U.S. patent application number 11/926685 was filed with the patent office on 2008-03-06 for substrate with a photocatalytic coating.
This patent application is currently assigned to SAINT-GOBAIN RECHERCHE. Invention is credited to Arnaud Marchal, Christian Marzolin, Xavier Talpaert.
Application Number | 20080053308 11/926685 |
Document ID | / |
Family ID | 9527213 |
Filed Date | 2008-03-06 |
United States Patent
Application |
20080053308 |
Kind Code |
A1 |
Marzolin; Christian ; et
al. |
March 6, 2008 |
SUBSTRATE WITH A PHOTOCATALYTIC COATING
Abstract
A gas guiding device including a conduit configured to pass a
gas, and a substrate on the conduit, the substrate including, a
fibrous material, and a coating provided at least (i) over a
portion of a surface of the fibrous material or (ii) within a
volume of the fibrous material, the coating being configured to
have photocatalytic properties and having at least a partially
crystallized semiconducting material which has photocatalytic
properties and which is of the oxide or sulphide type.
Inventors: |
Marzolin; Christian; (Paris,
FR) ; Marchal; Arnaud; (Ecouen, FR) ;
Talpaert; Xavier; (Paris, FR) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
SAINT-GOBAIN RECHERCHE
Aubervilliers Cedex
FR
|
Family ID: |
9527213 |
Appl. No.: |
11/926685 |
Filed: |
October 29, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09719153 |
Mar 16, 2001 |
7309664 |
|
|
PCT/FR99/01375 |
Jun 10, 1999 |
|
|
|
11926685 |
Oct 29, 2007 |
|
|
|
Current U.S.
Class: |
95/274 ; 427/595;
55/524 |
Current CPC
Class: |
C04B 2111/50 20130101;
Y10T 442/2344 20150401; Y10T 442/2311 20150401; C04B 41/5041
20130101; B01D 53/8668 20130101; C04B 41/009 20130101; C03C 25/47
20180101; C04B 41/009 20130101; B01D 2255/802 20130101; C03C
2217/71 20130101; B01J 35/004 20130101; Y10T 442/25 20150401; C04B
2111/52 20130101; B01D 2257/90 20130101; Y10T 428/249924 20150401;
Y10T 442/2738 20150401; C04B 41/0072 20130101; C04B 41/4535
20130101; C04B 41/4535 20130101; C04B 41/48 20130101; C04B 41/4922
20130101; C04B 41/0072 20130101; C04B 30/02 20130101; Y10T
428/31612 20150401; Y10S 428/905 20130101; Y10T 442/2402 20150401;
C03C 25/26 20130101; B01J 35/002 20130101; B01D 53/885 20130101;
Y10T 442/2475 20150401; Y10T 442/699 20150401; C04B 41/5041
20130101; Y10T 442/603 20150401; C03C 25/42 20130101; Y10T 442/605
20150401; C04B 41/5041 20130101; Y10T 442/2992 20150401; Y10T
442/604 20150401; Y10T 442/60 20150401 |
Class at
Publication: |
095/274 ;
427/595; 055/524 |
International
Class: |
B01D 24/00 20060101
B01D024/00; B01D 46/30 20060101 B01D046/30 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 10, 1998 |
FR |
98/07276 |
Claims
1. A gas guiding device comprising: a conduit configured to pass a
gas; and a substrate on the conduit, the substrate including, a
fibrous material, and a coating provided at least (i) over a
portion of a surface of the fibrous material or (ii) within a
volume of the fibrous material, the coating being configured to
have photocatalytic properties and having at least a partially
crystallized semiconducting material which has photocatalytic
properties and which is of the oxide or sulphide type.
2. The gas guiding device of claim 1, wherein the semiconductor
material is titanium oxide at least partially crystallized in
anatase form.
3. The gas guiding device of claim 1, further comprising: a source
of light configured to provide light to the substrate to activate
the photocatalytic properties of the substrate.
4. The gas guiding device of claim 3, wherein the source of light
is one of a halogen lamp and a fluorescent tube.
5. The gas guiding device of claim 1, wherein the substrate is
provided outside the conduit.
6. The gas guiding device of claim 1, wherein the substrate is
provided inside the conduit to apply the photocatalytic properties
to the passing gas.
7. The gas guiding device of claim 1, wherein the coating is
provided within a thickness of the fibrous material.
8. The gas guiding device of claim 1, wherein the semiconducting
material is introduced into the coating in the form of particles in
a colloidal suspension or in the form of powder.
9. The gas guiding device of claim 1, wherein the at least
partially crystallized semiconducting material includes titanium
oxide and originates from thermal decomposition of organometallic
or metal halide precursor(s) within the coating.
10. The gas guiding device of claim 1, further comprising: a
bonding agent that adheres the fibers of the fibrous material to
each other and an adhesion promoting agent that adheres the coating
to the fibers.
11. The gas guiding device of claim 10, wherein the bonding agent
includes the adhesion promoting agent.
