Heat-resistant degradable composite material and preparation method thereof

Abstract

The present application belongs to the technical field of degradable polymer composite materials, and particularly relates to a heat-resistant degradable composite material and a preparation method thereof. In the method, epoxy silane grafted zirconium titanium phytate layered microsheets, lactic acid modified silicon boron calcium phosphate whiskers and light calcium carbonate are premixed with ethylene bis-stearamide and monoglyceride, and then mixed with polybutylene succinate, polylactic acid, polybutylene terephthalate adipate, an epoxy chain extender and an antioxidant, and then subjected to double-screw melt blending, cooling and granulation, drying, molding and heat treatment to obtain the heat-resistant degradable composite material. Through the synergistic effect of the epoxy silane grafted zirconium titanium phytate layered microsheets, the lactic acid modified silicon boron calcium phosphate whiskers and the degradable polyester matrix, the heat resistance, dimensional stability, mechanical strength and processing stability of the material are improved.

Description

Technical Field

[0001] This invention belongs to the field of biodegradable polymer composite materials technology, specifically relating to a heat-resistant biodegradable composite material and its preparation method. Background Technology

[0002] With increasingly stringent environmental performance requirements for packaging materials, disposable tableware, agricultural products, and daily consumer goods, biodegradable polyester materials are gradually becoming an important alternative to traditional petroleum-based plastics. Biodegradable polyesters such as polybutylene succinate, polylactic acid, and polybutylene adipate terephthalate have advantages such as wide availability, good processability, and the ability to produce products through melt extrusion and molding processes. They can degrade under certain conditions, reducing the environmental burden of long-term plastic waste. However, biodegradable polyester materials still suffer from problems such as insufficient heat resistance, low heat distortion temperature, poor dimensional stability after heating, insufficient melt strength, and low mechanical property retention. Especially in applications such as hot beverage containers, heat-resistant packaging, lunch boxes, electronic product cushioning components, and high-temperature transport packaging, the materials are prone to softening, warping, collapsing, or strength reduction, limiting their wider application.

[0003] Existing technologies typically improve the processing and heat resistance of biodegradable polyester materials by adding inorganic fillers, nucleating agents, chain extenders, lubricants, or antioxidants. For example, inorganic fillers such as calcium carbonate, talc, silicates, and calcium phosphate can improve the rigidity and thermal stability of materials to some extent, chain extenders can improve the melt strength of polyester, and antioxidants can reduce thermo-oxidative degradation during processing. However, ordinary inorganic fillers have poor interfacial compatibility with the polyester matrix, easily agglomerating and forming stress concentration points, leading to reduced material toughness and impact resistance. Improving heat resistance solely with ordinary fillers often requires high addition amounts, which in turn affects the material's processing flowability and degradation uniformity. Conventional nucleating agents or reinforcing agents also struggle to simultaneously address crystallization control, interfacial reinforcement, heat resistance support, and compatibility with the biodegradable system. Therefore, how to construct a composite reinforcing system that improves heat resistance while maintaining the overall processability and mechanical properties of biodegradable polyester is a crucial problem that needs to be solved in this field.

[0004] Furthermore, biodegradable polyester composites face significant challenges in multi-component synergy during actual processing. Polybutylene succinate (PBS) exhibits good flexibility but insufficient heat resistance, while polylactic acid (PLA) boasts high rigidity but suffers from inadequate toughness and thermal processing stability. Polybutylene adipate (PEG) improves toughness but negatively impacts overall heat resistance and rigidity. Without effective interfacial bonding and structural support, stable synergistic networks are difficult to form between different polyester phases and between polyester and inorganic fillers. Therefore, it is necessary to develop a heat-resistant biodegradable composite material that leverages the synergistic effects of layered microplates, whiskers, and a polyester matrix. This allows the layered structure to provide a thermal barrier and interfacial bonding, while the whisker structure provides nucleation reinforcement and dimensional stability support. Combined with an epoxy chain extender system, this improves melt strength and compatibility, thereby enhancing the material's heat resistance, dimensional stability, mechanical strength, and processing stability while maintaining its biodegradability. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a heat-resistant and biodegradable composite material and its preparation method.

[0006] In a first aspect, the present invention provides a method for preparing a heat-resistant and biodegradable composite material, comprising the steps of: S1. By weight, 2.0-8.0 parts of dried epoxy silane-grafted zirconium titanate layered micro flakes, 3.0-10.0 parts of lactic acid-modified calcium borosilicate whiskers, and 3.0-12.0 parts of light calcium carbonate are mixed, and 0.2-0.8 parts of ethylene bis-stearamide and 0.2-0.8 parts of monoglyceride are added. The mixture is then mixed at 60-75℃ to obtain a composite reinforced premix powder. 55.0-75.0 parts of dried polybutylene succinate, 10.0-25.0 parts of polylactic acid, 3.0-12.0 parts of polybutylene adipate terephthalate, 0.3-1.2 parts of epoxy chain extender, 0.1-0.4 parts of antioxidant 1010, and 0.1-0.4 parts of antioxidant 168 are mixed, and the composite reinforced premix powder is added. The mixture is then further mixed to obtain a heat-resistant and biodegradable composite material premix. S2. Add the heat-resistant biodegradable composite premix to a twin-screw extruder for melt blending and extrusion, cool, pelletize, and dry to obtain heat-resistant biodegradable composite granules; then subject the heat-resistant biodegradable composite granules to molding and heat treatment in sequence.

