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

LIQUEFACTION OF PRINTED CIRCUIT BOARD
BY USING WASTE BIOMASS DERIVED TAR
Tohru Kamo*1, Liu.Yufeng2, Naoya Akaishi2,
Mariko Adachi2, Hajime Yasuda1, Hideki 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
E-mail: tohru-kamo@aist.go.jp

Abstract: Recovery of the useful materials from end-of-life electronic equipments is very
important not only for reduction of waste materials but also for effective use of limited naturalresources. Recently, we showed that approximately 50 wt% of epoxy board was dissolved intar derived from dry distillation of Japanese cedar at 220 °C under atmospheric pressure.
However, solubilization rate of the waste printed board was insufficient for practicalindustrializing.In this work, more than 70 wt% of Japanese cedar converted into tar by heating
it in some organic solvents at 300 °C. Epoxy printed circuit boards were solubilized almost
completely in the tar at 250-300 °C. Moreover, urethane, FRP, PET, and polycarbonate werealso solubilized. Character of the tar was very sensitive to the temperature of tar formation.
1. Introduction
End-of-life electric devices and automobiles contain a lot of useful materials such as gold,
palladium, and rare metals. Recovering the useful materials from the scrapped industrial
products is very important for reducing wastes and using limited resources effectively. We
have been developing two technologies, gasification in molten carbonates or liquefaction inbiomass derived tar, to recover metals in circuit boards.

waste biomass

circuit board

feedstock(1)
preparation(2)liquefaction(3)
reforming

circulation solvent

noble metals, rare metals

Fig.1 Outline of resources recovery process from the end-of-life electric devices- 186 -PARTⅣ BIOMASS DEGRADATION
Thermosetting resins such as epoxy resin used in the electric circuit boards is notliquefied by conventional pyrolysis. Recently, we showed approximately 50 % of epoxy
board was liquefied at 220 °C under atmospheric pressure in a tar which was produced fromJapanese cedar by dry distillation [1]. In order to increase the solbilzation rate of the epoxy
boards and to produce the tar from Japanese cedar efficiently, we are developing a newprocess in which a part of the liquefied product is used as a circulation solvent. This process
consists of three steps as shown in Fig.1, (1) preparation of the tar from waste biomass incirculation solvent, (2) liquefaction of the circuit boards in the tar, and (3) reforming of theliquefied product into the circulation solvent.
In this work, liquefaction of some plastics was carried out in the tar derived fromJapanese cedar, and benzyl alcohol was used as an alternative of the circulation solvent.
2. Experiment
Preparation of tar was carried out in an autoclave (200 ml) at 200- 350 ˚C for 120
minutes under an initial nitrogen pressure of 2.0 MPa. In the most of experiments, Japanesecedar powder (10 g, 100 mesh), benzyl alcohol (40 g), and sodium hydroxide (0.4 g) werecharged into the autoclave. In some experiments, cresols or sulfuric acid was used as solventor additives, respectively. The autoclave was heated up to the desired reaction temperature
within 20 minutes and quenched by blowing air after completion of the reaction. Gaseous
products were collected in a gas bag, and were analyzed with an automatic gas chromatograph(GL-Science, GC-312). Products were separated into liquid product and tar respectively byvacuum fractionation at 140˚C for 60 minutes. The liquid products were analyzed by gas
chromatography (Shimadzu, GC17A) with a capillary column (HP-5, 0.32 mm, 30 m).
Compounds in the liquid products were identified by GC-MS (Agilent Technology, HP-5973).
The molecular weight of tar was measured by gel permutation chromatography (Tosoh,SC08020) with a gel column (TSK gel Super HM-M).
Liquefaction of the epoxy board was carried out in a glass flask (300 ml) connected to awater cooling reflux condenser at 200 – 350 ˚C for 120 minutes under atmospheric pressure.
Epoxy sample pieces (5 mm square, 1 g) and the tar (10 g) were charged into the glass flask.
Products were washed with tetrahydrofuran, filtrated by a stainless steel net, and dried at110˚C for 12 hours under vacuum. Solubilization rate of the epoxy board was derived from anequation (1) shown below.
Solubilization rate (%) = 100 - (c-b)/(a-b) X 100(1)
a:weight of glass fiber composite epoxy board,
b:weight of glass fiber in the epoxy board
c:weight of solid residue- 187 -The 5th ISFR (October 11-14, 2009, Chengdu, China)
3. Results and discussion
Distributions of products derived from reaction of Japanese cedar powder (10 g) withsodium hydroxide (0.4 g) in benzyl alcohol (40 g) are shown in Fig. 2. The tar shown in thefigure indicates unreacted Japan cedar or a heavy product which was not distilled undervacuum at 140 ˚C. On the reaction of Japanese cedar in benzyl alcohol at 250 ˚C, the Japanesecedar powder changed to dark-brown particles, and its weight decreased to 14.6% bydecarbonation or dehydration. Benzyl alcohol was almost stable at 250 ˚C, becausebenzaldehyde was not detected in recovered solvent. Yield of the benzaldehyde increased
with temperature at 250-325 ˚C, and benzyl alcohol converted into toluene and benzene
dominantly at more than 350 ˚C. We estimated that Japanese cedar have some effects toaccelerate decomposition of benzyl alcohol, because aromatic compounds, such as
benzaldehyde or toluene shown in Fig.3, were not detected even if only benzyl alcohol washeated at 350˚C. Weight of the tar exceeded initial weight of the Japanese cedar powder atmore than 300˚C. From this experimental result, we estimate that a part of the solvent was
taken into tar at high temperature.
100Yield（%）

