U.S. patent application number 11/035502 was filed with the patent office on 2005-06-23 for process for preparing a non-woven fibrous web.
This patent application is currently assigned to APPLETON PAPERS INC.. Invention is credited to Bouchette, Michael Paul, Kendall, David Paul.
Application Number | 20050136774 11/035502 |
Document ID | / |
Family ID | 21694474 |
Filed Date | 2005-06-23 |
United States Patent
Application |
20050136774 |
Kind Code |
A1 |
Bouchette, Michael Paul ; et
al. |
June 23, 2005 |
Process for preparing a non-woven fibrous web
Abstract
Disclosed is a fibrous web which includes a microencapsulated
material, such as a microencapsulated phase change material,
adhered to the web. Preferably, the web is prepared in a
melt-blowing or spun-bonding process. In the melt-blowing process,
cooling water containing the microcapsules is used to cool melt
blown fibers prior to collection on a collector. In the
spun-bonding process, microcapsules are applied in liquid
suspension or in dry form to a heated web, for instance, after the
web has been calendared. The fibrous webs thus prepared have
numerous uses, and are particularly suited to the manufacture of
clothing.
Inventors: |
Bouchette, Michael Paul;
(Sherwood, WI) ; Kendall, David Paul; (Appleton,
WI) |
Correspondence
Address: |
BANNER & WITCOFF, LTD.
TEN SOUTH WACKER DRIVE
SUITE 3000
CHICAGO
IL
60606
US
|
Assignee: |
APPLETON PAPERS INC.
Appleton
WI
|
Family ID: |
21694474 |
Appl. No.: |
11/035502 |
Filed: |
January 14, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11035502 |
Jan 14, 2005 |
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10298200 |
Nov 15, 2002 |
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6843871 |
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10298200 |
Nov 15, 2002 |
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10001121 |
Nov 2, 2001 |
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6517648 |
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Current U.S.
Class: |
442/400 ;
442/417 |
Current CPC
Class: |
D04H 1/413 20130101;
Y10T 442/68 20150401; Y10T 442/699 20150401; D04H 3/16 20130101;
Y10T 428/238 20150115; D04H 1/4291 20130101; D04H 1/54 20130101;
D04H 1/4334 20130101; D06M 23/12 20130101; Y10S 428/913 20130101;
D04H 1/4309 20130101; D04H 3/14 20130101; D01F 11/04 20130101; D04H
1/56 20130101 |
Class at
Publication: |
442/400 ;
442/417 |
International
Class: |
D04H 001/56 |
Claims
What is claimed is:
1. A fibrous web, prepared by a process comprising: providing a
polymeric melt comprising a thermoplastic polymer; melt-blowing a
body of fibers from said melt, said body comprising a plurality of
fibers, said fibers being at a temperature sufficient to render
said fibers tacky; contacting said body with discrete plural
particles of an adherent, whereby at least some of said particles
adhere to said body; and collecting said body on a collector
thereby forming a web.
2. A fibrous web prepared according to claim 1, said polymeric melt
comprising a polymer selected from the group consisting of
polypropylene, polyethylene, polyvinyl alcohol, and polylactic
acid.
3. A fibrous web prepared according to claim 1, said polymeric melt
comprising a nylon.
4. A fibrous web, prepared by a process comprising: providing a
polymeric melt comprising a thermoplastic polymer; melt-blowing a
body of fibers from said solution, said body comprising a plurality
of fibers, said fibers being at a temperature sufficient to render
said fibers tacky; cooling said body with a cooling medium, said
cooling medium including a cooling fluid and discrete plural
particles of an adherent, whereby at least some of said discrete
plural particles adhere to said body; and collecting said body on a
collector thereby forming a web.
5. A fibrous web prepared according to claim 4, said body of fibers
being sufficiently permeable to said cooling medium such that said
at least some of said particles of adherent adhere to fibers within
said body.
6. A fibrous web prepared according to claim 5, said cooling fluid
comprising water.
7. A fibrous web prepared according to claim 5, said polymeric melt
comprising a polymer selected from the group consisting of
polypropylene, polyethylene, polyvinyl alcohol, and polylactic
acid.
8. A fibrous web, prepared by a process comprising: withdrawing a
body of fibers from a spinarette, said body comprising a plurality
of fibers of a thermoplastic material; heating said body of fibers
to a temperature at which said fibers become tacky; contacting said
body with discrete plural particles of an adherent, whereby at
least some of said discrete plural particles adhere to said body;
and collecting said body on a collector thereby forming a web.
