Simultaneous Recovery of Organic and Inorganic Materials by the Thermal
Decomposition of Plastic-Metal Composites
S. Kumagai 1,2, G. Grause1, T. Kameda1 and T. Yoshioka1,*
1 Graduate School of Environmental Studies, Tohoku University, 6-6-07 Aoba, Aramaki-aza, Aoba-ku, Sendai, Miyagi 980-8579, Japan

2 Japan Society for the Promotion of Science, 8 Ichibancho, Chiyoda-ku, Tokyo 102-8472, Japan

E-mail:yoshioka@env.che.tohoku.ac.jp; Phone & Fax:+81-22-795-7212

Abstract

In this investigation, we examined the possibility of the simultaneous recovery of oil and metal from metal containing
plastic composites. X-ray film, video tape, and prepaid cards based on poly(ethylene terephthalate) (PET) werehydrolyzed at 450 °C in steam atmosphere, resulting in volatile terephthalic acid (TPA). Metals were recovered together
with carbonaceous residue at an average yield of more than 90% of the initial content. In a second step, TPA wasdecarboxylized in the presence of calcium oxide (CaO) at 700 °C, producing benzene with an average yield of 34%. Also,
paper laminated printed-circuit boards (PCB) based on phenol and epoxy resin were decomposed in the presence andabsence of calcium hydroxide (Ca(OH)2) in a tube reactor, recovering both organic and inorganic products. As a result, oilwith an average yield of 7 wt%, consisting of phenol and phenol derivatives, was obtained.
Keywords: PET, printed circuit board, pyrolysis, hydrolysis, calcium oxide

1. Introduction

Plastic-metal composites are widely used in our daily life.
Poly(ethylene terephthalate) (PET), phenol resin, andepoxy resin are often used in electric and electronicequipment. Metals incorporated in the organic matrix are
silver, iron, indium, chrome, tin, copper, gold, antimony,etc. These metals are often of economic interest.
However, for the sake of the environment, the organic
matrix should be considered as a resource, as well.
One of the recycling methods for plastic-metal composite
is pyrolysis, which can convert plastics into organic
feedstock and simultaneously remove metals.
We reported earlier [1] that PET could be thermallydecomposed in the presence of calcium oxide (CaO),
resulting in oil with a high benzene content. In this work,
the reported benzene production process was applied toPET based X-ray film, video tape, and prepaid cards.
Additionally, paper laminated printed circuit boards (PCB)based on phenol and epoxy resin was pyrolyzed. The
possibility of the simultaneous recovery of organic
materials and metals from plastic-metal composites wasinvestigated[1]. In order to recover metals after degradation, samples
were filled into a perforated quarts holder. Samples werehydrolyzed at 450 °C in steam atmosphere. The resulting
TPA was decarboxylated by CaO at 700 °C.
PCB was pyrolyzed in the presence and absence ofCa(OH)2 in a horizontal tube reactor at 700 °C.
Liquids and gaseous products were analyzed by GC-MS,FID, and TCD. Metals were investigated by XRD andICP-AES. The Br content was quantified by IC and GCECD. Organic products were normalized on the basis of
the initial polymer weight (100 wt%).

3. Results and Discussion

3.1 PET Materials Degradation
The PET materials were hydrolyzed in the presence andabsence of CaO (Fig. 1). Sublimating substances werevisibly deposited at the reactor wall in the absence ofCaO. In addition, oxygen containing compounds such asacetophenone derived from the thermal decomposition of
PET [2] were observed. Benzene production wascomparable small.
Table 1. Elemental composition of the samples.

2. Materials and Methods

2.1 Materials
Cut PET bottles, X-ray film, video tape, and prepaid
cards (2.8 mm × 2.8 mm), and crushed paper laminated
PCB based on phenol and epoxy resin (0.3~1.0 mm)
were used (Table 1). CaO and calcium hydroxide(Ca(OH) 2) were used as catalyst.
2.2 Experiments and Analytical Methods
PET materials were decomposed in the presence andabsence of CaO using a two-step tube reactor with two
separated zones, one for the hydrolysis of PET and theother for the decarboxylation of terephthalic acid (TPA)CH
N
Br
PAgFeTi
AlCu
SbBottle

Film

Tape

Card

61.9
4.3
-

61.5
4.4
0.4
0.5
0.4
-

50.1
3.7
0.4
13.1
-

49.2
3.6
0.4

7.9
7.3
0.4

PCB(Phenol)
51.5
5.7
1.5
3.8
0.4
1.8
-

7th International Symposium on Feedstock Recycling of Polymeric Materials (7th ISFR 2013)
New Delhi, India, 23-26 October 2013

