CA1087343A - Hydrogenated copolymers of conjugated dienes and when desired a vinyl aromatic monomer are useful as oil additives - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A hydrogenated copolymer produced by copolymerization of from about 1 to about 10 mol. percent butadiene and at least one other C5 to C12 conjugated diene, and, if desired, in order to provide a block copolymer, up to 45 mol.
percent of a vinyl aromatic monomer, upon addition to lubricating oils containing a pour point depressing amount of an oil-soluble polymeric pour depressant, pro-vides viscosity modification, oxidative and shear stability with excellent low temperature viscometric properties.

Description

BACK~ROUND OF THE INVENTION -

2 Field of the Invention

3 This invention relates to polymeric oil additives

4 and to lubricating oil compositions containing these addi-tives. More particularly, the present invention relates to 6 hydrogenated, block copolymers of butadiene and another con-7 3ugated diene and, if desired, a v~nyl aromatic monomer, and 8 their addition to lubricating oil com~ositions containing 9 pour depressants with minimal *ffhcc on the pour point of said compositions.
- ll Description of the Prior Art 12 Various copolymers of butadiene with other olefins i 13 are known as oil additives. Thus, U.S. Patent No. 3,419,365 .
14 teaches hydrogenated copolymers ~f butadiene and styrene as pour point depressants for distillate fuel oil. Similarly, 16 U.S. Patent No. 3,393,057 teaches ccpolymers of butadiene, 17 Clo to C24 normal alpha-monoolefins and styrene or indene 18 as pour point depressants for fuel and lubricating oils.
19 U.S . Patent 3,635,685 discloses pour point depressants com-prising hydrogenated butad~ene-styrene copolymers which 21 contain a hydroxy, carboxyj or pyridyl terminal group.
22 U.S. Patent No. 3,312,621 discloses copolymers of 23 various coniugated diolefins, including butadiene and iso-24 prene which are predominantly in the 1,4-addition configura-tion as viscosity index (V.I.) improvers for lubricating 26 oils.
27 Other styrene-diene copolymers have been reported 28 for possible use in lubricants, including U.S. Patent 29 3,772,196 which shows lubricating oil compositions for ~ internal combustion engines containing a combination of 31 block copolymers comprising a first polymer block of sn 32 alkenyl arene, e.g. styrene,and a second essentislly com-.' ~

