Pre-dispersed polytetrafluoroethylene micro-powder, composite rubber material containing pre-dispersed polytetrafluoroethylene micro-powder and preparation method of composite rubber material

Abstract

The invention relates to pre-dispersed polytetrafluoroethylene micro powder, a composite rubber material containing the pre-dispersed polytetrafluoroethylene micro powder and a preparation method of the pre-dispersed polytetrafluoroethylene micro powder. The preparation method comprises the following steps: modifying dispersed polytetrafluoroethylene, mixing absolute ethyl alcohol and deionized water, adding glacial acetic acid to adjust the pH value of a mixed solution, then adding a compound silane coupling agent, stirring, and carrying out vacuum drying to obtain the pre-dispersed polytetrafluoroethylene micro powder. And finally adding polytetrafluoroethylene and white carbon black, stirring, and drying to obtain the pre-dispersed polytetrafluoroethylene micro-powder, which not only has excellent adhesive force, but also can improve the dispersion performance of polytetrafluoroethylene, and can be easily and uniformly blended with rubber, so that the service life of the polytetrafluoroethylene micro-powder is prolonged. The rubber material is applied to a composite rubber material comprising the following components: No.3 smoked sheet natural rubber, carbon black, white carbon black, a silane coupling agent Si-69, zinc oxide, stearic acid, paraffin, an anti-aging agent 4020, an anti-aging agent RD, environment-friendly aromatic oil, sulfur and an accelerant CZ, so that the rubber material not only has mechanical properties, but also greatly improves wear resistance and stability.

Description

Technical Field

[0001] The invention relates to the technical field of rubber materials, and in particular to pre-dispersed polytetrafluoroethylene micropowder, a composite rubber material containing the pre-dispersed polytetrafluoroethylene micropowder and a preparation method thereof. Background Art

[0002] The tipper is a large key equipment for loading and unloading railway wagons carrying materials. The wear plate of the tipper can effectively eliminate the rigid impact and wear between the tipper trailer plate and the side wall column of the railway wagon, and reduce the deformation and damage of the railway wagon body and the tipper itself. Therefore, the rubber material used as the wear plate of the tipper needs to have good wear resistance, tear resistance, elasticity and impact resistance to reduce the damage of railway vehicles and reduce the impact force on the tipper.

[0003] The wear resistance and strength of the wear plate for the tipping machine must meet the market demand. The wear resistance, strength and performance stability of the rubber material used for the wear plate of the tipping machine directly determine the service life of the wear plate of the tipping machine. At present, the composite rubber materials used in China generally use natural rubber and styrene-butadiene rubber or natural rubber and butadiene rubber. The filler uses high-wear-resistant carbon black to improve the wear resistance and strength, but this composite rubber material cannot take into account the wear resistance, heat generation and strength issues at the same time. For example, the blend of natural rubber and styrene-butadiene rubber has high heat generation and is prone to heat accumulation, resulting in rapid aging; the blend of natural rubber and butadiene rubber has the problem of easy falling off after aging; a large amount of high-wear-resistant carbon black filled has the disadvantages of poor carbon black dispersion and high heat generation.

[0004] Therefore, it is urgent to develop a technical solution to improve the wear performance of the wear plate of the tipping machine by developing a composite rubber material with high wear resistance, high strength and high stability. Summary of the invention

[0005] In view of the above problems, the present invention proposes a pre-dispersed polytetrafluoroethylene powder to improve the wear resistance, strength and stability of the composite rubber material, and proposes a composite rubber material containing the polytetrafluoroethylene powder.

[0006] To achieve the above purpose, the following technical scheme is adopted: a pre-dispersed polytetrafluoroethylene micropowder, characterized in that its preparation method comprises the following steps: 6) Mix silane coupling agent Si-69 and fluorosilicone coupling agent in a weight ratio of 1:1, stir evenly, and prepare a complex coupling agent; 7) Using ultrasonic waves to clean the polytetrafluoroethylene powder as the raw material, and drying it to obtain the pretreated polytetrafluoroethylene powder; 8) Mix 95 parts of anhydrous ethanol and 5 parts of deionized water according to weight ratio, add glacial acetic acid to the mixed solution, and adjust the pH value of the mixed solution to 4.0; 9) Add 3 parts of compound silane coupling agent to the mixed solution according to the weight ratio, stir for 30 minutes, weigh 25 parts of pretreated polytetrafluoroethylene powder and 5 parts of white carbon black and add them into the stirrer for secondary stirring. Control the secondary stirring temperature to 80°C and the time to 3 hours; 10) The mixed solution was placed in a vacuum drying oven, the drying temperature was controlled to be 70 °C, the drying time was 12 h, and the pre-dispersed polytetrafluoroethylene powder was obtained after drying.

