Triblock polyalkylene glycols for dual-phase lubricants

Abstract

A composition is disclosed that exhibits two phases at low temperatures (e.g., below about 50° C.) but only one phase at high temperatures (e.g., above about 90° C.). The composition includes a low-viscosity base oil that is a hydrocarbon oil, and a high-viscosity base oil that is a triblock polyalkylene glycol derived from a copolymer of 1,2-propylene oxide and 1,2-butylene oxide having a PO-BO-PO polymerization sequence with a PO / BO ratio of 25 / 75 to 90 / 10 wt %.

Description

[Technical field]

[0001] The present invention relates to a new class of materials suitable for use as lubricants. These materials are triblock polyalkylene glycols which, when blended with hydrocarbon oils, tend to exhibit two phases at one temperature and a single phase at another temperature.

[0002] Introduction Industrial lubricants are usually single-phase, fixed composition materials made from a base stock into which various performance-enhancing additives may be incorporated. Typically, lubricants are selected to optimize the performance, function and protection of the system being lubricated, such as a gear, a cam follower pair, a roller bearing, a hydrodynamic bearing or a pump, under the intended conditions of use.

[0003] To optimize system performance, lubricants are formulated by selecting one or more base stocks and additives that, when combined, meet the needs of the system. Viscosity characteristics are an important consideration when formulating lubricants, as proper viscosity balances energy loss (due to viscous drag) and wear (due to reduced oil film thickness and reduced viscosity). Anti-wear and anti-scuffing additives can help protect surfaces when the oil film between such surfaces becomes too thin. Depending on their composition, base stocks can have a variety of beneficial properties, such as antioxidant properties, good viscosity index, and low static friction.

[0004] Although it is possible to optimize lubricant selection for single-phase lubricants, optimal performance under the prevailing operating conditions (such as speed, load, and temperature) may be compromised when conditions change or when the same lubricant is used to lubricate several parts, each with its own unique lubrication needs. Often, for simplicity, one type of lubricant is used to lubricate a wide variety of machines.

[0005] The use of single-phase lubricants requires a compromise between premature machine failure due to wear, fatigue or scuffing because the lubricant is insufficiently viscous under one set of operating conditions, and excessive energy loss or overheating because the lubricant viscosity is too high for a second set of operating conditions. Because machine or plant operators prefer to minimize downtime, this compromise usually favors high viscosity lubricants, which reduces equipment failures but causes excessive energy loss during start-up periods when temperatures are low. When temperatures vary widely over the lubricant's intended use, the viscosity is typically optimized for use at its highest operating temperature, but because of the relationship between viscosity and temperature, a lot of energy is wasted because the lubricant viscosity is too high under normal lower operating temperatures.

[0006] There has been great innovation into developing lubricants that provide energy efficiency benefits that can improve fuel economy. This means that less energy is consumed in operating equipment when more energy efficient lubricants are selected. One way to improve efficiency is to reduce friction losses in equipment by developing lubricants that reduce friction between moving parts. This can be accomplished by using friction modifiers as an example, and / or by selecting base oils that have inherently low friction values. The second way is to simply reduce the viscosity of the lubricant. A lower viscosity lubricant consumes less energy in lubricant internal friction. However, if the viscosity of the lubricant becomes too low, excessive wear can occur and ultimately the equipment can be damaged due to an insufficient amount of lubricant film thickness.

[0007] Dual-phase lubricants for improving cold start of automotive engines are disclosed in French Patent No. 2,205,931 and U.S. Patent No. 5,602,085. These references disclose a process of combining a denser, low-viscosity phase with a less dense, high-viscosity phase such that when the engine is at its operating temperature, there is a homogeneous phase with the lubricating properties characteristic of conventional engine lubricants. When the engine is cold, the phases separate so that when the engine is started under cold conditions, only the low-viscosity, dense fluid is drawn into the oil pump. This improves engine cranking speed and eases starting by reducing viscous resistance. The lubricant phases mix as the engine warms up, and the mixed lubricant behaves in a conventional manner and exhibits a large viscosity change with temperature.

