Preparation method of polyacrylonitrile core material, vacuum insulation board, preparation method of vacuum insulation board and heat insulation equipment

Abstract

The invention discloses a preparation method of a polyacrylonitrile core material, a vacuum insulation board, a preparation method of the vacuum insulation board and thermal insulation equipment, and belongs to the technical field of vacuum thermal insulation materials. Comprising the following steps: dispersing organic fibers in a liquid to obtain an organic fiber suspension; the organic fiber suspension liquid is subjected to wet-process web forming and water controlling, then baking is conducted, and the polyacrylonitrile fiber cloth is obtained; a plurality of pieces of polyacrylonitrile fiber cloth are stacked and subjected to heat treatment, and a polyacrylonitrile core material is obtained; wherein the organic fiber is made of a polyacrylonitrile material, and the organic fiber has a special-shaped cross section. Depending on the synergistic effect of the low intrinsic heat conductivity coefficient of the polyacrylonitrile fiber and the large physical interval of the special-shaped section, the organic fiber suspension liquid can achieve the low heat conductivity coefficient during film forming, and when the obtained polyacrylonitrile core material is used for preparing the vacuum heat preservation plate, the heat conductivity coefficient of the vacuum heat preservation plate can be reduced.

Description

Technical Field

[0001] This invention belongs to the field of vacuum thermal insulation materials technology, specifically relating to a method for preparing polyacrylonitrile core material, a vacuum insulation board and its preparation method, and thermal insulation equipment. Background Technology

[0002] Vacuum insulation panels, as a new type of thermal insulation material, possess excellent thermal insulation performance, with a thermal conductivity as low as 1.5 mW / (m·K). To achieve the same insulation effect, the thickness of vacuum insulation panels is only one-tenth that of other traditional materials. This material saves a significant amount of space and is currently the most efficient insulation material; therefore, vacuum insulation panels are also known as super insulation materials. Vacuum insulation panels mainly consist of a core material, a getter / desiccant, and a protective film. The components of a vacuum insulation panel significantly impact its performance, with the core material being the core component. The selection and design of the core material are particularly crucial, as its material, structure, and composition greatly affect the thermal conductivity of the vacuum insulation panel.

[0003] Currently, the core materials of commercially available and mature vacuum insulation panels mainly consist of granular fumed silica and glass fiber. Under low vacuum conditions, fumed silica powder particles have numerous contact points, resulting in high contact thermal conductivity. Meanwhile, the thermal conductivity of vacuum insulation panels made with glass fiber as the core material is difficult to maintain below 1.5 mW / (m·K). Therefore, at this stage, using fumed silica and glass fiber as core materials also faces the technical challenge of not being able to further reduce the thermal conductivity of vacuum insulation panels in the desired low-conductivity scenario. Summary of the Invention

[0004] The embodiments of the present invention at least partially solve the technical problem of high thermal conductivity of the core material of vacuum insulation boards in application. To this end, the embodiments of the present invention provide a method for preparing polyacrylonitrile core material, a vacuum insulation board and its preparation method, and a heat insulation device.

[0005] In a first aspect, embodiments of the present invention provide a method for preparing a polyacrylonitrile core material, the method comprising:

[0006] Organic fibers are dispersed in a liquid to obtain an organic fiber suspension; and

[0007] The organic fiber suspension is wet-laid and water is controlled, and then baked to obtain polyacrylonitrile fiber cloth;

[0008] Multiple sheets of the aforementioned polyacrylonitrile fiber cloth are stacked and heat-treated to obtain a polyacrylonitrile core material.

[0009] The organic fiber is made of polyacrylonitrile and has an irregular cross-section. The shape of the irregular cross-section is one of the following: triangle, trefoil, cross, T, Y, crescent, dumbbell, pentagon, fan, and five-lobed.

[0010] As can be seen from the technical solution, in this embodiment, polyacrylonitrile fibers are first dispersed in a liquid to obtain an organic fiber suspension. The polyacrylonitrile molecular chains in this suspension are long and tightly packed, and the polyacrylonitrile molecules contain a large number of cyano groups (-CN). These cyano groups complicate the intermolecular forces, hindering rapid heat transfer. Furthermore, the disordered arrangement of the polyacrylonitrile molecular chains reduces heat conduction efficiency. Secondly, the irregular cross-section of the polyacrylonitrile fibers increases the physical spacing between them, reduces the contact area, and alters the heat conduction path, further reducing heat transfer efficiency. Subsequently, during the film-forming process of the organic fiber suspension, the irregular cross-section of the polyacrylonitrile fibers increases their dispersion in the suspension, improving film-forming properties during wet web formation. Finally, the synergistic effect of the low intrinsic thermal conductivity of the polyacrylonitrile fibers and the larger physical spacing of the irregular cross-section helps the organic fiber suspension achieve a low thermal conductivity during film formation. Therefore, the resulting polyacrylonitrile core material, when used to prepare vacuum insulation panels, can reduce the thermal conductivity of the vacuum insulation panels.

[0011] In some embodiments, the weight of the organic fiber is 0.01% to 0.1% of the total weight of the suspension.

[0012] In some embodiments, the organic fiber has a diameter of 0.5 μm to 50 μm.

[0013] In some embodiments, preferably, the diameter of the organic fiber is 3µm to 15µm.

[0014] In some embodiments, the organic fiber has a fiber length of 0.5 mm to 250 mm.

[0015] In some embodiments, the dispersion method includes mechanical stirring and microwave heating.

