CH710888B1 - Substrate comprising a surface covered with an epilam agent and method of epilamating such a substrate. - Google Patents

Abstract

The invention relates to a substrate comprising a surface at least part of which is covered with an epilam agent comprising at least one compound in the form of a random copolymer comprising M units, N units and optionally at least one unit. P, associated by covalent bonds by their main chains and distributed randomly, where or R 1, R 2, R 3, identical or different, are H, a C 1 -C 10 alkyl group, C 1 -C alkenyl 10, Y, X, identical or different, are spacer arms consisting of a heteroatom or of a hydrocarbon chain which may contain at least one heteroatom, comprising at least one carbon atom, A, identical or different, constitutes a group d anchoring to the substrate, and is chosen from thiols, thioethers, thioesters, sulfides, thioamides, silanols, alkoxysilanes, silane halides, hydroxyls, phosphates, protected or unprotected phosphonic acids, phosphonates protected or not, amines, ammoniums, nitrogenous heterocycles, carboxylic acids, anhydrides, catechol, L, identical or different, is a carbon group C 1 –C 20 halogen, R 4, identical or different, is H, CH 3, a hydrocarbon chain which may contain at least one heteroatom, comprising at least 2 carbon atoms. The invention also relates to a method of epilamating such a substrate, as well as a timepiece or jewelry comprising an element comprising such a substrate.

Description

Description

Field of the Invention The present invention relates to the field of mechanics and in particular to the field of watchmaking or jewelry. It relates more particularly to a substrate, in particular a substrate of an element of a timepiece or of jewelry comprising a surface covered at least partially with an epilam agent. It also relates to a method of epilamating such a substrate, as well as a timepiece or jewelry comprising an element comprising such a substrate.

BACKGROUND OF THE INVENTION There are various methods for modifying the surface state of a substrate by treatment with an appropriate agent so as to specifically improve certain surface properties. For example, in the field of mechanics, and in particular in the field of watchmaking, but also in the field of jewelry, epilamage of a surface of a part or of an element is often carried out means of an epilam agent in order to control and reduce the surface energy of said surface during its use. More particularly, the purpose of an epilam agent is to prevent the spreading of oils or lubricants on the elements of a timepiece or of jewelry by forming a hydrophobic and lipophobic surface allowing the lubricant to remain at a predetermined place of the treated surface.

However, the substances currently used for epilamage have various drawbacks. More specifically, the known epilâma agents, such as Fixodrop® FK / BS from Moebius® or the Fluorad ™ range from 3M ™, exhibit poor resistance to horological washing. The patent application US 2012/0 088 099 partially solves this problem by proposing to use an epilam agent carrying a catechol function at the end of the chain, this catechol function being capable of being fixed firmly to the surface of the substrates. However, the resistance to horological washing of these epilamic agents has not been improved on all substrates, in particular on gold and steel which are very common substrates in the field of watchmaking or jewelry. Thus, the use of known epilâma agents is generally limited to certain materials, which obliges the user to have at his disposal different types of epilâma agents depending on the nature of the surfaces to be treated. A solution to solve this problem is described, for example, in application WO 2012/085 130. This solution consists in using as a composition epilame a mixture of compounds of different nature (thiol and biphosphonic) whose synergistic effect promotes the adhesion of the epilame on the substrate. However, the synthesis of each of these compounds requires at least four steps, so that the synthesis process for the entire epilam composition is long and complex.

