Process for manufacturing polyalkenyl succinic anhydrides

A process in which a polymer of a C.sub.2 -C.sub.8 olefin having a number average molecular weight of about 250 and 30,000 undergoes reaction with an unsaturated aliphatic dicarboxylic acid anhydride in two stages in the presence of 5-500 ppm, based on said polymer, of a far and side product suppressing agent to form an alkenyl substituted anhydride, said process having a first stage comprising the following steps: (1) charging to a reaction zone said olefin polymer; (2) heating same to a reaction temperature of about 150.degree. C. to about 300.degree. C.; (3) charging about 30 to about 60 weight percent of the total amount of tar and side product suppressing agent intended for use in the reaction; (4) charging said anhydride to the heated reaction zone gradually over a period of about 1 to 3 hours and in an amount in the range of about 50 to about 75 weight percent of the total amount of anhydride intended for the reaction while maintaining said reaction temperature; and (5) allowing the reaction of the anhydride and polymer to proceed at said reaction temperature for a period of about 2 to 7 hours following completion of said anhydride addition, followed by a second state comprising the steps of: (1) charging the remaining tar and side product suppressing agent to the reaction zone; (2) charging the remaining anhydride to the reaction zone gradually over a 1 to 3 hour period; and (3) allowing the reaction of the anhydride and polymer to proceed to completion.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to the preparation of 
alkenyl-substituted intramolecular anhydrides of aliphatic dicarboxylic 
acids in the presence of catalysts or agents such as 1,3-dibromo-5,5 
dialkylhydantion which decrease unwanted by-product formation. More 
particularly, the invention is directed to a thermal process for preparing 
polyalkenyl-substituted anhydrides by reacting a polyalkene with an 
unsaturated aliphatic dicarboxylic acid anhydride in a reaction zone in 
the presence of a tar and side product suppressing agent, wherein the 
process comprises the step of adding the anhydride reactant and the tar 
and side product suppressing agent to the reaction zone in a plurality of 
stages to suppress formation of tar and other undesired side products. 
2. Discussion of the Prior Art 
Viscous polyalkenes having number average molecular weights of about 300 to 
about 3000 and having viscosities in the range of about 4 to about 5500 
centistokes at 100.degree. C. are commercially manufactured by 
Friedel-Crafts polymerization of feeds comprising C.sub.3 to C.sub.5 
hydrocarbons and have a wide variety of commercial applications. A 
principal use is as reactive intermediates in the manufacture of 
hydrocarbon soluble petroleum additives. 
The derivatives of particular interest in the present invention are the 
polyalkenyl-substituted intramolecular anhydrides of aliphatic 
dicarboxylic acids. For example, petroleum additive products derived from 
polybutenyl-substituted saturated aliphatic anhydrides can be added to 
fuels to inhibit rusting, carburetor deposits, and carburetor icing, 
corrosion and smoke, and to oils as rust inhibitors, wear inhibitors, 
dispersants, and VI improvers. 
Addition reactions between the viscous polyalkenes and intramolecular 
anhydrides of unsaturated aliphatic dicarboxylic acid can typically use 
any one of maleic anhydride, citraconic anhydride, itaconic anhydride, 
ethyl maleic anhydride, halo (e.g., chloro-) maleic anhydride, glutaconic 
anhydride, homoesaconic anhydride, and the like according to U.S. Pat. 
Nos. 2,628,942 and 2,634,256, among others. The addition reactions are, in 
general, conducted at temperatures in the range of 150.degree. to 
300.degree. C. using polyalkene to anhydride molar ratios of reactants in 
the range of 1.0:1.0-15. 
