FR2787455A1 - Binder for leather finishing composition comprises latex of acrylic copolymer including units derived from monomer containing ureido or thioureido group - Google Patents

Abstract

Binder for a leather finishing composition for use as a base, middle or top coat comprises an acrylic latex (I) prepared by emulsion copolymerization of radical-polymerizable ethylenically unsaturated monomers, one of which contains a ureido or thioureido group. Binder for a leather finishing composition for use as a base, middle or top coat comprises an acrylic latex (I) prepared by emulsion copolymerization of radical-polymerizable ethylenically unsaturated monomers, one of which contains a group of formula (II): X = O or S. Independent claims are also included for the following: (1) a leather finishing composition comprising (by weight) 2-100 parts (I) and 0-98 parts at least one other acrylic, polyurethane and/or polyurethane-acrylic latex; (2) leather coated with the composition of (1).

Description

BINDERS FOR LEATHER FINISHING PRODUCTS

  FINISHING INCORPORATING THESE BINDERS AND LEATHER THUS PROCESSED

  The present invention relates to binders for leather finishing products, to finishing products

  incorporating these binders and on the leathers thus treated.

  In leather finishing work, it is well known to those skilled in the art that this finishing depends on the quality of the skin. For full-grain leathers or corrected flowers, finishing, without changing the appearance of the grain, must provide some protection to the support. On the other hand, on a crust, the systematically pigmented finishing makes it possible to reconstitute an artificial flower and brings the required characteristics according to

the end use of the leather.

  Faced with the diversity of appearance of leathers and the diversity of manufacturing, it is impossible to treat all of the supports with the same finishing products and in a single application. Consequently, the surface condition and characteristics of each category of leather and the use to which it will be put are decisive in the

  choice of finishing products to use.

  However, the approach used is almost always the same: a finishing is essentially carried out by the successive application of layers of primer of different nature. The final thickness of the finish or coating will depend on the quality of the support. It is between 10 and 15 mm for full grain leather, 40 and 60 Lm for corrected leather, and can reach 200 mm for leather

varnish or coated crust.

  Generally, a finish is made up, depending on the quality of the leather and the end use, by two or three superimposed layers. The first, in contact with the leather

  and generally very flexible, constitutes the base layer.

  Depending on the final application, it can be transparent but colored or covering, therefore pigmented. The second layer or flank generally has a medium hardness. It is generally colored but does not cover much. The outer layer,

  called fixative or "top coat" is always transparent.

  It is it which is most in demand and which must have a high hardness (between 60 and 90 shore A), good resistance to friction in dry or in the presence of water and a

good adhesion.

  Fixative resins are often in solution in organic solvents or sometimes in aqueous emulsion. The binders for fixatives commonly used are polyurethanes, protein binders, or nitrocellulose binders which are often formulated with a crosslinker. There are a few fixatives in aqueous emulsion which are most often polyurethanes, such as those sold under the names BAYDEM 60, 80, 85 or 90 UD by the company BAYER, and sometimes acrylic copolymers, such as those sold under the names

  HYDRHOLAC AQS or PC by the company ROHM & HAAS.

  Seeking to improve the adhesion performance of products currently known for finishing leather, the Applicant Company has discovered that the use as an binder in at least one of the different layers constituting a leather finish of an acrylic copolymer in aqueous dispersion obtained by emulsion copolymerization of different comonomers, one or a part of which has a ureido-type function, made it possible to increase the adhesion of the finish to the leather, without degrading the other application properties. These are in particular hardness, resistance to friction

  and dynamic resistance to water penetration.

