Mixed silicone rubber and preparation method thereof

Abstract

The invention discloses mixed silicone rubber and a preparation method of the mixed silicone rubber. Comprising 80-95 parts of raw rubber with the molecular weight of 50-70 thousand and the vinyl chain link content of 0.03-0.1%, 5-20 parts of vinyl silicone oil with the viscosity of 5000-15000 mpa.s and the vinyl chain link content of 4-14%, 50-60 parts of white carbon black, 8-12 parts of a treating agent, 2-5 parts of a cross-linking agent, 0.01-0.1 part of tert-butyl dimethyl (pent-4-alkyne-1-yloxy) silane, 0.1 part of a release agent, 0.05-0.5 part of a catalyst and 0.01-1 part of an inhibitor, and the sum of the weight of the raw rubber and the weight of the vinyl silicone oil is 100 parts. The mixed silicone rubber disclosed by the invention has relatively high hardness (gt); 70A), which can also maintain a good elongation (gt; and the tensile strength is greater than 7.5 MPa, so that the problem that the high-hardness silicon rubber is fragile is effectively solved, and the high-hardness silicon rubber is particularly suitable for application scenes requiring high elongation.

Description

Technical Field

[0001] The invention belongs to the technical field of silicone rubber products, and in particular relates to a mixed silicone rubber and a preparation method thereof. Background Art

[0002] Silicone rubber is a material made of polyorganosiloxane (commonly known as raw rubber) mixed with reinforcing fillers. Due to its unique physical and chemical properties, such as good oil resistance, chemical resistance, high and low temperature resistance, environmental safety and weather resistance, it is widely used in the fields of food and medical devices. These applications include but are not limited to water cups, tableware, spatulas, pacifiers, infusion tubes, medical accessories, medicine boxes and peristaltic pump tubes. In order to ensure the safety and stability of the product, silicone rubber products used in the food and medical fields usually undergo a two-stage vulcanization treatment, and the performance indicators of the final product are also based on the test results after the two-stage vulcanization treatment.

[0003] The mainstream silicone rubber products on the market currently usually use linear high-polymerization polyethylene organosiloxane as the base polymer, and the reinforcing filler mainly selects various types of white carbon black, which can effectively improve the mechanical strength and physical properties of silicone rubber. However, for application scenarios that require higher hardness, the formula of silicone rubber needs to be further optimized. At present, the hardness of silicone rubber is usually increased by increasing the crosslinking density and the content of reinforcing fillers. Although this method can significantly improve the hardness of silicone rubber, it also brings about the problem of decreased elongation; for example, the first-stage elongation of conventional high-hardness silicone rubber (Shore hardness 70A and above) is generally between 300 and 600%, and after the second-stage treatment, the elongation can often only be maintained between 200 and 500%, which makes the product prone to brittleness and cannot meet the needs of some products with high elongation requirements.

[0004] In recent years, researchers have tried to improve the elongation of high-hardness silicone rubber through different approaches. For example, CN117361547A proposed a new method for preparing silica particles, which adjusts the reaction conditions of sodium silicate solution to obtain silica particles with better hardening and reinforcement effects, thereby solving the structural problem of silicone rubber and improving its plasticity to a certain extent; however, even so, the maximum elongation at break of the obtained high-hardness silicone rubber is only 352%. For another example, CN115926472A discloses a method of adding an appropriate amount of polyvinyl polysiloxane with a vinyl content of 20% and a vinyl polysiloxane with a vinyl content of 0.2% and then matching an appropriate amount of cross-linking agent so that the final product not only has high hardness, but also performs well in tensile strength, elongation and tear strength. Specifically, it can maintain an elongation of 510% when the hardness reaches 70A, and even when the hardness reaches 75A, the elongation can still be maintained at 460%. It is one of the high-hardness silicone rubbers with outstanding performance on the market. In addition, CN117777735A provides a method for preparing heat-vulcanized silicone rubber using a kneading machine, which not only simplifies the production process and improves production efficiency, but also ensures that the various properties of silicone rubber are more concentrated, with lower volatile matter and higher mechanical properties; however, even with the use of advanced manufacturing technology, the elongation of heat-vulcanized silicone rubber in the hardness range of 64-70A can still only reach 335-525%. In summary, although some progress has been made in improving the elongation of high-hardness silicone rubber, it is still a challenge to achieve a silicone rubber with an elongation of more than 1000% in the first stage and an elongation of more than 800% after the second stage treatment.

