The aim of this study is to enhance the recycled PVC related material property by formulation technology and develop the recycling product processing technology furthermore develop the chemical recycling technology for last stage of PVC wastes. The formulation technology is composed of pre-treatment (crushing, separation etc.) and post-treatment (material ratio, additives, stabilizer etc.) to enhance the recyclate property. The formulation for recycled PVC by application basis and processing technology is applied to produce the structural product for civil and construction application such as pipe fittings and water drainage cap for environmental waterway. Also chemical recycling technology for end life PVC scrap which causes environmental pollution by incineration or landfill is studied for producing hydrocarbon and hydrogen chloride for VCM

Bae, Jong Wook

Han, Jaemyung

Han, Sejong

Hong, Sukwon

Kye, Hyoungsan

Lee, Donghyun

English

Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)

   Article  Eco-friendly Technologies for Physical and Chemical Recycling of PVC-Related Wasteful Resources  Hyoungsan Kye1,*, Sejong Han2, Jaemyung Han2, Sukwon Hong3, Donghyun Lee4, and Jong Wook Bae4  1 Department of Applied Chemical Engineering, Mok Won University, Daejeon, 35349, Korea 2 Sunjin Concrete Co. Ltd., Buyeo, Chungnam, 33175, Korea 3 PPI Pyunghwa Co. Ltd., Hwaseong, Kyunggi, 18574, Korea  4 School of Chemical Engineering, Sung Kyun Kwan University, Suwon, 16419, Korea E-mail: *hskye@mokwon.ac.kr (Corresponding author)   Abstract. The aim of this study is to enhance the recycled PVC related material property by formulation technology and develop the recycling product processing technology furthermore develop the chemical recycling technology for last stage of PVC wastes. The formulation technology is composed of pre-treatment (crushing, separation etc.) and post-treatment (material ratio, additives, stabilizer etc.) to enhance the recyclate property. The formulation for recycled PVC by application basis and processing technology is applied to produce the structural product for civil and construction application such as pipe fittings and water drainage cap for environmental waterway. Also chemical recycling technology for end life PVC scrap which causes environmental pollution by incineration or landfill is studied for producing hydrocarbon and hydrogen chloride for VCM.  Keywords: Eco-friendly technology, mechanical recycling, chemical recycling, dehydrochlorination.   ENGINEERING JOURNAL Volume 20 Issue 4 Received 3 March 2016 Accepted 13 June 2016 Published 1 August 2016 Online at http://www.engj.org/ DOI:10.4186/ej.2016.20.4.19 DOI:10.4186/ej.2016.20.4.19 20 ENGINEERING JOURNAL Volume 20 Issue 4, ISSN 0125-8281 (http://www.engj.org/) 1. Introduction  Ever since the first industrial scale production of synthetic polymers (plastics) took place in the 1940s, the production, consumption and waste generation rate of plastic solid waste (PSW) has increased considerably. Thus, PSW recycling has been a focus of many researchers in the past few decades. Such research is also driven by changes in regulatory and environmental issues. Plastics are used in our daily lives in a number of applications. From greenhouses, mulches, coating and wiring, to packaging, films, covers, bags and containers. It is only reasonable to find a considerable amount of PSW in the final stream of municipal solid waste (MSW) [1, 2]. PVC (polyvinyl chloride) is one of the most widely used polymers in the world. The polymer was one of the first modern plastic materials to be discovered. Although first synthesized in the laboratory in the 19th century, commercial development of the polymer commenced in the mid-1920s and saw a dramatic growth during the 1950s. Today, about 37 million tons of PVC is produced worldwide. PVC is produced 900,000 tons in Korea and widely used in the field of civil and construction application. Low cost, excellent property make PVC’s wide acceptance in the market.  