GB2109902A - Noise reduction material - Google Patents

Abstract

Moulding of a porous material, for sound insulation, sound attenuation and anti-drumming treatment, consisting of a layer 2 of a porous material with cavities 4 which are open on the side facing the sound transmitter and which are filled with a fine-grained material 5 and, on the open side facing the sound transmitter, are closed by a thin flexible, resistant film 3. <IMAGE>

Description

SPECIFICATION Moulding for sound insulation The present invention relates to mouldings of a porous material, for anti-drumming treatment, sound insulation and sound attenuation, and to a process for the preparation of such mouldings and to a process for anti-drumming treatment, sound insulation and sound attenuation, using such mouldings.

Anti-drumming treatment, sound insulation and sound attenuation are nowadays of special importance, in particular with respect to protection of the environment. In the high-technology environment, man is nowadays quite generally exposed to the harmful effect of noise nuisances. This applies in particular to the noise from machines and vehicles, such as internal combustion engines, electrical machines and installations, construction machines, ventilating and cooling installations, pumps, pneumatic installations and the like. In the construction of vehicles, a reduction in the noise nuisance is also of considerable importance, such as in the construction of road vehicles, rail vehicles, watercraft or aircraft.

The noise nuisance can be reduced by both sound insulation and sound attenuation. Sound insulation is understood as the inhibition of sound propagation by means of reflecting with obstacles, for example by walls and the like. Sound attenuation is understood as the absorption of the sound, that is to say its destruction by conversion into heat. Both phenomena play a large role, especially in vehicle construction, for example in the construction of motor vehicles.

In the manufacture of motor vehicle bodies, it is necessary to take both sound-insulating and soundattenuating measures in order to reduce the transmission of air-borne sound and structure-borne sound.

For this purpose, the bodies are in general also faced with insulating materials on the inside. Examples of such insulating materials are foams or nonwoven mats, if appropriate with a heavy-weight layer, which are fitted for example, in body areas such as the underbody, bulkhead parts and the engine compartment. According to the corresponding vehicle type, they are frequently manufactured, and installed, in prefabricated shapes adapted to the contours of the underbody, transmission tunnel and the like. To obtain good sound insulation and attenuation, it has here proved necessary first to glue or to melt a bitumen-type or similar sheet for anti-drumming treatment from the inside onto the floor of the vehicle body, the mouldings used for sound insulation and attenuation then being glued as internal facings to the sheet.Hitherto, it has been possible to achieve sound insulation and attentuation in motor vehicles by such a combination of glued-on or melted-on sheets with mouldings, for example of foams or nonwoven material, placed on top.

The same applies to the sheeting or facing parts of machines, motors and the like.

The prior sound insulation and attenuation tech nology is labour-intensive and expensive because of the additional working step required for gluing or melting on, and also because of the additional material used, and moreover it is incompatible with the trend, observable in particular in motor vehicle construction, towards weight-saving.

It is therefore the object of the present invention to develop a process for sound insulation and sound attenuation with simultaneous anti-drumming treat ment and to develop a moulding which is suitable for this purpose and which is easier and less expensive to manufacture and moreover leads to a saving in weight.

This object is achieved by a moulding which consists of a layer of porous material with cavities which are open on the side facing the sound transmitter and which are filled with a fine-grained material and, on the open side facing the sound transmitter, are closed by a thin, flexible, resistant film.

The porous material can be a foam, woven fabric, knitted fabric, felt material and/or nonwoven material. The foams used are: filled and/or unfilled thermoplastics, thermosetting plastics and/or elastomers.

Suitable thermoplastics are polyurethanes, acrylonitrile/butadiene/styrene copolymers, polystyrene, polyolefins, such as polyethylene and polypropylene, polyvinyl halides, such as polyvinyl chloride, polyamides, polycarbonates, ethylene/vinyl acetate copolymers, styrene/acrylonitrile copolymers as well as mixtures and copolymers of the materials mentioned.

Suitable thermosetting plastics are polyurethanes, urea/formaldehyde resins, phenol/formaldehyde resins, melamine/formaldehyde resins and mixtures of the materials mentioned above.