~OB7343 ~ , .' ' ' ' .
1 piet~ly hydrogenat-ed polymer block of isoprene and certain 2 pu~r point depressants in a lubricant base stock; and, 3 U.S. Patent 3,795,615 which teaches that a hydrogenated .
4 copolymer of butadiene and isoprene may be incorporated S into mineral oil containing a polymeric pour point-~pres-6 sant to improve the viscosity index of the lubricating oil 7 blend.
8 SUMMARY OF THE INY~NTIO~ `
`9 It has been found that there is a type of copoly-mer which is highly useful as a viscosity modifier in lubri-11 cating oils contain~ng a polymer~c pour point depressant 12 since it prcvides excellent l~w temper~ture viscometric 13 performance to the blended oil while retaining the desired 14 levels of shear and cxida~ve stability. This type of ~ ~ 15 copolymer is an oil-soluble copolymer of'the ollowing 16 general fon~ula 17 - - ~ - (A)~ y~C~2 18 wherei~: ~
19 A~is a ccn~ugated diene of the formula ~ - - R
21 CH2 ~ ÇH - C 3 CH2 22 wherein R is a Cl to Cg alkyl group, preferably CH3, i.e.
23 isoprene, and present in mole % proportion as indicated by 24 ~ which may vary from 45-99 mole %;
B is butadiene and present in m~le % proportion 26 as indicated by y which may vary from 1-10, preferably 2-9, mole %; and C is a C8 to C20 moncvinyl aromatic compound and1or aromatic substltuted diene and present in weight Z
~ proportion as indicated by z which may vary from O to 45 31 mole %, preferably 5 to 40 mole %, and opt~mally 25 to 30 32 mole % whereby the mo~t u~eful composite properties o~
. .
: - 3 -. .
1 oxidat~ve ssabiLity. a~d -18C. viscosity of the lubrlcat~ng 2 oil blend is realized. . ~ .
3 Thus, this invention in its broadest form can be 4 characterized as a lubricating oil composition comprising: ~
S (a) a major amount of a mineral lubricating oil; ..
6 (b) a minor but effective amount of a polymeric 7 pour point depressant for said oil; and B (c) 0.1-30 percent by weight of a copolymer hav-9 . ing the structure (A)x(B)y(C)z ' ' ' 11 wherein: ;
12 A is a conjugated diene of the formula 13 . -~ R
14 CH2 ~ CH - C = CH2 15 wherein R ~s a Cl to C8 alkyl group, preferably CH3, opti~ :
16 mally isoprene and present in mole % proportion as indicated 17 by x which may vary from 45 to 99 mcle %;
18 B is butadiene and present in mole % proportion lq as indicated by y which may vary from 1 to 10 mole %; and C is a C8 to C20 monovinyl aromatic monomer, 21 preferably styrene, and present in mole % proportion as 22 indicated by z which may vary from 0 to 45 mole %. ~t is 23 preferred that about 75 to 95 percent of the diene monomers 24 are in the 1,4-configurat~on in the block copolymer and that substantially all of the olefinic bonds are saturated 26 as by hydrogenation.
27 In a more restricted sense, this invention is con-~ cerned with a lubricating oil composition comprising:
29 .(a) a ma~or amount of a mineral lubricating oil;
~ -(b) a minor but effective amount of an oil-31 soluble polymeric pour point depressant for ~aid oil; and 32 (c) 0.1-10 percent by weight of a hydrogenated ~087343 l block copolymer having the structure 2 (A)X(B)y(C)z 3 w~lerein:
4 A is isoprene and present in mole % proportion ~s indicated by~x which may vary from 50 to ~4 mole %:
6 B is butadiene and present in mole % proportion 7 as indicated by y which may vary from 1 to 10 mole %;
8 and 9 C is styrene and present in mole % proportion as l indicated by z which may vary from 5 to 40 mole %.
11 DETAI~ED DESC~IPTION
li A block copolymer according to this invention is l3 a copolymer obtained by anionically copolymerizing in hydro-l4 carbon solution the monomers of butadiene and at least one other conjugated diene in the presence of an alkali metal l6 or an alkali metal compound as a catalyst until at least 7 99% of the monomers have been incorporated into the copoly-18 mer and thereafter, if desired, incorporating a polymer 19 block of a monovinyl aromatic monomer. In contrast to a block copolymer, anionic copolymerization of a mixture of 21 l to 10 mole percent butadiene and from-90 to 99 mole per-22 cent of another conjugated diene (A of the formula) provides 23 a copolymer; another useful form of this invention.
24 The block copolymer differs materially from the r tapered-block copolymer disclosed in German Patent 26 Application OS2711226, which is obtained by 27 the polymeri~ation of a mixture of conjugated dienes and a 28 vinyl aromatic monomer. Since the tendency of the conju-~ gated dienes to be incorporated into the anionic copolymergreatly exceeds that of the monovinyl aromatic monomer, the , , , . - .

- 5 -' ~87343 ~s 1 composition of each tapered-block copolymer molecule formed 2 during copolymerization gradually changes from that of near- _ 3 ly pure polydienes to that of nearly pure poly-monovinyl 4 aromatic. Therefore, in these linear tapered-block copoly-S mer molecules, three longitudinal regions can be discerned

6 which gradually pass into each other and have no sharp

7 boundaries. In contrast, the block copolymers utilized in

8 this invention have a boundary which is sharp and discrete

9 between the conjugated dienes and vinyl aromatic twhen it is utilized to enhance oxidation stability of the block 11 copolymer). It is desirable for "single" block copol~ers 12 that the outer region consist of a homopolymeric block of ~ -13 units derived from C (the mon~vinyl aromatic monomer)_~nd 14 that less than a few units, e.g., no more than a~out 1 wt.
Z of A and B (conjugated dienes~ are present therein.
16 The copolymers and block copolymers of the present 17 invéntion may be conveniently prepared with known metallic 18 or organometallic catalystgsuch as lithium metal or sodium 19 metal and organo-lithium or organo-sodium catalysts. Suit-2~ able organo~lithium catalysts may be represented by the 21 formula RLi wherein R is a Cl to C20, e-g-~ C2 to C8, hydro-22 carbyl, e.g., alkyl, aralkyl or cycloalkyl group. Specific 23 examples of suitable catalysts include n-propyllithium, iso-24 propyllithium, n-butyllithium, tertiary butyllithium, etc.
with n-butyllithium being preferred, whereby 85 to 90% of 26 the diene mixture within the copolymer is in the optimal 27 1,4-microstructural configuration.
28 The solution copolymerization may be carried out ~ at any desired temperature in the range from -50C. to ~150C., and iq preferably effected at a temperature between 31 -20C. and +80C. The solvents used in polymerization are, 32 in preferred form, hydrocarbon solvents such as pentane, . - 6 -I.
.- .

