Process for the preparation of polyether glycol

In the process for preparing polyether glycol comprising (A) polymerizing tetrahydrofuran or a mixture of tetrahydrofuran and other copolymerizable cyclic ether(s) in the presence of a ring-opening polymerization catalyst comprising fuming sulfuric acid and/or fluorosulfuric acid as principal component, (B) adding water or an aqueous alkali solution to the polymerization product, and heating said reaction product under the strongly acidic condition to hydrolyze the same and (C) washing the hydrolysis product comprising polytetramethylene glycol and polyether glycol having oxytetramethylene groups as principal constituent, the polymerization of the tetrahydrofuran or the mixture of tetrahydrofuran and other copolymerizable cyclic ether(s) in the (A) step is carried out by (1) contacting the same with a ring-opening polymerization catalyst at a temperature within the range of -30.degree. C. to 10.degree. C. in the first stage, and (2) elevating the reaction temperature, when the conversion of said monomer into the polymer has reached 5% or more, to a temperature which falls within the range of 0.degree. C. to 40.degree. C. and is at least 10.degree. C. higher than the reaction temperature in the first stage and continuing the polymerization at this temperature. This process enables the effective and easy preparation of a highly functional polyether glycol having a relatively low molecular weight of about 500 to 5,000 and comprising oxytetramethylene groups as principal constituent, said polyether glycol being useful as a starting material for the preparation of polyurethanes, elastomeric polyesters, elastomeric polyamides and the like.

This invention relates to a process for the preparation of a polyether 
glycol, and more particularly the invention relates to a novel process for 
the effective and easy preparation of a highly functional polyether glycol 
having a relatively low molecular weight and comprising oxytetramethylene 
groups as principal constituent, said polyether glycol being useful as a 
starting material for the production of polyurethane, elastomeric 
polyesters, elastomeric polyamides and the like. 
It is well known that polytetramethylene glycol (hereinafter referred to as 
PTMG) and a polyether glycol having oxytetramethylene groups as principal 
constituent (both PTMG and said polyether glycol being hereinafter 
referred to collectively as PTMG type polyether glycol) can be produced by 
polymerizing tetrahydrofuran alone or a mixture of tetrahydrofuran and 
other copolymerizable cyclic ether(s) in the presence of a ring-opening 
polymerization catalyst and then hydrolyzing the polymerization product. 
The industrial importance of said PTMG type polyether glycol has recently 
been spotlighted because this material, when used for the preparation of 
polyurethanes, elastomeric polyesters, elastomeric polyamides and the 
like, can provide products with many excellent properties such as 
mechanical properties and antihydrolytic property, and nowadays this 
material is widely used in many fields of industry. For application to 
such uses, said material is usually required to have a relatively low 
molecular weight of about 500 to 5,000 in terms of number-average 
molecular weight, and it is also important that said material is 
hydroxyl-terminated at both ends of the molecule, and in other words, it 
has a high functionality (close to 2). There are known various types of 
ring-opening polymerization catalysts for tetrahydrofuran, but the 
catalysts capable of easily providing the hydroxyl-terminated PTMG type 
polyether glycol with a relatively low molecular weight are limited to few 
examples. Use of fuming sulfuric acid or fluorosulfuric acid as such a 
ring-opening polymerization catalyst is already known (see, for example, 
Japanese Patent Publication Nos. 25438/73, 28917/74 and 3104/70). 
According to these methods using a catalyst comprising as main component a 
strongly acidic protonic acid, there can easily be produced a 
polymerization product having a number-average molecular weight of about 
1,000 to 3,000, and it is also possible to easily obtain a 
hydroxyl-terminated PTMG type polyether glycol by hydrolyzing said 
polymerization reaction product under an acidic condition. However, these 
methods, when applied industrially, require use of a relatively large 
amount of the catalyst for obtaining a satisfactory conversion, and hence 
there are needed the large-scale facilities for the storage and handling 
of the catalyst. Furthermore, the release of a large amount of acids as 
waste material necessitates a great deal of labor and cost for their 
disposal. Such a large amount of the catalyst is required because the 
catalytic efficiency of said types of catalyst is low, resulting in an 
insufficient utilization of the catalyst added. Thus, the development of a 
method capable of improving the catalytic efficiency to allow the amount 
of the catalyst used to be decreased has been desired. Also, because these 
catalysts are strong protonic acid, a large amount of heat of mixing is 
evolved when the catalyst is contacted with tetrahydrofuran. Therefore, 
not only is it difficult to control the reaction temperature, but there 
are also caused undesirable phenomena such as coloration or decomposition 
of the polymerization product. In order to avoid such undesirable 
phenomena, the polymerization may be performed at a low temperature of not 
more than 0.degree. C., but at such low temperatures, the polymerization 
rate is lowered to require a long time for the reaction. In addition, when 
the molecular weight of the polymerization product obtained is 1,000 or 
more, the entire polymerization system could be solidified to lose 
fluidity in a high-conversion operation, making it impossible to carry out 
such operations as stirring, transport, etc. Moreover, the polymerization 
at such low temperatures tends to produce a polymerization product with a 
relatively high molecular weight and it is extremely difficult to obtain a 
PTMG type polyether glycol having a molecular weight of 1,000 or less. 
In view of these circumstances, the present inventors have conducted 
extensive research on the production of PTMG type polyether glycol, and 
have, as a result, found a novel process according to which the catalytic 
efficiency is markedly enhanced and the desired PTMG type polyether glycol 
can be produced at a high conversion without causing the coloration of the 
polymerization product and the solidification of the polymerization 
system. 
An object of this invention is provide a process for producing a PTMG type 
polyether glycol having a number-average molecular weight of about 500 to 
5,000, particularly 500 to 3,000, using fuming sulfuric acid or 
fluorosulfuric acid as a ring-opening polymerization catalyst, with a 
markedly enhanced catalytic efficiency. The term "catalytic efficiency" is 
here defined as the ratio of the number of moles of the PTMG type 
polyether glycol molecule obtained to the number of moles of the catalyst 
used for the polymerization, and the calculation formula thereof is shown 
in the Examples which appear hereinafter. 
Another object of this invention is to provide a process capable of easily 
producing a PTMG type polyether glycol without causing any undesirable 
phenomena such as the coloration of the polymerization product, the 
solidification of the polymerization system at a high conversion, or the 
like. 
Thus, according to the present invention, there is provided a process for 
preparing a polyether glycol which comprises (A) polymerizing 
tetrahydrofuran alone or a mixture of tetrahydrofuran and other 
copolymerizable cyclic ether(s) (both being hereinafter referred to 
collectively as tetrahydrofuran type monomer(s)) in the presence of a 
ring-opening polymerization catalyst comprising fuming sulfuric acid 
and/or fluorosulfuric acid as principal constituent, (B) adding water or 
an aqueous alkali solution to the polymerization product and heating the 
system under the strongly acidic condition to hydrolyze said 
polymerization product, and (C) washing the hydrolysis product comprising 
the PTMG type polyether glycol, characterized in that the polymerization 
of the tetrahydrofuran type monomer in the (A) step is carried out by (1) 
contacting the tetrahydrofuran type monomer with the ring-opening 
polymerization catalyst at a temperature within the range of -30.degree. 
to 10.degree. C. at the first stage and (2) elevating the reaction 
temperature, when the conversion of the tetrahydrofuran type monomer into 
the polymer has reached 5% or more, to a temperature which falls within 
the range of 0.degree. C. to 40.degree. C. and is at least 10.degree. C. 
higher than the reaction temperature at the first stage and continuing the 
polymerization at this temperature. 
According to the process of this invention, the polymerization of the 
tetrahydrofuran type monomer is effected in the specific two stages, 
whereby the catalytic efficiency can be greatly increased, thereby 
reducing the amount of the catalyst used and the catalyst cost as well as 
the amount of waste acids produced in the preparation process, and also 
decreasing the load for the treatment thereof. Also, the process of this 
invention is not accompanied by the undesirable phenomena such as 
coloration of the polymerization product and solidification of the 
polymerization system at a high-conversion unlike the conventional 
methods, so that it is possible to produce very easily a PTMG type 
polyether glycol having a number-average molecular weight of about 500 to 
5,000 which is most suited for the industrial uses. Since the process of 
this invention has thus many advantages, it is of extremely high 
industrial utility value. According to the conventional methods, 
particularly when using a catalyst comprising as principal component 
fuming sulfuric acid, the catalytic efficiency is low and also, because of 
high tendency of coloration of the polymerization product, the 
polymerization must be performed at a low temperature, which causes the 
problem of possible solidification of the polymerization system at a high 
conversion. For these reasons, the process of this invention proves to be 
particularly high in its utility value when applied to the polymerizations 
using a catalyst comprising, as principal component, fuming sulfuric acid. 
The present invention is described in further detail below. 
In the process of this invention, it is imperative that in the (A) step, 
the contact of the tetrahydrofuran type monomer with the catalyst to 
effect the polymerization reaction is first conducted at a low temperature 
(first stage), and then the temperature is elevated under the specific 
conditions and the polymerization is continued at such an elevated 
temperature (second stage). At the first stage, the reaction temperature 
is set within the range of -30.degree. C. to 10.degree. C. If the reaction 
temperature exceeds 10.degree. C. at the first stage, there is 
substantially no improvement of catalytic efficiency and further the 
reaction control becomes difficult owing to the evolution of heat when 
mixing the tetrahydrofuran type monomer with the catalyst, resulting in an 
increased tendency of coloration or decomposition of the polymerization 
product. On the other hand, when the reaction temperature at the first 
stage is below -30.degree. C., there is required a high-capacity cooling 
equipment and, in addition, the polymerization rate becomes very low, 
resulting in a reduced productivity. This is undesirable from the 
commercial viewpoint. Thus, in order to attain a particularly remarkable 
improvement of catalytic efficiency, it is desirable to control the 
first-stage reaction temperature within the range of -30.degree. C. to 
0.degree. C. 
