A class of silane coupling agents containing thiourea bonds, their preparation methods, and their application in the preparation of self-healing silicone rubber.

Abstract

This invention relates to a class of silane coupling agents containing thiourea bonds, their preparation methods, and their application in the preparation of self-healing silicone rubber. These silane coupling agents containing thiourea bonds are obtained by reacting amino-containing silanes with thiourea-containing raw materials. The reaction process does not require a catalyst, is fast, and the preparation method is simple, efficient, inexpensive, and practical. Due to the presence of the thiourea group, this type of silane coupling agent enhances intermolecular hydrogen bonding. Room temperature vulcanizing silicone rubber prepared using this type of coupling agent exhibits excellent self-healing properties, extends the service life of silicone rubber, reduces maintenance costs, and provides a new path for its application in fields such as biology, medicine, and construction.

Description

Technical fields:

[0001] This invention relates to a class of silane coupling agents containing thiourea bonds, their preparation methods, and their application in the preparation of self-healing silicone rubber, belonging to the field of organosilicon polymer materials technology. Background technology:

[0002] Silane coupling agents, as an important category of coupling agents, have been widely used in rubber products, resin composites, coatings, and adhesives. Structurally, silane coupling agents are organosilicon compounds with two or more different reactive groups, capable of chemically bonding organic and inorganic materials. Therefore, silane coupling agents are considered "molecular bridges" for the fusion of organic and inorganic interfaces. Currently, one of the important applications of silane coupling agents is as crosslinking agents in the preparation of room temperature vulcanizing silicone rubber, with a typical chemical formula of ZR-SiX3. Here, Z is a functional group that can react with organic matter, such as epoxy, vinyl, and amino groups; R is an alkyl chain; and X is a group bonded to the silicon atom that can undergo hydrolysis, such as alkoxy or halogen groups. Room temperature vulcanizing silicone rubber is widely used in construction, medical, and electrical engineering fields. More than a hundred silane coupling agents with known structures are known.

[0003] In recent years, self-healing silicone rubber has attracted much attention from researchers due to its promising applications in emerging fields such as wearable devices and smart coatings. Compared with traditional silicone rubber, it has a longer service life and lower maintenance costs. Intrinsic silicone rubber, for example, typically achieves its self-healing function by introducing supramolecular interactions such as dynamic covalent bonds, coordination bonds, and hydrogen bonds into the organosilicon system. However, these methods require the design of new organosilicon polymers, which are far more expensive than existing silicone rubber systems. Developing self-healing silicone rubbers using existing silicone rubber systems remains one of the problems that researchers urgently need to solve.

[0004] For example, Chinese patent document CN110218330A discloses a self-healing modified silicone rubber and its preparation method. In the self-healing polyimide modified silicone rubber, the dynamic covalent bonds, polyamide structure, and silicon-oxygen-silicon chemical bonds serve as both self-healing units and reinforcing and toughening units, synthesizing a high-strength, high-toughness copolymer with repair function. The system can react without a solvent, but this method requires the design of new organosilicon polymers, making the method complex and costly.

[0005] Therefore, there is an urgent need for a method to develop self-healing silicone rubber using existing silicone rubber systems. Summary of the Invention:

[0006] To address the shortcomings of existing technologies, this invention provides a class of silane coupling agents containing thiourea bonds, their preparation methods, and their application in the preparation of self-healing silicone rubber.

[0007] The silane coupling agent of this invention is obtained through a simple nucleophilic reaction between chemical substances. The preparation process does not require a catalyst and can be rapidly achieved at relatively low temperatures. When used as a crosslinking agent to prepare room temperature vulcanizing silicone rubber, the thiourea bonds enhance the intermolecular hydrogen bonding, thus endowing the room temperature vulcanizing silicone rubber with self-healing properties.

