EP2468127B1 - Jewellery item and method for manufacturing such an item - Google Patents

Description

Technical area

The present invention relates to jewelery pieces. The invention also relates to a method of manufacturing such parts.

In the present invention, a piece of jewelry refers to any object of adornment, but also components used in the watch industry or in jewelery. More particularly, the invention relates to bracelets, such as watch bracelets.

State of the art

It is already known to make certain components used in jewelery, and more specifically in watchmaking, from a composition comprising a polymer and fibers. For example, the patent US 7,575,800 discloses a sliding "horological" component, such as a wheel, a cam or a shaft, made of a material comprising a matrix, such as a PTFE or polycarbonate resin, and carbon fibers. However, it is specified that the amount of fibers must be greater than 3% by weight relative to the total weight of the composition.

The patent GB 2,349,239 discloses a watch case made of a composite material comprising a polymer matrix, such as epoxy or polyester, and fibers. No precise composition is however indicated. In addition, the specifications of a watch case does not correspond to the specifications of a bracelet for example.

In addition, the polymers used so far are generally not compatible with FDA or Reach standards. As a result, parts, such as bracelets, in contact with the skin, are not compatible with these standards either.

An object of the present invention is therefore to overcome these disadvantages, by providing jewelry parts to use materials compatible with FDA standards or the Reach standard while having properties to meet their specifications.

Disclosure of the invention

For this purpose, it is proposed a piece of jewelry, at least partially made of a composite material comprising an elastomeric matrix in which are dispersed reinforcing fillers selected from the group comprising microfibers, polytetrafluoroethylene nanoparticles, and mixtures thereof, said composite material being obtained from a composition comprising between 60% and 95% by weight of at least one elastomer, between 0% and 5% by weight of microfibers and between 0% and 40% by weight of polytetrafluoroethylene nanoparticles, relative to the total weight of the composition, at least one of said reinforcing fillers being present.

Such a composition makes it possible to obtain, particularly during the injection manufacturing process, structures such as watch straps with holes, because of interesting mechanical properties (rigidity) and good distribution of the fibers.

1. a) préparation d'une composition comprenant au moins un élastomère et des charges de renfort choisies parmi le groupe comprenant des microfibres, des nanoparticules de polytétrafluoroéthylène, et leurs mélanges, la quantité d'élastomère étant comprise entre 60% et 95% en poids, la quantité de microfibres étant comprise entre 0% et 5% en poids et la quantité de nanoparticules de polytétrafluoroéthylène étant comprise entre 0% et 40% en poids, par rapport au poids total de la composition, au moins l'une desdites charges de renfort étant présente
2. b) moulage de la composition obtenue à l'étape a), et
3. c) post-étuvage.

The present invention also relates to a method of manufacturing a piece of jewelery as defined above and comprising the following steps:

1. a) preparing a composition comprising at least one elastomer and reinforcing fillers chosen from the group comprising microfibers, polytetrafluoroethylene nanoparticles, and mixtures thereof, the amount of elastomer being between 60% and 95% by weight, the amount of microfibers being between 0% and 5% by weight and the amount of polytetrafluoroethylene nanoparticles being between 0% and 40% by weight, relative to the total weight of the composition, at least one of said reinforcing fillers; being present
2. b) molding the composition obtained in step a), and
3. c) post-steaming.

Brief description of the drawings

• la figure 1 représente des essais de traction simple (norme ISO 37) sur des échantillons conformes à l'invention, les charges de renfort étant des fibres ;
• la figure 2 représente des essais de tenue à la traction sur des échantillons conformes à l'invention et comparatif comprenant des trous d'ardillons, les charges de renfort étant des fibres, et
• la figure 3 représente des essais de tenue à la traction sur des échantillons conformes à l'invention et comparatif comprenant des trous d'ardillons, les charges de renfort étant des nanoparticules de polytétrafluoroéthylène.

