Paper pulp foam buffer material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of foam material preparation, in particular to a paper pulp foam buffer material and a preparation method and application thereof. Mixing wax with the nanocellulose solution, and dispersing to obtain a nanocellulose / wax emulsion; mixing paper pulp fibers with a flame retardant solution, and stirring to obtain a paper pulp / flame retardant mixture; and mixing the nanocellulose / waxy emulsion with the paper pulp / flame retardant mixture, removing a liquid phase, and drying to obtain the paper pulp foam buffer material. All the components of the paper pulp foam buffer material are compounded through physical interaction, the paper pulp foam buffer material is easy to mold, process and form, and the whole preparation process is free of chemical crosslinking, green and pollution-free; all the components can be disassembled and reprocessed, and can be completely degraded; the composite material has the characteristics of light weight, high strength, flame retardance, water resistance, normal-temperature and normal-pressure molding and cyclic processing.

Description

Technical Field

[0001] The invention relates to the technical field of foam material preparation, in particular to a pulp foam cushioning material and a preparation method and application thereof. Background Art

[0002] In the process of moving towards a green and low-carbon era, the development of high-performance biomass-based foam materials to replace traditional petroleum-based foam materials (polystyrene foam, polyurethane foam and polyethylene foam, etc.) has become a focus of global attention. Cellulose, which is widely available and renewable, is an ideal alternative material with important development and application potential. The construction of high-performance cellulose-based foams is often accompanied by chemical modification and grafting treatments to achieve cross-linking to promote the stability of the three-dimensional structure, but the introduction of chemical synthesis reagents usually reduces the environmental benefits of the materials. In addition, cellulose foams usually need to be freeze-dried and supercritically dried to overcome the capillary pressure of water to achieve uniform molding, which greatly enhances the complexity of the preparation process and faces the challenge of large-scale production. Therefore, it is of great research significance to achieve the construction of high-performance cellulose-based foams through a simple and fast drying method at room temperature and pressure.

[0003] At present, many researchers have devoted themselves to the development and research of cellulose foam materials. For example, patent CN116903921A discloses a method for preparing pulp foam materials, which takes pulp fiber as the main body, and combines gelatin, sodium hydroxide, polyvinyl alcohol and sepiolite processed by calcination, vacuum homogenization and low temperature and low pressure as functional components to realize the preparation and molding of paper-based foam materials; patent CN103131038A discloses a method for preparing wood cellulose foam, which realizes the construction of wood cellulose foam materials by crushing, grinding, dispersing and freeze-drying wood cellulose; CN109161057A discloses a method for preparing cellulose foam, which takes pulp, old cotton and mirabilite as raw materials, and realizes the preparation of cellulose-based foam materials through the process steps of alkalization, sulfonation, dissolution, mixing, injection molding, heating, cleaning, static stripping and rinsing. Although the preparation and processing methods of cellulose foam materials are constantly being developed, the above patents still have the following problems: (1) The preparation process of cellulose foam materials involves the use of a large amount of chemical synthesis reagents, which poses potential pollution and is difficult to completely degrade; (2) The preparation process is complicated; (3) It lacks water resistance and fire resistance and has a single function; (4) The mechanical properties are poor; and (5) It is difficult to form at room temperature and pressure after the introduction of high surface energy flame retardants. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a pulp foam cushioning material and a preparation method and application thereof. The apparent density of the pulp foam cushioning material is 0.08-0.15 g / cm 3, compression modulus is 0.20~1.50MPa, limiting oxygen index (LOI) is 25-33%, vertical combustion performance reaches UL-94V0 level, hydrophobic angle is 130-142°, with excellent comprehensive performance, it can be used in express packaging, cold chain transportation and building furniture and other scenes. With pulp fiber as the main body, nanocellulose is used as an emulsifier for hydrophobic waxy materials to realize the preparation of nanocellulose / wax emulsion, and the hydrophobic modification and interface enhancement of pulp fiber are realized through the physical composite process of emulsion and pulp fiber, and the green flame retardant is efficiently loaded through the solidified wax coating layer to give the foam material flame retardant properties, thereby realizing the preparation of high-performance pulp foam cushioning material. In view of the background, the preparation process of cellulose-based foam cushioning materials has chemical pollution, the foam is difficult to completely degrade, the preparation process is complicated, the function is single, the mechanical strength is poor, and it is difficult to form by drying at room temperature and pressure.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a pulp foam cushioning material, comprising the following steps:

