Note: Descriptions are shown in the official language in which they were submitted.
\
1 173189
This invention relates to an improved
coating composition which imparts superior
blood-barrier properties, as well as desirable
water-barrier, antistatic and antislip
characteristics to a fibrous polyolefin sheet coated
therewith. In particular, the invention concerns
such a coating composition which contains powdered
polytetrafluoroethylene, methods for preparing the
coating composition and fibrous polyolefin sheets
coated with the coating composition.
U.S. Patent 4,082,887 of D.M. Coates, issued
1978 April 04, discloses a coating composition which
imparts desirably high water-barrier, antislip and anti-
static properties to a fibrous polyolefin sheet coated
therewith. Such coated sheets have been used for
gowns and drapes in hospital operating rooms. The coating
composition of U.S. Patent 4,082,887 is in the form of
an aqueous dispersion that contains 10-40% by weight
solids. The solids consist essentially of effective
amounts of (a) a water-insoluble wax, (b) an antistat,
(c) a nonionic surfactant and (d) a water-insoluble
binder resin. Example 5 of the patent discloses such
a composition which also includes an anionic aqueous
dispersion of a fluoropolymer useful as an alcohol
repellent. This composition, when coated onto a
nonwoven fibrous polyolefin sheet and then dried, is
stated to provide the coated sheet with high
water-barrier, antistat, antislip and alcohol-barrier
properties. However, applicant has found that
improvements are needed in the blood-barrier
properties of such coated sheets.
The present invention provides an improved
coating composition which when applied to a fibrous
polyolefin sheet and then dried provides the coated
sheet with improved blood-barrier properties, as well
1 17318g
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as desirable water-barrier, antistatic and antislip
properties. The coating composition is of the
general type disclosed in U.S. Patent 4,082,887. The
composition is in the form of an aqueous dispersion
that contains ln-40% by weight solids. The solids of
U.S. Patent 4,082,887 include effective amounts of a
water-insoluble wax, an antistat, a nonionic
surfactant and a water-insoluble resin binder.
However, for the coatings of the present invention,
the antistat is not required; it is optional. The
improvement of the present invention comprises
including in this coating composition an effective
amount of finely divided particles of
polytetrafluoroethylene which provides improved
blood-barrier characteristics to the coated, dried
sheet. Usually the amount of polytetrafluoroethylene
in the coating composition is at least 10% on a dry
solids basis; the preferred amount is in the range of
10 to 35~.
The present invention also provides a
fibrous polyolefin sheet coated with the dried,
improved coating composition. Preferably, the sheet
is a nonwoven sheet comprised of polyolefin
film-fibrils, most preferably of polyethylene
film-fibrils.
The invention also provides novel processes
for preparing the above-described coating
composition. In another embodiment, the process
includes the steps of (a) forming a molten ~ixture of
the water-insoluble wax and the nonionic surfactant,
(b) dispersing the finely divided particles of
polytetrafluoroethylene in the molten mixture,
(c) adding steam and then liquid water to the thusly
prepared dispersion of the particles in the molten
mixture to form an aqueous dispersion, and (d) adding
11731~9
the water-insoluble resin binder to the aqueous
dispersion. A preferred process for preparing the
coating composition includes the steps of (a) forming
a molten mixture of the water-insoluble wax and the
nonionic surfactant, (b) preparing a slurry of the
finely divided particles of polytetrafluoroethylene
in an aqueous mixture of the water-insoluble resin
binder, and (c) dispersing the slurry in the molten
mixture while adding steam and then liquid water.
When antistat is desired in the coating composition,
it is added after the last-recited step in each of
these processes.
Except for the presence of finely divided
particles of polytetrafluoroethylene (and the
optional presence of antistat) in the improved
coating compositions of the present invention, the
present compositions are substantially the same as
those disclosed in U.S. Patent 4,082,887. Thus, the
present coating composition is in the form of an
aqueous dispersion containing 10-40% by weight
solids, of which the polytetrafluoroethylene
particles amount to 10-35% by weight of the dried
coating solids. The other ingredients of the present
coating composition comprise the known effective
amounts of a water-insoluble wax, an antistat, a
nonionic surfactant, a water-insoluble binder resin
and the requisite amount of water.
