Halogen-free flame-retardant organic silicon pouring sealant with good thermal conductivity and preparation method of halogen-free flame-retardant organic silicon pouring sealant

Abstract

The invention belongs to the technical field of pouring sealants, and particularly relates to a halogen-free flame-retardant organic silicon pouring sealant with good thermal conductivity and a preparation method thereof. The organic silicon pouring sealant comprises a component A and a component B. The component A comprises the following components in parts by weight: 40-60 parts of vinyl-terminated silicone oil, 32-48 parts of an alkylene-containing modified halogen-free flame retardant, 120-180 parts of an alkylene-containing modified heat-conducting filler and 0.3-0.7 part of a catalyst; the component B is prepared from 40 to 50 parts of vinyl-terminated silicone oil, 120 to 180 parts of alkylene-containing modified heat-conducting filler, 32 to 48 parts of alkylene-containing modified halogen-free flame retardant, 25 to 35 parts of cross-linking agent and 0.1 to 0.5 part of inhibitor; the alkylene-containing modified halogen-free flame retardant is prepared through an environment-friendly, safe, simple and convenient imidazole-phosphoric acid reaction, and the alkylene-containing modified heat-conducting filler is prepared by modifying a conventional heat-conducting filler through a phenol-amine co-deposition reaction. The modified flame retardant and the modified heat-conducting filler used in the invention can effectively enhance the flame retardant property and heat-conducting property of the organic silicon pouring sealant, and alkylene can participate in hydrosilylation reaction, so that the flame retardant and the heat-conducting filler are bonded in an organic silicon network to avoid migration and sedimentation; the performance stability and the durability of the organic silicon pouring sealant are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of potting adhesives, and in particular relates to a halogen-free and flame-retardant organic silicon potting adhesive with good thermal conductivity and a preparation method thereof. Background Art

[0002] With the continuous development and upgrading of new energy vehicles, instrumentation, communications and entertainment electronics, the demand for high-performance electronic potting glue in the domestic and foreign markets is also increasing day by day. The use of electronic potting glue can enhance the integrity of various electronic components in automobiles or instruments and equipment, protect integrated electronic components from the influence of factors such as working environment temperature and humidity, thereby improving the performance stability of various electronic equipment and extending their service life. At present, common potting glues include epoxy resin potting glue, polyurethane potting glue and silicone potting glue, among which silicone potting glue has excellent high and low temperature resistance, aging resistance, weather resistance, shock resistance and waterproof and moisture resistance, and has the advantages of good electrical insulation, good physical and chemical stability, non-toxic and odorless, etc., so it has become the preferred material in the current electronic packaging application field. However, the poor thermal conductivity of ordinary silicone potting glue makes it difficult to meet the demand for high heat dissipation of electronic components under the trend of intensive and miniaturized development. In addition, ordinary silicone potting glue has the disadvantage of being flammable. It cannot effectively achieve flame retardancy when electronic components, especially new energy vehicle battery supporting components, burn due to overheating or collision, which affects the overall fire safety. Therefore, effectively improving the thermal conductivity and flame retardancy of silicone potting glue has become a key research direction for the development of this type of material.

[0003] A more common method is to add the corresponding functional filler directly into the base polymer to improve the thermal conductivity and / or flame retardancy of the silicone potting compound. For example, patent CN102337033B first uses spherical aluminum oxide, boron nitride, and silicon carbide whiskers as thermal conductive fillers and mixes them into vinyl polydimethylsiloxane by vacuum kneading to prepare a base material, and then adds a crosslinking agent, an inhibitor, and a catalyst to the base material to prepare component A and component B, and then mixes them evenly to obtain an addition-type high thermal conductivity silicone electronic potting compound. Similarly, flame retardants such as aluminum hydroxide and magnesium hydroxide can also be mixed into silicone potting compounds to improve flame retardancy. However, the polarity of these inorganic fillers is large, resulting in poor compatibility with silicone components, resulting in reduced performance of silicone potting compounds.

[0004] To this end, many patents such as CN115491171B, CN115975596B, CN116694302B, etc. all propose to solve the compatibility problem between inorganic fillers and silicone components by adding coupling agents to the silicone potting glue components or modifying the fillers with coupling agents in advance. Although the use of coupling agents improves the compatibility of components, these thermally conductive and flame-retardant fillers still exist in the base polymer in a free state, and they lack groups that can undergo silyl hydroaddition reactions and cannot be organically chemically bonded with silicone rubber components. It is worth noting that the thermally conductive fillers and flame-retardant fillers in a free state will inevitably migrate in the silicone rubber after potting, and the large density of these free fillers also makes them easy to settle in the silicone rubber. With the extension of the use time of electronic packaging components, the migration and sedimentation of the fillers become more and more obvious, which will not only lead to the decline of the thermal conductivity and flame retardancy of the potting glue, but also cause the decline of its mechanical properties, and ultimately have a negative impact on the durability and safety of electronic products and equipment. Therefore, it is of great practical value and significance to prepare a modified filler capable of participating in the hydrosilylation reaction to invent a halogen-free flame-retardant organic silicone potting adhesive with good thermal conductivity. Summary of the invention

[0005] In view of the deficiencies in the above-mentioned prior art, the present invention provides a halogen-free flame-retardant silicone potting compound with good thermal conductivity, which not only has excellent thermal conductivity, flame retardancy and halogen-free safety, but also the added modified filler can participate in the hydrosilylation and organically combine with the three-dimensional elastic network structure of the silicone rubber to avoid its migration and sedimentation, so the potting compound exhibits good performance stability and durability. At the same time, the present invention also provides a preparation method of the silicone potting compound.

