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DE-102024132761-A1 - Lubricant for fasteners

DE102024132761A1DE 102024132761 A1DE102024132761 A1DE 102024132761A1DE-102024132761-A1

Abstract

A sliding coating for screw fasteners (1), in particular wheel bolts or wheel nuts, is provided, comprising 30 - 50 wt% of a polymer matrix, 25 - 50 wt.% fillers and/or corrosion protection pigments, 3 - 15 wt.% paint additives, 3 - 15 wt.% pigments, dyes and/or metallic effect pigments, 1.0 - 10.0 wt.% polyethylene wax and 0.5 - 5.0% by weight synthetic paraffins. Furthermore, a screw connection device (1) with a sliding lacquer coating and a method for its manufacture are provided.

Inventors

  • Holger Lamm
  • Matthias Kloda
  • Jörg Müller
  • Thomas Nitzsche

Assignees

  • HILLEBRAND CHEMICALS GMBH
  • KAMAX HOLDING GMBH & CO. KG

Dates

Publication Date
20260513
Application Date
20241111

Claims (13)

  1. Lubricating lacquer for screw fasteners (1), in particular for wheel bolts and wheel nuts, comprising 30–50 wt.% of a polymer matrix, 25–50 wt.% fillers and/or corrosion protection pigments, 3–15 wt.% lacquer additives, 3–15 wt.% pigments, dyes and/or metallic effect pigments, 1.0–10.0 wt.% polyethylene wax and 0.5–5.0 wt.% synthetic paraffins, wherein the wt. percent are based on the total wt. weight of the lubricating lacquer.
  2. Lubricant after Claim 1 , characterized in that the sliding lacquer contains ≤ 0.1 wt.%, preferably ≤ 0.01 wt.% polyfluorinated alkyl substances (PFAS), based on the total weight of the sliding lacquer.
  3. Lubricant after Claim 1 or 2 , characterized in that the synthetic paraffins are saturated hydrocarbons with a melting point of 80 - 125°C.
  4. Lubricating lacquer according to one of the preceding claims, characterized in that the polyethylene wax has a density of 0.93 to 0.98 g/cm 3 and a melting point of 120 - 140°C.
  5. Lubricating lacquer according to one of the preceding claims, characterized in that the molar mass of polyethylene in the polyethylene wax is 200,000 to 7,500,000 g/mol.
  6. Lubricating lacquer according to one of the preceding claims, characterized in that the synthetic paraffin and/or the polyethylene wax is in particle form, with a mean particle size d 50 of 3 - 12 µm.
  7. Lubricating lacquer according to one of the preceding claims, characterized in that the polymer matrix is a reaction product of a polymer resin and a crosslinker, preferably that the polymer resin is selected from the group consisting of polyamide, polyamide-imide, polyurethane, polyester, acrylate, epoxysilane, epoxysiloxane, phenoxy, epoxy and mixtures thereof and/or the crosslinker is selected from the group consisting of isocyanate resin, imidazole resin, phenol resin, amine resin and mixtures thereof.
  8. Use of a sliding lacquer after one of the Claims 1 - 7 for coating a screw fastener (1), in particular a wheel bolt and/or wheel nut.
  9. Screw fastener (1) with a sliding lacquer coating, wherein the screw fastener (1) has a surface characterized in that a layer of sliding lacquer according to one of the Claims 1 - 7 is upset.
  10. Screw fasteners (1) according to Claim 9 , characterized in that the screw connection (1) is a wheel bolt or wheel nut having a thread (20) and the layer of sliding lacquer is applied at least to a part of the thread (20).
  11. Screw fasteners (1) according to Claim 9 or 10 , characterized in that between the surface of the screw fastener (1) and the layer of sliding lacquer there is a further layer containing zinc, and optionally a layer of an adhesion promoter above it.
  12. Method for producing a screw fastener (1) with a sliding lacquer coating according to one of the Claims 9 until 11 , comprising the steps a) providing a screw fastener (1), b) dispersing a polymer resin as well as fillers and/or corrosion protection pigments, paint additives, as well as pigments, dyes and/or metallic effect pigments in a solvent, c) adding a crosslinker, polyethylene wax and synthetic paraffin and optionally further additives to the dispersion, d) mixing to form a sliding lacquer dispersion, e) optionally applying a zinc-containing layer and optionally applying a layer of an adhesion promoter to at least part of the surface of the screw fastener, f) Applying a layer of the sliding lacquer dispersion to at least part of the surface of the screw fastener, g) drying the layer and h) baking the dried layer at a temperature of 140 to 250 °C.
  13. Use of a screw fastener (1), in particular a wheel bolt or wheel nut, according to one of the Claims 9 - 11 for attaching a wheel, in particular for attaching a wheel to a vehicle.