The polytetrafluoroethylene particles for
use in the coating composition of the invention are
provided in an effective amount to significantly
improve the blood-barrier properties of the fibrous
polyolefin sheet coated therewith. This improvement
is in comparison to similar compositions in which the
polytetrafluoroethylene particles are not present.
Suitable polytetrafluoroethylene particles include
`` 11731~9
DLX-6000* and Teflon* 7A, each sold by E.I. du Pont
de Nemours and Company of Wilmington, Delaware. The
DLX-6000 product has a density of 2.3 grams/cm3, a
melting range of 320 to 340C, and an average
particle size of less than one micron, although the
particles may loosely agglomerate to clusters of
about 150-micron size. "Teflon" 7A has a particle
size of about 35 microns, a density of about 2.2
grams/cm3, and a melting point of about 327C.
As in the coating composition of afore-
mentioned U.S. Patent 4,082,887, the water-insoluble
wax suitable for use in the coating composition of the
invention is capable of being dispersed in water at a
concentration of 10%, based on the total weight of
wax and water. For dispersion in water, the
water-insoluble wax requires only a nonionic
surfactant or a mixture of two or more such
surfactants in an amount of from 15 to 100% by weight
based on the amount of wax. The nonionic surfactant
has a hydrophilic-lipophilic balance of from about
6-10~ The term "wax" as used herein denotes a
substance fulfilling the modern usage definition
given on page 721 of "Hackh's Chemical Dictionary",
4th ed., McGraw-Hill Co., NY, 1969.
A preferred wax for the composition of the
invention is an ethylene diamine bisamide wax, such
as Kenamide* W-5, sold by Humko-Sheffield of
Memphis, Tennessee, or Advawax* 225 sold by
Cincinnati Milacron Chemicals, Inc. of New Brunswick,
New Jersey. These waxes are known to be useful as
lubricants for thermoplastic and thermosetting resins
and provide antiblock, antitack and antistatic
properties. However, the level of antistatic
properties provided by the wax, when used in a
coating composition of the type disclosed herein
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~` -` 1 173189
without another antistat, is orders of magnitude
lower than that required for the uses intended for
the coated sheets of the present invention. Other
waxes suitable for the composition of the invention
include: "Advawax" 140 and "Advawax" 240, products
of Cincinnati Milacron Chemicals, Inc.; "Mooreflake"
160, a product of Moore and Munger, Inc.; and
"Mobilwax" 150 and "Mobilwax" 2-305, products af the
Mobil Oil Company. The wax is present in the
composition of the invention in an effective amount
such that when the composition is coated and dried on
a nonwoven polyolefin sheet at a desired level of
co~erage, water-barrier properties are imparted to
said sheet. Suitable concentrations of wax are from
about 15-40% by weight based on the amount of the
resin in the composition.
The coating composition of the invention
contains a nonionic surfactant, as disclosed in U.S.
Patent 4,082,887. The surfactant has a
hydrophilic-lipophilic balance (HLB) of from about
6-10. A HLB lower than 6 results in uneven
application of the coating whereas a value higher
than 10 causes loss of water resistance. HLB is
defined as the percentage weight of the hydrophilic
portion of a nonionic emulsifier molecule and is
described in "The Atlas HLB System", 4th printing,
edited and reprinted from Chemmunique, a publication
of Atlas Chemical Industries, Inc. The surfactant
should not cause the dispersion of binder resin to
coagulate. Among suitable, commercially available,
nonionic surfactants are the Spans*, which are
mixtures of the esters of the monolaurate, monoleate
and monostearate type and the Tweens*, which are the
polyoxyethylene derivatives of these esters. The
"Spans" and the "Tweens" are products of Atlas Powder
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1 1731~9
Company. A mixture containing 83% by weight of
"Span" 80 and 17% by weight of "Tween" 80 will
provide an HLB of 6. A mixture containing 46~ by
weight of "Span" 80 and 54~ by weight of "Tween" 80
will provide an HLB of 10.
The surfactant is employed in an amount in
the range of 15 to 100% by weight, based on the
amount oE wax. If surfactant is used in an amount
substantially in excess of the above prescribed
maximum, foaming of the coating composition and a
decrease in the hydrostatic barrier performance of
the coating made from the composition can result. It
is preferred that the amount of surfactant is just
sufficient to effect dispersion of the wax in water.
