CH719091A2 - Thermochromic manufactured object and process for its production. - Google Patents

Abstract

The invention relates to a manufactured object (10) at least partially made of an elastomeric material, such as in particular a rubber or a mixture of rubbers, said elastomeric material comprising a compound capable of thermochromism such that said elastomeric material has at least locally a thermochromic. It also relates to a method for producing such an object, comprising the following steps: a. acquire a preparation of elastomeric material (11) comprising a compound capable of thermochromism, b. affixing said preparation of elastomeric material (11) comprising a compound capable of thermochromism on all or part of a component of elastomeric material (12) of complementary nature, c. molding the preparation of elastomeric material (11) comprising a compound capable of thermochromism on said component (12) so as to at least partially crosslink said preparation on said component in a mold of suitable shape to form said at least one blank of said manufactured object or a part thereof comprising at least one thermochromic part, d. form a said manufactured object from said blank obtained in step c) or continue step c) until a said manufactured object is formed by this step c).

Description

Technical area

The present invention relates to the field of the manufacture of parts in elastomeric material, in particular based on rubber. It relates, more particularly, to a manufactured object at least partially made of elastomeric material endowed with thermochromism properties and its method of production.

[0002] Such a thermochromic object can in particular be used for covering timepieces but also in other industrial fields for decorative or functional purposes.

State of the art

It is known to manufacture parts such as watch straps, natural or synthetic rubber, or various plastics. These bracelets are generally made by molding, the mold optionally comprising molding structures making it possible to display graphic elements on the bracelet, such as a mark or a logo, or else particular decorative reliefs. Only the relief makes it possible to discern the shape or the inscription, without using any color.

[0004] It is also possible to produce all sorts of casing parts from these same materials, both for watches (dials, casebands) and for other applications.

[0005] Multicolored plastic or thermoplastic wristbands are already known, with or without colored reliefs or patterns in particular. The different colored portions can be obtained using various techniques, in particular by colored coating or by removing localized material from a part formed beforehand by molding a sandwich of several layers of calendered elastomeric material, of which at least one intermediate layer is of different color of a top layer.

[0006] To date, however, there are no known elastomer parts having thermochromic properties, either for decorative or functional purposes.

Disclosure of Invention

The present invention thus proposes, according to a first aspect, a manufactured object comprising an elastomeric material with a thermochromic character as well as, in a second aspect, its method of manufacture.

The manufactured object according to the present invention is at least partially made of an elastomeric material, such as in particular a rubber or a mixture of rubbers. This elastomeric material comprises a compound capable of thermochromism such that said elastomeric material has at least locally a thermochromic character.

In other words, the manufactured object according to the present invention is such that it has, at least where it is formed of elastomeric material, at least certain zones or sections in the elastomeric material which has a thermochromic character.

[0010] In the sense used here and in the appended claims, the term "thermochromic" is understood according to its classic assertion and designates the ability of a substance or an object to change color reversibly as a function of its temperature. . In the preceding sentence, the expression "change color" must be understood in the broad sense, in particular in that it covers a change of color as well as a transition from a colorless state to a colored state.

According to the invention, the thermochromic character of the manufactured object of the invention results from the integration in the mass of elastomeric material of a compound capable of thermochromism. This compound can in particular be a thermochromic pigment, also called thermochromic pigment.

According to one embodiment, the elastomeric material comprises at most 80% by weight of compound capable of thermochromism. The concentration of the thermochromic compound in the elastomeric material can be adapted to large extents by the person skilled in the art depending on the intensity of thermochromism desired for the manufactured product as well as the mechanical properties of the desired elastomeric material, in particular its vulcanization properties. and resistance to abrasion and/or breaking.

According to one embodiment, the compound capable of thermochromism is distributed homogeneously in the mass of elastomeric material.

[0014] Alternatively, the compound capable of thermochromism is localized or concentrated in a discrete manner, that is to say locally in certain exclusive zones such as lines, points or surfaces of the elastomeric material, whether on the surface or in a section of thickness of the elastomeric material, so as to provide a locally thermochromic character to the elastomeric material.

[0015] Preferably, the compound capable of thermochromism changes color at a temperature of between 0°C and 80°C. More preferably, the compound capable of thermochromism changes color at a temperature between 25°C and 65°C.

According to a second aspect, the invention also proposes a method for producing a manufactured object as defined above, this method comprising the following steps: a. acquire a preparation of elastomeric material comprising a compound capable of thermochromism, b. affixing said preparation of elastomeric material comprising a compound capable of thermochromism on all or part of an elastomeric material component of complementary nature, c. molding the preparation of elastomeric material comprising a compound capable of thermochromism on said component so as to at least partially crosslink said preparation on said component in a mold of suitable shape to form at least a blank of said manufactured object or part thereof ci comprising at least one thermochromic part, d. forming said manufactured object from said blank or continuing step c) until said manufactured object is formed by this step c).

