Recyclable and processable silicone rubber elastomer as well as preparation method and application thereof

Abstract

The invention provides a recyclable silicone rubber elastomer as well as a preparation method and application thereof, and the silicone rubber elastomer is prepared from the following raw materials in parts by weight: 100 parts of vinyl silicone rubber raw rubber, 1-5 parts of boric acid ester cross-linking agent, 10-65 parts of silicon dioxide, 4-20 parts of hydroxyl silicone oil and 0.1-5 parts of initiator. The silicone rubber elastomer adopts a cross-linking agent with a specific structure, boric acid ester bonds are introduced into the silicone rubber elastomer, and through synergistic interaction of silicon dioxide, hydroxyl silicone oil and the boric acid ester cross-linking agent, it is guaranteed that the silicone rubber elastomer has high strength, meanwhile, the toughness of the silicone rubber elastomer is remarkably improved, and more importantly, the service life of the silicone rubber elastomer is prolonged. The silicone rubber elastomer is good in reprocessability, and can still maintain relatively high mechanical properties after being processed for multiple times.

Description

Technical Field

[0001] The present invention belongs to the technical field of silicone rubber, and particularly relates to a recyclable silicone rubber elastomer, a preparation method thereof and an application thereof. Background Art

[0002] Silicone rubber is mainly composed of polysiloxane compounds with an inorganic silicon-oxygen backbone and organic side groups (such as methyl, phenyl or other functional groups). Due to its unique organic-inorganic hybrid structure, silicone rubber exhibits excellent thermal stability, electrical insulation and biocompatibility, and is widely used in industries such as automotive, electronics, healthcare and construction.

[0003] The preparation of silicone rubber is usually carried out through a vulcanization process, in which polysiloxane monomers, such as polydimethylsiloxane (PDMS) and polymethylvinylsiloxane (PMVS), are cross-linked by a curing agent to form an elastomer with a three-dimensional network structure. However, like other thermosetting rubbers, the three-dimensional cross-linked network structure of silicone rubber elastomers, although endowing silicone rubber with excellent elasticity and durability, also hinders the decomposition, recycling and reprocessing of silicone rubber. At present, it is estimated that 30 million tons of rubber waste are generated annually, most of which are incinerated or landfilled, resulting in a large amount of waste of resources and energy, and causing relatively serious environmental problems.

[0004] Therefore, developing a silicone rubber elastomer with good mechanical properties and capable of being reprocessed multiple times is an urgent problem to be solved in this field. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a recyclable silicone rubber elastomer, a preparation method thereof and an application thereof; the silicone rubber elastomer has good mechanical properties, is easy to decompose and recycle, and can be reprocessed multiple times. After being reprocessed multiple times, it still has good mechanical properties.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a recyclable silicone rubber elastomer. Based on parts by weight, the raw materials for preparing the silicone rubber elastomer include 100 parts of vinyl silicone rubber raw rubber, 1-5 parts of borate cross-linking agent, 10-65 parts of silica, 4-20 parts of hydroxyl silicone oil and 0.1-5 parts of initiator.

[0008] In the present invention, by selecting a borate crosslinking agent, borate bonds, which are dynamic covalent bonds, are introduced into the silicone rubber elastomer. Reversible crosslinking is achieved by using the dynamic covalent bonds to replace the permanent crosslinking bonds. On the premise of ensuring good mechanical properties of the silicone rubber elastomer, the silicone rubber elastomer can be recycled and processed multiple times, and still has good mechanical properties after multiple processing; moreover, compared with other dynamic covalent bonds, such as imine bonds, disulfide bonds, etc., borate bonds have a lower bond rearrangement temperature and a lower bond exchange activation energy, and can provide stronger mechanical properties; further, hydrogen bonds can be formed between silica, vinyl silicone rubber raw rubber and the borate crosslinking agent. The addition of silica can promote the dispersion of the borate crosslinking agent, prevent the aggregation and crystallization of the borate crosslinking agent after mixing with the vinyl silicone rubber raw rubber, and prevent the agglomeration of the borate crosslinking agent caused by crystallization. Through the synergistic effect of borate bonds and hydrogen bonds, the mechanical properties and reprocessability of the silicone rubber elastomer are further improved; in addition, silica itself can also be used as a reinforcing agent to improve the mechanical properties of the silicone rubber elastomer, and hydroxy silicone oil can reduce the processing viscosity. By compounding hydroxy silicone oil and silica, the silicone rubber elastomer has both good mechanical properties and processing properties.

[0009] In the present invention, 1 to 5 parts of the borate crosslinking agent can be, for example, 1 part, 1.2 parts, 1.5 parts, 1.8 parts, 2 parts, 2.2 parts, 2.5 parts, 2.8 parts, 3 parts, 3.2 parts, 3.5 parts, 3.8 parts, 4 parts, 4.2 parts, 4.5 parts, 4.8 parts, 5 parts, etc.

[0010] In the present invention, 10 to 65 parts of silica can be, for example, 10 parts, 15 parts, 18 parts, 20 parts, 22 parts, 25 parts, 28 parts, 30 parts, 32 parts, 35 parts, 38 parts, 40 parts, 42 parts, 45 parts, 48 parts, 50 parts, 52 parts, 55 parts, 58 parts, 60 parts, 62 parts, 65 parts, etc.

