Preparation method of natural rubber composite material based on recycling of modified waste rubber powder

Abstract

The invention provides a preparation method of a natural rubber composite material based on modified waste rubber powder recycling, and belongs to the technical field of waste rubber powder recycling and rubber mixing. The method comprises the following three main steps: firstly, preparing a deep eutectic solvent, mixing quaternary ammonium salt and a hydrogen bond donor, and stirring to obtain a uniform liquid; secondly, preparing modified waste rubber powder, mixing the waste rubber powder with a deep eutectic solvent, then carrying out ball milling treatment, destroying sulfur cross-linking bonds, and promoting the reaction of the deep eutectic solvent and the rubber powder; and finally, preparing the natural rubber composite material, namely mixing natural rubber, small materials, carbon black and the modified waste rubber powder in an internal mixer to obtain a final product. According to the method, energy consumption and pollutant emission are reduced, the production cost is reduced, and the application field of the rubber composite material is widened. By using the modified waste rubber powder, the mechanical property and the dynamic mechanical property of the composite material are close to or reach the level of an industrial carbon black / natural rubber composite material, and the composite material has remarkable environmental protection and economic benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of rubber mixing by recycling waste rubber powder, and in particular relates to a method for preparing a natural rubber composite material based on recycling modified waste rubber powder. Background Art

[0003] Waste rubber is processed through selection, cleaning, removal, cutting, etc. At present, waste rubber powder is produced by three main methods: normal temperature crushing method, low temperature crushing method and wet method.

[0004] Waste tires can only be recycled after relevant selection, cleaning, removal, cutting, crushing and other processing. Untreated waste rubber powder has a dense three-dimensional cross-linked network structure, inert surface properties, and low chemical reactivity. The surface properties of waste rubber powder are poorly compatible with polymers. If waste rubber powder is directly added to rubber materials, it is difficult for the two to form a good bonding interface, and as the amount of waste rubber powder added increases, the performance of the waste rubber powder / natural rubber composite material will gradually decrease. Therefore, in order to improve the recycling of rubber powder in rubber materials, it is necessary to modify and desulfurize the waste rubber powder to enhance its activity and compatibility.

[0005] Based on this, how to effectively desulfurize and modify waste rubber powder so that the performance of the rubber material prepared using it as raw material is improved is an important issue that needs to be solved in this field. Summary of the invention

[0006] In order to solve the problems existing in the background technology, the present invention provides a method for preparing a natural rubber composite material based on the recycling of modified waste rubber powder, which comprises the following steps:

[0007] S1: Preparation of deep eutectic solvent: mixing quaternary ammonium salt and hydrogen bond donor, sealing and stirring until a uniform liquid is obtained, and cooling at room temperature to obtain a deep eutectic solvent;

[0008] S2: preparing modified waste rubber powder: mixing the waste rubber powder with a deep eutectic solvent, and subjecting the mixture to a planetary ball milling treatment to destroy the sulfur cross-linking bond and promote the initial reaction between the deep eutectic solvent and the rubber powder, followed by oven drying for later use;

[0009] S3: Preparation of natural rubber composite materials: natural rubber, small materials, carbon black and modified waste rubber powder are added to an internal mixer in sequence, and mixed to obtain a mixed rubber; after treatment in an open mixer and vulcanization, a natural rubber composite material is finally obtained.

[0010] In the preferred embodiment, the specific process of S1 is: weigh a certain molar ratio of quaternary ammonium salt and hydrogen bond donor, mix them and place them in a beaker and seal them; place the beaker in a constant temperature magnetic stirrer, heat and stir until the mixture becomes a stable and uniform liquid; then, cool the mixture at room temperature to obtain the desired deep eutectic solvent.

[0011] In a preferred embodiment, the molar ratio of the quaternary ammonium salt to the hydrogen bond donor is 1:1 to 1:4.

[0012] In a preferred embodiment, the quaternary ammonium salt is at least one of choline chloride, tetrabutylammonium bromide and ethyltrimethylammonium chloride.

[0013] In a preferred embodiment, the hydrogen bond donor is at least one of lactic acid, tartaric acid, acrylic acid, acetic acid, oxalic acid, maleic acid, formamide, propionamide, glycerol, propylene glycol, and the like.

[0014] In a preferred embodiment, the rubber powder comes from waste tires, EPDM rubber, sealing rings, etc.

