Note: Descriptions are shown in the official language in which they were submitted.
3~ 3~ 4681
--x IMPROVED PROCESS EOR T~E PRODUCTION OF
ETHYLE~E GLYCOL MOI~OAR'iL ETHERS
l The present invention relates -to an improved
process for the monoethoxylation of phenols whereby
fragrance quality ethylene glycol monoar~l ethers,
such as ethylene glycol monophenyl ether, are pro-
5 duced.
Ethylene glycol monoaryl ethers are known.
These compounds are usually obtained by reacting
phenol with ethylene oxide in the presence of an
alkaline catalyst. Processes utilizing a variety of
lO basic catalysts such as ammonia, urea, amides, hy-
droxides and phenates of sodium and lithium, potassium
hydroxide and the ]ike are described in U.S. Patent
Nos. 2,852,566, 3,354,227, 3,364,267, 3,525,773,
3,642,911 and 3,64~,53~.
Whereas products obtained by such processes are
suitable for most commercial applications they are not
completely acceptable for use in cosmetic preparations
and fragrances due to the presence of an objectionable
pungent "metallic" odor. Ethylene glycol monophenyl
20 ether obtained by such processes, for example, cannot
be utilized in cosmetic preparations or as a solvent
and fixative for perfumes without further purification
since the undesirable metallic note masks the pleasant
odor of the ethylene glycol monophenyl ether and any
25 other fragrance chemicals employed therewi-th. Even
when the ethylene glycol monophenyl ether is carefully
distilled after ethoxylation to obtain high purity
water-white product essentially free of catalyst
residue, unreacted phenol and higher ethylene oxide
3 adducts, the undesirable metallic note is still not
completely removed.
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l In West German Offenlegun~schrift 3221170 a
post-treatment procedure whereby ethylene glycol
monophenyl ether is contacted with sodium borohydride
to eliminate the undesirable metallic note and thus
5 obtain a highly useful fragrance grade ethylene glycol
monophenyl ether is disclosed. Treating with sodium
borohydride also generally obviates the need for
distilling the product.
The post-treatment of polyethoxylated products
(having 3 to 80 moles ethylene oxide condensed there-
with) with sodium borohydride to improve color is
reported in the technical literature of Ventron
Corporation Chemicals Division in a brochure entitled
"Hydride Chemicals for Process Stream Purification."
15 It is also'suggested that another method of treatment
of the polyethoxylates would be toladd the sodium
borohydride with the caustic used as a catalyst for
the condensation to prevent the darkening that normally
occurs during reaction. A similar procedure is
20 suggested for the production of ethoxylated fatty
alcohol surfactants in PROCESS STREAM PURIFICATION
NEWSLETTER, December 1979, Issue No. 3, published by
Thiokol/Ven-tron Division. All of the above procedures
deal with the treatment or manufacture of polyethoxylates
and there is no indication that fragrance quality
ethylene glycol mo~oaryl ethers be obtained by similar
methods.
We have now unexpectedly discovered that high
quali~y fragrance grade ethylene glycol monoaryl ethers
30 can be obtained by an improved process whereby a phenol
is monoethoxylated in the presence of alkali metal
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1 hydroxide and alkali metal borohydride. Quite
suprisingly, in addition to obtaining product suitable
for fragrance applications and wherein essentially all
traces of the undesirable metallic note typically
5 associated with such products is eliminated it has
further been observed that the rate of reaction is
enhanced and, in some instances, the yield of mono-
ethoxylate increased.
The process of this invention involves reacting
10 essentially one molar equivalent ethylene oxide with
a phenol maintained at a temperature above its melting
point to which has been added from 0.01 to 1 weight
percent alkali metal hydroxide and 0.01 to 1 weight
percent alkali metal borohydride. The phenols corre~
15 spond to the formula
R ~
~ OH
R"
20 where R' and R" are hydrogen or an alkyl, al~enyl or
alkoxyl group having from 1 to 8 carbon atoms. The
process is parkicularly adaptable for use with phenol
and monosubstituted phenols wherein the substituent
has from 1 to 4 carbon atoms. Most generally, 0.05 to
25 0.5 weight percent lithium hydroxide, sodium hydroxide
or potassium hydroxide are employed with 0O05 to 0.5
weight percent sodium borohydride. Preferably the
monoethoxylation is carried out at a temperature from
110C. to 130C. and pressure from about 1 psi to 50
3 psi. The process is particularly adaptable for the
preparation of ethylene glycol monophenyl ether useful
in cosmetic and fragrance applications.
