CZ2000212A3 - Dispersion of titanium dioxide particles containing binding agent based on polyorganosiloxane, process of its preparation and use - Google Patents

Abstract

Dispersion of photocatalytic oxide particles is described titanium, wherein the liquid phase comprises at least crosslinking a catalyst and at least a polyorganosiloxane of formula I or formulas II. The use of this dispersion to treat substrates is also described.

Description

The invention relates to dispersions of photocatalytic titanium dioxide particles which can be used to treat substrates.

BACKGROUND OF THE INVENTION

It is known that titanium dioxide, by its photocatalytic activity, facilitates the degradation of organic or bioorganic molecules.

When this photocatalytic titanium dioxide is deposited on the support, the surface of the support will begin to oxidize and dirty stains, especially of organic origin, deposited on the surface will degrade by photooxidation. The surface is referred to as self-cleaning.

The deposition of titanium dioxide on the surface of the substrate can be carried out from dispersions of the titanium dioxide particles. Preferably, dispersions of small particle sizes, especially nanometer-size particles, are prepared so that translucent surfaces are obtained, as opposed to micrometre titanium dioxide particles, thereby obtaining white surfaces.

Treated surfaces can be glass, plastics, building materials (mortar, concrete, terracotta), ceramics, stones, paper or wood.

The deposition of titanium dioxide on these supports must adhere strongly to the support so that the treated surfaces can be installed and retain their self-cleaning properties at all times.

It is also necessary that the binder which allows the particles to adhere to the carrier is not sensitive to photocatalysis of the titanium dioxide particles.

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Several methods are used for this purpose, using different types of binders that allow the particles to be adhesively bonded to the substrate.

One method is to deposit a dispersion of titanium dioxide particles containing a precursor of binding to a substrate under hot conditions. For example, it has been proposed to use a dispersion of titanium dioxide particles and organometallic binders of the titanate or silicate type. The particles are then retained in a silica or titanium dioxide film (this principle is described, for example, in WO 97/10185). This inorganic binder has the advantage that it is not photodegradable.

The second method consists in applying the dispersion of titanium dioxide particles containing the organic binder to the substrate under cold conditions. The problem is that this binder must not be degraded by the photocatalytic properties of the titanium dioxide particles. Tiby has achieved this, it has been suggested, for example, to choose a binder from silicones.

However, although silicone binders do not degrade by contact with the photocatalytic particles, it has been observed that they do not always form a homogeneous, hard and adhesive coating. Very often, coatings are obtained which can be removed by simply scratching with your finger.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a dispersion of titanium dioxide particles and a non-photodegradable binder that can be used to form photocatalytic coatings on the substrate surface under cold conditions.

It is another object of the present invention to provide dispersions that produce homogeneous, hard and tacky coatings.

The present invention is directed to a dispersion of photocatalytic titanium dioxide particles which, in their liquid phase, contains at least one of the following:

-3, one crosslinking catalyst and at least one polyorganosiloxane of either Formula I

¹ ) or of formula II

M D 'T (0. o β Ϊ (I) (II) as defined below.

The invention also relates to the use of this dispersion to treat substrates.

The dispersions of the invention have the advantage that they are chemically neutral and do not react with the substrates on which they are applied.

They also have the advantage that cheap binders are used. In addition, they allow the preparation of transparent or translucent coatings under certain conditions of use.

In particular, the present invention relates to a dispersion of photocatalytic titanium dioxide particles which in the liquid phase contains at least one polyorganosiloxane of either formula I

M _and Q ₆ D _P (O _{i / 2} R ¹⁾ _£ (AND) where M Yippee R ₃ SiO _i / ₂ D Yippee R ysi0 _2/2 Q Yippee SiO _4/2 where R ¹¹ , which are the same or different, mean either

a linear or branched alkyl group having 1 to 8 carbon atoms or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms or an arylalkyl, alkylaryl, aryloxyalkyl or alkoxyaryl group in which the aryl group contains from 6 to 12 carbon atoms which may be optionally substituted • ·

at least one linear or branched alkyl or alkoxy group having 1 to 4 carbon atoms and wherein the alkyl or alkoxy group has up to 4 carbon atoms and is linear or branched, α, β and δ are molar fractions of silicon atoms of M, D and Q units , with α + β + δ = 1, and α <0.10, preferably α <0.010, β <0.85, δ> 0.10,

R ^1, which are identical or different, represent an alkyl group having 1 to 4 carbon atoms, ε represents the number 0 _;; R ^_1; units per silicon atom, or formula II wherein

M, D, R ¹ and ε have the meanings given above and

T = R "SiO _3/2 , where R ¹¹ is as defined above, α, β and γ mean the molar fractions of silicon atoms of M, D and T units, with α + β + γ = 1, and α <0 20, preferably α <0.010, β <0.60, γ> 0.30.