~ o87343 hexane, heptane, cyclohexane, benzene, toluene, xylene and 2 ethyl benzene, with benzene and hexane being the preferred 3 species.
~ The polymerization can be carried out under any p~essure, but since it is desirable to maintain the monomers 6 and the solvent substantially in the liquid phase, the pres-7 æure applied is preferably at least sufficient to keep the 8 nonomers and the solvent in the liquid state. The pressure -9 to be applied thus will depend on the temperature of the copolymerization and on the types of monomers and solvent 11 components used. If desired, higher pressures can be used, 12 for instance by pressurizing with an inert gas, such as 13 nitrogen.
14 The molecular weight of the hydrogenated copolymers of the mixed conjugated dienes and, if desired, 16 the monov~nyl aromatic ccmpound which after hydrogenation 17 are to be used as eomponents of the lubricant ccmpositions 18 according to the invention may vary between wide limits, - 19 for instanee between 2,000 and 500,000, preferably between j~
20 lO,000 and 150,000. These are expressed as number average ~
21 molecular weights, determined by membrane osmometry(for ~ r 22 Mn above 5000) or vapor pressure osmometry (for ~fn below ~!:
23 5000) methods. .¦
24 The Mn is regulated by the ratio of the number of moles of catalyst (e.g., butyllithium) to the number of 26 moles of monomers present during polymerization; the number ~ 27 of units originating from the monomers in a polymer molecule I ~ is substantially equal to the ratio of the number of moles 29 of monomer to the namber of moles of catalyst (assuming that each catalyst molecule contains one alkali metal atom) 31 present during polymerization, provided that no contaminants 32 which give rise to side reactions with the catalyst (such as ~ 7343 l oxygen, water, carbon dioxide) are present. If single 2 bl~ck copolymers are coupled together, the multiple block 3 copolymers formed have molecular weights which can be cal-4 culated from the molecular weight of the single block copoly-S ~ers (determined as abo~e) and the number thereof which are 6 coupled together.
7 When the copolymerization has been completed, the 8 biock copolymer thus obtained can be hydrogenated either 9 immediately or sfter recovery to obtain the desired hydro~
genated block copolymers according to the invention.
ll Methods of hydrogenation well known to one skilled l2 in the art are applicable. For example, any material func-13 tioning as ~n clefin hydrogenation catalyst can be used l4 to incorporAte hydrogen into the olef~nic bonds; suitable lS catalysts include Raney nickel, platinum oxide, platinum on l6 alumina, palladium on charcoal, copper chromate, nickel sup-17 ported on kleselguhr, etc.
l8 Hydrcgenation should be carried out until at least 19 90%, preferably 95%,of the olefinic double bonds but not 2~ more than 5% of the aromatic unsaturat~n has been satura~d.
21 After bringing the c~polymerization to an end, the 22 copolymer can be recovered in any desired way, for instance 23 by precipitation which can be effected by addition of rela-24 tively large ~mounts cf non-solvents for the copolymer such 2s as an alcohol, e.g., methanol, ethanol or isopropanol. Re-26 covery is not generally useful since the copolymer of the 27 invention is most likely utilized as an oil additive where-in the copolymer is formulated into the hydrocarbon lubri-cating oil as an oil concentrate of said copolymer obtained ~ indirectly from said hydrogenation step, e.g., by dilution 31 with oil followed by evaporation of the low boiling hydro-32 carbon solvent.
., . ~ .
1~87343 1 The block copolymer as used herein includes 2 ~u~tiple block copolymers" which term denotes copolymers 3 consisting of two or more of the single block copolymers 4 described above~ whi~h are bound to each other. A multiple s - block ccpolymer m~y, for example, be prepared by first 6 copolymerizing to completion a mixture of butadiene and 7 isoprene, thereafter polymer~zing styrene onto said copoly-8 mer and subsequently sequentially copolymerizing a mixture 9 of butadiene and isoprene foll~wed by said styrene onto the "living" block copolymer. For purposes of this disclo-ll sure, a "living" copolymer is one which remains stable over 12 an extended period of t~me dur~ng which additional monomers 13 can be add~to it.
14 Multiple bloek copolymers can also bQ obtained in lS other ways su¢h as by coupling of two or more "living"
16 block copolymer molecules. This can be achieved by addition 17 o~ a compound whioh reacts with two or more "living" single .r 18 block copclymer molecules. Examples cf this type of com-19 pound inelude compc~nds containing two or more ester groups, 2~ cGmpounds with more than one active halogen atom, e.g., di-21 and triehloromsthyl-benzene, ~ph~g~ne, dichlorGsilane, car- ;~
22 bon tetrachlor~de, d~methyldichlorssilane, 19 2-dichloro-23 ethane9 1,2Odibromomethane, and the like. Another possible 24 method for preparing multiple block copolymers consists in the preparation of sing1e blcck copolymer containing a reac-26 ti~e group in the molecule (e.g., a carboxyl group, which 27 i8, for example, obtained by bringing the pclymerization of 28 a single copolymer to an end by addition of carbon dioxide) 29 and coupling cf two cr more of the molecules, e.g., by ester-ifying them with a di- cr pclyvalent alcohol. Multiple 3l block copolymers h~e the further advantage that they can 32 be tailored to prcv~de the most useful additive properties _ g _ , , . 1~7343 1 wh~le ma~king one..or m~re undesirable properties lnherent 2 i~ any polymer block.
3 PolYmerie Pour Pcint Depres~nts 4 Many subs~ances are known for their.pour point ;:
S depressant activity in lubricating oils. The activity of ¦ -6 these substances, hcwever, can be decreased by the adverse ¦-7 influence of the polymeric V.I. improver. Oftentimes then ~.
8 the compounded lubricating oil ~epresents a compromise of 9 the chemical and physlcal properties so as to have suitable ...