Then, at the second stage, the reaction temperature is elevated to a 
temperature which falls within the range of 0.degree. C. to 40.degree. C. 
and is at least 10.degree. C. higher than that at the first stage when the 
conversion of the monomer into the polymer has reached 5% or more, and the 
polymerization reaction is further continued at this temperature. If the 
conversion at the end of the first stage is less than 5%, there can be 
obtained no significant improvement of catalytic efficiency. For 
maximizing the improvement of catalytic efficiency, the conversion at the 
end of the first stage should preferably be 10% or more. On the other 
hand, the upper limit of conversion at the end of the first stage may be 
varied depending on the monomer/catalyst ratio, the molecular weight of 
PTMG type polyether glycol to be produced and other factors, and cannot be 
determined uniquely, but usually said upper limit is set taking into 
account the facts that too high a conversion leads to a limited 
improvement of catalytic efficiency and that, in the case of a 
high-molecular-weight material, the viscosity of the polymerization system 
is increased and the entire system becomes finally a solid state. When 
considering both the catalytic efficiency-improving effect and the 
operational convenience, it is desirable that the conversion at the end of 
the first stage be set within the following ranges depending on the 
number-average molecular weight of the objective PTMG type polyether 
glycol: 
______________________________________ 
Number-average molecular 
Conversion at the end 
weight of PTMG type poly- 
of the first stage 
ether glycol (%) 
______________________________________ 
Below 1,000 10-40 
1,000-2,000 10-45 
Above 2,000 10-35 
______________________________________ 
If the reaction temperature at the second stage is below 0.degree. C., 
substantially no improvement of catalytic efficiency is obtained, and it 
also becomes very difficult to produce a PTMG type polyether glycol having 
a number-average molecular weight below 1,000. On the other hand, if the 
second-stage reaction temperature exceeds 40.degree. C., the final 
conversion becomes low owing to the influence of chemical equilibrium of 
the polymerization reaction, resulting in a reduced catalytic efficiency 
and an increased load for the recovery and purification of the unreacted 
monomer. There may also take place coloration or decomposition of the 
polymerization product. Also, substantially no improvement of catalytic 
efficiency is observed when the difference between the first-stage 
polymerization temperature and the second-stage polymerization temperature 
is less than 10.degree. C. For the reasons of maximized improvement of 
catalytic efficiency and operational advantages, it is desirable that the 
second-stage reaction temperature falls within the range of 10.degree. C. 
to 40.degree. C. and the difference between the reaction temperature at 
the first stage and that at the second stage is at least 15.degree. C. The 
polymerization time at the second stage is not specifically defined as it 
is variable depending on the monomer/catalyst ratio, the reaction 
temperature and the other factors, but usually the best result is obtained 
when said polymerization time is about 1-5 hours. 
The monomer used in the process of this invention is tetrahydrofuran alone 
or a mixture of tetrahydrofuran and other copolymerizable cyclic ether(s). 
Examples of the copolymerizable cyclic ethers usable in this invention are 
three-membered ring ethers such as ethylene oxide, propylene oxide, 
epichlorohydrin, etc.; four-membered ring ethers such as oxacyclobutane, 
3,3-dimethyloxacyclobutane, 3,3-bis(chloromethyl)oxacyclobutane, etc.; 
five-membered ring ethers such as 2-methyltetrahydrofuran, 
3-methyltetrahydrofuran, 2,5-dihydrofuran, etc.; tetrahydropyran; 
oxacycloheptane and the like. For obtaining a polyether glycol having 
oxytetramethylene groups as principal constituent according to this 
invention, said cyclic ethers copolymerizable with tetrahydrofuran are 
used in an amount of 100 parts by weight or less, preferably 50 parts by 
weight or less, per 100 parts by weight of tetrahydrofuran. 
In the process of this invention, there is used a catalyst comprising 
fuming sulfuric acid and/or fluorosulfuric acid as a ring-opening 
polymerization catalyst. Used as fuming sulfuric acid for said purpose is 
one having a free SO.sub.3 concentration of about 40% by weight or less, 
preferably 20-35% by weight, which is generally used for the production of 
PTMG-polyether glycol. 
Said fuming sulfuric acid may be used alone, but, if necessary, a suitable 
co-catalyst may be incorporated for the purpose of increasing the 
polymerization rate or adjusting the molecular weight. As the co-catalyst, 
there may be used known ones such as perchloric acid, perchlorate, 
metallic fluorides, metallic borofluorides or aromatic compounds, but for 
the reasons of easy availability and treatment and good effect, a metallic 
borofluoride, particularly sodium borofluoride or potassium borofluoride 
is preferred. Fluorosulfuric acid is usually used singly as a ring opening 
polymerization catalyst, but in some cases, an open-chain carboxylic acid 
anhydride or the like may be incorporated. 
In practicing the process of this invention, the amount of the ring-opening 
polymerization catalyst used is not critical, but usually such a catalyst 
is used in the following amount ranges: in the case of fuming sulfuric 
acid, it is used in an amount of 10 to 40 parts by weight per 100 parts by 
weight of the monomer, and in the case of further adding a co-catalyst, 
this co-catalyst is used in an amount of 0.05 to 20 parts by weight per 
100 parts by weight of fuming sulfuric acid. In the case of fluorosulfuric 
acid, it is used in an amount of 1 to 20 parts by weight per 100 parts by 
weight of the monomer, and if necessary, an open chain carboxylic acid 
anhydride or the like may additionally be added in an amount of 5 to 400 
parts by weight per 100 parts by weight of fluorosulfuric acid. Actually, 
the amount of said ring-opening polymerization catalyst used is properly 
selected according to the intended molecular weight of the PTMG type 
polyether glycol and other factors. The polymerization manner is not 
critical in this invention and the polymerization may be effected in a 
batchwise manner, a continuous manner or the like. When the polymerization 
is conducted in a batchwise manner, it is preferred to continuously add 
the ring-opening polymerization catalyst to the monomer at a suitable rate 
for facilitating the removal of heat of mixing. According to the process 
of this invention, the monomer may be polymerized in the presence of an 
inert solvent such as cyclohexane, dichloroethane, dichloromethane or the 
like, but it is preferred to conduct the polymerization without using the 
solvent excepting special cases. 
In the (B) step, water or an aqueous alkali solution is added to the 
polymerization product, and under the strongly acidic condition the 
product is heated to hydrolyze the product. The amount of water or an 
aqueous alkali solution added is preferably such that the sulfuric acid 
concentration in the aqueous layer after the treatment is within the range 
of 5 to 40% by weight. If the sulfuric acid concentration exceeds 40% by 
weight, there is the tendency that the equilibrium conversion in the 
hydrolysis reaction is decreased and the amount of the residual sulfuric 
acid ester groups is increased. On the other hand, if the sulfuric acid 
concentration is less than 5% by weight, the hydrolysis reaction rate 
becomes low, and a long period of time is required for the treatment and a 
large amount of water is also required. Since the majority of the sulfuric 
acid ester group at the ends of the polyether is hydrolyzed by the 
treatment to form sulfuric acid, the sulfuric acid concentration in the 
aqueous layer after the treatment is substantially equal to the amount of 
sulfuric acid produced from the reaction between water and the amount of 
fuming sulfuric acid and/or fluorosulfuric acid used in the polymerization 
(as expressed by the following reaction formulae (1) and (2)). Therefore, 
the sulfuric acid concentration can be calculated from the amount of 
sulfuric acid used, and, if an alkali is added, deducing the amount of the 
sulfuric acid neutralized with the alkali from said amount. 
EQU H.sub.2 SO.sub.4.xSO.sub.3 +H.sub.2 O.fwdarw.(1+x)H.sub.2 SO.sub.4 ( 1) 
EQU FSO.sub.3 H+H.sub.2 O.fwdarw.H.sub.2 SO.sub.4 +HF (2) 
The hydrolysis may be accomplished by adding water alone to the 
polymerization product, but in the case of using a ring-opening 
polymerization catalyst comprising fuming sulfuric acid as a principal 
component, a large amount of fuming sulfuric acid is used particularly in 
the production of a low molecular weight PTMG type polyether glycol, so 
that a considerably large amount of water becomes needed where water alone 
is added. In such a case, it is recommended to add an alkali together with 
the water so as to neutralize a part of the sulfuric acid. In this case, a 
small amount of water is sufficient and the amount of the PTMG type 
polyether glycol dissolved in the aqueous layer becomes small. The alkali 
used for said purpose may be, for example, a hydroxide or oxide of an 
alkali metal or an alkaline earth metal, or ammonia. An alkali metal 
hydroxide or oxide is preferred. The amount of the alkali used is 
preferably such as to be not less than 1/4 of the amount required for 
neutralizing the mixture of water and the amount of fuming sulfuric acid 
and/or fluorosulfuric acid used in the polymerization but is such that the 
hydrolysis reaction system remains as strongly acidic as a pH of 3 or 
less, preferably 1 or less. Such an alkali may be added in its entire 
amount prior to the hydrolysis treatment, or may be added stepwise or 
continuously during the hydrolysis treatment. 
This method enables not only the quick and perfect accomplishment of the 
hydrolysis of the polyether terminal groups without adding a large amount 
of water at the time of hydrolysis reaction but also the great decrease of 
the amount of the PTMG type polyether glycol dissolved in the acidic 
aqueous solution while maintaining an acidity required for the advancement 
of the hydrolysis reaction. 
