DE19934995A1 - Procedure for seam sealing - Google Patents

Abstract

There is a new method for sealing body sections, in particular for the seam sealing (5) of vehicle attachments, such as. B. of doors, tailgates or bonnets or sunroof covers described. The method according to the invention is based on a double pre-crosslinking (6, 8) of the sealing compound (5) in the body shell. In a first step, the surface of a UV-active sealing compound (5) is pre-crosslinked (6) by UV radiation, and in a second, immediately following step, the seamed adhesive (4) and the sealing compound (5) are hardened by thermal action ( 8th). The add-on parts produced by the method according to the invention are transportable and, after passing through the cleaning baths and after heat curing in the KTL furnace, have an optically and functionally perfect quality. Since the sealing is not carried out in the painting process, as is the case today, but in the body shell, the method according to the invention contains considerable savings potential.

Description

The invention relates to a method for seam sealing according to the preamble of claim 1 or 4.

When flanging seam sealing in motor vehicle construction is usually carried out according to the outside area of the fold a curable material, in particular in the form of a Caterpillar placed in a first curing process, for example inductive heating of the sheet in the area of the hardenable mass, gelled and in a downstream Hardening process, especially the KTL furnace, is fully cured. As hardenable mass is used here in particular PVC.

This procedure creates problems when the curable material contains air pockets covered or absorbed liquids or gases before final hardening, which expand during the subsequent hardening of the furnace and bubbles which are visible from the outside form. These bubbles disturb the optics (optical losses) and form other vulnerabilities of the seal against corrosive attacks.

In an alternative manufacturing in the manufacture of vehicle attachments, e.g. B. from Doors, tailgates and bonnets, sunroof covers etc. become two sheet metal parts connected. In the bodyshell, an oiled adhesive is applied first Metal sheet, mostly consisting of steel, hot-dip galvanized or electro-galvanized Steel or aluminum, generally along the edge of the outer part Vortex spray process (or Swirl) applied in a layer thickness of approx. 0.2 mm and after inserting the inner part, the outer edge of the outer part is around the Flanged periphery of the inner part. The corrosion-prone edge of the outer part is then only in the painting process mostly by hand with a sealant such. B. PVC plastisols, sealed. From production-related, qualitative and economic For reasons there is a desire to seal the seams from the painting process remove and move back to the body shell, d. that is to use the described method. In other words, in the painting process  no applications take place that affect the paint surface in any way could. To date, this wish has not yet been satisfactorily fulfilled leave, since no safe and economical process concept for this task is available.

DE 33 14 896 A1 describes an adhesive for seam sealing. which is pre-crosslinked by means of ultraviolet (UV) radiation and thermally after in the oven Pass through the cleaning baths at temperatures around 180 ° C together with the KTL primer (KTL = cathodic dip coating), is fully cured. In addition to the advantages of UV radiation, it has the disadvantage that the effect and thus networking is only possible from the outside in. For larger ones Layer thicknesses of more than 0.3 mm is also sufficient for pre-crosslinking longer exposure time is no longer guaranteed and the ones below Layers remain uncrosslinked in the pasty state. This pasty, under the Pre-crosslinked surface layer contains significant negative effects on the optical quality of the seal. First, because some of the components transported manually, this means that the adhesive is touchable, However, it is not easy to grasp, which leads to a visual loss of fingerprints can. Secondly, there is a risk that this uncrosslinked material will be used in thermal curing in the KTL furnace due to the between the crimp seam bonding and air enclosed in the seal is expressed on the side of the seal thirdly, this paste-like material turns again during the subsequent cooling pulled into the hem and fourthly, adhesives tend to, especially in uncrosslinked state to absorb moisture, which in the thermal Exposure to the KTL furnace leads to blistering. This one described above Circumstance is important in that it is for economic reasons it is desirable to have the components finished at a central location, i. H. including the Sealing, manufacture and from there external, even distant worldwide Forwarding production lines where they go directly to the cleaning baths - the first section of the painting process - arrive. This includes considerable savings potential because with the external production lines on a body shell and on the in Painting process undesirable sealing can be dispensed with anyway. Moreover should be the new procedure for sealing without major financial expense and can be perfectly integrated into existing production processes in the body shop. The An creating another furnace would be absolutely unacceptable.

The object of the invention is to carry out a seam sealing such that a bubble formation by trapped gases or liquids in the later Furnace treatment is suppressed or good handling of the sealed parts in the Overall process is guaranteed.

This object is achieved with the measures according to claim 1, 4, 6 and / or 8. The Subclaims show preferred embodiments.

