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Preparation and characterization of polymeric dispersants based on vegetable oils for printing ink application
Progress in Organic Coatings 111 (2017) 354–360
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Progress in Organic Coatings journal homepage: www.elsevier.com/locate/porgcoat
Preparation and characterization of polymeric dispersants based on vegetable oils for printing ink application
MARK
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Nadia A. Yossifa, Nadia G. Kandilea, Mohamed A. Abdelazizb, , Nabel A. Negmc a b c
Chemistry Department, Faculty of Women, Ain Shams University, Cairo, Egypt R & D Department, Degla Chemicals, Cairo, Egypt Petrochemicals Department, Egyptian Petroleum Research Institute, Cairo, Egypt
A R T I C L E I N F O
A B S T R A C T
Keywords: Vegetable oils Printing inks Polymeric dispersants Pigment Castor oil
In this work, a novel vegetable oil-based polymers were prepared by epoxidation of soybean oil (SBO) and castor oil (CO) followed by ring opening reaction of epoxidized oil with polyether amine and poly propylene glycol. The prepared polymers were characterized by FTIR and GPC. The properties of vegetable oils and epoxidized vegetable oil (EVO) were studied. The prepared polymers were employed as novel polymeric dispersants for pigment dispersion in solvent based printing ink application. The mechanical and optical properties of prepared ink were studied. The net technical properties of the new ink formulations are relatively comparable to the prepared printing ink from standard polymeric dispersant. The polymeric dispersant 2 (PD2) and polymeric dispersant 4 (PD4) gave the best optical and mechanical properties among the prepared polymers.
1. Introduction The manufacture of printing ink is a technologically advanced, highly specialized and complex process [1]. Preparation of stable, homogeneous and fine dispersion of pigment is not facile because it’s prone to aggregate. The dispersion of pigment is strongly affect the optical properties such as color strength, transparency, gloss and mechanical properties such as adhesion of printed ink film [2–4]. Stabilization of pigment dispersion is usually results from adsorption of dispersing agent molecules from solution onto the particle surface of the pigment creating repulsive forces between the particle in suspension either through electrostatic repulsion or from steric prevention of coagulation. The degree of dispersion of a particle suspension may be defined as the extent to which the individual powder particles become separated from one another in the liquid medium [4–6]. Polymeric pigment dispersants are copolymers with pigment affinic “anchoring groups” and soluble polymeric chains [7,8]. The polymeric dispersants are used to obtain homogeneous dispersion of the pigment in the liquid phase that leads to weak viscosity and allows high pigment loading and high tinting strength [9–11]. Coating and ink additives are used in small quantities; however their impact on coating performance and application can be dramatic. Their judicious use often spells the difference between meeting ultimate performance requirements or failure. There are over two dozen additive types employed in coatings and inks with global sales in 2009 of just over USD 5 billion. The main leading
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Corresponding author. E-mail address: [email protected] (M.A. Abdelaziz).
http://dx.doi.org/10.1016/j.porgcoat.2017.06.005 Received 5 January 2017; Received in revised form 3 June 2017; Accepted 3 June 2017 0300-9440/ © 2017 Elsevier B.V. All rights reserved.
types of these additives are dispersants, foam control agents, rheology modifiers, slip & rub materials, and wetting agents. Global consumption of these five additives in 2009 was 781,000 tons worth USD 3.47 billion. Overall, a 5.5% annual rate of growth is forecast for additives through 2010 [12]. Nowadays there are three groups of polydispersing agents produced by BASF: polyurethane of high-molecular-weight (Efka®4000 Series), and low molecular weight (Efka®5000 and Efka®6000 Series) and polyacrylate polymer dispersants (Dispex®, Pigment disperser and Ultradispers® range). Polyurethanes are the best dispersants for viscosity depression in the mill base. This gives higher pigment loadings, more economical mill base formulations with fewer volatile organic compounds (VOCs). Polyacrylates polydispersants have much wider compatibility in non-polar as well as highly polar systems. They generally have a higher molecular weight, which ensures effective inter-particle separation. Health-related issues, stringent environmental protection policies, search for cost-effective and alternative materials and the quest for renewability, sustainability and high-performance materials for technical applications have led to intense research in the production of renewable polymers from plant seed oils and shift in focus from the petrochemical based polymers [13,14]. Vegetable oils are a part of large family of chemical compounds known as fats or lipids which made up predominantly of triesters of glycerol and fatty acids (Fig. 1) which can be processed into high value oleochemicals for various industries [15,16]. The fatty acids of vegetable oils may be saturated and unsaturated
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2.2. Preparation of polymeric dispersants 2.2.1. Epoxidation of vegetable oil Vegetable oils (50 g) and acetic acid (11.4 mL, in case of castor oil) or formic acid (15 mL, in case of soybean oil) were mixed in a round bottom flask and stirred at 550 rpm under controlled temperature through using a water bath at a temperature of 50 ± 2 °C. To start the epoxidation, hydrogen peroxide 50% solution (26.4 mL) was added drop wisely into the reaction mixture during the first 2 h of the reaction. The molar ratio of the double bonds in the reacted oils (obtained from iodine value of the oil) to hydrogen peroxide (C]C:H2O2) was 1:1.7. After the charging of H2O2 was completed, the reaction continued under mixing and controlling the temperature at 50 °C for a further 5 h then the mixture was cooled to room temperature [41–43]. To purify the epoxidized oil, it was poured into a 500 mL separating funnel and the oil layer was washed successively with 5% sodium carbonate solution (50 mL) and 5% sodium chloride solution (50 mL), respectively. Ethyl acetate (50 mL) was added to enhance the separation of the oily product from the water phase. The water and solvent were then distilled off under a rotary vacuum evaporator; the oil phase was further dried above anhydrous magnesium sulfate and then filtered, (Scheme 1). A series of polymeric dispersants were prepared based on two different types of epoxidized vegetable oils (Epoxidized soybean oil, Epoxidized Castor oil) by conventional epoxidation method followed by ring opening using polyether amine and poly propylene glycol.
