Preparation method and application of isononyl isononanoate

Abstract

The application relates to the field of chemical synthesis, in particular to a preparation method of isononyl isononanoate and application thereof. The preparation method comprises the following steps: under the condition that the reaction temperature is not higher than 40 DEG C, reacting isononyl alcohol with a sulfonylation reagent in the presence of alkali to obtain isononyl sulfonate; reacting isononanoic acid with alkali metal carbonate in an aprotic organic solvent under the condition that the temperature is 75-90 DEG C and a physical dehydrating agent is present, to obtain a suspension reaction system containing isononanoic acid alkali metal salt; adding isononyl sulfonate, iodide and a phase transfer catalyst into the suspension reaction system containing isononanoic acid alkali metal salt, so that a nucleophilic substitution esterification reaction occurs, to obtain a mixture containing isononyl isononanoate; and finally, isononyl isononanoate is separated from the mixture. The preparation method effectively avoids side reactions caused by strong acid and high temperature conditions in a traditional dehydration esterification mode, improves the esterification reaction driving force and controllability, reduces the difficulty of separation and impurity removal, and prepares isononyl isononanoate with low acid value, low hydroxyl value, low colority and high purity.

Description

Technical Field

[0001] This application relates to the field of chemical synthesis, specifically to a method for preparing isononyl isononanoate and its application. Background Technology

[0002] Isonononyl isononanoate possesses excellent lubricity, spreadability, low viscosity, good oxidative stability, and low skin greasiness, making it widely used in cosmetic emollients, plasticizers, lubricating oil base esters, surface treatment additives, and other fine chemical fields. With the development of high-end personal care products, environmentally friendly plasticizers, and high-performance synthetic ester materials, the market has placed higher demands on the color, acid value, hydroxyl value, odor, purity, and residual impurities of isonononoate.

[0003] Existing methods for preparing isononyl isononanoate typically involve the direct esterification of isononanoic acid and isononol under an acidic catalyst, with the reaction equilibrium driven by reflux heating, vacuum dehydration, or azeotropic dehydration. However, the resulting isononyl isononanoate suffers from issues such as high color, high acid value, high hydroxyl value, and low purity, failing to meet higher market demands.

[0004] Therefore, there is an urgent need to develop a method for preparing high-quality isononyl isononanoate with low acid value, low hydroxyl value, and light color. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a method for preparing and applying isononyl isononanoate. The method involves first converting isononol to isononyl sulfonate, which has a good leaving group, then converting isononoic acid to an alkali metal salt of isononanoate, and finally allowing the isononyl sulfonate and the alkali metal salt of isononanoate to undergo a nucleophilic substitution esterification reaction under the combined action of iodide and a phase transfer catalyst. This yields isononyl isononanoate products with low acid value, low hydroxyl value, light color, and high purity.

[0006] The first aspect of this application provides a method for preparing isononyl isononanoate, comprising the following steps: S1, under the condition of controlling the reaction temperature not higher than 40°C, isononol reacting with a sulfonating agent in the presence of a base to obtain isononyl sulfonate; S2, under the condition of 75-90°C and in the presence of a physical dehydrating agent, isononanoic acid reacting with an alkali metal carbonate in an aprotic organic solvent for 150-210 min to obtain a suspension reaction system containing the alkali metal salt of isononanoate; S3, under the condition of 80-95°C, the isononyl sulfonate obtained in step S1, an iodide, and a phase transfer catalyst are added to the suspension reaction system containing the alkali metal salt of isononanoate obtained in step S2 to undergo a nucleophilic substitution esterification reaction to obtain a mixture including isononyl isononanoate; S4, isononyl isononanoate is separated from the mixture obtained in step S3.

[0007] In this application, "isononol" refers to 3,5,5-trimethyl-1-hexanol.

[0008] In this application, "isononanoic acid" refers to 3,5,5-trimethylhexanoic acid.

[0009] In this application, "sulfonating agent" refers to a substance containing a sulfonyl group R-SO2-, and sulfonation refers to the reaction of introducing a sulfonyl group R-SO2- into an organic molecule.

[0010] In this application, "physical dehydrating agent" refers to a substance that captures, fixes, or isolates water molecules present in a reaction system through physical adsorption or physical encapsulation, thereby reducing or eliminating the free water content in the system. Its dehydration effect does not involve irreversible chemical reactions with water, does not change the chemical composition of water molecules, and does not release protons, hydroxide ions, or other reactive species into the reaction system. Examples include molecular sieves, silica gel, and activated alumina. In this application, "aprotic organic solvent" refers to a general term for organic solvents that do not provide protons under reaction conditions and do not undergo acid-base neutralization or solvation deactivation with strong nucleophiles or basic substances in the system. Specifically, it includes, but is not limited to: aliphatic or aromatic nitriles, straight-chain or cyclic ethers, tertiary amine-substituted amides, sulfoxides, ketones, or halogenated hydrocarbons.

