Multi-layer body made of polycarbonate with high weathering resistance

1. A multilayer structure having high weathering stability comprising

a) a substrate layer having a light transmission (ISO 13468-2) of less than 1.0% and containing at least one thermoplastic polymer,

b) an outer layer at least on one side of the substrate layer,

wherein

the substrate layer further comprises:

a1) 0.02% by weight to 0.2% by weight of at least one anthraquinone-based colorant of the structure (1) or (2) with

structure (1)

where R 1 and R 2 are each independently H, OH, OR 5 , NH 2 or NHR 5 , where R 5 is alkyl, cycloalkyl, phenyl or substituted and fused phenyls and

where R 3 is H, alkyl or alkoxy and

where R 4 is H, OH or p-methylphenyl-NH—;

and with

structure (2):

a2) 0.01% by weight to 1.00% by weight of one or more demolding agents, and

the outer layer consists of a polysiloxane-based or polyacrylate-based or

polyurethane acrylate-based coating and contains at least one UV absorber and has a layer thickness of 2-15 μm.

2. The multilayer structure as claimed in claim 1 , wherein the dye a1) is selected from the group consisting of structures 1A to 1H

3. The multilayer structure as claimed in claim 1 , wherein the substrate layer a) further comprises at least one dyes selected from the group consisting of structures (3) to (7)

where R3 is halogen,

where n is an integer of 0-4 and,

R5-R20 radicals are each independently hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, thexyl, fluorine, chlorine, bromine, sulfone or CN,

M is aluminium, cobalt, iron, zinc, copper or manganese,

where

R1 and R2 are each independently a linear or branched alkyl radical or halogen,

n is a natural number from 0 to 4

4. The multilayer structure as claimed in claim 2 , wherein the substrate layer comprises one dye of the structure (1C) and one dye selected from the group consisting of structures (1H), (1G), (1D) and (2).

5. The multilayer structure as claimed in claim 1 , wherein the substrate layer is free of carbon black and perinone-based dyes.

6. The multilayer structure as claimed in claim 1 , wherein the substrate layer further comprises the following components:

a3) at least one thermal stabilizer in a proportion of 0.00% by weight-0.20% by weight,

a4) at least one processing stabilizer in a positive proportion of less than 0.05% by weight,

a5) at least one UV absorber in a proportion of 0.0% to 20.0% by weight, and

a6) at least one further additive in a proportion of 0.0% by weight to 5.0% by weight.

7. The multilayer structure as claimed in claim 1 , wherein the substrate layer further comprises the following components:

a3) at least one thermal stabilizer in a proportion of 0.01% by weight-0.10% by weight,

a4) at least one processing stabilizer in a proportion of 0.00005% by weight to 0.05000% by weight,

a5) at least one UV absorber in a proportion of 0.10% to 1.00% by weight, and

a6) at least one further additive in a proportion of 0.01% by weight to 1.00% by weight.

8. The multilayer structure as claimed in claim 1 , wherein the thermoplastic polymer in the substrate layer is a polycarbonate or a polycarbonate blend containing vinyl (co)polymers or polyesters.

9. The multilayer structure as claimed in claim 6 , wherein component a4) is triisooctyl phosphate.

10. The multilayer structure as claimed in claim 1 , wherein the outer layer is a polysiloxane-based coating.

11. The multilayer structure as claimed in claim 1 , wherein the outer layer has a thickness of 4.0 to 12.0 μm.

12. The multilayer structure as claimed in claim 1 , wherein an outer layer is disposed on both sides of the substrate layer.

13. The multilayer structure as claimed in claim 1 , wherein a primer layer is disposed between the outer layer and substrate layer.

14. The multilayer structure as claimed in claim 13 , wherein the primer layer has a thickness of 0.3 μm to 8.0 μm.

15. A process for producing a multilayer structure, wherein the process comprises the following steps:

producing a substrate material comprising polycarbonate having a light transmission (ISO 13468-2) of less than 1.0% and a melt volume flow rate (MVR) of 7 cm 3 /10 min to 25 cm 3 /10 min comprising

a1) 0.02% by weight to 0.2% by weight of at least one anthraquinone-based colorant of the structure (1) or (2) with

structure (1)

where R 1 and R 2 are each independently H, OH, OR 5 , NH 2 or NHR 5 ,

where R 5 is alkyl, cycloalkyl, phenyl or substituted and fused phenyls and

where R 3 is H, alkyl or alkoxy and

where R 4 is H, OH or p-methylphenyl-NH—;

and with

structure (2):

a2) 0.01% by weight to 1.00% by weight of one or more demolding agents and optionally components a3) to a6);

a3) at least one thermal stabilizer,

a4) at least one processing stabilizer,

a5) at least one UV absorber,

a6) at least one further additive

producing a molding in a specific framework geometry at high mold temperatures;

coating the molding in a flow-coating process with a primer solution comprising

a) organic binder material which enables adhesion between PC and a polysiloxane-based coating material, and

b) at least one UV absorber,

c) an alcohol-based solvent,

venting the molding at room temperature for 10-60 min and curing at 100-135° C. for 5 min to 60 min.,

coating the molding with a siloxane coating material in a flow-coating process comprising

a) organosilicon compounds of the formula R n SiX 4-n (with n from 1 to 4), where R represents aliphatic C1 to C10 radicals and aryl radicals, and X is H, aliphatic C1 to C10 radicals and aryl radicals, or partial condensates thereof,

b) at least one finely divided inorganic compound,

c) an alcohol-based solvent,

d) at least one UV absorber; and

venting the molding at room temperature for 10-60 min and curing at 100-140° C. for 10 min to 120 min.