U.S. patent application number 16/621292 was filed with the patent office on 2020-04-16 for fibers including a crystalline polyolefin and a hydrocarbon tackifier resin, and process for making same.
The applicant listed for this patent is 3M INNOVATIVE PROPERTIES COMPANY. Invention is credited to Saurabh Batra, Michael R. Berrigan, Eugene G. Joseph, Liyun Ren, Michael D. Romano, Sachin Talwar.
Application Number | 20200115833 16/621292 |
Document ID | / |
Family ID | 65232973 |
Filed Date | 2020-04-16 |
![](/patent/app/20200115833/US20200115833A1-20200416-M00001.png)
United States Patent
Application |
20200115833 |
Kind Code |
A1 |
Joseph; Eugene G. ; et
al. |
April 16, 2020 |
FIBERS INCLUDING A CRYSTALLINE POLYOLEFIN AND A HYDROCARBON
TACKIFIER RESIN, AND PROCESS FOR MAKING SAME
Abstract
Nonwoven fibrous webs including a multiplicity of (co)polymeric
fibers made of a mixture including from about 50% w/w to about 99%
w/w of at least one crystalline polyolefin (co)polymer, and from
about 1% w/w to about 40% w/w of at least one hydrocarbon tackifier
resin. A process for making the nonwoven fibrous webs includes
heating the foregoing mixture to at least a Melting Temperature of
the mixture to form a molten mixture, extruding this molten mixture
through at least one orifice to form at least one filament,
applying a gaseous stream to attenuate the at least one filament to
form a plurality of discrete, discontinuous fibers, and cooling the
plurality of discrete, discontinuous fibers to a temperature below
the Melting Temperature and collecting the discrete discontinuous
fibers as a nonwoven fibrous web. The nonwoven fibrous webs exhibit
a Heat of Fusion measured using Differential Scanning Calorimetry
of greater than 50 Joules/g.
Inventors: |
Joseph; Eugene G.;
(Blacksburg, VA) ; Batra; Saurabh; (Minneapolis,
MN) ; Ren; Liyun; (Woodbury, MN) ; Talwar;
Sachin; (Woodbury, MN) ; Romano; Michael D.;
(Circle Pines, MN) ; Berrigan; Michael R.;
(Oakdale, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
3M INNOVATIVE PROPERTIES COMPANY |
St. Paul |
MN |
US |
|
|
Family ID: |
65232973 |
Appl. No.: |
16/621292 |
Filed: |
July 30, 2018 |
PCT Filed: |
July 30, 2018 |
PCT NO: |
PCT/US2018/044301 |
371 Date: |
December 11, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62539242 |
Jul 31, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D04H 3/007 20130101;
D01D 5/08 20130101; D04H 5/00 20130101; D10B 2321/022 20130101;
D04H 1/64 20130101; D04H 1/4291 20130101; D04H 1/72 20130101; D04H
1/587 20130101 |
International
Class: |
D04H 1/587 20060101
D04H001/587; D01D 5/08 20060101 D01D005/08; D04H 1/64 20060101
D04H001/64; D04H 1/72 20060101 D04H001/72; D04H 1/4291 20060101
D04H001/4291 |
Claims
1. A nonwoven fibrous web, comprising: a plurality of (co)polymeric
fibers comprising from about 50% w/w to about 99% w/w of at least
one crystalline polyolefin (co)polymer, and from about 1% w/w to
about 40% wiw of at least one hydrocarbon tackifier resin, wherein
the nonwoven fibrous web exhibits a Heat of Fusion measured using
Differential Scanning Calorimetry of greater than 50 Joules/g.
2. The nonwoven fibrous web of claim 1, wherein the at least one
crystalline polyolefin (co)polymer is selected from the group
consisting of polyethylene, isotactic polypropylene, syndiotactic
polypropylene, isotactic polybutylene, syndiotactic polybutylene,
poly-4-methyl pentene and mixtures thereof.
3. The nonwoven fibrous web of claim 2, wherein the at least one
crystalline polyolefin (co)polymer exhibits a Heat of Fusion
measured greater than 50 Joules/g.
4. The nonwoven fibrous web of claim 1, wherein the at least one
hydrocarbon tackifier resin is a saturated hydrocarbon.
5. The nonwoven fibrous web of claim 1, wherein the at least one
hydrocarbon tackifier resin is selected from the group consisting
of C.sub.5 piperylene derivatives, C.sub.9 resin oil derivatives,
and mixtures thereof.
6. The nonwoven fibrous web of claim 1, wherein the at least one
hydrocarbon tackifier resin makes up from 2% to 40% by weight of
the (co)polymeric fibers.
7. The.nonwoven fibrous web of claim 6, wherein the at least one
hydrobarbon tackifier resin makes up from 5% to 30% by weight of
the (co)polymeric fibers.
8. The nonwoven fibrous web of claim 7, wherein the at least one
hydrocarbon taekifier resin makes up from 7% to 20% by weight of
the (co)polytheric fibers.
9. The nonwoven fibrous web of claim 1, wherein the plurality of
(co)polymeric fibers exhibit a mean Actual Fiber Diameter of from
about 100 nanometers to about 1 micrometer, inclusive, as
determined using Scanning Electron Microscopy.
10. The nonwoven fibrous web of claim 9, wherein the plurality of
(co)polymeric fibers exhibits a mean Effective Fiber Diameter of
between about 1 micrometer to about 20 micrometers.
11. The nonwoven fibrous web of claim 1, further comprising between
0 to about 30% of at least one plasticizer.
12. The nonwoven fibrous web of claim 11, wherein the at least one
plasticizer is selected from the group consisting of oligomers of
C.sub.5 to C.sub.14 olefins, and mixtures thereof.
13. The nonwoven fibrous web of claim 1, wherein the nonwoven
fibrous web exhibits a Maximum Load in the Machine Direction of at
least 5 Newtons as measured using the Tensile Strength Test.
14. The nonwoven fibrous web of claim 1, wherein the nonwoven
fibrous web-exhibits a Basis Weight of 1 gsm to 400 gsm.
15. The nonwoven fibrous web of claim 14, wherein the nonwoven
fibrous web exhibits a Basis Weight of 1 gsm to 50 gsm.
16. A process for making a nonwoven fibrous web, comprising: a)
heating a mixture of about 50% w/w to about 99% w/w of at least one
crystalline polyolefin(co)polymer, and from about 1% w/w to about
40% w/w of at least one hydrocarbon tackifier resin to at least a
Melting Temperature of the mixture to form a molten mixture; b)
extruding the molten mixture through at least one orifice to form
at least one filament; c) applying a gaseous stream to the at least
one filament to attenuate the at least one filament to form a
plurality of discrete, discontinuous fibers; and d) cooling the
plurality of discrete discontinuous fibers to temperature below the
Melting Temperature of the molten mixture to form a nonwoven
fibrous web, wherein at least one of the crystalline
polyolefin(co)polymer or the nonwoven fibrous web exhibits a Heat
of Fusion measured using Differential Scanning Calorimetry of
greater than 50 Joules/g.
17. The process of claim 16, wherein applying a gaseous stream to
the at least one filament to attenuate the at least one filament to
form a plurality of discrete, discontinuous fibers is accomplished
using a process selected from the group consisting of melt-blowing,
gas jet fibrillation, and combinations thereof.
18. The process of claim 16, further comprising at least one of
addition of a plurality of staple fibers to the plurality of
melt-blown fibers, or addition of a plurality of particulates to
the plurality of melt-blown fibers.
19. The process of claim 16, further comprising collecting the
plurality of discrete discontinuous fibers as the nonwoven fibrous
web on a collector.
20. The process of claim 19, further comprising processing the
collected nonwoven fibrous web using a process selected from the
group consisting of autogenous bonding, through-air bonding,
electret charging, embossing, needle-punching, needle tacking,
hydroentangling, or a combination thereof.
Description
TECHNICAL FIELD.
[0001] The present disclosure relates to (co)polyrneric fibers,
including a crystalline polyolefin, (co)polymer and a hydrocarbon
tackifier resin, and more particularly,to nonwoven fibrous webs
including such fibers, and methods for preparing such webs.
BACKGROUND
[0002] Melt-blowing is a process for forming nonwoven fibrous webs
of thermoplastic (co)polymeric fibers. In a typical melt-blowing
process, one or more thermoplastic (co)polymer streams are extruded
through a die containing closely arranged orifices and attenuated
by convergent streams of high-velocity hot air to form micro-fibers
which are collected to form a melt-blown nonwoven fibrous web.
[0003] Thermoplastic (co)polymers commonly used in forming
conventional melt-blown nonwoven fibrous webs include polyethylene
(PE) and polypropylene (PP). Melt-blown nonwoven fibrous webs are
used in a variety of applications, including acoustic and thermal
insulation, filtration media, surgical drapes, and wipes, among
others.
SUMMARY
[0004] Briefly, in one aspect, the present disclosure describes a
nonwoven fibrous web, including A multiplicity of (co)polymeric
fibers including from about 50%.w/W to about 99%o why of at least
one crystalline polyolefin(co)polymer, and from about 1% w/w to
about 40% w/w of at least one hydrocarbon tackifier resin, wherein
the nonwoven fibrous web exhibits a Heat of Fusion measured using
Differential Scanning calorimetry of greater than 50 Joules/g.
[0005] In some exemplary embodiments, the at least one crystalline
polyolefin (co)polymer is selected from polyethylene, isotactic
polypropylene, syndiotactic polypropylene, isotactic polybutylene,
syndiotactic polybutylene, poly-4-methyl pentene), and mixtures
thereof. In certain presently preferred embodiments, the at least
one crystalline polyolefin (co)polymer exhibits a Heat of Fusion
measured using Differential Scanning Calorimetry of greater than 50
Joules/g. In some such presently preferred embodiments, the at
least one crystalline polyolefin (co)polymer is selected to be
isotactic polypropylene, syndiotactic polypropylene and mixtures
thereof.
[0006] In certain embodiments; the at least one hydrocarbon
tackifier resift is a saturated hydrocarbon. In certain presently
preferred exemplary embodiments, the at least one hydrocarbon
tackifier resin is selected from C.sub.5 piperylene derivatives,
C.sub.9 resin oil derivatives, and mixtures thereof. In additional
presently preferred exemplary embodiments, the at least one
hydrocarbon tackifier resin makes up from 2% to 40% by weight of
the (co)polymeric fibers, more preferably from 5% to 30% by weight
of the (co)polymeric fibers, even more preferably from 7% to 20% by
weight of the (co)polymeric fibers.
[0007] In further presently preferred exemplary embodiments, the
multiplicity of (co)polymeric fibers exhibits a mean Actual Fiber
Diameter of from about 100 nanometers to about 10 micrometers, more
preferably from 100 nanometers to 1 micrometer, inclusive. In other
exemplary embodiments, the multiplicity of (co)polymeric fibers
exhibits a mean Effective Fiber Diameter of between about 1
micrometer and about 100 micrometers, more preferably greater than
1 micrometer to about 20 micrometers.
[0008] In certain exemplary embodiments, the (co)polymer fibers
further include between about 0 to 30% w/w of at least one
plasticizer. In some such embodiments the at least one plasticizer
is selected from oligomers of C.sub.5 to C.sub.14 olefins, and
mixtures thereof.
[0009] In another aspect, the, present disclosure describes a
process for making a nonwoven fibrous web, including heating a
mixture of about 50% w/w to about 99% w/w of at least one
crystalline polyolefin (co)polymer, and from about 1% w/w to about
40% w/w of at least one hydrocarbon tackifier resin to at least a
Melting Temperature of the mixture to form a molten mixture,
extruding the molten mixture through at least one orifice to form
at least one filament, applying a gaseous stream to the at least
one filament to attenuate the at least one filament to form a
plurality of discrete, discontinuous fibers, and cooling the
plurality of discrete discontinuous fibers to a temperature below
the Melting Temperature of the molten mixture to form a nonwoven
fibrous web, wherein at least one of the crystalline polyolefin
(co)polymer or the nonwoven fibrous web exhibits a Heat of Fusion
measured using Differential Scanning Calorimetry of greater than 50
Joules/g.
[0010] In certain such exemplary embodiments, applying a gaseous
stream to the at least one filament to attenuate the at least one
filament to form a plurality of discrete, discontinuous fibers is
accomplished using a process selected from melt-blowing, gas jet
fibrillation, and combinations thereof. In some such exemplary
embodiments, the process further includes at least one of addition
of a plurality of staple fibers to the plurality of discrete,
discontinuous fibers, or addition of a plurality of particulates to
the plurality of discrete, discontinuous fibers. In further such
exemplary embodiments, the process further includes collecting the
plurality of discrete, discontinuous fibers as the nonwoven fibrous
web on a collector. In some such embodiments, the process further
includes'processing the collected nonwoven fibrous web using a
process selected from autogenous bonding, through-air bonding,
electret charging, embossing, needle-punching, needle tacking,
hydroentangling, or a combination thereof.
[0011] Exemplary embodiments according to the present disclosure
may have certain surprising and unexpected advantages over the art.
One such advantage of exemplary embodiments of the present
disclosure relates to increased tensile strength exhibited by the
webs; even when prepared at low Basis Weight (i.e., less than or
equal to 50 g/m.sup.2, "gsm"). Increased tensile strength for low
Basis Weight webs is important for many insulation applications,
for example, thermal or acoustic insulation, more particularly
acoustic or thermal insulation mats used in motor vehicles (e.g.,
aircraft, trains, automobiles, trucks, ships, and
submersibles).
[0012] Thus, exemplary nonwoven fibrous webs as described herein
may advantageously exhibit a Maximum Load in the Machine Direction
of at least 5 Newtons as measured with the Tensile Strength Test as
defined herein.
[0013] In certain exemplary embodiments, the nonwoven fibrous webs
exhibit a Basis Weight of from 1 g/m.sup.2 (gsm) to 400 gsm, more
preferably from 1 gsm to 200 gsm, even more preferably from 1 gsm
to 100 gsm, or even 1 gsm to about 50 gsm.
[0014] Another advantage of exemplary embodiments may be to limit
or eliminate the possibility of newly formed fibers breaking and
forming fiber fragments ((i.e., "fly") which can fall onto the
collected nonwoven web and damage the web where they land.
