Flame retardant additive composition useful with polyolefins

A flame retarding additive composition, useful in thermoplastic polyolefins, is disclosed comprising a mixture of a halogenated bisphenol derivative and the copolymer of a halogenated vinyl aromatic grafted onto polyolefin. The preferred bisphenol derivative is tetrabromobisphenol A bis(dibromopropyl ether), and the preferred graft copolymer comprises bromostyrene grafted onto isotactic or syndiotactic polypropylene. Also disclosed are the flame retarded, thermoplastic polyolefins prepared using the foregoing additive compositions.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention pertains to a novel flame retarding additive useful in 
polyolefin compositions, as well as the resulting flame retarded 
polyolefin compositions. The inventive flame retarding compositions are 
comprised of a mixture of two flame retardant additives, a halogenated 
bisphenol derivative, for example tetrabromobisphenol A bis(dibromopropyl 
ether), also referred to as "TBBPA-bis(DBP)", and the copolymer of a 
halogenated vinyl aromatic, for example bromostyrene, grafted onto certain 
polymers, such as polypropylene. 
2. Description of the Prior Art 
Polyolefins have desirable properties for a variety of applications. For 
example, polypropylene is a versatile light weight plastic characterized 
by low cost, an attractive glossy surface, and excellent solvent and stain 
resistance. Its attractive fundamental properties have spurred its 
adaptation to a long list of applications including films, fibers and 
molded articles. Its use as a fiber in home, commercial and institutional 
settings--as well as its role in molded parts for electrical 
applications--have brought about the need for improved flame resistance. 
It is known that numerous bromine-based flame retarding agents can be added 
to polyolefins such as polypropylene to achieve desired ignition 
resistance. Examples of these additives are decabromodiphenyl oxide, 
hexabromocyclododecane, tetrabromobisphenol A, brominated polystyrene, 
bis(tribromophenoxy)ethane and the like. However, every one of the 
effective agents appears to impart one or more undesirable properties that 
result in compositions which are less attractive or acceptable than 
non-flame retardant Polypropylene. For example, most bromine-based flame 
retardants are fairly expensive and add signficantly to the cost of the 
propylene. Many bromine-based flame retardants are incompatible with 
polypropylene, and over time they exude to the surface, resulting in an 
oily or frosty appearance on molded parts. When spun into fibers, surface 
blooming flame retardants can be deposited onto textile handling 
equipment, building to the point that production must be stopped for 
cleaning. 
Polypropylene is thermally stable at normal processing temperatures. 
However, the more efficient brominated flame retardants contain labile 
aliphatic halogen which tends to degrade under standard processing 
conditions, resulting in discoloration and corrosion. Also, most 
brominated flame retardants with sufficient thermal stability to withstand 
high temperature spinning conditions contain the more stable--but less 
efficient--aromatic bromine. Besides requiring higher loadings to 
compensate for lower efficiency, many of the thermally stable flame 
retardants have melting points above typical polypropylene spinning 
temperatures. Thus, while polypropylene is readily spun into fibers, this 
can cause abrasion and/or plugging of spinnerettes. 
It is generally recognized in the industry that brominated flame retardants 
containing only aromatically bound bromine can lack efficiency in 
polyolefins, especially when the ignition source is a relatively cool 
flame. On the other hand, using flame retardants containing only the more 
loosely bound aliphatic bromine can result in decomposition during high 
temperature compounding. This will cause discoloration of the polymer and 
corrosion of the handling equipment. 
TBBPA-bis(DBP) is an established commercial flame retardant known to be 
especially efficient in polypropylene. Numerous patents on its use exist, 
including U.S. Pat. No. 3,883,481 issued to Kopetz et al. on May 13, 1975, 
which describes a composition comprising a polyolefin, antimony oxide and 
a series of brominated phenoxy derivatives. TBBPA-bis(DBP), by itself, 
does have the fire retarding efficiency that was predicted and has 
acceptable thermal stability for many polypropylene applications. However, 
it is fairly expensive and also has a major fault that prevents even 
broader use. Like many other brominated flame retardants, it "blooms" or 
"bleeds" to the surface of polypropylene. This gives a frosty appearance 
to molded parts that is easily smeared, leaving an unattractive surface. 
