CA2006134A1

CA2006134A1 - Thermally stable and light stable flame retardant thermoplastic polyolefin and polystyrene compositions

Info

Publication number: CA2006134A1
Application number: CA002006134A
Authority: CA
Inventors: Nicolai A. Favstritsky; Enrico J. Termine
Original assignee: Great Lakes Chemical Corp
Current assignee: Great Lakes Chemical Corp
Priority date: 1988-12-20
Filing date: 1989-12-20
Publication date: 1990-06-20
Also published as: EP0401366A1; KR910700007A; JPH03502820A; WO1990006691A1; EP0401366A4

Abstract

ABSTRACT
Thermally stable and light stable flame retardant polyolefin and polystyrene compositions comprise bicyclic phosphate compound(s), halogen-containing flame retardant(s) and polyolefin or polystyrene resins. These compositions exhibit a reduced tendancy to develop color, to change melt viscosity or to lose mechanical strength under conditions present during polymer processing and end use.

Description

Z [)~3S3L34 THERMAL AND LIGHT STABLE FLAME RETARDANT THERMOPLASTIC
POLYOLEFIN AND POLYSTYRENE COMPOSITIONS

BACKGROUND OF THE INVENTION
Field of the Invention. This invention relates to thermal and light stable ~lame retardant thermoplastic polyolein and polystyrene compositions. More particularly, this invention relates to thermoplastic compositions which are flame retardant and which resist thermal degradation or photochemically-induced degradation. These compositions comprise bicyclic phosphate compound(s); halogen-containing flame retardant(s); and polystyrene or polyolefin resin.
The compositions produced in accordance with this invention have a reduced tendency to develop color, to change melt viscosity, or to lose mechanical strength under conditions that are present during polymer processing or end-use.
De~cri~tion of the Prior Art.
It ~s known in the art that polystyrene and polyolefins, such as homopolymers and copolymers o polypropylene, polyethylene, and polybutylene, may be flame retarded with halogen-containing flame retardants.
Although efficient in suppressing the rate of combustion in a resin ~ystem, mo~t flame retardants tend to affect adversely one or more key properties of the resin. For example, many flame retardant additives are susceptible to thermal and photochemically-indu~ed - ",- ,: . :
- . .
'. . : ~, , ';

3~

degradation during processing of the thermoplastic resin, or during polymer u~e conditions.
Evidence of degradation may be seen in several Ways.
For example, the therm~plastic composition may develop ~
darkened appearance during processing, indicat~ng polymer or flame retardant chemical decomposition; or ~he thermoplastic composition may suffer an increase or decrease in melt viscosity, limiting, for example, the recycle of industrial scrap ("regrind") or environmental plastic waste; or the thermoplastic composition may lose mechanical strength, thus reducing the overall ~ervice life of the polymeric material.
Many prior art references describe the use of stabilizers, such as antioxidants, hindered phenols, hindered amines, phosphites, and the like, in polystyrene and polyolefins. A general treatise covering thi~ broad : topic includes PolYmer Stabilization and Dearadation, ACS
SYmPOSiUm Series. No. 280, P.P. Klemchuk, ed., American Chemical Society, Washington, D.C. (lg853.
However, the ~election of a suitable stabilizer for polystyrene and polyolefin r~sins is not predictable.
Stabilizer selection is particularly diff~cult when flame retardants are employedJ exacerbated by the complex interaction between the polymer and the halogen-containing compound.
Briti6h Patent No. 889,338 describes the production of bicyclic phosphites, phosphonates, thiophosphates, and selenophosphates. These compositions are ~aid to be stabilizers for vinyl halide resins. They are alleged to be useful as heat stabilizers for vinyl chloride resin, and as antioxidants for fats and oils. The British '338 Patent does not ~how any examples of bicylic phosphate~, 5 nor does it specify the use of bicyclic phosphates, ~uch as pentaerythritol-based bicyclic phosphates of the present invention, which can be employed as a stabilizer for polystyrene or polyolefin resin. Eurthermore, the British '338 Patent does not disclose that cyclic phosphates of the present invention could be used with halogen-containing flame retardants to produce flame retardant thermoplastic compositions which resis~ thermal or photochemically-induced degradation.
British Patent No. 999,793 describes a process to produce organic phosphates by subjecting organic phosphites to reaction with peracetic acid. This patent shows a method for producing the most preferred bicyclic phosphate of the present invention, 2,6,7-trioxa-1-phosphobicyclo[2.2.2]-octane-4-methanol-1-oxide (vide infra), and teaches the use of acetal ring-containing phosphates as plastisizer~ or functional fluid~. The British '793 Patent, however, does not disclose the composition6 of the present invention. It does not mention bicylic pho~phates as being useful for flame retardant thermoplastic resins, nor that the most preferred bicyclic phosphate of the pre ent invention can be used with halogen-containing flame retardant additives to yield improved thermoplastic composition ~3~8Ç~3~

