A heat-conducting paper and a method for manufacturing the same

Abstract

The present application relates to a kind of heat-conducting paper and its preparation method, belong to paper-based functional material field.The purpose of the present application is to overcome the shortcomings and deficiencies of prior art, provide a kind of heat-conducting paper with excellent heat-conducting performance and mechanical performance.The technical scheme of the present application is: first, wet-laid nanocellulose reinforced aramid paper is made, then carbon nanotubes are attached to aramid paper by impregnation method, and finally polyvinyl alcohol is impregnated on the surface of aramid paper to enhance the stability of heat-conducting paper.The advantages and effects of the present application are: the heat-conducting paper prepared by the present application has good heat-conducting effect, and has the characteristics of high strength and high toughness, and has broad application prospect.

Description

TECHNICAL FIELD

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

[0002] The heat-conducting paper is a paper-based material with high heat-conducting performance, mainly used for heat management of electronic products. The preparation methods of the heat-conducting paper mainly include wet papermaking, coating, filtration, layer-by-layer self-assembly by impregnation, evaporation-induced self-assembly, and aerogel infusion, etc. The heat-conducting performance of the paper can be improved by adding heat-conducting fillers in the paper or film. The heat-conducting paper is a paper-based material with high heat-conducting performance, mainly used for heat management of electronic products. The heat-conducting paper has the advantages of light weight, flexibility, cuttable, degradable, etc., and is suitable for flexible electronic devices, thin and light electronic equipment, batteries, etc., to help solve the heat dissipation problem. Compared with the cellulose-based heat-conducting paper, the aramid heat-conducting paper has higher ductility and toughness, and better thermal stability, and is suitable for application in the fields of motors, transformers, and capacitors as a flexible heat-conducting material.

[0003] In the prior art, in order to improve the heat-conducting performance of the paper, various heat-conducting fillers are often used to fill the pores of the paper, so as to achieve the effect of controlling the heat-conducting performance of the paper. For example, Chinese patent (201611080850.2) discloses a preparation method of a high-heat-conducting carbon nanotube modified carbon fiber reinforced paper-based friction material, which uses carbon nanotubes, aramid pulp and other materials to make a paper-based friction material with high heat-conducting and high wear-resisting performance. However, the method is complex and difficult to mass-produce. Chinese patent (202310507297.X) discloses a composite aramid paper and a preparation method, which adds a heat-conducting layer in two layers of aramid paper to improve the heat-conducting performance of the paper under the premise of ensuring the insulation performance. However, the method also has the problems of complex process and poor combination stability of the multi-layer aramid paper. SUMMARY

[0004] The primary purpose of the present application is to overcome the shortcomings and deficiencies of the prior art, and to provide a preparation method of a heat-conducting paper.

[0005] Another purpose of the present application is to provide a heat-conducting 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 heat-conducting paper, comprising the following steps:

[0008] (1) Preparation of dispersion liquid

[0009] The aramid short-cut fibers and the dispersant are added to the defibrator for defibration to obtain a dispersion liquid 1; the aramid fibrids and the nanocellulose are added to the defibrator for defibration to obtain a dispersion liquid 2; the two kinds of dispersion liquids are mixed to obtain a dispersion liquid 3;

[0010] (2) Preparation of paper sheet

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

[0012] (3) Impregnation and drying of paper sheet

[0013] Carbon nanotubes are added into a sodium dodecyl sulfate solution and stirred uniformly to prepare a carbon nanotube impregnating solution for impregnation; the aramid paper prepared in step (2) is impregnated in the carbon nanotube impregnating solution and then taken out and dried to obtain an aramid heat-conducting paper without heat pressing; this step can be repeated multiple times;

[0014] (4) Heat pressing treatment

[0015] The aramid heat-conducting paper without heat pressing obtained in step (3) is subjected to heat pressing treatment;

[0016] (5) Impregnation of polyvinyl alcohol impregnating solution

[0017] The aramid paper subjected to heat pressing treatment in step (4) is impregnated in a polyvinyl alcohol solution and then taken out and dried to obtain an aramid heat-conducting paper.

