FR2572023A1 - Process for producing a retroreflecting (backscattering) coating having a smooth surface on a moulded part, as well as a moulded component obtained according to the said process - Google Patents

Abstract

The invention relates to a method for producing a retroreflecting (backscattering) coating having a smooth surface on a moulded part such as a glass-fibre laminate. According to the characteristics of the invention, the process obtained by transfer includes the following steps: - the surface 1 of the mould 2 is covered with a fixing agent 3, - an excess of glass microspheres is deposited onto the said surface 1, - then a gel coat 6 is sprayed onto the surface 1 of the mould, the said gel coat covering the glass microspheres 5 and filling up the gaps existing between them, - and then the lamination by polymerisation is performed. The invention will find particular application in the field of night road markings.

Description

 The invention relates to the production of a retroreflective coating with a smooth surface on a molded part such as a fiberglass and polyester resin laminate, as well as a molded element with a smooth retroreflective surface obtained according to said method. It will particularly find its application in road signage, in particular for the formation of a covering element for crash barriers.

 In many areas, to increase night safety, it is essential to be able to mark a dangerous area or element. For this purpose, the surface of the hazardous element can be covered for example with an adhesive having reflective properties or with a paint having the same light characteristics.

 The use of adhesive or light paint gives good results; however, they can be criticized for several drawbacks.

 In particular, their installation can only be carried out on site or during the actual manufacture of the element which must be coated with it. This limitation greatly restricts the scope of the adhesive or paint.

 In terms of road signs, it is generally necessary to equip or renovate an existing infrastructure. Under these conditions, all operations must be carried out on site and in some cases, these works can be extremely inconvenient for road traffic.

 In addition, both the paint and the adhesive are not durable. These products, for outdoor use, are subject to weathering, the paint erodes while the adhesive peels off. Under these conditions, it is necessary to plan for their periodic replacement, which, for road applications, is extremely troublesome and expensive. .

 The retroreflective properties are currently given by -the incorporation, in the composition of the element, of microbeads. glass The use of these glass microbeads in the manufacture of paints intended for road use is widespread.

 Experiments have been carried out for. -ten-ter de-- develop a retroreflective coating which has these properties at the very heart of its structure. The retroreflective microelements being incorporated in its mass, such a material presents. durable characteristics and can withstand bad weather in outdoor use.

 To achieve this objective, until now, it is proceeded by incorporation of vera miorobeads in the pête of the material to be formed, for example in the case of molding.

 In this case, until now, the product obtained according to this process has a rough surface similar to that of sandpaper in rai ~ sound-microprokubérances- formed by the glass beads visible on the surface.

This surface roughness presents - real dangers of use and, as regards road signs, its use is prohibited.
The main object of the present invention is to present a method. - Realization of a retroreflective coating with a smooth surface on a molded part such as a laminate of glass fiber and polyester resin, or any other similar material. This process therefore makes it possible to obtain parts by molding, therefore with a reproducible and very competitive industrial feasibility.

 The smooth and retroreflective surface of the molded part allows the generalization of its application and, in particular its extension to road signs since all the dangers presented by the rough surfaces obtained until now have been eliminated.

 In addition, the coating comprises the retroreflective elements taken in its mass, hence an inalterability even in the long term which makes it possible to avoid all the maintenance, upkeep and renovation works encountered until now encountered with the use of paint or retroreflective adhesive.

 The method of the present invention calls, for its implementation, to conventional equipment, which allows investment to be limited by the use of standard equipment.

 Another object of the present invention is to present a molded element with a smooth retroreflective surface, having the safety and durability properties already stated, which can be used to mark up existing material.

 In particular, the safety barriers, more especially used on motorways, can advantageously be coated with retroreflective molded elements, giving the motorist information as to the structure of the road.

 Other objects and advantages of the present invention are given in the following nonlimiting description.

 The method of producing a retro-reflective coating with a smooth surface on a molded part, such as a laminate of glass fiber and polyester resin or any other similar material intended, in particular as regards road signs, to form covering elements for the crash barriers, information for the motorist on the characteristics of the road, said transfer process is characterized in that - the surface of the mold, corresponding to the retro-reflective surface of the element, is covered with a fixing agent , - micro-elements with reflecting power are deposited on said surface of the mold, - a gel-coat is sprayed onto the surface of the mold covered with micro-elements, - the element is laminated, for example by polymerization d '' one or more layers of polyester resins on glass fibers, with a catalytic system suitable for manufacturing.

