A honeycomb paper with a microporous surface and its preparation method, and a honeycomb core.

Abstract

This invention discloses a honeycomb paper with a microporous surface structure, comprising a base paper and a surface paper located on the surface of the base paper. The surface paper is prepared by adding a pore-forming agent during papermaking and removing the agent during post-processing to obtain the microporous structure. The average pore size of the microporous structure of the surface paper is 50-500 nm, and the porosity is 55-78%. This invention also provides a method for preparing the aforementioned honeycomb paper with a microporous surface structure and a honeycomb core. The honeycomb paper of this invention has a rich, uniform, and specific pore structure in its surface paper. The micro- and nano-pores enhance the node strength of the honeycomb paper without significantly affecting its mechanical properties and subsequent processing. This not only optimizes the wetting process of the honeycomb paper with the node adhesive and resin, improving the node strength, but also prevents resin from penetrating the base paper, improving problems such as insufficient honeycomb toughness and excessive brittleness, achieving a balance between node strength and mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of paper or paperboard products, and particularly relates to a honeycomb paper, its preparation method, and a honeycomb core. Background Technology

[0002] Paper-based honeycomb composites, due to their high specific stiffness and high specific strength, are widely used as lightweight structural materials in aerospace, aviation, and high-speed transportation. The manufacturing process of paper-based honeycomb products involves coating, stacking, and hot-pressing honeycomb paper to bond the layers together. This is followed by stretching and shaping to obtain a white honeycomb structure with honeycomb cells. Finally, resin is impregnated and cured at high temperature to obtain the paper-based honeycomb product. The coating and bonding processes of the honeycomb paper play a crucial role in binding the paper layers, and the strength of the joints at the adhesive bonding points affects subsequent processing steps such as stretching and shaping of the honeycomb core.

[0003] Patent application CN114211847A discloses a special aramid paper for aramid paper honeycomb and its preparation method. The method involves preparing multilayer composite aramid paper by bonding loose, porous para-aramid paper to both sides of dense meta-aramid paper. This multilayer composite aramid paper can improve node strength and mitigate problems such as resin impregnation and excessive honeycomb brittleness that may occur during the preparation of aramid paper honeycomb. However, this patent does not design, control, or improve the surface para-aramid paper. Ordinary para-aramid paper has poor uniformity, a loose structure, and low surface strength. Poor uniformity leads to unstable performance, a loose structure leads to low strength, and low surface strength leads to damage during processing and application. Therefore, this multilayer composite aramid paper is difficult to meet application requirements.

[0004] Therefore, providing a type of honeycomb paper that can improve the node strength between honeycomb paper nodes while ensuring the comprehensive performance of the honeycomb paper, such as mechanical properties and processing properties, is an urgent technical problem to be solved. Summary of the Invention

[0005] The technical problem to be solved by this invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a honeycomb paper with a microporous surface structure that has high adhesive joint strength and good mechanical properties, as well as its preparation method and honeycomb core. To solve the above technical problem, the technical solution proposed by this invention is as follows:

[0006] A honeycomb paper with a microporous structure on the surface includes a base paper and a surface paper located on the surface of the base paper. The surface paper is formed by adding a pore-forming agent during papermaking and removing the pore-forming agent in post-processing to obtain a microporous structure. The average pore size of the microporous structure of the surface paper is 50-500 nm, and the porosity is 55-78%.

[0007] In the aforementioned honeycomb paper with a microporous surface structure, preferably, the pore-forming aid includes one or more of polystyrene nanospheres, carbon nanospheres, melamine-formaldehyde polymer microspheres, polymethyl methacrylate microspheres, polylactic acid nanospheres, and silica microspheres.

[0008] In the above-mentioned honeycomb paper with a microporous surface, preferably, the diameter of the pore-forming aid is 20-500 nm, and the amount of the pore-forming aid added is 1-5% of the mass of the surface paper.

[0009] In the aforementioned honeycomb paper with a microporous surface structure, preferably, the base paper and the surface paper are composited into a "sandwich" structure, with the base paper accounting for 50-80% by weight and the surface paper accounting for 20-50% by weight. The base paper needs to provide high mechanical properties to meet application requirements and therefore requires a high basis weight; thus, the weight percentage of the base paper needs to be controlled at 50-80%.

