Corn starch-based full-degradable tableware material, preparation process and application of corn starch-based full-degradable tableware material in lunch box

Abstract

The invention relates to the technical field of biodegradable high polymer materials, and discloses a corn starch-based full-degradable tableware material, a preparation process and an application of the corn starch-based full-degradable tableware material in a meal box. The full-degradable tableware material is prepared from specific parts by weight of surface activated corn starch, poly (butylene succinate), polylactic acid, a novel polyfunctional group reactive chain extender / compatibilizer and a bio-based plasticizer through melt blending reaction and extrusion. The molecular structure of the novel multifunctional reactive chain extender / compatibilizer comprises functional groups which can react with active groups in corn starch, poly (butylene succinate) or polylactic acid to form stable chemical bonding; chemical bonds or groups which are easy to break preferentially in a specific degradation environment are also included; the invention further discloses a preparation method of the material and application of the material in preparation of disposable full-degradable meal boxes. The material provided by the invention has the advantages of excellent mechanical properties, good processability, controllable degradation behavior, environmental friendliness and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of biodegradable polymer materials, in particular to a corn starch-based fully degradable tableware material, a preparation process and application thereof in lunch boxes. Background Art

[0002] With growing global awareness of environmental protection and the increasingly severe problem of "white pollution," the development and use of biodegradable materials to replace traditional petroleum-based plastics has become a significant development trend and research hotspot. Among the many biodegradable materials, corn starch is considered one of the natural polymers with the greatest potential for large-scale replacement of traditional plastics due to its wide availability, low cost, complete biodegradability, and environmental friendliness.

[0003] However, natural corn starch itself has some inherent defects that severely limit its direct application as a structural material. For example, pure starch materials usually exhibit high hydrophilicity and are easily hygroscopic, resulting in decreased dimensional stability and mechanical properties. At the same time, their mechanical strength, especially toughness and impact resistance, often cannot meet the needs of practical applications and exhibit typical brittle characteristics. To improve these deficiencies, researchers usually blend corn starch with biodegradable polyesters (such as polylactic acid (PLA) and polybutylene succinate (PBS)) with better mechanical properties and hydrophobicity for modification.

[0004] Nevertheless, due to the significant polarity difference between the strong hydrophilicity of corn starch and the hydrophobicity of polyesters such as polylactic acid and polybutylene succinate, they are thermodynamically incompatible during melt blending, and the interfacial bonding force is very weak. This poor compatibility makes it easy to produce stress concentration points inside the composite material, which is manifested as the mechanical properties of the material, particularly elongation at break and impact strength, which still cannot reach the ideal level, and the material homogeneity and processing stability are also affected. In addition, although these composite materials are biodegradable as a whole, their degradation rate and process are often affected by multiple factors, lack an effective regulatory mechanism, and sometimes the degradation cycle is too long, or it is difficult to disintegrate quickly in the early stage of degradation, and it cannot fully adapt to efficient industrial composting or natural environment absorption requirements. Therefore, how to effectively improve the interfacial compatibility between corn starch and biodegradable polyester, and then significantly improve the comprehensive mechanical properties of the composite material, and give it a certain degree of controllable degradation characteristics, remains a key technical problem to be solved in the field of current starch-based fully degradable materials. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention provides a corn starch-based fully degradable tableware material, a preparation process and its application in lunch boxes, which solves the problems in the existing technology of corn starch-based degradable tableware materials, such as poor compatibility between starch and polyester matrix, insufficient comprehensive mechanical properties, and processing performance that needs to be improved. At the same time, its degradation behavior after disposal is often difficult to accurately control, which may lead to a slow degradation rate or the phased impact of degradation products on the environment.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0007] The first aspect of the present invention provides a corn starch-based fully degradable tableware material, which is prepared by melt blending and extrusion of the following components in parts by weight:

[0008] 40-60 parts of surface-activated corn starch;

[0009] 15-30 parts of polybutylene succinate;

[0010] 10-25 parts of polylactic acid;

[0011] 1 to 5 parts of multifunctional reactive chain extender / compatibilizer;

[0012] 3 to 8 parts of bio-based plasticizer.

[0013] The multifunctional reactive chain extender / compatibilizer is one of the core innovations of the present invention. The compatibilizer's molecular structure contains at least one functional group (e.g., an isocyanate group) that reacts with active groups (e.g., hydroxyl groups, carboxyl groups) in corn starch, polybutylene succinate, or polylactic acid to form a stable chemical bond. During the melt blending process, the compatibilizer forms chemical bridges between the starch and polyester phases, as well as between different polyester phases. This significantly improves the interfacial compatibility between the components and enhances stress transfer efficiency, thereby imparting excellent mechanical properties, particularly toughness and tensile strength, to the composite material.

[0014] More importantly, the molecular structure of the multifunctional reactive chain extender / compatibilizer also contains at least one chemical bond or group (such as acetal or ketal group) that is easily broken under a specific degradation environment (such as acidic, humid, hot or enzymatic conditions in a composting environment). These preset "weak links" make the degradation process of the material after it is discarded not completely random, but can occur preferentially along the path composed of these easily broken chemical bonds. This "energy-oriented" initial degradation can accelerate the fragmentation of the material, increase its contact area with microorganisms and moisture, and then promote the subsequent biodegradation process of the main polymer (polybutylene succinate, polylactic acid) and starch, achieving more controllable and potentially more efficient overall degradation.

[0015] The surface-activated corn starch is preferably obtained by treatment with a silane coupling agent or a low-temperature plasma. This surface activation treatment can increase the active sites on the corn starch surface or change its surface energy, thereby facilitating the formation of a stronger interface bond between the corn starch, the multifunctional reactive chain extender / compatibilizer, and the polyester matrix.

[0016] The bio-based plasticizer, such as tributyl citrate, can improve the processing fluidity and flexibility of the material.

