Environment-friendly degradable paper pulp molded product and preparation method thereof

Abstract

The invention relates to the technical field of pulp molding preparation, in particular to an environment-friendly degradable pulp molding product and a preparation method thereof.The preparation method comprises the steps that modified starch is added into deionized water for low-temperature pre-gelatinization, and a pre-gelatinized modified starch solution is obtained; mixing the pre-gelatinized modified starch solution with paper pulp fibers, and performing deep gelatinization to obtain starch-coated fiber slurry; adding a bio-based cross-linking agent into deionized water, and stirring to obtain a bio-based cross-linking agent solution; dropwise adding the bio-based cross-linking agent solution into the starch-coated fiber slurry in a pulse manner, stirring, and carrying out ultrasonic treatment to obtain composite paper pulp; adding a waterproof agent into the composite paper pulp, and stirring to obtain hydrophobic modified paper pulp; and the hydrophobic modified paper pulp is poured into forming equipment to be subjected to segmented pre-hot-pressing forming treatment and then put into steeping liquor to be steeped, then hot-pressing drying is conducted, and a paper pulp molded product is obtained. According to the preparation method, the surface strength and the internal binding force of the product are enhanced through the synergistic effect of the modified starch and the bio-based cross-linking agent.

Description

Technical Field

[0001] The present invention relates to the technical field of pulp molding preparation, and particularly relates to an environment-friendly and degradable pulp molding product and a preparation method thereof. Background Art

[0002] With the rapid development of social economy and the continuous improvement of people's living standards, the market has higher and higher requirements for the performance of packaging materials; especially in the packaging fields of sensitive and fragile items such as high-end electronic products and optical products, higher requirements are put forward for the surface strength and wear resistance of packaging materials. Pulp molding products have gradually become an important choice for packaging materials due to their environmental protection, renewable and other advantages. However, the current pulp molding preparation technology still encounters multiple challenges, especially the surface strength and internal bonding strength indicators cannot meet the needs of the high-end market. At present, the production of pulp molding products is generally restricted by the supply status of pulp raw materials and the technical level of production processes; common pulp raw materials mainly include wood fibers, waste paper recycled fibers, etc. Due to the diverse fiber structures of these raw materials, their physical and mechanical properties are significantly different, which directly affects the strength and durability of pulp molding products; in addition, during the production process, due to the lack of effective additives and the deficiency of process optimization means, the bonding strength between the surface layer and the internal fiber layer of the products is low, and problems such as hair loss and powder loss are likely to occur, which not only damages the appearance quality of the products, but also greatly reduces their practical application value.

[0003] In the context of increasingly diverse market demands, the existing pulp molding technology urgently needs to be upgraded and innovated. The existing patent, with the patent number CN202311727215.9, discloses a paper-plastic pulp, a paper-plastic product, and a paper-plastic manufacturing process. This method adds various additives, such as dispersants, fillers, wet strength agents, internal sizing agents, and retention aids, etc., and ensures that each additive can be efficiently deposited on the surface of pulp fibers. By utilizing the functions of each additive and the synergistic effects among them, the strength and hardness of the paper-plastic product are greatly improved. However, this method sacrifices the original flexibility of the fibers, resulting in a decrease in the flexibility of the paper-plastic product. Moreover, when compounded with inorganic fillers, it may weaken the waterproof effect of the paper-plastic product. The existing patent, with the patent number CN201811589785.5, discloses an internal additive for preventing chipping of pulp molding packaging products. By developing an internal additive, the produced pulp molding products form a structure with a smooth surface and tightly bonded internal fibers. However, the dosage of the nano-silica dispersion liquid in the formula reaches 10%, which will greatly increase the production cost of the products. And this patent mainly focuses on anti-chipping and surface properties, without mentioning whether key indicators such as waterproofness and compressive strength are improved simultaneously. The existing patent, with the patent number CN202310535457.1, discloses a bacterial cellulose-based pulp molding packaging material, its preparation method and application. By synthesizing bacterial cellulose through microbial fermentation and compounding it with bamboo pulp and plant cellulose nanofibrils, a multi-scale fiber network structure is formed. Although the mechanical strength and oxygen barrier performance of the packaging material have been greatly improved, in industrial production, factors such as raw material cost and production efficiency still need to be considered, and its practicality and popularization need to be further verified. The existing patent, with the patent number CN202211735353.7, discloses a preparation method of a pulp molding packaging product. This method prepares the pulp molding packaging product through dry injection molding, without using water and with high production efficiency. However, dry molding may cause loose fiber bonding, affecting its mechanical properties. And the formula contains more than 10 additives, most of which are petrochemical derivatives or non-biodegradable materials, which will affect its environmental protection and biodegradability. The existing patent, with the patent number CN202311061222.X, discloses a pulp molding product, its preparation method and application, and a product with an oil-proof grade (up to grade 11), a water absorption rate (as low as 26%), and a degradation time (60 days) is obtained, which can be applied to Chinese food tableware or cosmetic packaging. However, it involves alkaline cooking and multi-step mixing, with high energy consumption and low production efficiency, not meeting the low-carbon goal of green manufacturing. The existing patent, with the patent number CN201911001071.2, discloses a manufacturing method and a preparation system of pulp molded products. By adding wet strength and sizing to enhance the tensile strength (increased to 2.5 - 3.5 kN / m 2) Burst resistance (150 - 190 kPa) and hydrophobicity; however, bis(triazine amino) type fluorescent brighteners and azo dyes may migrate to food contact surfaces, posing safety hazards.

[0004] The above patents have improved certain properties of paper-plastic products from different perspectives by adding various additives, such as strength, hardness, anti-chipping, oxygen barrier performance, etc.; however, three major problems still remain: 1) The improvement of certain properties is often accompanied by the sacrifice of other properties; 2) The use of high-cost additives increases production costs, and some additives affect their environmental friendliness and biodegradability; 3) Some preparation processes are complex, with high energy consumption, low production efficiency, and potential food safety hazards, which are not conducive to green manufacturing and market promotion.

[0005] The present invention provides an environmentally friendly and biodegradable pulp molding product and its preparation method to solve the problems existing in the prior art, such as weak surface strength and internal bonding strength, insufficient waterproof performance, high production cost, and the adverse effects of some additives on its environmental friendliness and biodegradability of existing pulp molding. Summary of the Invention

[0006] The object of the present invention is to provide an environmentally friendly and biodegradable pulp molding product and its preparation method to solve the problems existing in the prior art, such as weak surface strength and internal bonding strength, insufficient waterproof performance, high production cost, and the adverse effects of some additives on its environmental friendliness and biodegradability of existing pulp molding.

