Process for the synthesis and recovery of tetrahydro-N-[1-methyl-1-[3-(1-methylethenyl)-phenyl]ethyl]-2-oxo-1-H-py rrolo-1-carboxamide

The present invention discloses a process for the preparation of tetrahydro-N-[1-methyl-1-[3-(1-methylethenyl)phenyl]ethyl]-2-oxo-1-H-pyrro lo-1-carboxamide which is comprised of (1) reacting m-isopropenyl .alpha.,.alpha.-dimethylbenzylisocyanate with 2-pyrrolidinone at a temperature which is within the range of about 80.degree. C. to about 150.degree. C. to produce a molten reaction product; (2) mixing the molten reaction product with an aqueous emulsifier solution to form an aqueous medium, wherein the aqueous emulsifier solution contains from about 0.1 weight percent to about 10 weight percent emulsifier, and wherein the weight ratio of the molten reaction product to the emulsifier solution in the aqueous medium is within the range of 1:0.5 to 1:100; (3) allowing the tetrahydro-N-[1-methyl-1-[3-(1-methylethenyl)phenyl]ethyl]-2-oxo-1-H-pyrro lo-1-carboxamide in the aqueous medium to crystallize under conditions of agitation into the form of essentially spherical particles; and (4) recovering the tetrahydro-N-[1-methyl-1-[3-(1-methylethenyl)phenyl]ethyl]-2-oxo-1-H-pyrro lo-1-carboxamide particles from the aqueous medium by filtration.

BACKGROUND OF THE INVENTION 
Tetrahydro-N-[1-methyl-1-[3-(1-methylethenyl)-phenyl]ethyl]-2-oxo-1-H-pyrro 
lo-1-carboxamide (TOPC) has the structural formula: 
##STR1## 
and is an excellent choice as a monomer having pendant blocked isocyanate 
groups which can be polymerized into rubbers. TOPC is a solid at room 
temperature and is readily soluble in most monomers commonly used in 
making synthetic rubber, such as styrene, acrylonitrile, 1,3-butadiene, 
isoprene, acrylates, vinylidene chloride, and the like. It will also 
readily polymerize by either solution or emulsion free radical means under 
a wide variety of conditions with varying initiator systems, such as azo 
compounds, peroxides, persulfates and redox systems. Additionally, TOPC 
will not retard normal polymerization rates. 
Rubbers having pendant blocked isocyanate groups which are made with TOPC 
do not deblock at temperatures below about 160.degree. C. This is highly 
desirable since deblocking at low temperatures can result in premature 
crosslinking (scorch) during coagulation, drying and/or compounding steps. 
Rubbers made with TOPC can also be coagulated by utilizing standard 
procedures. 
Rubbers which are made utilizing TOPC as a comonomer have units which are 
derived from TOPC incorporated therein. These repeat units which are 
derived from TOPC have the following structure: 
##STR2## 
and can be distributed throughout the polymer chains of the rubber in an 
essentially random manner. Such rubbers will also typically contain repeat 
units which are derived from conjugated diene monomers, such as isoprene 
or 1,3-butadiene and can be deblocked by simply heating to temperatures 
above about 160.degree. C. The deblocking reaction is very fast at 
temperatures within the range of about 180.degree. C. to about 200.degree. 
C. As a result of the deblocking reaction, repeat units having the 
structural formula: 
##STR3## 
which contain unblocked isocyanate groups are formed and 2-pyrrolidinone 
(2-pyrrolidone) is liberated. The 2-pyrrolidinone is believed to be 
relatively non-toxic and has a boiling point of 245.degree. C. 
U.S. Pat. No. 5,043,455 discloses that TOPC monomer can be synthesized by 
the reaction of TMI with 2-pyrrolidinone at a temperature within the range 
of about 80.degree. C. to 150.degree. C. In this reaction one mole of TMI 
reacts with one mole of 2-pyrrolidinone to produce one mole of TOPC. U.S. 
Pat. No. 5,043,455 indicates that the reaction product formed can be mixed 
into an aliphatic liquid hydrocarbon, such as hexane, pentane or octane, 
to induce crystallization of the TOPC. Unfortunately, there are 
environmental and safety problems associated with the use of such liquid 
organic compounds in inducing the crystallization of the TOPC. 
SUMMARY OF THE INVENTION 
This invention is based upon the unexpected discovery that aqueous 
emulsifier solutions can be used to induce the crystallization of TOPC. By 
utilizing the techniques of this invention, the need to use liquid organic 
compounds to induce the crystallization of TOPC is eliminated. 
Additionally, the TOPC which is recovered when the techniques of this 
invention are employed is in the form of dense, non-dusting discreet 
particles which are essentially spherical in form. Such particles can be 
easily recovered by filtration and are in a convenient form for further 
handling. 
