Highly heat-conductive silicone colorant and method for preparing the same

Abstract

This application relates to the field of colorants, and in particular to a high thermal conductivity organosilicon colorant and its preparation method. In this application, titanium dioxide is attached to the surface of long thermally conductive particles such as whiskers using a titanium source to form a titanium dioxide-long thermally conductive particle composite system, which is then dispersed in a polymer carrier. The attached titanium dioxide enhances the coloring performance of the long thermally conductive particles. Compared with directly mixing titanium dioxide and whiskers, this method provides better coloring and thermal conductivity at the same mass.

Description

Technical Field

[0001] This application relates to the field of colorants, and in particular to a high thermal conductivity organosilicon colorant and its preparation method. Background Technology

[0002] Organosilicon is a widely used polymer, applied in sealants, adhesives, packaging, and many other fields. The addition of colorants to organosilicon can adjust its color and also affect the mechanical properties of the system; therefore, the selection of colorants is crucial in organosilicon applications.

[0003] In the fields of semiconductors, electronic packaging, battery thermal management, power equipment, ultra-high voltage power transmission, aerospace and other technologies, a certain amount of heat may be generated during use. Therefore, there are certain requirements for the heat dissipation performance of organosilicon systems. They need to have the function of rapid heat dissipation and reducing heat accumulation, thereby reducing the impact of temperature rise on the system's working performance and safety.

[0004] For high thermal conductivity systems, black organosilicon systems can directly use graphite or carbon powder systems as thermally conductive and coloring materials. Graphite itself has strong thermal conductivity and good coloring properties. However, for white organosilicon systems, titanium dioxide is typically used as a colorant. But titanium dioxide has poor thermal conductivity. To improve thermal conductivity, other thermally conductive fillers are usually added as auxiliary agents. However, adding these auxiliary materials often causes the organosilicon to turn yellow or gray, making it difficult to balance whiteness and thermal conductivity. Another commonly used white colorant is alumina. Alumina has a thermal conductivity of 30 W / m·K, slightly higher than titanium dioxide's 5–10 W / m·K, but this level is still insufficient to improve thermal conductivity at lower doping levels. Another option is to use boron nitride. Boron nitride has significantly higher thermal conductivity than the two mentioned above, but its color coverage is poor. It usually requires a higher dosage to achieve uniform coloring, and the color is basically grayish-white. Therefore, it is usually necessary to add other components such as titanium dioxide to cover the color. This can also easily lead to an increase in the overall filler usage ratio, resulting in increased hardness and decreased toughness of silicone rubber. Summary of the Invention

[0005] Based on the above problems, the purpose of this application is to provide a colorant that can still achieve good coloring and high thermal conductivity at a low dosage.

[0006] First, this application provides a method for preparing a high thermal conductivity organosilicon colorant, which specifically includes the following steps:

[0007] S1. A titanium dioxide-long thermally conductive particle composite system is prepared by depositing a titanium source on the surface of long thermally conductive particles;

[0008] S2. Loading the titanium dioxide-long thermally conductive particle composite system with a polymer carrier;

[0009] The aspect ratio of the elongated thermally conductive particles is 20 to 30;

[0010] And / or,

[0011] The polymer carrier is silicone oil, which is liquid at 25°C.

[0012] In the above scheme, long thermally conductive particles with a high aspect ratio are first selected. Preferably, one or more of hexagonal boron nitride whiskers, zinc oxide whiskers, or aluminum borate whiskers can be selected. All three types of whiskers have good thermal conductivity, and the whiskers can form a bridging channel structure in the silicone rubber system, thus providing better thermal conductivity than powder. In addition, all three types of whisker systems have a white or light white or light gray base color, which will not have an overly strong impact on the color of the color paste.

[0013] However, compared to powdered granular structures, whiskers have poorer color coverage within the system. To achieve an overall white color, a larger filler content or additional components such as titanium dioxide are required. Therefore, the above technical solution, based on whisker-type products, further utilizes a titanium source to deposit titanium dioxide on their surface. After the titanium source undergoes hydrolysis in a solvent, titanium dioxide is deposited on the surface of elongated thermally conductive particles to form a component. Titanium dioxide has better scattering properties, thus significantly improving the color coverage of the material. Compared to adding thermally conductive particles and titanium dioxide separately, in this solution, the titanium dioxide is directly deposited on the surface of the whiskers and other thermally conductive particles, allowing the refracted light path to be more evenly distributed throughout the silicone rubber system. This also contributes to increasing the overall whiteness and color uniformity. Furthermore, compared to dispersing whiskers and titanium dioxide, the distribution of titanium dioxide in this solution can be controlled by the whiskers, thus improving thermal conductivity to some extent and helping to reduce the adverse effects on the toughness of silicone rubber.