In thin sections--and particularly in spun fibers--it may be possible to 
lose enough flame retardant to the surface that the fire retardancy is 
diminished. 
The effectiveness of TBBPA-bis(DBP) has been so widely recognized that a 
significant amount of research has been done to find ways to eliminate its 
tendency to bloom. To date all of these attempts have centered on the 
addition of compatibilizers to retard the migration of TBBPA-bis(DBP) to 
the surface. However, deficiencies in these systems have persisted, and 
there has remained a desire for polyolefin compositions which include 
TBBPA-bis(DBP) and which have improved flame retarding efficiency but 
which show reduced or no bloom or bleed. 
SUMMARY OF THE INVENTION 
Briefly describing one aspect of the Present invention, there is provided a 
flame retardant additive composition, useful in thermoplastic polyolefins, 
comprising a mixture of a halogenated bisphenol derivative and a ring 
halogenated vinyl aromatic grafted onto certain polymers, such as 
polyolefin. The halogenated bisphenol derivative, also referred to herein 
as TBBPA-bis(DBP), has the formula (I): 
##STR1## 
in which R.sub.1 to R.sub.4 =H, CH.sub.3 or halogen; R.sub.5 =H, 
dihaloethyl, dihalopropyl or dihalobutyl; and A=single bond, O, CO, S, 
SO.sub.2 or C(R.sub.6)(R.sub.7), where R.sub.6 and R.sub.7 =H or C.sub.1-4 
alkyl. Also provided are flame retarded thermoplastic polyolefin 
compositions including an effective amount of the foregoing flame 
retardant additive mixture. 
It is an object of the present invention to provide synergistic flame 
retardant additive mixtures which, when added to thermoplastic 
polyolefins, are highly effective flame retarding agents and which will 
show little or no bloom or bleed to the surface of fabricated articles, 
fibers or films over time. 
Another object of the present invention is to provide a flame retardant 
additive mixture which is readily fabricated in a convenient, non-dusting 
pelletized form. 
It is a further object of the present invention to provide flame retarded 
polyolefins which display minimal or no bloom or bleed of the incorporated 
flame retarding agents. 
Further objects and advantages will be apparent from the description of the 
preferred embodiment which follows. 
DESCRIPTION OF THE PREFERRED EMBODIMENT 
For the purposes of promoting an understanding of the Principles of the 
invention, reference will now be made to the preferred embodiment of the 
invention and specific language will be used to describe the same. It will 
nevertheless be understood that no limitation of the scope of the 
invention is thereby intended, such alterations, modifications and further 
applications of the principles of the invention being contemplated as 
would normally occur to one skilled in the art to which the invention 
relates. 
The flame retardant composition of our invention includes a mixture of two 
types of flame retardant additives. The mixture comprises (a) a 
halogenated bisphenol derivative and (b) a grafted polyolefin. The 
mixtures are useful as flame retardant additives, and surprisingly the 
components thereof show reduced bleed or bloom to the surface. 
The first component of our invention mixture is a halogenated bisphenol 
derivative having the general structure (I): 
##STR2## 
in which R.sub.1 to R.sub.4 =H, CH.sub.3 or halogen; R.sub.5 =H, 
dihaloethyl, dihalopropyl or dihalobutyl; and A=single bond, O, CO, S, 
SO.sub.2 or C( (R.sub.7), where R.sub.6 or R.sub.7 =H or C.sub.1-4 alkyl. 
A preferred class of compounds is represented by: 
##STR3## 
in which R.sub.1 to R.sub.4 and A are as previous defined. A more 
preferred class is represented by (II) above, but where R.sub.1 to R.sub.4 
=Br. The most preferred compound is TBBPA-bis(DBP). 
