Degradable biomass modified composite material and preparation method thereof

Abstract

The present application relates to the technical field of degradable materials, and particularly relates to a degradable biomass modified composite material and a preparation method thereof.The present application comprises the following raw materials by weight: oxidized double-bonded starch: 85-95 parts, ethylenediamine: 18-22 parts, sodium castor oil acid salt: 10-15 parts, and carboxylated nanocellulose: 8-12 parts.Through efficient cross-linking of aldehyde groups and ethylenediamine, directional grafting of castor oil acid flexible chains, and rigid cross-linking provided by carboxylated nanocellulose, a “rigid network-flexible chain-nano reinforcement” structure is formed, the elongation rate reaches 190-220%, the strength is maintained at 30-32 MPa, the strength is maintained at 95% or more after 40 DEG C / 70% RH for 6 months, the water contact angle of the material reaches 85-90 DEG, and the soil degradation is 80% or more after 60 days, thus solving the problem of “stability and degradation contradiction” faced by starch-based materials, and being suitable for fields such as food packaging, agricultural mulching film or disposable tableware.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of degradable materials, in particular to a degradable biomass modified composite material and a preparation method thereof. BACKGROUND

[0002] Under the background of increasingly stringent global environmental regulations, the "white pollution" problem caused by the non-degradability of traditional petroleum-based high molecular materials (such as polyethylene and polypropylene) is becoming increasingly prominent. According to statistics, about 800 million tons of plastic enters the natural environment every year, and it takes hundreds of years to completely degrade, causing irreversible damage to soil, water and ecosystems. Developing environmentally friendly and completely degradable alternative materials has become the core path to solve plastic pollution.

[0003] Biomass materials (using natural polymers such as starch, cellulose and vegetable oil as raw materials) are considered the most promising alternative to petroleum-based plastics due to their renewable source, low cost and complete biodegradability. Among them, starch-based materials have become a research hotspot due to their abundant starch reserves (global annual output exceeding 100 million tons) and good processing performance. However, pure starch materials have inherent defects:

[0004] Weak mechanical properties: starch molecular chains are connected by hydrogen bonds, with a loose structure, a tensile strength usually below 10 MPa, and an elongation at break less than 50%, which cannot meet the demand for structural strength in packaging and mulch;

[0005] Poor water resistance: the molecular chain is rich in hydroxyl groups (-OH) and has strong hydrophilicity, with a water contact angle generally below 70°, easy to absorb water and swell, and the performance quickly decays in a humid environment;

[0006] Insufficient structural stability: the glycosidic bond of the starch chain is easily enzymatically degraded by microorganisms, and unmodified starch materials are prone to natural degradation during storage, with a short mechanical property half-life (usually < 3 months);

[0007] To overcome the above bottlenecks, existing technologies improve performance through physical blending (such as blending with natural rubber and polycaprolactone) or chemical modification (such as esterification and crosslinking). Among them, chemical crosslinking is the mainstream method to improve the strength and water resistance of starch-based materials due to its ability to build a three-dimensional network structure. However, crosslinked starch-based materials still face the "stability and degradation contradiction", and how to achieve the performance balance of "high strength-high toughness-high water resistance-long storage-full degradation" through precise raw material design, reaction control and post-treatment optimization is still a key problem to be solved in the current industry. SUMMARY

[0008] Therefore, the present application aims to provide a degradable biomass modified composite material, which comprises the following raw materials in parts by weight: oxidized dialdehyde starch: 85-95 parts, ethylenediamine: 18-22 parts, sodium castor oil acid salt: 10-15 parts, and carboxylated nanocellulose: 8-12 parts.

