Flame retardant polylactic acid compounds

Abstract

A significant disadvantage of the use of polylactic acid (PLA), lack of flame retardance, has been overcome by the use of specific combinations of either polycarbonate or polyphosphonate-co-carbonate in combination with non-halogenated flame retardants of polyphosphazene or phosphate ester such as resorcinol bis (diphenyl phosphate) or metal hypophosphite, a drip suppressant, and optionally an inorganic synergist of either zinc borate or talc or both and optionally other ingredients. The compound achieves a UL 94 rating of V-0 or V-1 at 1.6 mm.

Claims

1. A heat resistant, flame retardant polylactic acid compound, consisting of: (a) from about 30 to about 39 weight percent, by weight of the compound, of polylactic acid; (b) a carbonate polymer selected from the group consisting of (i) polycarbonate, (ii) polyphosphonate-co-carbonate, and (iii) a combination of them; (c) a non-halogenated flame retardant selected from the group consisting of polyphosphates, phosphinates, polyphosphonates, phosphonates, phosphates, polyphosphonites, phosphonite salts, hypophosphite, hypophosphinite, phosphonite, phosphite, phosphorus oxide, phosphoramide, phosphoramidate, phosphorus nitrile, phospham, phosphoryl nitrile, phosphorus nitride amide, imidophosphazene, polyphosphazene, phosphazene, phosphorus oxynitride, organophosphates, red phosphorus, and combinations thereof; (d) a fluoropolymer drip suppressant; (e) optionally, an inorganic synergist selected from the group consisting of zinc borate, talc, and a combination of them; (f) optionally, a core/shell siloxane/(meth)acrylate copolymer impact modifier; (g) optionally, a oligomeric chain extender; and (h) optionally, one or more other additives selected from the group consisting of adhesion promoters; anti-fogging agents; anti-static agents; biocides; bonding, blowing and foaming agents; dispersants; initiators; lubricants; pigments, colorants and dyes; plasticizers; processing aids; release agents; slip and anti-blocking agents; stearates; ultraviolet light absorbers; viscosity regulators; waxes; and combinations of them; wherein the compound when molded into a plastic article has a UL 94 rating of V-0 when tested at a 3.2 mm thickness.

2. The compound of claim 1, wherein the polyphosphonate-co-carbonate is formed from at least one phosphonate oligomer or polyphosphonate block covalently linked to polycarbonate, wherein the covalent linkages are between the at least one phosphonate oligomer or polyphosphonate and the polycarbonate to provide a copolymer having a single glass transition temperature (Tg); and wherein the polyphosphonate-co-carbonate has a weight average molecular weight ranging from about 30,000 to about 50,000.

3. The compound of claim 2, wherein the phosphonate oligomer or polyphosphonate block has the structure of ##STR00008##

4. The compound of claim 3, wherein the polyphosphonate-co-carbonate is a blend of two different polyphosphonate-co-carbonates.

5. The compound of claim 1, wherein if the blended compound is essentially dried before shaping into a plastic article, then the blended compound after shaping into the plastic article has a heat deflection temperature of at least 60 C. at 66 pounds per square inch using the protocol of ASTM D648.

6. The compound of claim 1, wherein the polylactic acid comprises poly-D-lactide, poly-L-lactide, or a combination of both.

7. The compound of claim 1, wherein the oligomeric chain extender is present in the compound from about 0.25 to about 2 weight percent.

8. The compound of claim 1, wherein the impact modifier is present.

9. The compound of claim 1, wherein the drip suppressant is polytetrafluoroethylene.

10. The compound of claim 1, wherein the non-halogenated flame retardant is an organophosphate, and the organophosphate is resorcinol bis (diphenyl phosphate).

11. A plastic article shaped from the compound of claim 1.

12. The article of claim 11, wherein the article is molded or extruded and wherein the article is shaped for use in transportation, appliance, electronics, building and construction, packaging, or consumer markets.

