Production of acrylic monomers

Details Production of acrylic monomers Production of acrylic monomers

2001-07-13

2003-01-14

Kumar, Shailendra (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Amino nitrogen containing

C564S205000, C544S114000, C544S176000

Reexamination Certificate

active

06506939

ABSTRACT:

The present invention relates to a new synthetic process for producing N-substituted acrylamides and tertiary amines, for instance dialkylallylamine or triallylamine. Substituted acrylamides such as N,N-dimethylacrylamide can be polymerised optionally with other monomers to produce polymers useful as adhesives, fabric sizes and shale inhibitors etc. Allyl dialkyl amines such as allyldimethylamine can be salified or quaternised to produce water soluble monomers which can form water soluble polymers. An important use of allyl dialkyl amines is in the preparation of diallyldialkyl ammonium chloride which is commonly used to produce water soluble cationic polymers useful in coagulation and flocculation of solids in suspensions such as sewage sludge or paper making stock suspensions.
It is known to prepare N-substituted acrylamides from acid chlorides such as 3-chloropropionyl chloride. Typically the reaction would be carried out at temperatures between 0° C. and 50° C. A disadvantage of this particular route is the corrosive nature of the acid chlorides, and their high reactivity which can lead to various undesirable side products. It is also known to produce N-substituted acrylamides by pyrolysis of the corresponding aminoalkylamides in the presence of a suitable catalyst. Such processes are carried out at high temperatures, often above 150° C.
One problem with the prior art processes is the occurrence of side reactions which result in lower yields and undesirable impurities which if not removed can adversely affect the properties of the corresponding polymers. On a commercial scale it is often difficult to obtain good yields of N-substituted acrylamides greater than 95% purity.
Another problem with the prior processes is that at such high temperatures it is often necessary to use greater amounts of polymerisation inhibitors. However, the residual inhibitors would need to be removed once the process is complete. Insufficient levels of inhibitor could result in the substituted acrylamide undesirably forming polymers. Furthermore at these high temperatures there is always the risk that free radical species result in the formation of dimers. Even quite low concentrations of dimers or low molecular weight polymer species in the N-substituted acrylamide monomer could be disadvantageous and adversely affect the polymerisation reaction and thus the properties of the final polymer product.
For the reasons set out above it would be desirable to use a process that may if required be carried out at more ambient temperatures and which could be used to prepare N-substituted acrylamides of high purity, for instance above 96% and preferably at least 97%. Furthermore it would also be desirable to use a process that avoids the use of corrosive acid chlorides.
One aspect of the invention relates to a process for the preparation of a mixture comprising a compound of formula (1) and a compound of formula (2)
wherein
R
1
is an optionally substituted C
1-20
alkyl, optionally substituted C
3-4
alkenyl, optionally substituted C
5-7
cycloalkyl or optionally substituted benzyl,
R
2
is an optionally substituted C
1-20
alkyl, optionally substituted C
3-4
alkenyl or optionally substituted C
5-7
cycloalkyl,
A is either S or NR
3
R
3
is an optionally substituted C
1-20
alkyl, optionally substituted C
3-4
alkenyl or optionally substituted C
5-7
cycloalkyl, or R
2
and R
3
together form a 5-7 membered ring which can contain an oxygen atom,
R
4
is hydrogen or methyl,
R
5
is an optionally substituted C
1-20
alkyl, optionally substituted C
3-4
alkenyl, optionally substituted C
5-7
cycloalkyl or optionally substituted benzyl and,
R
6
is hydrogen or an optionally substituted C
1-20
alkyl, optionally substituted C
3-4
alkenyl or optionally substituted C
5-7
cycloalkyl, or R
5
and R
6
together form a 5-7 membered ring which can contain an oxygen atom,
