5-7 OCTOBER

ISFR

2011

57

TOLEDO (SPAIN)PYROLYSIS BEHAVIOR OF ABS WITH BROMINATED FLAME RETARDANTS
F. Takeuchi, K. Omote and K. Kimura
Environmental Technology Lab. Fujitsu Laboratories Ltd. , 10-1 Morinosato-Wakamiya Atsugi, Kanagawa, 243-0197, Japane-mail: takeuchi.fumiyo@jp.fujitsu.com

Abstract
Pyrolysis of acrylonitrile-butadiene-styrene (ABS) resin containing brominated flame retardants was carried out using abatch processing system. The pyrolysis products were classified into four groups; liquid, gas, residue and reddish-yellowprecipitate, which accumulated in the bifurcation area from the reactor to condenser tube. We investigated the bromine
content in liquid, residue and precipitate samples. The effect of pyrolysis temperature on the bromine content in the liquidsample was also evaluated. The majority of the bromine was found to be concentrated in the precipitate. The bromine
content in the liquid sample was around 2~3 %; the maximum at pyrolysis temperature of 400~450 ˚C. Stainless steel meshand glass wool were placed at the upper space of the reactor to promote precipitation of Br-rich compounds on the glass
wool, which would prevent condenser tube blocking. Under this pyrolysis condition, the bromine content in the liquid sample
was found to reduce to about one-half.

Keywords: pyrolysis, acrylonitrile-butadiene-styrene(ABS), brominated flame retardant, bromine content

1. Introduction
Electronic equipment and devices have become
indispensable in our daily life, and enormous amount of
personal computers, printers, displays and mobile
phones are being returned to our recycling centers. The
quantity of the plastics separated from electric equipment
is significantly increasing, and therefore, a well established recycling technology for plastic waste is required.
The pyrolysis of waste plastics into fuel oil is well known
today, and some industrial plants are already in operation.
However, major plastic materials processed in theseplants are found to be polyethylene (PE), poly-propylene(PP) and polystyrene (PS). On the other hand, theplastics used in electric equipment are mainly
acrylonitrile-butadiene-styrene (ABS), polycarbonate(PC),high impact polystyrene (HIPS) and their blends. Also,
they often contain brominated flame retardant materials.
Several lab-scale studies have been reported on thepyrolysis of ABS and HIPS containing brominated flame
retardants (ABS-Br, HIPS-Br) [1-3]. However, there arestill many problems that prevent the pyrolized products
put it into practical use. In this study, we investigated thepyrolysis behavior of ABS-Br resins, aiming to reducebromine content in the pyrolized oil products.

2-2. Pyrolysis system and procedure
Figure 1 shows a schematic diagram of the pyrolysis
system. A separable glass flask (1000 ml) was used as
the reactor, and an electric furnace was used for heating.
The temperature was monitored and controlled using a
digital controller (Chino, DZ3000). Condition 1 was set asgiven in fig.1, and condition 2 was set with stainless steel
mesh and glass wool placed at the upper space of thereactor.
After the sample was set in the flask, the reactor and all
the connecting tubes were purged with nitrogen gas. The
heater temperature was increased to 540 ˚C with heating
rate of 5 ˚C/min. The temperatures of the plastic sample
and released gas were monitored by thermo-couples
placed at the bottom of the flask and bifurcation area. AsGas bag
Water out䊹 N2Condenser

2. Materials and Methods
2-1. Materials
Here, commercially available virgin ABS-Br pellets (VW800 from UMGABS company) were used for pyrolysis.
They contain a brominated flame retardant (< 25 wt%)
and antimony trioxide (5 wt%) as a synergist. The grain
size was 1 x 1.5 x 3 mm3. 300 g of resin pellets wasemployed for each pyrolysis experiment.

interiores libro.indd 57

TC for gas

Water in

Separating
funnelFurnace
TC for sample
TC for heater

Fig 1. Schematic diagram of pyrolysis system

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6th International Symposium on Feedstock Recycling of Polymeric Materials

3. Results and Discussion

Temperature ( 䁸C)

