EPILAMIZATION METHOD OF AN ELEMENT OF A TIMEPIECE OR PIECE OF JEWELLERY

Abstract

The invention relates to a method for epilamization of at least one portion of a substrate surface comprising the steps of: a) preparing an epilame agent b) optionally, preparing the substrate surface c) placing the substrate and the epilame agent in a chamber at ambient pressure d) introducing CO.sub.2 into the hermetically sealed chamber at a pressure comprised between 25 bar and 74 bar and at a temperature comprised between 10 C. and 80 C. for a duration comprised between 1 minute and 30 minutes, e) reducing the pressure in the chamber, and f) removing the epilamized substrate from the chamber.

Claims

1. A epilamization method of at least one part of a substrate surface comprising the steps of: a) preparing an epilame agent b) optionally, preparing the substrate surface c) placing the substrate and the epilame agent in a chamber at ambient pressure d) introducing CO.sub.2 into the hermetically sealed chamber at a pressure comprised between 25 bar and 74 bar and at a temperature comprised between 10 C. and 80 C. for a duration comprised between 1 minute and 30 minutes. e) reducing the pressure in the chamber, and f) removing the epilamized substrate from the chamber.

2. The epilamization method according to claim 1, wherein the pressure in the hermetically sealed chamber in step d) is comprised between 45 bar and 70 bar.

3. The epilamization method according to claim 2, wherein the pressure in the hermetically sealed chamber in step d) is comprised between 50 bar and 60 bar.

4. The epilamization method according to claim 1, wherein the temperature in the hermetically sealed chamber in step d) is comprised between 25 C. and 60 C.

5. The epilamization method according to claim 4, wherein the temperature in the hermetically sealed chamber in step d) is comprised between 30 C. and 50 C.

6. The epilamization method according to claim 1, wherein the duration of step d) is comprised between 1 minute and 20 minutes.

7. The epilamization method according to claim 6, wherein the duration of step d) is comprised between 3 minutes and 15 minutes.

8. The epilamization method according to claim 1, wherein the method further comprises, between steps e) and f), a step g) of heat treatment of the epilamized substrate.

9. The epilamization method according to claim 1, wherein step b) comprises a CO.sub.2 treatment at a temperature comprised between 10 C. and 80 C. and a pressure comprised between 25 bar and 250 bar.

10. The epilamization method according to claim 1, wherein the epilame agent is in a pure form.

11. The epilamization method according to claim 1, wherein the epilame agent is in the form of a solution in a solvent, the concentration thereof in the solvent/CO.sub.2 mixture being comprised between 10 mg and 5 g per 1000 g of mixture (CO.sub.2+solvent).

12. The epilamization method according to claim 11, wherein the concentration of the epilame agent in the solvent/CO.sub.2 mixture is comprised between 50 mg and 1 g per 1000 g of mixture (CO.sub.2+solvent).

13. The epilamization method according to claim 12, wherein the concentration of the epilame agent in the solvent/CO.sub.2 mixture is comprised between 100 mg and 500 mg per 1000 g of mixture (CO.sub.2+solvent).

14. The epilamization method according to claim 11, wherein the solvent is a fluorinated solvent.

15. The epilamization method according to claim 1, wherein the epilame agent is fluorinated polymer.

16. The epilamization method according to claim 1, wherein the surface of the substrate, at least part of which is coated with the epilame agent, is made of a material chosen from the group consisting of metals, metal oxides, polymers, sapphire, ruby, silicon, silicon oxides, silicon nitrides, silicon carbides, DLC (Diamond like carbon), and alloys thereof.

17. The epilamization method according to claim 1, wherein the substrate belongs to an element of a timepiece or of a piece of jewelry.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0022] The epilamization method concerns the deposition of a layer of an epilame agent on the surface of a substrate generally belonging to an element of a timepiece or of a piece of jewelry intended to be in contact with a lubricating agent. The layer of epilame agent forms an invisible, hydrophobic and oleophobic molecular layer, avoiding the spread of lubricant.

