Low-temperature-resistant silicon-containing modified nitrile rubber as well as preparation method and application thereof

Abstract

The invention discloses a low-temperature-resistant silicon-containing modified nitrile rubber and a preparation method and application thereof, the low-temperature-resistant silicon-containing modified nitrile rubber has a structure as shown in a formula I: # imgabs0 #, x = 10-1000, y = 10-1000, z = 10-1000, x, y and z respectively represent polymerization degrees of corresponding structural units, R1 and R2 are respectively and independently selected from C1-C12 alkoxy or C1-C18 straight chain or branched chain alkyl; and X is selected from C1-C18 straight chain or branched chain alkyl. The low-temperature-resistant silicon-containing modified nitrile rubber as shown in the formula I is obtained through molecular design, the low-temperature resistance and thermal stability are remarkably improved, copolymerization and blending are not needed in the preparation process of the low-temperature-resistant silicon-containing modified nitrile rubber, and silicon-oxygen bonds are introduced into a main chain of the nitrile rubber through chemical modification one-step reaction.

Description

Technical Field

[0001] The invention relates to the technical field of modified nitrile rubber, and in particular to a low-temperature resistant silicon-containing modified nitrile rubber and a preparation method and application thereof. Background Art

[0002] As a typical nitrile rubber, nitrile rubber is produced by copolymerization of acrylonitrile and butadiene. Due to its excellent resistance to non-polar oils and low aromatic solvents, it is widely used in the production of rubber products and packaging products with high oil-resistant sealing performance. However, traditional nitrile rubber loses its elasticity and its sealing performance deteriorates at low temperatures. Therefore, its narrow temperature range, weak insulation and ozone resistance have limited its expanded application in the petroleum, automobile and aerospace industries. With the advancement of science and technology, modern industrial development has put forward more stringent performance requirements for nitrile rubber, such as oil resistance, wide temperature range applicability, and weather resistance.

[0003] Organosilicon materials have the properties of both organic polymers and inorganic materials. Due to their unique molecular chain structure, namely the "inorganic structure" of the organosiloxane main chain and the "organic group" structure of the side chain, organosilicon materials have excellent low-temperature resistance and aging resistance. If they are used to modify nitrile rubber, nitrile rubber will be given unique performance characteristics of silicon-containing materials on the basis of its existing advantages. They have high research value and broad application prospects.

[0004] For example, Chinese patent document CN102516558A discloses a method for synthesizing polysiloxane-modified nitrile rubber. The method uses nitrile rubber as raw material, polysiloxane as a modified monomer, and peroxide as an initiator. The modified nitrile rubber is prepared by a binary copolymerization method. The modified rubber not only has excellent mechanical properties and oil resistance, but also has good low temperature resistance.

[0005] Chinese patent document CN1656153A discloses a conjugated diene rubber, a method for producing the same and a method for producing a rubber composition. In the method, an organic siloxane is used as a third monomer to participate in a copolymerization reaction. After the reaction, silicon dioxide and a silane coupling agent are used to mix the rubber. The mixed material has good oil resistance and good low temperature resistance, as well as good wear resistance, heat resistance and ozone resistance.

[0006] Chinese patent document CN106700155A discloses a low-temperature oil-resistant nitrile rubber, which involves a medium-siloxane-modified nitrile rubber. The specific preparation method is: mixing nitrile rubber, siloxane, and initiator into a masterbatch, then grinding to disperse the materials, and finally re-refining, sheeting, and cooling. The low-temperature oil-resistant nitrile rubber has excellent low-temperature resistance.

[0007] Chinese patent document CN115043980A discloses a method for preparing a silicon-containing thermoplastic elastomer using linear or cyclic siloxanes such as methyl disiloxane as functional monomers, specifically: styrene and part of the emulsifier, part of or all of the regulator are added to a polymerization kettle, nitrogen pressure-vacuum replacement is used, conjugated diene is added, after stirring, part of or all of the initiator is added, emulsion polymerization is carried out under stirring, and part of the emulsifier and part of the acrylonitrile are added to the polymerization kettle when the reaction conversion rate reaches 20-35%; in the late reaction period, when the conversion rate reaches 50-60%, a mixture of emulsifier, remaining regulator, remaining initiator, remaining acrylonitrile and a fourth monomer is added, and when the reaction conversion rate reaches 85-90%, a terminator is added to terminate the reaction. Flash degassing is performed, and after the reaction is completed, the resultant emulsion is mixed with the antioxidant emulsion, and then condensed, filtered, dehydrated, and dried in sequence. This thermoplastic elastomer is characterized by its high and low temperature resistance, and is mainly used to make high and low temperature resistant products (rubber hoses, seals, etc.) and high temperature resistant wire and cable insulation layers. However, since the organic silicone monomer used in this scheme is a linear linear or cyclic siloxane such as methyl disiloxane, it is difficult to form a random structure in the emulsion polymerization system, which has a certain limiting effect on its performance.

