[0001] This invention relates to stable polymeric dispersant additives and viscosity-index
improvers for lubricating oils. More particularly, this invention relates to viscosity-stable
solutions of substantially saturated polymers comprising ethylene and one or more
C
3 to C
28 alpha-olefins, preferably propylene, which have been grafted in the presence of a
free radical initiator with an ethylenically-unsaturated dicarboxylic acid material,
preferably at an elevated temperature and in an inert atmosphere, and thereafter reacted
first with a polyamine, preferably an alkylene polyamine, having at: least two primary
amino groups, such as diethylene triamine, and then with an anhydride of an organic
acid, to form multifunctional polymar- ic reaction products characterized by viscosity-stabilising
aetivity in mineral oil solutions.
[0002] Ashless dispersants for lubricating oil compositions are known to enhance the sludge
dispersing ability of said compositions.
[0003] One type of dispcrsant is generally derived from a hydrocarbon-substituted dicarboxylic
acid material such as an alkenyl succinic acid or anhydride reacted with a nitrogen-containing
matcrial. United Kingdom Patent Specification 1,018,982 discloses the reaction of
said alkenyl succin- ic anhydride with a 2-imidazoline or pyrimidine (the latter is
obtained by the reaction of a carboxylic acid, a.g. acetic acid and an alkylene polyamine,
e.g. dictiylene triamine) to provide a sludge dispersant for lubricating oils. Similarly,
U.S. Patent 3,415,750 discloses polyalkenyl su\c-cinicimido imidazolines and bis-imidazolines
which can be used as said ashless detergents. The imidazoline is first prepared by
the reaction of a polyachylene polyamine wich a carboxylic acid or its anhydride,
e.g. acetic, which pr duct is thereafter reacted with a polyalkenyl succini; anhydride.
[0004] U.S. Patent 3,216,936 teaches that it is advar- tageous to ensure that the reaction
product of a mixture of a hydrocarbon-substituted succinic acid, a monocarboxylic
acid and an alkylene polyamine does not come from an intermediate reaction product
of said monocarboxylic acid and said amine in order to avoid destroying the sludge
dispersant activity of the final reaction product.
[0005] It is well known that the introduction of carboxylic acid groups onto ethylene copolymers
provides a means for derivatizing said copolymers which have viscosity index (V.I.)
improving activity when dissolved in mineral oils One means of introducing the carboxylic
groups is by grafting maleic anhydride onto said polymer as by a free radical mechanism.
[0006] Belgian Patent 843,360 teaches the production of soluble, sludge-dispersing additives
for hydrocarbon fuels and lubricating oils by the free-radical induced grafting in
solution of an ethylenically-unsaturated dicarboxyli.c acid material, such as maleic
anhydride, onto a substantially saturated copolymer comprising ethylene and ac least
one other alpha-olefin at an elevated temperature to provide, without substantial
polymer degradation, a useful precursor copolymer which can be subsequently reacted
with a carboxylic acid reacting polyfunctional material, such as a polyamine or a
hydroxyamine or mixtures of these. form multifunctional polymeric imidated derivatives
acting particular utility as engine sludge and varnish control additives for lubricating
oils.
[0007] It is often found that during the storage of oil solutions of these various imidated
grafted hydrocarbon polymers that the viscosity of the solution is increased. The
source of this increase appears to be at least in part the chain extension of the
polymer.
[0008] It has now been discovered that the reaction of the imidated products/byproducts
of the graft reaction with organic acid anhydrides, e.g. acetic anhydride, re- sults
in amide derivatiz
aticn of any primary amino groups of the imidated ethylene copolymer whereby viscosity
stabilizing activity is provided to said copolymers.
[0009] The subject matter of this invention is exemplified in a composition comprising a
lubricating oil having dissolved therein at least a viscosity index-improving amount,
generally ranging from about 0.1 to about 50 wt. %, based on the total weight of said
composition, of an oil-soluble C
1 to C
30 hydrocarbyl amide of an imide, preferably an alkylene polyamido-imide, grafted ethylene
polymeric viscosity index improver containing from about 0.001 to 8, preferably 0.1
to 2, wt. % of nitrogen.
[0010] The present invention also comprises the viscosity stabilization of an oil additive
concentrate comprising a hydrocarbon solvent, from .1 to 50 wt. % based on the total
weight of said concentrate of an imidated grafted ethylene C
3-C
28 alpha-olefin copolymeric viscosity index improver having a number average molecular
weight (M
n) of 700 to 500,000 and a weight average/numberaverage molecular weight (M
w/M
n) ratio of less than 7, comprising the step of reacting said concentrate with a hydrocarbyl-substituted
acid anhydride wherein the hydrocarbyl constituont has from about 1 to 30, preferably
1. to 18 carbon atoms by adding said acid anhydride in about 0.5-2.5, preferabl, 1-1.5,
moles per primary amino group of said concentrate and maintaining said concentrate
at a temperature ranging\ from about 50° to about 250°C., preferably 100 to 200°C.,
and for a period of 0.25 to 8, preferably 0.5 to 3 hours.
[0011] The reaction appears to be an acylation of pendant primary amine groups by their
reaction with the organic acid anhydride which can be represented as follows: Ethylene
copolymer chain -
Alkylene amino-imide of a grafted ethylene copolymer
i
[0012] This acylation of the free primary amino group with the anhydride produces an amide
structure which limits the multifunctionalized copolymers property of solution chain
extension thereby inhibiting viscosity increase of oil solutions containing the additives
of the invention.
