Synthesis method of pentaerythritol triacrylate

Abstract

The invention provides a synthesis method of pentaerythritol triacrylate, which comprises the following steps: mixing pentaerythritol, an acid catalyst and a polymerization inhibitor, condensing, vacuumizing, blowing inert gas, and drying to obtain a mixture; taking a solvent, blowing inert gas into the solvent, and mixing and stirring the solvent with the inert gas and the mixture until the solvent is completely dissolved to obtain a mixed solution; under the dark condition, acrylic acid is added into the mixed solution, inert gas is blown into the mixed solution again, heating reflux reaction, standing and washing are carried out, and the product is obtained. According to the synthesis method, the problems of complex process and long time consumption of the existing production process are solved, meanwhile, the conversion rate of materials and the yield of products can be effectively improved, and the generated pentaerythritol triacrylate is high in selectivity and purity, clear in color, colorless, transparent, non-yellowing and relatively high in quality.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical synthesis, and specifically belongs to a method for synthesizing pentaerythritol triacrylate. Background Art

[0002] Pentaerythritol triacrylate (PET3A) is an important fine chemical raw material. Due to its multifunctional characteristics, it can form a cross-linked polymer network through free radical polymerization. This network structure gives coatings and inks excellent physical properties, such as high strength, wear resistance, and chemical resistance. In recent years, with the continuous deepening of research on PET3A, its application in various fields has also been further expanded. For example, in the field of coatings, researchers have successfully prepared modified coatings with excellent water resistance and mechanical properties by introducing PET3A as a functional monomer; in addition, due to its excellent cross-linking properties, it has also been used in the field of adhesives. By copolymerizing with other monomers, adhesives with excellent bonding properties and durability can be prepared. In the field of adhesives, the cross-linking properties of PET3A are used to prepare high-strength and durable adhesives; in the field of organic synthesis, the application of PET3A as a functional reagent has also made significant progress.

[0003] There are various preparation methods for PET3A, among which the acyl chloride method is a more common preparation method. The method is simple in principle, easy to operate, and has high product yield and purity. However, due to the high cost of raw materials such as acyl chlorides, and the toxicity and corrosiveness of raw materials such as acyl chlorides, it is greatly detrimental to the development concept of green production. The traditional esterification synthesis method uses pentaerythritol and acrylic acid as raw materials, with sufficient market supply and relatively low cost. However, the commercially available product obtained by the existing method has a low purity of about 35%, and the content of pentaerythritol tetraacrylate is high. The product also has a certain amount of residual mixed solvent, so solvent separation is required in the later stage, resulting in a cumbersome process. At present, selecting different reaction conditions and raw material selections during the synthesis process will lead to a decrease in the yield and selectivity of the product. Therefore, a new process for the synthesis of pentaerythritol triacrylate is urgently needed.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The first purpose of the present invention is to provide a method for synthesizing pentaerythritol triacrylate, which solves the problem that the existing production process is complicated and time-consuming, and can effectively improve the conversion rate of materials and the yield of products. At the same time, the generated pentaerythritol triacrylate has high selectivity and high purity, and the product color is clear, colorless and transparent without yellowing, and has high quality.

[0006] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted: The present invention provides a method for synthesizing pentaerythritol triacrylate, comprising the following steps: Pentaerythritol, an acid catalyst and a polymerization inhibitor are mixed, condensed, vacuumized, and blown into an inert gas to obtain a mixture; Taking a solvent, blowing an inert gas into the solvent, mixing the solvent blown with the inert gas with the mixture and stirring until they are completely dissolved, to obtain a mixed solution; In dark conditions, acrylic acid is added to the mixed solution, and inert gas is bubbled into the solution again, and the mixture is heated to reflux for reaction, and the mixture is allowed to stand and washed to obtain the product.

[0007] During the synthesis of pentaerythritol triacrylate, since pentaerythritol triacrylate itself is an ester compound containing multiple branched olefins, it is very easy to undergo molecular polymerization under air and high temperature conditions, resulting in deterioration, thereby reducing the reaction yield. Therefore, it is necessary to screen the reaction steps and conditions during the synthesis process.

