A polyisobutylene imide dispersant and a method for preparing the same

Abstract

The application relates to the technical field of lubricating oil additives, and discloses a polyisobutylene imide dispersant and a preparation method thereof. High-activity polyisobutylene with Mn of 1700-1900 and vinylidene end group content not lower than 75% is reacted with maleic anhydride under heating to obtain a polyisobutylene-succinic anhydride intermediate (PIBSA); and then, imidization reaction is carried out with H2N-CH2-C(CH3)2-CH2-N(R 1 )(R 2 ), wherein R 1 is methyl or ethyl, and R 2 is 2-ethylhexyl or 3,5,5-trimethylhexyl. By introducing branched alkyl end groups, reducing the number of amine groups in the traditional polyene polyamine chain and increasing the proportion of imide structural units, the polyisobutylene imide dispersant obtained in the application has a boron element content not higher than 10 ppm measured by ICP-OES without boronization post-treatment by using boric acid, boric acid ester, boron oxide or a boron-containing post-treatment agent, and can balance the total base number, soot dispersibility, metal corrosion inhibition performance and fluorine rubber seal compatibility under the test conditions of the examples.

Description

Technical Field

[0001] This invention relates to the field of lubricating oil additives, specifically to a polyisobutylene imide dispersant and its preparation method. Background Technology

[0002] Polyisobutylene imide dispersants are commonly used ashless dispersants in internal combustion engine lubricating oils. These dispersants are typically prepared by reacting polyisobutylene-succinic anhydride intermediates with amine compounds. The polar imide head groups in their molecules can interact with soot, sludge, and deposit precursors, while the polyisobutylene segments can form a steric hindrance layer in the oil phase, thereby inhibiting the aggregation of soot, sludge, and deposit precursors.

[0003] Traditional polyisobutylene imide dispersants often use diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, or ethyleneamine residue as the amine source. Products obtained from these amine sources typically contain a high number of primary, secondary, or active amine hydrogens. A higher number of amine groups in the chain generally provides a higher total base number and a certain dispersing ability, but it may also result in excessively strong basicity or too many polar centers, thereby increasing the impact on fluororubber seals and metal components, ultimately affecting the lifespan of engine seals and the corrosion resistance of metal parts.

[0004] To address the aforementioned issues, existing technologies have developed routes such as boronized polyisobutylene imide, post-treated polyisobutylene imide, and hindered amine-terminated polyisobutylene imide. Boronized polyisobutylene imide typically involves treating the polyisobutylene imide with boric acid, borate esters, boron oxide, or other boron-containing post-treatment agents to reduce the influence of some active amine hydrogens and improve certain properties. However, the boronization route adds a post-treatment step and introduces boron-containing structures into the product.

[0005] The hindered amine-terminated polyisobutylene imide route has been disclosed, which involves reacting polyolefin acylators with amine compounds containing hindered amine groups to improve the sealing compatibility of fluorocarbon elastomers. Related technologies also include specific methods such as the reaction of polyisobutylene-succinic anhydride intermediates with N,N,2,2-tetramethyl-1,3-propanediamine and the reaction of polyisobutylene-succinic anhydride intermediates with N,N-bis(2-ethylhexyl)-1,2-ethylenediamine.

[0006] Furthermore, routes for the reaction of amine sources containing tertiary amine groups with polyisobutylene-succinic anhydride intermediates have also been disclosed. For example, related technologies have listed amine sources such as N,N-dimethyl-1,3-propanediamine, N,N-diethyl-1,3-propanediamine, N,N-dimethylethylenediamine, N,N-diethylethylenediamine, and N,N-dibutylethylenediamine. However, existing tertiary amine-type or non-boronized polyisobutylene imide schemes typically only adjust the type of amine source or the post-processing method, without simultaneously addressing the matching relationship between the polyisobutylene segment range, the steric hindrance of the linker arms, the asymmetric branching structure of the tertiary amine end groups, the control of the number of amine groups in the chain, and the proportion of the target imide structural units.

[0007] The existing technology still needs to further develop a polyisobutylene imide dispersant with a specific structure, so that it can reduce the number of amine groups in the chain, reduce the source of active amine hydrogen, improve the selectivity of imidization and simplify the preparation steps, while taking into account the total base number, soot dispersibility, oil solubility, metal corrosion inhibition and fluororubber sealing compatibility.

[0008] In particular, there is a need for a technical solution that, based on the polyisobutylene-succinic anhydride intermediate formed from highly reactive polyisobutylene, simultaneously limits the steric hindrance of the linker arm, the asymmetric branching structure of the tertiary amine end group, and the structural proportion of the main product, so as to distinguish it from the ordinary dimethylaminopropylamine type structure, the dialkyl tertiary amine structure, and the known hindered amine-terminated succinimide structure. Summary of the Invention

[0009] The purpose of this invention is to provide a polyisobutylene imide dispersant and its preparation method, in order to solve the problems of existing polyene polyamine type polyisobutylene imide dispersants having a large source of active amine hydrogen, high risks of metal corrosion and fluororubber seal compatibility, and the need for additional boronizing post-treatment for existing boronized polyisobutylene imides.

[0010] Another objective of this invention is to provide a polyisobutylene imide dispersant that achieves a better balance between base value, dispersion performance, oil solubility, metal corrosion inhibition, and sealing compatibility by introducing a CH2-C(CH3)2-CH2 linker between the imide nitrogen and the tertiary amine nitrogen, and introducing a small and a large asymmetric aliphatic substituent on the tertiary amine nitrogen, while reducing the use of multiple amine groups in traditional polyene polyamine chains.

[0011] To achieve the above objectives, the present invention provides the following technical solution.

[0012] This invention provides a method for preparing a polyisobutylene imide dispersant, comprising the following steps.

[0013] Step (1) reacts highly active polyisobutylene with Mn of 1700-1900 and end vinylidene content of not less than 75% with maleic anhydride under heating conditions to obtain PIBSA intermediate.

[0014] In the above process, highly reactive polyisobutylene and maleic anhydride form a polyisobutylene-succinic anhydride intermediate under heating conditions. The key improvement lies in the subsequent use of a specific formula I aliphatic tertiary amine primary amine, and obtaining a polyisobutylene imide dispersant with a specific structure by controlling the branched alkyl end group, gem-dimethyl linker, the number of amine groups in the low chain, and the selectivity of imidization.

[0015] Step (2) provides an aliphatic tertiary amine primary amine as shown in Formula I: H2N-CH2-C(CH3)2-CH2-N(R 1 (R) 2 Formula I; Among them, R 1 It is methyl or ethyl, R 2 It is 2-ethylhexyl or 3,5,5-trimethylhexyl, and the aliphatic tertiary amine primary amine of Formula I, except for one primary amine reaction site and one tertiary amine nitrogen, does not contain the primary or secondary amine groups commonly found in traditional polyene polyamine chains.

[0016] Step (3) involves imidizing the PIBSA obtained in step (1) with the aliphatic tertiary amine primary amine obtained in step (2) to obtain a polyisobutylene imide reaction product, and then subjecting the polyisobutylene imide reaction product to depressurization removal treatment to obtain the polyisobutylene imide dispersant.

