Patent Application
20130012659
A lubricant or lubricant additive that contains a polyolefin that is made by contacting an ethylene oligomerization catalyst with ethylene to form a series of α-olefins, and then copolymerizing those α-olefins with ethylene using a polymerization catalyst that contains a complex of a transition metal to form the polyolefin.
Lubricants are most commonly used to reduce friction between two moving parts in “contact” with each other, reducing wear of those parts, reducing corrosion of parts particularly metal parts, damping shock particularly in gears and forming seals as in between piston rings and engine cylinders. Probably the most common type of lubricant is used for machinery where metal, plastic, ceramic, etc. parts that rub against each other may be present in items such as internal combustion engines, transmissions, bearing assemblies, etc., but lubricants have other uses, for example in cosmetics.
Many lubricant compositions have a variety of ingredients in them, for instance heat stabilizers to prevent thermal degradation, antioxidants, viscosity index improvers, detergents, dispersants, pour point depressants, friction modifiers, demulsifiers, corrosion inhibitors, etc. Many of these additives and other ingredients are described in Morteier et al., Chemistry and Technology of Lubricants”, 2nd. Ed., London, Springer (1996) and Leslie R. Rudnick, Lubricant additives”: Chemistry and Applications,” New York, Marcel Dekker (2003), both of which are hereby included by reference. For lubricants that have to be useful over wide temperature ranges, such as internal combustion or jet engines, or are exposed to a wide range of ambient temperatures, it is important that the viscosity of the lubricant change little with temperature. This is often referred to as the “Viscosity Index,” (“VI”) and a higher number indicates less change in the viscosity as the temperature rises (this is usually good).
Two of the major polymeric ingredients that may have high Viscosity Indices (“VIs”) are typically “base oils,” which are often the ingredient present in the largest amount, and “viscosity index improvers.” These polymeric materials are generally classified into groups, and one group of such polymers is Group IV, polyalphaolefins (PAOs), which typically have high VIs. These are polymers or copolymers of one or more α-olefins of the formula H3C(CH2)yCH═CH2 wherein y is about 5 to about 27. In some instance the alkyl groups in the α-olefin may be branched.
U.S. Pat. Nos. 7,662,881 and 7,687,443 describe lubricants or lubricant components that include an ethylene copolymer with one or more α-olefins. These copolymers are said to be block copolymers and not random copolymers.
U.S. Patent Publication 2003/0195128 describes a lubricant additive that is an “olefin oligomer.” This olefin oligomer, “PAO fluid,” is made by polymerization of an α-olefin using “Friedel-Crafts catalyst” such as aluminum trichloride or boron trifluoride. Ethylene-alpha-olefin copolymers are also mentioned.
U.S. Pat. No. 6,568,723 describes the use of certain metallocene catalysts to make polyolefins from C3 to C20 olefins which may be meant to be used in lubricants. The use of ethylene as a comonomer is not mentioned.
This invention concerns a lubricant or a lubricant additive, comprising a polyolefin made by a process comprising:
(1) contacting under oligomerizing and polymerizing conditions
(a) an oligomerization catalyst that oligomerizes ethylene to a series of α-olefins having the formula H(CH2CH2)nCH═CH2 wherein n is an integer of one or more and said oligomerization catalyst has a Schulz-Flory constant of about 0.40 to about 0.95;
(b) a transition metal containing copolymerization catalyst that copolymerizes ethylene and said α-olefins; and
(c) ethylene;
or
(2) (a) contacting under oligomerizing conditions ethylene and said oligomerization catalyst that oligomerizes ethylene to a series of α-olefins having the formula H(CH2CH2)nCH═CH2 wherein n is an integer of one or more and said oligomerization catalyst has a Schulz-Flory constant of about 0.40 to about 0.95; and then
(b) contacting under polymerizing conditions said series of α-olefins, ethylene, and said transition metal containing copolymerization catalyst which copolymerizes ethylene and said α-olefins; and then
(3) optionally modifying said polyolefin to improve its properties for use in said lubricant or lubricant additive;
and wherein said polyolefin has a density of about 0.90 or less, and said polyolefin is a random copolymer.
It is to be noted that either step (1) (a-c) or step (2) (a-b) is carried out, optionally followed by step (3). Other features and advantages of the present invention will be better understood by reference to the detailed description that follows.