A known problem frequently encountered in the above-mentioned addition 
reaction is thermal decomposition and polymerization of the unsaturated 
anhydride reactant at temperatures above about 150.degree. C. See, e.g., 
U.S. Pat. No. 3,476,774. Such thermal decomposition in accompanied by 
evolution of water vapor and oxides of carbon, in a closed reaction 
vessel, is accompanied by an increase in internal pressure. Under some 
observed conditions the thermal decomposition can be so rapid as to be 
explosive. In the absence of explosive thermal decomposition a carbon 
containing tarry residue is also formed in addition to water vapor and 
oxides of carbon. Such residue is due to the fact that the anhydrides can 
react with the water to form the dicarboxylic acids and then isomerize to 
the trans form (which is insoluble in the system) or to polymerize. Such 
thermal decomposition and attendant isomerization or polymerization of the 
unsaturated anhydride reactant has been observed as occurring during its 
addition reaction with polymeric olefins, e.g. polybutenes and others, in 
a closed reaction vessel. The carbon-containing residue varies in nature 
from somewhat granular when the decomposition is only slight to a tarry 
material mainly adhering to internal surfaces of the reaction vessel when 
the decomposition is more extensive but well below explosive magnitude. 
The granular type residue amounts to from about 0.1 to about 0.3 weight 
percent of the total charge and is generally dispersed in the 
alkenyl-substituted saturated anhydride addition compound product diluted 
with unreacted components of the olefin polymer, and is readily separated 
therefrom by filtration. However, the tarry residual product, which for 
the most part fouls the internals of the reaction vessel can be as high as 
2-3 weight percent of the total charge. The tarry material not adhering to 
the internal surfaces of the reactor fouls the filter and interferes with 
filtration of the desired reaction product. Both types of residue are 
undesirable because of the above noted fouling characteristics and because 
their formation results in yield reduction of the desired 
alkenyl-substituted anhydride addition product. 
The patent literature discloses a number of compositions and methods which 
improve yield in the reaction of unsaturated dicarboxylic acid anhydrides 
(e.g. maleic anhydride), and propene or butene polymers by inhibiting the 
formation of tarry residual material and undesirable reaction side 
products which occur because of the above-described thermal decomposition 
and attendant isomerization or polymerization of the anhydride reactant. 
For example, Powell U.S. Pat. No. 4,414,397 discloses reaction of maleic 
anhydride and polyisobutylene in the presence of 
1,3-dibromo-5,5-dialkylhydantoin wherein the rate of addition of the 
maleic anhydride to the reaction mixture is controlled such that the 
anhydride is present in an amount less than about its maximum solubility 
in the reaction mixture in order to maintain the reaction mixture as a 
substantially homogeneous single phase system. The controlled anhydride 
addition stems from the patentee's conclusion that presence of a two phase 
system containing undissolved anhydride "is correlative with production of 
undesirable sludge or tar with resulting lower yield of desired product" 
(column 3, lines 7-19). The patent discloses several embodiments for 
achieving the desired controlled addition of maleic anhydride such as by 
the addition of equal or varying aliquots of the anhydride over the course 
of the reaction (column 4, lines 13-57). 
Powell U.S. Pat Nos. 4,496,746 and 4,434,071 are also directed to reducing 
by-product formation in the reaction of maleic anhydride with 
polyisobutylene. The '071 patent discloses, as a catalyst, a complex of 
polyisobutylene and a 1,3-dibromo dialkylhydantoin which is stated to 
reduce by-product formation. The '746 patent discloses addition of maleic 
anhydride in the form of a dispersion or emulsion in a carrier fluid to 
minimize sludge formation. At column 5, lines 16-23 of the '746 patent it 
is stated: 
"In the preferred embodiment, the olefin oligomer is added to the reaction 
vessel and the dispersion of the maleic anhydride is added thereafter. 
Although it is possible to add the dispersion to the reaction mixture in 
one aliquot, it is preferred to add it to the reaction mixture in one 
aliquot, it is preferred to add it to the reaction mixture gradually over 
the course of the reaction. When catalyst is employed [such as a 
brominated dialkylhydantoin referred to at column 4 line 33] it may be 
added with the oligomer or with the maleic anhydride or both." 
Of additional relevance to the present invention in view of their 
disclosures of tar and side product suppressing agents are Cengel et al. 