[0008] In the present invention, pentaerythritol, an acid catalyst and an inhibitor are first mixed. The reason is that pentaerythritol itself is a solid, and pentaerythritol itself is incompatible with acrylic acid. When pentaerythritol and acrylic acid are first mixed, the solid will not dissolve and cannot react with acrylic acid. However, when pentaerythritol, an acid catalyst and an inhibitor are first mixed in a solvent, pentaerythritol can be fully dissolved, thereby fully reacting.

[0009] After pentaerythritol, the acid catalyst and the polymerization inhibitor are mixed, an inert gas is introduced into the mixture. The reason for this is that acrylic acid itself has a high reactivity and is easily oxidized in an air or oxygen atmosphere, resulting in deterioration and the production of by-products that are difficult to separate. Therefore, it is necessary to create an inert gas atmosphere in the reaction system in advance to ensure the stability of acrylic acid entering the reaction system.

[0010] The solvent is then mixed with the prepared reactants. In this step, inert gas also needs to be blown into the solvent to create an inert atmosphere before protection to prevent the inert gas from escaping, thereby reducing the effect of the reaction. In addition, the selected solvent is an organic solvent and does not contain water. From the perspective of chemical equilibrium, water will promote the reaction to occur in the forward direction, thereby reducing the yield of the product.

[0011] After adding the solvent, another reactant, acrylic acid, is added last. Acrylic acid itself is a photosensitive substance. If it is not protected from light during the reaction, it will be exposed to light for a long time and undergo a decomposition reaction, and then deteriorate. In the next step, an inert gas is introduced again. At this time, the inert gas can protect the acrylic acid itself and prevent it from being deteriorated by oxygen; at the same time, it can also protect the generated pentaerythritol triacrylate and prevent it from deteriorating under high temperature conditions.

[0012] In the present invention, washing can be done with salt or water, and a 1% sodium hydroxide aqueous solution, a 5% NaCl solution or distilled water can be selected.

[0013] Preferably, as a further specific embodiment, the molar ratio of pentaerythritol, acrylic acid, polymerization inhibitor and acid catalyst is 1: (3.0-3.6): (0.05): (0.05); The molar ratio of pentaerythritol to acrylic acid may be 3.0:1.0; 3.1:1.0; 3.2:1.0; 3.3:1.0; 3.4:1.0; 3.5:1.0; 3.6:1.0; Preferably, the molar ratio of pentaerythritol, acrylic acid, polymerization inhibitor and acid catalyst is 1:(3.3):(0.05):(0.05).

[0014] In the present invention, the ratio between the reactants involved in the reaction is limited. The most important is the molar ratio of acrylic acid to pentaerythritol. From the reaction formula, one equivalent of PET3A is generated, and three equivalents of acrylic acid are required. Therefore, when the ratio of acrylic acid to pentaerythritol is lower than 3.0:1.0, a large amount of monoester and diester products will be produced. When the ratio is greater than 3.6:1.0, the triester produced in the system will be further esterified to generate fully esterified tetraester byproducts. Therefore, in order to ensure the purity of the product, the molar ratio of pentaerythritol to acrylic acid should be controlled within the range of 1:(3.0-3.6); and when the molar ratio of pentaerythritol to acrylic acid is 1:3.3, the triester product generated can be guaranteed to be the largest, effectively improving the yield of the reaction. The acid catalyst itself catalyzes the reaction, and the inhibitor can effectively prevent the generation of polymerization. These two substances will cause unnecessary waste when they are excessive, and will lead to reduced catalytic effect or inhibition effect when they are too little.

[0015] Preferably, as a further specific embodiment, the inert gas is any one of argon or nitrogen; Preferably, the inert gas is argon.

[0016] When selecting an inert gas, in theory, any inert gas with a high density can meet the reaction conditions of the present invention. However, considering the cost and the availability of raw materials in the actual reaction process, nitrogen and argon, which are commonly used in laboratories, are preferred in the present invention. However, the effect of argon is significantly better than that of nitrogen because argon itself has a high density and will settle and protect the upper part of the liquid surface during the reaction, further ensuring an inert reaction environment.

[0017] Preferably, as a further specific embodiment, the reaction temperature of the heating reflux reaction is 100°C-145°C, and can be 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C; Preferably, the reaction temperature is 125°C.