[0011] Silica has a large specific surface area, and the Si-O group has a high compatibility with vinyl silicone rubber raw rubber. Moreover, the surface of silica is rich in hydroxyl groups, and these hydroxyl groups can form hydrogen bonds with the oxygen atoms in the siloxane chain; these interactions improve the stress transfer and load distribution during the deformation process, thereby greatly enhancing the mechanical properties of the silicone rubber elastomer. However, due to the existence of a large number of silanol groups on its surface, excessive addition may cause agglomeration and is prone to a structuring effect (that is, it will cause the aggregation of silica in the uncured silicone rubber), resulting in poor processing properties and mechanical properties of the silicone rubber elastomer; therefore, when the silica content is within the above range, the silicone rubber elastomer has better comprehensive properties.

[0012] In the present invention, 4 to 20 parts of hydroxy silicone oil, for example, can be 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, etc.

[0013] In the present invention, the hydroxy silicone oil can promote the efficient dispersion of silica, relieve the structuring effect of silica, and reduce the processing viscosity; while ensuring the mechanical properties of the silicone rubber elastomer, improve the processing performance; if the addition amount is too much, the mechanical properties of the silicone rubber elastomer will become worse.

[0014] In the present invention, 0.1 to 5 parts of initiator, for example, can be 0.1 part, 0.2 part, 0.5 part, 0.8 part, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, etc.

[0015] Preferably, the vinyl silicone rubber includes at least one of raw methyl vinyl silicone rubber, raw methyl phenyl vinyl silicone rubber or vinyl-modified fluorosilicone rubber.

[0016] Preferably, the molar percentage content of carbon-carbon double bonds in the raw vinyl silicone rubber is 0.01 to 5 mol%, for example, it can be 0.01 mol%, 0.05 mol%, 0.1 mol%, 0.2 mol%, 0.4 mol%, 0.5 mol%, 0.52 mol%, 0.55 mol%, 0.58 mol%, 0.6 mol%, 0.62 mol%, 0.65 mol%, 0.68 mol%, 0.7 mol%, 0.72 mol%, 0.75 mol%, 0.78 mol%, 0.8 mol%, 0.82 mol%, 0.85 mol%, 0.88 mol%, 0.9 mol%, 0.92 mol%, 0.95 mol%, 0.98 mol%, 1 mol%, 1.1 mol%, 1.2 mol%, 1.3 mol%, 1.4 mol%, 1.5 mol%, 1.6 mol%, 1.7 mol%, 1.8 mol%, 1.9 mol%, 2 mol%, 2.5 mol%, 3 mol%, 3.5 mol%, 4 mol%, 4.5 mol%, 5 mol%, etc.

[0017] In the present invention, if the molar percentage content of carbon-carbon double bonds in the raw vinyl silicone rubber is too low, there are few crosslinking sites, and the mechanical properties and reprocessability of the silicone rubber elastomer are poor; if it is too high, the content of the borate crosslinking agent introduced is too high, and the borate crosslinking agent is prone to agglomeration, which also leads to poor mechanical properties and reprocessability of the silicone rubber elastomer.

[0018] Preferably, the crosslinkable functional groups in the borate crosslinking agent include mercapto group and / or carbon-carbon double bond.

[0019] Preferably, the molar ratio of the carbon-carbon double bonds in the vinyl silicone rubber raw rubber to the crosslinkable functional groups in the borate crosslinking agent is 1:(1-3), where the specific values in (1-3) can be, for example, 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, etc.

[0020] Preferably, the borate crosslinking agent has the structure shown in Formula I.

[0021]

[0022] In Formula I, R is selected from substituted or unsubstituted C6-C12 arylene groups; the substituents of the substituted ones are selected from any one of C1-C6 linear or branched alkyl groups and C1-C6 linear or branched alkoxy groups; R1 and R2 are each independently selected from a mercapto group or a carbon-carbon double bond; n1 and n2 are each independently selected from integers greater than or equal to 1.

[0023] In the present invention, the C6-C12 arylene group can be, for example, C6, C7, C8, C9, C10, C11, C12 arylene groups; such as phenylene group, naphthylene group, etc.; C1-C6 represents that the number of carbon atoms is 1-6, and can be, for example, 1, 2, 3, 4, 5, 6, etc.; n1 and n2 are each independently selected from integers greater than or equal to 1, and can be, for example, 1, 2, 3, 4, 5, etc.

[0024] Preferably, the borate crosslinking agent includes at least one of the following compounds.

[0025]

[0026] In the present invention, the borate crosslinking agent has a relatively high melting point. For example, the melting point of BDB is 107°C. And due to the high flexibility of the siloxane chain, after the borate crosslinking agent is mixed with the vinyl silicone rubber raw rubber and stored for a long time, the borate crosslinking agent is prone to aggregation and crystallization. Therefore, by adding silica, the dispersion of the borate crosslinking agent can be promoted, a stable material without aggregation phenomenon can be obtained, and further the mechanical properties and reprocessability of the silicone rubber elastomer can be improved.

[0027] In the present invention, the borate crosslinking agent can be derived from existing substances or can be prepared by conventional methods. Exemplarily, the preparation method includes the following steps:

[0028] Dissolve a boric acid compound and a polyol containing crosslinkable functional groups in a solvent, add magnesium sulfate and water thereto, react at room temperature for at least 24 h, filter and concentrate to remove magnesium sulfate, and after washing and drying, obtain the borate crosslinking agent; the boric acid compound is selected from R is selected from the same range as in Formula I; the polyol containing crosslinkable functional groups is selected from An integer where n ≥ 1; R3 is selected from a mercapto group or a carbon-carbon double bond.

