U.S. patent application number 09/883520 was filed with the patent office on 2003-01-09 for water dispersible, salt sensitive nonwoven materials.
Invention is credited to Eknoian, Michael, Parsons, John C., Pauls, Steven P. SR..
Application Number | 20030008591 09/883520 |
Document ID | / |
Family ID | 25382731 |
Filed Date | 2003-01-09 |
United States Patent
Application |
20030008591 |
Kind Code |
A1 |
Parsons, John C. ; et
al. |
January 9, 2003 |
Water dispersible, salt sensitive nonwoven materials
Abstract
The present invention is directed to a non-woven material having
an emulsion binder, which is dispersible in water, yet
non-dispersible in aqueous solutions containing 0.5 weight percent
or more of an inorganic salt. The water-dispersible polymer
comprises from 1 to 100 percent by weight of a hydrophilic monomer
and from 0 to 99 percent by weight of at least one non-hydrophilic
monomer, wherein a film formed from said polymer has a Tg of from
-40 to 105.degree. C. The dispersible non-woven material is useful
in forming disposable articles which can be disposed of by flushing
down a toilet.
Inventors: |
Parsons, John C.; (Easton,
PA) ; Pauls, Steven P. SR.; (Old Bridge, NJ) ;
Eknoian, Michael; (Warren, NJ) |
Correspondence
Address: |
Thomas F. Roland
NATIONAL STARCH AND CHEMICAL COMPANY
10 Finderne Avenue
Bridgewater
NJ
08807-0500
US
|
Family ID: |
25382731 |
Appl. No.: |
09/883520 |
Filed: |
June 18, 2001 |
Current U.S.
Class: |
442/414 ;
442/327 |
Current CPC
Class: |
A61L 15/62 20130101;
D04H 1/587 20130101; D21H 17/37 20130101; Y10T 442/60 20150401;
A47K 2010/3266 20130101; D21H 21/20 20130101; Y10T 442/696
20150401 |
Class at
Publication: |
442/414 ;
442/327 |
International
Class: |
D04H 001/00; D04H
003/00; D04H 005/00; D04H 013/00 |
Claims
What is claimed is:
1. A non-woven material comprising c) a web of fibers; and d) an
aqueous emulsion binder comprising a water-dispersible polymer
which is non-dispersible in aqueous solutions containing 0.5 weight
percent or more of an inorganic salt, wherein said
water-dispersible polymer comprises from 1 to 100 percent by weight
of a hydrophilic monomer and from 0 to 99 percent by weight of at
least one non-hydrophilic monomer, wherein a film formed from said
polymer has a Tg of from -40 to +105.degree. C.
2. The non-woven material of claim 1 wherein said fibers have a
length of less than 5 cm.
3. The non-woven material of claim 1 wherein said fibers have a
length of less than 2 cm.
4. The non-woven material of claim 1 comprising 50 to 98 percent by
weight of fibers.
5. The non-woven material of claim 1 comprising 70 to 85 percent by
weight of fibers.
6. The non-woven material of claim 1 wherein said material has a
binder add-on of from 2 to 50 percent by weight.
7. The non-woven material of claim 1 wherein said material has a
wet tensile strength in 3 percent aqueous inorganic salt solution
of at least 100 g/in, and a wet tensile strength in tap water of at
least 40 g/in.
8. The non-woven material of claim 1 wherein said binder further
comprises at least one component selected from the group consisting
of plasticizers, tackifiers, fillers, humectants, surfactants,
salts, fragrances, pigments, titanium dioxide, and encapsulated
components.
9. The non-woven material of claim 1 having a web basis weight of
from 20 to 200 gsm.
10. A non-woven article comprising the non-woven material of claim
1.
11. The non-woven article of claim 9 further comprising a lotion
containing at least one ingredient selected from the group
consisting of sodium chloride solution, preservatives, boric acid,
bicarbonates, moisturizers, emollients, surfactants, humectants,
alcohols, water, and fragrances.
12. The non-woven article of claim 9 further comprising at least
0.5 percent by weight of inorganic salt, or a mixture of inorganic
salts.
