Utilization of by-products of oil processing industries for PVC stabilizers

Transcription

1 Journal of Scientific & Industrial Research TOLIWAL & PATEL : USING BY-PRODUCTS OF OIL PROCESSING INDUSTRIES FOR PVC 229 Vol. 68, March 2009, pp Utilization of by-products of oil processing industries for PVC stabilizers S D Toliwal* and Kalpen Patel Department of Industrial Chemistry, Institute of Science and Technology for Advanced Studies and Research (ISTAR), Vallabh Vidyanagar , India Received 07 August 2007; revised 02 January 2009; accepted 06 January 2009 Epoxidised products from acid oil (AO) and oil recovered from spent bleaching earth (ORSBE) were prepared at 29 C using per acetic acid produced in situ by reacting H 2 O 2 (30% v/v) with various amounts of glacial acetic acid. Ba, Cd, Pb and Zn soaps of epoxidised oils were prepared by metathesis in alcohol solution. Thermal degradation studies on poly vinyl chloride (PVC) in presence of epoxidised oils and their metal soaps were carried out under non-oxidative and oxidative conditions at 180 C. Additives retarded dehydrochlorination rate of PVC and markedly reduced unsaturation level in degraded polymer. Chain scission has been found predominant reaction that accompanied dehydrochlorination. Additives reduced average number of chain scission per polymer molecule. Keywords: Acid oil, Dehydrochlorination, Epoxidised oils, Metal soaps, Oil recovered from spent bleaching earth (ORSBE), Peracetic acid, PVC Introduction Polyvinyl chloride (PVC), at elevated temperature, degrades by thermal dehydrochlorination accompanied by secondary reactions 1 (chain scission, cross-liking, cyclisation etc) and becomes discoloured due to formation of conjugated double bond in polymer chain. Heat stabilizers (metal carboxylates, organometallic compounds and inhibitors of radical chain reaction) and effect of epoxidised oils of rubber seed and jatropha seed, and its metal soaps on thermal degradation of PVC have been reported 2-6. Vegetable oil processing generates large quantities of by-products (gums, soap-stock, acid oil and spent bleaching earth), which contain oil (30-35%, dry wt). This study presents up-gradation and utilization of by-products of oils and allied industries. Materials and Methods Materials By products of oil processing industries [acid oil (AO) and oil recovered from spent bleaching earth (ORSBE)] were procured from Ashwin Vanaspti Ltd, Samlaya, India. Physico chemical characteristics of AO and ORSBE by standard BIS methods 7 were found to *Author for correspondence toliwalsd@yahoo.co.in be: sp gr 30 0C, 0.915, 0.921; acid value, , 18.82; iodine value, , ; saponification value, , Fatty acid composition of oils determined by gas liquid chromatography 8 (GLC) of methyl esters using capillary column (2 m x 0.32 mm) packed with 50% cynopropyl phenyl polysiloxane (BP225) at 220 C with nitrogen as carrier gas (flow rate 10 ml/min) using FID at an injector temperature of 250 C was found to be: i) AO - palmitic, 12.03; stearic, 10.26; oleic, 36.08; linoleic, 40.01; and linolenic, 1.2%; and ii) ORSBE - palmitic, 10.54; stearic, 4.62; oleic, 21.39; linoleic, 52.53; and linolenic, 6.09 %. All other chemicals used were of laboratory grade. Methods Epoxidation of Seed Oils 9-11 Oil (100 g) was taken with glacial acetic acid (9.2 g) in a three necked flask and mixture was warmed to 50 C and sulfuric acid (1.24 g) and hydrogen peroxide (21.8 g) were slowly added over 2 h. Samples were taken out at regular interval of 1 h until iodine value dropped below 5. Mixture was poured into separating funnel and kept overnight. Organic layer was washed with hot water to make it free from acid. The product analyzed for epoxy oxygen content as per AOCS method 12 gave oxirane

