An acetoxy fatty acid methyl ester environmentally-friendly plasticizer, and a preparation method and application thereof

Abstract

The application relates to the technical field of high polymer material processing, and particularly discloses an acetoxy fatty acid methyl ester environment-friendly plasticizer, a preparation method and application thereof, and the preparation comprises the following steps: hydrolyzing a refined diesel oil after sulfonation by sulfuric acid to obtain a mixture containing hydroxy fatty acid methyl ester; then, acetylation reaction is carried out on the mixture containing the hydroxy fatty acid methyl ester and acetic anhydride under the action of a catalyst to obtain a mixture containing acetoxy fatty acid methyl ester; after purification, the mixture is left to stand and is separated into an upper oil layer; the oil layer is cleaned to obtain the acetoxy fatty acid methyl ester environment-friendly plasticizer. The plasticizer has high plasticizing efficiency, small volatility, good compatibility with PVC, is not prone to migration and oil seepage, and has excellent low-temperature flexibility. The catalytic temperature of PVC prepared by using the plasticizer can be as low as -64 DEG C, and the product is not prone to breakage at low temperature.

Description

Technical Field

[0001] This invention relates to the field of polymer material processing technology, specifically to an acetoxy fatty acid methyl ester environmentally friendly plasticizer, its preparation method, and its application. Background Technology

[0002] Flexible plasticized polyvinyl chloride (PVC) plastic is inexpensive and of high quality, leading to increasing production and a growing demand for plasticizers. Currently, the main plasticizer is dioctyl phthalate (DOP), a petrochemical product. DOP has good overall performance and is inexpensive, making it widely used. However, with stricter environmental regulations, the use of phthalate plasticizers has been restricted. Plasticizers are gradually shifting towards recyclable biomass materials, and citrate plasticizers are gaining attention. The main citrate plasticizer is acetylthiose tributyl citrate (ATBC). However, ATBC has high volatility and relatively poor low-temperature flexibility.

[0003] CN107176910A discloses an acetylated citrate fatty acid ester plasticizer, its preparation method, and its application, including the preparation of epoxidized fatty acid esters; the ring-opening reaction of citric acid with epoxidized fatty acid esters to prepare citrate fatty acid esters; and the acetylation reaction to obtain the final product, the acetylated citrate fatty acid ester plasticizer. This invention is a bio-based plasticizer prepared primarily from citric acid and fatty acid esters. The raw materials are inexpensive and readily available, environmentally friendly, and can reduce dependence on petrochemical resources. Due to its larger molecular weight, higher polar bond content, and the presence of long fatty acid chains, it exhibits a higher flash point, better resistance to precipitation, better cold resistance, and better plasticizing efficiency compared to acetylated tributyl citrate and epoxidized fatty acid methyl esters. It can also improve the thermal stability of PVC products and can completely replace DOP in the preparation of PVC products with special properties.

[0004] However, this type of plasticizer has a large molecular weight terester structure. Although it solves the problem of high volatility, the terester structure has large steric hindrance, resulting in PVC products with high rigidity and poor flexibility, especially poor low-temperature flexibility, making it difficult to use for preparing soft PVC products.

[0005] CN 105085982 A discloses an environmentally friendly, migration-resistant epoxy fatty acid cyclohexyl ester plasticizer and its preparation method. This plasticizer is obtained by esterification of unsaturated fatty acids with cyclohexanol followed by epoxidation. Its migration rate in PVC is only about 1 / 5 that of traditional epoxy fatty acid methyl esters, and its flash point is 20-30℃ higher than that of traditional epoxy fatty acid methyl esters. It also has the advantages of being non-toxic and environmentally friendly, having good compatibility with polyvinyl chloride resin, and high plasticizing efficiency.

[0006] However, this plasticizer is only better than epoxy fatty acid methyl ester in terms of compatibility with PVC, and is far from being fully compatible with PVC. In products with high plasticization, it can only be used as an auxiliary plasticizer and mixed with main plasticizers such as DOP. If used alone, it will cause oil leakage. Summary of the Invention

[0007] This invention addresses the problems of poor compatibility, high volatility, and insufficient low-temperature flexibility of bio-based environmentally friendly plasticizers by providing an acetoxy fatty acid methyl ester environmentally friendly plasticizer. This plasticizer exhibits high plasticizing efficiency, good low-temperature flexibility, low volatility, good compatibility with PVC, and is less prone to migration and oil seepage. PVC prepared using this plasticizer can achieve a minimum embrittlement temperature of -64°C, and the products are less prone to breakage at low temperatures.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing an environmentally friendly plasticizer, consisting of the following steps:

[0010] Step 1: Remove saturated fatty acid methyl esters from biodiesel to obtain refined biodiesel. The refined biodiesel is composed of unsaturated fatty acid methyl esters.