The coating composition of the present
inventions contains, as does the coating composition
of U.S. Patent 4,082,887, a water-insoluble binder
resin which is capable of wetting the polyolefin
sheet (oleophilicity). Whether a particular binder
resin possesses the requisite oleophilicity for
purpose of the present invention is determined by a
test in which an aqueous dispersion of the particular
binder resin is diluted to 25% solids and then a film
of the diluted resin dispersion is drawn, with a
number 16 Meyer rod, onto a candidate substrate. If
the resulting wet film is smooth and unbroken and
remains intact upon drying, e.g., for three minutes
in air at 110C, the binder resin meets the criterion
of "wetting" as used herein. Furthermore, the binder
resin should not possess an excessive degree of
oleophilicity, i.e., it should not impregnate the
substrate under the conditions of the above-described
test.
Other requirements for binder resins which
are suitable for use in the present coating
` ` 1173189
composition include that the resin not impart
tackiness, brittleness or poor adhesion in coatings
made therewith. Resins having a glass transition
temperature, Tg, in the range of about 20 to 50C are
usually suitable. Also, the binder resin dispersions
suitable for the present invention do not coagulate
in the presence of the antistat. A test to determine
whether a particular binder resin dispersion
possesses this coagulation property can be performed
by diluting the particular binder resin dispersion in
water to 25% solids by weight, then mixing about 70
parts by weight of the diluted resin dispersion and
about 2 parts by weight of the a~ueous antistat, and
then observing whether coagulation occurs.
The proportion of binder resin employed in
the composition of the invention is not critical and
will depend upon the particular binder resin being
used. In a preferred embodiment the binder resin is
present in about 35-80% by weight, based upon the
weight of the coating composition when dried.
Suitable a~ueous dispersions of resins include an
ethylene/vinyl acetate copolymer dispersion and an
ethylene/methacrylic acid copolymer dispersion as
described in U.S. Patent 3,487,036; a dispersion of
cross-linked terpolymer of ethyl
acrylate/styrene/acrylonitrile having a Tg of 20C;
a dispersion of cross-linked terpolymer of ethyl
acrylate/styrene/acrylonitrile having a Tg of 33C;
and a dispersion of a copolymer of 85 parts
ethylene/15 parts methacrylic acid which has been
partially neutralized with potassium hydroxide as
described in U.S. Patent 3,264,272. Rohm and Haas
Rhoplex* P-310, an acrylic/vinyl acetate copolymer
dispersion resin having a Tg of 25C is also
suitable. These resin dispersions are usually
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supplied commercially with about 50% solids by
weight. Preferred resins for use in the composition
are the two aforementioned terpolymer compositions.
The coating composition of the invention may
also contain one or more pigments, usually in a
concentration in the range of from about 1-10% by
weight based upon the weight of the coating
composition when dried. Organic and/or inorganic
pigments are suitable. Examples of such pigments are
those made by E.I. du Pont de Nemours and Company
under the names of Dalamar* Yellow, Monastral* Blue
and Monastral* Red, which have approximately 29, 37
and 19% solids by weight, respectively.
The antistat, the presence of which is
optional in the coating composition of the present
invention, is set forth in U.S. Patent 4,082,887 and
has the formula MnR3 nPO4, where M is selected
from the group consisting of lithium, sodium,
potassium, and ammonium ions; R represents an alkyl
group containing 3 to 5 carbon atoms, and n is
selected from the integers 1 and 2. A preferred
antistat is a mixture of approximately equimolar
quantities of potassium dibutyl phosphate and
dipotassium butyl phosphate. The antistat is present
in an effective amount such that it imparts
antistatic properties to the fibrous polyolefin sheet
when coa~ed thereon and dried. Suitable amounts of
antistat usually are in the range of 0.001-0.005
(oz/yd2) or .034-0.17 g/m2 by weight (dry basis),
based upon the area of the sheet. Since, ordinarily,
the antistat is commercially available as an aqueous
solution, the amount of aqueous antistat employed
will be dependent upon the concentration of the
solution. Too much antistat in the composition will
cause a loss of hydrostatic barrier properties and
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` 1173189
will result in incompatability with the binder
dispersion.
