Multifunctional lubricant additives and selection methods

Abstract

The blend (320) for lubricating a surface includes a lubricant (322) and a polyepoxide co(ter)polymer additive (216) mixed with the lubricant (322). The polyepoxide co(ter)polymer additive (216) is a polyepoxide copolymer having a monomer M 1 and a monomer M 2 The first monomer M 1 comprises hexene oxide, HO, or octene oxide, OO, and the second monomer M 2 includes propylene oxide, PO.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority to U.S. Provisional Patent Application No. 63 / 161,087, filed on 15 March 2021, entitled “Multifunctional Lubricant Additive and Method for Preparing the Same,” the entire disclosure of which is incorporated herein by reference.

[0002] The embodiments disclosed herein generally relate to multifunctional lubricant additives and methods for selecting and / or forming them, and more particularly to designing and producing multifunctional lubricant additives that exhibit good oil solubility and high lubricity. [Background technology]

[0003] Lubricants are widely present in natural and artificial moving parts. They play a crucial role in mitigating parasitic friction energy loss, improving momentum transfer efficiency, and extending the operating life of machinery. Existing commercially available lubricants contain numerous additives such as friction modifiers, anti-wear agents, thickeners, pour point depressants, antioxidants, dispersants, and cleaning agents. Their complex chemical interactions make the formulation of effective lubricants particularly challenging. The automotive industry thus prefers to blend multi-functional lubricant additives with the oils used in combustion engines. For example, zinc dialkyldithiopyridinate (ZDDP) is well known to reduce friction and wear on sliding surfaces when operating in combustion engines while simultaneously increasing the oxidation stability of the lubricant. Nevertheless, consuming ZDDP in internal combustion (IC) engines generates corrosive sludge, which decomposes in the vehicle's exhaust after treatment, producing harmful SO2. x Releasing emissions. Increasingly stringent environmental regulations are putting pressure on the automotive industry to replace ZDDP with other additives.

[0004] Multifunctional polymer additives are considered suitable replacements for ZDDP. This is because the use of polymer materials involves extensive molecular design and combinations of many functionalities. For example, poly(alkyl methacrylate) (PAMA) is recognized for its multifunctional role in reducing friction, enhancing the wear resistance of materials, and improving the rheological properties of lubricants. However, PAMA can rapidly decompose in extreme environments, i.e., high temperatures and high-stress IC engine reciprocating motion, generating undesirable polymers and viscous friction species that degrade fuel efficiency. Extensive research has been conducted to improve the thermal and shear stability of PAMA. Industry and academia have also explored molecular designs of PAMA with various monomers, nanomaterials, polymer topologies, and chemical functional groups. Nevertheless, the search for other polymer materials that offer multifunctionality as lubricant additives remains limited.

[0005] Polyepoxides have been widely used in many industries, including the pharmaceutical, packaging, defoaming, and softening industries.[1] Due to their versatility, minimal environmental impact, and economic scalability, their application as lubricants has recently been explored.[2, 3] For example, poly(propylene oxide), also known as poly(propylene glycol), can be readily formulated as a commercial lubricant.[2] These oxides can also be mixed with other additives and used as base oils to enhance other oil lubrication properties. Poly(propylene oxide) copolymers are currently being studied as multifunctional lubricant additives.[3] They can enhance surface deposition control, enrich lubricants, and improve boundary lubrication performance.

[0006] However, existing lubricant additives based on these oxides do not mix readily with the oils used in various applications and are therefore not very efficient. Furthermore, the reactions currently used to manufacture these lubricant additives involve metallic or organometallic catalysts[2], resulting in catalyst residues that are difficult to remove. These metallic catalyst residues affect the properties of the lubricant additives and degrade the overall performance of the lubricant. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Thus, in addition to the need for other multi-functional lubricant additives, there is also a demand for new methods to produce lubricant additives that do not contain metal catalysts, enhance oil solubility, and improve lubrication performance. [Means for solving the problem]

[0008] According to the embodiment, a blend for lubricating a surface comprises a lubricant and a polyepoxydoco(ter) polymer additive mixed with the lubricant. The polyepoxydoco(ter) polymer additive comprises a first block having monomer M1 and a second block having monomer M2. The blend includes a first monomer M1 comprising hexene oxide, HO, or octenoxide, OO, and a second monomer M2 comprising propylene oxide, PO.

[0009] According to another embodiment, there is a polyepoxydoco(ter) polymer additive for lubricants, comprising a first monomer M1 containing hexene oxide, HO, or octen oxide, OO, or lauryl glycidyl ether, LGE, or 2-ethylhexyl glycidyl ether, EHGE; a second monomer M2 containing propylene oxide, PO; and a third monomer M3 containing styrene oxide, SO.

[0010] In yet another embodiment, there is a method for creating a blend for lubricating a surface. The method includes providing a lubricant, selecting a first monomer M1 having an aliphatic side chain that simultaneously increases the solubility of a polyepoxide co(ter)polymer additive in the lubricant and the viscosity of the lubricant, selecting a second monomer M2 that promotes the formation of a condensation polymer film and reduces metal contact of the rubbing surface between two metal surfaces, selecting a third monomer M3 that increases the thermal stability of the lubricant, creating a polyepoxide co(ter)polymer additive based on the first through third monomers (M1 through M3) by applying an organocatalyst ring-opening polymerization (ROP) process, and mixing the polyepoxide co(ter)polymer additive with the lubricant to obtain a blend. The polyepoxide co(ter)polymer additive is 5 wt% or less, and the lubricant is the remaining portion of the blend.