[0011] The applicant discovered through research that the reason why the isononyl isononanoate products in the prior art have high color, high acid value, high hydroxyl value and low purity is that the esterification reaction of isononanoic acid and isononol under the action of acid catalyst is a reversible equilibrium reaction. The water generated during the reaction will inhibit the esterification from continuing. It is necessary to promote the reaction equilibrium by means of heating and reflux, vacuum dehydration or azeotropic dehydration, which often requires high reaction temperature, long reaction time and continuous dehydration operation. Under strong acid catalysts (such as sulfuric acid, p-toluenesulfonic acid, etc.) and high temperatures (above 75°C), isononol, as an alcohol with a highly branched structure, is prone to side reactions, such as intramolecular dehydration to form chromogenic olefin impurities with conjugated double bonds, intermolecular dehydration to form ether impurities with irritating odors, and carbon skeleton rearrangement to form isomers. The boiling points of the products generated by these side reactions are close to those of the target product, isonononoic acid isononyl ester, which is difficult to completely remove through purification, resulting in increased product color and decreased purity. Furthermore, since esterification is a reversible equilibrium reaction, even with various dehydration operations, unreacted monomeric raw materials (isonononoic acid, isononol) and acidic catalysts inevitably remain in the system. It is extremely difficult to completely remove these impurities while ensuring product yield, ultimately leading to higher acid value, higher hydroxyl value, lower purity, and higher color in the isonononoic acid ester product.

[0012] The applicant further discovered through research that a synthetic route involving the sulfonation of isononol at low temperature and in the presence of an alkali, followed by an irreversible nucleophilic substitution reaction with an alkali metal salt of isononanoate, is advantageous for preparing isonononoate with low color, low acid value, and high purity. Specifically, in step S1, at a reaction temperature below 40°C, the reaction of isononol with the sulfonating agent in the presence of an alkali converts the hydroxyl group, which is prone to side reactions, into a readily available leaving group, the sulfonate ester group. The presence of the alkali neutralizes the acid generated in the reaction, allowing the reaction to proceed efficiently and avoiding acid-induced side reactions. This step avoids the dehydration, etherification, and isomerization of isononol under high temperature and strong acid conditions, which are common in traditional esterification synthetic routes. This helps reduce the color of the isonononoate product and provides a suitable leaving group for the subsequent nucleophilic substitution reaction. In step S2, isononanoic acid and alkali metal carbonate are reacted in an aprotic organic solvent at 75-90℃ in the presence of a physical dehydrating agent for 150-210 min, yielding a suspension reaction system containing isononanoic acid alkali metal salt. The physical dehydrating agent effectively adsorbs the water generated during the salt formation reaction, providing an anhydrous reaction environment for the subsequent nucleophilic substitution esterification reaction. This effectively prevents free water from being carried into the subsequent step S3 and reduces side reactions caused by water. The aprotic organic solvent, as the reaction medium, reduces side reactions and maintains the nucleophilic attack capability of the isononanoate ion. Converting isononanoic acid into the strongly nucleophilic isononanoate ion facilitates irreversible nucleophilic substitution with isononyl sulfonate, breaking the equilibrium limitation of traditional esterification and improving the driving force and controllability of the esterification reaction. Furthermore, the isononanoic acid alkali metal salt has poor solubility in the aprotic organic solvent and can be easily removed in subsequent reactions by means of filtration. In step S3, at 80-95℃, the obtained isononyl sulfonate, iodide, and phase transfer catalyst are added to the suspension reaction system containing isononyl alkali metal salt to carry out a nucleophilic substitution reaction. Iodide can convert isononyl sulfonate into a more active intermediate, and the phase transfer catalyst helps to transform the slow heterogeneous reaction on the solid surface of isononyl alkali metal salt into a fast reaction in the liquid homogeneous phase. The synergy of the two makes the nucleophilic substitution esterification reaction efficient and highly selective. In step S4, isononyl alkali metal salt, iodide, and phase transfer catalyst are easily removed by filtration, water washing, etc. Residual organic matter with a boiling point different from the target product isononyl isononyl ester is easily removed by distillation. The isononyl isononyl ester separated in step S4 has a low acid value and hydroxyl value, high purity, and light color.

[0013] In any embodiment, in step S1, the sulfonating agent includes methanesulfonyl chloride, and the base includes triethylamine.

[0014] Through experimental research, this application found that isononol has significant steric hindrance, which is unfavorable for sulfonation. Therefore, methanesulfonyl chloride was chosen as the sulfonating agent, as it has extremely high reactivity with the hydroxyl group of the alcohol. Under low-temperature conditions, it can react efficiently with isononol to generate isononyl sulfonate, converting the hydroxyl group into a good leaving group, the methanesulfonate group, further reducing the residual amount of isononol and the occurrence of side reactions. Triethylamine can combine with the strong acid hydrogen chloride generated in the reaction, acting as an excellent acid-binding agent to ensure that the reaction system is always in a mild, non-acidic environment, reducing the possibility of isononol undergoing acid-catalyzed side reactions, and the product triethylamine hydrochloride is easily removed. The selection of methanesulfonyl chloride and triethylamine is beneficial to further improve the purity of isononyl isononoate and further reduce the color of isononyl isononoate.

