DE3889533T2 - POINT-LOWING METHACRYLATE ADDITIVES AND COMPOSITIONS. - Google Patents

Description

The invention relates to pour point depressants for use in lubricating oils and, more particularly, to a new class of poly(methacrylate) polymer pour point depressants which provide significant advantages when used in lubricating oils.

Wax-containing lubricating oils are known to solidify into a semi-plastic mass when cooled below the crystallization point temperature of the wax contained in the lubricating oil. This change is determined by the pour point, which can be defined as the temperature at which the oil sample can no longer be considered flowable when subjected to the standardized quiescent cooling scheme described in ASTM D97-47. This problem is a major disadvantage in the use of lubricating oils in the petroleum industry.

The problem with lubricating oils containing any amount of wax is that the wax contained in the oil, the oil being a paraffin oil, will crystallize as the oil is cooled and, as it cools further, networks of wax crystals will form which will prevent the oil from flowing. The point at which the oil stops flowing is defined as the pour point temperature. Dewaxing an oil improves the pour point; however, this is an expensive process. Usually the process involves dewaxing an oil to a certain temperature and then adding pour point depressants to improve the low temperature properties. However, at the lower temperature the same amount of wax will continue to separate. The pour point depressants make They do not make the wax more soluble in the oil, but rather they destroy the wax network or prevent the formation of this network. Just 0.2% by weight of a good pour point depressant can lower the pour point of the paraffin oil or lubricant composition by 30 - 35ºC.

The wax networks will also cause an increase in oil viscosity. The increase in viscosity is generally temporary, as a "normal" internal combustion engine can generate a sufficiently large shear effect to destroy the wax networks and cause the oil to flow. It should be noted, however, that while physical rotation or cranking of the engine is generally not impeded, the temporary obstruction in oil flow can lead to increased bearing wear.

Investigations have shown that the amount of wax needed to prevent an oil from flowing or gelling is quite small. About 2% of precipitated wax will solidify middle distillates, and a similar amount is needed for lubricating oils.

Many different types of pour point depressants have been used in the prior art. The pour point depressants used to date are mainly oligomers with molecular weights of 1000 to 10,000 or polymers with molecular weights of more than 10,000. The early pour point depressants were either alkylated aromatic polymers or comb polymers. Comb polymers typically have long alkyl chains attached to the polymer backbone, with the alkyl groups having different carbon chain lengths.

The mechanism of action of pour point depressants was of great interest. Early evidence suggested that alkylated aromatic compounds act as pour point depressants by coating the surface of the wax crystals and preventing further growth. However, more recent studies seem to show that pour point depressants are either absorbed into the face of the wax crystal if the pour point depressant is an alkyl aromatic or co-crystallize with the wax crystal if it is a comb polymer. Thus, crystal growth is not prevented, but is simply directed or channeled to other pathways. Light microscopy suggests that wax crystals are typically thin plates or flakes and, when a pour point depressant is added to the system, these crystals are smaller and more branched and thus the pour point depressant can destroy crystal growth or redirect crystal growth from different directions to a single direction and larger crystals will form. These crystals can then only form networks at much lower temperatures, resulting in a lower pour point.

Reports on pour point investigations can be found in the publication by Gavlin et al. entitled "Pour Point Depression of Lubricating Oils", Industrial and Engineering Chemistry, Vol. 45, 1953, pages 2327 to 2335. The following publications are also of interest for background knowledge on pour point depressants: 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 paper by RL Stambaugh entitled "Low Temperature Pumpability of Engine Oils," Society of Automotive Engineers, Document No. 841388, 1984.

As stated above, the current interest in pour point depressants is focused on poly(methacrylate) polymers. In fact, methacrylate/acrylate polymers appear to be the most widely used class of pour point depressants at present. Commercially, a range of poly(methacrylate) pour point depressants are available from Rohm and Haas under the trademark Acryloid. In addition, similar products are available from Texaco under the trademark TLA followed by a number or TC followed by a number.

There has also been a great deal of activity in the patent field in the area of pour point depressants with poly(methacrylate) compositions. For example, U.S. Patent Nos. 3,607,749 and 4,203,854 disclose poly(methacrylate) as a viscosity index improver, but no low temperature performance data are given. In particular, U.S. Patent No. 3,607,749 discloses a blend of high molecular weight polymethacrylate with low molecular weight polymethacrylate as a viscosity index improver.

US Patent No. 3,598,736 discloses the addition of small amounts of oil-soluble polymethacrylates to lubricating oils to lower the pour point. The polyalkyl methacrylates are described as copolymers in which the alkyl side chain contains 10-20 carbon atoms with an average of between 13.8 and 14.8 carbon atoms. US Patent No. 3,679,644 is a divisional application of US 3,598,736 and contains the same Revelation content.

US Patent 4,073,738 discloses the use of a pour point depressant with an alkyl acrylate or alkyl methacrylate, wherein the side chain alkyl group has 8-30 carbon atoms and preferably 8-22 carbon atoms.

US Patent No. 4,088,589 discloses a combination of pour point depressants, where a pour point depressant can be an oil-soluble polymer of an alkyl acrylate or methacrylate containing a side chain of 10-18 carbon atoms in the alkyl group.