[0006] On the one hand, the present invention provides a halogen-free flame-retardant silicone potting adhesive with good thermal conductivity, comprising component A and component B;

[0007] The component A comprises, by weight, 40 to 60 parts of vinyl-terminated silicone oil, 32 to 48 parts of modified halogen-free flame retardant containing olefin groups, 120 to 180 parts of modified thermal conductive filler containing olefin groups, and 0.3 to 0.7 parts of catalyst;

[0008] The B component includes, by weight, 40 to 50 parts of vinyl-terminated silicone oil, 120 to 180 parts of modified thermal conductive filler containing olefin groups, 32 to 48 parts of modified halogen-free flame retardant containing olefin groups, 25 to 35 parts of cross-linking agent, and 0.1 to 0.5 parts of inhibitor;

[0009] The modified halogen-free flame retardant containing an olefin group has a structure as shown in the following formula (I):

[0010]

[0011] Where m is 0 or 1, n is 1 or 2, R 1 A hydrogen atom or a methyl group.

[0012] The modified thermally conductive filler containing olefin groups has a structure shown in the following formula (II):

[0013]

[0014] The DT inner core is a commercially available thermal conductive filler, the FA outer layer is an olefin-containing phenolamine co-deposited organic modified component, and p is 1, 2 or 3.

[0015] Preferably, the modified halogen-free flame retardant containing olefin groups is prepared according to the following steps:

[0016] S1: weigh an imidazole monomer containing an olefin group and add it to an appropriate amount of anhydrous ethanol, and stir it continuously at room temperature for 10 minutes to obtain a reaction solution with a certain molar concentration;

[0017] S2: weighing phenylphosphoric acid and its derivative monomers according to a preset molar ratio and adding them to the reaction solution obtained in step (1), first stirring and dispersing at room temperature for 10 minutes and then placing at a reaction temperature of 75 to 85° C. and continuously stirring under reflux for 2 to 4 hours;

[0018] S3: After the reaction is completed, the obtained solution is cooled to room temperature, and an equal volume of anhydrous ethanol is added for dilution, and then filtered, purified, and distilled under reduced pressure to obtain a viscous liquid, which is a modified halogen-free flame retardant containing olefin groups.

[0019] Preferably, in step S1, the imidazole monomer containing an olefin group is at least one of 1-allylimidazole, 1H-imidazole-1-carboxylic acid allyl ester, and 1H-imidazole-1-carboxylic acid-3-butylene ester, and the molar concentration thereof in the reaction solution is 1.0 to 1.5 mol / L;

[0020] In the step S2, the phenylphosphoric acid and its derivative monomers are at least one of phenylphosphoric acid and p-toluenephosphoric acid;

[0021] In the step S2, the molar ratio of phenylphosphoric acid and its derivative monomers to imidazole monomers containing olefin groups is 1:2.

[0022] Preferably, the modified thermally conductive filler containing olefin groups is prepared according to the following steps:

[0023] S1: Weigh the thermal conductive filler and add it to an appropriate amount of tris(hydroxymethyl)aminomethane-hydrochloric acid buffer solution, place it in an ice-water mixing bath at 0°C and ultrasonically disperse it for 0.5h to obtain a uniform dispersion with a certain concentration;

[0024] S2: according to the amount of thermally conductive filler, weigh the required dopamine hydrochloride according to the preset mass ratio and add it to the uniform dispersion obtained in step (1), and slowly stir it at room temperature for 5 minutes to dissolve and disperse the dopamine hydrochloride;

[0025] S3: according to the amount of dopamine hydrochloride, weigh the required olefin amine compound according to the preset molar ratio and add it to the mixed solution obtained in step S2, and then place it at room temperature and continue stirring for 6 to 24 hours to perform phenolamine co-precipitation modification reaction;

[0026] S4: After the reaction is completed, the crude product is filtered to obtain a crude product, which is then washed with deionized water and ethanol for multiple times to remove the residual unreacted products, and then vacuum dried at 60° C. for 48 hours to obtain a solid product, which is a modified thermal conductive filler containing olefin groups.

[0027] Preferably, in step S1, the thermally conductive filler includes one or more of aluminum oxide, zinc oxide, magnesium oxide, aluminum nitride, boron nitride, and silicon powder, and its dispersion concentration in tris (hydroxymethyl) aminomethane-hydrochloric acid buffer solution is 5-10 mg / mL;

[0028] In step S1, the pH value of the tris(hydroxymethyl)aminomethane-hydrochloric acid buffer solution is 8.5, and the concentration of tris(hydroxymethyl)aminomethane is 10 mmol / L;

[0029] In step S2, the preset mass ratio of the thermally conductive filler to dopamine hydrochloride is 1:(0.3-0.5), and in step S3, the preset molar ratio of dopamine hydrochloride to the olefin amine compound is 1:1;

[0030] In the step S3, the olefin amine compound is at least one of 3-butene-1-amine, 4-pentene-1-amine, and 5-hexene-1-amine.

