Esterification of wood with unsaturated carboxylic acids. I

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Esterification of wood with unsaturated carboxylic acids. I. :
Preparation of several wood-esters by the TFAA method
Nakagami, Terutaka; Amimoto, Hirotaka; Yokota, Tokuo
京都大学農学部演習林報告 = BULLETIN OF THE KYOTO
UNIVERSITY FORESTS (1974), 46: 217-224
1974-12-14
http://hdl.handle.net/2433/191566
Right
Type
Textversion
Departmental Bulletin Paper
publisher
Kyoto University
217
Esterification
of wood
carboxylic
Preparation
unsaturated
acids.
of several
the
Terutaka
with
TFAA
I.
wood-esters
by
method.
NAKAGAMI, Hirotaka AMIMOTO and Tokuo YOKOTA
不飽和カルボン酸による木材のエステル化(第1報)
TFAA法
中
神
照
による木材エステルの調製
太・網
本
博
孝・横
田
徳
郎
Contents
Resume
217
3.
1.
Introduction
217
References
2.
Experimental
218
要
旨
would
possess
Results
and
discussion・
・・・・・・・・・・・・・・…
219
.......................................222
・
224
Resume
In order
to prepare
end uses,
beech
anhydride
"impelling"
esterified
wood
meal
wood
was
method.
which
treated
The
with
esterified
improved
carboxylic
acids,
wood
examined
was
properties
using
the
for many
trifluoroacetic
by several
analytical
methods.
Monocarboxylic
di-
acids
and tribasic
unexpectedly.
steric
while
Different
configuration
esterification
action
acids,
reacted
on wood
esterification,
removal
degrees
of acids
in many
with
in some
combined
of very
Additional
but weight
cases.
The
1.
Cellulose
has been esterified
of new plastics
modification
stability
and textile
of wood
as a result
have been reported.
by
acylation
of decrease
The
purpose
and
has
acid catalyst
of wood
more
groups
well explained
was diminished
region
and
readily
was
in terms
brought
incomplete
of plc,
about
by its strongly
was easily
than
and
increasing
degradative
destroyed
by less
on wood.
Introduction
with various
fibers,
sulfuric
-treatment
degrees
trifluoroacetyl
were
increase
ordered
with EDA-pre
different
labile
of esterification
used.
cases,
wood in
carboxylic
improvement
mainly
in hygroscopicity
of the present
acids
of textile
been
carried
of wood.
investigation
for the purpose
properties,
of production
while
out to improve
A few prepared
was to prepare
chemical
dimensional
1,2)
of wood
esters
wood esterifi-
218
ed with
end
unsaturated
Recently,
trifluoroacetic
for the partial
the
carboxylic
acids,
which
would
possess
uses.
method
anhydride
esterification
form,
"impellent"
of cotton
was described
with
to have certain
no additional
and trifluoroacetic
fication
anhydride
anhydride
catalyst
method
retention
improved
3)
of the
advantages
was
properties
reported
fibrous
to be applicable
structure.
Furthermore,
; an esterifying
acid need not be in the
3)
groups are not introduced,
is needed,
trifluoroacetyl
4)
cellulose.
This procedure
may dissolve
for many
was applied
to esteri-
of wood.
2.
Experimental
2. I. Materials
Beech
extracted
wood meal
with
xylic acids
in Table
(Fagus
a boiling
and trifluoroacetic
1.
Benzene
crenata
BLUME, 42-60
ethanol-benzene
and
anhydride
the other
mesh)
(2 :1 v/v)
(TFAA)
used
mixture
were
in the study
for 24 hr.
was previously
Unsaturated
of reagent
grade,
also of reagent
grade.
and
carbo-
summarized
reagents
were
an acid
(0.3 g) was mixed with TFAA (0.7 ml) in
5)
2. 2. Esterification procedure
' I
n a typical ester preparation,
benzene (10 ml), followed by dissolution
30°C (a so-called aging process).
esterification
of the acid.
Oven-dried
medium for 24 hr at 30°C.
The
mixture
stood for 2-3 hr at
wood meal (0.5 g) was then treated by the
Esterified
samples were removed, washed succes-
sively in benzene, ethanol and de-ionized water, neutralized in aqueous 5 % sodium hydrogen
carbonate
solution for 2-3 hr at room temperature
and then soaked in water for 4-7 days, changing
followed by washing
the
water
were washed in acetone, dried in vacuo and finally weighed.
weight increase percent
divided
by molecular
weight
every
in water
day.