[0011] Step 2: The refined biodiesel is sulfonated with concentrated sulfuric acid and then hydrolyzed to obtain a mixture of hydroxy fatty acid methyl esters;

[0012] Step 3: The mixture of hydroxy fatty acid methyl esters is subjected to an acetylation reaction with acetic anhydride under the action of a catalyst to obtain a mixture containing acetoxy fatty acid methyl esters;

[0013] Step 4: Distillation removes unreacted acetic anhydride and byproduct acetic acid from the mixture containing acetoxy fatty acid methyl esters. Inorganic alkali solution is added to remove the catalyst and residual acetic anhydride and acetic acid. The mixture is then allowed to stand and separate into layers to obtain the upper oil layer. The oil layer is washed with water to obtain the acetoxy fatty acid methyl ester environmentally friendly plasticizer.

[0014] This invention uses biomass materials as raw materials, and biodiesel made from kitchen waste oil, palm oil, rice bran oil, etc. is used as the base. After removing saturated fatty acid esters such as stearates, its components are unsaturated fatty acid methyl esters, mainly monoene methyl oleate as the main component, and diene methyl linoleate, triene methyl linolenic acid, and monoene methyl erucic acid as minor components.

[0015] In this invention, refined biodiesel is sulfonated, hydrolyzed, and acetylated. Acetate esters are grafted onto any carbon atom of the unsaturated double bond to obtain a mixture with monoacetoxy fatty acid methyl ester as the main component and diacetoxy fatty acid methyl ester and triacetoxy fatty acid methyl ester as minor components. The main plasticizer component of this mixture is 9- or 10-acetoxy octadecanoate methyl ester, which contains two ester bonds in its molecular chain. Compared with the monoacetoxy structure, the diester structure has better compatibility with PVC, and even when added in large quantities to PVC, it is less prone to oil leakage. The diester bond contains 7-8 straight-chain methylene (CH2) structures, comparable to benchmark cold-resistant plasticizers DOS (8) and DOZ (7). The more straight-chain methylene groups between the two ester groups, the more flexible the molecular chain, the higher the plasticizing efficiency, and the better the low-temperature flexibility of the plasticized product. The introduction of acetoxy groups also increases the molecular weight and reduces volatility. The minor components, diacetoxy fatty acid methyl ester and triacetoxy fatty acid methyl ester, have better compatibility with PVC, larger molecular weight, and lower volatility.

[0016] The biodiesel is derived from waste cooking oil, palm oil, rice bran oil, etc.

[0017] In step 1, saturated fatty acid esters are removed by distillation or low-temperature freeze pressing. The main purpose is to remove saturated fatty acid monoesters such as methyl stearate and methyl palmitate, which are incompatible with PVC. These components cannot undergo sulfonation and are immiscible with PVC, thus preventing them from precipitating in plasticized PVC products and causing "oil seepage".

[0018] In step 2, the sulfonation reaction temperature is below 10℃, and the reaction solvent is petroleum ether. Concentrated sulfuric acid is mixed with refined biodiesel by dropwise addition for 0.5-2 hours, and the reaction continues for 2-3 hours after the addition is completed.

[0019] In step 2, the molar ratio of concentrated sulfuric acid to unsaturated double bonds in refined biodiesel is 1:2.5-4.

[0020] The specific process of the hydrolysis reaction in step 2 includes the following steps: After sulfonation, water and methanol are added, and the mixture is refluxed at 80-100℃ for 0.5-2 hours. After the reaction, the system is cooled and an inorganic base is added to adjust it to neutral. Methanol and petroleum ether are collected by distillation for recycling. The bottom material is allowed to stand and separate into layers to remove the water layer and retain the oil layer. The water added is at a temperature below 20℃ and is added slowly while stirring to prevent the concentrated sulfuric acid from diluting, causing exothermic boiling and splashing. The addition of cold water provides a water source for the hydrolysis of the sulfonation product sulfate ester and reduces the acidity and viscosity of the reaction system. The purpose of adding methanol is to protect the terminal methyl esters of unsaturated fatty acid methyl esters in refined biodiesel and prevent the terminal methyl esters from being hydrolyzed under acid catalysis.

[0021] The volume of water is 1-2 times the total volume of the reactants after the sulfonation reaction;

[0022] The molar amount of methanol is 4-8 times the approximate molar amount of biodiesel calculated by considering refined biodiesel as pure methyl oleate.