10 operational charaeteristies. This comprises features which

11 are quite ch~rac~eris~ic of multi~grade lubricating oils.

12 It has been discovered that the hydrogenated COPOD ~

13 lymers including the block eopolymers of the lnvention can ,:
1~ prcvide multi~fqlnctional V.I. impr~ement ln lubricating 15 olls blended wi~h polymeric pcur depress~nts without dele~
16 terious effect on the pour poin~ of said blended lubricating 17 oils. , r 18 Oil-soluble po~ymeric pcur depressants for lubri- ~:
19 .cating oils h~ve been widely disclcsed in the art9 e.g.:
20 U.S. 2,3799728 sh&ws o~efin polymers5 U.S. 2,460,035 shows 21 polyf-~arat2s; U.S. 29936,300 shows eopolymers of dialkyl 22 fumarate and vinyl ace~ate, and, U.S. 2,542,.542 shows copoly- :
23 mers of olefins and maleie anhydride esterified with a long 24 chain alcohol-25 Illustrative pour point depressan~s also include 26 copolymPrs of alpha~clefins and terpolymers of alpha-olefins 27 and styrene and/or alkyl styrenes. Thcse polymeric pour 28 ~epressants preferably used in accordance with this inven-~ tion ~re the alkyl aromatic compounds, ester base polymers 30 and ester~imides of copolymers of styrene and m$leic anhy-31 dride.
. , , The Long Chain Alkyl Aromatic Condensation Materials These materials are usually made by the Friedel-Crafts con-densation of a halogenated paraffin or an olefin with an aromatic hy-drocarbon. They are well known in the art, primarily as lube oil pour depressants and as dewaxing aids as previously mentioned. Usu-ally, the halogenated paraffin will contain from about 15 to about 60, e.g. 16 to about 50 carbons, and from about 5 to about 25 wt. %, e.g.
10 to 18 wt. %, chlorine. Typically, the halogenated paraffins are prepared by chlorinating to the above recited chlorine content a par-affin wax having a melting point within the range of about 38 to 94C.
The aromatic hydrocarbon used usually contains a maximum of three sub-stituent groups and/or condensed rings. It may be a hydroxy compound such as phenol, cresol, xylenol, or an amine such as aniline, but is preferably naphthalene, phenanthrene or anthracene. These long chain alkyl-aromatic hydrocarbon, usually alkylated naphthalene, condensa-tion products and their preparation are fully described in U.S. Pat-ents 1,815,022; 1,963,917; 1,963,918; 2,062,354; 2,087,682; and 2,174,246.
Ester Base Polymers ,,! 20 Usually these oil-soluble ester base polymers will have molecular weights in the range of 5,000 to 1,000,000, preferably 10,000 to 500,000 and most preferably 15,000 to 200,000 number average molecular weight (Mn). These ester base polymers are derived essen-tially, e.g. 80 wt. % or more of the total polymer, from C8 to C20, preferably C12 to C18, alkyl esters of a C3 to C8, preferably C3 to C5 mono- or dicarboxylic, monoethylenically unsaturated acid. Poly-mers of this ester type are well known in the art and are usually made by free radical initiation, e.g., a .

. .
' . ~ . .: ' . ' ,., . ' ' . ' . ' ~ ' ,, , ' ' ' . ;,; . .