[0007] 1) mixing and dispersing the wax and the nanocellulose solution to obtain a nanocellulose / wax emulsion;

[0008] 2) mixing and stirring the pulp fibers and the flame retardant solution to obtain a pulp / flame retardant mixture;

[0009] 3) mixing the nanocellulose / wax emulsion obtained in step 1) with the pulp / flame retardant mixture obtained in step 2), removing the liquid phase, and obtaining a wet pulp;

[0010] 4) Drying the wet pulp obtained in step 3) to obtain a pulp foam cushioning material.

[0011] Preferably, the wax in step 1) comprises one or more of palm wax, paraffin wax, beeswax, rice bran wax and rosin;

[0012] The nanocellulose in the nanocellulose solution includes one or more of cellulose nanofibers, cellulose nanocrystals and cellulose microfibers.

[0013] Preferably, in the step 1), the mass percentage of wax in the nanocellulose / wax emulsion is 0.2-0.6%, and the mass percentage of nanocellulose is 0.6-1.8%;

[0014] The dispersion conditions include: a rotation speed of 5000 to 8000 rpm and a time of 3 to 8 minutes.

[0015] Preferably, in the step 2), the mass percentage of pulp fiber in the pulp / flame retardant mixture is 1-10%, and the mass percentage of the flame retardant is 0.25-0.75%;

[0016] The stirring conditions include: a rotation speed of 600 to 1200 rpm and a time of 5 to 10 minutes.

[0017] Preferably, the pulp fibers in step 2) include one or more of bamboo pulp fibers, cotton stalk pulp fibers, spruce pulp fibers, masson pine pulp fibers, red pine pulp fibers, larch pulp fibers and fir pulp fibers;

[0018] The flame retardant includes one or more of phosphoric acid, phytic acid, ammonium polyphosphate, boric acid and borate.

[0019] Preferably, the mixing conditions of step 3) include: pouring the nanocellulose / wax emulsion into the pulp / flame retardant mixture at a pouring speed of 20 to 50 mL / s;

[0020] The volume ratio of the nanocellulose / wax emulsion to the pulp / flame retardant mixture is 1:2;

[0021] The mixing rotation speed is 600-1200 rpm.

[0022] Preferably, the method of removing the liquid phase in step 3) comprises: placing the mixture obtained after mixing in a cylindrical porous mold until no liquid drops; the bottom and side walls of the cylindrical porous mold are opened with a pore size of 100 meshes and a single hole spacing of less than 0.5 mm.

[0023] Preferably, the drying conditions in step 4) include: a temperature of 50 to 80° C. and a drying time of 8 to 16 hours.

[0024] The present invention also provides a pulp foam cushioning material prepared by the preparation method described in the above technical solution, wherein the apparent density of the pulp foam cushioning material is 0.08-0.15 g / cm 3 , compression modulus is 0.20~1.50MPa, limiting oxygen index is 25~33%, vertical combustion performance reaches UL-94V0 level, and hydrophobic angle is 130~142°.

[0025] The present invention also provides the use of the pulp foam cushioning material described in the above technical solution in improving the strength, flame retardancy and waterproof performance of the foam cushioning material.

[0026] In the present invention, pulp fiber, as a common and widely available cellulose aggregate, has the characteristics of being biodegradable and renewable; nanocellulose has the characteristics of small size, large aspect ratio, high strength and abundance of hydrogen bonds, and has a distinct rod-shaped or filamentous morphological structure, and can be used as a reinforcing component of the main material and an emulsifier of the oil wax material; by selecting and comparing the hydrophobic properties of various waxes and the auxiliary molding effects on the foam material, the morphological structure and waterproof ability of the foam are systematically controlled; at the same time, through the wax coating layer solidified on the surface of the pulp fiber, efficient loading of various green flame retardants can be achieved to obtain excellent flame retardant properties. In summary, the present invention aims at the existing problems, and through a simple and fast multi-level interface engineering design strategy and a full physical composite process, the normal temperature and normal pressure preparation and structural performance regulation of high-performance pulp foam cushioning materials with high strength, flame retardancy, normal temperature and normal pressure drying molding and waterproofing can be achieved. The excellent comprehensive performance, moldability and recyclability make the pulp foam material have the prospect of large-scale production.