[0014] Preferably, in step S1, the specific preparation method is as follows:

[0015] S1-1. Disperse the long thermally conductive particles in a solvent to obtain a dispersion system;

[0016] S1-2. Adjust the pH value to 4-6, add the titanium source to the dispersion system in step S1-1, and then heat to 80-120℃ to react, so that the titanium source is deposited on the surface of the long thermally conductive particles.

[0017] S1-3. After the reaction is complete, remove the solvent system and calcine the remaining components to convert the titanium source into titanium dioxide.

[0018] In the above scheme, a method of depositing titanium source followed by calcination is adopted, so that the titanium source is attached to the surface of long thermally conductive particles, thereby achieving uniform attachment of titanium. Then, calcination is carried out to form titanium dioxide. Since the titanium source can be uniformly attached to the surface of the whisker material in the above system, the masking performance of the whisker color is improved, the overall adhesion is improved, and the color of the whisker itself can be better masked. The overall light transmittance of the system is also reduced.

[0019] Preferably, in step S1, PMMA and 12-18 carbonates, accounting for 0.1-0.5% of the mass of the elongated thermally conductive particles, are also added.

[0020] In the above scheme, the introduction of a template agent first acts as a site occupant. After sintering, it can form a partial microporous structure on the titanium dioxide coating layer, thereby further improving the light scattering performance of the prepared particles. This improves both the overall whiteness and the uniformity of adhesion, resulting in a more uniform color. In the template agent, this scheme uses a compound system of PMMA and long-chain alkyl sulfonate. Long-chain alkyl sulfonate has better reactivity, preferentially adhering to the surface of elongated thermally conductive particles to form internal channels. PMMA, under the action of the hydrophobic system on the surface of long-chain alkyl sulfonate, forms hydrophobic interactions, thus forming non-continuous channels under the adhesion of long-chain alkyl sulfonate. This improves the photometric refractive properties, resulting in better color coverage at low addition levels. It also improves the permeability of silica gel to the channels, avoiding the loss of thermal conductivity caused by air residue in the channels. Simultaneously, it optimizes the interfacial contact between the elongated thermally conductive particles and the silica gel system, facilitating stable dispersion and better achieving the effects of thermal conductivity and improved whiteness.

[0021] Preferably, in steps S1-3, a two-stage calcination method is adopted, first calcining at 150-200℃ for 2-4 hours, and then raising the temperature to 400-500℃ and holding for 5-10 hours;

[0022] And / or,

[0023] In steps S1-3, the heating rate is 5-10℃ / min.

[0024] In the above scheme, calcination is first performed at 150–200℃ to remove organic matter from the system. It is important to note that calcination requires the presence of air or oxygen; otherwise, the titanium source compound cannot be converted into titanium dioxide. After the initial removal of the organic matter through calcination, the temperature is further increased to promote the conversion of the titanium source. In this step, the temperature is controlled at 400–500℃. This controls the pore closure, thus preserving the pores' ability to promote light scattering, and also forms anatase titanium dioxide, which has a white rather than gray color, thus improving the overall color.

[0025] Preferably, in step S1-1, the mass fraction of the elongated thermally conductive particles in the solvent is 10-20%; and / or, in step S1-2, the mass of titanium in the titanium source is 2-4% of the mass of the elongated thermally conductive particles; and / or, the solvent is a mixture of alcohol and DMAc.

[0026] In the above scheme, the overall accumulation of titanium source mass on the surface of elongated thermally conductive particles can be controlled. Simultaneously, the overall reaction process is relatively uniform, resulting in better and more uniform coloring properties and providing good thermal conductivity. Generally, the above system is carried out in a mixture of alcohol solvent and MDAC, such as isopropanol, propanol, ethanol, ethylene glycol, etc., which exhibits good overall dispersibility and relatively controllable reaction, making it less prone to titanium source agglomeration.

[0027] Preferably, the elongated thermally conductive particles are zinc oxide whiskers, the titanium source is a titanate ester having at least one alkyl ligand, and / or,

[0028] The elongated thermally conductive particles are hexagonal boron nitride whiskers or aluminum borate whiskers, and the titanium source is a pyrophosphate titanate.

