Degradable composite plastic for cosmetic shell and preparation method thereof

Abstract

The invention discloses degradable composite plastic for a cosmetic shell and a preparation method of the degradable composite plastic, belongs to the technical field of composite plastic preparation, and aims to solve the technical problem that in the prior art, the degradability and the mechanical property of natural fiber reinforced composite plastic need to be further improved. Comprising the following components in parts by weight: 60-80 parts of hydroxyl-terminated polylactic acid, 2-4 parts of a modified compatibilizer, 7-10 parts of modified bamboo fibers, 20-25 parts of maleic anhydride modified PBAT (poly (butylene adipate-co-terephthalate)) and 1-3 parts of an auxiliary material. Multi-point chemical bridging is constructed by reacting with hydroxyl-terminated polylactic acid and maleic anhydride modified PBAT, so that the mechanical property and the degradability of the composite plastic are synergistically improved.

Description

Technical Field

[0001] This invention relates to the field of composite plastic preparation technology, specifically to biodegradable composite plastics for cosmetic shells and their preparation methods. Background Technology

[0002] As the cosmetics industry continues to raise its requirements for appearance design, structural strength and environmental protection, the composite plastics used for cosmetic shells have gradually shifted from traditional petroleum-based materials such as ABS and PP to bio-based and biodegradable materials. Current products, while ensuring the molding precision, tensile strength and impact resistance of the shell, are beginning to introduce bio-based polymers such as polylactic acid (PLA) to reduce dependence on fossil resources and improve environmental friendliness.

[0003] Polylactic acid (PLA) in existing technologies suffers from poor intrinsic toughness, low elongation at break, and a narrow processing window, limiting its application in cosmetic shells requiring high strength. While PBAT possesses excellent toughness and ductility, its strength and modulus are relatively low, making it difficult to meet the structural strength, rigidity, and dimensional stability requirements of shell products when used alone. Blending PBAT with PLA can improve the mechanical strength of PLA materials, but due to the poor compatibility between PLA and PBAT, direct blending easily leads to significant phase separation interfaces, resulting in composite materials exhibiting reduced strength and insufficient impact resistance, failing to meet the high strength and toughness requirements of cosmetic shells. To improve mechanical properties, natural fibers such as bamboo fiber, wood flour, and straw fiber are added to PLA or PLA / PBAT systems to increase material stiffness, reduce costs, and improve degradability. However, natural fibers lack chemical reactivity, and their bonding with the polymer matrix is ​​mainly through physical interactions, making it difficult to form an effective load-transfer interface. Furthermore, the mismatch between fiber polarity and the hydrophobic polymer matrix results in weak interfacial bonding, making the fibers prone to pull-out or debonding within the matrix, ultimately reducing material strength.

[0004] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a biodegradable composite plastic for cosmetic shells and a method for preparing the same, in order to solve the technical problem that the biodegradability and mechanical properties of natural fiber reinforced composite plastics in the prior art need to be further improved.

[0006] The objective of this invention can be achieved through the following technical solutions: Biodegradable composite plastics for cosmetic shells comprise the following components by weight: 60-80 parts hydroxyl-terminated polylactic acid, 2-4 parts compatibilizer, 7-10 parts modified bamboo fiber, 20-25 parts maleic anhydride-modified PBAT, and 1-3 parts excipients. The modified compatibilizer is prepared by the following steps: A1. Place 2,2-bis(aminomethyl)propane-1,3-diol and ethanol in a reaction vessel under nitrogen atmosphere and stir. Add pyromellitic methylaldehyde, heat the reaction vessel to 70-80℃, and keep the reaction at this temperature for 4-6 hours. Post-treatment yields hyperbranched Schiff bases. A2. Place hyperbranched Schiff base, epichlorohydrin and tetrabutylammonium bromide in a reaction vessel under nitrogen atmosphere and stir. Heat the reaction vessel to 95-105℃ and keep it at this temperature for 1-3 hours. Then, cool the reaction vessel to 45-55℃, add sodium hydroxide aqueous solution, and keep it at this temperature for 2-4 hours. The modified compatibilizer is obtained after post-treatment.

[0007] The preparation reaction formula for the modified compatibilizer is as follows: Further, in step A1, the ratio of 2,2-bis(aminomethyl)propane-1,3-diol, ethanol, and trimesoaldehyde is 4-6g:100-120mL:2-4g. The post-treatment step includes: after the reaction is completed, wait for the reaction system to cool to room temperature, transfer the reaction solution to 150-200mL of deionized water to precipitate, filter, wash the filter cake with deionized water 2-4 times, transfer it to an oven at 50-60℃, and dry it for 10-12h to obtain a hyperbranched Schiff base. Furthermore, in A2, the ratio of the hyperbranched Schiff base, epichlorohydrin, tetrabutylammonium bromide, and sodium hydroxide aqueous solution is 4-6g:28-30g:0.3-0.5g:3-4mL, and the concentration of the sodium hydroxide aqueous solution is 35-40wt%. The post-treatment steps include: after the reaction is completed, after the reaction system cools to room temperature, deionized water is added to the reaction solution, the mixture is allowed to stand and separate into layers, the organic phase is dried with anhydrous sodium sulfate, and then transferred to a rotary evaporator at a temperature of 70-80℃ and evaporated under reduced pressure for 2-4 hours to obtain the modified compatibilizer.

