High-strength heat-dissipating paper-based material and preparation method thereof

Abstract

The present application relates to aromatic polyamide material, specifically relates to a kind of high-strength heat-dissipating paper-based material and its preparation method.The technical scheme of the present application is: aramid short fiber, aramid fibrid, nanocellulose, graphene and cellulose acetate are respectively defibrillated, then mixed into dispersion, by wet papermaking, drying and hot-pressing treatment, high-strength heat-dissipating paper is prepared.The present application adds cellulose acetate as the filling material of paper, under hot-pressing condition, cellulose acetate in paper melts, aramid short fiber in paper is bonded together, thereby forming a relatively stable structure, achieving the purpose of reinforcing the mechanical properties of aramid paper.Meanwhile, the addition of cellulose acetate also increases the roughness of paper fiber surface, thereby improving the retention rate of graphene.Therefore, the high-strength heat-dissipating paper prepared by the present application has the characteristics of high thermal conductivity, high strength, high toughness, etc., and has broad application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to an aromatic polyamide material, in particular to a high-strength heat-dissipating paper-based material and a preparation method thereof. BACKGROUND

[0002] Aramid fiber is a high-performance synthetic fiber with high strength, high modulus, high temperature resistance, wear resistance, flame resistance, and good dimensional stability, and is one of the world's recognized three high-performance fibers. Aramid paper is a special paper-based material made of aramid short fibers and aramid fibrids as the main raw materials, using wet forming technology, with the characteristics of easy processing, folding resistance, tear resistance, etc. Compared with common cellulose-based heat-conducting paper and carbon-based heat-conducting paper, aramid paper has higher mechanical properties and insulation properties, and is suitable for use as a flexible heat-conducting material in electrical equipment. During the use of these electrical equipment, a large amount of heat will be generated, and if the heat cannot be dissipated in time, it will affect the working efficiency and service life of the electrical equipment, and in severe cases, it may even pose a fire risk. However, the low thermal conductivity coefficient (0.13 W / mK) of aramid fiber makes the thermal conductivity of aramid paper unsatisfactory, making it difficult to meet the requirements of high-performance heat-conducting materials.

[0003] In the prior art, in order to improve the thermal conductivity of aramid paper, one feasible method is to dope nanomaterials with high thermal conductivity into aramid paper to form a nanocomposite heat-conducting paper. For example, Chinese patent (202211329652.0) discloses a heat-conducting insulating paper and a preparation method thereof, which uses two methods of filling and coating to control the content of boron nitride in the heat-conducting aramid paper, thereby increasing the insulation performance of the material by 4 times while ensuring the insulation performance. However, the production process and technology of the aramid paper are relatively complex and not suitable for large-scale production; Chinese patent (202310317355.2) discloses an industrial aramid paper with heat conduction and insulation and a preparation method thereof, which uses a modified micron diamond-boron nitride nanosheet hybrid structure heat-conducting filler to prepare an industrial aramid paper with heat conduction and insulation. The preparation process is simple and suitable for large-scale production, but the high cost of nanodiamonds makes the cost of this type of aramid heat-conducting paper high, making it difficult to be widely applied. SUMMARY

[0004] The primary purpose of the present application is to overcome the shortcomings and deficiencies of the prior art and provide a preparation method of a high-strength heat-dissipating paper-based material.

[0005] Another purpose of the present application is to provide a high-strength heat-dissipating paper prepared by the above method.

[0006] The purpose of the present application is achieved by the following technical solutions:

[0007] A preparation method of a high-strength heat-dissipating paper-based material, comprising the following steps:

[0008] (1) Preparation of dispersion liquid

[0009] The aramid short-cut fibers and the dispersant are added into a defibrator to perform defibration, to obtain a dispersion liquid 1; the aramid spunlaid fibers, the nanocellulose, the graphene and the cellulose acetate are added into a defibrator to perform defibration, to obtain a dispersion liquid 2; the dispersion liquid 1 and the dispersion liquid 2 are mixed to obtain a dispersion liquid 3;

[0010] (2) Preparation of paper sheet

[0011] The dispersion liquid 3 obtained in step (1) is dehydrated and formed into a wet paper sheet, and the wet paper sheet is heated and dried under reduced pressure to obtain an aramid paper.

[0012] (3) Heat pressing treatment

[0013] The aramid paper obtained in step (2) is subjected to heat pressing treatment to obtain a high-strength heat-dissipating paper.

[0014] The mass ratio (calculated based on the absolute dry mass) of the graphene, the nanocellulose, the cellulose acetate, the aramid short-cut fibers and the aramid spunlaid fibers in step (1) is 0.5-2.5:2:5:45.25-46.25:45.25-46.25.

[0015] The dispersant in step (1) is polyethylene oxide, and the addition amount of the polyethylene oxide is 0.2% of the absolute dry mass of the aramid short-cut fibers.

[0016] The polyethylene oxide is prepared into a polyethylene oxide aqueous solution with a mass fraction of 0.05% before use.

[0017] The defibration condition adopted in step (1) is 7000-10000 revolutions.