  The present invention therefore firstly relates to a binder for a composition intended to be applied as a finishing layer for leather, said finishing layer possibly being a base layer, a flank layer or a fixing layer, characterized by the fact it consists of an acrylic latex obtained by emulsion copolymerization of ethylenically unsaturated comonomers which can be polymerized by the radical route, one of these monomers or part of these monomers comprising a functional group (I): X Il

VS

/ \

- N NH (I)

  I 1 o X represents 0 or S. The functional group (I) above can in particular form part of the group of formula (II): X II

VS

/ \

- N NH (II)

  Il 12 R R in which: - X is as defined above; and - R1 and R2 each represent a hydrogen atom or a C1-C8 alkyl group, in particular C1-C5, or together form a chain - (CH2) n- with n = 2 to 4, which can be substituted up to two times with a C1-C4 alkyl and / or hydroxy and / or C1-C4 alkoxy group or which may be interrupted by a carbonyl; or of the group of formula (III): X Il 3o C

R3 - N NH (III)

\ /

AT

  I in which: - X is as defined above; - R3 represents a hydrogen atom or a C1-C8 alkyl group, in particular C1-C5; and - A is a C2-C4 trivalent hydrocarbon group which can be substituted up to twice by a C1-C4 alkyl group and / or hydroxy and / or C1-C4 alkoxy group or

  which can be interrupted by a carbonyl.

  The comonomer (s) carrying groups of formula (I) can in particular be chosen from the compounds of formula (IV) or (V):

X X

He he

CC

4 3

R4 - N NH (IV) R -N NH (V)

R R2 A

4

  R4 in which: - X, R1, R2 and R3 are as defined above; and - R4 is a residue which contains at least one ethylenically unsaturated bond C = C, polymerizable by the radical route. The rest R4 can in particular be chosen from:

* CH2 = CR5-

* CH2 = CR5-CH2-

2 2

* CH2 = CR5-C-

OH

530C 5 1

CH2 = CR CH2-O-CH2-CH- (CH2) n-

OH

* CH2 = CR5-CH2-O-CH-CH2-O- (CH2) n-

OH

1

  * CH2 = CR5-CH2-O-CH2-C-CHCH2-NH- (CH2) n-

* CH2 = CR5-O- (CH2) n-

* CH2 = CR5-O-CH2-C-O- (CH2) n-

OII O

* CH2 = CR5-C-O- (CH2) n-

He o

* CH2 = CR5-C-NH- (CH2) n-

o [

* CH2 = CR5-NH- (CH2) n-

* CH2 = CR5-C-O-CH 2-C-NH- (CH2) n-

0 0

* CH2 = CR5-O-CH2-C-NH- (CH2) n-

  il * N-di- (3-allyloxy-2-hydroxypropyl) aminoalkyl, with R5 = H, CH3 and n = 1 to 8, this list not being limiting. As examples of the comonomer (s) of formula (III), there may be mentioned: - N-vinyl ethylene urea; N- (2-methacryloxyacetoxyethyl) ethylene urea; - N-di (3-allyloxy-2-hydroxypropyl) aminoethyl ethylene urea; - N- (2acrylamidoethyl) ethylene urea; - N- (2-acryloyloxyethyl) ethylene urea; N-methacrylamidomethyl urea; - allyl alkyl ethylene ureas; - N- (2-methacryloyloxyacetamidoethyl) ethylene urea; - N- (2-acryloyloxyacetamidoethyl) ethylene urea; - N- (2methacryloyloxyethyl) ethylene urea [or 1- (2-methacryloyloxyethyl imidazolin-2-one); - N- (2-acryloyloxyethyl) ethylene urea; - N- (2-methacrylamidoethyl) ethylene urea; - la N (2-acrylamidoethyl) ethylene urea; - N- (3-allyloxy-2hydroxypropyl) aminoethyl ethylene urea; - N (methacrylamidomethyl) ethylene urea; - N- (acrylamidomethyl) ethylene urea; - N-vinyloxyethyl ethylene urea ; - N-methacrylaminoethyl ethylene urea - N-acrylaminoethyl ethylene urea; - Nmethacryloylurea; and

  - N- [3- (1,3-diazacyclohexan-2-one) propyl] -

  methacrylamide. Particularly preferred ureido-functional comonomers are N- (2-methacryloyloxyethyl) -ethylene urea

  [or (1- (2-methacryloyloxyethyl) -imidazolin-2-one] and N-

  (2-methacrylamidoethyl) ethylene urea.