Claims (14)

SUMMARY OF THE INVENTION The aim of the invention is in particular to overcome the various drawbacks of known epilateral agents. More specifically, an objective of the invention is to provide an epilam agent offering increased resistance to washing compared to known epilame agents. The invention also aims to provide a universal epilam agent which can be used for any type of material. The invention also aims to provide a simple epilame agent to manufacture in a few steps, or even in a single synthesis step. To this end, the present invention relates to a substrate comprising a surface at least part of which is covered with an epilam agent. According to the invention, said epilam agent comprises at least one compound in the form of a statistical copolymer comprising Μ units, N units and optionally at least one P unit, associated by covalent bonds by their main and distributed chains randomly where where R _1f R ₂ , R ₃ , identical or different, are H, a Cì-Cìo alkyl group, Cì-Cìo alkenyl, and preferably H, CH ₃ , Y, X, identical or different, are spacer arms consisting of a heteroatom or a hydrocarbon chain which may contain at least one linear or branched heteroatom, comprising at least one carbon atom, A, identical or different, constitutes an anchoring group to the substrate, and is chosen from the group comprising thiols, thioethers, thioesters, sulfides, thioamides, silanols, alkoxysilanes, silane halides, hydroxyls, phosphates, phosphonic acids, protected or not , protected or unprotected phosphonates, amines, ammoniums, nitrogenous heterocycles, carboxylic acids, anhydrides, catechol, CH 710 888 B1 L, identical or different, is a carbon group in Οί-Ο ₂ ο halogen, preferably fluorinated, R ₄ , identical or different, is H, CH ₃ , a hydrocarbon chain which may contain at least one heteroatom, linear or branched, saturated or unsaturated, comprising at least 2 carbon atoms. Such epilam agent has improved resistance to washing and has a universal character, allowing its use for any type of material. The present invention also relates to a process for epilamating at least part of a surface of a substrate comprising the steps of: a) preparation of an epilam agent comprising at least one random copolymer as defined above, b) optionally, preparation of the substrate surface, c) bringing the substrate surface into contact with the epilam agent, d) drying. The present invention also relates to the use of a statistical copolymer comprising Μ units, N units, and optionally at least one P unit, associated by covalent bonds by their main chains and distributed randomly, where where Rj, R ₂ , R ₃ , identical or different, are H, a Cj-Cjo alkyl group, Cj-Cjo alkenyl, and preferably H, CH ₃ , Y, X, identical or different, are spacer arms consisting of a heteroatom or a hydrocarbon chain which may contain at least one linear or branched heteroatom, comprising at least one carbon atom, A, identical or different, constitutes an anchoring group to the substrate, and is chosen from the group comprising thiols, thioethers, thioesters, sulfides, thioamides, silanols, alkoxysilanes, silane halides, hydroxyls, phosphates, phosphonic acids, protected or not , protected or unprotected phosphonates, amines, ammoniums, nitrogenous heterocycles, carboxylic acids, anhydrides, catechol, L, identical or different, is a carbon group in Οί-Ο ₂₀ halogen, preferably fluorinated, R ₄ , identical or different, is H, CH ₃ , a hydrocarbon chain which may contain at least one heteroatom, linear or branched, saturated or unsaturated, comprising at least 2 carbon atoms, as epilamic agent of at least part of a surface of a substrate, in particular intended for watchmaking or jewelry. The present invention also relates to a timepiece or jewelry comprising an element comprising a substrate as defined above. Detailed description of the invention In accordance with the present invention, a substrate, in particular a substrate of an element of a timepiece or of jewelry, comprises a surface of which at least part is covered with an agent. epilam, said epilam agent comprising at least one compound in the form of a random copolymer comprising Μ units, N units and optionally at least one P unit, associated by covalent bonds by their main chains and randomly distributed, where wherein R _4, R _2, R _3, identical or different, are H, alkyl, C- | -C ₁₀ alkenyl, C- | -C ₁₀ alkyl, and preferably H, CH _3, Y, X, identical or different, are spacer arms consisting of a heteroatom or of a hydrocarbon chain which may contain at least one heteroatom, linear or branched, comprising at least one carbon atom, A, identical or different, constitutes an anchoring group to the substrate, and is chosen from the group