9. A fibrous web prepared according to claim 8, said heating
comprising heating via a hot nip operation.
10. A fibrous web prepared according to claim 8, said heating
comprising introducing said body to radiant heat from a source of
radiant heat.
11. A fibrous web prepared according to claim 8, said heating
comprising contacting said body with a hot gas.
12. A fibrous web prepared according to claim 8, said adherent
being at least substantially dry.
13. A fibrous web prepared according to claim 8, said body of
fibers being sufficiently permeable such that at least some of said
particles of adherent adhere to fibers within said body.
14. A fibrous web prepared according to claim 8, said particles
being applied by contracting said body with a cooling medium
comprising said particles and a cooling fluid.
15. A fibrous web prepared according to claim 14, said cooling
fluid comprising water.
16. A non-woven substrate, said non-woven substrate comprising a
plurality of fibers, said fibers being composed of a thermoplastic
material, prepared by the process for adhering a microencapsulated
material to said substrate: heating said substrate to a temperature
at which said fibers become tacky; and contacting said fibers with
discrete plural microcapsules, each microcapsule comprising a core
material bounded by a wall material, whereby at least some of said
microcapsules adhere to said fibers.
17. A non-woven substrate prepared according to claim 16, said
substrate being sufficiently permeable such that at least some of
said microcapsules adhere to fibers within said body.
18. A non-woven substrate prepared according to claim 16, said
heating comprising heating via a hot nip operation.
19. A non-woven substrate prepared according to claim 16, said
heating comprising introducing said body to radiant heat from a
source of radiant heat.
20. A non-woven substrate prepared according to claim 16, said
heating comprising contacting said body with a hot gas.
Description
RELATED APPLICATIONS
[0001] This application is a Divisional of Ser. No. 10/298,200,
filed Nov. 15, 2002, which is a Divisional of U.S. Pat. No.
6,517,648, filed Nov. 2, 2001, and issued Feb. 11, 2003, for which
priority is claimed. These parent applications are incorporated
herein by reference in their entirety
TECHNICAL FIELD OF THE INVENTION
[0002] The invention is in the field of processes for preparing
fibrous webs. Preferred embodiments of the invention are in the
field of melt-blown and spun-bonded fibrous webs.
BACKGROUND OF THE INVENTION
[0003] The prior art has provided numerous processes for preparing
fibrous webs from thermoplastic materials such as polypropylene,
polyethylene, polyvinyl alcohol, polylactic acid, and nylons. In
many instances, fibrous webs are prepared via weaving of preformed
fibers; in other instances, non-woven fibrous webs are prepared via
a process such as melt blowing, spun-bonding, and melt-spinning.
Innumerable variations of these processes have been provided in the
prior art to produce fibrous webs suitable for use in the
manufacture of many products.
[0004] Some non-woven fibrous webs are useful in the manufacture of
clothing. In this regard, it has been known for some time that it
is useful to incorporate a temperature stabilizing agent, such as a
so-called "phase change material" or "moderate temperature phase
change material," into an article of clothing to provide
temperature stabilization. Moderate temperature phase change
materials are substances, which undergo a change in phase at a
temperature of about 60.degree.-90.degree. F. Because of the
well-known thermodynamic principle that a phase change occurs at
constant temperature, such materials are useful in preventing heat
loss from the body as ambient temperature drops, and conversely, in
preventing heat gain to the body as ambient temperature rises.
Examples of the use of such moderate temperature phase changes
materials are reported in numerous documents, for instance, U.S.
Pat. No. 4,856,294, which purports to disclose a vest made with
such phase change materials; U.S. Pat. No. 5,366,801, which
purports to disclose a fabric containing microcapsules of phase
change material; U.S. Pat. No. 5,415,222, which discloses a
"micro-climate" cooling garment comprising a vest which contains a
"macroencapsulated" phase change material contained within a
honeycomb structure, and U.S. Pat. No. 6,120,530, which purports to
disclose a passive thermocapacitor for cold water diving
garments.
[0005] Known moderate temperature phase change materials are
conveniently provided in microencapsulated form. The microcapsules
of phase change material may be secured to a substrate with the use
of a binder, as is purportedly taught in a number of prior patents,
including U.S. Pat. Nos. 5,955,188; 6,077,597; and 6,217,993.