[0008] The lubricant should consist of a high viscosity base oil and a low viscosity base oil, where the high viscosity base oil should have a higher density than the low viscosity base oil. At low temperatures and under static conditions (e.g., when the equipment is not operating), the high viscosity base oil separates and forms a bottom layer. The low viscosity base oil (which has a lower density) forms an upper layer.

[0009] It is well known that significant energy is consumed when a conventional single-phase lubricant is pumped around the equipment when the equipment is started (single-phase lubricants remain one phase over a wide operating temperature range). Energy losses due to viscous drag can be significant because the lubricant is cold and therefore more viscous (than at high temperatures).

[0010] In equipment such as gear or transmission systems, during equipment startup, the gears begin to rotate in the lubricant. However, at equipment startup, when the temperature is low (e.g., 20°C), if the lubricant exists as a two-phase lubricant, the gears will initially rotate in the low-viscosity base oil (upper phase). Thus, the churning energy loss is much lower than if the lubricant were homogeneous (one-phase) and existed as a higher-viscosity fluid. This concept can improve energy efficiency through lubricant design and the method of lubricating the equipment. When the lubricant temperature increases due to heat generation from friction, the high-viscosity base oil and the low-viscosity base oil mix to form a single phase of the lubricant and are miscible with each other.

[0011] Furthermore, it is well known that conventional lubricants, which are homogeneous (one-phase) at both low and high temperatures, exhibit a decrease in viscosity as the lubricant temperature increases, thus reducing the lubricant film thickness, thereby increasing the probability of wear between the frictional surfaces. However, in a two-phase system, at higher temperatures, the high viscosity base oil mixes with the low viscosity base oil to create a more viscous lubricant, resulting in a thicker film, thus helping to prevent wear from occurring.

[0012] Therefore, what is desired is a new lubricant solution or a method of using a new lubricant solution that can provide improved energy efficiency over conventional lubricants while also achieving the primary goal of minimizing wear.

[0013] New materials that can achieve a balance between energy efficiency and long term wear resistance are continually being sought. Summary of the Invention

[0014] The present invention relates to a composition that exhibits two phases at low temperatures (e.g., below about 35° C.) but only one phase at high temperatures (e.g., above about 90° C.). The composition comprises a low-viscosity base oil, which is a hydrocarbon oil, and a high-viscosity base oil, which is a triblock polyalkylene glycol derived from a copolymer of 1,2-propylene oxide and 1,2-butylene oxide having a PO-BO-PO polymerization sequence and a PO / BO ratio of 25 / 75 to 90 / 10 wt %. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention relates to a composition that exhibits two phases at low temperatures (e.g., below about 30° C., 40° C., or even 50° C.), but only one phase at high temperatures (e.g., above about 100° C., 95° C., or even 90° C.). The composition of the present invention comprises a low-viscosity base oil, which is a hydrocarbon oil, and a high-viscosity base oil, which is a triblock polyalkylene glycol derived from a copolymer of 1,2-propylene oxide and 1,2-butylene oxide having a PO-BO-PO polymerization sequence and a PO / BO ratio of 25 / 75 to 90 / 10 wt %.

[0016] The composition, or lubricant system, of the present invention comprises two major components: a low viscosity base oil, which is a hydrocarbon oil, and a high viscosity base oil, which is an ABA triblock polyalkylene glycol derived from 1,2-propylene oxide as the A unit and 1,2-butylene oxide as the B unit. Block polymers are well known in the art and should be distinguished from random polymers in which PO-derived and BO-derived units are polymerized simultaneously, resulting in a random distribution of monomers throughout the polymer backbone.

[0017] The American Petroleum Institute classifies base oils into five categories (API 1509, Appendix E). Classes I-III are refined from petroleum crude oil. Group IV base oils are fully synthetic (polyalphaolefin) oils. Group V relates to other base oils not included in any of Groups I-IV. Groups I-III can be distinguished as follows: Group I has less than 0.03% by weight sulfur and / or more than 90% by volume saturates and a viscosity index between 80 and 120; Group II has a sulfur content of 0.03% by weight or less, a saturates content of 90% by volume or more, and a viscosity index between 80 and 120; Group III has a sulfur content of 0.03% by weight or less, a saturates content of 90% by volume or more, and a viscosity index of more than 120.