[0015] In any embodiment, step S1 specifically includes: adding isononol, triethylamine, 4-dimethylaminopyridine and anhydrous dichloromethane into the reaction apparatus; controlling the dropping rate of methanesulfonyl chloride under a nitrogen atmosphere to maintain the reaction system temperature at 0-5°C; after the dropping is completed, stirring the reaction at 0-5°C for 50-70 min, then raising the temperature to 20-30°C and stirring the reaction for 100-140 min; after the reaction is completed, adding deionized water and stirring for 10-20 min; after standing and separating the layers, extracting the organic layer; washing, drying, filtering, and removing dichloromethane from the organic layer to obtain isononyl methanesulfonate.

[0016] 4-Dimethylaminopyridine catalyst, as a highly efficient sulfonation catalyst, enables the sulfonation reaction to be completed efficiently under mild, low-temperature conditions, further reducing the occurrence of side reactions. Controlling the dropping rate of methanesulfonyl chloride to maintain the reaction system temperature at 0-5℃ ensures high selectivity and further reduces the risk of side reactions. The above reaction process and post-treatment facilitate the preparation of high-purity isononyl methanesulfonate, resulting in further reduction of color and improvement of purity in the final isonononocyanate.

[0017] In any embodiment, in step S1, the molar ratio of isononol, triethylamine, 4-dimethylaminopyridine, and methanesulfonyl chloride is 1:(1.2-1.3):(0.02-0.03):(1.05-1.15).

[0018] The above-mentioned raw material ratio enables the sulfonation reaction to be complete and highly selective, reduces the entry of by-products and unreacted raw materials into the subsequent esterification system, and reduces the residue of free acid and free alcohol in the final product, thereby giving the prepared isononyl isononanoate a lower acid value, a lower hydroxyl value, and a lighter color.

[0019] In any embodiment, in step S2, the alkali metal carbonate includes anhydrous potassium carbonate, and the physical dehydrating agent includes activated 4Å molecular sieve.

[0020] This application, through experimental research, found that alkali metal carbonates, including anhydrous potassium carbonate, have a superior effect on increasing the rate of subsequent nucleophilic substitution reactions, which is beneficial for further improving the purity of the prepared isonononocyanate and further reducing its color, acid value, and hydroxyl value. Analysis suggests this may be due to the larger ionic radius of potassium ions and their weaker electrostatic binding force on the isononocyanate anion. This weak interaction allows the formed isononocyanate alkali metal salt to exhibit a higher degree of "exposedness" at the solution or phase interface, significantly enhancing the nucleophilic attack capability of the isononocyanate anion. Therefore, even when facing sterically hindered isononyl sulfonate esters, it can still maintain extremely high reactivity, contributing to further improving the efficiency and high conversion rate of the nucleophilic substitution esterification reaction. The physical dehydrating agent includes an activated 4Å molecular sieve, whose pore size (approximately 0.4 nm) is highly matched with the dynamic diameter of water molecules (approximately 0.28 nm), exhibiting excellent adsorption selectivity.

[0021] In any embodiment, step S2 specifically includes: adding isononanoic acid, anhydrous potassium carbonate, anhydrous acetonitrile, and activated 4Å molecular sieve to a reaction vessel equipped with a reflux condenser, and stirring the reaction for 150-210 min under a nitrogen atmosphere at 75-90°C to obtain a suspension reaction system containing potassium isononanoate.

[0022] The reflux condenser in step S2 effectively prevents the loss of solvent (anhydrous acetonitrile) during the reaction. As a nonprotic polar solvent, the use of anhydrous acetonitrile helps to further reduce the occurrence of side reactions in step S2, and the suspension reaction system containing potassium isononanoate can be directly used in step S3 for nucleophilic substitution esterification, omitting the purification step of potassium isononanoate and reducing the risk of byproduct generation. The above reaction process helps to further improve the purity of the prepared isononyl isononanoate and further reduce the color, acid value and hydroxyl value of isononyl isononanoate.

[0023] In any embodiment, in step S2, the molar ratio of isononanoic acid to anhydrous potassium carbonate is 1:(0.5-0.6), and the amount of molecular sieve added is 40%-60% of the mass of isononanoic acid.

[0024] The molar ratio of anhydrous potassium carbonate to isononanoic acid is controlled at 1:(0.5-0.6), which is beneficial for the complete conversion of isononanoic acid to potassium isononate, thereby further improving the conversion rate of the nucleophilic substitution reaction and reducing the residual free isononanoic acid in the system after the reaction. It also helps to reduce the risk of ester bond hydrolysis of the target product caused by excess alkali. The amount of molecular sieve added is controlled at 40%-60% of the mass of isononanoic acid, which can fully adsorb water in the reaction system, further preventing water from causing hydrolysis of isononyl sulfonate or reducing the activity of potassium isononate, thus further improving the reaction efficiency and selectivity of the nucleophilic substitution reaction. Maintaining the molar ratio of isononanoic acid to anhydrous potassium carbonate and the amount of molecular sieve added within the above ranges is beneficial for further improving the purity of the prepared isonononocyanate and further reducing the color, acid value, and hydroxyl value of isonononocyanate.

[0025] In any embodiment, the iodide in step S3 includes potassium iodide, and the phase transfer catalyst includes tetrabutylammonium bromide.