U.S. Patent No. 2,655,479 to Munday et al. relates to pour point depressants made from polyester, and it particularly relates to pour point depressants made from an acrylate polymer having an intermediate side chain length. The patent states in column 3, beginning at line 49, that polymers of simple esters or homopolymers are not good pour point depressants, but that copolymers are generally good pour point depressants. In 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 mole of monomer. However, in this patent, a combination of only two polymers is used to obtain this side chain length, and the results are not satisfactory.

U.S. Patent 3,598,737 discloses lubricant compositions containing copolymers of acrylate esters which are said to improve various properties including pour point. This patent specifies 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 in which the side chain has this value. but this patent shows the use of hydroxyalkyl esters in a poly(methacrylate).

U.S. Patent No. 3,897,353 discloses oil compositions comprising a lubricating oil and a pour point depressant which may be an alkyl methacrylate. These acrylates may be prepared as monomers wherein the alkyl portion of the ester or side chain has 12-18 carbon atoms and includes mixtures. The polymers of this patent, however, are prepared from nitrogen-containing monomers.

French Patent 2,135,252 and the corresponding US Patent 3,869,396 disclose lubricating oil compositions whose pour points are lowered by adding small amounts of an oil-soluble copolymer of polyalkyl methacrylates, the polyacyl methacrylates having (A) a mole percentage of alkyl methacrylates with branched alkyl chains of 5 to 25%, (B) at least 6 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 the alkyl methacrylates contain 9 to 18 carbon atoms with an average of 12.4 to 13.7 carbon atoms.

However, according to the invention, a pour point depressant is provided based on poly(methacrylate) polymer compositions which represent a narrow class of such compositions and which have advantageous properties in improving the low temperature properties of lubricant compositions while maintaining a good viscosity index.

It is therefore an object of the present invention to provide a new and improved pour point depressant composition.

It is a further object of the present invention to provide a unique and advantageous poly(methacrylate) polymer useful as a pour point depressant in lubricating oils.

It is a further object of the present invention to provide a lubricating oil composition containing a pour point depressant comprising a poly(methacrylate) polymer material having an alkyl side chain with a critical carbon chain length.

Further objects and advantages of the present invention will be disclosed by the following description.

The above-mentioned objects and advantages are achieved or provided according to the invention in that according to the present invention a pour point depressant for lubricating oils is provided which comprises a poly(methacrylate) polymer with the following 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 give a molecular weight of 10,000 to 300,000 for the polymer, wherein the polymer is a polymer formed from the reaction of 3 or 4 methacrylate monomers selected from C₁₀ to C₁₆ monomers, each of the monomers being present in an amount of not less than 25% by weight.

According to the invention there is further provided a lubricating oil containing an effective amount of the novel poly(methacrylate) polymer, the effective amount being sufficient to provide an oil that meets the Federal Stable Pour for a 5W-30 lubricating oil.

The application is described with reference to the following drawings:

Figure 1 is a graph showing the pour point efficiency of a polymer of the invention.

As already stated above, the present invention relates to a new class of pour point depressants and lubricating oils containing such pour point depressants. The pour point depressants of the present invention comprise a selected group of poly(methacrylate) polymers having 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, wherein the polymer is prepared from 3 or 4 methacrylate monomers in the C10 to C16 range, each of the monomers being present in an amount of not less than 25% by weight.

In accordance with the present invention, it has been discovered that a polymethacrylate must have an average carbon side chain length of 12.6 to 13.38 carbon atoms to be effective as a pour point depressant in a lubricating oil. When such a polymethacrylate pour point depressant is used in conjunction with a compatible viscosity index improver, a lubricating oil of 5W-30, 10W-30, 10W-40 and 15W-40 grades can be prepared to provide a formulation that will pass the required low temperature tests for such oils.

It has been found that whether the formulation will pass or fail the low temperature limits for a lubricating oil formulation depends to a large extent on the number and type of side chains present in the pour point depressant. A successful formulation is defined as one with a Federal Stable Pour of ≤ -35ºC, a viscosity of ≤ 3,500 cP at -25ºC in the Cold Cranking Simulator (CCS), and an MRV (mini-rotational viscometer) viscosity of ≤ 30,000 cP at -30º in both the 18 hour (D-3829) and TP-1 cooling cycles. A complete discussion of the low temperature rheology of multigrade engine oils can be found in the publication by Clevenger et al., Society of Automotive Engineers Document 831716, 1983. This publication sets out the requirements for various classes of engine oils, particularly in Table 1 on page 2 of this publication.

In this application, the term average carbon side chain length refers to the length of the carbon chain (R in the formula) in the alkyl group on the ester residue. The carbon chain length is determined by the alcohol used to esterify the methacrylic acid in preparing the methacrylate monomer.

According to the invention, it has been found that the type and number of ester side chains present in the pour point depressant determines the effectiveness of the formulation as determined by the above-mentioned tests. According to the invention, it has been found that only certain specific combinations with an average alkyl side chain length give acceptable results.