Alternatively, in the preparation of a fibrous substrate, the
microcapsule may be dispersed within a polymeric melt, and fibers
may be blown or otherwise prepared from the melt, as is purportedly
taught in U.S. Pat. No. 4,756,958. Both of these prior art
approaches suffer from a number of drawbacks. Although
microcapsules can be secured to a substrate with a binder, this
approach is unsatisfactory, because it is believed that
microcapsules are susceptible to being debound upon washing or wear
of the fabric thus made. Moreover, while in theory these problems
are mitigated by incorporating microcapsules into the polymeric
melt used to prepare the fibers, it is believed that in practice
the microcapsule chemistry is incompatible with the temperatures
required to process many thermoplastic polymers. In particular, it
is believed difficult to obtain non-woven nylon or polypropylene
fabric using such techniques.
[0006] It is a general object of the invention to provide, at least
in preferred embodiments, a process for incorporating moderate
temperature phase change materials into non-woven fibrous webs that
is different from the processes heretofore described. In highly
preferred embodiments, the invention has as an object to provide
nylon and polypropylene non-woven fibrous webs that incorporate
microencapsulated materials, and in particular microencapsulated
moderate temperature phase change materials.
THE INVENTION
[0007] It is now been found that an adherent, such as a
microencapsulated moderate temperature phase change material, can
be incorporated into a non-woven web during a melt-blowing or a
spun-bonding manufacturing process. In the melt-blowing operation,
fibers are melt-blown from a polymer melt of a thermoplastic
polymer. After the fibers are formed, they remain at an elevated
temperature for short period of time, during which time the fibers
remain tacky. In accordance with the invention, the adherent is
caused to be contacted with the fibers while they are in the tacky
state to cause the adherent to adhere to the fibers. In
conventional melt-blowing operations, the tacky fibers are cooled
with a cooling spray, which comprises a cooling fluid (typically
water). In accordance with the preferred embodiment of the
invention, the microencapsulated phase change material or other
adherent is provided as a suspension in this cooling spray. After
the hot fibers have been cooled with the cooling fluid, the fibers
are collected to thereby form a fibrous web.
[0008] The invention also contemplates other web forming
operations, such as spun-bonding. In a typical spun-bonding
operation, fibers exit a spinarette and travel as a body to a
subsequent heating stage, at which the fibrous body is heated to
enhance interfiber cohesion. Most typically, the body of fibers is
heated via a hot calendar or embossing roll. After exiting the
heating stage, the body of fibers is tacky, and the adherent can be
then caused to be contacted with the body of fibers to thereby
cause adherence to the body. Even more generally, a preformed body
of fibers can be heated and contacted with an adherent, which may
be a microencapsulated moderate temperature phase change material
or other temperature stabilizing agent, or, more generally, any
other microencapsulated material, to cause the adherent to adhere
to the body of fibers.
[0009] Other features and embodiments of the invention are
discussed hereinbelow and in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1. is a representation of a melt-blowing operation
useful in conjunction with the practice of the present
invention.
[0011] FIG. 2. is a representation of a spun-bonding operation
useful in conjunction with the practice of the invention.
[0012] FIG. 3. is a representation of a process for adhering a
microencapsulated material to a preformed non-woven fibrous
web.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0013] The invention is applicable to the preparation of non-woven
fibrous webs from a variety of polymeric melts. Polymers suitable
for use in conjunction with invention include polyvinyl alcohol,
polylactic acid, polypropylene, nylons (such as nylon 6, nylon 6-6,
nylon 612, nylon 11) and so forth. Other suitable thermoplastic
polymers include polybutylene terephthalate, polyethylene
terephthalate, poylmethylpentene, polycholorotrifluoroethylene,
poylphenylsulfide, poly(1,4-cyclohexylenedi-
-methylene)terephthalate, polyesters polymerized with an excess of
glycol, copolymers of any of the foregoing, and the like.
Generally, any thermoplastic polymer suitable for use in the
preparation of fibrous webs may be used in conjunction with the
invention.
[0014] The invention in preferred embodiments contemplates the
preparation of fibrous webs having microencapsulated material
incorporated therewith, which materials preferably are
microencapsulated moderate temperature phase change materials.
