Silicone rubber composition, modified silicone rubber and preparation method thereof

Abstract

The invention relates to a silicone rubber composition, modified silicone rubber and a preparation method thereof. The silicone rubber composition comprises the following components in parts by weight: 100 parts of methyl vinyl silicone rubber, 10-60 parts of fumed silica, 1-20 parts of a silicon-containing compound, 0.1-6 parts of peroxide and 0.1-10 parts of rare earth oxide, wherein the silicon-containing compound is selected from one or more of hydroxyl silicone oil, diphenyl silanediol, dimethyl dimethoxy silane, dimethyl diethoxy silane, methyl phenyl dimethoxy silane, methyl phenyl diethoxy silane and hexamethyl disilazane, and the silicon-containing compound is selected from one or more of hydroxyl silicone oil, diphenyl silanediol, dimethyl dimethoxy silane, dimethyl diethoxy silane, methyl phenyl diethoxy silane and hexamethyl disilazane; the rare earth element in the rare earth oxide is selected from one or more of La, Ce or Sm. The silicone rubber composition provided by the invention can improve the tensile strength and the retention rate of the elongation at break of the silicone rubber after high-temperature aging.

Description

Technical Field

[0001] This invention relates to a silicone rubber composition, modified silicone rubber, and a method for preparing the same. Background Technology

[0002] Silicone rubber is a widely used high-performance synthetic rubber. Its main chain consists of alternating silicon and oxygen atoms, while its side chains are organic groups. The bond energy of the Si-O bond in the silicone rubber main chain is 451 kJ / mol, giving it low chemical reactivity, good stability, and excellent resistance to heat and oxygen aging. With the continuous expansion of silicone rubber's applications, higher requirements are being placed on its heat resistance, especially in the aerospace field where silicone rubber products are used at temperatures exceeding 300℃. Conventional silicone rubber is prone to embrittlement and fracture at 300℃, failing to meet the requirements for high-temperature applications. Therefore, developing a high-temperature resistant silicone rubber material is essential.

[0003] Currently, methods to improve the high-temperature resistance of silicone rubber include modifying the main chain and side group structure, eliminating silanol groups, adding silicone resin, adding metal-containing organosilicon polymers, adding heat-resistant agents, and introducing heteroatoms. Adding heat-resistant agents is a simple and efficient method. Metal oxides or their complexes are uniformly dispersed into the silicone rubber matrix as heat-resistant agents, preventing oxidative degradation of the silicone rubber during high-temperature use and significantly improving its thermo-oxidative stability.

[0004] CN 116218227A discloses a high-temperature resistant silicone rubber and its preparation method. The high-temperature silicone rubber heat resistant agent (FS) described in this method is an inorganic compound containing iron and tin, prepared by mixing ferric chloride and tin chloride (molar ratio 1-3:5-7) via co-precipitation followed by sintering at 300-650℃. Sintering is performed at 300℃, 400℃, 500℃, and 600℃ for 1 hour each. This preparation method easily introduces iron, resulting in a reddish tint to the silicone rubber product.

[0005] CN 115746568A discloses a method for preparing a high-temperature resistant silicone rubber material. The method involves adding tungsten or molybdenum oxide to water or a mixture of water and an organic solvent; stirring for 1 hour; then adding ligand molecules such as alcohols, amines, or phenols, followed by the dispersion of nano-zirconia. The mixture is stirred until uniformly dispersed, washed with deionized water and ethanol, centrifuged, and dried below 60°C to obtain atomically sized tungsten-molybdenum oxide-supported nano-zirconia. This method is complex and costly. Summary of the Invention

[0006] In view of this, one object of the present invention is to provide a silicone rubber composition that can improve the retention rate of tensile strength and elongation at break of silicone rubber after high-temperature aging.

[0007] Another object of the present invention is to provide a method for preparing a silicone rubber composition.

[0008] Another object of the present invention is to provide a modified silicone rubber.

[0009] Another object of the present invention is to provide a method for preparing modified silicone rubber, which can improve the retention rate of tensile strength and elongation at break of silicone rubber after high-temperature aging.

