Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic -co- compound
Reexamination Certificate
1999-11-29
2002-02-26
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
C526S173000, C526S328500, C526S329700, C526S348600, C525S271000, C525S299000
Reexamination Certificate
active
06350723
ABSTRACT:
TECHNICAL FIELD
The present invention is directed to novel block copolymers and a process for the anionic polymerization of block copolymers comprising a block of at least one polymerized diene and at least one block of at least one polymerized long-chain alkyl methacrylate. The invention also relates to the use of said block copolymers in lubricating oil compositions.
BACKGROUND OF THE INVENTION
The use of polyalkyl methacrylates as viscosity index improvers and pour point depressants for lubricating oils is well known. Further, it is known to use olefin copolymers or hydrogenated block copolymers as viscosity index improvers and dispersants for lubricating oil compositions. It would be advantageous to provide to a lubricating oil a polylalkyl methacrylate polymer and also an olefin copolymer or a hydrogenated block polymer in order to obtain the advantages associated with both types of additive in a lubricating oil composition.
In practice, however, the use of both types of additive is not always feasible. At high concentrations of additive in the oil, physical mixtures of polyalkyl methacrylates and olefin copolymers or hydrogenated block polymers are immiscible and separate into two distinct phases. This is highly undesirable in lubricating oil formulations. Attempts have been made to chemically combine the polyalkyl methacrylate function and a polyalkadiene function in a single polymeric molecule and thereby avoid such compatibility problems. U.S. Pat. No. 4,533,482, describes random copolymers of alkyl acrylate or methacrylate and a conjugated diene wherein the aliphatic unsaturation has been hydrogenated. Such polymers are relatively high molecular weight materials having a molecular weight from about 80,000 to about 1,000,000.
European Patent Application No. 298,667, describes block copolymers in which one block is selected from hydrolyzable C2-C5 alkyl methacrylates, methacrylic acid or ionomers thereof, and at least one other block is a block of an anionically polymerized monomer other than methyl methacrylate. Illustrative of such monomers is butadiene and isoprene. The Application does not suggest the block polymers of the present invention or their use in lubricating oil compositions.
U.S. Pat. No. 5,002,676 teaches selectively hydrogenated block copolymers comprising at least one block of polymerized alkyl methacrylate and one block of at least one polymerized conjugated alkadiene and the use of said copolymers in lubricating oil compositions. The reference fails to teach the specific copolymers or the processes of the present invention.
SUMMARY OF THE INVENTION
The present invention is directed to block copolymers, processes for preparing said block copolymers and to lubricating oil compositions containing said copolymers. More particularly the present invention relates to block copolymers comprising at least one block of polymerized alkyl methacrylate monomer(s), wherein at least 50% by weight of the alkyl methacrylate monomers are C12-C30 alkyl methacrylates, and a block of a polymerized conjugated alkadiene. The block copolymers of the present invention are useful as viscosity index improvers in lubricating oil compositions as well as compatibilizers for compositions containing both polymethacrylates and olefin copolymers or hydrogenated block polymers.
The processes of the present invention allow one to predictably and reproducibly control the molecular weight, molecular weight distribution, copolymer composition and diene microstructure of the long-chain alkyl methacrylate/diene block copolymers.
DETAILED DESCRIPTION OF THE INVENTION
The block copolymers of the present invention are block copolymers having at least one block of polymerized long-chain alkyl methacrylate momomer(s) and a block derived from conjugated alkadiene monomer(s).
The nonhydrogenated block copolymers are termed A-B or A-B-A copolymers wherein A represents a block of polymerized long-chain alkyl methacrylate monomer(s) and B represents a block of conjugated alkadiene monomer(s).
A variety of conjugated alkadienes of up to 10 carbon atoms are useful as the precursor of the B block, e.g., 1,3-hexadiene, piperylene, 1,3-octadiene and 3-methyl-1,3 pentadiene. The preferred conjugated alkadienes for use in the block copolymers are butadiene and isoprene, most preferably isoprene. Preferably 50 to 100%, more preferably 90 to 100% of the monomers used in forming block B are conjugated dienes.
