WO2007065998A1

WO2007065998A1 - Method for producing an object from a magnetisable moulded synthetic material and object thus produced

Info

Publication number: WO2007065998A1
Application number: PCT/FR2006/002653
Authority: WO
Inventors: Mathieu Pivaudran; Bruno Pivaudran
Original assignee: Pivaudran Techniques Et Innovations
Priority date: 2005-12-08
Filing date: 2006-12-05
Publication date: 2007-06-14
Also published as: BRPI0619500A2; FR2894508B1; FR2894508A1

Abstract

The invention relates to a method for producing an object of which at least one portion (1) is made from a moulded ferromagnetic synthetic material which is magnetised such as to form a residual magnetic field corresponding to a pre-determined surface pattern to be formed. According to the invention, at least one layer (3) of a composition containing magnetic pigments is applied to at least one face (3) of the above-mentioned portion (1), such that the pattern appears on the surface of said layer under the effect of the residual magnetic field formed by the moulded ferromagnetic synthetic material.

Description

The invention relates to a process for the production of a molded plastic object having at least one surface pattern resulting from the application of at least one method of manufacturing a molded synthetic object which can be magnetized. layer of a curable liquid composition incorporating magnetic pigments.

Liquid curable compositions such as varnishes incorporating magnetic pigments, that is to say pigments capable of reacting to a magnetic field to form a three-dimensional pattern, are well known (cf. for example the magnetic varnish ref. Reflex base 690900 sold by AKZO NOBEL (PONT D'AIN, France)) There are currently essentially two techniques for producing a pattern from a layer of curable liquid composition incorporating magnetic pigments.

The most common technique consists in applying said curable liquid composition to the object, for example by spraying, then bringing this layer thus applied, before it hardens, to a magnetic source suitable for orienting the particles of magnetic pigments so as to form the desired pattern after hardening. Such a process is however not compatible with the constraints of mass production on an industrial scale. Indeed, it requires many successive steps, and special care must be taken in the magnetization step for bringing the magnetic source and the object coated with the layer of varnish with magnetic pigments. This known process is expensive and is therefore not used in practice on an industrial scale.

As such, it should be noted that the manufacturing cost constitutes a determining parameter in the field of mass production of molded objects such as objects forming packaging, for example bottles, plastic boxes or the like. , which must present patterns on the surface for aesthetic and / or informational purposes. Another technique has been proposed for a long time (cf. for example US 3791864) which consists in applying to the object a base layer containing particles with permanent magnetization, in drying this base layer then in magnetizing it according to the desired pattern. . Subsequently, a curable liquid layer containing magnetic particles is deposited on the base layer, then cured.

Here again, this technique requires a relatively large number of steps (production of the base layer, magnetization of this base layer, production of the final layer) which makes it non-competitive compared to other traditional decoration techniques (without varnish magnetic) which, in general, simply require the application of one or two coats of varnish.

In addition, the magnetic field resulting from the magnetization of the base layer is generally insufficient to provide the final pattern with sufficient quality, in particular in terms of resolution and fineness. In addition, this drawback cannot be resolved by applying a magnetic field of greater value to the base layer in order to magnetize it. Indeed, the application of a high value magnetic field is not compatible with the production of patterns having good resolution and great finesse, since the magnetic field will not only affect the particles of the layer background which are specifically opposite the main field lines, but also the particles which are in the vicinity.

In this context, the invention aims to propose a method of manufacturing an object in molded synthetic material having at least one surface pattern resulting from the application of a curable liquid composition incorporating magnetic pigments -notably producing an effect of depth in three dimensions, for example to reproduce drawings, signatures, logos, ...- and which can be implemented with a lower number of steps than in the previous techniques mentioned, so as to be compatible with the constraints of exploitation on an industrial scale, in particular in the context of mass production of objects such as objects forming packaging, for example bottles, plastic or other boxes, which must have patterns on the surface, in particular for aesthetic and / or informational purposes.

The invention aims more particularly to propose a manufacturing method which is competitive with other traditional methods of applying patterns on the surface of molded objects with non-magnetic pigment varnish compositions.

The invention also aims to propose such a manufacturing process which allows the production of various patterns, including with high resolution and great finesse.

