Preparation method of silicon-terminated hydrofluorosilicone polymer and method for modifying nitrile rubber

Abstract

The invention relates to a preparation method of a silicon-hydrogen-fluorine-silicon-terminated polymer and a method for modifying nitrile rubber, and the preparation method comprises the following steps: dissolving a fluorine-containing polymer with allyl-terminated ether in a fluorocarbon solvent, then adding double-terminated silicon-hydrogen siloxane and a catalyst, and reacting to obtain the silicon-hydrogen-fluorine-silicon-terminated polymer; the method for modifying the nitrile rubber comprises the following steps: adding the silicon-terminated hydrofluorosilicone polymer into unvulcanized nitrile rubber, and carrying out open milling and vulcanization to obtain the fluorosilicone polymer modified polydiene rubber. Compared with the prior art, in-situ chemical crosslinking of the silicon-terminated hydrofluorosilicone polymer and the NBR is realized through chemical synthesis, the friction effect in a molecular chain of the NBR is reduced, and the wear resistance of the NBR is improved. The Akron abrasion of the fluorosilicone polymer modified nitrile rubber is reduced by 15%-50%, the static (dynamic) friction coefficient is reduced by 15%-45%, and the loss factor peak value is improved by 5%-15%.

Description

Technical Field

[0001] The invention belongs to the technical field of rubber and relates to a method for preparing a terminal silicon-hydrogen-fluorine-silicon polymer and modifying nitrile rubber. Background Art

[0002] Nitrile rubber (NBR) has excellent oil resistance and good physical and wear resistance, and is widely used in the field of engineering machinery rubber products. In recent years, with the rapid development of new energy vehicles and the petroleum industry, the use of rubber sealing materials has increased, such as pneumatic parts, rubber plugs, O-rings, etc. These rubber sealing materials are mostly contact-type dynamic sealing parts. When the parts are in a dynamic working condition, they will produce friction on the surface of the friction pair, causing the surface of the rubber product to generate intense heat and wear. The sealing performance of the rubber product will also gradually weaken, eventually causing failure. Organic fluorine materials can effectively reduce the wear between rubber seals and friction pairs, improve the lubricity between the two, and reduce the roughness of the friction substrate surface, thereby increasing the service life of the sealing parts. Therefore, organic fluorine materials play a key role in rubber seals. At present, organic fluorine is mainly used to improve the friction resistance of rubber surfaces through the following three methods: (1) spraying fluorine-containing coatings on the surface of rubber products; (2) plasma fluorination treatment of the surface of rubber products; (3) adding polytetrafluoroethylene powder to the rubber mixing formula.

[0003] Zhang Lingxin et al. (Friction properties of HNBR modified by spraying fluorine-containing coating on the surface [J], Rubber Industry, 2011, 58(5): 261-268.) used water-based polytetrafluoroethylene coating to spray on the surface of hydrogenated nitrile rubber. The analysis showed that although this technical solution reduced the friction coefficient from 1.0 to 0.15-0.20, it had poor adhesion, short effective time, and could not penetrate into the interior of the colloid, and could not improve the problem of frictional heat generation within the molecular chain.

[0004] Mi Tong et al. (Study on the Friction Reduction Mechanism of Plasma Fluorination Modified Nitrile Rubber Surface Coating [J], Rubber Industry, 2013, 60(9): 527-532.) used carbon tetrafluoride as the reaction gas to perform plasma fluorination modification on the surface of nitrile rubber. They found that although the friction coefficient of this technical solution was reduced from 1.89 to 1.02-1.51, it could only fluorinate the surface of the nitrile rubber in a shallow layer. Once worn, it could not play a friction reduction role and had a short service life, which did not meet the requirements of long-term use. In addition, the surface fluorination treatment could easily destroy the rubber surface structure, generate free radicals, and easily cause the molecular chain to break. It also could not improve the problem of frictional heat generation within the molecular chain.