13. The article of claim 10, wherein the article has a heat deflection temperature increase of at least 5 C. more than the heat deflection temperature of a plastic article made of polylactic acid alone, when both are measured at 66 pounds per square inch using the protocol of ASTM D648.

14. The article of claim 13, wherein the article has a UL 94 rating of V-0 or V-1 when tested at a 1.6 mm thickness.

15. The compound of claim 1, wherein the optional inorganic synergist is present and is: (a) zinc borate, and wherein (i) the carbonate polymer is polycarbonate, the non-halogenated flame retardant is present in an amount of more than 10 weight percent by weight of the compound, and the oligomeric chain extender is present; or (ii) the carbonate polymer is polyphosphonate-co-carbonate and the non-halogenated flame retardant is present in an amount of 10 weight percent or less by weight of the compound; or (b) talc, and wherein the carbonate polymer is polycarbonate, the non-halogenated flame retardant comprises a combination of polyphosphazene and an organophosphate that is a bisphosphate ester, and the non-halogenated flame retardant is present in an amount of more than 10 weight percent by weight of the compound; or (c) a combination of zinc borate and talc, and wherein the carbonate polymer is polycarbonate, the non-halogenated flame retardant is present in an amount of more than 10 weight percent by weight of the compound, and the oligomeric chain extender is absent from the compound.

16. The compound of claim 1, wherein the optional inorganic synergist is not present, and wherein the carbonate polymer is polyphosphonate-co-carbonate, the non-halogenated flame retardant is polyphosphazene and is present in an amount of 10 weight percent or less by weight of the compound, and the compound when molded into a plastic article has a UL 94 rating of V-0 when tested at a 0.8 mm thickness.

17. A heat resistant, flame retardant polylactic acid compound, consisting of: (a) from about 30 to about 39 weight percent, by weight of the compound, of polylactic acid; (b) a carbonate polymer selected from the group consisting of (i) polycarbonate, (ii) polyphosphonate-co-carbonate, and (iii) a combination of them; (c) a non-halogenated flame retardant selected from the group consisting of polyphosphates, phosphinates, polyphosphonates, phosphonates, phosphates, polyphosphonites, phosphonite salts, hypophosphite, hypophosphinite, phosphonite, phosphite, phosphorus oxide, phosphoramide, phosphoramidate, phosphorus nitrile, phospham, phosphoryl nitrile, phosphorus nitride amide, imidophosphazene, polyphosphazene, phosphazene, phosphorus oxynitride, organophosphates, red phosphorus, and combinations thereof; (d) a fluoropolymer drip suppressant; (e) optionally, an inorganic synergist selected from the group consisting of zinc borate, talc, and a combination of them; (f) optionally, a oligomeric chain extender; and (g) optionally, one or more other additives selected from the group consisting of adhesion promoters; anti-fogging agents; anti-static agents; biocides; bonding, blowing and foaming agents; dispersants; initiators; lubricants; pigments, colorants and dyes; plasticizers; processing aids; release agents; slip and anti-blocking agents; stearates; ultraviolet light absorbers; viscosity regulators; waxes; and combinations of them; wherein the compound when molded into a plastic article has a UL 94 rating of V-0 when tested at a 3.2 mm thickness.

Description

EXAMPLES

Comparative Examples A-N and Examples 1-29

(1) These examples demonstrate the several failures of particular combinations of non-halogenated, phosphorus-containing flame retardants and other non-halogenated flame retardants to arrive at the alternative combinations of compounds which are acceptable for the present invention.

(2) Table 2 shows the list of ingredients. Table 3 shows the extruder conditions. Table 4 shows the processing conditions. Table 5 shows the molding conditions. Tables 6-11 show the recipes and the UL 94 flame retardance, Notched Izod impact according to ASTM D-256, and HDT at 66 psi according to ASTM D648.

(3) A no rating identified as NR in the Tables for the UL 94 flame retardance is a failure.