The invention also aims similarly to provide a molded object thus obtained, having the same advantages, that is to say the manufacturing cost of which is competitive, and which can present on the surface patterns of high resolution and great finesse.

To do this, the invention relates to a method of manufacturing an object of molded synthetic material having at least one surface pattern resulting from the application of at least one layer incorporating magnetic pigments, characterized in that.

at. preparing a composition of synthetic material, called ferromagnetic synthetic material, adapted to be able to be molded and incorporating a proportion of ferromagnetic material adapted so that, after molding, said molded ferromagnetic synthetic material is capable of being magnetized (to form a remanent magnetic field ) under the effect of an external magnetic field, according to a predetermined pattern corresponding to a pattern to be produced,

b. said ferromagnetic synthetic material is molded into the shape of at least a portion of the object to be manufactured, called molded portion, c. said ferromagnetic synthetic material is subjected to an external magnetic field adapted to magnetize it so that it forms, after surface molding of said molded portion, a residual magnetic field corresponding to said predetermined pattern to be produced, d. applying at least one face of said molded portion where said remanent magnetic field is formed, at least one layer of a composition incorporating magnetic pigments, so that the predetermined pattern appears on the surface of this layer under the effect of the field remanent magnetic formed on the surface of said molded portion by the magnetized molded ferromagnetic synthetic material.

Thus, in a method according to the invention, it is the ferromagnetic synthetic material constituting at least a portion of the molded object itself - in particular the entire molded object - which is magnetized so as to produce a magnetic field corresponding to a predetermined pattern to form on the surface of this object. The result is not only that the various steps enabling this result to be obtained are easy to perform and inexpensive, in small numbers, but also that the magnetic field produced can be of very good quality in terms of resolution and power. , so as to form patterns of great finesse, with a surprising and marked three-dimensional effect (impression of depth and relief).

It should be noted that the residual magnetic field produced by the magnetized molded ferromagnetic synthetic material must be sufficient to be effective at least until the composition with magnetic pigments is applied to form the visible pattern on the surface. Subsequently, the remanent magnetic field may disappear, either due to the normal behavior of the ferromagnetic synthetic material, or following a specific operation making it possible to inhibit this remanent magnetic field.

To magnetize the ferromagnetic synthetic material so that it forms said remanent magnetic field on the surface of said molded portion, different embodiments are possible. According to a first preferred variant, advantageously and according to the invention, said molded portion - in particular the molded object - is subjected to an external magnetic field to magnetize the ferromagnetic synthetic material molded immediately after the molding step. In particular, when the molded object (or in any case said molded portion of material synthetic ferromagnetic mold) is manufactured by injection molding in a press, it is easy and advantageous from the point of view of optimizing the production rates, to carry out the magnetization step immediately upon leaving the press. ie in the same industrial cycle of object processing.

In another alternative embodiment of the invention, the ferromagnetic synthetic material is subjected to an external magnetic field during the molding step, that is to say while said molded portion is being molded and formation, before its hardening and preferably until the end of its hardening. Since the ferromagnetic material consists of ferromagnetic particles (incorporated in a predetermined proportion into a composition of synthetic material chosen to allow molding), in this variant, the remanent magnetic field results not only from the magnetization of the ferromagnetic particles, but also from the orientation which can be imparted by the external magnetic field to these ferromagnetic particles during the molding step, while the ferromagnetic synthetic material is not yet solidified. These two variants can be combined, an external magnetic field being able to be applied both during the molding step and then, immediately after this molding step, on the molded portion.

As composition incorporating magnetic pigments, one can use in accordance with the invention any suitable composition which allows the achievement of the desired pattern on the surface. Advantageously and according to the invention, this composition is a curable liquid composition, in particular a varnish, which in particular after curing has a smooth and transparent appearance. This magnetic pigment composition can be applied by any suitable and known means, in particular by printing, spraying, spraying, chemical and / or physical deposition, coating, surface bonding, hot or cold lamination, etc.

Advantageously and according to the invention, a curable liquid composition with magnetic pigments is applied to said face of the molded portion (after the molding and magnetization steps), which results in the formation of the desired pattern by the action of the remanent magnetic field induced by matter ferromagnetic synthetic molded on the magnetic pigments of said curable liquid composition, then the layer of curable liquid composition is hardened.

