Background of the Invention

U.S. Patent No. 5,204,394 to J.C. Gosens et al. advocates the use of arylene-bridged oligomeric polyphosphate esters in the flame retarding of polycarbonate-containing polymer compositions.

An oligomeric phosphate or blend of oligomeric phosphates are disclosed by the Gosens et al. patent as having the formula

0 o

II n

Ri- (0) _ml -P-0- [X-O-P- (0)., ₄ -] _n -R ₄

I I R ₂ R ₃ where R _1; R ₂ , R ₃ , and R _« each represent an aryl or an alkaryl group chosen independently of each other and wherein X is an arylene group, ml, m2, m3, and m4, each independently of each other are 0 or 1 and wherein n=l, 2, 3, 4, or 5 or wherein, in the case of a blend of phosphates, n has an average value between l and 5.

Summary of the Invention

It has now been found that a mixture of an alkylene-bridged diphosphate compound and the foregoing type of arylene-bridged oligomeric polyphosphate ester is an effective flame retardant agent in the aforementioned types of polycarbonate-containing polymer compositions. It has been found that there is increased flame retardancy efficacy and improved processing characteristics for the mixture in such polymers.

Description of Preferred Embodiments

The polycarbonate-containing resins and the arylene-bridge oligomeric phosphate esters to which the present invention i applicable are described in the aforementioned U.S. Patent No. 5,

204,394 which is incorporated herein by reference in regard t such teaching.

The terminology "alkylene-bridged diphosphate compound" a used herein is to be understood to encompass monomeric and lo oligomeric species of the formula

RO 0 0 0 OR

\ II II tl / POR ¹ [OP-OR ^l -] _n -OP

/ I \

RO OR OR

Where R is aryl, such as unsubstituted phenyl, n is a numbe ranging from 0 to about 5, and R ¹ is alkylene of from 1 to carbon atoms.

The present invention contemplates using a mixtur comprising the arylene-bridged phosphate compositions and the alkylene-bridged compounds in a ratio of from about 1:2 to about 2:1 on a weight basis in the polycarbonate-containin compositions. Generally speaking, the amount of such mixtur used in the polycarbonate-containing compositions will vary fro about 1 % to about 25 % on the weight of the polycarbonate- containing composition. The present invention is illustrated by the Examples whic follow.

EXAMPLES 1-5

These Examples set forth cone calorimetric data (35.0 kW/m ² irradiance) on neat PC/ABS, neat resorcinol diphosphate (RDP) and blends of RDP and neopentylglycol diphosphate at various weight amounts.

The polymers composites were preblended to a five to one (PC/ABS) ratio and extruded in a twin screw extruder to a homogeneous blend. The phosphate flame retardant mixtures ("FR" in the Table given below) were preblended in the prescribed ratios before addition to the composites. The incorporation of the flame retardants was accomplished by metering the liquid components into the melt stream of the extruder through a side port injector. All flame retardant composites are formulated to contain a small amount of powdered TEFLON fluoropolymer antidrip agent.

TABLE I

Peak Heat Effective Hea

Release Total Heat of Combus l

FR USEP P (kW/m (KJ (MJ/kσ)

NONE 201 32.12 3.48

RDP (Neat) 0.91 69 17.79 2.04 RDP/NPGDP (2/1) 0.92 62 18.83 2.02 RDP/NPGDP (1/1) 0.71 52 14.66 1.61 RDP/NPGDP (1/2) 0.80 43 16.04 1.85

EXAMPLES 6 - 10

These Examples show the melt flow viscosity data (ASTM-1238, Condition "I", 230°C, 3.8 kg) for the blends tested in each of Examples 1-5, above.

FR Sample (from Ex. 1-5) α/10 minutes

NONE 13.0

RDP (Neat) 16.9

RDP/NPGDP (2/1) 18.8

RDP/NPGDP (1/1) 15.3

RDP/NPGDP (1/2) 17.3

The foregoing data is presented for purposes of illustrating certain embodiments of the present invention and, for that reason, should not be construed in a limiting sense. The scope of protection sought is set forth in the claims which follow.