GB1596607A

GB1596607A - Sound-insulating materials

Info

Publication number: GB1596607A
Application number: GB7996/78A
Authority: GB
Original assignee: Semperit AG Holding
Current assignee: Semperit AG Holding
Priority date: 1977-03-14
Filing date: 1978-03-01
Publication date: 1981-08-26
Also published as: FR2383782A1; DE2807384A1; FR2383782B1; IT1093576B; CH614155A5; IT7821177A0

Abstract

To increase sound insulation, filler with a density of 2.5 to 4 g/cm is added to a rubber layer (1). Layers (2, 3) which are adhesively bonded on one or both sides and consist of flexible polyurethane foam serve to increase the insulating effect by prefiltering the sound waves. <IMAGE>

Description

(54) IMPROVEMENTS IN OR RELATING TO SOUND-INSULATING MATERIALS (71) We, SEMPERIT AKTIENGESELLSCHAFT, an Austrian Company of Wiedner Hauptstrasse 63, A1041 Vienna 4, Austria, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to soundinsulating material comprising layers of different materials bonded together.

Sound-insulating materials are known which consist of a lead-filled polyvinyl chloride layer which is fixed on a face to a substrate of glass-cloth or like material and coated on the other face with a polyurethane foam. Such sound-insulating materials are fixed to a sound-generating object with the polyurethane foam layer in contact with the resonance face of the object. The sound-insulation is basically effected by the lead filling of the polyvinylchloride layer. The glass-cloth serves essen tally to improve the strength of the material.The service life of such soundinsulating materials is, however, limited, because as a result of migration of the plasticiser contained in the polyvinylchloride on the one hand, the adhesion to the resonance face is destroyed, and on the other hand embrittlement takes place, with consequent impairment of the soundinsulating properties. Another disadvantage of this known material from the economic standpoint, is the fact that cloth is required to provide strength and support.

The use of lead-filled rubber sheeting as a sound-insulating material is also known.

Such rubber sheeting is fixed directly to the resonance face and brings about a substantial reduction in radiated sound. The adhesion of the rubber to the resonance face presents some problems since the face is subjected to very high loadings because of the mechanical vibration. It is also a disadvantage that in practice, it is almost impossible to match the absorption performance to different sound frequency conditions because of the single-layer structure of the material.

It is an object of the present invention to provide a sound-insulating material which offers good sound-insulating characteristics for a wide variety of service conditions, which is readily fixed to a curved or irregular surface, and which has good temperature stability, good resistance to chemicals and, in many cases, good thermal insulating properties.

According to the invention, there is provided a sound-insulating material comprising a layer consisting of a filled unfoamed rubber mix and having on opposite sides thereof respectively a first and a second layer of a soft polyurethane foam.

If such a sound-insulating material is to be used for insulating a compressor, for example, the second layer of polyurethane foam is fixed to the inner wall of the compressor casing, so that the first layer of polyurethane foam faces the interior of the casing. The sound waves striking the polyurethane foam are prefiltered by this layer and only then reach the layer of filled unfoamed rubber mix, where the sound absorption basically takes place. The level of sound absorption depends upon the nature of the filler used and upon the thickness of the filled rubber layer. It will be obvious that the degree of sound absorption will increase as the thickness of the layer is increased. so that variation of this parameter allows a large degree of adaptation to particular needs.

However, it has been found that a surprising overall effect as regards attainable sound absorption is obtained by combining the layer of the rubber mix and the layers of soft polyurethane foam, in accordance with the invention. This may possibly be connected with the fact that, in contrast to polyvinylchloride which, as stated above, is already known as a binder for a sound-absorbing filler, filled rubber mixes have a very high vibration-damping coefficient, so that in the materials of the invention, the binder itself makes a considerable contribution to the sound absorption.

In the material of the present invention powders consisting of, for example, barium sulphate, lead sulphate, lead, copper, iron pyrites, and quartz sand, or mixtures thereof, can be used as fillers for the rubber mix.

The filler is preferably used in such an amount that the specific gravity of the filled rubber mix is in the range of 2.5 to 4 3 gm/cm3.

Particularly good sound-insulation properties are obtained if the rubber mix is unvulcanised. To begin with, unvulcanised rubber mixes have a high vibration-damping coefficient and are therefore particularly suitable for the present purpose. Another advantage with unvulcanised rubber mixes is their good adhesion properties. This advantage can be utilised, even if the rubber mix is initially unvulcanised but contains a vulcanising agent which will bring about vulcanisation of the mix when the soundinsulating material is in use. Through vulvanisation, the rubber acquires greater mechanical strength and an improved chemical resistance. If these qualities are particularly desired from the start, the rubber mix can be used in the vulcanised form.

The sound-insulating material in accordance with the invention has particularly good sound-insulating properties if the soft polyurethane foam is a soft polyesterpolyurethane foam with a density of 25 to 30 gm/dm3. Soft polyester-polyurethane foams, as compared with soft polyetherpolyurethane foams, have considerably better sound-absorption properties, which may possible be due to the more flexible physical linking provided by the ester bonds. This leads to a certain degree of distortability and thus a capacity for absorbing kinetic energy.

Particularly good sound-insulation properties are obtained if the layer of filled rubber mix is 3 to 6 mm thick, the first layer of soft polyurethane foam is 15 to 25 mm thick and the second layer of soft polyurethane foam is 3 to 10 mm, particularly 4 to 6 mm thick.

The covering of the other face of the layer of rubber mix with the second layer of soft polyurethane foam, so that the rubber layer is covered on both sides with the soft foam, has the advantage that the layer of the rubber mix is not fixed directly to the resonance face in use, so that vibrations in the rubber layer are not transmitted to this layer directly. The sound-insulating materials of the invention have proved to be particularly suitable for the sound-damping of machine casings.

