FR2754771A1 - Automobile glazing, equipped with peripheral joint - Google Patents

Abstract

Glazing, particularly automobile glazing, equipped with a joint, obtained by microwave or high frequency radiation curing, that itself has an insert that modifies the application of energy in the joint material from the radiation. Also claimed is production of the glazing by: (a) placing the glazing in a mould that is made essentially from H.F. or microwave permeable material; (b) placing an insert capable of modifying the application of the radiation energy in the cavity particularly at the glazing surface; (c) injecting a curable fluid into the cavity to form the joint; (d) apply hf or microwave energy to cure the material; and (e) cooling the joint. Also claimed is the insert.

Description

METHOD AND DEVICE FOR MAKING A JOINT
CONTAINING AN INSERT AND PRODUCT OBTAINED
The invention relates to techniques for depositing a seal at the periphery of an object, particularly a seal allowing the installation of glazing in a bodywork bay. The techniques concerned are those of the polymerization of a so-called plastisol suspension thanks to the intervention of an electromagnetic field of the microwave or high frequency type (hereinafter both designated by HF).

 In a modern automobile, glazing, particularly windshields and rear windows, are generally fixed by gluing. To glue a glazing in the bay of a bodywork, one generally proceeds in two stages the first stage, which is carried out most often in the workshop of manufacture of the glazing itself or close to this one, consists in deposit an elastomer gasket at the periphery which will be used during the second step to guide or support a second bead of laying adhesive which, when it sets, will allow firm and definitive fixing of the glazing in the bay.

 Many techniques are known for making the first elastomer seal. It is, for example, the encapsulation of a polyurethane of RIM type (Reaction Injection Molding) or else the encapsulation of a thermoplastic material which, when it is taken, constitutes an elastomer for example based PVC; another conventional technique is the extrusion at the periphery of the glazing directly onto the glass of a material which also provides an elastomer profile.

 The technique in question here consists in molding directly on the glazing a fluid material which is then subjected to an electromagnetic field to make it polymerize or pass from the liquid state to the solid state directly in situ. The fact that the material introduced into the mold is in a low viscosity form makes it possible to use low pressures and, consequently, molds themselves made of elastomer. In general, silicone resin molds are used. In general, the mold is embedded in the edge of the glazing and, on either side of the mold, substantially parallel to the glazing, there are two electrodes to which the electromagnetic or microwave field is applied. The material which will be used to make the joint is, for example, a PVC plastisol.

 It is a suspension of micro-particles of PVC resin in a mixture of plasticizers added with fillers, dyes, stabilizers, etc. It is a polar material whose physical and dielectric characteristics are particularly suitable for heating by high frequency electromagnetic radiation. At room temperature it is a viscous liquid, but it can easily be poured into a silicone mold at low pressure. It can be quickly heated by H.F., in particular with a frequency of 27.12 MHz, because it has a loss factor of 0.3 to 0.5 for a relative permittivity of 3.5 to 5.5. Its price is very low and therefore allows the production of seals which are very inexpensive. Other materials can be used, they are generally polar but it is also possible to add fillers to non-polar materials.

The previous technique has been described in particular in European patent application EP 0 436 438. In this document, the basic technique was described which allows the production of seals from plastisol polymerized under
HF with a particularity, that of being able to insert into the mold itself, before the injection of the plastisol, a foreign body which will then serve as a decorative rod at the periphery of the glazing when it is installed. The main purpose of the insert described in this document is to constitute a decorative element. It is also provided in this document that it can be used to improve the seal of the seal, for example when it is made of a porous material.

 In this same document, it is expected that the material will advantageously have a tangent of the dielectric loss angle less than or equal to 1/1000 at the frequency of microwaves or high frequency waves.

 This is in fact to avoid overheating of the material of the insert during the hardening of the joint.

