Plant starch composite material for children's toys and preparation method thereof

Abstract

The invention discloses a plant starch composite material for children's toys and a preparation method thereof, and belongs to the technical field of degradable materials.The preparation method comprises the steps that double-bond silicon dioxide microspheres are prepared through a sol-gel method and polymerized with methyl methacrylate, then a styrene-maleic anhydride copolymer is hydrolyzed under the acidic condition, and the plant starch composite material is obtained; the preparation method comprises the following steps: hydrolyzing a styrene-maleic anhydride copolymer to obtain a hydrolyzed copolymer containing a carboxyl group, carrying out esterification reaction on the hydrolyzed copolymer and starch, consuming a large amount of hydroxyl groups on the surface of the starch by the esterification reaction so as to increase the compatibility of the starch and PBAT, and forming a flexible coating layer on the surface of the starch by a long-chain structure of the hydrolyzed styrene-maleic anhydride copolymer so as to prevent agglomeration among starch particles; the coating layer has a relatively low friction coefficient, is easy to generate molecular chain slippage when being stressed, and endows the surface with self-lubricating property, so that the microspheres can disperse stress through sliding in the use or processing process, the coating layer forms a soft shell on the surfaces of the microspheres, and direct contact of the microspheres is prevented through steric hindrance, so that the microspheres are not easy to agglomerate.

Description

Technical Field

[0001] The invention belongs to the technical field of degradable materials, and in particular relates to a plant starch composite material for children's toys and a preparation method thereof. Background Art

[0002] As people's awareness of environmental protection increases, environmental pollution issues have attracted much attention. Therefore, it is of great significance to develop biodegradable, safe and environmentally friendly toys. The environmentally friendly and degradable materials in the existing technology mainly include polylactic acid (PLA), polybutylene succinate (PBS), polyhydroxyalkanoate (PHA), polybutylene adipate / terephthalate (PBAT), etc. Due to the high cost and insufficient physical properties of these materials, their application in toy manufacturing is limited. Plant starch comes from plants in nature. It is a natural substance with abundant resources and is relatively easy to extract. It does not produce harmful substances during production and use. It is friendly to the environment and is more easily biodegradable after disposal. Using it to prepare toys can significantly reduce costs.

[0003] Chinese patent CN120082156A discloses a degradable starch-based toy material, a children's toy, and a preparation method thereof. This invention incorporates a block copolymer of polyethylene glycol-grafted plant starch and polybutylene succinate as a compatibilizer. The compatibilizer in this invention has both starch-affinity segments (PEG-grafted plant starch segments) and PBAT-affinity segments, significantly enhancing the compatibility between the modified plant starch and modified PBAT, reducing phase separation, and thereby improving the overall performance and stability of the material, enabling it to meet toy performance requirements. However, in this solution, it is difficult for polyethylene glycol to effectively graft plant starch, and the compatibility between plant starch and PBAT cannot be improved. Summary of the Invention

[0004] The present invention aims to provide a plant starch composite material for children's toys and a preparation method thereof. Double-bonded silica microspheres are prepared by a sol-gel method, polymerized with methyl methacrylate, and then hydrolyzed under acidic conditions using styrene-maleic anhydride copolymer to obtain a hydrolyzed copolymer containing carboxyl groups. The hydrolyzed copolymer then undergoes an esterification reaction with starch. The esterification reaction consumes a large number of hydroxyl groups on the starch surface, thereby increasing the compatibility of starch with PBAT. In addition, the long-chain structure of the hydrolyzed styrene-maleic anhydride copolymer forms a flexible coating on the starch surface, preventing agglomeration between starch particles.

[0005] The purpose of the present invention can be achieved through the following technical solutions: A method for preparing a plant starch composite material for children's toys comprises the following steps: Step 1: Using the sol-gel method, ethyl orthosilicate and γ-methacryloxypropyltrimethoxysilane are first hydrolyzed and condensed under acidic conditions to form a sol. The sol is then mixed with other silanes and solvents to form an oil phase, which is then emulsified with an aqueous phase containing a surfactant through a microporous membrane and cross-linked and solidified into spheres to obtain double-bonded silica microspheres with double bonds on the surface.

