A high thermal conductivity powder coating and its preparation method and application

Abstract

The present invention relates to a high thermal conductivity powder coating, and in particular to a low gloss modified saturated polyester powder coating and its preparation method and application. In parts by weight, the high thermal conductivity powder coating includes the following components: 50-100 parts of graphene oxide modified high acid value saturated terminal carboxyl polyester resin, 50-100 parts of graphene oxide modified low acid value saturated terminal carboxyl polyester resin, 5-18 parts of curing agent, 5-30 parts of thermal conductive filler, 10-30 parts of pigment filler, and 1-8 parts of auxiliary agent. Wherein the graphene oxide modified high and low acid value saturated terminal carboxyl polyester resins are graphene oxide / terminated carboxyl polyester composite resins prepared by in-situ polymerization, and the acid values ​​of the two are 45-65 mgKOH / g and 15-25 mgKOH / g, respectively. The powder coating obtained by the present invention has the characteristics of low gloss, good adhesion and leveling performance, and excellent thermal conductivity and heat dissipation performance. The powder coating obtained by the present invention can be applied to the heat dissipation of LEDs, industrial equipment, automotive parts, 3C parts, etc.

Description

Technical Field

[0001] The invention relates to a high thermal conductivity powder coating, in particular to a low gloss modified saturated polyester powder coating and a preparation method and application thereof. Background Art

[0002] Thermal conductive coatings are generally based on polymers and then added with metal fillers with good thermal conductivity, mainly including traditional gold, copper, aluminum, and some non-metal fillers with high thermal conductivity such as aluminum nitride, silicon nitride, aluminum oxide, magnesium oxide, etc. Thermal conductive coatings not only have the function of radiative cooling, but also have good self-cleaning, corrosion resistance, waterproofness, fire resistance, insulation, and acid and alkali resistance. Therefore, thermal conductive coatings can be widely used in external coatings for substrate heat dissipation and pipeline heat dissipation.

[0003] Since graphene has extremely high thermal conductivity and strong emissivity, graphene thermal conductive coating prepared with graphene as raw material can greatly improve the thermal radiation coefficient of the substrate surface after being applied on the substrate surface, thereby improving the heat exchange efficiency of the surface of the object. In addition to excellent radiation heat dissipation performance, graphene thermal conductive coating also has excellent adhesion, good weather resistance and salt spray resistance, excellent temperature resistance, rich usage scenarios and other characteristics. It can be widely used in high-power LED heat sinks, CPU heat sinks, industrial equipment heat dissipation, automotive parts heat dissipation and other fields.

[0004] "Preparation and Performance Study of Graphene Polyester Resin for Heat Dissipation Powder Coatings" discloses that graphene polyester resin composite materials are prepared by adding graphene-containing raw materials during the synthesis of polyester resin, and then the graphene polyester resin composite materials are made into heat dissipation powder coatings. The study found that the introduction of graphene materials into the coating by this method does not affect the leveling, bending and reactivity of the coating. The introduction of graphene can significantly improve the heat dissipation performance of the coating, and within a certain thickness range, the heat dissipation capacity increases with the increase of coating thickness. At the same time, the study shows that graphene resin powder coatings have excellent heat dissipation capacity, weather resistance, heat resistance and water boiling resistance, and have potential application value in the fields of transformer heat dissipation, LED heat dissipation, 3C component heat dissipation, etc., which can achieve substrate protection while significantly reducing the surface temperature of components.

[0005] "Preparation and Performance Study of Carbon Nanotube / Epoxy Resin Composite Powder Coating" discloses the preparation of carbon nanotube / epoxy resin composite powder coating with epoxy resin as the matrix and carbon nanotubes as the reinforcing and thermal conductive filler. The study shows that when the mass percentage of carbon nanotubes in the powder coating is 3%, the application performance of the coating is the best. Compared with pure epoxy resin, the thermal conductivity of the coating is increased by 2.8 times.

[0006] CN106867360A discloses a graphene powder coating for radiator and its preparation process, wherein amino graphene is added to a powder coating of phenolic modified epoxy resin and hydroxyl saturated polyester resin system. However, the invention does not study the heat dissipation performance of the graphene powder coating.

[0007] CN107529540A discloses a heat dissipation coating, which is prepared into powder coating by graphene or carbon nanotubes and raw materials such as silicon carbide and polyurethane coating, epoxy resin coating, boron nitride, aluminum oxide, etc., and obtained by spraying the heat dissipation coating, and the coating is applied to the heat dissipation of LED light panels. However, polyurethane and epoxy resin have poor compatibility, and it is difficult to obtain a coating with good application performance by directly mixing the two resins to prepare the coating.