[0015] An additional advantage of exemplary embodiments relates to
an ability to use a higher melt temperature for the melt-blown
process; which leads to a lower mean Effective Fiber Diameter (EFD)
of about 5 thicrometers or less, and may even permit the production
of sub-micrometer fibers (i.e., nanofibers) having a mean Actual
Fiber Diameter (AFD) of one micrometer or less. Such nonwoven
fibrous webs including sub-micrometer fibers achieve better
acoustic and/or thermal insulation performance at equal or lower
Basis Weight than comparable microfiber webs, thus leading to
improved insulation performance at a lower production cost.
Embodiments of the present disclosure may exhibit higher production
rates due to the lower melt viscosities achieved during
melt-blowing of the fibers.
[0016] The following Listing of Exemplary Embodiments summarizes
the various exemplary illustrative embodiments of the present
disclosure.
Listing of Exemplary Embodiments
[0017] A. A nonwoven fibrous web, comprising:
[0018] a plurality of (co)polymeric fibers comprising from about
50% w/w to about 99% w/w of at least one crystalline polyolefin
(co)polymer, and
[0019] from about 1% w/w to about 40% w/w of at least one
hydrocarbon tackifier resin, wherein the nonwoven fibrous web
exhibits a Heat of Fusion measured using Differential Scanning
Calorimetry of greater than 50 Joules/g. [0020] B. The nonwoven
fibrous web of Embodiment A or any following Embodiment, wherein
the at least one crystalline polyolefin (co)polymer is selected
from the group consisting of polyethylene, isotactic polypropylene,
syndiotactic polypropylene, isotactic polybutylene, syndiotactic
polybutylene, poly-4-methyl pentene, and mixtures thereof. [0021]
C. The nonwoven fibrous web Embodiment B, wherein the at least one
crystalline polyolefin (co)polymer exhibits a Heat of Fusion
measured using Differential Scanning Calorimetry of greater than 50
Joules/g, [0022] D. The nonwoven fibrous web of any preceding or
following Embodiment, wherein the at least one hydrocarbon
tackifier resin is a saturated hydrocarbon. [0023] E. The nonwoven
fibrous web of any preceding or following Embodiment, wherein the
at least one hydrocarbon tackifier resin is selected from the group
consisting of C.sub.5 piperylene derivatives, C.sub.9 resin oil
derivatives, and mixtures thereof. [0024] F. The nonwoven fibrous
web of any preceding or following Embodiment, wherein the at least
one hydrocarbon tackifier resin makes up from 1% to 40% by weight
of the (co)polymeric fibers. [0025] G. The nonwoven fibrous web of
claim Embodiment. F. wherein the at least one hydrocarbon tackifier
resin makes up from 5% to 30% by weight.of the (co)polymeric
fibers. [0026] H. The nonwoven fibrous web of Embodiment G, wherein
the at least one hydrocarbon tackifier resin makes up from 7% to
20% by weight of the (co)polymeric fibers. [0027] I. The nonwoven
fibrous web of any preceding or following Embodiment, wherein the
plurality of (co)polymeric fibers exhibit a mean Actual Fiber
Diameter of from about 100 nanometers to about 20 micrometers.
[0028] J. The nonwoven fibrous web of Embodiment 1, wherein the
plurality of (co)polymeric fibers exhibits a mean. Actual Fiber
Diameter of between about 1 micrometer to about 10 micrometers.
[0029] K. The nonwoven fibrous web of any preceding or following
Embodiment, further comprising between about 0 to 30% of at least
one plasticizer. [0030] L. The nonwoven fibrous web of Embodiment
K, wherein the at least one plasticizer is selected from the group
consisting of oligomers of C.sub.5 to C.sub.14 olefins, and
mixtures thereof. [0031] M. The nonwoven fibrous web of any
preceding or following Embodiment, wherein the nonwoven fibrous web
exhibits a Maximum Load in the Machine Direction of at least 5
Newtons as measured using the Tensile Strength Test. [0032] M The
nonwoven fibrous web of any preceding or following Embodiment,
wherein the nonwoven fibrous web exhibits a Basis Weight of 1 gsm
to 400 gsm. [0033] N. The nonwoven fibrous web of Embodiment M,
wherein the nonwoven fibrosis web exhibits a Basis Weight of 1 gsm
to 50 gsm. [0034] O. A process for making a nonwoven fibrous web,
comprising:
[0035] a) heating a mixture of about 50% w/w to about 99% w/w of at
least one crystalline polyolefin (co)polymer, and from about 1% w/w
to about 40% w/w of at least one hydrocarbon tackifier resin to at
least a Melting Temperature of the mixture to form a molten
mixture;
[0036] b) extruding the molten mixture through at least one orifice
to form at least one filament;
[0037] e) applying gaseous stream to the at least one filament to
attenuate the at least one filament to form a plurality of
discrete, discontinuous fibers; and
[0038] d) cooling the plurality of discrete discontinuous fibers to
a temperature below the Melting Temperature of the molten mixture
to form a nonwoven fibrous web, wherein at least one of the
crystalline polyolefin (co)polymer or the nonwoven fibrous web
exhibits a Heat of Fusion measured using Differential. Scanning
Calorimetry of greater than 50 Joules/g,
[0039] P. The process of Embodiment O, Q, R or S; wherein applying
a gaseous stream to the at least one filament to attenuate the at
least one filament to form a plurality of discrete, discontinuous
fibers is accomplished using a process selected from the group
consisting of melt-blowing, gas jet fibrillation, and combinations
thereof. [0040] Q. The process of Embodiment O, P, R or S, further
comprising at least one of addition of a plurality of staple fibers
to the plurality of melt blown fibers, or addition of a plurality
of particulates to the plurality of melt-blown fibers. [0041] R.
The process of Embodiment O, P, Q, or S, further comprising
collecting the plurality of discrete discontinuous fibers as the
nonwoven fibrous web on a collector. [0042] S. The process of
Embodinnent O, P, Q, or R, further comprising processing the
collected nonwoven fibrous web using a process selected from the
group consisting of autogenous bonding, through-air bonding,
electret charging, calendering, embossing, needle-punching, needle
tacking, hydroentangling, or a combination thereof.
[0043] Various aspects and advantages of exemplary embodiments of
the disclosure have been summarized. The above Summary is not
intended to describe each illustrated embodiment or every
implementation of the present certain exemplary embodiments of the
present disclosure. The Detailed Description and Examples that
follow more particularly exemplify certain presently preferred
embodiments using the principles disclosed herein.
DETAILED DESCRIPTION
[0044] For the following Glossary of defined terms, these
definitions shall be applied for the entire application, unless a
different definition is provided in the claims or elsewhere in the
specification.
Glossary
[0045] Certain terms are used throughout the description and the
claims that, while for the most part are well known, may require
some explanation. It should be understood that:
[0046] The terms "(co)polymer" or "(co)polymers" includes
homopolymers and copolymers, as well as homopolymers or copolymers
that may be formed in a miscible blend, e.g., by coextrusion or by
reaction, including, e.g., transesterification. The term
"copolymer" includes random, block and star (e.g. dendritic)
copolymers.
[0047] The term "molecularly same (co)polymer" means one or more
(co)polymers that have essentially the same repeating molecular
unit, but which may differ in molecular weight, method of
manufacture, commercial form, and the like.
[0048] The term "nonwoven fibrous web" means a fibrous web
characterized by entanglement or point bonding of a plurality of
fibers.
[0049] The term "self-supporting" means a nonwoven fibrous web
having sufficient coherency and strength so as to be drapable and
handleable without substantial tearing or rupture.
[0050] The terms "melt-blowing" and "melt-blown process" mean a
process for forming a nonwoven fibrous web by extruding a
fiber-forming material through one or more orifices to form
filaments while contacting the filaments with air or other
attenuating fluid to attenuate the filaments into discrete
discontinuous fibers, and thereafter collecting a layer of the
attenuated discrete discontinuous fibers.
[0051] The term "die" means a processing assembly including one or
more orifices to form filaments for use in (co)polymer melt
processing and fiber extrusion processes, including but not limited
to melt-blowing processes.
[0052] The term "melt-blown fibers" means discrete fibers prepared
using a melt-blowing process.
[0053] The term "machine direction" means the Longitudinal
direction in which a nonwoven fibrous web of indeterminate length
is moved or wound onto a collector, and is distinguished from the
"cross-web" direction, which is the lateral direction extending
between the two lateral edges of the nonwoven fibrous web.
Generally, the crossweb direction is orthogonal to the machine
direction for a rectangular nonwoven fibrous web.
[0054] The term "composite nonwoven fibrous web" means a nonwoven
web having an open-structured entangled mass of melt-blown fibers,
for example, sub-micrometer melt-blown fibers and optionally
melt-blown microfibers.
[0055] The terms "particle and "particulate" are used substantially
interchangeably. Generally, a particle or particulate means a small
distinct piece or individual part of a material in finely divided
form. However; a particulate may also include a collection of
individual particles associated or clustered together in finely
divided form. Thus, individual particles used in certain exemplary
embodiments of the present disclosure may chimp, physically
intermesh, electro-statically associate, or otherwise associate to
form particulates. In certain instances, particulates in the form
of agglomerates of individual particles may be intentionally formed
such as those described in U.S. Pat. No. 5,332,426 (Tang et
al.).
[0056] The term "particle-loaded nonwoven fibrous web" means a
nonwoven fibrous web containing particles bonded to the fibers or
enmeshed among the fibers, the particles optionally being absorbent
and/or adsorbent.
[0057] The term "enmeshed" means that particles are distributed and
physically held in the fibers of the web. Generally, there is point
and line contact along the fibers and the particles so that nearly
the full surface area of the particles is available for interaction
with a fluid.
[0058] The term "autogenous bonding" means bonding between fibers
at an elevated temperature as obtained in an oven or with a
through-air bonder without application of solid contact pressure
such as in point-bonding or calendering
[0059] The term "calendering" means a process of passing a product,
such as a polymeric absorbent loaded web through rollers to obtain
a compressed material. The rollers may optionally be heated.
[0060] The term "densification" means a process whereby fibers
which have been deposited either directly or indirectly onto a
filter winding arbor or mandrel are compressed, either before or
after the deposition, and made to form an area, generally or
locally, of lower porosity, whether by design or as an artifact of
some process of handling the forming or formed filter.
Densification also includes the process of calendering webs.
[0061] The term "Actual Fiber Diameter" or "AFD" means the mean
number diameter on a population of melt-blown fibers determined by
measuring 500 individual fibers using Scanning Electron Microscopy
(SEM).
[0062] The term "Effective Fiber Diameter` or "EFD" means the
apparent diameter of the fibers in a nonwoven fibrous web based on
an air permeation test in which air at 1 atmosphere and room
temperature is passed at a face velocity of 5.3 cm/sec through a
web sample of known thickness, and the corresponding pressure drop
is measured. Based on the measured pressure drop, the Effective
Fiber Diameter is calculated set forth in Davies, C. N., The
Separation of Airborne Dust and Particles, Institution of
Mechanical Engineers, London Proceedings, 1B (1952).
[0063] The term "microfibers means a population of fibers having a
mean diameter of at least one micrometer (.mu.m) and preferably
less than 1.000 .mu.m.
[0064] The term "coarse microfibers" means a population of
microfibers having a mean diameter of at least 10 .mu.m and
preferably less than 1,000 .mu.m.
[0065] The term "fine microfibers" means a population of
microfibers having a mean diameter of from one .mu.m to less, than
10 .mu.m.
[0066] The term "ultrafine microfibers" means a population of
microfibers having a mean diameter of 2 .mu.m or less.
[0067] The term "nanofibers" means a population of fibers having a
mean diameter of 1 .mu.m or less.
[0068] The term "sub-micrometer fibers" means a population of
fibers having a mean diameter of less than 1 .mu.m.
[0069] The term "separately prepared microfibers" means a stream of
microfibers produced from a microfiber-forming apparatus (e.g., a
melt-blowing die) positioned such that the microfiber stream is
initially spatially separate (e.g., over a distance of about 1 inch
(25 mm) or more from, but will merge in flight and disperse into, a
stream of larger size microfibers.
[0070] The term "homogeneous" means exhibiting only a single phase
of matter when observed at a macroscopic scale.
[0071] The term "Web Basis Weight" is calculated from the weight of
a 10 cm.times.10 cm web sample.
[0072] The term "Web Thickness" is measured on a 10 cm.times.10 cm
web sample using a thickness testing gauge having a tester foot
with dimensions of 5 cm.times.12.5 cm at an applied pressure of 150
Pa.
[0073] The term "Polymer Density" is the mass per unit volume of
the (co)polymer or (co)polymer blend that is used to form the
nonwoven fibers of a nonwoven fibrous web. The Polymer Density for
a (co)polymer may generally be found in the literature, and the
Polymer Density of a (c)polymer blend may be calculated from the
weighted average of the component (co)polymer Polymer Densities,
based upon the weight percentages of the individual (co)polymers
used to make up the (co)polymer blend. The Polymer Density of
polypropylene resin is 0.91 g/cm.sup.3 and the Polymer Density of
the hydrocarbon tackifier resins used herein is about 1.00
g/cm.sup.3. For the calculations of Solidity provided herein using
the following formula, a Polymer Density of 0.91 g/cm.sup.3 was
used.
[0074] The term "Solidity" is defined by the equation:
Solidity ( % ) = [ 3.937 * Web Basis Weight ( g / m 2 ) ] [ Web
Thickness ( mils ) * Polymer Density ( g / cm 3 ) ]
##EQU00001##
wherein one mil is equivalent to 25 micrometers.
[0075] The term "Melting Temperature" as used herein, is the
highest magnitude peak among principal and any secondary
endothermic melting peaks in a cooling after first heating heat
flow curve plotted as a function of temperature, as obtained using
Differential Scanning Calorimetry (DSC).
[0076] The term "adjoining" with reference to a particular layer in
a multilayer nonwoven fibrous web means joined with attached to
another layer, in a position wherein the two layers are either next
to (i.e., adjacent to) and directly contacting each other, or
contiguous with each other but not in direct contact (i.e., there
are one or more additional layers intervening between the
layers).