[0023] Taking methyl oleate as an example, the reaction formulas for the sulfonation and hydrolysis processes in step 2 can be expressed as follows:

[0024]

[0025] In step 3, the molar amount of acetic anhydride is 1.1-2.5 times the molar amount of double bonds in the refined biodiesel; 1 mole of double bond is hydrolyzed by sulfonation to produce 1 mole of hydroxyl group, so the number of moles of double bonds in biodiesel is the same as the number of moles of hydroxyl groups in the intermediate product hydroxy fatty acid methyl ester. The mass of the catalyst is 0.1-1% of the mass of the refined biodiesel; step 3 is carried out at 80-110℃ for 1-3 hours.

[0026] The catalyst in step 3 includes one or more of concentrated sulfuric acid, p-toluenesulfonic acid, and cationic resin.

[0027] Taking the product of sulfonated hydrolysis of methyl oleate as an example, the reaction formula for acetylation in step 3 can be represented as follows:

[0028]

[0029] The inorganic alkaline solution includes aqueous solutions of any one or more of sodium carbonate and sodium bicarbonate.

[0030] In step 4, wash the oil layer three times with 1 to 1.2 times the volume of the oil layer.

[0031] Preferably, in step 4, the cleaned oil layer can be subjected to vacuum distillation to remove trace amounts of water and impurities.

[0032] This invention also provides an environmentally friendly plasticizer made from acetoxy fatty acid methyl esters prepared by the aforementioned method. The final plasticizer product mainly consists of acetoxy-octadecanoate methyl oleate (an acetylated product of methyl oleate), and minor components include diacetoxy-octadecanoate methyl linoleate (an acetylated product of methyl linoleate), triacetoxy-octadecanoate methyl linoleate (an acetylated product of methyl linoleate), and acetoxy-erucic acid methyl ester (an acetylated product of methyl erucic acid). Due to the indeterminate position of the hydroxyl substituents during sulfonation, the composition of the raw materials is relatively complex. Specifically, acetoxy-octadecanoate methyl oleate and acetoxy-dodecanoate methyl erucic acid each have two isomers; diacetoxy-octadecanoate methyl linoleate theoretically has at least four isomers; and triacetoxy-octadecanoate methyl linoleate theoretically has at least eight isomers. Therefore, the finished plasticizer product may contain at least the following compounds:

[0033]

[0034] The present invention also provides a plasticized PVC product, comprising the following raw materials by weight: 100 parts of PVC;

[0035] 60-70 parts of the aforementioned acetoxy fatty acid methyl ester environmentally friendly plasticizer;

[0036] 1-5 parts of tribasic lead sulfate;

[0037] 1-5 parts of dibasic lead phosphite;

[0038] 0.1-1 part calcium stearate;

[0039] PE wax 0.1-1 part.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The environmentally friendly acetoxy fatty acid methyl ester plasticizer prepared in this invention is bio-based. The raw materials are biodiesel derived from kitchen waste oil, palm oil, etc. After sulfonation, hydrolysis, and acetylation, an aliphatic mixture plasticizer containing at least two ester groups is obtained. The main component of this mixture plasticizer is 9- or 10-acetoxy octadecyl carbonate methyl ester. The molecular chain contains at least two ester bonds. Compared with the monoester structure, the diester structure has better compatibility with PVC, and it is not easy to cause oil leakage when added to PVC in large quantities. There are 7-8 straight-chain methylene (CH2) structures in the middle of the diester bond, which is comparable to the benchmark products of cold-resistant plasticizers, DOS (8) and DOZ (7). The more straight-chain methylene groups between the two ester groups, the more flexible the molecular chain, the higher the plasticizing efficiency, and the better the low-temperature flexibility of the plasticized product. The introduction of acetyl groups increases the molecular weight. The minor components, diacetoxy fatty acid methyl ester and triacetoxy fatty acid methyl ester, have larger molecular weights and reduced volatility. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the invention, should be covered within the protection scope of this invention.

[0043] The equipment used in the following specific embodiments includes: a 150-liter stainless steel reactor with a dual-circulation cooling and heating system, a vacuum distillation unit, and an oil-water separation and reflux unit. Raw materials were all purchased commercially, including refined biodiesel, No. 80 petroleum ether, methanol, concentrated sulfuric acid, acetic anhydride, sodium carbonate, and catalysts. The refined biodiesel is mainly derived from waste cooking oil, palm oil, rice bran oil, and other oils, obtained through distillation or multiple low-temperature freeze-pressing. The catalysts mainly include p-toluenesulfonic acid, sulfuric acid, and cationic resins, with sulfuric acid and p-toluenesulfonic acid being preferred.