[0007] In this invention, the preparation reaction mechanism of the heat-resistant and biodegradable composite material lies in the combined effects of dispersion and wetting of the composite reinforced premix powder, multiphase melt blending of polyester, compatibilization by epoxy chain extender, and heat treatment-induced crystallization. Epoxy silane-grafted zirconium-titanium phytate layered microflakes, lactic acid-modified calcium borosilicate whiskers, and light calcium carbonate are first mixed with ethylene bis-stearamide and monoglyceride. Ethylene bis-stearamide and monoglyceride can reduce the friction and interfacial tension between inorganic powders, improving the pre-dispersion state of the layered microflakes, whiskers, and light calcium carbonate in the subsequent melt system, forming the composite reinforced premix powder. Polybutylene succinate, as the continuous biodegradable polyester matrix, provides toughness and processing fluidity; polylactic acid provides rigidity and a heat-resistant skeleton; and polybutylene adipate terephthalate improves the toughness and impact resistance of the blend system. After the heat-resistant and biodegradable composite premix enters the twin-screw extruder, polybutylene succinate, polylactic acid, and polybutylene adipate terephthalate melt and form continuous and dispersed phase structures under shear. The epoxy groups of the epoxy chain extender undergo ring-opening reactions with the terminal carboxyl or hydroxyl groups of polybutylene succinate, polylactic acid, and polybutylene adipate terephthalate, improving the degree of chain segment connection and interphase bonding strength. Antioxidant 1010 and antioxidant 168 inhibit thermo-oxidative degradation during melt processing. Epoxy silane-grafted zirconium-titanium phytate layered microplates limit the high-temperature slippage of polyester segments through layered barrier and interfacial bonding. Lactic acid-modified calcium borosilicate whiskers improve the degree of crystallization perfection through whisker framework and nucleation. Light calcium carbonate provides filling reinforcement and rigid support. Molding and heat treatment further promote the stable distribution of polyester crystallization and multi-scale reinforcing phases, thereby improving the material's heat resistance, dimensional stability, mechanical strength, and processing stability.

[0008] According to a preferred embodiment of the present invention, in step S1, the mixing time at 60-75°C is 8-15 min; the epoxy chain extender is selected from at least one of ADR-4468, ADR-4368CS, ADR-4370, ADR-4385, ADR-4380, and ADR-4300.

[0009] According to a preferred embodiment of the present invention, in step S2, the temperatures of each zone of the twin-screw extruder are as follows: zone 1 temperature is 125-135℃, zone 2 temperature is 140-150℃, zone 3 temperature is 150-160℃, zone 4 temperature is 160-170℃, zone 5 temperature is 165-175℃, and the die head temperature is 160-170℃; the forming treatment temperature is 155-175℃; and the heat treatment temperature is 80-95℃.

[0010] According to a preferred embodiment of the present invention, the method for preparing the epoxysilane-grafted zirconium titanate layered microsheets includes: A1. By weight, add 50.0-70.0 parts of phytic acid solution to 250.0-350.0 parts of deionized water, stir at 25-30℃, add 10.0-18.0 parts of zirconium oxychloride octahydrate, and continue stirring to obtain a zirconium-phytic acid complex solution; add 6.0-12.0 parts of tetrabutyl titanate to 60.0-100.0 parts of anhydrous ethanol, add 1.0-3.0 parts of acetylacetone, and stir to obtain a stable titanium source solution; add the stable titanium source solution to the zirconium-phytic acid complex solution, adjust the pH to 3.5-4.0 with ammonia water, and react at 45-55℃ to obtain a zirconium-titanium phytate precursor dispersion; A2. Transfer the zirconium titanate phytate precursor dispersion to a reactor and perform a hydrothermal reaction at 115-130℃. After cooling, centrifugation, and washing, a wet filter cake is obtained. Disperse the wet filter cake in a mixture of 120.0-180.0 parts anhydrous ethanol and 30.0-60.0 parts deionized water, add 3.0-6.0 parts 3-(2,3-epoxypropoxy)propyltrimethoxysilane, adjust the pH to 4.0-4.8 with glacial acetic acid, react at 60-70℃, centrifuge, wash, dry, grind, and sieve.

[0011] In this invention, the preparation mechanism of epoxysilane-grafted zirconium-titanium phytate layered microsheets involves sequential coordination complexation, hydrolysis condensation, and surface silanization reactions between phytic acid solution, zirconium oxychloride octahydrate, tetrabutyl titanate, and 3-(2,3-epoxypropoxy)propyltrimethoxysilane. The phytic acid solution contains multiple phosphate groups, enabling multi-point coordination with the zirconium centers released from the zirconium oxychloride octahydrate, forming a cross-linked complex network of zirconium and phytic acid. After contacting acetylacetone in anhydrous ethanol, the titanium centers of tetrabutyl titanate are stabilized by complexation, inhibiting the hydrolysis rate. Upon addition of the zirconium and phytic acid complex solution, it gradually hydrolyzes under an acidic environment regulated by ammonia, generating a titanium-containing hydroxyl intermediate structure. This intermediate structure then undergoes condensation complexation with the zirconium and phytic acid complex network, resulting in a zirconium, titanium, and phytic acid forming a zirconium-titanium phytate precursor dispersion. The precursor undergoes further hydrolysis, condensation, coordination rearrangement, and lamellar growth under hydrothermal conditions to form a wet filter cake of zirconium-titanium phytate with a layered structure. After the wet filter cake is dispersed in a mixture of anhydrous ethanol and deionized water, 3-(2,3-epoxypropoxy)propyltrimethoxysilane undergoes moderate hydrolysis in a weakly acidic environment regulated by glacial acetic acid, generating an intermediate containing silanol groups. These silanol groups condense with phosphate hydroxyl, metal hydroxyl, or adsorbed hydroxyl groups on the surface of the zirconium-titanium phytate to form a silicon-oxygen linking layer. The epoxy groups are mainly retained on the outer surface of the layered microsheets, thus yielding epoxysilane-grafted zirconium-titanium phytate layered microsheets. In this structure, the zirconium-titanium phytate layered framework provides the microsheets with a heat-resistant barrier and inorganic support, while the surface epoxysilane layer enhances its wetting and interfacial reaction capabilities with the polyester matrix.

[0012] According to a preferred embodiment of the present invention, in step A1, the stirring time at 25-30°C is 30-50 min; the reaction time at 45-55°C is 2-4 h.

[0013] According to a preferred embodiment of the present invention, in step A2, the hydrothermal reaction time at 115-130°C is 6-10 hours; the reaction time at 60-70°C is 3-5 hours.

