Monofunctional polyepichlorohydrin and preparation method thereof

Abstract

The embodiment of the invention provides monofunctional polyepichlorohydrin and a preparation method thereof. The method comprises the following steps: carrying out cationic ring-opening polymerization reaction on an initiator and an epichlorohydrin monomer in an inert atmosphere under the action of a PTA-IL composite catalyst to obtain a product system; and carrying out post-treatment on the product system to obtain the monofunctional polyepichlorohydrin, the PTA-IL composite catalyst is prepared from phosphotungstic acid and carboxylic acid functionalized ionic liquid; the carboxylic acid functionalized ionic liquid is prepared from 1-carboxyethyl-3-methylimidazole chlorine salt. The method is used for achieving the effects of accurately controlling the molecular weight range of the monofunctional polyepichlorohydrin, inhibiting the formation of cyclic byproducts and efficiently recycling the catalyst.

Description

Technical Field

[0001] This application relates to the field of preparation of monofunctional polyepoxychloropropane, and more particularly to a monofunctional polyepoxychloropropane and its preparation method. Background Technology

[0002] Monofunctional polyepoxychloropropane (PECH) is a core precursor for a series of high-value chemicals in the synthesis of energetic materials, and is widely used in the preparation of low-sensitivity azid plasticizers such as GAPAE. Low molecular weight (number-average molecular weight M < 1000) PECH has a decisive influence on the performance of the final azid plasticizer: 1. Viscosity and compatibility control: Low molecular weight PECH can significantly reduce the viscosity of the plasticizer, improve its compatibility with binders (such as polysulfide rubber, polyurethane, etc.), thereby improving the processing performance of propellants or launchers. 2. Functionality and reactivity: The terminal hydroxyl functionality of monofunctional PECH directly affects the efficiency of the azidation reaction and the purity of the product. The higher the functionality (closer to 1.0), the more complete the azidation reaction, and the higher the thermal stability and energy density of the product. 3. Safety requirements: Low molecular weight PECH can reduce the crystallization tendency of the plasticizer system, reduce the risk of mechanical property fluctuations during storage or use, and meet the stringent safety requirements of high-energy materials.

[0003] Currently, both industry and academia widely employ boron trifluoride diethyl ether (BF3·Et2O) as a catalyst in cationic ring-opening polymerization to synthesize PECH. However, the preparation method using boron trifluoride diethyl ether (BF3·Et2O) as a catalyst has the following problems: 1. Due to the extremely high activity of BF3·Et2O, the reaction is difficult to control precisely, resulting in a wide molecular weight distribution of the product (K>1.5), making it difficult to stably obtain the target product with Mn in the range of 700-900. 2. The cationic active center is prone to triggering a "biting-back" reaction, generating a large number of five-membered cyclic oligomers (content can reach more than 15%). These cyclic oligomers do not contain terminal hydroxyl groups and cannot participate in subsequent azidation reactions, significantly reducing the functionality of the product (<0.90). 3. Alkaline washing and multiple water washing steps generate a large amount of acidic wastewater, resulting in high treatment costs and environmental burden. 4. BF3·Et2O is difficult to completely remove from the product, and residual catalyst can cause cross-linking and degradation of the product during storage or subsequent processing, affecting the stability of the material.

[0004] Therefore, there is an urgent need to develop a synthesis method for low molecular weight monofunctional polyepoxychloropropane that combines high efficiency, high selectivity, and environmental friendliness, so as to provide key raw material support for high-performance energetic materials. Summary of the Invention

[0005] This application provides a monofunctional polyepoxychloropropane and its preparation method to achieve a green and highly selective synthesis of low molecular weight monofunctional polyepoxychloropropane (PECH).

[0006] In a first aspect, embodiments of this application provide a method for preparing monofunctional polyepoxychloropropane, comprising: carrying out a cationic ring-opening polymerization reaction of an initiator and an epichlorohydrin monomer under the action of a PTA-IL composite catalyst in an inert atmosphere to obtain a product system;

[0007] The product system was post-processed to obtain a crude product solution;

[0008] The crude product solution was extracted using a mixed solution of alcohol solvent and water to obtain the monofunctional polyepoxychloropropane.

[0009] The PTA-IL composite catalyst was prepared from phosphotungstic acid and carboxylic acid-functionalized ionic liquid.

[0010] The carboxylic acid functionalized ionic liquid includes 1-carboxyethyl-3-methylimidazolium chloride.

[0011] In one possible implementation, the method for preparing the PTA-IL composite catalyst includes:

[0012] The phosphotungstic acid was dissolved in deionized water to obtain an aqueous solution of phosphotungstic acid;

[0013] The carboxylic acid-functionalized ionic liquid was added dropwise to the aqueous phosphotungstic acid solution to obtain the reaction system;

[0014] After reacting the reaction system at 50℃-60℃ for 4-5 hours, the water in the product system was removed by vacuum distillation to obtain the PTA-IL composite catalyst.

[0015] In one possible implementation, the molar concentration of the phosphotungstic acid aqueous solution is 0.01 mol / L to 0.05 mol / L;

[0016] And / or, the molar ratio of the phosphotungstic acid to the carboxylic acid functionalized ionic liquid is 1:(1.5-2.5).

