A viscosity index improver concentrate prepared in situ from low viscosity base oil and its preparation method.

Abstract

This invention relates to viscosity index improver concentrates for use in lubricating oils, and particularly to a viscosity index improver concentrate (a concentrate of a star-shaped hydrogenated styrene (S)-isoprene (I)-butadiene (B) terpolymer viscosity index improver) prepared in situ in low-viscosity base oils, and its preparation method. The star-shaped viscosity index improver is synthesized by polymerization, hydrogenation, and deashing in low-viscosity base oils at a monomer concentration of 5wt%-15wt%, directly yielding the viscosity index improver concentrate. This invention's method for in-situ synthesis of star-shaped viscosity index improvers in low-viscosity base oils reduces the steps of solvent removal, solvent recovery, product drying, and redissolution required in traditional viscosity index improver synthesis methods, thereby lowering production costs and ensuring product quality. This invention also provides a method for preparing the viscosity index improver concentrate prepared in situ in low-viscosity base oils.

Description

Technical Field

[0001] This invention relates to viscosity index improver concentrates for use in lubricating oils, and particularly to a viscosity index improver concentrate (a concentrate of a star-shaped hydrogenated styrene (S)-isoprene (I)-butadiene (B) terpolymer viscosity index improver) prepared in situ in low viscosity base oils and its preparation method. Background Technology

[0002] A combined method of anionic living polymerization and hydrogenation modification can be used to prepare viscosity index improvers with controllable structures, narrow molecular weight distributions, and diverse topologies. Among these, the star-shaped hydrogenated SIBR type viscosity index improver is the most well-known, with Infineum's SV260 holding the largest market share. The star-shaped viscosity index improver described in US Patent No. 4116917 has a polymer arm that is a hydrogenated poly(butadiene / isoprene) graded arm. Its preparation process uses cyclohexane as a solvent, styrene, butadiene, and isoprene as monomers, n-butyllithium as an initiator, and divinylbenzene as a coupling agent for anionic polymerization and coupling. After terminating the reaction, the star polymer is hydrogenated using nickel naphthenate as the main catalyst and triisobutylaluminum as a co-catalyst to obtain a saturated star polymer. The product undergoes catalyst removal, solvent flash evaporation, gel coagulation, solvent recovery, and product drying to obtain a dry star-shaped viscosity index improver. The product is available in both dry gel and concentrated form. The preparation method involves cumbersome steps such as solvent flash evaporation, gel coagulation, solvent recovery, product drying, and dissolving the dry gel in base oil, which prolongs the production cycle and increases production costs. Summary of the Invention

[0003] The purpose of this invention is to provide a viscosity index improver concentrate prepared in situ in low viscosity base oil and its preparation method.

[0004] To achieve the above objectives, the technical solution adopted is as follows:

[0005] A method for in-situ preparation of viscosity index improver concentrate in low viscosity base oil, wherein the star-shaped viscosity index improver is synthesized by polymerization, hydrogenation, and deashing in low viscosity base oil at a monomer concentration of 5wt%-15wt% to directly obtain viscosity index improver concentrate.

[0006] To elaborate further,

[0007] A: Isoprene and butadiene are added to base oil, and an alkyl lithium initiator is added. Polymerization is initiated at 20℃-90℃. When the conversion rate of isoprene and butadiene exceeds 95%, the reaction yields isoprene-butadiene random copolymer I / B. Styrene (S) is then added, and the reaction continues at 20℃-90℃. When the styrene conversion rate exceeds 95%, the I / BS diblock polymer is obtained. In the preparation of I / B, the mass ratio of total monomers to 2cst base oil is 1:4-1:19; the amount of alkyl lithium added is 1×10⁻⁶. -3 -1×10 -2 The mass ratio of I to B is 3:7-7:3, and the mass ratio of I / B to S is 98:2-90:10.

[0008] In the above steps, the distribution of monomers in the isoprene-butadiene copolymer I / B is controlled by adding a structure modifier. Random copolymers are obtained by adding a structure modifier. The amount added is generally between 10:1 and 50:1 molar ratio of THF to Li. The structure modifier is tetrahydrofuran. At the same time, gradient copolymers I / B can be obtained without adding a structure modifier.