[0006] Step 2: using the double bond in the structural formula of methyl methacrylate and the double bond on the surface of the double-bonded silica microspheres to polymerize in the presence of an initiator azobisisobutyronitrile to obtain a functional core-shell filler.

[0007] Step 3: hydrolyzing the styrene maleic anhydride copolymer under acidic conditions to obtain a hydrolyzed copolymer containing carboxyl groups, and then esterifying the copolymer with starch to obtain a compatible modified starch.

[0008] Step 4: PBAT, compatible modified starch, functional core-shell filler, cellulose nanocrystals, and quaternized chitosan are stirred and mixed to obtain a premix, which is then melt-extruded through a twin-screw extruder and granulated to obtain a plant starch composite material for children's toys.

[0009] Furthermore, the specific preparation steps of double-bonded silica microspheres are as follows: The sol, ethyl orthosilicate, phenyltrimethoxysilane and n-hexane are stirred and mixed as the oil phase, Tween 80, sodium lauryl sulfate, deionized water and ethanol are stirred and mixed as the water phase, the oil phase and the water phase are emulsified through a microporous membrane to form a uniform emulsion, and then triethanolamine is added. The mixture is heated to 35-40°C and reacted for 5-6 hours to solidify into spheres. The mixture is naturally cooled to room temperature and filtered. The precipitate is washed with deionized water and anhydrous ethanol 2-4 times, and vacuum dried at 60-70°C for 1-2 hours to obtain double-bonded silica microspheres with a particle size of 15-20 μm.

[0010] Furthermore, the usage ratio of sol, ethyl orthosilicate, phenyltrimethoxysilane, n-hexane, Tween 80, sodium lauryl sulfate, deionized water, ethanol and triethanolamine is 500-600 g: 200-300 mL: 60-70 g: 140-150 g: 60-70 g: 16-18 g: 6-7 L: 1-2 L: 300-400 g.

[0011] Furthermore, the specific preparation steps of the sol are as follows: Ethyl orthosilicate, γ-methacryloyloxypropyltrimethoxysilane, anhydrous methanol and deionized water were added to a reactor, stirred at 40-45°C and 500-600 r / min for 10-15 minutes, 1 mol / L acetic acid was added to adjust the pH to 3-4, and stirring was continued for 4-5 hours to obtain a sol.

[0012] Furthermore, the usage ratio of ethyl orthosilicate, γ-methacryloxypropyltrimethoxysilane, anhydrous methanol and deionized water is 700-800 mL: 300-400 g: 800-900 mL: 5-6 L.

[0013] Furthermore, the specific preparation steps of the functional core-shell filler are as follows: Methyl methacrylate, double-bonded silica microspheres and anhydrous tetrahydrofuran are added to a reactor, stirred at 20-25°C and 400-500 r / min for 20-30 minutes, and then an initiator azobisisobutyronitrile is added, ultrasonically dispersed for 20-30 minutes, heated to 60-70°C under nitrogen protection, and continued to stir and react for 12-14 hours. The mixture is naturally cooled to room temperature and filtered. The filter cake is washed with deionized water and anhydrous ethanol for 2-4 times, respectively, and vacuum dried at 60-70°C for 1-2 hours to obtain a functional core-shell filler.

[0014] Furthermore, the usage ratio of methyl methacrylate, double-bonded silica microspheres, anhydrous tetrahydrofuran and azobisisobutyronitrile is 500-600 mL: 300-400 g: 4-5 L: 10-12 g.

[0015] Furthermore, the specific preparation steps of the hydrolyzed copolymer are as follows: Styrene maleic anhydride copolymer and tetrahydrofuran are added to a reactor, stirred at 20-25°C and 400-500 r / min for 20-30 minutes, then 36.5% concentrated hydrochloric acid is added, heated to 55-60°C and reacted for 12-14 hours, deionized water is added to precipitate the polymer, the precipitate is washed with a large amount of deionized water 2-4 times, and freeze-dried to obtain a hydrolyzed copolymer.