[0010] The present invention achieves the above objectives using the following technical solutions.

[0011] On one hand, the present invention provides a silicone rubber composition comprising the following components:

[0012] 100 parts by weight of methyl vinyl silicone rubber,

[0013] 10-60 parts by weight of fumed silica,

[0014] 1-20 parts by weight of silicon-containing compound,

[0015] 0.1 to 6 parts by weight of peroxide, and

[0016] 0.1 to 10 parts by weight of rare earth oxides;

[0017] The silicon-containing compound is selected from one or more of hydroxyl silicone oil, diphenylsilanediol, dimethyldimethoxysilane, dimethyldiethoxysilane, methylphenyldimethoxysilane, methylphenyldiethoxysilane, or hexamethyldisilazane.

[0018] The rare earth elements in the rare earth oxides are selected from one or more of La, Ce, or Sm.

[0019] The silicone rubber composition of the present invention, based on 100 parts by weight of methyl vinyl silicone rubber, may use 15 to 50 parts by weight of fumed silica, preferably 15 to 40 parts by weight, and more preferably 15 to 25 parts by weight.

[0020] The silicone rubber composition of the present invention, based on 100 parts by weight of methyl vinyl silicone rubber, may contain 1 to 10 parts by weight of the silicone compound, preferably 1.5 to 5 parts by weight, and more preferably 1.7 to 2.5 parts by weight.

[0021] The silicone rubber composition of the present invention, based on 100 parts by weight of methyl vinyl silicone rubber, may contain 0.2 to 2 parts by weight of peroxide, preferably 0.2 to 1.5 parts by weight, and more preferably 0.25 to 0.5 parts by weight.

[0022] The silicone rubber composition of the present invention is based on 100 parts by weight of methyl vinyl silicone rubber, and the amount of rare earth oxide can be 0.2 to 10 parts by weight, preferably 0.3 to 8 parts by weight, and more preferably 0.3 to 5 parts by weight.

[0023] The present invention has found that controlling the above components within the above range can significantly improve the retention rate of tensile strength and elongation at break of aged silicone rubber.

[0024] According to the silicone rubber composition of the present invention, preferably, the loose bulk density of the rare earth oxide is ≤0.6 g / cm³. 3 .

[0025] In some embodiments, the loose packing density of the rare earth oxide is 0.2–0.6 g / m³. 3 The preferred concentration is 0.4–0.55 g / m³. 3 .

[0026] In some embodiments, the rare earth element in the rare earth oxide is Ce. In other embodiments, the rare earth element in the rare earth oxide is Ce, La, and Sm; the molar ratio of Ce, La, and Sm can be 2:(0.5-1.5):(0.5-1.5); preferably 2:(0.8-1.2):(0.8-1.2).

[0027] The rare earth oxide contains ≥92 wt% rare earth elements, calculated as REO. According to one embodiment of the present invention, the rare earth oxide contains ≥94 wt% rare earth elements.

[0028] In some embodiments, the silicon-containing compound is one or more of hydroxyl silicone oil or hexamethyldisilazane, preferably hydroxyl silicone oil.

[0029] According to the silicone rubber composition of the present invention, preferably, the peroxide is selected from one or more of benzoyl peroxide, dicumyl peroxide, and 2,5-di-tert-butylperoxide-2,5-dimethylhexane; more preferably, the peroxide is selected from one or more of dicumyl peroxide, 2,5-di-tert-butyl, or 2,5-dimethylhexane.

[0030] In the silicone rubber composition according to the present invention, preferably, the peroxide is dicumyl peroxide.

[0031] In the silicone rubber composition according to the present invention, preferably, the peroxide is 2,5-di-tert-butylperoxide-2,5-dimethylhexane.

[0032] According to the silicone rubber composition of the present invention, preferably, the silicon-containing compound is hexamethyldisilazane.

[0033] According to the silicone rubber composition of the present invention, preferably, the rare earth oxide is prepared by the following method:

[0034] (A) A solid-state reaction is carried out between rare earth inorganic salt solid and ammonium carbon inorganic salt solid to obtain the first product;

[0035] (B) The first product is mixed with a slurry at a temperature not lower than 40°C to form a first product slurry; then the first product slurry is reacted at 40-95°C to obtain the second product.

