# Patent

## Title
Stabilization of mixtures of mercaptoalkylnitriles and

## Abstract

This is a division, of application Ser. No. 402,487, filed Oct. 1, 1973, now U.S. Pat. No. 3,927,041 Dec. 16, 1975.

## Background
Viscous polybutenes of about 300 to about 3000 M.sub.n have viscosities in the range of about 4 to about 5500 centistokes at 100.degree. C. Such polybutenes are commercially available from polymerization of refinery butenes; isobutylene, cis-butene-2 and butene-1 generally present with butane in a C.sub.4 fraction. Commercially since about 1940 such C.sub.4 fractions with or without added isobutylene, or isobuytylene rich concentrates have been polymerized in the presence of Friedel-Crafts catalyst. The wide range in viscosity and in the molecular weight depends, as is known, on polymerization temperature, to a lesser extent on catalyst and its concentration, and on the olefin content of the feed. The viscous polybutenes are essentially water white and thermally decompose with no residue at temperatures above 275.degree. C. and have some use applications in engine oils as anti-scuff agents and viscosity index improvers and in fuels for internal combustion engines to reduce or suppress deposits in the fuel induction system.

The viscous polybutenes have also found use as components of caulking compounds, adhesives and electric-cable insulating oils. However, the greatest use of the viscous polybutenes has been as a raw material in the manufacture of addition agents for fuels and gasoline because the viscous polybutenes are reactive olefins and provide branched-chain alkyl structure in derivatives enhancing their solubility in petroleum products such as lubricant oils, fuels and refinery streams. The derivatives of most interest in the past 15 years are from the polybutenyl-substituted intramolecular anhydrides of aliphatic dicarboxylic acids such as succinic anhydride. The polybutenyl-substituted saturated aliphatic anhydrides have been used per se, or as diesters, amides, imides, amidines, imidines, and neutral or overbased basic metal salts as addition agents in petroleum products. The addition agents from polybutenes of M.sub.n below 500 are mainly used in fuels; for example in gasoline to inhibit rusting, carburetor deposits, and carburetor icing and in diesel fuels to inhibit rust, corrosion and smoke, and in motor oils and industrial oils as rust and wear inhibitors.

The addition agents from polybutenes of 500 to about 3000 M.sub.n have found extensive use as detergent-dispersants in motor oils and lesser use as carburetor detergents in gasoline, heat exchanger antifoulants in refinery streams, rust and corrosion inhibitors in surface coatings and as emulsifiers and demulsifiers.

The viscous polybutenes are complex mixtures of polymers, copolymers and interpolymers of isobutylene, cis-butene-2 and butene-1. The nature and relative amounts of the butene monomers involved in the polymerization leading to a particular M.sub.n polybutene are not indicative of the resulting polymer product because extensive isomerization occurs during polymerization. The viscous polybutenes, although largely mono-olefins, may contain 0 to 20% isoparaffins. The unsaturation in the viscous polybutene molecules is predominantly in a terminal or near terminal group which, as later illustrated, are of the trisubstituted or vinylidene type. The non-olefinic chain portion of the polybutene molecules is composed of normal butyl and isobutyl monomer unit and hence is a long and branched alkyl chain. Such long, branched alkyl chain of the lighter (below 500 M.sub.n) polybutenes contain relatively greater amounts of normal butyl units and lesser amounts of isobutyl units. The heavier (500-3000 M.sub.n) polybutenes contain relatively greater amounts of isobutyl units and lesser amounts of normal butyl units which are concentrated near the end of the long, branched alkyl chain. For example, the structures of a polydisperse polybutene of about 900 M.sub.n have in part been identified through the use of infrared spectroscopy (calibrated by NMR) and permanganate cleavage. The principal structures identified are shown below (in decreasing order of concentration): ##STR1## wherein R is the long, branched alkyl chain and comprises about 60 mole % (C.sub.4).sub.4 to 35, about 30 mole % (C.sub.4).sub.12 to 35 and about 10 mole % (C.sub.4)> .sub.35 ; R' is mainly methyl but is also ethyl; and the ratio of iso-C.sub.4 to n-C.sub.4 is about 3:1.

