl.
No.: |
05/458,315 |
Filed: |
April 5, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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223990 |
Feb 7, 1972 |
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Current U.S.
Class: |
128/849;
260/DIG.19; 428/189; 428/160; 428/219 |
Current CPC
Class: |
A61B
46/00 (20160201); Y10T 428/24752 (20150115); Y10S
260/19 (20130101); Y10T 428/24512 (20150115) |
Current International
Class: |
A61B
19/08 (20060101); A61B 19/00 (20060101); A61f
013/00 () |
Field of
Search: |
;128/132D,188
;161/39,59,86,88,145,164,149,151,159,160,170,190
;260/32.6N,DIG.19 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Recla; Henry J.
Attorney, Agent or Firm: Wolfe, Hubbard, Leydig, Voit &
Osann, Ltd.
Parent Case Text
RELATED APPLICATIONS
This is a continuation of application Ser. No. 223,990, filed Feb.
7, 1972, now abandoned.
Claims
What is claimed is:
1. In a disposable surgical drape having a primary operative area,
said drape comprising a fibrous base sheet, a fluid impervious
plastic layer covering said primary operative area, the improvement
comprising a sheet of flexible, normally hydrophobic, open celled
foam material bonded to the outer surface of said plastic layer,
said foam material having been treated with the reaction product of
a mineral acid and a fatty acid tertiary amine, said fatty acid
tertiary amine being neutralized less than about 34 percent to form
a fatty acid tertiary ammonium salt, said fatty acid tertiary amine
having the structural formula: ##EQU4## where R signifies an alkyl
group containing from 12 to 18 carbon atoms; said compound being
effective to render said foam material antistatic, while providing
increased rates of fluid absorption and reduced tendency for
lathering when said foam material is vigorously rubbed in the
presence of water.
2. In a disposable surgical drape as defined in claim 1 wherein
said reaction product is present in excess of about 0.125
gms/yd.sup.2 and the surface resistivity of the treated foam
material is less than about 5 .times. 10.sup.11 ohms.
3. In a surgical drape as defined in claim 1, wherein said mineral
acid is selected from the group consisting of phosphoric acid,
hydrochloric acid and sulfuric acid.
4. In a surgical drape as defined in claim 1 wherein said foam
material is a polyurethane foam.
Description
Donnelly, Ser. No. 17,431, filed Mar. 9, 1970 now U.S. Pat. No.
3,668,050.
Schrading and Winters, Ser. No. 58,336, filed July 27, 1970 now
U.S. Pat. No. 3,669,106.
DESCRIPTION OF THE INVENTION
The present invention relates generally to disposable surgical
drapes and, more particularly to surgical drapes having an
absorbent foam material covering the primary operative area.
There have been many new commercial developments in disposable
articles for use in hospitals, clinics, and the like, particularly
with respect to surgical drapes that are intended for only a single
use. Since such disposable surgical drapes are less expensive to
initially produce, coupled with the fact that they need not be
laundered and sterilized for repeated uses has resulted in their
capturing a significant commercial market, which is generally
predicted to increase as labor costs associated with laundering and
other handling increase. Among the more significant recent
developments in disposable surgical drapes are those drapes
disclosed in the Donnelly application Ser. No. 17,431, filed Mar.
9, 1970 now U.S. Pat. No. 3,668,050 as well as the Schrading and
Winters application, Ser. No. 58,336, filed July 27, 1970 now U.S.
Pat. No. 3,669,106 all of which are assignee to the assignee of the
present invention.
Features common to the surgical drape disclosed in these
applications involve a fibrous base sheet and a sheet of fluid
impervious plastic film attached to the base sheet as well as a
fluid absorbent plastic foam material bonded to the plastic film in
the primary operative area of the surgical drape.