[0017] In one possible implementation, the initiator comprises a monofunctional primary alcohol with a carbon chain length of C4-C8;

[0018] And / or, the molar ratio of the initiator to the epichlorohydrin monomer is 1:(10-40).

[0019] And / or, the mass ratio of the PTA-IL composite catalyst to the epichlorohydrin monomer is (0.01-0.03):1.

[0020] In one possible implementation, the initiator includes at least one of n-butanol and n-octanol.

[0021] In one possible implementation, the reaction temperature of the cationic ring-opening polymerization reaction is 40°C-60°C;

[0022] The reaction time for the cationic ring-opening polymerization reaction is 4-8 hours.

[0023] In one possible implementation, the post-processing includes:

[0024] An ester solvent was added to the product system, and the mixture was centrifuged at 4000 rpm-5000 rpm to obtain the PTA-IL composite catalyst and the crude product solution.

[0025] And / or, after extracting the crude product solution with a mixed solution of alcohol solvent and water, the method further includes:

[0026] The extract was washed with deionized water, dried, and the ester solvent was removed to obtain the monofunctional polyepoxychloropropane.

[0027] In one possible implementation, the volume ratio of the alcohol solvent to the water in the extractant is 3:1;

[0028] And / or, the extraction is repeated 2 to 3 times.

[0029] Secondly, embodiments of this application provide a monofunctional polyepoxychloropropane prepared by the above-described preparation method, wherein the number-average molecular weight of the monofunctional polyepoxychloropropane is 700 g / mol to 900 g / mol.

[0030] And / or, the molecular weight distribution of the monofunctional polyepoxychloropropane is less than or equal to 1.35;

[0031] And / or, the monofunctional polyepoxychloropropane contains a cyclic oligomer mass fraction of less than or equal to 5%;

[0032] And / or, the functionality of the monofunctional polyepoxychloropropane is greater than or equal to 0.96.

[0033] This application provides a monofunctional polyepoxychloropropane and its preparation method. By utilizing the ion exchange reaction between phosphotungstic acid (PTA) and a carboxylic acid-functionalized ionic liquid ([HOOCEMIm]Cl), a homogeneous-heterogeneous synergistic PTA-IL composite catalyst is constructed. This not only retains the strong acidic catalytic activity of the heteropolyacid, but also achieves efficient catalyst recovery through the hydrophobicity of the ionic liquid, thereby reducing the molecular weight distribution width of the monofunctional polyepoxychloropropane. Detailed Implementation

[0034] Exemplary embodiments will be described in detail below. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0035] In the existing technology, the cationic ring-opening polymerization process for synthesizing PECH using boron trifluoride diethyl ether (BF3·Et2O) as a catalyst has technical problems such as difficulty in controlling the molecular weight of the product, high levels of cyclic byproducts, and catalyst residue.

[0036] The method for preparing low molecular weight monofunctional polyepoxychloropropane provided in this application utilizes the ion exchange reaction of phosphotungstic acid (PTA) and carboxylic acid functionalized ionic liquid ([HOOCEMIm]Cl) to construct a homogeneous-heterogeneous synergistic PTA-IL composite catalyst, thus solving the technical problems of precise control of product molecular weight, suppression of cyclic by-products, and green recovery of catalyst.

[0037] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0038] This application provides a method for preparing monofunctional polyepoxychloropropane, comprising: carrying out a cationic ring-opening polymerization reaction of an initiator and an epichlorohydrin monomer under an inert atmosphere in the presence of a PTA-IL composite catalyst to obtain a product system; and performing post-treatment on the product system to obtain monofunctional polyepoxychloropropane; wherein the PTA-IL composite catalyst is prepared from phosphotungstic acid and a carboxylic acid functionalized ionic liquid; and the carboxylic acid functionalized ionic liquid includes 1-carboxyethyl-3-methylimidazolium chloride.

[0039] The chemical formula of phosphotungstic acid is H3[PW 12 O 40 •xH2O, its core is the classic Keggin-type structure [PW 12 O 40 ] 3- A giant heteropoly anion with three negative charges, and three H⁺ ions as counterions. 1-Carboxyethyl-3-methylimidazolium chloride is a functionalized imidazolium-based ionic liquid precursor or organic salt, with its cation being [1-carboxyethyl-3-methylimidazolium]. + The structural formula is: [(CH3)N1-N3(C2H4COOH)C + [The N1 and N3 are two nitrogen atoms on the imidazole ring. The proton H in phosphotungstic acid...] + It can react with the chloride ions Cl in 1-carboxyethyl-3-methylimidazolium chloride.- Ion exchange occurs simultaneously with the positively charged [1-carboxyethyl-3-methylimidazole]. + Cations, as novel counterions, interact strongly with negatively charged [PW] ions through electrostatic interactions. 12 O 40 ] 3- Heteropolyanions combine to obtain PTA-IL composite catalysts.

