Preparation of bromine-containing polymers and their application as flame retardants

Abstract

The invention provides a process for preparing bromine-containing polymers, comprising a Friedel-Crafts alkylation reaction of pentabromobenzyl halide with a polymer reactant which contains one or more six-membered aromatic ring(s) in its repeat unit, in the presence of at least one Friedel-Crafts catalyst. The so-formed bromine-containing polymers, having pendent CH.sub.2C.sub.6Br.sub.5 groups attached to at least a portion of the six-membered aromatic rings of the polymer, with a carbon ring atom of said six-membered aromatic ring being bonded to the aliphatic carbon of said CH.sub.2C.sub.6Br.sub.5 pendent group, are also provided. These bromine-containing polymers are useful as flame retarding agents.

Claims

1. A polymer comprising six-membered aromatic rings either as side chains or as a part of a backbone chain, wherein the polymer further comprises pendent CH.sub.2C.sub.6Br.sub.5 groups which are attached to at least a portion of said six-membered aromatic rings of the polymer, with a carbon ring atom of said six-membered aromatic ring being bonded to an aliphatic carbon of said CH.sub.2C.sub.6Br.sub.5 pendent group.

2. A polymer according to claim 1, represented by Formula I or II: ##STR00007## wherein in Formula I: R is Br or a linear or branched aliphatic chain; k is independently an integer from 0 to 4; y is an integer from 1 to (5-k); A is selected from the group consisting of null, CH.sub.2CH.sub.2, CH.sub.2CHCHCH.sub.2, CH(CH.sub.3)CH.sub.2, and CH.sub.2CHC(CH.sub.3)CH.sub.2; and n and m are the number of repeat units in the polymer chain, wherein n3; and wherein in Formula II: X is selected from the group consisting of null, O, S, CH.sub.2, and CH.sub.2CH.sub.2; and n is the number of units in the polymer chain, wherein n3.

3. A polymer of Formula I according to claim 2, which is pentabromobenzyl-substituted polystyrene.

4. A polymer of Formula II according to claim 2, which is pentabromobenzyl-substituted poly(phenylether).

5. A polymer according to claim 3, having bromine content of not less than 60% by weight.

6. A compound according to claim 4, having bromine content or not less than 70% by weight.

7. A flame-retarded composition, comprising a flammable material and the bromine-containing polymer according to claim 1.

8. A flame-retarded composition comprising a flammable material and a bromine-containing polymer, wherein the bromine-containing polymer is pentabromobenzyl-substituted polystyrene as defined in claim 5.

9. A flame-retarded composition according to claim 7, wherein the flammable polymer is polyamide.

10. A flame-retarded composition according to claim 7, wherein the flammable polymer is a polypropylene copolymer or impact modified polypropylene.

11. A flame-retarded composition according to claim 10, comprising 100 parts-by-weight polypropylene copolymer; from 5 to 50 parts-by-weight pentabromobenzyl-substituted polystyrene and from 2 to 20 parts-by-weight of antimony trioxide.

12. A flame-retarded composition according to claim 8, wherein the flammable polymer is polyamide.

13. A flame-retarded composition according to claim 8, wherein the flammable polymer is a polypropylene copolymer or impact modified polypropylene.

Description

EXAMPLES

(1) Methods

(2) The TGA analysis was performed by a Mettler-toledo instrument model 850. 10 mg sample were heated in aluminum oxide crucible from 35 C. to about 700 C. with heating rate of 10 C./min in nitrogen atmosphere.

