Preparation method of full-bio-based degradable plasticizer with high plasticizing efficiency and migration resistance

Abstract

The invention belongs to the technical field of bio-based plastic additives, and discloses a full-bio-based degradable plasticizer with high plasticizing efficiency and migration resistance. Green biomass raw materials including L-lactic acid, binary fatty alcohol and levulinic acid are used as raw materials, the L-lactic acid and the binary fatty alcohol are reacted under the action of a catalyst, and the plasticizer is prepared. Carrying out esterification reaction to obtain an intermediate product, namely a binary fatty alcohol lactate plasticizer; and further esterifying the intermediate product and levulinic acid to obtain a final product levulinic acid binary fatty alcohol lactate plasticizer, and reacting to obtain the full-bio-based degradable plasticizer with high plasticizing efficiency and migration resistance. In addition, the plasticizer is suitable for industrial production, and is expected to replace a traditional plasticizer, namely a phthalate plasticizer.

Description

Technical Field

[0001] The invention belongs to the field of bio-based plasticizers, and specifically relates to a method for preparing a fully bio-based degradable plasticizer with high plasticizing efficiency and migration resistance. Background Art

[0002] Polyvinyl chloride (PVC) is one of the most widely used varieties among the five major general-purpose resins at home and abroad. As a thermoplastic polymer, it is widely used in various fields around the world, such as cable and wire insulation, medical supplies, packaging materials, pipes, building materials and children's toys. Due to the presence of dipoles on each C-Cl bond and the interaction between polyvinyl chloride chains, PVC exhibits hard and brittle properties, which in turn hinders the movement of the chains. The most commonly used method is to add plasticizers to PVC materials to overcome this disadvantage. However, traditional orthophthalic plasticizers have poor bonding with the plastic matrix, and when plastic products are discarded or used, they will leach or migrate into the ecological environment. Traditional plasticizers cannot achieve the simultaneous improvement of plasticization efficiency and migration resistance, and the additives leached or migrated in the plastic matrix will decompose and produce some toxic substances. After degradation, some harmful substances will also be produced, which may exist in the environment for a long time and eventually endanger human health.

[0003] Patent CN117844139A prepared a high-efficiency plasticizer to modify polyvinyl chloride to obtain a hydrolysis-resistant polyvinyl chloride panel. Although the prepared plasticizer has a good plasticizing effect, the raw materials used are all non-renewable resources, which does not conform to the concept of green environmental protection. Patent CN114702613B and patent CN118240187A prepared castor oil-based and tung oil-based plasticizers for polyvinyl chloride and their preparation methods. Although the flexibility of the modified polyvinyl chloride resin is improved to a certain extent, its plasticizing efficiency is poor and it is easy to migrate, and it cannot be used for a long time. In addition, castor oil and tung oil also have certain biological toxicity, which is not conducive to human health. Patents CN112920394 A, CN106278888 A, CN 110951055A, CN202310135334.9 and CN116655695 A etc. use lactic acid as raw material to synthesize bio-based plasticizers. Although they can effectively improve the toughness of materials, some of their synthetic raw materials are petroleum-based monomers or toxic monomers, which is not conducive to green environmental protection. Therefore, in view of the shortcomings of existing environmentally friendly plasticizers, such as some of the raw materials are not environmentally friendly, low plasticizing efficiency, easy migration and not easy to degrade, designing a fully bio-based degradable plasticizer derived from all green raw materials, with high plasticizing efficiency and migration resistance is an urgent problem to be solved in the future plastics industry. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a fully bio-based degradable plasticizer with high plasticizing efficiency and migration resistance in view of the above-mentioned problems existing in the prior art. The bio-based plasticizer provided by the present invention can overcome the shortcomings of traditional plasticizers, have high plasticizing efficiency, migration resistance and degradable properties, and meet the long-term use requirements of polyvinyl chloride materials.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] The present invention provides a fully bio-based degradable plasticizer with high plasticizing efficiency and migration resistance, and its general structural formula is shown in Formula I:

[0007]

[0008] Wherein: n ranges from 1 to 3; R is a saturated alkyl group with 2 to 10 carbon atoms.