Suitable elastomers are natural rubber, synthetic rubber, polyurethanes and mixtures of the materials mentioned.

Examples of synthetic rubber are ethylene/propylene rubber, styrene/butadiene rubber, butadiene rubber, chloroprene rubber, isoprene rubber, nitrile rubber, butyl rubber and also synthetic rubbers cross-linked by peroxides, amines, isocyanates or the like, acrylate rubber, fluorinated rubber, chlorosulphonated polyethylene, nitroso rubber, silicone rubber, thioplasts and urethane rubber, and ethylene/vinyl acetate copolymers.

The woven fabrics, knitted fabrics, felt materials and/or nonwoven materials used can be those consisting of natural and/or man-made fibres, such as, for example, inorganic natural fibres, such as asbestos, mineral fibres (rock wool and basalt wool), organic natural fibres, such as wool, cotton, coconut fibres, jute, sisal, hemp, wood and the like, manmade fibres from natural raw materials, such as glass, ceramics, metal wool, cellulose, paper and the like, as well as man-made fibres from fully synthetic raw materials, such as polyethylene, polypropylene, polystyrene, polyamide, polyurethane, vinyl copolymers, acrylonitrile polymers and/or polyterephthalates and/or mixtures thereof.

The foams can be filled with inorganic fillers, such as barite, chalk, powdered rock, talc, kaolin, clay, powdered slate, mica, quartz, sand, glass fibres, glass powder, asbestos, metal powder, metal oxide powder, powdered brick, coal slag, powdered slag, powdered limestone and powdered basalt, as well as with organic fillers, such as wood flour, graphite, carbon black, coal dust, reclaimed rubber and/or mixtures of the materials mentioned.

The porous material has cavities which are open downwards and which are machined out of the porous material in a suitable manner. For example, the cavities can be obtained by cutting material out of a plate of the porous material. It is easier to produce the cavities by introducing removable in- serts into the mould at the areas where the cavities are to be obtained, or by correspondingly shaping the mould in these areas, so that the desired cavities are obtained without a further machining step. In a particular embodiment of the present invention, the cavities are obtained by introducing small bags, which are filled with the porous fine-grained material, into the mould at the desired areas.For example, when foam compositions are introduced into the moulds, the foam will flow around the filled bags, a foam being produced, the cavities of which are already completely filled with fine-grained material.

In the selection of suitable materials for the foam and the bags, direct adhesion between the foam and film can be achieved, for example, when polyurethane foam and polyurethane film are used.

The adhesion of the bags in the foam can also be effected by additional measures, such as, for example, gluing-in. The bag can also have perforated edge strips, through which the foam penetrates and fixes the bag in its position.

The plan of the cavities is in general square or rectangular, since these forms of plan are the easiest to produce. The plan can, however, also have a different shape, for example it can be circular, rhombic, triangular and polygonal and the like.

When the cavities are produced by means of inserted bags during foaming, the cavities have the same plan shapes as the contours of the bags. The latter are in general square or rectangular. The depth of the cavities depends on the quantity of the fine-grained material to be accommodated. It has proved advantageous to fill the cavities as completely as possible with fine-grained materials.

The underside of the cavities containing the fine-grained material is closed by a thin, resistant film. This film prevents falling-out of the fine-grained material filled into the cavities. Accordingly, the film must be sufficiently resistant to withstand the weight of the fine-grained material present in the cavity and, furthermore, to withstand the stresses arising in the production, working and installation of the moulding. The film therefore covers the cavities completely, it being advantageous to provide an edge strip, extending beyond the cavities, for fixing the film to the foam. The film can also extend over the entire lower surface of the foamed body, so that several cavities can be covered by a single film.

The film consists of a thin, resistant material which can withstand the stresses during production, working and use. The film materials used can be thermoplastics, thermosetting plastics and/or elastomers.

