Heat-conducting long-carbon-chain nylon and continuous preparation method thereof

Abstract

The invention discloses heat-conducting long-carbon-chain nylon and a continuous preparation method thereof.The heat-conducting long-carbon-chain nylon is prepared from long-carbon-chain nylon salt, graphene nanosheets, maleic anhydride, a catalyst and an antioxidant, the components are added into a continuous production line salt forming tank, and then salt forming, polymerization, shearing, cooling and drying are conducted to obtain the heat-conducting long-carbon-chain nylon. The dispersing agent maleic anhydride and the modified filler graphene nanosheet are added, so that the dispersion effect of the filler and a polymer matrix is enhanced, and the obtained long carbon chain nylon material has better mechanical property and heat-conducting property; secondly, a transverse shearing process is added, the filler is regularly oriented in the shearing direction of a scraper under the strong shearing induction action of the scraper, ordered arrangement of nylon molecular chains is promoted, and the heat-conducting long-carbon-chain nylon material with excellent performance is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of engineering plastics, and in particular relates to heat-conducting long carbon chain nylon based on the common orientation of graphene filler and matrix and a continuous preparation method thereof. Background Art

[0002] With the development of high integration and miniaturization of electronic components, the problem of heat accumulation in electronic equipment has become more and more serious. In the field of electronic thermal packaging such as chip auxiliary heat dissipation and automotive battery packaging, thermally conductive polymer composites have become the dominant materials for electronic equipment thermal management systems due to their excellent properties such as low density, easy processing, high sealing, and good thermal conductivity. The preparation of long carbon chain nylon materials with excellent thermal conductivity can effectively solve technical problems such as poor toughness of heat dissipation components, loose packaging, and low thermal conductivity. It has great potential application value in the fields of electronic packaging and electric energy.

[0003] The common preparation of thermally conductive long carbon chain nylon is to add modified thermally conductive fillers to the polymer matrix, and use the characteristics of the modified fillers to enhance the overall performance of the composite material. However, due to the interface mismatch between the filler and the matrix, the dispersion effect of the filler is poor, and the thermal conductivity is limited. In addition, there is little research on the arrangement of fillers after the fillers are added to the nylon matrix. In theory, the orderly arrangement of thermally conductive fillers and polymer matrices can improve the thermal resistance and thermal conductivity of the thermal conductive composite interface. However, due to the limitations of preparation technology, it is still difficult to achieve the orderly arrangement of fillers and matrices at the same time, and the synergistic heat transfer effect between them has not been effectively confirmed and utilized.

[0004] CN112029275A discloses a thermally conductive nylon material and a preparation method and application thereof. The thermally conductive nylon material comprises the following components in parts by weight: 30-40 parts by weight of nylon, 20-25 parts by weight of glass fiber, 5-10 parts by weight of maleic anhydride and 30-40 parts by weight of thermally conductive filler; the nylon is a combination of branched nylon 6 and nylon 12. The thermally conductive nylon material achieves a good balance in comprehensive properties such as thermal conductivity, mechanical strength and flexibility through the mutual coordination of nylon, glass fiber, maleic anhydride and thermally conductive filler. However, the thermal conductivity coefficient under this process is only 2.8W / mK, and the thermal conductivity performance is limited.

[0005] At present, the production method of long carbon chain nylon at home and abroad still adopts intermittent polymerization process, which has the disadvantages of low production efficiency, difficult heat management, limited product diversity, etc. Based on this, the development of continuous production process of nylon composite materials with excellent thermal conductivity has a positive progressive role in improving the field of thermal management materials for electronic devices. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides a heat-conducting long carbon chain nylon and a continuous preparation method thereof, wherein the heat-conducting long carbon chain nylon comprises the following components: long carbon chain nylon salt, graphene nanosheets, maleic anhydride, a catalyst and an antioxidant, and the above components are added to a salt-forming tank of a continuous production line, and then the heat-conducting long carbon chain nylon is obtained through salt-forming, polymerization, shearing, cooling and drying. The present invention enhances the dispersion effect of the filler and the polymer matrix by adding dispersant maleic anhydride (MA) and filler graphene nanosheets (GNP), so that the obtained long carbon chain nylon material has good mechanical properties and excellent thermal conductivity; secondly, a transverse shearing process is added in the nylon discharging stage, and the strong shearing induction effect of the scraper makes the filler oriented in a regular manner along the scraper shearing direction, further enhancing the mechanical and thermal conductivity of the nylon material.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A thermally conductive long carbon chain nylon, comprising the following components by mass:

[0009]

[0010] Furthermore, the mass ratio of maleic anhydride to graphene nanosheets is 1:2-6.