[0009] The technical solution of the present invention is a method for preparing a fully bio-based degradable plasticizer with high plasticizing efficiency and migration resistance, and the specific steps are as follows:

[0010] (1) subjecting L-lactic acid and dihydric fatty alcohol to a heating esterification reaction under the action of a catalyst and a water-carrying agent and under the protection of an inert gas, and the reaction product is post-treated to obtain a lactic acid ester intermediate;

[0011] (2) subjecting the lactate intermediate and levulinic acid to a heating esterification reaction under the action of a catalyst and a water-carrying agent and under the protection of an inert gas, and the reaction product is post-treated to obtain a fully bio-based degradable plasticizer having both high plasticizing efficiency and migration resistance;

[0012] Furthermore, in step (1), the dihydric fatty alcohol is one of ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol; and the molar ratio of L-lactic acid to the dihydric fatty alcohol is 1 to 5:1.

[0013] Furthermore, in steps (1) and (2), the catalyst is one or more of concentrated sulfuric acid, phosphoric acid, p-toluenesulfonic acid, zinc oxide, aluminum oxide, tin oxide, and stannous oxide, and the mass of the catalyst is 0.6-1.0% of the total mass of the reactants; the water-carrying agent is one of benzene, toluene or cyclohexane, and the amount of the water-carrying agent added is 5-40% of the total mass of the reactant raw materials, and further the amount of the water-carrying agent added is 80-100 ml.

[0014] Furthermore, the heating esterification reaction conditions in step (1) are: reflux reaction at 120-160° C. for 6-9 hours.

[0015] Furthermore, the molar ratio of the lactate intermediate to levulinic acid is 1:2.0 to 2.3.

[0016] Furthermore, the heating esterification reaction conditions in step (2) are: reflux reaction at 120-160° C. for 10-14 hours.

[0017] The preparation method of the bio-based plasticizer prepared by the invention belongs to a bio-based environmentally friendly plasticizer, has good compatibility with PVC, has high plasticizing efficiency and migration resistance, and can be used as a main plasticizer for polyvinyl chloride.

[0018] The beneficial effects of the present invention are:

[0019] (1) The present invention uses green monomers L-lactic acid, divalent fatty alcohols and levulinic acid as main raw materials, which not only avoids dependence on petrochemical raw materials, but also improves the use of bio-based raw materials. In addition, the present invention is completely decomposed in active soil and does not produce toxic substances, which is beneficial to environmental protection and is an environmentally friendly material.

[0020] (2) The present invention utilizes the characteristics of the molecular structure of L-lactic acid and levulinic acid to prepare a product whose structure contains a large number of polar functional groups, ester groups and ketone groups, which is beneficial to improving the compatibility of the plasticizer with the polyvinyl chloride resin.

[0021] (3) The bio-based plasticizer prepared by the present invention has high plasticizing efficiency and migration resistance and good compatibility with PVC. Compared with commercial plasticizers DOP and ATBC used in PVC, it has better plasticizing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the infrared spectrum of the product of Example 1-4 of the present invention.

[0023] Figure 2 The NMR spectra of the products of Examples 1-4 of the present invention are shown in FIG.

[0024] Figure 3 The tensile properties of pure polyvinyl chloride, polyvinyl chloride products prepared with plasticizers of Examples 1-4 and Comparative Examples 1-2 are shown in the figure.

[0025] Figure 4 The thermogravimetric analysis TGA curves of pure polyvinyl chloride, polyvinyl chloride products prepared with plasticizers in Examples 1-4 and Comparative Examples 1-2.

[0026] Figure 5 The volatilization curves of polyvinyl chloride products prepared with plasticizers of Examples 1-4 and Comparative Examples 1-2 are shown.

[0027] Figure 6 The migration curves of polyvinyl chloride products prepared with plasticizers of Examples 1-4 and Comparative Examples 1-2 in different solvents.

[0028] Figure 7 The infrared and nuclear magnetic resonance spectra of soil degradation of polyvinyl chloride prepared with the plasticizer in Example 4 of the present invention. DETAILED DESCRIPTION

[0029] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0030] In the present invention, the plasticizing method of the bio-based dihydric fatty alcohol lactate bio-based plasticizer preferably includes thermoplastic blending.

