Bamboo pulp molded fresh-keeping food packaging box as well as preparation method and application thereof

Abstract

The preparation method comprises the following steps: (1) preparing pulp: selecting dendrocalamus latiflorus pulp fiber pulp and sagittaria trifolia pulp fiber pulp, respectively performing defibering and dispersing treatment on the dendrocalamus latiflorus pulp fiber pulp and the sagittaria trifolia pulp fiber pulp, and uniformly mixing the dispersed pulp to obtain mixed pulp; (2) addition of an auxiliary agent: adding a modified plant fiber filler and a functional auxiliary agent into the mixed slurry, and uniformly stirring to obtain a composite slurry; (3) molding treatment: conveying the composite slurry to a molding machine, carrying out vacuum filtration and dehydration to form a wet blank, and then carrying out hot-pressing shaping and trimming treatment on the wet blank to obtain a preliminarily molded packaging box; and (4) post-treatment is conducted, specifically, the outer surface of the primarily-formed packaging box is sprayed with a fresh-keeping extracting solution, then drying treatment is conducted, and the bamboo pulp molding fresh-keeping food packaging box with the high barrier property is obtained. The invention further relates to a bamboo pulp molded fresh-keeping food packaging box and application thereof.

Description

Technical Field

[0001] The invention relates to the technical field of pulp molded packaging materials, and in particular to a bamboo pulp molded fresh-keeping food packaging box and a preparation method and application thereof. Background Art

[0002] In today's packaging materials sector, pulp molding products are attracting significant attention for their environmentally friendly properties. Made from fully recyclable plant fibers, they are vacuum-molded and utilize in-mold drying to create environmentally friendly, three-dimensional paper products of varying types and applications. In recent years, my country's pulp molding industry has experienced rapid growth, with production reaching 1.359 million tons in 2023 and domestic consumption reaching 1.218 million tons. The market size has grown from 6.41 billion yuan in 2016 to 21.55 billion yuan in 2023.

[0003] However, most current pulp molded products have significant drawbacks. For one thing, the long growth cycle and high price of wood, the raw material commonly used, not only restrict the industry's cost control and sustainable development but also exacerbate the shortage of wood resources. In contrast, bamboo offers significant advantages as a non-wood fiber raw material. Its strong carbon sequestration capacity effectively expands the source of plant-based fiber raw materials. It also grows quickly, is easy to cultivate, and is environmentally friendly. Bamboo fiber also boasts excellent properties such as breathability, wear resistance, antibacterial and mite-repellent properties, and UV resistance. my country, with abundant bamboo resources, leads the world in bamboo species, planted area, and production. China is vigorously promoting the bamboo-to-plastics initiative. Developing bamboo pulp molded products using bamboo fiber is a key path to promoting the high-quality development of bamboo-to-plastics alternatives in the food packaging sector. On the other hand, compared to plastic packaging materials, the application areas of pulp molded products are limited. They are primarily concentrated in mid- and low-end applications such as egg trays and lunch boxes, with limited applications in high-value packaging, preservation, and storage of agricultural products such as fruits and vegetables. Ordinary pulp molded products have poor hydrophobicity and antibacterial properties, are prone to breeding bacteria, and are difficult to meet the strict requirements of food packaging for freshness and hygiene, which greatly limits their application scope in the food field.

[0004] Therefore, how to develop a high-performance bamboo pulp molded fresh-keeping food packaging box based on bamboo pulp fiber to extend the shelf life of fruits and vegetables at room temperature, effectively ensure the quality of agricultural products and reduce post-harvest losses is an urgent problem that needs to be solved. Summary of the Invention

[0005] In response to the technical problems existing in the prior art, the first purpose of the present invention is to provide a method for preparing a bamboo pulp molded fresh-keeping food packaging box. By combining at least two types of bamboo pulp fibers with the addition of modified plant fiber fillers and functional additives, the mechanical strength, hydrophobicity and antibacterial properties of the packaging box can be effectively improved, breaking through the limitations of the insufficient performance of ordinary pulp molded products.

[0006] The second purpose of the present invention is to provide a bamboo pulp molded fresh-keeping food packaging box made using the preparation method, which has excellent performance, can effectively extend the shelf life of fruits and vegetables and other foods, reduce the material exchange between food and the external environment at room temperature, inhibit bacterial growth, ensure the quality of agricultural products, reduce post-harvest losses, and meet the high requirements of food packaging in terms of preservation and protection.

[0007] The third purpose of the present invention is to provide an application of a bamboo pulp molded fresh-keeping food packaging box, which can be widely used in the packaging of fruits and vegetables, fresh meat products, aquatic products and other foods.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for preparing a bamboo pulp molded fresh-keeping food packaging box, comprising:

[0010] (1) Slurry preparation: Selecting bamboo pulp fiber (MBF) slurry and bamboo pulp fiber (CBF) slurry, respectively performing a decomposition and dispersion treatment on them, mixing the dispersed slurries evenly and performing a beating treatment to obtain a mixed slurry (MBF / CBF); wherein, after the decomposition and dispersion treatment, a bamboo pulp fiber dispersion liquid and a bamboo pulp fiber dispersion liquid are obtained;

[0011] (2) Adding additives: adding modified plant fiber filler (MBP) and functional additives to the mixed slurry, stirring evenly, and obtaining a composite slurry (MBF / CBF / MBP);

[0012] (3) Molding process: the composite slurry is transported to a molding machine, and vacuum filtered and dehydrated to form a bamboo pulp molding wet embryo, and then the wet embryo is subjected to hot pressing, shaping and trimming to obtain a preliminarily formed packaging box;

[0013] (4) Post-processing: spraying the extract for preservation on the outer surface of the preliminarily formed packaging box, and then performing a drying process to obtain a bamboo pulp molded fresh-keeping food packaging box.