[0005] Therefore, there is an urgent need for a mixed silicone rubber and a preparation method thereof to solve the deficiencies of the prior art problems. Summary of the invention

[0006] In view of the above problems, the object of the present invention is to provide a compound silicone rubber and a preparation method thereof, which not only has a high hardness (>70A), but also maintains good elongation (>800%) and tensile strength (greater than 7.5MPa), effectively solving the problem of brittleness of high-hardness silicone rubber, and is particularly suitable for application scenarios requiring high elongation.

[0007] To achieve the above objectives, the first aspect of the present invention provides a mixed silicone rubber, which includes, by weight, 80 to 95 parts of raw rubber with a molecular weight of 500,000 to 700,000 and a vinyl segment content of 0.03 to 0.1%, 5 to 20 parts of vinyl silicone oil with a viscosity of 5000 to 15000 mPa.s and a vinyl segment content of 4 to 14%, 50 to 60 parts of white carbon black, 8 to 12 parts of a treating agent, 2 to 5 parts of a cross-linking agent, 0.01 to 0.1 parts of tert-butyldimethyl (pent-4-yn-1-yloxy) silane, 0.1 parts of a release agent, 0.05 to 0.5 parts of a catalyst, and 0.01 to 1 parts of an inhibitor, and the sum of the weight of the raw rubber and the vinyl silicone oil is 100 parts.

[0008] Compared with the prior art, the present invention selects 80-95 parts of raw rubber with high molecular weight (500,000-700,000) but low vinyl chain content (0.03-0.1%) and 5-20 parts of vinyl silicone oil with low viscosity (5000-15000 mPa.s) but high vinyl chain content (4-14%) as main components, and the combination of the two can significantly improve the elongation and tensile strength while ensuring the hardness. However, when the vinyl chain content in the vinyl silicone oil is too high, these highly active vinyl groups will quickly participate in the reaction at the initial stage of the reaction to form some local, overly dense cross-linked structures, and this local over-cross-linking will hinder the full cross-linking of other unreacted areas, resulting in uneven vulcanization process. Based on this, the present application also introduces tert-butyl dimethyl (pent-4-yn-1-yloxy) silane, which can effectively adjust the cross-linking density, avoid the occurrence of local excessive cross-linking, and ensure the uniformity and completeness of the vulcanization process, thereby playing a key role in protecting the elongation and tensile strength; at the same time, the introduced white carbon black can further enhance the tensile strength, thereby ensuring that the tensile strength can remain above 7.5MPa when the hardness is greater than 70A. Therefore, the mixed silicone rubber of the present invention not only has a higher hardness (>70A), but also maintains good elongation (>800%) and tensile strength (greater than 7.5MPa), which effectively solves the problem of brittleness of high-hardness silicone rubber, and is particularly suitable for application scenarios requiring high elongation.

[0009] Further, the raw rubber of the present invention is selected from at least one of 112 type methyl vinyl silicone rubber raw rubber and 110 type methyl vinyl silicone rubber raw rubber. Preferably, the raw rubber is selected from 110 type methyl vinyl silicone rubber raw rubber.

[0010] Furthermore, the white carbon black of the present invention is selected from at least one of precipitated white carbon black, fumed white carbon black, treated precipitated white carbon black, and treated fumed white carbon black. Preferably, the white carbon black is fumed white carbon black or treated fumed white carbon black. Specifically, the specific surface area of ​​the white carbon black is 130 to 420 m 2 / g, such as the specific surface area of ​​white carbon black can be but not limited to 150m 2 / g, 200m 2 / g, 250m 2 / g、300m 2 / g, 350m 2 / g, 400m 2 / g.