According to the invention, it has been found 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 polymer side chain length has been found to lower the pour point of a suitable lubricating oil from -17.78 to -37.22°C (0° to -35°F). Alkyl side chain averages below these values do not give acceptable results and polymers with average side chains greater than 13.50 lower the pour point to a lower value. When prepared from three or four monomers having an effective alkyl side chain average of 12.6 to 13.38 and used in accordance with the present 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 an engine oil which meets the required Federal Stable Pour standards.

The poly(methacrylate) pour point depressants of the present invention are those having an average carbon side chain length of 12.6 to 13.38. This value is obtained by using the proper mixture of monomers in preparing the polymer. The polymer is prepared by preparing the monomers, mixing and blending appropriately, and then polymerizing. The proper mixture to obtain a side chain agent 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, since the carbon chain is derived from the alcohol used for esterification. For example, a formulation of monomers containing 35-38% C₁₀ monomers, 31-34% C₁₄ monomers and 28-34% C₁₆ monomers will yield a polymer having an average chain length of 12.68 to 13.38. However, any combination of three or four methacrylate monomers in the C₁₀ to C₁₆ range may be selected in accordance with the invention, with no monomer present in an amount of less than 25% by weight, to yield the final polymethacrylate polymer having an average side chain length, or R value, of 12.6 to 13.38.

From the structure of the polymer it is apparent that the changes in chain length are introduced by the alcohol 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 R value from C₁₀ to C₁₆. The product obtained is thus a polymer in which the value of R may range from C₈ to C₂₀, but wherein the average or median value of the carbon chain length for R is from 12.6 to 13.38, provided that the average value is obtained with three or four monomers in the C₁₀ to C₁₆ range, the minimum Concentration of each monomer is at least 25 wt.%.

The method of calculating the average carbon side chain length in this invention is the method disclosed in U.S. Patent No. 3,814,690 at column 4, lines 31-49, where a method of calculating the "average chain length of molar equivalent" is discussed. This value is essentially the same as the "average side chain length, Cav" in the present patent application. The following formula is used:

where CN1 is the number of carbon atoms in the first chain, CN2 is the number of carbon atoms in the second chain, CNn is the number of carbon atoms in the nth chain, MP1 is the mole percent of the first component, MP2 is the mole percent of the second component, MPn is the mole percent of the nth component. The mole percent is equal to the mole fraction times 100%.

As the examples described below demonstrate, the pour point of the base oil can be lowered with any combination of chains alone that gives a chain average of 12.6 to 13.38; in formulated oils, the three to five monomers in the C10 to C16 range must be carefully selected since not all combinations with ethylene/propylene viscosity index (VI) improvers are effective. Any synergistic mixture of monomers to produce a polymer with this average side chain length or with this R value is within the scope of the present invention.

The monomers and the terpolymers resulting therefrom can be prepared by any method known from the prior art, see for example US patents 3,598,736 and 4,088,589, the disclosure content of which is hereby incorporated by reference in its entirety and which are included in this application for complete disclosure.

As indicated above, a pour point depressant is used in a lubricating oil or an engine oil to provide a formulation therefrom that will meet 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 available, particularly from the Amoco company. Other viscosity index improvers sold under the name TLA, which are ethylene/propylene copolymers to which a vinyl pyrrolidone has been polymerized to provide dispersant properties, may also be used in such formulations. Certain chain combinations of the pour point depressant will work with one or the other VI improver even if the pour point depressant has the required average side chain length of 12.6 to 13.38.

The pour point improvers are normally used with a suitable lubricating fluid or engine oil. A preferred such lubricant is sold by Pennzoil under the trademark Atlas, and in particular under the trademark Atlas 100N. Other starting feedstocks such as Ashland 100N or Exxon 100 LP are also suitable for use; these However, the list is not limited to the products mentioned. The lubricating oil can be of 5W-30, 10W-30, 10W-40 or 15W-40 quality.

As a result of the present applicants' research in this area, it has been found that an effective pour point depressant has an average side chain length of from 12.6 to 13.38, preferably from 12.6 to 13.30, and more preferably from 12.6 to 13.0, and this will lower the pour point of a 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 less than 12.6, a pour point depressant is obtained which is unable to meet the standards desired by the industry. Polymers having an average side chain of more than 13.38 will only lower the pour point to about -28.89°C (-20°F). To obtain this effective average side chain of 12.6 to 13.38, the polymers are formed from a group of the indicated monomer constituents to obtain the best results.

As a further requirement, the molecular weight of the polymer according to the invention must have a lower limit of about 30,000 Daltons and an upper limit in the range of 220,000 Daltons. Accordingly, the degree of polymerization is also important.

The amount of the pour point depressant of the present invention to be added to the lubricating oil is in the range of 0.001 to 1.0% by weight, and preferably in the range of about 0.01 to 0.50% by weight when the pour point depressant is a concentrate. The amount of the viscosity index improver added is preferably about 5 to 20% by weight of the depressant.

The lubricating oil composition will preferably also contain a detergent composition such as the commercially available Detergent packages. The pour point depressant compositions of the present invention are compatible with all such detergent packages.

Several different detergent packages are available for use in the invention and are preferably used at the SG detergent level. Various positions, i.e. protection classification levels, for lubricating oils have been introduced by the American Petroleum Institute, API. Several different engine tests, targeting different aspects of engine performance, must be met for the oil to be certified at this level. For example, the SE classification was introduced in 1972.