[0018] The low-viscosity base oil used in the present invention is selected from API Classes I to IV. The kinematic viscosity of the low-viscosity base oil at 40° C. is preferably 8 to 100 mm 2 / s, more preferably 15 to 50 mm 2 The kinematic viscosity of the low-viscosity base oil at 100°C is preferably in the range of 1.5 to 20 mm / s. 2 / s range, more preferably 2 to 15 mm 2 / s, and even more preferably 3 to 10 mm 2 The density of the low viscosity base oil at 15°C is preferably in the range of 0.80 to 0.90 g / cm 3 More preferably, the range is 0.820 to 0.86 g / cm 3 It should be understood that two or more different types of low viscosity base oils described herein may be used in combination.

[0019] In general, it has been found that Group I oils tend to be more soluble in the second component (i.e., ABA triblock polyalkylene glycol) than Group II oils, which are more soluble than Group III oils, which are more soluble than Group IV oils. Thus, Group IV oils tend to phase separate more easily with the second component than Group I oils. This allows some ability to tailor the lubricant system depending on the particular second component selected as well as the desired temperature for phase separation.

[0020] The second component of the lubricant system of the present invention is an ABA triblock polyalkylene glycol derived from 1,2-propylene oxide as the A units and 1,2-butylene oxide as the B units. The ratio of propylene oxide derived units to butylene oxide derived units is in the range of 1 / 3 to 10 / 1 by weight (i.e., the BO derived units constitute 10% to about 76% by weight of the second component), preferably in the range of 1 / 3 to 3 / 1 by weight, and more preferably in the range of 1 / 2 to 2 / 1 by weight.

[0021] The kinematic viscosity of the high-viscosity polyalkylene glycol base oil at 40°C is preferably 100 to 20,000 mm 2 / s range, more preferably 200 to 5000 mm 2 / s range, and even more preferably 400 to 1000 mm 2 The kinematic viscosity at 100°C is preferably in the range of 20 to 500 mm 2 / s range, more preferably 50 to 400 mm 2 / s range, and even more preferably 60 to 100 mm 2 The density of high viscosity polyalkylene glycol base oils at 15°C is in the range of 0.95 to 1.100 g / cm 3 More preferably, the range is 0.960 to 1.05 g / cm 3 It should be understood that two or more different types of high viscosity base oils described herein may be used in combination.

[0022] Typically, the ABA triblock polyalkylene glycols for use as the high viscosity base oils of the present invention have a molecular weight in the range of from 2000 to 8000 Daltons, preferably from 4000 to 6000 Daltons, more preferably from 4500 to 5500 Daltons, as determined by OH number measurement.

[0023] In general, it has been found that a higher level of BO in the ABA triblock polyalkylene glycol tends to increase the solubility of the second component in the first component, which also allows some tuning of the system to arrive at a lubricant system that exhibits a good balance of efficiency and lubricity at different operating temperatures.

[0024] Typically, the lubricant system of the present invention comprises 40 to 95 wt %, more preferably 50 to 85 wt %, of the low viscosity base oil and 5 to 60 wt %, more preferably 15 to 50 wt %, of the high viscosity oil. It should be understood that other oils or additives may be present in the lubricant system such that the weight percentages of the first component and the second component need not, but may, add up to 100%.

[0025] The lubricant systems of the present invention may advantageously include additives such as antiwear agents, rust inhibitors, metal deactivators, hydrolysis inhibitors, antistatic agents, antifoam agents, antioxidants, dispersants, detergents, extreme pressure additives, friction modifiers, viscosity index improvers, pour point depressants, tackifiers, metal detergents, ashless dispersants, and corrosion inhibitors, as are commonly known in the art. In some embodiments, the lubricant systems of the present invention may be characterized by the substantial absence of any aliphatic esters.