U.S. Patent No. 3,873 J 496 describes a flame retardant polyester composition which contains 5 to 25 percent of a hydroxymethyl bicyclic phosphate compound as a flame retardant additive. The patentee did not observe the ability of bicyclic phosphates to act as heat or melt ~tabilizers for thermoplastic resin compo ition~ ~hich employ halogenated compounds as the primary flame retardant additive.
U.S. Patent No. 4,341,694 discloses a composition comprising 2,6,7-trioxa-1-phosphobicyclo[~.2.2]octane-4-methanol-1-oxide and a nitrogen-containing co-additiveJ
which are intumescent and are adaptable to flame retard polyolefins, polyvinylaromatic resins, polycaxbonates, P~rC and blends thereof. The patentee did not observe any stabilization of the present invention.
Accordingly, a primary objec~ of this invention i~
to provide thermal and light stable flame retardant thermoplastic polyolefin and polystyrene compositions.
A related object is to provide compositions of the character de~cribed which re8i8t thermal degradation or photochemically induced degradation.
A further object i 8 to provide polyRtyrene or polyolefin resin compositions incorporating bicyclic phosphate compounds and halogenated flame retarda~t~.

SUMMARY OF 1~ INVENTION
The foregoing and other objects, advantages and features o~ the present invention may be achievable wi~h thermal and light stable thermoplastic polyolefin or .

2~:36~3~

polystyrene resin compositions incorporating an additive mixture comprising a halogen-containing flame retardant;
and a bicyclic phosphate compound of ~he the following Formula (I):
s O R

O=P ''' ~ CH
( ) X

where X is OH, OR', or OC(O)R'; R is H or a satur2ted or unsaturated ~traight-chain or branched-chain Cl-C17 alkyl; and R' is a saturated or unsaturated straight-chain or branched chain Cl-C17 alkyl.
DESCRIPTION OF THE PREEERRED EMBODIMENTS
This invention relates to thermal and light stable flame retardant theremoplastic polyolefin and poly~tyrene compositions. In particular, the invention xelate~ to thermopla~tic polyolefin and polystyrene resin composition5 which are flame retardant and which re~i3t thermal degradation or photochemically induced degradation and which incorporate an additiYe mi~ture comprising one or more bicyclic pho~phate compound~ and one or moxe halogen-containing 1ame retardant~.
Compositions produced in accordance with this invention 3~

have a reduced tendency to develop color, to chanye melt viscosity, or to lose mechanical ~trength under conditions present during polymer processing or in use.
Preferred bicyclic phosphates in accordance with ~his invention are compounds of Formula (I) where X is ~H or OC(O)R'. The most preferred bicyclic compounds are 2,6,7-trioxa-phosphobicyclo[2.2.2]-octane-4-methanol-1-oxide (Compound BCP, that is, Formula lI] when R is H and X is OH), and 2,6,7-trioxa-1-phosphobicyclo[2.2.2]-octane-4-methanol, acetate, 1-oxide (Compound BCP-A, that is, when R i~ H and X is OC(O)CH3).
The halogen-containing flame retardant compound may be any brominated or chlorinated aliphatic or aromatic oryanic compound that can be used in thermoplastic compositions. Preferred halogen-containing compounds are hexabromocyclododecane, tetrabromobisphenol A, - tetrabromobisphenol A bis-(dibromopropylether), dibromo(dibromoethyl)cyclohexane, tetrabromocyclooctane J
bi 8- ~ dibromonorbornane dicarboximido)ethane, bis-(tetrabromophthalimido)ethane, Diels-Alder adduct of chlorinated cyclopentadiene and unsaturated cycloaliphatic compound, bis-(tribromophenoxy-ethyl)tetrabromobisphenol A ether, pentabromodiphenyl ether, o~tabromodiphenyl ethar, decabromodiphenyl ether, bis-(tribromophenoxy)ethane, bis-(pentabromo-phenoxy) thane, chloropentabromocyclohexane, ~tribromophenoxy)-(dibromononylphenoxy)ethane J
pentabromoethylbenzene, pentabromododecylbenzene, 3~