[0023] According to the invention, the method for epilamization of at least one portion of a surface of said substrate comprises the steps of: [0024] a) preparing an epilame agent [0025] b) optionally, preparing the substrate surface [0026] c) placing the substrate and the epilame agent in a chamber at ambient pressure, i.e. a pressure comprised between 0.6 bar and 1.1 bar, and hermetically sealing the chamber [0027] d) introducing CO.sub.2 into the hermetically sealed chamber at a pressure comprised between 25 bar and 74 bar, preferably between 45 bar and 70 bar, and more preferentially between 50 bar and 60 bar, and at a temperature comprised between 10 C. and 80 C., and preferably between 25 C. and 60 C., and more preferentially between 30 C. and 50 C., for a duration comprised between 1 minute and 30 minutes, preferably between 1 minute and 20 minutes, and more preferentially between 3 minutes and 15 minutes. [0028] e) reducing the pressure in the chamber, and [0029] f) removing the epilamized substrate from the chamber.

[0030] In general, according to step b), the substrate surface must be carefully cleaned prior to epilamization so that it is perfectly clean. Any suitable surface preparation treatments known to those skilled in the art may be used. However, advantageously, step b) may comprise a CO.sub.2 surface treatment of the substrate at a temperature comprised between 10 C. and 80 C. and a pressure comprised between 25 bar and 250 bar, for a duration comprised between 1 minute and 60 minutes. Such a treatment makes it possible, in particular, to eliminate dust particles and grease from the surface. Advantageously, the treatment in step b) is performed in the same chamber as that used for step d), which allows the different steps of the invention to be performed one after the other, avoiding any handling of the components. In such case, the chamber in which the substrate was placed is closed for implementation of step b), then opened to place the epilame agent inside in step c), then closed again for implementation of step d).

[0031] In a particularly advantageous manner, any known epilame agent can be used in the method of the invention. Preferably, the epilame agent is a fluorinated polymer, and advantageously, the epilame agent is chosen from the group of epilame agents described in EP Patent Application 3070133 by the same Applicant. This choice advantageously produces an epilame film that is resistant to watchmakers' cleaning.

[0032] In a first embodiment, the epilame agent may be placed in the chamber in a pure form.

[0033] In a second embodiment, the epilame agent may be placed in the chamber in the form of a solution in a solvent. According to the chamber volume and CO.sub.2 pressure, a suitable volume and concentration of the epilame agent solution will be determined to produce a concentration of epilame agent in the solvent/CO.sub.2 mixture comprised between 10 mg and 5 g per 1000 g of mixture (CO.sub.2+solvent), preferably between 50 mg and 1 g per 1000 g of mixture (CO.sub.2+solvent), even more preferentially between 100 mg and 500 mg per 1000 g of mixture (CO.sub.2+solvent).

[0034] Preferably, said solvent is an organic solvent, preferably a fluorinated solvent, and more preferentially a perfluoroolefin.

[0035] Consequently, when the epilame agent is in solution in a fluorinated solvent, the quantity of fluorinated solvent implemented in the method of the invention is very small compared to the quantity used for a conventional epilame bath.

[0036] Preferably, the reduction in pressure in the chamber in step e) occurs slowly, in a duration comprised between a few seconds and several minutes, for example between 5 seconds and 10 minutes. Advantageously, the CO.sub.2 is recovered and recycled. Advantageously, the epilame agent is recovered and reused for epilamization of a subsequent batch.

[0037] Preferably, the epilamization method according to the invention further comprises, between steps e) and f), an additional heat treatment step g) of the epilamized substrate. For example, the epilamized substrate is heated in the chamber to a temperature comprised between 30 C. and 80 C. for a duration comprised between 2 minutes and 30 minutes. Such a heat treatment improves the adhesion of the epilame agent to the surface of the substrate treated.

[0038] Advantageously, the substrate surface, at least part of which is coated with epilame agent, is made of a material chosen from the group comprising metals, metal oxides, polymers, sapphire, ruby, silicon, silicon oxides, silicon nitrides, silicon carbides, DLC (Diamond like carbon), and their alloys.

