Cationic fluoro copolymers for the oleophobic and hydrophobic treatment of building materials

The invention relates to fluoro copolymers containing hydroxyl groups and amino groups in salified or quaternized form. With such a copolymer and a polyisocyanate, an aqueous composition which is useful for the oleophobic and hydrophobic treatment of building materials may be prepared.

FIELD OF THE INVENTION 
The present invention relates to the oleophobic and hydrophobic treatment 
of building materials, such as bricks, tiles, natural or reconstituted 
stone, ceramics, plasters, concretes, cements, mortars, wood, glass, 
metals and plastics, and relates more particularly to the anti-soiling and 
anti-graffiti treatment of the said materials. 
BACKGROUND OF THE INVENTION 
Products or compositions which allow either of these properties to be 
obtained in building materials are already known. There may firstly be 
mentioned silicones (patents FR 2,469,437 and 2,474,518) which effectively 
impart a hydrophobic nature, but which are not oil-repellent. 
Processes are also known (patent FR 2,313,987) which consist in applying, 
separately or as a mixture, a water-soluble polymer compound derived from 
unsaturated carboxylic acid and a solution of an organosilicon compound. 
However, these compounds are not easy to use and the oil-repellent and 
water-repellent properties only appear after a long period of drying at 
room temperature or after a heated drying. 
The use of hydroxylated copolymers of the acrylic-siloxane type, alone or 
crosslinked with other resins, has also been proposed. However, these 
water-resistant products offer no resistance to oils. 
The use of aluminium polyoxostearate, polyvinyl alcohol (patent FR 
2,607,821), acrylic polymers (patent U.S. Pat. Nos. 4,353,745 and 
4,241,141), waxes of plant or mineral origin (patents WO 80/01072 and FR 
2,445,361), polysaccharide (patent WO 88/10156) and isocyanate prepolymers 
(patents U.S. Pat. No. 4,716,056, EP 340,237 and EP 404,895) has also been 
proposed. However, these products do not have any oil-repellent property. 
In order for the treatment to be of lasting effectiveness, the coatings 
used are usually crosslinked. This crosslinking takes place in situ, on 
the substrate to be treated, and makes use of chemical groups capable of 
reacting at room temperature and without thermal activation, only 
catalysts being tolerated. In this perspective, the reaction of isocyanate 
units with hydroxyl groups (patents U.S. Pat. No. 4,716,056, EP 340,237, 
BE 901,692, GB 2,187,196 and EP 404,895) or with moisture present on the 
support (patent GB 2,187,196) is often exploited. Generally, the coating 
decomposes into two layers which are successively applied to the 
substrate: the first layer contains, for example, the hydroxyl groups and 
the second consists of urethane prepolymers containing free isocyanate 
units. The treatment may also be effected as one layer by mixing, prior to 
application, the compound containing the --OH groups and the prepolymer 
containing isocyanate units; however, in this case, the shelf life of the 
mixture in a container is short. Moreover, the reactivity of the 
isocyanates makes it necessary to dissolve the compounds in organic 
solvents containing no --OH groups (ketones, esters, white spirit, etc.). 
Coatings of this type generally have no oil-repellent property. 
In order to impart to the building materials water-repellent, 
oil-repellent, anti-graffiti and non-stick properties which are stable 
with respect to ageing and inclement weather, it has been proposed in 
patent FR 2,540,131 to use a composition comprising, by weight: 
from 0.1 to 25% of a fluoro copolymer containing OH groups, 
from 2 to 25% of an aliphatic or aromatic polyisocyanate or isocyanate 
prepolymer, 
from 0.1 to 10% of a catalyst, and 
one or more organic solvents for dilution in order to complete to 100%. 
This composition effectively imparts oil-repellent and water-repellent 
properties to the materials treated. However, it still requires the use of 
a dilution operation in a solvent medium. 
DESCRIPTION OF THE INVENTION 
It has now been found that this problem may be solved using fluoro 
copolymers containing not only OH groups but also amino groups in salified 
or quaternized form. With these novel cationic fluoro copolymers, aqueous 
compositions may be prepared which, when applied to stone, concrete and 
more generally to any building material, do not change the surface 
appearance of the materials and impart thereto, after a very brief period 
of drying, combined water-repellent, oil-repellent and anti-graffiti 
properties which are stable with respect to ageing and inclement weather. 