[0017] In some embodiments, the corn starch-based fully biodegradable tableware material may also contain 0.2 to 1 parts by weight of a catalyst, such as a complex of dibutyltin dilaurate and triethylenediamine. This catalyst is used to promote the chemical reaction between the reactive functional groups (such as isocyanate groups) in the multifunctional reactive chain extender / compatibilizer and the active groups (such as hydroxyl groups and carboxyl groups) in corn starch, polybutylene succinate, or polylactic acid, thereby improving reaction efficiency and ensuring the formation of interfacial chemical bonds.

[0018] The second aspect of the present invention further discloses a preferred preparation method and structural characteristics of the multifunctional reactive chain extender / compatibilizer. The multifunctional reactive chain extender / compatibilizer is a product prepared by the following steps:

[0019] (a) reacting a polyol containing at least two hydroxyl groups with an aldehyde or ketone in the presence of an acidic catalyst to generate a diol intermediate containing an acetal or ketal group and retaining at least two free hydroxyl groups;

[0020] (b) reacting the dried diol intermediate obtained in step (a) with a stoichiometric excess of polyisocyanate in an anhydrous organic solvent or in the absence of a solvent, so that the free hydroxyl groups in the diol intermediate react with part of the isocyanate groups in the polyisocyanate to obtain a prepolymer terminated at two or more ends by free isocyanate groups.

[0021] In step (a), the acetal or ketal group formed constitutes the aforementioned chemical bond that is easily broken under specific degradation conditions. This chemical bond is relatively sensitive to acidic hydrolysis or the action of specific enzymes.

[0022] In a specific example, the polyol containing at least two hydroxyl groups in step (a) can be pentaerythritol, and the aldehyde can be benzaldehyde. Pentaerythritol and benzaldehyde react under acid catalysis to primarily produce 5,5-bis(hydroxymethyl)-2-phenyl-1,3-dioxane, a molecular structure containing two free hydroxyl groups and an acid-sensitive phenylidene acetal group.

[0023] In step (b), described polyisocyanate can be isophorone diisocyanate.Containing two isocyanate groups different in reactive behavior in isophorone diisocyanate molecule, by controlling reaction conditions and mol ratio (for example, the mol ratio of isocyanate groups and hydroxyl is greater than 2: 1, preferably 2.2: 2 to 3.0: 2), after the diol intermediate that step (a) obtains and isophorone diisocyanate reaction, the end of product is mainly free isocyanate groups.These free isocyanate groups, when follow-up with corn starch, polybutylene succinate and polylactic acid melt blending, can react with the hydroxyl on these component surfaces or the hydroxyl, the carboxyl of chain end, form the covalent bonds such as urethane bond or amido bond, thus realize excellent interface volume expansion and chain extension effect.

[0024] A third aspect of the present invention provides a method for preparing any of the above-mentioned corn starch-based fully degradable tableware materials, comprising the following steps:

[0025] (S1) premixing the surface-activated corn starch, polybutylene succinate, polylactic acid, a multifunctional reactive chain extender / compatibilizer, a bio-based plasticizer, and a catalyst and / or other auxiliary additives (such as an antioxidant and a lubricant) as needed in a high-speed mixer according to the aforementioned weight parts to achieve preliminary uniform dispersion;

[0026] (S2) Add the premixed material obtained in step (S1) to a twin-screw extruder and perform melt blending and extrusion under set temperature conditions. During this process, due to high temperature and shearing, the reactive functional groups (such as isocyanate groups) in the multifunctional reactive chain extender / compatibilizer react in situ with the active groups in the surface-activated corn starch, polybutylene succinate and polylactic acid to form an interfacial chemical bonding network, and at the same time, groups sensitive to degradation (such as acetal / ketal groups) are introduced into the network structure. Preferably, the melt blending temperature range of the twin-screw extruder is 120-195°C to ensure that the material is fully plasticized, the reaction proceeds, and excessive degradation of the material is avoided;

[0027] (S3) cooling the strips extruded from the die head of the twin-screw extruder (such as water cooling or air cooling) and then cutting them into particles by a pelletizer to obtain the corn starch-based fully degradable tableware material.

[0028] This in-situ reactive extrusion process enables the compatibilizer to be more evenly dispersed and react promptly at the interface, which is conducive to the formation of a more effective interface layer and a more homogeneous composite material.

[0029] A fourth aspect of the present invention provides a corn starch-based fully degradable tableware, which is prepared from the corn starch-based fully degradable tableware material by a conventional plastic molding process.

[0030] Preferably, the tableware is a disposable lunch box prepared by injection molding, thermoforming or blister molding.

[0031] A fifth aspect of the present invention provides use of the corn starch-based fully degradable tableware material in preparing disposable fully degradable lunch boxes.

[0032] The present invention provides a corn starch-based fully degradable tableware material, a preparation process and application thereof in a lunch box.

[0033] It has the following beneficial effects:

[0034] 1. The present invention introduces a specially designed multifunctional reactive chain extender / compatibilizer and realizes an in-situ chemical reaction during the melt blending process, thereby effectively enhancing the interfacial bonding force between corn starch and polybutylene succinate and polylactic acid, enabling stress to be more effectively transferred between the phases, thereby improving the comprehensive mechanical properties of the composite material, such as tensile strength, elongation at break, and impact toughness, meeting the use requirements of disposable tableware.

[0035] 2. The pre-designed environmentally sensitive chemical bonds (e.g., acetal / ketal bonds) in the multifunctional reactive chain extender / compatibilizer of this invention establish an energy-directed, controllable degradation pathway for the composite material. This means that upon disposal, the initial degradation of the material can preferentially occur along these weak links, accelerating the material's disintegration and fragmentation, thereby promoting subsequent comprehensive biodegradation. This helps address the uncontrollable or slow degradation rates of traditional biodegradable materials.