[0029] When selecting zinc oxide whiskers, titanates with alkyl ligands, such as isopropyltrioleyloxytitanate or tetrabutyl titanate, are preferred because they have stronger reactivity and can adhere better to the zinc oxide surface. When the elongated thermally conductive particles are hexagonal boron nitride whiskers or aluminum borate whiskers, the reaction rate of pyrophosphate titanates is easier to control in the above system, the overall reaction is milder, and it is more economical in the case of scale-up reaction.

[0030] Preferably, in step S2, the viscosity of the silicone oil at 25°C is 350-10000 mm² / s; and / or, the silicone oil is methyl silicone oil or vinyl silicone oil.

[0031] The aforementioned titanium dioxide-long thermally conductive particle composite system was dispersed in a high-viscosity silicone oil. This dispersion allows for better early dispersibility during the incorporation into the organosilicon system, resulting in a well-dispersed system. Simultaneously, the higher viscosity silicone oil also inhibits agglomeration of the composite system. Therefore, in this system, the thermally conductive agent exhibits better storage stability and provides superior thermal conductivity and colorability.

[0032] Preferably, in step S2, polyethylene glycol is also added, wherein the amount of polyethylene glycol added is 0.1 to 1 times that of the titanium dioxide-long thermally conductive particle composite system, and the weight-average molecular weight of the polyethylene glycol is 1500 to 4000.

[0033] In step S2, a surfactant is also added, the mass of which is 0.01 to 0.05 times the mass of the titanium dioxide-long thermally conductive particle composite system.

[0034] In the above scheme, adding a certain amount of polyethylene glycol (PEG) can improve the stability of the composite system during storage, reduce agglomeration and sedimentation when stored in silicone oil, and adjust the viscosity of the system. This slightly improves the fluidity of the high-viscosity silicone oil, thereby enhancing the processability of the product and its compatibility with silicone rubber systems. Considering the relatively low solubility of PEG in silicone oil systems, a surfactant can be added to improve overall compatibility. Nonionic surfactants such as polyether-modified silicone oil and polyethylene glycol fatty acid esters can be selected.

[0035] In addition, this application also includes a high thermal conductivity organosilicon colorant prepared by the above preparation method. When added to an organosilicon system, the colorant has a good effect on improving the thermal conductivity of organosilicon, and only a small amount is needed to achieve a stable white coverage with uniform color and no graying.

[0036] In summary, this application relates to a high thermal conductivity organosilicon colorant, which modifies the surface of long, whisker-shaped thermally conductive particles by using a titanate coupling agent. This improves the light refraction properties of the long, thermally conductive particles while maintaining their thermal conductivity, thereby providing better color masking performance and giving the system better white coverage. Detailed Implementation

[0037] The technical solution of this application will be further described through the following specific embodiments.

[0038] First, the following preparation examples are set up to prepare a titanium dioxide-long thermally conductive particle composite system. In the preparation example series A, zinc oxide whiskers are selected as long thermally conductive particles for preparation. It should be noted that the zinc oxide whiskers have a four-needle structure. According to the sales specifications, its average central body diameter is 0.9 μm, the average needle diameter (middle region) is 0.8 μm, the average needle length is 20 μm, and its aspect ratio refers to the ratio of the average needle length to the average needle diameter (middle region), which is 25.

[0039] Using this zinc oxide as a substrate, the following preparation examples are specifically involved:

[0040] Preparation of Example A1, the specific preparation method includes the following steps:

[0041] S1-1. Disperse zinc oxide whiskers in DMAc / ethanol = 5 / 1 (v / v) at a mass ratio of 1:7, and fully disperse them by ultrasonic vibration, then transfer them to a sealed reaction vessel.

[0042] S1-2. Add hydrochloric acid / ammonium chloride (both hydrochloric acid and ammonium chloride have a molar concentration of 1 mmol / L) to the mixture from step S1-1, adjust the pH to 5, and then weigh isopropyltrioleoyl titanate according to a titanium:zinc oxide whisker mass ratio of 4:100 (i.e., add 79.6 g of isopropyltrioleoyl titanate per 100 g of zinc oxide whiskers). At the same time, weigh PMMA (weight average molecular weight 50) according to a ratio of 0.2 g of PMMA per 100 g of zinc oxide whiskers. 0000, PDI=1.8), weigh sodium octadecyl sulfonate according to the ratio of 0.2g sodium octadecyl sulfonate to 100g zinc oxide whiskers, add PMMA and sodium octadecyl sulfonate directly to the dispersion system in step S1-1, and dissolve isopropyl trioleoyl oxytitanate in a small amount of isopropanol, and uniformly add it to the above mixed system over 10min. During the addition process, maintain the reaction at 100℃, and continue the reaction after the addition is completed. The total reaction time is controlled to be 3h.