Advantageously and according to the invention, when said composition incorporating magnetic pigments is a curable liquid composition such as a varnish, this curable liquid composition is applied by spraying onto said face of the molded portion.

Advantageously and according to the invention, said ferromagnetic synthetic material is prepared by incorporating ferromagnetic particles in a composition of synthetic material chosen to be moldable, called molding composition, the ferromagnetic particles being incorporated in the molding composition in a proportion suitable for firstly allow the molding of the ferromagnetic synthetic material thus obtained, and, secondly, a magnetization of this ferromagnetic synthetic material capable of producing said remanent magnetic field. Advantageously and according to the invention, a proportion of between 1% and 30% by weight of ferromagnetic particles is incorporated into the ferromagnetic synthetic material. This proportion must be sufficient for the residual magnetic field to induce the production of the pattern later in the composition with magnetic pigments, and in particular with the properties desired for this pattern, for example in terms of fineness; it must however remain compatible with the mechanical properties of the ferromagnetic synthetic material molded, on the one hand to allow the molding operations, and, on the other hand, according to the final application of the object - in particular to give the molded part obtained appropriate mechanical strength. In particular, at least in certain applications - in particular in the field of packaging of cosmetic or perfume compositions - the molded ferromagnetic synthetic material is rigid, as is said molded portion which it forms. The invention however applies equally well to semi-rigid ferromagnetic synthetic materials, or even flexible after molding. Advantageously and according to the invention, the composition for molding the ferromagnetic synthetic material is chosen from the group formed by thermoplastic materials and thermosetting materials.

More particularly, advantageously and according to the invention, the object is molded by injection. In this embodiment in particular, advantageously and according to the invention, the composition for molding the ferromagnetic synthetic material is chosen from the group of thermoplastic materials. Thus, advantageously and on the invention, the composition for molding the ferromagnetic synthetic material is chosen from the group formed by polyolefins, polyamides and polyamide imides, vinyl polymers, acrylic polymers, styrenic polymers, styrene copolymers / acrylic, polyphenylenes, thermoplastic polyesters, polyurethanes, elastomers, polyacetals and other thermoplastic polyethers, polysulfones, fluorocarbon polymers, ionomers, their copolymers and their alloys.

The invention extends to an object obtained by a method according to the invention.

The invention therefore also relates to an object of molded synthetic material having at least one surface pattern resulting from the application of at least one layer incorporating magnetic pigments, characterized in that it comprises at least one portion, called molded portion , formed from a composition of molded ferromagnetic synthetic material incorporating a proportion of ferromagnetic material, and on the surface of this molded portion, at least one layer incorporating magnetic pigments, the proportion of ferromagnetic material in the molded ferromagnetic synthetic material being adapted so that this molded ferromagnetic synthetic material can be magnetized so as to form a remanent magnetic field capable of producing a predetermined pattern formed by said layer incorporating magnetic pigments.

The invention extends to an object which can be formed of several pieces or several portions, only one of which is made of a molded ferromagnetic synthetic material coated with at least one layer of pigments magnetic to form one or more visible pattern (s) on the surface. It also extends to an object that can be formed from several pieces or several portions, several of these pieces or portions being made of a molded ferromagnetic synthetic material coated with at least one layer of magnetic pigments to form one or more pattern (s). ) visible on the surface.

In an advantageous embodiment, an object according to the invention comprises a part mainly consisting of molded ferromagnetic synthetic material to which is applied at least one layer of composition incorporating magnetic pigments. It may for example be an object such as a packaging or a packaging part made of synthetic material, in particular for cosmetic composition, or for perfumery, or pharmaceutical, or for wines or spirits. By way of example, there may be mentioned: a powder case, a case for lipstick, a jar or bottle, a screw cap or a lid for a jar of cream, a stopper for a perfume bottle or bottle, an attached cover on a flask, a pot, or a bottle ... The invention can also be the subject of applications in other fields, for example for cases or shells for electronic, computer or multimedia devices such as telephones, radios, computers ... or for decorative pieces for the automobile.