[0008] CN107987688A discloses a heat dissipation powder coating, which uses graphite powder and copper powder as thermal conductive fillers of polyester system powder coating. However, the invention does not study the influence of graphite powder and copper powder on the thermal conductivity of the coating.

[0009] CN108300121A discloses a heat dissipation spray powder for household appliances, which is prepared by adding graphene as an additive to the powder coating. The invention discloses that the heat dissipation performance of the obtained heat dissipation coating is significantly improved compared with conventional coatings, but the invention does not disclose the effect of graphene on the heat dissipation performance of the powder coating.

[0010] CN108929624A discloses a heat-conducting and heat-dissipating powder coating, which uses epoxy resin and polyester resin as film-forming resins, and adds modified graphene powder and oriented carbon nanotube powder as heat-conducting fillers to the coating. The base powder and the oriented carbon nanotubes are bonded to form a powder coating. At the same time, a surface roughening agent is added to the coating. During the curing and film-forming process of the finished powder coating, the surface roughening agent reacts chemically with the epoxy resin to generate dot-shaped protrusions of micro-nano structure on the coating surface, so as to increase the surface roughness of the coating, thereby increasing the heat dissipation surface and enhancing the heat dissipation effect.

[0011] CN114410197A discloses a graphene high-performance thermally conductive powder coating, which is prepared by adding layered graphene with a thickness of less than 5 to the powder coating, and adding boron nitride or aluminum nitride as a thermally conductive filler. The added thermally conductive material improves the thermal conductivity and wear resistance of the coating.

[0012] CN 115746679A discloses a heat-conducting vapor barrier coating, wherein a flaky filler and a spherical filler are added to the coating, wherein the flaky filler can be selected from boron nitride, graphene, Mxene or graphite, and the spherical filler can be selected from alumina, aluminum nitride, silicon carbide. The obtained coating has water vapor barrier properties and heat-conducting properties.

[0013] CN 112029389A discloses a three-dimensional graphene heat dissipation powder coating, which is prepared by adding spherical three-dimensional graphene powder and non-carbon composite filler powder to a carboxyl unsaturated polyester resin powder coating to enhance the heat dissipation effect of the coating.

[0014] CN112048236A discloses a matte type thermal transfer powder coating, which is a mixture of component A containing a polyester resin with a high acid value and component B containing a polyester resin with a low acid value as a powder coating. Due to the difference in acid values ​​of the polyester resins in the powder coating, the two components form a relatively fast component and a slow component respectively during the curing process, resulting in a difference in gel time. After the polyester resin is melted and solidified, a microscopic rough surface is formed, which diffusely reflects light, thereby obtaining a low-gloss coating. However, the invention does not disclose the effect of the matte powder coating with a microscopic rough surface on the heat dissipation performance of the coating.

[0015] The present invention aims to provide a low-gloss high-thermal-conductivity powder coating containing graphene. On the one hand, the thermal conductivity of thermally conductive fillers such as graphene, graphene oxide, carbon nanotubes, aluminum nitride or boron nitride added to the powder coating is utilized to improve the thermal conductivity of the powder coating. On the other hand, the difference in curing speed of polyester resins with different acid values ​​in the powder coating is utilized to form a low-gloss micro-rough surface, increase the heat dissipation area of ​​the coating, and further improve the heat dissipation effect of the coating. Summary of the invention

[0016] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0017] A high thermal conductivity powder coating comprises the following components, measured in parts by weight: 50-100 parts of a saturated carboxyl-terminated polyester resin with a high acid value modified by graphene oxide, 50-100 parts of a saturated carboxyl-terminated polyester resin with a low acid value modified by graphene oxide, 5-18 parts of a curing agent, 5-30 parts of a thermal conductive filler, 10-30 parts of a pigment filler, and 1-8 parts of an auxiliary agent.

[0018] The graphene oxide modified high acid value saturated carboxyl-terminated polyester resin is a graphene oxide / carboxyl-terminated polyester composite resin prepared by an in-situ polymerization method, and its acid value is 45-65 mgKOH / g, or 50-65 mgKOH / g, or 55-65 mgKOH / g, or 60-65 mgKOH / g, or 45-50 mgKOH / g, or 45-55 mgKOH / g, or 45-60 mgKOH / g.

[0019] The graphene oxide modified low acid value saturated carboxyl-terminated polyester resin is a graphene oxide / carboxyl-terminated polyester composite resin prepared by an in-situ polymerization method, and its acid value is 15-25 mgKOH / g, or 15-20 mgKOH / g, or 15-18 mgKOH / g.

