CH639676A5 - Material for producing a structural sound-proofing covering - Google Patents

Description

The object of the invention is to achieve an improvement in the structure-borne noise reduction with constant or even reduced material expenditure. The reduction in material costs allows e.g. in vehicle construction a weight saving and thus a saving in fuel and material storage. This object is achieved by the material according to the invention, defined in claim 1.

Surprisingly, and in contrast to the previous view of the professional world, according to which structure-borne noise damping is achieved primarily by the weight of anti-drumming materials, which increase the weight of the body or object, the weight per volume is reduced by the porous structure aimed at according to the invention, but nevertheless one significantly better structure-borne noise reduction, e.g. with the noise reduction of sheet metal, up to 100% or more.

As has been shown, energy is swallowed by the cells rubbing against each other in a porous, anti-drumming compound provided with cells.

An additional achievable side effect is better thermal insulation.

For example, a deadening material that was previously applied to a body sheet in the form of a film of 2-3 mm thickness can be reduced to a thickness of 1-1.5 mm according to the invention and then provided with the porous structure without the damping values for change the structure-borne noise (loss factor or vibration damping factor).

The material according to the invention is produced by the method defined in claim 4. After being applied to the object whose structure-borne noise is to be damped, the material is subjected to a heat treatment in which a gas is released from the gas-releasing agent and the material is foamed and thereby largely adapts to the contours of the sheet.

This procedure is preferred because anti-drumming compounds, sheets or foils have been "melted" so far, for example in vehicle construction, when the paint is baked onto the metal sheet, so that they conform to any unevenness or shape of the body panel. The improvement according to the invention can thus take place without changing the previous basic method of application and subsequent heating.

According to the previous method of application, the sheets are exposed to temperatures of 90-220 ° C. Accordingly, it is preferred to use gas-releasing agents which emit gas in this temperature range, which is primarily nitrogen or CO2. Such means are e.g. Azodicarbonamide, cyanuric acid trihydrazide, N, N'-dimethyl-N, N '-dinitrosoterephthalamide, ammonium carbonate, diphenylsulfone-3,3'-disulfohydrazide, a, a-azidiiso-butyronitrile, diazoaminobenzene, benzenesulfonic acid hydrazide, 4,4'-oxybisopenzidamethonidylbenzylbenzene-benzylsulfonazole, 4,4'-oxybisopenzidomethene / or an optionally enclosed in microcapsules, low-boiling liquid, in particular a chlorine and / or fluorine-substituted hydrocarbon with 1-3 carbon atoms. However, means can also be used in which the gas elimination by a chemical reaction e.g. between isocyanate groups and water, as is possible with a material consisting of a polyalcohol capped with a polyisocyanate compound.

The invention is explained in more detail by the accompanying drawing. Here, a material 2 according to the invention on a body panel 1 is shown partially in section. The foamed material 2 has partially closed cells or pores 3, partially and in particular also open pores 4 on the surface, a foam structure being formed by these pores. It is preferred that at least 20%

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639 676

the pores are closed pores in order to maintain the mechanical strength of the material. However, the percentage can also be higher in order to ensure the required deadening effect.

example

The deadening effect of a comparison film of 1.5 mm thickness was measured, which had the following composition:

23 parts by weight of bitumen with the standard designation B 80 73 parts by weight of Ca CCb 4 parts by weight of mica.

The film was provided with a heat-activatable adhesive on one side and melted onto a test sheet of 1 mm thickness at 130-140 ° C for 20 min and then measured at 20 ° C in the bending vibration device according to s Oberst. The loss factor was 0.056 in the measuring range of 100-500 Hz.

A similarly composed embodiment of a film according to the invention with the same starting thickness of 1.5 mm, to which 4% by weight azodicarbonamide had been added, and which was also provided with the thermoplastic adhesive and was melted at the same temperature and duration, showed after melting a loss factor of 0.135 and the layer thickness was 5.2 mm.

B

1 sheet of drawings

Claims (10)

639 676 1. Material to achieve a structure-borne sound-absorbing covering based on bitumen, natural or synthetic resins including thermoplastic plastics or a mixture of such starting materials, characterized in that the material contains gas-releasing agents, so that the material is foamed into a porous, foam-like structure and thereby structure-borne sound-absorbing can be made. 2. Material according to claim 1, characterized in that it additionally enhancer filler. 2nd PATENT CLAIMS 3. Material according to claim 1 or 2 in the form of a bendable film or plate by heating. 4. A process for producing a material according to claim 1, characterized in that bitumen, natural or synthetic resins including thermoplastics or a mixture of such starting materials 0.1-10% by weight of gas-releasing agent is added and the mixture is brought into sheet or sheet form . 5. The method according to claim 4, characterized in that as the gas-releasing agent azodicarbonamide, Cya-nursäuretrihydrazid, N, N'-dimethyl-N, N'-dinitrosotereph-thalamide, ammonium carbonate, diphenylsulfone-3,3'-disul-fohydrazide, β, a-azodiisobutyronitrile, diazoamino-benzene, benzenesulfonic acid hydrazide, 4,4'-oxybisbenzenesulfonylhydrazide, dinitrosopentamethylenetetramine and / or a low-boiling liquid are used. 6. The method according to claim 4, characterized in that one uses as the gas-releasing agent a masked with a polyiso-cyanate compound polyalcohol. 7. The method according to any one of claims 4-6, characterized in that additional filler is added to the mixture. 8. Use of a material according to claim 1 for the deadening of sheet metal, wherein the material is applied to the sheet and then subjected to a heat treatment in which a gas is released from the gas-releasing agent and the material is foamed and thereby largely adapts to the contours of the sheet . 9. Use according to claim 8, wherein the material is foamed in such a way that at least 20% of the total pores formed are closed pores. 10. Use according to claim 8 or 9 for the anti-drumming of body panels, wherein a material is used which is coated on the back with a hot melt or pressure sensitive adhesive. It is known that objects, in particular body parts of motor vehicles, e.g. Floor plates provided with corrugations to be deadened by means of foils or masses which consist of bitumens or thermoplastic materials, for example polyvinyl acetate, optionally provided with fillers, such as mineral aggregates, in particular chalk, carbon black, graphite, barium sulfate, calcium sulfate, and optionally melt adhesive or pressure-sensitive adhesive on the back to improve adhesion, especially in the cold. Here, the structure-borne noise reduction measure is the loss factor T | referred to as the ratio of recovered energy to unrecovered energy, e.g. can be determined using the half-width method for electromagnetically excited metal strips on the bending vibration device according to Prof. Oberst.