A biodegradable plastic article and a method for producing the same

Abstract

The application belongs to the technical field of plastic products, and particularly relates to a biodegradable plastic product and a preparation method thereof. The biodegradable plastic product comprises the following raw materials in parts by weight: 75-90 parts of polylactic acid, 10-20 parts of polycaprolactone, 10-15 parts of a multifunctional additive, 0.2-0.5 parts of an antioxidant, 1-2 parts of a nucleating agent, and 3-5 parts of a plasticizer. The multifunctional additive is added to polylactic acid and polycaprolactone to endow the material with flame-retardant function and anti-aging function, so that the plastic product has excellent flame-retardant performance and anti-aging performance while maintaining excellent mechanical performance.

Description

Technical Field

[0001] This invention belongs to the field of plastic products technology, specifically relating to a biodegradable plastic product and its preparation method. Background Technology

[0002] Polylactic acid (PLA), as a typical bio-based polyester biodegradable plastic, possesses good biocompatibility and processing properties, and is considered one of the ideal alternatives to traditional petroleum-based plastics. However, inherent defects of PLA severely limit its application in high-end and durable products, mainly in the following three aspects: First, PLA's limiting oxygen index (LOI) is only about 19%, classifying it as a flammable material. When burning, it exhibits severe melting and dripping, posing significant safety hazards. This makes it difficult to directly apply PLA to fields such as electronics, automotive interiors, etc., where multifunctional additives are mandatory. Second, PLA has poor toughness and low elongation at break, making it prone to brittle fracture under impact or stress. Although toughening modifications are often made by adding plasticizers and elastomers (such as polycaprolactone), this often comes at the cost of sacrificing the material's rigidity, strength, and heat distortion temperature, making it difficult to achieve a high-performance balance. Third, it has poor weather resistance, especially weak resistance to ultraviolet aging. The ester bonds in the PLA molecular chain are prone to photo-oxidative degradation under ultraviolet radiation, leading to a decrease in molecular weight, yellowing of products, and a sharp loss of mechanical properties (such as tensile strength). This poses a serious challenge to the service life of PLA products in outdoor environments.

[0003] To improve the multifunctionality of PLA, multifunctional additives are typically required. However, traditional multifunctional additives (such as inorganic hydroxides, certain halogenated or phosphorus-based multifunctional additives) often face problems such as high dosage requirements, poor compatibility with the PLA matrix, severe deterioration of the material's mechanical properties, or easy migration and precipitation during processing and use. More importantly, these conventional multifunctional additives generally lack the ability to resist UV aging, failing to address the fundamental problem of PLA's poor weather resistance.

[0004] Therefore, developing a multifunctional additive that is compatible with PLA and can efficiently add multiple functions without damaging or even synergistically improve its mechanical properties and UV aging resistance has become a key technological challenge to promote the high-end and functional applications of PLA. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a biodegradable plastic product and a method for preparing the same.

[0006] The objective of this invention is achieved through the following technical solution: A biodegradable plastic product comprises the following raw materials in parts by weight: 75-90 parts polylactic acid, 10-20 parts polycaprolactone, 10-15 parts multifunctional additives, 0.2-0.5 parts antioxidants, 1-2 parts nucleating agents, and 3-5 parts plasticizers. The structural formula of the multifunctional additive is as follows: .

[0007] Furthermore, the preparation process of the multifunctional additive is as follows: (1) Trichlorocyanuric acid is added to dichloromethane and reacted with benzotriazole in the presence of diisopropylethylamine to obtain intermediate 1; the structural formula of intermediate 1 is as follows: ; (2) 3-Amino-1-propanol was added to tetrahydrofuran and reacted with intermediate 1 in the presence of potassium carbonate to obtain intermediate 2; the structural formula of intermediate 2 is as follows: ; (3) Add aminotrimethylphosphonic acid to dichloromethane and react it with intermediate 2 under the action of N,N-dicyclohexylcarbodiimide and 4-dimethylaminopyridine to obtain the multifunctional additive.

[0008] Further, in step (1), the molar ratio of cyanuric chloride, diisopropylethylamine and benzotriazole is 1:(2-2.4):(2-2.4); the reaction temperature is -5 to 0 °C and the time is 20 to 30 min.