The invention will be better understood on reading the description which follows, given by way of example and with reference to the drawings in which:

• the figure 1 represents simple tensile tests (ISO 37 standard) on samples according to the invention, the reinforcing fillers being fibers;
• the figure 2 represents tensile strength tests on samples according to the invention and comparative comprising barb holes, the reinforcing fillers being fibers, and
• the figure 3 represents tensile strength tests on samples according to the invention and comparative comprising barb holes, the reinforcing fillers being nanoparticles of polytetrafluoroethylene.

Mode (s) of realization of the invention

According to the invention, the piece of jewelery is made from a composition comprising at least one elastomer and reinforcing fillers chosen from the group comprising microfibers, polytetrafluoroethylene nanoparticles, and mixtures thereof.

Preferably, the elastomer is selected from the group consisting of nitrile elastomers and fluoroelastomers.

In the present invention, the term "fluoroelastomers" is used in the general sense independently of the fluorine content and refers to both fluorinated elastomers whose main chain is partially substituted, ie fluoroelastomers commonly known as FKM, as well as fluorinated elastomers whose main chain is entirely substituted, that is to say the perfluoroelastomers commonly called FFKM. These elastomers may be used alone or in admixture with other suitable elastomers or types of FKM or FFKM. Fluoroelastomers are amorphous polymers having a glass transition temperature below room temperature (25 ° C). They are distinguished from plastic polymers, such as PTFE. PTFE is a rigid thermoplastic polymer and not an elastomer.

Preferably, the elastomer is a fluoroelastomer, and more preferably a fluoroelastomer of FKM type.

The amount of elastomer is between 60% and 95% by weight, preferably between 70% and 90% by weight relative to the total weight of the composition.

According to a first variant embodiment, the reinforcing fillers are microfibres. Preferably, the composition according to the invention comprises between 0.1% and 4%, preferably between 0.2% and 2%, more preferably between 0.4% and 1.5%, and still more preferably between 0, 5% and 1.25% by weight of microfibers relative to the total weight of the composition.

In the present invention, the fibers used are microfibers defined by their average length of between 10 μm and 2 mm and by their mean diameter of between 50 μm and 0.5 mm.

Advantageously, the fibers are selected from the group consisting of aramid based fibers, wood fibers, glass fibers, carbon fibers and mixtures thereof. Preferably, aramid or Kevlar®-based fibers are used. These fibers may be incorporated into a masterbatch. Preferably, the masterbatch is chosen to meet FDA or Reach standards.

Preferably, the average length / mean diameter ratio of the fibers is between 20 and 150 and preferably between 40 and 100. More preferably, short fibers are used, with a mean length / mean diameter ratio greater than 50.

According to another variant embodiment, the reinforcing fillers are nanoparticles of polytetrafluoroethylene (PTFE). The composition preferably comprises between 10% and 40%, preferably between 15% and 35%, more preferably between 20% and 30% by weight of polytetrafluoroethylene nanoparticles relative to the total weight of the composition.

The nanoparticles of polytetrafluoroethylene may be incorporated into a masterbatch. Preferably, the masterbatch is chosen to meet FDA or Reach standards.

The PTFE nanoparticles may for example be generated in situ during the synthesis of the elastomer in order to have an interfacial connection of a chemical nature. More specifically, it is possible to use as an elastomer for the composition used in the invention, a fluoroelastomer comprising such nanoparticles of PTFE generated in situ such as Tecnoflon® elastomers produced according to the patented technology according to the patent EP 1031607 to Solvay Solexis .

It is obvious that microfibers and nanoparticles of PTFE can be used as a mixture.

Other fillers can be considered such as silica or carbon black.

The composition may also comprise vulcanizing or crosslinking agents specific to the elastomer, and other conventional additives commonly used by those skilled in the field of elastomer-based formulations, and more particularly fluoroelastomer-based formulations. . The crosslinking agents may be of the peroxide type, the concentration being optimized according to the practices known to those skilled in the art.

Advantageously, the composition may further comprise a coloring agent, such as a dye or, preferably, a pigment. Mixtures of dyes and / or pigments can be used.

Preferably, PTFE nanoparticles will be used for lightly loaded colors, such as light or pastel colors, and microfibers for charged colors, such as dark or bright colors.