The first subject of the present invention is thus fluoro copolymers in 
salified or quaternized form, characterized in that they are made up of (% 
by weight): 
(a) 50 to 92%, preferably 70 to 90%, of one or more polyfluoro monomers of 
general formula: 
##STR1## 
in which Rf represents a perfluoroalkyl radical with a straight or 
branched chain containing 2 to 20 carbon atoms, preferably 4 to 16 carbon 
atoms, X represents a divalent grouping linked to O by a carbon atom and 
possibly containing one or more oxygen, sulphur and/or nitrogen atoms, one 
of the symbols R represents a hydrogen atom and the other represents a 
hydrogen atom or an alkyl radical containing 1 to 4 carbon atoms; 
(b) 1 to 25%, preferably 2 to 18%, of one or more monomers of general 
formula: 
##STR2## 
in which Y represents a linear or branched alkylene radical containing 1 
to 4 carbon atoms, R' represents a hydrogen atom or an alkyl radical 
containing 1 to 4 carbon atoms, R.sup.1 and R.sup.2, which may be 
identical or different, each represent a hydrogen atom, a linear or 
branched alkyl radical containing 1 to 18 carbon atoms or a hydroxyethyl 
or benzyl radical, or R.sup.1 and R.sup.2, together with the nitrogen atom 
to which they are attached, form a morpholino, piperidino or pyrrolidinyl 
radical; 
(c) 1 to 25%, preferably 2 to 15%, of one or more monomers of general 
formula: 
##STR3## 
in which R" represents a hydrogen atom or an alkyl radical containing 1 to 
4 carbon atoms and Z represents an alkylene radical containing 2 to 4 
carbon atoms; and 
(d) 0 to 30%, preferably 0 to 8%, of one or more of any monomers other than 
the monomers of formulae I, II and III. 
The fluoro monomers of formula (I) may be prepared according to known 
processes, for example by esterification of the corresponding polyfluoro 
alcohols of formula: 
EQU Rf--X--OH (IV) 
using an alkenecarboxylic acid of formula: 
##STR4## 
such as, for example, acrylic acid, methacrylic acid or crotonic acid, in 
the presence of a catalyst such as sulphuric acid or p-toluenesulphonic 
acid. Instead of the acids of formula (V), the esters, anhydrides or 
halides thereof may also be used. Examples of polyfluoro alcohols of 
formula (IV) which may more particularly be mentioned are those of 
formulae (IV-1) to (IV-10) below: 
##STR5## 
in which R.sub.f and R have the same meanings as above, the symbols p and 
q, which may be identical or different, each represent an integer ranging 
from 1 to 20 and, preferably, equal to 2 or 4. 
For economic and practical reasons, it is particularly advantageous to use 
a mixture of compounds having different radicals R.sub.f. 
Examples of monomers of formula (II) which may more particularly be 
mentioned are the acrylates and methacrylates of the following amino 
alcohols: 2-dimethylaminoethanol, 2-diethylaminoethanol, 
2-dipropylaminoethanol, 2-diisobutylaminoethanol, 
2-N-tert-butylaminoethanol, 2-(N-tert-butyl-N-methylamino)ethanol, 
2-morpholinoethanol, 2-(N-methyl-N-dodecylamino)ethanol, 
2-(N-ethyl-N-octadecylamino)ethanol, 
2-N-ethyl-N-(2-ethylhexyl)amino!ethanol, 2-piperidinoethanol, 
2-(1-pyrrolidinyl)ethanol, 3-diethylamino-1-propanol, 
2-diethylamino-1-propanol, 1-dimethylamino-2-propanol, 
4-diethylamino-1-butanol, 4-diisobutylamino-1-butanol, 
1-dimethylamino-2-butanol, 4-diethylamino-2-butanol. These esters may be 
prepared, for example, according to the method described in U.S. Pat. No. 
2,138,763. The preferred monomer of formula (II) is dimethylaminoethyl 
methacrylate or N-tert-butylaminoethyl methacrylate. 