Herein certain terms are used and some of these are defined below:
By a “transition metal-containing copolymerization catalyst” is meant a catalyst that contains a transition metal of Groups 3-12 (IUPAC notation) and the lanthanides, such Zr, Hf, V, Ti, etc. Typically these may be metallocene catalysts, Ziegler-Natta catalysts, chromium catalysts, etc. These types of catalysts are well known in the polyolefin field, see for instance Angew. Chem., Int. Ed. Engl., vol. 34, p. 1143-1170 (1995), EP-A-0416815 and U.S. Pat. No. 5,198,401 for information about metallocene-type catalysts; and J. Boor Jr., Ziegler-Natta Catalysts and Polymerizations, Academic Press, New York, 1979 for information about Ziegler-Natta type catalysts, all of which are hereby included by reference. Chromium catalysts are also well known, see for instance E. Benham, et al., Ethylene Polymers, HDPE in Encyclopedia of Polymer Science and Technology (online), John Wiley & Sons, and D. M. 5 Simpson, et al., Ethylene Polymers, LLDPE, in Encyclopedia of Polymer Science and Technology (online), John Wiley & Sons, both of which are hereby included by reference.
By a “random copolymer” is meant that there is random sequencing of the copolymer repeat units in the polyolefin, see J. C. Randall, Encyclopedia of Polymer Science and Technology, (online), John Wiley & Sons, DOI 10.1002/0471440264.pst557 (2008), which is hereby included by reference.
By an “α-olefin” is meant a compound of the formula H(CH2CH2)nCH═CH2 wherein n is an integer of 1 or more.
By a “series” of α-olefins is meant compounds having the formula H(CH2CH2)nCH═CH2 wherein at least three, preferably 4, and more preferably 5, compounds having different n values are produced, and n is an integer of 1 or more. Preferably at least three of these values are 1, 2, and 3.
By “hydrocarbyl group” is meant a univalent group containing only carbon and hydrogen. As examples of hydrocarbyls may be mentioned unsubstituted alkyls, cycloalkyls and aryls. If not otherwise stated, it is preferred that hydrocarbyl groups (and alkyl groups) herein contain from 1 to about 30 carbon atoms.
By “substituted hydrocarbyl” herein is meant a hydrocarbyl group that contains one or more substituent groups that are inert under the process conditions to which the compound containing these groups is subjected (e.g., an inert functional group, see below). The substituent groups also do not substantially detrimentally interfere with the polymerization process or the operation of the polymerization catalyst system. If not otherwise stated, it is preferred that (substituted) hydrocarbyl groups herein contain from 1 to about 30 carbon atoms. Included in the meaning of “substituted” are rings containing one or more heteroatoms, such as nitrogen, oxygen and/or sulfur, and the free valence of the substituted hydrocarbyl may be to the heteroatom. In a substituted hydrocarbyl, all of the hydrogens may be substituted, as in trifluoromethyl.
By an “(inert) functional group” herein is meant a group, other than hydrocarbyl or substituted hydrocarbyl, that is inert under the process conditions to which the compound containing the group is subjected. The functional groups also do not substantially deleteriously interfere with any process described herein that the compound in which they are present may take part in. Examples of functional groups include halo (fluoro, chloro, bromo, and iodo), and ether such as —OR50 wherein R50 is hydrocarbyl or substituted hydrocarbyl. In cases in which the functional group may be near a transition metal atom, the functional group alone should not coordinate to the metal atom more strongly than the groups in those compounds that are shown as coordinating to the metal atom, that is, they should not displace the desired coordinating group.
By a “cocatalyst” or a “catalyst activator” is meant one or more compounds that react with a transition metal compound to form an activated catalyst species. One such catalyst activator is an “alkylaluminum compound,” which herein means a compound in which at least one alkyl group is bound to an aluminum atom. Other groups such as, for example, alkoxide, hydride, an oxygen atom bridging two aluminum atoms, and halogen may also be bound to aluminum atoms in the compound.