[0016] In some embodiments, the water control time is 5 min to 30 min; and / or

[0017] The baking temperature is 100℃~240℃.

[0018] In some embodiments, the areal density of the polyacrylonitrile fiber cloth is 2 g / m². 2 ~150g / m 2 .

[0019] In some embodiments, preferably, the areal density of the polyacrylonitrile fiber cloth is 5 g / m². 2 ~100g / m 2 .

[0020] In some embodiments, the polyacrylonitrile fiber cloth has a three-dimensional network structure.

[0021] In some implementations, the number of sheets is 100 to 500.

[0022] In some embodiments, the temperature of the heat treatment is 130°C to 200°C.

[0023] Secondly, embodiments of the present invention provide a vacuum insulation board, the vacuum insulation board comprising the polyacrylonitrile core material described in the first aspect.

[0024] Thirdly, embodiments of the present invention provide a method for preparing the vacuum insulation board described in the second aspect, the method comprising:

[0025] The polyacrylonitrile core material bag is placed into a protective film to obtain a bagged board;

[0026] The bagged plate is vacuumed, and when the vacuum degree of the bagged plate reaches the set vacuum degree, the bagged plate is heat-sealed to obtain a vacuum insulation plate.

[0027] In some embodiments, the set vacuum degree is 1.0*10 -4 Pa ~ 4.0 * 10 -3 Pa.

[0028] In some embodiments, the process parameters for the hot-press sealing include: voltage of 9V to 15V and time of 15s to 25s.

[0029] Fourthly, embodiments of the present invention provide a heat insulation device, wherein the heat insulation material of the heat insulation device includes the vacuum insulation board described in the third aspect. Attached Figure Description

[0030] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0031] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1A schematic flowchart illustrating a method for preparing a polyacrylonitrile core material provided in this application embodiment;

[0033] Figure 2 This is a schematic diagram of the structure of a vacuum insulation board provided in an embodiment of this application;

[0034] Figure 3 A schematic flowchart illustrating a method for preparing a vacuum insulation board according to an embodiment of this application;

[0035] Figure label:

[0036] 1-Polyacrylonitrile core material; 2-Protective film; 3-Getter. Detailed Implementation

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0038] Unless otherwise specified, the terminology used herein should be understood as having the meaning commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of any conflict, this specification shall prevail. All raw materials, reagents, instruments, and equipment used in this invention are commercially available or can be prepared by existing methods.

[0039] Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0040] In this document, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this invention, the terms "comprising," "including," etc., mean "including but not limited to." Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. For associations involving three or more related objects described using "and / or", it indicates that any one of the three related objects can exist alone, or at least two of them can exist simultaneously. For example, for A, and / or B, and / or C, it can mean that any one of A, B, and C exists alone, or any two of them exist simultaneously, or all three of them exist simultaneously. In this document, "at least one" means one or more, and "more" means two or more. "At least one", "at least one of the following", or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab, i.e., a and b, ac, bc, or abc, where a, b, and c can be single or multiple.

[0041] Furthermore, the present invention may repeat reference numerals and / or reference letters in different examples. Such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, the present invention provides examples of various specific processes and materials, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0042] Figure 1 This is a schematic flowchart illustrating a method for preparing a polyacrylonitrile core material according to an embodiment of this application.

[0043] Please see Figure 1This invention provides a method for preparing a polyacrylonitrile core material, the method comprising:

[0044] S101. Disperse organic fibers in a liquid to obtain an organic fiber suspension; and

[0045] S102. The organic fiber suspension is wet-laid and water is controlled, and then baked to obtain polyacrylonitrile fiber cloth.

[0046] S103. Stack and heat-treat multiple sheets of polyacrylonitrile fiber cloth to obtain polyacrylonitrile core material.

[0047] The organic fiber is made of polyacrylonitrile and has an irregular cross-section. The shape of the irregular cross-section is one of the following: triangle, trefoil, cross, T, Y, crescent, dumbbell, pentagon, fan, and five-lobed.

[0048] It should be noted that polyacrylonitrile (PAN) has the chemical formula (C3H3N). n Acrylonitrile (AC) is an important synthetic polymer material. It is produced by the free radical polymerization of acrylonitrile monomers and is the main raw material for synthetic fiber "acrylic fiber," also widely used in the preparation of other polymer materials. AC fiber possesses excellent physical properties, such as high strength, abrasion resistance, wrinkle resistance, and good elastic recovery. Its density is slightly greater than water, approximately 1.18 g / cm³. 3 It has a high melting point. The polyacrylonitrile molecular chain contains a large number of cyano groups (-CN), which gives it high chemical stability and makes it resistant to the attack of a variety of acids, alkalis and organic solvents.

[0049] Polyacrylonitrile has a relatively low intrinsic thermal conductivity. This is due to: (1) the presence of cyano groups: polyacrylonitrile molecular chains contain a large number of cyano groups (-CN), which make the intermolecular interaction forces complex, but do not directly facilitate the rapid transfer of heat. The presence of cyano groups increases the rigidity and cohesive force of the molecular chains, but may also hinder the smooth flow of heat to some extent. (2) the arrangement of molecular chains: the molecular chain arrangement of polyacrylonitrile may not be as ordered as some other polymer materials, and this disordered arrangement may reduce the efficiency of heat conduction. This is because heat conduction largely depends on the regularity and continuity of the internal microstructure of the material. Therefore, using polyacrylonitrile with low intrinsic thermal conductivity as the organic core material of vacuum insulation boards can reduce the thermal conductivity of vacuum insulation boards.

