Note: Descriptions are shown in the official language in which they were submitted.
1274504
This invention relates to an improved method of
preparing esters of rosin.
Rosln is mainly a mixture of C20, fused-ring,
monocarboxylic acids, typified by levopimaric and abietiG
acids, both of which are susceptible to numerous ~hemi~al
transformations. The rosins to which this invention
relates include gum rosin, wood rosin, and tall oil rosin
or the rosin acids contained therein as for example,
abietic acid, pimaric acid, sapinic acid, etc.
The natural separation and gradual conversion of
some of the hydrophilic components of sap and related
plant fluids from the cambium layer of a tree into
increasingly hydrophobic solids are the generic process of
forming diverse gums, resins and waxes. The oleoresin
intermediate in this proce6s i~ typified in pin gum, whiGh
flows~from hacks on the trunks of southern yellow pine in
southeastern Vnited States, in France, and in other
countries. Pine gum contains about ~OX ~gum) rosin and
about 20X turpentine.
Resinification from oleoresin can result from
elther natural evaporation of oll from an extrudate or
low collection in duct~ in sapwood and heartwood. Pinus
stumps are valuable enough to be harvested, chipped, and
extracted with hexane or higher-boiling paraffins to yield
wood rosin, wood turpentine, and other terpene-related
compounds by fractional distillation. In the kraft, i.e.,
sulfate, pulping process for making paper, pinewood is
d1gested w1th alkali producing crude tall oil and crude
ulf~ate turpentine as ~y-products. Fractionation of the
crude tall oil yields tall oil rosin and fatty acids.
The chemlcal transformation of gum, wood, and
tall~ oil resin which relates to this invention is
èoterification. The ~eneficial product characteristics
provided by ro~in esterification for various applications
have led to the development of many esterification
rQcedures~ particularly treatments with polyhydriG
alcohols. U.S. Patents 2,~6~,125, 2,5~0,~10 and 2,572,0
t~ch ro6in ecterification with glycerol and
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~2745~4
pentaerythritol, among other polyhydric alcohols, usually
preceded by a rosin disproportionation step.
U.S. Patent 3,780,012 teache~ pretreating tall
oil rosin with paraformaldehyde followed by di~tlllation
prior to the esterification reaction to achieve product
color improvement. U.S. Patent 3,~80,013 teaches the
incremental addition of a phenol sulfide compound during
tall oil rosin pentaerythritol esterification. The color
of the product of these procedures was claimed to be an M
on the V.S.D.A. scale. The rosin color standards referred
to in this invention are U.S.D.A. standards varying from
X, the lighte~t, to D, the darkest color. The scale of
colors i~ de~ignated as X, WW, WG, N, M, K, I, H, G, F, E,
and D. Also, due to the light color of the rosin ester
prvducts of the invention process, among X color rosins,
the designations of X-A, X-B and X-C indicate lighter than
X color, with X-C being the lighter color.
U.S. Patent 4,1~2,070 teaches employing
arylsulfonic acid in place of the traditional basic
esterification catalysts, such as calcium oxide, to reduce
the time for tall oil ro~in-pentaerythritol esterification
to obtain a rosin ester of improved oxygen stability,
color and melting point. This work is confounded,
however, by the unusually large amount of pentaerythritol
used (35% equivalent excess) which by itself would
markedly increase the rate of acid number drop. Products
with Ring and Ball melting points of 77C to 86.5C were
obtained. Normal commercial pentaerythritol esters of
rosins have Ring and Ball melting between ~5C and 105C.
The ob~ect of this invention is to provide a
novel method of preparing esters of rosin. It is a
further ob~ect of this invention to employ a catalyst
which accelerates the rosin esterification reaction rate
to result ln a reduced reaction time. It is a still
further ob~ect of this invention to permit a reduction in
the amount of polyhydric alcohol employed in the reaction,
resulting in reduced cost and higher, more desirable
melting points, i.e., from ~5C to 105C. It is a
~2~4~;0~
specific o~ect of this invention to provide a method of
preparing esters of rosin e~hibiting a color e~uivalent to
or lighter than the starting rosin.