carbonate oligomers of tetrabromobisphenol A, poly(brominated styrene), and brominated polystyrene, poly(brominated phenylene) ether, and mixtures thereof.
These halogenated compounds are added to thermoplastic resins at levels such that the resultant resin composi-tion may be rendered flame retardant.
Resin~ which may be treated in accordance with the invention include thermoplastics such as polystyrene and copolymers sf styrene with butadiene and acrylonitrile ("ABS copolymers") and homopolymers and copolymers of polyolefins such as polypropylene, polyethylene, and polybutylene. Polystyrene and polypropylene are preferred thermoplastics in accordance with this invention.
The polystyrene may be any thermoplastic polystyrene, especially impact modified grades, as described in Modern Plastics EncYclopedia, Vol. 63, No.
lOA, 74 (1986), or grades suitable for making ~oamed products. Preferably, the additives of the invention are used With impact grades classiied by notched impact values between 0.6 and 3.0 ft-lb/in, and most preferably between 1.0 and 2.5 ft-lb/in.
The polypropylene may be any thermoplastic polypropylene, especially homopolymer type, ~s de~cribed in Modern Plastics EncycloPedia, Vol. 63, No. lOA, 72 (1986)J or grades suitable for making foamed products.
Preferably, the additives of thiC i~vention are u~ed with grades cla~sified by melt flows between 2 and 30 g/10 3~

min., and most preferably between 4 and 10 g/}0 mln.
The compo itions of this invention al60 desirably incorporate one or more enhancing agents. Enhancing asent~ useful in accordance with this invention comprise the oxides and halides of groups IV-A and V-A of the periodic table; organic or inorganic compounds of phosphorus, nitrogen, boron sr sul~ur; and oxides and halides of, for example, zinc, magnesium and titanium, all as disclosed in U.S. Patent No. 4,016,139.
Preferred enhancing agents in accordance with thi~
invention are the oxides of antimony, ar~enic and bismuth, with the oxides of antimony being especially preferred.
Antimony trioxide i~ the most preferred enchancing agent used in the compositions of ~his invention.
~he compositions of this invention may additionally incorporate one or more antioxidant~, hindered amine light stabilizers, or acid scavengers. Especially preferred antioxidant is 2,2-bi 8 [ 13-[3,5-bi~(l,l-dimethylethyl)-4-hydroxyphenyl]-1- oxopropoxy]methyll1,3-propanediyl 3,5,-bis~l,1-dimethylethyl~-4-hydroxybenzenepropanoate;
e~pecially preferred hindered amine light stabilizer i~
bi~(2,2,6,6-tetramethyl-4-piperidinyl)-sebecate; and especially preferrsd acid ~cavenger i~ magne~it~m aluminum hydroxy carbonate Mg4 5A12(0H~13C03-The ~cope of ~he present invention includes ~he incorporation of other additives in the composition B0 far as to produce a particular end re~ult. Such additives include, without limitation, blowing agents, heat - ~
: :
- ~ ., stabilizers, light stabilizer6, plasticizer~, pigments, preservatives, ultraviolet light 6tabilizer6, filler~, antioxidants, antistatic agents and other materials well known to those 6killed in the art, for example, a~