[0077] The terms "about" or "approximately" with reference to a
numerical value or a shape means +/- five percent of the numerical
value or property or characteristic, but expressly includes the
exact numerical value. For example, a viscosity of "about" 1 Pa-sec
refers to a viscosity from 0.95 to 1.05 Pa-Sec, but also expressly
includes a viscosity of exactly 1 Pa-sec. Similarly, perimeter that
is "substantially square" is intended to describe a geometric shape
having four lateral edges in which each lateral edge has a length
which is from 95% to 105% of the length of any other lateral edge
but which also includes a geometric shape in which each lateral
edge has exactly the same length.
[0078] The term "substantially" used with reference to a property
or characteristic means that the property or characteristic is
exhibited to a greater extent than the opposite of that property or
characteristic is exhibited. For example, a substrate that is
"substantially" transparent refers to a substrate that transmits
more radiation (e.g. visible light) than it fails to transmit (e.g.
absorbs and reflects). Thus, a substrate that transmits more than
50% of the visible light incident upon its surface is substantially
transparent, but a substrate that transmits 50% or less of the
visible light incident upon its surface is not substantially
transparent.
[0079] By using terms of orientation such as "atop", "on", "over,"
"covering", "uppermost", "underlying" and the like for the location
of various elements in the disclosed coated articles, we refer to
the relative position of an element with respect to a horizontally
disposed, upwardly-facing substrate. However, unless otherwise
indicated, it is not intended that the substrate or articles should
have any particular orientation in space during or after
manufacture.
[0080] By using the term "overcoated" to describe the position of a
layer with respect to a substrate or other element of an article of
the present disclosure, we refer to the layer as being atop the
substrate or other element, but not necessarily contiguous to
either the substrate or the other element.
[0081] By using the term "separated by" to describe the position of
a layer with respect to other layers, we refer to the layer as
being positioned between two other layers but not necessarily
contiguous to or adjacent to either layer.
[0082] As used in this specification and the appended embodiments,
the singular forms "a", "an", and "the" include plural referents
unless the content clearly dictates otherwise. Thus, for example,
reference to fine fibers containing "a compound" includes a mixture
of two or more compounds. As used in this specification and the
appended embodiments, the term "or" is generally employed in its
sense including "and/or" unless the content clearly dictates
otherwise.
[0083] As used in this specification, the recitation of numerical
ranges by endpoints includes all numbers subsumed within that range
(e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.8, 4, and 5).
[0084] Unless otherwise indicated, all numbers expressing
quantities or ingredients, measurement of properties and so forth
used in the specification and embodiments are to be understood as
being modified in all instances by the term "about." Accordingly,
unless indicated to the contrary, the numerical parameters set
forth in the foregoing specification and attached listing of
embodiments can vary depending upon the desired properties sought
to be obtained by those skilled in the art utilizing the teachings
of the present disclosure. At the very least, and not as an attempt
to limit the application of the doctrine of equivalents to the
scope of the claimed embodiments, each numerical parameter should
at least be construed in light of the number of reported
significant digits and by applying ordinary rounding
techniques.
[0085] Various exemplary embodiments of the disclosure will now be
described. Exemplary embodiments of the present disclosure may take
on various modifications and alterations without departing from the
spirit and scope of the disclosure. Accordingly, it is to be
understood that the embodiments of the present disclosure are not
to be limited to the following described exemplary embodiments, but
are to be controlled by the limitations set forth in the claims and
any equivalents thereof.
Nonwoven Fibrous Webs
[0086] Thus, in one exemplary embodiment, the disclosure describes
a nonwoven fibrous web, comprising a plurality of (co)polymeric
fibers comprising from about 50% w/w to about 99% w/w of at least
one crystalline polyolefin (co)polymer, and from about 1% w/w to
about 40% w/w of at least one hydrocarbon tackifier resin, wherein
the nonwoven fibrous web exhibits a Heat of Fusion measured using
Differential Scanning Calorimetry of greater than 50 Joules/g.
[0087] In some exemplary embodiments, the nonwoven fibrous webs as
described herein may advantageously exhibit improved tensile
strength, as evidenced by a Maximum Tensile Load in the Machine
Direction as measured with the Tensile Strength Test as defined
herein, of at least 5 Newtons (N), at least 6 N, at least 7 N, at
least 8N, at least 9 N, or even at least 10 N. Generally, the
Maximum Tensile Load in the Machine Direction as measured with the
Tensile Strength Test as defined herein is less than 20 N, less
than 15 N, less than 14 N, or even less than 12 N.
Fibers
[0088] Nonwoven fibrous webs of the present disclosure generally
include fibers that may be regarded as discrete discontinuous
fibers. In some exemplary embodiments, the discrete discontinuous
fibers in the non-woven fibrous webs or composite webs comprise
microfibers and may advantageously exhibit a mean Effective Fiber
Diameter (determined using the test method described below) of
between about 1 micrometer and about 100 micrometers, more
preferably greater than 1 micrometer to about 20.0 micrometers,
inclusive, even more preferably from greater than 1 micrometer to
about 10.0 micrometers. In other exemplary embodiments, the
discrete discontinuous fibers in the nonwoven fibrous webs or
composite webs may comprise sub-micrometer fibers or nanofibers and
may advantageously exhibit a mean Actual Fiber Diameter (determined
using the test method described below) of from about 100 nanometers
(nm) to about 5 micrometers inclusive, more preferably from 100 nm
to 1 .mu.m, inclusive, even more preferably from about 100 nm, to
about 900 nm, or even 200 nm to 750 nm, or 250 nm to 500 nm,
inclusive.
[0089] The nonwoven fibrous web. May take a variety of forms;
including mats, webs, sheets; scrims; fabrics, and a combination
thereof.
Fiber Components
[0090] Melt-blown nonwoven fibrous webs or webs of the present
disclosure comprise fibers comprising from about 50% w/w to about
99% w/w of at least one crystalline polyolefin (co)polymer, and
from about 1% w/w to about 40% w/w at least one hydrocarbon
tackifier resin. In some embodiments, a single crystalline
polyolefin (co)polymer) may be mixed with a single hydrocarbon
tackifier resin. In other exemplary embodiments, a single
crystalline polyolefin (co)polymer may be advantageously mixed with
two or more hydrocarbon tackifier resins. In further exemplary
embodiments, two or more crystalline polyolefin (co)polymers may be
mixed with a single hydrocarbon tackifier resin. In other exemplary
embodiments, two or more crystalline polyolefin (co)polymers may be
advantageously mixed with two or more hydrocarbon tackifier
resins.
Crystalline Polyolefin (Co)Polymer
[0091] The crystalline polyolefin (co)polymers useful in practicing
embodiments of the present disclosure are generally crystalline
polyolefin (co)polymers with a moderate level of crystallinity.
Generally (co)polymer crystallinity arises from stereoregular
sequences in the (co)polymer, for example stereoregular ethylene;
propylene, or butylene sequences. For example the (co)polymer can
be: (A) a propylene homopolymer in which the stereoregularity is
disrupted in some manner such as by regio-inversions; (B) a random
propylene copolymer in which the propylene stereoregularity is
disrupted at least in part by co-monomers; or (C) a combination of
(A) and (B).
[0092] In some exemplary embodiments, the at least one crystalline
polyolefin (co)polymer is selected from polyethylene, isotactic
polypropylene, syndiotactic polypropylene, isotactic polybutylene,
syndiotactic polybutylene, poly-4-methyl pentene, and mixtures
thereof. The at least one crystalline polyolefin (co)polymer
preferably exhibits a Heat of Fusion measured using Differential
Scanning Calorimetry of greater than 5.0 Joules/g. In certain
presently preferred exemplary embodiments, the at least one
crystalline polyolefin (co)polymer is selected to be isotactic
polypropylene, syndiotactic polypropylene, and mixtures
thereof.
[0093] In some exemplary embodiments; the crystalline polyolefin
(co)polymer is a (co)polymer that includes a non-conjugated diene
monomer to aid in vulcanization and other chemical modification of
the blend composition. The amount of diene present in the
(co)polymer is preferably less than 10% by weight, and more
preferably less than 5% by weight. The diene may be any
non-conjugated diene which is commonly used for the vulcanization
of ethylene propylene rubbers including, but not limited to,
ethylidene norbornene, vinyl norbornene, and dicyclopentadiene.
[0094] In one exemplary embodiment, the crystalline polyolefin
(co)polymer is a random copolymer of propylene and at least one
co-nonomer selected from ethylene; C.sub.4-C.sub.12 alpha-olefins,
and combinations thereof. In one particular embodiment, the
copolymer includes ethylene-derived units in an amount ranging from
a lower limit of 2N, 5%, 6%, 8%, or 10% by weight to an upper limit
of 20%, 25%, 0.28% by weight. This embodiment also includes
propylene-derived units present in the copolymer in an amount
ranging from a lower limit of 72%, 75%, or 80% by weight to an
upper litnit of 98%, 95%, 94%; 92%, or 90% by weight. These
percentages by weight are based on the total weight of the
propylene and ethylene-derived units; i.e., based on the sum of
weight percent propylene-derived units and weight percent
ethylene-derived units being 109%.
[0095] In other exemplary embodiments, the crystalline polyolefin
(co)polymer is a random propylene copolymer having a narrow
compositional distribution. In certain presently preferred
embodiments, the crystalline polyolefin (co)polymer is a random
propylene copolymer exhibiting a Heat of Fusion determined using
DSC of greater than 50 J/g.
[0096] The copolymer is described as random because for a copolymer
comprising propylene, co-monomer, and optionally diene, the number
and distribution of co-monomer residues is consistent with the
random statistical polymerization of the monomers. In stereoblock
structures the number of block monomer residues of any one kind
adjacent to one another is greater than predicted from a
statistical distribution in random copblymers with a similar
composition. Historical ethylene-propylene copolymers with
stereoblock structure have a distribution of ethylene residues
consistent with these blocky structures rather than a random
statistical distribution of the monomer residues in the
(co)polymer. The intramolecular composition distribution (i.e.,
randomness) of the copolymer may be determined by .sup.13C NMR,
which locates the co-monomer residues in relation to the
neighboring propylene residues.
[0097] The crystallinity of the crystalline polyolefin (co)polymers
may be expressed in terms of heat of fusion. Embodiments of the
present disclosure include crystalline polyolefin (co)polymers
exhibiting a heat of fusion as determined using differential
scanning Calorimetry (DSC) greater than 50 J/g, greater than 51
J/g, greater than 55 J/g, greater than 60 J/g, greater than 70 J/g,
greater than 80 J/g, greater than 90 J/g, greater than 100 J/g, or
even about 110 J/g. Generally, the crystalline polyolefin
(co)polymers exhibit a heat of fusion as determined using. DSC less
than 210 J/g, less than 200 J/g, less than 190 J/g, less than 180
J/g, less than 170 J/g, less than 160 J/g, less than 150 J/g, less
than 140 J/g, less than 130 J/g, less than 120 J/g, less than 110
J/g, or even less than 100 J/g.
[0098] The level of crystallinity is also reflected in the Melting
Point. In one embodiment of the present disclosure, the (co)polymer
has a single Melting Point. Typically, a sample of propylene
(co)polymer will show secondary melting peaks adjacent to the
principal peak, which are considered together as a single Melting
Point. The highest of these peaks is considered to be the Melting
Point.
[0099] The crystalline polyolefin (co)polymer preferably has a
melting point determined using DSC ranging from an upper limit of
300.degree. C., 275.degree. C., 250.degree. C., 200.degree. C.,
175.degree. C., 150.degree. C., 125.degree. C., 110.degree. C., or
even about 105.degree. C., to a lower limit of about 105.degree.
C., 110.degree. C., 120.degree. C. , 125.degree. C., 130.degree. C.
140.degree. C. 150.degree. C., 160.degree. C., 175, 180.degree. C.,
190.degree. C., 200.degree. C., 225.degree. C., or even about
250.degree. C.
[0100] The crystalline polyolefin (co)polymers used in the
disclosure generally have a weight average molecular weight
(M.sub.w) within the range having an upper limit of 5,000,000
Daltons (Da or g/mol), 1,000,000 Da, or 500,000 Da, and a lower
limit of 10,000 Da, 20,000 Da, or 80,000 Da, and a molecular weight
distribution M.sub.w/M.sub.n (MWD), sometimes referred to as a
"polydispersity index" (PDI), ranging from a lower limit of 1.5,
1.8, or 2.0 to an upper limit of 40, 20, 10, 5, or 4.5. The M.sub.w
and MWD, as used herein, can be determined by a variety of methods,
including those in U.S. Pat. No. 4,540,753 to Cozewith, et al., and
references cited therein, or those methods found in Verstrate et
al., Macromolecules, v. 21, p. 3360 (1988), the descriptions of
which are incorporated by reference herein for purposes of U.S.
practices.
[0101] At least one crystalline polyolefin (co)polymer is generally
present in an amount from about 50% w/w (50.0% w/w, 55% w/w, 60%
w/w, 65% w/w, 70% w/w, 75% w/w, 80% wlw, 85% w/w, or even about 90%
w/w) to about 99% w/w (99.0% w/w, 98% w/w 97% w/w, 96% w/w, 95%
w/w, 90% w/w, 85% w/w, 80% w/w, 75% w/w, 70% w/w. 65% w/w, or even
about 60% w/w) based on the total weight of the composition.
Hydrocarbon Tackifier Resins
[0102] Various, types of natural and synthetic hydrocarbon
tackifier resins; alone or in admixture with each other, can be
used in preparing the fiber compositions described herein, provided
they meet the miscibility criteria described herein. Preferably,
the hydrocarbon tackifier resin is selected to be miscible (i.e.,
forms a homogenous melt) with the crystalline polyolefin
(co)polymer(s) when the mixture is in a molten state, that is, when
the mixture of the at least one crystalline polyolefin (co)polymer
and the at least one hydrocarbon tackifier resin is heated to a
temperature at or above the Melting Temperature (as determined
using DSC) of the mixture.
