Method of Functionalizing Polymers

This invention relates to a process for functionalizing polymers such as polyisobutylene, polypropylene, or ethylene-propylene copolymers etc. More particularly it relates to a novel product functionalized polymer.

As is well known to those skilled in the art, polyolefins such as polyisobutylene (PIB) may be functionalized with difficulty because of the hydrocarbon-like non-reactivity toward common chemical reagents. Prior art techniques for functionalizing polyisobutylene include (i) halogenation; (ii) reaction with phosphorus-sulfur compositions, typically P.sub.2 S.sub.5 ; (iii) reaction with maleic anhydride in an "ene" reaction; (iv) reaction with activated aromatics, eg phenols; etc. Although other reactions may be used, they are generally characterized by low yield or by the use of expensive reagents.

It is an object of this invention to provide a novel process for improving the dispersancy of lubricating oils. It is another object of this invention to provide a process for functionalizing polymers such as polyisobutylene. Other objects will be apparent to those skilled-in-the-art.

In accordance with certain of its aspects, the novel process of this invention for functionalizing a polymer which contains a carbon-to-carbon backbone chain and which includes a side chain containing a double bond with an allylic hydrogen atom on the gamma carbon atom may comprise reacting (i) said polymer which contains a carbon-to-carbon backbone chain and which includes a side chain containing an allylic hydrogen atom with (ii) an activated imine in the presence of (iii) a Lewis acid catalyst thereby forming a functionalized polymer characterized by the presence on said side chain of (i) a double bond newly formed between beta and gamma carbon atoms and pendant on said alpha carbon atom (ii) a substituted amino-methyl group; and

recovering said functionalized polymer charaterized by the presence of (i) a beta double bond pendent on said alpha carbon atom (ii) a substituted amino-methyl group.

The charge polymers which may be functionalized by the process of this invention include those which have a carbon-to-carbon backbone and preferably a polymer wherein the backbone consists essentially of carbon atoms. These polymers are characterized by the presence of pendant side chains (including end chains) which contain at least one allylic hydrogen atom. The allyl group may commonly be present as a grouping having the configuration ##STR1##

In this group, the allylic hydrogen is the one shown. Other groups may be present on the carbon atoms. The groups R.sub.1 through R.sub.5 may be hydrogen or hydrocarbon (typically alkyl groups) and at least one of R.sub.1 through R.sub.5 is a portion of the polymer backbone. The carbon atom which bears the double bond in I is designated the alpha carbon; the next carbon is designated the beta carbon. The allylic hydrogen is on the gamma carbon.

The allylic hydrogen atom may be on a pendant group or in a terminal position.

In the preferred embodiments, the backbone chain consists essentially of carbon atoms. Such polymers include those derived by polymerization (including copolymerization) of lower olefins and their derivatives including ethylene, propylene, and isobutylene; chloroprene; isobutylene; butadiene; styrene; ethylene-propylene; vinyl chloride; methyl or ethyl acrylate; etc. A preferred polymer may have a backbone chain derived from ethylene, propylene, and third monomer such as norbornene or 1,4-hexadiene, typified by the EPD composition: ethylene-propylene-1,4-hexadiene.

Typical preferred polymers may contain a backbone chain derived from the polymers noted in the following Table:

(a) EPD terpolymer prepared from ethylene, propylene, and 1,4-hexadiene and having a molecular weight M.sub.n of 300-100,000, preferably 20,000-70,000, say 68,000 as typified by the commercially available product marketed by DuPont under the trademark Nordel 1320;

(b) 1,2-polybutadiene (prepared by polymerizing a butadiene-1,3 in the presence of 15 w % butyl lithium in hexane or tetrahydrofuran at 0.degree. C.-60.degree. C.) having a molecular weight M.sub.n of 3,000-20,000;

(c) polypropylene having a molecular weight M.sub.n of 500-1500, typically 500-2600, say, 650-995;

(d) polyisobutylene having a molecular weight M.sub.n of 300-1900, typically 1300;

(e) a copolymer of ethylene and butylene having a weight M.sub.n of 810;

(f) an EPD terpolymer having a molecular weight M.sub.n of 3000-30,000, typically 3970-6950, prepared by copolymerizing ethylene, propylene, and 1,4-hexadiene at 0.degree. C.-20.degree. C. in the presence of tri-n-butyl vanadate catalyst and diethyl aluminum choride cocatalyst in n-heptane solvent in the presence of hydrogen. A typical such polymer contains 32 mole % propylene, 2.8 mole % 1,4-hexadiene, and 65.2 mole % ethylene, and has one double bond for each 1000-2000, say 1160-1880 molecular weight units.