Formulated oils meeting this classification level offered greater protection against corrosion, oil oxidation, rust and engine deposits than the earlier oils. The SC category was introduced in 1980. Formulated oils meeting this classification level had better oxidative stability and anti-wear performance than SE oils. The SG grade was introduced in 1988. Formulated oils meeting this classification level had better residue/sludge control and anti-wear performance than SF oils. The improvement in anti-wear performance is necessary due to the more extensive anti-wear regulations that must be met at present. The trend for formulated oils is to meet even higher requirements dictated by today's smaller, more demanding engines. Detergent Pack F uses a polyisobutylene dispersant chemistry. Detergent Pack G is a spike composed of calcium phenates and sulfonates to provide additional performance. Detergent Pack I uses a Mannich dispersant chemistry. Detergent Pack I contains approximately 23% dispersant by weight. Detergent Pack J uses polyisobutylene succinimide dispersant chemistry. The above description is purely qualitative as these packs are composed of other additives that serve different purposes.

Reference is now made to the accompanying drawing, in which Figure 1 is a graphical representation of the pour point of the lubricant fluid Atlas 100N as the pour point varies as a function of the average side chain length or the number of carbon atoms for the value R.

The following examples are only intended to illustrate the invention; the invention is not limited to these examples. Throughout the examples and description, parts are by weight unless otherwise stated.

example 1

In Table 1 below, the polymethacrylate polymer compositions used in Experiments 1 to 13 were prepared using the C4, C10, C11, C12, C14 and C16 monomers. Accordingly, the polymers were prepared using a combination of methacrylic acid esters wherein the alcohol used to esterify the methacrylic acid had the specified 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 an average chain length of 11.2. In the polymers described in the table, the chain length distribution (normalized weight distribution) of the methacrylate monomer mixture was determined prior to polymerization by gas chromatography on an SI-30 column. In one example, the monomer mixtures were isolated after polymerization and the composition was almost the same as the starting feed. Polymerizations were carried out in xylene under a nitrogen atmosphere with benzoyl peroxide as the free radical initiator. The reactions were carried out at 85 - 95°C for several hours. Molecular weights were determined by gel permeation chromatography relative to polystyrene.

The neat polymers were dissolved at 0.25 wt.% in Atlas 100N lubricating oil. The pour points were determined by the D-97 test. The results are also given in Table 1. A graphical representation 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. TABLE 1. Poly(methacrylate) compositions a and pour points of Atlas 100N b Polymer Molecular Weight Pour Point Comparison a Normalized weight distribution b Concentration is 0.25 wt. %

The analysis of the values in Table 1 leads to the following conclusions:

1) an average side chain length of 12.6 to 13.38 will lower the pour point of such a lubricating oil from -17.78 to -37.22ºC (from 0º to -35ºF). Lower side chain lengths such as those mentioned above, exemplified by polymers 1-3, are not effective; polymers with an average side chain length above this range, exemplified here by polymers 11 and 12, lower the pour point only to -28.89ºC (-20ºF).

2) Within the effective average side chain length of 12.6 - 13.38, polymers with two components (Polymer 9) are equally effective as polymers with three components (Polymer 8). A variety of chains with three components are effective (e.g. polymers 4, 5 or 10).

3) There is a lower limit to the Mw that a polymer needs to function. Polymer 13 has a Mw of 4300 but is ineffective, while polymer 6 is effective with a Mw of 34000. A Mw of about 30000 is considered a reasonable lower limit.

4) There is no difference in the effectiveness of the pour point depressants once the lower limit has been implemented. Polymers 5 and 6 are equally effective, even though polymer 5 has a Mw of 56200 and polymer 6 has a Mw of 34000.

5) The effectiveness of polymer 7 in lubricating oil shows that short chain groups can be present on the polymer, but do not affect the effectiveness of the polymer as long as the average value is in the range of 12.6 - 13.38 lies.

Example 2

In this example, various poly(methacrylates) described in Table 1 were prepared for testing along with some additional polymethacrylates having the desired average side chain length of 12.6 - 13.0 carbon atoms. The composition and molecular weight distribution of the latter group of polymethacrylate pour point depressants is described in Table 2. Table 2 illustrates how polymethacrylate pour point depressants can be prepared within the scope of the present invention using various combinations of monomeric components. Thus, the monomers were methacrylates wherein the esterification alcohol had a carbon chain length of 10 carbons to 16 carbons, so that the average carbon chain length for the polymers was 12.68 - 12.85. Table 2 is as follows: Table 2. Polymethacrylate Pour Point Depressant Polymer Molecular Weight Comparison

Example 3

In this example of a formulation study with viscosity index improvers and other additives, formulations are prepared to provide an engine oil with the appropriate properties to meet the Federal Stable Pour, MRV test, CCS, TP-1 refrigeration cycles. In Table 3, the heading for the PPD polymer refers to the numbered polymer prepared according to Tables 1 and/or 2. VI Improver A is an olefin copolymer of ethylene-propylene to which vinylpyrrolidone has been polymerized to provide dispersant properties. It has a molecular weight of approximately 180,000. Atlas 100N is the base oil to which these ingredients were added in the amounts indicated. In this example, two dispersants with olefin copolymers as viscosity index improvers were used in the formulations. VI improver A has a Mw of 189000 and a Mn of 43000. VI improver B has a bimodal molecular weight distribution. The lower fraction has a Mw of 189000 and a Mn of 76750. The higher fraction has a Mw > 1,000,000.