[0020] The mass ratio of the graphene oxide modified high- and low-acid-value saturated carboxyl-terminated polyester resins is 2:8-8:2, or 3:7-7:3, or 4:6-6:4, or 5:5.

[0021] The preparation method of the graphene oxide modified high acid value saturated carboxyl-terminated polyester resin comprises the following steps:

[0022] S1, dissolving one or more graphene oxide filter cakes of SE243PW, SE2430W, and SE243EW obtained from Changzhou Sixth Element Materials Technology Co., Ltd. in deionized water, and performing ultrasonic dispersion to obtain a graphene oxide dispersion having a solid content of 10-20%.

[0023] S2, adding measured diols, triols, graphene oxide dispersion, dibasic acid and esterification catalyst into a reaction kettle, passing nitrogen, then heating to 240-260 ° C and keeping warm, and when the acid value of the resin reaches 10-20 mgKOH / g, cooling to 190-220 ° C.

[0024] S3, adding a measured amount of acidolysis agent for acidolysis and end-capping, the end-capping temperature is 220-250°C. When the acid value of the polyester reaches 60-80 mgKOH / g, the temperature is rapidly reduced to 205-240°C.

[0025] S4, vacuum polycondensation, control the acid value of the polyester to be in the range of 45-65 mgKOH / g. Cool down to 180-220 °C, add antioxidant and keep warm for 30-120 min before discharging, and obtain graphene oxide modified high acid value saturated carboxyl-terminated polyester resin.

[0026] The preparation method of the graphene oxide modified low acid value saturated carboxyl-terminated polyester resin comprises the following steps:

[0027] SS1, dissolving one or more graphene oxide filter cakes of SE243PW, SE2430W, and SE243EW obtained from Changzhou Sixth Element Materials Technology Co., Ltd. in deionized water, and ultrasonically dispersing to obtain a graphene oxide dispersion with a solid content of 10-20%.

[0028] SS2, put the measured diol, triol, graphene oxide dispersion, dibasic acid and esterification catalyst into the reactor, pass nitrogen, then heat to 240-260 ℃ and keep warm, when the acid value of the resin reaches 6-18mgKOH / g, cool to 190-220 ℃.

[0029] SS3, add the measured acidolysis agent into the reactor to react for 3-5 hours, and the acid value reaches 33-38 mgKOH / g. After adding the measured heat stabilizer, vacuum polycondensate for 1-4 hours, and the acid value reaches 15-25 mgKOH / g. Add antioxidant and stir to disperse evenly, cool and discharge to obtain graphene oxide modified low acid value saturated carboxyl-terminated polyester resin.

[0030] Furthermore, the triol of the graphene oxide modified high acid value, low acid value saturated terminal carboxyl polyester resin is one or more of trimethylolpropane and trimethylolethane, the dibasic acid and the acidolysis agent are one or more of terephthalic acid, isophthalic acid, and adipic acid, the antioxidant is one or more of antioxidant 168, antioxidant 1076, and antioxidant 1010, and the esterification catalyst is monobutyl tin oxide.

[0031] Preferably, in order to take into account both the dispersibility of graphene oxide in polyester resin and the application performance of polyester resin, the diol in the raw material for preparing the graphene oxide-modified low acid value saturated carboxyl-terminated polyester resin is a combination of a diol with a long carbon chain structure in the side chain and a diol with a straight chain structure.

[0032] Adding a diol with a long carbon chain structure in the side chain during the preparation of the polyester resin will reduce the viscosity of the resin, thereby preventing the viscosity of the obtained low-acid value saturated carboxyl-terminated polyester resin from being too high, making it difficult for graphene oxide to be evenly dispersed in the polyester resin, thereby adversely affecting the application performance of the obtained coating. However, if all diols with a long carbon chain structure in the side chain are selected as diols for preparing the polyester resin, the corresponding coating has poor mechanical properties, and the adhesion and leveling properties to the substrate will also deteriorate. Therefore, in the present invention, the specific selection of diols in the raw material for preparing the graphene oxide-modified low-acid value saturated carboxyl-terminated polyester resin is a combination of diols with a long carbon chain structure in the side chain and diols with a straight chain structure.

[0033] Furthermore, the diol with a long carbon chain structure in the side chain includes one or more of 2-n-butyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, and 2-n-pentyl-1,3-propanediol. The linear diol is one or more of 1,3-propanediol and neopentyl glycol.

[0034] Furthermore, the molar ratio of the diol having a long carbon chain structure in the side chain to the diol having a straight chain structure is 2:8-8:2, or 4:6-6:4, or 1:1.

