A potting adhesive base, a potting adhesive and a preparation method and application thereof

Abstract

The application discloses a pouring sealant base material, a pouring sealant and a preparation method and application thereof. The application provides a preparation method of the pouring sealant base material, which comprises the following steps: 1) adding long-chain alkyl modified polyorganosiloxane into three kinds of alumina with different particle sizes, mixing, and standing to obtain dry-method modified alumina; and 2) mixing double-end ethylene polysiloxane and alkoxy single-end capped silicone oil, adding the dry-method modified alumina in batches for dispersion, and performing decompression and heating treatment to obtain the pouring sealant base material. The preparation method can not only obtain the dry-method modified alumina filler which has good modification effect, long storage time, convenient application and low cost, but also can prepare the pouring sealant which has low cost, low viscosity, good heat conduction performance, low oil permeation rate, good stability and anti-settling performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of adhesives, in particular to a pouring sealant base material, a pouring sealant and a preparation method and application thereof. BACKGROUND

[0002] The common organic silicon high-thermal-conductivity pouring sealant (thermal conductivity coefficient ≥ 2.0 W / (m·k)) on the market generally has problems such as poor flowability, serious settlement after storage, and silicone oil precipitation after aging, and is difficult to meet the requirements of high-demand industries such as new energy motor control. At present, the main ways to improve the thermal conductivity coefficient of the organic silicon thermal-conductivity pouring sealant are as follows: first, the filling amount of the thermal-conductivity filler is increased by powder compounding, but the increase of the filling amount will lead to poor flowability of the organic silicon pouring sealant; second, ultra-low viscosity non-reactive silicone oil (usually methyl silicone oil with a viscosity of 10-100 mPa·s) is used for dilution, but the addition of the low-viscosity non-reactive silicone oil has the risk of silicone oil exudation in the later aging process, and the silicone oil exudation will pollute electronic components, especially under high temperature and high pressure conditions, the exuded silicone oil is ionized to form SiO2 and adheres to the solder joints to cause electric leakage and quality accidents.

[0003] Therefore, it is urgent to develop a pouring sealant base material which is convenient to use, low in cost, simple to prepare and good in compatibility with other raw materials, and a pouring sealant which is good in flowability, long in storage life, low in oil exudation rate and high in thermal conductivity coefficient. SUMMARY

[0004] In order to overcome the problems existing in the prior art, the purpose of the present application is to provide a pouring sealant and a preparation method and application thereof.

[0005] The inventive concept of the present application is that, since there are a large number of voids on the surface of the powder, the smaller the particle size, the larger the void ratio, and thus the powder is more prone to moisture absorption. After moisture absorption, the powder gaps are completely filled with moisture, which is not conducive to subsequent wet modification. In the present application, the powder surface is first treated with long-chain alkyl silicone oil to fill and wrap the voids, and then the pouring sealant is prepared by wet modification. The finished product has excellent flow performance and good anti-settling effect. At the same time, since the long-chain alkyl silicone oil is used to treat the powder surface in advance, the long-chain alkyl silicone oil is completely embedded in the powder cavity, the surface polarity of the thermal-conductivity powder is reduced, the thermal-conductivity powder is more compatible with the organic silicon polymer, the long-chain alkyl structure has a powder plasticizing effect, and the powder filling amount of the system can be increased and the system viscosity can be reduced.

[0006] It should be noted that the viscosity in the summary is measured at 25℃; since the viscosity is related to the polymerization degree of the substance, and the polymer is basically a mixture, the viscosity characteristics are used in the summary to define different types of polysiloxane or siloxane.

[0007] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0008] In a first aspect, the present application provides a preparation method of a potting base, comprising the following steps:

[0009] 1) adding 15-30 parts by mass of long-chain alkyl-modified polyorganosiloxane to 3700-5500 parts by mass of alumina, mixing, and standing to obtain dry-modified alumina;

[0010] 2) mixing 150-300 parts by mass of double-end ethylene polysiloxane and 35-65 parts by mass of alkoxy mono-end capped silicone oil, adding part of the dry-modified alumina for dispersion, adding the remaining part of the dry-modified alumina, and performing reduced pressure and heating treatment to obtain a potting base;

[0011] In step 1), the alumina is composed of primary spherical alumina, secondary spherical alumina, and spherical-like alumina, and the mass ratio of the primary spherical alumina, the secondary spherical alumina, and the spherical-like alumina is (2-4):(0.5-1.5):1, the particle size of the primary spherical alumina is D 50 =40-50 μm, the particle size of the secondary spherical alumina is D 50 =5-7 μm, and the particle size of the spherical-like alumina is D 50 =1.0-2.0 μm;

[0012] In step 2), the end-capped alkoxy group in the alkoxy mono-end capped silicone oil is one or more of methoxy and ethoxy.

[0013] Specifically, different types of alumina are used in step 1) for compounding, which is beneficial to improving the anti-settling performance of the potting glue and forming a more excellent heat conduction channel in the composite material, thereby improving the thermal conductivity of the potting glue.

[0014] Preferably, the preparation method of the potting base comprises the following steps:

[0015] 1) adding 15-30 parts by mass of long-chain alkyl-modified polyorganosiloxane to 3700-5500 parts by mass of alumina, mixing, and standing to obtain dry-modified alumina;

[0016] 2) mixing 150-300 parts by mass of double-end ethylene polysiloxane and 35-65 parts by mass of alkoxy mono-end capped silicone oil, adding part of the dry-modified alumina for dispersion, adding the remaining part of the dry-modified alumina, and performing reduced pressure and heating treatment to obtain a potting base;

[0017] The alumina in step 1) is composed of primary spherical alumina, secondary spherical alumina and quasi-spherical alumina, and the mass ratio of the primary spherical alumina, the secondary spherical alumina and the quasi-spherical alumina is (2-4):(0.5-1.5):1, the particle size D 50 = 40-50 μm of the primary spherical alumina, the particle size D 50 = 5-7 μm of the secondary spherical alumina and the particle size D 50 = 1.0-2.0 μm of the quasi-spherical alumina.

[0018] The end-capped alkoxy group in the alkoxy mono-end-capped silicone oil in step 2) is one or more of methoxy and ethoxy.