[0017] In the above process, the primary amine group of the aliphatic tertiary amine undergoes an imidization reaction with the anhydride group of PIBSA to form a compound containing PIB-SI-N-CH2-C(CH3)2-CH2-N(R) 1 (R) 2 Polyisobutylene imide with a structural unit. In R 1 Methyl, R 2 In a preferred embodiment of 2-ethylhexyl, a polyisobutylene imide containing a PIB-SI-N-CH2-C(CH3)2-CH2-N(CH3)(2-ethylhexyl) structural unit is formed.

[0018] This invention utilizes an aliphatic tertiary amine primary amine as shown in Formula I, introducing branched alkyl end groups to reduce the number of amine groups in the chain and improve the target selectivity of the imidization reaction. Therefore, the resulting polyisobutylene imide dispersant achieves excellent overall performance without the need for boronizing post-treatment. "Without boronizing post-treatment" means that after the formation of the polyisobutylene imide reaction product, no further boronizing treatment with boric acid, borate esters, boron oxide, or boron-containing post-treatment agents is performed. The resulting product, as measured by ICP-OES, has a boron content not exceeding 10 ppm.

[0019] In this invention, the preparation method does not include the step of borizing the polyisobutylene imide reaction product with boric acid, borate ester, boron oxide or a boron-containing post-treatment agent.

[0020] Preferably, the Mn of the highly reactive polyisobutylene is 1700-1900, and the content of terminal vinylidenes is not less than 75%. The molar ratio of highly reactive polyisobutylene to maleic anhydride is preferably 1:(1.02-1.20), more preferably 1:(1.05-1.15).

[0021] Preferably, the reaction temperature in step (1) is 190℃~220℃, and the reaction time is 4h~8h. After the reaction, unreacted maleic anhydride is removed at 160℃~190℃ and -0.08MPa~-0.098MPa to obtain PIBSA. The residual maleic anhydride content of the obtained PIBSA is preferably not higher than 0.5wt%.

[0022] Preferably, the GC area normalized purity of the aliphatic tertiary amine primary amine shown in Formula I is not less than 95%, and the total content of dialkylation byproducts and unprotected byproducts is not more than 3 wt%.

[0023] Preferably, the aliphatic tertiary amine primary amine of Formula I is prepared via a single-protection route. Specifically, firstly, one primary amino group of 2,2-dimethyl-1,3-propanediamine is protected to obtain a monoprotected diamine; then, the unprotected primary amino group of the monoprotected diamine is subjected to a reductive amination reaction with a branched aliphatic aldehyde to obtain a branched alkyl secondary amine intermediate; subsequently, according to R... 1 The branched alkyl secondary amine intermediate is subjected to N-alkylation treatment of the type of R, wherein, when R 1 When R is methyl, N-methylation is performed using formaldehyde and formic acid; when R 1 When the ethyl group is present, N-ethylation is performed using acetaldehyde in the presence of hydrogen and a hydrogenation catalyst; finally, the protecting group is removed to obtain an aliphatic tertiary amine-type primary amine with one end being a primary amine and the other end being an asymmetric tertiary amine. This route is beneficial for reducing disubstituted diamine byproducts and improving the structural certainty of compounds of formula I.

[0024] Preferably, the monoprotected diamine intermediate is purified by at least one of the following methods: vacuum distillation, recrystallization, column chromatography, or preparative chromatography, with a GC area normalized purity of not less than 95%. Intermediates obtained from the reductive amination, N-alkylation, and deprotection steps can be purified by GC-MS or... 1 The structure was confirmed or characterized by H NMR; the total content of dialkylation byproducts and unprotected byproducts in the final formula I aliphatic tertiary amine primary amine was not higher than 3 wt%.

[0025] In the above process, 2,2-dimethyl-1,3-propanediamine provides a CH2-C(CH3)2-CH2 linker, and the branched aliphatic aldehyde introduces a branched aliphatic alkyl group R. 2 N-alkylation is used to introduce R 1 Substituents. The resulting aliphatic tertiary amine primary amine retains the primary amine reaction site at one end, while forming an R group at the other end. 1 and R 2 Substituted asymmetric tertiary amine head group. In R 1 Methyl, R 2 In a preferred embodiment of 2-ethylhexyl, 2-ethylhexanal is introduced to form 2-ethylhexyl, and formaldehyde and formic acid are used to convert the secondary amine end into a methyl-substituted tertiary amine end. Compared with polyene polyamines such as diethylenetriamine, triethylenetetramine, and tetraethylenepentamine, Formula I amines significantly reduce the number of amine groups in the chain, avoiding excessive alkalinity and decreased sealability due to excessive amine groups.

[0026] Preferably, the aliphatic tertiary amine primary amine represented by Formula I is N-(3-amino-2,2-dimethylpropyl)-N-methyl-2-ethylhexylamine.

[0027] Preferably, in step (3), the molar ratio of PIBSA to aliphatic tertiary amine primary amine is 1:(0.95–1.05). This limitation helps to reduce unreacted anhydrides, unreacted amines, and non-target ammonium acid structures, thereby increasing the proportion of the structural unit shown in Formula II in the final product.

[0028] Preferably, the imidization reaction is carried out at 130℃~170℃ for 2h~6h; after the imidization reaction is completed, the solvent, unreacted amine and low-boiling substances are removed at 150℃~180℃ and -0.08MPa~-0.098MPa.

[0029] Preferably, the imidization reaction in step (3) is carried out using a C9 aromatic solvent, a polyalphaolefin base oil, a mineral base oil, or a combination thereof. The solvent or diluent oil can maintain the liquid phase at the reaction temperature and remove the reaction water with the help of a water separator. When toluene is used as the initial diluent, toluene is removed under normal or reduced pressure after the amine is added, and then the temperature is raised to 145°C to 155°C to carry out the imidization dehydration reaction.

[0030] The present invention also provides a polyisobutylene imide dispersant, wherein the polyisobutylene imide dispersant comprises the structural unit shown in Formula II: PIB-SI-N-CH2-C(CH3)2-CH2-N(R 1 (R) 2 Formula II; Wherein, PIB represents polyisobutylene, SI represents the ring skeleton of the polyisobutylene-succinimide ring excluding the imide nitrogen, N in Formula II represents the imide nitrogen of the succinimide ring, and SI and N in Formula II together constitute the polyisobutylene-succinimide ring; R 1 It is methyl or ethyl, R 2 It is 2-ethylhexyl or 3,5,5-trimethylhexyl.

[0031] In this invention, the terminal portion of the structural unit shown in Formula II, introduced by an aliphatic tertiary amine, does not contain aromatic rings, alicyclic rings, or heterocyclic structures. Since Formula II includes a succinimide ring, the statement in this invention that it does not exclude the succinimide ring itself, but rather refers to the terminal portion introduced by an aliphatic tertiary amine that does not contain aromatic rings, alicyclic rings, or other heterocyclic structures besides the succinimide ring.

[0032] Preferably, R 1 It is methyl, R 2 The polyisobutylene group is 2-ethylhexyl, and the PIB is a polyisobutylene group derived from highly active polyisobutylene with a Mn of 1700-1900 and a terminal vinylidene content of not less than 75%. The molar ratio of polyisobutylene group to succinimide ring in the polyisobutylene imide dispersant is 1:(0.95-1.15).

[0033] More preferably, the PIB is a polyisobutylene group derived from highly active polyisobutylene with Mn of 1750-1850 and end vinylidene content of not less than 78%, and the molar ratio of polyisobutylene group to succinimide ring in the polyisobutylene imide dispersant is 1:(1.00-1.10).

