MIXTURE COMPLETING AN ADHESIVE AND A WAX-BASED FILLER

Abstract

The present invention relates to a mixture comprising an adhesive and a wax-based filler, the wax being in the form of fibers and / or fiber bundles forming one or more bulk structures, a method for producing such a mixture, and its use in vehicle construction. Furthermore, the present invention relates to the use of a wax-based filler, in which the wax is in the form of fibers and / or fiber bundles forming one or more bulk structures, as an adsorbent in adhesives.

Description

[0001] The present invention relates to a mixture comprising an adhesive and a wax-based filler, the wax being in the form of fibers and / or fiber bundles forming one or more bulk structures, a method for producing such a mixture, and its use in vehicle construction. Furthermore, the present invention relates to the use of a wax-based filler, in which the wax is in the form of fibers and / or fiber bundles forming one or more bulk structures, as an adsorbent in adhesives.

[0002] In the automotive industry, bonding has become a key technology and is gaining increasing importance. The number of components bonded together instead of welded is constantly rising. Bonding components not only makes it possible to significantly reduce vehicle weight, but it has also become a safety factor, as vehicles with primarily bonded components often receive better crash test ratings than vehicles consisting mainly of welded components.

[0003] To meet the diverse requirements for bonding the various components of a vehicle, a range of optimized adhesives have been developed, such as body adhesives, windshield adhesives, and surface adhesives. All these adhesives are applied differently and must meet different end-use requirements, necessitating the use of different adhesive types.

[0004] For example, automotive body adhesives are typically applied before cathodic dip painting and must pass through the process undamaged, as well as withstand the high temperatures during the drying of the dip coating. Adhesive runoff is just as undesirable as flowing out of already bonded areas. High washout resistance is essential, especially since very high forces can occur when passing close to nozzles during the dip process.

[0005] In this context, there is a need for adhesives that can be used in car body construction and, above all, exhibit high corrosion and moisture resistance as well as good compatibility with the process oils used in car body construction, such as drawing, forming, and corrosion protection oils. It is therefore the object of the present invention to provide such an adhesive.

[0006] It was surprisingly found that this task can be solved by a mixture which, in addition to an adhesive, contains a filler with adsorbing properties based on wax.

[0007] A first object of the present invention is therefore a mixture containing an adhesive and a filler based on wax, wherein the wax is in the form of fibers and / or fiber bundles which form one or more volume structures among themselves.

[0008] The addition of the filler significantly improved the corrosion and moisture resistance of various adhesives. Furthermore, the mixture demonstrated good compatibility with substances commonly used in the automotive industry, allowing it to be used in combination with a range of different oils and substrates.

[0009] The wax-based filler is in the form of fibers and / or fiber bundles that form one or more bulk structures. Within the scope of the present invention, a bulk structure is understood to be a structure of fibers and / or fiber bundles formed by the adhesion of the fibers and / or fiber bundles to one another. This is a three-dimensional, disordered network in which at least 80% of the fibers and / or fiber bundles are randomly intermeshed, and the bulk structure may contain air inclusions.

[0010] The filler used in the mixture according to the invention is preferably an adsorbent, in particular an adsorbent for hydrophobic substances. It was surprisingly found that the addition of an adsorbent improved the corrosion and moisture resistance of the mixture.

[0011] The filler used in the mixture according to the invention is a wax-based filler. For the purposes of this invention, "wax" refers to organic compounds that are solid at room temperature and form a low-viscosity liquid above their melting point. Within the scope of this invention, the wax forming the basis for the filler is preferably selected from the group consisting of natural and synthetic waxes. In a particularly preferred embodiment, the wax is selected from the group consisting of synthetic waxes, in particular polyethylene wax, polypropylene wax, polyethylene-polypropylene copolymer wax, and mixtures thereof. In an alternatively preferred embodiment, the wax is selected from the group consisting of natural waxes, in particular montan wax, carnauba wax, beeswax, and candelilla wax.

