Sorbitol diacetal nucleating agent and preparation method thereof

Abstract

The invention relates to a sorbitol diacetal nucleating agent and a preparation method thereof, the sorbitol diacetal nucleating agent is 1, 3: 2, 4-bis (3, 4-dimethylbenzylidene) sorbitol, sorbitol and 3, 4-dimethylbenzaldehyde are used as raw materials, aldol condensation is carried out under the action of an acid catalyst, after the reaction is completed, quenching is carried out with an ammonia methanol solution, and the 1, 3: 2, 4-bis (3, 4-dimethylbenzylidene) sorbitol is prepared. The melting point of the nucleating agent is 273 DEG C or above, a yellow eliminating agent is not added when the nucleating agent is applied to polyolefin, and the yellow index is low.

Description

Technical Field

[0001] This invention relates to the field of material additives, and more particularly to a high-performance transparent nucleating agent 1,3:2,4-bis(3,4-dimethylbenzyl)sorbitol and its preparation method. Background Technology

[0002] Polyolefin polymers such as polyethylene and polypropylene are widely used due to their advantages of being lightweight, inexpensive, non-toxic, odorless, and easy to process. Sorbitol acetal-based transparent nucleating agents for polypropylene can improve the transparency and overall mechanical properties of ordinary polypropylene. Third-generation sorbitol acetal-based transparent nucleating agents for polypropylene exhibit particularly outstanding performance. A representative example is the condensate of sorbitol and 3,4-dimethylbenzaldehyde (CAS: 135861-56-2, chemical name: 1,3:2,4-di(3,4-dimethylbenzyl)sorbitol, industry grade 3988), which results in PP transparent packaging products with minimal odor and odor migration, making them safe for use as transparent packaging materials, and highly suitable for food packaging and odor-sensitive packaging.

[0003] CN1511160A discloses a preparation method using inorganic acid as a catalyst and adding surfactant to carry out condensation in water. However, a large amount of powder is formed in the later stage of the reaction, which cannot be stirred, and the yield is only 65%~80%, resulting in low utilization of raw materials.

[0004] CN101434607A discloses a preparation method using p-toluenesulfonic acid as a catalyst, cyclohexane and methanol as solvents, a ternary azeotropic dehydration reaction followed by quenching, reflux with cyclohexane / isopropanol for 1 hour followed by filtration, and purification with acetone to obtain the product, with a yield of less than 80% and a melting point of less than 260℃.

[0005] The sorbitol-3,4-dimethylbenzaldehyde condensate disclosed in the prior art has low yield and low melting point. Summary of the Invention

[0006] To address the technical problems mentioned in the background art, this invention provides a method for preparing 1,3:2,4-bis(3,4-dimethylbenzyl)sorbitol. The product obtained has a high melting point and can exhibit good anti-yellowing effects in polyolefins without the need for the addition of anti-yellowing agents.

[0007] The first aspect of this invention provides a method for preparing a sorbitol diacetal nucleating agent, wherein the sorbitol diacetal nucleating agent is 1,3:2,4-di(3,4-dimethylbenzyl)sorbitol. The method uses sorbitol and 3,4-dimethylbenzaldehyde as raw materials, and performs aldol condensation under the action of an acid catalyst. After the reaction is completed, the reaction is quenched with ammonia-methanol solution to obtain 1,3:2,4-di(3,4-dimethylbenzyl)sorbitol.

[0008] In-depth research revealed that the melting point of the nucleating agent is related to the product preparation process. When the product completes the reaction, the material is in a near-gel state, during which some of the catalyst is encapsulated, making it difficult to remove in subsequent processes such as refining or purification. The residue of acidic catalyst has a certain impact on product performance, especially leading to a low melting point. This application found that using ammonia-methanol solution as a quencher can effectively remove the acidic catalyst, minimizing the acidic substances in the resulting product and allowing it to achieve a melting point above 273°C.

[0009] In one specific embodiment, an ammonia-methanol solution is used to quench the reaction, with the volume-to-weight (v / w, ml / g) ratio of the ammonia-methanol solution to the sorbitol being 0.5 to 1:1. For example, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, and 1:1. The ammonia-methanol solution allows for sufficient contact with the residual catalyst, effectively removing it. Controlling the amount of ammonia-methanol within the above range maximizes the efficiency of removing residual acidic catalyst.