[0019] The alkoxy mono-end-capped silicone oil in step 2) satisfies the following structural formula:

[0020]

[0021] In the formula, R1 is CH3 or CH2CH3; R2 is CH3, x, n and m are integers, and the value of x is 0-12, the value of n is 10-60, and the value of m is 1-3.

[0022] Further preferably, the alkoxy mono-end-capped silicone oil in step 2) is a methoxy mono-end-capped silane, and the methoxy mono-end-capped silane satisfies the following structural formula:

[0023]

[0024] In the formula, R1 is CH3; R2 is CH3, x, n and m are integers, and the value of x is 0-12, the value of n is 30-60, and the value of m is 1-3.

[0025] Specifically, the treatment effect is more excellent when the alkoxy mono-end-capped silicone oil is methoxy mono-end-capped.

[0026] Preferably, the viscosity of the alkoxy mono-end-capped silicone oil is 40-60 mPa·s.

[0027] Preferably, the mass ratio of the primary spherical alumina, the secondary spherical alumina and the quasi-spherical alumina in step 1) is 3:1:1.

[0028] Preferably, the primary spherical alumina in step 1) has a particle size D 50 = 40-50 μm, and a particle size D 90 ≤ 90 μm, and a spheroidization rate ≥ 93%.

[0029] Preferably, the secondary spherical alumina has a particle size D 50 = 5-7 μm, and a particle size D 90Alumina particles with a size of ≤ 20 μm and a spheroidization rate of ≥ 93%.

[0030] Preferably, the spheroidal alumina has a D 50 = 1.0-2.0 μm, and a D 90 Alumina particles with a size of ≤ 15 μm and a shape similar to a sphere.

[0031] Preferably, the long-chain alkyl-modified polyorganosiloxane of step 1) satisfies the following structural formula:

[0032] (CH3)3SiO[(CH3)2SiO] m [(R)(CH3)SiO] n Si(CH3)3,

[0033] wherein R is an alkyl group with a carbon number of 8-16, m and n are both positive integers, the value of m+n is 30-80, and the value of n is 10-30.

[0034] Further preferably, the long-chain alkyl-modified polyorganosiloxane satisfies the following structural formula:

[0035] (CH3)3SiO[(CH3)2SiO] m [(R)(CH3)SiO] n Si(CH3)3,

[0036] wherein R is a linear alkyl group with a carbon number of 8-16, m and n are both positive integers, the value of m+n is 30-80, and the value of n is 10-30.

[0037] Preferably, the long-chain alkyl-modified polyorganosiloxane has a viscosity of 30 mPa·s-150 mPa·s and an alkyl content of 10 wt%-50 wt%.

[0038] Further preferably, the long-chain alkyl-modified polyorganosiloxane has a viscosity of 20 mPa·s-80 mPa·s and an alkyl content of 20 wt%-40 wt%.

[0039] Preferably, the adding of step 1) is carried out by dropwise adding, and the dropwise adding rate is 0.1 g / s-0.5 g / s.

[0040] Preferably, the adding of step 1) is carried out for 1 min-3 min.

[0041] Preferably, step 1) further comprises the steps of cooling, packaging, and storing the product.

[0042] Specifically, the storage time is less than 3 half months, and 1 month is equivalent to 30 days.

[0043] Preferably, the standing time of step 1) is 20-60 hours. Specifically, 1 day is 24 hours.

[0044] Further preferably, the standing time of step 1) is 22-48 hours.

[0045] Specifically, if the time is too short, the long-chain alkyl silicone oil does not have enough time to soak into the gaps on the surface of the alumina powder, which increases the risk of aging and oil seepage of the later prepared potting adhesive. The present application sets the standing time to be 1-95 days to ensure that the long-chain alkyl modified polyorganosiloxane, the double-end ethylene polysiloxane, and the alkoxy single-end capped silicone oil can enter the surface gaps of the alumina in advance, form a dry modified alumina with good compatibility, relatively long storage time, and convenient direct use, thereby laying a foundation for quickly and simply preparing a potting adhesive base material, component A, and component B with good compatibility between raw materials, and further creating conditions for preparing a potting adhesive with a viscosity of ≤15000 mPa·s, a flow value of ≥5.8 cm, a thermal conductivity of ≥2.95 W / m·K, an oil seepage rate after aging of ≤0.2%, and a requirement of not producing hard settlement (i.e., a score of ≥7 after shaking) within at least 3 months.

[0046] Preferably, the mass ratio of the two times of dry modified alumina added in step 2) is 2:1-1:2.

[0047] Preferably, the viscosity of the double-end ethylene polysiloxane in step 2) is 80-500 mPa·s, and the vinyl content is 0.35-1.5 wt%.

[0048] Further preferably, the viscosity of the double-end ethylene polysiloxane in step 2) is 90-105 mPa·s, and the vinyl content is 0.42-1.2 wt%.

[0049] Specifically, the double-end ethylene polysiloxane satisfies the following structural formula:

[0050] wherein D is a positive integer, and the value range of D is 80-280.

[0051] Preferably, the mixing and dispersing in step 2) are carried out at a temperature of 80-160°C with stirring.

[0052] Further preferably, the mixing and dispersing in step 2) are carried out at a temperature of 90-110°C with stirring.

[0053] Preferably, the reduced pressure and heating treatment in step 2) is carried out at a gauge pressure of -0.1 to -0.092 MPa and a temperature of 115-170°C.

[0054] Further preferably, the reduced pressure and heating treatment in step 2) is performed at a temperature of 120-130°C and a gauge pressure of -0.098 MPa.

[0055] In a second aspect, the present application provides a potting adhesive base prepared by the method of the first aspect.

[0056] Specifically, the potting adhesive base comprises the following raw materials in mass fractions:

[0057] 4000-5000 parts of alumina;

[0058] 15-30 parts of long-chain alkyl-modified polyorganosiloxane;

[0059] 150-300 parts of di-terminated ethylene polysiloxane;

[0060] 40-60 parts of alkoxy mono-terminated silicone oil;

[0061] wherein the alumina is composed of primary spherical alumina, secondary spherical alumina and quasi-spherical alumina, and the mass ratio of the primary spherical alumina, secondary spherical alumina and quasi-spherical alumina is (2-4):(0.5-1.5):1, the particle size of the primary spherical alumina is D 50 =40-50 μm, the particle size of the secondary spherical alumina is D 50 =5-7 μm, and the particle size of the quasi-spherical alumina is D 50 =1.0-2.0 μm; and the terminal alkoxy group in the alkoxy mono-terminated silicone oil is one or more of methoxy and ethoxy.

