Insulated paperboard box material and method of making same

Abstract

This invention pertains to the manufacturing technology of cardboard boxes, and particularly relates to an insulated cardboard box material and its preparation method. The method includes: (1) mixing organic polymer, isocyanate, organic zirconium, silane and weak acid in a certain proportion to prepare a polymer precursor; (2) electrospinning and drying to prepare polymer fibers; (3) mixing polymer fibers, silane reagent, acyclic carboxylic acid and fatty ketone in a certain proportion to prepare a polymer fiber colloid; (4) adding the polymer fiber colloid to the pulp in a certain proportion during the pulping process of the cardboard box, and obtaining the insulated cardboard box material through conventional treatment. This invention provides a fiber material with good heat insulation effect and modifies it so that the fiber can be used in the preparation of insulated cardboard boxes. Through the microwave curing process of polymer fiber colloid, the mechanical properties of the insulated cardboard box are improved, and the energy dissipation inside the insulated cardboard box and the absorption and reflection of infrared radiation are optimized.

Description

Technical Field

[0001] This invention pertains to the technology of paperboard manufacturing for cardboard boxes, and particularly relates to an insulated cardboard box material and its preparation method. Background Technology

[0002] Cardboard boxes are widely used in production, transportation, warehousing, and daily life due to their low cost, diverse specifications, and light weight. In the current market environment, insulated cardboard boxes, as a new type of packaging material, have attracted much attention for their design concept and practicality. Among various technical solutions, the design of insulated boxes mainly uses aluminum foil as the base material, filled with high-density foam. This material combination gives insulated boxes a series of excellent characteristics: First, the combination of aluminum foil and high-density foam makes insulated cardboard boxes non-toxic, odorless, UV resistant, colorfast, smooth, and easy to clean. These characteristics endow insulated cardboard boxes with strong functionality, durability, pressure resistance, impact resistance, and moisture resistance, effectively protecting the contents and reducing damage during transportation and storage. Second, the design of insulated boxes also fully considers the convenience of foldable storage. This foldable structure greatly reduces logistics and warehousing costs and improves transportation efficiency.

[0003] However, it is worth noting that although aluminum foil-foamed insulated boxes have significant advantages in terms of performance and environmental friendliness, their high production cost is a major obstacle to their widespread application. In existing technological solutions, the production process and technology of insulated cardboard boxes still need further improvement to reduce costs and enhance their market competitiveness. Furthermore, the combination of aluminum foil and high-density foam materials also results in insulated boxes that lack the environmentally friendly characteristics of traditional cardboard boxes, especially since some foam materials are difficult and time-consuming to degrade, and the overall weight of the insulated box also increases significantly. Therefore, improving the thermal insulation performance of existing cardboard materials has become a key focus of research and development for special transport cardboard boxes. Summary of the Invention

[0004] The present invention addresses the problems of high manufacturing cost, limited environmental friendliness, and excessive weight of traditional insulated boxes by providing an insulated cardboard box material and its preparation method.

[0005] The main objective of this invention is:

[0006] 1. Improve the insulation effect of cardboard boxes;

[0007] II. Enhance the mechanical properties of cardboard boxes.

[0008] To achieve the above objectives, the present invention adopts the following technical solution.

[0009] A method for preparing thermal insulation cardboard box material.

[0010] The method includes:

[0011] (1) Mix organic polymer, isocyanate, organozirconium, silane and weak acid in proportion to prepare polymer precursor;

[0012] (2) Electrospinning, drying, and preparation of polymer fibers;

[0013] (3) Mix the polymer fiber, silane reagent, acyclic carboxylic acid and fatty ketone in proportion to prepare polymer fiber colloid;

[0014] (4) In the pulping process of the cardboard box, polymer fiber colloid is added to the pulp in proportion, and after subsequent papermaking, cutting, die-cutting, folding and bonding, the heat-insulating cardboard box material is obtained.

[0015] As a preferred option

[0016] The organic polymer mentioned in step (1) is polyvinylpyrrolidone;

[0017] The isocyanate in step (1) is 1,3,5-triglycidyl-S-triazinetrione;

[0018] The organozirconium mentioned in step (1) is zirconium n-butoxide;

[0019] The silane mentioned in step (1) is vinyltrimethoxysilane;

[0020] The weak acid mentioned in step (1) is acetic acid;

[0021] The organic polymer, isocyanate, organozirconium, silane and weak acid in step (1) are mixed evenly in a mass ratio of (0.8-1.2):6:3:1:(5-6).