[0036] (C) Separate the second product from the solid to the liquid to obtain a solid product; calcine the solid product at 300-450°C to obtain rare earth oxides;

[0037] Among them, rare earth inorganic salts are selected from one or more of rare earth chloride, rare earth sulfate, rare earth nitrate or rare earth acetate; ammonium carbon inorganic salts are selected from one or more of (NH4)2CO3 and NH4HCO3; and slurry is selected from one or more of water, ethanol, methanol or acetone.

[0038] In some embodiments, the rare earth inorganic salt is rare earth chloride. The rare earth element in the rare earth inorganic salt is selected from one or more of La, Ce, or Sm. The rare earth inorganic salt is selected from one of LaCl3, CeCl3, and SmCl3. In other embodiments, the rare earth inorganic salt is LaCl3, CeCl3, and SmCl3. The molar ratio of LaCl3, CeCl3, and SmCl3 can be (0.5–1.5):2:(0.5–1.5); preferably (0.8–1):2:(0.8–1).

[0039] In some schemes, the molar ratio of rare earth inorganic salt to ammonium carbon inorganic salt can be 1:(1-6); preferably 1:(2-5); more preferably 1:(2.3-3.5); and even more preferably 1:(3.0-3.3).

[0040] In some embodiments, the reaction temperature for the solid-state reaction is 40–95°C; preferably 70–95°C; the reaction time is 0.05–3 hours; preferably 0.1–2 hours; more preferably 0.1–1 hour. The rare earth inorganic salt solid and the ammonium carbonate inorganic salt undergo a solid-state reaction in the absence of liquid. In this invention, the rare earth inorganic salt is first reacted with ammonium carbonate or ammonium bicarbonate in a solid-state reaction to generate rare earth carbonate plate-like crystals, and then further reaction is carried out in the presence of liquid. This allows the generated rare earth carbonate to have a lower bulk density.

[0041] According to one embodiment of the present invention, the slurry is water. The temperature of the slurry is 40–95°C; more preferably 40–90°C; and even more preferably 40–80°C. According to one embodiment of the present invention, the temperature of the slurry is 57–63°C.

[0042] In some schemes, based on 1 mol of rare earth inorganic salt solid, the amount of slurry used can be 0.8 to 2.5 L; preferably 1 to 2.1 L; and even more preferably 1.2 to 1.8 L.

[0043] In some embodiments, in step (B), the reaction temperature is 40–95°C; preferably 70–95°C, more preferably 85–95°C; and the reaction time is 0.05–6 hours, preferably 0.1–5 hours, more preferably 0.1–1 hour. In step (B), the slurry dissolves some of the unreacted rare earth inorganic salts and ammonium salts, causing a reaction that generates a large number of highly active rare earth particles on the surface of the rare earth carbonate plate-like crystals. These active particles have a strong ability to bind free radicals, effectively preventing the silicone rubber from undergoing chain scission reactions.

[0044] In some methods, the solid product is washed, dried, and then calcined.

[0045] The drying temperature can be 50–200°C, preferably 80–180°C, and more preferably 100–120°C. The drying time can be 3–15 hours, preferably 4–12 hours, and more preferably 6–10 hours.

[0046] The calcination temperature is 300–450°C, preferably 350–450°C, and more preferably 390–410°C. The calcination time can be 3–15 hours, preferably 4–13 hours, and more preferably 6–12 hours.

[0047] In another aspect, the present invention also provides a method for preparing the above-mentioned silicone rubber composition, comprising the following steps:

[0048] Rare earth oxides and silicon-containing compounds are mixed evenly to obtain a first mixture;

[0049] The first mixture, methyl vinyl silicone rubber, fumed silica and peroxide are mixed to obtain a silicone rubber composition.

[0050] The selection and dosage of fumed silica, silicon-containing compounds, peroxides, and rare earth oxides are as described above and will not be repeated here.

[0051] On the other hand, the present invention also provides a modified silicone rubber, which is prepared from the above-described silicone rubber composition.

