A flame retardant silicone rubber material and its preparation method and application

Abstract

The present invention provides a flame retardant silicone rubber material and its preparation method and application, and relates to the technical field of polymer material processing. The flame retardant silicone rubber material is prepared by silicone rubber, filler, phosphorus-boron synergistic flame retardant, and vulcanizing agent, wherein the phosphorus-boron synergistic flame retardant is obtained by reacting 3-hydroxyphenylboronic acid methyliminodiacetate with bis(diethylamino)phosphoryl chloride and vinyl triacetoxysilane. In the present invention, the phenolic hydroxyl group in the molecular chain of 3-hydroxyphenylboronic acid methyliminodiacetate is highly reactive, and reacts with bis(diethylamino)phosphoryl chloride and vinyl triacetoxysilane to generate a phosphorus-boron synergistic flame retardant BPDM, such flame retardant does not contain halogen groups, and has good compatibility with silicone rubber, while improving the mechanical properties of silicone rubber, it can also improve the charring amount of silicone rubber during combustion, better suppress the generation of smoke, thereby achieving excellent flame retardant effect.

Description

Technical Field

[0001] The invention relates to the technical field of polymer material processing, and in particular to a flame retardant silicone rubber material and a preparation method and application thereof. Background Art

[0002] With the continuous increase in urban population density and the sustainable development of the electric power industry, the quality of life of the people has been continuously improved, and at the same time, higher requirements have been placed on the transmission capacity of the power cable transmission system. As an essential device for connecting the cable body and power transmission, cable accessories must not only meet the voltage level of 220KV and below, but also meet higher voltage levels.

[0003] The development of high-voltage cable accessories is a relatively complicated process. At present, the materials used in accessories are mainly EPDM rubber and silicone rubber. Due to its high hardness, EPDM rubber has certain difficulties in the installation process of accessories. Silicone rubber's excellent resistance to high and low temperatures, ozone, tearing, weathering and good insulation can largely meet the safety and reliability requirements of high-voltage cables for accessories, and it is easy to cross-link and cure when encountering high temperature or short circuit without melting. In view of the convenience of installation and maintenance of high-voltage cable accessories and the safety of operation, silicone rubber is also increasingly used in high-voltage cable accessories, such as 10-35KV line network detachable shielded cable accessories, cold shrink accessories, prefabricated stress cones and external insulation sleeves.

[0004] Since the fire resistance of silicone rubber cable accessories is average and accompanied by severe molten droplets, it is possible to ignite other surrounding materials while burning, thus limiting its further application in terms of high thermal stability and significant flame retardancy. Therefore, how to improve the flame retardancy of high-voltage cable accessories is still one of the problems that need to be solved. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a flame retardant silicone rubber material and a preparation method and application thereof, which can effectively improve the flame retardant properties of the flame retardant silicone rubber material while maintaining good physical and mechanical properties, so that it can be effectively used in the preparation of high-voltage cable accessory materials.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented through the following technical solutions:

[0007] A flame retardant silicone rubber material is made of the following raw materials in parts by weight: 100-110 parts of silicone rubber, 20-40 parts of filler, 10-45 parts of phosphorus-boron synergistic flame retardant, and 2-7 parts of vulcanizing agent; wherein the phosphorus-boron synergistic flame retardant is obtained by compounding 3-hydroxyphenylboronic acid methyliminodiacetate, bis(diethylamino)phosphoryl chloride and vinyl triacetoxysilane in a mass ratio of 1.1-3.5:1:0.2-0.6.

[0008] Preferably, the silicone rubber is methyl vinyl silicone rubber; the filler is white carbon black; and the vulcanizing agent is di-25.

[0009] The preparation method of the flame retardant silicone rubber material comprises the following steps:

[0010] (1) adding dimethylformamide dropwise to 3-hydroxyphenylboronic acid methyliminodiacetate and stirring to dissolve the mixture to obtain a solution for later use;

[0011] (2) adding bis(diethylamino)phosphoryl chloride to the above solution, mixing and reacting, filtering, washing, and drying to obtain a dry product for later use;

[0012] (3) adding vinyl triacetoxysilane to the dried product, stirring and dispersing the mixture to obtain a phosphorus-boron synergistic flame retardant;

[0013] (4) placing the silicone rubber on an open mixing mill and starting to plasticize, and after the plasticizing is completed, adding fillers and phosphorus-boron synergistic flame retardants and mixing to obtain a mixed rubber;

[0014] (5) Adding a vulcanizing agent into the mixed rubber, mixing and sheeting, and then vulcanizing the film to obtain a flame retardant silicone rubber material.