[0031] The synthetic route of the present invention is as follows:

[0032]

[0033] Wherein: n ranges from 1 to 3; R is a saturated alkyl group with 2 to 10 carbon atoms.

[0034] Example 1

[0035] (1) The synthesis steps of 1,4-butanediol lactate are as follows: L-lactic acid and 1,4-butanediol in a molar ratio of 3:1, 0.8% of the reactant mass of p-toluenesulfonic acid monohydrate (0.8% of the total mass of L-lactic acid and 1,4-butanediol) and 100 mL of cyclohexane are added to a round-bottom three-necked flask, the reaction temperature is 130°C, and the mixture is stirred and refluxed for 7 hours. A condenser and a water separator are connected to the round-bottom three-necked flask to receive the water produced during the reaction. After the reaction is completed, 1,4-butanediol lactate is finally obtained by washing, filtering and vacuum distillation.

[0036] (2) The synthesis steps of 1,4-butanediol lactate of levulinic acid are as follows: 1,4-butanediol lactate and levulinic acid in a molar ratio of 1:2, 0.8% of the reactant mass of p-toluenesulfonic acid monohydrate (0.8% of the total mass of 1,4-butanediol lactate and levulinic acid) and 100 mL of cyclohexane are added to a round-bottom three-necked flask, nitrogen is introduced as a protective gas, the reaction temperature is 140°C, and it is stirred and refluxed for 12 hours. A condenser and a water separator are connected to the round-bottom three-necked flask to receive the water produced during the reaction. After the reaction is completed, 1,4-butanediol lactate of levulinic acid is finally obtained by washing, filtering and vacuum distillation.

[0037] Example 2

[0038] (1) The synthesis steps of 1,6-hexanediol lactate are as follows: L-lactic acid and 1,6-hexanediol in a molar ratio of 3:1, 0.8% of the reactant mass of p-toluenesulfonic acid monohydrate (0.8% of the total mass of L-lactic acid and 1,6-hexanediol) and 100 mL of cyclohexane are added to a round-bottom three-necked flask, nitrogen is introduced as a protective gas, the reaction temperature is 130°C, and it is stirred and refluxed for 7 hours. A condenser and a water separator are connected to the round-bottom three-necked flask to receive the water produced during the reaction. After the reaction is completed, 1,6-hexanediol lactate is finally obtained by washing, filtering, and vacuum distillation.

[0039] (2) The synthesis steps of 1,6-hexanediol lactate of levulinic acid are as follows: 1,6-hexanediol lactate and levulinic acid in a molar ratio of 1:2, 0.8% of the mass of p-toluenesulfonic acid monohydrate (0.8% of the total mass of 1,6-hexanediol lactate and levulinic acid) and 100 mL of cyclohexane are added to a round-bottom three-necked flask, nitrogen is introduced as a protective gas, the reaction temperature is 140°C, and it is stirred and refluxed for 12 hours. A condenser and a water separator are connected to the round-bottom three-necked flask to receive the water produced during the reaction. After the reaction is completed, 1,6-hexanediol lactate of levulinic acid is finally obtained by washing, filtering and vacuum distillation.

[0040] Example 3

[0041] (1) The synthesis steps of 1,8-octanediol lactate are as follows: L-lactic acid and 1,8-octanediol in a molar ratio of 3:1, 0.8% of the reactant mass of p-toluenesulfonic acid monohydrate (0.8% of the total mass of L-lactic acid and 1,8-octanediol) and 100 mL of cyclohexane are added to a round-bottom three-necked flask, nitrogen is introduced as a protective gas, the reaction temperature is 130°C, and it is stirred and refluxed for 7 hours. A condenser and a water separator are connected to the round-bottom three-necked flask to receive the water produced during the reaction. After the reaction is completed, 1,8-octanediol lactate is finally obtained by washing, filtering, and vacuum distillation.

[0042] (2) The synthesis steps of 1,8-octanediol lactate of levulinic acid are as follows: 1,8-octanediol lactate and levulinic acid in a molar ratio of 1:2, 0.8% of the mass of p-toluenesulfonic acid monohydrate (0.8% of the total mass of 1,8-octanediol lactate and levulinic acid) and 100 mL of cyclohexane are added to a round-bottom three-necked flask, nitrogen is introduced as a protective gas, the reaction temperature is 140°C, and it is stirred and refluxed for 12 hours. A condenser and a water separator are connected to the round-bottom three-necked flask to receive the water produced during the reaction. After the reaction is completed, 1,8-octanediol lactate of levulinic acid is finally obtained by washing, filtering and vacuum distillation.