comprising thiols, thioethers, thioesters, sulfides, thioamides, silanols, alkoxysilanes, silane halides, hydroxyls, phosphates, CH 710 888 B1 protected or unprotected phosphonic acids, protected or unprotected phosphonates, amines, ammoniums, nitrogen heterocycles, such as imidazole or pyridine, carboxylic acids, anhydrides, catechol, L, which may be identical or different, is a halogenated, preferably fluorinated, carbon-C1-020 group, R _4, identical or different, is H, CH _3, a hydrocarbon chain which may contain at least one heteroatom, linear or branched, saturated or unsaturated, comprising at least 2 carbon atoms. Preferably, the statistical copolymer comprises Μ units, N units and optionally at least one P unit, associated by covalent bonds by their main chains and distributed randomly, where or R _4, R _2, R _3, identical or different, are H, alkyl, C- | -C ₁₀ alkenyl, C- | -C ₁₀ alkyl, and preferably H, CH _3, Y, X, identical or different, are spacer arms consisting of a heteroatom or of a hydrocarbon chain which may contain at least one heteroatom, linear or branched, comprising at least one carbon atom, A, identical or different, constitutes an anchoring group to the substrate, and is chosen from the group comprising thiols, thioethers, thioesters, sulfides, thioamides, silanols, alkoxysilanes, silane halides, hydroxyls, phosphates, phosphonic acids, protected or not , protected or unprotected phosphonates, amines, ammoniums, nitrogenous heterocycles, such as imidazole or pyridine, carboxylic acids, anhydrides, catechol, L, which may be identical or different, is a halogenated, preferably fluorinated, carbon-C1-020 group, R ₄ , identical or different, is H, CH ₃ , a hydrocarbon chain which may contain at least one heteroatom, linear or branched, saturated or unsaturated, comprising at least 2 carbon atoms, with the exception of the copolymer: ch ₂ Ah ₂ N h ₃ c ^x \ h ₃ F ₃ C (F ₂ Preferably, the statistical copolymer only comprises units Μ, N and optionally R [0017] The units Μ, N and P are statistically linked together by their main chain so that the statistical copolymer can be written under the form: Advantageously, the groups Y, X, identical or different, are chosen from the group comprising ester groups Cî-020, preferably C ₂ -C ₁₀ , more preferably C ₂ -C ₆ , and even more preferably in C ₂ -C ₅ , preferably alkyl ester groups, preferably linear, amide groups, and groups derived from styrene. The functional groups of interest A are capable of reacting with the surface of the substrate to be epilated, so as to form groups for anchoring the epilam agent to the surface of the substrate. Advantageously, groups A can also be provided at the end of the copolymer. Advantageously, the copolymer comprises at least two different A groups. The functional groups of interest L are responsible for the epilam effect. They comprise at least one halogen atom, preferably a fluorine atom. In a preferred manner, L is a carbon group C ₂ -C ₂ o, of pre CH 710 888 B1 C ₄ -C ₁₀ ference, and more preferably C ₆ -C _g . L is partially or completely halogen. Advantageously, L is an at least partially fluorinated group, and preferably completely fluorinated. L can also include a hydrogen atom on the terminal group. The functional groups of interest R ₄ of the P units are used to modify the properties of the epilam agent and / or provide other functions. For example, R ₄ may be an alkyl chain used to modify the contact angle obtained or a chain capable of constituting crosslinking points during a complementary crosslinking step (step e). Preferably, the random copolymer comprises between 0.1% and 50%, preferably between 5% and 30%, and more preferably between 5% and 20% of Μ units, between 1% and 99.9%, preferably between 50% and 99.9%, and more preferably between 80% and 95% of N units, and between 0% and 50%, preferably between 0% and 30%, and more preferably between 0% and 10% of P units , the percentages being expressed relative to the total number of units (x + y + z). Advantageously, the statistical copolymer comprises between 10 and 350 units (x + y + z). In a particularly advantageous manner, the units Μ, N, P are chosen to carry several groups A of different nature, several groups L, preferably of the same nature, and possibly one or more groups R ₄ which may be identical or of a different nature, so as to refine and improve the properties of the epilam agent, in order to obtain more specifically a universal epilam agent and having an improved affinity with the substrate. Preferably, the surface of the substrate, at least part of which is covered with the epilam agent, is made of a material chosen from the group comprising metals, metal oxides, doped or not, silicon, silicon