[0018] The addition ratio (based on the absolute dry mass) of aramid short-cut fibers, aramid fibrids and nanocellulose in step (1) is 49:49:2.

[0019] The dispersant in step (1) is polyethylene oxide (PEO), and the addition amount of polyethylene oxide is 0.2% of the absolute dry mass of aramid short-cut fibers.

[0020] The polyethylene oxide is prepared into a polyethylene oxide aqueous solution with a mass fraction of 0.05% before use.

[0021] The defibrillation condition adopted in step (1) is 8000-10000 revolutions.

[0022] The length of aramid short-cut fibers adopted in step (1) is 5-7 mm; the nanocellulose can be prepared by mechanical method, chemical method or biological method, and is preferably nanocellulose prepared by mechanical method.

[0023] The temperature of the heat and reduced pressure drying in step (2) is 88-92℃, the vacuum degree is -1.0 bar, and the drying time is 8-12 min.

[0024] The mass fraction of the sodium dodecyl sulfate solution in step (3) is 1%.

[0025] The mass fraction of carbon nanotubes in the carbon nanotube impregnating solution in step (3) is 5%.

[0026] The stirring condition in step (3) is 500 rpm for 3 min.

[0027] The impregnation condition in step (3) is 5 min, and the drying condition is 105 DEG C for 10 min.

[0028] The drying temperature in step (3) is 88-92 DEG C, the vacuum degree is -1.0 bar, and the drying time is 8-12 min.

[0029] The hot-pressing temperature in step (4) is 230-265 DEG C, the hot-pressing pressure is 4-6 MPa, and the hot-pressing time is 4-6 min.

[0030] The mass fraction of the polyvinyl alcohol solution in step (5) is 5-8%.

[0031] The impregnation time in step (5) is 5-10 s, and the drying condition is 105 DEG C for 10 min.

[0032] The heat-conducting paper prepared by the application 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.

[0033] The application has the following advantages and effects relative to the prior art:

[0034] (1) The nanocellulose prepared by the mechanical method is added to aramid paper, and the nanocellulose, as a nanofiber material, has the characteristics of large specific surface area, high porosity, considerable mechanical strength, and high surface activity, which is beneficial to the formation of hydrogen bonds between aramid fibers and the enhancement of the bonding strength between the aramid fibers. When the aramid paper is subjected to external force, the paper deforms, and the hydrogen bonds are continuously broken and recombined, which can disperse the stress received by the paper and enhance the toughness of the paper. Under the reinforcement of the nanocellulose, the aramid paper has stronger mechanical properties.

[0035] (2) The application uses the multi-walled carbon nanotubes that have been industrially produced, which are attached to the aramid paper by impregnation. The amount of the attached carbon nanotubes can be adjusted by adjusting the concentration of the impregnation liquid, the impregnation times, and other factors, so that papers with different carbon nanotube contents are prepared.

[0036] (3) The application uses SDS to prepare a carbon nanotube (CNT) impregnation liquid. The hydrophobic end of SDS can interact with CNT, and the hydrophilic end can enhance the hydrophilicity of CNT, thereby inhibiting the flocculation of CNT. The micelles formed by CNT and SDS overcome the van der Waals force between CNT through electrostatic repulsion and resistance, so that a stable CNT impregnation liquid can be formed.

[0037] (4) The polyvinyl alcohol impregnated carbon nanotube impregnating solution is used to impregnate aramid paper, so that the adhesion of carbon nanotubes in the paper is more stable, the powder dropping phenomenon of the paper is reduced, and the stability of the paper is enhanced.

[0038] (5) The aramid heat-conducting paper prepared by the application has good heat-conducting performance and mechanical properties.

[0039] (6) The application is simple to operate and suitable for large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 The preparation flow chart of the heat-conducting paper of the application is shown.