[0018] In the present invention, the reaction temperature is also limited. The esterification reaction usually requires a higher temperature to achieve intermolecular dehydration reaction. When the temperature is too low, the carboxyl group and the hydroxyl group cannot achieve decarboxylation esterification, which will cause the reaction to be unable to proceed. Therefore, it is necessary to appropriately increase the temperature to accelerate the reaction rate, thereby promoting the probability of intermolecular collision; and when the temperature is too high, the acrylic acid in the reaction system and the several esterification products generated will undergo self-or cross-high temperature polymerization, resulting in the generation of a large amount of insoluble white polymer block solids in the reaction solution, greatly reducing the reaction efficiency and conversion rate. Therefore, when the reaction temperature is 100°C-145°C, it is the optimal reaction interval of the present invention. In this reaction interval, the efficiency of the reaction and the conversion rate of the reaction can be effectively improved; when the reaction temperature is 125°C, it is the optimal reaction temperature. At the optimal reaction temperature, the yield and conversion rate of the reaction are the highest.

[0019] Preferably, as a further specific embodiment, the reaction time of the heating reflux reaction is 1 h-9 h, and 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h can be selected; Preferably, the reaction time is 6 hours.

[0020] In the present invention, the reaction time will affect the conversion rate of the reaction and the selectivity of the main product PET3A, because the triester PET3A is obtained by further esterification of the diester byproduct. If the reaction time is too short, it will lead to low material conversion rate, low yield of the main product, and more monoester and diester products will be produced at the same time. If the reaction time is too long, the yield of the triester main product will also be reduced, because the generated triester product will further undergo esterification reaction with the unreacted acrylic acid in the system again to generate tetraesters, thereby reducing the yield and selectivity of the triester. Therefore, the optimum reaction time of the present invention is 1h-9h, at which the yield and selectivity of the triester can be guaranteed; and at the optimum reaction time, the yield and selectivity of the triester are the maximum.

[0021] Preferably, as a further specific embodiment, the ratio of the volume of acrylic acid to the volume of the solvent = 1: (5.0-10.3); Preferably, the volume ratio of the solvent to the acrylic acid is 8.1:1.0.

[0022] The volume of the solvent affects the reaction concentration and has a great influence on the dehydration between molecules. When the volume ratio of the reaction solvent to the volume of the acrylic acid is greater than 1:5.0, the concentration of the reactants in the solution will decrease, which will greatly slow down the probability and rate of collision between the reactant molecules; and when the volume of the reaction solvent is appropriately reduced, the concentration of the reactants will increase and the reaction rate will be increased. However, when the volume ratio of the solvent to the volume of the acrylic acid is less than 1:10.3, the too small reaction volume will lead to excessive local concentration, which is not conducive to the uniform reaction. At the optimal volume ratio, the probability and rate of collision between molecules are the highest, and the reaction rate is the fastest.

[0023] Preferably, as a further specific embodiment, the polymerization inhibitor is any one or more of hydroquinone or p-hydroxyanisole.

[0024] Preferably, as a further specific embodiment, the acid catalyst is any one or more of solid phosphoric acid, phosphoric acid, p-toluenesulfonic acid, camphorsulfonic acid or sulfuric acid; Preferably, the acid catalyst is p-toluenesulfonic acid.

[0025] In the present invention, hydroquinone or p-hydroxyanisole is used as an inhibitor, which can quickly terminate the oxidative free radicals in the reactants, thereby extending the inhibition period; and the acid catalyst can effectively reduce the activation energy of the reaction, thereby accelerating the reaction.

[0026] Preferably, as a further specific embodiment, the solvent is any one or more of benzene, toluene, ethyl acetate, DMF, DMAc, and tetrahydrofuran; Preferably, the solvent is toluene or a mixture of toluene and N,N-dimethylformamide in a volume ratio of (100:1)-(1:1); Preferably, toluene or toluene and N,N-dimethylformamide can be mixed in a volume ratio of (100:1), (50:1), (10:1), (5:1) or (1:1); Preferably, the solvent is toluene or a mixture of toluene and N,N-dimethylformamide in a volume ratio of 100:1; More preferably, the solvent is toluene.

