U.S. patent number 3,663,266 [Application Number 05/039,531] was granted by the patent office on 1972-05-16 for moisture responsive synthetic microporous sheet material.
This patent grant is currently assigned to E. I. du Pont de Nemours and Company. Invention is credited to John I. Dye.
United States Patent |
3,663,266 |
Dye |
May 16, 1972 |
MOISTURE RESPONSIVE SYNTHETIC MICROPOROUS SHEET MATERIAL
Abstract
A coriaceous vapor permeable microporous sheet material that
absorbs water and expands under moist conditions is the subject of
this invention. The novel material is particularly useful for
making shoes and boots and provides better comfort and appearance
than natural leather. The novel coriaceous material has a coating
of a microporous polymer which is in firm adherence to a substrate
of a polymer impregnated non-woven synthetic fibrous web. The novel
sheet material under high humidity conditions as occur when a shoe
or boot is worn has a particular moisture absorption, area
expansion, and a decrease in tensile stress and also has a high
permeability to water vapors. These particular characteristics
provide a high degree of comfort to the wearer of shoes or boots
made from the novel sheet material of this invention. BACKGROUND OF
THE INVENTION This invention is related to a synthetic coriaceous
microporous sheet material, and in particular, to a synthetic
coriaceous microporous sheet material that absorbs moisture and
expands under moist conditions and is an extremely comfortable shoe
upper material. Synthetic coriaceous microporous sheet materials
are well known in the art and are currently being sold to the shoe
industry and are widely used in the manufacture of shoes. These
microporous sheet materials can be made according to the processes
taught in the following patents: Johnston et al. U.S. Pat. No.
3,000,757, issued Sept. 19, 1961; Holden U.S. Pat. No. 3,100,721,
issued Aug. 13, 1963; Yuan U.S. Pat. No. 3,190,766, issued June 22,
1965; Holder U.S. Pat. No. 3,208,875, issued Sept. 28, 1965;
Hulslander et al. U.S. Pat. No. 3,284,274,issued Nov. 8, 1966;
Patsis U.S. Pat. No. 3,364,098, issued Jan. 16, 1968; Manwaring
U.S. Pat. No. 3,391,049, issued July 2, 1968 and Einstman U.S. Pat.
No. 3,418,198, issued Dec. 24, 1968. While excellent synthetic
microporous sheet materials can be made according to the teachings
of the aforementioned patents, all of the products manufactured
according to these prior art patents have the same deficiency,
i.e., the materials are hydrophobic and, therefore, absorb very
little water and do not expand under moist conditions. For shoe
comfort, it is extremely desirable to have a shoe upper material
that is hydrophilic and will absorb water and expand under moist
conditions. The reason is that an average person's foot expands
during the day as the shoe is being worn; therefore, it is
desirable to have a shoe upper material that will absorb water and
expand under warm, moist conditions as exist in the interior of a
shoe. The novel coriaceous microporous sheet material of this
invention is hydrophilic and absorbs water and expands under high
humidity conditions as exist in the interior of a shoe; therefore,
the material is useful for making shoes and boots that are
surprisingly comfortable and also are attractive and have the
desirable characteristics of the prior art coriaceous synthetic
microporous materials, i.e., scuff and abrasion resistance,
excellent flexibility, and durability and leather-like appearance.
Another highly advantageous characteristic of the novel sheet
material of this invention is that the tensile stress of the
material decreases as water is absorbed. This characteristic
reduces the pressure on the wearer's foot in places where the shoe
upper is tightly fitted and thereby increases the comfort of the
shoe or boot. SUMMARY OF THE INVENTION A synthetic coriaceous
moisture responsive microporous sheet material of this invention
comprises a. a microporous topcoat of a synthetic polymeric
material in firm adherence to b. a porous fibrous substrate of 1. a
non-woven synthetic flexible fibrous web that has a density of
0.10- 0.40 grams/cubic centimeter and consists essentially of at
least 50 percent by weight of synthetic fibers that have a moisture
absorption of at least 5 percent by weight and in increase in
length of at least 2 percent when exposed to a change in relative
humidity of 0 to 95 percent at 25.degree. C.; 2. the non-woven web
is impregnated with a polymeric binder that has a wet tensile
strength of at least 500 pounds per square inch and has a moisture
absorption of 5- 25 percent by weight when exposed to a change in
relative humidity of 50 to 90 percent at 25.degree. C.; wherein the
substrate has a binder to fiber ratio of about 0.2 to about 2/1;
and wherein the coriaceous sheet material has an area expansion of
2- 10 percent, a moisture absorption of 0.5- 20 percent by weight
and a decrease in tensile stress at 5 percent elongation of 20- 60
percent when exposed to change in relative humidity of 50- 90
percent at 25.degree. C. and has a water vapor permeability of at
least 1,000 grams of water per 100 square meters of material per
hour.
Inventors: |
Dye; John I. (West Chester,
PA) |
Assignee: |
E. I. du Pont de Nemours and
Company (Wilmington, DE)
|
Family
ID: |
21905979 |
Appl.
No.: |
05/039,531 |
Filed: |
May 21, 1970 |
Current U.S.