All of the above objects are met by the
di~covery that phosphinic acid ~also called
hypophosphorous acid) reacts synergistically with a phenol
sulfide compound as a combined catalyst to accelerate the
rosin esterification reaction rate.
Accordingly, the invention provides a process
for esterifying rosin with a polyhydric alcohol which
comprises heating the rosin and polyhydric alcohol in the
presence of a catalytic amount of phosphinic acid and a
phenol sulfide compound in an inert environment.
Thus, the improvement of this invention lies in
reacting rosin and a polyhydric alcohol in the presence of
phosphinic acid (H3Po2) and a phenol sulfide compound, as
combined catalyst, to reduce the reacticn time for rosin
pentaerythritol ester formation and to provide a rosin
ester of improved color and oxidation stability.
Preferably, a rosin is reacted wlth at least an
equivalent amount of a polyhydric alcohol, preferably
glycerol or pentaerythritol, in the presence of from 0.1%
to 2.0% phosphinic acid and 0.05% to 1.0% of a phenol
sulfide, based on the weight of the rosin, at a
temperature of from about 180C to about 300C to produce
a rosin ester having a color equivalent to or lighter than
the starting rosin.
Phosphinic acid is a strong, reducing acid,
useful for its antioxidant or color-reducing properties in
the preparation of light colored fatty acid taurates (U.S.
Patent 3,232,968), carboxylic acid esters with
poly~oxyalkylene) compounds (British Patent 979,673) and
U.S. Patent 3,071,604), acrylic and methacrylic esters of
glycols ~Japanese Patent 73 11084), or in light colored
alkyl resins (Japanese Patent 12997). Also, phosphinic
acld has been used as a tall oil treatment agent to
convert the impurities and color bodies contained therein
,~
12~4504
to a non-distillable form and to promote decarboxyl~tion
or rosin acids present ~u.s. Patent 2,441,197).
A novel rosin esterifiGation process is now
provided involving the use of phosphinic acid in
combination with a phenol sulfide compound as the
esterification catalyst.
The gum, wood, and tall oil rosin materials to
which this invention relates may be subjected to other
treatments prior to esterification. For example, in
addition to the distillation treatment alluded to in the
fractionation extraction processes, the rosin material may
have been sub~ected to disproportionation, hydrogenation,
or polymerization, or some combination of these and/or
other treatments.
As polyhydric alcohols, ethylene glycol,
propylene glycol, diethylene glycol, triethylene glycol,
tetraethylene glycol, trimethylene glycol, glycerol,
pentaerythritol, dipentaerythritol, tripentaerythritol,
trimethylolethane, trimethylolpropane, mannitol, sorbital,
as well as combination~ of the aforementioned and other
similar polyhydric alcohols may be used. The amount of
the alcohol used in the esterification may be varied
widely but generally no more than an approximate 20%
exce~s over the equivalent combining proportion will be
necessary.
In general, the esterification is effected by
introducing the rosin, up to 50% eguivalent excess of a
polyhydric alcohol, preferably 15-20% eguivalent exce~s,
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~27~504
and from 0.1% to 2.0% phosphiniç acid, and from 0.05% to
1.0% phenol sulfide based on the weight of the rosin, into
a reaction vessel. The reaGtion temperature is raised to
from about 180C to about 300C, preferably from about
250C to about 280C, for up to about 15 hours of until
the rosin acid number ls reduced to about 15 or helow.
Longer reaction times may be employed, but the additional
time and energy costs generally outweigh any benefits
received. The preferred amount of phosphinic acid is from
about 0.2% to about 0.5%, based on the weight of the.
rosin, and no benefit i~ seen to be derived in employing
amount~ of 0.5% or more of the phosphinic acid. The
preferred amount of phenol sulfide i8 from about 0.2% to
about 0.5%, based on the weight of the rosin.
