U.S. patent application number 13/138696 was filed with the patent office on 2012-01-19 for fabric material composite construction for use as a filter means.
Invention is credited to Paolo Canonico, Liuba Napoli.
Application Number | 20120012523 13/138696 |
Document ID | / |
Family ID | 41278134 |
Filed Date | 2012-01-19 |
United States Patent
Application |
20120012523 |
Kind Code |
A1 |
Canonico; Paolo ; et
al. |
January 19, 2012 |
FABRIC MATERIAL COMPOSITE CONSTRUCTION FOR USE AS A FILTER
MEANS
Abstract
A fabric material composite construction, for use as a filter
means or media, characterized in that said construction comprises a
combination of one or more nanofiber layers and a synthetic
single-thread squarely knitted precision fabric.
Inventors: |
Canonico; Paolo; (Appiano
Gentile (CO), IT) ; Napoli; Liuba; (Appiano Gentile
(co), IT) |
Family ID: |
41278134 |
Appl. No.: |
13/138696 |
Filed: |
March 11, 2010 |
PCT Filed: |
March 11, 2010 |
PCT NO: |
PCT/EP2010/053110 |
371 Date: |
September 19, 2011 |
Current U.S.
Class: |
210/507 ;
425/174.8E |
Current CPC
Class: |
B01D 2239/025 20130101;
D04H 1/728 20130101; B01D 2239/065 20130101; B01D 2239/0478
20130101; B01D 2239/0471 20130101; B01D 46/546 20130101; B01D
39/083 20130101; B01D 2239/0681 20130101 |
Class at
Publication: |
210/507 ;
425/174.8E |
International
Class: |
B01D 29/00 20060101
B01D029/00; B29C 47/00 20060101 B29C047/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 29, 2009 |
IT |
MI2009A000730 |
Claims
1-11. (canceled)
12. A fabric material composite construction, for use as a filter
means or media, characterized in that said construction comprises
one or more nanofiber layers supported by a square-mesh knitted
precision fabric made of a synthetic single-thread, said nonofibers
having a nanofiber diameter from 100 TO 900 nm and said knitted
precision fabric having a mesh 5 .mu.m to 2000 .mu.m, thereby said
composite construction prevents particles having a particle size
from 1 to 2 .mu.m from passing through.
13. A composite construction, according to claim 12, characterized
in that said nanofiber layer is coated on said single-thread fabric
by an electro-spinning coating method and forms with said
supporting a single filtering means.
14. A composite construction, according to claim 12, characterized
in that said nanofiber layer is coated on a single side of said
fabric or on both sides of said fabric.
15. A composite construction, according to claim 12, characterized
in that said nanofiber layer is coated on said fabric after having
coated on said fabric an adhesive material.
16. A composite construction, according to claim 12, characterized
in that said construction further comprises an additional fabric
thereby providing a sandwich fabric arrangement including therein
said nanofiber layer.
17. A composite construction, according to claim 12, characterized
in that said composite construction provides a filtering means
having a filtering efficiency of 99% up to 2 .mu.m, and a high
filtering efficiency for particles having a particle size less than
5 .mu.m.
18. A composite construction, according to claim 12, characterized
in that said composite construction has an acoustic impedance less
than that of synthetic single-thread precision fabrics having a
similar mesh size value, said acoustic impedance being less by a
factor of 1.5 than that of any prior synthetic single-thread
precision fabric.
19. A composite construction, according to claim 12, characterized
in that said synthetic single-thread forming said knitted fabric is
selected from polyester, polyamide, polypropylene,
polyphenylsulphide, PEEK, PVDF and PTFE.
20. A composite construction, according to claim 12, characterized
in that said construction comprises organic polymers selected from
fluorine polymers, PA 6, PA 6/12, Polyaramide, PUR, PES, PVA, PVAC,
PAN, PEO, PS, electroconductive polymers, such as polythiophenes,
and/or biopolymers selected from kitosan, keratine, collagen and
peptides.
21. A fabric material construction, characterized in that said
nanofibers are processed by a plasma pre-processing step to improve
the adhesion of said nanofibers to said supporting fabric.
22. An apparatus for making a fabric construction, according to
claim 12, characterized in that said apparatus comprises a filament
providing dye arrangement (3) a polymeric solution vessel, a
syringe, a capillary and nozzle assembly, therefrom is ejected a
polymeric solution and which operates as a positive electrode, and
collector (4) thereon electrospun nanofibers are collected, and
which operates as a counter electrode, characterized in that a
distance between said dye arrangement and said counter-electrode is
such that said nanofibers are not in a dry condition as they
contact said supporting fabric.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a fabric material composite
construction for use as a filter means or media.