[0014] According to a preferred embodiment of the present invention, the method for preparing the lactic acid-modified calcium silicate borosilicate whiskers includes: B1. By weight, add 50.5-51.0 parts of calcium nitrate tetrahydrate to 300.0-450.0 parts of deionized water, stir at 25-30℃, add 0.5-2.0 parts of boric acid, and continue stirring to obtain a calcium-boron mixture; add 16.5-16.7 parts of diammonium hydrogen phosphate and 1.8-2.0 parts of sodium metasilicate nonahydrate to 180.0-260.0 parts of deionized water, stir, and obtain a silicon-phosphorus source solution; add the silicon-phosphorus source solution to the calcium-boron mixture, adjust the pH to 9.8-10.6 with ammonia water, and continue stirring to obtain a calcium-silicon-boron phosphate whisker precursor suspension; B2. Transfer the calcium borosilicate whisker precursor suspension to a reactor and perform a hydrothermal reaction at 150-170℃. After cooling, centrifugation, and washing, obtain a wet filter cake of calcium borosilicate whiskers. Disperse the wet filter cake of calcium borosilicate whiskers in 120.0-200.0 parts of deionized water, add 3.0-7.0 parts of lactic acid, adjust the pH to 5.6-6.2 with ammonia, react at 55-65℃, centrifuge, dry, grind, and sieve.

[0015] In this invention, the preparation mechanism of lactic acid-modified calcium silicate-boron-phosphate whiskers involves the precipitation of calcium nitrate tetrahydrate, boric acid, diammonium hydrogen phosphate, and sodium metasilicate nonahydrate in an alkaline aqueous phase, with silicate ions participating in substitution or co-deposition, and boron components regulating crystal defects and crystal face growth, forming a whisker-like structure under hydrothermal conditions. Calcium nitrate tetrahydrate, dissolved in deionized water, provides the calcium source. Boric acid, entering the calcium salt solution, participates in regulating the crystal growth environment as a weakly acidic boron-containing species. Diammonium hydrogen phosphate provides the phosphate source, and sodium metasilicate nonahydrate provides the silicate source. After forming a silicate-phosphate source solution, a calcium-boron mixture is added. In an alkaline environment regulated by ammonia, calcium ions and phosphate ions rapidly form a calcium-phosphate salt precursor. Silicate ions participate in the partial substitution of phosphate ions in the calcium phosphate lattice or co-deposition on the crystal surface. Boric acid participates in crystal defect regulation and selective crystal face growth, giving the calcium silicate-boron-phosphate whisker precursor suspension a basis for further hydrothermal directional growth. Following hydrothermal treatment, the precursor particles undergo dissolution, recrystallization, and oriented growth, gradually transforming into a wet filter cake of calcium borosilicate whiskers. The filter cake is then redispersed in deionized water. Lactic acid, under a weakly acidic to near-neutral environment regulated by ammonia, coordinates with calcium sites on the whisker surface via its carboxyl groups. Hydrogen bonds are formed between the carboxyl groups and the hydroxyl groups on the whisker surface, improving the surface polarity and polyester wettability of the whiskers and reducing the tendency for direct agglomeration. This ultimately results in lactic acid-modified calcium borosilicate whiskers. These whiskers provide rigid support, heterogeneous nucleation, and size stabilization in composite materials.

[0016] According to a preferred embodiment of the present invention, in step B1, the stirring time at 25-30°C is 20-40 min.

[0017] According to a preferred embodiment of the present invention, in step B2, the hydrothermal reaction time at 150-170°C is 8-12 hours; the reaction time at 55-65°C is 2-4 hours.

[0018] In a second aspect, the invention provides a heat-resistant biodegradable composite material prepared according to the method for preparing the aforementioned heat-resistant biodegradable composite material.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) In this invention, epoxy silane-grafted zirconium-titanium phytate layered microsheets, lactic acid-modified calcium borosilicate whiskers, and light calcium carbonate are premixed and dispersed with ethylene bis-stearamide and monoglyceride, so that the inorganic reinforcing components obtain a better pre-dispersion state before entering the polyester matrix. The epoxy silane-grafted zirconium-titanium phytate layered microsheets have a layered structure and a silane-containing interface layer, which can play a role in thermal barrier, interfacial bonding, and chain segment restriction in the composite system formed by polybutylene succinate, polylactic acid, and polybutylene adipate terephthalate, thereby reducing the tendency of the material to soften and deform after heating and improving its heat resistance stability.

[0020] (2) The lactic acid modified calcium borosilicate whiskers in this invention have whisker reinforcement and heterogeneous nucleation effects. After lactic acid modification, the wettability with polybutylene succinate, polylactic acid and polybutylene adipate terephthalate is improved, which can reduce stress concentration caused by whisker agglomeration and form a supporting structure inside the composite material. Light calcium carbonate further provides filling reinforcement and rigid support. The epoxy silane-grafted zirconium titanate layered microsheets, lactic acid modified calcium borosilicate whiskers and light calcium carbonate work together to enable the material to obtain better bending support, dimensional retention and heat deformation resistance while maintaining melt processability, thereby improving the problems of easy warping, easy collapse and insufficient rigidity of biodegradable polyester materials under thermal conditions.

[0021] (3) This invention uses polybutylene succinate, polylactic acid and polybutylene adipate terephthalate to combine flexibility, rigidity and processing fluidity; the epoxy chain extender improves the connection between polyester segments and the interphase bonding strength during melt blending, and antioxidants 1010 and 168 reduce thermo-oxidative degradation during processing. After melt blending, molding and heat treatment by a twin-screw extruder, the polyester matrix forms a stable composite structure with epoxy silane-grafted zirconium titanate layered microsheets, lactic acid-modified calcium borosilicate whiskers and light calcium carbonate, so that the resulting heat-resistant and biodegradable composite material has heat resistance, mechanical strength, dimensional stability and processing stability, and is suitable for packaging, tableware and injection molded products that require both heat resistance and environmental protection performance. Detailed Implementation