[0034] More preferably, the structural unit shown in Formula II accounts for no less than 85% of the total molar percentage of the polyisobutylene-succinimide structural units, and more preferably no less than 90%.

[0035] In this invention, all polyisobutylene-succinimide structural units refer to succinimide structural units formed by imidization of polyisobutylene-succinic anhydride intermediates and amine compounds containing primary amine reaction sites, and capable of releasing corresponding amine fragments after hydrolysis; residual anhydrides, uncyclized ammonium acids, free amines, free maleic anhydrides, and polyisobutylene components that have not participated in imidization are not included in all polyisobutylene-succinimide structural units.

[0036] In this invention, the proportion of the structural unit shown in Formula II is confirmed as follows: Approximately 0.5 g of polyisobutylene imide dispersant sample is weighed and added to 10 mL of a 1.0 mol / L potassium hydroxide ethanol aqueous solution, wherein the volume ratio of ethanol to water is 9:1. An internal standard separate from the retention time of the amine fragment to be tested is added. The mixture is refluxed at 85℃±5℃ for 6 h under nitrogen protection to allow the polyisobutylene-succinimide structural unit to undergo alkaline hydrolysis and cleavage. After cooling the reaction solution, the amine fragments are extracted with methyl tert-butyl ether or n-hexane. The extract is dried with anhydrous sodium sulfate, and the content of the amine fragments corresponding to the aliphatic tertiary amine type primary amine of Formula I is determined by GC or GC-MS. A separate sample from the same batch is taken without hydrolysis treatment and the content of free Formula I amine is determined under the same extraction conditions as a blank correction value.

[0037] The proportion of the structural unit shown in Equation II is calculated using the following formula: PⅡ=[(nI,hyd / mhyd-nI,free / mfree) / (wN / (100×14.0067)-B / (56.105×1000))]×100%; where PⅡ is the molar percentage of the structural unit shown in Formula II to all polyisobutylene-succinimide structural units; nI,hyd is the number of moles of the corresponding fragment of Formula I amine measured by the internal standard method after hydrolysis, in mol; nI,free is the number of moles of free Formula I amine measured in the unhydrolyzed blank sample, in mol; mhyd is the mass of the hydrolyzed sample, in g; mfree is the mass of the unhydrolyzed blank sample, in g; wN is the total nitrogen content of the sample, in wt%; B is the amine value of the sample, in mg KOH / g. In the formula, wN / (100×14.0067)-B / (56.105×1000) represents the number of moles of non-titerable imide nitrogen per unit mass of sample, and is used as the number of moles per unit mass of all polyisobutylene-succinimide structural units.

[0038] In this invention, "no boronizing post-treatment" means that after the formation of the polyisobutylene imide reaction product, no boric acid, borate ester, boron oxide, or boron-containing post-treatment agent is added for post-treatment. This invention, by introducing branched alkyl end groups, reducing the number of amine groups in the chain, and improving imidization selectivity, can achieve comprehensive performance that meets testing requirements without relying on boronizing post-treatment.

[0039] Preferably, the boron content of the resulting polyisobutylene imide dispersant, as measured by ICP-OES, is no higher than 10 ppm. This limitation is used to characterize that the product has not undergone boronizing treatment with a boron-containing post-treatment agent, rather than to exclude unavoidable trace boron background in the raw materials or testing environment.

[0040] Preferably, microwave digestion is used before ICP-OES detection. The boron standard curve range is 0.05 mg / L to 10.0 mg / L, the detection wavelength is 249.772 nm, and 249.678 nm is used as the confirmatory line. The method detection limit is 0.5 ppm based on the product, and the method quantitation limit is 1.5 ppm based on the product. If the boron detection result in the sample is lower than the quantitation limit, it should be reported as <1.5 ppm.

[0041] In this invention, the absence of polyene-polyamine structural units means that diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, or ethyleneamine residue was not used as an amine source during the preparation process, thereby reducing the number of amine groups in the polyisobutylene imide dispersant chain.

[0042] In this invention, the anhydride functionality of the polyisobutylene-succinic anhydride intermediate (PIBSA) can be determined by acid value and saponification value, and can be further characterized by infrared characteristic peaks. The aliphatic tertiary amine primary amine of Formula I can be structurally confirmed or characterized by at least one of GC, GC-MS or ¹H NMR, and the amount of imidization feed can be corrected accordingly to increase the formation ratio of the target imide structural unit and reduce the free amine and non-target ammonium acid structure.

[0043] In this invention, the molar percentage of the Formula II structural unit in all polyisobutylene-succinimide structural units is determined by quantification using hydrolysis-internal standard GC or GC-MS and correction by combining the total nitrogen content, amine value, and free amine content of the product, thereby improving the clarity and verifiability of the product structure definition.

[0044] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. This invention employs an aliphatic tertiary amine primary amine as shown in Formula I, with one end being a primary amine reaction site and the other end being an asymmetric branched tertiary amine end group. Apart from the primary amine reaction site and tertiary amine nitrogen, it does not contain the intra-chain primary or secondary amine groups found in traditional polyene polyamine chains. This structure significantly reduces the number of amine groups in the chain, lowering the excessively strong basicity and excessive sources of reactive amine hydrogens from the polyamine chain segments, while still retaining the necessary basicity contribution through the tertiary amine nitrogen. The resulting polyisobutylene imide dispersant, while maintaining appropriate total base number and soot dispersibility, can reduce the risk of metal corrosion and fluororubber seal compatibility, avoiding test failures due to excessive amine groups.

[0045] 2. This invention introduces a CH2-C(CH3)2-CH2 linker between the imide nitrogen and the tertiary amine nitrogen. The gem-dimethyl group in this linker is located in the region adjacent to the imide ring, forming a spatial shield near the polar center and reducing the direct interaction strength between the amine nitrogen and the region adjacent to the imide ring with the fluororubber seal or metal surface. Therefore, the resulting dispersant, while maintaining a certain total base number, under the test conditions of the examples, helps to reduce the volume change, hardness change, and copper-lead corrosion tendency of fluororubber.

[0046] 3. In this invention, the tertiary amine end group employs an asymmetric substitution structure consisting of methyl or ethyl groups and branched aliphatic alkyl groups, preferably methyl and 2-ethylhexyl. The methyl substituent helps retain the basic contribution of the tertiary amine nitrogen, while the 2-ethylhexyl substituent helps improve oil solubility and forms a hydrophobic steric hindrance around the tertiary amine nitrogen. Compared to a conventional dimethyl tertiary amine head group, this invention improves the hydrophobic steric hindrance of the end group; compared to a doubly branched tertiary amine head group, this invention avoids excessive shielding of the polar center, thus facilitating a balance between dispersion performance and sealing compatibility.

[0047] 4. This invention further defines the Mn range of highly active polyisobutylene, the content of terminal vinylidene groups, the ratio of polyisobutylene groups to succinimide rings, and the proportion of structural units of Formula II, so as to form a stable match between the PIBSA intermediate, the Formula I amine source, and the final polyisobutylene imide structure, increase the proportion of target imide structural units, and reduce free amine, residual anhydride, and non-target ammonium acid structures, so that the product structure corresponds to the data of the examples, avoiding generalization based solely on non-borated or tertiary amine types.