[0002] At present, particles having a particle size less than 1-2
microns cannot be separated by filtering fabric materials, because
of technologic limitations of the weaving process preventing from
weaving fabric materials with a mesh opening less than 5
microns.
SUMMARY OF THE INVENTION
[0003] Accordingly, the aim of the present invention is to provide
a fabric material composite construction preventing particles
having a particle size of 1-2 microns from passing
therethrough.
[0004] Within the scope of the above mentioned aim, a main object
of the invention is to provide such a fabric material composite
construction having precise and selective filtering properties like
those of precision fabrics, together with a powder filtering
capability.
[0005] Yet another object of the present invention is to provide
such a fabric material composite construction adapted to increase
the life span of filtering media made thereby.
[0006] Yet another object of the present invention is to provide
such fabric material composite construction having an acoustical
impedance less than that of fabric materials with a similar mesh
size, for use in acoustical applications also providing a
protective function, for example in a cellular phone where the
fabric also protect phone inner parts from magnetic and powder
particles, that is a fabric with a very small mesh size and a low
fabric impedance, while allowing sound to pass therethrough.
[0007] The above mentioned aim and objects, as well as yet other
objects, which will become more apparent hereinafter are achieved
by a fabric material composite construction for use as a filter
means or media, characterized in that said construction comprises a
combination of one or more nanofiber layers and a synthetic
single-thread squarely knitted precision fabric.
[0008] The nanofiber layer, in particular, is overlapped or coated
on said single-thread fabric by an electro-spinning coating method
and being embedded in said supporting fabric thereby forming a
single or cohesively bound filtering means or media.
[0009] A further adhesive material layer, for example an aqueous
solution acrylic glue material, may also be deposited on the above
fabric construction, to increase the fabric material and nanofibers
cohesive binding.
[0010] Thus, the above fabric material provides a very high
structural strength filtering membrane.
[0011] According to one aspect of the present invention, it is also
possible to deposit a nanofiber layer on both the fabric material
faces and/or to bind thereto an additional fabric layer thereby
forming a sandwich fabric arrangement including therein the
nanofiber layer, which is very advantageous in several filtering
applications such as acoustic, vehicle, white good, water,
diagnostic and medical filtering applications requiring highly
micrometric particle filtering efficient and permeable filtering
media preserving good flowrate properties.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Further characteristics and advantages of the present
invention will become more apparent hereinafter from the following
detailed disclosure of a preferred, though not exclusive,
embodiment of the invention, which is illustrated, by way of an
indicative, but not limitative, example, in the accompanying
drawings, where:
[0013] FIG. 1 schematically shows an electro-spinning
apparatus;
[0014] FIG. 2 shows a table showing the characterizing parameters
of the base PA 120.30 WO fabric material, together with its
filtering efficiency;
[0015] FIG. 3 is another table showing the characterizing
parameters of a coupled or laminated filtering material consisting
of a fabric material+PA 120.30 WO nanofibers;
[0016] FIG. 4 is another table showing the characterizing
parameters of a base PES AM 120.34 WB fabric material;
[0017] FIG. 5 is another table showing the characterizing
parameters of a laminated material consisting of a fabric
material+PES AM 120.34 WB nanofibers, the nanofiber layer being
deposited on a single side of the fabric;
[0018] FIG. 6 is another table showing the characterizing
parameters of a laminated material consisting of a fabric
material+PES AM 120.34 WB nanofibers, the nanofiber layer being
deposited both on a single side of the fabric and on the two sides
thereof;
[0019] FIG. 7 is another table showing the characterizing
parameters of a coupled or laminated material consisting of a
fabric material+PES AM 150.27 nanofibers, the nanofiber layer being
deposited on an adhesive coated single side of the fabric;
[0020] FIGS. 8, 9 and 10 are photos showing the filtering means or
media including a synthetic single-thread precision fabric material
with a randomly arranged nanofiber layer; and
[0021] FIGS. 11 and 12 are further photos of the filtering means or
media including a synthetic single-thread precision fabric material
and a nanofiber layer after a filtering efficiency test.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] With reference to the number references of the above
mentioned figures, the composite fabric construction according to
the present invention comprises a synthetic single-thread plain
mesh precision fabric material.