[0062] In a third aspect, the present application provides a potting adhesive comprising component A and component B.

[0063] The component A comprises the following raw materials in mass fractions:

[0064] The potting adhesive base of the first aspect or the second aspect: 4000-6000 parts;

[0065] Di-terminated ethylene polysiloxane: 200-300 parts;

[0066] Pt catalyst: 10-30 parts;

[0067] Carbon black paste: 1-3 parts;

[0068] The component B comprises the following raw materials in mass fractions:

[0069] The potting adhesive base of the first aspect or the second aspect: 4000-6000 parts;

[0070] End-hydrogen-containing polysiloxane: 100-300 parts;

[0071] Side-hydrogen-containing polysiloxane: 30-100 parts;

[0072] Inhibitor: 10-20 parts;

[0073] The mass ratio of the A component and the B component is 3:1-1:3.

[0074] Preferably, the mass ratio of the A component and the B component is 1:1-1:1.

[0075] Preferably, the viscosity of the double-end ethylene polysiloxane is 80 mPa·s-500 mPa·s, and the vinyl content is 0.35wt%-1.5wt%.

[0076] Further preferably, the viscosity of the double-end ethylene polysiloxane in step 2) is 90 mPa·s-105 mPa·s, and the vinyl content is 0.42wt%-1.2wt%.

[0077] Specifically, the double-end ethylene polysiloxane satisfies the following structural formula:

[0078] wherein D is a positive integer, and the value range of D is 80-280.

[0079] Preferably, the Pt catalyst includes at least one of divinyltetramethyldisiloxane platinum complex, divinyl octamethyl tetrasiloxane platinum complex, and chloroplatinic acid.

[0080] Further preferably, the Pt catalyst is a divinyltetramethyldisiloxane complex dilution solution with a concentration of 3000 ppm. For example, the Pt catalyst is Karestedt dilution solution with a concentration of 3000 ppm from HELLER.

[0081] Preferably, the carbon black paste is a vinyl carbon black paste. Specifically, the vinyl carbon black paste is commercially available, for example, carbon black paste from Gansheng New Materials, pigment content 15-35%, carrier type: vinyl silicone oil.

[0082] Preferably, the inhibitor includes at least one of ethynylcyclohexanol, methylbutynol, tetramethyldivinyl disiloxane, and trimethyl-dodecynol.

[0083] Further preferably, the inhibitor includes one of ethynylcyclohexanol, methylbutynol, and trimethyl-dodecynol.

[0084] Still further preferably, the inhibitor is composed of methyl silicone oil with a viscosity of 2000 mPa·s and ethynylcyclohexanol, and the mass ratio of the methyl silicone oil and the ethynyl ring is 9:1.

[0085] Specifically, the use of the inhibitor can control the reaction speed during the curing of the silicone pouring sealant, and the pouring sealant has excellent operability.

[0086] Preferably, the viscosity of the terminal hydrogen-containing polysiloxane is 10 mPa.s to 80 mPa.s, and the hydrogen content is 0.05 wt% to 0.18 wt%.

[0087] Further preferably, the viscosity of the terminal hydrogen-containing polysiloxane is 15 mPa.s to 30 mPa.s, and the hydrogen content is 0.09 wt% to 0.11 wt%.

[0088] Specifically, the terminal hydrogen-containing polysiloxane satisfies the following structural formula:

[0089]

[0090] wherein D is a positive integer, and the value range of D is 10 to 60.

[0091] Preferably, the viscosity of the terminal hydrogen-containing polysiloxane is 10 mPa.s to 80 mPa.s, and the hydrogen content is 0.05 wt% to 0.18 wt%.

[0092] Further preferably, the viscosity of the terminal hydrogen-containing polysiloxane is 15 mPa.s to 30 mPa.s, and the hydrogen content is 0.09 wt% to 0.11 wt%.

[0093] Specifically, the terminal hydrogen-containing polysiloxane satisfies the following structural formula:

[0094]

[0095] wherein D and D' are integers, the value range of D is 20 to 80, and the value range of D' is 5 to 10.

[0096] In a fourth aspect, the present application provides a preparation method of the pouring sealant, comprising the following steps:

[0097] 1) Preparation of component A: mixing the pouring sealant base, the double-end vinyl polysiloxane, the Pt catalyst and the carbon black paste according to the mass fraction to obtain component A,

[0098] Preparation of component B: mixing the pouring sealant base, the terminal hydrogen-containing polysiloxane, the side hydrogen-containing polysiloxane and the inhibitor according to the mass fraction to obtain component B;

[0099] 2) Mixing component A and component B in step 1) according to the mass ratio to obtain the pouring sealant;

[0100] The mixing in step 1) is preferably carried out under the conditions of a pressure of -0.095 MPa and a stirring rate of 600 r / min.

[0101] The mixing in step 1) is preferably carried out under the conditions of a pressure of -0.095 MPa and a stirring rate of 600 r / min.

[0102] The mixing in step 1) is preferably carried out under the conditions of a pressure of -0.095 MPa and a stirring rate of 600 r / min.

[0103] The mixing in step 1) is preferably carried out under the conditions of a pressure of -0.095 MPa and a stirring rate of 600 r / min.

[0104] The mixing in step 1) is preferably carried out under the conditions of a pressure of -0.095 MPa and a stirring rate of 600 r / min.

[0105] In a fifth aspect, the present application provides a use of the potting adhesive in the preparation of electronic components.

[0106] Preferably, the electronic components are one or more of 5G secondary power supplies and new energy vehicle on-board chargers (OBCs).

[0107] The present application has the following advantages: the present application provides a preparation method of a potting adhesive base material, which can obtain an alumina filler with good modification effect, long storage time, convenient application and low cost, and also obtain a base material suitable for potting adhesives. Meanwhile, the potting adhesive prepared by using the potting adhesive base material has simple preparation and can meet higher production requirements of potting adhesives.