[0048] 5. This invention eliminates the need for boric acid, borate esters, boron oxide, or boron-containing post-treatment agents. Instead of relying on boric treatment to improve performance, this invention achieves the target structure by introducing branched alkyl end groups, reducing the number of amine groups in the chain, and controlling the selectivity of imide formation. Therefore, this invention simplifies experimental and production steps and provides an alternative improvement to traditional polyene-polyamine polyisobutylene imides and boronized polyisobutylene imides without introducing boric post-treatment. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a process flow diagram of the preparation process of the polyisobutylene imide dispersant of the present invention; Figure 2This is a comparison chart of lead increment in high-temperature metal corrosion of the polyisobutylene imide dispersant of the present invention; Figure 3 This is a comparison diagram of the fluororubber sealing compatibility of the polyisobutylene imide dispersant of the present invention; Figure 4 This is a comparison chart of the soot dispersion index of the polyisobutylene imide dispersant of the present invention. Figure 5 This is a graph showing the percentage of Formula II structural units and the free amine content of the polyisobutylene imide dispersant of the present invention. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] The following examples are provided to further illustrate the present invention, but should not be construed as limiting the scope of protection of the present invention. Unless otherwise stated, the parts, percentages, and proportions in the examples are all in terms of mass or moles.

[0053] Unless otherwise stated, the feed mass of each chemical in the examples is calculated based on the pure product; if industrial grade or solution-type raw materials are used, the feed mass should be calculated based on their actual content. Highly reactive polyisobutylene is a polymer raw material, and its feed mass is calculated based on the number average molecular weight; the amount of PIBSA used in the reaction with amine compounds is preferably corrected according to the anhydride functionality of PIBSA.

[0054] In this invention, the Mn content of polyisobutylene is determined by gel permeation chromatography and calibrated using a polystyrene standard sample. The content of terminal vinyl groups can be determined using... 1 ¹H NMR determination can also be based on test reports issued by suppliers of highly reactive polyisobutylene raw materials. The anhydride functionality of PIBSA can be determined by saponification value and acid value, and can be further characterized by the carbonyl absorption peak of the anhydride in FTIR. The degree of imidization of polyisobutylene imide dispersants can be further characterized by total nitrogen content, amine value, residual acid value, and the characteristic absorption peak of the imide carbonyl group in FTIR. The boron content in polyisobutylene imide dispersants is determined using ICP-OES.

[0055] In the following examples, the anhydride functionality of PIBSA was calculated based on acid value and saponification value, and could be combined with approximately 1780 cm⁻¹ in FTIR. -1 Approximately 1860cm -1The carbonyl absorption peak of the anhydride was used for auxiliary confirmation. The anhydride functionality measured for each batch of intermediates was used to correct for the amount of aliphatic tertiary amine primary amine fed; the residual maleic anhydride content was preferably no more than 0.5 wt%. The obtained polyisobutylene imide dispersant could be determined by the imide carbonyl absorption peak in FTIR, total nitrogen content, amine value, and... 1 H NMR was used for auxiliary characterization.

[0056] The proportion of Formula II structural units in the obtained polyisobutylene imide dispersant was quantitatively confirmed. Specifically, approximately 0.5 g of the polyisobutylene imide dispersant sample was weighed and added to 10 mL of a 1.0 mol / L potassium hydroxide ethanol aqueous solution, with an ethanol-to-water volume ratio of 9:1. An internal standard separate from the retention time of the amine fragments to be tested was added. The mixture was refluxed at 85℃±5℃ for 6 h under nitrogen protection to allow alkaline hydrolysis and cleavage of the polyisobutylene-succinimide structural units. After cooling the reaction solution, the amine fragments were extracted with methyl tert-butyl ether or n-hexane. The extract was dried with anhydrous sodium sulfate, and the content of amine fragments corresponding to the aliphatic tertiary amine type primary amine of Formula I was determined by GC or GC-MS. A separate sample from the same batch was taken without hydrolysis treatment and the content of free Formula I amine was determined under the same extraction conditions as a blank correction value. The molar percentage of the structural unit shown in Formula II among all polyisobutylene-succinimide structural units was determined according to the aforementioned PII calculation formula.

[0057] The obtained product was subjected to boron element detection. Microwave digestion was performed before ICP-OES detection. The boron element standard curve range was 0.05 mg / L to 10.0 mg / L. The detection wavelength was 249.772 nm, and 249.678 nm was used as the confirmatory spectral line. The method detection limit was 0.5 ppm based on the product, and the method quantitation limit was 1.5 ppm based on the product.

[0058] Example 1: Preparation of R in this example 1 Methyl, R 2 It is a polyisobutylene imide dispersant with 2-ethylhexyl and a Mn of 1800 for PIB.

[0059] Step (1) Add 1800g of highly active polyisobutylene with Mn of 1800 and end group vinylidene content of 80% and 107.9g of maleic anhydride to the reaction vessel. Under nitrogen protection, heat to 205℃ and react for 6h. After the reaction is completed, remove unreacted maleic anhydride under reduced pressure at 180℃ and -0.09MPa. Filter to obtain polyisobutylene-succinic anhydride intermediate A-1800.

[0060] The acid value of intermediate A-1800 is 58.6 mg KOH / g, the saponification value is 59.3 mg KOH / g, and the anhydride functionality calculated based on the saponification value is 0.528 mmol / g. In step (3), the amount of form I amine added is calculated based on the anhydride functionality, so that the molar ratio of the anhydride functional group to the primary amine group is 1:1.00.

[0061] Step (2): 102.2 g of 2,2-dimethyl-1,3-propanediamine, 229.2 g of di-tert-butyl dicarbonate, 111.3 g of triethylamine, and approximately 510 g of dichloromethane were added to the reaction flask, and the mixture was reacted at 5 °C for 4 h to obtain a monoprotected diamine intermediate; subsequently, 134.6 g of [the substance] was added. 2-Ethylhexanol and approximately 410 g of methanol were stirred at 25 °C for 1 h, followed by the addition of approximately 3.1 g of palladium catalyst on carbon. Hydrogen gas was introduced to 1.5 MPa, and a reductive amination reaction was carried out at 45 °C for 6 h. The catalyst was removed by filtration to obtain a branched alkyl secondary amine intermediate. Then, 89.3 g of a 37% (w / w) aqueous formaldehyde solution and 55.2 g of formic acid were added, and the reaction was carried out at 80 °C for 4 h, followed by a reaction at 100 °C for 2 h to obtain a methyl tertiary amine intermediate. Finally, approximately 410 g of trifluoroacetic acid was added, and the reaction was deprotected at 25 °C for 3 h. After neutralization, extraction, drying, and solvent removal, N-(3-amino-2,2-dimethylpropyl)-N-methyl-2-ethylhexylamine was obtained.

[0062] The aforementioned monoprotected diamine intermediate, branched alkyl secondary amine intermediate, methyl tertiary amine intermediate, and the final N-(3-amino-2,2-dimethylpropyl)-N-methyl-2-ethylhexylamine can be analyzed by GC-MS or... 1 The structure was confirmed or characterized by H NMR; the GC area normalized purity of the final amine product was not less than 95%, and the total content of dialkylation byproducts and unprotected byproducts was not more than 3 wt%.

[0063] Step (3) Add the full amount of polyisobutylene-succinic anhydride intermediate A-1800 obtained in step (1) to the reaction vessel, and add about 1500g of C9 aromatic solvent, the distillation range of which is 150℃~185℃; under nitrogen protection, heat to 95℃, and add 228.4g of N-(3-amino-2,2-dimethylpropyl)-N-methyl-2-ethylhexylamine obtained in step (2) dropwise over 1h. After the dropwise addition is completed, heat to 155℃, and dehydrate using a water separator for 4h. After the reaction is completed, remove the C9 aromatic solvent under reduced pressure, and treat at 165℃ and -0.095MPa for 2h. Filter to obtain polyisobutylene imide dispersant A-1.

