U.S. patent application number 16/635392 was filed with the patent office on 2020-10-01 for production of metal oxide nanoparticles dispersed on fibres.
This patent application is currently assigned to UNIVERSIDAD EAFIT. The applicant listed for this patent is UNIVERSIDAD EAFIT. Invention is credited to Monica Lucia Alvarez Lainez, Julieth Carolina Cano Franco.
Application Number | 20200308760 16/635392 |
Document ID | / |
Family ID | 1000004955777 |
Filed Date | 2020-10-01 |
United States Patent
Application |
20200308760 |
Kind Code |
A1 |
Alvarez Lainez; Monica Lucia ;
et al. |
October 1, 2020 |
PRODUCTION OF METAL OXIDE NANOPARTICLES DISPERSED ON FIBRES
Abstract
The present invention relates to a method for obtaining
nanoparticles of metal oxides dispersed in fibers comprising
preparing a stable gel from nanoparticle precursors, immersing the
fibers in the stable gel and subjecting them to a hydrothermal
treatment until the fibers are coated with the nanoparticles in a
homogeneous way. The obtained fibers are used in the degradation of
organic pollutants.
Inventors: |
Alvarez Lainez; Monica Lucia;
(Medellin, CO) ; Cano Franco; Julieth Carolina;
(Medellin, CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UNIVERSIDAD EAFIT |
Medellin |
|
CO |
|
|
Assignee: |
UNIVERSIDAD EAFIT
Medellin
CO
|
Family ID: |
1000004955777 |
Appl. No.: |
16/635392 |
Filed: |
July 23, 2018 |
PCT Filed: |
July 23, 2018 |
PCT NO: |
PCT/IB2018/055469 |
371 Date: |
January 30, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D06M 11/46 20130101;
D06M 2400/02 20130101; B82Y 40/00 20130101; D06M 2101/06
20130101 |
International
Class: |
D06M 11/46 20060101
D06M011/46 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 3, 2017 |
CO |
NC2017/0007915 |
Claims
1. A method for modifying fibers with nanoparticles, the method
comprising: preparing a stable gel from nanoparticle precursors;
immersing one or more fibers in the stable gel; and subjecting the
one or more fibers to a hydrothermal treatment until the one or
more fibers are coated with the nanoparticles.
2. The method according to claim 1, wherein the stable gel is
prepared by a sol-gel technique.
3. The method according to claim 1, wherein the stable gel has a pH
lower than 5 and a solids content between 0.01 and 5.0%.
4. The method according to claim 1, wherein the nanoparticles are
metal oxides.
5. The method according to claim 1, wherein the nanoparticle
precursors are metal alkoxides.
6. The method according to claim 1, wherein the one or more fibers
are selected from the group of natural organic, synthetic organic
and inorganic fibers and combinations thereof, in nano or micro
scale.
7. The method according to claim 1, wherein the hydrothermal
treatment is carried out at a temperature between 100.degree. C.
and 300.degree. C., and for a period of time between 6 and 24
hours.
8. The method according to claim 1, further comprising washing the
fibers coated with the nanoparticles.
Description
TECHNICAL FIELD OF THE INVENTION
[0001] This invention is related to the industrial sector of
materials, particularly with the methods to form hybrid systems of
the textile industry that incorporate nanotechnology in polymeric
fibers or textiles forming functionalized fibers.
BACKGROUND OF THE INVENTION
[0002] The addition of nanoparticles on the textile fibers may have
disadvantages in the dispersion since the addition and
incorporation is critical and difficult to achieve. Taking into
account the nanometric sizes of metal oxide particles, there is a
limitation for their dispersion, since due to their size, they have
a high surface energy and a high tendency to agglomeration.
[0003] One of the techniques most used to obtain a hybrid material,
from a textile fiber with nanoparticles, consists of immersing the
fibers in sol-gel solutions that contain the precursors of the
metal oxides and generate the crystalline formation through a
calcination process. In this treatment, the fibers suffer
degradation phenomena, given their organic nature. Therefore, this
type of solution does not solve the problem of dispersion of
nanoparticles.