[0015] In a preferred solution, the specific process of step S2 includes:

[0016] Weigh 50 parts of waste rubber powder and 3-5 parts of deep eutectic solvent, mix the two and pour them into the ball mill of a planetary ball mill for ball milling. The rubber powder particles collide and shear with the zirconium oxide balls through high-speed rotation to destroy the sulfur cross-linking bonds in the rubber powder. The deep eutectic solvent is evenly distributed during the ball milling process and reacts preliminarily with the rubber powder. After the ball milling is completed, put the mixture into an oven and dry it at 90°C for 1-1.5 hours for use;

[0017] In a preferred embodiment, in step S2, the ball milling time is 1 hour.

[0018] In a preferred solution, the specific process of step S3 includes:

[0019] S31, adjusting the temperature of the internal mixer to 100°C and the speed to 90r / min;

[0020] S32, add 70 parts of natural rubber into the internal mixer, mix for 1 minute 20 seconds, then add small material, 30 parts of carbon black and 50 parts of modified waste rubber powder;

[0021] S33, continue mixing until the total time is 6 minutes and 30 seconds to obtain a mixed rubber;

[0022] S34, placing the mixed rubber and the vulcanization system mixture in an open mill after the roller distance is adjusted to a wrapping roller, the vulcanization system mixture including the accelerator DM and sulfur; performing triangle wrapping and rolling operations three times each, and then pressing into a sheet with a set thickness;

[0023] S35, after standing for 12 hours at room temperature, the mixed rubber is placed on a flat vulcanizer for vulcanization; the vulcanization temperature is 150°C, the pressure is 10MPa, and the vulcanization time is t 90 The t90 represents the time required for the rubber to reach the positive vulcanization state, that is, the time corresponding to when the torque in the vulcanization curve reaches 90% of the maximum torque.

[0024] In a preferred embodiment, the small material includes stearic acid and zinc oxide.

[0025] The beneficial effects achieved by the present invention are:

[0026] The invention significantly improves the recycling rate of waste rubber powder in rubber materials, effectively reduces the accumulation of rubber waste such as waste tires, and has a positive contribution to environmental protection. The modified waste rubber powder can be used as a filler for natural rubber composite materials.

[0027] Substituting part of carbon black reduces the dependence on new resources. At the same time, the mechanical properties and dynamic mechanical properties of the modified waste rubber powder / natural rubber composite material are significantly improved, approaching or even reaching the level of industrial carbon black / natural rubber composite materials, thanks to the improvement of the surface activity and dispersibility of the modified waste rubber powder, and the enhanced compatibility with natural rubber. In addition, the modifier deep eutectic solvent not only acts as a surfactant and modifier during the preparation process, but also promotes the vulcanization reaction and improves the vulcanization efficiency. Compared with the traditional method, the method of the present invention is more environmentally friendly, reduces energy consumption and pollutant emissions, and reduces greenhouse gas emissions and land occupation by avoiding the landfill and incineration of rubber waste such as waste tires. At the same time, the modified waste rubber powder as a filler reduces the production cost of natural rubber composite materials. The waste rubber powder is widely available and inexpensive, replacing part of expensive raw materials such as carbon black. The modified waste rubber powder / natural rubber composite material also has good performance, broadens its application field, is not limited to traditional tire manufacturing, but can also be used in the production of rubber products such as automotive seals, conveyor belts, and hoses. The preparation method of the present invention has simple process, convenient operation and high efficiency. The modification treatment of waste rubber powder can be completed by simple equipment such as a planetary ball mill and an oven, which is time-saving and efficient. Therefore, the method has strong scalability and is suitable for rubber product manufacturers of different sizes, providing an effective way to realize the recycling of waste rubber powder and improve the performance of rubber composite materials.

[0028] The present invention uses a planetary ball mill to dry grind waste rubber powder and deep eutectic solvent. During grinding, on the one hand, the principle of ball milling desulfurization of rubber powder is mainly to make the rubber powder particles strongly collide and shear with the zirconium oxide balls in the ball mill through the high-speed rotation of the ball mill, thereby destroying the sulfur cross-linking bonds in the rubber powder, reducing its degree of vulcanization, and improving the activity and reactivity of the rubber powder; on the other hand, the deep eutectic solvent is more evenly distributed in the unmodified waste rubber powder, so that the unmodified waste rubber powder can contact with the deep eutectic solvent, thereby obtaining a better modification effect, and also promoting vulcanization and other reactions for the deep eutectic solvent. Then, the treated waste rubber powder is placed in 90°C for 1-1.5 hours. Under the action of temperature, the rubber powder absorbs moisture and dries, and further reacts with the rubber powder and the deep eutectic solvent under the action of temperature, thereby strengthening the modification effect of the rubber powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the present invention. In addition, the forms of the various structures recorded in the following embodiments are merely illustrative, and the present invention is not limited to the various structures recorded in the following embodiments. All other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0031] The invention provides a method of using a modifier deep eutectic solvent as a surfactant and a modifier, which not only promotes the vulcanization reaction but also increases the activity of the rubber powder and the compatibility of the rubber during the process.