[0015] Preferably, the temperature for stirring and dissolving in step (1) is 30° C., and the stirring time is 15-20 min.

[0016] Preferably, the temperature of the mixing reaction in step (2) is 40-55°C, the reaction time is 4-7h, and the drying method is drying in an oven at 105°C for 2h.

[0017] Preferably, the speed of stirring and dispersing in step (3) is 1000-1500 r / min, and the stirring time is 10-15 s.

[0018] Preferably, in step (4), the mixing temperature of the open mixer is set to 30-40° C., and the mixing roller distance is adjusted to 4-5 mm.

[0019] Preferably, in step (4), the filler and the phosphorus-boron synergistic flame retardant are added in 3-6 times, with the interval between each addition being 2 to 8 minutes.

[0020] Preferably, in step (5), the lower sheet is mixed by adjusting the roller distance to 2-3 mm, mixing the lower sheet in a triangular bag manner, and the vulcanization temperature is 170-180° C., the vulcanization pressure is 10-15 MPa, and the vulcanization time is 3-10 min.

[0021] The flame retardant silicone rubber material obtained above can be used to prepare cable accessory materials.

[0022] The present invention provides a flame retardant silicone rubber material and a preparation method and application thereof, which have the following advantages over the prior art:

[0023] (1) The phenolic hydroxyl group in the 3-hydroxyphenylboronic acid methyliminodiacetate of the present invention has high reactivity and can react with bis(diethylamino)phosphoryl chloride under certain conditions. The reaction product of the two is combined with vinyl triacetoxysilane to generate a phosphorus-boron integrated synergistic BPDM flame retardant. This type of flame retardant has extremely high flame retardant efficiency in silicone rubber. Moreover, the BPDM flame retardant will dehydrate into a ring after being heated, and it is easy to form a boron-oxygen six-membered ring network structure. This structure will form more carbon layers containing BOC bonds after further combustion. The formation of such carbides can block the transfer of heat and prevent the silicone rubber from being further oxidized.

[0024] (2) The BPDM flame retardant containing phosphorus atoms in the present invention will produce phosphoric acid during the heating process. Phosphoric acid can not only condense with CO bonds to form polyphosphoric acid crosslinks, but also form stable BPO4 with boron at high temperatures. The dense protective carbon layer formed by the joint catalysis of the two can minimize the generation of gas phase products and carbonyl compounds.

[0025] (3) The BPDM prepared by the present invention is a low-molecular organic compound containing boron, phosphorus and silicon, which can react with the Si-OH group on the surface of silica, improve the affinity between silicone rubber and filler particles, reduce the formation of hydrogen bonds, prevent the occurrence of continuous structuring, promote the dispersion of silica in the rubber, and significantly improve the mixing process and storage stability;

[0026] (4) The presence of vinyl active groups in the BPDM prepared in the present invention enables a good interfacial bonding force to be generated between the BPDM flame retardant and the silicone rubber after the two are blended, and the two are tightly combined. Good compatibility will inevitably promote better dispersion of the flame retardant in the silicone rubber, thereby further improving the physical and mechanical properties such as tensile strength while improving the flame retardant performance;

[0027] (5) The synergistic flame retardant system composed of phosphorus and boron elements in the present invention can significantly improve its flame retardant efficiency in silicone rubber. A lower amount of flame retardant added can enable silicone rubber to achieve ideal flame retardant properties while ensuring the stability of mechanical properties.

[0028] (6) The flame retardant silicone rubber obtained by the present invention has good flame retardant properties and mechanical properties and can be used to prepare cable accessory materials, such as high-pressure cold shrinkage preforms. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The raw materials used in the following examples, unless otherwise specified, can be obtained from conventional commercial sources; the processes used, unless otherwise specified, are conventional processes in the art; the operating temperatures used, unless otherwise specified, are room temperature (20±5° C.).

[0031] Embodiment 1:

[0032] The flame retardant silicone rubber material in this embodiment includes the following raw materials in parts by weight: 100 parts of methyl vinyl silicone rubber, 40 parts of precipitated silica, 15 parts of 3-hydroxyphenylboronic acid methyliminodiacetate, 7.7 parts of bis(diethylamino)phosphoryl chloride, 2.3 parts of vinyl triacetoxysilane, and 5 parts of bis(diethylamino)dichloroethane.