The “Schulz-Flory constant” (“SFC”) of the mixtures of α-olefins produced is a measure of the molecular weights of the olefins obtained, usually denoted as factor K, from the Schulz-Flory theory (see for instance B. Elvers, et al., Ed. Ullmann's Encyclopedia of Industrial Chemistry, Vol. A13, VCH Verlagsgesellschaft mbH, Weinheim, 1989, p. 243-247 and 275-276). This is defined as:
K=n(Cn+2olefin)/n(Cn olefin)
wherein n(Cn olefin) is the number of moles of olefin containing n carbon atoms, and n(Cn+2 olefin) is the number of moles of olefin containing n+2 carbon atoms, or in other words the next higher oligomer of Cn olefin. From this can be determined the weight (mass) and/or mole fractions of the various olefins in the resulting oligomeric reaction product mixture.
By a “copolymerization catalyst” is meant a catalyst that can readily, under the process conditions, copolymerize ethylene and α-olefins of the formula H(CH2CH2)nCH═CH2 wherein n is an integer of one or more.
By “aryl” is meant a monovalent aromatic group in which the free valence is to the carbon atom of an aromatic ring. An aryl may have one or more aromatic rings, which may be fused, connected by single bonds or other groups.
By “substituted aryl” is meant a monovalent aromatic group substituted that contains one or more substituent groups that are inert under the process conditions to which the compound containing these groups is subjected (e.g., an inert functional group, see below). The substituent groups also do not substantially detrimentally interfere with the polymerization process or operation of the polymerization catalyst system. If not otherwise stated, it is preferred that (substituted) aryl groups herein contain from 1 to about 30 carbon atoms. Included in the meaning of “substituted” are rings containing one or more heteroatoms, such as nitrogen, oxygen and/or sulfur, and the free valence of the substituted hydrocarbyl may be to the heteroatom. In a substituted aryl all of the hydrogens may be substituted, as in trifluoromethyl. These substituents include (inert) functional groups. Similar to an aryl, a substituted aryl may have one or more aromatic rings, which rings may be fused or connected by single bonds or other groups; however, when the substituted aryl has a heteroaromatic ring, the free valence in the substituted aryl group can be to a heteroatom (such as nitrogen) of the heteroaromatic ring instead of a carbon.
By “process conditions” herein is meant conditions for producing the series of α-olefins, whether in the presence of the copolymerization catalyst or not. Such conditions may include temperature, pressure, and/or oligomerization method such as liquid phase, continuous, batch, and the like. Also included may be cocatalysts that are needed and/or desirable. If in the presence of the copolymerization catalyst, the SFC is measured under conditions in which the copolymerization catalyst is not present.
Many types of catalysts are useful as the copolymerization catalyst. For instance, so-called Ziegler-Natta, metallocene-type and/or chromium catalysts may be used. These types of catalysts are well known in the polyolefin field, see for instance Angew. Chem., Int. Ed. Engl., vol. 34, p. 1143-1170 (1995), EP-A-0416815 and U.S. Pat. No. 5,198,401 for information about metallocene-type catalysts; and J. Boor Jr., Ziegler-Natta Catalysts and Polymerizations, Academic Press, New York, 1979 for information about Ziegler-Natta type catalysts, all of which are hereby included by reference. Chromium catalysts are also well known, see for instance E. Benham, et al., Ethylene Polymers, HDPE in Encyclopedia of Polymer Science and Technology (online), John Wiley & Sons, and D. M. 5 Simpson, et al., Ethylene Polymers, LLDPE, in Encyclopedia of Polymer Science and Technology (online), John Wiley & Sons, both of which are hereby included by reference. Many of the useful polymerization conditions for these types of catalysts and the oligomerization catalyst coincide, so conditions for the process are easily accessible. Oftentimes a “cocatalyst” or “activator” is needed for metallocene or Ziegler-Natta type polymerizations, which cocatalyst is oftentimes the same as is sometimes needed for the oligomerization catalyst. In many instances cocatalysts or other compounds, such as an alkylaluminum compound, may be used with both types of catalysts.
Suitable catalysts for the copolymerization catalyst also include metallocene-type catalysts, as described in U.S. Pat. No. 5,324,800 and EP-A-0129368; particularly advantageous are bridged bis-indenyl metallocenes, for instance as described in U.S. Pat. No. 5,145,819 and EP-A-0485823. Another class of suitable catalysts comprises the well known constrained geometry catalysts, as described in EP-A-0416815, EP-A-0420436, EP-A-0671404, EP-A-0643066 W091104257. Also the class of transition metal complexes described in, for example, W098130609, U.S. Pat. Nos. 5,880,241, 5,955,555, 6,060,569 and 5,714,556 can be used. All of the aforementioned publications are incorporated by reference herein.