8060
dleiY
40
200feed

250℃ 275℃ 300℃ 325℃ 350℃ 375℃
Temerature （℃）
Temperature(℃)

Janaese cedar
dibenzyltar
benzaldehyde

benzyl alcohol
toluenedibenzyl ether
benzeneother liquidethylene

carbon dioxidemethanecarbon monoxidehydrogenethane
othersFig.2 Distribution of products derived from reaction between
Japanese cedar and benzyl alcohol.
OHO
CHO

Fig.3 Main products derived from thermal decomposition of benzyl alcohol.
The elemental analyses data of the tar, Japanese cedar, and benzylalcohol are shown inFig. 4. Two molar ratios of the tar, H/C and O/C, decreased with an increase in temperature of- 188 -PARTⅣ BIOMASS DEGRADATION
preparation, respectively. The solid lines are indicating theoretical elemental composition ofthe products which are formed from the Japanese cedar by dehydration, decarbonation,dehydrogenation, dealkalylation, and solvent addition. The elemental compositions of the tar
derived from these reactions are expected to lie on the lines respectively. We estimate that
two reactions, decarbonation and dehydration, occurred mainly in a reaction of the Japanesecedar and benzyl alcohol at 250˚C, because transfer of the solvent to the tar was not observed.
On the other hand, we estimate not only decarbonation or dehydration, but also solventaddition occurred, because weight increase of the tar derived from the Japanese cedar reaction
was observed at more than 250˚C.
2.0
decarbonation
solvent addition

1.5

H/C

dealkylation

CH/ 1.0
1.0

250℃
300℃
dehydration
350℃

0.5

dehydrogenation

0.0

0.0

0.2

0.4

Japanese cedarwith NaOH

0.6
O/C

0.8

1.0

benzyl alcohl
without NaOH

Fig. 4 Elemental analyses data of Japanese cedar, tar, and benzyl alcohol
Solvent extraction of the tar derived from Japanese cedar was carried out using methanolor tetrahydrofuran (THF). Fraction distributions of the tar prepared at various temperaturesare shown in Fig. 5. The Japanese cedar powder was hardly extracted by methanol or THF.
THF-insoluble fraction decreased and methanol-soluble fraction increased at high preparation
temperature. The increase of THF-insoluble fraction at 375˚C implies that condensation
reaction of the tar was promoted at high preparation temperature.

