J. Rusmirović et al. Production of rubber plasticizers based on waste PET ... 1 2 2 Jelena Rusmirović , Dragana Milošević , Zorica Veličić , Scientific paper Milica Karanac1, Mustafa Kalifa3, Jovana Nikolić2, Aleksandar 3 ISSN 0351-9465, E-ISSN 2466-2585 Marinković * UDC:678.46.004.8 1University of Belgrade, Innovation Center of Faculty of Technology doi: 10.5937/ZasMat1702189R and Metallurgy, Belgrade, Serbia, 2University of Belgrade, Institute for Chemistry, Technology and Metallurgy, Belgrade, Serbia, 3University of Belgrade, Faculty of Techology and Metallurgy, Zastita Materijala 58 (2) Belgrade, Serbia 189 – 197 (2017) Production of rubber plasticizers based on waste PET: techno-economical aspect ABSTRACT Production of rubber plasticizers, based on waste poly(ethylene terephthalate) (PET), and economic effectiveness of developed technologies are presented and discussed. Waste PET glycolyzates, named diisononyl terephthalate(DINTP), didecyl terephthalate (DDTP), dibenzyl terephthalate(DBTP) and diglyceryl terephthalate(DGTP), were obtained by catalytic depolymerization of PET with isononyl alcohol, decyl alcohol, benzyl alcohol and glycerol. The structural analysis of the synthesized plasticizers was done using elemental, FTIR and NMR spectral analysis. Physical-mechanical properties of the rubber products composed of 100 phr of 28 % nitrile butadiene caoutchouc (NBR) and 20.7 phr of plasticizer were investigated. Influence of the synthesized plasticizers on Shore hardness, breaking strength and elongation at break was investigated. Obtained results were compared with ones obtained for commercial plasticizer dioctyl phthatale (DOP). Evaluation of economic potential of new technology for plasticizers production, i.e. results of techno-economic analysis, was presented. Benefits of the presented technology was based on the use of waste PET which is related to both environmental protection and profitability aspects. Keywords: waste PET glycolysis, plasticizers, rubber, PET recycling. 1. INTRODUCTION economic activity – whether through material use Poly(ethylene terephthalate) is a semicrysta- or energy recovery. Economic benefits generated lline, thermoplastic polymer with excellent optical, using waste or recycled materials outweigh the barrier, thermal and mechanical properties [1, 2]. costs and improve productivity by reducing the use Accordingly, PET is widely used for three main of expensive raw materials, whether metal in applications categories: fibers, bottles and indus- industry, or paper in commerce. trial use [2]. The consequence of using this mate- Nitrile butadiene caoutchouc (NBR), as one of rial is formation of large amount of non-biodegra- the most widely used elastomer in the solid or latex dable PET waste. Environmental problems caused state, is mostly manufactured by the emulsion poly- by incineration or accumulation of PET waste on merization method [8]. In rubber production, plasti- landfills can be significantly reduced by chemical cizers are generally used to enhance rubber pro- recycling of this material and its use for manu- cessability, as well as, to reduce rubber relaxation facturing new products, such as polyester, epoxy time in order to improve its physical-mechanical and alkyd resins [3-5] and plasticizers [6]. The characteristics. Plasticizers used in the rubber in- recycling of waste PET can be primary (Pre- dustry are mainly diesters of dibasic acids and Consumer Industrial Scrap), secondary (Mecha- monohydroxy alcohols, and the most common are nical Recycling), tertiary (Chemical Recycling) and phthalates: di(2-ethylhexyl) phthalate, better known quaternary level (Energy Recovery) [7]. According as dioctyl phthalate (DOP), di-isononylphthalate (DINP) and mixture of esters of aliphatic hydrophilic to reusing possibility, recycling of waste PET is an acids with high molecular weight and some types of polycondensed and polymerized products and *Corresponding author: Aleksandar Marinković chlorinated hydrocarbons [9]. Xia [10] et al. studied E-mail: [email protected] the synthesis of plasticizer dioctyl terephthalate Paper received: 17. 02. 2017. (DOTP) using mixed purified terephthalic acid Paper accepted: 25. 03. 