[0035] Furthermore, the mass percentage of solid graphene oxide in the graphene oxide-modified high-acid value or low-acid value saturated carboxyl-terminated polyester resin is 0.1-5%, or 0.5-4%, or 1-3%, or 1.5-3%, or 1.5-2.9%, or 1.5-2.8%.

[0036] Preferably, the mass percentage of solid graphene oxide in the graphene oxide modified high acid value saturated carboxyl-terminated polyester resin is 1.5-3%. The mass percentage of solid graphene oxide in the graphene oxide modified low acid value saturated carboxyl-terminated polyester resin is greater than or equal to 1.5% and less than 3%.

[0037] The curing agent is TGIC triglycidyl isocyanurate or β-hydroxyalkylamide.

[0038] Thermally conductive fillers are functional materials that are added to coatings to improve the thermal conductivity of the coating. Common thermally conductive fillers are graphene, carbon nanotubes, metals, boron nitride and other materials. The thermal conductivity coefficients of common thermally conductive fillers are as follows:

[0039] The thermal conductivity of single-layer graphene is about 5000W / (m·K), the thermal conductivity of multilayer graphene is about 3000W / (m·K), the thermal conductivity of carbon nanotubes is about 2000W / (m·K), the thermal conductivity of aluminum nitride is 70 W / (m·K), the thermal conductivity of boron nitride is 100-200 W / (m·K), the thermal conductivity of silicon carbide is 23W / (m·K), the thermal conductivity of silicon nitride is 16.7W / (m·K), and the thermal conductivity of boron carbide is 17W / (m·K).

[0040] On the other hand, due to the lack of reactive functional groups on the surface of single-layer or multi-layer graphene, the compatibility with polymer resins is poor and it is easy to form agglomerates. More and more research has turned to graphene oxide or reduced graphene oxide. It is reported that the thermal conductivity of high thermal conductivity graphene film prepared based on graphene oxide method can reach 2000W / (m·K).

[0041] It can be seen that among the common thermal conductive fillers, single-layer or multi-layer graphene has the highest thermal conductivity, followed by carbon nanotubes and graphene oxide, and then thermal conductive fillers such as boron nitride.

[0042] In the present invention, the thermal conductive filler is specifically selected to be one or more of graphene, graphene oxide, aluminum nitride, boron nitride, and carbon nanotubes.

[0043] Preferably, the graphene in the thermally conductive filler is thermally conductive graphene SE1331 produced by Changzhou Sixth Element.

[0044] The pigment filler is one or more of titanium dioxide, calcium carbonate, barium sulfate, kaolin, and silicon powder.

[0045] The auxiliary agent is one or more of a leveling agent, a charge enhancer, benzoin, and a texture agent.

[0046] The present invention also discloses a method for preparing a high thermal conductivity powder coating, which is characterized by comprising the following steps:

[0047] Step 1, preparing graphene oxide modified high and low acid value saturated carboxyl-terminated polyester resin;

[0048] Step 2, weighing each raw material component of the coating, adding each raw material component into a high-speed mixer and mixing them evenly to obtain a mixture;

[0049] Step 3, adding the mixed material into an extruder for melt extrusion, wherein the feed temperature of the melt extrusion is 100-120° C. and the discharge temperature is 105-115° C.;

[0050] Step 4, feeding the melt-extruded material into a tablet press for tableting;

[0051] Step 5, sending the tabletted product into a pulverizer for pulverization, and then sieving to select particles with a particle size of 30-40 μm to obtain a finished powder coating product.

[0052] The present invention also discloses an application of a high thermal conductivity powder coating, which is characterized in that the high thermal conductivity powder coating is applied to the surface of substrates such as LEDs, industrial equipment, automotive parts, 3C parts, etc. by electrostatic spraying, and cured at 160-220°C for 5-15 minutes to obtain a low-gloss, high thermal conductivity coating.

[0053] The beneficial effects of the present invention are as follows:

[0054] The present invention adopts a combination of a high-acid-value saturated terminal carboxyl polyester resin and a low-acid-value saturated terminal carboxyl polyester resin as film-forming resins of the coating, and forms a microscopically rough coating according to the difference in curing speed of the polyester resins with different acid values ​​and the difference in compatibility of the molecular chain structures of the polyester resins, thereby not only obtaining a low-gloss coating but also improving the heat dissipation effect of the coating.

