A hydrogen-containing silane, surface-modified magnesium hydroxide, and a halogen-free flame-retardant silicone rubber composition, and a preparation method and application thereof

Abstract

The present invention provides a hydrogen-containing silane, a surface-modified magnesium hydroxide, a halogen-free flame-retardant silicone rubber composition, and a preparation method and application thereof. Using cyclic hydrogen-containing silicone oil as a raw material, an aromatic ring is introduced into it through a hydrosilylation reaction to obtain a hydrogen-containing silane. The hydrogen-containing silane and an epoxy group-containing silane coupling agent are used together to perform surface modification on magnesium hydroxide in an aqueous solution of alcohol, thereby preparing a surface-modified magnesium hydroxide. The hydroxyl groups on the surface of the magnesium hydroxide particles combine the hydrogen-containing silane and the epoxy group-containing silane coupling agent through condensation or hydrogen bonding. Subsequently, vinyl silicone oil, hydrogen-containing silicone oil, a tackifier, a structure control agent, and a catalyst are added to prepare a silicone rubber having a more balanced tensile strength and elongation at break, an excellent flame-retardant effect, and a stronger bonding property to the plastic / metal interface.

Description

Technical Field

[0001] The present invention relates to the technical field of silicone rubber, and specifically to a hydrogen-containing silane, surface-modified magnesium hydroxide and halogen-free flame-retardant silicone rubber composition, as well as a preparation method and application thereof. Background Art

[0002] Since domestic and international markets have demanded halogen-free flame retardancy in industries such as wire and cable, transportation, electronics, and construction, research and development of halogen-free flame retardant polymer materials has rapidly developed. Currently, the main halogen-free flame retardants are hydroxide-based flame retardants, including aluminum hydroxide and magnesium hydroxide. These flame retardants are widely available and inexpensive, but they have low flame retardant efficiency, require large addition amounts, and have poor compatibility with polymers. This not only increases the cost of the raw materials, but also impairs the physical and processing properties of the polymer substrate, resulting in a significant reduction in its mechanical properties. Effective solutions to the above problems include ultra-fine processing of flame retardants, microencapsulation, surface treatment, and synergistic compounding.

[0003] Silicone rubber, with its Si-O backbone, possesses high thermal stability, low flammability, low heat release rate, and low flame spread rate. Due to its flame retardancy and resistance to high and low temperatures, silicone rubber is widely used as a novel adhesive material in the electronics, aerospace, and automotive industries. However, conventional silicone rubber materials, due to the presence of carbon-containing groups such as methyl and vinyl groups in their molecular chain side groups, still have the disadvantage of being flammable and prone to smoldering, posing a significant safety hazard. Excessive temperatures and voltages can cause silicone rubber to transition from smoldering to flaming combustion, thus limiting its application in electrical and electric vehicle applications. Therefore, in order to adapt silicone rubber to higher temperatures and voltages and enhance its flame retardancy, it is necessary to find a method to effectively enhance the flame retardancy of silicone rubber while maintaining a significant degradation of its mechanical properties after curing, ensuring excellent bonding to substrates.

[0004] Ma Shugang et al. (Study on the Surface Modification of Magnesium Hydroxide and Its Flame Retardant Properties in Silicone Rubber, Ma Shugang, Wan Zian, Liu Xingchi, Wang Shirong, Li Xianggao, Hou Jingwei, Modern Chemical Industry, 2024-4, 146-151) used industrial-grade magnesium hydroxide (MH) as the raw material, vinyltriethoxysilane, 3-(aminopropyl)triethoxysilane, and ethyltriethoxysilane as modifiers, and prepared modified magnesium hydroxide by a wet process. After blending the modified magnesium hydroxide into silicone rubber, it was found that the magnesium hydroxide particles modified with vinyltriethoxysilane could be better blended and fused with silicone rubber, and the vulcanization network structure of the silicone rubber after blending was more solid, thus improving the mechanical properties of the composite material. However, the cohesive density and tensile strength of the silicone rubber composite prepared by them still need to be further improved to meet the requirements of adhesives, especially structural adhesives used to replace traditional mechanical fasteners, for the mechanical properties of silicone rubber. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above deficiencies and provide a hydrosilane and its preparation method, a surface-modified magnesium hydroxide, a halogen-free flame-retardant silicone rubber composition and its preparation method and application. By using a hydrosilane and a silane coupling agent containing an epoxy group to modify the surface of magnesium hydroxide, the flame retardant properties, mechanical properties and bonding properties of silicone rubber can be improved simultaneously.

[0006] To achieve the above technical objectives, the technical solutions adopted by the present invention are as follows:

[0007] In the first aspect, a hydrosilane has a structural general formula as follows:

[0008] Wherein, A contains 4 to 54 carbon atoms, A contains at least one aromatic ring, and does not contain N, S, P elements. Preferably, A contains at least one ester bond or ether bond;

[0009] In one or more embodiments, the structure of A is selected from:

[0010]

[0011] Or Any one of them.

[0012] In the second aspect, the preparation method of the above-mentioned hydrosilane includes: obtaining by subjecting a diene monomer and a cyclic hydrosiloxane to a hydrosilylation reaction.

[0013] Wherein, the diene monomer contains 4 to 54 carbon atoms and contains at least one aromatic ring. Preferably, the diene monomer contains at least one ester bond or ether bond;

[0014] The cyclic hydrosiloxane is tetramethylcyclotetrasiloxane;

[0015] Preferably, the diene monomer is a terminal diene monomer, i.e., the unsaturated double bond is located at both ends of the molecule.

[0016] In one or more embodiments, the diene monomer is selected from: Or Any one of them.