[0023] It should be pointed out that, owing to its very even and
coherent mesh structure, the inventive fabric has high strength and
good handling characteristics making said composite fabric an ideal
base material for filtering applications.
[0024] In fact, said composite fabric has a very even fabric
weight, thickness, surface properties, temperature resistance, much
improved with respect to those of multi-thread prior fabrics, the
above advantageous properties being held constant through the
overall length of the fabric roll and from one fabric batch to
another fabric batch.
[0025] However, the inventive precision fabric is made with very
narrow tolerance range, thereby providing a filtering means or
media having a consistent filtering efficiency and air flow
permeability, and this, as stated, with its constant pore size and
constant properties of the single thread or yarn used for weaving
it.
[0026] Moreover, the precision fabric has a very good resistance
against weather agents, water, and moisture, and may be easily made
on an industrial scale.
[0027] The above synthetic single-thread squarely knitted precision
fabric may be made of polyester, polyamide, polypropylene,
polyphenylsulphide, PEEK, PVDF, PTFE, with a mesh size in a mesh
size range from 2000 .mu.m to 5 .mu.m, and may be used as a
supporting base for supporting the nanofiber layer or membrane.
[0028] The fabric may also be made of organic polymers comprising:
PA 6, PA 6/12, Polyaramides, PUR, PES, PVA, PVAC, PAN, PEO, PS,
conductive polymers (polythiophenes), fluorine based polymers and
so on.
[0029] The fabric may also be made of biopolymers comprising
kitosan, keratine, collagen, peptides and so on.
[0030] The base fabric is selected based on its mesh size and
materials, the deposited nanofiber amount, the thickness of the
deposited layer and nanofiber forming polymer based on the
characteristics required for the intended application.
[0031] It is also possible to electrospin biopolymers adapted for
medical applications, not necessarily of a filtering type,
requiring a biocompatibility of the used material.
[0032] In studying the coupled or laminated fabric/nanofiber
membrane filtering means, a range of fabric materials of a class
Saati and an electrospinnable polymer class have been used.
[0033] In particular the nanofibers and substrate have been so
designed as to provide a maximum filtering efficiency with an
acceptable pressure loss and permeability.
[0034] In this connection it should be pointed out that the word
"filter" means herein any tridimensional systems where a
geometrical dimension can be considered as a main one with respect
to the other two.
[0035] In nanofibers, in particular, the diameter is less than 1
micron, and of the order of nanometers (100-900 nm).
[0036] The properties of said nanofibers and nanofiber fabric
material comprise a large specific surface, a high surface/volume
ratio, a small pore size, a high porosity, a tridimensional
pattern, a high permeability and a low air-flow resistance, a good
separation of the particles, a good capability of rejecting powder
materials and improved physical-mechanical properties thereby
allowing to achieve a self-evident-"gain" with respect to the fiber
active area, improved filtering properties and self-evident
advantages from a flow standpoint.
[0037] The above mentioned very good multifunctional properties
allow to use said nanofibers within a broad range of application
such as: [0038] technical textile materials; [0039] filtering means
or media, for filtering liquid and air; [0040] protective and
barrier fabric materials (in sanitary, military, cloth article
applications and so on); [0041] biomedical devices and materials
(drug releasing vectors, haemostatic devices, specialized organic
fabric and bandage materials); [0042] in medical and diagnostic
fields; [0043] in sound absorption applications; [0044] as a
composite material reinforcement; [0045] as a cosmetic skin mask
(cleansing agents and skin drug therapies); [0046] bridge
arrangements for organic fabric materials such as cutaneous porous
membranes, tubular arrangements for recovering blood vessels and
nervous tissues, tridimensional bridges for recovering bones and
cartilages).
[0047] Moreover, the fabric and nanofiber construction according to
the present invention may be also used in a system for depositing
polymeric nanofibers on a fabric substrate by an electrospinning
process which may be applied to a broad range of polymeric
materials which may be also modified by adding suitable additives
thereto, thereby providing improved performance fabric materials to
be used in specifically designed application.
[0048] As is known, an electrospinning process provides the
following main great advantages: [0049] a possibility of quickly
and simply switching from a laboratory scale to an industrial
scale; [0050] a high production yield; [0051] a good repeatability;
[0052] a precise control of the fiber size and pattern; [0053] a
precise control of the deposited fiber amount; [0054] an easy and
quick control of the fiber production yield; [0055] an easy
modification of the fabric material properties by merely adding
additives to the starting solution; [0056] a low consume of raw
materials (with a very light nanofiber weft pattern and accordingly
a consequent inexpensive production due to the material saving);
[0057] a room temperature of the process, without any risk of
degrading materials, and with a low power consume operating cost,
and a great economic efficiency; [0058] an easy maintenance and
servicing of the process systems; [0059] highly safe operating
characteristics.