Description
FIELD OF THE INVENTION
[0001] This invention relates to non-woven materials containing an
emulsion binder, and which are water dispersible, yet
non-dispersible in aqueous solution containing 0.5 percent or more
of an inorganic salt. The non-woven materials can be used to
produce non-woven articles, which can be disposed of by flushing
down a toilet, and break down into smaller pieces within the
wastewater stream.
BACKGROUND OF THE INVENTION
[0002] Non-woven fibrous webs have long been used to produce
disposable articles, such as garments, wipes, diapers and hygiene
articles.
[0003] U.S. Pat. No. 5,629,081 discloses pre-moistened,
dispersible, biodegradable wet wipes containing a binder containing
polyvinyl alcohol, or a polyvinyl alcohol stabilized emulsion.
[0004] It is convenient, and environmentally friendly to have a
non-woven article, which can be disposed of by flushing down a
toilet bowl. U.S. Pat. Nos. 5,509,913 and 6,127,593 disclose
flushable fibrous articles with solubility related to salt
concentration. U.S. Pat. No. 5,935,880 discloses dispersible
non-woven fabric and a method for making the fabric. The binder
dissolves in water at less than 50 parts per million (ppm) of
divalent ions, allowing for the non-woven material to be broken and
dispersed in water.
[0005] U.S. patent applications Ser. Nos. 09/540,033 and 09/823,318
describe salt sensitive aqueous emulsions which form films that are
water-dispersible, yet non-dispersible in aqueous solutions
containing 0.5 percent or more of an inorganic salt.
[0006] There is a need for a non-woven material formed with a
salt-sensitive emulsion binder. Surprisingly, a salt-sensitive
emulsion binder has been found which can be used to produce
non-woven articles, where both the binder and the fibrous web are
water-dispersible.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to a non-woven material
comprising
[0008] a) a web of fibers; and
[0009] b) an aqueous emulsion binder comprising a water-dispersible
polymer which is non-dispersible in aqueous solutions containing
0.5 weight percent or more of an inorganic salt, wherein said
water-dispersible polymer comprises from 1 to 100 percent by weight
of a hydrophilic monomer and from 0 to 99 percent by weight of at
least one non-hydrophilic monomer, wherein a film formed from said
polymer has a Tg of from -40 to +105.degree. C.
[0010] The present invention is also directed to a non-woven
article made of the novel non-woven material.
DETAILED DESCRIPTION OF THE INVENTION
[0011] The present invention relates to non-woven materials, formed
with emulsion binders, that are water dispersible, yet
non-dispersible in aqueous solution containing 0.5 percent or more
of an inorganic salt.
[0012] A non-woven material, as used herein, refers to materials
formed from loosely assembled webs of fibers, which are bound
together by a polymer. The binder plays an important role in the
properties of the non-woven material such as strength and feel.
[0013] Fibers from any source and of any suitable length may be
used in the present invention. To aid in dispersion, the fibers
preferably will be less than a maximum of 5 cm long and most
preferably less than 2 cm long. Fibers include those known in the
art including fibers from woody plants such as deciduous and
coniferous trees; non-woody plants, such as cotton, flax, esparto
grass, milkweed, straw, jute and bagasse; and synthetic fibers,
such as polyester, polypropylene, and rayon. Other fiber materials
used in the art, and mixtures of any fibers can be used in the
present invention. Preferred fibers are those typically used in
air-laid non-wovens, especially wood pulp fibers having a length of
less than 0.5 cm. Such fibers provide good biodegradable breakdown.
Fibers are present in the non-woven material at from 50 to 98
percent by weight, depending on the end use of the non-woven
material. For many uses, fibers make up about 70 to 85 percent by
weight of the non-woven material.
[0014] The binder is an emulsion polymer, which is salt sensitive.
Salt sensitive emulsion polymers are polymers which are formed by
an emulsion polymerization process, and which form films that are
dispersible in tap water, yet are non-dispersible in water
containing at least 0.5 percent by weight of an inorganic
monovalent, divalent, or trivalent salt, or mixtures thereof. The
films formed may be continuous or non-continuous.
[0015] The polymer is dispersible, rather than soluble, in water.