[0031] Preferably, the vinyl-terminated silicone oil is a divinyl-terminated polydimethylsiloxane, wherein the mass percentage of the vinyl group is 0.4-2%, and the viscosity at 25°C is 200-1500 mPa·s;

[0032] The catalyst is a platinum catalyst, which is one or more of a platinum-vinylsiloxane complex, an alcohol-modified chloroplatinic acid, and a platinum-alkyne complex, and the platinum content per kilogram is 2000-5000 mg;

[0033] The crosslinking agent is hydrogen-containing silicone oil, wherein the mass percentage of active hydrogen is 0.4-1.2%, and the viscosity at 25°C is 20-100 mPa·s;

[0034] The inhibitor is an alkynol compound, which is one or any combination of 1-ethynyl-1-cyclohexanol, 1-ethynyl-1-cyclopentanol, 2-methyl-3-butyn-2-ol, and 3-methyl-1-pentyn-3-ol.

[0035] On the other hand, the present invention also provides a method for preparing the halogen-free flame-retardant silicone potting adhesive with good thermal conductivity as described above, and the specific operations are as follows:

[0036] Preparation of component A: According to the formula, the required weight portions of vinyl-terminated silicone oil, olefin-containing modified halogen-free flame retardant, olefin-containing modified thermal conductive filler and catalyst are weighed and added into a vacuum kneader for blending until the mixture is evenly dispersed to obtain component A;

[0037] Preparation of component B: according to the formula, the required weight portions of the vinyl-terminated silicone oil, the modified thermal conductive filler containing an olefin group, the modified halogen-free flame retardant containing an olefin group, the crosslinking agent and the inhibitor are added into a vacuum kneader for blending until the mixture is evenly dispersed to obtain component B;

[0038] When in use, the component A and the component B are mixed evenly according to a certain proportion, and vacuumed and degassed to obtain the organic silicone potting adhesive.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1. The modified thermally conductive filler containing olefin groups is added to the silicone potting compound of the present invention, which is prepared by modifying a conventional inorganic thermally conductive filler through a phenolamine co-precipitation reaction. On the one hand, the introduction of alkane olefins reduces the polarity of the inorganic thermally conductive filler and effectively improves its compatibility in the silicone component, and the molecular weights of dopamine and olefin amine compounds used in the phenolamine co-precipitation reaction are lower than those of the commonly used silane coupling agents, which helps to avoid the problem of excessive density of the thermally conductive filler due to modification. On the other hand, the olefin groups on the surface of the modified thermally conductive filler can participate in the hydrosilylation reaction, so that it is bonded to the silicone network and remains stable, effectively reducing its accidental migration and sedimentation, thereby improving the stability and durability of the thermal conductivity of the prepared silicone potting compound.

[0041] 2. The modified halogen-free flame retardant containing olefin groups is added to the silicone potting glue of the present invention, which is prepared by an environmentally safe, simple and convenient acid-base reaction. On the one hand, the flame retardant does not contain halogens or harmful heavy metals, does not produce harmful substances or irritating odors during the synthesis and sizing application process, and has excellent flame retardant properties. On the other hand, the olefin groups contained in the flame retardant can participate in the hydrosilylation reaction, thereby being bonded and stabilized in the silicone network, avoiding free migration, and ensuring the stability and durability of the flame retardant properties of the silicone potting glue. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is the infrared spectrum of the modified halogen-free flame retardant containing olefin groups prepared in Example 1;

[0043] Figure 2 This is a scanning electron microscope image of the modified thermally conductive filler containing olefin groups prepared in Example 1; DETAILED DESCRIPTION

[0044] In order to make the content, technical scheme, etc. of the present invention clearer, the present invention is further described in detail below in conjunction with preparation examples and embodiments. It should be understood that the specific preparation examples and embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention.

[0045] It should be noted that the raw materials and reagents used in the present invention can be purchased from conventional commercial channels, and there are no special restrictions on the purchasing manufacturers. Here, in order to specifically implement the preparation examples and embodiments described in the present invention, the raw materials selected exemplarily include: vinyl-terminated silicone oil (CX-352-500 of Chensi Technology), platinum catalyst (ACS-Pt of Sibao Technology), thermal conductive filler (GD-QL005C spherical alumina of Jinge New Materials Company), cross-linking agent (hydrogen-containing silicone oil, CX-350D of Chensi Technology), and inhibitor (ME75 of Maitu Company).

[0046] Example 1

[0047] S1: Preparation of modified halogen-free flame retardant containing olefin groups

[0048] First, 38.9 g of 1-allylimidazole (0.36 mol) was weighed and added into 300 mL of anhydrous ethanol, and the mixture was stirred at room temperature for 10 min to obtain a reaction solution with a molar concentration of 1.2 mol / L.

[0049] Then, 28.5 g of phenylphosphoric acid (0.18 mol) was weighed and added to the above reaction solution. The mixture was stirred at room temperature for 10 min and then placed at 80° C. for 3 h.

[0050] After the reaction is completed, the resulting solution is cooled to room temperature, and an equal volume of anhydrous ethanol is added for dilution, and then filtered, purified, and distilled under reduced pressure to obtain a viscous liquid, which is a modified halogen-free flame retardant containing an olefin group and has the following structure:

[0051]

[0052] The infrared spectrum of the flame retardant synthesized in this example is as follows Figure 1 As shown, at 1645cm -1The C=C stretching vibration peak of the allyl group can be identified at 833 cm -1 and 1081cm -1 The characteristic peaks at 1546 cm -1 The C=C stretching vibration peak of the imidazole ring can be identified at 2500-2200 cm -1 The characteristic absorption peak of protonated amine group appeared in the range of 1505 cm -1 The NH bending vibration peak in the protonated amine group can be identified. The appearance of the above infrared characteristic peaks proves that the flame retardant in this example is successfully synthesized.