The most preferred charge polymer is that derived from polymerization of isobutylene.

These preferred polymers all contain at least one allylic hydrogen atom. The polyethylene polymer may for example be characterized by the formula: ##STR2##

The polyisobutylene may for example be characterized by the formula: ##STR3##

In these and other formulae, the subscript n represents the number of repeating units.

The typical charge polymer may contain 3-9 of the designated allylic groups, say 6 per 100 units of molecular weight M.sub.n of terpolymer. In the case of the preferred polyisobutylene of molecular weight M.sub.n of 200 -3000, say 1300 there may typically be present one allylic group per molecule of polymer.

The substituted imines which may be used in practice of the process of this invention may be characterized by the formula: ##STR4##

In this formula, the group R'" (and preferably also the groups R' and R") are electron-withdrawing groups; typical of such groups are --COOR groups, --SO.sub.3 R groups, --CX.sub.3. The preferred group may be --COOR. R' and R" may be hydrogen, CX3 (where X is halogen, preferably fluorine, chlorine, or bromine), hydrocarbyl typified by phenyl, etc. The electron-withdrawing group may be attached to the nitrogen or the carbon atom shown but preferably it is attached to the nitrogen atoms.

In the above compounds, R, R', and R" may preferably be a hydrocarbon radical selected from the group consisting of alkyl, aralkyl, cycloalkyl, aryl, alkaryl, alkenyl, and alkynyl including such radicals when inertly substituted. When R is alkyl, it may typically be methyl, ethyl, n-propyl, iso-propyl, n-butyl, i-butyl, sec-butyl, amyl, octyl, decyl, octadecyl, etc. When R is aralkyl, it may typically be benzyl, beta-phenylethyl, etc. When R is cycloalkyl, it may typically be cyclohexyl, cycloheptyl, cyclooctyl, 2-methylcycloheptyl, 3-butylcyclohexyl, 3-methylcyclohexyl, etc. When R is aryl, it may typically be phenyl, naphthyl, etc. When R is alkaryl, it may typically be tolyl, xylyl, etc. When R is alkenyl, it may typically be vinyl, allyl, 1-butenyl, etc. When R is alkynyl, it may typically be ethynyl, propynyl, butynyl, etc. R may be inertly substituted i.e. it may bear a non-reactive substituent such as alkyl, aryl, cycloalkyl, ether, halogen, nitro, etc. Typically inertly substituted R groups may include 3-chloropropyl, 2-ethoxyethyl, carboethoxymethyl, 4-methyl cyclohexyl, p-chlorophenyl, p-chlorobenzyl, 3-chloro-5-methylphenyl, etc. The preferred R groups may be lower alkyl, i.e. C.sub.1 -C.sub.10 alkyl, groups including, e.g. methyl, ethyl, n-propyl, i-propyl, butyls, amyls, hexyls, octyls, decyls, etc. R may be preferably be n-propyl.

Illustrative imines which may be used in practice of the process of this invention may include: ##STR5##

These imines may be available commercially or they may be conveniently prepared in accordance with procedures reported in the literature. See for example

(a) R. Albrecht and G. Kresge, Chem Ber 98 1431 (1965); and

(b) M. P. Cava, C. K. Wilkins, Jr., D. R. Dalton, and K. Bessho J. Org. Chem 30, 3772 (1965).

A preferred imine is the first of those listed in which R' and R" are hydrogen and R'" is --COOEt viz N-carboethoxymethylene imine. This imine may be prepared in situ (during the functionalization of the polymer) from e.g. methylene diurethane: ##STR6##

The catalyst which may be employed in practice of the process of this invention may be a Lewis Acid typified by the following:

boron trifluoride etherate

boron trichloride

aluminum tribromide

aluminum trichloride

ferric chloride

antimony pentachloride

zirconium tetrachloride

stannic chloride

antimony trichloride

The preferred of these Lewis Acid Catalysts may be boron trifluoride, used as its etherate with ethyl ether.