The present invention relates to a special method for the production of Vehicle attachments, in particular the invention relates to a new method for seam sealing. With the new process, the manufacturing process significantly simplified and the quality increased.

The aim of the present invention was to overcome the disadvantages of the prior art overcome and to provide a new method for seam sealing which meets all requirements for the safe manufacture of attachments and especially for a worldwide transport of the raw or oiled attachments, also known as parts tourism. The optical quality of the Folded seam sealing in the foreground, even after a long transport the add-on parts remain impeccable due to different climatic zones and a smooth Guaranteed surface without craters, cracks etc. The new process can be done without introduce larger investments in the body shell, and with the new Processes can gain significant manufacturing advantages.

According to the present invention, the sealing is hardened according to the a variant (also) by means of a photochemical reaction caused by light, especially UV light, is combined with multi-stage curing. Each depending on the type of sealing, the UV light has a penetration depth of approx. 0.01 to 1 mm, see above that a surface hardening of the seal is achieved. A deeper penetration of the UV radiation is also possible. The surface sealed in this way is protected against this Penetration of gases or liquids in the seal, so that one no bubbles are thrown up later during thermal hardening. It is also through the already existing surface hardening an escape of already enclosed gases suppressed to prevented during thermal curing.  

The photochemical curing is advantageously carried out in such a way that in the subsequent thermal curing of the already photochemically hardened area of the mass through the thermal curing is post-cured, d. H. that functional groups for both photochemical as well as for thermal curing side by side, the successively brought to the crosslinking (reaction) causing the hardening. This creates a particularly stable surface for the sealing compound.

It applies to all process variants that a seal can also be used, whose hardening is exothermic, which means that the hardening process initiated at least partly continued and correspondingly more advanced curing is achieved.

In an alternative embodiment, at least two are not according to the invention similar hardening processes before coating the sealed Body section performed. Preferably one of the curing processes is based on the turned off the outer surface of the seal and the other curing process on the Contact area of the seal to the body section. This ensures that the seal in the course of the coating process, especially one this upstream liquid cleaning (especially by means of an aqueous solution) or in a (aqueous) dip coating, for example KTL, no liquid absorbs the during a later thermal curing (e.g. in the KTL furnace) Blistering leads.

In a further alternative variant, the thermal curing takes place in at least one first stage oven-free or by only partially heating the with the seal provided body section. This results in an overall favorable process flow achieved by a sufficient hardening against later blistering without great Process effort is integrated into the overall process.

In a further alternative embodiment of the invention, the method is as follows carried out that the two not similar hardening processes in a temporal Interval of less than 2 hours. This will create a sufficient curing of the seal is achieved without this a significant amount of gases or liquids that can lead to the problems described above, can record. The time interval is advantageously less than one hour,  preferably less than 20 minutes and in particular less than 5 minutes, d. i.e., the both hardening processes advantageously take place simultaneously or (directly) successively, without another intermediate process step.

According to the invention, all alternative processes can advantageously be combined with one another.

The methods according to the invention are based on at least two (Pre) networking of the seams. In a first Production step for the UV-active sealing compound by means of UV radiation Reaction brought and in a second immediately following station is advantageous both the crimp seam adhesive and the internal sealing by thermal Warming (pre) networked.

External hardening by means of UV radiation partially crosslinks the Fold seam sealing and, firstly, brings about an important one for manual handling Touchability or grip, secondly, a wash-out resistance to the up to 70 ° C are hot, circulating liquids in the Cleaning baths for degreasing the oiled body, phosphating and the Passage through the cathodic immersion bath (KTL) and third because of the advanced networking a long period of exposure to the open, sometimes even in hot, humid conditions climatic conditions of more than 3 weeks. The open lay time defines the time within which the adhesive fulfills the specified function and no loss of quality after complete curing in the KTL furnace, which is at temperatures around 180 ° C done within about 25 minutes. The adhesive generally tends to do so in the not 100% cross-linked state to absorb water, which increases with heat curing Blistering leads and negatively affect both the appearance and strength can.

For the component of the adhesive that crosslinks with UV radiation, activated double bonds, such as. B. compounds containing acrylate groups, in question, the triggering of the radical polymer reaction via a photoinitiator - a radical initiator initiated with UV rays - takes place. Depending on the photoinitiator, the optimal wavelength is in the range of 200 to 400 nm. In order to obtain a satisfactory result with regard to grip strength, etc., an irradiation time of less than 30 s, in particular less than 5 s, with an intensity of in particular 0.001 to 50 watts / cm ² suitable. This enables a rational process in which, for. B. the UV radiation can be carried out directly after the application of the seal in the same step using a robot. The UV lamp is advantageously located behind the application nozzle for sealing.

