CH715694A2 - Decorative item made of a heavy composite material. - Google Patents

Abstract

The invention relates to a decorative article made of a molded material having a density of between 2 and 7 g / cm 3, the molded material comprising by weight: - 60 to 90% of a metallic or ceramic material having a density greater than or equal at 5 g / cm 3, - 10 to 32% of a plastic material comprising a thermoplastic resin and a coupling agent, - 0 to 8% of a reinforcement, - 0 to 3% of a pigment. The present invention also relates to the method of manufacturing by injection molding of this decorative article.

Description

TECHNICAL AREA

The present invention relates to a decorative article and in particular to a component for watchmaking, made of a heavy and impact resistant composite material. It also relates to its manufacturing process.

PRIOR ART

[0002] Many trim components such as the middle and the bracelets are made of plastic materials. These components can be produced by molding processes, which has the advantage of being able to obtain various shapes without any rework operation. These plastic material components have the characteristic of having a density close to 1 and therefore of being light. This can constitute a disadvantage for the user wishing to wear a watch having a certain weight on the wrist.

To remedy this drawback, it has been proposed, for example in document EP 2 482 142, to produce watch components, whether movement or trim, in plastic materials loaded with a high metal powder. density such as tungsten powder. These components are produced by an injection molding process, which makes it possible to keep the advantage of shaping in the mold without subsequent rework while increasing the density.

SUMMARY OF THE INVENTION

[0004] The object of the present invention is to provide a novel composition of heavy composite material meeting the aesthetic and mechanical criteria, and in particular toughness, of watchmaking applications.

[0005] To this end, the present invention provides a decorative article made of a material comprising by weight: <tb> - <SEP> 60 to 90% of a metallic or ceramic material having a density greater than or equal to 5 g / cm <3>, <tb> - <SEP> 10 to 32% of a plastic material comprising a thermoplastic resin or a mixture of thermoplastic resins and a coupling agent, <tb> - <SEP> 0 to 8% of a reinforcement, <tb> - <SEP> 0 to 3% of a pigment.

Preferably, the material comprises as metallic material a stainless steel, as thermoplastic resin an MABS (methyl methacrylate butadiene styrene) and as coupling agent an ethylene-methacrylic acid copolymer.

[0007] Advantageously, the material comprises a reinforcement in a percentage by weight greater than or equal to 1% in order to increase the toughness of the material and / or to limit the shrinkage of the material during molding. This reinforcement can be present in different forms, for example, in the form of fibers or particles.

[0008] Furthermore, the material may comprise an organic pigment such as carbon black.

[0009] The composite material thus developed has a density of between 2 and 7 g / cm3 and has good toughness.

[0010] In addition, the present invention relates to the process for manufacturing this material which is optimized to ensure a homogeneous mixture and good compatibility between the different components of the material.

[0011] Other characteristics and advantages of the present invention will become apparent from the following description of a preferred embodiment, presented by way of non-limiting example with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE FIGURE

[0012] Figure 1 shows a timepiece comprising a middle part made with the heavy composite material according to the invention.

DETAILED DESCRIPTION

The present invention relates to a decorative article made of a composite material comprising a plastic material and a metallic or ceramic material. The decorative article can be a component of watches, jewelry, bracelets, etc. In the watchmaking field, this article can be a covering component such as a caseband, a caseback, a bezel, a push-piece, a bracelet link, a dial, a hand, a dial index, etc. By way of illustration, a caseband 1 made with the composite material according to the invention is shown in FIG. 1.

[0014] The decorative article is made by injection molding. The manufacturing process includes the steps of: <tb> a) <SEP> Prepare granules of a few millimeters comprising by weight: <tb> <SEP> - <SEP> 60 to 90% of a metallic or ceramic material having a density greater than or equal to 5 g / cm <3>, <tb> <SEP> - <SEP> 9 to 25% of a thermoplastic resin or a mixture of thermoplastic resins, <tb> <SEP> - <SEP> 1 and 7% of a coupling agent, <tb> <SEP> - <SEP> 0 to 8% of a reinforcement, preferably between 1 and 6%, <tb> <SEP> - <SEP> 0 to 3% of a pigment, <tb> b) <SEP> Injection molding said granules to form the decorative article. The injection is carried out in a mold which has a temperature of the order of 90-100 ° C while the material during the injection has a temperature of between 200 and 300 ° C, and, preferably, between 220 and 280 ° C.