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1 In an especially useful embodimellt of this invention
the ethylene glycol monoaryl ether obtained by the above
process is steam sparged by the introduction of up to
about 10 wt. percent water. The water is introduced
5 subsurfacely and dispersed into the ethylene glycol
monoaryl which is maintained at an elevated temperature
and reduced pressure. Most generally, 0.5 to 5 wt.
percent water is employe~ for the sparging while main-
taining the ethylene glycol monoaryl ether at a tempera-
lO ture of 75 C. to 120 C. and pressure less than 100 mmHg.
In yet another embodiment, the pH of the ethylene
glycol monoaryl ether is lowered, generally to about
pH 6.5-7.5, by the addition of a suitable inorganic or
15 organic acid thereto. Di- and higher polycarboxylic
acids and hydroxy acids, particularly citric acid,
whose salts are insoluble in the ethylene glycol monoaryl
ether product and which therefore may be readily removed
by filtration are especially useful for this purpose.
20 Neutralized ethylene glycol monoaryl ethers may also
be stearn sparged to obtain high quality fragrance
grade products having consistent odor profiles and which
are free of any metallic odor.
~he improved process of this invention for the
25 preparation of ethylene glycol monoaryl ethers comprises
combining an alkali metal hydroxide and alkali metal
borohydride with a phenol maintained at a temperature
above its melting point and then reacting with essentially
one molar equivalent ethylene oxide at a temperature from
3~ about 100 C. to 150 and pressure from atmospheric up
to 1000 psi. In another embodiment of the invention
the resulting ethylene glycol monoaryl ether is then
5_
1 neutralized and, depending on the acid employed for the
neutralization, may be filtered to remove insoluble acid
salts which are formed. In yet another embodiment, the
process involves an additional step of sparging the
ethylene glycol rnonoaryl ether with steam.
Phenol or various substituted-phenols can be
monoethoxylated in accordance with the procedure o~
this invention. The phenols typically correspond to
the ~ormula
R'
,~O~i
R"
wherein R' and R" are hydrogen or an alkyl, alkenyl, or
alkoxyl group having from 1 to 8 carbon atoms. Especially
useful in the process are phenol and monosubstituted
phenols wherein the substituent contains from 1 to 4
carbon atoms. It should be noted that phenols having
substituents in the ortho ring position will react more
slowly than other substituted phenols. Illustrative
phenols which can be monoel:hoxylated in accordance with
this invention are phenol, cresol, ethyl phenol, methoxy
phenol, t-butyl phenol, di-methyl phenol, chavicol and
the like.
For the process, 0.01 weight percent up to 1 weight
percent, based on phenol, alkali metal hydroxide and
0.01 to 1 weight percent, based on phenol, alkali metal
borohydride are combined with the phenol prior to
introducing the ethylene oxide. The alkali metal boro-
30 hydride preferably employed is sodium borohydri.de, however,
other alkali metal borohydrides such as lithium borohydride
and potassium boxohydride can also be utilized in the
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process. Most preferably, 0.05 to 0.5 weight percentalkali metal hydroxide and 0.05 to 0.5 weight percent
sodium borohydride are utilized. Suitable alkali
metal hydroxides include lithium hydroxide, sodium
hydroxide and potassium hydroxide.
To facilitate addition of the alkali metal
hydroxide and alkali metal borohydride, -the phenol is
maintained in a molten state. The temperature of the
phenol can be any temperature above its melting point
up to the temperature at which the ethoxylation reaction
is to be carried out. In the usual practice the alkali
metal hydroxide and sodium borohydride are charged to
the reactor containin~ the phenol while it is being
raised to the reaction temperature.
The alkali metal hydroxide and sodium borohydride
may be added in any order or they may be added simul-
taneously~ The exact nature of the resulting specle
is not known, however, it is believed to be a mixture
of alkali metal and boron phenolates which results from
the reaction/in-teraction of the alkali metal hydroxide
and alkali metal borohydride with phenol.