[0026] The selection of potassium iodide is consistent with the selection of potassium carbonate in step S2 to introduce cations, which helps to further reduce the difficulty of subsequent impurity removal; tetrabutylammonium bromide has excellent phase transfer catalytic performance and excellent price, making it suitable for industrial production.

[0027] In any embodiment, step S3 specifically includes: adding isononyl methanesulfonate, potassium iodide, and tetrabutylammonium bromide obtained in step S1 to the suspension reaction system containing potassium isononate obtained in step S2, and conducting a nucleophilic substitution esterification reaction under a nitrogen atmosphere, at 80-95°C and 300-600 r / min; dynamically detecting the residual amount of isononyl methanesulfonate in the reaction system using gas chromatography, and terminating the reaction when the normalized content of the chromatographic peak area of ​​isononyl methanesulfonate decreases to below 0.50%, thereby obtaining a mixture including isononyl isononate.

[0028] Under the above process conditions, isononyl methanesulfonate and potassium isononate undergo a highly efficient irreversible nucleophilic substitution esterification reaction, avoiding the side reactions caused by high temperature and strong acid catalysts in traditional esterification reactions, as well as the problem of raw material residue caused by reversible equilibrium. This improves the driving force and controllability of the esterification reaction and reduces the difficulty of separation and impurity removal. By detecting the residual amount of isononyl methanesulfonate in the reaction system, the problem of raw material residue is further avoided, which helps to further improve the purity of the final isononyl isononate and reduce the color, acid value and hydroxyl value of isononyl isononate.

[0029] In any embodiment, step S4 specifically includes: cooling the mixture, filtering to remove solids, washing the filter cake with anhydrous acetonitrile and combining the filtrates, recovering acetonitrile under conditions of 50-60℃ and 10-20kPa to obtain crude isononyl isononanoate; washing the crude isonononanoate sequentially with deionized water and sodium chloride aqueous solution, then dehydrating it under conditions of 85-95℃ and 3-7kPa for 55-65min, followed by a thin-film evaporation purification process, with an evaporation temperature of 150-160℃, a system pressure of 70-90Pa, and a scraping speed of 250-350r / min to obtain isonononyl isononanoate.

[0030] The separation and purification process in step S4, in conjunction with the aforementioned reaction steps, utilizes simple and efficient processes such as filtration, distillation, neutral washing, and dehydration to separate impurities such as solids, acetonitrile, and water from the target product, isonononocyanate. Then, a thin-film evaporation purification process is employed to separate the target product, isonononocyanate, from organic compounds with different boiling points. This allows the target product, isonononocyanate, to be rapidly evaporated and condensed, reducing the probability of side reactions such as oxidation, hydrolysis, and thermal decomposition of isonononocyanate and other organic components, further protecting the product's color, acid value, hydroxyl value, and purity. The isonononocyanate preparation method provided in this application avoids the problems of emulsification and incomplete separation that easily occur when washing away acidic catalysts and acidic monomers dissolved in the liquid product using traditional direct esterification methods with alkaline washing and water washing, as well as the problems of close boiling points, high separation difficulty, incomplete separation, and long separation time during distillation. This method is beneficial for preparing isonononocyanate with light color, low acid value, low hydroxyl value, and high purity.

[0031] The second aspect of this application provides the application of isononyl isononanoate prepared by the preparation method of the first aspect in the fields of cosmetics and environmentally friendly plasticizers.

[0032] The isononyl isononanoate prepared in this application has the advantages of low color, low acid value, low hydroxyl value and high purity, which has significant advantages in the fields of cosmetics and environmentally friendly plasticizers, and meets the needs of the high-end market.

[0033] In summary, this application has the following beneficial effects:

[0034] (1) By designing the S1-S4 reaction route, isononol was converted into isononyl sulfonate under low temperature and no strong acid catalyst reaction conditions, which reduced the probability of side reactions such as dehydration, etherification and isomerization of branched isononol and reduced the generation of color-causing impurities. The hydroxyl group that is prone to side reactions was converted into a good leaving group sulfonate group, and isononoic acid was converted into isononoate anion with strong nucleophilic effect. The two underwent irreversible nucleophilic substitution esterification reaction in the presence of aprotic organic solvent, iodide and phase transfer catalyst, which broke the equilibrium limit of traditional esterification, improved the driving force and controllability of esterification reaction, reduced the difficulty of separation and impurity removal, and prepared isonononoate with light color, high purity and low acid value and hydroxyl value.

[0035] (2) In step S1, methanesulfonyl chloride is further selected as the sulfonating agent, triethylamine as the base, 4-dimethylaminopyridine catalyst as the acylation catalyst, and the dropping rate of methanesulfonyl chloride is controlled to keep the reaction system temperature at 0-5℃. The molar ratio of isononol, triethylamine, 4-dimethylaminopyridine and methanesulfonyl chloride is controlled to be 1:(1.2-1.3):(0.02-0.03):(1.05-1.15), which is beneficial to further improve the purity of isononyl isononanoate and further reduce the color, acid value and hydroxyl value of isononyl isononanoate.

