Clock component made of colored forged carbon and method for manufacturing such a clock component

Description

technical field

[0001] The present invention relates to a watch component comprising at least one portion made of colored forged carbon comprising cut carbon fibers, held together by a matrix comprising at least one resin as a constituent, and at least one pigment.

[0002] The present invention also relates to a method for manufacturing a colored forged carbon block for the production of a watch component.

[0003] In the remainder of this text, the expression "carbon fiber" will be used to refer to a strand comprising a plurality of individual carbon filaments arranged against each other substantially in the same direction. State of the art

[0004] Colored composite materials based on fiber-reinforced resin are already known, particularly in the field of watchmaking, as in document EP3795341A1 for example.

[0005] Two general approaches are typically implemented to produce such products.

[0006] In one approach, colored glass fibers are used to reinforce a resin, possibly in combination with conventional black carbon fibers. An example of a watch case made using this approach is shown here: https: / / www.lepoint.fr / montres / sihh-2019-girard-perregaux-presente-le-carbon-glass-14-01-2019-2285643_2648.php.

[0007] According to a second approach, a pigment is dissolved in the resin used to create the matrix of the composite compound. In this case, the manufacturer cannot control which areas of the final product will actually be colored due to the potential migration of resin portions containing the pigment. Furthermore, it is also impossible to produce, in a controlled manner, a composite block exhibiting at least two different colors due to the movement of the resin constituting the matrix, particularly during the heating process under pressure. Indeed, different colored portions of the resin mix with each other during this process, resulting in at least one combined color. Thus, the combined use of yellow and blue pigments would lead to green areas in the final product.

[0008] As an example, patent application WO 2021 / 099433 A1 discloses a method for manufacturing composite materials of the type just described. This patent application provides two embodiments of the manufacturing process. In one case, carbon or aramid fibers are pre-impregnated with a colored resin before being mixed with a matrix. In the other case, the matrix is ​​colored, while the carbon or aramid fibers are not necessarily colored. In both cases, the pigment used is dissolved in a resin and can therefore migrate, as explained above.

[0009] Therefore, there is still a need to be able to produce a good quality coloured forged carbon composite product in which the coloured areas are controlled by the manufacturer, both in terms of their location and their colour.

[0010] Furthermore, it should also be noted that currently known forged carbon compounds generally exhibit high porosity leading to fragility, making them unsuitable for the production of certain watch components, particularly watch components that could be subject to shocks and / or small watch components such as control pushers, for example. Disclosure of the invention

[0011] One aim of the present invention is to offer an alternative to known composite products of the prior art by offering a watch component exhibiting the mechanical qualities of forged carbon and an original colouring whose parameters are predefined, therefore controlled, by the manufacturer, both to allow the latter to obtain the desired appearance and a certain level of reproducibility if necessary.

[0012] To this end, the present invention relates to a watch component of the type mentioned above, characterized by the fact that the pigment(s) are in the form of solid particles that are not miscible with, or not soluble in, the resin(s) composing the matrix, and by the fact that the particles of the pigment(s) are located on the surface of at least some carbon fibers and located in one or more predefined regions of the portion of the watch component.

[0013] Thanks to these characteristics, it is possible to create a watch component with a predefined appearance, featuring pre-defined colored regions, unlike conventional products whose composition inevitably leads to a random final appearance. Furthermore, this composition also allows for the creation of a product with a predetermined number of colors, since the different pigment particles are neither miscible with nor soluble in the matrix. This prevents any mixing of colors, unlike in conventional products.

[0014] According to a preferred embodiment, it may be provided that the resin or at least one of the matrix resins is of the epoxy type.

[0015] Furthermore, it can be predicted that the matrix will have a cross-linked structure involving groups chosen from the group including isocyanates, blocked isocyanates, anhydrides, thiols, phenols, amines, and amides.

[0016] Preferably, carbon fibers can be expected to have a dry weight between 50 and 900g.m-2, more preferably between 150 and 600g.m-2.

[0017] It is also advantageous to provide that the carbon fibers have a width of between 1 and 15mm, preferably between 1 and 5mm and, possibly, that they have a Young's modulus greater than 45GPa (according to the ASTM D3039 standard), preferably greater than 50GPa.

[0018] It is also possible to predict that the carbon fibers will be grouped in the form of strands comprising between 1,500 and 50,000 filaments.

