Flame-retarded styrene-containing formulations

Abstract

A composition comprising: an impact modified styrene-containing polymer; at least one bromine-containing flame retardant; at least one dialkyl phosphinic acid metal salt M.sub.1.sup.n+(R.sup.1R.sup.2PO.sub.2).sub.n wherein M.sub.1 is a metal cation with valence n and R.sup.1, R.sup.2 are alkyl groups which may be the same or different; at least one anti-dripping agent, wherein the total concentration of the bromine-containing flame retardant and the dialkyl phosphinic acid metal salt is less than 28% by weight based on the sum of all components in the composition, wherein said composition is free of antimony and meets UL-94 V-1/1.6 mm or UL-94 V-0/1.6 mm test requirements.

Claims

1. A composition comprising: an impact modified styrene-containing polymer; wherein the impact modified styrene-containing polymer is selected from the group consisting of acrylonitrile-butadiene-styrene (ABS) and high impact polystyrene (HIPS); at least one bromine-containing flame retardant; at least one metal hypophosphite salt Mq+(H.sub.2PO.sub.2).sub.q, wherein M indicates a metal cation with valence q; and at least one anti-dripping agent, wherein the total concentration of the bromine-containing flame retardant and the metal hypophosphite is less than 28% by weight based on the sum of all components in the composition, wherein the bromine concentration of the composition is from 9.5 to 15.5% by weight based on the total weight of the composition, wherein the composition is antimony-free and meets UL-94 V-1/1.6 mm or UL-94 V-0/1.6 mm test requirements.

2. A composition according to claim 1, wherein the total concentration of the bromine-containing flame retardant and the metal hypophosphite is from 18 to 26% by weight.

3. A composition according to claim 1, wherein the concentration of the metal hypophosphite is from 2 to 9% by weight based on the total weight of the composition.

4. A composition according to claim 1, wherein the bromine-containing flame retardant has bromine content of 50% to 70% by weight and its bromine atoms are either all aromatically-bound or all aliphatically-bound and the metal hypophosphite is aluminum hypophosphite, calcium hypophosphite or a mixture thereof.

5. A composition according to claim 4, wherein the bromine-containing flame retardant is selected from the group consisting of: (i) Tris(2,4,6-tribromophenoxy)-s-triazine represented by the following formula: ##STR00008## (ii) Tris(tribromoneopentyl) phosphate represented by the following formula: ##STR00009## iii) Tetrabromobisphenol A represented by the following formula: ##STR00010## iv) brominated epoxy resins and end-capped derivatives thereof, represented by the formula: ##STR00011## wherein m indicates degree of polymerization, R.sub.1 and R.sub.2 are independently selected from the group consisting of: ##STR00012##

6. A composition according to claim 5, wherein the bromine-containing flame retardant is tris(2,4,6-tribromophenoxy)-s-triazine.

7. A composition according to claim 6, comprising from 60 to 80% by weight of ABS or HIPS, from 15 to 20% by weight of tris(2,4,6-tribromophenoxy)-s-triazine, from 3 to 9% by weight of Al(H.sub.2PO.sub.2)3, Ca(H.sub.2PO.sub.2)2 or a mixture thereof and from 0.1 to 0.5% by weight of polytetrafluoroethylene, based on the total weight of the composition.

8. A composition according to claim 5, wherein the bromine-containing flame retardant is tris(tribromoneopentyl) phosphate.

9. A composition according to claim 8, comprising from 60 to 80% by weight of ABS, from 15 to 20% by weight of tris(tribromoneopentyl) phosphate, from 3 to 9% by weight of Al(H.sub.2PO.sub.2)3, Ca(H.sub.2PO.sub.2)2 or a mixture thereof and from 0.1 to 0.5% by weight of polytetrafluoroethylene based on the total weight of the composition.

10. A composition according to claim 5, wherein the bromine-containing flame retardant is tetrabromobisphenol A.

11. A composition according to claim 10, comprising from 60 to 80% by weight of ABS, from 18 to 23% by weight of tetrabromobisphenol A, from 3 to 9% by weight of Al(H.sub.2PO.sub.2)3, Ca(H.sub.2PO.sub.2)2 or a mixture thereof and from 0.1 to 0.5% by weight of polytetrafluoroethylene based on the total weight of the composition.

12. A composition according to claim 5, wherein the bromine-containing flame retardant is tribromophenol end-capped low-molecular weight resin represented by the following Formula (IVa) and mixtures thereof: ##STR00013## wherein m is an integer in the range between 0 and 5 with number-average molecular weight from 1300 to 2500.

