CA1226386A

CA1226386A - Additives for lubricating oils containing styrene and heavy c in12 xx-c in20 xx alkyl esters of methacrylic acid, preparation method and applications

Info

Publication number: CA1226386A
Application number: CA000393913A
Authority: CA
Inventors: Yves Proux; Alain Perron
Original assignee: FRANCAISE D'ORGANO-SYNTHESE Ste
Current assignee: FRANCAISE D'ORGANO-SYNTHESE Ste
Priority date: 1981-01-12
Filing date: 1982-01-11
Publication date: 1987-09-01
Also published as: US4496691A; DE3265475D1; FR2497822A1; ATE15055T1; JPS57137391A; EP0056342A1; EP0056342B1; EP0056342B2; FR2497822B1

Abstract

ABSTRACT OF THE DISCLOSURE
The present invention relates to additives for lubricating oils, constituted by a copolymer prepared from 35-55%, and preferably 40-50%, of substituted or non-substituted styrene monomers, and from 65-45% and preferably 60-50% of heavy C12-C20 alkyl esters of methacrylic acid, said copolymer having a polydispersity which is as low as possible, a parameter of solubility close to that of the oil for which the additives are intended and a molecular weight of between 80,000 and 200,000. Preferably the heavy alkyl esters of methacrylic acid are constituted in at least 80% by C16-C20 alkyl esters. The copolymer may be modified by a comonomer and vinyl compounds. One application of the invention is the formulation of lubricating oils.

Description

~6 ?~3~

The present invention relates to additives for lubrica-ting oils based on styrene-corLiining compounds and heavy alkyl esters of methacrylic acid, possibly modified by an addltional comonomer and by grafting of vinyl compound(s), to their appli-5 cations ln improving the properties of such oils and to themethod for preparing sCame.
The technical field which is considered here is that of macromolecular compounds, and more particularly of poly meri~ation products as well as that of lubricating compositions.
Motor oils are required to have a viscosity which remains as constant as possible through a wide range of tem-peratures, and a low pour point. The aim is therefore to find additives which will give to oil s a high viscosity index (Viol, and strong thickening properties, which can be limited by the 15 stresses due to the mechanical shearing strength. Other charac-terlstlcs rnay also be sought, such as a clispersing power at high and low temperature.
Many oil additlves are known to have some of the aforesaid properties but, on the other hand, they do nothing to 20 improve the other characteristics required from oils. For example, heavy poly-methacrylic acid esters retain the vis-cosity with the temperature and lower the pour point of the oil, but, on the other hand, they have a limited thickening power. On the contrary, polyolefins such as ethylene-propylene copoly-25 mers or hydrogenated diene/styrene copolymers have a betterthickening power.
Attempts have already been made to regroup the properties of the polyesters of methacrylic acid and the diene-styrene compounds, but these have proved incompatible 30 and mixing them gives rise to decanting.
It is posslble to carry out a radical grafting in oily phase of heavy esters of methacrylic acid either on a polyolefin or on a hydrogenated diene-styrene copolymer. The resulting product is found to have no better properties than those of poly-35 esters of methacrylic acid or of polyolefins, indivi dually Onthe contrary, these polymers are then compatible with 6~

the hydrocarbon macromolecule used Ior grafting, the mixtures thus obtained having an increased efficiency.
From the practlcal standpoint, such a rnethod has proved dlfficult to perform: the hydrogenated styrene or olefin copolymers need to be prepared Then the esters of rnethacrylic acld have to be grafted and the mixture with the polyolefins is carried out thereafter.
The problem to be solved is to regroup all the essen-tial properties in one product intended to improve the charac-teristics of a lubricating oil.
This object ls attained in the present invention which proposes additives with properties at least equivalent to those of - the polyesters of methacrylic acid and corIlpatible with styrene polymers. Such additives are cor)s tituted by copolymers based on substituted or non-substituted styrene and at least one heavy C12--C20 alkyl ester of methacrylic acid, the percentage by weight o styrene monomers in relation to the total weight of the constituents, being between 35 and 55~0. Preferably said percentage of styrene monomer is between 40 and 50%.
Preferred additives are copolyrners based on styrene and heavy alkyl ester(s) of methacrylic acid selected from the C16-C20 and C12-C15 alkyl groups; the percentage by weight of C16-C20 alkyl ester of methacrylic acid in relation to the total welght of esters of methacrylic acid is at least about 80%. The copolymer is constituted by moietles of styrene and of heavy esters of methacrylic acid linking as regularly as possible and having as low a polydispersity as posslble, a parameter of solubility approaching that of the oil for which it is intended, and a a weight mean of molecular weight (I ) between 80 000 and 200 000 (G. P. C. method based on standard polystyrene).
Table I hereinafter gives the composition and certain properties of such additives. The preferred additives are seen to be terpolymers of the cetyl ester of methacrylic acld (50%)~yl eSter(~methacryllc acid (10%)/styrene (40%) type. The two tests referenced Pe 529 and LC~c 1295 correspond to two separate operators, which explains the slight difference between the