which comprises reacting a compound of formula (3)
wherein X
−
is an anion, and R
1
, R
2
, R
3
, R
4
, R
5
and R
6
have the same meaning as above,
in an alkaline medium.
In a preferred form of invention A is NR
3
and the compound of formula (1) is specifically a tertiary amine.
In one embodiment R
1
is allyl or methallyl.
In one embodiment R
2
is methyl or ethyl.
In another embodiment R
3
is methyl or ethyl.
In a further embodiment R
5
is C
1-8
alkyl but is preferably selected from methyl, ethyl, n-propyl, iso-propyl, n-butyl and tertiary butyl.
In one other embodiment R
6
is hydrogen or C
1-8
alkyl but is preferably selected from methyl, ethyl, n-propyl, iso-propyl, n-butyl and tertiary butyl and X
−
is a halide, preferably chloride.
In a preferred embodiment of the invention R
1
is allyl, R
2
is methyl or ethyl, R
3
is methyl or ethyl, R
5
is C
1-8
alkyl but is preferably selected from methyl, ethyl, n-propyl, iso-propyl, n-butyl and tertiary butyl, R
6
is hydrogen or C
1-8
alkyl but is preferably selected from methyl, ethyl, n-propyl, iso-propyl n-butyl and tertiary but, X
−
is preferably a halide, most preferably chloride.
According to the invention the mixtures of compounds of formula (1) and compound of formula (2) can conveniently be prepared by reacting a compound of formula (3) in the presence of a base or an alkali, such as an amine, metal oxide, metal hydroxide or ammonium hydroxide, for instance tertiary amine and/or hindered secondary amine, preferably sodium hydroxide, potassium hydroxide or calcium hydroxide. The reaction may be carried out in an aqueous medium at a pH greater than 8, preferably in the range 11 to 14. In one example the reaction is carried out at a temperature of up to 100° C., preferably 10 to 30° C. Desirably this can be achieved by addition of solid sodium hydroxide or other solid alkali metal hydroxides to the compound of formula (3). It is also possible to effect the elimination by adding an alkali solution, for example caustic soda solution. The alkali solution can be any alkali solution. The alkali is often above 10% strength preferably above 20%, more preferably above 30%, most preferably above 40%, for instance 46%.
Examples of compounds of formula (1) include allyldimethylamine, allyl diethylamine, allyl ethylmethylamine, dimethyl sulphide, allyl methyl sulphide and allyl ethyl sulphide.
Examples of compounds of formula (2) include N-methyl acrylamide, N-ethylacrylamide, N-n-propylacrylamide or N-isopropylacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N-n-propylmethacrylamide, N-(2-ethylhexyl)acrylamide or N,N-dimethylacrylamide, N,N-diethylacrylamide, N,N-di n-propylacrylamide, N,N-di iso-propylacrylamide or N,N-dioctyl acrylamide, N-ethyl-N-methylacrylamide, N-methyl-N-propylacrylamide.
Examples of typical mixtures include allyldimethylamine with N-methyl acrylamide, allyldimethylamine with N-ethylacrylamide, allyldimethylamine with n-propylacrylamide, allyldimethylamine with N-isopropylacrylamide, allyldimethylamine with N-methylmethacrylamide, allyldimethylamine with N-ethylmethacrylamide, allyldimethylamine with N-n-propylmethacrylamide, allyldimethylamine with N-(2-ethylhexyl)acrylamide, allyldimethylamine with N,N-dimethylacrylamide, allyldimethylamine with N,N-diethylacrylamide, allyldimethylamine with N,N-di n-propylacrylamide, allyldimethylamine with N,N-di iso-propylacrylamide, allyldimethylamine with N,N-di octyl acrylamide, allyldimethylamine with N-ethyl-N-methylacrylamide, allyldimethylamine with N-methyl-N-propylacrylamide, allyldiethylamine with N-methyl acrylamide, allyldiethylamine with N-ethylacrylamide, allyldiethylamine with n-propylacrylamide, allyldiethylamine with N-isopropylacrylamide, allyldiethylamine with N-methylmethacrylamide, allyldiethylamine with N-ethylmethacrylamide, allyldiethylamine with N-n-propylmethacrylamide, allyldiethylamine with N-(2-ethylhexyl)acrylamide, allyldiethylamine with N,N-dimethylacrylamide, allyldiethylamine with N,N-diethylacrylamide, allyldiethylamine with N,N-di n-propylacrylamide, allyldiethylamine with N,N-di iso-propylacrylamide, allyldiethylamine with N,N di octyl acrylamide, allyldiethylam

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