[0044] The preparation method of acetoxy fatty acid methyl ester environmentally friendly plasticizer specifically includes the following steps:

[0045] Step 1: Calculate the molar content of double bonds by testing the iodine value of refined biodiesel. Place an appropriate amount of refined biodiesel into a stainless steel reactor, add 0.5 to 1 volume of 80 to 100 petroleum ether to aid dissolution and reduce viscosity, and turn on the cooling circulation device to control the system reaction temperature to <10℃. While stirring continuously, add 2.5 to 4 times the molar amount of 98% concentrated H2SO4 of double bonds in the refined biodiesel dropwise over approximately 1 hour. After the reaction is complete, continue stirring for 2 to 3 hours to react the sulfuric acid with the unsaturated fatty acids in the refined biodiesel to form sulfate esters.

[0046] Step 2: After the reaction is complete, add 1 to 1.5 times the volume of cold water to all reactants, stir well, and then cool. To prevent hydrolysis of methyl oleate, add 4 to 8 times the molar amount of methanol (approximately calculated based on 100% methyl oleate) to the reaction system. Turn on the heating system and reflux condenser, heat to 80 to 100°C, and react for 0.5 to 1.5 hours. The sulfate ester will hydrolyze to form a mixture containing hydroxy fatty acid methyl esters. When cooled to below 60°C, adjust to neutral with sodium carbonate, turn on the distillation recovery system to recover methanol and petroleum ether, cool and let stand to separate the layers, remove the water layer and retain the oil layer.

[0047] Step 3: Add 97% acetic anhydride at 1.1 to 2.5 molar ratios of the double bonds in refined biodiesel to the oil layer. The molar ratio of the double bonds is calculated from the iodine value. Add 0.1 to 1% by mass of catalyst from refined biodiesel, stir evenly, and heat to 80 to 110°C for 1 to 3 hours. Open the vacuum distillation apparatus to remove unreacted acetic anhydride and acetic acid produced in the reaction. When the temperature drops below 60°C, add 5% sodium carbonate solution (sodium bicarbonate) to remove the catalyst, neutralize to neutral, allow to stand and separate into layers, remove the lower aqueous phase, retain the upper oil layer, and finally rinse the oil layer three times with 1 to 1.2 times the volume of water to obtain the finished acetoxy fatty acid methyl ester plasticizer. Vacuum distillation can be used to remove water and other impurities from the product to improve its color.

[0048] Example 1

[0049] Step 1: The iodine value of a certain batch of refined biodiesel was measured to be 86.02 gI2 / 100g. 15 kg (50.83 moles of double bonds) of this batch of refined biodiesel was weighed and placed in a stainless steel reactor. 8 kg of No. 80 petroleum ether was added to aid dissolution and reduce viscosity. The cooling circulation device was turned on to control the reaction temperature to <10℃. Under continuous stirring, 15.249 kg of 98% concentrated H2SO4 (152 mol) was added dropwise, which is about 3 times the double bond equivalent of refined biodiesel. The addition was completed in about 1 hour. The reaction was stirred for 2.5 hours.

[0050] Step 2: After the reaction in Step 1 is complete, add 40 kg of cold water (approximately 1.05 times the volume of the reactants), stir until homogeneous, and turn off the cooling. Then add 8.1 kg of methanol (252.95 mol, approximately 5 times the molar amount of refined biodiesel), turn on the heating system and reflux condenser, and react at 80°C for 30 minutes. The sulfate esters undergo hydrolysis. When the temperature drops to 50°C, adjust to neutral with sodium carbonate, turn on the distillation recovery system to recover methanol and petroleum ether, cool and allow to stand to separate the layers, remove the water layer and retain the oil layer, to obtain a homologue mixture of hydroxy fatty acid methyl esters.

[0051] Step 3: Add 0.08 kg of concentrated sulfuric acid catalyst (0.5% of the weight of refined biodiesel) to the oil layer from Step 2, and then add 9.63 kg of 97% acetic anhydride (91.5 mol, equivalent to 1.8 times the number of double bonds in refined biodiesel). After stirring evenly, heat to 85°C and react for 2 hours. Open the vacuum distillation apparatus to remove unreacted acetic anhydride and acetic acid produced by the reaction. When the temperature drops below 60°C, add 5% sodium carbonate aqueous solution to neutralize to remove the catalyst and any remaining acetic acid and acetic anhydride. After standing and separating the layers, remove the aqueous phase and retain the oil layer. Rinse three times with water equal in volume to obtain the acetoxy fatty acid methyl ester plasticizer of Example 1.