(4) TABLE-US-00003 TABLE 3 Product Purpose Chemistry Company Source PC Makrolon To blend with Polycarbonate Bayer 1239 PLA to improve properties CALIBRE To blend with Polycarbonate Dow 1060 DVD PLA to improve Chemical POLYCARBONATE properties RESIN INGEO 4032D Bio content Polylactic acid Nature- works LLC TEFLON 6C Drip Suppressant PTFE DuPont JoncrylADR 4300 Chain Extender Epoxy-functional BASF Styrene Acrylic copolymers Zinc Borate FR synergist 2ZnO:3B.sub.2O.sub.3:3.5 Borax (FireBrake) H.sub.2O METABLEN S-2030 Impact modifier Silicon Core Shell Mitsubishi impact modifier Rayon, Inc. TECHMASTER710021 Pigment concentrates Black Color Tech Blend for polymer Concentrate S.E.C. REOFOS RDP Flame Retardant Aromatic Oligomeric Great Lakes Phosphates Chemical SPB 100 Flame Retardant Polyphosphazene Otsuka JoncrylADR 4368 China Extender Epoxy Functional BASF Styrene-Acrylate Oligomer Talc (UltraTalc Filler a mineral composed Specialty 609) of hydrated Minerals magnesium silicate Talc Mistron Filler a mineral Luzenac Vapor-R composed of America, hydrated Inc. magnesium silicate FRX CO 45 Flame Retardant Copolymer of FRX Polymers POLYPHOSPHONATE polycarbonate and COPOLYMER polyphosphonate AFLAMMIT Flame Retardant pentaerythritol THOR PCO 960 spirobis (methylphosphonate) Melamine Flame Retardant/ Melamine Hangzhou JLS Cyanurate Synergist Cyanurate Flame Retardants Chemical Co., Ltd. Bayowet Charring agent for Perfluoro alkyl Lanxess masterbatch Polycarbonate sulfonate Salt Masterbatch, Polycarbonate is the carrier SPB-L Flame Retardant Polyphosphazene Otsuka WSFR-PX220 Flame Retardant Bisphosphate ester Zhejiang Wansheng Co. Ltd Phoslite Flame Retardant Metal Italmatch B85AX hypophosphite(s) Paraloid KM Impact Modifier Acrylic polymer Rohm & 334 Haas

(5) TABLE-US-00004 TABLE 4 Extruder Conditions All Comparative Examples and Examples Pre-Extruder Drying PLA, FRX CO45, and Polycarbonate resin and AFLAMMIT PCO 960 material was dried at 80 C. overnight to 0.02% moisture prior to extrusion Extruder Type Leistritz 18 mm Counter-Rotating Twin Screw Extruder Order of Addition All ingredients mixed together and fed into the extruder hopper except formulations with RDP and SPB-L. SPB-L and RDP were fed downstream using a liquid feeder. Process Parameters Run Rate (kg/hr): 6.82 Conditions Set Actual Zone 2 Temp ( C.): 230 230 Zone 3 Temp ( C.): 230 230 Zone 4 Temp ( C.): 230 230 Zone 5 Temp ( C.): 230 230 Zone 6 Temp ( C.): 230 230 Zone 7 Temp ( C.): 230 230 Zone 8 Temp ( C.): 230 230 Zone 9 Temp ( C.): 230 230 Die Temp ( C.): 230 230 Screw Speed (RPM) 400 Vacuum (mm of Hg) .sup.187.5 Melt Temp (Hand Probe) ( C.): 235 Die Pressure (mPa) .sup.4.8 Torque (%) 30~45 Water Bath 20~30% Submerged Pelletizer # N/A Pelletize Blade Speed (RPM) 600 Feed Roller Speed (RPM) 300 Classifier # N/A