Many of the poly(methacrylates) described in Table 1, along with various 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.

Polymers 19 and 20 were prepared in Atlas 100N and used as concentrates with an effective polymer concentration of 25 - 35 wt.% Viscosity Index Improver A with their D-97 pour points, Federal Stable Pour, -25ºC CCS viscosities, the CCS, the -30ºC viscosity determined in the 18 hour MRV (D-3829) and TP-1 cooling cycles and 100ºC viscosities are given in Table 3. The results of the Viscosity Index Improver B formulations are given in Table 4. Both formulation series used Detergent Pack A. Detergent Pack A consists of a borated succinate ester dispersant with a mixture of calcium and magnesium phenates used as dispersants. Other dispersant packages were used (see below); Detergent Pack B consisted of a polyisobutylene succinimide dispersant with a magnesium sulfonate detergent; Detergent Pack C contained a polyisobutylene succinimide dispersant with a calcium sulfonate detergent; Detergent pack D contained only a calcium sulfonate detergent and detergent pack E contained the same ingredients as detergent pack A but less calcium phenate. Detergent packs C and D were used together. All detergent packs contained zinc dialkyldithiophosphates. Detergent packs or detergent packets are commercial items with different ingredients and manufacturing processes, some of these packets being trade secrets whose exact nature and number of ingredients cannot be readily determined. Accordingly, the above description of the detergent packs is qualitative and not complete.

Olefin Copolymer VI Improver A Formulations

Formulations 4A, 5B, 10A, 10B, 12A and 12B meet the following low temperature standards for a 5W-30 oil; a CCS viscosity of ≤ 3500 cP at -25ºC, a Federal Stable Pour of ≤ -35ºC and an MRV viscosity of ≤ 30000 cP at -30ºC using the D-3829 and TP-1 refrigeration cycles.

Formulations 4A, 5b, 10A, 10B, 12A and 12B used polymers with chain compositions of 35-38% C10, 31-34% C14 and 28-34% C16 with an average side chain length of 12.68-13.0. The polymers are identical except for molecular weight. Polymer 10 used in formulations 4A-C has a Mw of 39,900 and a Mn of 11,700. Polymer 14 used in formulations 5A-B has a Mw of 68,000 and a Mn of 13,300. Polymer 19, used in Formulations 10A and 10B, has a Mw of 139,000 and a Mn of 30,000. Polymer 20 had a Mw of 195,700 and a Mn of 65,300. While successful compositions can be made with all of the polymers mentioned, higher concentrations of Polymer 20 (Formulations 4A-C) and 14 (Formulations 5A-B) must be used compared to Polymer 19 (Formulations 10A-B) or Polymer 20 (Formulations 12A and 12B) to achieve 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 about 0.07-0.10 wt%. Polymer 20 used in formulations 12A and 12B gave results similar to those of polymer 19. The higher molecular weight (Mw) polymers are more effective in the concentrated state.

The only other effective pour point depressant was Polymer 17 in Formulation 8. It was the only four-ingredient pour point depressant that gave satisfactory formulations. However, it is ineffective with VI Improver B (see below).

The other formulations were not effective. Formulations 1 and 3 were very poor. Formulations 2A, 2B and 6 had unacceptably high MRV (D-3829) viscosities Formulation 6 has the disadvantage of a high Federal Stable Pour. Formulation 9 has a high Federal Stable Pour, although its MRV (D3829) and TP-1 viscosities are acceptable.

Formulations 2A-2B and 7A-7B show that increasing the concentration of pour point depressant can cause 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 point increased in Formulations 7A and 7B as the concentration of Polymer 16 was increased.

Formulations 11A-C use Acryloid 154-70 as a pour point depressant. Formulations 11A and 11B exhibit stable pour problems. MRV viscosities also increase to unacceptably high levels when the Acryloid 154-70 concentration is increased to 1.0 wt% (Formulation 11C).

The three-ingredient pour point depressant with a C10, C14, and C16 chain distribution and the constituent pour point depressant with the C10, C10, C14, and C16 chain length distributions are the best pour point depressants studied. They produce formulations with better low temperature properties than either Acryloid 154-70 or any other experimental pour point depressants. For the latter polymers, it is unclear why certain three or four ingredients are effective in the presence of DOCP VI improvers and other three or four chain combinations are ineffective. It is still not clear why a three-ingredient pour point depressant should perform better than almost all four-ingredient pour point depressants and the five-ingredient pour point depressants.

Olefin Copolymer VI Improver B Formulations

The low temperature properties of the VI Improver B formulations are given in Table 4.