 Another document, application WO 95/10403 also relates to the same technique. It was in this request to find a way to improve the distribution of temperatures inside the seal when using an electric field created by two parallel flat electrodes on either side of the glazing and its mold in silicone. To achieve this result, an insert is placed in the material of the mold proper, that is to say in general in the silicone elastomer which constitutes it. The purpose of this insert is to deflect the lines of the electric field so that it occurs in the cavity where the joint must be polymerized as homogeneously as possible.

The present invention sets itself the task of improving the previous techniques so as to perfectly control the thermal gradients inside the joint during its polymerization under the effect of HF or microwave electromagnetic fields. Indeed, temperature differences are not desirable to obtain a good quality seal. If, in certain places, in particular on surfaces, the temperature is too low, the setting of the seal is incomplete and it risks sticking to the mold material or even degrading very quickly on contact with any object after demolding. . On the other hand, if in certain places, particularly inside the joint, the temperature is too high, at this time the plastisol based on
PVC is irreversibly degraded. The invention also relates to glazing obtained by this method.

 According to the invention, a glazing is proposed, in particular an automotive glazing equipped with a seal obtained by curing under microwave or HF radiation itself equipped with an insert in which the insert modifies the energy supply of said radiation. in the material of the joint.

 According to one of the variants of the invention, the insert causes the deflection of the radiation, in particular when it comprises an element made of a material whose relative permittivity differs from that of the original material of the joint. 5% more or less.

 According to another variant of the invention, the insert causes the absorption of the radiation in particular when it comprises an element made of a material whose loss factor s "differs from that of the original material of the joint. more than 5%.

 The two techniques of the invention which can moreover be combined with one another by the choice of two different materials to constitute the insert or the inserts offer a wide range of possibilities which allow, in each case of shape seal, to quickly obtain a uniform temperature throughout the seal.

 From the point of view of the geometrical position of the insert with respect to the joint, the invention envisages three possibilities either the insert is completely embedded in the material of the joint, or else it is flush with the surface of the joint.

The invention also provides a third possibility, it is that the insert is in contact with the seal but deposited on the surface of the glass in particular in the form of an enamelled deposit. These three possibilities show that the aesthetic effect is not decisive and that, on the contrary, the technical result is independent of this aesthetic aspect.

The invention also provides a method of manufacturing glazing fitted with a seal, in particular automotive glazing, in accordance with what has been described above and which comprises the following steps
a) installation of the glazing in a part of a mold which is connected to the surfaces of the glazing and whose internal shape is that to be given to the outside of the joint, the mold being essentially made of a material permeable to high radiation frequency or microwave,
b) placement inside the mold cavity of an insert capable of modifying the energy input of the HF or microwave radiation into the material of the joint, the insert being able to be placed directly at the limits of the cavity, in particular on the surface of the glazing,
c) injection into the cavity of a fluid capable of hardening under the effect of high frequency or microwave radiation,
d) application of high frequency or microwave radiation to the material of the joint,
e) cooling of the joint.

 It is also provided according to the invention that step b) of the method is carried out, at least in part, before step a), in particular in the case where the insert comprises a layer of material deposited on the surface of the glazing , such as an enamel.

 The invention also protects the insert intended to equip the seal with glazing, the seal hardening by the action of high frequency radiation or microwave, the insert being located in contact with the seal and associated with the glazing.

The figures and the description which follow will make it possible to understand the operation of the invention and to grasp all the advantages thereof.
. Figure 1 shows the section of the edge of a glazing with a seal and the equipotential curves when the plastisol has just filled the cavity of the silicone mold;
FIG. 2 represents the same joint after one minute of application of the HF field with its isotherms;
. Ia Figure 3 and Figure 4 show a seal with an insert whose function is to deflect and focus the electromagnetic field
Figures 5 and 6 always show the same seal but this time with an insert whose function is to deflect and dilute the electromagnetic field
the following figures 7, 8 and 9 show another form of seal
* in figure 7 we see the equipotential curves of the electromagnetic field
* in Figure 8 we see the thermal gradients shown by the isothermal curves as they are obtained without insert;
* in FIG. 9, the same gradients when an insert absorbing electromagnetic energy is introduced into the joint.