13. A composition according to claim 12, comprising from 60 to 80% by weight of ABS, from 18 to 23% by weight of tribromophenol end-capped low-molecular weight epoxy resin of Formula IVa, from 3 to 9% by weight of Al(H.sub.2PO.sub.2)3, Ca(H.sub.2PO.sub.2)2 or a mixture thereof and from 0.1 to 0.5% by weight of polytetrafluoroethylene based on the total weight of the composition.

14. A composition according to claim 13, wherein the composition further comprises an additive selected from the group consisting of aryl phosphate ester of hydroquinone, polydimethylsiloxane and novolac epoxy resins.

15. A composition according to claim 14, wherein the bromine concentration of the composition is from 10 to 15% by weight and the bromine/metal hypophosphite(s) weight ratio is greater than 2:1.

16. A composition according to claim 15, wherein the bromine/metal hypophosphite(s) weight ratio is from 3:1 to 7:1.

17. A composition according to claim 14, comprising from 60 to 80% by weight of ABS, from 15 to 20% by weight of tris(2,4,6-tribromophenoxy)-s-triazine, from 3 to 6% by weight of Al (H.sub.2PO.sub.2).sub.3, Ca(H.sub.2PO.sub.2).sub.2 or a mixture thereof, from 1 to 10% by weight of a combination consisting of aryl phosphate ester of hydroquinone and at least one of polydimethylsiloxane and novolac epoxy resins, and from 0.1 to 0.5% by weight of polytetrafluoroethylene based on the total weight of the composition.

18. A composition according to claim 14, comprising ABS, 10 to 15% by weight bromine supplied by the bromine-containing flame retardant, Ca(H2P02)2 and polydimethylsiloxane wherein the weight ratio bromine: Ca(H.sub.2PO.sub.2)2 is greater than 2:1 and the weight ratio Ca(H.sub.2PO.sub.2)2: polydimethylsiloxane is from 7:1 to 1:2.

19. A composition according to claim 18, wherein the total concentration of the Ca(H.sub.2PO.sub.2)2 +polydimethylsiloxane mixture is from 4 to 7% by weight based on the total weight of the composition.

20. A composition according to claim 19, comprising from 70 to 80% ABS, from 15 to 22.5% by weight of tris(2,4,6-tribromophenoxy)-s-triazine, from 2.0 to 5.0% by weight of Ca(H.sub.2PO.sub.2)2, from 0.5 to 4.0% polydimethylsiloxane and from 0.1 to 0.5% by weight of polytetrafluoroethylene based on the total weight of the composition.

21. A composition according to claim 13, further comprising from 0.5 to 3% by weight of talc based on the total weight of the composition.

22. A composition according to claim 21, comprising from 60 to 80% by weight of ABS, from 13 to 18% by weight of tris(2,4,6-tribromophenoxy)-s-triazine, from 4 to 8% by weight of Al(H.sub.2PO.sub.2).sub.3, Ca(H.sub.2PO.sub.2).sub.2 or a mixture thereof, from 0.5 to 3% by weight of talc and from 0.1 to 0.5% by weight of polytetrafluoroethylene based on the total weight of the composition.

23. A molded article comprising the composition of claim 1.

Description

EXAMPLES

(1) Materials used for preparing the formulations are tabulated in Table 1 (FR is the abbreviation of flame retardant):

(2) TABLE-US-00001 TABLE 1 Component (manufacturer) GENERAL DESCRIPTION FUNCTION ABS Magnum acrylonitrile-butadiene-styrene Plastic matrix 3404 (Styron) HIPS Styron high impact polystyrene Plastic matrix 1200 FR-245 Tris(2,4,6-tribromophenoxy)-s-triazine Brominated FR (ICL-IP) bromine content: 67 wt % F-3020 End-capped brominated epoxy resin Brominated FR (ICL-IP) MW = 2000, Bromine content: 56 wt % FR-1524 Tetrabromobisphenol-A Brominated FR (ICL-IP) Bromine content: 58.5 wt % FR-370 Tris(tribromoneopentyl)phosphate Brominated FR (ICL-IP) Bromine content: 70% Ca(H.sub.2PO.sub.2).sub.2 Calcium hypophosphite Flame (Sigma Aldrich retardancy or from Special enhancer Materials) Al(H.sub.2PO.sub.2).sub.3 Aluminum hypophosphite Flame (Hubei Sky retardancy Lake enhancer Chemical) HDP phenyl phosphate ester of hydroquinone P-FR (Example 1 of EP 2089402; from ICL-IP) Melapur 200 Melamine polyphosphate P-FR (BASF) ECN 1299 Epoxy cresol novolac Charring agent (Huntsman) DC 4-7081 PDMS Charring agent, (Dow Corning) impact modifier LSYI-300C Ultra high molecular weight PDMS Charring agent, (ChengDu (60% siloxane on 40% silica) impact Silike modifier Technology) talc MB 60% Talc in a masterbatch form filler (Kafrit) 60% w/w talc in LLDPE Hostaflon 2711 PTFE (Teflon) Anti-dripping (Dyneon) agent Irganox ® Phenol:phosphite 3:1 based stabilizer Antioxidant& B-225 (Ciba) heat stabilizer

