Effectively Terminal Functionalization of Precise Products
Obtained by Controlled Thermal Degradation of Polypropylenes
D. Sasaki1,*, Y. Yoshihiro1, T. Hoshi2, T. Hagiwara2, T. Sawaguchi2,*
1San-ei Kogyo Corporation, Research and Development Division
2Nihon University, College of Science and Technology,

e-mail: sasaki@misato-net.com; phone:+08-48-955-1632 & fax: +08-48-952-5543

Abstract
Developments of new chemical technologies for recycling of polypropylene wastes are desirable in order to meet thegoals of a society that is based on resource recycling. In order to add values to polypropylene, we tried to synthesize endreactive polymers by controlled thermal degradation of various polypropylenes. In the case of car battery wastes, theaverage number of double bonds per molecule of end-reactive polymer ranged from 1.54 to 1.31. This shows that 59 to
43 mol% of telechelic polymer having double bonds at either end. Thiol-ene reaction of end-reactive polymer and thiolcompounds was a method of quantitatively and effectively terminal functionalization.

Keywords: polypropylene, controlled thermal degradation, end-reactive polymer, telechelic polymer, thiol-ene reaction.

1. IntroductionPlastic wastes are the environmental subject of highly
developed societies. Mechanical recycling is the mostdesirable usage of plastic wastes. However, it has limits ofdecreasing quality after several cycles. Whereasliquefaction and gasification of polyolefins intohydrocarbons by pyrolysis with catalyst have been studied
actively for many years, economical problems remain to besolved in their practical use. The development of newprocesses which change these plastic wastes to valuable
chemical products is highly desirable.
Polypropylene is an environmental-friendly material
because of its high recyclability. In addition, polypropylene
is a broad class of materials ranging from high melting
plastics to low melting elastomers, and their properties arecontrolledbytheirmolecularstructure
andcopolymerization composition. Polyropylene copolymers(random and impact copolymers) are industrially important
as elastomers, impact modification materials, etc. There
has been much effort to introduce polar groups intopolyolefins using an appropriate catalyst technology inorder to overcome their lack of affinity to other polymers.
We have developed a controlled thermal degradation
technique for efficient production of end-reactive polymers
having one or two terminal double bonds [1]. End-reactive
polymers were functionalized by organic synthesis andcopolymerized by living polymerization [2, 3].
In this study, the feature of end-reactive polymer
obtained by controlled thermal degradation of vinyl
polymers and synthesis of novel copolymers from endreactive polymer are reported.

2. Materials and Methods
2.1 Controlled thermal degradation
Commercial polypropylene and polypropylene wastes(bottle cap, car battery and washer tank) were thermallydegraded in glass-apparatus (5g scale) or laboratory-scale

apparatus (1-2 kg scale) under reduced pressure (ca. 10mmHg) at 330-390 °C. In the reaction, molten polymer wasstirred by bubbles of N2 gas introduced. After the reaction,polymer residue in reactor was dissolved in hot xylene andnonvolatile polymer (PP-TVD) was reprecipitated withmethanol.

2.2. Thiol-ene reaction of iPP-TVD
Thiol-ene reaction is focused as click reaction andapplied to functionalization of polymer [4]. iPP-TVD wasprepared by controlled thermal degradation of commercial
iPP. The mixture of iPP-TVD, AIBN, and thiol compounds
were stirred in toluene at 80 °C for 8h. The mixture wasthen poured into methanol, and the precipitate was filteredand dried under reduced pressure.

nControlledthermaldegradationmCommercial iPP

iPP-TVDOO
SThiol-ene reaction

m+2SOHOH
iPP-TGA

ClH+N

NH+S

m+2Cl-S
iPP-DAEScheme. Controlled thermal degradation of PP
wastes and thiol-ene reaction of wPP-TVD.