[0014] Furthermore, in step (1), a fiber separator is used to decompose the hemp bamboo pulp fiber slurry and the ci bamboo pulp fiber slurry, the power of the fiber separator is 400W, the decomposition speed is 11000-18500r / min, the decomposition time is 5-15min, and the beating speed, concentration and beating degree are controlled during beating. The beating speed is 14500-17000 rpm, the beating concentration is 3.5-4.1%, and the beating degree is 38-44°SR.

[0015] Furthermore, the fiber disintegrator is used to decompose the bamboo pulp fiber slurry at a rotation speed of 11000-14000 r / min and the decomposition time is 5-9 minutes.

[0016] Furthermore, the fiber disintegrator is used to disintegrate the bamboo fiber slurry at a rotation speed of 15500-18500 r / min and a disintegration time of 11-15 min.

[0017] Furthermore, the length of the bamboo pulp fiber is 1540-6230 nm, and the width is 84-752 nm, and the length of the bamboo pulp fiber is 670-1380 nm, and the width is 45-367 nm.

[0018] Furthermore, the mass ratio of the hemp bamboo pulp fiber to the taro bamboo pulp fiber is (4-7): (3-6).

[0019] Furthermore, the beating process uses a Wali beater with a rotation speed of 7.6-8.7 r / s.

[0020] Furthermore, in step (2), the modified plant fiber filler is modified bamboo powder having a particle diameter of 45-380 nm, and the modified bamboo powder is made from bamboo pieces of bamboo older than three years, which are mechanically crushed and silanized, and the amount of the modified bamboo powder added is 2.5-5.5% of the absolute dry weight of the composite slurry. The mechanical crushing is repeated 3-5 times.

[0021] Furthermore, the silanization modification comprises adding a silane coupling agent to ethanol and reacting for 35-45 minutes, then adding the bamboo powder, stirring at room temperature for 50-60 minutes at a speed of 3000-5000 r / min, then stirring at high speed at 90-95°C for 150-180 minutes at a speed of 7000-9000 r / min, and finally washing away excess coupling agent with ethanol. The silane coupling agent is selected from methyltrimethoxysilane (MTMS).

[0022] Furthermore, the functional additive includes a waterproofing agent, which is an inorganic hybrid acrylic emulsion, and the amount of the waterproofing agent added is 1.5-3.5% of the mass of the absolute dry pulp. The inorganic hybrid acrylic emulsion does not contain fluorine and has a solid content of 25%.

[0023] Furthermore, the mass concentration of the composite slurry is 0.05-0.35%.

[0024] Furthermore, in step (3), the vacuum degree during vacuum filtration dehydration is -0.035-0.050 MPa, the dehydration time is 15-25 s, the moisture content after dehydration is 65-75%, and the pressure of hot pressing is 50-80 kg / cm 2 , temperature is 185-230℃, time is 16-22s.

[0025] Furthermore, in step (4), the extract is a bamboo leaf flavonoids aqueous solution with a concentration of 0.5-4.0% and a spraying amount of 0.5-2.5 g / m2 The drying method is infrared drying at 130-180℃ for 30-45min.

[0026] A bamboo pulp molded fresh-keeping food packaging box is obtained by the above-mentioned preparation method, wherein the performance indicators of the packaging box are as follows:

[0027] Basis weight is 35-39g / m 2 , tensile index is 73.8-82.6N·m / g, burst resistance index is 6.03-6.75kPa·m 2 / g, water contact angle is 112-137°, oxygen permeability is 0.46-0.57cm 3 / m 2 ·day·0.1MPa, water vapor transmission rate is 0.84-1.07g / m 2 ·day, the oil-proof grade is 9-12, and the antibacterial rate is 89-96%.

[0028] The application of the above-mentioned bamboo pulp molded fresh-keeping food packaging box in the field of food packaging.

[0029] Furthermore, the food packaging field is used for packaging of fruits and vegetables, fresh meat products, and aquatic products.

[0030] The present invention has the following advantages:

[0031] 1. The bamboo pulp molded fresh-keeping food packaging box of the present invention uses bamboo as the core raw material. As a non-wood fiber raw material, bamboo has a stronger carbon sequestration capacity than ordinary wood, which effectively alleviates the problem of limited wood resources, broadens the source of plant fiber raw materials, gives full play to the advantages of my country's rich bamboo resources, improves the utilization rate of bamboo, conforms to the green development concept of replacing plastic with bamboo, opens up a new path for the sustainable development of the packaging industry, and achieves the dual goals of efficient resource utilization and environmental protection.