U.S. Pat. Nos. 3,927,041; 3,935,249; 3,953,475; 3,954,812; 3,960,900; 
3,985,672; 4,008,168; and 4,086,251. The '041 and '672 patents disclose 
1,3-dibromo-5,5-dialkylhydantoins as tar and side product inhibiting 
compounds. The '812 and '168 patents disclose halogenated carboxylic or 
sulfonic acids as tar suppressants. The '900 patents discloses halogenated 
aliphatic or aromatic hydrocarbons as tar suppressants. The '475 discloses 
halogenated aliphatic or aromatic carbonyls for tar and by-product 
suppression, and the '249 patent discloses inorganic halogen compounds for 
tar suppression. The '251 patent discloses all of the above suppressants 
in a method for preparing polyalkenyl substituted anhydrides where 
unreacted maleic anhydride is recycled to the reaction mixture. 
In addition to the patents mentioned above which address the problem of 
reduced yields in the reaction of maleic anhydride and polyalkenes due to 
tar and by-product formation, it is, of course, also possible to increase 
the yield of the preferred polyisobutenyl succinic anhydride (PIBSA) by 
simply increasing the mole ratio of anhydride to polybutene in the 
reaction. However, this approach leads to a lower equivalent weight PIBSA 
which is undesirable in certain applications. 
Although the patents cited above address PIBSA yield improvement without 
need for increased ratios of maleic anhydride to polybutene in the 
reaction mixture, there is still need for improvement in the reduction of 
by-product formation in the preparation of alkenyl substituted anhydrides 
wherein a tar and side product suppressing agent is used. 
A general object of the present invention is therefore to provide an 
improved method for the manufacture of alkenyl-substituted anhydrides, 
other objects being evident hereinafter to those skilled in the art. 
SUMMARY OF THE INVENTION 
I have now discovered, in a process for preparing alkenyl-substituted 
anhydrides by reacting a polymer of a C.sub.2 to C.sub.8 olefin having a 
number average molecular weight of about 250-30,000 with an unsaturated 
aliphatic dicarboxylic acid anhydride in a reaction zone in which there is 
also present a tar and side product suppressing agent, wherein, the 
improvement step of charging said tar and side product suppressing 
composition to the reaction zone in a plurality of discrete stages, 
whereby there is achieved a reduction in unwanted tar and side products, 
with attendant increases in the yield of desired alkenyl substituted 
anhydride, surpassing that which is possible using the techniques of the 
prior art, which, to the best of my knowledge, utilize a single charge of 
tar and side product suppressing agent. Preferably, both the suppressing 
agent and the anhydride reactant are charged to the reaction zone in 
multiple stages to obtain a maximum enhancement in tar and by-product 
suppression. 
A principle advantage of the present invention is greater overall 
conversion of reactants to the desired alkenyl-substituted anhydrides 
without need for increasing the molar ratio of anhydride to polyalkene in 
the reaction mixture. Other things being equal, the ability to maximize 
conversion of the reactants to the desired polyalkenyl substituted 
anhydride, while maintaining a relatively low molar ratio of maleic 
anhydride to polyalkene, preferably in the range of about 1-2:1, favors 
the production of higher equivalent weight PIBSA which may be preferred in 
certain petroleum additive applications.

DETAILED DESCRIPTION 
Briefly, the process of the present invention, is carried out by reacting 
one mole of polymeric alkene based on C.sub.2 -C.sub.8 olefin and having a 
number average molecular weight of from about 200 to about 30,000 with 
about 0.8 to about 10 moles of an unsaturated aliphatic dicarboxylic acid 
anhydride. An effective amount, preferably about 5 to 500 ppm based on the 
weight of polymer, of one or more "tar and side product suppressing 
agents" (defined in detail below) are introduced into the reaction zone in 
a plurality of stages or aliquots. The materials can be reacted at a 
temperature of from about 150.degree. C. to about 300.degree. C. to form 
polyalkenyl-substituted anhydride. Preferably, using a batch process, the 
anhydride reactant is also introduced into the reaction zone in separate 
aliquots over the course of the reaction. 
The polymeric alkenes preferred for use in the present invention are 
propene or butene polymers having a number average molecular weight of 
from about 200 to about 3000 produced by commercial well known 
polymerization techniques. Particularly preferred becasue of commercial 
availability are polybutenes having number average molecular weights of 
about 600 to about 3000. 