[0011] Furthermore, the treatment agent of the present invention is selected from at least one of a,w-dihydroxy polydimethylsiloxane with a low degree of polymerization of 2 to 6% and a hydroxyl content, a,w-dihydroxy polydimethylsiloxane with a low degree of polymerization of 5 to 10%, methoxysilane, ethoxysilane, and hexamethyldisilazane. Preferably, the treatment agent is selected from at least one of methoxysilane, a,w-dihydroxy polydimethylsiloxane with a low degree of polymerization of 2 to 6% and a,w-dihydroxy polydimethylsiloxane with a low degree of polymerization of 5 to 10%. Specifically, the structure of methoxysilane is shown in Formula 2; the structure of a,w-dihydroxy polydimethylsiloxane with a low degree of polymerization is shown in Formula 3 below.

[0012]

[0013] Among them, n1=1~8, n2=4~10.

[0014] Furthermore, the crosslinking agent of the present invention is a linear polymethylhydrogensiloxane represented by Formula 1,

[0015]

[0016] Wherein, R is a methyl group, m+n=4-200 and the mass fraction of active hydrogen is greater than or equal to 0.75%.

[0017] Further, the catalyst of the present invention is selected from at least one of a Custer catalyst, an alcohol-modified chloroplatinic acid catalyst, and a platinum-alkyne-based complex. Specifically, the effective content of the catalyst is 1000 to 8000 PPM, such as the effective content of the catalyst may be but not limited to 1000 PPM, 2000 PPM, 3000 PPM, 4000 PPM, 5000 PPM, 6000 PPM, 7000 PPM, and 8000 PPM. Preferably, the catalyst is selected from a Custer catalyst; the structure of the Custer catalyst is shown in Formula 4 below.

[0018]

[0019] Further, the inhibitor of the present invention is selected from at least one of 3-methyl-1-butyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol, 1-ethynyl-1-cyclohexanol, 3-phenyl-1-butyn-3-ol, alkyne-oxy-containing polysiloxane, methylvinylcyclotetrasiloxane, amide compounds, and maleate compounds. Preferably, the inhibitor is at least one of 3,5-dimethyl-1-hexyn-3-ol, 1-ethynyl-1-cyclohexanol, and maleate compounds.

[0020] Furthermore, the release agent of the present invention is at least one of higher fatty acids and metal salts thereof, azo compounds, and liquid polyisobutylene. The release agent has almost no effect on the various properties of the compounded silicone rubber of the present invention, so the release agent is not limited to the types listed, and other types not listed within the scope of the release agent are also applicable.

[0021] Furthermore, the CAS number of the tert-butyldimethyl(pent-4-yn-1-yloxy)silane of the present invention is 61362-77-4, and the purity is required to be ≥95%.

[0022] Accordingly, the second aspect of the present invention also provides a method for preparing a mixed silicone rubber, comprising the steps of:

[0023] (1) mixing raw rubber, vinyl silicone oil, a treating agent, a releasing agent and white carbon black in a vacuum kneader to obtain a base rubber;

[0024] (2) mixing the base rubber, the cross-linking agent, tert-butyldimethyl (pent-4-yn-1-yloxy) silane, the inhibitor, and the catalyst in an open mill to obtain a mixed rubber material;

[0025] (3) performing a stage vulcanization on the mixed rubber material to obtain a stage of vulcanized silicone rubber;

[0026] (4) The first-stage vulcanized silicone rubber is subjected to second-stage vulcanization to obtain the mixed silicone rubber.

[0027] Furthermore, step (1) of the present invention also includes: putting raw rubber, vinyl silicone oil, treatment agent, release agent and white carbon black into a vacuum kneader, stirring and kneading the rubber into a mass under a nitrogen atmosphere, then heating to 150-200° C., vacuuming the rubber, stopping vacuum extraction, cooling, refining and filtering in sequence to obtain the base rubber.

[0028] Furthermore, the white carbon black of the present invention is added in multiple times, each time with an interval of 10 to 20 minutes, until all the white carbon black is added.