Examples of monomers of formula (III) which may more particularly be 
mentioned are the acrylates and methacrylates of alkylene glycols such as 
ethylene glycol and propylene glycol. The preferred monomer of formula 
(III) is 2-hydroxyethyl methacrylate. 
As examples of comonomers (d) which may be used within the context of the 
present invention, there may be mentioned: 
lower olefinic hydrocarbons, which may or may not contain halogen, such as 
ethylene, propylene, isobutene, 3-chloro-1-isobutene, butadiene, isoprene, 
chloro- and dichlorobutadienes, fluoro- and difluorobutadienes, 
2,5-dimethyl-1,5-hexadiene and diisobutylene; 
vinyl, allyl or vinylidene halides such as vinyl or vinylidene chloride, 
vinyl or vinylidene fluoride, allyl bromide and methallyl chloride; 
styrene and derivatives thereof, such as vinyltoluene, 
.alpha.-methylstyrene, .alpha.-cyanomethylstyrene, divinylbenzene and 
N-vinylcarbazole; 
alkyl vinyl ketones such as methyl vinyl ketone; 
unsaturated acids, such as acrylic acid, methacrylic acid, 
.alpha.-chloroacrylic acid, crotonic acid, maleic acid, fumaric acid, 
itaconic acid, citraconic acid and senecioic acid, the anhydrides thereof 
and the esters thereof such as the allyl, methyl, butyl, isobutyl, hexyl, 
heptyl, 2-ethylhexyl, cyclohexyl, lauryl, stearyl or cellosolve acrylates 
and methacrylates, dimethyl maleate, ethyl crotonate, methyl hydrogen 
maleate, butyl hydrogen itaconate, and the diacrylates and dimethacrylates 
of glycol or of polyalkylene glycol; 
the unsaturated esters of formula: 
##STR6## 
obtained by condensation of a fluoro epoxide: 
##STR7## 
with a monocarboxylic alkenoic acid of formula (V); 
the chlorides of formula: 
##STR8## 
obtained by addition of epichlorohydrin to an acid of formula (V); 
the ether acrylates and ether methacrylates of mono- and poly-ethylene 
glycols or -propylene glycols of formula: 
##STR9## 
in which R.sup.3 represents a hydrogen atom or a methyl radical, R.sup.4 
represents an alkyl radical and m is an integer between 1 and 50; 
the acrylates and methacrylates of polyethylene glycol or of polypropylene 
glycol of formula: 
##STR10## 
in which R and R.sup.3 have the same meanings as above and n is an integer 
between 2 and 50; 
acrylonitrile, methacrylonitrile, 2-chloroacrylonitrile, 2-cyanoethyl 
acrylate, methyleneglutaronitrile, vinylidene cyanide, alkyl 
cyanoacrylates such as isopropyl cyanoacrylate, 
trisacryloylhexahydro-s-triazine, vinyltrichlorosilane, 
vinyltrimethoxysilane, vinyltriethoxysilane; 
allyl alcohol, allyl glycolate, isobutenediol, allyloxyethanol, 
o-allylphenol, divinylcarbinol, glyceryl allyl ether, acrylamide, 
methacrylamide, maleamide and maleimide, N-(cyanoethyl) acrylamide, 
N-isopropylacrylamide, diacetoneacrylamide, N-(hydroxymethyl)-acrylamide 
and -methacrylamide, N-(alkoxymethyl)-acrylamides and -methacrylamides, 
glyoxalbisacrylamide, sodium acrylate or methacrylate, 2-sulphoethyl 
acrylate, vinylsulphonic acid and styrene-p-sulphonic acid and the alkali 
metal salts thereof, 3-aminocrotonitrile, monoallylamine, vinylpyridines, 
glycidyl acrylate or methacrylate, allyl glycidyl ether, acrolein; 
allyl esters such as allyl acetate and allyl heptanoate; 
vinyl esters such as vinyl acetate, vinyl propionate, vinyl esters of acids 
known on the market under the name "Versatic acids", vinyl isobutyrate, 
vinyl senecioate, vinyl isodecanoate, vinyl stearate; and 
alkyl vinyl ethers, which may or may not contain halogen, such as cetyl 
vinyl ether, dodecyl vinyl ether, isobutyl vinyl ether, ethyl vinyl ether 
and 2-chloroethyl vinyl ether. 