Unsaturated aliphatic dicarboxylic acid anhydrides which may be employed in 
the process of the present invention may be intramolecular anhydrides such 
as maleic, citraconic, itaconic, ethylmaleic, halomaleic, etc. The 
preferred anhydride is maleic anhydride, whereby the product obtained upon 
reaction thereof with polybutene is polybutenylsuccinic anhydride commonly 
referred to as "PIBSA". 
The "tar and side product suppressing additives" inhibit the formation of 
tarry residual material and undesirable reaction side products of maleic 
anhydride and/or improve yield in the reaction of maleic anhydride with 
propene or butene polymers, having a molecular weight from about 200 to 
about 3000, at a temperature from about 150.degree. C. to about 
300.degree. C. when said additives are present during the reaction between 
the polymer and the anhydride at a concentration of 5 to 550 ppm based on 
polymer. The mechanism by which these additives function is not well 
understood and shall not be speculated upon at this time. But it is known 
that many of the additives decompose during the alkene-anhydride reaction 
and may provide small amounts of halogen or halogen radical in the 
reaction mixture. These additives are high effective when incorporated 
into the reaction mixture at a concentration from about 5 to about 500 ppm 
based on polyolefin. While higher concentrations may also be effective, it 
is unnecessary to add more than about 5 to about 500 ppm additive. The 
nature and use of certain of these types of additives are described in 
Cengel et al. U.S. Pat. Nos. 3,927,041; 3,935,249; 3,954,812; 3,953,475; 
3,960,900; 3,985,672 and 4,008,168 all of which are incorporated herein by 
reference. 
A number of different types of compounds are effective as "tar and side 
product suppressing additives". One type is chlorinated and/or brominated 
aliphatic hydrocarbons or their halogenated derivatives. Such aliphatic 
hydrocarbons may be alkane, alkene, alkyne, or mixtures thereof. Typical, 
but not all inclusive of such compounds are: 
Cl and/or Br-containing aliphatic hydrocarbons such as ethyl bromide, 
n-propyl chloride, n- and isopropyl bromide, methylene chloride, methylene 
bromide, chloroform, bromoform, carbon tetrachloride, carbon tetrabromide, 
ethylene chloride, ethylene bromide, ethylidene chloride, ethylidene 
bromide, bromochloroethane, trichloroethane, tribromoethane, 
tetrachloroethane, tetrabromoethane, bromotrichloromethane, 
bromotrichloroethane, dibromodichloroethane, tetrachloroethylene, 
trichlorobutanes, tribromobutanes, bromochlorobutanes, bromobutanes, 
dibromobutanes, dibromochlorobutanes, dichlorobromobutanes, 
hexachloropropene, and others. 
Another type of "tar and side product suppressing additive" is chlorine 
and/or bromine containing derivatives of carboxylic or sulfonic acids, or 
N-chloro or N-bromo amides or imides of such acids. Typical, but not all 
inclusive of such compounds are: 
chloracetic acid, acetyl chloride, chloroacetyl chloride, 
N-chloroacetamide, bromoacetic acid, acetyl bromide, N-bromoacetamide, 
N-bromo-bromoacetamide, adipyl chloride, adipyl bromide, sebacyl chloride, 
sebacyl bromide, alpha-chloroadipic acid, alpha-bromo-adipic acid, 
N-bromo-adipamide, alpha-chloroadipoyl chloride, alpha-bromadipoyl 
bromide, 2-bromostearic acid, N-bromostearamide, maleyl dibromide, 
N-bromo-succinicimide, benzoyl chloride, benzoyl bromide, toluoyl 
chloride, toluoyl bromide, N-bromobenzamide, N-chlorophthalimide, 
N-bromophthalimide, N.sub.1, N.sub.2 -dibromoterephthalamide, 
benzenesulfonyl chloride, benzenesulfonyl bromides, 
N-bromobenzenesulfonamide, toluenesulfonyl chlorides, toluenesulfonyl 
bromides, N-chlorotoluenesulfonamides, N-bromotoluenesulfonamides, and the 
like. 
Another type of "tar and side product suppressing additive" is chlorinated 
and/or brominated intramolecular anhydrides of aliphatic carboxylic acids 
such as chloromaleic anhydride, bromomaleic anhydride and bromosuccinic 
anhydride, and others. 