Numerous suitable moderate temperature phase change materials have
been described in the art; example of such materials include
n-docosane, n-eicosane, n-heneicosane, n-heptacosane,
n-heptadecane, n-hexacosane, n-hexadecane, n-nonadecane,
n-octacosane, n-octadecane, n-pentacosane, n-pentadecane,
n-tetracosane, n-tetradecane, n-tricosane, and n-tridecane. More
generally, any material that undergoes a change in phase at a
desired temperature or within a useful temperature range (not
necessarily 60.degree.-90.degree. F.) or other temperature
stabilizing agent suitable for use in conjunction with the
invention may be employed therewith. For instance, it is
contemplated that non-microencapsulated temperature stabilizing
agents may be employed in conjunction with the invention. Certain
plastic materials such as 2,2-dimethyloyl-1,3-propanediol and
2-hydroxymethyl-2-methyl-1,3-propandi- -ol and the like are said to
have temperature stabilizing properties. When crystals of the
foregoing absorb thermal energy, the molecular structure is
temporarily modified without changing the phase of the material.
Such other temperature stabilizing agents may be employed in
connection with the invention.
[0015] The microencapsulated material may be provided in any
suitable microcapsule dimension and using any suitable capsule
chemistry. The microcapsule preferably is small relative to the
diameter of the fibers in the substrate. The microcapsules
generally range in nominal diameter from about 1 .mu. to about 100
.mu., but in the melt-blowing embodiments of the invention
preferably are provided in the range of about 1 .mu. to about 4
.mu. In other embodiments, particularly spun-bonding, large
microcapsules may be employed; preferably, these microcapsules
range to about 8 .mu. in diameter. Nominal capsules sizes typically
represent the approximate size of 50-70% by volume of the total
range of capsules produced. In the present invention, the
microcapsules employed had a nominal 4 .mu. dimension, and the
actual reserved measured target size portion of the microcapsule
mix was close to 90% of the total mixture.
[0016] The capsule walls preferably are sufficiently thick to avoid
rupture when the processed in accordance with the present
teachings. Those skilled in the art will appreciate that the
capsule size and wall thickness may be varied by many known
methods, for instance, adjusting the amount of mixing energy
applied to the materials immediately before wall formation
commences. Capsule wall thickness is also dependent upon many
variables, including primarily the mixing blade geometry and blade
rpm. In the examples which follow, the capsule wall represented
10-12% of the capsule weight.
[0017] With respect to the chemistry of the microcapsules, the
microcapsules generally comprise a microencapsulated material
contained within a wall bounded by a wall material, the wall
material preferably comprising a polyacrylate wall material, as
described in, for instance, U.S. Pat. No. 4,552,811. Gelatin
capsules, such as those described in U.S. Pat. Nos. 2,730,456;
2,800,457; 2,800,457; and 2,00,458, and gel-coated capsules, as
purportedly described in U.S. Pat. No. 6,099,894 further may be
employed in connection with the invention.
[0018] The microcapsules may be prepared by any suitable means, for
instance, via interfacial polymerization. Interfacial
polymerization is a process wherein a microcapsule wall of a
polyamide, an epoxy resin, a polyurethane, a polyurea or the like
is formed at an interface between two phases. U.S. Pat. No.
4,622,267 discloses an interfacial polymerization technique for
preparation of microcapsules. The core material is initially
dissolved in a solvent and an aliphatic diisocyanate soluble in the
solvent mixture is added. Subsequently, a nonsolvent for the
aliphatic diisocyanate is added until the turbidity point is just
barely reached. This organic phase is then emulsified in an aqueous
solution, and a reactive amine is added to the aqueous phase. The
amine diffuses to the interface, where it reacts with the
dissocyanate to form polymeric polyurethane shells. A similar
technique, used to encapsulate salts which are sparingly soluble in
water in polyurethane shells, is disclosed in U.S. Pat. No.
4,547,429. U.S. Pat. No. 3,516,941 teaches polymerization reactions
in which the material to be encapsulated, or core material, is
dissolved in an organic, hydrophobic oil phase which is dispersed
in an aqueous phase. The aqueous phase has dissolved materials
forming aminoplast resin which upon polymerization form the wall of
the microcapsule. A dispersion of fine oil droplets is prepared
using high shear agitation. Addition of an acid catalyst initiates
the polycondensation forming the aminoplast resin within the
aqueous phase, resulting in the formation of an aminoplast polymer,
which is insoluble in both phases. As the polymerization advances,
the aminoplast polymer separates from the aqueous phase and
deposits on the surface of the dispersed droplets of the oil phase
to form a capsule wall at the interface of the two phases, thus
encapsulating the core material. This process produces the
microcapsules. Polymerizations that involve amines and aldehydes
are known as aminoplast encapsulations. Urea-fornaldehyde (UF),
urea-resorcinol-formaldehyde (URF), urea-melamine-formaldehyde
(UMF), and melamine-formaldehyde (MF) capsule formations proceed in
a like manner. In interfacial polymerization, the materials to form
the capsule wall are in separate phases, one in an aqueous phase
and the other in a fill phase. Polymerization occurs at the phase
boundary. Thus, a polymeric capsule shell wall forms at the
interface of the two phases thereby encapsulating the core
material. Wall formation of polyester, polyamide, and polyurea
capsules proceeds via interfacial polymerization.