[0022] As a preferred option

[0023] The preparation of the polymer precursor in step (1) involves stirring at a temperature of 20–40°C and a rotation speed of 300 r / min for 6–8 h, followed by ultrasonic dispersion at a frequency of 20–25 kHz and an amplitude of 50 μm for 10–20 min.

[0024] As a preferred option

[0025] The electrospinning in step (2) is carried out under the following environmental conditions: ambient humidity of 35-45%, ambient temperature of 20-40℃, spinning voltage of 10-20kV, spinning rate of 2mL / hr, and spinning distance of 10-20cm.

[0026] As a preferred option

[0027] The drying process in step (2) involves placing the product in a forced-air drying oven at a temperature of 110–130°C for 1–3 hours.

[0028] As a preferred option

[0029] The silane reagent mentioned in step (3) is tetraethyl orthosilicate;

[0030] The acyclic carboxylic acid mentioned in step (3) is maleic acid;

[0031] The fatty ketone mentioned in step (3) is acetone;

[0032] In step (3), the polymer fiber, silane reagent, acyclic carboxylic acid and fatty ketone are mixed evenly in a mass ratio of (13-17):4:2:(25-35).

[0033] As a preferred option

[0034] The preparation of polymer fiber colloid in step (3) involves stirring for 6 to 8 hours at a temperature of 20 to 40°C and a rotation speed of 300 r / min, followed by microwave curing for 10 to 20 minutes at a frequency of 0.8 to 1.2 GHz and a wavelength of 30 to 40 cm.

[0035] As a preferred option

[0036] In step (4), the polymer fiber colloid is added to the pulp at a ratio of 300-700 g / L pulp.

[0037] A type of insulated cardboard box material.

[0038] The core of this invention lies in adding modified fiber colloids to pulp materials. This not only improves the mechanical strength of the cardboard box itself but also enhances its thermal insulation effect, allowing for the preparation of cardboard boxes with excellent thermal insulation performance through a simple process. Thermal conductivity is one of the important indicators for judging whether a material possesses thermal insulation properties. Under normal circumstances, the temperature difference between a material and an object causes heat energy to be spontaneously transferred directionally from high to low. The process of heat transfer can be broadly categorized into three mechanisms: thermal conduction, thermal convection, and thermal radiation. Thermal conduction is the most common heat transfer method, mainly caused by the propagation of heat energy and primarily existing between the solid and liquid phases, through phonon conduction generated by the vibration of the crystal lattice within the material. Thermal convection usually exists between the liquid and gas phases, caused by the change in the position of molecules between different phases leading to the conversion of heat energy. Thermal radiation exists in the form of electromagnetic waves, a phenomenon of energy transfer resulting from changes in the motion state of atoms and molecules within the material itself.

[0039] To enhance the thermal insulation performance of materials, it is necessary to address the three mechanisms mentioned above and implement targeted structural reinforcement.