[0108] (1) The preparation method of the potting adhesive base material of the present application is to modify a plurality of alumina by long-chain alkyl modified polyorganosiloxane in a dry method, and then add double-end ethylene polysiloxane and alkoxy single-end capped silicone oil in advance to obtain the base material. This method can not only prepare the alumina in a dry method in advance, but also can prepare the alumina in a dry method in batches in advance, which is convenient for raw material storage, transportation and storage, and further can save the management and transportation costs of the whole production of the potting adhesive.

[0109] (2) The potting adhesive base material provided by the present application can effectively prevent the problems caused by water absorption or hydrolysis of long-chain alkyl modified polyorganosiloxane by using an appropriate amount of long-chain alkyl modified polyorganosiloxane and designing a suitable standing time, thereby reducing the oil permeation rate of the potting adhesive.

[0110] (3) The potting adhesive base provided by the application contains three kinds of alumina particles with different particle sizes, so that the potting adhesive prepared by using the same has good heat resistance, heat conduction performance, aging resistance and sedimentation resistance;

[0111] (4) The potting adhesive prepared by using the long carbon alkyl silicone oil pretreated alumina has more excellent sedimentation resistance, and the long carbon chain alkyl structure is chemically bonded on the surface of the heat conduction powder, so that the surface polarity of the heat conduction powder is reduced and the heat conduction powder is more compatible with the organic silicon polymer, and the long carbon chain alkyl structure has a powder plasticizing effect, so that the filling amount of the powder in the system is increased and the viscosity of the system is reduced;

[0112] (5) The potting adhesive base provided by the application can simultaneously meet the requirements of viscosity ≤8000 mPa·s, flow value ≥6.0 cm, thermal conductivity coefficient ≥2.95 W / m·K, oil penetration rate ≤0.15%, and hard sedimentation (i.e., the score after shaking is ≥8) does not occur within at least 3 months, and is particularly suitable for the 5G power supply and motor electric control field of high-thermal-conductivity potting adhesive materials;

[0113] (6) The alumina filler content in the potting adhesive is relatively high, which is beneficial to reducing the production cost of the potting adhesive. DETAILED DESCRIPTION

[0114] The content of the application will be further described in detail through specific examples.

[0115] Unless otherwise specified, the raw materials used in the examples and comparative examples of the application are purchased on the market or obtained by using conventional preparation methods; the viscosity of the raw materials in the application is measured at 25 DEG C; and the percentages in the application are mass percentages.

[0116] Some raw material information used in the examples and comparative examples of the application is shown in Table 1.

[0117] Table 1 Parameters of some raw materials in examples and comparative examples

[0118]

[0119]

[0120] In the examples and comparative examples of the application, the "primary spherical alumina" refers to alumina particles with a particle size D 50 = 40-50 μm, D 90 ≤ 90 μm, sphericity ≥ 93%, and specific surface area ≤ 0.25 m 2 / g;

[0121] The "secondary spherical alumina" refers to alumina particles with a particle size D 50 = 5-7 μm, D 90≤ 20 μm, sphericity ≥ 93%, specific surface area 0.4-0.7 m 2 / g of alumina particles;

[0122] "Spherical alumina" refers to alumina particles having a particle size D 50 = 1.0-2.0 μm, D 90 ≤ 15 μm, specific surface area 2.6 m 2 / g of alumina particles having a shape similar to a sphere;

[0123] "Pt catalyst" refers to Karestedt dilution of Helios with a concentration of 3000 ppm (i.e. divinyltetramethyldisiloxane complex dilution);

[0124] "Carbon black paste" refers to JSLD2911 of Suncn Materials, pigment content 15wt%-35wt%, carrier type: vinyl silicone oil;

[0125] "Inhibitor" is composed of methyl silicone oil with a viscosity of 2000 mPa-s and acetylene cyclohexanol, and the mass ratio of methyl silicone oil and acetylene ring is 9:1.

[0126] Example 1

[0127] The present embodiment provides a preparation method of a pouring sealant base, comprising the following steps:

[0128] 1) Dry modification of the thermally conductive alumina filler: 4500 g of alumina is added to a rapid mixing modification device, 22.5 g of long-chain alkyl modified polyorganosiloxane (alkyl content 30wt%, wherein the long-chain alkyl group contains a straight-chain alkyl group with 12 carbon atoms) with a viscosity of 50 mPa-s is added by dripping (dripping rate: 0.2 g / s, ensuring that the treatment agent is added within 2 min), and mixed at a high speed (stirring rate 1500 r / min) under the condition of a temperature of 60°C for 10 min, and then cooled, discharged, packaged, and left to stand for 24 hours, so that the long-chain alkyl modified polyorganosiloxane treatment agent completely infiltrates the surface gap of the powder, to obtain the dry-modified alumina;

[0129] 2) Preparation of the base: 220 g of double-end ethylene polysiloxane (viscosity 95-105 mPa-s, vinyl content 0.95wt%-1.05wt%) and 50 g of alkoxy single-end capped silicone oil are mixed uniformly in a 2L dynamic mixer equipped with a stirring paddle, and heated to 100°C-110°C;

[0130] Into the reaction kettle, 2500 g of dry modified alumina is added, and stirring and dispersion is carried out under the conditions of 30 revolutions of the revolution number and 300 revolutions / min of the stirring speed for 5 min, then the remaining dry modified alumina is added, stirring and dispersion is carried out under the same stirring conditions for 5 min, the stirring is stopped, and a scraper treatment is carried out (powder adhered to the stirring paddle is scraped into the kettle, so as to facilitate uniform dispersion), to obtain a premix;

[0131] The reaction kettle is vacuumed to a gauge pressure of -0.098 MPa, the reaction kettle is set to be heated to 120°C, and after treatment at 120°C for 2 h, cooling is carried out, to obtain a base material;

[0132] In step 1), the alumina is composed of primary spherical alumina, secondary spherical alumina and spherical-like alumina, and the mass ratio of the primary spherical alumina, the secondary spherical alumina and the spherical-like alumina is 6:2:2;

[0133] The reaction kettle in step 2) is a dynamic mixer.

