Patent Grant
6905814
The present invention relates to the use of a film-forming dispersion of titanium dioxide nanoparticles for cleaning and/or disinfecting surfaces exposed to light. The invention also relates to a process for cleaning and/or disinfecting surfaces exposed to light by depositing on said surfaces a film of titanium dioxide nanoparticles, and to titanium dioxide nanoparticle dispersions whose film-forming properties are improved by the presence of a film-forming polymer.
The use of titanium dioxide nanoparticles as a bactericidal and photooxidizing agent in detergent compositions for the washing of laundry or of surfaces was described by the Applicant in its French patent application No. 95 00821 of Jan. 25, 1996.
The Applicant has observed that titanium dioxide nanoparticle dispersions are film-forming.
The object of the present invention is to utilize the photooxidizing properties of titanium dioxide nanoparticles and their film-forming nature to clean and/or disinfect surfaces on said surfaces of an impermanent film of titanium dioxide capable under light of generating free radicals which disinfect the surfaces and oxidize the soiling.
The creation of this film makes it possible
The invention first provides for the use of a titanium dioxide dispersion for cleaning and/or disinfecting surfaces exposed to light by deposition of a film of titanium dioxide on said surfaces, said titanium dioxide being in the form of elementary particles whose size is less than 100 nm, preferably less than 70 nm, and whose specific surface area is greater than 150 m2/g, preferably greater than 200 m2/g, the continuous phase of said dispersion comprising water and/or at least one alcohol whose boiling point is less than 120° C., preferably less than or equal to 100° C., said dispersion having, when it comprises waters, a pH different by at least 1 unit, preferably by at least 2 units, from the value of the isoelectric point of titanium dioxide in said dispersion.
The pH of the dispersion comprising water is of course the pH of the continuous phase.
The titanium dioxide employed is very particularly in the form of elementary particles whose size is of the order of from 20 to 60 nm and whose specific surface area is of the order of from 200 to 300 m2/g.
The specific surface area given is a BET surface. By BET surface is meant the specific surface area determined by nitrogen adsorption in accordance with the standard ASTM D 3663-78, based on the Brunauer —Emmett—Teller method described in the journal “The Journal of the american Society”,60, 309 (1938). The size of the elementary particles of titanium dioxide according to the invention is measured by transmission electron microscopy (TEM).
The nature of the elementary particles of titanium dioxide is preferably anatase (isoelectric point between 5.5 and 6 for pure anatase). Within said dispersion, said elementary particles may be present in the form of both aggregates and elementary particles.
For effective implementation of the invention, said dispersion may comprise in the order of from 0.01 to 15% of its weight, preferably in the order of from 0.1 to 10% of its weight, of titanium dioxide.
Among the alcohols which may constitute or be present in the continuous phase, mention may be made in particular of aliphatic monoalcohols whose boiling point is less than 100° C. such as ethanol, isopropanol, etc.
When the continuous phase consists of a water/alcohol(s) mixture whose boiling point is less than 120° C., the ratio between the water and the alcohol or alcohols is arbitrary.
A high boiling point alcohol (in particular a diol such as ethylene glycol) may, however, be present in the continuous phase, but may not represent more than 10% of the weight of said phase.
Preferentially, the continuous phase comprises water, preferably from 50 to 100%, preferably from 70 to 99.9% of its weight of water.
When the continuous phase comprises water, the pH values favorable to effective implementation of the invention may range from 0 to 14, preferably from 2 to 14, and are a function of other additives which may be present in the dispersion and capable of modifying the isoelectric point of the titanium dioxide.
When no additive capable of modifying the isoelectric point of titanium dioxide is present, the pH values favorable to effective implementation of the invention are situated below 4 or above 8; preferentially, the pH of the dispersion may range from 0 to 3 approximately or from 9 to 14 approximately.
If necessary, pH regulators may be present; mention may be made of mineral acids or organic acids such as hydrochloric, nitric, sulfuric, phosphoric, citric, glutaric, adipic and succinic acids, etc., and bases such as aqueous ammonia, alkali metal hydroxides, sodium carbonate, and triethanolamine, etc.
Said dispersion may further comprise other additives which are soluble or dispersible in the continuous phase, said additives possibly promoting its stability, wettability, augmenting its film-forming nature, its biocidal nature, or providing other supplementary properties.
Examples of additives which may be mentioned include:
One particular embodiment of the invention consists in improving the film-forming nature of the titanium dioxide nanoparticles by the presence within the dispersion of at least one organic or organosiloxane polymer of film-forming nature which may further impart one or more supplementary properties to said dispersion.
