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

Abstract

The application belongs to the technical field of bio-based plastic auxiliary agent, and discloses a full-bio-based degradable plasticizer with high plasticizing efficiency and migration resistance. Green biomass raw materials L-lactic acid, a binary fatty alcohol and acetypropionic acid are used as raw materials. Under the action of a catalyst, the L-lactic acid and the binary fatty alcohol are subjected to an esterification reaction to obtain an intermediate product, a binary fatty alcohol lactic acid ester plasticizer. The intermediate product and the acetypropionic acid are further subjected to an esterification reaction to obtain a final product, an acetypropionic acid binary fatty alcohol lactic acid ester plasticizer. The reaction obtains the full-bio-based degradable plasticizer with high plasticizing efficiency and migration resistance. In addition, the full-bio-based degradable plasticizer is suitable for industrial production and is expected to replace traditional plasticizers, i.e., phthalate plasticizers.

Description

Technical Field

[0001] This invention belongs to the field of bio-based plasticizers, specifically relating to a method for preparing a fully bio-based biodegradable plasticizer that combines high plasticizing efficiency and migration resistance. Background Technology

[0002] Polyvinyl chloride (PVC) is one of the most widely used general-purpose resins both domestically and internationally. As a thermoplastic polymer, it is widely used in various fields worldwide, such as cable and wire insulation, medical supplies, packaging materials, pipe fittings, building materials, and children's toys. Due to the presence of dipoles on each C-Cl bond and the interactions between PVC chains, PVC exhibits a hard and brittle nature, which hinders chain movement. The most common method is to add plasticizers to PVC materials to overcome this drawback. However, traditional phthalate plasticizers have poor bonding with the plastic matrix, and can leach or migrate into the environment when plastic products are discarded or used. Traditional plasticizers cannot simultaneously improve plasticizing efficiency and migration resistance, and additives that leach or migrate into the plastic matrix can decompose and produce toxic substances. After degradation, they can also produce harmful substances that may persist in the environment for a long time, ultimately endangering human health.

[0003] Patent CN117844139A prepared a high-efficiency plasticizer to modify polyvinyl chloride (PVC), resulting in hydrolysis-resistant PVC panels. While the prepared plasticizer exhibited good plasticizing effects, the raw materials used were all non-renewable resources, contradicting the concept of green environmental protection. Patents CN114702613B and CN118240187A prepared castor oil-based and tung oil-based plasticizers for PVC and their preparation methods. Although the modified PVC resin showed some improvement in flexibility, its plasticizing efficiency was poor, it was prone to migration, and could not be maintained for long-term use. Furthermore, castor oil and tung oil possess certain biotoxicity, which is detrimental to human health. Patents CN112920394 A, CN106278888 A, CN 110951055 A, CN202310135334.9, and CN116655695 A, among others, synthesize bio-based plasticizers using lactic acid as a raw material. While these plasticizers can effectively improve the toughness of materials, some of their synthetic raw materials are petroleum-based or toxic monomers, which is detrimental to environmental friendliness. Therefore, addressing the shortcomings of existing environmentally friendly plasticizers, such as the non-environmentally friendly nature of their raw materials, low plasticizing efficiency, easy migration, and poor biodegradability, designing a fully bio-based biodegradable plasticizer derived from entirely green raw materials, with high plasticizing efficiency and resistance to migration is a pressing issue for the plastics industry. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems in the prior art by providing a method for preparing a fully bio-based biodegradable plasticizer that combines high plasticizing efficiency and migration resistance. The bio-based plasticizer provided by this invention can overcome the shortcomings of traditional plasticizers, possessing high plasticizing efficiency, migration resistance, and biodegradability, while simultaneously meeting the long-term use requirements of polyvinyl chloride materials.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] The fully biodegradable plasticizer provided by this invention, which combines high plasticizing efficiency and migration resistance, has the general structural formula shown in Formula I:

[0007]

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

[0009] The technical solution of this invention provides a method for preparing a fully biodegradable plasticizer that combines high plasticizing efficiency and migration resistance. The specific steps are as follows:

[0010] (1) L-lactic acid and dihydroxy alcohol were subjected to a heating esterification reaction under the combined action of a catalyst and a dehydrating agent and under the protection of an inert gas. The reaction product was then post-treated to obtain a lactate intermediate.