[0012] It was surprisingly found that the adsorption properties of the filler in the mixture according to the invention could be significantly improved when waxes with a specific molecular weight were used, particularly those with a molecular weight of no more than 15,000 g / mol. Therefore, an embodiment is preferred in which the wax has a number-average molecular weight of less than 15,000 g / mol, particularly preferably 200 to 11,000 g / mol. The molecular weight of the wax can be determined, for example, by GPC.

[0013] The mixture according to the invention is particularly distinguished by its high moisture resistance. Without being bound to any specific theory, it is assumed that this is primarily due to the presence of the filler, which is in the form of a bulk structure formed by fibers and / or fiber bundles. It has proven particularly advantageous to use fibers produced by melt spinning for the formation of this bulk structure. Therefore, an embodiment of the present invention is preferred in which the fibers forming the bulk structure of the filler in the mixture according to the invention are produced by melt spinning followed by atomization.

[0014] The filler contained in the mixture according to the invention is in the form of a bulk structure composed of fibers and / or fiber bundles. There are no particular requirements regarding the length of the fibers and / or fiber bundles. Rather, fibers and / or fiber bundles with lengths ranging from a few millimeters to several meters can be used, with the use of fibers and / or fiber bundles of different lengths being preferred. Furthermore, it has proven advantageous to use fibers and / or fiber bundles of different diameters, with the fibers and / or fiber bundles preferably having a diameter of 20 nm to 5 mm, and particularly preferably 50 nm to 2 mm.

[0015] In a preferred embodiment, the mixture according to the invention has a proportion of 0.1 to 30 wt.%, preferably 0.5 to 10 wt.% of the filler, in each case based on the total weight of the mixture.

[0016] It was surprisingly discovered within the scope of the present invention that a number of different adhesives can be used in the mixture according to the invention. In a preferred embodiment, the adhesive contained in the mixture according to the invention is therefore selected from the group consisting of rubber adhesives, polyurethane adhesives, acrylate adhesives, epoxy adhesives, adhesives based on EVA (ethylene-vinyl acetate) polymers, and adhesives based on silane-modified polymers.

[0017] The mixture according to the invention can contain further components, such as additional fillers like calcium carbonate, and / or further polymeric additives. In a preferred embodiment, the mixture according to the invention further comprises a homopolymer based on polyunsaturated C4 to C14 alkyl chains. In a particularly preferred embodiment, the mixture according to the invention further comprises polybutadiene, preferably in an amount of 5 to 25 wt.%, particularly preferably 10 to 20 wt.%, in each case based on the total weight of the mixture.

[0018] The form in which the mixture according to the invention is present can be adapted depending on the field of application. In some applications, it may be desirable for the mixture to be in the form of a paste or liquid so that it can be easily applied to a substrate. Therefore, the mixture according to the invention is preferably in liquid, solid, or paste form.

[0019] The mixtures described in the prior art may have the disadvantage, among others, that they are only compatible with a limited number of substances used in the manufacture of automobiles, thus limiting their use. In contrast, the mixture according to the invention exhibits good compatibility with common substances used in the automotive industry and can be used in a range of applications, with further modifications possible for the respective application. Therefore, the mixtures can also be used when the substrate has been treated with oil and / or lubricant.Oil and / or lubricant on the surface of the substrate, wherein the oil and / or lubricant may be selected from the group consisting of natural and synthetic oils and natural and synthetic lubricants, in particular drawing oils, molding oils, corrosion protection oils and dry lubricants.

[0020] A further object of the present invention is a method for producing the mixture according to the invention. The method according to the invention comprises the steps of providing an adhesive and a filler based on wax, wherein the wax is in the form of fibers and / or fiber bundles that form one or more bulk structures among themselves, and mixing the adhesive and the filler. Depending on the consistency of the adhesive, the mixing can be carried out, for example, by means of horizontal kneaders or in stirring vessels.

