The present invention relates to a composition suitable for producing sheet material with sound dampening properties, and in particular to a composition that is also friendly to the environment. The present invention also relates to a process for producing sheet material from the composition.

Background to the invention

Sound dampening properties are found in materials with a high sound transmission loss. The sound transmission loss of a material is determined by various physical factors such as mass and stiffness. The mass per unit area of a material is the most important factor in controlling the transmission of sound through the material. The so-called mass law is worth repeating here, as it applies to most materials at most frequencies:

TL = 20 1og ₁₀ (m _s f) - 48.

where: TL = transmission loss (dB) m _s = mass per unit area (kg/m ² ) f = frequency of the sound (Hz)

Stiffness of the material is another factor that influences TL. Stiffer materials exhibit "coincidence dips" which are not explained by the above mass law. The coincidence or critical frequency is shown by:

f _c = A/t

where: A is a constant for a material t is the thickness of the material (mm)

An example of a composition that is commonly used to produce sheet material with sound

dampening properties is what is termed a loaded vinyl. In such a composition, a material with a high density is combined with vinyl at formulation stage. The resulting product has a high density whilst still maintaining high flexibility and thereby providing sound dampening properties.

However, vinyl is a product derived from petroleum sources so its cost and production is directly linked to the oil price and dictated by oil supply. Furthermore, vinyl does not biodegrade easily and in addition produces toxic fumes when burnt. This poses a particular problem when a loaded vinyl is used as a building material for its sound dampening properties.

Accordingly, there is a need for an alternative material that may be used to produce sheet material with sound dampening properties and which overcomes the disadvantages of loaded vinyl.

Summary of the invention

According to one aspect the present invention provides a composition for producing sheet material with sound dampening properties wherein the composition includes water, gelatine, glycerine and a filler material.

Preferably, the composition includes: 5 - 40 wt% water 5 - 30 wt% gelatine 5 - 40 wt% glycerine; and

20 - 60 wt% filler material

Preferably, the composition also includes 1 to 15 wt% of a group II metal chloride such as for example calcium chloride or magnesium chloride. More preferably, the composition includes 2 to 10 wt% magnesium chloride.

Preferably, the composition further includes 0.5 to 7 wt% starch or gluten. Preferably the starch is provided from the addition of cornflour to the composition.

Preferably, the filler material is a non-reactive material with a high density. Preferably the density is greater than 1 g/cm ³ , and more preferably the density of the filler material is approximately 2.0 to 3.0 g/cm ³ . The filler material may be chosen from any non-reactive material with a high density such as for example barium sulphate or KAOLIN.

Preferably the composition includes: 10 - 25 wt% water

5 - 20 wt% gelatine

10 - 25 wt% glycerine;

40 - 60 wt% filler material;

1 - 10 wt% magnesium chloride; and 0.5 - 3 wt% starch;

The composition may further include constituents such as for example ethylene and/or propylene glycols; polyvinyl alcohols; deodorisers; anti-oxidants and/or fungicides.

According to another aspect the present invention provides a sheet material with sound dampening properties wherein the sheet material is prepared from a composition including:

5 - 40 wt% water

5 - 30 wt% gelatine

5 - 40 wt% glycerine; and 20 - 60 wt% filler material.

Preferably, the composition also includes 1 to 15 wt% of a group II metal chloride such as for example calcium chloride or magnesium chloride. More preferably, the composition includes 2 to 10 wt% magnesium chloride.

Preferably, the composition further includes 0.5 to 7 wt% starch or gluten. Preferably the

starch is provided from the addition of cornflour to the composition.

Preferably the sheet material is produced in the form of a sheet of between 1 and 8 mm in thickness. Preferably the sheet material is 1.7mm in thickness up to 6 mm. The sheet material may be bonded on either or both planar surfaces to any suitable material to provide a composite layered material. Suitable materials may be aluminium film, plasterboard, timber, steel (colourbond roofing), fibre-cement sheeting, non-woven polyester, acoustic foam or any other natural fibre matting.

The sheet material may be affixed to other suitable materials by adhesive or during curing process at manufacturing stage.

The sheet material may be of any suitable density, preferably within a range of 1 g/cm ³ to 3 g/cm .

Preferably the sheet material is incorporated into a wall structure utilising, for example, staggered studs and a cavity filled with polyester batts or suitable sound absorptive material. The sheet material maybe incorporated into said wall structure by sandwiching the sheet material between two plasterboard sheets.

According to a further aspect the present invention provides a process for producing a sheet material with sound dampening properties including the steps of

(i) combining water, glycerine and cornflour and heating the resulting mixture to 80 - 90 ⁰ C until a gel forms; (ii) dissolving gelatine into the gel;

(iii) adding magnesium chloride to the gel;

(iv) mixing in the filler material to achieve a uniform composition; (v) extruding the resulting gel into a flat sheet of desired thickness; and (vi) cooling the sheet to room temperature whereby the sheet material cures.

According to one embodiment at step (v) of the process, the gel may be extruded onto an aluminium foil sheet or another suitable material whereby, once the sheet cures in step (vi), a composite sheet material is produced.

Detailed Description of the Invention

The composition according to the present invention may be used to provide an acoustic sheeting material that has significant sound dampening characteristics. The sheeting material once formed has a density at least greater than 1 g/cm ³ and preferably a density of about 2.5 g/cm ³ . In addition to the high density, the sheeting material is very flexible with a high elastic memory, thus providing excellent sound dampening properties.

As the composition of the present invention is made from non-petroleum based products, the acoustic sheeting material produced from the composition is biodegradable and non toxic. Furthermore, the cost of the sheeting material is independent from the oil price and oil supply.

Another advantage of the composition is that it is fire retardant and does not give off toxic fumes when burnt in contrast to the alternative product of loaded vinyl. This provides that the material may be used extensively in building materials to provide a safer and greener alternative to loaded vinyl.

During the process to produce the acoustic sheeting, the composition of the present invention may also be coloured by any suitable techniques, to produce sheeting in any colour that may be desired. Furthermore, the composition has excellent adhesion properties and does therefore not require gluing at the formation stage if bonded to a suitable substrate. Alternatively, once the sheeting material has cured, the material is also compatible with most glues and adhesives such that a composite material may be produced at that stage.

The present invention will become better understood from the following example of a preferred but non-limiting embodiment thereof.

Example

100 g of water together with 100 g of glycerine and 10 g of starch was mixed and then heated to a temperature of 85 °C. 80 g of gelatine and 20 g of magnesium chloride was then dissolved into the mixture and a gel was formed. 31O g of barium sulphate was then added to the gel providing a composition with good flexibility, elasticity, tensile strength, and density with good film forming properties. The composition had the following composition by weight:

16% water; 16% glycerine; 1.5% starch;

13% gelatine;

3.5% magnesium chloride; and 50% barium sulphate.

The composition was then extruded into a flat sheet and bonded onto an aluminium film and then brought down to room temperature whereby the composition cured to form a sheet of composite material of 4mm in thickness that showed excellent sound dampening properties.

Although several embodiments have been described in detail, it should be understood that various changes, substitutions, and alterations can be made herein by one ordinarily skilled in the art without departing from the spirit or scope of the present invention.