12. The gas guiding device of claim 10, wherein the adhesion
promoting agent is an organic, mineral or organo-mineral hybrid
mono- or multicomponent.
13. The gas guiding device of claim 10, wherein the adhesion
promoting agent comprises a silica-containing component of the
silane, silicone, or siloxane type.
14. The gas guiding device of claim 10, wherein the adhesion
promoting agent comprises one or more organic polymers which are
associated with additives which belong to the antioxidant series
and/or ultraviolet absorbers and/or stabilisers of the amine type
with steric hindrance.
15. The gas guiding device of claim 10, wherein the adhesion
promoting agent comprises at least one amorphous metal oxide of the
TiO.sub.2 or SiO.sub.2 type, which originates from a thermal
decomposition of silica-containing, organometallic or metal halide
precursor(s) within the coating.
16. The gas guiding device of claim 10, wherein the adhesion
promoting agent comprises at least one mineral component selected
from aluminium phosphates and potassium or calcium
aluminosilicates.
17. The gas guiding device of claim 1, wherein the fibrous material
is arranged in the form of a web, felt, shell, paper or loose
material.
18. The gas guiding device of claim 1, wherein the coating having
photocatalytic properties covers at least a portion of fibers of
the fibrous material over a thickness of at least 5 nm.
19. The gas guiding device of claim 1, wherein the coating is
provided both on the portion of the surface of the fibrous material
and within the volume of the fibrous material.
20. An air conditioning device comprising: a conduit configured to
pass a gas; and a substrate on the conduit, the substrate
including, a fibrous material, and a coating provided at least (i)
over a portion of a surface of the fibrous material or (ii) within
a volume of the fibrous material, the coating being configured to
have photocatalytic properties and having at least a partially
crystallized semiconducting material which has photocatalytic
properties of oxide or sulphide.
21. A filter made of a substrate comprising a fibrous material
which is provided, over at least a portion of its surface with a
coating with photocatalytic properties comprising a semi-conducting
material with photocatalytic properties of the oxide or sulphide
type, in particular titanium oxide at least partially crystallized
in anatase form, the said material being used in combination with a
promoter of adhesion to the said fibrous material, wherein the
adhesion promoter comprises at least one metal oxide of the
SiO.sub.2 type originating from the thermal decomposition of
silicon-comprising, organometallic or metal halide precursor(s)
within the coating.
22. A method for purifying gaseous effluents or atmosphere
comprising: circulating the gaseous effluents or atmosphere through
the filter of claim 21.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional of U.S. patent application
Ser. No. 09/719,153, filed Mar. 16, 2001, which is a 371 of
International Patent Application No. PCT/FR99/01375, filed Jun. 10,
1999, and claims priority to French Patent Application No.
98/07276, filed Jun. 10, 1998. The entire contents of these
applications are included herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to substrates provided with a
photocatalytic coating, and to the process for producing such a
coating and to its various applications.
[0004] It relates more particularly to coatings comprising
semi-conducting materials based on metal oxide, in particular on
titanium oxide, which are capable of initiating radical reactions
under the effect of radiation of appropriate wavelength, resulting
in the oxidation of organic products. These coatings thus make it
possible to confer novel functionalities on the materials which
they cover, in particular dirt-repellent, fungicidal, bactericidal,
algicidal or odour-controlling properties, optionally in
combination with hydrophilic or anti-condensation properties, and
the like.
[0005] 2. Discussion of the Background
[0006] Highly diverse substrates have to date been envisaged, in
particular construction materials used in the field of construction
or vehicles (windows, facing, cladding or roofing materials, and
the like) or materials used in purification processes.
[0007] International Patent Applications WO97/10186 and WO97/10185
have thus made known coatings comprising anatase crystallized
TiO.sub.2 with photocatalytic properties, coatings obtained from
the thermal decomposition of appropriate organometallic precursors
and/or from "precrystallized" TiO.sub.2 particles, suited in
particular to deposition as a thin layer on glass in order to
preserve its optical quality.
[0008] Patent Application EP-A-0,306,301 has also made known the
use of photocatalytic TiO.sub.2 on fibrous materials used to purify
the air, the deposition of the TiO.sub.2 being carried out by a
process of sol-gel type.
SUMMARY OF THE INVENTION
[0009] The aim of the invention is then the improvement of these
photocatalytic coatings, being targeted in particular at improving
their behaviour on any type of substrate and in particular
providing them with better adhesion and better durability,
particularly on substrates exhibiting characteristics of surface
roughness of porosity.
[0010] The subject-matter of the invention is first of all a
substrate comprising a fibrous material which is provided, over at
least a portion of its surface and/or within its thickness, with a
coating with photocatalytic properties comprising a semi-conducting
material with photocatalytic properties of the oxide or sulphide
type in combination with a promoter of adhesion to the said fibrous
material.