[0029] Preferably, the initiator includes 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

[0030] In a second aspect, the present invention provides a method for preparing a recyclable silicone rubber elastomer according to the first aspect. The preparation method includes the following steps:

[0031] Mix vinyl silicone rubber raw rubber, borate crosslinking agent, hydroxy silicone oil and initiator, and cure to obtain the silicone rubber elastomer.

[0032] Preferably, the temperature of the mixing is 90 - 110°C, such as 90°C, 95°C, 100°C, 105°C, 110°C, etc.; the time is 0.5 - 2 h, such as 0.5 h, 0.6 h, 0.8 h, 1 h, 1.5 h, 2 h, etc.

[0033] Preferably, the temperature of the curing is 140 - 180°C, such as 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, etc.; the time is 0.5 - 2 h, such as 0.5 h, 0.6 h, 0.8 h, 1 h, 1.5 h, 2 h, etc.

[0034] In a third aspect, the present invention provides a recyclable product. The material of the recyclable product includes the recyclable silicone rubber elastomer according to the first aspect.

[0035] The numerical ranges described in the present invention not only include the above-listed point values, but also include any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the ranges.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] The silicone rubber elastomer provided by the present invention uses a crosslinking agent with a specific structure to introduce borate bonds into the silicone rubber elastomer. And through the synergistic effect of silica, hydroxy silicone oil and borate crosslinking agent, while ensuring that the silicone rubber elastomer has high strength, its toughness is significantly improved. More importantly, the silicone rubber elastomer has good reprocessing performance and can still maintain high mechanical properties after multiple processing. Description of the Drawings

[0038] Figure 1 It is the stress-strain curve of the silicone rubber elastomers provided in Examples 1 - 3 and Comparative Example 1 of the present invention.

[0039] Figure 2 These are stress-strain curves of the silicone rubber elastomers provided in Comparative Examples 2 to 5 of the present invention.

[0040] Figure 3 These are stress-strain curves of the silicone rubber elastomers provided in Examples 2, 4-6 of the present invention.

[0041] Figure 4 These are stress-strain curves of the silicone rubber elastomer provided in Example 3 of the present invention after one reprocessing, two reprocessing, and three reprocessing.

[0042] Figure 5 This is a bar chart of data of the silicone rubber elastomer provided in Example 6 of the present invention after one reprocessing, two reprocessing, and three reprocessing.

[0043] Figure 6 This is a data graph of the mechanical property recovery rate of the silicone rubber elastomer provided in Examples 2, 4-6 of the present invention after one reprocessing.

[0044] Figure 7 This is a curve diagram of the elastic recovery rate change of the silicone rubber elastomer provided in Example 1 with increasing cycle times after one reprocessing, two reprocessing, and three reprocessing. DETAILED DESCRIPTION

[0045] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0046] The materials used in the present invention can be obtained from commercial sources or prepared by conventional methods. Unless otherwise specified, the materials used in the present invention are as follows:

[0047] Vinyl silicone rubber (A)

[0048] A1: methyl vinyl silicone rubber raw rubber, carbon-carbon double bond content of 1 mol%, purchased from Dongjue Organic Silicone Group Co., Ltd. No. 110-6 raw rubber.

[0049] A2: methyl vinyl silicone rubber raw rubber, carbon-carbon double bond content of 0.05 mol%, purchased from Dongjue Organic Silicone Group Co., Ltd. No. 110-1 raw rubber.

[0050] A3: methyl vinyl silicone rubber raw rubber, carbon-carbon double bond content of 0.15 mol%, purchased from Dongjue Organic Silicone Group Co., Ltd. 110-2 raw rubber.

[0051] A4: methyl vinyl silicone rubber raw rubber, carbon-carbon double bond content of 0.2 mol%, purchased from Dongjue Organic Silicone Group Co., Ltd. 110-3 raw rubber.

[0052] A5: methyl vinyl silicone rubber raw rubber, carbon-carbon double bond content of 0.5 mol%, purchased from Dongjue Organic Silicone Group Co., Ltd. No. 110-5 raw rubber.

[0053] A6: methyl vinyl silicone rubber raw rubber, carbon-carbon double bond content of 2 mol%, purchased from Dongjue Organic Silicone Group Co., Ltd. No. 110-7 raw rubber.

[0054] Boric acid ester crosslinking agent (B)

[0055] B1: 2,2'-(1,4-phenyl)-bis[4-mercapto-1,3,2-dioxaborane], structural formula: Abbreviated as BDB; the preparation method includes: dissolving benzene-1,4-diboronic acid (9.03g, 54.5mmol) and 1-mercaptoglycerol (12.03g, 111.2mmol) in tetrahydrofuran (THF, 160mL), and then adding MgSO4 (15.0g) and 0.3mL water. After stirring at room temperature for 24 hours, the obtained mixture is filtered and concentrated to remove MgSO4, and finally the target compound is obtained by rotary evaporation. The target compound is washed with n-heptane for multiple times and treated in a vacuum oven for 24 hours to obtain a white solid (15.07g, yield 88%), that is, the borate cross-linking agent is obtained.