: : ., .. . ~ . ., . :

1087;~43 . :~
. . , l peroxide, in a solvent.
2 Such esters from which the polymer is essentialLy 3 derived include: alkyl acrylate; alkyl methacryLate; dial-4 kyl fumarate; and dialkyl itaconate.
The most common of these oil-soluble esters are 6 polymers of acrylic esters represented by the formula 8 , CH2 - C ^ COOR' q wherein R represents hydrogen or methyl and R' represents an alkyl group of 8 to 24 carbon atoms. The alkyl group may be ll essentially straight chain and preferably contains 12 tQ 18 12 carbon atoms although methyl and ethyl branching can be 13 tolerated. The term "acrylic ester" in this invention in-

14 cludes both acrylates and methaerylates~ Mixtures of both alkyl acrylates and alkyl methacrylates may be used as well 16 as their partial esters.
17 Lower alkyl acrylic esters, here meaning esters 18 having alkyl groups smaller than 8 carbon atoms and derived 19 from acrylic or methacrylic acid, i.e. methyl, ethyl, pro-2~ pyl, butyl, amyl, and hexyl acrylates and methacrylates may 21 be employed in amounts ranging from O to 25 mole % with 22 said C8_24 alkyl esters.
23 In addition to the one or more of the above vinyl 24 mono- and dicarboxylic esters and the aforementioned lower alkyl acrylic esters, there may be used to form the backbone, 26 in minor amounts, one or more other miscellaneous free radi-27 cal polymerizable, monoethylenically unsaturated compounds, 28 particularly monovinylidene compounds, such as vinyl esters 29 as vinyL acetate, styrene and alkyl styrenes, vinyl alkyl ethers - which are represented by vinyl butyl ethe-, vinyl 3l dodecyl ether and vinyl octadecyl ether.

1~)87343 . .

1 In addition, nitrogen-containlng monomers can be 2 polymerized with the foregoing monomers, said nitrogen-3 containing monomers include those represented by the formula: ..4 R - C ~ C - H .
5 Rl R2 ~.
` 6 wherein Rl and.R2 can be hydrogen and/or alkyl radicals and 7 R is a 5- or 6-membered heterocyclic nitrogen-conta~ning B ring and whlch ccntains one or more substituent hydrocarbon ... 9 groups. In the above formula, the vinyl radlcal can be :~ lO attached to the nit~ogen or to a carbon atom in the radical , ,.
ll R. Examples of s~ch vinyl derivati~es include 2-vinyLpyri- `
: 12 dine, 4~vinylpyridine, 2-methyl-5-vinylpyridine, 2-ethyl- .-13 5-vinylpyridine, 4-methyl-5-~inylpyrid~ne, N~vinylpyrroli- l.
14 dcne, 4-vinylpyrrolidone, and the like. .
.. lS The n-alkyl methacrylates are typified by those t6 set forth in U.S. Patent 2,7109842.... Copolymers of di-n- .
.~ 17 alkyl fumarate and vinyl acetate are typified by those.set : 18 forth in U.S. Patent 3,048,479.
19 Ester-Imides of CopolYmers of Styrene and Maleic Anhydride ~
I ~ This class of useful po~r point depressants for ~:
, . -`~
21 lubricating oils are the oil-soluble reaction products of 22 copolymers fcrmed cf substantially equimolar portions of j~
I . 23 maleic anhydride and styrene alone or in admixture with an .i.
.l 24 alpha-olefin such 8S ethylene, propylene, isobutylene, ¦~
etc. These copolymers should have a number average molecu-26 lar weight in the range of about 500 to about 150,000 and 27 can readily be produced according to the teachings of U.S.
~ Patent 2,615,845.
29 - The carboxyl groups of the copolymer must be ester- -ified with at le~st a suffi¢ient amount to provide oil 801u- `
3l bility, preferably st least abcut 30% but not more than 32 about 95%, of aliphatic alcohol or mixture of alcohols having from about 2 to 26 carbon atoms. Examples of alcohols suitable for use in producing the esters include straight chain normal primary alcohols such as ethyl, propyl, butyl, hexyl, octyl, lauryl octadecyl, eicosyl, docosyl, tricosyl, tetracosyl, pentacosyl, hexacosyl, etc.
Commercially marketed mixtures of alcohols consisting essen-tially of saturated alcohols of the requisite chain length may be em-ployed in preparing the long chain esters. One such mixture is mar-keted under the trade name Behenyl alcohol and is a mixture of alco-hols derived from natural sources and consists primarily of docosyl and alcohols containing from 16 to 24 carbon atoms per molecule.
The balance of the carboxyl groups are reacted with an al-kylamine, preferably a diamine compound of the formula Rl R4 N-R -N ~
R2 ~ ~ H