(3) Preparation

(4) Polymer and all additives were premixed and the blend was fed via Feeder no. 1 into the main port of a twin-screw co-rotating extruder ZE25 with L/D=32 (Berstorff). Operating parameters of the extruder were as follows:

(5) Barrel temperature (from feed end to discharge end): 160° C., 180° C., 200° C., 200° C., 210° C., 220° C., 230° C., die—240° C. Screw rotation speed: 350 rpm; Feeding rate: 12 kg/hour.

(6) The strands produced were pelletized in a pelletizer 750/3 from Accrapak Systems Ltd. The resultant pellets were dried in a circulating air oven (Heraeus Instruments) at 80° C. for 3 hours. The dried pellets were injection molded into test specimens using Allrounder 500-150 from Arburg under the conditions tabulated below:

(7) TABLE-US-00002 TABLE 2 PARAMETER Set values T.sub.1 (Feeding zone) 210° C. T.sub.2 215° C. T.sub.3 220° C. T.sub.4 225° C. T.sub.5 (nozzle) 230° C. Mold temperature 35° C. Injection pressure 1300 bar Holding pressure 700 bar Back pressure 50 bar Holding time 11 s Cooling time 9 s Mold closing force 500 kN Filling volume 30 ccm (portion) Injection speed 35 ccm/sec

(8) Specimens of 1.6 mm thicknesses were prepared. The test specimens were conditioned for one week at 23° C., and then subjected to the several tests to determine their properties.

(9) Flammability Test

(10) A direct flame test was carried out according to the Underwriters-Laboratories standard UL 94 in a gas methane operated flammability hood, applying the vertical burn on specimens of 1.6 mm thickness.

(11) Mechanical Test

(12) The Notched Izod impact test was carried out according to ASTM D256-81 using Instron Ceast 9050 pendulum impact system. Tensile properties were determined according to ASTM D638 using Zwick 1435 material testing machine (type 2 dumbbells were used, with a speed test of 5 mm/min).

Examples 1-6 (all Comparative)

ABS Flame Retarded with Bromine-Containing Compounds or Metal Hypophosphite Alone

(13) In this set of examples, bromine-containing flame retardants were applied to reduce the flammability of ABS without the aid of antimony trioxide. Likewise, metal hypophosphite salts were tested as sole flame retardants in ABS. The compositions and the results of the flammability test are tabulated in Table 3.

(14) TABLE-US-00003 TABLE 3 Ex. 3 Ex.5 (Ex. 7 (Ex. C5 Ex. Ex. from WO Ex. from WO Ex. Example 1 2 2013/176868) 4 2015/170130) 6 composition ABS (wt %) 75.7 66.8 70.7 71.6 64.3 75.6 FR-245 (wt %) 23.9 32.8 23.9 (bromine wt %, (16) (22) (16.0) calculated) F-3020 28.0 (bromine wt %, (16) calculated) AMMP (wt %) 5 Al (H.sub.2PO.sub.2).sub.3 35 (wt %) Ca (H.sub.2PO.sub.2).sub.2 24.0 (wt %) PTFE (wt %) 0.2 0.2 0.2 0.2 0.3 0.2 Irganox B-225 0.2 0.2 0.2 0.2 — 0.2 (wt %) Flammability test UL 94 V NR V-0 V-0 NR NR NR 1.6 mm

(15) The results indicate that an amount of 16 wt % bromine in the composition, supplied by either FR-245 or F-3020, is insufficient when antimony trioxide is absent, seeing that UL-94 rating is achieved neither in Examples 1 nor 4. To achieve UL-94 V-0/1.6 mm rating when FR-245 is used solely in ABS, it is necessary to increase the amount of bromine to about 22 wt %, namely, unacceptably high loading level of the flame retardant (˜33%; Example 2). A fairly good replacement for antimony trioxide is the aluminum salt of methyl methylphosphonic acid (abbreviated AMMP), but 16% by weight of bromine are needed with a total loading level of the flame-retarding system being around 29% of the composition (Example 3).

