Polyethylene-propylene-3-methyl-1-butene polymer as well as preparation method and application thereof

Abstract

The invention discloses a polyethylene-propylene-3-methyl-1-butene polymer as well as a preparation method and application thereof, and belongs to the technical field of synthetic rubber. The polyethylene-propylene-3-methyl-1-butene polymer has the following molecular structure, wherein n and m are both polymerization degrees; y is branched nodes, and the number of the branched nodes is 5-6; n / (m + n) is equal to 0.38-0.42, the hydrogenation degree is 99.5-99.8%, and the viscosity index modifier is easy to dissolve in mineral oil, high in thickening capacity, low in shear shift index (SSI) and excellent in viscosity-temperature characteristic, has a good modification effect on lubricating oil and is particularly suitable for being used as a base oil viscosity index modifier.

Description

Technical Field

[0001] This invention relates to a polyethylene-propylene-3-methyl-1-butene polymer, specifically to a branched, highly hydrogenated polyisoprene polymer, a method for its preparation, and the application of the polyethylene-propylene-3-methyl-1-butene polymer as a viscosity index modifier for lubricating oils, belonging to the field of synthetic rubber technology. Background Technology

[0002] From an appearance standpoint, polyethylene-propylene-3-methyl-1-butene random copolymers can be copolymerized from ethylene, propylene, and 3-methyl-1-butene (α-isopentene). Existing polyethylene-1-butene elastomers (EBT) are copolymerized from ethylene and 1-butene, with 10-30% 1-butene in their molecular structure. The presence of 1-butene segments disrupts the regularity of the polyethylene chains in the EBT molecule, giving the copolymer elasticity. At room temperature, the crystallization of the polyethylene chains acts as physical crosslinking points, endowing the copolymer with plasticity, high tensile strength, and impact resistance. However, its disadvantages include high modulus, high hardness, and high crystallinity, and poor compatibility with mineral oils, making it unsuitable as a thickener for lubricating oils.

[0003] Chinese patent (CN104342231B) discloses a viscosity index improver for lubricating oil and its preparation method. This viscosity index improver is obtained by hydrogenation modification of a polyisoprene-b-polybutadiene-b-polystyrene triblock copolymer. The corresponding commercially available polymer SV-260 has a number-average molecular weight Mn = (32-36) × 10⁻⁶. 4 It is obtained by coupling and hydrogenation of isoprene-styrene polymer, and its number-average molecular weight before coupling is Mn = (5.5~6.5)×10. 4 Hydrogenated polymers are non-crystallizing and are mainly used as viscosity index improvers for lubricating oils. Their preparation method is proprietary technology of Kraton. These polymers have a thickening effect when added to mineral oils, but they have poor shear resistance, and the modified oils experience a significant decrease in viscosity over time, making them unsuitable for long-term use as internal combustion engine oils.

[0004] As a viscosity modifier in internal combustion engine oil, it is required to have high thickening power, low pour point, and low shear stability index. Existing ethylene-propylene copolymer (EPDM) viscosity modifiers, such as those from Jilin Petrochemical Company (J-0010, J-030, J-050), ExxonMobil (V-785, V8900, V9999), Dow Chemical (3430), Lion Chemical (Binary 5250), Eni Chemical (043, 058, 059), and Lubrizol (7067, 7065), are widely used. For example, Dow 3430 has a Mooney viscosity of 27, a vinyl content of 42%, and an ENB content of 0.8%, and is a non-crystalline polymer. Ethylene-propylene rubber used as a viscosity index modifier for lubricating oils should be selected based on the requirements of different grades of internal combustion engine oils. Currently, J-0010, J-0030, and J-0050 do not meet the industry standards for producing RHY-614 oil. For multi-grade internal combustion engine oils, adding viscosity index modifiers is essential. Polyolefin viscosity index modifiers, developed in the 1970s, remain the preferred choice. With increasingly stringent requirements for the viscosity-temperature characteristics and overall performance of lubricating oils, modifiers with good oxidation and shear stability, good oil solubility, low price, and long service life or duration have not yet emerged. Furthermore, the preparation and application of polyethylene-propylene-3-methyl-1-butene random copolymers have not been reported. Summary of the Invention

[0005] Existing viscosity index modifiers for polyolefins and styrene-dienes have shortcomings such as poor shear stability and viscosity-temperature properties, and cannot be used to prepare high-end lubricants.