Preliminary to a detailed description of the improved surgical
drape of the present invention, it should be pointed out that the
use of open celled foam material in at least the primary operative
area, including the fenestration area of a laparotomy sheet for
example, has experienced widespread acceptance, particularly when
it is combined with an underlayer of fluid impervious plastic or
film, since the combination is strong and abrasion resistant even
when exposed to liquids and when subjected to physical contact and
manipulation that are encountered during the course of an
operation. A laparotomy sheet is an elongated generally rectangular
sheet used to cover the patient during thoracic or abdominal
surgery, and is typically about 6 to 8 feet in length and about 3
to 6 feet in width. The layer or film of fluid impervious plastic
prevents the liquid encountered during operating procedures from
striking through the sheet and thereby prevents passage of bacteria
through the sheet. Moreover, the foam material has a high
frictional coefficient that prevents dislodgement of surgical
instruments, supplies and the like when placed on the surface of
the sheet during an operation. The foam material is stable at
conditions encountered during sterilization treatments either by
steam or ethylene oxide or the like, and the combination of film
and foam material has good draping characteristics which are
desirable for conforming the drape to the patient during an
operation. The open cell foam material is also fluid absorbent to
minimize fluid run-off that is invariably encountered during most
operations.
When drapes are used in anesthetizing locations, it is of utmost
importance to prevent sparking due to the buildup of static
electrical charges on the drapes, which can be hazardous since
explosive anesthetizing gases and oxygen are often present in
operating rooms. The governing criteria for electrical surface
resistivity of fabrics used in anesthetizing locations is set forth
in the Code for the Use of Flammable Anesthetics, (1960) published
by the National Fire Protection Association in their publication
No. 56 (hereinafter referred to as the Code). Appendix A, Section
3513-Textiles, requires that the surface resistivity of the fabric
should be measured at an ambient relative humidity of 50 percent
and temperature of 23.degree.C by method 76-59 of the American
Association of Textile Chemists and Colorists (U.S.A.C.L. 14.112-
1961) and states that the measured value should be less than 5
.times. 10.sup.11 ohms per square unit of the material.
Although many chemical treatments are known to provide antistatic
properties when applied to hydrophobic fibers, films and other
surfaces, many of such treatments have been found to be deficient
in one or more respects. For example, some compounds are simply
unsuitable in that they fail to provide sufficient conductivity or,
in other words, fail to lower the surface resistivity to acceptable
limits or values that satisfy the hereinbefore identified standard
when applied to materials used in locations that have flammable
anesthetics. Other chemicals are soluble only with isopropanol,
which is flammable and thus creates a hazardous environment and may
require expensive explosion proof processing equipment for its use.
Additionally, other antistatic agents, when applied to foam
materials, exhibit a severe lathering characteristic when treated
material is rubbed with water present on the material. Still other
chemical treatments are unsuitable because their use during the
process of treating the material is accompanied by the presence of
irritating vapors. Similarly, with some chemicals the resulting
treated material may cause dermatological problems with patients or
others coming in contact therewith.
One chemical that is available as an antistatic agent is a fatty
acid tertiary amine having the structural formula: ##EQU1## wherein
R signifies an alkyl group containing from 12 to 18 carbon atoms.
While the alkyl group may be a mixture of various fatty acids, one
desirable source is tallow. A tallow tertiary amine having the
above structural formula is supplied by the Armour Industrial
Chemical Company, Chicago, Illinois under the tradename "Ethomeen
T/12." The Ethomeen T/12 tallow fatty acid is sold as an antistatic
agent for use on most hydrophobic fibers and is also known to have
surfactant or wetting action properties.
Another source of an antistatic agent including a fatty acid
tertiary amine is sold by Paint Products Laboratory of Chicago,
Illinois, under the tradename of "Statex PC-319." This product,
comprising a fatty acid tertiary amine partially neutralized to the
corresponding ammonium salt, has been used, for example, as an
antistatic treatment for nylon, other textiles and airplane
windows. While use of this material does reduce the surface
resistivity of acceptable levels when applied to foam material, the
treated foam does exhibit the undesirable lathering characteristic
when vigorously rubbed with water present on the foam material.
It is a primary object of the present invention to provide a
disposable surgical drape having an open celled foam material on
the outer surface in at least the primary operative area, wherein
the foam material is treated to provide significantly improved
desirable attributes.