[0009] B: After obtaining the I / BS diblock polymer, a coupling agent is added to the system and reacted at 20℃-90℃. When the conversion rate of the coupling agent exceeds 95%, isopropanol is added to the system to terminate the coupling reaction, resulting in the base adhesive, namely the star-shaped block copolymer (I / BS). n -C; wherein the molar ratio of coupling agent to alkyl lithium is 3:1-20:1; and the molar ratio of isopropanol to alkyl lithium is 1:1;

[0010] C: Add hydrogenation catalyst to the base oil solution of the above base adhesive, mix evenly, and then pass hydrogenation through it. The hydrogenation reaction is carried out at a temperature of 40℃-90℃ and a hydrogen pressure of 1.0-6.0MPa. After the hydrogenation reaction is completed, add solid acid and hydrogen peroxide to precipitate the hydrogenation catalyst in solid form. Remove the catalyst residue by separation on a high-speed centrifuge to obtain a concentrated solution of viscosity index improver.

[0011] The base oil solvent is one or two of Group I, Group II, Group III, and Group IV base oils with a viscosity of 1-5 cSt.

[0012] The alkyllithium has the molecular formula RLi, where R is a hydrocarbon group with 4-20 carbon atoms, preferably n-butyllithium or sec-butyllithium; the coupling agent is an epoxide compound or a diene compound, including epoxidized soybean oil, epoxidized linseed oil, divinylbenzene (DVB), and 1,3-stilbene. The coupling agent is added in one step, in several steps, or continuously.

[0013] The hydrogenation catalyst is a main catalyst and a co-catalyst; the main catalyst is a nickel salt (such as nickel naphthenate, nickel octanoate, etc.); the co-catalyst is an alkyl aluminum (such as triisobutylaluminum, triethylaluminum, etc.).

[0014] The molar ratio of the alkylaluminum to the nickel salt is 2:1 to 6:1.

[0015] The hydrogenation process of the polymer can employ any suitable hydrogenation method. The hydrogenation catalyst comprises a Group VIII compound (i.e., iron, cobalt, and especially nickel), a non-precious metal, or a compound containing a non-precious metal. Specifically, it can be a mixture of triisobutylaluminum and nickel naphthenate, aged and then added to the reaction system as a hydrogenation catalyst, with a nickel content of 0.2-10 mg per gram of dry gel. The amount of triisobutylaluminum used is: the molar ratio of triisobutylaluminum to nickel naphthenate is 2:1-8:1.

[0016] The hydrogenation reaction results in a degree of hydrogenation of greater than 95% for the unsaturated double bonds of the diene in the copolymer, less than 5% for the unsaturated bonds of the aromatic hydrocarbon, and less than 30 ppm for the residual catalyst.

[0017] A star-shaped viscosity index copolymer for lubricating oil prepared by the method described above, wherein the structure of the hydrogenated precursor of the star-shaped viscosity index copolymer is: (I / BS) n -C, where: I / B is an isoprene-butadiene random copolymer, S is a styrene homopolymer, C is polyvinylbenzene residues, n is the average number of arms, and n is a natural number from 2 to 15; the total average molecular weight of the star-shaped viscosity index improver is 5 × 10⁻⁶. 4 -8×10 5 The number-average molecular weight of the arms is 1×10⁻⁶. 4 -1×10 5 The molecular weight distribution is 1-1.5.

[0018] In the hydrogenated precursor of the star-shaped viscosity index copolymer, the I / B block accounts for 75-95% of the total monomer mass, and the S block accounts for 5-25% of the total monomer mass; wherein, in the I / B block, monomer I accounts for 50-70%, and monomer B accounts for 30-50%; 1,2-B accounts for 5-80% of the B mass in the I / B block, and 3,4-I accounts for 5-80% of the I mass in the I / B block.