[0103] Suitable resins include, but are not limited to, natural
rosins and rosin esters, hydrogenated rosins and hydrogenated rosin
esters, coumarone-indene resins, petroleum resins, polyterpene
resins, and terpene-phenolic resins. Specific examples of suitable
petroleum resins include, but ate not limited to aliphatic
hydrocarbon tackifier resins, hydrogenated aliphatic hydrocarbon
tackifier resins, mixed aliphatic and aromatic hydrocarbon
tackifier resins, hydrogenated mixed aliphatic and aromatic
hydrocarbon tackifier resins, cycloaliphatic hydrocarbon tackifier
resins, hydrogenated cycloaliphatic resins, mixed cycloaliphatic
and aromatic hydrocarbon tackifier resins, hydrogenated mixed
cycloaliphatic and aromatic hydrocarbon tackifier resins, aromatic
hydrocarbon tackifier resins, substituted aromatic hydrocarbons,
and hydrogenated aromatic hydrocarbon tackifier resins.
[0104] As used herein, "hydrogenated" includes fully, substantially
and at least partially hydrogenated resins. Suitable aromatic
resins include aromatic modified aliphatic resins, aromatic
modified cycloaliphatic resin; and hydrogenated aromatic
hydrocarbon tackifies resins. Any of the above resins may be
grafted with an unsaturated ester or anhydride to provide enhanced
properties to the resin. Examples of grafted resins and their
Manufacture are described in the chapter titled Hydrocarbon Resins,
Kirk-Othmer, Encyclopedia of Chemical Technology, 4th Ed, v. 13,
pp. 717-743 (J. Wiley & Sons, 1995).
[0105] Hydrocarbon tackifier resins suitable for use as described
herein include EMPR 100, 101, 102, 103, 104, 105, 106, 107, 108,
109, 110, 116, 117, and 118 resins, OPPERA.TM. resins, and EMFR
resins available from Exxon-Mobil Chemical. Company (Spring, Tex.);
ARKON.TM. P140, P125, P115, M115, and M135 and SUPER ESTER.TM.
rosin esters available from Arakamid. Cherrileal Company (Osaka,
Japan); SYLVARES.TM. polyterpene resins, styrenatedterpene resins
and terpene phenolic resins, SYLVATAC.TM. and SYLVALITE.TM. rosin
esters available from Arizona Chemical Company LLC (Jacksonville,
Fla.); NORSOLENE.TM. aliphatic aromatic resins and WINGTACK.TM.
C.sub.5 resins available from TOTAL Cray Valley (Paris, France);
DERTOPHENE.TM. terpene phenolic resins and DERCOLYTET.TM.
polyterpene resins available from DRT Chemical Company (Dax Cedex,
France); EASTOTACT.TM. resins, PICCOTACT.TM. resins, REGALITE.TM.
and REGALREZT.TM. hydrogenated cycloaliphatic/aromatic resins
available from Eastman Chemical Company (Kingsport, Tenn.);
PICCOLYTE.TM. and PERMALYN.TM. polyterpene resins, rosins and rosin
esters available from Pinova, Inc. (Brunswick, Ga.);
coumerone/indene resins available from Neville Chemical Company
(Pittsburg, Pa.); QUINTONE.TM. acid modified C.sub.5 resins,
C.sub.5-C.sub.9 resins, and acid modified C.sub.5-C.sub.9 resins
available from Nippon Zeon (Tokyo, Japan); and CLEARON.TM.
hydrogenated terpene resins available from Yasuhara Chemical
Company, Ltd. (Tokyo. Japan). The preceding examples are,
illustrative only and by no means limiting.
[0106] In some exemplary embodiments, the hydrocarbon tackifier
resin has a number average molecular weight (M.sub.n) within the
range having an upper limit of 5,000 Da, or 2,000 Da, or 1,000 Da,
and a lower limit of 200 Da, or.400 Da, or 500 Da; a weight average
molecular weight (M.sub.w) ranging from 500 Data 10,000 Da or 600
to 5,000 Da or 700 to 4,000 Da; a Z average molecular weight
(M.sub.z) ranging from 500 Da to 10,000 Da, and a polydispersity
index (PDI) as measured by M.sub.w/M.sub.n, of from 1.5 to 3.5,
where M.sub.n, M.sub.w, and M.sub.z are determined using size
exclusion chromatography (SEC), or as provided by the supplier.
[0107] In other exemplary embodiments, the hydrocarbon tackifier
resin has a lower molecular weight than the crystalline polyolefin
(co)polymer.
[0108] The hydrocarbon tackifier resins of the present disclosure
are generally selected to be miscible with the crystalline
polyolefin (co)polymer in a molten state.
[0109] Hydrocarbon tackifier resins useful in embodiments of the
present disclosure may have a softening point within the range
having an upper limit of 180.degree. C., 150.degree. C., or
140.degree. C., and a lower limit of 80.degree. C., 120.degree. C.,
or 125.degree. C. Softening point (.degree. C.) is measured using a
ring and ball softening point device according to ASTM E-28
(Revision 1996).
[0110] Preferably, the hydrocarbon tackifier resin is a saturated
hydrocarbon. In certain presently preferred exemplary embodiments,
the hydrocarbon tackifier resin is selected from C.sub.5 piperylene
derivatives, C.sub.9 resin oil derivatives, and mixtures
thereof.
[0111] The hydrocarbon tackifier'resin makes up from about 2% w/w
(2.0% w/w, 3% w/w, 4% w/w, 5% w/w, 10% w/w, 15% w/w, 20% w/w) to
about 40% (40.0% w/w, 35% w/w, 30% w/w, or even 25% w/w) based on
the weight of the (co)poymeric fibers in the nonwoven fibrous web,
more preferably from 5% to 30% by weight of the (co)polymeric
fibers, even more preferably from 7% to 20% by weight of the
(co)polymeric fibers.
Optional Nonwoven Fibrous Web Components
[0112] In.further exemplary embodiments, the nonwoven melt-blown
fibrous webs of the present disclosure may further comprise one or
more optional components. The optional components may be used alone
or in any combination suitable for the end-use application of the
nonwoven melt-blown fibrous webs. Three non-limiting, currently
preferred optional components include optional electret fiber
components, optional non-melt-blown fiber components, and optional
particulate components as described further below.
Optional Plasticizer
[0113] In certain exemplary embodiments, the (co)polyineric fibers
further include a plasticizer in an amount between about 0% to
about 30% w/w of the fiber composition, more preferably from 1% to
20% w/w, 1% to 10% w/w, 1% to 5%, or even 1% to 2.5%. In some such
embodiments, the plasticizer is selected from oligomers of C.sub.5
to C.sub.14 olefins, and mixtures thereof. A non-limiting list of
suitable commercially available plasticizers includes SHF and
SUPEERSYNTm available from Exxon-Mobil Chemical Company (Houston,
Tex.); STNFLUID.TM. available from Chevron-Phillips Chemical Co,
(Pasadena, Tex.); DURASYN.TM. available from BP-Amoco Chemicals
(London, England); NEXBASE.TM. available from Fortuin Oil and Gas
Co. (Espoo, Finland); SYNTON.TM. available from Crompton
Corporation (Middlebury, Conn.); EMERY.TM. available from BASF GmbH
(Ludwigshafen, Germany), formerly. Cognis Corporation (Dayton,
Ohio).
Optional Electret Fiber Component
[0114] The nonwoven melt-blown fibrous webs of the present
disclosure may optionally comprise electret fibers. Suitable
electret fibers are described in U.S. Pat. Nos. 4,215,682;
5,641,555; 5,643,507; 5,658,640; 5,658,641; 6,420,024; 6,645,618,
6,849,329; and 7,691,168, the entire disclosures of which are
incorporated herein by reference.
[0115] Suitable electret fibers may be produced by meltblowing
fibers in an electric field, e.g. by melting a suitable dielectric
material such as'a (co)polymer or wax that contains polar
molecules, passing the molten Material through a melt-blowing die
to form discrete fibers, and then allowing the molten (co)polymer
to re-solidify while the discrete fibers are exposed to a powerful
electrostatic field. Electret fibers may also be made by embedding
excess charges into a highly insulating dielectric material such as
a (co)polymer or wax, e.g. by means of an electron beam, a corona
discharge, injection from an electron, electric breakdown across a
gap or a dielectric barrier, and the like. Particularly suitable
electret fibers are hydro-charged fibers.
Optional Non-Melt-Blown Fiber Component
[0116] In additional exemplary embodiments, the nonwoven fibrous
web optionally further comprises a plurality of non-melt-blown
fibers. Thus, in exemplary embodiments, the nonwoven fibrous web
may additionally comprise discrete non-melt-blown fibers.
Optionally, the discrete non-melt-blown fibers are staple fibers.
Generally, the discrete non-melt-blown fibers act as filling
fibers, e.g. to reduce the cost or improve the properties of the
melt-blown nonwoven fibrous web.
[0117] Non-limiting examples of suitable non-met-blown filling
fibers include single component synthetic fibers, semi-synthetic
fibers, polymeric fibers, metal fibers; carbon fibers, ceramic
fibers, and natural fibers. Synthetic and/or semi-synthetic
polymeric fibers include those made of polyester (i.e.,
polyethylene terephthalate), nylon (e.g., hexamethylene adipamide,
polycaprolactam), polypropylene, acrylic (formed from a (co)polymer
of acrylonitrile), rayon, cellulose acetate, polyvinylidene
chloride-vinyl chloride copolymers, vinyl chloride-acrylonitrile
copolymers, and the like.
[0118] Non-limiting examples of suitable metal fibers include
fibers made from any metal or metal alloy, for example, iron,
titanium, tungsten, platinum, copper, nickel, cobalt, and the
like.
[0119] Non-limiting examples of suitable carbon fibers include
graphite fibers, activated carbon fibers,
poly(acrylonitrile)-derived carbon fibers, and the like.
[0120] Non-limiting examples of suitable ceramic fibers include any
metal oxide, metal carbide, or metal nitride, including but not
limited to silicon oxide, aluminum oxide, zirconium oxide, silicon
carbide, tungsten carbide, silicon nitride, and the like.
[0121] Non-limiting examples of suitable natural fibers include
those of bamboo, cotton, wool, jute, agave, sisal, coconut,
soybean, hemp, and the like.
[0122] The fiber component used may be virgin fibers or recycled
waste fibers, for example, recycled fibers reclaimed from garment
cuttings, carpet manufacturing, fiber manufacturing, textile
processing, or the like.
[0123] The size and amount of discrete non-melt-blown filling
fibers, if included, used to form the nonwoven fibrous web, will
generally depend on the desired properties (i.e., loftiness,
openness, softness, drapability) of the nonwoven fibrous web 100
and the desired loading of the chemically active particulate.
Generally, the larger the fiber diameter, the larger the fiber
length, and the presence of a crimp in the fibers will result in a
more open and lofty nonwoven article. Generally, small and shorter
fibers will result in a more compact nonwoven article.
Optional Particulate Component
[0124] In certain exemplary embodiments, the nonwoven fibrous web
further comprises a plurality of particulates. Exemplary nonwoven
fibrous webs according to the present disclosure may advantageously
include a plurality of chemically active particulates. The
chemically active particulates can be any discrete particulate,
which is a solid at room temperature, and which is capable of
undergoing a chemical interaction with an external fluid phase.
Exemplary chemical interactions include adsorption, absorption,
chemical reaction, catalysis of a chemical reaction, dissolution,
and the like.
[0125] Additionally, in any of the foregoing exemplary embodiments,
the chemically active particulates may advantageously be selected
from sorbent particulates (e.g. adsorbent particulates, absorbent
particulates, and the like), desiccant particulates (e.g.
particulates comprising a hygroscopic substance such as, for
example, calcium chloride, calcium sulfate, and the like, that
induces or sustains a state of dryness in its local vicinity),
biocide particulates, microcapsules, and combinations thereof. In
any of the foregoing embodiments, the chemically active
particulates may be selected from activated carbon particulates,
activated alumina particulates, silica gel particulates anion
exchange resin particulates, cation exchange resin particulates,
molecular sieve particulates, diatomaceous earth particulates,
anti-microbial compound particulates, metal particulates, and
combinations thereof.
[0126] In one exemplary embodiment of a nonwoven fibrous web
particularly useful as a fluid filtration article, the chemically
active particulates are sorbent particulates. A variety of sorbent
particulates can be employed. Sorbent particulates include mineral
particulates, synthetic particulates, natural sorbent particulates
or a combination thereof. Desirably the sorbent particulates will
be capable of absorbing or adsorbing gases, aerosols, or liquids
expected to be present under the intended use conditions.
[0127] The sorbent particulates can be in any usable form including
beads, flakes, granules or agglomerates. Preferred sorbent
particulates include activated carbon; silica gel; activated
alumina and other metal oxides; metal particulates (e.g., silver
particulates) that can remove a component from a fluid by
adsorption or chemical reaction; particulate catalytic agents such
as hopcalite (which can catalyze the oxidation of carbon monoxide);
clay and other minerals treated with acidic solutions such as
acetic acid or alkaline solutions such as aqueous sodium hydroxide;
ion exchange resins; molecular sieves and other zeolites; biocides;
fungicides and virucides. Activated carbon and activated alumina
are presently particularly preferred sorbent particulates. Mixtures
of sorbent particulates can also be employed, e.g., to absorb
mixtures of gases, although in practice to deal with mixtures of
gases it may be better to fabricate a multilayer sheet article
employing separate sorbent particulates in the individual
layers.
[0128] In one exemplary embodiment of a nonwoven fibrous web
particularly useful as a gas filtration article, the chemically
active sorbent particulates are selected to be gas adsorbent or
absorbent particulates. For example, gas adsorbent particulates may
include activated carbon, charcoal, zeolites, molecular sieves, an
acid gas adsorbent, an arsenic reduction material, an iodinated
resin, and the like. For example, absorbent particulates may also
include naturally porous particulate materials such as diatomaceous
earth, clays, or synthetic particulate foams such as melamine,
rubber, urethane, polyester, polyethylene, silicones, and
cellulose. The absorbent particulates may also include
superabsorbent particulates such as sodium polyacrylates,
carboxymethyl cellulose, or granular polyvinyl alcohol.