[0036] 3. The component ratio and the addition of plasticizer selected in the present invention make the composite material have good melt fluidity, suitable for common plastic processing methods such as injection molding, hot pressing or blister molding, and easy to prepare tableware of various shapes.

[0037] 4. The main components of the material of this invention are all biodegradable substances, which can eventually decompose into carbon dioxide, water and biomass, with minimal impact on the environment. The design of a controllable degradation pathway further enhances its environmental friendliness. DETAILED DESCRIPTION

[0038] 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.

[0039] Unless otherwise stated, the conventional methods used in the examples of the present invention are conventional methods in the art unless otherwise stated. Unless otherwise stated, the materials, reagents, etc. used in the examples of the present invention are commercially available products unless otherwise stated.

[0040] Main ingredients:

[0041] Corn starch (CS): food grade; moisture content controlled to <1% (w / w) after drying; amylose content 25-28% (w / w); purchased from Shandong Zhucheng Xingmao Corn Development Co., Ltd. Dry in a forced air drying oven at 105±2°C for 6-8 hours before use.

[0042] Polybutylene succinate (PBS): brand TH803S; melt index (190°C, 2.16kg load) is 5-15g / 10min; density is 1.26g / cm 3 Purchased from Anhui Fengyuan Biotechnology Co., Ltd. Before use, dry in a forced air drying oven at 80±2℃ for 4-6 hours.

[0043] Polylactic acid (PLA): Brand 4032D (injection molding grade); melt index (210°C, 2.16 kg load) 3-10 g / 10 min; D-lactic acid content approximately 1.2-1.6%; purchased from NatureWorks LLC, USA. Dry in a forced air drying oven at 80 ± 2°C for 4-6 hours before use.

[0044] Novel Multifunctional Reactive Chain Extender / Compatibilizer (NMRCE): Made in the laboratory. The specific preparation method is detailed in the following.

[0045] Tributyl citrate (TBC): food grade; purity ≥99.0%; purchased from Jiangsu Raymond Chemical Technology Co., Ltd.

[0046] Dibutyltin dilaurate (DBTDL): analytical grade; purity ≥ 98.0%; purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0047] Triethylenediamine (DABCO): analytical grade; purity ≥ 99.0%; purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0048] Pentaerythritol (PER): analytical grade; purity ≥ 98.0%; purchased from Sinopharm Chemical Reagent Co., Ltd.

[0049] Benzaldehyde: analytical grade; purity ≥99.0%; used after fresh distillation; purchased from Tianjin Kemeiou Chemical Reagent Co., Ltd.

[0050] p-Toluenesulfonic acid (PTSA): analytical grade; monohydrate; purity ≥ 98.5%; purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0051] Isophorone diisocyanate (IPDI): industrial grade; NCO content ≥ 37.0%; purchased from Covestro AG, Germany.

[0052] Anhydrous toluene: analytical grade; dried over molecular sieves before use; purchased from Tianjin Fuyu Fine Chemical Co., Ltd.

[0053] Dibutylamine: analytical grade; purity ≥99.0%; purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0054] γ-(2,3-Epoxypropoxy)propyltrimethoxysilane (KH-560): analytical grade; purity ≥98.0%; purchased from Nanjing Shuguang Chemical Group Co., Ltd.

[0055] Antioxidant 1010 (Pentaerythritoltetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)): industrial grade; purchased from BASF.

[0056] Lubricant EBS (ethylene bisstearamide): industrial grade; purchased from Guangzhou Langqi Industrial Co., Ltd.

[0057] Preparation Example 1: Preparation of KH-560 Silane Coupling Agent Activated Corn Starch (ACS-1)

[0058] 1. Weigh 1000 g of pre-dried corn starch (moisture content < 1%).

[0059] 2. Weigh 10.0 g of KH-560 and add it to 100 mL of an ethanol-water mixture (ethanol:water = 95:5, v / v, adjust the pH to 4.0-4.5 with a small amount of acetic acid). Stir magnetically for 30 minutes for pre-hydrolysis.

[0060] 3. Slowly spray or drop the pre-hydrolyzed KH-560 solution onto the corn starch in a high-speed mixer while stirring. Mix at high speed at 60-70°C for 30-40 minutes to evenly disperse the silane coupling agent and initially react with the starch.

[0061] 4. Transfer the mixed material to an oven and perform curing reaction at 105-110°C for 1.5-2.0 hours to allow the silane coupling agent to fully react with the hydroxyl groups on the starch surface.

[0062] 5. After cooling, crush through a 100-mesh sieve to obtain surface-activated corn starch ACS-1, seal and set aside.

[0063] Preparation Example 2: Preparation of a Novel Multifunctional Reactive Chain Extender / Compatibilizer (NMRCE)

[0064] (a) Step 1: Synthesis of a diol intermediate containing a phenylene acetal group [5,5-bis(hydroxymethyl)-2-phenyl-1,3-dioxane, DIA-1]

[0065] 1. In a 500 mL three-necked round-bottom flask equipped with a mechanical stirrer, thermometer, Dean-Stark trap, and reflux condenser, 68.08 g (0.50 mol) of pentaerythritol (PER), 55.72 g (0.525 mol, 1.05 equivalents relative to PER) of freshly distilled benzaldehyde, 1.30 g (about 0.0068 mol) of p-toluenesulfonic acid monohydrate (PTSA) as a catalyst, and 200 mL of anhydrous toluene (as a water carrier and solvent) were added in sequence.

[0066] 2. Start stirring, heat in an oil bath, and control the temperature of the reaction system to allow the toluene to slowly reflux (usually at 110-120°C). Continuously remove the by-product water through a Dean-Stark trap.

[0067] 3. Continue the reaction for about 5-7 hours, until no obvious water droplets are formed in the water separator and the amount of water collected is close to the theoretical value (0.5 mol PER corresponds to 18.02 g water. Considering that benzaldehyde may react with a small amount of water or toluene may carry water, the actual collected amount may be slightly different).

