DE9013663U1 - Sound-absorbing plate - Google Patents

Description

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sound-damping plate

Description

The invention relates to a sound-absorbing sandwich panel, in particular for floor panels of automobiles and other body parts.

It is known to use meltable bituminous foils to dampen the sound of automobile floor panels. The damping properties of the foils are achieved by adding inorganic fillers such as mica or barite or polymers to the bitumen mass. The foils or cutouts are placed on the body parts and bond to them in the oven during the paint baking process. Walkable hard material panels are then glued to the damping foil and, if necessary, covered with carpet. Another acoustically effective layer of foam or felt can be placed between the hard material panel and the damping foil. To produce such sandwiches, US 4,830,916 proposes to cover the underside in a

The shape is pre-formed to match the surface structure of the floor panel. The grooves are then filled with a ^polyurethane filler. The disadvantage of this process is that several molds are required for each vehicle type for the corresponding body parts and that the process is therefore very complex.

The task was therefore to develop a sound-absorbing sandwich panel that was less complex to produce.

The object is achieved according to the invention by a flat sandwich panel 1 made of a bituminous damping film 2 on the underside and a hard material layer 3 on the upper side that is resistant to at least 160° C, which are connected by means of a meltable adhesive 4, the adhesive 4 having a softening point (ring and ball) of 60 to 150 ° C hac.

Standard films made of bituminous masses modified with mineral substances and/or polymers can be used as bituminous damping films. They can be perforated or embossed on the underside to prevent air bubbles from being trapped when melting onto the body parts. The underside can also be coated with an anti-blocking agent that is solid below 90°C or a bitumen-compatible adhesive that melts between 120 and 160°C. For body parts that are not arranged horizontally, it is advisable to use magnetized films whose bituminous masts contain a ferrite powder.

The hard material layer should preferably not be thicker than 1 mm, have sufficient impact resistance and be able to be punched or cut. A suitable material is, for example, a hard cardboard for the body or a nonwoven fabric soaked in ouromers, which must harden completely when it passes through the paint baking oven at the latest.

Since, on the one hand, the damping film can only be effective if it is completely in contact with the body part and firmly bonded to it, but on the other hand, the surface of the hard material layer must remain unchanged, both layers must partially separate from each other when heated. After cooling, however, they must be sufficiently firmly connected to each other again via the existing contact points. The problems resulting from these tasks are the reason why prefabricated, flat sandwich panels have not been used to date.

The problem of temperature-dependent adhesion between the hard material layer and the damping foil was initially solved by applying the adhesive in dots or strips. When the damping foil is melted onto the corrugated floor panel, gas from the edge of the panel penetrates into the cavities between the hard material layer and the foil that are formed by the foil partially sinking. The adhesive used only had to be compatible with bitumen and preferably had a softening point (R. u. K.) of up to 130° C. Since a dot or strip application of K ⁷ is difficult to manufacture,

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In a preferred embodiment, the adhesive is applied over the entire surface of the hard material layer, covered with a perforated release film, for example a siliconized paper, and connected to the damping film via the exposed adhesive points. The tinting effect can be further improved if a damping film is used that is laminated or hot-coated on the top with a thin film of a bitumen-compatible thermoplastic, e.g. a polyolefin.

Further development has surprisingly shown that the perforated release film can be dispensed with if an adhesive with a softening point (R. u. K.) of 60 to 100 ⁰ C is used. A bituminous adhesive with a softening point (R. u. K.) of 60 to 80 ' C is particularly suitable, which consists of a bitumen modified with 4 to 8 wt.% elastomers, 1 to 10 wt.% polyolefins, 1 to 3 wt.% tackifying resins and up to 5 wt.% fillers.

To improve the damping properties, an additional acoustically effective layer can be glued to the underside of the hard material layer. This layer consists of a material that is resistant to at least 160° C, such as a highly cross-linked nitric rubber or polyurethane foam, an expanded cork or even bituminous damping foil. Since the hard material layer and this additional acoustically effective layer should not separate from each other during the paint baking process,

The adhesives used are preferably those that have a softening point of preferably more than 130°C.

To ensure that during melting between

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To avoid this, it is advantageous to provide the damping foil and any laminated plastic foil with evenly spaced perforations. The hole diameter is approximately 1 mm. After melting, these openings are closed by the adhesive that flows in.

The invention is explained by way of example with reference to the drawings.