[0021] The good compatibility of the mixture according to the invention with other substances allows its use in a wide variety of applications. Surprisingly, however, the mixture has proven to be particularly suitable for use in vehicle manufacturing. Therefore, a further object of the present invention is the use of the mixture according to the invention in vehicle manufacturing. In a preferred embodiment, the mixture according to the invention is used in car body construction.

[0022] Another object of the present invention is the use of a wax-based filler, wherein the wax is in the form of fibers and / or fiber bundles forming one or more volume structures among themselves, as an adsorbent for hydrophobic substances in adhesives.

[0023] The present invention will be explained in more detail by means of the following examples, which, however, are in no way to be understood as a limitation of the inventive concept. Examples:

[0024] A mixture according to the invention was produced by mixing solid rubber, polybutadiene, calcium carbonate and a suitable wax-based filler together.

[0025] Suitable wax-based fillers are described, for example, in the publication EP 2 392 630, to which explicit reference is made here, and are commercially available under the trade name Deurex PURE from Deurex AG, Germany.

[0026] Moisture and corrosion resistance was tested under various conditions using the following substrates: EGS: Electro-galvanized steel outer skin (e.g., DX54D+ZE75 / 75, thickness ≥0.8 mm) HDG: Hot-dip galvanized steel outer skin (e.g., DX54D +Z100, thickness ≥0.8 mm) ALU: Aluminum (e.g., Al6-OUT Surfalex, thickness ≥0.8 mm)

[0027] The bond between the substrates was tested after the specified time: ++: very good +: good ○: satisfactory Folding seam adhesives

[0028] Table 1: Substrate: EGS / HDG mixed bonding Storage conditions 23 °C / 80% RH* 40 °C / 100% RH* Storage duration (weeks) 1 2 3 4 5 1 2 3 4 5 Without pre-hardening ++ ++ ++ ++ ++ ++ ++ ++ + + After 15 minutes at 160 °C ++ ++ ++ ++ ++ ++ + + ○ ○ After KTL oven curing (without pre-curing) ++ ++ ++ ++ ++ + + ○ ○ ○ Table 2: Substrate: ALU / ALU Storage conditions 23 °C / 80% RH* 40 °C / 100% RH* Storage duration (weeks) 1 2 3 4 5 1 2 3 4 5 Without pre-hardening ++ ++ ++ ++ ++ ++ ++ ++ + + After 15 minutes at 160 °C ++ ++ ++ ++ ++ ++ ++ ++ ○ ○ After KTL oven curing (without pre-curing) ++ ++ ++ ++ ++ ++ + + ○ ○ Lining adhesives

[0029] Table 3: Substrate: EGS / HDG mixed bonding Storage conditions 23 °C / 80% RH* 40°C / 100% RH* Storage duration (weeks) 1 2 3 4 5 1 2 3 4 5 Without pre-hardening ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ After 15 minutes at 160 °C ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ After KTL oven curing (without pre-curing) ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ Table 4: Substrate: ALU / ALU Storage conditions 23 °C / 80% RH* 40°C / 100% RH* Storage duration (weeks) 1 2 3 4 5 1 2 3 4 5 Without pre-hardening ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ After 15 minutes at 160 °C ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ After KTL oven curing (without pre-curing) ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ *) relative humidity

[0030] As can be seen from the data summarized in Tables 1 to 4, the mixture according to the invention has excellent moisture resistance and still shows excellent bonding properties even after 5 weeks under storage conditions of 40°C and 100% relative humidity.

