Matt, flame-retardant, co-extruded polyester film, a method for the production thereof and the use of the same

DETAILED DESCRIPTION OF THE INVENTION Flame retardancy means that in what is known as a fire protection test the film complies with the conditions of DIN 4102 Part 2 and in particular the conditions of DIN 4102 Part 1 and can be allocated to construction materials class B2 and in particular B1 for low-flammability materials.
The film is also intended to pass the UL 94 test "Vertical Burning Test for Flammability of Plastic Material", thus permitting its allocation to class 94 VTM-0.
This means that the film has ceased to burn 10 seconds afer removal of the Bunsen burner, and that after 30 seconds no smoldering is observed, and moreover no burning drops are observed.
Component I of the mixture or blend is a polyethylene terephthalate homopolymer or polyethylene terephthalate copolymer, or a mixture made from polyethylene terephthalate homo- or copolymers.
Component II of the mixture or blend is a polymer containing at least one sulfonate group, in particular a condensation product of the following monomers or of their derivatives capable of forming polyesters: A) from 65 to 95 mol % of isophthalic acid; B) from 0 to 30 mol % of at least one aliphatic dicarboxylic acid of the formula HOOC--(CH.
sub.
2).
sub.
n --COOH where n is from 1 to 11; C) from 5 to 15 mol % of at least one sulfomonomer containing an alkali metal sulfonate group on the aromatic moiety of a dicarboxylic acid; D) an aliphatic or cycloaliphatic glycol having from 2 to 11 carbon atoms, in the amount necessary to form 100 mol % of condensate; where each of the percentages given is based on the total amount of the monomers forming component II.
The good mechanical properties include high modulus of elasticity (E.
sub.
MD >3200 N/mm.
sup.
2 ; E.
sub.
TD >3500 N/mm.
sup.
2) and also good values for tensile strength at break (in MD>100 N/mm.
sup.
2 ; in TD>130 N/mm.
sup.
2).
Good orientability includes the capability of the film to give excellent orientation both longitudinally and transversely during its production, without break-offs