[0009] Further, in step (2), the molar ratio of intermediate 1, 3-amino-1-propanol and potassium carbonate is 1:(1-1.2):(5-6); the reaction time is 3-4 h.

[0010] Further, in step (3), the molar ratio of aminotrimethylphosphonic acid, N,N-dicyclohexylcarbodiimide, 4-dimethylaminopyridine and intermediate 2 is 1:(1.5-1.6):(0.4-0.5):(3-3.3); the reaction temperature is 50-60 °C and the time is 3-4 h.

[0011] Furthermore, the polylactic acid has a weight-average molecular weight of 150,000 to 250,000 g / mol; and the polycaprolactone has a weight-average molecular weight of 40,000 to 90,000 g / mol.

[0012] Further, the antioxidant is any one of antioxidant 168, antioxidant 1076, antioxidant 1010, antioxidant CA, antioxidant B900, antioxidant BHT, antioxidant 264, and antioxidant DLTP; the nucleating agent is talc; and the plasticizer is PEG.

[0013] A method for preparing the above-mentioned biodegradable plastic product includes the following steps: (a) The raw materials are dried and mixed to obtain a premix; the premix is ​​added to an extruder for melt extrusion and granulation to obtain composite particles; (b) The composite particles are dried and then injection molded and cooled to obtain the biodegradable plastic product.

[0014] Further, the mixing rate in step (a) is 500-1000 rpm and the time is 5-10 min; the temperature of the melt extrusion is 160-190 ℃ and the screw speed is 100-200 rpm.

[0015] Further, in step (b), the injection molding temperature is 180–200 °C and the pressure is 80–120 MPa; the cooling time is 20–30 s.

[0016] The present invention has the following advantages over the prior art: 1. The biodegradable plastic product of the present invention comprises raw materials such as polylactic acid, polycaprolactone, multifunctional additives and antioxidants. The plastic product maintains excellent mechanical properties while also possessing excellent flame retardant and anti-aging properties.

[0017] 2. The multifunctional additive prepared by this invention can endow materials with flame-retardant and anti-aging functions. This multifunctional additive uses cyanuric chloride as its core, grafting benzotriazole UV-absorbing units through etherification and amination reactions, followed by esterification and bonding with aminotrimethylphosphonic acid, constructing a star-shaped multi-arm molecule integrating phosphorus-nitrogen flame retardancy and UV stabilization. The phosphate ester groups and triazine rings in the molecule constitute a phosphorus-nitrogen synergistic flame-retardant system: upon heating, the phosphorus components catalyze polymer char formation, forming a dense char layer that isolates heat and oxygen, while the triazine rings and benzotriazole decompose to generate inert gases, diluting the combustible material and interrupting the combustion chain reaction, thereby achieving highly efficient flame retardancy without dripping at low addition levels. The benzotriazole unit, stably linked by ether bonds in the molecule, serves as a highly efficient UV absorber group. It can preferentially absorb and convert UV light energy, forming a "molecular-level" protective barrier before the polylactic acid molecular chain is subjected to photo-oxidative attack. This significantly delays the aging and degradation of the material from the root, giving the product excellent weather resistance.

[0018] 3. The multifunctional additive prepared by this invention has a star-shaped multi-arm structure. Its large rigid side groups can serve as physical cross-linking points, inducing crazing and absorbing impact energy to improve toughness. At the same time, the flexible propyl chain and moderate steric hindrance effect can suppress the brittleness caused by excessive crystallization of polylactic acid while avoiding the severe embrittlement often caused by the addition of rigid fillers. Thus, it can maintain good mechanical balance of the material while imparting multiple functions. In addition, it works synergistically with flexible components such as polycaprolactone and plasticizers in the formulation to further improve the toughness of the composite material. Detailed Implementation

[0019] The technical solution of the present invention will be further described below with reference to specific embodiments. However, those skilled in the art should understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the reagents or instruments used are all conventional products obtained through commercial channels.