[0010] In the aforementioned honeycomb paper with a microporous surface structure, preferably, the base paper is mainly made of synthetic fibers and / or natural fibers. The synthetic fibers include one or more of polyester fibers, polyacrylonitrile fibers, polyethylene fibers, polypropylene fibers, polysulfonamide fibers, poly(p-phenylenebenzodioxazole) fibers, aromatic polyoxadiazole fibers, poly(m-phenylene isophthalamide) fibers, poly(p-phenylene terephthalamide) fibers, aromatic nylon fibers, polyimide fibers, and carbon fibers. The natural fibers include one or more of wood pulp fibers, bamboo pulp fibers, hemp pulp fibers, cotton pulp fibers, and cellulose fibers.

[0011] In the aforementioned honeycomb paper with a microporous surface structure, preferably, the surface paper is mainly composed of nanofibers, including one or more of nanocellulose fibers, nanoaramid fibers, and nanocarbon fibers.

[0012] As a general technical concept, the present invention also provides a method for preparing the above-mentioned honeycomb paper with a microporous surface structure, comprising the following steps:

[0013] (1) The fiber raw material and pore-forming agent of the surface paper are added to a solvent to disperse, loosen and mix to obtain mixed pulp A. Mixed pulp A is formed into surface paper base paper.

[0014] (2) The fiber raw materials of the base paper are added to a solvent to disperse, loosen and mix to obtain mixed pulp B. Mixed pulp B is formed into base paper.

[0015] (3) The base paper and the surface paper are stacked and compounded, and the pore-forming agent is removed by post-treatment to obtain the honeycomb paper with microporous structure on the surface.

[0016] In the above preparation method, preferably, the paper forming of mixed slurry A is assisted by a PET filter membrane. Using a PET filter membrane for paper forming reduces the loss of nanomaterials and improves utilization.

[0017] In the above preparation method, preferably, the method of superimposing and laminating the base paper and the surface paper includes hot pressing and / or adhesive bonding.

[0018] In the above preparation method, preferably, the post-treatment method for removing the pore-forming aid includes one or more of thermal decomposition, dissolution, and chemical decomposition. The removal method for the pore-forming aid varies depending on the aid, including one or more of thermal decomposition, dissolution, and chemical decomposition. For example, polymethyl methacrylate microspheres can be removed by thermal decomposition, polystyrene nanospheres can be removed by dissolution, and melamine-formaldehyde polymer nanospheres can be removed by chemical decomposition.

[0019] As a general technical concept, this invention also provides a honeycomb core, which is obtained by bonding multiple layers of honeycomb paper with microporous structures on the surface. The preparation of the honeycomb paper into a honeycomb core material requires steps such as applying adhesive, lamination, hot pressing, stretching and shaping, and resin impregnation to obtain the honeycomb core.

[0020] The average pore size and porosity of existing honeycomb paper are related to the type and structure of the paper fibers. Taking aramid honeycomb paper as an example (single-layer paper, not multi-layer composite), after hot pressing, the surface of aramid honeycomb paper is dense with fewer pores. However, the middle part of the aramid honeycomb paper has a richer pore structure due to fiber overlap. That is, the actual rich overall structure is not visible due to the dense surface. This invention introduces a pore-forming agent to obtain a microporous structure in the dense surface layer of the honeycomb paper (most of the pore-forming agent added during papermaking fills the existing pores. After the pore-forming agent is removed in post-processing, the dense surface will have a porous structure like the interior), providing impregnation channels for the node adhesive. At the same time, it controls the size and number of pores, i.e., porosity and pore size (the pore size and number are similar to the original pore size), avoiding the introduction of additional pores as defects that cause a significant decrease in paper performance. Therefore, the particle size and amount of pore-forming agent should be controlled so that the porosity and pore size of the final honeycomb paper surface are similar to those of the intermediate layer, thus avoiding affecting the mechanical properties of the paper.

