Process for making particulate-free poly(phenylene ether) compositions and photovoltaic backsheet materials derived therefrom

1. A process for preparing a halogen-free melt-filtered polymer composition, comprising: filtering the melted composition through a filter to remove particulate impurities that are visible to the naked eye from a film fabricated with the composition which is produced in the process, wherein the throughput for making the composition is at least 20 kg/hr and wherein the composition comprises:

(a) 60 to 90 percent by weight of a poly(phenylene ether);

(b) 3 to 23 percent by weight of a styrenic polymer;

(c) 5-11 percent by weight of a halogen-free flame retardant comprising at least one organic phosphate flame retardant, wherein the composition has:

(i) a melt viscosity of 620 Pa·s or less as measured according at 280° C. and 1500 s −1 ; and

(ii) a heat deflection temperature that is 135° C. or more as measured according to ASTM D648 on 6.4 mm thick bars at 1.82 MPa.

2. The process of claim 1 , wherein the composition is prepared using an extruder having a terminal barrel and a die head.

3. The process of claim 2 , wherein the filter is positioned after the terminal barrel of the extruder.

4. The process of claim 3 , wherein the filter is positioned after the die head of the extruder.

5. The process of claim 4 , wherein the filtering occurs at a temperature of 260° C. to 380° C.

6. The process of claim 5 , wherein the filter is selected from the group consisting of a sieve, a sintered-metal filter, metal a mesh or screen filter, a fiber metal felt filter, and ceramic filters, and a combination of thereof.

7. The process of claim 6 , wherein the filter comprises a 200 mesh filter sandwiched between two 20 mesh filters.

8. The process of claim 7 , wherein the poly(phenylene ether) is poly(2,6-dimethyl-1,4-phenylene ether) having an intrinsic viscosity of approximately 0.375-29-0.49 dL/g as measured in chloroform at 25° C.

9. The process of claim 7 , wherein the styrenic polymer is a general purpose polystyrene, high impact polystyrene, or a styrenic block copolymer.

10. The process of claim 9 , wherein the styrenic block copolymer is selected from the group consisting of a styrene-butadiene-styrene (SBS), a styrene-isoprene-styrene (SIS)), a styrene-ethylene/butylene-styrene (SEBS) and a styrene-ethylene/propylene-styrene block copolymer (SEPS).

11. The process of claim 10 , wherein the styrenic block copolymer is selected from the group consisting of a styrene-ethylene/butylene-styrene (SEBS) and a styrene-ethylene/propylene-styrene block copolymer (SEPS).

12. The process of claim 7 , wherein the flame retardant comprises resorcinol bis-diphenylphosphate (RDP), bis-phenol A bis-diphenylphosphate (BDADP), or mixtures thereof.

13. The process of claim 12 , wherein the flame retardant comprises bis-phenol A bis-diphenylphosphate (BDADP).

14. The process of claim 7 , wherein the composition comprises:

(a) 70 to 90 percent by weight of poly(2,6-dimethyl-1,4-phenylene ether) having an intrinsic viscosity of approximately 0.37-0.47 dL/g as measured in chloroform at 25° C.;

(b) 3 to 9 percent by weight of a styrenic block copolymer;

(c) 7 to 9 percent by weight of a halogen-free flame retardant comprising at least one organic phosphate flame retardant, wherein the weight percent of flame retardant exceeds the weight percent of a styrenic polymer; and wherein the composition has:

(i) a melt viscosity of 620 Pa·s or less as measured according at 280° C. and 1500 s −1 ; and

(ii) a heat deflection temperature that is 135° C. or more as measured according to ASTM D648 on 6.4 mm thick bars at 1.82 MPa.

