Note: Descriptions are shown in the official language in which they were submitted.
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1
DURABLY WETT.~BLE, LIQUID PERVIOUS WEBS
' TECHNICAL FIELD
The present invention relates to a durably wettable, liquid pervious web chat
is particularly suitable
as a topsheet for absorbent articles. More particularly, the invention relates
to a polymeric film or
nonwoven to which is applied a thin coating of organic material onto at least
one surface of the film or
nonwoven. The thin organic coating is applied by a plasma-induced chemical
vapor deposition process.
The thin organic coating renders the web more permanently hydrophilic than
other methods known in the
art. The invention further relates to a process for making the durably
wettable, liquid pervious web, and to
articles containing the durably wettable, liquid pervious web as a topsheet.
BACKGROUND OF THE INVENTION
Polymeric and nonwoven webs are common components of disposable absorbant
articles, dryer
sheets and the like. More particularly, macroscopically expanded, three-
dimensional, polymeric films have
been utilized as topsheet materials for disposable absorbent ~ articles. As
used hcrcin, the term
"macroscopically expanded", when used to describe three-dimensional webs,
refers to webs which have
been caused to conform to the surface of a three-dimensional forming structure
so that both surfaces thereof
exhibit the three-dimensional pattern of the forming structure or webs that
have an inherent threc-
dimensional pattern arising from their structure. Regardless of whether the
three-dimensional pattern is
inherent or generated by application of a forming process, the pattern is
readily visible to the naked eye
when the petpertdicular distance between the viewei s eye and the plane of the
web is about 12 inches. By
way of contrast, the term "planar", when utilized herein to describe nonwovens
and polymeric films, refers
to the overall condition of the web when viewed by the naked eye on a
macroscopic scale. In this context
"planar" webs may include webs having fine-scale surface aberrations on one or
both sides, the surface
aberrations not being readily visible to the naked eye when the perpendicular
distance between the viewer's
eye and the plane of the web is about l2 inches or greater.
One macroscopically expanded. three-dimensional aperntred polymeric web which
is particularly
well suited to transferring liquid deposited on one surface thereof to its
opposite surface and thereafter
isolating the transferred liquid from a wearer's skin is disclosed in commonly
assigned U.S. Patent No.
3.929,135 issued to Thompson on Dec. 30, 1975.
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.2.
Thompson describes a macroscopically expanded, three dimensional web (e.g., a
topsheet) comprised of
liquid impermeable material, but provided with a pattern of tapered
capillaries, the capillaries having a base
opening in the plane of the topsheet and an apex opening remote from the plane
of the topsheet, the apex
opening being in intimate contact with the absorbent pad utilized in the
disposable absorbent article. The
40 Thompson topsheet allows the free transfer of liquids from the wearer's
body into the absorbent element of
the device while inhibiting the reverse flow of these liquids. This provides a
relatively much drier surface
in contact with the user than had previously been obtainable. Another
macroscopically expanded three-
dimensional apertured plastic web well suited for use as a topsheet on
absorbent articles such as sanitary
napkins is disclosed in commonly assigned U.S. Patent No. 4,342,314 issued to
Radel et al. on Aug. 3,
45 1982. The macroscopically expanded, three-dimensional plastic web disclosed
in the Radel patent exhibits
a fiber-like appearance and tactile impression which has been favorably
received by consumers when used
as a wearer contacting surface. According to the teachings of the commonly
assigned patents to Thompson
and to Radel, et al., plastic webs of the aforementioned type can be made by
applying a pressure
differential to the web while it is supported on a three-dimensional forming
structure until the web is
50 macroscopically expanded to comply with the three-dimensional cross-section
of the forming structure on
which it is supported. When aperiuring of the macroscopically expanded, three-
dimensional web is
desired, the pressure (vacuum is described) differential is applied
continuously until such time as
aperturixig of the web in areas coinciding with the apertures in the forming
structure has been completed.
A mufti-phase, liquid-based process such as that described in U.S. Patent No.
4.609,518, issued
55 September 2, 1986 to Curro et al. (hereafter referred to as "'518 patent"),
was also developed to provide a
film with very small and very large apertures immediately adjacent one
another. As the patent discloses,
the formation of the very small (inciudine micro-sized) apertures in the
direction opposite those formed for
large apertures hinders the ability of initially unabsorbed liquid from
running off the web's surface. Thus,
liquid not immediatciy transported through the large apertures is restrained
from running off the web's
60 surface, and is subsequently taken up through the larger apertures and is
deposited in the article's core
where the web is used as a topsheet material. These outwardly formed small
apertures also reduce the level
of web/skin contact and reduce the rigidity of the film, and thereby feel more
comfortable to the user.
Wearers have reported that such topsheets have a soft silky surface.
Altemativcly, the '518 patent discloses
films where the very small apcrtures are formed in the same direction as the
macro-apertures.
65 Regardless of the means employed for aperture formation, where a wettable
film material is
desired, the above refcrences generally obtain such a structure by surface
treating the naturally hydrophobic
polymeric web with a wetting agent. Surface treatment is generally
accomplished by either spraying
surfactant onto the web's surface or by dipping the web in a surfactant-
containing bath. Regardless of
which of these methods is employed, surface treatment suffers from the
inahiliry~ to precisely control the
70 location and level of treatmcnt, as well as adversc effecu caused by
migration of significant amounts of
surfactant into apertures and othcr components (e.g., absorbcnt core) when the
apertured film is used as a
topsheet in an absorbent article. Surface acatment further suffers from the
disadvantage that desirable
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wetting agents, or surfactants, tend to be washed off upon repeated exposure
to such liquids. Thus, when
75 used as a fopsheet in an absorbent article. the treated films lose their
ability to transport liquid away from
the skin and into the article's core after repeated wettings.
f U.S. Patent No. 4,535,020, issued to Thomas et al._on August 13, 1985,
addresses some of the
problems associated with surface treating vacuum-formed apertured films by
incorporating hydrophilic
surfactant in the polymeric resin before . extrusion for film formation
(referred to herein as "resin
80 incoiporated surfat:zant", or "RIS"). (Sec also commonly assigned U.S.
Patent No. 5,792,412 to Y. P.
Lee et al., issued August 11, 1998; U.S.. Patent No. 4,923,914 to Nohr et al.,
issued
May 8, ) 990; U.S. Patent No. 5,07,262 to Nohr et al., issued October 15,
1991; U.S. Patent No. 5,120,888
to Nohr et al., issued June 9. .1992.) According to the teachings of Thomas,
after extrusion of the
resin/surfactant mixture, and subsequent formation of the apertures, the
incompatible surfactant eventually
85- blooms to the film's surface to provide a more durably wettable web.