Fig. 1. Triglyceride chain containing three fatty acids by a glycerol center.
fatty acids. Castor oil, cottonseed oil, linseed oil, jatropha oil, rapeseed oil and soybean oil are examples on vegetable oils [16,17]. The unsaturation present (double bond) in vegetable oils can be chemically modified to form epoxidized vegetable oils [17–19]. Epoxidation of double bond has been studied in many papers [20–24]. Epoxidation is generally performed using organic peracids formed in situ via the attack of H2O2 on a carboxylic acid in aqueous solution [22]. Due to the high reactivity of the oxirane ring, epoxides can also be used for the synthesis of chemicals like olefinic, carbonyl compounds, alcohols, alkanolamines, glycols and polymers like polyurethanes, epoxy resin, polyesters [23–25]. Since vegetable oils are ecofriendly, sustainable and renewable; both castor oil and soybean oil were the target of this work. Castor oil is obtained from the seeds of the castor oil plant Ricinus. It consists of about 90% ricinoleic acid (12-hydroxy-cis-9-octodecenoicacid) which makes it a very useful for industrial purpose like cosmetics, paints, adhesives, plastics, rubbers, and pharmaceuticals [26–28]. Similarly, the major fatty acid in its chemical structure is linoleic acid. Thus these oils were greatly utilized in versatile industrial fields including: coatings, printing inks, adhesives, lubricants and plastics [29–36]. Figs. 2 and 3 represent the structures of castor oil and soybean oil, respectively. Among the various reactions of oxiranes aminolysis is a classical route to β-amino alcohols formation, an important class of compounds with pharmaceutical and biological properties [37]. Many compounds were prepared by the aminolysis of epoxides with amines under basic or acidic catalysts in organic solvents [38–40]. The chemical structure of Jeffamine is represented in Fig. 4. In the present study, we report the synthesis of ecofriendly polymeric dispersant for pigmented ink application by epoxidation of Soybean oil, Castor oil followed by ring opening using polyether amine and poly propylene glycol.
2.2.2. Preparation of polymeric dispersant 1 (PD1) PD1 was prepared by ring opening of epoxidized soybean oil in which epoxidized oil (20 g) was mixed with methanol (1.9 mL) in presence of p-toluene sulfonic acid as a catalyst and ethyl acetate (100 mL) as a solvent at 50°C for partially ring opening of epoxidized oil. The partially ring opened epoxidized oil was cool down, Jeffamine M-2005 (40 g) was added and the temperature was raised to 75−80°C in presence of ZnCl2 as a catalyst. The reaction mixture was left for 4 h then cooled to room temperature [44]. The prepared polymer was purified by filtration of solid catalyst. The excess ethyl acetate was distilled by vacuum distillation to obtain product of approximately 100% solid content. 2.2.3. Preparation of polymeric dispersant 2 (PD2) PD2 was prepared using epoxidized soybean oil (10 g) following the previous method for preparation of PD1, but using jeffamine M-2005 (20 g) for ring opening of the epoxidized oil [23].
2. Experimental 2.1. Materials
2.2.4. Preparation of polymeric dispersant 3 (PD3) PD3 was prepared by ring opening of epoxidized soybean oil (10 g) using polypropylene glycol (20 g), where epoxidized soybean oil and polypropylene glycol were mixed in 250 mL round bottom flask in the presence of p-toluene sulfonic acid as a catalyst at a temperature of 110°C for 8 h; ethyl acetate (100 mL) was added to the reaction mixture as a solvent [49]. The prepared polymer was filtered and washed by water to remove the catalyst. The excess water and ethyl acetate was distilled by vacuum distillation to obtain product of approximately100% solid content.
Chemicals were obtained as follows: polyether amine Jeffamine M2005 (MW = 2000 g/mol) (Huntsman-Belgium), polypropylene glycol (Invista Specialty Chemicals), castor oil (CO) and commercial cookinggrade soybean oil (SBO) (a local market), ethyl acetate and methanol (Petrochem-KSA), hydrogen peroxide 50% (Piochem), zinc chloride, magnesium sulfate and p-toluene sulfonic acid (Oxford), formic acid, acetic acid, sodium chloride, sodium carbonate (ADWIC-Egypt).
2.2.5. Preparation of polymeric dispersant 4 (PD4) PD4 was prepared by ring opening of epoxidized castor oil (ECO) where ECO (10 g) was mixed with Jeffamine M-2005 (20 g) in 250 mL round bottom flask in the presence of ZnCl2 as a catalyst at 60–70°C for 4 h. Ethyl acetate (100 mL) was added to the reaction mixture as a solvent [23]. The prepared polymer was purified by filtration of solid catalyst, and the excess ethyl acetate was distilled using vacuum distillation to obtain a product of approximately 100% solid content.
Fig. 2. Major triglyceride of castor oil.
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Fig. 3. Major triglyceride of soybean oil.
Table 1 Formulation of printing ink.
Fig. 4. Chemical structure of jeffamine M-2005.
Component
Weight%
Nitrocellulose varnish Pigment Cyan 15:3 Plasticizer (ATBC) Polymeric dispersant Ketonic resin Ethanol Ethyl acetate Total weight
30 g 12 g 3.5 g 1.5 g 5g 15 g 33 g 100 g
2.4. Printed ink characterization 2.4.1. Ink formulation The printing ink was formulated according to the formulation given in Table 1. The ink formulation was prepared by mixing varnish (nitrocellulose), Cyan 15:3 pigment, Acetyl Tributyl Citrate plasticizer, prepared dispersants, ketonic resin (cyclohexanone-formaldehyde resin), ethanol and ethyl acetate as solvents. The components were placed in a mixer with the pointed amounts in Table 1 and mixed for suitable time to obtain a homogeneous matrix.
Scheme 1. Reactions of epoxidation of oils with peracid formed in situ.
2.2.6. Titration of epoxy equivalent The extent of epoxy groups formed during the preparation steps of the different dispersants was determined according to AOCS Cd 9-57 standard method by using hydrogen bromide and acetic acid. The equivalent of oxirane content in epoxidized castor oil was 2.6 g/100 g; and 6.1 g/100 g epoxidized soybean oil.
2.4.1.1. Printed film thickness. The ink formulation was applied on polypropylene film (thickness 25 μ) using hand coater. The printed film thickness was measured by measuring the thickness of 10 sheets of plastic before and after printing. Then the average thickness of the printed film was calculated. The thickness was measured using KAFER micrometer (accuracy ± 0.1 μ) and was found to be 3 μ for all ink samples.
2.3. Characterization of the prepared additives 2.3.1. Acid value Acid value was determined according to DIN EN ISO 660 (Animal and vegetable fats and oils–determination of acid value and acidity).
2.4.1.2. Curling. The curling of the polypropylene printed ink film was carried out according to (ASTM D4825-97).
2.3.2. Iodine value Iodine value was determined according to DIN EN ISO 3961 (Animal and vegetable fats and oils-Determination of iodine value).
