Active agent delivery device

An active agent delivery device comprises (a) microporous material comprising a matrix consisting essentially of linear ultrahigh molecular weight polyolefin, a large proportion of finely divided water-insoluble filler of which at least about 50 percent by weight is siliceous, and interconnecting pores; and (b) a releasable active agent or precursor thereof associated with at least a portion of the filler.

The present invention is directed to an active agent delivery device based 
on microporous material characterized by a matrix consisting essentially 
of linear ultrahigh molecular weight polyolefin, a very large proportion 
of finely-divided particulate siliceous filler, and a high void content. 
Accordingly, one embodiment of the invention is an active agent delivery 
device which releases active agent over a prolonged period of time 
comprising (a) microporous material comprising (1) a matrix consisting 
essentially of essentially linear ultrahigh molecular weight polyolefin 
which is essentially linear ultrahigh molecular weight polyethylene having 
an intrinsic viscosity of at least about 18 deciliters/gram, essentially 
linear ultrahigh molecular weight polypropylene having an intrinsic 
viscosity of at least about 6 deciliters/gram, or a mixture thereof, (2) 
finely divided particulate substantially water-insoluble filler, of which 
at least about 50 percent by weight is siliceous, distributed throughout 
the matrix, the filler constituting from about 50 percent to about 90 
percent by weight of the microporous material, and (3) a network of 
interconnecting pores communicating throughout the microporous material, 
the pores constituting at least about 35 percent by volume of the 
microporous material, and (b) a releasable active agent or precursor 
thereof associated with at least a portion of the filler. 
Another embodiment of the invention is a process for producing an active 
agent delivery device which releases active agent over a prolonged period 
of time comprising treating microporous material comprising (a) a matrix 
consisting essentially of essentially linear ultrahigh molecular weight 
polyolefin which is essentially linear ultrahigh molecular weight 
polyethylene having an intrinsic viscosity of at least about 18 
deciliters/gram, essentially linear ultrahigh molecular weight 
polypropylene having an intrinsic viscosity of at least about 6 
deciliters/gram, or a mixture thereof, (b) finely divided particulate 
substantially water-insoluble filler, of which at least about 50 percent 
by weight is siliceous, distributed throughout the matrix, the filler 
constituting from about 50 percent to about 90 percent by weight of the 
microporous material, and (c) a network of interconnecting pores 
communicating throughout the microporous material, the pores constituting 
at leaast about 35 percent by volume of the microporous material, with a 
releasable active agent or precursor thereof to associate at least a 
portion of the releasable active agent or the precursor with at least a 
portion of the filler. 
The releasable active agent is a substance or mixture of substances which, 
when delivered by the delivery device to the surrounding environment is 
useful for one or more purposes in the surrounding environment. Examples 
of such releasable active agents include, but are not limited to, flavors, 
fragrances (such as perfumes, scents, and the like), deodorizers, 
medicaments (such as drugs and the like), biocides (such as insecticides, 
herbicides, fungicides, and the like), antistatic agents, lubricants, 
corrosion inhibitors, preservatives, fertilizers, and dyes. 
At least a portion of the active agent or precursor thereof is associated 
with at least a portion of the siliceous filler of the microporous 
material. The mechanism of the association may differ depending upon the 
nature of the active agent employed and the nature of the siliceous filler 
employed. Irrespective of the precise physical or chemical mechanism which 
prevails in a given situation, the association results from an interaction 
between the filler and the active agent or its precursor. 
The releasable active agent or its precursor may be liquid, solid, or 
occasionally a gas. It may be in admixture with other substances which aid 
in placement of the releasable active agent or the precursor in the 
microporous material and/or assist in regulating the rate of release of 
the active agent from the microporous material. Solvents and fixatives are 
examples of such other substances. 
Release of the active agent over a prolonged period of time may be due to 
any of a number of factors such as for example, volatilization, migration, 
diffusion, the breaking of physical or chemical bonds, or the reaction of 
one or more precursors to produce the releasable active agent in situ. The 
release may occur continuously as in the case of volatilization of liquid 
or solid, or it may be triggered by an external stimulus such as elevated 
temperature or absorption of catalyst or reactant into the microporous 
material. As an example of the last mechanism, a first precursor is 
introduced to the microporous material through one side and reacts within 
the microporous material with a second precursor already present in the 
microporous material to form an active agent which then proceeds out of 
the other side of the microporous material. 
The tortuous pores of the microporous material provide resistance to 
diffusion or migration of active agent from the interior of the 
microporous material. In some cases this resistance is the principal 
mechanism providing for prolonged release of the active agent, while in 
others it is a secondary, but helpful, mechanism contributing to the 
prolonged release. 
When desired, a reservoir of the releasable active agent or its precursor 
may be located on one side of the microporous material to replenish the 
microporous material with releasable active agent or precursor as 
releasable active agent is released from the microporous material or as 
precursor is consumed. 
Inasmuch as ultrahigh molecular weight (UHMW) polyolefin is not a thermoset 
polymer having an infinite molecular weight, it is technically classified 
as a thermoplastic. However, because the molecules are essentially very 
long chains, UHMW polyolefin, and especially UHMW polyethylene, softens 
when heated but does not flow as a molten liquid in a normal thermoplastic 
manner. The very long chains and the peculiar properties they provide to 
UHMW polyolefin are believed to contribute in large measure to the 
desirable properties of the microporous material. 
As indicated earlier, the intrinsic viscosity of the UHMW polyethylene is 
at least about 18 deciliters/gram. In many cases the intrinsic viscosity 
is at least about 19 deciliters/gram. Although there is no particular 
restriction on the upper limit of the intrinsic viscosity, the intrinsic 
viscosity is frequently in the range of from about 18 to about 39 
deciliters/gram. An intrinsic viscosity in the range of from about 18 to 
about 32 deciliters/gram is preferred. 
Also as indicated earlier the intrinsic viscosity of the UHMW polypropylene 
is at least about 6 deciliters/gram. In many cases the intrinsic viscosity 
is at least about 7 deciliters/gram. Although there is no particular 
restriction on the upper limit of the intrinsic viscosity, the intrinsic 
viscosity is often in the range of from about 6 to about 18 
deciliters/gram. An intrinsic viscosity in the range of from about 7 to 
about 16 deciliters/gram is preferred. 
As used herein and in the claims, intrinsic viscosity is determined by 
extrapolating to zero concentration the reduced viscosities or the 
inherent viscosities of several dilute solutions of the UHMW polyolefin 
where the solvent is freshly distilled decahydronaphthalene to which 0.2 
percent by weight, 3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid, 
neopentanetetrayl ester [CAS Registry No. 6683-19-8] has been added. The 
reduced viscosities or the inherent viscosities of the UHMW polyolefin are 
ascertained from relative viscosities obtained at 135.degree. C. using an 
Ubbelohde No. 1 viscometer in accordance with the general procedure of 
ASTM D 4020-81, except that several dilute solutions of differing 
concentration are employed. ASTM D 4020-81 is, in its entirety, 
incorporated herein by reference. 
The nominal molecular weight of UHMW polyethylene is empirically related to 
the intrinsic viscosity of the polymer according to the equation: 
EQU M=5.37.times.10.sup.4 [.eta.].sup.1.37 
where M is the nominal molecular weight and [.eta.] is the intrinsic 
viscosity of the UHMW polyethylene expressed in deciliters/gram. 
Similarly, the nominal molecular weight of UHMW polypropylene is 
empirically related to the intrinsic viscosity of the polymer according to 
the equation: 
EQU M=8.88.times.10.sup.4 [.eta.].sup.1.25 
where M is the nominal molecular weight and [.eta.] is the intrinsic 
viscosity of the UHMW polypropylene expressed in deciliters/gram. 
The essentially linear ultrahigh molecular weight polypropylene is most 
frequently essentially linear ultrahigh molecular weight isotactic 
polypropylene. Often the degree of isotacticity of such polymer is at 
least about 95 percent, while preferably it is at least about 98 percent. 
Sufficient UHMW polyolefin should be present in the matrix to provide its 
properties to the microporous material. Other thermoplastic organic 
polymer may also be present in the matrix so long as its presence does not 
materially affect the properties of the microporous material in an adverse 
manner. The amount of the other thermoplastic polymer which may be present 
depends upon the nature of such polymer. In general, a greater amount of 
other thermoplastic organic polymer may be used if the molecular structure 
contains little branching, few long sidechains, and few bulky side groups, 
than when there is a large amount of branching, many long sidechains, or 
many bulky side groups. For this reason, the preferred thermoplastic 
organic polymers which may optionally be present are low density 
polyethylene, high density polyethylene, poly(tetrafluoroethylene), 
polypropylene, copolymers of ethylene and propylene, copolymers of 
ethylene and acrylic acid, and copolymers of ethylene and methacrylic 
acid. If desired, all or a portion of the carboxyl groups of 
carboxyl-containing copolymers may be neutralized with sodium, zinc, or 
the like. It is our experience that usually at least about 50 percent UHMW 
polyolefin, based on the weight of the matrix, will provide the desired 
properties to the microporous material. Often at least about 70 percent by 
weight of the matrix is UHMW polyolefin. In many cases, however, the other 
thermoplastic organic polymer is substantially absent. 
The finely divided substantially water-insoluble siliceous filler used in 
the present invention is particulate. As present in the microporous 
material, the siliceous filler may be in the form of ultimate particles, 
aggregates of ultimate particles, or a combination of both. In most cases, 
at least about 90 percent by weight of the siliceous filler used in 
preparing the microporous material has gross particle sizes in the range 
of from about 5 to about 40 micrometers as determined by use of a Model 
TAII Coulter counter (Coulter Electronics, Inc.) according to ASTM C 
690-80 but modified by stirring the filler for 10 minutes uin Isoton II 
electrolyte (Curtin Matheson Scientific, Inc.) using a four-blade, 4.445 
centimeter diameter propeller stirrer. Preferably at least about 90 
percent by weight of the siliceous filler has gross particle sizes in the 
range of from about 10 to about 30 micrometers. It is expected that the 
sizes of filler agglomerates will be reduced during processing of the 
ingredients to prepare the microporous material. Accordingly, the 
distribution of gross particle sizes in the microporous material may be 
smaller than in the raw filler itself. ASTM C 690-80 is, in its entirety, 
incorporated herein by reference. 