[0011] Furthermore, the long carbon chain nylon salt is prepared from a dibasic acid, a diamine and water; the molar ratio of the dibasic acid, the diamine and water is 1:1-1.1:25; the dibasic acid is sebacic acid, adipic acid, undecanedioic acid or dodecanedioic acid; the diamine is hexamethylenediamine, decanediamine or dodecanediamine.

[0012] Furthermore, the catalyst is one or more of phosphorous acid, phosphoric acid, hypophosphorous acid, sodium phosphite, and sodium hypophosphite.

[0013] Furthermore, the antioxidant is one or more of hindered phenols, hindered amines, phosphites and thiols.

[0014] The present invention also provides a continuous preparation method of thermal conductive long carbon chain nylon: long carbon chain nylon salt, graphene nanosheets, maleic anhydride, catalyst, and antioxidant are added into a salt-forming tank of a continuous production line according to the above-mentioned mass fractions, and then the thermal conductive long carbon chain nylon is obtained through salt-forming, polymerization, shearing, cooling and drying.

[0015] The above continuous preparation method has the following specific steps:

[0016] (1) Salt formation: according to the above-mentioned component formula, the measured dibasic acid, diamine and pure water are added to the salt formation tank in sequence to prepare a long carbon chain nylon salt, the salt formation temperature is set to 60-70° C., and when the pH value of the sample test is 7-8, graphene nanosheets, maleic anhydride, catalyst and antioxidant are added while stirring at a stirring frequency of 15-25 Hz to obtain a mixed solution;

[0017] (2) Polymerization: The mixed solution obtained in step (1) is filtered through a filter with a mesh size of 180-220 mesh through potential difference and pressure difference to remove impurities, and then transported to a refined salt storage tank, and then pumped into a polymerization reactor by a reactor supply pump, and preliminarily heated in a polymerization reactor at 200-210° C., and then heated to 215-225° C. and the pressure increased to 1.5-2 MPa for dehydration for 2-2.5 hours, so that the concentration of the mixed solution is 90-95%; the mixed solution is pumped into a flash evaporator by a flash evaporator supply pump, and dehydrated at 260-280° C. and normal pressure for 2-4 hours to obtain nylon oligomers; the mixed solution enters a prepolymerizer and is dehydrated at 255-265° C. for 1-3 hours, and then pumped into a postpolymerizer by a postpolymerizer supply pump, and dehydrated and polymerized at 255-265° C. for 2-3 hours to obtain a polymer in a molten state;

[0018] (3) Shearing: placing the molten polymer obtained in step (2) on a processing machine preheated to 245-255° C., and starting a scraper to shear the polymer in the transverse direction to obtain a sheared molten polymer;

[0019] Furthermore, in step (3), the shearing thickness of the scraper is 0.5-2 mm, the shearing speed is 8-12 cm / s, and the shearing times is 1-2 times.

[0020] (4) Cooling and drying: The sheared molten polymer obtained in step (3) is cooled with pure water at room temperature and then sliced, and placed in a drying device for drying at 55-70° C. for 4-6 hours to obtain thermally conductive long carbon chain nylon.