[0134] The present embodiment provides a preparation method of a two-component pouring sealant, comprising the following steps:

[0135] 1) Preparation of a pouring sealant base material: the base material is prepared by using the preparation method of the pouring sealant base material in embodiment 1;

[0136] 2) Preparation of component A of the pouring sealant: 4770 g of the base material is added into a dynamic mixer, 250 g of double-end ethylene polysiloxane (viscosity 95-105 mPa·s, vinyl content 0.95wt%-1.05wt%) is added into the dynamic mixer, 20 g of a Pt catalyst and 0.2 g of carbon black paste are added into the dynamic mixer, stirring and mixing are carried out under the conditions of a gauge pressure of -0.095 MPa and a stirring speed of 600 r / min for 30 min, cooling water is used to control the temperature of the whole mixing process to be 15-45°C, and component A is obtained;

[0137] Preparation of component B of the pouring sealant: 4770 g of the base material is added into a dynamic mixer, 200 g of hydrogen-containing end polysiloxane (viscosity 15-30 mPa·s, hydrogen content 0.09wt%-0.11wt%), 50 g of hydrogen-containing side polysiloxane (viscosity 60-80 mPa·s, hydrogen content 0.16wt%-0.18wt%) and 15 g of an inhibitor are added into the dynamic mixer, stirring and mixing are carried out under the conditions of a gauge pressure of -0.095 MPa and a stirring speed of 600 r / min for 30 min, cooling water is used to control the temperature of the whole mixing process to be 15-35°C, and vacuum stirring is carried out for 30 min, to obtain component B;

[0138] 3) Preparation of the pouring sealant: component A of the pouring sealant and component A of the pouring sealant are mixed according to a mass ratio of 1:1, to obtain the pouring sealant.

[0139] Example 2

[0140] The present example provides a preparation method of a potting adhesive base material, which is different from that of Example 1 only in that the long-chain alkyl-modified polyorganosiloxane (alkyl content 30wt%, long-chain alkyl being a linear alkyl with 12 carbon atoms) with a viscosity of 70 mPa s is replaced by a long-chain alkyl-modified polyorganosiloxane (alkyl content 30wt%, long-chain alkyl being a linear alkyl with 12 carbon atoms) with a viscosity of 50 mPa s, and the rest of the preparation steps are the same as those of Example 1.

[0141] The present example provides a preparation method of a two-component potting adhesive, which is different from that of Example 1 only in that the potting adhesive base material in Example 2 is used, and the rest of the preparation steps are the same as those of Example 1, specifically comprising the following steps:

[0142] 1) Preparation of potting adhesive base material: the base material is prepared by the preparation method of the potting adhesive base material in Example 2;

[0143] 2) Preparation of Component A of the potting adhesive: 4770g of the base material is added to a dynamic mixer, and 250g of a double-end ethylene polysiloxane (viscosity 95-105 mPa s, vinyl content 0.95wt%-1.05wt%), 20g of a Pt catalyst, and 0.2g of carbon black paste are sequentially added to the dynamic mixer, stirred and mixed under the conditions of a table pressure of-0.095Mpa and a stirring rate of 600r / min for 30min, and the temperature of the whole mixing process is controlled at 15℃-45℃ by cooling water throughout the process, to obtain Component A;

[0144] Preparation of Component B of the potting adhesive: 4770g of the base material is added to a dynamic mixer, and 200g of a hydrogen-containing end-capped polysiloxane (viscosity 15-30 mPa s, hydrogen content 0.09wt%-0.11wt%), 50g of a hydrogen-containing side-capped polysiloxane (viscosity 60-80 mPa s, hydrogen content 0.16wt%-0.18wt%), and 15g of an inhibitor are added, stirred and mixed under the conditions of a table pressure of-0.095Mpa and a stirring rate of 600r / min for 30min, and the temperature of the whole mixing process is controlled at 15℃-35℃ by cooling water throughout the process, and vacuum stirring is performed for 30min, to obtain Component B;

[0145] 3) Preparation of the potting adhesive: Component A of the potting adhesive and Component A of the potting adhesive are mixed in a mass ratio of 1:1, to obtain the potting adhesive.

[0146] Example 3

[0147] The present example provides a preparation method of a potting adhesive base material, which is different from that of Example 1 only in that it further includes, after standing for 24 hours, storing for 3 months, and the rest of the preparation steps are the same as those of Example 1, specifically comprising the following steps:

[0148] 1) Dry method modification of the thermally conductive alumina filler: 4500 g of alumina was added to a rapid mixing modification device, 22.5 g of long-chain alkyl modified polyorganosiloxane (alkyl content 30 wt%, linear alkyl with 12 C atoms in the long-chain alkyl group) with a viscosity of 50 mPa·s was added by dropwise addition (dropwise addition rate: 0.2 g / s, ensuring that the treatment agent is added within 2 min), and mixed at a high speed (stirring rate 1500 r / min) at a temperature of 60 ℃ for 10 min. After cooling, the material was discharged, packaged, and allowed to stand for 24 hours to allow the long-chain alkyl modified polyorganosiloxane treatment agent to fully infiltrate the surface gaps of the powder. The modified alumina was stored for 3 months to obtain a dry modified alumina filler;

[0149] 2) Preparation of the base material: In a 2 L reaction kettle equipped with a stirring paddle, 220 g of a double-end ethylene polysiloxane (viscosity 95-105 mPa·s, vinyl content 0.95 wt%~1.05 wt%) and 50 g of an alkoxy single-end capped silicone oil were mixed uniformly and heated to 100-110 ℃;

[0150] 2500 g of the dry modified alumina was added to the reaction kettle and stirred and dispersed at a revolution speed of 30 revolutions and a stirring speed of 300 r / min for 5 min. The remaining dry modified alumina was then added and stirred for another 5 min under the same stirring conditions. The stirring was then turned off and a scraper was used to scrape the powder adhering to the stirring paddle into the kettle to facilitate uniform dispersion, thereby obtaining a premix;

[0151] The reaction kettle was vacuumed to a gauge pressure of -0.01 MPa, and the reaction kettle was set to heat to 120 ℃. After heating to 120 ℃ for 2 h, the reaction kettle was cooled to obtain the base material;

[0152] In step 1), the alumina is composed of primary spherical alumina, secondary spherical alumina, and spherical-like alumina, and the mass ratio of the primary spherical alumina, the secondary spherical alumina, and the spherical-like alumina is 6:2:2.

[0153] The reaction kettle equipped with a stirring paddle in step 2) is a dynamic mixer.

[0154] This example provides a two-component pouring sealant preparation method, which differs from example 1 only in that the pouring sealant base material in example 3 is used, and the remaining preparation steps are the same as those in example 1.