oxides , silicon nitrides, silicon carbides, and their alloys, DLC (Diamond Like Carbon), polymers, sapphire, ruby. More precisely, the surface of the substrate can be made of steel, or of noble metals such as gold, rhodium, palladium, platinum, or of metal oxides, doped or not with aluminum, zirconium, titanium, chromium, manganese, magnesium, iron, nickel, copper, zinc, molybdenum, silver, tungsten, as well as their alloys, or in polyoxymethylene or in acrylamide. The present invention also relates to a process for epilamating at least part of a surface of a substrate comprising the steps of: a) preparation of an epilam agent comprising at least one random copolymer as defined above, b) optionally, preparation of the surface of the substrate, in particular by cleaning according to standard watchmaking processes, c) bringing the substrate surface into contact with the epilam agent, d) drying. Preferably, the preparation of the epilam agent is carried out by statistical copolymerization of monomers capable of forming the Μ units with monomers capable of forming the N units and optionally with monomers capable of forming at least one R unit [0030 ] Statistical polymerization techniques are well known to those skilled in the art and do not require a detailed description. A particularly suitable mode of polymerization is free radical copolymerization, in solution or in emulsion. In a first variant, the random copolymer can be obtained in a single step by copolymerization, preferably radical, of monomers carrying the side chains Y-A with monomers carrying the side chains XL and optionally monomers carrying the side chains R ₄ . According to another variant, the random copolymer can be obtained by copolymerization, preferably radical, of monomers carrying the adequate side chains Y with monomers carrying the appropriate side chains X and optionally monomers carrying side chains intended to carry R ₄ , then the side chains are modified, for example by "click chemistry", to introduce into them the functional groups of interest A, L and the groups R ₄ . Preferably, the monomers are chosen from the group comprising the acrylate, methacrylate, acrylamide, methacrylamide, vinyl, diene, styrenic and olefinic monomers. The acrylate, methacrylate, acrylamide, methacrylamide, vinyl and styrenic monomers are particularly preferred. These products are known and for the most part available on the market or accessible in a synthesis step. The particularly preferred monomers are: CH 710 888 B1 R equal or different from R '= H, Alkyl, Si (Me) ₃ Thus, the copolymer used as an epilam agent can be easily obtained in a single step or a limited number of steps from marketed products. One of the copolymers preferably used in the present invention has the following structure (I) CH 710 888 B1 More particularly, a copolymer preferably used in the present invention has the following structure (H): MeO (H) The copolymers used in the invention can be obtained in the form of powder or viscous liquid. They can then be dissolved in a fluorinated solvent, such as perfluorinated or fluorinated hydrocarbons, perfluoropolyethers, hydrofluoroolefins, hydrofluoroethers, at concentrations preferably between 50 mg / L and 250 mg / L, in order to obtain a solution of epilam agent, which will be used for the treatment of the surfaces to be epilamated. According to the variants, the epilamage process according to the invention may further comprise, after step c), a step e) of additional crosslinking, made possible in particular by the presence of the functional groups of appropriate interest provided on the side chains R ₄ of the units R [0041] The substrate according to the invention has a surface covered with an epilam agent which is simple and economical to synthesize, having an affinity with any type of substrate and improved resistance to washing compared to known epilâma agents. An element or a part having a substrate in accordance with the invention can be used in any type of application in the mechanical field, and more particularly in precision mechanics, and in particular watchmaking and jewelry. The following examples illustrate the present invention without, however, limiting its scope. Synthesis of 3-methacryloxopropyl methyl thioether: In a three-necked flask with magnetic stirring placed under nitrogen are added thiomethylpropanol (4.05 mL), dichloromethane (100 mL) and triethylamine (8.2 mL). The solution is cooled in an ice bath and then methacrylate chloride (3.8 mL) is added dropwise over 10 min. The reaction mixture is stirred for 2 h at 0 ° C and then at room temperature overnight. 