[0011] For a more complete understanding of the present invention, reference is now made to the following description taken in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0012] [Figure 1] It is a flowchart of a method for creating a lubricant additive based on a polyepoxide copolymer or terpolymer. [Figure 2] It is a diagram schematically showing an organocatalyst ring-opening polymerization process used to create a polyepoxide co- or terpolymer additive. [Figure 3A] It is a diagram showing piston movement within a cylinder and the presence of a lubricating film between two. [Figure 3B] It is a diagram showing damage to the surfaces of a piston and a cylinder when using a traditional lubricant. [Figure 3C] It is a diagram showing a surface with less damage when using a novel polyepoxide co- or terpolymer additive. [Figure 3D] It is a diagram showing in more detail a polyepoxide co- or terpolymer additive in a lubricant. [Figure 3E]A diagram revealing various monomers of the polyepoxide terpolymer additive. [Figure 4] A diagram showing various polyepoxide co- or terpolymer additives starting from eicosanol and catalyzed by the t-BuP2 / TEB catalyst at room temperature. [Figure 5] A diagram showing the rheological properties of the polyepoxide co- or terpolymer additive blend oil. [Figure 6] A diagram showing the decomposition temperature of motor oil, homo-, di-, and triblock polyepoxide co- or terpolymer additive blend oils containing 2.5 and 5 wt% of the additive. [Figure 7] A diagram showing the calculated temperature and the deviation observed during the thermal decomposition of the blend lubricant. [Figure 8] A diagram showing the tribological parameters measured on various oil-lubricated surfaces. [Figure 9A] A diagram showing the friction coefficient values of the novel lubricant additive with respect to a programmed load from 50 N to 500 N and a surface temperature maintained at 50 °C. [Figure 9B] A diagram showing the electrical contact resistance values of the novel lubricant additive with respect to a programmed load from 50 N to 500 N and a surface temperature maintained at 50 °C. [Figure 10A] A diagram showing the same quantities as above with respect to a constant load of 50 N and a surface temperature raised from 50 to 200 °C. [Figure 10B] A diagram showing the same quantities as above with respect to a constant load of 50 N and a surface temperature raised from 50 to 200 °C. [Figure 11A] A diagram showing a comparison of the Raman spectra of the friction products deposited on the rubbed surfaces lubricated with various polyether blend oils. [Figure 11B] A diagram showing a comparison of the Raman spectra of the friction products deposited on the rubbed surfaces lubricated with various polyether blend oils. [Figure 12]This is a flowchart of a method for selecting components of polyepoxydocoat or terpolymer additives and preparing an additive oil blend. [Modes for carrying out the invention]

[0013] The following description of embodiments refers to the accompanying drawings. The same reference numerals in different drawings identify the same or similar elements. The following detailed description is not limiting to the present invention. Instead, the scope of the present invention is defined by the accompanying claims. For the sake of simplification, the embodiments below are discussed in relation to diblock- and triblock-coated or terpolymers selected to achieve high oil solubility and improved lubrication performance. Methods for constructing such multifunctional lubricant additives are also discussed, which avoid the metallic residues introduced by currently used methods. However, the embodiments discussed below are not limited to diblock- and triblock-coated or terpolymers and may apply to other polymers.

[0014] Throughout this specification, any reference to “one embodiment” or “embodiment” means that any particular feature, structure, or characteristic described in relation to an embodiment is included in at least one embodiment of the subject matter disclosed. Therefore, occurrences of the phrase “in one embodiment” or “in an embodiment” in various places throughout this specification do not necessarily refer to the same embodiment. Furthermore, any particular feature, structure, or characteristic may be combined in one or more embodiments in any suitable manner.

[0015] According to embodiments, a multifunctional lubricant additive, such as a polyepoxydoco- or terpolymer additive, is designed to include at least a first block comprising monomer M1, which includes hexene oxide, HO, or octen oxide, OO, or lauryl glycidyl ether, LGE, or 2-ethylhexyl glycidyl ether, EHGE. The multifunctional lubricant additive further comprises a second block comprising monomer M2, which may be propylene oxide-based. The multifunctional lubricant additive may further comprise a third block comprising M3, which has styrene oxide, SO. The multifunctional lubricant additive comprises at least two of these blocks. In this application, a block copolymer is a copolymer formed when two different homopolymers are covalently bonded together and form repeating units called “blocks”. For example, a polymer can be a block copolymer consisting of X and Y monomers joined together, such as -YYYYYYYYYXXXXXXXXXX- (wherein the formula -YYYYYYYYY and -XXXXX-XXXXX- groups are individual blocks). The smallest block may contain several monomers.

[0016] Ring-opening polymerization (ROP) is a synthetic method generally used for well-defined polyepoxydote or terpolymers [1]. The preparation of polyepoxyds often involves metallic or organometallic catalysts [2]. As discussed above, residual catalyst residues that are difficult to remove can adversely affect the properties of lubricant additives. Such challenges have led to the rapid development of organocatalytic ROP methods [4-6]. One of the most promising organocatalysts is the Lewis pair of triethylborane (TEB) and the phosphazene base t-BuP2. This catalyst / activator combination facilitates living / controlled ROP of epoxyds with high efficiency, good selectivity, and narrow polydispersibility. Organocatalytic ROP with TEB / t-BuP2 catalysts opens the way to producing well-defined, catalyst-residue-free polyepoxydote or terpolymers, while simultaneously providing the possibility of designing polyepoxydote or terpolymers with various molecular features to meet requirements. Having obtained these features, the inventors synthesized a metal residue-free functional polyepoxydocoat or terpolymer via TEB / t-BuP2-catalyzed ROP, which will be used as a lubricant additive.

[0017] More specifically, in order to realize high-performance multifunctional lubricant additives, three parameters need to be controlled: (a) thermal stability, (b) rheological properties, and (c) boundary lubrication performance (friction / wear resistance). The inventors have been able to design / synthesize polyether-based di- and triblock coat(ter) polymers that satisfy these requirements. According to one embodiment, the first block contains a polyether having aliphatic side chains (hexene oxide (HO) or octenoxide (OO)), which can simultaneously improve the solubility of the additive in the oil and the viscosity of the oil. Thus this block solves the problem faced by existing lubricant additives that do not mix well with the oil. The second block is selected to be poly(propylene oxide) PPO, which promotes the formation of a condensed polymer film and thus reduces metal contact between friction surfaces. The third block is selected to contain styrene oxide SO monomer, which is expected to improve the thermal stability of the lubricant. The motivation for achieving thermal stability is to meet the needs of highly compact turbocharged spark-ignition engines that operate under more extreme conditions (i.e., higher loads and temperatures).