[0008] Chinese patent document CN 102464767A discloses a method for preparing silicone rubber composite materials in situ. The preparation steps are: add water, emulsifier, monovinyl aromatic monomer and molecular weight regulator to the reactor in sequence, and then add organic silicon monomer containing carbon-carbon unsaturated bonds and conjugated diene under the protection of N2; start the polymerization kettle stirring, adjust the temperature of the reaction system in the polymerization kettle to the polymerization temperature, add initiator, start the reaction, the polymerization temperature is 5-30°C, the polymerization time is controlled at 7-12 hours, and when the total monomer conversion rate reaches 60-70%, add terminator to terminate the polymerization reaction; the latex is degassed, condensed and dried to obtain a solid product. This method is to improve the heat resistance and tensile properties of styrene-butadiene rubber through graft copolymerization.

[0009] Chinese patent document CN 102020752A discloses a method for in-situ hybrid grafting modification of polyconjugated diene latex by silicon, and the technical scheme adopted is (based on 100 parts of the dry rubber mass of the latex containing polyconjugated diene): 4 to 25 parts, preferably 10 to 15 parts, of an organosiloxane monomer containing an unsaturated bond are added to the latex containing polyconjugated diene, and the mixture is stirred and mixed evenly, and 0.20 to 0.36 parts of an initiator are added at a temperature of 5 to 85°C and under stirring conditions for grafting polymerization for 5 to 8 hours, and finally the grafted modified latex is condensed and dried. The content of the grafted silicon-containing group in this method is low, and the grafting can only be carried out at the end of the molecular chain, so the effect produced is small; and the method is to place the silicon-containing group in the side chain.

[0010] In 2013, the National Polymer Academic Paper Conference published an article entitled "Special polysiloxane grafted modified nitrile rubber to improve its low temperature performance". Specifically, mercaptomethyl end-capping agent and trifluoropropyl methyl cyclotrisiloxane were used to synthesize mercaptomethyl end-capped fluoropropyl silicone oil through cationic catalysis ring-opening polymerization, and then the synthesized mercaptomethyl end-capped fluoropropyl silicone oil was used to modify nitrile rubber in a Haake torque rheometer. The modified nitrile rubber was then blended with fluorosilicone rubber. The compatibility of the blended rubber of the modified nitrile rubber and fluorosilicone rubber was significantly improved, and a silicone modified nitrile rubber fluorosilicone rubber blend system with excellent mechanical and low temperature properties was obtained. However, this method involves many process steps and has a high production cost.

[0011] Chinese patent document CN1656153A discloses a high-performance nitrile rubber material and a preparation method thereof, which relates to the field of rubber technology. It uses nitrile rubber, silicone rubber and carbon quantum dots as main raw materials, and the particle size of the carbon quantum dots is 1-3nm; the weight ratio of the rubber to the silicone rubber and the carbon quantum dots is 50-80:20-50:0.5-10. The obtained material has good oil resistance and good low temperature resistance, as well as good wear resistance, heat resistance and ozone resistance. This method is a physical blending modification. When the amount of functional filler increases, phase separation will occur, which will have a negative impact on the comprehensive performance of the material.

[0012] Chinese patent document CN113429701A discloses a PVC / nitrile conveyor belt and its raw materials and preparation method, and specifically relates to a PVC / nitrile conveyor belt and its raw materials and preparation method. The raw materials for preparing the PVC / nitrile conveyor belt contain polyvinyl chloride, modified nitrile rubber, maleic anhydride grafted POE, polyetheretherketone particles, antioxidants and ultraviolet absorbers, and the polyetheretherketone particles are stored independently. The mass ratio of the modified nitrile rubber, maleic anhydride grafted POE, polyetheretherketone particles and polyvinyl chloride is (5-15): (2-10): (0.5-5): (60-80); the modified nitrile rubber is prepared by polymerizing acrylonitrile, butadiene and vinyl silane, and then coupling the obtained polymerization product with a mercaptosilane coupling agent. The PVC / nitrile conveyor belt prepared using the above raw materials has good wear resistance and low temperature grip.