[0009] The preparation process of the oxidized dialdehyde starch is as follows:

[0010] A1 100 parts by weight of corn starch is dispersed in 450-550 parts by weight of a mixed solvent, the volume ratio of water and ethanol in the mixed solvent is 3:1, and the swelling is performed at 45-55°C for 20-40 min;

[0011] A2 The uniform suspension is obtained by treating under the action of 40 kHz, 30-50 W ultrasonic wave for 20-40 min;

[0012] A3 0.45-0.55 mol of sodium periodate per mol of glucose unit is added to the suspension, the temperature is controlled at 35-45°C, the pH is 2.0±0.2, and the reaction is performed in the dark for 1.5-2.5 h;

[0013] A4 When the reaction is terminated, 10-15 parts by weight of ethylene glycol is added, and the stirring is continued for 10-20 min, followed by centrifugal separation and washing with deionized water until the starch-KI test paper is free of blue color;

[0014] A5 The obtained product is vacuum dried at 40-50°C for 8-12 h to obtain oxidized dialdehyde starch (DAS) with an aldehyde group molar content of 5-7 mmol / g;

[0015] In the glucose unit of corn starch, there is an adjacent diol structure (-CHOH-CHOH-) at the positions of C2 and C3. In step A, sodium periodate (NaIO4) is used as a selective oxidizing agent under acidic conditions (pH is 2.0±0.2), and the adjacent diol is oxidized into two aldehyde groups (-CHO) by breaking the C2-C3 bond to form a dialdehyde structure (2 aldehyde groups are generated per glucose unit). This reaction has high specificity and only targets the adjacent diol, avoiding the destruction of the main chain structure of the starch. After the reaction, ethylene glycol is added to terminate the reaction (the adjacent diol structure of ethylene glycol consumes excess sodium periodate), and the residual oxidizing agent is removed by washing (the starch-KI test paper is free of blue color, indicating that there is no excess NaIO4). The high aldehyde group content provides sufficient active sites for the subsequent cross-linking reaction with amines, and is the basis for the formation of a stable network structure.

[0016] The preparation process of the carboxylated nanocellulose is as follows:

[0017] B1 10 parts by weight of nanocellulose is dispersed in 90-110 parts by weight of deionized water to form a 1-3 wt% suspension;

[0018] B2 sequentially add 2,2,6,6-tetramethylpiperidinyloxy free radical (TEMPO) 0.08-0.12 mmol / g of cellulose, NaBr 0.8-1.2 mmol / g of cellulose and NaClO 1.2-1.4 mmol / g of cellulose, control the temperature at 20-30℃, pH at 10.0±0.2, and react for 1.5-2.5 h;

[0019] B3 after the reaction, filter, acidify with 0.1 mol / L hydrochloric acid to pH 3±0.2, and then wash with deionized water until the conductivity of the filtrate is <50 μS / cm;

[0020] B4 dry the solid at 55-65℃ under vacuum for 5-7 h to obtain carboxylated nanocellulose with a carboxyl molar content of 0.9-1.1 mmol / g;

[0021] The surface of nanocellulose (CNC) is rich in hydroxyl groups (-OH), among which the C6 position is a primary hydroxyl group (higher reactivity), and the C2 and C3 positions are secondary hydroxyl groups. Using a TEMPO / NaBr / NaClO oxidation system: TEMPO as a catalyst, under alkaline conditions (pH 10.0±0.2), the oxidation ability of NaClO (oxidant) is selectively transferred to the surface of CNC through mediation by NaBr (co-catalyst), and the primary hydroxyl group at the C6 position is selectively oxidized to a carboxyl group (-COOH), while the secondary hydroxyl groups at the C2 and C3 positions hardly react. By controlling the temperature (20-30℃) and pH, this process ensures high efficiency and selectivity of carboxylation, and finally obtains CNC-COOH with a carboxyl density of 0.9-1.1 mmol / g, which provides key carboxyl active sites for subsequent covalent combination with other components.

[0022] The sodium salt of ricinoleic acid is obtained by neutralization reaction of ricinoleic acid with an equimolar amount of sodium hydroxide.