[0011] The semi-conducting material "active" with respect to
photocatalysis can be, according to the invention, based on at
least partially crystallized metal oxide, for example zinc oxide,
tin oxide or tungsten oxide. The preferred example according to the
invention relates to titanium oxide at least partially crystallized
in anatase form, which is the crystalline phase which confers on
TiO.sub.2 its photocatalytic properties. It can also relate to
semi-conductors belonging to the family of the sulphides, also at
least partially crystallized, such as zinc sulphide or boron
sulphide. (In the continuation of the text, for greater simplicity,
mention will be made of titanium oxide, it being understood that
the information given will be just as valid for the other
semi-conducting materials mentioned above).
[0012] The term "fibrous material" is understood to mean, within
the meaning of the invention, any material comprising fibres, in
particular mineral fibres, more particularly organized fibres made
of glass or rock mineral wool, of the type of those used in
thermal/sound insulation or to constitute soilless culture
substrates. This term "fibrous material" also includes
fibres/filaments organized as strands, of the type of the strands
used in reinforcement, in particular made of glass.
[0013] These base fibrous materials are subsequently incorporated
in a "substrate", within the meaning of the invention, in various
forms: it can relate to felts, mats, webs, "moulds" intended for
the insulation of pipes, made of mineral wool, textile strands
assembled as fabrics, or non-woven web, made of substrates of paper
type, and the like.
[0014] A photocatalytic coating makes it possible to confer highly
advantageous novel functionalities on these known substrates. Thus,
the felts/mats of mineral wool mainly used in insulation can be
treated only superficially, only on one of their faces, for
example, or on each of their faces, and can acquire a
dirt-repellent/odour-controlling function on at least one of their
treated faces (the visible face and/or the hidden face) in false
ceiling structures of buildings, in antinoise screens alongside
roads or railways, and the like, the condition laid down being that
the photocatalytic coating is accessible to a natural or artificial
light source. Still in the field of insulation, the "moulds" can
also be treated on the inside and/or outside or over their entire
thickness, for example, in order to confer on them a dirt-repellent
and/or bactericidal or fungicidal function. In the form of mats or
of moulds, the substrates treated according to the invention can
advantageously be positioned around outlet conduits in any
ventilation or air-conditioning system but also by being positioned
inside these conduits, these devices being veritable breeding
grounds for bacteria, the condition being that it is necessary to
provide means for the photocatalytic coating to be exposed to
sufficient ultraviolet radiation to be effective: on a visible
external face, natural illumination may be sufficient. If not, the
substrates have to be combined with artificial illuminating means
of the halogen lamp or fluorescent tube type.
[0015] Another application relates to any system for reflecting
and/or scattering natural light or light originating from
artificial illuminating means, such as lampshades or curtains, when
the substrate is, for example, in the web form.
[0016] The other main application, apart from thermal or sound
insulation, of the substrates treated according to the invention
relates to the filtration or the purification of fluids.
[0017] It can relate to any filter used in the filtration of gases,
in particular of air, of paper web or filter paper type, used, for
example, in the ventilation/air-conditioning systems for dwellings
mentioned above or for industrial premises, vehicles or laboratory
rooms with a controlled level of dust, of the "clean" room
type.
[0018] The term "filter" covers two notions within the meaning of
the invention, both the notion of true filtration, where particles
are separated mechanically from the gas carrying them, and the
notion of diffuser, in particular of odour-controlling diffuser,
where the gas to be treated is not necessarily forced to pass
through the photocatalytic substrate, where it can in particular
simply be brought into contact with the latter, without retaining
the suspended particles.
[0019] Mention may be made of many other applications of the gas
"filters" according to the invention: they can also be used to
purify any type of industrial gaseous effluent or any atmosphere of
a given public place or building (as odour-controlling diffuser in
the underground, for example). They can in particular make it
possible to reduce the "VOC" (volatile organic compounds) level of
a given gas stream or of a given atmosphere.
[0020] The filters, surface-treated or treated throughout their
thickness, can become much more effective and much more durable;
this is because the treatment according to the invention gives them
the ability not only to remove microorganisms but also to decompose
organic residues of fatty type, for example, particles which
gradually block the filter. With the invention, these filters
therefore have a longer lifetime. In addition, they have an
odour-controlling function.
[0021] It can also relate to filters for liquids.
[0022] The liquid filters according to the invention have numerous
applications: they can be used for the recycling of wastewater or
for the recycling of water from systems for the irrigation of
soilless culture substrates (for disinfecting the water). They can
also fulfill a function of depollution, in particular depollution
of soils, or a function of reprocessing/depolluting industrial
liquid effluents.
[0023] The advantage of treating all these fibrous substrates
according to the present invention has been seen. However, to
furnish term with a photocatalytic coating was not, initially, very
easy. This was because the question arose of the method of
deposition of the coating on a substrate which is generally
non-smooth, non-flat and of rough and porous type, as well as the
question of the durability of this coating.