2~3~36 numerical results, Table I also sho~vs that a proportion of 100% of C16-C20 alkyl ester of n-ethacrylic acid (~vith respect to the esters of methacrylic acid ) L reerencesPe 511 and Pe 525/
does not give the best results, particularly when the styrene content is simultaneously low Pe 51~7, which leads to a very hlgh sensitivity to steering stresses ('I= 26, 6), this rendering the product inacceptable despite the very good thickening power (E = 3 6) In this speciIicatlon, the following abbreviations Jill have the following meanings MA Ce (cetyl) C16-C20 alkyl esters of methacrylic acid MA Lau (lauryl) C12-C15 alkyL esters of methacrylic acid MADAME methacrylate of dimethylaminoetnyl M TV weight mean of molecular weight E thickening power in 200 N (quantity of pure adcli-us tive necessary for obtaining 14 mm2/s or cSt at 100C = weigllt of copolymerjtotal weight Orbahn shearing rate (DIN 51382 ) P P pour point (C) L AFNOR standard P6010~/
Dp dispersing power measured by spot test at 220C
A2EH 2-ethylhexyl acrylate VIE index of viscosity NVP N-vinylpyrrolidone NVI N-vlnylimidazol e The spot test is conducted in empiric manner accor-ding to the method summed up hereunder The followillg operations are conducted - weighing bet~veen 0,16 g and 0 21 g oL additive to be tested and 30 then completing witll sludgc containing lajo of charcoal-colltaining material to obtain a concentration of 4, 2, 1 and 0 5~o - heating Up to 220C for 2 hours, and depositing 1 drop of each product on the Durieu~c 122bis paper, - measuring the dispersing power 2~ hours later with a standard 35 scale according to the following norms 5 very good dispersing po~ver 4 good dispersing power (the centre of the deposited spot is seen) *Trade Mark

3: average dispersing power 2: mediocre dispersing power 1: very poor dispersing power (the spot does not spread but goes through the paper) 0: no dispersing power.
The first figure on the left gives the dispersing power of the solution concentrated at 4%; for Pe 538~ it is 5, 4 indi-cating the dispersing power at 0. 5~ ( cf. Table III).
If the first three figures on the left are not equal to 10 5, the product is inefficient as dispersant. As to the figure on the rightg it must be as cl o se to 5 as possible, and the value 3 is basely acceptable.
The thickening power increases with the molecular weight; the shearing strength, on the contrary, decreases when 15 said molecular weight incl~Lses; it is therefore imperative to have a set molecuIar weight and a polydispersity inclex as close to 1 as possible.
As operation is carried out in bulk, polydispersities of about 2 to 2. 5 will b0 attained according to the inventlon.
In one embodiment, said copolymer is mixed with a st;yrene copolymer, for example in a ratio of 90/10 to 50/50 by weight. An antioxidant may also be added to said addltive The method for preparing such additives con~sts in a bulk poiymerization, in the presence of radical catalyst(s), 25 of the total quantity of styrene derivative and of esters of methacrylic acid after dissolution in a minimum quantity of sol vent.
This method will be described in detail hereinafter.
The main advantage of the invention is that these 30 new copolymers have the properties required for improving the qualities of the oil, in particular the VIE and the pour print (cf. Table II hereinafter).
E`urthermore, these new copolymers are compatible by being simply mixed with other copolymers such as styrene 35 polyn~ers; the thickening power of these new copolymers is thus improved, whilst maintaining their intrinsic properties.

