LU87682A1 - MICROBALLS CONSISTING OF GLASS BEADS CARRYING A COATING AND PIGMENT FOR SYNTHETIC POLYMERIC MATERIAL - Google Patents

Description

Microbeads made of glass beads with a coating and pigment for synthetic polymer material

The present invention relates to microbeads consisting of glass beads bearing a coating, to a synthetic polymer material incorporating such microbeads and to a pigment for synthetic polymer material. The invention also extends to microbeads for retro paint reflective.

It is well known to incorporate glass beads into a synthetic polymeric material. This can be done for different purposes. For example, glass beads can be used as a filler to modify the mechanical properties of the charged polymer, such as its flexibility or resistance to traction, or to facilitate its implementation. This incorporation is generally done by mixing the beads with a polymerizable liquid or containing the polymeric material.

It is also possible to incorporate microbeads consisting of glass beads carrying a coating, by choosing this coating so as to adapt the surface properties of the microbeads such as, for example, their chemical bonding properties or surface tension vis-à-vis the liquid.

In addition, the coloring of polymeric materials is frequently obtained using organic or inorganic pigments. Among the different types of possible pigments, metallic compounds are commonly used, chosen because of their heat, light and chemical resistance.

These pigments can be incorporated in the form of an insoluble powder formed of particles of metallic compound in the polymerizable material or containing the polymer, when the latter is in the liquid state.

There are certain difficulties in distributing these particles as regularly as necessary. Obtaining a uniform coloring obviously requires a regular and homogeneous distribution of the pigment particles in the material.

Such a distribution is not easy to obtain, it depends in particular on the viscosity characteristics and the dispersing power of the liquid material at the time of incorporation of the pigment, it is necessary to avoid the agglomeration of the insoluble particles and the obtaining of levels different colors throughout the polymer. In addition, these pigments being fairly expensive, it is preferable to use small quantities.

It is also possible to pre-disperse the pigment particles in a resin, so as to form a "coloring concentrate" which will then be distributed in the liquid material. However, the distribution operation remains a delicate operation and this pre-dispersion involves an additional manufacturing stage.

It is also common to incorporate glass beads into marking paints, to give them visible light-reflecting properties. Such paints, used for example for road markings, make it possible to improve visibility at night by reflecting the light from the headlights of a vehicle towards the driver of the vehicle.

Obtaining a retro-reflection effect requires that at least some of the pearls be exposed on the surface of the paint and that the glass and the paint have refractive indices sufficiently different for the light to be reflected at the interface between these two backgrounds.

In a conventional manner, the glass beads are incorporated into a liquid material constituted by the fresh paint. The degree of penetration into the paint can be easily adjusted by using microbeads made of glass beads with a coating which adjusts their wettability characteristics vis-à-vis the paint solvent.

The reflection of light at the glass-paint interface is obtained by incorporating pigments into the paint. These pigments, generally formed from particles of metallic compound with a high refractive index, must be distributed in the paint so as to be present in sufficient quantity around the glass beads or microbeads.

Some problems similar to those described in the context of synthetic polymeric materials may appear for retro-reflective paints; the pigments used are quite expensive and it is not always easy to distribute the insoluble particles in the paint as regularly as desired.

One of the objects of the present invention is to provide microbeads which contribute to the coloring of the material in which they are incorporated, which facilitate a good distribution of pigment in the material and which make it possible to reduce in a certain proportion the quantity of pigment required to color this color. matter.

The present invention relates to microbeads consisting of coated glass beads, characterized in that the coating comprises particles of metal compound with a refractive index greater than 2 distributed in a binder polymer and gives the microbeads a colored outer surface.

Due to their shape and size, it is generally much easier to distribute microbeads in a liquid or pasty material than to distribute very fine particles of pigment therein which tend to agglomerate and are difficult to distribute from Regularly in such a material. Since, according to the present invention, the external surface of the microbeads is colored by particles of metallic compound, a good distribution of the microbeads in a liquid or pasty material results in a good distribution of these particles in this material and preserves it when this material hardens and solidifies. Coloring can therefore be carried out more easily and more regularly in solid material.

In addition, it does not require a separate pigment incorporation operation, which makes it possible to reduce the number of steps necessary to obtain a colored article loaded with microbeads.

The invention also makes it easier to control the quantity of pigment incorporated in the material and the coloration obtained.

