The 5th ISFR (October 11-14, 2009, Chengdu, China)

STUDY ON THE RECYCLING TECHNOLOGY
OF A SYNTHETIC POLYMER
Shin Suzuki*1, Mariko Adachi1, Zar Zar Hlaing1, Masanori Ota1,
Hideki Nakagome1, Kuniyuki Kawabata2 and Shigehisa Uchiyama3
1

Graduate School of Engineering, Chiba University, Chiba 263-8522, Japan.
E-mail: shin-suzuki@graduate.chiba-u.jp
2
Altis Co. Ltd, Tokyo106-0041, Japan.
3
Department of Environmental Health, National Institute of Public Health,Wako 351-0197, Japan
Abstract: The pyrolysis of waste polycarbonate resin using various solvents was studied. In
the simple pyrolysis of resin of waste polycarbonate, the liquid product yield was 62wt%.
However, in the pyrolysis using sodium hydroxide as a catalyst and propylene glycol as asolvent, the liquid product yield was 82wt%. Furthermore, in the pyrolysis using p-cresol andpropylene glycol as solvents, the liquid product yield was 82wt% and was obtained in thelower temperature zone.

1. Introduction
Polycarbonate resin (PC) is an industrial plastic characteristic for its mechanicalcharacteristics, weatherability and transparency and approximately 2,200,000t is used per year
in the world [1]. Although it is thermoplastic resin, it is hard to decompose in a simple
pyrolysis since it has carbonic ester combination in the main chain. It is difficult to recycle itsince it generates many residual substances. Reinforcement materials and additives are mixedin according to purposes, recycling is difficult and it usually ends up in reclamation orincineration disposal.
With reference to researches to disassemble PC, studies to convert PC into monomers areunder progress [1,2]. However, it there are problems of safety and cost performance since it
requires high pressure and solvent in large quantities. This research aims to establish arecycling method by pyrolysis oil recovery under mild conditions from PC waste. Since PC
has a nature to swell or dissolve in aromatic hydrocarbon, ester and ketone, decomposition byadding aromatic hydrocarbon, cresol contained in the wood tar which is reported to beeffective in solubilization of the epoxy resin, whose structure of the organic solvent is similar,
was considered [3].

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2. Experiment
The sample is the waste of PC (SPC) 30% combined with reinforced glass filler which isactually in use. The experimental flow is shown in Fig.1. First, a reactor was filled with thesample and was heated in an electric tubular furnace after nitrogen substitution. Temperature
was conditioned to hold the heating rate of 5 °C/min and the outside temperature of thereactor was increased up to 500 °C and was maintained for 10 minutes. The gas emitted byheating was cooled in the cooling tube. The liquid product was accumulated in the separating
funnel, and a gasbag collected the gas product. Then the liquid product and gas product wereanalyzed using GC and GC/MS. The weight of the residue and liquid product was deductedfrom the weight of the sample, and it was considered as gas and other yields. The following
experiment was conducted using 50g of sample, 50g of solvent, 0.2g of sodium hydroxide(NaOH). Also, mixed solvents were made using 25g of solvents respectively.
A pyrolysis experiment was conducted to check each solvent independently and theproduct yield rate of SPC was estimated from the product yield rate. Further, glass filler
30wt% was considered as residue, and the pyrolysis product yield rate of the PC among SPC
which was the object of oilification.

Fig.1 Experimental flow
3. Result and discussion
3.1 Pyrolysis using various solvents
The product yield of pyrolysis using various solvents is shown in Fig.2. Ethylene glycol(EG) had the highest liquid product yield and the low residual substance yield. They wereapprox. 74 wt% and approx. 8 wt% respectively. Next, the amount of accumulated recoveryof the liquid product in accordance with the temperature change is shown in Fig.3. P-cresol(p-Cre) had the lowest temperature of 280°C when its accumulated liquid product amounted- 69 -