Class: |
442/77;
428/315.5; 428/904; 428/902; 442/275; 442/276; 442/281 |
Current CPC
Class: |
D06N
3/0015 (20130101); D06M 15/564 (20130101); D06N
3/14 (20130101); Y10T 428/249978 (20150401); Y10T
442/3764 (20150401); Y10T 442/3772 (20150401); Y10S
428/902 (20130101); Y10T 442/2148 (20150401); Y10T
442/3813 (20150401); Y10S 428/904 (20130101) |
Current International
Class: |
D06N
3/14 (20060101); D06N 3/00 (20060101); D06M
15/564 (20060101); D06M 15/37 (20060101); D06N
3/12 (20060101); D06n 003/00 (); D06n 003/08 () |
Field of
Search: |
;161/190
;117/63,76,135.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Sussman; Morris
Claims
What is claimed is:
1. A synthetic coriaceous moisture responsive sheet material
comprising
a. a microporous topcoat of a synthetic polymeric material wherein
the polymeric component has a secant tensile modulus at 5 percent
elongation of above about 600 pounds per square inch and is in firm
adherence to
b. a porous fibrous substrate consisting essentially of
1. a non-woven synthetic flexible fibrous web having a density of
0.10- 0.40 grams/cubic centimeter consisting essentially of at
least 50 percent by weight of synthetic fibers that have a moisture
absorption of at least 5 percent by weight and an increase in
length of at least 2 percent when exposed to a change in relative
humidity of 0 to 95 percent at 25.degree. C.: in which the
non-woven web consists essentially of at least 50 percent by weight
of polyamide fibers having the recurring structural unit of
##SPC2##
wherein R and R.sup.1 are divalent aliphatic hydrocarbon radicals
having 3- 8 carbon atoms and n is an integer sufficiently high to
give an inherent viscosity of at least 0.4 measured at 25.degree.
C. in m-cresol solvent and 0 to 50 percent by weight of rayon
fibers;
2.
2. said web being impregnated with a polymeric binder that has a
wet tensile strength of at least 500 pounds per square inch and has
a moisture absorption of 5- 25 percent by weight when exposed to a
change in relative humidity of 50 to 90 percent at 25.degree. C.;
in which the polymeric binder is a chain-extended polyurethane
which is the reaction product of an isocyanate terminated
prepolymer of a polyalkyleneether glycol and an organic
diisocyanate chain-extended with a compound having at least one
reactive hydrogen atom attached to each end of the compound;
wherein the substrate has a binder to fiber ratio of about 0.2/1 to
2/1, and
wherein the coriaceous sheet material has an area expansion of 2-
10 percent, a moisture absorption of 0.5 - 20 percent by weight and
a decrease in tensile stress at 5 percent elongation of 20- 60
percent when exposed to a change in relative humidity of 50- 90
percent at 25.degree. C. and has a water vapor permeability of at
least 1,000 and up to 12,000
grams of water per 100 square meters of material per hour. 2. The
sheet material of claim 1 in which the fibrous web is of 10- 30
percent rayon fibers and 90- 70 percent of said polyamide
fibers.
3. The sheet material of claim 1 in which the polyurethane is the
reaction products of an isocyanate terminated prepolymer of a
polyethyleneether glycol molecular weight about 500- 1,500,
methylene-bis-4-phenyl isocyanate and is chain-extended with
hydrazine.
4. The sheet material of claim 1 in which the polymeric binder is a
blend of a chain-extended polyurethane and a moisture absorbing
material.
5. The sheet material of claim 4 in which the chain-extended
polyurethane is an isocyanate terminated prepolymer of an aromatic
diisocyanate and a polymeric material having a molecular weight of
500-1,500 and having active hydrogen atoms selected from the group
consisting of polyalkyleneether glycol and a hydroxyl terminated
polyester and is chain extended with a compound having an active
hydrogen attached to each end of the compound and in which the
moisture absorbing material is polyvinyl pyrrolidone.
6. The sheet material of claim 5 in which the chain-extended
polyurethane is an isocyanate terminated prepolymer of a toluene
diisocyanate, methylene-bis-4-phenyl isocyanate
polytetramethyleneether glycol molecular weight 500-2,000 which is
chain-extended with a blend of hydrazine and
N,N-bis-(amino-propyl)methylamine.
7. The sheet material of claim 1 which has a fabric of polyamide
fibers between the microporous polymeric coating and the porous
fibrous substrate, the polymeric coating being sufficiently thick
to penetrate the fabric and firmly bond the fabric to the substrate
while the exposed surface of said coating is smooth.
8. The sheet material of claim 1 in which the fibrous web is
hydraulically needled and has a substantially uniform dense
structure of interentangled fibers characterized by random fiber
segments that are oriented transversely to the plane of the
substrate and have a fiber entanglement completeness of at least
0.5, and an entanglement frequency of at least 25 per inch when
measured in a bond-free condition.
9. The sheet material of claim 1 in which the polymeric component
of the microporous topcoat is a blend of a chain-extended
polyurethane and polyvinyl chloride and the non-woven web is of
polyhexamethylene adipamide fibers and the web is impregnated with
a chain-extended polyurethane of a polyalkyleneether glycol and
aromatic diisocyanate which is chain-extended with a compound
having at least one active hydrogen attached to each amino nitrogen
atom.
10. The sheet material of claim 1 in which the polymeric component
of the microporous topcoat is a blend of a chain-extended
polyurethane and polyvinyl chloride and the non-woven web is
hydraulically needled and has a substantially uniform dense
structure of interentangled fibers characterized by random fiber
segments that are oriented transversely to the plane of the
substrate and have a fiber entanglement completeness of at least
0.5, and an entanglement frequency of at least 25 per inch when
measured in a bond-free condition and the web is impregnated with a
chain-extended polyurethane of a polyalkyleneether glycol and
aromatic diisocyanate which is chain extended with a compound
having at least one active hydrogen attached to each amino nitrogen
atom.
11. The sheet material of claim 1 in which the polymeric component
of the microporous topcoat is a blend of a chain-extended
polyurethane and polyvinyl chloride and the non-woven web is a
blend of polyamide and rayon fibers and the web is impregnated with
a polymer blend of a chain-extended polyurethane of an aromatic
diisocyanate and a polyalkyleneether glycol chain-extended with
hydrazine and blended with polyvinyl pyrrolidone.
12. The sheet material of claim 1 in which the substrate is
impregnated with an acrylic binder and the microporous topcoat is
of a chain-extended polyurethane of an aromatic diisocyanate and a
polyalkyleneether glycol chain-extended with a glycol having 1-5
carbon atoms.
Description
DESCRIPTION OF THE INVENTION
The term "microporous" refers to a porous material in which the
individual pores are not discernible to the naked eye.
The increase in length of the fiber is determined by conditioning
the fiber at 0 percent relative humidity at 25.degree. C. and
determining the length, then the fiber is conditioned at 95 percent
relative humidity at 25.degree. C. and the length is determined.