[0023] The preparation method of the degradable biomass modified composite material comprises the following steps:

[0024] C1 disperse the oxidized dialdehyde starch in 450-550 parts by weight of a mixed solvent, the mixed solvent being water and ethanol in a volume ratio of 3:1, and remove oxygen by nitrogen;

[0025] C2 add ethylenediamine, adjust the pH to 5.4-5.6 with 0.1 mol / L hydrochloric acid, and react at 35-45℃ for 45-75 min; then add NaBH3CN, and continue to react at 35-45℃ for 20-40 min to reduce the Schiff base;

[0026] C3 maintain the pH at 5.4-5.6, and sequentially add the sodium salt of ricinoleic acid, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), and react at 35-45℃ for 20-40 min; ) and N-hydroxysuccinimide (NHS), and the temperature is raised to 45-55°C, and the reaction is carried out for 2.5-3.5h;

[0027] C4 The temperature is lowered to 40-50°C, and carboxylated nanocellulose, 4-(4,6-dimethoxytriazin-2-yl)-4-methylmorpholinium hydrochloride (DMTMM) and dimethylaminopyridine (DMAP) are added, the pH is adjusted to 4.9-5.1 with 0.1 mol / L hydrochloric acid, and the reaction is carried out at 40-50°C for 3.5-4.5h; then it is adjusted back to pH 6.8-7.2 with 0.1 mol / L NaOH, and the reaction is continued at 40-50°C for 1.5-2.5h;

[0028] After the reaction is completed, centrifugal separation is carried out, and the material is washed with deionized water for 2-4 times, and vacuum dried at 55-65°C for 10-14h to obtain the degradable biomass modified composite material.

[0029] The degradable biomass modified composite material has a soil degradation rate of ≥80% in 60 days under the condition of a 1mm thick test piece according to the ISO 20200 standard test, a tensile strength of 30-32MPa and an elongation at break of 190%-220% according to the ASTM D638 test, a water contact angle of 85°-90° according to the GB / T 30693 test, and a tensile strength decrease rate of ≤5% after being stored at 40°C and a relative humidity of 70% for 6 months.

[0030] The formation of the composite material is achieved by "stepwise covalent crosslinking + multi-component synergy", and the network structure is constructed in stages:

[0031] Basic crosslinking network construction (step C2): the nucleophilic addition reaction of the aldehyde group (-CHO) of DAS and the amino group (-NH2) of ethylenediamine occurs under weak acidic conditions (pH 5.4-5.6) to generate Schiff base (imine bond, -C=N-). Since ethylenediamine is a bifunctional group (two -NH2), each molecule can connect two DAS chains to form a preliminary crosslinking network. Then NaBH3CN (sodium cyanoborohydride) is added to reduce the unstable imine bond to a stable C-N single bond, significantly improving the chemical stability of the network (avoiding imine bond hydrolysis) and laying the foundation for the rigidity of the material.

[0032] Flexible chain segment grafting (step C3): the carboxyl group (-COOH) of sodium castor oil salt (castor oil acid is neutralized with an equal amount of NaOH to enhance the solubility in water / ethanol solvent) reacts with the amino group (-NH2) of DAS under the catalysis of DMAP to form an amide bond (-C=O-NH-), and the reaction is carried out at 40-50°C for 2-3h. ) in the presence of The residual amino group (-NH2) of ethylenediamine, which does not participate in the Schiff base reaction, is activated by the action of EDC (condensing agent) and NHS (activating agent) to form an amide bond (-CONH-), thereby grafting the long-chain hydrophobic structure of ricinoleic acid into the crosslinked network. This process introduces flexible segments to balance the rigidity and toughness of the material, providing support for high elongation at break (190%-220%).

[0033] Nanoreinforcement (step C4): The carboxyl group (-COOH) of CNC-COOH is activated by the action of DMTMM (high-efficiency condensing agent) and DMAP (catalyst) to react with the residual hydroxyl group (unoxidized hydroxyl group of DAS or reduced hydroxyl group) or amino group in the network, forming an ester bond (-COO-) or an amide bond (-CONH-), thereby anchoring CNC-COOH in the crosslinked network. CNC-COOH, as a nanoreinforcement, is uniformly dispersed through strong covalent interaction, significantly improving the tensile strength of the material (30-32 MPa). The pH is adjusted to neutral (6.8-7.2) after the reaction to ensure stable formation of covalent bonds.

[0034] Preferably, the amount of NaBH3CN in C2 is 0.8-1.2 wt% based on the dry weight of oxidized dialdehyde starch.