Bisphenols that are especially useful in the preparation of compounds of 
our invention are those which can be easily synthesized from phenol and 
ketones. Examples of these bisphenols are 2,2-bis(4-hydroxyphenyl)butane; 
3,3-bis(4-hydroxyphenyl)hexane and the like. The most preferred is 
2,2-bis(4-hydroxyphenyl)propane. The hydroxyphenyl portion of the molecule 
may be halogenated or contain methyl groups. The most preferred is 
2,6-dibromophenol, which is best obtained by bromination after synthesis 
of the bisphenol. 
Alternative bisphenols are those in which the hydroxyphenyl groups are 
directly connected (biphenyls), connected by oxygen (diphenyl ethers), by 
carbonyl (ketones), by sulfur (thioethers), and by SO.sub.2 (sulfonates). 
Ethers of the bisphenols are conveniently prepared using the Williamson 
synthesis. Typically, the bisphenol is converted to the sodium phenoxide 
and is then contacted with an unsaturated alkyl halide at a temperature 
sufficient to complete ether formation. The unsaturated portion of the 
ether is then combined with elemental halogen using conditions well known 
in the art. Suitable unsaturated alkyl halides include 1 bromo-2-butene, 
1-chloro-2-butene, 1-chloro-3-methylbutene, 3-chloro-cyclopentene and the 
like. The preferred alkyl halide is allyl chloride or bromide. 
The second component is a copolymer of ring halogenated polystyrene grafted 
onto a polyolefin. The base polyolefin may include, for example, polymers 
and copolymers of propylene ethylene, 1-butene, hexene, 
4-methyl-1-pentene, octene and vinyl acetate, and combinations thereof. 
The polyolefin may be Prepared by various conventional techniques such as 
follows. By way of example, crystalline polypropylene homopolymer 
(isotactic or syndiotactic) may be used as the base for the graft 
copolymer. Polymers with melt indices of 0.1 to 200 g/10 minutes may be 
preferably employed (as measured by ASTM D-1238). The preferred range of 
melt index is from 1 to 50 g/10 minutes. A suitable graft base, for 
example, has been determined to be resin 10-5219 (melt index=20) from 
Amoco Chemical Co. 
The preferred ring halogenated vinyl aromatic may contain bromine or 
chlorine, or mixtures of bromine and chlorine, and may also be ring 
substituted with one or more aliphatic groups such as methyl, ethyl, 
propyl isomers, t-butyl and the like. More preferred is a brominated 
styrene, which may contain from 1 to 4 bromine atoms per ring, or mixtures 
of degrees of bromination from 1 to 4, particularly so that the overall 
composition contains a high percentage of bromine while remaining in 
liquid form at room temperature. (Pure tri-, tetra- and pentabromostyrene 
are solids.) The most preferred monomer is dibromostyrene. As produced by 
Great Lakes Chemical Corporation, the dibromostyrene normally contains 
about 15% monobromostyrene and 3% tribromostyrene by weight. 
The graft copolymer is represented by the formula: 
##STR4## 
in which n is an integer &gt;1; P is a polyolefin; and S is a ring brominated 
vinyl aromatic side chain grafted to the polyolefin The side chain 
preferably comprises monomeric units of the formula: 
##STR5## 
in which x=1 to 4; R.sub.8 =H or CH.sub.3 ; R.sub.9 =H or C.sub.1-4 alkyl; 
R.sub.10 =Br or Cl. The graft copolymer may also include homopolymers of 
the ring halogenated monomer as well as non-grafted polyolefin. 
The halogenated monomer may also contain various storage stabilizers such 
as phenols or compounds of sulfur, nitrogen and phosphorus known to the 
industry to inhibit premature polymerization. 
The halogenated monomer is grafted to the polyolefin using known methods 
including irradiation, peroxidation by exposure to oxygen at elevated 
temperatures, and abstraction of protons by free radical initiators. The 
graft polymerization may be performed using solution, suspension, emulsion 
or bulk procedures. The preferred method uses a free radical initiator 
such as dicumylperoxide, benzoylperoxide, t-butylperbenzoate, 
2,2'-azobis(isobutyronitrile), cumenehydroperoxide or the like dissolved 
in the halogenated monomer at levels from 0.1% to 5% on weight of the 
monomer, preferably from 1% to 3%. The solution is added to agitated 
molten polyolefin. The grafting is best carried out in a kneading type 
mixer such as a Banbury, in an extruder, or on a two roll mill. 
