U.S. patent application number 13/991702 was filed with the patent office on 2013-09-26 for copolymers comprising ester groups and use thereof in lubricants.
This patent application is currently assigned to Evonik Oil Additives GmbH. The applicant listed for this patent is Boris Eisenberg, Torsten Stoehr, Ellen Suchert. Invention is credited to Boris Eisenberg, Torsten Stoehr, Ellen Suchert.
Application Number | 20130252866 13/991702 |
Document ID | / |
Family ID | 45614831 |
Filed Date | 2013-09-26 |
United States Patent
Application |
20130252866 |
Kind Code |
A1 |
Stoehr; Torsten ; et
al. |
September 26, 2013 |
COPOLYMERS COMPRISING ESTER GROUPS AND USE THEREOF IN
LUBRICANTS
Abstract
The present invention relates to copolymers comprising ester
groups and having at least one nonpolar segment P and at least one
polar segment D, the polar segment D having at least 8 repeat units
and the proportion by weight of dispersing repeat units in the
polar segment D being at least 30%, based on the weight of the
polar segment D, wherein the copolymer comprising ester groups is
obtainable by NMP (nitroxide mediated polymerization). The
invention further relates to lubricant oils having improved
friction properties and comprising said copolymers.
Inventors: |
Stoehr; Torsten; (Frankfurt,
DE) ; Eisenberg; Boris; (Heppenheim, DE) ;
Suchert; Ellen; (Bensheim, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Stoehr; Torsten
Eisenberg; Boris
Suchert; Ellen |
Frankfurt
Heppenheim
Bensheim |
|
DE
DE
DE |
|
|
Assignee: |
Evonik Oil Additives GmbH
Darmstadt
DE
|
Family ID: |
45614831 |
Appl. No.: |
13/991702 |
Filed: |
February 9, 2012 |
PCT Filed: |
February 9, 2012 |
PCT NO: |
PCT/EP12/52177 |
371 Date: |
June 5, 2013 |
Current U.S.
Class: |
508/471 ;
508/469; 526/302; 526/320; 526/329.2 |
Current CPC
Class: |
C10M 145/14 20130101;
C10M 2205/04 20130101; C10M 2209/086 20130101; C10N 2030/06
20130101; C10M 2203/1025 20130101; C10M 145/10 20130101; C10M
2217/024 20130101; C10N 2030/56 20200501; C10M 2221/02 20130101;
C10N 2030/04 20130101; C08F 2/38 20130101; C08F 2438/02 20130101;
C10M 2217/023 20130101; C10M 2209/084 20130101; C10M 2217/028
20130101; C10M 149/02 20130101; C10M 2203/1025 20130101; C10N
2020/02 20130101; C10M 2205/04 20130101; C10M 2209/084 20130101;
C10M 2203/1025 20130101; C10N 2020/02 20130101 |
Class at
Publication: |
508/471 ;
526/329.2; 526/302; 526/320; 508/469 |
International
Class: |
C10M 145/14 20060101
C10M145/14; C10M 149/02 20060101 C10M149/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 14, 2011 |
DE |
10 2011 005 493.6 |
Claims
1. A copolymer, comprising: an ester group, a nonpolar segment P,
and a polar segment D, wherein the polar segment D comprises at
least 8 repeat units, a proportion by weight of dispersing repeat
units in the polar segment D is at least 30%, based on a weight of
the polar segment D, and the copolymer is obtained via a nitroxide
mediated polymerization.
2. The copolymer according to claim 1, wherein the copolymer is
obtained via a multistage polymerization comprising a first stage
and a last stage, with the nonpolar segment P prepared in the first
stage and the polar segment D prepared in the last stage.
3. The copolymer according to claim 1, wherein a transferrable
nitroxyl radical compound in the nitroxide mediated polymerization
comprises a phosphorus atom.
4. The copolymer according to claim 2, wherein a transferrable
nitroxyl radical compound in the multistage polymerization
comprises a phosphorus atom, and the transferrable nitroxyl radical
compound is attached to an end of the polar segment D.
5. The copolymer according to claim 1, wherein the copolymer
comprises repeat units derived from styrene and methacrylate.
6. The copolymer according to claim 5, wherein a proportion of the
repeat units derived from styrene is of from 0.5 to 10% by
weight.
7. The copolymer according to claim 1, wherein a weight ratio of
the nonpolar segments P to the polar segments D is of from 100:1 to
1:1.
8. The copolymer according to claim 1, wherein the nonpolar segment
P is obtained by a process comprising: polymerizing a monomer
composition comprising, based on a total weight of the monomer
composition: a) 0 to 40% by weight of one or more ethylenically
unsaturated ester compounds of formula (I) ##STR00020## b) 5 to
100% by weight of one or more ethylenically unsaturated ester
compounds of formula (II) ##STR00021## c) 0 to 80% by weight of one
or more ethylenically unsaturated ester compounds of formula (III)
##STR00022## and d) 0 to 50% by weight of a comonomer, wherein: R
is hydrogen or methyl, R.sup.1 is a linear or branched alkyl
radical comprising 1 to 6 carbon atoms, R.sup.2 and R.sup.3 are
each independently hydrogen or a --COOR' group, wherein R' is
hydrogen or an alkyl group comprising 1 to 6 carbon atoms, R.sup.4
is a linear or branched alkyl radical comprising 7 to 15 carbon
atoms, R.sup.5 and R.sup.6 are each independently hydrogen or a
--COOR'' group, wherein R'' is hydrogen or an alkyl group
comprising 7 to 15 carbon atoms, R.sup.7 is a linear or branched
alkyl radical comprising 16 to 30 carbon atoms, and R.sup.8 and
R.sup.9 are each independently hydrogen or a --COOR''' group,
wherein R''' is hydrogen or an alkyl group comprising 16 to 30
carbon atoms.
9. The copolymer according to claim 1, wherein the dispersing
repeat units are derived from one or more ethylenically
unsaturated, polar ester compounds of formula (IV) ##STR00023##
wherein R is hydrogen or methyl, X is oxygen, sulfur or an amino
group of --NH-- or --NR.sup.a--, wherein R.sup.a is an alkyl
radical comprising 1 to 40 carbon atoms, R.sup.10 is a radical
comprising 2 to 1000 carbon atoms and at least one heteroatom, and
R.sup.11 and R.sup.12 are each independently hydrogen or a
--COX'R.sup.10' group, wherein X' is oxygen or an amino group of
--NH-- or --NR.sup.a'--, wherein R.sup.a' is an alkyl radical
comprising 1 to 40 carbon atoms, and R.sup.10' is a radical
comprising 1 to 100 carbon atoms and optionally from a heterocyclic
vinyl compound.
10. The copolymer according to claim 9, wherein R.sup.10 comprises
a --CO-- group.
11. The copolymer according to claim 10, wherein R.sup.10 comprises
at least two --CO-- groups.
12. The copolymer according to claim 11, wherein the at least two
CO-- groups are bonded to one another via atoms of not more than
four.
13. The copolymer according to claim 1, wherein the dispersing
repeat units in the polar segment D are derived from
2-acetoacetoxyethyl (meth)acrylate.
14. A lubricant, comprising the copolymer according to claim 1.
15. The lubricant according to claim 14, further comprising at
least 10% by weight of group III oil.
16. A method for improving a coefficient of friction of a
lubricant, the method comprising: including the copolymer according
to claim 1 in a lubricant in need thereof.
17. The method according to claim 16, wherein the coefficient of
friction is improved in a boundary lubrication range.
18. The method according to claim 16, wherein the coefficient of
friction determined by a high frequency reciprocating rig value is
improved.
19. A method for reducing wear, the method comprising: employing
the copolymer according to claim 1.
Description
[0001] The present invention relates to copolymers comprising ester
groups and to lubricants comprising these copolymers. The present
invention further describes the use of copolymers comprising ester
groups for improving the friction properties of lubricants.
[0002] For reasons of fuel economy, a task being addressed in
modern research is that of reducing churning loss and internal
friction of oils to an ever greater degree. As a result, there has
been a trend in the last few years toward ever lower viscosities of
the oils used and hence ever thinner lubricant films, especially at
high temperatures. Accordingly, there is a constant search for
solutions which compensate for the associated disadvantages.
[0003] WO 2004/087850 (Evonik RohMax) describes the film-forming,
friction-reducing effect of PAMA block polymers in lubricant oils,
for example block polymers based on 2-(4-morpholinyl)ethyl
methacrylate MoEMA or based on 2-hydroxyethyl methacrylate
(HEMA).
[0004] WO 2006/105926 (Evonik RohMax) describes a group of new
monomers, for example 2-acetoacetoxyethyl methacrylate (AcAcEMA)
and N-(2-methacryloyloxyethyl)ethyleneurea (EUMA; ethylene urea
methacrylate), and the random and block copolymers derived
therefrom and the use thereof in lubricant oils.
[0005] WO 2009/019065 (Evonik RohMax) describes sequential block or
graft polymers having film-forming properties for use as an
antifatigue additive.
[0006] Two Arkema documents describe block polymers which are
obtainable via NMP (nitroxide mediated polymerization) and the use
thereof in lubricant oils. WO 2005/056739 describes use as
viscosity index improvers, while EP 1 696 020 describes use as pour
point improvers. Similarly to the latter document, WO 2009/077396
(Ciba) describes block polymers obtainable via NMP for use as
biodiesel flow improvers.
[0007] The above-detailed polymers already lead to a significant
improvement in the friction properties of lubricant oils. However,
there is a constant need to improve the profile of properties of
lubricants, especially lubricant oils.
[0008] In view of the prior art, it is thus an object of the
present invention to provide an additive or a lubricant, preferably
a lubricant oil, having an improved profile of properties.
[0009] For example, the intention was to provide high-efficacy
additives which lead to a significant improvement in the
coefficient of friction of lubricants, especially lubricant
oils.
[0010] In this context, this improvement is to be achieved under
different conditions, more particularly also within the range of
boundary lubrication or boundary friction, in which the surfaces
are effectively in real contact, meaning that the separation of the
surfaces is lower than the surface roughness thereof--a state which
is attained especially at low speeds, low viscosities and/or high
stresses. Such a state exists, for example, on piston changeover in
the engine, and is simulated inter alia by the high frequency
reciprocating rig (HFRR) test. On this topic, see also: B. J.
Hamrock; B. O. Jacobson; S. R. Schmid: Fundamentals of Fluid Film
Lubrication, Marcel Dekker, New York, 2.sup.nd Ed., 2004.
[0011] Moreover, the additives were to be particularly inexpensive
to produce. It was therefore a further object of the present
invention to provide additives which have high dispersibility, high
corrosion protection (i.e. a high level of metal deactivator
properties), high stability against oxidation and thermal stress,
and high shear strength. In addition, the additives were also to be
soluble in large amounts even in very nonpolar lubricant oils, for
example in fully synthetic oils. It was a further object of the
present invention to provide additives which, as well as
friction-reducing action, additionally improve the flow properties
of the lubricant oil, i.e. have a viscosity index-improving action.
Moreover, the additives were to exhibit efficacy as an antiwear
additive and/or as an antifatigue additive.
[0012] A distinction is made here between two groups of defects on
the metallic surfaces of transmission systems, especially on
gearings and roller bearings:
[0013] 1. Wear resulting from continuous surface material removal
or scuffing as a result of abrupt material removal after surface
wear of both friction partners.
[0014] 2. Fatigue which becomes visible through gray staining
(surface fatigue, micro-pitting) or craters (sub-surface fatigue,
pitting). This damage is caused by flaking-off or breaking-out of
material owing to cracks, which are caused 20-40 .mu.m or 100-500
.mu.m below the surface by shear stresses in the metal lattice.
[0015] These objects, and further objects which are not stated
explicitly but are immediately derivable or discernible from the
connections discussed herein by way of introduction, are achieved
by copolymers having all the features of claim 1. Appropriate
modifications of the inventive copolymers are protected in the
claims referring back to claim 1.