[0041] Figure 2 The SEM picture of the multi-walled carbon nanotube used in the application is shown. DETAILED DESCRIPTION

[0042] In order to make the features and effects of the application clear to those skilled in the art, 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 general understanding of the application by those skilled in the art, and if there is any inconsistency, the definition herein shall prevail.

[0043] In this text, all possible combinations of technical features in various embodiments or examples are not written out for the sake of brevity. Therefore, any technical feature in various embodiments or examples can be combined at will as long as there is no conflict between the technical features, and these combinations should be considered as the scope contained herein.

[0044] Next, the application will be further illustrated by specific examples. Please note that these examples are only for the purpose of illustrating the application and do not limit the scope of the application. In addition, please note that those skilled in the art can make various modifications or changes to the application after reading this text, and these modifications or changes should also belong to the scope defined by the claims of this application.

[0045] The following examples use the instruments and equipment commonly used in the art. In the following examples, if not specifically stated, the experimental methods are carried out according to the conventional conditions or the recommended conditions of the manufacturer. The various raw materials used in the following examples are common commercially available products, and the specifications are commonly used in the art. In this text and the following examples, unless otherwise specified, "%" means weight percent, and the fiber mass is the absolute dry mass.

[0046] The nanocellulose used in the examples and comparative examples is mechanically prepared nanocellulose, and the aramid chopped fiber length used is 5-7mm.

[0047] Example 1

[0048] A method for preparing a heat-conductive paper, comprising the following steps:

[0049] Step 1: 3.768 g of polyethylene oxide aqueous solution (0.05 wt%) and 0.9232 g of aramid short-cut fibers are defibered in a defiberer at room temperature to obtain dispersion 1; 0.9232 g of aramid precipitated fiber and 0.0377 g of nanocellulose are defibered in a defiberer at room temperature to obtain dispersion 2. The two are mixed to obtain dispersion 3.

[0050] Step 2: The dispersion 3 obtained in step 1 is added to a sheet former, and dehydrated to obtain a wet paper sheet; the wet paper sheet is dried under reduced pressure for 10 min (temperature is 90°C, vacuum degree is -1.0 bar) to obtain a dry paper sheet with a basis weight of 60 g / m 2 , and cut into 4 cm x 4 cm paper sheets for standby.

[0051] Step 3: 12.5 g of multi-walled carbon nanotubes and 2.5 g of sodium dodecyl sulfate are weighed, the sodium dodecyl sulfate is first dissolved in water, the carbon nanotubes are mixed into the solution after the sodium dodecyl sulfate is fully dissolved, and a magnetic stirrer is used for stirring to prepare an impregnation solution of 250 ml of carbon nanotubes for impregnation.

[0052] Step 4: The 4 cm x 4 cm aramid paper sample obtained in step 2 is impregnated with the impregnation solution prepared in step 3, and dried in an oven at 105°C for 10 min.

[0053] Step 5: The dry paper sheet obtained in step 4 is subjected to hot pressing treatment at a temperature of 265°C and a pressure of 5 MPa for 5 min.

[0054] Step 6: 5 g of polyvinyl alcohol is dissolved in 45 g of deionized water, heated to 50°C and stirred for 30 min until the solid disappears to prepare a polyvinyl alcohol impregnation solution.

[0055] Step 7: The aramid paper after hot pressing treatment in step 5 is impregnated in the polyvinyl alcohol solution for 10 s, taken out and placed in an oven for drying, and dried in an oven at 105°C for 5 min to obtain a heat-conductive paper.

[0056] Example 2

[0057] A method for preparing a heat-conductive paper, comprising the following steps:

[0058] Steps 1-3: Same as Example 1.

[0059] Step 4: The 4 cm x 4 cm aramid paper sample obtained in step 2 is impregnated with the impregnation solution prepared in step 3, and dried in an oven at 105°C for 10 min, and this is repeated twice.

[0060] Steps 5-7: Same as Example 1.

[0061] Example 3

[0062] A method for preparing a heat-conductive paper, comprising the following steps:

[0063] Steps 1-3: same as Example 1.