The hydrolysis temperature is not critical, and a temperature of not less 
than 50.degree. C., particularly 50.degree. to 150.degree. C., is 
preferred. If the hydrolysis temperature is less than 50.degree. C., the 
hydrolysis reaction rate is reduced to prolong the treatment time and also 
layer separation after the hydrolysis treatment becomes difficult, 
particularly in the production of a PTMG type polyether glycol having a 
molecular weight of 2,000 or more. On the other hand, if the hydrolysis 
temperature exceeds 150.degree. C., decomposition or deterioration of the 
PTMG type polyether glycol tends to take place during the hydrolysis 
treatment, and also the corrosive action of sulfuric acid or hydrogen 
fluoride is intensified, so that a very constly acid-resistant material is 
required for the hydrolysis reactor. The most preferred range of the 
hydrolysis temperature is 60.degree.-120.degree. C. Such a hydrolysis 
temperature may be kept constant throughout the hydrolysis treatment, or 
the hydrolysis may be effected while raising or lowering the temperature 
stepwise or continuously with the lapse of time. The hydrolysis treatment 
time is also not critical and it may be varied depending on the treating 
temperature, the sulfuric acid concentration and the molecular weight of 
the PTMG type polyether glycol. The hydrolysis treatment time is usually 
1-10 hours under the above-said conditions. The hydrolysis manner is also 
not critical in this invention, and the hydrolysis may be conducted in a 
batchwise manner or a continuous manner. It is also preferable to stir the 
reaction system by a suitable means because the polymerization product and 
the aqueous solution undergo a phase separation in the course of the 
hydrolysis treatment, whereby the system becomes heterogeneous. 
The terminal sulfuric acid ester groups are converted into hydroxyl groups 
by this hydrolysis treatment, and in order to minimize the amount of the 
PTMG type polyether glycol dissolved or emulsified in the washings in the 
subsequent step (C), it is preferable that the amount of the residual 
sulfuric acid ester groups be kept not more than 100 ppm, in terms of 
SO.sub.4, based on the weight of PTMG type polyether glycol. Moreover, it 
is more preferably not more than 20 ppm for minimizing the time required 
for the separation of the PTMG type polyether glycol layer and the aqueous 
layer after washing. The following methods may be cited as the preferred 
method of hydrolysis for minimizing the amount of residual sulfuric acid 
ester groups in the PTMG type polyether glycol. The first method comprises 
adding water to the polymerization product in such an amount that the 
sulfuric acid concentration in the aqueous layer after the hydrolysis 
treatment becomes 10-40% by weight, heating the resulting mixture with 
stirring at a temperature of 60.degree.-120.degree. C. for a period of 2-5 
hours to hydrolyze the product, allowing the hydrolysis mixture to stand 
to cause layer-separation, withdrawing the aqueous layer, adding thereto 
water again in an amount of 50-200 parts by weight per 100 parts by weight 
of the polymer together with sulfuric acid or a part of the aqueous layer 
withdrawn in an amount of 1% by weight based on the weight of the water, 
and heating the resulting mixture with stirring at a temperature of 
80.degree.-120.degree. C. for a period of 2-5 hours. The second method 
comprises adding water to the polymerization product, heating and stirring 
the resulting mixture under the same conditions as in the first method, to 
hydrolyze the polymerization product to a certain degree, adding sodium 
hydroxide or an aqueous solution thereof in an amount required for 
neutralizing approximately 90% of said sulfuric acid, and then heating 
with stirring the resulting mixture under the same conditions. The third 
method comprises adding water to the polymerization product in such an 
amount that acid concentration becomes 50% by weight or less, adding to 
the system an aqueous solution of sodium hydroxide in an amount required 
for neutralizing 80-95% of said sulfuric acid continuously over a period 
of 1-3 hours while hydrolyzing a part of the polymerization product by 
heating the system with stirring at a temperature of 
60.degree.-120.degree. C., heating the system with stirring for a further 
1 to 5 hours after completion of the addition to complete the hydrolysis. 
Other various hydrolysis methods may be used. 
If an antioxidant, such as a phenolic one or an amine type one, is added to 
the polymerization product prior to the hydrolysis treatment, it is 
possible to prevent the coloration which may otherwise occur when the 
obtained PTMG type polyether glycol is reacted with a diisocyanate to form 
a polyurethane. The polymerization product contains the unreacted monomer. 
This unreacted monomer may be recovered by a suitable means such as 
distillation or the like prior to the hydrolysis treatment, and in this 
case, it is preferred that the unreacted monomer is recovered in the 
course of said hydrolysis treatment. Usually, after said hydrolysis 
treatment, the aqueous layer and the PTMG type polyether glycol layer are 
separated by a suitable means such as allowing the mixture to stand, 
subjecting to centrifugation, or the like, and the separated aqueous phase 
is then withdrawn. The temperature for the separation of layers is not 
critical, though a high temperature is preferred because of easier 
separation of layers and smaller solubility of PTMG type polyether glycol 
in the aqueous layer, and it is most preferable to perform the separation 
of layers at said hydrolysis temperature. 
However, in the case of using a basic magnesium salt in the subsequent (C) 
step, the aqueous layer need not be withdrawn after the hydrolysis 
treatment and the whole system comprising the aqueous layer having added 
thereto the basic magnesium salt may be washed as it is. 
After the separation of the aqueous layer from the PTMG type polyether 
glycol layer and the withdrawal of the aqueous layer, the acid in the PTMG 
type polyether glycol layer is removed by washing. The method of washing 
to remove the acid from the PTMG type polyether glycol is not critical and 
this may be achieved by, for example, neutralyzing the PTMG type polyether 
glycol layer with a solid alkali, removing the produced salt and the solid 
alkali by filtration and then removing the volatile matters under reduced 
pressure. 
It is, however, important that the PTMG type polyether glycol is 
substantially free from the terminal sulfuric acid ester groups of 
polyether produced during the polymerization and from the acids produced 
during the hydrolysis treatment of said terminal sulfuric acid ester 
groups, that is to say, the residual acid content is very important. When 
the residual acid content is large, the PTMG type polyether glycol is 
decomposed upon heating, and the urethanation and esterification are 
hindered, whereby undesirable side reactions are caused, resulting in the 
problems that there cannot be produced polyurethanes, elastomeric 
polyesters or elastomeric polyamides excellent in physical properties. A 
preferred washing method for removing such terminal sulfuric acid ester 
groups or residual acid matters is to wash the PTMG type polyether glycol 
with a neutral sulfate solution or a basic magnesium salt solution. In the 
case of using a neutral sulfate solution as the washing solution, the 
neutral sulfate should be such that the aqueous solution thereof is 
neutral and the solubility thereof in water at the treating temperature is 
at least 5% by weight. As the neutral sulfate, there are preferred sodium 
sulfate, potassium sulfate and magnesium sulfate from the viewpoint of 
easy availability, low cost and waste water quality. In order to 
effectively perform the treatment, the amount of the sulfate solution used 
is preferably within the range of 20-200 parts by weight per 100 parts by 
weight of the PTMG type polyether glycol. The sulfate solution may be 
freshly prepared for said purpose, and it is also possible to use the 
whole or a part of the aqueous layer withdrawn after the hydrolysis 
treatment in the (B) step which has been neutralized precisely to 
neutrality with an alkali and properly adjusted in concentration. In the 
case of adding an alkali during the hydrolysis treatment, it is convenient 
to use an alkali capable of forming a water-soluble neutral sulfate, and 
to neutralize the withdrawn aqueous layer with the same alkali. The 
washing treatment with such a neutral sulfate solution is preferably 
performed while heating the system to a temperature of at least 50.degree. 
C. If the washing treatment temperature is less than 50.degree. C., the 
separation of layers after the treatment proves difficult particularly in 
the case of producing a PTMG type polyether glycol having a molecular 
weight of at least 2,000. In addition, the reduction of the amounts of 
residual sulfuric ester groups and residual acid matters becomes 
difficult. From the viewpoint of the corrosion of apparatus discussed in 
relation to the (B) step, the treating pressure and the like, said 
treatment should be conducted at a temperature of not more than 
150.degree. C., preferably not more than 120.degree. C. The washing 
treatment temperature may be kept constant throughout the treatment or may 
be varied during the treatment. Any washing treatment time may be selected 
in this method depending upon the treating conditions such as treating 
temperature or the like, and usually, a period of about 0.5-5 hours 
suffices. The washing treatment may be conducted in various manners such 
as a batchwise manner, a continuous manner or the like, and also various 
types of treating apparatus may be used corresponding to the treating 
manners employed. In any case, it is desirable to stir the system by a 
suitable means. 
The amounts of residual sulfuric ester groups and residual acid matters can 
be reduced to a very low level by one washing treatment with a neutral 
sulfate solution, but if necessary, this washing treatment may be repeated 
twice or more times to reduce the amounts of residual sulfuric ester 
groups and residual acid matters to substantially zero. In the case of 
such a multi-stage washing treatment, when a batchwise treating method is 
employed, the aqueous layer separated after the treatment may be used as 
the treating solution in the subsequent stage after neutralizing said 
aqueous layer precisely to neutrality with an alkali. In the case of a 
continuous washing treatment, the aqueous layer separated after the 
treatment may as it is be supplied as the treating solution for the 
preceding stage to effect the so-called counter-current contact type 
treatment. Also, the aqueous layer withdrawn from the first stage may be 
supplied as the treating solution into the last stage after precisely 
neutralizing said aqueous layer with an alkali and properly adjusting the 
concentration and amount thereof, thereby enabling the majority of the 
treating solution to be recycled and used. By employing any of these 
methods, it is possible to greatly reduce the amount of the neutral 
sulfate used in the batchwise or continuous washing treatment. There may 
be employed various other washing manners. 