We can easily adapt the quantities of pigment associated with the microbeads by modifying the proportion of particles distributed in the binder polymer II is therefore easy to adjust the coloration of the material by adapting the quantity of micro-balls incorporated and the proportion of particles in their coating

The characteristics of the microbeads according to the present invention make it possible to limit the quantities of pigment and it is even possible to use less quantities of pigments than those necessary by using micro-beads or glass beads and pigment particles separately.

We have discovered that such microbeads can be incorporated into a marking paint and provide a retro-reflection effect from visible light. This is quite surprising since the microbeads alone have a dull and opaque appearance. However, these microbeads incorporated in the paint will produce, in use, a very effective retro-reflective effect.

By comparison with a synthetic polymer material, where it is generally sought to distribute a pigment as uniformly as possible in the polymer mass, in the case of retro-reflective paints, it is especially important to obtain pigment particles in sufficient quantity at the microbead-paint interfaces to allow good retro-reflection. Consequently, the present invention makes it possible to very well locate these particles since they are present on the very surface of the retro-reflection microbeads. In addition, this characteristic also makes it possible to reduce the amount of pigment required.

Surprisingly enough, in spite of the high density of a metallic compound compared to that of a binder polymer, provided that the metallic compound is in the form of particles of dimension making it possible to respect the total sphericity of the microbeads, the particles of metallic compound distributed in the Binder polymers do not appear to modify the wettability characteristics of microbeads, or only slightly, in comparison with microbeads which are otherwise similar but do not contain such particles. This characteristic is particularly advantageous because, provided that the polymer is chosen judiciously, microbeads can be obtained which will sink more or less strongly into the material in which they are incorporated. For example, microbeads can be obtained which, when introduced into fresh paint, float on the surface of the paint and will therefore be well exposed to reveal retro-reflection.

It has been found that a number of metallic compounds can be used to color the external surface of microbeads.

Among these, one can use, for example, zinc oxide particles to obtain a white coloring, lead chromate particles or cadmium sulphide to obtain a yellow coloring or even chromium oxide particles (ΠΙ) to get a green color.

It is especially preferred to color the outer surface with particles of titanium dioxide. Titanium dioxide, which provides excellent whiteness, has a refractive index of 2.9. Π opacifies synthéti¬ c polymer materials very well and allows good retro-reflection in marking paints.

In preferred embodiments of the invention, the coating comprises a coupling agent.

Coupling agents are useful for bonding organic materials to inorganic materials.

A coupling agent, by forming a bond between the glass and the binder polymer, makes it possible to easily fix the binder polymer to the glass beads and promotes good adhesion of the coating to the glass beads. This better cohesion facilitates the storage of the microbeads, their handling and their subsequent incorporation in a synthetic polymeric material or in a paint without risk of damaging them.

A coupling agent can also couple the metal compound particles and the binder polymer; a coupling agent can be chosen which increases the wettability of the particles of metallic compound vis-à-vis the fiant polymer and strengthens the adhesion between the particles and the binder polymer.

Organometallic compounds, such as silanes or organic titanates are particularly effective as coupling agents.

As examples of such coupling agents, mention may be made of ami-nopropylsilanes, methacryloxysilanes and isopropyltitanates.

Preferably, the coating comprises a surfactant.

A surfactant makes it possible to facilitate the dispersion of the particles of metallic compound in the material forming or containing the binder polymer; the particles are dispersed more easily and more evenly. It is thus possible to improve the distribution of the particles in the binder polymer.

Among the different types of surfactants, titanates can be used, for example, but a silane surfactant will preferably be chosen. It is possible to select a silane which acts both as a coupling agent and as a surfactant. This thus limits the number of components present in the coating while simultaneously ensuring two different functions.

Preferably, the coating comprises a thixotropic agent.

This promotes the flow (with stirring) of the liquid material containing the metal compound particles, which makes it possible to apply this material to the glass beads easily and without risk of premature hardening.

Thixotropic agents such as ethylcellulose or organophilic clays can be used, for example.

Π it is advantageous to use particles of metallic compound having an average diameter of less than 1 micron, and preferably their diameter lies between 0.1 and 0.7 microns.

Small particles make it possible to respect the total sphericity of the microbeads. In addition, compared to particles of higher dimension, which may tend to sink into the material forming or containing the binder polymer. During their dispersion, particles of small size disperse easily and evenly. They make it possible to obtain a coating of very homogeneous composition and to provide the microbeads with a substantially uniformly colored external surface.

On the other hand, it is preferable to avoid using particles whose dimension is small compared to the wavelengths of visible light. Carcels can present a harmful diffusing effect.

Preferably, the average diameter of the glass beads will be in the range of 100 microns to 2 mm.