[0018] In this or another embodiment, the inventors have found that a molecular weight of 100 kg mol provides greater resistance to mechanical cutting (i.e., greater shear stability) -1 The goal was further to create a polyether block coat polymer of less than 50. This minimizes the wear resistance caused by the frictional species of the decomposed polymer while also achieving boundary lubrication performance.

[0019] A method for forming a lubricating additive having the characteristics discussed above is presented below with reference to Figures 1 and 2. In a glove box (Ar atmosphere), in a dry polymerization flask equipped with a stirring rod, in step 100 (see flowchart of the method shown in Figure 1), 100 mg (0.168 mmol) of dehydrated eicosanol 200 (i.e., an aliphatic alcohol, C, as shown in Figure 2), which is a novel initiator for the lubricating additive, is added. 20 H 42O) was introduced. Further, 16.8 μL (3.36 μmol) of t-BuP2, and 134 μL (0.134 mmol) of TEB which is catalyst 202, and 1 mL of dehydrated toluene 204 were added to the flask. The mixture 200 / 202 / 204 was stirred in step 102 until all of the eicosanol 200 was completely dissolved at room temperature. The first monomer M1, for example OO (2 mL, 16.8 mmol), was added to the blend in step 104, and the polymerization was carried out at room temperature in a glove box to obtain the first polymerization blend 210. The first monomer M1 may be one of hexene oxide HO, lauryl glycidyl ether, LGE, or 2-ethylhexyl glycidyl ether, EHGE (the structures of these monomers are shown in Figure 2). In one application example, any cyclic ether having an alkyl side group, such as a linear or branched hexyl, heptyl, octyl, etc., may be used as the first monomer M1. The ROP was 1 monitored by 1H NMR spectroscopy. After 24 hours, the conversion rate of OO was almost 100%. In step 106, 1 mL of the polymerization mixture 210 was withdrawn and quenched with a benzoic acid solution in THF. In step 108, 2 mL of the second monomer M2, for example PO, was added to the remaining polymerization mixture 210 to synthesize the diblock copolymer 212. In step 110, 1 mL of the polymerization mixture 212 was withdrawn and quenched. In step 112, 2 mL of the third monomer M3, for example SO, was added to the living diblock copolymer 212 to form the third block and obtain the final triblock polymer (terpolymer) 214. After more than 20 hours, the polymerization was stopped by adding a benzoic acid solution in step 114. An aliquot was withdrawn into 3 drops, and the conversion rate of the second monomer was determined by NMR. The rest of the polymerization mixture was diluted with 5 mL of dichloromethane (DCM) in step 116, mixed, and stirred with neutral alumina powder for 1 hour to remove the catalyst residue. The final multifunctional co(ter)polymer 216 was concentrated under reduced pressure in step 118 and vacuum dried at 40 °C for 24 hours. The first monomer M1 is C4H9 or C6H 13 or C 11 H 25 O or C8H 18It should be noted that the second monomer M2 contains an R1 group which may be O, the second monomer M2 contains an R2 group which may be CH3, and the third monomer M3 contains an R3 group which may be C6H5. Figure 2 shows block copolymers and terpolymers, but random copolymers and terpolymers having the same chemical composition may also be formed and may be used as lubricant additives. It should be noted that a copolymer is understood herein as a polymer made from two different monomers, while a terpolymer is understood herein as a polymer made from three different monomers. The methods discussed above can be used to form any type of polymer.

[0020] The novel lubricant additives discussed above can be configured / designed / selected to achieve any combination of thermal stability, friction reduction, and viscosity improvement by selecting the appropriate combination of monomers. For example, Figures 3A to 3C show a possible use of a lubricant additive designed in this way within the context of an IC engine 300. Essentially, the piston 310 moves within the cylinder 312 in a typical up-and-down motion, resulting in strong friction at the interface 314 between the piston and the cylinder. When a typical lubricant is used, surface damage appears at the interface 314 as shown in Figure 3B, whereas the use of a lubricant mixed with the novel multifunctional copolymer 216 (i.e., blend 320) minimizes damage as shown in Figure 3C. Figure 3D shows blend 320 containing the lubricant 322 and multifunctional copolymer 216 present at the interface 314, and together Figure 3D shows the copolymer 216 having various monomers M1 to M3 capable of achieving the desired characteristics. It should be noted that each monomer is selected based on the method discussed above to achieve at least one functionality of the additive.

[0021] Two samples of lubricants blended with 2.5 to 5.0 mass% polyepoxide-based coat or polymer, as discussed above, were investigated. Their rheological properties were determined using a rheometer in accordance with ASTM D7042 standard. The thermal stability of the prepared lubricants was evaluated using a simultaneous thermal analyzer. Oil lubrication performance and their boundary film formation ability were studied using a frictional testing apparatus connected with an ECR sensor. Low sliding speeds (50 mm / s) were applied to simulate oil lubrication in boundary (and mixed) lubrication regimes. The load-bearing capacity of the compounded oils varied depending on the test load from 50 N to 500 N (corresponding to 1.7 to 3.7 GPa), while their thermal sensitivity was studied by changing the test surface temperature from 25 to 200 °C. The friction types generated on the wear track were investigated using Raman spectroscopy.