[0056] B2: The structural formula is The preparation method is different from B1 only in that benzene-1,4-diboronic acid is replaced by an equal molar amount of 5-methyl-4-propoxy-1,3-benzenediboronic acid, and the other steps are the same as B1.

[0057] B3: The structural formula is In the preparation method, 1-mercaptoglycerol is replaced by an equal molar amount of 2,3-dihydroxy-1-butene, and the other steps are the same as B1.

[0058] Hydroxy silicone oil: purchased from Shenzhen Jipeng Fluorosilicon Materials Co., Ltd., 30OS.

[0059] Example 1

[0060] The present embodiment provides a recyclable silicone rubber elastomer. The raw materials for preparing the silicone rubber elastomer include, in parts by weight, 100 parts of methyl vinyl silicone rubber raw rubber (A1), 2.1 parts of borate crosslinking agent BDB, 13 parts of silicon dioxide, 13 parts of hydroxy silicone oil and 1 part of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane; wherein the molar ratio of carbon-carbon double bonds in the methyl vinyl silicone rubber raw rubber to the thiol groups in the borate crosslinking agent is 1:1.

[0061] This embodiment provides a method for preparing a recyclable silicone rubber elastomer, which specifically includes the following steps:

[0062] The methyl vinyl silicone rubber raw rubber and BDB were added to a kneader and mixed at 100 °C. Then, silica, hydroxyl silicone oil, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane were successively added thereto and mixed at 100 °C for 1 h. Then, the obtained material was hot-pressed at 160 °C for 1 h to cure and form the silicone rubber elastomer, denoted as P 1 / 1 O 13 Si 13 V1, where P 1 / 1 represents that the molar ratio of the carbon-carbon double bond in the methyl vinyl silicone rubber raw rubber to the mercapto group in the borate crosslinking agent is 1:1; O 13 represents that 13 parts of hydroxyl silicone oil are added to 100 parts of vinyl silicone rubber raw rubber; Si 13 represents that 13 parts of silica are added to 100 parts of vinyl silicone rubber raw rubber; V1 represents that the molar percentage content of the carbon-carbon double bond in the methyl vinyl silicone rubber raw rubber is 1 mol%.

[0064] Example 2

[0065] This example provides a recyclable silicone rubber elastomer, which is different from Example 1 only in that the amount of the silica is 27 parts, and the other raw materials, dosages, and preparation methods are the same as those in Example 1; the silicone rubber elastomer is denoted as P 1 / 1 O 13 Si 27 V1.

[0066] Example 3

[0067] This example provides a recyclable silicone rubber elastomer, which is different from Example 1 only in that the amount of the silica is 49 parts, and the other raw materials, dosages, and preparation methods are the same as those in Example 1; the silicone rubber elastomer is denoted as P 1 / 1 O 13 Si 49 V1.

[0068] Example 4

[0069] This example provides a recyclable silicone rubber elastomer, which is different from Example 2 only in that the amount of the hydroxyl silicone oil is 10 parts, and the other raw materials, dosages, and preparation methods are the same as those in Example 2; the silicone rubber elastomer is denoted as P 1 / 1 O 10 Si 27 V1.

[0070] Example 5

[0071] This embodiment provides a recyclable silicone rubber elastomer, which is only different from Embodiment 2 in that the amount of the hydroxy silicone oil is 7 parts, and other raw materials, dosages and preparation methods are the same as those in Embodiment 2; the silicone rubber elastomer is denoted as P 1 / 1 O7Si 27 V1。

[0072] Embodiment 6

[0073] This embodiment provides a recyclable silicone rubber elastomer, which is only different from Embodiment 2 in that the amount of the hydroxy silicone oil is 4 parts, and other raw materials, dosages and preparation methods are the same as those in Embodiment 2; the silicone rubber elastomer is denoted as P 1 / 1 O4Si 27 V1。

[0074] Embodiment 7

[0075] This embodiment provides a recyclable silicone rubber elastomer, which is only different from Embodiment 6 in that the raw methyl vinyl silicone rubber is A2 (the carbon-carbon double bond content is 0.05 mol%), and the BDB content is adjusted so that the molar ratio of the carbon-carbon double bond in the raw methyl vinyl silicone rubber to the mercapto group in the borate crosslinking agent is 1:1, and other raw materials, dosages and preparation methods are the same as those in Embodiment 6.

[0076] Embodiment 8

[0077] This embodiment provides a recyclable silicone rubber elastomer, which is only different from Embodiment 6 in that the raw methyl vinyl silicone rubber is A3 (the carbon-carbon double bond content is 0.15 mol%), and the BDB content is adjusted so that the molar ratio of the carbon-carbon double bond in the raw methyl vinyl silicone rubber to the mercapto group in the borate crosslinking agent is 1:1, and other raw materials, dosages and preparation methods are the same as those in Embodiment 6.

[0078] Embodiment 9

[0079] This embodiment provides a recyclable silicone rubber elastomer, which is only different from Embodiment 6 in that the raw methyl vinyl silicone rubber is A4 (the carbon-carbon double bond content is 0.2 mol%), and the BDB content is adjusted so that the molar ratio of the carbon-carbon double bond in the raw methyl vinyl silicone rubber to the mercapto group in the borate crosslinking agent is 1:1, and other raw materials, dosages and preparation methods are the same as those in Embodiment 6.