In the case of using a basic magnesium salt solution, the basic magnesium 
salt may be, for example, magnesium hydroxide, magnesium oxide, magnesium 
carbonate, basic magnesium carbonate or a mixture thereof. Usually, these 
basic magnesium salts are low in solubility in water, so that in the case 
of adding such a salt in a small quantity, it may be used in the form of 
an aqueous solution, but when such a salt is added in a large amount, it 
may be used in the form of a suspension. Also, the magnesium salts such as 
magnesium carbonate or basic magnesium carbonate can be appreciably 
increased in solubility by blowing carbon dioxide gas into the aqueous 
solution thereof, and the thus prepared solution can be favorably used in 
this invention. Said basic magnesium salt may be dissolved or suspended in 
water alone, but for the production of a low molecular weight PTMG type 
polyether glycol, said magnesium salt may be dissolved or suspended in an 
aqueous solution of a suitable neutral salt for avoiding any loss of 
polyether glycol due to dissolution in the aqueous layer. In this case, a 
variety of neutral salts may be used, but the above-said neutral sulfates 
are most preferable. In the case of using a basic magnesium salt, it is, 
of course, possible to add water or a neutral salt solution to the 
unwashed PTMG type polyether glycol and then add a solid basic magnesium 
salt thereto. It is desirable to use such a basic magnesium salt in excess 
of the amount of residual acid matters in the system so that the pH of the 
system will always remain 7 or more. If the pH of the system becomes less 
than 7 in the course of the washing treatment due to the use of too small 
an amount of the basic magnesium salt, it becomes difficult to surely 
remove the residual acid matters from the system. 
The washing treatment with said basic magnesium salt solution may be 
accomplished by separating the layers in the system after the hydrolysis 
treatment, withdrawing the aqueous layer and then adding water containing 
a basic magnesium salt or an aqueous neutral salt solution containing a 
basic magnesium to the PTMG type polyether glycol layer, but in a 
preferred embodiment of this invention, said washing is carried out by 
directly adding an excess of a basic magnesium salt to keep the pH of the 
system above 7 without withdrawing the aqueous layer after the hydrolysis 
treatment. In this case, a relatively large amount of residual acid 
matters is contained in the aqueous layer just after the hydrolysis 
treatment, but it is not always necessary to neutralize the whole of the 
residual acid matters, but it is possible to add a basic magnesium salt of 
an amount sufficient to keep the pH of the system above 7 after 
neutralizing the aqueous layer with other alkali compounds such as sodium 
hydroxide, potassium hydroxide, sodium carbonate or sodium bicarbonate to 
such a degree that the pH of the aqueous layer remains below 7. In the 
case of using an alkali in an amount sufficient to neutralize a part of 
the sulfuric acid in the hydrolysis treatment, it is convenient to effect 
previously the neutralization with the same alkali. It is, of course, 
possible to use a basic magnesium salt as the alkali which is additionally 
used in the hydrolysis treatment. By such a method, it is possible to 
allow a neutral sulfate to exist in the aqueous layer, allowing the loss 
of PTMG type polyether glycol due to dissolution thereof in the aqueous 
layer to be greatly reduced particularly in the production of a low 
molecular weight PTMG type polyether glycol. Said basic magnesium salt may 
be used in a large excess, but in this case, a part of the magnesium salt 
remains undissolved because of low solubility thereof, resulting in a 
somewhat complicated operation. However, even in this case, the solids of 
the remaining basic magnesium salt can be easily separated from the PTMG 
type polyether glycol by a usual way such as filtration, or the like. 
In performing the washing treatment according to this invention, water 
containing a basic magnesium salt or an aqueous neutral salt solution 
containing a basic magnesium salt is used usually in an amount of 10-500 
parts by weight, preferably 20-200 parts by weight, per 100 parts by 
weight of the PTMG type polyether glycol. The treating temperature, 
treating time and treating method in the case of using an aqueous basic 
magnesium salt solution are the same as in the case of using a neutral 
sulfate solution. Particularly, in the case of performing washing with a 
neutral sulfate solution in the (C) step, the hydrolysis of the 
polymerization product polyether can be conducted in the region of a high 
sulfuric acid concentration in the aqueous layer, so that it is possible 
to decrease the amount of water added in the hydrolysis reaction and also 
there is no need of using a large-scale hydrolysis reactor. Furthermore, 
the loss of PTMG type polyether glycol due to its dissolution in the 
aqueous layer is lessened. 
Also, in the case of using a basic magnesium salt in the (C) step, there is 
no need of withdrawing the aqueous layer after the hydrolysis but said 
basic magnesium salt may be added to the said aqueous layer and the 
resulting mixture may be, as it is, subjected to washing. Thus, the 
troublesome works such as separation of the aqueous layer or adjustment of 
the basic magnesium salt solution for washing become unnecessary. 
Whichever washing method is employed in the (C) step, an alkali in an 
amount sufficient to neutralize a part of the sulfuric acid may, if 
necessary, be added along with water for the hydrolysis treatment in the 
(B) step, thereby further reducing the amount of water needed while also 
decreasing the amount of residual sulfuric ester groups. In particular, 
when a low molecular weight PTMG type polyether glycol having a molecular 
weight of 1,000 or less it is made possible to minimize the loss of the 
polyether glycol due to its dissolution in the aqueous layer. Further, 
such a solution permits very efficient extraction of the residual acid 
matters which are hard to extract with water, and the residual acid 
content can be reduced to nearly zero by repeating the washing several 
times. Also, the separation of layers after the treatment is very much 
facilitated, and further, in dissolution of the PTMG type polyether glycol 
in the aqueous layer during the treatment is minimized. 
After completion of the said washing treatment, the aqueous layer and the 
PTMG type polyether glycol layer are separated in a known manner such as 
allowing to stand or subjecting to centrifugation, and the aqueous layer 
is then withdrawn. The separation of layers is preferably conducted at a 
high temperature as in the case of the (B) step. 
Since the thus obtained PTMG type polyether glycol contains water in a 
fairly large amount, it is subjected to a suitable treatment such as 
heating under normal or reduced pressure to get rid of water and other 
volatile matters. Various devices such as rotary evaporator or thin film 
evaporator may be used for this purpose. In order to facilitate the 
removal of water, a small amount of a low-boiling solvent, which forms an 
azeotropic mixture with water, may be added, and the resulting mixture may 
be evaporated and dried. The removal of the volatile matters is preferably 
conducted under reduced pressure for preventing decomposition or 
deterioration of PTMG type polyether glycol at high temperatures. The 
resulting PTMG type polyether glycol may be immediately put to use as a 
starting material for the preparation of polyurethane and the like, but 
preferably it is further subjected to filtration with a suitable filter to 
eliminate the solid impurities. By conducting the filtration after 
perfectly removing water and volatile matters, it is possible to prevent 
the PTMG type polyether glycol from being contaminated by the neutral 
sulfate or basic magnesium salt even where the separation of layers after 
the washing treatment is imperfect. Such filtration is preferably 
performed at a high temperature of around 60.degree.-120.degree. C. for 
reducing the viscosity of the PTMG type polyether glycol and facilitating 
the filtration.

The present invention is described in further detail below referring to 
Examples, which are merely by way of illustration and not by way of 
limitation. In the following Examples, all of the number-average molecular 
weights were measured by using a vapor pressure osmometer, and the 
hydroxyl number (mg of KOH equivalent to OH group in 1 g of polymer) and 
acid number were determined by an analysis according to the method of 
JIS-K 1557-1970. 
EXAMPLE 1 
A four-necked separable flask having an internal volume of 1.2 liters and 
provided with a Teflon-made stirrer, a dropping funnel, a thermometer and 
a three-way cock was dried in vacuo and then purged with a nitrogen gas, 
after which 500 g of tetrahydrofuran dehydrated by molecular sieves to a 
water content of 80 ppm was placed in said flask and cooled to -20.degree. 
C. Then, 100 g of fuming sulfuric acid with a free SO.sub.3 concentration 
of 25% by weight (hereinafter referred to as 25% fuming sulfuric acid) was 
dropped into said tetrahydrofuran under stirring from the dropping funnel 
over 40 minutes. During this dropping, the reaction mixture was cooled so 
that its temperature was maintained at -20.degree. C..+-.2.degree. C. 
After completion of this dropwise addition of said 25% fuming sulfuric 
acid, the mixture was stirred and reacted at -20.degree. C. for 2 hours, 
and then a part of the reaction solution was sampled and the amount of 
unreacted tetrahydrofuran was measured by a gas chromatography to 
determine the conversion. It was 32%. Thereafter, the reaction mixture was 
heated to 10.degree. C. and further reacted with stirring for 2 hours. The 
reaction mixture remained colorless throughout the reaction, and the 
reaction system was not solidified but maintained in a homogeneous liquid 
state. Then, the conversion was determined in the same manner as said 
above. it was 58%. After completion of the reaction, 420 g of ion 
exchanged water was added to the reaction mixture with stirring to 
terminate to a 2-liter, three-necked separable flask provided with a 
Teflon-made stirrer and a distilling column, and heated in an oil bath at 
95.degree. C. with stirring for 2 hours to hydrolyze the polymerization 
product terminals while recovering the unreacted tetrahydrofuran by 
distillation. After completion of the hydrolysis, stirring was stopped and 
the reaction mixture was allowed to stand at room temperature to cool the 
same. The separated aqueous layer was withdrawn and to the remaining oil 
layer were added 600 g of toluene and 3 g of calcium hydroxide. The 
resulting mixture was stirred at room temperature for one hour. Then, the 
mixture was subjected to a rotary evaporator to remove by distillation a 
part of toluene along with the residual water under reduced pressure at 
about 60.degree. C. Then, the solids were removed by filtration, and the 
residue was again subjected to the rotary evaporator to perfectly remove 
the volative matters by distillation, thereby obtaining colorless PTMG. 
This product had a number-average molecular weight of 1,000 and a hydroxyl 
number of 112, and the functionality as calculated therefrom was 2.0. The 
catalytic efficiency .alpha., as calculated from the following equation 
(1), was 0.93. 
##EQU1## 
On the other hand, the separated aqueous layer was neutralized with sodium 
hydroxide pellets in a 1-liter beaker until the pH of the aqueous solution 
became 7, and then the aqueous solution was evaporated to dryness by means 
of a rotary evaporator. To the residue was added 300 ml of chloroform, and 
the resulting mixture was well stirred, after which the solids were 
removed by filtration and the filtrate was subjected to distillation under 
reduced pressure to remove chloroform, whereby the residual PTMG was 
recovered from the aqueous solution. The weight of the recovered PTMG was 
19.4 g (6.7% of the amount of PTMG formed which was calculated from the 
conversion). 
