Preparation method and application of hollow glass microsphere / cellulose composite foam material

Abstract

The invention discloses a preparation method and application of a hollow glass microsphere / cellulose composite foam material, and the preparation method comprises the following steps: carrying out beating pretreatment on a paper pulp fiber raw material until the beating degree is 30-45 degrees SR; mixing the pretreated paper pulp fibers with a sodium alginate aqueous solution and hollow glass microspheres according to a mass ratio of 1: (0.1-0.5): (0.1-1), and carrying out high-speed shearing dispersion at a speed of 2000-5000r / min to form a suspension; a foaming agent is added into the suspension liquid for foaming, the adding amount is 0.5-1.0 wt% of the total mass of the suspension liquid, and after the volume of wet foam is stable, the wet foam is injected into a mold for drainage forming; and injecting the wet foam into a mold, draining and molding, and drying at 60-80 DEG C for 6-8 hours to obtain the composite foam material with the three-dimensional porous structure. According to the invention, the blank of light, high-strength, flame-retardant, environment-friendly and recyclable foam materials in the prior art is filled, and an innovative solution is provided for the fields of building heat insulation, traffic flame-retardant liners and the like.

Description

Technical Field

[0001] This invention belongs to the field of composite foam materials technology, specifically relating to a method for preparing hollow glass microspheres / cellulose composite foam materials and their applications. Background Technology

[0002] In recent years, with the development of energy conservation and environmental protection, green building, new energy vehicles, and lightweight electronic equipment, the demand for high-performance lightweight porous materials has been increasing. Ideal lightweight materials need to possess low density, excellent mechanical properties, good thermal insulation and flame retardancy, while also being environmentally friendly and recyclable. Traditional foam materials (such as polyurethane and polystyrene), although lightweight, suffer from flammability, low mechanical strength, and non-degradability, limiting their application in high-end fields.

[0003] Cellulose, as a renewable and biodegradable biomass resource, has been widely used in the preparation of environmentally friendly porous materials. Cellulose foam has advantages such as low density, biodegradability, and good thermal insulation, but it also has disadvantages such as insufficient mechanical properties, flammability, and poor structural stability. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing hollow glass microspheres / cellulose composite foam materials and their applications, thereby solving the aforementioned technical problems in the prior art.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A method for preparing a hollow glass microsphere / cellulose composite foam material includes the following steps:

[0007] S1. Pre-treat the pulp fiber raw material by beating it to a freeness of 30-45°SR.

[0008] S2. The pretreated pulp fibers are mixed with sodium alginate aqueous solution and hollow glass microspheres at a mass ratio of 1:0.1-0.5:0.1-1, and dispersed by high-speed shearing at 2000-5000 r / min to form a suspension.

[0009] S3. Add foaming agent to the suspension and foam. The amount added is 0.5-1.0 wt% of the total mass of the suspension. After the wet foam volume stabilizes, pour it into the mold to drain and form.

[0010] S4. Inject the wet foam into the mold to drain and shape it, and dry it at 60-80℃ for 6-8 hours to obtain a three-dimensional porous composite foam material.

[0011] The resulting composite foam material includes the following performance parameters:

[0012] Density is 20-50 mg / cm³ 3 ;

[0013] Thermal conductivity ≤35mW / m·K;

[0014] Limiting oxygen index ≥ 26%;

[0015] Z-axis compression modulus ≥70kPa, X-axis compression modulus ≥180kPa;

[0016] Carbon residue at 600℃ ≥40wt%.

[0017] Furthermore, the hollow glass microspheres are made of borosilicate glass, with a particle size distribution of 10-100 μm, a wall thickness of 1-5 μm, and a true density of 0.15-0.40 g / cm³. 3 .

[0018] Furthermore, when the mass ratio of pulp fiber to hollow glass microspheres is 1:1, the density of the resulting foam material is 27-30 mg / cm³. 3 Thermal conductivity ≤30mW / m·K.

[0019] Furthermore, the foaming agent is at least one of sodium dodecyl sulfate, sodium fatty alcohol polyoxyethylene ether sulfate, or a protein-based foaming agent.

[0020] Furthermore, the surface of the hollow glass microspheres is modified with a silane coupling agent.

[0021] Furthermore, the microstructure of the composite foam material is a three-dimensional network formed by cross-linking cellulose fibers and hollow glass microspheres with sodium alginate, with a porosity ≥90% and an average pore size of 50-300 μm.