[0040] When preparing monofunctional polyepoxychloropropane using the PTA-IL composite catalyst, the carboxyl group (-COOH) at the end of the organic cation or the hydroxyl group (-OH) formed by pre-esterification / derivation can act as a monofunctional initiator for polymerization. This initiation site is "anchored" to the giant phosphotungstic acid anion via covalent or ionic bonds, forming a well-defined and completely consistent "active site." This ensures that each polymer chain grows from a single starting point, forming a truly linear monofunctional polymer and ensuring that the product functionality is greater than or equal to 0.90. All polymer chains grow from this identical site, achieving synchronous initiation. Simultaneously, the giant [PW] 12 O 40 ] 3- The anion, acting as a counterion, forms a compact but bulky ion pair with the oxonium cation. This ion pair is highly stable, and its large size acts as a "protective shield," isolating the active centers from each other and effectively suppressing uncontrollable interchain transfer and termination reactions (such as chain transfer to the monomer). This allows all chains to grow at almost the same rate and extends chain lifetime, thereby enabling precise control of the molecular weight of monofunctional polyepoxychloropropanes and a molecular weight distribution of less than 1.5.

[0041] Furthermore, in the cationic polymerization of epoxy monomers, the formation of cyclic oligomers (such as dimers and trimers) mainly originates from intramolecular back-biting reactions. The ion pair environment formed by phosphotungstic acid and the ionic liquid 1-carboxyethyl-3-methylimidazolium chloride stabilizes the cations at the ends of the growing chains, making them more "living polymers" and more prone to intermolecular monomer insertion rather than intramolecular cyclization. Moreover, functionalized ionic liquids, through their large volume and special solvation effects, can form certain spatial or electronic barriers around the growing chains, which are unfavorable for the oxygen atoms at the chain ends to back-bite and attack their own cation centers, thus significantly inhibiting the formation of cyclic oligomers.

[0042] Meanwhile, the formation of cyclic oligomers consumes monomers but does not increase the chain number, and they themselves do not have terminal functional groups. Suppressing the formation of cyclic oligomers means that the vast majority of products are linear polymers, and the terminal functional groups (determined by the initial monofunctionality initiator) are retained, thus ensuring the high functionality of the product (greater than 0.95).

[0043] In some specific embodiments, the preparation method of the PTA-IL composite catalyst includes: dissolving phosphotungstic acid in deionized water to obtain an aqueous solution of phosphotungstic acid; adding a carboxylic acid functionalized ionic liquid dropwise to the aqueous solution of phosphotungstic acid to obtain a reaction system; reacting the reaction system at 50℃-60℃ for 4h-5h, and then removing the water in the product system by vacuum distillation to obtain the PTA-IL composite catalyst.

[0044] In this application, phosphotungstic acid (H3PW) 12 O 40 The reaction between PTA and 1-carboxyethyl-3-methylimidazolium chloride ([HOOCEMIm]Cl) is an acid-base neutralization reaction and an ion exchange / self-assembly process. Upon dropwise addition of 1-carboxyethyl-3-methylimidazolium chloride to an aqueous solution of phosphotungstic acid, one or more protons (H+) in PTA... + The protons are transferred to the basic nitrogen atom of the imidazole ring. Thus, the original [HOOCEMIm]⁺ cation (although composed of imidazole and carboxyl groups, it is fundamentally basic) is further protonated to form a new salt, which is the PTA-IL composite catalyst of this application, and its structure can be represented as [(HOOCEMIm)H]. x [PW 12 O 40 This PTA-IL composite catalyst combines the strong catalytic activity of heteropolyanions with the low volatility and good solubility of ionic liquids. The catalytic active center of this PTA-IL composite catalyst remains the heteropolyanion [PW], which possesses strong acidity and redox capabilities. 12 O 40 ] 3- .

[0045] By controlling the preparation temperature of the PTA-IL composite catalyst to 50℃-60℃, the generated water can be effectively evaporated and removed from the reaction system. This temperature ensures effective evaporation of water while avoiding damage to the reactants or products caused by excessively high temperatures.

[0046] For example, the reaction temperature of the PTA-IL composite catalyst can be a range of 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C or any combination thereof; the reaction time can be a range of 4h, 4.5h, 5h or any combination thereof.

[0047] In some specific embodiments, the mass concentration of the phosphotungstic acid aqueous solution is 0.01 mol / L to 0.05 mol / L.

[0048] For example, the mass concentration of the phosphotungstic acid aqueous solution can be a range of 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, or any combination thereof.

[0049] In some specific embodiments, the molar ratio of phosphotungstic acid to carboxylic acid-functionalized ionic liquid is 1:(1.5-2.5).

[0050] Phosphotungstic acid (PTA) is a tribasic strong acid containing three ionizable protons (H⁺). The imidazole ring in 1-carboxyethyl-3-methylimidazolium chloride is a base site that can accept protons. Therefore, by controlling the molar ratio of phosphotungstic acid to carboxylic acid-functionalized ionic liquid to 1:(1.5-2.5), a PTA-IL composite catalyst with a balanced ratio of catalytic active center to chain transfer group can be obtained, ensuring the optimal match between chain transfer capability and initiation / propagation capability, thereby achieving low molecular weight and narrow distribution (PDI < 1.35).

[0051] For example, the molar ratio of phosphotungstic acid to carboxylic acid functionalized ionic liquid is 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2.0, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5 or any combination thereof.

[0052] In some specific embodiments, the initiator includes a monofunctional primary alcohol with a carbon chain length of C4-C8.