[0032] 2. The performance of the bamboo pulp molded fresh-keeping food packaging box of the present invention is significantly improved, specifically including the following aspects:

[0033] (1) In terms of mechanical properties, the mechanical properties of the packaging box are improved by compounding the MBF and CBF, and then reinforcing them with the filler of modified MBF powder. Among them, MBF is a large clumping bamboo with thick stems, long primary fibers, thick fiber cell walls, and a high degree of lignification; CBF is a medium-sized clumping bamboo with relatively thin and soft stems, short primary fibers, fine CBF fibers, and a low lignin content. Therefore, the MBF pulp fibers obtained from MBF are long and strong, which can significantly improve the physical strength; the CBF pulp fibers obtained from CBF are short and soft, and can be evenly filled between long fibers. The reasonable compounding of the two bamboo pulp fibers can effectively ensure the matching of length, hardness and softness, and close combination between fibers, thereby improving the compatibility of fiber interfaces.

[0034] Bamboo powder contains bamboo quinone, which is a natural antibacterial component produced by bamboo through its own biosynthesis during its growth. It has natural antibacterial, anti-mite and deodorizing medicinal properties. During the silanization modification process of bamboo powder, the silane coupling agent will form a hydrophobic layer with low surface energy on the surface of bamboo fiber. The silane coupling agent has a unique double-headed structure, with an organic functional group (hydrophobic end) at one end and a hydrolyzable siloxy group (inorganic end) at the other end. This structure enables the silane coupling agent to form a monolayer or a cross-linked network on the fiber surface, realizing the dual functions of "molecular anchoring + hydrophobic modification". Therefore, the modified bamboo powder has the effects of enhancement, antibacterial and moisture-proof. Judging from the data in the examples, the quantitative amount can reach 35-39g / m 2 , tensile index 73.8-82.6N·m / g, burst resistance index 6.03-6.75kPa·m 2 / g, can provide reliable physical protection for food during storage and transportation, and reduce damage caused by external forces.

[0035] (2) In terms of barrier properties, the addition of inorganic hybrid acrylic emulsion (fluorine-free) and modified bamboo powder enhances the waterproof and oil-proof and barrier properties of the packaging box. Its water contact angle reaches 112-137° and the oxygen permeability is 0.46-0.57cm 3 / m 2 ·day·0.1MPa, water vapor transmission rate 0.84-1.07g / m 2 ·day, it can effectively prevent the exchange of external moisture, oxygen and other substances with food, greatly extending the shelf life of food and maintaining the freshness and quality of food.

[0036] (3) In terms of antibacterial properties, the synergistic effect of modified bamboo powder and bamboo leaf flavonoids gives the packaging box antibacterial properties, with an inhibition rate of 89-96% against Staphylococcus aureus and Escherichia coli. This effectively inhibits bacterial growth, ensures food hygiene and safety, and reduces the risk of food spoilage during storage and sales. Among them, bamboo leaf flavonoids are a natural flavonoid compound extracted from bamboo leaves. It has multiple biological activities, including antioxidant, antibacterial, and anti-inflammatory effects, and has great potential in food preservation.

[0037] 3. The bamboo pulp molded fresh-keeping food packaging box of the present invention has broad application prospects in the food packaging field. For fruit and vegetable packaging, it can extend the shelf life and maintain the freshness and taste of the fruit. When used for packaging fresh meat products and aquatic products, it can prevent food spoilage and reduce nutrient loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The present invention is a schematic diagram of the process of preparing a bamboo pulp molded fresh-keeping food packaging box.

[0039] Figure 2 This is a product diagram of the bamboo pulp molded fresh-keeping food packaging box of the present invention. DETAILED DESCRIPTION

[0040] The present invention is described in further detail below with reference to the examples, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field. The test methods for which specific experimental conditions are not specified in the following examples are generally carried out under conventional experimental conditions. Unless otherwise specified, the reagents and raw materials used in the present invention can be obtained commercially. Among them, the hemp bamboo pulp fiber (MBF) and the ciba bamboo pulp fiber (CBF) involved in the embodiments of the present invention were obtained from the State Key Laboratory of Pulping and Papermaking Engineering. The inorganic hybrid acrylic emulsion involved in the embodiments of the present invention was purchased from a chemical company, methyltrimethoxysilane (MTMS) was purchased from Shanghai McLean Biochemical Technology Co., Ltd., and bamboo leaf flavonoids were purchased from Shanghai Ruichu Biotechnology Co., Ltd.

[0041] The various parameters involved in the embodiments of the present invention are tested according to national standard testing methods and industry standards, specifically:

[0042] ①Quantitative determination (GB / T 451.2-2002);

[0043] ②Tensile index (GB / T 453-2002);

[0044] ③ Burst index (GB / T 454-2002);

[0045] ④ Water contact angle (GB / T 30447-2013);

[0046] ⑤Oxygen permeability (GB / T 19789-2005);

[0047] ⑥ Water vapor transmission rate (GB / T 22921-2008).

[0048] ⑦Inhibition rate (GB15979-2002), the colonies selected were Staphylococcus aureus (BNCC188012) and Escherichia coli (BNCC364150), both purchased from a biotechnology company.

[0049] ⑧Oil-proof Kit Test Method: Prepare the oil-proof grade test reagent using the recipe in the kit formula table. Then, place a drop of the test reagent on the paper. After 15 seconds, wipe off the reagent. If there is no shadow stain on the paper surface, it indicates that the grade corresponding to this test reagent has been reached. By adding higher-grade test reagents in succession, the highest oil-proof grade of the grease-proof paper can be obtained.

