A foamed vulcanized silicone rubber, a method for preparing the same, and use thereof

Abstract

This invention provides a foamed vulcanized silicone rubber, its preparation method, and its application. The raw materials for preparing the foamed vulcanized silicone rubber, by weight, include the following components: 50-70 parts vinyl polysiloxane, 2-4 parts foaming agent, 15-25 parts silica, 0.1-1 parts structure control agent, 0.5-2 parts carbon black, 30-45 parts flame retardant, 0.1-1 parts inhibitor, 0.5-1 parts catalyst, and 1-2 parts vulcanizing agent. The vinyl polysiloxane includes vinyl short-chain silicone oil and vinyl long-chain raw rubber. The vinyl short-chain silicone oil has a molecular weight of 60,000-150,000; the vinyl long-chain raw rubber has a molecular weight of 600,000-700,000. This invention achieves a balance between low hardness, high creep resistance, and flame retardancy in the foamed vulcanized silicone rubber by compounding two vinyl polysiloxanes with different molecular weights with a foaming agent, flame retardant, and vulcanizing agent.

Description

Technical Field

[0001] This invention belongs to the field of silicone rubber technology, and particularly relates to a foamed vulcanized silicone rubber, its preparation method and application. Background Technology

[0002] In the modern industrial and consumer goods sectors, from automotive interiors and architectural spaces to medical protective gear and precision instrument packaging, the performance requirements for polymer foam materials are becoming increasingly diversified, refined, and complex. From the passenger experience in automotive interiors to fire safety in architectural spaces, from the human body fit of medical protective gear to the cushioning protection of precision instruments, traditional materials with single properties can no longer meet the comprehensive needs for comfort, safety, durability, and other properties in complex application scenarios.

[0003] As a widely used porous elastic material, traditional foam has certain basic properties in terms of cushioning, sealing and sound insulation, but its inherent material characteristics lead to a series of problems when dealing with high-end needs: (1) It is difficult to balance the hardness and fit of the material. Although rigid foam can provide sufficient mechanical support, it feels stiff. Soft foam has advantages in terms of comfort, but due to insufficient creep resistance, it is easy to deform under long-term pressure, which shortens its lifespan. (2) In order to achieve a high flame retardant rating, traditional foam often adds a large amount of flame retardant, which will seriously damage the flexibility and shaping ability of the foam, making the material brittle and hard.

[0004] CN119286039A discloses a process for preparing graphene-doped silicone rubber foam using supercritical foaming, comprising the following steps: S1, mixing: methyl vinyl silicone rubber, fumed silica, hydroxyl silicone oil, and reduced graphene oxide are added to a mixer and mixed under heating, then aged at room temperature to obtain compound 1; S2, vulcanizing agent mixing: compound 1 and vulcanizing agent are added to a mixer and mixed at room temperature to obtain compound 2; S3, pre-vulcanization: compound 2 is placed in a flat vulcanizing machine for pre-vulcanization to obtain the product to be foamed; S4, supercritical foaming: the product to be foamed is placed in a supercritical foaming device for foaming, then the foam obtained after foaming is heated and dried, and then heat-treated to obtain the final graphene-doped silicone rubber foam. This patent significantly improves the hardness of the material and has high creep resistance by doping with graphene and fumed silica, but it does not mention the flame retardant properties of the material, nor does it add flame retardant components.

[0005] CN110240767A discloses a bromine-free flame-retardant foamed polystyrene material with tensile creep resistance. The raw materials for preparing the polystyrene material include the following components in parts by weight: 35-60 parts of general-purpose polystyrene, 10-22 parts of phenolic resin, 8-17 parts of rock wool fiber, 9-20 parts of polyetherimide, 5-10 parts of polytetrafluoroethylene fiber, 7-13 parts of polypropylene mesh fiber, 0.5-1.5 parts of foaming agent, 2-5 parts of compatibilizer, 0.5-2 parts of coupling agent, 0.5-2 parts of lubricant, and 0.5-1 part of ultraviolet light absorber. This patent significantly improves the creep resistance and flame retardancy of the material through the compounding of multiple components. However, the phenolic resin itself has high hardness and tensile strength, which increases the hardness of the material and worsens its tactile feel.