[0016] The present invention accordingly provides a copolymer
comprising ester groups and having at least one nonpolar segment P
and at least one polar segment D, the polar segment D having at
least 8 repeat units and the proportion by weight of dispersing
repeat units in the polar segment D being at least 30%, based on
the weight of the polar segment D, which is characterized in that
the copolymer comprising ester groups is obtainable by NMP
(nitroxide mediated polymerization).
[0017] It is thus possible in an unforeseeable manner to provide an
additive for lubricants, especially lubricant oils, which exhibit a
particularly favorable profile of properties. For instance, the
inventive copolymers lead to lubricant oils having outstanding
friction properties. This improvement can surprisingly be achieved
over a wide frequency range. As a result, these copolymers protect
surfaces from wear.
[0018] Moreover, the use of the present copolymers can give a
reduction in material fatigue (antifatigue additive). At the same
time, these additives achieve a decrease in the above-detailed
formation of gray staining (surface fatigue, micro-pitting) or
craters (sub-surface fatigue, pitting).
[0019] Furthermore, these additives can be prepared in a simple and
inexpensive manner, and it is possible to use commercially
available components in particular. At the same time, production is
possible on the industrial scale, without new plants or plants of
complex construction being required for that purpose.
[0020] For instance, the polymers can be configured so as to be
surprisingly shear-stable, such that the lubricants have a very
long service life. In addition, the additive for use in accordance
with the invention may bring about a multitude of desirable
properties in the lubricant. For example, it is possible to produce
lubricants with outstanding low-temperature properties or viscosity
properties, which comprise the present polymers comprising ester
groups. This allows the number of different additives to be
minimized. Furthermore, the present polymers comprising ester
groups are compatible with many additives. This allows the
lubricants to be adjusted to a wide variety of different
requirements.
[0021] The copolymers of the present invention exhibit excellent
dispersion properties. As a result, these copolymers prevent any
formation of deposits. The copolymers provide excellent
anticorrosion properties, i.e. metal deactivator properties. The
inventive copolymers have excellent binding of metal ions. This
reduces premature oxidation of lubricant oils.
[0022] Furthermore, the additives for use do not exhibit any
adverse effects on fuel consumption or the environmental
compatibility of the lubricant.
[0023] Polymers comprising ester groups are understood in the
context of the present invention to mean polymers obtainable by
polymerizing monomer compositions which comprise ethylenically
unsaturated compounds having at least one ester group, which are
referred to hereinafter as ester monomers. Accordingly, these
polymers contain ester groups as part of the side chain. These
polymers include especially polyalkyl (meth)acrylates (PAMA),
polyalkyl fumarates and/or polyalkyl maleates.
[0024] Ester monomers are known per se. They include especially
(meth)acrylates, maleates and fumarates, which may have different
alcohol radicals. The expression "(meth)acrylates" encompasses
methacrylates and acrylates, and mixtures of the two. These
monomers are widely known.
[0025] The polymer comprising ester groups comprises preferably at
least 40% by weight, more preferably at least 60% by weight,
especially preferably at least 80% by weight and most preferably at
least 90% by weight of repeat units derived from ester
monomers.
[0026] Inventive copolymers comprise at least one nonpolar segment
P and at least one polar segment D, said polar segment D having at
least 8 repeat units and the proportion by weight of dispersing
repeat units in the polar segment D being at least 30%, based on
the weight of the polar segment D.
[0027] The term "repeat unit" is widely known in the technical
field. The present polymers are obtained by means of free-radical
polymerization of monomers by the NMP process. This opens up double
bonds to form covalent bonds. Accordingly, the repeat unit arises
from the monomers used.
[0028] The inventive polymers have polar and nonpolar segments. The
term "segment" in this context denotes a section of the polymer.
The segments may have an essentially constant composition composed
of one or more monomer units. In addition, the segments may have a
gradient, in which case the concentration of different monomer
units (repeat units) varies over the segment length. The polar
segments D differ from the nonpolar segments P via the proportion
of dispersing monomers. The nonpolar segments may have at most a
small proportion of dispersing repeat units (monomer units),
whereas the polar segments comprise a high proportion of dispersing
repeat units (monomer units).
[0029] Dispersing monomers are understood to mean especially
monomers with functional groups, for which it can be assumed that
polymers with these functional groups can keep particles,
especially soot particles, in solution (cf. R. M. Mortier, S. T.
Orszulik (eds.): "Chemistry and Technology of Lubricants", Blackie
Academic & Professional, London, 2.sup.nd ed. 1997). These
include especially monomers which have boron-, phosphorus-,
silicon-, sulfur-, oxygen- and nitrogen-containing groups,
preference being given to oxygen- and nitrogen-functionalized
monomers.
[0030] The polar segments D comprise, in accordance with the
invention, at least 8, preferably at least 12 and most preferably
at least 15 repeat units. At the same time, the polar segments D
comprise at least 30% by weight, preferably at least 40% by weight,
of dispersing repeat units, based on the weight of the polar
segment D. In addition to the dispersing repeat units, the polar
segment may also have repeat units which do not have any dispersing
effect. The polar segment may have a random structure, such that
the different repeat units have a random distribution over the
segment length. In addition, the polar segment may have a block
structure or a structure in the form of a gradient, such that the
non-dispersing repeat units and the dispersing repeat units within
the polar segment have an inhomogeneous distribution.
[0031] The nonpolar hydrophobic segment P may comprise a small
proportion of dispersing repeat units, which is preferably less
than 20% by weight, more preferably less than 10% by weight and
most preferably less than 5% by weight, based on the weight of the
nonpolar segment P. In a particularly appropriate configuration,
the nonpolar segment P comprises essentially no dispersing repeat
units.
[0032] The nonpolar segment P of the polymer comprising ester
groups may have 5 to 100% by weight, especially 20 to 98% by
weight, preferably 30 to 95 and most preferably 70 to 92% by weight
of repeat units derived from ester monomers having 7 to 15 carbon
atoms in the alcohol radical.
[0033] In a particular aspect, the nonpolar segment P of the
polymer comprising ester groups may have 0 to 80% by weight,
preferably 0.5 to 60% by weight, more preferably 2 to 50% by weight
and most preferably 5 to 20% by weight of repeat units derived from
ester monomers having 16 to 40 carbon atoms in the alcohol
radical.
[0034] In addition, the nonpolar segment P of the polymer
comprising ester groups may have 0 to 40% by weight, preferably 0.1
to 30% by weight and more preferably 0.5 to 20% by weight of repeat
units derived from ester monomers having 1 to 6 carbon atoms in the
alcohol radical.
[0035] The nonpolar segment P of the polymer comprising ester
groups comprises preferably at least 40% by weight, more preferably
at least 60% by weight, especially preferably at least 80% by
weight and most preferably at least 90% by weight of repeat units
derived from ester monomers.
[0036] Mixtures from which the nonpolar segments P of the inventive
polymers comprising ester groups are obtainable may contain 0 to
40% by weight, especially 0.1 to 30% by weight and more preferably
0.5 to 20% by weight of one or more ethylenically unsaturated ester
compounds of the formula (I)
##STR00001##
in which R is hydrogen or methyl, R.sup.1 is a linear or branched
alkyl radical having 1 to 6 carbon atoms, R.sup.2 and R.sup.3 are
each independently hydrogen or a group of the formula --COOR' in
which R' is hydrogen or an alkyl group having 1 to 6 carbon
atoms.
[0037] Examples of component (I) include
(meth)acrylates, fumarates and maleates which derive from saturated
alcohols, such as methyl (meth)acrylate, ethyl (meth)acrylate,
n-propyl (meth)acrylate, iso-propyl (meth)acrylate, n-butyl
(meth)acrylate, tert-butyl (meth)acrylate and pentyl
(meth)acrylate, hexyl (meth)acrylate; cycloalkyl (meth)acrylates
such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate;
(meth)acrylates which derive from unsaturated alcohols, such as
2-propynyl (meth)acrylate, allyl (meth)acrylate and vinyl
(meth)acrylate.
[0038] The compositions to be polymerized to prepare the nonpolar
segments P preferably contain 5 to 100% by weight, preferably 10 to
98% by weight and especially preferably 20 to 95% by weight of one
or more ethylenically unsaturated ester compounds of the formula
(II)
##STR00002##
in which R is hydrogen or methyl, R.sup.4 is a linear or branched
alkyl radical having 7 to 15 carbon atoms, R.sup.5 and R.sup.6 are
each independently hydrogen or a group of the formula --COOR'' in
which R'' is hydrogen or an alkyl group having 7 to 15 carbon
atoms.
[0039] Examples of component (II) include:
(meth)acrylates, fumarates and maleates which derive from saturated
alcohols, such as 2-ethylhexyl (meth)acrylate, heptyl
(meth)acrylate, 2-tert-butylheptyl (meth)acrylate, octyl
(meth)acrylate, 3-isopropylheptyl (meth)acrylate, nonyl
(meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate,
5-methylundecyl (meth)acrylate, dodecyl (meth)acrylate,
2-methyldodecyl (meth)acrylate, tridecyl (meth)acrylate,
5-methyltridecyl (meth)acrylate, tetradecyl (meth)acrylate,
pentadecyl (meth)acrylate; (meth)acrylates which derive from
unsaturated alcohols, for example oleyl (meth)acrylate; cycloalkyl
(meth)acrylates, such as 3-vinylcyclohexyl (meth)acrylate, bornyl
(meth)acrylate; and the corresponding fumarates and maleates.
[0040] In addition, preferred monomer compositions for preparing
the nonpolar segments P comprise 0 to 80% by weight, preferably 0.5
to 60% by weight, more preferably 2 to 50% by weight and most
preferably 5 to 20% by weight of one or more ethylenically
unsaturated ester compounds of the formula (III)
##STR00003##
in which R is hydrogen or methyl, R.sup.7 is a linear or branched
alkyl radical having 16 to 40, preferably 16 to 30, carbon atoms,
R.sup.8 and R.sup.9 are each independently hydrogen or a group of
the formula --COOR''' in which R''' is hydrogen or an alkyl group
having 16 to 40, preferably 16 to 30, carbon atoms.
[0041] Examples of component (III) include (meth)acrylates which
derive from saturated alcohols, such as hexadecyl (meth)acrylate,
2-methylhexadecyl (meth)acrylate, heptadecyl (meth)acrylate,
5-isopropylheptadecyl (meth)acrylate, 4-tert-butyloctadecyl
(meth)acrylate, 5-ethyloctadecyl (meth)acrylate,
3-isopropyloctadecyl (meth)acrylate, octadecyl (meth)acrylate,
nonadecyl (meth)acrylate, eicosyl (meth)acrylate, cetyleicosyl
(meth)acrylate, stearyleicosyl (meth)acrylate, docosyl
(meth)acrylate and/or eicosyltetratriacontyl (meth)acrylate;
cycloalkyl (meth)acrylates such as
2,4,5-tri-t-butyl-3-vinylcyclohexyl (meth)acrylate,
2,3,4,5-tetra-t-butylcyclohexyl (meth)acrylate; and the
corresponding fumarates and maleates.
[0042] The ester compounds with a long-chain alcohol radical,
especially components (II) and (III), can be obtained, for example,
by reacting (meth)acrylates, fumarates, maleates and/or the
corresponding acids with long-chain fatty alcohols, which generally
gives a mixture of esters, for example (meth)acrylates with
different long-chain alcohol radicals. These fatty alcohols include
Oxo Alcohol.RTM. 7911, Oxo Alcohol.RTM. 7900, Oxo Alcohol.RTM.
1100; Alfol.RTM. 610, Alfol.RTM. 810, Lial.RTM. 125 and Nafol.RTM.
types (Sasol); Alphanol.RTM. 79 (ICI); Epal.RTM. 610 and Epal.RTM.