[0050] Example 1

[0051] The specific preparation steps of this embodiment are as follows:

[0052] (1) Pulp preparation: The hemp bamboo pulp fiber pulp was dispersed in a fiber disintegrator (power: 400W) at a speed of 11000r / min for 5min to obtain MBF dispersion solution; the cycad bamboo pulp fiber pulp was dispersed in a fiber disintegrator (power: 400W) at a speed of 15500r / min for 11min to obtain CBF dispersion solution. Then, the MBF (length: 1540-6230nm, width: 84-752nm) solution and the CBF (length: 670-1380nm, width: 45-367nm) solution were mixed, and the absolute dry mass ratio of MBF fiber to CBF fiber was 7:3. The mixed pulp was then beaten in a Wali beater (speed: 7.6r / s) at a beating speed of 14500 rpm, a beating concentration of 3.5%, and a beating degree of 38°SR to obtain MBF / CBF mixed pulp;

[0053] (2) Adding auxiliary agents: adding modified bamboo powder (MBP) (particle diameter: 45-380 nm) to the MBF / CBF mixed slurry solution in step (1) under high-speed stirring (rotation speed: 6000 r / min), the amount of modified bamboo powder added is 2.5% of the absolute dry mass of the MBF / CBF / MBP mixed slurry, and mixing them uniformly to obtain MBF / CBF / MBP composite slurry; then adding inorganic hybrid acrylic emulsion (solid content of 25%), the amount of which is 1.5% of the absolute dry mass of the slurry, and stirring for 3 minutes with an electric stirrer (rotation speed of 4000 r / min) to obtain a composite slurry;

[0054] (3) Molding process: The composite slurry obtained in step (2) is transported to a molding machine through a pipeline at a mass concentration of 0.05%, and is dehydrated by vacuum filtration (vacuum degree is -0.035MPa, dehydration under negative suction pressure for 10s) to obtain a bamboo pulp molding wet embryo (moisture content is 75%). 2 , hot pressing for 16 seconds at 185℃, and then trimming to obtain a preliminarily formed packaging box;

[0055] (4) Post-treatment: The outer surface of the preliminarily formed packaging box obtained in step (3) is evenly sprayed with a 0.5% bamboo leaf flavonoids aqueous solution, with a surface spraying amount of 0.5 g / m 2 , and then infrared drying at 130°C for 30 minutes to prepare a bamboo pulp molded fresh-keeping food packaging box.

[0056] The performance indicators of the bamboo pulp molded fresh-keeping food packaging box prepared in this embodiment are as follows: Basis weight: 35g / m 2;Tensile index: 73.8N·m / g;Burst index: 6.03kPa·m 2 / g; water contact angle: 112°; oxygen permeability: 0.57cm 3 / m 2 ·day·0.1MPa; Water vapor transmission rate: 1.07g / m 2 ·day; oil-proof grade: 9; antibacterial rate: 89%.

[0057] Example 2

[0058] The specific preparation steps of this embodiment are as follows:

[0059] (1) Pulp preparation: The hemp bamboo pulp fiber pulp was dispersed in a fiber disintegrator (power: 400W) at a speed of 12000r / min for 7 minutes to obtain MBF dispersion solution; the cycad bamboo pulp fiber pulp was dispersed in a fiber disintegrator (power: 400W) at a speed of 16500r / min for 12 minutes to obtain CBF dispersion solution. Then, the MBF (length: 1540-6230nm, width: 84-752nm) solution and the CBF (length: 670-1380nm, width: 45-367nm) solution were mixed, and the absolute dry mass ratio of MBF fiber to CBF fiber was 6:4. The mixed pulp was then beaten in a Wali beater (speed: 8.1r / s) at a beating speed of 15500, a beating concentration of 3.7%, and a beating degree of 40°SR to obtain MBF / CBF mixed pulp;

[0060] (2) Adding auxiliary agents: adding modified bamboo powder (MBP) (particle diameter: 45-380 nm) to the MBF / CBF mixed slurry solution in step (1) under high-speed stirring (rotation speed: 6000 r / min), the amount of modified bamboo powder added is 3.5% of the absolute dry mass of the MBF / CBF / MBP mixed slurry, and mixing them uniformly to obtain MBF / CBF / MBP composite slurry; then adding inorganic hybrid acrylic emulsion (solid content of 25%), the amount of which is 2.5% of the absolute dry mass of the slurry, and stirring for 3 minutes with an electric stirrer (rotation speed of 4000 r / min) to obtain a composite slurry;

[0061] (3) Molding process: The composite slurry obtained in step (2) is transported to a molding machine through a pipeline at a mass concentration of 0.15%, and is dehydrated by vacuum filtration (vacuum degree is -0.040MPa, dehydration under negative suction pressure for 15s) to obtain a bamboo pulp molding wet embryo (moisture content is 72%). 2 , hot pressing for 18 seconds at a temperature of 195°C, and then trimming to obtain a preliminarily formed packaging box;

[0062] (4) Post-treatment: The outer surface of the preliminarily formed packaging box obtained in step (3) is evenly sprayed with a 1.5% aqueous solution of bamboo leaf flavonoids, with a surface spraying amount of 1.5 g / m 2 , and then infrared drying at 150°C for 35 minutes to prepare a bamboo pulp molded fresh-keeping food packaging box.

