alkyd resin

Abstract— Oil-modified alkyd resin was prepared from

crude castor oil. The experiment started with investigating the

optimum conditions for neutralization of crude castor oil and

bleaching of neutralized oil. Then the characteristics (iodine

value, viscosity, acid value, refractive index and color) of oils

were determined. Refined oil has iodine value of 90,

kinemetic viscosity of 4 St, free fatty acid value of 1,

refractive index of 1.474 and color number of 8. These results

showed that the refined oil was qualified to prepare

dehydrated castor oil. Dehydration of refined oil was carried

out at 210-220˚C under 600-640mmHg with the help of 1%

(wt%) NaHSO4 catalyst. The dehydrated castor oils were

analyzed for iodine value, viscosity and its set to touch time

and drying time were also investigated. Dehydrated castor oil

has iodine value of 140, kinemetic viscosity of 1.6 St, set to

touch time of 4 hr and drying time of 5 days. And then , oil

modified alkyd resin (acid value 6.6) was prepared from

dehydrated castor oil by alcoholysis method in excess of

glycerol and phthalic anhydride in the presence of 0.3% (wt%)

NaOH catalyst. The obtained resin was characterized by

Fourier Transform Infrared Spectrophotometer (FTIR) and the

properties were determined.

Keywords— Alcoholysis method, Alkyd resin, Castor oil,

Dehydrated castor oil, Polymerization

I. INTRODUCTION

Polymerization is one of the most important

industrial processes. Resins and emulsion are two main classes

of polymer. Alkyd resins are by far the most important class

of coating resins. It is estimated that alkyd resins contribute

about 70% to the conventional binders used in surface coating

today. The popularity of alky resins as vehicle for coatings is

largely due to their unique properties such as film hardness,

durability gloss and gloss retention, resistance to abrasion, etc.

impacted on them through modification with drying oil [1].

Alkyd resins are used in both clear and pigmented,

industrial and trade coating to protect and decorate a wide

variety of substances. The industrial coatings or finishes

generally are applied during the manufacturing process of the

item which they cover. Often they are specifically formulated

to meet both conditions desired for their application and the

1.Department of Chemical Engineering, Mandalay technological

University, Patheingyi Township, Mandalay, Myanmar, Myanmar 11011, e-

mail: [email protected]

2.Yangon Technological University, Gyongone, Insein, Yangon, Myanmar

11011, e-mail : [email protected]

endless use of the article of manufacture. The industrial

finishes include primers and top coats for refrigerators,

furniture, and electrical equipment. In view of the

development of these items and sectors, the positive growth is

expected for paint industry [2].

Further the paint industry envisages a future

expansion in view of development in Automobile Industry,

utility in Nuclear Power Station, development in Corrosion

Resistant Coatings, expansion in housing activity and other

industry uses. The demand of alkyd resin being an ingredient

in Paint, Varnish and Printing ink industry would be linked

with the Paint industry.

There are many significant efforts that have been

made to increase alkyd resin production. Many researchers

have attempted to search the different sources for alkyd resin

preparation. Airegumen I Aigbodion et al [3] studied

enhancing the quality of alkyd resins using methyl esters of

rubber seed oil in 2004.

A lot of alkyd resins were imported to Myanmar

Paint Industries every year. In order to save foreign currency

outflow, it is needed to produce alkyd resin in Myanmar.

The oils that are mostly employed for alkyd resin

synthesis are linseed oil, soybean oil, dehydrated castor oil,

fish oil and tall oil. Myanmar being rich in aquatic and

terrestrial resources, every state and division is pursuing the

target of putting 500,000 acres under physic nut (castor oil) in

three years. Rural development tasks are included in the

national development endeavors that are being carried out by

the Nation target.

Castor oil is useful directly in protective coatings as a

plasticizer in alkyd systems, and blown castor oil is an

important nitrocellulose plasticizer. In commercial

manufacture of dehydrated castor oil, the aim is to produce the

most valuable material for use as a drying oil. By far the most

important coatings use of castor oil is in the form of

dehydrated castor. Dehydrated castor oil is now recognized as

an individual drying oil with its own characteristic properties

and advantages. The drying oils owe their value as raw

materials for decorative and protective coatings to their ability

to polymerize or “dry” after they have been applied to a

surface to form tough, adherent, impervious, and abrasion

resistance films. The advantages claimed in surface coating

applications include excellent odor and heat bleachability,

good drying properties, more uniform polymer structure, and

lack of after-yellowing. The dehydrated castor oil is non-

yellowing oil and so this can give requirements of coating

industries [2,4,5,6,7].