More specifically, it is an object of the present invention to
provide an improved surgical drape of the hereinbefore described
type wherein the foam material is treated to equal or exceed
surface resistivity values that are required for use in operating
rooms or the like.
Still another object of the present invention provides for a
surgical drape wherein the foam material is treated to produce the
above mentioned surface resistivity and additionally exhibits
superior rates of fluid absorbency.
Yet another object is to provide a surgical drape that exhibits the
above desirable attributes, but which does not exhibit sudsing or
lathering characteristics when rubbed with water present on the
foam material.
A still further object of the invention lies in the provision of an
improved surgical drape having all of the aforementioned desirable
characteristics and yet which can be produced at such a low cost as
to permit disposal of the drape after a single use.
A related object is to provide an improved surgical drape that
enables the use of relatively low cost hydrophobic foam material,
and yet results in superior rates of fluid absorption comparable to
those exhibited by more expensive hydrophillic foam material.
Other objects and advantages of the invention will become readily
apparent from the ensuing detailed description and accompanying
drawings, in which:
FIG. 1 is a plan view of a surgical drape embodying the present
invention; and
FIG. 2 is a section taken generally along the line 2--2 in FIG.
1.
While the invention is susceptible of various modifications and
alternative forms, certain specific embodiments thereof have been
shown by way of example in the drawings and will be described in
detail herein. It should be understood, however, that it is not
intended to limit the invention to the particular forms disclosed,
but on the contrary, the intention is to cover all modifications,
equivalents and alternatives falling within the spirit and scope of
the invention as expressed in the appended claims. In this
connection, a laparotomy drape sheet has been shown in the
drawings. It should be understood that other types of drape sheets
may be used and that the invention is not limited to the type of
drape sheet illustrated. Similarly, the specific embodiment of the
base sheet is described as comprising outer layers of cellulosic
wadding and inner layers of highly drafted fibers. It should be
understood that the construction of the base sheet should not be
limited to the specific base sheet disclosed.
Turning now to the drawings, there is shown a surgical drape having
a primary operative area, which is the fenestration area of the
illustrated laparotomy sheet. The drape has a fibrous base sheet
10, over which a fluid impervious plastic layer or film 11 is
bonded. The film 11 may be bonded to the fibrous base sheet 10 by
any suitable means, such as by means of an adhesive. The film 11
provides a fluid impervious barrier in the primary operative area
so that any fluids contacting this area cannot strike through the
sheet. This prevents the transfer of bacteria through the sheet and
thereby helps insure that sterile conditions will be maintained in
the primary operative area. It should be understood that the film
must be capable of remaining stable under the conditions
encountered in the particular treatment to which the drape sheet is
subjected to render it sterile, e.g., temperatures of about
270.degree.F for steam sterilization or about 160.degree.F for
sterilization by means of ethylene oxide or the like.
Examples of suitable films are polyethylene e.g., 2 mil.
polyethylene film manufactured by Clopay Corp, Cincinnati, Ohio;
polypropylene, e.g., "Extrel II" available from Extrudo Film Corp,
New York, New York; polyethylene methylacrylate co-polymer film
manufactured by Edison Plastics Company; and vinyl chloride films.
The film should be substantially free of pin holes to provide the
desired sterility barrier, and thus must generally be at least 0.15
mil thick.
Overlying the fluid impervious film 11 is a foam material 12 which
may be bonded to the film 11 by any suitable means, but preferably
by means of an adhesive. The absorbency of the open celled foam 12
prevents excessive fluid run-off and yet the absorbed fluids cannot
strike through the drape because of the intermediate layer of fluid
impervious film 11. The relatively high coefficient of friction of
the foam material provides a substantially non-slip surface which
prevents accidental dislodgement of surgical instruments and the
like when they are placed on the surface of the foam material. In
addition, the foam material 12 preferably has a low glare which is
achieved in part by its open cellular structure and which may be
enhanced by tinting or coloring the foam during its manufacture or
subsequently. The foam thickness would generally be in the range of
about 25 mils to about 100 mils, and the absorbency of the foam
sheet should be at least about 150 percent by weight and for a 40
mil thick foam material preferably at least 575 percent and at
least 4.5 gm/4 inch by 4 inch sample. Examples of suitable foams
are 40 mil polyester polyurethane foam having a density of 1.7
lbs/ft.sup.3, available from Reeves Brothers Inc., New York, New
York or Tenneco Chemicals Inc., New York, New York and polyether
polyurethane foams.
