Use of fluorinated acrylic resins in these applications is well known, but has a number of disadvantages: slightly sticky feel, poor resistance to cleaning and abrasion, and slight modification of the appearance of the support. 
Compositions comprising perfluorinated groups and urethane linkages have already been proposed; see, for example, U.S. Pat.  Nos.  3,468,924, 3,503,915, 3,528,849, 3,896,035, 3,896,251 and 4,024,178, French Patent No.  2,062,244, German Patent No.  1,620,965, Canadian Patent No.  1,071,225, European Patent No.  103,752 and Swiss Patent Nos.  520,813 and 512,624.  Unfortunately, these products do not always prove satisfactory, either because the synthesis of the intermediates is difficult, or because they have to be combined with acrylic copolymers since they are not film-forming, do not withstand dry cleaning and/or do not have good stain-repellent properties, or alternatively because they have to be supplied as an aqueous emulsion as a result of their low solubility in solvents. 
To prevent the transfer of the printing powder during the preparation of transparencies by an electrographic process, the use of fluorinated polymers containing urethane groups has been proposed in European Patent No.  100,227.  In particular, polymers derived from the fluorinated diurethane of the following formula are described in this patent: ##STR2##
However, the polymers obtained from the fluorinated diurethane (I) have the disadvantage of forming insoluble gels or providing inadequate performance as regards their hydrophobic and oleophobic properties. 
It has now been found, quite unexpectedly, that this disadvantage can be remedied by using a fluorinated urethane in which the polyfluorinated chain is bound at position 4 and not at position 2 as in the compound of formula (I) according to European Patent 100,227.  The polymers derived from these diurethanes having a polyfluorinated chain at position 4 show good solubility in the usual solvents; they have excellent hydrophobic and oleophobic properties and are, in particular, entirely suitable for treating leather. 
The subject of the present invention is, first, as fluorinated acrylic monomers, the diurethanes of general formula: ##STR3## in which:
R.sub. F denotes a perfluoroalkyl radical having a straight or branched chain and containing from 2 to 20 carbon atoms (preferably 4 to 16),
R denotes hydrogen or, preferably, a methyl radical, PA1 A denotes a divalent linkage which has 2 to 9 carbon atoms and can contain one or more oxygen atoms, PA1 Q denotes an oxygen or sulphur atom or the group --NR'--, where R' denotes hydrogen or an alkyl radical containing 1 to 4 carbon atoms, and PA1 W denotes a divalent linkage linked to Q through a carbon atom and capable of containing one or more oxygen, sulphur and/or nitrogen atoms. 
The fluorinated acrylic monomers of formula (II) according to the invention can be prepared by reacting, in a first stage, toluene 2,4-diisocyanate with a substantially equimolar amount of a polyfluorinated compound of formula: EQU R.sub. F --W--Q--H (III)
to form a fluorinated urethane-isocyanate of formula: ##STR4## and then reacting this urethane-isocyanate with a substantially equimolar amount of an acrylic ester of formula: ##STR5##
The polyfluorinated compound (III) is a compound containing a mobile hydrogen atom in the form of a terminal hydroxyl, thiol or primary or secondary amino group linked to the perfluoroalkyl radical through an alkylene bridge directly or via a sulphonamido, carboxamido, ether, thioether, sulfonyl or carboxylic ester group. 
As examples of such polyfluorinated compounds, there may be mentioned more especially those of formulae:
______________________________________ R.sub.  F (CH.sub.2).sub.p OH (III-a) ##STR6## (III-b) ##STR7## (III-c) R.sub. F (CH.sub.2).sub.pO (CH.sub.2).sub.q OH (III-d) R.sub. F (CH.sub.2).sub.pS (CH.sub.2).sub.q OH (III-e) R.sub. F (CH.sub.2).sub.p (OCH.sub.2 CH.sub.2).sub.q OH (III-f) R.sub. F (CH.sub.2).sub.p SO.sub.2 (CH.sub.2).sub.q OH (III-g) ##STR8## (III-h) ##STR9## (III-i) R.sub. F CH CH (CH.sub.2).sub.p OH (III-j) R.sub. F (CH.sub.2).sub.pSH (III-k) R.sub. F (CH.sub.2).sub.pNH.sub.  2 (III-1) ##STR10## (III-m) ##STR11## (III-n) ______________________________________
in which R.sub. F and R" have the same meanings as above, and the symbols p and q, which may be identical or different, each denote an integer ranging from 1 to 20 and preferably equal to 2 or 4.  For economical and practical reasons, it is especially advantageous to use a mixture of compounds in which different radicals R.sub. F are represented. 
