Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-11-30
2002-06-11
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S318200, C526S318000, C526S317100, C526S328000, C526S328500, C526S090000, C526S095000
Reexamination Certificate
active
06403745
ABSTRACT:
This invention concerns gradient copolymers, concentrates and lubricant oils that contain these copolymers, method for preparation of these copolymers as well as their use as pour point depressants.
Lubricants, especially mineral oils obtained from petroleum by distillation, for example, contain as a rule long-chain n-alkanes, which on the one hand bring about good viscosity/temperature behavior, but on the other hand precipitate out in crystalline form upon cooling and in this way have an adverse effect on the flow of the oil or completely prevent (“plug”) it. An improvement of low temperature flow properties can be achieved, for example, by dewaxing. However, costs rise considerably if complete dewaxing is supposed to be achieved. For this reason a pour point up to a range of approximately −15° C. is achieved by partial dewaxing, and this pour point can be further lowered by the addition of the so-called pour point depressants or pour point improvers. These agents can effectively reduce the pour point even in concentrations of 0.01-1 wt %.
However, the mode of action of these compounds has not yet been completely clarified. In any case it is assumed that paraffin-like compounds become incorporated into the growing paraffin crystal surfaces and so stop further crystallization and in particular the formation of extended crystal structures.
Certain structural elements are known to have pour point depressant activity. In particular, polymers with sufficiently long alkyl side chains exhibit a pour point and flow improving effect. Here it is assumed that these alkyl groups become incorporated into the growing paraffin crystals and disrupt crystal growth (see Ullmann's Encyclopedia of Industrial Chemistry, 4
th
Edition, Vol. 20, Verlag Chemie, 1981, p. 548). On top of that, it is required of industrially usable pour point depressants that they have good thermal, oxidative and chemical stability, shear strength, etc. Moreover, it should be possible to produce the pour point and flow improvers on a cost favorable basis, since they are used in large quantities.
Polymethacrylates with long chain alkyl residues are used to a wide extent as pour point depressants. These compounds are described, for example, in U.S. Pat. No. 2,091,627, U.S. Pat. No. 2,100,993, U.S. Pat. No. 2,114,233 and EP-A-0 236 844. In general, these pour point depressants are produced by radical polymerization. Accordingly, they can be produced on a cost favorable basis.
EP-A-0 861 859 is cited as the closest prior art. It has been established that different pour point depressants have different performances in different lubricant oils. However, if the composition is varied over the reaction time of polymerization, one obtains additives that have high efficiency in very many mineral oils. By this method mixtures of statistical copolymers are produced, since the composition of the monomer mixture remains constant during the lifetime of the radicals (about 1 second).
The low temperature properties, which follow for example from the pour points in accordance with ASTM D-97, the minirotary viscosimetry test values in accordance with ASTM D-4684 or the scanning Brookfield results in accordance with ASTM D-5133, are usable for many applications, but all the same the low temperature properties are still not sufficient for many applications.
Here one should take into account that more effective additives could be added in a smaller quantity in order to achieve a desired flow property at low temperatures. With the amounts of lubricants and diesel biofuels that are used there would be a considerable potential for savings even with relatively small differences.
Taking into consideration the prior art, it is now a task of this invention to make available additives through which improved flow properties of lubricants and diesel biofuels at low temperatures can be achieved, compared to the traditional additives. In addition, a task of the invention was to make available additives that have high stability with respect to oxidation and thermal stress as well as high shear strength. At the same time, the new additives are supposed to be produceable in a simple and cost favorable way.
These as well as other not explicitly mentioned tasks, which, however, can easily be derived or developed from the introductory material, are solved by gradient polymers with all of the characteristics of Claim
1
. Expedient modifications of the copolymers in accordance with the invention are provided protection in the claims that refer back to Claim
1
. With regard to the concentrate as lubricant additive, Claim
6
provides the solution of the underlying task, while claims
8
and
10
protect lubricants or diesel biofuels that contain the polymers in accordance with the invention. Claim
12
represent a solution of the problem with respect to the method for preparation of gradient copolymers and their use.
Gradient copolymers that have high efficiency as pour point depressants or flow improvers are obtained by polymerizing a mixture of olefinically unsaturated monomers consisting of
a) 0 to 40 wt % of one or more ethylenically unsaturated ester compounds of formula (I)
where R is hydrogen or methyl, R
1
means a linear or branched alkyl residue with 1 to 5 carbon atoms, R
2
and R
3
independently represent hydrogen or a group of the formula —COOR′, where R′ means hydrogen or an alkyl group with 1 to 5 carbon atoms,
b) 10 to 98 wt % of one or more ethylenically unsaturated ester compounds of formula (II)
where R is hydrogen or methyl, R
4
means a linear or branched alkyl-residue with 6 to 15 carbon atoms, R
5
and R
6
independently are hydrogen or a group of the formula —COOR″, where R″ means hydrogen or an alkyl group with 6 to 15 carbon atoms,
c) 0 to 80 wt % of one or more ethylenically unsaturated ester compounds of formula (III)
where R is hydrogen or methyl, R
7
means a linear or branched alkyl residue with 16 to 30 carbon atoms, R
8
and R
9
independently are hydrogen or a group of the formula —COOR′″ where R′″ means hydrogen or an alkyl group with 16 to 30 carbon atoms,
d) 0 to 50 wt % comonomer,
where the mixture of ethylenically unsaturated monomers is varied during chain growth. The pour point depressant effect can be determined, for example, in accordance with ASTM D 97.
Moreover, lubricants that contain the gradient copolymers in accordance with the invention produce excellent minirotary viscosimetry values (MRV), which can be found in accordance with ASTM D 4684, and scanning Brookfield results, as are obtained in accordance with ASTM D 5133.
Diesel biofuels, which contains gradient copolymers of the present invention, exhibit exceptional results in cold filter plugging point measurements by IP 309 or low temperature flow tests in accordance with ASTM D 4539. If certain flow properties at a given temperature are supposed to be achieved, the amount of additive can be reduced through this invention.
At the same time a number of other advantages can be achieved through the copolymers in accordance with the invention. Among these are:
The copolymers of this invention are characterized by a narrow molecular weight distribution. A high stability toward shearing effects is achieved through this.
The gradient copolymers in accordance with the invention can be produced on a cost favorable basis.
The copolymers exhibit high resistance to oxidation and are chemically very stable.
The gradient copolymers exhibit excellent efficiency in many different mineral oils or diesel biofuels.
Gradient copolymers designate copolymers that have a gradient. Copolymers are substantially known and indicate polymers that are obtained by polymerization of two or more different monomers.
The term “gradient” refers to the distribution of the monomer units, also called repeating units, along the main chain of the copolymer. Here the concentration of at least one monomer unit is higher at one end of the polymer chain than at the other. If the main chain is divided into 10 equal segments, the concentra
Bollinger Joseph Martin
Scherer Markus
Souchik Joan
Cheung William K
RohMax Additives GmbH
Wu David W.
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