Examples of suitable siliceous fillers include silica, mica, 
montmorillonite, kaolinite, asbestos, talc, diatomaceous earth, 
vermiculite, natural and synthetic zeolites, cement, calcium silicate, 
aluminum silicate, sodium aluminum silicate, aluminum polysilicate, 
alumina silica gels, and glass particles. Silica and the clays are the 
preferred siliceous fillers. Of the silicas, precipitated silica, silica 
gel, or fumed silica is most often used. 
In addition to the siliceous filler, finely divided particulate 
substantially water-insoluble non-siliceous fillers may also be employed. 
Examples of such optional non-siliceous fillers include carbon black, 
charcoal, graphite, titanium oxide, iron oxide, copper oxide, zinc oxide, 
antimony oxide, zirconia, magnesia, alumina, molybdenum disulfide, zinc 
sulfide, barium sulfate, strontium sulfate, calcium carbonate, magnesium 
carbonate, magnesium hydroxide, and finely divided particulate 
substantially water-insoluble flame retardant filler such as 
ethylenebis(tetrabromophthalimide), octabromodiphenyl oxide, 
decabromodiphenyl oxide, and ethylenebisdibromonorbornane dicarboximide. 
The finely divided substantially water-insoluble non-siliceous filler used 
in the present invention is particulate. As present in the microporous 
material, the non-siliceous filler may be in the form of ultimate 
particles, aggregates of ultimate particles, or a combination of both. In 
most cases, at least about 75 percent by weight of the non-siliceous 
filler used in preparing the microporous material has gross particle sizes 
in the ranges of from about 0.1 to about 40 micrometers as determined by 
use of a Micromeretics Sedigraph 5000-D (Micromeretics Instrument Corp.) 
in accordance with the accompanying operating manual. The preferred ranges 
vary from filler to filler. For example, it is preferred that at least 
about 75 percent by weight of antimony oxide particles be in the range of 
from about 0.1 to about 3 micrometers, whereas it is preferred that at 
least about 75 percent by weight of barium sulfate particles be in the 
range of from about 1 to about 25 micrometers. It is expected that the 
sizes of filler agglomerates will be reduced during processing of the 
ingredients to prepare the microporous material. Therefore, the 
distribution of gross particle sizes in the microporous material may be 
smaller than in the raw non-siliceous filler itself. 
The particularly preferred finely divided particulate substantially 
water-insoluble siliceous filler is precipitated silica. Although both are 
silicas, it is important to distinguish precipitated silica from silica 
gel inasmuch as these different materials have different properties. 
Reference in this regard is made to R. K. Iler, The Chemistry of Silica, 
John Wiley & Sons, New York (1979), Library of Congress Catalog No. QD 
181.S6144, the entire disclosure of which is incorporated herein by 
reference. Note especially pages 15-29, 172-176, 218-233, 364-365, 
462-465, 554-564, and 578-579. Silica gel is usually produced commercially 
at low pH by acidifying an aqueous solution of a soluble metal silicate, 
typically sodium silicate, with acid. The acid employed is generally a 
strong mineral acid such as sulfuric acid or hydrochloric acid although 
carbon dioxide is sometimes used. Inasmuch as there is essentially no 
difference in density between gel phase and the surrounding liquid phase 
while the viscosity is low, the gel phase does not settle out, that is to 
say, it does not precipitate. Silica gel, then, may be described as a 
nonprecipitated, coherent, rigid, three-dimensional network of contiguous 
particles of colloidal amorphous silica. The state of subdivision ranges 
from large, solid masses to submicroscopic particles, and the degree of 
hydration from almost anhydrous silica to soft gelatinous masses 
containing on the the order of 100 parts of water per part of silica by 
weight, although the highly hydrated forms are only rarely used in the 
present invention. 
Precipitated silica is usually produced commercially by combining an 
aqueous solution of a soluble metal silicate, ordinarily alkali metal 
silicate such as sodium silicate, and an acid so that colloidal particles 
will grow in weakly alkaline solution and be coagulated by the alkali 
metal ions of the resulting soluble alkali metal salt. Various acids may 
be used, including the mineral acids and carbon dioxide. In the absence of 
a coagulant, silica is not precipitated from solution at any pH. The 
coagulant used to effect precipitation may be the soluble alkali metal 
salt produced during formation of the colloidal silica particles, it may 
be added electrolyte such as a soluble inorganic or organic salt, or it 
may be a combination of both. 
Precipitated silica, then, may be described as precipitated aggregates of 
ultimate particles of colloidal amorphous silica that have not at any 
point existed as macroscopic gel during the preparation. The sizes of the 
aggregates and the degree of hydration may vary widely. 
Precipitated silica powders differ from silica gels that have been 
pulverized in ordinarily having a more open structure, that is, a higher 
specific pore volume. However, the specific surface area of precipitated 
silica as measured by the Brunauer, Emmet, Teller (BET) method using 
nitrogen as the adsorbate, is often lower than that of silica gel. 
Many different precipitated silicas may be employed in the present 
invention, but the preferred precipitated silicas are those obtained by 
precipitation from an aqueous solution of sodium silicate using a suitable 
acid such as sulfuric acid, hydrochloric acid, or carbon dioxide. Such 
precipitated silicas are themselves known and processes for producing them 
are described in detail in U.S. Pat. No. 2,940,830, and in U.S. Pat. No. 
4,681,750, The entire disclosures of which are incorporated herein by 
reference, including especially the processes for making precipitated 
silicas and the properties of the products. 
In the case of the preferred filler, precipitated silica, the average 
ultimate particle size (irrespective of whether or not the ultimate 
particles are agglomerated) is less than about 0.1 micrometer as 
determined by transmission electron microscopy. Often the average ultimate 
particle size is less than about 0.05 micrometer. Preferably the average 
ultimate particle size of the precipitated silica is less than about 0.03 
micrometer. 
The finely divided particulate substatially water-insoluble filler 
constitutes from about 50 to 90 percent by weight of the microporous 
material. Frequently such filler constitutes from about 50 to about 85 
percent by weight of the microporous material. From about 60 percent to 
about 80 percent by weight is preferred. 
At least about 50 percent by weight of the finely divided particulate 
substantially water-insoluble filler is finely divided particulate 
substantially water-insoluble siliceous filler. In many cases at least 
about 65 percent by weight of the finely divided particulate substantially 
water-insoluble filler is siliceous. Often at least about 75 percent by 
weight of the finely divided particulate substantially water-insoluble 
filler is siliceous. Frequently at least about 85 percent by weight of the 
finely divided particulate water-insoluble filler is siliceous. In many 
instances all of the finely divided particulate water-insoluble filler is 
siliceous. 
Minor amounts, usually less than about 5 percent by weight, of other 
materials used in processing such as lubricant, processing plasticizer, 
organic extraction liquid, surfactant, water, and the like, may optionally 
also be present. Yet other materials introduced for particular purposes 
may optionally be present in the microporous material in small amounts, 
usually less than about 15 percent by weight. Examples of such materials 
include antioxidants, ultraviolet light absorbers, dyes, pigments, and the 
like. The balance of the microporous material, exclusive of filler and any 
impregnant applied for one or more special purposes is essentially the 
thermoplastic organic polymer. 
On an impregnant-free basis, pores constitute at least about 35 percent by 
volume of the microporous material. In many instances the pores constitute 
at least about 60 percent by volume of the microporous material. Often the 
pores constitute from at least about 35 percent to about 95 percent by 
volume of the microporous material. From about 60 percent to about 75 
percent by volume is preferred. As used herein and in the claims, the 
porosity (also known as void volume) of the microporous material, 
expressed as percent by volume, is determined according to the equation: 
EQU Porosity=100[1-d.sub.1 /d.sub.2 ] 
where d.sub.1 is the density of the sample which is determined from the 
sample weight and the sample volume as ascertained from measurements of 
the sample dimensions and d.sub.2 is the density of the solid portion of 
the sample which is determined from the sample weight and the volume of 
the solid portion of the sample. The volume of the solid portion of the 
same is determined using a Quantachrome stereopycnometer (Quantachrome 
Corp.) in accordance with the accompanying operating manual. 
The volume average diameter of the pores of the microporous material is 
determined by mercury porosimetry using an Autoscan mercury porosimeter 
(Quantachrome Corp.) in accordance with the accompanying operating manual. 
The volume average pore radius for a single scan is automatically 
determined by the porosimeter. In operating the porosimeter, a scan is 
made in the high pressure range (from about 138 kilopascals absolute to 
about 227 megapascals absolute). If about 2 percent or less of the total 
intruded volume occurs at the low end (from about 138 to about 250 
kilopascals absolute) of the high pressure range, the volume average pore 
diameter is taken as twice the volume average pore radius determined by 
the porosimeter. Otherwise, an additional scan is made in the low pressure 
range (from about 7 to about 165 kilopascals absolute) and the volume 
average pore diameter is calculated according to the equation: 
##EQU1## 
where d is the volume average pore diameter, v.sub.1 is the total volume 
of mercury intruded in the high pressure range, v.sub.2 is the total 
volume of mercury intruded in the low pressure range, r.sub.1 is the 
volume average pore radius determined from the high pressure scan, r.sub.2 
is the volume average pore radius determined from the low pressure scan, 
w.sub.1 is the weight of the sample subjected to the high pressure scan, 
and w.sub.2 is the weight of the sample subjected to the low pressures 
scan. Generally the volume average diameter of the pores is in the range 
of from about 0.02 to about 50 micrometers. Very often the volume average 
diameter of the pores is in the range of from about 0.04 to about 40 
micrometers. From about 0.05 to about 30 micrometers is preferred. 
In the course of determining the volume average pore diameter of the above 
procedure, the maximum pore radius detected is sometimes noted. This is 
taken from the low pressure range scan if run; otherwise it is taken from 
the high pressure range scan. The maximum pore diameter is twice the 
maximum pore radius. 
Microporous material may be produced according to the general principles 
and procedures of U.S. Pat. No. 3,351,495, the entire disclosure of which 
is incorporated herein by reference, including especially the processes 
for making microporous materials and the properties of the products. 