[0008] Furthermore, the preparation method of the maleic anhydride-modified PBAT is as follows: PBAT, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and maleic anhydride are placed in a torque rheometer, the torque rheometer is heated to 195-205℃, and the reaction is maintained at a speed of 80-100 r / min for 5-7 min. After cooling, the mixture is granulated to obtain maleic anhydride-modified PBAT.

[0009] Furthermore, the weight ratio of PBAT, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and maleic anhydride is 98-100:0.1-0.2:1-2.

[0010] Furthermore, the modified bamboo fiber is prepared by the following steps: B1. Place bamboo fiber, potassium hydroxide and deionized water in a reaction vessel and stir. Heat the reaction vessel to 40-50℃ and keep it at that temperature for 0.5-1h. Then, after processing, obtain alkali-treated bamboo fiber. B2. Alkali-treated bamboo fiber, ethanol, γ-aminopropyltriethoxysilane and deionized water are placed in a reaction vessel and stirred. An aqueous acetic acid solution is added to adjust the pH to 5-6. The reaction vessel is heated to 40-50℃ and kept at the temperature for 2-4 hours. After post-treatment, amino-modified bamboo fiber is obtained. B3. Place amino-modified bamboo fiber and N,N-dimethylformamide in a reaction vessel under nitrogen atmosphere and stir. Add succinic anhydride solution, heat the reaction vessel to 40-50℃, and keep the reaction at this temperature for 6-8 hours. Then, process the modified bamboo fiber.

[0011] Further, in step B1, the ratio of bamboo fiber, potassium hydroxide, and deionized water is 20-25g:28-30g:300-320mL. The post-treatment steps include: after the reaction is completed, the reaction system is cooled to room temperature, filtered, the filter cake is washed 2-4 times with deionized water, transferred to an oven at 50-60℃, and dried to constant weight to obtain alkali-treated bamboo fiber.

[0012] Further, in step B2, the ratio of the amount of alkali-treated bamboo fiber, ethanol, γ-aminopropyltriethoxysilane and deionized water is 10-15g:280-300mL:1-3g:10-15mL, and the concentration of the acetic acid aqueous solution is 3-5wt%. The post-treatment steps include: after the reaction is completed, the reaction system is cooled to room temperature, filtered, the filter cake is washed 2-4 times with deionized water and ethanol, transferred to an oven at 50-60℃, and dried to constant weight to obtain amino-modified bamboo fiber.

[0013] Further, in step B3, the ratio of amino-modified bamboo fiber, N,N-dimethylformamide, and succinic anhydride solution is 8-10g:150-170mL:30-40mL. The succinic anhydride solution is composed of succinic anhydride and N,N-dimethylformamide in a ratio of 1g:10mL. The post-treatment step includes: after the reaction is completed, the reaction system is cooled to room temperature, filtered, the filter cake is washed with deionized water and ethanol until neutral, transferred to an oven at 50-60℃, and dried to constant weight to obtain modified bamboo fiber.

[0014] The present invention also proposes a method for preparing a biodegradable composite plastic for cosmetic shells. The method for preparing the biodegradable composite plastic for cosmetic shells is as follows: hydroxyl-terminated polylactic acid, a modifier, a modified compatibilizer, modified bamboo fiber, maleic anhydride-modified PBAT and excipients are placed in a twin-screw extruder, melt-extruded, and pelletized to obtain the biodegradable composite plastic.

[0015] Furthermore, the excipients are composed of plasticizer, lubricant and antioxidant in a mass ratio of 4:4:3. The plasticizer is one or more of triethyl citrate, tributyl citrate and acetylated tributyl citrate. The lubricant is one or more of stearic acid, calcium stearate and glyceryl distearate. The antioxidant is one or more of tocopherol, di-tert-butylhydroxytoluene and tris(2,4-di-tert-butylphenyl) phosphite. The twin-screw extruder has six temperature zones from the feed inlet to the discharge outlet, with temperatures of 150-160℃, 160-170℃, 170-175℃, 175-180℃, 180-185℃, and 185-190℃ respectively. The die head temperature is 175-185℃, and the spindle speed of the twin-screw extruder is 120-160 rpm.