[0013] To enhance the freedom from hazs of the mineral oil solutions, the mineral oil compositions
of the invention can be further reacted with an oil-soluble hydrocarbyl substituted
acid having from about 10 to 70 carbon atoms having a pK of less than about 2.5, preferably
a polymethylene substituted benzene sulfonic acid, said polymethylene substituent
having from 18-40, optimally 24 to 32 carbons, in an amount of from about 0.01 wt.
% to 8 wt. % at a temperature within the range of about 150°C. to about 200°C. and
for a period from a bout 0.1 hour to about 20 hours, e.g. for 1 hour at 190°C. This
further step results in an additive oil composition of improved viscosity stability
which has no visually perceptible haze.
The Ethylene Copolymer
[0014] The ethylene copolymers to be grafted contain from about 2 to about 98, preferably
30 to 80 wt. % of ethylene, and about 2 to 98, preferably 20 t 70, wt. % of one or
more
C3 to
C28, preferably C
3 to C
18, more preferably C
3 to C
8, alpha-olefins, e.g. propylene. Such copolymers preferably have a degree of crystallinity
of less than 25 wt. %, as determined by X-ray and differential scanning calorimetry,
and a number average molecular weight (M
n) in the range of about 700 toabout 500,000, preferably 10,000 to 250,000, as determined
by vapor phase osmometry (VPO) or membrane osmometry. Copolymers of ethylene and propylene
are most preferred. Other alphs-olefins suitable in place of propylene to form the
copolymer or to be used in combination with ethylene and propylene to form a terpolymer
include 1-butene, 1-pentene, 1-hexene, 1-octene; also branched-chain alpha-olefins,
such as 5-methylpentene-1 and 6-methylheptene-1 and mixtures-thereof.
[0015] Terpolymers of ethylene, said alpha-olefin and non-conjugated diolefin or mixtures
of such diolefins may also be used. The amount of the non-conjugated diolafin ranges
from about 0.5 to 20 mole percent, preferably about 1 to about 7 mole percent, based
on the total amount of ethylene and alpha-olefin present. Representative diolefins
include cyclopentadiene, 2-methylene-5-norbornene, non- conjugated hexadiene, or any
other alicyclic or aliphatic non-conjugated diolefin having from 6 to 15 carbon atoms
per molecule, such as 2-methyl or ethyl norbornadiene, 2,4-dimethyl-2-octadiene, 3-(2-methyl-1-propene)
cyclopentene, ethylidene norbornene, etc.
[0016] These ethylene copolymers, this term including terpolymers, may be prepared using
the well-known Ziegler-Natta catalyst compositions as described in U.K. Patent 1,397,994.
[0017] Such polymerization may be effected to produce the ethylene copolymers by passing
0.1 to 15, for example, 5 parts of ethylene; 0.05 to 10, for example, 2.5 parts of
said higher alpha-olefin, typically propylene; and from 10 to 10,000 parts of hydrogen
per million parts of ethylene; into 100 parts of an inert liquid solvent containing
(a) from about 0.0017 to 0.017, for example, 0.0086 parts of a transition metal principal
catalyst, for example, VOC1
3; and (b) from about 0.0084 to 0.084, for example, 0.042 parts of cocatalyst, e.g.
(C
2H
5)
3Al
2Cl
3; at a temper- ature of about 25°C. and a pressure of 60 psig for a period of time
sufficient to effect optimum conversion, for example, 15 minutes to one-half hour;
all parts being parts by weight.
Ethylenically Unsaturated Carboxylic Acid Materials
[0018] These materials which are grafted (attached) onto the copolymer contain at least
one ethylenic bond and at least one, preferably two, carboxylic acid or its anhydride
groups or a polar group which is convertible into said carboxyl groups by oxidation
or hydrolysis. Maleic anhydride or a derivative thereof is preferred as it does not
appear to homopolymerize appreciably but grafts onto the ethylene copolymer or terpolymer
to give two carboxylic acid functionalities. Such preferred materials have the generic
formula
wherein R
1 and R
2 are hydrogen or a halogen and 0 is oxygen. Suitable examples additionally include
chloromaleic anhydride, itaconic anhydride, or the corresponding dicarboxylic acids,
such as maleic acid or fumaric acid or their monoesters.
Grafting of the Pollymer
[0019] The free=radical induced grafting of ethylenically unsaturated carboxylic acid materials
in solvents, such as benzene, is known in the art (see U.S. Patent 3,236,917). The
grafting according to the process of this invention is carried out at an elevated
temperature in the range of about 100°C. to 250°C., preferably 120 to 190°C. and more
preferably 150 to 180°C., e.g. above 160°C., in solvent, preferably a mineral lubricating
oil solution con taining, e.g. 1 to 50, preferably 5 to 30 wt. %, based on the initial
total oil solution, of the ethylene polymer and preferably under an inert environment.
The grafting is carried out in the presence of a high-temperature decomposable compound
capable of supplying free radicals at said elevated temperature.
[0020] The free-radical initiators which may be used are peroxides, hydroperoxides, and
azo compounds and preferably those which have a boiling point greater than about 100°C.
and decompose thermally within the grafting temperature range to provide said free
radicals. Representative of these free-radical initiators are azobutyronitrile and
2. 5-dimethyl-hex-3-yne-2,5 bis-tertiary-butyl peroxide, commercially sold as Lupersol
130 or its hexane analogue. The initiator is used at a level of between about 0.005%
and about 1%, based on the total weight of the polymer solution,
[0021] The ethylenically unsaturated carboxylic acid material, e.g. maleic anhydride, is
used in an amount ranging from about 0.01% to about 10%, preferably 0.1 to 2.0%, based
on the weight of the initial total oil solution. The aforesaid carboxylic acid material
and free radical initiator are used in a weight percent ratio range of 1.0:1 to 30:1,
preferably 2.0:1 to 7:1, more preferably 3.0:1 to 6:.L.