(3) Bromine content of the compounds is measured by the Parr Bomb method. The sample (0.08-0.12 g) is placed in a peroxide bomb vessel. Sucrose (0.5 g) is added and the full dipper of sodium peroxide is also added. The sample is subjected to oxidizing with sodium peroxide while a burner flame is applied to the bottom of the bomb; the bomb is heated up to about 200 C. and the burner is then turned off. The bomb is placed in cold water (2 liters). Gaseous products are absorbed by the alkaline mixture and are retained within the bomb, mostly in the form of sodium bromide. The content of the bomb is then combined with warm water. Hydrazine sulfate is added to destroy residual sodium peroxide. Nitric acid is added in portions, until the solution is completely neutralized and becomes acidic. The solution is cooled to room temperature and then subjected to titration with AgNO.sub.3 (0.1 N) to determine bromine content.

Example 1

Reaction of Polystyrene with PBBBr Using AlCl3 and SnCl4

(4) DBM (1.8 L) and polystyrene with MW of 170000-350000 (104.15 g) were placed in a 2 L reactor fitted with a mechanical stirrer, thermometer, condenser, HBr trap and N.sub.2 inlet. The mixture was heated to 66 C. to give a clear solution. PBBBr (565.5 g) was then dissolved in the solution. AlCl.sub.3 (3.1 g) and SnCl.sub.4 (4.8 g) were added and the mixture was heated to 84 C., following which the vigorous evolution of HBr started. The mixture was heated at 80 C. for about 6 hours until the PBBBr disappeared (by GC or HPLC). The reaction mixture was washed three times: with water (1.5 L), saturated NaHCO.sub.3 solution (1.5 L) to give pH=7, and again with water (1.5 L), taking 30 minutes for each washing. After that, the reaction mixture was added dropwise to acetone (6 L) to induce precipitation. The reaction mixture was cooled to 20 C. and the solid was filtered off and dried in an oven at 105 C. under reduced pressure for 12 hours, to give 509 g, corresponding to an 86% yield, based on PBBBr. According to elemental analysis, the content of bromine is about 68%, corresponding to about one PBBBr molecule per aromatic ring. The TGA profile of the product is tabulated below:

(5) TABLE-US-00003 Temperature T1 = 365 C. T2 = 381 C. T3 = 391 C. % weight loss 2.0 5.0 10.0

Example 2

Reaction of Polystyrene with PBBBr Using AlCl3

(6) The procedure of Example 1 was repeated, but using PBBBr (27.1 g), polystyrene (10.0 g), AlCl.sub.3 (0.2 g) and dichloroethane (100 ml) as the solvent. The weight of the product was 24.0 g, corresponding to 72% yield, based on PBBBr. The content of bromine is about 60.0%.

Example 3

Reaction of Polyphenylether with PBBBr

(7) Polyphenylether [Santovac 7, available from Santolubes LLC, MW450 (30 g)], PBBBr (366.4 g) and DBM (700 ml) were placed in a 1 L reactor fitted with a mechanical stirrer, thermometer, condenser, HBr trap and N.sub.2 inlet. The mixture was heated to 70 C. and AlCl.sub.3 (3.5 g) was added by portions. The mixture was stirred at 90 C. until the PBBBr disappeared (5-6 h). The reaction mixture was washed at 50 C. with water (250 ml) and SBS (2.5 ml, 28%), water (250 ml), 5% Na.sub.2CO.sub.3 (250 ml) and water (250 ml), taking 20 minutes for each washing. The solvent (150 ml) was evaporated under reduced pressure. The remainder, heated at 40-50 C., was added dropwise to IPA (450 ml) at 50 C., over 1 h, under vigorous stirring. The mixture was stirred at 50 C. for 1 h then cooled to 18 C. The solid was filtered off and washed with IPA (150 ml) on the filter. The solid was dried in the oven at 105 C., and at 150 C. under reduced pressure, for 3 and 7 hours respectively, to give a white powder product (318 g, corresponding to 92% yield, based on PBBBr). The content of bromine is about 75.0%. The TGA profile of the product is tabulated below:

(8) TABLE-US-00004 Temperature T1 = 351 C. T2 = 368 C. T3 = 375 C. % weight loss 2.0 5.0 10.0