[0016] The present invention has the following beneficial effects: 1. This invention relates to a biodegradable composite plastic for cosmetic shells. By constructing a reactive polar interface layer containing silicon-oxygen bonds, amide bonds, and carboxyl groups on the surface of bamboo fiber, the bamboo fiber can undergo various chemical reactions with hydroxyl-terminated polylactic acid (PLA), maleic anhydride-grafted PBAT, and an epoxy-containing hyperbranched Schiff base modifier during melt blending, forming a stable chemical bond interface. Simultaneously, the maleic anhydride-grafted PBAT, through anhydride ring-opening esterification with the hydroxyl-terminated PLA, forms a hydroxyl-terminated PLA-g-PBAT crosslinked structure, improving the two-phase crosslinking of hydroxyl-terminated PLA / PBAT. On the one hand, it improves compatibility and refines the dispersion morphology of the flexible PBAT phase. On the other hand, it provides additional reaction sites for the epoxy groups of the compatibilizer and the functional groups on the surface of the modified bamboo fiber. Based on this, the modified compatibilizer with a hyperbranched Schiff base skeleton relies on high-density epoxy end groups and three-dimensional hyperbranched structure to build multi-point bridging and network chemical structures between the hydroxyl-terminated polylactic acid phase, the PBAT phase and the modified bamboo fiber. This allows the load to be efficiently transferred between the fiber, the hydroxyl-terminated polylactic acid matrix and the tough PBAT phase, inhibiting interfacial debonding and fiber pull-out, thereby improving the impact resistance, tensile strength and flexural properties of the composite plastic.

[0017] 2. This invention relates to a biodegradable composite plastic for cosmetic shells. The polar functional groups such as carboxyl and amide groups introduced on the surface of modified bamboo fiber, together with the hydroxyl groups, residual hydroxyl groups, and imine structures after ring-opening of the hyperbranched Schiff base modifier epoxy, form a polar network channel that penetrates the interior of the composite material. This allows water and microbial enzymes to more easily penetrate into the interior of the material along the interface and around the fiber, thus avoiding the degradation of traditional materials only on the surface and maintaining the integrity of the interior. The succinic anhydride grafting and epoxy ring-opening reaction introduce a large number of hydrolyzable ester bonds, amide bonds, and imine bonds that can be broken under specific conditions at the bamboo fiber / hydroxyl-terminated polylactic acid / PBAT multiphase interface. This gives the overall skeleton of the material a continuous and controllable fracture path in composting and soil environments. Combined with the good biodegradability of PBAT itself, this improves the biodegradability of the composite plastic under industrial and household composting conditions.

[0018] 3. This invention relates to biodegradable composite plastics for cosmetic shells. In the hyperbranched Schiff base, the aromatic skeleton and imine bonds provide rigidity and structural stability, while the polyhydroxy groups and the numerous epoxy end groups formed after epichlorohydrin modification provide high-density active sites. During melt blending, the epoxy groups in this compatibilizer can undergo ring-opening or condensation reactions with the hydroxyl groups of terminal hydroxyl polylactic acid, the carboxyl groups and hydroxyl groups on the surface of modified bamboo fiber, and the carboxyl groups of maleic anhydride-grafted PBAT after ring-opening. This allows the compatibilizer to form multi-point chemical bonds with the terminal hydroxyl polylactic acid phase, the PBAT phase, and the surface of bamboo fiber, thereby constructing a network cross-linked composite structure at the interface. This improves the compatibility of terminal hydroxyl polylactic acid, PBAT, and bamboo fiber, inhibits coarse phase separation, fiber pull-out, and interface debonding, effectively improves the energy absorption capacity during impact fracture, and enhances the strength and toughness of the material. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The hydroxyl-terminated polylactic acid used in this invention is hydroxyl-terminated polylactic acid with an effective ingredient content of 99%, selected from commercially available products of Hubei Xinyuhong Biomedical Technology Co., Ltd., and has a molecular weight of 1000-1200.

[0021] The PBAT used in this invention was purchased from Dongguan Xingyuan Chemical Co., Ltd., with item number 11231 and brand name Xingyuan.

[0022] The bamboo fiber used in this invention was purchased from Chengjiang Mining Processing Plant in Lingshou County. The aspect ratio was 50-70:1, and the average fiber length was 500-1000μm.

[0023] Example 1 This embodiment provides a method for preparing modified bamboo fiber, including the following steps: Step I: Preparation of alkali-treated bamboo fiber Weigh 200g of bamboo fiber, 280g of potassium hydroxide and 3000mL of deionized water and place them in a reaction vessel and stir. Heat the reaction vessel to 40℃ and keep it at that temperature for 0.5h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake twice with deionized water, transfer it to an oven at 50℃ and dry it to constant weight to obtain alkali-treated bamboo fiber.

[0024] Step II: Preparation of amino-modified bamboo fiber Weigh out 100g of alkali-treated bamboo fiber, 2800mL of ethanol, 10g of γ-aminopropyltriethoxysilane, and 100mL of deionized water and place them in a reaction vessel. Stir the mixture and add 3wt% acetic acid aqueous solution to adjust the pH to 5. Heat the reaction vessel to 40℃ and keep it at that temperature for 2 hours. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake twice with deionized water and ethanol, transfer it to an oven at 50℃, and dry it to constant weight to obtain amino-modified bamboo fiber.