[0022] The grafting is preferably carried out in an inert atmosphere, such as by nitrogen
blanketing. While the grafting can be carried out in the presence of air, the yield
of the desired graft polymer is decreased as compared to grafting under an inert atmosphere.
The inert environment should be substantially free of oxygen. The grafting time ranges
from about 0..1 to 12 hours, preferably from about 0.5 to 6 hours, more preferably
0.5 to 3 hours. The graft reaction is carried out to at least approximately 4 times,
preferably at least about 6 times the half-life of the free-radical initiator at the
reaction temperature employed. e.g. with 2,5-dimethyl hex-3-yne-2, 5-bis(t-butyl peroxide)
2 hours at 160°C. and one hour at 170°C.
[0023] In the grafting process, the copolymer solution is first heated to grafting temperature
and thereafter said carboxylic acid material and initiator are added with agitation
although they could have been added prior to heating. When the reaction is complete,
the excess acid material is eliminated by an inert gas purge, e.g. nitrogen sparging.
[0024] In the grafting step, the maleic anhydride or other carboxylic acid material used
is grafted onto both the polymer and the solvent for the reaction. The wt. % grafted
onto the polymer is normally greater than the amount grafted onto the oil due to greater
reactivity of the polymer to grafting. However, the exact split between the two materials
depends upon the polymer and its reactivity, the reactivity and type of oil, and also
the concentration of the polymer in the oil. The split can be measured empirically
from the infrared analyses of product dialyzed into oil and polymer fractions and
measuring the anhydride peak absorbance in each.
[0025] The grafting is preferably carried out in a mineral lubricating oil which need not
be removed after the grafting step but can be used as the solvent in the subsequent
reaction of the graft polymer with the polyfunctional material and as a solvent for
the end product to form the concentrate.
Polyamines
[0026] Useful polyamines for reaction with the grafted ethylene-containing polymers are
those which have at least two primary amino groups, hereafter designated poly(primary
amines), i.e. one group to react with the dicarboxylic acid moiety to form the imido
linkage and one more group to react with the organic acid anhydride whereby an amide
is formed. Such poly(primary amines) can be represented by the formula
wherein R represents an alkylene group, an alkylene imino group, a hydrocarbyl group,
a saturated ring structure, an unsaturated ring structure or a nitrogen containing
heterocyclic ring structure. The useful poly(primary amines) include poly(primary
amines) of about 2 to 60, e.g. 3 to 20, total carbon atoms and about 2 to 12, e.g.
2 to 6 nitrogen .atoms in the molecule, which amines may be hydrocarbyl poly(primary
amines) or may be hydrocarbyl poly(primary amines) including other groups, e.g., cyano
groups, amide groups, imidazoline groups, and the like. Preferred amines are aliphatic
saturated poly(primary amines), including those of the general formula:
wherein R and R' are independently selected from the group consisting of hydrogen,
amino alkylene radicals, and C
1 to C
12 alkylamino C
2 to C
6 alkylene radicals, s is a number of from 2 to 6, preferably 2 to 4, and t is a number
of from 0 to 10, preferably 2 to 6.
[0027] Examples of suitable amine compounds include ethylene diamine, diaminomethane, 1,3-diaminopropane,
1,4-diaminobutane, 1,6-diaminohexane, diethylene triamine, triethylene tetraamine,
tetraethylene pentamine, 1,2-propylene diamine, di-(1,2-propylene) triamine, di-(1,3-propylene)
triamine, di-(1,4-butylene) triamine and N,N-di-(2-aminoethyl) ethylene diamine.
[0028] Other useful amine compounds include alicyclic diamines such as 1,4-di-(aminomethyl)
cyclohexane and heterocyclic nitrogen compounds, such as N-amino-alkyl piperazines
of the general formula:
wherein G is an omega-aminoalkylene radical of from 1 to 3 carbon atoms and p is an
integer of from 1 to 4. An example of such an amine is N,N'-di-(2-aminomethyl) piperazine.
[0029] Commercial mixtures of amine compounds may advantageously be used. For example, one
process for preparing alkylene amines involves the reaction of an alkylene dihalide
(such as ethylene dichloride or propylene dichloride) with ammonia, which results
in a complex mixture of alkylene groups, forming such compounds as diethylene triamine,
triethylenetetramine, tetraethylene pentamine and isomeric piperazines. Low cost poly(ethylene
amines) compourds having a composition approximating tetraethylene pentamine are available
commercially under the trade name Polyamine 400. Still other polyamines separated
by hetero atom chains such as polyethers or sulfides can be used.
Multifunctionalization (Imidization) Process
[0030] The grafted polymer, preferably in solution, can be readily reacted with said poly(primary
amine) and mixtures thereof by admixture together and heating at a temperature of
from about 100°C. to 250°C. for from 10 minutes to 30 hours, preferably 10 minutes
to 10 hours, usually about 15 minutes to about 3 hours. It is preferred to use 0.01
to 2.5 mole, more preferably 0.5 to 1.0 mole, of the poly-(primary amine) per mole
of grafted carboxylic material, such as maleic anhydride. The reaction of diethylene
triamine with the grafted ethylene-containing polymer occurs in 15 minutes or less
at 170°C. with a nitrogen blanket.