[0029] Furthermore, the present invention puts raw rubber, vinyl silicone oil, treating agent, release agent and white carbon black into a vacuum kneader, stirs and kneads at 30-90° C. in a nitrogen atmosphere until the rubber material is agglomerated, and the stirring frequency is 10-50 Hz.

[0030] Furthermore, the vacuum rubber mixing conditions of the present invention are: stirring at a vacuum degree of 0.05 to 0.1 MPa and a stirring frequency of 30 to 50 Hz for 1 to 4 hours.

[0031] Furthermore, in step (1) of the present invention, cooling includes cooling to below 90°C.

[0032] Furthermore, step (2) of the present invention comprises: mixing the base rubber, the crosslinking agent, tert-butyldimethyl(pent-4-yn-1-yloxy)silane and the inhibitor in an open mill, adding the catalyst and mixing them uniformly to obtain a mixed rubber material.

[0033] Furthermore, in step (3) of the present invention, the first stage vulcanization includes: vulcanization at 120-130° C. for 10 minutes; and the second stage vulcanization in step (4) includes: baking at 200° C. for 4 hours. DETAILED DESCRIPTION

[0034] In order to explain the purpose, content and beneficial effects of the present invention in detail, the following will further illustrate the present invention through specific examples and comparative examples.

[0035] The sources of the main raw materials used in the examples and comparative examples are as follows:

[0036]

[0037] Example 1

[0038] The present embodiment provides a mixed silicone rubber, which includes, by weight, 85 parts of 110 type methyl vinyl silicone rubber raw rubber with a molecular weight of 530,000 and a vinyl chain content of 0.06%, 15 parts of vinyl silicone oil with a viscosity of 15000 mPa.s and a vinyl chain content of 8%, and 53 parts of a specific surface area of ​​200 m 2 / g of fumed silica, 8 parts of a,w-dihydroxypolydimethylsiloxane with a low degree of polymerization and a hydroxyl content of 8%, 4.5 parts of linear polymethylhydrogensiloxane with an active hydrogen content of 1% and m+n=100, 0.04 parts of tert-butyldimethyl(pent-4-yn-1-yloxy)silane, 0.1 parts of stearate, 0.3 parts of Custer's catalyst with an effective content of 5000PPM, and 0.02 parts of 1-ethynyl-1-cyclohexanol.

[0039] This embodiment provides a method for preparing a mixed silicone rubber, comprising the steps of:

[0040] (1) kneading raw rubber, vinyl silicone oil, low-polymerization degree a, w-dihydroxy polydimethylsiloxane, stearate, and fumed silica in a vacuum kneader (kneading conditions: under nitrogen atmosphere, stirring frequency of 50 Hz, temperature of 70° C.), adding fumed silica in multiple times, each time with an interval of 15 minutes, until all the fumed silica is added, then heating to 180° C., and then stirring at a stirring frequency of 50 Hz for 3.5 hours under a vacuum degree of 0.08 MPa, stopping vacuuming, and then cooling to 30° C., refining, filtering, and obtaining a base rubber;

[0041] (2) mixing the base rubber, linear polymethylhydrogensiloxane, tert-butyldimethyl (pent-4-yn-1-yloxy) silane, and 1-ethynyl-1-cyclohexanol in an open mill, adding a Custer catalyst, and mixing well to obtain a mixed rubber material;

[0042] (3) vulcanizing the mixed rubber at 125° C. for 10 min to obtain a section of vulcanized silicone rubber;

[0043] (4) A section of vulcanized silicone rubber is baked at 200°C for 4 hours to obtain a mixed silicone rubber.