[0027] The introduction of flame retardants with high surface energy will increase the influence of high capillary pressure of the liquid phase on the foam material during the drying process at room temperature and pressure, thus causing structural shrinkage. The nanocellulose / wax emulsion is compounded and fixed on the surface of pulp fibers, which can reduce the surface energy of pulp fibers and encapsulate and fix the flame retardant, avoiding the interference of the introduction of high surface energy flame retardants on the foam material molding, thereby achieving uniform molding under room temperature and pressure drying.

[0028] Beneficial effects of the present invention:

[0029] The preparation process of the present invention does not involve the use of chemical synthesis reagents and chemical cross-linking processes, has no environmental pollution, and the pulp foam material can be completely degraded; the emulsification of hydrophobic wax is achieved through nanocellulose to achieve the preparation of fiber nanofiber / wax emulsion, which can be uniformly compounded with pulp fibers, thereby achieving hydrophobic modification and interface enhancement of pulp fibers, so that the hydrophobic angle of the foam can reach 142°, and the compressive strength of the foam can reach 1.50MPa; at the same time, the solidified wax coating layer can achieve efficient loading of green flame retardants, so that the limiting oxygen index (LOI) of the foam can reach 33%, and the vertical burning performance reaches UL-94V0 level; the foam material is compounded through the physical interaction of each component, and the preparation process is simple, fast, moldable and recyclable; in summary, the foam has excellent comprehensive properties and can be applied to scenes such as express packaging, cold chain transportation and building furniture. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments are briefly introduced below.

[0031] Figure 1The digital photo of the cellulose nanofiber / palm wax emulsion and the optical microscope image of the emulsion droplets in Example 1;

[0032] Figure 2 The effect of the amount of cellulose nanofibers on the mechanical properties of pulp foam materials in Examples 1-4;

[0033] Figure 3 This is the demonstration of the compressive strength of the pulp foam material in Example 1 (the foam bearing mass of the reactor is 2.5 kg);

[0034] Figure 4 This is the water contact angle image of the pulp foam material in Example 7;

[0035] Figure 5 This is a demonstration of the moldability of the foam material in Example 1;

[0036] Figure 6 It is a comparison diagram of the pulp foam cushioning material prepared in Example 1 and Comparative Example 1, wherein a and b correspond to the uniformly formed foam material obtained in Example 1, and c and d are the forming state and pore structure of the foam material without the composite nanocellulose / palm wax emulsion. DETAILED DESCRIPTION

[0037] The present invention provides a method for preparing a pulp foam cushioning material, comprising the following steps:

[0038] 1) mixing and dispersing the wax and the nanocellulose solution to obtain a nanocellulose / wax emulsion;

[0039] 2) mixing and stirring the pulp fibers and the flame retardant solution to obtain a pulp / flame retardant mixture;

[0040] 3) mixing the nanocellulose / wax emulsion obtained in step 1) with the pulp / flame retardant mixture obtained in step 2), removing the liquid phase, and obtaining a wet pulp;

[0041] 4) Drying the wet pulp obtained in step 3) to obtain a pulp foam cushioning material.

[0042] The present invention mixes and disperses wax with nanocellulose solution to obtain nanocellulose / wax emulsion. In the present invention, the wax preferably includes one or more of palm wax, paraffin wax, beeswax, rice bran wax and rosin. In the present invention, the wax is preferably wax particles with a particle size of 1 to 5 mm. The present invention has no special restrictions on the source of the wax, and it can be prepared by conventional commercial products or conventional preparation methods. In the present invention, the nanocellulose in the nanocellulose solution preferably includes one or more of cellulose nanofibers, cellulose nanocrystals and cellulose microfibers. The present invention has no special restrictions on the source of the nanocellulose, and it can be prepared by conventional commercial products or conventional preparation methods. In the present invention, the mass percentage of wax in the nanocellulose / wax emulsion is preferably 0.2 to 0.6%, and the mass percentage of nanocellulose is preferably 0.6 to 1.8%. In the present invention, the conditions for the dispersion preferably include: a rotation speed of 5000 to 8000 rpm and a time of 3 to 8 min. The present invention preferably disperses by a microfluidizer, so that the oil phase is emulsified, dispersed and stabilized by the nanocellulose. In the present invention, the wax and nanocellulose are preferably mixed and stirred at 90° C., so that the wax is completely melted into the oil phase.