[0006] The first objective of this invention is to provide a polyethylene-propylene-3-methyl-1-butene polymer that is non-crystalline, exhibits completely random chain segments, and has asymmetric branched chains. This polymer is readily soluble in mineral oil, has strong thickening ability, and also exhibits a low shear shift index (SSI) and excellent viscosity-temperature characteristics. It has a good effect on modifying lubricating oils and is particularly suitable as a base oil viscosity index modifier.

[0007] The second objective of this invention is to provide a method for preparing a polyethylene-propylene-3-methyl-1-butene polymer. This method is simple, low-cost, can be produced using existing mature equipment and processes, and is easy to industrialize.

[0008] The third objective of this invention is to provide a polyethylene-propylene-3-methyl-1-butene polymer as a lubricating oil viscosity index modifier, which, when added to lubricating oil, helps to stabilize the viscosity of the oil and extend its service life.

[0009] To achieve the above-mentioned technical objectives, the present invention provides a polyethylene-propylene-3-methyl-1-butene polymer having the following molecular structure:

[0010]

[0011] in,

[0012] Both n and m are degrees of polymerization;

[0013] Y is a branched node, with 5 to 6 branched nodes;

[0014] n / (m+n) = 0.38~0.42;

[0015] The degree of hydrogenation is 99.5%–99.8%.

[0016] In the polyethylene-propylene-3-methyl-1-butene polymer (or polyethylene-propylene-isoprene rubber, EPIR) of the present invention, m, n, and Y exhibit a disordered distribution, and its molecular structure model is as follows:

[0017]

[0018] Among them, in the molecular structure model The random chain segment is composed of m and n units. This segment is obtained by highly hydrogenating the random distribution of 3,4-polymer units and 1,4-polymer units formed by isoprene initiated by n-butyllithium. A single ethylidene and a single isopropylidene formed by hydrogenation of the 1,4-polymer unit constitute a polymer unit, and multiple chain segments can also be formed. Its degree of polymerization is m. The isoprene polymer unit is formed by isoprene through 3,4-polymerization and then hydrogenation. Its degree of polymerization is n. Single or multiple isoprene polymer units and m units exhibit a random distribution. Simultaneously, the m and n chains are connected by branching nodes "Y", thus forming an asymmetric long-chain branched EPIR molecule. The number of branching nodes Y = 5-6. Each carbon-carbon chain in the long chain contains a side methyl or side isopropyl group, or is connected to a poly(3-methyl-1-butene) polymer unit containing side isopropyl groups. The molecule contains a high proportion of side alkyl units, and the side alkyl groups in the entire molecule exhibit a random and disordered distribution. The EPIR molecule does not contain polyethylene homopolymer blocks, meaning the polymer crystallinity is zero, and it is completely amorphous. This is beneficial for the solubility of EPIR molecules in base oils and lowers the pour point of the oil. Furthermore, EPIR has a high degree of hydrogenation, which is beneficial for its high-temperature resistance and good resistance to thermal aging.

[0019] As a preferred embodiment, the number-average molecular weight M of the polyethylene-propylene-3-methyl-1-butene polymer is... n = (13~16)×10 4 Molecular weight distribution index Mw / M n =1.05~1.08.

[0020] As a preferred embodiment, the Mooney viscosity ML of the polyethylene-propylene-3-methyl-1-butene is... 100℃ It ranges from 25 to 30.

[0021] As a preferred embodiment, the iodine value of the polyethylene-propylene-3-methyl-1-butene is 1.5–2.0 g / 100 g. The trace double bonds remaining in polyethylene-propylene-3-methyl-1-butene are beneficial for maintaining the stability of the polymer's molecular weight and viscosity, and for prolonging the viscosity of the oil.

[0022] The EPIR of this invention has a narrow molecular weight distribution, a narrow molecular fraction, and fewer low molecular weight polymers, which is beneficial for thickening oils. However, if the Mooney viscosity of the polymer is too high, the molecular chain is too long, the molecular chain is easily sheared and broken, and the viscosity-temperature effect is poor.