[0006] CN110862693A discloses a two-component liquid silicone rubber for foam with ultra-low compression set, comprising the following raw material formulation: 50-200 parts of vinyl-terminated silicone oil, 5-20 parts of methyl-terminated hydrogen-containing silicone oil, 10-60 parts of methyl-terminated silicone oil with vinyl side chains, 10-40 parts of fumed silica, 1-16 parts of hexamethyldisilazane, 0.05-0.4 parts of divinyltetramethyldisilazane, 0.1-2 parts of divinyltetramethyldisiloxane, 3-25 ppm of platinum catalyst, 1-20 parts of n-butanol, and 0.5-4 parts of distilled water. The foam made from this two-component liquid silicone rubber has a lower compression set and suitable hardness, but the material is not flame-retardant.

[0007] The materials mentioned in the patents are all difficult to balance flame retardancy, low hardness, and high creep resistance. Especially in fields with stringent standards for safety, durability, and user experience, such as rail transit, interior decoration of high-rise buildings, electronic medical devices, and high-end rehabilitation aids, the performance shortcomings of traditional foam have become a key bottleneck restricting product upgrades and technological innovation.

[0008] Therefore, developing a foamed vulcanized silicone rubber that combines low hardness, high creep resistance, and high flame retardancy is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a foamed vulcanized silicone rubber, its preparation method, and its application. The foamed vulcanized silicone rubber is formulated by compounding two vinyl polysiloxanes of different molecular weights with a foaming agent, a flame retardant, and a vulcanizing agent, and simultaneously possesses low hardness, high creep resistance, and excellent flame retardancy.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides a foamed vulcanized silicone rubber, wherein the raw materials for preparing the foamed vulcanized silicone rubber comprise the following components by weight:

[0012] 50-70 parts of vinyl polysiloxane

[0013] 2-4 parts foaming agent

[0014] 15-25 parts of silica

[0015] Structure control agent 0.1-1 part

[0016] 0.5-2 parts carbon black

[0017] 30-45 parts flame retardant

[0018] Inhibitor 0.1-1 part

[0019] 0.5-1 part catalyst

[0020] 1-2 parts of vulcanizing agent;

[0021] The vinyl polysiloxane includes vinyl short-chain silicone oil and vinyl long-chain raw rubber;

[0022] The molecular weight of the vinyl short-chain silicone oil is 60,000-150,000;

[0023] The molecular weight of the vinyl long-chain raw rubber is 600,000 to 700,000.

[0024] This invention employs a combination of vinyl short-chain silicone oil and vinyl long-chain raw rubber to achieve a balance between the hardness and creep resistance of foamed vulcanized silicone rubber. Due to its shorter molecular chains, vinyl short-chain silicone oil can react with the vulcanizing agent to form a denser three-dimensional cross-linked network. This structure restricts molecular chain movement, significantly reducing the possibility of chain slippage and endowing the vulcanized silicone rubber with excellent creep resistance. However, if only vinyl short-chain silicone oil is used, the excessively high cross-linking density will lead to a decrease in the flexibility of the vulcanized silicone rubber, increasing its brittleness and making it prone to cracking. On the other hand, the longer vinyl long-chain raw rubber has a certain degree of flexibility, and its uniform distribution between cross-linking points can disperse stress and absorb energy, thereby reducing the hardness of the vulcanized silicone rubber and improving its flexibility. The structure control agent can react with the hydroxyl groups on the surface of silica, passivating the silica, eliminating active groups on the silica surface, and inhibiting the formation of random and disordered physical cross-linking points between silica and other components. This allows the subsequent major cross-linking reactions to proceed in a more controllable and uniform environment. This invention achieves a balance between low hardness and creep resistance in foamed vulcanized silicone rubber by compounding two vinyl polysiloxanes of different molecular weights with a foaming agent, a flame retardant, and a vulcanizing agent, while also exhibiting excellent flame retardancy.

[0025] The amount of the vinyl polysiloxane can be 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, 62 parts, 64 parts, 66 parts, 68 parts, or 70 parts, etc.

[0026] The amount of foaming agent can be 2 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts, 3 parts, 3.2 parts, 3.4 parts, 3.6 parts, 3.8 parts, or 4 parts, etc.

[0027] The amount of silica used can be 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, or 25 parts, etc.

[0028] The amount of the structure control agent can be 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, or 1 part, etc.

[0029] The amount of carbon black used can be 0.5 parts, 0.7 parts, 0.9 parts, 1.1 parts, 1.3 parts, 1.5 parts, 1.7 parts, 1.9 parts, or 2 parts, etc.

