Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic -co- compound
Reexamination Certificate
2000-11-01
2001-11-27
Howard, Jacqueline V. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic -co- compound
C252S079000, C525S304000, C508S470000, C526S329500, C526S329700
Reexamination Certificate
active
06323164
ABSTRACT:
TECHNICAL FIELD
This invention relates to novel dispersant (meth)acrylate copolymers having excellent low temperature properties in a wide variety of base oils. The present invention also relates to the use of these copolymers as viscosity index improvers for lubricating oils.
BACKGROUND OF THE INVENTION
Polymethacrylate viscosity index improvers (PMA VII's) are well known in the lubricating industry. Many attempts have been made to produce PMA VII's that have the desired balance of high temperature and low temperature viscometrics, as well as the required shear stability for a given application. Obtaining suitable low temperature performance has become even more difficult recently with the movement away from API Group I base oils and the increased utilization of Group II and Group III base oils. Further, refiners who blend with different base oils desire a single product which performs effectively in all of these different base oils. The present invention is directed to novel dispersant (meth) acrylate copolymers which exhibit excellent low temperature performance in a wide variety of base oils.
U.S. Pat. No. 5,112,509 teaches a method for making a methyl methacrylate-lauryl methacrylate copolymer. The '509 patent does not teach the copolymers of the present invention, which contain a dispersant monomer.
SUMMARY OF THE INVENTION
The present invention is directed to novel dispersant poly (meth)acrylates and their use as viscosity index improvers for lubricating oils.
The polyalkyl (meth)acrylate copolymers of the present invention comprise units derived from:
(A) about 12 to about 18 weight percent methyl methacrylate;
(B) about 75 to about 85, weight percent of a C
10
-C
15
alkyl (meth)acrylate; and
(C) about 2 to about 5, weight percent of a nitrogen-containing dispersant monomer.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to polyalkyl (meth)acrylate copolymers comprising units derived from:
(A) about 12 to about 18 weight percent methyl methacrylate;
(B) about 75 to about 85 weight percent of C
10
-C
15
alkyl (meth)acrylate(s); and
(C) about 2 to about 5 weight percent of a nitrogen-containing dispersant monomer.
The polyalkyl (meth)acrylate copolymers of the present invention comprise the reaction products of:
(A) from about 12 to about 18, weight percent methyl methacrylate;
(B) from about 75 to about 85, weight percent of C
10
-C
15
alkyl (meth)acrylate(s); and
(C) from about 2 to about 5, weight percent of a nitrogen-containing dispersant monomer.
As used herein, C
10
-C
15
alkyl (meth)acrylate means an alkyl ester of acrylic or methacrylic acid having a straight or branched alkyl group of 10 to 15 carbon atoms per group including, but not limited to, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, myristyl (meth)acrylate, dodecyl pentadecyl methacrylate, and mixtures thereof.
The alkyl (meth)acrylate comonomers containing 10 or more carbon atoms in the alkyl group are generally prepared by standard esterification procedures using technical grades of long chain aliphatic alcohols, and these commercially available alcohols are mixtures of alcohols of varying chain lengths in the alkyl groups. Consequently, for the purposes of this invention, alkyl (meth)acrylate is intended to include not only the individual alkyl (meth)acrylate product named, but also to include mixtures of the alkyl (meth)acrylates with a predominant amount of the particular alkyl (meth)acrylate named.
The nitrogen-containing dispersant monomers suitable for use in the present invention include dialkylamino alkyl (meth)acrylamides such as, N,N-dimethylaminopropyl methacrylamide; N,N-diethylaminopropyl methacrylamide; N,N-dimethylaminoethyl acrylamide and N,N-diethylaminoethyl acrylamide; and dialkylaminoalkyl (meth)acrylates such as N,N-dimethylaminoethyl methacrylate; N,N-diethylaminoethyl acrylate and N,N-dimethylaminoethyl thiomethacrylate.