[0080] Embodiment 10

[0081] This embodiment provides a recyclable silicone rubber elastomer, which is only different from Embodiment 6 in that the methyl vinyl silicone rubber raw rubber is A5 (the carbon-carbon double bond content is 0.5 mol%), and the content of BDB is adjusted so that the molar ratio of the carbon-carbon double bond in the methyl vinyl silicone rubber raw rubber to the mercapto group in the borate crosslinking agent is 1:1. Other raw materials, dosages, and preparation methods are the same as those in Embodiment 6.

[0082] Example 11

[0083] This embodiment provides a recyclable silicone rubber elastomer, which is only different from Embodiment 6 in that the methyl vinyl silicone rubber raw rubber is A6 (the carbon-carbon double bond content is 2 mol%), and the content of BDB is adjusted so that the molar ratio of the carbon-carbon double bond in the methyl vinyl silicone rubber raw rubber to the mercapto group in the borate crosslinking agent is 1:1. Other raw materials, dosages, and preparation methods are the same as those in Embodiment 6.

[0084] Example 12

[0085] This embodiment provides a recyclable silicone rubber elastomer, which is only different from Embodiment 6 in that BDB is replaced with an equimolar amount of B2. Other raw materials, dosages, and preparation methods are the same as those in Embodiment 6.

[0086] Example 13

[0087] This embodiment provides a recyclable silicone rubber elastomer, which is only different from Embodiment 6 in that BDB is replaced with an equimolar amount of B3. Other raw materials, dosages, and preparation methods are the same as those in Embodiment 6.

[0088] Comparative Example 1

[0089] This comparative example provides a recyclable silicone rubber elastomer, which is only different from Embodiment 1 in that the number of parts of silica is 0 part. Other raw materials, dosages, and preparation methods are the same as those in Embodiment 1; the silicone rubber elastomer is denoted as P 1 / 1 O 13 Si0V1.

[0090] Comparative Example 2

[0091] This comparative example provides a recyclable silicone rubber elastomer, which is only different from Embodiment 1 in that the number of parts of the borate crosslinking agent BDB is 0 part and the number of parts of silica is 0 part. Other raw materials, dosages, and preparation methods are the same as those in Embodiment 1; the silicone rubber elastomer is denoted as P 1 / 0 O 13 Si0V1.

[0092] Comparative Example 3

[0093] This comparative example provides a recyclable silicone elastomer, which is only different from Comparative Example 2 in that the amount of silica is 27 parts, and other raw materials, dosages, and preparation methods are the same as those in Comparative Example 2; the silicone elastomer is denoted as P 1 / 0 O 13 Si 27 V1。

[0094] Comparative Example 4

[0095] This comparative example provides a recyclable silicone elastomer, which is only different from Comparative Example 2 in that the amount of silica is 49 parts, and other raw materials, dosages, and preparation methods are the same as those in Comparative Example 2; the silicone elastomer is denoted as P 1 / 0 O 13 Si 49 V1。

[0096] Comparative Example 5

[0097] This comparative example provides a recyclable silicone elastomer, which is only different from Comparative Example 2 in that the amount of silica is 63 parts, and other raw materials, dosages, and preparation methods are the same as those in Comparative Example 2; the silicone elastomer is denoted as P 1 / 0 O 13 Si 63 V1。

[0098] Comparative Example 6

[0099] This comparative example provides a recyclable silicone elastomer, which is only different from Example 6 in that BDB is replaced with an equimolar amount of 1,3-benzenediboronic acid bis(pinacol) ester, and other raw materials, dosages, and preparation methods are the same as those in Example 6.

[0100] Comparative Example 7

[0101] This comparative example provides a recyclable silicone elastomer, which is only different from Example 6 in that BDB is replaced with an equimolar amount of 2,2′-(1,2-ethylenedioxy)bis(ethanethiol), and other raw materials, dosages, and preparation methods are the same as those in Example 6.

[0102] Comparative Example 8

[0103] This comparative example provides a recyclable silicone elastomer, which is only different from Example 6 in that the amount of silica is 70 parts, and other raw materials, dosages, and preparation methods are the same as those in Example 6.

[0104] Comparative Example 9

[0105] This comparative example provides a recyclable silicone rubber elastomer, which is only different from Example 6 in that the amount of the hydroxy silicone oil is 25 parts, and the other raw materials, dosages and preparation methods are the same as those in Example 6.

[0106] Performance Test

[0107] (1) Mechanical Properties

[0108] On a universal testing machine (Instron 34TM-30), mechanical property experiments were carried out at room temperature according to the ASTM D1708 standard. For the mechanical property tests of the silicone rubber elastomers provided in the examples and comparative examples, the stress-strain curves of the silicone rubber elastomers were obtained, and the Young's modulus (E), tensile strength (σ), elongation at break (ε) and tensile toughness (U T ) of the silicone rubber elastomer were obtained. The tensile toughness (UT) can be calculated as the area under the stress-strain curve, which represents the total energy absorbed by the material during the stretching process before fracture. The formula is:

[0109]

[0110] where σ(ε) is the function of stress and strain in the stress-strain curve, and ε max is the maximum strain at fracture.