[0013] In summary, the current prior art uses copolymerization or blending to prepare silicon-containing nitrile rubber. However, the blending method has many process steps, high production cost, and is prone to phase separation, resulting in unsatisfactory low-temperature resistance of the product. The copolymerization method has the problem of poor copolymerization controllability. If the direct ternary emulsion polymerization is used, the hydrolysis problem of silane monomer is difficult to solve, and the low-temperature resistance is limited and its subsequent application is limited. Therefore, a simple and feasible, non-copolymerization and blending method for preparing silicon-modified nitrile rubber is provided, and the application of nitrile rubber to obtain a silicon-modified nitrile rubber with stable product performance is of great significance. Summary of the invention

[0014] In view of the problems existing in the prior art and the directions for improvement, the present invention provides a low-temperature resistant silicon-containing modified nitrile rubber and a preparation method thereof, so as to solve the problems existing in the prior art when silicon-modified nitrile rubber is prepared by blending or copolymerization.

[0015] To achieve the above object, the present invention provides the following technical solutions:

[0016] A low temperature resistant silicon-containing modified nitrile rubber having a structure shown in Formula I:

[0017]

[0018] Wherein, x=10-1000, y=10-1000, z=10-1000, x, y, z represent the polymerization degree of the corresponding structural unit, R1 and R2 are independently selected from C1-C12 alkoxy, or C1-C18 straight chain or branched hydrocarbon group;

[0019] X is selected from C1-C18 straight chain or branched hydrocarbon groups.

[0020] Optionally, R1 and R2 are independently selected from C1-C6 alkoxy, or C1-C12 straight or branched hydrocarbon; preferably methyl, methoxy, ethyl, ethoxy, vinyl, propyl, propoxy, propenyl, allyl, isopropyl, butyl, or dodecyl, preferably methoxy or dodecyl;

[0021] X is selected from C1-C12 straight or branched hydrocarbon groups; preferably methyl, ethyl, vinyl, propyl, propenyl, allyl, isopropyl, butyl, or dodecyl, more preferably methyl, vinyl, or dodecyl.

[0022] The present invention also provides a method for preparing the above-mentioned low-temperature resistant silicon-containing modified nitrile rubber, wherein the hydroxy-terminated nitrile rubber shown in formula II and the organosiloxane shown in formula III are subjected to a condensation reaction to obtain the low-temperature resistant silicon-containing modified nitrile rubber shown in formula I;

[0023]

[0024] Wherein, x, y, z, R1 and R2 are defined as above;

[0025] R3 is selected from C1-C12 alkoxy, preferably C1-C5 alkoxy, more preferably methoxy, ethoxy, propoxy, isopropoxy, or n-butoxy.

[0026] Optionally, the method for preparing the low-temperature resistant silicon-containing modified nitrile rubber comprises the following steps:

[0027] Dissolving the hydroxy-terminated nitrile rubber represented by formula II and the organosiloxane represented by formula I in the same solvent to obtain a solution of the organosiloxane and a solution of the hydroxy-terminated nitrile rubber;

[0028] Under stirring conditions, the solution of the organosiloxane is added dropwise to the solution of the terminal hydroxyl nitrile rubber. After the addition is completed, a condensation reaction is carried out under nitrogen protection. After the reaction is completed, the reaction system is mixed with methanol for precipitation. The obtained solid is washed and dried to obtain a low-temperature resistant silicon-containing modified nitrile rubber.

[0029] Optionally, the organosiloxane represented by Formula I includes but is not limited to methyl siloxane, vinyl siloxane, or allyl siloxane, preferably methyltrimethoxysilane, vinyltrimethoxysilane, dimethoxymethylvinylsilane, or dodecylmethyldimethoxysilane.

[0030] Optionally, the molar ratio of the hydroxyl group in the hydroxy-terminated nitrile rubber to the organosiloxane is 1:1.2 to 1.5.