810 (Afton); Linevol.RTM. 79, Linevol.RTM. 911 and Neodol.RTM. 25E
(Shell); Dehydad.RTM., Hydrenol.RTM. and Lorol.RTM. types (Cognis);
Acropol.RTM. 35 and Exxal.RTM. 10 (Exxon Chemicals); Kalcol.RTM.
2465 (Kao Chemicals).
[0043] Among the ethylenically unsaturated ester compounds, the
(meth)acrylates are particularly preferred over the maleates and
fumarates, i.e. R.sup.2, R.sup.3, R.sup.5, R.sup.6, R.sup.8 and
R.sup.9 of the formulae (I), (II) and (III) are each hydrogen in
particularly preferred embodiments.
[0044] If a mixture of ester monomers of formula (II) and ester
monomers of formula (III) is used to produce the inventive
copolymers, the weight ratio of ester monomers of the formula (II)
to the ester monomers of the formula (III) may be within a wide
range. The ratio of ester compounds of the formula (II) which have
7 to 15 carbon atoms in the alcohol radical to the ester compounds
of the formula (III) which have 16 to 40 carbon atoms in the
alcohol radical is preferably in the range from 50:1 to 1:30, more
preferably in the range from 10:1 to 1:3, especially preferably 5:1
to 1:1.
[0045] In addition, the monomer mixture for preparing the nonpolar
segments may comprise ethylenically unsaturated monomers which can
be copolymerized with the ethylenically unsaturated ester compounds
of the formulae (I), (II) and/or (III).
[0046] Particularly suitable comonomers for polymerization
according to the present invention are those which correspond to
the formula:
##STR00004##
in which R.sup.1* and R.sup.2* are each independently selected from
the group consisting of hydrogen, halogens, CN, linear or branched
alkyl groups having 1 to 20, preferably 1 to 6 and more preferably
1 to 4, carbon atoms, which may be substituted by 1 to (2n+1)
halogen atoms, where n is the number of carbon atoms of the alkyl
group (for example CF.sub.3), .alpha.,.beta.-unsaturated linear or
branched alkenyl or alkynyl groups having 2 to 10, preferably 2 to
6 and more preferably 2 to 4 carbon atoms, which may be substituted
by 1 to (2n-1) halogen atoms, preferably chlorine, where n is the
number of carbon atoms of the alkyl group, for example
CH.sub.2.dbd.CCl--, cycloalkyl groups having 3 to 8 carbon atoms,
which may be substituted by 1 to (2n-1) halogen atoms, preferably
chlorine, where n is the number of carbon atoms of the cycloalkyl
group; aromatic or heteroaromatic groups having 3 to 40, preferably
5 to 18, carbon atoms which may be substituted by the groups
detailed above, preferably alkyl groups having 1 to 6 carbon atoms
or halogens; C(.dbd.Y*)R.sup.5*, C(.dbd.Y*)NR.sup.6*R.sup.7*,
Y*C(.dbd.Y*)R.sup.5*, SOR.sup.5*, SO.sub.2R.sup.5*,
OSO.sub.2R.sup.5*, NR.sup.8*SO.sub.2R.sup.5*, PR.sup.5*.sub.2,
P(.dbd.Y*)R.sup.5*.sub.2, Y*PR.sup.5*.sub.2,
Y*P(.dbd.Y*)R.sup.5*.sub.2, NR.sup.8*.sub.2 which may be
quaternized with an additional R.sup.8*, aryl or heterocyclyl
group, where Y* may be NR.sup.8*, S or O, preferably O; R.sup.5* is
an alkyl group having 1 to 20 carbon atoms, an alkylthio having 1
to 20 carbon atoms, OR.sup.15 (R.sup.15 is hydrogen or an alkali
metal), alkoxy of 1 to 20 carbon atoms, aryloxy or heterocyclyloxy;
R.sup.6* and R.sup.7* are each independently hydrogen or an alkyl
group having 1 to 20 carbon atoms, or R.sup.6* and R.sup.7*
together may form an alkylene group having 2 to 7 and preferably 2
to 5 carbon atoms, in which case they form a 3- to 8-membered and
preferably 3- to 6-membered ring, and R.sup.8* is hydrogen, linear
or branched alkyl or aryl groups having 1 to 20 carbon atoms;
[0047] R.sup.3* and R.sup.4* are independently selected from the
group consisting of hydrogen, halogen (preferably fluorine or
chlorine), alkyl groups having 1 to 6 carbon atoms and COOR.sup.9*
in which R.sup.9* is hydrogen, an alkali metal or an alkyl group
having 1 to 40 carbon atoms, or R.sup.1* and R.sup.3* together may
form a group of the formula (CH.sub.2).sub.n* which may be
substituted by 1 to 2n' halogen atoms or C.sub.1 to C.sub.4 alkyl
groups, or form the formula C(.dbd.O)--Y*--C(.dbd.O) where n' is 2
to 6, preferably 3 or 4, and Y* is as defined above; and where at
least 2 of the R.sup.1*, R.sup.2*, R.sup.3* and R.sup.4* radicals
are hydrogen or halogen.
[0048] The preferred comonomers include
vinyl halides, for example vinyl chloride, vinyl fluoride,
vinylidene chloride and vinylidene fluoride; styrene monomers, for
example styrene, substituted styrenes having an alkyl substituent
in the side chain, for example .alpha.-methylstyrene and
.alpha.-ethylstyrene, substituted styrenes having an alkyl
substituent on the ring, such as vinyltoluene and p-methylstyrene,
halogenated styrenes, for example monochiorostyrenes,
dichlorostyrenes, tribromostyrenes and tetrabromostyrenes; vinyl
and isoprenyl ethers; maleic acid and maleic acid derivatives
different from those mentioned under (I), (II) and (III), for
example maleic anhydride, methylmaleic anhydride, maleimide,
methylmaleimide; fumaric acid and fumaric acid derivatives
different from those mentioned under (I), (II) and (III).
[0049] In addition, monomer mixtures for preparing the nonpolar
segments may comprise dispersing monomers.
[0050] The proportion of comonomers is preferably 0 to 50% by
weight, more preferably 0.1 to 40% by weight and most preferably
0.5 to 20% by weight, based on the weight of the monomer
composition for preparing the nonpolar segment P.
[0051] In a particularly preferred embodiment, the nonpolar segment
P comprises repeat units derived from methacrylates having
preferably 7 to 40, more preferably 10 to 30, carbon atoms in the
alkyl radical, and repeat units derived from styrene monomers. The
proportion of styrene monomers is preferably 0 to 40% by weight,
more preferably 0.1 to 20% by weight and most preferably 0.5 to 5%
by weight, based on the weight of the monomer composition for
preparation of the nonpolar segment P. The proportion of
methacrylates is preferably at least 60% by weight, more preferably
at least 80% by weight and most preferably at least 90% by weight,
based on the weight of the monomer composition for preparation of
the nonpolar segment P.
[0052] In a further embodiment, the nonpolar segment P comprises
repeat units derived from methacrylates having preferably 7 to 40,
more preferably 10 to 30, carbon atoms in the alkyl radical, and
repeat units derived from acrylates having preferably 7 to 40, more
preferably 10 to 30, carbon atoms in the alkyl radical. The
proportion of acrylates having preferably 7 to 40, more preferably
10 to 30, carbon atoms in the alkyl radical is preferably 0 to 40%
by weight, more preferably 0.1 to 20% by weight and most preferably
0.5 to 5% by weight, based on the weight of the monomer composition
for preparation of the nonpolar segment P. The proportion of
methacrylates is preferably at least 60% by weight, more preferably
at least 80% by weight and most preferably at least 90% by weight,
based on the weight of the monomer composition for preparation of
the nonpolar segment P.
[0053] In addition to the nonpolar segment P, a polymer usable in
accordance with the invention comprises at least one polar segment
D which comprises repeat units derived from dispersing
monomers.
[0054] Dispersing monomers have been used for some time for
functionalizing polymeric additives in lubricant oils, and are
therefore known to those skilled in the art (cf. R. M. Mortier, S.
T. Orszulik (eds.): "Chemistry and Technology of Lubricants",
Blackie Academic & Professional, London, 2.sup.nd ed. 1997).
Appropriately, it is possible to use especially heterocyclic vinyl
compounds and/or ethylenically unsaturated, polar ester compounds
of the formula (IV)
##STR00005##
in which R is hydrogen or methyl, X is oxygen, sulfur or an amino
group of the formula --NH-- or --NR.sup.a-- in which R.sup.a is an
alkyl radical having 1 to 40 and preferably 1 to 4 carbon atoms,
R.sup.10 is a radical which comprises 2 to 1000, especially 2 to
100 and preferably 2 to 20 carbon atoms and has at least one
heteroatom, preferably at least two heteroatoms, R.sup.11 and
R.sup.12 are each independently hydrogen or a group of the formula
--COX'R.sup.10' in which X' is oxygen or an amino group of the
formula --NH-- or --NR.sup.a'-- in which R.sup.a' is an alkyl
radical having 1 to 40 and preferably 1 to 4 carbon atoms, and
R.sup.10' is a radical comprising 1 to 100, preferably 1 to 30 and
more preferably 1 to 15 carbon atoms, as dispersing monomers.
[0055] The expression "radical comprising 2 to 1000 carbon" denotes
radicals of organic compounds having 2 to 1000 carbon atoms.
Similar definitions apply for corresponding terms. It encompasses
aromatic and heteroaromatic groups, and alkyl, cycloalkyl, alkoxy,
cycloalkoxy, alkenyl, alkanoyl, alkoxycarbonyl groups, and also
heteroaliphatic groups. The groups mentioned may be branched or
unbranched. In addition, these groups may have customary
substituents. Substituents are, for example, linear and branched
alkyl groups having 1 to 6 carbon atoms, for example methyl, ethyl,
propyl, butyl, pentyl, 2-methylbutyl or hexyl; cycloalkyl groups,
for example cyclopentyl and cyclohexyl; aromatic groups such as
phenyl or naphthyl; amino groups, hydroxyl groups, ether groups,
ester groups and halides.
[0056] According to the invention, aromatic groups denote radicals
of mono- or polycyclic aromatic compounds having preferably 6 to 20
and especially 6 to 12 carbon atoms. Heteroaromatic groups denote
aryl radicals in which at least one CH group has been replaced by N
and/or at least two adjacent CH groups have been replaced by S, NH
or O, heteroaromatic groups having 3 to 19 carbon atoms.
[0057] Aromatic or heteroaromatic groups preferred in accordance
with the invention derive from benzene, naphthalene, biphenyl,
diphenyl ether, diphenylmethane, diphenyldimethylmethane,
bisphenone, diphenyl sulfone, thiophene, furan, pyrrole, thiazole,
oxazole, imidazole, isothiazole, isoxazole, pyrazole,
1,3,4-oxadiazole, 2,5-diphenyl-1,3,4-oxadiazole, 1,3,4-thiadiazole,
1,3,4-triazole, 2,5-diphenyl-1,3,4-triazole,
1,2,5-triphenyl-1,3,4-triazole, 1,2,4-oxadiazole,
1,2,4-thiadiazole, 1,2,4-triazole, 1,2,3-triazole,
1,2,3,4-tetrazole, benzo[b]thiophene, benzo[b]furan, indole,
benzo[c]thiophene, benzo[c]furan, isoindole, benzoxazole,
benzothiazole, benzimidazole, benzisoxazole, benzisothiazole,
benzopyrazole, benzothiadiazole, benzotriazole, dibenzofuran,
dibenzothiophene, carbazole, pyridine, bipyridine, pyrazine,
pyrazole, pyrimidine, pyridazine, 1,3,5-triazine, 1,2,4-triazine,
1,2,4,5-triazine, tetrazine, quinoline, isoquinoline, quinoxaline,
quinazoline, cinnoline, 1,8-naphthyridine, 1,5-naphthyridine,
1,6-naphthyridine, 1,7-naphthyridine, phthalazine,
pyridopyrimidine, purine, pteridine or quinolizine, 4H-quinolizine,
diphenyl ether, anthracene, benzopyrrole, benzoxathiadiazole,
benzoxadiazole, benzopyridine, benzopyrazine, benzopyrazidine,
benzopyrimidine, benzotriazine, indolizine, pyridopyridine,
imidazopyrimidine, pyrazinopyrimidine, carbazole, aciridine,
phenazine, benzoquinoline, phenoxazine, phenothiazine, acridizine,
benzopteridine, phenanthroline and phenanthrene, each of which may
also optionally be substituted.