5 de~cribed in Modern Plastics EncYcloPedia. Vol. 63, No.
lOA, Mc~raw-Hill, Inc. (1986).
The bicyclic phosphates of the present invention may be u~ed alone or as mixtures of any such compounds. When mixtures of bicyclic phosphates are employed, substantially any combinations of amounts and proportions of the individual compounds may be used. The u~e of Compound BCP and Compound BCP-A is especially preferred in accordance with this inventionO
The halogen-containing flame retardants of the present invention may be used alone or as mixtures of any such compounds. When mixtures of halogen-containing : phosphates are employed, substantially any combinations of amounts and proportions of the individual compound~
may be u~ed. The use of hexabromocyclododecane, tetrabromobisphenol A, chloropentabromocyclohexane, tetrabromobi~phenol A bis-~dibromopropylether), dibromo(dibromoethyl)cyclohexane, tetrabromocyclooctane, bi~-(dibromonorbornane dicarboximido~ethane, and Diel~-Alder adduct of hexachlorocyclopentadiene Gnd cyclooctadiene i~ especially preferred in accordance with thi~ invention.
Desirably, the bicyclic phosphate compound and 3~

halogen-containing flame retardant are provided as a mixture useful as an additive which may be added to polystyrene or polyolein resin compositions. The additive mixture utilize~ bicyclic phosphate in halogen-containing flame retardant in a weight ratio lying in the ran~e of about 0.001 to 0.200, most preferably, about 0.005 to 0.050.
~ he additive mixture is in~orporated into the polymer composition at a level such that the resulting resin composition i8 rendered flame retardant. In general, the additive mixture i~ provided in the flame retardant at a level of about 0.1 - 20.0 percent by weight of the resin composition, preferably about Q.5 - 20.0 percent by weight.
Practice of the present invention is illustrated by the following example~.
EXAMPLES
The following examples are given to illustrate the invention and ~hould not be construed a6 limiting its scope. All percentages are by weight. The t~rm polystyrene refers to polystyrene ava~lable from Hunt~man Chem~cal Corporation as PS 3037; the term polypropylene refers to polypropylene available from ~imont Chemical Company a~ Profax 6301; and the term acrylonitrile-butadiene-styrene refer~ to acrylonitrile-butadiene-styrene available from Borg Warner Corporation a~ Cycolac GSM 1000. All flame retardant compo~itions received a V-2 or V-0 ratin~ as mea~-ured by ~he UL-94 te~t.

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TABLE I contain~ examples which illustrate the effectiveness of bicyclic phosphate compound and halogen-containing flame retardant in polypropylene re~in to minimi~e a change in polymer melt viscosity during processing.
05 The thermoplastic compo~itions were compounded in a 3/4" single screw extruder (L/D 25:1) at 43Q F. The extrudate was pelletized and re-extruded ten time~. The melt viscosity of the final extrudate was measur~d by a melt flow technique.

EXAMPLES 1-2 and COMPARATIVE EXAMPLES 1-2 Examples 1-2 are flame retardant polypropylene compositions containing 4.0% hexabromocyclododecane (Flame Retardant HBCD), available under the trademark CD-75P
from Great Lakes Chemical Corporation, and, respectively, 0.1% and 0.2% 2,6,7-trioxa-1-phosphobicyclol2.2.2 octane-4-methanol-1-oxide (Compound BCP).
Comparative Example 1 shows the inherent melt vi~cosity of a non-flame retardant polypropylene composition which has be~n aub~ected to multiple extrusions. Comparative Example 2 shows ~hat Elame Retardant HBCD has a detrimental effect on polymer melt vi~cosity, as evidenced by an increase in melt flow from 29.3 g~10 min (Comparative Example 1) to 77.1 g~10 min (Comparative Example 2~.
Surprisingly, when Compound BCP i~ added to the composition, the damaging effect~ of Flame Retardant ~BCD
on the melt viscosity of polypropylene re~in are reduced.

`

13~ , Example 1 and Example 2 show less change in melt flow than Comparative Example 2.