[0007] The technical solution of the present invention is: an environmentally friendly and biodegradable pulp molding product and its preparation method, including the following steps:

[0008] S1. Add modified starch to deionized water, and perform low-temperature pregelatinization under a constant temperature condition of 45 - 60 °C, stir evenly to obtain a pregelatinized modified starch solution;

[0009] S2. Mix the pregelatinized modified starch solution with pulp fibers with a beating degree of 30 - 50 °SR, perform deep gelatinization under a constant temperature condition of 75 - 90 °C, stir evenly, and then perform a cooling treatment to obtain a starch-coated fiber slurry;

[0010] S3. Add a bio-based crosslinking agent to deionized water, stir for 20 - 50 min under a constant temperature condition of 40 - 65 °C to obtain a bio-based crosslinking agent solution;

[0011] S4. Add the bio-based crosslinking agent solution dropwise into the starch-coated fiber slurry in a pulsed manner at a dropping speed of 2 - 8 mL / min, and stir for 60 - 120 min under the constant temperature condition of 50 - 80 °C to form a bio-based crosslinked starch-coated fiber slurry. Control the stirring speed within the range of 200 - 500 rpm. Then, perform ultrasonic treatment to obtain the composite pulp;

[0012] S5. Add a water repellent to the composite pulp and perform stirring treatment to obtain a hydrophobic modified pulp;

[0013] S6. Pour the hydrophobic modified pulp into a forming device for segmented preheating and pressing to form a semi-finished product; then immerse the semi-finished product in an impregnating solution and quickly fish it out. After that, perform hot pressing and drying treatment to obtain a pulp molding product.

[0014] Preferably, in the pre-gelatinized modified starch solution, the mass ratio of the modified starch to deionized water is 1:(5 - 10);

[0015] The modified starch is one or more of oxidized starch, esterified starch, non-ionic starch, and amphoteric starch.

[0016] Preferably, in the starch-coated fiber slurry, the mass of the pre-gelatinized modified starch solution is 5 - 15% of the mass of the pulp raw material in absolute dry in the pulp fiber;

[0017] The pulp raw material of the pulp fiber is any one or more of pine fiber, poplar fiber, fir fiber, bagasse fiber, waste paper fiber, wheat straw fiber, and cotton straw fiber.

[0018] Preferably, the beating degree of the pulp fiber is 35 - 45 °SR;

[0019] In the starch-coated fiber slurry, the mass of the pre-gelatinized modified starch solution is 6 - 12% of the mass of the pulp raw material in absolute dry in the pulp fiber.

[0020] Preferably, in the bio-based crosslinking agent solution, the mass ratio of the bio-based crosslinking agent to deionized water is 1:(7 - 10);

[0021] The bio-based crosslinking agent is any one or more of soybean protein, whey protein, and gelatin.

[0022] Preferably, in the composite pulp, the mass of the bio-based crosslinking agent solution is 0.5 - 3% of the mass of the starch-coated fiber in absolute dry in the starch-coated fiber slurry;

[0023] The dropping speed is 3 - 6 mL / min.

[0024] Preferably, in the hydrophobically modified pulp, the mass of the water repellent is 0.8 - 2.5% of the mass of the bio-based cross-linked starch-coated fibers in the composite pulp on an absolutely dry basis;

[0025] The water repellent is any one or more of XSBR latex, ASA emulsion, and AKD emulsion.

[0026] Preferably, the segmented preheating and pressing forming treatment includes pre-pressing stage forming treatment, main-pressing stage forming treatment, and final-pressing stage forming treatment;

[0027] The constant temperature for the pre-pressing stage forming treatment is 80 - 100 °C, the pressure is 0.5 - 1 MPa, and the pre-pressing time is 30 - 60 s; the constant temperature for the main-pressing stage forming treatment is 120 - 150 °C, the pressure is 1.5 - 2.5 MPa, and the main-pressing time is 90 - 180 s; the constant temperature for the final-pressing stage forming treatment is 180 - 200 °C, the pressure is 0.8 - 1.2 MPa, and the final-pressing time is 30 - 45 s.

[0028] Preferably, the preparation method of the impregnating solution includes the following steps:

[0029] a. Mix the modified starch and deionized water at a mass ratio of 1:(5 - 10), and stir for 15 - 30 min under the constant temperature condition of 75 - 90 °C to obtain solution A;

[0030] b. Mix the bio-based cross-linking agent used in step S3 and deionized water at a mass ratio of 1:(7 - 10), and stir for 20 - 50 min under the constant temperature condition of 40 - 65 °C to obtain solution B;

[0031] c. Mix solution A and solution B, stir for 5 - 15 min, then add the water repellent, and perform ultrasonic treatment for 5 - 10 min to obtain the impregnating solution.

[0032] The present invention also provides an environmentally friendly degradable pulp molding product, which is prepared by the above preparation method.

[0033] Compared with the prior art, the advantages of the present invention are:

[0034] (1) An environmentally friendly degradable pulp molding product and its preparation method provided by the present invention. In this preparation method, modified starch is pre-gelatinized at low temperature and then mixed with pulp fibers, and undergoes deep gelatinization at high temperature to obtain starch-coated fibers. Immediately afterwards, a bio-based crosslinking agent is added dropwise in a pulsed manner to construct a three-dimensional crosslinking network, and a waterproofing agent is added to obtain hydrophobically modified pulp. Finally, the pulp molding product is prepared through segmented gradient hot pressing, re-impregnation with a mixed solution, and hot pressing and drying. By precisely controlling the temperature of the low-temperature pre-gelatinization and high-temperature deep gelatinization processes of the modified starch, the modified starch is evenly coated on the fiber surface. By precisely controlling the dropping method and dropping rate of the bio-based crosslinking agent solution and combining stirring shear force, the synergistic effect of the modified starch and the bio-based crosslinking agent is used to enhance the surface strength and internal bonding strength of the product, solving the problems of lint and powder shedding of traditional paper-plastic products. Bio-based raw materials and environmentally friendly waterproofing agents are used to improve the waterproof performance and biodegradability of the pulp molding product. And, through fine design of the formula, the use of high-cost nanomaterials or complex chemical reagents is reduced, and the performance of the pulp molding product is improved using inexpensive starch-based materials. At the same time, combined with the gradient hot pressing process, both efficiency and energy consumption are taken into account, and the overall production cost is reduced. The preparation method realizes the synchronous optimization of multiple performance indicators through the synergistic design of the starch coating layer and the crosslinking network, breaking through the technical bottleneck that it is difficult to balance the waterproofness and environmental friendliness of paper-plastic products when the strength of traditional paper-plastic products is improved. The pulp molding product prepared by this method has excellent comprehensive performance, conforms to the development trend of green packaging, and has broad application prospects. It solves the problems existing in the prior art, such as the weak surface strength and internal bonding strength, insufficient waterproof performance, high production cost of existing pulp molding, and the adverse effects of some additives on its environmental friendliness and biodegradability.