[0010] In one specific embodiment, the ammonia content in the ammonia-methanol solution is 5% to 20% by weight (i.e., the concentration of ammonia in methanol), which is more effective.

[0011] Preferably, the ammonia content in the ammonia-methanol solution is 5% to 15% by weight.

[0012] In one specific embodiment, the reaction is carried out in a mixed solvent, which includes a mixture of a nonpolar solvent and a polar solvent. Preferably, the nonpolar solvent is one or more of n-hexane, cyclohexane, toluene, and xylene; and the polar solvent is one or more of methanol, ethanol, and isopropanol.

[0013] For example, the mixed solvent in the reaction is cyclohexane and methanol, or cyclohexane and ethanol. The mixed solvent in the reaction system can form a ternary azeotropic system with water, carrying water out of the reaction mixture, which is beneficial to the forward reaction and promotes its progress.

[0014] Preferably, in the mixed solvent, the volume ratio (v / v) of the nonpolar solvent to the polar solvent is 1:0.1 to 1, for example, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, and any value between them. Controlling the proportion of the mixed solvent within this range can improve the stability of the reaction system, ensure that the reactants and catalysts are fully dissolved, and achieve the best reaction efficiency.

[0015] In one specific embodiment, the acid catalyst is selected from one or more of benzenesulfonic acid, p-toluenesulfonic acid, or 4-n-dodecylbenzenesulfonic acid. The catalyst used to prepare the nucleating agent is not particularly limited. For better results, the quenching agent should be able to effectively remove residual catalyst. The catalyst is selected from the above-mentioned components, and the optimal effect is achieved when the weight ratio (wt / wt) of the acid catalyst to sorbitol is in the range of 0.2~1:20~30. For example, the weight ratio of the acid catalyst to sorbitol can be 0.2:20~30, 0.3:20~30, 0.5:20~30, 0.8:20~30, 1:20~30, and any value between them.

[0016] In one specific embodiment, the weight ratio of sorbitol to 3,4-dimethylbenzaldehyde is 20-30:27-40. The amounts of the two raw materials can be any amounts known to those skilled in the art that enable the reaction. Generally, controlling the amount of 3,4-dimethylbenzaldehyde to be in excess is more conducive to the reaction; for example, the weight ratio (wt / wt) of sorbitol to 3,4-dimethylbenzaldehyde is 20:27-40, 25:27-40, 30:27-40, and any value between them.

[0017] In a specific embodiment of the present invention, the preparation method of the nucleating agent 1,3:2,4-bis(3,4-dimethylbenzyl)sorbitol further includes a purification step: dispersing the crude product in an ammonia-methanol solution or an ammonia-water methanol solution, stirring, filtering, and drying to obtain the product.

[0018] In one specific embodiment, in the refining process, the volume-to-weight ratio (v / w) of the ammonia-methanol solution or the methanol solution of ammonia water to the sorbitol is 10-20:1. For example, 10:1, 12:1, 15:1, 18:1, 20:1, and any value between them.

[0019] The ammonia-methanol solution contains 5% to 20% by weight of ammonia, preferably 5% to 15%. The volume fraction of the ammonia-methanol solution is 10% to 25%.

[0020] In one specific embodiment, the drying temperature is 80-100°C.

[0021] In one specific embodiment, the present invention provides a method for preparing the nucleating agent 1,3:2,4-bis(3,4-dimethylbenzyl)sorbitol, comprising the following steps: A. Preparation process: Weigh 20-30 parts of sorbitol, 27-40 parts of 3,4-dimethylbenzaldehyde, 0.2-1 parts of acid catalyst, 96-230 parts of non-polar solvent, and 40-160 parts of polar solvent and add them to the reactor. Create a slightly positive pressure environment with nitrogen gas, and heat and stir. React at 50-100℃ for 4-8 hours. After the reaction is completed, cool to 0℃, add 10-20 parts of ammonia-methanol solution, stir, and filter to obtain the crude product.