[0032] The present invention relates to a method for preparing a natural rubber composite material by recycling modified waste rubber powder. The process comprises three steps of preparing modified waste rubber powder, preparing waste rubber powder and a natural rubber composite material:

[0033] S1, preparation of deep eutectic solvent: weigh a certain molar ratio of quaternary ammonium salt and hydrogen bond donor and place them in a beaker, the molar ratio of quaternary ammonium salt to hydrogen bond donor is preferably 1:1 to 1:4. Use plastic wrap to seal the beaker; place the flask containing the mixture in a constant temperature magnetic stirrer, and heat and stir the mixture; after the mixture reacts to become a stable and uniform liquid, cool it at room temperature to obtain the desired deep eutectic solvent.

[0034] S2, preparation of modified waste rubber powder: weigh 50g of waste rubber powder and 3-5g of deep eutectic solvent. Pour it into the ball mill of a planetary ball mill for ball milling for 1h. After the ball milling is completed, put it into an oven and bake it at 90℃ for 1-1.5h for later use.

[0035] S3, preparation of natural rubber composite materials: adjust the temperature of the internal mixer to 100°C, the speed to 90r / min, add 70g of natural rubber to the internal mixer, drop the top bolt and internally mix for 1min20s, then add small materials and 30g of carbon black and 50g of modified waste rubber powder, the total internal mixing time is 6min30s, and obtain the mixed rubber. Then place the mixed rubber and the vulcanization system in an open mixer with the roller spacing adjusted to the wrapping roller, make a triangle bag and roll it three times each, press it into a set thickness, and let it stand at room temperature for 12h. The obtained mixed rubber is placed on a flat vulcanizer for vulcanization. The vulcanization temperature is 150°C, the pressure is 10MPa, and the vulcanization time is t 90 , that is, the activated waste rubber powder / carbon black / natural rubber composite material of the present invention is obtained.

[0036] The filler involved in the invention comprises industrial carbon black N234 and waste rubber powder; the small material comprises stearic acid and zinc oxide; and the vulcanization system comprises accelerator DM and sulfur.

[0037] The present invention will be further described below by way of embodiments in conjunction with the accompanying drawings.

[0038] Embodiment 1:

[0039] The specific process of the present embodiment involving a preparation method for recycling modified waste rubber powder is as follows:

[0040] (1) Preparation of deep eutectic solvent: Weigh a quaternary ammonium salt and a hydrogen bond donor in a molar ratio of 1:3 and place them in a beaker, and seal the beaker with plastic wrap; place the flask containing the mixture in a constant temperature magnetic stirrer, and heat and stir the mixture; after the mixture reacts to become a stable and uniform liquid, cool it to room temperature to obtain the desired deep eutectic solvent.

[0041] (2) Preparation of modified waste rubber powder: Weigh 50g of waste rubber powder and 3g of deep eutectic solvent. Pour it into the ball mill of a planetary ball mill for ball milling for 1h. After the ball milling, put it into an oven and bake it at 90℃ for 1-1.5h for later use.

[0042] (2) Preparation of waste rubber powder / carbon black / natural rubber composite materials: adjust the temperature of the internal mixer to 100°C and the speed to 90r / min, add 70g of natural rubber to the internal mixer, drop the top bolt and internally mix for 1min20s, then add small materials and 30g of carbon black and 50g of modified waste rubber powder. The total internal mixing time is 6min30s to obtain a rubber mixture. Then place the rubber mixture and the vulcanization system in an open mixer with the roller spacing adjusted to the wrap roller. After triangle wrapping and rolling three times each, press the sheet into a set thickness and let it stand at room temperature for 12h. Place the obtained rubber mixture on a flat vulcanizer for vulcanization. The vulcanization temperature is 150°C, the pressure is 10MPa, and the vulcanization time is t 90, that is, the activated waste rubber powder / carbon black / natural rubber composite material sample of the present invention is obtained.