[0019] Furthermore, it can be predicted that the pigment particles will have dimensions between 20 and 100µm, preferably between 20 and 80µm.

[0020] In general, pigments can preferably be chosen from the group including aluminum oxides, silicon dioxides, micas or mixtures thereof.

[0021] Generally, it is advantageous to stipulate that the watch component be a finishing element for a timepiece, preferably a case, a bezel, a case back, an external control element, in particular a crown or a pusher, or a bracelet component. Of course, the watch component may also be a watch movement component without departing from the scope of the invention as defined by the attached claims.

[0022] The present invention also relates to a method for manufacturing a colored forged carbon block for the production of a watch component, comprising the steps of: a) to obtain cut carbon fibers, impregnated with a first resin, on the surface of which are arranged solid particles of at least one pigment not miscible with, or not soluble in, the first resin, b) to place the cut carbon fibers in a mold, preferably with a matrix comprising the first resin and / or a second resin, of the same chemical nature as the first resin, as well as a crosslinking agent, c) to close the mold and apply a negative pressure, and d) to apply a suitable pressure and temperature increase cycle to achieve densification and crosslinking of the mixture formed in step b).

[0023] Advantageously, it can be predicted that the first resin or the first and second resins will have a viscosity greater than 3000mPa.s.

[0024] In addition, it can also be predicted that the mixture comprising the first resin or the first and second resins and the crosslinking agent will have a viscosity greater than 350mPa.s.

[0025] Preferably, the matrix can be expected to have a glass temperature (Tg) between 150 and 220°C.

[0026] Furthermore, it is advantageous to provide that the matrix has a resin content of between 70 and 90% by mass, preferably between 75 and 85%.

[0027] It can also be expected that the mixture formed in step b) will have a proportion of carbon fibers between 50 and 80% by mass, preferably between 60 and 75%.

[0028] As an alternative or in addition, it can be provided that the mixture formed in step b) has a proportion of pigment(s) between 0.5 and 10% by mass, preferably between 1 and 5%.

[0029] Furthermore, it can advantageously be foreseen that step d) includes the application of at least three different temperature steps, preferably at least four, more preferably at least five.

[0030] In general, it can be foreseen that the process according to the invention includes at least one additional machining step of the block obtained after the implementation of steps a) to d). Brief description of the drawings

[0031] Other features and advantages of the present invention will become more apparent upon reading the detailed description of a preferred embodiment that follows, made with reference to the accompanying drawings given by way of non-limiting examples and in which: THE Figures 1a and 1brepresent simplified diagrams illustrating a step in the implementation of a preferred embodiment of the process according to the invention, according to two different embodiment variants. figure 2 represents a photo of a block obtained according to the invention and exhibiting several distinct colors. Method(s) of embodiment of the invention

[0032] The present invention relates to a watch component comprising at least one portion made of colored forged carbon fibers held together by a matrix comprising at least one resin and at least one pigment. More specifically, the watch component according to the invention has a structure such that the pigment is in the form of solid particles immiscible with, or insoluble in, the resin(s) composing the matrix, and that the pigment particles are located on the surface of at least some of the carbon fibers and localized in one or more predefined regions of the relevant portion of the watch component.

[0033] Preferred characteristics of the watch component according to the present invention, as well as a preferred method of manufacture by molding a block of forged carbon, preferably of relatively low porosity to allow the production of such a high-quality watch component, will be described below.

[0034] Generally, several approaches are possible within the scope of the present invention with regard to the molding method. The mold used can have any shape that allows for the creation of a block which will then be machined to finalize a predefined portion of a watch component or a complete predefined watch component. Alternatively, it is possible to use a mold corresponding to the general shape of the portion of the watch component or the watch component but in larger dimensions ("near shape"), the molded product then typically being called a "rough casting" in the watchmaking industry.

[0035] While the use of a mold directly presenting the exact dimensions of the part to be obtained is not totally excluded within the framework of the present invention, it is not preferred for the following reasons: on the one hand, it may be difficult to obtain a good distribution between the carbon fibers and the matrix in sharp and / or re-entrant angles of the mold, if necessary, and, on the other hand, the part obtained after the molding step generally has a larger proportion of matrix on the surface, due to the fact that it undergoes a creep phenomenon during baking.In the latter case, the part obtained by molding may have a glossy plastic material appearance which not only is not necessarily suitable for the production of high-end watch components, but also implies a lower resistance to shocks and scratches than a portion of material in which the proportion between the matrix and the carbon fibers would be more balanced.