[0011] (2) The lactate intermediate and levulinic acid were heated and esterified under the combined action of a catalyst and a dehydrating agent and under the protection of an inert gas. The reaction product was post-treated to obtain a fully biodegradable plasticizer with both high plasticizing efficiency and migration resistance.

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

[0013] Further, 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 dehydrating agent is one of benzene, toluene, or cyclohexane, and the amount of dehydrating agent added is 5-40% of the total mass of the reactant raw materials, and the amount of dehydrating agent added is 80-100 ml.

[0014] Furthermore, the 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 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 in this invention belongs to a bio-based environmentally friendly plasticizer, which has good compatibility with PVC, and has both high plasticizing efficiency and migration resistance. It can be used as a main plasticizer for polyvinyl chloride.

[0018] The beneficial effects of this invention are:

[0019] (1) This invention uses green monomers L-lactic acid, dihydroxy alcohol and levulinic acid as the main raw materials, which avoids dependence on petrochemical raw materials and increases the use of bio-based raw materials. Furthermore, it is completely decomposed in active soil and will not produce toxic substances, which is beneficial to environmental protection and is an environmentally friendly material.

[0020] (2) The present invention utilizes the molecular structure characteristics 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 between plasticizer and 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. Attached Figure Description

[0022] Figure 1 The infrared spectra of the products of Examples 1-4 of this invention are shown.

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

[0024] Figure 3 Tensile properties of polyvinyl chloride products prepared using pure polyvinyl chloride and plasticizers from Examples 1-4 and Comparative Examples 1-2.

[0025] Figure 4 Thermogravimetric analysis (TGA) curves of polyvinyl chloride products prepared using plasticizers from pure polyvinyl chloride, Examples 1-4, and Comparative Examples 1-2.

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

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

[0028] Figure 7 The soil degradation infrared and nuclear magnetic resonance spectra of polyvinyl chloride prepared by the plasticizer in Example 4 of this invention are shown. Detailed Implementation

[0029] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

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

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

[0032]

[0033] Where: 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% p-toluenesulfonic acid monohydrate (total mass of L-lactic acid and 1,4-butanediol 0.8%), and 100 mL of cyclohexane are added to a round-bottom three-necked flask. The reaction temperature is 130℃, and the mixture is stirred and refluxed for 7 h. A condenser and a water separator are attached to the round-bottom three-necked flask to collect 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 levulinic acid lactate are as follows: 1,4-butanediol lactate and levulinic acid in a molar ratio of 1:2, 0.8% p-toluenesulfonic acid monohydrate (total mass of 1,4-butanediol lactate and levulinic acid 0.8%), and 100 mL of cyclohexane are added to a round-bottom three-necked flask. Nitrogen gas is introduced as a protective gas, the reaction temperature is 140℃, and the mixture is stirred and refluxed for 12 h. A condenser and a water separator are connected to the round-bottom three-necked flask to collect the water produced during the reaction. After the reaction is completed, 1,4-butanediol levulinic acid lactate 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% p-toluenesulfonic acid monohydrate (total mass of L-lactic acid and 1,6-hexanediol 0.8%), and 100 mL of cyclohexane are added to a round-bottom three-necked flask. Nitrogen gas is introduced as a protective gas, the reaction temperature is 130℃, and the mixture is stirred and refluxed for 7 h. A condenser and a water separator are connected to the round-bottom three-necked flask to collect 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 levulinic acid are as follows: 1,6-hexanediol lactate and levulinic acid in a molar ratio of 1:2, 0.8% p-toluenesulfonic acid monohydrate (total mass of 1,6-hexanediol lactate and levulinic acid 0.8%), and 100 mL of cyclohexane are added to a round-bottom three-necked flask. Nitrogen gas is introduced as a protective gas, and the reaction temperature is 140℃. The mixture is stirred and refluxed for 12 h. A condenser and a water separator are attached to the round-bottom three-necked flask to collect the water produced during the reaction. After the reaction is completed, 1,6-hexanediol lactate 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% p-toluenesulfonic acid monohydrate (total mass of L-lactic acid and 1,8-octanediol 0.8%), and 100 mL of cyclohexane are added to a round-bottom three-necked flask. Nitrogen gas is introduced as a protective gas, the reaction temperature is 130℃, and the mixture is stirred and refluxed for 7 h. A condenser and a water separator are connected to the round-bottom three-necked flask to collect 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 levulinic acid are as follows: 1,8-octanediol lactate and levulinic acid in a molar ratio of 1:2, 0.8% p-toluenesulfonic acid monohydrate (total mass of 1,8-octanediol lactate and levulinic acid 0.8%), and 100 mL of cyclohexane are added to a round-bottom three-necked flask. Nitrogen gas is introduced as a protective gas, the reaction temperature is 140℃, and the mixture is stirred and refluxed for 12 h. A condenser and a water separator are connected to the round-bottom three-necked flask to collect the water produced during the reaction. After the reaction is completed, 1,8-octanediol lactate 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% p-toluenesulfonic acid monohydrate (total mass of L-lactic acid and 1,10-decanediol 0.8%), and 100 mL of cyclohexane are added to a round-bottom three-necked flask. Nitrogen gas is introduced as a protective gas, the reaction temperature is 130℃, and the mixture is stirred and refluxed for 7 h. A condenser and a water separator are connected to the round-bottom three-necked flask to collect 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% p-toluenesulfonic acid monohydrate (total mass of 1,10-decanediol lactate and levulinic acid 0.8%), and 100 mL of cyclohexane are added to a round-bottom three-necked flask. Nitrogen gas is introduced as a protective gas, and the reaction temperature is 140℃. The mixture is stirred and refluxed for 12 h. A condenser and a water separator are attached to the round-bottom three-necked flask to collect 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 is provided by Shanghai Maclean Biochemical Technology Co., Ltd.