[0052] Furthermore, the present invention also provides a method for preparing modified silicone rubber, comprising the following steps:

[0053] Rare earth oxides and silicon-containing compounds are mixed evenly to obtain a first mixture;

[0054] The first mixture, methyl vinyl silicone rubber, fumed silica and peroxide are mixed to obtain a silicone rubber composition;

[0055] The silicone rubber composition is compounded and then vulcanized to obtain modified silicone rubber.

[0056] The selection and dosage of fumed silica, silicon-containing compounds, peroxides, and rare earth oxides are as described above and will not be repeated here.

[0057] In some technical solutions, the mixing temperature is 15-60℃, preferably 18-50℃, more preferably 25-40℃; the mixing time is 0.1-1h, preferably 0.15-0.8h, more preferably 0.2-0.5h.

[0058] The vulcanization includes primary vulcanization and secondary vulcanization;

[0059] The primary vulcanization temperature can be 150–170℃, preferably 155–165℃; the primary vulcanization time can be 0.05h–0.3h, preferably 0.1–0.2h; and the primary vulcanization pressure can be 8–12MPa, preferably 8–10MPa.

[0060] The secondary vulcanization temperature can be 190–220℃, preferably 195–205℃; the secondary vulcanization time can be 2–8h, preferably 3–5h; and the secondary vulcanization pressure is atmospheric pressure.

[0061] The silicone rubber composition of the present invention can improve the long-term high-temperature resistance of silicone rubber. The modified silicone rubber of the present invention has excellent long-term heat resistance, and still has high tensile strength and breaking productivity after being treated at 300°C for 96 hours. Detailed Implementation

[0062] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0063] Example 1

[0064] 1 mol of CeCl3 and 3 mol of NH4HCO3 were reacted in a solid-state reaction at 95 °C for 0.1 h. Then, 1200 mL of water at 60 °C was added, and the reaction was continued at 95 °C for another 0.1 h. The product was filtered, washed, dried at 100 °C for 7 h, and calcined at 400 °C for 10 h to obtain rare earth oxides. The rare earth content (REO) was 94.7%, and the loose bulk density was 0.48 g / cm³. 3 Rare earth content was tested using EDTA complexometric titration (GB / T 14635-2008). Loose packing density was measured using the funnel method (GB / T 31057.1-2014).

[0065] 0.5 parts by weight of the above rare earth oxides and 2 parts by weight of hydroxyl silicone oil were mixed evenly to obtain a first mixture. The first mixture, 100 parts by weight of methyl vinyl silicone rubber, 20 parts by weight of fumed silica, and 0.3 parts by weight of dicumyl peroxide were mixed to obtain a second mixture. The second mixture was kneaded at 30°C for 0.5 h, then vulcanized once at a pressure of 10 MPa and a temperature of 160°C for 0.2 h, and then vulcanized a second time at atmospheric pressure and a temperature of 200°C for 4 h to obtain modified silicone rubber.

[0066] Example 2

[0067] 0.5 mol CeCl3, 0.25 mol LaCl3, 0.25 mol SmCl3, and 3.2 mol NH4HCO3 were reacted in a solid-state reaction at 40 °C for 1 hour. Then, 1800 mL of water at 55 °C was added, and the reaction was repeated at 40 °C for 5 hours. The product was filtered, washed, dried at 110 °C for 7 hours, and calcined at 400 °C for 7 hours to obtain rare earth oxides. The rare earth content (REO) was 94.9%, and the bulk density was 0.53 g / cm³. 3 Rare earth content was tested using EDTA complexometric titration (GB / T 14635-2008). Loose packing density was measured using the funnel method (GB / T31057.1-2014).

[0068] Five parts by weight of rare earth oxides and five parts by weight of hexamethyldisilazane were mixed evenly to obtain a first mixture. The first mixture, 100 parts by weight of methyl vinyl silicone rubber, 30 parts by weight of fumed silica, and 1 part by weight of 2,5-di-tert-butylperoxide-2,5-dimethylhexane were mixed to obtain a second mixture. The second mixture was kneaded at 25°C for 0.2 h, then vulcanized once at a pressure of 9 MPa and a temperature of 165°C for 0.1 h, and then vulcanized a second time at atmospheric pressure and a temperature of 210°C for 3 h to obtain modified silicone rubber.