The reactants may be added to the reaction operation in the following molar parts:

Reaction is preferably carried out in batch operation and in liquid phase with agitation at 20.degree. C.-100.degree. C., preferably 50.degree. C.-80.degree. C., say 65.degree. C. at atmospheric pressure for 1-20 hours, preferably 1-8 hours, say 4 hours.

Reaction may be carried out neat or in the presence of 0.5-10 parts, preferably 0.5-3 part, say 1 part of inert diluent-solvent, typified by:

chloroform

toluene

heptane

xylene

During reaction, the alpha-double bond of the allyl group shifts to the beta position; the double bond of the imine group opens; the allylic hydrogen on the gamma carbon of the allyl group becomes bonded to the nitrogen of the imine; and the carbon (from the C=N portion of the imine) becomes bonded to the alpha carbon of the allyl group: e.g. ##STR7##

In these illustrative formulae, one of the R.sub.1 through R.sub.5 groups represents a polymer moiety with which the allyl group is associated.

At the conclusion of the reaction, solvent if present is stripped off, at 20.degree. C.-150.degree. C., preferably 50.degree. C.-100.degree. C., say 100.degree. C. and 0.1-760 mm Hg, preferably 0.1-10 mm Hg, say 5 mm Hg. The product, typically a viscous liquid, is then dissolved in 1-10, preferably 2-3, say 2.5 times in weight of solvent, typically hydrocarbon solvent such as n-heptane. The solution is washed preferably several times with 0.1-10, preferably 0.1-1.0, say 0.5 times its weight of alkanol, preferably methanol.

The resultant product is stripped at 20.degree. C.-200.degree. C., preferably 50.degree. C.-100.degree. C., say 80.degree. C. at 0.1-760- mm Hg, preferably 0.1-10mm Hg, say 5 mm Hg.

It is found that 10-100, preferably 40-80, say 60 mole percent of the allylic groups originally present may be functionalized by addition of the nitrogen-containing moiety. The reaction may readily be followed by the decrease in the 1710/cm.sup.-1 peak in the IR which represents the carbonyl stretching frequency and by the increase in 3413/cm.sup.-1 which represents the --NH stretching frequency--in one preferred embodiment.

The product functionalized polymer may typically be a solid or a viscous oil of light color, high solubility in hydrocarbon solvents, and high melting point.

The novel product polymer may be a polymer which bears an imine-derived functional group on at least some of the allylic groups originally present. Commonly it may be found that 10-100, preferably 40-80, say up to 60 mole % of the allylic groups may be functionalized.

The product polymer may be characterized by the presence of at least one (1-aminoethyl) propen-2-yl group where the amino group bears an electron withdrawing group. This group may have the formula: ##STR8## wherein R', R", and R'" are as noted supra.

In the preferred embodiment, the group may be designated either as a [1-(substituted-amino) mono- or di-substituted methyl] propen-2-yl group or a [1-(substituted-aminomethyl)] propen-2-yl group.

Typical products may be the following:

(a) EPD terpolymer prepared from ethylene, propylene, and 1,4-hexadiene and having a molecular weight M.sub.n of 300-100,000, preferably 20,000-70,000, say 68,000 as typified by the commercially available product marketed by DuPont under the trademark Nordel 1320 and which now contains pendent amine groups derived from the imine;

(b) 1,2-polybutadiene (prepared by polymerizing butadiene-1,3 in the prsence of 15 w % butyl lithium in hexane or tetrahydrofuran at 0.degree. C.-60.degree. C.) having a molecular M.sub.n of 3,000-20,000 and which now contains pendent amine groups derived from the imine;

(c) polypropylene having a molecular weight M.sub.n of 500-1500, typically 500-2600, say 650-995 and which now contains pendent amine groups derived from the imine.