In a preferred embodiment, the polyalkyl (meth)acrylate copolymers of the present invention consist essentially of the reaction products of (A), (B) and (C). However, those skilled in the art will appreciate that minor levels of other monomers, polymerizable with monomers (A), (B) and/or (C) disclosed herein, may be present as long as they do not adversely affect the low temperature properties of the fully formulated fluids. Typically additional monomers are present in an amount of less than about 5 weight percent, preferably in an amount of less than 3 weight percent, most preferably in an amount of less than 1 weight percent. For example, the addition of minor levels of monomers such as C
2
-C
9
alkyl (meth)acrylates, hydroxy- or alkoxy-containing alkyl (meth)acrylates, ethylene, propylene, styrene, vinyl acetate and the like are contemplated within the scope of this invention as long as the presence of these monomers do not adversely affect the low temperature properties of the copolymers. In a preferred embodiment the sum of the weight percent of (A), (B) and (C) equals 100%.
The copolymers may be prepared by various polymerization techniques including free-radical and anionic polymerization.
Conventional methods of free-radical polymerization can be used to prepare the copolymers of the present invention. Polymerization of the acrylic and/or methacrylic monomers can take place under a variety of conditions, including bulk polymerization, solution polymerization, usually in an organic solvent, preferably mineral oil, emulsion polymerization, suspension polymerization and non-aqueous dispersion techniques.
Solution polymerization is preferred. In the solution polymerization, a reaction mixture comprising a diluent, the alkyl (meth)acrylate monomers, a polymerization initiator and a chain transfer agent is prepared.
The diluent may be any inert hydrocarbon and is preferably a hydrocarbon lubricating oil that is compatible with or identical to the lubricating oil in which the copolymer is to be subsequently used. The mixture includes, e.g., from about 15 to about 400 parts by weight (pbw) diluent per 100 pbw total monomers and, more preferably, from about 50 to about 200 pbw diluent per 100 pbw total monomers. As used herein, “total monomer charge” means the combined amount of all monomers in the initial, i.e., unreacted, reaction mixture.
In preparing the copolymers of the present invention by free-radical polymerization, the acrylic monomers may be polymerized simultaneously or sequentially, in any order. In a preferred embodiment, the total monomer charge includes from 10 to 20, preferably 12 to 18, weight percent methyl methacrylate; 70 to 89, preferably 75 to 85, weight percent of at least one C
10
-C
15
alkyl (meth)acrylate; and 1 to 10, preferably 2 to 5, weight percent of a dispersant monomer.
Suitable polymerization initiators include initiators which disassociate upon heating to yield a free radical, e.g., peroxide compounds such as benzoyl peroxide, t-butyl perbenzoate, t-butyl peroctoate and cumene hydroperoxide; and azo compounds such as azoisobutyronitrile and 2,2′-azobis (2-methylbutanenitrile). The reaction mixture typically includes from about 0.01 wt % to about 1.0 wt % initiator relative to the total monomer mixture.
Suitable chain transfer agents include those conventional in the art, e.g., dodecyl mercaptan and ethyl mercaptan. The selection of the amount of chain transfer agent to be used is based on the desired molecular weight of the polymer being synthesized as well as the desired level of shear stability for the polymer, i.e., if a more shear stable polymer is desired, more chain transfer agent can be added to the reaction mixture. Preferably, the chain transfer agent is added to the reaction mixture in an amount of 0.01 to 3 weight percent, preferably 0.02 to 2.5 weight percent, relative to the monomer mixture.
By way of example and without limitation, the reaction mixture is charged to a reaction vessel that is equipped with a stirrer, a thermometer and a reflux condenser and heated with stirring under a nitrogen blanket to a tempera
Liesen Gregory P.
Srinivasan Sanjay
Ethyl Corporation
Hamilton Thomas
Howard Jacqueline V.
Moore James T.
LandOfFree
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