[0040] In this invention, the cyanate groups in the cyanate resin can generate triazine ring structures through cross-linking reactions, exhibiting high cross-linking density and low polarization. During curing, polyvinylpyrrolidone and 1,3,5-triglycidyl-S-triazine trione polymerize to form an interpenetrating network structure, thereby increasing the conversion rate of cyanate to triazine structures and simultaneously toughening the triazine trione resin system, contributing to improved flexural strength and modulus of the polymer fibers. Furthermore, under the catalysis of zirconium butoxide, the cyanate monomer forms a complex and undergoes a triazine cyclization reaction, thereby increasing the conversion rate of cyanate monomer during curing. This allows the polymer fibers to maintain high dimensional stability during curing. In this invention, the polymer fibers are incorporated into the pulp as insulating fibers. The effect is that gas molecules are isolated by the fiber skeleton, resulting in smaller internal pressure differences and a near-static gas state, thus reducing convective heat conduction. Furthermore, by adjusting the pore size to shorten the gas free path, the thermal conductivity of the material is further reduced. Simultaneously, by performing colloidal modification on the fibers, the fibers are evenly distributed in the pulp, reducing the thermal radiation of the pulp. Colloidal modification also increases the extinction coefficient of the pulp, blocking the thermal radiation path of the cardboard material, thereby reducing the thermal conductivity of the cardboard material. In the technical solution of this invention, the viscosity of the precursor has a significant impact on the electrospinning effect. When the precursor viscosity is too high or flocculent sedimentation occurs, the target fiber cannot be obtained by electrospinning. This invention constructs a bridging coordination structure with sufficient acetic acid and zirconium n-butoxide, while reducing the degree of polymerization, effectively inhibiting the formation of network polymers. The unreacted acetic acid can be used as a solvent to reduce the system viscosity, thus giving the precursor sol good fluidity. This invention abandons the method of preparing polymer fibers using sintering processes because sintering causes the amorphous state inside the fiber to transform into a crystalline state, leading to fiber structure collapse, a reduction in the number of pores, and thus affecting thermal insulation performance. Inside the polymer fiber, zirconium butoxide and vinyltrimethoxysilane work together to strengthen the structure, giving the fiber bendable and foldable deformable properties, thereby effectively improving the fiber's mechanical properties. Simultaneously, the fiber has a significant absorption and reflection effect on infrared radiation, reducing infrared transmittance and allowing the fiber to still maintain a certain degree of thermal insulation effect under high-temperature environments.

[0041] Another core aspect of this invention is the use of microwave curing to rearrange the modified materials on the fiber surface, thereby enhancing the structural properties of the fiber material. In the initial state of this invention, the colloidal viscosity is low, the modifying agent and fiber have not undergone cross-linking reaction, and polar groups can move freely. As the curing process progresses, the colloidal viscosity further decreases with increasing temperature, enhancing the dielectric polarization of polar molecules. Simultaneously, the polymer fiber undergoes a cross-linking reaction, and the molecular chain segments elongate. When the polyester fiber surface is nearly completely cured, the macromolecular chain segments cross-link with each other, forming a complex three-dimensional network structure. Using tetraethyl orthosilicate as the central particle, it forms clusters with maleic acid within a limited space. These clusters move randomly on the fiber surface. When a cluster enters the fiber interstices, it forms the next cluster in the same manner until all particles aggregate, ultimately forming a polymer fiber-aggregated particle system. At this point, the system no longer undergoes random Brownian motion but moves along the direction of heat transfer. The aggregated particles gather in the fiber interstices, forming a more compact polymer fiber-aggregated particle system, which is beneficial for improving the tensile and flexural strength of the fiber. In this invention, the uniformity of the internal temperature field of the polymer fiber colloid has a significant impact on the mechanical properties of the thermal insulation cardboard material. Uneven temperature field can lead to different thermal shrinkage of the cardboard material, creating performance and stress gradients inside the thermal insulation cardboard, thereby generating thermal stress. Internal stress may cause the cardboard material to warp, bend, or even crack and delaminate, severely impacting the mechanical properties of the thermal insulation cardboard. However, microwave curing not only disperses the internal stress of the colloid but also optimizes the energy dissipation inside the thermal insulation cardboard and the absorption and reflection of infrared radiation, resulting in improved thermal insulation performance.

[0042] The advantages of this invention are:

[0043] (1) The present invention provides a fiber material with good heat insulation effect and modifies it so that the fiber can be used in the preparation of heat-insulating cardboard boxes;

[0044] (2) The present invention improves the mechanical properties of the thermal insulation carton by using a microwave curing process for polymer fiber colloids, while optimizing the energy dissipation inside the thermal insulation carton and the absorption and reflection of infrared radiation. Detailed Implementation

[0045] The present invention will be further described clearly and in detail below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0046] Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commercially available or obtainable by those skilled in the art; unless otherwise specified, the methods used in the embodiments of the present invention are all methods mastered by those skilled in the art.

[0047] Unless otherwise specified, the diameter of the electrospun fibers in the embodiments and comparative examples of this invention is 100-300 nm.

[0048] Example 1

[0049] A method for preparing thermal insulation cardboard box material.

[0050] The method includes:

[0051] (1) Polyvinylpyrrolidone, 1,3,5-triglycidyl-S-triazinetrione, zirconium butoxide, vinyltrimethoxysilane and acetic acid were mixed evenly in a mass ratio of 0.8:6:3:1:5 and stirred for 8 hours at 20℃ and 300 r / min. After stirring, the mixture was ultrasonically dispersed for 20 minutes at a frequency of 20 kHz and an amplitude of 50 μm to prepare a polymer precursor.

