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

Abstract

The invention relates to the technical field of paper pulp foaming buffer material preparation, in particular to a paper pulp foaming buffer material and a preparation method and application thereof. Carrying out mechanical treatment on the paper pulp fiber suspension to obtain a fibrillated paper pulp fiber suspension; mixing the fibrillated paper pulp fiber suspension with an electrolyte to obtain a paper pulp / electrolyte mixed solution; mixing the paper pulp / electrolyte mixed solution with a surfactant, and foaming to obtain paper pulp / electrolyte foaming slurry; and placing the paper pulp / electrolyte foaming slurry in a porous mold to remove a liquid phase, and drying to obtain the paper pulp foaming buffer material. The paper pulp foaming buffer material provided by the invention has excellent mechanical property, heat insulation property, machinability and biodegradability, and the packaging buffer application of the paper pulp foaming material to articles such as light fragile products and temperature-sensitive products is obviously expanded.

Description

Technical Field

[0001] This invention relates to the field of pulp foaming cushioning material preparation technology, and in particular to a pulp foaming cushioning material, its preparation method and application. Background Technology

[0002] Developing high-performance biomass-based foam materials to replace traditional petroleum-based foams (such as polystyrene, polyurethane, and polyethylene foams) is a global focus in the process of moving towards a green and low-carbon era. Cellulose, with its wide availability and renewable resources, is an ideal alternative material with significant development and application potential. However, due to its hydrophilic nature, cellulose is susceptible to structural shrinkage and densification during drying due to capillary pressure from water. Therefore, cellulose-based foam materials typically have low expansion ratios and dense pore structures, resulting in poor thermal insulation performance and high density. Consequently, the current construction of high-performance cellulose foam materials mainly relies on freeze-drying and supercritical drying equipment, but these methods have long preparation cycles, complex processes, and high energy consumption, hindering large-scale production. Furthermore, the loose porous framework structure of cellulose foam materials typically results in poor cushioning performance and a low range of controllable compressive strength, severely limiting their application value in scenarios such as express packaging and cold chain transportation. Therefore, how to prepare high-performance cellulose-based foam materials through low-cost, short-cycle, ambient temperature and pressure drying methods has become a research hotspot.

[0003] Patent CN106835808A describes the preparation of a nano-cellulose-reinforced pulp foam material, combining cationic polyacrylamide as a binder and using a surfactant as a foaming agent to achieve lightweight construction of the foam material; Patent CN106008724A discloses a method for preparing cellulose foam, achieving the construction of cellulose foam through the bonding effect of alkali pretreatment of cellulose fibers and viscose solution. Therefore, cellulose-based foam materials are constantly being innovated and developed, but the aforementioned patents still have a series of problems: 1. Using only a single surfactant results in poor foaming effect and low expansion ratio, thus the foam material density remains high and its thermal insulation performance is poor; 2. Excessive use of chemical crosslinking leads to serious pollution during processing and increases the difficulty of foam material degradation; 3. The preparation process is complex and overly reliant on freeze-drying and supercritical drying equipment; 4. The structure and composition are simple, resulting in poor controllability of mechanical properties. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a pulp foam cushioning material, its preparation method, and its applications. The pulp foam cushioning material provided by this invention possesses excellent mechanical properties, thermal insulation properties, processability, and biodegradability, significantly expanding the application of pulp foaming materials in packaging and cushioning lightweight, fragile, and temperature-sensitive products.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing a pulp foam cushioning material, comprising the following steps: 1) Mechanically process the pulp fiber suspension to obtain a fibrillated pulp fiber suspension; 2) Mix the fibrillated pulp fiber suspension obtained in step 1) with an electrolyte to obtain a pulp / electrolyte mixture; 3) Mix the pulp / electrolyte mixture obtained in step 2) with a surfactant and foam it to obtain a pulp / electrolyte foamed pulp; 4) Place the pulp / electrolyte foaming slurry obtained in step 3) into a porous mold to remove the liquid phase, and dry it to obtain pulp foaming buffer material.

