Polycarbonate plates with improved flame resistance

1. A sheet comprising a

base layer comprising

polycarbonate and

0.15 to 3 wt. % of a flame retardant, wherein the flame retardant comprises at least one phosphorus compound of formula 1

wherein

R 1 , R 2 , R 3 and R 4 are phenyl,

n independently of one another represents 0 or 1,

q independently of one another represents 0, 1, 2, 3 or 4, and

N is 0.60 to 4.00,

R 5 and R 6 , independently of one another, represents a C 1 -C 4 alkyl, and

Y represents a C 1 -C 7 alkylidene, C 1 -C 7 alkylene, C 5 -C 12 cycloalkylene, C 5 -C 12 cycloalkylidene, —O—, —S—, —SO—, —SO 2 —, —CO— or a residue of formula (2) or (3)

wherein

Z represents carbon and

R 21 and R 22 can be selected for each Z individually and, independently of one another, represent hydrogen or C1-C6 alkyl,

m represents an integer from 4 to 7,

with the proviso that, on at least one Z atom, R 21 and R 22 are simultaneously alkyl and wherein the polycarbonate comprises a mixture of linear and branched polycarbonate and wherein the linear polycarbonate content is at least 40 wt. %, based on the total polycarbonate weight and the composition contains no anti-dripping agent and contains as flame retardants exclusively phosphorous compounds of general formula (1) and the sheet after one year of outdoor weathering meets the fire classification B1 according to DIN 4102 B1.

2. The sheet according to claim 1 , wherein the at least one phosphorus compound comprises a bisphenol A diphosphate.

3. An architectural glazing in roofing or a glazing for swimming pools, carports, greenhouses, industrial complexes or private buildings, or as a noise protection wall or screen wall comprising the sheet according to claim 1 .

4. The sheet according to claim 1 , wherein R 5 and R 6 , independently of one another, represents methyl and/or a halogen.

5. The sheet according to claim 1 , wherein the halogen comprises chlorine and/or bromine.

6. The sheet according to claim 1 , wherein R 21 and R 22 can be selected for each Z individually and, independently of one another, represent hydrogen, methyl and/or ethyl.

7. The sheet according to claim 1 , wherein m represents an integer from 4 to 5.

8. The sheet according to claim 1 , wherein N is 0.90 to 2.50.

9. The sheet according to claim 1 , wherein N is 1.00 to 1.15.

10. The sheet according to claim 1 , wherein the polycarbonate comprises homopolycarbonates, copolycarbonates and/or thermoplastic polyester carbonates.

11. The sheet according to claim 10 , wherein the sheet is additionally coated on one or both sides with at least one coextrusion layer comprising a UV absorber and

R 5 and R 6 , independently of one another, represent methyl and/or a halogen,

R 21 and R 22 can be selected for each Z individually and, independently of one another, represent hydrogen, methyl and/or ethyl,

m represents an integer from 4 to 5 and

N is 1.00 to 1.15.

12. The sheet according to claim 11 , wherein the base layer consists essentially of

at least 40 wt. % of the linear polycarbonate,

at least 40 wt. % of a branched polycarbonate,

0.15-5 wt. % of a flame retardant and

wherein the linear polycarbonate is present in the sheet in a higher amount than the branched polycarbonate.

13. The sheet according to claim 1 , wherein the sheet is additionally coated on one or both sides with at least one coextrusion layer comprising a UV absorber.

14. The sheet according to claim 13 , wherein the UV absorber comprises triazines, benzotriazoles, cyanoacrylates and/or bismalonates and the base layer comprises no UV absorbers or one or more UV absorbers selected from the group consisting of benzotriazoles, cyanoacrylates and bismalonates.

15. The sheet according to claim 1 , wherein the sheet is a multi-wall sheet.

16. The sheet according to claim 15 , wherein the weight per unit area of the multi-wall sheet is greater than 2.4 kg/m 2 .

17. The sheet according to claim 15 , wherein the sheet is a multi-wall sheet of the following geometry:

a. a 3-wall sheet with a thickness of 12 to 20 mm and a rib spacing of 12 to 20 mm,

b. a 6-wall sheet with a thickness of 12 to 22 mm and a rib spacing of 12 to 22 mm,

c. a 3-wall sheet with an X profile and a thickness of 12 to 20 mm wherein the X structure has a width of 20 to 30 mm, which is made up of 3 ribs,

d. a 5-wall sheet with an X profile and a thickness of 20 to 50 mm wherein the X structure has a width of 20 to 30 mm, which is made up of 3 ribs, or

e. a 5-wall sheet with an M profile and a thickness of 20 to 50 mm and the ribs have a spacing of 15 to 25 mm.

18. A sheet consisting essentially of a base layer consisting essentially of

polycarbonate and

0.05-6 wt. % of a flame retardant, wherein the flame retardant comprises at least one phosphorus compound of formula 1

wherein

R 1 , R 2 , R 3 and R 4 are phenyl,

n independently of one another represents 0 or 1,

q independently of one another represents 0, 1, 2, 3 or 4, and

N is 0.60 to 4.00,

R 5 and R 6 , independently of one another, represents a C 1 -C 4 alkyl, and

Y represents a C 1 -C 7 alkylidene, C 1 -C 7 alkylene, C 5 -C 12 cycloalkylidene, —O—, —S—, —SO—, —SO 2 —, —CO— or a residue of formula (2) or (3)

wherein

Z represents carbon and

R 21 and R 22 can be selected for each Z individually and, independently of one another, represent hydrogen or C1-C6 alkyl,

m represents an integer from 4 to 7,

with the proviso that, on at least one Z atom, R 21 and R 22 are simultaneously alkyl and wherein the polycarbonate consists essentially of a mixture of linear and branched polycarbonate and wherein the linear polycarbonate content is at least 40 wt. %, based on the total polycarbonate weight and the composition contains no anti-dripping agent and contains as flame retardants exclusively phosphorous compounds of general formula (1) and the sheet after one year of outdoor weathering meets the fire classification B1 according to DIN 4102 B1.