Polycarbonate compositions having improved chemical resistance, articles formed thereof, and methods of manufacture

1. A polycarbonate composition comprising:

75 to 99 wt % of one or more bisphenol A polycarbonate homopolymers based on the total weight of the polycarbonate composition;

a poly(carbonate-siloxane) comprising a siloxane content of 35 wt % to 65 wt % based on the total weight of the poly(carbonate-siloxane) and comprising a weight average molecular weight of 32,000 to 45,000 Da, measured by gel permeation chromatography using a crosslinked styrene-divinyl benzene column, at a sample concentration of 1 milligram per milliliter, and as calibrated with bisphenol A polycarbonate standards, wherein the polycarbonate composition comprises 4 to 10 wt % siloxane content; and

wherein a sample of the composition has improved chemical resistance as compared to a reference composition,

wherein a molded sample of the polycarbonate composition has

a tensile strength retention of 80% and higher after exposure of the bar for 168 hours to SANI-CLOTH AF3 at a temperature of 23° C. under 0.5% or 1% strain compared to a non-exposed molded sample of a reference composition tested at the same temperature, and

a tensile elongation retention of 65% and higher after exposure of the bar for 168 hours to SANI-CLOTH AF3 at a temperature of 23° C. under 0.5% or 1% strain compared to a non-exposed molded sample of a reference composition tested at the same temperature,

wherein the reference composition is the same as the polycarbonate composition, except that the reference composition comprises a reference poly(carbonate-siloxane) comprising a siloxane content of 20 wt %, based on the total weight of the reference poly(carbonate-siloxane).

2. The polycarbonate composition of claim 1 , wherein the poly(carbonate-siloxane) comprises a weight average molecular weight of 35,000 to 45,000 Da, measured by gel permeation chromatography using a crosslinked styrene-divinyl benzene column, at a sample concentration.

3. The composition of claim 1 , wherein

the poly(carbonate-siloxane) has a siloxane content of 35 wt % and up to 60 wt % based on the total weight of the poly(carbonate-siloxane); and

the poly(carbonate-siloxane) is present in an amount of 5 to 15 wt %, based on the total weight of the composition.

4. The composition of claim 1 , comprising

a first bisphenol A homopolycarbonate comprising an average molecular weight of 15,000 to 25,000 Daltons, and a second bisphenol A homopolycarbonate comprising an average molecular weight of 26,000 to 40,000 Daltons, each determined by gel permeation chromatography, using a crosslinked styrene-divinylbenzene column and calibrated to bisphenol A polycarbonate standards, wherein the weight ratio of the first bisphenol A polycarbonate homopolymer relative to the second bisphenol A polycarbonate homopolymer is 5:1 to 1:5.

5. The composition of claim 1 , wherein the poly(carbonate-siloxane) comprises siloxane units of the formula

or a combination thereof, wherein E has an average value of 10 to 100.

6. The composition of claim 1 , further comprising

a second poly(carbonate-siloxane) with a siloxane content of 5 to 25 wt % based on the total weight of the second poly(carbonate-siloxane),

wherein the polycarbonate composition has a total siloxane content of 4 to 10 wt % based on the total weight of the composition.

7. The composition of claim 1 , further comprising a flame retardant, wherein the flame retardant comprises an alkali metal salt of a sulfonate, an inorganic acid complex salt, phosphate, phosphazene, brominated flame retardant or a combination thereof.

8. The composition of claim 7 ,

wherein the flame retardant is potassium diphenylsulfone sulfonate, sodium toluene sulfonate, potassium perfluorobutane sulphonate, bisphenol A bis(diphenyl phosphate), resorcinol bis(diphenyl phosphate), poly(bis(phenoxy)phosphazene, a brominated polycarbonate, or a combination thereof.

9. The composition of claim 1 , further comprising up to 10 wt % of titanium dioxide, carbon black, an inorganic pigment, an organic pigment, a dye, or a combination thereof, based on the total weight of the composition.

10. The composition of claim 1 , further comprising no more than 5 wt %, based on the weight of the composition, of an anti-drip agent, a processing aid, a heat stabilizer, an antioxidant, an ultra violet light absorber, or a combination thereof.