The subject invention more specifically reveals a process for the 
preparation of tetrahydro-N-[1-methyl-1-[3-(1-methylethenyl)phenyl]ethyl 
-2-oxo-1-H-pyrrolo-1-carboxamide which is comprised of (1) reacting 
m-isopropenyl .alpha.,.alpha.-dimethylbenzylisocyanate with 
2-pyrrolidinone at a temperature which is within the range of about 
80.degree. C. to about 150.degree. C. to produce a molten reaction 
product; (2) mixing the molten reaction product with an aqueous emulsifier 
solution to form an aqueous medium, wherein the aqueous emulsifier 
solution contains from about 0.1 weight percent to about 10 weight percent 
emulsifier, and wherein the weight ratio of the molten reaction product to 
the emulsifier solution in the aqueous medium is within the range of 1:0.5 
to 1:100; (3) allowing the tetrahydro-N-[1-methyl-1-[3-(1-methylethenyl 
phenyl]ethyl]-2-oxo-1-H-pyrrolo-1-carboxamide in the aqueous medium to 
crystallize under conditions of agitation into the form of essentially 
spherical particles; and (4) recovering the 
tetrahydro-N-[1-methyl-1-[3-(1-methylethenyl)phenyl]ethyl]-2-oxo-1-H-pyrro 
lo-1-carboxamide particles from the aqueous medium by filtration. 
DETAILED DESCRIPTION OF THE INVENTION 
In the first step of the process of this invention, m-isopropenyl 
.alpha.,.alpha.-dimethylbenzylisocyanate, which is also known as 
1-(1-isocyanato-1-methylethyl)-3-(1-methylethenyl)-benzene or TMI, is 
reacted with 2-pyrrolidinone. This reaction can be carried out over a very 
wide temperature range with temperatures between about 80.degree. C. and 
about 150.degree. C. being typical. It is generally preferred for this 
reaction to be conducted at a temperature within the range of 90.degree. 
C. to 120.degree. C. with temperatures in the range of 95.degree. C. to 
110.degree. C. being most preferred. This reaction can be carried out in 
the absence of solvent and catalyst. However, the reaction can be 
catalyzed with dibutyltin dilaurate, alkyltin mercaptides, salts of 
bismuth, salts of lead, and the like. 
In this reaction, one mole of TMI reacts with one mole of 2-pyrrolidinone 
to produce one mole of TOPC. It is normally preferred for a slight excess 
of 2-pyrrolidinone to be utilized in the reaction. For example, it is 
generally advantageous to employ the 2-pyrrolidinone in an excess of about 
2 mole percent to about 5 mole percent. Larger excesses of 2-pyrrolidinone 
in this reaction slows the crystallization of TOPC. 
A listing of various emulsifiers which may be useful in this invention is 
given in the book "McCutcheon's Emulsifiers and Detergents 1981 Annuals", 
which is incorporated herein by reference in its entirety. The emulsifiers 
useful in this invention may be a combination of one or more emulsifiers 
of the anionic, cationic, non-ionic or amphoteric class of surfactants. 
Suitable anionic emulsifying agents are alkyl sulfonate, alkyl aryl 
sulfonates, condensed naphthalene sulfonate, alkyl sulfates, ethoxylated 
sulfates, phosphate esters, and esters of sulfosuccinic acid. 
Representative of these emulsifiers are sodium alpha-olefin (C.sub.14 
-C.sub.16) sulfonates, alkali metal or ammonium dodecylbenzene sulfonates, 
disodium dodecyl diphenyloxide disulfonate, disodium palmityl 
diphenyloxide disulfonate, sodium, potassium, or ammonium linear alkyl 
benzene sulfonate, sodium lauryl sulfate, ammonium alkyl phenolethoxylate 
sulfate, ammonium or sodium lauryl ether sulfate, ammonium alkyl ether 
sulfate, sodium alkyl ether sulfate, sodium dihexyl sulfosuccinate, sodium 
dicyclohexylsulfosuccinate, sodium diamyl sulfosuccinate, sodium 
diisobutylsulfosuccinate, disodium ethoxylated nonyl phenol half ester of 
sulfosuccinic acid, tetrasodium N-(1,2-dicarboxyethyl)-N-octadecyl 
sulfosuccinamate, disodium isodecyl sulfosuccinate, sodium bistridecyl 
sulfosuccinate, sodium salt of alkyl aryl polyether sulfate, lauryl 
alcohol ether sulfate, sodium salt of condensed napthalene sulfonic acid, 
complex phosphate ester of ethylene oxide adduct. 
The aqueous emulsifier solution will normally contain from about 0.1 weight 
percent to about 10 weight percent of the emulsifier. It is normally 
preferred for the aqueous emulsifier solution to contain from 0.5 weight 
percent to 5 weight percent emulsifier with it being more preferred for 
the aqueous emulsifier solution to contain from 1 weight percent to 2.5 
weight percent of the emulsifier. 