[0030] The amount of the flame retardant can be 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, 40 parts, 41 parts, 42 parts, 43 parts, 44 parts, or 45 parts, etc.

[0031] The dosage of the inhibitor can be 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, or 1 part, etc.

[0032] The amount of catalyst used can be 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, or 1 part, etc.

[0033] The amount of the vulcanizing agent can be 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, or 2 parts, etc.

[0034] The molecular weight of the vinyl short-chain silicone oil can be 60,000, 70,000, 80,000, 90,000, 100,000, 110,000, 120,000, 130,000, 140,000, or 150,000, etc.

[0035] The molecular weight of the vinyl long-chain raw rubber can be 600,000, 610,000, 620,000, 630,000, 640,000, 650,000, 660,000, 670,000, 680,000, 690,000, or 700,000, etc.

[0036] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0037] Preferably, the mass ratio of the vinyl short-chain silicone oil to the vinyl long-chain raw rubber is 1:(2-4), for example, 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3, 1:3.2, 1:3.4, 1:3.6, 1:3.8 or 1:4, etc.

[0038] In this invention, if the mass ratio of vinyl short-chain silicone oil to vinyl long-chain raw rubber is too small, that is, if the amount of vinyl short-chain silicone oil is too small, a sufficient cross-linked network structure cannot be formed, and the vulcanized silicone rubber will be very soft and unable to provide sufficient support. If the mass ratio of the two is too large, that is, if the amount of vinyl short-chain silicone oil is too large, the cross-linking density will be too large, resulting in increased brittleness, increased hardness, and a stiff feel to the vulcanized silicone rubber.

[0039] Preferably, the foaming agent comprises sodium bicarbonate.

[0040] Preferably, the structure control agent comprises hydroxyl silicone oil.

[0041] Preferably, the hydroxyl content in the hydroxyl silicone oil is 3.8-4.2%, such as 3.8%, 3.9%, 4%, 4.1% or 4.2%.

[0042] Preferably, the viscosity of the hydroxyl silicone oil is 38-45 mm. 2 / s, for example, 38mm 2 / s, 39mm 2 / s, 40mm 2 / s, 41mm 2 / s, 42mm 2 / s, 43mm 2 / s, 44mm 2 / s or 45mm 2 / s etc.

[0043] If the amount of foaming agent is too low, there will be no foaming effect, and the hardness of the vulcanized silicone rubber will be too high; if the amount of foaming agent is too high, the vulcanized silicone rubber will have too many cells, too low density, significantly reduced hardness, and loss of creep resistance.

[0044] Preferably, the foaming temperature of the foaming agent is 130-150℃, such as 130℃, 132℃, 134℃, 136℃, 138℃, 140℃, 142℃, 144℃, 146℃, 148℃ or 150℃.

[0045] Preferably, the flame retardant comprises aluminum hydroxide and zinc borate.

[0046] Aluminum hydroxide primarily exerts its physical flame-retardant effect by absorbing heat, cooling down, and releasing water vapor, while zinc borate exerts its chemical flame-retardant effect by promoting the formation of a highly insulating borosilicate glass layer. The two work together to construct a robust ceramic protective layer on the surface of silicone rubber, thereby achieving a highly efficient synergistic flame-retardant effect between the gas phase and the condensed phase.

[0047] Preferably, the mass percentage of aluminum hydroxide is 65-70%, for example, 65%, 66%, 67%, 68%, 69%, or 70%, based on 100% of the flame retardant.

[0048] The inhibitors include any one or a combination of at least two of 3,7,11-trimethyldodecyn-3-ol, 1-ethynylcyclohexanol, diallyl maleate, methylbutynol, or dimethylhexynol.

[0049] Preferably, the catalyst comprises a platinum catalyst.

[0050] Preferably, the vulcanizing agent comprises hydrogen-containing silicone oil.

[0051] Preferably, the content of silicon-hydrogen bonds in the hydrogen-containing silicone oil is 7-10 mmol / g, such as 7 mmol / g, 8 mmol / g, 9 mmol / g, or 10 mmol / g.

[0052] In a second aspect, the present invention provides a method for preparing foamed vulcanized silicone rubber as described in the first aspect, the method comprising the following steps:

[0053] (1) Mix vinyl polysiloxane, silica and structure control agent to obtain base adhesive A;

[0054] (2) The flame retardant, carbon black and the base adhesive A are mixed to obtain base adhesive B;

[0055] (3) Mix the vulcanizing agent, inhibitor, catalyst, foaming agent and the base rubber B, foam and vulcanize to obtain the foamed vulcanized silicone rubber.