[0052] (2) Electrospinning was carried out under the following environmental conditions: ambient humidity of 35%, ambient temperature of 20℃, spinning voltage of 10kV, spinning rate of 2mL / hr, and spinning distance of 10cm. The fibers were then dried in a forced-air drying oven at 110℃ for 3h to prepare polymer fibers.

[0053] (3) The polymer fiber, tetraethyl orthosilicate, maleic acid and acetone were mixed evenly in a mass ratio of 13:4:2:25 and stirred for 8 hours at a temperature of 20℃ and a speed of 300r / min. After stirring, the mixture was microwave cured for 20 minutes at a frequency of 0.8GHz and a wavelength of 30cm to prepare the polymer fiber colloid.

[0054] (4) In the pulping process of the cardboard box, polymer fiber colloid is added into the pulp at a ratio of 300g / L pulp. After subsequent papermaking, cutting, die-cutting, folding and bonding, the heat-insulating cardboard box material is obtained.

[0055] The thermal insulation cardboard box material prepared in the examples was subjected to performance testing. The performance testing included thermal conductivity characterization and mechanical property characterization. For mechanical property characterization, the paper was prepared into three-layer corrugated paper with a thickness of 2.0 mm by conventional processes such as papermaking, cutting, die-cutting, folding and bonding in step (4). For thermal conductivity characterization, three-layer corrugated paper with a thickness of 2.0 mm (specification number marked III-2.0), five-layer corrugated paper with a thickness of 3.5 mm (specification number marked V-3.5), and seven-layer corrugated paper with a thickness of 6.0 mm (specification number marked VII-6.0) were prepared as standard samples. The thermal conductivity of the material prepared in the examples was tested with reference to the ASTM-D5470 standard test method.

[0056] Specifically, the mechanical property characterization includes:

[0057] Tensile property testing: The tensile strength of the material prepared in the example was tested according to ASTM D3039 / D3039M-14 standard. The material was made into a test sample with a size of 200×15×2mm. The strength was tested at room temperature with a loading rate of 2mm / min. The tensile strength and tensile modulus of elasticity were calculated according to the formula.

[0058]

[0059] In the formula:

[0060] σ t —Tensile strength of material, MPa;

[0061] p max —Maximum load-bearing capacity of the test sample, in N;

[0062] w—width of the test sample, mm;

[0063] h — Sample thickness, mm.

[0064]

[0065] In the formula:

[0066] E chord —Tensile modulus of elasticity of the material, GPa;

[0067] Δσ — The increment of tensile stress corresponding to the maximum bearing capacity of the test sample, in MPa;

[0068] Δε — The strain increment of the test sample at maximum load capacity, in mm.

[0069] In addition, the elongation at break of the test sample was recorded.

[0070] Compression performance testing: The compressive strength of the material prepared in the example was tested according to ASTM D 6641D6641M-16 standard. The material was made into a size of 140×15×2mm and the compressive strength was tested at room temperature with a loading rate of 2mm / min. The compressive strength and compressive modulus were calculated according to the formula.

[0071]

[0072] In the formula:

[0073] σ c —Material compressive strength, MPa;

[0074] p max —Maximum load-bearing capacity of the test sample, in N;

[0075] w—width of the test sample, mm;

[0076] h — Sample thickness, mm.

[0077]

[0078] In the formula:

[0079] E c —Material compressive modulus, MPa;

[0080] ε x1 —The actual strain closest to the lower end of the test area of ​​the sample;

[0081] ε x2 —The actual strain closest to the upper end of the test area of ​​the sample;

[0082] P1—Load at the lower end of the test area of ​​the test sample, in N;

[0083] P2—Load at the upper end of the test area of ​​the test sample, in N;

[0084] w—width of the test sample, mm;

[0085] h — Sample thickness, mm.

[0086] In the process of characterizing thermal conductivity, the thermal conductivity of the cardboard box prepared in the example was calculated using the steady-state heat flow method in conjunction with the formula.