[0016] Furthermore, the usage ratio of styrene-maleic anhydride copolymer, tetrahydrofuran and concentrated hydrochloric acid is 400-500 g: 5-6 L: 50-60 mL.

[0017] Furthermore, the specific preparation steps of the compatible modified starch are as follows: The hydrolyzed copolymer, plant starch and toluene are added to a reactor, stirred at 40-45°C and 500-600 r / min for 10-15 minutes, and then the catalyst triethylamine is added. Under nitrogen protection, the mixture is heated to 90-100°C and stirred for reaction for 12-14 hours. The mixture is naturally cooled to room temperature and filtered. The filter cake is washed with deionized water and anhydrous ethanol for 2-4 times respectively, and freeze-dried to obtain a compatible modified starch.

[0018] Furthermore, the usage ratio of the hydrolyzed copolymer, the plant starch, the toluene and the triethylamine is 500-600 g: 1-2 kg: 5-6 L: 20-40 mL.

[0019] Furthermore, the plant starch is any one of corn starch, wheat starch, rice starch, potato starch or tapioca starch.

[0020] Furthermore, the specific preparation steps of the plant starch composite material are as follows: PBAT, compatible modified starch, functional core-shell filler, nucleating agent cellulose nanocrystals and antistatic agent quaternized chitosan are stirred and mixed for 10-15 minutes at a stirring speed of 500-800 r / min to obtain a premix. The premix is placed in a twin-screw extruder, melt-extruded at 140-150°C, naturally cooled to room temperature, and granulated to obtain a plant starch composite material for children's toys in the form of granules with a particle size of 3-5 mm.

[0021] Furthermore, the usage ratio of PBAT, compatible modified starch, functional core-shell filler, cellulose nanocrystals and quaternized chitosan is 7-8 kg: 500-600 g: 30-40 g: 12-14 g: 7-9 g.

[0022] Beneficial effects of the present invention: 1. The plant starch composite material for children's toys prepared by the present invention has good use strength, is not easy to be damaged, and is safe and non-toxic after being prepared into children's toys.

[0023] 2. The functional core-shell filler of the present invention utilizes a sol-gel method to obtain double-bonded silica microspheres with double bonds on the surface, which can be copolymerized with methyl methacrylate to generate a methyl methacrylate coating layer coated on the double-bonded silica microspheres, thereby increasing the polarity of the functional core-shell filler. The coating layer has a low friction coefficient, which is much lower than that of unmodified silica. Molecular chain slippage occurs easily when a force is applied, thus imparting self-lubricating properties to the surface, allowing the microspheres to disperse stress by sliding during use or processing. The coating layer forms a soft shell on the surface of the microspheres, which prevents direct contact of the microspheres through steric hindrance, making it less likely for them to agglomerate.

[0024] 3. The compatible modified starch of the present invention is obtained by exposing carboxyl groups after hydrolysis of styrene maleic anhydride copolymer to obtain a hydrolyzed copolymer containing carboxyl groups. The carboxyl groups are used to undergo esterification reaction with a large number of hydroxyl groups on the surface of plant starch. The starch molecular chain is rich in hydroxyl groups and can form a dense hydrogen bond network, which makes it have extremely high hydrophilic polarity. The PBAT molecular chain is mainly composed of aliphatic aromatic structures. Although the ester bond has weak polarity, it is hydrophobic as a whole. The esterification reaction deprives a large number of hydroxyl groups on the starch surface, thereby increasing the compatibility of starch and PBAT. In addition, the long chain structure of the hydrolyzed copolymer forms a flexible coating on the starch surface to prevent agglomeration between starch particles. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] Example 1: A method for preparing a plant starch composite material for children's toys, comprising the following steps: S1: 700mL of ethyl orthosilicate, 300g γ-Methacryloxypropyltrimethoxysilane, 800mL of anhydrous methanol and 5L of deionized water were added to a reactor, stirred at 40°C and 500r / min for 10min, 1mol / L acetic acid was added to adjust the pH to 3, and stirring was continued for 4h to obtain a sol; 500g of sol, 200mL of ethyl orthosilicate, 60g of phenyltrimethoxysilane and 140g of n-hexane were stirred and mixed as the oil phase, 60g of Tween 80, 16g of sodium lauryl sulfate, 6L of deionized water and 1L of ethanol were stirred and mixed as the aqueous phase, the oil phase and the aqueous phase were emulsified through a microporous membrane to form a uniform emulsion, and then 300g of triethanolamine was added, heated to 35°C for reaction for 5h to solidify into balls, naturally cooled to room temperature, filtered, and the precipitate was washed twice with deionized water and anhydrous ethanol, and vacuum dried at 60°C for 1h to obtain double-bonded silica microspheres with a particle size of 15μm.