[0025] Step III: Preparation of modified bamboo fiber Succinic anhydride and N,N-dimethylformamide were mixed evenly at a ratio of 1g:10mL to obtain a succinic anhydride solution for later use. Weigh 80g of amino-modified bamboo fiber and 1500mL of N,N-dimethylformamide and place them in a nitrogen-protected reactor. Stir and add 300mL of succinic anhydride solution. Heat the reactor to 40℃ and keep it at that temperature for 6 hours. After the reaction is complete, wait for the reaction system to cool to room temperature, filter, wash the filter cake with deionized water and ethanol until neutral, transfer it to an oven at 50℃ and dry it to constant weight to obtain modified bamboo fiber.

[0026] Under alkaline conditions, the alkali solution destroys some of the lignin, hemicellulose, and wax structures on the surface of bamboo fibers, and causes the cellulose molecular chains to swell, exposing and activating more hydroxyl groups. Furthermore, under weakly acidic conditions, γ-aminopropyltriethoxysilane undergoes hydrolysis to generate silanol. The silanol intermediate further undergoes a condensation reaction with the hydroxyl groups on the surface of bamboo fibers to form siloxane bonds on the fiber surface, while simultaneously introducing exposed amino functional groups to achieve amylation modification of bamboo fibers. Furthermore, succinic anhydride undergoes nucleophilic ring-opening with the amino groups on the surface of bamboo fibers to form modified bamboo fibers containing amide bonds and carboxylic acid groups.

[0027] Alkali treatment makes the fiber surface rougher and increases the number of active sites, providing greater accessibility for subsequent surface chemical reactions. Through silane coupling reaction, aminosilanes are stably bound to the bamboo fiber surface through silicon-oxygen bonds, realizing the transformation of the fiber from an inert surface to a reactive surface. By using succinic anhydride to react with amino groups on the fiber surface, a polar structural layer containing amide bonds and carboxyl groups is constructed on the bamboo fiber surface, giving the fiber stronger interfacial interaction capabilities.

[0028] Example 2 Step I: Preparation of alkali-treated bamboo fiber Weigh 225g of bamboo fiber, 290g of potassium hydroxide and 3100mL of deionized water and place them in a reaction vessel and stir. Heat the reaction vessel to 45℃ and keep it at that temperature for 1 hour. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake three times with deionized water, transfer it to an oven at 55℃ and dry it to constant weight to obtain alkali-treated bamboo fiber.

[0029] Step II: Preparation of amino-modified bamboo fiber Weigh out 125g of alkali-treated bamboo fiber, 2900mL of ethanol, 20g of γ-aminopropyltriethoxysilane, and 125mL of deionized water and place them in a reaction vessel. Stir the mixture and add 4wt% acetic acid aqueous solution to adjust the pH to 5.5. Heat the reaction vessel to 45℃ and keep it at that temperature for 3 hours. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake three times with deionized water and ethanol, transfer it to an oven at 55℃, and dry it to constant weight to obtain amino-modified bamboo fiber.

[0030] Step III: Preparation of modified bamboo fiber Succinic anhydride and N,N-dimethylformamide were mixed evenly at a ratio of 1g:10mL to obtain a succinic anhydride solution for later use. Weigh 90g of amino-modified bamboo fiber and 1600mL of N,N-dimethylformamide and place them in a nitrogen-protected reactor. Stir and add 350mL of succinic anhydride solution. Heat the reactor to 45℃ and keep it at that temperature for 7 hours. After the reaction is complete, wait for the reaction system to cool to room temperature, filter, wash the filter cake with deionized water and ethanol until neutral, transfer it to an oven at 55℃ and dry it to constant weight to obtain modified bamboo fiber.

[0031] Example 3 Step I: Preparation of alkali-treated bamboo fiber Weigh 250g of bamboo fiber, 300g of potassium hydroxide and 3200mL of deionized water and place them in a reaction vessel and stir. Heat the reaction vessel to 50℃ and keep it at that temperature for 1 hour. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake 4 times with deionized water, transfer it to an oven at 60℃ and dry it to constant weight to obtain alkali-treated bamboo fiber.

[0032] Step II: Preparation of amino-modified bamboo fiber Weigh out 150g of alkali-treated bamboo fiber, 3000mL of ethanol, 30g of γ-aminopropyltriethoxysilane, and 150mL of deionized water and place them in a reaction vessel. Stir the mixture and add 5wt% acetic acid aqueous solution to adjust the pH to 6. Heat the reaction vessel to 50℃ and keep it at that temperature for 4 hours. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake four times with deionized water and ethanol, transfer it to an oven at 60℃, and dry it to constant weight to obtain amino-modified bamboo fiber.

[0033] Step III: Preparation of modified bamboo fiber Succinic anhydride and N,N-dimethylformamide were mixed evenly at a ratio of 1g:10mL to obtain a succinic anhydride solution for later use. Weigh 100g of amino-modified bamboo fiber and 1700mL of N,N-dimethylformamide and place them in a nitrogen-protected reactor. Stir and add 400mL of succinic anhydride solution. Heat the reactor to 50℃ and keep it at that temperature for 8 hours. After the reaction is complete, wait for the reaction system to cool to room temperature, filter, wash the filter cake with deionized water and ethanol until neutral, transfer it to an oven at 60℃ and dry it to constant weight to obtain modified bamboo fiber.