where Rl and R2 are selected from the group consisting of allphatic hydrocarbon radicals having from 1 to 4 carbon atoms and the cyclo-- hexyl radical, R3 is an aliphatic hydrocarbon radical having from 2 to 4 carbon atoms, and R4 is selected from the class consisting of the hy-2~ drogen atom and aliphatic hydrocarbon radicals having from 1 to 4 carbon atoms. Illustrative diamines include: N,N-dimethyl-1,2-ethylenediamine; N,N-dimethyl-1,4-butylenediamine; N,N-dicyclohexyl-1,3-propylenediamine; etc.
The method of making the copolymers and the esterification-amidation or-imidation thereof using alcohol or amines is quite ade-quately broadly described in the prior art in U.S. 2,615,845 and more specifically in U.S. 3,329,658 - . . : - . . .. . .

, , , ": .
, ~ . , .
- - . .: . : . :

. .

1 ~tcd ~crcin by rcfcrcnce.
2 The copolymers of the invention can be employed 3 alone in lubricant compositions blended with the polymeric 4 pour depressants or they can be employed in combination 5 with other viscosity improvers. If desired, the copolymers 6 may be employed in combination with other additives, for 7 example ashless dispersants such as the reaction product of 8 polyisobutenyl succinic anhydride with tetraethylene penta-9 mine; detergent type additives, ~uch as barium nonyl phenol sulfide, calcium tertiaryamylphenol sulfide, calcium phenol 11 stearate, calcium petroleum sulfonate, etc. It is contem- -12 plated that the in~entive copolymers can be blended with 13 other polymers so as to impart various desired propert~es 14 thereto. `
As noted, it is a feature of this invention that 16 viscosity modification and shear and oxidative stability 17 can be imparted to a mineral lubricating oil blended with 18 a polymeric pour depressant with little or no adverse 19 effect on pour poin~ and in fact with the preferred depres-~ sants the pour point of said blend is improved.
21 The lubricating oil~s which may be particularly 22 improved by the technique of this invention include the ?3 following: -24 (a) Midcontinent having a ~15F. pour point;
(b) Midcontinent having a 0F. pour point;
26 (c) Pennsylvania having a 0F. pour point; and ~ (d) West Coast having a +15F. pour point.

.

1~87343 :~

1 EXAYPL~ 1 j 2 Into a clean, dry, polymerization vessel, under 3 a nitrogen atmosphere, was charged toluene (150 ml) and n-4 butyllithium (0.55 meq). Butadiene (1.9 g., 0.036 mole) S and isoprene (25.0 g., 0.368 mole) were simultaneously 6 added to the vessel cooled to -5C. Polymerization was 7 initiated by slowly heating the solution to 50C. The 8 solution was allowed to continue reacting for an additional 9 30 minutes whereupon there was added, at ambient tempera-ture, styrene (2.0 g., 0.029 mole) in 50 ml o toluene.
11 The resulting solution was slowly heated to 50C. and 12 allowed to continue reacting for an additional 30 minutes.
l3 -The reaction was terminated with 3 ml of methanol. The co-14 polymer was isolated by precLpitation into 2 liters of meth-anol containing 0.1 wt. % antioxidant and drying in a vacuum 16 oven at 100C. for 24 hours. mis yielded a clear block l7 copolymer (26.5 g., 88.4% of theoretical yield). This 18 copolymer had an (Mn) of 59,00O tmembrane osmometry) with l9 approximately 85% of the diene monomer units in a 1,4 con-.
figuration (determined by nuclear magnetic resonance (NMR)).

. .
22 Following the procedure of Example 1, isoprene 23 (17.7 g., 0.26 mole), butadiene (9.1 g., 0.168 mole) and 24 styrene (3.0 g.,.019 mole) were copolymerized with n-butyllithium (0.35 meq) in 250 ml toluene. An isolation 26 procedure as in Example 1 yielded a clear block terpolymer 27 (27.9 g., 93% of theoretical yield) having an (Mn) of 28 103,000 (membrane osmometry) of about 85%, 1,4-configuration.

The copolymers of Examples 1 and 2 were in turn 31 subjected to chemical hydrogenation as described in Die 32 Makromoleculare Chemie, 163 1 (1973) and Die Makromoleku-~087343 , . .' :
, ~:
1 lare ~hemie, 163, 13 (1973~. This hydrogenation is illus-2 tr~ted with the copolymer of Example 1 as follows:
3 Into a dry flask, under a nitrogen atmosphere, 4 w;~s carefully placed a sample of 5 g. of said copolymer, ~ylene (250 ml.) and p-toluenesulonylhydrazide (TSH) (35 g.) 6 ~nd the resulting solution maintained at reflux (135-140C.) 7 ~nder mild agitation for 2 hours. After this time, the 8 solution was hot filtéred (about 90C.), then cooled to 9 ambient temperature and isolated by precipitation from 1500 ml. methanol. The resulting polymer was washed with 11 methanol (500 ml), ~hen dried in a vacuum oven at 100C.
12 for 24 hours to yield 4.7 g. of a hydrogenated:butadiene 13 (8 mole %); iso~rene (85 mole %); styrene (7 mole %) block ~`~
14 terpolymer.