[0007] The invention also provides a composite rubber material containing pre-dispersed polytetrafluoroethylene micropowder, which comprises the following components and weight proportions: 100 parts of No. 3 tobacco natural rubber, 50-60 parts of carbon black, 10-15 parts of white carbon black, 5-15 parts of pre-dispersed polytetrafluoroethylene micropowder, 1-2 parts of silane coupling agent Si-69, 5 parts of zinc oxide, 2 parts of stearic acid, 2 parts of paraffin, 2 parts of antioxidant 4020, 1 part of antioxidant RD, 5-15 parts of environmentally friendly aromatic oil, 2 parts of sulfur, and 1.5 parts of accelerator CZ.

[0008] The present invention also provides a method for preparing a composite rubber material containing pre-dispersed polytetrafluoroethylene powder, comprising the following steps: S1. According to the weight ratio of each component in the composite rubber material, the natural rubber sheet No. 3 was masticated in an internal mixer, and 0.2 parts of a peptizer was added, and the temperature of the rubber was controlled at 110-120 ° C, and the mastication was performed for 10 min; S2. The plasticized No. 3 natural rubber sheet in S1 is mixed with zinc oxide, stearic acid, paraffin, antioxidant RD, antioxidant 4020, white carbon black, carbon black, pre-dispersed polytetrafluoroethylene powder, environmentally friendly aromatic oil and silane coupling agent Si-69 according to the weight proportion of each component, and the rubber is discharged from the internal mixer and parked after reaching the temperature to obtain an initial mixed rubber; S3. Add the initial mixed rubber obtained in S2 into an internal mixer, and add sulfur and accelerator CZ according to the weight proportion of each component for mixing. After mixing, discharge the rubber to obtain the final mixed rubber.

[0009] Preferably, the mixing time in S2 is 5-6 minutes, and when the mixing temperature reaches 150-160° C., the rubber material is discharged from the internal mixer.

[0010] Preferably, when the mixing temperature in S3 reaches 90-100° C., debinding is performed.

[0011] Beneficial effects of the present invention: Since polytetrafluoroethylene molecules are completely linear, without branched structures, the CF bond energy is large and the bond distance is short, and the F atoms are densely arranged around the CC bond, the surface energy is low, the surface tension is small, and the friction coefficient is low. Therefore, polytetrafluoroethylene powder (PTFE) has excellent properties such as excellent heat resistance, weather resistance, low friction coefficient and non-stickiness, but due to its small average particle size, it has poor compatibility with rubber. The use of the pre-dispersed polytetrafluoroethylene powder proposed by the present invention can improve the dispersion performance and can be easily and evenly blended with rubber. The reason is that the CF group in the fluorine-based coupling agent is very similar to the CF group in polytetrafluoroethylene. Therefore, in the mixing process, according to the principle of similar compatibility, the use of fluorine-containing coupling agents has better compatibility with polytetrafluoroethylene molecules.

[0012] The pre-dispersed polytetrafluoroethylene micropowder proposed in the present invention has excellent adhesion because the coupling agent forms a chemical bond between polytetrafluoroethylene and white carbon black to enhance the adhesion between them, and the surface wettability of polytetrafluoroethylene is improved, which helps to wet the adhesive or the base material, thereby improving the adhesion effect.

[0013] The pre-dispersed polytetrafluoroethylene micropowder proposed in the present invention improves the dispersibility of polytetrafluoroethylene because the white carbon black treated with the coupling agent is more evenly dispersed in the polytetrafluoroethylene matrix, reducing agglomeration.

[0014] Therefore, the polytetrafluoroethylene powder proposed in the present invention is applied to the composite rubber material, which greatly improves the wear resistance and stability of the rubber while maintaining the original mechanical properties of the rubber. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the preparation process of the pre-dispersed polytetrafluoroethylene micropowder proposed in the present invention. DETAILED DESCRIPTION

[0016] The technical solution of the present invention provides a pre-dispersed polytetrafluoroethylene micropowder, and the preparation method thereof comprises the following steps: 1) Mix silane coupling agent Si-69 and fluorosilicone coupling agent in a weight ratio of 1:1, stir evenly, and prepare a complex coupling agent; 2) using ultrasonic waves to clean the polytetrafluoroethylene powder as the raw material, and drying it to obtain the pretreated polytetrafluoroethylene powder; 3) Mix 95 parts of anhydrous ethanol and 5 parts of deionized water according to weight ratio, add glacial acetic acid to the mixed solution, and adjust the pH value of the mixed solution to 4.0; 4) Add 3 parts of compound silane coupling agent to the mixed solution according to the weight ratio, stir for 30 min, weigh 25 parts of pretreated polytetrafluoroethylene powder and 5 parts of white carbon black and add them into the stirrer for secondary stirring, control the secondary stirring temperature to 80°C, and the time to 3 h; 5) The mixed solution was placed in a vacuum drying oven, the drying temperature was controlled to be 70 °C, the drying time was 12 h, and the pre-dispersed polytetrafluoroethylene powder was obtained after drying.