In general, the size of the glass beads influences the properties of the material in which they are incorporated and their average diameter will be chosen according to the type of article to be produced and its field of use.

For example, microbeads or glass beads incorporated in synthetic polymeric materials are generally of smaller dimensions than beads or microbeads incorporated in retro-reflective paint.

In addition, according to the present invention, the size of the glass beads influences the properties of the microbeads and their average diameter will be chosen according to different criteria.

On the one hand, the specific surface of pearls of small diameter being proportionally greater than that of glass pearls of larger diameter, it will be possible to fix there a proportionally greater quantity of particles of metallic compound and to obtain microbeads whose external surface will be colored much more intensely. These microbeads will therefore be particularly effective in coloring the material in which they are incorporated.

On the other hand, as already mentioned, metal compound particles are generally quite expensive and we want to use them as small as possible.

Therefore, the average diameter of the glass beads will be chosen according to the desired result so as to obtain a good compromise between the different criteria listed above.

The particle size distribution of the glass beads also influences the properties of the material in which they are incorporated.

It is generally preferred that the glass beads have a fairly narrow particle size distribution, so as to easily obtain a good distribution of the microbeads; microbeads well distributed in a synthetic polymer material make it possible to ensure a coloration uniformly distributed in the mass and, incorporated in a marking paint, they will have a similar degree of penetration making it possible to obtain a high intensity of retro-reflection if they are exposed on the surface of the paint.

Preferably, the thickness of the coating is between 0.5 and 4 microns.

Coatings with a thickness between these values are sufficiently thick to allow good distribution of the metallic compound particles in the binder polymer. On the other hand, they make it possible to use small amounts of metallic compound and to respect the size and shape of the glass beads.

We have found that many polymers can act as a binder polymer, provided that the material forming or containing this polymer binder is in the form of a curable liquid. Thus, it is possible to disperse the particles of metallic compound in this liquid material, apply it to the glass beads and form the microbeads with an external surface colored by hardening of the material containing the particles of metallic compound.

Preferably, the binder polymer is chosen from silicones, polyurethanes, polyesters, acrylic polymers or epoxy resins.

These polymers meet the condition described above, they allow a good distribution of the particles of metallic compound, harden easily, for example by polymerization using a catalyst, by evaporation of solvent or by addition of a hardener, and adhere well to glass.

The binder polymer can be chosen according to the surface tension which it is desired to impart to the microbeads. For example, a silicone binder makes it possible to obtain microbeads which float in fresh paint and produce, after drying, microbeads which, while adhering properly to the paint, are well exposed to provide retro-reflection. It is also possible to introduce, at the same time, into the paint other microbeads, the coating of which comprises a binder polymer which confers different surface properties, for example if it is desired that the microbeads are distributed throughout the thickness of the paint.

Advantageously, the particles of metallic compound are distributed in the binding polymer in such a way that the external surface of the microbeads comprises particles of metallic compound of refractive index greater than 2 surrounded by binding polymer

The metal compound particles thus distributed can impart a well-colored outer surface without using large amounts of metal compound particles.

In addition, such a distribution makes it possible to obtain a very good adhesion of the microbeads to synthetic polymer materials or to paints: by comparison with microbeads whose external surface would be entirely covered with particles, a surface comprising of the binding polymer cling together with a synthetic polymer material or paint and will deform loaded articles with high cohesion.

The attachment of the microbeads can be adjusted by choosing the binder poly¬ according to the material in which the microbeads are incorporated; the binder polymer will preferably be of the same nature as this material in order to promote optimum compatibility, however a binder polymer different from the polymer incorporating the microbeads can be chosen. For example, it is possible to choose a polymer which, while being well compatible with the synthetic polymer material or with the paint as the case may be, gives the microbeads hydrophobicity properties and / or modifies the wettability characteristics of the microbeads.

Preferably, the microbeads are hydrophobic.

Therefore, they do not tend to absorb atmospheric humidity which could otherwise cause agglomeration of the microbeads and the loss of their fluidity properties, especially during storage prior to their incorporation or during their handling. . In addition, the accumulation of moisture on the surface of the microbeads can damage the cohesion between the microbeads and the material in which they are incorporated.

If you want to make a low density item, you can use hollow beads. However, it is generally preferred to use solid beads because of their greater mechanical strength.

It is believed that a synthetic polymeric material incorporating microbeads having one or more of the characteristics mentioned above has novel features and the invention therefore extends to a synthetic polymeric material incorporating microbeads, characterized in that at least some of the microbeads are microbeads consisting of glass pearls bearing a coating having one or more of the characteristics described above.