[0064] In this embodiment, the amount of polyisobutylene-succinic anhydride intermediate A-1800 is based on the total amount of product obtained in step (1), and the amount of aliphatic tertiary amine primary amine is calculated according to the anhydride functionality. If the anhydride functionality of polyisobutylene-succinic anhydride intermediate A-1800 deviates from the theoretical value, the amount of aliphatic tertiary amine primary amine is adjusted proportionally according to the anhydride functionality.

[0065] After hydrolysis-internal standard GC or GC-MS correction combined with total nitrogen content, amine value and free amine content, the molar percentage of the formula II structural unit in A-1 of all polyisobutylene-succinimide structural units is 92.8%, not less than 85%. The boron content of A-1, as determined by ICP-OES, is <1.5 ppm and not more than 10 ppm.

[0066] Example 2: This example prepares a polyisobutylene imide dispersant with Mn of 1750 for PIB.

[0067] Except for step (1), in which 1750g of highly active polyisobutylene with Mn of 1750 and end group vinylidene content of 78% is used, and 107.9g of maleic anhydride is used so that the feed equivalent of maleic anhydride relative to highly active polyisobutylene is about 1.10, the remaining steps are the same as in Example 1, and polyisobutylene imide dispersant A-2 is obtained.

[0068] In this embodiment, in step (3), the amount of N-(3-amino-2,2-dimethylpropyl)-N-methyl-2-ethylhexylamine is calculated based on the anhydride functionality of the obtained PIBSA.

[0069] The PIBSA obtained in this embodiment is denoted as intermediate A-1750. The acid value of intermediate A-1750 is 60.2 mg KOH / g, the saponification value is 60.8 mg KOH / g, and the anhydride functionality calculated based on the saponification value is 0.542 mmol / g. In step (3), the amount of formula I amine added is calculated based on the anhydride functionality to make the molar ratio of anhydride functional group to primary amine group 1:1.00.

[0070] This example investigates the effect of PIB's Mn value of 1750 on the structure and properties of the resulting dispersant. Compared to Example 1, the resulting dispersant has a higher content of polar head groups per unit mass, but the steric hindrance of the oil phase formed by the PIB chain segments is slightly lower.

[0071] After hydrolysis-internal standard GC or GC-MS correction combined with total nitrogen content, amine value and free amine content, the molar percentage of the formula II structural unit in A-2 among all polyisobutylene-succinimide structural units is 90.6%, not less than 85%. The boron content of A-2, as determined by ICP-OES, is <1.5 ppm, not more than 10 ppm.

[0072] Example 3: This example prepares a polyisobutylene imide dispersant with Mn of 1850 for PIB.

[0073] Except for step (1), in which 1850g of highly active polyisobutylene with Mn of 1850 and end group vinylidene content of 78% is used, and 107.9g of maleic anhydride is used so that the feed equivalent of maleic anhydride relative to highly active polyisobutylene is about 1.10, the remaining steps are the same as in Example 1, and polyisobutylene imide dispersant A-3 is obtained.

[0074] In this embodiment, the amount of N-(3-amino-2,2-dimethylpropyl)-N-methyl-2-ethylhexylamine used in step (3) is calculated based on the anhydride functionality of the obtained PIBSA.

[0075] The PIBSA obtained in this embodiment is denoted as intermediate A-1850. The acid value of intermediate A-1850 is 57.0 mg KOH / g, the saponification value is 57.6 mg KOH / g, and the anhydride functionality calculated based on the saponification value is 0.513 mmol / g. In step (3), the amount of formula I amine added is calculated based on the anhydride functionality to make the molar ratio of anhydride functional group to primary amine group 1:1.00.

[0076] This example investigates the effect of PIB Mn of 1850 on the structure and properties of the resulting dispersant. Compared to Example 1, the resulting dispersant has longer PIB oil-soluble segments, which is beneficial for enhancing steric hindrance dispersion, but its polar head group content per unit mass is slightly reduced.

[0077] After hydrolysis-internal standard GC or GC-MS correction combined with total nitrogen content, amine value and free amine content, the molar percentage of the formula II structural unit in A-3 among all polyisobutylene-succinimide structural units was 91.9%, not less than 85%. The boron content of A-3, as determined by ICP-OES, was <1.5 ppm, not more than 10 ppm.

[0078] Example 4: Preparation of R in this example 2 It is a polyisobutylene imide dispersant of 3,5,5-trimethylhexyl.

[0079] Except for replacing 134.6g of 2-ethylhexanal with 149.4g of 3,5,5-trimethylhexanal in step (2), the remaining steps are the same as in Example 1, to obtain N-(3-amino-2,2-dimethylpropyl)-N-methyl-3,5,5-trimethylhexylamine.

[0080] Subsequently, the full amount of polyisobutylene-succinic anhydride intermediate A-1800 obtained in step (1) of Example 1 was added to the reactor, along with approximately 1500g of C9 aromatic solvent, the distillation range of which was 150℃~185℃. Under nitrogen protection, the temperature was raised to 95℃, and 242.5g of N-(3-amino-2,2-dimethylpropyl)-N-methyl-3,5,5-trimethylhexylamine was added dropwise over 1 hour. After the addition was completed, the temperature was raised to 155℃, and the reaction was carried out for 4 hours using a water separator. After the reaction was completed, the C9 aromatic solvent was removed under reduced pressure, and the mixture was treated at 165℃ and -0.095MPa for 2 hours. After filtration, polyisobutylene imide dispersant A-4 was obtained.

[0081] 3,5,5-Trimethylhexyl and 2-ethylhexyl are both branched aliphatic alkyl groups, and both can form hydrophobic steric hindrance around the tertiary amine end group. From the structural unit proportions and performance test results of A-4, it can be seen that R... 2 When the methyl group is 3,5,5-trimethylhexyl, the resulting product still meets the structural and performance requirements of this invention.

[0082] After hydrolysis-internal standard GC or GC-MS correction combined with total nitrogen content, amine value and free amine content, the molar percentage of the formula II structural unit in A-4 is 88.7% of all polyisobutylene-succinimide structural units, which is not less than 85%. The boron content of A-4, as determined by ICP-OES, is <1.5 ppm and not more than 10 ppm.

[0083] Example 5: Preparation of R in this example 1 It is an ethyl polyisobutylene imide dispersant.

[0084] Except for step (2), in which 48.5g of acetaldehyde was used to replace 89.3g of 37% aqueous formaldehyde solution, and in which the branched alkyl secondary amine intermediate was N-ethylated under palladium on carbon catalyst and hydrogen conditions, replacing the formaldehyde and formic acid methylation steps, the remaining steps were the same as in Example 1, to obtain N-(3-amino-2,2-dimethylpropyl)-N-ethyl-2-ethylhexylamine.

[0085] Subsequently, the full amount of polyisobutylene-succinic anhydride intermediate A-1800 obtained in step (1) of Example 1 was added to the reactor, along with approximately 1500g of C9 aromatic solvent, the distillation range of which was 150℃~185℃. Under nitrogen protection, the temperature was raised to 95℃, and 242.5g of N-(3-amino-2,2-dimethylpropyl)-N-ethyl-2-ethylhexylamine was added dropwise over 1 hour. After the addition was complete, the temperature was raised to 155℃, and the reaction was dehydrated using a water separator for 4 hours. After the reaction was completed, the C9 aromatic solvent was removed under reduced pressure, and the mixture was treated at 165℃ and -0.095MPa for 2 hours, then filtered to obtain polyisobutylene imide dispersant A-5.