70 mL of water are added and the reaction mixture is transferred to a separatory funnel. The organic phase and the aqueous phase are separated. The organic phase is washed with an HCl solution (pH = 4) until pH = 7 is reached and then dried over Na ₂ SO ₄ . The solvent is then removed on a rotary evaporator to yield the expected product with a yield of 97%. ¹ H NMR (CDCI ₃ , 500 MHz): chemical shift (ppm): 6.10 (s, 1 H), 5.56 (s, 1 H), 4.24 (t, 2H), 2.58 (t, 2H), 2.11 (s, 3H), 1.99 (m, 2H), 1.94 (s, 3H) Example 1 An epilam agent is synthesized in the form of a random copolymer by free radical polymerization of: CH 710 888 B1 - 3-acryloxopropyl methyldimethoxysilane, - 1H, 1H, 2H, 2H-Perfluorodecylacrylate, - 3-methacryloxopropyl methyl thioether prepared as indicated above, according to the following procedure: in a Schlenk tube containing cyclohexanone (2.5 mL) previously degassed with nitrogen, are added 3-acryloxopropyl methyldimethoxysilane (189 pL) and 3-methacryloxopropyl methyl thioether (159 pL) then 1 H, 1 H, 2H, 2H-Perfluorodecylacrylate (2.3 mL). The reaction medium is bubbled for 5 min with nitrogen and then 0.8 mL of Novec ™ hydrofluoroether HFE-7200 (3M ™) previously bubbled with nitrogen are added. 0.5 mL of 0.228 mol / L azobisisobutyronitrile (AIBN) solution is added. The reaction medium is stirred and heated at 80 ° C for 3 h. The polymer is coagulated in methanol and then rinsed with 3 * 50mL. The polymer is obtained in the form of a white powder (yield = 90%). The following statistical copolymer is obtained: Example 2 An epilam agent is synthesized in the form of a random crosslinked copolymer by free radical polymerization of: - 3-acryloxopropyl methyldimethoxysilane, - 1H, 1H, 2H, 2H-Perfluorodecylacrylate, - 3-methacryloxopropyl methyl thioether, - 1,6-Hexanediol dimethacrylate, according to the following procedure: 3-acryloxopropyl methyldimethoxysilane (189 pL) and 3-methacryloxopropyl methyl thioether (159 pL), 1,6-Hexanediol dimethacrylate (12 pL) are added to a Schlenk tube containing cyclohexanone (2.5 mL) previously degassed with nitrogen. ) then 1 H, 1 H, 2H, 2H-Perfluorodecylacrylate (2.3 mL). The reaction medium is bubbled for 5 min with nitrogen and then 0.8 mL of Novec ™ HFE-7200 previously bubbled with nitrogen is added. 0.5 mL of a 0.228 mol / L AIBN solution is added. The reaction medium is stirred and heated at 80 ° C for 3 h. The polymer is coagulated in methanol and then rinsed with 3 * 50 mL. The polymer is obtained in the form of a white powder (yield = 97%). The following crosslinked statistical copolymer is obtained: CH 710 888 B1 In this copolymer, the side chain R ₄ of the units P is crosslinked with the side chain of another copolymer. Example 3 An epilam agent is synthesized in the form of a random post-crosslinkable copolymer by free radical polymerization of: - 3-acryloxopropyl methyldimethoxysilane, - 1H, 1H, 2H, 2H-Perfluorodecylacrylate, - 3-methacryloxopropyl methyl thioether, - 2-Cinnamoyloxyethyl acrylate (post-crosslinkable monomer), according to the following procedure: in a Schlenk tube containing cyclohexanone (2.5 mL) previously degassed with nitrogen, are added 3-acryloxopropyl methyldimethoxysilane (189 pL) and 3-methacryloxopropyl methyl thioether (159 pL), 2-Cinnamoyloxyethyl acrylate (92 mg) then 1H, 1H, 2H, 2H-Perfluorodecylacrylate (2.2 mL). The reaction medium is bubbled for 5 min with nitrogen and then 0.8 mL of Novec ™ HFE-7200 previously bubbled with nitrogen is added. 0.5 mL of a 0.228 mol / L AIBN solution is added. The reaction medium is stirred and heated at 80 ° C for 3 h. The polymer is coagulated in methanol and then washed with 3 * 50 mL. The polymer is obtained in the form of a white powder (yield = 90%). The following post-crosslinkable statistical copolymer is obtained: CH 710 888 B1 In this copolymer, the side chain R4 can be crosslinked with UV just after synthesis or after deposition on substrate. Example 4 An epilam agent is synthesized in the form of a random copolymer by free radical polymerization of: - 3-acryloxopropyl methyltrimethoxysilane, - 1H, 1H, 2H, 2H-Perfluorodecylacrylate, - (dimethoxyphosphoryl) methyl 2-methylacrylate, - 2-thioethyl methacrylamide (synthesized according to the procedure described in the publication: Synthesis and characterization of a high selective mercury (ll) -printed polymer using novel aminothiol monomer, Taianta, 101,261-266; 2012), according to the following procedure: 3-acryloxopropyl methyltrimethoxysilane (378 pL) and 2-thioethyl methacrylamide (132 pL) and then 1H, 1H, 2H, 2H-Perfluorodecylacrylate are added to a Schlenk tube containing cyclohexanone (2.5 mL) previously degassed with nitrogen. (2.3 mL). The reaction medium is bubbled for 5 min with nitrogen and then 0.8 mL of Novec ™ HFE-7200 previously bubbled with nitrogen is added. 