Advantageously and according to the invention, said layer incorporating magnetic pigments is a layer of varnish, that is to say a layer obtained by application of a curable liquid composition incorporating magnetic pigments and having been cured.

Advantageously and according to the invention, said ferromagnetic synthetic material comprises ferromagnetic particles incorporated into a composition of synthetic material chosen to be able to be molded, called molding composition, the ferromagnetic particles being incorporated into this molding composition according to an appropriate proportion of partly to be compatible with the mechanical strength of said molded portion, and, secondly, to allow magnetization of this ferromagnetic synthetic material capable of producing said remanent magnetic field. Advantageously and according to the invention, said material molded ferromagnetic synthetic incorporates between 1% and 30% by weight of ferromagnetic particles.

Advantageously and according to the invention, the composition for molding the molded ferromagnetic synthetic material is chosen from the group formed by thermoplastic materials and thermosetting materials. In particular, advantageously and according to the invention, the composition for molding the molded ferromagnetic synthetic material is chosen from the group formed by polyolefins, polyamides and polyamide imides, vinyl polymers, acrylic polymers, styrenic polymers, copolymers styrene / acrylic, polyphenylenes, thermoplastic polyesters, polyurethanes, elastomers, polyacetals and other thermoplastic polyethers, polysulfones, fluorocarbon polymers, ionomers, their copolymers and their alloys.

The invention also relates to a manufacturing method and a molded object characterized in combination by all or some of the characteristics mentioned above or below.

Other objects, characteristics and advantages of the invention will appear on reading the following description of one of its preferred embodiments, given solely by way of nonlimiting example and which refers to the appended figures in which:

FIG. 1 is a sectional diagram of an example of a cylindrical molded part of revolution according to the invention obtained after a molding step of a method according to the invention,

FIG. 2 is a diagram illustrating a step of magnetizing the part of FIG. 1, in a method according to the invention,

FIG. 3 is a diagram illustrating the part obtained at the end of the step of FIG. 2,

- Figure 4 is a diagram illustrating the part of Figures 1 to 3 on which a layer of magnetic pigments is applied to form a visible surface pattern, according to the invention. In a manufacturing process according to the invention, a composition of ferromagnetic synthetic material suitable for being able to be molded is prepared by incorporating a proportion of ferromagnetic material in a composition of synthetic material chosen to be able to be molded, called molding composition, and then produced , by molding this ferromagnetic synthetic material, a part such as the part 1 shown in FIG. 1 by way of example.

This ferromagnetic synthetic material, and in particular the molding composition, is first of all chosen to be able to be compatible with the envisaged molding.

In particular, the molding composition is a thermoplastic material, in particular if the molding step is carried out according to an injection molding technique, or blow molding technique, or rotational molding or other technique for molding thermoplastic material.

In this case, the molding composition of the ferromagnetic synthetic material is chosen from the group formed from polyolefins, polyamides and imide polyamides, vinyl polymers, acrylic polymers, styrenic polymers, styrene / acrylic copolymers, polyphenylenes, thermoplastic polyesters, polyurethanes, elastomers, polyacetals and other thermoplastic polyethers, polysulfones, fluorocarbon polymers, ionomers, their copolymers and their alloys.

Examples of polyolefins that may be mentioned include polyethylenes, polypropylenes (copolymers and homopolymers), cyclo-olefin copolymers, ethylene propylene diene (EPDM) and polymethyl pentene (PMP).

As an example of a vinyl polymer, mention may be made of polyvinyl chloride.

Examples of acrylic polymers that may be mentioned include methyl polylmethacrylate (PMMA) and polyacrylonitrile (PAN).

Examples of styrene polymers that may be mentioned include acrylonitrile butadiene styrene (ABS), acrylonitrile styrene acrylate, polystyrene, polystyrene butadiene, styrene acrylonitrile, styrene butadiene copolymer. Examples of polyphenylenes include polyphenylene oxide, and polyphenylene sulfone.

As examples of thermoplastic polyesters, mention may be made of polyburylene terephthalate (PBT), polyethylene terephthalate (PET), poly (cyclohexylene dimethylene terephthalate) (PCTA), poly (cyclohexylene dimethylene terephthalate) glycol (PCTG), poly (ethylene terephthalate) glycol

(PETG).