EXAMPLE 2 
In the same reaction apparatus as in Example 1, to 500 g of tetrahydrofuran 
was dropwise added, while maintaining the same at -10.degree. C., a 
solution prepared by dissolving 0.75 g of sodium borofluoride in 105 g of 
25% fuming sulfuric acid over a period of 40 minutes. After completion of 
this dropwise addition, the mixture was further subjected to reaction at 
-10.degree. C. for one hour. The conversion of tetrahydrofuran in this 
reaction was 40%. Then, the reaction mixture was heated to 30.degree. C. 
and further reacted for 2 hours. The conversion upon the termination of 
this reaction was 55%. There was observed neither solidification nor 
coloration of the reaction system throughout the reaction. Then, the 
polymerization product was treated in the same manner as in Example 1 to 
obtain colorless PTMG. The results of the analyses of this product and the 
catalytic efficiency .alpha. were as shown in Table 1. 
Also, PTMG was recovered from the aqueous solution in the same manner as in 
Example 1. The amount of the recovered PTMG was 7.0% of the amount of 
formed PTMG which was calculated from the conversion. 
EXAMPLE 3 
In the same reaction apparatus as in Example 1, 150 g of 25% fuming 
sulfuric acid was dropwise added over a period of one hour to 500 g of 
tetrahydrofuran while being maintained at -20.degree. C., and after 
completion of the dropwise addition, the mixture was further subjected to 
reaction at -20.degree. C. for 10 minutes. The conversion at this point 
was 14%. Then, the reaction temperature was elevated to 30.degree. C. and 
the reaction was continued for one hour. The conversion at the end of this 
reaction was 47%. Neither solidification nor coloration of the reaction 
system was observed throughout the period of the reaction. Then, 180 g of 
ion exchanged water was added to the reaction mixture with stirring well 
to terminate the reaction, followed by addition of 145 g of a 45% by 
weight sodium hydroxide solution to neutralize a part of the sulfuric 
acid. After replacing the dropping funnel by a distilling column, the 
reaction mixture was heated in an oil bath at 95.degree. C. for 2 hours 
to perform the hydrolysis of the polymerization product terminals while 
distilling off unreacted tetrahydrofuran. After completion of the 
reaction, the reaction product was allowed to stand at room temperature to 
cool the same. The separated aqueous layer was withdrawn and the residual 
oil layer was treated in the same manner as in Example 1 to obtain 
colorless liquid PTMG. The analytical results of the product and the 
catalytic efficiency .alpha. were as shown in Table 1. 
PTMG was recovered from the aqueous solution in the same manner as in 
Example 1. The yield was found to be 2.1% of the amount of the PTMG formed 
which was calculated from the conversion. 
EXAMPLE 4 
To 250 g of tetrahydrofuran in a 600-liter, four-necked separable flask 
prepared similarly to that in Example 1 was dropwise added a solution 
formed by dissolving 0.75 g of sodium borofluoride in 27.5 g of 25% fuming 
sulfuric acid over a period of 30 minutes while keeping the 
tetrahydrofuran at -10.degree. C. After completion of said dropwise 
addition, the mixture was subjected to reaction at -10.degree. C. for 2 
hours. The reaction mixture was then heated to 30.degree. C. and further 
subjected to reaction for 2 hours. The conversion at the end of the 
first-stage reaction was 37% and the final conversion was 59%. Neither 
solidification nor coloration of the reaction system was observed 
throughout the reaction. After completion of the reaction, the mixture was 
stirred and 195 g of ion exchanged water was added thereto to terminate 
the reaction, followed by the same treatment as in Example 1 to obtain 
colorless, half-solid PTMG. The results of the analyses of this product 
and the catalytic efficiency .alpha. were as shown in Table 1. 
Recovery of PTMG from the aqueous solution in the same way as in Example 1 
was 1.1% of the amount of the PTMG formed which was calculated from the 
conversion. 
EXAMPLE 5 
To 250 g of tetrahydrofuran in the same reaction apparatus as in Example 1 
was dropwise added a solution prepared by dissolving 0.75 g of sodium 
borofluoride in 27.5 g of 25% fuming sulfuric acid over a period of 30 
minutes while keeping the tetrahydrofuran at -20.degree. C., followed by 
reaction at -20.degree. C. for 2 hours. Then, the reaction mixture was 
heated to 10.degree. C. and further subjected to reaction for 2 hours. The 
conversion at the end of the first-stage reaction was 19% and the final 
conversion was 69%. Neither solidification nor coloration of the reaction 
mixture was observed throughout the reaction. The reaction product was 
treated in the same manner as in Example 1 to obtain colorless, half-solid 
PTMG. Its analytical results and the catalytic efficiency .alpha. were as 
shown in Table 1. 
EXAMPLE 6 
In the same reaction apparatus as in Example 1, a solution prepared by 
dissolving 0.82 g of potassium borofluoride in 105 g of 25% fuming 
sulfuric acid was drowpise added to 500 g of tetrahydrofuran at 
-10.degree. C. over a period of 40 minutes, and thereafter the mixture was 
subjected to reaction at -10.degree. C. for one hour. The tetrahydrofuran 
conversion at the end of this reaction was 38%. Then, the reaction mixture 
was heated to 10.degree. C. and further subjected to reaction for 2 hours. 
The conversion at the end of this reaction was 60%. Neither solidification 
nor coloration of the reaction system was observed in the entire course of 
the reaction. The polymerization product was then treated in the same 
manner as in Example 1 to obtain colorless PTMG. Its analytical results 
and the catalytic efficiency .alpha. were as shown in Table 1. 
COMATIVE EXAMPLE 1 
The reaction was carried out under the same conditions as in Example 1, 
except that the temperature during the dropwise addition of fuming 
sulfuric acid was kept at 10.degree. C. and that after said dropwise 
addition, the reaction was performed at the same temperature for 4 hours. 
The PTMG thus obtained was a light-yellow liquid, and its analytical 
results and the catalytic efficiency .alpha. were as shown in Table 1. 
Superiority of the process of this invention is clear from the comparison 
of the results of this Comparative Example with those of Example 1. 
COMATIVE EXAMPLE 2 
The reaction was carried out under the same conditions as in Example 1, 
except that at the end of the first stage reaction, the heating was not 
conducted and the reaction was further continued at -20.degree. C. for 4 
hours. The resultant polymerization mixture was wax-like, and stirring 
thereof was hardly possible. The final conversion was 45%. Colorless PTMG 
was recovered in the same manner as in Example 1, and its analytical 
results and the catalytic efficiency .alpha. were as shown in Table 1. 
COMATIVE EXAMPLE 3 
In the same reaction apparatus as in Example 1, 150 g of 25% fuming 
sulfuric acid was dropwise added over a period of one hour to 500 g of 
tetrahydrofuran maintained at 0.degree. C., and the mixture was subjected 
to reaction at 0.degree. C. for 2 hours. The reaction mixture remained 
liquid even after completion of the reaction, and the conversion was 68%. 
This reaction mixture was then treated in the same way as in Example 1, 
except that 630 g of ion exchanged water was added, to obtain colorless 
PTMG. The results of the analyses of the obtained PTMG and the catalytic 
efficiency .alpha. were as shown in Table 1, which indicates far lower 
catalyst utilization efficiency than in the process of this invention. In 
the hope of obtaining PTMG having a molecular weight of around 650 
according to this method, experiments were carried out by changing the 
amount of fuming sulfuric acid used, the SO.sub.3 concentration, the 
fuming sulfuric acid dropping rate and the polymerization time after 
dropping, but any of the resulting PTMG's had a molecular weight above 
850, and it was impossible to obtain PTMG with a molecular weight of 
around 650. 
COMATIVE EXAMPLE 4 
The procedure of Example 3 was repeated, except that at the end of the 
first-stage reaction, the reaction temperature was not elevated and the 
reaction was continued at -20.degree. C. for 3 hours. The reaction system 
was partly solidified and became white turbid at the end of this reaction. 
The final conversion was 58%. The obtained PTMG was colorless, and its 
analytical results and the catalytic efficiency .alpha. were as shown in 
Table 1. 
COMATIVE EXAMPLE 5 
The procedure of Example 3 was repeated, except that the temperature during 
dropping of fuming sulfuric acid was kept at 30.degree. C. and that after 
said dropping the reaction was carried out at the same temperature for 2 
hours. It was difficult to control the temperature of the reaction mixture 
owing to generation of heat during dropping of fuming sulfuric acid, and 
the reaction mixture become yellow about 5 minutes after the start of said 
dropping, and it was brown at the end of said dropping. The obtained PTMG 
was also brown, and its analytical results and the catalytic efficiency 
.alpha. were as shown in Table 1. 
COMATIVE EXAMPLE 6 
In the same reaction apparatus as in Example 4, a mixture of 50 g of 25% 
fuming sulfuric acid and 1.75 g of sodium borofluoride was dropwise added 
to 250 g of tetrahydrofuran at 0.degree. C. over a period of one hour, and 
they were subjected to reaction at the same temperature for 2 hours. The 
final conversion was 66%, and the reaction system was solidified to form a 
wax-like mass. This product was then treated similarly to Example 4 to 
obtain colorless PTMG. The results of the analyses of the thus obtained 
PTMG and the catalytic efficiency .alpha. were as shown in Table 1. 
COMATIVE EXAMPLE 7 
In the experiment in Example 4, the heating was not conducted after the 
completion of the first-stage reaction and the reaction was continued at 
-10.degree. C. About 5 hours after completion of the dropwise addition, 
the reaction system was solidified to form a wax-like mass and stirring 
was not possible. The reaction was stopped at this point and PTMG was 
recovered in the same way as in Example 4. The analytical results from 
this product and the catalytic efficiency .alpha. were as shown in Table 
1. 
