INTRODUCTION
Rosin is produced from pine resin. It remains as an involatile residue
after the distillation of turpentine. It is insoluble in water but soluble
in many organic solvents and is graded and sold on the basis of color,
those products with the palest shades of yellow-brown having the better
quality. It contains predominantly a mixture of abietic- and pimaric-type
acids. This intrinsic acidity enables it to be converted to a large number
of derivatives which have a wide range of applications. The derivatives
include salts, esters and maleic anhydride adducts and hydrogenated, disproportionated
and polymerized rosins. The most important of their uses in the manufacture
is for adhesives, paper sizing agents, printing inks, solders and fluxes,
various surface coatings, insulating materials for the electronics industry,
synthetic rubber, chewing gums, and soaps and detergents (Coppen and Hone,
1995). Zhaobang (1995) described that MPA, one of the derivatives of rosin,
is primarily used as a sizing agent in pulp and paper industries. It is
also utilized in painting, ink and other chemical industries. Other, commonly
used products made from rosin are glues, technical resins, synthetic rubbers
and cosmetic and dental materials (Hong Li et al., 2005). Indonesia,
as the world`s third biggest rosin-producing country after China and Portugal,
uses unmodified rosin in small quantities. Almost all the rosin, about
55,000 tons in 2006, is exported.
Previous study showed that the main constituents of rosin from Pinus
merkusii in Indonesia are abietic and palustric acids (Wiyono et
al., 2006) and these acids, including neoabietic acid, could be reacted
with MA or FA to form fortified rosin (Sundqvist et al., 2001).
Moreover, Diels-Alder reactions of abietic acid (AA) and MA or FA studied
and the adduct were identified by GC-MS using a Shimadzu QP 5050A. The
reaction product of abietic acid and maleic anhydride produced endo-maleopimaric
acid (MPA) and endo-maleopimaric acid tri carboxylic acid; while, the
reaction product of abietic acid and fumaric acid produced fumaropimaric
acid (FPA) and endo-MPA (Wiyono et al., 2007a). Further study indicated
that the relationship between molar ratio and the concentration of MPA
or FPA could be expressed as a quadratic equation. From the equation,
we predicted the best molar ratio to produce the highest yield of MPA
or FPA adducts. Using the equation Y = -0.8475 X2 + 10.448X
- 9.7125, at a reaction temperature of 200 °C, the greatest proportion
of MPA (around 22.5%) was obtained with a molar ratio of rosin to MA of
1:6.2. Meanwhile, using the equation Y = -0.46X2 + 5.268X -
4.47, at 200 °C, the greatest proportion of FPA (around 10.6%) was
obtained with a molar ratio of rosin to FA of 1:5.8.
Based on the above results, we obtained MPA and FPA by using a large
amount of rosin as a raw material. Further, these rosins were used as
raw materials for producing fortified rosin sizes. This research is directed
at characterizing purified MPA and looking at the amount of MPA and FPA
made with a large amount of rosin and MA or FA with various molar ratios
and sources of rosin. The last aim is to look at the properties of fortified
rosin sizes made from both MPA and FPA.
MATERIALS AND METHODS
Sources of chemicals: In this experiment, conducted in 2007, we
used abietic acid (AA), maleic anhydride (MA) and fumaric acids (FA),
purchased from Wako Pure Chemical Company Ltd., Japan. We also utilized
commercial fortified rosin obtained from Indo Picri Company and rosin
from Forest Estate Company, Indonesia. Other chemicals, such as sodium
hydroxide, potassium hydroxide, hydrochloric acid, etc. were procured
from Merck Corporation.
Synthesis of maleopimaric acid (MPA): After purification of abietic
acid by repeated crystallization from ethanol and water, mp 172-175 °C
(Anonymous, 2001), MPA was produced (Wiyono et al., 2007a). After
drying in a vacuum oven, 5 g of purified abietic acid and 10.06 g of maleic
anhydride (molar ratio of AA to MA 1:6.2) were well mixed in a mortar.
The powder was transferred to a small flask (25 mL) and heated at 200
°C for an hour under a nitrogen atmosphere. The brownish-red reaction
products were dissolved in toluene and extracted with water to remove
the excess of MA; dried with MgSO4, filtered and evaporated.