[0056] Preferably, in steps (1)-(3), the mixing temperature is not higher than 80°C, for example, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C or 75°C.

[0057] Preferably, in step (1), the mixing time is 0.8-1.5 h, for example 0.8 h, 1 h, 1.2 h, 1.4 h or 1.5 h.

[0058] Preferably, in step (2), the mixing includes room temperature mixing and hot vacuum mixing.

[0059] Preferably, the temperature of the thermal vacuum mixing is 150-160℃ (e.g., 150℃, 152℃, 154℃, 156℃, 158℃ or 160℃, etc.), and the vacuum degree is -0.1~-0.05MPa (e.g., -0.1MPa, -0.09MPa, -0.08MPa, -0.07MPa, -0.06MPa or -0.05MPa, etc.).

[0060] Preferably, in steps (1)-(2), the mixing is carried out in a kneader.

[0061] Preferably, in step (3), the mixing, foaming and vulcanization are carried out in an open mill.

[0062] Preferably, the foaming and vulcanization temperature is 140-150℃, such as 140℃, 142℃, 144℃, 146℃, 148℃, or 150℃.

[0063] Preferably, the total time for foaming and vulcanization is 35-50 min, such as 35 min, 37 min, 39 min, 41 min, 43 min, 45 min, 47 min, 49 min, or 50 min.

[0064] Thirdly, the present invention provides an application of the foamed vulcanized silicone rubber as described in the first aspect in automotive interiors or medical protective equipment.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] This invention achieves a balance between low hardness, high creep resistance, and flame retardancy in foamed vulcanized silicone rubber by compounding two vinyl polysiloxanes of different molecular weights with a foaming agent, a flame retardant, and a vulcanizing agent. Specifically, the foamed vulcanized silicone rubber has a compressive stress between 115-150 kPa (30% compressive stress), high creep resistance (creep ≤ 28.6%), and flame retardancy reaching V0 level. Detailed Implementation

[0067] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0068] The source information of some raw materials in this embodiment of the invention is as follows:

[0069] Vinyl short-chain silicone oil A: viscosity 20000 mPa·s, vinyl content 0.26-0.30%, Zhejiang Hengyecheng Organosilicon Co., Ltd., HV20K;

[0070] Vinyl short-chain silicone oil B: viscosity 10000 mPa·s, vinyl content 0.34-0.38%, Zhejiang Hengyecheng Organosilicon Co., Ltd., HV10K;

[0071] Vinyl short-chain silicone oil C: viscosity 100000 mPa·s, vinyl content 0.15-0.18%, Zhejiang Hengyecheng Organosilicon Co., Ltd., HV100K;

[0072] Vinyl long-chain raw rubber A: molecular weight 600,000-700,000, vinyl content 0.2%, Dow Corning, XIAMETER RBG-0702;

[0073] Vinyl long-chain raw rubber B: molecular weight 600,000-700,000, vinyl content 0.03%, Dow Corning, XIAMETER RBG-0701;

[0074] Vinyl long-chain raw rubber C: molecular weight 600,000-700,000, vinyl content 3.0%, Dow Corning, XIAMETER RBG-0730;

[0075] Hydroxy silicone oil: viscosity 38-45 mm 2 / s, hydroxyl content 3.8-4.2%, Dow Corning, XIAMETERPMX-0930;

[0076] Silica: Wacker Chemie AG, H2000;

[0077] Sodium bicarbonate: Shandong Haihua Group Co., Ltd.;

[0078] Carbon black: Cabot Chemicals, Inc., USA, Carbon Black 660R;

[0079] Catalyst: Heraeus Precious Metals Technologies Ltd., Karstedt catalyst;

[0080] Hydrogen-containing silicone oil: Dow Corning, XIAMETER MHX-1107;

[0081] Inhibitor: 3,7,11-trimethyldodecyn-3-ol, Hubei Xingyao Biomedical Technology Co., Ltd., 24424-78-0.

