Process for the preparation of polymers of definite viscosities

Process for the preparation of copolymers of definite specific viscosities from hydantoin vinyl ethers of the formula I and olefinically unsaturated compounds by free-radical polymerization of the monomers in a solvent mixture consisting of cyclohexane and toluene, it being possible to vary the specific viscosity of the copolymers within wide limits by altering the ratio of the two solvents. The meaning of the individual symbols can be seen in patent claim 1.

The present invention relates to a process for the preparation of polymers 
having definite viscosities from hydantoin vinyl ethers and olefinically 
unsaturated monomers, using a solvent consisting of cyclohexane and 
toluene. 
It is known that copolymers formed from hydantoin vinyl ethers and 
olefinically unsaturated compounds have a wide variety of possible uses. 
For example, it is apparent from U.S. Pat. Nos. 4,206,309 or its 
divisional U.S. Pat. No. 4,256,867 that these copolymers are suitable, 
inter alia, as thickeners, solubilisers, pseudoplasticisers or complexing 
agents. Polymers having definite molecular weights or specific viscosities 
are, however, necessary for these various applications. When regarded from 
the point of view of application, therefore, it is very important to be 
able to adjust the specific viscosity of polymers as desired over a wide 
range, since many central properties of the polymers, for example the 
complexing power or the thickening power, display, as is known, a marked 
dependence on the molecular weight or on the specific viscosity of the 
polymer. The said U.S. Pat. Nos. 4,206,309 or its divisional U.S. Pat. No. 
4,256,867 does not provide any information on which process conditions 
must be varied in order to obtain copolymers of a desired specific 
viscosity. 
Although U.S. Pat. No. 3,721,654, which has as its subject a process for 
the preparation of copolymers from maleic anhydride and 2-alkoxypropenes, 
discloses that copolymers having low viscosities are obtained if the 
maleic anhydride is employed in excess and that copolymers having high 
viscosities are obtained by employing the comonomers in equivalent 
quantities or using an excess of the 2-alkoxypropene, copolymers are 
obtained in unsatisfactory yields, in spite of relatively long 
polymerisation times. 
It has now been found that copolymers of hydantoin vinyl ethers and maleic 
anhydride which have viscosities differing in a controlled manner over a 
wide range are obtained in equally high yields even if equimolar 
quantities of comonomers are used, if the copolymerisation is carried out 
in a solvent mixture consisting of cyclohexane and toluene, copolymers 
having low specific viscosities being obtained using small proportions of 
cyclohexane in the solvent mixture and copolymers having higher 
viscosities being obtained using higher proportions of cyclohexane. 
The present invention therefore relates to a process for the preparation of 
copolymers having definite specific viscosities by copolymerising 
hydantoin vinyl ethers with copolymerisable compounds in an organic 
solvent and in the presence of a free-radical initiator, which comprises 
copolymerising, in the presence of an inert gas and within the temperature 
range from 20.degree. to 110.degree. C., 
(a) hydantoin vinyl ethers of the formula I 
##STR1## 
in which R.sub.1 represents hydrogen or an organic radical, R.sub.2 
represents an alkylene having 1 to 6 C atoms or the radical 
--alkylene--O).sub.n alkylene in which the alkylenes contain 1 to 6 C 
atoms and n represents a number from 1 to 6, and R.sub.3 and R.sub.4 
independently of one another each represent hydrogen, an alkyl having 1 to 
6 C atoms, or an aryl or R.sub.3 and R.sub.4 together represent the 
tetramethylene or pentamethylene radical, with 
(b) olefinically unsaturated compounds, in a molar ratio of a:b equal to 
1:0.01 up to 1:100, in a solvent mixture consisting of cyclohexane and 
toluene, the proportion of cyclohexane in the solvent mixture being 0.5 to 
95% by volume and 0.1 to 30 g of the comonomers (a) and (b) being employed 
for 100 ml of the solvent mixture. 
In the process according to the invention, it is preferable to use 
hydantoin vinyl ethers of the formula I in which R.sub.1 represents 
hydrogen or methyl, R.sub.2 represents ethylene, propylene or butylene and 
R.sub.3 and R.sub.4 independently of one another each represent hydrogen, 
methyl, ethyl or isopropyl or together represent the tetramethylene or 
pentamethylene radical; in particular, 
3-vinyloxyethyl-5,5-dimethylhydantoin is employed. 
The hydantoin vinyl ethers of the formula I are known compounds and can be 
prepared in accordance with the processes described in U.S. Pat. Nos. 
4,206,309 or its divisional U.S. Pat. No. 4,256,867 by reacting hydantoins 
with .omega.-chloroalkyl vinyl ethers. 