[0068] 4. After the reaction is complete, stop heating and allow the reaction mixture to cool to room temperature (about 25-30°C). Add an excess (about 5-10% w / v) saturated sodium bicarbonate aqueous solution (about 50 mL) to neutralize the PTSA catalyst and continue stirring for 30 minutes.

[0069] 5. Transfer the reaction mixture to a separatory funnel and allow the layers to separate. Separate the lower aqueous phase and retain the upper toluene organic phase.

[0070] 6. The organic phase was washed sequentially with saturated aqueous sodium chloride solution (2 x 50 mL) and then dried over anhydrous magnesium sulfate (about 10-15 g) overnight.

[0071] 7. Filter to remove the desiccant, and concentrate the filtrate under reduced pressure on a rotary evaporator (water bath temperature controlled at 50-60°C) to remove most of the toluene.

[0072] 8. Recrystallize the remaining viscous liquid or semisolid from an appropriate amount of anhydrous ethanol (approximately 80-100 mL). The specific steps are: heat to dissolve, slowly cool to crystallize, filter and collect the crystals, wash with a small amount of cold ethanol, and dry in a vacuum oven at 50°C to constant weight. This yields 5,5-bis(hydroxymethyl)-2-phenyl-1,3-dioxane (DIA-1) as a white, needle-like or powdery solid. The yield is typically between 75-85%.

[0073] (b) Step 2: Synthesis of NCO-terminated acetal-containing prepolymer (NMRCE-1)

[0074] 1. In a 250 mL clean, dry four-necked round-bottom flask equipped with a mechanical stirrer, thermometer, constant pressure dropping funnel, and nitrogen protection device, add 44.46 g (0.20 mol) of isophorone diisocyanate (IPDI).

[0075] 2. Dissolve 23.83 g (0.10 mol) of DIA-1 prepared and fully dried in step 1 in 80-100 mL of anhydrous toluene that had been dried with 4A molecular sieves.

[0076] 3. Under a nitrogen atmosphere, start stirring and slowly add the toluene solution of DIA-1 to the IPDI via a constant pressure dropping funnel. Control the addition rate to maintain the reaction system temperature at 55-65°C. The addition process typically takes 1.0-1.5 hours. (Note: This reaction is exothermic; control the addition rate and / or external cooling to maintain the temperature.)

[0077] 4. After the addition is complete, raise the temperature of the reaction system to 70-75°C and continue stirring the reaction at this temperature for 2.5-3.5 hours to ensure that the hydroxyl group and the isocyanate group react fully.

[0078] 5. During the reaction, samples can be taken periodically and the percentage of free -NCO groups in the system can be determined using the standard di-n-butylamine back titration method (GB / T12009.6-1989 or similar standard) until it reaches or slightly exceeds the theoretical calculated value (for the ideal end-capping case with an IPDI:DIA-1 molar ratio of 2:1, the goal is to have an average of approximately two free NCO groups per prepolymer molecule).

[0079] 6. When the -NCO content reaches a predetermined value, stop heating and remove the toluene solvent under reduced pressure (rotary evaporator, water bath temperature controlled at 60-70°C).

[0080] 7. Finally, a light yellow to light brown transparent viscous liquid or semisolid is obtained, which is the new multifunctional reactive chain extender / compatibilizer NMRCE-1. Seal it under nitrogen protection and store it in a dry and cool place until used.

[0081] Examples and Comparative Examples:

[0082] In order to verify the improvement effect of the multifunctional reactive chain extender / compatibilizer (NMRCE) of the present invention on the performance of corn starch-based composite materials, especially the effect of the acid-sensitive groups contained therein on the controllable degradation behavior of the material, the examples and comparative examples shown in Table 1 were designed.

[0083] Table 1: Composition of the Examples and Comparative Examples (parts by weight)

[0084]

[0085]

[0086] Note 1: Preparation of D2 (no acetal structure): For comparison, an NCO-terminated polyurethane chain extender was prepared. Its structure lacks the acid-sensitive acetal group found in NMRCE-1. The specific method involves reacting 1,4-butanediol (instead of DIA-1) with IPDI at a molar ratio of n(NCO) / n(OH) = 2.2:2 under conditions similar to those used in Step 2 of NMRCE-1. This yields a polyurethane prepolymer with primarily NCO groups at both ends. This chain extender primarily provides chemical chain extension / compatibility but lacks the intended acid-sensitive degradation sites.

[0087] Note 2: MAPP: Maleic anhydride grafted polypropylene, maleic anhydride grafting ratio 0.8-1.2%, melt index (190°C, 2.16kg) 5-10g / 10min. This is a commonly used compatibilizer in polyolefin / starch composites or polyester / starch systems, but its compatibilization mechanism and specificity for these systems differ from NMRCE.

[0088] The preparation process is as follows:

[0089] 1. Pretreatment: Weigh each component according to Table 1. Corn starch (ACS-1 or CS), PBS, and PLA are pre-dried as described in the main experimental materials section.

[0090] 2. Premixing: Add the weighed solid components (A1 or CS, B, C, D1 or D2 or MAPP, F, G1, G2) into a high-speed mixer and stir at high speed (about 1000-1500 rpm) at room temperature (about 25°C) for 10-15 minutes to achieve preliminary uniform dispersion.

[0091] 3. Melt blending extrusion:

[0092] The pre-mixed material is stably fed into the main feeding port of a co-rotating parallel twin-screw extruder (L / D=40) through a loss-in-weight feeder.

[0093] For formulations containing Catalyst E (DBTDL / DABCO mixture) (such as Examples 1, 2, and 3, and Comparative Example 2), the catalyst, premixed at a 1:1 mass ratio, was injected via a precision micropump through the side feed port of the second or third heating zone of the extruder. The injection rate was precisely controlled based on the main material feed rate and the catalyst ratio in the formulation.

