Polycarbonate composition having improved flame resistance for extrusion applications

1. A sheet comprising a composition comprising an aromatic polycarbonate and

a) 0.1 wt. % to 4 wt. % of an acrylate-based scattering additive,

b) 0.5 wt. % to 5 wt. % of an aromatic-aliphatic polyester, and

c) 0.5 wt. % to 8 wt. % of a phosphorus-based flame retardant,

wherein the sheet passes both the fire shaft test according to DIN 4102 B1 and the dripping test according to NF P 92-505;

wherein the aromatic polycarbonate is a mixture which comprises at least 70 wt. % linear polycarbonate and at least 10 wt. % branched polycarbonate;

wherein the sheet has a weight per unit area of greater than or equal to 2.4 kg/m 2 .

2. The sheet according to claim 1 , wherein the aromatic polyester comprises a polybutylene terephthalate.

3. The sheet according to claim 1 , wherein the aromatic polyester comprises a polyester of which the acid component comprises at least 85 mole % terephthalic acid and the diol component comprises at least 80 mole % of one or more diols selected from the group consisting of 1,4-butanediol, 1,2-ethanediol, 1,4-cyclohexanedimethanol, and combinations thereof.

4. The sheet according claim 1 , wherein the scattering additive is selected from the group consisting of acrylate scattering additives, containing core-shell polymers based on polymethyl acrylate and polybutyl acrylate, partially crosslinked spherical acrylate particles, fully crosslinked spherical acrylate particles, partially crosslinked non-spherical acrylate particles and fully crosslinked non-spherical acrylate particles.

5. The sheet according to claim 1 , wherein the phosphorus-based flame retardant is selected from the group consisting of one or more compounds of the formula (4)

wherein

R 1 , R 2 , R 3 and R 4 , independently of one another, represent optionally halogen-substituted C 1 -C 8 alkyl or, each optionally halogen- and/or alkyl-substituted, C 5 -C 6 cycloalkyl, C 6 -C 10 aryl or C 7 -C 12 aralkyl,

n independently of one another represents 0 or 1,

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

and

N is 0.6 to 4,

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

Y represents a C 1 -C 7 alkylidene, a C 1 -C 7 alkylene, a C 5 -C 12 cycloalkylene, a C 5 -C 12 cycloalkylidene, —O—, —S—, —SO—, —SO 2 —, —CO— or a residue of formula (5) or (6)

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 a C1-C6 alkyl,

m is an integer from 4 to 7,

with the proviso that, on at least one Z atom, R 21 and R 22 are simultaneously alkyl.

6. The composition according to claim 5 , wherein R5 and R6, independently of one another, represent methyl or a halogen.

7. The composition according to claim 5 , wherein R5 and R6, independently of one another, represent chlorine and/or bromine.

8. The sheet according to claim 5 , wherein R21 and R22 can be selected for each Z individually and, independently of one another, represent hydrogen, methyl or ethyl.

9. The sheet according to claim 5 , wherein m is an integer from 4 to 5.

10. The sheet according to claim 5 , wherein the phosphate-containing flame retardant comprises bisphenol A diphosphate.

11. The sheet according to claim 1 , wherein the sheet is a solid or multi-wall sheet.

12. The sheet according to claim 11 , wherein the sheet exhibits less burning drips and reduced maximum flue gas temperature in the event of fire compared with sheets that are not treated with the composition.

13. The sheet according to claim 1 , wherein the sheet is a multi-layer sheet comprising a base layer comprising the composition.

14. The sheet according to claim 13 , wherein the multi-layer sheet further comprises a coextruded covering layer on one side or a coextruded covering layer on both sides comprising UV absorbers.

15. The sheet according to claim 14 , wherein the UV absorber in the covering layer or covering layers is selected from one or more compounds from the group consisting of triazines, benzotriazoles, cyanoacrylates and bismalonates and the base layer contains no UV absorber or one or more UV absorbers selected from the group consisting of benzotriazoles, cyanoacrylates and bismalonates.

16. A process comprising coextruding the multi-layer sheet according to claim 14 .

17. The sheet according to claim 1 , wherein the scattering additive is a core-shell polymer with an average particle diameter of 2 to 15 μm.

18. The sheet according to claim 17 , wherein the core-shell polymer is based on polymethyl acrylate and polybutyl acrylate.

19. A sheet comprising

a base layer consisting of a composition consisting of an aromatic polycarbonate selected from the group consisting of linear aromatic polycarbonates, branched aromatic polycarbonates, and mixtures thereof, and

a) 0.1 wt. % to 4 wt. % of an acrylate-based scattering additive,

b) 0.5 wt. % to 5 wt. % of an aromatic-aliphatic polyester,

c) 0.5 wt. % to 8 wt. % of a phosphorus-based flame retardant, and

d) optionally additives selected from the group consisting of

fillers;

UV stabilisers;

heat stabilisers;

antistatic agents;

external mold release agents or free-flow agents selected from the group consisting of low-molecular weight carboxylic acid esters, chalk, silica flour, glass and carbon fibers, and mixtures thereof;

salts to further increase flame resistance selected from the group consisting of alkali or alkaline earth salts of aliphatic or aromatic sulfonic acid, sulfonamide or sulfonimide derivatives, sodium or potassium pentachlorobenzoate, sodium or potassium 2,4,6-trichlorobenzoate, sodium or potassium 2,4-dichlorozenzoate, trisodium or tripotassium hexafluoroaluminate, disodium or dipotassium hexafluorotitanate, disodium or dipotassium hexafluorosilicate, disodium or dipotassium hexafluorozirconate, sodium or potassium pyrophosphate, sodium or potassium metaphosphate, sodium or potassium tetrafluoroborate, and combinations thereof;

halogen-containing flame retardants;

polytetrafluoroethylene;

UV absorbers selected from the group consisting of benzotriazoles, triazines, cyanoacrylates, bismalonates, and mixtures thereof; and

mixtures thereof; and

(e) optionally plastics selected from the group consisting of polyamides, polyimides, polyester amides, polyacrylates, polymethacrylates, polyacetals, polyurethanes, polyolefins, halogen-containing polymers, polysulfones, polyether sulfones, polyether ketones, polysiloxanes, polybenzimidazoles, urea-formaldehyde resins, melamine-formaldehyde resins, phenol-formaldehyde resins, alkyd resins, epoxy resins, polystyrenes, copolymers of styrene or alpha-methylstyrene with dienes or acrylic derivatives, graft polymers based on acrylonitrile/butadiene/styrene, graft copolymers based on acrylate rubber or silicone rubbers, and mixtures thereof;

wherein the sheet passes both the fire shaft test according to DIN 4102 B1 and the dripping test according to NF P 92-505;

wherein the sheet has a weight per unit area of greater than or equal to 2.4 kg/m 2 .