Example 4

Bromination of the Product from Example 1

(9) DBM/DCM (1495 g/96 g) and product of Example 1 (191.3 g) were placed in a 2 L reactor fitted with a mechanical stirrer, a dropping funnel, thermometer, condenser, HBr trap and N.sub.2 inlet. The mixture was heated to 60 C. to give a clear solution. Br.sub.2 (38.2 g) was then added dropwise to the solution over 0.5 h. AlCl.sub.3 (1.0 g) and SnCl.sub.4 (2.0 g) were added and the mixture was heated to 65 C. and additional Br.sub.2 (76.4 g) was added dropwise, following which the vigorous evolution of HBr started. The mixture was heated at 65 C. for about 6 hours until the HBr evaluation was observed (by titration). The reaction mixture was washed: with water (1.0 L), saturated NaHCO.sub.3 solution (1.0 L) and again with water (1.0 L) to give pH=7, taking 30 minutes for each washing.

(10) After that, the reaction mixture was added dropwise to isopropanol (1.5 L) to induce precipitation. The reaction mixture was cooled to 20 C. and the solid was filtered off and dried in an oven at 105 C. under reduced pressure for 12 hours, to give 218 g, corresponding to an 89% yield.

(11) According to analysis, the content of bromine is about 72%, corresponding to about two bromine atoms per aromatic ring. The TGA profile of the product is tabulated below:

(12) TABLE-US-00005 Temperature T1 = 267 C. T2 = 330 C. T3 = 375 C. % weight loss 2.0 5.0 10.0

(13) In the studies reported in the following examples, the ability of pentabromobenzyl-substituted polystyrene of Example 1 to reduce the flammability of different thermoplastics was evaluated. Test specimens were prepared and subjected to the following tests:

(14) Flammability Test

(15) The flammability test was carried out according to the Underwriters-Laboratories standard UL 94, applying the vertical burn on specimens of 0.8 mm or 1.6 mm thickness.

(16) Mechanical Properties

(17) Impact strength was measured using the Izod notched test according to ASTM D-256-81, using pendulum impact tester type 5102 (Zwick).

(18) Tensile properties (tensile strength, tensile modulus, elongation at break) were measured in Zwick 1435 material testing machine according to ASTM D-638-95 (v=5 mm/min).

(19) Other Properties

(20) HDT (heat distortion temperature; this is the temperature at which a polymer sample deforms under a specific load) was measured according to ASTM D-648-72 with load of 1820 kPa and heating rate of 120 C./hour; the instrument is HDT/Vicat-plus from Davenport, Lloyd instruments.

(21) MFI (melt flow index) was determined according to ASTM D1238 (230 C./2.16 kg for PP; 250 C./1.2 kg for polyamide); the instrument is Meltflixer 2000 from Thermo Hake.

Example 5 (Comparative) and Example 6 (of the Invention)

V-0 Rated Polyamide 6,6 Formulation

(22) In this set of examples, pentabromobenzyl-substituted polystyrene of Example 1 was tested to evaluate its ability to reduce the flammability of polyamide 6,6. For the purpose of comparison, corresponding formulation was also prepared, where the flame retarding agent was another bromine-containing polymer (FR-803P; brominated polystyrene commercially available from IC-IP).

(23) Ingredients Used to Prepare the Compositions

(24) The materials employed in the experimental work are set out in Table 1 (the abbreviation FR indicates flame retardant):

(25) TABLE-US-00006 TABLE 1 Product (manufacturer) description function P-50FL (Nilit) Polyamide 66 Plastic matrix GF Chop Vantage Glass fibers Reinforcing agents 3660 (PPG) FR-803P (ICL-IP) Brominated polystyrene FR Product of Pentabromobenzyl-substituted FR Example 1 polystyrene AO M-0112 Antimony trioxide masterbatch FR-synergist (Kafrit) which contains 80% by weight Sb.sub.2O.sub.3 Ca stearate (Ciba) Calcium Stearate Lubricant Acrawax C Nitrogen-containing, hindered Antioxidant & heat (Lonza) phenol stabilizer Irganox 1171B N,N ethylene bisstearamide Antioxidant & heat (Ciba) stabilizer
Preparation of Polyamide Compositions and Test Specimens