[0021] This invention controls the diameter of the pore-forming agent to be 20-500 nm and the amount of pore-forming agent added to be 1-5% of the mass of the surface paper. This allows the average pore size of the microporous structure of the surface paper to be 50-500 nm and the porosity to be 55-70%. This microporous structure and porosity can optimize the wetting process of the surface honeycomb paper with the node adhesive and resin, improve the node adhesive strength of the honeycomb paper, and avoid introducing too many additional pores, thus avoiding the decline in the mechanical properties of the paper due to pore defects and achieving a balance between node strength and mechanical properties. The average pore size and porosity of the aforementioned microporous structure need to be precisely controlled. If the average pore size or porosity is too large, there will be numerous pores and defects in the paper, leading to a decrease in mechanical properties such as tensile strength. This decrease in paper strength will also cause the failure mode in node strength testing to shift to shear failure, resulting in a decline in node strength performance. If the average pore size or porosity is too small, the impregnation and bonding between the honeycomb paper and the node adhesive and resin during subsequent processing and application will be difficult, leading to a decrease in node strength. Simultaneously, it will also cause uneven impregnation and distribution of resin on the honeycomb paper, resulting in a decrease in the mechanical properties of the honeycomb core. The diameter of the aforementioned pore-forming aid needs to meet the requirement of an average pore size of 50-500 nm for the microporous structure; therefore, the diameter of the pore-forming aid should be controlled within the range of 20-500 nm. The amount of pore-forming aid used needs to meet the porosity requirements of the microporous structure; too much pore-forming aid will result in excessive porosity, while too little will result in insufficient porosity.

[0022] Compared with the prior art, the advantages of the present invention are as follows:

[0023] 1. The honeycomb paper with a microporous surface structure of the present invention improves the node strength by regulating the pore structure of the surface paper. The prepared surface paper with a microporous structure has a rich pore structure, which can optimize the wetting process of the surface paper with node adhesive and resin, and improve the node adhesive strength of the honeycomb paper.

[0024] 2. The honeycomb paper with a microporous structure on the surface layer of the present invention has a pore-forming agent added during the papermaking process and removed in the post-processing. This pore-forming method can control the pore size and porosity of the surface layer paper by controlling the particle size and amount of the pore-forming agent. The control process is simple and easy to implement, easy to process, and the obtained pores are uniformly distributed and have stable performance.

[0025] 3. The honeycomb paper of the present invention has a microporous structure on the surface. The surface paper has a rich, uniform and specific pore structure. The micro and nano pores improve the node strength of the honeycomb paper without significantly affecting the mechanical properties of the paper and have no impact on subsequent processing. It can not only optimize the wetting process of the honeycomb paper with node adhesive and resin, and improve the node strength of the honeycomb paper, but also prevent the resin from penetrating the base paper, improve the problems of insufficient honeycomb toughness and excessive brittleness, and achieve a balance between node strength and mechanical properties. Detailed Implementation

[0026] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0027] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0028] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0029] Example 1:

[0030] A honeycomb paper with a microporous structure on the surface includes a base paper and a surface paper disposed on the surface of the base paper. It is composed of two layers of surface paper and an intermediate layer of base paper. The weight percentage of the base paper is 62% and the weight percentage of the surface paper is 38%.

[0031] The surface paper is made of nano-meta-aramid fibers, chopped meta-aramid fibers, and polystyrene nanospheres. The nano-meta-aramid fibers have a diameter of 10-80 nm and an aspect ratio of 1000-5000. The chopped meta-aramid fibers are 5 mm long. The polystyrene nanospheres have a particle size of 50-100 nm.

[0032] The base paper is composed of meta-aramid precipitated fibers and meta-aramid chopped fibers. The length of the meta-aramid precipitated fibers is 0.8 mm. The length of the meta-aramid chopped fibers is 5 mm.

[0033] The method for preparing the above-mentioned honeycomb paper with a microporous surface includes the following steps:

[0034] 0.251 g of oven-dry meta-aramid fiber, 0.251 g of chopped meta-aramid fiber, and 0.005 g of polystyrene nanospheres were dissolved, dispersed, and mixed with 2 L of water to obtain mixed slurry A. Mixed slurry A was formed on a Kaiser rapid paper forming machine, filtered through a PET filter membrane, and dried to obtain a sheet with an area of ​​0.0314 m². 2 The quantitative value is 16g / m 2 The base paper of the surface layer contains a pore-forming agent.

[0035] 0.816 g of oven-dry meta-aramid precipitated fiber and 0.816 g of meta-aramid chopped fiber were added to 2 L of water, then dissolved, dispersed, and mixed to obtain mixed slurry B. Mixed slurry B was formed on a Kaiser rapid paper forming machine, and after drying, the prepared area was 0.0314 m². 2 The quantitative value is 52g / m2 The base paper of the base paper.