[0111] Among them, the stress-strain curves of the silicone rubber elastomers provided in Examples 1-3 and Comparative Example 1 are as Figure 1 shown; the stress-strain curves of the silicone rubber elastomers provided in Comparative Examples 2-5 are as Figure 2 shown; from Figure 1 and Figure 2 it can be seen that whether the silicone rubber elastomer contains borate bonds or not, when there is no silica in the preparation raw materials, the E, ε and U T of the silicone rubber elastomer are significantly lower and the mechanical properties are extremely poor; within the scope defined by the present invention, with the increase of the silica content, the E, σ, ε and U T of the silicone rubber elastomer increase and the mechanical properties are gradually improved.

[0112] From Figure 1 in P 1 / 1 O 13 Si 49 V1 (Example 3) and Figure 2 in P 1 / 0 O 13 Si 49 V1 (Comparative Example 4), it can be seen that when a borate crosslinking agent is added, while ensuring that the silicone rubber elastomer has a high strength, its elongation at break and tensile toughness can be significantly improved.

[0113] The stress-strain curves of the silicone rubber elastomers provided in Example 2 and Examples 4-6 are as follows Figure 3 shown; as can be seen from Figure 3 it, within the scope defined by the present invention, as the content of hydroxy silicone oil gradually increases, the tensile strength and tensile toughness decrease, but the elongation at break increases.

[0114] And the mechanical property data of the silicone rubber elastomers provided in Examples 1-13 and Comparative Examples 1-9 are recorded in Table 1; among them, P 1 / 1 O4Si 27 in B2 of P 1 / 1 O4Si 27 B3, B3 indicates that the borate crosslinking agent is selected from B2; correspondingly, P 1 / V1 O4Si 27 in V1, P 1 / V1 represents that the molar ratio of the carbon-carbon double bond in the methyl vinyl silicone rubber raw rubber to the borate bond in 1,3-phenylenediboronic acid bis(pinacol) ester is 1:1; P 1 / S1 O4Si 27 in V1, P 1 / S1 represents that the molar ratio of the carbon-carbon double bond in the methyl vinyl silicone rubber raw rubber to the mercapto group in 2,2′-(1,2-ethylenedioxy)bis(ethanethiol) is 1:1.

[0115] Table 1

[0116] Abbreviation E (MPa) σ (MPa) ε (%) <![CDATA[U T (MJ / m 3 )]]> Example 1 <![CDATA[P 1 / 1 O 13 Si 13 V1]]> 0.51±0.07 0.62±0.09 1333±29 4.25±0.61 Example 2 <![CDATA[P 1 / 1 O 13 Si 27 V1]]> 1.13±0.03 1.26±0.09 1300±87 9.43±0.19 Example 3 <![CDATA[P 1 / 1 O 13 Si 49 V1]]> 4.01±0.16 3.47±0.16 1350±50 24.81±0.55 Example 4 <![CDATA[P 1 / 1 O 10 Si 27 V1]]> 1.24±0.04 1.81±0.13 1317±29 11.21±0.8 Example 5 <![CDATA[P 1 / 1 O7Si 27 V1]]> 1.7±0.04 3.15±0.15 1108±52 16.07±1.79 Example 6 <![CDATA[P 1 / 1 O4Si 27 V1]]> 2.01±0.07 4.78±0.38 917±29 20.29±1 Example 7 <![CDATA[P 1 / 1 O4Si 27 V 0.05 > 0.17±0.02 0.11±0.03 5050±300 2.52±0.21 Example 8 <![CDATA[P 1 / 1 O4Si 27 V 0.15 > 0.28±0.12 0.31±0.04 3250±150 4.12±0.15 Example 9 <![CDATA[P 1 / 1 O4Si 27 V 0.2 > 0.56±0.15 0.40±0.07 2150±173 5.22±0.42 Example 10 <![CDATA[P 1 / 1 O4Si 27 V 0.5 > 0.59±0.11 0.65±0.08 1750±77 6.15±0.44 Example 11 <![CDATA[P 1 / 1 O4Si 27 V2]]> 2.42±0.26 3.48±0.26 700±27 11.26±0.82 Example 12 <![CDATA[P 1 / 1 O4Si 27 B2]]> 0.93±0.07 1.12±0.02 1270±65 7.49±0.23 Example 13 <![CDATA[P 1 / 1 O4Si 27 B3]]> 5.75±0.07 3.69±0.12 942±13 19.75±0.62 Comparative Example 1 <![CDATA[P 1 / 1 O 13 Si0 V1]]> 0.32±0.01 0.17±0.01 517±153 0.74±0.27 Comparative Example 2 <![CDATA[P 1 / 0 O 13 Si0 V1]]> 1.01±0.16 0.49±0.18 83±29 0.27±0.16 Comparative Example 3 <![CDATA[P 1 / 0 O 13 Si 27 V1]]> 2.94±0.05 3.29±0.26 192±14 3.08±0.42 Comparative Example 4 <![CDATA[P 1 / 0 O 13 Si 49 V1]]> 5.02±0.8 4.28±0.54 192±14 4.17±0.76 Comparative Example 5 <![CDATA[P 1 / 0 O 13 Si 63 V1]]> 6.82±0.27 5.22±0.65 208±14 5.72±1.06 Comparative Example 6 <![CDATA[P 1 / V1 O4Si 27 V1]]> 2.75±0.05 3.02±0.22 462±17 4.78±0.23 Comparative Example 7 <![CDATA[P 1 / S1 O4Si 27 V1]]> 2.91±0.07 3.31±0.21 211±17 3.28±0.21 Comparative Example 8 <![CDATA[P 1 / 1 O4Si 70 V1]]> 3.65±0.23 3.76±0.18 787±13 12.62±0.86 Comparative Example 9 <![CDATA[P 1 / 1 O 25 Si 27 V1]]> 1.07±0.12 0.56±0.29 3342±137 7.21±0.66