  Preferably, the comonomer (s) with functional group (I) represent from 0.1 to 20% by weight, in particular from 1 to 5% by weight, of the composition of the total comonomers; the dry extract of the acrylic latex according to the invention is generally between 30 and 70% by weight; and the particle size of said latex is

  in particular between 50 and 250 nm.

  The comonomers other than those with functional groups (I) are advantageously chosen so that the copolymer has the appropriate glass transition temperature Tg, by the combination, well known to those skilled in the art, of monomers capable of leading to homopolymers having a High Tg with monomers

  capable of leading to homopolymers having a low Tg.

  The appropriate Tg depends on the finishing layer for which the binder is intended: thus, in general, a copolymer having a low Tg (ie between -50 and C) is used in the case of a binder intended to enter the composition of a base coat; an intermediate Tg (ie between -30 and +30 C) in the case of a binder intended to enter into the composition of a flank layer; and a high Tg (ie between -10 and 50 C) in the case of a binder intended to enter into the composition of a fixing layer,

  these ranges are only given for information.

  Mention may be made, as examples of monomers capable of leading to homopolymers having a low Tg, of ethyl acrylate, butyl acrylate, 2-ethyl hexyl acrylate, nonyl acrylate, vinyl 2-ethyl hexanoate, etc. Mention may be made, as examples of monomers capable of leading to homopolymers having a high Tg, of methyl methacrylate, vinyl acetate, styrene, acrylic acid, methacrylic acid, acrylamide, etc. . The latex according to the invention, leading to homogeneous particles, is prepared by emulsion copolymerization under the conditions well known to those skilled in the art: - The reaction is preferably carried out under

  inert atmosphere in the presence of radical initiators.

  The priming system used can be a Red-

  Ox such as K2S208, (NH4) 2S208 / Na2S205, Na2SO3, a thermal system such as (NH4) 2S208, the quantities used being between 0.2 and 1.0% by weight relative to the total mass of the monomers, preferably between 0.25 and 0.5% by weight; - The emulsion polymerization reaction according to the invention is carried out at a temperature between and 85 C and depends on the nature of the initiation system used: 50-75 C for Red-Ox systems based on peroxodisulfate and metabisulfite, 70-85 C for thermal systems based on peroxodisulfate alone; the preparation of the dispersions according to the invention is

  preferably performed using a semi-type process

  continuous, making it possible to limit the drifts in composition which are a function of the differences in reactivity of the different monomers. The introduction of the monomers in the form of a pre-emulsion with part of the water and of the surfactants is thus generally carried out over a period of time from 3 hours 30 to 5 hours. It is also useful, although not essential, to seed from 1 to% of the monomers. The emulsifying systems used in the emulsion polymerization process according to the invention are chosen from the range of emulsifiers

  having a suitable hydrophilic / lipophilic balance.

  The preferred systems are constituted by the association of an anionic surfactant, such as sodium lauryl sulfate, nonylphenol sulfates ethoxylated in particular with 20 - 25 moles of ethylene oxide, benzene dodecylsulfonate and ethoxylated fatty alcohols sulfates, and a nonionic surfactant, such as ethoxylated nonylphenols in particular with 10 - 40 moles of ethylene oxide and ethoxylated fatty alcohols; the total amount of emulsifier is generally in the range of 1 to 5% by weight and preferably 2 to 4% by weight relative to the

monomers.

  The present invention also relates to a composition intended to be applied as a leather finishing layer, characterized in that it consists of a binder formed by: (a) 2 - 100 parts by weight of at least one latex as defined above; and (b) 0 - 98 parts by weight of at least one other latex chosen from acrylic, polyurethane and polyurethane-acrylic latexes. Furthermore, the composition according to the present invention may also comprise a crosslinker allowing the crosslinking at low temperature of acrylic emulsions, in particular a crosslinker chosen from polycarbodiimides, hydrazides, polyaziridines, dialdehydes and polyepoxides, and / or , in the case where the latex (s) comprise (s) acid functions, a crosslinking agent capable of reacting on said acid functions, and chosen in particular from polycarbodiimides, hydrazides, polyaziridines and polyisocyanates, the amount of crosslinking agent ( s) up to 20% by weight, in particular from 1 to 10% by weight, relative to the latex (s)

  (particle dispersion (s)) (a) and (b) above.