Suitable thermoplastics are polyolefines, such as polyethylene, polypropylene, polybutylene and polyisobutylene, polyamide, polyvinyl chloride, polycarbonate, polyurethanes, polyhalogen- olefines, such as polytetrafluoroethylene, polyoxymethylene, styrene polymers, such as polystyrene, styrene/butadiene copolymers, styrene/acrylonitrile copolymers and acrylonitrile/butadiene/styrene copolymers, polyesters, such as polycarbonate, polyethylene glycol terephthalate and polybutylene glycol terephthaiate, polysulphones, polyvinyl alcohol, cellulose derivatives, such as cellulose acetates, cellulose acetobutyrates and regenerated cellulose film (cellulose hydrates), polyvinyl halides, polyvinyl ethers, polyacrylates and polyether-sulphones.

Polyurethanes are an example of suitable thermosetting plastics.

Suitable elastomers are natural rubber, synthetic rubber, polyurethane and mixtures of the materials mentioned.

Examples of synthetic rubber are ethylene/propylene rubber, styrene/butadiene rubber, butadiene rubber, chloroprene rubber, isoprene rubber, nitrile rubber, butyl rubber and synthetic rubbers which are cross-linked by peroxides, amines, isocyanates and the like, acrylate rubber, fluorinated rubber, chlorosulphonated polyethylene, nitroso rubber, silicone rubber, thioplasts, urethane rubber and ethylene/ vinyl acetate copolymers.

The films can also consist of mixtures of the materials mentioned.

The films can be present as laminates, for example as a two-ply laminate or a three-ply laminate, or as a weave of tapes. Woven sheets of man-made fibres, such as glass, polyethylene, polypropylene, polystyrene, polyamide, polyurethane, vinyl copolymers, acrylonitrile polymers and/or polyterephthalates, can also be used.

The films have a thickness from about 1 lim to 1,000 m, preferably from about 5 lim to about 300 m and particularly preferably 15 Fm to 100 Fm.

The film is fixed to the underside of the porous material by suitable measures, such as gluing or welding.

Suitable fine-grained materials used for filling the cavities are mineral, inorganic or organic materials.

Mineral or inorganic fillers include: barite, chalk, powdered took, talc, kaolin, clay, expanded clay, powdered slate, mica, quartz, sand, for example sea sand, glass fibres, glass powder, asbestos, metal powders, metal oxide powders, powdered brick, brick chips, chippings, slags, limestone, iron filings, metal shot, for example of lead, metal pellets, gravel, basalt, fuller's earth and fireclay.

Organic materials include, for example, wood flour, graphite, carbon black, reclaimed rubber, cork, shredded cork, peat and the like.

Mixtures of the materials mentioned can also be used.

In general, the fine-grained materials have a grain size from 0.001 to 20 mm, and when sand or similar materials are used, preferably 0.01 to 2 mm and particularly preferably from 0.3 to 1 mm. If materials are used which can readily be comminuted, smaller grain sizes can also be used, for example from 0.001 to 0.1 mm, for example of barite or similar materials are used. If metal particles, gravel, slags or similar materials are used, larger grain sizes can also be used, for example in the range from 3 to 20 mm.

The fine-grained materials can have a grain size distribution over a fairly wide range, for example within the entire range of grain sizes indicated above. They can also have a uniform grain size.

Furthermore, they can also be used in the form of mixtures, even in the form of mixtures of different grain sizes, for example mixtures of chippings and barite of different grain size, for example in order to match the sound insulation, sound attenuation and anti-drumming treatment to a particular frequency spectrum. It has proved to be an advantage when the fine-particulate material has the lowest possible water content, since the attenuation properties of the fine-grained material are adversely affected by any moisture present.

To obtain good attenuation properties, the resis tantfilm, with which the cavities containing the porous material are closed on the underside, should be as thin as possible. Due to its mere weight, the fine-grained material then bears very closely against the film and hence via the film also against the surface located below, at which sound insulation and attenuation is to be effected. As a result, there is good coupling between the vibrating surface and the fine-grained material, and this effects good sound attenuation and anti-drumming treatment.

On the side facing away from the sound transmitter, the moulding can have a heavy-weight layer consisting of a compact material or a heavy-weight foam, this in general being a heavy-weight layer of filled polymer material, such as, for example, a highly filled polymer material. The polymer mate rials used for such heavy-weight layers are thermo plastics, thermosetting plastics or elastomers.