 The molded element with a retro-reflective & smooth ante surface, such as a laminate of glass fiber and polyester resin, which will find its application in night signaling, is characterized by the fact that it has a gel-coat coating, in which are embedded glass microbeads whose surface tangents that of said gel-coat.

 The invention will be better understood on reading the following description accompanied by drawings in the appendix, among which - Figures la, lb, lc, ld, le, If illustrate the different phases of the I process for producing a retroreflective coating according to the present invention, - Figures 2, 3 and 4 show detail views at the surface of the mold gilding the different phases of the process of the present invention.

 The invention relates to a method for producing a retro-reflective coating with a smooth surface on a molded part, such as a laminate of glass fiber and polyester or any other similar material, as well as the molded element with retro-reflective surface. smooth obtained by the implementation of said process.

 It will particularly find its application in matters of night marking and in particular for road signs.

 One of the main advantages of the present invention is to have been able to conciliate the production of a retroreflective coating which exhibits these light characteristics within the material itself, which guarantees the durability of these properties and, furthermore, smooth, non-grainy exterior surface that allows the manufacture of non-hazardous items, particularly for road traffic.

 The example given in the present description relates to an element for covering safety barriers generally used for bordering expressways, however, this is only an illustration and the invention may be extended to any other embodiment using, for the forming of the pieces, a mold.

 The advantage of molding lies mainly in the ease of reproduction of the parts obtained, which allows mass production at low cost.

 The manufacturing principle is called transfer, that is to say using a mold for the forming of parts whose dimensions and shapes are most diverse. It is a technique traditionally used for polyester.

 The main operations of the process for producing the present invention are illustrated schematically on the figures attached.

 The first phase, represented in FIG. 1 a, consists in covering the surface (1) of the mold (2) corresponding to the retroreflective surface of the molded element to be manufactured, with a fixing agent (3) which is in the form of '' a surface film.

 The mold (2) is shown in transverse section and the application of a film of fixing agent (3) on the bottom of the mold is obtained by spraying said product using a suitable nozzle (4). . The application of the fixing agent (3) on the surface (1) of the mold (2) is carried out over a small thickness, of the order of a few microns.

 The location of the surface (1) of the mold (2) covered by fixing agent (3) must be ensured with a certain precision and a mask not shown in FIG. 1a can be used on this occasion. Indeed, the surface (1) of the mold (2) covered by the fixing agent (3) corresponds very precisely to the surface of the element which will be molded which will have to have retroreflective properties.

 The second operation consists in depositing on the surface (1) of the roll (2), corresponding to the retroreflective surface of the element to be molded, micro-elements (5) with retroreflective power, as illustrated in the figure. lb.

 Prior to the deposition of the retroreflective micro-elements (5) 'mn Howled preferably allowed the fixing agent to benefit from a pre-drying time which ivi will allow to retain the micro-elements (5) in contact with it. The size of the micro-elements will be substantially greater than the thickness of the film (3) of the fixing agent, the thickness of the micro-elements will be of the order of a few tens of microns.

 The pre-drying time granted to the fixing agent (3) also allows it to stretch and therefore avoid the appearance of air bubbles or poorly covered areas.

 A detailed view of the micro-elements (5) in contact with the surface (1) of the mold, via the film (3) of the fixing agent, is given in FIG. 2. We can see that the lower layer of micro-elements (5) with retroreflective power rigorously follows the profile of the surface (1) of the mold and in this way, there is a certain arrangement of these micro-elements.

 The process of the present invention then continues by spraying a gel-coat (6) onto the surface (1) of the mold covered with micro-elements (5) as illustrated in FIG. 1d. The thickness of the gel-coat deposited is greater than that of the micro-elements (5) so that the latter are embedded in the gel-coat (6) as illustrated in fiber 4. This allows micro- elements (5) to be taken in the mass, which will make the optical properties of the molded element unalterable.

 The next phase consists in realizing ~ the stratification of the element (7) as illustrated in FIG, it is a conventional operation such as a polymerization of one or more layers of polyester resin on fiberglass with accelerator and catalyst or any other suitable catalytic system, followed by demolding to obtain the formed part (8) illustrated in FIG. 1f, having a surface (9) with retroreflective power.

 The retroreflective surface (9) is smooth since the micro-elements have been arranged according to the profile of the mold without any overflow.