The quantity of monomer added is such that an amount of bromine is present 
in the grafted composition to make it particularly useful as a flame 
retarding agent, normally from 1% to 20% bromine, with 3% to 15% bromine 
being preferred. Alternatively, an excess of halogenated monomer may be 
added to produce a concentrate with levels of 10% to 60% bromine, 
preferably 30% to 50%, which may be let down with ungrafted polyolefin to 
obtain the final composition. The advantage in the latter approach is the 
maximization of physical strength properties by the introduction of 
polyolefin into the composition which has not been exposed to the harsh 
conditions of the grafting process. 
Graft polymerization will typically result in the production of both 
grafted polyolefin and ungrafted homopolymer of the halogenated monomer. 
It has been found that the grafted polyolefin and any homopolymer present 
will remain well intermixed, even during processing. The homopolymer could 
alternatively be removed, but this is not necessary. The preferred 
composition therefore includes both grafted polyolefin and halogenated 
homopolymer. In addition, the composition may also include ungrafted 
polyolefin. 
Chain transfer agents may also be dissolved into the monomer prior to 
grafting in order to control the molecular weight of the halogenated 
polymer. Alkyl halides and mercaptans are particularly useful, with 
1-dodecanethiol being preferred. Loadings from 0.1% to 5% on weight of the 
monomer may be used with 0.5% to 3% being typical. 
During the grafting process a minor amount of other reactive unsaturated 
comonomers can be mixed into the halogenated styrene for the purpose of 
additional property modification. Examples of modifications that might be 
desirable include changes in color, clarity, lubricity, dyability, melt 
viscosity, softening point, thermal stability, ultraviolet stability, 
viscoelastic behavior, polarity, biodegradability, static charge 
dissipation, strength and stiffness. Examples of potential reactive 
comonomers are maleic anhydride, styrene, chloromethylstyrene, 
acrylonitrile, methylmethacrylate, acrylic acid, butene, butadiene and 
acrylamide. 
Further property modification of the composition may be accomplished by the 
inclusion of nonreactive additives. These may include antioxidants, 
ultraviolet absorbers, antistatic agents, pigments, dyes, nucleating 
agents, fillers, slip agents, lubricants, antiblocking agents, 
plasticizers, and antimicrobials. The additives may be incorporated into 
the composition prior to grafting, during the grafting process, or as a 
separate compounding step following the graft polymerization, the last of 
which having the advantage of avoiding the Possibility of harmful 
interaction between any of the property modifying additives and the 
chemistry of the grafting process. 
The grafting is carried out at temperatures sufficiently hot enough to 
reduce viscosity of the molten polyolefin, ensure thorough mixing during 
and after monomer addition, and promote decomposition of the initiator 
with the resulting rapid polymerization of the monomer. For example, when 
polypropylene is used then temperatures from 120.degree. C. to 230.degree. 
C. may be used depending on the molecular weight and crystallinity of the 
polypropylene, with ranges from 170.degree. C. to 200.degree. C. being 
preferred. 
The grafting proceeds readily at atmospheric pressure; the elevated 
pressures encountered in plastics processing equipment may also be used. 
Following polymerization, a vacuum may be applied to reduce the amount of 
unreacted monomer. 
The time necessary for the graft polymerization will depend on the 
temperature, choice of initiator and efficiency of mixing. Ranges from 1 
second to several hours may be used, but in the interest of efficiency a 
typical polymerization time of 10 to 300 seconds is employed. 