Further purification was performed by column chromatography on silica
gel eluted with hexane, hexane-ethyl acetate with increasing amounts of
ethyl acetate and decreasing amounts of hexane, ethyl acetate and acetic
acid and finally with methanol. The MPA product of the column chromatography
was then purified by recrystallization from diethyl ether and hexane (Nilsson
et al., 2002). After methylation, the purified product was analyzed
by GLC and MS.
Making MPA and FPA: The procedure to react the rosin from various
regions (East Java, Central Java and West Java, Indonesia) with MA or
FA follows a previous method (Wiyono et al., 2006). Around 5 g
of rosin and 10.06 g of MA with a ratio of 1:5.2, 1:6.2, or 1:7.2 were
mixed in a mortar, then transferred to a round flask and heated at 200
°C in an oil bath for one hour under a nitrogen stream. The brownish
reaction products were dissolved in toluene and then washed with water.
The remaining water was removed with anhydrous sodium sulphate, the toluene
solution was concentrated under a nitrogen stream and the concentrate
was dried in the vacuum oven.
The above procedure was also used to make FPA. Around 5 g of rosin and
11.14 g of FA with a ratio of 1:4.8, 1:5.8 or 1:6.8 were mixed in a mortar,
then transferred to a round flask and heated at 200 °C in an oil bath
for 1 h under a nitrogen stream. The reaction products were dissolved
in toluene and washed with water and the remaining water was removed with
anhydrous sodium sulphate. The toluene solution was concentrated under
a nitrogen stream and the concentrate was dried in the vacuum oven. After
methylation, the methylated products, both MPA and FPA, were analyzed
using GLC. The GLC-based analysis of reaction products was performed using
a HITACHI 3000 Gas chromatograph, equipped with an electronic Chromato-integrator
D-2500. The conditions followed those in a previous investigation (Wiyono
et al., 2007b).
The quantification of constituents was conducted with a GC-FID profile
obtained on a capillary column according to the peak area percent method
without response factor correction (Pteifhover, 2000).
Making and analyzing fortified rosin size properties: The procedure
to prepare fortified rosin size was the method of Leffler (Patent No.
4219382). A small quantity of MPA or FPA was heated at 95 °C and then
added to 10 mL of water containing 10 g of NaOH and 15 g of Na2CO3
to maintain the liquid moderately alkaline. The aqueous soap was filtered
off, leaving the insoluble polymeric rosinate and the insoluble product
was washed with alkaline water, heated to the point of melting and cooled.
It was a brown glassy solid. The fortified rosin sizes were then analyzed
as to their properties, covering free rosin, total rosin, combined rosin
and free alkali by using TAPPI standard (T628 cm-01).
RESULTS AND DISCUSSION
Reaction product of AA and MA: Abietic acid is the major component
of colophony and used as a starting material and useful synthetic intermediate.
Numerous common products can be obtained from abietic acid and they could
be utilized in paper size, printing ink, glue (Zhaobang, 1995).
 |
| Fig. 1: |
A chromatographic profile of the crude MPA reaction
product (before purification) |
 |
| Fig. 2: |
A chromatographic profile of the purified MPA reaction
product (after purification) |
Previously, using a small amount of AA (0.520 mg) and MA (0.380 mg),
we have investigated the reaction product of both chemicals (Wiyono et
al., 2007a). The Diels-Alder product, MPA, was purified by column
chromatography on a silica gel eluted with ethyl acetate with increasing
amounts of acetic acid, without any further purification after the isolation
of MPA. Even though identification by comparing mass spectra for the injected
samples to mass spectra studied by Mayr et al. (1984) gave similar
results, this MPA product was not a white solid as mentioned in several
references. In a recent study using much more AA (5 g) and MA (10.06 g)
to produce MPA, after purification of the product by column chromatography
on a silica gel eluted with a combination of hexane-ethyl acetate followed
by further purification and by recrystallization with diethyl ether-hexane,
a white crystal was produced by Nilsson et al. (2002). Then, the
products were analyzed by GLC before and after purification. Two peaks
appeared in both chromatograms (Fig. 1, 2).
However, some unreacted diterpene acids were also found in the chromatogram
(Fig. 1). During the purification process, almost all
unreacted diterpene acids were removed from the reaction product and pure
MPA remained. After purification, two peaks still appeared in the chromatogram
(Fig. 2). By comparing to a previous report (Wiyono
et al., 2006), both peaks could be identified, one as endo-maleopimaric
acid methyl ester, the other as endo- maleopimaric tri methyl ester. Further
analyses with MS indicated that the spectra contained not one compound
but two. If we look at a profile of spectra studied by Mayr et al.