[0019] Gelatin or gelatin-containing microcapsule wall materials
are well known. The teachings of the phase separation processes, or
coacervation processes, are described in U.S. Pat. Nos. 2,800,457
and 2,800,458, Uses of such capsules are described in U.S. Pat. No.
2,730,456.
[0020] More recent processes of microencapsulation involve the
polymerization of urea and formaldehyde, monomeric or low molecular
weight polymers of dimethylol urea or methylated dimethylol urea,
melamine and formaldehyde, monomeric or low molecular weight
polymers of methylol melamine or methylated methylol melamine, as
taught in U.S. Pat. No. 4,552,811. These materials are dispersed in
an aqueous vehicle and the reaction is conducted in the presence of
acrylic acid-alkyl acrylate copolymers. Preferably, the wall
forming material is free of carboxylic acid anhydride or limited so
as not to exceed 0.5 weight percent of the wall material.
[0021] Other microencapsulation methods are known. For instance, a
method of encapsulation by a reaction between urea and formaldehyde
or polycondensation of monomeric or low molecular weight polymers
of dimethylol urea or methylated dimethylol urea in an aqueous
vehicle conducted in the presence of negatively-charged,
carboxyl-substituted, linear aliphatic hydrocarbon polyelectrolyte
material dissolved in the vehicle, is taught in U.S. Pat. Nos.
4,001,140; 4,087,376; and 4,089,802. A method of encapsulating by
in situ polymerization, including a reaction between melamine and
formaldehyde or polycondensation of monomeric or low molecular
weight polymers of methylol melamine or etherified methylol
melamine in an aqueous vehicle conducted in the presence of
negatively-charged, carboxyl-substituted linear aliphatic
hydrocarbon polyelectrolyte material dissolved in the vehicle is
disclosed in U.S. Pat. No. 4,100,103. A method of encapsulating by
polymerizing urea and formaldehyde in the presence of gum arabic is
disclosed in U.S. Pat. No. 4,221,710. This patent further discloses
that anionic high molecular weight electrolytes can also be
employed with gum arabic. Examples of the anionic high molecular
weight electrolytes include acrylic acid copolymers. Specific
examples of acrylic acid copolymers include copolymers of alky
acrylates and acrylic acid including methyl acrylate-acrylic acid,
ethyl acrylate-acrylic acid, butyl acrylate-acrylic acid and octyl
acrylate-acrylic acid copolymers. Finally, a method for preparing
microcapsules by polymerizing urea and formaldehyde in the presence
of an anionic polyelectrolyte and an ammonium salt of an acid is
disclosed in U.S. Pat. Nos. 4,251,386 and 4,356,109. Examples of
the anionic polyelectrolytes include copolymers of acrylic acid.
Examples include copolymers of alkyl acrylates and acrylic acid
including methyl acrylate-acrylic acid, ethyl acrylate-acrylic
acid, butyl acrylate-acrylic acid and octyl acrylate-acrylic acid
copolymers.
[0022] Other microencapsulation processes known in the art or
otherwise found to be suitable for use with the invention may be
employed. More generally, the adherent may be provided in a form
other then microcapsules, such as the "macrocapsules" discussed in
U.S. Pat. No. 5,415,222. Moreover, whether microencapsulated or
provided in a different form, the material to be adhered to the
fibrous web is not limited to phase change materials, and it is
contemplated that, for instance, microencapsulated colorants and
fragrances, and conceivably other materials, could be incorporated
onto the fibrous web.
[0023] In accordance with the invention, discrete plural particles
of adherent, such as but not limited to the foregoing materials,
are caused to adhere to fibers in a fibrous web. The preferred
embodiments of the invention are practiced during the formation of
the web in a melt-blowing or spun-bonding process. As discussed
above, there are innumerable such processes known in the art.