2.4.1.3. Adhesion. Adhesion was measured according to (EN 15386:2007) and examined visually for the detached ink from the printed film. −sensitive tape is applied over the lattice and then removed, and adhesion is evaluated by comparison with descriptions in method.
2.3.3. FTIR analysis FTIR spectra were conducted using Bruker FTIR analyzer; ALPHAPlatinum FT-IR Spectrometer with ATR Platinum–Diamond sampling module from 4000 to 400 cm−1.
2.4.1.4. Stability test. Stability test of ink was performed according to (ASTM D 1849–95). The stability test measures the variation happened for the color of the printed film after certain time. The time of the stability test according to the ASTM standard is after 24 h of printing the colored film on the substrate. In this study, the stability test was measured after 15 min and 24 h, that is to follow the change in the film after short and long times.
2.3.4. Molecular weights determination The molecular weights were determined using GPC Agilent model 1515 pump system equipped with 1260 infinity refractive index detector and using THF as eluent, operating with a flow rate of 1.00 mL/ min at 35°C. Column PL-gel 3 Lm Mixed E 300 7.5 mm covering a molecular weight range of 600–400,000 mg/g was used and was calibrated using polystyrene standards.
2.4.1.5. X-rite measurements (Relative color strength* –Transparency). Printing ink strength, lightness and shade were ΔEab measured using EXACT–PANTONE X-rite spectrophotometer according to ASTM D 2244-02 standard, where; ΔE represents the differences between samples and standard in these three parameters L*, a*, b*.
2.3.5. Water content Water content was determined using the Karl Fischer Titrator model Metrohm 870 Titrino plus according to (DIN EN ISO 8534). 2.3.6. Solubility in common solvents The test was performed for the prepared polymeric dispersant in which a 50:50 solution was prepared from the polymer and common solvents are ethyl acetate, ethanol, isopropanol and toluene.
2.4.1.6. Gloss. The gloss of the printed film was measured on the printed polypropylene film using BIUGED BGD 514 (60 ͦ) gloss meter according to ASTM D 2457-03 standards. 356
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(ESBO) and epoxidized castor oil (ECO). The formation of the epoxy groups in the oil molecules was indicated by the appearance of absorption bands at 843 and 824 cm−1. The groups which did not incorporate in the epoxidation reaction were: C]O ester groups and the hydroxyl groups of the triglycerides which present at 1743 and 3460 cm−1, respectively. FTIR spectra of the prepared polymeric dispersants (PD1-PD4) were represented in Fig. 7. It is clear in Fig. 7 the appearance of the characteristic bands of Jeffamine® M2005: at 2875 cm−1 and 2970 cm−1 for symmetric and asymmetric stretching vibrations of CeH groups, respectively; 1450 cm−1 and 1370 cm−1 assigned for the bending vibrations of CeH groups, respectively; 1090 cm−1 assigned for ether CeOeC band of Jeffamine® M2005; 1743 cm−1 assigned for stretching of C]O ester groups of the triglyceride; and a signal at 3458 cm−1 assigned for the stretching vibration of the hydroxyl group, OH). The molecular weights of the prepared compounds and their starting materials (as they are obtained from the local market) were determined in terms of the number average molecular weight (Mn) and molecular weight polydispersity index (PDI) using Gel Permeation chromatography (GPC), Table 4. Data in Table 4 showed that the formation of the different polymeric dispersants is preceded by the reaction of one Jeffamine molecule and/ or polypropylene glycol molecule by each epoxide group in the epoxidized triglyceride molecule of the different oils as represented in Fig. 5.
Table 2 Fatty acid distribution of soybean oil and castor oil. Fatty acid%
Palmitic
Stearic
Oleic
Linoleic
Linolenic
Ricinoleic
other
Soybean Castor
11 1
4 1
26 3
52 4.2
7 0.3
– 89.5
– 1
3. Results and discussion 3.1. Characterization of oils Fatty acid composition of the used oils were determined for the free acids obtained from acid hydrolysis of the two oils using silica gel column chromatography using GC-7890A equipped with DB-23 column, 60 mm x 0.25 mm, i.d. of 0.25 μm. The obtained fatty acid compositions of the used oils were in good agreement by the reported data for these oils [45,46]. The fatty acid compositions of the used soybean oil and castor oil were listed in Table 2. Acid value and iodine value of the vegetable oils are two important parameters determine the free fatty acid content and unsaturation degree in the oils, respectively. The reported average acid values of soybean oil and castor oil were 2.85 and 2.76 (mg NaOH/g oil) [47]. While, the average iodine values were 120.6 and 86.3 (g I2/100 g oil) for soybean oil and castor oil [48]. The obtained acid values and iodine values for the soybean oil and castor oil used were in accordance with the published data for castor oil and soybean oil, (Table 3).
3.3. Properties of polymeric dispersant The main properties of the prepared polymeric dispersant which are effective in their processing and application are the solubility in different solvents, solid content (active matter) and their water content. Table 5 represents the characteristic features of the prepared polymeric dispersant (PD1-PD4). The prepared polymeric dispersants are characterized by their dual solubility in the different solvents used in the ink formulations. The good solubility of these dispersant in the different solvents can be attributed to their chemical structures. The fatty acid moieties in their chemical backbone are responsible for their solubility in the organic solvent (toluene), while the solubility in the polar solvents comes from the presence of the nonionic chains either the polypropylene glycol or Jeffamine M-2005. The solid contents of the prepared polymeric dispersants are ranged between 96.5% and 99.8%. These high values are economically important during the preparation of ink formulations. Similarly, the results showed the low water content of the prepared polymeric dispersants (PD1-PD4).