The total solids content of the composition
of the invention is usually in the range of 10-40% by
weight. Solids contents of less than about 10
generally are avoided because they are often
difficult to form into stable dispersions and require
excessively long drying times. Coating compositions
of more than 40% solids usually have high viscosity
and are difficult to apply uniformly by air-knife
coating.
To form the aqueous dispersions of the
coating compositions of the present invention with
polytetrafluoroethylene particles dispersed therein
required special novel procedures. A process for
preparing the coating composition is described in
Example 1 below. The process includes the steps of:
(a) forming a molten mixture of the
water-insoluble wax and the nonionic surfactant;
(b) dispersing the finely divided
polytetrafluoroethylene particles in the molten
mixture;
~c) adding live steam and then liquid water
to the molten mixture containing the
polytetrafluoroethylene particles to form an aqueous
dispersion;
(d) adding the water-insoluble resin binder
to the aqueous dispersion; and
(e) optionally adding the antistat.
A preferred process by which the coating composition
of the invention can be prepared is described in
detail in Example 2 below and includes the ~ollowing
steps:
(a) forming a molten mixture of the
water-insoluble wax and the nonionic surfactant;
~ 1 73189
tb) preparing a slurry o~ the finely divided
polytetrafluoroethylene particles in an aqueous
mixture of the water-insoluble resin;
(c) dispersing the slurry in the molten
mixture while adding live steam and then liquid water
thereto; and
(d) optionally adding the antistat.
In each of the above described processes, a
molten mixture of the wax and surfactant is
prepared. In the process described first, the
polytetrafluoroethylene particles are dispersed
directly into the molten mixtures. This results in
the formation of a very thick, viscous dough. A
powerful mixer is needed to knead and blend the dough
in order to uniformly disperse the particles
therein. Because the viscosity of the dough
increases with polytetrafluoroethylene content, this
method limits the concentration of
polytetrafluoroethylene in the final coating
composition prepared by this process to no more than
about 16~ by weight on a dry basis. Within the
dispersion step itself, the polytetrafluoroethylene
content of the resultant mixture before the step ~c)
steam and water addition is usually limited to no
more than about 60%, based on the total weight of the
mixture (before step c). By contrast, in the
preferred process described above, the combination of
the polytetrafluoroethylene particles/resin-binder
slurry with the molten mixture results in viscosities
that are relatively low ~compared to those of the
dough of the first process) and are maintained at
such levels by the simultaneous addition of steam
while the slurry and molten mixture are being
combined. As a result, the concentration of
polytetrafluoroethylene particles in the final
lQ
1173189
11
coating compositions prepared by the preferred
process can be 35% or higher, by weight of the final
coating composition on a dry basis.
The coating compositions described above can
be applied to fibrous polyolefin sheets in a variety
of known ways to obtain coated sheets of the
invention. For example, the coating composition can
be applied to a fibrous polyolefin substrate by
air-knife coating, Meyer-rod coating, gravure-roll
coating, the kiss-roll method, or the like.
Air-knife coating is preferred. When the coating
composition is applied to a nonwoven sheet of
polyethylene film-fibril elements, it is preferred
that the weight of the coating, on a dry basis, be in
the range of 1.7 to 3.4 g/m2 (0.05-0.1 oz/yd2).
After coating application, the coated substrate is
dried at an elevated temperature, such as in a hot
air oven. During drying, liquid evaporates from the
coating composition, the binder is coalesced and
cured, and the binder, polytetrafluoroethylene
particles and wax spread uniformly on the surface of
the substrate.
It should be noted that in the past,
dispersion of polytetrafluoroethylene particles in
water presented formidable problems, largely due to
the extreme hydrophobicity and high density of the
polymer. Prior methods for dispersing such particles
generally involved large amounts of powerful
surfactants. However, these surfactants also
substantially negated the desired hydrophobic effects
of the polytetrafluoroethylene in the dried coating.
In fact, some of the commercial aqueous dispersions
of polytetrafluoroethylene contained so much
surfactant that the dried coatings actually became
hydrophilic. Adding to these past difficulties, the
--`` 1173189
12
high density of the polytetrafluoroethylene particles
causes accelerated settling out of the particles in
water, which makes the dispersions unusable for
practical coating operations. In contrast, in the
dispersions of the compositions of the present
invention, the solids remain well dispersed for many
hours and are readily redispersed by simple mixing
without requiring excessive and undesirable
quantities of powerful surfactants.