[0019] The present invention has the following advantages:

[0020] This invention provides an in-situ prepared viscosity index improver in which isoprene and butadiene exist in a random copolymerization within the polymer segment, reducing the long-chain content of hydrogenated polyethylene and improving low-temperature performance. Styrene exists in a homopolymerization near the core, with polystyrene existing as short-chain segments, which improves coupling efficiency without significantly increasing polymer rigidity. The resulting viscosity index improver exhibits controllable molecular weight and microstructure, narrow molecular weight distribution, superior thickening ability, excellent shear stability, extremely high viscosity index, and excellent oxidation resistance, meeting the performance requirements of viscosity index improvers in various applications. This star-shaped hydrogenated SIBR-type viscosity index improver is polymerized, coupled, and hydrogenated in base oil, with the hydrogenation catalyst removed using a dry process. This process ensures that the water and impurity content of the resulting viscosity index improver concentrate meets the standards for general viscosity index improver concentrates. This process eliminates steps such as solvent flash evaporation, gel coagulation, solvent recovery, product drying, and dissolution of the dry gel in the base oil, simplifying the process, facilitating production, and effectively improving efficiency and reducing costs. Attached Figure Description

[0021] Figure 1 The dry adhesive in Example 1 of this invention 13 C10 NMR spectrum. Detailed Implementation

[0022] The present invention will be further explained below with reference to the embodiments. The solvent used in the embodiments is a Group II hydrotreated base oil with a viscosity of 2 cSt from CNOOC.

[0023] Example 1

[0024] In a 500 mL glass reaction flask equipped with an electromagnetic stirrer, 180 g of base oil with a viscosity of 2 cst, 12 g of isoprene (Ip), 6 g of butadiene (Bd), and 0.7 mL of tetrahydrofuran (THF) as a structure modifier were added. The mixture was heated to 70 °C, and n-butyllithium (n-BuLi) was added as an initiator to carry out polymerization. The amount of Li added was 1.43 × 10⁻⁶. -3 At a polymerization rate of mol / 100g, after 90 minutes, the conversion rates of Ip and Bd monomers exceeded 95%, yielding a random copolymer block I / B. Then, 2g of styrene (St) monomer was added, and the reaction continued at the same temperature (70℃) for another 90 minutes until the conversion rate of St monomer exceeded 95%, yielding a homopolymer block PS. Next, divinylbenzene (DVB) was added at 50℃ for a coupling reaction, with a DVB:Li molar ratio of 6:1, and the reaction was carried out for 120 minutes. The coupling reaction was terminated by adding isopropanol (the molar ratio of isopropanol to alkyllithium was 1:1), yielding a star-shaped isoprene / butadiene-styrene terpolymer (I / BS). n-C, where I / B is a random copolymer, S is a homopolymer, and the number-average molecular weight of the I / B blocks is 6.3 × 10⁻⁶. 4 The number-average molecular weight of the S-block is 0.7 × 10⁻⁶. 4 The number-average molecular weight of polymer arm I / B–S is 7.0 × 10⁻⁶. 4 The average number of arms is 7.0.

[0025] A hydrogenation catalyst was added to the obtained star-shaped polymer solution to be hydrogenated. After stirring evenly, hydrogen gas was introduced to carry out the hydrogenation reaction. The main catalyst of the hydrogenation reaction was nickel naphthenate, and the co-catalyst was triisobutylaluminum. The molar ratio of the co-catalyst (calculated as aluminum) to the main catalyst (calculated as nickel) was 4:1. The amount of hydrogenation catalyst used was 2 mg nickel / 100 g dry polymer. The reaction temperature was 60 °C, the reaction pressure was 3 MPa, and the reaction time was 2 hours, resulting in a hydrogenated star-shaped polymer. Solid sebacic acid was added and stirred, forming a precipitate with the catalyst. The precipitate was separated by a high-speed centrifuge at 10,000 rpm for 30 minutes to remove the solid precipitate and meet the impurity removal standard, yielding a concentrated viscosity index improver solution. The hydrogenation reaction conditions ensured that the degree of hydrogenation of the Ip and Bd units in the star-shaped hydrogenated polymer was greater than 98%, and the degree of hydrogenation of the St unit was less than 2%.

[0026] To further verify that the copolymer block I / B in the concentrate of the above examples is a random block, the dry gel was extracted using a Soxhlet extractor and then subjected to further processing. 13 1C NMR detection was used to calculate the sequence distribution of unary, binary, and ternary structures (see [reference]). Figure 1 ),Depend on Figure 1 Hydrogenation of unit I yields ethylene (e) and propylene (p) units, while hydrogenation of unit B yields ethylene (e) and butene (b) units. (Based on carbon NMR spectroscopy) 13 C10 NMR calculations yielded a unary ratio of e:p = 62:38, a binary ratio of ee:ep:pp = 23:77:0, and a ternary ratio of eee:eep:pep:epe:ppe:ppp = 17:18:30:35:0:0. Based on the distribution of the e and p microstructures, it can be concluded that the I and B monomer units exhibit a random distribution after polymerization.