3.2. Characterization of the polymeric dispersants and intermediates The reaction between the oils and the hydrogen peroxide involves formation of oxirane ring as a result of the reaction between the double bonds and the active oxygen in a neucleophilic attack reaction, Scheme 1. The formation of the polymeric dispersants proceeded by the ring opening of the oxirane rings of ECO and ESBO via hydrolysis reaction to obtain the four dispersants (PD1-PD4) is represented in Fig. 5. FTIR spectra of the prepared epoxidized oils are represented in Fig. 6. The chemical structure of soybean oil comprises five double bonds of linoleic and oleic acid moieties compared to the castor oil which contains three double bonds of three ricinoleic acid moieties. Epoxidation of the castor oil and soybean oil produces epoxidized products of the two oils. FTIR spectra of the two epoxidized oils (ESBO and ECO) (Fig. 6) showed the characteristic absorption bands of the oxirane rings in both epoxidized products. It is clear that the intensity of the two absorption bands at 846 cm−1 and 824 cm−1 in case of the epoxidized soybean oil (ESBO) is higher than those of epoxidized castor oil (ECO), indicating the higher content of oxirane groups formed in soybean oil. This result was confirmed by the equivalent epoxy titration of the oxirane contents of ESBO and ECO. The titration of epoxy groups equivalents in epoxidized castor oil showed lower content of oxirane rings formed during the epoxidation of castor oil (2.6 g/100 g ECO) compared to the oxirane rings formed during the epoxidation of soybean oil (6.1 g/100 g ESBO). Fig. 7 represents the FTIR spectra of the prepared polymeric dispersants (PD1-PD4) which showed the disappearance of the absorption bands of C]C-stretch at 3009 cm−1 in the fatty acids moieties, which demonstrates the conversion of the double bond of the oils to the epoxy group during the epoxidation reaction to obtain epoxidized soybean oil
3.4. Printed film properties The printing ink was formulated according to the formulation given in Table 1. All ink formulations were mixed and then were applied on polypropylene film using hand coater. The mechanical properties of the printed inks represent the physical behaviors of the printed ink film on the substrate. The two main important mechanical properties of the printed inks studied were the curling and the adhesion. The curling is the deformation of the printed substrate after printing the ink film. The adhesion of the printed film is defined as the detachment of the printed ink film from the printed substrate. It is clear from results listed in Table 6 that the ink formulations which formulated by using the prepared dispersants (PD1-PD4) have no curling. That is in a good agreement with the properties of the used standard (STD 340C). The adhesion properties of the ink formulations were varied between A and B, A: shows no removal of the ink film formed; B: shows less than 5% ink removal after printing and drying. After 15 min of printing, the ink formulations which formulated using PD1, PD2 and PD4 dispersants showed stable ink formulations during the printing on the polypropylene film surface. After 24 h of printing,
Table 3 Acid and iodine values of the used oils. Oil
Acid value, mg NaOH/g
Iodine value, g I2/100 g
Soybean oil Castor oil
1.42 1.98
125.8 84.6
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Fig. 5. Chemical structures of the prepared dispersants.
The optical properties of the printed ink film describe the interaction between the visible light and the ink film on the substrate. The measured optical properties of the ink films printed on the polypropylene film were: transparency, ΔS, ΔE and Gloss. The transparency defines the ratio between the amount of light transmitted through the
the printed films were in comparable to the printing film formulation which formulated using the standard (340C). Ink formulation formulated using PD3 dispersant showed ≈5% ink removal from the printed film after 24 h, while the others dispersants retain their adhesion stability compared to the results obtained after 15 min.
Fig. 6. FTIR spectra of soybean oil (SBO), castor oil (CO), epoxidized soybean oil (ESBO), partially ring opened epoxidized soybean oil (ROESB) and epoxidized castor oil (ECO).
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Fig. 7. The FTIR spectra of polymeric dispersant PD1, PD2, PD3, PD4 and Jeffamine M-2005.
printed ink film formulated using the prepared dispersants and the standard dispersant. The transparency values of the printed films using PD1-PD4 were 98.3, 99.0, 98.3, and 100.0 before stability. These values were decreased by a different degree depending on the type of the dispersant used to be 86.4, 97.8, 96.4, and 96.8, Table 6. It is clear from data in Table 6 that the amount of the JeffamineM2005 in both PD1 and PD2 has no considerable influence on either the mechanical or the optical properties. This showed the role of the vegetable oils structure in the dispersing of the inks. The role of both Jeffamine-M2005 and polypropylene glycol is to enhance the solubility of the dispersants in the formulations, i.e., act as nonionic co-emulsifier. Hydrolysis of the epoxidized soybean oil by jeffamine only or its partial hydrolysis by methanol yields two dispersant with comparable optical and mechanical properties. The ratio of Jeffamine-M2005 has an influence only on the transparency of the printed film using the formulation of PD1 after stability (86.4%) which is lower than those of formulations using PD2, PD3 and PD4. The data reported in Table 6 indicated that polymeric dispersants were prepared successfully by the partial substitution of petroleum polymers with vegetables oil derivative. Castor oil and soybean oil gave very comparable mechanical and optical properties.
Table 4 Gel permeation chromatographic data of the prepared polymeric dispersant. Sample
Mn
Mw
PDI
STD Soybean oil Castor oil Jeffamine PPG2000 PD1 PD2 PD3 PD4
2387 1267 1370 2519 2613 4103 4282 3739 3245
4979 1339 1454 3136 2919 5154 5483 5173 3702
2.08 1.05 1.06 1.24 1.11 1.25 1.28 1.38 1.14
Table 5 Characteristic features of polymeric dispersants. Polymeric dispersant
PD1 PD2 PD3 PD4
Solubility in solvents Ethanol
Ethyl acetate
Toluene
Iso-propanol
S S S S
S S S S
S S S S
S S S S
Solid content
Water content
98.6% 96.5% 99.1% 99.8%
0.12% 0.20% 0.16% 0.11%
4. Conclusions
S: Soluble, P: Partially soluble, I: Insoluble.
The present study demonstrated the preparation of polymeric dispersants based on castor oil and soybean oil via epoxidation of oils Table 6 Properties of printing ink. PD
STD (340C) PD1 PD2 PD3 PD4
Mechanical properties
Optical properties
Curling
Transparency%
No No No No No
Curling Curling Curling Curling Curling
Adhesion
ΔS
ΔE
Gloss, GU
After 15 min.
After 24 h
B*
A*
B*
A*
B*
A*
B*
A*
A A A B A
A A B B A
100 98.3 99 98.3 100.0
100 86.4 97.8 96.4 96.8
100 94.1 94 92.8 92.3
100 91.9 92.1 91.8 92.1
100 1.2 2 2.5 1.2
100 2.5 2.8 2.8 1.9
100 96.7 100 91 100
100 96.5 95.8 87.8 98.2
A: no ink removal; B: less than 5% ink removal. A*: After stability; B*: Before stability.
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followed by ring opening with different ring opening agents such as methanol, polypropylene glycol, and polyether amine. The prepared polymer was used in ink formulation to evaluate its efficiency. The results obtained were evaluated comparing to commercial polymeric dispersant. It indicates that all prepared dispersants show high optical and mechanical properties and high stability for ink before and after stability test. The polymeric dispersant 2 (PD2) and polymeric dispersant 4 (PD4) gave the best results (optical and mechanical) among the prepared polymer.