[0053] Monofunctional initiators (with only one hydroxyl group -OH) mean that each polymer chain has only one defined growth starting point. This ensures that the product is a strictly linear polymer, rather than a branched or network structure. Primary alcohols (-CH2OH) have the least steric hindrance and the strongest nucleophilicity. In the strongly acidic environment provided by the phosphotungstic acid / ionic liquid catalytic system, side reactions such as elimination and dehydration are less likely to occur, ensuring the controllability of the initiation step. It can be rapidly and efficiently geofused to form the active species (R-OH2). + ( ), which then reacts with epichlorohydrin, resulting in a fast and uniform initiation rate, which is beneficial for obtaining monofunctional polyepichlorohydrin with a narrow molecular weight distribution.

[0054] Using monofunctional primary alcohols with C4-C8 carbon chain lengths as initiators, the carbon chains (such as n-butanol, n-hexanol, and n-octanol) exhibit moderate amphiphilicity, ensuring good miscibility with polar catalytic systems and thorough mixing with epichlorohydrin monomers. This guarantees a homogeneous polymerization system, facilitating precise control of product molecular weight. Furthermore, when using C4-C8 monofunctional primary alcohols as initiators, the alkyl chain (R-) provides a moderately hydrophobic "spatial anchor" at the polymer initiation point. This flexible carbon chain of a certain length adopts a coiled conformation in the reaction system. This conformation provides a slight but effective spatial barrier to the back-biting cyclization at the ends of the growing chain. The C4-C8 length appropriately interferes with the near-conformation required for intramolecular cyclization, thereby significantly suppressing the formation of cyclic byproducts and ensuring that the product is predominantly linear.

[0055] For example, the initiator may include n-butanol (CAS: 71-36-3), n-pentanol (CAS: 71-41-0), n-hexanol (CAS: 111-27-3), n-heptanol (CAS: 111-70-6), n-octanol (CAS: 111-87-5), etc.

[0056] In some specific embodiments, the molar ratio of the initiator to the epichlorohydrin monomer is 1:(10-40).

[0057] It is understandable that the theoretical number-average molecular weight (Mn) of the product is... 理论 Mn is determined by the following formula: 理论 = (Monomer mass / Initiator moles) + Initiator molecular weight ≈ ([M]0 / [I]0 × Monomer molecular weight) + Initiator molecular weight, where [M]0 is the monomer molar amount and [I]0 is the initiator molar amount. Therefore, to obtain a low molecular weight product, a small [M]0 / [I]0 ratio must be used to limit the growth length of each chain. In this embodiment, to obtain a monofunctional polyepoxychloropropane with a theoretical number-average molecular weight of 700-900 g / mol, the molar ratio of the initiator to the epichlorohydrin monomer can be controlled to be 1:(10-40). Within this molar ratio range, all chains have a similar probability of growth from the monomer and are similarly regulated by the chain transfer agent (carboxyl group), allowing the chain segments in the reaction system to grow synchronously and undergo chain transfer. Simultaneously, a lower [M]0 / [I]0 ratio also means a higher relative concentration of the initiator (and the chain transfer agent introduced by the catalyst) in the system. This further enhances the controllable chain transfer / termination pathway, enabling the active chain to be effectively "captured" and stabilized before it has the opportunity to undergo unfavorable intramolecular cyclization, transforming it into a linear product and further inhibiting the formation of cyclic oligomers.

[0058] In some embodiments, the molar ratio of the initiator to the epichlorohydrin monomer can be 1:(10-15). In this case, the molecular weight of the resulting monofunctional polyepoxychlorohydrin can be controlled between 700 g / mol and 900 g / mol.

[0059] In this application, the molar ratio of the initiator to epichlorohydrin can be adjusted by the target molecular weight of the monofunctional polyepoxychlorohydrin. Exemplarily, the molar ratio of the initiator to the epichlorohydrin monomer can be a range of 1:10, 1:15, 1:20, 1:22, 1:24, 1:26, 1:28, 1:30, 1:32, 1:34, 1:36, 1:38, 1:40, or any combination thereof.

[0060] In some specific embodiments, the mass ratio of the PTA-IL composite catalyst to the epichlorohydrin monomer is (0.01-0.03):1.

[0061] In the cationic ring-opening polymerization of monofunctional polyepoxychloropropane, each initiator molecule requires a catalytically active site for "activation": ideally, each initiator (R-OH) molecule should be activated by a proton (H⁺) or Lewis acid site provided by the catalyst, forming the starting point of a growth chain. In this embodiment, by controlling the mass ratio of the PTA-IL composite catalyst to the epichlorohydrin monomer to be (0.01-0.03):1, it can be ensured that the number of active centers provided by the PTA-IL composite catalyst and the number of initiator molecules reach an optimal match, thereby achieving rapid and synchronous initiation and obtaining a product with a narrow molecular weight distribution.

[0062] For example, the mass ratio of the PTA-IL composite catalyst to the epichlorohydrin monomer can be 0.01:1, 0.02:1, 0.03:1, or any combination thereof.

[0063] In some specific embodiments, the reaction temperature of the cationic ring-opening polymerization reaction is 40℃-60℃; the reaction time of the cationic ring-opening polymerization reaction is 4h-8h.