[0043] Example 4

[0044] (1) The synthesis steps of 1,10-decanediol lactate are as follows: L-lactic acid and 1,10-decanediol in a molar ratio of 3:1, 0.8% of the reactant mass of p-toluenesulfonic acid monohydrate (0.8% of the total mass of L-lactic acid and 1,10-decanediol) and 100 mL of cyclohexane are added to a round-bottom three-necked flask, nitrogen is introduced as a protective gas, the reaction temperature is 130°C, and it is stirred and refluxed for 7 hours. A condenser and a water separator are connected to the round-bottom three-necked flask to receive the water produced during the reaction. After the reaction is completed, 1,10-decanediol lactate is finally obtained by washing, filtering, and vacuum distillation.

[0045] (2) The synthesis steps of 1,10-decanediol lactate of levulinic acid are as follows: 1,10-decanediol lactate and levulinic acid in a molar ratio of 1:2, 0.8% of the reactant mass of p-toluenesulfonic acid monohydrate (0.8% of the total mass of 1,10-decanediol lactate and levulinic acid) and 100 mL of cyclohexane are added to a round-bottom three-necked flask, nitrogen is introduced as a protective gas, the reaction temperature is 140°C, and it is stirred and refluxed for 12 hours. A condenser and a water separator are connected to the round-bottom three-necked flask to receive the water produced during the reaction. After the reaction is completed, 1,10-decanediol lactate of levulinic acid is finally obtained by washing, filtering and vacuum distillation.

[0046] Comparative Example 1

[0047] The commercially available plasticizer DOP was provided by Shanghai McLean Biochemical Technology Co., Ltd.

[0048] Comparative Example 2

[0049] The commercially available plasticizer ATBC was provided by Shanghai Haohong Biopharmaceutical Technology Co., Ltd.

[0050] In industrial production, the yield of the plasticizer product is used as an important indicator of the synthesis process. The control variable method is used to explore the product with the best plasticization efficiency through factors such as reaction time, reaction temperature, catalyst addition amount and monomer molar ratio. Therefore, based on Example 1, the reaction conditions were screened, and the results are as follows:

[0051] S1 Screening of reaction conditions based on Example 1:

[0052] Add L-lactic acid and 1,4-butanediol in a molar ratio of 2 to 3:1 to a round-bottom three-necked flask, then add p-toluenesulfonic acid monohydrate accounting for 0.6% to 1.0% of the total mass of the reactants, heat to 110 to 140°C, stir the reaction and reflux for 6 to 9 hours. Connect a condenser and a water separator to the round-bottom three-necked flask to receive the water produced during the reaction. After the reaction is completed, 1,4-butanediol lactate is finally obtained by vacuum distillation, washing and filtering.

[0053] Table 1S1 Condition screening

[0054]

[0055]

[0056] Conclusion: Taking 1,4-butanediol as an example, in the S1 reaction step, with the yield of the product as an indicator, by changing the molar ratio of monomers, the amount of catalyst, the reaction temperature and the reaction time, under the same reaction conditions, if the amount of catalyst is too little, the concentration in the reaction system is not enough, and the number of active centers that can be provided is small, which will affect the reaction rate. If the amount of catalyst is too much, the improvement of the reaction rate is limited; if the reaction temperature is too high and the reaction time is too long, side reactions will occur, resulting in a decrease in yield; if the reaction temperature is too low and the reaction time is too short, the reaction will not be complete; therefore, based on the above results, the following optimal reaction conditions can be selected: the molar ratio of L-lactic acid: dihydric fatty alcohol is 3:1; the amount of catalyst is 0.8%; the reaction temperature is 130℃; and the reaction time is 7h.