[0155] Comparative Example 1

[0156] This comparative example provides a pouring sealant base material preparation method, which differs from example 1 only in that the standing time in step 1) is replaced from "24 hours" to "2 hours", and the remaining preparation steps are the same as those in example 1.

[0157] This comparative example provides a preparation method of two-component pouring sealant, which is different from example 1 only in that the pouring sealant base material in comparative example 1 is used, and the remaining preparation steps are the same as those in example 1.

[0158] Comparative example 2

[0159] This comparative example provides a preparation method of pouring sealant base material, which is different from example 1 only in that the long-chain alkyl-modified polyorganosiloxane with a viscosity of 50 mPa s in step 1) is replaced by polydimethylsiloxane with a viscosity of 50 mPa s, and the remaining preparation steps are the same as those in example 1.

[0160] This comparative example provides a preparation method of two-component pouring sealant, which is different from example 1 only in that the pouring sealant base material in comparative example 2 is used, and the remaining preparation steps are the same as those in example 1.

[0161] Comparative example 3

[0162] This comparative example provides a preparation method of pouring sealant base material, which is different from example 1 only in that the long-chain alkyl-modified polyorganosiloxane with a viscosity of 50 mPa s in step 1) is replaced by methyltrimethoxysilane, and the remaining preparation steps are the same as those in example 1.

[0163] This comparative example provides a preparation method of two-component pouring sealant, which is different from example 1 only in that the pouring sealant base material in comparative example 3 is used, and the remaining preparation steps are the same as those in example 1.

[0164] Comparative example 4

[0165] This comparative example provides a preparation method of pouring sealant base material, which is different from example 1 only in that the long-chain alkyl-modified polyorganosiloxane with a viscosity of 50 mPa s in step 1) is replaced by dodecyltrimethoxysilane, and the remaining preparation steps are the same as those in example 1.

[0166] This comparative example provides a preparation method of two-component pouring sealant, which is different from example 1 only in that the pouring sealant base material in comparative example 4 is used, and the remaining preparation steps are the same as those in example 1.

[0167] Comparative example 5

[0168] This comparative example provides a preparation method of pouring sealant base material, which is different from example 1 only in that the long-chain alkyl-modified polyorganosiloxane with a viscosity of 50 mPa s in step 1) is replaced by dodecyltrimethoxysilane, and step 1) further includes a storage step of 3 months, and the remaining preparation steps are the same as those in example 1.

[0169] The comparative example provides a preparation method of a two-component pouring sealant, which is different from example 1 only in that the pouring sealant base material in comparative example 5 is used, and the rest of the preparation steps are the same as those in example 1.

[0170] Comparative example 6

[0171] The comparative example provides a preparation method of a pouring sealant base material, which is the same as example 1.

[0172] The comparative example provides a preparation method of a two-component pouring sealant, which is based on the method of CN 110564363 A and is adaptively adjusted and designed. The main difference between the comparative example and example 1 is that the preparation method of component A is different, specifically: a low-viscosity long-chain alkyl-modified polyorganosiloxane is used instead of part of the vinyl polysiloxane to prepare component A according to patent CN 110564363 A, which specifically includes the following steps:

[0173] 1) Preparation of pouring sealant base material: the base material is prepared by using the preparation method of the pouring sealant base material in comparative example 7;

[0174] 2) Preparation of component A in the pouring sealant: 4770g of the base material is added to a dynamic mixer, and 200g of a double-end ethylene polysiloxane (viscosity 95-105 mPa·s, vinyl content 0.95wt%-1.05wt%), 50g of a long-chain alkyl-modified polyorganosiloxane (viscosity 50 mPa·s, long-chain alkyl group being a straight-chain alkyl group with 12 carbon atoms), 20g of a Pt catalyst, and 0.2g of carbon black paste are sequentially added to the dynamic mixer. The mixture is stirred for 30min under the conditions of a table pressure of-0.098mpa and a stirring rate of 600r / min, and the temperature of the whole mixing process is controlled at 15℃-45℃ by using cooling water throughout the process, to obtain component A;

[0175] Preparation of component B in the pouring sealant: 4770g of the base material is added to a dynamic mixer, and 200g of a hydrogen-containing end polysiloxane (viscosity 15-30 mPa·s, hydrogen content 0.09wt%-0.11wt%), 50g of a hydrogen-containing side polysiloxane (viscosity 60-80 mPa·s, hydrogen content 0.16wt%-0.18wt%), and 15g of an inhibitor are added to the dynamic mixer. The mixture is stirred for 30min under the conditions of a table pressure of-0.098mpa and a stirring rate of 600r / min, and the temperature of the whole mixing process is controlled at 15℃-35℃ by using cooling water throughout the process, and vacuum stirring is performed for 30min, to obtain component B;

[0176] 3) Preparation of the pouring sealant: component A in the pouring sealant and component A in the pouring sealant are mixed in a mass ratio of 1:1, to obtain the pouring sealant.

[0177] Comparative example 7

[0178] This comparative example provides a method for preparing a potting adhesive base material, which is the same as that of Example 1.

[0179] This comparative example provides a method for preparing a two-component potting compound. The only difference between this comparative example and comparative example 6 is that when preparing component A, 50 mPa·s polydimethylsiloxane is used instead of 50 mPa·s long-chain alkyl-modified polyorganosiloxane.

[0180] Comparative Example 8

[0181] This comparative example provides a method for preparing a potting glue base material, which differs from Example 1 only in that the alumina raw materials and the standing time are different, wherein the alumina is composed of primary spherical alumina and secondary spherical alumina, and the mass ratio of the primary spherical alumina to the secondary spherical alumina is the same at 6:4.

[0182] This comparative example provides a method for preparing a two-component potting compound. The difference between this comparative example and Example 1 is that the potting compound base material in Comparative Example 8 is used, and the remaining preparation steps are the same as those in Example 1.

[0183] Performance Testing

[0184] The products of Examples 1 to 3 and Comparative Examples 1 to 8 were made into test samples to evaluate viscosity, thermal conductivity, flow value and anti-settling effect. The test results are shown in Table 2. The specific test methods are as follows:

[0185] 1. Viscosity test method:

[0186] Component A and component B in the potting compound were weighed in a weight ratio of 1:1 (±5% deviation allowed), stirred for 1 minute, and vacuumed (gauge pressure of -0.098 MPa) for 1 minute to obtain a two-component potting compound (as a viscosity test sample).