[0048] Comparative Example 2

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

[0050] In industrial production, the yield of plasticizer products is used as an important indicator of the synthesis process. Using a controlled variable method, factors such as reaction time, reaction temperature, catalyst dosage, and monomer molar ratio were considered to explore the product with the best plasticizing efficiency. Therefore, based on Example 1, reaction conditions were screened, and the results are as follows:

[0051] S1 screened reaction conditions based on Example 1:

[0052] L-lactic acid and 1,4-butanediol were added to a three-necked flask with a molar ratio of 2–3:1, followed by 0.6%–1.0% p-toluenesulfonic acid monohydrate by mass of the total reactants. The mixture was heated to 110–140°C, stirred, and refluxed for 6–9 hours. A condenser and a water separator were attached to the three-necked flask to collect the water produced during the reaction. After the reaction was complete, 1,4-butanediol lactate was obtained by vacuum distillation, washing, and filtration.

[0053] Table 1S1 Condition Filtering

[0054]

[0055]

[0056] Conclusion: Taking 1,4-butanediol as an example, in the S1 reaction step, using the product yield as an indicator, by changing the monomer molar ratio, catalyst dosage, reaction temperature, and reaction time, under the same reaction conditions, insufficient catalyst dosage results in insufficient concentration in the reaction system, providing fewer active centers and affecting the reaction rate; excessive catalyst dosage has limited effect on increasing the reaction rate; excessively high reaction temperature and excessively long reaction time lead to side reactions, resulting in a decrease in yield; excessively low reaction temperature and excessively short reaction time lead to incomplete reaction. Therefore, based on the above results, the following optimal reaction conditions can be selected: L-lactic acid:difatty alcohol molar ratio of 3:1; catalyst dosage of 0.8%; reaction temperature of 130℃; and reaction time of 7h.

[0057] S2 was screened based on the reaction conditions of Example 1.

[0058] In a round-bottom three-necked flask, 1,4-butanediol lactate and levulinic acid were added in a molar ratio of 1:1 to 2. Then, 0.6% to 1.0% (by mass) of p-toluenesulfonic acid monohydrate was added. The mixture was heated to 120–160 °C, stirred, and refluxed for 10–14 hours. A condenser and a water separator were attached to the flask to collect the water produced during the reaction. After the reaction was complete, 1,4-butanediol lactate levulinic acid was finally obtained by vacuum distillation, washing, and filtration.

[0059] Table 2S2 Condition Filtering

[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, the results are consistent with those of S1. Therefore, the optimal reaction conditions are: S1 product:levulinic acid ratio of 1:2, catalyst dosage of 0.8%, reaction temperature of 140℃, and reaction time of 12h.

[0063] Figure 1 The images show the infrared spectra of the intermediate products (different dihydroxyl lactates) and the final product (dihydroxyl lactate levulinate) from Examples 1-4. Observe all curves at 2991 and 2858 cm⁻¹. -1 The left and right sides show the asymmetric and symmetric stretching vibration peaks of -CH3-; 1745cm-1 The left and right peaks represent the stretching vibrations of the C=O carbon-oxygen double bond in the ester bond; 1094 and 1040 cm⁻¹. -1 The peak represents the asymmetric stretching vibration of COC in the ester bond; the above analysis demonstrates the successful synthesis of ester polymers.