[0022] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0023] Example 1 This embodiment provides a method for preparing a heat-resistant and biodegradable composite material, the steps of which include: Step S1: Epoxysilane-grafted zirconium-titanium phytate layered microsheets, lactic acid-modified calcium borosilicate whiskers, and light calcium carbonate were vacuum-dried at 80℃ for 8 hours. Polybutylene succinate, polylactic acid, and polybutylene adipate terephthalate were also vacuum-dried at 80℃ for 8 hours. 5.0g of the dried epoxysilane-grafted zirconium-titanium phytate layered microsheets, 6.5g of lactic acid-modified calcium borosilicate whiskers, and 7.5g of light calcium carbonate were added to a high-speed mixer. 0.5g of ethylene bis-stearamide and 0.5g of monoglyceride were added, and the mixture was mixed at 67.5℃ and 800 rpm. Mix at 25°C and 500 rpm for 11.5 min to obtain composite reinforced premix powder; take 65.0 g of dried polybutylene succinate, 17.5 g of polylactic acid, 7.5 g of polybutylene adipate terephthalate, 0.75 g of epoxy chain extender ADR-4300, 0.25 g of antioxidant 1010 and 0.25 g of antioxidant 168 and add them to a high-speed mixer, mix at 25°C and 500 rpm for 5 min, add the composite reinforced premix powder, and continue mixing at 25°C and 500 rpm for 10 min to obtain heat-resistant and biodegradable composite material premix.

[0024] Step S2: Add the heat-resistant biodegradable composite premix to a twin-screw extruder. The temperature of the twin-screw extruder is 130℃ in zone 1, 145℃ in zone 2, 155℃ in zone 3, 165℃ in zone 4, 170℃ in zone 5, and 165℃ at the die head. The screw speed is 260 r / min. Melt-blending extrusion is performed. The extrudate is water-cooled at 25℃ and then pelletized. The pellets are vacuum-dried at 75℃ for 5 hours to obtain heat-resistant biodegradable composite pellets. The heat-resistant biodegradable composite pellets are then injection molded at 165℃, with a die temperature of 60℃, a holding time of 20s, and a cooling time of 30s to obtain molded parts. The molded parts are then heat-treated at 87.5℃ for 2 hours and cooled to 25℃ to obtain the heat-resistant biodegradable composite material.

[0025] Preparation steps of epoxysilane-grafted zirconium-titanium phytate layered microsheets: Step A1: Add 60.0g of phytic acid solution to 300.0g of deionized water and place it in a reaction vessel equipped with a mechanical stirrer. Stir at 27.5℃ and 300r / min for 40min. Add 14.0g of zirconium oxychloride octahydrate and continue stirring at 27.5℃ and 300r / min for 40min to obtain a uniform zirconium-phytic acid complex solution. Add 9.0g of tetrabutyl titanate to 80.0g of anhydrous ethanol and 2.0g of acetylacetone. Stir at 25℃ and 300r / min for 30min to obtain a stable titanium source solution. Add the stable titanium source solution dropwise to the zirconium-phytic acid complex solution over 30min, maintaining stirring at 300r / min during the dropwise addition. After the dropwise addition is complete, adjust the pH to 3.8 with ammonia water and react at 50℃ and 300r / min for 3h to obtain a zirconium-titanium phytate precursor dispersion.

[0026] Step A2: Transfer the zirconium-titanium phytate precursor dispersion to a 1000 mL polytetrafluoroethylene-lined reactor and hydrothermally react at 122.5 °C for 8 h. After the reaction, allow it to cool naturally to 25 °C, centrifuge at 6000 r / min for 10 min, discard the supernatant, and wash the resulting solid three times with deionized water and twice with anhydrous ethanol. After each washing, centrifuge at 6000 r / min for 10 min to obtain a wet filter cake. Disperse the wet filter cake in 150.0 g of anhydrous ethanol and 45.0 g of ethanol. In a mixture of g deionized water, the mixture was stirred at 300 r / min for 20 min, and 4.5 g of 3-(2,3-epoxypropoxy)propyltrimethoxysilane was added. The pH was adjusted to 4.4 with glacial acetic acid, and the mixture was reacted at 65 °C and 300 r / min for 4 h. After the reaction was completed, the mixture was centrifuged at 6000 r / min for 10 min. The resulting solid was washed three times with anhydrous ethanol, dried under vacuum at 70 °C for 12 h, ground, and passed through a 25 μm sieve to obtain epoxysilane-grafted zirconium titanate layered microplates.

[0027] Preparation steps of lactic acid modified calcium silicate borosilicate whiskers: Step B1: Add 50.8g of calcium nitrate tetrahydrate to 375.0g of deionized water and place it in a reaction vessel equipped with a mechanical stirrer. Stir at 27.5℃ and 300r / min for 30min. Add 1.25g of boric acid and continue stirring at 27.5℃ and 300r / min for 30min to obtain a calcium-boron mixture. Add 16.6g of diammonium hydrogen phosphate and 1.9g of sodium metasilicate nonahydrate to 220.0g of deionized water and stir at 25℃ and 300r / min for 30min to obtain a silicon-phosphorus source solution. Add the silicon-phosphorus source solution to the calcium-boron mixture within 30min, maintaining stirring at 300r / min during the addition process. Adjust the pH to 10.2 with ammonia water and continue stirring at 27.5℃ and 300r / min for 60min to obtain a calcium-silicon-boron phosphate whisker precursor suspension.

[0028] Step B2: Transfer the calcium borosilicate whisker precursor suspension to a 1000 mL polytetrafluoroethylene-lined reactor and hydrothermally react at 160 °C for 10 h. After the reaction, allow it to cool naturally to 25 °C and centrifuge at 6000 r / min for 10 min. Wash the obtained solid three times with deionized water, centrifuging at 6000 r / min for 10 min after each wash to obtain a wet filter cake of calcium borosilicate whiskers. Disperse the wet filter cake of calcium borosilicate whiskers in 160.0 g of deionized water and stir at 300 r / min for 20 min. Add 5.0 g of lactic acid and adjust the pH to 5.9 with ammonia. React at 60 °C and 300 r / min for 3 h. After the reaction, centrifuge at 6000 r / min for 10 min and wash the obtained solid twice with deionized water. Vacuum dry at 75 °C for 12 h, grind, and pass through a 25 μm sieve to obtain lactic acid modified calcium borosilicate whiskers.

