PARTⅤ SOLVOLYSISPREPARATION OF RECYCLED PLASTICS FROMDEPOLYMERISED MATERIALS OF WASTE FRPS
Yugo Akinari,*1 Kazuo Yamada,1 Takeru Watanabe1, Fumiaki Tomonaga,2 Akio
Kamimura*,1
1Department Applied Molecular Bioscience, Graduate School of Medicine, Yamaguchi
University, Ube 755-8611 Japan.
2Yamaguchi Prefectural Industrial Technology Institute, Ube 755-0195, Japan.
E-mail: ak10@yamaguchi-u.ac.jp

The preparation of recycled plastic from the depolymerized materials is the final stage
for the chemical recycled process.[1] Recently, we have developed an efficient method todepolymerize waste fiber-reinforced plastics,[2] one of the formidable plastic to treat inchemical recycling scheme, by treatment with supercritical MeOH.[3] For this process,addition of catalytic amounts of DMAP, N,N-dimethylaminopyridine,[4] was essential for thecomplete break down of FRP. The monomeric material made by this way, however, failed forthe formation of recycled polymers due to the contamination of impurities derived from thedecomposition of DMAP. This is a problem to be overcome for establishing efficientchemical recycling of FRP. Removal of the impurities and purification of the recoveredmaterials were achieved by washing treatment with water and the purity of dimethylphthlate,
DMP, was enhanced to more than 90%.[5] Although this was a satisfactory solution of theproblem, the washing treatment was somewhat troublesome in the practical manipulation. As
a result, much simple method for the purification was desired. In this presentation, we report
the following two methodologies for the solution of the problem. One is the method in which
reduced amounts of DMAP was used for the depolymerization process. This method may
enable the rebuilding polymers without further purification. The second method was use ofactivated carbon for the removal of impurities in the recovered monomer. This method would
offer a simple operation for the purification of DMP. We will also present an improved
method for the formation of recycled polymer which was used for the preparation of a test
product.

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We firstly examined depolymerization reaction in the presence of less than 3% of DMAP.
Usually the depolymerization required more than 3% of DMAP for the complete
depolymerization and separation of recovered materials. Treatment of waste FRP in thepresence of 1% or 2% of DMAP resulted in the depolymerization of FRP to give monomericmaterials and insoluble residue. As we expected, the insoluble residue contaminated withpolymeric materials that could not be solved any kind of solvent. So the separation of glass
fibre and linker polymer failed. This was probably because the small amounts of DMAP
decomposed too quickly to progress sufficient transesterification reaction on linker molecules.
Thus, at least 3 % of DMAP should be needed to achieve the efficient separation of linkers
and inorganic contents.
The monomeric material made from 1% of DMAP contained DMP, glycol andN-methyl-4-pyridone,[6] decomposed product of DMAP. GC analysis revealed the content ofDMP was about 60%. The polymerization reaction of the material with adding new DMP invarious ratios was carried out under the standard conditions. Fortunately, the polymerization
took place smoothly in any ratios of new and recovered DMP. Even staring from 100%
recovered materials, recycled polymer was successfully obtained. Some of the recycled
polymers were shown below (Fig. 1).

Fig. 1 Obtained polymers from the monomeric material recovered from the reaction in thepresence of 1% of DMAP. From left, 20%, 40%, and 60% of recovered monomer was used
We then examined hardness tests for the polymers. Fig. 2 shows the HDD hardness test.
As shown in Fig. 2, the hardness of the polymer was unchanged in high level when the ratioof recovered material was less than 60%. As the ratio of recovered monomers exceeded morethan 60%, HDD values were slightly lowered, but still maintained sufficient hardness. Thus,
the present monomeric material was useful for the formation of recycled polymers.
We next examined to use activated carbon for the purification of the recovered monomer.
For these experiments, we used monoeric material made from the decomposition reaction inthe presence of 2% of DMAP. The original content of DMP was estimated to be 25% with
GC analysis. The recovered monomer was dissolved in various solvent and activated carbon
was added. Then the mixture was heated at refluxing temperature for 20 h. After cooling, the- 230 -PARTⅤ SOLVOLYSIS
mixture was filtered and the filtrate was concentrated. The contents of DMAP were examinedby GC analyses. The results are summarized in Fig.3.

HDD hardness

100908070HDD605040MaxMin30201000204060
Recovered DMP (%)

80100Fig. 2 HDD hardness tests for the rebuilt polymers
Use of MeOH did not change the purity and almost 100% of original DMP wasrecovered. This is due to strong polarity of MeOH which prevent absorption of impurities onactivated carbon. As the polarity of solvent decreased, the prutity was gradually improved.
For example, treatment in acetone, THF, EtOAc, and DCM resulted in slight improving thepurification of DMP up to 35% and nearly 100% of DMP was recovered. Use of less polar
Et2O and toluene much effectively recovered DMP and improved the purity to about 45%.
The purity increased about 70% when hexane was used as the solvent. In this case DMP
recovery just decreased, but more than 80% of original DMP was recovered through themanipulation. Thus, the purification with activated carbon was effective when non polar
solvent such as hexane was used for the treatment. However, the purity of DMP wasimproved about 70% level. Rebuilding of the polymer with these purified materials is now
investigating.
In the last section we will show an improved formation of recycled plastic. Use of amodified catalyst system for the formation of unsaturated polyester resulted in the preparationof recycled plastic with better quality than before. This material was applied to the synthesisof test products to promote chemical recycling of FRP in practice.
In conclusion, recovered monomers were useful directly for the re-polymerization
reaction to give recycled plastics although the depolymerization of FRP with reduced amountsof DMAP resulted in the incomplete decomposition of FRP. Treatment with activated carbon
provided a convenient method to purify the monomeric materials and it purity was improved
uo tp 70%.

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DMP contents after the treatment (wt%)
Recovery of DMP (wt%)

100

purity/recovery of DMP

9080
70
60
50
40
30
20
100hexane

toluene

Et2O

DCM

THF

EtOAc

acetone

MeOH

Solvent

Fig. 3 Purification/recovery of DMP on treatment with activated carbon.
References[1] Technology for Feedstock Recycling of Plastic Wastes, Research Association ofFeedstock Recycling of Plastics, 2005.
[2] S. Kubota, H. Mori, T. Maeda. Nettowaku Porymer 2003, 24, 22.
[3] A. Kamimura, Y. Yamada, T. Kuratani, Y. Oishi, T. Watanabe, T. Yoshida, F. Tomonaga.
ChemSusChem 2008, 1, 845-850.
[4] A. C. Spivey, S. Arseniyadis, Angew. Chem. Int. Ed. 2004, 43, 5436.
[5] A. Kamimura, E. Konno, S. Yamamoto, T. Watanabe, K. Yamada, F. Tomonaga. J. Mater.
Cycles Waste Manag. 2009, 10, 38-41.
[6] P. Guerry, R. Neier. Synthesis, 1984, 485-488.

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