The base sheet 10 preferably comprises outer layers of cellulosic
wadding and inner layers of highly drafted fibers disposed
angularly relative to each other. A spaced pattern of adhesive is
disposed between each fiber layer and its adjacent wadding layer
with the fibers in each layer partially embedded in and held by the
adhesive in the adjacent adhesive layer and partially embedded in
and held by the adhesive in the outer adhesive layer where it
extends between the fibers of its adjacent fiber layer and with a
portion of the adhesive in both adhesive layers joined where the
adhesive patterns are superimposed. This material is described in
more detail in copending Sokolowski et al application Ser. No.
546,067, filed Apr. 28, 1966 now U.S. Pat. No. 3,484,330 and
assigned to the assignee of the present invention.
Suitable adhesives for use in bonding the foam material to the film
and for bonding the film to the base sheet are preferably water
resistant adhesives that are solvent based, in solvents such as,
for example, methyl ethyl ketone or ethyl acetate. One adhesive is
a two component urethane solvent based system, available from the
Chemical Division of Borden, Inc., Chicago, Illinois under the
tradename "MA-5750." The adhesive is suitably applied to the film
at a loading of about 2 to 10 grams per square yard and may be
applied at room temperature. The adhesive is preferably applied in
a spaced pattern to maintain flexibility. The pressure used to
laminate the film to the foam material is relatively light, and is
just sufficient to make good contact between the film and foam
material. While the bonding of the film to the base sheet may be
performed using similar adhesive and loading, the adhesive is
preferably continuous around the fenestration and around the outer
periphery of the film.
In accordance with the present invention, the foam material 12 is
treated with an isopropanol-water solution of a fatty acid tertiary
amine, partially neutralized to a carefully controlled level to the
corresponding ammonium salt to achieve the necessary surface
resistivity superior rate of fluid absorbency and yet obviate the
undesirable lathering property.
The treating solution thus includes the reaction product of a fatty
acid tertiary amine having the structural formula: ##EQU2##
(wherein R signifies an alkyl group containing from 12 to 18 carbon
atoms) and a mineral acid. Among the mineral acids that can be used
are hydrochloric acid, sulfuric acid and phosphoric acid, although
phosphoric acid is preferred. The alkyl group may consist of a
single member or the amine may comprise a mixture having different
alkyl groups. In the latter instance, it has been found desirable
to use tallow as the source for R, viz.- the alkyl group.
In keeping with the present invention, the reaction product is
preferably applied in an isopropanol water solution in sufficient
quantity such that at least 0.125 gms/yd.sup.2 addon is applied to
the surface of the foam material. Although the solution may be
sprayed upon the surface of the foam material, it has been found
that flexographic printing of the solution is preferred, due to the
fact that quantities are more easily controlled and there is less
potential for creating a health hazard in terms of explosive vapor
concentrations than may be present if the solution is sprayed upon
the surface of the foam material. The particular solvent in which
the compound is dissolved has been found to be important. It is
preferred to use an isopropanol-water solvent wherein the
isopropanol comprises between about 30 and 80 percent by weight of
the solvent. If less than about 30 percent isopropanol is used, it
has been found difficult to dissolve the compound. If more than 80
percent isopropanol is used, the antistatic properties of the
resulting drape may be decreased below acceptable limits as set
forth in the hereinbefore mentioned Code.
Since the fatty acid tertiary amine is known to be a wetting agent
or surfactant, it would be expected that the free amine is the
cause of the lathering or sudsing characteristic. It would
accordingly be assumed that the lathering characteristic would be
minimized by tying up or neutralizing the free amine. Thus, it
would be anticipated that the greater the extent of neutralization
(causing a concomitant reduction in the pH), the less lathering or
sudsing would be a problem. Contrary to expected belief, however,
it has been found that neutralization must only be carried out to a
certain level, because further neutralization in fact results in
the unwanted lathering property in the treated drape.
