Heat-resistant additive for silicone rubber and preparation method of heat-resistant additive

Abstract

The invention belongs to the technical field of rubber heat-resistant additive preparation, and relates to a heat-resistant additive for silicone rubber and a preparation method thereof. And uniformly mixing the nano metal oxide dispersion liquid with the modified liquid, adding acetic acid, performing ultrasonic treatment, violently stirring and reacting overnight. And the reaction liquid is centrifuged, washed and dried, and the modified nano metal particles are obtained. And adding the modified nano metal particles into the silicone rubber base rubber to prepare the silicone rubber. The modified metal oxide is simple to operate, low in price, easy to purify, free of complex operation and extremely high in product success rate, and raw materials are easy to obtain. The product produced by adding the modified metal oxide into a rubber matrix has the advantages of obviously improved heat resistance, slower decomposition speed and prolonged service life.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of heat-resistant rubber additives, and relates to a heat-resistant additive for silicone rubber and a preparation method thereof. Background Art

[0002] Silicone rubber is widely used in electronic equipment, aerospace, and mechanical processing because of its excellent electrical insulation, UV resistance, flexibility, hydrophobicity, and high and low temperature resistance within a certain temperature range. However, during use, it will become hard and brittle and age. The usual solution is to add heat-resistant additives. This method has the advantages of easy operation, simple process, and low cost, and is suitable for industrial production.

[0003] In order to improve the thermal oxidation stability of silicone rubber and prevent the thermal oxidation of its side organic groups, thermal oxidation stabilizers (heat-resistant additives) can be added to the silicone rubber compound. Metal oxides (ZrO2, CeO2 and TiO2, etc.) have a capacity-enhancing effect on silicone materials and eliminate free radicals generated during the aging process, thereby preventing the free radicals from damaging the rubber molecules and greatly improving the heat-resistant air aging performance of silicone rubber. At the same time, metal oxides such as nano-CeO2 have the greatest impact on the heat resistance of silicone materials, but nano-cerium oxide is prone to agglomeration. Summary of the invention

[0004] Aiming at the problems existing in the traditional silicone rubber modification, the present invention proposes a novel heat-resistant additive for silicone rubber and a preparation method thereof.

[0005] In order to achieve the above object, the present invention is implemented by adopting the following technical solutions: A heat-resistant additive for silicone rubber is a mixture of nano CeO2, nano ZrO2 and nano TiO2 modified by a silane coupling agent.

[0006] Preferably, the method for preparing the heat-resistant additive for silicone rubber comprises the following steps: (1) Add nano-metal oxide to ethanol and mix well to obtain a nano-metal oxide dispersion; add a silane coupling agent to ethanol and mix well to obtain a modified solution; mix the nano-metal oxide dispersion and the modified solution well, add acetic acid, and stir vigorously to react overnight after ultrasonic treatment.

[0007] (2) The reaction solution is centrifuged, washed and dried to obtain modified nano-metal particles.

[0008] (3) Adding the modified nano-metal particles into silicone rubber base to prepare silicone rubber.

[0009] Preferably, the nano metal oxide in step (1) is nano CeO2, nano ZrO2 and nano TiO2. The three nano metal oxides can be modified by silane coupling agent separately and then mixed in proportion for use, or the three nano metal oxides can be mixed in proportion and then modified together. The silane coupling agent is any one or more of KH-550, KH-560, KH-570, KH792 and DL6021. The ultrasonic treatment time is more than 30 minutes, and the mass ratio of the nano metal oxide to the silane coupling agent is (5-8):1.

[0010] Preferably, in step (2), the reaction solution is washed with ethanol after centrifugation, and the centrifugation washing is repeated three times; and the drying process is performed at room temperature for more than 20 hours.

[0011] Preferably, the modified nano-metal particles in step (3) are a mixture of modified nano-CeO2, nano-ZrO2 and nano-TiO2, and the mass ratio of nano-CeO2, nano-ZrO2 and nano-TiO2 is: (2-4): 1: (1.5-2.5).

[0012] Silane coupling agent modification of nano-metal particles can reduce the content of hydroxyl groups on the surface of nano-metal particles, weaken or even eliminate the hydrogen bonding interaction between nano-particles, and thus prevent the nano-metal particles from approaching each other and agglomerating.

[0013] In high-temperature hot air, the side organic groups of the silicone rubber molecules will be oxidized, decomposing small molecules such as formaldehyde and formic acid, and causing cross-linking, making the silicone rubber products gradually brittle and losing elasticity. The addition of modified metal nanoparticles can prevent the free radical cross-linking aging reaction of the side chain methyl groups, and alleviate the gradual hardening and brittle cracking of silicone rubber. The three modified metal nanoparticles proposed in the present invention need to be compounded before use. Using one or two of the modified metal nanoparticles alone cannot achieve the desired effect. The amount and ratio of the three modified metal nanoparticles have a great influence on the final performance of silicone rubber.