[0022] Application of a composite foam material in building insulation, flame-retardant lining for transportation, fireproof encapsulation of electronic equipment, or environmentally friendly packaging materials.

[0023] A method for recycling composite foam materials includes the following steps:

[0024] S501. Soak the waste foam material in an acidic solution with pH = 1-5;

[0025] S02, ultrasonic treatment for 10-60 minutes to separate cellulose fibers from hollow glass microspheres;

[0026] S503, filtration and recovery of hollow glass microspheres, and cellulose fibers can be reused in foam preparation after pulping.

[0027] The beneficial effects of this invention are:

[0028] 1. This invention utilizes a composite of hollow glass microspheres (HGM) and cellulose fibers, resulting in a material density as low as 20-50 mg / cm³. 3 (Optimal 27-30 mg / cm) 3 The porosity is ≥90%, forming a stable three-dimensional porous network structure. The addition of HGM significantly improves the compressive strength, with the Z-direction and X-direction compressive moduli reaching 70kPa and 180kPa or more, respectively, and the anisotropy difference is reduced (the Z / X-direction strength ratio is 1.28:1 when the ratio is 1:1).

[0029] 2. The borosilicate material and cellulose of the HGM in this invention work synergistically to achieve a limiting oxygen index ≥26% and reduce the peak heat release rate (PHRR) by 52.9% to 63.4 kW / m³. 2 The self-extinguishing time is shortened to 3-5 seconds, and the amount of smoke produced is reduced by more than 40%. The thermal conductivity is ≤30mW / m·K, which is attributed to the HGM blocking thermal radiation and the high porosity inhibiting convection / conduction, which is better than the blank sample (49.63mW / m·K).

[0030] 3. This invention uses cellulose fibers as the matrix and sodium alginate as a green binder, avoiding pollution from traditional polymers. HGM and cellulose can be separated through acidic solution immersion and ultrasonic treatment (recovery rate >90%), achieving closed-loop material utilization. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0032] Figure 1 This is a flowchart illustrating the preparation process of the hollow glass microsphere fiber composite foam material according to an embodiment of the present invention.

[0033] Figure 2 This is a comparison diagram of the composite foam material of this invention and ordinary materials;

[0034] Figure 3 This is a scanning electron microscope image of the interior of the composite foam material according to an embodiment of the present invention;

[0035] Figure 4 This is a comparison diagram of the horizontal combustion state of the composite foam material according to an embodiment of the present invention;

[0036] Figure 5 This is a comparison diagram of the vertical combustion state of the composite foam material according to an embodiment of the present invention;

[0037] Figure 6 These are comparative images of horizontal (left) and vertical (right) combustion samples of composite foam materials according to embodiments of the present invention;

[0038] Figure 7These are mechanical performance test diagrams of an embodiment of the present invention;

[0039] Figure 8 This is a graph showing the change in thermal conductivity according to an embodiment of the present invention. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0041] like Figure 1 As shown, this embodiment of the invention provides a method for preparing a hollow glass microsphere / cellulose composite foam material, comprising the following steps:

[0042] S1. The pulp fiber raw materials are pre-treated by beating to a freeness of 30-45°SR to improve fiber dispersibility. The raw materials include: cellulose fibers: bleached softwood pulp (freeness 30-45°SR), providing a biodegradable matrix; hollow glass microspheres (HGM): borosilicate material, particle size 10-100μm, true density 0.15-0.40g / cm³. 3 It imparts lightweight and flame retardancy.

[0043] S2. The pretreated pulp fibers, sodium alginate aqueous solution, and hollow glass microspheres (the surface of the hollow glass microspheres is modified with a silane coupling agent) are mixed at a mass ratio of 1:0.1-0.5:0.1-1 and dispersed at high speed by shearing at 2000-5000 r / min to form a suspension. The hollow glass microspheres are made of borosilicate glass with a particle size distribution of 10-100 μm, a wall thickness of 1-5 μm, and a true density of 0.15-0.40 g / cm³. 3 .

[0044] S3. Add a foaming agent (sodium dodecyl sulfate, sodium fatty alcohol polyoxyethylene ether sulfate, or at least one of protein-based foaming agents) to the suspension to foam. The amount added is 0.5-1.0 wt% of the total mass of the suspension. After the wet foam volume stabilizes, pour it into a mold to drain and form.

[0045] S4. Inject the wet foam into the mold to drain and shape it, and dry it at 60-80℃ for 6-8 hours to obtain a three-dimensional porous composite foam material.