16 For the hydrogenation of the copolymer of Example 2, 17 the procedure of Example 3 was followed except for the fol-18 lowing changes:
19 7 g. of copolymer was used; 500 ml of xylenes was used; 28 g. of TSH was used; and mild agitation was for 4 hours 21 The resulting copolymer yield was 6.4 g. of a 22 hydrogenated:butadiene (35 mole %); isoprene (54 mole %);
23 styrene (11 mole %) block terpolymer.

To dem~nstrate their viscosity index improving 26 characteristics, the resulting hydrogenated polymers of 27 Examples 3 and 4 were blended to a viscosity of ca. 12.4 h 28 cs. in ENJ-102, a mineral lubricating oil. This oil was a 29 blend of two basic oils which contained 0.5 wt. % of a com-mercial polymeric pour point depressant. Both oils were 31 paraffinic, solvent refined neutral oils. The first had a 32 viscosity of about 150 SUS at 100F. and constituted 25.75 ~ 17 -~0~7343 ,`
1 weight percent of the blend. The second oil had a viscosity of about 300 SUS at 100F. and constituted 73.75 wt. % of . ~, . .~, ' A 3 the blend. Polyisobutylene (Paratone N, a commercially 4 available V.I. improver from Exxon Chemical Company) was S also blended with the test oil for comparison. The stabil-6 ity of the several lubricating oil test compositions was 7 examined by determining the extent of viscosity loss in a B sonic breakdown test.' The sonic breakdown test is a 9 measure of shear stability and is conducted according to the procedure described in ASTM Standards, vol. 1 (195L), ll p. 1160, "Test for Shear Stability of Polymer-Containing 12 Oils." The results of these tests are summarized in ~3 Table I.

. ~ ~ .
15Hydrogenated 2 4 16 Polymer of KV @ 210 Fl 0F. Pour Pt3 Sonic ~7 Example * cs Vis.P. F. Shear %
18 3 12.71 25.5 -35 22.8 ` 19 4 12.54 24.3 0 4.10 20 Paratone N 12.4 28.9 -37 22 21 * Additive is blended in an amount to provide a 22 viscosit~ of the composition approximating 12.4 23 cs. @210 F.
24 1. Determined in acco~dance with ASTM D-445.
2. Determined in accordance with ASTM D-2602.
26 3. Determined in accordance with ASTM D-97.
27 4. Run at 0.75 amps and 40C. for 15 minutes 28 according to ASTM standards, Vol. 1 (1961) 29 page 1160.
The block copolymer (Example 3) of the invention 31 has viscosity improving properties comparable to a commer-32 cial V.I. improver wi~h comparable shear stability and pour 33 point affect. The low temperature viscometrics provided 34 by a blend of the copolymer of the invention to the lubri-cating oil con~aining a pour depressant are somewhat better 3~ than available from a copolymer containing large amounts of 37 butadiene (the copolymer of Example 4) as evidenced by the : ~ ~ ~

lOB7343 l 0F. viscosity of each for the latter is 1.2 poises l~wer 2 It is submitted that such is surprising if one looks at 3 Table II of U.S. 3,772,196 wherein Sample E without any 4 butadiene content has a 0F viscosity of 6.8 poises lower than that of Sample H prepared from butadiene instead of isoprene, yet it has been found that an addition of 10%
7 butadiene to the isoprene in the copolymer does not adversely 8 affect the low temperature viscometrics.
` ef~c f~
9 A comparison of pour point ~ee~ between the ~-b: block copolymer of the invention and one prepared in accord-ll ance with U.S. 3,795,615 will be seen from the following 12 Table II wherein pour point data is presented using 4 con-13 trol blends of diverse commercial pour point depressants in 14 Solvent 150N Low Pour (pour point of ~5F.) mineral oil.
TABLE II
. . __ 7 PouroFpointsin 18 Solvent 150N LP 1.4 wei~ht % of Polymer of 19 Plus 0.5 wt % of None Exam~le ~ Example 4 Paraflow 1491 -35 -45 _5 21 Acryloid 1502 _30 _45 _0 22 Hitec 6723 _40 -45 0 23 Additive A4 -40 -40 -10 . . .
24 1. A wax/naphthalene condensation product available from Exxon Chemical Co. USA, Houston, Texas.
26 2. An ~ C 2) alkyl methacrylate polymer (ester 27 base po~ymer) having @210F. viscosity of ~700 28 cs, available from Rohm and Haas Co., Philadelphia, 29 Penna.
3. An esterified and imidated styrene/maleic anhydride 31 copolymer having an (Mn) of ~ 15,000 sold by Edwin 32 Cooper Inc. of St. Louis, Missouri.
33 4. A polymeric pour point depressant of a dialkyl fuma^
34 rate-viny~ acetate copo~ymer. ~` ~
5. Determined in accordance with ASI~I D-97.