The cationic fluoro copolymers according to the invention are prepared by 
copolymerization of the monomers in solution in an organic solvent or in a 
mixture of organic solvents such as acetone, tetrahydrofuran, dioxane, 
dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulphoxide, ethyl 
acetate, isopropyl acetate, butyl acetate, methyl ethyl ketone, methyl 
isobutyl ketone, ethanol and isopropanol. As polymerization solvent, it is 
preferred to use N-methyl-2-pyrrolidone (NMP), acetone or an NMP/acetone 
binary mixture. The total concentration of monomers may range from 5 to 
60% by weight. 
The polymerization is carried out in the presence of initiator(s) which is 
(are) used to a proportion of 0.1 to 1.5% relative to the total weight of 
monomers employed. Initiators which may be used are peroxides such as, for 
example, benzoyl peroxide, lauroyl peroxide, succinyl peroxide and 
tert-butyl perpivalate, or azo compounds such as 
2,2'-azobisisobutyronitrile, 4,4'-azobis(4-cyanopentanoic acid) and 
azodicarbonamide. The process may also be performed in the presence of UV 
radiation and photo-initiators such as benzophenone, 2-methylanthraquinone 
or 2-chlorothioxanthone. The length of the polymer chains may, if so 
desired, be controlled using chain transfer agents such as alkyl 
mercaptans, carbon tetrachloride or triphenylmethane, which are used to a 
proportion of 0.05 to 1% relative to the total weight of monomers. 
The reaction temperature may vary within a wide range, that is to say 
between room temperature and the boiling point of the reaction mixture. 
The process is preferably performed between 60.degree. and 90.degree. C. 
The copolymer may be salified using strong or moderately strong inorganic 
or organic acids, that is to say acids whose dissociation constant or 
whose first dissociation constant is greater than 10.sup.-5. There may, 
for example, be mentioned hydrochloric acid, hydrobromic acid, sulphuric 
acid, nitric acid, phosphoric acid, acetic acid, formic acid, propionic 
acid or lactic acid. Acetic acid is preferably used. 
Instead of converting the copolymer into a salt, it may be quaternized 
using a suitable quaternizing agent such as methyl iodide, ethyl iodide, 
dimethyl sulphate, diethyl sulphate, benzyl chloride, trimethyl phosphate 
or methyl p-toluenesulphonate. 
The cationic fluoro copolymer solution obtained is diluted with water. The 
lighter synthesis solvent(s), especially the acetone, may optionally be 
removed by distillation under vacuum at a temperature between 40.degree. 
and 90.degree. C. This operation makes it possible to obtain an aqueous 
solution of the fluoro copolymer with a flash point above 100.degree. C.; 
the aqueous solution remains stable after evaporation of the solvent. In 
the case of the use of a polymerization solvent containing a function 
liable to react with the isocyanate units, such as ethanol or isopropanol, 
distillation is necessary in order to avoid interfering reactions during 
use of the composition according to the invention. The weight-average 
molecular masses of the fluoro copolymers according to the invention are 
between 2000 and 50000 g/mol. These molecular masses may be determined by 
gel permeation. The copolymers according to the invention possess 
emulsifying properties, and a copolymer solution diluted to 10% by weight 
with water has a surface tension .gamma..sub.L of the order of 35 to 50 
mN/m. 
Another subject of the present invention is compositions comprising, by 
weight: 
(A) from 0.1 to 25%, preferably from 1 to 10%, of at least one cationic 
fluoro copolymer as described above; 
(B) from 0.1 to 25%, preferably from 0.1 to 10%, of at least one aliphatic, 
araliphatic or aromatic polyisocyanate; 
(C) from 0 to 35%, preferably from 0 to 15%, of one or more water-miscible 
solvents; and 
(D) water for dilution in order to complete to 100%, the proportions of the 
components being chosen such that the NCO/OH molar ratio is at least equal 
to 1.2 and such that the content of non-volatile materials in these 
compositions does not exceed 50% and is preferably less than 20%. 