[0017] Furthermore, the preparation method of the hydrosilane includes: carrying out a hydrosilylation reaction on tetramethylcyclotetrasiloxane and the diene monomer in a molar ratio of 2.5 - 3.5:1; preferably, carrying out a hydrosilylation reaction on tetramethylcyclotetrasiloxane and the diene monomer in a molar ratio of 2.5 - 3.0:1;

[0018] Furthermore, the preparation method of the hydrosilane includes: adding an inhibitor and a catalyst in the hydrosilylation reaction, reacting the hydrosilylation reaction at 70 - 90 °C for 2 - 4 hours, and then heating to 80 - 100 °C for heat preservation for 1 - 3 hours.

[0019] Among them, the inhibitor is selected from p-methylanisole;

[0020] The catalyst is selected from any one of chloroplatinic acid or chloroplatinic acid vinyl complex; preferably, the catalyst is selected from chloroplatinic acid - divinyltetramethyldisiloxane complex.

[0021] Furthermore, the preparation method further includes: cooling to 40 - 60 °C after the reaction and distilling off the solvent under reduced pressure;

[0022] Furthermore, the preparation method further includes: adding activated carbon to adsorb the residual catalyst in the product, and removing the catalyst by suction filtration to obtain the hydrosilane product.

[0023] In the third aspect, a use is provided, which is to use the above-mentioned hydrosilane as a modifier for surface modification treatment of magnesium hydroxide.

[0024] In the fourth aspect, a surface-modified magnesium hydroxide is provided, which is obtained by surface-modifying magnesium hydroxide with the above-mentioned hydrosilane and a silane coupling agent.

[0025] Preferably, for a surface-modified magnesium hydroxide, the silane coupling agent contains at least one epoxy group;

[0026] Preferably, the silane coupling agent is selected from any one or a combination of 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, or 3-glycidoxypropylmethyldiethoxysilane.

[0027] Among them, the specific steps of surface modification include:

[0028] S1. Thoroughly mix the above-mentioned hydrogen-containing silane, the above-mentioned silane coupling agent and the alcohol / water mixture, and then add magnesium hydroxide and mix evenly;

[0029] S2. Heat the uniformly mixed material in S1 to 80 - 180 °C to obtain surface-modified magnesium hydroxide.

[0030] Preferably, the silane coupling agent is selected from KH560;

[0031] Preferably, the alcohol is selected from any one or a combination of methanol, ethanol or isopropanol;

[0032] Preferably, the thorough mixing uses mechanical stirring and / or ultrasound;

[0033] Preferably, the average particle size of the magnesium hydroxide does not exceed 10 μm.

[0034] Furthermore, the mass ratio of magnesium hydroxide: hydrogen-containing silane to silane coupling agent is (5:1) - (6:1).

[0035] Fifth aspect, a halogen-free flame-retardant silicone rubber cured composition, comprising the following raw materials: vinyl silicone oil, the above-mentioned surface-modified magnesium hydroxide, cross-linking agent, tackifier, structure control agent and catalyst;

[0036] Among them, the content of vinyl in the vinyl silicone oil is 0.05 - 0.5 mmol / g;

[0037] The cross-linking agent is selected from hydrogen-containing silicone oil, and the content of active hydrogen in the hydrogen-containing silicone oil is preferably 0.1 - 1 wt%;

[0038] The structure control agent is selected from any one or more of 1-ethynyl-1-cyclohexanol, tetramethyltetravinylcyclotetrasiloxane, 2-methyl-3-butyn-2-ol, 3-methyl-1-ethynyl-3-ol, 3,5-dimethyl-1-hexyn-3-ol, 3-methyl-1-dodecyn-3-ol;

[0039] The catalyst is selected from any one or more of chloroplatinic acid, chloroplatinic acid-isopropanol complex or chloroplatinic acid-divinyl complex;

[0040] Preferably, the catalyst is selected from chloroplatinic acid-divinyltetramethyldisiloxane complex;

[0041] Preferably, the effective content of Pt in the catalyst is 2000 - 5000 ppm.

[0042] The structural general formula of the tackifier is:

[0043] Among them, X and Y are each independently selected from any one of vinyl, allyl, methacryloxypropyl, glycidyloxypropyl, and isocyanatopropyl, and X and Y are different;

[0044] Preferably, at least one of X and Y is selected from vinyl or allyl, and at least one of X and Y contains an unsaturated double bond.

[0045] Furthermore, a halogen-free flame-retardant silicone rubber cured composition is composed of the following components in parts by mass: 90-110 parts of vinyl silicone oil, 120-180 parts of the surface-modified magnesium hydroxide described above, 1-10 parts of a crosslinking agent, 1-10 parts of a tackifier, 0.1-1 part of a structure control agent, and 0.01-0.1 part of a catalyst;

[0046] In a sixth aspect, a method for preparing the halogen-free flame-retardant silicone rubber composition described above includes: uniformly mixing the above-mentioned raw materials, adding a catalyst, and then performing defoaming and curing, and the curing temperature is 100-200 °C.

[0047] In a seventh aspect, there is a use of using the halogen-free flame-retardant silicone rubber composition described above as an adhesive.

[0048] The beneficial effects of the present invention are as follows: A hydrogen-containing silane is prepared by introducing an aromatic ring into a cyclic hydrogen-containing silicone oil through a hydrosilylation reaction. The obtained hydrogen-containing silane and an epoxy group-containing silane coupling agent are used to surface-modify magnesium hydroxide in an aqueous solution of alcohol, thereby obtaining surface-modified magnesium hydroxide. The hydroxyl groups on the surface of the magnesium hydroxide particles are combined with the hydrogen-containing silane and the epoxy group-containing silane coupling agent through condensation or hydrogen bonding. Subsequently, vinyl silicone oil, hydrogen-containing silicone oil, tackifier, structure control agent, and catalyst are added to prepare a silicone rubber with more balanced tensile strength and elongation at break, excellent flame-retardant effect, and stronger bonding performance to the plastic / metal interface. Description of the Drawings

[0049] Figure 1 It is the appearance morphology diagram of the silicone rubber ash after the oxygen index test is completed for Examples 7 and 8 and Comparative Examples 1 and 3.