[0060] Moreover, the electrospinning process allows to "cold spin"
nanometric size polymeric fibers starting from a concentrated
polymeric solution subjected to a suitable outer electrical
field.
[0061] A very simple electrospinning apparatus for performing the
above process, generally indicated by the reference number 1 in
FIG. 1, comprises essentially the following three main component
elements:
[0062] a voltage source, generally indicated by the reference
number 2, adapted to generate a high potential difference (5-50
kV);
[0063] a die arrangement 3, that is a device providing filaments,
including a syringe, a capillary and nozzle assembly, a related
vessel, and so on, therefrom is ejected a polymeric solution and
which operates as a positive electrode; and
[0064] a collector 4 thereon the electrospun nanofibers are
collected and which operates as a counter-electrode.
[0065] In this apparatus, by applying the electric field, the
solution is charged thereby providing electrostatic forces opposing
to the surface tension, to generate an instability phenomenon
forming a jet.
[0066] By quickly evaporating the solvent the cross-section is
reduced with a great elongation of the jet which becomes a thin
continuous filament, which starts to solidify and is deposited on
the collector surface.
[0067] In the apparatus, the synthetic single-thread fabric
material is arranged on the counter-electrode, at a given suitable
distance from the die arrangement.
[0068] By applying a set potential difference between the two
electrodes, the nanofibers are jet deposited directly on the
filtering fabric material, or may also be deposited with a random
oriented pattern, to form on the fabric a weft pattern having a
high surface/volume ratio and a very small pore size, the deposited
nanofibers being bound to the fabric both by chemical and physical
forces, thereby providing an integral assembly therewith.
[0069] A plasma pre-processing of the fabric material may also be
used to further improve the adhesion of said nanofibers to the
sublayer and their depositing evenness.
[0070] To further increase this adhesion, it is moreover possible
to provide such a distance between the die arrangement and the
counter-electrode thereon the substrate is supported, that said
nanofibers are not in a dry condition as they contact the filtering
fabric.
[0071] The process parameters to be adjusted to achieve different
property nanofiber layers are the fiber size, pore average size,
deposited layer thickness and nanofiber layer weight
(g/m.sup.2).
[0072] The electrospinning process may be controlled by adjusting
the process parameters, material properties and environmental
conditions.
[0073] The nanofiber diameter, their characteristics and properties
may be easily modulated by further adjusting the process
parameters.
[0074] The starting solution is characterized by its viscosity,
polymer concentration, and solvent electric conductivity and
volatility.
[0075] The environmental conditions are characterized by the
relative moisture, temperature and pressure, while the process
conditions are characterized by the applied potential difference,
distance between the die arrangement and depositing surface,
distance between the electrodes, the solution flow and depositing
speed.
[0076] Upon testing the results of the present invention, it has
been possible to detect the most significative parameters of the
inventive process, and the tests have been repeated by varying the
values of said parameters, up to optimize the end product, to
provide geometrically homogeneous fibers having such a size and
construction as to provide a homogeneous and even distribution of
the pore size with a high efficiency in filtering micrometric
particles, while holding a controlled high permeability by
modulating the layer thickness and average pore size.
Experimental Results
[0077] Inventive fabric samples have been characterized with
respect to their filtering efficiency by using a filtering
efficiency test bench and a conventional Saati system to verify the
particle rates locked by the filtering means, the flow resistance
of the laminated or coupled material, determined by measuring its
permeability and the sound passage resistance determined by
acoustic impedance measurements.
[0078] A lot of different fabric samples made both of polyester and
nylon covered PA, PUR polymeric nanofibers have been made and
characterized.
[0079] The most significative results are listed thereinbelow.
[0080] PA 120.30 WO fabric covered by nanofiber
[0081] Characteristics of the base fabric:
[0082] Mesh size=55 .mu.m
[0083] High permeability 5600 I/m2 s
[0084] CA Fibrodat 111.9.degree.
[0085] The table of FIG. 2 shows the filtering efficiency
characterizing parameters of the inventive base fabric.
[0086] The table of FIG. 3 shows the characterizing parameters of
the fabric+nanofiber coupled or laminated material.