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Contents lists available at ScienceDirect
Progress in Organic Coatings journal homepage: www.elsevier.com/locate/porgcoat
Preparation and characterization of polymeric dispersants based on vegetable oils for printing ink application
MARK
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Nadia A. Yossifa, Nadia G. Kandilea, Mohamed A. Abdelazizb, , Nabel A. Negmc a b c
Chemistry Department, Faculty of Women, Ain Shams University, Cairo, Egypt R & D Department, Degla Chemicals, Cairo, Egypt Petrochemicals Department, Egyptian Petroleum Research Institute, Cairo, Egypt
A R T I C L E I N F O
A B S T R A C T
Keywords: Vegetable oils Printing inks Polymeric dispersants Pigment Castor oil
In this work, a novel vegetable oil-based polymers were prepared by epoxidation of soybean oil (SBO) and castor oil (CO) followed by ring opening reaction of epoxidized oil with polyether amine and poly propylene glycol. The prepared polymers were characterized by FTIR and GPC. The properties of vegetable oils and epoxidized vegetable oil (EVO) were studied. The prepared polymers were employed as novel polymeric dispersants for pigment dispersion in solvent based printing ink application. The mechanical and optical properties of prepared ink were studied. The net technical properties of the new ink formulations are relatively comparable to the prepared printing ink from standard polymeric dispersant. The polymeric dispersant 2 (PD2) and polymeric dispersant 4 (PD4) gave the best optical and mechanical properties among the prepared polymers.
1. Introduction The manufacture of printing ink is a technologically advanced, highly specialized and complex process [1]. Preparation of stable, homogeneous and fine dispersion of pigment is not facile because it’s prone to aggregate. The dispersion of pigment is strongly affect the optical properties such as color strength, transparency, gloss and mechanical properties such as adhesion of printed ink film [2–4]. Stabilization of pigment dispersion is usually results from adsorption of dispersing agent molecules from solution onto the particle surface of the pigment creating repulsive forces between the particle in suspension either through electrostatic repulsion or from steric prevention of coagulation. The degree of dispersion of a particle suspension may be defined as the extent to which the individual powder particles become separated from one another in the liquid medium [4–6]. Polymeric pigment dispersants are copolymers with pigment affinic “anchoring groups” and soluble polymeric chains [7,8]. The polymeric dispersants are used to obtain homogeneous dispersion of the pigment in the liquid phase that leads to weak viscosity and allows high pigment loading and high tinting strength [9–11]. Coating and ink additives are used in small quantities; however their impact on coating performance and application can be dramatic. Their judicious use often spells the difference between meeting ultimate performance requirements or failure. There are over two dozen additive types employed in coatings and inks with global sales in 2009 of just over USD 5 billion. The main leading
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Corresponding author. E-mail address: [email protected] (M.A. Abdelaziz).
http://dx.doi.org/10.1016/j.porgcoat.2017.06.005 Received 5 January 2017; Received in revised form 3 June 2017; Accepted 3 June 2017 0300-9440/ © 2017 Elsevier B.V. All rights reserved.
types of these additives are dispersants, foam control agents, rheology modifiers, slip & rub materials, and wetting agents. Global consumption of these five additives in 2009 was 781,000 tons worth USD 3.47 billion. Overall, a 5.5% annual rate of growth is forecast for additives through 2010 [12]. Nowadays there are three groups of polydispersing agents produced by BASF: polyurethane of high-molecular-weight (Efka®4000 Series), and low molecular weight (Efka®5000 and Efka®6000 Series) and polyacrylate polymer dispersants (Dispex®, Pigment disperser and Ultradispers® range). Polyurethanes are the best dispersants for viscosity depression in the mill base. This gives higher pigment loadings, more economical mill base formulations with fewer volatile organic compounds (VOCs). Polyacrylates polydispersants have much wider compatibility in non-polar as well as highly polar systems. They generally have a higher molecular weight, which ensures effective inter-particle separation. Health-related issues, stringent environmental protection policies, search for cost-effective and alternative materials and the quest for renewability, sustainability and high-performance materials for technical applications have led to intense research in the production of renewable polymers from plant seed oils and shift in focus from the petrochemical based polymers [13,14]. Vegetable oils are a part of large family of chemical compounds known as fats or lipids which made up predominantly of triesters of glycerol and fatty acids (Fig. 1) which can be processed into high value oleochemicals for various industries [15,16]. The fatty acids of vegetable oils may be saturated and unsaturated
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2.2. Preparation of polymeric dispersants 2.2.1. Epoxidation of vegetable oil Vegetable oils (50 g) and acetic acid (11.4 mL, in case of castor oil) or formic acid (15 mL, in case of soybean oil) were mixed in a round bottom flask and stirred at 550 rpm under controlled temperature through using a water bath at a temperature of 50 ± 2 °C. To start the epoxidation, hydrogen peroxide 50% solution (26.4 mL) was added drop wisely into the reaction mixture during the first 2 h of the reaction. The molar ratio of the double bonds in the reacted oils (obtained from iodine value of the oil) to hydrogen peroxide (C]C:H2O2) was 1:1.7. After the charging of H2O2 was completed, the reaction continued under mixing and controlling the temperature at 50 °C for a further 5 h then the mixture was cooled to room temperature [41–43]. To purify the epoxidized oil, it was poured into a 500 mL separating funnel and the oil layer was washed successively with 5% sodium carbonate solution (50 mL) and 5% sodium chloride solution (50 mL), respectively. Ethyl acetate (50 mL) was added to enhance the separation of the oily product from the water phase. The water and solvent were then distilled off under a rotary vacuum evaporator; the oil phase was further dried above anhydrous magnesium sulfate and then filtered, (Scheme 1). A series of polymeric dispersants were prepared based on two different types of epoxidized vegetable oils (Epoxidized soybean oil, Epoxidized Castor oil) by conventional epoxidation method followed by ring opening using polyether amine and poly propylene glycol.
