Abstract:
Novel flame-retardant composition incorporate as an active ingredient pentabromobenzylester monoacrylate, of a product of its in situ reaction. 
     Articles made of flammable synthetic resins can be rendered flame-retarded by the incorporation of the novel flame-retandant compositions.

Description:
FIELD OF THE INVENTION 
     The present invention relates to novel flame retardant compositions, to a method for rendering flammable synthetic resins flame-resistant, and to flame-resistant plastic compositions comprising them. 
     BACKGROUND OF THE INVENTION 
     It has been known for some time that petabromobenzylester polyacrylate (PBB-PA) is a valuable flame-retardant material, useful in a number of synthetic resins. PBB-PA is prepared by the polymerization of pentabromobenzylester monoacrylate (PBB-MA), e.g., by the process described in DE 25 27 802. The so-obtained PBB-PA polymeric flame-retardant material is then incorporated into the synthetic resin to which it is desired to impart flame-retardant properties, by techniques known to the skilled engineer. 
     SUMMARY OF THE INVENTION 
     It has now been most surprisingly found, and this is an object of the invention, that the monomer pentabromobenzylester monoacrylate also by himself can be employed as a flame-retardant agent as such, and can be incorporated into the synthetic resin, without first polymerizing it to obtain PBB-PA. 
     It has further been found, and this is another object of the invention, that synthetic resins which incorporate PBB-MA present substantially shorter total and maximal flaming times in the UL94 test. 
     Various advantages deriving from the use of PBB-MA, as compared to PBB-PA, are self evident, e.g., an entire reaction step--the polymerization of PBB-MA to PBB-PA--can be dispensed with. The precise nature of the product obtained when PBB-MA is incorporated into the synthetic resin is not known. Thus, it is unclear whether a mere dispersion of PBB-MA in the polymer matrix is obtained, or whether a partial graft polymer results, or whether part of the monomer polymerizes, or copolymerizes with the matrix. Any one of the above-noted processes, or the combination of two or more of them, may occur, and different behavior may be involved with different polymeric matrices. 
     Thus the present invention is directed to flame-retardant compositions which comprise, as an active ingredient, pentabromobenzyl monoacrylate, or the product of its in situ reaction. As will be apparent to those skilled in the art, the said compositions may further comprise additional additives, such as conventionally employed flame-retardant synergists, fillers, heat and UV stabilizers, antioxydants, lubricants, plasticizers, etc., and may be provided in substantially pure form, or in different compositions thereof, or in master batches. It should also be understood that the exact mechanism by means of which PBB-MA imparts flame retardancy to synthetic resins has not been elucidated, but the exact understanding of this phenomena is not critical. However, PBB-MA may at least partly react with other compounds or additives in the polymeric matrix, to give grafts or other types of compounds. However, as long as the result of such a reaction still provides an improvement of the flame retardancy, the goals of the invention are achieved. It should be therefore understood that the term &#34;the product of the in situ reaction&#34; of PBB-MA refer to any such compound formed during plastic processing, storage, handling or the like. 
     Also encompassed within the present invention is a method for imparting flame-retardant properties to a flammable synthetic resin, which method comprises incorporating into the said synthetic resin pentabromobenzyl monoacrylate. The incorporation method can be any of those commonly employed in the art, e.g., PBB-MA can be blended with the synthetic resin before processing thereof in the plastic processing apparatus, or mixed during processing. The actual incorporation method may affect the precise nature of the resulting dispersion of PBB-MA in the matrix, as hereinbefore detailed, but is not critical to the invention. The flame retarded plastic composition which incorporates PBB-MA, and which is obtained by the aforesaid method, also forms part of the invention. The invention is directed not only to compositions, methods and processes, but also to the use of PBB-MA as a flame retardant agent. 
     DETAILED DESCRIPTION 
     The above and other characteristics and advantages of the invention will be better understood from the following examples, in which non-limiting embodiments of the invention are described for the purpose of illustration. 
    
    
     EXAMPLE 1 
     In this and the following examples, contents of active material are given as percent of bromine in the product, to permit a comparison between PBB-MA- and PBB-PA-containing specimens. 
     Concentrates of PBB-PA and PBB-MA containing 10% bromine were prepared in the BUSS extruder compounder, according to the following formulations: 
     
         ______________________________________Component           (%)    (%)______________________________________PBB-PA              14.3   --PBB-MA              --     14.3Antimony            7.15   7.15TrioxidePBT - VALOX 420     78.55  78.55(ex General Electric)Bromine             10     10______________________________________ 
    
     The processing temperature profile was: CO-kneader: 220° C.; pellettizer: 215° C.; die: 207° C. The concentrates were &#34;diluted&#34; with pure PBT to the required bromine level, and specimens were prepared for the different tests with an Arburg injection-molding machine, at the following conditions: 
     Processing Temperature Profile: inlet: 210° C.; middle zone: 235° C., final zone: 250° C.; nozzle: 275° C. 
     Working Pressure: Injection Pressure: 60 Atm.; Holding Pressure: 40 Atm.; Back Pressure: 10 Atm. 
     Timing: Injection Time: 0.1 sec.; Holding Time: 4.0 sec.; Cooling Time: 14.0 sec.; Mould Opening Time: 0.1 sec.; Injection Delay: 0.5 sec.. 
     A 5% Br PBT (polybutyleneterephthalate) specimen (Valox-420) was prepared, using commercially available PBB-PA (FR 1025--Eurobrom, Holland) and PBB-MA (prepared by IMI, Haifa, Israel). 
     The data and results of tests carried out with these specimens are set forth in Table I below. The virtually zero flaming time of the composition of the invention should be noted. 
     EXAMPLE 2 
     Two HIPS (High Impact Polystyrene) specimens (10% Br and a 14% Br) were prepared according to the following procedure, and using the same PBB-MA as in Example 1. The formulation employed was the following: 
     