As examples of thermoplastic polyethers, mention may be made, in addition to polyacetals (polyoxymethylene and polyformaldehyde), of the polyether amide block (PEBA), the polyether etherketone (PEEK), the polyetherimide (PEI), the polyethersulfone (PES).

By way of example of a copolymer, mention may be made of methyl polylmethacrylate acrylonitrile butadiene styrene (MBS).

As an example of a fluorocarbon polymer, mention may be made of polytetrafluoroethylene.

Examples of alloys that may be mentioned include acrylonitrile butadiene styrene / polycarbonate, polyamide / polypropylene, acrylonitrile butadiene styrene / polyamide, polyethylene terephthalate / polyamide.

More particularly, in an advantageous embodiment, in particular in the case of the manufacture of lids, stoppering parts, jars or packaging cases, flasks, or cladding parts for packaging - especially for packaging of cosmetic compositions, a ferromagnetic synthetic material is used, the molding composition of which is chosen from the group formed by polypropylenes, acrylonitrile butadiene styrene and polyamides.

The ferromagnetic synthetic material can equally well be formed from a thermosetting material, in particular if the molding step is carried out by a compression molding technique, or by any other technique for molding thermosetting material. In this case, the ferromagnetic synthetic material is chosen from the group of aminiplasts. More particularly, in an advantageous embodiment, in particular in the case of the manufacture of cases or decorative pieces made of resin, a ferromagnetic synthetic material is used, the molding composition of which is chosen from the group formed by melamine formaldehyde (MF) and urea formaldehyde (UF).

Said ferromagnetic synthetic material also incorporates a proportion of ferromagnetic material adapted so that, after molding, this molded ferromagnetic synthetic material is capable of being magnetized according to a predetermined pattern corresponding to a pattern to be produced on the surface of the molded part by application, on at least one face of this molded part, with a layer incorporating magnetic pigments sensitive to the residual magnetic field formed by the molded ferromagnetic synthetic material.

The ferromagnetic material incorporated into the ferromagnetic synthetic material can be of any kind, as long as it is compatible with the molding operation under consideration, with the production of an appropriate remanent magnetic field, and with the intended application of the object thus manufactured.

Thus, as ferromagnetic material, ferromagnetic particles can be used dispersed in the ferromagnetic synthetic material prepared for the molding of the part. When the molding composition is in divided form, in particular in powder or in grains, the particles of ferromagnetic material can be either previously incorporated into the grains or particles forming this molding composition, which are then grains or particles of synthetic ferromagnetic material. , or simply mixed with the particles or grains of molding composition. Thus, the ferromagnetic synthetic material intended to be molded can be in the form of a masterbatch in the divided form of particles or grains of one (or more) synthetic material (s) forming the molding composition, and particles or grains of one (or more) ferromagnetic material (s). The ferromagnetic particles are preferably made of a soft ferromagnetic material, easy to magnetize and demagnetize. For example, ferrite particles such as strontium or barium ferrites can be used as ferromagnetic material; neodymium-iron-boron ferrites; cobalt samarium ferrites.

Once the molded part 1 is obtained, this part is subjected to an external magnetic field as shown in FIG. 2, in order to magnetize the molded ferromagnetic synthetic material. The external magnetic field is applied in accordance with the pattern which must be produced subsequently under the effect of the remanent magnetic field induced by the ferromagnetic molded magnetized synthetic material. To do this, any known technique can be used to apply an external magnetic field, in particular using permanent magnets and / or electromagnets having a frame inducing a coercive magnetic field along field lines distributed in accordance with reason to achieve. For example, the lines of the pattern to be produced correspond to field lines of the same polarity and are surrounded by zones or lines of opposite polarity.

As such, it should be noted that the residual magnetic field which must be formed in the molded synthetic material can be variable, depending on the nature and the technology of the layer with magnetic pigments subsequently used to form the surface pattern.