EXAMPLES 3-4 and COMPARATIVE EXAMæLES 3-4 Examples 3-4 are flame retardant polypropylene composition~ containing 0.1% hindered p~enolic antioxidant (Compound A0), which i8 available from Ciba-Geigy Corporation as Irganox 1010, and 0.1% acid scavenger (Compound AS), which is available from Kyowa Chemical Industry as DHT-4A, respectively.
Examples 3-4 and Comparative Examples 3-4 in TABLE I
illustrate also the utility of Compound BCP to inhibit changes in polymer melt viscosity when other additives are present in the thermoplastic resin. Example 3 ~hows the effectiveness of Compound BCP in the presence of a hindered phenolic antioxidant, and Example 4 6hows the effectiveness of Compound BCP in the presence o~ an acid 6cavenger.
TABLI; I

FLAME RETARDANT OTHER ADDITIVE ~ELT FLOW
BCP gllO min EXAMPLE ADDITIVE TYPE AMOUNT. TYPE ~MOUNT ASTM
NUMBERweight X weight % wsight X D-1238 _ O.1 HBCD 4.0 ~ 66.6 CONP 1 0.0 -- --~ 29.3 COMP 2 0.0 HBCD 4.0 -- --- 77.1 2 0.2 HBCD 4,0 -- --- 70.7 2~3G~3~

TABLE I (CONT.) FLAME RETARDANT OTHER ADDITIVE MELT FLOW

~CP - gllO min EXAMPLE ADDITIVE TYPE AMOUNT TYPE AMOUNT A~TM , NUMBERweight X weight % weight X D-1238 3 0.1 HBCD 4.0 AO 0.1 13.3 COMP 3 0.0 HBCD 4.0 AO 0.1 75.2 4 0.1 HBCD 4.0 AS --- 38.2 COMP 4 0.0 HBCD 4.0 AS 0.1 40.6 _ Note: Polypropylen~ resin, 430F.

TABLE II contains examples which illustrate the effectiveness of the preferred bicyclic phosphate compound and HBCD in polystyrene resin to minimi~e a change in polymer melt viscosity during processing.
EXAMPLE 5 and COMPARATIVE EXAMPLES 5-6 Example 5 is a ~lame retardant polystyrene formulation in accordance with this invention containin~ 0.1% Compound BCP and 2.0% Flame Retardant HBCD.
Example 5 illustrates an improvement in melt low over Comparative Example 5 and Comparative ~5~ample ~. l~u8, Compound BCP is effective in poly~tyrene when no additional additives are present (Comparative Example 5) or when an acid scavenger is present (Co~nparative Example 6).

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T~BLE I I

FLAME RET~RDANT OT}ER ~DDITIVE MELT ~LOW
BCP 8/10 ~in EXAMPLE I~DDITIVE TYP~AMOUNT TYPE QMOUNT ASTM
NUNBERwa~ht % wel~ ht X wel~ht X D-1238 0.1 HBCD2.0 -- --- 15.8 10 COMP 5O. O HBCD2. 0 -- --- >~0 CO~P 6O. O H~CD2. 0 AS 0.1 22.1 _ _ _ Nota: Polystyrene resin, 500F.

TABLE III show~ compositions of the present ~nvention which have less tendency to degrade thermally in various polymer systems.
Thermal degradation was measured by formulating compositions in a Brabender Plasticorder mixer (Model PL-V300) for 21 minutes, 50-70 rpm, and at the temper-atures as specified in TABLE III, Footnote 1. The polymer melt was sampled at three minute intervals, and vi~ual inspections of the appearance of the polymer composition ware made.
The color and description of the formulated composition~ are listed ~n Table III, and reflect the appearance of the composition when either the material showed total degradation ~that is, developed a black or dark red color or showed signs of decompo~ition, such a8 off-gassing), or when the 21 minute inter~al of the te~t was attained.

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EXAMPLES 6-10 and COMPARATIVE EXAMPLES 7-lZ
Examples 6-~ are flame retardant polystyrene compositions containing 0.2% Compound BCP and 4.0%, respectively, Flame Retardant B CD; dibromo(dibromoethyl) cyclohexane (Elame Retardant TBCH), available from ~thyl Corporation as BCL-462; Diel~-Alder adduct of hexachlorocyclopentadiene an~ cyclooctadiene (Elame Retardant CBCO), available from Occidental Corporation as Dechlorane Plus; and monochloropentabromocyclohexane (Flame Retardant CBCH), available from Dow Chemical Corporation as FR-651.
Example 10 is a flame retardant polystyrene composition containing 0.8% Compound BCP and 16.0%
tetrabromobisphenol A (Flame Retardant TBBP), a~ailable from Great Lakes Chemical Corporation as BA-59P.
Examples 6-10, as supported by comparisons to Comparative Examples 8-12 (specified in Table III) illustrate polystyrene compositions which resist ~hermal degradation and h~ve less tendency to develop color under processing conditions. Comparative Example 7 shows the inherent color development of non-flame retardant polystyrene resin which has been ~ub~ected to the te~t procedures .
Examples 6-10 illustrate al50 that Compound BCP i~
effective in the pre3ence of various halogen-conta~ning flame retardant additives.