[0004] Other methods of manufacturing the hybrid materials by
immersion include taking advantage of the exchange of the surface
charges that some polymeric fibers have to promote the anchoring of
the nanoparticles from a colloidal solution. These techniques have
many stages of manufacture and the need to maintain strict control
in each of them. In addition, the final hybrid fiber material may
have different coating thicknesses of metal oxide nanoparticles,
which may decrease the porosity between the fibers and increase the
stiffness.
[0005] The scientific article by Chaorong et al. "Functionalization
of Electrospun Nanofibers of Natural Cotton Cellulose by Cerium
Dioxide Nanoparticles for Ultraviolet Protection" develops a
process to form nanoparticles of metal oxides on fibers. This
research proposes the surface modification of cellulose acetate
nanofibers with CeO.sub.2 nanoparticles through a hydrothermal
treatment. However, the nanoparticles obtained are of sizes greater
than 100 nm and very little homogeneous.
[0006] On the other hand, it is known that after the synthesis of
inorganic nanoparticles it is necessary to perform calcining
processes at high temperatures to obtain the crystalline properties
that define the behavior of the material. Generally, the subsequent
thermal treatment is carried out at temperatures that are around
300 and 800.degree. C., temperatures in which a greater quantity of
crystalline material is obtained, avoiding the formation of an
amorphous structure. For example, the study by Mahshid S. et al.
"Synthesis of TiO.sub.2 nanoparticles by hydrolysis and peptization
of titanium isopropoxide solution" ([Periodic
publication]//Semicond.Physics, Quantum, Electron.-2006-pp. 65-68)
proposes a sol-gel synthesis and a heat treatment at different
temperatures. However, the minimum temperatures at which
crystallinity is acceptable are around 400 and 600.degree. C. It
results in a significantly aggressive process for the polymeric
fibers, therefore, for the processing of this type of
organic-inorganic hybrid material it is unlikely to use this
methodology.
[0007] Other existing techniques for depositing nanoparticles on
fibers include: manipulation of the fibers during and after
immersion, multiple immersions, hydrothermal treatment or
subsequent calcinations, which causes the polymer fibers to
degrade.
[0008] From these difficulties, the present development reduces the
amount of processes related to the immersion of the fibrous
substrates in the nanoparticle solutions, promotes the
crystallinity of the nanoparticles in a single step, without the
need to calcinate, and does not noticeably affect the porosity
between the fibers.
BRIEF DESCRIPTION OF THE INVENTION
[0009] The present invention refers to a manufacturing process of
nanoparticles of metal oxides dispersed in a fibrous hybrid
material (polymeric fibers). The process for obtaining the hybrid
material, that is to say the dispersion of the metal oxide
nanoparticles on the surface of the polymer fibers, is carried out
through the combination of the sol-gel technique and a hydrothermal
treatment in a single step.
BRIEF DESCRIPTION OF THE FIGURES
[0010] FIG. 1 SEM micrograph of the detail of hybrid nanofibers
obtained by post-functionalization of PAN nanofibers by sol-gel
with TiO.sub.2 compositions.
[0011] FIG. 2 SEM micrograph of the detail of the hybrid nanofibers
obtained by the post-functionalization of PAN nanofibers by sol-gel
with TiO.sub.2--CeO.sub.2 5% compositions.
[0012] FIG. 3 TEM micrographs of the post-functionalized nanofibers
with sol-gel with compositions: a) TiO.sub.2, b) detail at higher
resolution of the nanofibers with TiO.sub.2 g) TiO.sub.2--CeO.sub.2
5%, h) detail of nanofibers with TiO.sub.2--CeO.sub.2 5%, i)
diffraction pattern of rings of nanofibers with sol-gel of
TiO.sub.2--CeO.sub.2 5%.
[0013] FIG. 4 TEM micrograph of post-functionalized nanofibers by
sol-gel with TiO.sub.2--CeO.sub.2 5% composition.
[0014] FIG. 5 Difractograms of post-functionalized nanofibers by
sol-gel with TiO.sub.2 and in the range of TiO.sub.2--CeO.sub.2
compositions.