[0036] The base paper is stacked according to the structure of surface paper-base paper-surface paper, and composite honeycomb paper is prepared by hot pressing using a flatbed hot press and hot calendering is achieved.

[0037] The hot-pressed composite honeycomb paper was immersed in dimethylformamide solution for 30 minutes to dissolve and remove the polystyrene nanospheres, resulting in honeycomb paper with a microporous structure on the surface.

[0038] The honeycomb core of this embodiment can be obtained by bonding multiple layers of the above-mentioned honeycomb paper together.

[0039] Example 2:

[0040] A honeycomb paper with a microporous structure on the surface includes a base paper and a surface paper disposed on the surface of the base paper. It is composed of two layers of surface paper and an intermediate layer of base paper. The weight percentage of the base paper is 52.4% and the weight percentage of the surface paper is 47.6%.

[0041] The surface paper is composed of nano-para-aramid fibers, chopped para-aramid fibers, and melamine-formaldehyde polymer nanospheres. The nano-para-aramid fibers have a diameter of 10-80 nm and an aspect ratio of 1000-5000. The chopped para-aramid fibers are 5 mm long. The melamine-formaldehyde polymer nanospheres have a particle size of 50-120 nm.

[0042] The base paper is composed of meta-aramid precipitated fibers and chopped carbon fibers. The meta-aramid precipitated fibers are 0.8 mm long. The chopped carbon fibers are 5 mm long.

[0043] The method for preparing the above-mentioned honeycomb paper with a microporous surface includes the following steps:

[0044] 0.314 g of oven-dry para-aramid fiber, 0.314 g of chopped para-aramid fiber, and 0.012 g of melamine-formaldehyde polymer nanospheres were dissolved in 2 L of water to obtain mixed slurry A. Mixed slurry A was then used in a Kaiser rapid paper forming machine and filtered through a PET membrane to form a sheet with an area of ​​0.0314 m². 2 The quantitative value is 20g / m 2 The base paper of the face paper is mixed with a pore-forming agent.

[0045] Mixed slurry B was prepared by adding 0.829 g of oven-dry meta-aramid precipitated fiber and 0.553 g of chopped carbon fiber to 2 L of water and then dissolving the mixture. Mixed slurry B was then formed on a Kaiser rapid paper forming machine, and after drying, the prepared area was 0.0314 m². 2 The quantitative value is 44g / m 2 The base paper of the base paper.

[0046] Composite honeycomb paper is prepared by stacking the base paper, base paper, and top paper according to the structure of surface paper-base paper-surface paper, and then hot-pressing and calendering are achieved.

[0047] The composite honeycomb paper was soaked in a 10% hydrofluoric acid aqueous solution for 30 minutes to remove melamine-formaldehyde polymer nanospheres, resulting in honeycomb paper with a microporous structure on the surface.

[0048] The honeycomb core of this embodiment can be obtained by bonding multiple layers of the above-mentioned honeycomb paper together.

[0049] Example 3:

[0050] A honeycomb paper with a microporous structure on the surface includes a base paper and a surface paper disposed on the surface of the base paper. It is composed of two layers of surface paper and an intermediate layer of base paper. The weight percentage of the base paper is 62% and the weight percentage of the surface paper is 38%.

[0051] The surface paper is composed of nano-meta-aramid fibers, nano-cellulose fibers, and polylactic acid nanospheres. The nano-meta-aramid fibers have a diameter of 10-80 nm and an aspect ratio of 1000-5000. The nano-cellulose fibers have a diameter of 20-100 nm and an aspect ratio of 30-600. The polylactic acid nanospheres have a particle size of 80-120 nm.

[0052] The base paper is composed of meta-aramid precipitated fibers and chopped carbon fibers. The length of the meta-aramid precipitated fibers is 0.8 mm. The length of the chopped carbon fibers is 5 mm.

[0053] The method for preparing the above-mentioned honeycomb paper with a microporous surface includes the following steps:

[0054] 0.402 g of oven-dry meta-aramid fiber, 0.100 g of nano-cellulose fiber, and 0.010 g of polylactic acid nanospheres were dissolved, dispersed, and mixed with 2 L of water to obtain mixed slurry A. Mixed slurry A was formed on a Kaiser rapid paper forming machine, filtered through a PET filter membrane, and dried to obtain a sheet with an area of ​​0.0314 m². 2 The quantitative value is 16g / m 2 The base paper of the surface layer contains a pore-forming agent.