[0035] Preferably, the molar ratio of sodium ricinoleate, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and N-hydroxysuccinimide in C3 is 1.0-1.2:1.0:0.5.

[0036] Preferably, the molar ratio of carboxylated nanocellulose, 4-(4,6-dimethoxytriazin-2-yl)-4-methylmorpholinium hydrochloride, and dimethylaminopyridine in C4 is 1.0-1.2:1.0:0.1.

[0037] The resulting degradable biomass-modified composite material can be used for food packaging, agricultural mulch, or disposable tableware.

[0038] The beneficial effects of the present application are:

[0039] 1.The present application adopts biomass raw materials (starch, cellulose, ricinoleic acid), relies on the natural degradable characteristics of biomass materials, and makes the product have a soil degradation rate of ≥80% in 60 days (ISO 20200 standard), thus meeting the environmental protection requirements from the source. At the same time, through the efficient crosslinking of DAS with high aldehyde content and ethylenediamine, the nano-enhancing effect of TEMPO selective carboxylation CNC (carboxyl density 0.9-1.1 mmol / g), and the directional grafting of the flexible chain of ricinoleic acid, a multi-level synergistic structure of "rigid network-flexible chain-nano enhancement" is constructed, thus breaking through the bottleneck of traditional biomass materials "difficulty in balancing rigidity and toughness", and enabling the material to have high tensile strength (30-32 MPa, ASTM D638) and high elongation at break (190%-220%).

[0040] 2.The present application first constructs a stable rigid network through Schiff base reaction and NaBH3CN reduction, then introduces flexible chain segments through EDC / NHS activation of carboxyl groups, and finally realizes nano-enhancing combination through DMTMM catalysis, thus ensuring the covalent combination of components instead of physical mixing and significantly improving the structural stability: the tensile strength decreases by ≤5% after 6 months of storage at 40°C and 70% humidity, thus solving the problems of easy degradation and poor stability of traditional biomass materials.

[0041] 3.The present application introduces the hydrophobic long chain of ricinoleic acid to make the water contact angle of the material reach 85°-90° (GB / T30693), reduces the hydrophilicity to reduce the performance degradation caused by water absorption; at the same time, the degradability of the whole biomass component is combined with excellent mechanical properties and stability, so that the product can be widely used in food packaging, agricultural mulching film, disposable tableware and other fields, realizes the unity of "environmental protection, high performance and high stability", and meets the comprehensive requirements of materials in multiple scenes. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application is further described in detail below with specific examples.

[0043] Preparation Example 1-3 (oxidation of double-bonded dialdehyde starch)

[0044] Preparation Example 1:

[0045] A1 100 parts of corn starch were dispersed in 450 parts of water:ethanol=3:1 mixed solvent, and swelled at 45°C for 20 min;

[0046] A2 40 kHz / 30 W ultrasonic treatment for 20 min;

[0047] A3 0.45 mol of sodium periodate was added per mol of glucose unit, and the reaction was carried out at 35°C and pH 1.8 in the dark for 1.5 h;

[0048] A4 add 10 parts of ethylene glycol to quench, after washing and drying, the aldehyde group content of DAS is 5.2 mmol / g.

[0049] Preparation Example 2:

[0050] A1 take 100 parts of starch and disperse in 500 parts of mixed solvent, swell at 50℃ for 30 min;

[0051] A2 40 kHz / 40 W ultrasonic treatment for 30 min;

[0052] A3 add 0.50 mol of sodium periodate, react at 40℃ and pH 2.0 for 2.0 h;

[0053] A4 add 12 parts of ethylene glycol, and the aldehyde group content of DAS is 6.1 mmol / g.

[0054] Preparation Example 3:

[0055] A1 take 100 parts of starch and disperse in 550 parts of mixed solvent, swell at 55℃ for 40 min;

[0056] A2 40 kHz / 50 W ultrasonic treatment for 40 min;

[0057] A3 add 0.55 mol of sodium periodate, react at 45℃ and pH 2.2 for 2.5 h;

[0058] A4 add 15 parts of ethylene glycol, and the aldehyde group content of DAS is 6.7 mmol / g.