[0022] B. Refining process: Disperse the crude product in an ammonia-methanol solution or an ammonia-water-methanol solution (200-300 parts by weight), stir for 0.5-1 hour, and filter. Dry at 80-100℃ to obtain the final product.

[0023] In one specific embodiment, the nucleating agent 1,3:2,4-bis(3,4-dimethylbenzylene)sorbitol has a melting point of 273°C or higher. For example, any value between 273°C, 274°C, and 275°C.

[0024] Preferably, the melting range of the sorbitol diacetal nucleating agent is an initial melting point of 273.0~274.0℃ and a final melting point of 274.0~275.5℃, that is, the melting range of the sorbitol diacetal nucleating agent is 0.5~1.5℃.

[0025] The second aspect of the present invention provides a sorbitol diacetal nucleating agent, wherein the nucleating agent is 1,3:2,4-di(3,4-dimethylbenzyl)sorbitol, having the structural formula of compound I, and a melting point greater than 273°C.

[0026]

[0027] Formula I Studies have found that the sorbitol diacetal nucleating agents shown in Formula I of the existing technology have low melting points. Further research has revealed a correlation between the performance of the product shown in Formula I and its melting point. When the melting point of the product is above 273°C, it can inhibit the yellowing of polyolefin materials and has a low yellow index when applied to polyolefin materials.

[0028] In one specific embodiment, the melting point of the sorbitol diacetaldehyde nucleating agent is any value between 273°C, 274°C, and 275.5°C. Preferably, the melting point of the sorbitol diacetaldehyde nucleating agent is 273~275°C.

[0029] In one specific embodiment, the initial melting point of the sorbitol diacetal nucleating agent is 273.0~274.0℃, and the final melting point is 274.0~275.5℃, that is, the melting range of the sorbitol diacetal nucleating agent is 0.5~1.5℃.

[0030] Preferably, the sorbitol diacetal nucleating agent with a melting point greater than 273°C is prepared by the preparation method described in the first aspect of the present invention.

[0031] A third aspect of the present invention provides a composition comprising a polyolefin and 1,3:2,4-di(3,4-dimethylbenzyl)sorbitol obtained by the above-described melting point preparation method.

[0032] The polyolefins include polyethylene (PE), polypropylene (PP), polybutene (PB), and polyisobutylene (PIB), such as at least one of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), homopolymer polypropylene, and copolymer polypropylene.

[0033] In one specific embodiment, the amount of 1,3:2,4-bis(3,4-dimethylbenzylene)sorbitol added to the polyolefin is 0.05% to 1%. For example, 0.05%, 0.1%, 0.15%, 0.2%, 0.3%, 0.4%, 0.5%, and any value between these values.

[0034] The fourth aspect of the present invention provides the use of the nucleating agent obtained by the preparation method of the first aspect, the nucleating agent of the second aspect, and the composition of the third aspect as a transparent nucleating agent in polyolefin products.

[0035] Preferably, in the application, the nucleating agent is added at a rate of 0.05% to 1% of the mass of the polyolefin.

[0036] The present invention achieves the following positive effects: The sorbitol acetal nucleating agent of the present invention is white, odorless, and has a melting point above 273°C. When applied to polyolefins, no anti-yellowing agent is needed, and the yellow index is below 1.5. The nucleating agent product prepared using the preparation process of the present invention has a yield of over 95% and a purity of over 98%. It features a simple preparation process, easily controllable reaction conditions, high product yield and purity, high melting point, high whiteness, and ease of industrial production. Detailed Implementation

[0037] The present invention will be described in detail below with reference to specific embodiments, but it should be noted that the scope of protection of the present invention is not limited by these specific embodiments and principle explanations.

[0038] All features disclosed in this invention can be combined arbitrarily, and such combinations should be understood as the contents disclosed or recorded in this invention, unless those skilled in the art consider such combinations to be obviously unreasonable.

[0039] The numerical points disclosed in this specification include not only the numerical points specifically disclosed in the embodiments, but also the endpoints of each numerical range in the specification. Any combination of these numerical points should be regarded as the range disclosed or recorded in this invention.