[0043] S1-3. After the reaction is complete, centrifuge to remove the solvent, wash three times with ethanol, then dry, and calcine in a muffle furnace. The heating rate is controlled at 8℃ / min. First, heat to 180℃ and hold for 4 hours, then continue to heat to 500℃ and hold for 5 hours, and then cool to 25℃.

[0044] Preparation Example A2 differs from Preparation Example A1 in that, while keeping the mass of titanium constant, isopropyltrioleoyloxytitanate is replaced with tetrabutyl titanate, that is, 35.6g of tetrabutyl titanate is added per 100g of zinc oxide whiskers.

[0045] Preparation Example A3 differs from Preparation Example A1 in that, while keeping the mass of titanium constant, isopropyltrioleoyloxytitanate is replaced with isopropyltris(dioctylpyrophosphate)titanate, that is, 108.8g of isopropyltris(dioctylpyrophosphate)titanate is added per 100g of zinc oxide whiskers.

[0046] Preparation Example A4 differs from Preparation Example A1 in that the mass of isopropyltrioleoyloxytitanate is adjusted to 39.8 g, i.e., the mass ratio of titanium to zinc oxide whiskers is 2:100.

[0047] Preparation Example A5 differs from Preparation Example A1 in that the mass of isopropyltrioleoyloxytitanate is adjusted to 19.9 g, i.e., the mass ratio of titanium to zinc oxide whiskers is 1:100.

[0048] Preparation Example A6 differs from Preparation Example A1 in that the mass of isopropyltrioleoyloxytitanate is adjusted to 119.4 g, i.e., the mass ratio of titanium to zinc oxide whiskers is 6:100.

[0049] Preparation Example A7 differs from Preparation Example A1 in that the calcination conditions in steps S1-3 are modified as follows: the heating rate is controlled at 5℃ / min, the temperature is first raised to 200℃ and held for 2h, then the temperature is raised to 600℃ and held for 5h, and then cooled to 25℃.

[0050] Preparation Example A8 differs from Preparation Example A1 in that the calcination conditions in steps S1-3 are modified as follows: the heating rate is controlled at 10℃ / min, the temperature is first raised to 150℃ and held for 4 hours, then the temperature is raised to 400℃ and held for 10 hours, and then cooled to 25℃.

[0051] Preparation Example A9 differs from Preparation Example A1 in that the calcination conditions in steps S1-3 are modified as follows: the heating rate is controlled at 8℃ / min, the temperature is raised to 450℃, the temperature is maintained for 10h, and then cooled to 25℃.

[0052] Preparation Example A10 differs from Preparation Example A1 in that, in step S1, PMMA and sodium octadecyl sulfonate are weighed out separately at a ratio of 0.5g per 100g of zinc oxide whiskers (0.5g each).

[0053] Preparation Example A11 differs from Preparation Example A1 in that, in step S1, PMMA and sodium octadecyl sulfonate are weighed out at a ratio of 1.0g per 100g of zinc oxide whiskers.

[0054] Preparation Example A12 differs from Preparation Example A1 in that, in step S1, PMMA and sodium octadecyl sulfonate are weighed out at a ratio of 0.1g per 100g of zinc oxide whiskers.

[0055] Preparation Example A13 differs from Preparation Example A1 in that PMMA is not added in step S1, but replaced with an equal amount of sodium octadecyl sulfonate.

[0056] Preparation Example A14 differs from Preparation Example A1 in that, in step S1, sodium octadecyl sulfonate is not added, but replaced with an equal amount of PMMA.

[0057] Preparation Example A15 differs from Preparation Example A1 in that, in step S1, sodium octadecyl sulfonate is replaced by sodium dodecyl sulfonate by an equal mass.