[0036] (3) In step S2, anhydrous potassium carbonate is selected as an alkali metal carbonate, activated 4Å molecular sieve is selected as a physical dehydrating agent, a reflux condenser is set up, and the molar ratio of isononanoic acid to anhydrous potassium carbonate is controlled to be 1:(0.5-0.6). The amount of molecular sieve added is 40%-60% of the mass of isononanoic acid, which is beneficial to further improve the purity of isononyl isononanoate and further reduce the color, acid value and hydroxyl value of isononyl isononanoate.

[0037] (4) In step S2, anhydrous acetonitrile is selected as the reaction medium to prepare a suspension reaction system containing potassium isononate. This system is directly used in step S3 to react with isononyl sulfonate, ensuring an anhydrous and inert reaction environment in step S3. At the same time, it reduces the separation and drying steps of potassium isononate, improves the yield, and is suitable for industrial scale-up production.

[0038] (5) The separation and purification process in step S4 is beneficial to further improve the purity of isononyl isononanoate and further reduce the color, acid value and hydroxyl value of isononyl isononanoate. Attached Figure Description

[0039] Figure 1 This is a gas chromatogram of isononyl isononanoate prepared according to one embodiment of this application. Detailed Implementation

[0040] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents. The present application will be further described in detail below with reference to embodiments and comparative examples.

[0041] Example 1

[0042] S1. Add 144.25 g of isononol, 121.45 g of triethylamine, 2.44 g of 4-dimethylaminopyridine, and 350.00 g of anhydrous dichloromethane to a 1000 mL four-necked reaction flask equipped with a mechanical stirrer, thermometer, constant-pressure dropping funnel, and nitrogen inlet tube. Stir under nitrogen protection and cool to 2 °C. Maintaining the reaction system temperature at 2 °C, add 123.73 g of methanesulfonyl chloride dropwise through the constant-pressure dropping funnel at a dropping rate of 1.4 g / min. After the addition is complete, continue stirring at 2 °C for 60 min, then raise the temperature to 25 °C and stir for 120 min. After the reaction was completed, 300.00 g of deionized water was added to the reaction solution, stirred for 15 min, allowed to stand and separate into layers, and the organic layer was taken. The organic layer was washed successively with 250.00 g of 5.00% sodium bicarbonate aqueous solution and 250.00 g of deionized water, and then dried with 30.00 g of anhydrous sodium sulfate for 60 min. After filtration, the filtrate was subjected to a process of removing dichloromethane at 40 °C and 20 kPa to obtain isononyl methanesulfonate.

[0043] S2. To a 1000 mL four-necked reaction flask equipped with a mechanical stirrer, thermometer, reflux condenser, and nitrogen inlet tube, add 158.24 g of isononanoic acid, 76.02 g of anhydrous potassium carbonate, 420.00 g of anhydrous acetonitrile, and 80.00 g of 4Å molecular sieve activated at 400 °C for 4 hours. Under nitrogen protection, heat to 82 °C and stir for 180 min. During the reaction, maintain reflux to ensure complete salt formation of isononanoic acid and potassium carbonate, yielding a suspension reaction system containing potassium isononanoate.

[0044] S3. The prepared isononyl methanesulfonate, 8.30 g of potassium iodide, and 9.66 g of tetrabutylammonium bromide were added to the resulting suspension reaction system containing potassium isononate. Under nitrogen protection and at 82 °C, the mixture was stirred at 450 r / min to induce a nucleophilic substitution esterification reaction. During the reaction, samples were taken every 2 hours, and the residual amount of isononyl methanesulfonate was detected by gas chromatography. When the normalized peak area of ​​isononyl methanesulfonate was less than 0.50% after 8 hours of reaction, the reaction was terminated, yielding a mixture containing isononyl isononate.

[0045] S4. The mixture is cooled to 35°C, filtered to remove solids, and the filter cake is washed with 100.00 g of anhydrous acetonitrile. The filtrates are combined, and acetonitrile is recovered at 55°C and 15 kPa to obtain crude isononyl isononanoate. 300.00 g of deionized water is added to the crude isononyl isononanoate, stirred at 45°C for 20 min, allowed to stand for separation, and the organic layer is collected. The organic layer is then washed once with 300.00 g of 3.00% sodium chloride aqueous solution, and subsequently dehydrated at 90°C and 5 kPa for 60 min. The dehydrated crude isononyl isononanoate is then purified by thin-film evaporation at a temperature of 155°C, a system pressure of 80 Pa, and a scraper rotation speed of 300 r / min. Low-boiling-point impurities are preferentially evaporated and removed by the vacuum system. The target product, isononyl isononanoate, is then evaporated and condensed into liquid on a condenser, flowing out from the main fraction outlet. The collected liquid is the finished isononyl isononanoate product. The purity of the prepared isononyl isononanoate was determined to be 99.1% by gas chromatography.

[0046] Example 2

[0047] The preparation method of Example 2 is basically similar to that of Example 1, except that: in step S2, anhydrous sodium carbonate (58.3g) is used instead of anhydrous potassium carbonate; in step S3, sodium iodide (7.50g) is used instead of potassium iodide, and benzyltriethylammonium chloride (6.83g) is used instead of tetrabutylammonium bromide; when the reaction in step S3 proceeds for 10 hours, the normalized content of the isononyl methanesulfonate peak area is less than 0.50%, and the reaction is terminated. The rest is the same as in Example 1.