[0082] Example 1

[0083] This embodiment provides a foamed vulcanized silicone rubber and its preparation method. The raw materials for preparing the foamed vulcanized silicone rubber include the following components by weight:

[0084] Vinyl short-chain silicone oil A: 15 parts;

[0085] Vinyl long-chain raw rubber A: 47 parts;

[0086] Sodium bicarbonate: 3 parts;

[0087] Silica: 20 parts;

[0088] Hydroxy silicone oil: 0.5 parts;

[0089] Carbon black: 1 part;

[0090] Aluminum hydroxide: 20 parts;

[0091] Zinc borate: 12 parts;

[0092] Inhibitor: 0.2 parts;

[0093] Catalyst: 0.6 parts;

[0094] 1.2 parts of hydrogen-containing silicone oil;

[0095] The preparation method includes the following steps:

[0096] (1) According to the above formula dosage, vinyl short-chain silicone oil A, vinyl long-chain raw rubber A, silica and hydroxyl silicone oil are added to a kneader and mixed at room temperature for 1 hour, with the temperature controlled below 80°C, to obtain base rubber A;

[0097] (2) Add aluminum hydroxide, zinc borate, carbon black and the base adhesive A to a kneader, mix evenly at room temperature, heat to 155°C, vacuum -0.06MPa, and maintain for 1h to obtain base adhesive B;

[0098] (3) The hydrogen-containing silicone oil, inhibitor, catalyst, sodium bicarbonate and the base rubber B are mixed in a two-roll mill, and foamed and vulcanized at 140°C for 40 min to obtain the foamed vulcanized silicone rubber.

[0099] Example 2

[0100] This embodiment provides a foamed vulcanized silicone rubber and its preparation method. The raw materials for preparing the foamed vulcanized silicone rubber include the following components by weight:

[0101] Vinyl short-chain silicone oil B: 18 parts;

[0102] Vinyl long-chain raw rubber B: 36 parts;

[0103] Sodium bicarbonate: 4 parts;

[0104] Silica: 15 parts;

[0105] Hydroxysilicone oil: 3 parts;

[0106] Carbon black: 1 part;

[0107] Aluminum hydroxide: 25 parts;

[0108] Zinc borate: 15 parts;

[0109] Inhibitor: 0.3 parts;

[0110] Catalyst: 0.6 parts;

[0111] Hydrogen-containing silicone oil: 1.1 parts;

[0112] The preparation method includes the following steps:

[0113] (1) According to the above formula dosage, vinyl short-chain silicone oil B, vinyl long-chain raw rubber B, silica and hydroxyl silicone oil are added to a kneader and mixed at room temperature for 1.5 h, with the temperature controlled below 80℃, to obtain base rubber A;

[0114] (2) Add aluminum hydroxide, zinc borate, carbon black and the base adhesive A to a kneader, mix evenly at room temperature, heat to 150°C, vacuum -0.08MPa, and maintain for 1h to obtain base adhesive B;

[0115] (3) The hydrogen-containing silicone oil, inhibitor, catalyst, sodium bicarbonate and the base rubber B are mixed in a two-roll mill, and foamed and vulcanized at 130°C for 50 minutes to obtain the foamed vulcanized silicone rubber.

[0116] Example 3

[0117] This embodiment provides a foamed vulcanized silicone rubber and its preparation method. The raw materials for preparing the foamed vulcanized silicone rubber include the following components by weight:

[0118] Vinyl short-chain silicone oil C: 10 parts;

[0119] Vinyl long-chain raw rubber C: 40 parts;

[0120] Sodium bicarbonate: 2 parts;

[0121] Silica: 25 parts;

[0122] Hydroxysilicone oil: 3 parts;

[0123] Carbon black: 1 part;

[0124] Aluminum hydroxide: 29 parts;

[0125] Zinc borate: 15 parts;

[0126] Inhibitor: 0.3 parts;

[0127] Catalyst: 0.6 parts;

[0128] Hydrogen-containing silicone oil: 1.1 parts;

[0129] The preparation method includes the following steps:

[0130] (1) According to the above formula dosage, vinyl short-chain silicone oil C, vinyl long-chain raw rubber C, silica and hydroxyl silicone oil are added to a kneader and mixed at room temperature for 0.8 h, with the temperature controlled below 80℃, to obtain base rubber A;

[0131] (2) Add aluminum hydroxide, zinc borate, carbon black and the base adhesive A to a kneader, mix evenly at room temperature, heat to 160°C, vacuum -0.08MPa, and maintain for 1h to obtain base adhesive B;

[0132] (3) The hydrogen-containing silicone oil, inhibitor, catalyst, sodium bicarbonate and the base rubber B are mixed in a two-roll mill, foamed and vulcanized at 150°C for 35 minutes to obtain the foamed vulcanized silicone rubber.