[0027] In the present invention, when toluene is mixed with N,N-dimethylformamide, N,N-dimethylformamide can form a relatively stable microstructure with toluene, so that the reactant is better dissolved; however, N,N-dimethylformamide is easy to form steam during heating, thereby reducing the reaction efficiency. Therefore, when the proportion of N,N-dimethylformamide is low, the dissolution effect can be guaranteed while ensuring the reaction efficiency. When toluene is used alone, the solubility of the reactant can be guaranteed while not reducing the reaction effect.

[0028] Pentaerythritol triacrylate synthesized using the above-mentioned method for synthesizing pentaerythritol triacrylate.

[0029] Compared with the prior art, the present invention has the following beneficial effects: (1) Using an inert gas atmosphere instead of the traditional air atmosphere can effectively protect the reaction process and the products, while improving the quality of the products and increasing the reaction yield and efficiency.

[0030] (2) The reaction conditions, including reaction temperature, reaction time and the amount of reactants, were limited to improve the selectivity of the product and the water yield of the reaction, ensuring excellent selectivity for PET3A while achieving a high water yield.

[0031] (3) During the reaction process, strictly ensuring dry conditions without water or oxygen can improve the reaction yield according to the principle of reaction equilibrium. At the same time, establishing a dark environment can reduce the deterioration of the reactants and effectively improve the yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 : Pentaerythritol triacrylate H NMR spectrum; Figure 2 : Curve of the change of the water output volume over time for Schemes 1-8 in Example 1; Figure 3 : Curve of water yield variation over time for Schemes 1-8 in Example 1; Figure 4 : The selectivity curve of triesters of Schemes 1-8 in Example 1 over time; Figure 5 : Diagram of the reaction apparatus. DETAILED DESCRIPTION

[0033] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be appreciated by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work, all belong to the scope of protection of the present invention. If specific conditions are not indicated in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0034] Example 1

[0035] Weigh 1 mol of pentaerythritol, 0.05 mol of p-toluenesulfonic acid (acid catalyst), and 0.05 mol of hydroquinone (inhibitor), and put them into a 250 mL round-bottom flask to obtain a mixture, connect a water separator and a reflux condenser, evacuate and blow in argon, and then quickly dry.

[0036] 150 mL of toluene was taken and argon was bubbled into it by ultrasonic. The toluene and the mixture after the argon was bubbled were pre-stirred for 5 min to dissolve all the raw materials to obtain a mixed solution. Subsequently, 18.5 mL of 3.3 mol acrylic acid was added and argon was bubbled into it again.

[0037] The mixed raw materials were heated to 125°C and refluxed for 1h, 2h, 4h, 5h, 6h, 7h, 8h, and 9h, and the water yield at different reaction times was detected. The percentage of pentaerythritol triacrylate and pentaerythritol tetraacrylate was analyzed by liquid chromatography HPLC. The experimental results are shown in Table 1. The obtained pentaerythritol triacrylate was then allowed to stand, post-treated, and then washed with 10% sodium hydroxide aqueous solution to obtain the finished product. The conversion rate of the raw materials and the yield of triesters were then determined. The experimental results are shown in Table 1 and Figure 1-5 shown.

[0038] Table 1: Changes in the ratio of pentaerythritol triacrylate to pentaerythritol tetraacrylate, changes in raw material conversion rate and triester yield at different times by HPLC analysis

[0039] It can be seen from the above experimental results that Scheme 5, i.e. when the heating reflux reaction time is 6 hours, is the optimal scheme.

[0040] In the present invention, the evaluation index used is the water yield rate, which is obtained by measuring the water yield volume and then calculating the obtained water yield volume. The water yield rate can reflect the selectivity of a substance. The water yield volume refers to the fact that during the esterification reaction, one equivalent of pentaerythritol has four hydroxyl groups, one equivalent of acrylic acid has one carboxyl group, and one equivalent of PET3A produced requires three equivalents of acrylic acid and one equivalent of pentaerythritol for dehydration condensation to produce three equivalents of water. During the reaction process, we use the water separator in the reaction device to intuitively observe the volume of water produced by the reaction, thereby converting it into the amount of water, which is further converted into the conversion rate of the reaction. The higher the water yield rate, the better. After detailed demonstration, the selectivity is highest when the water yield rate is around 70%; based on the above reaction process, too high or too low water yield rates will affect the selectivity of pentaerythritol triacrylate. The selectivity in a chemical reaction is an important indicator for evaluating the specificity of a chemical reaction that can produce multiple products.