0.5 mL of 0.228 mol / L azobisisobutyronitrile (AIBN) solution is added. The reaction medium is stirred and heated at 80 ° C for 3 h. The polymer is coagulated in methanol and then rinsed with 3 * 50 mL. The polymer is obtained in the form of a white powder (yield = 90%). The following statistical copolymer is obtained: Example 5 An epilam agent is synthesized in the form of a random copolymer by free radical polymerization of: - 3-acryloxopropyl methyldimethoxysilane, - 1H, 1H, 2H, 2H-Perfluorooctylacrylate, - 3-acryloxopropyl methyl thioether (obtained according to the procedure described in the literature: Preparation of biomimetic polymer hydrogel materials for contact lenses Bertozzi, Carolyn et al. US 6 552 103), according to the following procedure: 3-acryloxopropyl methyldimethoxysilane (148 pL) and 3-acryloxopropyl methylthioether (108 pL) are added to a Schlenk tube containing cyclohexanone (2 mL) previously degassed with nitrogen, then 1 H, 1 H, 2H, 2H- Perfluorooctylacrylate (2.1 mL). The reaction medium is bubbled for 5 min with nitrogen and then 0.8 ml of hydrofluoroether (Novec HFE-7200) previously bubbled with nitrogen are added. 0.5 mL of 0.228 mol / L azobisisobutyronitrile (AIBN) solution is added. The reaction medium is stirred and heated at 80 ° C for 3 h. The polymer is coagulated in methanol and then rinsed with 3 * 50 mL. The polymer is obtained in the form of a translucent gel (yield = 90%). The following statistical copolymer is obtained: CH 710 888 B1 Example 6 Resistance to washing Procedures used: Preparation of substrates: Before the epi blade treatment, substrates of different types are cleaned by standard watchmaking processes. More particularly, the parts are cleaned with a solution of Rubisol in the presence of ultrasound, rinsed 3 times with isopropyl alcohol, then dried with hot air. Epilamous treatment of substrates: The substrates are epilamated by immersion (about 5 min) in a solution of the epilam agent (solvent: Vertrel® Suprion ™ from DuPont ™ at 250 mg / L) then drying with hot air. Resistance to washing: The resistance to washing of epilate agents is evaluated after 3 successive washes (standard watch washing with a solution of Rubisol) of the epilamated parts. Contact angles: The effectiveness of the epilam agent is evaluated by depositing drops of 2 lubricants: MOEBIUS Testöl 3 and 9010 oil. For each lubricant and each epilam agent, the contact angles between the substrates and the lubricants were measured on an OCA type Dataphysics device. Results: The different substrates are epilamated with either the epilam agent of example 1, or with the epilam agent of example 4. Then the substrates are washed with 3 watch washings. For comparison, different substrates are epilamated: - either with Moebius® Fixodrop® FK / BS (among the most used epilâmes on the market) - or with the epilam agent M51 below, described in publication WO 2014/009 058 followed by 3 horliger washes. CH 710 888 B1 Polymer M51 The epilame agent M51 is known as one of the epilame agents best resistant to horological washing. Drops of Testöl 3 oil, respectively of 9010 oil, are deposited on each epilam substrate and the contact angles between the substrates and the lubricants are measured. The results are shown in the tables below which report the values of the measured contact angles: Table 1: Contact angles measured with MOEBIUS 9010 oil substratum Epilam agent Sapphire Steel Nickel rhodium Gold Celanese Hostaform® polyoxymethylene Example 1 (inv.) 77 82 67 75 78 62 Example 4 (inv.) 74 75 69 60 72 * Μ 51 (comp.) 75 44 46 41 59 - Fixed rop® (comp.) 45 50 41 36 40 35 Table 2: Contact angles measured with MOEBIUS Testöl 3 oil CH 710 888 B1 substratum Epilam agent Sapphire Steel Nickel rhodium Gold POM Hostaform® Example 1 (Inv.) 62 59 54 53 63 47 Example 4 (Inv.) 56 58 53 45 55 * Μ 51 (comp.) 60 34 37 36 47 * Fixodrop® (Comp.) 34 32 29 24 33 30 Conclusion The above results show that the contact angles obtained after three horological washes with the two oils (Testöl 3 and 9010) are much higher for the epilamous substrates according to the invention compared to the epilamous substrate by an epilame agent. known. The epilame effect after three watch washes is therefore much greater with the epilate substrates according to the present invention. This demonstrates that the epilate substrates according to the invention have better resistance to washing, whatever their nature. claims 1. Substrate comprising a surface at least part of which is covered with an epilam agent, characterized in that said epilam agent comprises at least one compound in the form of a random copolymer comprising Μ units, N units and optionally at minus one P unit, associated by covalent bonds by their main