[0027] Example 2

[0028] The difference from Example 1 is that:

[0029] In a 1000mL glass reaction flask equipped with an electromagnetic stirrer, 450g of base oil with a viscosity of 2cst, 32g of Ip, 13g of Bd, and 0.4ml of THF were added. The mixture was heated to 90℃, and initiator n-BuLi was added to initiate polymerization. The amount of n-BuLi added was 0.72 × 10⁻⁶. -3At 100g / mol, after 90 minutes of polymerization, the conversion rates of Ip and Bd monomers exceeded 95%, yielding a random copolymer block I / B. Then, 2g of St monomer was added, and the reaction continued at the same temperature (90℃) for another 90 minutes until the St monomer conversion exceeded 95%, yielding a homopolymer block PS. Next, divinylbenzene (DVB) was added at 50℃ for a coupling reaction, with a DVB:Li molar ratio of 6:1, and the reaction was carried out for 120 minutes. The coupling reaction was terminated by adding isopropanol (the molar ratio of isopropanol to alkyllithium was 1:1), yielding a star-shaped isoprene / butadiene-styrene terpolymer (I / BS). n -C, where I / B is a random copolymer, S is a homopolymer, and the number-average molecular weight of the I / B blocks is 12.6 × 10⁻⁶. 4 The number-average molecular weight of the S-block is 1.4 × 10⁻⁶. 4 The number-average molecular weight of polymer arm I / B–S is 14.0 × 10⁻⁶. 4 The average number of arms is 5.3. In this embodiment, the same hydrogenation method as in Example 1 is used to obtain a saturated star-shaped polymer concentrate, namely a star-shaped viscosity index improver concentrate.

[0030] Example 3

[0031] In a 500 mL glass reaction flask equipped with an electromagnetic stirrer, 180 g of base oil with a viscosity of 2 cst, 12 g of Ip, 6 g of Bd, and 0.7 mL of THF were added. The mixture was heated to 90 °C, and initiator n-BuLi was added to initiate polymerization. The amount of n-BuLi added was 1.43 × 10⁻⁶. -3 At 100g / mol, after 70 minutes of polymerization, the conversion rates of Ip and Bd monomers exceeded 95%, yielding a random copolymer block I / B. Then, 2g of St monomer was added, and the reaction continued at the same temperature (90℃) for another 90 minutes until the St monomer conversion exceeded 95%, yielding a homopolymer block PS. Next, divinylbenzene (DVB) was added at 50℃ for a coupling reaction, with a DVB:Li molar ratio of 8:1, and the reaction was carried out for 120 minutes. The coupling reaction was terminated by adding isopropanol (the molar ratio of isopropanol to alkyllithium was 1:1), yielding a star-shaped isoprene / butadiene-styrene terpolymer (I / BS). n -C, where I / B is a random copolymer, S is a homopolymer, and the number-average molecular weight of the I / B blocks is 6.2 × 10⁻⁶. 4 The number-average molecular weight of the S-block is 0.9 × 10⁻⁶. 4 The number-average molecular weight of polymer arm I / B–S is 7.1 × 10⁻⁶. 4 The average number of arms is 8.1. In this embodiment, the same hydrogenation method as in Example 1 is used to obtain a saturated star-shaped polymer concentrate, namely a star-shaped viscosity index improver concentrate.

