Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1998-07-16
2001-12-18
Henderson, Christopher (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S264000, C526S265000, C526S307700, C526S312000
Reexamination Certificate
active
06331603
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to dispersant-viscosity improvers for lubricating oils, oil compositions and concentrates containing such dispersant-viscosity improvers, and a process for preparing such dispersant-viscosity improvers.
BACKGROUND OF THE INVENTION
The viscosity of oils of lubricating viscosity is generally dependent upon temperature. As the temperature of the oil is increased, the viscosity usually decreases, and as the temperature is reduced, the viscosity usually increases.
The function of a viscosity improver is to reduce the extent of the decrease in viscosity as the temperature is raised or to reduce the extent of the increase in viscosity as the temperature is lowered, or both. Thus, a viscosity improver ameliorates the change of viscosity of an oil containing it with changes in temperature. The fluidity characteristics of the oil are improved.
Viscosity improvers are usually polymeric materials and are often referred to as viscosity index improvers.
Ester group containing polymers are well-known additives for improving the fluidity characteristic of lubricating oils. Polyacrylate, particularly polymethacrylate ester polymers are well-known and are widely used for this purpose.
Dispersants are also well-known in the lubricating art. Dispersants are employed in lubricants to keep impurities, particularly those formed during operation of machinery, in suspension rather than allowing them to deposit on the surfaces of lubricated parts.
Multifunctional additives that provide both viscosity improving properties and dispersant properties are likewise known in the art. Such products are described in numerous publications including Dieter Klamann, “Lubricants and Related Products”, Verlag Chemie Gmbh (1984), pp. 185-193; C. V. Smalheer and R. K. Smith “Lubricant Additives”, Lezius-Hiles Co. (1967); M. W. Ranney, “Lubricant Additives”, Noyes Data Corp. (1973), pp. 92-145, M. W. Ranney, “Lubricant Additives, Recent Developments”, Noyes Data Corp. (1978), pp. 139-164; and M. W. Ranney, “Synthetic Oils and Additives for Lubricants”, Noyes Data Corp. (1980), pp. 96-166. Each of these publications is hereby expressly incorporated herein by reference.
Derivatives of polyacrylate esters are well-known as additives for lubricants that provide not only improved viscosity characteristics, but also may enhance dispersant properties of lubricants.
It is desirable that the viscosity improver or dispersant viscosity improver not adversely affect the low-temperature viscosity of the lubricant containing same. Frequently, while viscosity improvers or dispersant viscosity improvers enhance the high temperature viscosity characteristics of lubricating oil, that is, they reduce the loss of viscosity with increasing temperature, low temperature properties of the treated lubricant become worse.
One of the major requirements for automatic transmission fluids has been improved low temperature performance. This is demonstrated by requirements for maximum Brookfield viscosities of 50,000, 20,000, or even 10,000 centipoise at −40° C. The viscosity modifier, which can comprise nearly 50 weight percent and sometimes even more of the total additive system employed in an automatic transmission fluid can have a major impact on the low temperature performance. Such characteristics are also desirable in other applications such as in gear lubricants and manual transmission fluids. The copolymers of this invention are also useful in many other lubricating oil compositions including, but not limited to engine oils, hydraulic oils, industrial oils, etc.
Accordingly, it is desirable to provide compositions that reduce the extent of loss of viscosity at high temperatures while not adversely increasing the low temperature viscosity of lubricating oil compositions.
It is a primary object of this invention to provide novel multi-purpose lubricant additives.
A more specific object is to provide multi-purpose additives directed to improving the viscosity and dispersant properties of a lubricating composition.
A further object is to provide processes for preparing such multi-purpose additives.
Still another object is to provide additive concentrates containing the novel multi-purpose lubricant additives of this invention.
Yet another object is to provide lubricants having improved dispersant and viscosity properties.
Other objects will in part be obvious in view of this disclosure and will in part appear hereinafter.
SUMMARY OF THE INVENTION
The present invention is directed to a process for preparing a nitrogen containing copolymer comprising reacting, in the presence of a free radical initiator,
(A) from about 55% to about 99.9% by weight of one or more alkyl acrylate ester monomers containing from 1 to about 24 carbon atoms in the ester alkyl group, wherein at least about 50 mole % of the esters contain at least 6 carbon atoms in the ester alkyl group, and
(B) from about 0.1% to about 45% by weight of at least one nitrogen containing monomer selected from the group consisting of vinyl substituted nitrogen heterocyclic monomers, dialkylaminoalkyl acrylate monomers, dialkylaminoalkyl acrylamide monomers, N-tertiary alkyl acrylamides, and vinyl substituted amines provided that the total of (A) and (B) equals 100%, and optionally, in the presence of a chain transfer agent,
wherein monomer (A), the free radical initiator, and if used, the chain transfer agent, are first combined to form a mixture, whereupon from about 10% to about 80% of said mixture is mixed with monomer (B);
from about 20% to about 100% of the mixture of monomers (A) and (B) is heated until an exotherm is noted, then while maintaining reaction temperature, first adding the balance, if any, of the mixture of monomers (A) and (B), over about 0.25 hour to about 5 hours followed by addition over 0.25 to about 5 hours of the remaining mixture of monomer (A) and initiator, optionally adding additional initiator, whereupon the reaction is continued to completion.
This invention also relates to a polyacrylate ester, and more particularly a polymethacrylate ester based dispersant-viscosity improver for lubricating oil compositions. Specifically, the dispersant viscosity improvers of this invention are nitrogen-containing copolymers.
The present invention also relates to additive concentrates and lubricating oil compositions containing compositions prepared by the process of this invention.
As used herein, the terms “acrylate” and “acrylamide” include the 2-alkyl acrylates and 2-alkyl acrylamides, particularly C
1-4
alkyl-, and especially, methacrylates and methacrylamides.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention provides a process for preparing a composition of matter suitable for use as a dispersant-viscosity improver for lubricating oil compositions comprising nitrogen-containing copolymers derived from one or more alkyl acrylate ester monomers containing, from 1 to about 24 carbon atoms in the ester alkyl group and at least one nitrogen-containing monomer as described in greater detail hereinbelow.
As used herein, the terms “hydrocarbon”, “hydrocarbyl” or “hydrocarbon based” mean that the group being described has predominantly hydrocarbon character within the context of this invention. These include groups that are purely hydrocarbon in nature, that is, they contain only carbon and hydrogen. They may also include groups containing substituents or atoms which do not alter the predominantly hydrocarbon character of the group. Such substituents may include halo-, alkoxy-, nitro-, etc. These groups also may contain hetero atoms. Suitable hetero atoms will be apparent to those skilled in the art and include, for example, sulfur, nitrogen and oxygen. Therefore, while remaining predominantly hydrocarbon in character within the context of this invention, these groups may contain atoms other than carbon present in a chain or ring otherwise composed of carbon atoms.
In general, no more than about three non-hydrocarbon substituents or hetero atoms, and preferably no more than one, will be present for ever
Bryant Charles P.
Sivik Matthew R.
Fischer Joseph P.
Henderson Christopher
The Lubrizol Corporation
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