blended with HEFA in different ratios to prepare water based stoving compositions. Certain ... oils3-8 in water based coating formulations and malenized soyabean oil for other .... product was washed with water to remove free maleic anhydride. .... 17 BIS: 354, Methods of Sampling and tests for resin for paints. (Bureau of ...
Journal of Scientific & Industrial Research TOLIWAL et al: WATER-SOLUBLE BINDER SYSTEM FROM SOYABEAN OIL Vol. 67, February 2008, pp.141-146
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Water-soluble binder system from by product of refining of soyabean oil S D Toliwal*, C J Patel and Kalpen Patel Department of Industrial Chemistry, Institute of Science and Technology for Advanced Studies and Research (ISTAR), Vallabh Vidyanagar 388 120 Received 23 April 2007; revised 23 November 2007; accepted 30 November 2007 Oil recovered from spent bleaching earth (ORSBE), which is used for bleaching of soyabean oil, has been malenized at 210°C using three different mole ratios of oil and maleic anhydride till desirable acid value of resultant product is achieved. Malenized products were neutralized with triethylamine to make them water compatible. N, N-Bis (2-hydroxy ethyl) fatty amide (HEFA) was prepared by reacting ORSBE with diethanolamine using zinc oxide as catalyst. Water compatible malenized products were blended with HEFA in different ratios to prepare water based stoving compositions. Certain compositions had comparable performance with water based alkyd-HEFA compositions. Keywords: HEFA, Oil recovered, ORSBE, Spent bleaching earth, Soyabean oil, Water-soluble binder system
Introduction Water borne coatings1 are increasingly being used for decorative and industrial coating applications. Malenized drying oils are used for manufacture of water-reducible formulations for coatings2. Maleic anhydride can be reacted with unsaturated oils to produce maleic anhydride adduct. Pendent acid group can be neutralized with ammonia or amines to yield water-soluble oils (Fig. 1). Application of malenized oils3-8 in water based coating formulations and malenized soyabean oil for other applications9-10 are reported. Use of N, N-Bis (2-hydroxy ethyl) fatty amide (HEFA) as environment friendly substitute for conventional cross-linking agents for coating system has also been reported11-13. Vegetable oil processing generates large quantities of by-products14 like gums, soap-stock, acid oil and spent bleaching earth (oil, 30-35% dry wt basis). Oil associated with spent bleaching earth, being costliest component of bleaching, needs to be recovered as much as possible though it degrades in quality during the process of recovery. Oil recovered from spent bleaching earth (ORSBE) for soyabean oil is a by-product of semidrying nature, high in linoleic acid and similar in chemical composition with soyabean oil except physico-chemical *Author for correspondence E-mail: toliwalsd@ yahoo.co.in
characteristics. It can, therefore, be maleic modified for possible value added applications in water borne coatings. It can also be derivatized to HEFA, which could possibly be used as eco-friendly curing agent to substitute traditional toxic volatile cross linking agents for water-based coating formulation. In this study, water-based stoving compositions have been prepared using water compatible malenized products blended with HEFA. Materials and Methods Materials
ORSBE was procured from refining unit of Adani Wilmar Limited, Mundra (Gujarat). Physico-chemical analysis15 of oil gave: sp gr30°C, 0.913; acid value, 46.26; iodine value, 92.01; and sponification value, 188.63. Fatty acid composition16 of ORSBE was found to be: palmitic, 12.33; stearic, 2.1; oleic, 42.0; linoleic, 33.1; linolenic, 0.3; arachidic, 0.2 %. Commercial grade of conventional water soluble alkyd (CWSA), used as reference was medium oil soya based alkyd with pendent acid functionality in backbone of polymer, procured from Usha coatings, V U Nagar, (Gujarat) and its physical properties were determined as per BIS methods17 as: color (Gardner) 9; solids, 51.2% and acid value, 71.3. All other chemicals were of laboratory grade.