[0015] FIG. 6 Comparison of the photocatalytic degradation in the
modified nanofibers with the metal oxides through the processing
routes in which the modification occurs from the formation or
spinning of the fiber.
DETAILED DESCRIPTION OF THE INVENTION
[0016] The present invention discloses a method for coating fibers
with nanoparticles which comprises preparing a stable gel from
nanoparticle precursors, immersing fibers in said stable gel and
subjecting them to a hydrothermal treatment until the fibers are
coated with the nanoparticles.
[0017] For purposes of the present invention, fibers are understood
as any set of filaments or strands capable of being used to form
yarns and fabrics. The fibers are select from the group of natural
organic fibers, synthetic organic fibers and inorganic fibers and
combinations thereof. Among the natural organic fibers are fibers
of vegetable and animal origin, for example cotton, capoc, linen,
jute, hemp, ramina, sisal, coconut fiber, pineapple, wool, silk,
hair. Among the synthetic organic fibers are those of cellulose
composition (cellulose), non-cellulosic polymers, such as protein,
rubber, aliphatic polyamide, aromatic polyamide, polyester,
polyacrylonitrile PAN, polyurethane, polyethylene or polypropylene,
polyvinyl chloride, polyvinylidene chloride, phenol navolaca base,
tetrafluoropolyethylene, among others. Among the inorganic fibers
are metallic and non-metallic fibers, for example fiberglass,
carbon fiber, PAN carbon fibers, metal, boron, silica, silica
carbide and asbestos, among others.
[0018] The fibers can be nanofibers (NFs), microfibers or larger
fibers. Nanofibers may have a size of lower than 1000 nanometers,
lower than 500 nanometers, or lower than 100 nanometers,
microfibers a size between 10.0 and 0.5 micrometers, and the
largest fibers a size greater than 0.5 micrometers. The fibers can
be obtained by interfacial polymerization, electrospinning,
forcespinning or any other equivalent technique known to a person
of ordinary skill in the art.
[0019] By the method disclosed in the present invention, the above
described fibers are modified by post-functionalization of fibers
using a process that combines a method for the preparation of a gel
and a hydrothermal treatment. In the process, a polymer solution is
modified by adding metal oxide precursors and subjecting the fibers
to a hydrothermal treatment to promote the crystallinity of the
nanoparticles. Among its objectives, the method disclosed herein
has the modification of fibers that, once subjected to the process,
they exhibit morphologies different from the initial ones, giving
them improved properties in the absorption of radiation, UV
protection, antibacterial action, self-cleaning and high
photocatalytic activity. By the term "modify" it is understood to
cover or cover partially or totally, upholstery, lining, etc.
[0020] The first step of this process consists in preparing a
stable gel by any technique known to a person moderately skilled in
the art. Among the techniques to obtain a stable gel is the sol-gel
technique. For purposes of the present application, "stable gel" is
understood as a homogeneous solution that does not vary in time.
Not obtaining a stable gel could cause precipitation of the
particles and therefore a fiber with the characteristics of the
present invention would not be obtained.
[0021] The sol-gel technique is a technique used for the formation
of nanoparticles, which comprises low process temperatures, and may
also be easily modified according to the synthesis needs. Although
the sol-gel process may seem quite simple, many variables influence
the quality of the product. Among them there is the metal oxide
precursor, the solvent used, the use of acidic or basic catalysts
and complex agents.
[0022] The sol-gel chemistry involves the hydrolysis and
condensation reactions of the metal alkoxide. In addition, sol-gel
synthesis promotes small particle sizes and mesoporous
structures.
[0023] The stable gel has a pH lower than 5, pH between 4 and 5 or
pH between 3 and 4.5. The acidification of the stable gel can be
carried out by the addition of acidic aqueous solutions or by any
other technique known to a person of ordinary skill in the art, and
aims to maintain the colloidal stability of the nanoparticles. For
better results, the addition of acidic aqueous solutions is carried
out dropwise. The stable gel should have a solids content between
0.01% and 5.0% w/w, between 0.01% and 2.00% w/w or between 0.08%
and 1.2% w/w. Obtaining a gel with neutral pH can result in poor
stability, while acidic pH values favor the stability of the gels
and prevent the formation of precipitates.