[0050] Organic fibers with irregular cross-sections have lower thermal conductivity. This is because: (1) Compared with traditional circular cross-section fibers, irregular cross-section fibers have more complex cross-sectional shapes, such as triangles, trefoils, crosses, T-shapes, Y-shapes, crescents, dumbbells, pentagons, fans, and pentagons. This complex cross-sectional shape changes the heat conduction path inside the fiber, making the heat transfer in the fiber more complex and tortuous. Therefore, irregular cross-section fibers usually have lower thermal conductivity, which is beneficial for their application in the field of thermal insulation. (2) The cross-sectional shape of irregular cross-section fibers also affects their arrangement and gap size in the fiber layer. When the fibers are arranged parallel to the direction of heat radiation, the thermal conductivity is stronger; while when the fibers are arranged perpendicular to the direction of heat radiation, that is, when the fibers are arranged parallel to the fiber layer, the thermal conductivity is lower. Due to their complex cross-sectional shape, irregular cross-section fibers are more likely to form complex arrangement patterns, thereby reducing their thermal conductivity to a certain extent. In addition, the gaps between irregular cross-section fibers may also be relatively small, which also helps to reduce heat transfer.

[0051] This invention first disperses polyacrylonitrile (PA) fibers in a liquid to obtain an organic fiber suspension. The PA molecules in this suspension have long and tightly packed molecular chains, and the presence of numerous cyano groups (-CN) complicates intermolecular interactions, hindering rapid heat transfer. Furthermore, the disordered arrangement of the PA molecular chains reduces heat conduction efficiency. Secondly, the PA fibers have an irregular cross-section, increasing the physical spacing between fibers, reducing the contact area, and altering the heat conduction path, further reducing heat transfer efficiency. Subsequently, during film formation, the irregular cross-section of the PA fibers increases their dispersion within the suspension, improving film formation during wet web formation. Finally, the synergistic effect of the PA fibers' low intrinsic thermal conductivity and the larger physical spacing of the irregular cross-section helps the organic fiber suspension achieve a low thermal conductivity during film formation. The resulting PA core material, when used in the fabrication of vacuum insulation panels, can reduce the thermal conductivity of the vacuum insulation board.

[0052] In some embodiments, the weight of the organic fiber is 0.005% to 1.0% of the total weight of the suspension.

[0053] The weight of organic fibers has a significant impact on the properties of the suspension and the strength, abrasion resistance, and air permeability of the subsequently produced polyacrylonitrile fiber fabric. The weight percentage of organic fibers in the suspension is a key factor, directly affecting the physical properties and performance of the suspension. Limiting the weight of organic fibers to 0.005% to 1.0% of the total weight of the suspension improves the dispersion effect of the organic profiled fibers in the organic fiber suspension, thereby enhancing the film-forming properties of the organic fiber suspension and effectively blocking heat transfer efficiency, which is beneficial for achieving a low thermal conductivity during film formation. Simultaneously, it helps ensure the uniform distribution and interlacing degree of fibers during web formation. For example, the weight percentage of organic fibers relative to the total weight of the suspension includes, but is not limited to, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, and 0.1%.

[0054] In some embodiments, the organic fiber has a diameter of 0.5 μm to 50 μm.

[0055] Fiber diameter refers to the cross-sectional diameter of a single fiber. The size of the fiber diameter determines its properties such as softness, strength, elasticity, and hygroscopicity. Fiber diameters of 0.5µm to 50µm are generally suitable for film formation and low thermal conductivity. Excessively large fiber diameters can lead to poor film formation and shorten the heat propagation path, hindering the achievement of low thermal conductivity. For example, the fiber diameters of organic fibers include, but are not limited to, 0.5µm, 1µm, 5µm, 8µm, 10µm, 15µm, 20µm, 25µm, 28µm, 30µm, 35µm, 40µm, 45µm, and 50µm.

[0056] In some embodiments, preferably, the diameter of the organic fiber is 3µm to 15µm.

[0057] Preferably, the diameter of the organic fiber is limited to 3µm to 15µm, which can further satisfy the requirements of fiber film formation and low thermal conductivity.

[0058] In some embodiments, the organic fiber comprises at least one of the following:

[0059] Filament fibers, short fibers and ultra-short fibers; the organic fibers have a fiber length of 0.5 mm to 250 mm.

[0060] It should be noted that filament fiber, also known as continuous filament fiber, is a type of chemical fiber. A filament is a continuous, very long strand. Short fiber, also known as cut fiber, is a chemical fiber bundle that has been cut or broken into fibers equivalent to the lengths of various natural fibers. Miniature short fibers have a shorter cut length than conventional fibers and exhibit high dispersibility in a medium. The length of organic fibers is a crucial factor affecting their physical properties and performance; fibers of different lengths exhibit different behaviors and effects in suspensions. Long fibers typically have higher tensile strength and a better hand feel; medium-length fibers are generally soft, abrasion-resistant, and elastic; short fibers are typically soft and breathable; and miniature short fibers are generally soft and fluffy. In suspensions, fibers of different lengths can be mixed to adjust the physical properties and performance of the suspension.

[0061] In some embodiments, the short fiber has a fiber length of 25mm to 150mm, and the ultra-short fiber has a fiber length of 1mm to 12mm.