[0063] The performance indicators of the bamboo pulp molded fresh-keeping food packaging box prepared in this embodiment are as follows: Basis weight: 36g / m 2 ;Tensile index: 75.4N·m / g;Burst index: 6.24kPa·m 2 / g; water contact angle: 118°; oxygen permeability: 0.52cm 3 / m 2 ·day·0.1MPa; Water vapor transmission rate: 1.02g / m 2 ·day; oil-proof grade: 10; antibacterial rate: 92%.

[0064] Example 3

[0065] The specific preparation steps of this embodiment are as follows:

[0066] (1) Pulp preparation: The hemp bamboo pulp fiber pulp was dispersed in a fiber disintegrator (power: 400W) at a speed of 13000r / min for 8 minutes to obtain MBF dispersion solution; the cycad bamboo pulp fiber pulp was dispersed in a fiber disintegrator (power: 400W) at a speed of 17500r / min for 14 minutes to obtain CBF dispersion solution. Then, the MBF (length: 1540-6230nm, width: 84-752nm) solution and the CBF (length: 670-1380nm, width: 45-367nm) solution were mixed, and the absolute dry mass ratio of MBF fiber to CBF fiber was 5:5. The mixed pulp was then beaten in a Wali beater (speed: 8.4r / s) at a beating speed of 16500, a beating concentration of 3.9%, and a beating degree of 42°SR to obtain MBF / CBF mixed pulp;

[0067] (2) Adding auxiliary agents: adding modified bamboo powder (MBP) (particle diameter: 45-380 nm) to the MBF / CBF mixed slurry solution in step (1) under high-speed stirring (rotation speed: 6000 r / min), the amount of modified bamboo powder added is 4.5% of the absolute dry mass of the MBF / CBF / MBP mixed slurry, and mixing them uniformly to obtain MBF / CBF / MBP composite slurry; then adding inorganic hybrid acrylic emulsion (solid content of 25%), the amount of which is 3.0% of the absolute dry mass of the slurry, and stirring for 3 minutes with an electric stirrer (rotation speed of 4000 r / min) to obtain a composite slurry;

[0068] (3) Molding: The composite slurry obtained in step (2) was transported to a molding machine through a pipeline at a mass concentration of 0.25%, and vacuum filtered and dehydrated (vacuum degree of -0.045 MPa, dehydration under negative suction pressure for 20 seconds) to obtain a bamboo pulp molding wet embryo (moisture content of 68%). 2 2. Hot pressing for 20 seconds at a temperature of 215°C to set the shape, and then trimming to obtain a preliminarily formed packaging box;

[0069] (4) Post-treatment: The outer surface of the preliminarily formed packaging box obtained in step (3) is evenly sprayed with a 3.0% aqueous solution of bamboo leaf flavonoids, with a surface spraying amount of 2.0 g / m 2 , and then infrared drying at 170°C for 40 minutes to prepare a bamboo pulp molded fresh-keeping food packaging box.

[0070] The performance indicators of the bamboo pulp molded fresh-keeping food packaging box prepared in this embodiment are as follows: Basis weight: 38g / m 2 ;Tensile index: 79.3N·m / g;Burst index: 6.55kPa·m 2 / g; water contact angle: 126°; oxygen permeability: 0.48cm 3 / m 2 ·day·0.1MPa; Water vapor transmission rate: 0.95g / m 2 ·day; oil-proof grade: 11; antibacterial rate: 95%.

[0071] Example 4

[0072] The specific preparation steps of this embodiment are as follows:

[0073] (1) Preparation of bamboo pulp: The hemp bamboo pulp fiber pulp was dispersed in a fiber disintegrator (power: 400W) at a speed of 14000r / min for 9 minutes to obtain MBF dispersion solution; the ci bamboo pulp fiber pulp was dispersed in a fiber disintegrator (power: 400W) at a speed of 18500r / min for 15 minutes to obtain CBF dispersion solution. Then, the MBF (length: 1540-6230nm, width: 84-752nm) solution and the CBF (length: 670-1380nm, width: 45-367nm) solution were mixed, and the absolute dry mass ratio of MBF fiber to CBF fiber was 4:6. The mixed pulp was then beaten in a Wali beater (speed: 8.7r / s) at a beating speed of 17000, a beating concentration of 4.1%, and a beating degree of 44°SR to obtain MBF / CBF mixed pulp;

[0074] (2) Adding additives: adding modified bamboo powder (MBP) (particle diameter: 45-380 nm) to the MBF / CBF mixed slurry solution in step (1) under high-speed stirring (rotation speed: 6000 r / min), the amount of modified bamboo powder added is 5.5% of the absolute dry mass of the MBF / CBF / MBP mixed slurry, and mixing uniformly to obtain MBF / CBF / MBP composite slurry; then adding inorganic hybrid acrylic emulsion (solid content of 25%), the amount of which is 3.5% of the absolute dry mass of the slurry, and stirring for 3 minutes with an electric stirrer (rotation speed of 4000 r / min) to obtain a composite slurry;

[0075] (3) Molding process: The composite slurry obtained in step (2) is transported to a molding machine through a pipeline at a mass concentration of 0.35%, and is dehydrated by vacuum filtration (vacuum degree is -0.050MPa, dehydration under negative suction pressure for 25s) to obtain a bamboo pulp molding wet embryo (moisture content is 65%). 2 2. Hot pressing for 22 seconds at a temperature of 230°C to set the shape, and then trimming to obtain a preliminarily formed packaging box;

[0076] (4) Post-treatment: The outer surface of the preliminarily formed packaging box obtained in step (3) is evenly sprayed with a 4.0% aqueous solution of bamboo leaf flavonoids, with a surface spraying amount of 2.5 g / m 2 , and then infrared drying at 180°C for 45 minutes to prepare a bamboo pulp molded fresh-keeping food packaging box.