[0018] The length of the aramid short-cut fibers in step (1) is 5-7 mm; the nanocellulose can be prepared by a mechanical method, a chemical method or a biological method, and is preferably nanocellulose prepared by a mechanical method.

[0019] The drying temperature in step (2) is 88-92℃, the vacuum degree is -1.0 bar, and the drying time is 8-12 min.

[0020] The heat pressing treatment temperature in step (3) is 230-265℃, the heat pressing treatment pressure is 4-6 MPa, and the heat pressing treatment time is 4-6 min.

[0021] The high-strength heat-dissipating paper can be applied in the fields of electronics (such as flexible electronic devices, light and thin electronic equipment, batteries, etc.), electric power, military industry, aerospace, etc.

[0022] The present application has the following advantages and effects compared with the prior art:

[0023] (1) The present application adds mechanically prepared nanocellulose to aramid paper. As a nanofiber material, nanocellulose has the characteristics of large specific surface area, high porosity, considerable mechanical strength, and high surface activity, which is conducive to the formation of hydrogen bonds between aramid fibers and enhances the bonding strength between aramid fibers. When the aramid paper is subjected to external force, the paper deforms, and the hydrogen bonds continuously break and recombine, which can disperse the stress on the paper and enhance the toughness of the paper. The addition of nanocellulose can effectively improve the interfacial bonding strength of aramid paper, specifically the improvement of the tensile strength, tear strength and other mechanical properties of aramid paper, so that the paper has high mechanical strength.

[0024] (2) The present application uses mechanically exfoliated graphene which has been industrialized. Due to the characteristics of phonon heat transfer, graphene has high thermal conductivity. The use of powdered graphene to prepare heat-conducting paper can effectively build a heat-conducting network inside the aramid paper, achieving good heat-conducting effect.

[0025] (3) The present application adds cellulose acetate as a filler material for the paper. Under heat pressing conditions, the cellulose acetate in the paper melts and binds the aramid short fibers in the paper together, thereby forming a relatively stable structure to achieve the purpose of reinforcing the mechanical properties of aramid paper.

[0026] (4) The addition of cellulose acetate also increases the roughness of the fiber surface of the paper, thereby improving the retention rate of graphene. The prepared high-strength heat-dissipating paper is relatively stable, and the process is simple and suitable for large-scale production.

[0027] (5) The high-strength heat-dissipating paper prepared by the present application has strong heat conductivity. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The preparation flow chart of the high-strength heat-dissipating paper of the present application. DETAILED DESCRIPTION

[0029] In order for those skilled in the art to clearly understand the features and effects of the present application, some terms and phrases involved in the specification and claims will be briefly explained and defined herein. If not specifically stated, all technical and scientific terms in the text are in accordance with the usual understanding of those skilled in the art of the present application, and if there is any inconsistency, the definition herein shall prevail.

[0030] In order to describe simply, not all possible combinations of technical features in each embodiment or example are written in this paper. Therefore, as long as there is no conflict between technical features, any technical feature in each embodiment or example can be combined at will, and these combinations should be considered as the scope contained herein.

[0031] Next, the present application will be further described by specific examples. Note that these examples are only for illustrating the present application, and do not limit the scope of the present application. In addition, note that those skilled in the art can make various modifications or changes to the present application after reading this text, and these modifications or changes should also belong to the scope defined by the claims of the present application.

[0032] The following examples use apparatus and equipment commonly used in the art. In the following examples, if not specifically mentioned, the experimental methods are carried out according to the conventional conditions or the recommended conditions of the manufacturer. In the following examples, various raw materials used are, unless specifically mentioned, common commercially available products, and the specifications are commonly used specifications in the art. In this text and the following examples, if not specifically mentioned, "%" means weight percent, and the mass of the fiber is the absolute dry mass.

[0033] The nanocellulose used in the examples and comparative examples is mechanically prepared nanocellulose, and the aramid short-cut fiber has a length of 5-7 mm.

[0034] Example 1

[0035] A method for preparing a high-strength heat-dissipating paper-based material, comprising the following steps:

[0036] Step 1: At room temperature, 3.768 g of polyethylene oxide aqueous solution (0.05 wt%) and 0.8714 g of aramid short-cut fiber are added to about 1.5 L of water, and are defibrated in a defibrator to obtain dispersion 1; at room temperature, 0.8714 g of aramid fibrid, 0.0377 g of nanocellulose, 0.0094 g of graphene, and 0.0942 g of cellulose acetate are added to about 1.5 L of water, and are defibrated in a defibrator to obtain dispersion 2. The above dispersions are mixed to prepare dispersion 3.

[0037] Step 2: The dispersion 3 obtained in step 1 is added to a sheet former, and is dehydrated to obtain a wet paper sheet; the wet paper sheet is dried under reduced pressure for 10 min (temperature is 90°C, and vacuum degree is -1.0 bar), to obtain a dry paper sheet with a basis weight of 60 g / m 2

[0038] Step 3: The dry paper sheet obtained in step 2 is hot-pressed at a temperature of 265°C and a pressure of 5 MPa for 5 min to obtain a high-strength heat-dissipating paper-based material.