The olefinically unsaturated compounds (b) which are used are the monomers 
customary in free-radical polymerisation, such as vinyl acetate, 
acrylonitrile, vinyl ethers, diketene or derivatives of 
.alpha.,.beta.-unsaturated monocarboxylic or dicarboxylic acids. 
It is preferable to use as the monomer (b) the anhydrides of 
.alpha.,.beta.-unsaturated dicarboxylic acids, such as maleic acid, 
chloromaleic acid, methylmaleic acid, ethylmaleic acid, dichloromaleic 
acid, diphenylmaleic acid, n-butylmaleic acid, phenylmaleic acid, 
chloromethylmaleic acid, bromophenylmaleic acid or itaconic acid; maleic 
anhydride is employed in particular. 
When carrying out the process according to the invention in practice, the 
monomers and the solvent are initially taken and a clear solution is 
produced by warming. The free-radical initiator, dissolved in a little 
solvent is then added to this clear solution, after which the 
copolymerisation begins. In a preferred embodiment of the process 
according to the invention, the hydantoin vinyl ether of the formula I and 
the olefinically unsaturated compounds are employed in approximately 
equimolar quantities. 
As mentioned initially, copolymers having low specific viscosities are 
obtained if the proportion of cyclohexane in the solvent mixture is low. 
It is preferable to use 0.5 to 85, in particular 0.5 to 80, % by volume of 
cyclohexane, relative to the total volume of the solvent mixture 
consisting of toluene and cyclohexane; copolymers having specific 
viscosities within the range from about 0.5 to 5.5 are then obtained. 
The quantity of the comonomers in the solvent mixture can be varied within 
wide limits, but in general it should not exceed 30 g per 100 ml of 
solvent. It is preferable to employ 0.1 to 15 g, in particular between 5 
and 10 g, of monomers per 100 ml of solvent. 
The customary free-radical initiators can be used in the process according 
to the invention. Suitable initiators of this type are peroxides, for 
example potassium peroxysulfate or benzoyl peroxide, and also azo 
compounds, such as azoisobutyronitrile, or redox initiator systems, such 
as a mixture of iron(III) acetylacetonate, benzoin and benzoyl peroxide. 
It is also possible to use the temperature conditions customary for 
free-radical polymerisation in the process. In general, the reaction is 
carried out between room temperature and 110.degree. C., preferably 
between 50.degree. and 110.degree. C. and, in particular, within the 
temperature range from 50.degree. to 75.degree. C. 
The copolymers which are obtained by the process according to the invention 
are characterised by their specific viscosity, which is a measure of the 
molecular weight of a polymer. The viscosity measurements are carried out 
using solutions of 1 g of copolymer in 100 ml of dimethylformamide (DMF). 
As mentioned initially, the copolymers obtained by the process according to 
the invention can be used in many ways. Depending on their physical 
properties, they can be used as thickeners, solubilisers, crosslinking 
agents, flocculants, dispersants, adhesives, stiffening agents, binders, 
crystal growth regulators, pseudo-plasticisers (thixotropic agents), 
complexing agents and stabilising agents and also as builders for 
synthetic detergents, and are employed correspondingly in numerous 
branches of industry, for example in the paper industry as wet strength 
agents, in the textile industry as size, in the pharmaceutical and 
cosmetic industries and in the paint industry as thixotropic agents and in 
the agricultural chemicals industry as binders. 
The following examples illustrate the process according to the invention in 
greater detail without limiting it.

EXAMPLE 1 
Apparatus: a 350 ml flask equipped with a propeller stirrer, thermometer, 
condenser, heater and N.sub.2 inlet. 
______________________________________ 
Substances: 
______________________________________ 
3-Vinyloxyethyl-5,5-dimethyl- 
hydantoin 9.9 g (0.05 mol) 
Maleic anhydride (MA) 
4.9 g (0.05 mol) 
Azoisobutyronitrile 
0.074 g (0.5% relative to 
monomers) 
Cyclohexane and toluene, 
together 200 ml 
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(Monomers: solvent ratio = 7.4 g per 100 ml) 
The apparatus is flushed twice with N.sub.2. A gentle stream of nitrogen is 
then maintained for the whole duration of the experiment. The vinyl ether, 
MA, 40 ml of cyclohexane and 155 ml of toluene are initially taken and a 
solution is produced by stirring. The mixture is heated to 60.degree. C. 