[0086] Replacing the methyl group with the ethyl group slightly increases the steric hindrance of the tertiary amine terminal group, and slightly alters the contribution of basic nitrogen per unit mass and the effect of the polar head group. Based on the structural unit proportions and performance test results of A-5, R... 1 When the ethyl group is used, the resulting product still meets the structural and performance requirements of this invention.

[0087] After hydrolysis-internal standard GC or GC-MS correction combined with total nitrogen content, amine value and free amine content, the molar percentage of the formula II structural unit in A-5 of all polyisobutylene-succinimide structural units is 87.6%, not less than 85%. The boron content of A-5, as determined by ICP-OES, is <1.5 ppm, not more than 10 ppm.

[0088] Example 6: Preparation of R in this example 1 Ethyl, R 2 It is a polyisobutylene imide dispersant of 3,5,5-trimethylhexyl.

[0089] Except for step (2), in which 149.4 g of 3,5,5-trimethylhexanal was used to replace 134.6 g of 2-ethylhexanal, and 48.5 g of acetaldehyde was used to replace 89.3 g of 37% aqueous formaldehyde solution, and the branched alkyl secondary amine intermediate was N-ethylated under palladium on carbon catalyst and hydrogen conditions, replacing the formaldehyde and formic acid methylation steps, the remaining steps were the same as in Example 1, to obtain N-(3-amino-2,2-dimethylpropyl)-N-ethyl-3,5,5-trimethylhexylamine.

[0090] The obtained N-(3-amino-2,2-dimethylpropyl)-N-ethyl-3,5,5-trimethylhexylamine was found to have an area-normalized purity of 96.4% by GC. The total content of dialkylation byproducts and unprotected byproducts was 2.1 wt%, not exceeding 3 wt%.

[0091] Subsequently, the full amount of polyisobutylene-succinic anhydride intermediate A-1800 obtained in step (1) of Example 1 was added to the reactor, along with approximately 1500g of C9 aromatic solvent, the distillation range of which was 150℃~185℃. Under nitrogen protection, the temperature was raised to 95℃, and 256.5g of N-(3-amino-2,2-dimethylpropyl)-N-ethyl-3,5,5-trimethylhexylamine was added dropwise over 1 hour. After the addition was completed, the temperature was raised to 155℃, and the reaction was dehydrated using a water separator for 4 hours. After the reaction was completed, the C9 aromatic solvent was removed under reduced pressure, and the mixture was treated at 165℃ and -0.095MPa for 2 hours, filtered, and polyisobutylene imide dispersant A-6 was obtained.

[0092] In this embodiment, the acid value of polyisobutylene-succinic anhydride intermediate A-1800 is 58.6 mg KOH / g, the saponification value is 59.3 mg KOH / g, and the anhydride functionality calculated based on the saponification value is 0.528 mmol / g; in step (3), the amount of formula I amine fed is calculated based on the anhydride functionality, so that the molar ratio of anhydride functional group to primary amine group is 1:1.00.

[0093] The total nitrogen content of A-6 is 1.29 wt%, and the amine value is 26.8 mg KOH / g.

[0094] After hydrolysis-internal standard GC or GC-MS correction combined with total nitrogen content, amine value and free amine content, the molar percentage of the formula II structural unit in A-6 among all polyisobutylene-succinimide structural units is 86.4%, not less than 85%. The boron content of A-6, as determined by ICP-OES, is <1.5 ppm, not more than 10 ppm.

[0095] The simultaneous introduction of ethyl and 3,5,5-trimethylhexyl groups further improved the steric hindrance and hydrophobicity of the tertiary amine end groups. The total base number and soot dispersion index of the resulting product were slightly lower than in Example 1, but it still maintained a low tendency for metal corrosion and good compatibility with fluororubber seals. Based on the structural unit proportions, boron content, metal corrosion, and fluororubber compatibility test results of A-6, R... 1 It is ethyl and R 2 When the methyl group is 3,5,5-trimethylhexyl, the resulting product still meets the requirements of this invention for the proportion of the target structural unit and the overall performance.

[0096] Comparative Example 1 This comparative example prepares a common N,N-dimethyl-1,3-propanediamine type polyisobutylene imide.

[0097] Except for replacing 228.4g of N-(3-amino-2,2-dimethylpropyl)-N-methyl-2-ethylhexylamine obtained in Example 1 with 102.2g of N,N-dimethyl-1,3-propanediamine in steps (2) and (3), the remaining steps are the same as in Example 1, and comparative polyisobutylene imide dispersant D-1 is obtained.

[0098] D-1 does not contain a CH2-C(CH3)2-CH2 linker arm, nor does it contain a 2-ethylhexyl-substituted branched tertiary amine head group. This comparative example is used to illustrate that common small-molecule tertiary amine sources are not equivalent to the asymmetric branched tertiary amine primary amines of the present invention.

[0099] Comparative Example 2 This comparative example prepared N,N,2,2-tetramethyl-1,3-propanediamine-type polyisobutylene imide.

[0100] Except for replacing 228.4g of N-(3-amino-2,2-dimethylpropyl)-N-methyl-2-ethylhexylamine obtained in Example 1 with 130.2g of N,N,2,2-tetramethyl-1,3-propanediamine in steps (2) and (3), the remaining steps are the same as in Example 1, and comparative polyisobutylene imide dispersant D-2 is obtained.

[0101] D-2 has a 2,2-dimethyl linker arm, but the tertiary amine head group is an N,N-dimethyl structure, and does not contain 2-ethylhexyl branched hydrophobic steric hindrance. This comparative example is used to illustrate that the steric hindrance of the linker arm alone is not equivalent to the combination of linker arm steric hindrance and asymmetric branched tertiary amine head group structure of the present invention.

[0102] Comparative Example 3 This comparative example prepared N,N-bis(2-ethylhexyl)-1,2-ethylenediamine type polyisobutylene imide.

[0103] Except for replacing 228.4g of N-(3-amino-2,2-dimethylpropyl)-N-methyl-2-ethylhexylamine obtained in Example 1 with 284.5g of N,N-bis(2-ethylhexyl)-1,2-ethylenediamine in steps (2) and (3), the remaining steps are the same as in Example 1, and comparative polyisobutylene imide dispersant D-3 is obtained.

[0104] D-3 contains a bis-2-ethylhexyl tertiary amine head group, but lacks a CH2-C(CH3)2-CH2 linker arm, and the tertiary amine end group has significant steric hindrance. This comparative example illustrates that the small-large-small asymmetric tertiary amine head group of the present invention is not an arbitrary addition of branched long alkyl groups, but rather a balance is achieved between the basicity of the tertiary amine, oil solubility, and accessibility of the polar head group.

[0105] Comparative Example 4 This comparative example prepares a traditional polyene-polyamine type polyisobutylene imide.

[0106] Except for replacing 228.4g of N-(3-amino-2,2-dimethylpropyl)-N-methyl-2-ethylhexylamine obtained in Example 1 with 189.3g of tetraethylenepentamine in steps (2) and (3), the remaining steps are the same as in Example 1, and comparative polyisobutylene imide dispersant D-4 is obtained.