[0024] The solution of the invention consisted in adjusting the way
in which it was applied to the substrate, namely superficially or
throughout its thickness, according to the applications targeted as
a function of requirements, and in rendering the anatase TiO.sub.2
of the coating, which is responsible for the photocatalytic
performance, integral with the fibrous material via an appropriate
adhesion promoter. The latter can thus act as "matrix" for the
components of the coating which are "active" with respect to the
photocatalysis phenomenon.
[0025] According to a first embodiment of the present invention,
the titanium oxide is already at least partially precrystallized in
anatase form when it is incorporated in the coating, before being
deposited on the substrate. It can be introduced into the coating
in the form of crystalline particles in colloidal suspension or in
the form of a dry power composed of particles which are optionally
more or less agglomerated with one another. This alternative form
exhibits the advantage of not imposing a high specific heat
treatment on the coating/substrate on which it is deposited
(TiO.sub.2 crystallizes in the anatase form generally in the
vicinity of 400.degree. C.).
[0026] According to a second embodiment of the present invention
which can be combined with the first embodiment, the titanium oxide
originates from the thermal decomposition of precursors, in
particular of the organometallic or metal halide type, within the
coating. The anatase crystallized TiO.sub.2 can thus be
manufactured "in situ" in the coating, once applied to the
substrate, by providing for an ad hoc heat treatment, which must,
however, be compatible with the chosen substrate and the chosen
adhesion promoter.
[0027] The adhesion promoter can be single- or multicomponent, and
its component or components can be organic, inorganic or
organic/inorganic "hybrids".
[0028] It can thus comprise a silicon-comprising component, in
molecular form or in polymeric form, of the silane, silicone or
siloxane type, for example. This is because these components
exhibit a good affinity with the majority of mineral fibres, glass,
rock or even ceramic, affecting the invention. It is even possible,
in some cases, to speak of a kind of grafting of the crystallized
TiO.sub.2 to the inorganic fibres by this type of component.
[0029] The adhesion promoter can also comprise one or more polymers
of organic type. In fact, two scenarios exist: standard organic
polymers, for example of the acrylic or phenol-formaldehyde type,
or the like, can be chose. In this case, there is a risk of this
component being gradually decomposed by photocatalysis by the
TiO.sub.2, at least in the surface regions of the substrate liable
to be exposed to ultraviolet radiation. However, the process can in
fact prove to be advantageous in some applications, by thus
gradually "releasing" active TiO.sub.2. However, it may be
preferable to avoid or slow down as far as possible this
decomposition by choosing appropriate polymers, generally
fluorinated polymers, which are highly resistant to photocatalytic
attacks, for example of the fluorinated acrylic polymer type, of
the polytetrafluoroethylene (PTFE), poly (vinylidene fluoride)
(PVDF) or tetrafluoroethylene-ethylene copolymer (ETFE) type, and
the like.
[0030] One alternative is retaining an adhesion promoter based on
organic polymer(s) and thwarting their decomposition by appropriate
additives, in particular belonging to the family of the
antioxidants (such as the product sold under the name Irganox by
the company Ciba) and/or of the ultraviolet absorbers (such as the
product sold under the name Tinuvin by the same company) and/or of
stabilizers in the form of sterically hindered amines known under
the term "hindered amine light stabilizers" or "HALS".
[0031] The adhesive promoter can also comprise at least one metal
oxide of the TiO.sub.2 or SiO.sub.2 type originating from the
thermal decomposition of precursors of the silicon-comprising,
organometallic or metal halide type within the coating. In this
case, the TiO.sub.2 or SiO.sub.2 component is generated in situ in
the coating, in particular once applied to the substrate, by an
appropriate heat treatment compatible with the substrate. In the
case of TiO.sub.2, it is not, however, necessary to envisage very
high temperatures necessary for an anatase crystallization, if only
an adhesion promoter function is being sought: it can perfectly
well be amorphous or partially crystallized in various crystalline
forms, just like SiO.sub.2. It is thus possible to have a coating
of the amorphous metal oxide matrix type which fixes the "active"
particles of crystallized photocatalytic oxide.
[0032] The adhesion promoter can also comprise at least one
inorganic component chosen from aluminium phosphates and potassium
or calcium aluminosilicates.
[0033] One embodiment of the invention consists in that at least
one of the two essential components of the coating, namely, on the
one hand, the "active" (with regard to photocatalysis) components
and, on the other hand, the adhesion promoter, forms part of the
binder making possible the intrinsic cohesion of the fibrous
material.
[0034] This is because, if the material is glass or rock mineral
wool of the insulation type, such as that produced by Isover
Saint-Gobain, the latter is in numerous applications provided with
a binder generally denoted under the name of size and generally
applied in the liquid phase by spraying under the fiberizing
devices. The solvent/dispersant is generally aqueous and it
evaporates on contact with or in the vicinity of the hot fibres.
The agents for sticking the fibres to one another, generally of the
resin type, for example phenolic resin, such as
urea-phenol-formaldehyde polymers, cure under hot conditions. One
possibility then consists in adding the adhesion promoter and the
"active" components to the aqueous medium of the size or even in
using/adapting the components of the size in order for them to act
simultaneously as binder of the fibres to one another and of
promoter of fibres/"active" components adhesion.