[0094] The temperature of each heating zone of the twin-screw extruder is set as follows (from the feed port to the die head):

[0095] Zone 1 (feeding zone): 125-135°C;

[0096] Zone 2: 145-155°C;

[0097] Zone 3: 165-175℃;

[0098] Zone 4 (main reaction / mixing zone): 180-190°C;

[0099] Zone 5: 175-185℃;

[0100] Zone 6 (metering / pressure building zone): 170-180°C;

[0101] Die head: 170-175℃;

[0102] The screw speed is controlled at 180-220 rpm;

[0103] The total feeding rate is controlled at 10-15 kg / h.

[0104] 4. Cooling and pelletizing: The molten strips extruded from the extruder are forced to cool in a water tank (the water temperature is controlled at 15-25°C), and then cut into cylindrical or ellipsoidal particles with a length of about 3-4mm and a diameter of about 2-3mm by a rotary pelletizer.

[0105] 5. Drying: After the cut composite particles are collected, they are immediately placed in a forced air drying oven at 80±2°C and dried for 6-8 hours to reduce the moisture content of the particles to less than 0.1% (w / w). They are then vacuum-sealed in aluminum-plastic composite bags for subsequent injection molding of standard specimens and performance testing.

[0106] Test example:

[0107] In order to evaluate the comprehensive performance of the corn starch-based fully degradable tableware material of the present invention and to clarify the mechanism of action of each component, especially the novel multifunctional reactive chain extender / compatibilizer (NMRCE-1), the following performance tests were conducted on the composite materials prepared in the aforementioned examples and comparative examples.

[0108] Test Example 1: Mechanical Properties Testing and Analysis of Composite Materials

[0109] 1. Test method:

[0110] Tensile Properties: In accordance with GB / T 1040.2-2006, the tensile strength and elongation at break of injection-molded specimens were tested using an electronic universal materials testing machine at room temperature (23±2°C) and relative humidity (50±5%). The tensile rate was 10 mm / min.

[0111] Flexural Properties: Flexural strength and flexural modulus of injection-molded specimens were tested in accordance with GB / T 9341-2008 using an electronic universal testing machine under the same temperature and humidity conditions. Three-point bending was performed with a span of 64 mm and a loading rate of 2 mm / min.

[0112] Impact Performance: Notched impact strength of injection-molded strips (V-notch) was tested in accordance with GB / T 1843-2008 using an Izod impact tester under the same temperature and humidity conditions. At least five valid strips were selected for each performance test, and the results were calculated as the arithmetic mean.

[0113] 2. Test results:

[0114] The mechanical property test results of the composite materials prepared in Examples 1-3 and Comparative Examples 1-4 are shown in Table 2.

[0115] Table 2: Mechanical properties test results of composite materials

[0116]

[0117] As can be seen from the mechanical property data of Table 2, the composite materials of Examples 1-3 of the present invention all show significant advantages in key mechanical indicators such as tensile strength, elongation at break, flexural strength and notched impact strength compared to each comparative example. Comparative Example 1 adopts unactivated corn starch and does not add any compatibilizer, and its various mechanical properties are all at the lowest level. This is mainly due to the inherent poor compatibility between starch and hydrophobic polyester (PBS, PLA), and weak interfacial bonding force, resulting in large material brittleness and low strength. Comparative Example 4 uses conventional MAPP as compatibilizer, which is improved compared to Comparative Example 1, but its effect is far less than that of the embodiments of the present invention. This shows that the combination of specially designed surface-activated corn starch (ACS-1) and novel multifunctional reactive chain extension / compatibilizer (NMRCE-1) in the present invention has played a key role in improving the compatibility and mechanical properties of starch / polyester composites. During the melt blending process, the isocyanate (-NCO) groups in the NMRCE-1 molecular chain segments react in situ with the active hydroxyl groups on the surface of surface-activated corn starch, as well as any hydroxyl or carboxyl groups present at or on the ends of the PBS and PLA chains, to form robust urethane or amide bonds. This chemical bonding acts as a molecular bridge, tightly connecting the previously fuzzy or separated starch, PBS, and PLA phases. This significantly enhances interfacial adhesion between the phases, allowing stress to be more effectively transferred and dispersed between the phases under external forces, resulting in a significant improvement in the overall strength and toughness of the material.

[0118] Comparative Example 1 (using NMRCE-1 and catalyst) and Comparative Example 3 (using NMRCE-1 but not using catalyst), it can be seen that the addition of catalyst E (DBTDL / DABCO mixture) is crucial to the lifting of final mechanical properties. Under the condition of no catalyst (Comparative Example 3), although NMRCE-1 can still play a certain compatibilization effect by virtue of its reactive group, its reaction efficiency and the interfacial bonding density formed may be relatively low, resulting in a limited improvement in mechanical properties. The introduction of catalyst significantly promotes the reaction rate and the degree of reaction of the active group in-NCO group and matrix polymer in NMRCE-1, ensures that a more perfect and firmer interface layer is formed within a limited melt extrusion time, which is directly reflected in the obvious superiority of Example 1 relative to Comparative Example 3 in various mechanical indicators. Further comparing Example 1 with Comparative Example 2 (using the NCO end-capping chain extender D2 without acid-sensitive acetal groups, and using catalyst), both show good mechanical strengthening effect, showing that the chemical compatibilization mediated by-NCO group is the main way to improve the mechanical properties of materials. The acid-sensitive acetal group introduced in NMRCE-1 was originally designed to give the material the property of subsequent controllable degradation. In terms of its contribution to pure mechanical properties, compared with the chain extender D2, which has a similar structure but does not have this specific group, its core reactive compatibilization mechanism is common, and both achieve effective bonding with the matrix through the -NCO group.