[0017] The pre-dispersed polytetrafluoroethylene powder is used to prepare the composite rubber material used for the wear plate of the tipping machine. The components and weight parts of the composite rubber material are as follows: No. 3 cigarette sheet natural rubber is 100 parts, carbon black is 50-60 parts, white carbon black is 10-15 parts, pre-dispersed polytetrafluoroethylene powder is 5-15 parts, silane coupling agent Si-69 is 1-2 parts, zinc oxide is 5 parts, stearic acid is 2 parts, paraffin is 2 parts, antioxidant 4020 is 2 parts, antioxidant RD is 1 part, environmentally friendly aromatic oil is 5-15 parts, sulfur is 2 parts, and accelerator CZ is 1.5 parts.

[0018] The specific preparation method is as follows: S1.3 Natural Rubber Plasticized Smoked Sheet According to the weight ratio of each component in the composite rubber material, the No. 3 tobacco sheet natural rubber is plasticized in an internal mixer, and 0.2 parts of a plasticizer is added at the same time. The rubber temperature is controlled at 110-120° C. and plasticized for 10 minutes.

[0019] S2. Mixed rubber mixing The plasticized No. 3 tobacco sheet natural rubber in S1 is added with zinc oxide, stearic acid, paraffin, antioxidant RD, antioxidant 4020, white carbon black, carbon black, pre-dispersed polytetrafluoroethylene powder, environmentally friendly aromatic oil and silane coupling agent Si-69 according to the weight proportion of each component for mixing. The mixing time is 5-6 minutes. After the temperature reaches 150-160°C, the rubber material is discharged from the internal mixer and parked to obtain an initial mixed rubber.

[0020] S3. Vulcanization of mixed rubber The initial mixed rubber prepared by S2 is added into an internal mixer, and sulfur and accelerator CZ are added according to the weight proportion of each component for mixing. After the temperature reaches 90-100°C, the rubber is discharged to prepare the final mixed rubber.

[0021] The technical solution of the present invention is further described below in conjunction with embodiments.

[0022] The following examples all adopt the pre-dispersed polytetrafluoroethylene micropowder prepared by the method for preparing pre-dispersed polytetrafluoroethylene micropowder proposed in this embodiment.

[0023] Example 1-Example 3 and Comparative Example 1 The composite rubber material used for the wear plate of a rolling machine is prepared according to the preparation method proposed in the present invention. The specific gravity of each component is as shown in Table 1.

[0024] The pre-dispersed polytetrafluoroethylene powder prepared by the method for preparing pre-dispersed polytetrafluoroethylene powder proposed in this embodiment is not added in Comparative Example 1. The tensile strength and abrasion indexes of the composite rubber materials obtained in Examples 1-3 and Comparative Example 1 are shown in Table 2.

[0025] In terms of mechanical performance, the tensile strength of the composite rubber material with pre-dispersed polytetrafluoroethylene powder added in Examples 1-3 decreased slightly, but the mechanical property retention rate was above 85%. Under normal circumstances, a mechanical property retention rate of above 90% has no significant effect on use.

[0026] In terms of wear performance, the wear index of the composite rubber material in Comparative Example 1 without adding pre-dispersed polytetrafluoroethylene powder is obviously higher.

[0027] It is explained that the composite rubber material containing the pre-dispersed polytetrafluoroethylene powder proposed by the present invention can greatly improve the wear resistance of the original rubber while maintaining its mechanical properties.

[0028] Example 4 - Example 6 In order to study the effect of the amount of pre-dispersed polytetrafluoroethylene powder on the performance of the rubber compound, the composite rubber material used for the wear plate of the rollover machine was prepared according to the preparation method proposed in the present invention. The specific gravity of each component is as shown in Table 3, wherein the data of Example 3 and Comparative Example 1 are attached as references.

[0029] Wherein, the pre-dispersed polytetrafluoroethylene powder prepared by the method for preparing pre-dispersed polytetrafluoroethylene powder proposed in this embodiment is not added in Comparative Example 1. Under the condition that the other components are the same in number, the amount of pre-dispersed polytetrafluoroethylene powder is different, and the tensile strength and abrasion index of the composite rubber material are shown in Table 4.

[0030] The effect of the pre-dispersed polytetrafluoroethylene powder on the tensile strength of the rubber material is shown in Table 4. As the amount of pre-dispersed polytetrafluoroethylene powder increases, the tensile strength of the composite rubber material shows a trend of gradually decreasing. The modified polytetrafluoroethylene powder of the present invention improves the compatibility with the composite rubber material and basically maintains the mechanical properties of the original composite rubber material. As can be seen from Table 4, after adding 12 parts of pre-dispersed polytetrafluoroethylene powder, the mechanical property retention rate is still above 90%, and after adding 15 parts of pre-dispersed polytetrafluoroethylene powder, the mechanical property retention rate is above 85%. Under normal circumstances, the mechanical property retention rate of more than 90% has no significant effect on use.