[0055] 1.143 g of oven-dry meta-aramid precipitated fiber and 0.490 g of chopped carbon fiber were added to 2 L of water, then dissolved, dispersed, and mixed to obtain mixed slurry B. Mixed slurry B was formed on a Kaiser rapid paper forming machine, and after drying, the prepared area was 0.0314 m². 2 The quantitative value is 52g / m 2 The base paper of the base paper.

[0056] The base paper is stacked according to the structure of surface paper-base paper-surface paper, and composite honeycomb paper is prepared by hot pressing using a flatbed hot press and hot calendering is achieved.

[0057] The hot-pressed composite honeycomb paper was immersed in chloroform solution for 30 minutes to remove polylactic acid nanospheres, resulting in honeycomb paper with a microporous structure on the surface.

[0058] The honeycomb core of this embodiment can be obtained by bonding multiple layers of the above-mentioned honeycomb paper together.

[0059] Example 4:

[0060] A honeycomb paper with a microporous structure on the surface includes a base paper and a surface paper disposed on the surface of the base paper. It is composed of two layers of surface paper and an intermediate layer of base paper. The weight percentage of the base paper is 62% and the weight percentage of the surface paper is 38%.

[0061] The surface paper is composed of nano-meta-aramid fibers, chopped polyimide fibers, and polystyrene nanospheres. The nano-meta-aramid fibers have a diameter of 10-80 nm and an aspect ratio of 1000-5000. The chopped polyimide fibers are 5 mm long. The polystyrene nanospheres have a particle size of 200-500 nm.

[0062] The base paper is composed of meta-aramid precipitated fibers and chopped polyimide fibers. The meta-aramid precipitated fibers are 0.8 mm long. The chopped polyimide fibers are 5 mm long.

[0063] The method for preparing the above-mentioned honeycomb paper with a microporous surface includes the following steps:

[0064] 0.376 g of oven-dry meta-aramid fiber, 0.126 g of chopped polyimide fiber, and 0.010 g of polystyrene nanospheres were dissolved, dispersed, and mixed with 2 L of water to obtain mixed slurry A. Mixed slurry A was formed on a Kaiser rapid paper forming machine, filtered through a PET filter membrane, and dried to obtain a sheet with an area of ​​0.0314 m². 2 The quantitative value is 16g / m 2 The base paper of the surface layer contains a pore-forming agent.

[0065] 0.816 g of oven-dry meta-aramid precipitated fiber and 0.816 g of chopped polyimide fiber were added to 2 L of water, then dissolved, dispersed, and mixed to obtain mixed slurry B. Mixed slurry B was formed on a Kaiser rapid paper forming machine, and after drying, the prepared area was 0.0314 m². 2 The quantitative value is 52g / m 2 The base paper of the base paper.

[0066] The base paper is stacked according to the structure of surface paper-base paper-surface paper, and composite honeycomb paper is prepared by hot pressing using a flatbed hot press and hot calendering is achieved.

[0067] The hot-pressed composite honeycomb paper was immersed in dimethylformamide solution for 30 minutes to dissolve and remove the polystyrene nanospheres, resulting in honeycomb paper with a microporous structure on the surface.

[0068] The honeycomb core of this embodiment can be obtained by bonding multiple layers of the above-mentioned honeycomb paper together.

[0069] Example 5:

[0070] A honeycomb paper with a microporous structure on the surface includes a base paper and a surface paper disposed on the surface of the base paper. It is composed of two layers of surface paper and an intermediate layer of base paper. The weight percentage of the base paper is 62% and the weight percentage of the surface paper is 38%.

[0071] The surface paper is made of nano-meta-aramid fibers, chopped meta-aramid fibers, and polystyrene nanospheres. The nano-meta-aramid fibers have a diameter of 10-80 nm and an aspect ratio of 1000-5000. The chopped meta-aramid fibers are 5 mm long. The polystyrene nanospheres have a particle size of 50-100 nm.

[0072] The base paper is composed of meta-aramid precipitated fibers and meta-aramid chopped fibers. The length of the meta-aramid precipitated fibers is 0.8 mm. The length of the meta-aramid chopped fibers is 5 mm.