With respect to polybutene addition reactivity with unsaturated intramolecular anhydrides, it is believed that the olefinic terminal groups in the three structures shown above are in the decreasing reactivity order of III, I and II. In the uncatalyzed addition reaction, some of the slower reacting molecular species remain unreacted and with the isoparaffinic polymer species (0-20% of the total polymer product) which do not react at all, the desired polybutenyl-substituted saturated anhydride product can be obtained in maximum yields of 75-80% based on starting polymer.

Such addition reaction between the viscous polybutene and intramolecular anhydride 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, homomesaconic 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 polybutene to anhydride molar ratios of reactants in the range of 1.0:0.8-5.0, generally 1.0:1.05-1.15. In addition to the nonreaction of some olefinic species of polybutene and isoparaffinic entities thereof amounting to a total of up to 40-50% of the polybutene charged, there is also a problem with respect to thermal decompositon and polymerization of the unsaturated anhydride reactant at temperatures upward from 150.degree. C.

Thermal decomposition at temperatures upward from 150.degree. C. of unsaturated aliphatic dicarboxylic acids and their anydrides (e.g., maleic and its anhydride has been known and is reported, for example, in U.S. Pat. No. 3,476,774 which gives earlier documentation sources therefor. Such thermal decomposition is 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 substantially instantaneous as to be explosive. In the absence of explosive thermal decomposition a carbon-containing residue is also formed in addition to water vapor and oxides of carbon. Such thermal decomposition and attendant 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. There is the increase of internal pressure by involved water vapor and oxides of carbon (mainly CO.sub.2) but the attendant 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, in general, is dispersed in the product, the alkenyl-substituted saturated anhydride addition compound diluted with unreacted components of the olefin polymer, 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 residual material not adhering to reactor internals fouls the filter and interferes with filtration of the desired reacton 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.

Various means have been proposed and/or used to suppress thermal conversion of unsaturated anhydride reactant German Pat. No. 1,102,142 for its reaction of triene (e.g., 1,5,9-cyclododecatriene) with maleic anhydride to prepare a 1:1 addition product teaches the use of from 0.01 to 5 weight percent of thionine, phenothiazine, hydroquinone, and related inhibitors. U.S. Pat. No. 3,231,587 teaches the use of chlorine gas in molar amounts equal to maleic anhydride for its addition reaction with olefin polymers (the resulting alkenylsuccinic anhydride contains 0.4-0.5 weight percent chlorine) as a superior to earlier proposed first preparing a chlorinated olefinic polymer having 4-15 weight percent chlorine and reacting the chloro-polymer with maleic anhydride. U.S. Pat. No. 3,476,774 teaches the use of a hindered phenol nonreactive with the olefin polymer or maleic anhydride (e.g., 2,6-diterbutylphenol or 4,4'-methylenebis-2,6-ditert-butylphenol) to suppress thermal decomposition.

Such hindered phenols are not readily removed from the adduct product. The chloro-substituted adduct may not be useful in all cases for the preparation of addition agent derivatives.

In our laboratories the use of small, i.e., catalytic amounts of hydrogen chloride during the adduct formation between olefinic polymer and maleic anhydride achieved success in improving yield and reducing formation of undesired tarry material. A drawback of this method is the possible corrosive nature of stored polybutene. However, it is understood that hydrogen halides can react with the olefinic polymer forming alkyl halide. It is also recognized that at higher temperature, due to decomposition of the alkyl halides, hydrogen halide and halogen formation are possible. Hence it is recognized that addition of trace quantities of hydrogen halide or halogen or alkyl halide to the polymer could achieve the desired improvements in the said reaction. It was also realized that the effectiveness of the said halo-compounds will vary with the experimental conditions and the exact chemical nature and concentration of the added material.