[0035] For further details on typical sizing compositions and their
method of application to fibres, reference may advantageously be
made in particular to Patents EP-148,050, EP-246,952, EP-305,249,
EP-369,848, EP-403,347, EP-480,778 and EP-512,908. However, it
should be noted that, in specific applications, the mineral wool
can be devoid of binder, for example that composed of relatively
fine fibres used to prepare filter papers, as disclosed, for
example, in Patents EP-0,267,092 and EP-0,430,770, or needled
felts.
[0036] If the material is instead a fibrous material of reinforcing
strands or textile strands type, in particular such as that
manufactured by Vetrotex, the cohesiveness of the strands resulting
from the assembling of individual filaments under a bushing is
generally provided by application of a binder generally denoted
under the term of sizing composition. Here again, it is applied in
the liquid phase and comprises one or more agents "sticking
together" the fibres/filaments. It is therefore possible to choose
to add the "active" components and/or the adhesion promoter
according to the invention to the liquid medium or to adapt its
composition in order to make it act both as interfilament binder
and as promoter of strands/"active" components adhesion.
[0037] For further details on sizing compositions, reference may
advantageously be made in particular to Patents EP-243,275,
EP-394,090, EP-635,462, EP-657,396, EP-657,395, EP-678,485,
EP-761,619 and WO-98/18737.
[0038] Mention may also be made of Patent WO-98/51633, relating to
the deposition of size in two steps under the fiberizing device,
size in addition being capable of polymerizing at room temperature.
In this case, it is possible to choose to introduce the material
with photocatalytic properties either into the first sizing
composition or into the second or into both.
[0039] All these sizes mentioned above are generally applied, using
sizing rolls just under the bushing, to the fibrous material still
in the form of individual filaments in the course of being gathered
together into strands. There also exist binders, intended to ensure
the cohesion of mats obtained from a blanket of glass strands,
which are ejected onto continuous or non-continuous strands which
have already been sized. Mention may be made, by way of example, of
Patent WO-97/21861. The photocatalytic material can be incorporated
in this binder, which also acts as adhesion promoter.
[0040] The sizes or binders mentioned above are either in the
aqueous phase or in the non-aqueous phase. In the latter scenario,
a heat treatment is generally no longer necessary to remove the
water, the components chosen then being chosen so as to be able to
polymerize at room temperature. In this case, the incorporation of
materials with photocatalytic properties pre-existing independently
of any heat treatment is favoured, such as small crystallized
titanium oxide particles.
[0041] As mentioned above, the fibrous material according to the
invention can therefore be organized in the web (facing, for
example), felt or paper form or in various geometric forms (flat or
pleated paper type sheets, for example, panel, hollow cylindrical
"mould", woven or non-woven web, and the like). The fibrous
material can also be in bulk, in the form of optionally graded
short fibre or flocks.
[0042] The photocatalytic coating of the invention is
advantageously applied to the fibrous material so that at least a
portion of the "fibres" of the said material (including the notions
of fibres, of filaments and of strands) is sheathed with the
coating over a thickness of at least 5 nm, in particular over a
thickness of the order of 30 to 50 nm.
[0043] This sheathing ensures maximum effectiveness of the coating,
its photocatalytic activity increasing as it is distributed over a
greater specific surface. The preferred thickness takes into
account the most commonly encountered mean size of the anatase
TiO.sub.2 crystallites.
[0044] Another subject-matter of the invention is the processes for
the manufacture of the substrates defined above.
[0045] According to a first alternative form, the photocatalytic
coating is deposited, in the liquid phase, on the production line
itself for the fibrous material. The advantage to this alternative
form lies in the fact that the still semi-finished fibrous material
can be treated an the best use can be made of the temperature which
it is at, for example, resulting in a saving in terms of time and
of production cost. This, a first embodiment consists in "hot"
depositing the coating between the fiberizing devices and the
devices for receiving the fibres. The fiberizing devices can
consist of glass centrifuging dishes, known as "internal
centrifuging devices", such as ones disclosed, for example, in
Patents EP-0,189,534 and EP-0,519,797, making it possible to
fiberize mineral wool of glass type, or devices for fiberizing by
so-called external centrifuging using a succession of centrifuging
wheels, such as ones disclosed, for example, in Patents
EP-0,465,310 or EP-0,439,385, making it possible to obtain mineral
wool of basalt rock type. It can also relate to devices for
fiberizing by mechanical drawing, in order to obtain reinforcing
glass strands, by air blowing or by steam blowing, according to
processes well known to persons skilled in the art. Use is thus
made of the fact that the fibres are still at a relatively high
temperature by applying the coating, generally in
solution/dispersion, in a solvent, for example an aqueous solvent,
which evaporates on contact with or in the vicinity of the fibres.