  In the case in particular where said composition is intended to form a base layer or a flank layer, it may also comprise at least one pigment in an amount which can range up to 70 parts by weight per 100 parts by weight of the component ( a) plus, if applicable, component (b). The amount of pigment depends

among others of the pigment type.

  The composition according to the present invention can also comprise at least one additive chosen from: - waxes, such as polyethylene (PE) and polyamide (PA) waxes; - coalescing agents, such as glycol ethers and esters of glycol ethers; - solvents intended to promote spreading or penetration, such as ethanol and isopropanol (IPA); - spreading agents, such as butyldiglycol; - anti-foaming agents, such as fatty acids or

ethoxylated fatty acids.

  Furthermore, the dry extract of the composition

  according to the present invention is generally 10 -

  %, the value of said dry extract having been adjusted by

  addition of water to said composition.

  The present invention also relates to

  leathers treated with a composition as defined above

above.

  The following Examples illustrate the present invention without, however, limiting its scope. In these Examples, the parts and percentages are by weight except

otherwise indicated.

  In Example 1, the amounts of the ingredients of the formulations and of the monomers are expressed in parts

active ingredients.

  In Application Examples 3 and 4, the leather used was a semi-finished full-grain calfskin, spinned at 1.6-1.8 mm, from the company "COSTIL", and the characteristics of the different finishes were determined using the following tests known to man

of career.

  Peel strength The adhesion of the finishes on the leather was evaluated using a peel test at 90. A test piece was glued with cyanoacrylate adhesive, finishing side, on an aluminum support having a surface of x 50 mm2. Using a tensile machine (speed mm / min.), The breaking force was measured out of six

test tubes.

  Water absorption The dynamic resistance to water penetration of finishings was measured using a BALLY penetrometer, in accordance with standard NFG 52015 adapted to determine the kinetics of water absorption as a function of time. . To this end, after a light wiping, the weight gain of four test pieces was measured after 1, 3, 5 and 7 hours of stress on the BALLY penetrometer. According to the practice of a person skilled in the art, the water uptake of a well water-repellent finish must be less than 30% after

3 hours of contact.

  Resistance to friction The resistance to friction in dry conditions or in the presence of solvents: acetone, ethanol and water, was determined in accordance with standard NFG 52301, using a VESLIC friction device (the score varies from 1 to 5 : 5 is considered very

good and 1 is considered very bad).

  Bursting strength Bursting strength was determined on

  ten test pieces in accordance with standard NFG 52007.

  Flexural strength The flexural strength was determined using a BALLY flexometer on six identical test pieces

in accordance with IUP 20 standard.

  Gloss The gloss at 60 was determined using a three-beam gloss meter, in accordance with ISO 2813-73. Given the fact that the roughness of leather can vary greatly from one sample to another, the different fixatives have also been applied to standard contrast cards. The value given for each

  coating was the average of 12 measurements per sample.

  EXAMPLE 1 Synthesis of Latexes A to D General Procedure In a 3 1 reactor, equipped with a circulation of hot water in the double jacket, a central agitation and a condenser, a bottom of the vessel is introduced. formulated as follows: Water ........................

  ...... 75.0 parts * Nonylphenol ethoxylated with 25 moles of ethylene oxide at 35% in water (sold by the company WITCO under the name REWOPAL NOS 25) ....... 0 , 30 part * Sodium metabisulfite ............ 0.30 part Homogenize and bring to 55 C under nitrogen sweep (this is maintained throughout the duration of the synthesis) . When the bottom temperature reaches C, 10% of the preemulsion and the initiator solution are poured in 15 minutes, which are formulated as follows: Preemulsion * Water ....... DTD: .. ......................... 69.00 parts * Nonylphenol ethoxylated with 25 moles of ethylene oxide at 35% in water (REWOPAL OUR 25) ....... DTD: ........ 2.70 parts * Monomers ........................ .... 100.0 parts Initiator solution * Water .................................. 6.00 parts * Ammonium persulfate ................ 0.30 part A temperature plateau is carried out for minutes at 55 ° C., then the remainder of the preemulsion is poured in and of the initiator solution in 2 h 30 min. It is brought to 80 ° C.DTD: and it is left to react for 2 additional hours.