[0187] Then, according to the method specified in GB / T 2794-2013 Determination of viscosity of adhesives, the test was performed using a Brookfield viscometer with a No. 5 rotor at 20 rpm. The test temperature was 25°C ± 1°C, and the viscosity unit was mPa·s.

[0188] 2. Thermal conductivity test method:

[0189] The cured potting compounds of Examples 1 to 3 and Comparative Examples 1 to 8 were used as test samples, and thermal conductivity was tested using a Hot Disk probe according to the method specified in ISO 22007-2-2008. The test parameters were 10 s / 200 mW, sample size was 3 pieces, and the unit of thermal conductivity was W / m·K.

[0190] 3. Flow value test standard

[0191] After mixing the A component and the B component in Examples 1-3 and Comparative Examples 1-8 to prepare a potting adhesive (as a test sample) under vacuum, 10 g ± 0.05 g of the test sample was placed on a PCB or a steel plate (smooth surface without obvious scratches) (the PCB was kept horizontal), the glue was self-leveling, and the leveling diameter after 5 min was recorded, the unit of the flow value: cm (at least three data points were tested); the testing instrument can refer to the patent CN216208371U.

[0192] 4. Oil infiltration rate test method:

[0193] The A component and the B component in Examples 1-3 and Comparative Examples 1-8 were mixed according to a mass ratio of 1:1, vacuumized, and cured to prepare a test sample bar, the weight of the glue block before and after baking and aging was weighed, and the oil infiltration rate was calculated according to the formula of the oil infiltration rate.

[0194] Wherein,

[0195] The size of the test sample bar was 50x70x5mm.

[0196] The baking and aging conditions were 125°C, 3kg load, and 168h; the weight loss percentage before and after aging was tested.

[0197] The calculation formula of the oil infiltration rate was:

[0198] Oil infiltration rate (%) = (M 前 -M 后 ) / M 前 x 100%;

[0199] M 前 was the weight of the glue block before baking and aging;

[0200] M 后 was the weight of the glue block after baking and aging.

[0201] 5. Anti-settling effect evaluation:

[0202] Since the viscosity of the B component of the potting adhesive is generally lower than that of the A component, the B component is more prone to settling, so evaluating the settling of the B component can reflect the settling of the overall potting adhesive during storage.

[0203] Test sample: the B component in Examples 1-3 and Comparative Examples 1-8.

[0204] The test method was as follows: 1.2 kg of the B component in the potting adhesive was added to a 1.2L bucket, and the bottom of the bucket was vibrated every 24h to check the settling, and the bottom was checked for settling after 72h of vibration.

[0205] It should be noted that through the accumulation of previous experiments, the simulation of 72h shaking and standing for 3 months are basically equivalent in the evaluation of anti-settling effect.

[0206] Anti-settling effect evaluation criteria: no settling at the bottom 10 points, slight soft settling 9 points, more soft settling 7-8 points, slight hard settling 5-6 points, and a large amount of hard settling 1-4 points.

[0207] Table 2 Performance evaluation results of the potting sealant in Examples 1-3 and Comparative Examples 1-8

[0208]

[0209] Note: It should be noted that the requirements for high thermal conductivity potting sealant in the field of 5G power supply and motor electric control are as follows: viscosity ≤15000 mPa·s, flow value ≥5.8 cm, thermal conductivity coefficient ≥2.95 W / m·K, oil penetration rate after aging ≤0.2%, and at the same time, it is required that no hard settling occurs within at least 3 months (i.e. the score after shaking is ≥7 points).

[0210] As can be seen from Table 2, comparing Example 1 and Example 2, the higher the viscosity of the long-chain alkyl modified polyorganosiloxane used in the dry modified alumina, the higher the viscosity of the finished product of the potting sealant, and the anti-settling effect becomes worse; the main reason is that when the viscosity of the long-chain alkyl modified polyorganosiloxane is too high, it is difficult to control and disperse during dry modification, and it cannot be effectively and uniformly attached to the surface of the powder; moreover, the higher the viscosity and molecular weight of the long-chain alkyl modified polyorganosiloxane, the better it cannot be inserted into the gap of the powder after modification, thereby increasing the proportion of silicone oil in the potting sealant, causing the thermal conductivity coefficient to decrease, the modification effect to decrease, and the viscosity to increase.

[0211] Compared with Examples 1-3, Comparative Example 1 has a short standing time, and the gap between the surface of the dry modified alumina is not completely infiltrated by the long-chain alkyl modified polyorganosiloxane treatment agent, resulting in a higher viscosity, lower flow value, lower thermal conductivity coefficient, higher oil penetration rate, and poor anti-settling performance of the potting sealant prepared therefrom.

[0212] Comparing Example 1 with Comparative Examples 2-5, it is clear that when different silane coupling agents are used to dry-modify alumina, as the carbon chain length of the coupling agent increases (the hydrophobicity of the silane increases, making it more difficult to hydrolyze), the viscosity of the adhesive decreases and the fluidity increases after silane coupling agent treatment. In particular, the effect of Comparative Example 4 is barely acceptable. However, Comparative Example 5 shows that after the treated alumina powder is placed for 3 months and then reused, the viscosity of the potting compound increases dramatically, and the effect deteriorates. This is mainly due to the hydrolysis and crosslinking of the dodecyltrimethoxysilane during long-term storage. Comparative Examples 6 and 7 use polydimethylsiloxane or low-viscosity long-chain alkyl-modified polyorganosiloxane to replace part of the vinyl polysiloxane during the preparation of component A. Although the viscosity of the resulting potting compound decreases and the fluidity increases compared to the other comparative examples, polydimethylsiloxane and long-chain alkyl-modified polyorganosiloxane are non-reactive silicone oils and cannot participate in the crosslinking of the system. At the same time, comparing Examples 1 to 3 with Comparative Examples 6 to 7, these non-reactive silicone oils were not used for dry treatment of alumina in advance, so they could not enter the gaps on the powder surface in advance to fill and wrap them, resulting in serious oil leakage after aging.