15. The process of claim 7 , wherein the composition comprises:

(a) 80 to 90 percent by weight of poly(2,6-dimethyl-1,4-phenylene ether) an intrinsic viscosity of approximately 0.375 to 0.425 dL/g as measured in chloroform at 25° C.;

(b) 5 to 7 percent by weight of a styrene-ethylene/butylene-styrene copolymer;

(c) 7 to 9 percent by weight of RDP, BPADP, or mixtures thereof, wherein the composition has:

(i) a melt viscosity of 620 Pa·s or less as measured according at 280° C. and 1500 s −1 ; and

(ii) a heat deflection temperature that is 135° C. or more as measured according to ASTM D648 on 6.4 mm thick bars at 1.82 MPa.

16. The process of claim 1 , wherein the halogen-free melt-filtered polymer composition comprises:

(a) 60 to 90 percent by weight of a poly(phenylene ether);

(b) 3 to 23 percent by weight of a styrenic polymer;

(c) 5 to 11 percent by weight of a halogen-free flame retardant comprising at least one organic phosphate flame retardant, wherein the composition has:

(i) a melt viscosity of 620 Pa·s or less as measured according at 280° C. and 1500 s −1 ; and

(ii) a heat deflection temperature that is 135° C. or more as measured according to ASTM D648 on 6.4 mm thick bars at 1.82 MPa;

wherein the process comprises melting the composition and then filtering the composition through a filter.

17. The process of claim 16 , wherein the composition comprises

(a) 60 to 90 percent by weight of poly(2,6-dimethyl-1,4-phenylene ether) an intrinsic viscosity of approximately 0.375 to 0.425 dL/g as measured in chloroform at 25° C.;

(b) 5 to 7 percent by weight of a styrene-ethylene/butylene-styrene copolymer;

(c) 7-9 percent by weight of RDP, BPADP, or mixtures thereof, wherein the weight percent of flame retardant is the same as or exceeds the weight percent of a styrenic polymer; and wherein the composition has:

(i) a melt viscosity of 620 Pa·s or less as measured according at 280° C. and 1500 s −1 ; and

(ii) a heat deflection temperature that is 135° C. or more as measured according to ASTM D648 on 6.4 mm thick bars at 1.82 MPa.

wherein the process further comprises compounding the ingredients on an extruder equipped with a filter, wherein the filter is attached between the last barrel and the die.

18. A halogen-free melt-filtered polymer composition prepared by the process of claim 1 , comprising:

(a) 60 to 90 percent by weight of a poly(phenylene ether);

(b) 3 to 23 percent by weight of a styrenic polymer;

(c) 5-11 percent by weight of a halogen-free flame retardant comprising at least one organic phosphate flame retardant.

19. The composition of claim 18 , wherein the composition comprises:

(a) 80 to 90 percent by weight of poly(2,6-dimethyl-1,4-phenylene ether) an intrinsic viscosity of approximately 0.375 to 0.425 dL/g as measured in chloroform at 25° C.;

(b) 5 to 7 percent by weight of a styrene-ethylene/butylene-styrene copolymer;

(c) 7-9 percent by weight of RDP, BPADP, or mixtures thereof, wherein the weight percent of flame retardant is the same as or exceeds the weight percent of a styrenic polymer.

20. The composition of claim 18 which is a film, wherein the film is free of surface grits and pits that are visible to the naked eye.

21. A halogen-free melt-filtered polymer composition prepared according to claim 1 , which is a film that is free of surface grits and pits that are visible to the naked eye, comprising:

(a) 60 to 90 percent by weight of a poly(phenylene ether);

(b) 3 to 23 percent by weight of a styrenic polymer;

(c) 5-11 percent by weight of a halogen-free flame retardant comprising at least one organic phosphate flame retardant.

22. The film of claim 21 , comprising:

(a) 80 to 90 percent by weight of poly(2,6-dimethyl-1,4-phenylene ether) an intrinsic viscosity of approximately 0.375 to 0.425 dL/g as measured in chloroform at 25° C.;

(b) 5 to 7 percent by weight of a styrene-ethylene/butylene-styrene copolymer;

(c) 7-9 percent by weight of a halogen-free flame retardant which is RDP, BPADP, or mixtures thereof, wherein the weight percent of flame retardant is the same as or exceeds the weight percent of the styrenic polymer which is a styrene-ethylene/butylene-styrene copolymer.