[0036] As will be understood from the above, the manufacture of a watch component according to the invention involves the use of chopped carbon fibers, that is to say carbon filaments grouped in the form of strands of chopped filaments, these strands being called here carbon fibers, at least one resin, in particular to define a matrix, and solid particles of at least one pigment not miscible with, or not soluble in, the matrix.

[0037] In general, the manufacturing process for a colored forged carbon block, for the production of a watch component according to the present invention, advantageously comprises the steps of: a) to obtain cut carbon fibers, impregnated with a first resin, on the surface of which are arranged solid particles of at least one pigment not miscible with, or not soluble in, the first resin, b) to place the cut carbon fibers in a mold, preferably with a matrix comprising the first resin and / or a second resin, of the same chemical nature as the first resin, as well as a crosslinking agent, c) to close the mold and apply a negative pressure, and d) to apply a suitable pressure and temperature increase cycle to achieve densification and crosslinking of the mixture formed in step b).

[0038] The carbon fibers used in the implementation of the present invention are preferably unidirectional carbon fibers pre-impregnated with the first resin; that is, a certain quantity of the first resin is applied to the carbon fibers so that they exhibit non-zero adhesion at room temperature. Solid particles of one or more pigments can then be mixed with the pre-impregnated carbon fibers and adhere to their surface.

[0039] Such a pigmentation step of pre-impregnated carbon fibers can be implemented either before or after the carbon fibers are cut.

[0040] Pigment particles can be mixed with pre-impregnated carbon fibers randomly or in a predefined controlled manner.

[0041] Preferably, the carbon fibers may have a dry basis weight (without impregnation) of the order of 50 to 900 g / m², more preferably between 150 and 600 g / m², and each of them may comprise a number of filaments of the order of 1,500 to 50,000. Furthermore, the carbon fibers may advantageously have a width of between 1 and 15 mm, more preferably between 1 and 5 mm, and have a Young's modulus greater than 45 GPa, more preferably greater than 50 GPa (measured according to ASTM D3039).

[0042] As mentioned above, a single resin can be used both to pre-impregnate the carbon fibers and to form the matrix. Alternatively, the second resin used to form the matrix can be different from the first resin used to pre-impregnate the carbon fibers. In this case, both resins should have the same chemical composition.

[0043] Hereafter, we will speak of the resin or a resin in general, it being understood that the preferred characteristics which will be stated will apply to both resins, if applicable.

[0044] Preferably, the resin used in the implementation of the present invention is of the epoxy type and may advantageously be colorless so as not to affect the final coloring of the resulting block. The resin advantageously exhibits relatively low viscosity and good wettability to allow for homogeneous dispersion and the elimination of any air pockets that could lead to excessive porosity in the final block. Therefore, the viscosity of the resin will preferably be greater than 3000 mPa·s.

[0045] Conventionally, the matrix also includes a crosslinker or hardening agent, which may preferably be chosen from the group including isocyanates, blocked isocyanates, anhydrides, thiols, phenols, amines, and amides.

[0046] Preferably, the matrix contains between 70 and 90%, more preferably between 75 and 85%, by mass of resin.

[0047] The mixture comprising the resin and the crosslinking agent may preferably be made in such a way that its viscosity is greater than 350mPa.s, and in such a way that the glass temperature Tg of the matrix is ​​between 150 and 220°C.

[0048] Regarding the pigment(s) used, they should preferably be immiscible with, or insoluble in, the matrix to prevent migration during the firing process and remain on the surface of the carbon fibers onto which they have been deposited. When several different pigments are used simultaneously, this helps prevent them from mixing with each other.

[0049] The pigment(s) may preferably be chosen from the group comprising aluminum oxides, silicon dioxides, micas, and mixtures thereof. The pigment size, D-50, is preferably between 20 and 100 µm, and more preferably less than 80 µm.

[0050] The mixture formed in step b) above preferably has a proportion of carbon fibers between 50 and 80% by mass, preferably between 60 and 75%.

[0051] Moreover, this mixture preferably has a proportion of pigment(s) between 0.5 and 10% by mass, preferably between 1 and 5%.

[0052] Once the pre-impregnated and colored cut carbon fibers are arranged in a suitable mold, with additional resin possibly to finalize the matrix, a vacuum is applied, for example by applying a pressure less than atmospheric pressure by at least 30 mbar, for example 900 mbar, followed by a cycle of increasing pressure - for example 4 bar then 10 bar - and temperature suitable to achieve densification and crosslinking of the mixture, as mentioned in step d) above.