The component (B) of the compositions according to the invention is a 
polyisocyanate containing 5 to 25% by weight of free NCO units, which may 
be placed in emulsion in water or in a solution of the fluoro copolymer 
(A) diluted with water. 
The polyisocyanates of type (B) are described, for example, in patents EP 
206,059, EP 554,747 and U.S. Pat. No. 4,663,337. They are prepared from 
linear aliphatic, cycloaliphatic, araliphatic and/or aromatic molecules 
containing NCO groups. The polyisocyanates of biuret, isocyanurate and 
uret-dione structure mainly based on hexamethylene diisocyanates are 
particularly recommended. There may be mentioned, by way of example, 
N,N',N"-tris(6-isocyanatohexyl)biuret and 
N,N',N"-tris(6-isocyanatohexyl)isocyanurate. In order to facilitate their 
dispersion in water, the polyisocyanates (B) are generally made 
hydrophilic by reacting some of the isocyanate groups with molecules 
containing a reactive group (alcohol for example) and a cationic 
hydrophilic group (for example a tertiary amine salified with an acid or 
quaternized), an anionic hydrophilic group (for example a carboxylic group 
salified with a base) or a nonionic hydrophilic group (for example 
ethylene oxide units containing from 5 to 100 units). 
The polyisocyanates (B) may also be used in their hydrophobic form without 
modification intended to make them hydrophilic, since the emulsifying 
properties of the copolymers (A) enable them to be dispersed in water. In 
this case, the composition according to the invention is prepared by 
emulsifying the compound (B) in a solution of (A) diluted with water. 
If the polyisocyanate (B) used is hydrophilic, the composition according to 
the invention may be prepared either by dispersing the compound (B) in 
water with stirring and then by adding the copolymer (A) in solution 
diluted with water, or by dispersing the polyisocyanate (B) directly in a 
dilute solution of (A). 
The homogenization of the two components does not require the use of 
complicated technical means. However, for optimal homogenization, it is 
preferable to use at least a paddle stirrer mounted on a drill. Depending 
on the intensity of the stirring, the size of the particles in the 
dispersion is between 100 and 500 nm. On account of the surface properties 
of the compound (A), the molecules of the copolymer bind by adsorption to 
the droplets of polyisocyanate, in the same manner as molecules of 
emulsifying agent. 
The free NCO groups of the polyisocyanate may react with the OH functions 
of the copolymer (A) and with water. These reactions may lead to a marked 
increase in the viscosity of the composition. The interval before use of 
the preparation is directly dependent on this viscosification. 
Surprisingly, use of the system claimed containing a cationic copolymer (A) 
allows a long shelf life in a container, generally considerably longer 
than 24 hours. 
The interval before use is thus considerably increased compared with 
anionic systems. 
Since some of the NCO groups of the polyisocyanate (B) react with water, 
the process is generally performed with an excess of NCO groups relative 
to the alcohol functions borne by the copolymer (A). The NCO/OH ratio 
should be at least equal to 1.2 and is preferably at least equal to 1.5. 
The compositions according to the invention may be applied in one or more 
layers according to techniques which are well known per se, for example by 
spraying, immersion or spreading with a brush or a roller, so as to 
deposit 80 to 800 g of composition according to the invention per m.sup.2 
of surface to be treated. 
The coating obtained is conventionally dried at room temperature. It may 
also be dried at higher temperature, in an oven or a kiln. 
After applying the reactive mixture to the substrate, the water and the 
solvents which form the dispersion medium evaporate and allow the droplets 
of polyisocyanate (B) to agglomerate and allow the simultaneous diffusion 
of the molecules of the fluoro copolymer (A) into the droplets. 
The NCO and OH groups react: the film obtained with the composition claimed 
is crosslinked. 
According to another mode of the present invention, it is also possible to 
carry out the application by first depositing a solution of the component 
(A) on the support to be treated, followed by an aqueous dispersion of the 
component (B), or vice versa. 
As well as being suitable more particularly for the anti-soiling and 
anti-graffiti treatment of building materials, the cationic fluoro 
copolymers according to the invention may also be used, alone or in 
association with a polyisocyanate, for the oleophobic and hydrophobic 
treatment of other substrates such as paper, textiles, non-wovens, leather 
and moquette.