[0050] Figure 2 It is the TG curve of the silicone rubber cured product.

[0051] Figure 3 It is the DTG curve of the silicone rubber cured product. Detailed Embodiments

[0052] Combined with the embodiments of the present invention, the technical solutions in the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. It should be noted that the terms used herein are only for describing specific embodiments, rather than intending to limit the exemplary embodiments according to the present invention. As used herein, unless otherwise clearly specified in the context, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0053] If the specific experimental conditions are not specified in the embodiments, they are usually in accordance with the conventional conditions in the art or the conditions recommended by the reagent company; the materials, reagents, etc. used in the embodiments, unless otherwise specified, can be obtained through commercial channels.

[0054] Example 1

[0055] Preparation of hydrosilane: Add 0.365 g of the polymerization inhibitor p-methylanisole and 0.115 g of the catalyst chloroplatinic acid-divinyltetramethyldisiloxane complex to a flask, dissolve them with 50 mL of toluene. Dissolve 199.62 g (0.830 mol) of tetramethylcyclotetrasiloxane and 85.46 g (0.277 mol) of bisphenol A diallyl ether with 75 mL of toluene, and control the addition to the flask at 83 °C. During the reaction process, nitrogen is used to protect the reactants in the flask. The total dropping time of the added materials is 3 hours. After dropping, heat is raised to 90 °C and kept warm for 2 hours to end the heating. Then, the temperature is lowered, and the solvent is removed by vacuum distillation at 60 °C. Then, 18 g of activated carbon is added in batches to adsorb the catalyst in the product, and the catalyst is removed by suction filtration to obtain the hydrosilane product. The reaction formula is as follows:

[0056]

[0057] Perform structural confirmation on the hydrosilane product: 11H NMR (400 MHz): δ 0.24 - 0.35 (24H, 0.29 (s), 0.30 (s), 0.30 (s), 0.30 (s), 0.30 (s), 0.30 (s)), 0.88 - 1.05 (4H, 0.95 (t, J = 7.50 Hz), 0.98 (t, J = 7.50 Hz)), 1.49 (6H, s), 1.81 - 1.99 (4H, 1.90 (tt, J = 7.50, 7.43 Hz), 1.90 (tt, J = 7.50, 7.47 Hz)), 3.90 - 4.05 (4H, 3.97 (t, J = 7.47 Hz), 3.98 (t, J = 7.43 Hz)), 6.95 - 7.07 (4H, 7.01 (ddd, J = 8.87, 1.64, 0.55 Hz), 7.01 (ddd, J = 8.87, 1.65, 0.55 Hz)), 7.17 - 7.30 (4H, 7.24 (ddd, J = 8.87, 1.10, 0.55 Hz), 7.24 (ddd, J = 8.87, 1.10, 0.55 Hz)).

[0058] Surface modification of magnesium hydroxide with the hydrogen - containing silane prepared in Example 1:

[0059] S1. Mix 25 g of the above - mentioned hydrogen - containing silane, 15 g of the silane coupling agent 3 - glycidoxypropyltrimethoxysilane (KH560) with 30 mL of an ethanol / water mixture (volume ratio 1:1), stir for 10 min for thorough mixing, then ultrasonically disperse for 30 min. Subsequently, add 200 g of magnesium hydroxide portion - by - portion under stirring, and continuously stir the mixture for reaction for 30 min to obtain a crude product after the reaction is completed;

[0060] S2. Bake the crude product obtained in step S1 at 105 °C for 2 h to obtain surface - modified magnesium hydroxide.

[0061] Example 2

[0062] Preparation of hydrogen-containing silane: 0.425 g of the polymerization inhibitor p-methylanisole and 0.125 g of the catalyst chloroplatinic acid-divinyltetramethyldisiloxane complex were added to a flask and dissolved in 50 mL of toluene. 199.62 g (8.30 mol) of tetramethylcyclotetrasiloxane and 117.5 g (0.277 mol) of 2-acrylate(1-methylethylidene)bis(4,1-phenyleneoxy-2,1-ethanediyl)ester were dissolved in 85 mL of toluene, and were added dropwise to the flask at 85 °C. During the reaction process, nitrogen was used to protect the reactants in the flask. The total dropping time of the added materials was 3 hours. After dropping, the temperature was raised to 95 °C and kept warm for 2 hours to end the heating. Subsequently, the temperature was lowered, and the solvent was removed by distillation under reduced pressure at 60 °C. Then, 18 g of activated carbon was added in batches to adsorb the catalyst in the product, and the catalyst was removed by suction filtration to obtain the hydrogen-containing silane product. The reaction formula is as follows:

[0063]

[0064] Structural confirmation of the hydrogen-containing silane product: 1 H NMR (400 MHz): δ 0.24 - 0.35 (21H, 0.29 (s), 0.30 (s), 0.30 (s), 0.30 (s), 0.30 (s)), 1.22 - 1.36 (4H, 1.29 (t, J = 7.09 Hz), 1.30 (t, J = 7.08 Hz)), 1.49 (6H, s), 2.64 - 2.82 (4H, 2.70 (t, J = 7.09 Hz), 2.75 (t, J = 7.08 Hz)), 4.24 (2H, t, J = 7.39 Hz), 4.42 (2H, t, J = 7.39 Hz), 5.68 (2H, s), 6.92 - 7.16 (4H, 6.98 (ddd, J = 8.13, 1.25, 0.55 Hz), 7.09 (ddd, J = 8.50, 1.29, 0.55 Hz)), 7.18 - 7.31 (4H, 7.24 (ddd, J = 8.50, 1.10, 0.55 Hz), 7.25 (ddd, J = 8.13, 1.06, 0.55 Hz)).