[0073] The method for preparing the above-mentioned honeycomb paper with a microporous surface includes the following steps:

[0074] 0.251 g of oven-dry meta-aramid fiber, 0.251 g of chopped meta-aramid fiber, and 0.025 g of polystyrene nanospheres were dissolved, dispersed, and mixed with 2 L of water to obtain mixed slurry A. Mixed slurry A was formed on a Kaiser rapid paper forming machine, filtered through a PET filter membrane, and dried to obtain a sheet with an area of ​​0.0314 m². 2 The quantitative value is 16g / m 2 The base paper of the surface layer contains a pore-forming agent.

[0075] 0.816 g of oven-dry meta-aramid precipitated fiber and 0.816 g of meta-aramid chopped fiber were added to 2 L of water, then dissolved, dispersed, and mixed to obtain mixed slurry B. Mixed slurry B was formed on a Kaiser rapid paper forming machine, and after drying, the prepared area was 0.0314 m². 2 The quantitative value is 52g / m 2 The base paper of the base paper.

[0076] The base paper is stacked according to the structure of surface paper-base paper-surface paper, and composite honeycomb paper is prepared by hot pressing using a flatbed hot press and hot calendering is achieved.

[0077] The hot-pressed composite honeycomb paper was immersed in dimethylformamide solution for 30 minutes to dissolve and remove the polystyrene nanospheres, resulting in honeycomb paper with a microporous structure on the surface.

[0078] The honeycomb core of this embodiment can be obtained by bonding multiple layers of the above-mentioned honeycomb paper together.

[0079] Comparative Example 1:

[0080] A type of honeycomb paper is composed of two layers of surface paper and a middle layer of base paper, with the base paper accounting for 62% by weight and the surface paper accounting for 38% by weight.

[0081] The surface paper is composed of nano-meta-aramid fibers and chopped meta-aramid fibers. The nano-meta-aramid fibers have a diameter of 10-80 nm and an aspect ratio of 1000-5000. The chopped meta-aramid fibers have a length of 5 mm.

[0082] The base paper is composed of meta-aramid precipitated fibers and meta-aramid chopped fibers. The length of the meta-aramid precipitated fibers is 0.8 mm. The length of the meta-aramid chopped fibers is 5 mm.

[0083] The above-mentioned method for preparing honeycomb paper includes the following steps:

[0084] 0.251g of oven-dry meta-aramid fiber and 0.251g of chopped meta-aramid fiber were dissolved, dispersed, and mixed with 2L of water to obtain mixed slurry A. Mixed slurry A was formed on a Kaiser rapid paper forming machine, filtered and shaped using a PET filter membrane, and dried to obtain a sheet with an area of ​​0.0314m². 2 The quantitative value is 16g / m 2 The base paper of the surface layer contains a pore-forming agent.

[0085] 0.816 g of oven-dry meta-aramid precipitated fiber and 0.816 g of meta-aramid chopped fiber were added to 2 L of water, then dissolved, dispersed, and mixed to obtain mixed slurry B. Mixed slurry B was formed on a Kaiser rapid paper forming machine, and after drying, the prepared area was 0.0314 m². 2 The quantitative value is 52g / m 2 The base paper of the base paper.

[0086] The base paper is stacked according to the structure of surface paper-base paper-surface paper, and composite honeycomb paper is prepared by hot pressing using a flatbed hot press and hot calendering to obtain honeycomb paper.

[0087] Comparative Example 2:

[0088] A type of honeycomb paper is composed of two layers of surface paper and an intermediate layer of base paper, with the base paper accounting for 52.4% by weight and the surface paper accounting for 47.6% by weight.

[0089] The surface paper is composed of nano-para-aramid fibers and chopped para-aramid fibers. The nano-para-aramid fibers have a diameter of 10-80 nm and an aspect ratio of 1000-5000. The chopped para-aramid fibers have a length of 5 mm.

[0090] The base paper is composed of meta-aramid precipitated fibers and chopped carbon fibers. The meta-aramid precipitated fibers are 0.8 mm long. The chopped carbon fibers are 6 mm long.