In step a), the granules can be manufactured by cutting a rod resulting from the extrusion of the aforementioned raw materials. Advantageously, the metallic or ceramic material and the coupling agent both in powder form are introduced firstly into a hopper of the extruder so as to coat the metallic or ceramic powder with the coupling agent before introduce the thermoplastic resin and the reinforcement. Thus, in a second step, the thermoplastic resin and the reinforcement are introduced, for example laterally into another hopper of the extruder. The pigment can be introduced during extrusion and advantageously in the second step. It is also possible to envisage mixing it with the granules just before the injection.

[0016] The metal powder can, for example, be a powder of conventional carbon steel, stainless steel, copper, a copper alloy or a tungsten powder. A powder of precious metals or of an alloy of precious metals typically gold, silver or platinum can also be envisaged. Preferably, it is a nickel-free stainless steel powder. The steel powder is preferably present in a percentage by weight of between 60 and 80%. The tungsten powder is preferably present in a percentage by weight of between 65 and 90%. It can also be a ceramic powder such as a powder of ZrO2, CeO2, ZnO, etc. Certain ceramic powders may have the advantage of being white, which, in comparison with metallic powders, facilitates coloring by pigments. Advantageously, the metallic or ceramic powder is present in a percentage by weight of between 71 and 80%. The powder has a particle size such that d90 is less than or equal to 100 μm, preferably 30 μm, and more preferably 16 μm.

The thermoplastic resin can be a polyamide, an acrylic, a polyolefin, a polyester, a polycarbonate, an acrylonitrile butadiene styrene, a methylmethacrylate butadiene styrene, a polylactic acid, a polyphenylene sulfide, a polyetheretherketone, a polymethyl methacrylate, a polyoxymethylene, terephthalate (PBT), as well as thermoplastic elastomeric resins etc., or a mixture of the latter. Preferably, it is a methylmethacrylate butadiene styrene (MABS) which is a shade of transparent ABS. Preferably, the thermoplastic resin is introduced in the form of a powder to facilitate mixing during the preparation of the granules. In the case of MABS available commercially in the form of granules of a few millimeters in diameter, a step prior to step a) consists in micronizing the granules to obtain a powder with a d90 less than or equal to 500 μm and, preferably, to 315 µm.

[0018] The coupling agent is necessary to ensure good adhesion between the metal or ceramic powder and the thermoplastic resin. Advantageously, it is a copolymer of ethylene methacrylic acid with a percentage by weight of between 5 and 20% of methacrylic acid in the copolymer. Advantageously, this copolymer is used in combination with MABS as thermoplastic resin. This coupling agent can be introduced in the form of a powder with a d90 of less than or equal to 500 μm and, preferably, to 315 μm.

The reinforcement can be present in different forms, for example, in the form of fibers or particles. For example, they may be glass fibers, glass beads, carbon fibers and / or aramid fibers with a fiber length less than or equal to 300 μm, and, preferably, 200 μm. . Its object is to improve the toughness of the material and / or to limit the shrinkage of the material during injection.

[0020] The pigment is preferably an organic pigment having a greater power of coloring of the metallic or ceramic powder than the inorganic pigments. For example, it can be carbon black for black, diketopyrrolopyrrole for red (eg Irgazin Red K3840LW from BASF), copper phthalocyanine for blue (eg Heliogen Blue K7096 from BASF), a monoazo pigment for yellow (eg Paliotol Yellow K1760 from BASF), etc. According to one variant, the pigment can be fluroescent and / or phosphorescent.

The article thus obtained comprises a metallic or ceramic material and a plastic material, also called synthetic, comprising the thermoplastic resin, the coupling agent and a possible product resulting from the reaction between the resin and the coupling agent during extrusion or injection. It also has the reinforcement and the pigment, if there is pigment and reinforcement.

By way of example, tests have been carried out to manufacture by injection moldings starting from cylindrical granules having a diameter and a length respectively of the order of 3 mm. The granules consist of a homogeneous mixture by weight of 72% Ni-free stainless steel powder (Fe17Cr11Mn3Mo) from Carpenter with a d90 <16 µm, 18.5% of MABS (Terlux 2802) micronized with a d90 <315 µm, of 3.5 % ethylene-methacrylic acid with 15% acid (Coathylene RP 9065-34), 6% glass fiber 200 µm long (Glasfasser-Flocken from Suter-Kunststoffe AG). Another mixture having the same percentages of MABS and coupling agent but with 71% stainless steel and 1% carbon black (Printex 55 black) was prepared.

The aesthetic rendering of the middle pieces is good with a gray color for the composition without pigment and a black color for that with the pigment. The middle pieces thus obtained have a density of 3.05 g / cm3 for the gray version and of 3 g / cm <3> for the black version. Impact impact tests with a pendulum hammer followed by leaktightness tests on the middle parts integrated into cases have also demonstrated the good toughness of the middle parts produced with the above-mentioned composition.