[0064] Figure 2 The NMR spectra of the intermediate product, dihydroxyl lactate, and the final product, dihydroxyl levulinate lactate, from Examples 1-4 are shown. As can be seen from the figure, the signal peak at 7.26 ppm is attributed to the solvent peak of CDCl3. The signal peak at 1.41 ppm is attributed to the methyl (-CH3) proton peak in the lactic acid group, and the multiple peaks near 4.22 ppm are attributed to the methylene proton in the dihydroxyl alcohol fragment. The peaks at 1.36 ppm and 1.54 ppm correspond to the signal peaks of the hydroxyl proton (-OH) and carboxyl proton (-COOH), respectively. These peaks are related to the NMR spectra of 1,4-butanediol lactate, 1,6-hexanediol lactate, 1,8-octanediol lactate, and 1,10-decanediol lactate. 1 Compared to the 1H NMR spectrum, the hydroxyl proton peak disappeared, and a new peak was found at approximately 2.18 ppm in the spectra of Examples 1, 2, 3, and 4. This new peak belongs to the -CH3- proton peak of levulinic acid, thus confirming the occurrence of the reaction. Combined with the infrared spectra, this demonstrates the successful synthesis of the plasticizers in Examples 1, 2, 3, and 4.

[0065] Application Example 1

[0066] The application of the above-mentioned bio-based plasticizers with improved migration resistance and high plasticizing efficiency in the preparation of polyvinyl chloride (PVC) materials involved blending 40 parts and 60 parts of the bio-based plasticizers prepared in Examples 1-4 with 100 parts of PVC thermoplastic. The thermoplasticizing temperature was 150-165°C, the rotation speed was 30-50 rpm, and the processing time was 3 minutes. The resulting material was PVC modified with diol lactic acid-based plasticizer. Dumbbell-shaped samples for tensile testing were then prepared using an injection molding machine. The tensile tests were conducted according to 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. The thermoplastic temperature was 150–165℃, the rotation speed was 30–50 rpm, and the processing time was 3 minutes. The resulting material was modified PVC. Dumbbell-shaped samples for tensile testing were then prepared using an injection molding machine. The tensile tests were performed according to ASTM D638-2003, and the results are shown below. 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. The thermoplastic temperature was 150–165℃, the rotation speed was 30–50 rpm, and the processing time was 3 minutes. The resulting material was modified PVC. Dumbbell-shaped samples for tensile testing were then prepared using an injection molding machine. The tensile tests were performed according to ASTM D638-2003, and the results are shown below. Figure 3 .

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

[0072]

[0073]

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

[0075]

[0076]

[0077] Figure 3 The figures show tensile diagrams of PVC materials with different added plasticizers. As can be seen from the figures, the elongation at break of the PVC polymer increases with the increase of the amount of plasticizer added; the elongation at break of the PVC polymer also increases with the increase of the alkyl chain length. Compared to the known elongation at break of pure PVC (around 62.61%), the PVC polymer with the plasticizer in Example 4 (60 phr) exhibits an elongation at break as high as 625.13%, which is 10 times that of pure PVC. This is because the plasticizer inserts between the rigid PVC molecular chains, and the polar groups (ester and ketone groups) in the plasticizer interact with the PVC molecular chains, reducing the interaction forces between the PVC molecular chains. Furthermore, the addition of the plasticizer increases 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 PVC products prepared in Examples 1-4 of this invention all exhibit good plasticizing properties. Furthermore, as the alkyl chain length of the plasticizer increases, the elongation at break continuously rises; 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 its longest, the product possesses the best mechanical properties. A comprehensive comparison shows that the plasticizer prepared in this application has good plasticizing effect and easy processability. The bio-based dihydroxyl lactate plasticizer can be used as a plasticizer for PVC to obtain PVC products with excellent mechanical properties.

[0079] Compared with the comparative examples, the polyvinyl chloride (PVC) products modified with the bio-based plasticizer provided by this invention exhibit excellent plasticizing properties. Specifically, compared with the commercially available plasticizers ATBC and DOP in Examples 1-4 and Comparative Examples 1 and 2, the modified PVC products show a higher elongation at break, reaching 625.13%. This demonstrates that the bio-based binary 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 are shown in Table 4. Combined with Table 4, it can be seen that the thermal stability of plasticizer-modified PVC materials gradually increases with increasing plasticizer dosage. Furthermore, at the same dosage, the thermal stability of modified PVC materials gradually increases with increasing alkyl chain length of the plasticizer, indicating that bio-based dihydroxyl lactate plasticizers have good thermal stability.