[0064] In cationic ring-opening polymerization, controlling the temperature within a suitable range of 40℃-60℃ provides sufficient energy to ensure the polymerization proceeds at a reasonable and efficient rate, allowing the monomers to be fully converted into polymers. This is also essential for protecting the structural integrity and functional stability of the catalyst. More importantly, at this reaction temperature, while ensuring a sufficient polymerization rate, the conformational movement of the molecular chains is confined to a level unfavorable to the formation of stable ring structures, thereby effectively suppressing the cyclization content to below 5%.

[0065] For example, the reaction temperature of the cationic ring-opening polymerization reaction can be a range of 40°C, 45°C, 50°C, 55°C, 60°C or any combination thereof; the reaction time can be a range of 4h, 5h, 6h, 7h, 8h or any combination thereof.

[0066] In some specific embodiments, the post-processing includes: adding an ester solvent to the product system and centrifuging at 4000 rpm-5000 rpm to obtain the PTA-IL composite catalyst and the crude product solution; performing liquid-liquid extraction on the crude product solution using an extractant containing an alcohol solvent and water to obtain the crude product; washing the crude product with deionized water, drying it and removing the ester solvent to obtain monofunctional polyepoxychloropropane.

[0067] In some embodiments, the centrifugation speed can be 4500 rpm to 4800 rpm.

[0068] Specifically, the ester solvent used can be ethyl acetate. The hydrophobicity of ethyl acetate matches the hydrophobicity of the PTA-IL composite catalyst, enabling efficient catalyst recovery. The mixed solution of alcohol solvent and water selectively extracts cyclic oligomers due to their strong solubility and weak solubility in linear PECH, thereby removing byproducts.

[0069] In some specific embodiments, the volume ratio of alcohol solvent to water in the extractant is 3:1.

[0070] The extractant obtained by mixing alcohol solvent and water at a volume ratio of 3:1 provides a sufficiently moderately polar environment for the product, allowing the low molecular weight polyether to dissolve fully in the organic phase (alcohol phase). For the catalyst, a sufficient proportion of water ensures that the catalyst (especially heteropoly anions) is strongly "pulled" into and retained in the aqueous phase, achieving clear two-phase separation (alcohol-organic phase vs. aqueous phase). The product is efficiently enriched in the alcohol phase, while the catalyst and residual ions are effectively washed into the aqueous phase, further improving the extraction and separation efficiency.

[0071] In some specific embodiments, the alcohol solvent includes methanol.

[0072] In some specific implementations, the crude product may be subjected to liquid-liquid extraction repeated 2 times, 3 times, or other times.

[0073] The method for preparing monofunctional polyepoxychloropropane provided in this application utilizes the ion exchange reaction of phosphotungstic acid (PTA) and a carboxylic acid-functionalized ionic liquid ([HOOCEMIm]Cl) to construct a homogeneous-heterogeneous synergistic PTA-IL composite catalyst. This method retains the strong acidic catalytic activity of the heteropolyacid while achieving efficient catalyst recovery through the hydrophobicity of the ionic liquid, thereby reducing the molecular weight distribution width of the monofunctional polyepoxychloropropane. The homogeneous activity of the PTA-IL composite catalyst ensures efficient reaction, while its recyclability reduces production costs and environmental burden. Mild reaction conditions effectively suppress the formation of cyclic byproducts, and combined with alcohol solvent / water extraction technology, efficient removal of cyclic oligomers is achieved. The final product has a narrow molecular weight distribution and high functionality, and requires no complex neutralization steps, simplifying the post-processing procedure. This process not only solves the problems of high toxicity and non-recyclability of traditional BF3·Et2O catalysts, but also significantly improves product purity through solvent selective extraction technology, providing a green, economical and recyclable technical path for the industrial production of low molecular weight PECH.

[0074] This application also provides a monofunctional polyepoxychloropropane prepared by the above-described method, wherein the number-average molecular weight of the monofunctional polyepoxychloropropane is 700 g / mol to 900 g / mol, for example, it can be within the range of 780 g / mol, 790 g / mol, 800 g / mol, 810 g / mol, 830 g / mol, 850 g / mol, 870 g / mol, 900 g / mol, or any combination thereof.

[0075] In some specific embodiments, the molecular weight distribution of monofunctional polyepoxychloropropane is less than or equal to 1.35, for example, it can be 1.28, 1.30, 1.32, etc.

[0076] Specifically, in this application, the number-average molecular weight and molecular weight distribution of monofunctional polyepoxychloropropane can be determined using methods commonly used in the art, such as gel permeation chromatography (GPC) with polystyrene as the standard and tetrahydrofuran (THF) as the mobile phase.

[0077] In some specific embodiments, the monofunctional polyepoxychloropropane contains a cyclic oligomer mass fraction of less than or equal to 5%, for example, it can be... etc.

[0078] Specifically, in this application, the content of cyclic oligomers can be determined using methods commonly used in the art. For example, the characteristic signal peaks of five-membered cyclic oligomers can be detected by ¹H-NMR or gas chromatography-mass spectrometry (GC-MS), and the content can be calculated by combining the integral area.

[0079] In some specific implementations, the functionality of the monofunctional polyepoxychloropropane is greater than or equal to 0.96, for example, it can be 0.96, 0.97, etc.

[0080] Specifically, in this application, the functionality of monofunctional polyepoxychloropropane can be determined using methods commonly used in the art. For example, the functionality can be determined by analyzing the characteristic peak area ratio of terminal hydroxyl groups to epoxy groups using ¹H-NMR.