[0020] In the following examples or comparative examples, the weight-average molecular weight of polylactic acid is 200,000 g / mol; the weight-average molecular weight of polycaprolactone is 80,000 g / mol; the antioxidant is antioxidant 1010; the nucleating agent is talc; and the plasticizer is PEG600.

[0021] Example 1 Example 1 provides a biodegradable plastic product comprising the following raw materials in parts by weight: 80 parts polylactic acid, 15 parts polycaprolactone, 12 parts multifunctional additive, 0.4 parts antioxidant, 1.5 parts nucleating agent, and 4 parts plasticizer.

[0022] The above-mentioned multifunctional additive is prepared by the following process: (1) Dissolve cyanuric chloride (CAS: 108-77-0; 50 mmol) in dichloromethane (150 mL) at -5 °C, then add diisopropylethylamine (DIPEA, 110 mmol) and stir for 6 min. Add benzotriazole (CAS: 95-14-7, 110 mmol) dropwise to the reaction mixture over 9 min, and continue stirring at -5 °C for 25 min. Filter the mixture, wash the precipitate with water (100 mL) and ether (50 mL) successively, and dry to obtain intermediate 1 with a yield of 95.0%. 1 H NMR (C 15 H8ClN9O2, 400 MHz, d6-DMSO) δ 7.98 (d, 4H), 7.42 (t, 4H); HRMS (ESI +): [M+H] + The calculated value is 382.05, and the value is found to be 382.05.

[0023] (2) 3-Amino-1-propanol (CAS: 156-87-6, 11 mmol) was added to a tetrahydrofuran solution (60 mL) of intermediate 1 (10 mmol) and potassium carbonate (55 mmol). The mixture was stirred at room temperature for 3.5 h, then poured into water and extracted with ethyl acetate. The organic layer was washed with saturated brine, dried over sodium sulfate, concentrated and purified by silica gel column chromatography (petroleum ether / ethyl acetate = 5:1). Then it was recrystallized from dichloromethane to give intermediate 2 with a yield of 91.0%. 1 H NMR (C 18 H 16 N 10 HRMS (ESI) + ): [M+H] + The calculation yields 421.14, and the value is found to be 421.14.

[0024] (3) Add aminotrimethylphosphonic acid (CAS: 6419-19-8, 10 mmol) to a dichloromethane solution (100 mL), then add N,N-dicyclohexylcarbodiimide (DCC, 15 mmol) and 4-dimethylaminopyridine (DMAP, 4 mmol), stir at 55 °C for 1 h, then add intermediate 2 (32 mmol), and continue stirring at 55 °C for 3.5 h; after the reaction is complete, stir with a 10% NaOH mixed solution, separate the liquid and liquid phases, dry the organic phase with anhydrous sodium sulfate, concentrate and separate by rapid column chromatography (dichloromethane / methanol = 97:3) to obtain a multifunctional additive; 1 H NMR (C 57 H 54 N 31 O 15 P3, 400 MHz, d6-DMSO) δ 7.98(d, 12H), 7.42 (t, 12H), 7.02 (s, 3H), 4.82(s, 3H), 4.09-4.05(t, 6H), 3.42-3.39 (t, 6H), 2.78(s, 6H), 1.92-1.88 (m, 6H); HRMS (ESI + ): [M+H]+ The calculation yields 1506.36, and the solution is 1506.37.

[0025] Example 1 also provides a method for preparing the above-mentioned biodegradable plastic product, comprising the following steps: (a) Place each raw material in a vacuum drying oven and dry for 24 h to remove moisture; then, add each raw material to a high-speed mixer according to the above weight ratio and mix at 800 rpm for 8 min to obtain a premix; add the premix to a twin-screw extruder for melt extrusion, set the feed section temperature to 165 ℃, the blending section temperature to 185 ℃, the extrusion section temperature to 175 ℃, and the screw speed to 150 rpm; after extrusion, obtain composite granules by water cooling, stretching, and pelletizing. (b) The composite particles are dried, injection molded using an injection molding machine, and cooled to obtain the biodegradable plastic product; wherein the injection temperature is 190 °C, the pressure is 100 MPa, and the cooling time is 25 s.