[0058] In Preparation Example B series, compared to Preparation Example A series, the elongated thermally conductive particles were replaced with hexagonal boron nitride whiskers, wherein the hexagonal boron nitride whiskers have an average diameter of 1.2 μm, an average length of 26 μm, and an aspect ratio of 21.7. Specific preparation examples include those with the following settings:

[0059] Preparation of Example B1, the specific preparation method includes the following steps:

[0060] S1-1. Disperse hexagonal boron nitride whiskers in DMAc / ethanol = 5 / 1 (v / v) at a mass ratio of 1:9, and fully disperse them by ultrasonic vibration, then transfer them to a closed reaction vessel.

[0061] S1-2. Add hydrochloric acid / ammonium chloride (both hydrochloric acid and ammonium chloride have a molar concentration of 1 mmol / L) to the mixture in step S1, adjust the pH to 5, and then weigh isopropyltrioleoyl titanate according to the mass ratio of titanium to hexagonal boron nitride whiskers of 4:100 (i.e., add 79.6 g of isopropyltrioleoyl titanate per 100 g of hexagonal boron nitride whiskers). At the same time, weigh PMMA (weight average molecular weight) according to the ratio of 0.2 g of PMMA per 100 g of hexagonal boron nitride whiskers. 500000, PDI=1.8), weigh sodium octadecyl sulfonate according to the ratio of 0.2g sodium octadecyl sulfonate to 100g zinc oxide whiskers, add PMMA and sodium octadecyl sulfonate directly to the dispersion system in step S1-1, and dissolve isopropyl trioleoyl oxytitanate in a small amount of isopropanol, and uniformly add it to the above mixture over 10min. During the addition process, maintain the reaction at 100℃, and continue the reaction after the addition is completed. The total reaction time is controlled to be 3h.

[0062] S1-3. After the reaction is complete, centrifuge to remove the solvent, wash three times with ethanol, then dry, and calcine in a muffle furnace. The heating rate is controlled at 8℃ / min. First, heat to 180℃ and hold for 4 hours, then continue to heat to 500℃ and hold for 5 hours, and then cool to 25℃.

[0063] Preparation Example B2 differs from Preparation Example B1 in that, while keeping the mass of titanium constant, isopropyltrioleoyloxytitanate is replaced with isopropyltris(dioctylpyrophosphate)titanate, that is, 108.8g of isopropyltris(dioctylpyrophosphate)titanate is added per 100g of hexagonal boron nitride whiskers.

[0064] Preparation Example B3 differs from Preparation Example B1 in that, while keeping the mass of titanium constant, isopropyltrioleoyloxytitanate is replaced with tetrabutyl titanate, that is, 35.6g of tetrabutyl titanate is added per 100g of hexagonal boron nitride whiskers.

[0065] Preparation Example B4 differs from Preparation Example B2 in that PMMA is not added in step S1, but replaced with an equal amount of sodium octadecyl sulfonate.

[0066] Preparation Example B5 differs from Preparation Example B2 in that, in step S1, PMMA and sodium octadecyl sulfonate are weighed out at a ratio of 1.0g per 100g of hexagonal boron nitride whiskers.

[0067] Preparation Example B6 differs from Preparation Example B2 in that, in step S1, sodium octadecyl sulfonate is not added, but replaced with an equal amount of PMMA.

[0068] Preparation Example C series: Compared to Preparation Example A series, this preparation example replaces the long thermally conductive particles with aluminum borate whiskers. The aluminum borate whiskers have an average diameter of 0.7 μm, an average length of 20 μm, and an aspect ratio of 28.6. Specifically, it includes preparation examples with the following settings:

[0069] Preparation Example C1, S1-1: Aluminum borate whiskers were dispersed in acetic acid / ammonium acetate at a mass ratio of 1:8, and the dispersion was fully achieved by ultrasonic vibration, and then transferred to a closed reaction vessel.

[0070] S1-2. Add the hydrochloric acid / ammonium chloride mixture (both hydrochloric acid and ammonium chloride have a molar concentration of 1 mmol / L) to step S1, adjust the pH to 5, and then weigh isopropyltrioleoyl titanate according to a titanium:aluminum borate whisker mass ratio of 4:100 (i.e., add 79.6 g of isopropyltrioleoyl titanate per 100 g of aluminum borate whiskers). At the same time, weigh PMMA (weight average molecular weight 50) according to a ratio of 0.2 g of PMMA per 100 g of aluminum borate whiskers. 0000, PDI=1.8, weigh out sodium octadecyl sulfonate according to the ratio of 0.2g sodium octadecyl sulfonate to 100g zinc oxide whiskers, add PMMA and sodium octadecyl sulfonate directly to the dispersion system in step S1-1, and dissolve isopropyl trioleoyl oxytitanate in a small amount of isopropanol, and add it evenly to the above mixture over 10min. During the addition process, maintain the reaction at 100℃, and continue the reaction after the addition is completed. The total reaction time is controlled to be 3h.