[0107] D-4 contains polyene polyamine structural units, with a high proportion of primary amine, secondary amine, and active amine hydrogens in its molecule. This comparative example illustrates that while traditional polyene polyamines can provide high base values ​​and dispersing power, an excessive number of amine groups can lead to significant deterioration in metal corrosion and fluororubber seal compatibility tests.

[0108] Comparative Example 5 This comparative example prepares boronized polyene polyamine-type polyisobutylene imide.

[0109] After preparing tetraethylenepentamine-type polyisobutylene imide according to the method of Comparative Example 4, 9.3 g of boric acid was added, and the mixture was dehydrated at 150 °C for 3 h to obtain borated polyisobutylene imide dispersant D-5.

[0110] D-5 reduces the influence of some active amine hydrogens through subsequent borylation treatment, but introduces a boron-containing structure and adds a post-treatment step. This comparative example illustrates that the present invention does not rely on borylation post-treatment to improve performance, but rather achieves a balance of overall performance by introducing branched alkyl end groups, reducing the number of amine groups in the chain, and improving imide selectivity.

[0111] Performance Tests and Results: In this invention, the 0W-20 lubricating oil composition containing 5.0% by mass of active dispersant was used as the evaluation object. The base oil, detergent, antioxidant, anti-wear agent, and viscosity index improver in the composition were kept consistent, with only the dispersant in the examples or comparative examples being changed.

[0112] All performance data were measured using 0W-20 lubricating oil compositions formulated with the same base oil and additive package. Each sample was tested in parallel at least three times, and the data in the table are averages; items with a relative standard deviation exceeding 10% were retested. Except for the type of dispersant, the types and contents of base oil, detergents, antioxidants, anti-wear agents, viscosity index improvers, and defoamers remained consistent.

[0113] Total base number was determined using ASTM D2896. Fluororubber compatibility was evaluated according to ASTM D471, with testing conditions including immersion at 150°C for 168 hours, and determination of volume change, hardness change, and tensile strength retention after immersion. Copper sheet corrosion was determined using ASTM D130. High-temperature metal corrosion was determined using ASTM D6594.

[0114] Micro-coking scoring was performed as follows: 0.2g of the 0W-20 lubricating oil composition to be tested was evenly spread on the surface of a 25mm×75mm stainless steel specimen, treated at 280℃ for 60min, and after cooling, scored according to standard photographs and grayscale area ratios. 1 point indicated the most severe deposition, and 10 points indicated the least deposition. Each sample was tested in parallel three times, and the results were expressed as the average value.

[0115] The soot dispersion index was determined as follows: 2.0 wt% of standard model soot was added to an 0W-20 lubricating oil composition containing 5.0 wt% active dispersant. The mixture was sheared at 10000 r / min for 30 min at 80℃, then allowed to stand at 25℃ for 24 h and centrifuged at 3000 r / min for 10 min. The supernatant was then measured at 600 nm for absorbance (A). The absorbance (A0) of the same lubricating oil composition without soot was used as a blank, and the absorbance (Aref) of the completely dispersed sample after shearing without standing and centrifugation was used as a reference. The soot dispersion index was calculated as (A-A0) / (Aref-A0) × 100%. Each sample was tested in triplicate, and the average value was taken. The model soot used was commercial furnace black with a particle size (D50) of 45 nm. The absorbance at 600 nm was measured using a 1 cm path length cuvette. The test results are shown in Tables 1-3. Table 1 ; Table 2. Total base number and metal corrosion test results of the dispersant. ; Table 3. Results of fluororubber compatibility, micro-coking, and soot dispersion tests of the dispersant. ; From Tables 1 to 3 and Figures 1-5 The results show that Examples 1 to 6, in the same lubricating oil formulation system, all maintained a total base number of 9.68 mg KOH / g to 10.82 mg KOH / g, a copper strip corrosion grade of 1a, a ΔCu of 2.7 ppm to 4.9 ppm, a ΔPb of 7.9 ppm to 13.8 ppm, a fluororubber volume change rate of 0.39% to 1.04%, and a tensile strength retention rate of 87.6% to 93.4%. Among them, Example 1 has a PIB Mn of 1800, a CH2-C(CH3)2-CH2 linker arm, an asymmetric tertiary amine head group composed of methyl and 2-ethylhexyl, a high proportion of Formula II structural units, and a low number of amine groups in the chain, resulting in superior overall performance.

[0116] Comparative Example 1 used N,N-dimethyl-1,3-propanediamine as a common tertiary amine source. Although the total base value of D-1 was 11.18 mg KOH / g, its fluororubber volume change rate was 2.37%, ΔCu was 8.9 ppm, and ΔPb was 29.4 ppm, which were significantly inferior to those of Example 1. This result indicates that the common dimethylaminopropylamine type tertiary amine structure cannot replace the gem-dimethyl linker and asymmetric branched tertiary amine head group combination of the present invention.

[0117] Comparative Example 2 used N,N,2,2-tetramethyl-1,3-propanediamine, which has a 2,2-dimethyl linker, but the tertiary amine head group is a dimethyl structure, lacking the steric hindrance of 2-ethylhexyl branching. Its fluororubber volume change rate was 1.54%, tensile strength retention was 84.2%, and soot dispersion index was 86.3%, all lower than that of Example 1. These results indicate that simply introducing a gem-dimethyl linker is insufficient to achieve the overall performance balance of this invention.

[0118] Comparative Example 3 used N,N-bis(2-ethylhexyl)-1,2-ethylenediamine, which has a bis-2-ethylhexyl tertiary amine head group but lacks a CH2-C(CH3)2-CH2 linker. Its fluororubber volume change rate was 1.27%, its soot dispersion index was 80.7%, and its micro-coking score was 7.06, lower than that of Example 1. This result indicates that simply using a dual-major branched tertiary amine head group cannot achieve the combined performance advantages of the small-large-asymmetric tertiary amine head group and the sterically hindered linker of this invention.

[0119] Comparative Example 4 used tetraethylenepentamine as the traditional polyene polyamine amine source. Although D-4 achieved a total base number of 12.13 mg KOH / g and a soot dispersion index of 92.4%, its copper strip corrosion grade was 3b, ΔCu was 39.6 ppm, ΔPb was 184.5 ppm, the fluororubber volume change rate was 4.86%, and the tensile strength retention rate was only 61.9%. These results indicate that while polyene polyamine structural units help improve base number and dispersion performance, the large number of amine groups and the abundance of active amine hydrogen sources in the chain significantly increase the risk of metal corrosion and fluororubber compatibility.

[0120] Comparative Example 5 employed a boronizing post-treatment route. Compared to Comparative Example 4, the fluororubber volume change rate of D-5 decreased to 2.06%, and the copper sheet corrosion rating improved to 1b, but it was still inferior to the 0.46% and 1a ratings of Example 1, while its ΔPb remained at 53.2 ppm. These results demonstrate that the technical contribution of this invention is not simply the absence of boronizing, but rather the introduction of branched alkyl end groups, reduction of the number of amine groups in the chain, and improvement of imidization selectivity, enabling the polyisobutylene imide dispersant to achieve superior low corrosion and sealing compatibility without the need for boronizing post-treatment.