Examples of thermoplastics are: bitumen, pitch, tree resins or wood rosins, or synthetic thermoplas tics, such as polyvinyl chloride, polyolefins, such as polyethylene and polypropylene, polyurethanes, ethylene/vinyl acetate copolymers, polyvinyl ace tate, polyvinyl propionate, polymethacrylates, polyacrylates, polyvinyl esters of acids, polyethers, such as cellulose derivatives, polyacetals, hydrocar bon resins, styrene polymers, such as polystyrene, acrylonitrile/butadiene copolymers, styrene/acrylo nitrile copolymers, styrene/acrylonitrile/butadiene copolymers as well as mixtures and/or copolymers of the materials mentioned.

Examples of thermosetting plastics are epoxy resins, polyesters and/or polyurethane as well as mixtures and/or copolymers of the materials men tioned.

Examples of elastomers are natural rubbers, polyurethane and/or synthetic rubbers, such as ethylene/propylene rubbers, for example ethylene/ propylene rubber or ethylene/propylene terpolym ers, ethylene/vinyl acetate rubber, styrene/butadiene rubber, butadiene rubber, chloroprene rubber, isop rene rubber, nitrile rubber, butyl rubber and synthe tic rubbers cross-linked by peroxides, amines, isocyanates or the like, acrylate rubber, fluorinated rubber, chlorosulphonated polyethylene, nitroso rubber, silicone rubber, thioplasts, urethane rubber, ethylene/vinyl acetate copolymers and reclaimed rubbers.

Mixtures and copolymers of all the materials mentioned can also be used.

The heavy-weight layer can be filled with inorganic fillers, such as barite, chalk, powdered rock, talc, kaolin, clay, powdered slate, mica, quartz, sand, glass fibres, glass powder, asbestos, metal powder, metal oxide powder, powdered brick, coal slag, powdered slag, powdered limestone or powdered basalt, and with organic fillers, such as wood flour, graphite, carbon black, coal dust, reclaimed rubber and/or mixtures of the materials mentioned.

The heavy-weight layer can contain the conventional additives, such as plasticisers, waxes, slip agents, stabilisers, surfactants and the like.

The moulding according to the invention makes it possible, as compared with the state of the art, to improve the sound-insulating and soundattenuating or anti-drumming properties, at the same weight or a lower weight, by controlled spatial arrangement of the cavities filled with fine-grained material. The points which give optimum utilisation of the sound-insulating, sound-attenuating and antidrumming properties, coupled with the lowest weight, can be determined without difficulty by experiments for each body or for each body component.

The cavities can be located centrally over individual body components, and they can also be located in accordance with certain patterns, for example in the manner of a chess board, in the manner of a symmetrical pattern or even asymmetrically. The cavities can be of different sizes.

The moulding according to the invention makes sound insulation, sound attenuation and antidrumming treatment possible even on inclined and vertical surfaces.

In the following text, the invention is explained in greater detail by reference to the Figures which represent preferred embodiment of the present invention.

Figure 1 shows a cross-section through a moulding according to the invention.

Figure 2 shows a cross-section through another moulding according to the invention, which has been produced using a bag.

Figure 3 shows a view of a moulding according to the invention from below.

Figure 4 shows a view of a further moulding according to the invention from below.

Figure 5 shows a graphic representation of the sound attenuation of the mouldings according to the invention, as compared with the state of the art.

Figure 1 shows the construction of a moulding according to the invention from a cover layer 1 and a layer 2 of a porous material which has cavities 4. The cavities 4 are cut vertically into the porous material, which is a foam in the present case, and are filled with a fine-grained material 5 which consists of dry sand of a grain size from 0.3 to 1 mm. Underneath, the moulding is provided with a thin, resistant film 3 which extends over the entire lower surface of the moulding.

A further embodiment of a moulding according to the invention is shown in Figure 2. This moulding has been produced by filling bags 3 of a thin, resistant film, for example a film of polyurethane material, with fine-grained dry sand 5 of a grain size from 0.3 to 1 mm, and closing the bags by welding.

These mouldings were inserted into the foaming mould and foam-filled in the known manner with polyurethane foam. The moulding according to Figure 2 is thus formed, wherein the bag 3 filled with sand rests on the underside of the foam layer 2, the bag 3 being additionally held in its position by small tongues 7 of the foam, reaching around the bag, so that the bag cannot be released from the foam layer 2.