[0053] S2: Preparation of modified thermally conductive fillers containing olefin groups

[0054] First, a tris(hydroxymethyl)aminomethane-hydrochloric acid buffer solution was prepared, that is, 0.606 g of tris(hydroxymethyl)aminomethane (5 mmol) was weighed and dissolved in 450 mL of deionized water, and its pH value was randomly adjusted to 8.5 with 0.1 mol / L dilute hydrochloric acid solution, and then the volume was made up to 500 mL with deionized water to obtain a buffer solution with a tris(hydroxymethyl)aminomethane concentration of 10 mmol / L and a pH of 8.5.

[0055] Then, 5 g of spherical alumina (GD-QL005C from Jinge New Materials Co., Ltd.) was weighed and added to 500 mL of the above buffer solution, and ultrasonically dispersed in an ice-water mixing bath at 0°C for 0.5 h to obtain a uniform dispersion with a concentration of 10 mg / mL. Then, 2 g of dopamine hydrochloride (10.55 mmol) was added thereto, and stirred at room temperature for 5 min to dissolve and disperse the dopamine hydrochloride.

[0056] Subsequently, 0.75 g of 3-butene-1-amine (10.55 mmol) was weighed and added to the mixed solution, and then stirred and reacted for 12 h at room temperature. After the reaction was completed, the crude product was filtered to obtain a crude product, which was then washed with deionized water and ethanol for multiple times to remove the residual unreacted product, and then vacuum dried at 60°C for 48 h to obtain a solid product, which is a modified thermal conductive filler containing olefin groups and has the following structure:

[0057]

[0058] The scanning electron microscope image of the modified thermal conductive filler prepared in this embodiment is as follows: Figure 2 As shown, it was found that the thermal conductive filler after phenolamine co-deposition modification still maintained a uniform and regular spherical structure, and its average particle size was measured to be 5.95 microns.

[0059] S3: Preparation of halogen-free and flame-retardant silicone potting compound with good thermal conductivity

[0060] Add 50 parts of vinyl-terminated silicone oil (CX-352-500 from Chensi Technology), 40 parts of the above-synthesized modified halogen-free flame retardant containing olefin groups, 150 parts of the above-prepared modified thermal conductive filler containing olefin groups and 0.5 parts of platinum catalyst (ACS-Pt from Sibao Technology) into a vacuum kneader and blend until the mixture is evenly dispersed to obtain component A;

[0061] Add 50 parts of vinyl-terminated silicone oil (CX-352-500 from Chensi Technology), 150 parts of the above-prepared modified thermal conductive filler containing olefin groups, 40 parts of the above-synthesized modified halogen-free flame retardant containing olefin groups, 30 parts of a cross-linking agent (hydrogen-containing silicone oil, CX-350D from Chensi Technology) and 0.3 parts of an inhibitor (ME75 from Momentive) into a vacuum kneader and blend until the mixture is evenly dispersed to obtain component B;

[0062] When in use, the component A and the component B are mixed evenly in a weight ratio of 1:1, and vacuum degassing is performed to obtain the organic silicone potting adhesive.

[0063] Example 2

[0064] Most of the steps of this embodiment are the same as those of embodiment 1, except that the reaction temperature for synthesizing the modified halogen-free flame retardant containing olefin groups in step S1 is 75° C. and the reaction time is 4 h; the rest are the same as those of embodiment 1.

[0065] Example 3

[0066] Most of the steps of this embodiment are the same as those of embodiment 1, except that the reaction temperature for synthesizing the modified halogen-free flame retardant containing olefin groups in step S1 is 85° C. and the reaction time is 2 h; the rest are the same as those of embodiment 1.

[0067] Example 4

[0068] Most of the steps of this embodiment are the same as those of embodiment 1, except that the reaction temperature for synthesizing the modified halogen-free flame retardant containing olefin groups in step S1 is 65° C. and the reaction time is 3 h; the rest are the same as those of embodiment 1.

[0069] Example 5

[0070] Most of the steps of this embodiment are the same as those of embodiment 1, except that the reaction temperature for synthesizing the modified halogen-free flame retardant containing olefin groups in step S1 is 95° C. and the reaction time is 3 h; the rest are the same as those of embodiment 1.

[0071] Example 6

[0072] Most of the steps of this embodiment are the same as those of Example 1, except that: when synthesizing the modified halogen-free flame retardant containing an olefin group in step S1, the imidazole monomer containing an olefin group is 1H-imidazole-1-carboxylic acid allyl ester, that is, during the implementation, 54.8 g of 1H-imidazole-1-carboxylic acid allyl ester (0.36 mol) is first weighed and added to 360 mL of anhydrous ethanol, and stirred at room temperature for 10 min to obtain a reaction solution with a molar concentration of 1.0 mol / L; the rest is the same as Example 1.

[0073] Example 7

[0074] Most of the steps of this embodiment are the same as those of Example 1, except that: in step S1, when synthesizing the modified halogen-free flame retardant containing an olefin group, the imidazole monomer containing an olefin group is 1H-imidazole-1-carboxylic acid-3-butene ester, that is, during the implementation, 59.8 g of 1H-imidazole-1-carboxylic acid-3-butene ester (0.36 mol) is first weighed and added to 240 mL of anhydrous ethanol, and stirred at room temperature for 10 min to obtain a reaction solution with a molar concentration of 1.5 mol / L; the rest is the same as Example 1.