[0005] Liu Yang (Study on the Performance of Polytetrafluoroethylene Modified SBR / NBR, Northwest Normal University [D], 2014.) used polytetrafluoroethylene dispersion to blend with emulsion polytetrafluoroethylene butadiene rubber and found that this technical solution can improve the oil resistance and tensile strength of rubber, and to a certain extent improve the scorch resistance of the rubber, thereby improving processing safety. In addition, the use of polytetrafluoroethylene dispersion blended with nitrile rubber can also improve the oil resistance and tensile properties of nitrile rubber. However, this preparation technology has the problem that polytetrafluoroethylene powder is incompatible with the non-fluorine rubber matrix, which is easy to produce phase separation, resulting in changes in crosslinking density and affecting the performance of the product. During long-term use, polytetrafluoroethylene powder gradually precipitates on the rubber surface, resulting in cavities inside the rubber, which to a certain extent destroys the mechanical properties and heat stability of the product and greatly reduces its service life.

[0006] Therefore, the present invention develops a terminal silicon-hydrogen fluorosilicone polymer modifier through chemical synthesis. During the vulcanization process, peroxide is used to promote the addition of silicon-hydrogen groups to the side vinyl groups of NBR, which are embedded in the NBR molecular chain to achieve deep-level fluorosilicone polymer modification of NBR, thereby reducing the friction within the NBR molecular chain and improving its wear resistance. Summary of the invention

[0007] The purpose of the present invention is to provide a method for preparing a terminal silicon-hydrogen-fluorine-silicon polymer and a modified nitrile rubber, which realizes in-situ chemical crosslinking of the terminal silicon-hydrogen-fluorine-silicon polymer and NBR through chemical synthesis, reduces the friction effect within the NBR molecular chain, improves its wear resistance, and solves the problems of poor adhesion, short effective duration, gradual precipitation on the rubber surface, and generation of cavities inside. It has immeasurable economic value in rubber products.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] A method for preparing a terminal silicon-hydrogen-fluorosilicon polymer comprises: dissolving a fluorine-containing polymer having a terminal allyl ether as shown in Formula 1 in a fluorocarbon solvent, then adding a double-terminal silicon-hydrogen-siloxane as shown in Formula 2 and a catalyst, and reacting to obtain a terminal silicon-hydrogen-fluorosilicon polymer as shown in Formula 3;

[0010]

[0011]

[0012] In the formula, R f It is a perfluoropolyether as shown in Formula 4 or a liquid fluororubber as shown in Formula 5; wherein the value of p is 5 to 10, the value of q is 5 to 10, the value of x is 1 to 20, the value of y is 1 to 20, the value of z is 1 to 5, the value of m is 1 to 3, and the value of n is 1 to 50.

[0013] Furthermore, the fluorine-containing polymer is selected from at least one of K-type perfluoropolyether, Y-type perfluoropolyether, Z-type perfluoropolyether or liquid fluororubber 246.

[0014] As a preferred technical solution, the molecular weight of the fluorine-containing polymer is 1000-3000.

[0015] Furthermore, the biterminal siloxane is at least one of tetramethyldihydrogendisiloxane and biterminal siloxane polysiloxane.

[0016] As a preferred technical solution, the molecular weight of the biterminal silicon hydrogen polysiloxane is 1000-3000.

[0017] Furthermore, the molar ratio of the fluorine-containing polymer to the biterminal silicon hydrogen siloxane is 1:1-3.

[0018] Furthermore, the fluorocarbon solvent is selected from at least one of nonafluorobutyl ethyl ether, trifluorotoluene or 1,3-di(trifluoromethyl)benzene.

[0019] Furthermore, the catalyst is selected from at least one of a Custer catalyst, a Speier catalyst, Pt / C or tris(triphenylphosphine)rhodium chloride; and the amount used is 0.01%-10% of the total mass of the fluorine-containing polymer with terminal allyl ether and the biterminal silicon hydrogen siloxane.

[0020] Furthermore, the reaction conditions are: reaction temperature is 60-200° C., and reaction time is 0.5-72 h.

[0021] Furthermore, the reaction product mixture is mixed with an organic alcohol compound to obtain a lower fluorine phase mixture, and the solvent is removed by reduced pressure distillation to obtain a terminal silicon-hydrogen-fluorine-silicon polymer.

[0022] A method for modifying nitrile rubber, comprising: adding a terminal silicon-hydrogen fluorine-silicon polymer to unvulcanized nitrile rubber, performing open milling and vulcanization, and obtaining a fluorine-silicon polymer modified polydiene rubber;

[0023] Wherein, the terminal silicon-hydrogen-fluorine-silicon polymer is prepared by the method as described above.