[0057] S2 is based on the reaction conditions screening of Example 1

[0058] Add 1,4-butanediol lactate and levulinic acid in a molar ratio of 1:1-2 to a round-bottom three-necked flask, then add p-toluenesulfonic acid monohydrate accounting for 0.6%-1.0% of the total mass of the reactants, heat to 120-160°C, stir the reaction and reflux for 10-14 hours. Connect a condenser and a water separator to the round-bottom three-necked flask to receive the water produced during the reaction. After the reaction is completed, levulinic acid 1,4-butanediol lactate is finally obtained by vacuum distillation, washing and filtering.

[0059] Table 2S2 Condition screening

[0060]

[0061]

[0062] Conclusion: In the S2 reaction step, based on the S1 esterification reaction conditions, considering the effects of the monomer molar ratio of 1,4-butanediol lactate to levulinic acid, catalyst dosage, reaction time and reaction temperature on the product yield, it is consistent with the S1 conclusion. Therefore, the optimal reaction conditions are S1 product: levulinic acid is 1:2, the catalyst dosage is 0.8%; the reaction temperature is 140℃; and the reaction time is 12h.

[0063] Figure 1 The infrared spectra of different dibasic fatty alcohol lactates of the intermediate products of Examples 1 to 4 and the final product dibasic fatty alcohol lactate of levulinic acid are shown in Figure 1. -1 The left and right sides are the asymmetric and symmetric stretching vibration peaks of -CH3-; 1745cm-1 The left and right are the stretching vibration peaks of the carbon-oxygen double bond C=O in the ester bond; 1094, 1040cm -1 It is the asymmetric stretching vibration peak of COC in the ester bond; the above analysis shows that the ester polymer is successfully synthesized.

[0064] Figure 2 The NMR spectra of the intermediate product dibasic fatty alcohol lactate and the final product dibasic fatty alcohol lactate of levulinic acid in Examples 1 to 4. As can be seen from the figure, the signal peak at 7.26ppm belongs to the solvent peak of CDCl3. The signal peak at 1.41ppm belongs to the methyl (-CH3) proton peak in the lactic acid group, and the multi-peak at nearly 4.22ppm belongs to the methylene proton in the dibasic fatty alcohol fragment. The peaks at 1.36ppm and 1.54ppm correspond to the signal peaks of hydroxyl protons (-OH) and carboxyl protons (-COOH), respectively. Compared with 1,4-butanediol lactate, 1,6-hexanediol lactate, 1,8-octanediol lactate and 1,10-decanediol lactate 1 Compared with the H NMR spectrum, the hydroxyl proton peak disappeared, and a new peak was found at about 2.18 ppm in the spectra of Example 1, Example 2, Example 3, and Example 4, which belongs to the -CH3- proton peak in levulinic acid, thereby confirming the occurrence of the reaction. Combined with the infrared spectrum, it can be seen that the plasticizer Example 1, Example 2, Example 3, and Example 4 were successfully synthesized.

[0065] Application Example 1

[0066] The above-mentioned bio-based plasticizer for modifying migration resistance and high plasticizing efficiency is used in the preparation of polyvinyl chloride materials. 40 parts and 60 parts of the bio-based plasticizer prepared in Examples 1 to 4 are respectively blended with 100 parts of polyvinyl chloride thermoplastics, the thermoplastic temperature is 150 to 165°C, the rotation speed is 30 to 50 rpm, the processing time is 3 minutes, and the diol lactic acid-based plasticizer modified polyvinyl chloride material is obtained. Then, a dumbbell-shaped sample for tensile testing is prepared by an injection molding machine, and the tensile test is carried out in accordance with ASTM D638-2003. The test results are shown in Table 3.

[0067] Application Comparative Example 1

[0068] In this comparative example, 100 parts of PVC resin were thermoplastically blended with 40 parts and 60 parts of commercially available plasticizer DOP, respectively, at a thermoplastic temperature of 150-165°C, a rotation speed of 30-50 rpm, and a processing time of 3 minutes. The modified polyvinyl chloride material was then obtained by using an injection molding machine to prepare dumbbell-shaped samples for tensile testing. The tensile test was carried out in accordance with ASTM D638-2003. The results are shown in FIG. Figure 3 .