[0039] More specifically, the substrate surface may be made of steel, of noble metals such as gold, rhodium, palladium, platinum, or doped or undoped metal oxides of aluminium, zirconium, titanium, chromium, manganese, magnesium, iron, nickel, copper, zinc, molybdenum, silver, tungsten and their alloys, or of polyoxymethylene or acrylamide.

[0040] The method according to the invention makes batch treatment of components possible. Further, all the different steps can be performed in the same chamber, which avoids unnecessary handling. The method according to the invention obviates the use of an epilame bath made of expensive and toxic fluorinated solvent, and further obviates monitoring of the epilame bath. It is therefore environmentally friendly, economical and easy to implement. Further, the method according to the invention makes it possible to obtain an epilame quality that is at least identical to that obtained with a conventional dip coating epilamization method. In particular, the substrates treated according to the method of the invention do not have any residual trace of epilame agent, the effectiveness of the epilame agent is similar and the resistance to cleaning of the deposited epilame is at least identical.

[0041] The following examples illustrate the present invention without thereby limiting its scope.

[0042] There is used as epilame agent a compound described in EP Patent 3070133 by the same Applicant.

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Procedures Used:

Preparation of Substrates

[0043] Prior to the epilame treatment, different types of substrates are cleaned using standard watchmakers' methods. More specifically, the parts are cleaned with a Rubisol solution in the presence of ultrasound, rinsed several times with isopropyl alcohol, and then dried in hot air.

Epilame Treatment of Substrates According to the Invention (CO.SUB.2.-Assisted):

[0044] According to the invention, there is introduced into an autoclave (255 ml): [0045] substrates of a different nature to be epilamized [0046] 30 ml of a 1 g/L epilame agent solution in Vertrel Suprion

[0047] The autoclave is closed, then 225 ml of CO.sub.2 at a pressure of 55 bars and at a temperature of 40 C. is introduced into the autoclave. The epilamization time is set at 10 minutes, then the autoclave is slowly depressurized (depressurization time 40 seconds) and heated to 65 C. for 15 minutes. Finally, the epilamized substrates are retrieved and analysed.

Comparative Example Epilamization by Dip Coating

[0048] The substrates are epilamized by immersion (around 5 minutes) in a solution of the epilame agent (structure indicated above) (solvent: 250 mg/L DuPont Vertrel Suprion) and then dried in hot air.

Effectiveness and Property of Epilamization:

[0049] Aesthetic Appearance:

[0050] Substrates epilamized according to the method of the invention (CO.sub.2 assisted) and the comparative method (dip coating) are visually checked. In both cases, the epilame film is invisible.

[0051] Angles of Contact:

[0052] The effectiveness of the epilame agent is evaluated by depositing drops of lubricant: MOEBIUS 9010 oil. The angle of contact between the substrates and the lubricant was measured on a DataPhysics OCA measuring instrument.

[0053] The results were as follows:

TABLE-US-00001 Substrates Methylene Epilamization method Sapphire Steel Gold Ni Rh polyoxide CO.sub.2 assisted (inv.) 85 86 87 84 82 84 Dip coating (comp.) 81 83 85 78 78 87

[0054] Resistance to Cleaning

[0055] The resistance to cleaning of the epilame agents was evaluated after 3 successive cleaning operations (standard watchmakers' cleaning with a Rubisol solution) of the epilamized parts.

[0056] The results are as follows

TABLE-US-00002 Substrates Methylene Epilamization method Sapphire Steel Gold Ni Rh polyoxide CO.sub.2 assisted (inv.) 78 83 83 70 65 85 Dip coating (comp.) 77 82 78 48 71 73

CONCLUSION

[0057] The above results show that the angles of contact obtained just after epilamization and after three watchmaker's cleaning operations with 9010 oil are comparable in the method of the invention (CO.sub.2 assisted) and the comparative method (dip coating). In some cases (Ni or POM substrates), the resistance to cleaning of the epilame agent is even slightly superior when the latter is deposited by the method of the invention. This shows that the dip coating method, which uses a large quantity of solvent, can advantageously be replaced by a CO.sub.2 assisted epilamization method according to the invention, which is environmentally friendly and economical, without performance degradation (epilamization and resistance of epilamization).