[0052] Example 2

[0053] Step 1: The iodine value of a certain batch of refined biodiesel was measured to be 90.2 gI2 / 100g. 15 kg (50.90 mol of double bonds) of this batch of refined biodiesel was weighed and placed in a stainless steel reactor. 10 kg of No. 80 petroleum ether was added to aid dissolution and reduce viscosity. The cooling circulation device was turned on to control the reaction temperature to <10℃. Under continuous stirring, 17.248 kg of 98% concentrated H2SO4 (172.48 mol) was added dropwise, which is about 3.2 times the double bond equivalent of refined biodiesel. The addition was completed in about 1 hour. The reaction was stirred for 2.5 hours.

[0054] Step 2: After the reaction in Step 1 is complete, add 38 kg of cold water (about 1 times the volume of the reactants), stir until homogeneous, and turn off the cooling. Then add 9.713 kg of methanol (303.16 mol, about 6 times the molar amount of refined biodiesel), turn on the heating system and reflux condenser, and react at 80°C for 45 minutes. The sulfate esters will hydrolyze. When the temperature drops to 60°C, adjust to neutral with sodium carbonate, turn on the distillation recovery system to recover methanol and petroleum ether, cool and let stand to separate the layers, remove the water layer and retain the oil layer to obtain a homologue mixture of hydroxy fatty acid methyl esters.

[0055] Step 3: Add 0.1 kg of concentrated sulfuric acid catalyst (0.67% of the weight of refined biodiesel) to the oil layer from Step 2, and then add 12.47 kg of 97% acetic anhydride (118.58 mol, equivalent to 2.2 times the number of double bonds in refined biodiesel). After stirring evenly, heat to 85°C and react for 2 hours. Open the vacuum distillation apparatus to remove unreacted acetic anhydride and acetic acid produced by the reaction. When the temperature drops below 60°C, add 5% sodium carbonate aqueous solution to neutralize to neutral, remove the catalyst and any remaining acetic acid and acetic anhydride. After standing and separating, remove the aqueous phase, retain the oil layer, and rinse three times with water equal in volume to obtain the acetoxy fatty acid methyl ester plasticizer of Example 2.

[0056] Example 3

[0057] Step 1: The iodine value of a certain batch of refined biodiesel was measured to be 94.48 gI2 / 100g. 15 kg (55.84 moles of double bonds) of this batch of refined biodiesel was weighed and placed in a stainless steel reactor. 10 kg of No. 80 petroleum ether was added to aid dissolution and reduce viscosity. The cooling circulation device was turned on to control the reaction temperature to <10℃. 18.28 kg of 98% concentrated H2SO4 (167.52 mol), approximately 3 times the double bond equivalent of the refined biodiesel, was added dropwise under continuous stirring. The addition was completed in about 1 hour. The reaction was stirred for 2.5 hours.

[0058] Step 2: After the reaction in Step 1 is complete, add 40 kg of cold water (approximately 1.05 times the volume of the reactants), stir until homogeneous, and turn off the cooling. Then add 10.8 kg of methanol and 9.713 kg of methanol (303.16 mol, approximately 6 times the molar amount of refined biodiesel). Turn on the heating system and reflux condenser, and react at 80°C for 60 minutes. The sulfate esters undergo hydrolysis. When the temperature drops to 50°C, adjust to neutral with sodium carbonate. Turn on the distillation recovery system to recover methanol and petroleum ether. Cool and allow to stand to separate the layers, removing the water layer and retaining the oil layer to obtain a homologous mixture of hydroxy fatty acid methyl esters.

[0059] Step 3: Add 0.1 kg of concentrated sulfuric acid catalyst (0.67% of the weight of refined biodiesel) to the oil layer from Step 2, and then add 12.92 kg of 97% acetic anhydride (122.85 mol, equivalent to 2.2 times the number of double bonds in refined biodiesel). After stirring evenly, heat to 90°C and react for 1.5 hours. Open the vacuum distillation apparatus to remove unreacted acetic anhydride and acetic acid produced by the reaction. When the temperature drops below 60°C, add 5% sodium carbonate aqueous solution to neutralize to neutral, remove the catalyst and any remaining acetic acid and acetic anhydride. After standing and separating the layers, remove the aqueous phase, retain the oil layer, and rinse three times with water equal in volume to obtain the acetoxy fatty acid methyl ester plasticizer of Example 3.