[0026] Example 2 Example 2 provides a biodegradable plastic product comprising the following raw materials in parts by weight: 75 parts polylactic acid, 10 parts polycaprolactone, 10 parts multifunctional additive, 0.2 parts antioxidant, 1 part nucleating agent, and 3 parts plasticizer.

[0027] The above-mentioned multifunctional additive is prepared by the following process: (1) Dissolve 50 mmol of cyanuric chloride in 150 mL of dichloromethane at 0 °C, then add 100 mmol of diisopropylethylamine and stir for 5 min. Add 100 mmol of benzotriazole dropwise to the reaction mixture over 8 min and continue stirring at 0 °C for 20 min. Filter the mixture and wash the precipitate with 100 mL of water and 50 mL of ether. After drying, intermediate 1 is obtained with a yield of 94.2%.

[0028] (2) 3-amino-1-propanol (10 mmol) was added to a tetrahydrofuran solution (50 mL) of intermediate 1 (10 mmol) and potassium carbonate (50 mmol). The mixture was stirred at room temperature for 3 h, then poured into water and extracted with ethyl acetate. The organic layer was washed with saturated brine, dried over sodium sulfate, concentrated and purified by silica gel column chromatography (petroleum ether / ethyl acetate = 5:1). Then it was recrystallized with dichloromethane to give intermediate 2 with a yield of 90.1%.

[0029] (3) Add aminotrimethylphosphonic acid (CAS: 6419-19-8, 10 mmol) to a dichloromethane solution (100 mL), then add N,N-dicyclohexylcarbodiimide (DCC, 15 mmol) and 4-dimethylaminopyridine (DMAP, 5 mmol), stir at 50 °C for 1.5 h, then add intermediate 2 (30 mmol), and continue stirring at 50 °C for 4 h; after the reaction is complete, stir with a 10% NaOH mixed solution, separate the liquid and liquid phases, dry the organic phase with anhydrous sodium sulfate, concentrate and separate by rapid column chromatography (dichloromethane / methanol = 97:3) to obtain the multifunctional additive.

[0030] Example 2 also provides a method for preparing the above-mentioned biodegradable plastic product, comprising the following steps: (a) Place each raw material in a vacuum drying oven and dry for 24 h to remove moisture; then, add each raw material to a high-speed mixer according to the above weight ratio and mix at 500 rpm for 10 min to obtain a premix; add the premix to a twin-screw extruder for melt extrusion, set the feed section temperature to 160 ℃, the blending section temperature to 180 ℃, the extrusion section temperature to 170 ℃, and the screw speed to 200 rpm; after extrusion, obtain composite particles by water cooling, drawing, and pelletizing. (b) The composite particles are dried, injection molded using an injection molding machine, and cooled to obtain the biodegradable plastic product; wherein the injection temperature is 180 °C, the pressure is 120 MPa, and the cooling time is 20 s.

[0031] Example 3 Example 3 provides a biodegradable plastic product comprising the following raw materials in parts by weight: 90 parts polylactic acid, 20 parts polycaprolactone, 15 parts multifunctional additive, 0.5 parts antioxidant, 2 parts nucleating agent, and 5 parts plasticizer.

[0032] The above-mentioned multifunctional additive is prepared by the following process: (1) Dissolve 50 mmol of cyanuric chloride in 150 mL of dichloromethane at 0 °C, then add 120 mmol of diisopropylethylamine and stir for 8 min. Add 120 mmol of benzotriazole dropwise to the reaction mixture over 10 min and continue stirring at 0 °C for 30 min. Filter the mixture and wash the precipitate with 100 mL of water and 50 mL of ether. After drying, intermediate 1 is obtained with a yield of 92.6%.

[0033] (2) 3-amino-1-propanol (12 mmol) was added to a tetrahydrofuran solution (80 mL) of intermediate 1 (10 mmol) and potassium carbonate (60 mmol). The mixture was stirred at room temperature for 4 h, then poured into water and extracted with ethyl acetate. The organic layer was washed with saturated brine, dried over sodium sulfate, concentrated and purified by silica gel column chromatography (petroleum ether / ethyl acetate = 5:1). Then it was recrystallized with dichloromethane to give intermediate 2 with a yield of 89.4%.