Preferably, the polyorganosiloxanes have the formula I or II and R ¹ is a methyl or ethyl group. On average, the polyorganosiloxane also has silanol endings (R ¹ = Η), which do not account for more than 20% of all endings.

According to a first preferred alternative feature of the dispersion according to the invention it comprises a polyorganosiloxane of the formula II in which for each unit T = R? SiCf,?, R ¹¹ is methyl, for each unit D = R? SiO ₂ , one R ¹ is methyl and the second R ^1: is an octyl group, β is at most 0,10,

γ has a value of at least 0,70.

* According to a second preferred alternative aspect of the dispersions according to the invention comprises a polyorganosiloxane of formula II wherein, for each unit T = R @ ¹¹ SiO3 / 2, ^R11 is methyl, for each unit D = R 2 SiO ^IL _{second 2} , both R ¹¹ are methyl groups, β is at most 0.30, γ is at least 0.70.

According to a third alternative aspect of the dispersions according to the invention comprises a polyorganosiloxane of formula II wherein, for each unit T = R @ ¹¹ SiO3 / 2, ^R11 is propyl, for each unit D = R ¹¹ 2 SiO _2/2, each R ¹¹ are methyl groups , β is at most 0.40, γ is at least 0.40.

The dispersions of the invention may also contain a crosslinking catalyst. These may be organic titanium compounds (e.g. alkyl titanates) or tin organic compounds (e.g. dialkyltin dicarboxylate).

Alkyl titanates are preferred.

The use of this catalyst is recommended for use of the dispersion during the treatment of glass substrates.

The liquid phase of the dispersion according to the invention may contain only the polyorganosiloxane as defined above, or it may also contain a solvent.

The liquid phase dispersion solvent of the invention may be aqueous or organic.

It is usually an organic solvent. The solvent may be selected from solvents used for silicone polymers such as D4 (octamethylcyclotetrasiloxane) or other volatile siloxanes, white spirit, C 1 -C 8 alcohols or aliphatic or aromatic hydrocarbons such as cyclohexane or alkanes.

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The choice of solvent is made according to its compatibility with the polyorganosiloxane. It is thus possible to vary the transparency of the final coating.

The dispersion according to the invention preferably comprises a solvent,

in particular, j e-li required concentration reduction oxide titaničitý in coating to coatings were obtained larger translucency or greater transpare ntnosti.

The photocatalytic dispersion particles according to the invention are preferably titanium dioxide particles having a maximum size of 100 nm, in particular between 10 and 50 nm. The averages are measured by transmission electron microscopy (TEM).

By nature, the crystalline phase is preferably predominantly anatase crystalline form. It predominantly means that the level of anatase in the titanium dioxide particles is greater than 50% by weight. The particles preferably contain more than 80% anatase.

The degree of crystallization and the nature of the crystalline phase are measured by X-ray diffraction.

It is preferred to use monodisperse titanium dioxide particles to provide coatings with greater transparency. The monodisperse means that the diameter of dispersed particles have an index of at most 0.5, preferably at most 0.3, wherein the dispersive index is defined by the following equation R_ 08, -01, ¹ ~ 20 "

where 0 _e4 is the average particles, where 84 % by weight of particles has diameter less than 0 ₈₄ , 0 ₁₆ is the average particles, where 16 % by weight of particles has diameter less than 0 _i6 , 0 _5Ο is medium diameter of particles.

The averages used to determine the dispersion index are measured by centrifugal sedimentation of the dispersion particles, monitoring by X-rays using an Erookhaven-type XDC.

Monodisperse dispersion particles are preferably formed in a so-called solution or wet preparation process (thermolysis, thermal hydrolysis or precipitation of a titanium salt), as opposed to methods of high-temperature pyrolysis or oxidation of a titanium salt. These are, for example, titanium dioxide particles obtained by the method described in EP-A-0 335 773.

For example, it may be a method of preparing at least one compound of titanium A in the presence of at least one compound B selected from the group consisting of:

(1) acids having either a carboxyl group and at least two hydroxyl groups and / or amino groups,

- or at least two carboxyl groups and at least one hydroxyl group and / or amino group, (2) organic phosphoric acids of the following formulas

HO O \ II

HO O \ II

HIM

R2

P - (C) _{n -} P

HO O \ II

HIM

R1

OH

R3

O OH II /

OH

O OH II /

OH

O OH II /

P -OH

P - CH _{2 -} (CH ₂ ) _n b_N

HIM

CH;

o = P-OH

P-OH 11, 00H

OH

Where n and m are integers between 1 and 6 and p is an integer between 0 and 5, R1, R2 and R3, which are the same or different, represent a hydroxyl group, an amino group, an arylalkyl group (3) compounds capable of releasing sulphate ions in an acidic medium; (4) salts of the above-described acids, and in the presence of anatase titanium dioxide eyes having a size of not more than 5 nm and a TiO ₂ weight ratio present in the titers present before the introduction of the stitches in the hydrolysis medium, emitted as TiO ₂ , between 0.01% and 3%.