To achieve the objectives of the present invention, the amounts of
mineral acid and amine should thus be controlled to provide
neutralization of the amine to an extent not greater than about 34
percent. In keeping with the present invention the degree of
neutralization can be obtained by maintaining the pH within
carefully controlled limits. To this end, by insuring that the pH
does not drop below about 7.5 (as measured by a pH meter having
water in the probes) desired neutralization will result.
Where phosphoric acid is used and the pH of the treatment is about
7.5 or greater, it is believed that the principal reaction product
has the following structural formula ##EQU3## wherein R signifies
an alkyl group containing from 12 to 18 carbon atoms.
In accordance with a further aspect of the present invention, it
has been found that if the solution has a pH of greater than about
8.5, it is more difficult to dissolve the reaction product in the
solvent unless the solvent contains a greater amount of isopropanol
and, additionally, the reaction product tends to precipitate out.
As previously mentioned, the antistatic properties of the foam may
be impaired if the percentage of isopropanol in the solvent exceeds
about 80 percent.
In keeping with the present invention, it has been found that the
treatment of the foam material with the above mentioned reaction
product also significantly improves the rate of absorption of
liquids that come in contact with the foam material. While an open
celled foam material, even if it is normally hydrophobic, will
absorb fluids, normally hydrophobic open celled foam material often
requires considerable time before the fluid is absorbed into the
cellular structure of foam material. It should be understood that
the rate of absorbency of the foam material is important since any
liquids that come in contact with the foam material during an
operation should preferably be readily absorbed rather than remain
on the foam material surface where a physician or other member of a
surgical team would contact the fluid. Although polyurethane foam
having some degree of hydrophilicity is commercially available, the
cost of such foam is substantially greater than commercially
available hydrophobic polyurethane foam material. The present
invention, in addition to providing surface resistivity values
within the prescribed range as required by the Code, has the
additional effect of providing greatly increased rates of fluid
absorption, all of which may be achieved at a much lower cost since
normally hydrophobic foam material may be used.
As one specific example of treating the foam material in accordance
with the present invention, a disposable surgical drape having
exposed 40 mil polyester polyurethane, open celled foam material
was treated with a isopropanol water solution of the reaction
product of the tallow fatty acid tertiary amine and phosphoric acid
with the solution being adjusted to have a pH of about 7.5. The
isopropanol-water solvent contained about 40 percent isopropanol
and approximately 6.2 percent solids of the tallow fatty acid
tertiary amine that was about 34 percent neutralized to the tallow
fatty acid ammonium salt with phosphoric acid. The solution was
printed upon the outer surface of the foam material such that about
0.125 gm/yd.sup.2 add-on of the reaction product was present after
drying to eliminate the solvent. It was found that the rate of
water absorbency as measured by placing drops of water on the
surface and measuring the time required for it to be absorbed into
the foam material was less than a few seconds the majority of the
time as compared to in excess of 300 seconds for untreated
hydrophobic polyurethane foam. Similar tests were run to measure
the rate of absorption for drops of 1 percent sodium chloride
solution which is generally known as saline solution often used in
surgical operations. Drops of the saline solution were generally
absorbed in about 1 to 7 seconds as compared to in excess of 300
seconds for untreated polyurethane foam material. Surface
resistivity values of the treated foam material measured in
accordance with AATCC test method 76-1969 were about 1 .times.
10.sup.10 ohms per square unit as compared to about 5 .times.
10.sup.12 ohms for nontreated foam. The foam material did not
exhibit foaming when it was vigorously rubbed in the presence of
water.
Thus the disposable surgical drape of the present invention has
been shown to exhibit superior rates of absorption characteristics
as well as satisfy the surface resistivity requirements of the
National Fire Protection Association and failed to exhibit the
unwanted lathering characteristics.
* * * * *