., ~:263~

another advantage is their method for preparation whlch is simpler, shorter than in the prior art and as a result less expensive Such additives are also more economical due to the very nature of the starting components and to their preparation cost They may be proposed in the crude state or dissolved in a vehicle oil. They Iind an application in the formulation of motor and hydraulic oils.
The invention will be more readily understood on reading the following descrlption and examples given by way of non-limiting example.
The additives are copolymers obtained rom the following monomers:
1) styrenes substituted or non-substituted, for example by a lower alkyl group, in proportlons by weight with respect to the total weight of the components, oL 35 to 55% and preferably 40 to 50q'0 2) at least one heavy C12-C20 alkyl ester of methacrylic acid, in proportions by weight with respect to the total weight of the components, of 65 to 45%, and preferably 60 to 50~.
The heavy ester or esters of methacrylic acid con-tain at least 80% by weight of C16-C20 allcyl ester of methacrylic acid with respect to the total weight of the heavy alkyl esters of rnethacrylic acid These are natural or synthetic heavy alcohol esters of meth~crylic acïd.
It is possible when using heavy C16-C20 esters of methacrylic acid, to lower the parameter of solubility of the flnal copolymer and thus to increase the thickening power thereof.
The above additives according to the invention, of the terpolymer type, may very advantageously be modified by bulk copolymerl~ation of an additional comonomer, which gives a t~trapolymer, then by simultaneous double gralting of this tetra_ polymer by vinyl monomers.
Said additional comonomer will ba selected from the dialkylaminoalkyl esters of methacrylic acid, and used in a .Z2631~6 propc>rtion of 0. 5 to 5% witll respect to the total weight of the components .
The best results were obtained with the dimethyl-aminoethyl ester of methacrylic acid used at a rate of about 1% by weight with respect to the total weight of the components.
Said vinyl monomers will be selected from the deri-vatives containing a nitrogen function, and in particular N-vinyl-pyrrolidone, N-vinylimidazole and N-vinylpyridine, at a rate of 1 to 3% of the total weight of the components The best results were obtained with the combination of the N-vinylpyrrolidone and the N-vinylimidazole in a ratio of about 1/1 to 2/1.
A typical formulation of modified a.dditive, which glves excellent results, is as folLows:
- for 100 parts by weight of tetrapolymer (or for 1(~0 parts by weight of the modlfled addltlve):
- 1% by weight of MADAME (methacrylate of dimethyl-aminoethyl) bulk copolymerized;
- lo by weight of N-vinylpyrrolidone and 0. 5q~ but weight of ~-vinyli~idazole then orafted simultaneously.
It will be noted that it is essential for the nitro-geneous ester of methacrylic acid to be bulk copolymerized with the monomers of the terpolymer described hereinabove (accor-ding to a n~odus operandi described in detail hereinafter) and for the vinyl monomers to be grafted simultaneously thereafter.
If one of these conditlons is not fulfilled, for example it the nitrogeneous ester of methacrylic acid i6 grafted, mediocre results are obtained This is shown by Table III hereinafter in which the basic terpolyn~er contains in relativ0 % 50% MACe, 10%
MAlau and 40~0 styrene (Pe 529~.
I`ests LCMc 131~ and 1320 show that the nitrogeneous ester of nlethacrylic acid must be in~peratively bulk poly-merized and not grafted.
Test Pe 5381 despite the absence of NVI, may ~pp~r interesting; in fact, lt corresponds to 4% of modifying agents and is therefore very expensive This quantlty of 4% is im-possible to reduce as shown by test LCMc 130~.