[0027] S2: Add 500 mL of methyl methacrylate, 300 g of double-bonded silica microspheres and 4 L of anhydrous tetrahydrofuran into the reactor, stir at 20 ° C and 400 r / min for 20 min, then add 10 g of initiator azobisisobutyronitrile, ultrasonically disperse for 20 min, heat to 60 ° C under nitrogen protection, continue stirring and react for 12 h, cool naturally to room temperature, filter, wash the filter cake with deionized water and anhydrous ethanol twice respectively, and dry in vacuo at 60 ° C for 1 h to obtain a functional core-shell filler.

[0028] S3: Add 400 g of styrene-maleic anhydride copolymer and 5 L of tetrahydrofuran into a reactor, stir at 20°C and 400 r / min for 20 min, then add 50 mL of 36.5% concentrated hydrochloric acid, heat to 55°C and react for 12 h, add deionized water to precipitate the polymer, wash the precipitate twice with a large amount of deionized water, and freeze-dry to obtain a hydrolyzed copolymer.

[0029] S4: Add 500g of hydrolyzed copolymer, 1kg of rice starch and 5L of toluene into a reactor, stir at 40°C and 500r / min for 10min, then add 20mL of catalyst triethylamine, heat to 90°C under nitrogen protection, stir and react for 12h, cool naturally to room temperature, filter, wash the filter cake with deionized water and anhydrous ethanol twice respectively, and freeze-dry to obtain compatible modified starch.

[0030] S5: 7 kg PBAT, 500 g compatible modified starch, 30 g functional core-shell filler, 12 g nucleating agent cellulose nanocrystals and 7 g antistatic agent quaternized chitosan were stirred and mixed for 10 min at a stirring speed of 500 r / min to obtain a premix. The premix was placed in a twin-screw extruder, melt-extruded at 140°C, naturally cooled to room temperature, and granulated to obtain a plant starch composite material for children's toys in the form of granules with a particle size of 3 mm.

[0031] Example 2: A method for preparing a plant starch composite material for children's toys, comprising the following steps: S1: 750 mL of ethyl orthosilicate, 350 g of γ-methacryloxypropyltrimethoxysilane, 850 mL of anhydrous methanol and 5.5 L of deionized water were added to a reactor, stirred at 42.5 ° C and 550 r / min for 12.5 min, 1 mol / L acetic acid was added to adjust the pH value to 3.5, and stirring was continued for 4.5 h to obtain a sol; 550 g of sol, 250 mL of ethyl orthosilicate, 65 g of phenyltrimethoxysilane and 145 g of n-hexane were stirred and mixed as the oil phase, and 65 g of Tween 80, 17 g of sodium lauryl sulfate, 6.5 L of deionized water and 1.5 L of ethanol were stirred and mixed as the aqueous phase. The oil phase and the aqueous phase were emulsified through a microporous membrane to form a uniform emulsion. 350 g of triethanolamine was then added, and the mixture was heated to 37.5 ° C and reacted for 5.5 h to solidify into spheres. The mixture was naturally cooled to room temperature and filtered. The precipitate was washed three times with deionized water and anhydrous ethanol, and vacuum dried at 65 ° C for 1.5 h to obtain double-bonded silica microspheres with a particle size of 17.5 μm.