The ethoxylation reaction is typically being carried
out at a temperature from about 100C. to 150C., and,
more usually, from 110C. to 130C. Whereas the
reaction can be carried out at atmospheric pressure or
at superatmospheric pressures up to 1000 psi or higher,
most generally the pressure is between about 1 psi and
about 50 psi.
To obtaln the ethylene glycol monoaryl ethers one
molar equivalent ethylene oxide is -then reacted with the
phenol. The ethylene oxide can be added to the phenol
as a liquid or as a gas, however, to maximize the yield
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of monoethoxylate and minimize the formation of higher
ethoxy]ation products no more than 10 percent molar
excess should be charged if a closed system is employed.
Preferably, less than 5 percent molar excess ethylene
oxide will be present. While some water can be present
in the reaction mixture it is preferred that the amount
of water be kept as low as possible. Ethylene oxide
addition is maintained at a rate such that the reaction
exotherm can be controlled and so that a large excess
of ethylene oxide is not present in the reactor at any
time during the course of the reaction. An external
cooling source will typically be required to maintain
the reaction temperature within acceptable limits. The
reaction time is primarily dependent on the temperature
of the reaction and the particular phenol being used.
The reaction is terminated when essentially one molar
equivalent ethylene oxide has been reacted or all the
phenol has been ethoxylated. This is accomplished by
simply cooling the reaction mixture and ventlng any excess
ethylene oxide from the reactor.
The general procedure for conducting the reaction
consists of charging the phenol to a reactor with agitation.
E'or ease of handling the phenol is usually charged in a
molten state, however, this is not necessary. Heating is
then begun and the alkali metal hydroxide and sodium
borohydride charged. The mixture is usually agi-tated
and sparged with nitrogen while pulling a vacuum to
facilitate removal oE gases being evolved. When gas
evolution is essentially complete, the mixture is brought
to the reaction temperature and ethylene oxide charged.
The reaction is maintained at the desired temperature
until one molar equivalent of the ethylene oxide has
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reacted with the phenol. Whereas the process is typically
carried out in the above manner as a batch reaction, with
suitable equipment and modification it can also be per-
formed on a semi-continuous or continuous basis.
The ethylene glycol monoaryl ether as obtained by
the above procedure may be used as such and is suitable
for some general applications without further purification.
For example, this product is suitable for use in some
preservative and textile applications and is acceptable
for further reaction with various carboxylic acids for
the preparation of esters. Ethylene gylcol monophenyl
ether obtained by the above process has markedly improved
odor characteristics as compared to product prepared
under similar conditions but without the addition of sodium
borohydride to the reaction. This is quite surprising in view
of the fact that -the color of both products can be
essentially the same.
In spite of the much improved odor of products
obtained by the present process, where the product is
to be used for cosmetic and fragrance applications, it
is advantageous to further treat the product. In this
manner it is possible to obtain ethylene gylcol monoaryl
ethers, and particularly ethylene glycol monophenyl ether,
having consistent odor profiles with no -trace of undesirable
metall.ic odor. To achieve this result, in an especially
use;Eul embodiment of this invention, -the product is sparged
with steam at the completion of the ethoxylation reaction.
Stcam sparging is accomplished by subsurfacely introducing
and dispersing up to lO wt. percent water into the product
30 whi.ch is maintained at a -temperature from 75C. to 120C.
and at a pressure less than 100 mm Hg. The water is intro-
duced into the product through a sparge riny or other
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suitable apparatus. Preferably from 0.5 to 5 weight
percent water is employed and the sparging operation
is carried out at a temperature from 90CO to 110C.
and pressure less than 50 mm Hg. After the desired
amount of water has been introduced, the product is
then dried to the desired moisture level - usually less
than 1 percent and, more preferably, less than 0.5
percent. This is typically accomplished by maintaining
the vacuum and heating after the addition of wate:r has
been discontinued. ~ dry inert gas, such as nitrogen,
may be passed through the product to facilitate removal of
the water during the drying operation.