Dispersible, as used herein, means that in tap water, a film formed
from the polymer breaks into small discrete pieces or particles
that can be filtered out. These pieces are capable of being
separated from the water. While not being bound to a theory, it is
believed that the dispersion of the polymer film is related to the
fact that a film forms from an emulsion by coalescence of polymer
particles, forming weak bonds between particles. In water, some
bonds between the particles will break, resulting in clusters of
polymer particles. This is different from a solution polymer in
which polymer chains mix and entangle during film formation, and
this film dissolves into individual polymer chains, which cannot be
filtered. Since the polymer contains a high level of hydrophilic
monomer(s), when the emulsion dries to a film, the particles are
easily dispersed in water. Salt-sensitive emulsion polymers useful
in the present invention are described in U.S. patent application
Ser. No. 09/823,318, incorporated herein by reference.
[0016] The emulsion polymers of the present invention consist of a
polymer, which is stabilized by a hydrophilic polymeric colloid.
The polymer itself is not salt sensitive. The colloid may or may
not be salt sensitive. However, the colloid-stabilized polymer
particle is salt sensitive.
[0017] The polymer colloid contains at least one monomer, and
ideally two or more monomers. At least one of the monomers is a
hydrophilic monomer.
[0018] The hydrophilic monomer may be an acidic monomer containing
a carboxylic acid, a dicarboxylic acid, a sulfonic acid, or a
phosphonic acid group, or a mixture thereof. Examples of carboxylic
acid monomers include, but are not limited to, acrylic acid,
methacrylic acid, maleic acid, maleic acid half esters, maleic
anhydride, itaconic acid, and crotonic acid. Preferred carboxylic
acids include acrylic acid and methacrylic acid. Sulfonic acid
monomers include, but are not limited to styrene sulfonic acid,
2-acrylamido-2-methyl-1-propanesulfonic acid, vinylsulfonic acid,
and the salts of these acids. Examples of monomers containing a
phosphonic acid group include, but are not limited to styrene
phosphonic acid, sodium vinyl phosphonate, vinylphosphoric acid,
and CH.sub.2.dbd.C(CH.sub.3)COO(CH.sub.2).sub.nOPO.sub.3H, where n
is from 2 to 4. A preferred phosphoric acid monomer is vinyl
phosphonic acid. Other hydrophilic monomers include, but are not
limited to those containing a hydroxyl group, acrylamides and
methacrylamides.
[0019] The polymer colloid may also contain at least one other
ethylenically unsaturated monomer. Examples of monomers useful in
the present invention include, but are not limited to,
(meth)acrylates, maleates, (meth)acrylamides, vinyl esters,
itaconates, styrenics, unsaturated hydrocarbons, acrylonitrile,
nitrogen functional monomers, vinyl esters, alcohol functional
monomers.
[0020] The hydrophilic monomer(s) is present in the polymer colloid
at from 1 to 100 percent by weight. Other ethylenically unsaturated
monomers may be present at from 0 to 99 percent by weight.
Preferably the hydrophilic monomer is present in the polymer
colloid at from 10 to 100 percent and most preferably from 30 to
99.
[0021] A graft-linker and/or crosslinker can be incorporated into
the polymer colloid. Examples of graft-linkers and/or crosslinkers
useful in the present invention include, but are not limited to,
diallyl phthalate diallyl amine, allyl methacrylate, ethylene
glycol diacrylate, 1,6-hexane diacrylate, methylene bisacrylamide,
divinyl benzene, triallyl amine, triallyl cyanurate, and
trimethylolpropane triacrylate.
[0022] The polymer colloid may be used to stabilize a latex
polymer. The colloid itself can be either salt sensitive or
non-salt sensitive. The colloid can either be added to the
polymerization process separately, or be formed in situ
[0023] Examples of colloids that are salt sensitive include, but
are not limited to, poly(acrylic acid), poly(methacrylic acid), and
copolymers thereof.
[0024] Examples of colloids that are not salt sensitive include,
but are not limited to, the salts of
poly(2-acrylamido-2-methyl-1-propanesulfonic- ) acid, the salts of
polyphosphonic acid, and polyols.
[0025] The colloid is present in the latex polymer at from 0.1 to
100 percent by weight based on polymer solids, more preferably 1 to
75 weight percent, and most preferably from 3-75 weight
percent.