The increase in length of the fiber should be at least 2 percent
and preferably, 2- 5 percent to provide a microporous sheet
material that has excellent properties.
Similarly, the moisture absorption of the synthetic fibers used to
form the non-woven web of the microporous sheet material of this
invention is determined by the difference in moisture in the fiber
at 0 percent relative humidity, 25.degree. C. and 90 percent
relative humidity, 25.degree. C. The fibers should have a moisture
absorption under these conditions of at least 5 percent by weight,
and preferably, 8 to 30 percent by weight.
Tensile stress at 5 percent elongation is the force in pounds which
is required to elongate a sample 5 percent divided by the cross
section area of the sample with the results being expressed in
pound per square inch (psi). Two test samples of about 1 inch by 4
inches are cut at right angles and are conditioned at 50 percent
relative humidity and tested at 25.degree. C. The samples are
tested at the above temperature and humidity conditions on an
Instron Tensile Tester using about 1 inch between grips on the
sample, a cross-head speed of 2 inches per minute and a chart speed
of 10 inches per minute and the average value is recorded.
The wet tensile strength of the binder is determined by testing a
coalesced film of the binder on an Instron Tensile Tester using the
above test procedure except the sample is soaked in water and
tested at 25.degree. C. while the sample is wet with water. The wet
tensile strength of the binder should be at least 500 pounds per
square inch (psi) and up to 20,000 psi. Preferably, the wet tensile
strength of the binder should be about 800 to 5,000 psi.
The decrease in tensile stress at 5 percent elongation when the
microporous sheet material is subject to a change in relative
humidity of 50- 90 percent at 25.degree. C. is determined by
measuring the tensile stress, as indicated above, after the sample
is conditioned at 50 percent relative humidity and again when the
sample is conditioned at 90 percent relative humidity. The decrease
in tensile stress of the microporous sheet material should be about
20- 60 percent to provide a shoe upper material of excellent
comfort.
Binder/Fiber Ratio is the ratio of the weight of the polymeric
binder in the substrate of the novel sheet material of this
invention to the weight of the fiber in the substrate.
The moisture absorption of the binder is determined by conditioning
a film of the polymeric binder at 50 percent relative humidity,
25.degree. C. then at 90 percent relative humidity, 25.degree. C.
The moisture absorption under these conditions should be 5- 25
percent by weight, and preferably, 8- 20 percent by weight. The
moisture absorption of the resulting microporous sheet material is
similarly determined and should be about 0.5- 20 percent by weight,
and preferably 5- 15 percent by weight.
Area expansion of the microporous sheet material is determined by
conditioning the microporous sheet at 50 percent relative humidity,
25.degree.C. and then subjecting the sheet to 90 relative humidity,
25.degree. C. and determining the area increase. To form a
microporous sheet material which provides excellent comfort, the
sheet should have an area expansion of 2- 10 percent, and
preferably, 3- 5 percent.
Water vapor permeability value of the novel sheet material of this
invention is determined by sealing the sheet on top of a cup
containing CaC1.sub.2. This sealed cup is stored at 90 percent
relative humidity at 23.degree.C. and the weight increase of the
cup due to moisture permeating through the material is determined
and the water vapor permeability value of the sheet is calculated
in
The novel sheet material of this invention should have a water
vapor permeability of at least 1,000, and preferably, 2,000 -
12,000.
The novel microporous synthetic sheet material of this invention
comprises a polymer impregnated non-woven web which has in firm
adherence thereto a microporous coating. The polymer impregnated
non-woven fibrous web of the novel sheet material of this invention
gives the sheet its desirable characteristics that make the novel
sheet particularly useful for shoes. The substrate absorbs moisture
as the shoe is worn, and as the moisture is absorbed, the substrate
expands as the wearer's foot expands and thereby forms a
comfortable shoe. Another advantage of the novel sheet material of
this invention is that as the substrate expands from water
absorption, the tensile stress decreases and reduces pressure on a
portion of the shoe that is in contact with the wearer's foot.
Polyamide fibers preferably are used to form the non-woven web of
the novel sheet material of this invention. Polyamides absorb
moisture and expand under moist conditions and show a reduction in
tensile stress under these conditions and do not deteriorate but
still form a contiguous, tough web. Preferably, a polyamide fiber
or polymers that have the recurring structural unit of ##SPC1##
where R and R.sup.1 are divalent aliphatic hydrocarbon radicals
having 3- 8 carbon atoms and n is an integer sufficiently high to
give the polymer inherent viscosity of at least 0.4 when measured
at 25.degree. C. in m-cresol solvent. Preferably, polyamides are
used that have an inherent viscosity of 0.5 to 1.5.
Typical nylon fibers that can be used are nylon 4, a polymer of
pyrrolidone; nylon 6, condensation polymer of caprolactam; nylon
66, polyhexamethyleneadipamide, nylon 610,
polyhexamethylenesebacamide, nylon 7, polymer of
ethylamino-heptanoate. Bicomponent nylon fiber can also be used,
i.e., a composite fiber of two fibers having different physical
properties which are spun together.
A blend of fibers can also be used to form the web but at least 50
percent of the fibers of the blend must have the aforementioned
properties of moisture absorption and length increase. Typical
fibers which can be used in the blend are rayon, polyacrylonitrile,
polyvinyl chloride, blend of polyvinyl chloride and polyvinyl
acetate, polyesters, such as polyethylene terephthalate, polvinyl
alcohol, acrylic fibers, modified acrylic fibers, such as
polyacrylonitrile modified with polyvinyl chloride or methacrylic
acid. One preferred blend of fibers which forms a useful web
comprises about 10- 30 percent by weight of rayon fibers and 90- 70
percent by weight of one of the aforementioned polyamide
fibers.
The fibers used to form the web preferably have a denier of 0.5 to
5.0, and preferably, a denier of 1.0- 2.0 and a staple length of
about 0.5 to 4 inches, preferably, 1.0- 2.0 inches.
