CH717679A2 - Phosphorescent elastomer masterbatch and watchmaking component comprising such a mixture. - Google Patents

Abstract

The present invention relates to a masterbatch comprising: from 40 to 95% by weight of a photoluminescent pigment said pigment having a particle size limited by sieving to 30µm; 5 to 60% by weight of a polymer in the form of an elastomer or an elastomer precursor chosen from fluorinated polymers of the FKM family, the polyurethane (TPU) family, ethylene vinyl acetate copolymers (EVA), silicones, ethylene propylene rubbers (EPR) and their thermoplastic derivatives (TPO) and acrylic elastomers.

Description

Technical area

The invention relates to a masterbatch for a phosphorescent elastomeric composition and a watch or jewelry component comprising a component in such a masterbatch.

Technology background

[0002] Photoluminescent elastomeric materials are fairly widespread on the market and for various applications, such as tires, signaling accessories, etc. (For example: US6431236B1, JPH10121424A).

[0003] The known embodiment of these photoluminescent elastomeric materials is defined by the direct mixing of an elastomer and the photoluminescent pigment at a mass rate of 30% maximum (for example: JP4030196B2, JP2000044733A).

[0004] Watchmaking companies already offer phosphorescent bracelets based on silicone, but the company Bell & Ross has recently developed the offer by offering, in limited edition, a watch equipped with a phosphorescent rubber bracelet. For its luminescent synthetic rubber strap, Bell&Ross adds pigments directly into the material, which is then hot molded and pressed. In order to limit the wear of the mixing tool, the load rate has been limited to 20%: the performance suffers from this and is not satisfactory for this type of application.

[0005] These embodiments and the resulting mixtures have the following disadvantages: premature wear of the mixing tool, pollution of the mixture by metal particles resulting from wear of the mixing tool, limited light performance.

Summary of the invention

The invention aims to provide a phosphorescent composition which does not suffer from the drawbacks described above.

The present invention relates to a masterbatch comprising: from 40 to 95% by weight of a photoluminescent pigment said pigment having a particle size limited by sieving to 30µm; 5 to 60% by weight of a polymer in the form of an elastomer or an elastomer precursor chosen from fluorinated polymers of the FKM family (abbreviation in English for "fluoroelastomer materials"), the family of polyurethanes ( TPU), ethylene vinyl acetate (EVA) copolymers, silicones, ethylene propylene rubbers (EPR) and their thermoplastic derivatives (TPO) and acrylic elastomers, preferably.

Advantageously, the masterbatch of the invention comprises 0.2 to 2% by weight relative to the natural wax polymer (eg carnauba wax) or mineral (paraffins, petrolatum) and / or oil (mixtures of fatty alcohols, fatty acids or fatty acid esters such as triglycerides).

[0009] Preferably, the masterbatch comprises 0.1 to 2% of chromophores and/or fluorochromes.

[0010] Preferably, the polymer in the masterbatch is an FKM.

[0011] Advantageously, the masterbatch does not comprise any crosslinking agent, the latter, when necessary, being added separately to the final mixture.

A second aspect of the invention relates to a composition comprising 50 to 80% (preferably more than 60%) by weight of the masterbatch according to the invention.

[0013] The invention also relates to a watch component such as a watch bracelet, or a watch case comprising a composition according to the invention.

Finally, the invention relates to a method of manufacturing a photoluminescent timepiece component comprising the steps of: a. producing a masterbatch according to one of claims 1 to 5; b. mixing the masterbatch in a polymer compatible with said masterbatch to obtain a mixture according to one of claims 6 to 9; vs. shaping the composition obtained in b) to obtain a photoluminescent timepiece component.

detailed description

A first aspect of the invention relates to a concentrated polymeric composition (masterbatch) comprising a phosphorescent pigment (ARALON®, Radiant Color, etc.), said composition being suitable for use in a rubber, preferably of the fluoroelastomer type.

[0016] The use of such a masterbatch overcomes the aforementioned disadvantages.

According to the first aspect of the invention, the phosphorescent pigment, in powder form, is sieved so as to retain only the fraction with a size of less than 30 μm (size determined by the sieving itself). It has in fact been discovered that below this size, the abrasion of the tools for implementing the polymers was reduced. Larger phosphor particles can either be used for other applications or be ground down to a size of less than 30µm.

[0018] Next, the pigment is encapsulated in a polymer, in the form of a concentrated composition or masterbatch. This encapsulation makes it possible to reduce the direct contact with the final mixing tool of the polymeric mixture with a view to forming the targeted object.

[0019] The production of a masterbatch is a first way allowing the encapsulation of the pigment in a matrix whose properties do not interact with the absorption and emission domains of the photoluminescent pigment.

This masterbatch comprises an elastomer or an elastomer precursor that is optically transparent in the 360nm to 650nm range and chemically compatible with the desired elastomer in the mixture (elastomer content: from 2% to 10% by weight, from preferably 4 to 8%).

By elastomer precursor, we mean in the present description a polymer of low molecular mass often liquid at room temperature, or which can easily be made liquid by dissolution in a solvent and intended to be subsequently crosslinked with the elastomer of the mixture. final.

The elastomer or its precursor is preferably chosen from fluorinated elastomers such as those of the FKM family (crosslinkable fluoro or perfluoropolyalkylene) or thermoplastic elastomers such as TPUs (Polyurethanes), EVA (Ethylene vinyl acetate copolymer ), silicones, EPR (ethylene propylene rubber) and their thermoplastic derivatives (TPO) or from the family of acrylic elastomers.