 Preferably, the removal of retroreflective micro-elements as illustrated in FIG. 1b will be made by spraying onto the surface (1) of the mold coated with the fixing agent (3) with an excess of micro-elements (5) in order to ensure that the entire surface is covered. Then after an appropriate drying time, remove the excess mid-crobilles as illustrated in Figure lc. The elimination can for example be carried out by blowing compressed air using a nozzle (10) which will expel all the micro-elements which are not in contact with the fixing agent (3). In this way, we will obtain a distribution of micro-elements (5) as illustrated in Figure 3, that is to say micro-elements (5) distributed over the surface (1) of the mold in a single layer. The role of the fixing agent is to retain the micro-elements in contact with it, those of the upper layers having no retaining means are removed.

 Preferably, after demolding of the element, the remaining surface layer of fixing agent (3) is removed. In this way, the microbeads have a point of tangency open to the outside which will improve the reflective power of the element.

 Preferably, a fixing agent having properties facilitating release from the mold is used such as a release agent or "separating". Such properties are encountered for example with polyvinyl alcohol.

 In this case, the pre-drying time b ambient temperature is approximately five minutes after spraying onto the mold as illustrated in FIG. 1a and the drying necessary for the bonding of the mieré-elements (5) after their deposition and before blowing air to remove excess will tighten for a period of about fifteen minutes at room temperature.

 The micro-elements with retroreflective power used will preferably be glass miracles, the average size of which may be chosen between 50 and 100 microns.

The gel coat used will preferably be a white (6) polyester gel coat, which will act as a screen for microbeads by its opacity, which will improve their reflection by its color. This product t6) is inserted between the microbeads (5), as illustrated 6 in FIG. 4, which makes it possible to obtain a very smooth surface appearance and very resistance,
The su'pe-rficiel- outer layer of polyvinyl alcohol remaining- after demolding can easily be removed by washing - with water. Indeed, the polyvinyl alcohol is soluble in water.

 The invention also relates to the molded element (8) with retroreflective surface (9. 10) obtained according to said method. The main characteristic of such a product lies in the fact that it has a coating (6) of gel-coat in which are embedded glass microbeads (5), the. surface tangent to that of the gel-coat (6), as illustrated in FIG. 4.

This characteristic ensures the product a smooth surface and a retroreflective power.

 Other implementations of the invention, within the reach of those skilled in the art, could have been envisaged without departing from the framework thereof.

Claims (10)

 1. A method for producing a retro-reflective coating with a smooth surface, on a molded part such as a laminate of glass fiber and polyester resin, or any other similar material, intended, in particular as regards road signs, to form elC :: mcnts covering the safety barriers for the motorist's information on the characteristics of the road, the said transfer process being characterized in that - the surface (1) of the mold (2) corresponding to the surface is covered retroreflective of the element, of a fixing agent (3), - micro-elements (5) with retroreflective properties are deposited on said surface (1), - a gel-coat (6) is sprayed onto the surface (1 ) of the mold (2) covered with micro-elements (5), - the element is laminated, for example by polymerization of one or more layers of polyester resin (7) on glass fiber with a catalytic system suitable for manufacturing.  2. Method according to claim 1, characterized in that an excess of micro-elements (5) is deposited by spraying onto the surface (1) of the mold (2) covered with a fixing agent (3). with retroreflective power and after a drying period, the excess micro-elements (5) are eliminated.  3. Method according to claim 1, c a r a c t é r i s in that, after demolding, removing on the molded element (8) the surface layer of fixing agent (3) remaining.  4. Method according to claim 1, c 8 r a c t é r i sé in that the surface (1) of the mold (2) is covered with a fixing agent (3) having properties facilitating demolding.  5. Method according to claim 4, c a r a c t é r i sé in that the surface (1) of the mold (2) is covered with a polyvinyl alcohol.  6. Method according to claim 1, c a r a c t é r i s é an that is deposited by projection on the surface (1) of the mold (2) an excess of glass microbeads (5) ..  7. The method of claim 6, c a r a c t é r i sé in that the excess microbeads (5) are removed by blowing compressed air on the surface (1) of the mold (2).  8. Method according to claim 1, characterized in that a white polyester gel-coat (6) is projected onto the surface (1) of the mold (2) covered with microbeads (5) which fills the existing spaces between said microbeads (5).  9. Method according to claim 5, characterized in that the surface layer (3) of polyvinyl alcohol is removed on the molded element (8) by washing the retroreflective surface (9) with the water.  10. Molded element with retroreflective surface (10), such as a laminate of glass fiber and polyester resin which will notably find its application in terms of road signs to form elements for covering the information safety barriers of the motorist on the characteristics of the road, according to the method of claim 1, characterized by the fact that it has a retroreflective coating (9) of gel-coat (, 6) in which are embedded glass microbeads (5) of which  surface tangent to that of the gel-coat (6).