Preferably filler, thermoplastic organic polymer powder, processing 
plasticizer and minor amounts of lubricant and antioxidant are mixed until 
a substantially uniform mixture is obtained. The weight ratio of filler to 
polymer powder employed in forming the mixture is essentially the same as 
that of the microporous material to be produced. The mixture, together 
with additional processing plasticizer, is introduced to the heated barrel 
of a screw extruder. Attached to the extruder is a sheeting die. A 
continuous sheet formed by the die is forwarded without drawing to a pair 
of heated calender rolls acting cooperatively to form continuous sheet of 
lesser thickness than the continuous sheet exiting from the die. The 
continuous sheet from the calender then passes to a first extraction zone 
where the processing plasticizer is substantially removed by extraction 
with an organic liquid which is a good solvent for the processing 
plasticizer, a poor solvent for the organic polymer, and more volatile 
than the processing plasticizer. Usually, but not necessarily, both the 
processing plasticizer and the organic extraction liquid are substantially 
immiscible with water. The continuous sheet then passes to a second 
extraction zone where the residual organic extraction liquid is 
substantially removed by steam and/or water. The continuous sheet is then 
passed through a forced air dryer for substantial removal of residual 
water and remaining residual organic extraction liquid. From the dryer the 
continuous sheet, which is microporous material, is passed to a take-up 
roll. 
The processing plasticizer has little solvating effect on the thermoplastic 
organic polymer at 60.degree. C., only a moderate solvating effect at 
elevated temperatures on the order of about 100.degree. C., and a 
significant solvating effect at elevated temperatures on the order of 
about 200.degree. C. It is a liquid at room temperature and usually it is 
processing oil such as paraffinic oil, naphthenic oil, or aromatic oil. 
Suitable processing oils include those meeting the requirements of ASTM D 
2226-82, Types 103 and 104. Preferred are those oils which have a pour 
point of less than 22.degree. C. according to ASTM D 97-66 (reapproved 
1978). Particularly preferred are oils having a pour point of less than 
10.degree. C. Examples of suitable oils include Shellflex.RTM. 412 and 
Shellflex.RTM. 371 oil (Shell Oil Co.) which are solvent refined and 
hydrotreated oils derived from naphthenic crude. ASTM D 2226-82 and ASTM D 
97-66 (reapproved 1978) are, in their entireties, incorporated herein by 
reference. It is expected that other materials, including the phthalate 
ester plasticizers such as dibutyl phthalate, bis(2-ethylhexyl) phthalate, 
diisodecyl phthalate, dicyclohexyl phthalate, butyl benzyl phthalate, and 
ditridecyl phthalate will function satisfactorily as processing 
plasticizers. 
There are many organic extraction liquids that can be used. Examples of 
suitable organic extraction liquids include 1,1,2-trichloroethylene, 
perchloroethylene, 1,2-dichloroethane, 1,1,1-trichloroethane, 
1,1,2-trichloroethane, methylene chloride, chloroform, 
1,1,2-trichloro-1,2,2-trifluoroethane, isopropyl alcohol, diethyl ether 
and acetone. 
In the above described process for producing microporous material, 
extrusion and calendering are facilitated when the substantially 
water-insoluble filler carries much of the processing plasticizer. The 
capacity of the filler particles to absorb and hold the processing 
plasticizer is a function of the surface area of the filler. It is 
therefore preferred that the filler have a high surface area. High surface 
area fillers are materials of very small particle size, materials having a 
high degree of porosity or materials exhibiting both characteristics. 
Usually the surface area of the filler itself is in the range of from 
about 20 to about 400 square meters per gram as determined by the 
Brunauer, Emmett, Teller (BET) method according to ASTM C 819-77 using 
nitrogen as the adsorbate but modified by outgassing the system and the 
sample for one hour at 130.degree. C. Preferably the surface area is in 
the range of from about 25 to 350 square meters per gram. ASTM C 819-77 
is, in its entirety, incorporated herein by reference. 
Inasmuch as it is desirable to essentially retain the filler in the 
microporous material, it is preferred that the substantially 
water-insoluble filler be substantially insoluble in the processing 
plasticizer and substantially insoluble in the organic extraction liquid 
when microporous material is produced by the above process. 
The residual processing plasticizer content is usually less than 5 percent 
by weight of the microporous sheet and this may be reduced even further by 
additional extractions using the same or a different organic extraction 
liquid. 
Pores constitute from about 35 to about 80 percent by volume of the 
microporous material when made by the above-described process. In many 
cases the pores constitute from about 60 to about 75 percent by volume of 
the microporous material. 
The volume average diameter of the pores of the microporous material when 
made by the above-described process, is usually in the range of from about 
0.02 to about 0.5 micrometers. Frequently the average diameter of the 
pores is in the range of from about 0.04 to about 0.3 micrometers. From 
about 0.05 to about 0.25 micrometers is preferred. 
The microporous material produced by the above-described process may be 
used for producing articles of the present invention. However, it may 
optionally be stretched and the stretched microporous material used for 
producing such articles. When such stretching is employed, the product of 
the above-described process may be regarded as an intermediate product. 
It will be appreciated that the stretching both increases the void volume 
of the material and induces regions of molecular orientation in the 
ultrahigh molecular weight (UHMW) polyolefin. As is well known in the art, 
many of the physical properties of molecularly oriented thermoplastic 
organic polymer, including tensile strength, tensile modulus, Young's 
modulus, and others, differ considerably from those of the corresponding 
thermoplastic organic polymer having little or no molecular orientation. 
Although it is not desired to be bound by any theory, it is believed that 
the properties of the UHMW polyolefin, the regions of molecular 
orientation, the high levels of filler loading, and the high degrees of 
porosity cooperate to provide many of the desirable properties 
characteristic of the stretched microporous material used in the present 
invention. 
Stretched microporous material may be produced by stretching the 
intermediate product in at least one stretching direction above the 
elastic limit. Usually the stretch ratio is at least about 1.5. In many 
cases the stretch ratio is at least about 1.7. Preferably it is at least 
about 2. Frequently the stretch ratio is in the range of from about 1.5 to 
about 15. Often the stretch ratio is in the range of from about 1.7 to 
about 10. Preferably the stretch ratio is in the range of from about 2 to 
about 6. As used herein, the stretch ratio is determined by the formula: 
EQU S=L.sub.2 /L.sub.1 
where S is the stretch ratio, L.sub.1 is the distance between two reference 
points located on the intermediate product and on a line parallel to the 
stretching direction, and L.sub.2 is the distance between the same two 
reference points located on the stretched microporous material. 
The temperatures at which stretching is accomplished may vary widely. 
Stretching may be accomplished at about ambient room temperature, but 
usually elevated temperatures are employed. The intermediate product may 
be heated by any of a wide variety of techniques prior to, during, and/or 
after stretching. Examples of these techniques include radiative heating 
such as that provided by electrically heated or gas fired infrared 
heaters, convective heating such as that provided by recirculating hot 
air, and conductive heating such as that provided by contact with heated 
rolls. The temperatures which are measured for temperature control 
purposes may vary according to the apparatus used and personal preference. 
For example, temperature-measuring devices may be placed to ascertain the 
temperatures of the surfaces of infrared heaters, the interiors of 
infrared heaters, the air temperatures of points between the infrared 
heaters and the intermediate product, the temperatures of the circulating 
hot air at points within the apparatus, the temperature of hot air 
entering or leaving the apparatus, the temperatures of the surfaces of 
rolls used in the stretching process, the temperature of heat transfer 
fluid entering or leaving such rolls, or film surface temperatures. In 
general, the temperature or temperatures are controlled such that the 
intermediate product is stretched about evenly so that the variations, if 
any, in film thickness of the stretched microporous material are within 
acceptable limits and so that the amount of stretched microporous material 
outside of those limits is acceptably low. It will be apparent that the 
temperatures used for control purposes may or may not be close to those of 
the intermediate product itself since they depend upon the nature of the 
apparatus used, the locations of the temperature-measuring devices, and 
the identities of the substances or objects whose temperatures are being 
measured. 
In view of the locations of the heating devices and the line speeds usually 
employed during stretching, gradients of varying temperatures may or may 
not be present through the thickness of the intermediate product. Also 
because of such line speeds, it is impracticable to measure these 
temperature gradients. The presence of gradients of varying temperatures, 
when they occur, makes it unreasonable to refer to a singular film 
temperature. Accordingly, film surface temperatures, which can be 
measured, are best used for characterizing the thermal condition of the 
intermediate product. These are ordinarily about the same across the width 
of the intermediate product during stretching although they may be 
intentionally varied, asfor example, to compensate for intermediate 
product having a wedge-shaped cross-section across the sheet. Film surface 
temperatures along the length of the sheet may be about the same or they 
may be different during stretching. 
The film surface temperatures at which stretching is accomplished may vary 
widely, but in general they are such that the intermediate product is 
stretched about evenly, as explained above. In most cases, the film 
surface temperatures during stretching are in the range of form about 
20.degree. C. to about 220.degree. C. Often such temperatures are in the 
range of from about 50.degree. C. to about 200.degree. C. From about 
75.degree. C. to about 180.degree. C. is preferred. 
Stretching may be accomplished in a single step or a plurality of steps as 
desired. For example, when the intermediate product is to be stretched in 
a single direction (uniaxial stretching), the stretching may be 
accomplished by a single stretching step or a sequence of stretching steps 
until the desired final stretch ratio is attained. Similarly, when the 
intermediate product is to be stretched in two directions (biaxial 
stretching), the stretching can be conducted by a single biaxial 
stretching step or a sequence of biaxial stretching steps until the 
desired final stretch ratios are attained. Biaxial stretching may also be 
accomplished by a sequence of one of more uniaxial stretching steps in one 
direction and one or more uniaxial stretching steps in another direction. 
Biaxial stretching steps where the intermediate product is stretched 
simultaneously in two directions and uniaxial stretching steps may be 
conducted in sequence in any order. Stretching in more than two directions 
is within contemplation. It may be seen that the various permutations of 
steps are quite numerous. Other steps, such as cooling, heating, 
sintering, annealing, reeling, unreeling, and the like, may optionally be 
included in the overall process as desired. 
Various types of stretching apparatus are well known and may be used to 
accomplish stretching of the intermediate product. Uniaxial stretching is 
usually accomplished by stretching between two rollers wherein the second 
or downstream roller rotates at a greater peripheral speed than the first 
or upstream roller. Uniaxial stretching can also be accomplished on a 
standard tentering machine. Biaxial stretching may be accomplished by 
simultaneously stretching in two different directions on a tentering 
machine. More commonly, however, biaxial stretching is accomplished by 
first uniaxially stretching between two differentially rotating rollers as 
described above, followed by either uniaxially stretching in a different 
direction using a tenter machine or by biaxially stretching using a tenter 
machine. The most common type of biaxial stretching is where the two 
stretching directions are approximately at right angles to each other. In 
most cases where continuous sheet is being stretched, one stretching 
direction is at least approximately parallel to the long axis of the sheet 
(machine direction) and the other stretching direction is at least 
approximately perpendicular to the machine direction and is in the plane 
of the sheet (transverse direction). 