[0026] The lubricant system of the present invention may be further characterized by its ability to exhibit two phases at low temperatures (e.g., below about 30° C., 35° C., or even 40° C.), but only one phase at higher temperatures (e.g., above about 100° C., 95° C., or even 90° C.). The two phases may be evidenced by either a clear boundary between the phases, or simple cloudiness or turbidity, indicating that the phases are not miscible, but that there has not been enough time to completely form completely separate layers. EXAMPLES

[0027] Table I lists the materials used in the examples.

[0028] [Table 1]

[0029] Synthesis of experimental polymers Synthesis of experimental OSP-A (75 / 25 w / w PO / BO) A 15 L conical reaction vessel is fitted with a magnetically coupled stirrer head and temperature control device and charged with 163.3 g of P400 (polypropylene glycol with a nominal molecular weight of 430 Daltons) and 20.0 g of 45% aqueous potassium hydroxide. The solution is stirred at 200 rpm and heated to a temperature of 115° C. A vacuum is applied to maintain the solution at 30 mBar in order to remove water. Residual water is determined by Karl Fischer titration to be less than 1500 ppm after 2 hours under the above conditions. The solution is cooled to 110° C., nitrogen is introduced into the reaction vessel and the vacuum is released.

[0030] The alkoxylation reaction is carried out in three steps. In the first step, 760 g of 1,2-propylene oxide is fed to the solution at 110° C. with stirring at 320 rpm at a feed rate of 7 g / min. After all the oxides have been fed, the reaction is allowed to proceed for 5 hours at 110° C. to decompose all the oxides present. In the second step, 930 g of 1,2-butylene oxide is fed at 130° C. with a feed rate of 7 g / min. After all the oxides have been fed, the reaction is allowed to proceed for 8 hours at 130° C. to decompose all the oxides present. In the third reaction step, 1870 g of 1,2-propylene oxide is fed at 110° C. with a feed rate of 5 g / min. After all the oxides have been fed, the reaction is allowed to proceed for 18 hours at 110° C. to decompose all the oxides present. In all three steps of the alkoxylation reaction, the pressure in the reaction vessel is closely monitored and restrictions on the oxide feed are implemented to ensure that a pressure of 3.5 bar is not exceeded.

[0031] The solution is then cooled to 80°C and mixed with 102 g of magnesium silicate at a stirring speed of 350 rpm for 1 hour. The resulting solution is then removed from the reaction vessel and transferred to a porcelain Büchner filter funnel equipped with filter paper having a pore size of 20 μm and filtered under vacuum. The filtrate is maintained at a vacuum of less than 0.3 bar for 6 hours to obtain a clear solution.

[0032] Synthesis of experimental OSP-B (50 / 50 w / w PO / BO) A 15 L conical reaction vessel is fitted with a magnetically coupled stirrer head and temperature control device and charged with 333.7 g of P400 and 29.7 g of 45% aqueous sodium hydroxide. The solution is stirred at 200 rpm and heated to a temperature of 115° C. A vacuum is applied to maintain the solution at 30 mBar in order to remove water. Residual water is determined by Karl Fischer titration to be less than 1500 ppm after 2 hours under the above conditions. The solution is cooled to 110° C. and nitrogen is introduced into the reaction vessel and the vacuum is released.

[0033] The alkoxylation reaction is carried out in three steps. In the first step, 435 g of 1,2-propylene oxide are fed to the solution at 110° C. with stirring at 320 rpm at a feed rate of 7 g / min. After all the oxides have been fed, the reaction is allowed to proceed for 6 hours at 110° C. to decompose all the oxides present. In the second step, 3169 g of 1,2-butylene oxide are fed at 130° C. with a feed rate of 10 g / min. After all the oxides have been fed, the reaction is allowed to proceed for 14 hours at 130° C. to decompose all the oxides present. In the third reaction step, 1915 g of 1,2-propylene oxide are fed at 110° C. with a feed rate of 5 g / min. After all the oxides have been fed, the reaction is allowed to proceed for 14 hours at 110° C. to decompose all the oxides present. In all three steps of the alkoxylation reaction, the pressure in the reaction vessel is closely monitored and restrictions on the oxide feed are implemented to ensure that a pressure of 3.5 bar is not exceeded.