[0060] Example 4

[0061] Step 1: The iodine value of a certain batch of refined biodiesel was measured to be 97.58 gI2 / 100g. About 15 kg (57.67 moles of double bonds) of this batch of refined biodiesel was weighed and placed in a stainless steel reactor. 10 kg of No. 80 petroleum ether was added to aid dissolution and reduce viscosity. The cooling circulation device was turned on to control the reaction temperature to <10℃. Under continuous stirring, 14.6 kg of 98% concentrated H2SO4 (173 mol) was added dropwise, which is about 3 times the molar amount of double bonds in the refined biodiesel. The addition was completed in about 1 hour. The reaction was stirred for 2 hours.

[0062] Step 2: After the reaction in Step 1 is complete, add 42 kg of cold water (approximately 1.1 times the volume of the reactants), stir until homogeneous, and turn off the cooling. Then add 10.54 kg of methanol (328.84 mol, approximately 6.5 times the molar amount in refined biodiesel), turn on the heating system and reflux condenser, and react at 80°C for 90 minutes. The sulfate esters undergo hydrolysis. When the temperature drops to 60°C, adjust to neutral with sodium carbonate, turn on the distillation recovery system to recover methanol and petroleum ether, cool and allow to stand to separate the layers, remove the water layer and retain the oil layer, to obtain a homologue mixture of hydroxy fatty acid methyl esters.

[0063] Step 3: Add 0.08 kg of concentrated sulfuric acid catalyst (0.5% of the weight of refined biodiesel) to the oil layer from Step 2, and then add 11.765 kg of 97% acetic anhydride (115.34 mol, equivalent to twice the number of moles of double bonds in refined biodiesel). After stirring evenly, heat to 90°C and react for 2 hours. Open the vacuum distillation apparatus to remove unreacted acetic anhydride and the acetic acid produced by the reaction. When the temperature drops below 60°C, add 5% sodium carbonate aqueous solution to neutralize to neutral, remove the catalyst and any remaining acetic acid and acetic anhydride. After standing and separating, remove the aqueous phase, retain the oil layer, and rinse three times with water equal in volume to obtain the acetoxy fatty acid methyl ester plasticizer of Example 4.

[0064] Example 5

[0065] Step 1: The iodine value of a certain batch of refined biodiesel was measured to be 100.56 gI2 / 100g. About 15 kg (59.43 moles of double bonds) of this batch of refined biodiesel was weighed and placed in a stainless steel reactor. 10 kg of No. 80 petroleum ether was added to aid dissolution and reduce viscosity. The cooling circulation device was turned on to control the reaction temperature to <10℃. Under continuous stirring, 18 kg of 98% concentrated H2SO4 (180 mol) was added dropwise, which is about 3.03 times the number of moles of double bonds in the refined biodiesel. The addition was completed in about 1 hour. The reaction was stirred for 2.5 hours.

[0066] Step 2: After the reaction in Step 1 is complete, add 45 kg of cold water (approximately 1.15 times the volume of the reactants), stir until homogeneous, and turn off the cooling. Then add 10.21 kg of methanol (318.72 mol, approximately 6.3 times the molar amount in refined diesel), turn on the heating system and reflux condenser, and react at 80°C for 45 minutes. The sulfate esters undergo hydrolysis. When the temperature drops to 60°C, adjust to neutral with sodium carbonate, turn on the distillation recovery system to recover methanol and petroleum ether, cool and allow to stand to separate the layers, remove the water layer and retain the oil layer, to obtain a homologous mixture of hydroxy fatty acid methyl esters.

[0067] Step 3: Add 0.12 kg of concentrated sulfuric acid catalyst (0.8% of the weight of refined biodiesel) to the oil layer from Step 2, followed by 14.373 kg of 97% acetic anhydride (136.7 mol, equivalent to 2.3 times the number of double bonds in refined biodiesel). After stirring evenly, heat to 85°C and react for 2 hours. Open the vacuum distillation apparatus to remove unreacted acetic anhydride and the reacted acetic acid. When the temperature drops below 60°C, add 5% sodium carbonate aqueous solution to neutralize to neutral, remove the catalyst and any remaining acetic acid and acetic anhydride. After standing and separating, remove the aqueous phase, retain the oil layer, and rinse three times with water equal in volume to obtain the acetoxy fatty acid methyl ester plasticizer of Example 5.

[0068] Example 6

[0069] Step 1: The iodine value of a certain batch of refined biodiesel was measured to be 104.87 gI2 / 100g. About 15 kg (61.98 moles of double bonds) of this batch of refined biodiesel was weighed and placed in a stainless steel reactor. 10 kg of No. 80 petroleum ether was added to aid dissolution and reduce viscosity. The cooling circulation device was turned on to control the reaction temperature to <10℃. While stirring continuously, 18.59 kg of 98% concentrated H2SO4 (185.94 mol, about 3.03 times the number of moles of double bonds in the refined biodiesel) was added dropwise, which was completed in about 1 hour. The reaction was stirred for 2.5 hours.