The fibers are formed into a non-woven web having a thickness of
20- 60 mils and a density of 0.10- 0.40 grams per cubic centimeter
and, preferably, 0.18- 0.22 grams per cubic centimeter by
conventional techniques. The non-woven webs are prepared by forming
fibers into a loose batt by any known method, such as carding,
blowing fibers, dropping the fibers and the like. The batt is
compacted by pressing the batt under heat and pressure. Further
compaction can be accomplished by conventional techniques, such as
mechanical needling or hydraulic needling, or by any other
technique which will give a fiber entangled web. The resulting web
can be further compacted by shrinking, for example, by immersing
the web in the hot water. A web having properties of stretchability
or shrinkability balanced in each direction can be formed by
crosslapping the fibers into layers of dissimilar orientation
within the plane of the web. When uni-directional stretchability or
shrinkability is preferred, crosslapping is omitted and most of the
fibers are laid so that they have a similar orientation to the
plane of the web.
When the non-woven web is prepared by mechanical needling, a batt
of air blown fibers is needled to yield a total penetration of
about 200 to 20,000 holes per square inch to entangle the fibers. A
conventional needle loom used in the textile industry can be used
for this purpose. Preferably, a needle described in Weickert U.S.
Pat. No. 2,882,585, issued Apr. 21, 1959, is used since this needle
forms a high quality web with a high degree of fiber entanglement.
Preferably, webs that are formed by mechanically needling are heat
shrunk to further compact the web, preferably, by immersing the web
in a hot water bath. The web can be further compacted by the
palming technique in which the web is passed over a hot drying
drum.
The non-woven webs used in this invention can be formed by the
hydraulic needling technique. In this technique, the non-woven web
is prepared from fibers by air blowing the fibers into a loose
batt. The batt is then hydraulically needled using the process and
apparatus disclosed in Canadian Pat. No. 739,652, issued Aug. 2,
1966, which is hereby incorporated by reference. Another method
which forms a screen pattern on the non-woven web is disclosed in
British Pat. No. 1,088,376, published Oct. 25, 1967, which is also
incorporated by reference.
In the hydraulic needling technique, liquid jet streams penetrate
the non-woven batt and consolidate the fibers into a self-coherent
non-woven web. The non-woven web has areas of "fiber
interentanglement" which are different in area density then other
portions of non-woven web. Preferably, about 30- 10,000 apertures
or holes per square inch and more preferably, 400- 4,000 holes per
square inch are used to form these fiber entanglement areas.
The non-woven batt is placed on the supporting member prior to
treatment. Jetting liquid is supplied at the pressure of at least
200 psi gauge from orifices less than about 0.014 inches in
diameter. Fine streams of liquid having over 23,000 energy flux in
foot-poundals/square inch/second at the treatment distance are
formed. The supported batt is traversed by the streams along the
path of the layer centered less than about 0.1 inch apart to apply
treatment energy of at least 0.1 horsepower/hour/pound of fabric
product. Under one set of conditions, the liquid streams are formed
by jetting water from about 0.002 to 0.030 inch diameter orifices
placed in a manifold arrangement at a frequency between 5 to 1,000
orifices per inch, and preferably, 20 to 40 orifices per inch.
The above energy flux in foot-poundals/square inch/second is
calculated by the following formula:
Ef.sub.i = 77PG/a
where
P = liquid pressure in pounds per square inch gauge,
G = volumetric flow of the stream in cubic feet per minute, and
a = the initial cross-sectional area of the stream in square
inches.
The treatment energy of horsepower/hour/pound of fabric is
calculated by the following formula:
E.sub.1 = 0.125 (ypg/sb)
Y = number of orifices per linear inch of manifold
P = pressure of liquid in the manifold in pounds per square inch
gauge,
G = volumetric flow in cubic feet per minute per orifice,
S = speed of passage of the web under the stream in feet per
minute, and
b = the weight of the fabric produced in ounces per square
yard.
The total amount of energy expended in hydraulically needling the
web is the sum of the individual energy values for each
treatment.
In the hydraulic needling technique, the orifice size may be varied
depending on the material to be treated and the effect desired. In
general for treating loose fibrous batts, it is preferred to vary
the orifice size to the basis weight of the sheet material and the
denier of the fibers used therein. Preferably, a small diameter
orifice is used for a low basis weight, low denier materials,
larger diameter orifices are used as the weight or denier
increases.
By passing a sectionally columnar stream of liquid, such as water,
through the orifices and directly into contact with the non-woven
batt in a parallel and continuous pass, which can be straight,
curved or zigzagged, a non-woven web is produced that has lines of
entanglement in straight, curved or zigzagged patterns which
correspond to the number and frequency of the orifices. The
entanglement and strength of the web can be increased by repeating
treatment or by prolonged treatment, for example, by slow passage
of these streams over the substrate.
A non-patterned web of substantially uniformly entangled fibers can
be prepared by the hydraulic needling technique by oscillating the
jet streams at a high frequency, for example, 300 cycles per minute
for a 2 yard per minute web speed. Another method is to interrupt
the columnar streams before the stream reaches the batt and form
intermittent streams. This is normally accomplished by placing a
screen in the path of the streams between the orifices and the
plane of the batt. If desired, the screen may be oscillated through
the streams to provide interruptions during treatment. The screen
is not used to restrain the batt or to influence the rearrangement
of the fibers of the batt into a pattern but only to disrupt the
columnar streams of water. Also, suitable non-pattern webs can be
prepared by oscillating the columnar streams at a frequency as low
as 15 cycles per minute.
If desired, the batt may be treated first with a wetting agent or
other surface agents to increase the penetrating power of the
streams during processing. These agents may be included in the
liquid stream used to hydraulically needle the web. An example of a
particularly suitable agent is a high molecular weight polyethylene
oxide.
These hydraulically needled non-woven webs normally have an
entanglement completeness (c) of at least 0.5, and an entanglement
frequency (c) of at least 25 when measured under bond free
conditions. (For example, by bond free, it is meant that the fibers
of the non-woven fabric are not adhered with the binder or
interfiber fusion bonds. In other words, the non-woven web is
tested to determine the strength and other properties resulting
solely from fiber entanglement).