  Cool to room temperature, and

  it is filtered on a 100 micron canvas.

  Preparation of Latexes A to D The latexes A to D were synthesized from the monomers A to D as indicated in Table 1, in which the characteristics of the

latex obtained.

Table 1

  Monomers (per 100 parts) A B C D Ethyl acrylate 57, 1 57.1 57.9 57.1 Methyl methacrylate 36.9 32.9 37.1 37.9

5. Acrylic acid 1 5 5 -

  1- (2-Methacryloyloxyethyl) -imidazolin-2-one in 50% solution in methyl methacrylate, marketed by the company "ELF ATOCHEM" under the name "NORSOCRYL 104" 5 5 - 5 Latex ABCD Dry extract (%) 40.0 40.0 41.0 40.2 pH 1.9 1.8 1.8 1.8 Diameter (nm) 158 159 172 148 Viscosity (mPa.s) 28 30 18 20 Co n, EXAMPLE 2: Evaluation in application on leather with base layers A finishing in one layer has been applied to leather, having the following composition: * Water ........................

  ........ 50 parts * Latex as designated in the first line of Table 2 .......... 30 parts * Black pigment marketed under the name "NOIR LEPTON" by the Company BAYER. ................ 20 parts The dry matter content of the base layer is 15%. This layer is applied using a pneumatic gun in a crossed layer, the quantity deposited being between 120 and 130 g / m2. It is dried at 70 ° C. for 20 minutes, then saturated at 70 ° C.DTD: for 15 seconds under a load of 1 ton / m2.

  The peel strength, the water absorption, the friction resistance, the burst resistance and the shine of the finishes thus obtained on the leather were measured. The results are reported in the

Table 2.

Table 2

  Base layer obtained at BC (compare T1 (a) T2 (b) E (c) from rative latex) Weight (g / m3) 138 + 7 135 + 5 114 + 4 124 + 4 141 + 14 Peel strength (d (dN) 1 + 0.04 0.58 + 0.06 0.71 + 0.18 0.65 + 0.13 0.97 + 0.05 Friction resistance 10 50 100 150 10 50 100 150 10 50 100 150 10 50 100 150 10 50 100 150 (number of cycles) dry 5 5 5 5 5 5 5 5 5 5 5 55 5 5 in the presence of water 5 4/5 4/5 4/5 4 3/4 3 3 2/3 2 4/5 4/5 4/5 in the presence of ethanol 1 1 1 1 1 in the presence of acetone 1 1 1 1 1 Water absorption 1 h 15.6 + 1.4 21, 2 16.4 + 5.2 10.8 + 1.4 10.3 + 0.6 v 3 h 34.7 + 3.9 36.4 19.6 + 6 20 + 2.5 19.5 + 0 , 4 5 h 51.8 + 8.2 58.3 23.7 + 6.5 25.1 + 2.9 24.3 + 0.5 7 h 66.5 + 11.2 67.6 24.8 + 7.5 29 + 3.7 28.7 + 0.6 Burst resistance 8.4 8.6 (mm) Gloss (%) 8.7 8.4 (a) T1 control latex corresponding to a emulsion of copolymers of acrylic esters sold under the name "REPOLEM 3911" by the company ELF ATOCHEM (b) T2 control latex corresponding to a 50/50 mixture of the emulsions of acrylic ester copolymers sold under the names "REPOLEM 3911" and "REPOLEM 3110" respectively by the company ELF ATOCHEM J in (c) Latex E according to the present invention, corresponding to a 50/50 mixture latex B according to the invention and the "REPOLEM 3911" emulsion above (d) averaged over six measurements We therefore observe a significant improvement in the adhesion of the base layer obtained from the latex

  B without degradation of other application properties.