[0035] (2) An environmentally friendly degradable pulp molding product and its preparation method provided by the present invention. In this preparation method, through the synergistic effect of modified starch and a bio-based crosslinking agent, and by precisely controlling process parameters such as gelatinization temperature, dropping rate, and stirring shear force, a uniform coating layer and a three-dimensional crosslinking network are formed on the surface of pulp fibers. Combined with surface impregnation and film formation, the surface strength and internal bonding strength of the pulp molding product are significantly enhanced, effectively improving the defects of easy lint and powder shedding of traditional pulp molding. At the same time, the use of bio-based raw materials such as modified starch and whey protein, and environmentally friendly waterproofing agents can ensure the biodegradability of the product while improving the waterproof performance, avoiding the negative impact of petrochemical-based additives on the environment, and conforming to the development trend of green packaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention will be further described below in conjunction with the drawings and embodiments:

[0037] Figure 1 It is the process flow diagram of the preparation method of the environmentally friendly degradable pulp molding product described in the present invention. Detailed Embodiments

[0038] The following is a further detailed description of the content of the present invention in combination with specific embodiments:

[0039] Unless otherwise specified, the content of each component used in the present invention is in mass percentage. In the present invention, a beating degree of 30 - 50°SR means that after the pulp is beaten, the degree of fiber cutting, splitting, swelling, and hydration is between 30% and 50%; the measurement of the beating degree uses a Schopper - Riegler Air - Release Value instrument (SR value), and by measuring the Schopper value and using the conversion formula, the beating degree can be indirectly obtained.

[0040] The detection of various parameters involved in the embodiments and comparative examples of the present invention is carried out according to national standard detection methods and industry standards, specifically as follows:

[0041] (1) Tensile index (GB / T 453 - 2002);

[0042] (2) Bursting index (GB / T 454 - 2002);

[0043] (3) Water contact angle (GB / T 30447 - 2013);

[0044] Degradability test: environmental temperature 18 - 25°C; humidity 60%; the time for natural complete decomposition under soil conditions.

[0045] The raw material preparation methods adopted in the following embodiments: Preparation methods of 35°SR pine pulp and 35°SR poplar pulp: Use a Valmet beater with a weight of 5 kg and beat for about 40 minutes to obtain the above - mentioned 35°SR pine pulp and 35°SR poplar pulp. The beating methods of fiber pulps such as fir pulp, bagasse pulp, waste paper pulp, wheat straw pulp, and cotton straw pulp are the same as those of pine pulp and poplar pulp.

[0046] A preparation method of an environmentally friendly degradable pulp molding product, as Figure 1 shown, includes the following steps:

[0047] S1. Add the modified starch into deionized water, and conduct pre-gelatinization treatment under the constant temperature condition of 45 - 60 °C, with mechanical stirring for 15 - 30 min. Control the stirring speed within the range of 300 - 800 rpm. After stirring evenly, obtain a pre-gelatinized modified starch solution with the mass ratio of modified starch to deionized water being 1:(5 - 10); wherein, the modified starch is one or more of oxidized starch, esterified starch, non-ionic starch, and amphoteric starch that can be purchased on the market; in the pre-gelatinized modified starch solution, the mass ratio of modified starch to deionized water is preferably 1:(5 - 7); the pre-gelatinization treatment needs to be carried out under the constant temperature condition, and the temperature is preferably 55 - 60 °C; the stirring speed during the pre-gelatinization stirring process is preferably 400 - 600 rpm, and the stirring time is preferably 20 - 25 min. The modified starch used in preparing the pre-gelatinized modified starch solution is in its initial state (i.e., purchased on the market without further treatment or processing); and the mass ratio of modified starch to deionized water is calculated based on the mass of the modified starch in its initial state.

[0048] S2. Mix the above-mentioned pre-gelatinized modified starch solution with pulp fibers with a beating degree of 30 - 50 °SR, and conduct deep gelatinization treatment under the constant temperature condition of 75 - 90 °C to make the mixed starch granules fully expand, rupture, and dissolve. Stir for 5 - 15 min by mechanical stirring, and the stirring speed is 200 - 500 rpm. After stirring evenly, let it stand at room temperature for cooling treatment to obtain a uniformly mixed starch-coated fiber slurry; wherein, during the deep gelatinization process, the constant temperature is preferably 75 - 80 °C, the stirring speed is preferably 300 - 400 rpm, and the stirring time is preferably 7 - 10 min; the beating degree of the pulp fibers is preferably 35 - 45 °SR; the fiber raw materials of the pulp fibers include but are not limited to pine fibers, poplar fibers, fir fibers, bagasse fibers, waste paper fibers, wheat straw fibers, cotton straw fibers, etc.; in the starch-coated fiber slurry, the mass of the pre-gelatinized modified starch solution is 5 - 15% of the mass of the absolutely dry pulp raw materials in the pulp fibers; and preferably 6 - 12%; the absolutely dry pulp raw materials refer to the dry pulp boards without water that can be purchased on the existing market, such as pine fiber pulp boards, poplar fiber pulp boards, fir fiber pulp boards, bagasse fiber pulp boards, waste paper fiber pulp boards, wheat straw fiber pulp boards, cotton straw fiber pulp boards, etc. In this application, steps S1 and S2 dissolve the modified starch in deionized water for low-temperature pre-gelatinization treatment, aiming to promote the formation of a viscous layer that initially wraps the fibers by starch molecules; then add the pre-gelatinized modified starch into the pulp fibers for high-temperature deep gelatinization of the starch, and at the same time combine the stirring shear force to enhance the uniformity of the wrapping of the modified starch around the pulp fibers. The two are skillfully combined to improve the product performance involved in this application.

[0049] S3. Add the commercially available bio - based cross - linker (purchased at the conventional concentration) to deionized water, and mechanically stir for 20 - 50 min at a constant temperature of 40 - 65 °C with a stirring speed of 200 - 500 rpm to obtain a bio - based cross - linker solution with a mass ratio of bio - based cross - linker to deionized water of 1:(7 - 10); wherein, the bio - based cross - linker is any one or more of soybean protein, whey protein, and gelatin that can be purchased on the market; in the bio - based cross - linker solution, the mass ratio of bio - based cross - linker to deionized water is 1:(7 - 10), and more preferably 1:(7 - 9); in addition, during the preparation of the bio - based cross - linker solution, the constant temperature is more preferably 45 - 60 °C, the stirring speed is preferably 300 - 500 rpm, and the stirring time is preferably 30 - 45 min. The bio - based cross - linkers used in the preparation of the bio - based cross - linker solution are all in their initial state (i.e., purchased on the market without further treatment or processing); and the mass ratio of bio - based cross - linker to deionized water is calculated based on the mass of the bio - based cross - linker in its initial state.