[0069] Application Comparative Example 2

[0070] In this comparative example, 100 parts of PVC resin were thermoplastically blended with 40 parts and 60 parts of commercially available plasticizer ATBC, respectively, at a thermoplastic temperature of 150-165°C, a rotation speed of 30-50 rpm, and a processing time of 3 minutes. The modified polyvinyl chloride material was then obtained by using an injection molding machine to prepare dumbbell-shaped samples for tensile testing. The tensile test was carried out in accordance with ASTM D638-2003. The results are shown in FIG. Figure 3 .

[0071] Table 3 Tensile properties of modified polyvinyl chloride products

[0072]

[0073]

[0074] Table 4 Thermal stability of modified polyvinyl chloride products

[0075]

[0076]

[0077] Figure 3 The tensile diagram of PVC material with different plasticizers added. It can be seen from the figure that the elongation at break of PVC polymer increases with the increase of the amount of plasticizer added; the elongation at break of PVC polymer increases with the increase of the alkyl chain length. Compared with the known elongation at break of pure PVC at about 62.61%, the elongation at break of PVC polymer with the added amount of 60phr plasticizer in Example 4 is as high as 625.13%, which is 10 times that of pure PVC. This is because the plasticizer is inserted between the rigid PVC molecular chains, and the polar groups (ester groups and ketone groups) in the plasticizer interact with the PVC molecular chains, reducing the interaction force between the PVC molecular chains, and the addition of the plasticizer leads to an increase in the free volume between the PVC molecular chains, thereby increasing the flexibility of the PVC.

[0078] From Table 3 and Figure 3 It can be seen that the bio-based plasticizer-modified polyvinyl chloride products of Examples 1 to 4 prepared by the present invention all have good plasticizing properties. At the same time, as the length of the plasticizer alkyl chain continues to increase, the elongation at break continues to rise; as the plasticizer content increases, the elongation at break gradually increases. Therefore, the order of plasticizing efficiency of the four plasticizers prepared in the examples should be: Example 1 < Example 2 < Example 3 < Example 4. When the alkyl chain length reaches the longest, the product has the best mechanical properties. Comprehensive comparison shows that the plasticizer prepared in this application has good plasticizing effect and easy processability, and the bio-based dibasic fatty alcohol lactate plasticizer can be used as a plasticizer for polyvinyl chloride to obtain polyvinyl chloride products with excellent mechanical properties.

[0079] Compared with the comparative examples, the polyvinyl chloride products modified by the bio-based plasticizer provided by the present invention have excellent plasticizing properties, wherein the elongation at break of the modified polyvinyl chloride products of Examples 1 to 4 is higher than that of the commercially available plasticizers ATBC and DOP of Comparative Examples 1 and 2, reaching 625.13%, indicating that the bio-based dibasic fatty alcohol lactate plasticizer can completely replace the commercially available traditional plasticizers ATBC and DOP.

[0080] Figure 4 The TGA curves of PVC materials with different plasticizers added are shown in Table 4. Combined with Table 4, it can be seen that with the increase in the amount of plasticizer, the thermal stability of the plasticizer-modified PVC material gradually increases; in addition, at the same addition amount, with the increase in the length of the plasticizer alkyl chain, the thermal stability of the modified PVC material gradually increases, indicating that the bio-based dibasic fatty alcohol lactate plasticizer has good thermal stability.

[0081] As shown in Table 4 and Figure 4 As shown, it can be seen from the thermogravimetric curve that when the weight loss is 10%, the temperature of 60phr Example 4 / PVC is 284°C, which is 65°C higher than that of 60phr Comparative Example 1 / PVC (219°C); 31°C higher than that of 60phr Comparative Example 2 / PVC (253°C), indicating that the polyvinyl chloride products modified with bio-based dibasic fatty alcohol lactic acid plasticizers have better thermal stability than those modified with ATBC and DOP plasticizers.

[0082] From the above application examples and comparative examples, it can be seen that the bio-based dihydric fatty alcohol lactate plasticizer provided by the present invention has high plasticizing efficiency, migration resistance and degradability. In addition, the bio-based dihydric fatty alcohol lactate plasticizer provided by the present invention does not contain toxic substances, and the plasticizing effect can effectively replace DOP and ATBC.