[0029] Example 2 The difference between this embodiment and Embodiment 1 is that this embodiment provides a method for preparing a heat-resistant and biodegradable composite material, the steps of which include: Step S1: Dry the epoxy silane-grafted zirconium-titanium phytate layered microsheets, lactic acid-modified calcium borosilicate whiskers, light calcium carbonate, polybutylene succinate, polylactic acid, and polybutylene adipate terephthalate separately for later use; mix 2.0g of the dried epoxy silane-grafted zirconium-titanium phytate layered microsheets, 3.0g of lactic acid-modified calcium borosilicate whiskers, and 3.0g of light calcium carbonate, and add 0.2g of ethylene bis-stearamide and 0.2g of monoglyceride. Mix at 60℃ for 8 minutes to obtain composite reinforced premix powder; take 55.0g of dried polybutylene succinate, 10.0g of polylactic acid, 3.0g of polybutylene adipate terephthalate, 0.3g of epoxy chain extender ADR-4468, 0.1g of antioxidant 1010 and 0.1g of antioxidant 168 and mix them together, add the composite reinforced premix powder, and continue mixing until the material is evenly dispersed to obtain heat-resistant and biodegradable composite material premix.

[0030] Step S2: Add the heat-resistant biodegradable composite premix to a twin-screw extruder. The temperature of zone 1 is 125℃, zone 2 is 140℃, zone 3 is 150℃, zone 4 is 160℃, zone 5 is 165℃, and the die head temperature is 160℃. Perform melt blending extrusion, cool the extrudate, pelletize, and dry to obtain heat-resistant biodegradable composite granules. Mold the heat-resistant biodegradable composite granules at 155℃ and then heat treat them at 80℃ to obtain the heat-resistant biodegradable composite material.

[0031] Preparation steps of epoxysilane-grafted zirconium-titanium phytate layered microsheets: Step A1: Take 50.0g of phytic acid solution and add it to 250.0g of deionized water. Stir at 25℃ for 30min. Add 10.0g of zirconium oxychloride octahydrate and continue stirring until the zirconium oxychloride octahydrate is completely dissolved and a uniform zirconium-phytic acid complex solution is formed. Take 6.0g of tetrabutyl titanate and add it to 60.0g of anhydrous ethanol. Add 1.0g of acetylacetone and stir until a uniform and transparent stable titanium source solution is formed. Slowly add the stable titanium source solution to the zirconium-phytic acid complex solution while stirring. Adjust the pH to 3.5 with ammonia water and react at 45℃ for 2h to obtain a zirconium-titanium phytate precursor dispersion.

[0032] Step A2: Transfer the zirconium titanate phytate precursor dispersion to a reaction vessel and hydrothermally react at 115°C for 6 hours. After the reaction, cool to 25°C, centrifuge, and wash the obtained solid with deionized water and anhydrous ethanol to obtain a wet filter cake. Disperse the wet filter cake in a mixture of 120.0 g anhydrous ethanol and 30.0 g deionized water, add 3.0 g 3-(2,3-epoxypropoxy)propyltrimethoxysilane, adjust the pH to 4.0 with glacial acetic acid, react at 60°C for 3 hours, centrifuge, wash the obtained solid with anhydrous ethanol, dry at 70°C to constant weight, grind, and sieve to obtain epoxysilane-grafted zirconium titanate layered microplates.

[0033] Preparation steps of lactic acid modified calcium silicate borosilicate whiskers: Step B1: Add 50.5g of calcium nitrate tetrahydrate to 300.0g of deionized water, stir at 25℃ for 20min, add 0.5g of boric acid, and continue stirring until the boric acid is evenly dispersed to obtain a calcium-boron mixture; add 16.5g of diammonium hydrogen phosphate and 1.8g of sodium metasilicate nonahydrate to 180.0g of deionized water, and stir until completely dissolved to obtain a silicon-phosphorus source solution; add the silicon-phosphorus source solution to the calcium-boron mixture, adjust the pH to 9.8 with ammonia water, and continue stirring to obtain a calcium-silicon-boron phosphate whisker precursor suspension.

[0034] Step B2: Transfer the calcium borosilicate whisker precursor suspension to a reactor and hydrothermally react at 150°C for 8 hours. After the reaction, cool to 25°C, centrifuge, and wash the obtained solid with deionized water to obtain a wet filter cake of calcium borosilicate whiskers. Disperse the wet filter cake of calcium borosilicate whiskers in 120.0g of deionized water, add 3.0g of lactic acid, adjust the pH to 5.6 with ammonia, react at 55°C for 2 hours, centrifuge after the reaction, dry the obtained solid at 75°C to constant weight, grind, and sieve to obtain lactic acid modified calcium borosilicate whiskers.

[0035] Example 3 The difference between this embodiment and Embodiment 1 is that this embodiment provides a method for preparing a heat-resistant and biodegradable composite material, the steps of which include: Step S1: Dry the epoxy silane-grafted zirconium-titanium phytate layered microsheets, lactic acid-modified calcium borosilicate whiskers, light calcium carbonate, polybutylene succinate, polylactic acid, and polybutylene adipate terephthalate separately for later use; mix 8.0g of the dried epoxy silane-grafted zirconium-titanium phytate layered microsheets, 10.0g of lactic acid-modified calcium borosilicate whiskers, and 12.0g of light calcium carbonate, and add 0.8g of ethylene bis-stearamide and 0.8g of monoglyceride. Mix at 75℃ for 15 min to obtain composite reinforced premix powder; take 75.0g of dried polybutylene succinate, 25.0g of polylactic acid, 12.0g of polybutylene adipate terephthalate, 1.2g of epoxy chain extender ADR-4385, 0.4g of antioxidant 1010 and 0.4g of antioxidant 168 and mix them together, add the composite reinforced premix powder, and continue mixing until the material is evenly dispersed to obtain heat-resistant and biodegradable composite material premix.

[0036] Step S2: Add the heat-resistant biodegradable composite premix to a twin-screw extruder. The temperature of zone 1 is 135℃, zone 2 is 150℃, zone 3 is 160℃, zone 4 is 170℃, zone 5 is 175℃, and the die head temperature is 170℃. Perform melt blending extrusion, cool the extrudate, pelletize, and dry to obtain heat-resistant biodegradable composite granules. Mold the heat-resistant biodegradable composite granules at 175℃ and then heat treat them at 95℃ to obtain the heat-resistant biodegradable composite material.