[0031] Optionally, the content of the hydroxy-terminated nitrile rubber in the hydroxy-terminated nitrile rubber solution is 10 wt% to 12 wt%;

[0032] The content of the organosiloxane in the organosiloxane solution is 20 wt % to 30 wt %.

[0033] Optionally, the condensation reaction temperature is 60-80° C. and the reaction time is 6-8 hours.

[0034] Optionally, the solvent is selected from dimethylformamide, chlorobenzene, toluene, or xylene; preferably toluene and chlorobenzene.

[0035] The present invention also provides an application of the above-mentioned low-temperature resistant silicon-containing modified nitrile rubber, or the low-temperature resistant silicon-containing modified nitrile rubber prepared by the preparation method of the above-mentioned low-temperature resistant silicon-containing modified nitrile rubber. Due to the different structures of the organosiloxane in the low-temperature resistant silicon-containing modified nitrile rubber, it can be used in different application fields, such as including but not limited to the application in the preparation of epoxy resin or the preparation of composite materials, preferably in the preparation of epoxy resin adhesive. Specifically, when the organosiloxane is dimethoxysilane and trimethoxysilane, it can be used as a toughening agent for epoxy resin adhesive; when the organosiloxane is a vinyl silane, it can be used for copolymerization modification of composite materials, etc.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] Beneficial effect 1: When improving the low temperature resistance of nitrile rubber, the silicon-containing monomer is used through copolymerization or blending, and there are problems such as phase separation and poor controllability of copolymerization. The present invention provides a low-temperature resistant silicon-containing modified nitrile rubber with a structure shown in Formula I through molecular design, which significantly improves the low temperature resistance and thermal stability of the nitrile rubber. Compared with the unmodified hydroxy-terminated nitrile rubber, its glass transition temperature is reduced from -24.6°C to below -26.5°C, and the thermal decomposition temperature is increased from 377°C to above 396°C. In addition, the product does not require copolymerization and blending during the preparation process, but introduces silicon-oxygen bonds into the main chain of the nitrile rubber by chemical modification.

[0038] Beneficial effect 2: The method for preparing low-temperature resistant silicon-containing modified nitrile rubber provided by the present invention breaks the traditional method of preparing modified nitrile rubber by copolymerization or blending of silicon-containing monomers. It uses organic siloxane and terminal hydroxyl nitrile rubber as raw materials and obtains low-temperature resistant silicon-containing modified nitrile rubber in one step through condensation reaction. The method is simple and feasible, with mild reaction conditions, controllable unit structure and low cost. Since the structure of the organosiloxane is controllable, the low-temperature resistant silicon-containing modified nitrile rubber can be given different application prospects through structural regulation. For example, the low-temperature resistant silicon-containing modified nitrile rubber prepared with methyltrimethoxysilane as the organosiloxane raw material can be used to toughen epoxy resin. Compared with the traditional method, due to the presence of methoxy groups, a coupling grafting reaction can be directly carried out without adding a grafting agent. After direct curing without adding a grafting agent, the tensile strength and shear strength reach 27.21 MPa and 22.09 MPa respectively; after curing with the addition of a grafting agent, the tensile strength and shear strength reach 30.49 MPa and 24.19 MPa respectively. This shows that the modified nitrile rubber provided by the present invention has excellent mechanical properties and better strength after curing. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a comparison chart of the mechanical properties of epoxy resin before and after modification. DETAILED DESCRIPTION

[0040] The following is a detailed description of the embodiments of the present invention: This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and process are given, but the protection scope of the present invention is not limited to the following embodiments. The experimental methods in the following embodiments without specifying specific conditions are usually carried out under conventional conditions.

[0041] The raw materials involved in the examples, without specifying the manufacturer, are all conventional raw materials that can be obtained through commercial purchase.