1. a) préparation d'une composition telle que définie ci-dessus,
2. b) moulage de la composition obtenue à l'étape a) pour obtenir la forme désirée, et
3. c) post-étuvage.

The piece of jewelery according to the invention is obtained by a process comprising the following steps:

1. a) preparation of a composition as defined above,
2. b) molding the composition obtained in step a) to obtain the desired shape, and
3. c) post-steaming.

The molding can be done by any known method, such as injection or compression. The vulcanization (or cooking) is conducted in a known manner at a temperature generally between 130 ° C and 200 ° C, for a sufficient time that can vary depending on the room, for example between 60 and 300 seconds depending in particular on the cooking temperature, adopted vulcanization system and the kinetics of vulcanization of the composition.

A piece of jewelry according to the invention has improved mechanical strength. Furthermore, it has been observed, surprisingly, that the process according to the invention allows an improvement of the manufacturing process, namely a decrease in scrap. In addition, it has been observed a productivity gain with a decrease in the vulcanization time.

The piece of jewelry may be for example a bracelet, including a watch band. More specifically, a bracelet according to the invention may have particular shapes and cuts and nevertheless meet a stringent specifications in terms of mechanical strength, and more specifically in terms of tensile strength. The present invention makes it possible to use fluoroelastomers, especially of the FKM type, which are compatible with FDA standards and the Reach standard.

Examples

Example 1

Samples according to the invention were made with a FKM elastomer and 0.5%, 1.25% and 2% of Kevlar® microfibers. For comparison, a sample was made without microfiber.

The curves representing the stress as a function of the deformation are represented on the figure 1 .

The evolution of the stress is here given for deformations less than 150%, range of deformation in which the parts generally work at the macroscopic level.

Curve A corresponds to 0% microfibers, curve B corresponds to 0.5% microfibers, curve C corresponds to 1.25% microfibers and curve D corresponds to 2% microfibers.

The increasing rigidity of the introduction of fibers in greater concentration allows the manufacturer using this technology to optimize the mechanical strength of a given structure. However, it appears so surprisingly an optimum level of fiber concentration, given by better results relative to the criteria observed, in particular the injectability, the scrap rate, and the mechanical strength.

Example 2

Samples in accordance with the invention were made with a FKM elastomer (to be specified) and 0.5% by weight of Kevlar® microfibers. For comparison, a sample was made without microfiber.

The samples are rectangular specimens 20 mm wide and 3 mm thick. Rectangular holes spaced of different lengths were made in these specimens so as to simulate barb holes in a bracelet. The holes have a dimension of 4x2.5 mm, with a radius of curvature of 0.2.

The results appear on the figure 2 which represents the tensile strength as a function of the distance between the holes.

The letters A and B respectively represent the samples without and with microfibers.

The results show that, thanks to the presence of microfibres, for a distance between the holes of 3.5 mm, the gain in tensile strength is 31%, for a distance between the holes of 3 mm, the gain in holding tensile strength is 12%, for a distance between the holes of 2.5 mm, the gain in tensile strength is 43% and for a distance between the holes of 1.5 mm, the gain in holding at the traction is 48%.

Example 3

Samples according to the invention were made with a Solvay Solexis FKM Tecnoflon® elastomer comprising 23% by weight of PTFE nanoparticles. For comparison, a sample was made without nanoparticles.

The samples are rectangular specimens 20 mm wide and 3 mm thick. Circular holes, 2 mm in diameter, and spaced of different lengths were made in these specimens so as to simulate barb holes in a bracelet.

The results appear on the figure 3 which represents, on the one hand, the tensile strength as a function of the distance between the holes and, on the other hand, the gain obtained thanks to the presence of PTFE nanoparticles in the samples in accordance with the invention.

The curve comprising diamonds corresponds to the samples without nanoparticles and the curve comprising squares corresponds to the samples with nanoparticles of PTFE according to the invention.

The results show that, thanks to the presence of PTFE nanoparticles, the tensile strength is improved irrespective of the distance between the holes.