[0129] In certain exemplary embodiments of a nonwoven fibrous web
partitularly useful as a liquid filtration article, the sorbent
particulates comprise liquid an activated carbon, diatomaceous
earth, an ion exchange resin (e.g. an anion exchange resin, a
cation exchange resin, or combinations thereof), a molecular sieve,
a metal ion exchange sorbent, an activated alumina, an
antimicrobial compound, or combinations thereof. Certain exemplary
embodiments provide that the web has a sorbent particulate density
in the range of about 0.20 to about 0.5.g/cc.
[0130] Various,sizes and amdunts of sorbent chemically active
particulates may be used to create a nonwoven fibrous web. In one
exemplary embodiment, the sorbent particulates have a mean size
greater than 1 mm in diameter; In an other exemplary embodiment,
the sorbent particulates have a mean size less than 1 cm in
diameter. In further embodiments; a combination of particulate
sizes can be used. In one exemplary additional embodiment, the
sorbent particulates include a mixture of large particulates and
small particulates.
[0131] The desired sorbent particulate size can vary a great deal
and usually will be chosen based in part on the intended service
conditions. As a general guide, sorbent particitlates partitularly
useful for filtration applications may vary in size from about
0.001.to about 3000 .mu.m mean diameter. Generally, the sorbent
particulates are from about 0.01 to about 1500 .mu.m mean diameter,
more generally from about 0.02 to about 750 .mu.m mean diameter,
and most generally from about 0.05 to about 300 .mu.5m mean
diameter.
[0132] In certain exemplary embodiments, the sorbent particulates
may comprise nano-particulates having a population mean diameter
less than 1 .mu.m. Porous nano-particulates may have the advantage
of providing high surface area for sorption of contaminants from a
fluid medium (e.g., absorption and/or adsorption). In such
exemplary embodiments using ultrafine or nano-particulates, it may
be preferred that the particulates are adhesively bonded to the
fibers using an adhesive, for example a hot melt adhesive, and/or
the application of heat to the melt-blown nonwoven fibrous web
(i.e., thermal bonding).
[0133] Mixtures (e.g., bimodal mixtures) of sorbent particulates
having different size ranges can also be employed, although in
practice it may be better to fabricate a multilayer sheet article
employing larger sorbent particulates in an upstream layer and
smaller sorbent particulates in a downstream layer. At least 80
weight percent sorbent particulates, more generally at least 84
weight percent and most generally at least 90 weight percent
sorbent are enmeshed in the web. Expressed in terms of the web
Basis Weight, the sorbent particulate loading level may for example
be at least about 500 gsm for relatively fine (e.g.,
sub-micrometer-sized) sorbent particulates, and at least about
2,000 gsm for relatively coarse (e.g., micron-sized) sorbent
particulates.
[0134] In some exemplary embodiments, the chemically active
particulates are metal particulates. The metal particulates may be
used to create a polishing nonwoven fibrous web. The metal
particulates may be in the form of short fiber or ribbon-like
sections or may be in the form of grain-like particulates. The
metal particulates can include any type of metal such as but not
limited to silver (which has antibacterial/antimicrobial
properties), copper (which has properties of an algaecide), or
blends of one or more of chemically active metals.
[0135] In other exemplary embodiments, the chemically active
particulates are solid biocides or antimicrobial agents. Examples
of solid biocide and antimicrobial agents include halogen
containing compounds such as sodium dichloroisocyanurate dihydrate,
benzalkonium chloride, halogenated dialkylhydantoins, and
triclosan.
[0136] In further exemplary embodiments, the chemically active
particulates are microcapsules. Microcapsules are described in U.S.
Pat. No. 3,516,941 (Matson), and include examples of the
microcapsules that can be used as the chemically active
particulates. The microcapsules may be loaded with solid or liquid
biocides or antimicrobial agents. One of the main qualities of a
microcapsule is that by means of mechanical stress the particulates
can be broken in order to release the material contained within
them. Therefore, during use of the nonwoven fibrous web, the
microcapsules will be broken due to the pressure exerted on the
nonwoven fibrous web, which will release the material contained
within the microcapsule.
[0137] In certain such exemplary embodiments, it may be
advantageous to use at least one particulate that has a surface,
that can be made adhesive or "sticky" so as to bond together the
particulates to form a mesh or support nonwoven fibrous web for the
fiber component. In this regard, useful particulates may comprise a
(co)polymer, for example, a thermoplastic (co)polymer, which may be
in the form of discontinuous fibers. Suitable polymers include
polyolefins, particularly thermoplastic elastomers (TPE's) (e.g.,
VISTAMAXX.TM., available from Exxon-Mobil. Chemical Company,
Houston, Tex.). In further exemplary embodiments, particulates
comprising a TPE, particularly as a surface layer or surface
coating, may be preferred, as TPE's are generally somewhat tacky,
which may assist bonding together of the particulates to form a
three-dimensional network before addition of the fibers to form the
nonwoven fibrous web. In certain exemplary embodiments,
particulates comprising a VISTAMAXX.TM. TPE may offer improved
resistance to harsh chemical environments, particularly at low pH
(e.g, pH no greater than about 3) and high pH (e.g., pH of at least
about 9) and in organic solvents.
[0138] Any suitable size or shape of particulate material may be
selected. Suitable particulates may have .a variety of physical
forms (e.g, solid particulates, porous particulates, hollow
bubbles, agglomerates, discontinuous fibers, staple fibers, flakes,
and the like); shapes (e.g., spherical, elliptical, polygonal,
needle-like, and the like); shape uniformities (e.g. monodisperse,
substantially. uniform, non-uniform or irregular; and the like);
composition (e,g. inorganic particulates, organic particulates, or
combination thereof); and size (e.g., sub-micrometer-sized,
micro-sized, and the like).
[0139] With particular reference to particulate size, in some
exemplary embodiments, it may be desirable to control the size of a
population of the particulates. In certain exemplary embodiments,
particulates are physically entrained or trapped in the fiber
nonwoven fibrous web. In such embodiments, the population of
particulates is generally selected to have a mean diameter of at
least 50 .mu.m, more generally at least 7.5 .mu.m, still more
generally at least 100 .mu.m.
[0140] In other exemplary embodiments, it may be preferred to use
finer particulates that are adhesively bonded to the fibers using
an adhesive, for example a hot melt adhesive, and/or the
application of heat to one or both of thermoplastic particulates or
thermoplastic fibers (i.e., thermal bonding). In such embodiments,
it is generally preferred that the particulates have a mean
diameter of at least 25 .mu., more generally at least 30 .mu.m,
most generally at least 40 .mu.m. In some exemplary embodiments,
the chemically active particulates have a mean size less than 1 cm
in diameter. In other embodiments, the chemically active
particulates have a mean size of less than 1 mm, more generally
less than 25 micrometers, even more generally less than 10
micrometers.
[0141] However, in other exemplary embodiments in which both an
adhesive and thermal bonding are used to adhere the particulates to
the fibers, the particulates may comprise a population of
sub-micrometer-sized particulates having a population mean diameter
of less than one micrometer (.mu.m) more generally less than about
0.9 .mu.m, even more generally less than about 0.5 .mu.m, most
generally less than about 0.25 .mu.m. Such sub-micrometer-sized
particulates may be particularly useful in applications where high
surface area and/or high absorbency and/or adsorbent capacity is
desired. In further exemplary embodiments the population of
sub-micrometer-sized particulates has a population mean diameter of
at least 0.001 .mu.m, more generally at least about 0.1 .mu.m, most
generally at least about 0.1 .mu.m, most generally at least 0.2
.mu.m.
[0142] In further exemplary embodiments, the particulates comprise
a population of micro-sized particulates having a population mean
diameter of at most about 2,000 .mu.m, more generally at most about
1,000 .mu.gm, most generally at most about 500 .mu.m. In other
exemplary embodiments, the particulates comprise a population of
micro-sized particulates having a population mean diameter of at
most about 10 .mu.m, more generally at most about 5 .mu.m, even
more generally at most about 2 .mu.m (e.g., ultrafine
micro-fibers).
[0143] Multiple types of particulates may also be used within a
single finished web. Using multiple types of particulates, it may
be possible to generate continuous particulate webs even if one of
the particulate types does not bond with other particulates of the
same type. An example of this type of system would be one where two
types are particulates are used, one that bonds the particulates
together (e.g., a discontinuous polymeric fiber particulate), and
another that acts as an active particulate for the desired purpose
of the web (e.g., a sorbent particulate such as activated carbon).
Such exemplary embodiments may be particularly useful for fluid
filtration applications.
[0144] Depending, for example, on the density of the chemically
active particulate, size of the chemically active particulate,
and/or desired attributes of the final nonwoven fibrous web
article, a variety of different loadings of the chemically active
particulates may be used relative to the total weight of the
fibrous web. In one embodiment, the chemically active particulates
comprise less than 90% wt. of the total nonwoven article weight. In
one embodiment, the chemically active particulates comprise at
least 10% wt. of the total nonwoven article weight.
[0145] In any of the foregoing embodiments, the chemically active
particulates may be advantageously distributed throughout the
entire thickness of the nonwoven fibrous web. However, in some of
the foregoing embodiments, the chemically active particulates are
preferentially distributed substantially on a major surface of the
nonwoven fibrous web.
[0146] Furthermore, it is to be understood that any combination one
or more of the above described chemically active particulates maybe
used to form nonwoven fibrous webs according to the present
disclosure.
Processes for Forming Fibers
[0147] In another aspect, the present disclosure describes a
process for making a nonwoven fibrous web, comprising heating a
mixture of about 50% w/w to about 99% w/w of a crystalline
polyolefin (co)polymer, and from about 1% w/w to about 40% w/w of a
hydrocarbon tackifies resin to at least a Melting Temperature of
the mixture to form a molten mixture, extruding the molten mixture
through at least one orifice to form at least one filament,
applying a gaseous stream to the at least one filament to attenuate
the at least one filament to form a plurality of discrete,
discontinuous fibers, and cooling the plurality of discrete
discontinuous fibers to a temperature below the Melting Temperature
of the molten mixture to form a nonwoven fibrous web, wherein at
least one of the crystalline polyolefin (co)polymer or the nonwoven
fibrous web exhibits a Heat of Fusion measured using Differential
Scanning Calorimetry of greater than 50 Joules/g.
[0148] A number of processes may be used to produce a microfiber
stream, including, but not limited to, melt-blowing, gas jet
fibrillation, or a combination thereof. Suitable processes for
forming microfibers are described in U.S. Pat. Nos. 6,315,806
(Torobin), 6,114,017 (Fabbricante et al.), 6,382,526 B1 (Reneker et
al.), and 6,861.025 B2 (Erickson et al.).
[0149] Alternatively, a population of microfibers may be formed or
converted to staple fibers and combined with a population of
sub-micrometer fibers using, for example, using a process as
described in U.S. Pat. No. 4,118,531 (Hauser).
[0150] A number of processes may be used advantageously to produce
a sub-micrometer fiber stream from the molten (co)polymer mixture,
including, but not limited to meIt-blowing, gas jet fibrillation,
or a combination thereof. Particularly suitable processes include,
but are not limited to, processes disclosed in U.S. Pat. Nos.
3,874,886 (Levecque et al.), 4,363,646 (Torobin), 4,536,361
(Torobin), 5,227,107 (Dickenson et al.), 6,183,670 (Torobin),
6,269,513 (Torobin), 6,315,806 (Torobin), 6,743,273 (Chung et al.),
6,800,226 (Gerking) and 9,382,643 (Moore et al.); German Patent DP
19929709 C2 (Gerking); Pub. PCT App. No. WO 2007/001990 A2 (Krause
et al.).
[0151] Sub-micrometer fibers separately formed using processes
other than melt-blowing and/or gas jet fibrillation may also be
combined with a population of microfibers and/or sub-micrometer
fibers formed by melt-blowing and/or gas jet fibrillation. Suitable
processes for separately forming sub-micrometer include
electrospinning processes, for example, those processes described
in U.S. Pat. No. 1,975,504 (Formhals).
[0152] Other suitable processes for forming sub-micrometer fibers
are described in U.S. Pat. Nos. 6,114,017 (Fabbricante et al.),
6,382,526 B1 (Reneker et al.); and 6,861,025 B2 (Erickson et
al.).
Melt-Blowing Processes
[0153] In the melt-blowing process, the crystalline polyolefin
(co)polymer/hydrocarbon resin tackifier mixture is melted to form a
molten mixture, which is then extruded through one or more orifices
of a melt-blowing die, applying a gaseous stream to the at least
one filament to attenuate the at least one filament to form a
plurality of discrete, discontinuous fibers.
[0154] In any of the foregoing processes, the melt-blowing should
be performed within a range of temperatures hot enough to enable
the crystalline polyolefin (co)polymer/hydrocarbon resin tackifier
mixture to be melt-blown but not so hot as to cause unacceptable
deterioration of the crystalline polyolefin (co)polymer/hydrocarbon
resin tackifier mixture. For example, the melt-blowing can be
performed at a temperature that causes the molten mixture of the
crystalline polyolefin (co)polymer and hydrocarbon resin tackifier
to reach a processing temperature at least 40-50.degree. C. above
the melting temperature.
[0155] Preferably, the processing temperature of the molten mixture
is selected to be 200.degree. C., 225.degree. C., 250.degree. C.,
260.degree. C., 270.degree. C., 280.degree. C., or even at least
290.degree. C.; to less than or equal to about 360.degree. C.,
350.degree. C., 340.degree. C., 330.degree. C., 320.degree. C.,
310.degree. C., or even 300.degree. C.
Processes for Forming Composite Nonwoven Fibrous Webs
[0156] In some such exemplary embodiments, the process further
includes at least one of addition of a plurality of staple fibers
to the plurality of discrete, discontinuous fibers, or addition of
a plurality of particulates to the plurality of discrete,
discontinuous fibers, to form a composite nonwoven fibrous web.
[0157] In some exemplary embodiments, the method of making a
composite nonwoven fibrous web comprises combining the microfiber
or coarse microfiber population with the fine microfiber
population, the ultrafine microfiber population, or the
sub-micrometer fiber population by mixing fiber streams,
hydroentangling, wet forming, plexifilament formation, or a
combination thereof.
