Continuous superfine rubber powder preparation method based on grinding and crushing of frozen-pressed preform

Abstract

The invention discloses a continuous superfine rubber powder preparation method based on grinding and crushing of a frozen-pressed preform, and belongs to the field of elastomer crushing. The method comprises the following steps: pre-cooling crushed rubber particles, freezing a water-based raw material, crushing the water-based raw material into frozen water particles, mixing the frozen water particles with the rubber particles in proportion, carrying out pressure forming to obtain a mixed solid bar, continuously grinding the bar to obtain liquid rubber cement containing superfine rubber powder, and finally dehydrating and drying to obtain a finished product. The core of the method is that continuous production under the shallow cooling condition is achieved through the freezing-pressing process of the mixed solid bars. Freezing water particles absorb friction heat through phase change in the grinding process, and high-temperature coking of rubber is effectively avoided. The mixing and pressing process enhances the internal uniformity of the bar, solves the problems of particle deposition, gas gaps and splashing in a traditional freezing method, and remarkably reduces energy consumption. The obtained rubber powder is uniform in particle size and stable in performance, and has the advantages of low production cost, high process continuity, controllable finished product quality and the like.

Description

Technical Field

[0001] The invention relates to a method for preparing continuous ultra-fine rubber powder based on grinding and pulverizing a freeze-pressed preform, and belongs to the field of elastomer pulverization. Background Art

[0002] As the number of motor vehicles in the world continues to rise, the amount of scrap tires being replaced has increased dramatically. One of the important means of resource utilization of these scrap tires is to crush them into rubber powder and then use them to fill similar rubber products. In order to obtain good performance after rubber powder filling, a finer rubber powder is generally required, which is called ultra-fine rubber powder in the industry. Since scrap tires are elastomers with excellent mechanical properties, conventional crushing technology will inevitably generate a lot of heat during the process, which can easily cause the raw rubber to coke and deteriorate. Therefore, liquid nitrogen, dry ice or gas expansion are currently used to deep-freeze the raw rubber, so that it reaches or approaches the brittle temperature of the colloid during the crushing process, and then it is finely crushed by high-speed hammering and other methods. The above technology is generally referred to as the freezing method in the industry. The freezing process of this method consumes a lot of energy and has high production costs.

[0003] National invention patent CN202211113697.4 discloses a method for preparing waste rubber powder. The method involves putting a working fluid and raw rubber particles into the hopper of a single-screw conveyor. Under the rotating conveyor of the screw, the raw rubber particles and the working fluid enter a freezing tube and are fully frozen into ice to form a raw material core rod for subsequent grinding. Under the thrust of the rotating conveying screw, the raw material core rod contacts the rotating grinding wheel in the grinding chamber with a certain pressure. Under the grinding action, the mixture of rubber particles and ice is ground into a rubber powder slurry. However, this method requires continuous cooling in the freezing tube, and the energy consumption is still high. In addition, during the formation of the raw material core rod in the barrel, the density of the rubber particles is greater than the liquid working medium, so that a large number of rubber particles are deposited in the lower layer of the raw material core rod. The ice has poor wrapping of the rubber particles. The direction of the raw material core rod is frozen layer by layer from the outside to the inside, resulting in the outermost layer of the raw material core rod and the inner wall of the barrel being firmly frozen, and the friction resistance with the inner wall of the barrel is increased. In addition, due to the large amount of deposition of rubber particles during the grinding process, there are still a large number of gas voids and rubber particle agglomerates in the raw material core rod. During grinding, the rubber particle agglomerates fail to obtain the auxiliary cooling and sufficient and effective all-round fixed grip of the ice phase in the raw material core rod, which aggravates the coking of the rubber powder and the extrusion and scattering of the rubber particles, bringing more uncertainty to the particle size of the finished product and bringing difficulties to the subsequent screening and definition of the finished product mesh size. Summary of the Invention

[0004] In view of the shortcomings of the prior art in the above background technology, the present invention provides a continuous preparation method of ultra-fine rubber powder based on freezing-pressing preform grinding and pulverization, which can realize the integrated molding of material column and shallow cold grinding of ultra-fine rubber powder:

[0005] 1. Crushing the rubber to be processed into rubber particles with a particle size of 2 to 80 mesh, and making the whole material reach the temperature T1 by pre-cooling or room temperature;

[0006] 2. Freeze all readily available water-based raw materials, such as pure water or tap water, to T2, preferably tap water;

[0007] 3. Crush the frozen water in step 2 to a particle size D that is 40% to 140% of the selected rubber particles;

[0008] 4. The rubber particles at temperature T1 in step 1 and the frozen water particles in step 3 are uniformly mixed and pressed under pressure P to form a mixed solid rod. The three parameters T1, T2 and the mixing ratio of the rubber particles and the frozen water particles should be such that the temperature of the mixed solid rod is not greater than 0 degrees Celsius.