The amount of polymer that may be present may represent in the order of from 0.005 to 15%, preferably in the order of from 0.01 to 10% of the weight of said dispersion.
Among the film-forming organic or organosiloxane polymers that may be employed, very particular mention may be made of:
One very particularly advantageous embodiment of the invention consists in the use of titanium dioxide dispersions further comprising a film-forming organic polymer which is preferably hydrophilic and is capable of interacting with the surface of the titanium dioxide particles, preferably by electrostatic bonding.
Said dispersions are preferably aqueous and have a pH of the order of from 4 to 9.
They may comprise in the order of from 0.005 to 10%, preferably from 0.01 to 5%, very particularly from 0.01 to 2% by weight of film-forming organic polymer.
Among the film-forming polymers which may be present, mention may be made of:
By way of example of cationic film-forming homopolymers or copolymers derived from cationic monomers containing ethylenic unsaturation, mention may be made from those derived from at least one of the following cationic monomers
Very particular mention may be made of DIQUAT homopolymers, such as MIRAPOL CLASTA from Rhodia, and DADMAC homopolymers, such as MIRAPOL 100 from Rhodia.
By way of example of amphoteric film-forming copolymers derived from cationic monomers containing ethylenic unsaturation, mention may be made of those derived from at least one of the abovementioned cationic monomers and at least one anionic monomer such as
Very particular mention may be made of the following copolymers or terpolymers:
Said cationic or amphoteric film-forming homopolymers or copolymers derived from cationic monomers containing ethylenic unsaturation preferably have a molecular mass of less than 100,000 (molecular mass by weight, expressed in g/mol, determinable by aqueous gel permeation chromatography (GPC) or measurement of the viscosity in IN NaNO3 solution.
The invention secondly provides a film-forming dispersion comprising
Preferential or more particular features regarding the nature of the titanium dioxide, the continuous phase, pH regulators, other additives that may be present, and respective amounts of various components, have already been indicated above.
Examples of film-forming alkoxylated organosiloxane or organic polymers which may be employed to improve the film-forming nature of the titanium nanoparticles have already been mentioned above.
Said dispersion may be obtained by mixing its various components at ambient temperature.
An especially advantageous film-forming dispersion comprises
They are preferably aqueous and have a pH of the order of from 4 to 9.
Examples of film-forming organic polymers which may be employed for interacting with the surface of the titanium dioxide particles, preferably by electrostatic bonding, have already been stated above.
The invention lastly provides a process for cleaning and/or disinfecting surfaces exposed to light by depositing and then drying on said surfaces a film-forming titanium dioxide dispersion, said titanium dioxide being in the form of elementary particles whose size is less than 100 nm, preferably less than 70 nm, and whose specific surface area is greater than 150 m2/g, preferably greater than 200 m2/g, the continuous phase of said dispersion comprising water and/or at least one alcohol whose boiling point is lower than 120° C., preferably lower than or equal to 100° C., said dispersion having, when it comprises water, a pH different by at least 1 unit, preferably by at least 2 units, from the value of the isoelectric point of titanium dioxide in the dispersion.
Preferential or more particular features regarding the nature of the titanium dioxide, the continuous phase, pH regulators, other additives that may be present, especially film-forming polymers, and respective amounts of various components, have already been mentioned above.
The titanium dioxide nanoparticle dispersion may be deposited on these surfaces by fine spraying onto the surface to be treated, by application with the aid of a sponge, a cloth or with the aid of a preimpregnated cellulosic material, or any other means, in such a way as to deposit in the order of from 0.01 to 10 g of titanium dioxide per m2 of the surface to be treated, preferably in the order of from 0.05 to 5 g of titanium dioxide per m2 of the surface to be treated.
The examples which follow are given by way of illustration.
A dispersion is prepared of titanium dioxide (anatase) in the form of elementary particles of 40 nm whose specific surface area is 250 m2/g after drying at 200° C., in a water/alcohol mixture, whose composition is as follows:
by introducing the film-forming antisoiling copolymer into the dispersion of titanium dioxide in ethylene glycol, followed by addition of the water/isopropanol mixture and then adjustment of the pH to 2.5 using hydrochloric acid.
A dispersion is prepared of titanium dioxide (anatase) in the form of elementary particles of 40 nm whose specific surface area is 250 m2/g after drying at 200° C., in a water/alcohol mixture, whose composition is as follows:
by introducing the film-forming antisoiling copolymer into the colloidal aqueous dispersion of titanium dioxide, followed by addition of the water/isopropanol mixture and then adjustment of the pH to 2.5.
