Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2000-08-18
2001-05-01
McKane, Joseph K. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C549S240000
Reexamination Certificate
active
06225475
ABSTRACT:
TECHNICAL FIELD
This invention relates to a new way of producing mixtures of hydrocarbyl anhydridcs which can be used, for example, as curing agents for epoxy resins.
BACKGROUND
Aliphatic and cycloaliphatic anhydrides such as commercial grades of dodecenyl succinic anhydride (DDSA) and of methyl tetrahydrophthalic anhydride (MTHPA) are used as curing agents in the production of epoxy resins. In some cases these aliphatic and cycloaliphatic anhydrides are used individually and in some cases they are used in combination with each other. If DDSA is used by itself, the resultant epoxy resin has a relatively low glass transition temperature (in the order of about 80° C.). On the other hand, use of MTHPA produces epoxy resins having higher glass transition temperatures (in the order of about 140° C.). Therefore, mixtures of DDSA and MTHPA are used to provide epoxy resins having physical properties required for use under various actual service conditions, such as, for example, desired glass transition temperatures, suitable polymer modulus, and the like.
Heretofore, the desired mixture of DDSA and MTHPA has been produced either by purchasing the individual products and mixing them together at the polymerization site prior to conducting the polymerization or by purchasing a preformed mixture of the DDSA and MTHPA from the supplier. So far as is known, the supplier forms such preformed mixtures from DDSA and MTHPA which have been produced in separate chemical operations.
Typically, the alkenyl succinic anhydrides are formed by reacting a branched olefin such as propylene tetramer with maleic anhydride. During the reaction it is desirable to consume the majority, if not all, of the maleic anhydride so that little if any unreacted maleic anhydride will need to be recycled. One way of improving the consumption of the maleic anhydride during the reaction is to perform the reaction at an elevated temperature. In the case of DDSA production temperatures as high as 250° C. are required in order to achieve sufficient reaction kinetics (rapidity of reaction). Unfortunately at such temperatures, side reactions may occur even though short reaction times are used. Such side reactions can and often do result in formation of products having unattractive dark coloration. From a commercial standpoint, it would be advantageous to provide a product possessing improved color characteristics.
A need thus exists for a method in which the DDSA can be produced rapidly and without appreciable color development during its synthesis thereby obviating the need for use of purification procedures such as distillation or decolorization.
The conventional method for producing commercial grade MTHPA involves the reaction of maleic anhydride with isoprene, piperylene, or butadiene, or a mixture containing these dienes. The resultant product of this Diels-Alder reaction is a solid at room temperature. A liquid form of this product is highly desired in the marketplace. To fulfill this requirement, it has been the practice heretofore to subject the product either to hydrogenation whereby the double bond is saturated by hydrogen, or to isomerize the product usually in the presence of a catalyst. Both such operations are not only time consuming, but add substantial capital and processing costs to the operation.
A need thus exists for a way of producing a liquid product containing MTHPA without requiring recourse to hydrogenation or isomerization.
SUMMARY OF THE INVENTION
Pursuant to this invention, both of the foregoing needs are fulfilled in a single unitary operation.
Provided by this invention in one of its embodiments is a process which comprises:
a) heating a mixture formed from maleic anhydride and at least one liquid monoolefin to produce a reaction mass containing a liquid phase, such liquid phase comprising at least one alkenyl succinic anhydride, maleic anhydride, and at least one monoolefin; and
b) mixing at least one conjugated diene hydrocarbon with reaction mass from a) and having the temperature of the resultant mixture sufficient to form a reaction mass comprising at least tetrahydrophthalic anhydride and/or alkyl-substituted tetrahydrophthalic anhydride and at least one alkenyl succinic anhydride.
The resulting product is readily recovered in suitable form for commercial uses, even commercial uses requiring light-colored materials. For example, product recovery can be accomplished by flashing or vaporizing the residual amounts of unreacted starting materials, mostly olefin, from the reaction mixture. Thus, no hydrogenation or isomerization and no product decolorization is required—all such operations can be eliminated in their entirety. Moreover, unlike present commercial operations wherein two separate reactions are used in order to prepare DDSA on the one hand and MTHPA on the other, this invention has made it possible to produce both products as a liquid mixture in a unitary operation. And from an operational standpoint, the processes of this invention enable significant increases in plant throughput.
It is therefore preferable to recover the residual amount of unreacted starting materials from the reaction mass formed in b), most preferably by distillation. It is also preferred to recycle at least a portion of the recovered residual amount of unreacted starting materials as a part of the feed to a subsequent reaction. If more than about 10 wt % of the recovered residual amount of unreacted starting materials is composed of diene hydrocarbon(s), the portion used in the recycle will usually be, and preferably is, fed to step b). On the other hand, when less than about 10 wt % of the recovered residual amount of unreacted starting materials is composed of diene hydrocarbon(s), it is usually preferable to recycle at least a portion of this residual amount as feed to a). However, common sense should of course be used when deciding to which step the recycled material(s) should fed.
Another embodiment of this invention is a process which comprises:
a) heating a mixture formed from maleic anhydride and a stoichiometric excess of at least one branched olefin and/or internal linear olefin having in the range of about 6 to about 18 carbon atoms in the molecule at a temperature in the range of about 180 to about 280° C. to form a reaction mass containing a liquid phase, such liquid phase comprising at least one alkenyl succinic anhydride in which the alkenyl group contains in the range of about 6 to about 18 carbon atoms, maleic anhydride, and at least one olefin containing in the range of about 6 to about 18 carbon atoms in the molecule; and
b) mixing at least one conjugated diene hydrocarbon having in the range of 4 to about 12 carbon atoms with reaction mass from a) and having the temperature of the resultant mixture in the range of about 20 to about 180° C. to form a reaction mass comprising at least tetrahydrophthalic anhydride and/or alkyl-substituted tetrahydrophthalic anhydride, and at least one alkenyl succinic anhydride.
Still another embodiment of this invention is a process which comprises:
a) heating a mixture formed from maleic anhydride and a stoichiometric excess of olefin consisting essentially of at least one C
12
branched olefin and/or at least one internal linear olefin at a temperature in the range of about 180 to about 280° C. to form a reaction mass containing a liquid phase, the liquid phase comprising at least one C
12
alkenyl succinic anhydride, residual maleic anhydride, and C
12
branched and/or internal linear olefin; and
b) mixing with reaction mass from a) at least one conjugated diene hydrocarbon having in the range of 4 to about 6 carbon atoms in an amount at least stoichiometrically equivalent to the amount of residual maleic anhydride present in the reaction mass from a), and thereafter having the temperature of the resultant mixture in the range of about 40 to about 150° C. to form a reaction mass comprising at least tetrahydrophthalic anhydride and/or alkyl-substituted tetrahydrophthalic anhydride, and at least one C
12
alkenyl succinic anhydride.
In each of the embodiments
Hu Patrick C.
Legloahec Valerie N.
Albemarle Corporation
McKane Joseph K.
Murray Joseph
Pippenger Philip M.
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