[0062] The short fibers are limited to a length of 25mm to 150mm, and the ultra-short fibers are limited to a length of 1mm to 12mm. This improves the dispersion of organic shaped fibers in the organic fiber suspension, thereby enhancing the film-forming properties of the organic fiber suspension and facilitating the achievement of a low thermal conductivity during film formation. The short fibers, with a length of 25mm to 150mm, ensure good softness and breathability. The ultra-short fibers, with a length of 1mm to 12mm, provide ultimate softness and fluffiness. For example, the fiber lengths of the short fibers include, but are not limited to, 25mm, 30mm, 40mm, 50mm, 60mm, 70mm, 75mm, 80mm, 90mm, 100mm, 125mm, and 150mm; the fiber lengths of the ultra-short fibers include, but are not limited to, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, and 12mm.

[0063] In some embodiments, the dispersion method includes mechanical stirring and microwave heating.

[0064] Dispersing organic fibers in liquids offers significant advantages for both the subsequent fabrication process and the fabric itself. Uniformly dispersed fibers are easier to handle and process in liquids, reducing fiber entanglement and knotting, thus improving the smoothness of the fibers during weaving or forming. Simultaneously, well-dispersed fibers can form a more uniform and denser fiber network during forming, contributing to improved fabric density and uniformity. Mechanical stirring, a form of intense turbulent motion, helps break down the mutual attraction and entanglement between fibers, allowing them to achieve better dispersion in the solution. Microwave heating utilizes microwave radiation to heat substances non-contactly, generating heat by inducing vibration and friction of polar molecules within the substance. In aqueous solutions of organic fibers, water molecules are the predominantly polar molecules; they rapidly heat up after absorbing microwave energy, thereby promoting fiber dispersion. Through the dispersion effect of mechanical stirring or microwave heating, organic fibers are more easily dispersed in aqueous solutions, reducing fiber tangling and increasing monofilament dispersion. This improvement has a positive impact on achieving low thermal conductivity in the subsequent film formation process of the organic fiber suspension.

[0065] It should be noted that wet web forming is a process in which fiber suspension is processed into a web in a wet state using specific equipment (such as a wet web forming machine). The fibers are dispersed in water containing chemical additives to form a suspension. The water in the suspension is filtered out using papermaking felts or screens, and the deposited fibers form a fiber web.

[0066] In some embodiments, the water control time is 5 min to 30 min; and / or

[0067] The baking temperature is 100℃ to 240℃. Preferably, the baking temperature is 140℃ to 200℃.

[0068] Water control specifically involves removing excess liquid from the fiber web through methods such as squeezing and vacuum dewatering, reducing energy consumption and time in the subsequent baking process. Water control reduces the moisture content of the fiber web while preventing excessive compression between fibers that could lead to structural damage, thus producing polyacrylonitrile fiber cloth with excellent performance and a specific cross-sectional shape. Limiting the water control time to 5-30 minutes helps improve the efficiency of subsequent baking and dewatering. For example, the water control time includes, but is not limited to, 5, 7, 9, 10, 12, 15, 18, 20, 22, 25, 28, and 30 minutes. Baking involves placing the water-controlled fiber web into an baking oven and heating it with hot air or infrared radiation to form a stable bond between the fibers, ultimately resulting in the fiber cloth. Baking ensures the bonding strength between fibers and the consistency of the product, thus producing fiber cloth with excellent performance and a specific cross-sectional shape. Limiting the baking temperature to 100℃-240℃ improves the water removal efficiency and effect of the fiber cloth. Baking temperatures that are too low, below 100℃, result in low dehydration efficiency and poor dehydration effect to some extent; baking temperatures that are too high, above 240℃, result in the melting and sticking of organic fibers to some extent. Exemplary baking temperatures include, but are not limited to, 100℃, 120℃, 140℃, 150℃, 160℃, 170℃, 180℃, 200℃, 220℃, 230℃, and 240℃. Preferably, the baking temperature is between 140℃ and 200℃. Limiting the baking temperature to between 140℃ and 200℃ can further improve the dehydration efficiency and effect of the fiber cloth.

[0069] In some embodiments, the areal density of the polyacrylonitrile fiber cloth is 2 g / m². 2 ~150g / m 2 .

[0070] Areal density is the mass per unit area of ​​a fabric, expressed in meters. 2 The weight of the dried fabric is expressed in grams (g). Weight per unit area is an indicator of fabric quality and cost; a higher value indicates a denser and heavier knitted fabric, but also requires more raw materials, increasing fabric cost. Theoretically, the lower the areal density of the fiber fabric, the simpler the overlap between fibers and the fewer contact points between multiple fibers, which is beneficial for achieving ultra-low thermal conductivity. The areal density of the fiber fabric is limited to 2 g / m². 2 ~150g / m 2On the one hand, this meets the quality requirements of the fiber cloth, making it suitable for use in the preparation of the inner core of vacuum insulation panels; on the other hand, it facilitates the achievement of ultra-low thermal conductivity. If the areal density is too high, the fiber twisting will increase, correspondingly increasing the thermal conductivity; if the areal density is too low, it is detrimental to the preparation of the inner core of the vacuum insulation panel. For example, the areal density of the fiber cloth includes, but is not limited to, 2 g / m³. 2 5g / m 2 10g / m 2 20g / m 2 30g / m 2 40g / m 2 50g / m 2 60g / m 2 70g / m 2 80g / m 2 90g / m 2 100g / m 2 120g / m 2 140g / m 2 150g / m 2 wait.