[0044] Example 2

[0045] The present embodiment provides a mixed silicone rubber, which includes, by weight, 85 parts of 110 type methyl vinyl silicone rubber raw rubber with a molecular weight of 530,000 and a vinyl chain content of 0.06%, 15 parts of vinyl silicone oil with a viscosity of 15000 mPa.s and a vinyl chain content of 8%, and 53 parts of a specific surface area of ​​400 m 2 / g of fumed silica, 11 parts of a,w-dihydroxypolydimethylsiloxane with a low degree of polymerization and a hydroxyl content of 8%, 4.5 parts of linear polymethylhydrogensiloxane with an active hydrogen content of 1% and m+n=100, 0.04 parts of tert-butyldimethyl(pent-4-yn-1-yloxy)silane, 0.1 parts of stearate, 0.3 parts of Custer catalyst with an effective content of 5000PPM, and 0.02 parts of 1-ethynyl-1-cyclohexanol.

[0046] This embodiment provides a method for preparing a mixed silicone rubber, comprising the steps of:

[0047] (1) kneading raw rubber, vinyl silicone oil, low-polymerization degree a, w-dihydroxy polydimethylsiloxane, stearate, and fumed silica in a vacuum kneader (kneading conditions: under nitrogen atmosphere, stirring frequency of 45 Hz, temperature of 80° C.), adding fumed silica in multiple times, each time with an interval of 15 minutes, until all the fumed silica is added, then heating to 190° C., and then stirring at a stirring frequency of 40 Hz for 3 hours under a vacuum degree of 0.1 MPa, stopping vacuuming, and then cooling to 35° C., refining, filtering, and obtaining a base rubber;

[0048] (2) mixing the base rubber, linear polymethylhydrogensiloxane, tert-butyldimethyl (pent-4-yn-1-yloxy) silane, and 1-ethynyl-1-cyclohexanol in an open mill, adding a Custer catalyst, and mixing well to obtain a mixed rubber material;

[0049] (3) vulcanizing the mixed rubber at 128° C. for 10 min to obtain a section of vulcanized silicone rubber;

[0050] (4) A section of vulcanized silicone rubber is baked at 200°C for 4 hours to obtain a mixed silicone rubber.

[0051] Example 3

[0052] The present embodiment provides a mixed silicone rubber, which includes, by weight, 90 parts of 110-type methyl vinyl silicone rubber raw rubber with a molecular weight of 530,000 and a vinyl link content of 0.06%, 10 parts of vinyl silicone oil with a viscosity of 15000 mPa.s and a vinyl link content of 8%, and 60 parts of a specific surface area of ​​400 m 2 / g of fumed silica, 12 parts of a,w-dihydroxypolydimethylsiloxane with a low degree of polymerization and a hydroxyl content of 8%, 3 parts of linear polymethylhydrogensiloxane with an active hydrogen content of 1% and m+n=100, 0.06 parts of tert-butyldimethyl(pent-4-yn-1-yloxy)silane, 0.1 parts of stearate, 0.3 parts of Custer catalyst with an effective content of 5000PPM, and 0.02 parts of 1-ethynyl-1-cyclohexanol.

[0053] This embodiment provides a method for preparing a mixed silicone rubber, comprising the steps of:

[0054] (1) kneading raw rubber, vinyl silicone oil, low-polymerization degree a, w-dihydroxy polydimethylsiloxane, stearate, and fumed silica in a vacuum kneader (kneading conditions: under nitrogen atmosphere, stirring frequency of 50 Hz, temperature of 60° C.), adding fumed silica in multiple times, each time with an interval of 18 minutes, until all the fumed silica is added, then heating to 160° C., and then stirring at a stirring frequency of 40 Hz for 3.2 hours under a vacuum degree of 0.07 MPa, stopping vacuuming, and then cooling to 38° C., refining, filtering, and obtaining a base rubber;

[0055] (2) mixing the base rubber, linear polymethylhydrogensiloxane, tert-butyldimethyl (pent-4-yn-1-yloxy) silane, and 1-ethynyl-1-cyclohexanol in an open mill, adding a Custer catalyst, and mixing well to obtain a mixed rubber material;

[0056] (3) vulcanizing the mixed rubber material at 122° C. for 10 min to obtain a section of vulcanized silicone rubber;

[0057] (4) A section of vulcanized silicone rubber is baked at 200°C for 4 hours to obtain a mixed silicone rubber.