[0119] In summary, the corn starch-based fully degradable tableware material provided by the present invention successfully overcomes the defects of poor compatibility and insufficient mechanical properties of traditional starch-based materials through the synergistic effect of surface-activated corn starch and a new multifunctional reactive chain extender / compatibilizer (NMRCE-1), supplemented by a catalyst to promote in-situ reaction. The unique molecular structure of NMRCE-1 enables it to efficiently play multiple roles in the ternary composite system of starch, PBS and PLA: its reactive end group (-NCO) forms chemical bonds with each component to build a strong interfacial bond, thereby giving the material excellent tensile properties, bending properties and impact toughness, enabling it to meet the mechanical requirements of applications such as disposable tableware. This strong in-situ compatibilization between multiple components achieved through molecular design is the key to achieving high performance of the material of the present invention, and also reflects the innovation of the present invention in the field of modification of bio-based degradable materials. The increase in the amount of NMRCE-1 in Example 2 further improved the comprehensive mechanical properties of the material, indicating that the content of NMRCE-1 has a positive effect on performance within a certain range. In Example 3, the ratio of the main components was adjusted and excellent mechanical properties were also obtained, which shows that the formulation system has a certain degree of adjustment flexibility.

[0120] Test Example 2: Evaluation of melt flow properties of composite materials

[0121] 1. Test method:

[0122] Melt Flow Index (MFI): The melt mass flow rate (MFR) of the composite material was measured using a melt flow rate instrument according to GB / T 3682-2000. Test conditions were: 190°C, 2.16 kg load. Prior to testing, the sample was dried in a forced air drying oven at 80±2°C for 6-8 hours until the moisture content was less than 0.1%.

[0123] 2. Test results:

[0124] The melt flow performance test results of the composite materials prepared in Examples 1-3 and Comparative Examples 1-4 are shown in Table 3.

[0125] Table 3: Melt flow properties test results of composite materials

[0126]

[0127] As shown in Table 3, the composite materials of Examples 1, 2, and 3 of the present invention all exhibit moderate melt indices, indicating good melt processing properties and suitability for tableware production via common thermoplastic processing methods such as injection molding. Comparative Example 1 (unactivated starch and no compatibilizer) exhibits the highest MFI value. This is likely due to the extremely poor compatibility of starch with the polyester matrix in this system, weak interfacial forces, and almost no effective physical entanglement or chemical bonding between the molecular chains. This results in relatively low melt viscosity and high fluidity, but this is often accompanied by very poor mechanical properties.

[0128] Compared to Comparative Example 1, the MFI values of all formulations with added chain extenders / compatibilizers (Examples 1-3, Comparative Examples 2, 3, and 4) decreased, which is in line with expectations. When a chain extender / compatibilizer is introduced, its reactive groups (such as the -NCO groups in NMRCE-1 or D2, or the anhydride groups in MAPP) react with the active groups in the matrix polymer, resulting in the extension of the molecular chain (chain extension) and / or the formation of chemical bridges (compatibilization / crosslinking) between different phases. This growth of molecular chains and the formation of network structures increase the viscosity of the melt, thereby reducing the melt flow rate (MFR), i.e., a decrease in the MFI value. The MFI values of Examples 1, 2, and 3 show that although the introduction of NMRCE-1 significantly enhances the interfacial interaction and the overall mechanical properties of the material, its melt fluidity remains within a range suitable for processing. In Example 2, the amount of NMRCE-1 used is higher, and its MFI value is slightly lower than that of Examples 1 and 3, which further confirms that the chain extension / crosslinking effect of NMRCE-1 increases with its amount used, resulting in an increase in melt viscosity.

[0129] Comparative Example 1 and Comparative Example 3 (without catalyst), both MFI values are close, but the mechanical property of Comparative Example 3 is relatively poor, this may mean that under the condition of no catalyst, although a certain degree of reaction has also occurred to cause melt viscosity to increase, the interfacial bonding strength and the effectiveness of formation are not enough. The MFI value of Comparative Example 2 (using the chain extender D2 without acid-sensitive groups) is also relatively close to Example 1, illustrating that the acid-sensitive acetal group introduced in NMRCE-1 itself is little on the direct impact of melt fluidity, and main viscosity changes or derives from the reactivity of-NCO groups. The MFI value of Comparative Example 4 (using MAPP) also shows decline, but its mechanical property improves limited, illustrating that its volume expansion mechanism and efficiency are different from NMRCE-1. Generally speaking, the embodiment of the present invention, by the effective effect of NMRCE-1, while significantly improving material mechanical properties, still can maintain good processing fluidity, achieves the good balance of performance and processability, and this is most important for actual production application.

[0130] Test Example 3: Thermal Performance Evaluation of Composite Materials

[0131] 1. Test method:

[0132] Heat Deflection Temperature (HDT): The heat deflection temperature (HDT) of composite materials was measured using a heat deflection temperature / Vicat softening point tester in accordance with GB / T 1634.2-2019. Standard injection-molded specimens were tested under an applied bending stress of 0.45 MPa and a heating rate of 120°C / h. Samples were conditioned at 23±2°C and 50±5% relative humidity for at least 40 hours prior to testing.

[0133] 2. Test results:

[0134] The thermal performance test results of the composite materials prepared in Examples 1-3 and Comparative Examples 1-4 are shown in Table 4.

[0135] Table 4: Thermal performance test results of composite materials

[0136]

[0137] As shown in Table 4, the composite materials of Examples 1, 2, and 3 of the present invention all exhibit high heat deformation temperatures, significantly exceeding those of Comparative Example 1 (no activated starch and no compatibilizer) and Comparative Example 4 (using conventional MAPP compatibilizer). Comparative Example 1 has the lowest HDT value, which is directly related to its loose internal structure and weak interfacial bonding, allowing the material to soften and deform at relatively low temperatures.