[0034] Example 4 This embodiment provides a method for preparing a modified compatibilizer, including the following steps: Step ①: Preparation of hyperbranched Schiff bases Weigh 40g of 2,2-bis(aminomethyl)propane-1,3-diol and 1000mL of ethanol and place them in a reaction vessel under a nitrogen atmosphere. Stir the mixture and add 20g of trimesin. Heat the reaction vessel to 70℃ and maintain the temperature for 4h. After the reaction is complete, wait for the reaction system to cool to room temperature. Transfer the reaction solution to 1500mL of deionized water to precipitate the precipitate. Filter the precipitate and wash it with deionized water until neutral. Dry the precipitate and transfer it to an oven at 50℃ for 10h to obtain a hyperbranched Schiff base.

[0035] Step 2: Preparation of modified compatibilizer Weigh out 40g of hyperbranched Schiff base, 280g of epichlorohydrin and 3g of tetrabutylammonium bromide and place them in a reaction vessel under nitrogen atmosphere. Stir the mixture and heat the reaction vessel to 95℃. Maintain the temperature for 1 hour. Then, cool the reaction vessel to 45℃ and add 30mL of 35wt% sodium hydroxide aqueous solution. Maintain the temperature for 2 hours. After the reaction is complete, wait for the reaction system to cool to room temperature, add deionized water to the reaction solution, and allow it to stand for separation. Dry the organic phase with anhydrous sodium sulfate and transfer it to a rotary evaporator at 70℃. Evaporate under reduced pressure for 2 hours to obtain the modified compatibilizer.

[0036] The amino group of 2,2-bis(aminomethyl)propane-1,3-diol reacts with the aldehyde group of trimesoaldehyde via an amino-aldehyde condensation reaction to form a hyperbranched Schiff base. Under the catalysis of tetrabutylammonium bromide and in the presence of excess epichlorohydrin, the hydroxyl group in the intermediate reacts with the chloromethyl site of epichlorohydrin via a nucleophilic substitution reaction to form a chlorohydrin ether-type intermediate structure. After the addition of an aqueous sodium hydroxide solution, the chlorohydrin structure undergoes an intramolecular dehydrohalogenation reaction under alkaline conditions, resulting in ring closure and the formation of an epoxy group, thus yielding a modified compatibilizer containing a Schiff base skeleton and epoxy active functional groups.

[0037] By constructing a rigid aromatic skeleton containing imine bonds while retaining the polyhydroxy structure in the molecule, the intermediate possesses both structural stability and subsequent chemical reactivity. Under phase transfer catalysis and excess epichlorohydrin conditions, the hydroxyl groups undergo a directional substitution reaction, achieving controllable grafting of functional side chains. Under mild alkaline conditions, the chlorohydrin structure undergoes an intramolecular ring-closing reaction to generate epoxy groups, giving the product a highly reactive epoxy functional structure while maintaining the integrity of the original Schiff base skeleton, thus forming a modified compatibilizer that combines rigidity and reactivity.

[0038] Example 5 This embodiment provides a method for preparing a modified compatibilizer, including the following steps: Step ①: Preparation of hyperbranched Schiff bases Weigh 50g of 2,2-bis(aminomethyl)propane-1,3-diol and 1100mL of ethanol and place them in a reaction vessel under nitrogen atmosphere and stir. Add 30g of trimesin and heat the reaction vessel to 75℃ and keep it at that temperature for 5h. After the reaction is complete, wait for the reaction system to cool to room temperature, transfer the reaction solution to 1750mL of deionized water to precipitate, filter, wash the filter cake with deionized water until neutral and then dry it. Transfer the filter cake to an oven at 55℃ and dry it for 11h to obtain hyperbranched Schiff base.

[0039] Step 2: Preparation of modified compatibilizer Weigh out 50g of hyperbranched Schiff base, 290g of epichlorohydrin and 4g of tetrabutylammonium bromide and place them in a reaction vessel under nitrogen atmosphere. Stir the mixture and heat the reaction vessel to 100℃. Maintain the temperature for 2 hours. Then, cool the reaction vessel to 50℃ and add 35mL of 37.5wt% sodium hydroxide aqueous solution. Maintain the temperature for 3 hours. After the reaction is complete, wait for the reaction system to cool to room temperature, add deionized water to the reaction solution, and allow it to stand to separate into layers. Dry the organic phase with anhydrous sodium sulfate and transfer it to a rotary evaporator at 75℃. Evaporate under reduced pressure for 3 hours to obtain the modified compatibilizer.