Example 11 is a flame retardant poly~tyrene com~o-. .
:

sition containing 0.2% acetate derivative of Compound BCP
(designated Compound BCP-A) and 4.0% Flame Retardant HBCD. Example 11 i8 an illustration of a bicyclic pho~-phate other than Compound BCP which ~ 8 within the scope of this ~nvention.
EXAMPLE 12 and COMPARATIVE EXAMPLES 13-14 Example 12 iB a ~lame retardant acrylonitrile-butadiene-~tyrene ("ABS") composition containing 0.5% Compou~d BCP, 4.0% Sb20~, and 16.0% Flame Retardant TBBP.
Example 12, as supported by comparison to Comparative 10 Examples 14 (specified in Table III), i8 an illustration of utility of the present invention in ~BS resin.
Comparative Example 13 shows the inherent color develop-ment of non-flame retardant ABS resin which has been subjected to the test procedure~.
EXAMPLES 13-14 and COMæARATIVE EXAMPLES 15-17 Examples 13-14 are flame retardant polypropylene composition~ containing 0.5% Compound BCP, 1.0% Sb203, and, respectively, 3.0% tetrabromobisphenol A bi~(dibromo-propylether) (Flame Retardant TBPE) and 5.0% Flame Retardant HBCD.
Example~ 13-14, a~ supported ~y comparison to Comparative Examples 16-17 (specified in Table III), illustrate the e~fectivene~ of the present invention to reduce the tendency ~or di6coloratlon in flame retardant polypropylene compo~itions. Comparative Example 15 hows the i~herent color development of non-flame retardant polypropylene resin which has been ~ubjected to ~he te~t procedures.

2 ~ 3 TABLE III
-FLAME RETARDANT

EXAMPLE ADDITIVE RESI~ TYPE AMOUNT 2 NUMBER weight % TYPE weight X COLOR DESCRIPTION

6 0.2 A HBCD 4.0 0 IRANSPARENT
COMP 7 O.D A ~ O TRANSPARENT
COMP 8 0.0 A HBCD 4.0 10 OPAQUE

7 0.2 A TBCH 4.0 2 TRANSPARENT
COMP 9 0.0 A TBCH 4.0 10 OPAQUE

8 0.2 A CBCO 4.0 0 OPAQOE
COMP 10 0.0 A CBCO 4.0 3 OPAQUE

9 0.2 A CBCH 4.0 4 OPAQUE
COMP 11 0.0 A CBCN 4.0 10 OPAQUE
0.8 A TBBP 16.0 2 OPAQUE
COMP 12 0.0 A TBBP 16.0 8 OPAQUE
11 0.2 A HBCD 4.0 2 TRANSPARENT
12 0.5 B TBBP 16.0 5 OPAQUE
25 COMP 13 0.O B -- --- 1 OPAQUE
COMP 14 0.0 B TBBP 16.0 8 OPAQUE
13 0.5 C TBPE 3.0 6 OPAQUE
COMP 15 0.O C -~ 1 OPAQUE
COMP 16 0.0 C TBPE 3.0 10 OPAQUE
14 0.5 C HBCD 5.0 1 OPAQUE
COMP 17 0.O C HBCD 5.0 10 OPAQUE

NOTE 1: A) Polystyrene resin, 450F; B) Acrylonitrilebut~diene-styrene resln, 4.0X Sb203, 500F; C) Polypropylene, 1.0% Sb203, NOT~ 2: O~colorless; l=white; 2=light yellow; 3=yellow; 4=dark yellow; 5=light tan; 6=tan; 7=dark tan; 8-brown; 9=dark brown;

10=black, red or decomposed.