  It is also noted that the base layer obtained by mixing an emulsion of a copolymer comprising ureido groups (latex B) with a standard acrylic emulsion (mixture E) has not only good adhesion to the leather, but also a good dynamic resistance to water penetration, the mixture thus having the best properties of each latex taken separately. In addition, compared with the layer obtained from latex T2, there is an improvement in the resistance to wet friction and in adhesion, the resistance to

  however, water penetration remains equivalent.

  EXAMPLE 3: Evaluation in application on leather of

base layers then fixatives.

  A two-layer finish was applied to leather. The first layer or base layer had the following composition: * Water .......

  .......................... 50 parts * Latex T2 as defined in point (b) of Table 2 ........ ................... 30 parts * Black pigment (NOIR LEPTON from the company BAYER) .................. .... 20 parts This base coat formulation has a dry extract of 15%. It is applied using a pneumatic gun in a crossed layer. The quantity deposited is between 120 and 130 g / m2. The base layer is dried at 70 ° C. for 20 minutes, then satinized for 15 seconds at 70 ° C. under a load of the order of 1 ton / m2. The finishing or fixing layer is applied in the same way. Its composition is as follows: * Water ............................ DTD:. 50 parts * Latex as designated in the first line of Table 3 ..... 30 parts * Black pigment (NOIR LEPTON from the company BAYER) ............ 20 parts As before, the dry matter content of the fixative is 15%. Contrary to the normal mode of use of a fixative which is generally transparent, a pigment was introduced during the tests to allow a better evaluation of the resistance to friction when dry or in the presence of solvents: water, acetone, ethanol, finishing . This last layer is dried at C for 20 minutes, then saturated at 70 C for 15 seconds under a load of 1 ton / m2. The amount of fixative deposited is between 100 and 120 g / m2. The fixatives according to the invention were applied without difficulty to the base layer. The spread of the hairspray was good. The different finishes thus obtained did not have a tacky character, and the hand..DTD: leather was good.

  The results are reported in Table 3 below.

after.

Table 3

  Fixative obtained from latex A BCD - (a) BR (b) DRb) T3 (c) T4 (d) Forcedepelage (dN) 0.9 + 0.11 1.1 +0.2 0.47 + 0.1 1.2 + 0.1 0.6 + 0.04 0.78 + 0.1 0.59 + 0.070.58 + 0.040.90 + 0.13 Water absorption (mg) 1 h ..... .

  ..................... 11 10.1 9 8.3 11 7 11.7 10 10.9 3 h .......... ................... 21 16.3 16 12.6 20 12.6 22.3 15 18.2 h ........... ................... 27 20.4 21.5 14.7 25 15 27.6 20 22.3 7 h .......... ... DTD: ................ 29.5 24.3 26 15.5 29 15.7 32 24.5 27.8 Resistance to dry friction (150 cycles) .... 5 5 5 5 5 5 5 5 5 wet (100 cycles) .... 4 3 - 4 4 3-4 2 3 2-3 1 1 alcohol (10 cycles) ...... 1 1 1 1 1 2 1 1 1 Acetone (10 cycles) .... DTD:. 1 1 1 1 1 1-2 1 1 1 Burst resistance (mm) 10.7 11.8 11.3 8.3 9.9 10.7 11.2 10.6 11..DTD: Resistance to flexion (cycles) 33470 (no> 100,000 33,470 (no 22,300 (no - - - -

  degradation degradation degradation)

"48750" <48750 << 33470

  (degradation) (degradation) (degradation) Gloss (%) "on leather ................