[0081] This application provides a highly active and selective precursor for subsequent azidation reactions by precisely controlling the molecular weight and functionality of the obtained polyepoxychloropropane. Its narrow molecular weight distribution ensures the homogeneity of the plasticizer system, while the low cyclic content avoids interference from byproducts in the azidation reaction, thereby improving the thermal stability and energy density of the final plasticizer. The high functionality (≥0.96) guarantees the complete reaction of the terminal hydroxyl groups, significantly reducing the negative impact of unreacted groups on the mechanical properties of the material. This structural design not only meets the stringent requirements of high-performance energetic materials for raw materials but also reduces environmental risks during production through a green synthesis process, providing crucial support for the sustainable development of energetic materials.

[0082] This application also provides an azide plasticizer, comprising monofunctional polyepoxychloropropane prepared by the above preparation method or prepared by the above monofunctional polyepoxychloropropane and an azide agent.

[0083] The azide plasticizer provided in this embodiment can perform the method provided in the above method embodiment, and its implementation principle and technical effect are similar, so it will not be described in detail here.

[0084] The technical solution of this application will be further described below using specific embodiments.

[0085] First, the PTA-IL composite catalyst required in the preparation examples:

[0086] PTA-IL composite catalyst #1

[0087] Preparation process: In a 250 mL round-bottom flask, 2.88 g (1.0 mmol) of phosphotungstic acid (PTA) was dissolved in 50 mL of deionized water. While stirring, 2 mL of an aqueous solution containing 0.98 g (2.0 mmol) of [HOOCEMIm]Cl was slowly added dropwise. After the addition was complete, the reaction mixture was stirred at 60°C for 4 h. After the reaction was complete, the reaction solution was transferred to a rotary evaporator, and all water was evaporated under reduced pressure at 60°C to obtain a white or light yellow solid powder, which is the PTA-IL composite catalyst #1, and stored in a desiccator for later use.

[0088] PTA-IL composite catalyst #2

[0089] The preparation process is basically the same as that of PTA-IL composite catalyst #1, except that the molar ratio of phosphotungstic acid to [HOOCEMIm]Cl is 1:1.5.

[0090] PTA-IL composite catalyst #3

[0091] The preparation process is basically the same as that of PTA-IL composite catalyst #1, except that the molar ratio of phosphotungstic acid to [HOOCEMIm]Cl is 1:2.5.

[0092] Example 1

[0093] A method for preparing monofunctional polyepoxychloropropane, comprising the following steps:

[0094] Feeding: In a dry 100mL three-necked flask, add 1.85g n-butanol (initiator, 25mmol), 23.15g epichlorohydrin (monomer, 250mmol), and 0.46g PTA-IL composite catalyst #1 (2.0% based on monomer mass).

[0095] Polymerization: The system was stirred in a constant temperature oil bath at 50°C for 6 hours under nitrogen protection to obtain a reaction solution;

[0096] Post-processing: The reaction solution was cooled to room temperature, diluted with 40 mL of ethyl acetate, transferred to a centrifuge tube, centrifuged at 5000 rpm for 5 min, and the supernatant was decanted. The PTA-IL composite catalyst #1 solid at the bottom was recovered (recovery rate 93%). The obtained supernatant was transferred to a separatory funnel and extracted three times with 30 mL of methanol / water (3:1, v / v) mixed solvent. The ethyl acetate phases were combined, washed with water until neutral, dried over anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation under reduced pressure to obtain monofunctional polyepoxychloropropane.

[0097] Example 2

[0098] A method for preparing monofunctional polyepoxychloropropane is basically the same as that in Example 1, except that n-butanol is replaced with n-octanol as the initiator.

[0099] Example 3

[0100] A method for preparing monofunctional polyepoxychloropropane is basically the same as that in Example 1, except that n-butanol is replaced with n-pentanol as the initiator.

[0101] Example 4

[0102] A method for preparing monofunctional polyepoxychloropropane is basically the same as that in Example 1, except that n-butanol is replaced with n-hexanol as the initiator.

[0103] Example 5

[0104] A method for preparing monofunctional polyepoxychloropropane is basically the same as that in Example 1, except that the amount of PTA-IL composite catalyst #1 is 1.0% of the monomer mass and the reaction time is extended to 8 hours.

[0105] Example 6

[0106] A method for preparing monofunctional polyepoxychloropropane is basically the same as that in Example 5, except that the amount of PTA-IL composite catalyst #1 is 0.5% of the monomer mass.

[0107] Example 7

[0108] A method for preparing monofunctional polyepoxychloropropane is basically the same as that in Example 1, except that the amount of PTA-IL composite catalyst #1 is 3.0% of the monomer mass.

[0109] Example 8

[0110] A method for preparing monofunctional polyepoxychloropropane is basically the same as that in Example 7, except that the amount of PTA-IL composite catalyst #1 is 3.5% of the monomer mass.

[0111] Example 9

[0112] A method for preparing monofunctional polyepoxychloropropane is basically the same as that in Example 1, except that PTA-IL composite catalyst #1 is replaced with PTA-IL composite catalyst #2.