Among the compounds (III), those of formulae (III-a), (III-c) and (III-k), in which p and q are equal to 2, are especially preferred. 
As examples of esters of formula (V), there may be mentioned, more especially, monoacrylates and monomethacrylates of diols or of polyalkylene glycols, such as ethylene glycol, propylene glycol, 1,3-propanediol, butanediols, 3-phenoxy-1,2-propanediol and triethylene glycol.  Ethylene glycol monomethacrylate is preferably used. 
The synthesis of the fluorinated acrylic monomers (II) according to the invention can be performed in an organic solvent, for example ketonic solvents such as methyl ethyl ketone or methyl isobutyl ketone, esters such as ethyl acetate or butyl acetate, aromatic solvents such as toluene, alkanes such as hexane, heptane or cyclohexane, ethers such as diisopropyl ether or tetrahydrofuran, halogenated solvents such as 1,1,1- trichloroethane or trichlorotrifluoroethane, and also dimethylformamide and N-methylpyrrolidone. 
The addition reactions of the polyfluorinated compound R.sub. F --W--Q--H and the acrylic ester (V) to the --N.dbd. C.dbd. O groups are performed at between 30.degree.  and 90.degree.  C. under an inert atmosphere, for example under anhydrous nitrogen.  Since the addition of the polyfluorinated compound is slow, it is preferable to work in the presence of a catalyst, such as, for example, a tertiary amine such as triethylamine, triethylenediamine and N-methylmorpholine, a tin salt such as dibutyltin dilaurate and tin octoate or a lead salt such as lead naphthenate, this catalyst being used in the proportion of 0.05 to 1% relative to the total weight of the reagents and introduced with either of the reagents or boch. 
In order to limit the concomitant formation of symmetrical addition products, that is to say products of the formulae: ##STR12## it is preferable to add the polyfluorinated compound (III) slowly, under conditions of dilution and temperature such that the reaction is virtually instantaneous and that there is always an excess of toluene diisocyanate relative to compound (III).  Although it is not possible to completely prevent the formation of symmetrical addition products, the presence of these products in the solutions of acrylic monomers (II) which are intended for polymerization does not cause interference.  It is, however, possible, if so desired, to remove them by fractional crystallization and filtration, since they are less soluble in solvents than the monomers (II). 
Instead of using pure 2,4-toluene diisocyanate, which is very expensive, it is economically advantageous to use a technical grade toluene diisocyanate which can contain up to approximately 35% by weight (preferably up to approximately 20%) of the 2,6-isomer.  In effect, insofar as their proportion remains relatively low, the presence of products of addition to this 2,6-isomer does not cause disadvantages for the applications in question. 
The subject of the invention is also the polymers containing units of formula: ##STR13## in which the various symbols have the same meanings as above.  These polymers can be obtained from the monomers of formula (II) by homopolymerization or by copolymerization with other monomers, fluorinated or otherwise, in a proportion ranging up to 90% by weight (preferably up to approximately 50%) relative to the total weight of monomers. 
As examples of comonomers which can be used in the context of the present invention, the following may be mentioned:
lower olefinic hydrocarbons, halogenated or otherwise, such as ethylene, propylene, isobutene, 3- chloro-1-isobutene, butadiene, isoprene, chloro- and dichlorobutadienes, fluoro- and difluorobutadienes, 2,5-dimethyl-1,5-hexadiene, diisobutylene;
vinyl, allyl or vinylidene halides, such as vinyl or vinylidene chloride, vinyl or vinylidene fluoride, allyl bromide, methallyl chloride;
styrene and its derivatives, such as vinyltoluene, .alpha.-methylstyrene, .alpha.-cyanomethylstyrene, divinylbenzene, N-vinylcarbazole;
vinyl esters such as vinyl acetate, vinyl propionate, the vinyl esters of the acids known commercially by the name "Versatic acids", vinyl isobutyrate, vinyl senecioate, vinyl succinate, vinyl isodecanoate, vinyl stearate, divinyl carbonate;
allyl esters such as allyl acetate and allyl heptanoate;
alkyl vinyl or alkyl allyl ethers, halogenated or otherwise, such as cetyl vinyl ether, dodecyl vinyl ether, isobutyl vinyl ether, ethyl vinyl ether, 2-chloroethyl vinyl ether, tetra allyloxyethane;
