CH713072B1 - Process for epilaming an element of a timepiece or piece of jewelry. - Google Patents

Abstract

The invention relates to a process for epilaming at least part of a surface of a substrate comprising the steps of: a) preparing an epilame agent b) optionally, preparing the surface of the substrate c) placement of the substrate and the epilame agent in an enclosure at ambient pressure d) introduction into the hermetically sealed enclosure of CO 2 at a pressure of between 25 bar and 74 bar and at a temperature of between 10°C and 80°C , for a period of between 1 min and 30 min, e) reduction of the pressure in the enclosure, and f) removal of the epilamé substrate from the enclosure.

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 process for epilaming at least part of a surface of a substrate present in a timepiece or piece of jewelry.

Background of the invention

[0002] There are various methods for modifying the surface condition 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 jewellery, the epilaming of a surface of a part or of an element is often carried out means of an epilame agent in order to control and reduce the surface energy of said surface during its use. More particularly, an epilame agent is intended to prevent the spreading of oils or lubricants on the elements of a timepiece or piece of jewelery by forming an invisible hydrophobic and lipophobic molecular layer on the surface of the element allowing the lubricant to remain at a predetermined location on the treated surface and thus prevent it from spreading. Maintaining the lubricant in its operating zone increases its durability.

[0003] At present, the vast majority of epilame agents available on the market, such as Fixodrop® FK/BS from Moebius® or the Fluorad™ range from 3M™ (FC-722 and others), consist of a fluorinated polymer dissolved in a perfluorinated or fluorinated solvent. The epilaming process is traditionally carried out by dipping (dip coating) the parts to be epilamed in an epilaming bath consisting of a perfluorinated or fluorinated solvent solution loaded with epilame agent.

[0004] The most widely used fluorinated solvents until recently were tetradecafluorohexane and HFE-7100 from 3M™. However, tetradecafluorohexane in particular has the disadvantage of constituting, once volatilized, a greenhouse gas, since it remains stable for 3200 years in the air and has a greenhouse potential of 7400 CO2 equivalent.

[0005] Since the use of such solvents has been prohibited by new environmental regulations, new fluorinated solvents have been developed. However, even though these next generation fluorinated solvents (such as 3M™ HFE-7200) are less stable in air, they still have an impact on the environment. They therefore require the use of closed machines or other equipment and risk being impacted by future even more stringent regulations. In addition, these new generation fluorinated solvents are relatively expensive.

[0006] To replace the traditional epilaming process using polluting and expensive fluorinated solvents, application EP 1 927 648 proposes an epilaming process with a solution of epilame molecule in a water/propanol mixture. This epilaming process has the drawback of only being able to be used with a very limited number of epilame agents since the epilame molecules must be soluble in the water/propanol mixture. However, it is well known to those skilled in the art that the best epilame properties are obtained with fluorinated molecules which therefore have a very low solubility in a water/propanol mixture.

[0007] Finally, the concentrations of epilame agent used in the traditional epilaming process by dipping are very low (typically between 20 mg/L and 250 mg/L) and the fluorinated solvents used are volatile (lower boiling temperature at 100°C). As a result, the industrial management of epilame baths is complex on a daily basis because it is necessary to regularly control the concentration of epilame agent in the epilame bath by dosing and to add a concentrated solution of epilame agent or solvent in depending on the evolution of the composition of the epilaming bath.

Summary of the invention

[0008] The object of the invention is in particular to overcome the various drawbacks of known epilaming methods.

[0009] More specifically, an object of the invention is to provide a new epilaming method making it possible to obtain epilaming of the same or higher quality than that obtained with a traditional epilaming method by dipping.

[0010] Another object of the invention is to provide a new ecological epilaming process making it possible to eliminate the use of a large quantity of polluting fluorinated solvents.

[0011] Another object of the invention is to provide a new economical epilaming process making it possible to eliminate the use of a large quantity of expensive fluorinated solvents.

[0012] Another object of the invention is to provide a new epilaming process making it possible to simplify the daily management of epilaming baths.

To this end, the present invention relates to a process for epilaming at least part of a surface of a substrate comprising the steps of: a) preparing an epilame agent b) optionally, preparing the surface of the substrate c) placement of the substrate and the epilame agent in an enclosure at ambient pressure d) introduction into the hermetically closed enclosure of CO2 at a pressure of between 25 bar and 74 bar and at a temperature of between 10°C and 80° C. for a period of between 1 min and 30 min, e) reduction of the pressure in the enclosure, and f) removal of the epilamé substrate from the enclosure.

According to the invention, the CO2 is used in a form close to supercritical conditions to convey the epilame agent and carry out the deposition of an invisible hydrophobic and oleophobic molecular layer of said epilame agent. Thus, the method according to the invention drastically reduces or even no longer requires the use of fluorinated solvent, so that the method of the invention is ecological and economical, while preserving the quality of the epilamage.