Thus, this process for preparing particles comprises several steps and, first, a step of preparing a starting solution comprising titanium compound A, compound B as defined above, and titanium dioxide guides.

The starting solution to be hydrolyzed is preferably completely aqueous. Optionally, an additional solvent, such as an alcohol, may be added provided that the titanium compound A and compound B used are then substantially soluble in the mixture.

With respect to the titanium compound A, it is usually selected from titanium halides, oxyhalides or alkoxides, sulfates and especially synthetic sulfates.

Synthetic sulphates are titanyl sulphate solutions produced by ion exchange from very pure titanium chloride solutions or by reaction of sulfuric acid with titanium alkoxide.

The preparation is preferably carried out with titanium compounds selected from titanium halides or titanium oxyhalides. Titanium halides or titanium oxyhalides especially used in the present invention are the fluorides, chlorides, bromides and iodides (optionally oxyfluorides, oxychlorides, oxybromides and oxy iodides) of titanium.

A particularly preferred form of the titanium compound is titanium oxychloride TiOCl.

<* »

-9 · · · · 9 9 9 9 9 9 9 9 9

The amount of titanium compound A present in the solution to be hydrolyzed is not critical.

The original solution additionally contains at least one compound B as defined above. Non-limiting examples of compounds B that may be considered include, but are not limited to:

hydroxypolycarboxylic acids and in particular hydroxydicarboxylic or hydroxytricarboxylic acids such as citric acid, maleic acid and tartaric acid, (polyhydroxy) monocarboxylic acids such as glucoheptonic acid and gluconic acid, (hydroxycarboxylic acid) poles such as tartaric acid, dicarboxyamino acids and their the corresponding amides such as aspartic acid, aspartic acid and glutamic acid, hydroxylated or non-hydroxylated monocarboxyaminic acids such as lysine, serine and threonine, aminotri (methylene phosphonate), ethylenediaminotetra (methylene phosphonate), triethylenetetaminophenonephenethylenephenamine (ethylenepetaminophenone), pentaethylenehexaaminookta (methylene phosphonate),

- methylenediphosphonate, 1,1-ethylenediphosphonate, 1,2-ethylenediphosphonate, 1,1-propylenediphosphonate, 1,3-propylenediphosphonate,

1,6-hexamethylenediphosphonate, 2,4-dihydroxypentamethylene-2,4-diphosphonate, 2,5-dihydroxyhexamethylene-2,5-diphosphonate, 2,3-dihydrobutylene-2,3-diphosphonate, 1-hydroxybenzyl-1,1- diphosphonate, 1-aminoethylene-1,1-diphosphonate, hydroxymethylene diphosphonate, 1-hydroxyethylene-1,1-diphosphonate, 1-hydroxypropylene-1,1-diphosphonate, 1-hydroxybutylene-1,1-diphosphonate or 1-hydroxyhexamethylene-1, 1-diphosphonate.

As already indicated, all salts of the above acids can also be used as compound B. In particular, these salts are alkali metal salts, especially sodium salts, or ammonium salts.

-10 · · t t t t t t t t ··········································

These compounds can also be selected from sulfuric acid and ammonium or potassium sulfates.

The compounds B defined above are preferably aliphatic hydrocarbon compounds. In this case, the length of the main hydrocarbon chain preferably does not exceed 15 carbon atoms and even more preferably 10 carbon atoms.

The amount of compound B is not critical. The molar concentration of Compound B relative to the titanium compound A is generally between 0.2 and 10% and preferably between 1 and 5%.

Finally, the starting solution contains titanium dioxide eyes used in a specific manner.

In particular, the titanium dioxide guides used in the present invention must have a maximum size of 5 nm, as measured by X-ray diffraction. Titanium dioxide guides of between 3 and 5 nm are preferably used.

Consequently, the ratio of the weight of titanium dioxide present in the stitches to the titanium present in the hydrolysis medium prior to the introduction of the stitches (i.e. titanium coating compound A 'and expressed as TiO ₂ ) is between 0.01 and 3%. Together, these two conditions in terms of stitches (size and weight ratio), in combination with the method described above, allow precise control of the final particle size of the titanium dioxide while the stitch level is associated with the particle size. , whose size varies between 5 and 100 nm.

The use of titanium dioxide eyes in the anatase form causes the precipitation of titanium dioxide in the anatase form. Generally, due to their small size, these eyes tend to exist in the form of poorly crystallized anatase. The seeds are generally obtained in the form of an aqueous suspension composed of titanium dioxide. They can be obtained by a known procedure for neutralizing the titanium salt base.