As a consequence, post-consumer PVC waste amount increases with over durability life product and dumped from reconstruction housing development. It was commonly known the PVC waste causes environmental pollution when treat inadequately such as landfill, incineration and so on. So many researches were performed to find effective treatment method [3, 4] but there were no particular alternatives than re-use and landfill. PVC resin is one of the typical resins which need various kinds of additives to control the property for each application. The different end-use wastes were mixed together during the collecting process, one facing the difficulties to recycle waste scrap. Currently most widely recycled end use products were pipe and fittings, profiles and flooring product in Korea. These scraps were easy to collect and have simple formulation so it is relatively easy to recycle.  As a result many companies produce lower grade products using these post-consumer PVC scrap. There were no specific recycling method for PVC composite with other polymers, soft PVC product such as PVC films and durability life overdue products were difficult to collect and facing difficulties to recycle due to various kinds of additives are used. So these wastes are landfill or incinerate in most cases. Recently a research for using low grade PVC waste as a RPF for furnace, but it stopped for low economic feasibility. In Europe, 150,000 tons of post-consumer PVC waste was recycled in 2007. In order to achieve the demanding target of 800,000 tons/year recycled by 2020, Vinyl Plus tries to develop innovative technologies. Within this target is a contribution of 100,000 tons from ‘more difficult to recycle’ PVC waste [5]. Japan government strongly forced to recycle plastic waste by basic law for establishing the recycling-based society and waste management and public cleansing law and so on [6]. As a result 61 % of PVC pipes and 70 % of agricultural films were recycled on the floor covering application, low quality waste such as deteriorated films and wall covers were chemically recycled through 19 large size chemical recycling plants, but start to investigate new physical recycling process because of energy recovery processing cost problems.  850,000 tons of PVC was used in Korea annually, 340,000 tons for films, 115,000 tons for pipe and fittings, 115,000 tons for wire and cable covering, 15,000 tons for electrical components, 134,000 tons for window profiles and 120,000 tons of PVC were used for other usage. The collected post-consumer PVC was 105,000 tons and 30,000 tons of PVC were imported from foreign countries and recycled to low quality hose and pipes. The mechanical recycling of post-consumer PVC was very business-like but energy recovery and feedstock for PVC were dull and chemical recycle is not studied ever before because of low economic feasibility [7]. In this study, mechanical recycling is performed for dumped PVC waste to develop a total recycling system and try to develop chemical recycling technology for low quality PVC wastes. The basic mechanical properties and collecting forms and composition investigated and analyzed. Also basic catalyst study and PVC conversion ratio with catalysts were investigated.  2. Experimental  2.1. Material  Three different class of post-consumer PVC wastes: Rigid composite scrap (RC), Pipe scrap (PC), Cloth collar scrap (CC), were used in this study. The RC consists of various post-consumer rigid PVC scraps DOI:10.4186/ej.2016.20.4.19 ENGINEERING JOURNAL Volume 20 Issue 4, ISSN 0125-8281 (http://www.engj.org/) 21 which were not identified the origins and usage, PC were mainly collected from the pressure and non-pressure pipes, CC were recycled from Y-shirt collar scrap. The characteristics of materials used in this study are presented in Table 1. A virgin PVC resin was used for comparison purposes.  