chains and distributed randomly, where where Rj, R ₂ , R ₃ , identical or different, are H, a Cj-Cjo alkyl group, Cj-Cjo alkenyl, and preferably H, CH ₃ , Y, X, identical or different, are spacer arms consisting of a heteroatom or of a hydrocarbon chain which may contain at least one heteroatom, linear or branched, comprising at least one carbon atom, A, identical or different, constitutes an anchoring group to the substrate, and is chosen from thiols, thioethers, thioesters, sulfides, thioamides, silanols, alkoxysilanes, silane halides, hydroxyls, phosphates, protected or unprotected phosphonic acids, protected phosphonates or not, amines, ammoniums, nitrogen heterocycles, carboxylic acids, anhydrides, catechol, L, which may be identical or different, is a halogenated, preferably fluorinated, carbon-C1-020 group, R ₄ , identical or different, is H, CH ₃ , a hydrocarbon chain which may contain at least one heteroatom, linear or branched, saturated or unsaturated, comprising at least 2 carbon atoms. 2. Substrate according to claim 1, characterized in that Y, X, which are identical or different, are chosen from C ₁ O 20, preferably C ₂ -C ₁₀ ester groups, amide groups, and groups derived from styrene . 3. Substrate according to one of the preceding claims, characterized in that the copolymer comprises at least two different groups A. 4. Substrate according to one of the preceding claims, characterized in that L is a carbon group in C ₂ -C ₂ o, preferably in C ₄ -C ₁₀ . CH 710 888 B1 5. Substrate according to one of the preceding claims, characterized in that L is an at least partially fluorinated group, preferably completely fluorinated. 6. Substrate according to one of the preceding claims, characterized in that the random copolymer comprises between O. 1% and 50%, preferably between 5% and 30% of Μ units, between 1% and 99.9%, preferably between 50% and 99.9% of N units, and between 0% and 50%, of preferably between 0% and 30% of P units. 7. Substrate according to one of the preceding claims, characterized in that the random copolymer comprises between 10 and 350 units. 8. Substrate according to one of the preceding claims, characterized in that its surface at least part of which is covered with the epilam agent is produced from a material chosen from metals, metal oxides, silicon, silicon oxides , silicon nitrides, silicon carbides, and their alloys, DLC Diamond Like Carbon, polymers, sapphire, ruby. 9. A method of epilamating at least part of a surface of a substrate comprising the steps of: a) preparation of an epilam agent comprising at least one random copolymer as defined in claims 1 to 7, b) optionally, preparation of the substrate surface, c) bringing the substrate surface into contact with the epilam agent, d) drying. 10. epilamage method according to claim 9, characterized in that the preparation of the epilam agent is carried out by free statistical free radical copolymerization of monomers capable of forming Μ units with monomers capable of forming N units and optionally with monomers capable of forming at least one P unit. 11. depilating method according to one of claims 9 to 10, characterized in that it further comprises, after step c), a step e) of additional crosslinking. 12. depilamation process according to one of claims 9 to 11, characterized in that the monomers are chosen from acrylates, methacrylates, acrylamides, methacry lam ides, vinyl and styrenic monomers. 13. Use of a statistical copolymer comprising Μ units, N units and optionally at least one unit P, associated by covalent bonds by their main chains and distributed randomly, where where R _1f R ₂ , R ₃ , identical or different, are H, a C,-Cì alkyl, Cì-C alk alkenyl, and preferably H, CH ₃ , Y, X, identical or different, are spacer arms consisting of a heteroatom or of a hydrocarbon chain which may contain at least one heteroatom, linear or branched, comprising at least one carbon atom, A, identical or different, constitutes an anchoring group to the substrate, and is chosen from thiols, thioethers, thioesters, sulfides, thioamides, silanols, alkoxysilanes, silane halides, hydroxyls, phosphates, protected or unprotected phosphonic acids, protected phosphonates or not, amines, ammoniums, nitrogen heterocycles, carboxylic acids, anhydrides, catechol, L, identical or different, is a carbon group in Οί-Ο ₂₀ halogen, preferably fluorinated, R ₄ , identical or different, is H, CH ₃ , a hydrocarbon chain which may contain at least one heteroatom, linear or branched, saturated or unsaturated, comprising at least 2 carbon atoms, as epilamic agent of at least part of a surface of a substrate. 14. Timepiece or jewelry comprising an element comprising a substrate according to any one of claims 1 to 8.