The halogenated bisphenol component and the halostyrene graft component are 
compounded into thermoplastic polyolefins using methods well known in the 
industry. These may employ the use of Banbury type mixers, extruders, two 
roll mills, or other common plastics compounding equipment. The components 
may be added as individual ingredients, or alternatively the two flame 
retardants may be precombined to provide a single convenient package. It 
is an advantage of our invention that the precombined package can be 
produced in the form of easily conveyed, metered, and compounded 
non-dusting plastic pellets. This is a significant benefit to those 
incorporating the flame retardants since the most preferred bisphenol is a 
low-melting dusty powder. In addition, the bisphenol is difficult to mix 
into plastics because of its low melt viscosity. The precombined package 
circumvents these problems. 
The two components are used at ratios selected to provide low or no bloom 
of the bisphenol, and at a total loading to provide the desired level of 
flame retardancy. Weight ratios of bisphenol to graft copolymer may range 
from 99:1 to 1:99. A more preferred ratio range is from 50:50 to 1:99. The 
most preferred ratio is 15:85. The components may be added to polyolefins 
at levels to provide an overall concentration of from 0.1% to 25% halogen 
based on the weight of the entire composition More preferred loadings are 
from 0.5% to 15% halogen. The most preferred loadings result in 1% to 10% 
halogen in the final composition. 
In addition to the halogenated components of our invention, supplemental 
flame retardants may be utilized. Examples of these materials - sometimes 
referred to as synergists - include Sb.sub.2 O.sub.3, Sb.sub.3 O.sub.5, 
Bi.sub.2 O.sub.3, MoO.sub.3, NH.sub.4 NO.sub.3, trityl compounds, 
2,3-dimethyl-2,3-diphenylbutane, peroxides, and various phosphorus 
containing materials. These may be added during the final compounding step 
or may be included in the precombined package of the halogenated 
components. 
The flame retardant mixture of our invention may be blended --along with 
any desired stabilizers, modifiers, synergists or the like--into a wide 
range of thermoplastic polyolefins. For example, the thermoplastic 
polymers include polypropylene, polyethylene, polybutylene and 
polystyrene. The more preferred polyolefins include copolymers containing 
at least 50% by weight of copolymerized propylene monomer. Examples of 
other suitable monomers are ethylene, butene, 2-methyl-propene-1 and the 
like. Mixtures of the above polymers may also be utilized. The most 
preferred polyolefin is polypropylene.

The invention will be further described with reference to the following 
specific Examples. It will be understood that these Examples are 
illustrative and not restrictive in nature. In the following Examples, 
percents indicated are percents by weight unless indicated otherwise. 
EXAMPLE 1 
A concentrate of dibromostyrene grafted to polypropylene was prepared as 
follows: 2.1 g of dicumylperoxide were dissolved into 210 g of Great Lakes 
Dibromostyrene. In a batch process, the monomer plus peroxide solution was 
added to 138 g of molten polypropylene homopolymer (Amoco 10-5219) in a 
Brabender Prep Center mixer. Bowl temperature was maintained at 
180.degree. C. while mixing at 50 rpm's as the monomer was being added 
over a 10 minute period. Following the addition of the last of the 
monomer, the mixture was held an additional 5 minutes at 180.degree. C. 
The product (PP-g-BS) was emptied from the bowl, cooled to room 
temperature and granulated. The graft concentrate contained a calculated 
36% bromine. 
EXAMPLE 2 
A 90:10 weight ratio blend of PP-g-BS and TBBPA-bis(DBP) was prepared as 
follows. 4,500 g of PP-g-BS prepared as described in Example 1 were dry 
blended with 500 g of TBBPA-bis(DBP) (PE-68 from Great Lakes Chemical 
Corp.). The mixture was fed into a Brabender Prep Center single screw 
extruder (L/d =25/1, all zones at 180.degree. C., die=200.degree., 60 
rpm's). The molten blend was stranded, cooled in a water bath and 
pelletized to obtain off-white, non-dusting plastic pellets with a 
calculated bromine content of 39.2%. 