[0075] Example 8

[0076] Most of the steps in this embodiment are the same as those in Example 1, except that: in step S1, when synthesizing the modified halogen-free flame retardant containing olefin groups, the phenyl phosphoric acid and its derivative monomers used are p-toluene phosphoric acid, that is, 31.0 g of p-toluene phosphoric acid (0.18 mol) is weighed and added to a solution containing imidazole monomers for reaction; the rest is the same as in Example 1.

[0077] Example 9

[0078] Most of the steps in this embodiment are the same as those in Embodiment 6, except that: in step S1, when synthesizing the modified halogen-free flame retardant containing olefin groups, the phenyl phosphate and its derivative monomers used are p-toluene phosphate, that is, 31.0 g of p-toluene phosphate (0.18 mol) is weighed and added to a solution containing imidazole monomers for reaction; the rest is the same as in Embodiment 6.

[0079] Example 10

[0080] Most of the steps of this embodiment are the same as those of Embodiment 7, except that: in step S1, when synthesizing the modified halogen-free flame retardant containing olefin groups, the phenyl phosphate and its derivative monomers used are p-toluene phosphate, that is, 31.0 g of p-toluene phosphate (0.18 mol) is weighed and added to a solution containing imidazole monomers for reaction; the rest is the same as Embodiment 7.

[0081] Embodiment 11

[0082] Most of the steps of this embodiment are the same as those of embodiment 1, except that the reaction time of the phenolamine co-deposition modification reaction in preparing the modified thermal conductive filler containing olefin groups in step S2 is 6 hours; the rest is the same as embodiment 1.

[0083] Example 12

[0084] Most of the steps of this embodiment are the same as those of embodiment 1, except that the reaction time of the phenolamine co-deposition modification reaction in preparing the modified thermal conductive filler containing olefin groups in step S2 is 24 hours; the rest is the same as embodiment 1.

[0085] Embodiment 13

[0086] Most of the steps in this embodiment are the same as those in Embodiment 1, except that the reaction time of the phenolamine co-deposition modification reaction in step S2 when preparing the modified thermal conductive filler containing olefin groups is 3 hours; the rest is the same as in Embodiment 1.

[0087] Embodiment 14

[0088] Most of the steps in this embodiment are the same as those in Embodiment 1, except that the reaction time of the phenolamine co-deposition modification reaction in step S2 for preparing the modified thermally conductive filler containing olefin groups is 48 hours; the rest is the same as in Embodiment 1.

[0089] Embodiment 15

[0090] Most of the steps in this embodiment are the same as those in Example 1, except that: when preparing the modified thermally conductive filler containing olefin groups in step S2, 4 g of spherical alumina is weighed and added to 800 mL of tris(hydroxymethyl)aminomethane-hydrochloric acid buffer solution, and a uniform dispersion with a concentration of 5 mg / mL is obtained by ultrasound; the rest is the same as Example 1.

[0091] Example 16

[0092] Most of the steps in this embodiment are the same as those in Example 1, except that: when preparing the modified thermally conductive filler containing olefin groups in step S2, 6.7 g of spherical alumina is weighed and added to 800 mL of tris(hydroxymethyl)aminomethane-hydrochloric acid buffer solution, and a uniform dispersion with a concentration of 8.4 mg / mL is obtained by ultrasound; the rest is the same as Example 1.

[0093] Embodiment 17

[0094] Most of the steps in this embodiment are the same as those in Example 1, except that: when preparing the modified thermally conductive filler containing olefin groups in step S2, 2 g of spherical alumina is weighed and added to 800 mL of tris(hydroxymethyl)aminomethane-hydrochloric acid buffer solution, and a uniform dispersion with a concentration of 2.5 mg / mL is obtained by ultrasound; the rest is the same as Example 1.

[0095] Embodiment 18

[0096] Most of the steps in this embodiment are the same as those in Example 1, except that: when preparing the modified thermally conductive filler containing olefin groups in step S2, 10 g of spherical alumina is weighed and added to 800 mL of tris(hydroxymethyl)aminomethane-hydrochloric acid buffer solution, and a uniform dispersion with a concentration of 12.5 mg / mL is obtained by ultrasound; the rest is the same as Example 1.

[0097] Embodiment 19

[0098] Most of the steps of this embodiment are the same as those of Example 1, except that in step S2, when preparing the modified thermally conductive filler containing olefin groups, the olefin amine compound used is 4-penten-1-amine, and its amount is 0.90 g (10.55 mmol); the rest is the same as Example 1.

[0099] Embodiment 20

[0100] Most of the steps of this embodiment are the same as those of Example 1, except that in step S2, when preparing the modified thermally conductive filler containing olefin groups, the olefin amine compound used is 5-hexen-1-amine, and its amount is 1.05 g (10.55 mmol); the rest is the same as Example 1.

[0101] Examples 21 to 32 and Comparative Examples 1 to 9

[0102] Most of the steps of Examples 21 to 32 and Comparative Examples 1 to 9 are the same as those of Example 1, except that in step S3, component A and component B are different, as shown in Table 1.

[0103] Table 1

[0104]

[0105]

[0106] Performance Test:

[0107] The halogen-free flame-retardant organic silicone potting adhesives with good thermal conductivity prepared in the above-mentioned embodiments and comparative examples were subjected to performance tests, including viscosity, thermal conductivity, limiting oxygen index and flame retardancy grade.