[0022] The polyepoxydo coats or terpolymers prepared as described below were investigated with respect to three parameters required for effective lubricant formulations: (a) thermal stability, (b) rheological properties, and (c) boundary lubrication performance (friction / wear resistance). As discussed above, the lubricant additives prepared by the inventors used ROP of various monomers, namely epoxides having HO, OO, LGE, or EHGE as the first type monomer and PO as the second monomer. Furthermore, triblock terpolymers of OO, PO, and SO were synthesized according to the same method. Based on the study of these lubricant additives, it was observed that the first monomer M1 containing an aliphatic chain simultaneously improved / increased the solubility of the additive in the lubricant and the friction / wear reduction ability of the additive / lubricant. Two lipophilic homopolymers containing poly(hexene oxide) (PHO) and poly(octene oxide) (POO) were used during testing to act as benchmarks. The second monomer M2 of the novel lubricant additive is designed to promote the formation of a condensation polymerization film that reduces metal-to-metal contact between friction surfaces. PO is sequentially block copolymerized with HO and OO and one of LGE and EHGE to realize poly(hexene oxide-block-propylene oxide) (PHO-b-PPO) and / or poly(octene oxide-block-propylene oxide) (POO-b-PPO) and / or poly(laurylglycidyl ether-b-poly(propylene oxide), PLGE-b-PPO) and / or poly(2-ethylhexylglycidyl ether)-b-(poly(propylene oxide), PEHGE-b-PPO). The third monomer M3, for example SO, is further rib POO-b-PPO-b-PSO is copolymerized from the chain ends to maximize the thermal stability of the lubricant oil (PHO-b-PPO-b-PSO may be generated using the same method). In one application, ROP of low molecular weight polyepoxydocoated or terrapolymers was targeted because the lubricant additive obtained under these conditions achieves even stronger resistance to mechanical cutting (i.e., greater shear stability). Note that SO monomers can be added to any of the other block copolymers listed above.

[0023] Polyepoxydoco(ter) polymers with numerous blocks involve complex intramolecular and intermolecular interactions. To determine or characterize these interactions, the inventors applied electrical contact resistance (ECR) measurements to track the occurrence of metal-to-metal contacts on oil-lubricated surfaces. ECR measurements successfully evaluated the boundary film-forming ability of lubricants when blended with various additives, including functionalized polymers, ionic liquids, nanoparticles, ZDDP, and organic friction modifiers. The measured ECR curvature, used to estimate the number of metal-to-metal contacts on the oil-lubricated surface, can be explained by the effectiveness of boundary film formation on the smooth surface by various lubricant additives. The analyzed dynamic features of boundary film formation on the smooth surface can be further linked to lubrication performance, i.e., friction and wear, and can be used to interpret the relevant interfacial interactions obtained from the blended additives.

[0024] The synthesized additive 216 was blended with lubricants, such as Group II base oils (AramcoPrima Grade 230 oil, AP230), at 2.5% and 5.0% by mass, respectively. The mass percentage of the lubricant and the blended additive could range from 1% to 10% by mass. All copolymers 216 exhibited excellent solubility. Nevertheless, prior to testing, all prepared lubricant formulations were ultrasonically treated in a water bath at room temperature for 30 seconds. The rheological properties of the prepared lubricant blend 320, containing polyepoxide, were determined according to ASTM D7042. The kinematic viscosity of each lubricant at 40°C and 100°C was measured by viscosity index calculated according to the method specified in ASTM D2270 / ISO 2909. The thermal stability of the prepared lubricants was investigated using a thermogravimetric analyzer (TGA). TGA was performed using a simultaneous thermal analyzer (STA) under a continuous 20 sccm (i.e., standard cubic centimeters per minute) nitrogen purge, heating from room temperature to 500°C at a rate of 10°C / min. Mass loss profiles by thermogravimetric and differential thermogravimetric measurements were obtained for AP230 base oil, polyepoxide, and their respective lubricant blends (2.5% and 5.0% by mass).

[0025] The tribological properties of each lubricant formulation were studied using a standardized tribological testing apparatus. Approximately 50 μL of lubricant was placed in a ball-on-disk configuration. Their boundary lubrication performance was evaluated under a controlled load of 50 N, at a temperature of 50°C and a sliding speed of 50 mm / sec (equivalent to a 1 mm, 25 Hz stroke) for 30 minutes of linear reciprocating motion. The load-bearing capacity of the formulated lubricants was studied from 50 N to 500 N while maintaining the temperature and sliding speed at 50°C and 50 mm / sec, respectively; each step was held for 5 minutes and increased to a different load level without stopping. Temperature sensitivity was studied from 50°C to 200°C. Each temperature step was held for 5 minutes. The applied load and sliding speed were controlled at 50 N and 50 mm / sec, respectively. All tribological test results for oils blended with polyepoxide showed good reproducibility.

[0026] We first studied boundary film growth. An electrical contact resistance sensor was installed in a tribological testing apparatus. The sensor had an adjustable current (±1 μA to ±250 mA). The dynamics of boundary film growth (or the number of metal contacts) were evaluated by in-situ measured electrical resistance (R) on a smooth surface:

[0027]

number

[0028] In the equation, V is the electric potential, and I is the current flowing between the ball and the disk.

[0029] Prior to all surface analysis, all contact pairs were gently rinsed with petroleum ether and then vacuum-dried overnight. Lubricant wear resistance performance was assessed by ball wear volume (V Ball ) is evaluated using the following equation:

[0030]

number

[0031] The calculation was performed using the formula, where d is the abrasion mark diameter, r is the ball radius, N is the normal load, and S is the sliding distance. The abrasion mark diameter of the rubbed ball was measured using an optical microscope.

[0032] The chemical composition profile of the generated abrasion marks (rubbed discs) was analyzed using Raman spectroscopy. Relevant Raman spectra were induced using visible light (473 nm) from a cobalt source with appropriate light intensity (20 mW). The spectra were then measured at 200 cm². -1 From 3000cm -1 And, 1800cm -1 The data was collected from the grating, integrated over 5 seconds, and accumulated three times. Three to five random spots were measured to show steady-state chemical composition profiles generated from various oil-lubricated surfaces.