2 230 J SCI IND RES VOL 68 MARCH 2009 number at 4.3 and 3.8 for epoxidised AO and epoxidised ORSBE respectively. Epoxidised oils were stored at 7 C. Preparation of Metallic Soaps Metal soaps of oils (epoxidised and unepoxidised) were prepared by metathesis in alcohol solution 13. Sodium soaps of oils were first prepared by dissolving oil sample (9.2 g) in hot ethanol (50 ml) followed by treatment of mixture with 20 % (w/v) sodium hydroxide (20 ml) solution. To this mixture, 100 ml of 30 % (w/v) solution of metal salt {BaCl 2. 2H 2 O; Cd (NO 3 ) 4H O; ZnSO ; Pb (NO 3 ) } were slowly added with continuous stirring. 2 Precipitated metal soap was washed with warm water and air-dried. Degradation Studies Non-oxidative Degradation Dehydrochlorination studies were carried out at 180 C first using PVC mixed with 10% (by wt) of epoxidised and unepoxidised oils separately and then by using PVC mixed with 3%( by wt) of metal soaps of epoxidised and unepoxidised oils separately under nitrogen atmosphere. In a typical experiment, polymer sample (1.5 g) was mixed thoroughly with appropriate amount of additive and transferred to a degradation tube, which was connected to a source of nitrogen (flow rate, 60 ml/min). Degradation tube was immersed into a thermostatic oil bath controlled to better than ±1 C. HCl evolved was passed into a known volume of standard NaOH solution. HCl evolved was determined by titration after various periods of time. Characterization of Degraded PVC Dehydrochlorinated PVC and PVC powder were characterized by determining their weight loss in thermo gravimetric analysis (TGA) using Perkin Elmer (TGA-7) equipment with temperature (range, ambient to 650 C) and TG measurement (sensitivity of ± 0.2g). Sample was heated from 35 C to 300 C at the rate of 10 C / min with 1 min holding time. Weight loss (%) for best and second best metal soaps in terms of stabilizing ability of epoxidised AO (Fig. 1), and epoxidised ORSBE (Fig. 2) were found out. Oxidative Degradation Thermoxidative degradation studies were carried out at 180 C in air as described for non-oxidative degradation except that rate of dehydrochlorination was not monitored. Degradation was allowed to proceed for 30 and 60 min. After this, degradation tube was allowed to cool and degraded polymer was recovered and stored in the dark. Color Change Color change of all PVC samples before and after degradation was visually compared by placing them on a white paper. Color change of PVC samples during oxidative and non-oxidative degradation was also noted after every 15 min. Results and Discussion Reasonably high iodine values justify selection of oils for epoxidation. Reasonably high amounts of unsaturated fatty acids (oleic, linoleic and linolenic) of oils are capable of undergoing epoxidation. Oxirane numbers of two-epoxidised oils indicate fair amount of epoxidation and introduction of epoxy group. Unsaturation levels of PVC degraded in air (oxidative degradation) at 180 C for 30 min and 60 min (Table 1) presents a comparative account of stabilization action for PVC offered by unepoxidised oils, epoxidised oils and their metal soaps. Elimination of HCl during thermal degradation of PVC leads to formation of olefinic bonds in polymer molecule. Higher iodine value (IV) is an indication of higher degradation. Unepoxidised oils (AO & ORSBE) are found poor stabilizers than their epoxidised derivatives as seen from higher amount of degradation in PVC, containing them as additives, after 30 and 60 min (Table 1). Metal soaps of epoxidised oils exhibited better stabilizing action than those of unepoxidised oils. Among metallic soaps of unepoxidised oils, Cd soap was best followed by Zn for AO, and Cd soap afforded best stabilizing effect followed by Pb for ORSBE. Among metallic soaps of epoxidised oils, Cd soap was best in stabilizing action followed by Zn for epoxidised AO and Cd soap offered best stabilizing action followed by Pb soap for epoxidised ORSBE. Comparative account of non-oxidative degradation studies conducted on thermal dehydrochlorination of PVC carried out at 180 C using metal soaps (3% by wt on PVC) of two oils (Table 2) and identical details of the study carried out using metal soaps of epoxidised oils (Table 3) indicate that at high temperature nonoxidative degradation of PVC under nitrogen atmosphere results in evolution of HCl and this liberation of HCl gas is minimized/ suppressed by addition of stabilizers. Best stabilizer gives least

3 TOLIWAL & PATEL : USING BY-PRODUCTS OF OIL PROCESSING INDUSTRIES FOR PVC 231 conversion (%). Metallic soaps of epoxidised oils offer better stabilizing action than that afforded by metal soaps of unepoxidised oils against non oxidative degradation of PVC, as is evident from cumulative percentage conversion values (mentioned in bracket) obtained after 60 min of degradation. From among metallic soaps of epoxidised oils, Cd salts of both epoxidised oils exhibited best stabilizing action indicated by least % conversion values on PVC against non-oxidative degradation. Ba salts of both epoxidised oils were second best with Fig. 1 TGA of: a) Cd soap of EAO; and b) Zn Soap of EAO respect to stabilizing action on PVC against nonoxidative degradation. Zn salts of both oils exhibited poorest and insignificant stabilization characteristics. These results are in agreement with reported studies 14. Thermo Gravimetric Analysis (TGA) Weight loss (%) values at different temperatures are given for PVC with added metal soaps for EAO (Fig. 1) and EORSBE (Fig. 2), and for PVC (Fig. 3) without any additive during dehydrochlorination studies. PVC

4 232 J SCI IND RES VOL 68 MARCH 2009 Fig. 2 TGA of: a) Cd soap of ORSBE; and b) Zn soap of EORSBE added with metal soaps of EAO after non-oxidative degradation exhibits lowest weight loss up to 250 C for Cd (Fig. 1a) and highest weight loss up to 250 C for Zn (Fig. 1b) soaps of EAO indicating best and poorest stabilization ability respectively. PVC added with metal soaps of EORSBE after non-oxidative degradation exhibits lowest weight loss up to 250 C for Cd (Fig. 2a) and highest weight loss up to 250 C for Zn (Fig. 2b) soaps of EORSBE indicating best and poorest stabilization ability respectively.