[0034] The solution is then cooled to 80 ° C and mixed with 104 g of magnesium silicate at a stirring speed of 350 rpm for 1 hour. The resulting solution is then removed from the reaction vessel and transferred to a porcelain Büchner filter funnel equipped with filter paper having a pore size of 20 μm and filtered under vacuum. The filtrate is maintained at a vacuum of less than 0.3 bar for 7 hours to obtain a clear solution.

[0035] Synthesis of experimental OSP C (25 / 75 w / w PO / BO) A 15 L conical reaction vessel equipped with a magnetically coupled stirrer head and temperature control is charged with 201.5 g of P400 and 24.6 g of 45% aqueous potassium hydroxide. The solution is stirred at 200 rpm and heated to a temperature of 115° C. A vacuum is applied to maintain the solution at 30 mBar in order to remove water. Residual water is determined by Karl Fischer titration to be less than 1500 ppm after 2 hours under the above conditions. The solution is cooled to 110° C., nitrogen is introduced into the reaction vessel and the vacuum is released.

[0036] The alkoxylation reaction is carried out in three steps. In the first step, 285 g of 1,2-propylene oxide is fed to the solution at 110° C. with stirring at 320 rpm at a feed rate of 10 g / min. After all the oxides have been fed, the reaction is allowed to proceed for 6 hours at 110° C. to decompose all the oxides present. In the second step, 2910 g of 1,2-butylene oxide is fed at 130° C. with a feed rate of 7 g / min. After all the oxides have been fed, the reaction is allowed to proceed for 12 hours at 130° C. to decompose all the oxides present. In the third reaction step, 485 g of 1,2-propylene oxide is fed at 110° C. with a feed rate of 5 g / min. After all the oxides have been fed, the reaction is allowed to proceed for 14 hours at 110° C. to decompose all the oxides present. In all three steps of the alkoxylation reaction, the pressure in the reaction vessel is closely monitored and restrictions on the oxide feed are implemented to ensure that a pressure of 3.5 bar is not exceeded.

[0037] The solution is then cooled to 80 ° C and mixed with 104 g of magnesium silicate at a stirring speed of 350 rpm for 1 hour. The resulting solution is then removed from the reaction vessel and transferred to a porcelain Büchner filter funnel equipped with filter paper having a pore size of 20 μm and filtered under vacuum. The filtrate is maintained at a vacuum of less than 0.3 bar for 7 hours to obtain a clear solution.

[0038] Synthesis of experimental OSP D (50 / 50 w / w PO / BO) A 15 L conical reaction vessel equipped with a magnetically coupled stirrer head and temperature control device is charged with 234 g of B700 (polybutylene glycol with a nominal MW of 700 Da) and 18.3 g of 45% aqueous sodium hydroxide. The solution is stirred at 200 rpm and heated to a temperature of 115° C. A vacuum is applied to maintain the solution at 30 mBar in order to remove water. Residual water is determined by Karl Fischer titration to be less than 1500 ppm after 2 hours under the above conditions. The solution is cooled to 110° C., nitrogen is introduced into the reaction vessel and the vacuum is released.

[0039] The alkoxylation reaction is carried out in one step. 2042 g of 1,2-propylene oxide and 1851 g of 1,2-butylene oxide are co-fed to the solution at a feed rate of 12 g / min at 130° C. with stirring at 320 rpm. After all the oxides have been fed, the reaction is allowed to proceed at 130° C. for 4 hours to decompose any oxides present. During the alkoxylation reaction, the pressure in the reactor is closely monitored and restrictions on the oxide feed are made to ensure that a pressure of 3.5 bar is not exceeded.

