Flame resistant polyester compositions, method of manufacture, and articles therof

1. A thermoplastic polyester composition comprising, based on the weight of the composition, a chlorine- and bromine-free combination of:

(a) from 40 to 60 wt % of a modified poly(1,4-butylene terephthalate) that (1) is derived from consisting of a poly(ethylene terephthalate) copolymer comprising a mixture of ethylene glycol groups, diethylene glycol groups, terephthalic acid groups, and isophthalic acid groups, and 1,4-butanediol, and (2) comprises a mixture of 1,4-butanediol groups, ethylene groups, diethylene glycol groups, terephthalic acid groups, and isophthalic acid groups;

(b) from 25 to 35 wt % of a glass fiber filler;

(c) from 2 to 8 wt % of a flame retardant synergist selected from the group consisting of melamine polyphosphate, melamine cyanurate, melamine pyrophosphate, melamine phosphate, and combinations thereof;

(d) from more than 10 to 15 wt % of a phosphorus flame retardant comprising: a phosphinate of formula (I)

[(R 1 )(R 2 )(PO)—O] − m M m+   (I),

a diphosphinate of formula (II)

[(O—POR 1 )(R 3 )(POR 2 —O)] 2− n M m+ x   (II), and/or

a polymer derived from the phosphinate of formula (I) or the diphosphinate of the formula (II),

wherein R 1 and R 2 are identical or different and are H, linear or branched C 1 -C 6 alkyl, or C 6 -C 10 aryl; R 3 is C 1 -C 10 , linear or branched alkylene, C 6 -C 10 arylene, C 7 -C 11 alkylarylene, or C 7 -C 11 arylalkylene; M is an alkaline earth metal, alkali metal, Al, Ti, Zn, Fe, or B; m is 1, 2, 3 or 4; n is 1, 2, or 3; and x is 1 or 2;

(e) at least 1% to less than 5 weight % of impact modifier component comprising a combination of (i) a poly(ether-ester) elastomer and (ii) a core-shell (meth)acrylate impact modifier;

wherein the poly(ether-ester) elastomer comprises long-chain ester units of formula (III):

-GOCOR′COO—  (III);

and short-chain ester units having units of formula (IV):

-DOCOR′COO—  (IV),

wherein R′ is a divalent aromatic radical remaining after removal of carboxyl groups from terephthalic acid, isophthalic acid, or a combination of terephthalic acid and isophthalic acid; G is a divalent polyalkylene oxide radical remaining after removal of terminal hydroxyl groups from a poly(alkylene oxide)glycol having a number-average molecular weight of 100 to 2500; and D is a divalent alkylene radical remaining after removal of hydroxyl groups from aliphatic diols having a molecular weight from 62 to 286; and

wherein the core-shell meth(acrylate) impact modifier has a crosslinked poly(butyl acrylate) core with a grafted poly(methyl methacrylate) shell;

(f) from more than 0 to 5 wt % poly(tetrafluoroethylene) encapsulated by a styrene-acrylonitrile copolymer; and

(g) from more than 0 wt % to 2 wt % of a stabilizer;

wherein the thermoplastic polyester composition contains less than 3 wt % of a polyetherimide; and

wherein an article molded from the composition exhibits

(a) a flexural modulus that is more than 9800 MPa to less than or equal to 20,000 MPa, measured on 3.2 mm thick bars in accordance with ASTM D 790;

(b) a flexural stress that is more than 150 MPa to less than or equal to 190 MPa, measured on 3.2 mm thick bars in accordance with ASTM D 790;

(c) an unnotched Izod impact strength that is more than 470 Joules/meter to less than or equal to 700 Joules/meter, measured on 75 mm×12.5 mm×3.2 mm bars at 23 °C. in accordance with ASTM D 256; and

(d) a V0 rating, measured on 0.8 m thick flame bars after conditioning for 48 hours at 23 °C., and 0.8 mm thick flame bars after conditioning for 168 hours at 70 °C., in accordance with UL 94.

2. The thermoplastic polyester composition of claim 1 , wherein the poly(ether-ester) elastomer is a poly(butylene terephthalate-polytetrahydrofuran) block copolymer.

3. The thermoplastic polyester composition of claim 1 , wherein the phosphorus flame retardant is present in an amount ranging from 11 to 12.5 wt %.