[0059] Preparation Examples 4-6 (carboxylated nanocellulose preparation)

[0060] Preparation Example 4:

[0061] B1 10 parts of nanocellulose are dispersed in 90 parts of water;

[0062] B2 add 0.08 mmol / g TEMPO, 0.8 mmol / g NaBr, 1.2 mmol / g NaClO, react at 20℃ and pH 9.8 for 1.5 h;

[0063] B3 after acidification and washing, the carboxyl content of CNC is 0.9 mmol / g.

[0064] Preparation Example 5:

[0065] B1 10 parts of nanocellulose are dispersed in 100 parts of water;

[0066] B2 add 0.10 mmol / g TEMPO, 1.0 mmol / g NaBr, 1.3 mmol / g NaClO, react at 25℃ and pH 10.0 for 2.0 h;

[0067] B3 carboxyl content of 1.0 mmol / g of CNC is obtained.

[0068] Preparation Example 6:

[0069] B1 10 parts of nanocellulose is dispersed in 110 parts of water;

[0070] B2 0.12 mmol / g TEMPO, 1.2 mmol / g NaBr, 1.4 mmol / g NaClO is added, 30°C, pH 10.2, reaction for 2.5 h;

[0071] B3 carboxyl content of 1.1 mmol / g of CNC is obtained.

[0072] Example 1:

[0073] Preparation Example 1 aldehyde group containing DAS and Preparation Example 4 carboxyl group containing CNC are used:

[0074] C1 85 parts of DAS is dispersed in 450 parts of mixed solvent;

[0075] C2 18 parts of ethylenediamine is added, pH 5.4, 35°C, reaction for 45 min, then 0.8 wt% NaBH3CN is added, reaction for 20 min;

[0076] C3 10 parts of sodium salt of ricinoleic acid is added, EDC / NHS is 1.0:1.0:0.5, 45°C, reaction for 2.5 h;

[0077] C4 8 parts of CNC is added, DMTMM / DMAP is 1.0:1.0:0.1, pH 4.9, reaction for 3.5 h, after pH 6.8, reaction for 1.5 h.

[0078] Example 2:

[0079] Preparation Example 2 aldehyde group containing DAS and Preparation Example 5 carboxyl group containing CNC are used:

[0080] C1 90 parts of DAS is dispersed in 500 parts of solvent;

[0081] C2 20 parts of ethylenediamine is added, pH 5.5, 40°C, reaction for 60 min, then 1.0 wt% NaBH3CN is added, reaction for 30 min;

[0082] C3 12 parts of sodium salt of ricinoleic acid is added, EDC / NHS is 1.1:1.0:0.5, 50°C, reaction for 3.0 h;

[0083] C4 10 parts of CNC is added, DMTMM / DMAP is 1.1:1.0:0.1, pH 5.0, reaction for 4.0 h, after pH 7.0, reaction for 2.0 h.

[0084] Example 3:

[0085] Example 3:

[0086] C1 95 parts of DAS were dispersed in 550 parts of solvent;

[0087] C2 22 parts of ethylenediamine were added, pH was 5.6, 45℃ for 75 min, 1.2 wt% NaBH3CN was added for 40 min;

[0088] C3 15 parts of sodium castor oil salt were added, EDC / NHS was 1.2:1.0:0.5, 55℃ for 3.5 h;

[0089] C4 12 parts of CNC were added, DMTMM / DMAP was 1.2:1.0:0.1, pH was 5.1 for 4.5 h, pH was 7.2 for 2.5 h.

[0090] Comparative Example 1: without castor oil

[0091] All conditions were the same as Example 2, but sodium castor oil salt and related reaction step C3 were omitted.

[0092] Comparative Example 2: without CNC-COOH crosslinking

[0093] All conditions were the same as Example 2, but CNC-COOH, DMTMM and DMAP and related reaction step C4 were omitted.

[0094] Comparative Example 3: traditional physical blending

[0095] 90 g of DAS of Preparation 2 and 10 g of CNC-COOH of Preparation 5 and 12 g of sodium castor oil salt were melt blended in a twin-screw extruder at 180℃ for 5 min without any chemical crosslinking.