The next step consists in hydrolyzing this starting solution to any person skilled in the art in a known manner and generally by heating. In the case of heating, the hydrolysis is preferably 9

-11 operating at a temperature greater than or equal to 70 ° C. It is also possible to work first at a temperature below the boiling point of the medium and then to maintain the hydrolysis medium at the boiling point.

After hydrolysis, the obtained titanium dioxide particles are isolated by separating the precipitated solid from the mother liquors. They are then redispersed in an aqueous liquid medium to obtain a titanium dioxide dispersion. The liquid medium may be acidic or alkaline.

It has been observed that the titanium dioxide particles resulting from the so-called solution process or the wet preparation process, and in particular the particles resulting from the above-described hydrolysis process at about 100 ° C, have a lower refractive index due to their porosity than the titanium dioxide particles produced by other methods. This property is of great importance when the particles are used to prepare coatings on glass substrates, since the obtained coating also has a low refractive index. This optical advantage is important because the titanium dioxide layer with a higher refractive index has an increasing light reflection of the glass carrier and thus a decreasing light transmission. In fact, in certain applications, particularly in the field of glazing of vehicle equipment, it is desirable to have a high light transmittance level (a minimum light transmittance of 75% is required for the windscreen).

The dispersion particles preferably have a BET specific surface area of at least 70 m ² / g.

BET specific surface means a specific surface determined by nitrogen adsorption according to ASTM Standard D 3663-78, designed according to the Brunauer-Emmett-Teller method described in The Journal of the American Chemical Society, 60, 309 (1938). When measuring the specific surface area of the particles of the present invention in the form of a dispersion, it is necessary to follow the measurement protocol, the dispersion, which consists in removing the liquid phase from drying the particles under reduced pressure at 150 ° C for at least 4 hours.

Preferably, the dispersion particles also have a relative density of the order of 2.4. Ordinarily, the relative density is 2.4 ± 0.2. This relative density value is low relative to the normal relative density of anatase titanium dioxide, which is 3.8. This relative density is evaluated by measuring pore volumes.

These specific surface area and relative density values can be obtained for titanium dioxide particles formed by a so-called solution process or a wet process. ⁱⁿ particular formed by the above-described process with hydrolysis at about 100 ° C.

The proportions of the particles to the polyorganosiloxane in the dispersion according to the invention vary according to the use for which the dispersion is prepared. Thus, for applying the dispersion as a coating on concrete, the proportion of particles is generally at least 5% by weight of the particle + polyorganosiloxane mixture, on the other hand for dispersion as a coating on glass, the proportion of particles is usually at least 10% by weight of the particle + polyorganosiloxane + crosslinking catalyst, preferably at least 50% and generally at most 90%.

The dispersion solvent of the invention is usually present in an amount such that the solids content, such as titanium dioxide particles, is at least 0.5% by weight.

When a crosslinking catalyst is present in the dispersion, it is usually at least 5% by weight of the polyorganosiloxane + catalyst mixture and preferably at most 50% by weight.

The invention also relates to a process for the preparation of the above-mentioned dispersions which consists in simple mixing of titanium dioxide particles and polyorganosiloxane.

The polyorganosiloxanes used in the dispersion are known and are commercially available.

Titanium dioxide particles can also be obtained commercially. They may be available in various forms.

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In particular, they may be in the form of aqueous dispersions of titanium dioxide particles as sold by Rhone-Poulenc under the name S5-300 or dispersions prepared by the method of EP-A-0 335 773 as described above.

Preferably, basic aqueous dispersions are prepared because it has been found that these dispersions provide coatings of greater transparency than acidic aqueous dispersions. In the case of coating on glass, this difference is reduced if the glass is activated with NaOH prior to coating.

There may also be organic dispersions of the titanium dioxide particles. These are prepared from aqueous dispersions of the titanium dioxide particles by phase transfer, for example according to one of the following procedures:

washing with acetone or the desired solvent by centrifugation and redispersion in an organic solvent, azeotropic distillation of the water / solvent mixture if the water and solvent are immiscible and form an azeotrope, evaporation of water on a rotary evaporator if the solvent is miscible with water and boiling above is the boiling point of water, by mixing an aqueous dispersion with an organic medium containing a cationic transfer agent when the particles are negatively charged, which is possible for a transfer agent selected particularly from quaternary amines or quaternary ammonium salts, or with anionic transfer agent containing media if particles positively charged (this process is described in particular in GB-A-988 330).

Titanium dioxide powder may also be used. These powders are commercially available, including G5 or DT51D powders sold by Rhodia Chimie. Powders can also be obtained by atomizing the aqueous dispersion as described above.