[0058] The preferred alkyl groups include the methyl, ethyl,
propyl, isopropyl, 1-butyl, 2-butyl, 2-methylpropyl, tert-butyl
radical, pentyl, 2-methylbutyl, 1,1-dimethylpropyl, hexyl, heptyl,
octyl, 1,1,3,3-tetramethylbutyl, nonyl, 1-decyl, 2-decyl, undecyl,
dodecyl, pentadecyl and the eicosyl group.
[0059] The preferred cycloalkyl groups include the cyclopropyl,
cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and the cyclooctyl
group, each of which is optionally substituted with branched or
unbranched alkyl groups.
[0060] The preferred alkanoyl groups include the formyl, acetyl,
propionyl, 2-methylpropionyl, butyryl, valeroyl, pivaloyl,
hexanoyl, decanoyl and the dodecanoyl group.
[0061] The preferred alkoxycarbonyl groups include the
methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl,
tert-butoxycarbonyl group, hexyloxycarbonyl,
2-methylhexyloxycarbonyl, decyloxycarbonyl or dodecyloxycarbonyl
group.
[0062] The preferred alkoxy groups include alkoxy groups whose
hydrocarbon radical is one of the aforementioned preferred alkyl
groups.
[0063] The preferred cycloalkoxy groups include cycloalkoxy groups
whose hydrocarbon radical is one of the aforementioned preferred
cycloalkyl groups.
[0064] The preferred heteroatoms which are present in the R.sup.10
radical include oxygen, nitrogen, sulfur, boron, silicon and
phosphorus, preference being given to oxygen and nitrogen.
[0065] The R.sup.10 radical comprises at least one, preferably at
least two, preferentially at least three, heteroatoms.
[0066] The R.sup.10 radical in ester compounds of the formula (IV)
preferably has at least 2 different heteroatoms. In this case, the
R.sup.10 radical in at least one of the ester compounds of the
formula (IV) may comprise at least one nitrogen atom and at least
one oxygen atom.
[0067] Examples of ethylenically unsaturated, polar ester compounds
of the formula (IV) include aminoalkyl (meth)acrylates, aminoalkyl
(meth)acrylamides, hydroxyalkyl (meth)acrylates, heterocyclic
(meth)acrylates and/or carbonyl-containing (meth)acrylates.
[0068] The hydroxyalkyl (meth)acrylates include [0069]
2-hydroxypropyl (meth)acrylate, [0070] 3,4-dihydroxybutyl
(meth)acrylate, [0071] 2-hydroxyethyl (meth)acrylate, [0072]
3-hydroxypropyl (meth)acrylate, [0073] 2,5-dimethyl-1,6-hexanediol
(meth)acrylate and [0074] 1,10-decanediol (meth)acrylate.
[0075] Appropriate carbonyl-containing (meth)acrylates include, for
example, [0076] 2-carboxyethyl (meth)acrylate, [0077] carboxymethyl
(meth)acrylate, [0078] oxazolidinylethyl (meth)acrylate, [0079]
N-(methacryloyloxy)formamide, [0080] acetonyl (meth)acrylate,
[0081] 2-acetoacetoxyethyl (meth)acrylate, [0082]
mono-2-(meth)acryloyloxyethyl succinate, [0083]
N-(meth)acryloylmorpholine, [0084]
N-(meth)acryloyl-2-pyrrolidinone, [0085]
N-(2-(meth)acryloyloxyethyl)-2-pyrrolidinone, [0086]
N-(3-(meth)acryloyloxypropyl)-2-pyrrolidinone, [0087]
N-(2-(meth)acryloyloxypentadecyl)-2-pyrrolidinone, [0088]
N-(3-(meth)acryloyloxyheptadecyl)-2-pyrrolidinone and [0089]
N-(2-(meth)acryloyloxyethyl)ethyleneurea.
[0090] The heterocyclic (meth)acrylates include [0091]
2-(1-imidazolyl)ethyl (meth)acrylate, 2-(4-morpholinyl)ethyl
(meth)acrylate and [0092]
1-(2-(meth)acryloyloxyethyl)-2-pyrrolidone.
[0093] Of particular interest are additionally aminoalkyl
(meth)acrylates and aminoalkyl [0094] (meth)acrylate amides, for
example [0095] dimethylaminopropyl (meth)acrylate, [0096]
dimethylaminodiglycol (meth)acrylate, [0097] dimethylaminoethyl
(meth)acrylate, [0098] dimethylaminopropyl(meth)acrylamide, [0099]
3-diethylaminopentyl (meth)acrylate and [0100]
3-dibutylaminohexadecyl (meth)acrylate.
[0101] In addition, it is possible to use phosphorus-, boron-
and/or silicon-containing (meth)acrylates to prepare the polar
segments D, such as [0102] 2-(dimethylphosphato)propyl
(meth)acrylate, [0103] 2-(ethylenephosphito)propyl (meth)acrylate,
[0104] dimethylphosphinomethyl (meth)acrylate, [0105]
dimethylphosphonoethyl (meth)acrylate, [0106] diethyl(meth)acryloyl
phosphonate, [0107] dipropyl(meth)acryloyl phosphate,
2-(dibutylphosphono)ethyl (meth)acrylate, [0108]
2,3-butylene(meth)acryloylethyl borate, [0109]
methyldiethoxy(meth)acryloylethoxysilane, [0110]
diethylphosphatoethyl (meth)acrylate.
[0111] The preferred heterocyclic vinyl compounds include
2-vinylpyridine, 3-vinylpyridine, 2-methyl-5-vinylpyridine,
3-ethyl-4-vinylpyridine, 2,3 dimethyl-5-vinylpyridine,
vinylpyrimidine, vinylpiperidine, 9-vinylcarbazole,
3-vinylcarbazole, 4-vinylcarbazole, 1-vinylimidazole,
N-vinylimidazole, 2-methyl-1-vinylimidazole, N-vinylpyrrolidone,
2-vinylpyrrolidone, N-vinylpyrrolidine, 3-vinylpyrrolidine,
N-vinylcaprolactam, N-vinylbutyrolactam, vinyloxolane, vinylfuran,
vinylthiophene, vinylthiolane, vinylthiazoles and hydrogenated
vinylthiazoles, vinyloxazoles and hydrogenated vinyloxazoles,
particular preference being given to using N-vinylimidazole and
N-vinylpyrrolidone for functionalization.
[0112] The monomers detailed above can be used individually or as a
mixture.
[0113] In a particular aspect of the present invention, at least
one heteroatom in the R.sup.10 radical in at least one of the ester
compounds of the formula (IV) may be separated from the X group via
at least 4 atoms, more preferably via at least 6 atoms.
[0114] The R.sup.10 radical in at least one of the ester compounds
of formula (IV) is preferably a group of the formula (V)
##STR00006##
in which A is a joining group having 1 to 500 carbon atoms,
preferably 1 to 100 carbon atoms and more preferably 1 to 50 carbon
atoms, and the R.sup.13 and R.sup.14 radicals are each
independently hydrogen or an alkyl group having 1 to 40 carbon
atoms, more preferably 1 to 20 carbon atoms and most preferably 1
to 4 carbon atoms. The expression "joining group having 1 to 500
carbon atoms" denotes radicals of organic compounds comprising 1 to
500 carbon atoms. It comprises aromatic and heteroaromatic groups,
and alkyl, cycloalkyl, alkoxy, cycloalkoxy, alkenyl, alkanoyl,
alkoxycarbonyl groups, and heteroaliphatic groups. These radicals
have been illustrated in detail above.
[0115] The preferred joining groups in formula (V) include groups
of the formula (VI)
##STR00007##
in which n is an integer in the range from 1 to 8, preferably 1 to
6 and more preferably 1 to 3.
[0116] The R.sup.10 radical in at least one ester compound of the
formula (IV) is preferably a group of the formula (VII)
##STR00008##
[0117] More preferably, the dispersing monomer used may be
dimethylaminodiglycol methacrylate
(2-[2-(dimethylamino)ethoxy]ethyl methacrylate;
2-[2-(dimethylamino)ethoxy]ethyl 2-methyl-2-propenoate) of formula
(VIII)
##STR00009##
[0118] In a further aspect of the present invention, the R.sup.10
radical in at least one of the ester compounds of formula (IV) may
comprise at least one group, more preferably at least two groups,
of the formula --CO--. The groups of the formula --CO-- may be
carbonyl groups of ketones and/or aldehydes, carbonyl groups of
carboxylic acids, carboxylic esters and/or carboxamides and/or
carbonyl groups of carbonic acid derivatives, especially of urea
groups and/or urethane groups.
[0119] It is possible here for at least two groups of the formula
--CO-- to be joined to one another via not more than 4 atoms.
[0120] Preferably, the R.sup.10 radical in at least one ester
compound of the formula (IV) may be a group of the formula (IX)
##STR00010##
[0121] More preferably, component d) comprises
mono-2-methacryloyloxyethyl succinate of formula (X)
##STR00011##
[0122] Preferably, the R.sup.10 radical in at least one ester
compound of the formula (IV) may be a group of the formula (XI)
##STR00012##
[0123] More preferably, the dispersing monomer may be
2-acetoacetoxyethyl methacrylate
2-[(2-methyl-1-oxo-2-propenyl)oxy]ethyl 3-oxobutanoate) of formula
(XII)
##STR00013##
[0124] In a further aspect of the present invention, the R.sup.10
radical in at least one of the ester compounds of formula (IV) may
comprise at least one group of the formula --CO-- and at least one
nitrogen atom.
[0125] In this case, the R.sup.10 radical in at least one of the
ester compounds of formula (IV) may have at least one urea group,
and urea groups can generally be illustrated by the formula
--NR.sup.b--CO--NR.sup.c-- in which the R.sup.b and R.sup.c
radicals are each independently hydrogen or a group having 1 to 40
carbon atoms, preferably 1 to 20 carbon atoms and more preferably 1
to 4 carbon atoms, or the R.sup.b and R.sup.c radicals may form a
ring having 1 to 80 carbon atoms.
[0126] Preferably, the R.sup.10 radical in at least one ester
compound of the formula (IV) may be a group of the formula
(XIII)
##STR00014##
in which A is a joining group having 1 to 500 carbon atoms,
preferably 1 to 100 carbon atoms and more preferably 1 to 50 carbon
atoms. The term "joining group having 1 to 500 carbon atoms" has
been illustrated in detail above.
[0127] More preferably, the dispersing monomer used may be
N-(2-methacryloyloxyethyl)ethylene-urea(2-(2-oxo-1-imidazolidinyl)ethyl
2-methyl-2-propenoate) of formula (XIV)
##STR00015##
[0128] Of particular interest are especially polymers comprising
ester groups which are obtained using 2-hydroxypropyl methacrylate,
2-hydroxyethyl methacrylate, mono-2-methacryloyloxy-ethyl
succinate, N-(2-methacryloyloxyethyl)ethyleneurea,
2-acetoacetoxyethyl methacrylate, 2-(4-morpholinyl)ethyl
methacrylate, dimethylaminodiglycol methacrylate,
dimethylaminoethyl methacrylate and/or
dimethylaminopropylmethacrylamide, and the use of
N-(2-methacryloyloxyethyl)ethyleneurea, 2-acetoacetoxyethyl
methacrylate, 2-(4-morpholinyl)ethyl methacrylate is associated
with particular advantages. In this context, very particular
preference is given to 2-acetoacetoxyethyl methacrylate.