[0021] Mechanism of action: The hydrophilic property of maleic anhydride is utilized to form strong hydrogen bonds between the oxygen-containing groups (=O) of maleic anhydride and graphene nanosheets in the salt-forming stage, so that the graphene nanofiller is fully dispersed in the polymerized salt solution. In the subsequent polymerization process, the anhydride groups (-OCO-O-) on the maleic anhydride can react with the carboxyl groups (-COOH) on the long carbon chain nylon to be grafted into the nylon molecular chain. At the same time, during the grafting process, the strong attraction of hydrogen bonds pulls the GNP nanosheets to be evenly dispersed in the long carbon chain nylon. Then, a continuous production line is used to prepare a polymer composite melt with a uniform filler mixture. A device containing a scraper shear is added in the discharging stage. At the moment of melt discharging, the scraper quickly shears in the melt at a certain thickness and speed. The shear effect brought by the polymer flow is used to achieve the arrangement and orientation of the filler nanosheets. At the same time, the limited flow between the GNP sheets and the long carbon chain molecular chains is used to achieve the orderly arrangement of the nylon molecular chains. A double ordered "brick-mortar" structure is formed in the prepared thermally conductive long carbon chain nylon material. The formed thermal conductive path can provide rapid heat transfer, which significantly improves the thermal conductivity of the long carbon chain nylon material and has good mechanical properties.

[0022] Beneficial effects:

[0023] (1) The present invention adds maleic anhydride as a dispersant and graphene nanosheets as a filler, so that the anhydride groups can be grafted onto the molecular chains of the nylon matrix through shrinkage polymerization. There is a strong hydrogen bond interaction between the anhydride groups and GNPs, so that the GNPs are pulled by the hydrogen bond force and evenly distributed around the molecular chains of the nylon matrix, thereby enhancing the dispersion effect of the filler and the polymer matrix, avoiding the occurrence of filler agglomeration that affects the performance of the long-carbon chain nylon material, and making the obtained long-carbon chain nylon material have better mechanical properties and excellent thermal conductivity.

[0024] (2) The present invention adds a transverse shearing process during the nylon discharging stage. The strong shearing induction effect of the scraper makes the filler regularly oriented along the scraper shearing direction, thereby enhancing the orientation arrangement of the GNP nanosheets and the formation of a regular structure of the filler. A thermal conductive path for rapid heat transfer is formed between the materials. On the basis of enhancing the thermal conductivity of the filler itself, the thermal conductivity of the nylon material is further enhanced from a structural perspective. The dual effects jointly enhance the thermal conductivity of the long carbon chain nylon, forming a high thermal conductivity long carbon chain nylon material.

[0025] (3) The present invention adopts a continuous production line to produce long-chain nylon materials, which significantly improves production efficiency and obtains uniform product performance; it has universal applicability and can be applied to the preparation of polymer composite materials with melt processability and plasticity. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of scraper shearing molten polymer;

[0027] Figure 2 This is a simplified process flow chart of the synthesis of thermally conductive long carbon chain nylon;

[0028] Figure 3 The figures are dispersion effect diagrams of a mixed solution of maleic anhydride and graphene nanosheets; (a) is a dispersion effect diagram of a mixed solution left standing for 60 minutes; (b) is a dispersion effect diagram of a mixed solution left standing for 90 minutes; (c) is a dispersion effect diagram of a mixed solution left standing for 120 minutes;

[0029] Figure 4 The electron microscope scanning images of long carbon chain nylon materials; (a) is a cross-sectional scanning electron microscope image of long carbon chain nylon materials; (b) is an enlarged image of the orientation of GNP fillers along the transverse shear force direction;

[0030] Figure 5 The WAXD image and two-dimensional curve of the cross-section of graphene nanosheets in long carbon chain nylon material. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be specifically described below in conjunction with the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0032] The raw materials used in the examples and comparative examples all use the same commercially available products from the following sources:

[0033] Hexamethylenediamine: Shanghai Cathay Biotechnology Co., Ltd.; sebacic acid: Shanghai Gaoming Chemical Co., Ltd.; catalyst: phosphorous acid, Suzhou Lianxiong Fine Chemical Technology Co., Ltd.; antioxidant: antioxidant 1098, Tianjin Lianlong New Materials Co., Ltd.; graphene nanosheets: Kaina Graphene Technologies Co., Ltd.; maleic anhydride: Thermo Fisher Scientific Co., Ltd.