3 L~

TABLE IV ~hows polypropylen~ compositions of the present invention which have less tendency to lose mechanical strength, when such compositions are exposed to radi Ati on.
Thermoplastic compositions were compounded and injection molded into test specimens, m~asuring 5.0~
x 0.5" x 0.062n. The ends of the test specimens were clamped together, placed in an Xenon Arc Weatherometer (Atlas Model Ci-35), and irradiated according to ASTM
D-4459 procedures for 3000 hours. The te~t ~pecimens were observed periodically for signs of cracks or crazing. The time at which failure occured was noted.

EXAMPLES 15-16 and COMPARATIVE EXAMPLES 18-19 Examples 15-16 are flame retardant polypropylene compositions containing 0.5% Compound BCP, 10.0% Flame Retardant TBPE, 3.3% Sb203, and~ respectively, 0.5%
hindered amine light stabilizer (Compound HALS), available from Ciba-Geigy Corporation as TIN W IN 770, and O.5%
20 Compound AS.
Examples 15-16, as supported by comparison to Comparative Examples 18-19 (specified ~n Table IV) J
illu~trate the effectiveness of the present invention to reduce the tendency for photochemically-induced mechanical failure in flame retardant polypropylene composition~.

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TABLE IV

FLA~ RETARD~NT OTHEP~ ~DDITIVE
TIME TO
~CP STRESS
EX~MPLE ~DDITIV~; TYPl; ~MOI)NT TYPE ~MOI~NT FAILURE
Nl)MBER wei~ht % wei~ht X weight X hours -0 . 5 TBPE 10 . O }~LS O . 5 2900 10 CONP 18 0 . O TBPE 10 . O }~LS 0. 5 2500 16 0 . 5 TBPE 10 . O AS O . 5 ~3000 COMP 19 0 . O TBPE 10 . 0 AS O . 5 - 150 Polypropylene resln and 3. 3% Sb203.

TABLE V shows polypropylene composition~ of ~he present invention which have less tendency to discolor, when such compositions are exposed to radiation.
ThermoplasticR compositions were compounded, injection molded into 3.0" x 1.0" x 0.125'~ test specimen~, and irradiated in a Xenon Arc Weatherometer ~Atlas Model - Ci-35), according to ASTM D-44~9 procedure~ for 2000 hours.
Changes in color were measured as Delta E values, accord-ing to ASTM-2244 procedures.

EXAMPLES 17-20 and COMPARATIVE EXAMPLES 20-22 Example~ 17-18 ar~ 1nme retardant polypropylene compositions containing 3.3% Sb2O3, 10.0~ Flame Retardant TBPE, andJ respectively, 1.0% BCP Compou~d and 0.5%
Compound BCP.
Examples 19-20 are ~lame retardant polypropylene compositions containin~ 0.~% Compound BCP, 10.0% Flame ' ' ,- . ` - -': .. .
-:, - .
. ~ :
... . ., . ,, 2~)~6~3~

Retardant TBPE, and, respectively, 0.5% hinder2d amine light ~tabilizer Compound HALS and 0.5% alkytin-containing stabilizer (Compound TLS), available from Witco Chemical Company as Mark 1413.
Example~ 17-20, as supported by comparison ts Comparative Example~ 20-22 (~pecified in Table V~ J
lllustrate the effectivenes~ of ~he present invention to reduce the tendency for photochemically-induced discoloration in flame retardant polypropylene composi-tions.
TABLE V
_ FLAME RETARDANT OTH~R ~DDITIVE
COLOR
BCP LIGHT
EXAMPLE ADDITIVE TYPE AMOUNT TYPE AMOUNT STABILITY
N~MBER weight % weight X weight X Delta E

17 1.0 TBPE 10.0 -.- --- 4.90 18 0.5 TBPE 10.0 --^ --- 4.08 COMP 20 0.0 TBPE 10.0 --- --- 7.90 19 0.5 TBPE lO.O HALS O.5 2.03 COMP 21 0.0 TBPE 10.0 HALS 0.5 4.05 0.5 TBPE 10.0 TLS 0.5 3.02 CO~P 22 0.O TBRE 10.0 TIS O.5 5.27 __ Polypropylene resin and 3.3X Sb203.