[0050] S4. Pulse - wise add the bio - based cross - linker solution to the starch - coated fiber slurry, control the dropping speed within the range of 2 - 8 mL / min, and mechanically stir at a constant temperature of 50 - 80 °C with the stirring speed controlled within the range of 200 - 500 rpm for 60 - 120 min to form a bio - based cross - linked starch - coated fiber slurry, and then perform ultrasonic treatment to obtain composite pulp; wherein, during the process of pulse - wise adding the bio - based cross - linker solution to the starch - coated fiber slurry, the dropping speed of the bio - based cross - linker solution is more preferably 3 - 6 mL / min; the constant temperature during stirring is preferably 65 - 80 °C, the stirring speed is preferably 350 - 500 rpm, and the stirring time is preferably 90 - 120 min; in addition, in the composite pulp, the mass of the bio - based cross - linker solution is 0.5 - 3% of the mass of the starch - coated fiber in absolute dryness in the starch - coated fiber slurry, and more preferably 1 - 1.5%; wherein, the mass of the starch - coated fiber in absolute dryness refers to the sum of the mass of the modified starch and the mass of the paper pulp raw material in absolute dryness in the starch - coated fiber slurry prepared in step S2. In this application, by pulse - wise introducing the bio - based cross - linker solution and controlling its dropping speed and stirring shear force, a complex three - dimensional cross - linked network can be constructed through the bio - based cross - linker, thereby significantly enhancing the interaction force and binding stability between fibers and the film - forming property of starch.

[0051] S5. Add a water repellent to the composite pulp and carry out stirring treatment at a stirring speed of 200-500 rpm. After stirring for 30-90 minutes, a hydrophobically modified pulp is obtained; wherein, the water repellent is one or more of XSBR latex, ASA emulsion, AKD emulsion, etc. that can be purchased on the market; during the stirring process, the stirring speed is more preferably 350-500 rpm, and the stirring time is more preferably 45-90 minutes; in the formed hydrophobically modified pulp, the mass of the water repellent is 0.8-2.5% of the mass of the bio-based cross-linked starch-coated fibers in the composite pulp, and more preferably 1.0-2.2%; wherein, the mass of the bio-based cross-linked starch-coated fibers refers to the sum of the mass of the bio-based cross-linking agent and the mass of the starch-coated fibers in absolute dryness in the bio-based cross-linked starch-coated fiber slurry prepared in step S4. In this application, the purpose of adding the water repellent is to further optimize and improve the waterproof performance of the pulp molding product. XSBR latex is a styrene-butadiene latex made by emulsion copolymerization of butadiene and styrene; ASA emulsion is an emulsion with alkenyl succinic anhydride (ASA) as the core component; AKD emulsion is an alkyl ketene dimer emulsion. The water repellents used in this application are all in their initial state (i.e., purchased on the market without further treatment or processing), and the addition amount of the water repellent is calculated based on the mass of the water repellent in its initial state.

[0052] S6. Pour the hydrophobically modified pulp into a forming device for staged preheating and pressing forming treatment to form a semi-finished product. Then, immerse the semi-finished product in an impregnating solution and quickly fish it out. After that, conduct hot pressing and drying treatment to obtain a pulp molding product. Among them, the staged preheating and pressing forming treatment includes three stages: pre-pressing stage forming treatment, main pressing stage forming treatment, and final pressing stage forming treatment. The constant temperature during the pre-pressing stage forming treatment can be 80 - 100°C, preferably 95 - 100°C; the pressure can be 0.5 - 1 MPa, preferably 0.8 MPa; the pre-pressing time can be 30 - 60 s, preferably 45 - 60 s. The constant temperature during the main pressing stage forming treatment can be 120 - 150°C, preferably 120 - 145°C, the pressure can be 1.5 - 2.5 MPa, preferably 1.5 - 2.0 MPa, and the main pressing time can be 90 - 180 s, preferably 120 - 150 s. The constant temperature during the final pressing stage forming treatment can be 180 - 200°C, preferably 180°C, the pressure can be 0.8 - 1.2 MPa, preferably 1.0 - 1.2 MPa, and the final pressing time can be 30 - 45 s, preferably 40 - 45 s. During the process of staged preheating and pressing forming treatment in a molding machine, the modified starch and the bio-based cross-linking agent will interact to form a microgel film, which not only interweaves inside the fibers but also covers the surface of the semi-finished product, thus greatly enhancing the overall internal bonding strength and surface strength of the pulp molding.The time for impregnating the semi-finished product in the impregnating solution should not be too long and needs to be controlled within the range of 2 - 20 s; the purpose of impregnation is to coat a thin layer of the impregnating solution on the surface of the semi-finished product, and after subsequent hot pressing and drying treatments, a gel film is formed on its surface, thereby further improving the performance of the product; the preparation method of the impregnating solution used includes the following specific steps: a. Mix the modified starch and deionized water at a mass ratio of 1:(5 - 10), and stir at a rotation speed of 300 - 500 rpm for 15 - 30 min under the constant temperature condition of 75 - 90 °C to obtain solution A; among them, the modified starch used here is also selected from one or more of oxidized starch, esterified starch, non-ionic starch, and amphoteric starch that can be purchased on the market, and moreover, the modified starch used here can be the same as or different from the modified starch used in the above step S1; to avoid affecting the bonding strength and compactness of the gel film formed on its surface due to material changes and differences in the bonding properties between different materials, ensure the stability of the performance of the pulp molding product, and at the same time reduce the complexity of production, it is preferred to use the modified starch used in the above step S1; the mass ratio of the modified starch to deionized water is calculated according to the mass of the modified starch in its initial state; b. Mix the bio-based cross-linking agent used in the above step S3 and deionized water at a mass ratio of 1:(7 - 10), and stir at a rotation speed of 200 - 500 rpm for 20 - 50 min under the constant temperature condition of 40 - 65 °C to obtain solution B; the mass ratio of the bio-based cross-linking agent to deionized water is calculated according to the mass of the bio-based cross-linking agent in its initial state; c. Mix solution A and solution B, stir for 5 - 15 min and then perform ultrasonic treatment, add a waterproof agent after ultrasonic treatment for 5 - 10 min, and stir evenly to obtain the impregnating solution. The hot pressing and drying treatment performed on the impregnated semi-finished product has the same treatment method as the forming treatment method in the final pressing stage. After the hot pressing and drying treatment, the starch granules can undergo a coupling effect with the waterproof agent as bio-based fillers, further enhancing the mechanical strength and waterproof performance of the pulp molding product.