[0026] The latex polymers useful in the present invention have a Tg
of from -40 to +105.degree. C.
[0027] The process for producing salt sensitive emulsions of the
invention involves the formation of a colloid stabilizer, followed
by an emulsion polymerization using said stabilizer by means known
in the art. The stabilizer may either be formed in situ, or added
separately. A useful process for producing the salt sensitive
emulsions is found in U.S. patent application Ser. No. 09/540,033,
incorporated herein by reference. The emulsion polymerization may
be a batch, semi-batch, or continuous process.
[0028] One preferred process involves an in situ colloid process in
which a polymer seed is polymerized from one or more monomers
selected from unsaturated acidic monomers, alkyl(meth)acrylates and
vinyl monomers which are neutralized to between 1 and 100 percent
with base to form a stabilizer. Using this stabilizer, monomers are
added and polymerized by means known in the art of emulsion
polymers.
[0029] Another preferred process involves the use of a hydrophilic
polymer colloid, as described above as a stabilizer in the
synthesis of an ethylene-vinyl acetate copolymer, where the level
of ethylene in the copolymer is at least 55 percent by weight of
the polymer.
[0030] The binder may be formulated with other components known in
the art in conventional amounts, prior to being applied to the
fiber web. The other components may include, but are not limited
to, plasticizers, tackifiers, fillers, humectants, surfactants,
salts, fragrances, pigments, titanium dioxide, and encapsulated
components. The emulsion binder is present at from 25 to 100 weight
percent based on all the components, and preferably at from 50 to
100 percent.
[0031] Water may also be added to the binder formulation to adjust
the solids level and viscosity required for application to the
fiber web. Typically the binder formulation is applied at a solids
level of from 2 to 60 percent, preferably from 5 to 40 percent and
most preferably from 10 to 25 percent. The non-woven material will
generally have an add-on value of from 2 to 50 percent by weight,
preferably from 15 to 30 percent by weight.
[0032] Non-woven materials of the present invention have a wet
tensile strength of at least 100 g/in in an aqueous solution
containing three percent or greater of an inorganic salt,
preferably sodium chloride. The materials have a wet tensile
strength of at least 40 g/in, and preferably at least 60 g/in in
tap water. Tap water, as used herein refers to refers to water as
sourced to commercial and residential properties. Tap water
generally has a hardness level of from 50 to 300.
[0033] Wet tensile strength as used herein is measured by the TAPPI
UM 656 procedure. The non-woven material was soaked in 3 percent
sodium chloride solution for 24 hours, and in hard water for 5
minutes.
[0034] The non-woven is formed by any process known in the art,
such as, but not limited to airlaid, wetlaid, drylaid, carded
fiber. Preferably the fiber web formed has a basis weight of from
20-200 grams per square meter (gsm). The binder is applied to the
non-woven fibers by means known in the art such as, printing,
spraying with and without air, saturation, creping, and
foam-application.
[0035] In addition to the binder, pre-moistened products produced
with the non-woven material of the present invention may also
contain a lotion. The lotion contains one or more additives, which
include, but are not limited to, sodium chloride solution,
preservatives, boric acid, bicarbonates, moisturizers, emollients,
surfactants, humectants, alcohols, water, and fragrances. The
lotion must contain at least 0.5 percent by weight of an inorganic
salt to maintain the integrity of the binder. The lotion is present
at up to 500 percentage by weight based on the weight of the
non-woven material, and preferably up to 250 percent. The lotion is
generally added as a secondary treatment of the non-woven that has
been prepared with the salt-sensitive binder and then converted for
use. This wet solution treatment can occur just prior to packaging,
or after the non-woven has been placed Wet-use products have a
stable wet strength of measurable tensile value and integrity, yet
disperse when placed in tap water, allowing the product to be
flushed in sewer or septic systems without blockage. In water,
dispersion of the non-woven begins immediately. The rate of
dispersion can be tailored for different applications.
[0036] Dry products formed with the non-woven material of the
present invention may also contain up to 50 percent by weight, and
preferably up to 30 percent by weight, of other ingredient
including, but not limited to, perfumes, plasticizers, colorants,
antifoams, bactericides, bacteriostats, thickeners, and
fillers.