[0024] It is important to clarify that, in the literature, the
reports found with the modification of nanofibers by sol-gel
immerse the nanofibers in the gel and then wash them with distilled
water and subject them to temperature. In the preliminary tests of
the present invention said procedures were performed with
unfavorable results due to the fact that nanofibers covered in a
uniform manner were not achieved, but the formation of agglomerates
of important sizes in the nanofibers. The method employed in this
invention is a new way for the modification of nanofibers through
of the sun-gel technique, avoiding immersion and washing steps
before the hydrothermal treatment.
[0025] The stable gel is made from nanoparticle precursors. For
purposes of the present invention, the nanoparticle precursors are
metal alkoxides or transition metal alkoxides Among the
nanoparticle precursors which are used in the present invention are
titanium isopropoxide (TTIP), tetraethyl orthosilicate (TEOS),
titanium ethoxide Ti(OCH.sub.2CH.sub.3).sub.4, zinc acetate
(Zn(CH.sub.3COO).sub.22H.sub.2O), titanium butoxide
Ti(OCH.sub.2CH.sub.2CH.sub.2CH.sub.3).sub.4, titanium
tetraisopropoxide Ti(OCH(CH.sub.3)CH.sub.2).sub.4, magnesium di
(1-propoxide), aluminum tri(2-isopropoxide), and combinations of
the above with transition metal salts such as zinc nitrate
(Zn(NO.sub.3).sub.26H.sub.2O, cerium nitrate
(Ce(NO.sub.3).sub.26H.sub.2O, silver nitrate (AgNO.sub.3) and
titanium chloride (TiCl.sub.4), among others. Optionally, additives
such as solvents, stabilizing agents and/or additives to control pH
are added. Among the solvents are for example isopropanol, ethanol,
deionized water and acetone, among others. Stabilizing agents are
selected from acetylacetone, polyethylene glycol, propylene glycol,
polyacrylamide, ethylene glycol, cetyl trimethylammon bromide, and
hydroxymethylcellulose, among others. Among the possible additives
to control the pH are nitric acid, acetic acid, hydrochloric acid,
ammonia, ammonium hydroxide.
[0026] The nanoparticles (NPs) depend on the precursors used to
prepare the stable gel. For purposes of the present invention, the
nanoparticles are metal oxides (NPsOm) or metalloid oxides. Among
the nanoparticles (metal oxides) with which the fibers can be
modified are: Au.sub.2O.sub.3, Ag.sub.2O.sub.3, Ag.sub.2O, BaO,
CaO, CaO.sub.2, Cu.sub.2O, Cu.sub.2O.sub.2, CuO, CoO, CrO,
Cr.sub.2O.sub.3, CrO.sub.3, FeO, Fe.sub.2O.sub.3, HgO, KO.sub.2,
K.sub.2O.sub.2, MgO, MnO, Mn.sub.2O.sub.3, MnO.sub.2,
Mn.sub.2O.sub.7, Na.sub.2O, Na.sub.2O.sub.2, NiO, Ni.sub.2O.sub.3,
PbO, Li.sub.2O, SnO, SnO.sub.2, TiO, Ti.sub.2O.sub.3, TiO.sub.2,
SiO.sub.2, SiO, ZnO, ZnO.sub.2, B.sub.2O.sub.3, GeO.sub.2,
As.sub.4O.sub.6, Sb.sub.2O.sub.3, Sb.sub.2O.sub.5, TeO.sub.2 and a
combination thereof.
[0027] After immersing the fiber in the stable gel with the
precursors, a hydrothermal treatment is carried out, which promotes
the crystallinity of the nanoparticles. The hydrothermal treatment
can occur in any equipment known by a person moderately skilled in
the art who subjects the material (fiber) to temperatures between
110 and 210.degree. C. The hydrothermal treatment can be carried
out, for example, in an autoclave where the fibers are immersed in
the stable gel. The hydrothermal treatment is carried out at a
heating rate between 1.degree. C./min and 15.degree. C./min,
between 2.degree. C./min and 8.degree. C./min, and/or between
5.degree. C./min and 20.degree. C./min, a temperature between
110.degree. C. and 210.degree. C., a temperature between
140.degree. C. and 180.degree. C., a temperature between
155.degree. C. and 170.degree. C., for a holding time between 2 and
48 hours, between 6 and 24 hours, between 10 hours and 15 hours.