[0129] As well as the dispersing monomers, a composition for
preparation of the polar segments may also comprise non-dispersing
monomers which have been detailed above. These especially include
ethylenically unsaturated ester compounds of the formulae (I), (II)
and/or (III).
[0130] In a particularly preferred embodiment, the polar segment D
comprises repeat units derived from dispersing methacrylates of
formula (IV) and repeat units derived from styrene monomers. The
proportion of styrene monomers is preferably 0 to 40% by weight,
more preferably 0.1 to 30% by weight and most preferably 0.5 to 20%
by weight, based on the weight of the monomer composition for
preparation of the polar segment D. The proportion of dispersing
methacrylates of formula (IV) is preferably at least 50% by weight,
more preferably at least 70% by weight and most preferably at least
80% by weight, based on the weight of the monomer composition for
preparation of the polar segment D.
[0131] In a particularly preferred embodiment, the polar segment D
comprises repeat units derived from dispersing methacrylates of
formula (IV) and repeat units derived from acrylates. The
proportion of acrylates is preferably 0 to 40% by weight, more
preferably 0.1 to 30% by weight and most preferably 0.5 to 20% by
weight, based on the weight of the monomer composition for
preparation of the polar segment D. The proportion of dispersing
methacrylates of formula (IV) is preferably at least 50% by weight,
more preferably at least 70% by weight and most preferably at least
80% by weight, based on the weight of the monomer composition for
preparation of the polar segment D.
[0132] Appropriately, the weight ratio of the hydrophobic segments
to the polar segments may be in the range from 100:1 to 1:1, more
preferably in the range from 30:1 to 2:1 and most preferably in the
range from 10:1 to 4:1.
[0133] The length of the hydrophobic and polar segments may vary
within wide ranges. The nonpolar segments P preferably possess a
weight-average degree of polymerization of at least 10, especially
at least 40. The weight-average degree of polymerization of the
hydrophobic segments is preferably in the range from 20 to 5000,
especially from 50 to 2000.
[0134] The proportion of dispersing repeat units, based on the
weight of the polymer comprising ester groups, is preferably in the
range from 0.5% by weight to 20% by weight, more preferably in the
range from 1.5% by weight to 15% by weight and most preferably in
the range from 2.5% by weight to 10% by weight. At the same time,
these repeat units preferably form a segment-like structure within
the polymer comprising ester groups, such that preferably at least
70% by weight, more preferably at least 80% by weight, based on the
total weight of the dispersing repeat units, are part of a polar
segment D.
[0135] The proportion of repeat units derived from styrene
monomers, based on the weight of the polymer comprising ester
groups, may preferably be in the range from 0% by weight to 40% by
weight, especially in the range from 0.1 to 25% by weight, more
preferably in the range from 0.5% by weight to 10% by weight and
most preferably in the range from 1% by weight to 5% by weight.
[0136] The present invention describes polymers which preferably
have a high oil solubility. The term "oil-soluble" means that a
mixture of a base oil and a polymer comprising ester groups is
preparable without macroscopic phase formation, which has at least
0.1% by weight, preferably at least 0.5% by weight, of the
polymers. The polymer may be present in dispersed and/or dissolved
form in this mixture. The oil solubility depends especially on the
proportion of the lipophilic side chains and on the base oil. This
property is known to those skilled in the art and can be adjusted
readily for the particular base oil via the proportion of
lipophilic monomers.
[0137] Of particular interest, among others, are polymers which
comprise ester groups and preferably have a weight-average
molecular weight M.sub.w in the range from 7500 to 1 000 000 g/mol,
more preferably 10 000 to 600 000 g/mol and most preferably 15 000
to 80 000 g/mol.
[0138] The number-average molecular weight M.sub.n may preferably
be in the range from 5000 to 800 000 g/mol, more preferably 7500 to
500 000 g/mol and most preferably 10 000 to 80 000 g/mol.
[0139] Additionally appropriate are polymers which comprise ester
groups and whose polydispersity index M.sub.w/M.sub.n is in the
range from 1 to 5, more preferably in the range from 1.05 to 4. The
number-average and weight-average molecular weights can be
determined by known processes, for example gel permeation
chromatography (GPC).
[0140] The polymer comprising ester groups may have a variety of
structures. For example, the polymer may be present as a diblock,
triblock, multiblock, comb and/or star copolymer which has
corresponding polar and nonpolar segments. According to the
invention, the copolymer is obtainable by NMP (=nitroxide mediated
polymerization). The NMP process is known to those skilled in the
art and is described, for example, in K. Matyjaszewski, T. P.
Davis, Handbook of Radical Polymerization, Wiley Interscience,
Hoboken 2002.
[0141] A characteristic feature of these processes is the presence
of stable nitroxyl radical compounds, also called N-oxyl radical
compounds, which are assumed to be able to react reversibly with
the chain ends.
[0142] The particularly preferred nitroxyl radical compounds
preferably include compounds of the structure (XV)
##STR00016##
in which R.sup.16, R.sup.17, R.sup.18, R.sup.19, R.sup.20 and
R.sup.21 are each independently a radical comprising 1 to 100,
preferably 1 to 30 and more preferably 1 to 15 carbon atoms, where
two or more R.sup.16, R.sup.17, R.sup.18, R.sup.19, R.sup.20 and
R.sup.21 radicals may form a ring, preferably a
C.sub.1-C.sub.10-alkyl, C.sub.1-C.sub.10-alkenyl,
C.sub.1-C.sub.10-alkoxy, C.sub.6-C.sub.18-aryl,
C.sub.7-C.sub.19-aralkyl,
C.sub.6-C.sub.18-aryl-C.sub.1-C.sub.8-alkyl or
C.sub.3-C.sub.18-heteroaryl group, where the R.sup.18 and R.sup.19
radicals together may preferably form a ring, more preferably a
(C.sub.1-C.sub.4)-alkylene bridge, which may be saturated or
unsaturated, unsubstituted or substituted, especially by one or
more substituents selected from a radical comprising 1 to 30 carbon
atoms, C.sub.1-C.sub.8-amido, halogen, oxy, hydroxy, amino,
alkylamino, dialkylamino, arylamino, diarylamino, alkylcarbonyloxy,
arylcarbonyloxy, alkylcarbonylamino and arylcarbonylamino group.
The R.sup.16, R.sup.17, R.sup.18, R.sup.19, R.sup.20 and R.sup.21
radicals here may contain heteroatoms which may be terminal or
incorporated within the carbon chain. The particularly preferred
heteroatoms include phosphorus atoms in particular. Accordingly,
particularly preferred nitroxyl radical compounds have at least one
phosphorus atom.
[0143] In a particular configuration of the present invention, at
least one of the R.sup.16, R.sup.17, R.sup.18, R.sup.19, R.sup.20
and R.sup.21 radicals is a group of the formula (XVI)
##STR00017##
in which the R.sup.22 and R.sup.23 radicals are each independently
a halogen atom, especially a chlorine, bromine, fluorine or iodine
atom, or a radical comprising 1 to 50, preferably 1 to 30 and more
preferably 1 to 15 carbon atoms, preferably an alkyl, cycloalkyl,
alkoxy, aryloxy, aryl, aralkyloxy, perfluoroalkyl, aralkyl having 1
to 20 carbon atoms; and the dotted line represents the bond of the
group of formula (XVI) to the carbon atom bonded to the nitrogen
atom of the N-oxide group.
[0144] The above-detailed nitroxyl radical compounds can be used
individually or as a mixture.
[0145] The nitroxyl radical compounds used are preferably
2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) and/or the derivatives
of 2,2,6,6-tetramethylpiperidine 1-oxyl substituted at the 4
position of the heterocycle, where the derivatives have one or more
substituents selected from a radical comprising 1 to 30 carbon
atoms, C.sub.1-C.sub.8-amido, halogen, oxy, hydroxy, amino,
alkylamino, dialkylamino, arylamino, diarylamino, alkylcarbonyloxy,
arylcarbonyloxy, alkylcarbonylamino and arylcarbonylamino groups,
in which the radical comprising 1 to 30 carbon atoms is more
preferably a (C.sub.1-C.sub.10)-alkyl, (C.sub.1-C.sub.10)-alkenyl,
(C.sub.1-C.sub.10)-alkoxy, (C.sub.6-C.sub.18)-aryl,
(C.sub.7-C.sub.19)-aralkyl,
(C.sub.6-C.sub.18)-aryl-(C.sub.1-C.sub.8)-alkyl or
(C.sub.3-C.sub.18)-heteroaryl group.
[0146] More preferably, the following nitroxyl radical compounds
are used: 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO),
4-methoxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4-MeO-TEMPO),
4-oxo-2,2,6,6-tetramethylpiperidine 1-oxyl (4-oxo-TEMPO),
4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4-hydroxy-TEMPO),
4-benzoyloxy-2,2,6,6-tetramethylpiperidine 1-oxyl (BnO-TEMPO),
4-acetamido-2,2,6,6-tetramethylpiperidine 1-oxyl,
4-acetamino-2,2,6,6-tetramethylpiperidine 1-oxyl (AA-TEMPO),
4-amino-2,2,6,6-tetramethylpiperidine 1-oxyl,
N,N-dimethylamino-2,2,6,6-tetramethylpiperidine 1-oxyl
(NNDMA-TEMPO), 3,6-dihydro-2,2,6,6-tetramethyl-1(2H)-pyridinyloxyl
(DH-TEMPO), bis(2,2,6,6-tetramethylpiperidin-1-oxyl-4-yl)sebacate,
or a mixture of two or more of these compounds.
[0147] Very particular preference is given to nitroxyl radical
compounds selected from: [0148]
N-tert-butyl-1-phenyl-2-methylpropyl N-oxide, [0149]
N-tert-butyl-1-(2-naphthyl)-2-methylpropyl N-oxide, [0150]
N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl N-oxide, [0151]
N-tert-butyl-1-dibenzylphosphono-2,2-dimethylpropyl N-oxide, [0152]
N-phenyl-1-diethylphosphono-2,2-dimethylpropyl N-oxide, [0153]
N-phenyl-1-diethylphosphono-1-methylethyl N-oxide, [0154]
N-1-(phenyl-2-methylpropyl)-1-diethylphosphono-1-methylethyl-N-oxide.
[0155] The stable free radical can be used in the reaction mixture
of the polymerization or copolymerization in an amount of 0.005 to
5% by weight of the sum of the mass of polymerizable monomers and
stable free radicals.
[0156] According to the method of polymerization, a separately
added polymerization initiator can be used. These include the azo
initiators widely known in the technical field, such as AIBN and
1,1-azobiscyclohexanecarbonitrile, and also peroxy compounds such
as methyl ethyl ketone peroxide, acetylacetone peroxide, dilauryl
peroxide, tert-butyl per-2-ethylhexanoate, ketone peroxide,
tert-butyl peroctoate, methyl isobutyl ketone peroxide,
cyclohexanone peroxide, dibenzoyl peroxide, tert-butyl
peroxybenzoate, tert-butyl peroxyisopropyl-carbonate,
2,5-bis(2-ethylhexanoylperoxy)-2,5-dimethylhexane, tert-butyl
peroxy-2-ethylhexanoate, tert-butyl
peroxy-3,5,5-trimethylhexanoate, dicumyl peroxide,
1,1-bis(tert-butylperoxy)cyclohexane,
1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, cumyl
hydroperoxide, tert-butyl hydroperoxide,
bis(4-tert-butylcyclohexyl) peroxydicarbonate, mixtures of two or
more of the aforementioned compounds with one another, and mixtures
of the aforementioned compounds with compounds which have not been
mentioned but can likewise form free radicals.
[0157] The separately added polymerization initiator can be used in
the customary amounts, though the amount of nitroxyl radical
compounds must be sufficient to ensure controlled
polymerization.
[0158] The nitroxyl radical compounds detailed above may, in a
particular aspect, be used in the form of an initiator in the
polymerization process, this releasing said nitroxyl radical
compounds and at least one free-radical initiator.