[0071] In some embodiments, preferably, the areal density of the polyacrylonitrile fiber cloth is 5 g / m². 2 ~100g / m 2 .

[0072] Preferably, the areal density of the fiber cloth is defined as 5 g / m². 2 ~100g / m 2 On the one hand, it can further meet the quality requirements of fiber cloth, so that it can be used to prepare the inner core of vacuum insulation board; on the other hand, it can be more conducive to achieving ultra-low thermal conductivity.

[0073] In some embodiments, the polyacrylonitrile fiber cloth has a three-dimensional network structure.

[0074] The three-dimensional network architecture means that polyacrylonitrile fibers not only interweave in a planar manner within the fabric but also form a certain sense of layering and spatial structure in the vertical direction. This three-dimensional network architecture of polyacrylonitrile fiber fabric brings multiple advantages, including structural stability, superior physical properties, excellent thermal properties, strong chemical stability, and excellent processing performance. In particular, the overlapping structure between fibers, which is a disordered three-dimensional network shape at the microscopic level, allows heat to be transferred within the overlapping fibers. Heat transfer between fibers occurs through contact points, increasing the difficulty of heat transfer. This helps to reduce the thermal conductivity of the fiber fabric, contributing to its excellent thermal performance.

[0075] In some implementations, the number of sheets is 100 to 500.

[0076] By stacking multiple sheets of polyacrylonitrile (PA) fiber cloth to form a multi-layered structure with a certain thickness and size, the thickness and density of the PA core material can be significantly increased, thereby further improving its overall strength and stability. Simultaneously, the three-dimensional network structure of the multiple PA fibers interweaves and fuses during the stacking process, forming a more complex and stable overall structure, which helps to improve the compressive strength, shear strength, and bending strength of the PA core material. For example, the number of PA fibers stacked may include, but is not limited to, 100, 200, 300, 320, 340, 350, 370, 390, 400, 420, 440, 460, 480, and 500 sheets.

[0077] In some embodiments, the heat treatment temperature is 130°C to 200°C. Preferably, the heat treatment temperature is 160°C to 180°C.

[0078] Heat treatment not only promotes further cross-linking and fusion between fibers, enhancing the overall strength and stability of the polyacrylonitrile core material, but also improves its thermal and chemical properties to a certain extent, thereby further optimizing the internal structure and performance of the polyacrylonitrile core material. Simultaneously, limiting the heat treatment temperature to 130℃~200℃ can further accelerate the dehydration and drying effect of the polyacrylonitrile core material, reducing its adsorption of moisture from the air. If the heat treatment temperature is too low (below 130℃), it will result in low dehydration efficiency and poor dehydration effect; if the heat treatment temperature is too high (above 200℃), it will easily cause the organic fibers to melt and stick together. Preferably, limiting the heat treatment temperature to 160℃~180℃ can further accelerate the dehydration and drying effect of the polyacrylonitrile core material, reducing its adsorption of moisture from the air. Exemplary heat treatment temperatures include, but are not limited to, 130℃, 135℃, 140℃, 150℃, 155℃, 160℃, 165℃, 170℃, 175℃, 180℃, 185℃, 190℃, and 200℃.

[0079] This invention provides a polyacrylonitrile (PA) core material, prepared by the aforementioned method. This PA core material not only fully utilizes the excellent properties of PA fiber cloth itself, such as high strength, abrasion resistance, heat resistance, and structural stability brought by its three-dimensional network architecture, but also possesses new properties and application potential through a unique processing method.

[0080] Figure 2 This is a schematic diagram of the structure of a vacuum insulation board provided in an embodiment of this application.

[0081] Please see Figure 2Based on a general inventive concept, embodiments of the present invention provide a vacuum insulation board, wherein the vacuum insulation board includes the polyacrylonitrile core material 1 described in any of the above embodiments.

[0082] In this invention, the thermal conductivity of the vacuum insulation board mainly depends on the thermal conductivity of its internal polyacrylonitrile core material 1 and the insulation effect of the vacuum layer. The polyacrylonitrile core material 1 prepared by this invention is used in the vacuum insulation board, thereby significantly reducing the overall thermal conductivity of the vacuum insulation board. This helps to reduce heat transfer from the high-temperature side to the low-temperature side, improving the insulation effect of the vacuum insulation board.

[0083] Figure 2 This is a schematic diagram of the structure of a vacuum insulation board provided in an embodiment of this application.

[0084] Please see Figure 2 Based on a general inventive concept, embodiments of the present invention provide a vacuum insulation board, wherein the vacuum insulation board includes the polyacrylonitrile core material 1 described in any of the above embodiments.

[0085] In this invention, the thermal conductivity of the vacuum insulation board mainly depends on the thermal conductivity of its internal polyacrylonitrile core material 1 and the insulation effect of the vacuum layer. The polyacrylonitrile core material 1 prepared by this invention is used in the vacuum insulation board, thereby significantly reducing the overall thermal conductivity of the vacuum insulation board. This helps to reduce heat transfer from the high-temperature side to the low-temperature side, improving the insulation effect of the vacuum insulation board.

[0086] In some embodiments, the vacuum insulation board further includes a protective film 2 and a getter 3.