[0158] In combining the microfiber or coarse microfiber population
with the fine, ultrafine or sub-micrometer fiber populations,
multiple streams of one or both types of fibers may be used, and
the streams may be combined in any order. In this manner, nonwoven
composite fibrous webs may be formed exhibiting various desired
concentration gradients and/or layered structures.
[0159] For example, in certain exemplary embodiments, the
population of fine, ultrafine or sub-micrometer fibers may be
combined with the population of microfibers or coarse microfibers
to form an inhomogenons mixture of fibers. In certain exemplary
embodiments, at least a portion of the population of fine,
ultrafine, or sub-micrometer fibers is intermixed with at least a
portion of the population of microfibers. In other exemplary
embodiments, the population of fine, ultrafine or sub-micrometer
fibers maybe formed as an overlayer on an underlayer comprising the
population of microfibers. In certain other exemplary embodiments,
the population of microfibers may be formed as an overlayer or an
underlayer comprising the population of fine, ultrafine or
sub-micrometer fibers.
Optional Particulate Loading Processes
[0160] In many applications, substantially uniform distribution of
particles throughout the web is desired. There may also be
instances where non-uniform distributions may be advantageous. In
certain exemplary embodiments, a particulate density gradient may
advantageously be created within the composite nonwoven fibrous
web. For example, gradients through the depth of the web may create
changes to the pore size distribution that could be used for depth
filtration. Webs with a surface loading of particles could be
formed into a filter where the fluid is exposed to the particles
early in the flow path and the balance of the web provides a
support structure and means to prevent sloughing of the particles.
The flow path could also be reversed so the web can act as a
pre-filter to remove some contaminants prior to the fluid reaching
the active surface of the particles.
[0161] Various methods are known for adding a stream of
particulates to a nonwoven fiber stream. Suitable methods are
described in U.S. Pat. Nos. 4,118,531 (Hauser), 6,872,311 (Koslow),
and 6,494,974 (Riddell); and in U.S. Patent Application Publication
Nos. 2005/0266760 (Chhabra and Isele), 2005/0287891 (Park) and
2006/0096911 (Grey et al.).
[0162] In other exemplary embodiments, the optional particulates
could be added to a nonwoven fiber stream by air laying a fiber
web, adding particulates to the fiber web (e.g., by passing the web
through a fluidized bed of particulates), optionally with post
heating of the particulate-loaded web to bond the particulates to
the fibers. Alternatively, a pre-formed web could be sprayed with a
pre-formed dispersion of particulates in a volatile fluid (e.g. an
organic solvent, or even water), optionally with post heating of
the particulate-loaded web to remove the volatile fluid and bond
the particulates to the fibers.
[0163] In further exemplary embodiments, the process further
includes collecting the plurality of discrete, discontinuous fibers
as the nonwoven fibrous web on a collector. In certain such
exemplary embodiments, the composite nonwoven fibrous web may be
formed by depositing the population of fine, ultrafine or
sub-micrometer fibers directly onto a collector surface; or onto an
optional support layer on the collector surface, the support layer
optionally comprising microfibers, so as to form a population of
fine; ultrafine or sub-micrometer fibers on the porous support
layer.
[0164] The process may include a step wherein the optional support
layer, which optionally may comprise polymeric microfibers, is
passed through a fiber stream of fine, ultrafine or sub-micrometer
fibers. While passing through the fiber stream, fine, ultrafine or
sub-micrometer fibers may be deposited onto the support layer so as
to be temporarily or permanently bonded to the support layer. When
the fibers are deposited onto the support layer, the fibers may
optionally bond to one another, and may further harden While on the
support layer.
[0165] In certain exemplary embodiments, the fine, ultrafine or
sub-micrometer fiber population is combined with an optional porous
support layer that comprises at least a portion of the coarse
microfiber population. In some exemplary embodiments, the
microfibers forming the porous support layer are compositionally
the same as the population of microfibers that forms the first
layer. In other presently preferred embodiments, the fine,
ultrafine or sub-micrometer fiber population is combined with an
optional porous support layer and subsequently combined with at
least a portion of the coarse microfiber population. In certain
other presently preferred embodiments, the porous support layer
adjoins the second layer opposite the first layer.
[0166] In other exemplary embodiments, the porous support layer
comprises a nonwoven fabric, a woven fabric, a knitted fabric, a
foam layer, a screen, a porous film, a perforated film, an array of
filaments; or a combination thereof. In some exemplary embodiments,
the porous support layer comprises a thermoplastic mesh.
Optional Processing Steps
[0167] In some embodiments, the process further includes processing
the collected nonwoven fibrous web using a process selected from
autogenous bonding (e.g., through-air bonding, calendering, and the
like), electret charging, embossing, needle-punching, needle
tacking, hydroentangling, or a combination thereof.
Optional Bonding Processes
[0168] Depending on the condition of the fibers and the relative
proportion of microfibers and sub-micrometer fibers, some bonding
may occur between the fibers themselves (e.g., autogenous bonding)
and between the fibers and any optional particulates, before or
during collection. However, further bonding between the fibers
themselves and between the fibers and any optional particulates in
the collected web may be desirable to provide a matrix of desired
coherency, making the web more handle-able and better able to hold
any sub-micrometer fibers within the matrix ("bonding" fibers,
themselves means adhering the fibers together firmly, so they
generally do not separate when the web is subjected to normal
handling).
[0169] In certain exemplary embodiments, a blend of microfibers and
sub-micrometer fibers may be bonded together. Bonding may be
achieved, for example, using thermal bonding, adhesive bonding,
powdered binder, hydroentangling, needle-punching, calendering, or
a combination thereof. Conventional bonding techniques using heat
and pressure applied in a point-bonding process or by smooth
calender rolls can be used, though such processes may cause
undesired deformation of fibers or excessive compaction of the
web.
[0170] A presently preferred technique for bonding fibers,
particularly microfibers, is the autogenous bonding method
disclosed in U.S. Patent Application Publication No. U.S.
200810038976 A1.
Optional Electret Charging Processes
[0171] In some particular embodiments, the melt-blown fibers may be
advantageously electrostatically charged. Thus, in certain
exemplary embodiments, the melt-blown fibers may be subjected to an
electret charging process. An exemplary electret charging process
is hydro-charging. Hydro-charging of fibers may be carried out
using a variety of techniques including impinging, soaking or
condensing a polar fluid onto the fiber, followed by drying, so
that the fiber becomes charged. Representative patents describing
hydro-charging include U.S. Pat. Nos. 5,496,507; 5,908,598;
6,375,886 B1; 6,406,657 B1; 6,454,986 and 6,743,464 B1. Preferably
water is employed as the polar hydro-charging liquid, and the media
preferably is exposed to the polar hydro-charging liquid using jets
of the liquid or a stream of liquid droplets provided by any
suitable spray means.
[0172] Devices useful for hydraulically entangling fibers are
generally useful for carrying out hydro-charging, although the
operation is carried out at lower pressures in hydro-charging than
generally used in hydro-entangling. U.S. Pat. No. 5,496,507
describes an exemplary apparatus in which jets of water or a stream
of water droplets are impinged upon the fibers in web form at a
pressure sufficient to provide the subsequently-dried media with a
filtration-enhancing electret charge.
[0173] The pressure necessary to achieve optimum results may vary
depending on the type of sprayer used, the type of (co)polymer from
which the fiber is formed, the thickness and density of the web,
and whether pretreatment such as corona charging was carried out
before hydro-charging. Generally, pressures in the range of about
69 kPa to about 3450 kPa are suitable. Preferably, the water used
to provide the water droplets is relatively pure. Distilled or
deionized water is preferable to tap water.
[0174] The electret fibers may be subjected to other charging
techniques in addition to or alternatively to hydro-charging,
including electrostatic charging (e.g., as described in U.S. Pat.
Nos. 4,215,682, 5,401,446 and 6,119,691), tribo-charging (e.g., as
described in U.S. Pat. No. 4,798,850) or plasma fluorination (e.g.,
as described in U.S. Pat. No. 6,397,458 131). Corona charging
followed by hydro-charging and plasma fluorination followed by
hydro-charging are particularly suitable charging techniques used
in combination.
Optional Post-Collection Processing Steps
[0175] Various processes conventionally used as adjuncts to
fiber-forming processes may be used in connection with fibers as
they exit from one or more orifices of the belt blowing die. Such
processes include spraying of finishes, adhesives or other
materials onto the fibers, application of an electrostatic charge
to the fibers, application of water mists to the fibers, and the
like. In addition, various materials may be added to a collected
web, including bonding agents, adhesives, finishes, and other webs
or films. For example, prior to collection, extruded fibers or
fibers may be subjected to a number of additional processing steps,
e.g., further drawing, spraying, and the like. Various fluids may
also be advantageously applied to the fibers before or during
collection, including water sprayed onto the fibers, e.g., heated
water or steam to heat the fibers, or cold water to quench the
fibers.
[0176] After collection, the collected mass may additionally or
alternatively be wound into a storage roll for later processing if
desired. Generally, once the collected melt-blown nonwoven fibrous
web has been collected, it may be conveyed to other apparatus such
as a calender, embossing stations, laminators, cutters and the
like; or it may be passed through drive rolls and wound into a
storage roll.
[0177] Thus, in addition to the foregoing methods of making and
optionally bonding or electret charging a nonwoven fibrous web, one
or more of the following process steps May optionally be carried
out on the web once formed:
[0178] (1) advancing the composite nonwoven fibrous web along a
process pathway toward further processing operations;
[0179] (2) bringing one or more additional layers into contact with
an outer surface of the sub-micrometer fiber component, the
microfiber component, and/or the optional support layer;
[0180] (3) calendering the composite nonwoven fibrous web;
[0181] (4) coating the composite nonwoven fibrous web with a
surface treatment or other composition (e.g., a fire-retardant
composition, an adhesive composition, or a print layer);
[0182] (5) attaching the composite nonwoven fibrous web to a
cardboard or plastic tube;
[0183] (6) winding-up the composite nonwoven fibrous web in the
form of a roll;
[0184] (7) slitting the composite nonwoven fibrous web to form two
or more slit rolls and/or a plurality of slit sheets;
[0185] (8) placing the composite nonwoven fibrous web in a mold and
molding the composite nonwoven fibrous web into a new shape;
and
[0186] (9) applying a release liner over an exposed optional
pressure-sensitive adhesive layer, when present.
Articles Incorporating Nonwoven Fibrous Webs
[0187] Nonwoven fibrous webs can be made using the foregoing
processes. In some exemplary embodiments, the nonwoven fibrous web
or composite web takes the form of a mat, web, sheet, a scrim, or a
combination thereof.
[0188] In some particular exemplary embodiments, the nonwoven
fibrous web or composite web may advantageously include charged
melt-blown fibers, e.g., electret fibers. In certain exemplary
embodiments, the melt-blown nonwoven fibrous web or web is porous.
In some additional exemplary embodiments, the nonwoven fibrous web
or composite web may advantageously be self-supporting. In further
exemplary embodiments, the melt-blown nonwoven fibrous web or
composite web advantageously may be pleated, e.g., to form a
filtration medium, such as a liquid (e.g., water) or gas (e.g.,
air) filter, a heating, ventilation or air conditioning (HVAC)
filter, or a respirator for personal protection. For example, U.S.
Pat. No. 6,740,137 discloses nonwoven webs used in a collapsible
pleated filter element.
[0189] Webs of the present disclosure may be used by themselves,
e.g., for filtration media, decorative fabric, or a protective or
cover stock. Or they may be used in combination with other webs or
structures, e.g., as a support for other fibrous layers deposited
or laminated onto the web, as in a multilayer filtration media, or
a substrate onto which a membrane may be cast. They may be
processed after preparation as by passing them through smooth
calendering rolls to form a smooth surfaced web, or through shaping
apparatus to form them into shapes.
[0190] A nonwoven fibrous web or composite web of the present
disclosure can further comprise at least one or a plurality of
other types of fibers (not shown) such as, for example, staple or
otherwise discontinuous fibers, melt spun continuous fibers or a
combination thereof. The present exemplary fibrous webs can be
formed, for example, into a non-woven web that can be wound about a
tube or other core to form a roll, and either stored for subsequent
processing or transferred directly to a further processing step.
The web may also be cut into individual sheets or mats directly
after the web is manufactured, or sometime thereafter.
[0191] The melt-blown nonwoven fibrous webs or composite webs can
be used to make any suitable article such as, for example, a
thermal insulation article, an acoustic insulation article, a fluid
filtration article, a wipe, a surgical drape, a wound dressing, a
garment, a respirator, or a combination thereof. The thermal or
acoustic insulation articles may be used as an insulation component
for vehicles. (e.g.,trains, airplanes, automobiles and boats).
Other articles such as, for example, bedding, shelters, tents,
insulation, insulating articles, liquid and gas filters, wipes,
garments, garment components, personal protective equipment,
respirators, and the like, can also be made using melt nonwoven
fibrous webs of the present disclosure.
[0192] Flexible, drape-able and compact nonwoven fibrous webs maybe
preferred for certain applications, for examples as furnace filters
or gas filtration respirators. Such nonwoven fibrous webs typically
have a density greater than 75 kg/m.sup.3 and typically greater
than 100 kg/m.sup.3 or even 120 kg/m.sup.3. However, open, lofty
nonwoven fibrous webs suitable for use in certain fluid filtration
applications generally have a maximum density of 60 kg/m.sup.3.
[0193] Thus, in certain exemplary embodiments, the nonwoven fibrous
webs exhibit a Basis Weight of from 1 gsm to 400 gsm, more
preferably from 1 gsm to 200 gsm, even more preferably from 1 gsm
to 100 gsm, or even 1 gsm to about 50 gsm.
[0194] Certain presently-preferred nonwoven fibrous webs according
to the present disclosure may have a Solidity less than 50%, 340%,
30%, 20%, or more preferably less than 15%; even more preferably
less than10%.
[0195] The operation of the processes of the present disclosure to
produce nonwoven fibrous webs as described herein, will be further
described with regard to the following detailed examples. These
examples are offered to further illustrate the various specific and
preferred embodiments and techniques. It should be understood,
however, that many variations and modifications may be made while
remaining within the scope of the present disclosure.