The alkyl methacrylate block(s), block A, is obtained by the polymerization of alkyl methacrylate monomer(s) wherein 50% to 100%, preferably 80 to 100%, by weight of the monomer(s) used for forming block A are C12-C30 alkyl methacrylates.
As used herein, C12-C30 alkyl methacrylate means an alkyl ester of methacrylic acid having a straight or branched alkyl group of 12 to 30 carbon atoms per group such as lauryl methacrylate, myristyl methacrylate, stearyl methacrylate, cetyl methacrylate, heptadecyl methacrylate, nonadecyl methacrylate, eicosyl methacrylate, and mixtures thereof such as cetyl-eicosyl methacrylate and cetyl-stearyl methacrylate. The preferred alkyl methacrylate is lauryl methacrylate. The polymerized alkyl methacrylate blocks may contain minor amounts, i.e., less than 50%, preferably less than 30% and more preferably less than 5%, by weight, of C1-C11 alkyl methacrylates.
Additional monomers may be used in forming the block copolymers of the present invention. These monomers include styrene, alpha-methylstyrene, vinyl toluene, t-butyl styrene, chlorostyrene, 1,1-diphenylethylene, vinyl naphthalene, 2-vinylpyridine, 4-vinylpyridine, N-vinylimidazole, N-vinylpyrrolidone, alkyl (meth) acrylates containing dispersant moieties and alkyl (meth) acrylamides containing dispersant moieties. Suitable (meth) acrylate and (meth) acrylamide dispersant monomers include N,N-dimethylamino propyl methacrylamide, N,N-diethylamino propyl methacrylamide, N,N-dimethylaminoethyl acrylamide, N,N-diethylaminoethyl acrylamide, N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl acrylate, N,N-diethylaminoethyl methacrylate, N,N-dimethylaminoethyl thiomethacrylate, poly(ethylene glycol) ethyl ether methacrylate, poly(ethylene glycol) 4-nonylphenyl ether acrylate and poly(ethylene glycol) phenyl ether acrylate. These additional monomers may be incorporated into either block as long as they do not interfere with the polymerization of that block, i.e., the desired molecular weight and molecular weight distribution of the resulting block and block copolymer is still obtained. Typically, the non-polar monomers, if used, will be incorporated into the alkadiene block, while the polar monomer, if used, will be added during the polymerization of the alkyl methacrylate block. In a preferred embodiment of the present invention, these additional monomers will be present in an amount of 0 to 25, preferably 0 to 10, wt. % based on the total weight of monomers used in forming the block in which these additional monomers are to be added.
In one particularly preferred embodiment of the present invention, 95 to 100 wt. % of the monomer used for forming the polyalkadienyl block is isoprene and 95 to 100 wt. % of the monomer used for forming the alkyl methacrylate block is lauryl methacrylate.
The block polymers of the present invention are preferably made in accordance with the teachings of the Ph.D. Dissertation, Porzio, R. S.,
Anionic Synthesis of Block, Functionalized and Star-Branched Poly
(
Alkyl Methacrylates
), University of Akron, December 1997, incorporated herein by reference.
The alkyl methacrylate monomer(s) must be purified. Purification of the alkyl methacrylate monomer(s) may be conducted by those methods commonly used in the art such as distillation from trialkylaluminum or standard fractional distillation. Due to the high amount of long-chain alkyl methacrylate monomers, i.e., 50-100 wt. % C12-C30 alkyl methacrylates, used in forming the polymethacrylate block(s) of the copolymers of the present invention, standard fractional distillation is a preferred method of purifying the methacrylate monomers. Standar
Mishra Munmaya K.
Porzio Robert S.
Quirk Roderic P.
Ethyl Corporation
Howard Jacqueline V.
Rainear Dennis H.
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