EXAMPLES 3-7 
A series of PP-g-BS : TBBPA-bis(DBP) ratios were blended into polypropylene 
to determine the extent of surface bloom and to compare flame retarding 
efficiences. The flame retardants were dry blended with Amoco 10-6352 
polypropylene homopolymer, black color concentrate (to make surface bloom 
easier to determine), and antimony trioxide to provide 1% Sb.sub.2 O.sub.3 
in the final composition. The blends were compounded in a Brabender Prep 
Center mixer at 180.degree. C. and 50 rpm's, cooled, granulated, and 
injection molded using a Newbury Injection Molding Machine (Model HI-30 
RS, Newbury Industries, Inc., Newbury, OH). Molding conditions are shown 
in Table 1: 
TABLE 1 
______________________________________ 
CONDITIONS FOR INJECTION MOLDING 
______________________________________ 
Injection Pressure, psi 
500 
Cycle Time, sec 30 
Rear Temperature, .degree.F. 
410 
Front Temperature, .degree.F. 
410 
Mold Temperature, .degree.F. 
75 
Screw Speed, rpm 200 
Injection Time, sec 
10 
______________________________________ 
The injection molded specimens were tested for flame retardancy and 
tendency to bloom. The results are shown in Table 2: 
TABLE 2 
__________________________________________________________________________ 
EFFECT OF BLEND RATIOS ON FLAME RETARDANCY AND BLOOM 
Example 
Wt. Ratio PP-g-BS: 
Br From 
Br From Total 
UL-94 
Number 
TBBPA-bis(DBP) 
PP-g-BS, % 
TBBPA-bis(DBP), % 
Br, % 
Rating.sup.1 
Bloom?.sup.2 
__________________________________________________________________________ 
3 100:0 3.00 0.00 3.00 
Fail 
No 
4 91:9 2.48 0.48 2.96 
V-2 No 
5 85:15 2.23 0.75 2.98 
V-2 No 
6 50:50 0.72 1.36 2.08 
V-2 Yes 
7 0:100 0.00 0.75 0.75 
Fail 
Yes 
__________________________________________________________________________ 
.sup.1 Underwriters Laboratories Test For Flammability of Plastic 
Materials Standard UL94. Tested a 1/8 inch thickness. 
.sup.2 After 168 hours at 50.degree. C. molded specimens were tested for 
bloom by wiping a portion of the surface and comparing with unwiped areas 
 
Example 3 demonstrates that PP-g-BS at a 3% bromine loading does not show 
any surface bloom, but does not meet the requirements for any of the UL-94 
ratings. Example 4 shows that if a small amount of bromine from Example 3 
is substituted with bromine from TBBPA-bis(DBP), a UL-94 V-2 rating is 
obtained without causing surface bloom. In Example 5, the portion of 
bromine from TBBPA-bis(DBP) is further increased without causing bloom. 
However, in Example 6 most of the bromine is provided by TBBPA-bis(DBP). 
Excellent flame retarding efficiency is demonstrated (a V-2 rating is 
maintained at lower total bromine), but bloom is observed. Finally, in 
Example 7, TBBPA-bis(DBP) as the only flame retardant is loaded at the 
same concentration as in Example 5. The result is a loss of flame 
retardancy and the generation of bloom. Only at the ratios in Examples 4 
and 5 were V-2 ratings maintained without causing surface bloom. 
EXAMPLES 8 AND 9 
A PP-g-BS/TBBPA-bis(DBP) blend was compared with PP-g-BS by itself as a 
flame retardant for melt spun polypropylene. The additives were dry 
blended into Amoco 10-6352 polypropylene homopolymer, then melt spun on a 
pilot scale fiber spinning line from Hills, Inc. A melt temperature of 
270.degree. C. was maintained with a draw ratio of 3:1. Fibers of 15 dpf 
were produced with a yarn denier of 1,080. In order to test flame 
retardancy, the yarns were knitted into 9.1 oz/sq.yd. fabrics using a 
Brother Model KH-836 knitting machine. Efficiency of the flame retardants 
was compared using the NFPA-701 vertical burn test. Results are shown in 
Table 3. 