The catalyst for the copolymerization of the ethylene and the α-olefin series should preferably be a catalyst that can copolymerize ethylene and α-olefins so that the relative rate of copolymerization of these two types of monomers are very roughly equal. Metallocene-type catalysts are most preferred, and preferred metallocene catalysts are those listed in previously incorporated World Patent Application 1999/150318, which is hereby included by reference. Other types of preferred metallocene catalysts, which are said to be especially useful for larger olefins, are described in U.S. Pat. Nos. 6,642,169 and 6,509,228, both of which are hereby included by reference.
It is to be understood that “oliogomerization catalyst” and “copolymerization catalyst” may also include other compounds such as cocatalysts and/or other compounds normally used with the oliogomerization catalyst and/or copolymerization catalyst to render that particular catalyst active for the polymerization or oligomerization it is meant to carry out.
A preferred oligomerization catalyst is an iron complex of a ligand of the formula:
wherein: R1, R2 and R3 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl or an inert functional group, provided that any two of R1, R2, and R3 vicinal to one another, taken together may form a ring; R4 and R5 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl or an inert functional group, provided that R1 and R4 and/or R3 and R5 taken together may form a ring; and R6 and R7 are each independently aryl or substituted aryl.
In an iron complex of (I), (I) is usually thought of as a tridentate ligand coordinated to the iron atom through the two imino nitrogen atoms and the nitrogen atom of pyridine ring. It is generally thought that the more sterically crowded it is about the iron atom the higher the molecular weight of the polymerized olefin (ethylene). In order to make α-olefins, and especially to make in a process the desired SFC (such as 0.40-0.95) very little steric crowding about the iron atom is desired.
Such compounds of (I) are readily available. For instance in WO2005/092821 it is demonstrated that the iron complex in which R4 and R5 are both hydrogen, and R6 and R7 are both phenyl, has a SFC of about 0.29 (this reference states the SFC is about 0.4, but this apparently based incorrectly on the weight fraction of the olefins produced, not correctly mole fraction). In G. J. P. Britovsek et al., Chem. Eur. J., vol. 6 (No. 12), p. 2221-2231 (2000), which is hereby included by reference, a ligand in which R4 and R5 are both hydrogen and R6 and R7 are both 2-methylphenyl, gives an oligomerization at 50° C. in which the SFC is reported to be 0.50. Other combinations of groups would give ligands with useful relatively low SFCs. For instance, R4 and R5 may both be methyl or hydrogen (or one could be methyl and one could be hydrogen) and R6 could be phenyl, while R7 could be 2-fluorophenyl or 2-methylphenyl or 2-chlorophenyl; or R6 and R7 could both be 2-fluorophenyl; or R6 and R7 could both be 4-isopropylphenyl; or both R6 and R7 could both be 4-methylphenyl. Other variations in which just small increments of steric hindrance are added or subtracted about the iron atom are obvious to those skilled in the art. It is also believed that in addition to these steric effects that electron withdrawing groups on R6 and/or R7 tend to lower the SFC.
For “moderate” SFCs, those in the approximate range of about 0.55 to about 0.70 R4 and R5 may both be methyl and R6 and R7 may both be 2-methylphenyl or 2-ethylphenyl, or R4 and R5 may both be methyl and R6 may be 2,6-dimethylphneyl and R7 may phenyl. See for instance U.S. Pat. Nos. 6,103,946, 7,049,442 and 7,053,020, all of which are hereby included by reference.
For higher SFCs somewhat more sterically crowded complexes can be used. R4 and R5 may both be methyl and R6 may both be 2,6-dimethylphenyl and R7 may be 2-methylphenyl, or R4 and R5 may both be methyl and R6 may be 2,6-diisopropyllphenyl and R7 may 2-isopropylphenyl.
The synthesis of the ligands (I) and their iron complexes are well known, see for instance U.S. Pat. Nos. 6,103,946, 7,049,442 and 7,053,020, G. J. P. Britovsek, et al., cited above, and World Patent Application WO2005/092821, World Patent Applications 1999/012981 and 2000/050470, all of which are hereby included by reference.