(1984), there was a peak with a base peak at m/z = 146 with a molecular
weight of 460 with a prominent ion at m/z = 187, another small ion at
m/z = 121 and a significant ion at m/z = 400 and 428. Figure
3 indicated endo-maleopimaric tri methyl ester. Further, there was
also a base peak at m/z = 146 with a molecular weight of 414 and ions
at m/z = 316 and 386, which indicated an endo-maleopimaric acid methyl
ester. During this recent research, when a sample of MPA was subjected
to Mass Spectrometry using DIEI, all these ions were found in the spectra
of DIEI results, even though the base peak and mass spectra were not as
high as in the reference, as shown in Fig. 3.
 |
| Fig. 3: |
A mass spectrum of Endo-maleopimaric acid methyl ester
mixed with Endo-maleopimaric acid tri methyl ester |
Reaction products of rosin and MA or FA: The modification of rosin
achieved by heating it with maleic anhydride is important in its industrial
utilization. The most important reaction to occur during this treatment
is the formation of maleopimaric acid from the abietic type acids, covering
palustric, neoabietic and abietic acids. By heating a mixture of rosin
and MA, a very small proportion of levopimaric acid reacts with the maleic
anhydride to give the Diels-Alder product, MPA (Gafvert, 1994).
Earlier studies have investigated the relationship between the molar
ratio and the concentration of MPA or FPA by using a regression analysis
(Wiyono et al., 2007b), the regression analysis showed that there
was a relationship between the molar ratio and the concentration of MPA
or FPA expressed as quadratic equations for both adducts. MPA and the
molar ratio at a reaction temperature of 200 °C could be expressed
as Y = -0.8475 X2 + 10.448X - 9.7125 with a coefficient determination
(R2) = 0.999. At a similar reaction temperature, the relationship
between the molar ratio and the concentration of FPA was expressed as
a quadratic equation, Y = -0.46X2 + 5.268X - 4.47 with a coefficient
determination (R2) = 0.97. Based on these equations, there
could be predicted the best molar ratio to produce the highest MPA or
FPA adducts. Using the equation Y = -0.8475 X2 + 10.448X -
9.7125, at a reaction temperature of 200 °C, the highest proportion
of MPA (around 22.5%) could be achieved by using a molar ratio of rosin
to MA of 1:6.2. Using the equation Y = -0.46X2 + 5.268X - 4.47,
at a similar reaction temperature, the highest proportion of FPA (around
10.6%) could be achieved by using a molar ratio of rosin to MA of 1:5.8.
With these molar ratios we made MPA or FPA using much more rosin as a
raw material compared to previously, with not only rosin obtained from
East and Central Java but also rosin from West Java as a raw material.
We applied three molar ratios and one reaction temperatures, 200 °C,
for one hour in making MPA and FPA.
Using rosin obtained from one of the enterprises in East Java-Indonesia,
the increase in molar ratio at the reaction temperature of 200 °C
initially gave a higher yield of endo-maleopimaric acid, then, it decreased
with further increase in the molar ratio (Table 1).
The amount of reaction product, endo-maleopimaric acid, was in the range
of 42-56%. The highest proportion of this product was obtained at a molar
ratio of 1:6.2 (55.8%). This study confirmed that using a molar ratio
of 1:6.2 was best for making MPA as mentioned previously (Wiyono et
al., 2007b). In terms of the yield of the reaction product, this recent
research almost tripled previous findings that were 8-20% (Nilsson et
al., 2002). Wiyono et al. (2007b) found 12-23%. The difference
in the yield of MPA in this study was probably due to the use of a large
amount of rosin (almost seventeen times higher amount used compared to
earlier studies) in the making of MPA.
| Table 1: |
MPA and FPA content at various molar ratios (rosin
and MA) |
 |
Besides using rosin from East Java, another source of rosin as a raw
material for producing MPA is Central Java (Table 1).
The result indicated that the increase in molar ratio from 1:5.2 to 1:7.2
with a similar reaction temperature a higher yield of endo-maleopimaric
acid was first obtained. Then, with the increase in the molar ratio, the
reaction product was decreased. The product was in a range of 43-66%.
The highest proportion of this product was obtained at a molar ratio of
1:6.2 (65.5%). This study also confirmed that using a molar ratio of 1:6.2
was best for making MPA. Relating to the amount of the reaction product,
this recent research provided more than three times that were obtained
in a previous study (Nilsson et al., 2002; Wiyono et al.,
2007b).