[0087] Vacuum insulation panels, as a highly efficient and energy-saving insulation material, possess excellent thermal insulation performance due to their unique structure and material composition. Besides the polyacrylonitrile core material 1, the vacuum insulation panel also includes a protective film 2 and a getter 3. These components work together to achieve its superior insulation effect. The protective film 2 is the outer protective layer of the vacuum insulation panel, its main function being to isolate the external environment from the internal vacuum environment, preventing gas infiltration and heat transfer. The getter 3 is an indispensable part of the vacuum insulation panel, its main function being to adsorb excess gas generated due to infiltration or material release, thereby maintaining the stability of the internal vacuum environment. The selection of the getter 3 is crucial to the performance of the vacuum insulation panel. In certain specific applications, additional desiccants may be used to further reduce internal humidity and improve the performance of the vacuum insulation panel. In summary, the vacuum insulation panel consists of a polyacrylonitrile core material, a protective film, and a getter / desiccant. These components work together to form the unique structure and excellent thermal insulation performance of the vacuum insulation panel.

[0088] Figure 3This is a schematic flowchart illustrating a method for preparing a vacuum insulation board according to an embodiment of this application.

[0089] Please see Figure 3 This invention provides a method for preparing the vacuum insulation board described in the above embodiments, the method comprising:

[0090] S104. The polyacrylonitrile core material bag is placed into the protective film to obtain a bagged plate;

[0091] S105. Vacuum treatment is performed on the bagged plate. When the vacuum degree of the bagged plate reaches the set vacuum degree, the bagged plate is heat-sealed to obtain a vacuum insulation plate.

[0092] In some embodiments, the set vacuum degree is 1.0*10 -4 Pa ~ 4.0 * 10 -3 Pa.

[0093] In the manufacturing process of vacuum insulation panels, vacuuming is a crucial step that directly affects the thermal insulation performance and service life of the panels. By limiting the vacuum level during vacuuming, heat loss through gas molecule conduction can be reduced, thereby significantly improving the thermal insulation performance of the vacuum insulation panel. For example, the vacuum level during vacuuming may include, but is not limited to, 1.0*10⁻⁶. -4 Pa, 1.2*10 -4 Pa, 1.5*10 -4 Pa, 1.8*10 -4 Pa, 2.0*10 -4 Pa, 2.2*10 - 4 Pa, 2.5*10 -4 Pa, 2.8*10 -4 Pa, 3.0*10 -4 Pa, 3.2*10 -4 Pa, 3.5*10 -4 Pa, 3.8*10 -4 Pa, 4.0*10 -3 Pa, etc.

[0094] In some embodiments, the process parameters for the hot-press sealing include: voltage of 9V to 15V and time of 15s to 25s.

[0095] In the manufacturing process of vacuum insulation panels, hot-press sealing is a crucial step that decisively affects the product's sealing performance and final properties. By specifying voltage and time parameters, hot-press sealing can effectively improve the heat-fusion bonding effect of the inner layer of the film bag, thereby ensuring the sealing and thermal insulation performance of the vacuum insulation panel. For example, the voltage for hot-press sealing includes, but is not limited to, 9V, 9.5V, 10V, 10.5V, 11V, 11.5V, 12V, 12.5V, 13V, 13.5V, 14V, 14.5V, and 15V, and the sealing time includes, but is not limited to, 15s, 16s, 17s, 18s, 19s, 20s, 21s, 22s, 23s, 24s, and 25s.

[0096] In some embodiments, the present invention provides a heat insulation device, wherein the heat insulation material of the heat insulation device includes the vacuum insulation board described in the above embodiments.

[0097] The vacuum insulation board provided by this invention can be used in various applications, including but not limited to thermal insulation equipment, as well as for building exterior wall insulation, RV insulation, and spacecraft thermal insulation.

[0098] In some embodiments, the heat insulation equipment includes, but is not limited to, refrigerators, freezers, refrigerated trucks, and ice-freezing trucks.

[0099] The present application is further illustrated below with specific embodiments and experimental data. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If no corresponding national standard exists, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0100] Example 1

[0101] This embodiment provides a fiber cloth, the preparation method of which includes:

[0102] S111. Disperse organic fibers in water to obtain an organic fiber suspension; wherein the organic fibers are triangular polyacrylonitrile fibers with a diameter of 7 μm and a length of 5 mm, and the weight of the polyacrylonitrile fibers is 0.05% of the total weight of the suspension.

[0103] S112. The organic fiber suspension is wet-laid and the water is controlled for 5 minutes. Then it is placed in an oven at 180℃ for 2 hours and demolded to obtain a surface density of 15 g / m². 2 Fiber cloth;

[0104] S113. Stack multiple sheets of the polyacrylonitrile fiber cloth, and then bake them again at 200°C for 2 hours in an oven to obtain polyacrylonitrile core material.

[0105] Based on the polyacrylonitrile core material of this embodiment, this embodiment also provides a vacuum insulation board, the preparation method of which includes:

[0106] S114. The organic core material bag obtained in S113 is placed into a protective film to obtain a bagged board;

[0107] S115. Place the bagged plate obtained in S114 into a vacuum sealing machine and perform vacuum treatment on the bagged plate until the vacuum degree of the bagged plate reaches 3.5*10. -3 At pressure Pa, the bagged plate is heat-sealed for 15 seconds at a heat-sealing voltage of 13V. Then, the getter shell is punctured by pressing to further reduce the internal pressure, thus obtaining a vacuum insulation plate.

[0108] Example 2

[0109] The difference between this embodiment and Embodiment 1 is that the organic fiber is a clover-shaped polyacrylonitrile fiber with a diameter of 7 μm and a length of 5 mm.