[0031] For comparison, the results of the same mixture without a wax-based filler are shown below: Folding seam adhesives

[0032] Table 5: Substrate: EGS / HDG mixed bonding Storage conditions 23 °C / 80% RH* 40 °C / 100% RH* Storage duration (weeks) 1 2 3 4 5 1 2 3 4 5 Without pre-hardening ++ + ○ - - ++ + ○ - - After 15 minutes at 160 °C ++ + ○ - - + ○ - - - After KTL oven curing (without pre-curing) + ○ - - - ○ - - - - Table 6: Substrate: ALU / ALU Storage conditions 23 °C / 80% RH* 40 °C / 100% RH* Storage duration (weeks) 1 2 3 4 5 1 2 3 4 5 Without pre-hardening ++ + ○ - - ++ + ○ - - After 15 minutes at 160°C ++ + ○ - - + ○ - - - After KTL oven curing (without pre-curing) + ○ - - - ○ - - - - Lining adhesives

[0033] Table 7: Substrate: EGS / HDG mixed bonding Storage conditions 23 °C / 80% RH* 40°C / 100% RH* Storage duration (weeks) 1 2 3 4 5 1 2 3 4 5 Without pre-hardening ++ ++ + ○ - ++ + ○ ○ - After 15 minutes at 160 °C ++ + + ○ - + ○ - - - After KTL oven curing (without pre-curing) + + ○ - - + ○ - - - Table 8: Substrate: ALU / ALU Storage conditions 23 °C / 80% RH* 40°C / 100% RH* Storage duration (weeks) 1 2 3 4 5 1 2 3 4 5 Without pre-hardening ++ ++ + ○ - ++ + ○ ○ - After 15 minutes at 160 °C ++ + + ○ - + ○ - - - After KTL oven curing (without pre-curing) + + ○ - - + ○ - - -

[0034] As can be seen from the comparison of the data from Tables 1 to 4 with those from Tables 5 to 8, the mixture according to the invention exhibits significantly improved moisture resistance.

Claims

1. Mixture comprising an adhesive and a wax-based filler, characterized by the fact that the wax is present in the form of fibers and / or fiber bundles that form one or more volume structures among themselves.

2. Mixture according to claim 1, characterized by the fact that The filler is a filler for hydrophobic substances.

3. Mixture according to at least one of the preceding claims, characterized by the fact that The wax is selected from the group consisting of natural and synthetic waxes.

4. Mixture according to claim 3, characterized by the fact that The wax is selected from the group consisting of polyethylene wax, polypropylene wax, polyethylene-polypropylene copolymer wax and mixtures thereof.

5. Mixture according to claim 3, characterized by the fact that The wax is selected from the group consisting of montan wax, carnauba wax, beeswax and candelilla wax.

6. Mixture according to at least one of the preceding claims, characterized by the fact that The wax has a number-average molecular weight of no more than 15,000 g / mol, preferably of 200 to 11,000 g / mol, determined by GPC.

7. Mixture according to at least one of the preceding claims, characterized by the fact that The fibers are produced using melt spinning and subsequent atomization.

8. Mixture according to at least one of the preceding claims, characterized by the fact that the filler is present in an amount of 0.1 to 30 wt.%, preferably 0.5 to 10 wt.%, in each case based on the total weight of the mixture.

9. Mixture according to at least one of the preceding claims, characterized by the fact that The adhesive is selected from the group consisting of rubber adhesives, polyurethane adhesives, acrylate adhesives, epoxy adhesives, adhesives based on EVA (ethylene vinyl acetate) polymers and adhesives based on silane-modified polymers.

10. Mixture according to at least one of the preceding claims, characterized by the fact that the mixture is in liquid, solid or pasty form.

11. Method for producing a mixture according to at least one of claims 1 to 10, wherein the method comprises the steps of providing an adhesive and a filler based on wax, wherein the wax is in the form of fibers and / or fiber bundles forming one or more bulk structures among themselves, and mixing the adhesive and the filler.

12. Use of a mixture according to at least one of claims 1 to 10 in vehicle manufacturing.

13. Use of a wax-based filler, wherein the wax is in the form of fibers and / or fiber bundles forming one or more volume structures among themselves, as an adsorbent for hydrophobic substances in adhesives.