[0040] Example 6 This embodiment provides a method for preparing a modified compatibilizer, including the following steps: Step ①: Preparation of hyperbranched Schiff bases Weigh 60g of 2,2-bis(aminomethyl)propane-1,3-diol and 1200mL of ethanol and place them in a reaction vessel under a nitrogen atmosphere. Stir the mixture and add 40g of trimesin. Heat the reaction vessel to 80℃ and maintain the temperature for 6h. After the reaction is complete, wait for the reaction system to cool to room temperature. Transfer the reaction solution to 2000mL of deionized water to precipitate the mixture. Filter the mixture and wash the filter cake with deionized water until neutral. Dry the filter cake and transfer it to an oven at 60℃ for 12h to obtain a hyperbranched Schiff base.

[0041] Step 2: Preparation of modified compatibilizer Weigh out 60g of hyperbranched Schiff base, 300g of epichlorohydrin and 5g of tetrabutylammonium bromide and place them in a reaction vessel under nitrogen atmosphere. Stir the mixture and heat the reaction vessel to 105℃. Maintain the temperature for 3 hours. Then, cool the reaction vessel to 55℃ and add 40mL of 40wt% sodium hydroxide aqueous solution. Maintain the temperature for 4 hours. After the reaction is complete, wait for the reaction system to cool to room temperature, add deionized water to the reaction solution, and allow it to stand for separation. Dry the organic phase with anhydrous sodium sulfate and transfer it to a rotary evaporator at 80℃. Evaporate under reduced pressure for 4 hours to obtain the modified compatibilizer.

[0042] Example 7 This embodiment provides a method for preparing a biodegradable composite plastic for cosmetic casings, including the following steps: Step (1): Preparation of maleic anhydride-modified PBAT Weigh out: 980g of PBAT, 1g of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and 10g of maleic anhydride and place them in a torque rheometer. Heat the torque rheometer to 195℃ and keep it at 80r / min for 5min. After cooling, granulate to obtain maleic anhydride modified PBAT.

[0043] Initiated by 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, the PBAT backbone generates free radicals under high-temperature shearing conditions. Maleic anhydride is then grafted onto the PBAT molecular chain via a free radical reaction, introducing an anhydride active functional group.

[0044] Step 2: Preparation of biodegradable composite plastics Tributyl citrate, calcium stearate, di-tert-butylhydroxytoluene and tris(2,4-di-tert-butylphenyl) phosphite were mixed evenly in a mass ratio of 4:4:3 to obtain the excipients for later use. Weigh out the following by weight: 60 parts of hydroxyl-terminated polylactic acid, 2 parts of the modified compatibilizer prepared in Example 4, 7 parts of the modified bamboo fiber prepared in Example 1, 20 parts of maleic anhydride-modified PBAT and 1 part of auxiliary materials, place them in a twin-screw extruder, melt extrude, and pelletize to obtain a biodegradable composite plastic. The twin-screw extruder has six temperature zones with temperatures ranging from 150°C, 160°C, 170°C, 175°C, 180°C, and 185°C from the feed inlet to the discharge outlet. The die head temperature is 175°C, and the spindle speed of the twin-screw extruder is 120 rpm.

[0045] During the twin-screw melt blending process, the terminal hydroxyl groups of hydroxyl-terminated polylactic acid and the carboxyl groups of modified bamboo fiber can undergo ring-opening reactions with the epoxy groups in the compatibilizer. At the same time, the terminal hydroxyl groups of hydroxyl-terminated polylactic acid can also undergo ring-opening reactions with the anhydride groups on maleic anhydride-modified PBAT. The additives play a role in plasticizing, lubrication and thermo-oxidative stabilization, ultimately forming a multiphase network structure mainly connected by chemical bonds, resulting in biodegradable composite plastics.

[0046] Example 8 This embodiment provides a method for preparing a biodegradable composite plastic for cosmetic casings, including the following steps: Step (1): Preparation of maleic anhydride-modified PBAT Weigh out: 990g of PBAT, 1.5g of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and 15g of maleic anhydride and place them in a torque rheometer. Heat the torque rheometer to 200℃ and keep it at 90r / min for 6min. After cooling, granulate to obtain maleic anhydride modified PBAT.

[0047] Step 2: Preparation of biodegradable composite plastics Tributyl citrate, calcium stearate, di-tert-butylhydroxytoluene and tris(2,4-di-tert-butylphenyl) phosphite were mixed evenly in a mass ratio of 4:4:3 to obtain the excipients for later use. Weigh out the following by weight: 70 parts of hydroxyl-terminated polylactic acid, 3 parts of the modified compatibilizer prepared in Example 5, 8.5 parts of the modified bamboo fiber prepared in Example 2, 22.5 parts of maleic anhydride-modified PBAT, and 2 parts of auxiliary materials. Place them in a twin-screw extruder, melt extrude, and pelletize to obtain a biodegradable composite plastic. The twin-screw extruder has six temperature zones with temperatures ranging from the feed inlet to the discharge outlet: 155°C, 165°C, 173°C, 177°C, 183°C, and 187°C, respectively. The die head temperature is 180°C, and the spindle speed of the twin-screw extruder is 140 rpm.