Table 1. The characteristics of materials used in this study. Item Contents Type Source RC Rigid Composite PVC  Scrap powder Nam Yang PC   Pipe  Scrap powder PPI CC  Cloth collar  Scrap powder Nam Yang P-1000 Pure resin Fine Powder Hanhwa Chemical  2.2. Specimen Preparation  The high impact resistant pressure pipe formulation is adopted for post-consumer PVC scrap characterization. The formulations consists of base resin 100 phr, stabilizer 5 phr, impact modifier 8 phr, processing lubricant 2 phr, filler 2 phr. The compounds were mixed with 120 C, 2100 rpm by Henschel mixer. The mixtures were processed into sheet by mixing roll with 6 minutes and 4 layers of sheet were laminated onto 3 mm thick sheet for preparing mechanical specimens by mold press, and the processing conditions are shown in Table 2.  Table 2. Sample preparation process condition. Item Condition Henschel mixer  2,100 rpm, 120 C Mixing roll 6 minute, 190 C Mold press  3 mm, 195 C  The specimens prepared are shown in Fig. 1.    CC scrap formulation  RC scrap formulation PC scrap formulation   CC scrap Roll sheet RC scrap Roll sheet PC scrap Roll sheet    CC scrap press specimen RC scrap press specimen PC scrap press specimen Fig. 1. The post-consumer PVC scrap formulation and specimen preparation. DOI:10.4186/ej.2016.20.4.19 22 ENGINEERING JOURNAL Volume 20 Issue 4, ISSN 0125-8281 (http://www.engj.org/) 2.3. Mechanical Properties of Recycled Scrap  The mechanical properties of scrap materials are compared by virgin specimen. The tensile strength, VICAT and IZOD impact resistance were measured by the Korea Standard (KS) M 3401 which specifies rigid pressure pipe specification. The tensile mechanical properties of the specimen we prepared were measured using a Testometric’s Micro 350 tensile tester. The testing procedures were carried out according to ASTM D 638. The specimen was fixed using a compressed air grip. A cross-head speed of 12.5 mm/min with 1,000 kgf load cell was used in this experiment. IZOD impact properties were measured by Daekyung’s DTI-602 IZOD impact tester with 2 lb IZOD by ASTM D 256. The IZOD notch was made by Kibae’s model KPM-080 notch cutter with feed speed of 25 and cutter speed of 55.  Tensile and IZOD impact specimens were dried in a convection drying oven at 80 C for 24 hours.  3. Results and Discussion  3.1. Mechanical Properties of Recycled Scrap  The mechanical properties of recycled scrap specimen compared with virgin PVC (P-1000) specimen. Tensile strength, VICT softening temperature and IZOD impact properties were measured by KS M 3401, and the results were summarized in Table 3.  Table 3. Mechanical properties of post-consumer PVC scrap.  Item  P-1000 CC scrap RC scrap PC scrap Base resin content 100 100 100 100 IZOD(kgcm/cm) 47.9 20.1 5.7 13.3 VICAT(C, 5 kg) 84.4 62.8 83.9 97.2 Tensile Strength (kgf/cm2) 532 495 305 490  As shown in Table 3, the VICAT temperature of three different scrap shows no tendency and shows no significant differences. Impact resistance of virgin PVC shows 47.9 kgcm/cm but the CC shows 20.1 kgcm/cm, which are 41 % of virgin PVC, PC and RC shows 13.3 kgcm/cm, 5.7 kgcm/cm in sequence.  Which were 27 % and 12 % of virgin PVC’s impact resistance. Tensile strength shows same tendency with IZOD.  Tensile strength of SC shows lowest value among the specimen and this result mainly caused by the composition of SC. SC scrap consist of several different end used rigid PVC recycled materials. CC scrap show much better mechanical properties among the specimen especially on the impact resistance, we guess the CC consists of one source waste scrap also certain amount of impact modifier were already exist for former usage.  3.2. Mechanical Properties of Post-Consumer PVC Scrap with Scrap Ratio  To investigate the mechanical property variation with the amount of scrap ratio, we compound virgin material with three different scraps of 10, 30, 50 phr using base formulation. The results were shown in Tables 4~6 and Figures 2~4.  