[0032] S2: Add 550 mL of methyl methacrylate, 350 g of double-bonded silica microspheres and 4.5 L of anhydrous tetrahydrofuran into the reactor, stir at 22.5 ° C and 450 r / min for 25 minutes, then add 11 g of initiator azobisisobutyronitrile, ultrasonically disperse for 25 minutes, heat to 65 ° C under nitrogen protection, continue stirring and react for 13 hours, cool naturally to room temperature, filter, wash the filter cake with deionized water and anhydrous ethanol three times respectively, and vacuum dry at 65 ° C for 1.5 hours to obtain a functional core-shell filler.

[0033] S3: Add 450 g of styrene-maleic anhydride copolymer and 5.5 L of tetrahydrofuran into a reactor, stir at 22.5°C and 450 r / min for 25 min, then add 55 mL of 36.5% concentrated hydrochloric acid, heat to 57.5°C and react for 13 h, add deionized water to precipitate the polymer, wash the precipitate three times with a large amount of deionized water, and freeze-dry to obtain a hydrolyzed copolymer.

[0034] S4: Add 550g of hydrolyzed copolymer, 1.5kg of rice starch and 5.5L of toluene into the reactor, stir at 42.5℃ and 550r / min for 12.5min, then add 30mL of catalyst triethylamine, heat to 95℃ and stir under nitrogen protection for 13h, cool naturally to room temperature, filter, wash the filter cake with deionized water and anhydrous ethanol three times respectively, and freeze-dry to obtain compatible modified starch.

[0035] S5: 7.5 kg PBAT, 550 g compatible modified starch, 35 g functional core-shell filler, 13 g nucleating agent cellulose nanocrystals and 8 g antistatic agent quaternized chitosan were stirred and mixed for 12.5 min at a stirring speed of 650 r / min to obtain a premix. The premix was placed in a twin-screw extruder, melt-extruded at 145°C, naturally cooled to room temperature, and granulated to obtain a plant starch composite material for children's toys in the form of granules with a particle size of 4 mm.

[0036] Example 3: A method for preparing a plant starch composite material for children's toys, comprising the following steps: S1: 800mL of ethyl orthosilicate, 400g γ-Methacryloxypropyltrimethoxysilane, 900 mL of anhydrous methanol and 6 L of deionized water were added to a reactor, stirred at 45 ° C and 600 r / min for 15 minutes, acetic acid with a concentration of 1 mol / L was added to adjust the pH value to 4, and stirring was continued for 5 hours to obtain a sol; 600 g of sol, 300 mL of ethyl orthosilicate, 70 g of phenyltrimethoxysilane and 150 g of n-hexane were stirred and mixed as the oil phase, 70 g of Tween 80, 18 g of sodium lauryl sulfate, 7 L of deionized water and 2 L of ethanol were stirred and mixed as the aqueous phase, the oil phase and the aqueous phase were emulsified through a microporous membrane to form a uniform emulsion, and then 400 g of triethanolamine was added, heated to 40 ° C for 6 hours to solidify into balls, naturally cooled to room temperature, filtered, and the precipitate was washed with deionized water and anhydrous ethanol 4 times, and vacuum dried at 70 ° C for 2 hours to obtain double-bonded silica microspheres with a particle size of 20 μm.

[0037] S2: Add 600 mL of methyl methacrylate, 400 g of double-bonded silica microspheres and 5 L of anhydrous tetrahydrofuran into the reactor, stir at 25 ° C and 500 r / min for 30 minutes, then add 12 g of initiator azobisisobutyronitrile, ultrasonically disperse for 30 minutes, heat to 70 ° C under nitrogen protection, continue stirring and react for 14 hours, cool naturally to room temperature, filter, wash the filter cake with deionized water and anhydrous ethanol four times respectively, and vacuum dry at 70 ° C for 2 hours to obtain a functional core-shell filler.