[0006] Preferably, the mass percentage of pulp fiber in the pulp fiber suspension in step 1) is 1-3%; The pulp fiber suspension contains one or more of the following: bamboo pulp fiber, straw pulp fiber, cotton stalk pulp fiber, hemp stalk fiber, fir pulp fiber, and pine pulp fiber.

[0007] Preferably, the mechanical treatment conditions in step 1) include: mechanical treatment with a Valley pulper for 4 to 12 hours, followed by treatment with a colloid mill for 1 hour.

[0008] Preferably, the electrolyte in step 2) includes one or more of sodium phytate, sodium chloride, sodium citrate, zinc chloride, ammonium polyphosphate, and sodium tetraborate.

[0009] Preferably, in step 2), the mass ratio of the fibrillated pulp fiber suspension to the electrolyte is 100:0.02~2; The mixing conditions include stirring at a speed of 400-800 rpm for 5-8 minutes.

[0010] Preferably, in step 2), the mass ratio of the fibrillated pulp fiber suspension to the electrolyte is 100:0.06~1.

[0011] Preferably, the surfactant in step 3) includes one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and hexadecyltrimethylammonium bromide; The mass ratio of the pulp / electrolyte mixture to the surfactant is 100:0.02~0.08; The foaming conditions include: stirring at 1000~3000 rpm for 5~10 minutes until the volume of the mixture expands to a stable state.

[0012] Preferably, the bottom and sidewalls of the porous mold in step 4) have openings with a mesh size of 60 and a single hole spacing of 0.3 mm. The drying conditions include a temperature of 50-80°C and a time of 4-10 hours.

[0013] The present invention also provides a pulp foaming buffer material prepared by the preparation method described above, wherein the apparent density of the pulp foaming buffer material is 7.3~41.6 mg / cm³. 3 The compression thickness recovery rate under 60% compressive strain is >90%, and the thermal conductivity is 0.029~0.040 W / (m·K).

[0014] The present invention also provides the application of the pulp foaming cushioning material described in the above technical solution in improving the cushioning performance, thermal insulation performance, mechanical properties and lightweight of foam cushioning materials.

[0015] 1. Controllable fibrillation of pulp fibers is achieved through multi-stage mechanical processing, which can significantly increase the physical entanglement and cohesion of pulp fibers, thereby endowing pulp foaming materials with excellent and controllable mechanical properties and structural stability. 2. High-ratio foaming of pulp mixtures can be achieved by using electrolyte-assisted surfactants for mechanical foaming; 3. Electrolytes can undergo interfacial composite formation with pulp fibers, further improving the controllable mechanical strength range of pulp foam materials; 4. The components of the foamed material are compounded only through physical interactions, without any chemical cross-linking process. The material is fully biodegradable and recyclable. 5. This foaming material is prepared at room temperature and pressure, without relying on freeze drying or supercritical drying, and has low equipment requirements and a short preparation cycle.

[0016] The beneficial effects of this invention are: This invention obtains pulp fibers with a fibrillated structure through a mechanical processing process, and then combines this with an electrolyte-assisted surfactant for mechanical foaming, achieving the room temperature and pressure preparation of a lightweight, highly elastic, and low thermal conductivity pulp foamed cushioning material. Specifically, the electrolyte-assisted surfactant mechanical foaming process achieves a foaming ratio of up to 280% in the pulp mixture, resulting in an apparent density as low as 7.3 mg / cm³ of the foamed material. 3 By adjusting the mechanical processing and time, the fibrillation structure is controlled, thereby regulating the physical entanglement and cohesion of pulp fibers to improve the structural stability of the foamed material. Its thickness recovery rate can reach 96.6% (at 60% compressive strain). Simultaneously, the electrolyte can undergo interfacial composite with the pulp fibers, playing an auxiliary reinforcing role and synergistically improving the mechanical strength of the pulp foamed material, with a compressive modulus of 3.2~59.2 kPa. Furthermore, thanks to its rich hierarchical pore structure, the foamed material prepared in Example 1 has a low thermal conductivity of 0.029 W / (m·K) (International Standard ISO 22007-2). Figure 4Compared to petroleum-based foam materials (such as EPS), pulp foam has superior thermal insulation properties. Pulp foam possesses excellent mechanical properties, thermal insulation performance, processability, and biodegradability, significantly expanding its application in packaging and cushioning lightweight, fragile, and temperature-sensitive products. Figure 5 ). Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly described below.

