Process and device for depositing a primer or sealer of a programmed shade on any substrate, in particular a vehicle body, comprising the mixture of a neutral base of the primer and a pigmented paste at the moment of deposition.

0001The invention essentially relates to a method and an apparatus for depositing a primer or "Sealer" of programmed shade on any object, in particular a motor vehicle body, comprising the mixture of a neutral base of primer and of one or more pigmented pastes at the time of its deposition on said object.

0002There are already known in the industry, in particular the automobile industry, numerous devices for depositing paint on any object, in particular a bodywork of a motor vehicle.

0003In general, vehicles are "recognized" by computer for finish colors.

0004Various projection devices are used in practice, in particular electrostatic projection devices which may include a bowl-shaped rotating head system. Such devices can be coupled to an automatic shade changer. This set then allows the complete unit to change the colors of the vehicles. In addition, before applying the final color of the vehicle, known as the finish color, in the majority of cases a primer still called "Sealer" is generally applied, of single gray color. However, for a certain number of finishing colors, particularly yellow or red colors, known for their lower opacifying power, the gray primer is not satisfactory and thus contributes to significantly increasing the recycling rate for defects.

0005The use in chain of "false shade" finishes, that is to say shades close to those of finishes, which would allow easier industrialization of finishes with low opacifying power, has hitherto encountered a number of constraints.

0006Indeed, a production site works on average with a palette of 15 to 20 different colors. Thus, in order not to overly complicate the management and the installations, it would be wise to consider 3, 4 or 5 "false shade" primers.

0007However, existing installations generally do not allow the establishment of one or more circulation circuit (s), also called "circulating", additional (s) and the cost of such "circulating", necessary for the introducing new shades of primer on the chain has often been judged to be far too important.

0008In the case of new installation, the additional cost resulting from this choice is prohibitive for the additional equipment to be installed as well as for the storage of the necessary materials and in addition, it has been observed that even in the case of the presence of 3, 4 or 5 "false shade" color primers, there was not sufficient capacity to adapt the color of the primer to the particular finish colors, so that there was still an unacceptable level of recycling for defects, especially if one takes into account the increase in the cost of production resulting from the presence of this plurality of primers as well as several circulatings.

0009The present invention therefore aims to solve the new technical problem consisting in the supply of a solution making it possible to simplify the technology of primers thanks to the use of a single priming requiring a single main circulating which can be adapted on the site to willingness to an appropriate primer shade depending on the particular finish shade.

0010Another object of the invention is to solve the complementary technical problem consisting in limiting product losses linked to the purging operations during color changes. If we used color changers such as those known for finishes.

0011Another object of the present invention is to solve the technical problem consisting in providing a method and an apparatus making it possible to reduce investment costs as much as possible.

0012All these technical problems are satisfactorily resolved for the first time by the present invention.

0013Thus, according to a first aspect, the present invention provides a method for depositing a primer or "Sealer" of programmed shade on any object, in particular a bodywork of a motor vehicle, characterized in that the first preparation is , on the one hand a neutral base of primer and on the other hand at least a mono or polypigmented paste; and mixing said neutral primer base and said pigmented paste to form said primer when it is deposited on said object.

0014According to an advantageous characteristic of the method according to the invention, the dosage of the pigmented paste is carried out which determines the shade of the desired finish.

0015According to another characteristic of the process according to the invention, in which a spraying or spraying of the primer is carried out, said process according to the invention is characterized in that said neutral base and said pigmented paste are brought independently to the device spraying so as to produce the above mixture simultaneously with the spraying or spraying.

0016Thus, if the primer is deposited for example by the technique known as electrostatic deposition, the neutral base and the pigmented paste are independently brought to the electrostatic device which can advantageously be rotating and then include an electrostatic bowl. This supply of the neutral base and of the pigmented paste can be carried out independently substantially up to the level of the projecting surface of the bowl or at the rear of the bowl, allowing mixing at least partially before the projecting surface. According to another characteristic of the process, the procedure is as follows:<ul id="ul0001" list-style="none"><li>a) a classification and distribution into families of all the finish colors is carried out according to their colorimetric characteristics, which are measured by means of a spectrophotocolorimeter, possibly assisted by computer;</li><li>b) determining the average colorimetric values ​​of the shades to be given to the primers for each family so as to determine the formulation of the corresponding pigmented compositions;</li><li>c) the corresponding pigmented pastes are prepared from said compositions;</li><li>d) a neutral primer base having volume pigment concentration values ​​substantially identical to the pigment paste thus chosen is prepared;</li><li>e) the independent supply of the neutral primer base and of the pigmented paste is made to the projection or spraying device on the aforementioned object.</li></ul>

0017The invention also relates, according to a second aspect, to an apparatus for depositing a finish of programmed shade on any object, in particular a bodywork of a motor vehicle, comprising means allowing the deposit of the finish on said object, characterized in that it comprises first means for supplying a neutral base of primer to said means for depositing primer advantageously from a circulator of neutral base connected to a reserve of neutral base; and second means for supplying pigmented paste to said means for depositing primer, independent of said first means for depositing primer, connected to a reserve of pigmented paste; said first means and second means cooperating with the deposition means so as to ensure the mixing of the neutral base with the pigmented paste.