[0031] The solution grafting step when carried out in the presence of a high temperature
decomposable peroxide is accomplished without significant degradation of the chain
length (molecular weight) of the ethylene-containing polymer. Measurement of molecular
weights and degradation can be evaluated by determination of the thickening efficiency
of the polymer.
[0032] Thickening efficiency (T.E.) is defined as the ratio of the weight percent of a polyisobutylene
(sold as an oil solution by Exxon Chemical Co. as Parutane N), having a Staudinger
Molecular Weight of 20,000, required to thicken a solvent-extracted neutral mineral
lubricating oil, having a viscosity of 150 SUS at 37.8°C., a viscosity index of 105
and an ASTM pour point of 0°F., (Solvent 150 Neutral) to a viscosity of 12.4 centistokes
at 98.9°C., to the weight percent of a test copolymer required to thicken the same
oil to the same viscosity at the same temperature. T.E. is related to (M
n) and is a convenient, useful measurement for the formulation of lubricating oils
of various grades.
[0033] The oil having attached grafted carboxyl, e.g. maleic anhydride, groups when reacted
with the polyfunctional derivatives, e.g. polyamine, is also converted to the corresponding
derivatives.
[0034] The imidization reaction product contains in the range of 0.001 to 8, preferably
0.01 to 2, wt. % nitrogen and/or oxygen and ha a M
n in the range of 700 to 500,000, preferably 700 to 250,000.
Amide Reaction
[0035] The imidization reaction product is readily reacted with the organic acid anhydride
to achieve amidation of the imidized grafted ethylene copolymer.
[0036] Suitable organic acid anhydrides include both (a) the anhydride of a monocarboxylic
acid represented by the structure
wherein R is selected from an alkyl, substituted alkyl, cycloalkyl, substituted cycloalkyl,
alkenyl, substituted alkenyl, aryl, substituted aryl or heterocyclic radical and a
substituted heterocyclic radical and can contain from one to 30 carbon atoms; and
(b) the anhydride of a dicarboxylic acid represented by the structure
wherein Z is selected from alkylene, arylene and alkenylene and contains from 2 to
10 carbon atoms.
[0037] For the anhydrides of the monocarboxylic acids, the anhydrides of the following acids
are representative.
(a) Aliphatic monocarboxylic acids
(i) Where R is an alkyl or substituted alkyl radical, i.e. acetic acid, fluoroacetic
acid, propionic acid, beta-chloropropionic acid, butyric acid, isobutyric acid, nitroisobutyric
acid, valeric acid, isovalericacid, hexanoic acid, heptanoic acid, 2-ethylhexanoic
acid, nonanoic acid, decanoic acid, dodecanoic acid, undecanoic acid, tetradecanoic
acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, eicosanoic acid, docosanic
acid and tri- acontanoic acid.
(ii) Where R is an alkenyl or substituted alkenyl radical, i.e. butenic acid, pentenic
acid, hexenic acid, teracrylic acid, hypogeic acid, oleic acid, elaidic acid, linoleic
acid, alpha-eleostearic acid, beta-eleostearic acid, alpha-linolenic acid,acrylic
acid, beta-chloroacrylic acid, methacrylic acid,crotonic acid, isocrotonic acid, 3-butenoic
acid, angelic acid, senecioic acid, hydrosorbic acid, sorbic acid and 4-tetradecenoic
acid.
(b) Alicyclic monocarboxylic acids.
[0038] Cychopropanecarboxylic acid, cyclopentane-carboxylic acid, cyclohexanoic acid, hydrocapric
acid, chaulmoogric acid, naphthenic acid, 2,3,4,5-tetrahydrobenzoic acid and cyclodecanecarboxylic
acid.
[0039] (c) Aromatic monocarboxylic acids.
[0040] Benzoic acid, 1-naphthoic acid, 2-naphthoic acid, o-toluic acid, m-toluic acid, p-toluic
acid, o-chlorobenzoic acid,m-chlorobenzoic acid, p-chlorobenzoic acid, 2,3-di- bromobenzoic
acid, 3,4-dichlorobenzoic acid, o-nitrobenzoic acid, m-nitrobenzoic acid, p-nitrobenzoic
acid, 2,3-dinitrobenzoic acid, salicylic acid, m-hydroxybenzoic acid, p-hydroGenzoic
acid, gallic acid, anisic acid, phenylacetic acid and beta-phenylpropionic acid.
[0041] (d) Heterocyclic monocarboxylic acids.
[0042] Picolinic acid, nicotinic acid, furylacrylic acid, piperic acid, indoxylic acid,
3-indoleacetic acid, cinchoni- nic acid, furoic acid, 2-thiophenecarboxylic acid,
2-pyrrolecarboxylic acid, 9-acridancarboxylic acid, quinaldic acid, pyrazionic acid
and antipyric acid.
[0043] For the anhydrides of the dicarboxylic acids the anhydrides of the following acids
are representative.
(a) Aliphatic dicarboxylic acids.
(i) Where Z is an alkylene radical, e.g. succinic acid and glutaric acid.
(ii) Where Z is ar. alkenylene radical, i.e. maleic acid, fumaric acid, glutaconic
acid, citraconicacid and itaconic acid.
(b) Aromatic dicarboxylic acids, e.g. phthalic acid.
