Chain Stop Alkyds from Solvent Fractionated Aregemone and Rubber Seed Oils

Transcription

1 Journal of Scientific & Industrial Research Vol. 59 October 2000, pp Chain Stop Alkyds from Solvent Fractionated Aregemone and Rubber Seed Oils A K Dighe, S D Toliwal* and R R Khotpal* * Department of Industrial Chemistry, Institute of Science and Technology for Advanced Studies and Research (ISTAR), Vallabh Vidyanagar , India Revised received: 07 April, 2000; accepted: 04 July, 2000 The solvent fractionation of non-traditional oil s like argemone and rubber seed in hexane and ethyl acetate, respectively is reported. The high iodine value (liquid) fraction is desolventized by distillation, and the oil so obtained is saponified and acidulated to get mixed fa tty acids with high iodine value. The use of these high iodine value fatty acids for making chain stop alkyds is reported. The properties of sample alkyds have been compared with those of standard soya fatty acids based alkyds. Fairly good results have been found. Introduction The non-traditional oils of semi drying type like argemone and rubber seed, vary considerably in their drying properties. The poor drying properties result from the presence of appreciable amounts of saturated fatty acids and the fact that the unsaturated acids present dry only slowly. The proportion of unsaturated acids can be increased by a process known as segregation. These acids can be used to replace the vegetable oil fatty acids in whole or in part, in some types of alkyds. Improved drying properties are obtained by fractionation of oils by means of liquid-liquid fractionation. Segregated soybean and I in seed perform better as coating vehicle than unmodified oils but are not used due to unfavourable economics. But cheap and plentiful non-traditional oils like argemone and rubber seed can be improved for their drying characteristics by separating from them slow or poor drying triglycerides so that value added products isolated from them can be used for speciality alkyds 1 Chain Stop Alkyd Resins Chain stop alkyd resins are produced by incorporation of benzoic acid or para-tertiary-buty- *To whom all correspondence should be addressed. **Department of Oil & Paint Technology, LIT, Nagpur, Indi a benzoic acid (ptbba) to reduce the functionality of the system to control polymerization. The hi gh functionality is due to high dose of pentaerythritol (functionality = 4) to confer hardness and robust mechanical strength comparable to those of NC (nitro cellulose) laquers and stoving enamels. The added mono functional acid reacts with the hydroxyl groups of the pentaerythritol, preventing further chain extension. In this way, the molecular weight (and hence viscosity) of the resins is effectively controlled (so the name chain stop alkyds). Para-tertiary butyl benzoic acid is frequently used as mono functional acid because of the improved film hardness properties which it confers. Chain-stop alkyds resins are used in rapid air-drying finishes and industrial stoving finishes. Methods and Materials Analysis of Oils The argemone oil was purchased from the local market whereas the rubber seed oil was procured from Kerala. The oils were analysed for their physicochemical characteristics by standard BIS methods 2. All the other materials used for the study were of laboratory grade.