[0034] (3) Add aminotrimethylphosphonic acid (CAS: 6419-19-8, 10 mmol) to a dichloromethane solution (100 mL), then add N,N-dicyclohexylcarbodiimide (DCC, 16 mmol) and 4-dimethylaminopyridine (DMAP, 5 mmol), stir at 60 °C for 1 h, then add intermediate 2 (33 mmol), and continue stirring at 60 °C for 3 h; after the reaction is complete, stir with a 10% NaOH mixed solution, separate the liquid and liquid phases, dry the organic phase with anhydrous sodium sulfate, concentrate and separate by rapid column chromatography (dichloromethane / methanol = 97:3) to obtain a multifunctional additive.

[0035] Example 3 also provides a method for preparing the above-mentioned biodegradable plastic product, comprising the following steps: (a) Place each raw material in a vacuum drying oven and dry for 24 h to remove moisture; then, add each raw material to a high-speed mixer according to the above weight ratio and mix at 1000 rpm for 5 min to obtain a premix; add the premix to a twin-screw extruder for melt extrusion, set the feed section temperature to 170 ℃, the blending section temperature to 190 ℃, the extrusion section temperature to 180 ℃, and the screw speed to 200 rpm; after extrusion, obtain composite particles by water cooling, drawing, and pelletizing. (b) The composite particles are dried, injection molded using an injection molding machine, and cooled to obtain the biodegradable plastic product; wherein the injection temperature is 200 °C, the pressure is 80 MPa, and the cooling time is 30 s.

[0036] Comparative Example 1 Comparative Example 1 is basically the same as Example 1, except that the multifunctional additive is omitted.

[0037] Test case The plastic products prepared in Examples 1-3 and Comparative Example 1 were subjected to the following performance tests.

[0038] Mechanical properties: Tensile strength and elongation at break were tested according to GB / T 1040.3-2006; Flame retardant performance: Limiting oxygen index (LOI) tested according to GB / T 2406.2-2009; vertical burning performance tested and rated according to UL94 VTM; Anti-aging performance: The plastic products obtained in Examples 1-3 and Comparative Example 1 were placed in a xenon lamp aging chamber and subjected to an aging test at 80°C for 200 hours. The tensile strength of the examples and comparative examples after UV aging treatment was tested according to GB / T1040.3-2006, and the change rate of tensile strength of the examples and comparative examples before and after UV aging treatment was calculated; Tensile strength change rate = (Tensile strength after UV aging treatment / Original tensile strength of the sample) × 100%; The test results are shown in Table 1.

[0039] Table 1 Performance test results of the plastic products obtained in Examples 1-3 and Comparative Example 1 As can be seen from Table 1, the plastic products prepared by this invention maintain excellent mechanical properties while also possessing excellent flame retardant and anti-aging properties.

[0040] Compared to Comparative Example 1, which omitted the multifunctional additive, the mechanical properties of the plastic product obtained in Example 1 did not decrease significantly, indicating that the multifunctional additive prepared in this invention can achieve a "rigid-toughness balance" in mechanical properties. Specific analysis reveals that this multifunctional additive has a star-shaped multi-arm structure. Its large rigid side groups can serve as physical crosslinking points, inducing crazing and absorbing impact energy, thus improving toughness. Simultaneously, the flexible propyl chain and moderate steric hindrance effect suppress brittleness caused by excessive polylactic acid crystallization while avoiding the severe embrittlement often caused by adding rigid fillers. Therefore, while providing multiple functions, it maintains a good mechanical balance in the material. Furthermore, its synergistic effect with flexible components such as polycaprolactone and plasticizers in the formulation further enhances the toughness of the composite material.