(d) polybutylene having a molecular weight M.sub.n of 300-1900, typically 1300 and which now contains pendant amine groups derived from the imine;

(e) a copolymer of ethylene and butylene having a molecular weight MHD n of 810 and which now contains pendant amine groups derived from the imine;

(f) an EPD terpolymer having a molecular weight MHD n of 3000-30,000, typically 3970-6970, prepared by copolymerizing ethylene, propylene, and 1,4-hexadiene at 0.degree. C.-20.degree. C. in the presence of tri-n-butyl vanadate catalyst and diethyl aluminum chloride cocatalyst in n-heptane solvent in the presence of hydrogen (typically such a polymer contains 32 mole % propylene-derived units, 2.8 mole % 0,4-hexadiene-derived units, and 65.2 mole % ethylene-derived units and which now contains pendant amine groups derived from the imine.

A preferred product of the process of this invention may be that prepared from polyisobutylene (M.sub.n of 1290) which has been reacted with the nitrogen substituted acyl-imine CH.sub.2 .dbd.N-COOEt (the later derived by splitting methylene diurethane in situ) and which has a molecular weight M.sub.n of 1330, and contains 0.37 wt. % nitrogen corresponding to the addition of nitrogen-containing imine-derived moieties at 40% of the allylic double bonds originally present in the polymer.

A typical product polymer molecule may have the formula ##STR9##

In the case of a preferred polyisobutylene-derived product, a typical product may be characterized by the formula ##STR10## wherein x is 5-300, say 25, and the product has a molecular weight M.sub.n of 300-17,000, say 1400.

The polymer composition useful in practice of the process of this invention may contain a wide range of pendant groups in the molecule.

Where it is desired to utilize the product in an oil system, the number of pendant groups may typically be one for each 300-10,000 molecular weight units, preferably one for each 1000-5000 molecular weight units, say one for each 1800 molecular weight units. The greatest solubility in lube oil systems may be achieved when the polymer base has a molecular weight M.sub.n of 300-15,000.

Another preferred polymer composition used in practice of the invention may be derived from polymers of ethylene-propylene-third monomer-most preferably from a terpolymer of ethylene-propylene-1, 4-hexadiene which, when prepared by the process of this invention may have the following repeating groups in the polymer chain: ##STR11## wherein x, x', and x" may be integers.

Such a polymer may typically contain 40 mole %-80 mole % derived from ethylene, 20 mole %-60 mole % derived from propylene, and 0.1 mole %-5 mole % derived from third monomer.

These novel reaction products of a polymer and an imine, which are characterized by the presence of amine functionality, may generally be used in the same manner and for the same purposes as the unfunctionalized polymers. In these uses, the system may be benefited by the presence of the amine functionality. For example, the amine-functionalized polymer wherein the backbone is derived from a polyisobutylene or a polypropylene moiety may (as such or after hydrogenation) be used as blending agents in lubricating oils or in motor fuels. Clearly the use in motor fuels may be more desirable when the backbone is of lower molecular weight, e.g. derived from diisobutylene or trimers or tetramers; and use in lubricating oils may be more desirable for the polymers of high molecular weight, e.g. 1000 up to say 10,000 or more.

These materials may also be used as adhesives, bonding agents, or laminating agents either alone or in admixture with other resins such as coumarone-indene resins, polystyrenes, etc. They may also be used as reactant in a wide variety of systems to produce products which are useful as additives. For example, the typical polyisobutylene-derived polymer bearing amine functionality may be reacted with (i) phenols to give anti-oxidants or with (ii) maleic acid anhydride to give amine-substituted polyisobutylene-succinic acid anhydride type derivatives which are useful as surface active agents and as additives to lubricating oils or motor fuels.

These novel products may find particular use as additives to lubricating oils, petroleum base or synthetic (e.g. ester type such as polyester oils); it may be found that by presence of these novel compounds, the dispersancy of such oils may be improved.

Commonly these products may be useful in the form of concentrates containing 10-70 parts, preferably 20-60 parts, say 50 parts of polymer per 30-90 parts, preferably 20-80 parts, say 50 parts diluent-solvent. Inert diluent-solvents may include hydrocarbons such as toluene, and more preferably oils including lubricating oils--synthetic or petroleum based. A typical concentrate may include 35 parts of the novel polymer in 65 parts of 100 E Pale Stock HF (a paraffinic distillate oil 39 SUS viscosity at 210.degree. F.) lubricating oil.