(26) The ingredients were compounded in a twin-screw co-rotating extruder (Berstorff ZE25) with L/D=32. The polyamide, the bromine-containing flame retardant and all other additiveswith the exception of glass fiberswere weighed and mixed, and the resultant blend was fed into the main feeding port of the extruder. The glass fibers were fed into the fifth section of the extruder via lateral side feeding. A set temperature profile of 250-260-265-265-265-270-275-280 C. was employed. The screw speed was 350 rpm, and the feeding rate was 12 kg per hour.

(27) The extrudates obtained were pelletized in pelletizer 750/3 (Accrapac Systems Limited). The resultant pellets were dried in a circulating air oven at 120 C. for four hours and at 80 C. in a vacuum oven overnight.

(28) The dried pellets were injection molded into test specimens using Allrounder 500-150 (Arburg). The conditions of the injection molding are set out in Table 2.

(29) TABLE-US-00007 TABLE 2 PARAMETER UNITS Set values T.sub.1 (Feeding zone) C. 265 T.sub.2 C. 270 T.sub.3 C. 275 T.sub.4 C. 280 T.sub.5 (nozzle) C. 285 Mold temperature C. 85 Injection pressure bar 1200 Holding pressure bar 500 Back pressure bar 80 Holding time sec 2 Cooling time sec 13 Filling volume ccm 19 (portion) Injection speed ccm/sec 35 Switch over point [ccm] 12

(30) The specimens produced were conditioned at 23 C. for a week and were then subjected to a series of tests. The compositions produced and the results of the tests are set out in Table 3.

(31) TABLE-US-00008 TABLE 3 Examples and FR used Example 5 Example 6 (comparative) (invention) Composition Polyamide 66 (P-50FL) 43.8 44.3 Glass fibers (GF Chop Vantage 3660) 30.0 30.0 Flame retardant 19.5 (Brominated polystyrene FR-803P) Flame retardant 19.1 (Pentabromobenzyl-substituted polystyrene of Example 1) Sb.sub.2O.sub.3 (as M-0112; containing 80% 6.0 6.0 Sb.sub.2O.sub.3) Antioxidant & heat stabilizer (Acrawax C) 0.2 0.2 Antioxidant & heat stabilizer 0.2 0.2 (Irganox B1171) Lubricant (calcium stearate) 0.2 0.2 Bromine (calculated wt %) 13.0 13.0 Sb.sub.2O.sub.3 (calculated wt %) 4.8 4.8 properties Flammability test: UL-94 vertical burning test at 0.8 mm thickness Max flaming time (s) 1 1 Total flaming time (s) 10 10 Number of specimens dripped 5 5 Number of specimens igniting cotton 0 0 UL 94 Rating V-0 V-0 Mechanical properties Izod notched impact (J/m) 96 97 Tensile strength (MPa) 149 137 Tensile modulus (MPa) 10462 10450 elongation at break (%) 3.7 3.5

(32) The results set out in Table 3 indicate that pentabromobenzyl-substituted polystyrene and commercial brominated polystyrene show equally good performance as flame retarding agents in polyamide. The flammability and mechanical properties of the exemplified polyamide formulations are comparable.

Example 7-8 (Comparative) and Example 9 (of the Invention)

V-0 Rated Talc-Free Polypropylene Formulations

(33) Pentabromobenzyl-substituted polystyrene of Example 1 was tested to evaluate its ability to reduce the flammability of polypropylene copolymers (talc-free). For the purpose of comparison, two corresponding formulations was prepared, using decabromodiphenyl ethane and poly(pentabromobenzyl acrylate) as flame retarding agents (FR-1410 and FR-1025, respectively; both are commercially available from ICL-IP). Materials used for preparing the compositions are tabulated in Table 4.