The heat can also make it possible to cure the component or
components of the adhesion promoter, if they are of the resin type,
or to decompose them thermally, if they are of the
silicon-comprising precursor or metallic precursor type mentioned
above.
[0046] As mentioned above, the coating in the liquid phase can be
applied at the same time as an optional "binder" of the sizing
composition type or even form part of it. It may also be preferable
to apply it to the fibrous material before or after the said
"binder".
[0047] According to a second embodiment of this first alternative
form, the photocatalytic coating, still generally in the liquid
phase, can be deposited "after" the receiving devices which collect
the fibres/filaments or strands resulting from the fiberizing
devices and in particular before or during the post-fiberizing heat
treatment of the fibrous material. Thus, for mineral wool of
insulation type, the receiving devices are generally composed of a
suction conveyor belt which gathers together the mineral wool and
passes it into a forming oven. It can be judicious to apply the
coating between the two devices (fiberizing/receiving), for example
superficially, and to use the heat of the oven to cure or complete
the coating, if necessary.
[0048] Likewise, in the field of reinforcing glass, the strands are
drawn and wound off in the form of spools or cut up under the
bushing, after having been appropriately sized, and then generally
dried in heated chambers, before being converted and/or used.
[0049] As mentioned above, it is therefore possible to deposit the
photocatalytic coating just under the bushing, in particular
concomitantly with the deposition of the size, in which it can be
incorporated. It is also possible to deposit it during the stage of
finishing the spooled strands into finished products: it can, for
example, relate to the conversion operation targeted at
manufacturing mats of chopped strands, in a subsequent operation;
it is also possible to deposit it on the downstream line, in
particular during the conversion of the continuous strands,
gathered together as a blanket, into a mat of continuous
strands.
[0050] In the last two cases, the photocatalytic coating can be
deposited by an ejection system of the adjusted sprayer type,
before, during or at the same time as the binder used (or be used
in combination with it in the same liquid phase).
[0051] According to a second alternative form, the photocatalytic
coating is deposited in the liquid phase on the finished fibrous
material, in a subsequent operation. What this involves is instead
a "cold" treatment, requiring a post-deposition heat treatment in
order to evaporate the solvent and optionally to cure or to
complete, to constitute the coating.
[0052] Whatever the alternative form chosen, the coating can be
deposited by different techniques. If the coating comprises
"active" anatase crystallized TiO.sub.2 powder or particles from
the start, it is not necessary for the fibrous substrate to be very
hot; temperatures of less than 300.degree. C. and even of less than
200.degree. C. may suffice, indeed even room temperature, and
therefore temperatures which are found on production lines for the
commonest mineral fibrous materials, temperatures which are in
addition compatible with the sizes for these materials, which are
generally organic, at least partly. If, on the other hand, it is
necessary to generate anatase TiO.sub.2 "in situ", it is necessary
to envisage temperatures of the order of 400.degree. C., instead
with fibrous materials devoid of binder in the general sense of the
term and in a subsequent operation, for example by a process of
sol-gel type.
[0053] In concrete terms, it is possible to choose to impregnate
the fibrous material to the core and to use a technique of
"dip-coating" type, where the fibrous material is at least
partially immersed in a bath comprising the coating in the liquid
phase. It is also possible to choose coating or spraying adapted to
a surface treatment. The deposition can also be carried out in a
fluid which is non-liquid in the usual sense of the term, for
example in a hypercritical fluid.
[0054] Another subject-matter of the invention relates to the
application of these treated substrates to thermal/sound insulation
or facing materials, with a dirt-repellent, fungicidal,
antibacterial or odour-controlling function, or to liquid or gas
filters of paper type or of felt or mould type.
BRIEF DESCRIPTION OF THE DRAWINGS
[0055] Other advantageous details and characteristics of the
invention become apparent from the non-limiting embodiments
described below in reference to the following figures:
[0056] FIG. 1 shows a scanning electron microscopy (SEM) photograph
of the surface of a fibrous material treated according to an
embodiment of the invention;
[0057] FIG. 2 is another SEM photograph showing the surface of the
fibrous material shown in FIG. 1; and
[0058] FIG. 3 is yet another SEM photograph showing the surface of
the fibrous material shown in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0059] All the following examples relate to the deposition of a
coating for which the photocatalytic "active" components are made
of anatase crystallized TiO.sub.2. As mentioned above, the
invention applies in the same way to semi-conducting "active"
components with photocatalytic properties similar to anatase
TiO.sub.2 and which can be provided in the same form, in particular
zinc oxide, tin oxide and tungsten oxide.
EXAMPLE 1
[0060] a needled felt (dimensions 210.times.297.times.5 mm.sup.3),
composed of glass fibers of insulating type obtained by binder-free
internal centrifuging and with a relative density of 55 kg/m.sup.3,
was sprayed with an aqueous TiO.sub.2 solution, sold under the
trade name "ToSol" by Saga Ceramics, over its entire thickness.
[0061] This solution containing particles of TiO.sub.2 crystallized
in anatase form, probably composed of crystallite agglomerates,
these agglomerates having a mean size of the order of 20 to 80 nm.