[0042] The general reaction formula involved in the following embodiments is as follows:

[0043] general formula:

[0044] Take methyltrimethoxysilane as an example:

[0045]

[0046] Example 1

[0047] This embodiment provides a low-temperature resistant silicon-containing modified nitrile rubber, and the specific preparation method is as follows:

[0048] A hydroxyl-terminated liquid nitrile rubber (molecular weight 2000) having a hydroxyl content of 0.62 mol / kg was dissolved in toluene to prepare a 10 wt% hydroxyl-terminated nitrile rubber solution;

[0049] 2.02 g (0.01488 mol) of methyltrimethoxysilane was dissolved in toluene to obtain a 30 wt% methyltrimethoxysilane solution;

[0050] In a 500mL three-necked flask equipped with a stirrer, 200g (hydroxyl content is 0.0124mol) of the above-mentioned terminal hydroxyl nitrile rubber solution was added, and the above-mentioned methyltrimethoxysilane solution was slowly added dropwise to the three-necked flask. After the addition was completed, nitrogen was introduced, and the temperature was raised to 60°C under nitrogen protection for reaction for 6h; after the reaction was completed, the obtained reaction mixture was slowly poured into methanol, stirred and precipitated, and after the product was precipitated, it was washed with methanol 3 times, and the methanol was removed by vacuum drying to obtain the low-temperature resistant silicon-containing modified nitrile rubber.

[0051] Example 2

[0052] This embodiment provides a low-temperature resistant silicon-containing modified nitrile rubber, and the specific preparation method is as follows:

[0053] A hydroxyl-terminated liquid nitrile rubber (molecular weight 2000) having a hydroxyl content of 0.62 mol / kg was dissolved in toluene to prepare a 12 wt % hydroxyl-terminated nitrile rubber solution;

[0054] 3.04 g (0.02232 mol) of methyltrimethoxysilane was dissolved in toluene to obtain a 20 wt% methyltrimethoxysilane solution;

[0055] In a 500mL three-necked flask equipped with a stirrer, 200g (hydroxyl content 0.01488mol) of the above-mentioned terminal hydroxyl nitrile rubber solution was added, and the above-mentioned methyltrimethoxysilane solution was slowly added dropwise to the three-necked flask. After the addition was completed, nitrogen was introduced, and the temperature was raised to 80°C under nitrogen protection to react for 8h; after the reaction was completed, the obtained reaction mixture was slowly poured into methanol, stirred and precipitated, and after the product was precipitated, it was washed with methanol 3 times, and the methanol was removed by vacuum drying to obtain the low-temperature resistant silicon-containing modified nitrile rubber.

[0056] Example 3

[0057] This embodiment provides a low-temperature resistant silicon-containing modified nitrile rubber, and the specific preparation method is as follows:

[0058] A hydroxyl-terminated liquid nitrile rubber (average molecular weight 2000) having a hydroxyl content of 0.62 mol / kg is dissolved in toluene to prepare a 10 wt % hydroxyl-terminated nitrile rubber solution;

[0059] 2.46 g (0.0186 mol) of dimethoxymethylvinylsilane was dissolved in toluene to obtain a 25 wt% methyltrimethoxysilane solution;

[0060] 200 g (hydroxyl content 0.0124 mol) of the above-mentioned hydroxy-terminated nitrile rubber solution was added to a 500 mL three-necked flask equipped with a stirrer, and the above-mentioned dimethoxymethylvinylsilane solution was slowly added dropwise to the three-necked flask. After the addition was completed, nitrogen was introduced, and the temperature was raised to 60° C. under nitrogen protection to react for 8 hours; after the reaction was completed, the resulting reaction mixture was slowly poured into methanol, stirred and precipitated, and after the product was precipitated, it was washed with methanol 3 times, and the methanol was removed by vacuum drying to obtain the low-temperature resistant silicon-containing modified nitrile rubber.

[0061] Example 4

[0062] This embodiment provides a low-temperature resistant silicon-containing modified nitrile rubber, and the specific preparation method is as follows:

[0063] A hydroxyl-terminated liquid nitrile rubber (average molecular weight 2500) having a hydroxyl content of 0.78 mol / kg is dissolved in toluene to prepare a 12 wt % hydroxyl-terminated nitrile rubber solution;

[0064] 2.96 g (0.02239 mol) of dimethoxymethylvinylsilane was dissolved in toluene to obtain a 20 wt% methyltrimethoxysilane solution;

[0065] 200 g (hydroxyl content 0.01872 mol) of the above-mentioned hydroxy-terminated nitrile rubber solution was added to a 500 mL three-necked flask equipped with a stirrer, and the above-mentioned dimethoxymethylvinylsilane solution was slowly added dropwise to the three-necked flask. After the addition was completed, nitrogen was introduced, and the temperature was raised to 80° C. under nitrogen protection for reaction for 6 hours. After the reaction was completed, the obtained reaction mixture was slowly poured into methanol, stirred and precipitated, and after the product was precipitated, it was washed with methanol 3 times, and the methanol was removed by vacuum drying to obtain the low-temperature resistant silicon-containing modified nitrile rubber.