This step of magnetizing the molded ferromagnetic synthetic material can be carried out immediately after the molding step, in particular at the press outlet when an injection molding is carried out. Thus, this magnetization step can be carried out at the press outlet during the same treatment step, without additional handling. This step does not therefore entail any significant additional cost in terms of labor or manufacturing time. This magnetization step can be carried out automatically and robotically using a manipulator which places each molded part opposite a magnetization device (permanent magnets and / or electromagnets) for a time sufficient to magnetize the molded ferromagnetic synthetic material, the part thus magnetized then being reintroduced into the manufacturing cycle. Several successive magnetization steps can be provided, for example if several patterns are to be produced.

FIG. 3 represents a purely schematic example of a molded and magnetized part obtained at the end of this magnetization step. The magnetized ferromagnetic synthetic material constituting this molded part induces a residual magnetic field which is capable of acting on magnetic pigments to form a pattern.

Thus, when a layer 3 with magnetic pigments is then applied to the free external surface 2 of the molded part 1 magnetized opposite the field lines of the remanent magnetic field as shown in FIG. 4, the magnetic pigments of this layer are oriented according to the pattern which becomes visible on the outer surface 4 of this layer 3.

The invention is applicable with all known technologies for applying layers 3 with magnetic pigments to the surface of a molded part. In a preferred embodiment, this layer 3 with magnetic pigments is formed by application, on the free external face 2 of the molded and magnetized part 1, of a curable liquid composition incorporating magnetic pigments and then by hardening of this composition. Such a curable liquid composition is advantageously a varnish which can in particular be applied by spraying, using at least one spraying nozzle or a spray gun. It should be noted that this application can be carried out at any time after magnetization, provided that the remanent magnetic field remains sufficiently active.

As liquid curable composition with magnetic pigments which can be advantageously used in the context of the invention, there may be mentioned for example the magnetic varnish ref. reflex base 690900 sold by AKZO NOBEL (PONT D'AIN, France). It should be noted however that any other varnish incorporating magnetic pigments in the form of dispersed particles and compatible with its application to the object to achieve the desired pattern, can be used in the context of the invention. For example, we can use varnishes based chosen from the group formed of acrylic bases, polyurethane bases, urethane alkyd bases, epoxy bases, and polyester bases, nitro-cellulosic bases, aminoplast bases, methacrylate bases, hydropliolite bases, glycerophthalic bases, to air or ultraviolet or other drying.

The fineness of the pattern that can be obtained depends on different parameters. First of all, the proportion of ferromagnetic particles incorporated in the ferromagnetic synthetic material forming the molded part influences on the one hand the value of the remanent magnetic field which can be obtained after magnetization, on the other hand the fineness of the field lines corresponding to the pattern obtainable. But, as indicated above, this proportion is actually limited by the considerations linked to the molding step on the one hand and to the mechanical strength of the part obtained according to its application, on the other hand.

Furthermore, the step of magnetization by an external magnetic field also influences the quality of the pattern that can be obtained. Thus, the higher the value of the coercive field, the smaller the distance between the magnetization device and the face of the molded portion, and the longer the duration of magnetization, the better the quality of this magnetization and therefore also the fineness of the pattern obtainable.

Finally, the viscosity of the varnish incorporating magnetic pigments, and the density of the magnetic pigments contained in this varnish also directly influence the quality of the pattern, in particular its contrast and its finesse.

Example 1:

Lids of packaging boxes for cosmetic composition are produced by injection molding.

First of all, a ferromagnetic synthetic material is prepared by producing solid particles with an average particle size of 2.5 mm, from ABS sold by the company Bayer AG (Leverkusen, Germany), and incorporating 15% by weight of ferrites. of powdered strontium in these particles. These particles solids can be obtained in the traditional way by using a twin-screw extruder with gravimetric metering.

With this ferromagnetic synthetic material, molded parts are formed, using an injection press, forming covers of slightly domed cosmetic cases of 9 cm x 6.5 cm. A four-cavity mold is used and a 130 t press associated with a demoulding robot arm. On leaving the press, this robot arm places the convex external face of each molded part for approximately 3 s in contact with a permanent magnet formed by a solid disc of neodymium-ferro-boron having an external diameter of 5 cm.

