Low Mooney viscosity regenerated rubber composite material and preparation method thereof

Abstract

The invention discloses a low-Mooney-viscosity regenerated rubber composite material and a preparation method thereof, and belongs to the technical field of rubber composite material production. The low-Mooney-viscosity regenerated rubber composite material is prepared from the following components in parts by mass: 100 parts of regenerated rubber; 5-20 parts of hollow microspheres of which the surfaces are grafted with zinc oxide; 0.2 to 1 part of stearic acid; 1 to 2.5 parts of sulfur; and 0.5 to 1.5 parts of an accelerant TBBS. According to the preparation method, ZnSO4. 7H2O is taken as a precursor, zinc oxide is generated on the surface of the hollow microsphere in situ, and the hollow microsphere with the surface grafted with zinc oxide is prepared. The low-Mooney viscosity regenerated rubber composite material prepared by using the hollow microspheres grafted with zinc oxide on the surfaces as a filler has relatively low Mooney viscosity and good vulcanization characteristics, and has a relatively good application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of rubber composite material production, and particularly relates to a low-Mooney viscosity recycled rubber composite material and a preparation method thereof. Background Art

[0002] Zinc oxide, as a commonly used vulcanization activator for rubber products, can work together with sulfur, vulcanizing agents and other additives during the vulcanization process to promote the vulcanization reaction, accelerate the cross-linking of sulfur atoms, and increase the vulcanization speed and degree of rubber.

[0003] The main method for preparing zinc oxide in large quantities in industry is the calcination method, which is to calcine zinc powder or zinc ore in air at high temperature to oxidize it to produce zinc oxide. The calcination method usually requires the use of zinc ore or zinc compounds as raw materials, and has high requirements for the purity and quality of the raw materials. If the raw materials contain impurities, it will affect the quality and performance of zinc oxide.

[0004] In addition, although zinc oxide can effectively enhance the vulcanization properties of rubber, it is an environmental pollutant, especially highly toxic to aquatic organisms, and may have long-term adverse effects on the aquatic environment.

[0005] Therefore, it is urgent to develop an environmentally friendly process to improve the vulcanization performance of recycled rubber composites and reduce the amount of zinc oxide added in the formulation of recycled rubber products to achieve sustainable development of the rubber manufacturing process. Summary of the invention

[0006] In view of the problems existing in the prior art, the object of the present invention is to provide a low Mooney viscosity recycled rubber composite material and a preparation method thereof.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A low Mooney viscosity recycled rubber composite material is prepared from the following components in parts by mass:

[0009] 100 parts of recycled rubber; 5-20 parts of hollow microspheres with zinc oxide grafted on the surface; 0.2-1 parts of stearic acid; 1-2.5 parts of sulfur; 0.5-1.5 parts of accelerator TBBS;

[0010] The hollow microspheres grafted with zinc oxide on the surface are ZnSO 4 7H 2 O was used as a precursor to generate zinc hydroxide in situ on the surface of the hollow microspheres in an alkaline environment, and hollow microspheres with zinc oxide grafted on the surface were obtained after dehydration treatment.

[0011] On the basis of the above scheme, the low Mooney viscosity recycled rubber composite material is prepared from the following components in parts by mass:

[0012] 100 parts of recycled rubber; 5 parts of hollow microspheres with zinc oxide grafted on the surface; 0.3 parts of stearic acid; 1.2 parts of sulfur; and 0.8 parts of accelerator TBBS.

[0013] On the basis of the above scheme, the hollow microspheres with surface grafted zinc oxide are prepared by the following method:

[0014] ① ZnSO 4 7H 2 O was added to deionized water to fully dissolve, and then the hollow microspheres were added and stirred at 50-65°C in a water bath for 0.5-1.5h;

[0015] ② After the stirring in step ① is completed, ammonia water is dripped into the solution until the solution becomes alkaline, and the solution is stirred at a speed of 800-1200 rpm in a water bath at 60-75°C for 2-5 hours; after the reaction is completed, the sample is filtered, and the obtained sample is alternately washed with anhydrous ethanol and deionized water, and the obtained solid is dried at 120-150°C for 8-12 hours.

[0016] The preparation method of the above-mentioned low Mooney viscosity recycled rubber composite material comprises the following steps:

[0017] (1) adding regenerated rubber and stearic acid to an internal mixer, mixing for 1-2 minutes, and then adding half of the hollow microspheres with surface grafted zinc oxide by weight; after mixing for 2 minutes, adding the remaining hollow microspheres with surface grafted zinc oxide, mixing for 1-2 minutes, and then draining the rubber;

[0018] (2) After cooling to room temperature, sulfur and accelerator TBBS are added and mixed on an open mill. After mixing evenly, the sheet is cooled;

[0019] (3) placing the rubber mixture obtained in step (2) into a flat vulcanizer for vulcanization and cooling to obtain a low Mooney viscosity recycled rubber composite material.