5 TOLIWAL & PATEL : USING BY-PRODUCTS OF OIL PROCESSING INDUSTRIES FOR PVC 233 Table 1 Oxidative degradation studies at 180 C of PVC using acid oil epoxidised acid oil, ORSBE, epoxidised ORSBE and their metal soaps Sl No. Additive added to PVC Level of Iodine value of additive degraded PVC after % 30 min 60 min 1 AO EAO Cd soap of AO Cd soap of EAO Pb soap of AO Pb soap of EAO Zn soap of AO Zn soap of EAO Ba soap of AO Ba soap of EAO ORSBE EORSBE Cd soap of ORSBE Cd soap of EORSBE Pb soap of ORSBE Pb soap of EORSBE Zn soap of ORSBE Zn soap of EORSBE Ba soap of ORSBE Ba soap of EORSBE AO = acid oil; EAO = epoxidised acid oil; ORSBE = oil recovered from spent bleaching earth ; EORSBE = epoxidised oil recovered from spent bleaching earth; Iodine value of undegraded PVC = 9.8 Fig. 3 TGA of PVC

6 234 J SCI IND RES VOL 68 MARCH 2009 Table 2 Effect of metal soaps of oils (3% w/w in PVC) on conversion and liberated HCl during non oxidative thermal dehydrochlorination of PVC at 180 C Degradation Cd soap of Pb soap of Ba soap of Zn soap of time, min AO ORSBE AO ORSBE AO ORSBE AO ORSBE a (0.9) b 6.02 (1.6) 4.23 (1.2) (2.1) 3.26 (1.0) 8.4 (2.1) 9.62 (3.6) 9.31 (2.4) (1.6) (1.7) 5.20 (1.9) (2.2) 5.20 (1.9) (2.6) (4.1) (2.8) (1.7) (1.9) (2.3) (2.4) (2.1) (3.1) (4.8) (3.3) (2.2) (2.2) (2.6) (3.8) (2.3) (3.9) (5.2) (4.1) a = % conversion; b = HCl liberated Table 3 Effect of metal soaps of epoxidised oils (3% w/w in PVC) on conversion and liberated HCl during non oxidative thermal dehydrochlorination of PVC at 180 C Degradation Cd soap of Pb soap of Ba soap of Zn soap of time, min AO ORSBE AO ORSBE AO ORSBE AO ORSBE a (1.0) b 4.10(1.5) 1.87(1.1) 3.83(1.4) 4.26(1.8) 5.75(2.1) (1.2) 8.49(1.6) 3.83(1.4) 8.76(1.8) 6.02(2.2) 12.05(2.3) (2.0) 13.15(1.7) 9.04(1.9) 13.97(2.1) 13.42(2.7) 19.17(2.6) (2.1) 18.01(1.8) 15.06(2.2) 19.72(2.4) 21.91(3.1) 21.12(2.9) a = % conversion; b = HCl liberated Conclusions Epoxidised oils are better stabilizers than nonepoxidised oils for PVC. Metallic soaps of epoxidised oils are better in action than the metallic soaps of unepoxidised oils in terms of stabilizing effect. Among metallic soaps, Cd soap, of both epoxidised oils exhibited best stabilizing characteristics on PVC. References 1 Sogbaike C E & Okieimen F E Evaluation of epoxidised jatropha seed oil as thermal stabilizer for poly vinyl chloride, J Oil Technol Assoc India, 39 (2003) Aigbodin A I & Okieimen F E, Estimation of dilute solution viscosity parameters of rubberseed oils alkyds, J Rubb Res Inst, 75 (1995) Aigbodin A I & Okieimen F E, Kinetics of the preparation of rubber seed oil alkyds, Eur Polyl J, 32 (1996) Okieimen F E & Aigbodin A I, Studies in molecular weight determination of rubber seed oil alkyds, Ind Crops Products, 6 (1997) Okieimen F E & Aigbodin A I, Kinetics of the preparation of melon seed oil alkyds, J Appl Polym. Sci, 60 (1998) Sogbaike C E & Okiimen F E, Investigation of oxirane ring opening reaction in epoxidised rubber seed oil alkyds, J Oil Techno. Assoc India, 35 (2003) BIS: 548, Part I, Methods of sampling and tests for oils and fats (Bureau of Indian Standards, New Delhi) BIS: 548, Part III, Analysis of gas liquid Chromatography (Bureau of Indian Standards, New Delhi) Joglekar M V, Momin S A & Subrahmanyam V V R, Butter- Like products from indigenous hard fats, J Oil Technol Assoc India, 20 (1990) French W H, A facile synthesis of aminohydroxy triglycerides from new crop oils, US Pat 3, 360, 531 (to Ashland Oil and Refining Co.) (1971). 11 Xiaoguang Z, Zhimin D, Manufacture of non toxic epoxidised soyabean oil plasticizers for food packaging, Chem Abstr, 110 (1989) American Oil Chemists Soc, Official and Tentative Methods, Method Cd-9-57 (AOCS, USA). 13 Odilora C A, Thermal stabilization of PVC with khaya seed oil, Acta Polymerica, 40 (1989) Benaniba M T, Delhaneche-bensemra N & Gelbard G, Stabilizing effect of epoxidised sunflower oil on the thermal degradation of poly vinyl chloride, Chem Abstr, 136 (2002)