[0041] In Scheme 1 and Scheme 2, the reaction system has just started to react, and there are a large amount of pentaerythritol monoacrylate (hereinafter referred to as monoester) and pentaerythritol diacrylate (hereinafter referred to as diester) in the reaction system, and the two have not yet started to undergo further conversion, so there is no pentaerythritol triacrylate (hereinafter referred to as triester) and pentaerythritol tetraacrylate (hereinafter referred to as tetraester) in the reaction system. However, since monoester and diester are continuously generated during the reaction, water will continuously be produced in the reaction system.

[0042] In Scheme 3 and Scheme 4, although the diester in the reaction system will be converted into a large amount, making the proportion of triester higher, there are still a large amount of raw materials remaining in the reaction system and the reaction has not reached equilibrium. If the product is removed at this time, the chemical equilibrium will change, resulting in a decrease in the yield of the product. Therefore, the effects of Scheme 3 and Scheme 4 are slightly inferior to Scheme 5.

[0043] In Schemes 7 and 8, the reaction equilibrium is reached, and the yield of triesters is relatively high at this time. However, due to the long reaction time and high water yield, the triester products generated will further undergo esterification reaction with the unreacted acrylic acid in the system to generate tetraesters, thereby reducing the yield and selectivity of triesters. Therefore, the reaction effect is slightly inferior to that of Scheme 5.

[0044] Example 2 The specific implementation method is consistent with Scheme 5 of Example 1, the molar ratio of pentaerythritol, acrylic acid, hydroquinone and p-toluenesulfonic acid. The change of the molar ratio will affect the water yield, triester yield and raw material conversion rate of the reaction.

[0045] In the present invention, the calculation formula of raw material conversion rate is: Raw material conversion rate = (pentaerythritol monoacrylate + pentaerythritol diacrylate + pentaerythritol triacrylate + pentaerythritol tetraacrylate) / pentaerythritol × 100%.

[0046] The raw material conversion rate can well reflect the effect of chemical reactions, and can reflect the degree and efficiency of the reaction. The higher the raw material conversion rate, the more complete the reaction is and the higher the efficiency of the reaction.

[0047] The triester yield in the present invention is obtained by HPLC monitoring.

[0048] The specific changes are shown in Table 2, and the experimental results are shown in Table 2 and Table 2-1.

[0049] Table 2: Changes in the amount and molar ratio of pentaerythritol, acrylic acid, hydroquinone and p-toluenesulfonic acid

[0050] Table 2-1: Water yield and HPLC analysis of pentaerythritol triacrylate to pentaerythritol tetraacrylate ratio, yield and purity at different molar ratios of pentaerythritol, acrylic acid, hydroquinone and toluenesulfonic acid

[0051] In Example 2, the molar ratio of pentaerythritol, acrylic acid, hydroquinone and toluenesulfonic acid was changed. It can be seen from the reaction formula that three equivalents of acrylic acid are required to generate one equivalent of triester. Therefore, when the molar ratio of pentaerythritol to acrylic acid is maintained at 1: (3.0-3.6), the water yield will be maintained within a relatively reasonable range, and the amount of triester generated is relatively high; and when the molar ratio of pentaerythritol to acrylic acid is 1: 3.3, the yield and selectivity of triester are both optimal. When the ratio of acrylic acid to pentaerythritol is lower than 3.0: 1.0, a large amount of monoester and diester products will be produced, and the water yield is high at this time, which will reduce the selectivity and yield of triester; and when the ratio of acrylic acid to pentaerythritol is greater than 3.6: 1, the triester is further esterified to generate fully esterified tetraester by-products, and the selectivity and yield of triester will also decrease.

[0052] The amount of polymerization inhibitor and acid catalyst does not affect the water output rate of the reaction system. However, when the amount of catalyst is too small, it is not conducive to reducing the activation energy of the reaction system and will increase the reaction time invisibly. When the content of polymerization inhibitor is too low, the raw materials will polymerize and produce high molecular polymers, resulting in a decrease in the yield of triesters. Excessive amounts of polymerization inhibitor and acid catalyst will cause unnecessary waste and be detrimental to the development of green chemistry. Example 3 The specific implementation method is consistent with Scheme 5 of Example 1, and the inert gas of the reaction system is changed as shown in Table 3.

