CA1195696A - Process for the production of ethylene glycol monoaryl ethers - Google Patents
Process for the production of ethylene glycol monoaryl ethersInfo
- Publication number
- CA1195696A CA1195696A CA000424783A CA424783A CA1195696A CA 1195696 A CA1195696 A CA 1195696A CA 000424783 A CA000424783 A CA 000424783A CA 424783 A CA424783 A CA 424783A CA 1195696 A CA1195696 A CA 1195696A
- Authority
- CA
- Canada
- Prior art keywords
- ethylene glycol
- phenol
- alkali metal
- acid
- ether
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C43/00—Ethers; Compounds having groups, groups or groups
- C07C43/02—Ethers
- C07C43/20—Ethers having an ether-oxygen atom bound to a carbon atom of a six-membered aromatic ring
- C07C43/23—Ethers having an ether-oxygen atom bound to a carbon atom of a six-membered aromatic ring containing hydroxy or O-metal groups
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C41/00—Preparation of ethers; Preparation of compounds having groups, groups or groups
- C07C41/01—Preparation of ethers
- C07C41/02—Preparation of ethers from oxiranes
- C07C41/03—Preparation of ethers from oxiranes by reaction of oxirane rings with hydroxy groups
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C41/00—Preparation of ethers; Preparation of compounds having groups, groups or groups
- C07C41/01—Preparation of ethers
- C07C41/34—Separation; Purification; Stabilisation; Use of additives
- C07C41/44—Separation; Purification; Stabilisation; Use of additives by treatments giving rise to a chemical modification
-
- C—CHEMISTRY; METALLURGY
- C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
- C11B—PRODUCING, e.g. BY PRESSING RAW MATERIALS OR BY EXTRACTION FROM WASTE MATERIALS, REFINING OR PRESERVING FATS, FATTY SUBSTANCES, e.g. LANOLIN, FATTY OILS OR WAXES; ESSENTIAL OILS; PERFUMES
- C11B9/00—Essential oils; Perfumes
- C11B9/0061—Essential oils; Perfumes compounds containing a six-membered aromatic ring not condensed with another ring
Abstract
ABSTRACT OF THE DISCLOSURE
Ethylene glycol monoaryl ethers useful as fragrance chemicals are obtained by the process of this invention whereby a phenol containing an alkali metal borohydride and alkali metal hydroxide is monoethoxylated. Ethylene glycol monophenyl ether having a consistent mild rose odor profile and free of undesirable metallic notes is obtained by the present process.
Ethylene glycol monoaryl ethers useful as fragrance chemicals are obtained by the process of this invention whereby a phenol containing an alkali metal borohydride and alkali metal hydroxide is monoethoxylated. Ethylene glycol monophenyl ether having a consistent mild rose odor profile and free of undesirable metallic notes is obtained by the present process.
Description
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.
$
~2--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 s~
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 ` ~ ~
~s~
.-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 ~?`\!
s~
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 ~s~
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 `` '1 ~95~i9~
g 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 ~0 ;`~", ~ . .
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~
~o --il.--, 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.
''5 3o 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.
~i 40 5~
~
-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.
3o 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.
3o s~g~
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 ~rj 3o ~ ~156~ ~ ~
,, ~
] x~ rLr VI
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.
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.
3o ~ ~ -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.
~0 ~0
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.
$
~2--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 s~
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.
~5~:3q~
~,, ''":
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 ` ~ ~
~s~
.-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 ~?`\!
s~
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 ~s~
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 `` '1 ~95~i9~
g 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 ~0 ;`~", ~ . .
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~
~o --il.--, 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.
''5 3o 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.
~i 40 5~
~
-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.
3o 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.
3o s~g~
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 ~rj 3o ~ ~156~ ~ ~
,, ~
] x~ rLr VI
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.
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.
3o ~ ~ -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.
~0 ~0
Claims (10)
1. A process for the preparation of ethylene glycol monoaryl ethers which comprises combining 0.01 to 1.0 wt. percent, based on phenol, alkali metal hydroxide and 0.01 to 1 weight percent, based on phenol, alkali metal bordered with a phenolic compound of the formula Where R' and R" are hydrogen or an alkyl, alkenyl or alkoxyl group having from 1 to 8 carbon atoms, said phenol maintained at a temperature above its melting point, and reacting with essentially one molar equivalent ethylene oxide at a temperature from 100° C.
to 150° C. and pressure from atmospheric up to 1000 psi.
to 150° C. and pressure from atmospheric up to 1000 psi.