I_ . ~
~0~7343 1 Inspection of Table II demonstrates that the 2 hydrogenated copolymer of Example 3 which contains about 8 3 mole % butadiene has markedly superior blend pour point 4 activity than the hydrogenated copolymer of Example 4 which A $ contains about ~ mole % of butadiene (the copolymer of 6 U.S. 3,795,615). This pour point activity of the copolymer (containing a small amount of butadiene) of the invention 8 in blends of commercial polymeric pour point depressants . 9 and mineral lubricating oil is unexpected in light of the data of Table I of the above-referenced U.S. 3,772,196.
11 Specifically, a comparison of Samples B and C of Table I
12 shows that a block copolymer of polystyrene-hydrogenated 3 polyisoprene does not adversely affect the pour point of 14 the compounded oil yet a copolymer of polystyrene-hydrogen-ated butadiene does markedly adversely affect the pour point . 16 by incre.asin~ it by 40.
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Claims (12)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A lubricating oil composition comprising:
(a) a major amount of a mineral lubricating oil;
(b) a minor pour point-depressing amount of a pour point depressant for said oil selected from the group consisting of:
(i) long-chain C15 to C60 alkyl aromatics wherein the aromatic may be hydrocarbon or a hydroxy-substituted hydrocarbon, said aromatic containing a maximum of three said substituent groups, condensed rings, or mixtures thereof;
(ii) polymers comprising C8 to C20 alkyl esters of monoethylen-ically unsaturated C3 to C8 mono- or dicarboxylic acids; and (iii) copolymers comprising styrene and maleic anhydride esteri-fied with C2 to C26 alcohols; and (c) 0.1-10 percent by weight of an oil-soluble hydrogenated block terpolymer viscosity index improver compatible with said pour point depressant, said terpolymer having the structure (A)x(B)y(C)z wherein:
A is a conjugated diene of the formula wherein R is a C1 to C8 alkyl group and present in mole % proportion as indicated by x which may vary from 45 to 99 mole %;
B is butadiene and present in mole % proportion as indicated by y which may vary from 2 to 9 mole %; and C is a C8 to C20 monovinyl aromatic hydrocarbon monomer, and present in mole % proportion as indicated by z which may vary from 5 to 40 mole %;

said block terpolymer being prepared by copolymerizing A and B to form a first block, and then copolymerizing C to form a second block and wherein 75 to 95%
of the diene monomers are in the 1,4-configuration.

2. The composition of claim 1 wherein said conjugated diene is isoprene and said aromatic monomer is styrene.

3. The composition of claim 1 or 2 wherein the (?n) of said block terpolymer ranges between 10,000 and 150,000.

4. The composition of claim 1 wherein said conjugated diene is isoprene and is present in an amount ranging from 90 to 99 mole percent, and at least 95% of the olefinic double bonds but not more than 5% of the aromatic unsaturated double bonds have been saturated.

5. The composition of claims 1 or 2 wherein said pour point depressant is said alkyl aromatic.

6. The composition of claims 1 or 2 wherein said pour point depressant is said polymer of C8-C20 alkyl ester.

7. The composition of claims 1 or 2 wherein said pour point depressant is said copolymer of styrene and esterified maleic anhydride.

8. The composition of claim 1 wherein said block terpolymer contains 8 mole % butadiene, 85 mole % isoprene and 7 mole % styrene.

9. The composition of claim 1 wherein said pour point depressant comprises essentially C12 alkyl methacrylate polymer.

10. The composition of claim 1 wherein said pour point depressant is a dialkyl fumarate-vinyl acetate copolymer.

11. The composition of claim 1 wherein said pour point depressant is an esterified and imidated styrene/maleic anhydride copolymer having an (?n) of 15,000.

12. The composition of claim 1 wherein said pour point depressant is wax-alkylated naphthalene.