[0053] Table 3: Changes in inert gas

[0054] In the present invention, nitrogen, helium or argon can be used to protect the reaction system. Considering the cost and availability in the laboratory, argon is finally selected as the protective gas. The density of argon is greater than that of nitrogen. During the reaction, it will settle on the liquid surface to protect it, creating a better inert gas atmosphere, which is more conducive to the reaction system.

[0055] Example 4 The specific implementation method is consistent with Scheme 5 of Example 1, and the reaction temperature is changed, as shown in Table 4.

[0056] It was found through experiments that the change in temperature did not affect the water yield of the product, and the water yield was generally consistent with that of Scheme 5 of Example 1; the change in temperature mainly affected the yield of triesters and the conversion rate of raw materials in the reaction system.

[0057] In this example, the determination method and calculation formula of triester yield and raw material conversion rate are consistent with those in Example 2.

[0058] Table 4: Effect of changing the reaction temperature on the conversion rate and yield of the reaction

[0059] In the present invention, the reaction temperature will affect the conversion rate and reaction rate of the reaction raw materials. When the reaction temperature is low, it is difficult to react, the carboxyl group and the hydroxyl group cannot achieve decarboxylation esterification, and the dehydration reaction between molecules cannot be carried out. Therefore, it is necessary to appropriately increase the temperature during the reaction to promote the collision probability between molecules and accelerate the reaction rate; but the reaction temperature should not be too high. When the temperature is high, acrylic acid and several esterification products generated will undergo self-or cross-high temperature polymerization, resulting in the generation of a large amount of insoluble white polymer block solids in the reaction solution, which will not only reduce the efficiency and conversion rate of the reaction, but also reflect from the experimental data that the purity of triesters decreases, that is, the yield of triesters decreases.

[0060] Example 5 The specific implementation method is consistent with Scheme 5 of Example 1. The volume ratio of toluene and acrylic acid is changed as shown in Table 5. The experimental results are shown in Table 5-1.

[0061] Through experiments, it was found that the change in the volume ratio of solvent to acrylic acid did not affect the water yield of the reaction, and the water yield and conversion rate were basically consistent with the data of Scheme 5 of Example 1; the change in the volume ratio of solvent to acrylic acid affected the yield of triester and the conversion rate of raw materials, and the calculation formula was consistent with Example 2.

[0062] Table 5: Volume changes of solvent and acrylic acid

[0063] Table 5-1: Conversion rate of reaction raw materials and yield of triesters at different volumes

[0064] Changes in reaction volume will affect changes in the concentration of the entire reaction system and have a greater impact on dehydration between molecules. When the volume of the reaction system is too large, the concentration of the reactants will be reduced, reducing the probability and rate of collision between molecules, thereby extending the reaction time and causing the water output rate of the reaction to decrease. When the volume of the reaction system is small, the concentration of the reactants in the reaction system becomes higher, and since the entire reaction system is not a uniform system during the reaction, it will lead to excessive local concentrations, resulting in a higher content of by-products and a decrease in the yield of triesters.

[0065] Example 6 The specific implementation method is consistent with Scheme 5 of Example 1, and the reaction raw materials are changed, as shown in Table 6. The experimental results are shown in Table 6-1.

[0066] When the raw materials of the reaction are changed but are still the raw materials selected by the present invention, the water output rate of the system and the percentage of pentaerythritol triacrylate and pentaerythritol tetraacrylate will be affected, but at this time the yield of triesters and the conversion rate of the raw materials are basically the same as those of Scheme 5 of Example 1.

[0067] Table 6: Changes in the water yield and ratio of pentaerythritol triacrylate to pentaerythritol tetraacrylate by HPLC analysis after raw material changes

[0068] In the present invention, the selection of raw materials will affect the water yield, especially the selection of solvent. When toluene and N,N-dimethylformamide are mixed, the two may form some molecular bonds during the reaction, and these molecular bonds will eventually affect the water yield of triester.

[0069] Although the catalyst and polymerization inhibitor selected by the present invention themselves also have an impact on the water yield of triesters, the impact is not significant. When other catalysts and polymerization inhibitors are used, the selectivity and yield of the product will be reduced.