The azoisobutyronitrile, dissolved in 5 ml of toluene, is added to the 
clear solution of the monomers. After a few minutes the solution becomes 
slightly cloudy and the polymerisation begins. After a polymerisation time 
of 6.4 hours altogether at 60.+-.2.degree. C., the mixture is cooled to 
room temperature and the product is filtered off under vacuum and dried to 
a constant weight in vacuo at 50.degree. C. 
Yield: 14.6 g=98.6% of theory. 
Specific viscosity: 0.8250 (1% solution in DMF [dimethylformamide] at 
25.degree. C.) 
EXAMPLES 2 TO 9 
The following examples are carried out under the same conditions as in 
Example 1, but varying the cyclohexane:toluene ratio in the mixture. The 
results are shown in the following table: 
TABLE 
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Specific 
viscosity 
Solvent mixture (1% solu- 
Cyclohexane Polymerisa- 
Yield tion in 
Ex- % by Toluene 
tion time 
% of DMF 
amples 
ml volume ml (hours) theory 
at 25.degree. C.) 
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1 20 10 180 6.6 99.0 0.6242 
3 1 0.5 199 6.3 99.3 0.5267 
4 60 30 140 6.3 98.6 1.1815 
5 80 40 120 6.5 98.6 1.6807 
6 100 50 100 6.3 99.3 2.2013 
7 120 60 80 6.3 98.6 2.9504 
8 140 70 60 6.3 98.6 4.1642 
9 160 80 40 6.3 98.6 5.2086 
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Examples 1-9 show how it is possible, with the aid of the process according 
to the invention, to vary the specific viscosity of the copolymers over a 
wide range without reducing the yields. 
EXAMPLES 10 AND 11 
When the following substances are used, the viscosities indicated in the 
table are achieved, using the apparatus described in Example 1 and 
applying the conditions indicated in the following table. 
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Substances: 
______________________________________ 
3-Vinyloxyethyl-5-ethyl-5- 
methylhydantoin 10.6 g (0.05 mol) 
Maleic anhydride 
4.9 g (0.05 mol) 
Azoisobutyronitrile 
0.0775 g (0.05%, relative to 
monomers) 
Cyclohexane and toluene, 
together 200 ml 
(Monomers: solvent ratio = 7.8 g per 100 ml) 
______________________________________ 
Specific 
viscosity 
Solvent mixture (1% solu- 
Cyclohexane Polymerisa- 
Yield tion in 
Ex- % by Toluene 
tion time 
% of DMF 
amples 
ml volume ml (hours) theory 
at 25.degree. C.) 
______________________________________ 
10 1 0.5 199 5.9 98.7 0.4327 
11 160 80 40 5.9 99.5 5.4733 
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EXAMPLES 12 AND 13 
The process is carried out as described in Examples 10 and 11, but using 
1-cyanoethyl-3-vinyloxyethyl-5,5-dimethylhydantoin as the hydantoin vinyl 
ether. 
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Substances: 
______________________________________ 
1-Cyanoethyl-3-vinyloxy- 
ethyl-5,5-dimethylhydantoin 
12.6 g (0.05 mol) 
Maleic anhydride 4.9 g (0.05 mol) 
Azoisobutyronitrile 
0.087 g (0.5% relative to 
monomers) 
Cyclohexane and toluene, 
together 200 ml 
(Monomers: solvent ratio = 8.75 g per 100 ml) 
______________________________________ 
Specific 
viscosity 
Solvent mixture (1% solu- 
Cyclohexane Polymerisa- 
Yield tion in 
Ex- % by Toluene 
tion time 
% of DMF 
amples 
ml volume ml (hours) theory 
at 25.degree. C.) 
______________________________________ 
12 1 0.5 199 5.9 98.8 0.3225 
13 110 55 90 6 96.0 0.9136 
______________________________________ 
EXAMPLES 14 AND 15 
The process is carried out as described in Examples 10 and 11, but using 
twice the quantity of monomers per 100 ml of solvent. 
______________________________________ 
Substances: 
______________________________________ 
3-Vinyloxyethyl-5,5- 
dimethylhydantoin 20.1 g 
Maleic anhydride 9.9 g 
Azoisobutyronitrile 0.15 g 
Cyclohexane and toluene, together 
200 ml 
(Monomers: solvent ratio = 15 g per 100 ml) 
______________________________________ 
Specific 
viscosity 
Solvent mixture (1% solu- 
Cyclohexane Polymerisa- 
Yield tion in 
Ex- % by Toluene 
tion time 
% of DMF 
amples 
ml volume ml (hours) theory 
at 25.degree. C.) 
______________________________________ 
14 1 0.5 199 6 98 1.0956 
15 140 80 60 5.9 96 16.7893 
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