[0066] Example 5

[0067] This embodiment provides a low-temperature resistant silicon-containing modified nitrile rubber, and the specific preparation method is as follows:

[0068] A hydroxyl-terminated liquid nitrile rubber (average molecular weight 2500) having a hydroxyl content of 0.78 mol / kg is dissolved in chlorobenzene to prepare a hydroxyl-terminated nitrile rubber solution having a concentration of 11 wt %;

[0069] 3.55 g (0.02395 mol) of vinyltrimethoxysilane was dissolved in chlorobenzene to obtain a 27 wt % vinyltrimethoxysilane solution;

[0070] In a 500mL three-necked flask equipped with a stirrer, 200g (hydroxyl content 0.01716mol) of the above-mentioned hydroxy-terminated nitrile rubber solution was added, and the above-mentioned vinyltrimethoxysilane solution was slowly added dropwise to the three-necked flask. After the addition was completed, nitrogen was introduced, and the temperature was raised to 60°C under nitrogen protection for 7h. After the reaction was completed, the obtained reaction mixture was slowly poured into methanol, stirred and precipitated, and after the product was precipitated, it was washed with methanol 3 times, and the methanol was removed by vacuum drying to obtain the low-temperature resistant silicon-containing modified nitrile rubber.

[0071] Example 6

[0072] This embodiment provides a low-temperature resistant silicon-containing modified nitrile rubber, and the specific preparation method is as follows:

[0073] A hydroxyl-terminated liquid nitrile rubber (average molecular weight 2500) having a hydroxyl content of 0.78 mol / kg is dissolved in chlorobenzene to prepare a hydroxyl-terminated nitrile rubber solution having a concentration of 11 wt %;

[0074] 3.81 g (0.02570 mol) of vinyltrimethoxysilane was dissolved in chlorobenzene to obtain a 22 wt% vinyltrimethoxysilane solution;

[0075] In a 500mL three-necked flask equipped with a stirrer, 200g (hydroxyl content 0.01716mol) of the above-mentioned hydroxy-terminated nitrile rubber solution was added, and the above-mentioned vinyltrimethoxysilane solution was slowly added dropwise to the three-necked flask. After the addition was completed, nitrogen was introduced, and the temperature was raised to 70°C under nitrogen protection for 8h. After the reaction was completed, the obtained reaction mixture was slowly poured into methanol, stirred and precipitated, and after the product was precipitated, it was washed with methanol 3 times, and the methanol was removed by vacuum drying to obtain the low-temperature resistant silicon-containing modified nitrile rubber.

[0076] Example 7

[0077] This embodiment provides a low-temperature resistant silicon-containing modified nitrile rubber, and the specific preparation method is as follows:

[0078] A hydroxyl-terminated liquid nitrile rubber (average molecular weight 3400) having a hydroxyl content of 0.58 mol / kg is dissolved in chlorobenzene to prepare a 10 wt% hydroxyl-terminated nitrile rubber solution;

[0079] 2.58 g (0.0174 mol) of vinyltrimethoxysilane was dissolved in chlorobenzene to obtain a 30 wt% vinyltrimethoxysilane solution;

[0080] 200 g (hydroxyl content 0.0116 mol) of the above-mentioned hydroxy-terminated nitrile rubber solution was added to a 500 mL three-necked flask equipped with a stirrer, and the above-mentioned vinyl trimethoxysilane solution was slowly added dropwise to the three-necked flask. After the addition was completed, nitrogen was introduced, and the temperature was raised to 80° C. under nitrogen protection for 7 hours. After the reaction was completed, the obtained reaction mixture was slowly poured into methanol, stirred and precipitated, and after the product was precipitated, it was washed with methanol 3 times, and the methanol was removed by vacuum drying to obtain the low-temperature resistant silicon-containing modified nitrile rubber.