[0213] Comparing Example 1 with Comparative Example 8, Example 1 exhibits superior anti-settling properties due to the use of multi-grade and multi-shaped alumina powders. This demonstrates that the addition of secondary spherical alumina, primary spherical alumina, and quasi-spherical alumina during the dry-process modified alumina preparation significantly enhances anti-settling properties, and the addition of small-particle alumina facilitates the formation of heat conduction channels, thereby increasing thermal conductivity. It should also be noted that in CN 110564363 A, long-chain alkyl silicone oil is used as a diluent instead of methyl silicone oil, primarily due to the principle of similar miscibility between the long carbon chains of the long-chain alkyl silicone oil and the long carbon chains of the compounded alumina powder surface modifier (long-chain alkyl silane), resulting in a potting compound with a lower viscosity than that obtained with the addition of methyl silicone oil. However, this method not only adds long-chain alkyl silane to modify the compounded alumina in the early stage but also adds long-chain alkyl silicone oil as a diluent in the later stage. First, the powder modified with long-chain silane has a short shelf life due to the hydrolysis of silane. Secondly, compared with CN 110564363 A, the technical solution in the present invention uses long-chain alkyl silicone oil as a diluent for dry-modification of the compounded alumina in advance, which can reduce the amount of long-chain silane, thereby increasing the proportion of powder in the glue, while ensuring the viscosity effect and improving the thermal conductivity. Thirdly, the long-chain silicone oil is used in advance for dry-modification of the powder, and the long-chain silicone oil can be completely embedded in the gaps between the powders, and the oil permeation rate is lower during the later aging process. Finally, the alumina used in CN 110564363 A is compounded with 40um and 5um particles. Due to the lack of small-particle powder, although the viscosity is low, the anti-settling effect is average.

[0214] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above embodiments, and any changes, modifications, substitutions, combinations, simplifications, etc. made without departing from the spirit and principles of the present application should be equivalent replacement manners and should be included in the protection scope of the present application.

Claims

1. A process for the preparation of a potted sealant base, characterized in that, The method comprises the following steps: 1) adding 15-30 parts by mass of long-chain alkyl-modified polyorganosiloxane to 3700-5500 parts by mass of alumina, mixing, and standing to obtain dry-modified alumina; 2) mixing 150-300 parts by mass of double-end ethylene polysiloxane and 35-65 parts by mass of alkoxy mono-end capped silicone oil, adding part of the dry-modified alumina for dispersion, adding the remaining dry-modified alumina, and performing vacuum and heating treatment to obtain a potting adhesive base material; In step 1), the alumina is composed of primary spherical alumina, secondary spherical alumina and spherical-like alumina, and the mass ratio of the primary spherical alumina, the secondary spherical alumina and the spherical-like alumina is (2-4):(0.5-1.5):1, the particle size D50 of the primary spherical alumina is 40-50 μm, the particle size D50 of the secondary spherical alumina is 5-7 μm, and the particle size D50 of the spherical-like alumina is 1.0-2.0 μm; The long-chain alkyl-modified polyorganosiloxane in step 1) satisfies the following structural formula: (CH3)3SiO[(CH3)2SiO] m [(R)(CH3)SiO] n Si(CH3)3, In the formula, R is an alkane group with 8-16 carbon atoms, m and n are positive integers, the value of m+n is 30-80, and the value of n is 10-30; the viscosity of the long-chain alkyl-modified polyorganosiloxane is 30 mPa·s-150 mPa·s, and the alkyl content is 10wt%-50wt%. The standing time in step 1) is 20-60 hours. In step 2), the end-capped alkoxy in the alkoxy mono-end capped silicone oil is one or more of methoxy and ethoxy.

2. The method of claim 1, wherein: The viscosity of the double-end ethylene polysiloxane in step 2) is 80 mPa·s-500 mPa·s, and the vinyl content is 0.35wt%-1.5wt%.

3. The method of claim 1, wherein the sealant base is prepared by: The mixing and dispersion in step 2) are performed at a temperature of 80-160℃ with stirring; and the vacuum and heating treatment in step 2) is performed at a table pressure of -0.1 MPa to -0.092 MPa and a temperature of 115-170℃.

4. A potting adhesive base material prepared by the method of any one of claims 1-3.

5. A potting compound, characterized in that The potting adhesive base material of claim 4: 4000-6000 parts; Double-end ethylene polysiloxane: 200-300 parts; Pt catalyst: 10-30 parts; Carbon black paste: 1-3 parts; The B component is composed of the following raw materials in parts by mass: The potting adhesive base material of claim 4: 4000-6000 parts; End-hydrogen-containing polysiloxane: 100-300 parts; Side-hydrogen-containing polysiloxane: 30-100 parts; Inhibitor: 10-20 parts; The mass ratio of the A component to the B component is 3:1-1:

3. The viscosity of the end-hydrogen-containing polysiloxane is 10 mPa·s-80 mPa·s, and the hydrogen content is 0.05wt%-0.18wt%; the viscosity of the side-hydrogen-containing polysiloxane is 30 mPa·s-100 mPa·s, and the hydrogen content is 0.08wt%-0.20wt%. ​ 6. The potting compound of claim 5, wherein: ​ 7. The potting compound according to claim 5 or 6, characterized in that: The Pt catalyst includes at least one of a divinyltetramethyl disiloxane platinum complex, a divinyl octamethyl tetrasiloxane platinum complex, and chloroplatinic acid; and the inhibitor includes at least one of ethynylcyclohexanol, methylbutynol, tetramethyldivinyl disiloxane, and trimethyl-dodecynol.

8. The method of claim 5 to 7, characterized in that, The method comprises the following steps: 1) Preparation of the A component: mixing a potting base material, a double-end vinyl polysiloxane, a Pt catalyst, and a carbon black paste according to mass fractions to obtain the A component, Preparation of the B component: mixing a potting base material, a terminal hydrogen-containing polysiloxane, a side hydrogen-containing polysiloxane, and an inhibitor according to mass fractions to obtain the B component; 2) Mixing the A component and the B component in step 1) according to a mass ratio to obtain the potting sealant. In step 1), the mixing is performed under the conditions of a gauge pressure of-0.08 MPa to-0.1 MPa, a stirring rate of 400 r / min to 800 r / min, and a temperature of 30°C to 50°C. In step 1), the mixing time is 20 min to 40 min.

9. Use of the potting sealant according to any one of claims 5 to 7 in the preparation of electronic components.

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