[0058] Example 4

[0059] The present embodiment provides a mixed silicone rubber, which includes, by weight, 90 parts of 110-type methyl vinyl silicone rubber raw rubber with a molecular weight of 530,000 and a vinyl chain content of 0.1%, 10 parts of vinyl silicone oil with a viscosity of 8000 mPa.s and a vinyl chain content of 11%, and 53 parts of a specific surface area of ​​300 m 2 / g of fumed silica, 11 parts of a,w-dihydroxypolydimethylsiloxane with a low degree of polymerization and a hydroxyl content of 8%, 3 parts of linear polymethylhydrogensiloxane with an active hydrogen content of 1% and m+n=100, 0.06 parts of tert-butyldimethyl(pent-4-yn-1-yloxy)silane, 0.1 parts of stearate, 0.3 parts of Custer catalyst with an effective content of 5000PPM, and 0.02 parts of 1-ethynyl-1-cyclohexanol.

[0060] This embodiment provides a method for preparing a mixed silicone rubber, comprising the steps of:

[0061] (1) kneading raw rubber, vinyl silicone oil, low-polymerization degree a, w-dihydroxy polydimethylsiloxane, stearate, and fumed silica in a vacuum kneader (kneading conditions: under nitrogen atmosphere, stirring frequency of 50 Hz, temperature of 70° C.), adding fumed silica in multiple times, each time with an interval of 15 minutes, until all the fumed silica is added, then heating to 180° C., and then stirring at a stirring frequency of 50 Hz for 3.5 hours under a vacuum degree of 0.08 MPa, stopping vacuuming, and then cooling to 30° C., refining, filtering, and obtaining a base rubber;

[0062] (2) mixing the base rubber, linear polymethylhydrogensiloxane, tert-butyldimethyl (pent-4-yn-1-yloxy) silane, and 1-ethynyl-1-cyclohexanol in an open mill, adding a Custer catalyst, and mixing well to obtain a mixed rubber material;

[0063] (3) vulcanizing the mixed rubber at 125° C. for 10 min to obtain a section of vulcanized silicone rubber;

[0064] (4) A section of vulcanized silicone rubber is baked at 200°C for 4 hours to obtain a mixed silicone rubber.

[0065] Example 5

[0066] The present embodiment provides a mixed silicone rubber, which includes, by weight, 90 parts of 110-type methyl vinyl silicone rubber raw rubber with a molecular weight of 530,000 and a vinyl chain content of 0.06%, 10 parts of vinyl silicone oil with a viscosity of 8000 mPa.s and a vinyl chain content of 11%, and 53 parts of a specific surface area of ​​300 m2 / g of fumed silica, 12 parts of a,w-dihydroxypolydimethylsiloxane with a low degree of polymerization and a hydroxyl content of 8%, 3.5 parts of linear polymethylhydrogensiloxane with an active hydrogen content of 1% and m+n=100, 0.1 parts of tert-butyldimethyl(pent-4-yn-1-yloxy)silane, 0.1 parts of stearate, 0.3 parts of Custer catalyst with an effective content of 5000PPM, and 0.02 parts of 1-ethynyl-1-cyclohexanol.

[0067] This embodiment provides a method for preparing a mixed silicone rubber, comprising the steps of:

[0068] (1) kneading raw rubber, vinyl silicone oil, low-polymerization degree a, w-dihydroxy polydimethylsiloxane, stearate, and fumed silica in a vacuum kneader (kneading conditions: under nitrogen atmosphere, stirring frequency of 50 Hz, temperature of 70° C.), adding fumed silica in multiple times, each time with an interval of 15 minutes, until all the fumed silica is added, then heating to 180° C., and then stirring at a stirring frequency of 50 Hz for 3.5 hours under a vacuum degree of 0.08 MPa, stopping vacuuming, and then cooling to 30° C., refining, filtering, and obtaining a base rubber;

[0069] (2) mixing the base rubber, linear polymethylhydrogensiloxane, tert-butyldimethyl (pent-4-yn-1-yloxy) silane, and 1-ethynyl-1-cyclohexanol in an open mill, adding a Custer catalyst, and mixing well to obtain a mixed rubber material;

[0070] (3) vulcanizing the mixed rubber at 125° C. for 10 min to obtain a section of vulcanized silicone rubber;

[0071] (4) A section of vulcanized silicone rubber is baked at 200°C for 4 hours to obtain a mixed silicone rubber.