[0032] Example 4

[0033] In a 1000mL glass reaction flask equipped with an electromagnetic stirrer, 450g of base oil with a viscosity of 2cst, 28g of Ip, 17g of Bd, and 0.7ml of THF were added. The mixture was heated to 50℃, and initiator n-BuLi was added to initiate polymerization. The amount of n-BuLi added was 1.43 × 10⁻⁶. -3 At 100g / mol, after 90 minutes of polymerization, the conversion rates of Ip and Bd monomers exceeded 95%, yielding a random copolymer block I / B. Then, 2g of St monomer was added, and the reaction continued at the same temperature (50℃) for another 90 minutes until the St monomer conversion exceeded 95%, yielding a homopolymer block PS. Next, divinylbenzene (DVB) was added at 50℃ for a coupling reaction, with a DVB:Li molar ratio of 10:1, and the reaction was carried out for 120 minutes. The coupling reaction was terminated by adding isopropanol (the molar ratio of isopropanol to alkyllithium was 1:1), yielding a star-shaped isoprene / butadiene-styrene terpolymer (I / BS). n -C, where I / B is a random copolymer, S is a homopolymer, and the number-average molecular weight of the I / B blocks is 6.1 × 10⁻⁶. 4 The number-average molecular weight of the S-block is 0.8 × 10⁻⁶. 4 The number-average molecular weight of polymer arm I / B–S is 6.9 × 10⁻⁶. 4 The average number of arms is 8.7. In this embodiment, the same hydrogenation method as in Example 1 is used to obtain a saturated star-shaped polymer concentrate, namely a star-shaped viscosity index improver concentrate.

[0034] Example 5

[0035] In a 1000mL glass reaction flask equipped with an electromagnetic stirrer, 450g of base oil with a viscosity of 2cst, 28g of Ip, 17g of Bd, and 0.7ml of THF were added. The mixture was heated to 50℃, and initiator n-BuLi was added to initiate polymerization. The amount of n-BuLi added was 1.43 × 10⁻⁶. -3 At 100g / mol, after 90 minutes of polymerization, the conversion rates of Ip and Bd monomers exceeded 95%, yielding a random copolymer block I / B. Then, 2g of St monomer was added, and the reaction continued at the same temperature (50℃) for another 90 minutes until the St monomer conversion exceeded 95%, yielding a homopolymer block PS. Next, divinylbenzene (DVB) was added at 50℃ for a coupling reaction, with a DVB:Li molar ratio of 12:1, and the reaction was carried out for 120 minutes. The coupling reaction was terminated by adding isopropanol (the molar ratio of isopropanol to alkyllithium was 1:1), yielding a star-shaped isoprene / butadiene-styrene terpolymer (I / BS). n-C, where I / B is a random copolymer, S is a homopolymer, and the number-average molecular weight of the I / B blocks is 6.2 × 10⁻⁶. 4 The number-average molecular weight of the S-block is 0.7 × 10⁻⁶. 4 The number-average molecular weight of polymer arm I / B–S is 6.9 × 10⁻⁶. 4 The average number of arms is 9.1. In this embodiment, the same hydrogenation method as in Example 1 is used to obtain a saturated star-shaped polymer concentrate, namely a star-shaped viscosity index improver concentrate.

[0036] The application performance of the products obtained in the above embodiments was determined:

[0037] The residual aluminum-nickel content in the products obtained in Examples 1-5 and the concentrated viscosity index improver SV261 (Comparative Example 1) was tested using the Chinese Environmental Protection Standard HJ700-2014. The thickening capacity, viscosity index increment, shear stability, and low-temperature dynamic viscosity of Examples 1-5 and Comparative Example 1 after the addition of 150N base oil were tested using the industry standard SH / T0622-2007. All measurements were performed according to GB / T265 "Determination of Kinematic Viscosity and Calculation of Dynamic Viscosity of Petroleum Products," measuring the kinematic viscosity and viscosity index of the oil samples at 100℃. The shear stability test was conducted using SH / T0103-2007 "Determination of Shear Stability of Polymer-Containing Oils - Diesel Nozzle Method." The main method involves the degradation of polymer molecules when polymer-containing oil passes through a diesel nozzle at a certain shear rate. This degradation leads to a decrease in the kinematic viscosity of the sample. The mechanical shear stability of the polymer-containing oil is expressed as a percentage of viscosity loss. The smaller the viscosity change rate of the polymer-containing oil before and after shearing at the diesel nozzle, the better the shear stability of the viscosity index improver. A higher viscosity at 100℃ indicates a better thickening effect of the viscosity index improver. The apparent viscosity (CCS) of lubricating oil at low temperature (-20℃) was measured using a cold start simulator according to GB / T6538 "Test Method for Apparent Viscosity of Engine Oil". A lower CCS value indicates better low-temperature stability of the viscosity index improver. A comparison of their application performance is shown in Table 1.

