Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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1059153
The present invention relates to a process for the
continuous etherification of trimethylolalkanes with allyl
chloride in the presence of aqueous sodium hydroxide solution
to give allyl ethers.
German Patent Specificatio~ 1,182,653 and 1,222,041
describe the acid-catalysed etherification of trimethylol-
alkanes with alkenols at an elevated temperature. However,
olefines are formed as undesir~ble by-products during acid-
catalysed etherifications.
It is known from German Patent Specification 1,178,840,
column 1, lines 1 - 9, to prepare allyl ethers of polyhydric
alcohols by reacting the polyol with allyl bromide in an excess
ofaq~us s~Lm h~x~esoh~tion at elevated temperatures. How-
ever, even using reaction times of more than 20 hours the
yields obtained are still unsatisfactory. The same publica-
tion relates to a variant according to which the reaction is
supposed to take place in dimethylsulphoxide, preferably at
between 95 and 140C.
German Patent Specification 1,021,346 has disclosed a
process for the preparation of monohydroxy-diethers, according
to which 1 mol of a polyhydric alcohol having three hydroxy-
alkyl groups on one carbon atom is reacted with at least 2 mols
of an alkylhalide or arylhalide and an equivalent amount of an
alkali metal hydroxide. If the alkali metal hydroxide and the
alkali metal halide are introduced into the trimethylolalkane,
the alkali metal salts of the trimethylolalkanes, formed in
the first stage, precipitate. Accordingly, one has the choice
of either ensuring, through alternate addition of alkali metal
hydroxide and alkyl halide, that the entire reaction mixture
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does not solidify, or of suspending the salts, through using
larger amounts of solvents (for example of the ether to be
produced),to the pointwhere it becomes possible at all to stir
the alkyl halides, which are in most cases volatile, into the
mixture. Even if a solvent is used the reaction only takes
place slowly, particularly at the beginning of the reaction;
the consequence of this is an unsatisfactory space-time yield.
The processes mentioned above give unsatisfactory
space-time yields and cannot be used for a continuous proce-
dure and so the present ivention seeks to provide asuitable process for continuous etherification-.
Surprisingly, it has now been found that the process
can be so modified, by simple measures, that it is suitable
for continuous running and gives a much increased space-
time yield.
The subject of the invention is a process for the
continuous etherification of trimethylolalkanes with allyl
chloride under an inert gas atmosphere in the presence of
aqueous sodium hydroxide solution, to give allyl ethers of the
formula
~ H (CH ) C / ~H ~ - (OCH2 - CH = CU2)
wherein
x denotes 0 or 1 and
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,'! n denotes 1, 2 or 3, preferably 2, comprising (i) introducing
an amount of the ether to be produced into a series of at least two reaction
zones (ii) continuously introducing from 1.05 to 1.3 mols sodium hydroxide,
as an aqueous solution, and 1.0 to 1.2 mols of aIlyl chloride, per mol of
hydroxyl group to be etherified while stirring and maintaining a concentra-
' tion such that sodium salts of trimethylolalkane do not precipitate, (iii)
maintaining a temperature in the range of from 80 to 130 C and the presence
of 0.5 to 1.7 parts by weight of toluene, relative to 1 part by weight of
sodium hydroxide, and distilling off a toluene water azlotrope until the con-
version~ relative to the trimethylolalkane, exceeds 99%.
The preferred temperature is between 90 and 110C and the prefer-
red weight of toluene is 0.7 to 1.0 parts by weight.
A stirred kettle cascade is an example of a suitable reaction
apparatus for the process according to the invention. The starting materials
are fed continuously into the first reactor of the cascade; in order, however,
to keep the reaction temperature at about 100C even if the throughput is
increased, it is advantageous to introduce an extra portion of allyl chloride,
consisting of 5 to 30 % of the allyl chloride employed, into the second
reactor of the cascade.
Since the concentration of sodium hydroxide solution and allyl -;
chloride is kept so low, even in the first reactor, that no sodium salts of
the trimethylolalkanes precipitate, the reaction mixture - essentially con-
sisting of trimethylolalkane allyl ether and sodium chloride which has pre-
cipitated - remains mobile. The use of a suitable stirrer therefore guaran-
tees complete mixing of the reactants, which is the precondition for a high
conversion rate.