These particles are therefore the "active" components in terms of
photocatalysis. The solution also contains an organometallic
TiO.sub.2 precursor which will decompose into predominantly
amorphous TiO.sub.2 by heat treatment and which will act as
adhesion promoter.
[0062] The coating obtained was baked at 200.degree. C. for 2 hours
and contains anatase nanocrystals in an amorphous TiO.sub.2 matrix.
The yellow colour of the filter thus manufactured testifies to the
presence of organic compounds originating from the precursor
solution. After exposure to ultraviolet A radiation under a dose of
4 W/m2 for 2 hours, the yellow colour has completely disappeared,
which shows complete decomposition of the residual organic
pollutants.
EXAMPLE 2
[0063] Glass fibre of insulation type obtained by binder-free
internal centrifuging was converted by the papermaking route in
pure water. The paper obtained, circular with a diameter of 100 mm
and a weight per unit area of 150 g/m2, was subsequently
impregnated over its entire thickness by dip-coating it in an
alcoholic dispersion containing, by volume, 5% water, 1%
tetraethoxysilane (the adhesion promoter) and 1% anatase
crystallized TiO.sub.2 particles with a mean diameter of 30 nm (the
"active" components). The paper was dried in the open air and then
baked in an oven at 450 C for 30 minutes. This filter was
subsequently placed over an inlet orifice of a fume cupboard. A
control filter, without anatase TiO.sub.2, was placed over the
neighbouring orifice. An ultraviolet A lamp shines on these filters
at a dose of 4 W/m2. After the cupboard had been operated for 15
days, the treated filter was still white, whereas the untreated
filter was fouled.
EXAMPLE 3
[0064] A composition for the sizing of glass wool of insulation
type obtained by internal centrifuging was manufactured by
mixing:
[0065] 55 G of resin obtained by condensation of phenol and
formaldehyde in an initial formaldehyde/phenol molar ratio of
approximately 3.2/1, which condensation is carried out
conventionally with a catalyst in the form of sodium hydroxide at
5.5% by weight with respect to the phenol,
[0066] 45 g of urea,
[0067] 3 g of aminopropyltrimethoxysilane,
[0068] 0.3 g of ammonium sulphate,
[0069] 6 g of 30% by volume aqueous ammonia,
[0070] 1200 g of a 25% by weight dispersion in water of anatase
crystallized TiO.sub.2 particles, and
[0071] 34 litres of water.
[0072] The TiO.sub.2 particles have a mean diameter of
approximately 45 nm. The adhesion promoter for the latter can be
regarded as all the other components of the size and very
particularly the silane.
[0073] This composition was sprayed via the sizing ring during a
fiberizing of the glass wool under the centrifuging dishes. The
felt obtained was subsequently passed on the line into an oven at
180.degree. C. for 2 minutes. The felt has a weight per unit area
of 560 g/m.sup.2 and a loss on ignition of 1.4% (measurement known
to a person skilled in the art, expressed by weight, by heating the
felt at a temperature sufficient to remove all the organic
compounds). A 1.times.20.times.40 mm.sup.3 piece was removed and
placed in a vessel with 20 g of an aqueous solution comprising 1
g/l of ethanol and 15 mg/l of hydrogen peroxide. The solution was
shone on by a mercury lamp producing 4 W/m.sup.2 of ultraviolet
radiation and the concentration of hydrogen peroxide was monitored
by colorimetry. Oxidation of ethanol by hydrogen peroxide,
catalysed by the anatase TiO.sub.2 irradiated with ultraviolet
radiation, is observed.
[0074] The photocatalytic activity of the felt was evaluated by
measuring the weight of hydrogen peroxide H.sub.2O.sub.2 in
milligrams which disappears per gram of fibre in the solution and
per hour. The result was 4.4 mg H.sub.2O.sub.2/gfibre/hour.
[0075] Samples of 200.times.300.times.200 mm3, coming from the same
treatment, have been subjected to naturel sun exposure. Gradually
the yellow colour, that is characteristic for the resin used,
disappeared from the exposed surfaces and to some centimetres in
depth. This vanishing clearly indicated a degradation of the
phenolic resin used as well as the penetration of the
photocatalytic effect inside the material. Similar results were
obtained und controlled UVA radiation of 4 W/m.sup.2 for 24
hours.
EXAMPLE 4
[0076] 280 g of glycidoxypropyltrimethoxysilane were added to a
sizing composition similar to that of Example 3 (other silane
combining with the above to act as adhesion promoter). The felt
obtained by fiberizing and sizing with this solution was staved at
180.degree. C. for 2 minutes. The felt has a weight per unit area
of 1 kg/m.sup.2 and a loss on ignition of 1.4%. The measurement of
the photocatalytic activity, carried out as in Example 3, gave a
value of 3 mg H.sub.2O.sub.2/gfibre/hour.