[0008] This invention is achieved using the following technical solution:

[0009] A class of silane coupling agents containing thiourea bonds, the molecular structure of which is as follows:

[0010]

[0011] Among them, Y1 and Y2 are selected from C1-C 18 Straight-chain or branched alkanes, cyclic hydrocarbons, aromatic hydrocarbons, or hydrocarbon groups or cycloalkanes or aromatic hydrocarbons with O, S, or N heteroatoms, Y1 = Y2 is allowed;

[0012] R2 and R5 are selected from C1-C 18 Straight-chain or branched alkanes, cyclic hydrocarbons, aromatic hydrocarbons, or hydrocarbon groups, cycloalkanes, or aromatic hydrocarbons with O, S, or N heteroatoms, where R2 = R5 is allowed;

[0013] R1, R3, R4, and R6 are C1-C 18 Straight-chain or branched alkanes, cyclic hydrocarbons, aromatic hydrocarbons, or hydrocarbon groups, cycloalkanes, or aromatic hydrocarbons with O, S, or N heteroatoms, or OR2, OR5, with R1=R3=R4=R6 allowed.

[0014] This invention also provides a method for preparing the aforementioned type of silane coupling agent containing thiourea bonds, wherein the raw material is subjected to a nucleophilic reaction with a silane containing terminal amino groups, and the silane coupling agent containing thiourea bonds is obtained by distillation after the nucleophilic reaction. The specific implementation method is as follows:

[0015] The raw material is dissolved in an organic solvent at low temperature, and then an amino-containing silane is added and mixed. An inert gas is introduced, the mixture is heated and stirred, and the solvent and excess raw material are distilled off under reduced pressure to obtain a silane coupling agent containing thiourea bonds.

[0016] According to a preferred embodiment of the present invention, the raw materials are selected from isothiocyanate, phosgene, thiocarbonyl diimidazole, and carbon disulfide.

[0017] According to a preferred embodiment of the present invention, the organic solvent is one or a mixture of two or more of N,N-dimethylformamide, benzene, toluene, dichloromethane or acetonitrile.

[0018] According to a preferred embodiment of the present invention, the molar ratio of the silane containing the terminal amino group to the raw material is 2:(1-5).

[0019] According to a preferred embodiment of the present invention, the reaction temperature is 0-150°C.

[0020] Further preferred, the reaction temperature is 40-80℃.

[0021] According to a preferred embodiment of the present invention, the reaction time is 0.5-24 h.

[0022] A further preferred option is a reaction time of 1-10 hours.

[0023] A self-healing room temperature vulcanizing silicone rubber is prepared using the above-mentioned silane coupling agent containing thiourea bonds.

[0024] According to a preferred method of the present invention, the preparation method of self-healing room temperature vulcanizing silicone rubber is as follows:

[0025] The base rubber, reinforcing filler, catalyst, and the silane coupling agent containing thiourea bonds are physically mixed, and then the mixture is transferred to a rubber mixing mill to obtain a uniformly mixed viscous liquid. The liquid is then placed into a mold and cured at room temperature to prepare room temperature vulcanized silicone rubber.

[0026] According to a preferred embodiment of the present invention, the base adhesive is α,ω-dihydroxypolyalkylsiloxane, with the following structural formula:

[0027]

[0028] In the formula, R7 and R8 can be selected as Me, Et, CH2CH2CF3, or Ph;

[0029] According to a preferred embodiment of the present invention, the amount of silane coupling agent containing thiourea bonds added is 0.03 to 10 wt% of the mass of the base adhesive.

[0030] According to a preferred embodiment of the present invention, the reinforcing filler is diatomaceous earth, silica, calcium carbonate, titanium dioxide, or kaolin, and more preferably, the reinforcing filler is calcium carbonate or silica.

[0031] According to a preferred embodiment of the present invention, the catalyst is a tin-based compound.

[0032] According to a preferred embodiment of the present invention, the catalyst is dibutyltin disilicate or stannous octoate.

[0033] Reinforcing fillers and catalysts shall be applied in accordance with conventional practices in this field.

[0034] The beneficial effects of this invention are as follows:

[0035] 1. The silane coupling agent containing thiourea bonds of the present invention does not require a catalyst during the reaction process, can be carried out at low temperature, has a fast reaction rate, and reduces costs.

[0036] 2. The silane coupling agent containing thiourea bonds of the present invention has high reactivity, short reaction time, and uses inexpensive and readily available raw materials. It also has low energy consumption, good controllability, high repeatability, and is easy to mass-produce on an industrial scale.