[0064] Step 4: the 4 cm x 4 cm aramid paper sample obtained in Step 2 was impregnated with the impregnating solution prepared in Step 3, and dried in an oven at 105°C for 10 min, and this was repeated 3 times.

[0065] Steps 5-7: same as Example 1.

[0066] Example 4

[0067] A method for preparing a heat-conductive paper, comprising the following steps:

[0068] Steps 1-3: same as Example 1.

[0069] Step 4: the 4 cm x 4 cm aramid paper sample obtained in Step 2 was impregnated with the impregnating solution prepared in Step 3, and dried in an oven at 105°C for 10 min, and this was repeated 4 times.

[0070] Steps 5-7: same as Example 1.

[0071] Example 5

[0072] A method for preparing a heat-conductive paper, comprising the following steps:

[0073] Steps 1-3: same as Example 1.

[0074] Step 4: the 4 cm x 4 cm aramid paper sample obtained in Step 2 was impregnated with the impregnating solution prepared in Step 3, and dried in an oven at 105°C for 10 min, and this was repeated 5 times.

[0075] Steps 5-7: same as Example 1.

[0076] For the convenience of comparison, the mass changes (unit: g) of the aramid paper prepared in Examples 1-5 after impregnation with the carbon nanotube impregnating solution and drying are listed in the form of a table, as shown in Table 1. As can be seen from the table, the mass increment of the carbon nanotubes gradually increases and then stabilizes with each impregnation. The reason is that carbon nanotubes are prone to agglomeration, and as the number of impregnations increases, the amount of carbon nanotubes attached to the surface of the paper increases, exposing more binding sites, thereby allowing more carbon nanotubes to be attached.

[0077] Table 1

[0078]

[0079]

[0080] Examples 6-8

[0081] A method for preparing a heat conductive paper, comprising the following steps:

[0082] Step 1: same as Example 1.

[0083] Step 2: add the dispersion liquid 3 obtained in Step 1 into a sheet former, and dehydrate to obtain a wet paper sheet; dry the wet paper sheet under reduced pressure for 10 min to obtain a dry paper sheet. 2

[0084] Step 3: same as Example 1.

[0085] Step 4: impregnate the dry paper sheet obtained in Step 2 with the impregnating liquid prepared in Step 3, and dry in an oven at 105°C for 10 min, repeat for 3 times.

[0086] Steps 5-7: same as Example 1.

[0087] Comparative Example 1

[0088] Step 1: at room temperature, disperse 3.768 g of polyethylene oxide aqueous solution (0.05 wt%) and 0.9232 g of aramid short-cut fibers in a defibrator to obtain a dispersion liquid 1; at room temperature, disperse 0.9232 g of aramid fibrid and 0.0377 g of nanocellulose in a defibrator to obtain a dispersion liquid 2. Mix the above two to obtain a dispersion liquid 3.

[0089] Step 2: add the dispersion liquid 3 obtained in Step 1 into a sheet former, and dehydrate to obtain a wet paper sheet; dry the wet paper sheet under reduced pressure for 10 min to obtain a dry paper sheet.

[0090] Step 3: hot-press the dry paper sheet obtained in Step 2 at a temperature of 265°C and a pressure of 5 MPa for 5 min.

[0091] Step 4: dissolve 5 g of polyvinyl alcohol in 45 g of deionized water, heat to 50°C and stir for 30 min until the solid disappears to prepare a polyvinyl alcohol impregnating liquid. Dip the hot-pressed paper in the polyvinyl alcohol solution for 10 s, take it out and dry in an oven, and dry in the oven at 105°C for 5 min to obtain a comparative heat conductive paper.

[0092] The mechanical property indexes and basis weight of the heat conductive papers prepared in Examples 6-8 and Comparative Example 1 are listed in the form of a table. The impregnation operation of the carbon nanotube impregnating liquid and the impregnation operation of the polyvinyl alcohol can increase the basis weight of the paper, as shown in Table 2, the basis weight of the paper is greatly increased compared with Comparative Example 1. The tensile strength index and tear strength index are lower than those of Comparative Example 1, but still maintain a relatively high strength.