[0117] As can be seen from Table 1, in Comparative Examples 2-5, as the content of silica increases, the mechanical properties of the silicone rubber elastomer are significantly improved; specifically: the Young's modulus increases from 1.01 MPa to 6.82 MPa, the tensile strength increases from 0.49 MPa to 5.2 MPa, the elongation at break increases from 100% to 225%, and the tensile toughness increases from 0.27 MJ / m 3 to 5.72 MJ / m 3 ; however, when no borate bond is introduced into the silicone rubber elastomer, although the addition of silica significantly improves the mechanical properties of the silicone rubber elastomer, the increase in the elongation at break and tensile toughness is relatively moderate.

[0118] And from Comparative Example 1 and Examples 1-3, it can be seen that in the presence of borate bonds, as the content of silica increases, the elongation at break of the silicone rubber elastomer increases from 517% to 1350%, and the tensile toughness increases from 0.74 MJ / m 3 to 24.81 MJ / m 3; Meanwhile, the Young's modulus and tensile strength are increased from 0.32 MPa and 0.17 MPa to 4.01 MPa and 3.47 MPa respectively. It can be seen that the presence of borate bonds can significantly improve the elongation at break and tensile toughness of silicone rubber elasticity.

[0119] Furthermore, from Comparative Examples 1, 3, 4 and Examples 2, 3, it can be seen that when silica and borate bonds coexist, the elongation at break and tensile toughness are significantly improved with a large improvement amplitude. At the same time, it has a relatively high Young's modulus and tensile strength. When there is no silica or borate bond, the elongation at break and tensile toughness of the silicone rubber elastomer are extremely low. It can be seen that silica can synergistically enhance the effect with borate crosslinking agents, ensuring that the silicone rubber elastomer has a relatively high strength while significantly improving the toughness of the silicone rubber elastomer.

[0120] From Examples 2, 4 - 6, it can be seen that when the silicone oil content gradually increases, the tensile strength decreases from 4.78 MPa to 1.26 MPa, while the elongation at break increases from 917% to 1350%, and the tensile toughness decreases from 20.29 MJ / m 3 to 9.43 MJ / m 3 ; From Examples 1 - 6, it can be seen that by compounding a specific content of hydroxyl silicone oil and a specific content of silica, a silicone rubber elastomer with better overall mechanical properties can be obtained. The silicone rubber elastomer provided by the present invention has a Young's modulus ≥ 0.51 MPa, a tensile strength ≥ 0.62 MPa, an elongation at break ≥ 917%, and a tensile toughness ≥ 4.25 MJ / m 3 ; Furthermore, the silicone rubber elastomer provided by the present invention can even achieve a Young's modulus ≥ 4 MPa, a tensile strength ≥ 3 MPa, an elongation at break ≥ 1300%, and a tensile toughness ≥ 20 MJ / m 3 effect.

[0121] (2) Reprocessing performance

[0122] The silicone rubber elastomers provided in the examples and comparative examples were cut into samples with dimensions of 75 mm × 12.5 mm × 0.55 mm, and hot-pressed at 130 °C under a pressure of 20 MPa for the first reprocessing (marked as 1st); the samples obtained from the first reprocessing were cut into samples with dimensions of 75 mm × 12.5 mm × 0.55 mm, and hot-pressed at 130 °C under a pressure of 20 MPa for the second reprocessing (marked as 2nd); the samples obtained from the second reprocessing were cut into samples with dimensions of 75 mm × 12.5 mm × 0.55 mm, and hot-pressed at 130 °C under a pressure of 20 MPa for the third reprocessing (marked as 3rd), and so on; the stress-strain curves of the samples after each reprocessing were tested by the method in (1), and the Young's modulus (E), tensile strength (σ), elongation at break (ε), and tensile toughness (U T ) of the silicone rubber elastomer after multiple reprocessings were obtained.

[0123] Among them, for the silicone rubber elastomer provided in Example 3, the stress-strain curves of the original sample (P 1 / 1 O 13 Si 49 V1-Original), the sample after the first reprocessing (P 1 / 1 O 13 Si 49 V1-1st), the sample after the second reprocessing (P 1 / 1 O 13 Si 49 V1-2nd), and the sample after the third reprocessing (P 1 / 1O 13 Si 49 V1-3rd) are as Figure 4 shown.

[0124] For the silicone rubber elastomer provided in Example 6, the bar chart of the data of the original sample (Original), the sample after the first reprocessing (1st), the sample after the second reprocessing (2nd), and the sample after the third reprocessing (3rd) is as Figure 5 shown.

[0125] And the reprocessing performance data of the silicone rubber elastomers provided in Examples 1 to 13 and Comparative Examples 1, 4, 6 to 9 are recorded in Table 2; among them, " / " indicates that reprocessing cannot be carried out and it cannot be reused.