[0077] The performance indicators of the bamboo pulp molded fresh-keeping food packaging box prepared in this embodiment are as follows: Basis weight: 39g / m 2 ;Tensile index: 82.6N·m / g;Burst index: 6.75kPa·m 2 / g; water contact angle: 137°; oxygen permeability: 0.46cm 3 / m 2 ·day·0.1MPa; Water vapor transmission rate: 0.84g / m 2 ·day; oil-proof grade: 12; antibacterial rate: 96%.

[0078] Comparative Example 1

[0079] This comparative example differs from Example 1 in that modified bamboo powder is not added. The specific preparation steps are as follows:

[0080] (1) Pulp preparation: The hemp bamboo pulp fiber pulp was dispersed in a fiber disintegrator (power: 400W) at a speed of 11000r / min for 5min to obtain MBF dispersion solution; the cycad bamboo pulp fiber pulp was dispersed in a fiber disintegrator (power: 400W) at a speed of 15500r / min for 11min to obtain CBF dispersion solution. Then, the MBF (length: 1540-6230nm, width: 84-752nm) solution and the CBF (length: 670-1380nm, width: 45-367nm) solution were mixed, and the absolute dry mass ratio of MBF fiber to CBF fiber was 7:3. The mixed pulp was then beaten in a Wali beater (speed: 7.6r / s) at a beating speed of 14500 rpm, a beating concentration of 3.5%, and a beating degree of 38°SR to obtain MBF / CBF mixed pulp;

[0081] (2) Adding an auxiliary agent: adding an inorganic hybrid acrylic emulsion (solid content of 25%) to the MBF / CBF mixed slurry solution in step (1) in an amount of 1.5% of the absolute dry slurry mass, stirring for 3 minutes with an electric stirrer (speed of 4000 r / min) to obtain a composite slurry;

[0082] (3) Molding process: The composite slurry obtained in step (2) is transported to a molding machine through a pipeline at a mass concentration of 0.05%, and is dehydrated by vacuum filtration (vacuum degree is -0.035MPa, dehydration under negative suction pressure for 10s) to obtain a bamboo pulp molding wet embryo (moisture content is 75%). 2 , hot pressing for 16 seconds at 185℃, and then trimming to obtain a preliminarily formed packaging box;

[0083] (4) Post-treatment: The outer surface of the preliminarily formed packaging box obtained in step (3) is evenly sprayed with a 0.5% bamboo leaf flavonoids aqueous solution, with a surface spraying amount of 0.5 g / m 2 , and then infrared drying at 130°C for 30 minutes to prepare a bamboo pulp molded fresh-keeping food packaging box.

[0084] The performance indicators of the bamboo pulp molded fresh-keeping food packaging box prepared in this comparative example are as follows: Basis weight: 35g / m 2 ;Tensile index: 51.7N·m / g;Burst index: 4.82kPa·m 2 / g; water contact angle: 96°; oxygen permeability: 1.26cm 3 / m 2 ·day·0.1MPa; Water vapor transmission rate: 3.54g / m 2 ·day; oil-proof grade: 7; antibacterial rate: 74%.

[0085] Comparative Example 2

[0086] The difference between this comparative example and Example 1 is that no inorganic hybrid acrylic emulsion is added. The specific preparation steps are as follows:

[0087] (1) Pulp preparation: The hemp bamboo pulp fiber pulp was dispersed in a fiber disintegrator (power: 400W) at a speed of 11000r / min for 5min to obtain MBF dispersion solution; the cycad bamboo pulp fiber pulp was dispersed in a fiber disintegrator (power: 400W) at a speed of 15500r / min for 11min to obtain CBF dispersion solution. Then, the MBF (length: 1540-6230nm, width: 84-752nm) solution and the CBF (length: 670-1380nm, width: 45-367nm) solution were mixed, and the absolute dry mass ratio of MBF fiber to CBF fiber was 7:3. The mixed pulp was then beaten in a Wali beater (speed: 7.6r / s) at a beating speed of 14500 rpm, a beating concentration of 3.5%, and a beating degree of 38°SR to obtain MBF / CBF mixed pulp;

[0088] (2) Adding an auxiliary agent: adding modified bamboo powder (MBP) (particle diameter: 45-380 nm) to the MBF / CBF mixed slurry solution in step (1) under high-speed stirring (rotation speed: 6000 r / min), wherein the amount of modified bamboo powder added is 2.5% of the absolute dry mass of the MBF / CBF / MBP mixed slurry, and mixing uniformly to obtain a composite slurry;

[0089] (3) Molding process: The composite slurry obtained in step (2) is transported to a molding machine through a pipeline at a mass concentration of 0.05%, and is dehydrated by vacuum filtration (vacuum degree is -0.035MPa, dehydration under negative suction pressure for 10s) to obtain a bamboo pulp molding wet embryo (moisture content is 75%). 2 , hot pressing for 16 seconds at 185℃, and then trimming to obtain a preliminarily formed packaging box;

[0090] (4) Post-treatment: The outer surface of the preliminarily formed packaging box obtained in step (3) is evenly sprayed with a 0.5% bamboo leaf flavonoids aqueous solution, with a surface spraying amount of 0.5 g / m 2 , and then infrared drying at 130°C for 30 minutes to prepare a bamboo pulp molded fresh-keeping food packaging box.