Z~

Tests P 573 to LCMc 1339 are therefore the only ones to correspond to very good, inexpensive products.
The mociified additives with dispersing properties, according to the invention, are therefore specific by their 5 composition, method for preparation and their properties These additlves, i. e. the terpolymers of styrene and of heavy esters of methacrylic acid or their rnodified form, (doubly grafted tetrapolymers) are physically compatible with - the copolymers which are known for their excellent thickening 10 power such as those based on styrene: hydrogenated styrene/
isoprene, hydrogenated styrene/butadiene, styrene/isobutene copolymers. Contrary to the prior art, such a styrene copoly-mer need not be subjected to a chemical reaction in order to obtain a homogeneous product. In the present case, the two 15 copolymers are simply mlxed together. This property offers the a~lvantage of proposing products Will a reinforced thicke-ning power or of allowlng the user to make his o-vn mixture if the need arises.
An extremely advantageous "mixture" will be that of 20 the Inodified form of the additive according to the invention (i. e. grafted tetrapolymer) and of one of the styrene copolymers indicated hereinabove, slnce the latter present in fact no dis-persing power, which is in that case brought into the "mixture"
by the modified additive according to the invention.
According to another variant, a conventional anti-oxidant may be added to the copolymers, in known manner According to the invention, the method used for ob-tainlng the terpolyn~ers consists in a radical bulk polymeric tion with virtually no solvent, A minimum of solvent is used, 30 less in any case than in the prior art which uses about 30% of the weight of the starting components. In the present method, on the contrary, no more than 5-10% by weight of solvent is used in relation to the total weight of the starting monomers so that the solvent has but little effect on the polymerization.
This polymerization and the percentages of starting monomers make it possible to obtain a final copolymer of which 3~

the styrene-ester of methacrylic acid moietieC are linked as regularly as possible, tending towards a uniform distribution oL the moieties as a Lunction of the proportions o the mono-mers .
The weight mean of molecular weight of the final copolymer is between 80 000 and 200 000 (measured by the G. P. C. method, with standard polystyrene), its polydis-persity is as low as possible, and its parameter of solubility as close as possible to the parameter oL solubility of the oil and oL the other pc>ssible additives, i. e. generally around 8.
The copolymers obtained are in compact mass orm, and can be sold either in the crude state or disolved in the oil with, as a variant, presentation as a mi.Yture with a styrene copolymer. Mixtures of additive (or modified additive) with styrene polymer are between about 90/10 and 50/50 by ~veight.
Table IV shows the viscosity at 100C (in mm2/s or cSt) of a mixture of additive Pe 529 (cf. Table 1) and of hydrogenated styrene-isoprene, in the proportion of 3~10 in 200 NEUTRAL
oil, as a Lunction of the relative percentage of hydrogenated styrene isoprene in the mixture. The shearing rate is clearly lower than that of the known polyesters of methacrylic acid .
The application of such a copolymer to the improve-ment of lubricating oils, such as for example those marketed 25 under the name "150 Neutral", "200 Neutral", is achieved by adding from 1 to 5'r~o oE the weigllt of copolymer of styrene and ester oE methacry1ic acid witll respect to the total weight, to obtain the final viscosity required for the oil treated this way, for example about 14 cSt at 100C for the "200 Neutral" o;l The terpolymers according to tl-e invelltioll are pre-pared in the following manner: the n~onomers have a quantity of toluene (or another equivalent light solvent) equal to 10~o of the total weight oL the monomers, and about 3 /oo oE an adequate radical catalyst, such as azobisisobutyronitrile (AIBN), added 35 thereto. One tenth of this reaction mass is irlroduced, in a neutral atmosphere (and particularly in a nitrogen atmosphere), j t into a reactor and talcen to about 85C, with stirring, then *Tracle Mark the rest of the initial reactional mass is poured in two to three hours. The temperature is maintained at about 85C for one hour after the end of the flow The bulk temperature is taken to about lZ5C, and a radical end-of-polymeriz;ation catalyst, of the 5 tertiary butyl perbenzoate type, is then added in the proportions known to the man skilled in the art. The reaction is then finished.
The toluene is finally distilled under reduced pressure, the bulk temperature being progressively taken towards 140C. The resin is cast hot To prepare the doubly grafted tetrapolymers, the following modus operandi is preferably carried out:
- bulk polymerization of the Iour monomers forming the tetra-polymer, according to the above-described technique fo r the terpolymers, but with only 4/5 of the quantity of the catalyst, 15 then - reactivation of the macromolecular chains by the last 1/5th of the quantity of the catalyst, - addition of the mixture of the vinyl monomers (particularly NV P a nd .~IVT ) .
20 - heating to 125C and termination of the reaction as described he reinabove A variant of this method consistsl instead of effec-ting the temperature rise to 125C and adding the end-of-polymerization catalyst, in remaining for a longer time at 25 85C, without adding any end-of-polymeri~ation catalyst, but continuing the addition of portions of AIBN Properties are then obtainecl wlIich may be slightly modified.
The toluene is clistilled and the resin is cast as befo rehand Two examples of dispersing powers will be found hereinbelow whiclI nnay be obtained uncler these conclitions according to the invention ~iodified additive Pe 611 (tetrapolymer 50-10-~0 ,'o of MACe, M~Lau and styrene respectively, l'lo MADAME and 35 1 and 0. 5% respectively of NVP and NVl:
- alone: spot test 5 5 5 4+
- 80%/20% mixture ol Pe 611 and oi "Sl--IELL~/IS"*
'`'7 *Trace Mark ~z~