[0048] Example 9 This embodiment provides a method for preparing a biodegradable composite plastic for cosmetic casings, including the following steps: Step (1): Preparation of maleic anhydride-modified PBAT Weigh out: 1000g of PBAT, 2g of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and 20g of maleic anhydride and place them in a torque rheometer. Heat the torque rheometer to 205℃ and keep it at 100r / min for 7min. After cooling, granulate to obtain maleic anhydride modified PBAT.

[0049] Step 2: Preparation of biodegradable composite plastics Tributyl citrate, calcium stearate, di-tert-butylhydroxytoluene and tris(2,4-di-tert-butylphenyl) phosphite were mixed evenly in a mass ratio of 4:4:3 to obtain the excipients for later use. Weigh out the following by weight: 80 parts of hydroxyl-terminated polylactic acid, 4 parts of the modified compatibilizer prepared in Example 6, 10 parts of the modified bamboo fiber prepared in Example 3, 25 parts of maleic anhydride-modified PBAT, and 3 parts of auxiliary materials. Place them in a twin-screw extruder, melt extrude, and pelletize to obtain a biodegradable composite plastic. The twin-screw extruder has six temperature zones with temperatures ranging from 160°C, 170°C, 175°C, 180°C, 185°C, and 190°C from the feed inlet to the discharge outlet. The die head temperature is 185°C, and the spindle speed of the twin-screw extruder is 160 rpm.

[0050] Comparative Example 1 The difference between this comparative example and Example 9 is that, in step (2) when preparing the biodegradable composite plastic, an equal amount of alkali-treated bamboo fiber is used instead of modified bamboo fiber.

[0051] Comparative Example 2 The difference between this comparative example and Example 9 is that the compatibilizer was omitted in step (2) when preparing the biodegradable composite plastic.

[0052] Comparative Example 3 The difference between this comparative example and Example 9 is that, in step (2) when preparing the biodegradable composite plastic, PBAT is replaced with an equal amount of maleic anhydride to modify PBAT.

[0053] Performance testing: The notched cantilever beam impact strength of biodegradable composite plastic samples with a thickness of 1±0.1 mm prepared in Examples 7-9 and Comparative Examples 1-3 was determined in accordance with the standard GB / T 1843-2008 "Determination of impact strength of plastic cantilever beam". The tensile strength of biodegradable composite plastic specimens with a thickness of 1±0.1 mm prepared in Examples 7-9 and Comparative Examples 1-3 was determined according to standard GB / T 1040.1-2025 "Determination of tensile properties of plastics - Part 1: General". The test speed was 2 mm / min. The flexural strength of biodegradable composite plastic samples with a thickness of 1±0.1 mm prepared in Examples 7-9 and Comparative Examples 1-3 was determined according to the standard GB / T 9341-2008 "Determination of Flexural Properties of Plastics" at a test speed of 2 mm / min. Referring to the standard GB / T 41010-2021 "Degradation Performance and Labeling Requirements of Biodegradable Plastics and Products", the degradable composite plastic samples with a thickness of 1±0.1 mm prepared in Examples 7-9 and Comparative Examples 1-3 were tested for disintegration rate at 12 weeks and biodegradation rate at 180 days under industrial composting and household composting conditions, as well as biodegradation rate at 180 days, 1 year and 2 years under soil conditions. Specific data are shown in Table 1.

[0054] Table 1 - Performance Test Data for Each Sample Data Analysis: A comparative analysis of Table 1 above reveals that the cantilever beam notched impact strength of the biodegradable composite plastic sample prepared in this invention is 12.92 kJ·m. -2 The tensile strength was 58.65 MPa and the flexural strength was 99.48 MPa. The prepared biodegradable composite plastic sample achieved a disintegration rate of 92.6% after 12 weeks and a biodegradation rate of 87.4% after 180 days under industrial composting conditions. Under household composting conditions, the disintegration rate reached 84.9% after 12 weeks and the biodegradation rate reached 75.2% after 180 days. Under soil conditions, the biodegradable composite plastic sample achieved a biodegradation rate of 25.4% after 180 days, 48.7% after 1 year, and 66.9% after 2 years. All performance parameters were superior to the comparative example. Therefore, this invention constructs a carboxyl / amide layer on the surface of bamboo fiber and synthesizes a modified compatibilizer containing a Schiff base skeleton and epoxy groups. During the melt blending process, the terminal hydroxyl polylactic acid reacts chemically with the anhydride groups of maleic anhydride-modified PBAT and the epoxy groups of the modified compatibilizer to form multi-point chemical bridges. This, combined with maleic anhydride-modified PBAT, achieves a unity of flexibility and toughness and interface strengthening, improving the mechanical properties and biodegradability of the composite plastic, and achieving synergistic optimization of high performance and environmental friendliness.