[0034] Example 1

[0035] A continuous preparation method of thermal conductive long carbon chain nylon, the specific steps are as follows:

[0036] (1) Salt formation: The measured hexamethylenediamine, sebacic acid and pure water were added to the salt formation tank in a molar ratio of 1:1.05:25 in sequence to prepare 75 parts of long carbon chain nylon salt. The salt formation temperature was set to 65° C. After reaching the reaction end point, the salt solution was sampled to test the pH value. When the pH value was 7.5, 20 parts of graphene nanosheets, 5 parts of maleic anhydride, 0.01 parts of phosphorous acid and 0.02 parts of antioxidant 1098 were added while stirring at a stirring frequency of 20 Hz to obtain a mixed solution;

[0037] (2) Polymerization: The mixed solution obtained in step (1) is filtered through a filter with a mesh size of 200 meshes through potential difference and pressure difference to remove impurities, and then transported to a refined salt storage tank, and then pumped into a polymerization reactor by a reactor supply pump, and preliminarily heated in a polymerization reactor at 205° C., and then heated to 220° C. and the pressure increased to 1.8 MPa for dehydration for 2.2 hours, so that the concentration of the mixed solution is 90-95%; the mixed solution is pumped into a flash evaporator by a flash evaporator supply pump, and dehydrated at 270° C. and normal pressure for 3 hours to obtain nylon oligomers; the mixed solution is entered into a prepolymerizer and dehydrated at 260° C. for 2 hours, and then pumped into a postpolymerizer by a postpolymerizer supply pump, and dehydrated and polymerized at 260° C. for 2.5 hours to obtain a polymer in a molten state;

[0038] (3) Shearing: The molten polymer obtained in step (2) is placed on a processing machine preheated to 250° C., and a scraper is started to shear the polymer in the transverse direction. The shearing thickness of the scraper is 1 mm, the shearing speed is 10 cm / s, and the shearing number is 1, to obtain a sheared molten polymer. The schematic diagram of the scraper shearing the molten polymer is as shown in FIG. Figure 1 As shown;

[0039] (4) Cooling and drying: The sheared molten polymer obtained in step (3) is cooled with pure water at room temperature and then sliced, and placed in a drying device for drying at 60°C for 5 hours to obtain thermally conductive long carbon chain nylon. The above-mentioned thermally conductive long carbon chain nylon synthesis process flow chart is as follows Figure 2 shown.

[0040] Examples 2-5 and Comparative Examples 1-2 adopt the same continuous synthesis steps as Example 1 to obtain different long carbon chain nylon composite materials.

[0041] The specific formulas of Examples 2-5 and Comparative Examples 1-2 are shown in Table 1:

[0042] Table 1 Formulas of Examples and Comparative Examples

[0043] formula Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Long carbon chain nylon mass fraction 75 75 75 75 65 100 75 GNP mass fraction 20 20 20 20 30 0 20 Maleic anhydride mass fraction 5 5 5 5 5 0 5 Catalyst mass fraction 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Antioxidant mass fraction 0.02 0.02 0.02 0.02 0.02 0.02 0.02 Scraper shear thickness (mm) 1 0.5 1.5 2 1 0 0

[0044] Test example

[0045] 1. Verification of the dispersion effect of maleic anhydride on graphene nanosheets

[0046] Maleic anhydride and graphene nanosheets were mixed uniformly in a gradient ratio of 1:1, 1:2, 1:4, and 1:8 by mass, dissolved in water, and allowed to stand, numbered 1, 2, 3, and 4, respectively, and the dispersion effect of maleic anhydride on graphene nanosheets was observed at 60 min, 90 min, and 120 min.

[0047] Depend on Figure 3It can be seen that the dispersion effect of the ratio of maleic anhydride to graphene nanosheets of 1:4 is the best, and the dispersibility of other ratios decreases with the extension of the standing time. Although the 1:4 ratio also has sedimentation, the effect weakens the slowest. This is because the hydrogen bond force between maleic anhydride and graphene nanosheets is weak when the mass ratio is too low, and a strong connecting bond cannot be formed; and when the mass ratio is too high, agglomeration will form between the fillers, and large particles will settle, thereby reducing the dispersing effect of maleic anhydride.

