Plastic powder production technology and application

There are two main methods for the recycling of used rubber: the use of mechanical methods to crush or grind waste tires into fine particles, so-called colloidal particles and powders; to destroy the plastic chemical network structure through disengagement technology to make so-called recycled rubber. . This article briefly introduces the production technology of rubber powder.

1. Method for producing rubber powder

Waste rubber pre-processing. Waste rubber products generally have non-rubber skeleton materials such as fibers and metals, plus a wide variety of rubber products. Therefore, pre-processing is required before the waste rubber is crushed, including sorting, removal, cutting, cleaning and other processing. The waste rubber should also be inspected and classified. The waste rubber and its products of different types and sources should be categorized according to requirements. The most ideal method is to adopt a recycling management cycle method and to process the waste rubber according to its destination. For larger products such as waste tires, the bead is removed, and a tread separator is also used to separate the tread from the carcass. The rubber shoes mainly recycle the soles of the shoes, while the inner tubes need to remove valve tips.

After the sorting and removal of non-rubber components of waste rubber, because of varying lengths, uneven thickness, can not be directly crushed, must cut the waste rubber. In foreign countries, tires are generally used to cut into 25mmx25mm rubber blocks. The big piece of plastic is returned to the cutting machine and cut again.

Waste rubber, especially tires, rubber footwear products, due to long-term contact with the ground, mixed with a lot of impurities such as sediment, it should first use the barrel washing machine to clean, in order to ensure the quality of rubber powder.

Frozen crushing method. The basic principle of low-temperature freezing and crushing method is that when the polymer material such as rubber is below the glass transition temperature (Tg), it is brittle. In this case, it is easily crushed into a powder by a mechanical action. Made according to this principle.

There are two kinds of freezing and smashing processes: one is a low-temperature freezing and smashing process. The other is a low-temperature and room-temperature grinding process. The former is the use of liquid nitrogen as a refrigerant. The waste rubber is cryogenically pulverized with a hammer mill or a roller mill after deep cooling. The fine rubber powder production line is produced using the latter method. The liquid nitrogen deep-cooling technology is used to process the used tires into fine rubber powder with 80 mesh or more. The temperature, speed, and overload in the production process are all controlled by a closed-loop chain microcomputer and have no pollution to the environment. The entire production process of the production line adopts compressed air-powered feeders and closed pipeline transportation. The entire line is closed except for the waste tire input and product packaging. In addition, due to the production by freezing, there is no high-temperature odor, so no secondary pollution occurs. Through the heat exchange process of fine powder and coarse powder, the purpose of fully utilizing energy and reducing energy consumption is to reduce product cost.

Room temperature grinding method. After the waste rubber is pre-processed, it is crushed at room temperature, generally divided into coarse and finely divided. At present, two kinds of comminution methods are commonly used in reclaimed rubber factories in China. One is coarse smashing and fine smashing, and the other is smashing and smashing on two different devices. The former is suitable for production in small factories.

The method of coarse crushing and fine crushing is carried out at the same time: One surface of the two rollers for this operation is provided with a groove, and the other surface is not grooved, that is, a grooved roller machine. Firstly, the washed rubber block is sent into the two rollers through the conveyor belt to break the glue, and then the broken rubber block and the powder are dropped into the reciprocating screen at the bottom of the device to reach the particle size requirements from the screen. Through the conveyor into the warehouse; did not meet the requirements of the plastic block, by turning over the material and then enter the groove roller machine to continue crushing.
The coarse crushing and the fine crushing are carried out on two pieces of equipment: coarse smashing is performed on grooved roller machines with grooves on the surface of both rollers, and the size of the coarsely crushed rubber pieces is generally 6-8 mm. Then enter the light roller crusher for fine smashing, the particle size is generally 0.8-1.0mm (26-32 mesh). The pulverized coal factory smashing equipment is different from the traditional reclaimed rubber smashing equipment. They are special waste rubber crushers, medium crushers, and fine crushers.

2. Activation and modification of rubber powder

The so-called activated rubber powder is a powder chemically treated on its surface in order to improve the properties of the rubber powder complex. There are many activation modification methods for rubber powder, which are roughly divided into: grafting method; interpenetrating polymer network (IPN) method; surface degradation regeneration method; oligomer modification method; adjustment * system; other activation methods. For example, a saturation amount accelerator treatment method. This method uses 2-3 parts of the accelerator to mechanically process the 420 μm (40 mesh) powder. The treated rubber powder is evenly coated with a layer of accelerator on the surface of the rubber powder. The crosslinks at the interface with the matrix gum increase, and the entire rubber compound becomes a uniform cross-linked product. This rubber powder is applied to tires, although its static performance is slightly reduced, but its dynamic performance is improved. .

Liquid polymer materials plus * chemical treatment. This method is to use about 12 parts of liquid unsaturated unsaturated polymer materials and blending agents, and then the mechanical treatment of rubber powder obtained. The liquid polymer materials that can be used are liquid nitrile rubber, liquid styrene-butadiene rubber, liquid ethylene-propylene rubber, and so on. Which liquid polymer material to use may be determined according to the type and use of the rubber powder. Through the treated rubber powder, it can be well cross-linked with the matrix rubber, and given its oil resistance, ozone resistance and other characteristics according to the type of liquid polymer used. According to the application test, high proportions (40%-80%) can be used in areas where the physical properties do not exceed the allowable range.

3. Application of rubber powder

The application of rubber powder can be divided into two major areas: First, the direct molding or the use of new rubber products made of products, which belong to the rubber industry category; Second, the application of a wide range of non-rubber industry. Nowadays, more and more manufacturers worldwide use plastic powder instead of primary materials, which is not only beneficial to environmental protection, but more importantly, the use of rubber powder can effectively reduce costs, improve performance, and obtain effects that other materials cannot obtain. It can be widely used as rubber, filler and composite materials for tires, hoses, adhesive tapes, rubber shoes, rubber industrial products, wires, cables and building materials. The rubber powder can also be used together with plastics, such as polyethylene, polyvinyl chloride, polypropylene, polyurethane, etc. to improve performance and reduce costs.

The modification of paving asphalt with rubber powder is also widely used in highway applications. Roads covered with rubber-modified asphalt are used in many developed countries such as Canada, the United States, Belgium, France, and the Netherlands. Some provinces and cities in China have entered Jiangxi, Hubei, Guangzhou, and Beijing, and they have successively laid experimental sections. Practice has proved that roads covered with rubber-modified asphalt can reduce road cracking and softening, and the roads are less prone to freezing and slipping. This improves driving safety and can improve road life. The service life is at least higher than that of ordinary asphalt pavements. Doubled.