0018On the other hand, in the case where the deposition is carried out by the so-called electrostatic deposition technique, this device comprises an electrostatic deposition device, generally having the shape of a bowl, which is advantageously made to rotate. In this case, the independent supply of the neutral primer base and the pigmented paste independently opens substantially in the vicinity of the projecting surface of the bowl, according to a first embodiment, currently preferred. However, one can also provide an independent supply of the neutral primer base and the pigmented paste at the back of the bowl, for example along its axis.

0019The following advantages are obtained:<ul id="ul0002" list-style="dash"><li>a single circulating of the base primer is used, which represents approximately 70 to 90% of the total primer plus a small reservoir of pigmented paste, representing approximately 10 to 30% of the total of the primer, for each shade desired primer;</li><li>the dose of pigmented paste added at the time of use can be dosed precisely, at will;</li><li>this dose of pigmented paste is programmable at will and therefore allows the use of a programmable controller;</li></ul>    In the simplified version, the ratio neutral base / pigmented paste is fixed 9: 1 for example, and determined practically by the relative surface area of ​​the respective injectors of base and pigmented paste, both supplied by circulations where the pressure is maintained at an identical value.<ul id="ul0003" list-style="dash"><li>the invention has a universal character so that all spraying or spraying devices can be used, as well as all types of paints, whether they have a high solids content, with water or with solvent;</li><li>the mixing of the neutral primer base and the pigmented paste is advantageously carried out at a point as close as possible to the spraying-spraying, which makes it possible to limit the losses of products linked to the purging operations during color changes.</li></ul>

0020The pigmented pastes are prepared in several shades and are delivered selectively from a dispensing means comprising as many lines as there are shades.

0021The stock problem is also solved in important reports since, for example, the use of 4 tinted Sealers no longer roughly corresponds to quadrupling the stock but only increasing it by around 40% compared to using a sealer. single gray.

0022If the power supply of the bases can be programmed, it is therefore easy and quick to change the color on 2 consecutive vehicles.

0023Practical experience on a chain has shown that in the proposed configuration, the change was possible in less than 10 s.

0024Practical tests have shown that with tinted Sealers, it is possible to work in a single layer on interiors, moreover, the rate of reject linked to the lack of covering on the edges is significantly reduced.

0025Manual lacquer operations are also reduced.

0026With feed circuits of the bowl, having sections of injection orifice in a fixed ratio of for example between 1 and 10, the dosing precision is satisfactory and this device makes it possible to do without a more sophisticated system therefore more costly. such as metering pump devices.

0027The first step in implementing the process of the invention consists in selecting the tinted Sealer colors.

0028For this purpose, it is planned to analyze and classify in families all the finish colors by means of a spectrophotometer coupled to a computer. Each shade is defined by three numerical values ​​representing the coordinates of a point in "color space".

0029T is the Tone - value between 0 and 999 describing on a circle the whole range of hues of the spectrum

0030C is Clarity - value between 0 and 99 illustrating the whiteness level on a vertical axis crossing the circle in its center

0031P is Purity - value between 0 and 99, 0 = very degraded shade; 99 = very pure hue, illustrating the degree of saturation. This value corresponds to the radius of Circle T.

Representation of "color space"

0032<img file="EP0263757A2_D0001.tif" />

0033From these values, the closest shades are grouped into families corresponding to a scattering of points.

0034The barycenter, standardized in TCP value, will be the most favorable Sealer shade to receive a given set of finish shades since it is at the center of this dispersion.

0035However, for very light finish colors, it has been shown that clarity C is a determining factor, in which case the reflectance value of the sealer will be adopted at the higher value of the reflectance values ​​of the finishes considered.

0036A computerized Color database makes it possible to physically identify the shade if necessary. From these TCP values ​​and using a computerized color formulation program, it is possible to determine the pigment composition best suited for use in an automotive sealer.

0037The TCP values ​​are given by way of example, any other known color classification system could also be used: Lab, Lab *, XYZ, etc. It is also possible to move the barycenter to take account of the specific problems of certain colors making up the group, in particular their own opacifying power, their popularity, their recycling rate for which these colors are responsible.

0038This operation also makes it possible to fix the number and the color of the tinted Sealers to be used.