[0048] 2. Material performance test

[0049] (1) Test method

[0050] ① Test of graphene nanosheet filler orientation: Wide-angle X-ray diffraction analysis was performed using a Bruker D8 Discovery X-ray device equipped with a Cu-Kα light source. The distance from the sample to the detector was 135 mm, and images and two-dimensional curves were collected using a VANTEC-500 detector.

[0051] In order to reflect the shearing effect of the scraper on the filler, the Hermann orientation factor f is introduced to represent the regularity of the graphene nanosheet (the value is between 0 and 1, the closer it is to 1, the higher the degree of orientation). The calculation method can be obtained from formulas (1) and (2):

[0052]

[0053] Among them, 〈cos 2 θ〉 is the average value of the cosine square of the angle where the characteristic peak of the crystal form in the horizontal direction of the graphene nanosheet is located, and I(θ) is the signal intensity at the azimuth angle θ;

[0054] ② Thermal conductivity test: The thermal diffusion coefficient is obtained by testing the plane and vertical point temperature of the material at room temperature 25°C using LFA 467HyperFlash. The thermal conductivity k is calculated using formula (3):

[0055] k=ρC p α (3)

[0056] Where ρ is the density of the sample, C P is the specific heat capacity of the sample, α is the experimentally measured thermal diffusion coefficient;

[0057] ③ The tensile properties were tested according to GB / T 1040-2006 "Determination of tensile properties of plastics", the test temperature was 23°C, and the tensile rate was 50 mm / min;

[0058] ④ The simply supported beam notched impact strength is tested according to GB / T 1043-2008 “Determination of impact properties of simply supported beams of plastics”, using a V-notched specimen, the test temperature is 23°C, and the pendulum energy is 5.5J.

[0059] (2) Results Analysis

[0060] ① The thermal conductive nylon material obtained in Example 1 was observed by electron microscope. Figure 4 From the scanning electron microscope image of the cross section of the long carbon chain nylon material and the magnified image of the orientation of the GNP filler along the transverse shear force direction, it can be seen that the cross section of the nylon material after shearing is regular and oriented in the transverse direction, and the shearing effect is effective.

[0061] ② If Figure 5 As shown in the WAXD image and two-dimensional curve of the cross-section of long carbon chain nylon graphene nanosheets, the extremely arc-shaped graphene nanosheet image shows that the graphene nanosheets have a high orientation arrangement in the parallel direction, and the two-dimensional curve also shows a narrow half-peak width, which shows that the graphene nanosheets are successfully processed by the transverse shearing process both qualitatively and quantitatively.

[0062] ③ After testing, the performance test results of the long carbon chain nylon materials obtained in Examples 1-5 and Comparative Examples 1-2 are shown in Table 2:

[0063] Table 2 Performance test results of long carbon chain nylon materials

[0064]

[0065] It can be seen from the test results in Table 2 that from Comparative Examples 1-2, Example 1, and Example 5, regardless of whether shearing is performed or not, the addition of maleic anhydride and graphene nanosheets can effectively improve the thermal conductivity of the long carbon chain nylon material, and as the amount of addition increases, the thermal conductivity of the long carbon chain nylon material becomes better. However, if too much is added, the mechanical properties of the material will be significantly reduced, which may limit the use of the material.

[0066] It can be seen from Comparative Example 2 and Examples 1-4 that the larger the Hermann orientation factor, the better the orientation effect of the graphene nanosheets, and the stronger the thermal conductivity of the long carbon chain nylon. This is because a graphene thermal conduction path for rapid heat flow transfer is formed in the material. Too large or too small a shear thickness will affect the Hermann orientation factor and reduce the thermal conductivity of the material. Under a suitable raw material ratio, the scraper shear thickness of 1 mm is the best, which can effectively improve the flow shear effect and nano-confined flow of the nylon material, and the thermal conductivity is increased from 18.5 W / mK to 27.4 W / mK; at the same time, the dual ordered structure of the filler and the matrix molecular chain also greatly improves the mechanical properties of the nylon material, the tensile strength is increased from 61 MPa to 65 MPa, and the notched impact strength is increased from 14 KJ / m 2 Increase to 18KJ / m 2 .