However, as with surface treatment,
RIS suffers from some degree of surfactant wash-off during use and/or during
manufacture, particularly if
liquid pressure differentials are used to form the web's apertures. Also,
hydrophilic webs formed using RIS
techniques arc not immediately wettable. and depending on the relationship
between the resin and the
surfactant and environmental conditions, may not become wettable for finite
periods of time. Similarly,
90 when such webs are used in absorbent articles, there will be some time
delay before surfactant (that is
washed off during wear) is replenished at the we'b's surface.
In spite of the teachings of the prior art, there remains a need for a liquid
pervious web or film
material that offers improved durable wenabiiiry after the passage of time
and/or after exposure to. liquid
insults. Such materials have particular suitability for use in disposable
absorbent structures. There also
9~ remains the need for a process that provides such a durably wettable,
liquid pervious web.
Accordingly, it is an object of an aspect of the present invention to provide
a liquid pervious web
having improved durable wettability. This durable wettabiiity is attained by
applying a plasma-induced
hydrophilic coating onto at least one surface of the starting web, to render
the resulting web durably
hydrophilic.
100
SUMMARY OF THE INVENTION
The present invention relates to a durably wettable, liquid pervious web that
is particularly useful
as a topshect material for absorbent articles. In one respect, the inventions
relates to a durably-wettable,
liquid pervious web which comprises:
105 (t) a web selected from the group consisting of polymeric fiitns and
nonwovens;
(ii) a substantially continous hydrophilic coating, less than about 2.5
microns thick, on at
least one surface of the web, wherein said hydrophilic coating is applied to
the web by
plasma polymerization;
wherein at least one surface of the durably-wettablc, liquid pervious web has
a Post Aging contact angle
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4
110 that is not more than about 60 degrees greater than the Pre Aging contact
angle.
In a similar aspect respect, at least one surface of the treated web will have
a Post
Washing contact angle that is not more than about 60 degrees greater than the
Pre Washing
contact angle. Preferably, both conditions will exist in a single web.
The invention also relates to an absorbent article comprising a durably
wettable,
115 liquid pervious topsheet, the topsheet comprising a web and a hydrophilic
coating on at least
one surface of the web, wherein the hydrophilic coating is applied to the
substrate by plasma
polymerization.
According to an aspect of the present invention, there is provided a process
for
making a durably wettable, liquid pervious apertured web for use as a topsheet
in an
120, absorbent article, the process comprising the steps of:
a) forming apertures in a web, which is a polymeric film or nonwoven web;
b) direct plasma polymerizing the apertured web of step (a) by:
(i) introducing the web in a plasma reaction zone; and
(ii) coating at least one surface of the web with a coating of polymerized
125 monomers, wherein the coating is less than 2.5 microns thick and is
derived from a monomer
gas stream that provides a hydrophilic coating upon plasma polymerization,
whereby the
polymerized monomers cause the at least one surface of the web to become
durably wettable.
According to an aspect of the present invention, there is provided the use of
a web
produced by the process described above for use as a topsheet in an absorbent
article.
130 Finally, the invention relates to a plasma polymerization process for
making the
durably wettable, liquid pervious webs described herein.
DETAILED DESCRIPTION OF THE INVENTION
135 I. Durably Wettable, Liquid Pervious Webs
As discussed in detail below, the present invention relates to a durably
wettable web
that is prepared by applying a hydrophilic coating to a starting polymeric
film or nonwoven,
using a plasma polymerization process.
As used herein, the term "web" refers to the starting substrate (i.e., a
polymeric film
140 or nonwoven) to which the hydrophilic coating is applied. In contrast, the
terms "durably
wettable, liquid pervious web" or "treated web" refer to the final product -
the polymer film
or nonwoven having the durable hydrophilic coating.
As used herein, the term "liquid pervious" refers to the ability of a web or
treated web
to transport liquids from one surface of the web or treated web to the
opposite surface of the
145 web or treated web in a sufficiently efficient manner so as to allow the
treated web to be used
CA 02340972 2004-02-04
4a
as a component of a disposable article. Webs may be inherently liquid pervious
or may be
made liquid pervious by application of a processing step. such as, aperturing.
As used herein, the term "substantially continuous" means sufficiently
continuous to
provide the hydrophilic or wettable properties as defined by the stated or
claimed contact
150 angle limitations.
As used herein, the terms "hydrophilic" and "wettable" are used
interchangeably and
refer to surfaces that are wettable by aqueous liquids (e.g., aqueous body
liquids) deposited on
these surfaces. Hydrophilicity and wettability are typically defined in terms
of contact angle
and the surface tension of the liquids and solids involved. This is discussed
in detail in the
155 American Chemical Society publication entitled Contact Angle, Wettability
and Adhesion,
edited by Robert F. Gould (Copyright 1964). A web surface is said to be wetted
by a liquid
(i.e., hydrophilic) when either the contact angle between the liquid and the
web surface is less
than 900, or when the liquid tends to spread spontaneously across the surface
of the web, both
conditions normally co-existing. Conversely, a surface is considered to be
hydrophobic if the
160 contact angle is greater than 900 and the liquid does not spread
spontaneously across the
surface of the web. In general, the lower the contact angle between the
surface and the liquid,
the more hydrophilic the surface.
The durably wettable, liquid pervious webs of the present invention are
"durably
wettable", insofar as the hydrophilic character engendered to the otherwise
more hydrophobic
165 film is maintained over time
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WO 00/16913 PCT/US99/21709
-5-
and after exposure to liquids. As discussed above, prior approaches directed
at making hydrophobic films
wettable result in initial improvements in wettability, but suffer from the
negative attribute that wettability
is lost over time and/or exposure to liquids. While not being bound by theory,
it is believed that typical
150 hydrophilic polymer and surface-treated polymer systems, such as corona
discharge treatments, go through
a "hydrophobic recovery" process. During the hydrophobic recovery process,
surface wettabiliky tends to
decay over time because thermodynamics favors the exposure of lower surface
energy molecular chain
segments at polymer surface. Upon aging, hydrophilic molecular segments
reorient and embed themselves
and expose hydrophobic segments at polymer surface. If chemical crosslinking
is induced at the polymer
155 surface, the crosslinking tends to limit polymer chain mobility, thus
significantly slowing the "hydrophobic
recovery" process and therefore preserving polymer surface wettability over
time. Since Applicants'
invention provides for polymer chemical crosslinking, via a radiation curing
process, a durably wettable,
liquid pervious web can be produced.