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(A C
C
CHCH2C
CH2C
CHC
C
C
Conjucated carban
Non conjucted unsatuarted carban atom
CH2C
CHC
C
+
C
Conjucated carban
C O
C
C
C O
O
Maleic anhydride O (B) H2C
OCOR
HC
OCOR
+ HN
CH2CH2OH
H2C OCOR Oil
C
C
C
C
O maleic adduct
O CH2CH2OH
ZnO
R C
200
C
C
C
N
CH2CH2OH
+
CH2CH2OH
Diethanolamine
O
CH2 OH CH2 OH CH2 OH Glycerol
(C
C2H
+ COO
COO
3N
COO
C2H
COON+(C2H5)
COON+H(C H5)
(D
COO
C2H
COON+(C2H5)
O COO
+
COO
R C
N
CH2CH2OH CH2CH2OH
O COO
C
O
CH2CH
N C
R
CH2CH2O
Fig. 1—Reaction scheme for: (A) Malenization of unsaturated oil; (B) Preparation of HEFA; (C) Neutralization of malenized oil; (D) Curing reaction Preparation of HEFA 18
Oil and diethanolamine (1:1) were taken in a threenecked flask and heated at 190 ± 5°C using 0.02 M zinc oxide as catalyst with constant stirring for 3 h. Temperature was raised to 200°C and maintained till
methanol solubility test19. Samples were periodically withdrawn with a siphoning device to study progress of reaction by TLC technique. Heating was stopped when sample (1 vol) got mixed with methanol (2 vols) at room temperature. After cooling, product was extracted with
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TOLIWAL et al: WATER-SOLUBLE BINDER SYSTEM FROM SOYABEAN OIL
diethyl ether and washed 2-3 times with distilled water to separate glycerol and unreacted amine. Ether extract was dried over anhydrous sodium sulphate, filtered and ether removed. Product was cooled and stored in anhydrous condition at room temperature. Physicochemical analysis of HEFA gave: sp gr 30°C, 0.91; viscosity25°C (Gardner), 4.0 poise; acid value, 2.42; and nitrogen content, 3.02 (practical) and 4.86 (theoretical) %(wt basis). Malenization of ORSBE
Oil and maleic anhydride20 were taken in three-necked flask and heated at 200-210°C under constant agitation for 3 h. Reaction mass was cooled below 50°C and product was washed with water to remove free maleic anhydride. Three sets of malenized oil were prepared (Table 1).
Neutralization of Malenized Oil with Triethyl Amine
Malenized oil was neutralized with triethyl amine (TEA) to get solubility (Table 1). Neutralized mass was diluted (50% solids) using isopropyl alcohol (10%) and water (40%). Preparation and Characterization of Stoving Compositions
Diluted solution (50%) of neutralized malenized oil was blended with water soluble HEFA in four proportions (85:15, 80:20, 75:25 and 70:30, wt basis) and resulting mixture was diluted (40% solids) and applied on test panels. Similarly, stoving composition was prepared using CWSA: HEFA (75:25) and applied on test panels. Coated panels were stoved at 120°C for 45 min for complete curing of the films. Coatings were tested for non-volatile matter, viscosity, specific gravity, color and drying and curing characteristics as per BIS methods21 (Table 2). IR spectrum of HEFA, malenized
Table 1 – Composition and chemical characteristics of malenized ORSBE Composition code
Mole ratio of ORSBE: maleic anhydride
Free* Acid value (unreacted) maleic anhydride malenized oil %
Amount of TEA required for (100 g)
Set I 1.0: 1.0 10.18 110.33 Set II 2.0: 1.0 15.32 78.10 Set III 3.0: 1.0 16.01 46.32 * On the basis of maleic anhydride taken for the reaction
19.23 10.24 8.53
Table 2—Physical properties of malenized ORSBE-HEFA based stoving composition Set No.