[0033] Among them, the number average molecular weight of methyl vinyl silicone rubber is 560,000, the vinyl content is 0.25%, and the volatile matter is ≤3.0%; the purity of 3-hydroxyphenylboronic acid methyliminodiacetate is ≥96%, and the acidity coefficient is 3.7-4.1pKa; the purity of bis(diethylamino)phosphoryl chloride is ≥95%, and the water content is ≤0.5%; the effective substance content of vinyl triacetoxysilane is ≥95%;

[0034] The specific preparation method of the flame retardant silicone rubber material is as follows:

[0035] (1) Add the formulated amount of 3-hydroxyphenylboronic acid methyliminodiacetate into a three-necked flask, drop dimethylformamide into it and stir to dissolve it. The stirring and dissolving temperature is controlled at 30° C. and the stirring time is 18 min.

[0036] (2) gradually adding the corresponding bis(diethylamino)phosphoryl chloride, the mixed reaction temperature is 50°C, the reaction time is 6 hours, after the reaction is completed, the reaction product is filtered, washed with distilled water, and placed in an oven at 105°C to dry for 2 hours.

[0037] (3) The reaction product was placed in an F-type high-speed disperser, and a formulated amount of vinyl triacetoxysilane was added. The stirring speed was set to 1200 r / min, and after stirring for 12 seconds, a phosphorus-boron synergistic flame retardant BPDM was obtained.

[0038] (4) placing the formulated amount of methyl vinyl silicone rubber on an open mill with a roller temperature of 35° C., adjusting the mixing roller distance to 4.0 mm, and starting plastication;

[0039] (5) After the plastication is completed, add the formulated amount of white carbon black and BPDM into the silicone rubber in 5 times with an interval of 8 minutes;

[0040] (6) Adding dipentadienyl vulcanizing agent to the above-mentioned mixed rubber, adjusting the roller distance to 3 mm, and mixing and sheeting in a triangular bag manner;

[0041] (7) The film obtained after the mixing is vulcanized at a vulcanization temperature of 170° C., a vulcanization pressure of 12 MPa, and a vulcanization time of 7 min to obtain a flame retardant silicone rubber material.

[0042] Embodiment 2:

[0043] The flame retardant silicone rubber material in this embodiment includes the following raw materials in parts by weight: 80 parts of methyl vinyl silicone rubber with a number average molecular weight of 520,000, 20 parts of methyl vinyl silicone rubber with a number average molecular weight of 630,000, 35 parts of fumed silica, 25.6 parts of 3-hydroxyphenylboronic acid methyliminodiacetate, 10.3 parts of bis(diethylamino)phosphoryl chloride, 4.1 parts of vinyl triacetoxysilane, and 4.5 parts of bis(diethylamino)phosphoryl chloride.

[0044] Among them, the methyl vinyl silicone rubber with a number average molecular weight of 520,000, a vinyl content of 0.21%, and a volatile matter of ≤3.0%; the methyl vinyl silicone rubber with a number average molecular weight of 630,000, a vinyl content of 0.28%, and a volatile matter of ≤3.0%; the purity of 3-hydroxyphenylboronic acid methyliminodiacetate is ≥96%, and the acidity coefficient is 3.7-4.1pKa; the purity of bis(diethylamino)phosphoryl chloride is ≥95%, and the water content is ≤0.5%; the effective substance content of vinyl triacetoxysilane is ≥95%;

[0045] The specific preparation method of the flame retardant silicone rubber material is as follows:

[0046] (1) Add the formulated amount of 3-hydroxyphenylboronic acid methyliminodiacetate into a three-necked flask, drop dimethylformamide into it and stir to dissolve it. The stirring and dissolving temperature is controlled at 30° C. and the stirring time is 18 min.

[0047] (2) gradually adding the corresponding bis(diethylamino)phosphoryl chloride, the mixed reaction temperature is 50°C, the reaction time is 6 hours, after the reaction is completed, the reaction product is filtered, washed with distilled water, and placed in an oven at 105°C to dry for 2 hours.

[0048] (3) The reaction product was placed in an F-type high-speed disperser, and a formulated amount of vinyl triacetoxysilane was added. The stirring speed was set to 1200 r / min, and after stirring for 12 seconds, a phosphorus-boron synergistic flame retardant BPDM was obtained.

[0049] (4) placing the formulated amount of methyl vinyl silicone rubber on an open mill with a roller temperature of 35° C., adjusting the mixing roller distance to 4.0 mm, and starting plastication;

[0050] (5) After the plastication is completed, the formulated amount of white carbon black and BPDM is added to the silicone rubber in 5 times, and the addition interval is 8 minutes;

[0051] (6) Adding dipentadienyl vulcanizing agent to the above-mentioned mixed rubber, adjusting the roller distance to 3 mm, and mixing and sheeting in a triangular bag manner;

[0052] (7) The film obtained after the mixing is vulcanized at a vulcanization temperature of 170° C., a vulcanization pressure of 12 MPa, and a vulcanization time of 7 min to obtain a flame retardant silicone rubber material.

