[0001] This invention relates to pour point depressants for use in lubricating oils and
more particularly to a new and novel class of poly(methacrylate) polymeric pour point
depressants which provide substantial advantages when used in lubricating oils.
[0002] Wax-bearing lubricating oils are known to set to a semi-plastic mass on cooling below
the temperature of the crystallization point of the wax contained in the lubricating
oil. This change is measured in terms of pour point which may be defined as the temperature
at which the oil sample is no longer considered to flow when subjected to the standardized
schedule of quiescent cooling prescribed by ASTM D97-47. This problem presents a substantial
disadvantage in the use of lubricating oils by the petroleum industry.
[0003] The problem with lubricating oils which contain any amount of waxes is that the wax
contained in the oil, which is a paraffinic oil, will crystallize when the oil is
cooled, and networks of wax crystals will then form on further cooling which will
prevent the oil from flowing. The point at which the oil stops flowing is defined
as the pour point temperature. Dewaxing of an oil improves the pour point, but this
is an expensive procedure. Usually, the procedure is to dewax an oil to a certain
temperature and then add pour point depressants to improve the low temperature properties.
However, at the lower temperature, the same amount of wax will still separate. The
pour point depressants do not make the wax more soluble in oil; they function rather
by disrupting or preventing the formation of the waxy network. As little as 0.2 wt.
% of a good pour point depressant can lower the pour point of the paraffinic oil or
lubricating composition by 30-35'C.
[0004] The wax networks will also lead to an increase in oil viscosity. The increase in
viscosity is generally temporary as a "normal" internal combustion engine can generate
sufficient shear to disrupt the wax networks and allow the oil to flow. However, it
should be emphasized that while the physical turning or cranking of the engine is
usually unimpeded, the temporary disruption in the oil flow can lead to an increase
in bearing wear.
[0005] Studies have indicated that the amount of wax needed to prevent flow or gel for an
oil is quite small. Approximately 2% precipitated wax will gel middle distillates,
and a similar amount is needed for lubricating oils.
[0006] Many different types of pour point depressants have been used in the prior art. Previously
used pour point depressants are predominantly oligomers having molecular weights of
1,000 to 10,000, or polymers which have molecular weights greater than 10,000. The
early point depressants were either alkylated aromatic polymers or comb polymers.
Comb polymers characteristically have long alkyl chains attached to the backbone of
the polymer, with the alkyl groups being of different carbon chain lengths.
[0007] The mechanism of action for pour point depressants has been the subject of much interest.
Early indications were that alkylated aromatic compounds function as pour point depressants
by coating the surface of the wax crystals and preventing further growth. More recently,
however, it appears that the pour point depressants are either absorbed into the faces
of the wax crystal if the pour point depressant is an alkyl aromatic or co-crystallize
with the wax crystal if it is comb polymer. Thus, crystal growth is not prohibited,
it is simply directed or channeled along different routes. Light microscopy suggests
that wax crystals are typically thin plates or blades, and when a pour point depressant
is added to the system, those crystals are smaller and more branched, and thus the
pour point depressant may disrupt or redirect crystal growth from different directions
into a single direction, and bulkier crystals will be formed. These crystals then
can form networks only at much lower temperatures which results in a lower pour point.
[0008] Reports on pour points studies may be found in the publication of Gavlin et al entitled
"Pour Point Depression of Lubricating Oils",
Industrial and Engineering Chemistry, Vol. 45, 1953, pages 2327 to 2335. Also of interest in background with respect to
pour point depressants is the publication by Clevenger et al, entitled "Low Temperature
Rheology of Multigrade Engine Oils--Formulary Effects", 1983 Society of Automotive
Engineers, Inc., Publication No. 831716; a publication by Henderson et al entitled
"New Mini-Rotary Viscometer Temperature Profiles that Predict Engine Oil Pumpability",
Society of Automotive Engineers, Inc. 1985, Document No. 850443; a publication by
Lorensen, "Symposium on Polymers in Lubricating Oil Presented Before the Division
of Petroleum Chemistry, American Chemical Society, Atlantic City Meeting, September
9-14, 1962, Preprint, Vol. 7, No. 4; and a publication by R. L. Stambaugh entitled
"Low Temperature Pumpability of Engine Oils", Society of Automotive Engineers, Document
No. 841388, 1984.
[0009] As pointed out above, the most recent interest in pour point depressants is found
in poly(methacrylate) polymers. Indeed, methacrylate/acrylate polymers appear to be
the most popular class of pour point depressants now in use. There is available commercially
a line of poly(methacrylate) pour point depressants from the Rohm and Haas Company
under the tradename Acryloid. Also available are similar products from Texaco under
a trade designation of TLA followed by a numerical suffix or TC followed by a numerical
suffix.
[0010] There has also been substantial patent activity concerned with pour point depressants
which comprise poly(methacrylate) compositions. Thus U. S. Patents 3,607,749 and 4,203,854
disclose poly(methacrylate) as viscosity index improvers, but without any data as
to their low temperature performance. In particular, No. 3,607,749 discloses a blend
of a high molecular weight polymethacrylate with a low molecular weight polymethacrylate
as a viscosity index improver.
[0011] Patent No. 3,598,736 discloses the addition of small amounts of oil soluble polymethacrylates
to lubricating oils to reduce the pour point. The polyalkylmethacrylates are described
as copolymers wherein the alkyl side chain contains from 10 to 20 carbon atoms with
an average of between 13.8 and 14.8 carbon atoms. Patent No. 3,679,644 is a division
of 3,598,736 and contains the same disclosure.