[0033] The molecular weights of the synthesized polyepoxide additive 216 were determined using NMR spectroscopy and gel permeation chromatography (GPC), and are listed in Table 1 in Figure 4. NMR spectra were analyzed to confirm the successful synthesis of each target polyepoxide coat or copolymer in Table 1. All GPC trajectories for homopolymers and copolymers showed a narrow distribution, indicating well-controlled copolymer or ternary polymerization catalyzed by t-BuP2 / TEB. DSC analysis showed that all copolymers underwent low T25°C (below 0°C). g It was revealed that all copolymers have low T gThis was obtained from the flexible CO bonds along the polyepoxide main chain and the high mobility of the alkyl side chains. Overall, the synthesized polyepoxides in Table 1 had low molecular weights in the range of approximately 10 to 22 kg / mol, narrow polydispersity, and no residue. The well-defined polyepoxide(ter)polymers 216 were subjected to the following analyses to understand their precise behavior as lubricant additives and to discuss the underlying lubrication mechanisms. Note that the ratios of various monomers M1 to M3, catalysts t-BuP2 and TEB, and initiator I can vary within ±20%. In one application example, for the POO-b-PPO-b-PSO polyepoxide polymer, when formed in an organocatalytic ROP process, the partial ratio of OO:PO:SO was 100:120:35, and the complete ratio of OO:PO:SO:I:P2:TEB was 100:120:35:1:0.6:0.3. However, the partial ratio may be (100):(50~200):(25~100), and the perfect ratio may be (100):(50~200):(25~100):1:(0.6±0.12):(0.3±0.06).

[0034] Table 2 in Figure 5 shows high viscosity indices for the novel polyepoxide additive 216 at low processing rates (2.5 to 5.0 mass%). Polyepoxides with longer alkyl chains, namely POO and POO-b-PPO, generally resulted in better viscosity adjustment for AP230 oil. Blending 2.5 to 5.0 mass% of POO improved the viscosity index (VI) from approximately 100 to 160, while the addition of PHO increased VI to approximately 120. In particular, the PPO-derived copolymer, despite having a 50% higher molecular weight, showed similar viscosity index improvements compared to its respective homopolymer, namely POO. This behavior is attributed to the unbalanced thickening power of POO-b-PPO at various temperatures, i.e., good oil thickening power at lower temperatures but insufficient oil thickening at higher temperatures. This phenomenon can be understood by thermally induced molecular coil swelling due to alkyl pendant groups of different sizes. Longer alkyl chains, such as POO, result in more molecular coil entanglement in the dispersed fluid (AP230 oil), leading to strong oil viscosity at both low and high temperatures. Conversely, even shorter alkyl chains, which result in stronger intramolecular hydrogen bonding, inhibit molecular coil expansion, and at higher temperatures, the hydrocarbon-based base oil reduces molecular coil entanglement. Therefore, POO-b-PPO-blended oils showed only limited improvement in viscosity index through copolymerization with PPO blocks.

[0035] In particular, the addition of PSO blocks to POO-b-PPO showed a strong antagonistic effect on the rheological behavior of the oil. The POO-b-PPO-b-PSO terpolymer reduced the viscosity index to 90, which was unexpected, especially due to their relatively small proportion (approximately 20 mass%). This rheological behavior is attributed to the viscosity-enhancing power of the oil, which was only effective at lower temperatures. At lower temperatures, the π-π interaction was mainly intramolecular, whereas at higher temperatures, the interaction extended to intramolecular and intermolecular forces. Such behavior limited their thermally induced coil expansion, creating entanglement with the base fluid, thereby reducing the viscosity index of the POO-b-PPO-b-PSO-compound oil. This finding is applicable to the rheological properties of lubricants containing styrene-derived copolymers. The strong viscosity-enhancing power of the oil was demonstrated only at low temperatures and showed drawbacks in typical IC engine applications, such as difficult cold starts, high shear forces, and poor fuel economy.

[0036] It is noteworthy that the polyepoxides used in these embodiments have low molecular weights ranging from approximately 10 to 20 kg / mol, as illustrated in both Table 1 and Table 2 of Figures 4 and 5, respectively. While the low molecular weight of polyepoxide 216 is one reason for its resistance to high shear stress in extreme environment applications, their viscosity-modulating power is typically not very efficient. Nevertheless, the inventors observed that even low molecular weight polyepoxide copolymers could impart similar viscosity-modulating power to high molecular weight poly(alkyl methacrylates), ranging from 100 kg / mol to 300 kg / mol. The viscosity index improvement by polyepoxide copolymers required only 2 to 5 mass%, which was significantly lower than the viscosity-modulating power of low molecular weight poly(alkyl methacrylates) (up to 12.5 mass%). Despite this, the polymer structure also played a role in their oil-modulating power.

[0037] The thermal stability of oils containing AP230 oil, homo- and block-polyepoxide 216, and 2.5 and 5.0 mass% additives (i.e., blend 320) was also investigated, as shown in Table 3 of Figure 6. This table provides the temperatures recorded at 5% and 50% mass losses of the prepared lubricant samples described above. The temperatures corresponding to specific mass losses were higher in the lubricants with polymer blends than in the original base oil (AP230). For example, the temperature (T) at the rate of maximum mass loss in the differential mass loss profile. max ) shifted to a higher regime. This shift may be due to the thermal stability provided by the blended polyepoxydoco(ter)polymer 216. T regarding AP230 max The temperature range is approximately 325°C, while when blended with polyepoxydocor(ter) polymers, it was found to shift to a higher regime (approximately 400°C). In particular, oil blended with POO-b-PPO-b-PSO yielded the highest temperature range. max (Approximately 405°C) is generated, which confirms the synthesis strategy shown in Figure 1, utilizing SO as a radical scavenger to enhance the thermal stability of the lubricant.

[0038] The interaction between the oil and the blended polyepoxydoco(ter) polymer is expressed by the following equation:

[0039]

number

[0040] Based on the analysis, in the formula, T dx% The x% represents the experimental temperature at which the mass loss was x%, and the blend fraction (of polyepoxide) ranged from 2.5% to 5.0% by mass, as shown in Table 3 of Figure 6.

[0041]

number

[0042] ΔT was shown as the ideal temperature produced by mixing the polymer and oil. x with x% mass loss,

[0043]

number

[0044] and,

[0045]

number

[0046] The difference between the two is recorded, and the interaction between the base oil and the polymer is quantized.

[0047] Table 4 in Figure 7 shows the synergistic effect between oil and polyepoxydoco(ter)polymer 216. ΔT was calculated for all formulated lubricants. 5% and ΔT 50% The value was positive and greater than 50°C. The increase in the concentration of the polyepoxydoco(ter) polymer blend was greater than ΔT. 5% and ΔT 50% The temperature was further increased by approximately 5°C, resulting in enhanced thermal stability. In particular, the maximum ΔT 5% and ΔT 50% It is a lubricant blended with a copolymer composed of PPO, exhibiting a synergistic effect of high thermal stability with the PO block, and further enhanced by the SO block.