[0133] Example 4

[0134] The only difference between this embodiment and Example 1 is that the amount of vinyl short-chain silicone oil A is 10 parts, the amount of vinyl long-chain raw rubber A is 52 parts, and the amount of other components and the preparation method are the same as in Example 1.

[0135] Example 5

[0136] The only difference between this embodiment and Example 1 is that the amount of vinyl short-chain silicone oil A is 31 parts, the amount of vinyl long-chain raw rubber A is 31 parts, and the amount of other components and the preparation method are the same as in Example 1.

[0137] Example 6

[0138] The only difference between this embodiment and Example 1 is that the foaming temperature in step (3) is 120°C, while the amount of other components and the preparation method are the same as in Example 1.

[0139] Example 7

[0140] The only difference between this embodiment and Example 1 is that the foaming temperature in step (3) is 160°C, while the amount of other components and the preparation method are the same as in Example 1.

[0141] Example 8

[0142] The only difference between this embodiment and Example 1 is that the amount of aluminum hydroxide used is 24 parts, the amount of zinc borate used is 8 parts, and the amount of other components and the preparation method are the same as in Example 1.

[0143] Example 9

[0144] The only difference between this embodiment and Example 1 is that the amount of aluminum hydroxide used is 20 parts, the amount of zinc borate used is 12 parts, and the amount of other components and the preparation method are the same as in Example 1.

[0145] Comparative Example 1

[0146] The only difference between this comparative example and Example 1 is that the amount of vinyl short-chain silicone oil A is 62 parts, and vinyl long-chain raw rubber A is not used. The amounts of other components and the preparation methods are the same as in Example 1.

[0147] Comparative Example 2

[0148] The only difference between this comparative example and Example 1 is that the amount of vinyl long-chain raw rubber A is 62 parts, and vinyl short-chain silicone oil A is not used. The amounts of other components and the preparation methods are the same as in Example 1.

[0149] Comparative Example 3

[0150] The only difference between this comparative example and Example 1 is that the amount of sodium bicarbonate used is 1.5 parts, while the amounts of the other components and the preparation methods are the same as in Example 1.

[0151] Comparative Example 4

[0152] The only difference between this comparative example and Example 1 is that the amount of sodium bicarbonate used is 6 parts, while the amounts and preparation methods of the other components are the same as in Example 1.

[0153] Performance testing

[0154] (1) Compressive stress: Tested according to ASTM D1056 compressive stress test standard.

[0155] (2) Creep resistance: The sample was cut to an initial width of 7 mm, the compression rate was adjusted to 50%, the sample was compressed, and the width change before and after compression was calculated.

[0156] (3) Flame retardancy: tested according to UL94 standard.

[0157] Following the above test methods, the performance of the foamed vulcanized silicone rubbers provided in the examples and comparative examples was tested, and the results are shown in Table 1:

[0158] Table 1

[0159]

[0160] This invention achieves a balance between low hardness, high creep resistance, and flame retardancy in foamed vulcanized silicone rubber by compounding two vinyl polysiloxanes of different molecular weights with a foaming agent, a flame retardant, and a vulcanizing agent. Specifically, the foamed vulcanized silicone rubber prepared in Examples 1-3 has a compressive stress between 115-150 kPa (30% compressive stress), high creep resistance (creep ≤ 28.6%), and flame retardancy reaching V0 level.

[0161] The comparison between Examples 1 and Examples 4-5 shows that Example 4 used less vinyl short-chain silicone oil, resulting in excessively soft vulcanized silicone rubber that could not provide sufficient support; Example 5 used more vinyl short-chain silicone oil, resulting in increased brittleness, increased hardness, and decreased tactile feel of the vulcanized silicone rubber. This indicates that a mass ratio of vinyl short-chain silicone oil to vinyl long-chain raw rubber in the range of 1:(2-4) can achieve a balance between low hardness and high creep resistance.

[0162] A comparison of Examples 1 and 6-7 shows that the foaming temperature of Example 6 is lower, resulting in greater hardness and improved creep resistance of the vulcanized silicone rubber; while the foaming temperature of Example 7 is higher, resulting in more cells, lower density of the vulcanized silicone rubber, and decreased creep resistance.