[0012] Patent No. 4,073,738 discloses the use of a pour point depressant which comprises
an alkyl acrylate or alkyl methacrylate wherein the alkyl group side chain can have
from 8 to 30 carbon atoms and preferably from 8 to 22 carbon atoms.
[0013] U. S. Patent No. 4,088,589 discloses a combination of pour point depressants of which
one can be an oil soluble polymer of an alkyl acrylate or methacrylate which contains
a side chain comprising 10 to 18 carbon atoms in the alkyl group.
[0014] U. S. Patent No. 2,655,479 of Munday et al is directed to polyester pour depressants
and is particularly concerned with average side chain length of acrylate polymer pour
depressants. The patent states in column 3, beginning at line 49 that polymers of
single esters or homopolymers are not good pour point depressants but that copolymers
are generally good pour point depressants. At column 4, beginning at line 44, it is
stated that it is necessary that the average side chain length be in the range of
about 11.0 to about 13.5 carbon atoms per mol of monomer. However, this patentee uses
a combination of only two polymer to obtain this side chain length and the results
are unsatisfactory.
[0015] U. S. Patent 3,598,737 discloses lubricant compositions which contain copolymers
of acrylate esters which are said to improve various characteristics including pour
point. This patent states that the average number of carbon atoms should be at least
12.5 to 14.3. These compounds do not appear to be acrylate esters wherein the side
chain is this value, but rather this patent shows the use of hydroxyalkyl esters in
a poly(methacrylate).
[0016] U. S. Patent No. 3,897,353 discloses oil compositions comprising lubricating oil
and a pour depressant which can be an alkylmethacrylate. These acrylates may be made
from monomers wherein the alkyl portion of the ester or the side chain has from 12
to 18 carbon atoms and includes mixtures. However, the polymers of this patent are
made from nitrogen-containing monomers.
[0017] French Patent 2,135,252 and corresponding U.S. Patent 3,869,396 disclose lubricating
oil compositions whose pour points are depressed by adding small amounts of an oil
soluble copolymer of polyalkylmethacrylates having (A) a molar percentage of alkylmethacrylates
with branched alkyl chains from 5 to 25%, (B) at least six alkyl chains with a different
number of carbon atoms, and (C) a number average molecular weight of 2,000 to 2,000,000,
wherein the alkyl groups in said alkylmethacrylates contain 9 to 18 carbon atoms with
an average of from 12.4 to 13.7 carbon atoms.
[0018] The present invention, however, provides a pour point depressant based on poly(methacrylate)
polymeric compositions which represent a narrow class of such compositions and which
have advantageous properties in improving the low temperature properties of lubricating
compositions while maintaining a good viscosity index.
[0019] It is accordingly one object of the present invention to provide a new and improved
pour point depressant composition.
[0020] A further object of the invention is to provide a unique and advantageous poly(methacrylate)
polymer useful as a pour point depressant in lubricating oils.
[0021] A still further object of the present invention is to provide a lubricating oil composition
which contains a pour point depressant comprising a poly(methacrylate) polymeric material
having an alkyl side chain of critical carbon chain length.
[0022] Other objects and advantages of the present invention will become apparent as the
description thereof proceeds.
[0023] In satisfaction of the foregoing objects and advantages, there is provided by this
invention a pour point depressant for lubricating oils which comprises a poly(methacrylate)
polymer having the repeating unit
wherein R is an alkyl group having an average chain length in the polymer of 12.6
to 13.38, and n is an integer indicating the number of repeating units, the value
of n being sufficient to provide a molecular weight of 10,000 to 300,000 for the polymer,
said polymer being a polymer formed from the reaction of three or four methacrylate
monomers selected from C₁₀ to C₁₆ monomers each of which is present in an amount of
not less than 25 wt.%.
[0024] Also provided by the present invention is a lubricating oil which contains an effective
amount of the novel poly(methacrylate) polymer, the effective amount being sufficient
to provide an oil which meets the Federal Stable Pour for a 5W-30 lubricating oil.
[0025] Reference is now made to the drawings accompanying the application wherein:
Figure 1 is a graph showing the pour point effectiveness of a polymer of the invention;
[0026] As pointed out, above, this invention relates to a new class of pour point depressants
and lubricating oils which contain such pour point depressants. The pour point depressants
of the present invention comprise a selective group of poly(methacrylate) polymers
which have the following repeating unit:
In the above repeating unit, R is an alkyl group having an average carbon chain
length in the polymer of 12.6 to 13.38, and n is an integer indicating the number
of repeating units, the value of n being sufficient to provide a molecular weight
of 10,000 to 300,000, preferably 30,000 to 220,000 for the polymer, the polymer having
been prepared from three or four methacrylate monomers in the C₁₀ to C₁₆ range each
of which is present in an amount of not less than 25 Wt. %.
[0027] It has been found according to the present invention that for a polymethacrylate
to be effective as a pour point depressant in a lubricating oil, it must have an average
side carbon chain length of 12.6 to 13.38 carbon atoms. When a polymethacrylate pour
point depressant of this type is used in conjunction with a compatible viscosity index
improver, a lubricating oil of the 5W-30, 10W-30, 10W-40 and 15W-40 qualities can
be produced to provide a formulation which will pass the required low temperature
tests for such oils.