[0113] Example 10

[0114] A method for preparing monofunctional polyepoxychloropropane is basically the same as that in Example 1, except that PTA-IL composite catalyst #1 is replaced with PTA-IL composite catalyst #3.

[0115] Example 11

[0116] A method for preparing monofunctional polyepoxychloropropane is basically the same as that in Example 1, except that the molar ratio of the initiator to epichlorohydrin is 1:5.

[0117] Example 12

[0118] A method for preparing monofunctional polyepoxychloropropane is basically the same as that in Example 1, except that the molar ratio of the initiator to epichlorohydrin is 1:15.

[0119] Example 13

[0120] A method for preparing monofunctional polyepoxychloropropane is basically the same as that in Example 1, except that the molar ratio of the initiator to epichlorohydrin is 1:40.

[0121] Example 14

[0122] A method for preparing monofunctional polyepoxychloropropane is basically the same as that in Example 13, except that the molar ratio of the initiator to epichlorohydrin is 1:45.

[0123] Comparative Example 1

[0124] A method for preparing monofunctional polyepoxychloropropane is basically the same as that in Example 1, except that the PTA-IL composite catalyst #1 is replaced with BF3•Et2O (1.0wt%).

[0125] Comparative Example 2

[0126] A method for preparing monofunctional polyepoxychloropropane is basically the same as that in Example 1, except that extraction is not performed.

[0127] Product performance testing

[0128] The PECH prepared in Examples 1-14 and Comparative Examples 1-2 were subjected to the following tests:

[0129] Yield: Maleic acid was selected as the internal standard and mixed with the dried product in a deuterated solvent (such as CDCl3). Sufficient relaxation delay time was used to ensure that all proton signals could be fully relaxed. Quantitative ¹H NMR spectra were acquired by quantitative nuclear magnetic resonance. An isolated, well-defined proton signal was selected as the internal standard signal for integration, and its integral value was set as A. IS The signal corresponds to the number of protons n. IS The initiator terminal matrix signal is selected as the product characteristic signal for integration. Let the integral value of the selected signal be A. P The signal represents n protons. P According to the principle of quantitative NMR, the mass of a substance is proportional to the integral value of its characteristic signal: (m P,实际 / M P ) / n P =(m IS / M IS ) / n IS ×(A P / A IS ), where M p This is the actual number-average molecular weight of the product (which can be measured by GPC or using theoretical Mn), M IS The molecular weight of the internal standard is given; therefore, the yield (%) = (m P,实际 / msample )×(m sample总 (theoretical yield) × 100%, where m sample总 It is the total dried mass of the product.

[0130] Number-average molecular weight: The solution of the product in CDCl3 was prepared, and high-resolution ¹H NMR spectra were acquired using a Bruker JEOL ECZ400 / 500 instrument. The terminal proton signals introduced by the initiator were identified, and regions with clear, non-overlapping proton signals in repeating units were selected. For example, the -CH2-CH(Cl)-CH2-O- unit formed by the ring opening of epichlorohydrin, with its main chain methylene protons (-CH2-, ~3.4-3.7 ppm). Let A be the integral area of ​​the terminal characteristic signals. end The corresponding number of protons is n end (e.g., -CH3 corresponds to 3 H); Let the integral area of ​​the characteristic signal of the repeating unit be A. unit The total number of protons corresponding to a repeating unit is n. unit (For PECH, the total number of protons, including methylene groups, in the main chain is usually 3 or 4 H atoms, which needs to be determined based on the exact structure); Degree of polymerization = [(A unit / n unit ) / (A end / n end Absolute number-average molecular weight = (degree of polymerization × molecular weight of repeating unit) + molecular weight of initiator.

[0131] Molecular weight distribution Đ: Gel permeation chromatography was used to establish a calibration curve using narrow-distribution polyethylene oxide or standards, and a distribution curve with elution volume as the x-axis and detector response as the y-axis was obtained. The number-average molecular weight Mn, weight-average molecular weight Mw, and Z-average molecular weight were calculated from the calibration curve; Đ = Mw / Mn.

[0132] Functionality: Functionality is the degree of aggregation = [(A unit / n unit ) / (A end / n end )).

[0133] Cyclic oligomer content: High-resolution, high signal-to-noise ratio ¹H NMR spectra of the collected products are used to identify and assign characteristic proton signals belonging to cyclic oligomers (especially the most abundant low-ring-number protons, such as dimers and trimers) in the spectra; a proton signal belonging to both the linear main chain and the cyclic structure is selected as an internal reference (e.g., protons of the main chain -O-CH2-), and its integral value is set to A. total The integral belongs only to the characteristic proton signal of the ring-shaped object, and its integral value is set to A. cyclic ; Mole fraction of cyclic compounds ≈ (A cyclic / n Hcyclic ) / (Atotal / n Htotal ), where n Hcyclic and n Htotal These represent the number of protons in the corresponding integration region.

[0134] The test results are detailed in Table 1.

[0135] Table 1

[0136]

[0137] As shown in Table 1, the monofunctional polyepoxychloropropane prepared by the preparation method provided in this application has a molecular weight distribution of less than 1.5, a functionality of greater than or equal to 0.90, and the content of cyclic oligomers in the product is less than 8%.