[0087]

[0088] In the formula:

[0089] λ—The thermal conductivity of the sample, W / m·K;

[0090] Qh — Heat flux output of the thermal sensor at the top of the sample, W / m2 ;

[0091] Qc — Heat flow output of the thermal sensor at the lower end of the sample, W / m 2 ;

[0092] L—thickness of the sample, in meters;

[0093] ΔT — Temperature difference between the upper and lower surfaces of the sample, in K.

[0094] In addition, the characterization of thermal conductivity also includes the extinction coefficient test, which is performed by characterizing the radiative thermal conductivity.

[0095] Extinction coefficient test: The extinction coefficient refers to the degree of attenuation of radiant energy caused by scattering and absorption of infrared radiation after passing through a material. The test sample is III-2.0. In an environment with a temperature of 26.85℃, a beam of parallel monochromatic light is shone onto the test sample, and the radiative thermal conductivity of the test sample is calculated using Lambert-Beer's law.

[0096]

[0097] In the formula:

[0098] λ r —Radiative thermal conductivity of the sample, W / m·K;

[0099] k B —Stephen Boltzmann constant;

[0100] n—the refractive index of the sample being tested;

[0101] T—sample temperature, K;

[0102] e – extinction coefficient;

[0103] ρ — density of the sample, kg / m³ 3 .

[0104] Based on the above testing and characterization methods, the mechanical property characterization results are shown below.

[0105]

[0106] Analysis of the above characterization results shows that this invention improves the mechanical properties of the thermal insulation cardboard box through colloid modification of polymer fibers and a unique microwave curing process. Within the polymer fibers, zirconium butoxide and vinyltrimethoxysilane work together to strengthen the structure, giving the polymer fibers bendable and foldable deformation characteristics, thereby effectively improving the mechanical properties of the fibers and consequently increasing the tensile strength and tensile modulus of the thermal insulation cardboard. During the microwave curing process, polyvinylpyrrolidone and 1,3,5-triglycidyl-S-triazine trione polymerize to form an interpenetrating network structure, which toughens the triazine trione fiber system and helps improve the compressive strength and compressive modulus of the polymer fibers.

[0107] The results of the thermal conductivity characterization test are shown in the table below.

[0108] III-2.0 thermal conductivity V-3.5 thermal conductivity VII-6.0 thermal conductivity Radiative thermal conductivity 0.039 W / m·K 0.037 W / m·K 0.036 W / m·K 0.041 W / m·K

[0109] The thermal conductivity of insulation materials is one of the important indicators for evaluating their insulation performance. The lower the thermal conductivity, the better the insulation performance. According to Chinese national regulations, materials with a thermal conductivity of no more than 0.12 W / m·K at an average temperature not exceeding 350℃ are classified as insulation materials, and materials with a thermal conductivity below 0.05 W / m·K are classified as high-efficiency insulation materials. Based on the above characterization results, the insulation cardboard box material of this invention exhibits excellent thermal insulation performance and can achieve superior thermal insulation effects.

[0110] Example 2

[0111] A method for preparing thermal insulation cardboard box material.

[0112] The method includes:

[0113] (1) Polyvinylpyrrolidone, 1,3,5-triglycidyl-S-triazinetrione, zirconium butoxide, vinyltrimethoxysilane and acetic acid were mixed evenly in a mass ratio of 1:6:3:1:5.5 and stirred for 7 h at a temperature of 30 °C and a speed of 300 r / min. After stirring, the mixture was ultrasonically dispersed for 15 min at a frequency of 23 kHz and an amplitude of 50 μm to prepare a polymer precursor.

[0114] (2) Electrospinning was carried out under the following environmental conditions: ambient humidity of 40%, ambient temperature of 30℃, spinning voltage of 15kV, spinning rate of 2mL / hr, and spinning distance of 15cm. The fibers were dried in a forced-air drying oven at 120℃ for 2h to prepare polymer fibers.

[0115] (3) Mix the polymer fiber, tetraethyl orthosilicate, maleic acid and acetone in a mass ratio of 15:4:2:30 and stir for 6-8 hours at a temperature of 30℃ and a speed of 300r / min. After stirring, microwave solidify for 15 minutes at a frequency of 1GHz and a wavelength of 35cm to prepare polymer fiber colloid.

[0116] (4) In the pulping process of the cardboard box, polymer fiber colloid is added into the pulp at a ratio of 500g / L pulp. After subsequent papermaking, cutting, die-cutting, folding and bonding, the heat-insulating cardboard box material is obtained.