[0069] Example 3

[0070] 1 mol of LaCl3 and 2.5 mol of NH4HCO3 were reacted in a solid-state reaction at 60 °C for 0.4 h. Then, 1200 mL of ethanol at 60 °C was added, and the reaction was continued at 60 °C for 0.3 h. The product was filtered, washed, dried at 50 °C for 10 h, and calcined at 450 °C for 3 h to obtain rare earth oxides. The rare earth content (REO) was 95.2%, and the loose bulk density was 0.52 g / cm³. 3Rare earth content was tested using EDTA complexometric titration (GB / T 14635-2008). Loose packing density was measured using the funnel method (GB / T 31057.1-2014).

[0071] Ten parts by weight of the above rare earth oxides and eight parts by weight of hydroxyl silicone oil were mixed evenly to obtain a first mixture. The first mixture, 100 parts by weight of methyl vinyl silicone rubber, 40 parts by weight of fumed silica, and 1 part by weight of dicumyl peroxide were mixed to obtain a second mixture. The second mixture was kneaded at 40°C for 0.3 h, then vulcanized once at a pressure of 12 MPa and a temperature of 170°C for 0.1 h, and then vulcanized a second time at atmospheric pressure and a temperature of 210°C for 3 h to obtain modified silicone rubber.

[0072] Example 4

[0073] 1 mol of SmCl3 and 3.5 mol of NH4HCO3 were reacted in a solid-state reaction at 80 °C for 0.4 h. 1500 mL of water at 50 °C was added, and the reaction was carried out again at 50 °C for 2 h. The product was filtered, washed, dried at 120 °C for 6 h, and calcined at 380 °C for 12 h to obtain rare earth oxides. The rare earth content (REO) was 96.3%, and the loose bulk density was 0.55 g / cm³. 3 Rare earth content was tested using EDTA complexometric titration (GB / T 14635-2008). Loose packing density was measured using the funnel method (GB / T 31057.1-2014).

[0074] Three parts by weight of rare earth oxides and six parts by weight of hexamethyldisilazane were mixed evenly to obtain a first mixture. The first mixture, 100 parts by weight of methyl vinyl silicone rubber, 40 parts by weight of fumed silica, and 2 parts by weight of 2,5-di-tert-butylperoxide-2,5-dimethylhexane were mixed to obtain a second mixture. The second mixture was kneaded at 40°C for 0.3 h, then vulcanized once at a pressure of 8 MPa and a temperature of 155°C for 0.3 h, and then vulcanized a second time at atmospheric pressure and a temperature of 195°C for 5 h to obtain modified silicone rubber.

[0075] Comparative Example 1

[0076] Five parts by weight of commercially available cerium dioxide (compliant with GB / T 4155-2012 standard) and five parts by weight of hexamethyldisilazane were mixed evenly to obtain a first mixture. The first mixture, 100 parts by weight of methyl vinyl silicone rubber, 30 parts by weight of fumed silica, and 1 part by weight of 2,5-di-tert-butylperoxide-2,5-dimethylhexane were mixed to obtain a second mixture. The second mixture was kneaded at 30°C for 0.5 h, then vulcanized once at a pressure of 10 MPa and a temperature of 160°C for 0.2 h, and then vulcanized a second time at atmospheric pressure and a temperature of 200°C for 4 h to obtain modified silicone rubber.

[0077] Experimental Example 1

[0078] Modified silicone rubber was treated at 300℃ for 96 hours to obtain aged modified silicone rubber. The tensile strength and elongation at break of the modified silicone rubber before and after aging were tested according to the methods specified in GB / T 528-2009, and the retention rates of tensile strength and elongation at break before and after aging were calculated respectively.

[0079] Tensile strength retention rate before and after aging = tensile strength after aging ÷ original tensile strength;

[0080] Elongation at break retention rate before and after aging = Elongation at break after aging ÷ Original elongation at break;

[0081] The results are shown in Table 1.