Other relatively small aryl groups may also be used, such as 1-pyrrolyl, made from substituted or unsubstituted 1-aminopyrrole (see for instance World Patent Application 2006/0178490, which is hereby included by reference). Analogous substitution patterns to those carried out in phenyl rings may also be used to attain the desired degree of steric hindrance, and hence the desired SFC. Aryl groups containing 5-membered rings such as 1-pyrrolyl may especially useful for obtaining low SFCs, since they are generally less sterically crowding than 6-membered rings. Preferred aryl groups for R6 and R7 are phenyl and substituted phenyl.
While steric hindrance about the iron atom is usually the dominant item controlling the SFC, process conditions may have a lesser effect. Higher process temperatures generally give lower SFCs, while higher ethylene pressures (concentrations) generally give a higher SFC, all other conditions being equal. In order to measure the SFC of the oligomerization during the manufacture of the branched polyethylene the process is carried out using the same conditions as the process to produce the branched polyethylene, but the copolymerization catalyst is omitted and any cocatalysts are scaled back in relationship to the total amount of oliogomerization catalyst present compared to the total of the copolymerization catalyst and oligomerization catalyst usually used. However it is to be noted that somewhat more than normal cocatalyst, such as an alkylaluminum compound, may have to be used to remove traces of any process poisons present such as water.
To determine the SFC, the resulting mixture of α-olefins is analyzed to determine their molecular ratios. This is most conveniently done by standard gas chromatography using appropriate standards for calibration. Preferably the ratios (as defined by the equation for “K,” above) between olefins from C4 to C12 are each measured and then averaged to obtain the SFC. If the ratios of higher olefins, such as C12/C10 are too small to measure accurately, they may be omitted from the calculation of the constant.
Under a given set of process conditions, generally the higher the molar ratio of oligomerization catalyst to copolymerization catalyst, the higher the branching level in the branched polyethylene produced. This is true because the higher the relative concentration of oligomerization catalyst present, the more α-olefins that will be produced for a given amount of polymerization, and so the concentration of α-olefins in the process will be higher, particularly under equilibrium conditions in a continuous process. If the oligomerization step and copolymerization step are done separately, the larger the amount of α-olefins added per amount of copolymerization catalyst present, the higher the branching level will be.
In turn the branching level affects the density of the resulting polyolefin. This higher branching level usually the lowers the density of the resulting polyolefin. Preferably the density is less than 0.89 g/mL, more preferably less than 0.88 g/mL, especially preferably less than 0.87 g/mL and very preferably less than 0.86 g/mL. When the copolymer is a “solid”, i.e. can hold its shape for the test, density is measured by ASTM Method D792-08, Method A. When the copolymer is a “liquid”, i.e. flows too much for the D792-08 test, the density is measured using ASTM Method D4052-09 at a temperature of 23° C. A preferred minimum density is 0.80 g/mL. It is to be understood that a preferred density range may be formed from any preferred minimum and maximum density.
It is preferred that the polyolefin described herein have a VI of about 125 or more, more preferably about 140 or more, and very preferably about 150 or more. VI is measured by ASTM Method D2270-04.
The choice of the desired SFC is somewhat complex. It is believed that to achieve a relatively high VI the branches on the polymer should be relatively long, but if the branches are very long they themselves may have a tendency to crystallize, thereby possibly having a deleterious effect on low temperature properties such as pour point. Short branches are believed to be relatively ineffective in increasing VI. Therefore the desired SFC will often be a compromise between these and other factors. The higher the SFC the larger the proportion of relatively long chain α-olefins produced, and hence long branches incorporated into the polyolefin. The lower the SFC the relatively higher amount of short chain α-olefins produced and the short branches incorporated into the polyolefin. A preferred SFC range is about 0.50 to about 0.90, more preferably about 0.55 to about 0.85.
Another factor to be considered in synthesis of the polyolefin is the level of branching of the polyolefin. As noted above the higher the branching level, the lower the density. Lower densities mean decreased crystallinity from ethylene segments in the main chain until, eventually the crystallinity has been reduced to a level where the polyolefin may be amorphous (an elastomer). For improved lower temperature properties of the lubricant or lubricant additive, it is usually preferred that the polyolefin exhibit lesser amounts of crystallinity. Determination of the branching level of the polymer in mole percent α-olefin incorporated is complicated by the fact that a series of α-olefins is produced and incorporated into the polyolefin in the process. Generally speaking it is impossible to distinguish by 13C NMR between branches having 10 or more carbon atoms, and on most NMR equipment between branches having 6 or more carbon atoms. However one can calculate what the branching level should be based on the SFC of the oligomerization catalyst and the amount of methine carbon atoms in the polyolefin, which may be readily determined by NMR.