A dispersion is prepared of titanium dioxide (anatase) in the form of elementary particles of 40 nm whose specific surface area is 250 m2/g after drying at 200° C., in a water/alcohol mixture, whose composition is as follows:
by introducing the film-forming antisoiling copolymer into the colloidal aqueous dispersion of titanium dioxide, followed by addition of the water/isopropanol mixture and then adjustment of the pH to 2.5.
A dispersion is prepared of titanium dioxide (anatase) in the form of elementary particles of 40 nm whose specific surface area is 250 m2/g after drying at 200° C., in a water/alcohol mixture, whose composition is as follows:
by introducing the film-forming polymer (imparting brightness and oleophobicity) into the colloidal aqueous dispersion of titanium dioxide, followed by addition of the water/isopropanol mixture and then adjustment of the pH to 2.5.
A dispersion is prepared of titanium dioxide (anatase) in the form of elementary particles of 40 nm whose specific surface area is 250 m2/g after drying at 200° C., in a water/alcohol mixture, whose composition is as follows:
by introducing the bacteriostatic film-forming polymer into the colloidal aqueous dispersion of titanium dioxide, followed by addition of the water/isopropanol mixture and then adjustment of the pH to 2.5.
A dispersion is prepared of titanium dioxide (anatase) in the form of elementary particles of 40 nm whose specific surface area is 250 m2/g after drying at 200° C., in a water/alcohol mixture, whose composition is as follows:
The pH of the dispersion is subsequently adjusted by adding sodium hydroxide to pH =6.5. In the presence of cationic polymer (test A) the dispersion remains homogeneous and the particle size measurement by laser scattering confirms the absence of aggregation of titanium dioxide (particle size: 40 nm). In the case of the solution without cationic polymer (test B) severe precipitation is observed when sodium hydroxide is added.
The two neutralized solutions A and B are deposited on a black ceramic tile with the aid of adsorbent paper. The amount deposited is of the order of 0.5 mg/cm2.
After drying in the open air, the solution A gives a layer of titanium invisible to the eye. In contrast, solution B gives very distinct white marks. Observation by optical microscopy confirms that the polymer allows an effective state of dispersion to be obtained during drying.
A model soil, stearic acid, is subsequently deposited on each ceramic tile which had been treated before and with formulas A and B. The layer of stearic acid is of approximately 0.01 mg/m2 and it is obtained by depositing a it solution in isopropanol. After drying, the tiles are exposed to visible light for 48 hours.
Following exposure, the ceramic tile treated with solution A has virtually no trace of stearic acid visible to the eye.
The tile treated with solution B exhibits visible traces of stearic acid.
On a ceramic tile, a film corresponding to 3 or 6 g of titanium dioxide per m2 of tile surface is formed by-spreading the dispersion from example 2 over said tile using a film-drawing device.
The film is left to dry in ambient air overnight. A suspension of bacteria (Pseudomonas Aeruginosa) is deposited over the entire surface of the tile. The tile, covered with a UV-impervious cover (for the purpose of preventing excessive dehydration of the bacteria), is exposed to UV light (365 nm) for 6 hours. The number of colonies is counted and compared with that obtained by depositing the same bacteria suspension on an untreated tile.
The results obtained are as follows:
| Number | Date | Country | Kind |
|---|---|---|---|
| 99 01938 | Feb 1999 | FR | national |
This aplication is an application under 35 U.S.C. 371 of International Application Number PCT/FR00/00371 filed on Feb. 15, 2000.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FR00/00371 | 2/15/2000 | WO | 00 | 12/4/2001 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO00/49119 | 8/24/2000 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5616532 | Heller et al. | Apr 1997 | A |
| 5753322 | Yamaguchi et al. | May 1998 | A |
| 5853866 | Watanabe et al. | Dec 1998 | A |
| 5961843 | Hayakawa et al. | Oct 1999 | A |
| 6107241 | Ogata et al. | Aug 2000 | A |
| 6340711 | Ohmori et al. | Jan 2002 | B1 |
| 6355308 | Sato et al. | Mar 2002 | B1 |
| 6429169 | Ichinose | Aug 2002 | B1 |
| 6479031 | Ohmori et al. | Nov 2002 | B2 |
| Number | Date | Country |
|---|---|---|
| 2260803 | Jan 1998 | CA |
| 857 770 | Aug 1998 | EP |
| 2 729 673 | Jul 1996 | FR |
| 2 766 494 | Jan 1999 | FR |