[0070] Comparative Example 1 The specific implementation method is the same as that of Scheme 5 of Example 1, and the reaction is carried out in an oxygen environment.

[0071] Comparative Example 2 Pentaerythritol triacrylate is synthesized by using acrylic acid and pentaerythritol for eleven hours, and then undergoes the process of water washing, alkali neutralization, extraction, water washing, and then desolventizing, and finally separating the solvent to obtain the product.

[0072] Table 7: Comparison of experimental results of Example 1, Scheme 5, Comparative Examples 1 and 2

[0073] Based on the above data, we can draw the following conclusions: It can be seen from the experimental data of the embodiments and comparative examples that in the present invention, the reaction temperature, time, raw material selection, the ratio between the raw materials and the choice of the reaction environment affect many factors, such as the yield of triesters, the water yield and the conversion rate of the raw materials, etc., and the change of a certain condition will affect different factors. Therefore, in the present invention, it is necessary to improve the synthesis method to ensure that the various factors can be balanced, so as to achieve high selectivity, high purity, high yield and high conversion rate of the reaction product; at the same time, the reaction steps should be simplified so that the generated pentaerythritol triacrylate product has a clear color, is colorless and transparent, and does not turn yellow, and has a high quality.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for synthesizing pentaerythritol triacrylate, characterized in that: The steps include: Pentaerythritol, an acid catalyst and a polymerization inhibitor are mixed, condensed, vacuumized, and blown into an inert gas to obtain a mixture; Taking a solvent, blowing an inert gas into the solvent, mixing the solvent blown with the inert gas with the mixture and stirring until they are completely dissolved, to obtain a mixed solution; In dark conditions, acrylic acid is added to the mixed solution, and inert gas is bubbled into the solution again, and the mixture is heated to reflux for reaction, and the mixture is allowed to stand and washed to obtain the product.

2. The method for synthesizing pentaerythritol triacrylate according to claim 1, characterized in that: The molar ratio of pentaerythritol, acrylic acid, polymerization inhibitor and acid catalyst is 1: (3.0-3.6): (0.05): (0.05); Preferably, the molar ratio of pentaerythritol, acrylic acid, polymerization inhibitor and acid catalyst is 1:(3.3):(0.05):(0.05).

3. The method for synthesizing pentaerythritol triacrylate according to claim 1, characterized in that: The inert gas is any one of argon or nitrogen; Preferably, the inert gas is argon.

4. The method for synthesizing pentaerythritol triacrylate according to claim 1, characterized in that: The reaction temperature of the heating reflux reaction is 100°C-145°C; Preferably, the reaction temperature is 125°C.

5. The method for synthesizing pentaerythritol triacrylate according to claim 1, characterized in that: The reaction time of the heating reflux reaction is 1h-9h; Preferably, the reaction time is 6 hours.

6. The method for synthesizing pentaerythritol triacrylate according to claim 1, characterized in that: The ratio of the volume of the acrylic acid to the volume of the solvent = 1: (5.0-10.3); Preferably, the volume ratio of the solvent to the acrylic acid is 8.1:1.

0.

7. The method for synthesizing pentaerythritol triacrylate according to claim 1, characterized in that: The polymerization inhibitor is any one or more of hydroquinone or p-hydroxyanisole.

8. The method for synthesizing pentaerythritol triacrylate according to claim 1, characterized in that: The acid catalyst is any one or more of solid phosphoric acid, phosphoric acid, p-toluenesulfonic acid, camphorsulfonic acid or sulfuric acid; Preferably, the acid catalyst is p-toluenesulfonic acid.

9. The method for synthesizing pentaerythritol triacrylate according to claim 1, characterized in that: The solvent is any one or more of benzene, toluene, ethyl acetate, DMF, DMAc, and tetrahydrofuran; Preferably, the solvent is toluene or a mixture of toluene and N,N-dimethylformamide in a volume ratio of (100:1)-(1:1); Preferably, the solvent is toluene or a mixture of toluene and N,N-dimethylformamide in a volume ratio of 100:1; More preferably, the solvent is toluene.

10. Pentaerythritol triacrylate synthesized by the method for synthesizing pentaerythritol triacrylate according to any one of claims 1 to 9.

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