EXAMPLES
[0196] These Examples are merely for illustrative purposes and are
not meant to be overly limiting on the scope of the appended
claims. Notwithstanding that the numerical ranges and parameters
setting forth the broad scope of the present disclosure are
approximations, the numerical values set forth in the specific
examples are reported as precisely as possible. Any numerical
value, however, inherently contains certain errors necessarily
resulting from the standard deviation found in the respective
testing measurements. At the very least, and not as an attempt to
limit the application of the doctrine of equivalents to the scope
of the claims, each numerical parameter should at least be
construed in light of the number of reported significant digits and
by applying ordinary rounding techniques.
Summary of Materials
[0197] Unless otherwise noted, all parts, percentages, ratios, etc.
in the Examples and the rest of the specification are by weight.
Solvents and other reagents used may be obtained from Sigma-Aldrich
Chemical Company (Milwaukee, Wis.).
Test Methods
[0198] The following test methods have been used in evaluating some
of the Examples of the present disclosure,
Tensile Strength Test
[0199] The tensile properties of webs in the Examples were measured
by pulling to failure a 1 inch by 6 inch sample (2.5 cm by 15.2
cm). The thickness of the nonwoven fibrous web samples was about
0.15 cm. The Tensile Strength. Test was carried out using
commercially available tensile test apparatus designated as Instron
Model 5544, available from Instron Company (Canton, Mass.). The
gauge length was 4 inches (10.2 cm), and the cross-head speed was
308 millimeters/per minute. The. Maximum Tensile Load (in Newtons)
was determined in the machine direction of the nonwoven fibrous
web.
Actual Fiber Diameter
[0200] The Actual Fiber Diameter (AFD) was determined using a
Scanning Electron Microscope (SEM). The samples were sputter coated
with gold in a vacuum chamber (Denton Vacuum, Moorestown, N.J.).
The specimens were then analyzed using a Phenom Pure SEM
(Phenom-World, Eindhoven, Netherlands). The AFD is the average
(mean) number diameter determined from measurements taken on 500
individual fibers in the nonwoven fibrous web sample using.
SEM.
Effective Fiber Diameter
[0201] The Effective Fiber Diameter (EFD) was determined using an
air flow rate of 32 L/min (corresponding to a face velocity of 5.3
cm/sec), using the method set forth in Davies, C. N., "The
Separation of Airborne Dust and Particles," Institution of
Mechanical Engineers, London, Proceedings IB. 1952.
Actual Fiber Diameter
[0202] The Actual Fiber Diameter (AFD) was determined using a
Scanning Electron Microscope (SEM). The samples were sputter coated
in a vacuum chamber (Denton Vacuum, Moorestown, N.J.). The
specimens were then analyzed using a Phenom Pure SEM (Phenom-World,
Eindhoven, Netherlands). The AFD is the average (mean) fiber
diameter determined from measurement of 500 individual fibers.
Differential Scanning Calorimtry (Melting Temperature and Heat of
Fusion)
[0203] Differential Scanning Calorimetry (DSC) was used to
determine the Melting Temperature and Heat of Fusion of the
crystalline polyolefin, the mixture of the crystalline polyolefin
with the hydrocarbon tackifier resin, and the nonwoven fibrous webs
produced from the mixture.
[0204] The DSC analysis was carried out using a Model DSC Q2000
available from Ta Instruments Co. (New Castle, Del.). Approximately
1.5 mg to 10 mg of the crystalline polyolefin, the mixture of the
crystalline polyolefin with the hydrocarbon tackifier resin, or the
nonwoven fibrous web produced from the mixture, was loaded and
sealed in an aluminum pan and placed in the DSC Q2000
apparatus.
[0205] DSC measurements on each sample was carried out using the
following sequential Heating-Cooling-Heating cycle. Each sample was
initially heated from -20.degree. C. to 250.degree. C. (or at least
30.degree. C. above the Melting Temperature of the sample) at a
rate of 10.degree. C./minute. Each sample was then held for 1
minute at 250.degree. C., and then subsequently cooled down to
-20.degree. C. (or at least 50.degree. C. below the crystallization
temperature of the sample) at a rate of 20.degree. C./min. Each
sample was then held for 1 minute at -20.degree. C. and then
subsequently heated from -20.degree. C. to 200.degree. C. at
10.degree. C./min.
[0206] The temperature corresponding to the highest-temperature
endothermic peak was reported as the Melting Temperature (.degree.
C.), and the area tinder the same highest-temperature endothermic
peak was reported as the Heat of Fusion.
EXAMPLES OF BLOWN MICROFIBER (BMF) AND COMPOSITE BMF WEBS
[0207] The following illustrate Examples of the preparation of
various nonwoven fibrous webs prepared according to the processes
described in the present disclosure, as well as Comparative
Examples.
Comparative Example C-1
[0208] A melt-blown (blown microfiber, BMF) nonwoven fibrous web
was made using a crystalline polypropylene (crystalline polyolefin
(co)polymer) resin having a 1200 melt flow rate (MFR), commercially
available as METOCENE.TM. MF650X from Lyondell-Basell (Houston,
Tex.X). A conventional melt-blowing process was employed, similar
to that described, for example, in Wente, Van A., "Superfine
Thermoplastic Fibers" in Industrial Engineering Chemistry, Vol.48,
pages 1342 et seq. (1956) or in Report No.4364 of the Naval
Research Laboratories, published May 25, 1954, entitled
"Manufacture of Superfine Organic Fibers" by Wente, Van A.; Boone,
C. D.; and Fluharty, E. L.
[0209] More particularly, the melt-blowing die had circular smooth
surfaced orifices, spaced 10 to the centimeter, with a 5:1 Length
to diameter ratio. Molten (c)polymer was delivered to the die by a
20 mm twin screw extruder commercially available from Steer of
Uniontown, Ohio. This extruder was equipped with two weight loss
feeders to control the feeding of the (co)polymer resins to the
extruder barrel, and a gear pump to control the (co)polymer melt
flow to a die. The extruder temperature was at about 250.degree. C.
and it delivered the melt stream to the BMF die, which itself
maintained at 250.degree. C. The gear pump was adjusted so that a
0.268 kg/hr/cm die (1.5 lb/hr/inch die width) (co)polymer
throughput rate was maintained at the die. The primary air
temperature of the air knives adjacent to the die orifices was
maintained at approximately 325.degree. C.
[0210] This produced a web on a rotating collector spaced 43 cm
from the die. The web had a Basis Weight of approximately 55
g/m.sup.2. Significant fly was visually observed with the un-aided
human eye under illumination with fluorescent lighting at a
distance of about 30 cm.
Example 1
[0211] A BMF web was prepared generally as described in Comparative
Example C-1, except that the polymer was a blend at a (95/5) ratio
of METOCENE.TM. MF650X and a hydrocarbon tackifier resin
commercially available as OPPERA.TM. PR100A from Exxon Mobil Corp.
of Irving, Tex. The web thus produced had b. Basis Weight of
approximately 55 g/m.sup.2, and a Solidity of approximately 4.37%.
No fly was visually observed with the un-aided human eye under
illumination with fluorescent lighting at a distance of about 30
cm.
Example 2
[0212] A BMF web was made as described in Example 1, except that
the extruder temperature was about 275.degree.C., the BMF die was
maintained at approximately 275.degree. C. and the primary air
temperature was at approximately 375.degree. C. No fly was visually
observed with the un-aided human eye under illumination with
fluorescent lighting at a distance of about 30 cm.
Example 3
[0213] A BMF web was made as described iii Example 1, except that
the extruder temperature was about 285.degree. C., the BMF die was
maintained at approximately 285.degree. C. and the primary air
temperature was at approximately 375.degree. C. No fly was visually
observed with the un-aided human eyp under illumination with
fluorescent lighting at a distance olabout 30cm.
Example 4
[0214] A BMF web was made as described in Example 3, except that
the web was made using a blend of METOCENE.TM. MF650X and
OPPERA.TM. PR100A at a (90/10) ratio. No fly was visually observed
with the un-aided human eye under illumination with fluorescent
lighting at a distance of about 30 cm.
Example 5
[0215] A BMF web was made as described in Example 4, except web was
collected at2 BMF die to collector distance of 35.6 cm. No fly was
visually observed with the un-aided human eye under illumination
with fluorescent lighting ata distance of about 34 cm.
Example 6
[0216] A BMF web was made as described in Example 5, except that
the web was made using a blend of METOCENE.TM. MF650X and
OPPERA.TM. PR100A ata (85/15) ratio. No fly was visually observed
with the un-aided human eye under illumination with fluorescent
lighting at a distance of about 30 cm.
Example 7
[0217] A BMF web was made as described in Example 5, except that
the extruder temperature was about 295.degree. C., the. BMF die was
maintained at approximately 295.degree. C. and the primary air
temperature was at approximately 400.degree. C. No fly was visually
observed with the un-aided human eye under illumination with
fluorescent lighting at a distance of about 30 cm.
Example 8
[0218] A BMF web was made as described in Example 6, except that
the extruder temperature was about 295.degree. C., the BMF die was
maintained at approximately 295.degree. C. and the primary air
temperature was at approximately 400.degree. C. No fly was visually
observed with the un-aided human eye under illumination with
fluorescent lighting at a distance of about 30 cm.
[0219] Exemplary results for Comparative Example C-1 and Examples
1-8 are summarized in Table 1.
TABLE-US-00001 TABLE 1 Maximum Die (Melt) Distance Tensile
Temperature of the Load in (.degree. C.) and Die from the [Heat of
the Machine Fusion Collector Direction Example (Joules/g] (inches)
EFD (MD) Number Material by DSC [cm] (micrometers) (N) C-1 PP 650 X
250 17 8.5 5.4 [43.18] 1 PP 650 X/ 250 17 9.3 8.9 OPPERA .TM.
[43.18] 100 (95%/5% w/w) 2 PP 650 X/ 275 17 5.7 7.5 OPPERA .TM.
[43.18] 100 (95%/5% w/w) 3 PP 650 X/ 285 17 5.1 7.6 OPPERA .TM.
[43.18] 100 (95%/5% w/w) 4 PP 650 X/ 285 17 5.4 8.7 OPPERA .TM.
[43.18] 100 (90%/10% w/w) 5 PP 650 X/ 285 14 5.2 8.8 OPPERA .TM.
[35.56] 100 (90%/10% w/w) 6 PP 650 X/ 285 14 5.1 9.3 OPPERA .TM.
[35.56] 100 (85%/15% w/w) 7 PP 650 X/ 295 14 4.8 8.9 OPPERA .TM.
[35.56] 100 (90%/10% w/w) 8 PP 650 X/ 295 14 4.7 9.4 OPPERA .TM.
[35.56] 100 (85%/15% w/w)
Comparative Example C-2
[0220] A BMF web was made as described in Comparative Example C-1,
except for the following details. The polymer used was a
polypropylene resin commercially available as METOCENE.TM. MF650Y
from Lyondell-Basell (Houston. Tex.). The extruder temperature was
approximately 255.degree. C. and it delivered the METOCENE.TM.
MF650X melt stream to the BMF die maintained at 255.degree. C. The
primary air temperature was maintained at approximately 335.degree.
C. The die to collector distance was about 17 inches (43.18
cm).
[0221] Significant fly was visually observed with the un-aided
human eye under illumination with fluorescent lighting at a
distance of about 30 cm.
Example 9
[0222] A BMF web was generally as described in Comparative Example
C-2, except for the following details. The polymer was a blend at a
(95/5) ratio of METOCENE.TM. MF650Y and a hydrocarbon tackifier
resin commercially available as OPPERA.TM. PR100A from Exxon Mobil
Corp. of Irving, Tex. The extruder temperature was approximately
260.degree. C. and it delivered the blend melt stream to the BMF
die maintained at 260.degree. C. The primary air temperature was
maintained at approximately 335.degree. C. The resulting web had a
Basis Weight of approximately 55 g/m.sup.2. No fly was visually
observed with the un-aided human eye under illumination with
fluorescent lighting at a distance of about 30 cm.
Example 10
[0223] A BMF web was made as described in Example. 9, except that
the blend ratio of METOCENE.TM. MF650Y to OPPERA.TM. PR100A was
(90/10). No fly was visually observed with the un-aided human eye
under illumination with fluorescent lighting ata distance of about
30 cm.
Example 11
[0224] A BMF web was made as described in Example 10, except the
extruder temperature was at about 270.degree. C. and it delivered
the blend melt stream to the BMF die maintained at 270.degree. C.
No fly was visually observed with the un-aided human eye under
illumination with fluorescent lighting at a distance of about 30
cm.
Example 12
[0225] A BMF web was made as described in Example 11, except that
the blend ratio of METOCENE.TM. MF650Y to OPPERA.TM. PR100A was
(85/15). No fly was visually observed with the un-aided human eye
under illumination with fluorescent lighting at a distance of about
30 cm.
Example 13
[0226] A BMF web was made generally as described in Example 9,
except for the following details. The blend ratio of METOCENE.TM.
MF650Y to OPPERA.TM. PR100A was (90/10). The extruder temperature
was at approximately 270.degree. C. and it delivered the blend melt
stream to the BMF `die maintained at 270.degree. C. The.gearpurnp
was adjusted so that a 0.536 kg/hr/em die width (3.0 lb/hr/inch die
width) polymer throughput rate was maintained at the BMF die. The
primary air temperature was maintained at approximately 335.degree.
C. The resulting web had a Basis Weight of approximately 55
g/m.sup.2. No fly was visually observed with the un-aided human eye
under illumination with fluorescent lighting at a distance of about
30 cm.
Example 14
[0227] A BMF web was made as described in Example 13, except that
the blend ratio of METOCENE.TM. MF650Y to OPPERA.TM. PR100A was
(85/15). No fly was visually observed with the un-aided human eye
under illumination with fluorescent lighting at a distance of about
30 cm.
Example 15
[0228] A BMF web was made generally as described in Example 10,
except for the following details. Instead of the OPPERA.TM. PR100A
resin, the METOCENE.TM. MF650Y resin was blended with a
cycloaliphatic hydrocarbon tackifier resin commercially available
as ESCOREZ.TM. 5400 from Exxon Mobil Corp., at blend ratio of
(90/10). The extruder temperature was at approximately 250.degree.