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The amount of the ether initially introduced as the
solvent is, per reaction chamber (cascade), usually 8 to 12
times the amount of trimethylolalkane introduced per hour.
One economic advantage of the process accord-
ing to the invention is the use of aqueous sodium hydroxide
solution instead of solid sodium hydroxide. Viewed from the
technical aspect, the trouble-free metering of sodium hydroxide
solution must also be reg~rded as, in many respects, more
advantageous than the introduction of solid sodium hydroxide
into a reaction vessel filled with allyl chloride vapour.
However, unless a high proportion of the water is distilled
off azeotropically, a not inconsiderable part of the allyl
chloride reacts to form allyl alcohol and diallyl ether.
However, it is to be borne in mind that too high a content of
the toluene added as the entraining agent lowers the solu-
bility of the sodium salt of the trimethylolalkane to the
pointwhere it precipitates. The concentration of the sodium
hydroxide solution should be 40 to 50% by weight; this means
that the sodium hydroxide solution produced during the alkali
electrolysis can be employed directly as such.
Though the high reaction temperature, which is sub-
stantially above the boiling point of allyl chloride, namely
45C, keeps the concentration of the allyl chloride in the
reaction mixture very low, the high reaction rate of allyl
; 25 chloride under these conditions makes it possible to obtain
a very good space-time yield even under normal pressure pro-
vided atmospheric oxygen is kept away from the allyl compounds
by using an inert gas atmosphere.
The average residence time is as a rule between 8 and
16 hours.
Trimethylolalkane diallyl ethers are valuable starting
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materials for the preparation of air-drying synthetic resins.
Examples:
The ~ indicated in the text which follows are % by
weight.
5 Example 1:
Trimethylolpropane diallyl ether
- The reaction vessels used are two 5 1 vessels connec-
ted by a pipeline and each equipped with a stirrer, heating
and water separator.
At the beginning of the reaction, 3 1 of trimethylol
allyl ether mixture, as obtained from the reaction described,
are introduced into each vessel.
362 g of trimethylolpropane, 525 g of 50% strength
sodium hydroxide solution, 160 g of toluene and 342 g of allyl
15 chloride are introduced hourly into the first vessel.
The temperature in the liquid phase is kept at 90 -
100C by heating. m e temperature of the gas phase is 80 -
85C. 190 - 210 ml of water are separated off per hour.
A further 120 g/hour of allyl chloride are introduced
20 into the second vessel. Using appropriate heating, 170 -
180 ml/hour of water are separated off. The temperature of
the liquid phase is 95 - 105C and that of the gas phase is
85 - goc.
The reaction mixture runs from the first into the
25 second reactor and is run off continuously from there. me
crude product is neutralised with hydrochloric acid and the
sodium chloride is filtered off.
The conversion, relative to trimethylolpropane, is in
excess of 99%. Distillation of 200 g of crude product gives:
50 g of first runnings P760 mm Hg : 4 - 110C
: 132 g of main fraction bP0.2_0.4 mm Hg:98 - 140C
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8 g of residue.
The main fraction consists of 7% of trimethylolprop-
ane triallyl ether, 77% of trimethylolpropane diallyl ether
and 16~ of trimethylolpropane monoallyl ether.
Example 2
Trimethylolethane diallyl ether
The procedure followed is as described in Example 1
but the 362 g/hour of trimethylolpropane are replaced by
; 325 g/hour of trimethylolethane.
The distillation of 200 g of crude product gives:
65 g of first runnings bP760 mm Hg 45 - 110C
125 g of main fraction Po.2 - 0.3 mm Hg 95 - 134C
9 g of residue
The main fraction is composed of 8% of trimethylol-
ethane triallyl ether, 78% of trimethylolethane diallyl etherand 14% of trimethylolethane monoallyl ether.
The quantitative and qualitative analysis o~ the pro -
j ducts was carried out by means of calibrated gas chromatography.
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