Claims

1. A thermally stable and light stable thermo-plastic resin composition comprising a polyolefin or polystyrene resin and a mixture comprising;
at least one halogen-containing flame retardant;
and at least one bicyclic phosphate compound of the formula:

where X is OH, OR', or OC(O)R'; R is H or a saturated or unsaturated straight-chain or branched-chain C1-C17 alkyl;
and R' is a saturated or unsaturated straight-chain or branched chain C1-C17 alkyl.

2. A composition, as claimed in claim 1, wherein the halogen-containing flame retardant is a member selected from the group consisting of hexabromocyclodode-cane, tetrabromobisphenol A, chloropentabromocyclohexane, tetrabromobisphenol A bis-(dibromopropylether), dibromo(dibromoethyl)cyclohexane, tetrabromocyclooctane, bis-(dibromonorbornane dicarboximido)ethane, Diels-Alder adducts of hexachlorocyclopentadiene and cyclooctadiene and mixtures thereof.

3. A composition, as claimed in claim 1, wherein the bicyclic phosphate compound i8 2,6,7-trioxa-phospho-bicyclo[2.2.2]-octane-4-methanol-1-oxide; or 2,6,7-trioxa-l-phosphobicylo[2.2.2]-octane-4-methanol, acetate, 1-oxide.

4. A composition, as claimed in claim 1, wherein the resin is a member selected from the group consisting of polystyrene, acrylonitrile-butadiene-styrene resin, and polyethylene, polypropylene and polybutylene homo-and copolymers.

5. A composition, as claimed in claim 4, wherein the member is polypropylene or polystyrene.

6. A composition, as claimed in claim 1, wherein the weight ratio of bicyclic phosphate compound to halogen-containing flame retardant lies in the range of about 0.001 to 0.200.

7. A composition, as claimed in claim 1, wherein the mixture of bicyclic phosphate compound and halogen-containing flame retardant is provided in the resin composition at a level lying in the range of about 0.1 - 20.0 percent by weight of the overall composition.

8. A composition, as claimed in claim 1, and further comprising at least one member selected from the group consisting of antioxidants, hindered amine light stabilizers, and acid scavengers.

9. A composition, as claimed in claim 8, wherein the antioxidant is 2,2-bis[[3-[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-1- oxopropoxy]methyl]1,3-propanediyl 3,5,-bis(1,1-dimethylethyl)-4- hydroxybenzenepropanoate.

10. A composition, as claimed in claim 8, wherein the hindered amine light stabilizer is bis-(2,2,6,6-tetramethyl -4-piperidinyl)-sebecate.

11. A composition, as claimed in claim 8, wherein the acid scavenger is magnesium aluminum hydroxy carbonate Mg4.5A12(OH)13CO3.

12. A flame retardant stabilizing additive mixture for polyolefin or polystyrene resin compositions compris-ing:
a halogen-containing flame retardant; and a bicyclic phosphate compound of the formula:
where X is OH, OR', or OC(O)R'; R is H or a saturated or unsaturated straight-chain or branched-chain C1-C17 alkyl;
and R' is a saturated or unsaturated straight-chain or branched chain C1-C17 alkyl.

13. A mixture as claimed in claim 12, wherein the flame retardant is a member selected from the group consisting of hexabromocyclododecane, tetrabromobisphenol A, chloropentaoromocyclohexane, tetrabromobisphenol A bis-(dibromopropylether), dibromo(dibromoethyl)cyclohexane, tetrabromocyclooctane, bis-(dibromonorbornane dicarboximido)ethane, Diels-Alder adducts of hexachlorocyclopentadiene and cyclooctadiene and mixtures thereof.

14. A mixture, as claimed in claim 12, wherein the bicyclic phosphate compound is 2,6,7-trioxa-phosphobicyclo [2.2.2]-octane-4-methanol-1-oxide; or 2,6,7-trioxa-1-phosphobicylo[2.2.2]-octane-4-methanol, acetate, 1-oxide.

15. A mixture, as claimed in claim 12, wherein the weight ratio of bicyclic phosphate compound to halogen-containing flame retardant lies in the range of about 0.001 to 0.200.