Acoustic laminated glazing, acoustic interlayer and method for selecting the interlayer for optimal acoustic damping

1. A glazing comprising at least two glass sheets and a viscoelastic plastic insert arranged between the glass sheets, said insert comprising at least two damping films, one of the damping films being made of a material A and the other damping film being made of another material B, so that material A has, over a temperature range t A , a loss factor tan δ greater than 0.6 and a shear modulus G′ less than 2×10 7 Pa, and material B has, over a temperature range t B , a loss factor tan δ greater than 0.6 and a shear modulus G′ less than 2×10 7 Pa, wherein the insert provides acoustic comfort to the glazing over at least two distinct temperature ranges t 1 and t 2 , the temperature range t 1 being included within the temperate range t A and the temperature range t 2 being included within the temperature range t B , and in that the film which has, at a frequency of 200 Hz and for one of the two temperature ranges t 1 or t 2 , the highest loss factor tan δ, has an equivalent shear modulus G′ eq , such that

G

eq

′

=

G

′

⁢

e

tot

e

where G′ is the shear modulus of the material constituting the film, e is the thickness of the film and e tot the total thickness of the insert, which is less than the equivalent shear modulus or moduli of the other film or films for said temperature range t 1 or t 2 .

2. The glazing according to claim 1 wherein, over a temperature range t 3 between the two distinct temperature ranges t 1 and t 2 , the ratio between the equivalent shear moduli of the films lies between 0.2 and 5.

3. The glazing according to claim 2 , wherein the shear modulus G′ of the insert is less than 2×10 7 Pa and the loss factor tan δ of the insert is greater than 0.6 over the temperature range t 3 between the distinct temperature ranges t 1 and t 2 .

4. The glazing according to claim 1 , wherein the shear modulus G′ of the insert is less than 2×10 7 Pa and the loss factor tan δ of the insert is greater than 0.6 over at least the two distinct temperature ranges t 1 and t 2 .

5. The glazing according to claim 1 , wherein the films are laminated so as to form the insert.

6. The glazing according to claim 1 , wherein the films form the insert by coextrusion of the materials.

7. The glazing according to claim 1 , wherein it is used in a motor vehicle.

8. The glazing according to claim 1 , wherein it is used in a building.

9. A viscoelastic plastic insert intended to be incorporated between two glass sheets of a glazing panel, comprising at least two damping films, one of the damping films being made of a material A and the other damping film being made of another material B, so that material A has, over a temperature range t A , a loss factor tan δ greater than 0.6 and a shear modulus G′ less than 2×10 7 Pa, and material B has, over a temperature range t B , a loss factor tan δ greater than 0.6 and a shear modulus G′ less than 2×10 7 Pa, wherein the film has a high loss factor tan δ for a given temperature range t 1 or t 2 , the temperature range t 1 being included within the temperature range t A and the temperature range t 2 being included within the temperature range t B , and at a frequency of 200 Hz, has an equivalent shear modulus G′ eq , such that

G

eq

′

=

G

′

⁢

e

tot

e

where G′ is the shear modulus of the material constituting the film, e is the thickness of the film and e tot the total thickness of the insert which is less than the equivalent shear modulus or moduli of the other film or films for said temperature range t 1 or t 2 .

10. The insert according to claim 9 , wherein, over a temperature range t 3 between the two distinct ranges t 1 and t 2 , the ratio between the equivalent shear moduli of the films lies between 0.2 and 5.

11. The insert according to claim 9 , wherein it has a shear modulus G′ less than 2×10 7 Pa and a loss factor tan δ greater than 0.6 over the two temperature ranges t A and t B .

12. The insert according to claim 9 , wherein the films are laminated.

13. The insert according to claim 9 , wherein the films are assembled by coextruding the materials.

14. A method for selecting an insert with a view to incorporating it into a laminated glazing panel to provide the glazing panel with acoustic damping properties, said insert comprising at least two damping films, one of the damping films being made of a material A and the other damping film being made of another material B, so that material A has, over a temperature range t A , a loss factor tan δ greater than 0.6 and a shear modulus G′ less than 2×10 7 Pa, and material B has, over a temperature range t B , a loss factor tan δ greater than 0.6 and a shear modulus G′ less than 2×10 7 Pa, wherein each of the films is chosen so that, over at least two distinct temperature ranges t 1 and t 2 , the temperature range t 1 being included within the temperature range t A and the temperature range t 2 being included within the temperature range t B , and at a frequency of 200 Hz, the film which has a high loss factor tan δ for a given temperature range t 1 or t 2 , has an equivalent shear modulus G′ eq such that

G

eq

′

=

G

′

⁢

e

tot

e

where G′ is the shear modulus of the material constituting the film, e is the thickness of the film and e tot the total thickness of the insert, which is less than the equivalent shear modulus or moduli of the other film or films for said temperature range t 1 or t 2 .

15. The method according to claim 14 , wherein, over a temperature range t 3 between the two distinct temperature ranges t 1 and t 2 , the ratio between the equivalent shear moduli of the films lies between 0.2 and 5.

16. The method according to claim 14 , wherein after selecting the films, the films are brought together to form an insert that is incorporated in a laminated glazing panel.

17. The method according to claim 16 applied to a glazing panel of a building or to a vehicle.