Formulations 2A, 2B, 3, 8 and 12 have acceptably 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 their molecular weight. There appears to be no difference in the overall performance of the formulation due to molecular weight for polymers 5 or 6. Only polymer 19 or polymer 20 (see Table 5) work effectively with either VI improver A or VI improver B. The other polymers work successfully with only one VI improver. Polymer 5 does not work 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 works with VI Improver A, Formulation 8 in Table 3, but does not work with VI Improver B, Formulation 10 in Table 4. Polymer 15 is effective with VI Improver B, Formulation 8 in Table 4, but is ineffective with VI Improver A, Formulation 6 in Table 3. These results demonstrate that a pour point depressant can be tailored for each DOCP VI improver.

The other formulations exhibit high MRV viscosities in the standard refrigeration cycle (Formulation 7) or with the TP-1 cycle (Formulations 7, 9-11).

Formulation 13 contains Acryloid 154-70. While it has acceptable MRV viscosities in both D-3829 and TP-1 cooling cycles, the stable pour is too high. The experimental pour point depressants described in Tables 1 and 2 result in better 5W-30 formulations.

The failure of Polymer 7 in Formulation 4 is an interesting contrast to the successful use 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 can affect the success of the formulation.

Different formulations

Various VI/DI packing combinations were tested with Polymers 19 or 20 in Atlas 100N as potential 5W-30 formulations. The low temperature viscosometric properties of the formulations are given in Table 5. Both pour point depressant concentrates, Polymers 19 and 20, work efficiently with a range of VI/DI packing combinations providing formulations with very good low temperature properties. The poly(methacrylate) with a C10, C14 and C16 chain distribution with a Cav of 12.6 - 13.0 is a versatile pour point depressant.

Some 10W-30 and 10W-40 formulations were tested with Polymer 20 in Atlas or Chevron base batches. The low temperature results of the formulations are summarized in Table 7. The 10W series is required to have a ≤ -30ºC Federal Stable Pour, a CCS viscosity of ≤ 3500 cP at -20ºC, and a viscosity of ≤ 30000 cP at -25ºC in both the 18 hour and TP-1 refrigeration cycles. The formulations with Polymer 20 met these requirements fairly easily. The fact that the pour point depressant is effective in 5W-30s, 10W-30s, and 10W-40s makes it an attractive, versatile additive.

The pour point depressant polymer 19 was tested in Ashland 100N with very good results (see Table 7). The 5W-30 formulations showed very good low temperature properties, demonstrating that the pour point depressant is not limited to just one base approach.

In summary, 11 poly(methacrylates) with an effective side chain length of 12.6 to 13.0 carbon atoms in Atlas 100N were effective pour point depressants in the absence of other additives. When the pour point depressants were tested in formulations containing a detergent package and a DOCP VI improver, only one of the 11 pour point depressants was compatible with the two DOCP VI improvers. This single pour point depressant has a specific combination of three chain lengths, C₁₀, C₁₄ and C₁₆. Pour point depressants with 2, 4 or 5 chains result in formulations with compatibility problems, poor low temperature properties, or are only effective with one of the DOCP VI improvers. Pour point depressants with three components that are not C₁₀, C₁₄ and C₁₆ and C₁₆ also cause formulation problems. Table 3. Formulations with Olefin Copolymer VI Improver A Formulation Polymer Atlas Stable Pour Pour Point Comparison Table 3. Formulations with Olefin Copolymer VI Improver A Formulation Polymer Atlas stable pour pour point comparison acryloid yield stress b concentrate Table 4. Olefin Copolymer VI Improver B Formulation Polymer Atlas stable pour pour point comparison frozen yield stress Table 4. Olefin Copolymer VI B Formulation PPD Polymer Atlas Point ºC stable pour ºC comparison Acryloid a concentrate Table 5 Pour point depressant performance with various DI/VI packing combinations. Concentration in weight percent. Base formulation is Atlas 100N. stable Pour ºC Table 6 Pour point depressant performance in 10W30S and 10W40s with selected base formulations. Polymer 20, Table 2, was used as the pour point depressant. Base formulations Stable Pour ºC Vis 100ºC Atlas a 10W30 b 10W40 Table 7 Pour point depressant performance in Ashland 100N 5W-30 formulation; Polymer 19, Table 2 is the pour point depressant. Concentration is in weight percent. Stable Pour Improver Pack

Example 4

To compare a preferred pour point depressant of the present invention, calculations are performed using the calculation formula of U.S. Patent No. 3,814,690 to compare the average carbon side chain length of the polymer 19 of the present invention to the pour point depressant polymers disclosed in U.S. Patent No. 3,897,353. Example A shows the calculation of the Cav for a 200 g alcohol mixture mentioned in column 6 of U.S. Patent No. 3,897,353 and composed of 150 g Neodol 25L and 50 g Alfol 1620 SP. The relative weight distribution shown was calculated by multiplying each alcohol mixture by its respective weight distribution as described above and adding together the overlapping components and then normalizing the new distribution. If one starts with a 100 g sample of alcohol, there will be 24 g of C12OH (0.24 x 100 g), 24 g of C13OH, etc., as indicated in the third column in the calculation. The molecular weights, g/mole, are shown in the fourth column, with the moles of each component easily obtained by dividing the weight of the alcohol by its molecular weight, giving the results shown in column 5. The last column, column 6, shows the mole % of each alcohol, 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 calculation of the average chain length is shown. The Cav value is 13.2 for Example A. The chain average, Cav, for the mixture was calculated to be 14.07.