[0020] On the basis of the above scheme, the temperature of the internal mixer is set to 80-100°C, and the rotor speed is set to 60-70r / min.

[0021] On the basis of the above scheme, the vulcanization is carried out at a temperature of 150° C., a pressure of 10 MPa, and a time of 1.3×Tc90.

[0022] Advantages of the technical solution of the present invention

[0023] The present invention adopts zinc sulfate heptahydrate (ZnSO 4 7H 2O) is used as a precursor to in-situ generate zinc oxide on the surface of the hollow microspheres to obtain hollow microspheres with surface grafted zinc oxide. The reaction conditions are mild, the safety is high, the purity of zinc oxide is high, and the impurity content is low, which overcomes the shortcomings of the traditional calcination method.

[0024] The present invention adopts hollow microspheres with surface grafted zinc oxide as fillers, and uses a mechanical blending method to blend them with recycled rubber (RR) to prepare RR / HMS@ZnO composite materials. The research results show that the addition of hollow microspheres reduces the Mooney viscosity of recycled rubber, increases the crosslinking density of the composite material, and accelerates the vulcanization rate.

[0025] The filler used for reinforcing the recycled rubber in the present invention is hollow microspheres made from industrial byproducts, and green processing is achieved in the preparation process of the rubber product.

[0026] The present invention uses ZnSO 4 7H 2 The hollow microspheres with surface grafted zinc oxide prepared by using zinc oxide as a precursor can reduce the amount of zinc oxide added during the mixing process instead of directly adding zinc oxide as a filler to reinforce the recycled rubber.

[0027] In addition, hollow microspheres are hollow silicate materials made by sintering industrial waste such as coal gangue, diatomaceous earth, marble powder, fly ash and other materials. The hollow structure has the characteristics of light weight, low thermal conductivity, good sound insulation, good thermal stability, etc., and its main component contains a certain amount of Al 2 O 3 It has a promoting effect on vulcanization. Moreover, the hollow microspheres are spherical structures and can move inside the rubber in a similar way to a ball, which can enhance the fluidity of the rubber by reducing internal friction, reduce viscosity, and thus improve the processing performance of recycled rubber composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Surface morphology of hollow microspheres (where a is the microscopic morphology of hollow microspheres without zinc oxide grafting, and b is the microscopic morphology of hollow microspheres with zinc oxide grafted on the surface);

[0029] Figure 2 Change in Mooney viscosity of low Mooney viscosity recycled rubber composites over 20 days. DETAILED DESCRIPTION

[0030] The terms used in the present invention, unless otherwise specified, generally have the meanings commonly understood by those of ordinary skill in the art. The present invention will be further described in detail below in conjunction with specific examples and with reference to data. The following examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention in any way.

[0031] The experimental methods in the following examples, unless otherwise specified, are all conventional methods, and are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The experimental materials, reagents, drugs, etc. used in the following examples, unless otherwise specified, can all be purchased through general channels.

[0032] Principle of the technical solution of the present invention:

[0033] ZnSO 4 7H 2 O as a precursor to graft zinc oxide on the surface of hollow microspheres: ZnSO 4 7H 2 O can provide Zn 2+ In an alkaline environment, zinc hydroxide will be generated on the surface of the hollow microspheres, and zinc oxide will be grafted on the surface of the hollow microspheres after dehydration treatment.

[0034] In the following embodiments:

[0035] Recycled rubber refers to waste vulcanized rubber that has undergone physical and chemical processes such as crushing, heating, mechanical and chemical treatment, so that it changes from an elastic state to a rubber with a certain plasticity and viscosity that can be processed and re-vulcanized.

[0036] Hollow microspheres are hollow structure products made of silicate (surface morphology such as Figure 1 The main components include calcium oxide and silicon dioxide, and the main components are shown in Table 1:

[0037] Table 1 Main components of hollow microspheres

[0038]

[0039]

[0040] The hollow microspheres used in the following examples have a diameter of 10-90 μm and are provided by the School of Materials Science and Engineering of Tsinghua University (State Key Laboratory of New Ceramics and Fine Technology).

[0041] Example 1

[0042] A low Mooney viscosity recycled rubber composite material is prepared from the following components in parts by mass:

[0043] 100 parts of recycled rubber; 5 parts of hollow microspheres with zinc oxide grafted on the surface; 0.3 parts of stearic acid; 1.2 parts of sulfur; and 0.8 parts of accelerator TBBS.