[0108] Among them, the viscosity test method refers to GB / T 2794-2013 standard; the thermal conductivity test method refers to ASTMD5470-2001 standard; the limiting oxygen index test method refers to GB / T 10707-2008 standard; the flame retardant grade test refers to UL94-2009 standard.

[0109] The test results of Example 1 and Examples 2 to 20 are shown in Table 2. The test results of Example 1, Examples 21 to 32 and Comparative Examples 1 to 9 are shown in Table 3.

[0110] Table 2

[0111]

[0112] From the data in Table 2, we can see that:

[0113] By comparing Example 1 with Example 2 and Example 3, it can be found that when the modified halogen-free flame retardant containing olefin groups is synthesized, within the required reaction temperature and time range, the reaction follows the "time-temperature equivalence" principle, the difference of the synthesized modified halogen-free flame retardant is small, and the various properties of the final product are stable. Compared with Example 4, the reaction temperature in Example 4 is lower than 75-85°C, resulting in a slow reaction rate and incomplete reaction within the specified time, and the residual phenylphosphoric acid and 1-allyl imidazole are reacted in accordance with 1:1 to obtain the product and 1-allyl imidazole. Although the viscosity of the final product decreases, which is beneficial to sizing, the phosphorus-nitrogen (PN) group that plays a flame retardant role is reduced, resulting in a decrease in the flame retardant performance of the product. Compared with Example 5, the reaction temperature in Example 5 is higher than 75-85°C, and the excessively high reaction temperature will cause the olefin double bonds to polymerize and produce chemical crosslinking. These crosslinking components not only cause the product viscosity to be too high, but also seriously affect the dispersion uniformity of the modified halogen-free flame retardant and the thermal conductive filler, resulting in a decrease in the flame retardant and thermal conductivity of the product.

[0114] By comparing Example 1 with Example 6 and Example 7, it can be found that when the modified halogen-free flame retardant is synthesized, the arbitrarily selected required imidazole monomer has no effect on the viscosity, thermal conductivity and flame retardant grade of the final product, indicating that the flame retardant prepared as required has stable and effective performance and is less affected by the concentration of imidazole monomer in the reaction system. The change in the limiting oxygen index of the product in Example 6 and Example 7 may be caused by the increase in the molecular weight of the imidazole monomer, which causes the increase in the molecular weight of the flame retardant. That is, when the number of flame retardant additions is fixed, the increase in the molecular weight of the flame retardant will cause its total molar content to decrease, resulting in a decrease in the content of phosphorus-nitrogen (PN) groups, and then a slight decrease in the limiting oxygen index.

[0115] By comparing Example 8, Example 9, and Example 10 with Example 1, Example 6, and Example 7, it can be found that the use of p-toluene phosphate instead of phenyl phosphate in the synthesis of the modified halogen-free flame retardant does not affect the product performance, reflecting the rationality and effectiveness of the scheme design and requirements. In addition, the difference in limiting oxygen index between Example 8, Example 9, and Example 10 is also caused by the change in the molecular weight of the imidazole monomer.

[0116] Comparing Example 1 with Example 11 and Example 12, it can be found that within the required phenolamine co-precipitation modification reaction time range (6 to 24 hours), the difference of the prepared modified thermally conductive filler is small, and the various properties of the final product are stable. Compared with Example 13, the reaction time in Example 13 is less than 6 hours, resulting in incomplete reaction and poor dispersion of the thermally conductive filler, easy agglomeration, and thus causing the thermal conductivity of the final product to decrease. Compared with Example 14, the reaction time in Example 14 exceeds 24 hours, and the specific gravity of the organic shell layer of the prepared modified thermally conductive filler increases. When a fixed number of portions are added, the actual content of the thermally conductive component decreases, thereby causing the thermal conductivity to decrease.

[0117] By comparing Example 1 with Example 15 and Example 16, it can be found that when the modified thermally conductive filler is prepared, the mass ratio of the thermally conductive filler to dopamine hydrochloride is within the range of 1: (0.3-0.5), and the dispersion concentration of the thermally conductive filler is within the range of 5-10 mg / mL. The difference in the prepared modified thermally conductive filler is small, and the various properties of the final product are stable. Compared with Example 17, the mass ratio of the thermally conductive filler to dopamine hydrochloride in Example 17 is lower than the range of 1: (0.3-0.5), and the thermal conductivity and viscosity of the obtained product decrease, which may be caused by the large proportion of the organic shell layer in the prepared modified thermally conductive filler. Compared with Example 18, the mass ratio of the thermally conductive filler to dopamine hydrochloride in Example 18 is higher than the range of 1: (0.3-0.5), and the surface modification of the thermally conductive filler is insufficient and easy to agglomerate, which not only causes the thermal conductivity of the final product to decrease, but also indirectly leads to a decrease in its flame retardant properties.

[0118] By comparing Example 1 with Example 19 and Example 20, it can be found that when preparing the modified thermally conductive filler, any selection within the required range of olefin amine compounds will not affect the performance of the modified thermally conductive filler and the final product, which illustrates the rationality and effectiveness of the design and requirements.