  ...... 5.8 6 7 9.3 5 11 11 3 5.7 overcoat 5.8 6 7 9.3 5 il 11 3 5.7..DTD: on contrast card ..... ..33.8 22 21.2 - - -18.3 -

  (a) No fixative (primer alone) (b) Crosslinked latexes: in the finishing composition, 10% by weight was added relative to the carbodiimide latexes sold under the name "UCARLNK XL 29 SE" by the Company CARBID UNION; The application of the formulation, its drying and its satin finish were carried out under the conditions of Example 3 (c) Control latex T3 corresponding to a polyurethane emulsion marketed under the name BAYDERM 80 UD by the company BAYER 'a 2 5 (d) Control latex T4 corresponding to an acrylic emulsion marketed under the name HYDRHOLAC AQS by the company cn

ROHM & HAAS.

  In the table, "- means that the measurement has not been made All the binders containing 1 (-2- methacryloyloxyethyl) -imidazolin- 2-one have good

  adhesion on leather, which is higher than that of the various witnesses. Compared to reference composition C, the incorporation of 1- (2-methacryloyloxyethyl) -imidazolin-

  2-one (composition B) also leads to an improvement in the flexural strength, without degrading the other application properties. The addition of a crosslinker, although leading to a decrease in adhesion which remains despite everything greater than that of composition C and better than a polyurethane emulsion, induces a decrease in water absorption and an increase from the outfit to

  friction in the presence of solvents (acetone and alcohol).

Claims (10)