[0044] The preparation method is as follows:

[0045] (1) Add regenerated rubber and stearic acid into an internal mixer, set the rotor speed at 70 r / min at 90° C., mix for 1 min, and then add half of the hollow microspheres grafted with zinc oxide on the surface by weight; after mixing for 2 min, add the remaining hollow microspheres grafted with zinc oxide on the surface, mix for 2 min, and then discharge the rubber.

[0046] (2) After cooling to room temperature, sulfur and accelerator TBBS are added and mixed on an open mill. After mixing evenly, the sheet is cooled.

[0047] (3) placing the rubber mixture obtained in step (2) into a flat vulcanizer, setting the temperature to 150° C., the pressure to 10 MPa, and the vulcanization time to 1.3×Tc90, and cooling at room temperature for 8-10 hours after the vulcanization is completed to obtain a low Mooney viscosity recycled rubber composite material.

[0048] The hollow microspheres with zinc oxide grafted on the surface are prepared by the following method:

[0049] ① Weigh 21.8g of ZnSO 4 7H 2 O was added into 200 mL of deionized water to fully dissolve, and then 6.17 g of hollow microspheres were added into the above solution, and stirred at 600 rpm in a water bath at 60 °C for 1 h.

[0050] ② After the stirring of step ① is completed, 25% ammonia water is dripped into the solution until the solution becomes obviously alkaline, so that all the zinc ions in the solution are precipitated (in order to avoid incomplete reaction, 20 mL of 25% ammonia water can be added for every 30 g of zinc sulfate heptahydrate for reaction), and the solution is stirred at 800 rpm for 2 hours in a 70°C water bath. After the reaction is completed, the solution is filtered, and the obtained sample is alternately washed with anhydrous ethanol and deionized water. The obtained solid is placed in a 130°C forced air drying oven and dried for 12 hours to obtain hollow microspheres with surface grafted zinc oxide, recorded as HMS@ZnO, with a surface morphology as shown in FIG. Figure 1 As shown in b.

[0051] Comparative Example

[0052] A recycled rubber composite material is prepared from the following components in parts by mass:

[0053] 100 parts of recycled rubber; 5 parts of zinc oxide; 0.3 parts of stearic acid; 1.2 parts of sulfur; 0.8 parts of accelerator TBBS.

[0054] The preparation method is as follows:

[0055] First, reclaimed rubber, zinc oxide, and stearic acid were added to an internal mixer and mixed for 5 minutes before rubber removal. After the rubber was cooled to room temperature, sulfur and accelerator TBBS were added and mixed on an open mixer. After mixing evenly, the sheet was cooled. The remaining steps were the same as in Example 1. The reclaimed rubber composite material was obtained.

[0056] Vulcanization performance test

[0057] The torque, scorch time, positive vulcanization time and vulcanization rate of the recycled rubber composite material prepared by the method described in Example 1 and the comparative example were measured using a rotorless vulcanizer. The results are shown in Table 2.

[0058] Table 2 Performance test of recycled rubber composite materials

[0059]

[0060] A small amount of hollow microspheres can achieve good dispersion in the regenerated rubber, which can improve the interaction with the rubber molecular chain, thereby increasing the vulcanization rate of the composite material. As shown in Table 2, compared with the regenerated rubber of the comparative example (no hollow microspheres are added, zinc oxide is directly added), the vulcanization time (Tc90) of the regenerated rubber composite material (Example 1) reinforced with hollow microspheres grafted with zinc oxide gradually decreases. This shows that the production efficiency of the composite material has been improved. This is attributed to the metal oxide Al contained in the composition of the hollow microspheres. 2 O 3 , which can be used as an accelerator to accelerate the vulcanization of rubber. The scorch time (Tc10) of the composite material did not change significantly. This result shows that the scorch time can remain stable even when hollow microspheres are added, indicating that the processing safety of the composite material is basically the same.

[0061] Mooney performance test

[0062] The recycled rubber composite materials prepared by the methods described in Example 1 and the comparative example were tested using a Mooney rheometer to determine their Mooney viscosity values. The flow characteristics of the material during processing can be reflected by analyzing the Mooney viscosity value.

[0063] The results are as follows Figure 2 As shown, the change in Mooney viscosity of the recycled rubber composites can be observed. Figure 2First, it can be seen that the recycled rubber composite material has a relatively strong Mooney rebound phenomenon (the phenomenon that the Mooney viscosity value gradually increases over time), and the initial Mooney viscosity value of the recycled rubber composite material reinforced by adding hollow microspheres grafted with zinc oxide (Example 1) decreased by 12.9%, which shows that the rubber can flow more easily under the same shear force. This is because the hollow microspheres are hollow spherical powder materials, which can move in a ball-like manner in the rubber matrix under stress, reduce internal friction, thereby enhancing the fluidity of the rubber and reducing the Mooney viscosity.