[0028] It has been found that whether the formulation will pass or fail the low temperature
limits for a lubricating oil formulation will depend, in large measure, on the number
and kind of side chains present in the pour point depressant. A successful formulation
is defined as one with a Federal Stable Pour of ≦ -35'C, a viscosity of ≦ 3,500 cP
at -25'C in the Cold Cranking Simulator (CCS), and a MRV (mini- rotary viscometer)
viscosity of ≦ 30,000 cP at -30' in both the 18 hour (D-3829) and TP-1 cooling cycles.
A complete discussion of the low temperature rheology of multi-grade engine oils may
be found in the publication by Clevenger et al, Document 831716 of the Society of
Automotive Engineers, 1983. This publication sets forth the specifications for various
grades of engine oils, particularly as may be seen in Table 1 on page 2 of the publication.
[0029] In this application, the reference to average side carbon chain length refers to
the length of the carbon chain (R in the formula) in the alkyl group on the ester
moiety. The carbon chain length is determined by the alcohol used to esterify the
methacrylic acid in preparation of the methacrylate monomer.
[0030] In this invention it has been discovered that the identity and number of the ester
side chains present in the pour point depressant determines the effectiveness of the
formulation as measured by the above tests. According to this invention, it has been
found that only certain specific combinations of average side chain alkyl length provide
acceptable results.
[0031] In this invention it has been discovered that the average side chain length (R) of
a poly(methacrylate) pour point depressant must be in the range of 12.6 to 13.38.
This average side chain length of the polymer has been found to depress the pour point
of a suitable lubricating oil from -17.78 to -37.22°C (0° to -35°F). Alkyl side chain
averages lower than this do not provide acceptable results, and polymers with side
chain averages larger than 13.50 lower the pour point a lesser amount. When the effective
alkyl side chain average of 12.6 to 13.38 is prepared from three or four monomers
and used in accordance with this invention, a poly(methacrylate) polymer is provided
which is an effective pour point depressant and, when used with a suitable viscosity
index improver, provides a pour point depressant combination and engine oil which
meets the required standards of the Federal Stable Pour.
[0032] The poly(methacrylate) pour point depressants of this invention are described as
having an average side chain carbon length of 12.6 to 13.38. This value is obtained
by using the correct mix of monomers in preparation of the polymer. The polymer is
prepared by preparation of the monomers, mixing and blending properly and then subjecting
to polymerization. The appropriate mix to obtain an average side chain in the range
of 12.6 to 13.38 carbon atoms requires a mixture of three or four monomers of a mixture
of C₁₀ to C₁₆ monomers. These references to side chains refer to the esterified portion
of the methacrylate or R in Formula I as the carbon chain is supplied by the alcohol
used for esterification. For example, a formulation of monomers which includes 35-38%
of C₁₀ monomers, 31-34% C₁₄ monomers and 28-34% C₁₆ monomers will provide a polymer
having an average chain length of 12.68 to 13.38. It is within the scope of the present
invention, however, to select any combination of three or four methacrylate monomers
in the C₁₀ to C₁₆ range, with no monomer present in less than 23 wt. % which will
provide the final polymethacrylate polymer with an average side chain length, or value
of R, of 12.6 to 13.38.
[0033] As will be apparent from the structure of the polymer, the variations in the chain
length are provided by the alcohol which is used to form the ester monomer of methacrylic
acid. Thus, the value of R in the monomer is from C₁₀ to C₁₆. A preferred group of
monomers will have the value of R ranging from C₁₀ to C₁₆. The resulting product is
therefore a polymer in which the value of R may range from C₈ to C₂₀, but wherein
the average value or average carbon chain length for R is 12.6 to 13.38 provided that
the average is obtained with three or four monomers in the C₁₀ to C₁₆ range where
the minimum concentration of each monomer is at least 25% by weight.
[0034] The method of calculation of the average side chain carbon length in this invention
is the method disclosed in column 4, lines 31-49 of U.S. Patent No. 3,814,690 where
a method for calculating "mole equivalent average chain length" is discussed. This
value is essentially the same as "average side chain length, Cav" in this patent application.
The following formula is used:
when CN₁ is the number of chain carbons in the first chain, CN₂ is the number of chain
carbons in the second chain, CN
n is the number of chain carbons in the nth chain, MP₁ is the mole percent of first
component, MP₂ is the mole percent of the second component, MP
n is the mole percent of the nth component. Mole percent is equal to the mole fraction
times 100%.
[0035] As shown in the examples described hereinafter, the pour point of the base oil alone
can be depressed with any combination of chains that will yield a 12.6-13.38 chain
average; however, with formulated oils the 3 to 5 monomers in the C₁₀ to C₁₆ range
must be carefully chosen as not all combinations will work with ethylene-propylene
viscosity index (VI) improvers. Any synergistic mixture of monomers to produce a polymer
having this average side chain length or value of R is considered to be within the
scope of the invention.
[0036] The monomers and resulting terpolymers may be produced by methods well known to the
art described, for example, in United States Patents 3,598,736, and 4,088,589, the
disclosures of which are incorporated herein by reference.