[0046] The resulting composite foam material includes the following performance parameters:

[0047] Density is 20-50 mg / cm³ 3 ;

[0048] Thermal conductivity ≤35mW / m·K;

[0049] Limiting oxygen index ≥ 26%;

[0050] Z-axis compression modulus ≥70kPa, X-axis compression modulus ≥180kPa;

[0051] Carbon residue at 600℃ ≥40wt%.

[0052] When the mass ratio of pulp fiber to hollow glass microspheres is 1:1, the density of the resulting foam material is 27-30 mg / cm³. 3 Thermal conductivity ≤30mW / m·K.

[0053] Table 1

[0054] HGM: Cellulose <![CDATA[Density (mg / cm 3 )]]> <![CDATA[PHRR(kW / m 2 )]]> Compressive strength (kPa) 1:4 35.2 98.5 42.1 1:2 31.8 75.3 58.6 3:4 29.5 68.2 64.3 1:1 27.9 63.4 67.9

[0055] As shown in Table 1 above, increasing the HGM ratio can reduce density and enhance flame retardancy and mechanical properties, but excessive amounts (>1:1) may lead to a fragile foam structure.

[0056] Peak heat release rate (PHRR) ≤ 65 kW / m 2 (35kW / m 2 (Under heat flow);

[0057] The microstructure of the composite foam material is a three-dimensional network formed by cross-linking cellulose fibers and hollow glass microspheres with sodium alginate, with a porosity ≥90% and an average pore size of 50-300μm.

[0058] Application of a composite foam material in building insulation, flame-retardant lining for transportation, fireproof encapsulation of electronic equipment, or environmentally friendly packaging materials.

[0059] A method for recycling composite foam materials includes the following steps:

[0060] S501. Soak the waste foam material in an acidic solution with pH = 1-5;

[0061] S02, ultrasonic treatment for 10-60 minutes to separate cellulose fibers from hollow glass microspheres;

[0062] S503, filtration and recovery of hollow glass microspheres, and cellulose fibers can be reused in foam preparation after pulping.

[0063] The specific experimental method is as follows: First, 1.0 g of sodium alginate was added to 200 mL of deionized water and heated at 80 °C for 5 min using a magnetic stirrer, then cooled to room temperature to prepare an aqueous sodium alginate solution for later use. 20 g (octane-dry) of bleached softwood pulp was weighed and added to a fiber dissociator. Water was added to adjust the suspension concentration to 2 wt%, and the mixture was stirred at 3000 rpm for dissociation. Then, 200 mL of the sodium alginate aqueous solution and 20 g of hollow glass microspheres were added to the dissociator, and stirring continued until fully mixed. After the solution was homogeneous, 0.8 g of sodium dodecyl sulfate was added to the mixture and stirred at high speed. When the wet foam reached its maximum volume and remained constant, it was quickly poured into a mold with a nylon filament bottom to remove excess water and dried in an oven at 60 °C for 6 h. Experiments were conducted in groups with pulp fiber to hollow glass microsphere ratios of 1:1, 1:0.75, 1:0.5, 1:0.25, and 1:0, respectively. A blank control group was prepared by foaming materials without sodium alginate and hollow glass microspheres.

[0064] Foam materials are prepared by mixing cellulose with hollow glass microspheres, in which the hollow glass microspheres are attached to the fiber surface, and sodium alginate acts as a binder. The three components work synergistically to form a lightweight, porous foam material, such as... Figure 2 (Left). The foam sample was cut into pieces approximately 50×50×40mm. 3 The weight is 27.86g, and the calculated density is 27.86mg / cm³. 3 This demonstrates that the addition of hollow glass microspheres has little effect on cellulose foam, and the material remains ultra-low density. Comparison between the sample and the blank control reveals significant differences in shape and appearance. The cellulose foam with added hollow glass microspheres exhibits a uniform appearance and stable structure, while the control group... Figure 2 (Right) After foaming, the structure collapsed severely and showed irregular patterns.

[0065] The microstructure of the internal fibers of the material was observed using SEM. All six groups of samples were examined using scanning electron microscopy. Figure 3 The top images show ratios of 1:1, 1:0.75, 1:0.5, 1:0.25, and 1:0, respectively, while the bottom images show observations at higher magnification. It is clearly visible that the 1:1 sample, under the same magnification, exhibits the highest number of hollow glass microspheres, distributed on the fiber surface. This contributes to a more stable foam structure and improves mechanical and flame-retardant properties. Furthermore, as the incorporation ratio decreases, the distribution of hollow glass microspheres within the foam significantly diminishes.