[0072] Comparative Example 1

[0073] The only difference between this comparative example and Example 1 is that the amount of fumed silica is 35 parts, the amount of the treating agent is 6.5 parts, and the rest is the same as Example 1.

[0074] Comparative Example 2

[0075] The only difference between this comparative example and Example 2 is that: 75 parts of 110 type methyl vinyl silicone rubber raw rubber with a molecular weight of 530,000 and a vinyl chain content of 0.06% are used, and 25 parts of vinyl silicone oil with a viscosity of 15000mPa.s and a vinyl chain content of 8% are used. The rest is the same as Example 2.

[0076] Comparative Example 3

[0077] The only difference between this comparative example and Example 3 is that tert-butyldimethyl(pent-4-yn-1-yloxy)silane is removed, and the rest is the same as Example 3.

[0078] Comparative Example 4

[0079] The only difference between this comparative example and Example 4 is that the vinyl segment content in the vinyl silicone oil is 2%, and the rest is the same as Example 4.

[0080] Comparative Example 5

[0081] The only difference between this comparative example and Example 5 is that the vinyl segment content in the 110 type methyl vinyl silicone rubber raw rubber is 0.24%, and the rest is the same as Example 5.

[0082] The Shore hardness, tensile strength, elongation at break and tear strength of the one-stage vulcanized silicone rubber and the mixed silicone rubber obtained after the two-stage vulcanization in Examples 1 to 5 and Comparative Examples 1 to 5 were tested. The test results are shown in Table 1. The standards based on the tests are shown below.

[0083] The Shore hardness test refers to GB / T 531.1-2008 Vulcanized rubber or thermoplastic rubber indentation hardness test method;

[0084] The tensile strength test refers to GB / T 528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber;

[0085] The elongation at break test refers to GB / T 528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber;

[0086] The tear strength test refers to GB / T 529-2008 Determination of tear strength of vulcanized rubber or thermoplastic rubber.

[0087] Table 1

[0088]

[0089]

[0090] It can be seen from Table 1 that the elongation of the first-stage vulcanized silicone rubber of Examples 1 to 5 is ≥1000%, and the mixed silicone rubber obtained after the second-stage vulcanization not only has a higher hardness (>70A), but also maintains good elongation (>800%), tensile strength (greater than 7.5MPa) and tear strength (greater than 30KN / m), wherein the elongation is close to that of the conventional 40-50A high-performance silicone rubber, which solves the brittleness problem of high-hardness silicone rubber and is particularly suitable for application scenarios requiring high elongation.

[0091] Comparing Example 1 with Comparative Example 1, it can be seen that when the content of fumed silica is less than 50 parts, although the elongation is improved, the hardness is low and it is difficult to reach a hardness value of more than 70A. Comparing Example 2 with Comparative Example 2, it can be seen that when the content of vinyl silicone oil exceeds 20 parts, the elongation will be significantly reduced. Comparing Example 3 with Comparative Example 3, it can be seen that without adding tert-butyl dimethyl (pent-4-yn-1-yloxy) silane, the mixed silicone rubber is prone to uneven vulcanization, which in turn leads to abnormal mechanical properties. Comparing Example 4 with Comparative Example 4, it can be seen that if the vinyl content of the vinyl silicone oil is less than 4%, although the elongation can be improved, it is difficult to reach a hardness value of more than 70A. Comparing Example 5 with Comparative Example 5, it can be seen that if the vinyl content of the raw rubber exceeds 0.1%, the corresponding elongation is difficult to exceed 800%. In summary, by controlling the content of fumed silica, the content of vinyl silicone oil and the vinyl content therein, the vinyl content of raw rubber and the vinyl content therein, and introducing tert-butyldimethyl(pent-4-yn-1-yloxy)silane, it can be ensured that the mixed silicone rubber obtained after the two-stage vulcanization not only has a higher hardness, but also maintains good elongation, tensile strength and tear strength.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A mixed silicone rubber, characterized in that: Calculated by weight, it includes 80 to 95 parts of raw rubber with a molecular weight of 500,000 to 700,000 and a vinyl segment content of 0.03 to 0.1%, 5 to 20 parts of vinyl silicone oil with a viscosity of 5000 to 15000 mPa.s and a vinyl segment content of 4 to 14%, 50 to 60 parts of white carbon black, 8 to 12 parts of a treating agent, 2 to 5 parts of a cross-linking agent, 0.01 to 0.1 parts of tert-butyldimethyl (pent-4-yn-1-yloxy) silane, 0.1 parts of a release agent, 0.05 to 0.5 parts of a catalyst, and 0.01 to 1 parts of an inhibitor. The total weight of the raw rubber and the vinyl silicone oil is 100 parts.