The present invention also relates to a pigment for synthetic polymeric material characterized in that it comprises microbeads constituted by glass beads carrying a coating which comprises particles of metallic compound with refractive index greater than 2 distributed in a binder polymer and which confers on the microbeads a colored outer surface.

Such a pigment is very advantageous since it is generally much easier to distribute in a liquid or pasty material than a pigment consisting of particles of metallic compound and it makes it possible very easily to obtain, after hardening of the liquid or pasty material, a colored article of uniform way.

In addition, this pigment makes it possible to limit the quantities of particles of metallic compound and even, in certain cases, to use quantities of particles smaller than those required by using a pigment in the form of particles of metallic compound while obtaining a similar coloring.

Preferably, the pigment comprises microbeads having one or more of the characteristics described above.

The invention also extends to microbeads for retro-reflective paint, characterized in that they comprise microbeads made up of glass beads carrying a coating which comprises metallic decomposed particles of refractive index greater than 2 distributed in a binder polymer which gives the microbeads a colored outer surface.

Quite surprisingly in view of their dull and opaque appearance, these microbeads are very suitable for imparting retro-reflection properties to the paints in which they are incorporated. In fact, the microbeads present on the surface of the paint will be exposed to abrasion due to traffic and the particles of metallic compound will be torn off while the portion of clothing which is immersed in the paint will not undergo this modification. The retro-reflection can then be very effective since the particles of metallic compound necessary to obtain the light reflection are present on the very surface of the microbeads.

This localization of the pigment particles on the surface of the retro-reflection micro¬ balls has an additional advantage; it makes it possible to use lesser quantities of pigment than before. Indeed, by the conventional method, the pigment particles must be distributed as regularly as possible throughout the paint so as to ensure that the glass beads incorporated by the following are sufficiently in contact with them to allow the retro-reflection while, according to the present invention, the microbeads have directly on their external surface the particles of metallic compound required for the retro-reflection.

The metal compound particles have a fairly high density, however, surprisingly, they do not seem to modify the wettability characteristics of the microbeads in a significant manner, in comparison with microbeads which are otherwise similar but do not include these particles. We can therefore choose the binder polymer depending on the depth of the micro-balls in the paint that we want to obtain. This makes it possible to produce micro-balls which remain on the surface of a paint or which sink into it or still use a mixture of microbeads of different wettability so as to distribute the microbeads in the thickness of the paint.

Preferably, the microbeads for retro-reflective paint comprise microbeads having one or more of the characteristics described above.

Various preferred embodiments will now be described by way of example.

EXAMPLE 1

Microbeads are manufactured to be introduced into a road marking paint. The glass beads are full and have a diameter between 250 and 650μ.

Titanium oxide particles with an average diameter of 0.5 μ are gradually mixed in a solution of Ethyl Silicate VP 2262 (from Wacker), using 200 g of titanium dioxide per 100 ml of solution. A small amount of toluene is added to adjust the viscosity. 40 ml of this mixture are taken to treat 1 kg of glass beads. The mixture is poured onto the glass beads. The whole is mixed with stirring, then dried at 80 ° C. Ethyl Silicate hardens by hydrolysis and condensation, and microbeads are obtained with a silicon coating.

The microbeads obtained have a fairly dull white outer surface. They are hydrophobic and the coating thickness is about 1 micron.

The microbeads are incorporated into an epoxy resin marking paint and remain well exposed on the surface. They produce very satisfactory retro-reflection.

As a variant of this example, the whiteness of the microbeads obtained is increased by adding a small amount of cobalt stannate to the mixture containing titanium dioxide. These microbeads are incorporated into a vinyl paint.

EXAMPLE 2

Microbeads with a yellow outer surface are prepared intended to color and charge a synthetic polymeric material.

25 μg of lead chromate are slowly mixed in 100 ml of polyester resin of the Palatal P51 type (from B.A.S.F.) to which 0.5% by weight of methacryloxypropyltriethoxysilane has been added beforehand. After homogenization, tert-butyl peroxide is added as a polymerization catalyst. The pasty mixture obtained is dispersed, using a rapid stirrer, on glass beads whose diameter is between 20 and 60 μ. The whole is brought to 140 ° C for a few minutes to harden the coating.

The microbeads formed are sieved, then incorporated into polypropylene at a rate of 40% by weight. The polypropylene thus loaded has a yellow coloration.