[0023] The present invention also provides a method for preparing a polyethylene-propylene-3-methyl-1-butene polymer. The method involves heating an anionic polymerization system containing a branching agent and a structure modifier to 55-65°C, adding an initiator and isoprene to initiate polymerization, maintaining the system temperature at no more than 70°C during polymerization, and subjecting the resulting adhesive to catalytic hydrogenation after polymerization.

[0024] In the process of preparing polyisoprene polymer, since isoprene tends to 1,4-polymerize at high temperatures, the polymerization temperature should not be too high in order to obtain a high proportion of 3,4-polymer units.

[0025] As a preferred embodiment, the structure modifier is at least one selected from tetrahydrofurfuryl ethyl ether, tetrahydrofurfuryl hexyl ether, and bis(tetrahydrofurfuryl propane). The preferred structure modifier exhibits high moderating ability on the 3,4-polymerization units of isoprene at low temperatures.

[0026] As a preferred embodiment, the amount of the structure modifier is 120–160 mg / kg solvent. The amount of structure modifier affects its modulating ability; at the preferred amount of structure modifier, polyisoprene with 38–42% 3,4-polymer units can be obtained.

[0027] As a preferred embodiment, the branching agent is divinylbenzene (DVB). As a more preferred embodiment, the amount of branching agent is 1 / 1.8 to 1 / 2.0 of the molar amount of the initiator. The preferred amount of branching agent ensures that the number of branching nodes in the EPIR molecule is between 5 and 6. However, excessive DVB usage results in an excessively large polymer molecular weight, and may also lead to crosslinking and gelation.

[0028] As a preferred embodiment, the polymerization time is 30 to 35 minutes.

[0029] As a preferred embodiment, the catalytic hydrogenation reaction conditions are: hydrogen pressure of 13–16 bar, temperature of 75–110 °C, and hydrogenation time of not less than 120 min. Under these preferred hydrogenation conditions, a high hydrogenation rate can be guaranteed, and the iodine value (number of residual double bonds in the EPIR dry adhesive) of the resulting EPIR after hydrogenation is 1.5–2.0 g / 100 g adhesive, i.e., the degree of hydrogenation of IR is 99.5–99.8%. It is worth noting that the small number of double bonds in the EPIR dry adhesive molecules is beneficial for modifying and thickening the viscosity index of lubricating oils. As is well known, EPDM (ethylene propylene diene monomer) rubber, used as an existing viscosity thickener for lubricating oils, employs a small amount of the third monomer, ethylene-1,3-norvideene. The purpose is to introduce a small number of double bonds into the EPDM molecule. Without affecting its resistance to thermal aging, under the unfavorable conditions of shear degradation and molecular chain breakage leading to decreased oil viscosity in oils, the small number of double bonds in the molecule can undergo self-radical crosslinking under heat, producing micro-thermal polymerization. This is beneficial for maintaining the stability of the polymer's molecular weight and viscosity, and extending the viscosity of the oil. However, the iodine value of the EPIR in this invention should not be too high, otherwise the aging resistance of the EPIR will decrease; if the iodine value is too low (saturation too high), the viscosity-enhancing durability in oils will decrease.

[0030] As a preferred embodiment, the catalytic hydrogenation employs a nickel-based catalytic system. The catalytic hydrogenation utilizes a nickel-based catalytic system well-known to those skilled in the art for the hydrogenation of polystyrene-isoprene block copolymer (SIS) to SEPS, such as an aged cyclohexane solution of triisobutylaluminum (Al) / nickel isooctanoate (Ni), with a preferred Al / Ni (mol ratio) of 3–4 and a Ni dosage of 3.5–4.5 mmol / 100g polymer.

[0031] The present invention also provides an application of the polyethylene-propylene-3-methyl-1-butene polymer as a lubricating oil viscosity index modifier.

[0032] As a preferred embodiment, the amount of EPIR added to the lubricating oil is 1.0 to 1.5 g / 100 g lubricating oil.

[0033] As a preferred embodiment, the anionic polymerization system uses cyclohexane as a solvent, and the concentration of the solvent in the isoprene monomer is 12-14 g / 100 g.

[0034] The preferred preparation method of EPIR of the present invention is as follows:

[0035] Step 1: In a cyclohexane solution polymerization system containing a structure modifier, heat the solution to 55-65°C, then add a measured amount of n-butyllithium (NBL), followed by a measured amount of DVB isoprene monomer to carry out homopolymerization for 25-35 minutes, during which the maximum polymerization temperature is maintained below 70°C to obtain polyisoprene (IR) raw material.