[0055] The present invention obtains a high- and low-acid-value terminal carboxyl polyester composite resin in which graphene oxide is uniformly dispersed by copolymerizing the reaction raw materials of graphene oxide and high- and low-acid-value saturated carboxyl polyester resins, and by selecting a combination of a diol containing a long carbon chain structure in the side chain and a diol with a straight chain structure as a diol component for preparing a low-acid-value saturated carboxyl polyester resin, and uses it as a powder coating film-forming resin. The experimental results of the present application show that when graphene oxide is copolymerized with the reaction raw materials of high- and low-acid-value carboxyl polyesters, the hydroxyl group, carboxyl group and other reactive functional groups in the graphene oxide can participate in the reaction, and the dispersion of the graphene oxide in the composite resin is better, and compared with directly adding graphene to the raw materials of high- and low-acid-value carboxyl polyesters, the dispersion of the graphene material in the obtained coating is better, and the application performance of the coating such as thermal conductivity and heat dissipation is better. Specific embodiments

[0056] The present invention will be further described below in conjunction with specific embodiments:

[0057] It should be understood that the specific embodiments described herein are part of the embodiments of the present invention, rather than all of the embodiments, and are merely used to explain the embodiments of the present invention, and are not used to limit the embodiments of the present invention. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0058] (A) Synthesis of graphene oxide modified high and low acid value saturated carboxyl-terminated polyester resins.

[0059] Synthesis Example 1-3

[0060] As shown in Table 1, Synthesis Examples 1-3 are for preparing graphene oxide modified high acid value saturated carboxyl-terminated polyester resins with graphene oxide contents of 0%, 1.5%, and 3.0% respectively in terms of solid content. The amounts of each raw material used are shown in Table 1.

[0061] Synthesis Example 1-3, the preparation method of the graphene oxide modified high acid value saturated carboxyl-terminated polyester resin is as follows:

[0062] S1, dissolving the SE243PW graphene oxide filter cake obtained from Changzhou Sixth Element Materials Technology Co., Ltd. in deionized water and ultrasonically dispersing it to obtain a graphene oxide dispersion with a solid content of 20%.

[0063] S2, adding measured amounts of neopentyl glycol, trimethylolpropane, graphene oxide dispersion, terephthalic acid, isophthalic acid and monobutyl tin oxide into a reaction kettle, passing nitrogen, then heating to 250°C and keeping the temperature, and when the acid value of the resin reaches about 12 mgKOH / g, cooling to 200°C.

[0064] S3, adding a measured amount of acidolysis agent isophthalic acid for acidolysis and end-capping, and the end-capping temperature is 235° C. When the acid value of the polyester reaches about 80 mgKOH / g, the temperature is rapidly lowered to 220° C.

[0065] S4, vacuum polycondensation, control the acid value of the polyester to be about 50 mgKOH / g. Cool down to 190 °C, add antioxidant 168 and keep warm for 30 minutes before discharging the material to obtain graphene oxide modified high acid value saturated carboxyl-terminated polyester resin.

[0066] As shown in Table 1, Synthesis Examples 4-6 are for preparing graphene oxide modified low acid value saturated carboxyl-terminated polyester resins with graphene oxide contents of 0%, 1.5%, and 3.0% respectively in terms of solid content. The amounts of each raw material used are shown in Table 1.

[0067] Synthesis Example 4-6

[0068] The preparation method of the graphene oxide modified low acid value saturated carboxyl-terminated polyester resin comprises the following steps:

[0069] SS1, dissolving the SE243PW graphene oxide filter cake obtained from Changzhou Sixth Element Material Technology Co., Ltd. in deionized water and ultrasonically dispersing it to obtain a graphene oxide dispersion with a solid content of 20%.

[0070] SS2, put measured amounts of neopentyl glycol, 2-n-pentyl-1,3-propanediol, trimethylolpropane, graphene oxide dispersion, terephthalic acid, isophthalic acid and monobutyltin oxide into a reactor, pass nitrogen, then heat to 250 °C and keep warm, and when the acid value of the resin reaches about 8 mgKOH / g, cool to 200 °C.

[0071] SS3, add the measured amount of acidolysis agent isophthalic acid into the reactor to react for 4 hours, and the acid value reaches about 35 mgKOH / g. After adding the measured amount of heat stabilizer, vacuum polycondensate is carried out for 3 hours, and the acid value reaches about 18 mgKOH / g. Antioxidant 168 is added, stirred and dispersed evenly, and the temperature is lowered to obtain the graphene oxide modified low acid value saturated terminal carboxyl polyester resin.

[0072] Synthesis Example 7

[0073] On the basis of Synthesis Example 5, all 2-n-pentyl-1,3-propanediol in Synthesis Example 5 was replaced by an equimolar amount of neopentyl glycol, and the preparation method of Synthesis Example 7 was the same as that of Synthesis Example 5. That is, Synthesis Example 7 prepared a graphene oxide-modified low acid value saturated carboxyl-terminated polyester resin without long carbon chain side chains and with a graphene oxide content of 1.5%.