[0071] S1-3. After the reaction is complete, centrifuge to remove the solvent, wash three times with ethanol, then dry, and calcine in a muffle furnace. The heating rate is controlled at 8℃ / min. First, heat to 180℃ and hold for 4 hours, then continue to heat to 500℃ and hold for 5 hours, and then cool to 25℃.

[0072] Preparation Example C2 differs from Preparation Example C1 in that, while keeping the mass of titanium constant, isopropyltrioleoyloxytitanate is replaced with isopropyltris(dioctylpyrophosphate)titanate, that is, 108.8g of isopropyltris(dioctylpyrophosphate)titanate is added for every 100g of aluminum borate whiskers.

[0073] Preparation Example C3 differs from Preparation Example C1 in that, while keeping the mass of titanium constant, isopropyltrioleoyloxytitanate is replaced with tetrabutyl titanate, that is, 35.6g of tetrabutyl titanate is added per 100g of aluminum borate whiskers.

[0074] Preparation Example C4 differs from Preparation Example C2 in that PMMA is not added in step S1, but replaced with an equal amount of sodium octadecyl sulfonate.

[0075] Preparation Example C5 differs from Preparation Example C2 in that, in step S1, PMMA and sodium octadecyl sulfonate are weighed out at a ratio of 1.0g per 100g of aluminum borate whiskers.

[0076] Preparation Example C6 differs from Preparation Example C2 in that, in step S1, sodium octadecyl sulfonate is not added, but replaced with an equal amount of PMMA.

[0077] Preparation Example C7 differs from Preparation Example C2 in that the calcination conditions in steps S1-3 are modified as follows: the heating rate is controlled at 8℃ / min, the temperature is raised to 450℃, the temperature is maintained for 10h, and then cooled to 25℃.

[0078] The titanium dioxide-long thermally conductive particle composite system prepared in the above preparation examples was mixed with dimethyl silicone oil (viscosity 3000 mm² / s) at a mass ratio of 1:4 according to the corresponding serial numbers in Table 1. Polyethylene glycol PEG-2000 (i.e., weight average molecular weight of 2000) was added at 0.5 times the mass of the titanium dioxide-long thermally conductive particle composite system, and PEG-150 oleic acid monoester was added at 0.03 times the mass of the titanium dioxide-long thermally conductive particle composite system. The mixture was stirred at 200 rpm for 5 min in a high-speed shear mill and then discharged to obtain the colorants of Examples 1 to 28.

[0079] For Examples 1-28, the titanium dioxide-long thermally conductive particle composite system was added to LSR silicone rubber at a mass fraction of 3% (i.e., the dosage of the titanium dioxide-long thermally conductive particle composite system was 0.6%), and at the same time, alumina powder accounting for 8% of the mass of silicone rubber was added. After stirring evenly, the mixture was added to a mold and molded at 130°C and 3MPa for 5 minutes. Then, the mixture was demolded and tested.

[0080] The thermal conductivity of the sample was determined in accordance with GB / T 10297-2015 "Determination of Thermal Conductivity of Non-metallic Solid Materials - Hot Wire Method".

[0081] Referring to GB / T 529-2008 "Determination of tear strength of vulcanized rubber or thermoplastic rubber", method A was used to conduct the experiment and determine the tear strength of the sample.

[0082] Referring to GB / T 528-2009 "Vulcanized rubber or thermoplastic rubber - Determination of tensile stress-strain properties", the specimens were cut according to the Type 1 size standard, and the tensile strength and elongation at break of the specimens were measured.

[0083] Color: Visually inspect the vulcanized silicone rubber to determine if it is transparent, grayish, or unevenly colored.

[0084] Stability: The prepared colorant was left to stand for 15 days to observe whether there was any solid precipitation or agglomeration.

[0085] The specific preparation examples used in Examples 1 to 28 and their experimental results are shown in Table 1.

[0086]

[0087] Additionally, it should be noted that in the comparative examples, adding titanium dioxide or whiskers refers to directly adding titanium dioxide or whiskers to the silicone rubber system. The mass of titanium dioxide and whiskers is the same as the mass of the titanium dioxide-long thermally conductive particle composite system in each embodiment, i.e., added according to 0.6% of the mass of silicone rubber. In Comparative Example 5, the same mass ratio of titanium dioxide / zinc oxide whiskers of 1:1 was used as filler in the experiment.