It may also be desirable to lower the p~ of the
ethylene glycol monoaryl ether, which as obtained from
-the process, typically has a pH of 9 or above. For
many applications, primarily those involving cosmetic,
preservative and fragrance formulations, the ethylene
gylcol monaryl ether should be essentially neutral
(pH 6~5-7.5) and in these instances the product is
neutralized by the addition of an inorganic or organic
acid. Inorganic acids, such as sulfuric acid and
phosphoric acid, can be used. Useful organic acids
include monocarboxylic acids, polycarboxylic aci.ds and
hydroxy carboxylic acids such as formic acid, acet.ic acid,
propionic acid, octanoic acid, pelargonic acid, lauric
acid, stea:ric acid, isostearic acid, phenylstearic acid,
benzoic acid, toluic acid, oxalic acid, malonic acid,
ad.ipic acid, azelaic acid, dodecanedioic acid, phthalic
acid, citric acid, tartaric acid, gylcolic acid, lactic
acld and the like.
If the product is to be neutralized, it is
especially advantageous to utilize an organic acid which
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1 forms salts which are insoluble in the ethylene glycol
monoaryl ether and which therefore can be readily
removed by filtration. useful organic acids for -this
purpose include hydroxy acids and di- and higher poly-
5 carboxylic acids~ The organic acids usually containfrom about 2 to 16 and, more preferably 4 to 12, carbon
atoms and aliphatic organic acids are especially useful.
Especially useful aliphatic dicarboxylic acids include
adipic acid, azelaic acid, sebacic acid and dodecanedioic
10 acid. Especially useful hydroxyaliphatic acids include
glycolic acid, lactic acid, tartaric acid and ci-tric
acid, with the latter being particularly useful for these
neutralizations. To facilitate addition o:E the acid to
the ethylene glycol monoaryl ether, the acid may be added
15 as an aqueous solution. Ethylene glycol monoaryl ethers
which have been neutralized may also be steam sparged in
accordance with the previously described procedure to
further enhance the odor qualities of the neutralized
product.
The invention is more fully illustrated by the
following examples~
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1 EXAM~LE I
Phenol was heated to 60 C. under nitrogen and
charged to a standard e-thoxylation kettle. After
sparging the phenol with nitrogen, 0.1 weight percent
potassium hydroxide and 0.1 weight percent sodium
borohydride were added to the phenol. A vacuum was
applied to the reactor and when a vacuum of 30 mm Hg
could be maintained the reactor was sealed, heated to
110 C. and ethylene oxide added. The rate of addition
1~ of ethylene oxide was controlled to achieve a maximum
pressure of 25 psig while maintaining the temperature
at 120 C. to 130 C. with full cooling. The reaction
mixture was continuously sampled and when the phenol
content reached 500 ppm, ethylene oxide addition was
~5 terminated, the reactor cooled to under 100 C. and
vented. The resulting product which contained 94~
monoethoxylate (ethylene glycol monophenyl ether) had
a color of 98/100 (percent transmittance measured at
440 and 550 m~). The product had a pleasant mild rose
odor and there was no detectable metallic odor associ-
ated with the product.
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EXAMPLE II
For the purpose of comparison and to demonstrate
the superior quality of the product obtained by the
improved process of this invention, -the above process
was repeated omitting the sodium borohydrideO Potassium
hydroxide was added to the phenol at a 0.2 weight percent
level. The ethoxylation was accomplished without
difficulty but at a somewhat slower rate. The final
product had a color of 76/94 tpercent transmittance
measured at 440 and 550 m~) and contained 90% mono-
ethoxylate (ethylene glycol monophenyl ether). There
was, however, a harsh pungent metallic odor associated
with the product which essentially masked the subtle
rose notes of the ethylene glycol monophenyl ether.
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-I EXA~IPLE III
_
To demonstrate the ability ~o further enhance the
desirable fragrance characteristics ol products obtained
by the process of this invention, ethylene ~lycol
monophenyl ether product obtained by the process of
E~ample I was neutralizecl to a plI of 7 by the addition
of 50~ aqueous citric acid solution and then steam
sparged. Stearn sparging was accomplished by heating
to 115 C. while adding 1.5 weight percent water through
a sparge ring in -~he bottom of the reactor. The rate
of addition was controlled so that a vacuum of 60 mm Hg.
was maintained. When water addition was complete, the
heating was continued under vacuum until the water
content was less than 0.2 weight percent. The product
was cooled and filtered to remove insoluble salts formed
as a result of the neutralization. The ethylene glycol
monophenyl ether (boiling point 245 C.) contained 94%
monoethoxylate and had no measurable phenol content.