[0065] Surface modification of magnesium hydroxide with the hydrogen-containing silane prepared in Example 2:

[0066] S1. 25 g of the above-mentioned hydrogen-containing silane, 15 g of the silane coupling agent 3-glycidoxypropyltrimethoxysilane (KH560) and 30 mL of an ethanol / water mixture (volume ratio 1:1) were mixed and stirred for 10 min. After thorough mixing, ultrasonic dispersion was carried out for 30 min. Subsequently, 200 g of magnesium hydroxide was added in batches under stirring, and the mixture was continuously stirred and reacted for 30 min to obtain a crude product;

[0067] S2. Bake the crude product obtained in step S1 at 105 °C for 2 h to obtain surface-modified magnesium hydroxide.

[0068] Example 3

[0069] Preparation of hydrogen-containing silane: Add 0.398 g of the polymerization inhibitor p-methylanisole and 0.115 g of the catalyst chloroplatinic acid-divinyltetramethyldisiloxane complex to a flask, dissolve with 50 mL of toluene. Dissolve 199.62 g (0.830 mol) of tetramethylcyclotetrasiloxane and 74.25 g (0.302 mol) of diallyl phthalate with 70 mL of toluene, and control the dropping to the flask at 82 °C. During the reaction process, nitrogen is used to protect the reactants in the flask. The total dropping time of the added materials is 3 hours. After dropping, raise the temperature to 92 °C and keep it warm for 2 hours to end the heating. Then cool down, and distill off the solvent under reduced pressure at 60 °C. Then add 16 g of activated carbon in batches to adsorb the catalyst in the product, and remove the catalyst by suction filtration to obtain the hydrogen-containing silane product. The reaction formula is as follows:

[0070]

[0071] Perform structural confirmation on the hydrogen-containing silane product: 1 H NMR (400 MHz): δ 0.25 - 0.35 (18H, 0.30(s), 0.30(s)), 0.98 (4H, t, J = 7.50 Hz), 1.91 (4H, tt, J = 7.52, 7.50 Hz), 4.18 (4H, t, J = 7.52 Hz), 7.64 - 7.82 (4H, 7.71(ddd, J = 7.81, 7.70, 1.32 Hz), 7.76(ddd, J = 7.81, 1.32, 0.54 Hz)).

[0072] Surface modification of magnesium hydroxide with the hydrogen-containing silane prepared in Example 3:

[0073] S1. Mix 25 g of the above-mentioned hydrogen-containing silane, 15 g of the silane coupling agent 3-glycidoxypropyltrimethoxysilane (KH560) with 30 mL of an ethanol / water mixture (volume ratio 1:1), stir for 10 min for full mixing, then ultrasonically disperse for 30 min. Subsequently, add 210 g of magnesium hydroxide in batches under stirring, and continuously stir the mixture for reaction for 30 min to obtain a crude product after the reaction.

[0074] S2. Bake the crude product obtained in step S1 at 105 °C for 2 h to obtain surface-modified magnesium hydroxide.

[0075] Example 4

[0076] Preparation of hydrogen-containing silane: 0.412 g of the polymerization inhibitor p-methylanisole and 0.125 g of the catalyst chloroplatinic acid-divinyltetramethyldisiloxane complex were added to a flask and dissolved in 50 mL of toluene. 199.62 g (0.830 mol) of tetramethylcyclotetrasiloxane and 119.26 g (0.277 mol) of 9,9-bis(4-allyloxyphenyl)fluorene were dissolved in 85 mL of toluene, and the solution was added dropwise to the flask at 87 °C. During the reaction process, nitrogen was used to protect the reactants in the flask. The total dropping time of the added materials was 3 hours. After the dropping was completed, the temperature was raised to 95 °C and kept warm for 2 hours to end the heating. Subsequently, the temperature was lowered, and the solvent was removed by distillation under reduced pressure at 60 °C. Then, 18 g of activated carbon was added in batches to adsorb the catalyst in the product, and the catalyst was removed by suction filtration to obtain the hydrogen-containing silane product. The reaction formula is as follows:

[0077]

[0078] Structural confirmation of the hydrogen-containing silane product: 1 H NMR (400 MHz): δ 0.24 - 0.36 (24H, 0.29 (s), 0.30 (s), 0.31 (s)), 0.95 (4H, t, J = 7.50 Hz), 1.90 (4H, tt, J = 7.50, 7.43 Hz), 3.98 (4H, t, J = 7.43 Hz), 6.85 (4H, ddd, J = 8.50, 1.09, 0.55 Hz), 7.14 (4H, ddd, J = 8.50, 1.13, 0.55 Hz), 7.31 - 7.45 (4H, 7.38 (ddd, J = 8.47, 6.90, 1.42 Hz), 7.38 (ddd, J = 8.07, 6.90, 1.50 Hz)), 7.64 (2H, ddd, J = 8.07, 1.42, 0.52 Hz), 7.85 (2H, ddd, J = 8.47, 1.50, 0.52 Hz).

[0079] Surface modification of magnesium hydroxide with the hydrogen-containing silane prepared in Example 4:

[0080] S1. 25 g of the above-mentioned hydrogen-containing silane, 15 g of the silane coupling agent 3-glycidoxypropyltrimethoxysilane (KH560), and 30 mL of an ethanol / water mixture (volume ratio 1:1) were mixed and stirred for 10 min. After sufficient mixing, the mixture was ultrasonically dispersed for 30 min. Subsequently, 220 g of magnesium hydroxide was added in batches under stirring, and the mixture was continuously stirred and reacted for 30 min to obtain a crude product.