2. Materials and Methods

2.1. Neutralization of Crude Castor Oil

Manufacture of Alkyd Resin from Castor Oil

Nway Nay Hlaing1, Mya Mya Oo2

World Academy of Science, Engineering and Technology 48 2008

155

Oil (100g) was heated to 55˚C. Then, the calculated

amount of strong (45˚Be, 2N NaOH) lye was added to

neutralize the free fatty acids exactly, with constant stirring.

Completion of neutralization reaction was determined by

testing the mixture with phenolphthalein indicator. When the

indicator color of the sample mixture turned to pink,

neutralization was completed. Then NaCl solution was heated

to 90˚C and 20ml of hot NaCl solution was added to the

mixture to ensure adequate salting or graining out of

soapstock. After that the mixture was poured into separating

funnel. Three hours later, the mixture was separated into two

distinct layers. Then the lower layer or soap layer was drain

out. The upper layer or oil layer was washed with hot water.

Washing was carried out until color of phenolphthalein

indicator did not change to pink. After complete washing, the

oil was dried at 100˚C in oven to evaporate the moisture.

Drying and cooling was carried out until the weight of dried

oil remained unchanged.

The neutralized oils were weighed to calculate oil

loss and then their free fatty acid content (FFA) were

determined [8]. The characteristics of crude oil and

neutralized oil were determined by American Society of

Testing and Materials (ASTM) standard methods.

2.2. Bleaching of Neutralized Oil

The neutralized oils were heated to 100˚C and different

amounts of activated charcoal were added. After the mixture

was stirred for 45 minutes, the mixture was cooled to room

temperature and activated charcoal was removed by filtering

with filter paper.

The neutralized oils were also bleached with different

amounts of bentonite and a mixture of activated charcoal and

bentonite (1:1 ratio). Then the process was carried out above

procedure.

The colors of bleached oil samples were determined

by a spectrophotometric method [11]. In this method, optical

densities were measured at the wavelength of 460nm, 550nm,

620nm and 670nm. Then the photometric colors were

calculated by the following equation.

Photometric color = 1.29D460 + 69.7D550 + 41.2D650 –

56.4D670 [4]

2.3. Dehydration of Castor Oil

Bleached oil (50g) and 2% (wt%) of NaHSO4 catalyst were

placed into round bottom flask and the apparatus was set up as

shown in figure (1). The system was heated to 210-220˚C for

dehydration time were taken for 15, 30, 45, 60, 75 minutes.

Dehydration was also carried out under 600-640

mmHg (vacuum) as described in the above process. In this

process, the effect of NaHSO4 catalyst amount on the

properties of dehydrated castor oil was also investigated.

Then, the iodine values of dehydrated castor oil were

determined by ASTM D1541-86 and viscosities were

determined by ASTM D 1545-63 method. The drying time

and set to touch time were also determined by ASTM D 1953-

70 [9].

Figure 2.1.Dehydration of Castor Oil

2.4. Preparation of Alkyd Resin

Oil modified alkyd resin was prepared with

dehydrated castor oil, glycerol and phthalic anhydride using

NaOH catalyst. The preparation was done in a 4-neck round

bottom flask fitted with a motorized stirrer, a nitrogen inlet, a

thermometer pocked and a hold for sampling. The system was

shown in Fig. 2. In the preparation of alkyd resin, two stages

were involved. The first stage was alcoholysis stage and the

second stage was esterification stage.

Raw material Weight (g) Weight (%)

Dehydrate castor oil

(DCO)

114.27 60.437

Phthalic anhydride (PA) 43.364 22.935

Glycerol (G) 31.44 16.63

Total 189.074 100

Stage 1 (alcoholysis): In this stage, monoglyceride was first

prepared by reacting the oil with glycerol. Alcoholysis of oil

was carried out with different percentages of (0.03%, 0.05%,

0.1%) (by weight) PbO catalyst and (0.1%, 0.2%, 0.3%)(by

weight) NaOH catalysts.