[0036] Step 2: Add a certain amount of Al / Ni hydrogenation catalyst to the IR raw solution, and perform the hydrogenation reaction for no less than 120 minutes under the conditions of hydrogen pressure of 13-16 bar and temperature of 75-110℃ to obtain the EPIR solution.

[0037] Step 3: Wash the EPIR adhesive with a measured amount of citric acid aqueous solution. The amount of citric acid used is citric acid / Ni (mol ratio) = 1.5 to 1.8. Remove the residual catalyst residue in the adhesive by sedimentation. Remove the solvent from the clear and colorless adhesive by water vapor condensation. After drying and pressing, the EPIR dry adhesive is obtained.

[0038] The EPIR of this invention is directly added to mineral oil, along with antioxidants and other additives known in the lubricant industry. The mixture is stirred at 80–100°C until the mineral oil is completely dissolved. The mineral oil is a base oil known in the lubricant industry, such as commercially available 150BS. The antioxidant is at least one of antioxidants 3114 and 1076, with a preferred dosage of 0.3–0.4 g / 100 g lubricant.

[0039] Compared with existing technologies, the beneficial effects of the technical solution of this invention are as follows:

[0040] Compared to traditional ethylene propylene rubber, the EPIR molecular chain segments of this invention exhibit a random distribution, the absence of ethylene repeating polymerization units on the main chain, and the addition of short-chain alkyl groups with one or two carbon atoms in the side branches, preventing polymer crystallization and resulting in better oil solubility. The higher carbon chain side alkyl groups result in a larger internal space within the molecular chain, exhibiting resistance to high and low temperatures, better molecular flexibility, and excellent viscosity-temperature characteristics. The asymmetric long branches are easily soluble in base oils, have strong thickening ability, and also exhibit a low shear shift index (SSI). The small number of unsaturated double bonds on the main chain and side alkenyl groups are more prone to micro-crosslinking compared to the double bonds on the side chains of EPDM, which is beneficial for stabilizing the viscosity of the oil and extending its service life.

[0041] The EPIR and temperature characteristics of this invention refer to the modified oil maintaining better viscosity over a wide temperature range. At low temperatures, the EPIR modifier has relatively low solubility in oil, and the polymer chains exhibit a coiled and contracted state, having little impact on oil viscosity. However, the solubility of EPIR increases at high temperatures, and the molecular chains are fully extended under shear traction, increasing oil viscosity and thus altering the oil's lubricity. Compared to ethylene propylene rubber of the same molecular weight, EPIR benefits from the asymmetric long-chain branching and abundant side methyl and side isopropyl groups in its molecular chains, resulting in greater resistance to oil movement than the side methyl movement resistance in ethylene propylene rubber molecules, thus providing a better modification effect on the oil.

[0042] The EPIR preparation process of this invention is a homogeneous reaction, simple to prepare, and can be synthesized using existing mature processes, making it easy to control and industrialize. Attached Figure Description

[0043] Figure 1 The GPC spectrum of the polymer EPIR raw rubber in Example 1 is shown.

[0044] Figure 2 H of the polymer EPIR raw rubber in Example 1 1 -NMR.

[0045] Figure 3 H is the hydrogenated polymer EPIR of Example 1. 1 -NMR. Detailed Implementation

[0046] The following examples are intended to further illustrate and describe the content of the present invention, and do not constitute a limitation on the scope of protection of the claims of the present invention.

[0047] In the following examples, the number-average molecular weight and molecular weight distribution index of the polymers were determined using gel permeation chromatography (GPC); H2 was used. 1 - Quantitative determination of polymer microstructure using NMR spectroscopy; kinematic viscosity of modified oil (100℃ / mm) 2 / s) Tested according to GB / T265 method; flash point (°C) tested according to GB / T3536 method; thickening ability (mm) 2 / s) tested according to Q / SY4001RHY method, shear stability index tested according to Q / SY RHY3001 method, pour point (°C) tested according to GB / T3535 method, low temperature dynamic viscosity / MPa.s (-30°C) tested according to GB / T6538 method, high temperature shear viscosity (150°C, 10) 6 s -1 Test ) / MPa.s according to SH / T0618 method.