[0048] Example 3

[0049] The preparation method of Example 3 is basically similar to that of Example 1, except that: in step S1, diisopropylethylamine (155.10g) is used instead of triethylamine, and p-toluenesulfonyl chloride (200.18g) is used instead of methanesulfonyl chloride; when the reaction in step S3 proceeds for 10 hours, the normalized content of the peak area of ​​isononyl p-toluenesulfonate is less than 0.50%, and the reaction is terminated. The rest is the same as in Example 1.

[0050] Example 4

[0051] The preparation method of Example 4 is basically similar to that of Example 1, except that step S4 is modified as follows:

[0052] The mixture was cooled to 35°C, filtered to remove the solids, and the filter cake was washed with 100.00 g of anhydrous acetonitrile. The filtrates were combined, and the acetonitrile was recovered at 55°C and 15 kPa to obtain crude isononyl isononanoate. 300.00 g of deionized water was added to the crude isononyl isononanoate, and the mixture was stirred at 45°C for 20 min. After standing and separating the layers, the organic layer was collected. The organic layer was then washed once with 300.00 g of a 3.00% sodium chloride aqueous solution. Subsequently, the mixture was distilled under reduced pressure at 120°C to obtain the final product, isononyl isononanoate.

[0053] Comparative Example 1

[0054] In a 1000 mL reaction flask equipped with a reflux device and a thermometer, 144.25 g of isononol, 158.24 g of isononanoic acid, and 3.5 g of p-toluenesulfonic acid (as an acidic catalyst) were added, along with 100.00 g of xylene as a dehydrating agent. The mixture was heated to 90 °C for esterification and dehydration reaction, followed by azeotropic dehydration for 8 hours. After cooling, the reaction solution was washed with a saturated sodium bicarbonate solution until the aqueous phase was neutral. The mixture was then allowed to stand and separate into layers (obvious emulsification was observed, requiring a long standing time). The organic phase was separated, and the mixture was washed three times with water. Finally, it was distilled under reduced pressure at 120 °C to obtain the final product, isononyl isononanoate.

[0055] Comparative Example 2

[0056] The preparation method of Comparative Example 2 is basically similar to that of Example 1, except that: in step S3, potassium iodide is not added, only 9.66 g of tetrabutylammonium bromide is retained, and the reaction time is 10 h. At this time, the normalized content of isononyl methanesulfonate peak area is 21%, and the rest is the same as that of Example 1.

[0057] Performance testing

[0058] 1. Purity

[0059] The target product was detected using gas chromatography (GC), and the signal response was analyzed using a flame ionization detector (FID). The relative mass fraction of the target product in the sample was calculated using the area normalization method. This method was used to determine the purity of isononyl isononanoate prepared in step S4. The same method was used in step S3 to test the normalized content of isononyl methanesulfonate and monitor the reaction endpoint.

[0060] 2. Color

[0061] The color of the sample was determined according to GB / T 3143-1982, "Determination of Color of Liquid Chemical Products" (platinum-cobalt color number). The color of the sample was visually compared with the colors of a series of standard colorimetric solutions with known platinum-cobalt color numbers, and the color number of the standard colorimetric solution that was closest to the sample was taken as the color of the sample.

[0062] 3. Acid value

[0063] The acid value of plasticizers was determined according to GB / T 1668-2008, "Determination of Acid Value of Plasticizers". Using the principle of acid-base titration, the free acid was titrated with potassium hydroxide standard solution in a mixed solvent, using phenolphthalein as an indicator. The volume of standard solution consumed was recorded, and the content of free acid was calculated using the formula.

[0064] 4. Hydroxyl value

[0065] The hydroxyl value was determined according to GB / T 7383-2007, "Determination of Hydroxyl Value of Nonionic Surfactants". A quantitative esterification reaction was carried out between the residual alcohol hydroxyl groups in the sample and excess acetic anhydride-pyridine acylation reagent under heating conditions. After the reaction, water was added to hydrolyze the excess acetic anhydride to acetic acid. Finally, the generated acetic acid was titrated with a standard potassium hydroxide solution. A blank test was also performed, and the hydroxyl content was calculated by the difference.

[0066] The isononyl isononanoate prepared in Examples 1-4 and Comparative Examples 1-2 were tested, and the test results are shown in Tables 1, 2 and 3.

[0067] Table 1 Performance test results of isononyl isononanoate in Examples 1-3 and Comparative Example 2

[0068] experimental group Purity (GC, %) Chromaticity (APHA) Acid value (mg KOH / g) Hydroxyl value (mg KOH / g) Example 1 99.1 10 0.02 0.10 Example 2 98.8 15 0.04 0.16 Example 3 98.5 20 0.05 0.22 Comparative Example 2 85.7 40 0.34 1.45

[0069] Based on Table 1 above, comparing the test results of Examples 1-3 of this application with those of Comparative Example 2, it can be seen that, compared to Comparative Example 2 where step S3 lacks an iodide catalyst, Examples 1-3, by controlling the reaction temperature to not exceed 40°C, allow isononyl sulfonate to be obtained by reacting isononyl alcohol with a sulfonating agent in the presence of a base. Then, isononoic acid is reacted with an alkali metal carbonate under reactive conditions and in the presence of a physical dehydrating agent to obtain an alkali metal salt of isononoic acid. The isononyl sulfonate and the alkali metal salt of isononoic acid undergo a nucleophilic substitution esterification reaction in an aprotic organic solvent, in the presence of iodide and a phase transfer catalyst. This allows the nucleophilic substitution esterification reaction to proceed efficiently and selectively, thereby preparing isonononoic acid ester with light color, high purity, and low acid and hydroxyl values.