3.2.1. CC Scrap  As shown in Table 4 and Fig. 2, the impact resistance and tensile strength decreases with increasing scrap ratio. But the impact resistance and tensile strength of CC compound itself shows highest among the other post-consumer PVC scraps, the decreasing value gaps were lowest.       DOI:10.4186/ej.2016.20.4.19 ENGINEERING JOURNAL Volume 20 Issue 4, ISSN 0125-8281 (http://www.engj.org/) 23 Table 4. Mechanical properties of CC compound with scrap ratio.  Item  P-1000 CC scrap   CC-1 CC-2 CC-3 Base recipe Scrap Ratio 100 0 100 10 100 30 100   50 IZOD(kgcm/cm) 47.9 45.1 43.2 42.6 VICAT(C, 5 kg) 84.4 82.6 79.2 77.4 Tensile Strength (kgf/cm2) 532 517 492 454   Fig. 2. The overall mechanical properties of CC compound with scrap ratio.   3.2.2. RC Scrap  As shown in Table 5 and Fig. 3, the 10, 30, 50 phr RC scrap were mixed with virgin material, impact resistance dropped sharply than virgin specimen. And impact resistance decrease with RC ratio increase. This means the basic property of RC scrap is lower than virgin material so RC affects to decrease mechanical properties of virgin material. Same tendency were shown for the tensile strength. But no significant difference is shown for VICAT.  Table 5. Mechanical properties of RC compound with scrap ratio.  Item  P-1000 RC scrap   RC-1 RC-2 RC-3 Base recipe Scrap Ratio 100 0 100 10 100 30 100   50 IZOD(kgcm/cm) 47.9 20.3 17.9 10.9 VICAT(C, 5 kg) 84.4 84.3 83.8 84.3 Tensile Strength (kgf/cm2) 532 414 396 373  DOI:10.4186/ej.2016.20.4.19 24 ENGINEERING JOURNAL Volume 20 Issue 4, ISSN 0125-8281 (http://www.engj.org/)  Fig. 3. The overall mechanical properties of RC compound with scrap ratio.   3.2.3. PC Scrap  As shown in Table 6 and Fig. 4, impact resistance of PC scrap decreases with increasing scrap ratio, but the amount of decreased value gaps were less than CC and RC compound, same tendency were shown for VICAT and tensile strength properties. This phenomena were caused by PC scraps were collected from pipe application, so basic property is quite similar than RC scrap.  Table 6. Mechanical properties of PC compound with scrap ratio.  Item  P-1000 PC scrap   PC-1 PC-2 PC-3 Base recipe Scrap Ratio 100 0 100 10 100 30 100   50 IZOD(kgcm/cm) 47.9 29.1 24.9 23.6 VICAT(C, 5 kg) 84.4 84.7 84.7 85.4 Tensile Strength (kgf/cm2) 532 506 509 506   Fig. 4. The overall mechanical properties of PC compound with scrap ratio. DOI:10.4186/ej.2016.20.4.19 ENGINEERING JOURNAL Volume 20 Issue 4, ISSN 0125-8281 (http://www.engj.org/) 25 3.3. Physical Recycling Application of Post-Consumer PVC Waste Scrap  Based on the comparison test result, impact resistance of waste compounds decrease with increasing scrap ratio. Impact resistance of CC compound shows highest among the other scrap compound and RC and PC scrap’s impact resistance were low. As a result, their impact resistance dropped drastically with increasing scrap ratio. Tensile strength of scrap shows decreasing tendency with increasing scrap ratio, but the VICT temperature shows no specific tendency with ratio and scrap. To utilize the PVC scrap as a useful resource, we adopt the mechanical test result of several compounds to produce civil application. Some of the application is shown in Fig. 5 and 6.   Fig. 5. A pipe fitting outer layer made by post-consumer CC compound.   Fig. 6. A conduit cap made by post-consumer PC compound.  4. Chemical Recycle  Basic chemical recycling investigations for low quality PVC waste were performed. A hydrochloric acid were recovered by the dehydrochlorination reaction and the catalyst system study is investigated  4.1. Reaction Catalyst System  Ionic liquid {[Bmim]Cl (1-butyl-3-methylimidazolium chloride)} and PEG were chosen for a solvent for dehydrochlorination reaction. Virgin PVC is used to find a reaction condition, such as reaction temperature and amount of catalyst and so on. The FT-IR spectrums of carbon double bond on the titration solution after dehydrochlorination reaction completed were shown in Figure 7.  DOI:10.4186/ej.2016.20.4.19 26 ENGINEERING JOURNAL Volume 20 Issue 4, ISSN 0125-8281 (http://www.engj.org/)  Fig. 7. FT-IR result to confirm C=C bond result from dehydrochlorination.   