[0039] Example 2

[0040] A method for preparing a high-strength heat-dissipating paper-based material, comprising the following steps:

[0041] ​Step 1: 3.768 g polyethylene oxide aqueous solution (0.05 wt%) and 0.8619 g aramid short fibers were defibrated in a defibrator at room temperature to obtain dispersion 1; 0.8619 g aramid fibers, 0.0377 g nanocellulose, 0.0283 g graphene and 0.0942 g cellulose acetate were defibrated in a defibrator at room temperature to obtain dispersion 2. The two were mixed to prepare dispersion 3.

[0042] Step 2 and Step 3 are the same as Example 1.

[0043] Example 3

[0044] A method for preparing a high-strength heat-dissipating paper-based material, comprising the following steps:

[0045] Step 1: 3.768 g polyethylene oxide aqueous solution (0.05 wt%) and 0.8619 g aramid short fibers were defibrated in a defibrator at room temperature to obtain dispersion 1; 0.8619 g aramid fibers, 0.0377 g nanocellulose, 0.0283 g graphene and 0.0942 g cellulose acetate were defibrated in a defibrator at room temperature to obtain dispersion 2. The two were mixed to prepare dispersion 3.

[0046] Step 2 and Step 3 are the same as Example 1.

[0047] Example 4

[0048] A method for preparing a high-strength heat-dissipating paper-based material, comprising the following steps:

[0049] Step 1: 3.768 g polyethylene oxide aqueous solution (0.05 wt%) and 0.8619 g aramid short fibers were defibrated in a defibrator at room temperature to obtain dispersion 1; 0.8619 g aramid fibers, 0.0377 g nanocellulose, 0.0283 g graphene and 0.0942 g cellulose acetate were defibrated in a defibrator at room temperature to obtain dispersion 2. The two were mixed to prepare dispersion 3.

[0050] Step 2 and Step 3 are the same as Example 1.

[0051] Example 5

[0052] A method for preparing a high-strength heat-dissipating paper-based material, comprising the following steps:

[0053] Step 1: 3.768 g polyoxyethylene aqueous solution (0.05 wt%) and 0.8525 g aramid short fibers were defibrated in a defibrator at room temperature to obtain dispersion 1; 0.8525 g aramid precipitated fibers, 0.0377 g nanocellulose, 0.0471 g graphene and 0.0942 g cellulose acetate were defibrated in a defibrator at room temperature to obtain dispersion 2. The above two were mixed to prepare dispersion 3.

[0054] Steps 2 and 3 are the same as in Example 1.

[0055] Table 1 is the mechanical property test results of the high-strength heat-dissipating paper-based material prepared in Examples 1-5.

[0056] Table 1

[0057]

[0058] Note: The quantitative analysis was performed according to GB / T451.3-2002; the tensile strength and elongation were performed according to GB / T12914-2008; and the tear strength was performed according to GB / TN12914-2002.

[0059] As can be seen from the above table, with the increase of the amount of graphene, the mechanical properties of the paper show a downward trend, but still maintain a strong mechanical strength.

[0060] The high-strength heat-dissipating paper-based material prepared in Example 5 has a thermal conductivity of 0.183 W / (m·K) after testing.

[0061] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement methods and shall be included in the protection scope of the present application.

Claims

1. A method for preparing a high-strength heat-dissipating paper-based material, characterized in that, Includes the following steps: (1) Add aramid short-cut fibers and dispersant to a dispersing machine for dispersing to obtain dispersion 1; add aramid precipitated fibers, nanocellulose, graphene and cellulose acetate to a dispersing machine for dispersing to obtain dispersion 2; mix dispersion 1 and dispersion 2 to obtain dispersion 3; the mass ratio of graphene, nanocellulose, cellulose acetate, aramid short-cut fibers and aramid precipitated fibers is 0.5~2.5 : 2 : 5 : 45.25~46.25 : 45.25~46.25, based on oven-dry weight; (2) Dehydrate the dispersion 3 and form it into a wet paper sheet. Heat the wet paper sheet and dry it under reduced pressure to obtain aramid paper. (3) The aramid paper is hot-pressed at 230~265℃ to obtain high-strength heat dissipation paper.

2. The method according to claim 1, characterized in that: The dispersant in step (1) is polyethylene oxide, and the amount of polyethylene oxide added is 0.2% of the oven-dry weight of aramid chopped fibers.

3. The method according to claim 1 or 2, characterized in that: The evacuation conditions used in step (1) are 7000~10000 revolutions.

4. The method according to claim 1 or 2, characterized in that: The aramid short-cut fibers used in step (1) have a length of 5-7 mm, and the nanocellulose is nanocellulose obtained by mechanical, chemical or biological methods.

5. The method according to claim 1 or 2, characterized in that: The drying temperature in step (2) is 88~92℃, the vacuum degree is -1.0 bar, and the drying time is 8~12 min.

6. The method according to claim 1 or 2, characterized in that: The pressure of the hot pressing process in step (3) is 4~6 MPa, and the hot pressing time is 4~6 min.

7. A high-strength heat dissipation paper prepared by the method according to any one of claims 1 to 6.

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