[0037] As indicated above, a pour point depressant is used in a lubricating oil or engine
oil in order to provide a resulting formulation which will pass the low temperature
tests required for such fluids, such as the Federal Stable Pour test. The pour point
depressant is often used in combination with a viscosity index improver, VI, of which
many different types are available. For example, ethylene/propylene viscosity index
improvers are particularly available from Amoco. Other viscosity index improvers sold
under the name TLA, which are ethylene-propylene copolymers to which a vinyl pyrrolidone
has been grafted to provide dispersing characteristics, may also be used with such
formulations. Certain chain combinations of the pour point depressant will function
with one or the other VI improvers even though the pour point depressant has the requisite
12.6-13.38 side chain average.
[0038] The pour point improvers are normally used with a suitable lubricating fluid or engine
oil. A preferred lubricating oil of this type is sold by Pennzoil Company under the
tradename Atlas, and particularly Atlas 100N. Other base stocks such as, but not limited
to, Ashland 100N or Exxon 100 LP are also suitable for use. The lubricating oil may
be a 5W-30, 10W-30, 10W-40 or 15W-40 grade.
[0039] As a result of Applicants' research in this area, it has been discovered that an
effective pour point depressant will have an average side chain length of 12.6 to
13.38, preferably 12.6 to 13.30, more preferably 12.6 to 13.0 and this will depress
the pour point of lubricating fluid such as Atlas 100N from -17.78 to -37.22 °C (0°
down to -35°F). Where the value of R or the side chain length is lower than 12.6,
a pour point depressant is provided which is not effective to meet industry standards.
Polymers with side chain averages higher, than 13.38 will lower the pour point only
to about -28.89°C (-20°F). To achieve the effective side chain average of 12.6 to
13.38, the polymers are formed from a group of indicated monomer components to provide
the best results.
[0040] There is also a requirement that the molecular weight of the polymer of the invention
have a lower limit of about 30,000 dalton and an upper limit in the range of 220,000
dalton. Thus the degree of polymerization is also important.
[0041] The amount of pour point depressant of this invention to be added to the lubricating
oil will range from 0.001 to 1.0 wt.% and preferably range from about 0.01 to 0.50
wt. % when the pour point depressant is a concentrate. The amount of viscosity index
improver added is preferably about 5 to 20 wt.% depressant.
[0042] The lubricating oil composition will also preferably contain a detergent composition
such as the commercially available detergent packages. The pour point depressant compositions
of this invention are compatible with all such detergent packages.
[0043] Several different detergent packages are available for use in the invention, and
are preferably used at the SG level of detergency. The American Petroleum Institute,
API, has established different service i.e., protection classification levels, for
lubricating oils. Several different engine tests that emphasize different aspects
of engine performance must be passed to allow the oil to be certified at that level.
For example, the SE classification was introduced in 1972.
[0044] Formulated oils that met this classification level offered more protection against
corrosion, oil oxidation, rust and engine deposits than earlier oils. The SF category
was introduced in 1980. Formulated oils that met this classification level had better
oxidative stability and anti-wear performance than SE oils. The SG level was introduced
in 1988. Formulated oils that met this classification level had better sludge control
and anti-wear performance than SF oils. The improvement in anti-wear performance is
needed because of the extended warranties that are currently available. The trend
has been for formulated oils to meet more exciting performance requirements dictated
by today's smaller more demanding engines. Detergent package F uses polyisobutylene
dispersant chemistry. Detergent package G is a spike composed of calcium phenates
and sulfonates to give additional performance. Detergent package I uses Mannich dispersant
chemistry. Detergent package I is approximately 23 wt% dispersant. Detergent package
J employs polyisobutylene succinimide dispersant chemistry. The above description
is merely qualitative as these packages are composed of other additives that serve
different purposes.
[0045] Reference is now made to the drawings accompanying the application, wherein Figure
1 is a graph illustrating the pour point of the lubricating fluid Atlas 100N as the
pour point changes depending on the average side chain length or the number of carbons
for the value of R.
[0046] The following examples are presented to illustrate the invention, but the invention
is not to be considered as limited thereto. In the examples and throughout the specification,
parts are by weight unless otherwise indicated.
Example 1
[0047] In the following Table 1, the polymethacrylate polymer compositions set forth in
Experiments 1-13 were prepared using the monomers indicated as C₄, C₁₀, C₁₁, C₁₂,
C₁₄ and C₁₆. Thus, the polymers were produced using a combination of methacrylic acid
esters wherein the alcohol used to esterify the methacrylic acid had the indicated
C value. For example, in Experiment 1, the polymer was prepared from a mixture of
three monomers, 45.1% C₁₀, 43.1% C₁₂ and 11.8% C₁₄ for a chain length average of 11.2.
In the polymers described in the table, the chain length distribution (normalized
weight distribution) was determined by gas chromatography on an SE-30 column of the
methacrylate monomer mixture prior to polymerization. In one example, the monomer
mixtures was isolated after polymerization, and the composition was nearly the same
as the initial charge. Polymerizations were conducted in xylene under a nitrogen atmosphere
with benzoyl peroxide as the free radical initiator. Reactions were conducted at 85-95'C
for a period of several hours. Molecular weights were measured by gel permeation chromatography,
relative to polystyrene.
[0048] The neat polymers were dissolved at 0.25 wt. % in the lube oil Atlas 100N. The pour
points were determined by the D-97 test. The results are also displayed in Table 1.
A graph of the pour point of Atlas 100N as a function of the average side chain length
of the polymethacrylate) PPD is shown in Figure 1.