According to one embodiment of the method of the invention, said preparation is affixed in liquid form or a calendered sheet on one side of said component.

According to one embodiment, said component coated with the preparation of elastomeric material comprising a compound capable of molded thermochromism is partially crosslinked after molding.

[0019] According to one embodiment, step d) comprises a step of overmolding said blank on or by a piece of elastomeric material of a complementary nature, also partially crosslinked, so as to assemble them by total crosslinking one on the another to form said manufactured object.

Once said manufactured object has been obtained, it can be subjected to one or more finishing operations intended to delimit the thermochromic part on a surface of said object. In particular, a material removal operation can be carried out. This removal of material may in particular consist of at least one deburring operation, which may be mechanical using a manual or automatic tool or even physical, in particular by heating using a laser beam, so to clearly delimit the lines, bands or shapes constituting the thermochromic part with respect to the rest of the manufactured object or to make them stand out in the mass of the object. This makes it possible to increase the distinction between the non-thermochromic parts made of elastomeric material devoid of thermochromic compound and the thermochromic parts.

According to a preferred embodiment of the method of the invention, the thermochromic part of the object covers or forms all or part of a relief on the piece of molded elastomeric material.

According to one embodiment of the method, the elastomeric material component on which is affixed the preparation comprising a compound capable of thermochromism comprises one or more sheets of calendered elastomeric material at least partially vulcanized.

According to one embodiment of the method of the invention, the elastomeric material of the preparation and/or of the component to which it is affixed is a fluoroelastomer (preferably an FKM, that is to say a fluoroelastomer made from vinylidene fluoride).

According to one embodiment of the method of the invention, the thermochromic compound of the preparation is a thermochromic pigment (also called thermochromic pigment). Such a pigment may in particular be incorporated into the preparation in a concentration of at most 80% by weight of compound capable of thermochromism.

Brief description of the drawings

Other features of the present invention will appear more clearly on reading the description which follows, made with reference to the accompanying drawings, in which FIG. 1 synthetically represents the steps of a manufacturing method according to a embodiment of the invention and FIG. 2 represents a manufactured object according to an embodiment of the invention, obtained according to this method.

Embodiment(s) of the Invention

In the following description, an embodiment of the invention will be described, by way of non-limiting example, in relation to the production of a manufactured object 10 such as a watch strap strand, a dial or even a watchcase trim element made of elastomeric material, in particular rubber, comprising in its mass or on one surface at least one thermochromic compound.

The invention is however not limited to this single pigment but applies generally to the integration of any compound capable of thermochromism in a manufactured object made of elastomeric material in order to confer on it thermochromic properties.

The manufactured object 10 of the invention is made at least partially of elastomeric material and of which at least a part has a thermochromic character.

It is thus understood that all or part of the manufactured object 10 can be made of said elastomeric material, and all or part of this elastomeric material can include a pigment giving it its thermochromism properties. The manufactured object 10 may thus comprise on a surface or in a section one or more discrete zones such as lines, points or surfaces in which a said thermochromic pigment provides a locally thermochromic character to the object.

The manufactured object 10 can also be made entirely of elastomeric material in which said thermochromic pigment is integrated and distributed homogeneously throughout the mass and over the entire surface of the object such as the manufactured object 10 in its entirety has a thermochromic character.

By way of example and preferably, the elastomer used to produce all or part of the manufactured object 10 can be a fluoroelastomer (for example an FKM). Although a fluoroelastomer is preferred, another elastomer can also be used. Still by way of example, the elastomer(s) used to produce all or part of the manufactured object 10 of the invention may be chosen from general elastomers, such as natural rubber, polyisoprene, a copolymer of butadiene and styrene, known by the abbreviation SBR, or polybutadiene. The elastomer(s) can also be chosen from special elastomers, such as for example a copolymer of isobutylene and isoprene, known by the abbreviation of IIR, polychloroprene, a copolymer of ethylene and propylene-diene, known under the name of EPDM, or a copolymer of ethylene and propylene, known under the name of EPM.

Said manufactured object may in particular be made of one or more sheets of calendered elastomeric material as previously defined. The sheets of calendered material can be assembled on top of each other by vulcanization, in a conventional manner per se for the manufacture of elastomer parts. Each sheet of calendered material forming part of the blank may in particular be of a thickness preferably comprised between 0.5 mm and 10 mm, more preferably comprised between 0.8 mm and 3.0 mm.