The non-woven web is impregnated with a polymeric binder to provide
a substrate which has a binder to fiber ratio of about 0.2/1 to
2/1. A variety of binders can be used provided the binder has a wet
tensile strength of about 500- 15,000 pounds per square inch,
preferably 800- 5,000 pounds per square inch and a moisture
absorption when exposed to a change in relative humidity of 50 to
90 percent, 25.degree. C. of 5- 25 percent by weight, and
preferably, 8- 20 percent by weight. The web may be impregnated by
any of the well-known techniques and the binder may be applied from
a solution, dispersion, latex or from an organosol and coagulated
by any of the well-known techniques. One preferred process is
disclosed in Einstman U.S. Pat. No. 3,492,154, issued Jan. 27,
1970.
The polymers used to impregnate the web should be moisture
responsive, i.e., absorb moisture and show a decrease in tensile
stress when the moisture content of the polymer increases. This can
be accomplished by using a moisture responsive polymer or a blend
of a non-moisture responsive polymer with a moisture responsive
polymer such as polyvinyl acetate or polyvinyl pyrrolidone.
Typical polymers, or blends of polymers, that can be used to
impregnate the web are, for example, polyurethanes, such as
polyether urethanes and polyester urethanes, chain-extended
polyether and/or polyester urethanes wherein the chain-extender is
either a diamine or a glycol, blends of one of the aforementioned
polyurethanes, polyvinyl chloride, polyureas, vinyl addition
polymers, such as acrylics, conjugated diene polymers, such as a
polymer of styrene/butadiene, butadiene/alkyl methacrylate or
acrylate, carboxy modified polymer of styrene/butadiene, natural
rubber, polychloroprene, copolymers of ethylene/vinyl acetate,
polyvinyl acetate, polyvinyl pyrrolidone and the like.
One useful binder composition comprises 10- 40 percent by weight of
polyvinyl pyrrolidone and 10- 60 percent by weight of a
polyurethane of a polyalkyleneether glycol and an organic
diisocyanate which is chain extended with hydrazine or a
diamine.
The microporous layer of the novel sheet material of this invention
is about 2- 50 mils in thickness, preferably 5 to 15 mils thick,
and can be formed in a number of methods, for example, the
processes disclosed in Johnston et al. U.S. Pat. No. 3,000,757;
Holden U.S. Pat. No. 3,100,721; Yuan U.S. Pat. No. 3,190,766;
Holden U.S. Pat. No. 3,208,875; Einstman U.S. Pat. No. 3,418,198,
can be used. A suede layer can be formed according to the teachings
of Hulslander et al. U.S. Pat. No. 3,284,274, issued Nov. 8,
1966.
One method for applying the microporous layer to the substrate is
to cast a microporous film on a separate support, coagulate and dry
the film and then laminate the film to the polymer impregnated
non-woven web using a water vapor permeable adhesive, for example,
a latex of an acrylic polymer or a polyurethane, to adhere the
microporous coat to the substrate.
The preferred method for preparing a microporous coating is to form
a solution having as essential constituents a polymeric component
and a solvent for the polymeric component. A liquid miscible with
the solvent but a non-solvent for the polymeric component is
admixed with the solution in an mount up to and including the
quantity which starts to transform the polymer solution into a
substantially colloidal polymeric dispersion. When a substantially
colloidal dispersion is used, it should have a viscosity greater
than about 1 poise and a polymer concentration of greater than
about 7 percent by weight. Finally, the polymeric dispersion is
coated onto an impregnated web and the coating is bathed with an
inert liquid which contains a non-solvent for the polymeric
component and is miscible with the solvent, then the resulting
product is dried.
In producing the microporous materials suitable for shoe uppers,
however, it is an additional requirement that the polymeric
component of the microporous coating has a secant tensile modulus
at 5 percent elongation of above about 600 psi during the entire
processing cycle, i.e., from the time the polymeric component is
coagulated into a microporous structure until it is dried.
Generally, a microporous structure formed from a polymer which in
consolidated form has a secant tensile modulus below about 600 psi
collapses as the liquid is being removed or after the liquid is
removed from the micropores of the structure so that a relatively
impermeable product is formed. Preferably, the secant modulus at 5
percent elongation of the polymer during the cycle is about 600 to
25,000 psi and more preferably, about 800 to 3,000 psi. The secant
tensile modulus is the ratio of the stress to the strain at 5
percent elongation of the sample determined from the tensile
stress-strain curve and is expressed as force per unit area, e.g.,
pounds/square inch. The secant tensile modulus measurement is
carried out according to ASTM-D-882- 64-T modified as described in
the aforementioned Einstman patent.
A preferred major polymeric component useful in this invention for
forming the microporous coating of the novel sheet material of this
invention is a polyurethane made by reacting an organic
diisocyanate with an active hydrogen-containing polymeric material,
such as a polyalkyleneether glycol or a hydroxyl terminated
polyester to form an isocyanate terminated prepolymer. This
prepolymer is then chain extended with hydrazine, substituted
hydrazines, diamines such as N-methyl bispropylamine, diamines such
as 1,4-diamino-piperazine, ethylene diamine and the like. Glycols
and diols can also be used as chain-extenders, such as ethylene
glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol and the
like. Ethylene glycol, hydrazine and a mixture of hydrazine and
N-methylaminobis-propylamine are preferred chain-extenders.
The chain-extension reaction is usually carried out at a
temperature below 120.degree. C. and often at about room
temperature, particularly for hydrazine-extended polymers. During
the reaction, prepolymer molecules are joined together into a
substantially linear polyurethane polymer, the molecular weight of
which is usually at least 5,000 and sometimes as high as 300,000 .
The reaction can be carried out without a solvent in heavy duty
mixing equipment or it can be carried out in a homogeneous
solution. In the latter case, it is convenient to use as a solvent
one of the organic solvents to be employed in the polymer solution
for preparing the microporous coating.