In accordance with certain of its aspects, the lubricating oils which may be improved by use of the products of this invention may include various lubricating oils such as hydrocarbon oils derived from petroleum or synthetically prepared lubricating oils.

Natural oils may include mineral oils such as those obtained from petroleum, including distillate and residual lubricating oils. Typical of these may be:

1. An SAE 10 Mid-continent, solvent refined lubricating oil with the following flow properties:

2. An SAE 30 Pennsylvania type lubricating oil with the following flow properties:

3. An SAE 30 Naphthenic solvent-refined lubricating oil with the following properties:

Other such oils useful in the practice of this invention are well-known in those skilled in the art.

The synthetic lubricating oils which may be improved by use of this invention may include liquid high molecular weight esters, fluorocarbons, polyethers, polysilicones, etc.

Typically, the synthetic oil may be an ester formed by the reaction of (a) a C.sub.3 -C.sub.30 aliphatic acid R.sup.2 (COOH).sub.n is an aliphatic hydrocarbon (including inertly-substituted hydrocarbon) residue and n is typically 1-3, preferably 1, with (b) a C.sub.4 -C.sub.20 aliphatic alcohol R.sup.3 (OH).sub.m wherein R.sup.3 is an aliphatic hydrocarbon (including inertly-substituted hydrocarbon) residue and m is an integer, preferably 1-6, more preferably 1-4, most preferably 3-4.

The base oil may, in one embodiment, be a liquid ester product of an aliphatic monocarboxylic acid and a polyol. The preferred of these acids may contain 5-36 carbon atoms. Illustrative of such acids may be:

More preferably, C.sub.6 -C.sub.10 acids may be used. Typical of such acids may be:

The most preferable, however, are enanthic and pelargonic acids.

The polyols which may be reacted with the noted aliphatic monocarboxylic acids, to form esters, .may include R.sup.3 (OH).sub.m wherein R.sup.3 is an aliphatic hydrocarbon moiety and m is an integer preferably 2-6, more preferably 2-4. The preferred polyols may be the C.sub.2 -C.sub.10, say C.sub.2 -C.sub.4 polyols. Typical of such polyols may be:

neopentylglycol

trimethylol ethane

trimethylol propane

trimethylol butane

pentaerythritol

dipentaerythritol

The preferred glycol may be pentaerythritol.

Typical esters of aliphatic monocarboxylic acids and polyols may be

including the following illustrative examples:

pentaerythritol tetra-valerate

pentaerythritol tetra-caproate

pentaerythritol tetra-pelargonate

dipentaerythritol hexa-valerate

dipentaerythritol hexa-pelargonate

dipentaerythritol hexa-caproate

trimethylol propane tri-caproate

trimethylol propane tri-butyrate

trimethylol propane tri-valerate

trimethylol propane tri-pelargonate

A preferred ester may be pentaerythritol tetra-caproate.

In another embodiment, the liquid synthetic ester may be the product of reaction of an aliphatic polycarboxylic acid and aliphatic monohydroxy alcohol.

Preferably, the aliphatic polycarboxylic acid may have the formula R.sup.2 (COOH).sub.n, wherein n is greater than 1 and preferably 2-3. Typical polycarboxylic acids may include:

adipic acid

azelaic acid

sebacic acid

dodecanedioic acid

succinic acid

1,2,4 butane tricarboxylic acid

Preferred acids may be adipic acid and azelaic acid.

Preferably the alcohol may have the formula R.sup.3 OH where R.sup.3 may be a saturated aliphatic group which may be inertly substituted. Typical alcohols may include methanol, n-butanol, 2-ethyl-n-butanol, pentanol, 1-hexanol, 2-ethylhexanol, 1-decanol, 2-ethyl-octanol, and 2-ethoxy ethanol.

Specific illustration of this type of synthetic ester lubricating oils which may be used in this invention are:

di-2-ethylhexyl sebacate

di-2-ethylhexyl ozelate

di-2-ethylhexyl adipate

di-n-amyl sebacate

di-2-ethyl octyl succinate

di-2-ethoxyethyl sebacate

di-2-ethyl octyl adipate

di-2-ethyl octyl azelate

tri-pentyl-1,2,4 butane carboxylate

Preferred esters may be di-2-ethylhexyl azelate and di-2-ethylhexyl adipate.