Durable wettability is described herein in terms of the ability of a durably
wettable, liquid pervious
160 web (as indicated, also referred to herein as a "treated web", to
distinguish from the starting more
hydrophobic "web") to retain its wettable character after aging (referred to
as "Post Aging") and/or after
exposure to liquids (referred to as "Post Washing"). The methods for measuring
Post Aging contact angle
and Post Washing contact angle are discussed below.
As indicated, the durable wettability of the present durably wettable, liquid
pervious webs is
165 attained by use of a plasma process. Plasma is often referred to as the
fourth state of matter. When energy
is applied to a solid (e.g., a polymeric film or nonwoven), the solid can
undergo a transition to the liquid
state. If further energy is applied, the liquid becomes a gas. If additional
energy of the proper kind is
applied, the gas dissociates and becomes plasma. Plasmas exist in a variety of
forms. The preferred plasma
useful herein is a low pressure or vacuum process, which allows processing of
the web at or near ambient
170 temperature, i.e.: about 20°C. This prevents thermal degradation of
the web being processed andior
thermal distortion of the formed web that is being treated. Within the plasma
chamber where the web is to
be treated, active species in the form of electrons, free-radicals, ions and
energetic neutrals collide with the
surface of the web, e.g. polymer, breaking molecular bonds and creating new
functional groups on the
surface. These active and energetic species also react in the gas phase,
resulting in a thin coating being
175 deposited on at least one surface of the web.
Suitable plasma systems for use in the present invention incorporate a
parallel plate electrode
design where materials to be treated are exposed directly to the primary field
of RF energy, but are not part
of the circuitry. The subsequent primary plasma is particularly more uniform
and more efficient since the
part is exposed in al! three dimensions to the glow discharge. With higher
pressure processes (but still
180 within the general definition of a cold gas plasma), some form of gas
delivery system, designed to create a
uniform laminar flow of process gas throughout the entire chamber volume is
beneficial. In multiple
electrode/shelf designs, it is important that each of the electrodes receive
equal amounts of RF energy. In
this manner a uniform glow discharge is created between each shelf or in each
plasma zone. Solid state
components and microprocessor control of the system parameters of process
time, flow rate, power level,
CA 02340972 2004-02-04
.6-
185 and working pressure, will also ensure process uniformity, efficiency, and
repeatability.
Since plasmas are electrically conductive atmosphetta, they carry a
charactetutic impedance to the
output of the RF generator. Therefore, the preferred plasma process utilizes a
matching netwotk to
constantly tune the plasma impedance to the output irttpedance of the RF
generator. Advanced plasma
systems suitable Yor use in the present invention art: available from HIMONT
Plasma Science; Foster City,
190 CaliC. (a btuinas unit of HIMONT U.SA., lac.), and incorporate an
automatic matching type of network
and provisions for crro~r checking during the process. . . .
'the low temperature plasma is generated in a gaseous atmosphere at reduced
pressure of from
about 0.001 to about 10 Torn, preferably from about 0.01 to about 5 'Corn,
more preferably from about 0.05
to about 1 Totr, and most preferably from about 0.05 to about 0.4 Totz. The
electric power can be suppliod
195 to the equipment at a high radio frequency, from about 40 Kliz to about 3
GHz, preferably from about 13
to about 27 MHz, and most conveniently at about 14 MHz. To achieve the desired
plasma condition in the
gaseous atmosphere, the electric power delivered to the apparatus can vary
over a range of from about 10 to
about IO,fi00 watts; preferably from about 50 to.about 5,000 watts, more
preferably from about 250 to
about 3000 watts, most preferably from about 500 to about 2500 watts. The
power used is somewhat
200 dependent on the chamber's working volume. The mo *prefeaed range of about
500 to about 2500 watts
is appropriate for HIMONT Plasma 'Science PSOSOOD gas plasma apparatus with a
working vohvae of
about 5.0 cubic feet. The plasma acatment time varies from a few seconds to
several minutes, preferably
from about 20 seconds to about 30 minutes, most preferably from about 60
seconds to about 20 asiautes.
h should be appreciated that treatment presstue, time and power are
intemlated, rather than
205 independent, variables. The effect of the level selected for each of these
variables will determine the extent
of web surface modification and/or coating thickness; also related are the
chamber vohtme and geometry as
well as the sample size and surface geometry. 'The selection of the level for
these variables is well within
the ordinary skill of practitioners in the art to which this invention
pertains.
The hydrophilic coating layer is deposited onto the surface of a suitable web
(either previously
210 apertured or unapertured) by low temperature plastna~induced vapor
deposition (i.e., polymtrization) of a
monomer or a combination of monomers, such that a hydrophilic coating will be
applied to the web. In a
prefetsed embodiment, the monomers will be silicon-containing compounds having
one to three silicon
atoms. which compounds are selected from the group consisting of (i) silanes
of the formuL SiR, where
each R is the same or different and is selected from H; a C,~C, linear or
branched alkyl or alkoxy; a C6-C,°
215 aryl, unsubstituted or substituted with C,-C, linear or branched alkyl; a
vinyl radical, i.e. --CH~CH=; or a
C~~C~ allyl radical; provided that when R is H only one or two Rs are H; (ii)
organosilicones based on a
structure consisting of alternate silicon and oxygen atoms with various
organic radicals attached to the
silicon having the formula R'R"R'"Si-[-O-Si(R')(R")-]~ R'", where R', R" and
R'" can be the same or
different and are C,~C, linear or branched alkyl or alkoxy, R' and R" can also
be hydrogen provided that no
220 more than 50% of the R' and R" groups are hydrogen, and n is 1, 2 or 3;
and (iii) mixtures thereof.
Representative silicon compounds include, but are not limited to,
hcxamethyldisiloxane
(HMDSO), methyltrimethoxy silanc (MTMS), vinyltrimethoxy silane (VTMS),
vinyltriethoxy silane
. ,
* = Trade-mark
CA 02340972 2004-02-04
.7.
(VTES), cthylmcthoxy silane (EMS), ethyltrimeehoxy silane (ETMS), tetraethoxy
silane (TES),
cyclohexylmcthyl-dimethoxy silane (CMDMS), diryclopenryl-dimethoxy siltae
(DCDMS),
225 phenyltriethoxy silane (PES), diphenyldimethoxy silaate
(DPDMS),.tetramethyldisiloxane (TMDSO);~and
hexamethyltrisiloxane (HMTSO), The silicon corrrpounds employed are introduced
into thr plasma
deposition chamber in the gaseous state. Prior to being introduced into the
chariiber, the silicon compound
is heated to a tempennue of from about 40° to about 100°C,
generally from about 40° to about 60°C, to
vaporize the compound and create sufficient vapor pressure such that the
coating is deposited at a
. 230 reasonable speed. Oxygen in gaseous form and argon are fed into the
deposition chartibtr simultaneously
with, but etit:h with a separatt iceding means end ttaass flow controller, the
gaseous silicon compound.