2 DIGHE eta/.: CHAIN STOP ALKYDS FROM AREGEMONE & RUBBER SEED OILS 809 Solvent Fractionation of Oils 3 A known volume of oil was taken in a 500-mL beaker and solvent was added to the oil with oil: solvent ratio I : 2 (vol/vol). The beaker was placed inside the chilling cabinet and the solvent solution of oil was cooled to 0 C for 24 h, so as to allow crystallization of low IV (iodine value) fraction. The crystals thus obtained were separated from high I V fraction (liquid phase) by filtration carried out inside the chilling cabinet at a temperature below 5 C to ensure that the solid fraction did not melt during filtration. The filtrate was distilled to recover the solvent. The high I V fraction (liquid phase) which remained in the flask, was collected. The high I V and low I V fractions were weighed and the percentage recovery of each fraction was recorded. The high iodine value fraction was analyzed for iodine value and utilized in the next step. Preparation of Mixed Fatty Acids from High IV Fraction Oil:/ In a I 000-mL round bottom flask, a known volume of high IV fraction of oil was placed and to it an equal amount of 30% alcoholic KOH solution was added and was refluxed on a water bath using air condenser for about 2-5 h. After the completion of saponification reaction, condenser was removed and excess alcohol was distilled off on a water bath. The resultant soap was then di ssolved in di stilled water to make soap solution. This soap solution was then acidified using 1: I H 2 S0 4 solution to effect separation of fatty acids. The material was then transferred to a separating funnel and the aqueous layer was separated out from the organic layer and discarded. The organic layer was then di ssolved in hexane and washed several times with water. Organic layer was dried over anhydrous sodium sulphate and then hexane was distilled off to get mixed fatty acids. These were analyzed for acid value, iodine value, saponification value and moisture content. Processing of Alkyds 5 FAOFA- and SOFA-based Benzoic Acid Modified Chain Stop Alkyd Resins All the ingredients as per Recipe - 1 (Table I ) were charged together in a three-neck flask equipped with a stirrer, and a thermometer and having provision for inert gas sparging and sample checking device. The temperature with constant stirring was raised gradually to 240 C and the reaction was continued until the acid value dropped to less than 15 mg KOH/g and viscosity at 60% solids in xylene was 70 s. In Ford cup No. 4 at 30 C. total processing time was around 7 h. Tne FAOFA and SOFA based alkyds were analyzed for general and film (Air-dried) properties. FRSOFA- and SOFA-based p-tertiary-butyl Benzoic Acid Modified Chain Stop Alkyd Resins Since the Recipe-2 (Table 1) highlighted an early danger of incipient gelation (90.5%) due to hi gh average functionality of the system (2.20), the batch was processed at a temperature of 220 C in xylene as a refluxing solvent. The butyl group in para positi on of para-tertiary-butylbenzoic acid controlled the molecular size of polymer effectively The reaction was continued until acid value dropped to below I 5 and viscosity at 40% solids in IPCL solvent CIX (B.P., C) was between seconds in Ford Cup No.4 at 30 C. the alkyds were analyzed for general and film (air-dried) properties. Testing and Analysis of Products of Fra ctionation and Chain Stop Alkyd Resins The iodine value and percentage yield of products of fractionation were determined. The chain stop alkyds were tested for general properties like Table I - Receipes for alkyd resins Sl No. Ingredients Weight,% FAOFNSOFA Recipe - I Recipe -2 FRAOFNSOFA Phthalic anhydride Benzoic acid Para tertiary- butyl benzoic acid Pentaerythritol Total

3 percent(%) non-volatile, viscosity, acid value, weight per litre, colour and drying and curing characteristics by BIS methods 6. The performance properties I ike adhesion and flexibility, scratch hardness, stripping test, impact resistance, gloss and water resistance of chain stop alkyds were evaluated by BIS methods 7. Results and Discussion The physico-chemical characteristics and fractionation parameters of argemone oil and rubber seed oil are given in Tables 2 and 3, respectively. The results of analysis of fractionation products of argemone oil and rubber seed oil are shown in Table 4 and those of mixed fatty acids made from high iodine value fractions of these oils are given in Table 5, which reveal following salient features: High iodine value and fatty acids composition of the oils selected for study justify their choice for the purpose. By solvent fractionation, the high iodine value fractions in fairly good yields were obtained; it was 94% for AO and 88% for RSO. Table 2- Physicochemical characteristi cs of argemone oil and rubber seed oil Sl No. Characteristics Argemone Rubber seed o il oil Sp. Gravity Acid value (A V) Saponification value (S V) 4 Iodine value (IV) Refractive index For AO, hexane with oil: solvent ratio I : 2 was found to be most effective solvent for fractionation. For RSO, methyl ketone and ethyl acetate with oil: solvent ratio I: 2 were found to be most effective solvent for fractionation but latter was found to be more cost-effective. The fractionation of AO and RSO was also attempted using other solvents like acetone, isopropyl alcohol, ethyl alcohol in different oil: solvent ratios but encouraging results were not found. The properties of benzoic acid modified chain stop alkyds based on FAOFA and SOFA (reference) presented in Tables 6 and 7 highlight the following points: (i) (ii) Table 3 - FAOFA-based alkyd requires longer cooking time than SOFA-based alkyd. FAOFA-based alkyd has less viscosity than SOFA-based alkyd. Fractionation parameters for argemone and rubber seed oi l Fractionation of Argemone oi I Rubber seed oil Solvent used Hexane Ethyl acetate Quantity of oil taken, ml Oil : Solvent ratio, v/v: 1:2 1:2 Solvent recovery, % Temperature, oc 0 0 Time, h 24 24: Table 4- Analysis of fractionation products from argemone oil and rubber seed oil Sl No. Fraction Volume, ml Recovery, % Iod ine value Argemone oi I Rubber seed oi I Argemone oi I Rubber seed oil Argemone oil Rubber seed oil Solid Liquid Table 5- Analysis of mixed fatty acid made from hi gh iodine value fractions of fractionated argemone oi l and rubber seed oil Sl No. Sample Acid value Iodine value Saponification value Moisture content, % 2 FAOFA* FRSOFA I * For abbreviations, see nomenclature