[0018] Figure 1 The effect of sodium dodecyl sulfate on the expansion ratio of pulp / sodium phytate foaming pulp; Figure 2 The effect of sodium phytate on the expansion ratio of pulp / sodium phytate foamed pulp; Figure 3 The effect of mechanical processing time on the thickness recovery rate of pulp foam materials; Figure 4 The thermal conductivity of pulp foam and polystyrene foam (EPS); Figure 5 This refers to the application of pulp foam materials in the field of packaging cushioning. Detailed Implementation

[0019] This invention provides a method for preparing a pulp foam cushioning material, comprising the following steps: 1) Mechanically process the pulp fiber suspension to obtain a fibrillated pulp fiber suspension; 2) Mix the fibrillated pulp fiber suspension obtained in step 1) with an electrolyte to obtain a pulp / electrolyte mixture; 3) Mix the pulp / electrolyte mixture obtained in step 2) with a surfactant and foam it to obtain a pulp / electrolyte foamed pulp; 4) Place the pulp / electrolyte foaming slurry obtained in step 3) into a porous mold to remove the liquid phase, and dry it to obtain pulp foaming buffer material.

[0020] This invention mechanically processes a pulp fiber suspension to obtain a fibrillated pulp fiber suspension. In this invention, the mass percentage of pulp fibers in the pulp fiber suspension is preferably 1-3%. Preferably, the pulp fibers in the pulp fiber suspension include one or more of bamboo pulp fibers, straw pulp fibers, cotton stalk pulp fibers, hemp stalk fibers, fir pulp fibers, and pine pulp fibers. The mechanical processing conditions preferably include: mechanical processing with a Valley beater for 4-12 hours (at 600 rpm), followed by processing with a colloid mill for 1 hour.

[0021] This invention involves mixing a fibrillated pulp fiber suspension with an electrolyte to obtain a pulp / electrolyte mixture. In this invention, the electrolyte preferably includes one or more of sodium phytate, sodium chloride, sodium citrate, zinc chloride, ammonium polyphosphate, and sodium tetraborate. In this invention, the mass ratio of the fibrillated pulp fiber suspension to the electrolyte is preferably 100:0.02~2. In this invention, the mixing conditions preferably include stirring at 400~800 rpm for 5~8 min. In this invention, the mass ratio of the fibrillated pulp fiber suspension to the electrolyte is preferably 100:0.06~1.

[0022] This invention involves mixing and foaming a pulp / electrolyte mixture with a surfactant to obtain a foamed pulp / electrolyte slurry. In this invention, the surfactant preferably includes one or more of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, and hexadecyltrimethylammonium bromide. In this invention, the mass ratio of the pulp / electrolyte mixture to the surfactant is preferably 100:0.02~0.08. In this invention, the foaming conditions preferably include stirring at 1000~3000 rpm for 5~10 min until the mixture volume expands to a stable state.

[0023] This invention involves placing the pulp / electrolyte foaming slurry in a porous mold to remove the liquid phase, followed by drying to obtain a pulp foaming buffer material. In this invention, the porous mold has openings at the bottom and side walls, with a pore size of 60 mesh and a single-pore spacing of 0.3 mm. This invention does not limit the shape of the porous mold used; any shape is acceptable, such as a cylindrical mold. In this invention, the preferred drying conditions include a temperature of 50-80°C and a time of 4-10 hours.

[0024] The present invention also provides a pulp foaming buffer material prepared by the preparation method described above, wherein the apparent density of the pulp foaming buffer material is 7.3~41.6 mg / cm³. 3 The compression thickness recovery rate under 60% compressive strain is >90%, and the thermal conductivity is 0.029~0.040 W / (m·K).

[0025] The present invention also provides the application of the pulp foaming cushioning material described in the above technical solution in improving the cushioning performance, thermal insulation performance, mechanical properties and lightweight of foam cushioning materials.