Thus, the use of microfibers and / or nanoparticles of PTFE associated with a fluoroelastomer-type elastomer makes it possible to obtain a piece of jewelery such as a watch bracelet that may have particular shapes and cutouts and still respond to a severe specifications in terms of mechanical strength, and more specifically in terms of tensile strength, and in terms of compatibility with FDA standards and the Reach standard.

Claims (16)

1. A jewelry item, characterized in that it is at least partially made from a composite material comprising an elastomer matrix in which reinforcing fillers are dispersed chosen from among the group comprising microfibers, polytetrafluoroethylene nanoparticles, and mixtures thereof, said composite material being obtained from a composition comprising between 60 wt% and 95 wt% of at least one elastomer, between 0 wt% and 5 wt% of microfibers, and between 0 wt% and 40 wt% of polytetrafluoroethylene nanoparticles, relative to the total weight of the composition, at least one of said reinforcing fillers being present.
2. The item according to claim 1, characterized in that the elastomer is a fluoroelastomer.
3. The jewelry item according to any one of claims 1 and 2, characterized in that said composite material is obtained from a composition comprising between 0.1 wt% and 4 wt%, preferably between 0.2 wt% and 2 wt%, more preferably between 0.4 wt% and 1.5 wt%, and still more preferably between 0.5 wt% and 1.25 wt% of microfibers relative to the total weight of the composition.
4. The item according to any one of the preceding claims, characterized in that the fibers are chosen from among the group comprising aramid fibers, wood fibers, glass fibers, carbon fibers and mixtures thereof.
5. The item according to any one of the preceding claims, characterized in that the mean length / mean diameter ratio of the fibers is comprised between 20 and 150, and preferably comprised between 40 and 100.
6. The jewelry item according to any one of the preceding claims, characterized in that said composite material is obtained from a composition comprising between 10 wt% and 40 wt%, preferably between 15 wt% and 35 wt%, more preferably between 20 wt% and 30 wt% of polytetrafluoroethylene nanoparticles relative to the total weight of the composition.
7. The item according to any one of the preceding claims, characterized in that the material further comprises a coloring agent.
8. The item according to any one of the preceding claims, characterized in that the material further comprises cross-linking agents.
9. A method for manufacturing a jewelry item according to any one of claims 1 to 8, characterized in that it comprises the following steps:

   a) preparing a composition comprising at least one elastomer and reinforcing fillers chosen from among the group comprising microfibers, polytetrafluoroethylene nanoparticles and mixtures thereof, the quantity of elastomer being comprised between 60 wt% and 95 wt%, the quantity of microfibers being comprised between 0 wt% and 5 wt%, and the quantity of polytetrafluoroethylene nanoparticles being comprised between 0 wt% and 40 wt%, relative to the total weight of the composition, at least one of said reinforcing fillers being present,

   b) molding the composition obtained in step a), and

   c) post-baking.
10. The method according to claim 9, characterized in that the elastomer is a fluoroelastomer.
11. The method according to any one of claims 9 and 10, characterized in that said composition comprises between 0.1 wt% and 4 wt%, preferably between 0.2 wt% and 2 wt%, more preferably between 0.4 wt% and 1.5 wt%, and still more preferably between 0.5 wt% and 1.25 wt% of microfibers relative to the total weight of the composition.
12. The method according to any one of claims 9 to 11, characterized in that the fibers are chosen from among the group comprising aramid fibers, wood fibers, glass fibers, carbon fibers and mixtures thereof.
13. The method according to any one of claims 9 to 12, characterized in that the mean length / mean diameter ratio of the fibers is comprised between 20 and 150, and preferably comprised between 40 and 100.
14. The method according to any one of claims 9 to 13, characterized in that said composition comprises between 10 wt% and 40 wt%, preferably between 15 wt% and 35 wt%, more preferably between 20 wt% and 30 wt% of polytetrafluoroethylene nanoparticles relative to the total weight of the composition.
15. The method according to any one of claims 9 to 13, characterized in that the composition further comprises a coloring agent.
16. The method according to any one of claims 9 to 15, characterized in that the composition further comprises cross-linking agents.

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