STUDIES ON THE CHEMICAL RECYCLING OF WASTES CONTAINING
PVC, PVDC AND PPS
K. Ohkubo, H. Tagaya
Yamagata University, Graduate School of Science and Engineering
e-mail: trf91544@st.yamagata-u.ac.jp

Abstract
Pyrolysis process for waste plastics may be an alternative process to obtain chemicals and valuable liquid fuels from waste
plastics. Although waste plastics such as PVC, PVDC and PPS are considered as valuable organic resources, they containchlorine suggesting the production of chlorinated compounds in the course of the pyrolysis process. Production of suchchlorinated compounds is very detrimental either in order to supply chemicals or to use them directly as fuels. It isconsidered that calcium hydroxide modified by organic compound is effective for improving the quality of products inpyrolysis process for polymeric materials because such modified calcium compounds are dispersed effectively into organic
polymeric materials.
Keywords: Modified calcium compound, Pyrolysis, Wastes plastics, Chemical recycling, Chlorinated compounds

1. Introduction
Pyrolysis is an alternative process for recycling of waste
plastics. By this technique valuable fuels and chemicals
are obtained by means of thermal cracking of waste
plastics. The pyrolysis process consists in heating thematerials in an oxygen free atmosphere; the organic
components of the materials are decomposed andgenerating liquid and gaseous products are evolved fromthe reactor while the inorganic materials remain
unaltered in the reactor together with a carbonaceous
solid formed in the process called as char. Pyrolysis is anespecially appropriate recycling technique for waste
plastics containing different plastics and other polymericmaterials, since no separation operations are needed
prior to the pyrolysis process. This confers the pyrolysis
process an advantageous position with respect tomechanical recycling, which requires quite pure polymers
to be successfully used.
On the other hand, the waste plastics such as polyvinylchloride (PVC), polyvinylidene chloride (PVDC) andpolyphenylenesulfide (PPS) contain chlorine. Therefore,chlorinated compounds should be produced in thepyrolysis liquids and this is very detrimental either inorder to supply chemicals and liquids as fuels. Therefore,
in the current process, the addition of alkali adsorbents isessential to avoid the production of chlorinatedcompounds.
It is suggested the occurrence of trapping in physicaland/or chemical adsorption process [1]. However, thismethod is still inadequate because of un-sufficient
dispersion of alkali adsorbent such as calcium hydroxide
leading to incomplete dechlorination.
The objective of this study is to improve theeffectiveness of alkali adsorbents. Usually calcium
hydroxide (Ca(OH)2) has been used as alkali adsorbentsof chlorinated compounds. Because it abounds inamount of deposit and is cheap and least disruptive tothe human body and the environment. In addition it isable to trap chlorinated compounds as calcium chloride(CaCl2). However its affinity with organic compounds
such as plastics is low and aggregates easily in polymer
matrix. Therefore, its effectiveness is limited and needed
too much amount. In this study calcium hydroxide
reacted with organic carboxylic acid to improve on theperformance as alkali adsorbents of chlorinatedcompounds as shown in Figure .1 [1].

Ca(OH)2

Organic carboxylic acid＋

calcium compound modified byorganic compounds

Figure 1 Preparation procedure of calcium compoundmodified by organic compounds in the reaction ofcalcium hydroxide with organic carboxylic acid.

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

2. Materials and Methods
2.1 Reaction of calcium hydroxide with organic carboxylicacid.
Calcium hydroxide was reacted with organic carboxylic
acid in mixed solvent of water and acetonitrile. After thereaction, products were measured by thermogravimetry(TG) and scanning electron microscope (SEM) as shownin Figure 2.

adding calcium hydroxide itself had the aggregate ofcalcium. In comparison, PS adding with calcium
compound modified by organic compounds didn’t haveany aggregate of calcium. Thus, it is considered thatcalcium compound modified by organic compounds has
higher affinity for PS than calcium hydroxide itself.
(a)Water and acetonitrile
Ca(OH)2 andorganic carboxylic acid(b)

60oC, 6h, stirrer
vacuum drying
TG and SEM
Figure 2 Reaction of calcium hydroxide with organiccarboxylic acid.
2.2 Calcium compound modified by organic compounds
expecting high affinity with plastics.
Calcium compound modified with organic compound or
calcium hydroxide was added to polyvinyl alcohol (PVA)
film and polystyrene (PS), polyethylene (PE) andpolypropylene (PP) to make sure of the affinity ofmodified calcium with plastics.

Figure 3 Transparency of PVA film with (a) calcium
hydroxide (2 wt%) and (b) calcium compound modified
by organic compounds.
(a)

(b)

3. Results and Discussion
3.1. The affinity of calcium compound modified byorganic compound with PVA.
We have made sure the transparency of PVA film after
adding calcium compound modified by organic
compounds or calcium hydroxide itself as shown in
Figure 3. As a result, PVA film adding calcium hydroxideitself was opacity. In comparison, PVA film adding
calcium compound modified by organic compounds wastransparency. Thus, it suggested the higher affinity ofcalcium compound modified by organic compounds withPVA than calcium hydroxide.
3.2. Addition of calcium compound modified by organic
compounds or calcium hydroxide to PS.
Calcium compound modified by organic compounds orcalcium hydroxide itself was added to PS, and measured
by SEM and energy Dispersive X-ray Spectroscopy(EDX) of calcium as shown in Figure 4. As a result, PSFigure 4 EDX (left) and SEM (right) images of (a) PS /calcium hydroxide and (b) PS / calcium compoundmodified by organic compounds.

4. Conclusions
Calcium compound modified by organic compounds wassuccessfully prepared. Calcium compound modified byorganic compounds had high affinity with plastics.

References[1] H-Tagaya, Bottom-up, Nanofabrication, ASP (2009)283-300

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