Subsequently, a cooling is carried out, which can be performed, for
example, by natural convection. The fibers are then removed, washed
with distilled water and dried until a fiber modified with
nanoparticles is obtained.
[0028] "Hydrothermal treatment" means a process which involves a
solvent and temperature, wherein the solvent is generally water,
which can be mixed with alcohols or other types of solvents.
[0029] As observed in the SEM micrographs (FIG. 1 and FIG. 2),
quite heterogeneous surfaces are observed due to the growth of the
nanoparticles, which also shows how the nanofibers are covered in a
uniform way and confirms that there is no clogging of the pores
between fibers. This implies that the nucleation and growth of the
nanoparticles occurs directly on the nanofibers.
[0030] The present invention can be used for photocatalytic
degradation, which is one of the most widely-studied methods, due
to the fact that it efficiently converts solar energy into
effective chemical energy. Therefore, it is used to degrade
hazardous organic materials in air and water, absorb heavy metals,
break down bacteria and viruses, among others. Also the product of
the present invention is used in filtration and purification,
wherein it is necessary to have porous substrates with permeation
properties and which at the same time degrade harmful
substances.
[0031] The present invention provides a method for obtaining
modified fibers with nanoparticles with high yields, a good use of
raw material, low temperatures and short process times. Reducing
the amount of processes related to the immersion of the fibrous
substrates in the solutions, promoting the crystallinity of the
metal oxide nanoparticles (NpsOm) in a single stage without the
need to calcinate (process at low temperature) and without
significantly affecting the porosity between the fibers.
[0032] It should be understood that the present invention is not
limited to the embodiments described and illustrated, so as it will
be evident to a person skilled in the art there are possible
variations and modifications that do not depart from the spirit of
the invention, which is only defined by the claims.
Example 1.
[0033] The PAN polymer is dissolved in the DMF solvent for a
solution with a concentration of 8% w/v. This solution is
electrospinned and the fibers obtained are kept apart for the
hydrothermal treatment.
Example 2. Process for Obtaining Modified Nanofibers with TiO.sub.2
Nanoparticles
[0034] a) Prepare a Stable Gel from Nanoparticle Precursors:
[0035] For the preparation of a stable gel TTIP (as a precursor of
TiO.sub.2) was added by mixing the TTIP with magnetic stirring in
an isopropanol and acetylacetone solution, until a homogeneous
solution was obtained. After homogenization, this solution was
added dropwise in water with addition of glacial acetic acid (pH 2)
and kept in vigorous agitation for 2 hours. By proceeding with the
following molar ratio:
TABLE-US-00001 Reagent TTIP Acac IsoOH Water Molar ratio 1 0.25 2.0
20.0
[0036] The stable gel obtained was diluted in water with addition
of acids (pH 2) until obtaining a solids percentage of 0.1% A
stable diluted gel is obtained.
[0037] b) Immerse Some Fibers in the Stable Gel and Subject them to
a Hydrothermal Treatment until the Fibers are Coated with the
Nanoparticles:
[0038] About 80 mg of polyacrylonitrile nanofibers (PAN) obtained
by Example 1 were taken and immersed in 70 mL of the stable gel
diluted in step (a). Subsequently, they are subjected to a
hydrothermal treatment in an autoclave at 160.degree. C. for 12
hours. It is suggested that the equipment be filled to a volume
between 50% and 80%.
[0039] c) Washing
[0040] After the thermal treatment, the polyacrylonitrile
nanofibers were removed from the autoclave and washed 5 times with
distilled water until the excess of generated nanoparticles was
removed.
[0041] With the proposed process, PAN nanofibers covered in the
surface were obtained by TiO.sub.2 nanoparticles, as shown in the
micrograph of FIG. 1. This implies that the nucleation and growth
of the nanoparticles occurs directly on the nanofibers.