The phenol sulfide is set forth in ~.8. Patent
3,~80,013. As stated
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Case Docket No. C~IR 85-20
in the aorementioned patent, the tr~ating agent may be
represented by the structure: ¦
.i . I
(Hl)n ~(HI)n _ (lH)n
(Aryl) -_ sx- ~ Aryl)sx ~ Aryl)
(R)m (R)m --p (R)m
'~here n is an integer from 1 to 3 inclusive, p is an integer from
0 to 100 and preferably about 5 to 20 inclusive, and the sum of m
,and n on each aryl is between 1 and 5 inclusive, x is 1, 2, or 3,
and R is a hydrocarbon group, e.g., alkyl cycloalkyl and
substituted alkyl, e.g., Cl-C8, wherein the substituents are
,cycloalkyl, aryl, alkaryl, and the like. R desirably contains
., "
from 1 to 22 carbon atoms inclusive~ Preferred alkyl groups are
st-aight chain secondary and tertiary alkyl groups containing up
to 8 carbon atoms inclusive. Preferred aryl groups are those
containing 6 to 18 carbon atoms, inclusive, typically phenyl,
naphthyl and anthracyl. Typical cycloalkyl groups con~ain 3-
~carbon atoms in the ring, e.g., cyclopropyl, cyclopentyl and
~cyclohexyl.
!' Advantageously, the esteriiication reaction should be
accomplished in the presence of an inert atmosphere, provided by
'a n trogen purge on the reaction vessel prior to addition of the
reactants and a nitrogen sparge during the reaction. Since light
color is ~ desirable property of the rosin ester and the color is
sensitive to oxygen exposure, such exposure must be minimized.
Also, since an a~vancnge of the comblned phosphinic
acid and phenol sulfide catalyst is minimal color degradation
,during esterification, the rosin ester color is primarily
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i27450A
Case Docket No. C~R 85-20
,dependent upon the color of the starting rosin. When rosin is
esterified, the combined catalysts of the invention process
permit production of an ester~of an equivalent or lighter color
jthan the starting rosin.
'1 In a preferred embodiment of the invention process, the
,;rosin starting material is melted in an inert atmosphere in the
1Ireaction vessel, followed by the addition of 0.2~ (based on the
;~weight of the rosin) of phosphinic acid (50% active in water),
0.5% (based on the weight of the rosln) of a phenol sulfide, and
¦15-20% equivalent excess pentaerythritol. A very low inert gas
sparge, such as nitrogen or carbon dioxide, is maintained as the
~mixture is heated to 250C with agitation, which temperature is
'maintained for about three hours. The reaction temperature then
',is increased to 275C until the reaction product acid number is ' i,
decreased to 15 or below, or for a time of about 2 to 12 hours.
iAfter about 5 to l5 hours from initiating the reaction, the inert
ga~ sparge is replaced with a steam sparge, followed by addition
- of about 0.053% solid sodium hydroxide (or other basic compound),
ba6ed on the weight of the rosin, to neutralize the phosphinic
acid catalyst, and the mixture is cooled to 220-230C and
1sparged with nitrogen to remove all moisture. (Alternatively, a
'~50% a~ueous sodium hydroxide solution may be used.)
;1, The following examples serve to illustrate the
unexpected color improvement in rosin estcrs made by the
invention process, as well as the reduced reaction time. Unless
"otherwise speciied, the parts are by weight. ~;
!~ Example l
1 In a suitable reaction vessel 500 parts of a tall oil ~ -
- 'rosin with a U.S.D.A. color of WW was melted at 200C with a
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1274504
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Case Docket No. CHR 84-20
: nitrogen blanket. Pentaerythritol in the amount of 65 parts was
added slowly at 200C. This mixture was heated to 250C for
. i.
three hours with agitation, after which the temperature was
increased to 275C and held until the reaction product acid
number was 15. The total reaction time was 43 hours and the
final ester had a U. S.D.A. color of I.