[0163] As can be seen from the comparison between Examples 1 and Examples 8-9, aluminum hydroxide and zinc borate must be used in appropriate proportions to enable vulcanized silicone rubber to have both excellent flame retardancy and low hardness.

[0164] The comparison between Example 1 and Comparative Examples 1-2 shows that Comparative Example 1, which lacks vinyl long-chain raw rubber, has increased brittleness and a stiff feel; Comparative Example 2, which lacks vinyl short-chain silicone oil, has lost its creep resistance.

[0165] As can be seen from the comparison between Example 1 and Comparative Examples 3-4, if the amount of foaming agent is too low, there will be no foaming effect; if the amount of foaming agent is too high, the density of the vulcanized silicone rubber will be too low, the hardness will decrease significantly, and the creep resistance will disappear.

[0166] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A foamed vulcanized silicone rubber, characterized by, The raw materials for preparing the foamed vulcanized silicone rubber include the following components by weight: 50-70 parts of vinyl polysiloxane 2-4 parts of foaming agent 15-25 parts of silica Structure control agent 0.1-1 part 0.5-2 parts carbon black 30-45 parts flame retardant Inhibitor 0.1-1 part 0.5-1 part catalyst 1-2 parts of vulcanizing agent; The vinyl polysiloxane includes vinyl short-chain silicone oil and vinyl long-chain raw rubber; The molecular weight of the vinyl short-chain silicone oil is 60,000-150,000; The molecular weight of the vinyl long-chain raw rubber is 600,000 to 700,000.

2. The expanded vulcanizing silicone rubber according to claim 1, characterized by The mass ratio of the vinyl short-chain silicone oil to the vinyl long-chain raw rubber is 1:(2-4); Preferably, the foaming agent comprises sodium bicarbonate; Preferably, the foaming temperature of the foaming agent is 130-150℃.

3. The foamed vulcanized silicone rubber according to claim 1 or 2, characterized in that, The structure control agent includes hydroxyl silicone oil; Preferably, the hydroxyl content in the hydroxyl silicone oil is 3.8-4.2%; Preferably, the viscosity of the hydroxyl silicone oil is 38-45 mm 2 / s.

4. The expanded vulcanizing silicone rubber according to any one of claims 1 to 3, characterized in that, The flame retardant includes aluminum hydroxide and zinc borate; Preferably, the aluminum hydroxide comprises 65-70% by mass, based on 100% of the flame retardant. Preferably, the inhibitor comprises any one or a combination of at least two of 3,7,11-trimethyldodecyn-3-ol, 1-ethynylcyclohexanol, diallyl maleate, methylbutynol, or dimethylhexynol.

5. The expanded vulcanizing silicone rubber according to any one of claims 1 to 4, characterized in that, The catalyst includes a platinum catalyst.

6. The expanded vulcanizing silicone rubber according to any one of claims 1 to 5, characterized in that, The vulcanizing agent includes hydrogen-containing silicone oil; Preferably, the content of silicon-hydrogen bonds in the hydrogen-containing silicone oil is 7-10 mmol / g.

7. A process for the production of the foamed vulcanized silicone rubber according to any one of claims 1 to 6, characterized in that, The preparation method includes the following steps: (1) Mix vinyl polysiloxane, silica and structure control agent to obtain base adhesive A; (2) Mix the flame retardant, carbon black and the base adhesive A to obtain base adhesive B; (3) Mix the vulcanizing agent, inhibitor, catalyst, foaming agent and the base rubber B, foam and vulcanize to obtain the foamed vulcanized silicone rubber.

8. The preparation method according to claim 7, characterized in that, In step (1), the mixing temperature is not higher than 80°C; Preferably, in step (1), the mixing time is 0.8-1.5 hours; Preferably, in step (2), the mixing includes room temperature mixing and hot vacuum mixing; Preferably, the temperature of the thermal vacuum mixing is 150-160℃, and the vacuum degree is -0.1~-0.05MPa.

9. The production method according to claim 7 or 8, characterized by, In steps (1)-(2), the mixing is carried out in a kneader; Preferably, in step (3), the mixing, foaming, and vulcanization are carried out in an open mill; Preferably, the foaming and vulcanization temperature is 130-150°C; Preferably, the total time for foaming and vulcanization is 35-50 minutes.

10. The application of a foamed vulcanized silicone rubber as described in any one of claims 1-6 in automotive interiors or medical protective gear.

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