[0117] The thermal insulation cardboard box material prepared in this example was subjected to the same performance characterization as in Example 1, and the characterization results are shown in the table below.

[0118]

[0119] Example 3

[0120] A method for preparing thermal insulation cardboard box material.

[0121] The method includes:

[0122] (1) Polyvinylpyrrolidone, 1,3,5-triglycidyl-S-triazinetrione, zirconium butoxide, vinyltrimethoxysilane and acetic acid were mixed evenly in a mass ratio of 1.2:6:3:1:6 and stirred for 6 h at a temperature of 40 °C and a speed of 300 r / min. After stirring, the mixture was ultrasonically dispersed for 10 min at a frequency of 25 kHz and an amplitude of 50 μm to prepare a polymer precursor.

[0123] (2) Electrospinning was carried out under the following environmental conditions: ambient humidity of 45%, ambient temperature of 40℃, spinning voltage of 20kV, spinning rate of 2mL / hr, and spinning distance of 20cm. The fibers were dried in a forced-air drying oven at 130℃ for 1h to prepare polymer fibers.

[0124] (3) The polymer fiber, tetraethyl orthosilicate, maleic acid and acetone were mixed evenly in a mass ratio of 17:4:2:35 and stirred for 6 hours at a temperature of 40℃ and a speed of 300r / min. After stirring, the mixture was microwave cured for 10 minutes at a frequency of 1.2GHz and a wavelength of 40cm to prepare the polymer fiber colloid.

[0125] (4) In the pulping process of the cardboard box, polymer fiber colloid is added into the pulp at a ratio of 700g / L pulp. After subsequent papermaking, cutting, die-cutting, folding and bonding, the heat-insulating cardboard box material is obtained.

[0126] The thermal insulation cardboard box material prepared in this example was subjected to the same performance characterization as in Example 1, and the characterization results are shown in the table below.

[0127]

[0128] Because this invention enhances the mechanical strength of fibers through the addition of fibers, based on the cohesion model analysis of this invention, clusters are formed in a limited space with tetraethyl orthosilicate as the central particle. Due to the random movement between molecules, the clusters gradually form in the gaps between polymer fibers, eventually forming a polymer fiber-cohesive particle system. At this time, the system is affected by the heat transfer effect, forming a more compact polymer fiber-cohesive particle system. Furthermore, through the performance testing conducted by the inventors in the further analysis of the embodiments, the thermal insulation carton prepared by this invention has excellent thermal insulation performance and mechanical strength.

[0129] Furthermore, in the technical solution of this invention, by increasing the extinction coefficient of the cardboard material through the fiber colloid, the reflectivity of the cardboard to infrared radiation is enhanced, thereby achieving the purpose of reducing the radiative thermal conductivity.

[0130] Furthermore, the thermal insulation cardboard box materials obtained in Examples 1-3 of this invention were prepared in two specifications: 100×80cm in size and III-2.0 and VII-6.0. These were then placed at -35℃ for 12 hours and then at 95℃ for 12 hours, repeated for 7 days. The thermal conductivity was characterized, and the results showed that it remained at 0.039–0.040 W / m·K (III-2.0 specification) and 0.037–0.038 W / m·K (VII-6.0 specification), effectively maintaining its thermal insulation capacity. It also exhibited strong resistance to freeze-thaw cycles. In contrast, conventional aluminum foil-foam composite board insulation materials, due to the characteristics of the composite layer materials, may experience interlayer peeling and separation due to differences in the coefficients of thermal expansion between different materials, ultimately leading to a rapid and significant decrease in their thermal insulation performance.

[0131] Comparative Example 1

[0132] A method for preparing an insulated cardboard box material is the same as in Example 2, except that the polymer fiber component unique to this invention is modified by using an equal amount of commercially available palladium acetate instead of zirconium butoxide to prepare the insulated cardboard box. The specific operation is as follows:

[0133] 1) Polyvinylpyrrolidone, 1,3,5-triglycidyl-S-triazinetrione, palladium acetate, vinyltrimethoxysilane and acetic acid were mixed evenly in a mass ratio of 1:6:3:1:5.5 and stirred for 7 h at 30 °C and 300 r / min. After stirring, the mixture was ultrasonically dispersed for 15 min at a frequency of 23 kHz and an amplitude of 50 μm to prepare a polymer precursor.