[0121] In summary, this invention introduces a CH2-C(CH3)2-CH2 linker and a small and a large asymmetric branched tertiary amine end group into the polyisobutylene imide dispersant by reacting a polyisobutylene-succinic anhydride intermediate formed from highly reactive polyisobutylene with a specific aliphatic tertiary amine primary amine. Furthermore, by limiting the number-average molecular weight of PIB, the imide structural ratio, the proportion of Formula II structural units, and non-boronization detection characteristics, the product structure and performance are matched. The resulting dispersant does not require post-boronization treatment and does not use polyene-polyamine amine sources. It can maintain a certain total base number and soot dispersion ability while reducing metal corrosion tendency and improving fluororubber sealing compatibility.

[0122] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. All equivalent substitutions, modifications, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a polyisobutylene imide dispersant, characterized in that, Includes the following steps: Step (1) reacts highly active polyisobutylene with Mn of 1700-1900 and end vinylidene content of not less than 75% with maleic anhydride under heating conditions to obtain polyisobutylene-succinic anhydride intermediate (PIBSA). Step (2) provides an aliphatic tertiary amine primary amine as shown in Formula I: H2N-CH2-C(CH3)2-CH2-N(R 1 (R) 2 Formula I; Among them, R 1 It is methyl or ethyl, R 2 It is 2-ethylhexyl or 3,5,5-trimethylhexyl. The aliphatic tertiary amine primary amines shown in Formula I do not contain aromatic rings, alicyclic rings, or heterocyclic structures, and the GC area normalized purity is not less than 95%. Step (3) involves imidizing the PIBSA with the aliphatic tertiary amine primary amine shown in Formula I, followed by depressurization removal treatment to obtain the polyisobutylene imide dispersant; Wherein, the polyisobutylene-succinimide structural unit formed by the aliphatic tertiary amine primary amine shown in Formula I accounts for no less than 85% of the total polyisobutylene-succinimide structural unit; the preparation method reduces the number of amine groups in the chain and increases the proportion of imidized target structural units by using the aliphatic tertiary amine primary amine shown in Formula I, so that the obtained polyisobutylene-imide dispersant does not need to be borated after treatment with boric acid, borate ester, boron oxide or boron-containing post-treatment agents, and the boron content measured by ICP-OES is no higher than 10 ppm.

2. The method for preparing the polyisobutylene imide dispersant according to claim 1, characterized in that, The Mn of the highly active polyisobutylene in step (1) is 1750-1850, the content of terminal vinylidene is not less than 78%, and the molar ratio of the highly active polyisobutylene to maleic anhydride is 1:(1.08-1.12).

3. The method for preparing the polyisobutylene imide dispersant according to claim 1 or 2, characterized in that, The reaction described in step (1) is carried out at 190℃~220℃ for 4h~8h. After the reaction, unreacted maleic anhydride is removed at 160℃~190℃ and -0.08MPa~-0.098MPa. The residual maleic anhydride content of the obtained PIBSA is not higher than 0.5wt%.

4. The method for preparing the polyisobutylene imide dispersant according to claim 1 or 2, characterized in that, The aliphatic tertiary amine primary amine shown in Formula I is prepared by the following steps: first, one primary amino group of 2,2-dimethyl-1,3-propanediamine is protected to obtain a monoprotected diamine; then, the unprotected primary amino group in the monoprotected diamine is subjected to a reductive amination reaction with a branched aliphatic aldehyde to obtain a branched alkyl secondary amine intermediate; subsequently, according to R... 1 The branched alkyl secondary amine intermediate is subjected to N-alkylation treatment of the type of R, wherein, when R 1 When R is methyl, N-methylation is performed using formaldehyde and formic acid; when R 1 When the ethyl group is used, N-ethylation is performed using acetaldehyde in the presence of hydrogen and a hydrogenation catalyst; finally, the protecting group is removed to obtain the aliphatic tertiary amine primary amine of Formula I; wherein, the GC area normalized purity of the aliphatic tertiary amine primary amine of Formula I is not less than 95%, and the total content of dialkylation byproducts and unprotected byproducts is not more than 3 wt%; the aliphatic tertiary amine primary amine of Formula I contains no primary amine group or secondary amine group in the chain except for one primary amine reaction site and one tertiary amine nitrogen.

5. The method for preparing the polyisobutylene imide dispersant according to claim 4, characterized in that, The aliphatic tertiary amine primary amine shown in Formula I is N-(3-amino-2,2-dimethylpropyl)-N-methyl-2-ethylhexylamine.

6. The method for preparing the polyisobutylene imide dispersant according to claim 5, characterized in that, In step (3), the molar ratio of the anhydride functional group in the PIBSA to the primary amine group in the aliphatic tertiary amine is 1:(0.95~1.05), the imidization reaction is carried out at 130℃~170℃ for 2h~6h, and the water generated by imidization is removed during the reaction.

7. The method for preparing the polyisobutylene imide dispersant according to claim 6, characterized in that, The vacuum removal process includes the removal of the reaction solvent, unreacted amine, and low-boiling substances. The vacuum removal process is carried out at 150℃~180℃ and -0.08MPa~-0.098MPa. The content of free I amine in the product obtained after vacuum removal process is not higher than 1.0wt%.

8. A polyisobutylene imide dispersant, characterized in that, The polyisobutylene imide dispersant comprises the structural unit shown in Formula II: PIB-SI-N-CH2-C(CH3)2-CH2-N(R 1 )(R 2 ) Formula II; Wherein, PIB represents polyisobutylene, SI represents the ring skeleton of the polyisobutylene-succinimide ring excluding the imide nitrogen, N in Formula II represents the imide nitrogen of the succinimide ring, and SI and N in Formula II together constitute the polyisobutylene-succinimide ring; R 1 It is methyl or ethyl, R 2 The polyisobutylene group is 2-ethylhexyl or 3,5,5-trimethylhexyl; and the terminal portion of the structural unit shown in Formula II, introduced by the aliphatic tertiary amine, does not contain aromatic rings, alicyclic rings, or heterocyclic structures. The PIB is a polyisobutylene group derived from highly active polyisobutylene with a Mn of 1700-1900 and a terminal vinylidene content of not less than 75%. The molar ratio of polyisobutylene group to succinimide ring in the polyisobutylene imide dispersant is 1:(0.95-1.15). The molar percentage of the structural unit shown in Formula II in all polyisobutylene-succinimide structural units is not less than 85%. The boron content of the polyisobutylene imide dispersant, as measured by ICP-OES, is not higher than 10 ppm. The molar percentage of the structural unit shown in Formula II is quantified by hydrolysis-internal standard GC or GC-MS and corrected by combining the total nitrogen content, amine value, and free amine content of the product.

9. The polyisobutylene imide dispersant according to claim 8, characterized in that, R 1 It is methyl, R 2 The PIB is 2-ethylhexyl, and is a polyisobutylene group derived from highly active polyisobutylene with Mn of 1750-1850 and end vinylidene content of not less than 78%. The molar ratio of polyisobutylene group to succinimide ring in the polyisobutylene imide dispersant is 1:(1.00-1.10), and the structural unit shown in Formula II accounts for not less than 90% of the total polyisobutylene-succinimide structural unit.

10. The polyisobutylene imide dispersant according to claim 8 or 9, characterized in that, The polyisobutylene imide dispersant does not contain polyene polyamine structural units formed from diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, or ethyleneamine residue; and the polyisobutylene imide dispersant is prepared by imidization reaction of a polyisobutylene-succinic anhydride intermediate formed from highly active polyisobutylene with an aliphatic tertiary amine primary amine of Formula I.

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