COMATIVE EXAMPLE 8 
In the experiment in Example 4, fuming sulfuric acid was added dropwise to 
tetrahydrofuran while maintaining its temperature at 30.degree. C. and 
then the reaction was continued at said temperature for 4 hours. The 
experimental procedures were otherwise the same as in Example 4. The final 
conversion was 30%, and the recovered PTMG was light brown. Its analytical 
results and the catalytic efficiency .alpha. were as shown in Table 1. 
COMATIVE EXAMPLE 9 
The experiment was carried out under the same conditions as in Example 5, 
except that the first-stage reaction time was 30 minutes after completion 
of the dropwise addition and the second-stage reaction time was 2.5 hours. 
The conversion at the end of the first-stage reaction was 1.5% and the 
final conversion was 63%. The results of the analyses of the resultant 
product and the catalytic efficiency .alpha. were as shown in Table 1. The 
results show that almost no increase of catalytic efficiency is confirmed 
when the conversion in the first-stage reaction is less than 5%. 
COMATIVE EXAMPLE 10 
In the experiment of Example 1, the temperature during the dropwise 
addition of the catalyst and the reaction temperature at the first stage 
were maintained at 5.degree. C. and the experiment was carried out under 
otherwise the same conditions. The final conversion was 46%, and the 
results of the analyses of the obtained colorless PTMG and the catalytic 
efficiency .alpha. were as shown in Table 1. The results indicate that 
substantially no increase of catalytic efficiency is seen when the 
difference between the first-stage reaction temperature and the 
second-stage reaction temperature is less than 10.degree. C. 
TABLE 1 
______________________________________ 
PTMG analytical results 
Number- 
average Color 
molecular Hydroxyl Functio- Catalytic 
tone of 
weight number nality efficiency 
PTMG 
______________________________________ 
Example 
1 1,000 112 2.0 0.93 Colorless 
2 970 116 2.0 0.86 Colorless 
3 580 193 2.0 0.87 Colorless 
4 1,830 61 2.0 0.94 Colorless 
5 2,380 47 2.0 0.84 Colorless 
6 1,090 103 2.0 0.87 Colorless 
Comp. 
Ex. 
1 970 116 2.0 0.73 Light- 
yellow 
2 1,180 95 2.0 0.61 Colorless 
3 1,050 107 2.0 0.69 Colorless 
4 1,040 108 2.0 0.59 Colorless 
5 910 123 2.0 0.49 Brown 
6 1,080 104 2.0 0.85 Colorless 
7 2,520 45 2.0 0.60 Colorless 
8 1,390 81 2.0 0.63 Light- 
brown 
9 2,450 46 2.0 0.75 Colorless 
10 970 116 2.0 0.76 Colorless 
______________________________________ 
EXAMPLE 7 
To 250 g of tetrahydrofuran in the same reaction apparatus as in Example 4, 
while maintaining the tetrahydrofuran at 0.degree. C., was dropwise added 
20 g of fluorosulfuric acid over a period of 30 minutes, followed by 
reaction at 0.degree. C. for one hour. Then, the reaction temperature was 
elevated to 20.degree. C. and the mixture was subjected to reaction for 5 
hours. The conversion at the end of the first-stage reaction was 18% and 
the final conversion was 72%. Neither solidification nor coloration of the 
reaction system was observed throughout the polymerization reaction. At 
the end of the reaction, the mixture was stirred and 135 g of ion 
exchanged water was added thereto. The resulting mixture was then treated 
in the same manner as in Example 4 to recover colorless PTMG. This product 
had a number-average molecular weight of 1,880, a hydroxyl number of 60 
and a functionality of 2.0. The catalytic efficiency .beta. as calculated 
from the following equation (2) was 0.96. 
##EQU2## 
The amount (weight) of the PTMG recovered from the aqueous solution in the 
same manner as in Example 1 was 1.2% of the amount of the PTMG formed 
which was calculated from the conversion. 
EXAMPLE 8 
The same procedure as in Example 1 was repeated except that a mixture 
consisting of 225 g of tetrahydrofuran and 25 g of 
3,3-dimethyloxacyclobutane was used as the monomer. The conversion at the 
end of the first-stage reaction was 40% and the final conversion was 64%. 
Neither solidification nor coloration of the reaction system was observed 
throughout the course of the reaction. The colorless liquid polyether 
glycol thus obtained had a number-average molecular weight of 2,050, a 
hydroxyl number of 54 and a functionality of 2.0. The catalytic efficiency 
.alpha. was 0.91. 
Also, polyether glycol was recovered from the aqueous solution in the same 
manner as in Example 1. Its amount was 0.9% of the amount calculated from 
the conversion. 
EXAMPLE 9 
The same procedure as in Example 7 was repeated, except that the 
temperature during the dropping of fluorosulfuric acid and the reaction 
temperature at the first-stage reaction were both 5.degree. C. and that 
the reaction time after said dropping was 40 minutes. The conversion at 
the end of the first-stage reaction and the final conversion were 21% and 
71%, respectively, and neither solidification nor coloration of the 
reaction system was observed throughout the course of polymerization. The 
number-average molecular weight of the obtained PTMG was 1,900, the 
hydroxyl number was 59, the functionality was 2.0, and the catalytic 
efficiency .beta. was 0.93. 
COMATIVE EXAMPLE 11 
In the experiment in Example 7, the heating was not effected at the end of 
the first-stage reaction and the reaction was continued at 0.degree. C. 
for 5 hours. The final conversion was 68% and the reaction system was 
solidified when the reaction was completed. The reaction product was 
treated in the same manner as in Example 7 to recover colorless PTMG. It 
had a number-average molecular weight of 2,020, a hydroxyl number of 52 
and a functionality of 2.0, and the catalytic efficiency .beta. was 0.84. 
COMATIVE EXAMPLE 12 
In the experiment in Example 7, fluorosulfuric acid was added to 
tetrahydrofuran while maintaining the latter at 20.degree. C. and they 
were reacted at the same temperature for 6 hours and then treated in the 
same manner as in Example 7 to obtain colorless PTMG. The final conversion 
was 67%, and the obtained PTMG had a number-average molecular weight of 
1,930, a hydroxyl number of 58 and a functionality of 2.0. The catalytic 
efficiency .beta. was 0.87. 
EXAMPLE 10 
After the polymerization was conducted under the same conditions as in 
Example 1, the dropping funnel was replaced by the distilling column, and 
a solution prepared by dissolving 43 g of sodium hydroxide in 210 g of 
water (neutralization rate: 50%, equivalent to the sulfuric acid 
concentration of 20% after the treatment) was added to the contents in the 
apparatus with vegorous stirring. Then the mixture was heated with 
stirring in an oil bath at 95.degree. C. for 2 hours to conduct the 
hydrolysis reaction while recovering the unreacted tetrahydrofuran. After 
the reaction, the stirring was stopped and the reaction mixture was 
allowed to stand at room temperature to cool the same, whereby the mixture 
was separated into two layers. Thereafter, the same treatment as in 
Example 1 was repeated to recover PTMG from the oil layer and also from 
the aqueous solution. The former had a number-average molecular weight of 
960, a hydroxyl number of 117 and a functionality of 2.0. The amount of 
the PTMG recovered from the aqueous solution was 0.8% of the amount of 
PTMG formed which was calculated from the conversion. 
EXAMPLE 11 
The polymerization was performed under the same conditions as in Example 2 
and the resulting product was treated in the same manner as in Example 10. 
The PTMG recovered from the oil layer had a number-average molecular 
weight of 930 and a hydroxyl number of 121, and the amount of the PTMG 
recovered from the aqueous solution was 0.7% of the PTMG formed which was 
calculated from the conversion. 
EXAMPLE 12 
After the polymerization was conducted under the same conditions as in 
Example 4, the dropping funnel was replaced by the distilling column and 
then 250 g of ion exchanged water and 25 g of a 48% by weight sodium 
hydroxide solution were added, followed by the same treatment as in 
Example 10. The PTMG recovered from the oil layer had a number-average 
molecular weight of 1,840 and a hydroxyl number of 61 while the amount of 
the PTMG recovered from the aqueous solution was 0.1% of the amount of the 
PTMG formed which was calculated from the conversion. 
EXAMPLE 13 
After the polymerization was conducted under the same conditions as in 
Example 7, 100 g of ion exchanged water and 25 g of a 48% by weight sodium 
hydroxide solution were added and the reaction mixture was treated in the 
same manner as in Example 10. 
The amount of the PTMG recovered from the aqueous solution was 0.1% of the 
amount of PTMG formed which was calculated from the conversion and the 
analytical values of PTMG recovered from the oil layer were the same as 
those in Example 7. 
EXAMPLE 14 
After the polymerization was conducted under the same conditions as in 
Example 8, 250 g of ion exchanged water and 25 g of a 48% by weight sodium 
hydroxide solution were added and thereafter the same treatment as in 
Example 10 was conducted. 
The amount of the PTMG recovered from the aqueous solution was 0.1% of the 
PTMG formed which was calculated from the conversion, and the analytical 
values of PTMG recovered from the oil layer were identical with those of 
Example 8. 
EXAMPLE 15 
A four-necked separable flask having an internal capacity of 2 liters and 
equipped with a glass-made stirrer, a dropping funnel, a thermometer and a 
three-way cock was dried in vacuo and then filled with dry nitrogen gas. 
In this flask was placed 600 g of tetrahydrofuran which had been 
distilled, dehydrated and cooled to -10.degree. C., and then 66 g of 25% 
fuming sulfuric acid having dissolved therein 1.8 g of sodium borofluoride 
was dropwise added to said tetrahydrofuran with stirring from the dropping 
funnel over 30 minutes. During this dropwise addition, the cooling was 
controlled to maintain the internal temperature at -10.degree. C. After 
said dropwise addition, the mixture was subjected to reaction at 
-10.degree. C. for one hour and the conversion was determined. It was 21%. 