In alcoholysis reaction, the oil was heated with

agitation speed of (700 rpm) and N2 sparging rate of about

(0.06ft3/sec) to 230-240˚C. Glycerol and selected catalyst was

added and alcoholysis reaction was carried out at 230-240˚C.

The reaction was continued until a sample of the reaction

mixture became soluble in two to four volumes of anhydrous

methanol. After alcoholysis reaction was completed, the

reaction mixture was cooled to 140˚C.

Stage 2 (esterification): In this stage, phthalic anhydride was

added to the monoglyceride mixture. The temperature was

maintained at the range of 230-240˚C and maintained at this

temperature. The sparging rate of N2 was increased to

(0.1ft3/sec). The reaction was monitored by periodic

determination of the acid value of the mixture until acid value

dropped to nearly 5.

The acid value of alkyd resin was determined by ASTM D

1639-90 and the chemical resistances also determined. The

prepared resin was standardized by FTIR [12, 13].

Fig.3.3.Alkyd Resin Preparation


156

3. Results and Discussion

3.1. Results

3.1.1. Characterization of Crude Castor Oil

The characteristics of crude castor oil are shown in

Table 3.1.

Table 3.1. The Characteristics of Crude Castor Oil

Characteristics Crude castor oil

Free fatty acid value 19

Color, photometric -

Refractive index -

Specific gravity 0.9633

Viscosity(Stroke) 4.5

Iodine value, wiji’s 89.5

3.1.2. Neutralization of Crude Castor Oil

Table 3.2 show the FFA content of neutralized oil.

Initial weight of crude castor oil = 100g

FFA (%) of crude oil = 19%

Neutralization temperature = 55˚C

20% NaCL solution = 40ml

Sr.

no

2N

NaOH

Neutralization

time(minutes)

FFA (%)

of

Neutralized

oil

Weight of

Neutralized

oil (g)

1 15.2 5 8.448 65.09

2 30 10 0.987 60.43

3 30 10 0.988 51.79

4.1.3. Characterization of Refined Castor Oil

The characteristics of refined castor are described in

Table 3.3 by comparing with ASTM standard castor oil.

Table 3.3.Characteristics of Refined Castor Oil

Source [6]

3.1.4. Bleaching of Neutralized Castor Oil

Effect of bleaching on color and yield of neutralized castor

oil is shown in Table 3.4. Oil was bleached with 0-11% of

activated carbon, 0-9% of bentonite and 0-7% of 1:1 mixture

of activated charcoal and bentonite

Table 3.4. Effect of Bleaching On Color and Yield of

Neutralized Castor Oil

Initial weight of neutralized oil = 100 g

Bleaching temperature = 100˚C

Bleaching time = 45 minutes

*Photometric color = 1.29D460 + 69.7D620 + 41.2D650

56.4D670 [4].

3.1.5. Dehydration of Refined Castor Oil

Table 3.5 present the yield of dehydrated castor oil at

different dehydration conditions. The changes of iodine value

and viscosity by dehydration of castor oil at different

dehydration conditions are shown in Fig. 3.1 and Fig. 3.2.

Table 3.5. Yield of Dehydrated Castor Oil at Different

Dehydration Conditions

Initial weight of sample C2 = 50g

Characteristics Refined

castor oil

Castor oil

(ASTM D 960-79)

Free fatty acid value 1 1.00

Color, photometric 8 -

Refractive index 1.474 1.476 to 1.4778

Specific gravity 0.9614 0.957 to 0.961

Viscosity(Stroke) 4 6.3 to 8.9

Iodine value, wiji’s 90 83 to 88

Sample

no.