There are two reasons why the presence of
antistat is optional, rather than required, in the
coating of the present invention. Firstly, the blood
barrier properties of sheets coated with compositions
of the present invention without antistat present in
the coating are insignificantly different from those
coated with compositions that include the antistat in
it. Secondly, even when antistatic protection is
desired for sheets coated with compositions of the
invention, as in operating-room surgical drapes, the
antistat can be applied separately from the coating.
For example, the coating of the invention ~not
containing antistat) can be applied to one side of
the sheet and the antistat can be applied to the
other side of the sheet. This method is illustrated
in Example 3 below.
Fibrous polyolefin sheets which can be
coated with the present composition include nonwoven
sheets of linear polyethylene, blends of linear
polyethylene and minor amounts of branched
polyethylene, polypropylene, polybutene, and
polyisobutylene. The nonwoven sheet can be composed
of continuous filaments, staple fibers or fibrillated
films. A preferred substrate is a nonwoven sheet of
film-fibril elements of polyolefin, most preferably
of linear polyethylene. Nonwoven sheets of
-` 117~189
13
film-fibril elements of polyolefin can be pLepared by
the process of U.S. Patent 3,169,899. Coated sheets
of the invention comprising nonwoven sheets of
film-fibril elements of polyethylene coated with the
composition of the invention possess high
blood-barrier properties, in addition to desirable
water-barrier, antistatic, antislip, softness and
aesthetic properties, thereby making the coated
sheets highly suited for use in hospital
operating-room gowns.
Antistat protection provided by a coating
prepared from a composition of the invention can be
determined by submitting a coated sample which was
previously conditioned at least 24 hours at 23.9C
(75F)/55% R.H. (relative humidity), to test NFPA
(National Fire Protection Association) Code 56A,
Section 25433, paragrah A, part 3. The result is
reported as "Log R" with values of 10.5 or lower
representing acceptable antistatic properties and a
value of about 9.5 being preferred. The "Log R"
value is determined as the average of measurements
for several different portions of the coated sample.
Water-barrier performance of a coated sample is
measured by the "hydrostatic head" test ASTM D-583,
paragraph 53A, Method II The expression "high water
barrier" as used herein means a "hydrostatic head" of
at least 63.5 cm (25 inches) as measured by this test.
The resistance to blood strike-through can
be measured by the following "blood strike-through
testH. A modified AATCC (American Association of
Textile Chemists and Colorists) crockmeter is
employed in this test. The head of the unit is
fitted with a pair of rubber rollers and weighted
with 500 grams. A piece of foam rubber is covered
with a plastic film and taped to the frame to form a
1 173189
14
pad. A blotter (or folded absorbant paper) is placed
over the pad. A test specimen, with the coated side
up, is then placed on the blotter. One milliliter of
synthetic blood is applied to the coated surface of
the specimen. The crockmeter is then run for 20
cycles at a rate of one cycle per second, during
which the weighted rubber rollers push the synthetic
blood into the test specimen. Blood that passes
through the specimen is absorbed on the blotter. By
determining the weight of the blotter, before and
after the test, a measure of the amount of blood
strike-through is obtained. The synthetic blood,
which has approximately the same surface tension as
real blood, consists of 10 grams of Pontamine* Fast
Red 8 B~X (a dye sold by E.I. du Pont de Nemours and
Company) and 25 grams of Acrysol* G110 (a surfactant
sold by Rohm and Haas of Philadelphia, Pennsylvania),
added to sufficient distilled water to provide one
liter of solution.
The following examples illustrate the
invention and show the advantage in blood
strike-through characteristics of coated sheets of
the invention. Unless otherwise specified, the
weights given for the amounts of resin binder and
pigment added to the coating composition refer to the
aqueous dispersions of these ingredients. The
amounts of the various ingredients used in each
- example and comparison are summarized in Tables I
through IV.