A vinyl chloride polymer is another suitable component of the
polymer solution when making microporous coatings for leather-like
sheet materials. Superior product abrasion resistance is obtainable
when a vinyl chloride polymer is used in combination with an
elastomer such as the polyurethane described above. When making a
shoe upper material or the like from a blend of polyurethane
elastomer and vinyl chloride polymer, it is generally preferred to
employ over 30 weight percent, preferably 75 percent of a
polyurethane with the balance being polyvinyl chloride.
Useful vinyl chloride polymers include polyvinyl chloride and
copolymers having a major proportion, preferably at least 80
percent, of vinyl chloride and can contain a minor proportion of
another ethylenically unsaturated monomer, such as vinyl acetate,
vinylidene chloride, or diethyl maleate.
Within the secant tensile modulus range specified above, the
polymeric component of the solution from which coating is formed
can contain one or more of numerous types of polymers, which are
exemplified by the following: polyurethanes, vinyl halide polymers,
polyamides, polyesteramides, polyesters, polyvinyl butyral,
polyalphamethylstyrene, polyvinylidene chloride, alkyl esters of
acrylic and methacrylic acids, chlorosulfonated polyethylene,
copolymers of butadiene and acrylonitrile.
When a polymer is used which is known to be compatible with
plasticizers, for example, a vinyl chloride polymer, it can be
blended with known plasticizers therefor in an amount up to but not
including the amount which causes the secant tensile modulus at 5
percent elongation to drop below 600 psi. Other known additives for
polymeric compositions can also be added to the polymeric
component, such as pigments, fillers, stabilizers and
antioxidants.
The polymer component selected is dissolved in enough solvent to
yield a solution having the desired solids content and viscosity.
For applying the microporous coatings, it is usually preferred to
use a solution which, after addition of non-solvent, if any is
employed, the solution has a polymer content of about 10 to 30
weight percent and a viscosity of about 10 to 500 poises. The
organic solvent used in the solution should be one that is
miscible, preferably, completely miscible, with the non-solvent
liquid to be used in practicing the invention. N,N-dimethyl
formamide is a preferred solvent for the polymers soluble therein
in view of its high solvent power for many of the preferred
polymers as well as its high miscibility with the generally
preferred non-solvent liquids including water. Other useful
solvents include dimethyl sulfoxide, tetrahydrofuran, tetramethyl
urea, N,N-dimethyl acetamide, N-methyl-2 -pyrrolidone, ethyl
acetate, dioxane, butyl carbitol, phenol, chloroform and
gamma-buryrolactone.
After the coating solution is applied to the polymer impregnated
web, the web is immersed into a bath of a non-solvent, preferably
water, to coagulate the polymer into a microporous layer and after
coagulation the material is washed in non-solvent, preferably
water, and then dried to remove the non-solvent. The resulting
sheet material then can be dyed according to the process described
in Manwaring U.S. Pat. No. 3,337,289, issued Aug. 22, 1967. The
finish is then applied to the dyed microporous sheet material to
give the material a polished leather-like appearance. Typical
finishes that can be used and the process for applying this finish
are described in Dye U.S. Pat. No. 3,455,727, issued July 15, 1969,
U.S. Pat. No. 3,481,766 and U.S. Pat. No. 3,481,767, both to Craven
et al., and both issued Dec. 2, 1969, Hochberg et al. U.S. Pat. No.
3,501,326, issued Mar. 17, 1970.
It is possible to cast a film of the finish, dry the film and then
laminate the film of the finish to the microporous topcoat. An
adhesive of a latex of a moisture permeable polyurethane or an
acrylic polymer can be used to adhere the finish to the microporous
topcoat.
The following examples illustrate the invention and all parts and
percentages are by weight unless otherwise specified.
EXAMPLE 1
A non-woven web is prepared by forming a batt of loosely entangled
Nylon 6,6 fibers (polyhexamethylene adipamide) of 1.5 denier nylon,
about 11/2 inch in length. These fibers have a moisture absorption
of about 8 percent and an increase in length of about 2.4 percent
when subjected to a change in relative humidity of 0- 95 percent at
25.degree. C. The batt is then mechanically needled using about
1,000 penetrations per square inch on a conventional needle loom.
The resulting web is then heat shrunk in water at 125.degree. C.,
and is consolidated further by passing the web over a roll heated
to 150.degree. C. The resulting web has a density of 0.19 and an
average tensile strength in both directions of about 4.8 pounds per
ounce per inch per square yard.
A chain-extended polyurethane for impregnating the above prepared
web is then formed by using conventional polymerization techniques.
About 0.5 moles of polyethyleneether glycol, molecular weight
1,000, is reacted with about 1.0 moles of methylene-bis-4 -phenol
isocyanate to form an isocyanate terminated prepolymer. The
prepolymer is diluted to 50 percent solids with dimethyl formamide
and chain-extended with a hydrazine hydrate solution to form an
amine terminated polymer. Dimethyl formamide is added to form a 12
percent solids polymer solution that has a viscosity of about 10
poises. The polymer has a wet tensile strength when measured
according to ASTM D 882- 64T of 1,900 pounds per square inch.
The resulting polymer solution is cast on a glass plate and dried
in an oven at 100.degree. C. The resulting polymer film has the
following physical properties when subjected to a change in
relative humidity from 50 percent relative humidity at 25.degree.
C. to 90 percent relative humidity at 25.degree. C.: moisture
absorption 20 percent by weight; area expansion 9.9 percent; change
in tensile stress at 5 percent elongation -50 percent.
The above prepared web is impregnated with the aforementioned
polymer solution by immersing the web in the polymer solution for
about 5 minutes and removing the web from the solution and removing
excess polymer solution. The polymer is then coagulated in the web
by immersing the web in water at 25.degree. C. for about 30 minutes
and then the impregnated web is dried at 100.degree. C. for about
15 minutes.