Fig. 1. Triglyceride chain containing three fatty acids by a glycerol center.
fatty acids. Castor oil, cottonseed oil, linseed oil, jatropha oil, rapeseed oil and soybean oil are examples on vegetable oils [16,17]. The unsaturation present (double bond) in vegetable oils can be chemically modified to form epoxidized vegetable oils [17–19]. Epoxidation of double bond has been studied in many papers [20–24]. Epoxidation is generally performed using organic peracids formed in situ via the attack of H2O2 on a carboxylic acid in aqueous solution [22]. Due to the high reactivity of the oxirane ring, epoxides can also be used for the synthesis of chemicals like olefinic, carbonyl compounds, alcohols, alkanolamines, glycols and polymers like polyurethanes, epoxy resin, polyesters [23–25]. Since vegetable oils are ecofriendly, sustainable and renewable; both castor oil and soybean oil were the target of this work. Castor oil is obtained from the seeds of the castor oil plant Ricinus. It consists of about 90% ricinoleic acid (12-hydroxy-cis-9-octodecenoicacid) which makes it a very useful for industrial purpose like cosmetics, paints, adhesives, plastics, rubbers, and pharmaceuticals [26–28]. Similarly, the major fatty acid in its chemical structure is linoleic acid. Thus these oils were greatly utilized in versatile industrial fields including: coatings, printing inks, adhesives, lubricants and plastics [29–36]. Figs. 2 and 3 represent the structures of castor oil and soybean oil, respectively. Among the various reactions of oxiranes aminolysis is a classical route to β-amino alcohols formation, an important class of compounds with pharmaceutical and biological properties [37]. Many compounds were prepared by the aminolysis of epoxides with amines under basic or acidic catalysts in organic solvents [38–40]. The chemical structure of Jeffamine is represented in Fig. 4. In the present study, we report the synthesis of ecofriendly polymeric dispersant for pigmented ink application by epoxidation of Soybean oil, Castor oil followed by ring opening using polyether amine and poly propylene glycol.
2.2.2. Preparation of polymeric dispersant 1 (PD1) PD1 was prepared by ring opening of epoxidized soybean oil in which epoxidized oil (20 g) was mixed with methanol (1.9 mL) in presence of p-toluene sulfonic acid as a catalyst and ethyl acetate (100 mL) as a solvent at 50°C for partially ring opening of epoxidized oil. The partially ring opened epoxidized oil was cool down, Jeffamine M-2005 (40 g) was added and the temperature was raised to 75−80°C in presence of ZnCl2 as a catalyst. The reaction mixture was left for 4 h then cooled to room temperature [44]. The prepared polymer was purified by filtration of solid catalyst. The excess ethyl acetate was distilled by vacuum distillation to obtain product of approximately 100% solid content. 2.2.3. Preparation of polymeric dispersant 2 (PD2) PD2 was prepared using epoxidized soybean oil (10 g) following the previous method for preparation of PD1, but using jeffamine M-2005 (20 g) for ring opening of the epoxidized oil [23].
2. Experimental 2.1. Materials
2.2.4. Preparation of polymeric dispersant 3 (PD3) PD3 was prepared by ring opening of epoxidized soybean oil (10 g) using polypropylene glycol (20 g), where epoxidized soybean oil and polypropylene glycol were mixed in 250 mL round bottom flask in the presence of p-toluene sulfonic acid as a catalyst at a temperature of 110°C for 8 h; ethyl acetate (100 mL) was added to the reaction mixture as a solvent [49]. The prepared polymer was filtered and washed by water to remove the catalyst. The excess water and ethyl acetate was distilled by vacuum distillation to obtain product of approximately100% solid content.
Chemicals were obtained as follows: polyether amine Jeffamine M2005 (MW = 2000 g/mol) (Huntsman-Belgium), polypropylene glycol (Invista Specialty Chemicals), castor oil (CO) and commercial cookinggrade soybean oil (SBO) (a local market), ethyl acetate and methanol (Petrochem-KSA), hydrogen peroxide 50% (Piochem), zinc chloride, magnesium sulfate and p-toluene sulfonic acid (Oxford), formic acid, acetic acid, sodium chloride, sodium carbonate (ADWIC-Egypt).
2.2.5. Preparation of polymeric dispersant 4 (PD4) PD4 was prepared by ring opening of epoxidized castor oil (ECO) where ECO (10 g) was mixed with Jeffamine M-2005 (20 g) in 250 mL round bottom flask in the presence of ZnCl2 as a catalyst at 60–70°C for 4 h. Ethyl acetate (100 mL) was added to the reaction mixture as a solvent [23]. The prepared polymer was purified by filtration of solid catalyst, and the excess ethyl acetate was distilled using vacuum distillation to obtain a product of approximately 100% solid content.
Fig. 2. Major triglyceride of castor oil.
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Fig. 3. Major triglyceride of soybean oil.
Table 1 Formulation of printing ink.
Fig. 4. Chemical structure of jeffamine M-2005.
Component
Weight%
Nitrocellulose varnish Pigment Cyan 15:3 Plasticizer (ATBC) Polymeric dispersant Ketonic resin Ethanol Ethyl acetate Total weight
30 g 12 g 3.5 g 1.5 g 5g 15 g 33 g 100 g
2.4. Printed ink characterization 2.4.1. Ink formulation The printing ink was formulated according to the formulation given in Table 1. The ink formulation was prepared by mixing varnish (nitrocellulose), Cyan 15:3 pigment, Acetyl Tributyl Citrate plasticizer, prepared dispersants, ketonic resin (cyclohexanone-formaldehyde resin), ethanol and ethyl acetate as solvents. The components were placed in a mixer with the pointed amounts in Table 1 and mixed for suitable time to obtain a homogeneous matrix.
Scheme 1. Reactions of epoxidation of oils with peracid formed in situ.
2.2.6. Titration of epoxy equivalent The extent of epoxy groups formed during the preparation steps of the different dispersants was determined according to AOCS Cd 9-57 standard method by using hydrogen bromide and acetic acid. The equivalent of oxirane content in epoxidized castor oil was 2.6 g/100 g; and 6.1 g/100 g epoxidized soybean oil.
2.4.1.1. Printed film thickness. The ink formulation was applied on polypropylene film (thickness 25 μ) using hand coater. The printed film thickness was measured by measuring the thickness of 10 sheets of plastic before and after printing. Then the average thickness of the printed film was calculated. The thickness was measured using KAFER micrometer (accuracy ± 0.1 μ) and was found to be 3 μ for all ink samples.
2.3. Characterization of the prepared additives 2.3.1. Acid value Acid value was determined according to DIN EN ISO 660 (Animal and vegetable fats and oils–determination of acid value and acidity).
2.4.1.2. Curling. The curling of the polypropylene printed ink film was carried out according to (ASTM D4825-97).
2.3.2. Iodine value Iodine value was determined according to DIN EN ISO 3961 (Animal and vegetable fats and oils-Determination of iodine value).