[0037] Preparation steps of epoxysilane-grafted zirconium-titanium phytate layered microsheets: Step A1: Take 70.0g of phytic acid solution and add it to 350.0g of deionized water. Stir at 30℃ for 50min. Add 18.0g of zirconium oxychloride octahydrate and continue stirring until the zirconium oxychloride octahydrate is completely dissolved and a uniform zirconium-phytic acid complex solution is formed. Take 12.0g of tetrabutyl titanate and add it to 100.0g of anhydrous ethanol. Add 3.0g of acetylacetone and stir until a uniform and transparent stable titanium source solution is formed. Slowly add the stable titanium source solution to the zirconium-phytic acid complex solution while stirring. Adjust the pH to 4.0 with ammonia water and react at 55℃ for 4h to obtain a zirconium-titanium phytate precursor dispersion.

[0038] Step A2: Transfer the zirconium titanate phytate precursor dispersion to a reactor and hydrothermally react at 130°C for 10 h. After the reaction, cool to 25°C, centrifuge, and wash the obtained solid with deionized water and anhydrous ethanol to obtain a wet filter cake. Disperse the wet filter cake in a mixture of 180.0 g anhydrous ethanol and 60.0 g deionized water, add 6.0 g 3-(2,3-epoxypropoxy)propyltrimethoxysilane, adjust the pH to 4.8 with glacial acetic acid, and react at 70°C for 5 h. After the reaction, centrifuge, wash the obtained solid with anhydrous ethanol, dry at 70°C to constant weight, grind, and sieve to obtain epoxysilane-grafted zirconium titanate layered micro flakes.

[0039] Preparation steps of lactic acid modified calcium silicate borosilicate whiskers: Step B1: Add 51.0g of calcium nitrate tetrahydrate to 450.0g of deionized water and stir at 30℃ for 40min. Add 2.0g of boric acid and continue stirring until the boric acid is evenly dispersed to obtain a calcium-boron mixture. Add 16.7g of diammonium hydrogen phosphate and 2.0g of sodium metasilicate nonahydrate to 260.0g of deionized water and stir until completely dissolved to obtain a silicon-phosphorus source solution. Add the silicon-phosphorus source solution to the calcium-boron mixture, adjust the pH to 10.6 with ammonia water, and continue stirring to obtain a calcium-silicon-boron phosphate whisker precursor suspension.

[0040] Step B2: Transfer the calcium borosilicate whisker precursor suspension to a reactor and hydrothermally react at 170°C for 12 hours. After the reaction, cool to 25°C, centrifuge, and wash the obtained solid with deionized water to obtain a wet filter cake of calcium borosilicate whiskers. Disperse the wet filter cake of calcium borosilicate whiskers in 200.0 g of deionized water, add 7.0 g of lactic acid, adjust the pH to 6.2 with ammonia, and react at 65°C for 4 hours. After the reaction, centrifuge, dry the obtained solid at 75°C to constant weight, grind, and sieve to obtain lactic acid modified calcium borosilicate whiskers.

[0041] Comparative Example 1 The difference between this comparative example and Example 1 is that in step S1, 5.0g of epoxysilane-grafted zirconium titanate layered microsheets are not added, and 5.0g of polybutylene succinate is used to make up the mass. The rest is the same as in Example 1.

[0042] Comparative Example 2 The difference between this comparative example and Example 1 is that in step S1, 6.5g of lactic acid modified calcium borosilicate whiskers are not added, and 6.5g of polybutylene succinate is used to make up the mass. The rest is the same as in Example 1.

[0043] Comparative Example 3 The difference between this comparative example and Example 1 is that in step S1, 7.5g of light calcium carbonate is not added, and 7.5g of polybutylene succinate is used to make up the mass, while the rest is the same as in Example 1.

[0044] The performance of the heat-resistant and biodegradable composite materials obtained in Examples 1-3 and Comparative Examples 1-3 were tested in accordance with national and industry standard testing specifications.

[0045] The heat-resistant and biodegradable composite material granules obtained in Examples 1-3 and Comparative Examples 1-3 were dried in a vacuum drying oven at 80°C for 6 hours. After drying, test samples were prepared by injection molding using the same injection molding machine. The injection barrel temperature was 165°C, the mold temperature was 60°C, the holding time was 20 seconds, and the cooling time was 30 seconds. After the sample preparation was completed, it was placed in a constant temperature and humidity environment of 23°C and 50% relative humidity for 24 hours before testing.

[0046] During the heat distortion temperature test, take a strip sample with dimensions of 80mm×10mm×4mm. The sample surface should be flat, free of bubbles and obvious gaps. Place the sample flat on the support of the heat distortion tester with a support span of 64mm. Apply a bending stress of 0.45MPa and heat at a rate of 2℃ / min. Record the corresponding temperature when the deformation at the midpoint of the sample reaches 0.34mm. The unit is ℃. Test 5 samples in each group and take the average value.

[0047] For tensile strength testing, dumbbell-shaped specimens made by injection molding are used. Before testing, the width and thickness of the specimen are measured at the center. The specimen is clamped in the fixture of the universal testing machine with a fixture spacing of 50 mm and a tensile speed of 50 mm / min. The maximum load is recorded during the test, and the tensile strength is calculated by dividing the maximum load by the original cross-sectional area at the center of the specimen. The unit is MPa. Five specimens are tested in each group and the average value is taken.

[0048] For the bending modulus test, a long strip specimen with dimensions of 80mm×10mm×4mm was taken and placed on a three-point bending fixture with a span of 64mm. The loading head was located at the midpoint of the specimen, and the loading speed was 2mm / min. The load and deflection in the initial elastic deformation stage were recorded. The bending modulus was calculated based on the load, span, specimen width, specimen thickness, and deflection, with the unit being MPa. Five specimens were tested in each group, and the average value was taken.