After stretching has been accomplished, the microporous material may 
optionally be sintered, annealed, heat set and/or otherwise heat treated. 
During these optional steps, the stretched microporous material is usually 
held under tension so that it will not markedly shrink at the elevated 
temperatures employed, although some relaxation amounting to a small 
fraction of the maximum stretch ratio is frequently permitted. 
Following stretching and any heat treatments employed, tension is released 
from the stretched microporous material after the microporous material has 
been brought to a temperature at which, except for a small amount of 
elastic recovery amounting to a small fraction of the stretch ratio, it is 
essentially dimensionally stable in the absence of tension. Elastic 
recovery under these conditions usually does not amount to more than about 
10 percent of the stretch ratio. 
The stretched microporous material may then be further processed as 
desired. Examples of such further processing steps include reeling, 
cutting, stacking, treatment to remove residual processing plasticizer or 
extraction solvent, and fabrication into shapes for various end uses. 
In all cases, the porosity of the stretched microporous material is, unless 
impregnated after stretching, greater than that of the intermediate 
product. On an impregnant-free basis, pores usually constitute more than 
80 percent by volume of the stretched microporous material. In many 
instances the pores constitute at least about 85 percent by volume of the 
stretched microporous material. Often the pores constitute from more than 
80 percent to about 95 percent by volume of the stretched microporous 
material. From about 85 percent to about 95 percent by volume is 
preferred. 
Generally the volume average diameter of the pores of the stretched 
microporous material is in the range of from 0.6 to about 50 micrometers. 
Very often the volume average diameter of the pores is in the range of 
from about 1 to about 40 micrometers. From about 2 to about 30 micrometers 
is preferred. 
The microporous material, whether or not stretched, may be printed with a 
wide variety of printing inks using a wide variety of printing processes. 
Both the printing inks and the printing processes are themselves 
conventional. 
There are many advantages in using the microporous material described 
herein as a printing substrate. 
One such advantage is that the substrate need not be pretreated with any of 
the pretreatments customarily used to improve adhesion between the 
printing ink and polyolefin substrate such as flame treatment, 
chlorination, or especially corona discharge treatment which is most 
commonly employed. This is surprising inasmuch as untreated polyolefins 
such as polyethylene and polypropylene cannot ordinarily be successfully 
printed because of a lack of adhesion between the polyolefin printing ink 
and the polyolefin substrate. The microporous material substrates used in 
the present invention may be pretreated to further improve ink-substrate 
adhesion, but commercially satisfactory results can ordinarily be attained 
without employing such methods. 
Another advantage is that the microporous material substrates accept a wide 
variety of printing inks, including most organic solvent-based inks which 
are incompatible with water, organic solvent-based inks which are 
compatible with water, and water-based inks. 
Yet another advantage is very rapid drying of most inks to the tack-free 
state upon printing the microporous material substrates. This advantage is 
quite important in high speed press runs, in multicolor printing, and in 
reducing or even eliminating blocking of stacks or coils of the printed 
substrate. 
A further advantage is the sharpness of the printed image that can be 
attained. This is especially important in graphic arts applications where 
fine lines, detailed drawings, or halftone images are to be printed. 
Halftone images printed on the microporous material substrates ordinarily 
exhibit high degrees of dot resolution. 
Ink jet printing, especially when a water-based ink jet printing ink is 
used, is particularly suitable for printing bar codes on microporous 
material substrates. The resulting bars are sharp and of high resolution, 
which are important factors in reducing errors when the codes are read by 
conventional methods and equipment. The ink dries very rapidly when 
applied, thereby minimizing loss of bar resolution due to smearing in 
subsequent handling operations. 
Printing processes, printing equipment, and printing inks have been 
extensively discussed and documented. Examples of reference works that may 
be consulted include L. M. Larsen, Industrial Printing Ink, Reinhold 
Publishing Corp., (1962); Kirk-Othmer, Encyclopedia of Chemical 
Technology, 2d Ed., John Wiley & Sons, Inc., Vol. 11, pages 611-632 (1966) 
and Vol. 16, pages 494-546 (1968); and R. N. Blair, The Lithographers 
Manual, The Graphic Arts Technical Foundation, Inc., 7th Ed. (1983). 
For a more detailed description of printing on microporous material of the 
kind employed in the present invention, see U.S. Pat. No. 4,861,644, the 
entire disclosure of which is incorporated herein by reference. 
The microporous material may be treated (such as by spraying, coating, 
impregnating, dipping, imbibing, the use of elevated pressure and/or 
vacuum to force liquid to the interior, and the like) with one or more 
substances which alter the transmission characteristics of the microporous 
material. The treatment, however, should not be carried out to the degree 
that the microporous material becomes impervious. For example, the rate of 
release of active agent may be reduced by treating the microporous 
material with any of various organic film-forming materials, of which many 
are well known, which effectively reduce the porosity of the microporous 
material. As another example, the microporous material may be treated with 
any of the various organic silanes or siloxanes to change the 
hydrophobic/hydrophilic or oleophobic/oleophilic characteristics of the 
microporous material and hence the active agent transmission rate. 
The microporous material may be treated with releasable active agent or 
precursor thereof to associate at least a portion of the releasable active 
agent or the precursor with at least a portion of the filler. In most 
cases the material used to treat the microporous material is a liquid. The 
use of a liquid is preferred because it enhances association of the 
releasable active agent or its precursor with the filler. Solid active 
agent or precursor is frequently dissolved in volatile solvent or heated 
above its melting point and the resulting liquid used for treatment. 
Liquid active agent or precursor is often combined with volatile liquid 
carrier to assist in treatment and/or to act as a diluent to regulate the 
amount of active agent or precursor applied. The volatility of the solvent 
or other carrier is usually considerably greater than that of the active 
agent or precursor. Many techniques are known for treating porous or 
microporous substances with liquids and may be used to treat the 
microporous material in accordance with the present invention. Examples of 
such techniques include spraying, coating, impregnating, dipping, 
imbibing, the use of elevated pressure and/or vacuum to force liquid to 
the interior. Upon completion of the treatment, the microporous material 
may be essentially saturated with the liquid or, as is more usually the 
case, less than saturated. Volatile solvent or other volatile carrier, if 
present, may be removed by evaporation if desired. 
In some cases the material used to treat the microporous material is a gas 
which becomes adsorbed on the filler. Treatment may be carried out by 
exposing the microporous material to the gas at the desired pressure which 
may be ambient atmospheric pressure, or above or below ambient atmospheric 
pressure. Usually the microporous material is degassed using vacuum and/or 
elevated temperatures before exposure to the gas. 
The active agent delivery devices of the present invention have many and 
varied uses including shelf liners, drawer liners, animal litter, 
components of diapers and incontinence pads, and artificial flower petals 
which slowly release fragrance (including but not limited to perfume, 
scent and cologne) or deodorizer; strips, sheets, patches, or components 
of animal flea and tick collars which slowly release insecticide; strips, 
sheets, or patches which slowly release pheromone or other attractant; 
strips, sheets, or patches which, when placed in a laundry drier with wet 
clothing, slowly release fabric softener and/or antistatic agent; 
transdermal patches which, when placed in contact with the skin, slowly 
release medicament (including but not limited to one or more drugs); wraps 
which slowly release corrosion inhibitor to protect the article wrapped; 
lubricant devices which slowly release lubricant to protect delicate 
machinery, as for example mechanical clocks. These uses are only exemplary 
and it will be apparent that the active agent delivery devices of the 
present invention have a multitude of additional uses where controlled, 
sustained, or delayed release of active agent is advantageous. 
The invention is further described in conjunction with the following 
examples which are to be considered illustrative rather than limiting.

EXAMPLES 
Microporous Material Formation 
The preparation of the above described materials is illustrated by the 
following descriptive examples. Processing oil was used as the processing 
plasticizer. Silica, polymer, lubricant and antioxidant in the amount 
specified in Table I were placed in a high intensity mixer and mixed at 
high speed for 30 seconds to thoroughly blend the dry ingredients. The 
processing oil needed to formulate the batch was pumped into the mixer 
over a period of 2-3 minutes with low speed agitation. After the 
completion of the processing oil addition a 2 minute low speed mix period 
was used to distribute the processing oil uniformly throughout the 
mixture. 
TABLE I 
__________________________________________________________________________ 
Formulations 
Example No. 
1 2 3 4 5 6 7 8 9 
__________________________________________________________________________ 
Ingredient 
UHMWPE 5.67 
9.98 
4.25 
8.57 
6.12 9.98 
3.49 
5.73 11.84 
(1), kg 
Polypropylene 
0 0 1.42 
0 0 0 0 0 0 
(2), kg 
Precipitated 
19.96 
19.96 
19.96 
19.96 
13.02 
9.98 
19.96 
20.17 
20.87 
Sillca (3), kg 
Silica Gel, kg 
0 0 0 0 6.49 0 0 0 0 
Clay, kg 0 0 0 9.98 
0 0 0 0 0 
Lubricant (4), g 
100 100 100 100 100 50 100 100 100 
Antioxidant (5), g 
100 100 100 100 100 50 100 100 100 
Processing Oil 
(6), kg 
in Batch 31.21 
31.21 
31.21 
37.58 
33.44 
16.89 
31.72 
31.29 
34.13 
at Extruder 
13.61 
41.59 
30.39 
28.60 
.about.14 
18.72 
13.61 
.about.10.96 
.about.51.93 
__________________________________________________________________________ 
(1) UHMWPE = Ultrahigh Molecular Weight Polyethylene, Himont 1900, Himont 
U.S.A., Inc. 
(2) Profax .RTM. 6801, Himont U.S.A., Inc. 
(3) HiSil .RTM. SBG, PPG Industries, Inc. 
(4) Petrac .RTM. CZ81, Desoto, Inc., Chemical Speciality Division 
(5) Irganox .RTM. B215, CibaGeigy Corp. 
(6) Shellflex .RTM. 412, Shell Chemical Co. 
The batch was then conveyed to a ribbon blender where usually it was mixed 
with up to two additional batches of the same composition. Material was 
fed from the ribbon blender to a twin screw extruder by a variable rate 
screw feeder. Additional processing oil was added via a metering pump into 
the feed throat of the extruder. The extruder mixed and melted the 
formulation and extruded it through a 76.2 centimeter.times.0.3175 
centimeter slot die. The extruded sheet was then calendered. A description 
of one type of calender that may be used may be found in the U.S. Pat. No. 
