Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic -co- compound
Reexamination Certificate
1999-09-22
2001-07-03
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic -co- compound
C526S329500, C526S329700
Reexamination Certificate
active
06255261
ABSTRACT:
TECHNICAL FIELD
This invention relates to polyalkyl (meth) acrylate copolymers having excellent low temperature properties. The present invention also relates to the use of these copolymers as pour point depressants for lubricating oils.
BACKGROUND OF THE INVENTION
Polymethacrylate pour point depressants (PMA PPD's) are well known in the lubricating industry. Many attempts have been made to produce PMA PPD's that improve the low temperature viscometrics of various lubricating compositions.
PPD additives improve the low-temperature performance of an oil by modifying the wax crystallization process. A wide variety of chemical types are currently available, and include polyalkylmethacrylates, styrenated polyesters, alkylated polystyrenes and alkylated naphthalenes. The present invention is directed to novel alkyl (meth)acrylate polymers which exhibit desired low temperature viscometrics. More specifically, the invention is directed to PMA PPDs that exhibit outstanding low temperature properties in lubricating oils for applications such as crankcase lubricants and automatic transmission fluids. The oil chemist is constantly searching for PPDs that achieve optimum low-temperature performance at low concentrations. The present invention addresses the need for an improved PPD.
U.S. Pat. No. 2,655,479 to Munday et al. claims a pour point depressant composition consisting of a blend of two copolymers, the first copolymer having an average side chain length of about 12.7 while the second copolymer has an average side chain length of about 11.2.
U.K. Patent No. 1,559,952 discloses a mixture of two classes of oil soluble polyalkyl (meth)acrylates as pour point depressants.
U.S. Pat. No. 4,146,492 discloses lubricating oil compositions comprising between about 0.5 and 30 wt. % of a specifically defined ethylene-propylene copolymer and between about 0.005 to 10 wt. % of a neat interpolymeric polyalkylacrylate of (A) C
1
-C
15
alkylacrylate and (B) C
16
-C
22
alkylacrylate having a weight ratio of A:B of between about 90:10 and 50:50, a molecular weight of from 1000 to 25,000 and an average alkyl side chain length of between about 11 and 16 carbons.
U.S. Pat. No. 4,867,894 discloses pour point improving additives for mineral oils comprising from 10 to 30 mole percent methyl methacrylate, 10 to 70 mole percent of a linear C16 to C30 alkyl methacrylate, from 10 to 80 mole percent of a C4-C15 linear alkyl methacrylate and/or a C4 to C40 branched methacrylate, and from 0 to 30 mole percent of a free-radically polymerizable nitrogen-containing monomer having dispersing action.
U.S. Pat. Nos. 5,312,884 and 5,368,761 disclose copolymers useful as pour point depressants for lubricating oils comprising 15-67 mole percent C8-C15 alkyl (meth) acrylates, 3-40 mole percent C16-C24 (meth) acrylates, and from greater than 30-65 mole percent C1-C4 methacrylates. These patents do not teach copolymers containing the specific monomers in the specific proportions required by the present claims.
U.S. Pat. No. 5,534,175 discloses copolymers of unsaturated fatty esters derived from 12-20 mass % of a C1-C3 (meth) acrylate, 45-72 mass % of a C11-C15 (meth) acrylate and 14-30 mass % of a C16-C25 (meth) acrylate.
EP 0 236 844 B1 teaches pour point improving agents derived from methyl methacrylate.
SUMMARY OF THE INVENTION
The present invention is directed to novel polyalkyl (meth) acrylates and their use as pour point depressants for lubricating oils.
The polyalkyl (meth) acrylate copolymers of the present invention comprise units derived from:
(A) about 5 to about 60, preferably 15 to 50, weight percent of a C11-C15 alkyl (meth) acrylate; and
(B) about 95 to about 40, preferably 85 to 50, weight percent of a C16-C30 alkyl (meth) acrylate.
Another embodiment of the present invention comprises lubricating oil compositions containing a mixture of at least one pour point depressant as described above and at least one viscosity index improver.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to polyalkyl (meth) acrylate copolymers comprising units derived from:
(A) from about 5 to about 60 weight percent of a C11-C15 alkyl (meth) acrylate; and
(B) from about 95 to about 40 weight percent of a C16-C30 alkyl (meth) acrylate.
The polyalkyl (meth) acrylate copolymers of the present invention comprise the reaction products of:
(A) from about 5 to about 60, preferably 15 to 50, weight percent of a C11-C15 alkyl (meth) acrylate; and
(B) from about 95 to about 40, preferably 85 to 50, weight percent of a C16-C30 alkyl (meth) acrylate.
The copolymers of the present invention have a relative number average molecular weight of from about 5,000 to about 5,000,000. The copolymers typically have a relative number average molecular weight, as determined by gel permeation chromatography using polymethyl methacrylate standards, between 5,000 and 300,000 when prepared by free-radical polymerization.
As used herein, C11-C15 alkyl (meth) acrylate means an alkyl ester of acrylic or methacrylic acid having a straight or branched alkyl group of 11 to 15 carbon atoms per group such as, undecyl (meth) acrylate, lauryl (meth) acrylate, myristyl (meth) acrylate, dodecyl pentadecyl methacrylate, and mixtures thereof.
As used herein, C16-C30 alkyl (meth) acrylate means an alkyl ester of acrylic or methacrylic acid having a straight or branched alkyl group of 16 to 30 carbon atoms per group such as, stearyl (meth) acrylate, cetyl (meth) acrylate, heptadecyl (meth) acrylate, nonadecyl (meth) acrylate, eicosyl (meth) acrylate, and mixture thereof such as, cetyl-eicosyl (meth) acrylate and cetyl-stearyl (meth) acrylate.
The alkyl (meth) acrylate comonomers containing 11 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 containing between 11 and 20 carbon atoms 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.
In a preferred embodiment, the polyalkyl (meth) acrylate copolymers of the present invention consist essentially of monomers (A) and (B). However, those skilled in the art will appreciate that minor levels of other monomers, polymerizable with the alkyl (meth)acrylates disclosed herein, may be present as long as they do not adversely affect the low temperature properties of the fully formulated fluids, for example, increasing the low temperature pumping viscosity of a lubricating fluid when the pour point depressant is used in combination with a dispersant VI improver. 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 C1-C10 alkyl (meth) acrylates, nitrogen-containing 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 materially increase the polarity of the copolymers. In a preferred embodiment the sum of (A) and (B) equals 100%. Thus in a preferred embodiment the low polarity PPD polymers according to the invention do not contain C1-C10 alkyl (meth) acrylates, dispersant (meth) acrylates or other polymerizable non-alkyl (meth) acrylate monomers.
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 o
Jao Tze Chi
Li Shoutian
Liesen Gregory P.
Ethyl Corporation
Hamilton Thomas
McAvoy Ellen M.
Moore James T.
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