[0091] The performance indicators of the bamboo pulp molded fresh-keeping food packaging box prepared in this comparative example are as follows: Basis weight: 35g / m 2 ;Tensile index: 61.4N·m / g;Burst index: 5.32kPa·m 2 / g; water contact angle: 84°; oxygen permeability: 1.73cm 3 / m 2 ·day·0.1MPa; Water vapor transmission rate: 2.85g / m 2 ·day; oil-proof grade: 4; antibacterial rate: 87%.

[0092] Comparative Example 3

[0093] The difference between this comparative example and Example 1 is that no bamboo leaf flavonoids aqueous solution is added, and the specific preparation steps are as follows:

[0094] (1) Pulp preparation: The hemp bamboo pulp fiber pulp was dispersed in a fiber disintegrator (power: 400W) at a speed of 11000r / min for 5min to obtain MBF dispersion solution; the cycad bamboo pulp fiber pulp was dispersed in a fiber disintegrator (power: 400W) at a speed of 15500r / min for 11min to obtain CBF dispersion solution. Then, the MBF (length: 1540-6230nm, width: 84-752nm) solution and the CBF (length: 670-1380nm, width: 45-367nm) solution were mixed, and the absolute dry mass ratio of MBF fiber to CBF fiber was 7:3. The mixed pulp was then beaten in a Wali beater (speed: 7.6r / s) at a beating speed of 14500 rpm, a beating concentration of 3.5%, and a beating degree of 38°SR to obtain MBF / CBF mixed pulp;

[0095] (2) Adding auxiliary agents: adding modified bamboo powder (MBP) (particle diameter: 45-380 nm) to the MBF / CBF mixed slurry solution in step (1) under high-speed stirring (rotation speed: 6000 r / min), the amount of modified bamboo powder added is 2.5% of the absolute dry mass of the MBF / CBF / MBP mixed slurry, and mixing them uniformly to obtain MBF / CBF / MBP composite slurry; then adding inorganic hybrid acrylic emulsion (solid content of 25%), the amount of which is 1.5% of the absolute dry mass of the slurry, and stirring for 3 minutes with an electric stirrer (rotation speed of 4000 r / min) to obtain a composite slurry;

[0096] (3) Molding process: The composite slurry obtained in step (2) is transported to a molding machine through a pipeline at a mass concentration of 0.05%, and is dehydrated by vacuum filtration (vacuum degree is -0.035MPa, dehydration under negative suction pressure for 10s) to obtain a bamboo pulp molding wet embryo (moisture content is 75%). 2 , hot pressing for 16 seconds at a temperature of 185°C, trimming, and then infrared drying at 130°C for 30 minutes to prepare a bamboo pulp molded fresh-keeping food packaging box.

[0097] The performance indicators of the bamboo pulp molded fresh-keeping food packaging box prepared in this comparative example are as follows: Basis weight: 35g / m 2 ;Tensile index: 67.3N·m / g;Burst index: 5.66kPa·m 2 / g; water contact angle: 109°; oxygen permeability: 0.83cm 3 / m 2 ·day·0.1MPa; Water vapor transmission rate: 1.45g / m 2 ·day; oil-proof grade: 9; antibacterial rate: 62%.

[0098] Comparative Example 4

[0099] The difference between this comparative example and Example 1 is that the pulp is a mixture of moso bamboo pulp fiber and green bamboo pulp fiber. The specific preparation steps are as follows:

[0100] (1) Pulp preparation: The moso bamboo pulp fiber pulp was dispersed in a fiber disintegrator (power: 400W) at a speed of 11000r / min for 5min to obtain a GBF dispersion solution; the green bamboo pulp fiber pulp was dispersed in a fiber disintegrator (power: 400W) at a speed of 15500r / min for 11min to obtain a LBF dispersion solution. The GBF (length: 337-873nm, width: 48-279nm) solution and the LBF (length: 284-585nm, width: 36-272nm) solution were then mixed, and the absolute dry weight ratio of GBF fiber to LBF fiber was 7:3. The mixed pulp was then beaten in a Wali beater (speed: 7.6r / s) at a beating speed of 14500 rpm, a beating concentration of 3.5%, and a beating degree of 38°SR to obtain a GBF / LBF mixed pulp.