[0043] The invention mixes and stirs pulp fiber and flame retardant solution to obtain a pulp / flame retardant mixture.

[0044] In the present invention, the mass percentage of pulp fiber in the pulp / flame retardant mixture is preferably 1-10%, and the mass percentage of flame retardant is preferably 0.25-0.75%. In the present invention, the stirring conditions preferably include: a rotation speed of 600-1200rpm and a time of 5-10min. In the present invention, the pulp fiber preferably includes one or more of bamboo pulp fiber, cotton stalk pulp fiber, spruce pulp fiber, masson pine pulp fiber, red pine pulp fiber, larch pulp fiber and fir pulp fiber. In the present invention, the flame retardant preferably includes one or more of phosphoric acid, phytic acid, ammonium polyphosphate, boric acid and borate. In the present invention, the flame retardant is preferably added to water and stirred for 20 minutes, and then mechanically stirred with the pulp fiber, so that the pulp fiber absorbs water and swells, and the flame retardant is adsorbed.

[0045] The invention mixes the obtained nanocellulose / wax emulsion with the obtained pulp / flame retardant mixture, removes the liquid phase, and obtains wet pulp.

[0046] In the present invention, the mixing conditions preferably include: pouring the nanocellulose / wax emulsion into the pulp / flame retardant mixture at a pouring speed of 20 to 50 mL / s. In the present invention, the volume ratio of the nanocellulose / wax emulsion to the pulp / flame retardant mixture is preferably 1:2. In the present invention, the mixing speed is preferably 600 to 1200 rpm, and the temperature is preferably 90°C. In the present invention, the method of removing the liquid phase preferably includes: placing the mixture obtained after mixing in a cylindrical porous mold until no liquid drops; the bottom and side walls of the cylindrical porous mold are opened with a pore size of 100 mesh and a single hole spacing of <0.5 mm.

[0047] The present invention dries the obtained wet pulp to obtain pulp foam cushioning material. In the present invention, the drying conditions preferably include: a temperature of 50 to 80° C. and a drying time of 8 to 16 hours.

[0048] The present invention provides a pulp foam cushioning material prepared by the preparation method described in the above technical solution, wherein the apparent density of the pulp foam cushioning material is 0.08-0.15 g / cm 3 , compression modulus is 0.20~1.50MPa, limiting oxygen index is 25~33%, vertical combustion performance reaches UL-94V0 level, and hydrophobic angle is 130~142°.

[0049] The present invention also provides the use of the pulp foam cushioning material described in the above technical solution in improving the strength, flame retardancy and waterproof performance of the foam cushioning material.

[0050] In order to further illustrate the present invention, the present invention is described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0051] Example 1

[0052] A method for preparing a pulp foam cushioning material, comprising the following steps:

[0053] Step (1) Preparation of nanocellulose / palm wax emulsion:

[0054] 0.6 g of palm wax particles were added to 100 mL of 0.6 wt % cellulose nanofiber (prepared by organic acid-mechanical method) (Zhao H, Sun L, Yu Y, et al. Low-cost, scale production of 0 nanocellulose from bamboo wastes via a recyclable and stable strategy [J]. Biomass Conversion and Biorefinery, 2024: 1-10.) dispersion, stirred and heated to 90 ° C to completely melt the wax particles into an oil phase; the cellulose nanofiber / palm wax dispersion was dispersed at high speed (6000 rpm 5 min) by a microjet high-speed homogenizer, so that the oil phase formed after the palm wax was melted was emulsified, dispersed and stabilized by the cellulose nanofiber to obtain a cellulose nanofiber / palm wax emulsion (such as Figure 1 shown).

[0055] Step (2) Preparation of pulp / flame retardant mixture:

[0056] Phosphoric acid as a flame retardant is added to water and stirred for 20 minutes to obtain a phosphoric acid solution, wherein the mass fraction of phosphoric acid in the phosphoric acid solution is maintained at 0.50wt%; 6g of bamboo pulp fiber is added to the phosphoric acid solution, and the pulp / phosphoric acid dispersion is stirred at high speed (800rpm for 5min) by a mechanical stirrer to obtain a mixed solution of pulp and phosphoric acid, wherein the pulp fiber absorbs water and swells, and adsorption of phosphoric acid is achieved.