[0067] In summary, the present invention uses maleic anhydride as a dispersant and graphene nanosheets as a filler. After shearing, densely stacked and highly oriented GNP fillers form a highly ordered heat conduction path in the long carbon chain nylon material, which can effectively achieve rapid heat transfer in the form of phonons. At the same time, the shear effect and limited flow cause the matrix to form a regular interface structure along the GNP surface, thereby reducing the interface thermal resistance between the matrix and the filler. Therefore, the synergistic heat conduction mechanism of high-oriented heat conduction path and low interface thermal resistance enhances the thermal conductivity of the long carbon chain nylon material, and the dual ordered structure of the filler and matrix molecular chain further improves the mechanical properties of the nylon material.

Claims

1. A thermally conductive long carbon chain nylon, characterized in that: The components include the following by mass: The continuous preparation method of the thermal conductive long carbon chain nylon comprises the following steps: adding long carbon chain nylon salt, graphene nanosheets, maleic anhydride, a catalyst and an antioxidant into a salt-forming tank of a continuous production line, and then performing salt-forming, polymerization, shearing, cooling and drying to obtain the thermal conductive long carbon chain nylon.

2. The thermally conductive long carbon chain nylon according to claim 1, characterized in that: The mass ratio of the maleic anhydride to the graphene nanosheets is 1:2-6.

3. The thermally conductive long carbon chain nylon according to claim 1, characterized in that: The long carbon chain nylon salt is prepared from a dibasic acid, a diamine and water; the molar ratio of the dibasic acid to the diamine is 1:1-1.1; the dibasic acid is sebacic acid, adipic acid, undecanedioic acid or dodecanedioic acid; the diamine is hexamethylenediamine, decanediamine or dodecanediamine.

4. The thermally conductive long carbon chain nylon according to claim 1, characterized in that: The catalyst is one or more of phosphorous acid, phosphoric acid, hypophosphorous acid, sodium phosphite, and sodium hypophosphite.

5. The thermally conductive long carbon chain nylon according to claim 1, characterized in that: The antioxidant is one or more of hindered phenols, hindered amines, phosphites and thiols.

6. The continuous preparation method of thermally conductive long carbon chain nylon according to claim 3, characterized in that: The following steps are involved: (1) Salt formation: Add measured dibasic acid, diamine and pure water into a salt formation tank in sequence to prepare a long carbon chain nylon salt, set the salt formation temperature to 60-70° C., take a sample and test the pH value to 7-8, then add graphene nanosheets, maleic anhydride, catalyst and antioxidant while stirring at a stirring frequency of 15-25 Hz to obtain a mixed solution; (2) Polymerization: The mixed solution obtained in step (1) is filtered through a filter with a mesh size of 180-220 mesh through potential difference and pressure difference to remove impurities, and then transported to a refined salt storage tank, and then pumped into a polymerization reactor by a reactor supply pump, and preliminarily heated in a polymerization reactor at 200-210° C., and then heated to 215-225° C. and the pressure increased to 1.5-2 MPa for dehydration for 2-2.5 hours, so that the concentration of the mixed solution is 90-95%; the mixed solution is pumped into a flash evaporator by a flash evaporator supply pump, and dehydrated at 260-280° C. and normal pressure for 2-4 hours to obtain nylon oligomers; the mixed solution enters a prepolymerizer and is dehydrated at 255-265° C. for 1-3 hours, and then pumped into a postpolymerizer by a postpolymerizer supply pump, and dehydrated and polymerized at 255-265° C. for 2-3 hours to obtain a polymer in a molten state; (3) Shearing: placing the molten polymer obtained in step (2) on a processing machine preheated to 245-255° C., and starting a scraper to shear the polymer in the transverse direction to obtain a sheared molten polymer; (4) Cooling and drying: The sheared molten polymer obtained in step (3) is cooled with pure water at room temperature and then sliced, and placed in a drying device for drying at 55-70° C. for 4-6 hours to obtain thermally conductive long carbon chain nylon.

7. The continuous preparation method according to claim 6, characterized in that: The shearing thickness of the scraper in step (3) is 0.5-2 mm, the shearing speed is 8-12 cm / s, and the shearing times is 1-2 times.

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