[0038] Table 1 Application performance of Examples 1-5 and Comparative Example 1

[0039]

[0040] In Table 1, the products of Examples 1-5 showed better thickening ability and viscosity index increment than Comparative Example 1. Examples 1 and 3-5 also exhibited significantly better shear stability and low-temperature dynamic viscosity than Comparative Example 1. Example 2, with its larger molecular weight, showed better thickening ability than Comparative Example 1, but its shear stability and low-temperature dynamic viscosity were slightly lower. Overall, the star-shaped hydrogenated SIBR viscosity index concentrate obtained by this invention showed increased thickening ability and viscosity index increment with increasing molecular weight, while shear stability decreased. Compared with Comparative Example 1, it demonstrated superior comprehensive application performance, and the preparation process was simple and feasible, effectively reducing production costs.

[0041] It is evident that the SIBR base oil solution of this invention, after hydrogenation, is a high-performance lubricating oil viscosity index improver concentrate, exhibiting excellent thickening ability, shear stability, and low-temperature performance, thus meeting the performance requirements of lubricating oils in various applications. The preparation method is simple, convenient, and yields high output; the polymer structure and molecular weight are controllable, and the molecular weight distribution is narrow.

Claims

1. A method for in-situ preparation of a viscosity index improver concentrate in low-viscosity base oil, characterized in that: The star-shaped viscosity index improver is synthesized by polymerization, hydrogenation, and deashing in low viscosity base oil at a monomer concentration of 5wt%-15wt% to directly obtain a concentrated viscosity index improver solution. The specific preparation method is as follows: A: Isoprene and butadiene are added to base oil, and an alkyl lithium initiator is added. Polymerization is initiated at 20℃-90℃. When the conversion rate of isoprene and butadiene exceeds 95%, the reaction yields isoprene-butadiene random copolymer I / B. Styrene is then added, and the reaction continues at 20℃-90℃. When the styrene conversion rate exceeds 95%, the I / BS diblock polymer is obtained. In the preparation of I / B, the mass ratio of total monomers to 2cst base oil is 1:4-1:19; the amount of alkyl lithium added is 1×10⁻⁶. -3 -1×10 - 2 The mass ratio of I to B is 3:7-7:3, and the mass ratio of I / B to S is 98:2-90:

10. B: After obtaining the I / BS diblock polymer, a coupling agent is added to the system and reacted at 20℃-90℃. When the conversion rate of the coupling agent exceeds 95%, isopropanol is added to the system to terminate the coupling reaction, resulting in the base adhesive, namely the star-shaped block copolymer (I / BS). n -C; wherein the molar ratio of coupling agent to alkyl lithium is 3:1-20:1; and the molar ratio of isopropanol to alkyl lithium is 1:1; C: Add hydrogenation catalyst to the base oil solution of the above base adhesive, mix evenly, and pass hydrogenation through it. Carry out the hydrogenation reaction at a temperature of 40℃-90℃ and a hydrogen pressure of 1.0-6.0MPa. After the hydrogenation reaction is completed, add solid acid and hydrogen peroxide to precipitate the hydrogenation catalyst in solid form. Remove the catalyst residue by separation on a high-speed centrifuge to obtain a concentrated solution of viscosity index improver. The base oil solvent is one or two of Group I, Group II, Group III, and Group IV base oils with a viscosity of 1-5 cSt.

2. The preparation method according to claim 1, characterized in that: The alkyllithium has the molecular formula RLi, where R is a hydrocarbon group with 4-20 carbon atoms; the coupling agent is an epoxy compound or a diene compound.

3. The preparation method according to claim 1, characterized in that: The hydrogenation catalyst is a main catalyst and a co-catalyst; the main catalyst is a nickel salt; and the co-catalyst is an alkyl aluminum.

4. The preparation method according to claim 3, characterized in that: The molar ratio of the alkylaluminum to the nickel salt is 2:1 to 6:

1.

5. The preparation method according to claim 1, characterized in that: The hydrogenation reaction results in a degree of hydrogenation of greater than 95% for the unsaturated double bonds of the diene in the copolymer, less than 5% for the unsaturated bonds of the aromatic hydrocarbon, and a catalyst residue of less than 30 ppm.

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