[0024] Further, the unvulcanized nitrile rubber comprises the following components and contents in parts by weight:

[0025]

[0026]

[0027] The mass ratio of the terminal silicon hydrogen fluorine silicon polymer to the unvulcanized nitrile rubber is (8-12): 1,

[0028] The conditions for the first smelting are: the temperature is room temperature to 45°C, and the time is 15-25 minutes;

[0029] The vulcanization conditions are: temperature 140-180°C, molding pressure 65-75MPa, and time 25-35min.

[0030] Compared with the prior art, the present invention has the following characteristics:

[0031] The invention discloses a terminal silicon-hydrogen fluorosilicone polymer modified nitrile rubber and a preparation method thereof. Through chemical synthesis, the terminal silicon-hydrogen fluorosilicone polymer and NBR are chemically cross-linked in situ, the friction effect within the NBR molecular chain is reduced, and the wear resistance is improved. The Akron wear of the fluorosilicone polymer modified nitrile rubber is reduced by 15% to 50%, the static (dynamic) friction coefficient is reduced by 15% to 45%, and the loss factor peak value is increased by 5% to 15%. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is the infrared spectrum of the terminal silicon-hydrogen-fluorine-silicon polymer A prepared in Example 1;

[0033] Figure 2 is the infrared spectrum of the terminal silicon-hydrogen-fluorine-silicon polymer B prepared in Example 1;

[0034] Figure 3 This is the infrared spectrum of the terminal silicon-hydrogen-fluorine-silicon polymer C prepared in Example 1. DETAILED DESCRIPTION

[0035] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The following embodiments are implemented based on the above technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0036] The following examples of raw materials: terminal allyl ether Z-type perfluoropolyether, terminal allyl ether Y-type perfluoropolyether, terminal allyl ether liquid fluororubber 246, double-terminal hydrogen-containing silicone oil (containing active hydrogen mass fraction M w =1205, 2435, 3846), nonafluorobutyl ether, terminal silicon hydrogen fluorosilicone oil: industrial grade, Shenzhen Tianke New Materials Co., Ltd. Nitrile rubber (combined with acrylonitrile, 35% to 40%), zinc oxide, stearic acid, sulfur, accelerator CZ, N550, dioctyl phthalate, vulcanizer DCP and crosslinker TAIC: industrial grade, PetroChina Lanzhou Chemical Research Center. Trifluorotoluene, Speier catalyst, tris(triphenylphosphine) rhodium chloride, anhydrous methanol: analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0037] The evaluation and analysis methods used in the embodiments of the present invention are: DMA: test temperature range: -50°C to 120°C, heating rate: 3°C / min, force: 2.5N, frequency: 5Hz, displacement: 0.8μm. Akron wear volume: in accordance with GB / T1689-1998. Friction coefficient: in accordance with GB / T 22895-2008.

[0038] Example 1

[0039] A terminal silicon-hydrogen-fluorine-silicon polymer, the preparation method of which comprises:

[0040] 50g(M w =1580,0.032mol) terminal allyl ether Z type perfluoropolyether and 77.1g (M w =1205, 0.064mol) double-terminal hydrogen-containing silicone oil was added to a three-necked flask, and then 50mL of nonafluorobutyl ether and 0.013g of Speier catalyst were added, and stirred at 60°C for 20h; after the reaction was completed, it was cooled to room temperature, 50mL of methanol was added, and the lower fluorine phase mixture was separated; the solvent was removed by distillation under reduced pressure to obtain about 125g of terminal silicon hydrogen fluorine silicon polymer A, and its infrared spectrum was as shown Figure 1 shown.

[0041] Example 2

[0042] A terminal silicon-hydrogen-fluorine-silicon polymer, the preparation method of which comprises:

[0043] 50g(M w =1280,0.039mol) terminal allyl ether Y-type perfluoropolyether and 70.5g (M w =1205, 0.059 mol) double-terminal hydrogen-containing silicone oil was added to a three-necked flask, and then 50 mL of nonafluorobutyl ether and 0.013 g of Speier catalyst were added, and stirred at 150 ° C for 5 h; after the reaction was completed, it was cooled to room temperature, 50 mL of methanol was added, and the lower fluorine phase mixture was separated; the solvent was removed by distillation under reduced pressure to obtain about 112 g of terminal silicon hydrogen fluorine silicon polymer B, and its infrared spectrum is shown as follows Figure 2 shown.