[0066] The infrared spectrum of the foam shows a typical characteristic peak of cellulose at 3320 cm⁻¹. -1 (OH stretching), 1631cm -1 (OH bending) and 1367cm -1(CH bend). Also at 1422cm -1 The peak values ​​at each point are related to the CO bending vibration of sodium alginate.

[0067] The flame-retardant properties of hollow glass microsphere cellulose foam materials were investigated using vertical and horizontal burning tests. Figure 4 , Figure 5 As shown in the figure. The ignition time is approximately 10 seconds. The blank sample foam exhibits significant combustion effects, with horizontal and vertical combustion times of 40 seconds and 25 seconds (and complete combustion), respectively. During the combustion of the blank sample, the foam material shows obvious structural collapse and shrinkage, ultimately forming a fragile black residue. Correspondingly, the foam with a certain proportion of hollow glass microspheres added exhibits self-extinguishing characteristics. With the ignition time remaining constant at 10 seconds, the ignition time gradually decreases, and eventually the sample is almost unignited. The horizontal ignition time is reduced to less than 3 seconds, and the vertical combustion time is around 5 seconds. The comparison images after combustion are shown in the figure. Figure 6 (Left: horizontal combustion residue; Right: vertical combustion residue).

[0068] The sample and blank control were tested using a cone calorimeter. After combustion, the sample left a large amount of residue, indicating good flame retardant properties; however, the blank sample burned completely. Further analysis was conducted on combustion data of different foam samples, including carbon dioxide yield, smoke production, total heat release, and heat release rate. The HRR comparison showed that the highest heat release rate was 52.9% lower than the blank fiber foam, with a PHRR of 63.4 kW / m³. 2 Further observation of the THR comparison curves revealed the same trend, with sample 1 showing a THR value of 5.07 MJ / m. 2 Sample 2 has a concentration of 8.47 MJ / m³. 2 This represents a decrease of approximately 40.14%.

[0069] The rate of carbon dioxide production during combustion also has a significant impact, greatly affecting human respiratory safety. The maximum amount of carbon dioxide produced by the sample was much smaller than that of the foam material without hollow glass microspheres modification; the control group had a rate of 0.052 g / s, while the sample had a rate of 0.032 g / s. Along with the production of dense smoke, the foam material with hollow glass microspheres produced smoke slowly and in small amounts, with the concentration remaining low for the first 100 seconds. However, the control group reached 0.002408 m³ / s in just 2 seconds. 2 / s.

[0070] To investigate the effect of adding hollow glass microspheres on the mechanical properties of foam materials, a static compression test was conducted. The direction of gravity along the foam sample was set as the Z-axis, and the direction parallel to gravity was set as the X-axis. Figure 7 z and Figure 7x represents the stress-strain curves of six groups of foam material samples in the Z and X directions. The compression curves in the Z direction were observed to exhibit two distinct stages, while the compression curves in the X direction, due to the linear, smooth, and compacted nature of the layered structure, showed a linear phase in the first 10% of the compression curve, followed by a yielding phase where the stress decreased. Figure 7 b shows that the compressive moduli in the Z-direction are 77.27 kPa, 31.15 kPa, 45.86 kPa, 33.57 kPa, 18.68 kPa, and 11.62 kPa, respectively, and in the X-direction are 182.33 kPa, 107.44 kPa, 65.50 kPa, 80.35 kPa, 59.44 kPa, and 16.51 kPa, respectively. The lower compressive moduli in the Z-direction for sample 1 and in the X-direction for sample 2 may be due to errors in controlling the slurry concentration during the preparation experiment, but this does not affect the overall decreasing trend of the compressive moduli. Figure 7 The compressive strengths in the Z direction are 67.90 kPa, 22.13 kPa, 28.72 kPa, 23.30 kPa, 14.58 kPa, and 9.60 kPa, respectively. In the X direction, they are 53.22 kPa, 31.86 kPa, 34.18 kPa, 29.20 kPa, 16.99 kPa, and 14.42 kPa, respectively. The addition of hollow glass microspheres improved the compressive strength of the material. The sample with the highest addition ratio showed the smallest difference in compressive strength between the Z and X directions, at 67.90 kPa and 53.22 kPa, respectively. The compressive modulus in the Z and X directions is 77.27 kPa and 182.33 kPa, respectively, showing a significant difference. Compared with the blank experiment, the compressive strength in the Z and X directions was 9.6 kPa and 14.42 kPa, respectively, and the compressive modulus in the Z and X directions was 11.62 kPa and 16.51 kPa, respectively. The sample with hollow glass microspheres showed significantly improved compressive strength. The specific compressive modulus of the foam sample was calculated to be 9.31 MPa / cm². 3 .