[0038] S3: Add 500 g of styrene-maleic anhydride copolymer and 6 L of tetrahydrofuran into a reactor, stir at 25°C and 500 r / min for 30 min, then add 60 mL of 36.5% concentrated hydrochloric acid, heat to 60°C and react for 14 h, add deionized water to precipitate the polymer, wash the precipitate four times with a large amount of deionized water, and freeze-dry to obtain a hydrolyzed copolymer.

[0039] S4: Add 600g of hydrolyzed copolymer, 2kg of rice starch and 6L of toluene into a reactor, stir at 45°C and 600r / min for 15min, then add 40mL of catalyst triethylamine, heat to 100°C under nitrogen protection and stir to react for 14h, cool naturally to room temperature, filter, wash the filter cake with deionized water and anhydrous ethanol four times respectively, and freeze-dry to obtain compatible modified starch.

[0040] S5: 8 kg PBAT, 600 g compatible modified starch, 40 g functional core-shell filler, 14 g nucleating agent cellulose nanocrystals and 9 g antistatic agent quaternized chitosan were stirred and mixed for 15 minutes at a stirring speed of 800 r / min to obtain a premix. The premix was placed in a twin-screw extruder, melt-extruded at 150°C, naturally cooled to room temperature, and granulated to obtain a plant starch composite material for children's toys in the form of granules with a particle size of 5 mm.

[0041] Comparative Example 1: Based on Example 3, the double-bonded silica microspheres in step S2 were replaced with conventional commercially available silica microspheres with a particle size of 15-20 μm.

[0042] Comparative Example 2: Based on Example 3, without the treatment in step S2, the functional core-shell filler in step S5 is replaced by the double-bonded silica microspheres prepared in step S1.

[0043] Comparative Example 3: Based on Example 3, step S4 is not performed, and the compatible modified starch in step S5 is replaced by rice starch.

[0044] The plant starch composite materials for children's toys obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were injection molded to produce children's toys, and performance testing was performed. The tensile strength, elongation at break, and elastic modulus were tested according to GB / T1040.2-2022; the notched impact strength was tested according to GB / T1843-2008; and the specific safety requirements of GB6675.1-2014 "Safety of Toys - Part 1: Basic Specifications": Safety requirements: Toys and materials designed for children's play must not cause any harm to children. Manufacturing requirements include avoiding sharp edges, small parts that may cause choking hazards, and toys that should not contain hazardous substances. Referring to the testing approach of GB / T1733-1993, the children's toys were soaked in water for 12 hours, and the toy material powder was scraped off with a blade. The plasticizer content in the products was tested using gas chromatography-mass spectrometry (GC-MS), using dibutyl phthalate as an example. The results are shown in Table 1: Table 1 Children's Toy Performance Test Table As can be seen from Table 1, the tensile strength, elongation at break, elastic modulus and notched impact strength of the children's toys prepared from the plant starch composite materials obtained in Examples 1-3 are significantly better than those of the comparative example, indicating that the children's toys prepared from the plant starch composite materials prepared by the present invention have sufficient strength, are not easily damaged, and are safe and non-toxic.

[0045] In Comparative Example 1, the double-bonded silica microspheres are replaced with conventional commercially available silica microspheres. The double-bonded silica microspheres are prepared by a sol-gel method. First, tetraethyl orthosilicate and γ-methacryloxypropyltrimethoxysilane are hydrolyzed and condensed under acidic conditions to form a sol. Then, an oil phase is prepared with tetraethyl orthosilicate, phenyltrimethoxysilane and n-hexane. The oil phase is then emulsified with an aqueous phase containing a surfactant through a microporous membrane and cross-linked and solidified into balls to obtain double-bonded silica microspheres with double bonds on the surface. The formation of double bonds is conducive to copolymerization with methyl methacrylate, so that a methyl methacrylate coating layer is formed on the double-bonded silica microspheres, which increases the polarity of the functional core-shell filler and makes it less likely to agglomerate.