Still another type of "tar and side product suppressing additive" is 
chlorinated and/or brominated aliphatic or aromatic ketones and acetals. 
Typical but not all inclusive of such compounds are: 
(A) The halo-ketones such as alpha-chloro or bromo ketones and 
di(alpha-chloro- or bromo) ketones. The former include mono, di- and 
tri-alpha chloro- or bromo-acetone; mono- and di-alpha chloro- or 
bromo-acetone; mono- and di-alpha chloro- or bromo-methylethyl ketone, 
di-ethyl ketone, methylpropyl ketone, ethylpropyl ketone, ethylisopropyl 
ketone, diisopropyl ketone, di-n-propyl ketone, methyl n-butyl ketone, 
ethyl isobutyl ketone, methyl tertbutyl ketone, n-butyl isopropyl ketone, 
n-propyl isobutyl ketone, n-propyl tertbutyl ketone, di-n-butyl ketone, 
diisobutyl ketone, etc. of the symmetrical and mixed alkyl ketones having 
in addition to the keto carbonyl carbon up to a total of twenty carbon 
atoms. The alpha-chloro- or bromo-alkyl diketones are those having two 
keto-carbonyl carbons in a chain of carbon atoms which are otherwise alkyl 
as in a chain of 4 to 22 carbon atoms wherein the chlorine or bromine atom 
or atoms is attached to a chain carbon adjacent to a keto carbonyl carbon. 
Such alpha chloro- or bromo-diketones are illustrated by 1,4-dichloro or 
dibromo-2,3-butanedione; 1,5-dichloro or 
dibromo-3,3-dimethyl-2,4-pentanedione; 2,6-chloro or 
dibromo-4,4-dimethyl-3,5-hexanedione; 2,6-dichloro or 
dibromo-4,4-dimethyl-3,5-heptanedione; 1,4-dichloro or 
dibromo-2,3-pentanedione; 2,5-dichloro- or dibromo-3,4-hexanedione, and 
the like. The alpha-chloro- or bromo aromatic ketones are preferably mixed 
alkyl aryl ketones with the chlorine or bromine on the alpha alkyl carbon 
as in alpha-chloro or alpha-bromo acetonaphthone, and the like. 
(B) The alpha-chloro or alpha-bromo acetals such as C.sub.1 -C.sub.10 
dialkyl acetals of alpha-chloro- or alpha-bromo-acetaldehyde because the 
acetaldehyde acetals are more available than acetals of other aldehydes. 
Of such alpha-chloro or alpha-bromo-acetaldehydes, diethyl acetals are 
most preferred. 
Still another type of "tar and side product suppressing additive" is 1,3 
dibromo-5,5-dialkyl substituted hydantoin. A typical example of such has 
methyl or ethyl alkyl groups. These are derivatives of hydantoic acid 
which is a carboxylic acid. 
Still another type of "tar and side product suppressing additive" is the 
group of inorganic acids and salts consisting of dry halogen chloride, 
calcium bromide and iodine mono chloride, etc. 
Still another type of "tar and side product suppressing additive" is the 
group consisting of chlorine, bromine and iodine. 
Still another type of "tar and side product suppressing agent" is the group 
of boron compounds as disclosed in commonly assigned U.S. Ser. No. 551,181 
now U.S. Pat. No. 4,736,044 (incorporated herein by reference) such as 
boric acid, boric acid salts such as ammonium borate, amine salts of boric 
acid, sodium borate, potassium borate, calcium borate, magnesium borate, 
meta borates, etc., boron oxides such as B.sub.2 O.sub.3, etc., boron 
salts such as boron arsenate, borohydride compounds such as diborane, 
dihydrotetraborane, pentaborane, hexaborane, organo boron compounds such 
as trialkyl borate or trialkoxy boron, for example trimethyl borate, 
triethylborate, diethyl propyl borate, triisopropyl borate, tri-t-butyl 
borate, tridecyl borate, etc, and other organo boron compounds such as 
aryl boronic acids, triaryl boroxene, trimethyl-borane, amino-borane 
compounds, and borazene. 