[0081] S2. The crude product obtained in step S1 was baked at 105 °C for 2 h to obtain surface-modified magnesium hydroxide.

[0082] Example 5

[0083] Preparation of hydrogen-containing silane: 0.428 g of the polymerization inhibitor p-methylanisole and 0.125 g of the catalyst chloroplatinic acid-divinyltetramethyldisiloxane complex were added to a flask and dissolved in 50 mL of toluene. 199.62 g (0.830 mol) of tetramethylcyclotetrasiloxane and 62.30 g (0.302 mol) of 4,4'-divinyl-1,1'-biphenyl were dissolved in 70 mL of toluene, and were added dropwise to the flask at 83 °C. During the reaction process, nitrogen was used to protect the reactants in the flask. The total dropping time of the added materials was 3 hours. After dropping, the temperature was raised to 92 °C and kept warm for 2 hours to end the heating. Subsequently, the temperature was lowered, and the solvent was removed by distillation under reduced pressure at 60 °C. Then, 16 g of activated carbon was added in batches to adsorb the catalyst in the product, and the catalyst was removed by suction filtration to obtain the hydrogen-containing silane product. The reaction formula is as follows:

[0084]

[0085] Structural confirmation of the hydrogen-containing silane product: 1 H NMR (400 MHz): δ 0.25 - 0.35 (18H, 0.30(s), 0.30(s)), 0.98 (4H, t, J = 7.50 Hz), 1.91 (4H, tt, J = 7.52, 7.50 Hz), 4.18 (4H, t, J = 7.52 Hz), 7.64 - 7.82 (4H, 7.71(ddd, J = 7.81, 7.70, 1.32 Hz), 7.76(ddd, J = 7.81, 1.32, 0.54 Hz)).

[0086] Surface modification of magnesium hydroxide with the hydrogen-containing silane prepared in Example 5:

[0087] S1. 25 g of the above-mentioned hydrogen-containing silane, 15 g of the silane coupling agent 3-glycidoxypropyltrimethoxysilane (KH560), and 30 mL of an ethanol / water mixture (volume ratio 1:1) were mixed and stirred for 10 min. After sufficient mixing, ultrasonic dispersion was carried out for 30 min. Subsequently, 200 g of magnesium hydroxide was added in batches under stirring, and the mixture was continuously stirred and reacted for 30 min to obtain a crude product.

[0088] S2. The crude product obtained in step S1 was baked at 105 °C for 2 h to obtain surface-modified magnesium hydroxide.

[0089] Example 6

[0090] Preparation of hydrogen-containing silane: 0.428 g of the polymerization inhibitor p-methylanisole and 0.125 g of the catalyst chloroplatinic acid-divinyltetramethyldisiloxane complex were added to a flask and dissolved in 50 mL of toluene. 199.62 g (0.830 mol) of tetramethylcyclotetrasiloxane and 67.13 g (0.302 mol) of 4,4'-divinyl-1,1'-biphenyl ether were dissolved in 70 mL of toluene and added dropwise to the flask at 83 °C. During the reaction process, nitrogen was used to protect the reactants in the flask. The total dropping time of the added materials was 3 hours. After dropping, the temperature was raised to 92 °C and kept warm for 2 hours to end the heating. Subsequently, the temperature was lowered, and the solvent was removed by vacuum distillation at 60 °C. Then, 16 g of activated carbon was added in batches to adsorb the catalyst in the product, and the catalyst was removed by suction filtration to obtain the hydrogen-containing silane product. The reaction formula is as follows:

[0091]

[0092] Structure confirmation of the hydrogen-containing silane product: 1 H NMR (400 MHz): δ 0.24 - 0.36 (24H, 0.29 (s), 0.30 (s), 0.31 (s)), 1.14 (4H, t, J = 7.49 Hz), 2.74 (4H, t, J = 7.49 Hz), 6.91 (4H, ddd, J = 8.30, 1.79, 0.55 Hz), 7.05 (4H, ddd, J = 8.30, 1.00, 0.55 Hz).

[0093] Surface modification of magnesium hydroxide with the hydrogen-containing silane prepared in Example 6:

[0094] S1. 25 g of the above-mentioned hydrogen-containing silane, 15 g of the silane coupling agent 3-glycidoxypropyltrimethoxysilane (KH560), and 30 mL of an ethanol / water mixture (volume ratio 1:1) were mixed and stirred for 10 min. After thorough mixing, ultrasonic dispersion was carried out for 30 min. Subsequently, 200 g of magnesium hydroxide was added in batches under stirring, and the mixture was continuously stirred and reacted for 30 min to obtain a crude product.

[0095] S2. The crude product obtained in step S1 was baked at 105 °C for 2 h to obtain surface-modified magnesium hydroxide.

[0096] Components in the addition-type silicone rubber formulation:

[0097] Vinyl silicone oil with a vinyl content of 1.92% (Zhejiang Xin'an Chemical Industry Group) and vinyl silicone oil with a vinyl content of 0.8% (Zhejiang Xin'an Chemical Industry Group) were pre-mixed evenly according to a mass ratio of 4:6. After mixing, the terminal vinyl content of the mixed vinyl silicone oil was calculated to be 0.168 mmol / g, and the viscosity of the mixed vinyl silicone oil was 2270 mPa·s.