Dtpeading upon the application, the O, flow rate ranges from about 25 standard
cubic ceatimeter/minute
("seem") to about 1200 seem, the gaseous silicon compound flow is from about
10 seem to about 25Q .
seem, and Ar flow is from about 1 scan to about 150 acccrs.. Argon is used to
enhance the rate of deposition
235 of the gaseous materials being employed sad, therefore, it is. pKferable
to use Argon iin the process. With
respect to the flow rates for argon and oxygen versus the monomer (e.g HMDSO)
flow rate, the following
are preferred: assuming that the mass flow Q1 represents 3% argon and 97. %
oxygen and vapor mass flow
Q2 represents the mass flow for the monomer, the prefered ratio of Qi:Q2 is
from about 10:1 to about 1:2,
more prefered is from about 5:1 to about 1: J, and most preferred is about
3:2.
240 Oxygen is essential to the plasma deposition process with the silicon
compounds according to this
invention. Without oxygen, it is not possible to obtain a plasr»a~induccd
hydrophilic'coating using the
aforementioned silicon compounds. Whatever oxidizing effect it bas, it'sppears
to be necessary to utilize
oxygen it one is to obtain the hydrophilic coatings of this invention.
The total vapor pressure of the gaseous materials introduced into the plasma
deposition chamber
245 for the deposition of the hydrophilic coating layer is about 0.04 to about
0:5 Torr, preferably about 0.35 to
about 0.45 Torn, most preferably about 0.4 Torn. The process pressure must be
such that a low bias
potential on the RF-driven electrode is achieved. The total vapor pressure for
the hydrophilic coating Layer
is from about 0.04 to about 0.4 Totr, preferably from about 0.06 to aboutØ13
Torn, depending on the
process used and the substrate being treated.
250 Alternatively, monomer deposition may be achieved via the flash
vapori2ation technique that
is described in U.S, Patent No. 4,842,893.issued to Yializia on Apr. 29, 1988.
" The web to be subjected to plasma polymerization may be flat (two
dimensional) or complex
(three dimensional, including previously apertured films and nonwovens). That
is, plasma treatment may
be conducted either before or after fottnacion of the apertures of the web. In
a preferred embodiment,
255 plasma treatment will be conducted after aperture formation, so as to
better preserve a uniform hydrophilic
coating on the web's surface.
Tht* forementioned advanced plasma systems available from HIMONT Plasma
Science, such as
the' PSOSOOD rtactor are equipped with a throttle valve, thereby making it
possible to achieve a range of
process pressures with the same gas flow rate.
* = Trade-mark
CA 02340972 2004-02-04
_$_
The plasma treatment time for obtaining the desired hydrophilic coatings is
from typically about 1
minute to about 10 minutes, preferably about 1.5 to about 4 minutes, most
preferably about t.5 to about 2.5
minutes; and the RF power used to cause reaction of the vapor is typically
from about 200 to about 1500
watts, preferably about 1000 to about 1400 watts, most preferably about 1100
to about 1300 watts. The RF
265 power typically employs ranges from about 1200 to about 2500 watts and
depends on the substrate being
treated and the throughput requirements. The resulting hydrophilic coatings
can be produced in different
thicknesses, but are typically from about 0.1 to about 2.S micmns; preferably
about 1 to about 2 microns.
As indicated, the plasma induced hydrophilic coating exhibits a contact angle
for water of less
than about 90 degree, such that any water placed on the treated web will tend
to spread spontaneously over
270 the treated web's coated surface. In a preferred embodiment, the treated
web may be further treated by
exposure to a low temperature plasma gas composition (also referred to herein
as a "surface modifying gas
saearri') or an energy source (also referred herein as "radiation curing")
such as an apparatus that emits,
including but not limited to, infra red, election beam, thermionic or ultra
violet radiation. Apparatuses that
are suitable as energy sources in the present invention are disclosed in U.S.
Patent No. 4,842,893 issued to
275 Yializis on Apr. 29, 1988.
In the surface modifying gas stream embodiment the gas stream preferably
comprises N:O and
CO=, to enhance the durability of the hydrophilic coating. In one such
preferred embodiment, the plasma
gas composition will comprise from about 80 to about 40 mol % N:O and from
about 20 to about 60 mol
CO:, preferably from about 70 to about 4S mol % N:O and from about 30 to about
55 mol % CO=, most
280 preferably from about 60 to about 45 mol % N,O and from about 40 to about
SS mol % CO,, where the
amount of 1;:0 and CO= in the mixture equals 100 to 10 mol %, for a time
sufficient to modify the surface
of the hydrophilic coating to enhance its durability.
In the radiation curing embodiment, the radiation source is preferably a gas
discharge electron
beam gun. The gun directs a flow of electrons through a emitter window onto
the monomer, thereby
28S further curing the monomer, which enhances the durability of the
hydrophilic coating. Curing is controlled
by matching the electron beam voltage to the dielectric thickness of the
monomer coating. For example, a
Kv electron voltage will penetrate about 1 micron of deposited monomer.
The plasma process is generally practiced as follows. The starting web to be
treated is placed into
a vacuum chamber and the chamber pressure is reduced, typically to about 0.005
Totr. The process gas or
290 gas mixture employed is introduced to the chamber and the chamber pressure
is stabilized at a pressure of
0.04-0.4 Torn. The interior dimension of the work area is approximately 1.73.X
0.7G~.X 1.02 meters (width
x height x depth) Cor a total working volume of 1.34 cubic meters. A suitable
high frequency form of
energy, typically 13.56 MHz radio frequency energy, is used to create the
plasma: in the system described,
this is achieved with a total power input capacity of up to 2500 watts. The RF
energy dissociates the gas,
295 creating a plasma characterized by a distinctive glow. Since the process
is conducted at reduced pressures,
the bulk temperature of the gas is near ambient temperature, thus the
reference to a cold gas plasma, a glow
discharge, or a cold gas glow discharge. Because the web being subjected to
the plasma conditions is
located within the electric fie'id. the process is referred to as direct
plasma polymerization. In contrast, see
CA 02340972 2004-02-04
_g.
The electrons or ions created in the plasma bombard the web's surface,
abstracting atoms or breaking
300 bonds, creating free radicals. These free radicals are unstable and seek
to satisfy a more stable state by
reacting with free radicals or groups within the plasma gas, also establishing
new moieties on the surface of
the web. In addition, the energetic electrons in the glow discharge fragment
the molecules in the gas phase,
leading to complex chemical reactions that result in a thin hydrophilic
coating being deposited on at least
one surface of the web.