Bleaching

agents

(wt%) of

bleachin

g agent

Photometric

color

number

Wt. of

Refined oil

(g)

A1

A2

A3

A4

A5

Activated

charcoal

(A)

3

5

7

9

11

7.25

6.35

7.16

8.32

9.29

57.437

57.400

57.36

57.254

57.217

B1

B2

B3

B4

Bentonite

(B)

3

5

7

9

3.80

3.40

4.40

4.47

58.118

57.386

57.380

57.311

C1

C2

C3

Activated

charcoal

and

bentonite

(1:1 ratio)

(C)

3

5

7

4.0

3.0

4.46

57.405

57.342

57.254


157

Fig. 3.1.Change of Iodine Value with Reaction Time

for Dehydration Temperature at 210-220˚C

Fig.3.2. Change of Viscosity with Reaction Time

for Dehydration Temperature at 210-220˚C

4.1.6. Characterization of Dehydrated Castor Oils

The characteristics of typical dehydrated castor were

presented in Table 3.6 by comparing with ASTM standard

dehydrated castor oil.

Table 3.6.Characteristics of Typical Dehydrated Castor Oils

Vacuum pressure = 600-640 mmHg

1dehydration with 1% NaHSO4 catalyst for 60 minutes 2dehydration with 2% NaHSO4 catalyst for 45 minutes

3.1.7. Preparation of Alkyd Resin

Reaction condition of alcoholysis reaction condition

in alkyd resin preparation is described in Table 3.7. Fig. 3.3

shows the acid value control of esterification reaction. Yield

of dehydrated castor oil-modified alkyd resin and the

calculation for percentage of reaction complection are

presented in Table 3.8. The appearances of gel type resin,

dehydrated castor oil-modified alkyd resin are shown in Fig.

3.4.

Table 3.7. 1st Stage Alcoholysis Reaction Conditions

Reaction temperature = 230-240˚C

Agitation speed = 500 rpm

N2 sparging rate = 0.06 ft3/minutes

Alcoholysi

s catalysts

Catalyst

% (wt%)

Reaction

time (hr)

Completion of

alcoholysis

reaction*

0.03 4 Not complete

0.05 4 Not complete

PbO

0.1 4 Not complete

0.1 4 Not complete

0.2 4 Not complete

NaOH

0.3 2 complete

*It was determined by testing the solubility of alcoholysis

mixture in anhydrous methanol.

Fig.3.3. Acid Value Control of Esterification Reaction

Table 3.8. Yield of Dehydrated Castor Oil-Modified Alkyd

Resin

Dehydration time (minutes)/Yield (%) NaHSO4

catalyst

(%)

V.P

(mm

Hg)15 30 45 60 75

2 760 0.5 90.37 89.88 89.56 89.55

2 600-

640

90.9 90.11 89.5 89.13

5

89.06

1 600-

640

90.2 90.035 89.67 89.39 89.28

Characteristics Dehydrated

castor oil1Dehydrated

castor oil 2Standard

dehydrated

castor oil

(ASTM

D961-86)

Iodine value 140.01 139.05 125-145

Viscosity

(Stroke)

1.600 1.686 1.5-1.8

Set to touch

time (hour)

4 3.5 2.5,approxi

mately

Drying time

(hour)

5 5 -

10 20 30 40 50 60 70 80

100

105

110

115

120

125

130

135

140

2%NaHS

O4(with

out vacuu

m)

2%NaHSO 4

(600-640mmHg,vacuum)

1%NaHSO 4(600-640mmHg, vacuum)

Iodi

ne V

alue

Dehydration Time(min)

1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0

1 .4

1 .6

1 .8

2 .0

2 .2

2 .4

2 .6

2 .8

3 .0

3 .2

3 .4

3 .6

3 .8

4 .0

4 .2

4 .4

4 .6

2%NaHSO

4 (600-640mmHg,vacuum)

1%NaHSO 4 (600 -640

mmHg, vacuum

)

2%NaHSO 4 (w

ithou t vacuum)

Visc

osity

(Str

oke)

D e h y d ra t io n T im e (m in )

1

10

100

30 60 90 120 150

reaction time (minutes)

acid

val

ue


158

I.W-initial weight

F.W-final weight

Y-yield

IAV-initial acid value

FVA-final acid value

P-degree of reaction complection

3.1.8. Characterization of Alkyd Resin

The physico-chemical properties of alkyd resin are

presented in Table 3.9. The chemical resistances of alkyd resin

film are shown in Table 3.10. Table 3.11 show FTIR

absorption band of dehydrated castor oil-modified alkyd resin.