C. and it delivered the blend melt stream to the. BMF die
maintained at 250.degree. C. The gear pump was adjusted so that a.
0.268 kg/fir/cm die (1.5 lb/hr/inch die width) polymer throughput
rate was maintained at the BMF die. The primary air temperature was
maintained at approximately 335.degree. C. This produced a web On a
rotating collector spaced 30.5 cm from the die. This web and had a
Basis Weight of approximately 64 g/m.sup.2. No fly was visually
observed with the un-aided human eye under illumination with
fluorescent lighting at a distance f about 30 cm.
Example 16
[0229] A BMF web was made generally as described in Example 15,
except for the following details. The ESCOREZ.TM. 5400 was replaced
by ESCOREZ.TM. 5415, commercially available from Exxon Mobil Corp.
(Houston, Tex.). The resulting web had a Basis Weight of
approximately 60 g/m.sup.2. No fly was visually observed with the
un-aided human eye under illumination with fluorescent lighting at
a distance of about 30 cm.
Example 17
[0230] A BMF web was made generally as described in Example 15,
except for the following details. The ESCOREZ.TM. 5400 was replaced
by a hydrocarbon tackifier resin commercially available as
ARKON.TM. P-100 from Arakawa Chemical of Osaka, JP. The resulting
web had a Basis Weight of approximately 61 g/m.sup.2. No fly was
visually observed with the un-aided human eye under illumination
with fluorescent Hating at a distance of about 30 cm.
[0231] Exemplary results for Comparative Examples C-2 and Examples
9-17 are summarized in Table 2.
TABLE-US-00002 TABLE 2 Maximum Tensile Load in the Machine Molten
Die Direction Polymer Example Temperature EFD (MD) Flow Rate Number
Material (.degree. C.) (micrometers) (N) (kg/hr/in) C-2 PP 650 Y
255 5.3 4.28 0.268 9 PP 650 Y/OPPERA .TM. 260 5.1 5.59 0.268 PR100
(95%/5% w/w) 10 PP 650 Y/OPPERA .TM. 260 5.2 7.55 0.268 PR100
(90%/10% w/w) 11 PP 650 Y/OPPERA .TM. 270 4.7 6.1 0.268 PR100
(90%/10% w/w) 12 PP 650 Y/OPPERA .TM. 270 4.8 6.86 0.268 PR100
(85%/15% w/w) 13 PP 650 Y/OPPERA .TM. 270 6 6.01 0.536 PR100
(90%/10% w/w) 14 PP 650 Y/OPPERA .TM. 270 5.8 5.65 0.536 PR100
(85%/15% w/w) 15 PP 650 Y/ESCOREZ .TM. 250 8.3 10.07 0.268 5400
(90%/10% w/w) 16 PP 650 Y/ 250 7.7 10.77 0.268 ESCOREZ .TM. 5415
(90%/10% w/w) 17 PP 650 Y/ARKON .TM. 250 6.9 9.61 0.268 P100
(90%/10% w/w)
Example 18
[0232] A composite web was made using an apparatus generally as
disclosed in FIG. 2 of U.S. Pat. No. 7,989,371. Blown microfibers
were included in the composite web using a blend of PP 650Y and
OPPERA.TM. PR100A at a (90/10) ratio. These fibers had an EFD of
approximately 4.7. Crimped 6 denier polyethylene terephthalate
staple fibers, commercially available from Invista of Wichita, Ks.,
were also included in the composite web, with the ratio of blown
microfibers to staple fibers being approximately 65 to 35. No fly
was visually observed with the un-aided human eye under
illumination with fluorescent lighting at a distance of about 30
cm.
Camparaiive Example C-3
[0233] A BMF web was made generally according to Comparative
Example C-1, except for the following details. The polymer used was
a polypropylene resin commercially available as TOTAL Polypropylene
3860X from TOTAL, Houston, Tex. The extruder temperature was set at
about 310.degree. C. and it delivered the melt stream to the BMP
die maintained at 310.degree. C. The gear pump was adjusted so that
a 0.268 kg/hr/cm die (1.5 lb/hr/inch die width) polymer throughput
rate was maintained at the BMF die. The primary air temperature was
maintained at approximately 400.degree. C., The resulting web was
collected at a BMF die to collector distance of 19 inches (48.3 cm)
and had a Basis Weight of approximately 54 g/m.sup.2. The web had a
Solidity of approximately 6.97%. Significant fly was visually
observed with the un-aided human eye under illumination with
fluorescent lighting at a distance of about 30 cm.
Example 19
[0234] A BMF web was made, generally according to Comparative
Example C-3, except for the following details. The extruder was
charged with using a blend of polypropylene and polymethyl pentene
polymer where the polymethyl pentene used had a melt flow rate of
180, commercially available as TPX DX820 from Mitsui Chemicals
.sub.of. Tokyo, JP, PP3860 and TPX DX820 were blended at a (95/5)
ratio. The resulting web had a Basis Weight of approximately 53
g/m.sup.2. The web had a Solidity of approximately 6.90%. No fly
was visually observed with the un-aided human eye under
illumina.tion with fluorescent lighting at a distance of about 30
cm.
Example 20
[0235] A BMF web was made as described in Example 19, except that
the PP3860/TPX DX820 blend ratio was (90/10) and the extruder and
die temperatures were maintained at 315.degree. C. The resulting
web had a Basis Weight of approximately 56 g/m.sup.2. The web had a
Solidity of approximately 7.21%. No fly was visually observed with
the un-aided human eye under illumination with fluorescent lighting
at a distance of about 30 cm.
Example 21
[0236] A BMF web was made as described in Example 20, except that
Oppera PR100A was added to the polymer blend at the ratio
PP3860/TPX DX820/OPPERA.TM. PR100A (90/5/5). The resulting web had
a Basis Weight of approximately 54 g/m.sup.2. The web had a
Solidity of approximately 9.93%. No fly was visually observed with
the un-aided human eye under illumination with fluorescent lighting
at a distance of about 30 cm.
[0237] Exemplary results for Comparative Example C-3 and Examples
19-21 are summarized in Table 3.
TABLE-US-00003 TABLE 3 Maximum Tensile Distance of Load in the Die
the from the Machine Die Collector Direction Example Temperature
(inches) EFD (MD) Number Material (.degree. C.) [cm] (micrometers)
(N) C-3 PP 3860 315 19 12.1 7.49 [48.26] 19 PP 3860/TPX 315 19 13.4
4.23 820DX [48.26] (95%/5% w/w) 20 PP 3860/TPX 315 19 14.1 3.75
820DX (90%/10% w/w) [48.26] 21 PP 3860/TPX 315 19 16.2 5.03 820DX/
[48.26] OPPERA .TM. PR 100A (95%/5%/5% w/w/w)
Comparative Example C-4
[0238] A BMF web was made as described in Example 9, except for the
following details. The BMF die used in the example consists of
small orifice size ranging from 150 um and high orifice density of
10 hole/cm (25 hole/inch). In addition, the molten polymer was
delivered to the die by a 12.7 mm single screw. The extrusion rate
was maintained at 0.09 kg/hr/cm (0.5 lb/hr/inch die width). The
extruder temperature was approximately 260.degree. C. and it
delivered the METOCENE.TM. MF650Y melt stream to the BMF die
maintained at 270.degree. C. The primary air temperature was
maintained at approximately 240.degree. C. Significant fly was
visually observed with the un-aided human eye under illumination
with fluorescent lighting at a distance of about 30 cm.
Example 22
[0239] A BMF web was made as described in Comparative Example C-4,
except that METOCENE.TM. MF 650Y was blended with OPPERA.TM.
PR100A. The blend ratio of METOCENE.TM. MF650Y to OPPERA.TM. PR100A
was (95%/5% w/w). No fly was visually observed with the unaided
human eye under illumination with fluorescent lighting at a
distance of about 30 cm.
Example 23
[0240] A BMF web was made as described in Example 22, except that
the extrusion temperature was about 280.degree. C. No fly was
visually observed with the un-aided human eye under illumination
with fluorescent lighting at a distance of about 30 cm.
Example 24
[0241] A BMF web was made as described in. Example 22, except that
the blend ratio of METOCENE.TM. MF650Y to OPPERA.TM. PR100A was
(90/10 w/w) and the extrusion temperature was 295.degree. C. No fly
was visually observed with the un-aided human eye under
illumination with fluorescent lighting at a distance of about 30
cm.
Example 25
[0242] A BMF web was made as described in Example 22, except that
the blend ratio'of METOCENE.TM. MF650Y to OPPERA.TM. PR100A was
(85/15 w/w) and the extrusion temperature was 315.degree. C. No fly
was visually observed with the un-aided human eye under
illumination with fluorescent lighting ata distance of about 30
cm.
[0243] Exemplary results for Comparative Example C-4 and Example
22-25 are summarized in Table 4.
TABLE-US-00004 TABLE 4 Distance of the Die from the Die Collector
Example Temperature (inches) AFD Number Material (.degree. C.) [cm]
(micrometers) C-4 PP 650 Y 260 12 0.71 [30.48] 22 PP 650 Y/ 260 12
0.94 OPPERA .TM. 100 [30.48] (95%/5% w/w) 23 PP 650 Y/ 280 12 0.85
OPPERA .TM. 100 [30.48] (95%/5% w/w) 24 PP 650 Y/ 295 12 0.63
OPPERA .TM. 100 [30.48] (90%/10% w/w) 25 PP 650 Y/ 315 12 0.51
OPPERA .TM. 100 [30.48] (85%/15% w/w)
[0244] Differential Scanning Calorimetry (DSC) measurements
according to the foregoing test method were carried out to
determine the Melting Temperature and Heat of Fusion of the
crystalline polyolefin, the mixture of the crystalline polyolefin
with the hydrocarbon tackifier resin, and the nonwoven fibrous webs
produced from the mixture, for Comparative Example C1-C4 and
Examples 1-25. These results are summarized in Table 5.
TABLE-US-00005 TABLE 5 Melting Example Temperature Number Material
(.degree. C.) Heat of Fusion (J/g) C-1 PP 650 X 156.3 93.8 1 PP 650
X/OPPERA .TM. 100 (95%/5% w/w) 154.3 92.8 2 PP 650 X/OPPERA .TM.
100 (95%/5% w/w) Same as Same as Example 1 Example 1 3 PP 650
X/OPPERA .TM. 100 (95%/5% w/w) Same as Same as Example 1 Example 1
4 PP 650 X/OPPERA .TM. 100 (90%/10% w/w) 153.8 91.0 5 PP 650
X/OPPERA .TM. 100 (90%/10% w/w) Same as Same as Example 4 Example 4
6 PP 650 X/OPPERA .TM. 100 (85%/15% w/w) 152.8 83.15 7 PP 650
X/OPPERA .TM. 100 (90%/10% w/w) Same as Same as Example 4 Example 4
8 PP 650 X/OPPERA .TM. 100 (85%/15% w/w) Same as Same as Example 6
Example 6 C-2 PP 650 Y 156.2 88.1 9 PP 650 Y/OPPERA .TM. PR100
155.0 85.9 (95%/5% w/w) 10 PP 650 Y/OPPERA .TM. PR100 154.1 82.1
(90%/10% w/w) 11 PP 650 Y/OPPERA .TM. PR100 Same as Same as
(90%/10% w/w) Example 10 Example 10 12 PP 650 Y/OPPERA .TM. PR100
153.9 77.7 (85%/15% w/w) 13 PP 650 Y/OPPERA .TM. PR100 Same as Same
as (90%/10% w/w) Example 10 Example 10 14 PP 650 Y/OPPERA .TM.
PR100 Same as Same as (85%/15% w/w) Example 12 Example 12 15 PP 650
Y/ESCOREZ .TM.5400 157.4 81.2 (90%/10% w/w) 16 PP 650 Y/ESCOREZ
.TM. 5415 156.8 81.5 (90%/10% w/w) 17 PP 650 Y/ARKON .TM. P100
(90%/10% w/w) 157.2 85.5 C-3 PP 3860 161.5 111.1 19 PP 3860/TPX
820DX 159.3 103.9 (95%/5% w/w) 20 PP 3860/TPX 820DX (90%/10% w/w)
159.2 98.24 21 PP 3860/TPX 820DX/ 158.7 104.2 OPPERA .TM. PR 100A
(90%/5%/5% w/w/w) C-4 PP 650 Y Same as C-2 Same as C-2 22 PP 650
Y/OPPERA .TM. 100 Same as Same as (95%/5% w/w) Example 9 Example 9
23 PP 650 Y/OPPERA .TM. 100 (95%/5% w/w) Same as Same as Example 9
Example 9 24 PP 650 Y/OPPERA .TM. 100 (90%/10% w/w) Same as Same as
Example 10 Example 10 25 PP 650 Y/OPPERA .TM. 100 (85%/15% w/w)
Same as Same as Example 12 Example 12
[0245] Reference throughout this specification to "one embodiment,"
"certain embodiments," "one or more embodiments" or "an
embodiment," whether or not including the term "exemplary"
preceding the term "embodiment," means that a particular feature,
structure, material, or characteristic described in connection with
the embodiment is included in at least one embodiment of the
certain exemplary embodiments of the present disclosure. Thus, the
appearances of the phrases such as "in one or more embodiments,"
"in certain embodiments," "in one embodiment" or "in an embodiment"
in various places throughout this specification are not necessarily
referring to the same embodiment of the certain exemplary
embodiments of the present disclosure. Furthermore, the particular
features, structures, materials, or characteristics may be combined
in any suitable manner in one or more embodiments.
[0246] While the specification has described in detail certain
exemplary embodiments, it will be appreciated that those skilled in
the art, upon attaining an understanding of the foregoing, may
readily conceive of alterations to, variations of, and equivalents
to these embodiments. Accordingly, it should be understood that
this disclosure is not to be unduly limited to the illustrative
embodiments set forth hereinabove. In addition, all numbers used
herein are assumed to be modified by the term "about."
[0247] Furthermore, all publications and patents referenced herein
are incorporated by reference in their entirety to the same extent
as if each individual publication or patent was specifically and
individually indicated to be incorporated by reference. Various
exemplary embodiments have been described. These and other
embodiments are within the scope of the following claims.
* * * * *