Then, the reaction mixture was heated to 20.degree. C. and subjected to 
reaction for 2 hours. The final conversion was 60%. After completion of 
the reaction, 5 g of water was added to terminate the polymerization. To 
the polymerization product was added 280 g of water (the sulfuric acid 
concentration after the treatment was about 20% by weight), and the 
dropping funnel was replaced by the distilling column, after which the 
flask was immersed in an oil bath at 90.degree. C. and the contents 
therein were vigorously stirred and heated for 2 hours to hydrolyze the 
product while recovering the unreacted tetrahydrofuran by distillation. 
After this treatment, stirring was stopped and the flask was allowed to 
stand in the oil bath. After the contents were separated perfectly into 
two layers, the aqueous layer was withdrawn. To the residual PTMG layer 
was added 350 g of a 20% by weight sodium sulfate solution, and then 
heated at 120.degree. C. for 2 hours, followed by a washing treatment and 
recovery of unreacted tetrahydrofuran. After separating and withdrawing 
the aqueous layer, to the residue was again added 200 g of a 20% by weight 
sodium sulfate solution, heated at 95.degree. C. for 2 hours and then 
washed. After the contents were perfectly separated into two layers, the 
aqueous layer was withdrawn and then the volatile matters were perfectly 
removed from the PTMG layer by using a rotary evaporator under reduced 
pressure at 80.degree. C. The number-average molecular weight, hydroxyl 
number, acid number, amount of residual sulfuric ester groups and amount 
of residual acid matters of the obtained PTMG are shown in Table 2. 
Method for determination of the contents of sulfuric ester groups and 
residual acid matters in PTMG type polyether glycol 
About 5 g of PTMG specimen was accurately weighed and put in a cell for 
colorimetric titration and then 5 ml of 0.01 N hydrochloric acid and 50 ml 
of isopropyl alcohol were added thereto to form a homogeneous solution. 
The sulfate ions in this solution were subjected to colorimetric titration 
with a 0.01 N barium perchlorate solution according to Japan Rubber 
Association Standards SRIS 3401-1976 using carboxyarsenazo as indicator to 
determine the sulfate ion content A (ppm) in the PTMG type polyether 
glycol. Separately, about 5 g of the specimen was accurately weighed and 
put in a 100-ml flask provided with a reflux cooler, and after adding 
thereto 5 ml of 0.01 N hydrochloric acid, the mixture was heated with 
stirring at 100.degree. C. for 2 hours. After being cooled to room 
temperature, the contents were transferred to the cell for colorimetric 
titration using 50 ml of isopropyl alcohol and subjected to colorimetric 
titration in the same way as above to determine the sulfate ion content B 
(ppm) in the PTMG type polyether glycol. The amount of the residual 
sulfuric ester is given by (B-A) and the amount of residual acid matters 
(and salts) is given by A. The amounts of residual sulfuric ester and 
residual acid matters were all determined by this method in the 
experiments described below. 
EXAMPLE 16 
In the same reaction apparatus as in Example 15, 126 g of 25% fuming 
sulfuric acid containing 0.9 g of sodium borofluoride was dropped from the 
dropping funnel into 600 g of tetrahydrofuran at -10.degree. C. with 
stirring over 40 minutes, after which the resulting mixture was subjected 
to reaction at -10.degree. C. for one hour. The conversion at the end of 
this reaction was 39%. Then, the reaction mixture was heated to 30.degree. 
C. and subjected to reaction at this temperature for 2 hours, after which 
10 g of water was added to the mixture to terminate the polymerization. 
The final conversion was 60%. Then, 530 g of water was added (sulfuric 
acid concentration was about 20%), and the reaction solution was heated 
and hydrolyzed in an oil bath at 80.degree. C. while distilling off the 
unreacted tetrahydrofuran in the same manner as in Example 1, and then 204 
g of a 48% by weight sodium hydroxide solution (corresponding to 90% 
neutralization degree) was added continuously over a period of one hour 
while the internal temperature was kept at 100.degree. C. to continue the 
hydrolysis. The recovery of unreacted tetrahydrofuran by distillation was 
continued during these operations. Then, in the same manner as in Example 
1, the reaction mixture was allowed to stand to cause separation of 
layers, after which the aqueous layer was withdrawn. The PTMG layer was 
washed at 80.degree. C. for one hour with 350 g of a 20% by weight aqueous 
sodium sulfate solution. After separating and withdrawing the aqueous 
layer again, the volatile matters were removed in the same manner as in 
the foregoing Examples and the residue was filtered through a 10-.mu. mesh 
membrane filter to obtain PTMG. The results of the analyses of the thus 
obtained PTMG were as shown in Table 2. 
EXAMPLE 17 
In the same reaction apparatus as in Example 15, 120 g of 25% fuming 
sulfuric acid was dropped from the dropping funnel into 600 g of 
tetrahydrofuran at -20.degree. C. with stirring over a period of 40 
minutes, and then the resulting mixture was subjected to reaction at 
-20.degree. C. for 2 hours. The conversion at the end of this reaction was 
32%. Then, the internal temperature was elevated to 10.degree. C., at 
which the mixture was subjected to reaction for 2 hours. Thereafter, 10 g 
of water was added to terminate the polymerization. The final conversion 
was 57%. Then, the dropping funnel was replaced by the distilling column, 
and the contents in the apparatus were stirred vigorously and mixed with a 
solution prepared by dissolving 52 g of sodium hydroxide in 250 g of water 
(neutralization degree: 50%, corresponding to 20% by weight sulfuric acid 
concentration), and the mixture was heated and hydrolyzed in an oil bath 
at 80.degree. C. for 2 hours while recovering unreacted tetrahydrofuran. 
In the same manner as in Example 15, the reaction mixture was allowed to 
stand to cause separation of layers. The aqueous layer was withdrawn and 
the PTMG layer was subjected twice to a heating and washing treatment with 
300 g of a 15% by weight sodium sulfate solution at 120.degree. C. The 
residual unreacted tetrahydrofuran was recovered in the first treatment. 
Thereafter, the same treatment as in Example 15 was conducted and finally 
the reaction product was filtered through a 10-.mu. mesh membrane filter 
to obtain PTMG. The results of analyses thereof were as shown in Table 2. 
EXAMPLE 18 
In the experiment in Example 17, the amount of 25% fuming sulfuric acid was 
changed to 180 g and the dropping thereof was conducted over one hour. The 
conversion after this treatment was 12%. Upon completion of said dropping, 
the internal temperature was elevated to 30.degree. C. and the reaction 
was continued for one hour. Then, 130 g of water was added to terminate 
the polymerization and the conversion was measured. It was 52%. After 
replacing the dropping funnel by the distilling column, a solution 
prepared by dissolving 101 g of sodium hydroxide in 130 g of water was 
added continuously over one hour and heated in an oil bath at 80.degree. 
C., and after said addition, the mixture was further heated and hydrolyzed 
at 80.degree. C. for one hour. Unreacted tetrahydrofuran was 
simultaneously recovered by distillation during this operation. Then, a 
solution prepared by dissolving 23 g of sodium hydroxide in 25 g of water 
was added again continuously over one hour. At the same time, the oil bath 
temperature was raised to 100.degree. C., and the mixture was heated and 
hydrolyzed while recovering unreacted tetrahydrofuran. After this 
treatment, the reaction mixture was allowed to stand to cause separation 
of layers, after which approximately 90% of the aqueous layer was taken 
out, and to the residue was added 150 g of a 20% by weight aqueous sodium 
sulfate solution and the resulting mixture was subjected to a heating and 
washing treatment at 100.degree. C. for 2 hours. Then, in the same manner 
as in the preceding Examples, the aqueous layer was removed and the PTMG 
layer was again subjected to a heating and washing treatment at 80.degree. 
C. for 30 minutes, after which the same operation was repeated once more. 
The resulting product was treated in the same way as in Example 17 to 
obtain PTMG. The results of its analyses are shown in Table 2. 
EXAMPLE 19 
The same experimental procedures as in Example 17 was repeated till the 
stage of separation of the aqueous layer after the heating and hydrolysis 
treatment at 80.degree. C. with a sodium hydroxide solution. Thereafter, 
the withdrawn aqueous layer was neutralized with a 10% by weight aqueous 
sodium hydroxide solution till the pH of the solution became nearly 6. 
After further adding a 1% by weight aqueous sodium carbonate solution 
until the pH of the solution reached 7, water was added to adjust the 
sodium sulfate concentration in the solution to 15% by weight, and then by 
using 300-g portions of the obtained solution instead of the sodium 
sulfate solution, the same washing treatment as in Example 17 was carried 
out. The results of the analyses of the thus obtained PTMG were as shown 
in Table 2. 
EXAMPLE 20 
In the same procedure as in Example 17, the aqueous layer withdrawn after 
the first washing treatment with a sodium sulfate solution was neutralized 
to a pH of 7 by using a 1% by weight aqueous sodium carbonate solution, 
and the obtained solution was added to the PTMG layer followed by the same 
washing treatment as in Example 17 to obtain PTMG. The results of its 
analyses are shown in Table 2. 
EXAMPLE 21 
The same procedure as in Example 16 was repeated, except that 300 g of a 
20% by weight aqueous magnesium sulfate solution was substituted for the 
sodium sulfate solution, and the obtained PTMG was analyzed in the same 
manner as in the foregoing Examples to obtain the results shown in Table 
2. 
EXAMPLE 22 
The same procedure as in Example 15 was repeated, except that a mixture 
consisting of 500 g of tetrahydrofuran and 100 g of 
3,3-dimethyloxacyclobutane was substituted for the tetrahydrofuran alone. 
In this case, the conversion by the reaction at -10.degree. C. was 41% and 
the final conversion was 72%. The results of the analyses of the obtained 
copolymerized polyether glycol were as shown in Table 2. 