[0049] For notched impact strength testing, a long strip specimen measuring 80mm × 10mm × 4mm is taken. A V-shaped notch with a depth of 2mm is machined in the middle of the specimen. The bottom of the notch should be flat and free of cracks. The specimen is placed on a simply supported beam impact testing machine with the notch facing away from the impact direction. The energy absorbed by the specimen at fracture is recorded, and the notched impact strength is calculated by dividing the absorbed energy by the remaining cross-sectional area at the notch. The unit is kJ / m². 2 Five samples were tested in each group and the average value was taken.

[0050] For the thermal dimensional change rate test, a sheet sample with dimensions of 100mm×100mm×2mm was taken. The initial dimensions in the length and width directions were measured with vernier calipers at 23℃. Three measurements were taken in each direction and the average value was taken. The sample was then placed flat in a 90℃ hot air circulating oven for 2 hours. After being removed, it was placed in a 23℃ environment for 1 hour. The dimensions in the length and width directions were measured again at the same positions. The dimensional change rates in the length and width directions were calculated separately, and the average value of the two directions was taken as the thermal dimensional change rate, with the unit being 0.5%.

[0051] For the compost mass loss rate test, a sheet sample with dimensions of 50mm×50mm×2mm was taken, wiped with anhydrous ethanol, and dried at 60℃ to constant weight. The initial mass was recorded. The sample was then buried in composting medium with a moisture content of 55% at a depth of 50mm. The composting temperature was maintained at 58℃, and the composting time was 180 days. After the test, the sample was removed, the surface adhering substances were washed with deionized water, and dried at 60℃ to constant weight. The remaining mass was recorded. The compost mass loss rate was calculated by dividing the difference between the initial mass and the remaining mass by the initial mass and then multiplying by 100%. The unit is 1.

[0052] The performance test data above are shown in Table 1.

[0053] Table 1 Performance Test Results

[0054] The test results in Table 1 above clearly show that Examples 1-3, compared with Comparative Examples 1-3, can effectively solve the problems of insufficient heat resistance, poor dimensional stability under thermal conditions, insufficient dispersion and interfacial bonding of inorganic reinforcing components, and difficulty in achieving both mechanical properties in existing biodegradable polyester materials.

[0055] The heat distortion temperatures of Examples 1-3 were 108.6℃, 101.3℃, and 116.2℃, respectively, all significantly higher than those of Comparative Example 1 (91.5℃) and Comparative Example 2 (88.7℃). This indicates that the combined use of epoxy silane-grafted zirconium-titanium phytate layered microsheets and lactic acid-modified calcium borosilicate whiskers can improve the material's structural retention after heating through layered barrier, whisker support, and heterogeneous nucleation. The heat distortion temperature of Example 3 reached 116.2℃, 27.5℃ higher than that of Comparative Example 2, indicating that the lack of lactic acid-modified calcium borosilicate whiskers significantly reduced the material's heat resistance support and nucleation reinforcement.

[0056] The tensile strengths of Examples 1-3 were 48.9 MPa, 44.2 MPa, and 51.4 MPa, respectively, all higher than those of Comparative Example 1 (39.8 MPa), Comparative Example 2 (40.5 MPa), and Comparative Example 3 (42.6 MPa). This indicates that when epoxy silane-grafted zirconium-titanium phytate layered microsheets, lactic acid-modified calcium borosilicate whiskers, and light calcium carbonate coexist, the composite reinforcing phase can form a more effective interfacial force transfer structure with polybutylene succinate, polylactic acid, and polybutylene adipate terephthalate, thereby improving the material's ability to withstand tensile loads.

[0057] The flexural moduli of Examples 1-3 were 2360 MPa, 2110 MPa, and 2780 MPa, respectively. Among them, the flexural modulus of Example 3 was 820 MPa higher than that of Comparative Example 3 (1960 MPa), indicating that although light calcium carbonate is a conventional filler and reinforcing component, it can further improve the rigidity and flexural support capacity of the material when combined with epoxy silane-grafted zirconium titanium phytate layered microsheets and lactic acid-modified calcium silicate borosilicate whiskers. The flexural modulus of Comparative Example 3 without the addition of light calcium carbonate was significantly lower than that of Examples 1 and 3, proving that light calcium carbonate has a direct contribution to improving the insufficient rigidity.

[0058] The thermal dimensional change rates of Examples 1-3 were 0.62%, 0.95%, and 0.48%, respectively, which were significantly lower than those of Comparative Example 1 (1.38%), Comparative Example 2 (1.56%), and Comparative Example 3 (1.02%). Comparative Example 2 had the highest thermal dimensional change rate, indicating that without lactic acid-modified calcium borosilicate whiskers, the material lacked an effective whisker framework and nucleation support, making it more prone to shrinkage and deformation after heating. Example 3 had the lowest thermal dimensional change rate, indicating that higher contents of epoxy silane-grafted zirconium titanate layered microsheets, lactic acid-modified calcium borosilicate whiskers, and light calcium carbonate could significantly improve the thermal dimensional retention capability.

[0059] Regarding the notched impact strength, Example 1 shows 9.8 kJ / m. 2 Example 2 shows a value of 11.2 kJ / m³. 2 All of them are higher than the 7.1 kJ / m² of Comparative Example 1. 2 Compared to Comparative Example 2, 6.8 kJ / m 2 This indicates that epoxysilane-grafted zirconium-titanium phytate layered microsheets and lactic acid-modified calcium borosilicate whiskers not only improve heat resistance and rigidity, but also reduce brittle fracture caused by inorganic phase agglomeration through interface modification.

[0060] Regarding the compost quality loss rate, Examples 1-3 were 77.2%, 76.8%, and 74.1%, respectively, which are close to those of Comparative Example 1 (68.9%), Comparative Example 2 (72.6%), and Comparative Example 3 (73.4%). This indicates that the addition of epoxysilane-grafted zirconium titanate layered microsheets, lactic acid-modified calcium silicate borosilicate whiskers, and light calcium carbonate did not significantly sacrifice the biodegradability of the material.