[0044] The amidation of the imide grafted ethylene copolymer, which imidization reaction
was preferentially carried.out in a mineral oil solution, can be preferentially conducted
as a continuation of the imidization reaction by subsequently injecting the organic
acid anhydride directly into the system. If desired, amidation can be a separate non-integrated
reaction step. A sufficient amount of the organic acid anhydride is introduced into
the heated solution containing the imidized grafted ethylene copolymer and the reaction
carried on for a period of 0.25 to 8 hours at a temperature ranging from 50 to 250°C.,
a temperature of about 100 to 200°C. being preferred. In order to fully complete the
reaction, it is useful to utilize a slight excess, i.e. 1 to 30, more usually about
1 to 10, percent by weight of the injected anhydride. The entire reaction is carried
out under an inert atmosphere, for example, a nitrogen blanket and the organic acid
byproduct removed from the system by sparging or other means in order to complete
the reaction. With a low boiling acid, e.g. acetic acid, this is accomplished by nitrogen
sparging.
[0045] The amidation process step is preferentially conducted on an imidized graft ethylene
copolymeric mineral oil solution wherein the excess poly(primary amine) e.g. alkylene
polyamine is reduced to a level of less than about 0.05, optimally less than about
0.02, weight percent free (unreacted) amine.
[0046] The amidation reaction can be monitored by differential infrared analysis of the
reaction medium. Differential infrared analysis involves absorption comparison of
a sample of the starting material placed in the reference beam with a test sample
placed in the sample beam using matched cells. It has been found that amidation results
in the development of maximum absorption at an amide band of 1630-1670 whereas the
acid absorption band of between 1720 and 1740
cm-
1 first increases and then decreases as the reaction is completed since the excess
anhydride and acid byproducts responsible for acid absorption are depleted through
remova The best method of monitoring completion of the amidation of the imide grafted
ethylene copolymer is to continue the reaction until absorption at the 1650-1670 cm
-1 band is at a maximum.
[0047] Illustrative of such differential I.R. monitoring of the reaction is the following
Table I which shows the varying levels of absorption for the amide and acid bands
during amidation with acetic acid anhydride.
Haze-Treating Step
[0048] The mineral oil additive composition containing the ethylene copolymer dispersant
additives usually contain from about .1 to about 50 wt. % based upon the total weight
of the hydrocarbon solution of the amidated-imidated, graft ethylene copolymer additive.
In some instances, these oil additive compositions are found to be hazy because they
contain a hazing material derived from homopolymerization of the grafted moieties
and/or low molecular weight polar species insoluble in oil. It is therefore useful
to treat the composition by adding at least a haze-removing amount of an oil-soluble
acid having a.pK of less than.-about 2.5, e.g. a dialkylbenzene sulfonic acid.
[0049] It has been found useful to carry out the haze removing process by treating said
copolymer containing oil composition with said organic acid in an. amount within the
range of from about 0.1 to about 2.5 molar equivalents of oil-soluble organic acid
per molar equivalent of haze material. Preferably said acid is added in an amount
of 1 equivalent per equivalent of haze. A molar equivalent of haze material is measured
by reference to the total molar amount of polyfunctional material which reacts with
said grafted copolymer, e.g. one mole of said material equals one molar equivalent
of haze material.
[0050] The treatment of the haze-containing oil composition is carried out at a temperature
of about room temperature to about 250°C., preferably from about 150 to about 200°C.
and for a time period of about 0.1 hour up to about 20 hours, preferably from 0.5
to about 3 hours. The oil-soluble acid preferably has a pK of from about 0.001 to
about 2.5,optimally from about 0.1 to about 2. The term pK for the purpose of this
disclosure is used herein to express the extent of the dissociation of the acid used
to treat the haze causing substance. Thus, pK can be defined as the negative logarithm
to the base 10 of the equilibrium constant for the dissociation of the oil-soluble
strong acid.
[0051] Useful acids which eliminate the hazing property of the hazing substance are represented
by oil-soluble derivatives of alkyl carboxylic acids, such as isostearic acid, maleic
acid, malonic acid, phosphoric acid, thiophosphoric acids, phosphonic acid, thiophosphonic
acids, phosphinic acid, thiophosphinic acids, sulfonic acid, sulfuric acid, sulfinic
acid and alpha-substituted halo- or nitro- or nitrilo-carboxylic acids wherein the
oil solubilizing group or groups are hydrocarbyl and containing from about 3 to about
70, preferably from about 18 to 40, optimally 25 to 32 carbon atoms.
[0052] Particularly preferred for use in this invention for treating the hazing substance
are the oil-soluble sulfonic acids which are typically alkaryl sulfonic acids. These
alkylaryl sulfonic acids generally have from 9 to 76, preferably 24 to 46, total carbons.
The alkyl substituent or substituents preferably have 18 to 40, optimally 24 to 32,
total carbons.
[0053] Especially preferred alkyl mono-aryl sulfonic acids are those acids that are formed
by alkylating benzene with oligomers of propylene or C
4-C
10 1-alkenes containing 20 to 40 carbon atoms and thereafter sulfonating the resulting
alkylate. The class of compounds may thus be identified as the polyalkyl benzene sulfonic
acids. An especially preferred compound is the octacosyl benzene sulfonic acid wherein
the alkyl radical is derived from a nominal 28 carbon propylene oligomer.