[0053] The core of the preparation method of the above-mentioned environmentally friendly and degradable pulp molding product lies in: through a series of carefully designed steps, efficiently integrating the modified starch, bio-based cross-linking agent, and waterproof agent into the pulp fiber system, thereby greatly improving the comprehensive performance of the pulp molding product in terms of surface strength, internal bonding strength, and waterproof performance. It should be noted that the entire preparation process strictly follows the principles of environmental protection and sustainable development, not only ensuring the ecological friendliness of the product but also reflecting the innovative contribution of the present invention in the fields of green chemistry and pulp molding.

[0054] Example 1: Esterified starch + gluten + ASA emulsion system

[0055] S1. Add 0.18 g of modified starch to 1.42 g of deionized water, and perform low-temperature pre-gelatinization in a constant-temperature water bath at 55 °C. Stir at a stirring speed of 600 rpm for 25 min to obtain a pre-gelatinized modified starch solution;

[0056] S2. Mix the pre-gelatinized modified starch solution with 400 g of pulp fibers with a pulp concentration of 5% and a beating degree of 40 °SR, and perform high-temperature deep gelatinization under constant-temperature conditions at 80 °C. Stir at a stirring speed of 350 rpm for 8 min, and then perform a cooling treatment to obtain a starch-coated fiber slurry;

[0057] S3. Add 0.3 g of gluten to 2.7 g of deionized water, and stir at a stirring speed of 400 rpm for 25 min under constant-temperature conditions at 60 °C to obtain a bio-based cross-linking agent solution;

[0058] S4. Pulse the bio-based cross-linking agent solution and add it dropwise to the starch-coated fiber slurry at a dropping speed of 3 mL / min (8 s drop / 4 s stop), and stir at a stirring speed of 450 rpm for 100 min under constant-temperature conditions at 65 °C to form a bio-based cross-linked starch-coated fiber slurry. Then, perform ultrasonic treatment for 10 min to obtain a composite pulp;

[0059] S5. Add 0.4 g of ASA emulsion to the composite pulp and perform a stirring treatment. Stir at a stirring speed of 300 rpm for 60 min to obtain a hydrophobically modified pulp;

[0060] S6. Pour the hydrophobically modified pulp into a molding machine for segmented preheating and pressing forming treatment. Among them, the temperature of the forming treatment in the pre-pressing stage is 85 °C, the pressure is 0.7 MPa, and the pre-pressing time is maintained for 50 s; the temperature of the forming treatment in the main pressing stage is 130 °C, the pressure is 2.2 MPa, and the main pressing time is maintained for 150 s; the temperature of the forming treatment in the final pressing stage is 180 °C, the pressure is 1.1 MPa, and the final pressing time is maintained for 35 s; a semi-finished product is obtained; then, the semi-finished product is immersed in the impregnating solution and quickly fished out, and then, a hot pressing and drying treatment is performed, that is, it is maintained for 35 s under the conditions of 180 °C and 1.1 MPa to obtain a pulp molding product, P1. Among them, the preparation method of the impregnating solution includes the following steps: a. Add 0.18 g of modified starch to 1.42 g of deionized water, and stir at a rotation speed of 600 rpm for 25 min under constant-temperature conditions at 55 °C to obtain solution A; b. Add 0.3 g of gluten to 2.7 g of deionized water, and stir at a rotation speed of 400 rpm for 25 min under constant-temperature conditions at 60 to obtain solution B; c. Mix solution A and solution B, stir for 10 min, then add 0.4 g of ASA emulsion and perform ultrasonic treatment. After ultrasonic treatment for 10 min, an impregnating solution is obtained.

[0061] Example 2: Amphoteric starch + fish glue + XSBR latex system

[0062] S1. Add 0.27 g of amphoteric starch to 2.13 g of deionized water, and perform low-temperature pregelatinization in a constant-temperature water bath at 50 °C, and stir at a stirring speed of 700 rpm for 15 min to obtain a pregelatinized modified starch solution;

[0063] S2. Mix the pregelatinized modified starch solution with 400 g of pulp fibers with a pulp concentration of 5% and a beating degree of 40 °SR, and perform high-temperature deep gelatinization under constant-temperature conditions at 75 °C, and stir at a stirring speed of 500 rpm for 12 min, and then perform a cooling treatment to obtain a starch-coated fiber slurry;

[0064] S3. Add 0.16 g of fish glue to 1.44 g of deionized water, and stir at a stirring speed of 200 rpm for 40 min under constant-temperature conditions at 45 °C to obtain a bio-based cross-linking agent solution;

[0065] S4. Pulse the bio-based cross-linking agent solution and add it dropwise to the starch-coated fiber slurry at a dropping speed of 7 mL / min (12 s drop / 6 s stop), and stir at a stirring speed of 300 rpm for 70 min under constant-temperature conditions at 75 °C to form a bio-based cross-linked starch-coated fiber slurry, and then ultrasonicate for 20 min to obtain a composite pulp;

[0066] S5. Add 0.24 g of XSBR latex to the composite pulp and perform a stirring treatment, and stir at a stirring speed of 400 rpm for 45 min to obtain a hydrophobic modified pulp;

[0067] S6. Pour the hydrophobically modified pulp into a molding machine for staged preheating and compression molding. Among them, the temperature for the pre-pressing stage of molding is 95 °C, the pressure is 0.9 MPa, and the pre-pressing time is maintained for 55 s; the temperature for the main pressing stage of molding is 150 °C, the pressure is 2.4 MPa, and the main pressing time is maintained for 160 s; the temperature for the final pressing stage of molding is 195 °C, the pressure is 1.2 MPa, and the final pressing time is maintained for 30 s; to obtain a semi-finished product; then immerse the semi-finished product in the impregnating solution and quickly fish it out, and then perform hot pressing and drying treatment, that is, maintain it at 195 °C and 1.2 MPa for 30 s to obtain a pulp molding product, P2. Among them, the preparation method of the impregnating solution includes the following steps: a. Add 0.27 g of amphoteric starch to 2.13 g of deionized water, and stir at a stirring speed of 700 rpm under the constant temperature condition of 50 °C for 15 min to obtain solution A; b. Add 0.16 g of fish glue to 1.44 g of deionized water, and stir at a stirring speed of 200 rpm under the constant temperature condition of 45 °C for 40 min to obtain solution B; c. Mix solution A and solution B, stir for 10 min, then add 0.24 g of XSBR latex and perform ultrasonic treatment. After ultrasonic treatment for 20 min, the impregnating solution is obtained.