[0061] Based on the above data, Examples 1-3 are superior to Comparative Examples 1-3 in terms of heat distortion temperature, tensile strength, flexural modulus, and thermal dimensional change rate. They also maintain good notched impact strength while keeping the compost mass loss rate. This demonstrates that the present invention solves the problems of insufficient heat resistance, poor thermal dimensional stability, weak interfacial effect of reinforcing fillers, difficulty in balancing rigidity and toughness, and easy impact on degradation performance after improving heat resistance by using epoxy silane-grafted zirconium-titanium phytate layered microsheets, lactic acid-modified calcium borosilicate whiskers, and light calcium carbonate.

Claims

1. A method for preparing a heat-resistant and biodegradable composite material, characterized in that the steps include... include: S1. By weight, 2.0-8.0 parts of dried epoxy silane-grafted zirconium titanate layered micro flakes, 3.0-10.0 parts of lactic acid-modified calcium borosilicate whiskers, and 3.0-12.0 parts of light calcium carbonate are mixed, and 0.2-0.8 parts of ethylene bis-stearamide and 0.2-0.8 parts of monoglyceride are added. The mixture is then mixed at 60-75℃ to obtain a composite reinforced premix powder. 55.0-75.0 parts of dried polybutylene succinate, 10.0-25.0 parts of polylactic acid, 3.0-12.0 parts of polybutylene adipate terephthalate, 0.3-1.2 parts of epoxy chain extender, 0.1-0.4 parts of antioxidant 1010, and 0.1-0.4 parts of antioxidant 168 are mixed, and the composite reinforced premix powder is added. The mixture is then further mixed to obtain a heat-resistant and biodegradable composite material premix. S2. Add the heat-resistant biodegradable composite premix to a twin-screw extruder for melt blending and extrusion, cool, pelletize, and dry to obtain heat-resistant biodegradable composite granules; then subject the heat-resistant biodegradable composite granules to molding and heat treatment in sequence.

2. The method for preparing the heat-resistant and biodegradable composite material according to claim 1, characterized in that, In step S1, the mixing time at 60-75℃ is 8-15 min; the epoxy chain extender is selected from at least one of ADR-4468, ADR-4368CS, ADR-4370, ADR-4385, ADR-4380, and ADR-4300.

3. The method for preparing the heat-resistant and biodegradable composite material according to claim 1, characterized in that, In step S2, the temperatures of each zone of the twin-screw extruder are as follows: Zone 1: 125-135℃; Zone 2: 140-150℃; Zone 3: 150-160℃; Zone 4: 160-170℃; Zone 5: 165-175℃; and the die head temperature: 160-170℃. The forming process temperature is 155-175℃, and the heat treatment temperature is 80-95℃.

4. The method for preparing the heat-resistant and biodegradable composite material according to claim 1, characterized in that, The preparation method of the epoxysilane-grafted zirconium-titanium phytate layered microsheets includes: A1. By weight, add 50.0-70.0 parts of phytic acid solution to 250.0-350.0 parts of deionized water, stir at 25-30℃, add 10.0-18.0 parts of zirconium oxychloride octahydrate, and continue stirring to obtain a zirconium-phytic acid complex solution; add 6.0-12.0 parts of tetrabutyl titanate to 60.0-100.0 parts of anhydrous ethanol, add 1.0-3.0 parts of acetylacetone, and stir to obtain a stable titanium source solution; add the stable titanium source solution to the zirconium-phytic acid complex solution, adjust the pH to 3.5-4.0 with ammonia water, and react at 45-55℃ to obtain a zirconium-titanium phytate precursor dispersion; A2. Transfer the zirconium titanate phytate precursor dispersion to a reactor and perform a hydrothermal reaction at 115-130℃. After cooling, centrifugation, and washing, a wet filter cake is obtained. Disperse the wet filter cake in a mixture of 120.0-180.0 parts anhydrous ethanol and 30.0-60.0 parts deionized water, add 3.0-6.0 parts 3-(2,3-epoxypropoxy)propyltrimethoxysilane, adjust the pH to 4.0-4.8 with glacial acetic acid, react at 60-70℃, centrifuge, wash, dry, grind, and sieve.

5. The method for preparing the heat-resistant and biodegradable composite material according to claim 4, characterized in that, In step A1, the stirring time is 30-50 min at 25-30℃; the reaction time is 2-4 h at 45-55℃.

6. The method for preparing the heat-resistant and biodegradable composite material according to claim 4, characterized in that, In step A2, the hydrothermal reaction time is 6-10 hours at 115-130℃ and 3-5 hours at 60-70℃.

7. The method for preparing the heat-resistant and biodegradable composite material according to claim 1, characterized in that, The preparation method of the lactic acid modified calcium silicate borosilicate whiskers includes: B1. By weight, add 50.5-51.0 parts of calcium nitrate tetrahydrate to 300.0-450.0 parts of deionized water, stir at 25-30℃, add 0.5-2.0 parts of boric acid, and continue stirring to obtain a calcium-boron mixture; add 16.5-16.7 parts of diammonium hydrogen phosphate and 1.8-2.0 parts of sodium metasilicate nonahydrate to 180.0-260.0 parts of deionized water, stir, and obtain a silicon-phosphorus source solution; add the silicon-phosphorus source solution to the calcium-boron mixture, adjust the pH to 9.8-10.6 with ammonia water, and continue stirring to obtain a calcium-silicon-boron phosphate whisker precursor suspension; B2. Transfer the calcium borosilicate whisker precursor suspension to a reactor and perform a hydrothermal reaction at 150-170℃. After cooling, centrifugation, and washing, obtain a wet filter cake of calcium borosilicate whiskers. Disperse the wet filter cake of calcium borosilicate whiskers in 120.0-200.0 parts of deionized water, add 3.0-7.0 parts of lactic acid, adjust the pH to 5.6-6.2 with ammonia, react at 55-65℃, centrifuge, dry, grind, and sieve.

8. The method for preparing the heat-resistant and biodegradable composite material according to claim 7, characterized in that, In step B1, the stirring time is 20-40 minutes at 25-30℃.

9. The method for preparing the heat-resistant and biodegradable composite material according to claim 7, characterized in that, In step B2, the hydrothermal reaction time is 8-12 hours at 150-170℃ and 2-4 hours at 55-65℃.

10. A heat-resistant and biodegradable composite material, characterized in that, The heat-resistant biodegradable composite material is prepared by the method according to any one of claims 1-9.

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