[0046] In Comparative Example 2, the functional core-shell filler is replaced with double-bonded silica microspheres. The polymethyl methacrylate coating has a low friction coefficient, which is much lower than that of unmodified silica. Molecular chain slippage occurs easily when subjected to force, giving the surface self-lubrication, so that the microspheres can disperse stress by sliding during use or processing. In addition, the methyl methacrylate coating layer is coated on the double-bonded silica microspheres, which can increase the polarity of the functional core-shell filler and prevent direct contact of the microspheres through steric hindrance, making it less likely to agglomerate.

[0047] In Comparative Example 3, the compatible modified starch is replaced with rice starch. The carboxyl groups are exposed after hydrolysis of the styrene maleic anhydride copolymer to obtain a carboxyl-containing hydrolyzed copolymer. The carboxyl groups are used to undergo esterification reaction with a large number of hydroxyl groups on the surface of the plant starch. The starch molecular chain is rich in hydroxyl groups (-OH) and can form a dense hydrogen bond network, which makes it have extremely high hydrophilic polarity. The PBAT molecular chain is mainly composed of aliphatic aromatic structures. Although the ester bond has weak polarity, it is hydrophobic as a whole. The esterification reaction deprives a large number of hydroxyl groups on the starch surface, thereby increasing the compatibility of starch and PBAT, and the long-chain structure of the hydrolyzed copolymer forms a flexible coating on the starch surface to prevent agglomeration between starch particles.

[0048] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a plant starch composite material for children's toys, characterized in that: The steps include: Step 1: Using the sol-gel method, ethyl orthosilicate and γ-methacryloxypropyltrimethoxysilane are first hydrolyzed and condensed under acidic conditions to form a sol. The sol is then mixed with other silanes and a solvent to form an oil phase, which is then emulsified with an aqueous phase containing a surfactant through a microporous membrane and cross-linked and solidified into spheres to obtain double-bonded silica microspheres with double bonds on the surface. Step 2: using the double bond in the structural formula of methyl methacrylate and the double bond on the surface of the double-bonded silica microspheres to polymerize with the initiator azobisisobutyronitrile to obtain a functional core-shell filler; Step 3: hydrolyzing the styrene maleic anhydride copolymer under acidic conditions to obtain a hydrolyzed copolymer containing carboxyl groups, and then esterifying the copolymer with starch to obtain a compatible modified starch; Step 4: PBAT, compatible modified starch, functional core-shell filler, cellulose nanocrystals, and quaternized chitosan are stirred and mixed to obtain a premix, which is then melt-extruded through a twin-screw extruder and granulated to obtain a plant starch composite material for children's toys.

2. The method for preparing a plant starch composite material for children's toys according to claim 1, characterized in that: The specific preparation steps of the double-bonded silica microspheres are as follows: The sol, ethyl orthosilicate, phenyltrimethoxysilane and n-hexane are stirred and mixed as the oil phase, Tween 80, sodium lauryl sulfate, deionized water and ethanol are stirred and mixed as the water phase, the oil phase and the water phase are emulsified through a microporous membrane to form a uniform emulsion, and then triethanolamine is added. The mixture is heated to 35-40°C and reacted for 5-6 hours to solidify into balls. The mixture is naturally cooled, filtered, washed, and vacuum dried to obtain double-bonded silica microspheres.

3. The method for preparing a plant starch composite material for children's toys according to claim 2, characterized in that: The usage ratio of the sol, ethyl orthosilicate, phenyltrimethoxysilane, n-hexane, Tween 80, sodium lauryl sulfate, deionized water, ethanol and triethanolamine is 500-600 g: 200-300 mL: 60-70 g: 140-150 g: 60-70 g: 16-18 g: 6-7 L: 1-2 L: 300-400 g.