         ______________________________________                 Thickness [mm]Component             1.6    3.2______________________________________HIPS/Huels VESTYRON 638                 74.4   81.5ANTIMONY TRIOXIDE     5.1    3.6(Blue Star - Campine)Mg-Stearate (ex WITCO)                 0.5    0.5TINUVIN P             0.5    0.5(ex CIBA-GEIGY)PBB-PA/PBB-MA         19.5   13.9Br/Sb Atomic Ratio    5      5Bromine               14     10______________________________________ 
    
     The formulations were compounded in a Brabender Plastograph at 200° C. for 4 minutes at 40 RPM, and subsequently cooled to 130° C. at 20 RPM (total processing time: 15-16 mins.). The resulting melt was pressplated 1 min. at 200° C. at 1 Atm., and during another minute at 100 Atm., after which it was cooled during 4 mins. to 120° C. 
     Specimens were prepared with a ribbon saw. 
     The results are shown in Table II below. 
     EXAMPLE 3 
     Example 2 was repeated, but using ABS (Acrylonitrile-Butadiene-Styrene) as the matrix, to give final 10, 12 and 14% Br contents. The results are detailed in Table III below. 
     EXAMPLE 4 
     Flame-retarded Nylon 6 specimens (Capron 8200 MS) were prepared, following the procedures of Example 1, to give a final 9% Br content. The results are set forth in Table IV. 
     The above description and examples have been given for the purpose of illustration and are not intended to be limitative. Many different synthetic resins, compounding conditions and additives can be employed, together with PBB-MA, without exceeding the scope of the invention. 
     
                       TABLE I______________________________________5% Br in PBT (Valox-420)        Flame-retardant Additive        PBB-PA   PBB-MA    None______________________________________Flame-Retardancy(UL 94 - 3.2 mm)Max Flam. (sec)           5         0         &gt;180Total Flam. (sec)          10         0         &gt;900Drip           no         no         5Rating         V0         V0        NRHDT (°C.)*          198 ± 2  201 ± 0.4                               205Mechanical PropertiesIZOD Notched (J/m)           87 ± 4 91 ± 6 100Tensile strength at          104 ± 3 109 ± 1                               115break (MPa)Elongation at break (%)           2.4 ± 0.3                      2.4 ± 0.0                                3Tensile Modulus (MPa)           9500 ± 470                     9910 ± 530                               8000Flexural Strength (MPa)          175 ± 8 172 ± 2                               190Flexural Modulus (MPa)           6910 ± 380                     7560 ± 220                               7500CTI (V)        240-260    250-270   460-520______________________________________ *Heat Distortion Temperature at 264 psi. 
    
     
                       TABLE II______________________________________FR - HIPS            Formulation No.Component        1      2        3    4______________________________________Bromine (%)      10     10       14   14HIPS - VESTYRON 638            81.5   81.1     74.4 73.9(ex Huels)PBB-PA (ex Eurobrom)            --     14.3     --   20PBB-MA ex IMI    13.9   --       19.5 --Antimony Trioxide            3.6    3.6      5.1  5.1(ex Campine)Mg-Stearate (ex WITCO)            0.5    0.5      0.5  0.5TINUVIN P        0.5    0.5      0.5  0.5(ex Ciba-Geigy)PROPERTIES:UL-941.6 mm thickness --     --       V0   V03.2 mm thickness V0     V0       --   --IZOD NOTCHED     49     38       --   --IMPACT [J/m]HDT [°C.] at 1.82 KPa load            73     79       --   --______________________________________ 
    
     
                       TABLE III______________________________________FR - ABS           Formulation No.Component       1        2      3      4______________________________________Bromine (%)     14       12     12     10ABS (ex Borg-Warner)           75.8     79.3   79.7   83.1PBB-PA (ex Eurobrom)           20.0     17.1   --     --PBB-MA ex IMI   --       --     16.7   13.9Antimony Trioxide           4.2      3.6    3.6    3.0(ex Campine)PROPERTIES:UL-94           V0       V0     V0     V0/V1(1.6 mm thickness)IZOD NOTCHED    85       --     --     --IMPACT [J/m]HDT [°C.] at 1.82 KPa load           61       --     --     --______________________________________ 
    
     
                       TABLE IV______________________________________FR - Nylon 6 (CAPRON 8200 HS)            Formulation No.Component        1         2       3______________________________________Bromine (%)      10        9       9CAPRON 8200 HS   79.5      81.3    81.3(ex Allied Chem. Corp)PBB-PA (ex Eurobrom)            14.3      12.9    --PBB-MA ex IMI    --        --      12.9Antimony Trioxide            4.8       4.3     4.3(ex Campine)Mg-Stearate (ex WITCO)            0.5       0.5     0.5HOSTAFLON TF 9202            1.0       1.0     1.0(ex Hoechst)PROPERTIES:UL-941.6 mmMax. Flam. [sec] 8         11      5Total. Flam. [sec]            33        36      14DRIP             no        1       noRATING           V0        V0/V1   V0______________________________________