TABLE 3 
______________________________________ 
COMISON OF BLEND 
EFFICIENCY IN KNITTED FABRICS 
Example Number 8 9 
______________________________________ 
Flame Retardant Used 
PP-g-BS 90:10 Blend 
(Example 1) 
(Example 2) 
Amount of Flame Retardant, g 
757 697 
Amount of Polypropylene, g 
8323 8383 
Calculated Br in Fiber, % 
3.0 3.0 
Average Burn Time, sec..sup.1 
45 0 
Average Burn Length, in..sup.2 
6.4 3.4 
Flaming Drips?.sup.3 
Yes No 
______________________________________ 
.sup.1 Average time for the specimen to selfextinguish following the 12 
second ignition. 
.sup.2 Burn length was measured from the bottom of the specimen holder to 
the highest point of fabric melt. 
.sup.3 If molten polymer continued to burn on the test chamber floor, the 
sample was considered to have flaming drips. 
These results dramatically demonstrate that the flame retarding efficiency 
of a 90:10 blend of PP-g-BS : TBBPA-bis(DBP) is much greater than that of 
PP-g-BS on an equal bromine basis. The data in Table 2 already have shown 
that the blends have excellent efficiency in molded articles (without 
surface bloom); the results in Table 3 show that the improvement extends 
into the fiber area. 
EXAMPLE 10 
The preparation of Example 1 is repeated to produce polypropylenes grated 
with dibromostyrene to have percentages of bromine, based on the overall 
compound, of 1, 3, 10, 15, 20, 30, 50 and 60 weight percent. Suitable 
graft polymers useful in combination with the bisphenol derivatives of the 
present invention are produced. The foregoing preparations are repeated 
with different halogenated monomers, including monomers including 1, 2, 3 
and 4 bromines per unit, and suitable products are obtained. 
The various halogenated monomers above described are combined with 
different polyolefins. The polyolefins include polymers and copolymers of 
propylene, ethylene, 1-butene, hexene, 4-methyl-1-pentene, octene, vinyl 
acetate and mixtures thereof. Useful flame retardant additives suited for 
use with the bisphenol derivatives of the present invention result. 
EXAMPLE 11 
Mixtures of graft copolymer compositions, as previously described, are made 
with halogenated bisphenol derivatives. The bisphenol derivatives have the 
formula: 
##STR6## 
in which R.sub.1 to R.sub.4 =H, CH.sub.3 or halogen; R.sub.5 =H, 
dihaloethyl, dihalopropyl or dihalobutyl; and A=a single bond, O, CO, S, 
SO.sub.2 or C(R.sub.6)(R.sub.7), wherein R.sub.6 and R.sub.7 = H or 
C.sub.1-4 alkyl. The bisphenol derivatives further specifically include 
those having the formula: 
##STR7## 
in which R.sub.1 to R.sub.4 and A are as previous defined. Mixtures of the 
foregoing bisphenol derivatives and graft copolymer compositions yield 
flame retardant additive compositions useful with a variety of 
thermoplastic polyolefins. The ratios of the bisphenol derivative to the 
graft copolymer include 99:1, 15:85, 50:50 and 1:99, and yield desirable 
flame retardant additives. 
EXAMPLE 12 
Upon addition of the foreoing flame retardant additives of Example 11 to 
thermoplastic polyolefins, namely polypropylene, polyethylene, 
polybutylene and polystyrene, flame retardant polyolefins are obtained. 
The mixtures of the flame retardant additives and thermoplastic 
polyolefins are made at bromine levels (based on weight percent of the 
overall composition) of 0.1, 0.5, 1, 10, 15 and 25%, and improved flame 
retardancy for the thermoplastic polyolefins, over the non-additive 
containing thermoplastic polyolefins, is achieved. 
While the invention has been illustrated and described in detail in the 
foregoing description, the same is to be considered as illustrative and 
not restrictive in character, it being understood that only the preferred 
embodiment has been shown and described and that all changes and 
modifications that come within the spirit of the invention are desired to 
be protected.