[0014] Compared with the prior art, the advantages and positive effects of the present invention are: 1. The modified metal oxide of the present invention is simple to operate, low in price, and the raw materials are readily available and easy to purify, without the need for complicated operations, and the product success rate is extremely high.

[0015] 2. The heat resistance of the product produced by adding the modified metal oxide of the present invention into the rubber matrix is ​​significantly improved, the decomposition speed is slower, and the service life is extended.

[0016] 3. The composite modified nano-metal particles proposed in the present invention will have different effects on the properties of rubber when mixed in different proportions, providing more possibilities for the further development of new rubber products. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 a is the infrared spectrum of nano-CeO2 before modification in Example 1 of the present invention, Figure 1 b is the infrared spectrum of modified nano-CeO2 in Example 1 of the present invention.

[0018] Figure 2 a is the infrared spectrum of nano ZrO2 before modification in Example 1 of the present invention, Figure 2 b is the infrared spectrum of the modified nano ZrO2 in Example 1 of the present invention.

[0019] Figure 3 a is the infrared spectrum of nano-TiO2 before modification in Example 1 of the present invention, Figure 3 b is the infrared spectrum of the modified nano-TiO2 in Example 1 of the present invention. DETAILED DESCRIPTION

[0020] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described below in conjunction with specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0021] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways than those described herein. Therefore, the present invention is not limited to the specific embodiments of the following disclosure.

[0022] In the following embodiments, nano-CeO2 was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with a particle size of <5 μm; nano-ZrO2 was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with a particle size of <5 μm; nano-TiO2 was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with a particle size of <5 μm; and the silicone rubber base was provided by Zhejiang Xin'an Chemical Group.

[0023] Example 1 In this embodiment, three kinds of metal nanoparticles are modified separately and then mixed.

[0024] Add 30g of nano CeO2 to a 500ml beaker equipped with a magnetic stirrer, add 35ml of anhydrous ethanol and mix well to obtain a dispersion. Weigh 7.24g of silane coupling agent KH560 and put it into 20ml of anhydrous ethanol and stir it thoroughly until it is mixed well to obtain a modifier. Pour the modifier into the dispersion and mix well, add 10ml of acetic acid, and perform ultrasound for more than 30min. After ultrasound, seal the beaker with plastic wrap and place it on a magnetic stirrer and stir vigorously at room temperature overnight.

[0025] According to the above method, 30g of nano ZrO2 was weighed and modified with 2.7g of KH560; 30g of nano TiO2 was modified with 4.53g of KH560, and the other conditions were the same as the above nano CeO2 modification conditions. In this way, three groups of modified metal nano particle reaction solutions can be prepared at one time.

[0026] The three groups of reaction solutions were placed in different centrifuge tubes for centrifugation. After centrifugation, the upper layer of liquid was poured out, 5-10 ml of ethanol was added and shaken vigorously for washing, and then centrifuged again and repeated three times to completely remove the residual acetic acid. After the last centrifugation, the upper layer of liquid was poured out, and then the solid was placed in an oven and dried at room temperature for more than 20 hours. The three kinds of dried and modified nano metal oxides were obtained, and then they were crushed and sealed for use.

[0027] Weigh 3g of nano CeO2, 1g of nano ZrO2, and 2g of nano TiO2, add them to 200g of silicone rubber base, knead the components into shape with a kneader, divide the rubber into blocks, and store them for 2 hours, then heat it to about 160°C in the kneader for high-temperature internal mixing, keep it warm, remove low molecular weight substances, and discharge the rubber after it cools to below 100°C. Divide the rubber into sheet rubber to obtain high-temperature resistant silicone rubber, cool it for more than 30 minutes, open-mix, filter the rubber, weigh it, and package it to obtain a high-temperature resistant silicone rubber product. Take 100 parts of the high-temperature resistant silicone rubber product, mix and disperse 1 part of 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane with a 150mm open mill to prepare a curable silicone rubber composition, and perform flat vulcanization (i.e., first-stage vulcanization) on the curable silicone rubber composition at 170°C for 10 minutes, and also perform post-vulcanization (i.e., second-stage vulcanization) at 200°C for 2 hours, and test its mechanical properties.

[0028] The rubber obtained after the second stage vulcanization was treated in a muffle furnace, and the treatment process was aging at 350° C. for 5 hours. After testing, the rubber obtained in this embodiment had a tensile strength of 3.20 MPa, an elongation at break of 240%, and a hardness of 64A after aging at 350° C. for 5 hours.

[0029] The infrared spectra of nano CeO23g, nano ZrO21g and nano TiO2 before and after modification are as follows: Figure 1-3 As shown, 3300cm -1 The absorption peak is -OH absorption peak. Figure 1-3 The disappearance of this peak indicates that the hydroxyl groups on the surface of each nanoparticle are successfully coated by the silane coupling agent.