These
again,
samples
Weight increase percent and
of acids (m mol of acid/100 g of
wood) were calculated for the esterified wood, based on the weight of the original wood.
2. 3. Ethylenediamine
pre-treatment
on wood meal
Wood meal (2 g) was soaked in ethylenediamine
replaced stepwise by benzene through
(EDA) for 24 hr at room temperature,
four benzene-EDA
mixture of given ratios.
2. 4. IR absorption spectrophotometry, hygroscopicity measurement
and x-ray
diffractometry
IR spectra were measured with a Hitachi EPI-G3 spectrophotometer,
technique.
Ratios among intensities
of absorption
by the KBr disk
bands at 3400 (OH), 2880 (CH),
1740
(C--=-0), and 1640 (C=C) cm-1 were calculated.
Moisture content measurements were made on esterified samples which were previously
oven-dried
and then conditioned
sodium nitrite.
at 65 % RH and 20°C, over aqueous saturated solution of
Moisture contehts were expressed in percent increase,
weight of samples.
based
on the dry
219
X-ray
diffractometer
traces
goniometer
using
Wood
(0.2 g) was pressed
meal
Crystallinity
were
nickel-filtered
index
ated)
radiation
under
beech
examples,
carboxylic
conditions
a molar
is advisable
acids
wood meal extracted
fixed
As hydrophobic
than
that
weight
hydrophilic
in Table
angles
of 2.03
to the method
Flex 2011 B)
5 and
ton/cm2
of Segal
35°
(2 0).6
.)
for 1 min.
7)
et al.
Discussion
groups
of unreacted
bands
be
group
for
mixture
all
of
the
was not considered
place
in moisture
ester
groups
Moisture
value of each
acids ; that
ester
which
removed.
in
were
carried
acids
used ; for
the
while it
is said
Complexity
1.
in some
dicarboxylic
increase
These
of ester
by
degree
esterified
less stable
and
wood were lower
Weight
esterified
to be much
esterificaintroduction
rise to decrystallization
wood.
correct
groups,
is no
of all esterified
Fig.
esterified
is well
indicate
give
contents
is due to formation
is, wood
not
which
if there
percent
facts suggest
linkages
the
TFAA
wood
than
than
method.
(Fig.
normal
of wood seems to cause difficult
that
rather
of esterification,
Table 1 Partial esters of beech
oeecn
wood
wooa
meal
meat
esterified
esterinea
with
witn
unsaturated
Acid
(untre-
carefully,
hydroxyl
content,
%), as shown
study,
may
of hydrophilic
at 1780, 1160, 775 and 745 cm-'
and easily
suitable
take the
wood (10-11
increase
of trifluoroacetic
of the original
with a ethanol-benzene
not
in wood.
in the present
weight
1, esterifications
decrease
cause
also to saponification
However,
acid esters
shown
acid or bulky
hydroxyl
deposition
remain
and
to a carboxyl
8)
1 : 1.
ester linkages
increase,
absorption
the
(Geiger
to be about
of the original
corresponded
Results
might
ratio of TFAA
tion of wood will generally
new accessible
between
a pressure
according
previously
which
for the ratio
of unreacted
Denki
of wood-esters
several
out under
a Rygaku
copper
(Cr. I) was determined
3. 1. Preparation
on
to a pellet
3.
Using
taken
since
2)
show
carboxylic
and incomplete
mono- and
acids
acids
Weight
increase
(%)5)
Acrylic
Vinylacetic
Methacrylic
trans-Crotonic
Tiglic
9. 37
23. 54
54
5. 13
13
33. 92
30. 84
64
jl-Methylcrotonic
Sorbic
10-Undecylenic
Linoleic
Elaidic
18. 25
25
59. h9
59
25. 95
95
8. 57
57
27.2"
20
TAT..inc
inc .Acid
Wt.
Acid
1V101. Wt.
W T.increase
Mol.
Weight
increase
Wt. inc.
Mol. Wt.
(%)
x 10-3
0. 95
0.34
3. 96
0. 13
- 0. 23
8
3
31
1
- 2
- 0. 48
11.32
2.88
26.71
10.74
- 3
78
15
445
38
x 10-3
130
F”malir•
Fumalic
273
273
60
394
308
306
Maleic
Maleic
Mesaconic
Mesaconic
Citraconic
itaconic
Itaconic
183
183
Phthalic
Phthalic
532
141
141
32
32
96
Vb
Adioic
532
(1 3g,
Q.