In Figure 3, the moulding according to the invention of Figure 2 is shown in a view from below. The bag 3 resting in the foam layer 2 can be seen. As viewed from below, the bag 3 filled with sand 5 is located in the centre of the foam body 2.

Figure 4 shows a further embodiment of the mouldings according to the invention, five bags 3 filled with sand being distributed close to each of the corners and in the middle of the moulding. It has been found that, even in such an arrangement, the bag ensures excellent sound attenuation.

Figure 5 shows a graphic representation of the sound attenuation at various frequencies, the sound attenuation A dB as a function of frequency, in mouldings according to Figures 3 and 4, being compared with a flexible foam plate which does not have any cavities filled with sand. It can be seen that the embodiment according to Figure 3 (curve 2), effects a better sound attenuation in all frequency ranges than the state of the art, whilst the embodiment according to Figure 4 (curve 3), although the resulting sound attenuation at lower frequencies up to 200 Hz is somewhat poorer than in the state of the art (curve 1), effects a substantially better sound attenuation at higher frequencies, which is even better than that of the embodiment according to Figure 3.

Claims (21)

1. A moulding of a porous material, for use as sound insulation, sound attenuation or for an antidrumming treatment, which comprises a layer of a porous material having cavities opening onto one side thereof, said cavities being filled with a finegrained material and, on said one side, being closed by a thin flexible, resistant film.

2. A moulding according to claim 1, wherein a heavy-weight layer is provided on said porous layer on the side opposed to said one side.

3. A moulding according to claim 1 or 2, wherein the porous material is a foam, woven fabric, knitted fabric, felt material and/or nonwoven material.

4. A moulding according to claim 1,2 or 3, wherein the fine-grained material is a mineral filler, an inorganic or organic material or a mixture thereof.

5. A moulding according to any of claims 1 to 4, wherein the thin, resistant film is a thermoplastic, a thermosetting plastic and/or an elastomer.

6. A moulding according to any of claims 1 to 5, wherein the thin, resistant film has a thickness from 1 lim to 1,000 lim.

7. A moulding according to claim 6, wherein said thickness is from 5 lim to 300 lim.

8. A moulding according to claim 7, wherein said thickness is from 15 um to 100 um.

9. A moulding according to any of claims 1 to 8, wherein the film is part of a bag which is inserted into the cavity and containing the fine-grained material.

10. A moulding according to claim 9, wherein the bag material is a film of a thermoplastic, a thermosetting plastic and/or an elastomer.

11. A moulding according to any of claims 1 to 10, wherein the fine-grained material has a grain size from 1 Fm to 20 mm.

12. Amoulding according to claim 11,wherein the fine-grained material is sand of a grain size from 0.3to2 mm.

13. A moulding according to claim 2, wherein the heavy-weight layer is a thermoplastic, a thermosetting plastic and/or an elastomer.

14. A moulding according to claim 2 or 13, wherein the heavy-weight layer contains a filler.

15. A moulding according to claim 14, wherein the filler is a mineral filler or an inorganic and/or organic filler.

16. A moulding to claim 3, wherein the foam is a filled and/or unfilled thermoplastic, thermosetting plastic and/or an elastomer foam.

17. A moulding according to claim 3, wherein the woven fabric, knitted fabric, felt material and/or nonwoven material is a natural and/or synthetic fibre.

18. Aprocessforthe preparation of a moulding according to claim 1, which comprises filling cavities in a moulding with a fine-grained material, and closing the cavities with a thin, resistant film.

19. A process according to claim 18, which comprises inserting bags of a thin, resistant film containing a fine-grained material into a mould, and forming said porous layer by providing a foamed layer in said mould around said bags.

20. A process for anti-drumming, sound insulation or sound attenuation, wherein a moulding is applied to the surface where sound insulation, attenuation or anti-drumming is to be effected, in such a way that cavities filled with fine-grained material lie against those areas of the surface where an anti-drumming, insulation or attenuation effect is to be achieved.

21. A moulding of a porous material substantially as herein described with reference to Figure 1 or 2 of the accompanying drawings.