[0049] Analysis of the data of Table 1 reveals the following conclusions:
1) An average side chain length of 12.6-13.50 will depress the pour point of a lube
oil of this type from -17.78 to -37.22°C (0' to -35'F). Side chain averages lower
than this, Polymers 1-3, do not work; polymers with side chain averages larger than
this range, Polymers 11 and 12, only lower the pour point to -28.89°C (-20°F).
2) Within the effective side chain average of 12.6-13.50, polymers with two components
(Polymer 9) work as well as polymers with 3 components (polymer 8). A variety of 3
component chains work, (e.g., Polymers 4, 5 or 10).
3) There is a lower limit on the Mw that a polymer needs to function. Polymer 13 has
an Mw of 4300 but does not work while polymer 6 functions with a Mw of 34,000. A Mw
of about 30,000 is considered a reasonable lower limit.
4) There is no difference in effectiveness of the pour point depressants once the
lower limit has been reacted. Polymers 5 and 6 are equally effective even though Polymer
5 has Mw of 56,200 and Polymer 6 has an Mw of 34,000.
5) The effectiveness of Polymer 7 in the lube oil indicates that short chain groups
may be present on the polymer but will not interfere with the polymer's effectiveness
so long as the average is within the range 12.6-13.50.
Example 2
[0050] In this example, several of the poly(methacrylates) described in Table 1, together
with several additional polymethacrylates which had the desired average side chain
length of 12.6 to 13.0 carbon atoms, were prepared for testing. The composition and
molecular weight distribution of this latter group of polymethacrylate pour point
depressants is described in Table 2. Table 2 illustrates how polymethacrylate pour
point depressants within the scope of the invention can be prepared using different
combinations of monomeric components. Thus, the monomers were methacrylates wherein
the esterifying alcohol had a carbon chain ranging from 10 carbons to 16 carbons,
so that the average carbon chain length for the polymers ranged from 12.68 to 12.85.
Table 2 is as follows:
Example 3
[0051] In this example of a formulation study with Viscosity Index Improvers and other additives,
formulations are prepared to represent a motor oil having the proper components to
meet the Federal Stable Pour, the MRV test, the CCS, the TP-1 cooling cycles. In Table
3, the heading for PPD Polymer refers to the numbered polymer prepared in Tables 1
and/or 2. The VI improver A is an olefin copolymer of ethylene-propylene to which
vinyl pyrrolidone has been grafted to give dispersing characteristics. It has a molecular
weight of about 180,000. Atlas 100N is the base oil to which these components are
added in the amounts indicated.
[0052] In this example, two dispersant olefin copolymers Viscosity Index improvers were
used in the formulations. VI improver A has a Mw - of 189,000 and Mn of 43,000. VI
improver B has a bimodel molecular weight distribution. The lower fraction has an
Mw of 189,000 and Mn of 76,750. The higher fraction has an Mw > of 1,000,000.
[0053] Many of the poly(methacrylates) described in Table 1, along with several additional
polymethacrylates that had the desired average side chain length of 12.6-13.0 carbon
atoms, were tested in the formulations. The composition and molecular weight distribution
of this latter group of poly(methacrylate) PPDs is described in Table 2.
[0054] Polymers 19 and 20 were prepared in Atlas 100N and used as concentrates with an effective
polymer concentration of 25-35% wt. The Viscosity Index Improver A with their D-97
pour points, Federal Stable Pour, -25°C CCS viscosities, the CCS, the -30°C viscosity
as measured in the MRV with an 18 hour (D 3829) and TP-1 cooling cycles, and 100'C
viscosities are displayed in Table 3. The results of the Viscosity Index Improver
B formulations are shown in Table 4.
[0055] Both series of formulations used detergent package A. Detergent package A consists
of a borated succinate ester dispersant with a mixture of calcium and magnesium phenates
used as detergents. Other detergent packages were used (see below); detergent package
B was composed of a polyisobutylene succinimide dispersant with a magnesium sulfonate
detergent; detergent package C contained a polyisobutylene succinimide dispersant
with a calcium sulfonate detergent; detergent package D contained only a calcium sulfonate
detergent and detergent package E, which has similar constituents as detergent package
A but with less calcium phenate. Detergent packages C and D were used together. All
detergent packages contained zinc dialkyldithiophosphates. Detergent packages are
items of commerce with varied ingredients and methods of preparation, some of which
are trade secrets, such that the exact nature or number of compound cannot be readily
determined. Consequently the above description of the detergent packages is qualitative
and is not exhaustive.
Olefin Copolymer VI Improver A Formulations
[0056] Formulations 4A, 5B, 10A, 10B, 12A and 12B met the following low temperature standards
for a 5W-30 oil; a CCS viscosity of ≦ 3,500 cP at -25°C, a Federal Stable Pour of
≦ -35°C, and a MRV viscosity of ≦ 30,000 cP at -30°C with the D-3829 and TP-1 cooling
cycles.
[0057] Formulations 4A, 5B, 10A, 10B, 12A and 12B used polymers with chain compositions
that were 35-38% C₁₀, 31-34% C₁₄, and 28-34% C₁₆ with a side chain average of 12.68-13.0.
The polymers are identical except for the molecular weight. Polymer 10, used in formulations
4A-C, has Mw of 39,900 and Mn of 11,700. Polymer 14, used in formulations 5A-B, has
a Mw of 68,000 and Mn of 13,300. Polymer 19, used in formulations 10A and 10B has
a Mw of 139,000 and Mn of 30,000. Polymer 20 had a Mw of 195,700 and a Mn of 65,300.