[0138] The HDT values of Examples 1-3 were significantly improved, primarily due to the effective introduction and in-situ reaction of the novel multifunctional reactive chain extender / compatibilizer (NMRCE-1). NMRCE-1 chemically bonds with surface-activated corn starch, PBS, and PLA via its terminal -NCO groups, forming a tighter and more stable interfacial network structure in the multiphase system. This enhanced interfacial interaction limits the movement of molecular segments when heated, improving the material's resistance to thermal deformation. Furthermore, the chain extension effect of NMRCE-1 also increases the effective molecular weight and entanglement point density of the polymer chain, further enhancing the material's heat resistance. In Example 2, where a higher amount of NMRCE-1 was used, the HDT value reached the highest value, indicating that increasing the amount of compatibilizer, within a certain range, is beneficial for improving the thermal stability of the material.

[0139] Comparing Example 1 with Comparative Example 3 (without catalyst), the HDT value of Example 1 is significantly higher than that of Comparative Example 3, which is consistent with the trend of mechanical properties, and once again proves the importance of catalyst E for promoting in-situ reaction between NMRCE-1 and matrix components and forming an efficient and stable interface structure. More sufficient interfacial reaction makes the overall rigidity and thermal stability of the material more effectively improved. Comparative Example 2 (using chain extender D2 without acid-sensitive groups) also shows a higher HDT value, similar to Example 1, which shows that the improvement of the heat resistance of the material is mainly due to the chemical compatibilization and chain extension effect mediated by the -NCO group, rather than the direct contribution of the specific acid-sensitive groups in NMRCE-1. However, NMRCE-1 can have the potential for subsequent controlled degradation while providing excellent heat resistance, which is its unique advantage relative to conventional chain extenders. The good heat deformation temperature shown by the embodiment of the present invention material enables it to better adapt to the temperature changes that disposable tableware may encounter in actual use, ensuring the safety and reliability of the product.

[0140] Test Example 4: Evaluation of Controllable Degradation Performance of Composite Materials

[0141] In order to verify the regulatory effect of the acid-sensitive group (i.e., phenylacetal group) introduced into the novel multifunctional reactive chain extender / compatibilizer (NMRCE-1) of the present invention on the degradation behavior of the composite material, the following simulated degradation experiment was designed.

[0142] 1. Test method:

[0143] (a) Simulated acidic hydrolysis weight loss test:

[0144] 1) The composite materials prepared in each embodiment and comparative example were injection molded into standard samples with a size of 20 mm×20 mm×2 mm.

[0145] 2) The sample was dried in a vacuum drying oven at 60±2°C to a constant weight, and its initial dry weight (W0) was accurately weighed.

[0146] 3) The dried sample was completely immersed in a pre-prepared acetate buffer solution (0.1 M) with a pH of 4.5 and placed in a constant temperature water bath shaker at 55±1°C (shaking frequency 60 rpm to ensure full contact between the solution and the sample).

[0147] 4) Take out the samples at the preset time points (7th day, 15th day, 30th day, 45th day), rinse the surface gently with plenty of deionized water to remove the attached matter, and then dry them in a vacuum drying oven at 60±2℃ to constant weight. Accurately weigh the remaining dry weight (W t ).

[0148] 5) Calculate the weight loss rate: Weight loss rate (%) = [(W0-W t ) / W0]×100%. At least three parallel samples were tested for each sample group at each time point, and the results were averaged.

[0149] (b) Observation and evaluation of the initial disintegration of simulated compost:

[0150] 1) The composite materials prepared in each embodiment and comparative example were injection molded into standard samples with a size of 50 mm×50 mm×2 mm.

[0151] 2) Prepare a simulated composting environment: Prepare a simulated composting medium (e.g., a mixture of mature compost, sawdust, corn starch, rabbit feed, urea, etc., with a moisture content adjusted to 50-60% and a C / N ratio of 20:1-40:1) in accordance with the guidelines in GB / T 19277.1-2011 for testing the ultimate aerobic biodegradability and disintegration capacity of plastic materials under laboratory-scale controlled composting conditions.

[0152] 3) Place the specimens in a container filled with simulated composting medium, ensuring they are completely covered and not touching each other. Place the container in an incubator at 58 ± 2°C, turning the material regularly and adjusting the humidity to maintain composting conditions.

[0153] 4) Carefully remove the sample at the preset time points (15th day, 30th day, 45th day) and gently remove the compost medium attached to the surface.

[0154] 5) Observe the macroscopic morphological changes of the sample, such as the degree of fragmentation and integrity.

[0155] 6) Quantitative evaluation of disintegration degree: After the sample (or its residue) is gently washed and dried, it is sieved through a standard sieve with a pore size of 2 mm. The mass of the residue that fails to pass through the 2 mm sieve is weighed (M r ), and calculate the disintegration rate: disintegration rate (%) = [(M0-M r ) / M0]×100%, where M0 is the initial dry weight of the sample.

[0156] 2. Test results:

[0157] The simulated degradation performance test results of Examples 1-3 and Comparative Examples 1, 2, and 4 are shown in Tables 5 and 6.

[0158] Table 5: Weight loss of composite materials in pH = 4.5 acetate buffer solution (55 ° C) (%)

[0159]

[0160]

[0161] Table 6: Disintegration rate (%) of composite materials under simulated composting conditions (58°C) (through 2 mm sieve)

[0162] time Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 4 15 days 30 35 28 5 10 8 30 days 72 78 69 18 32 25 45 days >90* >90* >90* 35 55 45

[0163] Note: >90 means that at 45 days, the sample is almost completely disintegrated and residues larger than 2 mm cannot be accurately collected, or the mass of the residue is less than 10% of the initial mass.