[0048] Example 1

[0049] Under nitrogen protection, 3200 mL of cyclohexane, 0.40 mL of tetrahydrofurfuryl ethyl ether (ETE), and 0.2 mL of divinylbenzene (DVB), along with 6 mL of 0.50 mol / L NBL, were added to a 5 L polymerization reactor. The mixture was heated to 55 °C with hot water, and then 400 mL of isoprene was added. Polymerization was carried out for 30 min at a nitrogen pressure of 4.0 bar, with the maximum polymerization temperature controlled to not exceed 70 °C. This yields the IR raw rubber (the GPC and H of the raw rubber IR). 1 -NMR spectra are shown below Figure 1 and Figure 2 ).

[0050] The gel solution was pressurized into a hydrogenation reactor under nitrogen gas, and 20.8 mL of a cyclohexane aging solution with a nickel content of 0.5 mol / L (triisobutylaluminum (Al) / nickel isooctanoate (Ni)) of 3.5 mol / L was added. The mixture was stirred and hydrogenated at 14 bar and 100°C for 125 min to obtain the EPIR gel solution. The product was then discharged, and 38 mL of a 0.5 mol / L citric acid aqueous solution was added to the hydrogenated gel solution. The mixture was stirred at room temperature for 30 min, allowed to stand for 60 min, and the lower green nickel-containing aqueous phase was removed. The upper colorless hydrogenated gel solution was then subjected to steam condensation at 98°C, extrusion, and drying to obtain EPIR block gel (labeled as 1). Its H... 1 -NMR spectrum see Figure 3 The characteristic behaviors of the polymers are shown in Table 1.

[0051] Example 2

[0052] The relevant process conditions in Example 1 were kept unchanged, except that during polymerization, 0.50 mL of ETE and 0.22 mL of DVB, 5.5 mL of 0.50 mol / L NBL, and the hydrogenation time were changed to 130 min.

[0053] The characteristic behavior of the polymer (calibrated as 2) was measured and is shown in Table 1.

[0054] Example 3

[0055] The relevant process conditions in Example 1 were kept unchanged, except that the modifiers used during polymerization were changed to 0.52 mL of bis(tetrahydrofurfuryl)propane, 0.20 mL of DVB, and 5.0 mL of 0.50 mol / L NBL, and the hydrogenation time was 135 min.

[0056] The measured characteristic behaviors of the polymer (calibrated as 3) are shown in Table 1.

[0057] Example 4

[0058] The relevant process conditions in Example 3 were kept unchanged, except that the amount of DVB 0.18 mL and 0.50 mol / L NBL 4.5 mL were changed during polymerization.

[0059] The characteristic behavior of the polymer (calibrated as 4) was measured and is shown in Table 1.

[0060] Example 5 (Comparative Example)

[0061] The relevant process conditions in Example 1 were kept unchanged, except that the regulator used during polymerization was changed to 0.60 mL of bis(tetrahydrofurfuryl)propane and 7.0 mL of 0.50 mol / L NBL.

[0062] The characteristic behavior of the polymer (calibrated to 5) was measured and is shown in Table 1.

[0063] Example 6

[0064] The relevant process conditions in Example 1 were kept unchanged, except that the amount of DVB 0.26 mL and 0.50 mol / L NBL 4.0 mL were changed during polymerization.

[0065] The characteristic behavior of the polymer (calibrated as 6) was measured and is shown in Table 1.

[0066] Example 7

[0067] The relevant polymerization and hydrogenation process conditions in Example 1 were kept unchanged, except that the amount of hydrogenation catalyst was changed to 25.0 mL.

[0068] The characteristic behavior of the polymer (calibrated as 7) was measured and is shown in Table 1.

[0069] Example 8

[0070] The relevant process conditions in Example 1 were kept unchanged, except that the ETE was changed to 0.30 mL, the catalyst dosage was changed to 17 mL, and the hydrogenation time was changed to 110 min during polymerization.

[0071] The characteristic behavior of the polymer (calibrated as 8) was measured and is shown in Table 1.

[0072] Table 1. Characteristic analysis of IR and EPIR of raw gum and hydrogenated gum in the examples.