[0053] Embodiment 3:

[0054] The flame retardant silicone rubber material in this embodiment includes the following raw materials in parts by weight: 40 parts of methyl vinyl silicone rubber with a number average molecular weight of 520,000, 60 parts of methyl vinyl silicone rubber with a number average molecular weight of 630,000, 20 parts of precipitated silica, 25 parts of fumed silica, 23.4 parts of 3-hydroxyphenylboronic acid methyliminodiacetate, 7.8 parts of bis(diethylamino)phosphoryl chloride, 3.8 parts of vinyl triacetoxysilane, and 6 parts of bis(diethylamino)silane.

[0055] In the cable accessory material formula of this embodiment, the methyl vinyl silicone rubber with a number average molecular weight of 520,000, a vinyl content of 0.21%, and a volatile matter of ≤3.0%; the methyl vinyl silicone rubber with a number average molecular weight of 630,000, a vinyl content of 0.28%, and a volatile matter of ≤3.0%; the purity of 3-hydroxyphenylboronic acid methyliminodiacetate is ≥96%, and the acidity coefficient is 3.7-4.1pKa; the purity of bis(diethylamino)phosphoryl chloride is ≥95%, and the moisture content is ≤0.5%; the effective substance content of vinyl triacetoxysilane is ≥95%;

[0056] The specific preparation method of the flame retardant silicone rubber material is as follows:

[0057] (1) Add the formulated amount of 3-hydroxyphenylboronic acid methyliminodiacetate into a three-necked flask, drop dimethylformamide into it and stir to dissolve it. The stirring and dissolving temperature is controlled at 30° C. and the stirring time is 18 min.

[0058] (2) gradually adding the corresponding bis(diethylamino)phosphoryl chloride, the mixed reaction temperature is 50°C, the reaction time is 6 hours, after the reaction is completed, the reaction product is filtered, washed with distilled water, and placed in an oven at 105°C to dry for 2 hours.

[0059] (3) The reaction product was placed in an F-type high-speed disperser, and a formulated amount of vinyl triacetoxysilane was added. The stirring speed was set to 1200 r / min, and after stirring for 12 seconds, a phosphorus-boron synergistic flame retardant BPDM was obtained.

[0060] (4) placing the formulated amount of methyl vinyl silicone rubber on an open mill with a roller temperature of 35° C., adjusting the mixing roller distance to 4.0 mm, and starting plastication;

[0061] (5) After the plastication is completed, the formulated amount of white carbon black and BPDM is added to the silicone rubber in 5 times, and the addition interval is 8 minutes;

[0062] (6) Adding dipentadienyl vulcanizing agent to the above-mentioned mixed rubber, adjusting the roller distance to 3 mm, and mixing and sheeting in a triangular bag manner;

[0063] (7) The film obtained after the mixing is vulcanized at a vulcanization temperature of 170° C., a vulcanization pressure of 12 MPa, and a vulcanization time of 7 min to obtain a flame retardant silicone rubber material.

[0064] Comparative Example 1:

[0065] The difference between this comparative example and Example 1 is that 3-hydroxyphenylboronic acid methyliminodiacetate, bis(diethylamino)phosphoryl chloride and vinyltriacetoxysilane are omitted; the flame-retardant silicone rubber cable accessory material in this comparative example includes the following raw materials in parts by weight: 100 parts of methyl vinyl silicone rubber, 40 parts of precipitated silica, and 5 parts of di-25.

[0066] In the rubber material formula of this comparative example, the number average molecular weight of the methyl vinyl silicone rubber is 560,000, the vinyl content is 0.25%, and the volatile matter is ≤3.0%;

[0067] The specific preparation method of flame retardant silicone rubber is as follows:

[0068] (1) Place the formulated amount of methyl vinyl silicone rubber on an open mill with a roller temperature of 35° C., adjust the mixing roller distance to 4.0 mm, and start plasticating;

[0069] (2) After the plastication is completed, add the formulated amount of white carbon black into the silicone rubber in 5 times, with an interval of 8 minutes;

[0070] (3) Adding dipentadienyl vulcanizing agent to the above-mentioned mixed rubber, adjusting the roller distance to 3 mm, and mixing and sheeting in a triangular bag manner;

[0071] (4) The film obtained after the mixing is vulcanized at a vulcanization temperature of 170° C., a vulcanization pressure of 12 MPa, and a vulcanization time of 7 min to obtain a flame retardant silicone rubber material.