0039Other objects, characteristics and advantages of the invention will appear clearly in the light of the explanatory description which follows, made with reference to the appended drawings, in which:<ul id="ul0004" list-style="dash"><li>FIG. 1 represents a sectional view of a projection or spraying device for electrostatic deposition, of the rotating bowl type comprising supply means independent of the neutral base and of the pigmented paste, ending substantially at the level of the rotating bowl so as to mix them on the rotating bowl;</li><li>FIG. 2 represents a second embodiment of an apparatus according to the invention according to which the mixing of the neutral primer base and the pigmented paste is carried out at the rear of the rotating bowl by an axial injection.</li></ul>

0040With reference to FIG. 1, an apparatus for depositing a programmed tint primer on any object, in particular a motor vehicle body, comprises means represented by the general reference number 1 enabling the primer to be deposited on the object.

0041According to the invention, this device comprises first means 2 for supplying a neutral primer base by means of primer deposition, from a circulator (not shown) of neutral base connected to a reserve of neutral base (also not shown), and second means 4 for supplying pigmented paste, independent of the first means 2, connected to a reserve of pigmented paste (not shown) the first means 2 and the second means 4 cooperating with the deposition means 1 so as to mix the neutral base with the pigmented paste in an appropriate manner, equivalent to a conventional preliminary preparation of a primer of predetermined shade.

0042According to the embodiment shown in Figure 1, which is currently preferred, the deposition apparatus is constituted by an electrostatic deposition apparatus comprising a rotating bowl 6 rotatably mounted on a drive shaft 8 driven in rotation by conventional means , well known to those skilled in the art. More specifically, the rotating bowl 6 comprises a central part 10 fixed to the rotating shaft 8 and a peripheral envelope 12 of substantially frustoconical shape projecting on either side of the central part 10 which has an apparent surface 14 in the form of a disc. substantially planar. At the junction of the central part 10 and the peripheral part 12, one or more orifices 16, 18 are provided allowing the primer to pass in the vicinity of the internal surface 20 of the envelope 12, and which constitutes the projection surface of the rotating bowl.

0043It is easily understood that the first means 2 and the second means 4 respectively comprise a first conduit 5 and a second conduit 7 ending in the receiving cavity 22 defined between the rear frustoconical part 12a of the casing 12 and the central part 10 of the bowl turning 6.

0044It will be noted that the conduit 5 intended to bring the neutral primer base is of a larger cross section than the conduit 7 intended to bring the pigmented paste, due to the differences in flow rate, the pigmented paste generally constituting only approximately the tenth and the neutral base nine-tenths of the primer. Advantageously, the conduits 5 and 7 open into the cavity 22 through a calibrated orifice 24, 26 respectively. On the other hand, injection devices 28, 30 are provided respectively allowing an unlimited, programmable dosage of the neutral base and especially of the pigmented paste.

0045During operation, it is clear that the mixing of the neutral primer base and the pigmented paste takes place in the cavity 22 and during projection by the rotating bowl.

0046The invention is particularly suitable for electrostatic type deposition, although other deposition techniques can be used without limitation.

0047Referring to Figure 2, there is shown an alternative embodiment for axial injection. The same reference numbers as those in FIG. 1 were used, increased by 100 to designate the parts of identical function.

0048In this alternative embodiment, the mixing of the neutral base and the pigment paste takes place at the rear of the rotating bowl 106, the independent conduits of neutral base of primer 105 and of pigment paste 107 ending in a common axial conduit 109 opening out inside the rotating bowl 106, which makes it possible to show that the invention is not limited to a particular mixing mode, but that on the contrary a large number of variant embodiments is possible. Thus, the invention includes all the means constituting technical equivalents of the means described as well as their various combinations.

0049Static mixers (knuckle tube for example) or dynamic mixers (mixing turbine for example) can be placed upstream of the head of the projector but practical tests have demonstrated their uselessness.

0050In the present description and the claims, the terms "neutral primer base" denote in particular a base of substantially neutral color obtained with the use of a zero or small quantity of pigments but which may contain a very large quantity of fillers which do not have no opacifying power, like talc, kaolin, baryte sulfate, etc. The addition of fillers makes it possible to achieve identical or similar pigment volume concentration values ​​between the so-called neutral primer base and the pigmented paste. On the other hand, the two components of the sealer are formulated with identical resin scales, which results in a great compatibility of the two components allowing an easy and rapid mixing and the constant maintenance of all the properties of the final product even in case variations in dosage ratios.

0051A cosmetic gravel test was carried out and evaluated by spectrophotocolorimetric measurement.

0052We proceed to the graveling of a painting system. This gravel reveals a given area of ​​generally gray sealer. The revelation of this color contrast can be appreciated by measuring the change in color between the gravel zone and the non-gravel zone.

0053By replacing the conventional gray sealer with the "false shade" sealer considered, produced according to the invention, the same measurements can be made, the comparison of the results showing the improvement factor obtained by the invention. (See table).<tables id="tabl0001" num="0001"><img file="EP0263757A2_D0002.tif" /></tables>