[0088] Based on the above experimental results, it is evident that in the above embodiments, regardless of whether hexagonal boron nitride whiskers, zinc oxide whiskers, or aluminum borate whiskers are used as the substrate, carbon-titanium deposition on their surface achieves good color coverage, with the overall color being white. Hexagonal boron nitride whiskers provide higher overall thermal conductivity, while tetragonal zinc oxide whiskers better balance strength. Furthermore, subsequent experiments revealed that when using the colorant from Example 1 at a concentration of 1%, the overall color remains white. Therefore, the colorant from Example 1 exhibits stronger coloring performance. The overall coloring in the above embodiments is relatively uniform, and long-term storage stability is also good. Their coloring performance is stronger than that of individual whiskers or whisker-titanium dioxide composite systems. Compared to Comparative Example 5, Example 1 provides significantly stronger thermal conductivity, which is essentially close to that of Comparative Example 3. Therefore, it is demonstrated that the above technical solutions can better balance coloring performance and thermal conductivity.

[0089] Based on the above, a comparison shows that the amount of titanium dioxide attached will have a certain impact on the performance of the system. Specifically, it will affect the thermal conductivity. As the amount of titanium dioxide attached increases, there will be a problem of the color turning white and the thermal conductivity slightly decreasing. Overall, in the added titanate system, it is more appropriate to control the titanium content in the range of 2 to 4% of the whisker mass. In addition, excessive titanium load will also lead to increased costs, so it is not suitable for large-scale production.

[0090] In addition, there are two key process points in the preparation process. Firstly, a certain amount of PMMA and long-chain alkyl sulfonate are added during preparation. Both act as template agents, retaining certain channels when titanium dioxide is formed on the particle surface. This provides better light scattering properties, enhancing the system's light-shielding performance, specifically reducing the system's light transmittance. However, excessive addition can lead to ash content during construction, affecting the overall color and the mechanical properties of the silicone rubber, while also slightly impacting thermal conductivity. Experiments show that the combination of PMMA and sodium octadecyl sulfonate improves overall color coverage. The creation of channels with different diameters and morphologies within the system results in better light refraction paths, leading to stronger color masking of the internal structure. It also helps to better disperse and bind to the silicone molecular chains within the silicone system, thus improving overall strength. The preparation process also requires two-stage sintering. The first stage of sintering promotes the desorption of the template agent, while the second stage promotes the formation of titanium dioxide and induces the formation of anatase crystals. Excessive temperature can lead to a certain degree of graying in the system, possibly due to the transformation of titanium dioxide from anatase to a mixed anatase-rutile crystal form. This phenomenon is observed in all three whisker substrates, but its impact on thermal conductivity is not significant. Direct one-stage sintering also reduces the system's coloring properties, specifically resulting in a slightly transparent (rather than pure white) color, and a certain degree of graying when using aluminum borate whiskers.

[0091] Furthermore, the choice of titanium source affects the color and uniformity of the system. For example, using isopropyltrioleoyloxytitanate or tetrabutyl titanate achieves better coloring performance for zinc oxide whiskers, while using isopropyltris(dioctylpyrophosphate)titanate results in two problems due to its insufficient reactivity on the zinc oxide surface: 1. Decreased stability of the system in silicone oil; 2. Reduced coloring uniformity. Similarly, in aluminum borate whiskers and hexagonal boron nitride whiskers, the use of isopropyltrioleoyloxytitanate or tetrabutyl titanate produces a small amount of gray spots, which are speckled structures formed by rapid titanium dioxide deposition, also leading to poor coloring uniformity.

[0092] Furthermore, based on Example 1, the overall selection of colorant using polymer substrate and additives was further studied, resulting in the following examples.

[0093] Example 29 differs from Example 1 in that the organic carrier is replaced with 350 silicone oil, i.e., dimethyl silicone oil with a viscosity of 350 mm² / s.

[0094] Example 30 differs from Example 1 in that the polymer carrier is replaced with dimethyl silicone oil with a viscosity of 1000 mm² / s.

[0095] Example 31 differs from Example 1 in that polyethylene glycol is not added.

[0096] Example 32 differs from Example 1 in that the amount of polyethylene glycol added is 0.1 times that of the titanium dioxide-long thermally conductive particle composite system.