2017. (PTA) and waste terephthalic acid as raw materials Paper is available on the website: and octyl alcohol along with catalyst. Comparison www.idk.org.rs/journal of mechanical properties of DOTP with DOP it was ZASTITA MATERIJALA 58 (2017) broj 2 189 J. Rusmirović et al. Production of rubber plasticizers based on waste PET ... concluded that DOTP have excellent performance dichloromethane to remove impurities and residual and higher heat resistance. Considering the aspect adhesives. m-Xylene, isononyl alcohol (INA), of health impacts, DOP is a possible cancer glycerol (Gly), benzyl alcohol (BA), decyl alcohol causing agent in humans that increase cell proli- (DA), zinc oxide (ZnO), stearic acid and tetrabutyl- feration, decrease apoptosis, oxidative damage, titanate (TBT) were purchased from Sigma-Aldrich and selective clonal expansion of the initiated cells. and were used without further purification. Due to that, European Union (EU) banned the use Nitrile butadiene rubber (NBR), Europrene N of DOP along with several other phthalates in toys 3980, 28% acrylonitrile (AcN) content, was sup- for young children. Strict regulation which limit plied from Versalis, Italy. Commercial rubber further use of the most common DOP plasticizer additives: Faktis - RheinChemie, Germany; create needs for development of new products with VULKANOX MB-2/MG, mixture of 4- and 5-methyl- improved properties and competitive market cost. 2-mercapto-benzimidazole (MMBI), Lanxess, It was shown that di-ethylene glycol tereph- Germany; Carbon black Soot N – 550 and Soot N thalate, obtained from PET waste by alcoholic gly- – 660 (Scorpio Investment Ltd, Russian Fede- colysis and further modified with maleic anhydride, ration); VULKANOL FH, Xylene formaldehyde re- shows good properties as plasticizer which gave sin, Lanxess, Germany; Ultrasil VN – 3 is syn- material with good mechanical properties [11]. Ge- thetically produced amorphous silicon dioxide nerally, terephthalate based plasticizers indicate (Evonik Industries, Germany); Sulfur, Eastman excellent durability in products, flexibility on low Chemical Company, Netherland; Vulkacit CBS temperatures and better electrical insulation [12]. amine based accelerator (N-cyclohexyl-2-benzothi- In this paper, the terephthalic acid moiety pre- azolesulfenamide) (Lanxess, Germany), and sent in PET structure is used as source of dibasic Vulkacit TMTD - tetramethylthiuram disulfide acid in plasticizers synthesis. Presented recycling (Lanxess, Germany) was used as received. method proposes to make use of waste PET to Dioctylphthalate (DOP) was supplied by BRENTAG produce value-added product/plasticizers: diiso- CEE GMBH, Serbia. nonyl terephthalate (DINTP), didecyl terephthalate (DDTP), dibenzyl terephthalate (DBTP) and digly- 2.2. Plasticizer production ceryl terephthalate (DGTP). Plasticizers were General procedure used for glycolysis of waste obtained by a known method of catalytic PET: In three-necked round bottom flask of 500 depolymerization (transesterification) of PET with mL, equipped with magnetic stirrer, condenser, isononyl alcohol, decyl alcohol, benzyl alcohol and Dean-Stark separator and thermometer, certain glycerol. The overall reaction involves substituting amount of PET and alcohol were charged. Rea- commercial phthalic anhydride with PTA which ction mixture was heated to 115 °C and maintained originates from waste PET. The physical-chemical until the water evaporation was not observed, whe- properties of the obtained rubber products, based reupon 0.4% of TBT catalyst was added and on DOP and PET based plasticiyers, were temperature was raised to 190 °C. m-Xylene, (3% determined and compared. Plasticizers based on on the reaction mixture), was used as the agent for waste PET glycolyzates showed significant impro- azeotropic removal of ethylene glycol (EG). After vement of physical-mechanical properties in NBR completion of the synthesis obtained products was products. In order to test the commercial viability of purified by removing residual reactants using plasticizer technology the preliminary techno- vacuum distillation, hot product was filtered using economic analysis was performed. diatomaceous earth and used for compounding of rubber products. Waste PET glycolysis products 2. EXPERIMENTAL obtained by a catalytic depolymerization of PET 2.1. Materials with INA, DA, BA and Gly were designated DINTP, DDTP, DBTP and DGTP, respectively. Quantity of Waste PET, used for unsaturated polyester reactants used for syntheses of PET based resin production, was collected from soft beverage plasticizers is given in Table 1. bottles. PET bottles were crushed into small pieces (app. 0.5 × 0.5 cm) and washed with ethanol and Table 1. Quantity of reactants used for syntheses of PET based plasticizers Tabela 1. Količina reaktanata korišćenih za sinteze plastifikatora na bazi PET-a DINTP DDTP DBTP DGTP Reactant Amount, Amount, Amount, Amount, Weight, g Weight, g Weight, g Weight, g mol mol mol mol PET 92 0.48 92 0.48 92 0.48 80 0.41 INA 170 1.19 - - - - - - DA - - 170 1.19 - - - - BA - - - - 75.4 0.69 - - Gly - - - - - - 191 2.1 190 ZASTITA MATERIJALA 58 (2017) broj 2 J. Rusmirović et al. Production of rubber plasticizers based on waste PET ... 2.3. Rubber production phases: production of base without sulfur and accelerators, and after 24 hours and mixing