From the standpoint of both the manufacturer-merchant of the viscous polybutenes and the purchasers-users thereof it would be desirable to modifiy such polybutene compositions by addition of a small amount of material which enhances reactivity of the polybutenes and suppresses formation of the undesirable tarry material without undesirable added effects. It would be further desirable that such modification of the polybutenes be accomplished by a simple, single process step of not only combining a small amount of material with the polybutene to effect the desired reactivity enhancement and tarry material suppression but also by use of a material which is readily removable from the adduct reaction product. For this latter benefit it is pointed out that unreacted anhydride, including that used in slight molar excess per mole of polybutene, is removed from the adduct reaction product by evaporation at an absolute pressure in the range of 5 to 760 mm Hg. and at a temperature below reaction temperature. Thus it is beneficial to add to the polybutene such material having the above-beneficial effects on the adduct reaction and at the same time readily removable at said temperature and pressure conditions at which unreacted unsaturated anhydride is removed.

It has now been discovered that viscous polybutenes of from about 300 to about 3000 M.sub.n containing 5 to 200, preferably from 10 to 200 ppm on weight basis of 1,3-dibromo-5,5-dialkylhydantoin provides a novel, uniquely modified polybutene composition. Such polybutene composition can be reacted at temperatures of 150.degree.-300.degree. C. with unsaturated anhydride without affecting chemical substitution of either the reactants or the adduct product. The bromine-containing additive or its decomposition product is readily removed from the adduct product under conditions of removing unreacted unsaturated-anhydride, enhances polybutene conversion to adduct, and suppresses tarry material formation during adduct formation.

To be most readily removable with unreacted unsaturated anhydride at 5 to 760 mm Hg., the bromine-containing hydantoin additives combined with viscous polybutene should have sufficient vapor pressure at such pressures to facilitate their removal. Preferred sub-class of the bromine-containing hydantoin additives should have a normal (atmospheric pressure) boiling point up to 225.degree. C. but can be as low as 40.degree. C.

Typical, but not all-inclusive, of such 1,3-dibromo-5,5-dialkylhydantoin additives are those whose alkyl-substituents have a total of from 2 to 21 carbon atoms. The alkyl-substituents can be the same or they can be different. Typical alkyl-substituents are methyl-, ethyl-, propyl-, butyl-, pentyl-, hexyl-, heptyl-, octyl-, nonyl-, decyl-, hendecyl-, dodecyl-, tridecyl-, tetradecyl-, pentadecyl-, hexadecyl-, heptadecyl-, octadecyl-, nonadecyl-, and eicosanyl- substitutents.

The reaction between the viscous polybutenes and the anhydrides of unsaturated aliphatic dicarboxylic acids known to the art to be useful for the addition reaction producing alkenyl-substituted saturated anhydride, is conducted commercially in a batchwise or continuous manner in a stirred-tank type autoclave or equivalent reaction vessel providing intimate contact between the reactants. For batchwise operation the reactants are charged to the closed reaction vessel with or without displacing its air with oxygen-free, (e.g., nitrogen) atmosphere at ambient pressure. The reactants can be at ambient temperature but the polybutene reactant is usually at an elevated temperature to facilitate charging the viscous polymer and to reduce the time for the reacton mixture to reach reaction temperature. Solid anhydride reactant can be charged alone or dispersed in the polybutene or alone as a melt. The reaction mixture is stirred while being heated to reaction temperature and during reaction.

Continuous conduct of the addition reaction is maintained by charging to the reaction vessel containing the stirred adduct forming reaction mixture a melt of the anhydride reactant and preheated viscous polybutene so that their combined heat supplies the heat input needed during reaction.

Reaction time for batchwise operation is, in general, 4-8 hours. Continuous operation requires, in general, a shorter residence time, for example 1-3 hours.

Thermal decomposition of anhydride reactant, which evolves CO.sub.2 and water vapor, causes an undesirable pressure increase as well as formation of undesirable tarry material during the adduct reaction. Such pressure increase, although undesirable, can be used as an indicator of failure to suppress formation of such tarry material by a component of the polybutene composition. The actual extent of formation of such tarry material is, of course, determined gravimetrically after termination of the addition reaction and removal of unreacted anhydride reactant at the before-mentioned pressure in the range of 5 to 760 mm Hg.