[0073]

[0074] Example 9

[0075] The hydride EPIR prepared in Examples 1, 2, 3, 4, 5, 6, 7, and 8, and commercially available ethylene propylene rubber Dow 3430 were respectively added to 150BS base oil at a ratio of 1.0 g / 100 g oil, along with 0.25 g / 100 g of antioxidant 3114. The mixtures were stirred at 85°C for 2 hours, and then the oils containing the polymers were tested.

[0076] The results showed that the oil prepared from sample 6 contained a small amount of insoluble swollen gel. The physical behavior of other samples is shown in Table 2.

[0077] Table 2 Measured values ​​of different polymers as viscosity index modifiers

[0078]

[0079] As shown in Table 2, within its defined range, the EPIR of the present invention exhibits better viscosity-temperature characteristics, better shear stability, and better overall physical properties in base oil compared to EPDM 3430, and can be used as a viscosity index modifier for high-end lubricating oils.

Claims

1. A polyethylene-propylene-3-methyl-1-butene polymer, characterized in that: It has the following molecular structure: in, Both n and m are degrees of polymerization; Y is a branched node, with 5 to 6 branched nodes; n / (m+n) = 0.38~0.42; The degree of hydrogenation is 99.5%–99.8%.

2. The polyethylene-propylene-3-methyl-1-butene polymer according to claim 1, characterized in that: The number-average molecular weight M of the polyethylene-propylene-3-methyl-1-butene polymer n = (13~16)×10 4 Molecular weight distribution index M w / M n =1.05~1.

08.

3. The polyethylene-propylene-3-methyl-1-butene polymer according to claim 1, characterized in that: The Mooney viscosity (ML) of the polyethylene-propylene-3-methyl-1-butene 100℃ It ranges from 25 to 30.

4. The polyethylene-propylene-3-methyl-1-butene polymer according to claim 1, characterized in that: The iodine value of the polyethylene-propylene-3-methyl-1-butene is 1.5 to 2.0 g / 100g.

5. A method for preparing a polyethylene-propylene-3-methyl-1-butene polymer according to any one of claims 1 to 4, characterized in that: An anionic polymerization system containing a branching agent and a structure modifier is heated to 55–65°C, and an initiator and isoprene are added to initiate polymerization. During the polymerization process, the system temperature is maintained below 70°C. After polymerization, the resulting solution is subjected to catalytic hydrogenation to obtain the final product.

6. The method for preparing a polyethylene-propylene-3-methyl-1-butene polymer according to claim 5, characterized in that: The structure modifier is at least one of tetrahydrofurfuryl ethyl ether, tetrahydrofurfuryl hexyl ether, and bis(tetrahydrofurfuryl propane).

7. A method for preparing a polyethylene-propylene-3-methyl-1-butene polymer according to claim 5 or 6, characterized in that: The amount of the structure modifier is 120-160 mg / kg solvent.

8. The method for preparing a polyethylene-propylene-3-methyl-1-butene polymer according to claim 5, characterized in that: The branching agent is divinylbenzene.

9. A method for preparing a polyethylene-propylene-3-methyl-1-butene polymer according to claim 5 or 8, characterized in that: The amount of the branching agent is 1 / 1.8 to 1 / 2.0 of the molar amount of the initiator.

10. The method for preparing a polyethylene-propylene-3-methyl-1-butene polymer according to claim 5, characterized in that: The polymerization time is 30-35 minutes.

11. The method for preparing a polyethylene-propylene-3-methyl-1-butene polymer according to claim 5, characterized in that: The conditions for the catalytic hydrogenation reaction are: hydrogen pressure of 13-16 bar, temperature of 75-110°C, and hydrogenation time of not less than 120 min.

12. The method for preparing a polyethylene-propylene-3-methyl-1-butene polymer according to claim 11, characterized in that: The catalytic hydrogenation uses a nickel-based catalytic system.

13. The application of the polyethylene-propylene-3-methyl-1-butene polymer according to any one of claims 1 to 4, characterized in that: It is used as a viscosity index modifier for lubricating oils.

14. The application of the polyethylene-propylene-3-methyl-1-butene polymer according to claim 13, characterized in that: The amount of the polyethylene-propylene-3-methyl-1-butene polymer added to the lubricating oil is 1.0 to 1.5 g / 100 g lubricating oil.

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