The 5th ISFR (October 11-14, 2009, Chengdu, China)
to 50g. Benzyl alcohol and Ethylene glycol had the amount of recovery increased at thetemperature range of 350 to 400°C.
This result suggests that [guaiacol, p-cresol and xylenol] which are contained in wood tar,and [benzyl alcohol and ethylene glycol] have different decomposition mechanisms. The
former relates to the low temperature of PC pyrolysis temperature region of SPC, and thelatter has an influence over promotion of decomposition.
In the following paragraph, another experiment is described using glycol series assolvents because the solvent that most influenced the product yield was ethylene glycol. The
aim is to clarify the decomposition mechanism. Also, p-cresol and the glycol series solventthat lowered the temperature of the pyrolysis temperature range of PC part were mixed andpyrolysis was performed.
80
Amount of oil sum [g]7060

Guaiacol50

p-Cresol

40
Xylenol

30

Benzyl Alcohol

20Ethylene Glycol

100150200250300 350 400 450temperature [℃]500550600

Fig.2 The product yield of pyrolysis using various
3.2 Pyrolysis using a glycol series solvent and a mixed solvent
OilGas diffResidue

Yield of products [wt%]1009080706050(none)
SPC

Guaiacol p-Cresol Xylenol

Benzylalcohol

EthyleneglycolFig.3 The amount of accumulation recoveries of the liquid productof pyrolysis using various solvents- 70 -PARTⅠ PYROLYSISThe product yield of pyrolysis using a glycol series solvent and a mixed solvent is shownin Fig.4. Similar to ethylene glycol, diethylene glycol and propylene glycol (PG), comparedwith other solvents, had the effect f increasing the liquid product yield and reducing theresidual substance yield. The mixed solvents increased the liquid product yield and decreased
the residual substance yield compared with the solvent of a simple substance. Next, theaccumulation recovery rate of the liquid product in a temperature change is shown in Fig.5.
Although Ethylene glycol and diethylene glycol have the different the boiling points, they
were similar in the recovery of liquid product. Also in a mixed solvent, there was an effect tolower the temperature of the pyrolysis temperature region of PC part of p-cresol.
80

Amount of oil sum [g]7060p-Cresol50

Ethylene Glycol

40Diethylene glycol30

Propylene glycol

20EG+p-Cre

10PG+p-Cre

0150

200

250300 350 400 450
temperature [℃]500550600Fig.4 The product yield of pyrolysis using a glycol series solvent and mixed solvents
This result suggests that the glycol series solvent as well as EG has an effect ofpromoting the decomposition of PC part. Further, in the mixed solvent, it has the effects of[lowering the temperature of a pyrolysis temperature region] of PC part of p-cresol and[pyrolysis promotion] of PC part of a glycol series solvent. The influence on thedecomposition is considered to be independent even though it is a mixed solvent.
OilGas diffResidue

Yield of products [wt%]

100
90
80
70
60
50
SPC(none)p-Cresol

Ethylene Diethylene Propylene EG+p-Cre PG+p-Cre
glycolglycolglycolFig.5 Amount of accumulated recovery of pyrolysis using glycol
series solvent and mixed solvents- 71 -The 5th ISFR (October 11-14, 2009, Chengdu, China)
4. Conclusion
In this research, pyrolysis was performed using various solvents. Glycol series solvents
has an effect of promoting the decomposition of PC and solvents such as p-cresol which iscontained in wood tar had an effect of lowering the temperature at which PC was decomposed.
Also the mixed solvent had both those effects and also achieved an improvement in a liquid
product yield greater than the glycol series solvent alone.
References[1] Y. Sato, Y. Kondo, K. Tsujita, Noboru Kawai, Polymer Degradation and Stability, 2005,
89, 317-326.
[2] A. Oku, S. Tanaka, S. Hata, Polymer, 2000, 41, 6749-6753.
[3] T. Kamo, N. Akaishi, B. Wu, M. Adachi, H. Yasuda, H. Nakagome, Proceedings of the4th international symposium of feedstockrecycling of plastics & other polymeric materials,
2007, 159-163.

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