(6) TABLE-US-00005 TABLE 5 Molding Conditions All Comparative Examples and Examples 120 ton DeMag molding machine Drying Conditions before Molding: Temperature ( C.) 60 Time (h) 10-12 Temperatures: Nozzle ( C.) 215~226 Zone 1 ( C.) 210~226 Zone 2 ( C.) 204~221 Zone 3 ( C.) 204~215 Mold ( C.) .sup.49~65.5 Oil Temp ( C.) 29 Speeds: Screw RPM (%) 29 % Shot - Inj Vel Stg 1 10 % Shot - Inj Vel Stg 2 15 % Shot - Inj Vel Stg 3 18 % Shot - Inj Vel Stg 4 20 % Shot - Inj Vel Stg 5 20 Pressures: Hold Stg 1 (mPa) - Time(sec) 4.85 Hold Stg 2 (mPa) - Time(sec) N/A Timers: Injection Hold (sec) N/A Cooling Time (sec) 15 Operation Settings: Shot Size (mm) 30 Cushion (mm) 6

(7) TABLE-US-00006 TABLE 6 Example No. A B C D E F G H PC Makrolon 1239 44 58.98 53.98 49.8 39 44 CALIBRE 1060 DVD 44.8 44 POLYCARBONATE RESIN INGEO 4032D 30 30 30 29.98 29.98 30 30 30 TEFLON 6C (refrigerated) 0.7 1.5 1.5 0.70 0.70 0.7 1.5 1.5 Joncryl ADR 4300 0.5 0.5 0.5 0.50 0.50 0.5 0.5 0.5 Zinc Borate (FireBrake) METABLEN S-2030 9 9 9 9.00 9.00 9 9 7 TECHMASTER 710021 REOFOS RDP 15 15 15 20 SPB 100 15.00 AFLAMMIT PCO 960 5.00 10.00 Melamine Cyanurate 2.0 Bayowet masterbatch 0.84 0.84 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Testing HDT @ 66 psi (C.) 72 70 70 128 104 83 53 87 Notched Izod Impact (ft-lb/in) 1.5 1.6 6.7 20.5 17.6 1.9 2.0 9.4 UL94 rating (3.2 mm) V-0 V-0 V-0 NR NR V-1 V-0 V-0 UL94 rating (1.6 mm) NR NR NR NR NR NR V-0 NR UL94 rating (0.8 mm) NR NR NR NR NR NR NR NR

(8) TABLE-US-00007 TABLE 7 Example No. 1 2 3 4 5 6 7 I PC Makrolon 1239 44 34 24 7 44.8 44 44.8 44.8 INGEO 4032D 30 30 30 30 30 30 30 30 TEFLON 6C (refrigerated) 1.5 1.5 1.5 1.5 0.7 1.5 0.7 0.7 Joncryl ADR 4300 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Zinc Borate (FireBrake) 2.00 2.00 2.00 5.00 7.00 METABLEN S-2030 7 9 9 9 5 5 5 5 TECHMASTER 710021 2.00 2.00 2.00 2.00 REOFOS RDP 15 15 10 SPB 100 15.00 15.00 15.00 12.00 10.00 FRX CO 45 10 20 42 POLYPHOSPHONATE COPOLYMER Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Testing HDT @ 66 psi (C.) 86 62 60 72 87 89 88 89 Notched Izod Impact (ft-lb/in) 5.7 2.3 2.0 2.0 8.8 3.0 2.5 2.2 UL94 rating (3.2 mm) V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0 UL94 rating (1.6 mm) V-0 V-0 V-0 V-0 V-0 V-0 V-0 NR UL94 rating (0.8 mm) NR NR V-1 V-1 NR NR NR NR

(9) TABLE-US-00008 TABLE 8 Example No. 8 9 J K 10 11 12 L PC Makrolon 1239 44.8 44.8 54.3 47.3 45.3 45.1 45.1 46.8 INGEO 4032D 30 30 30 30 30 30 30 30 TEFLON 6C (refrigerated) 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 Joncryl ADR 4300 0.5 0.5 0.2 0.5 Zinc Borate (FireBrake) 2.00 2.00 2.00 2.00 2.00 METABLEN S-2030 5 5 5 5 5 5 5 TECHMASTER 710021 2.00 2.00 2.00 2.00 2.00 2.00 2.00 REOFOS RDP 5 10 SPB 100 10.00 5.00 15.00 15.00 15.00 15.00 15.00 15.00 Joncryl ADR 4368 0.2 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Testing HDT @ 66 psi (C.) 85 70 92 85 87 88 88 90 Notched Izod Impact (ft-lb/in) 2.8 2.0 0.9 12.7 4.5 6.8 6.5 14.1 UL94 rating (3.2 mm) V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0 UL94 rating (1.6 mm) V-0 V-1 NR NR V-1 V-0 V-1 NR UL94 rating (0.8 mm) NR NR NR NR NR NR NR NR