Another source of rosin as a raw material for producing MPA is that from
West Java (Table 1). The result was similar to that
above, where the increase in molar ratio from 1:5.2 to 1:7.2 initially
increased the amount of reaction product and then decreased it. The product
was in a range of 26-40%. The highest proportion of this product was obtained
at a molar ratio of 1:6.2 (39.2%). Again, this study confirmed that a
molar ratio of 1:6.2 produced the most MPA. Relating to the amount of
the reaction product, this recent research provided more than three times
previous amounts (Nilsson et al., 2002; Wiyono et al., 2007b).
The rosin from Central Java produced the best reaction product, MPA.
At the best molar ratio, 1:6.2, the modification of rosin by heating with
maleic anhydride for one hour 200 °C produced the highest yield of
MPA, around 66%. Second was the rosin from East Java, followed by the
rosin from West java. If we looked at the previous results, rosin from
Central Java contained more resin acids (abietic, palustric and neoabietic
acids) which could react with MA. Central Java rosin contained around
66% resin acids. Resin acids in East Java rosin were about 50%; while,
West Java rosin had around 31% (Wiyono et al., 2007b).
The result of the recent study in modifying rosin to FPA showed that
for all sources of rosin (East, Central and West Java) the increase in
molar ratio at a reaction temperature of 200 °C for one hour gave
an increase in yield of the reaction product, fumaropimaric acid (FPA).
The reaction product was in a range of 24-39%. The highest yield of this
product was not obtained at a molar ratio of 1:5.8 as we predicted from
the equation. The best molar ratio to produce FPA should be found. In
terms of the yield of the reaction product, this recent research gave
more FPA than previous results (Wiyono et al., 2007b). The difference
in the yield of FPA was probably because the rosin still contained more
resin acids (abietic, palustric and neoabietic acids) which could react
with FA. This means that to obtain the highest yield of the reaction product
of FPA, we need more FA.
MPA or FPA contained unreacted diterpene acids and the reacted form (Fig.
4, 5, Table 1). Unreacted diterpene
acid contained pimaric acid, dehydroabietic acid (DHA), etc. As described
earlier, Wiyono et al. (2007b), one compound is formed during the
reaction, i.e., pimaric acid and the amount of one compound in the unreacted
product, dehydroabietic acid (DHA), increases. Some resin acids were isomerized
into pimaric acid during the process. Moreover, the increase in the concentration
of DHA, which does not react with MA or FA, was due to the fact that abietic
type resin acids easily isomerize upon the action of heat or mineral acids.
Thermal isomerization of some resin acids is actually catalyzed by the
carboxyl group (Takeda et al., 1969). The heating of levopimaric
acid yielded DHA, besides the abietic type isomers plus. These side reactions
were found to be enhanced by trace amounts of oxygen. Furthermore, owing
to oxidation, palustric acid was converted into DHA, while abietic and
neoabietic acids were not (Enoki, 1976). All these factors led to the
increase in the DHA concentration in the reaction product.
 |
| Fig. 4: |
An example of chromatograms of crude MPA |
 |
| Fig. 5: |
An example of chromatograms of crude FPA |
Fortified rosin size: Internal sizing is a process of providing
paper and paperboard with resistance to liquid wetting, penetration and
absorption by using a sizing agent during paper production (Zou et
al., 2005; Casey, 1981). The common objective of paper sizing is to
inhibit aqueous liquid penetration to give the cellulose product some
desirable end-use characteristics, such as control of water and ink penetration.
The use of a sizing agents could contribute to the grade of paper produced
(Casey, 1981). One of the most important sizing agents in use is rosin,
used for internal and external sizing. The carboxyl group and the hydrophobic
bulk of the chemical compound in rosin play a critical role in sizing.
It is considered that fortified rosin size is more efficient than unfortified
rosin sizes, where a given sizing result can be obtained with less sizing
agent. The economics offered to the paper maker by fortification are such
that almost all the rosin size currently used is fortified form (Casey,
1981; Wang et al., 1998).