[0068] Example 3: Esterified starch + whey protein + ASA emulsion system

[0069] S1. Add 0.22 g of esterified starch to 1.78 g of deionized water, and perform low-temperature pre-gelatinization in a 75 °C constant temperature water bath, and stir at a stirring speed of 400 rpm for 20 min to obtain a pre-gelatinized modified starch solution;

[0070] S2. Mix the pre-gelatinized modified starch solution with 400 g of pulp fibers with a pulp concentration of 5% and a beating degree of 40 °SR, and perform high-temperature deep gelatinization under the constant temperature condition of 80 °C, and stir at a stirring speed of 350 rpm for 10 min, and then perform a cooling treatment to obtain a starch-coated fiber slurry;

[0071] S3. Add 0.3 g of whey protein to 2.7 g of deionized water, and stir at a stirring speed of 300 rpm under the constant temperature condition of 55 °C for 30 min to obtain a bio-based cross-linking agent solution;

[0072] S4. Pulse the bio-based cross-linking agent solution at a dropping speed of 4 mL / min (drop for 10 s and stop for 5 s) and add it dropwise to the starch-coated fiber slurry, and stir at a stirring speed of 400 rpm under the constant temperature condition of 65 °C for 100 min to form a bio-based cross-linked starch-coated fiber slurry. Then, perform ultrasonic treatment for 10 min to obtain a composite pulp;

[0073] S5. Add 0.4 g of ASA emulsion to the composite pulp and conduct stirring treatment. Stir at a stirring speed of 250 rpm for 75 min to obtain hydrophobically modified pulp;

[0074] S6. Pour the hydrophobically modified pulp into a molding machine for segmented preheating and compression molding. Among them, the temperature for the pre-pressing stage of molding is 85 °C, the pressure is 0.7 MPa, and the pre-pressing time is maintained for 50 s; the temperature for the main pressing stage of molding is 140 °C, the pressure is 2.2 MPa, and the main pressing time is maintained for 150 s; the temperature for the final pressing stage of molding is 185 °C, the pressure is 1.1 MPa, and the final pressing time is maintained for 35 s; to obtain a semi-finished product; then immerse the semi-finished product in the impregnating solution and quickly fish it out, and then conduct hot pressing and drying treatment, that is, maintain it at 185 °C and 1.1 MPa for 35 s to obtain a pulp molding product, P3. Among them, the preparation method of the impregnating solution includes the following steps: a. Add 0.22 g of esterified starch to 1.78 g of deionized water, and stir at a stirring speed of 400 rpm for 20 min under the constant temperature condition of 75 °C to obtain solution A; b. Add 0.3 g of whey protein to 2.7 g of deionized water, and stir at a stirring speed of 300 rpm for 30 min under the constant temperature condition of 55 °C to obtain solution B; c. Mix solution A and solution B, stir for 10 min, then add 0.4 g of ASA emulsion and conduct ultrasonic treatment. After ultrasonic treatment for 20 min, obtain the impregnating solution.

[0075] Example 4: Non-ionic starch + whey protein + AKD emulsion system

[0076] S1. Add 0.17 g of non-ionic starch to 0.83 g of deionized water, and conduct low-temperature pre-gelatinization in a constant temperature water bath at 45 °C. Stir at a stirring speed of 300 rpm for 30 min to obtain a pre-gelatinized modified starch solution;

[0077] S2. Mix the pre-gelatinized modified starch solution with 400 g of pulp fibers with a pulp concentration of 5% and a beating degree of 40 °SR, and conduct high-temperature deep gelatinization under the constant temperature condition of 75 °C. Stir at a stirring speed of 200 rpm for 15 min, and then conduct cooling treatment to obtain a starch-coated fiber slurry;

[0078] S3. Add 0.6 g of whey protein to 5.4 g of deionized water, and stir at a stirring speed of 500 rpm for 20 min under the constant temperature condition of 65 °C to obtain a bio-based cross-linking agent solution;

[0079] S4. Pulse-wise add the bio-based crosslinking agent solution to the starch-coated fiber slurry at a dropping rate of 8 mL / min (5 s drop / 2 s pause), and stir at a stirring speed of 500 rpm for 60 min under the constant temperature condition of 80 °C to form a bio-based crosslinked starch-coated fiber slurry. Then, perform ultrasonic treatment for 10 min to obtain a composite pulp;

[0080] S5. Add 0.5 g of AKD emulsion to the composite pulp and perform stirring treatment. Stir at a stirring speed of 500 rpm for 30 min to obtain a hydrophobically modified pulp;

[0081] S6. Pour the hydrophobically modified pulp into a molding machine for segmented preheating and compression molding. Among them, the temperature for the pre-pressing stage of molding is 100 °C, the pressure is 1.0 MPa, and the pre-pressing time is maintained for 30 s; the temperature for the main pressing stage of molding is 150 °C, the pressure is 2.5 MPa, and the main pressing time is maintained for 90 s; the temperature for the final pressing stage of molding is 200 °C, the pressure is 1.2 MPa, and the final pressing time is maintained for 30 s; to obtain a semi-finished product. Then, immerse the semi-finished product in the impregnating solution and quickly fish it out. After that, perform hot pressing and drying treatment, that is, maintain it at 200 °C and 1.2 MPa for 30 s to obtain a pulp molding product, P4. Among them, the preparation method of the impregnating solution includes the following steps: a. Add 0.17 g of non-ionic starch to 0.83 g of deionized water, and stir at a stirring speed of 300 rpm for 30 min under the constant temperature condition of 45 °C to obtain solution A; b. Add 0.6 g of whey protein to 5.4 g of deionized water, and stir at a stirring speed of 500 rpm for 20 min under the constant temperature condition of 65 °C to obtain solution B; c. Mix solution A and solution B, stir for 10 min, then add 0.5 g of AKD emulsion and mix and perform ultrasonic treatment. After ultrasonic treatment for 20 min, obtain the impregnating solution.