Example B shows the methacrylate distribution for polymer 19, Table 2 of this application. Using the formulas used for Example Using the procedure described in A, the Cav value was calculated to be 12.83.

The tables for these calculations are as follows: Table 8A Example A. Blenda of Neodol 25L (150g) Alfol 1620 SP (50g) Mole % Rel. Wt % Weight Mole (Mole Fraction x 100%) Cav 14.08 a) Two assumptions are made. In the Alfol 1620 SP blend, the fraction which is "C₁₄OH and lighter" is assumed to be 100% C₁₄OH. In the Neodol 25L blend, the fraction which is "lighter than C₁₂OH" is not taken into account. If this fraction is assumed to be pure C₁₀OH, then Cav is equal to 13.90. TABLE 8B Example B. Polymer 19 Rel. wt.% Weight Mol (Mole Fraction x 100%) Meth

From Example A it can be seen that the calculations show that the average side chain length is 14.08. In Example B, polymer 19 of the present application, the average side chain length is 12.83.

Example 5

The pour point depressants of the present invention were evaluated with various detergent packages used in lubricating oils. In the present work, additional pour point depressants were prepared.

The compositions and molecular weight distributions (MWD) of the three pour point depressants which contain the same components decyl methacrylate (C10 meth), tetradecyl methacrylate (C14 meth) and hexadecyl methacrylate (C16 meth) but in different proportions to give three different average chain lengths, Cav, are given in Table 9. The polymers in concentrates 21, 22 and 23 have very similar molecular weight distributions as well as polymer contents. It is noted that polymers 19 and 20 in Table 2 of the application are actual concentrates containing these polymers. The polymers in concentrations 20 and 21 are essentially the same; both have the same methacrylate compositions which give essentially identical Cavs and very similar molecular weight distributions. The only difference between the two concentrates is that concentrate 20 has about 25 wt% polymer while concentrate 21 has about 40-45 wt% polymer. Table 9 Composition of pour point depressants. Normalized weight distribution of the methacrylate monomer starting mixture, average side chain length, Cav, molecular weight distribution of the resulting polymer and polymer content of the concentrate. Concentrate meth. Polymer

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. It is believed that the lower molecular weight makes it less likely to undergo shear in the engine. Viscosity Index (VI) improvers with this property have only recently been introduced into the industry. They are referred to as shear stable VI improvers.

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 the formulations shown in Tables 10 and 11. It uses polyisobutylene dispersant chemistry. The SF version of this DI package, designated as Detergent package H, is used in Table 11. Detergent package F is a 25 wt% dispersant while H is a 19 wt% dispersant. Dispersant pack G is a spike composed of calcium phenates and sulfonates to provide additional calcium phenates and sulfonates and additional performance. Detergent pack I uses Mannich dispersant chemistry. Detergent pack I contains approximately 23 wt% dispersant. Detergent pack J uses polyisobutylene succinimide dispersant chemistry. The above description is purely qualitative as these packs are composed of other additives serving different purposes. The low temperature properties of the 5W-30 formulations with the various PPD concentrates are given in Table 10.

The 18 hour and TP-1 MRV viscosities are essentially the same. In the 5W-30 formulations, the viscosities are independent of treatment level and Cav.

The stable pour data shows a trend toward higher stable pours with increasing concentrate treat levels. Compare entries 1-3 for concentrate 21 where the stable pour increases from <-41 to -36ºC as treat levels increase from 0.06 wt% to 0.31 wt%. Within error, there is an increase in the stable pour as Cav increases (at low treat levels). Compare entry 1, where the stable pour is < -41ºC at a treat level of 0.07 wt% for the concentrate with a Cav of 12.78, to entry 4, where the stable pour is -39ºC at a treat level of 0.15 wt% for the concentrate with a Cav of 13.16, to entry 6, where the stable pour is -36ºC at a treat level of 0.10 wt% for the concentrate with a Cav of 13.38. While for a 5W-30 oil a stable pour of -36 is acceptable, it would be more desirable to have a formulation with a lower stable pour due to the better low temperature properties. which it gives to the formulation and also because of the cushion it provides within the 3ºC error limit allowed in the measurement.

The trend toward higher pour points with increasing Cav was shown in the D-97 pour points discussed earlier, see Figure 1. It should be noted that the D-97 pour point and the stable pour are only similar in name; they are completely different tests. A D-97 pour point test is run over a few hours and is basically a pure cooling test. In refining, it is used as a quality control test for base batches. While originally used in formulation, it has been made redundant by a number of other tests, including the stable pour. At least one company renamed their pour point depressants to lube oil flow improvers to reflect this change. The stable pour test is run over a seven-day period with heating and cooling cycles. It is used for formulations because there is a certain relationship between the test and the performance level of the formulation in reality. Its main disadvantage is that it takes seven days to complete and is therefore not a good quality control tool for production work.