[0070] Table 2. Changes in isononyl methanesulfonate residue in Comparative Example 2 with reaction time.

[0071] Reaction time (h) Comparative Example 2 (%) 10 21.0 24 14.6 48 13.1

[0072] In Comparative Example 2, step S3 lacked an iodide catalyst. After 10 hours of reaction, the normalized peak area of ​​isononyl methanesulfonate was 21%, which was much higher than the 0.5% in Examples 1-3. This is because in the nucleophilic substitution reaction in step S3, if there is only a phase transfer catalyst and no iodide catalyst, the large steric hindrance of the branched chain prevents the isononate anion from effectively attacking the isononyl sulfonate directly. The reaction is constrained by an extremely high activation energy barrier, resulting in a slow reaction rate, which increases the risk of side reactions and leaves a large amount of unconverted isononyl sulfonate. This leads to an increase in the content of isononyl sulfonate that undergoes hydrolysis and thermal decomposition in subsequent vacuum dehydration and high-temperature distillation. The product contains a large number of impurities that are difficult to completely separate, resulting in an increase in the hydroxyl value, acid value, and color of the final product, which seriously deteriorates the reaction yield and product purity. As shown in Table 2, even if the reaction time of step S3 is extended to 48 hours or more, it is still difficult to reduce the normalized content of isononyl methanesulfonate peak area to 0.5%. Moreover, the long-term high-temperature reaction greatly increases the probability of side reactions, making it difficult to prepare isononyl isononanoate of excellent quality and unsuitable for industrial production.

[0073] As can be seen from Examples 1-3, by adjusting the alkali metal carbonate (potassium carbonate or sodium carbonate), the base (triethylamine or diisopropylethylamine), the sulfonating agent (methanesulfonyl chloride or p-toluenesulfonyl chloride), and using different dual-catalytic systems (potassium iodide + tetrabutylammonium bromide or sodium iodide + benzyltriethylammonium chloride), isononyl isononate with light color, high purity, and low acid value and hydroxyl value can be prepared.

[0074] As can be seen from the comparison of Examples 1, 2 and 3, choosing potassium carbonate as the alkali metal carbonate, potassium iodide as the iodide, tetrabutylammonium bromide as the phase transfer catalyst, triethylamine as the base, and methanesulfonyl chloride as the sulfonating agent is beneficial to further improve the purity of isononyl isononanoate and further reduce the color, acid value and hydroxyl value of isononyl isononanoate.

[0075] Table 3 Performance test results of isononyl isononanoate in Examples 1, 4 and Comparative Example 1

[0076] experimental group Purity (GC, %) Chromaticity (APHA) Acid value (mg KOH / g) Hydroxyl value (mg KOH / g) Example 1 99.1 10 0.02 0.10 Example 4 98.1 30 0.14 0.82 Comparative Example 1 91.4 80 1.95 5.23

[0077] Based on Table 3 above, a comparison between Example 4 and Comparative Example 1 shows that, compared to Comparative Example 1 which uses the traditional high-temperature acidic catalytic direct esterification method, Example 4 employs a novel synthetic route that converts isononol to isononyl sulfonate and isononoic acid to a strongly nucleophilic alkali metal salt of isononoic acid under low-temperature reaction conditions without a strong acid catalyst. The two undergo an irreversible nucleophilic substitution esterification reaction in the presence of aprotic organic solvents, iodides, and phase transfer catalysts. This effectively avoids side reactions such as dehydration to olefins, intermolecular etherification, and skeletal rearrangement of highly branched isononol under high-temperature and strong acid conditions, significantly reducing the generation of color-causing impurities and lowering the color of the isonononoic acid ester product. Simultaneously, the irreversible nucleophilic substitution reaction breaks the limitations of traditional esterification equilibrium, improving the driving force and controllability of the esterification reaction, reducing the difficulty of separation and impurity removal, and preparing isonononoic acid ester with light color, high purity, and low acid and hydroxyl values.

[0078] Comparative Example 1 uses the traditional p-toluenesulfonic acid catalytic direct esterification method. Due to the limitation of the reaction by thermodynamic reversible equilibrium, even after 8 hours of azeotropic reaction with water, unreacted isononanoic acid, isononol, and acid catalyst remain in the product, which are difficult to completely separate. This results in extremely high acid value (1.95) and hydroxyl value (5.23) of the product. Furthermore, under the high temperature of 90℃ and strong acid environment, isononol undergoes a large number of uncontrollable side reactions. The byproducts that are difficult to completely separate result in a product color of up to 80, making it difficult to improve purity and hindering its application in high-end fields.