One first calculates the average branch length in the polyolefin using the SFC, on the assumption that all α-olefins are incorporated into the polyolefin in the same molar proportions in which they are produced by the oligomerization catalyst. Average branch lengths for selected SFCs are shown in Table 1.
These average branch lengths are obtained by calculating the mole percent of each branch length obtained, multiplying that by the number of carbon atoms in that branch (which contains two fewer carbon atoms than the corresponding α-olefin), and then adding this value for each of the branches. This sum is the average branch length.
As can be seen from Table 1, an SFC of 0.75 gives an average branch length that happens to correspond to the branch length in poly-1-decene, 8 carbon atoms. However it should be noted that because a range of α-olefins is produced, 25% of the branches are ethyl (2 carbons), and 1.06 mole percent of the branches have 24 carbon atoms, with lesser amounts of longer branches.
Using the average branch length as calculated above for any SFC of an oligomerization catalyst, one can then calculate the branching level. One measures the total methine carbon atoms per 1,000 carbon atoms present. For this example we will assume it is 60, and the SFC is 0.75. This would mean in 1,000 carbon atoms there were 600 carbon atoms “contributed” by the α-olefins which formed branches (10 carbon atoms per α-olefin times 60 branches), and the remainder of 400 carbon atoms were derived from ethylene. Therefore the molar ratio of ethylene:α-olefin incorporated is 200:60, so the branching level is 23.1 [(60/260)×100] mole percent. Analogous calculations can be carried out at other methine carbon atoms levels and SFC values. This calculation is the definition of “mole percent branching level” herein.
It is preferred that the minimum mole percent branching level is 5%, more preferably 10%, very preferably 15%, and especially preferably 20%. A preferred maximum mole percent branching level is 40%, more preferably 35%, very preferably 30%, and especially preferably 25%. It is to be understood that any preferred minimum mole percent branching level may be combined with any maximum mole percent branching level to form a preferred mole percent branching level range.
The polyolefin of the present invention has a relatively low melting point or no melting point, and the crystallinity level is generally low or nil. Thus, generally gas phase or liquid suspension polymerization may be used to produce a polyolefin in the higher part of the density range, liquid solution polymerization will most likely be preferred method for carrying out the oligomerization and polymerization parts (simultaneously or sequentially) of the process. Solution oligomerization/polymerizations of these types are well known, see for instance Y. V. Kissin, Polyethylene, Linear Low Density, Kirk-Othmer Encyclopedia of Chemical Technology (online), John Wiley & Sons, DOI 10.1002/0471238961.10209149511091919.a01.pub2 (2005), which is hereby included by reference for the polymerization, and for the separate oligomerization see U.S. Pat. Nos. 6,103,946, 6,534,691, 7,053,259, 7,049,442 and 7,053,020, and World Patent Applications 1999/012981 and 2000/050470, all of which are hereby included by reference.
It is preferred that the polymerization and oligomerization be carried out simultaneously in a vessel. Conditions which are mutually applicable to both the polymerization and oligomerization catalysts may be used. For instance the temperature may be in the range of about 60° C. to about 150° C., and a mutually useable solvent such as an alkane or mixture of alkanes and/or an aromatic hydrocarbon may be used. Many activators/cocatalysts are useful for both of these types of catalysts, such as alkylaluminum compounds, for instance methylaluminoxane. If the process is a solution process wherein oligomerization and polymerization are done simultaneously it may be advisable to add the oligomerization catalyst to the vessel first to build up a supply of olefins in the process before adding the polymerization catalyst so that higher melting polyethylene is not formed before the process reaches steady state. The higher melting polyethylene may foul the vessel by precipitating, before the α-olefin concentration in the vessel builds up to produce the lower melting (and lower density) desired polyolefin.
If the oligomerization and polymerization parts of the process are done sequentially, conditions for the oligomerization and polymerization may be different, conditions suitable for each type of catalyst being used in that part of the overall process. After the oligomerization is done the stream of the series of α-olefins can be treated in a number of ways, for instance solvent may be removed, the oligomerization catalyst be deactivated, or the stream of α-olefins be partially fractioned to remove, for instance, lower boiling compounds (under this condition a mole percent branching cannot be calculated as shown above). The α-olefin stream is preferably added as a liquid to the polymerization part of the process.