The dispersions according to the invention are preferably prepared from the particles in the form of dispersions, especially if it is necessary to make them transparent

4

-14444 · · · · 4 44

4 * 4 4 · 4,444 ·

44444 4 4 44

4,444,444

Surface treatment, powders generally provide coatings of reduced transparency.

The invention also relates to the use of the above-mentioned dispersions for surface treatment of substrates.

The polyorganosiloxane acts as a binder that attaches particles to the substrate.

The substrates may be of various kinds: for example, glass, polymers (plastics), building materials such as mortar, concrete or terracotta, ceramics, stones, wood, metals or paper.

In the case of treatment of alkaline substrates and in particular of concrete, the dispersion defined herein as the third alternative, namely a dispersion comprising at least one polyorganosiloxane of formula II, wherein for each unit T = R R SiCl ^, R ¹¹ is a propyl group, unit D = PhhSiCL ^, both R ¹¹ are methyl groups, β is at most 0.40, γ is at least 0.40.

If polyorganosiloxanes exhibit innate properties, such as substrate protection (water repellency and the like), it has been found that by mixing them with titanium dioxide particles, their properties are not modified. This is the case, for example, with a coating using polyorganosiloxane in a third alternative form, whereby a coating that adheres firmly to the alkaline substrate and repels water specific for the siloxane binder can be obtained.

The coating can be carried out in any conventional way: rolling, brushing, spray gun, spraying.

The following examples illustrate the present invention in more detail without limiting its scope.

it also provides the property of this type of polyorgano-15 • 4 4 4 4 4 4 4 4 4 4 4 4

444 44 44 4 4 4 4 · · ·

DETAILED DESCRIPTION OF THE INVENTION

Example 1

Preparation of Polyorganosiloxanes of Formula I

In a 2 L jacketed cylindrical glass reactor equipped with an anchor stirrer were placed 4 moles (609 g) methyl orthosilicate, 3 moles (890 g) octamethylcyclotetrasiloxane, 1.6 g aqueous potassium hydroxide solution containing 39% potassium hydroxide and 72 g water. The mixture is heated to 70 ° C and the stationary phase temperature is maintained at 70 ± 3 ° C for 6 hours. The reaction mixture was then cooled, and 0.41 g of hydrochloric acid was added as a 30% by weight aqueous solution. The reaction mixture was finally [gap] in the presence of a filter substance (Clarcel).

There were obtained 1247 g of silicone oil having a kinematic viscosity of 1.32 mm ² / s and formula (determined by ²⁹ Si NMR) of (Me ₂ SiO _2/2) c, 8 c (SiO _{4/2) 0j20} (O _1/2 Me) _{0 74}

Example 2

Preparation of the polyorganosiloxanes of formula II

3.5 moles of dimethyldichlorosilane and 3.5 moles of propyltrichlorosilane are charged to a 2 liter reactor. The temperature was adjusted to 60 ° C and then a mixture of ethanol and water (6.12 mol of ethanol and 6.6 mol of water) was fed over 2 hours with stirring and heating to 80 ° C. The acidic ethanol is then removed by distillation for 1 hour 50 minutes at 120 ° C.

The resulting chlorine is then removed by washing with 166 g of ethanol and 5.7 g of water (thereby adjusting to the desired

And then distilled for 1 hour and 5 minutes at 120 ° C. The mixture was cooled to 100 ° C and neutralized with sodium bicarbonate (11.1 g) at 100 ° C for 1 hour. After filtration, 515 g of resin are obtained.

This resin has a kinematic viscosity of 87.7 mm ² / s at 25 ° C.

The following formula of this polyorganosiloxane is determined by ²⁵ Si NMR:

(Me ₂ SiO _2/2 ) _C , _4C (n-PrSiO _3/2 ) _c , _eo (0 _1/2 Et) _and _Example 3

Preparation of the Polyorganosiloxanes of Formula II

A round-bottomed glass flask equipped with a paddle, stirrer and reflux condenser is charged with 282 g of absolute ethanol and 0.30 g of potassium silanolate obtained by the reaction of aqueous potassium hydroxide, octamethylcyclotetrasiloxane and hexamethyldisiloxane, known as Rhodosil Cata 104. both many moles of silanolate and 12% potassium hydroxide solution. The mixture is heated to 65 ° C and then a stream of trimethylsilyl-terminated polymethylhydrosiloxane with a medium degree of polymerization of 50 is introduced. 200 g of this polymer are introduced in 4 hours and 30 minutes. The temperature is raised for a while

After cooling, 0.59 g of solution 110, a silylated phosphoric acid ester manufactured by Rhone-Poulenc Silicones, was cooled. Evaporation on a rotary evaporator at a pressure of 666 Pa and at the temperature of the hours after the mixture is carried out at 0 DEG C. and maintained with polymethylhydrosiloxane.

294 g of a polymer having a viscosity of 30 nm / s at 25 ° C are isolated at -1770 ° C.