[0009] 5. The combination of the five parameters T1, T2, D, P and the mixing ratio of rubber particles and frozen water particles should be sufficient to achieve the pressing of mixed solid rods in step 4, and the strength of the solid rods should be such that the crushing rate in the subsequent crushing is no more than 30%;

[0010] 6. The pressure in step 4 is preferably generated by a screw, but may also be generated by other mechanical means that produce material cohesion;

[0011] 7. Grind the mixed solid rods obtained in step 4 sequentially in a grinding form to obtain a liquid slurry containing ultra-fine rubber powder;

[0012] 8. Dehydrate the liquid slurry obtained in step 7 to obtain ultra-fine rubber powder.

[0013] The present invention advantageously combines the rubber being processed with frozen water particles to produce a mixed solid rod with sufficient strength to meet grinding requirements. This eliminates the need for fixed rubber, such as when whole tires must be ground, and overcomes the centrifugal splashing of rubber particles during grinding. Pre-freezing the mixed material avoids the effects of freezing and sticking to equipment during the post-mixing and subsequent freezing process, enabling continuous production throughout the present invention. The low-temperature mixed solid rod absorbs significant frictional heat during the grinding process through the phase transition of the frozen water, effectively protecting the rubber from surface denaturation at high temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the implementation of the method of the present invention.

[0015] Figure 2 This is a scanning electron microscope image comparing the ultra-fine rubber powder of the present invention (right) and other representative methods (left).

[0016] Figure 3 It is the application data of the ultra-fine rubber powder of the present invention. DETAILED DESCRIPTION

[0017] The present invention provides a continuous method for preparing ultra-fine rubber powder based on the grinding and pulverization of a freeze-pressed preform.

[0018] 1. Crush the rubber to be processed into rubber particles with a particle size of about 10 mesh, and pre-cool the material to a temperature of -5°C;

[0019] 2. Freeze tap water to -5°C;

[0020] 3. Crush the frozen water in step 2 to an average particle size of 1 mm and keep it warm to prevent it from melting;

[0021] 4. The pre-cooled rubber particles from step 1 and the frozen water particles from step 3 are uniformly mixed and fed into a screw feeder. The flow resistance of the variable diameter end of the screw feeder generates natural pressure on the mixed material, thereby forming the mixed solid rod and achieving the strength required for grinding and crushing. That is, during the grinding and crushing process, the rubber particles in the mixed solid rod do not separate from the mixed solid rod system;

[0022] 5. Grind the mixed solid rod obtained in step 4 in a continuous manner in a rotary grinding process to obtain a liquid slurry containing ultra-fine rubber powder;

[0023] 6. The liquid slurry obtained in step 5 is centrifugally dehydrated and dried to obtain ultra-fine rubber powder.

Claims

1. A method for preparing continuous ultra-fine rubber powder based on freezing-pressing preform grinding and pulverization, characterized in that: (1) Crushing the rubber to be treated into rubber particles with a particle size of 2 to 80 mesh, and bringing the material to a temperature of T1 by precooling or at room temperature; (2) Freezing any readily available water-based raw materials such as pure water or tap water to a temperature of T2, preferably tap water; (3) Crushing the frozen water in step (2) to a particle size D of 40% to 140% of the selected rubber particles; (4) Evenly mixing the rubber particles at temperature T1 in step (1) with the frozen water particles in step (3) and applying pressure P to press them into a mixed solid rod, wherein the three parameters T1, T2 and the mixing ratio of the rubber particles to the frozen water particles should reach to make the temperature of the mixed solid rod no greater than 0 degrees Celsius; (5) the combination of the five parameters T1, T2, D, P and the mixing ratio of rubber particles and frozen water particles should be achieved to achieve the pressing of the mixed solid rod in step (4), and the strength of the solid rod should be no greater than 30% in the subsequent crushing; (6) the pressure in step (4) is preferably generated in the form of a screw, but can also be other mechanical forms that produce material cohesion; (7) the mixed solid rod obtained in step (4) is sequentially ground in the form of grinding to obtain a liquid slurry containing ultra-fine rubber powder; (8) the liquid slurry obtained in step (7) is dehydrated to obtain ultra-fine rubber powder.

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