[0072] Comparative Example 2:

[0073] The main difference between this comparative example and Example 2 is that 10.3 parts of bis(diethylamino)phosphoryl chloride and 4.1 parts of vinyl triacetoxysilane are replaced by 3-hydroxyphenylboronic acid methyliminodiacetate in equal amounts. The flame retardant silicone rubber material in this comparative example includes the following raw materials in parts by weight: 80 parts of methylvinyl silicone rubber with a number average molecular weight of 520,000, 20 parts of methylvinyl silicone rubber with a number average molecular weight of 630,000, 35 parts of fumed silica, 40 parts of 3-hydroxyphenylboronic acid methyliminodiacetate, and 4.5 parts of bis(250).

[0074] In the cable accessory material formula of this comparative example, the methyl vinyl silicone rubber has a number average molecular weight of 520,000, a vinyl content of 0.21%, and a volatile matter of ≤3.0%; the methyl vinyl silicone rubber has a number average molecular weight of 630,000, a vinyl content of 0.28%, and a volatile matter of ≤3.0%; the purity of 3-hydroxyphenylboronic acid methyliminodiacetate is ≥96%, and the acidity coefficient is 3.7-4.1pKa;

[0075] The specific preparation method of flame retardant silicone rubber is as follows:

[0076] (1) Place the formulated amount of methyl vinyl silicone rubber on an open mill with a roller temperature of 35° C., adjust the mixing roller distance to 4.0 mm, and start plasticating;

[0077] (2) After the plasticizing is completed, the formulated amount of white carbon black and 3-hydroxyphenylboronic acid methyliminodiacetate are added to the silicone rubber in 5 times, with an interval of 8 minutes;

[0078] (6) Adding dipentadienyl vulcanizing agent to the above-mentioned mixed rubber, adjusting the roller distance to 3 mm, and mixing and sheeting in a triangular bag manner;

[0079] (7) The film obtained after the mixing is vulcanized at a vulcanization temperature of 170° C., a vulcanization pressure of 12 MPa, and a vulcanization time of 7 min to obtain a flame retardant silicone rubber material.

[0080] Comparative Example 3:

[0081] The main difference between this comparative example and Example 2 is that 25.6 parts of 3-hydroxyphenylboronic acid methyliminodiacetate and 4.1 parts of vinyl triacetoxysilane are replaced by bis(diethylamino)phosphoryl chloride in equal amounts. The flame-retardant silicone rubber cable accessory material in this comparative example includes the following raw materials in parts by weight: 80 parts of methylvinyl silicone rubber with a number average molecular weight of 520,000, 20 parts of methylvinyl silicone rubber with a number average molecular weight of 630,000, 35 parts of fumed silica, 40 parts of bis(diethylamino)phosphoryl chloride, and 4.5 parts of di-25.

[0082] In the cable accessory material formula of this comparative example, the methyl vinyl silicone rubber with a number average molecular weight of 520,000, a vinyl content of 0.21%, and a volatile matter of ≤3.0%; the methyl vinyl silicone rubber with a number average molecular weight of 630,000, a vinyl content of 0.28%, and a volatile matter of ≤3.0%; the purity of bis(diethylamino)phosphoryl chloride is ≥95%, and the moisture content is ≤0.5%;

[0083] The specific preparation method of flame retardant silicone rubber material is as follows:

[0084] (1) Place the formulated amount of methyl vinyl silicone rubber on an open mill with a roller temperature of 35° C., adjust the mixing roller distance to 4.0 mm, and start plasticating;

[0085] (2) After the plasticization is completed, the formulated amount of white carbon black and bis(diethylamino)phosphoryl chloride are added to the silicone rubber in 5 times with an interval of 8 minutes;

[0086] (6) Adding dipentadienyl vulcanizing agent to the above-mentioned mixed rubber, adjusting the roller distance to 3 mm, and mixing and sheeting in a triangular bag manner;

[0087] (7) The film obtained after the mixing is vulcanized at a vulcanization temperature of 170° C., a vulcanization pressure of 12 MPa, and a vulcanization time of 7 min to obtain a flame retardant silicone rubber material.