Description

The present invention relates to a sliding lacquer for screw fasteners, in particular wheel bolts or wheel nuts, a use of the sliding lacquer for coating screw fasteners, a screw fastener with a sliding lacquer coating and a method for producing a screw fastener with a sliding lacquer coating. Sliding coatings are coatings that provide lubricating properties, for example, through the inclusion of solid lubricants. Sliding coatings for bolted fasteners, such as wheel bolts or wheel nuts, are applied to their surface and serve to provide corrosion protection and ensure consistent friction behavior even after numerous assembly and disassembly cycles. Sufficient mechanical resistance is therefore essential. In the case of a wheel bolt, one of the biggest challenges of a bolted fastener, in addition to maintaining consistent friction during and after repeated assembly, it is also desirable that the lubricant allows for controlled loosening of the bolts during and after high thermal and mechanical stresses, such as those occurring during high-speed cornering with sharp braking maneuvers, ensuring that the wheel bolts are neither too loose nor too tight. A standardized test drive is a so-called thermodynamic tightness test, which involves high thermal and mechanical stresses. These properties of known sliding coatings still require improvement. In particular, a more consistent lubrication performance at room temperature (statically) with a tendency towards better sliding during repeated tightening and loosening is desirable, as is higher friction and thus poorer sliding during and after thermal stress, since the friction of known sliding coatings typically decreases significantly under thermal stress of 150°C and above. For wheel bolts coated with sliding coating, it is particularly desirable that the ratio of the loosening torque at room temperature after thermal stress, especially a thermodynamic tightness test, to the tightening torque before thermal stress is > 60%, ideally > 70%. Another disadvantage of many well-known sliding coatings is that they contain polyfluoroalkyl substances (PFAS). PFAS are a group of mainly synthetically produced substances used in numerous applications. These applications include their use in textiles, (food) packaging, lubricants, coolants, electronics, construction, and many other fields. The substances are used as individual components (either non-polymeric or polymeric) and as constituents of mixtures and (complex) products for consumer, commercial, and industrial purposes. A problem with all PFAS and/or their degradation products that fall within the scope of the EU restriction proposal (Annex XV, version 2 of 22 March 2023) is their very high persistence, which far exceeds the criterion for very persistent (vP) according to Annex XIII of the REACH Regulation. PFAS and their degradation products can remain in the environment longer than any other man-made chemicals. Further reasons for concern include their bioaccumulation, mobility, long-range transport potential (LRTP), bioaccumulation in plants, global warming potential, and (eco)toxicological effects. PFAS enter the environment through emissions during manufacturing, use, and waste. If these substances and their degradation products continue to be released into the environment, the concentration in the environment will increase, as mineralization under natural conditions does not occur for the PFAS that fall within the scope of the EU restriction proposal. Once PFAS are present in the environment, their removal from surface water, groundwater, soil, and sediment is technically extremely difficult and costly, if not impossible. Environmental monitoring of PFAS shows that they are ubiquitous, even in organisms, drinking water sources, and foodstuffs, as well as in remote and pristine areas, making exposure for present and future generations unavoidable and irreversible. Ideally, the production and release of new PFAS should be avoided as much as possible. The object of the invention is therefore to provide a sliding coating for screw fasteners, in particular for wheel fastening, which exhibits good corrosion resistance and withstands multiple months of use. The lubricant should exhibit the most consistent friction behavior possible, both during and after periods of high thermal and mechanical stress. It is also important that the lubricant coating requires as few polyfluoroalkyl substances as possible. This problem is solved by a sliding lacquer for screw fasteners, in particular wheel fasteners and especially wheel bolts and wheel nuts, according to claim 1, a use according to claim 8, a screw fastener with a sliding lacquer coating according to claim 9, a method for manufacturing a screw fastener according to claim 12, and a use of the screw fastener for fastening a wheel according to claim 13. Further features, embodiments, and advantages will become apparent from the dependent claims and the description. One aspect of th