[0087] A plasma pre-processed nanofiber-covered PES AM 120.34 WB
fabric:
[0088] Characteristics of the base fabric
[0089] Mesh size=47 .mu.m
[0090] Air permeability 4500 I/m2 s
[0091] The table of FIG. 4 further shows the characterizing
parameter of the base fabric.
[0092] The table of FIG. 5 shows the characterizing parameters of
the fabric+nanofiber coupled or laminated material, with the
nanofiber layer deposited on a single side or face of the fabric,
and the table of FIG. 6 shows the characterizing parameters of the
fabric+nanofiber coupled material with the nanofiber layer
deposited both on a single fabric side and on the two fabric
sides.
[0093] A black water repellent nanofiber covered PES AM 150.27
fabric.
Characteristics of the Base Fabric
[0094] Mesh size=38 .mu.m
[0095] Air permeability 4500 I/m2 s
[0096] Acoustic impedance=47 MKS Rayls
[0097] The table of FIG. 3 shows the characteristic parameters of
the fabric+nanofiber coupled material, with the nanofiber layer
deposited on a single face of the fabric.
[0098] The fabric material composite construction according to the
present invention has a permeability larger than that of synthetic
single-thread precision fabrics with similar values of the mesh
size: in fact, the mesh size being the same, the permeability of
the coupled filtering media or means is increased by a 2.5 factor
with respect to that of a synthetic single-thread precision
fabric.
[0099] The inventive fabric material composite construction,
moreover, provides filtering media having a filtering efficiency of
99% up to 2 .mu.m, and accordingly a high filtering efficiency for
particles having a particle size <5 .mu.m (which is the
filtering limit of prior filtering precision fabrics).
[0100] Moreover, the fabric material composite construction
according to the present invention provides a powder rejecting
capability, though limited to the filtering fabrics, and has an
acoustic impedance less than that of synthetic single thread
precision fabrics having similar mesh size values: in fact, the
opening mesh size being the same, the sound passage resistance of
the inventive coupled filtering means is less by a factor of 1.5
than that of a synthetic single thread precision fabric.
[0101] Further important characteristics of the inventive fabric
material composite construction are that it has a long duration
efficient filtering characteristic with a large life span of the
nanofiber coating.
Morphologic Characterizing Parameters of the Filtering Means of
Media According to the Present Invention
[0102] The morphology and diameter distribution of the electrospun
filaments have been characterized by a SEM investigation, showing
that the nanofibers have diameters varying from 80 to 850 .mu.m,
depending on the selected sample, and are interconnected to one
another to define a thin weft pattern with a very small pore
size.
[0103] FIGS. 8, 9 and 10 show SEM photos of the filtering media
constituted by a synthetic single-thread precision fabric and a
nanofiber layer arranged in a random manner.
[0104] FIGS. 11 and 12 are further SEM photos of the filtering
media constituted by a synthetic single-thread precision fabric and
a nanofiber layer after a filtering efficiency test.
[0105] It should be apparent that the particles contained in the
test solution were firmly locked by the fabric component and
trapped in the nanofiber component of the inventive filtering
media.
[0106] It has been found that the invention fully achieves the
intended aim and objects.
[0107] In fact, the invention has provided a fabric material
composite construction for use as a filter means or media allowing
to prevent the passage of particles having particle size of 1-2
microns which, up to now, could not be separated by prior filtering
fabrics, because of the above mentioned technological limitations
of prior weaving processes not allowing to make fabrics having a
mesh size less than 5 microns.
[0108] Moreover, the composite fabric construction according to the
invention provides a precision and selective filtering like that of
a typical precision fabric together with a powder rejecting
capability (though limited because of the small thickness of the
nanofiber layer).
[0109] Moreover, the composite fabric construction according to the
invention allows the average useful life of the filtering media to
be increased due to the provision of the nanofiber layer trapping
the particles in the thickness thereof.
[0110] The pore size being the same, the permeability is larger,
with a consequent less flow/pressure drop between the upstream and
downstream portions of the filters.
[0111] Moreover, the inventive composite fabric construction has an
acoustic impedance smaller than that of prior fabrics having
similar mesh size values, which feature is very important for
acoustical application where the fabric material also provides a
protective function for inner parts of apparatus (such as cellular
phones) from ferromagnetic and powder particles.
[0112] Finally, the present invention overcomes the use limits of
nanofiber membranes due to their poor mechanical strength.
[0113] In practicing the invention, the used materials, and the
contingent size and shapes, can be any, according to
requirements.
* * * * *