[0081] Example 8

[0082] This embodiment provides a low-temperature resistant silicon-containing modified nitrile rubber, and the specific preparation method is as follows:

[0083] A hydroxyl-terminated liquid nitrile rubber (average molecular weight 3400) having a hydroxyl content of 0.58 mol / kg is dissolved in chlorobenzene to prepare a 12 wt % hydroxyl-terminated nitrile rubber solution;

[0084] 2.88 g (0.01943 mol) of vinyltrimethoxysilane was dissolved in chlorobenzene to obtain a 20 wt% vinyltrimethoxysilane solution;

[0085] 200 g (hydroxyl content 0.01392 mol) of the above-mentioned hydroxy-terminated nitrile rubber solution was added to a 500 mL three-necked flask equipped with a stirrer, and the above-mentioned vinyl trimethoxysilane solution was slowly added dropwise to the three-necked flask. After the addition was completed, nitrogen was introduced, and the temperature was raised to 70° C. under nitrogen protection for 6 hours. After the reaction was completed, the obtained reaction mixture was slowly poured into methanol, stirred and precipitated, and after the product was precipitated, it was washed with methanol 3 times, and the methanol was removed by vacuum drying to obtain the low-temperature resistant silicon-containing modified nitrile rubber.

[0086] Performance Characterization

[0087] The low temperature resistant silicon-containing modified nitrile rubber prepared in each embodiment was subjected to corresponding performance tests, and the corresponding unmodified hydroxy-terminated nitrile rubber was used as a control sample.

[0088] Referring to GB / T 29611-2013, the glass transition temperature of the sample was measured using DMA (dimethylacetamide), with a heating rate of 5°C / min, a frequency of 10 Hz, and a temperature range of -70 to 60°C;

[0089] Referring to GB / T14837.2, using a thermogravimetric analyzer, in a nitrogen atmosphere, the temperature was raised from 20°C to 650°C at a rate of 20°C / min. The temperature at which the mass retention rate dropped to 90wt% was the thermal weight loss temperature, which was used to characterize the heat resistance of the sample.

[0090] Table 1

[0091]

[0092]

[0093] As can be seen from the data in the above table, the low temperature resistant silicon-containing modified nitrile rubber provided by the present invention has a significantly lower glass transition temperature than the comparative example (unmodified hydroxy-terminated nitrile rubber), and its low temperature resistance is significantly improved. The thermal decomposition temperature data of each embodiment are better than the control sample (unmodified hydroxy-terminated nitrile rubber), indicating that the low temperature resistant silicon-containing modified nitrile rubber provided by the present invention exhibits good temperature resistance.

[0094] In order to further characterize the application performance of the low-temperature resistant silicon-containing modified nitrile rubber provided by the present invention, the low-temperature resistant silicon-containing modified nitrile rubber prepared in Example 2 and the corresponding unmodified terminal hydroxyl nitrile rubber were respectively subjected to toughening tests on epoxy resin, and epoxy resin (without adding nitrile rubber) was used as a control.

[0095] Test conditions:

[0096] Add toughening agent (low temperature resistant silicon-containing modified nitrile rubber or corresponding unmodified hydroxy-terminated nitrile rubber) to epoxy resin, stir and mix in a 140°C oil bath for 1 hour, take out the blend and cool naturally, then add grafting agent (TDI), stir evenly and degas, then preliminarily cure at room temperature for 1 hour, then place in an oven and cure at 130°C for 2 hours. Wherein, based on 100 parts by weight of epoxy resin, toughening agent is 25 parts by weight, and grafting agent is 15 parts by weight.

[0097] A toughening agent (low-temperature resistant silicon-containing modified nitrile rubber) was added to the epoxy resin and stirred in an oil bath at 140°C for 1 hour. The mixture was taken out and naturally cooled to room temperature and initially cured at room temperature for 1 hour, and then placed in an oven and cured at 130°C for 2 hours.

[0098] The specific experimental results are as follows Figure 1 shown.

[0099] from Figure 1 It can be seen that under the condition of adding the grafting agent TDI, the tensile strength and shear strength of the epoxy resin toughened with the low-temperature resistant silicon-containing modified nitrile rubber provided in Example 2 reached 30.49 MPa and 24.19 MPa, respectively, compared with the blank epoxy resin (tensile strength of 25.34, shear strength of 20.62) and the epoxy resin toughened with unmodified terminal hydroxyl nitrile rubber (tensile strength of 27.32, shear strength of 22.89), showing better mechanical properties and better strength after curing.