30S Typically, and preferably, before plasma deposition of the hydrophilic
coating onto the web, an
initial step is performed. The purpose of this step is to clean the web's
surface to promote adhesion of the
subsequently deposited thin hydrophilic coating. Cleaning may be accomplished
by subjecting the web's
i surface to radiation (herein referred to as radiation cleaning) from an
energy source including but not
limited to, infra red, electron beam, thermionic or ultra violet radiation or
by plasma cleaning. Apparatuses
310 that are suitable' as energy sources in the prcscnt invention are
disclosed in U.S. Patent No. 4,842,893
issued to Yializis on Apr. 29, 1988. In the radiation cleaning embodiment, the
radiation source is
preferably a gas discharge electron beam gun. The gun directs a flow of
electrons through a emitter
window onto the web's surface, thereby abstracting atoms or breaking bonds,
thus creating free radicals.
These free radicals are unstable and seek to satisfy a more stable state thus
they serve as bonding sites for
31 S the monomers that are used to produce the web's hydrophilic coating.
Cleaning is controlled by matching
the electron beam voltage to the dielectric thickness or depth of cleaning
that is desired. For example, a 10
Kv electron voltage will penetrate to a web depth of about 1 micron.
In the plasma cleaning embodiment, the gases are usually either Ar alone, O,
alone, or mixtures
(e.g.. l:1 ratio) of Ar and O,. Gas flow rates are typically in the range of
about 20 to about 100 seem
320 (standard cc/min), preferably about 40 to about 80 seem, and most
preferably about 50 to about 60 seem.
RF power is approximately 1100 watts, and process pressure is about 0.040
Torn.
After the optional initial step, the next step is the plasma deposition of the
hydrophilic coating, as
described above and in more detail in the examples below. Often, but not
always, a step subsequent to the
CO. and N:O surface treating step is used to enhance the durability or
uniformity of the plasma coating.
325 Useful process gases are Ar andlor O=. Process times are usually about 1
to about 3 minutes, with about 2
minutes typically being optimum. Gas flows range from about 40 to about 250
seem, with process
pressures from about 0.200 to about 0.400 Torn, and RF input power from about
150 to about 1500 watts.
The materials useful as polymeric films to be plasma treated to provide a
hydrophilic coating will
be derived from thermoplastic polymers. In general, the term "thermoplastic
polymei' is used herein to
330 mean any thcrtnoplastic polymer which can be used for the preparation of
films. Examples of
thermoplastic polymers include, by way of illustration only, end-capped
polyacetals, such as
poly(oxymethylene) or ', polyfottnaldehyde, poly(trichloroacetaldehyde),
poly(n-valeraldehyde),
poly(acetaldehyde), poly(propionaldehyde), and the like: acrylic polymers,
such as polyacrylamide,
CA 02340972 2001-02-16
WO 00/16913 PCT/US99/21709
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poly(acrylic acid), poly(methacrylic acid), poly(ethyl acrylate), poly(methyl
methacrylate), and the like;
fluorocarbon polymers, such as poly(tetrafluoroethylene), perfluorinated
ethylene-propylene copolymers,
ethylene-tetrafluoroethylene copolymers, poly(chlorotrifluoroethylene),
ethylene-chlorotrifluoroethylene
340 copolymers, poly(vinylidene fluoride), polyvinyl fluoride), and the like;
polyamides, such as poly(6-
aminocaproic acid) or poly(s-caprolactam), poly(hexamethylene adipamide),
poly(hexamethylene
sebacamide), poly(11-aminoundecanoic acid), and the like; polyaramides, such
as poly(imino-I,3-
phenyleneiminoisophthaloyl) or poly(m-phenylene isophthalamide), and the like;
polyarylenes, such as
poly-p-xylylene, poly(chloro-p-xylylene), and the like; polyaryl ethers, such
as poly(oxy-2,6-dimethyl-1,4-
345 phenylene) or polyp-phenylene oxide), and the like; polyaryl sulfones,
such as poly(oxy-1,4-
phenylenesulfonyl-I,4-phenyleneoxy-1,4-phenyIene-isopropylidene-1,4-
phenylene), poly(sulfonyl-1,4-
phenyleneoxy-1,4-phenylene-sulfonyl-4,4'-biphenylene), and the like;
polycarbonates, such as
poly(bisphenol A) or poly(carbonyldioxy-1,4-phenylene-isopropylidene-1,4-
phenylene), and the like;
polyesters, such as polyethylene terephthalate), poly(tetramethylene
terephthalate), poly(cyclohexyiene-
350 1,4-dimethylene terephthalate) or poly(oxymethylene-1,4-cyclohexyl-
enemethyleneoxyterephthaloyl), and
the like; polyaryl sulfides, such as polyp-phenylene sulfide) or poly(thio-1,4-
phenylene), and the Like;
polyimides, such as poly(pyromellitimido-1,4-phenylene), and the like;
polyolefins, such as polyethylene,
polypropylene, poly(1-butene), poiy(2-butene), poly(1-pentene), poly(2-
pentene), poly(3-methyl-1-
pentene), poiy(4-methyl-1-pentene), 1,2-poly-1,3-butadiene, 1,4-poly-1,3-
butadiene, poiyisoprene,
355 polychloroprene, polyacrylonitrile, polyvinyl acetate), poly(vinylidene
chloride), polystyrene, and the like;
copolymers of the foregoing, such as acrylonitrile-butadiene-styrene (ABS)
copolymers, and the like.
Preferred polymers are polyolefins and polyesters, with polyolefins being more
preferred. Even
more preferred are those polyolefins which contain only hydrogen and carbon
atoms and which are
prepared by the addition polymerization of one or more unsaturated monomers.
Examples of such
360 polyolefins include, among others, polyethylene, polypropylene, poly( 1-
butene), poly(2-butene), poly( 1
pentene), poly(2-pentene), poly(3-methyl-1-pentene), poly{4-methyl-1-pentene),
1,2-poly-1,3-butadiene,
1,4-poly-1,3-butadiene, polyisoprene, and the like. In addition, such term is
meant to include blends of two
or more polyolefins and random and block copolymers prepared from two or more
different unsaturated
monomers. Because of their commercial importance, the most preferred
polyolefins are polyethylene and
365 polypropylene.