Beech wood meal 0. 5g, carboxylic acid O.
for 24 hr.
Adipic
Citric
Citric
Acetic
Acetic
Stearic
tearic
FAA 0fl 7m1, and benzene
WA
10m1; at 30°C,
removal
of trifluoroacetyl
it is soaked
in water
weight
increase
express
correctly
for esterified
cate
Fig. 1 shows that higher
hydrophobicity
groups,
even
for 7 days.
percent
will
if
Hence,
not
always
the extent of esterification
wood,
but is thought
to indi-
it approximately.
(i. e., lower moisture
content)
was given by
acids of long chain length (lower line in Fig. 1) rather than shorter analogues (upper line)
because
of the increasingly
hydrophobic
nature of acids with increasing
Moisture content was not changed by esterification
with adipic acid.
chain
length.
Campbell and Francis
obtained similar results, explained by formation of diester cross linkages not always giving
rise to diminishing
moisture
content
for cellulose esterified
with diacids
length, but which may be simply due to formation of the monoester
The finding that two repeated experiments
71. 51 %, in the case of esterification
gave dissimilar weight increase
of wood with j9-methylcrotonic
lution of the esterified wood into the reaction
cellulose-ester
of short
chain
of these dibasic acid.
of 18. 25 and
acid, suggests
medium followed by weight-loss,
disso-
since the
is soluble in benzene.
Both saturated
and unsaturated
monocarboxylic
acids reacted
readily with wood in the
presence of TFAA "impellent", but the degree of esterification with di- and tribasic acids
a)
was very low, except for adipic acid (Table 1). In the work of Cambell et al., similar low
reactivities
of dibasic acids in the range Cy to C5 were observed.
this study are considered
consistent
to have a main-chain
with the finding
described
is
by Campbell et al. Moreover, the facts were explained
in terms of less dissolution of acids in benzene containing
by TFAA, and preferred
As dibasic acids used in
length of four carbon atoms, the result
formation of intramolecular
acids were less reactive, the last interpretation
TFAA, decomposition
cyclic anhydride.
Although
of acids
dibasic
seems to explain satisfactorily that trans-type
acids such as fumalic and mesaconic acids, which were less soluble
in the
esterification
medium, reacted more readily with wood than cis-type acids such as maleic and citraconic
acids,
which
medium,
and
were
and
itaconic
stable
completely
also than
acids
which
intramolecular
prepared
each
acid,
found
acyl
large
acids.
the
acids
of TFAA
to affect
and acids.
for acids
of similar
molecular
molecular
acid analogues
acids
than
acids
can reasonably
That
sulfuric
of acrylic,
Table
2
between
structure.
the
carboxyl
with
and
adipic
Esterification
catalyst
acids
of
ca wooa
wood
on pK.
one
rather
of the
anhydride
than
for esterification
was described
Again,
groups,
unsaturated
by Matsuzaki
and
unsaturated
low reactivities
acids employed
of dibasic
were stronger
Weight
Wt
Wt.
increase
Mol. Wt.1.
(%)
in-3
x 10-3
294
- 72. 26
- 839
839
)8
13. 08
meal 0. 6g, carboxylic
for 24 hr.
esterification,
is in agreement
unsaturatea
unsaturated
inc.
215
215
pic
increasing
2),
carboxylic
car ooxync
acids
with
in the cases
recommended
in the presence
acid1d
18. 51
10m1; at 30°C,
to
result
; dibasic
brought
(Table
witn
with
21. 21
wood
hydroxyl
acids.
Methacrylic
Beech
small pK.
of esterification,
and
to depend
of acetic
acid catalyst,
by their
extents
and important
is joined
A similar
a mixture
of sulfuric
Acrylic
trans-Crotonic
is found
group
and
of carboxyl
also to be effective
to the other.
be explained
pK.
bands
Reactivity
It seems
that
between
of absorption
cellulose
of sulfuric
Acid
of each
relationship
acid as an additional
methacrylic
acid
being
acidity
groups
monobasic
and
general
systems
in the presence
the other
of the
with acids,
above.
atoms, and methyl
11)
Miyata, who esterified
carboxylic
to
equilibrium
carbon
and
of
attributed
of intensities
size, as cited
acrylic
strong
of solution
by
Fig. 3 gives
in the ratio
for
they
is preferentially
present in these
to)
in this respect.