These oils may be blended with other synthetic esters as noted supra or with other oils, such as castor oil, lard oil, polymerized olefins, copolymers of alkylene glycols or aliphatic alcohols with organic acids, etc.

The lubricant compositions of the present invention may contain other additives, typically present in amount of 0.001-10 wt.%, including:

a. oxidation inhibitors such as aromatic amines e.g., phenothiazine;

b. metal corrosion inhibitors such as benzotriazole;

c. metal passivating and load-carrying agents, such as tricresyl phosphate;

d. anti-foamants such as silicone, etc.

Although the preferred compositions of this invention may be lubricating oils characterized by improved dispersancy and/or by improved viscosity index, it is a feature of this invention that the additives disclosed herein may permit attainment of improvements in crude oils, in residual oils, in reduced crudes, in fuel oils, in distillates, in wax-containing compositions, etc.

In practice of this invention, the preferred composition may contain a dispersing amount of the novel product. Typically this dispersing amount may be 0.1-10 parts, preferably 1-4, say 2 parts of product per 100 parts of oil.

In the case of lubricating oils, the novel polymer product may commonly impart improved viscosity index, and the viscosity index improving amount may be 0.1-10, preferably 0.5-3, say 1.6 parts of polymer per 100 parts of oil. They may be used alone or in combination with other dispersing agents or viscosity index improving agents.

The dispersant properties of the additive of this invention may be tested for its effectiveness in mineral lubricating oil compositions in the Bench V-C Test.

The Bench V-C Test is conducted by heating the test oil mixed with a synthetic hydrocarbon blowby and a diluent oil ar a fixed temperature for a fixed time period. After heating, the turbidity of the resultant mixture is measured. Ratings of 0-100 are assigned. A lower number is an indication of an improvement in dispersancy.

Viscosity index of lubricating oils may be measured in standard manner; and improvement in viscosity index of 30-50 units may be common.

Practice of the process of this invention may be apparent to those skilled in the art from inspection of the following examples wherein, as elsewhere in the specification, all parts are parts per weight unless otherwise stated. In the examples, as elsewhere, unfilled valence bonds may be filled with hydrogen atoms.

There is added to a one-liter flask:

(i) 89 g (1 mole) urethane in 500 ml water;

(ii) 40.5 g (0.5 moles) 37% aqueous formaldehyde; and;

(iii) 1.5 g (0.02 moles) concentrated hydrochloric acid as catalyst.

The solution is maintained overnight, as crystals form. Crystals (76 grams), representing a 40% yield are obtained by filtering; and cooling of the mother liquor gives additional crystals to increase the yield to 85% of product which is identified by NMR and melting point.

In this example, there is added to a 500 ml flask:

(i) 100 g (0.078 moles) of Indopol H-300 brand of polyisobutylene (M.sub.n of 1290);

(ii) 14.8 g [0.078 moles) of methylene diurethane;

(iii) 100 ml chloroform; and `(iv) 3.1 g boron trifluoride BF.sub.3 etherate

The reaction mixture is refluxed 4 hours and then stripped under vacuum. The product is then dissolved in 200 ml heptane, washed twice with 50 ml aliquote of anhydrous methanol, and stripped under vacuum.

The product is found to have a molecular weight M.sub.n of 1330 and a nitrogen content of 0.37%. By chromatography, it is determined that 40% of the allylic groups are converted to nitrogen-containing groups. The major product corresponds to: ##STR13##

Results comparable to Example II, may be attained if the charge polymer is

It will be noted that polymers which contain no allylic group as characterized supra, are not functionalized by the process of this invention, e.g.:

In this example, the product of Example II is added to a standard lubricating oil.

The lubricating oil plus the product of Example II is tested for dispersancy. The results are as follows:

From the above, it is apparent that the product of this invention shows evidence of dispersing ability in lubricating oils.

Although this invention has been illustrated by reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modification may be made which clearly fall within the scope of this invention.