In addition, MgO and CaO adsorption agent were used to collect HCl during the simultaneous (dehydrochlorination + adsorption) reaction. The result were shown in Fig. 8,  the activity of CaO is better than MgO and FT-IR spectrum shows carbon-carbon double bond were created and XRD result shows CaO and MgO maintain its structure. So adsorption reaction (2) proceeds faster than chlorination reaction (1) on the (dehydrochlorination + adsorption).  (1) MgO (or CaO) + 2HCl → MgCl2 (or CaCl2) + H2O (high temperature chlorination reaction) (2) MgO (or CaO) + xHCl → MgO·xHCl (or CaO·xHCl) (low temperature adsorption reaction)    Fig. 8. FT-IR and XRD result for (dehydrochlorination+ adsorption) reaction.  In case of simultaneous use of PEG 400 and ionic liquid([Bmin]Cl) for dehydrochlorination reaction for post-consumer low quality PVC waste, 80 % of reaction conversion was achieved. If we use metal oxide adsorbent with above mentioned solvent, then over 88 % of reaction conversion is achieved.  5. Conclusion  The mechanical properties of three different post-consumer PVC waste from different end-use applications mechanical properties with their scrap ratio were investigated. Also basic reaction conditions for chemical recycling of low quality post-consumer PVC waste were studied.   DOI:10.4186/ej.2016.20.4.19 ENGINEERING JOURNAL Volume 20 Issue 4, ISSN 0125-8281 (http://www.engj.org/) 27 (1) VICAT softening temperature of post-consumer PVC is lower than virgin resin but it shows not too low and no specific tendency compared with virgin PVC. Impact resistance and tensile strength were in the order of CC > PC > RC.   (2) Impact resistance of CC, PC and RC compound decreased with increasing scrap ratio. The CC compound has highest impact resistance and value gap deviation is much lower than the other compounds.  The decreasing value deviation of RC and PC shows big for impact resistance with increasing scrap ratio. (3) CC, RC and PC compound show no specific tendency of VICAT softening temperature.   When PEG 400 solvent and ionic liquids ([Bmim]Cl  and [Bmim]BF4) with metal oxide (CaO) were used for chemical reaction, the conversion rate increased up to 88 %. Also PEG400 solvent with  [Bmim]Cl were used and metal oxides as adsorbent leads dehydrochlorination reaction prevailed. As a result the conversion increased. Further MgO (or CaO) + xHCl → MgO·xHCl (or CaO·xHCl) reaction proceed dominantly to enhance the PVC conversion.  Acknowledgement  This study was supported by the R&D Center for Valuable Recycling (Global-Top Environmental Technology Development Program) funded by the Ministry of Environment. (Project No.: GT-14-C-01-038-0).  References  [1] J. Lee et. al, “Recycling technology of PVC waste,” Polym. Sci. Technol., vol. 13, no. 3, pp. 332-341, June, 2002. [2] S. M. Al-Salem, P. Lettieri, and J. Baeyens, “Recycling and recovery routes of solid waste (PSW): A review,” Waste Manag., vol. 29, pp. 2625-2643, 2009. [3] J. Hopewell et. al, “Plastics recycling: challenges and opportunities,” Phil. Trans. R. Soc. B, vol. 364, pp. 2115-2126, 2009. [4] “The Voluntary Commitment of the European PVC industry,” Vinyl Plus, 2011. [5] I. Leveson, “Vinyl: 2020 Ten years later,” World Vinyl Forum III, September, 2007. [6] VinylPlus, Vinyl Plus PVC recycling technologies, 2014. [7] S. Seki, F. Osakada and T. Yoshooka, “Developments in an industry-led R&D program for recycling PVC products in Japan,” J. Mat. Cycles & Waste Manag., vol. 16, no. 3, pp. 332-341, 2014. [8] S. Kim et. al, “ 2012 Industrial competition for PVC industry”, KIET, 2012.  

Eco-friendly Technologies for Physical and Chemical Recycling of PVC-Related Wasteful Resources

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Eco-friendly Technologies for Physical and Chemical Recycling of PVC-Related Wasteful Resources

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Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)