[0064] Effect of HMS@ZnO addition on mechanical properties of recycled rubber

[0065] Based on the formula and preparation method of Example 1, the effect of the addition amount of HMS@ZnO (0-20phr) on the mechanical properties of recycled rubber was investigated.

[0066] In the preparation of 5 phr ZnO@HMS, the mass ratio of zinc sulfate heptahydrate to hollow microspheres was 21.8:6.17;

[0067] In the preparation of 10 phr ZnO@HMS, the mass ratio of zinc sulfate heptahydrate to hollow microspheres was 20.88:17.68;

[0068] In the preparation of 15 phr ZnO@HMS, the mass ratio of zinc sulfate heptahydrate to hollow microspheres was 19.96:28.18;

[0069] In the preparation of 20 phr ZnO@HMS, the mass ratio of zinc sulfate heptahydrate to hollow microspheres was 19.14:37.8.

[0070] The preparation method of ZnO@HMS is the same as that in Example 1.

[0071] Recycled rubber composites were prepared by adding different amounts of HMS@ZnO, and their mechanical properties were tested. The results are shown in Table 3.

[0072] Table 3 Mechanical properties of recycled rubber with different amounts of HMS@ZnO added

[0073]

[0074] As shown in Table 3, with the increase of HMS@ZnO dosage, the mechanical properties of recycled rubber composites show a downward trend. This is because hollow microspheres (HMS) are hollow silicate materials made by sintering industrial waste such as coal gangue, diatomaceous earth, marble powder, fly ash, etc., and the composition is a variety of inorganic oxides, which have poor interface bonding with rubber. When the dosage of hollow microspheres is 5 parts, the recycled rubber composite still has a good mechanical property retention rate.

[0075] The above 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 above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A low Mooney viscosity recycled rubber composite material, characterized in that: It is prepared by the following components in parts by mass: 100 parts of recycled rubber; 5-20 parts of hollow microspheres with zinc oxide grafted on the surface; 0.2-1 parts of stearic acid; 1-2.5 parts of sulfur; Accelerator TBBS 0.5-1.5 parts; The hollow microspheres with surface grafted zinc oxide use ZnSO4·7H2O as a precursor, generate zinc hydroxide in situ on the surface of the hollow microspheres in an alkaline environment, and obtain the hollow microspheres with surface grafted zinc oxide after dehydration treatment.

2. The low Mooney viscosity recycled rubber composite material according to claim 1, characterized in that: It is prepared by the following components in parts by mass: 100 parts of recycled rubber; 5 parts of hollow microspheres with zinc oxide grafted on the surface; 0.3 parts of stearic acid; 1.2 parts of sulfur; Accelerator TBBS 0.8 parts.

3. The low Mooney viscosity recycled rubber composite material according to claim 1, characterized in that: The hollow microspheres with zinc oxide grafted on the surface are prepared by the following method: ① Add ZnSO4·7H2O to deionized water and fully dissolve it, then add hollow microspheres, and stir at 400-600 rpm in a water bath at 50-65℃ for 0.5-1.5h; ② After the stirring in step ① is completed, ammonia water is dripped into the solution until the solution becomes alkaline, and the solution is stirred at a speed of 800-1200 rpm in a water bath at 60-75°C for 2-5 hours; after the reaction is completed, the sample is filtered, and the obtained sample is alternately washed with anhydrous ethanol and deionized water, and the obtained solid is dried at 120-150°C for 8-12 hours.

4. The method for preparing the low Mooney viscosity recycled rubber composite material according to any one of claims 1 to 3, characterized in that: Here are the steps: (1) adding regenerated rubber and stearic acid to an internal mixer, mixing for 1-2 minutes, and then adding half of the hollow microspheres with surface grafted zinc oxide by weight; after mixing for 2 minutes, adding the remaining hollow microspheres with surface grafted zinc oxide, mixing for 1-2 minutes, and then draining the rubber; (2) After cooling to room temperature, sulfur and accelerator TBBS are added and mixed on an open mill. After mixing evenly, the sheet is cooled; (3) placing the rubber mixture obtained in step (2) into a flat vulcanizer for vulcanization and cooling to obtain a low Mooney viscosity recycled rubber composite material.

5. The method for preparing the low Mooney viscosity recycled rubber composite material according to claim 4, characterized in that: The temperature of the internal mixer is set at 80-100° C., and the rotor speed is set at 60-70 r / min.

6. The method for preparing the low Mooney viscosity recycled rubber composite material according to claim 4, characterized in that: The vulcanization is performed at a temperature of 150° C., a pressure of 10 MPa, and a time of 1.3×Tc90.

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