A layer of a polyurethane magnetic pigment lacquer series 69 09 00 ref. 7LCS153 sold by the company AKZO NOBEL (PONT D'AIN, France) is then applied to the surface portion thus magnetized. This magnetic lacquer can be applied by spraying on a thickness of approximately 6 μm. A desolvation step is then carried out under infrared at about 60 ° C. to remove the residual solvents. A new varnishing step is then carried out using a colorless finishing varnish, with a thickness of about 15 μm, then a new desolvation step identical to the previous one followed by polymerization under ultraviolet.

A pattern is then obtained on the surface formed by the magnetic pigments of the layer of magnetic lacquer, in the form of a brilliant circular ring giving a specific effect of depth in three dimensions.

Example 2:

Cosmetic cream jar lids are produced by injection molding.

First of all, a ferromagnetic synthetic material is prepared by producing solid particles with an average particle size of 2.5 mm, from a polypropylene copolymer marketed by the company BOREALIS COORDINATION CENTER NV (MECHELEN, Belgium) and by incorporating into these particles. 15% by weight of powdered strontium ferrites and a navy blue dye These solid particles can be obtained as described in Example 1. The step of molding and the magnetization step are identical to those described in Example 1. The mold is suitable for forming covers with internal thread (for screwing on a pot) having a diameter of the order of 7 cm and a height of around 15 mm.

On the parts resulting from molding, one proceeds to a cleaning then to a flaming (passage of an oxidizing flame to make the surface adherent), then one applies a varnish ref. PAl 384 marketed by AKZO NOBEL (PONT D'AIN, France) serving as a primer.

The magnetic lacquer is then applied as described in example 1, then the steps of desolvation, application of a finishing varnish, new desolvation and polymerization under UV as described in example 1 are carried out.

Again, we observe the appearance of a brilliant circular ring giving a specific effect of depth in three dimensions on the surface of the covers.

In the two examples, the parts can be manufactured with a rate of between 4000 and 8000 parts per hour, depending on the dimensions of the molded parts.

After the lacquer with magnetic pigments has dried, the parts can be advantageously demagnetized so as not to interfere with the subsequent stages of storage, transport and use. To do this, it suffices to pass them through a heterogeneous demagnetizing magnetic field, in a manner known per se.

It goes without saying that the invention is the subject of very numerous variants and various applications. In particular, nothing prevents the application of one or more intermediate layers between the molded ferromagnetic synthetic material and the layer with magnetic pigments. Likewise, nothing prevents the application of several layers with magnetic pigments of similar or different natures, with identical or different techniques. For example, a first layer of opaque and / or colored varnish with magnetic pigments can be applied, then a second layer of transparent varnish incorporating or not incorporating magnetic pigments. In another example, a first layer of transparent varnish can be applied and colorless with magnetic pigments, then a second layer of colored varnish without magnetic pigments. Other variations are possible.

The invention can be applied for the manufacture of any object having on the surface at least one pattern at least partially produced using magnetic pigments.

Claims

1 / - Method for manufacturing an object in molded synthetic material having at least one surface pattern resulting from the application of at least one layer incorporating magnetic pigments, characterized in that:

at. preparing a composition of synthetic material, called ferromagnetic synthetic material, adapted to be able to be molded and incorporating a proportion of ferromagnetic material adapted so that, after molding, said molded ferromagnetic synthetic material is capable of being magnetized under the effect of a external magnetic field, according to a predetermined pattern corresponding to a pattern to be produced,

b. said ferromagnetic synthetic material is molded in the form of at least a portion of the object to be manufactured, called molded portion (1),

vs. said ferromagnetic synthetic material is subjected to an external magnetic field adapted to magnetize it so that it forms, after surface molding of said molded portion (1), a remanent magnetic field corresponding to said predetermined pattern to be produced,

d. applying to at least one face (2) of said molded portion (1) where said remanent magnetic field is formed, at least one layer (3) of a composition incorporating magnetic pigments, so that the predetermined pattern appears on the surface of this layer under the effect of the remanent magnetic field formed on the surface of said portion (1) molded by the ferromagnetic synthetic material molded magnetized.

2 / - Method according to claim 1, characterized in that said portion (1) molded is subjected to an external magnetic field to magnetize the ferromagnetic synthetic material molded immediately after the molding step. 3 / - Method according to one of claims 1 or 2, characterized in that the ferromagnetic synthetic material is subjected to an external magnetic field during the molding step.