[0037] 3. The silane coupling agent containing thiourea bonds of the present invention, used as a crosslinking agent, successfully prepared a self-healing room temperature vulcanizing silicone rubber using the existing silicone rubber system. Utilizing the strong hydrogen bonding effect of thiourea, the obtained room temperature vulcanizing silicone rubber has excellent self-healing properties, extending the service life of silicone rubber. While ensuring its safety and integrity, it reduces maintenance costs and also provides a new path for expanding the application range of silane coupling agents. Attached image description:

[0038] Figure 1 The 1H NMR spectrum of the silane coupling agent when Y1 and Y2 are propyl, R2 = R5 = Me, and R1 = R3 = R4 = R6 = OMe is shown in Example 1.

[0039] Figure 2 The 1H NMR spectrum of the silane coupling agent when Y1 and Y2 are propyl, R2 = R5 = Et, and R1 = R3 = R4 = R6 = OEt is shown in Example 2.

[0040] Figure 3 The 1H NMR spectrum of the silane coupling agent in Example 3, where Y1 and Y2 are propyl, R1 = R4 = OEt, R2 = R5 = Et, and R3 = R6 = Me.

[0041] Figure 4 The 1H NMR spectrum of the silane coupling agent in Example 4, where Y1 and Y2 are propyl, R1 = R4 = OMe, R2 = R5 = Me, and R3 = R6 = Me.

[0042] Figure 5 Example 5, where Y1 and Y2 are propyl, R2 = R5 = Et, and R1 = R3 = R4 = R6 = OEt, demonstrates the self-healing properties of the silane coupling agent. Detailed implementation method:

[0043] The present invention will be further described below with reference to specific embodiments and accompanying drawings, but these embodiments should not be construed as limiting the technical solution.

[0044] Example 1:

[0045] Nitrogen gas was introduced into the three-necked flask to purge the air from the apparatus. 4.6 g of CS2 was added and dissolved in an appropriate amount of DMF. The mixture was stirred in an ice bath, and 17.93 g of aminopropyltrimethoxysilane was added dropwise. The temperature was raised to 40 °C to carry out the reaction. After the reaction was completed, the mixture was cooled to room temperature and distilled under reduced pressure to obtain 16 g of a viscous reddish-yellow liquid. Figure 1 The silane coupling agent prepared in Example 11 The HNMR spectrum shows that the position and integral of the characteristic peak of proton hydrogen are consistent with the theory, indicating that the synthesis was successful.

[0046] Example 2:

[0047] Nitrogen gas was passed through the three-necked flask to purge air from the apparatus. 10.68 g of thiocarbonyldiimidazole was added and dissolved in an appropriate amount of acetonitrile. The mixture was stirred in an ice bath, and 22.14 g of aminopropyltriethoxysilane was added dropwise. The temperature was then raised to 60 °C to allow the reaction to proceed. After the reaction was complete, the mixture was cooled to room temperature and distilled under reduced pressure to obtain 17.5 g of a viscous, reddish-yellow liquid. Figure 2 The silane coupling agent prepared in Example 2 1 The HNMR spectrum shows that the position and integral of the characteristic peak of proton hydrogen are consistent with the theory, indicating that the synthesis was successful.

[0048] Example 3:

[0049] Nitrogen gas was introduced into the three-necked flask to purge air from the apparatus. 6.9 g of phosgene was injected and dissolved in a suitable amount of benzene. The mixture was stirred in an ice bath, and then 19.14 g of aminopropylmethyldiethoxysilane was added dropwise. The temperature was then raised to 80 °C and the reaction was carried out for 2 hours. After the reaction was complete, the mixture was cooled to room temperature and distilled under reduced pressure to obtain 16 g of a viscous yellow liquid. Figure 3 The silane coupling agent prepared in Example 3 1 The HNMR spectrum shows that the position and integral of the characteristic peak of proton hydrogen are consistent with the theory, indicating that the synthesis was successful.