Of course, in the same manufactured object 10, it is possible to integrate several different types of thermochromic pigment, either as a mixture or else according to distinct discrete positions within the elastomeric material constituting the object in order to provide different zones thermochromics of distinct hues and/or distinct behaviors in the object. For example, pigments of a first type changing color at a first temperature and pigments of a second type changing color at a second temperature can be present in the same manufactured object 10. The first temperature can be equal to the second temperature or it may be different from this second temperature. In either case, the shade of the pigments of the first type at a temperature below the first temperature and the shade of the pigments of the second type at a temperature below the second temperature may be different or substantially identical, and/ or the tint of the pigments of the first type at a temperature above the first temperature and the tint of the pigments of the second type at a temperature above the second temperature can be different or substantially identical.

One or more non-thermochromic pigments may also be incorporated into the elastomeric material of article 10. A non-thermochromic pigment may be present in only one or more localized regions of the elastomeric material. A non-thermochromic pigment may also be present throughout the elastomeric material. It can be provided that, in the elastomeric material, there is both a first type of region where the thermochromic pigment and the non-thermochromic pigment are both present, and a second type of region where only one of these two pigments is here. In this way, it is possible to obtain that the effects of thermochromism on the same manufactured object 10 are varied rather than uniform.

The manufactured object 10 according to one embodiment of the invention can advantageously be obtained by implementing the following process.

A first step 1 consists first of all in having a preparation 11 of elastomeric material in which is integrated a said thermochromic pigment. The preparation of elastomeric material 11 essentially consists initially of an elastomeric material base, for example of fluoroelastomer (for example an FKM), of natural rubber, of EPDM or of EPM, in which one mixes between 1 % and 60% by weight of thermochromic pigment, preferably between 5% and 50% by weight of thermochromic pigment depending on the intensity of thermochromism that it is desired to give to the manufactured manufactured object. The pigment and the elastomeric paste are mixed so as to obtain a homogeneous mixture in which the pigment is preferably uniformly distributed.

This preparation 11 is then reserved, in liquid form or even raw calendered sheets of this elastomeric preparation, intended for the production of vulcanized assemblies with other components of elastomeric material 12, identical or of complementary nature in order to be able to be cross-linked together.

In a second step, is then affixed in a second step 2 the preparation 11 on all or part of a component 12 of elastomeric material of complementary nature, formed for example of calendered elastomeric material. This affixing may consist of arranging a raw preparation sheet 11, or strips of raw sheets, or lines, points or shapes cut from a raw preparation sheet 11 on a surface of the component 12 to form a thermochromic surface relief on the component or between two sheets of calendered material in order to form a sandwich, an intermediate layer of which will be thermochromic once the sandwich has been vulcanized in a third step.

Once the preparation has been affixed to the component, one proceeds in a third step 3 to molding the preparation of elastomeric material 11 comprising a compound capable of thermochromism with the component 12 so as to at least partially crosslink said preparation on said component. in a mold 13 of suitable shape to form a blank of said manufactured object 10 or a part thereof comprising at least one thermochromic part.

[0040] Preferably, the blank thus formed has at least substantially the shape of the manufactured object 10 that it is desired to obtain. This blank can be the final object 10, to which only an optional finishing operation 4 such as material removal can be applied in addition to deburr the blank after molding and/or properly delimit the thermochromic zones of the object 10 from those not thermochromic. This removal of material may in particular consist of at least one deburring operation, which may be mechanical using a manual or automatic tool or even physical, in particular by heating using a laser beam, so to clearly delimit the lines, bands or shapes constituting the thermochromic part with respect to the rest of the manufactured object or to make them stand out in the mass of the object. This makes it possible to increase the distinction between the non-thermochromic parts made of elastomeric material devoid of thermochromic compound and the thermochromic parts.

[0041] When the preparation 11 has been sandwiched between two sheets of non-thermochromic elastomeric material, it is possible in particular by laser abrasion to draw any shape, logo, writing, graphic representation of one's choice in the mass of the blank in order to reveal recessed therein the thermochromic areas underlying a non-thermochromic surface layer. A "mysterious" manufactured object 10 is thus obtained, which will project a so-called thermochromic form as changing color in its mass after the object has been subjected to a change in temperature.

If the preparation 11 has been affixed to the surface of a component of a different color, this will then form, after molding, an element of thermochromic relief on the surface of the blank, the relief of which will be exacerbated after the object will have been subjected to a change in temperature, in particular if the compound capable of thermochromism is such that one of its two alternative hues is colorless.