[0082] Example 5

[0083] S1. Add 0.22 g of esterified starch to 1.78 g of deionized water, and perform low-temperature pre-gelatinization in a 75 °C constant temperature water bath. Stir at a stirring speed of 400 rpm for 20 min to obtain a pre-gelatinized modified starch solution;

[0084] S2. Mix the pre-gelatinized modified starch solution with 400 g of pulp fibers with a pulp concentration of 5% and a beating degree of 40 °SR, and perform high-temperature deep gelatinization under the constant temperature condition of 80 °C. Stir at a stirring speed of 350 rpm for 10 min, and then perform a cooling treatment to obtain a starch-coated fiber slurry;

[0085] S3. Add 0.4 g of ASA emulsion to the starch-coated fiber slurry and perform stirring treatment. Stir at a stirring speed of 250 rpm for 75 min to obtain a hydrophobically modified pulp;

[0086] S4. Pour the hydrophobically modified pulp into a molding machine for segmented preheating and compression molding. Among them, the temperature for the molding process in the pre-pressing stage is 85 °C, the pressure is 0.7 MPa, and the pre-pressing time is maintained for 50 s; the temperature for the molding process in the main pressing stage is 140 °C, the pressure is 2.2 MPa, and the main pressing time is maintained for 150 s; the temperature for the molding process in the final pressing stage is 185 °C, the pressure is 1.1 MPa, and the final pressing time is maintained for 35 s; to obtain a semi-finished product; then immerse the semi-finished product in the impregnating solution and quickly fish it out, and then carry out hot pressing and drying treatment, that is, maintain it at 185 °C and 1.1 MPa for 35 s to obtain a pulp molded product, P5. Among them, the preparation method of the impregnating solution includes the following steps: a. Add 0.22 g of esterified starch to 1.78 g of deionized water, and stir at a stirring speed of 400 rpm under a constant temperature condition of 75 °C for 20 min to obtain solution A; b. Mix solution A with 0.4 g of ASA emulsion and carry out ultrasonic treatment. After ultrasonic treatment for 20 min, an impregnating solution is obtained.

[0087] Example 6

[0088] S1. Add 0.22 g of esterified starch to 1.78 g of deionized water and mix evenly to obtain a modified starch solution;

[0089] S2. Mix the modified starch solution with 400 g of pulp fibers with a pulp concentration of 5% and a beating degree of 40 °SR, and carry out high-temperature deep gelatinization under a constant temperature condition of 80 °C, stir at a stirring speed of 350 rpm for 10 min, and then carry out a cooling treatment to obtain a starch-coated fiber slurry;

[0090] S3. Add 0.3 g of whey protein to 2.7 g of deionized water, and stir at a stirring speed of 300 rpm under a constant temperature condition of 55 °C for 30 min to obtain a bio-based crosslinking agent solution;

[0091] S4. Pulse the bio-based crosslinking agent solution at a dropping speed of 4 mL / min (drop for 10 s and stop for 5 s) and add it dropwise to the starch-coated fiber slurry, and stir at a stirring speed of 400 rpm under a constant temperature condition of 65 °C for 100 min to form a bio-based crosslinked starch-coated fiber slurry. Then, carry out ultrasonic treatment for 10 min to obtain a composite pulp;

[0092] S5. Add 0.4 g of ASA emulsion to the composite pulp and carry out a stirring treatment, stir at a stirring speed of 250 rpm for 75 min to obtain a hydrophobically modified pulp;

[0093] S6. Pour the hydrophobically modified pulp into a molding machine for staged preheating and compression molding. Among them, the temperature for the molding process in the pre-pressing stage is 85 °C, the pressure is 0.7 MPa, and the pre-pressing time is maintained for 50 s; the temperature for the molding process in the main pressing stage is 140 °C, the pressure is 2.2 MPa, and the main pressing time is maintained for 150 s; the temperature for the molding process in the final pressing stage is 185 °C, the pressure is 1.1 MPa, and the final pressing time is maintained for 35 s; a semi-finished product is obtained; then the semi-finished product is immersed in the impregnating solution and quickly fished out. After that, hot pressing and drying treatment is carried out, that is, it is maintained at 185 °C and 1.1 MPa for 35 s to obtain a pulp molding product, P6. Among them, the preparation method of the impregnating solution includes the following steps: a. Add 0.22 g of esterified starch to 1.78 g of deionized water and mix evenly to obtain solution A; b. Add 0.3 g of whey protein to 2.7 g of deionized water and stir at a stirring speed of 300 rpm under a constant temperature condition of 55 °C for 30 min to obtain solution B; c. Mix solution A and solution B, stir for 10 min, then add 0.4 g of ASA emulsion and perform ultrasonic treatment. After ultrasonic treatment for 20 min, the impregnating solution is obtained.

[0094] Example 7

[0095] The difference between this comparative example and Example 3 is that in step S4, the bio-based crosslinking agent solution is added to the starch-coated fiber slurry at one time, and stirred at a stirring speed of 400 rpm under a constant temperature condition of 65 °C for 100 min to form a bio-based crosslinked starch-coated fiber slurry. After that, ultrasonic treatment is carried out for 10 min to obtain a composite pulp; finally, a pulp molding product, P7, is obtained. A preparation method for an environmentally friendly and degradable pulp molding product

[0096] Example 8

[0097] The difference between this comparative example and Example 3 is that in step S6, the semi-finished product is directly subjected to hot pressing and drying treatment without impregnating the semi-finished product; that is, the semi-finished product is directly maintained at 185 °C and 1.1 MPa for 35 s to obtain a pulp molding product, P8.

[0098] Test the properties of the pulp molding products P1-P8 prepared in Examples 1-8 in terms of tensile index, burst index, water contact angle, etc. The test data are shown in Table 1;

[0099] Table 1. Test results of the properties of the pulp molding products P1-P8 prepared in Examples 1-8

[0100]

[0101] As can be seen from Table 1, the test results of the pulp molding products P1-P4 prepared in Examples 1-4, such as tensile index, bursting index, and water contact angle, are significantly better than those of the pulp molding product P5 prepared in Example 5. This further indicates that the pulp molding products prepared using modified starch combined with a bio-based crosslinking agent exhibit excellent comprehensive properties. Comparing the pulp molding product P3 prepared in Example 3 with the pulp molding products P6-P8 prepared in Examples 6-8, it can be seen that the tensile index, bursting index, and water contact angle of the pulp molding product P3 prepared in Example 3 are significantly higher than those of the pulp molding products P6-P8 prepared in Examples 6-8. Moreover, the degradation performance of the pulp molding product P3 prepared in Example 3 is comparable to that of the pulp molding products P6-P8 prepared in Examples 6-8. This further demonstrates that through the synergistic effects among processes such as forming a starch viscous layer by stepwise gelatinization, constructing a three-dimensional network by pulsed crosslinking, and reinforcing the surface microgel film by double dipping, the tensile strength and bursting strength of the prepared pulp molding products can be greatly improved. At the same time, comparing the pulp molding products P1-P4 prepared in Examples 1-4 with each other, it can be seen that by choosing the type of waterproofing agent, flexible regulation of hydrophobicity and degradability can be achieved. Thus, the prepared pulp molding products have the characteristics of high environmental performance, high surface strength, and high internal bonding strength, solving the pain points of low mechanical strength and waterproofing relying on petrochemical materials in existing pulp molding. In addition, the data corresponding to Examples 1-5 also reversely verifies the necessity of the stepwise gelatinization, bio-based crosslinking, pulsed dropping, and double dipping processes in the preparation method provided by the present invention.