[0096] Performance test methods:

[0097] 1. Tensile strength and elongation at break: according to ASTM D638, type IV dumbbell, tensile rate 10 mm / min, 25℃, 50% RH. -1

[0098] 2. Water contact angle: according to GB / T 30693, static sessile drop method, 25℃, 5 μL water drop, 5 times average.

[0099] 3. Soil degradation rate: according to ISO 20200, 1 mm thick test pieces were prepared, buried in moist soil at 25℃, mass loss was measured after 60 d.

[0100] ​4. Storage stability: After the sample was placed in a constant temperature and humidity box at 40°C and 70% RH for 6 months, the tensile strength was measured according to ASTM D638, and the retention rate was calculated.

[0101] The above test results are shown in Table 1:

[0102] Table 1. Performance test of biomass modified composite material

[0103]

[0104] Data analysis:

[0105] Mechanical property analysis:

[0106] (1) In terms of tensile strength, Examples 1-3 (30.2-32.4 MPa) are significantly better than Comparative Examples 2 (21.3 MPa) and 3 (18.6 MPa), demonstrating the key role of the chemical crosslinking network. It is particularly noteworthy that Example 3, which uses a combination of high aldehyde group DAS (7.0 mmol / g) and high carboxyl group CNC (1.1 mmol / g), achieves a maximum strength of 32.4 MPa, which is 74% higher than the physically blended Comparative Example 3.

[0107] (2) The breaking elongation data is more breakthrough, Example 2 reaches 225±7%, which is 87% higher than Comparative Example 1 (120±5%), fully verifying the toughening effect of the castor oil acid flexible chain. This "rigid skeleton-flexible segment" synergistic design successfully solves the industry problem of difficult to balance strength and toughness of bio-based materials.

[0108] Functional property analysis:

[0109] (1) Hydrophobic performance: Comparative Example 1 (without castor oil acid) has the lowest contact angle (74°), and Examples 1-3 (85-89°) are significantly better than traditional materials (usually <65°). The hydrophobic chain of sodium castor oil salt improves hydrophobicity while the crosslinking reaction involving its carboxyl group moderately reduces the contact angle, achieving a balance of performance.

[0110] (2) Degradation performance: The degradation rate of all groups is >79% in 60 days, among which Comparative Example 3 (physical blending) reaches 92%, but at the cost of sacrificing mechanical properties (strength only 18.6 MPa). Example 2 maintains a strength of 31.5 MPa while the degradation rate reaches 81%, achieving the best balance of "performance-environmental friendliness".

[0111] Stability verification:

[0112] After 6 months of hot and humid aging, the strength retention rate (94-98%) of the chemically cross-linked example group is much higher than that of the physically blended comparative example 3 (72%). In particular, example 3 still retains 98% of the strength under high temperature and humidity conditions, proving that the Schiff base network reduced by NaBH3CN has stability.

[0113] The innovative value of the present application is that through the triple design of "oxidation degree regulation-stepwise cross-linking-interface enhancement", the comprehensive performance of >30MPa strength, >200% elongation and >80% degradation rate is realized on the bio-based material for the first time, and the technical index has reached the level of petroleum-based general plastics, providing a feasible solution for replacing traditional plastics.

[0114] Those skilled in the art will understand that the discussion of any of the above embodiments is merely exemplary and is not intended to suggest that the scope of the application is limited to these examples; the above embodiments or technical features among different embodiments can also be combined, and the steps can be implemented in any order, and there are many other changes of different aspects of the application as described above. In order to be brief, they are not provided in detail.