[0074] Synthesis example 8

[0075] On the basis of Synthesis Example 6, all 2-n-pentyl-1,3-propanediol in Synthesis Example 6 was replaced by an equimolar amount of neopentyl glycol, and the preparation method of Synthesis Example 8 was the same as that of Synthesis Example 6. That is, Synthesis Example 8 prepared a graphene oxide-modified low acid value saturated carboxyl-terminated polyester resin containing no long carbon chain side chains and 3.0% graphene oxide content.

[0076] The sources and manufacturers of the raw materials in Synthesis Examples 1-8 are as follows:

[0077] Terephthalic acid, produced by Zhuhai BP Chemical Co., Ltd.; isophthalic acid, produced by Yanshan Petrochemical; neopentyl glycol, produced by Jilin BASF Co., Ltd.; trimethylolpropane, produced by Pasto Chemical; monobutyl tin oxide, produced by Arkema; ​​antioxidant 168, produced by BASF; 2-n-pentylpropane-1,3-diol, obtained from Shanghai MacLean Biochemical Technology Co., Ltd.; graphene oxide SE243PW, obtained from Changzhou Sixth Element Materials Technology Co., Ltd.

[0078] Table 1. Raw material formula and physical indicators for the preparation of high and low acid value saturated carboxyl-terminated polyester resins modified with graphene oxide.

[0079]

[0080] (II) Preparation of high thermal conductivity powder coating

[0081] The carboxyl polyester resin obtained in the above-mentioned synthesis examples 1-8 was used to prepare a high thermal conductive powder coating, and the corresponding powder coating is Example 1-5. The raw material components and amounts of the powder coating are shown in Table 2.

[0082] Table 2, raw material components and amounts of the powder coatings of Examples 1-7 and Comparative Examples 1-2.

[0083]

[0084] The selection of each raw material in the above examples and comparative examples is as follows:

[0085] TGIC: Changzhou Niutang Chemical Plant; leveling agent GLP588, Ningbo Nanhai Chemical; benzoin, Ningbo Nanhai Chemical. Graphene SE1331 was obtained from Changzhou Sixth Element Materials Technology Co., Ltd., and barium sulfate was purchased from the market.

[0086] The preparation method of powder coating comprises the following steps:

[0087] Step 1, weighing the raw material components of the coating according to the powder coating formula, adding the raw material components into a high-speed mixer and mixing them evenly to obtain a mixture;

[0088] Step 2, adding the mixed material into an extruder for melt extrusion, wherein the feed temperature of the melt extrusion is 100° C. and the discharge temperature is 105° C.;

[0089] Step 3, feeding the melt-extruded material into a tablet press for tableting;

[0090] Step 4, the tabletted product is sent to a pulverizer for pulverization, and then sieved to select particles with a particle size of 30-40 μm to obtain a finished powder coating product.

[0091] Coating preparation and performance testing

[0092] The powder coating is sprayed on the metal substrate using an electrostatic spray gun with a spray thickness of 60-80μm. It is cured at 200℃ / 15min and then tested for application performance such as thermal conductivity and heat dissipation.

[0093] Table 3, coating performance test table of Examples 1-7 and Comparative Examples 1-2

[0094]

[0095] From the coating performance test results of Examples 1-7 and Comparative Examples 1-2, it can be seen that the high and low acid saturated carboxyl-terminated polyester resins of the coating of Example 1 do not contain graphene oxide, and the hardness of the obtained coating is slightly poor, and the thermal conductivity and cooling effect of the coating are significantly worse than the coating of the powder coating obtained by the high and low acid saturated carboxyl-terminated polyester resins modified by graphene oxide in Examples 2-5. It can be seen that during the synthesis of the saturated carboxyl-terminated polyester resin, graphene oxide is added for in-situ polymerization, and the thermal conductivity and heat dissipation effect of the obtained coating are significantly improved. And from the above test results, it can be seen that the application performance of the coating obtained in Example 5 is the best. It is speculated that after the content of graphene oxide in the low acid saturated carboxyl-terminated polyester exceeds 1.5%, due to the high viscosity of the resin, the dispersibility of graphene oxide becomes poor, and it is difficult to further improve the application performance of the corresponding coating by increasing the content of graphene oxide.

[0096] The low-acid saturated polyester resin in Examples 6-7 does not use branched diols as raw materials, and the viscosity of the obtained graphene oxide-modified low-acid polyester is relatively large, and the dispersibility of graphene oxide is relatively poor. The reason is presumably that the viscosity of the low-acid saturated carboxyl-terminated polyester resin is relatively large, making it difficult to evenly disperse the graphene oxide, and thus it is difficult to effectively improve the thermal conductivity of the coating. On the other hand, since the polyester containing branched diol segments has poor compatibility with the polyester not containing branched diol segments, the polyester containing branched diol segments can more effectively improve the surface roughness of the coating, thereby improving the heat dissipation effect of the coating. Therefore, the heat dissipation performance of the coating of Examples 6-7 of the polyester resin not containing a branched diol structure is relatively poor.