[0119] Table 3

[0120]

[0121] From the data in Table 3, we can see that:

[0122] By comparing Example 1 with Comparative Examples 3 to 5, it can be found that neither the A component nor the B component in Comparative Example 3 contains modified flame retardant and modified thermal conductive filler, and the thermal conductivity and flame retardant properties of the prepared silicone potting glue are poor; only modified thermal conductive filler is added to the A component and the B component of Comparative Example 4 without flame retardant, and the thermal conductivity of the prepared silicone flame retardant is good, but the flame retardant property is poor; only modified halogen-free flame retardant is added to the A component and the B component of Comparative Example 5 without thermal conductive filler, and the flame retardant property of the prepared silicone potting glue reaches the standard, but the thermal conductivity is poor. This shows that adding the modified halogen-free flame retardant containing olefin groups and the modified thermal conductive filler containing olefin groups required by this application to the A component and the B component can effectively improve the thermal conductivity, limiting oxygen index, and flame retardant grade of the silicone potting glue, so that it exhibits excellent thermal conductivity and flame retardant properties.

[0123] Comparison of Example 1, Examples 21 to 24 and Comparative Examples 1 and 2 shows that component A includes 40 to 60 parts of vinyl-terminated silicone oil, 32 to 48 parts of modified halogen-free flame retardant containing olefin groups, 120 to 180 parts of modified thermally conductive filler containing olefin groups, and 0.3 to 0.7 parts of catalyst; component B includes 40 to 50 parts of vinyl-terminated silicone oil, 120 to 180 parts of modified thermally conductive filler containing olefin groups, 32 to 48 parts of modified halogen-free flame retardant containing olefin groups, 25 to 35 parts of cross-linking agent, and 0.1 to 0.5 parts of inhibitor; the thermal conductivity, limiting oxygen index, and flame retardant grade of the silicone potting glue prepared in this way are all high, showing excellent thermal conductivity and flame retardant properties.

[0124] Example 1, Example 25 to 28 and Comparative Example 6 and Comparative Example 7 are compared. The modified halogen-free flame retardant containing olefin groups in the A component of Comparative Example 6 and Comparative Example 7 is not in the range of 32 to 48 parts, and the modified halogen-free flame retardant containing olefin groups in the B component is not in the range of 32 to 48 parts. Among them, the modified halogen-free flame retardant in Comparative Example 6 is lower than the range, and the prepared silicone potting glue has a low limiting oxygen index and a decreased flame retardant performance. The modified halogen-free flame retardant in Comparative Example 7 is higher than the range. Although the flame retardant performance of the prepared silicone potting glue remains good, the thermal conductivity is significantly reduced, indicating that adding too much modified halogen-free flame retardant will cause the proportion of modified thermal conductive fillers to decrease and affect thermal conductivity, and at the same time increase the cost. This shows that when the modified halogen-free flame retardant containing olefin groups in components A and B meets the range of parts specified in this application, the prepared silicone potting glue has good thermal conductivity and flame retardant properties.

[0125] Example 1, Examples 29 to 32 and Comparative Examples 8 and 9 are compared. The modified thermally conductive filler containing olefin groups in component A of Comparative Examples 8 and 9 is not in the range of 120 to 180 parts, and the modified thermally conductive filler containing olefin groups in component B is not in the range of 120 to 180 parts. Among them, the modified thermally conductive filler in Comparative Example 8 is lower than the range, and the thermal conductivity of the prepared silicone potting glue is low, and the thermal conductivity performance is reduced. The number of modified thermally conductive fillers in Comparative Example 9 is higher than the range, and the viscosity of the prepared silicone potting glue increases, and the thermal conductivity and flame retardant properties are reduced, indicating that adding too much modified thermally conductive filler will cause the dispersion uniformity to decrease and affect the thermal conductivity, and cause the proportion of flame retardants to decrease and affect the flame retardancy, and at the same time increase the cost. This shows that when the modified thermally conductive fillers containing olefin groups in components A and B meet the range of parts specified in this application, the prepared silicone potting glue has good thermal conductivity and flame retardant properties.

[0126] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that the technical solutions described in the above embodiments can still be modified, or some of the technical features can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention.

Claims

1. A halogen-free flame-retardant silicone potting adhesive with good thermal conductivity, characterized in that: It includes component A and component B; The component A comprises, by weight, 40 to 60 parts of vinyl-terminated silicone oil, 32 to 48 parts of modified halogen-free flame retardant containing olefin groups, 120 to 180 parts of modified thermal conductive filler containing olefin groups, and 0.3 to 0.7 parts of catalyst; The B component includes, by weight, 40 to 50 parts of vinyl-terminated silicone oil, 120 to 180 parts of modified thermal conductive filler containing olefin groups, 32 to 48 parts of modified halogen-free flame retardant containing olefin groups, 25 to 35 parts of cross-linking agent, and 0.1 to 0.5 parts of inhibitor; The modified halogen-free flame retardant containing an olefin group has a structure as shown in the following formula (I): Wherein, m is 0 or 1, n is 1 or 2, and R1 is a hydrogen atom or a methyl group. The modified thermally conductive filler containing olefin groups has a structure shown in the following formula (II): The DT inner core is a commercially available thermal conductive filler, the FA outer layer is an olefin-containing phenolamine co-deposited organic modified component, and p is 1, 2 or 3.