EXAMPLES 
The following tests were used to evaluate the performance of the substrates 
treated according to the invention: 
Oleophobicity Tests 
The oleophobicity was measured according to the method described in "AATCC 
Technical Manual", Test Method 118, which evaluates the non-wettability of 
the substrate by a series of oily liquids whose surface tensions are 
increasingly weaker. 
Another test consists in measuring the penetration time of a drop of 
dodecane (oil No. 5 of the test AATCC 118) placed on the support. 
Hydrophobicity Tests 
In order to test the hydrophobicity of the supports, the penetration time 
of a drop of water in the material was measured. 
The water uptake of a 43 cm.sup.2 surface of the support subjected to a 
height of 11 cm of water for one hour is also measured. 
Anti-Graffiti Test 
A plate of the support to be tested is written on with a black indelible 
felt-tip pen of reference NSO Pentel Pen Permanent Marker. After allowing 
to dry for 24 hours, the plate is cleaned by spreading methyl ethyl ketone 
over its surface. The cleaning is stopped when the solvent removes no more 
ink, and the appearance of the surface of the material is rated from 0 to 
5 in the following manner: 
5. After cleaning with methyl ethyl ketone, the plate has regained its 
original appearance: no felt-tip pen trace remains. 
4. The ink has almost entirely disappeared after cleaning with methyl ethyl 
ketone: only a slight trace remains. 
3. After cleaning with methyl ethyl ketone, there is partial and 
heterogeneous attenuation of the graffiti: more than 50% of the writing is 
removed. 
2. After cleaning with methyl ethyl ketone, there is partial and 
heterogeneous attenuation of the graffiti: less than 50% of the writing is 
removed. 
1. After cleaning with methyl ethyl ketone, there is only a very slight 
attenuation of the graffiti. 
0. The cleaning has no effect. 
The examples which follow, in which the parts and percentages are expressed 
by weight, except where otherwise mentioned, illustrate the invention 
without limiting it. 
Example 1 
122 parts of N-methyl-2-pyrrolidone, 27 parts of acetone, 10 parts of 
dimethylaminoethyl methacrylate, 5 parts of 2-hydroxyethyl methacrylate, 
0.8 part of 4,4'-azobis(4-cyanopentanoic) acid, 81.4 parts of a mixture of 
fluoroalkyl acrylates of formula: 
##STR11## 
where n is equal to 5, 7, 9, 11, 13 in average and respective weight 
ratios of 1/63/25/9/3, were loaded into a 500-part by volume reactor 
fitted with a stirrer, a thermometer, a reflux condenser, a dropping 
funnel, a nitrogen inlet and a heating device. 
The mixture was heated at 85.degree. C. under a nitrogen atmosphere for 6 
hours, followed by addition of 5 parts of acetic acid in 145 parts of 
water. The mixture was maintained for a further one hour at 75.degree. C. 
and then allowed to cool to room temperature. 396 parts of a solution of a 
fluoro copolymer according to the invention, which contains 24.3% dry 
material and 13% fluorine (solution S hereinbelow), was thus obtained. 
Using this solution and an aliphatic polyisocyanate based on a 
hexamethylene diisocyanate trimer rendered hydrophilic by reaction with a 
polyethoxylated alcohol so as to have an NCO content of 17.3% and a 
viscosity at 23.degree. C. of 3500 mPa s (polyisocyanate P hereinbelow), a 
composition (C.sub.1) according to the invention was prepared by 
dispersing 0.3 part of polyisocyanate (P) in 91.4 parts of water with 
stirring (magnetic bar: 200 rev/min), followed by addition of 8.3 parts of 
solution (S). 
The NCO/OH ratio of the composition (C.sub.1) is 1.5 and its shelf life in 
a container is longer than 48 hours. 
This composition was applied, at a rate of 90 g/m.sup.2, to earthenware 
paving stones. 
By way of comparison, the following compositions were applied in the same 
manner to similar supports: 
Composition C.sub.a 
solution (S) 8.6 parts 
water 91.4 parts 
Composition C.sub.b 
polyisocyanate (P) 8.6 parts 
water 91.4 parts 
The results obtained by subjecting the paving stones treated with the 
compositions C.sub.1, C.sub.a and C.sub.b and an untreated paving stone to 
the tests described above are collated in the following table. 