[0054] A wide range, e.g. 0.001 to 50 wt. %, preferably 0.005 to 20%, of the oil-soluble
nitrogen and/or oxygen containing graft polymers treated in accordance with this invention
can be incorporated into about a major amount of an oleaginous material, such as a
lubricating oil or hydrocarbon fuel. When used in lubricating oil compositions, e.g.,
automotive or diesel crankcase lubricating oil, the treated polymer concentrations
are within the range of about 0.01 to 20 wt. %, e.g., 0.1 to 15.0 wt. %, preferably
0.25 to 10.0 wt. %, of the total composition. The lubricating oils to which the products
of this invention can be added include not only hydrocarbon oil derived from petro
leum, but also include synthetic lubricating oils such as esters of dibasic acids
and complex esters made by esterification of monobasic acids, polyglycols, dibasic
acids and alcohols.
[0055] The amidated-imidaced graft polymers of the invention may be utilized in a concentrate
form, e.g., from about 10 wt. % to about 50 wt. %, preferably 15 to 49 wt. % in oil,
e.g., mineral lubricating oil, for ease of handling.
[0056] The above concentrates and lubricating oil compositions may contain other conventional
additives, such as dyes, pour point depressants, antiwear agents, antioxidants, other
viscosity-index improvers, dispersants and the like.
[0057] In the following examples, as elsewhere in this specification, all parts are by weight
unless specifically indicated otherwise; all nitrogen analyses were determined by
the Kjeldahl Method.
EXAMPLE 1
PREPARATION OF IMIDE GRAFT ETHYLENE COPOLYMERS
[0058] 5314 kilograms of a 20.2 wt. % solution of an ethylene-propylene copolymer concentrats
Ziegler-Natta process using H
2 moderated VOCl
3/aluminum sesquichloride catalyst having a crystallinity less than 25%; containing
about 45 wt. % ethylene and 55 wt. % propylene; and having a T.E. of 1.4 (H
n = 27,000) in S130H (Solver 130 Neutral Mineral Oil) was heated to 250°F. under N
2 sparge and stirring, taking 1 hour and 5 min. Under N
2 blanket 31 kilograms of maleic anhydride were added over 10 minutes. The solution
was heated to 310°F. during a period of 2 hours and 15 minutes; 6 kilograms of Lupersol
130 (2,5-dimethyl hex-3-yne-2,5-bis-tertiary butyl peroxide) was added in three equal
charges over a 2 hour and 50 min. period. Excess maleic anhydride was stripped out
with N
2 over 2 hours and 20 minutes. 20 kg of diethylene triamine (DETA) was charged and
allowed to react for 1.5 hrs. Excess DETA was stripped with vacuum and N
2 for 6 hours. The resulting material was diluted with S130N to 14 wt. % polymer and
cooled. The final material had about 0.262 wt. % DETA incorporated.
EXAMPLE 2
PREPARATION OF ACYLAMIDATE OF
MALEIMIDE GRAFT OF ETHYLENE COPOLYMER
[0059] 2528 grams (0.065 moles of DETA) of the product of Example 1 was heated to 120°C.
under a nitrogen sparge. To this heated solution, 16.9 grams (0.669 wt. %, 0.166 moles,
an excess) of acetic anhydride was slowly added over a period of 30 minutes with stirring.
The mixture is allowe to soak at a temperature of about 120°C. under the nitrogen
blanket for 1.5 hours after which the reaction byproducts including the acetic anhydride
were sparged off for two hours at a temperature of 120°C. with nitrogen. The resulting
product shows under differential I.R. a substantial absorption peak at 1650 cm
-1 and a lack of acetic acid, since there is substantially no absorption at 1720 cm
-1. The resulting copolymer solution had a color of 5 with a haze reading of 108 nephelos
(unchanged from the starting material); as measured on a naphelometer purchased from
Kohlmann Industries, Maywood, Ill. and identified as Model 9. This material had a
viscosity of 1543 centistokes at 210°F., active ingredient of 15.42 wt. % by dialysis,
N wt. % of 0.12% (0.49 wt. % N on polymer), flash point of 420°F. and T.E. of 1.43.
On blends with a test oil of 6.2 cs, 9.5 wt. % gave a 12.8 cs. 210°F. viscosity, 13%
sonic shear breakdown, a pour-point (with 0.4 wt. % of a vinyl acetate/ fumarate pour
depressant) of less than -35°C., and a 0°F. viscosity of 25.3 poise in a Cold Cranking
Simulator (ASTM method).
EXAMPLE 3
[0060] 68.1 Kg of 20% by weight of 1.4 T.E. ethylene-propylene rubber in S130N were added
to a 200 liter kettle. Under N
2 blanket this was heated to 121°C. It was sparged for 1 hour. 0.413 Kg of maleic anhydride
were added and the solution heated to 154°C. under N
2 blanket. Then 0.086 Kg of Lupersol 130 was added over 1-1/2 hours in 3 equal amounts.
The reaction continued 30 minutes. The mixture was then N
2 stripped to eliminate free maleic anhydride for 1-1/2 hours. Then 0.27 Kg of DETA
were added and reacted for 1 hour. The solution was stripped for 1 hour with N
2 and 84 kilopascals of vacuum. 0.34 Kg of acetic anhydride were charged, reacted for
1 hour and the mixture stripped for 3 hours with N
2 and vacuum. The material was then diluted to 14 wt. % with S130N. The final product
had the following characteristics:
EXAMPLE 4
[0061] 300 grams of Example 1 product was charged into a 4-necked 1 liter flask and heated
to 125°C. while stirring and N
2 blanketing. 1 gram of acetic anhydride was added and reacted for.1 hour. The mixture
was stripped for 1 hour at 125°C. The temperature was then raised to 170°C. and 3
grams of C
24 ave. alkylbenzene sulfonic acid were added. Reaction continued for 4 hours. The haze
was reduced from 108 (initial) to 16 nephelos.