TABLE 2 
______________________________________ 
Analytical results of PTMG type of polyether glycol 
Amount of 
Amount of 
Ex- Number- sulfuric 
residual 
am- average Hydroxyl Acid ester acid 
ple molecular number number groups matters 
No. weight (mgKOH/g) (ppm*.sup.1) 
(ppm*.sup.1) 
______________________________________ 
15 1,910 59.3 0.023 &lt;3*.sup.2 
5 
16 980 115 0.025 &lt;3*.sup.2 
&lt;3*.sup.2 
17 990 112 0.022 &lt;3*.sup.2 
&lt;3*.sup.2 
18 690 165 0.025 5 &lt;3*.sup.2 
19 990 113 0.015 5 6 
20 990 112 0.024 &lt;3*.sup.2 
&lt;3*.sup.2 
21 970 115 0.033 6 &lt;3*.sup.2 
22 2,320 48.8 0.016 &lt;3*.sup.2 
&lt;3*.sup.2 
______________________________________ 
Note:- 
*.sup.1 Content (ppm) in terms of SO.sub.4.sup.2.crclbar. in PTMG type 
polyether glycol. 
*.sup.2 Below analytical limits 
EXAMPLE 23 
In the same reaction apparatus as in Example 15, 100 g of 25% fuming 
sulfuric acid was dropped into 500 g of tetrahydrofuran at -20.degree. C. 
over 40 minutes, and then the resulting mixture was subjected to reaction 
at -20.degree. C. for 2 hours. The conversion at this point was 31%. Then 
the reaction mixture was heated to 10.degree. C. and subjected to reaction 
for 2 hours, after which 10 g of water was added to the mixture to 
terminate the polymerization. The final conversion was 58%. Thereafter, 
400 g of water was added to the polymerization mixture, and the dropping 
funnel was replaced by the distilling column, after which the contents in 
the flask were heated and hydrolyzed in an oil bath at 100.degree. C. with 
stirring for 2 hours while distilling off and recovering unreacted 
tetrahydrofuran. Then, the contents in the flask were allowed to stand at 
100.degree. C. to cause separation of layers and the aqueous layer was 
withdrawn. To the obtained PTMG layer were again added 230 g of water and 
20 g of the withdrawn aqueous layer, and the resulting mixture was 
refluxed with heating and hydrolyzed in an oil bath at 120.degree. C. with 
stirring for 2 hours and then allowed to stand at 100.degree. C. to cause 
separation of layers, after which the separated aqueous layer was 
withdrawn. The amount of residual sulfuric ester groups in PTMG was 5 ppm 
and the acid number was 0.21. To the resulting PTMG layer was further 
added 250 g of water having suspended therein 0.25 g of basic magnesium 
carbonate, and the resulting mixture was subjected to heating and washing 
treatment in an oil bath at 100.degree. C. for one hour while stirring the 
mixture vigorously, after which the mixture was allowed to stand to cause 
separation of layers. The mixture was not emulsified throughout the 
treatment, and upon allowing the mixture to stand, the mixture underwent 
separation of layers in a very short time, and the PTMG layer after the 
separation of layers was almost transparent. After removing the aqueous 
layer, the PTMG layer was subjected to perfect evaporation of volatile 
matters under reduced pressure at 80.degree. C., and then filtered through 
a 10-.mu. mesh membrane filter to obtain 260 g of colorless transparent 
PTMG (yield: 52%). The thus obtained PTMG was analyzed to determine its 
number-average molecular weight, hydroxyl number, acid number, and amount 
of residual sulfuric ester groups, all of which are shown in Table 3. 
EXAMPLE 24 
The same procedure as in Example 23 was repeated, except that 0.15 g of 
magnesium hydroxide was substituted for the basic magnesium carbonate. The 
analytical results of the resulting PTMG were as shown in Table 3. 
EXAMPLE 25 
The same procedure as in Example 23 was repeated, except that the water 
having suspended therein basic magnesium carbonate was replaced by 
solution prepared by blowing an appropriate amount of carbon dioxide gas 
into water having suspended therein 0.25 g of magnesium carbonate. The 
resulting PTMG was analyzed to obtain the results shown in Table 3. 
EXAMPLE 26 
440 g of water was added to the polymerization product obtained by 
effecting the polymerization under the same conditions as in Example 23, 
and the mixture was heated and hydrolyzed in an oil bath at 80.degree. C. 
with stirring for one hour while recovering the unreacted tetrahydrofuran. 
Then, the oil bath temperature was elevated to 100.degree. C. and 170 g of 
a 48% by weight sodium hydroxide solution was added continuously over a 
period of one hour, and the mixture was further stirred and hydrolyzed at 
100.degree. C. for 2 hours while recovering the unreacted tetrahydrofuran 
and then allowed to stand at 100.degree. C. to cause separation of layers. 
A part of the separated PTMG layer was sampled and the amount of residual 
sulfuric ester groups and acid value were measured. They were below 3 ppm 
and 0.25, respectively. Then, 5.4 g of solid basic magnesium carbonate was 
added to the system without withdrawing the aqueous layer and the system 
was stirred gently. Consequently, the best portion of the solids were 
dissolved in the aqueous layer and the pH of the mixture became 8. Then, 
the system was heated in an oil bath at 80.degree. C. for 2 hours, washed 
with stirring and then allowed to stand at 80.degree. C. to cause 
separation of layers. The pH of the system remained around 8 throughout 
these treatments. Also, the system stayed free of emulsification and 
substantially no difficulty was met for separation of layers, and the PTMG 
layer separated was almost transparent. This PTMG layer was treated in the 
same manner as in Example 17 to obtain PTMG and the latter was analyzed to 
obtain the results shown in Table 3. 
EXAMPLE 27 
The same procedure as in Example 26 was repeated till the hydrolysis 
treatment, and thereafter, without withdrawing the aqueous layer, 21 g of 
a 20% by weight aqueous sodium hydroxide solution was added and the 
mixture was heated in an oil bath at 80.degree. C. with stirring for about 
20 minutes. The pH of the mixture at this point was about 5. Then 1.5 g of 
a 15% by weight basic magnesium carbonate suspension in water was added 
and the mixed system was heated and washed with stirring at 80.degree. C. 
for one hour and then allowed to stand to cause separation of layers. The 
pH of the mixture stayed around 8 throughout the treatment, the mixture 
remained free of emulsification, the separation of layers occured easily, 
and the separated PTMG layer was almost transparent. PTMG was obtained by 
the same treatment as in Example 17 and analyzed in the same manner as in 
Example 17 to obtain the results shown in Table 3. 
EXAMPLE 28 
In the same manner as in Example 17, a solution prepared by dissolving 1.5 
g of sodium borofluoride in 55 g of 25% fuming sulfuric acid was dropped 
into 500 g of tetrahydrofuran at -10.degree. C. over 30 minutes, and the 
mixture was subjected to reaction at -10.degree. C. for one hour. The 
conversion at this point was 20%. Then the reaction mixture was heated to 
20.degree. C. and subjected to reaction at this temperature for 2 hours. 
The final conversion was 61%. Then, to the polymerization product was 
added 520 g of water and heated in an oil bath at 80.degree. C. with 
stirring for 2 hours while distilling off and recovering the unreacted 
tetrahydrofuran. Then, the oil bath temperature was elevated to 
100.degree. C. and 50 g of a 48% by weight aqueous sodium hydroxide 
solution was added continuously over a period of one hour to accomplish 
the hydrolysis of the reaction mixture. Recovery of the unreacted 
tetrahydrofuran was continued during said addition, and upon completion of 
said addition, the mixture was allowed to stand at 100.degree. C. to cause 
the separation of layers. The aqueous layer was withdrawn, and to the 
remaining PTMG layer was added 250 g of water and a part of the withdrawn 
aqueous layer, after which the sulfuric acid concentration in the aqueous 
layer was adjusted to about 1% by weight, and the mixture was again heated 
and stirred in an oil bath at 100.degree. C. for 2 hours to complete the 
hydrolysis and then allowed to stand at 100.degree. C. to cause separation 
of layers. A part of the separated PTMG layer was sampled and analyzed to 
determined the amount of residual sulfuric ester groups and acid number. 
They were 4 ppm and 0.27, respectively. Then, without withdrawing the 
aqueous layer, 9.7 g of a 20% by weight aqueous sodium hydroxide solution 
was added and the mixed system was heated and stirred in an oil bath at 
80.degree. C. for about 15 minutes and then, 1.3 g of a 15% by weight 
aqueous suspension of a basic magnesium carbonate to adjust the pH of the 
mixture about 8, followed by additional heating and washing with stirring 
in an oil bath at 80.degree. C. for 2 hours. Then, the mixture was allowed 
to stand to cause separation of layers. The mixture showed no 
emulsification phenomenon throughout the treatment, the separation of 
layers was easy, and the separated PTMG layer was only slightly turbid. 
After removing the aqueous layer, the remaining PTMG layer was treated in 
the same manner as in Example 17 to obtain PTMG. Its analytical results 
are shown in Table 3. 
TABLE 3 
__________________________________________________________________________ 
Analytical results of PTMG type polyether glycol 
Amount of 
Separation 
Amount of 
Number-average 
Hydroxyl 
Acid residual 
of layers 
residual 
Example 
molecular 
number 
number 
sulfuric ester 
after acid matters 
No. weight (mgKOH/g) groups (ppm*.sup.1) 
washing 
(ppm*.sup.1) 
__________________________________________________________________________ 
23 980 116 0.025 
4 Separated 
6 
in short time 
24 980 115 0.024 
5 Separated 
4 
in short time 
25 970 115 0.020 
&lt;3*.sup.2 
Separated 
&lt;3*.sup.2 
in short time 
26 970 116 0.018 
&lt;3*.sup.2 
Separated 
&lt;3*.sup.2 
in short time 
27 970 116 0.020 
&lt;3*.sup.2 
Separated 
&lt;3*.sup.2 
in short time 
28 1,940 57.9 0.030 
4 Separated 
5 
in short time 
__________________________________________________________________________ 
Note:- 
*.sup.1, *.sup.2 See Table 2.