[0030] Example 2 In this embodiment, three kinds of metal nanoparticles are mixed and modified collectively before use.

[0031] Add 30g of nano CeO2, 10g of nano ZrO2, and 25g of nano TiO2 to a 500ml beaker equipped with a magnetic stirrer, add 70ml of anhydrous ethanol and mix well to obtain a dispersion. Weigh 12.5g of silane coupling agent KH792 and put it into 20ml of anhydrous ethanol and stir it thoroughly until it is mixed well to obtain a modifier. Pour the modifier into the dispersion and mix well, add 30 ml of acetic acid, and perform ultrasound for more than 30 minutes. After ultrasound, seal the beaker with plastic wrap and place it on a magnetic stirrer and stir vigorously at room temperature overnight.

[0032] The reaction solution is placed in a centrifuge tube for centrifugation. After centrifugation, the upper layer of liquid is poured out, 5-10 ml of ethanol is added and shaken vigorously for washing, and centrifugation is repeated three times after washing to completely remove the residual acetic acid. After the last centrifugation, the upper layer of liquid is poured out, and then the solid is placed in an oven and dried at room temperature for more than 20 hours. A mixture of three kinds of dried and modified nano metal oxides is obtained, which is then crushed and sealed for later use.

[0033] 6 g of the modified mixture of nano-CeO2, nano-ZrO2 and nano-TiO2 was weighed and added to 200 g of silicone rubber base, and the rubber was prepared by the method in Example 1. After testing, the two-stage vulcanized rubber prepared in this example had a tensile strength of 3.54 MPa, an elongation at break of 245%, and a hardness of 66A after aging at 350°C for 5 hours.

[0034] Comparative Example 1 The difference between this comparative example and Example 1 is that the nanoparticles are directly added to the silicone rubber matrix without surface modification, and the rubber obtained has no mechanical strength after aging at 350°C for 5 hours. This shows that the surface modification of metal nanoparticles plays an important role in increasing the dispersibility of nanoparticles, preventing their agglomeration and increasing interfacial compatibility.

[0035] Comparative Example 2 The difference between this comparative example and Example 1 is that the surface-modified nano CeO2 particles are used alone as heat-resistant additives, and the rubber obtained has no mechanical strength after aging at 350°C for 5 hours. This shows that the type and content of surface-modified metal nanoparticles play an important role in enhancing the heat resistance of silicone rubber.

[0036] Comparative Example 3 The difference between this comparative example and Example 1 is that the surface-modified nano-TiO2 particles: nano-TiO2 particles: nano-TiO2 particles are used as heat-resistant additives in a mass ratio of 1:3:3. After aging at 350°C for 5 hours, the rubber obtained has a tensile strength of 1.28 MPa, an elongation at break of 77%, and a hardness of 75 A. This shows that the type and content of surface-modified metal nanoparticles play an important role in enhancing the heat resistance of silicone rubber.

[0037] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A heat-resistant additive for silicone rubber, characterized in that: The heat-resistant additive for silicone rubber is a mixture of nano CeO2, nano ZrO2 and nano TiO2 modified by a silane coupling agent.

2. The method for preparing the heat-resistant additive for silicone rubber according to claim 1, characterized in that: Here are the steps: (1) adding nano-metal oxide to ethanol and mixing them evenly to obtain a nano-metal oxide dispersion; adding a silane coupling agent to ethanol and mixing them evenly to obtain a modified solution; mixing the nano-metal oxide dispersion and the modified solution evenly, adding acetic acid, and then ultrasonically treating and vigorously stirring to react overnight; (2) The reaction solution is centrifuged, washed, and then dried to obtain modified nano-metal particles; (3) Adding the modified nano-metal particles into silicone rubber base to prepare silicone rubber.

3. The method for preparing the heat-resistant additive for silicone rubber according to claim 2, characterized in that: The nano metal oxide in step (1) is nano CeO2, nano ZrO2 and nano TiO2, and the silane coupling agent is any one or more of KH-550, KH-560, KH-570, KH792 and DL6021; the ultrasonic treatment time is more than 30 minutes, and the mass ratio of the nano metal oxide to the silane coupling agent is (5-8):

1.

4. The method for preparing the heat-resistant additive for silicone rubber according to claim 2, characterized in that: In step (2), the reaction solution is centrifuged and then washed with ethanol, and the centrifugal washing is repeated three times; the drying process is performed at room temperature for more than 20 hours.

5. The method for preparing the heat-resistant additive for silicone rubber according to claim 2, characterized in that: The modified nano-metal particles in step (3) are a mixture of modified nano-CeO2, nano-ZrO2 and nano-TiO2, and the mass ratio of nano-CeO2, nano-ZrO2 and nano-TiO2 is: (2-4): 1: (1.5-2.5).

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