[0091] The above-mentioned method for preparing honeycomb paper includes the following steps:

[0092] 0.314g of oven-dry nano-para-aramid fiber and 0.314g of chopped para-aramid fiber were added to 2L of water and then dissolved to obtain mixed slurry A. Mixed slurry A was formed on a Kaiser rapid paper forming machine and filtered through a PET membrane to obtain a sheet with an area of ​​0.0314m². 2 The quantitative value is 20g / m 2 The base paper of the surface layer contains a pore-forming agent.

[0093] Mixed slurry B was prepared by adding 0.829 g of oven-dry meta-aramid precipitated fiber and 0.553 g of chopped carbon fiber to 2 L of water and then dissolving the mixture. Mixed slurry B was then formed on a Kaiser rapid paper forming machine, and after drying, the prepared area was 0.0314 m². 2 The quantitative value is 44g / m 2 The base paper of the base paper.

[0094] The base paper is stacked according to the structure of surface paper-base paper-surface paper, and composite honeycomb paper is prepared by hot pressing and then hot calendering to obtain honeycomb paper.

[0095] Comparative Example 3:

[0096] A honeycomb paper with a microporous structure on the surface includes a base paper and a surface paper disposed on the surface of the base paper. It is composed of two layers of surface paper and an intermediate layer of base paper. The weight percentage of the base paper is 62% and the weight percentage of the surface paper is 38%.

[0097] The surface paper is made of nano-meta-aramid fibers, chopped meta-aramid fibers, and polystyrene nanospheres. The nano-meta-aramid fibers have a diameter of 10-80 nm and an aspect ratio of 1000-5000. The chopped meta-aramid fibers are 5 mm long. The polystyrene nanospheres have a particle size of 50-100 nm.

[0098] The base paper is composed of meta-aramid precipitated fibers and meta-aramid chopped fibers. The length of the meta-aramid precipitated fibers is 0.8 mm. The length of the meta-aramid chopped fibers is 5 mm.

[0099] The method for preparing the above-mentioned honeycomb paper with a microporous surface includes the following steps:

[0100] 0.251 g of oven-dry meta-aramid fiber, 0.251 g of chopped meta-aramid fiber, and 0.05 g of polystyrene nanospheres were dissolved, dispersed, and mixed with 2 L of water to obtain mixed slurry A. Mixed slurry A was formed on a Kaiser rapid paper forming machine, filtered through a PET filter membrane, and dried to obtain a sheet with an area of ​​0.0314 m². 2 The quantitative value is 16g / m 2 The base paper of the surface layer contains a pore-forming agent.

[0101] 0.816 g of oven-dry meta-aramid precipitated fiber and 0.816 g of meta-aramid chopped fiber were added to 2 L of water, then dissolved, dispersed, and mixed to obtain mixed slurry B. Mixed slurry B was formed on a Kaiser rapid paper forming machine, and after drying, the prepared area was 0.0314 m2, and the basis weight was 52 g / m2. 2 The base paper of the base paper.

[0102] The base paper is stacked according to the structure of surface paper-base paper-surface paper, and composite honeycomb paper is prepared by hot pressing using a flatbed hot press and hot calendering is achieved.

[0103] The hot-pressed composite honeycomb paper was immersed in dimethylformamide solution for 30 minutes to dissolve and remove the polystyrene nanospheres, resulting in honeycomb paper with a microporous structure on the surface.

[0104] Comparative Example 4:

[0105] A honeycomb paper with a microporous structure on the surface includes a base paper and a surface paper disposed on the surface of the base paper. It is composed of two layers of surface paper and an intermediate layer of base paper. The weight percentage of the base paper is 62% and the weight percentage of the surface paper is 38%.

[0106] The surface paper is made of nano-meta-aramid fibers, chopped meta-aramid fibers, and polystyrene nanospheres. The nano-meta-aramid fibers have a diameter of 10-80 nm and an aspect ratio of 1000-5000. The chopped meta-aramid fibers are 5 mm long. The polystyrene nanospheres have a particle size of 500-800 nm.

[0107] The base paper is composed of meta-aramid precipitated fibers and meta-aramid chopped fibers. The length of the meta-aramid precipitated fibers is 0.8 mm. The length of the meta-aramid chopped fibers is 5 mm.