In addition to polymeric films, webs that can be used to produce the durably
wettable, liquid
pervious webs of the present invention include but are not limited to spun
bonded, hydroentangled, needled
and polymericly bound nonwovens. Suitable nonwoven webs are typically formed
from organic textile
fibers including but not limited to cotton, wool, wood, jute, viscous rayon,
nylon, polyester, polyolefins,
370 carbon, or mixtures thereof. Inorganic fibers such as glass and metal can
be used alone or in combination or
further combined with organic fibers . In the case of staple fibers, fiber
length varies from about 1/4 inch to
about 2 or more inches. In the case of spun bonded webs, the fiber lengths are
indefinite. The staple fibers
used in hydroentangled, needled and polymericly bound nonwovens are processed
through conventional
textile machinery.
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WO 00/16913 PCT/US99/21709
375 For example, in producing a polymericly bound, nonwoven web, a carding
machine may be used
to form a continuous length of rather two-dimensional loosely associated
fibers known as a carded web.
These webs may be assembled to form a multiple layer or three-dimensional
fibrous web of significant
weight, e.g., from about several grams to thousands of grams per yard. In
continuous nonwoven fibrous
webs, the textile fibers are arrayed at various angles to the lengthwise axis
of the web. When a web is
380 fomled by the action of a carding machine, the fibers are usually
predominantly oriented in the machine
direction and. on the other hand, isotropic webs may be formed such as by air-
laying. The fibrous webs
described above are typically impregnated with a polymeric binding agent
(polymericly bound). In a
preferred form, the polymeric binders are applied as emulsions of acrylic,
polyvinylacetate, or similar
polymeric nature, and mixtures thereof. Preferably, the fibers are unwoven and
substantially haphazardly
385 oriented and adhesively bonded together with polymeric binder.
Hydroentangled and needled webs are distinct from polyrnericly bound webs as
they rely
principally on the physical entanglement of their fibers to provide web
integrity. In contrast to polymericly
bound and physically entangled webs, spun bond webs typically are composed of
fibers of infinite length
that are bound together through solvent or melt processes.
390 As indicated, the webs may be in the form of a flat film or may be a
previously apertured three
dimensional film. The coatings are durable and increase the surface energy of
the web to render the treated
web more wettable. The coating is durable, in that it is maintained ov er
time, even after exposure to water
or other aqueous liquids. In this regard, the webs of the present invention
are described in one respect in
terms of their ability to remain wettable over time and/or after exposure to
liquids. The ability to remain
395 wenable over time is assessed by measuring the web's Post Aging contact
angle. This measurement
involves storing the treated web at 60° C for 16 hours, to artificially
age the treated web, before measuring
contact angle. The ability to remain wettable after exposure to liquids is
assessed by measuring the web's
Post Washing contact angle. This measurement involves placing a 2 in. x 2 in.
sample of treated web in a
250 ml water bath at 65°C for 90 sec. with vigorous agitation prior to
measuring contact angle. Procedures
400 and devices for measuring contact angle between a liquid and a web surface
are well known in the art:
However, water contact angle, measured with a goniometer (Model # 100-00, Rame-
Hart, Inc., Mountain
Lakes, NJ), is used to assess the web wettability of the present invention.
All contact ankle measurements
are rcponcd as the average measurements on 3 samples.
In one aspect, the treated web of the present invention will have a Post Aging
contact angle that is
405 not more than about 60 degrees greater than the treated web's Pre Aging
contact angle (i.e., the contact
angle as measured before storage at 60°C for 16 hours). Preferably, the
treated web will have a Post Aging
contact angle that is not more than about 40 degrees, more preferably not more
than about 20 degrees, still
more preferably not mare than about 10 degrees, greater than the Pre Aging
contact angle. In another
respect, the treated web of the present invention will have a Post Washing
contact angle that is not more
410 than about 60 degrees greater than the treated web's Pre Washing contact
angle (i.e., the contact angle as
measured before the treated web is placed in a 250 ml water bath at 65°
C for 90 sec with vigorous
agitation). In this regard, the treated web will preferably have a Post
Washing contact angle that is not
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WO 00/16913 PCT/US99/21709
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more than about 40 degrees, more preferably not more than about 20 degrees,
still more preferably not
more than about 10 degrees, greater than the Pre Washing contact angle. In a
prefeaed aspect, the treated
415 web of the present invention will exhibit both the Post Aging and Post
Washing requirements discussed
above.
The treated webs of the present invention will exhibit either (preferably
both) a Post Aging or a Post
Washing contact angle of less than about 90 degrees, preferably not more than
about 70 degrees, more
preferably not more than about 50 degrees. still more preferably not more than
about 30 degrees, and most
420 preferably not more than about 20 degrees.
II Absorbent Articles
As used herein, the term "absorbent article" refers generally to devices used
to absorb and contain
425 body exudates, and more specifically refers to devices which are placed
against or in proximity to the body
of the wearer to absorb and contain the various exudates discharged from the
body. The term "absorbent
article" is intended to include diapers, catamenial pads, tampons, sanitary
napkins, incontinent pads,
training pants and the like, as well as wipes, bandages and wound dressings.
The term "disposable" is used
herein to describe absorbent articles which are not intended to be laundered
or otherwise restored or reused
430 as an absorbent article (i.e., they are intended to be discarded after
limited use, and, preferably, to be
recycled, composted or otherwise disposed of in an environmentally compatible
manner). A "unitary"
absorbent article refers to absorbent articles which are formed as a single
structure or as separate parts
united together to form a coordinated entity so that they do not require
separate manipulative parts such as a
separate holder and pad.
435 It is to be understood that the overall size, shape, and/or configuration
of the absorbent article, if
any, into which the treated webs according to the present invention are
incorporated, or utilized in
conjunction with, have no criticality or functional relationship to the
principles of the present invention.
Such parameters, however, must be considered along with the intended liquid
and intended functionality
when determining appropriate web configurations.
440 In addition to the treated webs of the present invention, absorbent
articles will also comprise an
absorbent core for retention of any absorbed body liquids. Exemplary absorbent
structures for use as the
absorbent core in the present invention are described in U.S. Patent No.
4,950,264 issued to Osborn on
August 21, 1990; U.S. Patent No. 4,610,678 issued to Weisman et al. on
September 9, 1986; U.S. Patent
No. 4,834,735 issued to Alemany et al. on May 30, 1989; European Patent
Application No. 0 198 683, the
445 Procter & Gamble Company, published October 22, 1986 in the name of Duenk
et al.; U.S. Patent No.
4,673,402 issued to Weisman et al, on June 16, 1987; and U.S. Patent No.