[0048] The oil lubrication performance of oil and oil blended with polyepoxydoco(ter)polymer 216 was also investigated, as shown in Table 5 in Figure 8. Table 5 shows the improved boundary lubrication performance with various polyepoxydoco(ter)polymers 216. Blending PHO and POO into the oil reduced friction by approximately 10 to 25%, and ball wear volume by approximately 15 to 50%. The use of diblock copolymers 216, PHO-b-PPO and POO-b-PPO, reduced friction and wear by approximately 40% and 85%, respectively, which were significant improvements compared to PHO and POO polymers. The ter polymer, namely POO-b-PPO-b-PSO, also showed improved oil lubrication performance compared to the simple polymer, with friction and wear reductions of approximately 35% and 75%, respectively. The high lubrication performance may be due to the boundary film formation by polyepoxydoco(ter)polymer 216 on the smooth surface. Nevertheless, the increase in blend concentration from 2.5 to 5.0 mass%, as shown in Table 5, resulted in non-significant changes, which may be due to saturation interactions between the blend polymer and the smooth surface, such as complete surface coating by the polymer boundary film.

[0049] Table 5 also demonstrates the inverse relationship between average ECR and boundary lubrication performance, i.e., friction and wear volume. For example, surfaces lubricated with AP230 oil resulted in the lowest average ECR (approximately 20 mΩ) and the worst lubrication performance, such as maximum friction and wear. Blending polyepoxydo homopolymer into AP230 oil increased the average ECR to approximately 90 mΩ. The use of polyepoxydoco(ter)polymer 216 further increased the average ECR to several hundred mΩ. The increased average ECR indicates a more electrically insulating material generated on the smooth surface. The formation of these electrically insulating materials is responsible for improved boundary lubrication. These are either surface adsorbent polymers, thickening oil films, or friction types commonly called tribofilms. More specifically, lubrication with oils having less metal contact resulted in reduced friction and wear in the boundary lubrication regime.

[0050] Of note, the third block containing monomer M3, such as PSO, degrades boundary lubrication performance. Compared to the POO-b-PPO oil blend, the POO-b-PPO-b-PSO oil blend showed less friction and wear reduction. Furthermore, their surfaces were measured at approximately 100 to 300 mΩ, indicating more metal-to-metal contact than the PPO-b-PPO oil blend.

[0051] Figures 9A and 9B show how the friction and ECR values ​​for pure oil, oil with known additives, and oil with novel additive 216 change with respect to various test loads. Surfaces lubricated with AP230 oil showed higher friction at the start of linear motion. The zigzag friction curve 910 in Figure 9A may be due to frequent metal-to-metal contact and inadequate oil lubrication during the break-in period. Increasing the test load produced a sharp friction curve peak on the AP230 oil-lubricated surface, indicating that oil lubrication with AP230 alone has insufficient load-bearing capacity. On the other hand, the load-bearing capacity increased from 50 to 100 N for the POO and POO-b-PPO-b-PSO additives, and up to 200 N for the POO-b-PPO additive. As shown by the ECR measured in Figure 9B, the high load-bearing capacity may be due to surface adsorbed polyepoxides, thickening oil films, or friction generation formation. Notably, increasing the load reduced the ECR for all oil-lubricated surfaces. One possible explanation is the stress-assisted removal of the electrical insulating material on the smooth surface. Another possible reason is the plastic deformation of the contact pair at higher contact pressures, which increases the number of metal-to-metal contact areas and reduces the ECR value. Nevertheless, the boundary film resistance to high loads and high-frequency linear reciprocating motion explains the mechanism of the lubricant's load-bearing capacity.

[0052] Figures 10A and 10B show the effect of temperature rise on various oil-lubricated surfaces (see curves 1010 and 1012). As indicated by the measured ECR, the amount of electrical insulating material was negligible on AP230 oil-lubricated surfaces at all temperatures. Surfaces lubricated with POO-b-PPO and POO-b-PPO-b-PSO additives generated higher ECRs and effectively reduced COF at temperatures below 150°C. The measured COFs demonstrated that polyepoxydoco(ter) polymers can ensure their boundary lubrication performance in IC engine-related applications. Another interesting feature regarding surface temperature rise was that for all oil-lubricated surfaces, their COF and ECR curvature were converted to approximately 0.15 and 100 mΩ, respectively. Presumably, the higher surface temperatures caused the oil film to contract and the heated iron substrate to undergo plastic deformation due to high-frequency and high-load surface friction. The continuous linear reciprocating motion removed oil, polished the smooth surface, generated a similar number of metallic contacts, and ultimately resulted in the same COF and ECR.

[0053] Images of the surface morphology of friction surfaces lubricated with various polyepoxydoco(ter) polymer oil blends were obtained, showing that the friction surfaces were covered with a dark, carbon-like material commonly produced by hydrocarbon lubricants. All friction surfaces were cleaned with petroleum ether to remove most oils, polymers, and decomposed species. The resulting Raman spectra showed chemical species strongly bound to the surface. Numerous Raman spectra were provided from selected regimes to show chemical composition profiles representing the generated friction species.

[0054] Figures 11A and 11B show Raman spectra indicating various chemical species formed on the friction surface. These include iron oxide, disordered graphite, and various friction species from decomposed lubricants. The first four peaks are goethite (α-FeOOH, approximately 275, 475, and 580 cm⁻¹). -1 (and lepidocrocite (γ-FeOOH, approximately 380 cm) -1This may be due to various iron oxides, including ( ). They were driven by various mechanical energy distributions on the friction surface. Surface roughness led to material wear or further interaction with penetrating oxygen molecules that formed iron oxides, when the activation energy was reduced by surface sliding. The friction of hydrocarbons due to these surface roughness also induced their decomposition, adsorption, and polymerization, which are the causes of carbonaceous material formation. For example, at approximately 1350 cm² -1 The broad spectrum, centered at approximately 1580 cm⁻¹, may be due to disordered D-mode graphite, but is not as pronounced. -1 The peak located at [location] may be attributed to G-mode graphite (in-plane vibration of carbon atoms). On the other hand, numerous peaks may be attributable to various friction species decomposed from AP230 oil, as shown in Figures 11A and 11B. Nevertheless, the inventors did not observe any particular spectra featured by various polyepoxydoco(ter) polymer oil blends compared to surfaces lubricated with AP230 oil. This indicates that the chemical species of deposited friction products were similar on surfaces lubricated with various lubricants.