While all of the polymers will produce successful formulations, higher concentrations
of Polymer 10 (Formulations 4A-C) and 14 (Formulations 5A-B) must be used as compared
to Polymer 19 (Formulations 10A-B) or Polymer 20 (Formulations 12A and 12B) to get
these results. Polymers 10 and 14 were used neat while Polymers 19 and 20 were used
as concentrates. The actual amount of Polymer 19 used in formulation 13A is approximately
0.07 to 0.10 wt.%. Polymer 20, used in Formulations 12A and 12B, yielded results similar
to those of Polymer 19. The higher molecular weight (Mw) polymers are more effective
on the basis of concentration.
[0058] The only other effective pour point depressant was Polymer 17 used in formulation
8. It was the only four component pour point depressant which produced satisfactory
formulations. However, it is not effective with VI Improver B (see below).
[0059] The other formulations do not work. Formulations 1 and 3 fail miserably. Formulations
2A, 2B and 6 have unacceptably high MRV (D-3829) viscosities. Formulation 6 also suffers
from a high Federal Stable Pour. Formulation 9 has a high Federal Stable Pour although
its MRV (D-3829) and TP-1 viscosities are acceptable.
[0060] Formulations 2A-2B and 7A-7B demonstrate that increasing the pour point depressant
concentration can cause a deterioration in the properties of the formulations. The
MRV viscosity, with the D-3829 cooling cycle, increases for Polymer 5 in formulations
2A and 2B. The stable pour increased in formulations 7A and 7B when the concentration
and Polymer 16 was increased.
[0061] Formulations 11A-C use Acryloid 154-70 as the pour point depressant. Formulations
11A and 11B have stable pour problems. The MRV viscosities also increase to unacceptably
high levels when the Acryloid 154-70 concentration is increased to 1.0 wt.% (Formulation
11C).
[0062] The three component pour point depressant that has a C₁₀, C₁₄, and C₁₆ chain distribution
and the four component pour point depressant with the C₁₀, C₁₁, C₁₄ and C₁₆ chain
length distributions are the best pour point depressants tested. They produce formulations
with better low temperature properties than either Acryloid 154-70 or any of the other
experimental pour point depressants. For the latter polymers, it is not clear why
certain three or four components function in the presence of DOCP VI improvers and
other three or four chain combinations do not. It is also not clear why a three component
pour point depressant should work better than almost all of the four component pour
point depressants and the five component pour point depressants.
Olefin Copolymer VI Improver B Formulations
[0063] The low temperature properties of the VI Improver B formulations are displayed in
Table 4.
[0064] Formulations 2A, 2B, 3, 8 and 12 have acceptable stable pours, CCS viscosities and
MRV (D-3829) viscosities. Formulations 2-3 contain Polymers 5 or 6; these polymers
contain the same chain distribution, and they differ only in molecular weight. There
does not seem to be any difference in overall performance of the formulation due to
molecular weight for Polymers 5 or 6. Only Polymer 19 or Polymer 20 (see Table 5)
functions effectively with both VI Improver A or VI Improver B. The other polymers
work successfully with only one of the VI improvers. Polymer 5 fails with VI Improver
A, formulation 2A-B in Table 3, but works effectively with VI Improver B, formulations
2A-B in Table 4. Polymer 17 functions with VI Improver A, formulation 8 in Table 3,
but fails with VI Improver B, formulation 10 in Table 4. Polymer 15 functions effectively
with VI Improver B, formulation 8, in Table 4, but is not effective with VI Improver
A, formulation 6, Table 3. These results indicate that a pour point depressant can
be tailored for each DOCP VI improver.
[0065] The other formulations have high MRV viscosities in the standard cooling cycle (formulation
7) or with the TP-1 cycle (Formulations 7, 9-11).
[0066] Formulation 13 contains Acryloid 154-70. While it has acceptable MRV viscosities
in both the D-3829 and TP-1 cooling cycles, the stable pour is too high. The experimental
pour point depressants described in Tables 1 and 2 produce better 5W-30 formulations.
[0067] The failure of Polymer 7 in formulation 4 is an interesting contrast to the success
of Polymer 6 in Formulation 3. The only difference between the two pour point depressant
polymers is that Polymer 7 contains butyl groups. The butyl groups may be interfering
with the success of the formulation.
Miscellaneous Formulations
[0068] Various VI/DI package combinations were tested with polymers 19 or 20 in Atlas 100N
as potential 5W-30 formulations. The low-temperature viscometric properties of the
formulations are displayed in Table 5. Both pour point depressant concentrates, polymers
19 and 20, function effectively with a variety of VI/DI package combinations, producing
formulations with very good low-temperature properties. The poly (methacrylate) with
a C₁₀, C₁₄, and C₁₆ chain distribution with a C
av of 12.6-13.0 is a versatile pour point depressant.
[0069] Several 10W-30 and 10W-40 formulations were tested with Polymer 20 in Atlas or Chevron
base stocks. The low-temperature results of the formulations are collated in Table
7. The 10W series is required to have ≦ -30°C Federal Stable Pour, a CCS viscosity
of ≦ 3500 cP at -20°C, and a viscosity of ≦ 30,000 cP at -25°C in both the 18-hour
and TP-1 cooling cycles. The formulations with Polymer 20 quite easily surpassed these
requirements. The fact that the pour point depressant functions in 5W-30s, 10W-30s,
and 10W-40s makes it an attractive, versatile additive.