4 DIG HE et al.: CHAIN STOP ALKYDS FROM AREGEMONE & RUBBER SEED OILS 811 Table 6- General properties of SOFA and FAOFA based chain stop alkyd resins Sl No. Characteristics Chain stop alkyd based on Non volatile, % (80% Xylene+ 20% MTO, Pbw) 2 Viscosity, Stokes (27 C) 3 Vi scosity, Ford Cup N0.4 at 29 C, sec 4 Acid Value (100% solid) mg of KOH 5 Wt/L, kg 6 Colour, Gardner 7 Clarity 8 Curing Characteristics : a) Air Drying (Pb = 0.5%, Co= 0.5%, Mn = 0.05%) Surface Dry Hard Dry Track Free Dry b) Staving Schedule 120 C/30 min SOFA(reference) Good- Excellent 25 min 2)12 h 3 h Hard and mar proof film FAOFA to Poor 36 min 3 h 3)12 h Hard and mar proof film Table 7- Air-dried film properties* of SOFA- and FAOFA- based chain stop alkyd resins Sl No. Characteristics Chain Stop alkyd based on SOFA (reference) FAOFA Adhesion (Cross hatch) Passes Passes 2 Scratch hardness after 48 h, kg Passes Passes Flexibility and adhesion after 96 h on \18" mandrel Passes Passes 4 Stripping test after 96 h Flexible film Flexible film 5 Impact test after 48 h No dents No dents 6 Gloss (visual) reflection of tube li ght Di stinct Diffused 7 Water resistance Passes Passes *Testing was done on 6" x 2" tin coated panels and 6" x 2" glass panels (iii) (iv) (v) (vi) FAOFA-based alkyd has darker colour and poorer clarity than that of SOFA-based alkyd. FAOFA-based alkyd has longer drying time than that of SOFA-based alkyd. Both form hard and mar proof film on stoving. Both exhibit fairly good and comparable adhesion. (vii) FAOFA-based alkyd film shows less hardness than that of SOFA-based alkyd. (viii) Flexibility-wise both are at par. (ix) (x) They show reasonable match with respect to impact and water resistance. Diffused and distinct images of tube light reflection on the air-dried film of FAOFAbased alkyd and SOFA-based alkyd,