______________________________________ 
Water Penetration 
uptake time of 
Composition 
(g/m.sup.2) AATCC 118 dodecane 
______________________________________ 
C.sub.1 81 8 &gt;24 hours 
C.sub.a 251 8 &gt;24 hours 
C.sub.b 12100 0 10 minutes 
Untreated 12121 0 0 
paving 
stone 
______________________________________ 
Examination of the results shows that the paving stones treated with the 
compositions C.sub.1 and C.sub.a containing the solution (S) are the only 
ones to exhibit real hydrophobic and oleophobic properties. 
Composition C.sub.1 according to the invention allows the hydrophobicity of 
the support to be improved greatly, since the water uptake is divided by a 
factor of 3 compared with the composition C.sub.a. 
Example 2 
Using the solution (S) and the polyisocyanate (P), two compositions 
according to the invention were prepared, comprising: 
______________________________________ 
Composition C.sub.2 
Composition C.sub.3 
______________________________________ 
solution (s) 7.9 parts 6.4 parts 
polyisocyanate 
0.7 parts 2.2 parts 
water 91.4 parts 91.4 parts 
______________________________________ 
Compositions C.sub.2 and C.sub.3 differ from the composition C.sub.1 in the 
NCO/OH ratio: 
For the composition C.sub.2 : NCO/OH=3.6 
For the composition C.sub.3 : NCO/OH=14.2 
The container shelf life of the compositions C.sub.2 and C.sub.3 is not 
modified compared with the composition C.sub.1. 
These compositions were applied, at a rate of 90 g/m.sup.2, to earthenware 
paving stones. 
______________________________________ 
Water Penetration 
uptake time of 
Composition 
(g/m.sup.2) AATCC 118 dodecane 
______________________________________ 
C.sub.1 81 8 &gt;24 hours 
C.sub.2 70 8 &gt;24 hours 
C.sub.3 70 8 &gt;24 hours 
______________________________________ 
Examination of the results shows that the NCO/OH ratio may vary over a very 
wide range without noticeably modifying the performance of the treated 
paving slabs. 
Example 3 
Using 9.65 parts of solution (S), 0.35 part of polyisocyanate (P) and 90 
parts of water, a composition C.sub.4 having an NCO/OH ratio of 1.5 and a 
container shelf life of longer than 48 hours was prepared. 
This composition was applied, at a rate of 300 g/m.sup.2, to slabs of 
fascia concrete. 
By way of comparison, the following compositions were applied in the same 
manner to similar supports: 
Composition C.sub.c 
solution (S) 10 parts 
water 90 parts 
Composition C.sub.d 
polyisocyanate (P) 10 parts 
water 90 parts 
The results obtained by subjecting the slabs treated with the compositions 
C.sub.4, C.sub.c and C.sub.d and an untreated slab to the anti-graffiti 
test described above are collated in the following table. In order to test 
the persistence of the coating, successive graffiti-cleaning sequences 
were carried out. The appearance of the surface of the material is rated 
after each cleaning. 
______________________________________ 
initial 1st 2nd 3rd 4th 5th 9th 
Composi- 
appear- graf- graf- graf- 
graf- graf- 
graf- 
tion ance fiti fiti fiti fiti fiti fiti 
______________________________________ 
C.sub.4 
5 5 4 4 4 3 3 
C.sub.c 
5 4 3 2 2 1 1 
C.sub.d 
5 1 1 1 1 1 1 
______________________________________ 
Rating of the Surface Appearance After One or More Graffiti-Cleaning 
Sequences 
Examination of the results shows that only the composition C.sub.4 
according to the invention provides the support with genuine anti-graffiti 
properties. 
In addition, the permanence of the treatment is good, since at least 5 
graffiti-cleaning cycles are required in order to degrade substantially 
the appearance of the treated support. 
Although the invention has been described in conjunction with specific 
embodiments, it is evident that many alternatives and variations will be 
apparent to those skilled in the art in light of the foregoing 
description. Accordingly, the invention is intended to embrace all of the 
alternatives and variations that fall within the spirit and scope of the 
appended claims. The above references are hereby incorporated by 
reference.