Example 1
A mixture of nonionic surfactants consisting
of 680 grams of "Span" 80 and 374 grams of "Tween" 80
was mixed with 3207 grams "Advawax" 240 ethylene
diamine bisamide wax and heated to a temperature in
the range of 115 to 120C. The wax-surfactant
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14
~1,~
~ 1731~9
mixture melted and formed a homogeneous,
amber-colored liquid. With the temperature of the
molten mixture maintained at 115 to 1~0C and
stirring being provided by a twin-spiral-bladed
mixer, 5.348 kilograms of DLX 6000 micronized
polytetrafluoroethylene powder was added slowly to
the molten mixture. A viscous, dough-like mass
resulted. Heating was then stopped and a total of
64.18 kilograms of water were added, initially as
live steam and then as liquid water, each at about
100C. The resulting aqueous dispersion of
polytetrafluoroethylene particles was then cooled
to about room temperature and provided a base for
the remainder of the coating composition.
To the cooled aqueous dispersion, 3.688
kilograms of Polywax* 2000 micronized polyethylene
powder (a product of Petrolite Corp. Bareco Division,
of Wayne, Pennsylvania) were added while providing
high shear mixing. Then, with the mixing being
carried on at low shear, 66.34 kilograms of Surlyn*
56220 ethylene-methacrylic acid copolymer aqueous
latex, 726 grams of Dowfax* 2A-l surfactant
stabilizer (a product of Dow Chemical Company, of
Midland, Michigan), 431 grams of Nopco* 267A
antifoam agent (a product of Diamond Shamrock of
Morristown, New Jersey), 7.4 kg Chemcor* 973-A
polyethylene binder (a product of Chemical Corp. of
America of East Rutherford, New Jersey), and 24.2
kilograms of water were added along with pigments
consisting of 7.584 kilograms of Super Imperse* Blue
X2688 la product of Ciba-Geigy of Ardsley, New York),
7.289 kilograms of "Monastral" Red RW768P, and 0.934
kilograms of "Dalmar" Yellow YW768P.
Just prior to coating a substrate with the
above-described composition, 2.268 kilograms of a 30%
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- 1173189
aqueous solution of Zelec* TY potassium butyl
phosphate antistat (a product of E.I. du Pont
de Nemours and Company) which had been adjusted to a
pH of 9.5 by addition of ammonium hydroxide, were
added to the composition to complete the coating
formulation.
The coating formulation was applied to a
lightly bonded, polyethylene film-fibril, nonwoven
sheet (i.e., a Tyvek* spunbonded olefin sheet
product of E.I. du Pont de Nemours and Company)
weighina 42.4 grams per square meter ~1.25 oz./yd2)
at an add-on weight of 1.7 g/m2 (0 05 oz/yd2), on
a dry basis. The coated sheet exhibited much better
barrier properties against blood strike-through than
did other "Tyvek" sheets coated with similar
compositions that did not contain
polytetrafluoroethylene.
Example 2
A slurry was formed from 303 kilograms of
"Surlyn" 56220 latex resin, 84.03 kilograms of
"Teflon" 7A polytetrafluoroethylene particles and
1.68 kilograms of "Surynol" 104 acetylenic glycol
surfactant (a product of Air Products of Allentown,
Pennsylvania) by mixing these ingredients at high
speed and high shear. In a separate vessel, a molten
mixture was formed at a temperature of 115 to 120C
from 7,044 kilograms of "Span" 80, 3.81 kilograms of
"Tween" 80 and 32.89 kilograms of "Kenamide" W-5
bisamide wax. The slurry was then added, over a
10 minute period, to the molten mixture while
simultaneously adding 101.6 kilograms of steam and
mixing the mass with a "Lightenin" prop mixer.
Mixing was then changed and provided by a high shear,
saw-toothed mixer blade. The following were then
added: 3.35 kg of "Nopco" 267A, 5.366 kg of "Dowfax"
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16
i~
~173189
17
2A-1, 54.4 kg of "Chemcor" 973A, 584.7 kg of water,
17.1 kg of "Super Imperse Blue" X2668, 17.5 kg of
"Monastral" Red RW768P, and 2.27 kg of "Dalamar"
Yellow YW718P. Finally, 27.22 kg of the "Zelec" TY
solution of Example 1 was added just prior to use of
the composition for application to a fibrous
polyolefin sheet. The coating composition was then
applied to a 42.4-g/m2, lightly bonded "Tyvek"
spunbonded olefin sheet with an air-knife coater and
dried to provide an add-on weight (dry basis) of
approximately 1.7 g/m2 (0.05 oz/Yd2).