2. The halogen-free, flame-retardant silicone potting adhesive with good thermal conductivity according to claim 1, characterized in that: The modified halogen-free flame retardant containing olefin groups is prepared according to the following steps: S1: weigh an imidazole monomer containing an olefin group and add it to an appropriate amount of anhydrous ethanol, and stir it continuously at room temperature for 10 minutes to obtain a reaction solution with a certain molar concentration; S2: weighing phenylphosphoric acid and its derivative monomers according to a preset molar ratio and adding them to the reaction solution obtained in step (1), first stirring and dispersing at room temperature for 10 minutes and then placing at a reaction temperature of 75 to 85° C. and continuously stirring under reflux for 2 to 4 hours; S3: After the reaction is completed, the obtained solution is cooled to room temperature, and an equal volume of anhydrous ethanol is added for dilution, and then filtered, purified, and distilled under reduced pressure to obtain a viscous liquid, which is a modified halogen-free flame retardant containing olefin groups.

3. The halogen-free, flame-retardant organic silicone potting adhesive with good thermal conductivity according to claim 2, characterized in that: In the step S1, the imidazole monomer containing an olefin group is at least one of 1-allylimidazole, 1H-imidazole-1-carboxylic acid allyl ester, and 1H-imidazole-1-carboxylic acid-3-butylene ester, and the molar concentration thereof in the reaction solution is 1.0 to 1.5 mol / L; In the step S2, the phenylphosphoric acid and its derivative monomers are at least one of phenylphosphoric acid and p-toluenephosphoric acid; In the step S2, the molar ratio of phenylphosphoric acid and its derivative monomers to imidazole monomers containing olefin groups is 1:

2.

4. The halogen-free, flame-retardant organic silicone potting adhesive with good thermal conductivity according to claim 1, characterized in that: The modified thermally conductive filler containing olefin groups is prepared according to the following steps: S1: Weigh the thermal conductive filler and add it to an appropriate amount of tris(hydroxymethyl)aminomethane-hydrochloric acid buffer solution, place it in an ice-water mixing bath at 0°C and ultrasonically disperse it for 0.5h to obtain a uniform dispersion with a certain concentration; S2: according to the amount of thermally conductive filler, weigh the required dopamine hydrochloride according to the preset mass ratio and add it to the uniform dispersion obtained in step (1), and slowly stir it at room temperature for 5 minutes to dissolve and disperse the dopamine hydrochloride; S3: according to the amount of dopamine hydrochloride, weigh the required olefin amine compound according to the preset molar ratio and add it to the mixed solution obtained in step S2, and then place it at room temperature and continue stirring for 6 to 24 hours to perform phenolamine co-precipitation modification reaction; S4: After the reaction is completed, the crude product is filtered to obtain a crude product, which is then washed with deionized water and ethanol for multiple times to remove the residual unreacted products, and then vacuum dried at 60° C. for 48 hours to obtain a solid product, which is a modified thermal conductive filler containing olefin groups.

5. The halogen-free, flame-retardant organic silicone potting adhesive with good thermal conductivity according to claim 4, characterized in that: In step S1, the thermal conductive filler includes one or more of aluminum oxide, zinc oxide, magnesium oxide, aluminum nitride, boron nitride, and silicon powder, and its dispersion concentration in tris (hydroxymethyl) aminomethane-hydrochloric acid buffer solution is 5-10 mg / mL; In step S1, the pH value of the tris(hydroxymethyl)aminomethane-hydrochloric acid buffer solution is 8.5, and the concentration of tris(hydroxymethyl)aminomethane is 10 mmol / L; In step S2, the preset mass ratio of the thermally conductive filler to dopamine hydrochloride is 1:(0.3-0.5), and in step S3, the preset molar ratio of dopamine hydrochloride to the olefin amine compound is 1:1; In the step S3, the olefin amine compound is at least one of 3-butene-1-amine, 4-pentene-1-amine, and 5-hexene-1-amine.

6. The halogen-free, flame-retardant organic silicone potting adhesive with good thermal conductivity according to claim 1, characterized in that: The vinyl-terminated silicone oil is a divinyl-terminated polydimethylsiloxane, wherein the mass percentage of the vinyl group is 0.4-2%, and the viscosity at 25°C is 200-1500 mPa·s; The catalyst is a platinum catalyst, which is one or more of a platinum-vinylsiloxane complex, an alcohol-modified chloroplatinic acid, and a platinum-alkyne complex, and the platinum content per kilogram is 2000-5000 mg; The crosslinking agent is hydrogen-containing silicone oil, wherein the mass percentage of active hydrogen is 0.4-1.2%, and the viscosity at 25°C is 20-100 mPa·s; The inhibitor is an alkynol compound, which is one or any combination of 1-ethynyl-1-cyclohexanol, 1-ethynyl-1-cyclopentanol, 2-methyl-3-butyn-2-ol, and 3-methyl-1-pentyn-3-ol.

7. A method for preparing the halogen-free flame-retardant organic silicone potting adhesive with good thermal conductivity as claimed in any one of claims 1 to 6, characterized in that: The specific operations are as follows: Preparation of component A: According to the formula, the required weight portions of vinyl-terminated silicone oil, olefin-containing modified halogen-free flame retardant, olefin-containing modified thermal conductive filler and catalyst are weighed and added into a vacuum kneader for blending until the mixture is evenly dispersed to obtain component A; Preparation of component B: according to the formula, the required weight portions of the vinyl-terminated silicone oil, the modified thermal conductive filler containing an olefin group, the modified halogen-free flame retardant containing an olefin group, the crosslinking agent and the inhibitor are added into a vacuum kneader for blending until the mixture is evenly dispersed to obtain component B; When in use, the component A and the component B are mixed evenly according to a certain proportion, and vacuumed and degassed to obtain the organic silicone potting adhesive.

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