Claims (26)

1. Decorative article made of a molded material having a density of between 2 and 7 g / cm <3>, the molded material comprising by weight: - 60 to 90% of a metallic or ceramic material having a density greater than or equal to 5 g / cm <3>, - 10 to 32% of a plastic material comprising a thermoplastic resin or a mixture of thermoplastic resins and a coupling agent, - 0 to 8% of a reinforcement, - 0 to 3% of a pigment. 2. Article according to claim 1, characterized in that the metallic material is a conventional carbon steel, a stainless steel, tungsten, copper or a copper alloy. 3. Article according to claim 1 or 2, characterized in that the metallic material is a stainless steel present in the molded material in a percentage by weight of between 60 and 80%. 4. Article according to claim 1 or 2, characterized in that the metallic material is tungsten present in the molded material in a percentage by weight of between 65 and 90%. 5. Article according to claim 1, characterized in that the ceramic material is an oxide of zinc, an oxide of zirconium or an oxide of cerium. 6. Article according to claim 1, characterized in that the metallic material is a precious metal or an alloy of precious metals. 7. Article according to any one of the preceding claims, characterized in that the metallic or ceramic material is present in a percentage by weight of between 71 and 80%. 8. Article according to any one of the preceding claims, characterized in that the thermoplastic resin is chosen from the list comprising a polyamide, an acrylic, a polyolefin, a polyesther, a polycarbonate, an acrylonitrile butadiene styrene, a methyl methacrylate butadiene styrene, polylactic acid, polyphenylene sulfide, polyetheretherketone, polymethyl methacrylate and polyoxymethylene, polyurethane. 9. Article according to any one of the preceding claims, characterized in that the thermoplastic resin is methylmethacrylate butadiene styrene. 10. Article according to any one of the preceding claims, characterized in that the thermoplastic resin is present in a percentage by weight relative to the molded material of between 15 and 20%. 11. Article according to any one of the preceding claims, characterized in that the coupling agent is an ethylene-methacrylic acid copolymer. 12. Article according to claim 10, characterized in that the methacrylic acid is present in a percentage by weight of between 5 and 20% in the copolymer. 13. Article according to any one of the preceding claims, characterized in that the reinforcement is formed of glass fibers, glass beads, carbon fibers and / or aramid fibers. 14. Article according to any one of the preceding claims, characterized in that the reinforcement is present in a percentage by weight of between 1 and 6%. 15. Article according to any one of the preceding claims, characterized in that the pigment is organic. 16. Article according to claim 15, characterized in that the pigment is fluroescent and / or phosphorescent. 17. Article according to any one of the preceding claims, characterized in that it is a watchmaking trim component chosen from the list comprising a caseband, a back, a bezel, a pusher, a link. bracelet, a dial, a hand and a dial index. 18. A method of manufacturing a decorative article comprising the successive steps consisting in: a) Prepare granules comprising - 60 to 90% of a metallic or ceramic material having a density greater than or equal to 5 g / cm <3>, - 9 to 25% of a thermoplastic resin, - 1 to 7% of a coupling agent, - 0 to 8% of a reinforcement, - 0 to 3% of a pigment, b) Injection molding said granules to form the decorative article. 19. The method of claim 16, characterized in that the thermoplastic resin is a methylmethacrylate butadiene styrene. 20. The method of claim 17, characterized in that the methylmethacrylate butadiene styrene is in powder form with a d90 less than or equal to 500 microns, preferably 315 microns. 21. The method of claim 17 or 18, characterized in that the percentage by weight of methylmethacrylate butadiene styrene is between 15 and 25% by weight, preferably between 15 and 20%. 22. Method according to any one of claims 16 to 19, characterized in that the coupling agent is a copolymer of ethylene methacrylic acid in powder form with a d90 less than or equal to 500 μm, preferably 315 μm. 23. Method according to any one of claims 16 to 20, characterized in that the metal or ceramic powder has a d90 less than or equal to 100 μm, preferably 30 μm, and more preferably 16 μm. 24. Method according to any one of claims 16 to 21, characterized in that the reinforcement is in the form of fibers having a length less than or equal to 300 microns, preferably 200 microns. 25. The method of claim 16, characterized in that step a) carried out by extrusion consists in introducing, firstly, into a hopper of an extruder a powder of the metallic or ceramic material and a powder of the agent. coupling and, secondly, in another side hopper of the extruder the thermoplastic resin and the reinforcement so as to coat the powder of the metallic or ceramic material with the coupling agent before introducing the thermoplastic resin and the reinforcement. 26. The method of claim 23, characterized in that the pigment is introduced into the other side hopper or during injection molding.