EXAMPLE 3

2% by weight of N- [2- (vinylbenzylamino) -ethyl] -3-aminopropyitrimethoxysilane are dissolved in 100 ml of toluene. 100 g of titanium dioxide are then added with stirring. When the dispersion is ensured, 50 (¾ of acrylic resin Plexilith 402 (from Rohm) and 1% by weight of Plexilith 492 are incorporated.

We use 50 ml of this mixture to treat 1 kg of pearls of 400 microns in average diameter. At the end of the operation, a polymerization polymer such as benzoyl peroxide is added. The polymerization lasts about 30 minutes. The microbeads are then dried and sieved.

The whiteness of these microbeads is evaluated by measuring their lumi¬nance (L). The luminance is 83 for the microbeads according to the example whereas it is 90 for titanium oxide alone and 63.4 for untreated glass beads.

EXAMPLE 4

An Araldite GY260 epoxy resin having an initial viscosity of 12,000 to 16,000 mPa-s is diluted with toluene, at a rate of 50 ml of toluene per 10 (¾ of resin, so as to reduce the viscosity between 1500 and 1600 mPa-s. Then add a organophilic clay to make the solution thixotropic After homogenization, 150 g of cadmium sulfide are incorporated with energetic stirring, then 0.5% by weight of isopropyltriisostearoyl titanate, then a polyamine hardener.

We take 4Qg of this solution to treat 11¾ of glass beads with an average diameter of about 60 microns. The solvent is evaporated in vacuo and the resin hardens rapidly by heating to 100 ° C.

The microbeads have a yellow external surface and can be incorporated in a paint or in a synthetic polymer material.

In a variant, microbeads of similar appearance are obtained by using a polyurethane as binder polymer.

Claims (18)

1. Microbeads consisting of glass beads carrying a coating, characterized in that the coating comprises particles of metallic compound with a refractive index greater than 2 distributed in a binding polymer and gives the microbeads a colored external surface. 2. Microbeads consisting of glass beads carrying a coating according to claim 1, characterized in that the particles of metallic compound are particles of titanium dioxide. 3. Microbeads consisting of glass beads carrying a coating according to claim 1 or 2, characterized in that the coating comprises a coupling agent. 4. Microbeads consisting of glass beads carrying a coating according to one of claims 1 to 3, characterized in that the coating comprises a surfactant. 5. Microbeads consisting of glass beads carrying a coating according to one of claims 1 to 4, characterized in that the coating comprises a thixotropic agent. 6. Microbeads consisting of glass beads carrying a coating according to one of claims 1 to 5, characterized in that the metal decomposed particles have an average diameter of less than 1 micron. 7. Microbeads consisting of glass beads carrying a coating according to one of claims 1 to 6, characterized in that the metallic compound particles have a diameter between 0.1 and 0.7 micron. 8. Microbeads consisting of glass beads carrying a coating according to one of claims 1 to 7, characterized in that the average diameter of glass beads is between 100 microns and 2 mm. 9. Microbeads consisting of glass beads carrying a coating according to one of claims 1 to 8, characterized in that the thickness of the coating is between 0.5 and 4 microns. 10. Microbeads consisting of glass beads carrying a coating according to one of claims 1 to 9, characterized in that the binder polymer is selected from silicones, polyurethanes, polyesters, acrylic polymers or epoxy resins. 11. Microbeads consisting of glass beads carrying a coating according to one of claims 1 to 10, characterized in that their external surface comprises particles of metallic compound with a refractive index greater than 2 surrounded by binder polymer. 12. Microbeads consisting of glass beads carrying a coating according to one of claims 1 to 11, characterized in that they are hydrophobic. 13. Microbeads consisting of glass beads carrying a coating according to one of claims 1 to 12, characterized in that the glass beads are full. 14. Synthetic polymer material incorporating microbeads, charac¬ terized in that at least some of the microbeads are microbeads consisting of glass beads bearing a coating according to one of claims 1 to 13. 15. Pigment for synthetic polymer material, characterized in that it comprises microbeads consisting of glass beads carrying a coating which comprises particles of metallic compound with refractive index greater than 2 distributed in a binder polymer and which gives the microspheres a surface colored external. 16. Pigment for synthetic polymer material according to claim 15, characterized in that it comprises microbeads consisting of glass beads bearing a coating according to one of claims 2 to 13. 17. Microbeads for retro-reflective paint, characterized in that they comprise microbeads consisting of glass beads carrying a coating which comprises particles of metallic compound with refractive index greater than 2 distributed in a binder polymer and which gives the microbeads an external surface colorful. 18. Microbeads for retro-reflecting paint according to claim 17, characterized in that they comprise microbeads constituted by glass beads carrying a coating according to one of claims 2 to 13.