[0057] Step (3) Mixing of pulp / phosphoric acid mixture and nanocellulose / palm wax emulsion:

[0058] The pulp / phosphoric acid mixture was heated to 90°C, and the prepared cellulose nanofiber / palm wax emulsion was slowly (20 mL / s) added to the pulp / phosphoric acid mixture that was being stirred at high speed, and fully dispersed at 800 rpm for 30 min. The volume ratio of cellulose nanofiber / palm wax emulsion and pulp / phosphoric acid mixture was 1:2, so that the pulp fibers loaded with phosphoric acid were fully adsorbed by the cellulose nanofiber / palm wax emulsion, thereby achieving the initial combination of each functional component with the pulp fibers.

[0059] Step (4) Drying the pulp foam cushioning material at room temperature and pressure:

[0060] The pulp / phosphoric acid / cellulose nanofiber / palm wax dispersion is transferred to a cylindrical porous container, and the excess liquid phase is naturally discharged to obtain a pulp wet slurry. The bottom and side walls of the cylindrical porous mold are opened with a pore size of 100 meshes and a single hole spacing of <0.5mm; wherein the solidified cellulose nanofiber / palm wax coating layer realizes efficient loading of the flame retardant component. The pulp wet slurry is transferred to an oven for drying (70°C for 12 hours) to obtain a high-strength, flame-retardant and waterproof pulp foam cushioning material.

[0061] The composite process of full physical interaction of each component in the preparation process of pulp foam material gives the foam material excellent moldability and easy processing, and can be processed into special shapes (such as Figure 5 shown).

[0062] Embodiment 2-4

[0063] In step (1) of Example 1, the mass fraction of cellulose nanofibers was taken as a variable to obtain different cellulose nanofiber / palm wax emulsions.

[0064] In the process conditions of Examples 1-4, the effects of the amount of cellulose nanofibers on the stress-strain curve and compression modulus of the pulp foam cushioning material during compression are as follows: Figure 2 As shown in Table 1, the foam material loads 2.5 kg of the reactor as shown in Figure 3 shown.

[0065] Table 1 Effect of cellulose nanofiber dosage on compression modulus of foam material

[0066]

[0067] From the results in Table 1, it can be seen that, when other variables are kept constant, as the amount of cellulose nanofibers in the cellulose nanofiber / palm wax emulsion increases, the compression modulus of the foam material increases and the compression resistance improves. When the amount of nanocellulose is above 1.8%, the excess nanocellulose will increase the influence of the capillary pressure of water on the system, making molding more difficult, resulting in an uneven morphology of the foam material after drying.

[0068] Embodiment 5-7

[0069] In step (1) of Example 1, the mass fraction of palm wax was taken as a variable to obtain different cellulose nanofiber / palm wax emulsions.

[0070] In the process conditions of Examples 1 and 5-7, the effect of the amount of palm wax on the water contact angle of the pulp foam cushioning material is shown in Table 2; when the mass fraction of palm wax is 0.6wt%, the water contact angle image of the foam material is as follows: Figure 4 shown.

[0071] Table 2 Effect of palm wax dosage on water contact angle of foam material

[0072]

[0073]

[0074] From the results in Table 2, it can be seen that, when other variables are kept constant, as the amount of palm wax in the cellulose nanofiber / palm wax emulsion increases, the hydrophobic angle of the foam material increases and the waterproof ability is improved. When the amount of AKD is above 0.6%, AKD is excessive in the system, and further increase will not significantly affect the hydrophobic angle.

[0075] Embodiment 8-10

[0076] In step (2) of Example 1, the mass fraction of phosphoric acid is used as a variable to obtain different phosphoric acid solutions.

[0077] In the process conditions of Examples 1 and 8-10, the effects of the amount of phosphoric acid on the limiting oxygen index (LOI) and vertical burning performance (UL-94) of the pulp foam cushioning material are shown in Table 3.

[0078] Table 3 Effect of phosphoric acid dosage on limiting oxygen index (LOI) and vertical burning performance (UL-94) of foam materials

[0079]

[0080] From the results in Table 3, it can be seen that, when other variables are kept constant, as the amount of phosphoric acid in the phosphoric acid solution increases, the limiting oxygen index of the foam material increases; with the loading of phosphoric acid, the UL-94 vertical combustion performance of the foam material can reach the V0 level; the foam material obtains excellent flame retardancy.