[0082] Table 1

[0083] serial number Tensile strength retention rate before and after aging Elongation at break retention rate before and after aging Example 1 0.55 0.30 Example 2 0.52 0.29 Example 3 0.49 0.27 Example 4 0.47 0.28 Comparative Example 1 0.16 0.09

[0084] As shown in the table above, the modified silicone rubbers of Examples 1-4 exhibited significantly better retention rates of tensile strength and elongation at break after 96 hours of high-temperature aging at 300°C compared to Comparative Example 1. This indicates that the rare earth oxides of the present invention have a significant impact on the retention rates of tensile strength and elongation at break of the modified silicone rubber, and are not a conventional choice. Furthermore, the effect of Example 1 is superior to that of Example 2, demonstrating that the types of components in the composition have a significant impact on the retention rates of tensile strength and elongation at break of the modified silicone rubber, and are not a conventional choice.

[0085] This invention is not limited to the above-described embodiments. Any modifications, improvements, or substitutions that can be conceived by those skilled in the art without departing from the essential content of this invention fall within the scope of this invention.

Claims

1. A silicone rubber composition, characterized in that, It includes the following components: 100 parts by weight of methyl vinyl silicone rubber, 10-60 parts by weight of fumed silica, 1-20 parts by weight of silicon-containing compound, 0.1 to 6 parts by weight of peroxide, and 0.1 to 10 parts by weight of rare earth oxides; The silicon-containing compound is selected from one or more of hydroxyl silicone oil, diphenylsilanediol, dimethyldimethoxysilane, dimethyldiethoxysilane, methylphenyldimethoxysilane, methylphenyldiethoxysilane, or hexamethyldisilazane. The rare earth elements in the rare earth oxides are selected from one or more of La, Ce, or Sm.

2. The silicone rubber composition according to claim 1, characterized in that, The loose bulk density of the rare earth oxide is ≤0.6 g / cm³. 3 .

3. The silicone rubber composition according to claim 1, characterized in that, The peroxide is selected from one or more of benzoyl peroxide, dicumyl peroxide, and 2,5-di-tert-butylperoxide-2,5-dimethylhexane.

4. The silicone rubber composition according to claim 3, characterized in that, The peroxide is diisopropylbenzene peroxide.

5. The silicone rubber composition according to claim 3, characterized in that, The peroxide is 2,5-di-tert-butylperoxide-2,5-dimethylhexane.

6. The silicone rubber composition according to claim 5, characterized in that, The silicon-containing compound is hexamethyldisilazane.

7. The silicone rubber composition according to claim 1, characterized in that, The rare earth oxides were prepared using the following method: (A) A solid-state reaction is carried out between a rare earth inorganic salt solid and an ammonium carbon inorganic salt solid to obtain the first product; (B) The first product is mixed with a slurry at a temperature not lower than 40°C to form a first product slurry; then the first product slurry is reacted at 40-95°C to obtain the second product. (C) Separate the second product from its liquid state to obtain a solid product; The solid product was calcined at 300–450 °C to obtain rare earth oxides; Among them, rare earth inorganic salts are selected from one or more of rare earth chloride, rare earth sulfate, rare earth nitrate or rare earth acetate; ammonium carbon inorganic salts are selected from one or more of (NH4)2CO3 and NH4HCO3; and slurry is selected from one or more of water, ethanol, methanol or acetone.

8. The method for preparing the silicone rubber composition according to claim 1, characterized in that, Includes the following steps: Rare earth oxides and silicon-containing compounds are mixed evenly to obtain a first mixture; The first mixture, silicone rubber, fumed silica, and peroxide are mixed to obtain a silicone rubber composition.

9. A modified silicone rubber, characterized in that, The modified silicone rubber is prepared from the silicone rubber composition according to any one of claims 1 to 7.

10. The method for preparing modified silicone rubber according to claim 9, characterized in that, Includes the following steps: Rare earth oxides and silicon-containing compounds are mixed evenly to obtain a first mixture; The first mixture, silicone rubber, fumed silica and peroxide are mixed to obtain a silicone rubber composition; The silicone rubber composition is compounded and then vulcanized to obtain modified silicone rubber.