[0134] (2) Electrospinning was carried out under the following environmental conditions: ambient humidity of 40%, ambient temperature of 30℃, spinning voltage of 15kV, spinning rate of 2mL / hr, and spinning distance of 15cm. The fibers were dried in a forced-air drying oven at 120℃ for 2h to prepare polymer fibers.

[0135] (3) The polymer fiber, tetraethyl orthosilicate, maleic acid and acetone were mixed evenly in a mass ratio of 15:4:2:30 and stirred for 7 hours at a temperature of 30℃ and a speed of 300r / min. After stirring, the mixture was microwaved for 15 minutes at a frequency of 1GHz and a wavelength of 35cm to prepare the polymer fiber colloid.

[0136] (4) In the pulping process of the cardboard box, polymer fiber colloid is added into the pulp at a ratio of 500g / L pulp. After subsequent papermaking, cutting, die-cutting, folding and bonding, the heat-insulating cardboard box material is obtained.

[0137] After preparing insulated cardboard boxes using the above comparative steps, the inventors discovered that the polymer precursor produced flocculent precipitation, making electrospinning impossible. Even reducing the proportion of palladium acetate in the fiber component did not prevent precipitation. Further research revealed that the structural characteristics of the cyanate ester resin significantly influence its delayed gelation phenomenon in this invention. Delayed gelation is more likely to occur when the structure contains a rigid backbone or highly reactive substituents. Conversely, a higher proportion of flexible aliphatic chains or flexible substituents results in an actual gel point closer to the theoretical value. While palladium acetate has broad catalytic activity in organic synthesis reactions, in this invention, Pd(II) activates olefins through coordination, leading to attack by nucleophiles and a decrease in monomer viscosity, thus causing delayed gelation.

[0138] Comparative Example 2

[0139] A method for preparing an insulated cardboard box material, the specific preparation method is the same as in Example 2, except that the microwave curing process unique to this invention is not used. The specific operation is as follows:

[0140] 1) Polyvinylpyrrolidone, 1,3,5-triglycidyl-S-triazinetrione, zirconium butoxide, vinyltrimethoxysilane and acetic acid were mixed evenly in a mass ratio of 1:6:3:1:5.5 and stirred for 7 h at 30 °C and 300 r / min. After stirring, the mixture was ultrasonically dispersed for 15 min at a frequency of 23 kHz and an amplitude of 50 μm to prepare a polymer precursor.

[0141] (2) Electrospinning was carried out under the following environmental conditions: ambient humidity of 40%, ambient temperature of 30℃, spinning voltage of 15kV, spinning rate of 2mL / hr, and spinning distance of 15cm. The fibers were dried in a forced-air drying oven at 120℃ for 2h to prepare polymer fibers.

[0142] (3) Mix the polymer fiber, tetraethyl orthosilicate, maleic acid and acetone in a mass ratio of 15:4:2:30 and stir for 6-8 hours at a temperature of 30℃ and a speed of 300r / min to prepare polymer fiber colloid.

[0143] (4) In the pulping process of the cardboard box, polymer fiber colloid is added into the pulp at a ratio of 500g / L pulp. After subsequent papermaking, cutting, die-cutting, folding and bonding, the heat-insulating cardboard box material is obtained.

[0144] The thermal insulation cardboard box material prepared in the comparative example was subjected to performance testing in the same manner as that in Example 1, and the characterization results are as follows.

[0145]

[0146] Analysis of the above characterization results, compared with Examples 1 and 3, shows a significant decrease in the mechanical properties and radiative thermal conductivity of the insulated cardboard box material prepared in the comparative examples. Further research by the inventors revealed that, without microwave curing, the initial viscosity of the polymer fiber colloid was low, and the modifying agent did not undergo cross-linking reaction with the fiber, failing to form a uniform and dense fiber structure. Therefore, the absorption and reflectivity of thermal radiation were insufficient. Due to the uneven temperature and curing fields within the insulated cardboard box material, differences in thermal shrinkage occur, leading to performance and stress gradients within the product, inducing thermal stress and curing absorption stress. Under external environmental interference, this phenomenon macroscopically manifests as warping and delamination of the insulated cardboard board. Furthermore, it generates additional energy dissipation during actual insulation, severely impacting the mechanical and insulation properties of the insulated cardboard box.