4. The thermoplastic polyester composition of claim 1 , wherein the impact modifier is present in an amount ranging from 2 to 2.5 wt %.

5. The thermoplastic polyester composition of claim 1 , wherein the composition contains no polyetherimide, and an article extruded from the composition exhibits a CTI (Comparative Tracking Index) of 600 volts.

6. The thermoplastic polyester composition of claim 1 , wherein the flame retardant comprises the phosphinate of formula (I).

7. An article comprising the thermoplastic polyester composition of claim 1 .

8. The article of claim 7 , wherein the article is selected from the group consisting of computer fans, electrical connectors, automotive battery housings, and lighting sockets.

9. A thermoplastic polyester composition comprising, based on the weight of the composition, a halogen-free combination of:

(a) from 40 to 60 wt % of a modified poly(1,4-butylene terephthalate) that (1) is derived from consisting of a poly(ethylene terephthalate) copolymer comprising a mixture of ethylene glycol groups, diethylene glycol groups, terephthalic acid groups, and isophthalic acid groups, and 1,4-butanediol, and (2) comprises a mixture of 1,4-butanediol groups, ethylene glycol groups, diethylene glycol groups, terephthalic acid groups, and isophthalic acid groups;

(b) from 25 to 35 wt % glass fiber filler;

(c) from 2 to 8 wt % of a flame retardant synergist selected from the group consisting of melamine polyphosphate, melamine cyanurate, melamine pyrophosphate, melamine phosphate, and combinations thereof;

(d) from more than 10 to 15 wt % a phosphinate of formula (I)

[(R 1 )(R 2 )(PO)—O] − m M m+   (I),

a diphosphinate of formula (II)

[(O—POR 1 )(R 3 )(POR 2 —O)] 2− n M m+ x   (II), and/or

a polymer derived from the phosphinate of formula (I) or the diphosphinate of the formula (II),

wherein R 1 and R 2 are identical or different and are H, or linear or branched C 1 -C 6 alkyl; R 3 is C 1 -C 10 , linear or branched alkylene; M is aluminum; m is 3; n is 3; and x is 1 or 2;

(e) at least 1 to less than 5 wt % of impact modifier component comprising a combination of (i) a poly(butylene terephthalate-polytetrahydrofuran) block copolymer and (ii) a core-shell (meth)acrylate impact modifier having a crosslinked poly(butyl acrylate) core with a grafted poly(methyl methacrylate) shell;

(f) from more than 0 to 5 wt % poly(tetrafluoroethylene) encapsulated by a styrene-acrylonitrile copolymer; and

(g) from more than 0 wt % to 2 wt % of a stabilizer;

wherein the thermoplastic polyester composition contains less than 2 wt % of a polyetherimide; and

wherein an article molded from the composition exhibits

(a) a flexural modulus that is more than 9800 MPa to less than or equal to 20,000 MPa, measured on 3.2 mm thick bars in accordance with ASTM D 790;

(b) a flexural stress is more than 150 MPa to less than or equal to 190 MPa measured on 3.2 mm thick bars in accordance with ASTM D 790;

(c) an unnotched Izod impact strength that is more than 470 Joules/meter to less than or equal to 700 Joules/meter, measured on 75 mm×12.5 mm×3.2 mm bars at 23 °C. in accordance with ASTM D 256; and

(d) a V0 rating, measured on 0.8 mm thick flame bars after conditioning for 48 hours at 23 °C., and on 0.8 mm thick flame bars after conditioning for 168 hours at 70 °C., in accordance with UL 94.

10. An article comprising the composition of claim 9 .

11. The article of claim 10 , wherein the article is selected from the group consisting of computer fans, electrical connectors, automotive battery housings, and lighting sockets.

12. The thermoplastic polyester composition of claim 1 , wherein the thermoplastic polyester composition contains less than 1 wt % of the polyetherimide.

13. The thermoplastic polyester composition of claim 1 , wherein the impact modifier component comprises from 2 to 4 wt % of a combination of a poly(butylene terephthalate-polytetrahydrofuran) block copolymer and the core-shell (meth)acrylate impact modifier having a crosslinked poly(butyl acrylate) core with a grafted poly(methyl methacrylate) shell.