[0040] The solution is then cooled to 80 ° C and mixed with 90 g of magnesium silicate at a stirring speed of 350 rpm for 1 hour. The resulting solution is then removed from the reaction vessel and transferred to a porcelain Büchner filter funnel equipped with filter paper having a pore size of 20 μm and filtered under vacuum. The filtrate is maintained at a vacuum of less than 0.3 bar for 7 hours to obtain a clear solution.

[0041] Synthesis of experimental OSP E (25 / 75 w / w PO / BO) A 15 L conical reaction vessel equipped with a magnetically coupled stirrer head and temperature control device is charged with 248.5 g of B700 (polybutylene glycol with a nominal MW of 700 Da) and 19.1 g of 45% aqueous sodium hydroxide. The solution is stirred at 200 rpm and heated to a temperature of 115° C. A vacuum is applied to maintain the solution at 30 mBar in order to remove water. Residual water is determined by Karl Fischer titration to be less than 1500 ppm after 2 hours under the above conditions. The solution is cooled to 110° C., nitrogen is introduced into the reaction vessel and the vacuum is released.

[0042] The alkoxylation reaction is carried out in one step. 888 g of 1,2-propylene oxide and 2493 g of 1,2-butylene oxide are co-fed to the solution at a feed rate of 14 g / min at 130° C. with stirring at 320 rpm. After all the oxides have been fed, the reaction is allowed to proceed at 130° C. for 4 hours to decompose any oxides present. During the alkoxylation reaction, the pressure in the reactor is closely monitored and restrictions on the oxide feed are made to ensure that a pressure of 3.5 bar is not exceeded.

[0043] The solution is then cooled to 80 ° C and mixed with 95 g of magnesium silicate at a stirring speed of 350 rpm for 1 hour. The resulting solution is then removed from the reaction vessel and transferred to a porcelain Büchner filter funnel equipped with filter paper having a pore size of 20 μm and filtered under vacuum. The filtrate is maintained at a vacuum of less than 0.3 bar for 7 hours to obtain a clear solution.

[0044] Preparation of blends. 100 mL of each lubricant composition is prepared by adding each component to a 200 mL glass beaker using the weight percentages shown in the table below. The blends are stirred at ambient temperature using a magnetic stirrer. Some blends form homogeneous, clear, one-phase compositions. For blends that do not form homogeneous one-phase compositions, but instead appear as two phases at ambient temperature, their separation temperatures are measured according to the procedure set forth below.

[0045] Measurement of separation temperature and kinematic viscosity Separation temperatures are measured only for compositions that exhibit two phases (either separate phases or observation of cloudiness or turbidity) at room temperature.

[0046] Add 50 mL of the lubricant composition to a 100 mL beaker equipped with a thermometer and a magnetic stirrer at room temperature. Heat to 120°C with stirring for 10-15 minutes, then turn off the heat and allow the lubricant composition to cool to room temperature. If the solution becomes cloudy or shows a visual separation into two phases, record the temperature at which this occurs as the separation temperature. When the temperature is 40°C, if the upper layer (called the supernatant) has separated into two phases, take a sample from it and measure the kinematic viscosity at 40°C. If there is no separation at 40°C, simply measure the kinematic viscosity of the homogenous one-phase composition at 40°C. Also measure the kinematic viscosity of the homogenous one-phase blend at 100°C.

[0047] Examples (Ex.) of the present invention and comparative examples (C.Ex) are shown below in different tables according to the selected low viscosity oil and high viscosity base oil.

[0048] [Table 2]

[0049]

Table 3

[0050]

Table 4

[0051]

Table 5

[0052]

Table 6

[0053]

Table 7

[0054]

Table 8

[0055]

Table 9

[0056]

Table 10

[0057]

Table 11

[0058]

Table 12

[0059] [Table 13] * The phase separation temperature is very close to the sampling temperature (40° C.), therefore the sample state is not very stable.