[0070] The pour point depressant, Polymer 19, was tested in Ashland 100N with very good
results shown in Table 7. The 5W-30 formulations had very good low-temperature properties,
indicating that the pour point depressant is not limited to only one base stock.
Example 4
[0072] In order to compare a preferred pour point depressant of the present invention, calculations
are made using the calculation formula of U.S. Patent 3,814,690 to compare the average
carbon side chain length of Polymer 19 of this invention with pour point depressant
polymers disclosed in U.S. Patent No. 3,897,353. Example A shows the calculation of
the Cav for one 200 gram alcohol mixture mentioned in column 6 of the U. S. Patent
3,897,353 composed of 150 g of Neodol 25L and 50 g of Alfol 1620 SP. The relative
weight distribution shown was calculated by multiplying each alcohol mixture by its
respective weight distribution, as described above, adding together the components
that overlapped, and then normalizing the new distribution. In the calculation, if
a 100 gram alcohol sample is assumed, then there will be 24 g of C₁₂OH (0.24 x 100
g), 24 g of C₁₃OH, etc., as shown in the third column. As the molecular weights, g/mole,
are shown in the fourth column, the moles of each component are easily obtained by
dividing the weight of alcohol by its molecular weight with the results shown in column
5. The last column, column 6, shows the mole percent of each alcohol which was obtained
by multiplying the mole fraction by 100%. The mole fraction is simply the mole of
each component divided by the total number of moles. The side chain average calculation
is shown. The Cav is 13.32 for Example A. The chain average, Cav, for the mixture
was calculated to be 14.07.
[0073] Example B shows the methacrylate distribution for polymer 19, Table 2 of this application.
By following the same procedures as outlined for Example A, the Cav was calculated
to be 12.83.
[0074] The tables for these calculations are as follows:
[0075] As will be seen from Example A, the calculations show that the average side chain
length is 14.08. In Example B, which is Applicants' polymer 19, the average side chain
length is 12.83.
Example 5
[0076] The pour point depressants of this invention were evaluated with various detergent
packages used in lubricating oils. In this work, additional pour point depressants
were prepared.
[0077] Compositions and molecular weight distributions, (MWDs), of three pour point depressants
that share the same components decyl methacrylate (C₁₀ meth), tetradecyl methacrylate
(C₁₄ meth), and hexadecyl methacrylate (C₁₆ meth), but in different proportions, to
give three different side chain averages, Cav, are shown in Table 9. The polymers
in concentrates 21, 22 and 23 have very similar MWDS as well as polymer loads. It
should be pointed out the polymers 19 and 20 in Table 2 of the application are really
concentrates containing those polymers. The polymers in concentrates 20 and 21 are
essentially the same; both have the same methacrylate compositions that yield basically
identical Cavs and very similar MWDS. The only difference between the two concentrates
is that concentrate 20 is approximately 25 wt% polymer while concentrate 21 is approximately
40-45 wt% polymer.
[0078] Olefin copolymer viscosity index improver concentrate C was used in the formulations.
It is similar in nature to olefin copolymer concentrate A discussed in Example 3 of
the application. However, it has a lower molecular weight than A. The lower molecular
weight is believed to make the polymer less likely to shear in the engine. Viscosity
Index (VI) improvers with this property have only recently been introduced in the
industry; they are called shear stable VI improvers.
[0079] Several different detergent packages were used in the formulations. They are at the
SG level of detergency. Detergent package F, at SG performance levels, is used in
formulations displayed in Tables 10 and 11. It uses polyisobutylene dispersant chemistry.
The SF version of this DI package, identified as detergent package H, is used in Table
11. Detergent package F is 25 wt% dispersant while H is 19 wt% dispersant. Detergent
package G is a spike composed of calcium phenates and sulfonates to give additional
calcium phenates and sulfonates to give additional performance. Detergent package
I uses Mannich dispersant chemistry. Detergent package I is approximately 23 wt% dispersant.
Detergent package J employs polyisobutylene succinimide dispersant chemistry. The
above description is merely qualitative as these packages are composed of other additives
that serve different purposes. The low temperature properties of the 5W30 formulations
with the various PPD concentrates are displayed in Table 10.
[0080] The 18 hr and TP-1 MRV viscosities are essentially the same. In the 5W30 formulations,
the viscosities are independent of treat level and Cav.
[0081] The stable pour data does show a trend toward higher stable pours with increasing
treat rates of the concentrates. Compare entries 1-3 for concentrate 21 where the
stable pour increases from <-41 to -36°C as the treat rates increases from 0.06 wt%
to 0.31 wt%. Within the limits of experimental error, there is an increase in the
stable pour as the Cav increases (at low treat rates). Compare entry 1, where the
stable pour is <-41°C at a treat rate of 0.07 wt% for the concentrate with a Cav of
12.78, to entry 4, where the stable pour is -39°C at a treat rate of 0.15 wt% for
the concentrate with a Cav of 13.16, to entry 6, where the stable pour is -36°C at
a treat rate of 0.10 wt% for the concentrate with a Cav of 13.38. While a stable pour
of -36 is acceptable for a 5W30 oil, it would be more desirable to have a formulation
with a lower stable pour because of the better low temperature properties it affords
the formulation as well as the cushion it affords in the 3°C margin of error allowed
in the measurement.