4,734,229, the entire disclosure of which is incorporated herein by 
reference, including the structures of the devices and their modes of 
operation. Other calenders of different design may alternatively be used; 
such calenders and their modes of operation are well known in the art. The 
hot, calendered sheet was then passed around a chill roll to cool the 
sheet. The rough edges of the cooled calendered sheet were trimmed by 
rotary knives to the desired width. 
The oil filled sheet was conveyed to the extractor unit where it was 
contacted by both liquid and vaporized 1,1,2-trichloroethylene (TCE). The 
sheet was transported over a series of rollers in a serpentine fashion to 
provide multiple, sequential vapor/liquid/vapor contacts. The extraction 
liquid in the sump was maintained at a temperature of 
65.degree.-88.degree. C. Overflow from the sump of the TCE extractor was 
returned to a still which recovered the TCE and the processing oil for 
reuse in the process. The bulk of the TCE was extracted from the sheet by 
steam as the sheet was passed through a second extractor unit. A 
description of these types of extractors may be found in European Patent 
Application Publication No. EP 0 191 615, the entire disclosure of which 
is incorporated herein by reference, including especially the structures 
of the devices and their modes of operation. The sheet was dried by 
radiant heat and convective air flow. The dried sheet was wound on cores 
to provide roll stock for further processing. 
The microporous sheets, as well as the hereinafter described biaxially 
stretched microporous sheets produced therefrom, were tested for various 
physical properties. Table II identifies the properties with the methods 
used for their determination. The various ASTM test methods and Method 502 
C, referenced in Table II, are, in their entireties, incorporated herein 
by reference. The results of physical testing of the unstretched 
microporous sheets are shown in Table III. 
Property values indicated by MD (machine direction) were obtained on 
samples whose major axis was oriented along the length of the sheet. TD 
(transverse direction; cross machine direction) properties were obtained 
from samples whose major axis was oriented across the sheet. 
TABLE II 
__________________________________________________________________________ 
Physical Test Methods 
Property Test Method 
__________________________________________________________________________ 
Tensile Strength ASTM D 412-83. 
Elongation 
Porosity As described in the text above. 
Matrix Tensile Strength 
Tensile Strength determined in 
accordance with ASTM D 412-83 
multiplied by the quantity 
100/(100-Porosity). 
Tear Strength, Die C 
ASTM D 624-81. 
Processing Oil Content 
Method 502 C in "Standard Methods 
for the Examination of Water and 
Wastewater", 14th Ed., APHA-AWWA- 
WPCF (1975). 
Maximum Pore Diaster 
Mercury Porosimetry, as described in the 
text above. 
Volume Average Pore Diameter 
Mercury Porosimetry, as described in 
the text above. 
Gurley Air Flow ASTM D 726-58 (reapproved 1971), Method A. 
Mullens Hydrostatic Resistance 
ASTM D 751-79, Sec. 30-34, Method A. 
MVTR (Moisture Vapor 
ASTM E 96-80. 
Transmission Rate) 
Methanol Bubble Pressure 
ASTM F 316-80, using methanol. 
Maximum Limiting Pore Diameter 
ASTM F316-80, using methanol 
where c.gamma. = 22.34 (.mu.m)(kPa). 
Heat Shrinkage ASTM D 1204-84, using 15.24 cm x 
20.32 cm sample, 1 hr at 100.degree. C. 
Strip Tensile Strength 
ASTM D 828-60. 
and Elongation 
Breaking Factor ASTM D 882-83. 
and Elongation 
__________________________________________________________________________ 
TALBE III 
__________________________________________________________________________ 
Physical Properties of Microporous Sheet 
Example No. 
1 2 3 4 5 6 7 8 9 
__________________________________________________________________________ 
Thickness, mm 
0.229 
0.279 
0.229 
0.381 
0.483 
0.254 
0.229 
0.356 
0.305 
Matrix Tensile 
Strength, MPa 
MD 23.82 
34.33 
25.66 
27.79 
29.21 
70.47 
20.35 
31.90 
51.37 
TD 9.94 
14.91 
10.38 
19.05 
15.55 
26.39 
5.97 
15.82 
21.25 
Elongation at 
break, % 
MD 250 279 227 14 110 264 
TD 108 140 112 546 470 482 214 466 
Tear Strength, 
kN/m 
MD 36.25 
61.47 
47.81 
56.39 
57.09 
93.34 
24.52 
53.06 
87.04 
TD 18.04 
39.93 
23.12 
39.75 
32.22 
89.66 
7.36 
32.57 
56.39 
Porosity, vol % 
71 66 68 57.9 
59.3 
58.9 77 66 66.9 
Processing Oil 
4.1 2.7 2.4 2.7 2.4 
Content, wt % 
Maximum Pore 
0.86 
0.30 0.28 
1.34 
6.11 
0.16 
Diameter, .mu.m 
Volume Average 
0.11 
0.065 
0.069 
0.099 
0.111 
0.12 
Pore Diameter, .mu.m 
Gurley Air 
904 1711 955 4098 422 1757 1792 
Flow, 
sec/lOO cc 
__________________________________________________________________________ 
Biaxial Stretching of Microporous Sheet 
Portions of the microporous materials produced in Examples 1-3 and 
microporous material taken from a different roll of microporous material 
produced during the same production run as the microporous material of 
Example 8 were unwound from cores and biaxially stretched by first 
uniaxially stretching in the machine direction using a single stage 
roll-to-roll machine direction stretching (MDS) unit and then essentially 
uniaxially stretching in the transverse direction using a moving clip 
tenter frame as a transverse direction stretching (TDS) unit. A preheat 
roll was employed with the MDS unit to heat the sheet prior to stretching. 
In the TDS unit, the sheet was heated by infrared radiant heater. The 
Preheat and Stretch I Zones of the TDS unit each contained both upper and 
lower banks of such heaters. The upper banks were located about 10.16 
centimeters above the intermediate product while the lower banks were 
located about 15.24 centimeters below the intermediate product. Electrical 
power to the heaters of each lower bank was controlled by an on-off 
controller in response to the difference between a set point and the 
signal provided by a thermocouple mounted in one heater of the bank. 
Autotransformers were used to adjust electrical power to the heaters of 
the upper banks. The Stretch II, Stretch III, Sinter I, and Sinter II 
Zones each contained upper banks of infrared radiant heaters located about 
10.16 centimeters above the intermediate product. There were no lower 
banks in these zones. Electrical power to the heaters of each upper bank 
was controlled as described in respect of the heaters of each lower bank 
in the Preheat and Stretch I Zones. For a description of a typical TDS 
unit, see FIG. 2 and column 2, lines 43-69, of U.S. Pat. No. 2,823,421, 
the entire disclosure of which is incorporated herein by reference. 
The MDS stretch ratio was varied by controlling the relative peripheral 
speeds of the feed rolls and the takeoff rolls of the MDS unit. The chain 
track positions in the tenter frame were set to achieve the desired 
stretch ratio and then to essentially maintain that stretch ratio during 
sintering. For each of the Examples 10-31, the settings of one of the 
first four vertical columns under the heading "Approximate Transverse 
Stretch Ratio" in Table IV were employed. The correct column may be 
ascertained by matching up the TD stretch ratio of the example with the 
final stretch ratio of the column. For Examples 32 and 33, the settings of 
the fifth vertical column under the same heading in Table IV were 
employed. 
TABLE IV 
______________________________________ 
Transverse Direction Stretching 
Cumulative Dis- 
tance from Beginn- 
Approximate 
Zone ing of Oven, meters 
Transverse Stretch Ratio 
______________________________________ 
Preheat 0 1 1 1 1 1 
Stretch I 
2.794 1 1 1 1 1 
Stretch II 
4.318 1.33 1.44 1.65 1.87 1.45 
Stretch III 
8.890 2.31 2.75 3.62 4.49 2.95 
Sinter I 
9.779 2.5 3 4 5 3 
Sinter II 
11.430 2.5 3 4 5 3 
13.716 2.5 3 4 5 3 
______________________________________ 
The microporous sheet stock of Examples 1-3 and microporous sheet stock 
taken from a different roll of microporous material produced during the 
same production run as the microporous material of Example 8 were fed over 
the preheat roll of the MDS unit which was heated to the temperature 
indicated in Tables V-VIII. The sheet was then stretched to the indicated 
stretch ratio by maintaining the relative peripheral speeds of the second 
and first stretch rolls at essentially the same ratio as the stretch 
ratio. The line speed given in Tables V-VIII is the output speed of the 
MDS unit and the machine direction speed of the TDS unit. The linear feed 
rate from the roll stock of microporous material to the MDS unit was set 
at a value given by the line speed divided by the MDS stretch ratio. Thus, 
with a line speed of 24 m/min and a MDS stretch ratio of 2, the linear 
feed rate from the roll stock of the MDS unit would be 12 m/min. The 
properties of several representative examples of biaxially stretched 
sheets are given in Tables V-VIII. 
TABLE V 
__________________________________________________________________________ 
Properties of Biaxially Stretched Microporous Sheets 
Produced from Microporous Sheet of Example 1 
Example No. 
10 11 12 13 14 15 16 17 18 
__________________________________________________________________________ 
Thickness, mm 
0.178 
0.152 
0.127 
0.076 
0.076 
0.102 
0.127 
0.102 
0.076 
Stretch Ratio 
MD 2 2 2 2 3 3 3 3 3 
TD 3 3 4 5 3 3 3 3 4 
Line Speed 
48.8 
24.4 
24.4 
24.4 
24.4 
24.4 
24.4 
24.4 
24.4 
m/min 
MDS Preheat 
79 79 79 79 79 79 79 79 79 
Temp., .degree.C. 
TDS Average 
149 177 177 149 149 149 177 149 177 
Zonal Set 
Point Temps.,.degree.C. 