The manner and nature of enhanced adduct yield by the present inventive polybutene composition comprising a viscous polybutene of about 300 to about 3000 M.sub.n and 5 to 200 ppm 1,3-dibromo-5,5-dialkylhydantoin (DDH) and suppressed formation of undesirable tarry material is not understood. We speculate that isomerization of the olefin double bond to a more reactive species may be accomplished under the catalytic effect of traces of decomposition products derived from the DDH additive. Further, these trace impurities may also act as radical quenchers and inhibit the decomposition and/or polymerization of the unsaturated anhydride to tar.

The use of the present inventive polybutene compositions and the benefits to be derived therefrom in addition reactions with the before-mentioned unsaturated anhydride will now be illustrated using maleic anhydride, the most commonly, commercially used of those anhydride reactants. These examples are conducted with reactant molar ratio of polybutene to maleic anhydride of 1.0:1.1 in a method which closely approaches commercial practice of using stirred-tank type reactions conducted batchwise followed by removal of unreacted maleic anhydride by evaporation and then filtration of the reaction product.

In the following examples there is illustrated the yield enhancing benefits of using the DDH additives. These examples were conducted in small scale reactivity test using an autoclave having a dual-impeller, motor driven stirrer, automatic heat control, pressure gauge and means for sampling the reaction product before its discharge from the autoclave. The condensation reaction is conducted at a temperature of 243.degree.-247.degree. C. After the reaction period, excess maleic anhydride was stripped off, the product was filtered and the filtrate analyzed for yield.

The unreacted polybutene component was determined for calculation of reacted polybutene by chromatographing on silica gel columns a weighed aliquot of each filtered product and eluting said component retained by the columns with hexane. Hexane is removed from the eluted solution to obtain the amount of unreacted polybutene. The yield of polybutenylsuccinic anhydride is reported as "% yield" on a stoichiometric basis taking into account unreacted maleic anhydride and unreacted polybutene.

A gravitimetric determination of the tar formed was also made. Tar was collected from both the filter cakes and reactor itself and such total tar reported as a "WT % Tar," based upon the entire reaction charge.

In the following table identification of the M.sub.n of the polybutenes used, the addition agent and concentration thereof in ppm by weight, yield percent, and total tar from autoclave tests are presented. The brominated hydantoin additive used was 1,3-dibromo-5,5-dimethylhydantoin. Example  Polybutene Additive Adduct Tar % Tar Number   M.sub.n ppm  Yield % %   in Reactor __________________________________________________________________________ Comparative 1 957   none 61.4  1.20 75 1        957   90   69.8  0.30 48 Comparative 2 911   none 62.4  0.80 78 2        911   90   70.1  0.35 59 __________________________________________________________________________

Adduct yields of 70 weight percent are considered to be acceptable for commercial practice but 61-62% yields are unacceptable. The respective 75 and 56% reduction in tar formation and reduction of tar in the reactor effected by the use of the bromine-containing hydantoin additive provides a substantial commercial advantage for the present inventive polybutene additives.

While the foregoing examples illustrate benefits afforded by present inventive polybutene compositions containing viscous polybutenes having M.sub.n of 900-950, the use of other viscous polybutenes in the M.sub.n range of about 300 to 3000 will provide polybutene compositions affording yield improvement and tarry material suppression in the manner and nature above illustrated for the maleic anhydride reactions illustrated. Similar benefits can be expected by the use of the present inventive polybutene compositions with other of the before-named unsaturated anhydrides of aliphatic dicarboxylic acids. Furthermore, the use of other of the 1,3-dibromo-5,5-dialkylhydantoin additives in the 300-3000 M.sub.n polybutenes can be extended to other of the 300-3000 M.sub.n polybutenes in their reaction with the unsaturated intramolecular anhydrides of dicarboxylic acids and achieve results as above indicated.

## Claims

1. A butene polymer composition comprising butene polymer having a M.sub.n in the range of 300-3000 and having an additive concentration of 5-200 ppm of 1,3-dibromo-5,5-dialkyl-substituted hydantoin based on said butene polymer, wherein the alkyl-substituents have a total of 2 to 21 carbon atoms.

2. The composition of claim 1 wherein said substituted hydantoin additive is 1,3-dibromo-5,5-dimethylhydantoin.

3. The composition of claim 2 wherein the butene polymer has a M.sub.n of about 900 to about 950 and said additive concentration is 90 ppm.