4. The method for preparing a plant starch composite material for children's toys according to claim 2, characterized in that: The specific preparation steps of the sol are as follows: Add ethyl orthosilicate, γ-methacryloxypropyltrimethoxysilane, anhydrous methanol and deionized water into a reaction kettle, stir at 40-45°C and 500-600 r / min for 10-15 minutes, add acetic acid with a concentration of 1 mol / L to adjust the pH to 3-4, and continue stirring for 4-5 hours to obtain a sol; The usage ratio of the ethyl orthosilicate, γ-methacryloxypropyltrimethoxysilane, anhydrous methanol and deionized water is 700-800 mL: 300-400 g: 800-900 mL: 5-6 L.

5. The method for preparing a plant starch composite material for children's toys according to claim 1, characterized in that: The specific preparation steps of the functional core-shell filler are as follows: Methyl methacrylate, double-bonded silica microspheres and anhydrous tetrahydrofuran were added to a reaction kettle, stirred at 20-25°C and 400-500 r / min for 20-30 minutes, and then azobisisobutyronitrile was added, ultrasonically dispersed for 20-30 minutes, heated to 60-70°C under nitrogen protection, and continued to stir and react for 12-14 hours, cooled naturally, filtered, washed, and vacuum dried to obtain a functional core-shell filler; The usage ratio of the methyl methacrylate, double-bonded silica microspheres, anhydrous tetrahydrofuran and azobisisobutyronitrile is 500-600 mL: 300-400 g: 4-5 L: 10-12 g.

6. The method for preparing a plant starch composite material for children's toys according to claim 1, characterized in that: The specific preparation steps of the hydrolyzed copolymer are as follows: Add styrene maleic anhydride copolymer and tetrahydrofuran into a reactor, stir at 20-25°C and 400-500 r / min for 20-30 minutes, then add 36.5wt% concentrated hydrochloric acid, heat to 55-60°C, react for 12-14 hours, add deionized water to precipitate the polymer, wash the precipitate with a large amount of deionized water 2-4 times, and freeze-dry to obtain a hydrolyzed copolymer; The usage ratio of the styrene-maleic anhydride copolymer, tetrahydrofuran and concentrated hydrochloric acid is 400-500 g: 5-6 L: 50-60 mL.

7. The method for preparing a plant starch composite material for children's toys according to claim 1, characterized in that: The specific preparation steps of the compatible modified starch are as follows: The hydrolyzed copolymer, plant starch and toluene are added to a reactor, stirred at 40-45°C and 500-600 r / min for 10-15 minutes, and then 20-40 mL of triethylamine is added. Under nitrogen protection, the mixture is heated to 90-100°C and stirred for reaction for 12-14 hours. The mixture is naturally cooled, filtered, washed and freeze-dried to obtain a compatible modified starch.

8. The method for preparing a plant starch composite material for children's toys according to claim 7, characterized in that: The usage ratio of the hydrolyzed copolymer, plant starch, toluene and triethylamine is 500-600 g: 1-2 kg: 5-6 L: 20-40 mL; the plant starch is any one of corn starch, wheat starch, rice starch, potato starch or cassava starch.

9. The method for preparing a plant starch composite material for children's toys according to claim 1, characterized in that: The specific preparation steps of the plant starch composite material are as follows: PBAT, compatible modified starch, functional core-shell filler, nucleating agent cellulose nanocrystals and antistatic agent quaternized chitosan are stirred and mixed for 10-15 minutes at a stirring speed of 500-800 r / min to obtain a premix, and the premix is placed in a twin-screw extruder, melt-extruded at 140-150° C., naturally cooled, and granulated to obtain a plant starch composite material for children's toys in the form of granules with a particle size of 3-5 mm; The usage ratio of the PBAT, compatible modified starch, functional core-shell filler, cellulose nanocrystal and quaternized chitosan is 7-8 kg: 500-600 g: 30-40 g: 12-14 g: 7-9 g.

10. A plant starch composite material for children's toys, characterized in that: Prepared by the preparation method according to any one of claims 1 to 9.

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