[0037] Non-woven materials of the present invention are used to
form a variety of both dry and moist finished products. These
products include, but are not limited to wet products such as
personal cleansing wipes for personal hygiene uses such as
bathroom, facial, and make-up removal; and dry products such as
diaper and adult incontinence top sheets, back sheets, acquisition
layers and absorbent core; feminine hygiene products; industrial
towels/wipes for aqueous and solvent use; surgical gowns and
towels.
[0038] One key attribute of the non-woven materials of the present
invention is their ability to retain insult durability in use, then
disperse during flushing in water.
[0039] The following examples are presented to further illustrate
and explain the present invention and should not be taken as
limiting in any regard.
EXAMPLE 1
[0040] A 60 gsm air-laid cellulosic fiber (Weyerhauser NB416) was
pad saturated with a 12% solids formulation of salt-sensitive
emulsion polymer of MAA/AMPS/MMA/BA in a weight ratio of 57/5/14/24
to a dry add-on of 15%. The wet web was drum dried at 210.degree.
F. The web was subsequently heated for 5 minutes at 266.degree. F.
in a forced-air oven. After conditioning, the web was tested for
its tensile strength in 3% NaCl and then in tap water for 5 minutes
after soaking in the 3% NaCl for 4 days, 10 days, and 22 days.
Tensiles were pulled using the TAPPI UM 656 procedure. Following is
the data that was generated.
1 Tensile, g/in 3% NaCl.fwdarw.5 min soak in Age 3% NaCl tap water
4 days 135 44 10 days 101 45 22 days 100 45
EXAMPLE 2
[0041] Whatman #4 Chromatography Paper was pad saturated with a 15%
solids formulation of salt-sensitive emulsion polymer of
MAA/AMPS/MMA/BA in a weight ratio of 57/5/14/24 to a dry add-on of
15%. The wet web was drum dried at 210.degree. F. The web was
subsequently heated for 5 minutes at 266.degree. F. After
conditioning, the web was tested for its tensile strength in DI
water, and 1%, 3%, and 5% NaCl solutions. A non-crosslinking VA/BA
polymer was used as a reference. Tensile strength was measured
using the TAPPI UM 656 procedure. Following is the data that was
generated to demonstrate the effect of ionic strength on tensile
strength of the non-woven.
2 Tensiles, g/in 0% 1% NaCl 3% NaCl 5% NaCl BA/VA 196 218 223 260
MAA/AMPS/MMA/BA 80 158 323 766
EXAMPLE 3
[0042] A 60 gsm air-laid cellulosic fiber (Weyerhauser NB416) was
pad saturated with a 15% solids formulation of surfactant
stabilized salt-sensitive emulsion polymer of MAA/MMA/BA in a
weight ratio of 60/15/25 to a dry add-on of 20%. The wet web was
drum dried at 210.degree. F. The web was subsequently heated for 5
minutes at 266.degree. F. After conditioning, the web was tested
for its tensile strength in 3% NaCl, 3% CaCl.sub.2, and 3%
MgCl.sub.2. The web was also tested for its strength in tap water.