Detailed description of the invention

[0015] The epilaming process relates to the deposition of a layer of an epilame agent on the surface of a substrate generally belonging to an element of a timepiece or piece of jewelery intended to be in contact with an agent. lubricant. The epilame agent layer forms an invisible hydrophobic and oleophobic molecular layer, preventing the lubricant from spreading.

According to the invention, the process for epilaming at least part of a surface of said substrate comprises the steps of: a) preparing an epilame agent b) optionally, preparing the surface of the substrate c ) placement of the substrate and the epilame agent in an enclosure at ambient pressure, i.e. a pressure of between 0.6 bar and 1.1 bar, and hermetic closure of the enclosure d) introduction into the hermetically sealed enclosure of CO2 at a pressure of between 25 bar and 74 bar, preferably between 45 bar and 70 bar, and more preferably between 50 bar and 60 bar, and at a temperature between 10°C and 80°C, and preferably between 25°C and 60°C , and more preferably between 30° C. and 50° C., for a period of between 1 min and 30 min, preferably between 1 min and 20 min, and more preferably between 3 min and 15 min, e) reduction of the pressure in the enclosure, and f) removing the epilamé substrate from the enclosure.

[0017] In general, in accordance with step b), the surface of the substrate must be carefully cleaned before epilaming to be perfectly clean. All suitable surface preparation treatments known to those skilled in the art can be used. However, in an advantageous manner, step b) may comprise a treatment of the surface of the substrate with CO2 at a temperature between 10° C. and 80° C. and a pressure between 25 bar and 250 bar, for a period of time between between 1 min and 60 min. Such a treatment allows in particular the elimination of dust particles and the degreasing of the surface. Advantageously, the treatment according to step b) is carried out in the same enclosure as that provided for step d), which makes it possible to be able to chain the different steps of the method of the invention while avoiding any manipulation of the rooms. In this case, the enclosure in which the substrate has been placed is closed for the implementation of step b), then opened to place the epilame agent therein according to step c) then closed for the implementation of step d).

[0018] 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 patent application EP 3,070,133 by the same applicant. By this choice, an epilame film is advantageously obtained which is resistant to watchmaking washes.

According to a first implementation variant, the epilame agent can be placed in the enclosure in a pure form.

According to a second implementation variant, the epilame agent can be placed in the enclosure in the form of a solution in a solvent. Depending on the volume of the enclosure and the CO2 pressure, an adequate volume and concentration of the epilame agent solution will be determined so as to have a concentration of the epilame agent in the solvent/CO2 mixture between 10 mg and 5 g per 1000 g of mixture (CO2+solvent), preferably between 50 mg and 1 g per 1000 g of mixture (CO2+solvent), even more preferably between 100 mg and 500 mg per 1000 g of mixture (CO2+solvent ).

Preferably, said solvent is an organic solvent, preferably a fluorinated solvent, and more preferably a perfluoroolefin.

[0022] Therefore, when the epilame agent is in solution in a fluorinated solvent, the amount of fluorinated solvent used in the process of the invention is very low compared to the amount used for an epilaming bath. traditional.

[0023] Preferably, the reduction in pressure in the enclosure during step e) takes place slowly, for a period of between a few seconds and a few minutes, for example between 5 s and 10 min. Advantageously, the CO2 is recovered and recycled. Advantageously, the epilame agent is recovered and reused for epilaming a subsequent batch.

Preferably, the epilaming method according to the invention further comprises, between steps e) and f), an additional step g) of heat treatment of the epilamed substrate. For example, the epilamé substrate is heated in the enclosure to a temperature of between 30° C. and 80° C. for a period of between 2 min and 30 min. Such a heat treatment makes it possible to improve the anchoring of the epilame agent to the surface of the treated substrate.

Advantageously, the surface of the substrate, at least part of which is covered 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 their alloys.

More specifically, 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 polyoxymethylene or acrylamide.

The method according to the invention allows batch processing of the parts. In addition, all of the different steps can be carried out in a single and same enclosure, which avoids any unnecessary handling. The method according to the invention makes it possible to eliminate the use of an epilaming bath based on a polluting and expensive fluorinated solvent, and moreover to eliminate any control of the epilaming bath. It is therefore ecological, economical, and easy to implement. In addition, the method according to the invention makes it possible to obtain a quality of epilaming at least identical to the quality obtained with a traditional method of epilaming by dipping. In particular, the substrates treated according to the process of the invention do not show any residual trace of epilame agent, the effectiveness of the epilame agent is similar and the resistance to washing of the epilame agent deposited is at least identical.

The following examples illustrate the present invention without however limiting its scope.