Fig. 1 shows the structure of a panel according to the invention with point-by-point bonding between

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Fig. 2 shows a cross-section through the plate according to Fig. 1 in the installed state.

Fig. 3 shows the structure of a plate according to the invention with full-surface bonding between the hard material plate and the damping film.

Fig. 4 shows a cross-section through the plate according to Fig. 3 in the installed state.

Examples
example 1

As shown in Fig. 1, the sound-absorbing plate 1 is made of a 1 mm thick

Bodywork hardboard 3, which is completely coated on the underside with a 0.3 mm thick hot melt adhesive layer 4 based on SBR rubber with a softening point (R. u. K.) of 100 ^° C.

The free surface of the hot melt adhesive layer 4 is covered with a perforated, siliconized paper 5. The holes have a diameter of 5 mm and are arranged at the intersection points of a square grid at a distance of 5 cm. A bituminous damping film 2 is connected to the hard pad 3 via the uncovered adhesive points.

The damping film 2 is 1.5 mm thick and has a 0.25 mm deep embossing 6 on the underside and a coating 7 made of 40 g/m ² of a hot melt adhesive based on EVA with a softening point (R. u. K.) of 130 ⁰ C. The coating 7 prevents the plates from sticking to one another during storage and improves the adhesion of the damping film 2 after it has been melted onto the body sheet 8.

The embossing 6 facilitates the escape of air during melting in the area of the beads 9. D,u Damping film 2 has the following composition:

35 wt.-S Bitumen 85/25
62 wt.% calcium carbonate
3 wt.-« glass fibers

The plate i is placed horizontally on a test sheet 8 with a 5 cm wide and 1 cm deep bead 9

and place in a warming cabinet at 160 ⁰ C for 20 minutes

After cooling, the sample was

(Fig. 2). The damping foil 2 was also in the \

Area of the bead 9 free of bubbles with the test sheet 8 ;

glued. The hard cardboard 3 was also sufficient

firmly connected to the damping foil 2. I

According to the test method described in DIN 53440, the loss factor at 20 °C and 200 Hz was determined to be 0.1 for the damping foil alone and 0.18 for the plate 1 according to the invention as a whole.

Example 2

As shown in Fig. 3, in this embodiment of the sound-absorbing plate 1, the bodywork cardboard is fully bonded to the damping film 2. The 0.5 mm thick bituminous adhesive layer 4 has the following composition:

80 wt.-5 bitumen B 30U 8 wt.-5 SBR rubber

4 wt. % polypropylene 3 wt.-» rosin

5 parts by weight of slate powder.

The adhesive has a softening point (R. u. K.) of 80 ⁰ C. The damping film 2 contains:

20 wt.-X Bitumen 85/25 66 wt.-X Calcium carbonate 10 wt.- % GI Always

2 wt. % glass fibres

2 wt.-3 coumarone-indene resin.

All other features correspond to those of the example

The loss factor of the damping foil 2 at 20 ^° C and <i 200 Hz is 0.14%, while that of the plate 1 is 0.22.

When the sample sheet 8 was melted in ^accordance with Example 1, the damping film 2 was bonded to the sample sheet 8 over the entire surface in the area of the beads 9 without any bubbles. Part of the bituminous adhesive 4 still adhered to the hard cardboard 3. The connection between the hard cardboard 3 and the damping film 2 was better than in Example 1.

Claims (5)

Protection claims 1. Sound-damping plate, characterized in that it consists on the underside of a bituminous damping film (2) and on the upper side of a hard material layer (0) resistant to at least 160 ^° C, which are connected by means of a meltable adhesive (4), the adhesive (4) having a softening point (ring and ball) of 6 °C to 150 ^° C. 2. Sound-absorbing plate according to claim 1, characterized in that the damping film (2) is glued pointwise to the hard material layer (0), the adhesive (4) having a softening point (ring and ball) of 100 to ¹³⁰ °C. 3. Sound-absorbing plate according to claim 1, characterized in that the damping film (2) is connected over its entire surface to the hard material layer (1) by means of a bituminous adhesive (4), the bituminous adhesive (4) having a softening point (ring and ball) of 60 to 80 ^° C. 4, Sound-absorbing plate according to claim 1, characterized in that a perforated separating film (5) is arranged between the adhesive layer (4) and the damping film (2). 5. Sound-absorbing plate according to claim 1, characterized in that an acoustically effective layer which is resistant to at least 160 ^° C is arranged between the adhesive layer (4) and the hard material layer (3).