2. The mixed silicone rubber according to claim 1, characterized in that The raw rubber is selected from at least one of 112 type methyl vinyl silicone rubber raw rubber and 110 type methyl vinyl silicone rubber raw rubber.

3. The mixed silicone rubber according to claim 1, characterized in that The white carbon black is selected from at least one of precipitated white carbon black, fumed white carbon black, treated precipitated white carbon black, and treated fumed white carbon black.

4. The mixed silicone rubber according to claim 1, characterized in that The treating agent is selected from at least one of a,w-dihydroxy polydimethylsiloxane with a low polymerization degree of 2-6% and a hydroxyl content, a,w-dihydroxy polydimethylsiloxane with a low polymerization degree of 5-10% and a methoxysilane, ethoxysilane and hexamethyldisilazane.

5. The mixed silicone rubber according to claim 1, characterized in that The crosslinking agent is a linear polymethylhydrogensiloxane as shown in Formula 1, Wherein, R is a methyl group, m+n=4-200 and the mass fraction of active hydrogen is greater than or equal to 0.75%.

6. The mixed silicone rubber according to claim 1, characterized in that The catalyst is selected from at least one of a Custer catalyst, an alcohol-modified chloroplatinic acid catalyst, and a platinum-alkyne-based complex.

7. The compounded silicone rubber according to claim 1, characterized in that: The inhibitor is selected from at least one of 3-methyl-1-butyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol, 1-ethynyl-1-cyclohexanol, 3-phenyl-1-butyn-3-ol, alkyne-oxy-containing polysiloxane, methylvinylcyclotetrasiloxane, amide compounds, and maleate compounds.

8. The method for preparing the mixed silicone rubber according to any one of claims 1 to 7, characterized in that: Includes steps: (1) mixing raw rubber, vinyl silicone oil, a treating agent, a releasing agent and white carbon black in a vacuum kneader to obtain a base rubber; (2) mixing the base rubber, a cross-linking agent, tert-butyldimethyl (pent-4-yn-1-yloxy) silane, an inhibitor, and a catalyst in an open mill to obtain a mixed rubber material; (3) subjecting the mixed rubber material to a stage of vulcanization to obtain a stage of vulcanized silicone rubber; (4) The one-stage vulcanized silicone rubber is subjected to two-stage vulcanization to obtain a mixed silicone rubber.

9. The method for preparing the mixed silicone rubber according to claim 8, characterized in that: Step (1) also includes: putting raw rubber, vinyl silicone oil, treatment agent, release agent and white carbon black into a vacuum kneader, stirring and kneading the rubber into a mass under a nitrogen atmosphere, then heating to 150-200° C., vacuuming the rubber, stopping vacuuming, cooling, refining and filtering in sequence to obtain the base rubber.

10. The method for preparing the mixed silicone rubber according to claim 8, characterized in that: The first stage vulcanization in step (3) includes: vulcanization at 120-130°C for 10 minutes; the second stage vulcanization in step (4) includes: baking at 200°C for 4 hours.

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