[0077] FIGS. 1, 2 and 3 show, in three different scales, a fibre
covered with the photocatalytic coating. FIG. 1 shows more
particularly a fibre, at the surface of which is clearly
distinguished a sheathing of TiO.sub.2 particles, two successive
magnifications being shown in FIGS. 2 and 3.
[0078] In conclusion, it is found that the coating of the invention
exhibits a proven photocatalytic activity on fibres, whatever the
implementational alternative forms:
[0079] Example 1 illustrates a deposition "in a subsequent
operation", outside the line for the production of mineral wool,
using "precrystallized" TiO.sub.2 particles and an inorganic
adhesion promoter manufactured in situ, on a fibrous substrate of
felt type.
[0080] Example 2 also illustrates a deposition "in a subsequent
operation", on a fibrous substrate of paper type, with
precrystallized TiO.sub.2 particles and a silicon-comprising
adhesion promoter.
[0081] Examples 3 and 4 illustrate an in-line hot deposition under
the fiberizing devices, which will make possible treatment within
the thickness of the fibrous material, with "precrystallized"
TiO.sub.2 particles and adhesion promoters of the family of the
silanes in combination with the components of a standard size, in
the aqueous phase.
[0082] Photocatalytic webs based on mineral fibres were
manufactured using a plant which makes it possible to carry out the
impregnation of a glass web in a sizing solution, the application
Os suction to this web (in order to remove the excess binder) and,
finally, its baking in an oven, the entire process being carried
out in-line and continuously. The web is unwound on a conveyor
belt, conveyed into the sizing bath via an impregnation roller,
passes above a negative-pressure tank (suction device) and is
finally conveyed by a second conveyor belt into the baking
oven.
[0083] Various types of photocatalytic media were synthesized
according to this process, in accordance with the following
examples:
EXAMPLE 5
A Medium for the Purification of Gases
[0084] An 80 g/m2 glass web was impregnated with an aqueous
solution containing 3.1% of Glymo (glycidoxypropyltrimethoxysilane)
and 2.9% of titanium dioxide nanoparticles at a rate of 0.2
m/min.
[0085] This web, having been subjected to a suction equivalent to a
water column of 35 mm, was subsequently baked at 200.degree. C. for
10 minutes. The resulting loss on ignition is 7%.
[0086] Measurements of effectiveness in the gas phase were then
carried out under the following conditions: 150.times.200 mm.sup.2
of the resulting product were placed in a cylindrical
photocatalysis reactor. This reactor is composed of an axial UV-A
lamp (365 nm), around which is surrounded, with a spacing of 1 cm,
the photocatalytic medium in 3 layers, and of an aluminium jacket.
The intensity of the irradiation on the web is 1 mW/cm.sup.2. The
reactor is inserted in a closed circuit, with recirculation, the
gas passing through the medium from the inside of the closed
cylinder over the web towards the outside.
[0087] The volume of the cell (photocatalysis reactor) is 0.9 l and
that of the complete circuit (immobilized volume) is one litre. The
experiments consisted in evaluating the photocatalytic
decomposition of n-hexane.
[0088] To do this, various amounts of n-hexane (ranging up to 2000
ppm in air) were injected into the circuit, the flow rate of the
latter being regulated at 1 l/min. At regular intervals, 50 .mu.l
samples of gas were withdrawn in order to measure the
concerntration of n-hexane present in the circuit.
[0089] It was shown that the direct decomposition by UV of n-hexane
is negligible, just as its absorption by the medium. In constrat,
n-hexane is virtually 100% decomposed in less than one hour when it
passes through the photocatalytic medium, though under weak UV
irradiation.
EXAMPLE 6
A Medium for Liquid Purification
[0090] According to the same process, a 60 g/m glass web was
impregnated in an aqueous solution comprising 1 g/l of A1100 silane
and 5 g/l of titanium dioxide (sold under the name P25 by Degussa)
held in suspension by appropriate means.
[0091] The web was impregnated in-line at 0.6 m/min, the excess
binder having been removed under a negative pressure of 90 mm of
water column. The product was baked at 300.degree. C. for 30
minutes. Measurements of effectiveness in the liquid phase were
then carried out in order to describe this material.
[0092] A circular specimen of web (diameter 100 mm) was placed at
mid-height in a 300 ml beaker. The bottom and the edges of the
receptacle having been rendered opaque, the beaker is illuminated
by a bank of UV-A lamps (365 mm) delivering a power of 3.5 mW/cm2
to the web. An aqueous solution (deionized water) containing 10
mg/l of phenol is poured into the device and is kept stirred
magnetically. The decrease in concentration of the phenol is then
monitored, samples being withdrawn at regular time intervals, by a
UV spectrometer sold by Dr Lange.
[0093] It could be confirmed that virtually 100% of the phenol had
disappeared over approximately at most one hour.
[0094] More generally, these last two examples show the advantage
of the use of a web formed of photocatalytic mineral fibres, such
as those manufactured, in purification operations in a liquid
medium as in the gas phase.
* * * * *