 As mentioned above, the insert can be located in the joint or attached to the joint projecting or not projecting from the joint. Its geometry, its nature and its location allow it to act on the heat input into the material of the joint which surrounds it under the dielectrothermal effect of high frequencies and makes it possible to homogenize the final thermal state of the joint in section and perimeter.

 The control of the thermal gradients inside the seal that the invention allows has the consequence of reducing the thickness of the molds, which is important in particular with silicone elastomers which have poor thermal conductivity and a high cost.

 The insert can be hollow or solid, of any material or assembly of materials; its dielectric and thermal characteristics need only be appropriate to the scenario that one wishes to achieve.

 Three types of configuration can arise? : either we wish to deflect and concentrate the equipotentials to obtain heating of the seal, or else we wish to deflect and dilute the equipotentials to avoid overheating of the seal, or else we simply wish to heat the seal using an insert which is itself a source of heat.

 In FIG. 1, it is necessary to imagine, in the upper and lower parts of the square of the figure, the electrodes not shown which are for example aluminum plates and which will be subjected to the high frequency electric field or microwave. Approximately centered between the electrodes, we see the cavity of the seal which is limited by the surfaces and the edge of the glazing 1 and by the mold, in particular made of silicone elastomer 2. The cavity 3 is filled with a plastisol which is for example that described in patent application EP 0 436 438. In the figure, the lines substantially parallel to the upper and lower parts of the square constitute the equipotentials of the field. It can be seen that in the vicinity of the glass these are slightly deviated.

 In Figure 2, the state of the isotherms is shown after the application of an electric field which provides a power of about 20 kW. The isotherms were plotted while the application of the field had lasted for about a minute. It can be seen that inside the joint, the temperatures range from 660C to 2300C. The temperature of 700C is too low to obtain good gelation and that of 2300C is already at the limit of what can be supported by the plastisol without any degradation being observed.

 In order to obtain a uniform gelation at all points of the joint, an insert was introduced which had a floating potential. It is metallic, in fact the metal is crossed by the electric field only at the surface. However, another material is necessary to support the metal part. We therefore have an insert made of two materials.

 In FIG. 3, the insert embedded in the joint therefore consists of two parts: a square 4 which is made of plastic, for example polytetrafluoroethylene (PTFE), and the metal part 5 which is substituted for PTFE in the height of the square. We can see very clearly in the figure how the field lines are deflected by the metal. Here again we have observed and shown in Figure 4 the isotherms as they appear in the joint with the same field as before after about 1 min. It is seen, this time, that the points at the lowest temperature of the joint approach the temperature of 1000C which is sufficient to already obtain a good solidification of the material of the joint while the highest temperatures do not exceed 2400 C. The effect of the mixed insert of FIG. 3 is therefore to obtain both a deflection of the field to separate it from the zones where there was previously overheating and a concentration in the zones which, until then, were not very heated. This is the case of the lower end 6 of the seal.

 In Figure 5 there is shown an insert which has undergone a slight modification compared to the previous one. We have indeed increased the volume of the area of the right angle of the square in a plastic material such as PTFE.

This material has as permittivity s "a value close to zero and one observes as a consequence a very weak variation of the distribution of the equipotentials. However the consequence is, figure 6, a more homogeneous distribution of the isotherms. The plastic of the square with an almost zero result that, in this area, there is a very low heat dissipation. We can see that areas which were at 1 900C or even 2600C are respectively reduced to 1030C or 151 0C at the end of the same time. There was thus obtained an equipotential dilution effect and an overheating of the material surrounding the zone concerned was avoided.

 The following figures show, as we have seen, another form of seal which is considerably thicker and, consequently, even more difficult to homogenize without the means of the invention.

 In FIG. 7, we see the equipotentials which are practically all parallel and in FIG. 8 the distribution of the isotherms where we see a very hot upper zone at the heart of the material at 2450C, a lower zone also quite hot at around 2220C and the ends of the surface seal which are not hot enough to obtain good gelation. In order to cook this area, an insert is integrated into the joint which heats up faster than the joint itself and thus allows heat to be transmitted to the joint which surrounds it. The equipotentials have not been shown in the case of the insert in question: they are little different from those in FIG. 7.