Product distribution(%)

100
j80in 60
iotubirt 40
sidtcu 20dor
P0Japanese
cedar
Methanol soluble

250℃

300℃

325℃

Methanol insoluble-THF soluble

375℃
THF insoluble

Fig.5 Fraction distributions of the tar prepared at various temperatures- 189 -The 5th ISFR (October 11-14, 2009, Chengdu, China)
Hydrogen contained in tar was classified as shown following by the chemical shift valuethat was measured by 1H-NMR, a-hydrogen (2.0-4.2 ppm), b-hydrogen (2.0-1.0 ppm),
g-hydrogen (0.5-1.0 ppm), and aromatic hydrogen (6.5- ppm), (Fig.6). Comparatively muchb-hydrogen and g-hydrogen were contained in the tar prepared at 250 ˚C. However, at a highpreparation temperature, the percentage of b-hydrogen or g-hydrogen decreased and that ofaromatic hydrogen increased. These analysis results suggest that comparatively muchalkylchains exist in the tar prepared at low temperature, however, decomposition ofalkylchain and condensation of aromatic compounds are accelerated at high temperature.

Hydrogen distribution(%)8080)6060%(noituib
rt4040s
idnegor2020dy
H00
250

300
350
Temperature（℃）
a-hydrogenß-hydrogen

400?-hydrogenaromatic hydrogenγFig.6 Distributions of hydrogen contained in tar classified by 1H-NMR

Solubilization rates of the epoxy board which was liquefied at 300˚C for 120 minutes inthe tar derived from Japanese cedar are shown in Fig.7. The epoxy board was liquefied nearlycompletely in the tar prepared at 300 ˚C (Fig. 8), but it was not liquefied in the tar prepared at250˚C. At higher temperature, the solubilization rate of the epoxy board decreased with anincrease in temperature drastically. These experimental results show that the liquefaction rateof an epoxy board is very sensitive to the preparation temperature of tar, and it is very
important to investigate the relationship between the chemical structure of the tar and aliquefaction reaction mechanism.

- 190 -PARTⅣ BIOMASS DEGRADATION
100Solubilization rate(%)

ji80etra 60
niotazlii 40
bulo
S
20

0250

300
350
Temperature (℃)

400Fig. 7 Effect of tar preparation temperature for solubilization rate of epoxy board

Fig.8 Recovered glass fiber from epoxy board by using tar prepared at 300˚C

The solubilization rate of FRP (glass fiber reinforced unsaturated polyester), urethaneresin, PET (polyethylene terephthalate), and polycarbonate were shown in Fig.9. Theseliquefactions were carried out at 250˚C or 300˚C for 120 minutes in the tar prepared at 300˚C.
These plastics which have used widely in electric devices were liquefied almost completely at250˚C or 300˚C in the tar derived from Japanese cedar. Our experimental results suggest thatliquefaction of the plastics used in electric devices is an effective method to recover useful
resources from end-of-life industrial products.

- 191 -

The 5th ISFR (October 11-14, 2009, Chengdu, China)
100
100
300℃ 250℃

Solubilization rate(%)

8080)

%60
i60
ert
ra40
n40oitaziil20b20oS00
Epoxy

FRP

UrethanPET Polycarbonate

Fig. 9 Solbilization rate of various plastics on the liquefactionin the tar derived from Japanese cedar
4. Conclusion
Liquefaction of epoxy resin board was carried out to recover useful resources fromend-of-life electric equipments. The epoxy board was liquefied almost completely at
250-300°C under atmospheric pressure in the tar derived from Japanese cedar. Yields of thetar, which was derived from a reaction of Japanese cedar and benzyl alcohol, were muchlarger than that of conventional dry distillation. Preparation temperature of the tar is very
important to increase the solubilization rate of the epoxy board. By using the tar derived froma reaction of Japanese cedar and benzylalcohol, many kind of plastics, epoxy board, urethane,FRP, PET, and polycarbonate, were liquefied almost completely.
References[1] T. Kamo, N. Akaishi, B. L. Wu, M. Adachi, H. Yasuda, H. Nakagome, Proceeding of the4th International Symposium on Feedstock Recycling of Plastics. 2007,159.

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