[0060] [Table 14]

[0061] [Table 15]

[0062] [Table 16]

[0063] Group III base oils and experimental OSP-A in Table 7, Group III base oils and experimental OSP-B in Table 8, Group IV base oils and experimental OSP-A in Table 11, Group IV base oils and experimental OSP-B in Table 12, and Group IV base oils and experimental OSP-C in Table 14 all show similar phase separation temperatures, but the blend viscosity and VI could be increased, if desired, by increasing the amount of high viscosity PAG component. Group III base oils and experimental OSP-C in Table 9 did not show separation upon blending, but it is believed that this example could be made to separate at a lower temperature by either moving to a higher classification level IV for the low viscosity base oil or decreasing the relative amount of BO in the ABA triblock high viscosity component.

[0064] Considering the higher viscosity of the high viscosity PAG polymers used in dual phase lubricants, a higher VI can be achieved with the same amount of such PAG polymer, and it is highly desirable to use high viscosity PAGs with kinematic viscosities of greater than 600 cst at 40° C. The random polymers produced (OSP-D and OSP-E) did not meet this goal and therefore were not tested with the low viscosity component to determine if they would exhibit the desired phase separation characteristics.

[0065] For the examples listed in Table 16, experimental OSP-C showed significantly higher viscosity at a significantly lower theoretical MW than comparative OSP-E, and experimental OSP-B showed significantly higher viscosity at a significantly lower theoretical MW than comparative OSP-D. In the normal synthesis route of PO / BO copolymers (i.e., copolymers formed by random addition of PO and BO units), it would be very difficult to achieve a kinematic viscosity of more than 600 cst at 40° C. because side reactions (unsaturation due to isomerization of PO and BO) may initiate alkoxylation, thereby limiting the molecular weight increase and thus the viscosity. Experimental OSP-A, OSP-B, and OSP-C feed PO and BO separately at different temperatures. PO is fed at 110° C., which would result in lower unsaturation and higher MW, and thus higher viscosity.

Claims

1. 1. A lubricant system comprising a low viscosity base oil and a high viscosity base oil, wherein the low viscosity base oil is a hydrocarbon oil within American Petroleum Institute Classifications I-IV, and the high viscosity base oil is an ABA triblock polyalkylene glycol derived from 1,2-propylene oxide as the A units and 1,2-butylene oxide as the B units, and wherein the ratio of units derived from propylene oxide to units derived from butylene oxide ranges from 1 / 3 to 10 / 1 by weight.

2. 2. The lubricant system of claim 1, wherein the ratio of propylene oxide derived units to butylene oxide derived units ranges from 1 / 3 to 3 / 1 by weight.

3. 2. The lubricant system of claim 1, wherein the ratio of propylene oxide derived units to butylene oxide derived units ranges from 1 / 2 to 2 / 1 by weight.

4. 2. The lubricant system of claim 1, wherein the low viscosity base oil is an API Group IV oil.

5. 2. The lubricant system of claim 1, wherein the ABA triblock polyalkylene glycol has a molecular weight in the range of 2000 to 8000 Daltons.

6. 2. The lubricant system of claim 1, wherein the low viscosity base oil comprises 40 to 95 weight percent of the system.

7. The low viscosity base oil has a viscosity of 8 to 100 mm at 40° C. ２ 10. The lubricant system of claim 1 having a kinematic viscosity in the range of less than 100 / s.

8. The low viscosity base oil has a viscosity of 15 to 50 mm at 40° C. ２ 8. The lubricant system of claim 7 having a kinematic viscosity in the range of 1:1 / s.

9. The high viscosity base oil has a viscosity of 100 mm at 40° C. ２ / s~20,000mm ２ 10. The lubricant system of claim 1 having a kinematic viscosity in the range of 100 / s.

10. The high viscosity base oil has a viscosity of 400 mm at 40° C. ２ / s~1,000mm ２ 10. The lubricant system of claim 1 having a kinematic viscosity in the range of 100 / s.

11. The low viscosity base oil has a viscosity of 0.80 to 0.90 g / cm at 15°C. ３ 10. The lubricant system of claim 1 having a density in the range of

12. The high viscosity base oil has a viscosity of 0.95 to 1.10 g / cm at 15°C. ３ 10. The lubricant system of claim 1 having a density in the range of

Images