[0023] In the case of the use of an elastomer precursor, the crosslinking system (typically, an initiator, for example an organic peroxide, accompanied by a crosslinking co-agent) can either be integrated into the mixture -master or later in the final mix.

This latter solution, having the advantage of a stable masterbatch over time, is preferred. In particular, the masterbatch can then be carried out in the presence of a solvent allowing a strong reduction in the viscosity. This reduction in viscosity then allows the use of a rapid mixer such as a Turrax®. The absence of the crosslinking system in the masterbatch then makes it possible to eliminate the solvent by hot evaporation without the crosslinking starting at an inopportune moment.

[0025] In the case of a thermoplastic, the masterbatch is prepared in a conventional mixing installation of the twin-screw, co-rotating or counter-rotating extrusion type. In this case, the quality of the dispersion in the masterbatch can be improved by the use of polymer of reduced viscosity compared to the final mixture. This reduction in viscosity can also be obtained or improved by the use of waxes.

[0026] Those skilled in the art will easily understand that, in general, the matrix used in the masterbatch is preferably compatible with the matrix in which the masterbatch is to be dispersed. Ideally, the matrix of the masterbatch is of the same nature as the matrix of the final composition.

Advantageously, the masterbatch also contains oils or waxes at a mass rate of 0.2 to 2%, preferably 0.4 to 1.8% by weight relative to the polymer. These waxes and oils, by reducing the viscosity, allow greater incorporation of photoluminescent pigments. These waxes and oils are selected from optically transparent waxes and oils in the 360nm to 650nm range.

The masterbatch can thus contain up to 95% (by mass) of photoluminescent pigments, which guarantees high luminescent performance.

The masterbatch can advantageously contain fluorochromes or chromophores (optical brighteners, pigments or dyes, etc.) making it possible to boost the luminescent properties or to cause a photochemical cascade in order to obtain colored luminescent emissions different from that of the photoluminescent pigment chosen initially.

The masterbatch thus formed is then dispersed in the final composition according to milder mixing conditions (heating and limited shear rate): in the case of crosslinked systems, the final mixing is then typically carried out in an open mixer such as a calender, or, in the case of thermoplastics in a single-screw extruder comprising mixing sections and/or static mixer(s).

In order to incorporate a large quantity of pigment into the final mixture, the masterbatch, after evaporation of any solvent, is mixed from 50 to 80% by weight in the final mixture.

The resulting mixture is then molded or extruded into its final shape, for example a watch strap.

Example of photoluminescent mixture preparation

The following masterbatch is produced:

[0034] Solvay's pure Tecnoflon<®>P-457 FKM grade which is manufactured on a clean line and which is transparent is used as the matrix of the masterbatch.

The Tecnoflon<®>P-457 is diluted in a 1:1 ratio in Methyl Ether Ketone (MEK) or in Ethyl Acetate.

The photoluminescent pigment previously screened at 30 μm is incorporated into the mixture obtained in the previous step, the quantity of pigment being in a 1:1 ratio with respect to the Tecnoflon<®>P-457 and the whole is mixed on a high-speed mixer at 3000 rpm.

A fluorochrome is introduced at 0.5% relative to the total (i.e. 1.5% relative to the FKM polymer) and the whole is again mixed on a high-speed mixer, for example at 3000 rpm. 1.

The solvent is evaporated in an oven at around 80° C. until the solvent is eliminated.

The masterbatch prepared beforehand is incorporated up to a minimum of 60% in a pure FKM P-457 by working on an open mixer.

At the end of the mixture, a vulcanization system is added (2.5% by weight of Luperox® 101XL-45 + 3% by weight of Drimix® TAIC 75%, the percentages being expressed relative to the polymer).

Preferably, Nafol 1822B™ oil marketed by Sasol (up to 1.8%) is also added. The whole constitutes the optimized photoluminescent FKM mixture, ready to be shaped and crosslinked.

The resulting mixture is then compression molded and crosslinked into its final shape. The component thus obtained has a pigment concentration of 30%, and the pigments are distributed homogeneously, without agglomeration of particles, which allows optimal optical properties of photoluminescence.

Claims (10)

1. Masterbatch comprising: – from 40 to 95% by weight of a photoluminescent pigment, said pigment having a particle size limited by sieving to 30 μm; – 5 to 60% by weight of a polymer in the form of an elastomer or an elastomer precursor chosen from fluorinated polymers of the FKM family, the polyurethane (TPU) family, Ethylene vinyl copolymers acetate (EVA), silicones, ethylene propylene rubbers (EPR) and their thermoplastic derivatives (TPO) and acrylic elastomers. 2. Masterbatch according to claim 1 comprising 0.2 to 2% wax and/or oil. 3. Masterbatch according to one of the preceding claims comprising 0.1 to 2% of chromophores and/or fluorochromes. 4. Masterbatch according to one of the preceding claims, in which the polymer is an FKM. 5. Masterbatch according to one of the preceding claims comprising no crosslinking agent. 6. Polymer composition comprising 50 to 80% by weight of the masterbatch according to one of the preceding claims. 7. Polymer composition according to claim 6 comprising at least 60% masterbatch. 8. Composition according to one of claims 6 or 7 comprising a crosslinking system comprising an organic peroxide and a co-crosslinking agent. 9. Watchmaker or jeweler component comprising a composition according to one of claims 6 to 8. 10. Method for manufacturing a photoluminescent timepiece component comprising the steps of: at. producing a masterbatch according to one of claims 1 to 5; b. mixing the masterbatch in a polymer compatible with said masterbatch to obtain a mixture according to one of claims 6 to 9; vs. shaping the composition obtained in b) to obtain a photoluminescent timepiece component.