Further examples of "tar and side product suppressing additives" suitable 
in the present invention are: 
(a) 1,3-dibromo-5,5-dialkyl-substituted hydantoin wherein the 
alkyl-substituents have a total of 2 to 21 carbon atoms, such as 
1,3-dibromo-5,5-dimethyl-hydantoin; 
(b) dry hydrogen chloride or calcium bromide; 
(c) aliphatic hydrocarbon containing chlorine, bromine or chlorine and 
bromine, such as tetrabromomethane or bromotrichloromethane, or 
chlorinated or brominated polybutene; 
(d) acetyle bromide, bromacetyl bromide, benzoyl bromide, N-bromo 
succinimide, or mixtures thereof; and 
(e) alpha-bromo dialkyl ketone having in addition to the keto-carbonyl 
carbon atom up to a total of twenty carbon atoms, 
alpha-dibromo-substituted alkyl diketone wherein its two-keto-carbonyl 
carbon atoms are in a chain of from 4 to 22 carbon atoms and each 
bromo-substituent is on a chain carbon atom and adjacent to a 
keto-carbonyl carbon atom, or alpha-bromo aceto-phenone or napthone, or 
C.sub.1 -C.sub.10 dialkyl acetal of alpha-bromo acetaldehyde which 
additive has a normal boiling point in the range of from about 40.degree. 
C. to about 225.degree. C., such as 1,4-dibromo-2,3-butanedione. 
Especially preferred "tar and side product suppressing additives" are 
N-bromosuccinimide, bromotrichloromethane, N-bromoacetamide and 
1,3-dibromo-5,5-dimethylhydantoin. Other preferred additives are 
.alpha.-bromoacetophenone, and 1,4 dibromo-2,3-butanedione. Two or more 
side product suppressants may be used. 
Often it is desirable to minimize the contamination of the substituted 
anhydride product with the "tar and side product suppressing additive" or 
its reaction decomposition products. This can be achieved by using a "tar 
and side product suppressing additive" which can/or whose reaction 
decomposition products can be removed by distillation at a pressure of 5 
to 760 mm Hg. To be most readily removable with unreacted unsaturated 
anhydride, the side product suppressant or its reaction decomposition 
products should have a boiling point between 40.degree.-300.degree. C. at 
atmospheric pressure. 
In somewhat greater detail, the reaction between the polyalkene and the 
dicarboxylic acid anhydride compound is carried out in standard commercial 
well-known procedures. The art recognizes both batchwise reaction or 
continuous reaction in stirred tanks, pressurized reactors, continuous 
reaction zones, or other equivalent reaction vessels to provide intimate 
contact between the reactants. 
For batchwise operation the reactants are charged to the closed reaction 
vessel with or without an inert (oxygen-free) atmosphere at ambient or 
elevated pressure. The reactants can be added to the vessel at ambient 
temperature. However, the polyalkene can be used at an elevated 
temperature to reduce the time for reaction and to reduce viscosity. The 
anhydride reactant can be charged in solid form or dispersed in a portion 
of the unsaturated hydrocarbon or can be heated and added to the reactant 
mixture as a melt. During the reaction the mixture is stirred while the 
reaction temperature is controlled. Convenient conduct of the reaction can 
be maintained by charging to the reaction vessel a melt of the anhydride 
compound and preheated polymer so that the combined reactants provide 
sufficient heat to drive the reaction. At the end of the reaction, excess 
anhydride compound can be removed by distillation. The product which can 
be filtered and used. Reaction time for batchwise operation can be 4 to 24 
hours and greater. 
In continuous operation, ambient or heated streams of the dicarboxylic acid 
compound and unsaturated hydrocarbon can be charged to one end of a 
horizontal or vertical reaction zone. The reactants can be intimately 
contacted within the zone for a sufficient time at a sufficient 
temperature and pressure. The product can be withdrawn from the zone to 
appropriate strippers and filters. In order to maximize conversions of the 
reactant and to minimize formation of solid or tarry or resinous 
degradation products, the reaction can be carried out with a continuous 
anhydride reflux. The reflux rate can be in slight excess of the reaction 
requirements for the dicarboxylic acid compound. In this way the reaction 
solution is kept saturated with the anhydride compound throughout the 
reaction. Any anhydride compound in excess over that required to saturate 
the reaction zone continuously distills from the reaction zone overhead 
avoiding the appearance of separate anhydride compound phase in the 
reactor and the consequent contamination of the reaction product. The 
reduction in the concentration of the anhydride also reduces the products 
of degradation. The unsaturated hydrocarbon feed can also be controlled so 
that the rate of reflux and the feed rate of the unsaturated hydrocarbon 
are balanced to match the stoichiometric ratio of reactants. In continuous 
operation a shorter residence time is possible, for example, 1 to 8 hours. 