[0164] The data in Tables 5 and 6 clearly demonstrate the significant advantages of the materials of the present invention in simulated acidic hydrolysis and simulated initial composting disintegration. In an acidic buffer solution at pH 4.5, the weight loss rates of Examples 1, 2, and 3 were significantly higher than those of all comparative examples. This is primarily due to the phenylidene acetal groups intentionally introduced into the molecular structure of the novel multifunctional reactive chain extender / compatibilizer (NMRCE-1) employed in this invention. Acetal and ketal chemical bonds are very sensitive to acidic conditions and are easily hydrolytically broken in acidic aqueous solutions. When the composite material is placed in an acidic environment, these pre-defined weak links preferentially undergo chemical degradation, causing the NMRCE-1 molecular chains to break at these sites. Because NMRCE-1 acts as a bridge connecting the starch, PBS, and PLA phases in the composite material, its own breakage directly disrupts the interfacial network structure within the material, accelerating the material's disintegration and exposing the matrix polymer, resulting in faster weight loss.

[0165] Comparative Example 2 has used the NCO end-capping chain extender D2 that does not contain acid-sensitive acetal group, although it has also formed chemical bonding with matrix by-NCO group, in acidic hydrolysis test, its weight loss rate is obviously lower than embodiment of the present invention, this has effectively proved that acid-sensitive acetal group in NMRCE-1 is for accelerating the key role of material initial stage degradation under acidic conditions.The weight loss rate of Comparative Example 1 (without compatibilizer) and Comparative Example 4 (using MAPP) is lower, shows that the stability of its internal structure under acidic conditions is relatively high (or degraded slowly), lacks this rapid initial disintegration mechanism guided by specific chemical groups.This means that the design of the present invention's material, by embedding the chemical bond that is sensitive to specific environmental factors (such as acidity) in key interface compatibilizer molecule, has successfully constructed the initial degradation path of energy-oriented type or triggered type.

[0166] The disintegration test results (Table 6) in the early stage of simulated composting further confirm the above mechanism. Examples 1, 2, and 3 of the present invention show a disintegration rate much faster than that of the comparative example under simulated composting conditions. The composting environment is usually weakly acidic and contains a large amount of microorganisms and moisture. These conditions are also conducive to the hydrolysis of the acetal group in NMRCE-1. The initial chemical hydrolysis fracture causes the material structure to be loose and fragmented, increasing the specific surface area of the material, making it easier for microorganisms to erode and utilize the biodegradable components such as starch, PBS, and PLA therein, thereby accelerating the entire biodegradation and disintegration process. Although Comparative Example 2 is also a biodegradable material, its disintegration rate is relatively slow due to the lack of this preferred chemical disintegration pathway. This fully reflects the innovativeness of the present invention in that it effectively regulates the early disintegration behavior of the material under a specific waste environment by presetting the degradation switch at the molecular level. This controllable rapid disintegration characteristic is of great significance for reducing the persistence of plastic waste in the environment and improving composting efficiency.

[0167] While 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 may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. Corn starch-based fully degradable tableware material, characterized in that: The material is prepared by mixing the following components in parts by weight: 40-60 parts of surface-activated corn starch; 15-30 parts of polybutylene succinate; 10-25 parts of polylactic acid; 1 to 5 parts of multifunctional reactive chain extender / compatibilizer; 3-8 parts of bio-based plasticizer; Among them, the molecular structure of the multifunctional reactive chain extender / compatibilizer contains at least one functional group that can react with the active groups in corn starch, polybutylene succinate or polylactic acid to form a chemical bond, and contains at least one chemical bond or group that is easily broken under a specific degradation environment to construct an energy-oriented controllable degradation path.

2. The corn starch-based fully degradable tableware material according to claim 1, characterized in that: The multifunctional reactive chain extender / compatibilizer is a product prepared by the following steps: (a) reacting a polyol containing at least two hydroxyl groups with an aldehyde or ketone in the presence of an acidic catalyst to generate a diol intermediate containing an acetal or ketal group and retaining at least two hydroxyl groups; (b) reacting the diol intermediate obtained in step (a) with an excess of polyisocyanate to obtain a prepolymer having two or more ends blocked with isocyanate groups; The acetal or ketal groups form chemical bonds that are easily broken under specific degradation conditions.

3. The corn starch-based fully degradable tableware material according to claim 2, characterized in that: In step (a), the polyol containing at least two hydroxyl groups is pentaerythritol, and the aldehyde is benzaldehyde; and in step (b), the polyisocyanate is isophorone diisocyanate.

4. The corn starch-based fully degradable tableware material according to claim 1, characterized in that: The surface activated corn starch is obtained by treating with a silane coupling agent or low-temperature plasma.

5. The corn starch-based fully degradable tableware material according to claim 1, characterized in that: The invention also contains 0.2 to 1 parts by weight of a catalyst, which is used to promote the reaction between the multifunctional reactive chain extender / compatibilizer and corn starch, polybutylene succinate or polylactic acid.

6. A process for preparing the corn starch-based fully degradable tableware material according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Premixing surface-activated corn starch, polybutylene succinate, polylactic acid, a multifunctional reactive chain extender / compatibilizer, a bio-based plasticizer, and optional catalysts and auxiliary additives; S2. Melt-blending and extruding the premixed material obtained in step S1 in a twin-screw extruder. During the melt-blending process, the multifunctional reactive chain extender / compatibilizer reacts in situ with the surface-activated corn starch, polybutylene succinate, and polylactic acid; S3. Cooling the extrudate and pelletizing it to obtain the corn starch-based fully degradable tableware material.

7. The preparation process according to claim 6, characterized in that: The melt blending temperature range of the twin-screw extruder in step S2 is 120-195°C.

8. A corn starch-based fully biodegradable tableware, characterized in that: The tableware is made of the corn starch-based fully degradable tableware material according to any one of claims 1 to 5.

9. The corn starch-based fully biodegradable tableware according to claim 8, characterized in that: The tableware is a lunch box prepared by injection molding, hot pressing molding or blister molding.

10. Use of the corn starch-based fully degradable tableware material according to any one of claims 1 to 5 in preparing a disposable fully degradable lunch box.

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