[0098] The crosslinking agent is hydrogen-containing silicone oil (Shandong Dayi Chemical Co., Ltd.) with an active hydrogen content of 0.50 wt%;

[0099] The structure control agent is 1-ethynyl-1-cyclohexanol (Shanghai Macklin Biochemical Co., Ltd.), with an effective content of 99%;

[0100] The catalyst is chloroplatinic acid-divinyltetramethyldisiloxane complex, with an effective Pt content of 3000 ppm (Dongguan BETELY New Materials);

[0101] The tackifier is prepared according to the following method: 87.12 g (0.5 mol) of trimethylolpropane monoallyl ether and 110.17 g (0.5 mol) of 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane are added to a flask. After stirring evenly at room temperature, 2 g of the catalyst tetrabutyl titanate (TNBT) is added. The mixture in the flask is continuously stirred and a nitrogen gas stream is introduced. Under these conditions, the temperature is raised to 95 °C and the reaction is carried out for 3 hours. Then, when the temperature is lowered to 65 °C, the reaction is changed to a reduced-pressure condition and carried out for 1 hour. The reaction formula for the preparation of the tackifier is as follows:

[0102]

[0103] Example 7

[0104] 100 parts of the above-mentioned mixed vinyl silicone oil and 150 parts of the surface-modified magnesium hydroxide prepared in Example 1 are stirred evenly by a high-speed disperser to obtain a base material. Then, 5 parts of hydrogen-containing silicone oil, 4.5 parts of tackifier, and 0.5 part of 1-ethynyl-1-cyclohexanol are added and mixed evenly. Finally, 0.05 part of chloroplatinic acid-divinyltetramethyldisiloxane complex with an effective Pt content of 3000 ppm is added. Finally, the mixture is placed in a vacuum drying oven for vacuum degassing for 15 min to obtain a halogen-free flame-retardant addition-curable silicone rubber.

[0105] Example 8

[0106] The silicone rubber formulation uses 7 parts of hydrogen-containing silicone oil and 2.5 parts of tackifier, and the rest is the same as in Example 7.

[0107] Example 9

[0108] The silicone rubber formulation uses 150 parts of the surface-modified magnesium hydroxide prepared in Example 2, and the rest is the same as in Example 7.

[0109] Example 10

[0110] The silicone rubber formulation uses 7 parts of hydrogen-containing silicone oil and 2.5 parts of tackifier, and the rest is the same as in Example 7.

[0111] Example 11

[0112] The silicone rubber formulation uses 150 parts of surface-modified magnesium hydroxide prepared in Example 3, and the rest is the same as in Example 7.

[0113] Example 12

[0114] The silicone rubber formulation uses 7 parts of hydrogen-containing silicone oil and 2.5 parts of tackifier, and the rest is the same as in Example 7.

[0115] Example 13

[0116] The silicone rubber formulation uses 150 parts of surface-modified magnesium hydroxide prepared in Example 4, and the rest is the same as in Example 7.

[0117] Example 14

[0118] The silicone rubber formulation uses 7 parts of hydrogen-containing silicone oil and 2.5 parts of tackifier, and the rest is the same as in Example 7.

[0119] Example 15

[0120] The silicone rubber formulation uses 150 parts of surface-modified magnesium hydroxide prepared in Example 5, and the rest is the same as in Example 7.

[0121] Example 16

[0122] The silicone rubber formulation uses 7 parts of hydrogen-containing silicone oil and 2.5 parts of tackifier, and the rest is the same as in Example 7.

[0123] Example 17

[0124] The silicone rubber formulation uses 150 parts of surface-modified magnesium hydroxide prepared in Example 6, and the rest is the same as in Example 7.

[0125] Example 18

[0126] The silicone rubber formulation uses 7 parts of hydrogen-containing silicone oil and 2.5 parts of tackifier, and the rest is the same as in Example 7.

[0127] Comparative Example 1

[0128] 100 parts of the above-mentioned mixed vinyl silicone oil and 150 parts of magnesium hydroxide were stirred evenly under the action of a high-speed disperser to prepare a base material, then 5 parts of hydrogen-containing silicone oil, 4.5 parts of tackifier and 0.5 part of 1-ethynyl-1-cyclohexanol were added and mixed evenly. Finally, 0.05 part of chloroplatinic acid-divinyltetramethyldisiloxane complex with an effective Pt content of 3000 ppm was added. Finally, the mixture was put into a vacuum drying oven for vacuum defoaming for 15 min to obtain a halogen-free flame-retardant addition-cured silicone rubber.

[0129] Comparative Example 2

[0130] Surface modification of magnesium hydroxide using the hydrogen-containing silane prepared in Example 1:

[0131] S1. Mix more than 25 g of the above-mentioned hydrogen-containing silane with 30 mL of ethanol and stir for 10 min for sufficient mixing. Then, ultrasonically disperse for 30 min. Subsequently, add 200 g of magnesium hydroxide portion by portion under stirring, and continuously stir the mixture for reaction for 30 min. After the reaction is completed, a crude product is obtained.

[0132] S2. Bake the crude product obtained in step S1 at 105 °C for 2 h to obtain surface-modified magnesium hydroxide.

[0133] Mix 100 parts of the above-mentioned vinyl silicone oil with 150 parts of the surface-modified magnesium hydroxide prepared by the above method and stir evenly under the action of a high-speed disperser to prepare a base material. Then, add 5 parts of hydrogen-containing silicone oil, 4.5 parts of tackifier, and 0.5 part of 1-ethynyl-1-cyclohexanol and mix evenly. Finally, add 0.05 part of chloroplatinic acid-divinyltetramethyldisiloxane complex with an effective Pt content of 3000 ppm. Finally, put the mixture into a vacuum drying oven for vacuum defoaming for 15 min to obtain a halogen-free flame-retardant addition-cured silicone rubber.

[0134] Comparative Example 3

[0135] Surface modification of magnesium hydroxide using KH560 alone:

[0136] S1. Mix 15 g of the silane coupling agent 3-glycidoxypropyltrimethoxysilane (KH560) with 30 mL of ethanol and stir for 10 min for sufficient mixing. Then, ultrasonically disperse for 30 min. Subsequently, add 200 g of magnesium hydroxide portion by portion under stirring, and continuously stir the mixture for reaction for 30 min. After the reaction is completed, a crude product is obtained.