[0043] Embodiment 2:

[0044] The specific process of the method for preparing a composite material of activated waste rubber powder to replace natural rubber and carbon black is the same as that of Example 1, except that 5 g of deep eutectic solvent is added to the modified waste rubber powder in this example.

[0045] Comparative Example 1:

[0046] The specific process of the preparation method of carbon black / natural rubber composite materials involved in this comparative example is different from that of the embodiment in that this comparative example uses industrial carbon black N234, the carbon black is not processed, and dry mixing technology is used. The specific process is as follows: adjust the temperature of the internal mixer to 100°C, the speed to 90r / min, add 100g of natural rubber to the internal mixer, drop the top bolt and internally mix for 1min20s, then add carbon black and small materials, the total internal mixing time is 6min30s, and a rubber mix is ​​obtained. Then the rubber mix and the vulcanization system are placed in an open mill with the roller spacing adjusted to the wrapping roller. After triangle wrapping and rolling three times each, the sheet is pressed into a set thickness and left to stand at room temperature for 12h. The obtained rubber mix is ​​placed on a flat vulcanizer for vulcanization. The vulcanization temperature is 150°C, the pressure is 10MPa, and the vulcanization time is t 90 , that is, the carbon black / natural rubber composite material sample is obtained.

[0047] Comparative Example 2:

[0048] The specific process of the preparation method of the pyrolysis carbon black / natural rubber composite material in this comparative example is the same as that of Example 1, except that only rubber powder is used in the ball milling process in this comparative example. The specific process is as follows: 50g of waste rubber powder is weighed and poured into the ball milling tank of a planetary ball mill for ball milling for 1 hour. After the ball milling is completed, it is placed in an oven and dried at 90°C for 1-1.5 hours for use.

[0049] Performance Test:

[0050] The obtained comparative example 1, comparative example 2, embodiment 1 and embodiment 2 were subjected to various performance tests, and the results are shown in the following table:

[0051] Table 1, Performance Test of Examples 1-2 and Comparative Examples 1-2

[0052]

[0053] From Table 1, we can see that:

[0054] The comprehensive performance of the composite material replaced by the rubber powder in Comparative Example 2 is significantly different from that of the N234 composite material in Comparative Example 1. H -M L (Cross-linking density) was reduced by 38.7%, hardness was reduced by 7.73%, 300% tensile stress was reduced by 19.1%, and wear resistance in dynamic force performance was improved by 21.4%, so it is very important to modify the rubber powder.

[0055] The comprehensive performance of the composite materials of Examples 1 and 2 is improved compared with that of the composite material of Comparative Example 2, indicating that the ball milling activation treatment of the deep eutectic solvent makes the rubber powder surface active and has good dispersibility, and the ball milling improves the contact between the rubber powder and the deep eutectic solvent.

[0056] The comprehensive performance of the composite materials of Examples 1 and 2 is close to that of the composite materials of Comparative Example 1, which proves the correctness of using deep eutectic solvent ball-milled rubber powder to replace carbon black and natural rubber.

[0057] The comprehensive performance of the composite material of Example 2 is similar to that of the composite material of Example 1, which indicates that as the fraction of deep eutectic solvent increases, the modification effect on the rubber powder is not greatly improved, and the 60°C tanδ increases with the increase in fraction.

[0058] Compared with the composite material of Comparative Example 1, some properties of the composite materials of Examples 1 and 2 are very close to the properties of the industrial carbon black N234 / natural rubber composite material, which proves the correctness of the treatment of rubber powder and compounding to replace natural rubber and the carbon black preparation process.

[0059] Compared with comparative example 1, the heat generation in the dynamic force performance of Example 1 is reduced by 11.11%, and other properties are close to those of the industrial carbon black N234 / natural rubber composite material, which proves the reliability of the preparation method for recycling modified waste rubber powder involved in the present invention.