(16) As to the metal hypophosphite salts, they are clearly inefficient when used alone (Examples 5 and 6). Even at loading levels as high as 25-35% by weight, metal hypophosphite-containing ABS is unable to attain UL-94 rating.

Examples 7-12

ABS Flame Retarded with Bromine-Containing Compound and Metal Hypophosphite

(17) As shown in this set of examples, a variety of bromine-containing flame retardants available in the market can be combined with aluminum or calcium hypophosphite to achieve antimony-free ABS compositions that are UL 94 V-1/1.6 mm or UL 94 V-0/1.6 mm rated. The amount of brominated flame retardant incorporated into the composition was adjusted to supply 12% by weight bromine concentration in the composition—a customary bromine concentration in many commercial ABS formulations.

(18) TABLE-US-00004 TABLE 4 Example Example Example Example Example Example 7 8 9 10 11 12 composition ABS (wt %) 75.7 72.2 73.1 76.5 75.7 72.2 FR-245 17.9 17.9 (wt %) (12) (12) (bromine wt %, cal.) F-3020 21.4 21.4 (bromine (12) (12) wt %, cal.) FR-1524 20.5 (bromine (12) wt %, cal.) FR-370 17.1 (bromine (12) wt %, cal.) Al (H.sub.2PO.sub.2).sub.3 6.0 6.0 6.0 6.0 (wt %) Ca (H.sub.2PO.sub.2).sub.2 6.0 6.0 (wt %) PTFE (wt %) 0.2 0.2 0.2 0.2 0.2 0.2 Irganox 0.2 0.2 0.2 0.2 0.2 0.2 B-225 (wt %) Flammability test UL 94 V-0 V-0 V-0 V-0 V-0 V-1 1.6 mm

(19) The results tabulated in Table 4 indicate that metal hypophosphite functions as an effective replacement for antimony trioxide in ABS.

Examples 13-18

ABS Flame Retarded with Bromine-Containing Compound and Metal Hypophosphite

(20) As shown in this set of examples, antimony-free ABS flame retarded with a bromine-containing compound {Tris(2,4,6-tribromophenoxy)-s-triazine, FR-245)] in the presence of metal hypophosphite can benefit from the incorporation of other additives into the composition. A phosphorus-containing flame retardant, charring agents and talc were tested as auxiliary additives.

(21) The compositions and the results are tabulated in Table 5.

(22) TABLE-US-00005 TABLE 5 Example Example Example Example Example Example 13 14 15 16 17 18 Composition ABS (wt %) 70.7 70.7 74.7 77.2 75.7 75.7 FR-245 (wt %) 17.9 17.9 17.9 14.9 17.9 17.9 (bromine (12) (12) (12) (10) (12) (12) wt %, cal.) Al (H.sub.2PO.sub.2).sub.3 3.0 3.0 4.0 6.0 4.5 (wt %) Ca (H.sub.2PO.sub.2).sub.2 4.5 (wt %) HDP ® (wt %) 3.0 3.0 2.0 Cresol 5.0 1.0 Novolac (wt %) PDMS (wt %) 5.0 Talc MB 1.5 1.5 1.5 (Talc wt %, (0.9) (0.9) (0.9) calculated) PTFE (wt %) 0.2 0.2 0.2 0.2 0.2 0.2 Irganox 1010 0.2 0.2 0.2 0.2 0.2 0.2 (wt %) Flammability test UL 94 V-0 V-1 V-1 V-1 V-1 V-0 1.6 mm Mechanical properties Izod notched 83 ND ND ND ND 108 impact (J/m) Tensile 39.3 ND ND ND ND 45.8 strength (MPa) Tensile 2159 ND ND ND ND 2619 modulus (MPa) Elongation at 3.3 ND ND ND ND 5.2 break (%)

(23) The effect of added talc is particularly notable, seeing that the addition of talc supplied in a masterbatch form leads to improved mechanical properties of the ABS while keeping the total amount of flame retardant enhancers aiding FR-245 within the acceptable loading level of ˜6-7% by weight. It is also observed that antimony-free, UL 94 V-1/1.6 mm rated ABS composition is reached with bromine concentration of only 10% by weight and a total loading level of flame retardant system (consisting of FR-245+metal hypophosphite+talc masterbatch) of less than 23% by weight.