[0026] To further illustrate the present invention, the following detailed description is provided in conjunction with embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0027] Example 1:

[0028] A method for preparing a pulp foam cushioning material, comprising the following steps: Step (1) Preparation of fibrillated pulp fibers: A 1 wt% pulp fiber suspension was mechanically treated for 8 h using a Valley beater, followed by treatment with a colloid mill for 1 h to obtain a fibrillated pulp fiber suspension. The pulp fiber used was bamboo pulp fiber. Step (2) Preparation of pulp / electrolyte mixture: The pulp fiber suspension was drained and concentrated to 1.5 wt%. Sodium phytate with a final concentration of 0.06 wt% was added, and the mixture was stirred at 800 rpm for 8 min to obtain a pulp / sodium phytate mixture. Step (3) Preparation of pulp / electrolyte foaming pulp: Sodium dodecyl sulfate with a final concentration of 0.06 wt% was added to the pulp / sodium phytate mixture as a foaming agent. The mixture was stirred and foamed at 2000 rpm using a high-speed stirrer until the mixture expanded to a stable state, thus obtaining the pulp / sodium phytate foamed pulp. Step (4) Preparation of pulp foam cushioning material at room temperature and pressure: The pulp / sodium phytate foaming slurry was transferred to a polypropylene mold and allowed to drain naturally until no obvious dripping occurred. It was then transferred to an oven and dried at 70 °C for 8 hours to obtain the pulp foaming buffer material. The bottom and side walls of the polypropylene cylindrical porous mold used were perforated with a pore size of 60 mesh and a single-pore spacing of 0.3 mm.

[0029] Examples 2-5:

[0030] Using the mass fraction of sodium dodecyl sulfate in step (2) of Example 1 as a variable, different pulp / sodium phytate foaming pulps were obtained. Figure 1 ).

[0031] The expansion ratio of pulp / sodium phytate foamed pulp is calculated as follows: (volume of liquid phase after foaming - volume of initial liquid phase) / volume of initial liquid phase × 100%.

[0032] Table 1 includes Examples 1 and 2-5.

[0033] Table 1. Effect of sodium phytate dosage on the expansion ratio and apparent density of pulp / sodium phytate foaming pulp.

[0034] As shown in Table 1, under the condition that other variables are kept constant, the expansion ratio of pulp / sodium phytate foaming pulp increases with the increase of sodium dodecyl sulfate in pulp / sodium phytate mixture. When the dosage reaches 0.06 wt%, the volume expansion ratio reaches the upper limit.

[0035] Examples 6-8:

[0036] Using the mass fraction of sodium phytate in step (2) of Example 1 as a variable, different pulp / sodium phytate foaming pulps were obtained. Figure 2 ).

[0037] Apparent density is measured according to GB / T 6343-2009.

[0038] Table 2 includes Examples 1 and 6-8.

[0039] Table 2. Effect of sodium phytate dosage on the expansion ratio and apparent density of pulp / sodium phytate foaming pulp.

[0040] As shown in Table 2, under the condition that other variables are kept constant, the expansion ratio of pulp / sodium phytate foaming pulp increases with the increase of sodium phytate content in pulp / sodium phytate mixture, reaching up to 280% of the initial volume of liquid phase, compared to only 117% without sodium phytate. This fully demonstrates that sodium phytate can assist sodium dodecyl sulfate in achieving high-ratio mechanical foaming.

[0041] Examples 9-11: In step (2) of Example 1, the mechanical treatment time of pulp fibers using a Valley beater was used as a variable (the treatment time of the colloid mill was fixed at 1 h) to obtain different pulp / sodium phytate foaming pulps.

[0042] Thickness recovery rate conforms to GB / T 8168-2008; Compression modulus: doi.org / 10.1021 / acssuschemeng.1c01816.

[0043] Table 3 includes Examples 1 and 9-11.

[0044] Table 3. Effect of Valley pulper mechanical processing time on pulp / sodium phytate foamed pulp thickness recovery rate ( Figure 3 The influence of ) and compressive modulus

[0045] As shown in Table 3, under the condition that other variables are kept constant, the thickness recovery rate of pulp foam material increases with the increase of mechanical processing time, and the compression modulus increases accordingly, which fully demonstrates the beneficial effect of the fibrillation process of pulp fibers on mechanical properties.