Thus,
expressed
with
which
is accelerated
is thought
were
is,
from ionization
anhydride
TFAA
important
TFAA
and small
properties
derived
esters
plc. ; that
acids
by interaction
catalyst,
of these
their
are generally
ionization
acid
on
acylating
unsymmetrical
formed
be able to form
in TFAA
acyl ion (RCO*)
the
the
phthalic
data of various cellulose3)
et al. in pKa of
contents
for weak
The
weak
would
in
as
by Hamalainen
to depend
were
such
cyclic anhydrides.
On rearranging
esters
dissolved
acids
":
Acid
Wt. inc.
increase
Mol. Wt.
(96)
Fumalic
I
90
90Phth
acid
Weight
rr
0. 3g,
- 0. 32
x 10-3
- 3
Maleic
Maleic
0. 06
1
Mesaconic
Mesaconic
8. 05
62
Citraconic
- 0. 94
alic
- 2.88
A A O 7m1, H2SO4
i-T
FAA
0. Olml, and
- 7Adi
- 17
benzene
222
addition of strong acid, together
with
the monochloroacetic
usually large decrease in the weight of wood esterified
anhydride
with
"impellent".
trans-crotonic
Un-
acid, in the
presence of additional sulfuric acid, is considered to be due to degradation of cellulose and
hemicellulose components by sulfuric acid, followed by dissolution of the esterified suger
into the reaction medium, since it is easily soluble in benzene.
The mild nature of TFAA
and the great value of the TFAA method seem to be clearly shown
in Tables 1 and 2,
comparing very little degradation
by sulfuric acid.
3. 2. Effect
of EDA-pre-treatment
The fine structure
determining
by TFAA with remarkable
decrease
on wood
of cellulose has long been considered
to be the overriding
factor in
chemical reactivity, since reaction takes place most readily in the region of
12) l
molecular order. Therefore, decrystallization of wood is hoped to
ow, three-dimensional,
bring about increasing
ester-formation.
However, saponification
were 2.32, 4.32, 4.63 and 2.95 meq/g for the untreated
meq/g
for the EDA-treated
10-undecylenic
esterification,
crotonic,
sorbic
and
did not always lead to increasing
of the untreated
wood by the
into account.
A similar tendency was clarified by measuring
bands of unsaturated carbons (1640 cm-'). This unexpected result
in the term of insufficient
EDA suppressed
acid-catalyzed
with methacrylic,
The EDA-treatment
even if loss of acetyl groups (about 2 meq/g)
pre-treatment
is taken
intensities of absorption
is explained
wood, on esterifying
acids, respectively.
values in the present work
wood, and 0.50, 2.98, 3.95 and 1.96
the esterification
solvent-replacement.
In other words, remaining
reaction, since a basic substance
inhibits
the important
ionization cited above.
A little
esterification
wood showed
remarkable
but increasing
Cr. I for
4).
the
EDA-swollen
tely reverts
structure
decrease
ester-formation
diminishing
(Fig.
of the EDA-treated
back
after
in its Cr.I,
gave gradually
untreated
wood
wood almost comple-
to the
soaking
original
in
cellulose
water
and
I
polar
solvents,
but only a little in nonpolar solvents
13)
such as chloroform
and benzene.
In the present
study,
EDA which
wood
was then
is considered
complex
which
was
replaced
to have been
structure,
that
treated
by
with
benzene
in EDA-cellulose
is, in a loose
arran-
gement than original cellulose I. During the
subsequent
esterification
process, polar acids
in the
reaction
medium
would,
able to remove
the diamine
in the
wood,
swollen
place of the diamine
region.