Examples 19 (Comparative)

(24) Antimony-free ABS formulation was prepared and tested according to the procedures set forth above. The composition and the results are set out in Table 6.

(25) TABLE-US-00006 TABLE 6 Example 19 composition ABS (wt %) 75.7  FR-245 (wt %) 17.9  (bromine wt %, calculated) (12)   MPP 6.0 PTFE (wt %) 0.2 Irganox B-225 (wt %) 0.2 Flammability test UL 94 1.6 mm NR

(26) Example 19 indicates that adding phosphorous-based flame retardant such as melamine polyphosphate (MPP) to ABS which is flame retarded with FR-245 does not compensate effectively for the absence of Sb.sub.2O.sub.3, seeing that the resultant formulation fails to achieve UL 94 1.6 mm rating with MPP loading level of 6.0 wt %.

Examples 20-25

ABS Flame Retarded with Bromine-Containing Compound, Calcium Hypophosphite and Polydimethylsiloxane

(27) The amount of brominated flame retardant added to the ABS compositions was adjusted such that the bromine concentration in the compositions varied over the range of ˜10% to 14 wt %. As pointed out above, this is a customary bromine concentration range in many commercial ABS formulations. Imparting good flame retardancy to such formulations without the benefit gained by added antimony synergist is a challenging goal.

(28) Thus, 10-14 wt % bromine-containing, antimony-free, ABS compositions were prepared in which calcium hypophosphite was tested as antimony replacement, aided by polydimethylsiloxane. The results are tabulated in Table 7.

(29) TABLE-US-00007 TABLE 7 Example Example Example Example Example Example 20 21 22* 23* 24 25 Composition ABS (wt %) 77.4 78.9 75.7 76.7 73.7 73.7 FR-245 15.7 15.7 17.9 17.9 20.9 20.9 (wt %) (10.5) (10.5) (12.0) (12.0) (14.0) (14.0) (bromine wt %, cal.) Ca (H.sub.2PO.sub.2).sub.2 5.0 3.5 3.0 2.5 3.5 2.0 (wt %) LYSI-300C 1.5 1.5 3.0 2.5 1.5 3.0 (wt %) (60% PDMS on 40% silica) PTFE (wt %) 0.2 0.2 0.2 0.2 0.2 0.2 Irganox 0.2 0.2 0.2 0.2 0.2 0.2 1010 (wt %) Flammability test UL 94 1.6 mm V-0 V-0 V-0 V-1 V-0 V-0 Mechanical properties Izod notched 102 115.3 119.2 127.4 104.2 111.2 impact (J/m) *conditioned at 65° C. and 90% RH (relative humidity) for one week.

(30) The results show that UL 94/1.6 mm V-0 (or V-1) rating is attainable over the range of ˜10 to ˜14 wt % bromine-containing ABS compositions in the absence of antimony, owing to addition of a fairly low amount of calcium hypophosphite and polydimethylsiloxane, producing ABS compositions displaying reduced flammability combined with satisfactory impact strength. It should be noted that an ABS composition related to Examples 22 (Br.sub.Fr 245=12 wt %, calcium hypophosphite 6 wt %) displays izod notched impact of 102 J/m; hence it is seen that replacing part of the calcium hypophosphite with polydimethylsiloxane retains the reduced flammability and improves the mechanical properties; a similar trend is observed in Examples 24 and 25.

Examples 26-27

HIPS Flame-Retarded with a Combination Consisting of Bromine-Containing Compound and Metal Hypophosphite

(31) This set of examples show that HIPS can also be flame retarded effectively with bromine-containing compound {Tris(2,4,6-tribromophenoxy)-s-triazine, FR-245)] in the absence of antimony trioxide but with added metal hypophosphite.

(32) TABLE-US-00008 TABLE 8 Example 26 Example 27 composition HIPS (wt %) 75.7  75.7  FR-245 (wt %) 17.9  17.9  (bromine wt %, calculated) (12)   (12)   Al(H.sub.2PO.sub.2).sub.3 (wt %) 6.0 Ca(H.sub.2PO.sub.2).sub.2 (wt %) 6.0 PTFE (wt %) 0.2 0.2 Irganox B-225 (wt %) 0.2 0.2 Flammability test UL 94 1.6 mm V-0 V-1