[0097] Comparative Examples 1-2 respectively use graphene oxide modified high and low acid value polyester resins as film-forming resins of the coatings. Since the molecular weight of the high acid value saturated carboxyl-terminated polyester resin is relatively small, the heat resistance of the coating obtained in Comparative Example 1 is relatively poor. Compared with Example 2, the thermal conductivity and cooling effect of the coatings obtained in Comparative Examples 1 and 2 are relatively poor. The reason is presumably that the coatings obtained in Comparative Examples 1-2 are relatively smooth and have a high glossiness, and a coating with a rough microstructure cannot be obtained, thereby failing to further improve the thermal conductivity and heat dissipation effects of the coatings.

[0098] 3. The influence of thermal conductive fillers in high thermal conductivity powder coatings on the application performance of coatings

[0099] Example 8

[0100] Based on Example 5, graphene SE1331 is not added.

[0101] Example 9

[0102] On the basis of Example 5, the addition amount of graphene SE1331 is 9.8 Kg. That is, on the basis of Example 5, the percentage content of graphene SE1331 in the coating is increased to 4%.

[0103] Example 10

[0104] On the basis of Example 5, graphene oxide powder of the same mass was used to replace graphene SE1331. The preparation method of graphene oxide powder is as follows: graphene oxide SE243PW (yellow-brown paste) was dried at 100° C., and then the solid was ground and passed through a 400-mesh sieve to obtain graphene oxide powder.

[0105] Embodiment 11

[0106] On the basis of Example 5, the graphene SE1331 was replaced by carbon nanotubes of equal mass. The carbon nanotubes were specifically selected as Beike Nano-carboxylated double-walled carbon nanotubes CNTs-005C.

[0107] Example 12

[0108] On the basis of Example 5, the graphene SE1331 is replaced by boron nitride of equal mass. The specific boron nitride is Tianyuan Aerospace Materials H-BN-F.

[0109] Embodiment 13

[0110] On the basis of Example 5, the graphene SE1331 is replaced by aluminum nitride of the same mass. The specific choice of aluminum nitride is Brofos-ALN from Bohuas Nanotechnology.

[0111] Embodiment 14

[0112] On the basis of Example 5, the specific selection of the thermal conductive filler is a combination of graphene SE1331 and carbon nanotubes, and the mass ratio of the two is 1:1.

[0113] Embodiment 15

[0114] On the basis of Example 5, the specific selection of the thermal conductive filler is a combination of graphene SE1331, carbon nanotubes, and aluminum nitride, and the mass ratio of the three is 2:1:1.

[0115] Comparative Example 4

[0116] On the basis of Example 5, SE243PW graphene oxide was replaced with graphene SE1331 to prepare high and low acid value saturated carboxyl-terminated polyesters. The preparation methods of high and low acid value saturated carboxyl-terminated polyesters were the same, and the percentages of graphene SE1331 and SE243PW graphene oxide in high and low acid value saturated carboxyl-terminated polyesters were the same.

[0117] Table 4, coating performance test table of Examples 8-15 and Comparative Example 4

[0118]

[0119] From Examples 8-13, it can be seen that adding thermal conductive fillers such as graphene, graphene oxide, carbon nanotubes, boron nitride, and aluminum nitride to powder coatings can significantly improve the thermal conductivity and heat dissipation performance of the coatings. However, when the content of added graphene reaches 4%, the dispersion of graphene in the coating is poor, and the application performance of the resulting coating is poor. The application performance of the corresponding coating is better when graphene and carbon nanotubes are used as thermal conductive fillers.

[0120] As can be seen from Example 10, when graphene oxide powder is directly added during the preparation of the powder coating, the graphene oxide will react when the powder coating is cured, thereby improving its uniformity of dispersion in the coating, improving the glossiness of the coating, making the coating smooth, and worsening the heat dissipation effect of the coating structure. Secondly, the thermal conductivity of graphene oxide is worse than that of graphene, resulting in the thermal conductivity and heat dissipation effect of the coating obtained in Example 10 being worse than those of the coating in Example 5.