3. Results and Discussion
3.1. Controlled thermal degradation ofpolypropylene waste
As an example of polypropylene wastes, the result of carbattery waste is shown. Molecular structure of car battery
waste was random PP with ethylene. The monomer

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

Table 1. Degradation condition, yield of residue and molecular characteristics of nonvolatile polymer obtained bycontrolled thermal degradation of car battery wastes.
Degradation contition
Yield ofNonvolatile polymer
Residue, wt%
Temp., °C
Time, hMn, x103
Mw/Mn
Tm, °CfTVD
Original sample
64.0
5.2
167.7
370
1
96.9
20.5
1.9
157.91.31
370
287.2
7.7
1.7
148.8
1.52
370
3
87.7
7.5
1.8
146.0
1.47
390
185.2
7.3
1.7
151.1
1.54
390
266.0
6.5
1.6
136.6
1.46
390
337.6
4.4
1.6
117.1
1.33
composition is propylene[P]: ethylene[E]=87.9:12.1 mol%and triad monomer composition is [EEE]:[PEE+EEP]:[PEP]:[EPE]:[PPE+EPP]:[PPP]=8.4:2.0:1.7:1.7:2.1:84.1
mol%. Degradation condition, yield of residue andmolecular characteristics of nonvolatile polymer are shownin Table 1. The yield of residue and Mn of nonvolatile
polymer decreased depending on degradation temperatureand time. Mw/Mn values of nonvolatile polymer ranged from
1.6 to 1.9, lower than original sample. Tm determined by
DSC decreased from 165.7 °C to about 130 °C. The fTVD
value in right column of Table 1 is average number ofterminal double bond per molecule and estimated by 13CNMR spectrum (Fig. 1). The saturated end groups (n-propyland long chain n-alkyl groups) were detected at 12.5 and12.0 ppm. The signals at 20.4 and 20.5 ppm were assignedto methyl carbons of terminal vinylidene moieties adjacentto propylene and ethylene.

compounds were converted into various functional groups
in one step. Thioglycolic acid (TGA) showed high reactivity
on thiol-ene reaction (Fig. 2). The reaction quantitatively
proceeded on iPP-TVD (1mmol, 2mmol/C=C), AIBN (0.2mmol), and TGA (3 mmol) for 4 h. On the other hand, 2dimethylaminoethanethiol hydrochloride (DAE) had very
low thiol-ene reactivity, required for quantitative reaction ofexcess of AIBN. This reaction without side reaction isregarded as the important method for functionalized
polypropylene with controlled structure.

ghhOHSO

iPP-TGAabfgeec
iPP-TVDd, fdba, caf543
Chemical shift, ppm from TMS

210Fig. 2. 1H-NMR spectra of iPP-TVD and iPP-TGA.

4. Conclusions

20.5

20.4

50

45

40

3530

25

12.5 12.0

201510Chemical shift, ppm from HMDSFig. 1. 13C- NMR spectrum of nonvolatile oligomer
obtained by controlled thermal degradation of carbattery waste at 390 °C for 3hNonvolatile polymer with fTVD=1.54 consisted of 59 %telechelic polymer, 36 % monochelic polymer and 5 %paraffin. On the other hand, fTVD value is 1.8 in the case of
nonvolatile polymer obtained by controlled thermal
degradation of commercial iPP. The low fTVD value isconsidered as due to copolymer with ethylene and original
sample with low Mn.

3.2. Thiol-ene reaction of iPP-TVD
Although terminal vinylidene group of iPP-TVD showed
little or no polymerization reactivity, it was convertible forfunctional groups, such as hydroxyl, carboxyl and epoxy
groups. The thiol-ene reaction of iPP-TVD and various thiolThe nonvolatile polymer obtained by controlled thermal
degradation of polypropylene waste had Mn=4,000 to
20,500 and fTVD=1.31 to 1.54. The fTVD value lower thanthe case of commercial iPP is considered as due tocopolymer with ethylene and original sample with low Mn.
Thiol-ene reaction of iPP-TVD showed widely different
reactivity depend on thiol compounds. The low reactivity
compounds required excess AIBN as radical source. The
thiol-ene reaction is an efficient synthetic method offunctionalized polypropylene.

References[1] T. Sawaguchi, T. Ikemura and M. Seno,Macromolecules 28 (1995) 7973-7978.
[2] T. Hagiwara, H. Saitoh, A. Tobe, D. Sasaki, S. Yanoand T. Sawaguchi, Macromolecules, 38 (2005) 1037310378.
[3] D. Sasaki, Y. Suzuki, T. Hagiwara, S. Yano and T.
Sawaguchi, Polymer 49 (2008) 4094-4100.
[4] C. E. Hoyle and C. N. Bowman, Angew. Chem. Int. Ed.,49 (2010) 1540-1573.

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