The thermal hardening from the inside partially cross-links the seam and the -sealing and causes a positional stability, which is a displacement of the two Sheet metal parts, d. H. Inner part to outer part, excludes each other. As thermal sources come z. B. induction, infrared (IR) radiation, hot air dryer etc. in question. In case of IR radiation can be an expensive investment for an induction system can be dispensed with, but is not as efficient as inductive heating.

With the invention it was found that the double-stage hardening without complete hardening for sufficient positional stability of the attachments is sufficient, since the seal hardened with UV radiation also contributes to structural strength. It is also conceivable to switch the IR lamps directly after the UV Tracking radiation with the robot. For a perfect quality of the Sealing surface, it is advantageous if the UV radiation before the thermal Loading takes place. This ensures that, if applicable, between the Flaring seam bonding and sealing existing air during thermal Heating is held back by the UV pre-crosslinked sealing surface.

In addition, in a preferred embodiment, that induced with UV radiation Reaction can be accelerated by the sealing compound z. B. on temperatures is heated to 60 ° C. This can be done in that the to be applied Sealing compound itself and / or the crimp fold shortly before the application of the Sealing compound z. B. is heated by means of a hot air dryer and / or inductively, so that the then preheat the applied sealant.

In particular, heating by means of IR or a hot-air dryer is advantageous, since it does so the risk of warping of the components is significantly reduced or eliminated as this are less thermally stressed, as z. B. in the inductive heating of Case is.  

An optical loss is due to air pockets in the flare between the Bonding and sealing greatly reduced, since the adhesive with the double Pre-crosslinking builds up a sufficiently high strength in a short time and thus both Air gaps when heated in the KTL furnace as well as the pulling in of glue material in the flare prevented during cooling.

Since the sealing is not done by hand in the paint shop as it is today, but in the body shop using robots to save material and therefore more economical resources, such as space and time required in the paint shop, can be saved become.

The method according to the invention includes property advantages, such as good ones Handling and positional stability as well as long open time, thus fulfills all Demands for safe transport both internally and externally and overcome the disadvantages of the prior art, where the quality due to bubbles education is reduced. The advantages according to the invention allow a central one Manufacturing of components such as B. of doors, tailgates and bonnets, sunroof lids etc., and their dispatch to external production lines. This parts tourism will also known as CKD (= completely knocked down) and is economical because of it Investments for the production of the body shell can be dispensed with.

The seamed adhesive is intended for optimal processing in thin layers be applicable and have good oil wetting. After heat curing in the KTL- Oven is a good and aging-resistant adhesion to the metallic substrates, a strength of more than 15 MPa and an elongation at break of at least 5% required.

The same adhesive can be used for sealing, but then this Contains components in the best design with both UV radiation can also be reacted thermally. Furthermore, the Elongation at break is at least 15%, better 30%, in the thermal Tensions not risking cracking.

The adhesives described above are usually based on the epoxy Technology, rubber technology or acrylate technology etc. and also in  Combination with suitable polyurethane components or organic polymer fillers formulated. DE 33 14 896 A1 provides some examples, to which also reference is made in particular to the reaction conditions.

The sealing is advantageously applied in a thickness of 150-4000 µm, especially in the range of 350-1000 µm. Preferably the seal is in shape a caterpillar applied, the caterpillar application z. B. can be done as a swirl.

Light-induced curing, in particular by means of UV light, can advantageously be carried out immediately after applying the seal, preferably at the latest a few minutes after the order. The UV radiation can be carried out simultaneously, before or later with one further hardening is carried out, in particular IR, hot air dryer or induction hardening, in which the sheet metal areas to be sealed or immediately adjacent sheet metal areas be heated.

Depending on the seal used, care should be taken that in particular with a insufficient exothermic curing may not occur if the hardening process is not carried out with sufficient intensity. For Ensuring the success of the hardening process is accordingly with a sufficient intensity of the parameters causing the hardening (UV light, heat, etc.) to work.

Sealing with a material in which the Minimum curing temperature is set to, for example, ≦ 140 ° C, whereby in particular induction hardening is possible. The commonly used Epoxy resins with a required hardening temperature of = 150 ° C, in particular = 170 ° C, are less suitable here. However, such epoxies can be found inside the fold can be used, as this will later be easily cured in the KTL furnace.

The invention is described below with reference to two drawings.

Show it

Figure 1 is a section through a door rebate with applied sealing. and

Fig. 2 shows a section through a door rebate with a possible sealing problem.