[0159] The initiators which are usable with particular preference
and can release said nitroxyl radicals include compounds of formula
(XVII)
##STR00018##
in which the R.sup.16, R.sup.17, R.sup.16, R.sup.19, R.sup.20 and
R.sup.21 radicals are each as defined above in formula (XV), n is
an integer in the range from 1 to 10, preferably 1 to 5 and most
preferably 1, and the A group is a radical comprising 1 to 50,
preferably 1 to 30 and more preferably 1 to 15 carbon atoms. More
preferably, the A group in formula (XVII) comprises at least one
carboxylic acid, ester and/or cyano group and/or at least one
halogen atom, preferably a fluorine atom. It is also possible here
to use derivatives of the groups mentioned, for example salts.
[0160] Initiators which release the nitroxyl radical compounds
mentioned are described, inter alia, in U.S. Pat. No. 6,657,043,
filed Mar. 15, 2002 at the American Patent Office (USPTO) with
application Ser. No. 09/979,124; WO 2004/014926 A, filed Jul. 23,
2003 at the French Patent Office with application number
PCT/FR2003/002328; WO 00/49027 A, filed Feb. 10, 2000 at the French
Patent Office with application number PCT/FR00/00335; the
initiators mentioned therein are incorporated into the present
application for the purposes of disclosure.
[0161] The initiators mentioned which release both a free-radical
initiator and a nitroxyl radical compound include especially
hydroxylamine compounds, for example
2-methyl-2-(N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl-N-oxyl)pro-
panoic acid,
2-methyl-2-(N-tert-butyl-1-dibenzylphosphono-2,2-dimethylpropyl-N-oxyl)pr-
opanoic acid,
2-methyl-2-(N-phenyl-1-diethylphosphono-2,2-dimethylpropyl-N-oxyl)propano-
ic acid,
2-methyl-2-(N-phenyl-1-diethylphosphono-1-methylethyl-N-oxyl)prop-
anoic acid and/or
2-methyl-2-(N-1-(phenyl-2-methylpropyl)-1-diethylphosphono-1-methylethyl--
N-oxyl)propanoic acid. The compounds mentioned can also be used as
salts or propanoic esters, for example methyl esters.
[0162] A particularly preferred initiator
(2-methyl-2-(N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl-N-oxyl)pr-
opanoic acid) which simultaneously provides both free-radical
source/initiator and a nitroxyl radical in one molecule is
available under the tradename BlocBuilder.RTM. MA:
##STR00019##
[0163] In a preferred embodiment of the present invention, the
copolymer is obtainable by a multistage polymerization, wherein a
nonpolar segment P is produced in the first stage and a polar
segment D in the last stage. More preferably, it is possible here
to perform a multistage polymerization using a transferrable
nitroxyl radical compound having at least one phosphorus atom, in
such a way that the transferrable nitroxyl radical compound having
at least one phosphorus atom is localized at the end of the polar
segment D.
[0164] The polymerization may be carried out at standard pressure,
reduced pressure or elevated pressure. The polymerization
temperature too is uncritical. However, it is generally in the
range of -20.degree.-200.degree. C., preferably
50.degree.-150.degree. C. and more preferably
80.degree.-130.degree. C.
[0165] The polymerization may be carried out with or without
solvent. The term solvent is to be understood here in a broad
sense. The solvent is selected according to the polarity of the
monomers used, preference being given to using 100N oil, relatively
light gas oil and/or aromatic hydrocarbons, for example toluene or
xylene.
[0166] The inventive additives are used especially in lubricants,
preferably lubricant oils, also referred to herein as lubricant oil
compositions, in order to improve the friction properties thereof.
Lubricant oils denote lubricants which are free-flowing at room
temperature. These lubricants typically comprise a base oil. The
preferred base oils include especially mineral oils, synthetic oils
and natural oils.
[0167] Mineral oils are known per se and commercially available.
They are generally obtained from mineral oil or crude oil by
distillation and/or refining and optionally further purification
and finishing processes, the term mineral oil including in
particular the higher-boiling fractions of crude or mineral oil. In
general, the boiling point of mineral oil is higher than
200.degree. C., preferably higher than 300.degree. C., at 5000 Pa.
The production by low-temperature carbonization of shale oil,
coking of bituminous coal, distillation of brown coal with
exclusion of air, and also hydrogenation of bituminous or brown
coal is likewise possible. Accordingly, mineral oils have,
depending on their origin, different proportions of aromatic,
cyclic, branched and linear hydrocarbons.
[0168] In general, a distinction is drawn between paraffin-base,
naphthenic and aromatic fractions in crude oils or mineral oils, in
which the term paraffin-base fraction represents longer-chain or
highly branched isoalkanes, and naphthenic fraction represents
cycloalkanes. In addition, mineral oils, depending on their origin
and finishing, have different fractions of n-alkanes, isoalkanes
having a low degree of branching, known as mono-methyl-branched
paraffins, and compounds having heteroatoms, in particular O, N
and/or S, to which a degree of polar properties are attributed.
However, the assignment is difficult, since individual alkane
molecules may have both long-chain branched groups and cycloalkane
radicals, and aromatic parts. For the purposes of the present
invention, the assignment can be effected to DIN 51 378, for
example. Polar fractions can also be determined to ASTM D 2007.
[0169] The proportion of n-alkanes in preferred mineral oils is
less than 3% by weight, the fraction of O-, N- and/or S-containing
compounds less than 6% by weight. The fraction of the aromatics and
of the mono-methyl-branched paraffins is generally in each case in
the range from 0 to 40% by weight. In one interesting aspect,
mineral oil comprises mainly naphthenic and paraffin-base alkanes
which have generally more than 13, preferably more than 18 and most
preferably more than 20 carbon atoms. The fraction of these
compounds is generally .gtoreq.60% by weight, preferably
.gtoreq.80% by weight, without any intention that this should
impose a restriction. A preferred mineral oil contains 0.5 to 30%
by weight of aromatic fractions, 15 to 40% by weight of naphthenic
fractions, 35 to 80% by weight of paraffin-base fractions, up to 3%
by weight of n-alkanes and 0.05 to 5% by weight of polar compounds,
based in each case on the total weight of the mineral oil.
[0170] An analysis of particularly preferred mineral oils, which
was effected by means of conventional processes such as urea
separation and liquid chromatography on silica gel, shows, for
example, the following constituents, the percentages relating to
the total weight of the particular mineral oil used: [0171]
n-alkanes having about 18 to 31 carbon atoms: [0172] 0.7-1.0%,
[0173] slightly branched alkanes having 18 to 31 carbon atoms:
[0174] 1.0-8.0%, [0175] aromatics having 14 to 32 carbon atoms:
[0176] 0.4-10.7%, [0177] iso- and cycloalkanes having 20 to 32
carbon atoms: [0178] 60.7-82.4%, [0179] polar compounds: [0180]
0.1-0.8%, [0181] loss: [0182] 6.9-19.4%.
[0183] An improved class of mineral oils (reduced sulfur content,
reduced nitrogen content, higher viscosity index, lower pour point)
results from hydrogen treatment of the mineral oils
(hydroisomerization, hydrocracking, hydrotreatment,
hydrofinishing). In the presence of hydrogen, this essentially
reduces aromatic components and builds up naphthenic
components.
[0184] Valuable information with regard to the analysis of mineral
oils and a list of mineral oils which have a different composition
can be found, for example, in T. Mang, W. Dresel (eds.):
"Lubricants and Lubrication", Wiley-VCH, Weinheim 2001; R. M.
Mortier, S. T. Orszulik (eds.): "Chemistry and Technology of
Lubricants", Blackie Academic & Professional, London, 2.sup.nd
ed. 1997; or J. Bartz: "Additive fur Schmierstoffe", Expert-Verlag,
Renningen-Malmsheim 1994.
[0185] Synthetic oils include organic esters, for example diesters
and polyesters, polyalkylene glycols, polyethers, synthetic
hydrocarbons, especially polyolefins, among which preference is
given to polyalphaolefins (PAOs), silicone oils and perfluoroalkyl
ethers. In addition, it is possible to use synthetic base oils
originating from gas to liquid (GTL), coal to liquid (CTL) or
biomass to liquid (BTL) processes. They are usually somewhat more
expensive than the mineral oils, but have advantages with regard to
their performance.
[0186] Natural oils are animal or vegetable oils, for example
neatsfoot oils or jojoba oils.
[0187] Base oils for lubricant oil formulations are divided into
groups according to API (American Petroleum Institute). Mineral
oils are divided into group I (non-hydrogen-treated) and, depending
on the degree of saturation, sulfur content and viscosity index,
into groups II and III (both hydrogen-treated). PAOs correspond to
group IV. All other base oils are encompassed in group V. Preferred
lubricants preferably contain at least one base oil according to
group II and/or III, more preferably according to group III, of the
classification detailed above.
[0188] These base oils may also be used as mixtures and are in many
cases commercially available.
[0189] The concentration of the polymers comprising ester groups in
the lubricant oil composition is preferably in the range of 0.01 to
40% by weight, more preferably in the range of 0.5-25% by weight
and most preferably in the range of 1-15% by weight, based on the
total weight of the composition.
[0190] In addition to the polymers comprising ester groups for use
in accordance with the invention, the lubricant oil compositions
detailed here may also comprise further additives. These additives
include VI improvers, pour point improvers and DI additives
(dispersants, detergents, defoamers, corrosion inhibitors,
antioxidants, antiwear and extreme pressure additives, friction
modifiers).
[0191] The additionally usable VI improvers include especially
polyalkyl (meth)acrylates having 1 to 30 carbon atoms in the
alcohol group (PAMA; partly N/O-functional with advantageous
additional properties as dispersants, antiwear additives and/or
friction modifiers), which differ from the copolymers detailed in
claim 1, and poly(iso)butenes (PIB), fumarate-olefin copolymers,
styrene-maleate copolymers, hydrogenated styrene-diene copolymers
(HSD) and olefin copolymers (OCP).
[0192] The pour point improvers include especially polyalkyl
(meth)acrylates (PAMA) having 1 to 30 carbon atoms in the alcohol
group.
[0193] Compilations of VI improvers and pour point improvers for
lubricant oils are also detailed in T. Mang, W. Dresel (eds.):
"Lubricants and Lubrication", Wiley-VCH, Weinheim 2001: R. M.
Mortier, S. T. Orszulik (eds.): "Chemistry and Technology of
Lubricants", Blackie Academic & Professional, London, 2nd ed.
1997; or J. Bartz: "Additive fur Schmierstoffe", Expert-Verlag,
Renningen-Malmsheim 1994.
[0194] Appropriate dispersants include poly(isobutylene)
derivatives, e.g. poly(isobutylene)succinimides (PIBSIs);
ethylene-propylene oligomers with N/O functionalities.
[0195] The preferred detergents include metal-containing compounds,
for example phenoxides; salicylates; thiophosphonates, especially
thiopyrophosphonates, thiophosphonates and phosphonates; sulfonates
and carbonates. As metals, these compounds may comprise especially
calcium, magnesium and barium. These compounds may be used
preferably in neutral or overbased form.
[0196] Of particular interest are additionally defoamers, which are
in many cases divided into silicone-containing and silicone-free
defoamers. The silicone-containing defoamers include linear
poly(dimethylsiloxane) and cyclic poly(dimethylsiloxane). The
silicone-free defoamers which may be used are in many cases
polyethers, for example poly(ethylene glycol) or tributyl
phosphate.
[0197] In a particular embodiment, the inventive lubricant oil
compositions may comprise corrosion inhibitors. These are in many
cases divided into antirust additives and metal
passivators/deactivators. The antirust additives used may, inter
alia, be sulfonates, for example petroleumsulfonates or (in many
cases overbased) synthetic alkylbenzenesulfonates, e.g.
dinonylnaphthenesulfonates; carboxylic acid derivatives, for
example lanolin (wool fat), oxidized paraffins, zinc naphthenates,
alkylated succinic acids, 4-nonylphenoxy-acetic acid, amides and
imides (N-acylsarcosine, imidazoline derivatives);
amine-neutralized mono- and dialkyl phosphates; morpholine,
dicyclohexylamine or diethanolamine. The metal
passivators/deactivators include benzotriazole, tolyltriazole,
2-mercaptobenzothiazole, dialkyl-2,5-dimercapto-1,3,4-thiadiazole;
N,N'-disalicylideneethylenediamine,
N,N'-disalicylidenepropylenediamine; zinc dialkyldithiophosphates
and dialkyl dithiocarbamates.