ExAMPLE 5
ACETIC ACID SALT OF MALEIMIDE OF GRAFT ETHYLENE COPOLYMER
[0062] 3000 grams (.077 moles of DETA) of the product of Example 1 were charged to a flask
and heated to 118°C. with N
2 sparge. 10 grams (0.167 moles, an excess) of glacial acetic acid were injected. The
resulting admixture was reacted at 118°C. with stirring and under a nitrogen blanket
and maintained at 118°C. for about 1 hour. The solution was then heated to 155°C.
and maintained there for 2 hours with nitrogen blanket. The mixture was then. sparged
at 155°C. for two hours. The differential IR showed presence of acetic acid during
reaction, which was almost completely lost after sparging. Storage stability tests
showed no improvement in stability over the starting, material. Thus, there is no
significant amidation when the acid itself is used rather than the anhydride. Literature
information indicates that excessive heat and pressure (if the acid is volatile) is
necessary to convert the acid salt to the amide.
EXAMPLE-6
[0063] Acid anhydrides are known not to react with tertiary amines. However, they may react
with secondary amines. From the stoichiometry of the reaction of acetic anhydride
with an imide made from DETA, as derived from their amide measurements, only the primary
amine, not the secondary amine, reacts in this case.
EXAMPLE 7
[0064] The utility of the inventive additives were measured by subjecting the products of
Examples 1 and 2 to a standard engine test of blended formulations containing these
additives. A 15W50 SAE crankcase oil formulation was made up using 12.5 wt. % of the
oil concentrate of Example 2, 2 volume % of an ashless dispersant additive, 1.1 volume
% of an overbased magnesium sulfonate, 0.8 volume % of overbased calcium phenate,
0.5 volume % of an antioxidant, and 1.43 volume % of a zinc dialkyldithiophosphate
and a mineral lubricating oil blend of base stocks. For comparison purposes, a formulation
was made up in the same manner replac- inc the oil concentrate of Example 2 with the
same weight percent of the oil concentrate of Example 1. The above formulations were
tested in the Sequence V-C Engine Test, which is described in "Multicylinder Test
Sequences for Evaluating Automotive Engine 0,ils," ASTM Special Technical Publication
315F, page 133ff (1973). The V-C Test evaluates the ability of an oil to keep sludge
in suspension and prevent the deposition of varnish deposits on pistons, valves, and
other engine parts. The test results given below shew that the two blends are not
statistically different in performance.
In the above tests, the ratings are on a scale of 0 to 10, with 0 being an excessive
amount of sludge and varnish while 10 being a completely clean engine.
EXAMPLE 8
[0065] In order to show the surprising viscosity stability provided to the maleimide amide
graft products of ethylene copolymeric V.I. improvers provided according to the teachings
of this invention, the resulting products Examples 1, 2 and 5 were subjected to a
test whereby the change in viscosity of the products were measured over a period of
two hours while maintaining the solutions at 99°C. The results are as follows in Table
III.
The above results show that there is a surprising enhancement of the viscosity stabilization
activity of solutions of polymer in oil when the products of the invention are used.
This two-hour test has been found to correlate with the long-term storage stability
results when the solutions containing polymer are stored at temperatures of about
180°F. for periods of up to two months.
1. An ethylene polymeric viscosity index improver having dispersancy properties and
containing in the range of from about 0.001 to 8 wt. % of nitrogen, which improver
has been formed by grafting an ethylene copolymer comprising about 30 to 80 wt. %
ethylene and about 20 to 70 wt. % C3 to C28 alpha olefir:, with an ethyleniently unsaturated acid material selected from the
group consisting of unsaturated carboxylic acids and anhydrides of carboxylic acid,
reacting said grafted ethylene copolymer with polyamine of 2 to 60 carbons and 2 to
12 nitrogens and having at least two primary amine groups, wherein essentially one
of said primary amime groups reacts with an acid moiety of said grafted ethylene copolymer,
and reacting with an anhydride of an acid having a Cl to C30 hydrocarbyl group to thereby stabilize the resulting ethylene polymeric viscosity
index improver.
2. A viscosity index improver according to claim 1, which is an ethylene-propylene
copolymer having a number average molecular weight from about 700 to 500,000 which
is grafted with maleic anhydride, reacted with said polyamine, and then reacted with
acetic anhydride.
3. A process for preparing a polymeric viscosity index improver which comprises solution
grafting an ethylenically unsaturated dicarboxylic acid material onto a copolymer
comprised of ethylene and at least one C3-C18 alpha-olefin at a temperature of from about 100°C. to about 250°C., in the presence
of a high-temperature decomposable free-radical initiator having a boiling point in
excess of about 100°C., which grafted polymer is then derivatized by reaction with
an alkylene polyamine having from 3 to 20 total carbons and about 2 to 6 nitrogen
atoms to provide a product having sludge dispersant activity and thereafter reacted
with from about 0.5 to 2.5 moles of an anhydride of an acid having a C1 to C30 hydrocarbyl group per primary amino group in said product.
4. A process according to claim 3 wherein said copolymer is of ethylene.and propylene
having from about 38 to 70 wt. % of ethylene, said dicarboxylic acid material is maleic
acid anhydride, said solution grafting is carried out under an inert environment using
a mineral lubricating oil as solvent, said polyamine is diethylene triamine and said
0.5 to 2.5 moles of anhydride is of acetic anhydride.