2. The process of Claim 1 wherein the alkali metal borohydride is sodium borohydride, and the alkali metal hydroxide and sodium borohydride are both utilized in amounts from 0.05 to 0.5 weight percent, based on the phenol, and the phenolic compound is phenol or a monosubstituted phenol wherein the substituent contains from 1 to 4 carbon atoms.
3. The process of Claim 2 wherein the alkali metal hydroxide is potassium hydroxide and the etho-xylation is carried out at a temperature from 110° C.
to 130° C. and pressure between about 1 psi and 50 psi.
to 130° C. and pressure between about 1 psi and 50 psi.
4. The process of any of Claims 1 to 3 comprising the further step of reducing the pH of the ethylene glycol monoaryl ether by the addition of an inorganic or organic acid thereto.
5. The process of Claim 1 wherein the ethylene glycol monoaryl ether is neutralized to pH 6.5-7.5 with an aliphatic di- or higher polycarboxylic acid or hydroxy carboxylic acid having from 2 to 16 carbon atoms.
6. The process of Claim 5 wherein the ethylene glycol monoaryl ether is neutralized with citric acid.
7. The process of Claim 1 comprising the further steps of sparging the ethylene glycol monoaryl ether by subsurfacely introducing and dispersing up to 10 weight percent water therein at a temperature of 75° C. and 120° C. and pressure less than 100 mm Hg and drying to a moisture content less than 1 percent.
8. The process of Claim 7 wherein the sparging is carried out at a temperature of 90° C. to 110° C.
and pressure less than 50 mm Hg utilizing from 0.5 to 5 weight percent water.
and pressure less than 50 mm Hg utilizing from 0.5 to 5 weight percent water.
9. The process of Claim 8 wherein the ethylene glycol monoaryl ether is ethylene glycol monophenyl ether.
10. The process of Claim 9 comprising the additional step of filtering the ethylene glycol monophenyl ether to remove any insoluble salts present therein.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US36712882A | 1982-04-09 | 1982-04-09 | |
| US367,128 | 1982-04-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1195696A true CA1195696A (en) | 1985-10-22 |
Family
ID=23446020
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000424783A Expired CA1195696A (en) | 1982-04-09 | 1983-03-29 | Process for the production of ethylene glycol monoaryl ethers |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS58198432A (en) |
| CA (1) | CA1195696A (en) |
| DE (1) | DE3312684A1 (en) |
| GB (1) | GB2119373B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104326887A (en) * | 2014-10-11 | 2015-02-04 | 江苏常州酞青新材料科技有限公司 | Method for removing phenol in ethylene glycol phenyl ether refining course |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE10161351A1 (en) * | 2001-12-13 | 2003-06-26 | Cognis Deutschland Gmbh | Process for the production of alkoxylated nonionic surfactants |
| US9187392B2 (en) * | 2008-01-17 | 2015-11-17 | Lyondell Chemical Technology, L.P. | Production of propylene glycol monoalkyl ether |
| CN101712600A (en) * | 2008-10-07 | 2010-05-26 | 抚顺佳化聚氨酯有限公司 | Method for preparing ethylene glycol phenyl ether, propylene glycol phenyl ether and butylene glycol phenyl ether |
| CN111318311B (en) * | 2020-04-22 | 2022-09-06 | 上海多纶化工有限公司 | Cocatalyst, catalyst and application thereof |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2852566A (en) * | 1954-02-23 | 1958-09-16 | Koppers Co Inc | Production of aryl ethers |
| DE1133556B (en) * | 1960-02-05 | 1962-07-19 | Mo Och Domsjoe Ab | Process for bleaching polyalkylene ethers |
| US4404407A (en) * | 1981-06-08 | 1983-09-13 | Emery Industries, Inc. | Process for enhancing the fragrance qualities of ethylene glycol monoaryl ethers |
-
1983
- 1983-03-29 CA CA000424783A patent/CA1195696A/en not_active Expired
- 1983-04-06 JP JP5938983A patent/JPS58198432A/en active Granted
- 1983-04-08 DE DE19833312684 patent/DE3312684A1/en active Granted
- 1983-04-11 GB GB8309788A patent/GB2119373B/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104326887A (en) * | 2014-10-11 | 2015-02-04 | 江苏常州酞青新材料科技有限公司 | Method for removing phenol in ethylene glycol phenyl ether refining course |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2119373B (en) | 1985-11-27 |
| GB2119373A (en) | 1983-11-16 |
| JPH0333694B2 (en) | 1991-05-20 |
| DE3312684C2 (en) | 1991-07-04 |
| JPS58198432A (en) | 1983-11-18 |
| GB8309788D0 (en) | 1983-05-18 |
| DE3312684A1 (en) | 1983-10-13 |
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