[0198] A further preferred group of additives is that of
antioxidants. The antioxidants include, for example, phenols, for
example 2,6-di-tert-butylphenol (2,6-DTB), butylated hydroxytoluene
(BHT), 2,6-di-tert-butyl-4-methylphenol,
4,4'-methylenebis(2,6-di-tert-butylphenol); aromatic amines,
especially alkylated diphenylamines, N-phenyl-1-naphthylamine
(PNA), polymeric 2,2,4-trimethyldihydroquinone (TMQ); compounds
containing sulfur and phosphorus, for example metal
dithiophosphates, e.g. zinc dithiophosphates (ZnDTP), "OOS
triesters"=reaction products of dithiophosphoric acid with
activated double bonds from olefins, cyclopentadiene,
norbornadiene, alpha-pinene, polybutene, acrylic esters, maleic
esters (ashless on combustion); organosulfur compounds, for example
dialkyl sulfides, diaryl sulfides, polysulfides, modified thiols,
thiophene derivatives, xanthates, thioglycols, thioaldehydes,
sulfur-containing carboxylic acids; heterocyclic sulfur/nitrogen
compounds, especially dialkyldimercaptothiadiazoles,
2-mercaptobenzimidazoles; zinc and methylene
bis(dialkyldithiocarbamate); organophosphorus compounds, for
example triaryl and trialkyl phosphites; organocopper compounds and
overbased calcium- and magnesium-based phenolates and
salicylates.
[0199] The preferred antiwear (AW) and extreme pressure (EP)
additives include phosphorus compounds, for example trialkyl
phosphates, triaryl phosphates, e.g. tricresyl phosphate,
amine-neutralized mono- and dialkyl phosphates, ethoxylated mono-
and dialkyl phosphates, phosphites, phosphonates, phosphines;
compounds containing sulfur and phosphorus, for example metal
dithiophosphates, e.g. zinc C.sub.3-12dialkyldithiophosphates
(ZnDTPs), ammonium dialkyldithiophosphates, antimony
dialkyldithiophosphates, molybdenum dialkyldithiophosphates, lead
dialkyldithiophosphates, "OOS triesters"=reaction products of
dithiophosphoric acid with activated double bonds from olefins,
cyclopentadiene, norbornadiene, alpha-pinene, polybutene, acrylic
esters, maleic esters, triphenylphosphorothionate (TPPT); compounds
containing sulfur and nitrogen, for example zinc bis(amyl
dithiocarbamate) or methylenebis(di-n-butyl dithiocarbamate);
sulfur compounds containing elemental sulfur and
H.sub.2S-sulfurized hydrocarbons (diisobutylene, terpene);
sulfurized glycerides and fatty acid esters; overbased sulfonates;
chlorine compounds or solids such as graphite or molybdenum
disulfide.
[0200] A further preferred group of additives is that of friction
modifiers. The friction modifiers used may include mechanically
active compounds, for example molybdenum disulfide, graphite
(including fluorinated graphite), poly(trifluoroethylene),
polyamide, polyimide; compounds which form adsorption layers, for
example long-chain carboxylic acids, fatty acid esters, ethers,
alcohols, amines, amides, imides; compounds which form layers
through tribochemical reactions, for example saturated fatty acids,
phosphoric acid and thiophosphoric esters, xanthogenates,
sulfurized fatty acids; compounds which form polymer-like layers,
for example ethoxylated dicarboxylic acid partial esters, dialkyl
phthalates, methacrylates, unsaturated fatty acids, sulfurized
olefins or organometallic compounds, for example molybdenum
compounds (molybdenum dithiophosphates and molybdenum
dithiocarbamates MoDTC) and their combinations with ZnDTPs,
copper-containing organic compounds.
[0201] Some of the additives detailed above may fulfill multiple
functions. ZnDTP, for example, is primarily an antiwear additive
and extreme pressure additive, but also has the character of an
antioxidant and corrosion inhibitor (here: metal
passivator/deactivator).
[0202] The additives detailed above are described in more detail,
inter alia, in T. Mang, W. Dresel (eds.): "Lubricants and
Lubrication", Wiley-VCH, Weinheim 2001; J. Bartz: "Additive fur
Schmierstoffe", Expert-Verlag, Renningen-Malmsheim 1994; R. M.
Mortier, S. T. Orszulik (eds.): "Chemistry and Technology of
Lubricants", Blackie Academic & Professional, London, 2.sup.nd
ed. 1997.
[0203] Preferred lubricant oil compositions have a viscosity,
measured at 40.degree. C. to ASTM D 445, in the range of 10 to 120
mm.sup.2/s, more preferably in the range of 20 to 100 mm.sup.2/s.
The kinematic viscosity KV.sub.100 measured at 100.degree. C. is
preferably at least 3.5 mm.sup.2/s, more preferably at least 4.0
mm.sup.2/s and most preferably at least 4.5 mm.sup.2/s.
[0204] In a particular aspect of the present invention, preferred
lubricant oil compositions have a viscosity index determined to
ASTM D 2270 in the range of 100 to 400, more preferably in the
range of 125 to 325 and most preferably in the range of 150 to
250.
[0205] Appropriate lubricant oil compositions have a PSSI to DIN
51350-6 (20 h, tapered roller bearing) less than or equal to 100.
The PSSI is more preferably less than or equal to 65, especially
preferably less than or equal to 25.
[0206] The present lubricant oil compositions can be used
especially as a transmission oil, motor oil or hydraulic oil.
Surprising advantages can be achieved especially when the present
lubricants are used in manual, automated manual, double clutch or
direct-shift gearboxes (DSG), automatic and continuous variable
transmissions (CVCs). In addition, the present lubricants can be
used especially in transfer cases and axle or differential
gearings.
[0207] The present polymers comprising ester groups can
additionally serve as antifatigue additives in lubricants. It has
been found that, surprisingly, these additives counteract material
fatigue, such that the lifetime of transmissions, engines or
hydraulic systems can be increased. This finding can be established
by various methods. The fatigue time (crater resistance) of the
lubricant oil formulations can be determined either by methods for
gearings or for roller bearings. The methods which follow cover a
wide range of Hertzian pressures.
[0208] The fatigue time (number of rotations) can be determined,
for example, on a standardized four-ball apparatus (FBA) to DIN
51350-1, in which a rotating ball under load is pressed onto three
identical, likewise rotating balls. The test method employed is
VW-PV-1444 of Volkswagen AG ("Grubchenfestigkeit von Bauteilen mit
Walzreibung-Pittingtest" [Crater resistance of components with
rolling friction-pitting test], VW-PV-1444, Volkswagen AG).
[0209] The test temperature is 120.degree. C. With a load of 4.8 kN
and a rotational speed of 4000 rpm, the entrainment speed is 5.684
m/s at a maximum Hertzian pressure of 7.67 GPa. Fatigue occurs as
soon as an acceleration sensor registers vibrations in the
frequency band of the rollover frequencies of the test bodies
greater than 0.25 g (acceleration due to gravity g=9.81 m/s.sup.2).
This typically indicates craters on the rolling path of diameter
1-2 mm. This test is referred to hereinafter as the FBA test.
[0210] In addition, fatigue can be determined by means of an FAG
FE8 test. To this end, the FE8 roller bearing lubricant test rig to
DIN 51819-1 from FAG (Schaeffler KG, Schweinfurt) can be used.
Here, the fatigue time (in hours) of two cylindrical roller thrust
bearings mounted together in each case is examined according to
test method VW-PV-1483 ("Prufung der Grubchentragfahigkeit in
Walzlagern-Ermudungstest" [Testing of crater resistance in roller
bearings--fatigue test], VW-PV-1483, Volkswagen AG, drafted
September 2006; constituent of oil standards VW TL52512/2005 for
manual transmissions and VW TL52182/2005 for double-clutch
transmissions of Volkswagen AG). Bearing washers with an arithmetic
roughness of 0.1-0.3 .mu.m are used.
[0211] Measurement is effected at 120.degree. C. With a load of 60
kN and a rotational speed of 500 rpm, the entrainment speed is
1.885 m/s at a maximum Hertzian pressure of 1.445 GPa. Fatigue
occurs as soon as the torque (i.e. the moment of friction) has an
increase by more than 10%, i.e. even in the case of fatigue only to
one cylindrical roller thrust bearing.
[0212] In principle, the FE8 roller bearing lubricant test rig can
also be operated according to the more severe ZF-702-232/2003
method of ZF Friedrichshafen AG (cf. "ZF Bearing Pitting Test",
ZF-702-232, ZF Friedrichshafen AG, 2004).
[0213] The Unisteel Machine according to IP 305/79 based on a
roller bearing with 11 balls (in modifications also only with 3
balls), which is widespread in industry, also offers a method of
determining the fatigue time of bearings.
[0214] In addition, it is possible to use a gear rig test machine
from FZG (Institute for Machine Elements--Gear Research Center of
the Technical University of Munich) to DIN 51354-1. On this test
machine, the fatigue time (in hours) is determined using specified
PT-C (pitting test type C) gears. The method is described in FVA
Information Sheet 2/IV (cf. U. Schedl: "FVA-Forschungsvorhaben
2/IV: Pittingtest-Einfluss der Schmierstoffs auf die
Grubchenlebensdauer einsatzgeharteter Zahnrader im Einstufen-und
Lastkollektivversuch", Forschungsvereinigung Antriebstechnik, Book
530, Frankfurt 1997; "Pittingtest-Einfluss der Schmierstoffs auf
die Grubchenlebensdauer einsatzgeharteter Zahnrader im
Einstufen-und Lastkollektivversuch", FVA Information Sheet 2/IV,
Forschungsvereinigung Antriebstechnik, Frankfurt 1997).
[0215] Measurement is effected at 120.degree. C. At load level 10
(i.e. a torque of 373 Nm) and a rotational speed of 1450 rpm, the
entrainment speed is 5.678 m/s at a maximum Hertzian pressure of
1.834 GPa. Fatigue occurs when craters of total area >=5
mm.sup.2 are observed. This method is referred to hereinafter as
FZG PT-C 10/120 test.
[0216] The utilization of the further-developed PTX-C test gearing,
which is close to reality, in the FZG gear rig test machine to DIN
51354-1 leads to improved repeatability and comparability of the
fatigue time. The method is described in FVA Information Sheet 371
(cf. T. Radev: "FVA-Forschungsvorhaben 371: Entwicklung eines
praxisnahen Pittingtests", Forschungsvereinigung Antriebstechnik,
Book 710, Frankfurt 2003; "Development of a Practice Relevant
Pitting Test", FVA Information Sheet 371, Forschungsvereinigung
Antriebstechnik, Frankfurt 2006).
[0217] Measurement is effected at 90.degree. C. At load level 10
(i.e. a torque of 373 Nm) and a rotational speed of 1450 rpm, the
entrainment speed is 5.678 m/s at a maximum Hertzian pressure of
2.240 GPa. Fatigue occurs when craters of total area >=5
mm.sup.2 are observed. This method is referred to hereinafter as
FZG PTX-C 10/90 test.
[0218] The inventive lubricants exhibit excellent friction
properties which can be demonstrated under a wide variety of
different conditions. Accordingly, the present invention also
provides for the use of the copolymers comprising ester groups for
improvement of friction properties.