The following formula of this polyorganosiloxane was determined by ²⁹ Si NMR:

_(Me3 SiO _{1/2) 0 54} (MESI _{2.3) 0 96 (1/2} Et) _{0 S6}

Example 4

Preparation of comparative polyorganosiloxane

In a 500 ml three-necked round-bottomed flask equipped with a mechanical stirrer, a thermometer and a dropping funnel, 300 ml of ethanol previously dried in a nitrogen atmosphere are introduced.

3.10 * * nm molecular sieve and 10 μΐ of Karstedt catalyst (10% in hexane). The mixture is stirred at 65 ° C and polymethylhydrosiloxane (40 g, degree of polymerisation DP _n = 50} is added dropwise. A significant evolution of hydrogen is observed. The rate of introduction of liquid Si-H is adjusted to control the hydrogen flow rate and exothermic After the addition of the polymethylhydrosiloxane was complete, the mixture was allowed to stir for 1 hour.

36 g of 1-octene are then added dropwise. After this addition, the reaction mixture was heated to 60 ° C until all Si-H functional groups were consumed. The excess alcohol and octene are then evaporated. 80 g of pure and slightly colored oil are obtained. The structure of:

Me

Me-Si-O ^-

AND

Me r ~ Me -i

AND

-Si-0

AND

OEi "

Me ~

AND

-Si — O

Me

AND

Si-Me ithf = 35 RH = 15

Me • ·

Example 5

Preparation of basic aqueous dispersion of titanium dioxide particles

An aqueous dispersion of titanium dioxide nanoparticles is prepared according to patent application EP-A-0 335 773, in the presence of stitches.

To 394.7 g of a 1.9 mol / kg solution of titanium oxychloride A is gradually added

42.02 g of 36% HCl

4.73 g of citric acid

547.1 g purified water

11.36 g (0.2% by weight relative to the titanium solution)

A, expressed as TiO ₂ ) dispersed anatase sticks having a TiO ₂ content of 10 g / kg and having a size between 5 and 6 nm, at a temperature of 75 ° C. This temperature is maintained for 2 hours.

The mixture is brought to the boiling point (0.8 ° C / min) and maintained at this temperature for 3 hours.

The solution is then resolved by settling, re-milled and neutralized to pH 6 and washed until the chlorides and Na ions have been removed.

The particles are then redispersed with NaOH to pH 9 and to a solids content of about 12%.

The particle size, measured by TEM, is 45 nm. The XDC analysis showed an agglomerate-free monopopulation and a dispersion index of 0.2.

X-ray analysis shows that the particles contain 80% by weight of TiO ₂ in anatase form. They are porous with a relative density of 2.54 g / cm ³ .

Example 6

Preparation of basic aqueous dispersion of titanium dioxide particles

• ·

Aqueous dispersion of titanium dioxide nanoparticles is prepared according to patent application EP-A-0 335 773, in the presence of stitches.

To 394.7 g of a 1.9 mol / kg solution of titanium oxychloride A is gradually added

42.02 g of 36% HCl

4.73 g of citric acid

501.7 g purified water

56.8 g (1% by weight with respect to titanium solution A, expressed as TiO ₂ ) of dispersed anatase stitches having a TiO ₂ content of 10 g / kg and having a size between 5 and 6 nm, at 75 ° C. This temperature is maintained for 2 hours.

The mixture is brought to the boiling point (0.8 ° C / min) and maintained at this temperature for 3 hours.

The solution is then separated by settling, re-milled and neutralized to pH 6 and washed until the chlorides and Na + ions are removed.

The particles are then redispersed with NaOH to a pH of 9 and a solids content of approximately 12%

The particle size, measured by TEM, is 25 nm.

X-ray analysis shows that the particles contain 80% by weight of TiO ₂ in anatase form.

Example 7

Preparation of an organic dispersion of titanium dioxide particles

200 g of the dispersion according to Example 5, whose solids content was reduced to 10%, was introduced into a round-bottomed flask.

180 g of octamethylcyclotetrasiloxane (D4), to which 15 g of isostearic acid was previously added, are added. The mixture was then heated and distilled on a Vigreux column. The azeotrope distills at 97 ° C with a water / D4 mixture of approximately 40/60. Recycle D4 to a round bottom flask. After 3 hours, a suspension of TiO ₂ in D 4 with a solids content of 10% was obtained.

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Example 8

Synthesis of dispersions of titanium dioxide particles and polyorganosiloxane drinkers

The dispersions are prepared from the polyorganosiloxane according to Examples 1 to 4 and the titanium dioxide dispersions according to Examples 5 to 7, or from a commercially available titanium dioxide dispersion S5-300.