[0100] At the same time, it can be seen that without adding a grafting agent, the tensile strength and shear strength of the epoxy resin toughened with the low-temperature resistant silicon-containing modified nitrile rubber provided in Example 2 can still reach 27.21 MPa and 22.09 MPa, respectively, indicating that the low-temperature resistant silicon-containing modified nitrile rubber can directly undergo coupling grafting due to the presence of methoxy groups without adding a grafting agent, indicating that the low-temperature resistant silicon-containing modified nitrile rubber has better application prospects.

[0101] The above embodiments are typical examples listed to illustrate the technical solutions of the present invention in detail. The present invention is subject to the protection scope of the claims and the content of the invention and is not limited by the implementation scheme. Simple replacement or modification of the present invention is still within the protection scope of the present invention.

Claims

1. A low temperature resistant silicon-containing modified nitrile rubber, characterized in that: It has the structure shown in Formula I: Wherein, x=10-1000, y=10-1000, z=10-1000, x, y, z represent the polymerization degree of the corresponding structural unit, R1 and R2 are independently selected from C1-C12 alkoxy, or C1-C18 straight chain or branched hydrocarbon group; X is selected from C1-C18 straight chain or branched hydrocarbon groups.

2. The low temperature resistant silicon-containing modified nitrile rubber according to claim 1, characterized in that: R1 and R2 are independently selected from C1-C6 alkoxy, or C1-C12 straight or branched hydrocarbon; preferably methyl, methoxy, ethyl, ethoxy, vinyl, propyl, propoxy, propenyl, allyl, isopropyl, butyl, or dodecyl, more preferably methoxy or dodecyl; X is selected from C1-C12 straight or branched hydrocarbon groups; preferably methyl, ethyl, vinyl, propyl, propenyl, allyl, isopropyl, butyl, or dodecyl, more preferably methyl, vinyl, or dodecyl.

3. A method for preparing a low-temperature resistant silicon-containing modified nitrile rubber, characterized in that: The hydroxy-terminated nitrile rubber represented by formula II reacts with the organosiloxane represented by formula III to obtain the low-temperature resistant silicon-containing modified nitrile rubber represented by formula I; Wherein, x, y, z, R1 and R2 are defined as in claim 1; R3 is selected from C1-C12 alkoxy, preferably C1-C5 alkoxy, more preferably methoxy, ethoxy, propoxy, isopropoxy, or n-butoxy.

4. The preparation method according to claim 3, characterized in that: The steps include: Dissolving the hydroxy-terminated nitrile rubber represented by formula II and the organosiloxane represented by formula I in the same solvent to obtain a solution of the organosiloxane and a solution of the hydroxy-terminated nitrile rubber; Under stirring conditions, the solution of the organosiloxane is added dropwise to the solution of the terminal hydroxyl nitrile rubber. After the addition is completed, a condensation reaction is carried out under nitrogen protection. After the reaction is completed, the reaction system is mixed with methanol for precipitation. The obtained solid is washed and dried to obtain a low-temperature resistant silicon-containing modified nitrile rubber.

5. The preparation method according to claim 3, characterized in that: The organosiloxane represented by formula III is selected from methyl siloxane, vinyl siloxane, or allyl siloxane, preferably methyltrimethoxysilane, vinyltrimethoxysilane, dimethoxymethylvinylsilane, or dodecylmethyldimethoxysilane.

6. The preparation method according to claim 3, characterized in that: The molar ratio of the hydroxyl group in the hydroxy-terminated nitrile rubber to the organic siloxane is 1:1.2-1.

5.

7. The preparation method according to claim 3, characterized in that: The content of the hydroxy-terminated nitrile rubber in the hydroxy-terminated nitrile rubber solution is 10 wt % to 12 wt %; and / or The content of the organosiloxane in the organosiloxane solution is 20 wt % to 30 wt %.

8. The preparation method according to claim 3, characterized in that: The temperature of the condensation reaction is 60-80° C. and the time is 6-8 hours.

9. The preparation method according to claim 3, characterized in that: The solvent is selected from dimethylformamide, chlorobenzene, toluene, or xylene; preferably toluene and chlorobenzene.

10. Use of the low-temperature-resistant silicon-containing modified nitrile rubber according to claim 1 or 2, or the low-temperature-resistant silicon-containing modified nitrile rubber prepared by the preparation method of the low-temperature-resistant silicon-containing modified nitrile rubber according to any one of claims 3 to 9 in the preparation of epoxy resin adhesives or composite materials.

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