[0060] On the one hand, the present invention solves the problem that the use of waste rubber powder after modification in the prior art is mainly for construction and roads, while the use of rubber composite materials is less, thereby realizing the effective utilization of waste rubber powder. It provides a new direction for the recycling of waste rubber and reduces the pollution caused by waste rubber. On the other hand, by replacing carbon black and natural rubber, the use of carbon black and rubber is reduced, further shortening the performance gap with industrial carbon black and natural rubber composite materials.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a natural rubber composite material based on the recycling of modified waste rubber powder, characterized in that: It includes the following steps: S1: Preparation of deep eutectic solvent: mixing quaternary ammonium salt and hydrogen bond donor, sealing, heating and stirring until a uniform liquid is obtained, and cooling to room temperature to obtain a deep eutectic solvent; S2: preparing modified waste rubber powder: mixing the waste rubber powder with a deep eutectic solvent, and subjecting the mixture to a planetary ball milling treatment to destroy the sulfur cross-linking bond and promote the initial reaction between the deep eutectic solvent and the rubber powder, followed by oven drying for later use; S3: Preparation of natural rubber composite materials: natural rubber, small materials, carbon black and modified waste rubber powder are added to an internal mixer in sequence, and mixed to obtain a mixed rubber; after treatment in an open mixer and vulcanization, a natural rubber composite material is finally obtained.

2. The method for preparing a natural rubber composite material based on the recycling of modified waste rubber powder as claimed in claim 1, characterized in that: The specific process of S1 is: weigh a certain molar ratio of quaternary ammonium salt and hydrogen bond donor, mix them and place them in a beaker and seal them; place the beaker in a constant temperature magnetic stirrer, heat and stir until the mixture becomes a stable and uniform liquid; then, cool the mixture at room temperature to obtain the desired deep eutectic solvent.

3. The method for preparing a natural rubber composite material based on the recycling of modified waste rubber powder as claimed in claim 2, characterized in that: The molar ratio of the quaternary ammonium salt to the hydrogen bond donor is 1:1 to 1:

4.

4. The method for preparing a natural rubber composite material based on the recycling of modified waste rubber powder as claimed in claim 2, characterized in that: The quaternary ammonium salt is at least one of choline chloride, tetrabutylammonium bromide and ethyltrimethylammonium chloride.

5. The method for preparing a natural rubber composite material based on the recycling of modified waste rubber powder as claimed in claim 2, characterized in that: The hydrogen bond donor is at least one of lactic acid, tartaric acid, acrylic acid, acetic acid, oxalic acid, maleic acid, formamide, propionamide, glycerol, propylene glycol, and the like.

6. The method for preparing a natural rubber composite material based on the recycling of modified waste rubber powder as claimed in claim 2, characterized in that: The rubber powder comes from waste tires or EPDM rubber or sealing rings, etc.

7. The method for preparing a natural rubber composite material based on the recycling of modified waste rubber powder according to claim 1, characterized in that: The specific process of step S2 includes: Weigh 50 parts of waste rubber powder and 3-5 parts of deep eutectic solvent, mix the two and pour them into the ball mill of a planetary ball mill for ball milling. The high-speed rotation makes the rubber powder particles collide and shear with the zirconium oxide balls to destroy the sulfur cross-linking bonds in the rubber powder. The deep eutectic solvent is evenly distributed during the ball milling process and reacts preliminarily with the rubber powder. After the ball milling is completed, put the mixture into an oven and dry it at 90°C for 1-1.5 hours for use.

8. The method for preparing a natural rubber composite material based on the recycling of modified waste rubber powder according to claim 7, characterized in that: In step S2, the ball milling time is 1 h.

9. The method for preparing a natural rubber composite material based on the recycling of modified waste rubber powder according to claim 1, characterized in that: The specific process of step S3 includes: S31, adjusting the temperature of the internal mixer to 100°C and the speed to 90r / min; S32, add 70 parts of natural rubber into the internal mixer, mix for 1 minute 20 seconds, then add small material, 30 parts of carbon black and 50 parts of modified waste rubber powder; S33, continue mixing until the total time is 6 minutes and 30 seconds to obtain a mixed rubber; S34, placing the mixed rubber and the vulcanization system mixture in an open mill after the roller distance is adjusted to a wrapping roller, the vulcanization system mixture including the accelerator DM and sulfur; performing triangle wrapping and rolling operations three times each, and then pressing into a sheet with a set thickness; S35, after standing for 12 hours at room temperature, the mixed rubber is placed on a flat vulcanizer for vulcanization; the vulcanization temperature is 150°C, the pressure is 10MPa, and the vulcanization time is t 90 The process is carried out to finally obtain a natural rubber composite material; the t90 represents the time required for the rubber to reach a positive vulcanization state, that is, the time corresponding to when the torque in the vulcanization curve reaches 90% of the maximum torque.

10. The method for preparing a natural rubber composite material based on the recycling of modified waste rubber powder according to claim 9, characterized in that: Small ingredients include stearic acid and zinc oxide.

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