[0102] In summary, this preparation method aims to optimize the distribution and binding mechanism of additives in pulp fibers through a finely designed chemical and physical process, thereby significantly improving the comprehensive properties of pulp molding products, especially their surface strength, internal bonding strength, and waterproof performance, without increasing production costs. At the same time, this preparation method strictly follows the principles of green chemistry, ensuring the environmental compatibility and biodegradability of the products while improving their performance, providing strong technical support for the sustainable development of the pulp molding industry.

[0103] The above embodiments are only used to illustrate the technical concept and features of the present invention. Their purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and it should not be used to limit the protection scope of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to embrace all changes that fall within the meaning and scope of the equivalent elements of the claims in the present invention.

Claims

1. A preparation method of an environment-friendly degradable pulp molding product, characterized in that, It includes the following steps: S1. Add the modified starch into deionized water, conduct low-temperature pre-gelatinization under the constant temperature condition of 45 - 60 °C, stir evenly to obtain a pre-gelatinized modified starch solution; S2. Mix the pre-gelatinized modified starch solution with pulp fibers with a beating degree of 30 - 50 °SR, conduct deep gelatinization under the constant temperature condition of 75 - 90 °C, stir evenly, and then conduct a cooling treatment to obtain a starch-coated fiber slurry; S3. Add the bio-based crosslinking agent into deionized water, stir for 20 - 50 min under the constant temperature condition of 40 - 65 °C to obtain a bio-based crosslinking agent solution; S4. Drop the bio-based crosslinking agent solution into the starch-coated fiber slurry in a pulsed manner at a dropping speed of 2 - 8 mL / min, and stir for 60 - 120 min under the constant temperature condition of 50 - 80 °C to form a bio-based crosslinked starch-coated fiber slurry. Control the stirring speed within the range of 200 - 500 rpm. Then, conduct ultrasonic treatment to obtain a composite pulp; S5. Add a waterproofing agent to the composite pulp and conduct a stirring treatment to obtain a hydrophobic modified pulp; S6. Pour the hydrophobic modified pulp into a forming device for segmented preheating and pressing forming treatment to obtain a semi-finished product; then immerse the semi-finished product in an impregnating solution and quickly fish it out. After that, conduct hot pressing and drying treatment to obtain a pulp molding product.

2. The preparation method of an environment-friendly degradable pulp molding product according to claim 1, characterized in that: In the pre-gelatinized modified starch solution, the mass ratio of the modified starch to deionized water is 1:(5 - 10); The modified starch is one or more of oxidized starch, esterified starch, non-ionic starch, and amphoteric starch.

3. The preparation method of an environmentally friendly degradable pulp molding product according to claim 1, characterized in that: In the starch-coated fiber slurry, the mass of the pre-gelatinized modified starch solution is 5 - 15% of the mass of the pulp raw material in absolute dry in the pulp fibers; The pulp raw material of the pulp fibers is any one or more of pine fibers, poplar fibers, fir fibers, bagasse fibers, waste paper fibers, wheat straw fibers, and cotton straw fibers.

4. The preparation method of an environment-friendly degradable pulp molding product according to claim 3, characterized in that: The beating degree of the pulp fibers is 35 - 45 °SR; In the starch-coated fiber slurry, the mass of the pre-gelatinized modified starch solution is 6 - 12% of the mass of the pulp raw material in absolute dry in the pulp fibers.

5. The preparation method of an environmentally friendly degradable pulp molding product according to claim 1, characterized in that, In the bio-based crosslinking agent solution, the mass ratio of the bio-based crosslinking agent to deionized water is 1:(7 - 10); The bio-based crosslinking agent is any one or more of soy protein, whey protein, and gelatin.

6. The preparation method of an environmentally friendly degradable pulp molding product according to claim 1, characterized in that: In the composite pulp, the mass of the bio-based crosslinking agent solution is 0.5 - 3% of the mass of the starch-coated fiber in absolute dry in the starch-coated fiber slurry; The dropping speed is 3 - 6 mL / min.

7. The preparation method of an environmentally friendly degradable pulp molding product according to claim 1, characterized in that: In the hydrophobic modified pulp, the mass of the waterproofing agent is 0.8 - 2.5% of the mass of the bio-based crosslinked starch-coated fiber in absolute dry in the composite pulp; The waterproofing agent is any one or more of XSBR latex, ASA emulsion, and AKD emulsion.

8. The preparation method of an environmentally friendly degradable pulp molding product according to claim 1, characterized in that: The segmented preheating and pressing forming treatment includes pre-pressing stage forming treatment, main-pressing stage forming treatment, and final-pressing stage forming treatment; The constant temperature during the pre-pressing stage forming treatment is 80 - 100 °C, the pressure is 0.5 - 1 MPa, and the pre-pressing time is 30 - 60 s; the constant temperature during the main pressing stage forming treatment is 120 - 150 °C, the pressure is 1.5 - 2.5 MPa, and the main pressing time is 90 - 180 s; the constant temperature during the final pressing stage forming treatment is 180 - 200 °C, the pressure is 0.8 - 1.2 MPa, and the final pressing time is 30 - 45 s.

9. The preparation method of an environment-friendly degradable pulp molding product according to claim 1, characterized in that: The preparation method of the impregnating solution includes the following steps: a. Mix the modified starch and deionized water in a mass ratio of 1:(5 - 10), and stir for 15 - 30 min under the condition of constant temperature at 75 - 90 °C to obtain solution A; b. Mix the bio-based cross-linking agent used in step S3 and deionized water in a mass ratio of 1:(7 - 10), and stir for 20 - 50 min under the condition of constant temperature at 40 - 65 °C to obtain solution B; c. Mix solution A and solution B, stir for 5 - 15 min, then add a waterproofing agent, and perform ultrasonic treatment for 5 - 10 min to obtain the impregnating solution.

10. An environmentally friendly degradable pulp molding product, characterized in that: Prepared by using the preparation method according to any one of claims 1 - 9.

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