[0044] Example 3

[0045] A terminal silicon-hydrogen-fluorine-silicon polymer, the preparation method of which comprises:

[0046] 50g(M w =3200, 0.016 mol) terminal allyl ether liquid fluororubber 246 and 38.6 g (M w=1205, 0.032mol) double-terminal hydrogen-containing silicone oil was added to a three-necked flask, and then 50mL of trifluorotoluene and 0.2g of tri(triphenylphosphine)rhodium chloride were added, and stirred at 180°C for 12h; after the reaction was completed, it was cooled to room temperature, 100mL of methanol was added, and the lower fluorine phase mixture was separated; the solvent was removed by distillation under reduced pressure to obtain about 76g of terminal silicon-hydrogen-fluorine-silicon polymer C, and its infrared spectrum is shown as follows Figure 3 shown.

[0047] Example 4

[0048] A terminal silicon-hydrogen-fluorine-silicon polymer, the preparation method of which comprises:

[0049] 50g(M w =1580,0.032mol) terminal allyl ether Z type perfluoropolyether and 170.5g (M w =2435, 0.070 mol) double-terminal hydrogen-containing silicone oil was added into a three-necked flask, and then 100 mL of trifluorotoluene and 0.022 g of Speier catalyst were added, and stirred at 150° C. for 8 h; after the reaction was completed, the mixture was cooled to room temperature, 80 mL of methanol was added, and the lower fluorine phase mixture was separated; the solvent was removed by distillation under reduced pressure to obtain about 198 g of terminal silicon-hydrogen-fluorine-silicon polymer D.

[0050] Example 5

[0051] A terminal silicon-hydrogen-fluorine-silicon polymer, the preparation method of which comprises:

[0052] 50g(M w =1580,0.032mol) terminal allyl ether Z type perfluoropolyether and 269g (M w =3846, 0.070 mol) double-terminal hydrogen-containing silicone oil was added into a three-necked flask, and then 100 mL of trifluorotoluene and 0.032 Speier catalyst were added, and stirred at 150° C. for 8 h; after the reaction was completed, it was cooled to room temperature, 80 mL of methanol was added, and the lower fluorine phase mixture was separated; the solvent was removed by distillation under reduced pressure to obtain about 281 g of terminal silicon-hydrogen-fluorine-silicon polymer E.

[0053] Example 6

[0054] A terminal silicon-hydrogen-fluorine-silicon polymer, the preparation method of which comprises:

[0055] 50g(M w =3200, 0.016mol) terminal allyl ether liquid fluororubber 246 and 123g (M w=3846, 0.032mol) double-terminal hydrogen-containing silicone oil was added into a three-necked flask, and then 100mL of trifluorotoluene and 0.5g of tri(triphenylphosphine)rhodium chloride were added, and stirred at 180°C for 12h; after the reaction was completed, the mixture was cooled to room temperature, 200mL of methanol was added, and the lower fluorine phase mixture was separated; the solvent was removed by distillation under reduced pressure to obtain about 154g of terminal silicon-hydrogen-fluorine-silicon polymer F.

[0056] Comparative Example

[0057] A terminal silicon hydrogen fluorine silicon polymer is a terminal silicon hydrogen fluorine silicone oil with a molecular weight of about 6000.

[0058] Preparation of fluorosilicone polymer modified nitrile rubber:

[0059] 2.4kg of unvulcanized nitrile rubber (formulation is 100 parts of nitrile rubber NBR, 5 parts of zinc oxide, 1 part of stearic acid, 1 part of sulfur, 1.8 parts of accelerator CZ, 70 parts of N550, 10 parts of dioctyl phthalate, 3 parts of vulcanizing agent DCP and 1.2 parts of crosslinking agent TAIC) is divided into 8 parts, each rubber mass is 300g. Take 30g of each of the terminal silicon hydrogen fluorine silicon polymer prepared in Examples 1 to 6 and the comparative example, add them into 7 parts of unvulcanized nitrile rubber in turn, and openly grind them respectively, the roller surface temperature is room temperature to 45°C, and the time is 20min. Then vulcanize at 160°C, mold pressure is 70MPa, and the time is 30min to prepare fluorosilicone polymer modified nitrile rubber samples 1 to 7. The properties of samples 1 to 7 are shown in Table 1.