[0070] Step 2: After the reaction in Step 1 is complete, add 45 kg of cold water (approximately 1.12 times the volume of the reactants), stir until homogeneous, and turn off the cooling. Then add 10.8 kg of methanol (9.713 kg of methanol, 303.16 mol, approximately 6 times the molar amount of refined biodiesel), turn on the heating system and reflux condenser, and react at 85°C for 45 minutes. The sulfate esters undergo hydrolysis. When the temperature drops below 60°C, adjust to neutral with sodium carbonate, turn on the distillation recovery system to recover methanol and petroleum ether, cool and allow to stand to separate the layers, remove the water layer and retain the oil layer, to obtain a homologue mixture of hydroxy fatty acid methyl esters.

[0071] Step 3: Add 0.09 kg of concentrated sulfuric acid catalyst (0.6% of the weight of refined diesel) to the oil layer from Step 2, along with 13.35 kg of 97% acetic anhydride (123.96 mol, equivalent to twice the number of double bonds in refined biodiesel). After stirring evenly, heat to 90°C and react for 2 hours. Open the vacuum distillation apparatus to remove unreacted acetic anhydride and the reacted acetic acid. When the temperature drops below 60°C, add 5% sodium carbonate aqueous solution to neutralize to remove the catalyst and any remaining acetic acid and acetic anhydride. After standing and separating, remove the aqueous phase and rinse the oil layer three times with water equal in volume to obtain the acetoxy fatty acid methyl ester plasticizer of Example 5.

[0072] Application examples

[0073] Weigh out 65 parts by weight of the acetoxy fatty acid methyl ester plasticizer prepared in Examples 1-6 and the comparative plasticizer acetylthiol tributyl citrate (ATBC), and the PVC blank formulation (see Table 1). Put them into a high-speed mixer and mix until the plasticizer is completely absorbed. Extrude the plasticizer into sheets at 150-180°C using an extruder. Feed the sheets into a special mold and press them into two types of sheets with standard thicknesses of 1 mm and 2 mm using a flat vulcanizing machine at 155-175°C. The 1 mm sheet with a plasticizer content of 38.08% was used to test the volatility of the plasticizer, and the 2 mm sheet was used to test the embrittlement temperature.

[0074] 5.1 Low-Temperature Resistance Test: A 2mm thick PVC plasticized sheet was cut into standard test pieces 20mm long and 2.5mm wide using a special sampling die. The embrittlement temperature at 50% failure was determined using Method A specified in GB / T 5470-2008 "Determination of Embrittlement Temperature of Plastics by Impact Test". All data were used for comparison to demonstrate the excellent low-temperature resistance of the plasticizer of this invention. Better low-temperature resistance results in higher plasticizing efficiency.

[0075] 5.2 The test shall be conducted according to Method A of HG / T 4458–2012 "Determination of Plasticizer Loss in Plastics by Activated Carbon Method". To enhance the effect, the temperature of the ventilated thermal aging chamber shall be increased to 86–88℃.

[0076] Take a 1mm thick PVC sample sheet, punch out a 50mm diameter disc using a standard punch, weigh the disc using an analytical balance, and record the weight m0.

[0077] Baking at 86–88°C for 24 hours. Measure and record the weight m1 of the test piece. Since the components in the basic formulation are essentially non-volatile, almost all the volatile components in the test piece are plasticizers. To make the data more intuitive, in this patent, the evaporation loss rate refers to the evaporation loss rate of the plasticizer, not the loss rate of the plastic test piece.

[0078] Δm=(m0-m1) / (m0*38.08%)*100%

[0079] Table 1: Blank PVC Formulation

[0080] PVC 100 Formosa Plastics 70 powder, degree of polymerization 1300 Tribasic lead sulfate 3 Lead dibasic phosphite 2 Calcium stearate 0.4 PE wax 0.3 total 105.7

[0081] The application examples use plasticizers from different embodiments. In Comparative Example 1, acetylacetic tributyl citrate (ATBC) was used as the plasticizer. The properties of the PVC products obtained are shown in Table 2.

[0082] Table 2 shows the embrittlement temperature and volatility of PVC in application examples.