The resulting polymer impregnated web has the following physical
properties:
Binder to fiber ratio 0.5/1 Density 0.3 grams/cubic centimeter
A microporous topcoating is then applied to the above prepared
polymer impregnated substrate to form a leather-like material. The
microporous topcoating is prepared according to the procedure
described in Example 1 of Holden U.S. Pat. No. 3,100,721, issued
Aug. 13, 1963. The final coating is about 15 mils thick. An acrylic
finish is then applied and dried. The acrylic finish is described
in Example 1 of Dye U.S. Pat. No. 3,455,727 except the finish is
pigmented with titanium dioxide pigment. The material is then
embossed to give a surface grain pattern.
The resulting microporous sheet material has the following physical
properties when subjected to a change in relative humidity of 50
percent relative humidity, 25.degree. C. to 90 percent relative
humidity, 25.degree. C.:
moisture absorption 9.6% by weight Area expansion 4.5% Change in
Tensile stress at 5% elongation -33%
The water vapor permeability of the microporous sheet is about
3,600 grams/100 m..sup.2 /hour.
The microporous sheet material is formed into shoes. Wearers of
these shoes indicate that the shoes are very comfortable and have
an excellent appearance and are scuff and abrasion resistant.
EXAMPLE 2
A non-woven web of 6.0 oz./square yard is prepared from nylon
fibers described in Example 1 by forming a batt of closely
entangled fibers by a conventional air laying technique. This web
is then treated with columnar streams of water using the apparatus
disclosed in Canadian Pat. No. 739,652, issued Aug. 2, 1966. In
this apparatus, the liquid stream is passed through a 0.005 inch
diameter orifices drilled into a manifold and are spaced at about
40 holes per inch. Special care is taken in cleaning and boring of
the orifices to insure a sharp entry into the orifice. The
cylindrical filter is mounted coaxially within the manifold
assembly and is used to insure a uniform distribution of water to
the orifices. The filter is a fine mesh wire screen that has 100
.times. 100 wires per square inch and a 30 percent open area.
The above prepared web is placed on a 40 .times. 40 mesh woven wire
screen with a 36 percent open area and is passed under two streams
of essentially columnar water at 30.degree. C. The liquid pressure
in the manifold is approximately 200 pounds per square inch (psi.)
in the first stream and 1,000 psi. in the second stream. The
distance from the manifold to the web is approximately 1 inch. The
web is then reversed and the treatment is repeated on the opposite
side of the web. The web is dried under a blanket which applies a
pressure of about 4 psi. The resulting web is smooth and dense and
has the following properties:
thickness about 40 mils, density 0.23 gram per cubic centimeter,
entanglement completeness 0.88, entanglement frequency 59, basis
weight 6.0 oz. square yard.
This web is then impregnated with the polymer solution of Example 1
using the impregnation procedure of Example 1. The resulting
impregnated web has a binder to fiber ratio of 0.6/1.
The web is then topcoated, finished and embossed using the
identical constituents and procedure as used in Example 1. The
resulting microporous sheet material has the following physical
properties when subjected to a change in humidity of 50 percent
relative humidity, 25.degree. C. to 90 percent relative humidity,
25.degree. C:
moisture absorption 12.3% area expansion 3.6% change in tensile
stress at 5% elongation -48%
The water vapor permeability of the microporous sheet is about
3,000.
The microporous sheet material is formed into shoes. Wearers of
these shoes indicate that the shoes are very comfortable and have
an excellent appearance and are scuff and abrasion resistant.
EXAMPLE 3
A nonwoven web is prepared by forming a batt of loosely entangled
Nylon 6,6 fibers and rayon fibers by a conventional air laying
technique. The weight ratio of nylon to rayon fibers is 3:1. The
nylon fibers are described in Example 1. The rayon fibers are
three-quarter inch in length, 1.5 denier and have a moisture
absorption of 27 percent and an increase in length of 3.4 percent
when subjected to the humidity change described in Example 1. The
batt is then hydraulically needled using the procedure described in
Example 2.
The resulting web is smooth and dense and has the following
properties: Thickness of about 40 mils, density of about 0.19 gram
per cubic centimeter, entanglement completeness about 0.88,
entanglement frequency 59, basis weight of about 6.0 oz. per square
yard.
A chain-extended polyurethane solution is then prepared to
impregnate the web. The chain-extended polyurethane polymer is
prepared by forming a hydroxyl terminated dimer by reacting 2 mols
of polytetramethylene glycol molecular weight 1,000 and 1 mol of
toluene-2,4 -diisocyanate. One mol of this hydroxyl terminated
dimer is then reacted with 2 mols of methylene bis(4-phenyl
isocyanate) to form an isocyanate terminated prepolymer. This
prepolymer is then chain-extended with hydrazine hydrate to form a
solution of a chain-extended polyurethane having a viscosity of
about 115 poises and a polymer solid content of about 25 percent.
This chain-extended polyurethane solution is blended with polyvinyl
pyrrolidone and dimethyl formamide. The resulting solution contains
about 15 percent polymer solids and the polymer solids content
consists of chain extended polyurethane and polyvinyl pyrrolidone
in a 80:20 weight ratio.
A film is cast from the above prepared polymer solution then dried.
The polymer film has a wet tensile strength of about 3,000 psi and
a moisture absorption of 5.2 percent when exposed to a humidity
increase of 50- 90 percent at 25.degree. C.
The above prepared web is immersed in the polymer solution and
impregnated. The web is removed from the polymer solution then
excess polymer is scraped from the surface of the web. The
impregnated web is then immersed in water to coagulate the polymer
and the web is dried. The resulting web has a binder to fiber ratio
of about 0.6/1.
A microporous sheet is then formed by coating a 60 mil wet film on
a glass plate of the polymer dispersion of Example 1 of Holden U.S.