[0110] Example 3

[0111] The difference between this embodiment and Embodiment 1 is that the organic fiber is a cross-shaped polyacrylonitrile fiber with a diameter of 7 μm and a length of 5 mm.

[0112] Example 4

[0113] The difference between this embodiment and Embodiment 1 is that the organic fiber is a T-shaped polyacrylonitrile fiber with a diameter of 7 μm and a length of 5 mm.

[0114] Example 5

[0115] The difference between this embodiment and Embodiment 1 is that the organic fiber is a Y-shaped polyacrylonitrile fiber with a diameter of 7 μm and a length of 5 mm.

[0116] Example 6

[0117] The difference between this embodiment and Embodiment 1 is that the organic fiber is a crescent-shaped polyacrylonitrile fiber with a diameter of 7 μm and a length of 5 mm.

[0118] Example 7

[0119] The difference between this embodiment and Embodiment 1 is that the organic fiber is a dumbbell-shaped polyacrylonitrile fiber with a diameter of 7 μm and a length of 5 mm.

[0120] Example 8

[0121] The difference between this embodiment and Embodiment 1 is that the organic fiber is a five-pointed star-shaped polyacrylonitrile fiber with a diameter of 7 μm and a length of 5 mm.

[0122] Example 9

[0123] The difference between this embodiment and Embodiment 1 is that the organic fiber is a fan-shaped polyacrylonitrile fiber with a diameter of 7 μm and a length of 5 mm.

[0124] Example 10

[0125] The difference between this embodiment and Embodiment 1 is that the organic fiber is a five-lobed polyacrylonitrile fiber with a diameter of 7 μm and a length of 5 mm.

[0126] Example 11

[0127] The difference between this embodiment and Embodiment 1 is that the weight of the polyacrylonitrile fiber is 0.01% of the total weight of the suspension.

[0128] Example 12

[0129] The difference between this embodiment and Embodiment 1 is that the weight of the polyacrylonitrile fiber is 0.1% of the total weight of the suspension.

[0130] Example 13

[0131] The difference between this embodiment and Embodiment 1 is that the diameter of the polyacrylonitrile fiber is 3 μm.

[0132] Example 14

[0133] The difference between this embodiment and Embodiment 1 is that the diameter of the polyacrylonitrile fiber is 15 μm.

[0134] Example 15

[0135] The difference between this embodiment and Embodiment 1 is that the fiber length of the polyacrylonitrile fiber is 25 mm.

[0136] Example 16

[0137] The difference between this embodiment and Embodiment 1 is that the fiber length of the polyacrylonitrile fiber is 1 mm.

[0138] Example 17

[0139] The difference between this embodiment and Embodiment 1 is that the fiber length of the polyacrylonitrile fiber is 50 mm.

[0140] Example 18

[0141] The difference between this embodiment and Embodiment 1 is that the areal density of the fiber cloth is 5 g / m². 2 .

[0142] Example 19

[0143] The difference between this embodiment and Embodiment 1 is that the areal density of the fiber cloth is 100 g / m². 2 .

[0144] Example 20

[0145] The difference between this embodiment and Embodiment 1 is that the baking temperature for preparing the fiber cloth is 100℃.

[0146] Example 21

[0147] The difference between this embodiment and Embodiment 1 is that the baking temperature for preparing the fiber cloth is 240℃.

[0148] Comparative Example 1

[0149] This comparative example provides a vacuum insulation board, the preparation method of which includes:

[0150] S121. Disperse circular glass fibers with a diameter of 7 μm and a length of 5 mm in water to obtain a glass fiber suspension.

[0151] S122. The glass fiber suspension is wet-laid and the water is controlled for 5 minutes. Then it is placed in an oven at 180℃ and baked for 2 hours. After demolding, the surface density is 25 g / m³. 2 Fiberglass mat;

[0152] S123. Stack the glass fiber mat into a core material, and then place it in the drying tunnel to bake again at 200℃ for 2 hours to obtain the glass fiber core material.

[0153] S124. Pack the fiberglass core material bag into the protective film to obtain the bagged board;

[0154] S125. Place the bagged plate in a vacuum sealing machine and vacuum the bagged plate until the vacuum degree of the bagged plate reaches 3.5*10. -3 At pressure Pa, the bagged plate is heat-sealed for 15 seconds at a heat-sealing voltage of 13V. Then, the getter shell is punctured by pressing to further reduce the internal pressure, thus obtaining a vacuum insulation plate.

[0155] Comparative Example 2

[0156] The difference between this comparative example and Example 1 is that the organic fiber is a circular polyacrylonitrile fiber with a diameter of 7 μm and a length of 5 mm.

[0157] Comparative Example 3

[0158] The difference between this comparative example and Example 1 is that the weight of the polyacrylonitrile fiber is 2% of the total weight of the suspension.

[0159] Comparative Example 4

[0160] The difference between this comparative example and Example 1 is that the weight of the polyacrylonitrile fiber is 0.001% of the total weight of the suspension.

[0161] Comparative Example 5

[0162] The difference between this comparative example and Example 1 is that the diameter of the organic fiber is 0.1 μm.

[0163] Comparative Example 6

[0164] The difference between this comparative example and Example 1 is that the diameter of the organic fiber is 60 μm.

[0165] Comparative Example 7

[0166] The difference between this comparative example and Example 1 is that the baking temperature for preparing the fiber cloth is 300°C.