Tensiles were pulled using the TAPPI UM 656 procedure. Following is
the data that was generated to demonstrate the effect of different
cations on tensile strength of the non-woven:
3 Tensile, g/in 3% NaCl 3% CaCl.sub.2 3% MgCl.sub.2 75 240 194 Tap
Water 20 88 42
EXAMPLE 4
[0043] A 60 gsm air-laid cellulosic fiber (Weyerhauser NB416) was
pad saturated with a 16% solids formulation of surfactant
stabilized salt-sensitive emulsion polymer of MAA/AMPS/MMA/BA in a
weight ratio of 57/5/14/24 to a dry add-on of 20%. The wet web was
drum dried at 210.degree. F. The web was subsequently heated for 5
minutes at 300.degree. F. After conditioning, the web was tested
for its tensile strength in 3% and 5% NaCl and then in hard water
(625 ppm calcium carbonate) for 5 minutes after soaking in the 5%
NaCl for 7 days. The web was also tested in for its strength in
de-ionized water. Tensiles were pulled using the TAPPI UM 656
procedure. Following is the data that was generated:
4 Tensile, g/in 3% NaCl.fwdarw. 5% NaCl.fwdarw. 3% NaCl Hard Water
5% NaCl Hard Water DI Water 221 224 198 118 223
EXAMPLE 5
[0044] A 60 gsm air-laid cellulosic fiber (Weyerhauser NB416) was
pad saturated with a 16% solids formulation of surfactant
stabilized salt-sensitive emulsion polymer of MAA/AMPS/MMA/BA in a
weight ratio of 57/5/14/24 to a dry add-on of 20%. The wet web was
drum dried at 210.degree. F. The web was subsequently heated for 2
minutes at 250.degree. F. After conditioning, the web was tested
for its tensile strength in 3% and 5% NaCl and then in hard water
(625 ppm calcium carbonate) for 5 minutes after soaking in the 5%
NaCl for 7 days. The web was also tested in for its strength in
de-ionized water. Tensiles were pulled using the TAPPI UM 656
procedure. Following is the data that was generated:
5 Tensile, g/in 3% NaCl.fwdarw. 5% NaCl.fwdarw. 3% NaCl Hard Water
5% NaCl Hard Water DI Water 168 127 174 145 124
EXAMPLE 6
[0045] A 60 gsm air-laid cellulosic fiber (Weyerhauser NB416) was
pad saturated with a 16% solids formulation of surfactant
stabilized salt-sensitive emulsion polymer of MAA/AMPS/MMA/BA in a
weight ratio of 57/5/14/24 to a dry add-on of 20%. The wet web was
drum dried at 210.degree. F. The web was subsequently heated for 2
minutes at 250.degree. F. After conditioning, the web was tested
for its tensile strength in 3% and 5% NaCl and then in hard water
(625 ppm calcium carbonate) for 5 minutes after soaking in the 5%
NaCl for 7 days. The web was also tested in for its strength in
de-ionized water. Tensiles were pulled using the TAPPI UM 656
procedure. Following is the data that was generated:
6 Tensile, g/in 3% NaCl.fwdarw. 5% NaCl.fwdarw. 3% NaCl Hard Water
5% NaCl Hard Water DI Water 221 224 198 118 223
EXAMPLE 7
[0046] A 60 gsm air-laid cellulosic fiber (Weyerhauser NB416) was
pad saturated with a 16% solids formulation of salt-sensitive
emulsion polymer of MAA/AMPS/MMA/BA in a weight ratio of 57/5/14/24
to a dry add-on of 20%. The wet web was drum dried at 210.degree.
F. The web was subsequently heated for 2 minutes at 250.degree. F.
After conditioning, the web was tested for its tensile strength in
3% and 5% NaCl and then in hard water (625 ppm calcium carbonate)
for 5 minutes after soaking in the 5% NaCl for 7 days. The web was
also tested in for its strength in de-ionized water. Tensiles were
pulled using the TAPPI UM 656 procedure. Following is the data that
was generated:
7 Tensile, g/in 3% NaCl.fwdarw. 5% NaCl.fwdarw. 3% NaCl Hard Water
5% NaCl Hard Water DI Water 148 113 259 171 9
EXAMPLE 8
[0047] A 60 gsm air-laid cellulosic fiber (Weyerhauser NB416) was
pad saturated with a 16% solids formulation of salt-sensitive
emulsion polymer of MAA/AMPS/MMA/BA in a weight ratio of 57/5/14/24
to a dry add-on of 20%. The wet web was drum dried at 210.degree.
F. The web was subsequently heated for 5 minutes at 300.degree. F.
After conditioning, the web was tested for its tensile strength in
3% and 5% NaCl and then in hard water (625 ppm calcium carbonate)
for 5 minutes after soaking in the 5% NaCl for 7 days. The web was
also tested in for its strength in de-ionized water. Tensiles were
pulled using the TAPPI UM 656 procedure. Following is the data that
was generated:
8 Tensile, gf 3% NaCl.fwdarw. 5% NaCl.fwdarw. 3% NaCl Hard Water 5%
NaCl Hard Water DI Water 356 239 444 295 97
* * * * *