[0083] The test method for the volatilization loss of plasticizers is as follows: Cut the PVC test piece into two pieces of 50mm×50mm, mark the cut test pieces and dry them at room temperature for 6 hours, then take out the test piece and weigh its mass on the analytical balance and record it as m0 (accurate to 0.0001g). Place the sample in an oven at 100℃ for 72 hours, then take it out and place it in a dryer to dry for 2 hours, and measure the weight after heating as m. The final result is the average of the mass loss rates of the two groups of samples. The calculation method of the mass loss rate of the PVC test piece refers to the following formula:

[0084]

[0085] W: PVC test piece mass loss rate, %;

[0086] m0: mass of PVC specimen before volatilization, g;

[0087] m: The mass of the PVC specimen after volatilization, g.

[0088] Figure 5 The figure is a volatilization diagram of PVC materials with different plasticizers added. Obviously, whether the plasticizer content is 40phr or 60phr, the order of volatilization loss of plasticizers in plasticized PVC samples is as follows: PVC / DOP>PVC / ATBC>PVC / Example 1>PVC / Example 2>PVC / Example 3>PVC / Example 4. Therefore, compared with commercially available plasticizers DOP and ATBC, the bio-based plasticizer in this patent has better anti-volatility performance.

[0089] The migration resistance test method of plasticizers is as follows: cut the PVC test piece into two pieces of 50mm×50mm, mark the cut test pieces and dry them at room temperature for 6 hours, then take out the test pieces and weigh them on the analytical balance to record their mass as m0 (accurate to 0.0001g). Soak the samples in sealed glass bottles containing the same volume of solvents (deionized water, anhydrous ethanol and n-hexane), put them in a constant temperature water bath at 30°C, take out the test pieces after 3 days, wipe off the residual solvent on the surface of the test pieces with filter paper, and finally place them flat in a blast drying oven at a temperature of 30°C to fully dry them. After drying, weigh their mass and record them as m. The final result is the average of the mass loss rates of the two groups of samples. The calculation method of the mass loss rate of PVC test pieces refers to the following formula:

[0090]

[0091] n: PVC test piece mass loss rate, %;

[0092] m0: mass of PVC test piece before immersion, g;

[0093] m: mass of PVC test piece after immersion, g.

[0094] Figure 6 The migration diagram of PVC materials with different plasticizers added in different solvents. As can be seen from the figure, the trend of the data is consistent. In deionized water, as the content of Example 4 increases, the leaching mass loss increases, but the mass loss rate after 48 hours is basically less than 1%; in anhydrous ethanol and n-hexane, the mass loss rate of Example 4 after 48 hours is less than 2%, showing high solvent resistance, which is mainly attributed to the good compatibility of Example 4 with the PVC matrix and is not easy to be soaked and extracted from the polymer. Example 4 contains more polar groups (ester groups, ketone groups) and has the synergistic effect of a suitable molecular chain length structure, which makes Example 4 more tightly entangled with the PVC molecular chain and not easy to migrate out of the matrix resin. Therefore, it has good durability in solvent media. Therefore, compared with the commercially available plasticizers DOP and ATBC, the bio-based plasticizer in this patent has better anti-migration properties.

[0095] The plasticizer was subjected to a biodegradation experiment in active soil, and the experimental method is as follows: First, 1.0 g of Example 4 was mixed with 500 g of active soil. The resulting mixture was stored in a constant humidity incubator for one month. 500 mL of the dichloromethane and soil mixture was extracted, filtered, and the dichloromethane was removed by a rotary evaporator for analysis to obtain degradation products. As described above, the treatment procedure of a pure active soil sample (500 g) without plasticizer was carried out.

[0096] Figure 7 The infrared and nuclear magnetic spectra of blank soil and soil after adding Example 4 for degradation. The toxicity and non-degradability of traditional plastic additives seriously endanger the natural environment and human health. 1 H NMR analysis of soil extracts showed Figure 7 Soil contains many complex compounds with unknown chemical structures, which leads to the 1 The HNMR spectrum is complex. In the FTIR spectra of the soil extracts with and without Example 4, some similar characteristic absorption peaks appeared, such as 3442 cm -1 The -OH peak of carboxylic acid or alcohol in the soil is 2989 cm -1 and 2858cm -1 The symmetrical absorption peak of the long alkyl chain (-CH2-) is 1740 cm -1 The characteristic peak of ester group (C=O) is 1456cm -1 The absorption peak of the long alkyl chain (-CC-) is 868 cm -1 -1258cm -1 It is the characteristic absorption peak of long alkyl chain (-CH-O-CH-). However, when the soil extract of Example 4 was added, the peak intensity of -OH, -CH2-, C=O and -CC- increased, indicating that the plasticizer has been successfully degraded into small molecular compounds by microorganisms in the soil. 1 It can be seen from the HNMR spectrum that signals are shown at δ = 0.01ppm (-CH3) and δ = 0.80-1.53ppm (-CH2-), and the new peak at δ = 3.57-4.04ppm is derived from the long alkyl chain (-CH-O-CH-). It can be seen from the infrared and nuclear magnetic spectra that Example 4 is completely degraded into small molecular compounds and does not produce toxic substances.