[0083] Application Example 1 Example 1 86.02 -64 15.4 Application Example 2 Example 2 90.2 -63 15.0 Application Example 3 Example 3 94.48 -61 14.2 Application Example 4 Example 4 97.58 -59 13.7 Application Example 5 Example 5 100.56 -57 13.1 Application Example 6 Example 6 104.87 -55 12.8 Comparative Example 1 ATBC / -42 17.8

[0084] As can be seen from Application Examples 1-6 and the Comparative Examples, the acetoxy fatty acid methyl ester plasticizers prepared in Examples 1-6 of this invention have significantly better low-temperature resistance (plasticizing efficiency) and volatility than the commonly used environmentally friendly bio-based plasticizer acetylated tributyl citrate (ATBC). The table also shows that as the iodine value of the refined biodiesel increases, the low-temperature resistance and volatility of the acetoxy fatty acid methyl ester plasticizer decrease. This is because with the increase of iodine value, the amount of fatty acid esters with multiple double bond structures, such as methyl linoleate and methyl linolenic acid, increases, resulting in a higher content of polyacetoxy fatty acid methyl esters in the product. The steric hindrance effect of polyacetoxy fatty acid methyl esters increases, leading to less flexible molecular chain movement and a decrease in low-temperature resistance, although it is still superior to acetylated tributyl citrate (ATBC). Simultaneously, the presence of polyacetoxy groups increases the molecular weight, leading to a decrease in volatility.

Claims

1. A method for preparing an environmentally friendly plasticizer made of acetoxy fatty acid methyl ester, characterized in that, Including the following steps: Step 1: Remove saturated fatty acid methyl esters from biodiesel to obtain refined biodiesel; Step 2 involves sulfonating the refined biodiesel with concentrated sulfuric acid followed by hydrolysis to obtain a mixture of hydroxy fatty acid methyl esters. The sulfonation reaction temperature in Step 2 is below 10°C, and the reaction solvent is petroleum ether. Concentrated sulfuric acid is added dropwise to the refined biodiesel over a period of 0.5-2 hours, and the reaction continues for 2-3 hours after the addition is complete. The molar ratio of sulfuric acid to the unsaturated double bonds in the refined biodiesel is 1:2.5-4. The specific process of the hydrolysis reaction includes the following steps: after sulfonation, water and methanol are added; the reaction is refluxed at 80-100℃ for 0.5-2 hours; after the reaction, the system is cooled and an inorganic base is added to adjust it to neutral; petroleum ether and methanol are removed by distillation; the bottom material is allowed to stand and separate into layers, retaining the oil layer; the temperature of the added water is below 20℃; the volume of the water is 1-2 times the total volume of the reactants after the sulfonation reaction; the molar amount of the methanol is 4-8 times the molar amount of refined biodiesel. Step 3: The mixture of hydroxy fatty acid methyl esters is reacted with acetic anhydride under the action of a catalyst to obtain a mixture of acetoxy fatty acid methyl esters; Step 4: Distill to remove unreacted acetic anhydride and byproduct acetic acid from the mixture of acetoxy fatty acid methyl esters. After adding inorganic alkali solution to remove the catalyst and residual acetic anhydride and acetic acid, the mixture is allowed to stand and separate into layers to obtain the upper oil layer. The oil layer is washed with water to obtain the acetoxy fatty acid methyl ester environmentally friendly plasticizer.

2. The preparation method of the acetoxy fatty acid methyl ester environmentally friendly plasticizer according to claim 1, characterized in that, In step 3, the molar amount of acetic anhydride is 1.1-2.5 times the molar amount of double bonds in refined biodiesel, and the mass of the catalyst is 0.1-1% of the mass of refined biodiesel.

3. The preparation method of the acetoxy fatty acid methyl ester environmentally friendly plasticizer according to claim 1, characterized in that, Step 3 involves reacting at 80-110℃ for 1-3 hours.

4. The preparation method of the acetoxy fatty acid methyl ester environmentally friendly plasticizer according to claim 1, characterized in that, The catalyst in step 3 includes one or more of sulfuric acid, p-toluenesulfonic acid, and cationic resin; the inorganic base includes one or more of sodium carbonate and sodium bicarbonate.

5. An environmentally friendly plasticizer of acetoxy fatty acid methyl ester prepared by the preparation method according to any one of claims 1-4.

6. A plasticized PVC product, characterized in that, The ingredients are as follows, by weight: 100 portions of PVC; 60-70 parts of the acetoxy fatty acid methyl ester environmentally friendly plasticizer according to claim 5; 1-5 parts of tribasic lead sulfate; 1-5 parts of dibasic lead phosphite; 0.1-1 part calcium stearate; PE wax 0.1-1 part.

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