The PPD concentrates were also tested in 10W-30 formulations. The results of one of the 10W-30 series are given in Table 11. The SF grade detergent pack H is used in entry 1. The concentrate 21 with a Cav of 12.78 is quite effective in the formulation. The concentrate does not work when the detergent pack is changed to the SG detergent pack F. The formulation freezes in the TP-1 MRV, entry 2. The situation improves as the treatment amount increases, however the Results still not satisfactory, entry 3. The situation improves dramatically 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, is used.

The appearance of yield stress and subsequent relaxation occurred in a second series of 10W-30 formulations shown in Table 12. SG detergent pack I was used. Concentrate 21 with a Cav of 12.78 exhibited yield stress at two different treatment levels, 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, entry 4, was used. The stable pours in both 10W-30 series are quite acceptable.

Concentrate 21 was tested in 10W-30s and 10W-40s, composed of Chevron base stocks. The concentrates and low temperature results are shown in Table 13. The results are excellent.

Finally, concentrate 21 was tested in 15W-40s. The formulations and results are given in Table 14. The results are excellent. Table 15 summarizes the low temperature requirements for a 5W, 10W and 15W oil.

For the 5W-30 and 10W-30s that were tested, the following conclusions can be drawn;

1) in 5W-30s the stable pours, but not the TP-1 MRV viscosities, depend on the Cav.

2) In the 10W-30s, the TP-1 MRV viscosities, but not the stable pours, were affected by the Cav.

Tables 10, 11, 12, 13, 14 and 15 are given below. TABLE 10. Pour point depressant performance in 5W-30 oil. A general formulation composed of 9.07 wt.% olefin copolymer concentrate C, 11.25% detergent pack F, 2.0% detergent pack G and 77.08% Atlas 100N was used. The formulation has a kinetic viscosity of 11.65 cSts at 100ºC. Concentrate Stable Pour ºC TABLE 11. Pour point depressant performance in 10W-30. The batch formulation was composed of 6.39 wt% Olefin Copolymer Concentrate C, 11.90% Detergent Pack F, 28.0% Atlas 325 and 54.3% Atlas 100N. Entry 1 used Detergent Pack H at 11.28 wt%, Olefin Copolymer Concentrate C at 6.38%, Atlas 100N at 54.33% and 28.0% Atlas 325N. Concentrate stable Pour ºC Solid TABLE 12. Pour point depressant performance in 10W-30. Composed of 6.5% Olefin Copolymer Concentrate C, 12.2% Detergent Pack I, 58.9% Atlas 100N and 22.3% Atlas 325N. Concentrate Cav %PPD Stable Pour TABLE 13. Performance of Pour Point Depressant Concentrate 22 in 10W30s and 10W40s formulated from Chevron base stocks. Wt% PPD Olefin Copolymer Detergent Pack Chevron Results Stable Pour ºC TABLE 14. Performance of Pour Point Depressant Concentrate 22 in 15W40s. Wt% PPD Detergent Pack Olefin Copolymer Atlas Chevron Brightstock Results Stable Pour ºC TABLE 15. Low temperature performance requirements of 5W, 10W and 15W oils. MRV Viscosity Yield Stress Stable Pour, ºC

Claims (10)

1. Pour point depressant for lubricating oils, comprising a poly(methacrylate) polymer having the repeating unit wherein R is an alkyl group having an average chain length in the polymer and n is an integer indicating the number of repeating units, wherein the value of n is sufficient to provide a molecular weight of 10,000 to 300,000 for the polymer, characterized in that in the formula the average chain length of R has a value of 12.6 to 13.38, the polymer is a polymer formed by the reaction of three or four methacrylate monomers selected from C₁₀ to C₁₆ monomers, each of the monomers being present in an amount of not less than 25% by weight. 2. Pour point depressant according to claim 1, wherein the polymer is obtained by polymerization of three or four methacrylate monomers of the formula is formed, wherein R is an alkyl group having 10 to 16 carbon atoms. 3. Pour point depressant according to claim 2, wherein in the three or four methacrylate monomers R is selected from C₁₀, C₁₁₋, C₁₂₋, C₁₄ and C₁₆ alkyl groups. 4. Pour point depressant according to claim 3, wherein the polymer is formed from monomer mixtures wherein R are C₁₀, C₁₄ and C₁₆ alkyl groups. 5. Pour point depressant according to any one of claims 1 to 4, wherein the average chain length of R is 12.6 to 13.30. 6. Pour point depressant according to claim 5, wherein the average chain length of R is 12.6 to 13.0. 7. A lubricating oil composition comprising a wax-containing hydrocarbon lubricating oil, wherein the lubricating oil contains a sufficient amount of a pour point depressant according to claim 1 to reduce the stable pour point to -35°C. 8. A lubricating oil composition according to claim 7, wherein the polymer is formed from a mixture of monomers, wherein R are C₁₀, C₁₄ and C₁₆ alkyl groups, each monomer comprises at least 25% of the polymer and wherein the average chain length of the polymer is 12.6 to 13.38. 9. A lubricating oil composition according to claim 7, which also contains a viscosity number improver, a detergent or a mixture thereof. 10. A method for lowering the pour point of a lubricating oil composition comprising adding to the lubricating oil an effective amount of a pour point depressant comprising 0.001 to 1.0 weight percent of a poly(methacrylate) polymer according to claim 1.