8.1. Disperse 1 (comparative)

Acid dispersion S5-300 (HNO ₃ , pH = 1) is used. The XDC analysis shows that the particles are monopopulation particles free of agglomerates and their dispersion index is 0.41. Measurement of the particle size by TEM yields a size of 45 nm. Their BET specific surface area (measured according to the protocol above) is greater than 250 m ² / g. The crystalline structure, as measured by X-ray analysis, is anatase.

This dispersion, reduced to a solids content of 10%, is mixed with the polyorganosiloxane of Example 4 in proportions by weight of 82.4% titanium dioxide and 17.6% polyorganosiloxane.

This mixture is then applied to the glass substrate.

The coating is applied by brushing onto glass panes which have been previously washed with acetone and then air dried. The coating is then allowed to air dry freely.

The film obtained is inhomogeneous, white and non-stick. It is simply removed by scratching your finger over the glass plate.

8.2. Disperse 2 (according to the invention)

The dispersion S5-300 described above with a reduced solids content of 10% is mixed with the polyorganosiloxane-based M1 mixture according to Example 1, which mixture comprises:

-21 • ·

- 5% by weight of the polyorganosiloxanes according to Example 1,

- 5% by weight of poly (propyl silicate),

- 1% by weight of butyl titanate,

- 89% by weight of Petrol E.

Poly (propylsilikštem) refers to the poly (propyl) propylpotom neutralization hydrolysis formula (SiO) _(0: n-Pr) _2, _ _M orthosilicate for the use of HCl prepared by the acid and bicarbonate and filtration. It's a binder.

Petrol E is a fraction consisting of aliphatic hydrocarbons boiling in the range of 96 to 113 ° C at standard pressure.

Diperse S5-300 and M1 are mixed in parts by weight

20.1% titanium dioxide and 79.9% polyorganosiloxanes according to Example 1 + butyl titanate.

The mixture is then diluted with isopropanol to give a dispersion having a solids content of 1.3% by weight of titanium dioxide.

The coating is applied to the glass plate as in dispersion 1.

The film obtained is <

aJ.e mime dark white, and hard (pencil hardness 5H after 1 week).

.3. Disperse 3 (according to the invention)

The basic titanium dioxide dispersion according to Example 6 was used.

This dispersion is mixed with the above mixture M1.

The dispersion and the mixture M1 were mixed in weight fractions of 20.1% titanium dioxide and 79.9% polyorganosiloxanes according to Example 1 + butyl titanate.

The resulting mixture is then diluted with isopropanol to give a dispersion having a solids content of 0.75% by weight of titanium dioxide.

The application is carried out on the glass plate as described above.

-22 The film obtained is homogeneous and translucent (can be read through). Hardness of pencil 7H after 1 week.

The photocatalytic efficiency of this film is measured. The photooxidation test consists in monitoring the degradation of the isobutane gas contacted with the glass treated according to the invention.

This is done by introducing the test glass and an amount of isobutane equal to 20 of the total reactor volume into a rotating reactor.

The test apparatus consists of about 1 and consists of a rotating disk of low-pressure UVA lamps with an emission of between 300 and 400 nm. The reactors containing the glasses to be evaluated are placed on the turntable, the face of the glass to be evaluated on the side of the UVA radiation. Depending on their position and the number of lamps switched on, each UVA glass receives radiation up to 30 W / m ² . The irradiation lasts 8 to 22 hours. The isobutane photo degradation procedure is determined quantitatively using a gas chromatograph by monitoring en1

G 'is expressed using the O ₂ extinction rate constant in mol / h / cm ² .

This test carried out with polyorganosiloxane alone in the presence of air shows no O ₂ consumption. The resin does not degrade under UVA radiation.

This test, carried out with the resin in the presence of TiO ₂ and air, still shows no consumption of O ₂ . The resin does not degrade under UVA radiation.

In the presence of isobutane and air, the plate containing the resin and TiO ₂ shows consumption of 1 to 1.5

O- within 17 hours, indicating the photocatalytic efficiency of the plate.

.4. Disperse 4 (according to the invention;

The particle dispersion of Example 6 is mixed with the M2 polyorganosiloxane-based mixture of Example 3, wherein the mixture comprises:

• ·

- 7% by weight of the polyorganosiloxane according to Example 3,

- 5% by weight of butyl titanate,

88% by weight of hexamethyldisiloxane.

The dispersion of Example 6 and the mixture of M2 were mixed in weight fractions of 15% titanium dioxide and 85% polyorganosiloxane according to Example 3 + butyl titanate.

The application is carried out on the glass plate as described above.

The film obtained is homogeneous, translucent (readable through it) and hard.

8.5. Disperse 5 (according to the invention)

The titanium dioxide dispersion according to Example 7 was used.

Prepare a dispersion of the invention comprising the polyorganosiloxane of Example 2 diluted to 8% by weight with white spirit and 1% by weight TiO _2, relative to the whole.