(10) TABLE-US-00009 TABLE 9 Example No. 13 14 15 M 16 17 18 PC Makrolon 1239 44.8 44.8 43.3 45.3 45.3 45.3 45.3 INGEO 4032D 30 30 30 30 30 30 30 TEFLON 6C (refrigerated) 0.7 0.7 0.7 0.7 0.7 0.7 0.7 Joncryl ADR 4300 0.5 0.5 Zinc Borate (FireBrake) 2.00 2 2 METABLEN S-2030 5 5 5 5 5 5 5 TECHMASTER 710021 2.00 2 2 2 2 2 2 REOFOS RDP 5 10 10 SPB 100 15.00 15 15 15 10 5 5 Talc (UltraTalc 609) 2.00 Talc Mistron Vapor-R 2.00 2.00 2.00 2.00 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Testing HDT @ 66 psi (C.) 89 86 83 81 78 74 70 Notched Izod Impact (ft-lb/in) 8.8 10.0 2.0 5.3 3.0 2.1 2.5 UL94 rating (3.2 mm) V-0 V-0 V-0 V-0 V-0 V-0 V-0 UL94 rating (1.6 mm) V-0 V-0 V-0 NR V-0 V-0 V-0 UL94 rating (0.8 mm) NR NR NR NR NR NR NR

(11) TABLE-US-00010 TABLE 10 Example No. N 19 20 21 22 23 24 25 26 PC Makrolon 1239 44.8 44.8 INGEO 4032D 30 30 30 30 30 30 30 30 30 TEFLON 6C (refrigerated) 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 Joncryl ADR 4300 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Zinc Borate (FireBrake) 2 2 2 2 METABLEN S-2030 5.2 5.2 5.2 5.2 5.2 5.2 5.2 5 5 TECHMASTER 710021 2 2 2 2 2 2 2 2 2 SPB 100 5 10 5 10 10 FRX CO 45 61.6 56.6 51.6 54.6 49.6 56.6 51.6 POLYPHOSPHONATE COPOLYMER SPB-L 5.00 10.00 15.00 WSFR PX-220 5 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Testing HDT @ 66 psi (C.) 110 98 88 98 86 90 81 79 82 Notched Izod Impact (ft-lb/in) 8.5 2.2 1.3 1.7 1.5 1.2 1.1 6.7 4.8 UL94 rating (3.2 mm) V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0 UL94 rating (1.6 mm) V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0 UL94 rating (0.8 mm) NR V-0 V-0 NR NR V-0 V-0 NR NR

(12) TABLE-US-00011 TABLE 11 Example No. 27 28 29 PC Makrolon 1239 63.5 58.5 53.5 INGEO 4032D 30 30 30 TEFLON 6C (refrigerated) 0.5 0.5 0.5 Joncryl ADR 4300 1 1 1 Phoslite B85AX 5 10 10 Paraloid KM 334 5 Total 100.00 100.00 100.00 Testing HDT @ 66 psi (C.) 132 126 125 Notched Izod Impact (ft-lb/in) 1.7 1.7 1.7 UL 94 rating (3.2 mm) V-0 V-0 V-0 UL94 rating (1.6 mm) V-1 V-0 V-0 UL94 rating (0.8 mm) NR V-0 V-0

(13) The requirement of acceptability is a HDT of at least 60 C. and a V-0 rating at 3.2 mm thickness and either a V-0 or a V-1 rating at 1.6 mm thickness, with a preference for a V-0 rating at 1.6 mm thickness. The experiments yielded Comparative Examples A-L and Examples 1-22. The experiments were reported chronologically, except Examples 27-29 which were conducted after Example 13 and before Example 14. All experiments used 30 weight percent of PLA, at a significant component level as defined above.