Preheat 
(lower banks) 
Stretch I 
149 177 177 149 149 149 177 149 177 
(lower Banks) 
Stretch II 
189 171 171 189 189 189 171 189 171 
Stretch III 
149 142 142 149 149 149 142 149 142 
Sinter I 149 144 144 149 149 149 144 149 144 
Sinter II 
204 227 227 204 149 204 227 260 227 
Weight, g/m.sup.2 
27 24 17 14 14 10 14 14 10 
Porosity, vol % 
91 90 92 90 89 93 93 93 91 
Matrix Tensile 
Strength, MPa 
MD 53.70 
32.96 
40.25 
25.30 
29.52 
62.74 
67.77 
41.96 
56.69 
TD 40.14 
29.30 
65.76 
46.54 
61.99 
45.41 
43.93 
57.62 
55.77 
Elongation at 
break, % 
MD 57 56 60 67 26 23 34 18 33 
TD 27 41 13 9 23 27 30 31 12 
Gurley Air 
47 45 40 29 32 28 37 28 36 
Flow, 
sec/1OO cc 
Tear Strength, 
kN/m 
MD 9.28 
5.78 
7.01 
3.85 
2.28 
5.08 
6.30 
5.60 
5.08 
TD 4.90 
4.90 
7.01 
8.23 
7.53 
1.93 
4.38 
4.55 
4.73 
Mullens 483 434 490 448 476 503 496 434 510 
Hydrostatic, 
kPa 
MVTR 935 963 
g/m.sup.2 day 
Methanol 290 276 296 234 145 276 324 55 317 
Bubble Point 
Pressure, kPa 
Maximum 0.077 
0.081 
0.075 
0.095 
0.154 
0.081 
0.069 
0.404 
0.070 
Limiting Pore 
Diameter, .mu.m 
Maximum Pore 155 
Diameter, .mu.m 
Volume Average 17.92 
Pore Diameter, 
.mu.m 
Heat Shrinkage 
after 1 hr at 
100.degree. C., % 
MD 19.0 9.4 12.0 19.3 
24.1 
21.2 
TD 23.2 22.5 
28.3 25.7 
29.1 
30.8 
__________________________________________________________________________ 
The biaxially stretched microporous sheet of Example 16 was examined by 
scanning electron microscopy at a magnification of 430.times.. A section 
taken in a plane perpendicular to the sheet surface (viz., looking into 
the thickness) and along the machine direction showed substantial pore 
elongation. A section taken in a plane perpendicular to the sheet surface 
and along the transverse direction showed pore elongation which was not as 
pronounced as along the machine direction. A view of the sheet surface 
(not sectioned) showed that large void structures were not as numerous as 
in views of either of the sections looking into the thickness. 
TABLE VI 
__________________________________________________________________________ 
Properties of Biaxially Stretched Microporous Sheets 
Produced from Microporous Sheet of Example 2 
Example No. 
19 20 21 22 23 24 25 26 27 
__________________________________________________________________________ 
Thickness, mm 
0.203 
0.152 
0.178 
0.127 
0.152 
0.127 
0.102 
0.076 
0.178 
Stretch Ratio 
MD 2 2 2 2 2 3 3 3 3 
TD 2.5 3 3 3 4 3 3 3 4 
Line Speed 
24.4 
24.4 
15.2 
24.4 
15.2 
24.4 15.2 
24.4 
15.2 
m/min 
MDS Preheat 
104 104 121 79 121 104 121 79 121 
Temp., .degree.C. 
TDS Average 
177 177 149 149 149 177 149 149 149 
Zonal Set 
Point Temps.,.degree.C. 
Preheat 
(lower banks) 
Stretch I 
177 177 149 149 149 177 149 149 149 
(lower Banks) 
Stretch II 
171 171 188 188 188 171 188 188 188 
Stretch III 
142 142 144 149 144 142 144 149 144 
Sinter I 144 144 200 149 144 144 144 149 144 
Sinter II 
227 227 255 316 255 227 255 316 255 
Weight, g/m.sup.2 
44 24 24 17 14 31 
Porosity, vol % 
86 90 90 92 90 90 
Matrix Tensile 
Strength, MPa 
MD 52.94 
61.50 36.61 
96.18 73.91 
37.51 
TD 44.47 
67.98 109.49 
54.38 75.01 
117.21 
Elongation at 
break, % 
MD 58 54 161 41 87 31 13 19 111 
TD 51 39 15 16 9 42 16 16 7 
Tear Strength, 
kN/m 
MD 20.31 
12.61 
17.51 
6.13 
13.13 
12.26 
8.41 
5.95 
18.56 
TD 13.31 
12.78 
21.02 
7.18 
11.03 
9.11 5.25 
7.53 
19.44 
Gurley Air 
81 40 46 45 52 
Flow, 
sec/100 cc 
Mullens 745 689 676 496 745 717 641 503 703 
Hydrostatic, 
kPa 
MVTR 868 761 947 913 827 
g/m.sup.2 day 
Methanol 290 303 303 365 290 
Bubble Point 
Pressure, kPa 
Maximum 0.077 
0.074 0.074 
0.061 0.077 
Limiting Pore 
Diameter, .mu.m 
Maximum Pore 111 &gt;146 
Diameter, .mu.m 
Volume Average 
7.13 4.70 
Pore Diameter, 
.mu.m 
Heat Shrinkage 
after 1 hr at 
100.degree. C., % 
MD 11.7 3.8 7.1 12.3 15.3 
6.3 7.7 
TD 24.4 23.6 
11.8 
22.0 34.1 
18.9 
21.5 
__________________________________________________________________________ 
The biaxially stretched microporous sheet of Example 24 was examined by 
scanning electron microscopy at a magnification of 430.times.. A section 
taken in a plane perpendicular to the sheet surface and along the 
transverse direction showed pore elongation which was not as pronounced as 
that seen in a similar section taken along the machine direction. A view 
of the sheet surface (not sectioned) showed that large void structures 
were not as numerous as in views of either of the sections looking into 
the thickness. 
TABLE VII 
______________________________________ 
Properties of Biaxially Stretched Microporous Sheets 
Produced from Microporous Sheet of Example 3 
Example No. 28 29 30 31 
______________________________________ 
Thickness, mm 
0.178 0.102 0.127 0.102 
Stretch Ratio 
MD 2 2 3 3 
TD 3 3 3 4 
Line Speed 24.4 24.4 24.4 24.4 
m/min 
MDS Preheat 79 79 79 79 
Temp., .degree.C. 
TDS Average 177 149 177 177 
Zonal Set 
Point Temps.,.degree.C. 
Preheat 
(lower banks) 
Stretch I 177 149 177 177 
(lower Banks) 
Stretch II 171 188 171 171 
Stretch III 142 149 142 142 
Sinter I 144 149 144 144 
Sinter II 227 260 227 227 
Weight, g/m.sup.2 
27 14 20 14 
Porosity, vol % 
90 91 90 92 
Matrix Tensile 
Strength, MPa 
MD 29.58 52.94 77.84 109.89 
TD 122.73 44.43 32.96 39.90 
Elongation at 
break, % 
MD 90 47 27 17 
TD 9 24 32 30 
Tear Strength, 
kN/m 
MD 15.41 10.51 15.24 7.18 
TD 21.02 5.43 4.20 3.50 
Gurley Air 56 33 36 
Flow, 
sec/100 cc 
Mullens 552 655 641 586 
Hydrostatic, 
kPa 
MVTR 843 815 862 982 
g/m.sup.2 day 
Methanol 303 276 317 
Bubble Point 
Pressure, kPa 
Maximum 0.074 0.081 0.070 
Limiting Pore 
Diameter, .mu.m 
Heat Shrinkage 
after 1 hr at 
100.degree. C., % 
MD 24.1 16.5 26.4 
TD 40.1 31.4 34.8 
______________________________________ 
TABLE VIII 
______________________________________ 
Properties of Biaxially Stretched Microporous Sheets 
Produced from Microporous Sheet Similar to that of Example 8 
Example No. 32 33 
______________________________________ 
Thickness, mm 0.160 0.165 
Stretch Ratio 
MD 2 3 
TD 3 3 
Line Speed 15.5 15.54 
m/min 
MDS Preheat 93 93 
Temp., .degree.C. 
TDS Average 232 232 
Zonal Set 
Point Temps.,.degree.C. 
Preheat 
(lower banks) 
Stretch I 149 149 
(lower Banks) 
Stretch II 204 204 
Stretch III 127 149 
Sinter I 149 149 
Sinter II 149 149 
Weight, g/m.sup.2 19.7 19.3 
Porosity, vol % 91.6 92.5 
Matrix Tensile 
Strength, MPa 
MD 52.63 80.80 
TD 24.53 23.62 
Elongation at 
break, % 
MD 29.7 14.3 
TD 24.4 29.2 
Tear Strength, 
kN/m 
MD 53.06 46.58 
TD 32.57 33.62 
Gurley Air 25 18 
Flow, 
sec/100 cc 
Mullens 345 359 
Hydrostatic, 
kPa 
MVTR 1004 928 
g/m.sup.2 day 
Methanol 165 159 
Bubble Point 
Pressure, kPa 
Maximum 0.135 0.141 
Limiting Pore 
Diameter, .mu.m 
______________________________________ 
Microporous Material Formation 
Larger batch mixing equipment was employed than was used for Examples 1-9. 
Processing oil was used as the processing plasticizer. Silica, polymer, 
lubricant, and antioxidant in the amount specified in Table IX were placed 
in a high intensity mixer and mixed at high speed for 6 minutes. The 
processing oil needed to formulate the batch was pumped into the mixer 
over a period of 12-18 minutes with high speed agitation. After completion 
of the processing oil addition a 6 minute high speed mix period was used 
to complete the distribution of the processing oil uniformly throughout 
the mixture. 
TABLE IX 
______________________________________ 
Formulations 
Example No. 34 35 36 
______________________________________ 
Ingredient 
UHMWPE (1), kg 
24.04 17.24 17.24 
HDPE (2), kg 0.00 6.80 6.80 
Precipitated 59.87 59.87 59.87 
Silica (3), kg 
Lubricant (4), g 
300.0 300.0 600.0 
Antioxidant (5), g 
300.0 300.0 0.0 
(6), g 0.0 0.0 100.0 
Processing Oil 
(7), kg 
in Batch 91.63 91.63 91.63 
at Extruder .about.35.14 
.about.35.14 
.about.35.14 
______________________________________ 
(1) UHMWPE = Ultrahigh Molecular Weight Polyethylene, Himont 1900, Himont 
U.S.A., Inc. 
(2) HDPE = High Density Polyethylene, Chevron 9690T, Chevron Chemical Co. 
(3) HiSil .RTM. SBG, PPG Industries, Inc. 
(4) Petrac .RTM. CZ81, Desoto, Inc., Chemical Speciality Division 
(5) Irganox .RTM. B215, CibaGeigy Corp. 
(6) Irganox .RTM. 1010, CibaGeigy Corp. 
(7) Shellflex .RTM. 371, Shell Chemical Co. 
The batch was then processed according to the general procedures described 
in respect of Examples 1-9 to form microporous sheets. 