[0040] As described in the background section, adding nucleating agents to polyolefins improves product transparency. CN102757601A discloses a method for preparing transparent polypropylene masterbatch material, using Milliken's 3988 as a transparent nucleating agent, combined with anti-yellowing agent ZC-02, which can reduce the yellow index to around 2.2. This indicates that Milliken's 3988 alone, without the anti-yellowing agent, cannot produce polypropylene masterbatch material with a low yellow index. Research has found that 1,3:2,4-di(3,4-dimethylbenzylene)sorbitol darkens in color with increasing temperature, especially above 200°C. This is related to its yellowing at high temperatures when used in polyolefins. This application addresses the issue of inhibiting yellowing of 1,3:2,4-di(3,4-dimethylbenzylene)sorbitol under high-temperature heating. By controlling the melting point and melting range of the product, it is possible to inhibit yellowing of polyolefin materials without adding an anti-yellowing agent.

[0041] In this invention, the technical and scientific terms that are given a definition shall be used as defined thereon, and those that are not given a definition shall be understood according to their common meaning in the art.

[0042] Melting range refers to the temperature range from when a substance begins to melt to when it is completely melted. Specifically, it is the temperature interval between the initial melting temperature (the temperature at which the liquid phase begins to appear) and the final melting temperature (the temperature at which the substance is completely transformed into a liquid phase).

[0043] Unless otherwise indicated, the terms “comprising” and “including” as used herein are used in their open, non-restrictive sense.

[0044] As used herein, the terms “compound” and “one or more compounds of the invention” are used interchangeably to indicate any compound specifically or generally disclosed herein, including its acceptable salts, hydrates, or solvates. In one embodiment, the compounds of the invention are compounds of Formula I or variations thereof, as well as their hydrates or solvates.

[0045] As used herein, the term "mmol" is intended to mean millimole. The term "mL" is intended to mean milliliters. The term "g" is intended to mean grams. The term "kg" is intended to mean kilograms. The term "μg" is intended to mean micrograms. The term "h" is intended to mean hours. The term "min" is intended to mean minutes. The term "M" is intended to mean moles. The term "μL" is intended to mean microliters. The term "wt / wt" is intended to mean weight / weight. The term "v / v" is intended to mean volume / volume. The term "v / w" is intended to mean volume / weight. The term "MS" is intended to mean mass spectrometry. The term "HPLC" is intended to mean high-performance liquid chromatography.

[0046] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. Example 1

[0047] 100 mL of toluene and 60 mL of ethanol were added to a four-necked flask, along with 20 g of sorbitol (0.11 mol), 35 g of 3,4-dimethylbenzaldehyde (0.26 mol), and 1 g of p-toluenesulfonic acid. The mixture was heated and stirred under nitrogen protection. After reflux, the water and ethanol mixture was separated using a liquid-liquid separator. After reacting for 6 hours, the mixture was cooled to 0-5°C. Ammonia-methanol solution (15%, 10 mL) was added to the reaction flask, and the mixture was stirred for 1 hour and filtered. The filter cake was slurried with ammonia-methanol solution (20% ammonia by volume, 150 mL) for 1 hour, filtered, and dried at 80°C. The product yield was 96.4%, purity (HPLC area normalized) was 98.3%, melting point (transmitted melting point apparatus) was 273.2-274.1°C, and whiteness was 99.1. Example 2

[0048] 200 mL of cyclohexane and 60 mL of methanol were added to a four-necked flask, along with 20 g of sorbitol, 33 g of 3,4-dimethylbenzaldehyde, and 0.5 g of 4-dodecylbenzenesulfonic acid. The mixture was heated and stirred under nitrogen protection. After reflux, the water and methanol mixture was separated using a liquid-liquid separator. After reacting for 6 hours, the mixture was cooled to 0-5°C. An 8% ammonia-methanol solution (16 mL) was added to the reaction flask, and the mixture was stirred for 1 hour and then filtered. The filter cake was slurried with an 8% ammonia-methanol solution (150 mL) for 1 hour, filtered, and dried at 80°C. The product yield was 97.2%, purity was 99.1%, melting point was 273.8-275.0°C, and whiteness was 98.9. Example 3