[0137] S2. Bake the crude product obtained in step S1 at 105 °C for 2 h to obtain surface-modified magnesium hydroxide.

[0138] Mix 100 parts of the above-mentioned vinyl silicone oil with 150 parts of the surface-modified magnesium hydroxide prepared by the above method and stir evenly under the action of a high-speed disperser to prepare a base material. Then, add 5 parts of hydrogen-containing silicone oil, 4.5 parts of tackifier, and 0.5 part of 1-ethynyl-1-cyclohexanol and mix evenly. Finally, add 0.05 part of chloroplatinic acid-divinyltetramethyldisiloxane complex with an effective Pt content of 3000 ppm. Finally, put the mixture into a vacuum drying oven for vacuum defoaming for 15 min to obtain a halogen-free flame-retardant addition-cured silicone rubber.

[0139] Curing conditions: Place the silicone rubber compounds prepared in Examples 7-18 and Comparative Examples 1-3 in a flat vulcanizer and heat and cure at 150 °C for 2 min. Finally, cool the material to room temperature for standby.

[0140] Testing section

[0141] The tensile strength and elongation at break were measured using an electronic universal testing machine in accordance with the standard of GB / T 528-2009. The specimen was dumbbell-shaped with a thickness of 2 mm. The tensile rate was 500 mm / min. After the cured specimen was cooled, it was placed at room temperature for 12 hours before testing the mechanical properties.

[0142] Flame retardancy test: Referring to Method B of GB / T 2406.2-2009, the limiting oxygen index of the specimen was tested using an oxygen index meter to test the flame retardancy of the sample. Referring to the standard ISO 5660, a FTT cone calorimeter was used to test the 100×100×3 mm 3 sheet. Thus, the ignition time (TTI) was obtained. The shorter the ignition time, the worse the flame retardancy of the material to be tested.

[0143] After the oxygen index test, the appearance of the silicone rubber ash. The limiting oxygen index of the silicone rubber samples prepared in Comparative Examples 1 and 3 and Examples 7 and 8 was tested. After completion, the ash was photographed to observe the external morphology, as Figure 1 shown.

[0144] Thermogravimetric analysis: Thermogravimetric tests were carried out on silicone rubber without added flame retardant, silicone rubber prepared in Comparative Examples 1-3, and silicone rubber prepared in Examples 7 and 8 under a nitrogen atmosphere. The temperature range for heating was from room temperature to 700 °C, and the heating rate was 20 °C / min. The TG curve and DTG curve were obtained by plotting the weight loss percentage and weight loss rate against temperature, respectively, as Figure 2 and Figure 3 shown.

[0145] Adhesion test of metal and plastic interface: The adhesives of Examples 7-18 and Comparative Examples 1-4 were used to perform tensile shear experiments on the interface of PET sheet and aluminum sheet after curing by bonding. The curing conditions were 130 °C * 2 min. 10 specimens were made for each sample. By observing the tensile shear, whether cohesive failure occurred in the cured addition-type silicone rubber or interface failure occurred at the bonding interfaces of silicone rubber / aluminum and silicone rubber / PET was checked.

[0146] The test results of Examples 7-18 and Comparative Examples 1-3 are listed in Table 1.

[0147] Table 1

[0148]

[0149]

[0150] Through the data analysis in Table 1, the addition-type silicone rubber with magnesium hydroxide surface-modified by using hydrogen-containing silane and KH560 has more balanced tensile strength and elongation at break. Moreover, the limiting oxygen index ≥ 34%, and the ignition time ≥ 67 s. Compared with Comparative Examples 1 and 3 with the same amount of magnesium hydroxide, it has obvious advantages in flame retardancy. Compared with Comparative Example 2 with the same amount of magnesium hydroxide, it has obvious advantages in mechanical properties. At the same time, the adhesion of the silicone rubber to plastics and metals can achieve complete cohesive failure after tensile shear, without interface failure between the silicone rubber and the adherend, indicating that the surface-modified magnesium hydroxide can also act as a tackifier. Introducing polar ester bonds or ether bonds in the hydrogen-containing silane can provide adhesion at the metal / plastic interface. In Example 5, polar ester bonds or ether bonds were not introduced during the preparation of the hydrogen-containing silane, and the adhesion effect of the addition-type silicone rubber in corresponding Examples 15 and 16 is relatively low.

[0151] In Comparative Example 1, magnesium hydroxide was not surface-modified with hydrogen-containing silane and KH560. Water molecules can be adsorbed on the surface of magnesium hydroxide and undergo a certain degree of dissociation with water molecules to form surface hydroxyl groups. The surface hydroxyl groups endow magnesium hydroxide with certain hydrophilicity, resulting in poor compatibility with strongly hydrophobic monomers such as vinyl silicone oil and tackifier. After curing, it cannot be evenly dispersed in the silicone rubber molecular chain, resulting in very low mechanical properties. The flame retardant effect is also not ideal compared with Examples 7 - 18. From the perspective of the interface adhesion effect, the adhesion at the metal / plastic interface in Comparative Example 1 is poor.

[0152] In Comparative Example 2, only the hydrogen-containing silane prepared in Example 1 was used to surface-modify magnesium hydroxide, and KH560 which can condense with silanol groups after hydrolysis was not used. As a result, the content of reactive silicon-hydrogen bonds and silanols on the surface of magnesium hydroxide after modification is too high, which can provide more crosslinking sites, thus increasing the overall crosslinking degree of the silicone rubber. Its elongation at break decreases significantly, and the crosslinking sites are too dense, resulting in difficulty for the tackifier in the silicone rubber to form effective interaction with the surface of the adherend, thereby reducing the adhesion performance.