[0138] The test results of Examples 5-8 show that when the mass ratio of PTA-IL composite catalyst to epichlorohydrin monomer is (0.01-0.03):1, monofunctional polyepoxychlorohydrin with a molecular weight distribution less than or equal to 1.35 and a functionality greater than or equal to 0.96 can be obtained, and the content of cyclic oligomers in the obtained monofunctional polyepoxychlorohydrin can be less than 5%.

[0139] The results from Examples 1 and 11-14 show that when the molar ratio of the initiator to epichlorohydrin is 1:(10-40), monofunctional polyepoxychlorohydrin with a molecular weight distribution less than or equal to 1.35 and a functionality greater than or equal to 0.96 can be obtained; when the molar ratio of the initiator to epichlorohydrin is 1:(10-15), the molecular weight of the obtained monofunctional polyepoxychlorohydrin can be further controlled within 700 g / mol-900 g / mol.

[0140] Catalyst cycle performance:

[0141] The PTA-IL composite catalyst #1 recovered in Example 1 was vacuum dried at 60°C for 2 hours and then directly used in a new round of synthesis reaction under the same preparation conditions as in Example 1. The number-average molecular weight, molecular weight distribution, and catalyst recovery rate of the products were determined in the first, third, and fifth cycles according to the above method. The results are detailed in Table 2.

[0142] Table 2

[0143]

[0144] The data in Table 2 show that the PTA-IL composite catalyst prepared in this application has good cycle stability.

[0145] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and various modifications and changes may be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for preparing monofunctional polyepoxychloropropane, characterized in that, include: The initiator and epichlorohydrin monomer were subjected to cationic ring-opening polymerization under an inert atmosphere in the presence of a PTA-IL composite catalyst to obtain the product system. The product system was post-processed to obtain a crude product solution; The crude product solution was extracted using a mixed solution of alcohol solvent and water to obtain the monofunctional polyepoxychloropropane. The PTA-IL composite catalyst was prepared from phosphotungstic acid and carboxylic acid-functionalized ionic liquid. The carboxylic acid functionalized ionic liquid includes 1-carboxyethyl-3-methylimidazolium chloride.

2. The method for preparing monofunctional polyepoxychloropropane according to claim 1, characterized in that, The preparation method of the PTA-IL composite catalyst includes: The phosphotungstic acid was dissolved in deionized water to obtain an aqueous solution of phosphotungstic acid; The carboxylic acid-functionalized ionic liquid was added dropwise to the aqueous phosphotungstic acid solution to obtain the reaction system; After reacting the reaction system at 50℃-60℃ for 4-5 hours, the water in the product system was removed by vacuum distillation to obtain the PTA-IL composite catalyst.

3. The method for preparing monofunctional polyepoxychloropropane according to claim 2, characterized in that, The molar concentration of the phosphotungstic acid aqueous solution is 0.01 mol / L to 0.05 mol / L; And / or, the molar ratio of the phosphotungstic acid to the carboxylic acid functionalized ionic liquid is 1:(1.5-2.5).

4. The method for preparing monofunctional polyepoxychloropropane according to claim 1, characterized in that, The initiator includes a monofunctional primary alcohol with a carbon chain length of C4-C8; And / or, the molar ratio of the initiator to the epichlorohydrin monomer is 1:(10-40). And / or, the mass ratio of the PTA-IL composite catalyst to the epichlorohydrin monomer is (0.01-0.03):

1.

5. The method for preparing monofunctional polyepoxychloropropane according to claim 4, characterized in that, The initiator includes at least one of n-butanol and n-octanol; And / or, the molar ratio of the initiator to the epichlorohydrin monomer is 1:(20-25).

6. The method for preparing monofunctional polyepoxychloropropane according to any one of claims 1-5, characterized in that, The reaction temperature for the cationic ring-opening polymerization reaction is 40℃-60℃; The reaction time for the cationic ring-opening polymerization reaction is 4-8 hours.

7. The method for preparing monofunctional polyepoxychloropropane according to any one of claims 1-6, characterized in that, The post-processing includes: An ester solvent was added to the product system, and the mixture was centrifuged at 4000 rpm-5000 rpm to obtain the PTA-IL composite catalyst and the crude product solution. And / or, after extracting the crude product solution with a mixed solution of an alcohol solvent and water, the method further includes: The extract was washed with deionized water, dried, and the ester solvent was removed to obtain the monofunctional polyepoxychloropropane.

8. The method for preparing monofunctional polyepoxychloropropane according to claim 7, characterized in that, The centrifuge speed is 4500rpm-4800rpm; And / or, the volume ratio of the alcohol solvent to the water is 1:(1~3); And / or, the extraction is repeated 2 to 3 times; And / or, the alcohol solvent includes methanol.

9. A monofunctional polyepoxychloropropane, characterized in that, Prepared by the preparation method according to any one of claims 1-8.

10. The monofunctional polyepoxychloropropane according to claim 9, characterized in that, The monofunctional polyepoxychloropropane has a number-average molecular weight of 700 g / mol to 900 g / mol. And / or, the molecular weight distribution of the monofunctional polyepoxychloropropane is less than or equal to 1.35; And / or, the monofunctional polyepoxychloropropane contains a cyclic oligomer mass fraction of less than or equal to 5%; And / or, the functionality of the monofunctional polyepoxychloropropane is greater than or equal to 0.96.

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