(34) TABLE-US-00009 TABLE 4 Material (manufacturer) GENERAL DESCRIPTION FUNCTION PP Capilene polypropylene impact copolymer plastic SL-50 (Caol) matrix FR 1410 decabromodiphenyl ethane FR FR 1025 poly(pentabromobenzyl acrylate FR Product of pentabromobenzyl-substituted polystyrene FR Example 1 M0112 Antimony trioxide masterbatch which FR synergist (Kafrit) contains 80% by weight Sb.sub.2O.sub.3 Irganox B 225 50% tris(2,4-ditert-butylphenyl)phosphite Antioxidant (Ciba) and 50% pentaerythritol tetrakis[3-[3,5-di- & heat tert-butyl-4-hydroxyphenyl]propionate] stabilizer.
Preparation of Polypropylene Compositions and Test Specimens

(35) The compounding was performed in a twin-screw co-rotating extruder ZE25 with L/D=32. Temperature profile of 120-180-200-200-200-210-220-230 C. was employed. The screw speed was 350 rpm, and the feeding rate was 12 kg per hour.

(36) The extrudtaes produced were pelletized in a pelletizer 750/3 from Accrapak Systems Ltd. The resultant pellets were dried in a circulating air oven at 80 C. for 3 hours. The dried pellets were injection molded into test specimens (1.6 mm thick) using Allrounder 500-150 from Arburg as tabulated in Table 5.

(37) TABLE-US-00010 TABLE 5 PARAMETER UNITS Set values T.sub.1 (Feeding zone) C. 210 T.sub.2 C. 215 T.sub.3 C. 220 T.sub.4 C. 225 T.sub.5 (nozzle) C. 230 Mold temperature C. 35 Injection pressure bar 1300 Holding pressure bar 600 Back pressure bar 60 Holding time sec 7 Cooling time sec 13 Filling volume (portion) ccm 38 Injection speed ccm/sec 35

(38) The specimens were conditioned for one week at 23 C., and were subjected to a set of tests. The results are shown in Table 7.

(39) TABLE-US-00011 TABLE 7 Example 7 8 9 (comparative) (comparative) (invention) Composition (by weight %) Polypropylene 57.4 57.4 60 FR 1410 28 FR 1025 28 product of Example 1 27.9 Sb.sub.2O.sub.3 (as M-0112; 14.4 14.4 11.9 containing 80% Sb.sub.2O.sub.3) Irganox B 225 0.2 0.2 0.2 Br content, % calculated 22 20 19.0 Sb.sub.2O.sub.3, % calculated 11.5 11.5 9.5 Properties Flammability test: UL-94 vertical burning test at 1.6 mm thickness Maximal flaming 6 8 9 time (sec) Total Flaming time (sec) 17 47 63 Maximal glow time + 25 35 3 second flaming (sec) Number of specimen 5 5 5 Number of Specimens 4 0 5 dripped Number of cotton 0 0 0 ignition Rating V-0 V-0 V-0 Mechanical Properties Impact strength (J/m) 34 29 44 Tensile strength (MPa) 21 24 20 Elongation at break (%) 46 7 61 Tensile modulus (MPa) 2010 1725 1478 Other properties HDT ( C.) 58 85 62 MFI (gr/10 min) 4.8 7.7 4.12

(40) The results show that pentabromobenzyl-substituted polystyrene is successfully added to polypropylene copolymer at a relatively low concentration in comparison to other bromine-containing flame retarding agents, to pass the UL-94 V-0 flammability test. Pentabromobenzyl-substituted polystyrene of the invention is able to achieve UL-94 V-0 rating in polypropylene copolymers at a bromine content of 19% by weight, with the aid of 9.5% by weight antimony trioxide. The comparative brominated flame retardants tested require higher bromine and antimony trioxide loading to impart UL-94 V-0 rating to polypropylene copolymers.