[0055] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

[0056] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0057] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. Degradable composite plastic for cosmetic enclosures, characterized in that, Comprise the following components by weight parts: 60-80 parts of hydroxyl-terminated polylactic acid, 2-4 parts of modified compatibilizer, 7-10 parts of modified bamboo fiber, 20-25 parts of maleic anhydride modified PBAT and 1-3 parts of auxiliary materials; The modified compatibilizer is prepared by the following steps: A1, 2, 2-bis (aminomethyl) propane-1, 3-diol and ethanol are placed in a reaction kettle protected by nitrogen atmosphere and stirred, and trimesic aldehyde is added, the reaction kettle is heated to 70-80 DEG C, and the reaction is kept for 4-6h, and the post-processing is obtained. Hyperbranched Schiff base; A2, the hyperbranched Schiff base, epichlorohydrin and tetrabutylammonium bromide are placed in a reaction kettle protected by nitrogen atmosphere and stirred, the reaction kettle is heated to 95-105 DEG C, and the reaction is kept for 1-3h, the reaction kettle is cooled to 45-55 DEG C, and sodium hydroxide aqueous solution is added, and the reaction is kept for 2-4h, and the post-processing is obtained. Modified compatibilizer.

2. The degradable composite plastic for a cosmetic case according to claim 1, wherein, In step A1, the amount ratio of 2, 2-bis (aminomethyl) propane-1, 3-diol, ethanol and trimesic aldehyde is 4-6g:100-120mL:2-4g; in step A2, the amount ratio of hyperbranched Schiff base, epichlorohydrin, tetrabutylammonium bromide and sodium hydroxide aqueous solution is 4-6g:28-30g:0.3-0.5g:3-4mL, and the concentration of sodium hydroxide aqueous solution is 35-40wt%.

3. The degradable composite plastic for a cosmetic case according to claim 1, wherein, The preparation method of the maleic anhydride modified PBAT is as follows: PBAT, 2, 5-dimethyl-2, 5-di (tert-butyl peroxide) hexane and maleic anhydride are placed in a torque rheometer, the torque rheometer is heated to 195-205 DEG C, and the reaction is kept for 5-7min at a speed of 80-100r / min, and then the particles are cut after cooling to obtain maleic anhydride modified PBAT.

4. The degradable composite plastic for a cosmetic case according to claim 3, characterized by, The weight ratio of the PBAT, 2, 5-dimethyl-2, 5-di (tert-butyl peroxide) hexane and maleic anhydride is 98-100:0.1-0.2:1-2.

5. The degradable composite plastic for a cosmetic case according to claim 1, wherein The modified bamboo fiber is prepared by the following steps: B1, the bamboo fiber, potassium hydroxide and deionized water are placed in a reaction kettle and stirred, the reaction kettle is heated to 40-50 DEG C, and the reaction is kept for 0.5-1h, and the post-processing is obtained. Alkali treated bamboo fiber; B2, the alkali treated bamboo fiber, ethanol, γ-aminopropyl triethoxysilane and deionized water are placed in a reaction kettle and stirred, and the pH is adjusted to 5-6 by adding acetic acid aqueous solution, the reaction kettle is heated to 40-50 DEG C, and the reaction is kept for 2-4h, and the post-processing is obtained. Amino modified bamboo fiber; B3, the amino modified bamboo fiber and N, N-dimethylformamide are placed in a reaction kettle protected by nitrogen atmosphere and stirred, and succinic anhydride solution is added, the reaction kettle is heated to 40-50 DEG C, and the reaction is kept for 6-8h, and the post-processing is obtained. Modified bamboo fiber.

6. The degradable composite plastic for a cosmetic case according to claim 5, wherein In step B1, the amount ratio of the bamboo fiber, potassium hydroxide and deionized water is 20-25g:28-30g:300-320mL; in step B2, the amount ratio of the alkali-treated bamboo fiber, ethanol, gamma-aminopropyltriethoxysilane and deionized water is 10-15g:280-300mL:1-3g:10-15mL, and the concentration of the acetic acid aqueous solution is 3-5wt%; in step B3, the amount ratio of the amino-modified bamboo fiber, N,N-dimethylformamide and succinic anhydride solution is 8-10g:150-170mL:30-40mL, and the succinic anhydride solution is composed of succinic anhydride and N,N-dimethylformamide with an amount ratio of 1g:10mL.

7. A method of producing a degradable composite plastic for a cosmetic case according to any one of claims 1 to 6, characterized by, The preparation method of the degradable composite plastic for cosmetic shells comprises the following steps: placing hydroxyl-terminated polylactic acid, modified compatibilizer, modified bamboo fiber, maleic anhydride-modified PBAT and auxiliary materials in a double-screw extruder, melt-extruding, granulating, and obtaining the degradable composite plastic.

8. The method for preparing degradable composite plastic for a cosmetic case according to claim 7, characterized by, The auxiliary materials are composed of plasticizers, lubricants and antioxidants with a mass ratio of 4:4:3, the plasticizers are one or more of triethyl citrate, tributyl citrate and acetyl tributyl citrate, the lubricants are one or more of stearic acid, calcium stearate and glycerol distearate, and the antioxidants are one or more of tocopherol, di-tert-butyl hydroxytoluene and tris(2,4-di-tert-butylphenyl)phosphite.

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