[0167] Experimental Test

[0168] To better illustrate the thermal insulation performance of the vacuum insulation board provided by the present invention, the thermal conductivity of the vacuum insulation boards obtained in Examples 1 to 21 and Comparative Examples 1 to 7 was tested, and the results are shown in Table 1.

[0169] Table 1. Thermal conductivity of the vacuum insulation panels obtained in Examples 1-21 and Comparative Examples 1-7

[0170]

[0171]

[0172] As shown in Table 1, compared to vacuum insulation boards with glass fiber and traditional circular polyacrylonitrile fiber cores, the vacuum insulation board with shaped polyacrylonitrile fiber cores provided by this invention has a lower thermal conductivity and better insulation effect. Furthermore, as shown in Examples 1-21, the thermal conductivity of the vacuum insulation board with organic shaped polyacrylonitrile fiber cores is strongly correlated with the fiber cross-sectional morphology. The thermal conductivity of the vacuum insulation board with a cross-shaped cross-section fiber core is lower than that of other non-circular cross-sections; therefore, in practical applications, vacuum insulation boards with cross-shaped cross-section polyacrylonitrile fiber cores can be selectively prepared. In addition, as shown in Comparative Example 1, the thermal conductivity of the vacuum insulation board prepared with shaped polyacrylonitrile fibers is significantly better than that with glass fiber; and as shown in Comparative Example 2, the thermal conductivity of the vacuum insulation board prepared with non-circular cross-section polyacrylonitrile fibers is significantly better than that with circular cross-section polyacrylonitrile fibers.

[0173] Furthermore, one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0174] In this embodiment of the invention, organic shaped fiber materials are used to replace fumed silica or glass fiber and applied to the main material of the core material of vacuum insulation board, overcoming the problems of cost, environmental harm and inability to achieve ultra-low thermal conductivity.

[0175] In this embodiment of the invention, the efficient suspension and dispersion of organic irregularly shaped fibers creates conditions for the low basis weight of the fiber cloth after wet web formation. Simultaneously, the high rigidity of the organic irregularly shaped fiber material provides support for the three-dimensional network structure of the vacuum insulation board core material. Heat transfer occurs within the three-dimensional fiber network architecture, fully utilizing the low intrinsic thermal conductivity of the organic irregularly shaped fibers, their irregular cross-sections, and the infinitely increased heat conduction path created by constructing a three-dimensional structure, ultimately resulting in a vacuum insulation board with ultra-low thermal conductivity.

[0176] In this embodiment of the invention, the initial thermal conductivity of the provided vacuum insulation board is less than 2 mW*(m K). -1 .

[0177] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

Claims

1. A process for the preparation of a polyacrylonitrile core material, characterized in that, The method comprises: dispersing organic fibers in a liquid to obtain an organic fiber suspension; and wet-laying and controlling water of the organic fiber suspension, and then baking to obtain a polyacrylonitrile fiber cloth; stacking and heat-treating a plurality of the polyacrylonitrile fiber cloths to obtain a polyacrylonitrile core material; The organic fiber is made of polyacrylonitrile, and the organic fiber has a special cross-section, which is one of triangular, trilobal, cross-shaped, T-shaped, Y-shaped, crescent-shaped, dumbbell-shaped, five-pointed star-shaped, fan-shaped, and five-lobed.

2. The method of claim 1, wherein, The weight of the organic fiber is 0.01% to 0.1% of the total weight of the suspension.

3. The method of claim 1, wherein, The fiber diameter of the organic fiber is 0.5um to 50um.

4. The method of claim 3, wherein, Preferably, the fiber diameter of the organic fiber is 3um to 15um.

5. The method of claim 1, wherein, The fiber length of the organic fiber is 0.5mm to 250mm.

6. The method of claim 1, wherein, The dispersion method includes mechanical stirring and microwave heating.

7. The method of claim 1, wherein, The water control time is 5min to 30min; and / or The baking temperature is 100℃ to 240℃.

8. The method of claim 1, wherein, The areal density of the polyacrylonitrile fiber cloth is 2 g / m 2 ~ 150 g / m 2 .

9. The method of claim 8, wherein, Preferably, the areal density of the polyacrylonitrile fiber cloth is 5 g / m 2 ~ 100 g / m 2 .

10. The method of claim 1, wherein, The polyacrylonitrile fiber cloth has a three-dimensional network structure.

11. The method of claim 1, wherein, The plurality is 100 to 500.

12. The method of claim 1, wherein, The heat treatment temperature is 130℃ to 200℃.

13. A vacuum insulation panel, characterized in that The vacuum insulation board comprises the polyacrylonitrile core material according to any one of claims 1 to 12.

14. A method of producing a vacuum thermal insulation panel according to claim 13, characterized in that The method comprises: bagging the polyacrylonitrile core material in a protective film to obtain a bagged board; performing vacuumizing treatment on the bagged board, and when the vacuum degree of the bagged board reaches a set vacuum degree, performing hot-pressing sealing on the bagged board to obtain a vacuum insulation board.

15. The method of claim 14, wherein, The set vacuum degree is 1.0*10 -4 Pa~4.0*10 - 3 Pa.

16. The method of claim 14, wherein, The process parameters of the hot-pressing sealing include a voltage of 9V to 15V and a time of 15s to 25s.

17. A thermal insulation device, characterized by The thermal insulation material of the thermal insulation equipment comprises the vacuum insulation board according to claim 13.

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