The resulting product had a pleasant mild rose odor with
~O subtle fresh green nuances and is a highly useful and
desirable extender for the rose note of phenethyl
alcohol in various fragrance formulations. For example,
formulating 5 parts phenethyl alcohol, 2 parts d-citro-
nellol, 2 parts l-citronellol, 5 parts geraniol and 1.5
~r) parts of the ethylene glycol monophenyl ether yields
a fragrance having excellent rose notes.
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EXA~1PLE IV
To demonstrate the versatility of the present
process and the ability to obtain mon,oethoxylated
products derived from substituted phenols the following
reaction was conducted. A reactor was charged with
300 gms p-(t-butyl)phenol, 0.56 gm potassium hydroxide
and 0.59 ~m sodium borohydride. The reaction mixture
was heated to 125 C. and sparged with nitrogen. When
there was no further evidence of gas evolution, the
reactor was sealed and 98 gms ethylene oxide added at
a rate such that the temperature and pressure were
maintained at 130-140~ C. and 30-40 psig, respectively.
The reaction was continued for an additional 30 minutes.
There was no trace of any undesirable metallic odor
in the resulting ethylene glycol mono-p-~t-butyl)phenyl
ether product.
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XAMPLE V
Ethylene glyeol monophenyl ether containing 96%
monoethoxylate and 0.05% phenol was prepared in a
manner similar to that described in Example I. After
ethoxylation, the produet had a pH of 11.8. Samples
of the product were neutralized with a variety of
organic and inorganic aeids to lower the pH as follows-
Acid Final pH
Phosphorie aeid 6.76
Hydroehlorie aeid 6.83
Formie aeid 6.68
Acetic aeid 7.10
Propionic acid 6.97
Oetanole aeid 7.16
Pelargonic acid 6~46
Lauric acid 7.02
Stearie acid 6.00
Benzoic aeid 7.05
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In a r,lanner similar to that of Example V, samplesof the ethylene glycol monophenyl etner were neutralized
with various organic dicarboxylic acids and organic
hydroxy acids as follows:
Acid Final pH
Malonic acid 6.68
Adipic acid 7.17
Azelaic acid 7.06
Dodecanedloic acid 6.84
He~adecanedioic acid 7.07
Glycolic acid 7.05
Citric acid 6.41
Insoluble salts were formed during the neutralization
witll all of the above acids. The neutralized products
were then steam sparged with about 1.5 weight percent
water in accordance with the usual procedure~ ~fter
drying to a moisture content of less than 0.2%, the
products were filtered to remove the insoluble preci-
pitates and the ethylene glycol r~lonophenyl ether recovered.In all instances the odor of the ethylene glycol mono-
phenyl ether products thus obtained was significantly
improved over that of the starting material.
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EXAMPL~ VII
The following comparative experiments demonstrate
the abili-ty to obtain improved rates of reaction by the
process of this invention. For this example two
experir,~ents were carried out reacting 300 gms phenol
with 157 gms ethylene oxide at 125-135~ C. and 30-~0
psig. For the first reaction (identified as Run A~
0.9 gm potassium hydroxide and 0.9 gm sodium borohydride
were added to the phenol in accordance with the process
l~ of this invention prior to carrying out the ethoxylation
and in the second reaction ~identified as Run B) only
potassium hydroxide (1.82 gms) was added to the phenol.
For Run A, reaction with ethylene oxide was complete
in 45 minutes and the resulting product was devoid
of any metallic odor. Sixty minutes were required to
complete the ethoxylation for Run B and the resulting
product had a severe metallic odor. The marked
superiority of the odor qualities of the ethylene
glycol monophenyl ether obtained from Run A was quite
^O surprising in view of the fact that both products had
essentially the same color.
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1 EXAMPLE VIII
In accordance with the previously described
procedures 300 gms p-methoxyphenol/ 0.67 gm potassium
hydroxide and 0.70 gm sodium borohydride were charged
''? to an autoclave. Ethylene oxide was then added over
a 2-1/2 hour period while maintaining the temperature
at 130-140 ~. and pressure in the range 30-40 psig.
When the ethylene oxide addition was complete heating
was continued at 135 C. for 30 minutes. There was
no trace of undesirable metallic odor in the resulting
product which was confirmed by chromatographic analysis
to contain 95.2% monoethoxylated product.
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