[0079] A comparison of Examples 1 and 4 shows that step S4 in Example 1 uses a thin-film evaporation process to remove substances. Under the same reaction conditions in steps S1 to S3, the thin-film evaporation purification process replaces the traditional vacuum distillation. Because the material forms an extremely thin liquid film on the heating surface during the thin-film evaporation process, the residence time is short and the heat transfer efficiency is high, which can achieve efficient separation under a lower heat load. This process quickly removes organic matter with a boiling point different from that of isononyl isononanoate, effectively reducing the probability of side reactions such as oxidation and hydrolysis of isononyl isononanoate and decomposition of isononyl methanesulfonate caused by prolonged heating. As a result, the obtained isononyl isononanoate has higher purity, lower color, lower acid value, and lower hydroxyl value.

[0080] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing isononyl isononanoate, characterized in that, Includes the following steps: S1. Under the condition that the reaction temperature is controlled not to exceed 40℃, isononol reacts with sulfonating reagent in the presence of base to obtain isononyl sulfonate. S2. At 75-90℃ in the presence of a physical dehydrating agent, isononanoic acid and alkali metal carbonate are reacted in an aprotic organic solvent for 150-210 min to obtain a suspension reaction system containing isononanoic acid alkali metal salt. S3. At 80-95℃, the isononyl sulfonate, iodide and phase transfer catalyst obtained in step S1 are added to the suspension reaction system containing the alkali metal salt of isononanoic acid obtained in step S2 to undergo nucleophilic substitution esterification reaction to obtain a mixture including isononyl isononanoic acid. S4. Isonononate isononanoate is separated from the mixture obtained in step S3.

2. The preparation method according to claim 1, characterized in that, In step S1, the sulfonating agent includes methanesulfonyl chloride, and the base includes triethylamine.

3. The preparation method according to claim 1, characterized in that, Step S1 specifically includes: Isononol, triethylamine, 4-dimethylaminopyridine, and anhydrous dichloromethane were added to the reaction apparatus. Under a nitrogen atmosphere, the dropping rate of methanesulfonyl chloride was controlled to maintain the reaction system temperature at 0-5°C. After the addition was complete, the mixture was stirred at 0-5°C for 50-70 min, and then heated to 20-30°C and stirred for 100-140 min. After the reaction was completed, deionized water was added and stirred for 10-20 min. After standing and separating the layers, the organic layer was extracted. The organic layer was washed, dried, filtered, and dichloromethane was removed to obtain isononyl methanesulfonate.

4. The preparation method according to claim 3, characterized in that, In step S1, the molar ratio of isononol, triethylamine, 4-dimethylaminopyridine, and methanesulfonyl chloride is 1:(1.2-1.3):(0.02-0.03):(1.05-1.15).

5. The preparation method according to claim 1, characterized in that, In step S2, the alkali metal carbonate includes anhydrous potassium carbonate, and the physical dehydrating agent includes activated 4Å molecular sieve.

6. The preparation method according to claim 3, characterized in that, Step S2 specifically includes: Isonononanoic acid, anhydrous potassium carbonate, anhydrous acetonitrile, and activated 4Å molecular sieve were added to a reaction vessel equipped with a reflux condenser. The reaction was carried out under a nitrogen atmosphere at 75-90℃ and stirred for 150-210 min to obtain a suspension reaction system containing potassium isononanoate.

7. The preparation method according to claim 6, characterized in that, In step S2, the molar ratio of isonononic acid to anhydrous potassium carbonate is 1:(0.5-0.6), and the amount of molecular sieve added is 40%-60% of the mass of isonononic acid.

8. The preparation method according to claim 6, characterized in that, The iodide mentioned in step S3 includes potassium iodide, and the phase transfer catalyst includes tetrabutylammonium bromide; step S3 specifically includes: The isononyl methanesulfonate, potassium iodide, and tetrabutylammonium bromide obtained in step S1 were added to the suspension reaction system containing potassium isononate obtained in step S2. Nucleophilic substitution esterification reaction was carried out under a nitrogen atmosphere, at 80-95℃ and 300-600 r / min. The residual amount of isononyl methanesulfonate in the reaction system was dynamically detected by gas chromatography. When the normalized content of the chromatographic peak area of ​​isononyl methanesulfonate decreased to below 0.50%, the reaction was terminated to obtain a mixture including isononyl isononate.

9. The preparation method according to claim 8, characterized in that, Step S4 specifically includes: The mixture was cooled, filtered to remove solids, and the filter cake was washed with anhydrous acetonitrile. The filtrates were combined, and the acetonitrile was recovered at 50-60°C and 10-20 kPa to obtain crude isononyl isononanoate. The crude isononyl isononanoate was washed sequentially with deionized water and sodium chloride aqueous solution, and then dehydrated at 85-95°C and 3-7 kPa for 55-65 min. After that, it was purified by thin-film evaporation at an evaporation temperature of 150-160°C, a system pressure of 70-90 Pa, and a scraping speed of 250-350 r / min to obtain isononyl isononanoate.

10. The application of isononyl isononanoate prepared by any one of claims 1-9 in the fields of cosmetics and environmentally friendly plasticizers.

Images