Table 3.9. Characteristics of Dehydrated Castor Oil-modified

Alkyd Resin

Properties DCO

alkyd

resin

RSO alkyd

resin*

DCO

alkyd

resin

Acid value 6.6 12.7 4-11

Iodine

value

80.24 66.3 -

Color Yellow Brown -

Refractive

index

1.477 1.5050 -

Gouge

hardness

HB HB -

Scratch

hardness

F H -

RSO- rubber seed oil

Source [1, 14]

Table 3.10. Chemical Resistances of Alkyd Resin Films

Media Immersion

time (hours)

Appearance of

film*

Distilled water 18 Not effect

8 Whitening

16 Blistering 3 N NaOH

24 Removal

*It was examined after the films were air dried for 30 minutes.

Table 3.11. FTIR Absorption Band of Dehydrated Castor Oil-

Modified Alkyd Resin

Band

No.

Experimental

frequency

(cm-1)

Literature

frequency

(cm-1)

Remark

1

2

3

4

3008.99

2926.74

3514.21

1169.21

2855.67

1460.43

1738.64

1730.30

Near 3030

3570-3200

Near 1100

2926-2850

1485-1440

1750-1735

1730-1717

=C-H

O-H

O-H

C-H

CH2

CH3COOCH3

5

1125.26 1150-1060

O=C-O-C-

3.2. Discussion

3.2.1. Discussion on Characteristics of Crude Castor Oil

According to Table 4.1 FFA content of crude castor oil

was high and it was not within the ASTM specification limit.

The color and refractive index of crude oil can not be

determined because the transparency of crude oil was very

poor. The viscosity of crude oil was slightly lower than that of

ASTM standard oil [6]. Even though, the specific gravity and

iodine value of crude oil were in the range of ASTM

specification limit, the FFA content of crude oil was differed

from ASTM standard. The only reason to reduce the FFA

content of oil was to neutralize the crude oil.

4.2.2. Discussion on Neutralization of Crude Castor Oil

In neutralization process, it was found that 30 ml of 2

N NaOH per 100g of oil was required to obtain neutralized oil

with an acceptable FFA content and to be a minimum of oil

loss. The neutralization time of 10 minutes was sufficient to

reduce FFA content from 19% to 1%. In neutralization of oil,

free fatty acid content of oil was converted in oil soluble

soaps. Small amount of impurities such as phosphotides,

proteins or protein fragments, and gummy or mucilaginous

substances were also removed by neutralization process.

Therefore, the initial weight of oil was decreased as well as

the yield of oil was decreased. In neutralization process, there

was a difficulty to separate the soap and oil layer because FFA

content in crude oil was very high. The two layers can be

easily separated when NaCL solution was added to the

neutralized mixture because NaCL can help to ensure

adequate salting or graining out of the soapstock. Other

impurities in oil were removed by washing with hot water. In

washing step, there has a little loss of oil. So, the average

yield of oil was 64%.

3.2.3. Discussion on Characteristic of Neutralized Castor Oil

From Table 3.3., it can be seen that the neutralization

process can reduce the FFA content of crude oil from 19% to

1%. Then, it can give the refined oil color of 8 and refractive

index of 1.474. Therefore, neutralization process can offer

great effect on FFA content, color and refractive index of oil.

Moreover, the refined oil has specific gravity of 0.9614,

viscosity of 4 and iodine value of 90. These results were

nearly the same as that of the crude oil. Although the

neutralization technique reduced significantly FFA content in

I..W(g) F.W

(g)

Y

(%)

IAV FAV P

(%)

DCO

alkyd

resin

(100%

solid) 189.58

2

140 73.85 298.58

8

6.6 97.72

COO


159

oil, it gave slightly effect on specific gravity, viscosity and

iodine value of oil.

3.2.4. Discussion on bleaching of neutralized oil

In Table 3.4, it can be seen that the highest color removal

efficiency was obtained by bleaching with 5% of bleaching

agents. 5% of activated carbon, 5% of bentonite and 5% of

(1:1) mixture of activated charcoal and bentonite can give the

oil with photometric color of 6.35, 3.4 and 3.0 respectively.