(hydrogenated styrene/isoprene copolymer):
spot test 5 5 5 4 The heavy alkyl esters of methacrylic acid used are a mixture containing "impu r ities": for example, in the compo-5 sition of C12-C 15 alkyl esters of methacrylic acid, it is possible to find C10 Cll and/o, C16 compounds which do not exceed 3%, and in that of the C16-C20 alkyl esters of methacrylic acid, the presence is detected of C12-C14 compounds in an overall proportlon of 6alo at the most.
The invention is in no way limited to the products and method described hereinabove, and, on the contrary, covers any modifications which can be made thereto by the man skilled in the art, without departing from the scope thereof.

ll TABLE

In~luenccof the comnosition on the thickening po~Ner and the rate of shearillg ..
Test MA Ce MA Lau .A OH Styrene Mw E
__ _ Pe 511 75 25 183450 3,6 26D6 Pe 522 50 2525 106470 5~5 6 Pe 524 50 . 50 101280 5~5 5o4 Pe 525 60 40 209800 4~1 14.5 Pe 526 50 50 151400 4~7 13,3 Pe 529 50 ].0 hO 169400 4~3 9 L,CMc1295 50 ]0 40 188800 4,1 11.,2 Pe 548 30 30 4() l74800 5 7~6 _ _ TABLL Il . . I
T VII. Pour point est (0. 3%/200 N) __ Pe 525 (13h8%) - 36 __ _____ _ _ Pi 5~6 - 387,~5 _ 30 Pe 529 (13~9~) _ 30 3 8gj TABLE I I I
Dispersing cllaracter _ _ MAl)~ME MADAML NVP NVI Spot test Test (bu1k poly- ,. (grated) grafted (grafted) m e rl :~ ed ) _ Pe 531 4 0 0 0 0 Pe 541 2 0 0 0 0 LCMc 1299 4 5 4 3 3 LCMc 1307 2 4 3 3 2 Pe 538 2 2 5 5 5 4 LCMc 1309 1 l 5 5 Pe 559 2 2 5 4 4 1 LCMc 1316 4 5 5 4 LCMc 1320 4 2 2 2 0 Pe 567 2 1 005 5 5 5 4 Pe 573 1 1 0,5 5 5 5 4 LCMc 1337 1 1 0~5 5 5 5 4 Pe 574 1 1 0,5 5 5 5 4 LCMc 1339 1 0,5 5 5 5 4 . .

TABI.E I V

Propertles of mixtures Pe 529/ SI~ELLVIS 50"

l L.~-lS" E
Test (mm2/s) (mm2/s) /7~
_ _, ___ _ LCMc 1305/1 75 37~4 LC'Mc 1305/2 60 2502 1~7 13,5() 4~25 LCMc 1305 / 3 50 20,8 2 1 :3, 8n, 6 LCMc 1305/4 4n 17,5 2,3 1:3~,92 6"7 LCMc 1305/5 25 14,6 2,9 14,05 6,8 LCMc 13()5/7 10 1201 3,85 14,01 9 Pe 529 ._ 11 4 4,3 _~ ____~___ = viscosity at 10( C of a sollltion at 3 I: of active rnatter.
= viscosityat 100 C oftlle solution corresponding to the thickerling power.