[0053] THE Figures 1a and 1b schematically illustrate two different general approaches for the placement of carbon fibers in a mold, leading to two different results for the block 1 finally obtained.

[0054] There figure 1aThe diagram schematically illustrates, on the left, a random arrangement of carbon fibers in a mold (not shown), using four groups of carbon fibers: uncolored A fibers, B fibers colored with a first pigment, C fibers colored with a second pigment different from the first, and D fibers colored with a third pigment different from the first two. Block 1, obtained after firing, is schematically illustrated on the right. figure 1aBlock 1 ultimately exhibits a random distribution of the different carbon fibers, corresponding to their distribution in the mold before the firing cycle. The pigment particles remained on the surface of the carbon fibers they coated before the firing cycle, and no mixing of the corresponding colors is observed. Thus, for example, when yellow, red, and blue pigments are used, no purple, orange, or green color areas are observed in the final Block 1. It is also observed that Block 1 exhibits color throughout, since the colored carbon fibers that were positioned in the center of the mixture in the mold before the firing cycle are still located in the center of the final Block 1.

[0055] Similarly, the figure 1bThe diagram schematically illustrates, on the left, an arrangement of carbon fibers in a mold (not shown) in the form of superimposed layers. The carbon fibers are divided into three groups, by way of illustration but not limitation: uncolored A fibers, B fibers colored with a first pigment, and C fibers colored with a second pigment, different from the first. Block 1 obtained after firing is schematically illustrated on the right. figure 1b . Block 1 finally shows a distribution of the different carbon fibers A, B and C in the form of layers corresponding to the layers deposited in the mold before the baking cycle.

[0056] Thus, it appears that the appearance of the block finally obtained after the cooking cycle is predictable or even controllable, and it is possible to make a watch component from block 1 which has a predefined distribution of colored carbon fibers.

[0057] An example of a firing cycle to obtain the preferred properties, namely a porosity of less than 5%, more preferably less than 3%, even more preferably less than 1%, and very good mechanical resistance, particularly to impact, could be: Duration startup 15 min 8h 3h 3h 2h 1h 3h Temperature (°C) Tamb Tamb 50 90 120 150 200 Tamb Pressure Patm Patm-70mbar 4 bar 10 bar 10 bar 8 bar 2 bar Patm (Tamb=ambient temperature; Patm=atmospheric pressure)

[0058] In general, it is preferable to implement at least two different temperature stages, and more preferably at least three stages, to improve the quality of the block finally obtained in terms of porosity and mechanical resistance.

[0059] There figure 2 represents a photograph of an example block obtained after the firing cycle, containing different regions of distinct colors. The block visible in the figure 2This was achieved, as a non-limiting example, by arranging colored carbon fibers in the mold, grouping fibers of the same color by region. This results in adjacent regions of different colors, without mixing between the colors used.

[0060] As mentioned previously, the block obtained after the firing cycle can be machined, if necessary, to produce the desired portion of the watch component or the entire watch component, depending on the situation. Machining can be carried out using any suitable known method, including laser or CNC machining.

[0061] Thanks to the process just described, it is possible to produce a watch component with high-level mechanical properties, particularly in terms of shock and scratch resistance, while also having an attractive appearance due to an original design, notably featuring regions of different colors distributed according to a predefined pattern.

[0062] Thus, thanks to the process according to the present invention, a manufacturer of watch components will be able to offer a robust and attractive watch component, whether it is intended to be integrated into a watch movement or whether it is intended for the production of a casing element for a watch part, preferably a case, a bezel, a case back, an external control organ, in particular a crown or a pusher, or a bracelet element.

[0063] The preceding description is intended to describe a preferred embodiment by way of illustration, in a non-limiting manner, and a person skilled in the art will not encounter any particular difficulty in adapting the content of this disclosure to their own needs without departing from the scope of the present invention as defined by the attached claims.

Claims

1. Horological component comprising at least one portion made of coloured forged carbon comprising cut carbon fibres, secured to one another by a matrix comprising at least one resin as component, and at least one pigment, characterized in that said at least one pigment takes the form of solid particles that cannot be mixed with, or are not soluble in, the resin or resins of which said matrix is composed, and in that said particles of said at least one pigment are situated on the surface of at least some of said carbon fibres and located in one or more predefined regions of said portion.

