5-7 OCTOBER

ISFR

2011

137

TOLEDO (SPAIN)RECOVERY OF USEFUL RESOURCES FROM WEEE BY USING RECYCLABLESOLVENT
T.Kamo1, H.Ito2, Zou, Zhuoyi2, M.Adachi2, T.Imai3, H.Matsui3, and H.Nakagome2
1 National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba 305-8569, Japan
2 Chiba University, Faculty of Engineering, 1-33 Yayoi-cho, Inage-ku Chiba-shi 263-8522, Japan
3 Toshiba, 1-1-1 Shibaura, Minato-ku, Tokyo 105-8001, Japane-mail:tohru-kamo@aist.go.jp

Abstract
Development of technology for recovering useful materials from waste of electric and electronic equipments (WEEE) is very
important for securing long stable supply of indispensable resources to high technology industries. Fiber reinforced epoxyboard was decomposed at 600 - 900 ˚C for 60 min to produce solvent for liquefaction of the circuit board. Yield of the liquid
product was higher than 75% at these temperatures. Many kinds of cresol derivatives were observed in the liquid product.
Tar solvent was prepared from the liquid product by removing light fraction. Epoxy board was liquefied almost completely inthe tar solvent at 250 °C for 120 min under atmospheric pressure. Finally, relatively much amount liquid product wasrecovered from thermal decomposition of the once liquefied epoxy board at 600 - 900°C. These experimental results indicatethat the liquid product can be used as a solvent repeatedly.

Keywords: WEEE, E-waste, Recycle, thermosetting resin, Metal recovery

1. Introduction
Precious metal and rare-earth elements areindispensable resources to high technology industries.
Long stable supply of these resources is serious concern,
because remarkable expansion of demand for them isexpected by spread of IT devices. The waste of electricand electronic equipments (WEEE) is valuable domestic
resources for Japan, and recovery technology of these
metals from WEEE is very important.
Printed circuit board cannot be decomposed byconventional pyrolysis, because thermosetting resin suchas epoxy resin or phenol resin have three dimensional
network structure. Liquefaction of printed circuit board insupercritical solvents or in specific solvents [1], [2] havebeen proposed. However, commercial viability of themwas difficult due to using an expensive high pressure
vessel or organic solvent. Recently we showed thatepoxy circuit board can be dissolved in biomass derived
tar solvent at 250 - 300 ˚C under atmospheric pressure,and copper or glass fiber could be recovered easily(Fig.1) [3]. Cresol derivatives that were derived fromdegradation of lignin contained in biomass were effective
to liquefaction of epoxy board. Liquid product derived

from thermal decomposition of epoxy board is expected
to contain a lot of cresol derivatives, as well as biomass
derived liquid product.
In this work, epoxy board was dissolved in liquid productderived from epoxy board in the first step, and the onceliquefied epoxy board was decomposed to recoverrecyclable solvent in the next step.

2. Materials and Methods
Experimental procedure was shown in Fig.2. Glass fiber
reinforced epoxy board (Hitachi Chemical Co. Ltd.) wascharged in a fused quartz reactor (D=30 mm, L=300 mm)
and the sample was decomposed at 600 - 900 ˚C for 60min. Distillate liquid product was collected into a iced
flask through a glass tube. Gaseous product wascollected in an aluminium laminated gas bag, and it wasanalyzed by an automatic GC (GL Sciences).
Liquefaction of epoxy board was carried out at 250 ˚C for
120 min with addition of trace amount of sulfuric acid in
the tar solvent which was prepared from the liquid
product by removing light fraction. In the most ofexperiments, the liquefied epoxy baord was heated up
again, and was decomposed at 600 – 900 ˚C for 60 min.
In some experiments, the liquefied epoxy sample wasextracted by tetrahydrofuran for at least 10 hours.
Liquefaction rate was calculated by using equation (1).
Liquefaction rate(%) = 100 - (c-b)/(a-b)X100 (1)a : weight of epoxy board
b : weight of glass fiber in the sample
c : weight of carbon residue

Fig.1 Liquefied circuit board in biomass derived tar solvent.

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6th International Symposium on Feedstock Recycling of Polymeric Materials

was decomposed independently, yield of liquid or residue
is expected to be on the calculated dashed straight lines,
respectively. However, yield of liquid product decreased
with increasing of initial weight ratio of epoxy board, andmuch more residue was produced from thermal
decomposition of the once liquefied epoxy board.
When weight ratio of epoxy board in tar solvent was lessthan 10%, relatively much amount solvent was recoveredfrom thermal decomposition of the once liquefied epoxy
board, even if residue was produced by condensation.
We expect that liquid product formed from the onceliquefied epoxy circuit board can be used as solvent
repeatedly and shortage of solvent is replenished byliquid product derived from biomass.
Fig. 2. Experimental procedure

3. Results and Discussion
Product distribution of thermal decomposition of epoxy
board at 600 – 900 °C was shown in Fig.3. Yields ofproduct were calculated from weight of only epoxy resin
excluding glass fiber. Yields of gas, liquid, solid products
were 6.5%, 75.1%, and 20.6% at 600 °C, respectively.
Liquid yield increased with temperature slightly, itindicates that residue was converted to liquid product at
higher temperature. A lot of cresol derivatives such asalkyl phenol were observed in the liquid product.

Fig. 4. Distributions of products derived from thermal
decomposition of the liquefied epoxy board. (700 °C)

4. Conclusions

Fig.3. Distribution of products from thermal
decomposition of epoxy board.
Epoxy board was dissolved almost completely at 250 °C
for 120 min in the tar solvent which was prepared fromliquefaction product of thermal decomposition of theepoxy board itself by removing light fraction. Particularly,
tar solvent prepared at high temperature was effective,
even if epoxy board was added more than 20% of the tarsolvent weight, the epoxy board was dissolved almost
completely.
Distributions of products derived from thermal
decomposition at 700 °C of the once liquefied epoxy
board were shown in Fig.4. If tar solvent or epoxy board

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Many kinds of cresol derivatives were observed in theliquid product derived from thermal decomposition ofepoxy board. Epoxy board was liquefied almost
completely in the tar solvent that was derived fromthermal decomposition of epoxy board. Relatively muchamount liquid product was recovered from the onceliquefied epoxy circuit board. The liquid product can beused as recyclable solvent repeatedly.

References[1] Y.Sato, Y.Kodera, and T.Kamo, Energy & Fuels, 13,364(1999).
[2] K.Maekawa, K.Shibata, M.Iwai, A.Endo, Hitachi Chem.
Technic. Rept.,42(1), 21(2004).
[3] T.Kamo, L.Yufeng, N.Akaishi, M.Adachi, H.Yasuda,and H.Nakagome, Proceeding 5th International
Symposium of Feedstock Recycling, 186(2009).

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