[0081] As shown in Table 4 and Figure 4 As shown in the thermogravimetric curves, when the weight loss is 10%, the temperature of 60 phr Example 4 / PVC is 284℃, which is 65℃ higher than that of 60 phr Comparative Example 1 / PVC (219℃) and 31℃ higher than that of 60 phr Comparative Example 2 / PVC (253℃). This indicates that the PVC products modified with bio-based di-fatty alcohol lactic acid plasticizer have better thermal stability than the PVC products modified with ATBC and DOP plasticizers.

[0082] As can be seen from the above application examples and comparative examples, the bio-based dihydroxyl lactate plasticizer provided by the present invention possesses high plasticizing efficiency, migration resistance, and biodegradability. Furthermore, the bio-based dihydroxyl lactate plasticizer provided by the present invention does not contain toxic substances, and its plasticizing effect can effectively replace DOP and ATBC.

[0083] The test method for the volatilization loss of plasticizers is as follows: Cut two 50mm×50mm samples from a PVC test piece. Mark the cut samples and dry them at room temperature for 6 hours. Then, remove the samples and weigh them on an analytical balance, recording the mass as m0 (accurate to 0.0001g). Place the sample in an oven at 100℃ for 72 hours, then remove it and dry it in a desiccator for 2 hours. Measure the weight after heating, recording it as m. The final result is the average of the mass loss rates of the two groups of samples. The calculation method for the mass loss rate of the PVC test piece is as follows:

[0084]

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

[0086] m0: Mass of PVC sample before volatilization, g;

[0087] m: Mass of the PVC sample after volatilization, in grams.

[0088] Figure 5 The following are volatilization diagrams for PVC materials with different plasticizers. It is evident that, regardless of whether the plasticizer content is 40 phr or 60 phr, the order of plasticizer volatilization loss in the plasticized PVC samples is as follows: PVC / DOP > PVC / ATBC > PVC / Example 1 > PVC / Example 2 > PVC / Example 3 > PVC / Example 4. Therefore, compared to commercially available plasticizers DOP and ATBC, the bio-based plasticizer in this patent exhibits better anti-vaporization properties.

[0089] The migration resistance test method for plasticizers is as follows: Cut PVC test pieces into two 50mm × 50mm samples. Mark the cut samples and dry them at room temperature for 6 hours. Then, remove the samples and weigh them on an analytical balance, recording their mass as m0 (accurate to 0.0001g). Immerse the samples in sealed glass bottles containing the same volume of solvent (deionized water, anhydrous ethanol, and n-hexane), respectively. Place the bottles in a 30℃ constant temperature water bath for 3 days. After 3 days, remove the samples, wipe off any residual solvent with filter paper, and finally dry them thoroughly in a 30℃ forced-air drying oven. After drying, weigh the samples and record their mass as m. The final result is the average of the mass loss rates of the two groups of samples. The calculation method for the mass loss rate of PVC test pieces is as follows:

[0090]

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

[0092] m0: Mass of the PVC sample before immersion, in g;

[0093] m: Mass of PVC sample after immersion, in g.

[0094] Figure 6 The graph shows the migration of PVC materials with different plasticizers in different solvents. As can be seen from the graph, the data shows a consistent trend: in deionized water, the leaching mass loss increases with the increase of the content of Example 4, but the mass loss rate after 48 hours is basically <1%; in anhydrous ethanol and n-hexane, the mass loss rate of Example 4 after 48 hours is <2%, exhibiting high solvent resistance. This is mainly attributed to the good compatibility of Example 4 with the PVC matrix, making it difficult to be extracted from the polymer. Example 4 contains more polar groups (ester groups, ketone groups) and has a synergistic effect of suitable molecular chain length structure, making Example 4 more tightly entangled with the PVC molecular chain and less likely to migrate from the matrix resin. Therefore, it has good durability in solvent media. Therefore, compared with commercially available plasticizers DOP and ATBC, the bio-based plasticizer in this patent has better anti-migration performance.