[0060] Table 1 Wear resistance and loss factor of samples 1 to 7

[0061]

[0062]

[0063] From the data analysis of Table 1, it can be seen that the use of the fluorosilicone polymer provided in the embodiment of the present invention as a vulcanized rubber additive effectively improves the wear resistance of nitrile rubber, reduces the friction coefficient of the colloid surface, and thus can greatly increase the service life of nitrile rubber dynamic seals.

[0064] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing a terminal silicon-hydrogen-fluorine-silicon polymer, It is characterized in that include: Dissolving a fluorine-containing polymer having a terminal allyl ether as shown in Formula 1 in a fluorocarbon solvent, then adding a biterminal siloxane as shown in Formula 2 and a catalyst to react to obtain a terminal siloxane fluorine-containing polymer as shown in Formula 3; In the formula, R f It is a perfluoropolyether as shown in Formula 4 or a liquid fluororubber as shown in Formula 5; wherein the value of p is 5 to 10, the value of q is 5 to 10, the value of x is 1 to 20, the value of y is 1 to 20, the value of z is 1 to 5, the value of m is 1 to 3, and the value of n is 1 to 50.

2. The method for preparing the terminal silicon-hydrogen-fluorine-silicon polymer according to claim 1, It is characterized in that The fluorine-containing polymer is selected from at least one of K-type perfluoropolyether, Y-type perfluoropolyether, Z-type perfluoropolyether or liquid fluororubber 246.

3. The method for preparing the terminal silicon-hydrogen-fluorine-silicon polymer according to claim 1, It is characterized in that The biterminal siloxane is at least one of tetramethyldihydrogendisiloxane and biterminal siloxane.

4. The method for preparing the terminal silicon-hydrogen-fluorine-silicon polymer according to claim 1, It is characterized in that The molar ratio of the fluorine-containing polymer to the biterminal silicon hydrogen siloxane is 1:1-3.

5. The method for preparing the terminal silicon-hydrogen-fluorine-silicon polymer according to claim 1, It is characterized in that The fluorocarbon solvent is selected from at least one of nonafluorobutyl ethyl ether, trifluorotoluene or 1,3-bis(trifluoromethyl)benzene.

6. The method for preparing the terminal silicon-hydrogen-fluorine-silicon polymer according to claim 1, It is characterized in that The catalyst is selected from at least one of a Custer catalyst, a Speier catalyst, Pt / C or tris(triphenylphosphine)rhodium chloride; and the amount used is 0.01%-10% of the total mass of the fluorine-containing polymer with terminal allyl ether and the double-terminal silicon hydrogen siloxane.

7. The method for preparing the terminal silicon-hydrogen-fluorine-silicon polymer according to claim 1, It is characterized in that The reaction conditions are: reaction temperature is 60-200°C, and reaction time is 0.5-72h.

8. The method for preparing the terminal silicon-hydrogen-fluorine-silicon polymer according to claim 1, It is characterized in that The reaction product mixture is mixed with an organic alcohol compound to obtain a lower fluorine phase mixture, and the solvent is removed by distillation under reduced pressure to obtain a terminal silicon-hydrogen-fluorine-silicon polymer.

9. A method for modifying nitrile rubber, It is characterized in that include: Adding the terminal silicon-hydrogen fluorosilicone polymer to the unvulcanized nitrile rubber for refining and vulcanization to obtain the fluorosilicone polymer modified polydiene rubber; Wherein, the terminal silicon-hydrogen-fluorine-silicon polymer is prepared by the method as described in any one of claims 1 to 8.

10. The method for modifying nitrile rubber according to claim 9, It is characterized in that The unvulcanized nitrile rubber comprises the following components and contents in parts by weight: The mass ratio of the terminal silicon hydrogen fluorine silicon polymer to the unvulcanized nitrile rubber is (8-12): 1, The conditions for the first smelting are: the temperature is room temperature to 45°C, and the time is 15-25 minutes; The vulcanization conditions are: temperature 140-180°C, molding pressure 65-75MPa, and time 25-35min.

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