''~
' Example 2
j This and the following example show the benefits from
employing a traditional rosin esterification catalyst in the
reaction. The reaction was carried out as in Example 1 except, I
prior to the pentaerythritol addition, 1.076 parts of calcium
,formate were added as catalyst at 200C. The reaction time at
!275C required to achieve a reaction product acid number of 15
,was only 6-1/2 hours for a total reaction time of 9-1/2 hours.
;Also, the final ester had a U.S.D.A. color from M to K and a Ring
aI~d Ball melting point of 100C.
E~ample 3
The reaction was carried out as in Example 2 except
,,1 part of calcium hydroxide was added as catalyst in place of
'calcium formate. The total reaction time required to achieve an
acid number of 15 was 10 hours. The final es~er had a U.S.D.A.
- ~'color of ~,
" Thus, the catalysts of Examples 2 and 3 provide reduced
reaction time, but no real benefits in product color are
achieved.
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i274504 1 ~
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Case Docket No. CHR 85-20
Example 4 1 ';
To determine the benefits received from employing an
arylsulfonic acid as a catalyst for the rosin esterification (as ¦ '
taught by U. S. Patent 4,172,070), the reaction was carried out j '~
'
,as in Example 1 except that after the pentaerythritol was added
to the melted rosin and mixed well at 200C, 1 part of I ,
iparatoluenesulfonic acid was added. The time required to achieve
,an acid number of 15 or less was twelve hours. The final es~er ,,
!l . .
had a U.S.D.A.,color of WW to WG. IJhile the reaction time was
reduced over no catalyst and product color was better than that .'
provided with the catalysts of Examples 2 and 3, little or no ¦
,,color reduction (lightening) from the starting rosin was noted. ¦ ,~
!
l :
~I Example 5
I, F`~
jl To determine whether an advantage is achieved by a
,'catalyst combination of an arylsulfonic acid and a phenol F'
'isul~ide, the reaction was carried out as in Example 4 except, ',
,after addition of the paratoluenesulfonic acid, phenol sulfide '
(Vultac@~ 2, an amyl phenol sulfide polymer sold by Pennwalt) was
li
''added incrementally in amounts of 0.5 parts each at the beginning
of the reaction, four hours later at 275C and, finally, four
hours later at 275C. The total reaction time required to
achieve an acid number below 15 was 10 hours, and the final ester
jhad a U.S.D.A. color of X to WW. Thus, no significant
''improvement was noted over either of the catalysts used alone.
.1 ,
, E~ample 6
To show the synergistic catalytic and product color 1'
,improvement effect of the combination of phenol sulfide and
"phosphinic acid in rosin esterification, the reaction was carried
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Case Docket No. CHR 85-20 1 ;''
out as in Example 5 except, in place of the paratoluenesulfonic ¦ '
acid, 1 part of 50Z active phosphinic acid was added. Also, !
rather than incremental addition, all the phenol sulfide ! ~;
(1.5 parts) was added with the other reactants at the beginning
of the reaction. After reaction for three hours at 250C, the
'temperature was increased to 275C for four hours to produce a
'final ester having an acid number below 13 and a U.S.D.A. color ,
of X-B to X-C.
I! i i
! ~
Example 7 i
To show the benefit of the invention process for gum
~'ro3in esterification, the reaci~ion was carried O-lt as in
- Example 6 except that gum rosin with a U.S.D.A. color of WG was ;.
employed as the starting rosin material. The final ester had an 1 '
acid number of 11 and a U.S.D.~. color of X-A to X-B.
,' Clearly, ~he marke~ improvement in the reaction time '
'required to achieve the desired product acid number and the
marked improvement (i.e., lightening) of product color using the
catalyst combination of this invention exhibit an unexpected and
unobvious synergistic catalytic effect for rosin esterification.
~'~ . While the invention has been described and illustrated
'herein by references to various specific materials, procedures
'and examples, it i8 understood that the invention is not
'reEitricted to the particular m~terials, combinations of
'materials~ and procedures selected for tha~ p~lrpose. ~umerous
!l !
variations of such detail~i can ~e cmployed, as ~7ill ~e
appreclated by those slcilled ~n the art.
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