500
400

300
250
200

300

150200

100

100

500

Amount of Oil (g)Heater Temp.
Gas Temp.
Sample Temp.
Amount of oil

0050
100
Heating time (min)Fig.2. Temperature profile of condition 1As Bhaskar et al. already reported [1], reddish-yellow
precipitate, which they called wax residue, appeared at
the bifurcation area from reactor to the condenser tube
around 350 ˚C. And then, this wax completely blocked
the condenser tubes. The bromine content of this precipitate was found to be 52.5 wt%, and it was confirmed thatbromine is mostly condensed in the precipitate. The
treatment of these brominated compounds is an
important issue in the pyrolysis technology of engineering
plastics, if these products are to be put into practical use.
In the present study, in order to promote precipitation ofbrominated compounds in the reactor, stainless steel
mesh and glass wool were placed at the upper space ofthe reactor (condition 2), thus to prevent the condenser
tube blocking. This method brought us impressive results.
There was a drastic reduction in the amount ofprecipitate in the condenser tube of setting condition 2
compared with that of the condition 1. The yields of theliquid product of condition 1 and 2 were 40.6 % and42.2 %, respectively.

interiores libro.indd 58

Condition 1Condition 2

3
2.5
2
1.5
10.5
0350

400
450500Sample Temperature (䁸C)550

Fig.3. Bromine content of the liquid products

The temperature profile of a typical process (condition 1)
was shown in figure 2. When the sample temperature
was around 350 ˚C, the sample started to melt, and thetemperature rising rate became slow. Then, the gas
temperature increased rapidly, and the oil release started.
The liquid production rate was found to be maximum
around 400~450 ˚C.
600

3.5

Br Content䚷(% )pyrolysis starts, the gas temperature begins to increase,and the condensable gaseous product was collected as aliquid product through the cold water condenser into theseparating funnel. Pyrolysis product sampling was doneat 5 min intervals.
2-3. Analytical procedure
The weight of the liquid product was measured, and thenthe yield was calculated for each pyrolysis temperature.
The analysis of the constituents of the liquid products
was carried out by gas chromatography mass
spectroscopy (GC-MS). The bromine contents of all theproducts were measured by combustion ion
chromatography (Combustion-IC).

The bromine contents of the liquid product collected atvarious temperatures were evaluated by Combustion-IC,
and the result is summarized in figure 3. The bromine
content was found to be maximum at the temperature of
400~450 ˚C. This result suggests that keeping away theBr-rich precipitate from the liquid is effective to reducethe bromine content in the collected liquid products.
From the GC-MS data, it was found that the major
constituents of the liquid products were ethyl benzene,
isopropyl benzene, and styrene. A slight amount ofbrominated compounds were also detected, even though
their chemical structures were yet to be identified. This
result suggests that only precipitate separation is notenough to remove bromine completely from the liquidproducts, if the products are to be used as fuel. Some
catalytic reactions through chemical treatments may benecessary in the pyrolysis process for the production ofoil for commercial applications.

4. Conclusions
Pyrolysis of ABS-Br was carried out under twoconditions. In the pyrolysis product, Br-rich precipitate
was confirmed, and keeping it away from the liquid wasfound to be effective to reduce the bromine content in theliquid. However, from the GC-MS analysis of the liquidsamples collected in our experiments with Br elimination
methods, a slight amount of brominated compounds wasdetected in the liquid samples. Therefore, further studies
for complete removal of bromine will be needed.

References[1] T. Bhaskar et al. Studies on thermal degradation ofacrylonitrile-butadiene-styrene copolymer (ABS-Br) containing brominated flame retardant. J. Anal. Appl. Pyrolysis 70 (2003) 369–381.
[2] W. J. Hall and P. T. Williams. Pyrolysis of brominatedfeedstock plastic in a fluidised bed reactor. J. Anal. Appl.
Pyrolysis 77 (2006) 75–82.
[3] Y. Sakata. In: Pyrolysis. Proc. Int. Symposium on
Feedstock and Material Recycling of Polymeric Materials,
pp. 10–14, Chengdu, China, 11-14 October 2009.

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