4,888,231 issued to Angstadt on
December 19, 1989. The absorbent core may further comprise the dual core
system containing an
acquisition/distribution core of chemically stiffened fibers positioned over
an absorbent storage core as
detailed in U.S. Patent No. 5,234,423, entitled "Absorbent Article With
Elastic Waist Feature and Enhanced
450 Absorbency" issued to Aiemany et al., on August 10, 1993; and in U.S.
Patent No. 5,147,345, entitled
CA 02340972 2004-02-04
_13_
"High Efficiency Absorbent Anicles For Incontinence Management" issued to
Young, LaVon and Taylor
on September 15, 1992.
A preferred embodiment of a unitary disposable absorbent article made in
accordance herewith a
a catamenial pad, or sanitary napkin, As used herein, the term "sanitary
napkin" refers to an absorbent
455 article which is worn by females adjacent to the pudendal region,
generally external to the urogenital
region, and which is intended to absorb and contain menstrual liquids and
other vaginal discharges from the
wearer's body (e.g., blood, menses, and urine). Interlabial devices which
reside partially within and
partially external to the wearer's vestibule are also within the scope of this
invention. Suitable feminine
hygiene articles are disclosed in U.S. Patent No. 4,556,146, issued to Swanson
et al. on Dec. 3, 1985. U.S.
460 Patent No. 4,589,876, issued to Van Tilberg on April 27, 1993, U.S. Patent
No. 4,687,478, issued to Van
Tilburg on Aug. 18, 1987, U.S. Patent No. 4,950,264, issued to Osborn, III on
Aug. 21, 1990, U.S. Patent
No. 5,009,653, issued to Osborn, III on April 23, 1991, U.S. Patent 5,267,992,
issued to Van Tilburg on
Dec. 7, 1993, U.S. Patent No. 5,389,094, issued to Lavash et al. on Feb. 14,
1995, U.S. Patent No.
5,413,568, issued to Roach et al. on May 9, 1995, U.S. Patent No. 5,460,623,
issued to Emenaker et al. on
465 Oct. 24, 1995, U.S. Patent No. 5.489,283, issued Van Tilburg on Feb. 6,
1996, U.S. Patent No. 5,569.231,
issued to Emenaker et al. on Oct. 29, 1996, and U.S. Patent No. 5,620,430,
issued to Bamber on April 15,
1997.
In a preferred embodiment of the present invention, the sanitary napkin has
two flaps each of
which arc adjacent to and extend laterally from the side edge of the absorbent
core. The flaps are
.t70 configured to drape over the edges of the wearer's panties in the crotch
region so that the flaps are disposed
between the edges of the wearer's panties and the thighs. The flaps serve at
least two purposes. First, the
flaps help serve to prevent soiling of the wearer's body and panties by
menstrual liquid, preferably by
forming a double wall barrier alone the edges of the panty. Second, the flaps
are preferably provided with
attachment means on their garment surface so that the flaps can be folded back
under the panty and attached
475 to the garment facing side of the panty. In this way, the flaps serve to
keep the sanitary napkin properly
positioned in the panty. The flaps can be constructed of various materials
including materials similar to the
topshect, backsheet, tissue, or combination of these materials. Further, the
flaps may be a separate element
attached to the main body of the napkin or can comprise extensions of the
topsheet and backsheet (i.e.,
unitary). A number of sanitary napkins having flaps suitable or adaptable for
use with the sanitary napkins
480 of the present invention are disclosed in U.S. Patent No. 4,687,478
entitled "Shaped Sanitary Napkin With
Flaps", which issued to Van Tilburg on August 18, 1987; and U.S. Patent No.
4,589,876 entitled "Sanitary
Napkin", which issued to Van Tilburg on May 20, 1986.
In a preferred embodiment of the present invention, an acquisition layers) may
be positioned
between the topsheet and the absorbent core. The acquisition layer may serve
several functions including
485 improving wicking of exudates over and into the absorbent core. There are
several reasons why the
improved wicking of exudates is important, including providing a more even
distribution of the exudates
throughout the absorbent core. and allowing the sanitary napkin to be made
relatively thin. The wicking
CA 02340972 2004-02-04
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referred to herein may encompass the transportation of liquids in one, two or
all directions (i.e., in the x-y
490 plane and/or in the z-direction). The acquisition layer may be comprised
of several different materials
including nonwoven or woven webs of synthetic fibers including polyester,
polypropylene; or
polyethylene. natural fibers including cotton or cellulose; blends of such
fibers; or any equivalent materials
or combinations of materials. An example of a sanitary napkin having an
acquisition layer and a topsheet
is more fully described in U.S. Patent No. 4,950,264 issued to Osborn. In a
preferred embodiment. the
495 acquisition layer may be joined with the topsheet by any of the
conventional means for joining webs
together, most preferably by fusion bonds as is more fully described in the
referenced Cree application.
Catamenial pads may be constructed as follows. Onto silicone-coated release
paper a spiral pattern
of Ii2031 Findlay hot melt adhesive is applied at 0.04 glint. This adhesive
layer is transferred onto the top
(wearer-facing) side of a secondary topsheet by rolling the secondary topsheet
and coated release paper
500 together with a hand roller. The secondary topsheet is fortrred of a
nonwoven material known as Fort James
Airlaid Tissue, Grade 817, commercially available from the Fort James Corp. of
Green Bay, Wisconsin. A
topsheet of the present invention is applied to the adhesive side of the
secondary topsheet and the two are
bonded by gently pressing them together with a hand roller. Two strips of one-
quarter-inch double-sided
tape are applied along both long edges of a polyethylene backsheet. The
absorbent core is added to
505 construct the complete absorbent structure.
As used herein, the term "diaper" refers to a garment generally worn by
infants and incontinent
persons that is worn about the cower torso of the wearer. It should be
understood. however, that the present
. invention is also applicable to other absorbent arricies such as incontinent
briefs, incontinent pads. training
pants, diaper inserts, facial tissues, paper towels, and the like. In general,
a diaper of the presem invention
510 ~ will comprise a liquid pervious topsheet of the present invention; a
liquid impervious backsheet joined with
the topsheet; and an absorbent core positioned between the topsheet and the
backsheet. Additional
structural features such as elastic members and fastening means for securing
the diaper in place upon a
wearer (such as tape tab fasteners) may also be included.
While the topsheet, the backsheet, and the absorbent core can be assembled in
a variety of well
515 known configurations, a preferred diaper configuration is described
generally in U.S. Patent No. 3,860,003
(Buell), issued January 14, 1975. Alternatively, preferred configurations for
disposable diapers herein are
also disclosed in U.S. Patent No. 4,808,178 (Aziz et al.), issued February 28,
1989; U.S. Patent No.