Bleaching with (1:1) mixture of activated charcoal and

bentonite can offer better result. So, it can be chosen as

bleaching agents in bleaching of neutralized oil.

Beside decoloring, bleaching of neutralized oil served the

important function of largely removal of trace amount of soap.

After bleaching process, the average oil yield was 69%. The

oil yield was decreased during the bleaching process due to

the adsorption of oil on the surface of adsorbents and the

filtration of oil with filter paper.

4.2.5. Discussion on Dehydration of Castor Oil

According to the Table 3.5, the yield of dehydrated

castor oil decreased with increasing the dehydration time.

Then, there was a slightly different in yield of dehydrated

castor oil although the dehydration process was carried out

different dehydration conditions.

In Fig. 3.1 and 3.2, it was observed that the

dehydrated castor oil with a maximum iodine value and a

minimum viscosity could be obtained at the proper reaction

time. The iodine values of dehydrated castor oil increased

with the reaction time and reached a maximum value. Then, it

decreased because prolong heating leads to polymerization

with a consequence drop in iodine value and a step rise in

viscosity. The minimum viscosity occurs at or near the point

of maximum iodine value.

From Fig. 3.1, the dehydration of oil without vacuum

system could not give acceptable iodine value to qualify as

drying oil because the iodine value of oil was below 125 (the

lower limit of ASTM dehydrated castor oil) . In this process, a

lot of fumes were evolved during dehydration of oil and these

fumes were condensed and dripped back into the dehydrated

oil. It was undesirable effect. Therefore, it is required to use a

current of inert gas such as carbon dioxide or nitrogen in order

to remove the decomposition products. The most effective

way of removing of fume is by using the vacuum pressure. By

this means, the problem of condensing the fume into the

dehydrated oil was largely avoided. Therefore, dehydration of

refined castor oil was carried out under vacuum system.

When dehydration of oil was done by using 1% of NaHSO4

catalyst and vacuum pressure of 600-640 mmHg and the

optimum reaction time is 60 minutes, this system could give

dehydrated castor oil with iodine value of 140. When

dehydration of oil was done by using 2% of catalyst and

vacuum pressure of 600-640 mmHg and the optimum reaction

time is 45 minutes, this system could give the dehydrated

castor oil with iodine value of 139.05. Although the

dehydration time was decreased with increasing the amount of

catalyst percent, the refractive index of the dehydrated oil was

increased.

4.2.6. Discussion on Characteristics of Dehydrated Castor Oils

The iodine value and viscosity control the extent of reaction

and set to touch time and drying time show the drying

properties of dehydrated castor oil. Table 4.7 described that

the iodine value and viscosity of dehydrated castor oils were

in the limit of ASTM standard dehydrated castor oil. Then the

drying time and set to touch time also gave satisfactory result.

Therefore, these dehydrated castor oils were acceptable to

prepare drying oil-modified alkyd resin.

4.2.7. Discussion on Preparation of Alkyd Resin

According to the literature [3], the alcoholysis

reaction is usually completed within an hr or two hrs after the

batch had reached operating temperature. In Table 4.8, it was

found that the samples of the alcoholysis mixture did not

completely soluble in anhydrous methanol although the

alcoholysis reactions were carried out for 4hr by using

different amount of litharge catalysts (0.03%, 0.05%, 0.1%)

and NaOH catalysts (0.1%, 0.2%). It should not be tried to use

the amount of PbO catalyst more than 0.1% (wt%) because the

preferred PbO catalyst percent for alcoholysis reaction is 0.01-

0.1 in literature. Then, large quantities of catalyst lead to dark

the color of alkyd resin and detract from the water and alkali

resistances of alkyd resin. In alcoholysis of oil with 0.1%

(wt%) and 0.2% (wt%) NaOH catalyst, it cannot also give

complete alcoholysis mixture after reaction was carried out for

2 hrs. The degree of alcoholysis has an important bearing on

the properties of the resulting resin. During the final reaction

with phthalic anhydride, esterification of the free hydroxyl

groups of the monoglyceride must compete with any

unreacted or excess glycerol. The latter reaction leads to

glyceryl phthalate which is insoluble in the oil-acid-glyceryl

phthalate and unreacted glyceride oil. Unless sufficient

monoglyceride is present prior to the addition of the phthalic

anhydride, the reaction product will be unsoluble gel of

glyceryl phthalate suspended in oily mixed glycerides. Such a

product is worthless.