Claims

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

1. Additives for lubricating oils, essentially constituted by copolymers prepared from styrene monomers and at least one, heavy C12-C20 alkyl ester of methacrylic acid, wherein the percentage of styrene monomer(s), expressed by weight and in relation to the total weight of the monomers, is between 35 and 55%, and said copolymers have a polydispersity which is as low as possible, a parameter of solubility which is close to that of the oils to which said additives are intended and a weight means of molecular weight which is between 80,000 and 200,000, said heavy alkyl ester or esters of methacrylic acid is or are selected from the following group of compounds: alkyl C16-C20 and C12-C15, and a (C16-C20 alkyl) ester of methacrylic acid is at least present for 80% by weight in relation to the total weight of the heavy alkyl esters of methacrylic acid, in that they are modified by an additional copolymerized ester of methacrylic acid, selected from the group formed by the dialkylaminoalkyl esters of methacrylic acid, and by at least one grafted dispersing monomer selected from N-vinylpyrrolidone, N-vinylimidazole, and N-vinylpyridine.

2. The additives according to claim 1, characterized in that the percentage of styrene monomer(s), expressed by weight and in relation to the total weight of the monomers, is between 40 and 50%.

3. The additives according to claim 1, characterized in that they consist of terpolymers of styrene, (C12-C15 alkyl) ester of methacrylic acid and (C16-C20) ester of methacrylic acid.

4. The additives according to claim 3, characterized in that they consist of terpolymers of styrene, lauryl ester of methacrylic acid and cetyl ester of methacrylic acid.

5. The additives according to claim 4, characterized in that they consist of a bulk tetrapolymer of styrene, lauryl ester of methacrylic acid, cetyl ester of methacrylic acid and dimethylaminoethyl ester of methacrylic acid, comprising a double grafting of N-vinylpyrrolidone and N-vinylimidazole.

6. The additives according to claim 5, characterized in that the proportions of dialkylaminoalkyl ester of methacrylic acid represent from 0.5 to 5% of the total weight of the components, and the total proportions of dispersing monomers from 1 to 3% of the total weight of the components.

7. The additive according to claim 6, characterized in that the N-vinylpyrrolidone and the N-vinylimidazole, which are used in a ratio of between 1/1 and 2/1, are selected as dispersing monomers.

8. The additive according to claim 1, characterized in that it consists of a tetrapolymer (styrene/lauryl ester of methacrylic acid/cetyl ester of methacrylic acid/dimethylaminoethyl ester of methacrylic acid [1%]) with simulanteous double grafting N-vinylpyrrolidone (1%) and N-vinylimidazole (0.5%) subsequently.

9. The additive according to claim 1, characterized in that it comprises an efficient quantity of a conventional antioxidant.

10. Mixtures for improving lubricating oils, characterized in that they are obtained by mixing an additive according to claim 1 with a styrene polymer.

11. The mixture according to claim 10, characterized in that the additive/styrene polymer ratio is from about 90/10 to 50/50 by weight.

12. The mixtures according to claims 10 or 11, characterized in that the styrene polymers are selected from the copolymers known for their thickening power, namely hydrogenated styrene-isoprene; hydrogenated styrene-butadiene, and styrene-isobutene.

13. Process of improving lubricating oils which comprises adding an additive according to claim 1 to said oil, in a proportion of 1 to 5% by weight, so as to modify the viscosity of the oil.

14. Method for preparing the additives of the grafted tetrapolymer type, according to claim 1, comprising the steps of bulk polymerizing the total quantity of styrene, heavy alkyl esters of methacrylic acid and dialkylaminoalkyl ester of methacrylic acid monomers, in the presence of a radical catalyst such as azobisisobutyronitrile and at about 85°C, and taking the temperature to about 125°C after at least 1 hour of reaction or a fraction of said total quantity of monomers is polymerized by taking the temperature to about 85°C and, when the latter is attained, the rest of said quantity is introduced in the reaction mixture and the quantity of solvent used is at the most 5-10% of the total weight of the monomers, characterized by the following steps:
bulk polymerization of the four monomers forming the tetrapolymer, according to the technique described above, but with only 4/5 of the quantity of the catalyst, then;
reactivation of the macromolecular chains by the last 1/5th of the quantity of the catalyst;
addition of the mixture of the vinyl monomers (particularly NVP and NVI); and temperature rise to 125°C and termination of the reaction.