To To protect the material against particular- ly aggressive media, it may be desirable to provide each of the layers of soft polyurethane foam with a covering in the form of a sheet of, for example, polyester, polytetrafluoroethylene, silicone or the like plastics material, on its face remote from the layer of rubber mix. In order further to improve the inherently good thermal insulation properties of the sound-insulating material in accordance with the invention, it may be expedient to coat the plastics sheet with metal, e.g. aluminium, by vapour deposition. This enables it to reflect radiant heat.

In order to improve ambient soundinsulation performance. the side of the first polyurethane foam layer remote from the layer of rubber mix may be given a textured surface; for example, the surface can be provided with knobs or pyramidal projections. This improves the sound-absorbing performance.

The sound-insulating material in accordance with the invention can be particularly easily applied if it is provided with a self-adhesive coating e.g. on the exposed face of the second polyurethane foam layer; such self-adhesive coatings are only usable, however, within a limited temperature range (up to about 70"C) since they fail at higher temperatures.

The soft polyurethane foam used for the sound-insulating material of the invention can also be rendered fire-resistant (e.g. to Austrian Standard B 3.800), so that, even in this respect, every demand made on a sound-insulating material is well satisfied.

The invention will now be further described with reference to the drawing, in which Figures 1 to 4 are similar schematic views of part of a sound-insulating material to illustrate four embodiments of the invention.

In Figures 1 to 4, like parts have been given the same reference numeral.

The sound-insulating material illustrated in Figure 1 consists of a layer 1 of a filled unfoamed rubber mix bonded at one face to a first layer 2 of soft polyurethane foam, and at the other face to a second layer 3 of soft polyurethane foam, The layer 2 may be 20 mm thick, for example, the layer 1, 3 mm thick, and the layer 3, 5 mm thick. With such a format, the mean sound-insulation value Rm is 37.4 dBA. The weight of such a sound-insulating material is about 9.5 kg/m (specific gravity of the layers 1-3).

In the embodiment of Figure 2, the layer 3 is provided with a self-adhesive coating 4; this makes application of the material particularly easy.

In order to improve its resistance to aggressive media, the sound-insulating material shown in Figure 3 is provided with a sheet 5 of polyester, covering the outer face of the layer 2.

The sound-insulating material shown in Figure 4 consists of a layer 1 of a filled unfoamed rubber mix and layers 3 and 6 of a soft polyurethane foam bonded respectively to opposite faces of the layer 1; the layer 6 has a textured surface 7 the texture being in the form of projecting knobs.

WHAT WE CLAIM IS: 1. A sound-insulating material comprising a layer consisting of a filled rubber mix and having on opposite sides thereof respectivelv a first and a second layer of a soft polyurethane foam.

2. A sound-insulating material as claimed in Claim 1, wherein said rubber mix is filled with powdered barium sulphate, lead sulphate, lead, copper, iron, pyrites, or quartz sand, or a mixture of two or more of these powdered substances.

3. A sound-insulating material as claimed in Claim 1 of Claim 2, wherein said rubber mix is unvulcanised.

4. A sound-insulating material as claimed in Claim 3, wherein said rubber mix is initially unvulcanised but contains a vulcanisation agent which will effect vulcanisation of said mix under the conditions of use of the sound-insulating material.

5. A sound-insulating material as claimed in Claim 1, or Claim 2, wherein said rubber mix is vulcanised.

6. A sound-insulating material as claimed in any one of the preceding Claims, wherein said soft polyurethane foam is a soft polyester-polyurethane foam with a denisty of 25 to 30 gm/dm3.

7. A sound-insulating material as claimed in any one of the preceding Claims, wherein the thickness of said layer of filled unfoamed rubber mix is 3 to 6 mm, and the thickness of said first layer of polyurethane foam is 15 to 25 mm.

8. A sound-insulating material as claimed any one of the preceding claims, wherein said second layer of soft polyurethane foam has a thickness of 3 to 10 mm.

9. A sound-insulating material as claimed in Claim 8, wherein said second layer of soft polurethane foam has a thickness of 4 to 6 mm.

10. A sound-insulating material as claimed in any one of the preceding Claims, wherein at its face remote from said layer of filled unfoamed rubber mix, said layers at least one of soft polyurethane foam is bonded to a sheet made of a plastics material.

11. A sound-insulating material as claimed in Claim 10, wherein said plastics material is a polyester, polytetrafluoroethylene, or a silicone.

12. A sound-insulating material as claimed in Claim 10 or Claim 11, wherein said plastics sheet is itself coated with a metal.

13. A sound-insulating material as claimed in Claim 12, wherein said metal coating is of vapour-deposited aluminium.

14. A sound-insulating material as claimed in any one of Claims 1 to 9, wherein the face of said first layer of soft polyurethane foam remote from said layer of filled unfoamed rubber mix is textured.

15. A sound-insulating material as claimed in any one of the preceding Claims, having on one face thereof a self-adhesive coating.

16. A sound-insulating material substantially as hereinbefore described with reference to and as illustrated in any of Figures 1 to 4 of the drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. aggressive media, the sound-insulating material shown in Figure 3 is provided with a sheet 5 of polyester, covering the outer face of the layer 2. The sound-insulating material shown in Figure 4 consists of a layer 1 of a filled unfoamed rubber mix and layers 3 and 6 of a soft polyurethane foam bonded respectively to opposite faces of the layer 1; the layer 6 has a textured surface 7 the texture being in the form of projecting knobs. WHAT WE CLAIM IS:

1. A sound-insulating material comprising a layer consisting of a filled rubber mix and having on opposite sides thereof respectivelv a first and a second layer of a soft polyurethane foam.