2.4.1.3. Adhesion. Adhesion was measured according to (EN 15386:2007) and examined visually for the detached ink from the printed film. −sensitive tape is applied over the lattice and then removed, and adhesion is evaluated by comparison with descriptions in method.
2.3.3. FTIR analysis FTIR spectra were conducted using Bruker FTIR analyzer; ALPHAPlatinum FT-IR Spectrometer with ATR Platinum–Diamond sampling module from 4000 to 400 cm−1.
2.4.1.4. Stability test. Stability test of ink was performed according to (ASTM D 1849–95). The stability test measures the variation happened for the color of the printed film after certain time. The time of the stability test according to the ASTM standard is after 24 h of printing the colored film on the substrate. In this study, the stability test was measured after 15 min and 24 h, that is to follow the change in the film after short and long times.
2.3.4. Molecular weights determination The molecular weights were determined using GPC Agilent model 1515 pump system equipped with 1260 infinity refractive index detector and using THF as eluent, operating with a flow rate of 1.00 mL/ min at 35°C. Column PL-gel 3 Lm Mixed E 300 7.5 mm covering a molecular weight range of 600–400,000 mg/g was used and was calibrated using polystyrene standards.
2.4.1.5. X-rite measurements (Relative color strength* –Transparency). Printing ink strength, lightness and shade were ΔEab measured using EXACT–PANTONE X-rite spectrophotometer according to ASTM D 2244-02 standard, where; ΔE represents the differences between samples and standard in these three parameters L*, a*, b*.
2.3.5. Water content Water content was determined using the Karl Fischer Titrator model Metrohm 870 Titrino plus according to (DIN EN ISO 8534). 2.3.6. Solubility in common solvents The test was performed for the prepared polymeric dispersant in which a 50:50 solution was prepared from the polymer and common solvents are ethyl acetate, ethanol, isopropanol and toluene.
2.4.1.6. Gloss. The gloss of the printed film was measured on the printed polypropylene film using BIUGED BGD 514 (60 ͦ) gloss meter according to ASTM D 2457-03 standards. 356
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(ESBO) and epoxidized castor oil (ECO). The formation of the epoxy groups in the oil molecules was indicated by the appearance of absorption bands at 843 and 824 cm−1. The groups which did not incorporate in the epoxidation reaction were: C]O ester groups and the hydroxyl groups of the triglycerides which present at 1743 and 3460 cm−1, respectively. FTIR spectra of the prepared polymeric dispersants (PD1-PD4) were represented in Fig. 7. It is clear in Fig. 7 the appearance of the characteristic bands of Jeffamine® M2005: at 2875 cm−1 and 2970 cm−1 for symmetric and asymmetric stretching vibrations of CeH groups, respectively; 1450 cm−1 and 1370 cm−1 assigned for the bending vibrations of CeH groups, respectively; 1090 cm−1 assigned for ether CeOeC band of Jeffamine® M2005; 1743 cm−1 assigned for stretching of C]O ester groups of the triglyceride; and a signal at 3458 cm−1 assigned for the stretching vibration of the hydroxyl group, OH). The molecular weights of the prepared compounds and their starting materials (as they are obtained from the local market) were determined in terms of the number average molecular weight (Mn) and molecular weight polydispersity index (PDI) using Gel Permeation chromatography (GPC), Table 4. Data in Table 4 showed that the formation of the different polymeric dispersants is preceded by the reaction of one Jeffamine molecule and/ or polypropylene glycol molecule by each epoxide group in the epoxidized triglyceride molecule of the different oils as represented in Fig. 5.
Table 2 Fatty acid distribution of soybean oil and castor oil. Fatty acid%
Palmitic
Stearic
Oleic
Linoleic
Linolenic
Ricinoleic
other
Soybean Castor
11 1
4 1
26 3
52 4.2
7 0.3
– 89.5
– 1
3. Results and discussion 3.1. Characterization of oils Fatty acid composition of the used oils were determined for the free acids obtained from acid hydrolysis of the two oils using silica gel column chromatography using GC-7890A equipped with DB-23 column, 60 mm x 0.25 mm, i.d. of 0.25 μm. The obtained fatty acid compositions of the used oils were in good agreement by the reported data for these oils [45,46]. The fatty acid compositions of the used soybean oil and castor oil were listed in Table 2. Acid value and iodine value of the vegetable oils are two important parameters determine the free fatty acid content and unsaturation degree in the oils, respectively. The reported average acid values of soybean oil and castor oil were 2.85 and 2.76 (mg NaOH/g oil) [47]. While, the average iodine values were 120.6 and 86.3 (g I2/100 g oil) for soybean oil and castor oil [48]. The obtained acid values and iodine values for the soybean oil and castor oil used were in accordance with the published data for castor oil and soybean oil, (Table 3).
3.3. Properties of polymeric dispersant The main properties of the prepared polymeric dispersant which are effective in their processing and application are the solubility in different solvents, solid content (active matter) and their water content. Table 5 represents the characteristic features of the prepared polymeric dispersant (PD1-PD4). The prepared polymeric dispersants are characterized by their dual solubility in the different solvents used in the ink formulations. The good solubility of these dispersant in the different solvents can be attributed to their chemical structures. The fatty acid moieties in their chemical backbone are responsible for their solubility in the organic solvent (toluene), while the solubility in the polar solvents comes from the presence of the nonionic chains either the polypropylene glycol or Jeffamine M-2005. The solid contents of the prepared polymeric dispersants are ranged between 96.5% and 99.8%. These high values are economically important during the preparation of ink formulations. Similarly, the results showed the low water content of the prepared polymeric dispersants (PD1-PD4).