[0043] This molding operation makes it possible to provide on one side of the blank a shape in relief, for example of a geometric shape, rabbet, a logo, an icon, a name or any other shape that one wishes to render apparent by color contrast on one side of the bracelet strand to be made from the blank 10.

In the context of the present invention, the term “embossed shape” means any shape, whether regular or not, resulting from a hollow or a protrusion conferring a variation in localized thickness, preferably of the order of 1 to 5 mm at most, on one side of the blank and extending along one or more straight or curved segments. The shape in relief may be produced locally in a singular manner on the face of the blank, or else repeatedly at different positions thereof.

[0045] The blank can also be an intermediate component intended to be then overmolded by total crosslinking with one or more other elastomeric components according to conventional molding methods to produce the final manufactured object.

If the preparation is applied in liquid form, sprayed or not, on the component 12, it is possible advantageously to coat all or part of reliefs previously produced according to conventional molding processes of elastomer components 12 in order to produce during the molding only the final vulcanization and therefore the adhesion of the elastomeric material of the preparation to the component 12. It is thus possible to coat a relief in its entirety or else only certain portions thereof such as flat or non-flat sides or faces, ribs or counterbores, on which it is desired to apply a thermochromic coating so as to provide a very localized thermochromic effect, such as after material abrasion as previously presented, between the relief and the rest of the blank forming the major part of the manufactured object 10.

The molding parameters of preparation 11 on component 12 to obtain assembly by more or less partial vulcanization are common to processes for molding elastomeric materials together as known to those skilled in the art, who may adapting the various parameters according to the elastomer used and the dimensions of the manufactured object(s) 10 to be obtained.

The method according to the invention can also be used to produce various manufactured objects 10 in elastomer such as bracelets, inserts or others such as, for example, parts of the bottoms of watch cases or any other parts which can be produced in elastomers. and on which it may be interesting to affix a thermochromic decorative element.

Claims (15)

1. Manufactured object (10) at least partially made of an elastomeric material, such as in particular a rubber or a mixture of rubbers, characterized in that said elastomeric material comprises a compound capable of thermochromism such that said elastomeric material has at least locally a thermochromic character. 2. Manufactured object according to claim 1, characterized in that the elastomeric material comprises a thermochromic pigment. 3. Manufactured article according to one of claims 1 or 2, characterized in that the elastomeric material comprises at most 80% by weight of compound capable of thermochromism. 4. Manufactured object according to one of claims 1 to 3, characterized in that the compound capable of thermochromism is distributed homogeneously in the mass of said elastomeric material. 5. Manufactured object according to one of claims 1 to 3, characterized in that the compound capable of thermochromism is located in discrete areas such as lines, points or surfaces so as to provide a locally thermochromic character to the elastomeric material. 6. Manufactured article according to one of claims 1 to 5, characterized in that the elastomeric material is a fluoroelastomer. 7. Method for producing a manufactured object according to one of claims 1 to 6, this method comprising the following steps: To. acquire a preparation of elastomeric material (11) comprising a compound capable of thermochromism, b. affixing said preparation of elastomeric material (11) comprising a compound capable of thermochromism on all or part of an elastomeric material component (12) of complementary nature, vs. molding the preparation of elastomeric material (11) comprising a compound capable of thermochromism on said component (12) so as to at least partially crosslink said preparation (11) on said component (12) in a mold of suitable shape to form at least one blank of said manufactured object or part thereof comprising at least one thermochromic part, d. form a said manufactured object from said blank obtained in step c) or continue step c) until a said manufactured object is formed by this step c). 8. Method according to claim 7, characterized in that said preparation is affixed in liquid form or a calendered sheet on one side of said component. 9. Method according to claim 7 or 8, characterized in that said component coated with the preparation is partially crosslinked after molding. 10. Method according to one of claims 7 to 9, characterized in that step d) comprises a step of overmolding said blank on or by a piece of elastomeric material of complementary nature also partially crosslinked so as to assemble them by total reticulation one on the other to form said manufactured object. 11. Method according to one of claims 7 to 10, characterized in that one proceeds to a material removal operation after the formation of the blank. 12. Method according to one of claims 7 to 11, characterized in that the thermochromic part of the object covers or forms all or part of a relief on the piece of molded elastomeric material. 13. Method according to one of claims 7 to 12, characterized in that the component of elastomeric material on which is affixed the preparation comprising a compound capable of thermochromism comprises one or more sheets of calendered elastomeric material at least partially vulcanized. 14. Method according to one of claims 7 to 13, characterized in that the elastomeric material of the preparation and/or of the component to which it is affixed is a fluoroelastomer. 15. Method according to one of claims 7 to 14, characterized in that the thermochromic compound of the preparation is a thermochromic pigment.