[0049] 180 mL of cyclohexane and 60 mL of ethanol were added to a four-necked flask, along with 20 g of sorbitol, 29 g of 3,4-dimethylbenzaldehyde, and 0.7 g of 4-dodecylbenzenesulfonic acid. The mixture was heated and stirred under nitrogen protection. After reflux, a mixture of water and methanol was separated using a liquid-liquid separator. The reaction was allowed to proceed for 6 hours, then cooled to 0-5°C. Ammonia-methanol solution (6%, 10 mL) was added to the reaction flask, and the mixture was stirred for 1 hour and filtered. The filter cake was then slurried with ammonia-methanol solution (5% ammonia by weight, 200 mL) for 1 hour, filtered, and dried at 80°C. The product yield was 96.5%, purity 99.3%, melting point 273.0-275.1°C, and whiteness 98.6. Example 4

[0050] Add 130 mL of toluene and 60 mL of methanol to a four-necked flask, along with 20 g of sorbitol, 32 g of 3,4-dimethylbenzaldehyde, and 0.8 g of p-toluenesulfonic acid. Under nitrogen protection, heat and stir. After reflux, separate the water and ethanol mixture using a liquid-liquid separator. After reacting for 6 hours, cool to 0-5°C. Add 18 mL of 6% ammonia-methanol solution to the reaction flask, stir for 1 hour, and filter. Pulverize the filter cake with 200 mL of ammonia-methanol solution (25% ammonia by volume) for 1 hour, filter, and dry at 80°C. Product yield: 96.9%, purity: 98.8%, melting point: 273.7-274.4°C, whiteness: 98.7. Comparative Example 1

[0051] The feed ratio and reaction process were the same as in Example 2. After cooling, an ammonia-methanol solution (8%, 16 mL) was added to the reaction flask, stirred for 1 hour, and then filtered. The filter cake was slurried with methanol solution (150 mL) for 1 hour, filtered, and then dried at 80°C. The product yield was 95.4%, purity was 99.0%, melting point was 226.8-229.3°C, and whiteness was 98.2. Comparative Example 2

[0052] The feed ratio and reaction process were the same as in Example 3. After cooling, an ammonia-methanol solution (6%, 6 mL) was added to the reaction flask, stirred for 1 hour, and then filtered. The filter cake was slurried with an ammonia-methanol solution (5% ammonia by weight, 200 mL) for 1 hour, filtered, and then dried at 80°C. The product yield was 96.2%, purity was 98.7%, melting point was 239.7-241.0°C, and whiteness was 98.0. Comparative Example 3

[0053] The feed ratio and reaction process were the same as in Example 1. After cooling, methanol (16 mL) and sodium bicarbonate (3.5 g) were added to the reaction flask, stirred for 0.5 hours, and filtered. The filter cake was slurried with methanol (150 mL) for 1 hour, filtered, and dried at 80°C. The product yield was 96.7%, purity was 98.6%, melting point was 218.3-220.2°C, and whiteness was 97.6.

[0054] Application Testing: Preparation and Performance Testing of Transparent Polypropylene The relevant test standards and methods in the embodiments are as follows:

[0055] GB / T3682-2000: National Standard for Melt Index Test.

[0056] GB / T1040-1992: National Standard for Tensile Strength Test

[0057] GB / T2410-2000: National Standard for Haze Testing.

[0058] GB / T2410-2000: National Standard for Light Transmittance Testing.

[0059] GB / T2409-1998: National Standard for Yellow Index Testing.

[0060] ISO 75-2:1993: Standard for testing heat distortion temperature.

[0061] Transparent polypropylene was prepared by uniformly mixing a prepared or commercially available transparent nucleating agent, antioxidant 1010, antioxidant 168, calcium stearate, and polypropylene matrix resin in a mass ratio of 2:3:0.5:1:0.5:1000 in a high-speed mixer. The mixture was then extruded through a twin-screw extruder to obtain transparent polypropylene. The temperatures of each zone from the feed port to the die head of the extruder were 190℃, 200℃, 210℃, 218℃, 210℃, 200℃, and 190℃, respectively.

[0062] The performance indicators of the prepared polypropylene are as follows.