[0082] The trend toward higher pour points with increasing Cav was demonstrated in D-97
pour points discussed earlier, see figure 1. It is pointed out that the D-97 pour
point and the stable pour are similar in name only; they are completely different
tests. A D-97 pour point test is conducted over a few hours and is basically a straight
cooling test. Refiners use it as a quality control test for base stocks. While it
was originally used in formulation work, it has been rendered obsolete by a battery
of other tests, including the stable pour. At least one company has renamed their
pour point depressants lube oil flow improvers to reflect this change. The stable
pour test is conducted over a period of 7 days with heating and cooling cycles. It
is used for formulations because there is some relationship between the test and the
performance of the formulation in the real world. Its major flaw is that it takes
7 days to complete and is therefore not a good quality control tool for production
work.
[0083] The PPD concentrates were also tested in 10W30 formulations. The results of one 10W30
series is displayed in Table 11. The detergent package H, of SF quality, is used in
entry 1. Concentrate 21 with a Cav of 12.78 is fairly effective in the formulation.
The concentrate does not function when the detergent package is switched to the SG
detergent package F. The formulation freezes solid in the TP-1 MRV, entry 2. The situation
improves when the treat rate is increased, but the results are still not acceptable,
entry 3. The situation dramatically improves when the concentrates with the higher
Cavs are used. The yield stress disappears when concentrate 22 with a Cav of 13.6,
entry 4, or concentrate 23 with a Cav of 13.38, entry 5, are employed.
[0084] The occurrence of yield stress and its subsequent relief occurred in a second 10W30
formulation series shown in Table 12. The SG detergent package I was used. Concentrate
21 with a Cav of 12.78 displayed yield stress at two different treat rates, entries
1 and 2. The yield stress disappeared when concentrate 22 with a Cav of 13.16, entry
3, or concentrate 23 with a Cav of 13.38 are employed, entry 4. The stable pours in
both 10W30 series are quite acceptable.
[0085] Concentrate 21 was tested in 10W30s and 10W40s composed of Chevron basestocks. The
concentrates and low temperature results are displayed in Table 13. The results are
excellent.
[0086] Finally, concentrate 21 was tested in 15W40s. The formulations and results are displayed
in Table 14. The results are excellent. Table 15 summarizes the low temperature requirements
at a 5W, 10W, and 15W oil.
[0087] For the 5W30 and 10W30s that were examined the following conclusions can be drawn;
1) In 5W30s, the stable pours but not the TP-1 MRV viscosities are dependent on the
Cav.
2) In the 10W30s, the TP-1 MRV viscosities but not the stable pours were affected
by the Cav.
[0088] Tables 10, 11, 12, 13, 14 and 15 are presented below.
Table 12
Pour point depressant performance in 10W-30 composed of 6.5% Olefin Copolymer Concentrate
C, 12.2% Detergent Package I, 58.9% Atlas 100N and 22.3% Atlas 325N. |
Concentrate |
Cav |
% PPD |
MRV, -25°C |
TP-1, -25°C |
Stable Pour |
1) 21 |
12.78 |
0.11 |
10,800 YS=140 |
58,000 |
-30 |
2) 21 |
12.78 |
0.20 |
10,500 YS=70 |
32,100 |
-36 |
3) 22 |
13.16 |
0.19 |
15,300 |
15,300 |
-39 |
4) 23 |
13.38 |
0.198 |
13,900 |
14,000 |
-36 |
Table 13
Performance of pour point depressant concentrate 22 in 10W30s and 10W40s composed
of Chevron basestocks. |
|
10W30 |
10W30 |
10W40 |
Wt % PPD |
0.154 |
0.155 |
0.16 |
Olefin Copolymer C |
7.11 |
6.45 |
11.03 |
Detergent Package I |
10.14 |
12.10 |
11.33 |
Chevron 100N |
59.13 |
52.43 |
60.95 |
Chevron 240N |
23.45 |
28.93 |
16.53 |
Results |
|
|
|
Stable Pour, °C |
<-41 |
<-41 |
<-41 |
TP-1 MRV, -25°C |
9,200 |
10,800 |
12,200 |
18 hr MRV, -25°C |
15,300 |
7,700 |
9,700 |
Table 14
Performance of pour point depressant concentrate 22 in 15W40s |
Wt% PPD |
0.2 |
0.14 |
Detergent Package I |
13.78 |
14.10 |
Olefin Copolymer C |
9.07 |
10.35 |
Atlas 100N |
40.47 |
- |
Atlas 325N |
27.41 |
- |
Chevron 100N |
- |
28.88 |
Chevron 240N |
- |
36.98 |
Brightstock |
9.07 |
9.56 |
Results |
|
|
Stable Pour, °C |
-36 |
<-41 |
TP-1 MRV, -20°C |
11,700 |
11,800 |
18 hr MRV, -20°C |
10,200 |
13,300 |
Table 15
Low temperature performance requirements of 5W, 10W, and 15W oil. |
5W |
18 hr MRV viscosity <30,000 at -30°C |
TP-1 MRV viscosity <30,000 cP at -35°C Yield Stress <35 pa |
Stable pour,°C ≦ -35 |
10W |
<30,000 at -25°C |
<30,000 cP at -25°C Yield Stress <35 pa |
≦ -30 |
15W |
<30,000 at -20°C |
<30,000 cP at -20°C Yield Stress <35 pa |
≦ -25 |