PCB(Epoxy)
55.9
6.4
4.0
7.7
0.5
2.00.6

In contrast, benzene yields increased drastically in thepresence of CaO, resulting in an average yield of 34%.
However, less benzene was obtained than reported
earlier (benzene yield: 74%, purity: 96%) [1] because of
the inefficient hydrolysis of PET in the sample holder.
TPA and other oxygen containing compounds were notobserved. Hence, these compounds were decomposedin the presence of CaO.
25( ):Benzene yield/%
21.8

21.1

22.8

21.7

13.6
(33.4)

15

14.4(35.4)

13.0(31.9)

14.0(34.5)

Ag
Film

105
00.3(0.8)

0.6(1.5)

BottleBottle12/CaO

Film
30.4(0.9)
Film
4/CaO

Tape
50.1(0.3)
Tape
6/CaO

Card
7

Card8/CaO

BenzeneOther hydrocarbons
Oxygen-containing compounds
Sublimating substances (terephthalic acid+benzoic acid)

Fig. 1. Weight fraction of liquid products and sublimating
substances obtained from PET hydrolysis in thepresence and absence of CaO.
3.2 PCB Materials Degradation
The PCB materials were pyrolyzed in the presence andabsence of Ca(OH)2, resulting in an average of 7 wt% ofliquid products (Fig. 2). The liquid products consisted
mainly of phenol and derivatives. Brominated organiccompounds and phosphor-based flame retardants weredrastically decreased in the presence of Ca(OH)2, sincebromine and phosphorus could be fixed by Ca(OH)2.
Because of the degradation of brominated organiccompounds and phosphor-based flame retardants, yieldsof phenol and phenol derivatives, especially phenol andcresol, increased in the presence of Ca(OH)2. The
bromine content in the oil was reduced by 95% by adding
Ca(OH)2.

100

Oil yield/wt%
7.3
6.4

5.7

8.5

Weight fraction/wt%

8060
71.5

51.6

50.6

PhenolPhenol Epoxy Epoxy/Ca(OH)2/Ca(OH)2200

Phenol and derivatives

γ-Fe2O3

TiO2 (anatase)

Cu

Tape

Card
PCB (phenol)0

10 20 30 40 50 60
2θ/degree (CuKα)

70 80 90

Fig.3 XRD patterns of metal containing carbonaceous
residue after sample degradation.

4. Conclusion

Simultaneous recovery of benzene and metals from PETmetal composites was achieved, resulting in an averagebenzene yield of 34%. Calcium oxide was an efficient
catalyst for the recovery of benzene. In contrast, little oil
was recovered from PCB (maximum oil yield: 8.5 wt%) in
the presence of Ca(OH)2. Although Ca(OH) 2 increased
the oil production only to a small extent, the bromine
content in the oil decreased significantly in the presenceof Ca(OH)2. Furthermore, metals were recovered bymore than 90% in average compared with the initial
content and incorporated within the carbonaceous
residue. After enhancing the oil yield, this method can beapplied to plastic-metal composites which cannot berecycled effectively otherwise.

5. Acknowledgment

76.3

40

Intensity/arb.unit

Weight fraction/wt%

20

3.3 Metal Recovery
The metal containing carbonaceous residue wasqualitatively analyzed by XRD (Fig. 3). According to ICP
analysis, an average yield of over 90% of the initial metal
content was recovered from PET samples. More than
80% of copper was recovered from PCB. The
composition and crystal structure of the recovered metals
did not change after the degradation. However, antimony
yielded 22% and 65% in the absence and presence ofCa(OH)2, respectively, because of the formation ofvolatile antimony bromide (SbBr3, b.p. 280 °C). Moreantimony was recovered in the presence of Ca(OH)2,
since bromine was fixed by Ca(OH)2, suppressing thebromination of antimony.

Other organic compounds

Phosphated flame retardants

Brominated organic compounds

Fig. 2. Weight fraction of liquid products obtained from
PCB materials in the presence and absence of Ca(OH)2.

This work was partially supported by the Ministry ofEducation, Culture, Sports, Science and Technology(MEXT), Grant-in-Aid for Scientific Research (A),
21241018, and by the Japan Society for the Promotion ofScience (JSPS), Grant-in-Aid for JSPS Fellows, 24-4996.

6. References[1] G. Grause, T. Handa, T. Kameda, T. Mizoguchi andT. Yoshioka. Chem. Eng. J., 166 (2011), 523-528.
[2] M. E. Bednas, M. Day, K. Ho, R. Sander and D. M.
Wiles. J. Anal. Appl. Pyrol., 26 (19811111), 277-289.

7th International Symposium on Feedstock Recycling of Polymeric Materials (7th ISFR 2013)
New Delhi, India, 23-26 October 2013