[0063] Test Project Melting point ℃ Tensile strength (MPa) Haze% transmittance % Yellow Index Heat distortion temperature (°C) Commercially available product 3988-1 241.6-242.7 35 5.4 90 2.9 112 Commercially available product 3988-2 254.3-255.6 33 5.7 92 2.7 110 Comparative Example 1 226.8-229.3 31 5.7 92 3.3 108 Example 1 273.2-274.1 34 5.5 90 0.9 115 Example 2 273.8-275.0 35 5.4 93 1.1 111 Example 3 273.0-273.9 35 5.3 91 1.5 118 Example 4 273.7-274.4 34 5.4 90 0.9 114 The products obtained using the embodiments of the present invention all meet the following requirements: Yield: 95%~98% Purity: greater than 98% (HPLC area normalized). Whiteness WI: greater than 98 Melting point (transmitted melting point apparatus): greater than 273℃.

[0064] As can be seen from the table above, the transparent polypropylene using the transparent nucleating agent of this invention has excellent physical properties. Its tensile strength, haze, light transmittance and heat distortion temperature are comparable to those of commercially available competing products, but the yellow index is significantly reduced.

[0065] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing sorbitol diacetal nucleating agents, characterized in that, The nucleating agent is 1,3:2,4-di(3,4-dimethylbenzyl)sorbitol. The method uses sorbitol and 3,4-dimethylbenzaldehyde as raw materials to carry out aldol condensation under the action of acid catalyst. After the reaction is completed, the reaction is quenched with ammonia methanol solution to obtain 1,3:2,4-di(3,4-dimethylbenzyl)sorbitol.

2. The preparation method according to claim 1, characterized in that, The volume-to-weight ratio of the ammonia-methanol solution to the sorbitol solution is 0.5 to 1:1; preferably, the ammonia content in the ammonia-methanol solution is 5% to 20% by weight.

3. The preparation method according to claim 1, characterized in that, The reaction is carried out in a mixed solvent, which is a mixture of nonpolar and polar solvents; preferably, the nonpolar solvent is one or more of n-hexane, cyclohexane, toluene, and xylene; the polar solvent is one or more of methanol, ethanol, and isopropanol; and / or, the weight ratio of sorbitol to 3,4-dimethylbenzaldehyde is 20-30:27-40.

4. The preparation method according to claim 1, characterized in that, The acid catalyst is selected from one or more of benzenesulfonic acid, p-toluenesulfonic acid, or 4-n-dodecylbenzenesulfonic acid; preferably, the weight ratio of the acid catalyst to sorbitol is 0.2~1: 20~30.

5. The preparation method according to claim 3, characterized in that, After quenching, a refining step is also included: the crude product is dispersed in an ammonia-methanol solution or an ammonia-water methanol solution, stirred, filtered, and dried to obtain pure 1,3:2,4-di(3,4-dimethylbenzyl)sorbitol.

6. The preparation method according to claim 5, characterized in that, The volume-to-weight ratio (v / w) of the methanol solution or ammonia water used in the ammonia methanol solution to the sorbitol used is 10-20:1; preferably, the weight content of ammonia in the ammonia methanol solution is 5%-20%.

7. The preparation method according to any one of claims 1 to 6, characterized in that, The nucleating agent 1,3:2,4-bis(3,4-dimethylbenzyl)sorbitol obtained has a melting point above 273℃.

8. A sorbitol diacetal nucleating agent, wherein the nucleating agent is 1,3:2,4-bis(3,4-dimethylbenzyl)sorbitol, and the melting point is above 273°C; preferably, the initial melting point of the sorbitol diacetal nucleating agent is 273.0~274.0°C, and the final melting point is 274.0~275.5°C.

9. A composition comprising a polyolefin and 1,3:2,4-di(3,4-dimethylbenzyl)sorbitol prepared by any one of claims 1 to 7 or 1,3:2,4-di(3,4-dimethylbenzyl)sorbitol as described in claim 8; preferably, the polyolefin comprises polyethylene (PE), polypropylene (PP), polybutene (PB), or polyisobutylene (PIB).

10. The preparation method according to claims 1 to 7, the sorbitol diacetal nucleating agent according to claim 8, and the composition according to claim 9 in polyolefin products.

Images