Claims

1. A biodegradable biomass-modified composite material, characterized in that, The raw materials include the following parts by weight: oxidized dialdehyde starch: 85-95 parts, ethylenediamine: 18-22 parts, sodium ricinoleate: 10-15 parts, and carboxylated nanocellulose: 8-12 parts; The preparation process of the oxidized dialdehyde starch is as follows: A1. Disperse 100 parts by weight of corn starch in 450-550 parts by weight of mixed solvent, wherein the volume ratio of water to ethanol in the mixed solvent is 3:1, and swell at 45-55℃ for 20-40 min. A2 was treated with ultrasound at 40kHz and 30-50W for 20-40 minutes to obtain a uniform suspension. A3 Add 0.45-0.55 mol sodium periodate per mole of glucose unit to the suspension, control the temperature at 35-45℃, the pH at 2.0±0.2, and react in the dark for 1.5-2.5 h; When the A4 reaction is terminated, add 10-15 parts by weight of ethylene glycol, continue stirring for 10-20 minutes, then centrifuge and wash with deionized water until the starch-KI test paper is free of blue. A5 dried the obtained product under vacuum at 40-50℃ for 8-12 h to obtain oxidized dialdehyde starch with an aldehyde molar content of 5.2-6.7 mmol / g; The preparation process of the carboxylated cellulose nanoparticles is as follows: B1 disperses 10 parts by weight of nanocellulose in 90-110 parts by weight of deionized water to form a suspension of 1-3 wt%. B2 is added sequentially with 0.08-0.12 mmol / g cellulose of 2,2,6,6-tetramethylpiperidine oxygen radical, 0.8-1.2 mmol / g cellulose of NaBr, and 1.2-1.4 mmol / g cellulose of NaClO. The temperature is controlled at 20-30℃ and the pH is 10.0±0.2, and the reaction is carried out for 1.5-2.5 h. After the B3 reaction is complete, filter the solution, acidify it with 0.1 mol / L hydrochloric acid to pH 3 ± 0.2, and then wash it with deionized water until the conductivity of the filtrate is < 50 μS / cm. B4 The solid was vacuum dried at 55-65℃ for 5-7h to obtain carboxylated nanocellulose with a carboxyl molar content of 0.9-1.1 mmol / g; The sodium ricinoleate salt is prepared by neutralization reaction of ricinoleic acid with an equimolar amount of sodium hydroxide; The preparation method of the biodegradable biomass modified composite material includes the following steps: C1 disperses oxidized dialdehyde starch in 450-550 parts by weight of a mixed solvent, the mixed solvent being water and ethanol in a volume ratio of 3:1, and removes oxygen by purging with nitrogen. C2 is added with ethylenediamine, and the pH is adjusted to 5.4-5.6 with 0.1 mol / L hydrochloric acid. The reaction is carried out at 35-45℃ for 45-75 min. Then NaBH3CN is added, and the reaction is continued at 35-45℃ for 20-40 min to reduce the Schiff base. C3 is maintained at pH 5.4-5.6, and sodium ricinoleate, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide are added sequentially. The temperature is raised to 45-55℃ and the reaction is carried out for 2.5-3.5 hours. C4 is cooled to 40-50℃, and carboxylated nanocellulose, 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride and dimethylaminopyridine are added. The pH is adjusted to 4.9-5.1 with 0.1 mol / L hydrochloric acid, and the reaction is carried out at 40-50℃ for 3.5-4.5 h. Then, the pH is adjusted back to 6.8-7.2 with 0.1 mol / L NaOH, and the reaction is continued at 40-50℃ for 1.5-2.5 h. After the C5 reaction is completed, the mixture is centrifuged, washed 2-4 times with deionized water, and vacuum dried at 55-65℃ for 10-14 hours to obtain the biodegradable biomass modified composite material.

2. The biodegradable biomass-modified composite material according to claim 1, characterized in that, The amount of NaBH3CN used in C2 is 0.8-1.2 wt% of the dry weight of oxidized dialdehyde starch.

3. The biodegradable biomass-modified composite material according to claim 1, characterized in that, The molar ratio of sodium ricinoleate, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and N-hydroxysuccinimide in C3 is 1.0-1.2:1.0:0.

5.

4. The biodegradable biomass-modified composite material according to claim 1, characterized in that, The molar ratio of carboxylated nanocellulose, 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride and dimethylaminopyridine in C4 is 1.0-1.2:1.0:0.

1.

5. The application of the biodegradable biomass modified composite material according to any one of claims 1-4 in food packaging, agricultural mulch film or disposable tableware.

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