Pat. No. 3,100,721 and coagulating the film in water, washing the
film and air drying the film. The resulting microporous film is
then laminated to the above prepared substrate applying a thin
layer of an acrylic latex that has a high water vapor permeability
between the microporous film and the substrate. The resulting sheet
is then dried. A finish layer is then applied by this lamination
technique. A sheet of the finish is prepared from the finish
composition used in Example 1 by casting a film of the finish on a
glass plate and drying the film. This film is then laminated to the
microporous sheet by applying the same acrylic latex between the
finish layer and the microporous layer. The resulting sheet is then
dried and embossed with a grain pattern.
The resulting microporous sheet material has the following physical
properties when subjected to a relative humidity change of 50-
90percent, 25.degree. C.:
moisture absorption 9% area expansion 2% change in tensile stress
at 5% elongation -55%
The water vapor permeability of the microporous sheet material is
about 3,500.
The microporous sheet material is made into shoes. Wearers of these
shoes indicate that the shoes are very comfortable and have an
excellent appearance and are scuff and abrasion resistant.
EXAMPLE 4
The polymer impregnated non-woven web of Example 1 is used to
prepare a microporous sheet material. A nylon tricot fabric of 15
denier, Nylon 6,6 (polyhexamethylene adipamide) have a basis weight
of 2 ounces per square yard is used as an interlayer fabric and is
positioned between the substrate and the microporous topcoat of the
sheet material. The microporous sheet material is prepared by using
the process of Example 1 of Einstman U.S. Pat. No. 3,418,198. The
coating composition for the microporous topcoat is the same as
composition used in Example 1.
The resulting sheet is dried and a finish is applied as in Example
1 and has the following physical properties when exposed to a
relative humidity change of 50- 90 percent, 25.degree. C.:
moisture absorption 9% area expansion 3% change in tensile stress
at 5% elongation -21%
The water vapor permeability of the microporous sheet is about
3,000 grams/100m.sup.2 /hour.
The microporous sheet material is made into shoes. Wearers of these
shoes indicate that the shoes are very comfortable and have an
excellent appearance and are scuff and abrasion resistant.
EXAMPLE 5
A nonwoven web is prepared by laminating together four layers of a
spun bonded Nylon 6,6 web having a basis weight of 1.2
oz/yd..sup.2. The individual webs are adhered together by using a
thin acrylic latex layer between the webs. The web is then dried
and then the web is impregnated with the polymer solution of
Example 1 using the same procedure as in Example 1. The resulting
web has a binder to fiber ratio of about 0.5/1.
A microporous topcoat is applied and the sheet is finished using
the identical constituents and procedures used in Example 1. The
resulting microporous sheet material has the following physical
properties when subjected to a relative humidity change of 50- 90
percent, 25.degree. C.:
moisture absorption 8% area expansion 3% change in tensile stress
at 5% elongation -40%
The water vapor permeability of the sheet material is about 3,300
grams/100m..sup.2 /hour.
The microporous sheet material is made into shoes. Wearers of these
shoes indicate that the shoes are very comfortable and have an
excellent appearance and are scuff and abrasion resistant.
EXAMPLE 6
A nonwoven web of Example 2 is impregnated with an acrylic latex of
a copolymer of methylmethacrylate and butyl acrylate. The polymer
is coagulated and the web is dried. The resulting web has a binder
to fiber ratio of about 0.8/1.
A chain extended polyurethane for forming the microporous topcoat
on the web is prepared by using the following procedure.
About 647 pounds of poly(tetramethyleneether) glycol molecular
weight 2,088, 52 pounds of ethylene glycol, 1,825 pounds of
dimethyl formamide are charged into the batch reactor. These
materials are mixed in he batch reactor for about 45 minutes while
being blended with the agitator running at about 100 rpm. The
temperature during admixing is held at about 45.degree. C. and
after the ingredients are mixed, the temperature is raised to
52.degree. C. 291 pounds of a mixture of methylene-bis- (4-phenyl
isocyanate) and about 0.05 percent by weight, based on the weight
of the mixture of benzoyl chloride are charged into the kettle over
a 3 -minute period with the ingredients being constantly agitated.
During the addition, the temperature rises to 70.degree. C. because
of the heat of the reaction. The recycle pump is engaged and the
ingredients were recycled at a rate of 125 gallons per minute and
the temperature of the kettle is controlled at 70.degree. C. and
the agitator is set at 60 rpm. The reaction mixture is held at
70.degree. C. under constant agitation for about 3 hours and the
viscosity of the mixture increased to 124 poises.
2.3 pounds of N-butyl amine dissolved in 17 pounds of dimethyl
formamide are then charged into the reactor while the ingredients
are being agitated. Agitation is continued 3 minutes. A constant
pressure across the viscometer indicates the reaction has stopped.
The intrinsic viscosity of the polymer is about 0.63. The resulting
polymer solution has a 35 percent polymer solids content and the
polymer has a weight average molecular weight of about 100,000 and
a -NH-content of about 3.53 percent by weight.
2,200 pounds of a 15 percent polyvinyl chloride solution in
dimethyl formamide are blended with the above prepared
chain-extended glycol extended polyurethane to form a coating
composition. The temperature of the blend is heated to 45.degree.
C. and about 4 percent by weight, based on the weight of the total
composition, of water, is added and blended with the composition.
The resulting composition has a 21 percent solids content. The
temperature is then reduced to about 35.degree. C. and a colloidal
dispersion which is useful for preparing microporous coatings is
formed.
This dispersion is then coated at about 35.degree. C. onto the
above prepared web with a doctor blade using a wet coating
thickness of about 50 mils. The coating is then coagulated by
immersing the coated sheet in water to form a microporous
structure. The sheet material is then washed with water and a white
finish is applied as in Example 1. The resulting sheet material has
a microporous coating about 15- 20 mils in thickness, and has the
following physical properties when subjected to a change in
relative humidity of 50-90, 25.degree. C.:
moisture absorption 2.5% area expansion 2.0% change in tensile
stress at 5% elongation -21%
The water vapor permeability of the sheet material is about 3,000 -
4,000 grams/100 m..sup.2 /hour.
The microporous sheet material is made into shoes. Wearers of these
shoes indicate that the shoes are very comfortable and have an
excellent appearance and are scuff and abrasion resistant.
* * * * *