[0088] Comparative Example 4:

[0089] The main difference between this comparative example and Example 3 is that 3.8 parts of vinyl triacetoxysilane are replaced by 3-hydroxyphenylboronic acid methyliminodiacetate and bis(diethylamino)phosphoryl chloride in an equal amount of 3:1. The flame-retardant silicone rubber cable accessory material in this comparative example includes the following raw materials in parts by weight: 40 parts of methylvinyl silicone rubber with a number average molecular weight of 520,000, 60 parts of methylvinyl silicone rubber with a number average molecular weight of 630,000, 20 parts of precipitated silica, 25 parts of fumed silica, 26.3 parts of 3-hydroxyphenylboronic acid methyliminodiacetate, 8.7 parts of bis(diethylamino)phosphoryl chloride, and 6 parts of di-25.

[0090] In the cable accessory material formula of this comparative example, the methyl vinyl silicone rubber with a number average molecular weight of 520,000, a vinyl content of 0.21%, and a volatile matter of ≤3.0%; the methyl vinyl silicone rubber with a number average molecular weight of 630,000, a vinyl content of 0.28%, and a volatile matter of ≤3.0%; the purity of 3-hydroxyphenylboronic acid methyliminodiacetate is ≥96%, and the acidity coefficient is 3.7-4.1pKa; the purity of bis(diethylamino)phosphoryl chloride is ≥95%, and the moisture content is ≤0.5%;

[0091] The specific preparation method of flame retardant silicone rubber material is as follows:

[0092] (1) Add the formulated amount of 3-hydroxyphenylboronic acid methyliminodiacetate into a three-necked flask, drop dimethylformamide into it and stir to dissolve it. The stirring and dissolving temperature is controlled at 30° C. and the stirring time is 18 min.

[0093] (2) gradually adding the corresponding bis(diethylamino)phosphoryl chloride, the mixed reaction temperature is 50°C, the reaction time is 6 hours, after the reaction is completed, the reaction product is filtered, washed with distilled water, and placed in an oven at 105°C for 2 hours to obtain a phosphorus-boron flame retardant.

[0094] (4) Place the formulated amount of methyl vinyl silicone rubber on an open mill with a roller temperature of 35°C, adjust the mixing roller distance to 4.0 mm, and start plasticating.

[0095] (5) After the plasticization is completed, the formulated amount of white carbon black and the above-mentioned phosphorus-boron flame retardant are added to the silicone rubber in 5 times, with an interval of 8 minutes.

[0096] (6) Add dipentadienyl vulcanizer to the above mixed rubber, adjust the roller distance to 3 mm, and mix and knead the sheets in a triangle bag manner.

[0097] (7) The film obtained after the mixing is vulcanized at a vulcanization temperature of 170° C., a vulcanization pressure of 12 MPa, and a vulcanization time of 7 min to obtain a flame retardant silicone rubber material.

[0098] Comparative Example 5:

[0099] The main difference between this comparative example and Example 3 is that the formula amount of 3-hydroxyphenylboronic acid methyliminodiacetate, bis(diethylamino)phosphoryl chloride and vinyl triacetoxysilane is directly added to the open mill to blend with silicone rubber. The flame-retardant silicone rubber cable accessory material in this comparative example includes the following raw materials in parts by weight: 40 parts of methyl vinyl silicone rubber with a number average molecular weight of 520,000, 60 parts of methyl vinyl silicone rubber with a number average molecular weight of 630,000, 20 parts of precipitated silica, 25 parts of fumed silica, 23.4 parts of 3-hydroxyphenylboronic acid methyliminodiacetate, 7.8 parts of bis(diethylamino)phosphoryl chloride, 3.8 parts of vinyl triacetoxysilane, and 6 parts of bis(diethylamino)phosphoryl chloride.

[0100] In the cable accessory material formula of this comparative example, the methyl vinyl silicone rubber with a number average molecular weight of 520,000, a vinyl content of 0.21%, and a volatile matter of ≤3.0%; the methyl vinyl silicone rubber with a number average molecular weight of 630,000, a vinyl content of 0.28%, and a volatile matter of ≤3.0%; the purity of 3-hydroxyphenylboronic acid methyliminodiacetate is ≥96%, and the acidity coefficient is 3.7-4.1pKa; the purity of bis(diethylamino)phosphoryl chloride is ≥95%, and the moisture content is ≤0.5%; the effective substance content of vinyl triacetoxysilane is ≥95%;

[0101] The specific preparation method of flame retardant silicone rubber material is as follows:

[0102] (1) Place the formulated amount of methyl vinyl silicone rubber on an open mill with a roller temperature of 35°C, adjust the mixing roller distance to 4.0 mm, and start plasticating.

[0103] (5) After the plasticization is completed, the formulated amount of white carbon black, 3-hydroxyphenylboronic acid methyliminodiacetate, bis(diethylamino)phosphoryl chloride and vinyl triacetoxysilane are added to the silicone rubber in 5 times with an interval of 8 minutes.