4 / - Method according to one of claims 1 to 3, characterized in that said composition incorporating magnetic pigments is a curable liquid composition, and in that this curable liquid composition is applied to said face of the molded portion, then the layer (3) of curable liquid composition is hardened.

5 / - Method according to claim 4, characterized in that said curable liquid composition is a varnish.

6 / - Method according to one of claims 4 or 5, characterized in that said curable liquid composition is applied by spraying.

It - Method according to one of claims 1 to 6, characterized in that the said ferromagnetic synthetic material is prepared by incorporating ferromagnetic particles in a synthetic material composition chosen to be able to be molded, called the molding composition, the ferromagnetic particles being incorporated into this molding composition in a proportion suitable for on the one hand allowing the molding of the ferromagnetic synthetic material thus obtained, and, on the other hand, a magnetization of this ferromagnetic synthetic material capable of producing said remanent magnetic field.

8 / - Method according to claim 7, characterized in that the ferromagnetic synthetic material comprises a proportion between 1% and 30% by weight of ferromagnetic particles.

9 / - Method according to one of claims 1 to 8, characterized in that the composition for molding the ferromagnetic synthetic material is chosen from the group formed by thermoplastics and thermosetting materials.

10 / - Method according to one of claims 1 to 9, characterized in that the object is molded by injection. 11 / - Method according to one of claims 1 to 10, characterized in that the molding composition of the ferromagnetic synthetic material is chosen from the group formed of polyolefins, polyamides and imide polyamides, vinyl polymers, acrylic polymers , styrenic polymers, styrene / acrylic copolymers, polyphenylenes, thermoplastic polyesters, polyurethanes, elastomers, polyacetals and other thermoplastic polyethers, polysulfones, fluorocarbon polymers, ionomers, their copolymers and their alloys.

12 / - Object in molded synthetic material having at least one surface pattern resulting from the application of at least one layer incorporating magnetic pigments, characterized in that it comprises at least one portion, called portion (1) molded, formed from a composition of molded ferromagnetic synthetic material incorporating a proportion of ferromagnetic material, and on the surface of this molded portion (1), at least one layer (3) incorporating magnetic pigments, the proportion of ferromagnetic material in the ferromagnetic synthetic material molded being adapted so that this molded ferromagnetic synthetic material can be magnetized so as to form a remanent magnetic field capable of giving rise to a predetermined pattern formed by said layer (3) incorporating magnetic pigments.

13 / - Object according to claim 12, characterized in that it comprises a part (1) mainly consisting of molded ferromagnetic synthetic material on which is applied at least one layer (3) of composition incorporating magnetic pigments.

14 / - Object according to one of claims 12 or 13, characterized in that said layer (3) incorporating magnetic pigments is a layer of varnish.

15 / - Object according to one of claims 12 to 14, characterized in that said ferromagnetic synthetic material comprises ferromagnetic particles incorporated in a synthetic material composition chosen to be able to be molded, called molding composition, the particles ferromagnetics being incorporated into this molding composition in a proportion suitable on the one hand to be compatible with the mechanical strength of said molded portion (1), and, on the other hand, to allow a magnetization of this ferromagnetic synthetic material capable of producing said remanent magnetic field.

16 / - Object according to claim 15, characterized in that said molded ferromagnetic synthetic material incorporates between 1% and 30% by weight of ferromagnetic particles.

17 / - Object according to one of claims 12 to 16, characterized in that the molding composition of the molded ferromagnetic synthetic material is chosen from the group formed by thermoplastic materials and thermosetting materials.

18 / - Object according to one of claims 12 to 17, characterized in that the molding composition of the molded ferromagnetic synthetic material is chosen from the group formed of polyolefins, polyamides and imide polyamides, vinyl polymers, polymers acrylics, styrene polymers, styrene / acrylic copolymers, polyphenylenes, thermoplastic polyesters, polyurethanes, elastomers, polyacetals and other thermoplastic polyethers, polysulfones, fluorocarbon polymers, ionomers, their copolymers and their alloys .

19 / - Object according to one of claims 12 to 18, characterized in that it is a packaging or a packaging part of synthetic material.