The Mn (number average molecular weight of the polyolefin is preferably in the range of about 300 to about 20,000. The Mn is measured by standard methods using Size Exclusion Chromatography (some called Gel Permeation Chromatography) using a linear polyethylene standard. A more preferred minimum Mn is about 1000, especially preferably about 2000. A more preferred maximum Mn is about 15,000, more preferably about 10,000 and very preferably about 5,000. It is to be understood that any preferred minimum Mn may be combined with any preferred maximum Mn to form a preferred Mn range for the polyolefin. The molecular weight of the polyolefin may be controlled to some extent by the polymerization conditions, but may also be controlled by the addition of a compound which can decrease Mn, such as the commonly used hydrogen. Hydrogen has the advantage, if one does not want unsaturation in the polyolefin, of producing a saturated polymer end when it causes chain transfer.
After the polyolefin has been formed it may undergo treatment, chemical and/or physical to make more suitable component in a lubricant. In most cases it would be desirable to remove any solvent or other liquid from the polyolefin formed in the polymerization process, and to remove, to the practical extent possible any unreacted α-olefins in the polyolefin. Both of these may be accomplished by distilling or otherwise volatilizing the solvent and α-olefins. Other treatments may also be done, for instance it may be fractionated so that only a certain molecular weight portion is used, and/or it may be hydrogenated to remove unsaturation, and/or treated with activated carbon to remove color. Other similar treatments known for PAOs in the art may also be used. It is preferred that the polyolefin is not treated to add (as by grafting) polar groups, as to make, for instance, the polyolefin useful as a dispersant. If suitable the polyolefin may be used without post treatment in a lubricant or lubricant additive.
As noted above PAOs are usually made from previously synthesized, and often purified, α-olefins, such as 1-octene, and/or 1-decene and/or 1-dodecene. These olefins are significantly more expensive than ethylene from which they are usually made. The present process makes the olefins that are copolymerized with ethylene in situ, especially when the oligomerization and polymerization are simultaneous in a single vessel. This saves considerable cost in the manufacture of the polyolefin.
It is theorized that the presence of ethylene repeat units in the polyolefin also helps the low temperature properties of the polyolefin when it is used as a lubricant component. For instance the range of branch lengths in the polyolefin, as opposed to a polymer with only one or two branch lengths in it, may help slow the crystallization of longer branches, another potential improvement in low temperature properties. This may improve low temperature properties such as pour point. According to J. Brandrup, et al., Ed., Polymer Handbook, 2nd Ed., John Wiley & Sons, New York (1975), p. II-143 to II-144, the glass transition temperature (Tg) polyethylene is −125° C., while the Tg of poly-1-decene is −41° C. and the Tg of poly-1-dodecene is −32° C. It would be expected for the present polyolefin to have a Tg lower than that of either poly-1-decene or poly1-1dodecene since Tg's of copolymers generally are intermediate between those of the consistent monomer's polymers. Again this may improve low temperature properties such as pour point.
In lubricants, the polyolefins of the present invention are particularly useful as base oil or a viscosity index improver. For instance, the present polyolefin may be part of a lubricant additive that improves the VI of an already formulated lubricant. Use as a base for the lubricant may also help improve the lubricant VI.
The present invention is not limited to the embodiments described and exemplified above, but is capable of variation and modification without departure from the scope of the appended claims.
This application claims the benefit of priority of U.S. Provisional Application Nos. 61/318,556 filed on Mar. 29, 2010; 61/318,570 filed on Mar. 29, 2010; 61/362,563 filed on Jul. 8, 2010; 61/357,362 filed on Jun. 22, 2010 and 61/357,368 filed on Jun. 22, 2010 which are herein incorporated by reference in their entirety.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US11/30128 | 3/28/2011 | WO | 00 | 9/20/2012 |
| Number | Date | Country | |
|---|---|---|---|
| 61318570 | Mar 2010 | US | |
| 61318556 | Mar 2010 | US | |
| 61357368 | Jun 2010 | US | |
| 61357362 | Jun 2010 | US | |
| 61362563 | Jul 2010 | US | |
| 61390365 | Oct 2010 | US |