The epilame agent used is a compound described in publication EP 3 070 133 by the same applicant, of the formula shown below:

Procedures used:

Preparation of substrates:

[0030] Before the epilame treatment, substrates of different kinds are cleaned by standard watchmaking processes. More specifically, the parts are cleaned with a Rubisol solution in the presence of ultrasound, rinsed several times with isopropyl alcohol, then dried with hot air.

Epilame treatment of the substrates according to the invention (CO2 assisted):

In accordance with the invention are introduced into an autoclave (255 mL): substrates of different nature to be epilamed 30 mL of a 1g/L solution of epilame agent in Vertrel Suprion

The autoclave is closed and then 225 mL of CO2 at a pressure of 55 bars and at a temperature of 40° C. are introduced into the autoclave. The epilaming time is fixed at 10 min then the autoclave is depressurized slowly (depressurization time 40 s) and heated at 65° C. for 15 min. Finally, the waxed substrates are recovered and analyzed.

Comparative example: Epilamage by the soaking process (Dip Coating)

The substrates are epilamed by immersion (approximately 5 min) in a solution of the epilame agent (structure indicated above) (solvent: Vertrel® Suprion™ from DuPont™ at 250mg/L) then air-drying hot.

[0034] Efficiency and property of the epilamage: - Aesthetic aspect: The epilamé substrates according to the process of the invention (CO2 assisted) and the comparative process (dip coating) are checked by eye. In both cases, the epilame film is invisible. – Contact angles: The effectiveness of the epilame agent is evaluated by depositing drops of lubricants: MOEBIUS 9010 oil. The contact angle between the substrates and the lubricant was measured on an OCA-type Dataphysics device.

[0035] The results are as follows: Epilaming process Sapphire Steel Gold Ni Rh Methylene polyoxide CO2 assisted (inv.) 85 86 87 84 82 84 Dip coating (comp.) 81 83 85 78 78 87 – Resistance to washing La Resistance to washing by epilame agents is evaluated after 3 successive washes (standard watchmaker wash with a Rubisol solution) of the epilame parts.

The results are as follows: Epilaming process Sapphire Steel Gold Ni Rh Methylene polyoxide CO2 assisted (inv.) 78 83 83 70 65 85 Dip coating (comp.) 77 82 78 48 71 73

Conclusion :

The above results show that the contact angles obtained just after epilaming and after three watchmaker washes with 9010 oil are comparable between the process of the invention (CO2 assisted) and the comparative process (dip coating). In some cases (Ni or POM substrates), the washing resistance of the epilame agent is even slightly higher when the latter is deposited by the process of the invention. This shows that the dipping process (dip coating), which consumes a lot of solvent, can be advantageously replaced by a CO2-assisted depilation process according to the invention, which is ecological and economical, without degradation of performance (depilation and resistance of epilaming).

Claims (9)

1. Method for epilaming at least part of a surface of a substrate comprising the steps of: a) preparation of an epilame agent, b) optionally, preparation of the surface of the substrate, c) placing the substrate and the epilame agent in an enclosure at ambient pressure, i.e. a pressure of between 0.6 bar and 1.1 bar, d) introduction into the hermetically sealed enclosure of CO2 at a pressure of between 25 bar and 74 bar, preferably between 45 and 70 bar, and more preferably between 50 bar and 60 bar, and at a temperature of between 10°C and 80 °C, and preferably between 25°C and 60°C, and more preferably between 30°C and 50°C, for a period of between 1 min and 30 min, preferably between 1 min and 20 min, and more preferably between 3 mins and 15 mins, e) decrease in pressure in the enclosure, and f) exit of the epilamé substrate from the enclosure. 2. Epilaming method according to claim 1, characterized in that the method further comprises, between steps e) and f), a step g) of heat treatment of the epilamed substrate. 3. Epilaming process according to one of the preceding claims, characterized in that step b) comprises a treatment with CO2 at a temperature between 10°C and 80°C and a pressure between 25 bar and 250 bar. 4. Epilaming process according to one of the preceding claims, characterized in that the epilame agent is in a pure form not mixed in a solvent. 5. Epilaming process according to one of claims 1 to 3, characterized in that the epilame agent is in the form of a solution in a solvent, its concentration in the solvent/CO2 mixture being between 10 mg and 5 g per 1000 g of CO2+solvent mixture, preferably between 50 mg and 1 g per 1000 g of CO2+solvent mixture, even more preferably between 100 mg and 500 mg per 1000 g of CO2+solvent mixture. 6. Epilaming process according to claim 5, characterized in that the solvent is a fluorinated solvent. 7. Epilaming process according to one of the preceding claims, characterized in that the epilame agent is a fluorinated polymer. 8. Epilaming process according to one of the preceding claims, characterized in that the surface of the substrate, of which at least a part is covered 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 their alloys. 9. Epilaming process according to one of the preceding claims, characterized in that the substrate belongs to an element of a timepiece or piece of jewelry.