[0104] (6) Add dipentadienyl vulcanizer to the above mixed rubber, adjust the roller distance to 3 mm, and mix and knead the sheets in a triangle bag manner.

[0105] (7) The film obtained after the mixing is vulcanized at a vulcanization temperature of 170° C., a vulcanization pressure of 12 MPa, and a vulcanization time of 7 min to obtain the flame-retardant silicone rubber cable accessory material.

[0106] Detection:

[0107] (1) Physical and mechanical properties test

[0108] According to the test methods described in the standards in Table 1, the physical and mechanical properties of the flame retardant silicone rubber materials prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were tested respectively, and the test results are recorded in Table 1 below.

[0109] Table 1 Physical and mechanical properties test results of flame retardant silicone rubber cable accessory materials in Examples 1 to 3 and Comparative Examples 1 to 5

[0110]

[0111]

[0112] It can be seen from the test results in Table 1 that the overall physical and mechanical properties of the flame-retardant silicone rubber cable accessory materials in Examples 1 to 3 of the present invention are better than those in Comparative Examples 1 to 5. Due to the presence of the vinyl active group, the BPDM phosphorus-boron synergistic flame retardant generated by the reaction of 3-hydroxyphenylboronic acid methyliminodiacetate, bis(diethylamino)phosphoryl chloride and vinyltriacetoxysilane under certain conditions is blended with silicone rubber, and a good interface bonding force is generated between the two. The good compatibility makes the two closely combined, ensuring that it meets the flame retardant requirements of cable accessory materials with a small amount of addition while achieving the stability of physical and mechanical properties such as tensile strength. In addition, BPDM, as a low-molecular organic compound containing boron, phosphorus and silicon, can act with the Si-OH group on the surface of white carbon black, improve the affinity between silicone rubber and filler particles, reduce the formation of hydrogen bonds, prevent the occurrence of continuous structuring, promote the dispersion of white carbon black in the rubber, prevent the rubber from hardening, and significantly improve the mixing process and storage stability.

[0113] (2) Flame retardant performance test

[0114] The flame retardant properties of the flame retardant silicone rubber cable accessory materials prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were tested according to the test methods described in the standard in Table 2, and the test results are recorded in Tables 2, 3 and 4. Tables 2 and 3 respectively test the oxygen index, smoke density and UL94 self-extinguishing properties of the flame retardant silicone rubber cable accessory materials after vulcanization, and Table 4 tests the flame retardant self-extinguishing properties of the vulcanized specimens after water bath treatment. The water bath treatment conditions are as follows: the specimens are placed in a 70°C water bath for 120 hours, then the specimens are wiped dry, dried at 110°C for 30 minutes, cooled to room temperature, and then the specimens are subjected to a vertical combustion test to determine the flame retardant level of the specimens after boiling.

[0115] Table 2 Flame retardant properties test results of flame retardant silicone rubber cable accessory materials in Examples 1 to 3 and Comparative Examples 1 to 5

[0116]

[0117] Table 3 Self-extinguishing test results of flame retardant silicone rubber cable accessory materials in Examples 1 to 3 and Comparative Examples 1 to 5

[0118]

[0119] Table 4 Self-extinguishing test results of flame retardant silicone rubber cable accessory materials in Examples 1 to 3 and Comparative Examples 1 to 5 after being subjected to a 70°C × 120h water bath

[0120]

[0121] It can be seen from Table 2 that the flame retardant silicone rubber cable accessory materials obtained in Examples 1 to 3 of the present invention have a higher oxygen index and a lower smoke density. It can be seen from the various flame retardant performance test results in Tables 3 and 4 that the flame retardant silicone rubber cable accessory materials in Examples 1 to 3 of the present invention are not completely burned in the two flame extension processes under the two conditions of no water bath treatment and 70°C×120h water bath treatment, and the cotton at the bottom can not be ignited while no dripping phenomenon occurs. Both combustions can reach the state of extinguishing immediately after leaving the fire. This phenomenon can fully demonstrate that the BPDM flame retardant will dehydrate into a ring after being heated to form a boron oxygen six-membered ring network structure. This structure will form more carbon layers containing BOC bonds after further combustion. The formation of such carbides can block the transfer of heat and prevent the silicone rubber from being further oxidized.

[0122] BPDM flame retardant containing phosphorus atoms will produce phosphoric acid during the heating process. Phosphoric acid can not only condense with CO bonds to form polyphosphoric acid cross-links, but also form stable BPO4 with boron at high temperatures. The dense protective carbon layer formed by the joint catalysis of the two can minimize the production of gas phase products and carbonyl compounds.