[0081] Comparative Example 1

[0082] The difference from Example 1 is that no nanocellulose / palm wax emulsion was added, and the prepared pulp foam cushioning material shrank after molding. Figure 6 (c, d).

[0083] In summary, the present invention realizes the preparation of recyclable and degradable pulp foam cushioning materials through green and pollution-free material selection and a composite method based on physical interaction. The control method of the effects of different concentrations and types of nanocellulose, hydrophobic wax and green flame retardant on the mechanical properties, hydrophobic properties and flame retardant properties of pulp foam materials is studied. Solutions are proposed to address the problems of chemical pollution, difficulty in complete degradation of foam, complex preparation process, single function and poor mechanical strength in the preparation process of conventional cellulose-based foam cushioning materials in the background, so as to realize the construction and structural control of green, sustainable, high-strength, flame-retardant and waterproof high-performance paper-based foam cushioning materials.

[0084] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a pulp foam cushioning material, characterized in that: The following steps are involved: 1) mixing and dispersing the wax and the nanocellulose solution to obtain a nanocellulose / wax emulsion; 2) mixing and stirring the pulp fibers and the flame retardant solution to obtain a pulp / flame retardant mixture; 3) mixing the nanocellulose / wax emulsion obtained in step 1) with the pulp / flame retardant mixture obtained in step 2), removing the liquid phase, and obtaining a wet pulp; 4) Drying the wet pulp obtained in step 3) to obtain a pulp foam cushioning material.

2. The preparation method according to claim 1, characterized in that: The wax in step 1) comprises one or more of palm wax, paraffin wax, beeswax, rice bran wax and rosin; The nanocellulose in the nanocellulose solution includes one or more of cellulose nanofibers, cellulose nanocrystals and cellulose microfibers.

3. The preparation method according to claim 1, characterized in that: In the step 1), the mass percentage of wax in the nanocellulose / wax emulsion is 0.2-0.6%, and the mass percentage of nanocellulose is 0.6-1.8%; The dispersion conditions include: a rotation speed of 5000 to 8000 rpm and a time of 3 to 8 minutes.

4. The preparation method according to claim 1, characterized in that: In the step 2), the mass percentage of pulp fiber in the pulp / flame retardant mixture is 1-10%, and the mass percentage of the flame retardant is 0.25-0.75%; The stirring conditions include: a rotation speed of 600 to 1200 rpm and a time of 5 to 10 minutes.

5. The preparation method according to claim 1, characterized in that: The pulp fibers in step 2) include one or more of bamboo pulp fibers, cotton stalk pulp fibers, spruce pulp fibers, masson pine pulp fibers, red pine pulp fibers, larch pulp fibers, and fir pulp fibers; The flame retardant includes one or more of phosphoric acid, phytic acid, ammonium polyphosphate, boric acid and borate.

6. The preparation method according to claim 1, characterized in that: The mixing conditions of step 3) include: pouring the nanocellulose / wax emulsion into the pulp / flame retardant mixture at a pouring speed of 20 to 50 mL / s; The volume ratio of the nanocellulose / wax emulsion to the pulp / flame retardant mixture is 1:2; The mixing rotation speed is 600-1200 rpm.

7. The preparation method according to claim 1, characterized in that: The method of removing the liquid phase in step 3) includes: placing the mixture obtained after mixing in a cylindrical porous mold until no liquid drops; the bottom and side walls of the cylindrical porous mold are opened with a pore size of 100 meshes and a single hole interval of less than 0.5 mm.

8. The preparation method according to claim 1, characterized in that: The drying conditions in step 4) include: a temperature of 50 to 80° C. and a drying time of 8 to 16 hours.

9. A pulp foam cushioning material prepared by the preparation method according to any one of claims 1 to 8, wherein the apparent density of the pulp foam cushioning material is 0.08 to 0.15 g / cm 3 , compression modulus is 0.20~1.50MPa, limiting oxygen index is 25~33%, vertical combustion performance reaches UL-94V0 level, and hydrophobic angle is 130~142°.

10. Use of the pulp foam cushioning material according to claim 9 in improving the strength, flame retardancy and waterproof properties of foam cushioning materials.

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