Examples 10-12 (of the Invention)

V-1 Rated Talc-Containing Polypropylene Formulations

(41) The aim of this set of examples is to evaluate the ability of pentabromobenzyl-substituted polystyrene of Example 1 to reduce the flammability of talc-containing polypropylene formulations.

(42) Ingredients Used to Prepare the Compositions

(43) The materials used for preparing the polypropylene compositions are tabulated in Table 8.

(44) TABLE-US-00012 TABLE 8 Component (manufacturer) GENERAL DESCRIPTION FUNCTION PP Capilene polypropylene impact copolymer plastic SL-50 (Caol) matrix Product of Pentabromobenzyl-substituted FR Example 1 polystyrene M0112 Antimony trioxide masterbatch which FR synergist (Kafrit) contains 80% by weight Sb.sub.2O.sub.3 Talc MB Talc masterbatch of IOTALC Filler (Kafrit) IOTALC Talc powder Filler Irganox B 225 50% tris(2,4-ditert-butylphenyl)phosphite Antioxidant (Ciba) and 50% pentaerythritol tetrakis[3-[3,5-di- & heat tert-butyl-4-hydroxyphenyl]propionate] stabilizer.
Preparation of Polypropylene Compositions and Test Specimens

(45) The ingredients were compounded in a twin-screw co-rotating extruder (Berstorff ZE25) with L/D=32. Temperature profile of 120-180-200-200-200-210-220-230 C. was employed. The screw speed was 350 rpm, and the feeding rate was 12 kg per hour.

(46) The extrudates produced were pelletized in a pelletizer 750/3 from Accrapak Systems Ltd. The resultant pellets were dried in a circulating air oven at 80 C. for 3 hours.

(47) The dried pellets were injection molded into test specimens using Allrounder 500-150 from Arburg according to the parameters set out in Table 9.

(48) TABLE-US-00013 TABLE 9 PARAMETER UNITS Set values T.sub.1 (Feeding zone) C. 210 T.sub.2 C. 215 T.sub.3 C. 220 T.sub.4 C. 225 T.sub.5 (nozzle) C. 230 Mold temperature C. 35 Injection pressure bar 1300 Holding pressure bar 600 Back pressure bar 60 Holding time sec 7 Cooling time sec 13 Filling volume (portion) ccm 38 Injection speed ccm/sec 35

(49) The specimens were conditioned for one week at 23 C., and were then tested. The compositions and the results of the tests are set out in Table 10.

(50) TABLE-US-00014 TABLE 10 Example 10 11 12 Composition (by weight %) Polypropylene 59.6 55.8 49.2 product of Example 1 23.5 26.5 26.5 Sb.sub.2O.sub.3 (as M-0112; containing 80% Sb.sub.2O.sub.3) 6.7 7.5 7.5 IOtalc 10.0 10.0 Talc masterbatch 16.7 Irganox B 225 0.2 0.2 0.2 Bromine content, % calculated 16 18 18.0 Antimony trioxide, % calculated 5.3 6.0 6.0 Talc, % calculated 10 10 10 Properties Flammability test: UL-94 vertical burning test at 1.6 mm thickness Maximal flaming time (sec) 16 19 15 Total Flaming time (sec) 73 67 Maximal glow time + second flaming 0 6 28 Number of specimen 2 5 5 Number of Specimens dripped 2 5 5 Number of cotton ignition 2 0 0 Rating V-2 V-1 V-1 Mechanical Properties Impact strength (J/m) ND 32 35 Tensile strength (MPa) ND 21 18 Elongation at break (%) ND 30 55 Tensile modulus (MPa) ND 1924 1616 Other properties HDT ( C.) ND 62 57 MFI (g/10 min) ND 3.45 3.08