(14) Comparative Examples A-F demonstrated that use of RDP of at least 15 weight percent could achieve a V-0 rating at 3.2 mm thickness (Comp. Examples A-C), whereas no flame retardant (Comp. Example D) or use of Aflammit PCO 960 flame retardant at either 5 or 10 weight percent (Comp. Examples E or F) did not. The results were not affected by the type of PC employed (Comp. Examples A and B vs. C).

(15) Comparative Example G would have been an acceptable formulation, which used 20 weight percent of RDP, compared with Comparative Example C, but the HDT value was unacceptably as low as PLA itself or even lower.

(16) Comparative Example H and Example 1 compared the use of SPB 100 with either melanine cyanurate or zinc borate, respectively, with the latter providing both an acceptable HDT and V-0 results at both 3.2 mm and 1.6 mm thicknesses.

(17) Examples 2-4 studied the acceptable performance of the use of varying amounts of RDP and polyphosphonate-co-carbonate as the flame retardant components. The amount of RDP ranged from 10-15 weight percent while the amount of polyphosphonate-co-carbonate ranged from 10-42 weight percent.

(18) Examples 5-9 and Comparative Example I studied the acceptable performance of SPB 100 with other ingredients. All of Examples 5-9 had less than 7 weight percent of zinc borate. All of Examples 5-7 had more than 10 weight percent of SPB 100. The trio of Comparative Example I and Examples 8 and 9 demonstrated that if SPB 100 were to be used at 10 weight percent or less, the amount of RDP needed to be at least 5 weight percent and preferably 10 weight percent.

(19) Comparative Examples J-L, as compared with Examples 10-12, demonstrated that if the carbonate polymer is the conventional polycarbonate polymer, then the absence of zinc borate results in unacceptable formulations.

(20) Examples 13-15 (Examples 13 and 14 being the same formulation) explored the addition of talc in Example 15 which reduced Notched Izod impact.

(21) Comparative Example M and Example 16 demonstrated that the absence of zinc borate yielded an unacceptable UL Rating at 1.6 mm thickness.

(22) Examples 16-18 demonstrated that if the amount of SPB 100 is 10 weight percent of the compound or less and RDP is present, then talc alone can be used with the conventional polycarbonate polymer to yield acceptable HDT and flame ratings.

(23) Comparative Example N was a successful result of a prior invention, serving in this application as a control. Examples 19-22 demonstrated that the addition of SPB 100 in amounts of 10 weight percent or less with polyphosphonate-co-carbonate resulted in V-0 flame retardant ratings for both 3.2 and 1.6 mm and even 0.8 mm for Examples 19 and 20 without either zinc borate or talc being used as inorganic synergists. The results of Examples 19 and 20 were duplicated using the SPB-L polyphosphazene in Examples 23 and 24. Example 25 duplicated the results of Example 14 also using SPB-L polyphosphazene for flame retardance, though HDT was reduced in Example 15 compared with Example 14.

(24) Example 26 demonstrated that a different type of bisphosphate ester also yielded acceptable results.

(25) Examples 27-29 demonstrated that a different type of non-halogenated flame retardant, a metal hypophosphite, also yielded acceptable results, although the Notched Izod impact toughness was not as robust as other Examples.

(26) The aggregation of these 14 Comparative Examples and 29 Examples provides to a person having an ordinary skill in the art, without undue experimentation, a plan of variations in choices of carbonate polymer, flame retardant, and inorganic synergist, if needed, to permit that person to select a successful flame retardant compound in which PLA is a significant component according to ultimate thickness of V-0 UL flame retardance; HDT; and impact toughness, as well as cost, depending on the availability and price of the various non-halogenated flame retardants.

(27) The invention is not limited to the above embodiments. The claims follow.