[0050] Example 4:

[0051] Nitrogen gas was introduced into the three-necked flask to purge air from the apparatus. 4.6 g of CS2 was injected and dissolved in an appropriate amount of DMF. The mixture was stirred in an ice bath, and then 19.14 g of aminopropylmethyldimethoxysilane was added dropwise. The temperature was then raised to 40 °C and the reaction was carried out for 2 hours. After the reaction was completed, the mixture was cooled to room temperature and distilled under reduced pressure to obtain 17.28 g of a viscous yellow liquid. Figure 4 The silane coupling agent prepared in Example 4 1 The HNMR spectrum shows that the position and integral of the characteristic peak of proton hydrogen are consistent with the theory, indicating that the synthesis was successful.

[0052] Example 5:

[0053] The preparation method of self-healing room temperature vulcanizing silicone rubber is as follows:

[0054] Add 10g of α,ω-dihydroxypolydimethylsiloxane, 2g of fumed silica TS530, 0.5g of the silane coupling agent prepared in Example 2, and 0.02g of the catalyst dibutyltin dilaurate to the reactor. Mix them into a uniform viscous liquid on a rubber mixing mill. Place the mixture in a mold and let it cure at room temperature for 3 days.

[0055] Its tensile properties were tested; see attached document. Figure 5 (T1 curve). It was then cut into small pieces, and the fragments were brought close together to allow for self-healing of the material. Its tensile properties were then tested; see attached figure. Figure 5 (T2 curve). It can be seen that the self-healing room temperature vulcanizing silicone rubber still has good tensile properties, with a repair efficiency of 81.4%.

[0056] In summary, the self-healing room temperature vulcanizing silicone rubber prepared using the silane coupling agent containing thiourea bonds of this invention exhibits excellent mechanical properties and can spontaneously repair itself at room temperature after being damaged.

Claims

1. A process for the preparation of a self-repairing room temperature vulcanizing silicone rubber, characterized in that, The application relates to a room-temperature vulcanized silicone rubber and a preparation method thereof. The preparation process of the silane coupling agent containing a thiourethane bond comprises the following steps: nucleophilic reaction of raw materials and a silane containing an end amino group, and distillation after the nucleophilic reaction to obtain the silane coupling agent containing the thiourethane bond. The raw materials are dissolved in an organic solvent at low temperature, then a silane containing an amino group is added and mixed, inert gas is introduced, and the temperature is increased for stirring; the solvent and excess raw materials are distilled out through reduced pressure distillation to obtain the silane coupling agent containing the thiourethane bond. The raw materials are selected from isothiocyanate, sulfur light, sulfur carbonyl diimidazole and carbon disulfide; the organic solvent is one or a mixture of two or more of N, N-dimethylformamide, benzene, toluene, dichloromethane and acetonitrile; the molar ratio of the silane containing an end amino group and the raw materials is 2: (1-5); the reaction temperature is 40-80 DEG C, and the reaction time is 1-10 h; The molecular structure of the prepared silane coupling agent containing a thiourethane bond is as follows: The base rubber is alpha, omega-dihydroxyl polyalkyl siloxane, and the structural formula is as follows: wherein Y1, Y2are selected from C1-C 18 linear or branched alkanes, cycloalkanes, arenes or hydrocarbyl groups or cycloalkanes or arenes with O, S, N heteroatoms, Y1= Y2is allowed; R2, R5are selected from linear or branched alkane, cycloalkane, arene or hydrocarbon radical with O, S, N heteroatoms, cycloalkane or arene, R2= R5being allowed; 18 R2, R5are selected from linear or branched alkane, cycloalkane, arene or hydrocarbon radical with O, S, N heteroatoms, cycloalkane or arene, R2= R5being allowed; R1, R3, R4, and R6 are C1-C 18 Straight-chain or branched alkanes, cyclic hydrocarbons, aromatic hydrocarbons, or hydrocarbon groups, cycloalkanes, or aromatic hydrocarbons with O, S, or N heteroatoms, or OR2 or OR5, with R1 = R3 = R4 = R6 allowed; In the formula, R7 and R8 can be Me, Et, CH2CH2CF3 and Ph; The adding amount of the silane coupling agent containing a thiourethane bond is 0.03-10 wt% of the adding amount of the base rubber; the reinforcing filler is diatomite, white carbon black, calcium carbonate, titanium dioxide or kaolin; and the catalyst is dibutyl tin dimethyl silicate or stannous octoate. ​

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