[0101] (2) Adding auxiliary agents: adding modified bamboo powder (MBP) (particle diameter: 45-380 nm) to the GBF / LBF mixed slurry solution in step (1) under high-speed stirring (rotation speed: 6000 r / min), the amount of modified bamboo powder added is 2.5% of the absolute dry mass of the GBF / LBF / MBP mixed slurry, and mixing uniformly to obtain a GBF / LBF / MBP composite slurry; then adding an inorganic hybrid acrylic emulsion (solid content of 25%), the amount of which is 1.5% of the absolute dry mass of the slurry, and stirring for 3 minutes with an electric stirrer (rotation speed of 4000 r / min) to obtain a composite slurry;

[0102] (3) Molding process: The composite slurry obtained in step (2) is transported to a molding machine through a pipeline at a mass concentration of 0.05%, and is dehydrated by vacuum filtration (vacuum degree is -0.035MPa, dehydration under negative suction pressure for 10s) to obtain a bamboo pulp molding wet embryo (moisture content is 75%). 2 , hot pressing for 16 seconds at 185℃, and then trimming to obtain a preliminarily formed packaging box;

[0103] (4) Post-treatment: The outer surface of the preliminarily formed packaging box obtained in step (3) is evenly sprayed with a 0.5% bamboo leaf flavonoids aqueous solution, with a surface spraying amount of 0.5 g / m 2 , and then infrared drying at 130°C for 30 minutes to prepare a bamboo pulp molded fresh-keeping food packaging box.

[0104] The performance indicators of the bamboo pulp molded fresh-keeping food packaging box prepared in this comparative example are as follows: Basis weight: 35g / m 2 ;Tensile index: 51.7N·m / g;Burst index: 4.86kPa·m 2 / g; water contact angle: 97°; oxygen permeability: 1.14cm 3 / m 2 ·day·0.1MPa; Water vapor transmission rate: 3.63g / m 2 ·day; oil-proof grade: 9; antibacterial rate: 76%.

[0105] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a bamboo pulp molded fresh-keeping food packaging box, characterized in that: The following steps are involved: (1) Slurry preparation: selecting hemp bamboo pulp fiber slurry and ci bamboo pulp fiber slurry, respectively performing dispersing treatment on them, and mixing the dispersed slurries to obtain a mixed slurry; (2) Adding additives: adding modified plant fiber fillers and functional additives to the mixed slurry, stirring evenly, to obtain a composite slurry; (3) Molding: The composite slurry is transported to a molding machine, dehydrated by vacuum filtration to form a wet embryo, and then the wet embryo is subjected to hot pressing, shaping, and trimming to obtain a preliminarily formed packaging box; (4) Post-processing: spraying the extract for preservation on the outer surface of the preliminarily formed packaging box, and then performing a drying process to obtain a bamboo pulp molded fresh-keeping food packaging box.

2. The preparation method according to claim 1, characterized in that In step (1), a fiber separator is used to decompose the hemp bamboo pulp fiber slurry and the ci bamboo pulp fiber slurry, the decomposition speed is 11000-18500r / min, the decomposition time is 5-15min, and the beating speed, concentration and beating degree are controlled during beating. The beating speed is 14500-17000 rpm, the beating concentration is 3.5-4.1%, and the beating degree is 38-44°SR.

3. The preparation method according to claim 1, characterized in that In step (2), the modified plant fiber filler is modified bamboo powder, which is made from bamboo slices through mechanical crushing and silanization modification. The added amount of the modified bamboo powder accounts for 2.5-5.5% of the absolute dry mass of the compound slurry.

4. The preparation method according to claim 3, characterized in that The silanization modification comprises adding a silane coupling agent into ethanol and reacting for 35-45 minutes, then adding the bamboo powder, stirring at room temperature for 50-60 minutes, then stirring at high speed at 90-95° C. for 150-180 minutes, and finally washing away excess coupling agent with ethanol.

5. The preparation method according to claim 1, characterized in that The functional additive includes a waterproofing agent, which is an inorganic hybrid acrylic emulsion, and the addition amount thereof is 1.5-3.5% of the mass of the absolute dry pulp.

6. The preparation method according to claim 1, characterized in that In step (3), the vacuum degree during vacuum filtration and dehydration is -0.035 to 0.050 MPa, the dehydration time is 15 to 25 seconds, and the pressure during hot pressing is 50 to 80 kg / cm 2 , temperature is 185-230℃, time is 16-22s.

7. The preparation method according to claim 1, characterized in that In step (4), the extract is a bamboo leaf flavonoids aqueous solution with a concentration of 0.5-4.0% and a spraying amount of 0.5-2.5 g / m 2 The drying method is infrared drying at 130-180℃ for 30-45min.

8. A bamboo pulp molded fresh-keeping food packaging box, characterized in that: The packaging box is obtained by the preparation method according to any one of claims 1 to 7, wherein the performance indicators of the packaging box are as follows: Basis weight is 35-39g / m 2 , tensile index is 73.8-82.6N·m / g, burst resistance index is 6.03-6.75kPa·m 2 / g, water contact angle is 112-137°, oxygen permeability is 0.46-0.57cm 3 / m 2 ·day·0.1MPa, water vapor transmission rate is 0.84-1.07g / m 2 ·day, the oil-proof grade is 9-12, and the antibacterial rate is 89-96%.

9. Use of the bamboo pulp molded fresh-keeping food packaging box according to claim 8 in the field of food packaging.

10. The use according to claim 9, characterized in that The food packaging field is used for packaging of fruits and vegetables, fresh meat products, and aquatic products.

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