This dispersion was sprayed at a ratio of 200 g / m @ ² onto a concrete slab which had previously been sprayed with the titanium dioxide dispersion of Example 7 having a solids content of 1% by weight, also at a ratio of 200 g / ml.

The film obtained is homogeneous and adhesive. The color of the concrete is not damaged by the film.

It has been observed that the coating has water-repellent properties equivalent to polyorganosiloxane alone. The water uptake by concrete is as low in the treatment of concrete with the polyorganosiloxane itself as in the treatment of the dispersions of the invention.

• ·

Claims (14)

A dispersion of photocatalytic titanium dioxide particles, characterized in that the liquid phase comprises at least one polyorganosiloxane of either formula I M _and D _p Q10 _1/2 RO _£ (I) where M D Q wherein R is R ^ SiO ^ is R ¹¹ ₂ SiO _2/2 is SiO _4/2 which are the same or different, are either linear or branched alkyl having 1 to 8 carbon atoms or substituted or unsubstituted aryl having 6 to 12 atoms or an arylalkyl, an arylaryl, an aryloxyalkyl or an alkoxyaryl group in which the aryl group contains from 6 to 12 carbon atoms, which may optionally be substituted by at least one linear or branched alkyl or C 1 -C 4 alkoxy group, and wherein the alkyl group or the alkoxy group has 1 to 4 carbon atoms and is linear or branched, α, β and δ mean the molar fractions of silicon atoms of M, D and Q units, with α + β + δ = 1, aa <0.10, s preferably α <0.010, β <0.85, δ> 0.10, R ¹ , which may be the same or different, denotes an alkyl group having 1 to 4 carbon atoms, ε denotes the number of CH 2 R ¹ units per silicon atom, or formula II M _o D _p T _; (O- ₂ Rb (II)) · · · · · · · · · · · · · · · · · · · · · · · · · · -25 ····· · · · · · · · · · · · · · · · · · where · where M, D, R ¹ and ε have the meanings given above and T = R ¹¹ SiO _3/2 , where R ¹¹ is as defined above, α, β and γ mean the molar fractions of the silicon atoms of M, D and T units, with α + β + γ = 1, and α <0, 20, preferably α <0.010, β <0.60, γ> 0.30. Dispersion according to claim 1, characterized in that the polyorganosiloxane has the formula I or II and R ¹ is an ethyl group or a methyl group. Dispersion according to claim 1 or 2, characterized in that the polyorganosiloxane has the formula II and for each unit T = R ' ¹ SiO _3/2 , R ** is a methyl group, for each unit D = F / hSiCy; one R ¹¹ is a methyl group J θ octyl, β has a value of at most 0.10, γ has a value of at least 0.70. Dispersion according to claim 1 or 2, characterized in that the polyorganosiloxane has the formula II and for each unit T = R 1 SiCy, R ¹¹ is a methyl group, for each unit D = R ^{1: 12} SiO _2/2 , both R ¹¹ are methyl groups, β is at most 0.30, γ is at least 0.70. The dispersion according to claim 1 or 2, characterized in that the polyorganosiloxane has the formula II and for each unit T = R Si SiCy, "R ¹¹ is a propyl group, for each unit D = R"^; 2SiO _2/2 , both R ¹¹ are methyl groups, β has a maximum value of 0.40, γ 'has a value of at least 0.40. Dispersion according to any one of the preceding claims, characterized in that the liquid phase comprises a crosslinking catalyst. Dispersion according to claim 1, characterized in that it comprises dicarboxylate compounds. wherein the crosslinking catalyst is selected from organic compounds of titanium or tin, in particular alkyl titanates, selected from the group of organic dialkyl tin Dispersion according to any one of the preceding claims, characterized in that the liquid phase comprises an organic solvent selected from the group consisting of solvents for silicone polymers such as D4 (octamethylcyclotetrasiloxane) or other volatile siloxanes, white spirit, C 1 -C 8 alcohols. or aliphatic or aromatic hydrocarbons. Dispersion according to any one of the preceding claims, characterized in that the titanium dioxide particles have a particle size of at most 100 nm. Dispersion according to any one of the preceding claims, characterized in that the particle to polyorganosiloxane ratios are such that the particles represent at least 5% by weight of the particle + polyorganosiloxane mixture. Dispersion according to any one of the preceding claims, characterized in that it comprises at least Ξ% · * Disp Disp Disp Disp alespoň alespoň The weight of the crosslinking catalyst relative to the polyorganosiloxane + catalyst catalyst mixture. A process for the preparation of a dispersion according to any one of the preceding claims, characterized in that the titanium dioxide particles and the polyorganosiloxane are mixed. Use of a dispersion according to any one of claims 1 to 11 for treating the surface of a substrate. 14. Use of a dispersion according to claim 5 for treating an alkaline substrate.