vinyl alkyl ketones such as vinyl methyl ketone; unsaturated acids, for example acrylic, methacrylic, .alpha.-chloroacrylic, crotonic, maleic, fumaric, itaconic citraconic and senecioic acids, their anhydrides and their esters such as vinyl, allyl, methyl, butyl, isobutyl, hexyl, heptyl, ethyl-2-hexyl, cyclohexyl, lauryl, stearyl and 2-alkoxyethyl acrylates and methacrylates, dimethyl maleate, ethyl crotonate, acid methyl maleate, acid butyl itaconate, glycol or polyalkylene glycol diacrylates and dimethacrylates, such as ethylene glycol or triethylene glycol dimethacrylate, dichlorophosphatoalkyl acrylates and methacrylates such as dichlorophosphatoethyl methacrylate, and also acid bis(methacryloyloxyethyl) phosphate and methacryloyloxypropyltrimethoxysilane;
acrylonitrile, methacrylonitrile, 2-chloroacrylonitrile, 2-cyanoethyl acrylate, methyleneglutaronitrile, vinylidene cyanide, alkyl cyanoacrylates such as isopropyl cyanoacrylate, trisacryloylhexahydro-s-triazine, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, N-vinyl-2-pyrrolidone;
allyl alcohol, allyl glycolate, isobutenediol, allyloxyethanol, o-allylphenyl, divinylcarbinol, glycerol allyl ether, acrylamide, methacrylamide, maleamide and maleimide, N-(cyanoethyl)acrylamide, N-isopropylacrylamide, diacetoneacrylamide, N-(hydroxymethyl)acrylamide and -methacrylamide, N-(alkoxymethyl)acrylamides and methacrylamides, glyoxal bisacrylamide, sodium acrylate or methacrylate, 2-sulphoethyl acrylate, vinylsulphonic and styrene-p-sulphonic acids and their alkali metal salts, 3-aminocrotono- nitrile, monoallyl amine, vinylpyridines, glycidyl acrylate or methacrylate, allyl glycidyl ether, acrolein, N,N-dimethylaminoethyl or N-tert-butylamino ethyl methacrylate;
the unsaturated fluorine esters of the general formula: ##STR14## in which R.sub. F, R and W have the same meanings as above. 
These comonomers can be prepared according to known processes, for example by esterification of the corresponding polyfluorinated alcohols of formula: EQU R.sub. F --W--OH (X)
by means of an alkenemonocarboxylic acid of formula: ##STR15## 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 (XI), it is also possible to use their esters, anhydrides or halides.  As examples of polyfluorinated alcohols of formula (X), there may be mentioned more especially those of formulae (III-a) to (III-j) above. 
By way of comonomers which can be used in the context of the present invention, the following may also be mentioned:
the products of formula (VII) above;
the unsaturated esters of formula: ##STR16## obtained by condensation of a fluorinated epoxide: ##STR17## with an alkenemonocarboxylic acid of formula (XI); the acrylates and methacrylates of ethers of polyethylene glycols or polypropylene glycols of formula: ##STR18## in which R.sub.3 denotes a hydrogen atom or a methyl radical, R.sub.4 denotes an alkyl radical and n is an integer between 2 and 10; and
the compounds of formula: ##STR19## in which the symbols Q, R, R.sub. F and W have the same meanings as above, A' denotes an alkylene group having 2 or 3 carbon atoms, R.sub.5 denotes an alkyl, cycloalkyl or piperazinyl radical, and Z denotes an aliphatic, cycloaliphatic or aromatic divalent linkage. 
These compounds, which form the subject of a U.S. application filed Oct. 16, 1986, which claims priority to French Patent application No.  85/15,347 filed on Oct. 16th 1985, can be prepared by reacting substantially equimolar amounts of a poly-fluorinated compound of formula (III) and an acrylic ester containing a secondary amino group, of formula: ##STR20## with an aliphatic, cycloaliphatic or aromatic diisocyanate, under working conditions similar to those described above for the preparation of the monomers (II). 
Among the above-mentioned comonomers, more special preference is given to simple alkyl acrylates and methacrylates or those containing a hydroxyl, amino or sulphonic acid functional group, the fluorinated compounds (IX) and (XV), methacrylates of polyethylene glycol ethers, vinyl ethers, vinyl or vinylidene chloride and fluoride, vinyl pyrrolidone, acrylamide and its derivatives, and acrylic or methacrylic acid. 
The fluorinated polymers according to the invention can be prepared in a manner known per se, by polymerization in an organic solvent or in an aqueous emulsion, at a temperature which can range from room temperature to the boiling point of the reaction medium.  It is preferable to work at between 70.degree.  and 110.degree.  C. The total concentration of the monomers can vary from 5 to 60% by weight. 