[0108] The method for preparing the above-mentioned honeycomb paper with a microporous surface includes the following steps:

[0109] 0.251 g of oven-dry meta-aramid fiber, 0.251 g of chopped meta-aramid fiber, and 0.035 g of polystyrene nanospheres were dissolved, dispersed, and mixed with 2 L of water to obtain mixed slurry A. Mixed slurry A was formed on a Kaiser rapid paper forming machine, filtered through a PET filter membrane, and dried to obtain a sheet with an area of ​​0.0314 m². 2 The quantitative value is 16g / m 2 The base paper of the surface layer contains a pore-forming agent.

[0110] 0.816 g of oven-dry meta-aramid precipitated fiber and 0.816 g of meta-aramid chopped fiber were added to 2 L of water, then dissolved, dispersed, and mixed to obtain mixed slurry B. Mixed slurry B was formed on a Kaiser rapid paper forming machine, and after drying, the prepared area was 0.0314 m². 2 The quantitative value is 52g / m 2 The base paper of the base paper.

[0111] The base paper is stacked according to the structure of surface paper-base paper-surface paper, and composite honeycomb paper is prepared by hot pressing using a flatbed hot press and hot calendering is achieved.

[0112] The hot-pressed composite honeycomb paper was immersed in dimethylformamide solution for 30 minutes to dissolve and remove the polystyrene nanospheres, resulting in honeycomb paper with a microporous structure on the surface.

[0113] The mechanical strength, joint strength, and pore structure of the paper samples in the examples and comparative examples were tested in accordance with GB / T 12914-2018 "Determination of tensile strength of paper and paperboard", JC / T 781-2006 "Test method for separation strength of honeycomb core adhesive strips" and ASTM F-316-03 "Standard test method for determining the pore size characteristics of membrane filters by bubble point and average flow rate orifice test". The test results are shown in Table 1 below.

[0114] Table 1: Performance test data of paper samples from the examples and comparative examples

[0115]

Claims

1. A method for producing a honeycomb paper having a micro-porous structure on a surface, characterized by, The preparation method comprises the following steps: (1) respectively adding water to the fiber raw material of the surface layer paper and the pore-forming aid to perform defibration, dispersion and mixing to obtain mixed slurry A, and the mixed slurry A is formed on a paper sheet former and filtered by a PET filter film to form a mixed slurry A, and the mixed slurry A is dried to obtain the surface layer paper raw paper mixed with the pore-forming aid; (2) adding water to the fiber raw material of the base layer paper to perform defibration, dispersion and mixing to obtain mixed slurry B, and the mixed slurry B is formed on a paper sheet former to form a mixed slurry B, and the mixed slurry B is dried to obtain the base layer paper raw paper; (3) stacking the raw papers according to the structure of surface layer paper-base layer paper-surface layer paper, and using a hot press to prepare the composite honeycomb paper by hot pressing and to realize hot calendering; (4) removing the pore-forming aid by dissolution to obtain the honeycomb paper with a micro-porous structure on the surface layer; The average pore diameter of the micro-porous structure of the surface layer paper is 50-500 nm, and the porosity is 55-78%; The pore-forming aid is one of polystyrene nano microspheres and polylactic acid nano microspheres; The diameter of the pore-forming aid is 20-500 nm, and the addition amount of the pore-forming aid is 1-5% of the mass of the surface layer paper.

2. The production method according to claim 1, characterized by, The weight percentage of the base layer paper is 50-80%, and the weight percentage of the surface layer paper is 20-50%.

3. The production method according to claim 1, characterized by, The base layer paper is composed of meta-aramid fibrids and chopped fibers, and the chopped fibers are one of meta-aramid chopped fibers, chopped carbon fibers and chopped polyimide fibers.

4. The method of claim 1, wherein, The fiber raw material of the surface layer paper is composed of nano meta-aramid fibers and meta-aramid chopped fibers; or the fiber raw material of the surface layer paper is composed of nano para-aramid fibers and para-aramid chopped fibers; or the fiber raw material of the surface layer paper is composed of nano meta-aramid fibers and nano cellulose fibers; or the fiber raw material of the surface layer paper is composed of nano meta-aramid fibers and chopped polyimide fibers.

5. The honeycomb paper with a micro-porous structure on the surface layer prepared by the preparation method in any one of claims 1-4.

6. A honeycomb core characterized by, The honeycomb paper with a micro-porous structure on the surface layer prepared by the preparation method in any one of claims 1-4 is glued to obtain a multi-layer product, or the honeycomb paper with a micro-porous structure on the surface layer in claim 5 is glued to obtain a multi-layer product.

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