[0095] The plasticizer was biodegraded in activated soil using the following method: First, 1.0 g of Example 4 was mixed with 500 g of activated soil. The resulting mixture was stored in a humidity incubator for one month. 500 mL of the dichloromethane-soil mixture was extracted, filtered, and the dichloromethane was removed by a rotary evaporator for analysis to obtain the degradation products. The same procedure was followed for processing a 500 g sample of pure activated soil without the plasticizer.

[0096] Figure 7 Infrared and nuclear magnetic resonance spectra of blank soil and soil after degradation using the additives from Example 4. The toxicity and non-degradability of traditional plastic additives seriously endanger the natural environment and human health. Using FTIR and... 1 ¹H NMR analysis of soil extracts yielded the following results: Figure 7 As shown. The soil contains many complex compounds with unknown chemical structures, leading to difficulties in FTIR and... 1 The HNMR spectra were complex. Comparing the FTIR spectra of the soil extracts with and without Example 4, some similar characteristic absorption peaks appeared, such as at 3442 cm⁻¹. -1 The peak at 2989 cm⁻¹ represents the -OH peak of carboxylic acids or alcohols in the soil. -1 and 2858cm -1 The peak at 1740 cm⁻¹ is a symmetrical absorption peak for long alkyl chains (-CH₂-). -1 The peak at 1456 cm⁻¹ is a characteristic peak of the ester group (C=O). -1 The absorption peak at 868 cm⁻¹ is for long alkyl chains (-CC-). -1 -1258cm -1 The characteristic absorption peaks are for long alkyl chains (-CH-O-CH-). However, in the soil extract of Example 4, the peak intensities of -OH, -CH2-, C=O, and -CC- increased, indicating that the plasticizer had been successfully degraded into smaller molecule compounds by soil microorganisms. 1 The HNMR spectrum shows signals at δ = 0.01 ppm (-CH3) and δ = 0.80-1.53 ​​ppm (-CH2-), and the new peak at δ = 3.57-4.04 ppm originates from the long alkyl chain (-CH-O-CH-). Infrared and NMR spectra indicate that Example 4 was completely degraded into small molecule compounds without producing toxic substances.

[0097] The above description is only a few preferred embodiments of the present invention. Any modifications or alterations made by those skilled in the art in accordance with the spirit and scope of the present invention should be included within the scope of the present invention.

[0098] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A fully biodegradable plasticizer with both high plasticizing efficiency and migration resistance, characterized in that, The structural formula of the fully bio-based biodegradable plasticizer is shown in Formula I: Where: 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 biodegradable plasticizer with both high plasticizing efficiency and migration resistance according to claim 1, characterized in that: First, L-lactic acid and dihydroxy alcohol are esterified to obtain a lactate intermediate containing ester groups. Then, the lactate intermediate and levulinic acid are esterified to obtain a fully biodegradable plasticizer with both high plasticizing efficiency and migration resistance.

3. The method for preparing a fully biodegradable plasticizer with both high plasticizing efficiency and migration resistance according to claim 2, characterized in that: The specific preparation steps are as follows: (1) L-lactic acid and dihydroxy alcohol were subjected to a heating esterification reaction under the combined action of a catalyst and a dehydrating agent and under the protection of an inert gas. The reaction product was then post-treated to obtain a lactate intermediate. (2) The lactate intermediate and levulinic acid are heated and esterified under the combined action of a catalyst and a dehydrating agent and under the protection of an inert gas. The reaction product is then post-treated to obtain a fully biodegradable plasticizer with both high plasticizing efficiency and migration resistance.

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

1.

5. The method for preparing a fully biodegradable plasticizer with both 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 biodegradable plasticizer with both high plasticizing efficiency and migration resistance according to claim 3, characterized in that... In steps (1) and (2), the dehydrating agent is one of benzene, toluene or cyclohexane.

7. The method for preparing a fully biodegradable plasticizer with both high plasticizing efficiency and migration resistance according to claim 3, characterized in that: The conditions for the heating esterification reaction in step (1) are: reflux reaction at 120-160℃ for 6-9 hours.

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

3.

9. The method for preparing a fully biodegradable plasticizer with both high plasticizing efficiency and migration resistance according to claim 3, characterized in that: The conditions for the heating esterification reaction in step (2) are: reflux reaction at 120-160℃ for 10-14 hours.

10. The application of the fully biodegradable plasticizer with high plasticizing efficiency and migration resistance as described in claim 1 in the preparation of polyvinyl chloride materials.

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