Example 3. Process for Obtaining Modified Nanofibers with TiO.sub.2
and CeO.sub.2 Nanoparticles
[0042] A second precursor was added, this time a precursor of
CeO.sub.2 nanoparticles, wherein the nanoparticle precursor was
Ce(NO.sub.3).sub.3. 6H.sub.2O obtaining the combination of
TiO.sub.2--CeO.sub.2. For a 5% molar ratio of CeO.sub.2, 133 mg of
Ce(NO.sub.3).sub.3. 6H.sub.2O were placed to obtain 5 mL of stable
gel. The micrograph obtained for this example is seen in FIG.
2.
Example 4. Other Nanofibers Modified with Nanoparticles
TABLE-US-00002 [0043] Solids Temperature Time Fiber Precursor NP
content (.degree. C.) (hours) Cotton (natural TTIP TiO.sub.2 0.1%
110 12 organic fiber) Cellulose TEOS SiO.sub.2 0.5% 200 10
Polypropylene Zinc acetate ZnO.sub.2 1.5% 250 8
(Zn(CH.sub.3COO).sub.2.cndot.2H.sub.2O) Glass TTIP and
Ce(NO3)3.cndot.6H2O TiO.sub.2--CeO.sub.2 4.0% 120 24 (inorganic
fiber)
Example 5. Characterization of Crystalline Properties
[0044] Characterization of the crystalline properties of the
samples disclosed in Examples 2 and 3 with different ratios of
TiO.sub.2 and CeO.sub.2 was made. In the diffractograms (FIG. 5)
diffraction peaks are observed related to the formation of
crystalline nanoparticles in the composition range TiO.sub.2 and
CeO.sub.2 tested. At 26.degree. C. the characteristic peak of the
anatase crystalline phase of TiO.sub.2 is observed, which indicates
that the process carried out at low temperatures ensuring the
formation of TiO.sub.2 crystals on the fibers.
Example 6. Characterization of Nanofibers by SEM Micrographs
[0045] Through the method of the present invention where, due to
the post-functionalization of the PAN nanofibers with the TiO.sub.2
sol-gel in the hydrothermal treatment of Example 2, hybrid
nanofibers were obtained, as shown in the SEM FIG. 1.
[0046] The surface detail of the sol-gel modified nanofibers of
Example 3 is seen in FIG. 2. The nanofibers are covered in a
uniform way, which implies that the nucleation and growth of the
nanoparticles occurs directly on the nanofibers.
Example 7. Characterization of the Nanofibers by TEM Microraphs and
Diffractograms
[0047] The average diameter of the nanofibers obtained through
post-functionalization with sol-gel is not expected to change
significantly with respect to the initial value of the fibers. The
results of crystallinity of the fibers obtained by Example 2 are
seen in FIG. 3a and FIG. 3b. The hydrothermal treatment is
favorable to promote the crystallinity of the TiO.sub.2--CeO.sub.2
5% nanoparticles obtained by Example 3. This is seen in the ring
diffraction pattern of FIG. 3i, which are related to the
crystallinity of the polymer nanofibers by the plane (0 0 2), and
planes (1 0 1), (0 0 4), (2 0 0) and (1 0 2) of the anatase crystal
phase. In the same way, this is confirmed by the X-ray
diffractograms obtained for the samples in FIG. 5.
Example 8. Degradation Efficiency Measures
[0048] The degradation efficiency evaluation of methylene blue as a
model substance for the simulation of an organic pollutant in the
presence of solar radiation using the modified nanofibers obtained
by means of Examples 2 and 3 was carried out.
[0049] The comparison of the degradation efficiencies of methylene
blue are observed in FIG. 6, wherein they are compared to two other
nanoparticle incorporation processes in nanofiber in which the
modification occurs from the formation or spinning of the fiber.
When the nanoparticles are incorporated into the nanofibers in an
immersion process (NFs+NPs), the lowest efficiencies are obtained.
When the nanofibers are immersed in the precursors
(NFs+precursors), the efficiency is increased and finally, when
carried out by the process of the present invention, the efficiency
is much more increased. In conclusion, the samples obtained with
the process proposed in the present invention had higher yields
than those exhibited by the other processes tested.
* * * * *