Except for the step of adhering the phase change material or other
adherent to the web, the process of the invention may be a
conventional process, or other process as may be suitable for use
in conjunction with the invention.
[0024] With reference to the melt-blowing operation depicted in
FIG. 1, the polymer melt is delivered from a feeder (not shown) to
an extruder 10. From the extruder, the melt is delivered through
conduit 11 to a die 12 by means of gear pump 13. The polymer melt
is extruded through the die 12 to form fibers, which are formed by
blowing through the die 12. Air is delivered through air manifolds
14, 15. Before being collected on a collector 16, the blown fibers
are cooled with a cooling fluid delivered from a sprayer 17. The
cooling fluid typically water, and, in accordance with the
invention, comprises a suspension of water and the adherent. In
other embodiments, the cooling fluid could be air (it is even
contemplated that heated air, which would serve to retard cooling
oil but which would allow more time for capsule adhesion, could be
employed). The melt-blowing operation depicted in FIG. 1 is highly
idealized, and in practice the operation and apparatus may comprise
other steps and components respectively. For instance the capsule
and fluid could be applied separately. While those skilled in the
art would appreciate and understand the various parameters that
affect the melt-blowing, it should here be noted that some of the
parameters that may affect the melt-blowing process include the
distance between the die and collector (i.e., the die-collector
distance, or DCD), the distance between the cooling fluid spray
head and the body of fibers blown from the die, the number of
individual dies in the die manifold, the angle of impingement of
the cooling spray onto the body of fibers, whether the spray is
directed toward or away from the die manifold, the geometry of the
spray of cooling fluid (e.g., whether the spray is conical or
nearly linear) and the temperature of the cooling fluid.
Preferably, the operation is such that the body of fibers is at
least substantially permeable to cooling fluid, such that the
adherent permeates the body of fibers and adheres to fibers within
the body. Other melt-blowing embodiments are possible; for
instance, the adherent may be applied in dry form contemporaneously
with the application of cooling fluid.
[0025] With reference now to the spun-bonding operation depicted in
FIG. 2, the melt passes from a resin feeder 19 and through an
extruder 20 into a spinarette 21 (one is shown for convenience but
in fact multiple spinarettes may be combined into one or more
spinpaks). Fibers exiting the spinarette 21 enter a fiber
attenuator/randomizer 22 and exit as a spun bond web onto a forming
wire 23. In the illustrated embodiment, suction is applied at
suction box 24 with air exiting through aperture 25, and the
forming wire 23 travels in a continuous loop in direction of arrow
26 over rollers 27. Upon exiting the suction box 24, the spun-bond
webs has cooled to a point where the fibers that comprise the web
are not tacky, or are only very slightly tacky. The web next passes
through a hot nip operation, which, in the illustrated embodiment,
is conducted via pair of calendar rollers 28, 29, at least one of
which is a hot calendar. The hot nip alternatively may be
accomplished via an embossing roller or other suitable device. Upon
exiting the rollers, the fibers of the web are hot and tacky. At
this point, the adherent is applied. When the adherent comprises a
microencapsulated product, the adherent is preferably in dry form,
and is "dusted" onto the web in via a dry capsule spraying device
30. Once again, FIG. 2 depicts an idealized process, and in
practice, numerous operating parameters may be adjusted, and steps
may be removed or added. For instance, an optional preheater 31 may
be employed, and, in this embodiment, the capsules spray device may
be employed in position 32. Additional heated rollers 33, 34 may be
employed for further heating steps. More generally, any suitable
technique may be employed. For instance, instead of heating via a
hot nip operation, the fibers may be heated via irradiation from a
source of radiant heat or via hot gasses.
[0026] With reference now to FIG. 3, in this embodiment of the
invention a performed web 36 is heated, preferable using calendar
rollers 37, 38, to a temperature at which the fibers in the web are
tacky. The heated body of fibers is then dusted with a
microencapsulated material or another form of temperature
stabilizing agent via delivery device 40. Again, the operation
depicted in FIG. 3 is highly idealized, and those skilled in the
art will find innumerable variants of the forgoing process.
[0027] The fibrous web prepared in accordance with the invention is
suitable for use in the preparation of fabrics, which can be used
for the manufacture of clothing, including hats, vests, pants,
scarves, jackets, sweaters, gloves, socks, and so forth, and also
can be used in connection with the preparation of other material,
such as upholstery for outdoor furniture. The invention should not
be deemed limited to the foregoing applications, however, and
indeed it is contemplated that to the contrary the fibrous webs
prepared in accordance with the invention will find numerous other
uses.