[0219] In a preferred aspect of the present invention, particularly
the friction properties in the boundary lubrication range detailed
above can be improved. This range is characterized by a surface
separation R which is less than the surface roughness, this being
given as the mean roughness Ra which can be measured by tactile
methods (cf. DIN EN ISO 4287). The excellent friction properties
can be determined inter alia by means of UTFI (Ultrathin Film
Interferometry), MTM (Mini-Traction Machine) or HFRR (High
Frequency Reciprocating Rig).
[0220] To determine the tribological properties by means of
ultrathin film interferometry (UTFI), a steel ball which rolls
under load on a coated glass pane is used. The change in the film
thickness between ball and pane is studied as a function of rolling
speed by optical interferometry.
[0221] The UTFI values can preferably be determined using the
following test parameters: Young's modulus (AISI 52100 steel)=210
GPa, Young's modulus (glass)=75 GPa, root mean square (RMS)
roughness (steel)=10-13 nm, RMS roughness (glass)=3 nm, load=20 N,
resulting maximum Hertzian pressure=0.54 GPa, rolling or
entrainment speed=0.005-1.5 m/s, temperature=120.degree. C.
[0222] To determine the tribological properties by means of a
mini-traction machine (MTM), a steel ball of diameter 19 mm is
used, which slides or rolls on a polished steel sheet. The ball and
sheet are driven independently by means of electric motors, such
that different sliding/rolling ratios (SRR) can be established. The
coefficient of friction is studied as a function of mean rolling
speed. As a result of a friction experiment, Stribeck curves were
obtained, from which the coefficients of friction are obtained.
[0223] The MTM values can preferably be determined using the
following test parameters: Young's modulus (AISI 52100 steel)=210
GPa, roughness (steel ball)=10-13 nm, roughness (steel sheet)=25-30
nm, load=30 N, resulting maximum Hertzian pressure=0.93 GPa,
SSR=50%, mean rolling speed or entrainment speed=0.005-2.5 m/s,
temperature=120.degree. C.
[0224] To determine the tribological properties by means of a high
frequency reciprocating rig (HFRR), a steel ball of diameter 6 mm
is fixed in a clamp device and pressed under load onto the surface
of a steel sheet of diameter 10 mm. The coefficient of friction is
recorded continuously, and the wear scar diameter is determined at
the end of the experiment.
[0225] The HFRR values can preferably be determined using the
following test parameters: Young's modulus (AISI 52100 steel
ball)=210 GPa, hard VPN 800 steel sheets, rather than soft sheets
typically used for fuel studies, load=4 N, deflection=2 mm,
frequency=20 s.sup.-1, friction time=75 min,
temperature=120.degree. C.
[0226] In this test, the inventive polymers exhibit a surprisingly
large improvement in the HFRR values. After a measurement for 75
minutes with the parameters detailed above, preferred lubricants
exhibit a relative wear of not more than 0.8, preferably not more
than 0.75 and more preferably not more than 0.65. The relative wear
is based here on a comparable lubricant without the addition of the
inventive additives. The absolute wear, measured as the wear scar
diameter, is preferably not more than 280 .mu.m, especially not
more than 260 .mu.m, more preferably not more than 240 .mu.m and
most preferably not more than 220 .mu.m. In addition, preferred
lubricants according to the HFRR test exhibit a friction value of
not more than 0.2, especially not more than 0.15, more preferably
not more than 0.10. Based on a comparable lubricant without the
addition, the relative friction value is preferably at most 0.8,
preferably at most 0.75 and more preferably at most 0.65 (relative
friction value=friction value with copolymer/friction value of
reference oil).
[0227] Accordingly, the present invention also provides for the use
of the copolymers comprising ester groups for reducing wear.
[0228] Additionally of particular interest are lubricant oil
compositions having a high-shear viscosity HTHS measured at
150.degree. C. of at least 1.6 mPas, more preferably at least 2.0
mPas. The high-shear viscosity HTHS measured at 100.degree. C. is
preferably at most 10 mPas, more preferably at most 7 mPas and most
preferably at most 5 mPas. The difference in the high-shear
viscosities HTHS which are measured at 100.degree. C. and
150.degree. C., HTHS.sub.100-HTHS.sub.150, is preferably at most 4
mPas, more preferably at most 3.3 mPas and most preferably at most
2.5 mPas. The ratio of high-shear viscosity at 100.degree. C.
HTHS.sub.100 to high-shear viscosity at 150.degree. C.
HTHS.sub.150, HTHS.sub.100/HTHS.sub.150, is preferably at most 2.0,
more preferably at most 1.9. The high-shear viscosity HTHS can be
measured at the respective temperature to ASTM D4683.
[0229] The present invention is to be illustrated hereinafter by
examples and comparative examples, without any intention that this
should impose a restriction.
EXAMPLE 1
[0230] A reaction flask equipped with a heating mantle, internal
temperature regulation, stirrer, nitrogen inlet and condenser is
initially charged with 945 g of 12/15-alkyl methacrylate and 42 g
of styrene. The mixture is degassed thoroughly with dry ice and
heated to 80.degree. C. with introduction of nitrogen. During the
heating phase, at 60.degree. C., the polymerization is started by
addition of 19 g of initiator (BlocBuilder.RTM. MA). Later, the
conversion of the 12/15-alkyl methacrylate is monitored via the
refractive index. After about 4 h, at a conversion of 90%, the
degassed mixture of 52 g of hydroxyethyl methacrylate (HEMA) and 10
g of styrene is added. The reaction mixture is stirred at
80.degree. C. for a further 16 hours. The weight-average molecular
weight of the polymer, determined by means of GPC, was about 25 000
g/mol.
[0231] The properties of the polymer were examined in an HFRR test.
For this purpose, a lubricant oil formulation was produced using a
group III oil (NexBase 3030), and the kinematic viscosity at
120.degree. C. was adjusted to approx. 4.73 mm.sup.2/s. The
concentration of the polymer was 13.3% by weight. The coefficient
of friction determined by HFRR was 0.132. A group III reference oil
composed of Nexbase 3080+Nexbase 3060 having a kinematic viscosity
at 120.degree. C. of 4.74 mm.sup.2/s exhibited a coefficient of
friction of approx. 0.21.
EXAMPLE 2
[0232] Example 1 is essentially repeated, except that the nonpolar
segment P is prepared using an initial charge of 914 g of
12/15-alkyl methacrylate and 32 g of styrene. On attainment of 90%
conversion, the polar segment D is then prepared by adding the
degassed mixture of 84 g of N-(2-methacryloyloxyethyl)ethyleneurea
(EUMA) and 21 g of styrene, and the reaction mixture is likewise
stirred at 80.degree. C. for 16 hours.
[0233] The weight-average molecular weight of the polymer,
determined by means of GPC, was about 25 000 g/mol.
[0234] The properties of the polymer were examined in an HFRR test.
For this purpose, a lubricant oil formulation was produced using a
group III oil (NexBase 3030), and the kinematic viscosity at
120.degree. C. was adjusted to approx. 4.70 mm.sup.2/s. The
concentration of the polymer was 13.2% by weight. The coefficient
of friction determined by HFRR was 0.096. A group III reference oil
composed of Nexbase 3080+Nexbase 3060 having a kinematic viscosity
at 120.degree. C. of 4.74 mm.sup.2/s exhibited a coefficient of
friction of approx. 0.21.
EXAMPLE 3
[0235] Example 1 is essentially repeated, except that the nonpolar
segment P is prepared using an initial charge of 914 g of
12/15-alkyl methacrylate and 42 g of styrene. On attainment of 90%
conversion, the polar segment D is then prepared by adding the
degassed mixture of 84 g of acetoacetoxyethyl methacrylate
(AcAcEMA) and 11 g of styrene, and the reaction mixture is likewise
stirred at 80.degree. C. for 16 hours.
[0236] The weight-average molecular weight of the polymer,
determined by means of GPC, was about 25 000 g/mol.
[0237] The properties of the polymer were examined in an HFRR test.
For this purpose, a lubricant oil formulation was produced using a
group III oil (NexBase 3030), and the kinematic viscosity at
120.degree. C. was adjusted to approx. 4.74 mm.sup.2/s. The
concentration of the polymer was 14.8% by weight. The coefficient
of friction determined by HFRR was 0.085. A group III reference oil
composed of Nexbase 3080+Nexbase 3060 having a kinematic viscosity
at 120.degree. C. of 4.74 mm.sup.2/s exhibited a coefficient of
friction of approx. 0.21. In addition, the copolymer exhibited an
absolute wear of approx. 208 .mu.m, whereas the reference oil
exhibited wear of approx. 334 .mu.m.
COMPARATIVE EXAMPLE 1
[0238] A 2 l reaction flask equipped with a heating mantle,
internal temperature regulation, stirrer, nitrogen inlet and
condenser is initially charged with 900 g of isoC12-C15-alkyl
methacrylate, 225 g of butyl acetate and 6.75 g of cumyl
dithiobenzoate (initiator for RAFT). The mixture is thoroughly
degassed with dry ice and heated to 90.degree. C. with introduction
of nitrogen. On attainment of the reaction temperature, the
polymerization is started by addition of 1.8 g of tBPO (tert-butyl
per-2-ethylhexanoate). After four and eight hours of reaction time,
0.9 g of tBPO is added in each case and then the mixture is stirred
for a further fifteen hours. This is followed by the addition of
71.9 g of N-(2-methacryloyloxyethyl)ethyleneurea (EUMA) in 300 g of
butyl acetate and 0.97 g of tBPO. After a further four hours, the
mixture is diluted with 647.9 g of oil. Subsequently, the mixture
is degassed on a rotary evaporator at 120.degree. C. and a final
vacuum of 12 mbar.
[0239] The weight-average molecular weight of the polymer,
determined by means of GPC, was about 75 000 g/mol.
[0240] The properties of the polymer were examined in an HFRR test.
For this purpose, a lubricant oil formulation was produced using a
group I oil (Enerpar 11=150N), and the kinematic viscosity at
120.degree. C. was adjusted to approx. 9.21 mm.sup.2/s. The
concentration of the polymer was 7.0% by weight. The coefficient of
friction determined by HFRR was 0.18. A group I reference oil
composed of Ergenol BS+Esso 600N having a kinematic viscosity at
120.degree. C. of approx. 9.24 mm.sup.2/s exhibited a coefficient
of friction of approx. 0.20.
COMPARATIVE EXAMPLE 2
[0241] A 2 l reaction flask equipped with a heating mantle,
internal temperature regulation, stirrer, nitrogen inlet and
condenser is initially charged with 900 g of isoC12-C15-alkyl
methacrylate, 225 g of butyl acetate and 6.75 g of cumyl
dithiobenzoate (initiator for RAFT). The mixture is thoroughly
degassed with dry ice and heated to 85.degree. C. with introduction
of nitrogen. On attainment of the reaction temperature, the
polymerization is started by addition of 1.8 g of tBPO (tert-butyl
per-2-ethylhexanoate). After five hours of reaction time, 0.9 g of
tBPO is added. After a further five hours of reaction time, 78.3 g
of acetoacetoxyethyl methacrylate (AcAcEMA) in 300 g of butyl
acetate and 0.98 g of tBPO are added. Subsequently, the mixture is
stirred at 85.degree. C. for a further 30 hours. Thereafter, the
mixture is diluted with 526.8 g of oil and degassed on a rotary
evaporator at 120.degree. C. and a final vacuum of 12 mbar. The
weight-average molecular weight of the polymer, determined by means
of GPC, was about 150 000 g/mol.
[0242] The properties of the polymer were examined in an HFRR test.
For this purpose, a lubricant oil formulation was produced using a
group I oil (Enerpar 11=150N), and the kinematic viscosity at
120.degree. C. was adjusted to approx. 9.12 mm.sup.2/s. The
concentration of the polymer was 5.5% by weight. The coefficient of
friction determined by HFRR was 0.19. A group I reference oil
composed of Ergenol BS+Esso 600N having a kinematic viscosity at
120.degree. C. of approx. 9.24 mm.sup.2/s exhibited a coefficient
of friction of approx. 0.20.
* * * * *