Hence,
however,
and easily penetrate
into the original
the reaction
be
from the complex
in
ordered
in the crystalline
region
would
wood
proceed
than
cellulose
I by
would
ester
in
be
inhibited
into
of
their
electrostatic
other
the
hand,
the
cellulose
and
x-ray
in the
of the
the
moisture
smaller
was
larger
when
they
content
TFAA
on
region),
of both
due to changes
method,
that
that
and chemical
moisture
in
EDA-
and
disordered
with
wood
content
of wood usually determine
will be increased
by exchanging
degree
of change
in submicroscopic
more
the
untreated
in moisture
composition
content
but be reduced
(increase
combined
of
esterified
to the expression
of decrease
suggest
content
than
were
Thus,
linkages
restricted
results
for
cellulose
structure
absorbed.
ester
degree
I
Cr.
moisture
one,
amorphous
be mainly
These
in
Submicroscopic
esterification,
the
slow esterification
wood
of moisture
(increasing
On
crystalline
amorphous
or by
different
by simply
non-esterified
of decrease
untreated
hydrophobic
in
caused
new
region,
region.
degree
(Fig. 5).
of
groups.
to be
esterified
EDA-treated
amount
this
of
to
reaction
and
OH
decrease
seems
treated
crystalline
effects
to
diffractogram,
ordered
The
the
introduction
gradual
peaks
after
original
bulky
wood
overlapping
the
by
the
in the
Regeneration
in water
properties
original
readily
untreated.
soaking
groups
because
more
the
hydrophilic
in the
that
manner.
wood
degree
of
Therefore,
a
to
of wood.
by less esterification
and subsequent
for
will affect
is considered
is, decrystallization
wood will be prepared
the EDA-treatment
The
composition,
same
of the EDA-treated
structure,
OH groups
of esterification).
in chemical
the
by decrystallization
in
solvent-replacement.
References
1)
2)
3)
4)
5)
6)
7)
8)
9)
H. Tarkow, A. J. Stamm and E. C. O. Frickson : Acetylated wood, U. S. Dept. Agric. Circ., No.
1593 (1955)
R. Popper and M. Bariska : Die Azylierung des Holzes, Holz Roll Werkstoff, 30, 289 (1972)
C. Hamalainen, R. H. Wade and E. M. Buras, Jr. : Fibrous cellulose esters by trifluoroacetic
anhydride method, Text. Res. J., 27, 168 (1957)
0. Nakao : New method for dissolving cellulose and/or cellulose graft copolymer, Fiber Sci.
Ind., 4, 128 (1971)
M. D. Cruz-Lagrange,
C. Hamalainen and A. S. Cooper, Jr. : Preparation and evaluation of
selected aliphatic acid esters of cotton fiber, Amer. Dyest. Rep., 51, 428 (1962)
N. Shiraishi, T. Yokota, T. Kimura and K. Sumizawa : The interaction of wood with organic
solvents, Mokuzai Gakkaishi, 18, 215 (1972)
L. Segal, J. J. Creely, A. E. Martin, Jr. and C. M. Conrad : An empirical method for estimating
the degree of crystallinity of native cellulose using the x-ray diffractometer,
Text. Res. J., 29,
786 (1959)
H. J. Campbell and T. Francis : The cross-linking of cotton cellulose by aliphatic dicarboxylic
acids, Text. Res. J., 35, 260 (1965)
E. J. Brourne, M. Stacey, J. C. Tatlow and J. M. Tedder : Studies on trifluoroacetic acid, J.
224
10)
11)
12)
13)
Chem. Soc., 1949. 2976
J. M. Tedder : The use of trifluoroacetic anhydride and related compounds in organic synthesis,
Chem. Rev., 55, 787 (1955)
K. Matsuzaki and T. Miyata : Reactions of cellulose with a, (l-unsaturated carboxylic acids-acetic
anhydride mixture, Kogyo Kagaku Zasshi, 70, 770 (1967)
D. M. Jones : Structure and some reactions of cellulose, Adv. Carb. Chcm. 19, 219 (1964)
L. Loeb and L. Segal : Studies of the ethylenediamine-cellulose
complex, J. Polym. Sci., 15, 343
(1955)
要
旨
無水トリフルオロ酢酸法を用いて,木材の不飽和カルボン酸エステルを調製し,木材の改質を
試みた。エステル化木材を赤外線吸収,X線
回折,吸湿およびけん化法で検討し,次の結果を得
た。
1)
エステル化度は酸の種類により大きい差異があった。これは主として酸のpKaで
れたが,分子構造(ア
スとトランス配置など)も影響した。2)反
あった。3)硫
説明さ
グリル酸系列でのメチル基とカルポキシル基の相互位置,二塩基酸でのシ
応後,ト
リフルオロ酢酸を除くことは意外に困難で
酸の少量添加はエステル化を促進したが,木材の分解ももたらした。4)木
材を
エチレンジアミンで前処理すると,わずかのエステル化で木材の非晶化が行なえる結果も示され
た。

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