[0028] The following examples are provided to illustrate the
present invention. The examples should not be construed as limiting
the scope of the invention.
[0029] Capsule Formation
[0030] A water phase component consisting of 23.9 g alkyl acrylate
acrylic acid copolymer, 17.9 g 5% NaOH, and 152.6 g water is
prepared and heated to 65.degree. C. In a separate vessel, 266.9 g
of n-octadecane are heated to 70.degree. C. The water phase
component is added to a blender with temperature control set to
65.degree. C. and mixed at low speed. Alkylated melamine
formaldehyde (such as etherified methylol melamine), 3.8 g, are
slowly added to the blender. After approximately 20 minutes of
additional blending, 266.9 g n-octadecane are added slowly with
stirring. The ingredients are mixed on a high setting for about 30
minutes.
[0031] In a separate container, 22.2 g of the alkyl acrylate
acrylic acid copolymer, 5.2 g 5% NaOH, and 40.1 g water are mixed
with a magnetic stirrer. After about 25 minutes of mixing, 23.5 g
alkylated melamine formaldehyde are added to the blend, and mixed
for another 5 minutes.
[0032] The two solutions are blended at low speed. Three g
Na.sub.2SO.sub.4 are added and heated with stirring at 65.degree.
C. for 8.5 hours.
[0033] This mixture is allowed to then cool to room temperature,
and neutralized with NH.sub.4OH to a pH of 8.2 to 8.5. Water is
added to a final solution weight of 550 g
EXAMPLE 1
[0034] Polypropylene Web
[0035] This example illustrates the preparation of a polypropylene
web with polyacrylate microcapsules containing n-octadecane
disposed thereon.
[0036] Microcapsules of approximately 4. mu. in diameter were
suspended in water at a solids level of 50%. The product was
introduced in to a reservoir, serviced by a CAT pump, model 270
(max. vol. 3.5 gal/min, max pressure 1500 psi). The pump fed the
capsules into a spray manifold consisting of nine nozzles in a
bank, each nozzle being rated at 0.4 gal/hr at 100 psi. The melt
blowing apparatuses used was a 20 in. pilot line made by Accurate
Products. The extrusion die had 501 holes, with hole diameters of
0.0145 in. The unit had 4 barrel zone extruders (melt chambers),
and 5 die zone temperature regulators. Three hot air furnace were
used to generate the hot air used in the extrusion. The Air Gap and
Set Back settings (for the introduction of hot air at the die
extrusion tips) were both 0.030 in. The melt blown web exited the
manifold in horizontal mode, traveling across a dead space to a
collector which comprised a wind-up reel. The quench spray manifold
was located approximately 15 in. below the exiting web, and the
spray angle could be adjusted to hit the web straight on (i.e.,
vertical), or at an angle away from the web or towards the
manifold. The vertical height (i.e., the distance from the web)
also could be adjusted. Pump spray pressures were held constant at
about 400 psi.
[0037] The barrel zone extruder temperature, the die zone
temperature, and the air furnace temperature were each set at
480.degree. F. Air pressure at the die extrusion tips was 3 psi,
and the DCD was 10 in. Flow rate per hole was estimated at 0.4
g/min. A line speed of 29 ft/min was used. An initial sample was
run without quenching. The final basis weight of the web was
predicted to be 44.63 g/m.sup.2. The actual measured basis weight
of the final sample was 24.8 g/m.sup.2. The reason for the
discrepancies between the predicted and actual basis weights is not
understood.
[0038] For the first example, a quench spray comprising a 50%
microcapsule suspension was introduced at a spray angle of about 15
to 20.degree. towards the take up reel. It became quickly visible
evident that the efficiency of capsule spraying was low. The
visible mist of capsules being sprayed did not appear to follow the
direction of the web, and much overspray was noted on floor and
surrounding equipment. The predicted basis weight of the
capsule-containing product was estimated to 72.66 g/m.sup.2, while
the actual measure basis weight of the final product was only 24.5
g/m.sup.2, approximately the same as the untreated control. SEM
photographs confirmed that a few capsules did adhere to the
web.