[0097] The above are only several preferred embodiments of the present invention. Any modifications or changes made by technicians familiar with this field according to the spirit and scope of the present invention should be included in the scope of the technical solution of the present invention.

[0098] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A fully bio-based degradable plasticizer having both high plasticizing efficiency and migration resistance, characterized in that: The structural formula of the fully bio-based degradable plasticizer is shown in Formula I: Wherein: n ranges from 1 to 3; R is a saturated alkyl group with 2 to 10 carbon atoms.

2. The method for preparing a fully bio-based degradable plasticizer having high plasticizing efficiency and migration resistance according to claim 1, characterized in that: First, L-lactic acid and dihydric fatty alcohol are subjected to an esterification reaction to obtain a lactate intermediate containing an ester group, and then the lactate intermediate and levulinic acid are subjected to an esterification reaction to obtain a fully bio-based degradable plasticizer with high plasticizing efficiency and migration resistance.

3. The method for preparing a fully bio-based degradable plasticizer having high plasticizing efficiency and migration resistance according to claim 2, characterized in that: The specific preparation steps are: (1) subjecting L-lactic acid and dihydric fatty alcohol to a heating esterification reaction under the action of a catalyst and a water-carrying agent and under the protection of an inert gas, and the reaction product is post-treated to obtain a lactic acid ester intermediate; (2) The lactate intermediate and levulinic acid are subjected to a heating esterification reaction under the action of a catalyst and a water-carrying agent and under the protection of an inert gas. The reaction product is post-treated to obtain a fully bio-based degradable plasticizer with high plasticizing efficiency and migration resistance.

4. The method for preparing a fully bio-based degradable plasticizer having high plasticizing efficiency and migration resistance according to claim 3, characterized in that: In step (1), the dihydric fatty alcohol is one of ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol; and the molar ratio of L-lactic acid to the dihydric fatty alcohol is 1 to 5:

1.

5. A method for preparing a fully bio-based degradable plasticizer having high plasticizing efficiency and migration resistance according to claim 3, characterized in that : In steps (1) and (2), the catalyst is one or more of concentrated sulfuric acid, phosphoric acid, p-toluenesulfonic acid, zinc oxide, aluminum oxide, tin oxide, and stannous oxide. The mass of the catalyst in steps (1) and (2) is 0.6 to 1.0% of the total mass of the reactants.

6. The method for preparing a fully bio-based degradable plasticizer having high plasticizing efficiency and migration resistance according to claim 3, characterized in that : In steps (1) and (2), the water-carrying agent is one of benzene, toluene or cyclohexane.

7. The method for preparing a fully bio-based degradable plasticizer having high plasticizing efficiency and migration resistance according to claim 3, characterized in that: The heating esterification reaction conditions in step (1) are: reflux reaction at 120-160° C. for 6-9 hours.

8. The method for preparing a fully bio-based degradable plasticizer having high plasticizing efficiency and migration resistance according to claim 3, characterized in that: The molar ratio of the lactate intermediate to levulinic acid in step (2) is 1:2.0-2.

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9. The method for preparing a fully bio-based degradable plasticizer having high plasticizing efficiency and migration resistance according to claim 3, characterized in that: The heating esterification reaction conditions in step (2) are: reflux reaction at 120-160° C. for 10-14 hours.

10. Use of the fully bio-based degradable plasticizer having high plasticizing efficiency and migration resistance according to claim 1 in the preparation of polyvinyl chloride materials.

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