4,695,278 (Lawson), issued September 22, 1987; and U.S. Patent No. 4,816,025
(Foreman), issued March
28, 1989. Suitable incontinence articles for adult wearers are disclosed in
U.S. Patent No. 4,253,461 issued
520 to Strickland, et al. on March 3, 1981; U.S. Patent Nos. 4,597,760 and
4,597,761 issued to Buell; U.S.
Patent No. 4,704,115; U.S. Patent No. 4,909,802 issued to Ahr, et al.: U.S.
Patent No. 4,964,860 issued to
Gipson, et al, on October 23, 1990; and in
CA 02340972 2004-02-04
PCT Publication No. WO 92/11830 published on July 23, 1992.
The absorbent core of the diaper is positioned between the topsheet and the
backsheet. The
absorbent core can be manufactured in a wide variety of sizes and shapes
(e.g., rectangular, hourglass,
530 asymmetrical, etc.). The total absorbent capacity of the absorbent core
should, however, be compatible
with the design liquid loading for the intended use of the absorbent article
or diaper. Further, the size and
absorbent capacity of the absorbent core can vary to accommodate wearers
ranging from infants through
adults.
As indicated, the absorbent core may include a liquid distribution member. In
a preferred
535 configuration, the absorbent core preferably further includes an
acquisition layer or member in liquid
communication with the liquid distribution member and located between the
liquid distribution member and
the topsheet. The acquisition layer or member may be comprised of several
different materials including
nonwoven or woven webs of synthetic fibers including polyester, polypropylene,
or polyethylene, natural
fibers including conon or cellulose, blends of such fibers, or any equivalent
materials or combinations of
540 materials.
In a preferred embodiment. the diaper will comprise elasticized Icg cuffs. The
elasticized leg cuffs
can be constructed in a number of different configurations, including those
described in U.S. Patent No.
3,860.003; U.S. Patent No. 4,909,803, issued to Aziz et al. on Mar: 20, 1990;
U.S. Patent No. 4,695,278,
issued to Lawson on Sep. 22, 1987; and U.S. Patent No. 4,795,454, issued to
Dragoo on Jan. 3, 1989.
545 In use, the diaper is applied to a wearer by positioning the back
waistband region under the
wearer's back, and drawing the reminder of the diaper between the wearer's
legs so that the front
waistband region is positioned across the front of the wearer. The tape-tab or
other fasteners are then
secured preferably to outwardly facing areas of the diaper.
CA 02340972 2004-02-04
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III. x I s -
The following examples are illustrative and are not meant as a limitation of
the invention disclosed
and-claimed herein. With respect to Example 2, the mass flow controller used
to deliver the silicon-
eontaining monomer compound for the deposition processes was calibrated for
the flow rate of HMDSO.
~ The flow rates of other gases were calculated based on the specific heats of
the respective eases. The
accuracy of the mass flow controllers in these cases is ~ 5% or better.
xa le
This example illustrates the plasma treatment process and benefit of this
invention in applying a
permanent hydrophilic coating to a flat polyethylene film. Flat polyethylene
(PE) film having a 1 mil
560 average thickness is obtained from T*cdegar Film Products, Inc. (Terrc
Haute, IN) with material
composition designation code X-8318-I. Three-sup plasma treatments are
conducted in a plasma reactor
(Advanced Plasma System, Model D, radio frequency (RF) : 40 KHz), with the gas
input and process
conditions indicated in Table 1.
Ta 1
Step t~ Gas Input Flow Rate RF Power Treatmem Time
lsccml" (Watt) (min)
1 Ar/O. 1173 500 Z
? Ar/O,/HMDSO 2/73150 S00 10
3 Ar/O. 2173 _ 1
_
~ 500
s6~ ': Ar: Argon; 0,: oxygen; HMDSO: hexamcthyl disiloxane
": seem: standard cm'/minute
The rcsuhing plasma treated web samples are then tested for surface
wetiability both before and
after rapid aeine_ conditions. Rapid acing condition refers to conditioning
the web sample at 60° C for 16
Hours prior to wenabiliry measurement. Water contact angle, measured with a
goniometer (Model # 100-
570 00, Rame-Hart, Inc., Mountain Lakes, Nl), is used to assess web
wettability. Strong wetting durability of
EiMDSO-derived plasma coating is established, as demonstrated by comparable
contact angles seen
between pre-aged and post-aged samples (see Table 2). .
Ta 1
Sample Water Contact
Anele'ldeereesl
Pre-Aeed Post-Aeed
Untreated PE film 96 (3 96 (31
HMDSO- lasma treated 26 ( 1 ) 26 (31
PE web
': Contact angle measured 3 times on the same treated web is averaged and
standard deviation is reported
575 in parenthesis.
a a
This example illustrates the alternate plasma treatment process and benefit of
this invention in
applying a permanent hydrophilic coating to a slat PE film. Flat PE film
having a 1 mil average thickness
is obtained from Trcdegar Film Products, Inc. (Tcrte Haute, IN) with material
composition designation
* = Trade-mark
CA 02340972 2004-02-04
580 code X-8318-1. Three-step plasma trcatmenu are conducted in a plasma
reactor. (Plasma Science
PSOSOOD), with gas input and process conditions indicated in Table 3.
Table 3 '
Ste # Gas Input Flow Rate RF Power Treatment
" Time
Isccm)' (Watt) Iminl
1 Ar 58 1080 1
2 ArlO-/I-IMDSO43/1560152 1200 2
3 N.O/CO- 200/207 1325
' seem : standard cm'/minuu
" Ar: Argon; O;: oxygen; HMDSO: hexamethyl disiloxane; N:O: nitrous oxide;
585 CO,: carbon dioxide
The resuhing plasma treated web samples are then evaluated for surface
wettabiliry before and
after the water wash test. Water wash test refers to immersing a 2 in. x 2 in,
web sample in a 250 ml water
bath at 65° C for 90 sec with vigorous agitation (with a Teflon coated
stir bar). Water contact angle,
measured with a goniomcter (model # 100-00, Rame-Hart, lnc., Mountain Lakes,
N.J.), is used to assess the
590 webs' wct:abiliry. Strong wetting durability of HMDSO-derived plasrna
coating is established, as is
demonstrated by comparing contact angle between pre-washed and post-washed
samples (see Table 4).
Ta 4
Sample W atcr Contact
Ane )e ' (decrccs
1
Pre-washed Post-washed
_ 96 t31 96 (3)
Untreated PE Film
HMDSO- lasma treated 7 ( 11 14 ( 11
PE web
': contact angle measured 3 times on the same filmiweb is averaged and
standard deviation is reported in
parenthesis.
595 While specific embodiments of the invention have been described in
considerable detail, variations
and modifications of these embodiments can be effected without departing from
the spirit and scope of the
invention as described and claimed.
* = Trade-mark