[0121] From Examples 14-15, it can be seen that the combination of thermally conductive fillers such as graphene, carbon nanotubes, and aluminum nitride is selected as the thermally conductive filler component of the coating, and the thermal conductivity of the resulting coating is close to that of the coating using graphene alone as the thermally conductive filler, but the heat dissipation effect is worse than that of the coating using graphene alone as the thermally conductive filler. It is speculated that the reason may be that a combination of multiple thermally conductive fillers is selected, and the thermal conductivity of different thermally conductive fillers varies greatly, making it difficult to conduct heat quickly, and thermally conductive fillers of different morphologies will fill the gaps in the microscopically rough coating, making the roughness of the coating smaller, thereby causing the heat dissipation effect of the coating to deteriorate.

[0122] From comparison 4, it can be seen that the application performance of the coating corresponding to the direct addition of graphene in the synthesis process of saturated carboxyl-terminated polyester resin is worse than that of the coating corresponding to the addition of graphene oxide. This is because graphene oxide has some reactive functional groups and can participate in polymerization reactions during the synthesis process of polyester resin. Graphene oxide has better dispersibility in the coating, which is more conducive to improving the thermal conductivity and heat dissipation performance of the coating. Adding graphene powder during the synthesis of polyester resin still cannot effectively improve the dispersibility of graphene. Graphene is easy to agglomerate in the obtained coating, and the leveling performance, adhesion, thermal conductivity and heat dissipation performance of the obtained coating are relatively poor.

[0123] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high thermal conductivity powder coating, comprising the following components, by weight: 50-100 parts of a graphene oxide modified high acid value saturated carboxyl-terminated polyester resin, 50-100 parts of a graphene oxide modified low acid value saturated carboxyl-terminated polyester resin, 5-18 parts of a curing agent, 5-30 parts of a thermal conductive filler, 10-30 parts of a pigment filler, and 1-8 parts of an additive; The graphene oxide modified high and low acid value saturated carboxyl-terminated polyester resins are both graphene oxide / carboxyl-terminated polyester composite resins prepared by in-situ polymerization, and the acid values ​​of the two are 45-65 mgKOH / g and 15-25 mgKOH / g, respectively; The mass ratio of the graphene oxide modified high and low acid value saturated carboxyl-terminated polyester resins in the coating is 2:8-8:2; The raw materials for preparing the graphene oxide modified low acid value saturated carboxyl-terminated polyester resin include diols, wherein the diols are a combination of diols with long carbon chain structures on the side chains and diols with straight chain structures; the diols with long carbon chain structures on the side chains are 2-n-pentyl-1,3-propanediol, the diols with straight chain structures are neopentyl glycol, and the molar ratio of the diols with long carbon chain structures on the side chains to the diols with straight chain structures is 4:6-6:4; The mass percentage of solid graphene oxide in the graphene oxide-modified high-acid-value saturated carboxyl-terminated polyester resin is 1.5-3.0%, and the mass percentage of solid graphene oxide in the graphene oxide-modified low-acid-value saturated carboxyl-terminated polyester resin is 1.5-2.9%; The thermally conductive filler is one or more of graphene, graphene oxide, aluminum nitride, boron nitride, and carbon nanotubes.

2. A high thermal conductivity powder coating according to claim 1, characterized in that: The raw materials for preparing the graphene oxide modified high and low acid value saturated carboxyl-terminated polyester resin include dibasic acid, diol, triol, esterification catalyst and antioxidant.

3. A high thermal conductivity powder coating according to claim 1, characterized in that: The curing agent is TGIC triglycidyl isocyanurate or β-hydroxyalkylamide.

4. The high thermal conductivity powder coating according to claim 1, characterized in that: The pigment filler is one or more of titanium dioxide, calcium carbonate, barium sulfate, kaolin, and silicon powder.

5. The high thermal conductivity powder coating according to claim 1, characterized in that: The auxiliary agent is one or more of a leveling agent, a charge enhancer, benzoin, and a texture agent.

6. The method for preparing a high thermal conductive powder coating according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, preparing graphene oxide modified high and low acid value saturated carboxyl-terminated polyester resin; S2, weighing each raw material component of the coating, adding each raw material component into a high-speed mixer and mixing them evenly to obtain a mixture; S3, adding the mixed material into an extruder for melt extrusion, wherein the feed temperature of the melt extrusion is 100-120° C. and the discharge temperature is 105-115° C.; S4, sending the melt-extruded material into a tablet press for tableting; S5, sending the tabletted product into a pulverizer for pulverization, and then sieving, selecting particles with a particle size of 30-40 μm to obtain a finished powder coating product.

7. The use of the high thermal conductivity powder coating according to any one of claims 1 to 5, characterized in that: Applied to LED heat dissipation, industrial equipment heat dissipation, automotive parts heat dissipation and 3C parts heat dissipation.

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