3.2. Characterization of the polymeric dispersants and intermediates The reaction between the oils and the hydrogen peroxide involves formation of oxirane ring as a result of the reaction between the double bonds and the active oxygen in a neucleophilic attack reaction, Scheme 1. The formation of the polymeric dispersants proceeded by the ring opening of the oxirane rings of ECO and ESBO via hydrolysis reaction to obtain the four dispersants (PD1-PD4) is represented in Fig. 5. FTIR spectra of the prepared epoxidized oils are represented in Fig. 6. The chemical structure of soybean oil comprises five double bonds of linoleic and oleic acid moieties compared to the castor oil which contains three double bonds of three ricinoleic acid moieties. Epoxidation of the castor oil and soybean oil produces epoxidized products of the two oils. FTIR spectra of the two epoxidized oils (ESBO and ECO) (Fig. 6) showed the characteristic absorption bands of the oxirane rings in both epoxidized products. It is clear that the intensity of the two absorption bands at 846 cm−1 and 824 cm−1 in case of the epoxidized soybean oil (ESBO) is higher than those of epoxidized castor oil (ECO), indicating the higher content of oxirane groups formed in soybean oil. This result was confirmed by the equivalent epoxy titration of the oxirane contents of ESBO and ECO. The titration of epoxy groups equivalents in epoxidized castor oil showed lower content of oxirane rings formed during the epoxidation of castor oil (2.6 g/100 g ECO) compared to the oxirane rings formed during the epoxidation of soybean oil (6.1 g/100 g ESBO). Fig. 7 represents the FTIR spectra of the prepared polymeric dispersants (PD1-PD4) which showed the disappearance of the absorption bands of C]C-stretch at 3009 cm−1 in the fatty acids moieties, which demonstrates the conversion of the double bond of the oils to the epoxy group during the epoxidation reaction to obtain epoxidized soybean oil
3.4. Printed film properties The printing ink was formulated according to the formulation given in Table 1. All ink formulations were mixed and then were applied on polypropylene film using hand coater. The mechanical properties of the printed inks represent the physical behaviors of the printed ink film on the substrate. The two main important mechanical properties of the printed inks studied were the curling and the adhesion. The curling is the deformation of the printed substrate after printing the ink film. The adhesion of the printed film is defined as the detachment of the printed ink film from the printed substrate. It is clear from results listed in Table 6 that the ink formulations which formulated by using the prepared dispersants (PD1-PD4) have no curling. That is in a good agreement with the properties of the used standard (STD 340C). The adhesion properties of the ink formulations were varied between A and B, A: shows no removal of the ink film formed; B: shows less than 5% ink removal after printing and drying. After 15 min of printing, the ink formulations which formulated using PD1, PD2 and PD4 dispersants showed stable ink formulations during the printing on the polypropylene film surface. After 24 h of printing,
Table 3 Acid and iodine values of the used oils. Oil
Acid value, mg NaOH/g
Iodine value, g I2/100 g
Soybean oil Castor oil
1.42 1.98
125.8 84.6
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Fig. 5. Chemical structures of the prepared dispersants.
The optical properties of the printed ink film describe the interaction between the visible light and the ink film on the substrate. The measured optical properties of the ink films printed on the polypropylene film were: transparency, ΔS, ΔE and Gloss. The transparency defines the ratio between the amount of light transmitted through the
the printed films were in comparable to the printing film formulation which formulated using the standard (340C). Ink formulation formulated using PD3 dispersant showed ≈5% ink removal from the printed film after 24 h, while the others dispersants retain their adhesion stability compared to the results obtained after 15 min.
Fig. 6. FTIR spectra of soybean oil (SBO), castor oil (CO), epoxidized soybean oil (ESBO), partially ring opened epoxidized soybean oil (ROESB) and epoxidized castor oil (ECO).
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Fig. 7. The FTIR spectra of polymeric dispersant PD1, PD2, PD3, PD4 and Jeffamine M-2005.
printed ink film formulated using the prepared dispersants and the standard dispersant. The transparency values of the printed films using PD1-PD4 were 98.3, 99.0, 98.3, and 100.0 before stability. These values were decreased by a different degree depending on the type of the dispersant used to be 86.4, 97.8, 96.4, and 96.8, Table 6. It is clear from data in Table 6 that the amount of the JeffamineM2005 in both PD1 and PD2 has no considerable influence on either the mechanical or the optical properties. This showed the role of the vegetable oils structure in the dispersing of the inks. The role of both Jeffamine-M2005 and polypropylene glycol is to enhance the solubility of the dispersants in the formulations, i.e., act as nonionic co-emulsifier. Hydrolysis of the epoxidized soybean oil by jeffamine only or its partial hydrolysis by methanol yields two dispersant with comparable optical and mechanical properties. The ratio of Jeffamine-M2005 has an influence only on the transparency of the printed film using the formulation of PD1 after stability (86.4%) which is lower than those of formulations using PD2, PD3 and PD4. The data reported in Table 6 indicated that polymeric dispersants were prepared successfully by the partial substitution of petroleum polymers with vegetables oil derivative. Castor oil and soybean oil gave very comparable mechanical and optical properties.
Table 4 Gel permeation chromatographic data of the prepared polymeric dispersant. Sample
Mn
Mw
PDI
STD Soybean oil Castor oil Jeffamine PPG2000 PD1 PD2 PD3 PD4
2387 1267 1370 2519 2613 4103 4282 3739 3245
4979 1339 1454 3136 2919 5154 5483 5173 3702
2.08 1.05 1.06 1.24 1.11 1.25 1.28 1.38 1.14
Table 5 Characteristic features of polymeric dispersants. Polymeric dispersant
PD1 PD2 PD3 PD4
Solubility in solvents Ethanol
Ethyl acetate
Toluene
Iso-propanol
S S S S
S S S S
S S S S
S S S S
Solid content
Water content
98.6% 96.5% 99.1% 99.8%
0.12% 0.20% 0.16% 0.11%
4. Conclusions
S: Soluble, P: Partially soluble, I: Insoluble.
The present study demonstrated the preparation of polymeric dispersants based on castor oil and soybean oil via epoxidation of oils Table 6 Properties of printing ink. PD
STD (340C) PD1 PD2 PD3 PD4
Mechanical properties
Optical properties
Curling
Transparency%
No No No No No
Curling Curling Curling Curling Curling
Adhesion
ΔS
ΔE
Gloss, GU
After 15 min.
After 24 h
B*
A*
B*
A*
B*
A*
B*
A*
A A A B A
A A B B A
100 98.3 99 98.3 100.0
100 86.4 97.8 96.4 96.8
100 94.1 94 92.8 92.3
100 91.9 92.1 91.8 92.1
100 1.2 2 2.5 1.2
100 2.5 2.8 2.8 1.9
100 96.7 100 91 100
100 96.5 95.8 87.8 98.2
A: no ink removal; B: less than 5% ink removal. A*: After stability; B*: Before stability.
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followed by ring opening with different ring opening agents such as methanol, polypropylene glycol, and polyether amine. The prepared polymer was used in ink formulation to evaluate its efficiency. The results obtained were evaluated comparing to commercial polymeric dispersant. It indicates that all prepared dispersants show high optical and mechanical properties and high stability for ink before and after stability test. The polymeric dispersant 2 (PD2) and polymeric dispersant 4 (PD4) gave the best results (optical and mechanical) among the prepared polymer.
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