[0153] In Comparative Example 3, only KH560 was used to surface-modify magnesium hydroxide, lacking the crosslinking sites of hydrogen-containing silane and the carbon skeleton structure containing aromatic rings, resulting in insufficient tensile strength of the silicone rubber and poor flame retardant effect. At the same time, due to the lack of hydrogen-containing silane, the adhesion to the metal / plastic adherend interface is not high.

[0154] By Figure 1From the observation of the ash after the oxygen index test of the silicone rubber, it can be seen that the ash of Comparative Examples 1 and 3 is a brittle and hard white powder, which is SiO2 generated after the combustion of the silicone rubber. In Examples 7 and 8, by adding the powder obtained by surface modification of magnesium hydroxide with the hydrosilane prepared in Example 1 and KH560, the internal cross-section of the dense coating layer of the ash after combustion shows a gray carbon layer, indicating that the carbon skeleton structure containing aromatic rings introduced in the hydrosilane can coat the surface of magnesium hydroxide to play a charring role, thereby achieving the effects of heat insulation and flame retardancy. This carbon layer prevents the transfer of heat and oxygen to the internal materials of the silicone rubber to delay the spread of the flame, thus increasing the limiting oxygen index of the silicone rubber.

[0155] By analyzing Figure 2 the TG curve of Figure 3 and the DTG curve of

[0156] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent substitutions for some of them. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. Although the specific implementation manners of the present invention have been described above, it does not limit the protection scope of the present invention. Those skilled in the art should understand that based on the technical solutions of the present invention, various modifications or deformations that can be made without creative efforts by those skilled in the art are still within the protection scope of the present invention.

Claims

1. A use, characterized in that, Use of hydrogen-containing silane and silane coupling agent as modifiers for surface modification of magnesium hydroxide; Among them, the structural general formula of the hydrogen-containing silane is as follows: The structure of A is selected from: any one of the above.

2. The use according to claim 1, wherein The hydrogen-containing silane is obtained by a hydrosilylation reaction between a diene monomer and a cyclic hydrogen-containing silicone oil.

3. The use according to claim 2, wherein The cyclic hydrogenated silicone oil and the diene monomer are reacted in a molar ratio of (2.5-3.5):1; and / or, the diene monomer contains at least one aromatic ring; And / or, the annular hydrogen-containing silicone oil is tetramethylcyclotetrasiloxane; and / or, the diene monomer is a terminal diene monomer; And / or, a method for preparing hydrosilane comprising: adding a polymerization inhibitor and a catalyst to the reaction, reacting at 70-90° C. for 2-4 hours, then heating to 80-100° C. and keeping the temperature for 1-3 hours, wherein the polymerization inhibitor is selected from p-methylanisole, and the catalyst is selected from any one of chloroplatinic acid and chloroplatinic acid vinyl complex; And / or, the preparation method of hydrosilane comprises: cooling to 40-60° C. after the reaction is completed and distilling off the solvent under reduced pressure; And / or, the method for preparing the hydrosilane includes: adding a catalyst remaining in the activated carbon adsorption product, removing the catalyst by suction filtration, and obtaining the hydrosilane product.

4. A surface-modified magnesium hydroxide, characterized in that, The magnesium hydroxide is obtained by surface-modifying the magnesium hydroxide using the hydrogen-containing silane and the silane coupling agent as claimed in claim 1.

5. The surface-modified magnesium hydroxide according to claim 4, wherein, The silane coupling agent contains at least one epoxy group; And / or, the specific steps of the surface modification include: S1, fully mixing the hydrosilane, the silane coupling agent and the alcohol / water mixture, and then adding magnesium hydroxide and mixing evenly; S2, heating the uniformly mixed materials in S1 to 80-180° C. to obtain surface-modified magnesium hydroxide; And / or, the mass ratio of magnesium hydroxide:hydrogen-containing silane to the total amount of silane coupling agent is (5:1)-(6:1).

6. A halogen-free flame-retardant silicone rubber cured product composition, characterized in that, The invention comprises the following raw materials: vinyl silicone oil, the surface-modified magnesium hydroxide according to any one of claims 4 to 5, a cross-linking agent, a tackifier, a structure control agent and a catalyst.

7. The halogen-free flame-retardant silicone rubber cured product composition according to claim 6, wherein The vinyl content in the vinyl silicone oil is 0.05-0.5 mmol / g; And / or, the cross-linking agent is hydrogen-containing silicone oil, and the content of active hydrogen in the hydrogen-containing silicone oil is 0.1-1 wt%; and / or, the structure control agent is selected from any one or more of 1-ethynyl-1-cyclohexanol, tetramethyltetravinylcyclotetrasiloxane, 2-methyl-3-butynyl-2-ol, 3-methyl-1-ethynyl-3-ol, 3,5-dimethyl-1-hexynyl-3-ol and 3-methyl-1-dodecyn-3-ol; And / or, the catalyst is selected from any one or more of chloroplatinic acid, chloroplatinic acid-isopropanol complex or chloroplatinic acid-divinyl complex; And / or, the general structural formula of the tackifier is: Wherein, X and Y are each independently selected from any one of vinyl, allyl, methacryloxypropyl, glycidyloxypropyl, and isocyanatopropyl, and X and Y are different; And / or, the halogen-free flame retardant silicone rubber cured composition is composed of the following components in parts by weight: 90-110 parts of vinyl silicone oil, 120-180 parts of the surface-modified magnesium hydroxide, 1-10 parts of a crosslinking agent, 1-10 parts of a tackifier, and 0.1-1 part of a structure control agent.

8. A method for preparing a halogen-free flame-retardant silicone rubber cured product, characterized in that, The raw materials according to claim 6 are mixed uniformly, and after adding a catalyst, degassing and curing are carried out at a curing temperature of 100-200°C.

9. A use, characterized in that, Use of the halogen-free flame-retardant silicone rubber composition according to any one of claims 6-7 as an adhesive.

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