The tar and side product suppressing agent can be present in the reaction 
at a concentration of about 1 to about 100,000 parts per million of weight 
of polyalkene and preferably about 100 to 500 ppm. 
In accordance with the improvement step of the present invention, the total 
amount of tar and side product suppressing agent intended for co-reaction 
with the anhydride and polyalkene reactants is introduced to the reaction 
zone in a plurality of separate aliguots spaced over the course of the 
reaction. 
Preferably, using a batch process, both the anhydride reactant and the tar 
and side product suppressing agent can be added to the reaction zone 
containing polyalkene in multiple stages, whereby a portion of the tar and 
side product suppressing agent, preferably about 30 to 60% of the total 
amount intended for use in the reaction is initially charged at once to 
the reaction zone at the beginning of the reaction, and about 50 to about 
75% of the total anhydride intended for the reaction is likewise initially 
charged, preferably over a period of about 1 to 3 hours, to the reaction, 
after which the reaction is allowed to proceed for about 2 to 7 horus. 
After this initial reaction period the remaining tar and side product 
suppressant is added at once, and the remaining anhydride is charged over 
a 1 to 3 hour period, following which the reaction is carried out to 
completion. If desired, the anhydride reactant can be added in a single 
stage, quickly, or over a 1 to 10 hour continuous metered addition. 
The multiple stage addition of the tar and side product suppressing agent 
according to the present invention can also be employed where the reaction 
of the anhydride and the polyalkene is carried out continuously be 
charging to the reaction vessel a melt of the anhydride reactant and 
polymeric alkene. Similar to the batch process summarized above, a portion 
of the tar and side product suppressing agent is present initially, and 
then additional separate aliquots can be added during the course of the 
reaction. 
The following examples are illustrative and should not be construed as 
limiting the scope of the invention. 
EXAMPLE I 
Charge 580 grams of polybutene having a number average molecular weight of 
about 2068 to a one liter resin kettle and heat to 221.degree. C. under 
nitrogen sparge. Into the kettle charge an initial aliquot of 0.12 g 
1,3-dibromo-5,5-dialkylhydantoin (DBH). Over a 2 hour period meter 29.1 g 
of maleic anhydride into the kettle and react the mixture at 221.degree. 
C. for 4 hours under reflux. Charge a second aliquot of 0.11 g DBH at once 
and meter a second charge of 12.5 g maleic over a 1 hour period into the 
reaction kettle and react further for 15 hours under reflux at 221.degree. 
C. Cool the reaction mixture to 198.degree. C. and reflux under 5" vacuum 
for 1 hour. Strip under 28" Hg vacuum for 2 hours. The reaction product is 
bright and clear and has the following analyses: % PIBSA in the product is 
70.3; ASTM color is &gt;5.5; 100.degree. C. viscosity is 1240 cSt; equivalent 
weight is 1,814. 
EXAMPLE II 
The basic procedure of Example I using a multiple (50/50) DBH charge was 
compared to the same procedure using a single charge of DBH at the 
beginning of the reaction. The results set forth in Table I below 
demonstrate increased conversion to PIBSA afforded by the multiple DBH 
charge of the present invention. 
TABLE I 
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Total 
Molar DBH % PIBSA 
Ratio Charge, DBH Charge In Equiv. 
MAN: PIB 
PPM Method Product Wt. 
______________________________________ 
1.5 200 Single 65.1 1,690 
1.5 200 Multiple (50/50) 
70.8 1,800 
1.5 400 Single 68.7 1,726 
1.5 400 Multiple (50/50) 
71.1 1,800 
1.5 400 Single 69.0 1,962 
1.5 400 Multiple (50/50) 
70.3 1,814 
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