5 812 J SCIIND RES VOL 59 OCTOBER 2000 Table 8- General properties of SOFA and FRSOFA, para-tertiary butylbenzoic acid modified chain stop alkyds Sl No. Characteristics Chain stop alkyd based on Non-volatile, % 2 Viscosity at 27 C, Stokes 3 Viscosity at 29 C, Ford Cup No.4, sec 4 Acid value (100% solid) mg of KOH 5 Wt/L, kg 6 Colour, Gardner 7 Clarity 8 Curing Characteristics : a) Air Drying (Pb = 0.5 %, Co= 0.5%, Mn = 0.05%) Surface Dry Hard Dry Track Free Dry b) Staving Schedule 120 C/30 min SOFA (reference) Excellent 30 min 2V! h 3h Hard and mar proof fi lm FRSOFA Good lh 4h Hard and mar proof film Table 9- Air-dried film properties* of SOFA and FRSOFA para-tertiary butylbenzoic acid modified chain stop alkyd resins Sl No. Characteristics Chain stop alkyd based on SOFA FRSOFA Adhesion (cross hatch) Passes Passes 2 Scratch hardness after 48 h, kg Passes Passes Flexibility and adhesion after 96 h on Ys" mandrel Passes Passes 4 Stripping test after 96 h Flexible lilm Flexible film 5 Impact test after 48 h No dents No dents 6 Gloss (visual) reflection of tube light Distinct Diffused 7 Water resistance Passes Passes *Testing was done on 6" x 2" tin coated panels and 6" x 2" glass panels respectively show poor gloss for FAOFA film relative to SOFA film. The properties of para-tertiary-butylbenzoic acid modified chain stop alkyd based on SOFA (reference) and FRSOFA enumerated in Tables 8 and 9 emphasize following notable details of significance: (i) (ii) FRSOFA-based alkyd requires longer processing time than SOFA-based alkyd. The viscosity of FRSOFA-based alkyd is a shade lesser than that of SOFA-based alkyd. (iii) (iv) (v) (vi) (vii) FRSOFA-based alkyd possesses darker colour and poorer clarity than SOFA--based alkyd, as revealed by the gloss of the film. The drying time of FRSOFA-based alkyd ts longer than that of SOFA-based alkyd. Both produce hard and mar proof film. Adhesion and flexibility is better in FRSOFA alkyd film than that in SOFA alkyd film. The hardness of FRSOFA-based alkyd is less than that of SOFA-based alkyd.

6 DIGHE et al.: CHAIN STOP ALKYDS FROM AREGEMONE & RUBBER SEED OILS 8 13 (viii) With respect to impact and water resistance both are identical. (ix) Conclusion Diffused and distinct images of tube light reflection on the ai r-dried film of FRSOFAbased alkyd and SOFA-based alkyd, respectively show poor gloss for FRSOFA film relative to SOFA film. It is concluded that the fractionation of argemone oil and rubber seed oil yields high iodine value fractions usable in chain stop alkyds. Since the FAOFA and FRSOFA alkyd compositions give longer cooking and drying time and, less hardness than SOFA-based alkyd compositions, it has been concluded that FAOFA and FRSOFA have somewhat less reactivity than SOFA and can be used as partial replacements for SOFA and also for benzoic acid in the chain stop alkyd formul ations. Alone FAOFA and FRSOFA chain stop alkyds can be used as plasticizing alkyds for thermoplastic resins (nitrocellulose and acrylic lacquers). The hardness can be improved by using paratertiary-butylbenzoic acid in place of benzoic acid for FAOFA-based chain stop alkyd and by increasing the amount of para-tertiary-butylbenzoic acid for FRSOFA-based chain stop alkyd formulations. Acknowledgement The authors are thankful to Dr B P Swadas, Director & Head, ISTAR for his support and encouragement and UGC Regional office Pune, for financing a research project of which the present study was a part. References Daniel Swern, Bailey's Industrial Oil and Fat Products, Vol. I (John Wi ley & Sons, New York) 1985, p BIS : 548 (Part-!) : Methods of Sampling and Test for Oils and Fats (Bureau of Indian Standards, New Delhi). 3 Thomas H Applewhite, Bailey's Industrial Oil and Fat Products, Yol.3 (John Wiley & Sons, New York) 1985, p BIS : 548 (Part-!) : Methods of Sampling and Test for Oils and Fats (Bureau of Indian Standards, New Delhi ), p Oldring P K T & Hayward, A Manual for Resins for Swface Coatings (Sita Technologies, England) 1987, p BIS : : Specification for Alkyd Resins (Bureau of Indian Standards, New Delhi). 7 BIS : : Methods of Sampling and Test for Resins for Paints (Bureau of Indian Standards, New Delh Nomenclature AO = Argemone oil RSO = Kubber seed oil FAOFA= SOFA = FRSOFA= Fractionated argemone oil fatty acids. Soybean oil fatty ac ids Fractionated rubber seed oil fatty acids.