[0147] Comparative Example 3

[0148] A commercially available insulated box composite board material (9.5mm thick) has a material structure that consists of three layers of insulation material made of pearl cotton and aluminum foil laminated inside the original corrugated cardboard box. The performance of the commercially available insulated cardboard box is the same as that of Examples 1, 2, and 3, and the specific performance results are as follows.

[0149]

[0150] Analysis of the above characterization results shows that a commercially available insulated box composite board material has a lower thermal conductivity and radiative thermal conductivity due to the aluminum foil composite, and its insulation performance is slightly better than that of the insulated cardboard material of the present invention. However, it has limited optimization of the mechanical properties of the cardboard itself. Meanwhile, since the material of the present invention directly modifies the pulp, it has greater molding capacity.

[0151] Furthermore, the thermal insulation box material obtained by this invention has an area density of approximately 107 g / m² when manufactured to specification VII-6.0. 2 The composite panel material used in commercially available insulated boxes has a surface area density as high as 282 g / m². 2 The insulation performance of the original material is more than two times, or even nearly three times, that of the present invention, but it is far less lightweight than the present invention, and the insulation performance is not significantly improved. Therefore, considering overall performance, the insulated cardboard box material of the present invention is superior to commercially available composite insulation boards.

[0152] In addition, the same freeze-thaw cycle test as in Examples 1-3 was conducted, sequentially placing the material at -35°C for 12 hours and then at 95°C for 12 hours, repeating this process for 7 days. The thermal conductivity was characterized, and the results showed a significant increase to 0.112 W / m·K, indicating a very obvious jump. This demonstrates that it does not possess good freeze-thaw resistance, as mentioned earlier, a defect present in existing composite insulation materials. When used for rapid cooling of cooked food, it easily leads to a significant impact on insulation performance, thereby reducing its effectiveness.

Claims

1. A method for preparing an insulated cardboard box material, characterized in that, The method includes: (1) Polyvinylpyrrolidone, 1,3,5-triglycidyl-S-triazinetrione, organozirconium, silane and weak acid are mixed evenly in a mass ratio of (0.8-1.2):6:3:1:(5-6) to prepare a polymer precursor; (2) Electrospinning, drying, and preparation of polymer fibers; (3) Mix the polymer fiber, tetraethyl orthosilicate, maleic acid and acetone in a mass ratio of (13-17):4:2:(25-35) to prepare polymer fiber colloid; (4) In the pulping process of the cardboard box, polymer fiber colloid is added to the pulp in proportion, and after subsequent papermaking, cutting, die-cutting, folding and bonding, heat-insulating cardboard box material is obtained; The preparation of polymer fiber colloid in step (3) involves stirring for 6 to 8 hours at a temperature of 20 to 40 ℃ and a rotation speed of 300 r / min, followed by microwave curing for 10 to 20 minutes at a frequency of 0.8 to 1.2 GHz and a wavelength of 30 to 40 cm. In step (4), the polymer fiber colloid is added to the pulp at a ratio of 300 to 700 g / L pulp.

2. The method for preparing a thermally insulated cardboard box material according to claim 1, characterized in that, The organozirconium mentioned in step (1) is zirconium n-butoxide; The silane mentioned in step (1) is vinyltrimethoxysilane; The weak acid mentioned in step (1) is acetic acid.

3. A method for preparing a thermally insulated cardboard box material according to claim 1 or 2, characterized in that, The preparation of the polymer precursor in step (1) involves stirring for 6 to 8 hours at a temperature of 20 to 40 ℃ and a rotation speed of 300 r / min, followed by ultrasonic dispersion for 10 to 20 minutes at a frequency of 20 to 25 kHz and an amplitude of 50 μm.

4. The method for preparing a thermally insulated cardboard box material according to claim 1, characterized in that, The electrospinning in step (2) is carried out under the following environmental conditions: ambient humidity of 35-45%, ambient temperature of 20-40℃, spinning voltage of 10-20 kV, spinning rate of 2 mL / hr, and spinning distance of 10-20 cm.

5. The method for preparing a thermally insulated cardboard box material according to claim 1, characterized in that, The drying process in step (2) involves placing the product in a forced-air drying oven at a temperature of 110–130 °C for 1–3 h.

6. An insulated cardboard box material prepared by any one of the methods described in claims 1 to 5.

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