Fig. 1 shows an outer door panel 3 , which is folded over an inner door panel 2 and is connected in the area of the fold 1 with a flange seam adhesive 4 . The flange seam adhesive 4 is applied before folding and is dimensioned in such a quantity that it fills the entire seam area at a distance a (inner door panel 2 - seam bend). Over the outer fold area, a seal 5 is applied, which is pre-crosslinked by UV radiation from the outside 6 and by inductive heating of the fold area 1 from below 8 to the extent that it is easy to grip, tight against inflating gases and tight against the penetration of gases or liquids is.

In Fig. 2 the same fold 1 is shown as in Fig. 1, but with a displacement b of the door inner panel 2 with respect to the door outer panel 3 , so that the amount of beaded adhesive 4 introduced does not completely fill the fold. As a result, an overlap with the seal 5 can enclose an air bubble 7 , which expands in the KTL furnace during the previously carried out curing processes and inflates the seal 5 . In the method according to the invention, however, the seal 5 is double-6, 8 pre-hardened, so that the enclosed air bubble 7 can no longer break through in a later final hardening in the KTL furnace.

Reference list

1

Door rebate

2nd

Inner sheet

3rd

Outer sheet

4th

Crimp fold adhesive

5

Sealant

6

UV-hardened surface

7

Trapped air

8th

thermal curing
a to b sheet displacement

Claims (16)

1. A method for sealing a body section by applying a sealing compound to the body section and hardening the sealing compound by means of at least two different hardening processes, one of the hardening processes including a photochemical and another a thermal hardening, characterized in that the thermal hardening is carried out in several stages. 2. The method according to claim 1, characterized in that the photochemical Hardening and / or the first stage of thermal hardening before coating or wetting the body section. 3. The method according to claim 2, characterized in that the partial hardening before painting the body section. 4. Method of sealing a body section by applying one Sealing compound on the body section and hardening of the Sealing compound, characterized in that the sealing compound by means of two not identical hardening processes is hardened, which before one Coating or wetting of the body section, in particular one Painting can be done. 5. The method according to claim 4, characterized in that one of the Hardening processes especially the outer surface of the sealer hardens and the other hardening process either in particular the contact area of the Sealing with the body section or inner areas of the seal hardens. 6. The method according to any one of the preceding claims, characterized in that that the thermal hardening by only partially heating the  Body section and / or at least in a first stage is oven-free, in particular by inductive heating, IR radiation and / or a hot air dryer. 7. Method of sealing a body section by applying one Sealing compound on the body section and hardening of the Sealing compound by means of at least two non-similar types Hardening processes, one of the hardening processes being a photochemical and a further includes thermal curing, characterized in that the thermal hardening due to only partial heating of the body section and / or at least in a first stage is oven-free, in particular by inductive heating, IR radiation and / or hot air dryer. 8. The method according to any one of the preceding claims, characterized in that the not similar hardening processes at a time interval of be done in less than two hours. 9. Method of sealing a body section by applying one Sealing compound on the body section and hardening of the Sealing compound, characterized in that the sealing compound by means of two different hardening processes, which are hardened in one time Interval of less than two hours. 10. The method according to claim 8 or 9, characterized in that the Hardening processes at intervals of less than one hour, in particular less than 20 minutes and preferably at a distance of less than 5 minutes. 11. The method according to any one of the preceding claims, characterized in that that the hardening processes are selected from an oven hardening, inductive Hardening, hardening by means of a hot air dryer, photochemical hardening, reactive Post-curing without special energy supply. 12. The method according to any one of the preceding claims, characterized in that that the non-similar hardening processes at least to a surface hardness the sealing compound for a touchability or grip for a manual  Handling are carried out and / or to a wash-out resistance with Up to 70 ° C hot, circulating cleaning baths for degreasing oiled Body parts, phosphating and / or electronic dip painting and / or an open lay time under tropical climatic conditions of more than three weeks. 13. The method according to any one of the preceding claims, characterized in that that one of the first curing processes is carried out until the seal at least one strength, especially in the contact area with the Body section that has optical losses in the further process sequence due to air pockets between the bond and the seal are reduced. 14. The method according to any one of the preceding claims, characterized in that that the sealing compound to accelerate the by means of UV radiation induced pre-crosslinking heated via the thermally preheated crimp fold becomes. 15. The method according to claim 14, characterized in that the thermal Warming up the flare with a hot air dryer shortly before applying the Sealing compound takes place. 16. The method according to any one of the preceding claims, characterized in that the body rebate sealing with UV rays as well can also be thermally pre-cured together with the flange seam gluing, so manufactured attachments are transported and then, after passage through at least one cleaning bath and painting, especially without optical or functional loss of the seal, in the oven together with the paint be fully thermally hardened.