5. The process according to claims 3 or 4 wherein the resulting solution from said
reaction with said 0.5 to 2.5 moles of anhydride is treated with an oil-soluble alkyl
aryl sulfanic acid containing from about 9 to 76 carbon atoms.
6. The process according to claim 5 wherein said sulfonic acid is C24 (average) alkylbenzene sulfonic acid..
7. A lubricating oil composition comprising a major amount of a lubricating oil having
dissolved therein at least a viscosity index-improving amount of an oil-soluble ethylene
polymeric viscosity index improver having dispersancy properties and containing in
the range of from about 0.001 to 8 wt. % of nitrogen, which improver has been formed
by grafting an ethylene copolymer comprising about 30 to 80 wt. % ethylene and about
20 to 70 wt. % C3 to C28,alpha-olefin, with an ethylenically-unsaturated acid material selected from
the group consisting of unsaturated carboxylic acids and anhydrides of carboxylic
acid, reacting said grafted ethylene copolymer with polyamine of 2 to 60 carbons and
2 to 12 nitrogens and having at least two primary amine groups, wherein essentially
one of said primary amine groups reacts with an acid moiety of said grafted ethylene
copolymer, and reacting with an anhydride of an acid having a Cl to C30 hydrocarbyl group to thereby stabilize the resulting ethylene polymeric viscosity
index improver and inhibit viscosity increase of said oil composition upon aging.
8. A composition according to claim 7 wherein said viscosity index improver is present
in an amount of from about 0.1 to 50 wt. %, based upon the total weight of said composition,
and is an ethylene-propylene copolymer having a number average molecular weight from
about 700 to 500,000 which is grafted with maleic anhydride, reacted with said polyamine,
and then reacted with acetic anhydride.
9. A composition according to claims 7 or 8 wherein said viscosity index improver
is prepared by solution grafting an ethylenically unsaturated dicarboxylic acid material
onto a copolymer comprised of ethylene and at least one C3-C18 alpha-olefin at a temperature of from about 100°C. to about 250°C., in the presence
of a high-temperature decomposable free-radical, initiator having a boiling point
in excess of about 100°C., which grafted polymer is then derivatized by reaction with
an alkylene polyamine having from 3 to 20 total carbons and about 2'to 6 nitrogen
atoms to provide a product having sludge dispersant activity and thereafter reacted
with from about 0.5 to 2.5 moles of said anhydride per primary amino group in said
product.
10. A composition according to claims 7-9 wherein said copolymer is of ethylene and
propylene having from about 38 to 70 wt. % of ethylene and is present in said composition
in an amount ranging from about 0.1 to about 15 wt. %, said dicarboxylic acid material
is maleic acid anhydride, said solution grafting is carried out under an inert environment
using a mineral lubricating oil as solvent, said polyamine is diethylene triamine
and said 0.5 to 2.5 moles of anhydride is acetic anhydride.
11. A composition according to claims 7-10 wherein the resulting solution from said
reaction with said 0.5 to 2.5 moles of anhydride is treated with an oil-soluble alkyl
aryl sulfonic acid containing from about 9 to 76 carbons to inhibit haze.
12. A composition according to claim 11 wherein said sulfonic acid is C24 (average) alkylbenzene sulfonic acid.
13. A process for improving the viscosity stability of an oil additive concentrate
consisting essentially of a hydrocarbon solvent and from .1 to 50 wt. %, based on
the total weight of said concentrate, of an imidated grafted ethylene/C3-C28 alpha-olefin copolymeric viscosity index improver having a molecular weight (Mn) of 700 to 500,000 and a Mw/Mn ratio of less than 7, said viscosity index improver having dispersancy properties
and being formed by grafting maleic anhydride onto an ethylene copolymer comprising
about 30 to 80 wt. % ethylene and about 20 to 70 wt. % of said C3-C28 alpha-olefin, followed by reartion of said maleic anhydride moieties with a polyamine
of 2 to 50 carbon atoms and 2 to 12 nitrogen atoms and having at least two primary
amine groups, wherein at least some of said plimary amine groups remain unreacted,
said process comprising the step of reacting said concentrate with a hydrocarbyl-substituted
acid anhydride having from about 2 to 30 carbons by adding said scid anhydride in
an amount to provide an excess of at least about 5% based on the primary amino concentration
in said concentrate and maintaining said concentrate at a temperature ranging from
about 50° to about 250°C. and for a period of 0.25 to 8 hours and thereafter removing
all unreacted anhydride and byproducts of said reaction while maintaining said concentrate
under an inert and water-free environment.
14. A process according to claim 13 wherein said concentrate contains less than about
0.02 wt. % unreacted alkylene polyamine, said hydrocarbyl-substituted acid anhydride
is acetic anhydride and said temperature is maintained until maximum absorption at
1650-1670 cm-1 is found by differential infrared testing to be at a maximum and said removing is
by nitrogen sparging until said absorption is at a minimum at 1650-1670 cm-1.
15. A process according.to claims 13 or 14 wherein there is a further process step
of treating said concentrate with an oil-soluble hydrocarbyl substituted strong acid
containing a hydrogen dissociating moiety which has a pK of less than about 2.5 and
containing about 10 to,70 carbon atoms.
16. A process according to claim 15 wherein said strong acid is a dialkyl substituted
benzene sulfonic acid present in an amount ranging from about 0.1 to 2.5 molar equivalents
per molar equivalent of nitrogen material introduced onto said graft copolymeric viscosity
index improver and said treating is at a temperature ranging from 20°C. to 250°C.
for a period rang. ing from 0.1 to 20 hours.