[0097] Example 33 differs from Example 1 in that the amount of polyethylene glycol added is 1 times that of the titanium dioxide-long thermally conductive particle composite system.

[0098] Example 34 differs from Example 1 in that polyethylene glycol is selected in equal amounts as PEG-4000.

[0099] Example 35 differs from Example 1 in that polyethylene glycol is selected in equal amounts as PEG-8000.

[0100] Example 36 differs from Example 1 in that polyethylene glycol is selected in equal amounts as PEG-800.

[0101] Example 37 differs from Example 1 in that polyethylene glycol is selected in equal mass as PEG-1500.

[0102] The thermal conductivity of the above embodiments was measured, and the color of the silicone rubber and the stability of the colorant were observed. The results are shown in Table 2.

[0103]

[0104] The above experiments show that the carrier has little overall impact on the thermal conductivity, indicating that the polymer carrier mainly plays a dispersing role in the titanium dioxide-long thermally conductive particle composite system, and its small amount of agglomeration has no significant impact on the thermal conductivity. However, from another perspective, the viscosity of the silicone oil will affect the uniformity of the system, which will have a significant impact on the storage performance of the colorant and the uniformity of subsequent coloring. If the coloring is uneven, more colorant will need to be added, which will not only increase the production cost, but also have a potential impact on the mechanical properties of silicone rubber.

[0105] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing a high thermal conductivity organosilicon colorant, characterized in that, Specifically, the steps include the following: S1. A titanium dioxide-long thermally conductive particle composite system is prepared by depositing a titanium source on the surface of long thermally conductive particles; S2. Loading the titanium dioxide-long thermally conductive particle composite system with a polymer carrier; In step S1, the specific preparation method is as follows: S1-1. Disperse the long thermally conductive particles in a solvent to obtain a dispersion system; S1-2. Adjust the pH value to 4-6, add the titanium source to the dispersion system in step S1-1, and then heat to 80-120℃ to react, so that the titanium source is deposited on the surface of the long thermally conductive particles. S1-3. After the reaction is complete, remove the solvent system and calcine the remaining components to convert the titanium source into titanium dioxide. The aspect ratio of the elongated thermally conductive particles is 20 to 30; The polymer carrier is silicone oil, which is liquid at 25°C, and the mass of the polymer carrier is 2 to 20 times the mass of the titanium dioxide-long thermally conductive particle composite system. The elongated thermally conductive particles are hexagonal boron nitride whiskers, zinc oxide whiskers, or aluminum borate whiskers. The viscosity of the silicone oil at 25°C is 350-10000 mm. 2 / s; In step S1, PMMA and 12-18 carbonates, accounting for 0.1-0.5% of the mass of the long thermally conductive particles, are also added.

2. The preparation method according to claim 1, characterized in that, In steps S1-3, a two-stage calcination method is adopted. First, calcination is carried out at 150-200℃ for 2-4 hours, and then the temperature is raised to 400-500℃ and held for 5-10 hours. In steps S1-3, the heating rate is 5-10℃ / min.

3. The preparation method according to claim 1, characterized in that, In step S1-1, the mass fraction of the elongated thermally conductive particles in the solvent is 10-20%; And / or, In steps S1-2, the mass of titanium in the titanium source is 2-4% of the mass of the elongated thermally conductive particles; And / or, The solvent is a mixture of alcohol and DMAc.

4. The preparation method according to claim 1, characterized in that, The elongated thermally conductive particles are zinc oxide whiskers, and the titanium source is oleyloxytitanate or tetrabutyl titanate, or... The elongated thermally conductive particles are hexagonal boron nitride whiskers or aluminum borate whiskers, and the titanium source is a pyrophosphate titanate.

5. The preparation method according to claim 1, characterized in that, In step S2, The silicone oil is methyl silicone oil or vinyl silicone oil.

6. The preparation method according to claim 1, characterized in that, In step S2, polyethylene glycol is also added. The amount of polyethylene glycol added is 0.1 to 1 times that of the titanium dioxide-long thermally conductive particle composite system, and the weight-average molecular weight of the polyethylene glycol is 1500 to 4000. In step S2, a surfactant is also added. The mass of the surfactant is 0.01 to 0.05 times the mass of the titanium dioxide-long thermally conductive particle composite system. The surfactant is polyether-modified silicone oil or polyethylene glycol fatty acid ester.

7. The high thermal conductivity organosilicon colorant prepared by the preparation method according to any one of claims 1 to 6.

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