For the purposes of comparison, a prior art
coating composition was made and applied to a similar
"Tyvek" sheet. A copolymer of 85 parts ethylene/15
parts methacrylic acid (which had been partially
neutralized with potassium hydroxide as described in
U.S. Patent 3,264,272) was employed as a binder resin
in the form of a 30% solids aqueous dispersion.
Although this dispersion as received can coagulate on
addition of "Zelec" TY, it was stabilized by addition
of a suitable nonionic surfactant and by employing a
suitable mixing procedure. The "as received" binder
resin dispersion was stabilized by adding to 20 grams
of it a solution of 0.5 grams of a surfactant
consisting of 65% "Span" 80 and 35% "Tween" 80 in 20
grams of water. The resultant mixture was stirred at
moderate speed. After ten minutes, a solution of 2
grams "Zelec" TY and 30 grams of water was added
dropwise to the mixture. When addition of the
"Zelec" solution was completed, the following
ingredients were added in succession: 0.7 grams of
"Monastral" Blue; 1.4 grams of "Monastral" Red B; 0.4
grams of "Dalamar" Yellow; 10 grams of Zepel* 2373
(a 22% solids anionic aqueous dispersion of a
fluoropolymer sold by E.I. du Pont de Nemours and
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17
e ~
1 173189
18
Company); and 20 grams of a wax emulsion prepared as
described in aforementioned U.S. Patent 4,082,887,
column 6, lines 49 through 58, from "Advawax" 225
and "Span" 80 and ~Tween~' 80 surfactants. This coating
is applied in the same manner as the coating of the
invention given a~ove in this example.
soth the comparative sample and a sample
coated with the coating of the invention (as given in
this example) were subjected to the "blood
strike-through" test. The product coated with the
polytetrafluoroethylene-containing product made
according to the invention had a strike-through of
0.029 gram as compared to a 0.155 gram strike-through
for the comparison sample.
XAMPLE 3
The same ingredients and methods as were
used in Example 2 were employed in this example,
except that (1) the quantities were somewhat
different and (2) the antistat, instead of being
included in the coating composition, is applied
separately to the nonwoven polyolefin film-fibril
sheet.
In accordance with the general procedure of
Example 2, a dispersion was made of 137.9 kilograms
of "Teflon" 7A, 2.04 kilograms of "Sulfonyl" 104,
495.7 kilograms of "Surlyn" 56220, 53.98 kilograms of
"Kenamide" W-5, 6.35 kilograms of "Tween" 80, 11.57
kilograms of "Span" 80, and 1117.6 kilograms of
water. Then, the following were added: 5.58
kilograms of "Nopco" 267A, 4.54 kilograms of "Dowfax"
2A-1, 89.81 kilograms of "Chemcor" 973-A, 49.89
kilograms of "Super Imperse" Blue X2688, 58.97
kilograms of "Monastral" Red RW768P and 19.05
kilograms of "Dalamar" Yellow YE718T. Before
applying the coating composition to a 45.8-g/m2
18
~" 1173~g
19
lightly bonded, "Tyvek" spun-bonded olefin sheet,
"Zelec" TY was applied to the sheet in a sufficient
quantity to provide the sheet, when dried, with a
log R of less than 9.0 on that side of the sheet.
The "Zelec" antistat was applied by a "brush-flicker"
method. The "brush-flicker" method involves a solid
kiss-roll which rotates in a pan of aqueous
antistat. A rotating brush in contact with the
kiss-roll picks up antistat and "flicks" it from the
bristle tips onto the polyolefin sheet, in a manner
similar to spatter painting. While the sheet was
still wet from the antistat application, the coating
composition was applied by means of an air-knife
coater to the dry side of the sheet (i.e., the side
opposite from the side on which the an~istat had been
applied). The coated and antistatted sheet was dried
at 200-230F (93-110C) in an air oven. The total
add-on weight (dry basis) of the coating and antistat
was approximately 1.7 g/m2.
Samples of the thusly prepared sheet were
subjected to the blood strike-through test. No
detectible difference in strike-through was found
between these samples and the samples of coated sheet
in which the antistat wa~ added directly to the
coating composition as in Example 2. Also, complete
absence of antistat from the sheet, whether from the
coating or from the opposite side of the sheet,
insignificantly affected blood strike-through
properties.