[0031] Taking Akron abrasion value as the measure of rubber wear resistance, in comparative example 1, the wear index of the composite rubber material without pre-dispersed polytetrafluoroethylene powder is obviously higher, and the wear resistance of the rubber is increased by 100% by adding 12 parts of pre-dispersed polytetrafluoroethylene powder. The improvement of the friction performance of the rubber surface and the improvement of the self-lubrication degree are beneficial to improve the wear resistance of the rubber. The effect of pre-dispersed polytetrafluoroethylene powder on the wear amount of the composite rubber material is shown in Table 4. With the increase of the amount of pre-dispersed polytetrafluoroethylene powder, the Akron wear amount first decreases and then increases. The reason is analyzed as follows: due to the good non-stickiness and low friction coefficient of pre-dispersed polytetrafluoroethylene powder, the friction coefficient of the rubber surface is greatly reduced. Because the pre-dispersed polytetrafluoroethylene powder has poor compatibility with rubber, it continuously seeps out to the surface to form a good protective layer, so the rubber can maintain good wear resistance for a long time.

[0032] From a comprehensive comparison, when the dosage of pre-dispersed polytetrafluoroethylene micropowder reaches 12phr, the product has the best tensile strength and wear resistance.

[0033] Although the embodiments of the present invention have been shown and described above, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A pre-dispersed polytetrafluoroethylene powder, characterized in that: The preparation method thereof comprises the following steps: 1) Mix silane coupling agent Si-69 and fluorosilicone coupling agent in a weight ratio of 1:1, stir evenly, and prepare a complex coupling agent; 2) using ultrasonic waves to clean the polytetrafluoroethylene powder as the raw material, and drying it to obtain the pretreated polytetrafluoroethylene powder; 3) Mix 95 parts of anhydrous ethanol and 5 parts of deionized water according to weight ratio, add glacial acetic acid to the mixed solution, and adjust the pH value of the mixed solution to 4.0; 4) Add 3 parts of compound silane coupling agent to the mixed solution according to the weight ratio, stir for 30 min, weigh 25 parts of pretreated polytetrafluoroethylene powder and 5 parts of white carbon black and add them into the stirrer for secondary stirring, control the secondary stirring temperature to 80°C, and the time to 3 h; 5) The mixed solution was placed in a vacuum drying oven, the drying temperature was controlled to be 70 °C, the drying time was 12 h, and the pre-dispersed polytetrafluoroethylene powder was obtained after drying.

2. A composite rubber material containing pre-dispersed polytetrafluoroethylene powder, characterized in that: The components and weight portions included are: 100 parts of No. 3 natural rubber, 50-60 parts of carbon black, 10-15 parts of white carbon black, 5-15 parts of pre-dispersed polytetrafluoroethylene micropowder, 1-2 parts of silane coupling agent Si-69, 5 parts of zinc oxide, 2 parts of stearic acid, 2 parts of paraffin, 2 parts of antioxidant 4020, 1 part of antioxidant RD, 5-15 parts of environmentally friendly aromatic oil, 2 parts of sulfur, and 1.5 parts of accelerator CZ.

3. The method for preparing a composite rubber material according to claim 2, characterized in that: The steps include: S1. According to the weight ratio of each component in the composite rubber material, the natural rubber sheet No. 3 was plasticized in an internal mixer, and 0.2 parts of a plasticizer was added, and the temperature of the rubber was controlled at 110-120 ° C, and plasticized for 10 min; S2. The plasticized No. 3 natural rubber sheet in S1 is mixed with zinc oxide, stearic acid, paraffin, antioxidant RD, antioxidant 4020, white carbon black, carbon black, pre-dispersed polytetrafluoroethylene powder, environmentally friendly aromatic oil and silane coupling agent Si-69 according to the weight proportion of each component, and the rubber is discharged from the internal mixer and parked after reaching the temperature to obtain an initial mixed rubber; S3. Add the initial mixed rubber obtained in S2 into an internal mixer, and add sulfur and accelerator CZ according to the weight proportion of each component for mixing. After mixing, discharge the rubber to obtain the final mixed rubber.

4. The method for preparing a composite rubber material according to claim 3, characterized in that: The mixing time in S2 is 5-6 minutes. When the mixing temperature reaches 150-160° C., the rubber material is discharged from the internal mixer.

5. The method for preparing a composite rubber material according to claim 4, characterized in that: When the mixing temperature in S3 reaches 90-100°C, debinding is performed.

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