In this investigation, maleopimaric acid and fumaropimaric acid obtained
by reacting MA or FA with rosin were then saponified to make fortified
rosin size. The results are shown in Table 2. Using
rosin from East Java, the solid content of fortified rosin size was in
a range of 75-81% for maleopimaric rosin size (MPRS) and around 69-75%
for fumaropimaric rosin size (FPRS)(Gafvert et al., 1995). A solid
content of around 50-80% is categorized as a paste fortified rosin size
(TAPPI Standards). Based on solid content, there are three types of rosin
size, i.e., dry rosin size with solid content at a maximum of 12%, emulsified
rosin size and paste rosin size with a solid content 50-80%. So, the fortified
rosin sizes that we made were categorized as paste rosin size. Further,
using rosin from Central and West Java, it seems that the solid content
of fortified rosin sizes was around 71-85% for MPRS and around 59-70%
for FPRS. Moreover, among sources of rosin, MPRS made of rosin from Central
Java was the highest, followed by MPRS from East Java, then from West
Java. In addition, if we looked at the effect of molar ratio on the solid
content of fortified rosin size, the molar ratio did not affect the solid
content of fortified rosin size, as can be shown in Table
2. The solid content of fortified rosin size varied along with an
increase in the molar ratio. Further, based on total solid of the sizing,
these fortified sizes still met with the requirement of solid content
for size being produced by New Tech-Polymer Ltd-India, which divide into
two classes, minimal total solid at 50% and at 70% with a pH of around
9-12. Meanwhile, the pH of the fortified rosin sizes that we made was
around 9-10, as can be seen in Table 2, which also met
the standard requirement, including the Indonesian National Standard (1990).
| Table 2: |
Maleo- and fumaro-pimaric rosin sizes properties at
various molar ratios (rosin and MA or FA) |
 |
Total rosin is the amount of rosin in fortified rosin size, both free
and combined. In this research, total rosin was equal with combined rosin.
During the analysis of free rosin, to the rosin solution was added the
phenolphthalein indicator. If the solution turned red, it did not contain
free rosin. This means that all rosin acids in the sizing have been saponified
during the making of rosin sizes. Based on this property, the fortified
rosin sizes that we made were in a good quality. The National Indonesian
standard for rosin size gives a requirement of free rosin a maximum of
6%. Relating to the free alkali property, even though fortified rosins
have been fully saponified, there was remaining alkali in the sizing in
a range 4-6%. Moreover, the increase in a molar ratio, free alkali in
the size was also varied. Among sources of rosin, free alkali in the rosin
size made of West Java rosin was smaller than other sources of rosins
(Central and East Java). Unfortunately, compared to the requirement of
free alkali in the Indonesian National Standard, these sizings did not
meet the requirement, a maximum of only 0.25%. Further, compared to the
commercial fortified rosin size, a free alkali property of maleo- and
fumaro-pimaric rosin sizes was still better as it indicated that their
free alkali property was lower than that of the commercial one (Table
2).
Drawn back from the above discussion, identification of the Diels-Alder
adduct of abietic acid and maleic anhydride using an DIEI (Mass spectrometry)
revealed that the reaction of abietic acid with maleic anhydride produced
endo-maleopimaric acid methyl ester with endo-maleopimaric acid tri methyl
ester, as indicated by a fragment ion at m/z =146 with a molecular weight
of 414 and fragment ions at m/z = 121, 187, 316 and 386, which indicated
an endo-maleopimaric acid methyl ester. A fragment ion at m/z =146 with
a molecular weight of 460 was also found in the spectrum, along with other
fragment ions at m/z = 400 and 428, which indicated endo-maleopimaric
tri methyl ester. Using a large amount of rosin as a raw material to produce
MPA, the equation Y = -0.8475 X2 + 10.448X - 9.7125, at a reaction
temperature of 200 °C is still relevant as it denoted that a molar
ratio of 1:6.2 (rosin and MA) is the best to produce MPA. However, the
equation Y = -0.46X2 + 5.268X - 4.47 did not apply for FPA.
Using a large amount of rosin, the increase in molar ratio led to an increase
in FPA products. In terms of free rosin and pH, the maleo- and fumaro-pimaric
rosin sizes have met the requirement of the Indonesian national standards
for paste rosin size. In terms of the free alkali property, the size of
made maleo- and fumaro-pimaric rosin sizes was better compared to the
free alkali of the commercial form.
ACKNOWLEDGMENTS
We thank JSPS (The Japan Society for the Promotion of Science) under
the Ronpaku (Dissertation Ph.D.) programme for providing a fellowship
during Fiscal year 2007 to conduct research in the Faculty of Agriculture,
Ehime University, Japan and the Forest Product Research and Development
Centre, Indonesia. We also thank Mr. Furuyama, a Master student, for helping
with the purification of MPA for this research.
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