[0093] Table 2 ​

[0094]

[0095]

[0096] Note: Quantitative GB / T451.3-2002; tensile strength and elongation GB / T12914-2008; tear degree GB / TN12914-2002.

[0097] The thermal conductivity of the heat-conductive paper prepared in Example 5 is 0.425 W / (m·K).

[0098] Comparative Example 2

[0099] Step 1: Same as Example 1.

[0100] Step 2: The dispersion solution 3 obtained in Step 1 was added to a sheet former, and dehydrated to obtain a wet paper sheet; the wet paper sheet was dried under reduced pressure for 10 min to obtain a dry paper sheet.

[0101] Step 3-4: Same as Example 1.

[0102] Step 5: The dry paper sheet obtained in Step 5 was subjected to hot-pressing treatment to obtain a comparative heat-conductive paper, at a temperature of 265°C and a pressure of 5 MPa for 5 min.

[0103] The surface of the heat-conductive paper prepared in Comparative Example 2 and Example 1 was wiped by hand, and the heat-conductive paper prepared in Comparative Example 2 had obvious powder dropping phenomenon, while the heat-conductive paper prepared in Example 1 did not have obvious powder dropping phenomenon, because the impregnated polyvinyl alcohol formed a thin film on the surface of the heat-conductive paper, which prevented powder dropping.

[0104] 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, simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, and are all included in the protection scope of the present application.

Claims

1. A method for preparing thermally conductive paper, characterized in that, Includes the following steps: (1) Add aramid short-cut fibers and dispersant to a disintegration machine to disintegrate and obtain dispersion 1; disintegrate aramid precipitated fibers and nanocellulose in a disintegration machine to obtain dispersion 2; mix the two dispersions to obtain dispersion 3; (2) The dispersion 3 obtained in step (1) is dehydrated and formed into a wet paper sheet. The wet paper sheet is heated and dried under reduced pressure to obtain aramid paper. (3) Add carbon nanotubes to sodium dodecyl sulfate solution and stir evenly to prepare carbon nanotube impregnation solution for impregnation; after impregnating the aramid paper obtained in step (2) in carbon nanotube impregnation solution, take it out and dry it to obtain aramid thermal conductive paper without hot pressing. (4) The aramid thermally conductive paper obtained in step (3) without hot pressing is subjected to hot pressing treatment; (5) After the aramid paper is hot-pressed in step (4), it is immersed in a polyvinyl alcohol solution and then taken out and dried to obtain aramid thermal conductive paper.

2. The method according to claim 1, characterized in that, In step (1), the addition ratio of aramid chopped fiber, aramid precipitated fiber and nanocellulose is 49:49:2, based on oven-dry weight.

3. 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; The aramid short-cut fibers used in step (1) have a length of 5-7 mm; the nanocellulose is prepared by mechanical, chemical or biological methods.

4. The method according to claim 1, characterized in that, The drying temperature in step (2) is 88-92°C, the vacuum degree is -1.0 bar, and the drying time is 8-12 min.

5. The method according to claim 1, characterized in that, The sodium dodecyl sulfate solution in step (3) has a mass fraction of 1%. The carbon nanotubes in the carbon nanotube impregnation solution described in step (3) have a mass fraction of 5%. The stirring conditions described in step (3) are 500 rpm and 3 min; The immersion conditions in step (3) are 5 minutes, and the drying conditions are 105°C for 10 minutes.

6. The method according to claim 1, characterized in that, The impregnation process described in step (3) is repeated more than once.

7. The method according to claim 1, characterized in that, The hot pressing treatment in step (4) is performed at a temperature of 230-265°C, a pressure of 4-6 MPa, and a time of 4-6 min.

8. The method according to claim 1, characterized in that, The mass fraction of the polyvinyl alcohol solution in step (5) is 5-8%; The soaking time in step (5) is 5 to 10 seconds, and the drying conditions are 105°C for 10 minutes.

9. A thermally conductive paper prepared by the method described in any one of claims 1 to 8.

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