[0126] Table 2

[0127]

[0128]

[0129] As can be seen from Table 2, the silicone rubber elastomer provided by the present invention can still maintain high strength and toughness after multiple processing. For example, P 1 / 1 O4Si 27 , after the first reprocessing, the retention rate of Young's modulus reaches 92.7%, the retention rate of tensile strength reaches 85.6%, the retention rate of elongation at break reaches 94.4%, and the retention rate of tensile toughness reaches 86.1%, showing excellent reprocessing performance.

[0130] (3) Elastic recovery performance

[0131] Using a universal testing machine (Instron 34TM-30), an elastic recovery experiment was carried out at room temperature according to the ASTM D1708 standard. The material was stretched to the same 200% strain at a speed of 50 mm·min -1 and 10 cycles were performed. The elastic recovery rate (ER) was calculated by the following formula.

[0132]

[0133] In the formula, ε is the applied strain, and ε R，n is the residual strain after the tensile test with the number of cycles being n.

[0134] Among them, the mechanical property recovery effect diagrams of the silicone rubber elastomers provided in Examples 2, 4-6 after one reprocessing are as Figure 6 shown; from Figure 6 it can be seen that the silicone rubber elastomers provided by the present invention still have good mechanical properties after multiple reprocessings, and the mechanical property recovery rate is above 50%.

[0135] For the silicone rubber elastomer provided in Example 1, the original sample (P 1 / 1 O 13 Si 13 V1-Original), the first reprocessed sample (P 1 / 1 O 13 Si 13 V1-1st), the second reprocessed sample (P 1 / 1 O 13 Si 13 V1-2nd) and the third reprocessed sample (P 1 / 1O 13 Si 13 V1-3rd), as the number of cycles increases, the curve diagram of the change in elastic recovery rate is as Figure 7 shown; from Figure 7It can be seen that after three reprocessings and 10 cycles, its elastic recovery rate increased significantly from 48.3% to 62.9%; this improvement in elastic recovery may be attributed to the selective oxidation of borate bonds during high-temperature reprocessing, which promotes irreversible crosslinking and leads to the chemical strengthening of the network.

[0136] In summary, the silicone rubber elastomer provided in the present invention uses a borate crosslinking agent to introduce borate bonds, and at the same time compound silica and hydroxy silicone oil. Through the combination of dynamic borate bonds and hydrogen bonds, the silicone rubber elastomer has excellent mechanical properties and reprocessing properties. When reprocessing at 130 °C, the dynamic covalent bond exchange is sufficient. After hot pressing, a smooth and defect-free film can be reformed. After three reprocessing cycles, the mechanical property loss is extremely small, and with the increase of the number of processing times, the elastic recovery performance is improved. The present invention provides a new idea for designing dynamic crosslinked silicone rubber materials with enhanced mechanical properties and recyclability, and lays a foundation for promoting the large-scale recycling of actual silicone rubber.

[0137] The applicant declares that 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 thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A recyclable and processable silicone rubber elastomer, characterized in that, The raw materials for preparing the silicone rubber elastomer include, by weight parts, 100 parts of vinyl silicone rubber raw rubber, 1 to 5 parts of borate crosslinking agent, 10 to 65 parts of silica, 4 to 20 parts of hydroxyl silicone oil, and 0.1 to 5 parts of initiator.

2. The silicone rubber elastomer according to claim 1, wherein The vinyl silicone rubber includes at least one of methyl vinyl silicone rubber raw rubber, methyl phenyl vinyl silicone rubber raw rubber, or vinyl-modified fluorosilicone rubber raw rubber.

3. The silicone rubber elastomer according to claim 1 or 2, characterized in that, The molar percentage content of carbon-carbon double bonds in the vinyl silicone rubber raw rubber is 0.01 to 5 mol%; Preferably, the crosslinkable functional groups in the borate crosslinking agent include mercapto group and / or carbon-carbon double bond; Preferably, the molar ratio of the carbon-carbon double bonds in the vinyl silicone rubber raw rubber to the crosslinkable functional groups in the borate crosslinking agent is 1:(1 to 3).

4. The silicone rubber elastomer according to any one of claims 1 to 3, characterized in that, The borate crosslinking agent has the structure shown in Formula I; In Formula I, R is selected from substituted or unsubstituted C6-C12 arylene; the substituents of the substituted ones are selected from any one of C1-C6 straight-chain or branched-chain alkyl groups and C1-C6 straight-chain or branched-chain alkoxy groups; R1 and R2 are each independently selected from mercapto group or carbon-carbon double bond; n1 and n2 are each independently selected from integers greater than or equal to 1.

5. The silicone rubber elastomer according to any one of claims 1 to 4, characterized in that, The borate crosslinking agent includes at least one of the following compounds; 6. The silicone rubber elastomer according to any one of claims 1 to 5, characterized in that, The initiator includes 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

7. A method for preparing a recyclable silicone rubber elastomer according to any one of claims 1 to 6, characterized in that, The preparation method includes the following steps: Mix the vinyl silicone rubber raw rubber, borate crosslinking agent, hydroxyl silicone oil, and initiator, and cure to obtain the silicone rubber elastomer.

8. The preparation method according to claim 7, wherein The temperature of the mixing is 90 to 110 °C, and the time is 0.5 to 2 h.

9. The preparation method according to claim 7 or 8, characterized in that, The temperature of the curing is 140 to 180 °C, and the time is 0.5 to 2 h.

10. A recyclable processed product, characterized in that, The material of the recyclable processed product includes the recyclable processed silicone rubber elastomer according to any one of claims 1 to 6.

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