[0041] Compared to Comparative Example 1, the plastic product obtained in Example 1 achieved an LOI of 33.5%, a UL94 rating of VTM0, and a tensile strength retention rate of 98.2% after aging in a xenon lamp aging chamber for 200 hours. This demonstrates that the multifunctional additive prepared in this invention can impart excellent flame retardant and UV aging resistance to the material. This is because the phosphate ester groups and triazine rings in the multifunctional additive molecule constitute a phosphorus-nitrogen synergistic flame retardant system: when heated, the phosphorus components catalyze the polymer to form char, creating a dense char layer that isolates heat and oxygen (condensed phase flame retardancy), while the triazine rings and benzotriazole decompose to generate inert gases, diluting the combustibles and interrupting the combustion chain reaction (gas phase flame retardancy), thereby achieving highly efficient flame retardancy without dripping at low addition levels. The benzotriazole unit, stably linked by ether bonds in the molecule, serves as a highly efficient UV absorber group. It can preferentially absorb and convert UV light energy, forming a "molecular-level" protective barrier before the polylactic acid molecular chain is subjected to photo-oxidative attack. This significantly delays the aging and degradation of the material from the root, giving the product excellent anti-aging properties.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A biodegradable plastic product, characterized in that, The raw materials include the following parts by weight: 75-90 parts polylactic acid, 10-20 parts polycaprolactone, 10-15 parts multifunctional additives, 0.2-0.5 parts antioxidants, 1-2 parts nucleating agents, and 3-5 parts plasticizers; The structural formula of the multifunctional additive is as follows: 。 2. The biodegradable plastic product according to claim 1, characterized in that, The preparation process of the multifunctional additive is as follows: (1) Trichlorocyanuric acid is added to dichloromethane and reacted with 1-hydroxybenzotriazole in the presence of diisopropylethylamine to obtain intermediate 1; the structural formula of intermediate 1 is as follows: ； (2) 3-Amino-1-propanol was added to tetrahydrofuran and reacted with intermediate 1 in the presence of potassium carbonate to obtain intermediate 2; the structural formula of intermediate 2 is as follows: ； (3) Add aminotrimethylphosphonic acid to dichloromethane and react it with intermediate 2 under the action of N,N-dicyclohexylcarbodiimide and 4-dimethylaminopyridine to obtain the multifunctional additive.

3. The biodegradable plastic product according to claim 2, characterized in that, The molar ratio of cyanuric chloride, diisopropylethylamine and 1-hydroxybenzotriazole in step (1) is 1:(2-2.4):(2-2.4); the reaction temperature is -5 to 0 °C and the time is 20 to 30 min.

4. The biodegradable plastic product according to claim 2, characterized in that, The molar ratio of intermediate 1, 3-amino-1-propanol and potassium carbonate in step (2) is 1:(1-1.2):(5-6); the reaction time is 3-4 h.

5. The biodegradable plastic product according to claim 2, characterized in that, In step (3), the molar ratio of aminotrimethylphosphonic acid, N,N-dicyclohexylcarbodiimide, 4-dimethylaminopyridine and intermediate 2 is 1:(1.5-1.6):(0.4-0.5):(3-3.3); the reaction temperature is 50-60 °C and the time is 3-4 h.

6. The biodegradable plastic product according to claim 1, characterized in that, The polylactic acid has a weight-average molecular weight of 150,000 to 250,000 g / mol; the polycaprolactone has a weight-average molecular weight of 40,000 to 90,000 g / mol.

7. The biodegradable plastic product according to claim 1, characterized in that, The antioxidant is any one of antioxidant 168, antioxidant 1076, antioxidant 1010, antioxidant CA, antioxidant B900, antioxidant BHT, antioxidant 264, and antioxidant DLTP; the nucleating agent is talc; and the plasticizer is PEG.

8. A method for preparing a biodegradable plastic article according to any one of claims 1 to 7, characterized in that, Includes the following steps: (a) The raw materials are dried and mixed to obtain a premix; the premix is ​​added to an extruder for melt extrusion and granulation to obtain composite particles; (b) The composite particles are dried and then injection molded and cooled to obtain the biodegradable plastic product.

9. The method for preparing the biodegradable plastic product according to claim 8, characterized in that, The mixing rate in step (a) is 500–1000 rpm and the time is 5–10 min; the temperature of the melt extrusion is 160–190 ℃ and the screw speed is 100–200 rpm.

10. The method for preparing the biodegradable plastic product according to claim 8, characterized in that, The injection molding temperature in step (b) is 180–200 °C, and the pressure is 80–120 MPa; the cooling time is 20–30 s.

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