2. Horological component according to Claim 1, characterized in that it comprises at least one additional pigment taking the form of solid particles that cannot be mixed with, or are not soluble in, the resin or resins of which said matrix is composed, and in that said particles of said at least one additional pigment are situated on the surface of at least some of said carbon fibres and located in one or more additional predefined regions of said portion distinct from said predefined regions.

3. Horological component according to Claim 1 or 2, characterized in that the at least one resin of said matrix is of epoxy type.

4. Horological component according to one of the preceding claims, characterized in that said matrix has a crosslinked structure involving groups chosen from among the group comprising isocyanates, blocked isocyanates, anhydrides, thiols, phenols, amines and amides.

5. Horological component according to one of the preceding claims, characterized in that said carbon fibres have a dry basis weight of between 50 and 900 g.m-2, more preferably between 150 and 600 g.m-2.

6. Horological component according to one of the preceding claims, characterized in that said carbon fibres have a width of between 1 and 15 mm, preferably between 1 and 5 mm.

7. Horological component according to one of the preceding claims, characterized in that said carbon fibres have a Young's modulus greater than 45 GPa (according to the ASTM D3039 standard), preferably greater than 50 GPa.

8. Horological component according to one of the preceding claims, characterized in that said carbon fibres are grouped together in the form of strands comprising between 1'500 and 50'000 filaments.

9. Horological component according to one of the preceding claims, characterized in that said particles of pigment(s) have dimensions of between 20 and 100 µm, preferably between 20 and 80 µm.

10. Horological component according to one of the preceding claims, characterized in that said pigment or pigments are chosen from the group comprising aluminium oxides, silicon dioxides, micas or mixtures thereof.

11. Horological component according to one of the preceding claims, characterized in that it is a cladding element for a timepiece, preferably a middle, a bezel, a bottom, an external control member, notably a crown or a push-piece, or a wristlet element.

12. Method for manufacturing a block (1) made of coloured forged carbon, for the production of a horological component, comprising the steps of: a) obtaining cut carbon fibres, impregnated with a first resin, on the surface of which are arranged solid particles of at least one pigment that cannot be mixed with, or is not soluble in, said first resin, b) arranging said cut carbon fibres in a mould, preferably with a matrix comprising said first resin and / or a second resin, of the same chemical nature as said first resin, and a crosslinking agent, c) closing the mould and applying a negative pressure thereto, and d) applying a pressure-raising and temperature-raising cycle suitable for producing a densification and a crosslinking of the mixture formed in the step b).

13. Method according to Claim 11, characterized in that said first resin or said first and second resins are of epoxy type.

14. Method according to Claim 11 or 12, characterized in that said first resin or said first and second resins have a viscosity greater than 3000 mPa.s.

15. Method according to one of Claims 11 to 13, characterized in that said crosslinking agent is chosen from the group comprising isocyanates, blocked isocyanates, amines and amides.

16. Method according to one of Claims 11 to 14, characterized in that the mixture comprising said first resin or said first and second resins and the crosslinking agent has a viscosity greater than 350 mPa.s.

17. Method according to one of Claims 11 to 15, characterized in that said matrix has a glass transition temperature (Tg) of between 150 and 220°C.

18. Method according to one of Claims 11 to 16, characterized in that said matrix has a proportion of resin of between 70 and 90% by weight, preferably between 75 and 85%.

19. Method according to one of Claims 11 to 17, characterized in that said mixture formed in the step b) has a proportion of carbon fibres of between 50 and 80% by weight, preferably between 60 and 75%.

20. Method according to one of Claims 11 to 18, characterized in that said mixture formed in the step b) has a proportion of pigment(s) of between 0.5 and 10% by weight, preferably between 1 and 5%.

21. Method according to one of Claims 11 to 19, characterized in that said particles of pigment(s) have dimensions of between 20 and 100 µm, preferably between 20 and 80 µm.

22. Method according to one of Claims 11 to 20, characterized in that said pigment or pigments are chosen from the group comprising aluminium oxides, silicon dioxides, micas or mixtures thereof.

23. Method according to one of Claims 11 to 21, characterized in that the step d) comprises the application of at least three different temperature levels, preferably at least four, more preferably at least five.

24. Method according to one of Claims 11 to 22, characterized in that it comprises at least one additional step of machining of said block (1) obtained after the implementation of the steps a) to d).