The weight ratio of the molten reaction product to the aqueous emulsifier 
solution mixed in this step will normally be within the ratio of 1:0.5 to 
1:100. It is normally preferred for the weight ratio of the molten 
reaction product to the aqueous emulsifier solution to be within the range 
of 1:0.7 to 1:10. It is generally most preferred for the ratio of molten 
reaction product to aqueous emulsifier solution to be within the range of 
1:0.9 to 1:3. 
In the second step of the process of this invention, the molten reaction 
product produced in the first step is mixed with an aqueous emulsifier 
solution. This can be done by adding the molten reaction product to the 
aqueous emulsifier solution or it can be accomplished by adding the 
aqueous emulsifier solution to the molten reaction product. In many cases, 
it will be desirable to conduct both the reaction and the crystallization 
in the same vessel. In such cases, the aqueous emulsifier solution will be 
added to the molten reaction product. 
This mixing of the molten reaction product with the aqueous emulsifier 
solution is normally conducted under conditions of vigorous agitation. It 
is normally preferred for the molten reaction product to be cooled to a 
temperature within the range of about 40.degree. C. to about 70.degree. C. 
before it is mixed with the aqueous emulsifier solution. This facilitates 
a faster rate of crystallization. 
The aqueous medium formed by mixing the molten reaction product and the 
aqueous emulsifier solution is then allowed to cool. As the aqueous medium 
cools, fine droplets of the liquid reaction product which are stabilized 
by the emulsifier in the mixture begin to crystallize into particles or 
beads which are essentially spherical in form. It is important to maintain 
the aqueous medium under conditions of agitation until the crystallization 
is complete to insure that an essentially spherical particulate product is 
formed. As this crystallization occurs, heat is given off. This heat of 
crystallization causes the temperature of the aqueous medium to increase 
to a measurable degree. By monitoring the temperature of the aqueous 
medium, the point at which crystallization is occurring can be detected by 
this increase in temperature. In the third step of the process of this 
invention, the TOPC is simply allowed to crystallize into discreet 
particles. 
After the TOPC has crystallized, it is recovered in the fourth step of the 
process of this invention by filtration. The TOPC beads which are formed 
can be recovered by simply passing the aqueous medium containing such TOPC 
particles through a screen having a mesh size which is small enough to 
prevent them from passing through it. In most cases, a 100 mesh screen 
will be adequate for this purpose. 
It may be desirable to wash the TOPC beads which are recovered with pure 
water. The beads can then, of course, be dried using any of a variety of 
standard drying procedures. For instance, the TOPC beads can be dried in 
warm dry air or under vacuum. The drying of TOPC will normally be done at 
a temperature of less than about 45.degree. C. since TOPC has a melting 
range of about 52.degree. C. to 55.degree. C. 
The following examples are merely for the purpose of illustration and are 
not to be regarded as limiting the scope of the invention or the manner in 
which it can be practiced. Unless specifically indicated otherwise, parts 
and percentages are given by weight.

EXAMPLE 
A two liter, three-neck flask equipped with a large magnetic stir bar, 
condenser, dropping funnel, thermometer and nitrogen inlet tube was 
charged with 342.57 grams (4.025 moles) of 2-pyrrolidinone and 100 grams 
(0.497 moles) of distilled meta-TMI. The mixture was heated under nitrogen 
to a temperature of 100.degree. C. where a slight exotherm was noted (CA. 
4.degree. C.). At this point, an additional 704 grams of distilled 
meta-TMI (3.5 moles) was added with gel warming at a rate sufficient to 
maintain a reaction temperature of approximately 100.degree. C. The 
mixture was allowed to react at this temperature for 23 hours. The 
reaction progress was periodically monitored by infrared analysis 
following the disappearance of the isocyanate absorption at 2255 
cm.sup.-1. 
Then 300 grams of the reaction product was added to a one liter beaker at 
65.degree. C. Then 300 grams of an aqueous emulsifier solution containing 
1 percent of a mixed fatty acid potassium soap was added to the molten 
reaction product in the beaker. The aqueous medium formed was vigorously 
agitated to form a uniform dispersion. After the aqueous medium had cooled 
to about 25.degree. C., crystallization began. The heat given off by 
crystallization caused the temperature of the aqueous medium to increase 
to about 33.degree. C. As soon as the temperature began to fall again, the 
agitation was stopped and the aqueous medium was filtered through a 100 
mesh screen. White spherical particulate beads were recovered on the 
screen. They were subsequently washed with 1,200 ml of water and air 
dried. The beads which were recovered weighed 294 grams which represents a 
yield of 99.8 percent. Accordingly, this example shows that by utilizing 
the techniques of this invention, that TOPC can be synthesized and 
recovered at extremely high yields. 
While certain representative embodiments and details have been shown for 
the purpose of illustrating the subject invention, it will be apparent to 
those skilled in this art that various changes and modifications can be 
made therein without departing from the scope of the subject invention.