11. The composition of claim 1 , wherein the composition has one or more of the following properties:

a UL-94 flammability rating of V1 or better as measured on a flame bar having a thickness of 1.5 mm;

a melt flow rate higher than 5 g/10 min determined in accordance with ASTM D1238 under a load of 1.2 kg at 300° C. with a dwelling time of 300 seconds;

an Izod notched impact energy of at least 550 J/m measured at −30° C. on a sample of 3.2 mm thickness according to ASTM D256-10; or

a multi-axial impact of greater than 50 J measured at −30° C. and 3.3 m/s on a sample of 3.2 mm thickness according to ASTM D3763.

12. An article comprising the composition of claim 1 , wherein the article is a molded article, a thermoformed article, an extruded film, an extruded sheet, a honeycomb structure, one or more layers of a multi-layer article, a substrate for a coated article, or a substrate for a metallized article.

13. The article of claim 12 , wherein:

the article is a component of a consumer electronic device,

or the article is an electronic housing for an adapter, a cell phone, a smart phone, a GPS device, a laptop computer, a tablet computer, an e-reader, a copier, or a solar apparatus,

or the article is an electrical junction box, an electrical connector, an electrical vehicle charger, an outdoor electrical enclosure, a smart meter enclosure, a smart grid power node, a photovoltaic frame, or a miniature circuit breaker,

or the article is an automotive, scooter, or motorcycle exterior or interior component, preferably a panel, a quarter panel, a rocker panel, a trim, fender, a battery cover, a door, a deck-lid, a trunk lid, a hood, a bonnet, a roof, a bumper, a fascia, grille, a mirror housing, a pillar appliqué, a cladding, body side molding, a wheel cover, a hubcap, a door handle, a spoiler, a window frame, a headlamp bezel, a headlamp, a tail lamp, a tail lamp housing, a tail lamp bezel, a license plate enclosure, a roof rack, or a running board,

or the article is a component of a healthcare product.

14. A method of manufacture of an article, comprising molding, extruding, casting, or shaping the composition of claim 1 to form the article.

15. A polycarbonate composition comprising:

75 to 99 wt % of one or more bisphenol A polycarbonate homopolymers based on the total weight of the polycarbonate composition;

a poly(carbonate-siloxane) comprising a siloxane content of 35 wt % to 65 wt %, based on the total weight of the poly(carbonate-siloxane) and comprising a weight average molecular weight of 32,000 Da to 40,000 Da, measured by gel permeation chromatography using a crosslinked styrene-divinyl benzene column, at a sample concentration of 1 milligram per milliliter, and as calibrated with bisphenol A polycarbonate standards, wherein the poly(carbonate-siloxane) comprising a siloxane content of 35 wt % to 65 wt % is present in an amount effective to provide a total siloxane content of 4 to 10 wt % based on the total weight of the polycarbonate composition,

wherein a molded sample of the polycarbonate composition has improved resistance to sunscreen as compared to a reference composition comprising 75 to 99 wt % of one or more bisphenol A polycarbonate homopolymers and a poly(carbonate-siloxane) comprising a siloxane content of 20 wt % based on the total weight of the reference poly(carbonate-siloxane), wherein the reference composition has the same total siloxane content as the polycarbonate composition comprising 75 to 99 wt % of one or more bisphenol A polycarbonate homopolymers and a poly(carbonate-siloxane) comprising a siloxane content of 35 wt % to 65 wt %.

16. The composition of claim 15 , comprising, based on the total weight of the composition,

85 to 98 wt % of one or more bisphenol homopolycarbonates;

2 to 15 wt % of the poly(carbonate-siloxane); and

0 to 10 wt % of a flame retardant, provided that the total weight of the composition does not exceed 100 wt %;

wherein the composition has

a notched Izod impact of greater than 500 J/m as measured according to ASTM D256-10 at −30° C. on a sample of 3.2 mm thickness; and

a ductility of greater than 80% as measured according to ASTM D256-10 at −30° C. on a sample of 3.2 mm thickness.