The microporous sheets, as well as the hereinafter described biaxially 
stretched microporous sheets produced therefrom, were tested for various 
physical properties. Table II identifies the properties with the methods 
used for their determination. The results of physical testing of the 
microporous sheets are shown in Table X. The abbreviations MD and TD have 
the same meanings previously discussed. 
TABLE X 
______________________________________ 
Physical Properties of Microporous Sheet 
Example No. 34 35 36 
______________________________________ 
Thickness, mm 0.267 0.254 0.255 
Strip Tensile 
Strength, kN/m 
MD 3.42 
TD 1.52 
Breaking Factor, kN/m 
MD 3.44 3.23 
TD 1.42 1.52 
Elongation at 
break, % 
MD 391 477 688 
TD 448 451 704 
Processing Oil 2.8 3.3 3.1 
Content, wt % 
______________________________________ 
Biaxial Stretching of Microporous Sheet 
Portions of the microporous materials prouduced in Examples 34 and 35 were 
unwound from cores and biaxially stretched by first uniaxially stretching 
in the machine direction using a single stage roll-to-roll MDS unit and 
then essentially uniaxially stretching in the transverse direction using a 
moving clip tenter frame as a TDS unit. 
Operation of the MDS unit can be characterized by the temperatures and line 
speeds shown in Table XI. 
TABLE XI 
______________________________________ 
MDS Unit Parameters 
Temp- 
erature, 
Peripheral 
Roll No. 
Function Diameter, mm 
.degree.C. 
Speed, m/min 
______________________________________ 
1 Preheat 305 116 3.84 
2 Preheat 305 116 3.84 
3 Stretching 
152 127 3.84 
4 Stretching 
152 127 11.52 
5 Annealing 305 79 11.53 
6 Cooling 305 38 11.53 
______________________________________ 
The gap between the slow and fast stretching rolls (Rolls 3 and 4, 
respectively) was 0.533 millimeter. 
The TDS unit was a typical chain and clip tentering frame machine. It 
comprised three contiguous heating zones, each 2.54 meters in length where 
the beginning of the first heating zone coincided with the entrance to the 
TDS unit. The microporous sheet was heated by recirculating hot air in the 
heating zones. The heating zone temperatures are indicated in Table XII, 
where heating zone numbers increase in the direction of sheet travel. 
TABLE XII 
______________________________________ 
Heating Zone Temperature 
Heating Zone Temperature, .degree.C. 
______________________________________ 
1 107 
2 116 
3 121 
______________________________________ 
Stretching was controlled by positioning the tracks in which the chains 
holding the gripping clips rode. Microporous sheets, which had been 
uniaxially stretched in the machine direction as described above, were 
introduced to the TDS unit which had the track geometry shown in Table 
XIII. 
TABLE XIII 
______________________________________ 
Track Geometry of TDS Unit 
Distance from Entrance, meters 
Width, meters 
______________________________________ 
-0.30 0.53 
+1.22 0.53 
2.01 0.53 
2.74 0.74 
3.51 0.97 
4.27 1.17 
5.03 1.38 
5.79 1.60 
7.32 1.60 
7.92 1.57 
______________________________________ 
The properties of representative samples of biaxially stretched microporous 
sheets are given in Table XIV. 
TABLE XIV 
______________________________________ 
Properties of Biaxially Stretched Microporous Sheets 
Example No. 37 38 
______________________________________ 
Microporous Sheet 34 35 
Feedstock, Example No. 
Thickness, mm 0.228 0.250 
Stretch Ratio 
MD 3 3 
TD 3 3 
Line Speed, m/min 13.4 13.4 
Weight, g/m.sup.2 19.67 21.56 
Porosity, vol % 92.1 91.1 
Breaking Factor, kN/m 
MD 1.175 1.158 
TD 0.716 0.412 
Elongation at 
break, % 
MD 41 39 
TD 54 61 
Gurley Air Flow, 41 48 
sec/100 cc 
Mullens Hydrostic, 600 579 
kPa 
______________________________________ 
EXAMPLE 39 
A first solution was prepared by dissolving about 15 cubic centimeters of 
No. 7 Rose Pink RIT.RTM. dye (CPC International, Inc.) in about 600 
milliliters of water. 
A second solution was prepared by adding 40 drops of No. 4001 Rose Petal 
fragrance (Chemia Corp.). and 20 drops of No. 3008 Rose fragrance (Chemia 
Corp.) to about 400 milliliters of absolute ethanol. 
A dying and perfuming solution was prepared by admixing all of the first 
and second solutions. 
A portion of biaxially stretched microporous sheet produced in accordance 
with the principles heretofore described was immersed in the above dying 
and perfuming solution at room temperature until the microporous material 
was dyed a light pink color. The dyed and perfumed microporous material 
was then removed from the dying and perfuming solution and allowed to dry. 
During immersion and/or drying, the microporous material shrunk slightly. 
The dry microporous material was gently stretched by hand both in the 
machine direction and in the transverse direction, but not so much as to 
restore it to the original dimensions. 
A PRETTY PETALS.RTM. No. 3R-30 Silky Sweetheart Rose artificial flower kit 
(Signaigo & Rossi, Inc., d.b.a. Sirocraft) was purchased. One of the 
tetrapetalous No. 3R rose cuts from the kit was used as a pattern from 
which a die was fabricated. The die was used to cut three identical 
tetrapetalous artificial petal elements from the above dyed and perfumed 
microporous material and a small hole was punched in the center of each. 
The artificial petals of each artificial petal element were stretched 
slightly over a large ball bearing to provide the gentle dish-shaped 
appearance characteristic of true rose petals. The tips of opposing petals 
were about 7.8 centimeters apart while the innermost points of opposing 
sinuses were about 1.8 centimeters apart. 
A No. 717 white cotton mold from the kit comprised a generally 
teardrop-shaped mold head formed of cotton wrapped about a wire. The 
cotton was sized to increase firmness and to hold the cotton in place. The 
equator of the mold head is a narrow region encircling the surface of mold 
head at its largest cross-section perpendicular to the axis of symmetry. 
The diameter of the equator was about 1.6 centimeters while the length of 
the mold head along the axis of symmetry was about 2.0 centimeters. A band 
of white glue was placed on the mold head along the equator. 
White glue was placed locally on both lateral regions of the slightly 
concave sides of each of the artificial petals of the first artificial 
petal element. With the glue on the artificial petals facing upwardly, the 
wire of the mold was inserted downwardly through the small hole in the 
artificial petal element until the coalescence at the base of the 
artificial petals touched the bottom of the mold head. The artificial 
petals were then wrapped around the mold head in the order (referenced to 
the first petal) first petal, adjacent petal, adjacent petal, opposite 
petal, and held until the glue along the equator and on lateral regions 
had dried at least sufficiently to hold the artificial petals in place. 
The lateral extremities of the first artificial petal when in place on the 
mold head did not quite overlap while the portions near the tip 
substantially sheathed the upper portion of the mold head. The portions 
near the tips of the other three artificial petals were progressively less 
enveloping of the upper portion of the mold head in accordance with the 
order in which they were positioned. 
White glue was placed locally on only one lateral region of the slightly 
concave sides of each of the artificial petals of the second artificial 
petal element. With the glue on the artificial petals facing upwardly, the 
wire of the mold was inserted downwardly through the small hole in the 
second artificial petal element until the coalescence at the base of the 
artificial petals of the second artificial petal element touched the 
coalescence of the previously positioned first artificial petal element. 
The second petal element was rotated until the axes of symmetry through 
opposing sinuses was at about 45 degrees from the corresponding axes of 
symmetry of the first artificial petal element. Proceeding in clockwise 
order, the artificial petals of the second artificial petal element were 
then subsequently wrapped around the previously positioned artificial 
petals of the first artificial petal element and held until the glue on 
the lateral regions of the artificial petals of the second artificial 
petal element had dried at least sufficiently to hold the newly positioned 
artificial petals in place. 
White glue was applied to the artificial petals of a third artificial petal 
element and the artificial petals were wrapped around the previously 
positioned artificial petals of the second artificial petal element, all 
in a manner analogous to that of the second artificial petal element, 
including the 45 degree rotational offset. 
White glue was placed on the edge of a No. P-200B artificial calyx from the 
kit and the wire of the mold was inserted into the central hole of the 
artificial calyx. The artificial calyx was then pushed up the wire until 
it enveloped the coalescence of the previously positioned third petal 
element. The glue was allowed to dry. 
A J740s artificial leaf from the kit comprises an artificial blade of sized 
green fabric which had been glued to a green paper-covered wire. The 
portion of the covered wire in contact with the artificial blade functions 
as an artificial midrib while the remainder functions as an artificial 
petiole. The artificial leaf was placed such that the artificial petiole 
portion of the covered wire was parallel to and in contact with the wire 
of the mold and such that the lower portion of the artificial blade was in 
contact with the lower portion of the artificial calyx. The lower portion 
of the artificial calyx, the artificial petiole portion of the covered 
wire, and the wire of the mold were wrapped together in helical fashion 
with green florist's tape, beginning at the lower portion of the 
artificial calyx and continuing past the lower end of the covered wire to 
the lower end of the wire of the mold, to form an artificial stem. 
The tips of some of the artificial petals were bent back slightly into a 
recurved position. Upon minor adjustment of the artificial petals 
according to individual preference, the artificial rose was complete. 
For a more complete description of artificial flowers having artificial 
petals of fragrance delivery devices of the present invention see 
application Ser. No. 250,015, filed Sept. 27, 1988, which is a 
continuation-in-part of application Ser. No. 110,147, filed Oct. 19, 1987, 
the entire disclosures of which are incorporated herein by reference. 
EXAMPLE 40 
A Nalgene filter holder with receiver (Catalog No. 300-4000) was modified 
by using the top which was threaded on the large end, the associated 
threaded bottom, and the intervening O-ring as a container for determining 
the rates of release of active agent from microporous materials. The 
procedure was to cut from microporous material a disc having a diameter as 
large as or a little larger than the interior of the container bottom. 
After treatment with active agent, the disc was placed on the interior of 
the container bottom. The O-ring was placed in position and the bottom and 
top were screwed together. Wax or high vacuum grease was placed on the 
outside of the joint to provide additional insurance against leakage. The 
assembled apparatus was analogous to a beaker with a disc of active 
agent-containing microporous material held flush against the bottom. The 
capacity of the assembled apparatus was about 300 milliliters. The 
apparatus was placed in a controlled substantially constant temperature 
water bath, an appropriate solvent was added, and the solvent was stirred 
with a glass stirrer. Samples were taken from time to time and analyzed 
for active agent. From this information release rates were calculated. 