[0071] By comparing the columnar thermal conductivity Figure 8 (The content of hollow glass microspheres gradually decreases from left to right). It can be seen that the thermal conductivity only decreases significantly to 28.02 mW / mK when the ratio reaches a certain level. It remains almost unchanged when the ratio is between 1:0.75 and 1:0, while the thermal conductivity of pure air increases significantly to nearly 49.63 mW / mK. For porous foam materials, there are three forms of heat conduction (conduction, convection, and radiation), which depend on the solid phase, gas phase, and radiation conduction, respectively. The foam contains a large amount of air and hollow glass microspheres. The high porosity of the foam greatly reduces the thermal conductivity of the solid and gas phases, while the presence of hollow glass microspheres leads to a reduction in radiation conduction.

[0072] This invention fills the gap in existing technologies for lightweight, high-strength, flame-retardant, environmentally friendly, and recyclable foam materials, and provides innovative solutions for fields such as building insulation and fire-retardant linings for transportation.

[0073] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for producing a hollow glass microsphere / cellulose composite foam material, characterized by, The method comprises the following steps: S1, pulp fiber raw materials are pretreated by beating to a beating degree of 30-45°SR; S2, the pretreated pulp fibers are mixed with a sodium alginate aqueous solution and hollow glass microspheres at a mass ratio of 1:0.1-0.5:0.1-1, and a suspension is formed by high-speed shearing and dispersion at 2000-5000 r / min; S3, a foaming agent is added to the suspension for foaming, and the addition amount is 0.5-1.0 wt% of the total mass of the suspension; after the wet foam volume is stable, the wet foam is injected into a mold for drainage forming; S4, the wet foam is injected into the mold for drainage forming, and dried at 60-80℃ for 6-8h to obtain a three-dimensional porous composite foam material; The formed composite foam material has the following parameter performances: Density 20-50 mg / cm 3 ; thermal conductivity ≤ 35 mW / m·K; limiting oxygen index ≥ 26%; Z-direction compressive modulus ≥ 70 kPa, X-direction compressive modulus ≥ 180 kPa; 600℃ carbon residue rate ≥ 40wt%.

2. The method for preparing hollow glass microspheres / cellulose composite foam material according to claim 1, characterized in that: The hollow glass microspheres are borosilicate glass material, with particle size distribution of 10-100 μm, wall thickness of 1-5 μm, and true density of 0.15-0.40 g / cm 3 .

3. The method for preparing hollow glass microspheres / cellulose composite foam material according to claim 1, characterized in that: The mass ratio of the pulp fiber and the hollow glass microsphere is 1:1, the density of the obtained foam material is 27-30 mg / cm 3 , and the thermal conductivity is ≤30 mW / m·K.

4. The method for preparing hollow glass microspheres / cellulose composite foam material according to claim 1, characterized in that: The foaming agent is at least one of sodium dodecyl sulfate, sodium fatty alcohol polyoxyethylene ether sulfate, or a protein foaming agent.

5. The method for preparing hollow glass microspheres / cellulose composite foam material according to claim 1, characterized in that: The surface of the hollow glass microspheres is modified by a silane coupling agent.

6. The method for preparing hollow glass microspheres / cellulose composite foam material according to claim 1, characterized in that: The microstructure of the composite foam material is a three-dimensional network formed by cellulose fibers and hollow glass microspheres crosslinked by sodium alginate, with a porosity ≥ 90% and an average pore size of 50-300μm.

7. A composite foam material characterized by, The application in building insulation, transportation flame-retardant lining, electronic device fireproof packaging, or environmental protection packaging materials.

8. A method of recycling a composite foam material, characterized by, The method comprises the following steps: S501, the waste foam material is soaked in an acidic solution with pH = 1-5; S502, ultrasonic treatment for 10-60min to separate the cellulose fibers from the hollow glass microspheres; S503, the hollow glass microspheres are recovered by filtration, and the cellulose fibers can be reused for foam preparation after beating.

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