The polymerization in a solvent medium can be carried out in ketonic solvents (for example acetone, methyl ethyl ketone, methyl isobutyl ketone), alcohols (for example isopropanol), esters (for example ethyl acetate or butyl acetate), ethers (for example diisopropyl ether, ethylene glycol ethyl or methyl ether, tetrahydrofuran, dioxane), aliphatic or aromatic hydrocarbons, halogenated hydrocarbons (for example per-chloroethylene, 1,1,1-trichloroethane, trichlorotri fluoroethane), dimethylformamide or N-methyl-2 pyrrolidone. 
The polymerization is performed in the presence of one or more initiators, which can be used in the proportion of 0.1 to 1.5% relative to the total weight of the monomers involved.  As initiators, peroxides can be used, such as, for example, benzoyl peroxide, lauroyl peroxide, succinyl peroxide and tert-butyl perpivalate, or azo compounds such as, for example, 2,2'-azo- bisisobutyronitrile, 4,4,'-azobis(4-cyanopentanoic acid) and azodicarbonamide.  It is also possible to work in the presence of UV radiation and photoinitiators such as benzophenone, 2-methylanthraquinone or 2 chlorothioxanthone.  The length of the polymeric chains can, if so desired, be adjusted by means of chain transfer agents such as alkyl mercaptans, carbon tetrachloride or triphenylmethane, used in the proportion of 0.05 to 0.5% relative to the total weight of monomers. 
The polymerization in aqueous emulsion can be carried out according to well-known techniques, in discontinuous or continuous fashion.  The surfactants to be used for the emulsification can be cationic, anionic or nonionic, according to the ionic nature desired for the final latex, and are preferably chosen from the best oil-in-water emulsifers which are as little wetting as possible.  Cationic/nonionic or anionic/nonionic surfactant systems are preferably used.  As examples of surfactants which can be used, the following may be mentioned more especially:
in the cationic series, long-chain tertiary amine salts such as N,N-dimethyloctadecylamine acetate, and the quaternary ammonium salts of fatty amines such as trimethylcetylammonium bromide or trimethyldodecyl ammonium chloride;
in the anionic series, alkali metal salts of long-chain alkylsulphonic acids and alkali metal arylalkyl sulphonates;
in the nonionic series, condensation products of ethylene oxide with fatty alcohols or with alkyl phenols. 
It can also be advantageous to use surfactants having a perfluorinated hydrophobic chain, such as, for example, ammonium perfluorooctanoate or potassium N-perfluorooctylsulphonyl-N-ethylaminoacetate. 
To facilitate the emulsification of the monomers, it is generally necessary to use organic solvents such as, for example, ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone), glycols or ethylene glycol ethers, alcohols (methanol, ethanol, isopropanol), or mixtures of these solvents.  The amount of solvent should not generally exceed the total weight of the monomers. 
As initiators of polymerization in aqueous emulsion, it is possible to use water-soluble products, such as inorganic peroxides (for example hydrogen peroxide) and persalts (for example potassium persulphate), or initiators which are insoluble in water such as organic peroxides and the azo compounds mentioned above. 
The fluorinated polymers according to the invention can also be prepared by grafting a fluorinated urethane-isocyanate of formula (IV) onto an acrylic polymer having pendent OH groups, which is obtained by homopolymerization of an acrylic ester of formula (V) or by copolymerization of such an ester with one or more of the comonomers mentioned above.  The grafting operation can be carried out under the same conditions as the addition of ester (V) to the fluorinated urethane-isocyanate (IV).  The acrylic polymer having pendent OH groups can itself be obtained by polymerization in a solvent medium under conditions similar to those described above for the polymerization of the monomers of formula (II). 
Regardless of the method by which they are obtained, the fluorinated polymers according to the invention can optionally be isolated according to methods known per se, such as, for example, precipitation or evaporation of the solvent. 
The fluorinated polymers according to the invention prove to be excellent hydrophobic and oleophobic agents on very diverse materials such as paper, nonwoven articles, textiles based on natural, artificial or synthetic fibres, plastics, wood, metals, glass, stone and cement, but are intended especially for the protection of leathers, both for the finishing thereof and for the maintenance of leather articles such as clothing, shoes, fancy leather goods, seats, etc. 
For application, the solutions of polymers are generally diluted with a solvent identical to or compatible with that used for the polymerization, while the emulsions of polymers are diluted with water.  The application of the dilute products can be carried out according to different techniques, such as spraying, brush-coating and padding.  Depending on their nature, the substrates treated can be dried at room temperature or at temperatures which can range up to 200.degree.  C.
The amount of polymer to be employed can vary within wide limits, depending on the nature of the support and the fluorine content of the polymer.  On leather, this amount is generally within the range of about 1 to 10 g/m.sup.2.