I
II
III
Ratio oil: ORSBE
Non-volatile matter (120oC/2h) %
Viscosity by
Color
Sp.gravity
FCB IV at 30oC
(Gardner)
at 30oC
85:15 80:20 75:25 70:30
50.07 49.36 46.28 42.13
186 sec 180 sec 166 sec 140 sec
14 13 12 12
1.02 1.04 1.06 1.06
85:15 80:20 75:25 70:30
51.24 48.13 44.26 41.18
190 sec 172 sec 160 sec 148 sec
13 12 12 13
1.00 1.00 1.04 1.05
85:15 80:20 75:25 70:30
48.33 45.11 41.06 40.23
188 sec 182 sec 174 sec 153 sec
14 13 12 12
1.02 1.04 1.06 1.06
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Table 3–Stoved film properties of the stoving compositions Chemical resistance unaffected Set No
I
II
III
IV
Ratio Oil- HEFA
Scratch Hardness kg (Passes)
Impact resistance lb.inches (Passes)
Flexibility 1/8 “ mendral
NaOH (3 %) 2h
HCl (5 %) 24 h
Xylene 72 h
Water 48 h
85:15 80:20 75:25 70:30
1.000 1.200 1.400 1.500
55 50 55 60
P F F P
0 2 3 4
1 2 4 5
3 2 2 5
2 4 3 4
85:15 80:20 75:25 70:30
1.150 1.250 1.350 2.000
50 35 55 65
P F F P
0 1 3 3
2 3 3 4
2 3 1 5
5 4 2 4
85:15 80:20 75:25 70:30
1.400 1.600 1.700 2.200
60 45 50 70
P F P P
0 1 3 5
2 4 3 5
3 3 4 4
0 3 4 5
CWSA
2.500
76
P
5
4
3
5
P = Passes the test; F = Fails; 0 = Film completely removed; 1 = Slight swelling & cracking; 2 = Film partially cracked; 3 = loss in gloss; 4 = slight loss in gloss; 5 = unaffected
Fig. 2—IR spectrum of HEFA
ORSBE and malenized ORSBE and HEFA cured film was determined (Fig. 2). Cured films were evaluated for flexibility, scratch hardness, impact strength and resistance to chemicals, water and solvent (Table 3).
Results and Discussion Mechanical Properties
Scratch hardness is found to be better with higher HEFA ratio for all the experimental sets due to more
TOLIWAL et al: WATER-SOLUBLE BINDER SYSTEM FROM SOYABEAN OIL
145
Fig. 3—IR spectrum of malenized ORSBE
Fig. 4—IR spectrum of cured film
cross-link density22 and better integrity of the film. CWSA based coating showed satisfactory scratch hardness. Flexibility and impact resistance are better for compositions with higher oil content and unsatisfactory with higher HEFA ratio, due to plasticizing effect of oil in the film. CWSA based coating exhibited good flexibility and impact resistance.
resistance due to higher cross linking. Like-wise, acid resistance of compositions for set I to III was reasonably satisfactory. Sets II and III were superior to set I compositions in overall properties of chemical resistance, may be due to higher acid value of set I than those of sets II and III. CWSA based coating showed good alkali and acid resistance.
Chemical Resistance
Solvent and Water resistance
Alkali resistance was inferior in low oil containing compositions due to less cross-link density resulting in a permeable film, while compositions with oil: HEFA [set I (70:30); set II (75:25)] showed good alkali
Sets II and III with higher HEFA show better solvent resistance due to better film curing supported by IR spectra. Water resistance was found to be better with Oil: HEFA (70:30). Sets II and III show better
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J SCI IND RES VOL 67 FEBRUARY 2008
performance as compared to set I due to less acidity, which makes them less polar and less prone to attack by water molecules. CWSA based coating showed very good water and solvent resistance.
3 4
5 IR Spectrum
A strong adsorption band (1464.68 cm -1) in IR spectrum of HEFA can be attributed to tertiary amide. A strong adsorption (2854.55-3008.55 cm-1) may be due to –C-H stretching. A broad band (3389.63 cm -1) may be due to free –OH group. IR spectrum (Fig. 3) of malenized ORSBE at 1743 cm-1 is attributed to ester stretching vibrations. Bands at 2858 and 2939 cm-1 are attributed to (C-H stretching) alkane, which is due to fatty chain of oil. Band at 1775 cm-1 is due to anhydride stretching vibrations, which confirms acid anhydride ring structure in malenized oil. IR spectrum (Fig. 4) of cured film shows characteristic bands at 1340 and 1407 cm-1 for aryl nitrogen stretching, which reveals incorporation of HEFA in polymer network of cured film. The band (1561 cm-1) showed presence of secondary amides, resulting from reaction between HEFA and malenized ORSBE, supporting curing of HEFA and malenized oil film. Disappearance of band at 3389.63 cm-1 from IR spectrum of HEFA (Fig. 2) due to –OH group supports participation of –OH group of HEFA in curing reaction. Conclusions Stoving composition with oil: HEFA (70:30) exhibits better overall properties. Performance of some coatings has been found very similar to those of conventional water based alkyd coatings and therefore can be recommended for use in industrial finishes, where good mechanical properties with mild chemical resistance are required.
6
7 8
9
10
11
12
13
14 15 16 17 18
19
References 1
2
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