[0046] Examples 12-13:

[0047] By using the mass fraction of sodium phytate in step (2) of Example 1 as a variable, different pulp / sodium phytate foaming pulps were obtained.

[0048] Compression modulus, specific compression modulus, and energy absorption were determined according to doi.org / 10.1021 / acssuschemeng.1c01816.

[0049] Table 4 includes Examples 1 and 12-13.

[0050] Table 4. Effect of sodium phytate dosage on the mechanical properties of pulp / sodium phytate foaming materials

[0051] As shown in Table 4, when other variables are kept constant, the compression modulus and specific compression modulus of the pulp foam material increase significantly with the increase of sodium phytate dosage, which fully demonstrates that sodium phytate can adjust the mechanical properties of pulp foam material.

[0052] Examples 14-16: Table 5 includes Examples 1 and 14-16, in which sodium phytate was replaced with other electrolytes while the mass fraction remained unchanged.

[0053] Table 5. Effect of electrolyte dosage on foaming ratio of the mixture

[0054] As shown in Table 5, when other variables are kept constant, different electrolytes significantly improve the foaming ratio of the mixture, with sodium phytate showing the best effect at the same mass fraction.

[0055] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, 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, Includes the following steps: 1) Mechanically process the pulp fiber suspension to obtain a fibrillated pulp fiber suspension; 2) Mix the fibrillated pulp fiber suspension obtained in step 1) with an electrolyte to obtain a pulp / electrolyte mixture; 3) Mix the pulp / electrolyte mixture obtained in step 2) with a surfactant and foam it to obtain a pulp / electrolyte foamed pulp; 4) Place the pulp / electrolyte foaming slurry obtained in step 3) into a porous mold to remove the liquid phase, and dry it to obtain pulp foaming buffer material.

2. The preparation method according to claim 1, characterized in that, Step 1) The pulp fiber suspension contains 1-3% pulp fiber by mass. The pulp fiber suspension contains one or more of the following: bamboo pulp fiber, straw pulp fiber, cotton stalk pulp fiber, hemp stalk fiber, fir pulp fiber, and pine pulp fiber.

3. The preparation method according to claim 1, characterized in that, The mechanical treatment conditions in step 1) include: mechanical treatment with a Valley pulper for 4 to 12 hours, followed by treatment with a colloid mill for 1 hour.

4. The preparation method according to claim 1, characterized in that, Step 2) The electrolyte includes one or more of sodium phytate, sodium chloride, sodium citrate, zinc chloride, ammonium polyphosphate, and sodium tetraborate.

5. The preparation method according to claim 1, characterized in that, Step 2) The mass ratio of the fibrillated pulp fiber suspension to the electrolyte is 100:0.02~2; The mixing conditions include stirring at a speed of 400-800 rpm for 5-8 minutes.

6. The preparation method according to claim 1, characterized in that, Step 2) The mass ratio of the fibrillated pulp fiber suspension to the electrolyte is 100:0.06~1.

7. The preparation method according to claim 1, characterized in that, Step 3) The surfactant includes one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and hexadecyltrimethylammonium bromide; The mass ratio of the pulp / electrolyte mixture to the surfactant is 100:0.02~0.08; The foaming conditions include: stirring at 1000~3000 rpm for 5~10 minutes until the volume of the mixture expands to a stable state.

8. The preparation method according to claim 1, characterized in that, Step 4) The bottom and side walls of the porous mold are perforated with a mesh size of 60 mesh and a single hole spacing of 0.3 mm; The drying conditions include a temperature of 50-80°C and a time of 4-10 hours.

9. A pulp foamed cushioning material prepared by the preparation method according to any one of claims 1 to 8, wherein the apparent density of the pulp foamed cushioning material is 7.3 to 41.6 mg / cm³. 3 The compression thickness recovery rate under 60% compressive strain is >90%, and the thermal conductivity is 0.029~0.040 W / (m·K).

10. The application of the pulp foaming cushioning material according to claim 9 in improving the cushioning performance, thermal insulation performance, mechanical properties and lightweighting of foam cushioning materials.

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