An 8 centimeter diameter disc cut from microporous material similar to that 
of Example 1 was extracted with 1,1,2-trichloro-1,2,2-trifluoroethane to 
remove substantially all of the residual processing plasticizer. The disc 
was placed in a desiccator for about 2 weeks to dry to a constant weight 
of 0.7813 gram. The disc was then soaked in a 50 percent by weight aqueous 
solution of procain hydrochloride. The disc was blotted with No. 41 
Whatman filter paper and weighed. The weight was 1.9737 grams. The disc 
was dried overnight in the desiccator and weighed. The weight was 1.4386 
grams. The container described above was assembled with a 1.0197 g portion 
of the disc in position and placed in a 33.degree. C.-34.degree. C. water 
bath. Two hundred milliliters of water buffered at pH 7.4 with KH.sub.2 
PO.sub.4 and Na.sub.2 HPO.sub.4 was added to the container. Stirring was 
begun and the timer was started. Samples (3 milliliters each) were taken 
at timed intervals, diluted, and analyzed for procain hydrochloride using 
an ultraviolet spectrophotometer at 289.3 nanometers. The release rates, 
each averaged over the time interval since the previous sample showing an 
increase in concentration, were calculated. The results are shown in Table 
XV. 
TABLE XV 
______________________________________ 
Procain Hydrochloride Release Rates 
Procain .RTM. HCl 
Extract Release 
Cumulative Time, 
Concentration, mg/L 
Volume, Rate 
hours:minutes 
Measured Difference 
milliliters 
mg/min. 
______________________________________ 
0:01 750 750 200 150 
0:02.5 1280 530 197 69.6 
0:05 1290 10 194 0.8 
0:07.5 1360 70 191 5.3 
0:10 1400 40 188 3.0 
0:12.5 1450 50 185 3.7 
0:15 1390 0 182 0 
0:20 1450 0 179 0 
0:25 1415 0 176 0 
0:30 1450 0 173 0 
0:45 1460 10 170 0.1 
1:00 1380 0 167 0 
1:30 1500 40 164 0.1 
2:00 1450 0 161 0 
20:00 1670 170 158 &lt;0.1 
______________________________________ 
EXAMPLE 41 
An 8 centimeter diameter disc cut from microporous material similar to that 
of Example 1 was extracted with ethanol to remove substantially all of the 
residual processing plasticizer and then dried for about 2 days in a 
desiccator. The weight of the dried disc was 0.8502 gram. A solution of 
salicylic acid in ethanol was prepared by admixing 40 grams of salicylic 
acid and 113 milliliters of ethanol having a density of 0.789 
gram/milliliter. The disc was soaked for one hour in the salicylic 
acid-ethanol solution. The disc was blotted with absorbent paper and 
weighed. The weight was 1.9502 grams. After drying overnight, the disc 
weighed 1.4780 grams. The container described in Example 40 was assembled 
with the disc in the position and placed in a 32.degree. C. water bath. 
Two hundred milliliters of water buffered at pH 7.4 as in Example 40 was 
added to the container. Stirring was begun and the timer was started. 
Samples (3 milliliters each) were taken at timed intervals, diluted, and 
analyzed for salicylic acid by ultraviolet spectrophotometry and infrared 
spectroscopy. The release rates, each averaged over the time interval 
since the previous sample showing an increase in concentration, were 
calculated. The results are shown in Table XVI. 
TABLE XVI 
______________________________________ 
Salicylic Acid Release Rates 
Salicylic Acid 
Extract Release 
Cumulative Time 
Concentration, mg/L 
Volume, Rate 
hours:minutes 
Measured Difference 
milliliters 
mg/min. 
______________________________________ 
0:01 257 257 200 51 
0:02.5 502 245 197 32 
0:05 711 209 194 16 
0:07.5 854 143 191 11 
0:10 931 77 188 5.8 
0:12.5 1041 110 185 8.1 
0:15 1134 93 182 6.8 
0:20 1261 127 179 4.5 
0:25 1340 79 176 2.8 
0:30 1353 13 173 0.45 
0:45 1375 22 170 0.25 
1:00 1388 13 167 0.14 
1:30 1405 17 164 0.09 
2:00 1410 5 161 0.03 
16:00 1511 101 158 0.02 
______________________________________ 
EXAMPLE 42 
An 8 centimeter diameter disc cut from microporous material similar to that 
of Example 1 was extracted with ethanol to remove substantially all of the 
residual processing plasticizer and then dried for about 2 days in a 
desiccator. The weight of the dried disc was 0.7854 gram. The disc was 
then exposed to vapors of hexamethyldisilazane for several hours. Upon 
completion of the hexamethyldisilazane vapor treatment the disc weighed 
0.7874 gram. The disc was soaked for one hour in the salicylic acid 
ethanol solution of Example 41. The disc was blotted with absorbent paper 
and weighed. The weight was 1.7673 grams. The disc was then dried. The 
container described in Example 40 was assembled with the dried disc in 
position and placed in a 32.degree. C. water bath. Two hundred milliliters 
of water buffered at pH 7.4 as in Example 40 was added to the container. 
Stirring was begun and the timer was started. Samples (3 milliliters each) 
were taken at timed intervals, diluted, and analyzed for salicylic acid by 
ultraviolet spectrophotometry, and infrared spectroscopy. The release 
rates, each averaged over the time interval since the previous sample 
showing an increase in concentration, were calculated. The results are 
shown in Table XVII. 
TABLE XVII 
______________________________________ 
Salicylic Acid Release Rates 
Salicylic Acid 
Extract Release 
Cumulative Time, 
Concentration, mg/L 
Volume, Rate 
hours:minutes 
Measured Difference 
milliliters 
mg/min. 
______________________________________ 
0:01 224 224 200 45 
0:02.5 442 218 197 29 
0:05 607 165 194 13 
0:07.5 740 133 191 10 
0:10 839 99 188 7.4 
0:12.5 936 97 185 7.2 
0:15 1024 88 182 6.4 
0:20 1138 114 179 4.1 
0:25 1230 92 176 3.2 
0:30 1257 27 173 0.93 
0:45 1292 35 170 0.40 
1:00 1318 26 167 0.29 
1:30 1336 18 164 0.10 
2:00 1362 26 161 0.14 
20:00 1437 75 158 0.01 
______________________________________ 
EXAMPLE 43 
A 21.59 centimeter.times.27.94 centimeter sheet of the microporous material 
of Example 8 was treated on one side with a spray application of 0.50 gram 
of N-trimethoxysilylpropyl ethylene diamine triacetic acid, trisodium salt 
(Petrarch Systems T2913) in 10 milliliters of toluene. The sprayed sheet 
was heated in an air oven at 110.degree. C. for 2 hours to couple the 
silane to the silica. The reverse side was then treated with 0.01 gram of 
hexamethyldisilazane (Petrarch Systems H7300) in 10 milliliters of dry 
methylene chloride by spray application. The sheet was allowed to dry in 
the hood for 2 hours at ambient temperature, then heated in an oven at 
40.degree. C. for 3 hours and finally at 110.degree. C. for 30 minutes. 
N-Trimethoxysilylpropyl ethylene diamine triacetic acid, sodium salt, is 
hydrophilic, whereas hexamethyldisilazane is hydrophobic. Consequently, 
the treated sheet had a hydrophilic surface and a hydrophobic opposite 
surface. 
MVTR testing of both the treated microporous sheet and an untreated sheet 
of the microporous material of Example 8 was done using a modified ASTM 
E96 test procedure: Test Temperature was 21.degree. C.; Relative Humidty 
was 60%; Air Velocity was 342 meters/minute. Each sample was tested twice, 
once with one surface facing the water of an upright cup, and then with 
the opposite surface facing the water of an upright cup. The results are 
shown in Table XVIII. 
TABLE XVIII 
______________________________________ 
Modified Moisture Vapor Transmission Rates 
Sample Side Facing Water 
Modified MVTR, g/m.sup.2 day 
______________________________________ 
Treated Hydrophobic 3427 
Treated Hydrophilic 1216 
Untreated 
First 3816 
Untreated 
Opposite 2823 
______________________________________ 
The results show that the moisture vapor transmission rates for the treated 
sample were substantially different, depending upon whether the 
hydrophobic side or the hydrophilic side was facing the water. The results 
also show that the moisture vapor transmission rates for the untreated 
sample were significantly different, depending upon which side was facing 
the water. 
EXAMPLE 44 
A sample of microporous material similar to that of Example 8 (viz., 
unstretched microporous material, other portions of which were biaxially 
stretched to produce the product of Example 32), and samples of the 
biaxially stretched microporous materials of Examples 24, 31, 32, and 33, 
were tested for moisture vapor transmission rates according to the 
procedure of ASTM E96. For upright cup measurements, liquid water in the 
cup was not in contact with the microporous material. For inverted cup 
measurements, the cup was inverted so that liquid water in the cup 
contacted the microporous material. The results are shown in Table XIX. 
TABLE XIX 
______________________________________ 
Moisture Vapor Transmission Rates 
MVTR, g/m.sup.2 day 
Sample Upright Cup 
Inverted Cup 
______________________________________ 
Similar to Example 8 
947 17459 
Example 24 947 14043 
Example 31 982 14051 
Example 32 1004 15743 
Example 33 928 12073 
______________________________________ 
EXAMPLE 45 
A sample of microporous material similar to the microporous material of 
Example 1 and weighing 4.44 grams was extracted twice for 5 minutes with 
50 milliliters of 1,1,2-trichloro-1,2,2-trifluoroethane and then air 
dried. The dried sample weighed 4.00 grams. A solution was prepared by 
admixing 2.5 grams of bis(hydrogenated tallow alkyl) dimethylammonium 
chloride (Arquad.RTM. 2HT75; Akzo Chemie America) [CAS Registry No. 
61789-80-8] and 100 milliliters of 2-propanol. The dried sample of 
microporous material was impregnated with the solution, dried under 
vaccuum, and then further dried in air. The treated sample weighed 5.64 
grams and is useful for inclusion with clothes during drying to reduce 
accumulation of static electricity by the dried clothes. 
Although the present invention has been described with reference to 
specific details of certain embodiments thereof, it is not intended that 
such details should be regarded as limitations upon the scope of the 
invention except insofar as they are included in the accompanying claims.