EXAMPLE 2
[0039] Polypropylene Web
[0040] A polypropylene web was prepared as per example 1, except
that the angle of the spray manifold was changed to about
10-15.degree. towards the extrusion manifold. An attempt was made
to spray the cooling fluid as close as possible to the exit point
of the fibers from the extrusion manifold, while trying to minimize
the spray that actually contacted the manifold. It was readily
apparent that this modification significantly improved the capsule
adhesion. Visible overspray was virtually eliminated, and the spray
mist could actually be seen to follow the web. The predicted final
basis weight was 72.66 g/m.sup.2, while the final measured basis
weight was 27.3 g/m.sup.2. While the discrepancy between the
predicted and final basis weight is not well understood, it was
noted that the weight of the capsules increased the weight of the
web by about 10% over the final weight measured in Example 1. SEM
photographs provided visual confirmation of significant capsule
adhesion.
EXAMPLE 3
[0041] Polypropylene Web
[0042] A polypropylene web was prepared as per Example 1, except
the line speed was decreased to 14 fpm to increase the dwell time
of the web in the capsule spray mist. The predicted untreated web
weight was calculated to be 92.4 g/m.sup.2, while the actual final
basis weighted was 44.9 g/m.sup.2. Again, this discrepancy is not
well understood.
[0043] For the example, the capsule spray was introduced, with the
spray manifold used in a position of 10-15.degree. off vertical
toward the extrusion manifold. The predicted final basis weight of
the product was calculated to be 150.51 g/m.sup.2. The actual basis
weight of the web was 52.7 g/m.sup.2. Thus, although the
discrepancy between predicated and actual basis weights is not well
understood, the weight of the web increased by 17% via the addition
of the capsules. SEM photographs provided visual confirmation of
the capsule adhesion.
EXAMPLE 4
[0044] Nylon Web
[0045] In this example, a nylon 6 web was prepared. It was believed
that nylon 6 was a more "sticky" polymer then polypropylene, and
that capsule addition would therefore be enhanced.
[0046] The barrel zone extruder temperature, the die zone
temperature, and the air furnace temperature were all raised to
580.degree. F. The DCD was increased to 17 in., and the hole flow
rates were decreased to 0.26 gal/hr. The air pressure at the
extrusion tips was increased to 4 psi.
[0047] An untreated nylon web was prepared at a line speed of 14
ft/min. The predicted base weight of the web was estimated to be
60.1 g/m.sup.2, which is in good agreement with the actual measured
basis weight of 58.4 g/m.sup.2.
[0048] For the example, the line speed was increased to 29 fpm. It
was believed that the increase in line speed decreased the basis
weight of the web. The predicted basis weight for the untreated was
29.4 g/m.sup.2, while the predicted basis weight for the
capsule-containing web was 57.04 g/m.sup.2, which was in good
agreement with the actual measured basis weight of 61.5 g/m.sup.2.
It was believed that the addition of the capsules increased the
weight of the base web by approximately 100% over the predicted
untreated value. SEM photographs revealed a very good distribution
of capsules in the web, and a substantial increase in adhesion over
the polypropylene webs of the previous examples. It was further
noted that capsules appeared to be uniformly distributed throughout
the web. Additional SEM photographs were taken on the side of the
web opposite the side contacted by the capsule spray; these
appeared to be virtually identical to the SEM photographs taken on
the treated side of the web.
[0049] A sample of the web was immersed in a water bath and very
gently agitated, removed, and allowed to dry. Some capsules were
evident in the rinse water, but a subsequent SEM photograph showed
no significant reduction in the amount of capsules present on the
washed web.
EXAMPLE 5
[0050] Nylon Webs
[0051] Example 4 was repeated, except that the capsule suspension
spray heads were cleaned. No significant difference was seen in the
basis weight of the final product or in the SEM photographs.
EXAMPLE 6
[0052] A polypropylene web is prepared in a spun-bonding process.
After the web has been formed, it is passed through a pair of
heated calendar rollers. Upon exiting the calendar rollers, dry
polyacrylate microcapsules containing n-octadecane are dusted onto
the web.
EXAMPLE 7
[0053] A polypropylene web is provided. The web is heated between a
pair of hot calendar rollers. Dry capsules of n-octadecane are
dusted on to the web after the web exits the calendar rollers.
[0054] Thus, it is seen that the foregoing general object has been
satisfied. The invention provides processes for preparing fibrous
webs having microencapsulated materials adhered thereto.
[0055] While particular embodiments of the invention have been
described, the invention should not be deemed limited thereto.
Instead, the scope of the patent should be defined by the appended
claims. All references cited herein are hereby incorporated by
reference in their entireties.
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