[0055] Analysis of the spectral ratios in Figures 11A and 11B showed that iron oxide was the dominant species on all friction surfaces, regardless of the type of lubricant blended. On the other hand, oils blended with polyepoxide reduced the formation of iron oxide, G-mode graphite, and numerous friction species featured by the decomposed AP230 oil. This phenomenon is attributed to the friction chemical reactions directed by the polyepoxide polymer blend oil. The measured ECR curvature supports this conclusion. Less metal-metal contact was interpreted as a reduction in mechanical energy at contact with the surface when lubricated with polyepoxide polymer. The mechanical energy confirmed to be consumed by AP230 oil was transferred to the surface-adsorbed polyepoxide, thereby reducing the decomposition of AP230 oil and also reducing the generation of iron oxide on the smooth surface. The polyepoxydoco(ter) polymer oil blend produced a spectrum characterized by CO-O-CO anhydride, which indicates the depletion of oxygen atoms on the smooth surface; thereby, the friction chemical reactions associated with oil decomposition or surface oxidation were quenched by reduced oxygen penetration into the oil film and friction surface.

[0056] All these tests show that surfaces lubricated with pure AP230 and various polyepoxydo-blend oils exhibited similar spectra (see Figures 11A and 11B). The higher average ECR was a result of polymer boundary film formation, as shown in Table 4, which contributed to the reduction of friction and wear. Furthermore, these tests suggest that the enhanced boundary lubrication with polyepoxydo-coat or terpolymer oil blends was more dominant by the polymer boundary film growth dynamics (see Figures 9A to 10B) than by the generated friction species (see Figures 11A and 11B). This is because the generated friction species had little effect on the lubrication performance of the oil, regardless of the various polyepoxydo-coat or terpolymer formulations. Instead, the various oil formulations affected the time to generate the ECR increase, resulting in faster surface protection (see Figures 9A to 10B), more efficient boundary film formation, and enhanced boundary lubrication performance (see Table 4).

[0057] Therefore, it can be concluded that the introduced polyepoxydoco- or terpolymers exhibit various behaviors compared to existing polymer-based additives, possessing one or more of the following molecular features:

[0058] Lipophilic blocks, namely PHO and POO, enable thermally induced molecular coil expansion, effectively thickening the lubricant and increasing its viscosity index.

[0059] The hydrophilic block, i.e., PPO, induces thicker and faster boundary film formation and improved boundary oil lubrication performance.

[0060] The benzyl-containing block, i.e., PSO, improves the thermal stability of the oil, while the π-π intramolecular and intermolecular interactions reduce the viscosity index of the polyepoxide and prevent boundary film formation.

[0061] Therefore, by changing the alkyl chain length, it is possible to effectively design the rheology and boundary lubrication performance of polyepoxydocoates or terpolymers. The use of polyepoxydocoates or terpolymers composed of aryl groups should be avoided because it reduces the viscosity-modulating ability of the polymer. This is due to strong π-π intramolecular and intermolecular interactions that inhibit molecular coil expansion and their entanglement with lubricants.

[0062] A method for preparing a blend 320 for lubricating a surface is discussed next with reference to Figure 12. The method includes the steps of: preparing a lubricant, which may be motor oil; selecting a first monomer M1 having aliphatic side chains, and simultaneously increasing the solubility of the polyepoxydocoate or terpolymer additive in the lubricant and the viscosity of the lubricant; selecting a second monomer M2 to promote the formation of a condensation polymer film to reduce metal-to-metal contact between two metal surfaces; selecting a third monomer M3 to increase the thermal stability of the lubricant; preparing a polyepoxydocoate or terpolymer additive based on the first to third monomers (M1 to M3) by an organocatalytic ring-opening polymerization (ROP) process; and mixing the polyepoxydocoate or terpolymer additive with the lubricant to obtain a blend. The polyepoxydocoate or terpolymer additive is 5% by mass or less, and the lubricant is the remainder of the blend.

[0063] In one embodiment, the ratio of OO:PO:SO when formed is (100±20):(120±24):(35±7). The organocatalytic ROP process uses triethylborane, TEB, and a phosphazene base, t-BuP2, as catalysts and initiator I. The complete ratio of OO:PO:SO:I:P2:TEB is (100±20):(120±24):(35±7):1:(0.6±0.12):(0.3±0.06). The polyepoxydocoate or terpolymer additive is block polymerized. The polyepoxydocoate or terpolymer additive has a molecular weight in the range of about 10 to 22 kg / mol.

[0064] The disclosed embodiments provide polymer lubricant additives having various monomers, each monomer selected to achieve desired properties, such as thermal stability, friction reduction, oil solubility, and viscosity improvement. For example, POO-b-PPO and PHO-b-PPO are best suited for lubricant formulations to increase viscosity and reduce the coefficient of friction. On the other hand, POO-b-PPO-b-PSO provides better thermal stability, but the increase in viscosity and reduction of COF are less than in the case of POO-b-PPO and PHO-b-PPO. This description should be understood not to limit the invention. In contrast, the embodiments shall encompass alternatives, modifications, and equivalents that fall within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the detailed description of the embodiments, numerous specific details are described to provide a comprehensive understanding of the invention as described in the claims. However, those skilled in the art will understand that various embodiments can be carried out without such specific details.

[0065] While the features and elements of the embodiments of the present invention are described in the embodiments in specific combinations, each feature or element can be used alone without other features and elements of the embodiments, or in various combinations with or without other features and elements disclosed herein.