[0123] Compared with the direct addition of three single-category organic compounds, namely 3-hydroxyphenylboronic acid methyliminodiacetate, bis(diethylamino)phosphorus oxychloride and vinyl triacetoxysilane, the BPDM phosphorus-boron synergistic flame retardant formed by combining the three elements of phosphorus, boron and silicon under certain conditions can certainly achieve higher flame retardant efficiency at a lower addition amount. The good compatibility and dispersibility of BPDM create more possibilities for the dual improvement of flame retardancy and physical and mechanical properties of silicone rubber cable accessory materials.

[0124] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may 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.

Claims

1. A flame retardant silicone rubber material, characterized in that: The flame retardant silicone rubber material is made of the following raw materials in parts by weight: 100-110 parts of silicone rubber, 20-40 parts of filler, 10-45 parts of phosphorus-boron synergistic flame retardant, and 2-7 parts of vulcanizing agent; The phosphorus-boron synergistic flame retardant is obtained by compounding 3-hydroxyphenylboronic acid methyliminodiacetate, bis(diethylamino)phosphorus oxychloride and vinyl triacetoxysilane in a mass ratio of 1.1-3.5:1:0.2-0.6, and the preparation method of the phosphorus-boron synergistic flame retardant includes the following steps: (1) adding dimethylformamide dropwise to 3-hydroxyphenylboronic acid methyliminodiacetate and stirring to dissolve the mixture to obtain a solution for later use; (2) adding bis(diethylamino)phosphoryl chloride to the above solution, mixing and reacting, filtering, washing, and drying to obtain a dry product for later use; (3) Add the above dried product to vinyl triacetoxysilane, stir and disperse to obtain a phosphorus-boron synergistic flame retardant.

2. The flame retardant silicone rubber material according to claim 1, characterized in that: The silicone rubber is methyl vinyl silicone rubber; the filler is white carbon black; and the vulcanizing agent is di-25.

3. A method for preparing the flame retardant silicone rubber material according to any one of claims 1-2, characterized in that: The preparation method comprises the following steps: (1) adding dimethylformamide dropwise to 3-hydroxyphenylboronic acid methyliminodiacetate and stirring to dissolve the mixture to obtain a solution for later use; (2) adding bis(diethylamino)phosphoryl chloride to the above solution, mixing and reacting, filtering, washing, and drying to obtain a dry product for later use; (3) adding vinyl triacetoxysilane to the dried product, stirring and dispersing the mixture to obtain a phosphorus-boron synergistic flame retardant; (4) placing the silicone rubber on an open mixing mill and starting to plasticize, and after the plasticizing is completed, adding fillers and phosphorus-boron synergistic flame retardants and mixing to obtain a mixed rubber; (5) Adding a vulcanizing agent into the mixed rubber, mixing and sheeting, and then vulcanizing the film to obtain a flame retardant silicone rubber material.

4. The method for preparing a flame retardant silicone rubber material according to claim 3, characterized in that: The stirring and dissolving temperature in step (1) is 30° C. and the stirring time is 15-20 min.

5. The method for preparing a flame retardant silicone rubber material according to claim 3, characterized in that: The temperature of the mixing reaction in step (2) is 40-55° C., the reaction time is 4-7 hours, and the drying method is drying in an oven at 105° C. for 2 hours.

6. The method for preparing a flame retardant silicone rubber material according to claim 3, characterized in that: The rotation speed of the stirring and dispersing in the step (3) is 1000-1500 r / min, and the stirring time is 10-15 s.

7. The method for preparing a flame retardant silicone rubber material according to claim 3, characterized in that: In the step (4), the mixing temperature of the open mixer is set to 30-40° C., and the mixing roller distance is adjusted to 4-5 mm.

8. The method for preparing a flame retardant silicone rubber material according to claim 3, characterized in that: In the step (4), the filler and the phosphorus-boron synergistic flame retardant are added in 3-6 times, and the interval between each addition is 2-8 minutes.

9. The method for preparing a flame retardant silicone rubber material according to claim 3, characterized in that: In the step (5), the lower sheet is mixed by adjusting the roller distance to 2-3 mm and mixing the lower sheet in a triangular bag manner, and the vulcanization temperature is 170-180° C., the vulcanization pressure is 10-15 MPa, and the vulcanization time is 3-10 min.

10. Use of the flame retardant silicone rubber material according to any one of claims 1 to 2 in preparing high voltage cable accessory materials.

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