 In FIG. 9, on the other hand, the isotherms are represented and, this time, we see a very interesting effect of the heat absorbing insert. We see that the temperature differences which went from 600C to 2450C are now reduced from 900C to 1660C. The material of the insert which must heat up more than the material which surrounds it must preferably have an E "larger than that of the joint and / or an E 'smaller than that of the joint. The two sizes which define the behavior of a material with respect to high frequency radiation or microwaves are the relative permittivity E 'and the loss factor E ".

 It is by playing on the relative value of these two quantities compared to the value that they have in the material of the joint that we can make the insert play the three different roles that we described above, the first role being to deflect the field to concentrate the energy in the joint area that we want to heat, the second role being to absorb and / or deflect the field to dilute it in the area which we want to avoid overheating or degradation, the third role finally consists in heating by taking the insert as a heat source or by absorbing the field, in this case E 'of the insert must be less than E' of the joint, or by restoring the heat with E "of the insert larger than E" of the joint.

 Another possibility is that the insert is neutral from the point of view of the field at this time E 'of the insert is equal to E' of the joint and the heat is restored thanks to E "of the insert larger than E "of the joint. Finally we can reflect the field with E 'of the insert greater than E' of the joint and E "of the insert greater than" of the joint or else equal.

Of course the ranges of variation of the two parameters' and "are quite wide, it is difficult to specify values for these constants because, in each case, the values to be chosen depend on the geometries of the different materials as well as on the applied frequency HF or microwave. We could say that preferentially 'and "must differ for the insert and for the joint by at least 5% more or less to obtain a significant result,
A person skilled in the art proceeds by successive approximations (possibly using mathematical simulation methods) to define the value to be retained.

Claims (9)

 1. Glazing, in particular automotive glazing, equipped with a seal obtained by curing under microwave or high frequency radiation, itself equipped with an insert characterized in that the insert modifies the energy supply of said radiation in the material of the joint.  2. Glazing according to claim 1, characterized in that the insert causes the deflection of the radiation, in particular when it comprises an element made of a material whose relative permittivity 'differs from that of the original material of the seal. more than 5% more or less.  3. Glazing according to claim 1, characterized in that the insert causes the absorption of radiation, especially when it comprises an element made of a material whose loss factor "" deviates from that of the original material of the joint by more than 5%.  4. Glazing according to one of the preceding claims, characterized in that the insert is embedded in the material of the seal.  5. Glazing according to claim 4, characterized in that the insert is flush with the surface of the seal.  6. Glazing according to one of claims 1 to 3, characterized in that the insert is placed on the surface of the seal, in particular in the form of an enamelled deposit on the surface of the glass.  7. A method of manufacturing a glazing unit fitted with a seal, in particular an automobile glazing unit, according to one of the preceding claims, characterized in that it comprises the following steps  a) installation of the glazing in a part of a mold which is connected to the surfaces of the glazing and whose internal shape is that to be given to the outside of the joint, the mold being essentially made of a material permeable to HF radiation or microwave,  b) placement inside the mold cavity of an insert capable of modifying the energy supply of high frequency or microwave radiation into the material of the seal, the insert being able to be placed directly at the limits of the cavity, in particular on the surface of the glazing,  c) injection into the cavity of a fluid capable of hardening under the effect of high frequency or microwave radiation,  d) application of high frequency or microwave radiation to the material of the joint,  e) cooling of the joint.  8. Method according to claim 7, characterized in that step b) of the method is carried out, at least in part, before step a), in particular in the case where the insert comprises a layer of material deposited at the glazing surface, such as enamel.  9. Insert intended to equip the seal with glazing, the seal hardening by the action of HF radiation or microwave, characterized in that the insert is located in contact with the seal and is associated with the glazing.