[0066] This written description uses the disclosed examples of the subject matter to enable a person skilled in the art to carry it out, including making and using any device or system and any incorporated method. The patentable scope of the subject matter is defined by the claims and may include other examples that a person skilled in the art can imagine. Such other examples shall be within the scope of the claims.

[0067] The entire contents of all publications listed herein are incorporated into this patent application by reference. (References) TIFF0007837995000007.tif159153 [Explanation of Symbols]

[0068] 210 First Polymerization Blend 212 Diblock Copolymer 214 Triblock polymer 216 Functional Coating Polymers 300 IC organizations 310 Piston 312 cylinders 314 Interface 320 Blend 322 Lubricant 910 Friction curve 1010 Temperature rise curve 1012 Temperature rise curve M1 first monomer M2 second monomer M3 third monomer

Claims

1. A blend (320) for lubricating surfaces, Lubricant (322), and A polyepoxydoter polymer additive (216) mixed with the aforementioned lubricant (322) Includes, The polyepoxydoter polymer additive (216) comprises a first block containing R1 group, a second block containing R2 group, and a third block containing R3 group. The R1 group contains C4H9 or C6H13, the R2 group contains CH3, and the R3 group contains C6H5. blend.

2. The blend according to claim 1, wherein the polyepoxydoter polymer additive is made from first to third monomers, the first monomer M1 comprises hexene oxide (HO) or octenoxide (OO), the second monomer M2 comprises propylene oxide (PO), and the third monomer M3 comprises styrene oxide (SO).

3. The blend according to claim 2, wherein the molecular weight ratio of OO to PO to SO is (100):(50-200):(25-100) when formed by organocatalytic ring-opening polymerization (ROP).

4. The blend according to claim 3, wherein the organocatalytic ring-opening polymerization (ROP) is performed using triethylborane (TEB) and t-BuP2 (P2) as catalysts and initiator I, and the total molecular weight ratio of OO:PO:SO:I:P2:TEB is (100):(50-200):(25-100):1:(0.6±0.12):(0.3±0.06).

5. The blend according to claim 4, wherein the initiator I is eicosanol and the lubricant is motor oil.

6. The first monomer M 1 The blend according to claim 2, wherein the HO or OO is selected to have aliphatic side chains that simultaneously increase the solubility of the polyepoxydoter polymer additive in the lubricant and the viscosity of the lubricant.

7. The second monomer M 2 The blend according to claim 6, wherein the PO is selected to promote the formation of a condensed polymer film and reduce metal-to-metal contact between two metal surfaces.

8. The third monomer M 3 The blend according to claim 7, wherein the SO is selected to increase the thermal stability of the lubricant.

9. The blend according to claim 1, wherein the polyepoxydoter polymer additive comprises only three blocks.

10. The blend according to claim 1, wherein the polyepoxydoter polymer additive has a molecular weight in the range of about 10 to 22 kg / mol.

11. The blend according to claim 1, wherein the polyepoxydoter polymer additive is 5% by mass or less, and the lubricant is the remainder.

12. A polyepoxydoter polymer additive (216) for lubricants (322), A first monomer M comprising an R1 group containing C4H9 or C6H13, and containing hexene oxide (HO), octenoxide (OO), lauryl glycidyl ether (LGE), or 2-ethylhexyl glycidyl ether (EHGE). 1 The R1 group obtained from, A second monomer M containing CH3, which is an R2 group containing propylene oxide (PO). 2 The R2 groups obtained from, and A third monomer M containing C6H5, which is an R3 group containing styrene oxide (SO). 3 The R3 units obtained from Polyepoxydoter polymer additive (216), including the above.

13. The additive according to claim 12, wherein the molecular weight ratio of OO to PO to SO is (100):(50-200):(25-100) when formed by organocatalytic ring-opening polymerization (ROP).

14. The additive according to claim 13, wherein the organocatalytic ring-opening polymerization (ROP) uses triethylborane (TEB) and t-BuP2 (P2) as catalysts and initiator I, and the total molecular weight ratio of OO:PO:SO:I:P2:TEB is (100):(50-200):(25-100):1:(0.6±0.12):(0.3±0.06), and the initiator I is eicosanol.

15. A method for preparing a blend (320) for lubricating a surface, Step (1200) to prepare a lubricant (322), The first monomer M has an aliphatic side chain. 1 The step (1202) is to select the following, and to simultaneously increase the solubility of the polyepoxydoter polymer additive (216) in the lubricant (322) and the viscosity of the lubricant (1202), To reduce metal-to-metal contact between the two metal surfaces, a second monomer M is added to promote the formation of a condensation polymer film. 2 The process of selecting (1204), Step (1206) of selecting a third monomer M so as to increase the thermal stability of the lubricant (322) 3 and By applying an organocatalytic ring-opening polymerization (ROP) process, the first to third monomers (M 1 From M 3 A step (1208) to prepare the polyepoxydoter polymer additive (216) based on ), and The step (1210) of mixing the polyepoxydoter polymer additive (216) with the lubricant (322) to obtain the blend (320). Includes, The polyepoxydoter polymer additive (216) is 5% by mass or less, and the lubricant (322) is the remainder of the blend (320). The terpolymer additive comprises a first block containing an R1 group of C4H9 or C6H13, a second block containing an R2 group of CH3, and a third block containing an R3 group of C6H5. method.

16. The method according to claim 15, wherein the molecular weight ratio of OO to PO to SO is (100):(50-200):(25-100) when formed.

17. The method according to claim 16, wherein the organocatalytic ring-opening polymerization (ROP) process uses triethylborane (TEB) and t-BuP2 (P2) as catalysts and eicosanol as initiator I.

18. The method according to claim 17, wherein the total molecular weight ratio of OO:PO:SO:I:P2:TEB is (100):(50-200):(25-100):1:(0.6±0.12):(0.3±0.06).

19. The method according to claim 15, wherein the polyepoxydoter polymer additive comprises only the first to third blocks.

20. The method according to claim 15, wherein the polyepoxydoter polymer additive has a molecular weight in the range of about 10 to 22 kg / mol.

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