Low smoke halogen free flame retardant thermoplastic elastomer compositions

1. A halogen-free flame retardant polymer composition comprising:

a) one or more thermoplastic elastomers; and

b) a flame retardant mixture comprising:

b1) magnesium hydroxide;

b2) aluminium trihydrate;

b3) melamine cyanurate;

b4) and optionally a phosphate ester flame retardant;

wherein the one or more thermoplastic elastomers are copolyetherester elastomers;

wherein the amount of the one or more thermoplastic elastomers is from about 40 weight percent to about 80 weight percent;

wherein the sum of the amount of b1) and the amount of b2) is lower than or equal to about 20 weight percent;

and wherein the amount of the optional phosphate ester flame retardant b4), when present, is lower than or equal to 15 weight percent; and

wherein the weight percentages are based on the total weight of the flame retardant polymer composition.

2. The halogen-free flame retardant polymer composition of claim 1 , wherein the one or more thermoplastic elastomers are copolyetherester elastomers having a multiplicity of recurring long-chain ester units and short-chain ester units joined head-to-tail through ester linkages, said long-chain ester units being represented by formula (A):

and said short-chain ester units being represented by formula (B):

wherein:

G is a divalent radical remaining after the removal of terminal hydroxyl groups from poly(alkylene oxide)glycols having a number average molecular weight of between about 400 and about 6000;

R is a divalent radical remaining after removal of carboxyl groups from a dicarboxylic acid having a molecular weight of less than about 300; and

D is a divalent radical remaining after removal of hydroxyl groups from a diol having a molecular weight less than about 250.

3. The halogen-free flame retardant polymer composition of claim 1 , wherein the one or more thermoplastic elastomers are copolyetherester elastomers prepared from monomers comprising (1) poly(tetramethylene oxide) glycol; (2) a dicarboxylic acid selected from the group consisting of isophthalic acid, terephthalic acid and mixtures thereof; and (3) a diol selected from the group consisting of 1,4-butanediol, 1,3-propanediol and mixtures thereof.

4. The halogen-free flame retardant polymer composition of claim 1 , wherein the one or more thermoplastic elastomers are copolyetherester elastomers prepared from monomers comprising (1) poly(trimethylene oxide) glycol; (2) a dicarboxylic acid selected from the group consisting of isophthalic acid, terephthalic acid and mixtures thereof; and (3) a diol selected from the group consisting of 1,4-butanediol, 1,3-propanediol and mixtures thereof.

5. The halogen-free flame retardant polymer composition of claim 1 , wherein the one or more thermoplastic elastomers are copolyetherester elastomers prepared from monomers comprising (1) ethylene oxide-capped poly(propylene oxide) glycol; (2) dicarboxylic acids selected from the group consisting of isophthalic acid, terephthalic acid and mixtures thereof; and (3) a diol selected from the group consisting of 1,4-butanediol, 1,3-propanediol and mixtures thereof.

6. The halogen-free flame retardant polymer composition of claim 1 , wherein the amount of flame retardants b1) to b4) is from about 20 to about 50 weight percent, based on the total weight of the flame retardant polymer composition.

7. The halogen-free flame retardant polymer composition of claim 1 , wherein the amount of b3) is from about 10 to about 30 weight percent, based on the total weight of the flame retardant polymer composition.

8. The halogen-free flame retardant polymer composition of claim 1 , wherein the phosphate ester flame retardant b4) is resorcinol bis(di-2,6-dimethylphenyl phosphate).

9. The halogen-free flame retardant polymer composition of claim 1 , wherein the flame retardant mixture b) comprises magnesium hydroxide b1) and aluminium trihydrate b2) in a total amount of about 1 to about 20 weight percent; melamine cyanurate b3) in an amount of about 10 to 30 weight percent; and a phosphate ester flame retardant b4) in an amount of about 0 to 15 weight percent; and wherein the weight percentages of b1), b2), b3) and b4) are based on the total weight of the flame retardant polymer composition.

10. The halogen-free flame retardant polymer composition of claim 1 , having a maximum smoke density Ds,m of about less than or equal to 300 and a VOF4 of about less than or equal to 300, as measured according to ASTM E662 Flaming Mode.

11. The halogen-free flame retardant polymer composition of claim 1 , having a minimum light transmittance of greater than or about 60%, as measured according to IEC61034.

12. A molded, extruded, or shaped article and a fiber or a filament comprising the halogen-free flame retardant polymer composition of claim 1 .

13. A wire, a cable or an optical cable comprising a coating made of the halogen-free flame retardant polymer composition of claim 1 .