  1 - Binder for a composition intended to be applied as a finishing layer for leather, said finishing layer possibly being a base layer, a flank layer or a fixing layer, characterized in that it consists of an acrylic latex obtained by emulsion copolymerization of comonomers with ethylenically unsaturated radical-polymerizable, one of these monomers or a part of these monomers comprising a functional group (I): X II C / \ - N NH (I)   I I o X represents O or S. 2 - Binder according to claim 1, characterized in that the functional group (I) as defined in claim 1 is part of the group of formula (II): X Il VS / \ - N NH (II)   Il 12 R R in which: - X is as defined in claim 1; and R1 and R2 each represent a hydrogen atom or a C1-C8, in particular C1-C5 alkyl group, or together form a chain - (CH2) navec n = 2 to 4, which can be substituted up to twice with a C1-C4 alkyl and / or hydroxy and / or C1-C4 alkoxy group or which may be interrupted by a carbonyl; or of the group of formula (III): X II C / \ R3 - N NH (III)   \ / A I in which: - X is as defined in claim 1; - R3 represents a hydrogen atom or a C1-C8 alkyl group, in particular C1-C5; and - A is a C2-C4 trivalent hydrocarbon group which can be substituted up to twice by a C1-C4 alkyl group and / or hydroxy and / or C1-C4 alkoxy group or   which can be interrupted by a carbonyl.   3 - Binder according to claim 2, characterized in that the comonomer or comonomers carrying groups of formula (I) are chosen from the compounds of formula (IV) or (V): X X He II CC / \ 3 / R4 - N NH (IV) R -N NH (V) R 'R2 A R   in which: - X, R1, R2 and R3 are as defined in claim 2; and - R4 is a residue which contains at least one ethylenically unsaturated bond C = C, polymerizable by the radical route. 4 Binder according to claim 3, characterized in that the remainder R4 is chosen from * CH2 = CR5- * CH2 = CR5-CH2 * CH2 = CR5-C- 52 Il O OH 1- * CH2 = CR5-CH2-O-CH2-CH- (CH2) n- OH * CH2 = CR5-CH2-O-CH-CH2-0- (CH2) n- OH 1 5   * CH2 = CR5-CH2-O-CH2-CH-CH2-NH- (CH2) n- * CH2 = CR -O- (CH2) n- * CH2 = CR5-O-CH2-C-O- (CH2) n- O * CH2 = CR5-C-O- (CH2) n- * CH2 = CR 5-C-NH- (CH2) n- I where * CH2 = CR5-NH- (CH2) n- He he * C2 = CR --- C2CNH- (CH2) n- IlIl O O   * N-di- (3-allyloxy-2-hydroxypropyl) aminoalkyl with R5 = H, CH3 and n = 1 to 8.   - Binder according to one of claims 3 and 4,   characterized in that the comonomer (s) of formula (III) are chosen from: - N-vinyl ethylene urea; - N- (2methacryloxyacetoxyethyl) ethylene urea; - N-di- (3-allyloxy-2hydroxypropyl) aminoethyl ethylene urea; - N- (2acrylamidoethyl) ethylene urea; - N- (2-acryloyloxyethyl) ethylene urea; N-methacrylamidomethyl urea; - allyl alkyl ethylene ureas; - N- (2-methacryloyloxyacetamidoethyl) ethylene urea; - N- (2-acryloyloxyacetamidoethyl) ethylene urea; - N- (2methacryloyloxyethyl) ethylene urea [or 1- (2-methacryloyloxyethyl imidazolin-2-one); - N- (2-acryloyloxyethyl) ethylene urea; - N- (2-methacrylamidoethyl) ethylene urea; - la N (2-acrylamidoethyl) ethylene urea; - N- (3-allyloxy-2hydroxypropyl) aminoethyl ethylene urea; - N (methacrylamidomethyl) ethylene urea; - N- (acrylamidomethyl) ethylene urea; - N-vinyloxyethyl ethylene urea ; - N-methacrylaminoethyl ethylene urea; - N-acrylaminoethyl ethylene urea; - Nmethacryloylurea; and   - N- [3- (1,3-diazacyclohexan-2-one) propyl] - methacrylamide.   6 - Binder according to one of claims 1 to 5,   characterized in that the (co) monomer (s) with functional group (I) represent from 0.1 to 20% by weight, in particular from 1 to 5% by weight, of the composition of total comonomers.   7 - Binder according to one of claims 1 to 6,   characterized by the fact that the dry extract of the latex is between 30 and 70% by weight.   8 - Binder according to one of claims 1 to 7,   characterized by the fact that the particle size of the   latex is between 50 and 250 nm.   9 - Binder according to one of claims 1 to 8,   characterized in that the comonomers other than the comonomers with functional groups (I) are chosen so that the copolymer has the appropriate glass transition temperature Tg, by the combination of monomers capable of leading to homopolymers having a high Tg with monomers capable of leading to homopolymers having a low Tg. - Binder according to claim 9, characterized in that: the monomers capable of leading to homopolymers having a low Tg are chosen from ethyl acrylate, acrylate from butyl, 2-ethyl hexyl acrylate, nonyl acrylate, vinyl 2-ethyl hexanoate; and the monomers capable of leading to homopolymers having a high Tg are chosen from methyl methacrylate, vinyl acetate, styrene, acid   acrylic, methacrylic acid, acrylamide.   11 - Composition intended to be applied as a finishing layer for leather, characterized in that it comprises a binder formed by: (a) 2 - 100 parts by weight of at least one latex such as   defined in one of claims 1 to 10; and   (b) 0 - 98 parts by weight of at least one other latex chosen from acrylic, polyurethane and polyurethane-acrylic latexes. 12 Composition according to Claim 11, characterized in that it also comprises at least one crosslinker chosen in particular from polycarbodiimides, hydrazides, polyaziridines, dialdehydes and polyepoxides, and / or, in the case where the (s ) latex comprises (s) acid functions, a crosslinking agent capable of reacting on said acid functions, and chosen in particular from polycarbodiimides, hydrazides, polyaziridines and polyisocyanates, the amount of crosslinking agent (s) being able to range up to 20% by weight, being in particular from 1 to 10% by weight, relative to the latex (s) as defined in   claim 11 (dispersion (s) of particles).   13 - Composition according to one of claims 11   and 12, intended to form a base layer or a flank layer, characterized in that it further comprises at least one pigment in an amount of up to 70 parts by weight per 100 parts by weight of the component   (a) plus, if applicable, component (b).   14 - Composition according to one of claims 11 to 13, characterized in that it further comprises at least one additive chosen from waxes, coalescing agents, solvents intended to promote spreading or penetration, spreading agents and defoaming agents.   - Composition according to one of claims 11   to 14, characterized in that its dry extract is 10 to 20%, the value of said dry extract having been adjusted by   addition of water to said composition.   16 - Leather treated with a composition such as   defined in one of claims 11 to 15.