In esterification reaction, it was observed that the

longer the reaction time, the more viscous the mixture is. In

this stage, adequate agitation was necessary for complete

mixing of monoglyceride mixture and phthalic anhydride.

Unless adequate mixing was supplied in this stage, the

unqualify alkyd resin would be resulted. So, the N2 sparging

rate was increased in order to remove liberated reaction

product and to increase the heat and mass transfer of chemical

reaction. In Fig. 3.3, the oil-modified alkyd resin with acid

number of 6.6 was obtained after the esterification reaction

was carried out for 150 minutes. It should not try to proceed

the reaction after the acid number of alkyd resin had dropped

to 6.6 because the reaction was closed to gel point.

In Table 3.8, it was observed that 97.72 % of reaction

was completed when the final acid number of alkyd resin was

6.6. Then, the yield of alkyd resin was 73.87%.

3.2.8. Discussion on Characteristics of Alkyd Resin

In Table 3.9, there is no common standard to compare

alkyds resins. Each alkyd resin has its own properties. The

alkyd resin that has acid number of less than 15 is suitable for

application of paint, according to literature [1, 7, 8]. The

scratch hardness of alkyd resin was F and gouge hardness was


160

HB. The refractive index of alkyd resin was 1.447 and color

was yellow.

4.2.9. Discussion on Chemical Resistance of Alkyd Resin

Film

The resistance of alkyd film was determined in two media,

distilled water and NaOH solution. Table 3.10 described that

there was no effect on alkyd film after immersion in distilled

water for 18 hours. The immersion of alkyd film in water for

18 hours was sufficient time to examine the water resistance.

When the alkyd film was immersed in strong alkali solution,

3N NaOH, the film got whitening after immersion time for 8

hours, blistering after immersion time for 16 hours and

removal after immersion time for 24 hours. So, these results

show that the prepared alkyd resin has high chemical

resistance.

4.2.10. Discussion on FTIR Adsorption of Dehydrated Castor

Oil-Modified Alkyd Resin

The FTIR spectrum of prepared alkyd resin exhibits a

characteristic of straight chain ester band at 1738.64 cm-1 and

aromatic ring ester band at 1730.09 cm-1. The present of O=C-

O-C- also exhibit a characteristic ester band at 1125.26 cm-1.

The appearance of CH2, -CH- confirms the present of methyl

group at 1460.43 cm-1 and 2856.67 cm-1. The adsorption band

at 3008.99 cm-1 is characteristic of alkene carbon (=C-H)

according to literature [12, 13].

4. Conclusion

The characteristics of refined castor oils were found

to be standardized with ASTM standard castor oils and it was

suitable to carry out the next step. The refined castor oil was

done by using NaHSO4 catalyst to carry out the dehydration

process. Dehydration under vacuum pressure system was

effective processing method and this pressure influenced the

quality of dehydrated castor oil. A typical dehydrated castor

oil (iodine value 140, viscosity 1.6 stroke, set to touch time

3.5 hr and drying time 5 day) was prepared with 1% NaHSO4

catalyst under vacuum of 600-640 mmHg at 210-220˚C. In

alcoholysis of oil by using 0.3% (wt%) NaOH catalyst, it gave

complete alcoholohysis mixture to preceed the esterification

reaction after reaction time for 2 hrs. Dehydrated castor oil

has been used in the preparation alkyd resin. Dehydrated

castor oil-modified alkyd resin (acid value 6.6) was prepared

by alcoholysis method from dehydrated castor oil, glycerol

and phthalic anhydride with a help of 0.3% NaOH catalyst.

The physico-chemical properties and high chemical resistance

of alkyd resin film showed that they were promising in

formulating of paint.

Acknowledgements

The financial support of Ministry of Science and

Technology is gratefully acknowledged. The author wishs to

extend her gratitude to Prof. Dr. Mya Mya Oo for stimulating

discussion.

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