3~
19
1~73189
TABLE I
Coatinq Composition of ExamPle 1
Amounts Included
* As Added Dry Basis
5 Ingredients kg kg %
Polytetrafluorethylene
powder DLX 6000 5.3485.34812.8
Water-insoluble Wax
"Advawax" 240 3.2073.2077.69
10 Antistat
"Zelec" TY 2.2680.6801.63
Non-lonic Surfactants
"Span" 80 0.6800.6801.63
"Tween" 80 0.3740.3740.90
15 Water-Insoluble Resin Latex
nSurlyn" 56220 66.3420.89750.10
Pigments
nMonas~ral" Red 7.2891.3993.35
"Dalamar" Yellow 0.9340.2710.65
"Super Imperse" Blue 7.5842.1545.16
20 Other
Water 88.38 0 0
"Nopco" 267A 0.4310.4311.03
"Chemcor n 973-A 7.4 2.220 5.32
nPolywax" 2000 3.6883.6888.84
"Dowfax" 2A-1 0.7260.3630.87
*Note - All ingredients listed by tradenames are
defined in the text.
1 723189
TABLE II
Coating Composition of Example 2
Amounts Included
As Added Dry Basis
Ingredients* kg kg %
Polytetrafluorethylene
powder DLX
"Teflon" 7A 84.03 84.03 31.8
Water-insoluble Wax
"Kenamide" W-5 32.89 32.89 12.4
Antistat
"Zelec" TY 27.22 8.166 3.09
Non-Ionic Surfactants
"Span" 80 7.044 7.044 2.67
"Tween" 80 3.81 3.81 1.44
"Surfonyl" 104 1.68 1.68 0.64
Water-Insoluble Resin Latex
"Surlyn" 56220 303.0 95.445 36.11
Pigments
"Monastral" Red 17.5 3.36 1.27
"Dalamar n Yellow 2.27 0.658 0.25
"Super Imperse~ Blue 17.1 4.856 1.84
Other
Water 686.3 0 0
"Nopco" 267A 3.35 3.35 1.27
"Chemcor n 973-A 54.4 16.32 6.17
~Dowfax" 2A-1 5.366 2.683 1.02
*Note - All ingredients listed by tradenames are
d~ ed in the text.
21
'';
11731~9
22
TABLE III
Comparison ComPosition of Example 2
Amounts In-cluded
As Added Dry Basis
5 Ingredlents* grams grams %
nZepeln 2373B aqueous
fluoropolymer
dispersion 10.0 2.2 16.67
Water-insoluble Wax
nAdvawax" 225 1.71 1.7112.96
Antistat
~Zelec" TY 32.0 1.0027.59
Non-Ionic Surfactants
"Span~ 80 1.065 1.0658.08
"Tween" 80 0.575 0.5754.36
15 Binder Resin Latex 20.0 6.0 45.48
Pigments
~Monastral" Red 1.4 0.2692.04
~Dalamarn Yellow 0.4 0.1160.88
nMonastral" Blue 0.7 0.2571.95
Water 37.1 0 0
*Note - All ingredients listed by tradenames are
defined in the text.
22
-
1173189
~3
TABLE_IV
Coatin~ Composltl n of ExamPle 3
Amounts Included
* As Added Dry Basis
Ingredients kg kg
Polytetrafluorethylene
powder DLX
"Teflon" 7A 137.9 137.9 31.3
Water-insoluble Wax
"Kenamide" W-5 53.98 53.98 12.3
10 NOn_IOnic SurfactantS
"Span" 80 11.57 11.57 2.63
"Tween" 80 6.35 6.35 1.44
"Surfonyl" 104 2.04 2.04 0.46
Water-Insoluble Resin Latex
"Surlyn" 56220 495.7 156.1 35.46
Pigments
"Monastral~ Red 58.97 11.32 2.57
~Dalamar" Yellow 19.05 5.52 1.25
"Super Imperse" Blue 49.89 14.17 3.22
Other
Water 1,117.6 0 0
nNopco" 267A 5.58 5.58 1.27
"Chemcor" 973-A 89.81 33.95 7.71
"Dowfax" 2A-1 4.54 1.72 0.39
*Note - A11 ingredients listed by tradenames are
defined in the text.
