What Types of Products Are Made From Recycled Rubber?

Recycled rubber is a kind of rubber that has been processed from the vulcanized corner waste in the production of rubber products and has a certain degree of plasticity. According to the used waste rubber, recycled rubber is divided into outer tires, inner tires, rubber shoes and so on.

Recycled rubber

Recycled rubber can be used in place of raw rubber for rubber products in order to save raw rubber and carbon black. It is also beneficial to improve processing performance and some properties of rubber products. The regeneration process is a process in which the plastic waste (softener and activator), oxygen, heat and mechanical shear break the molecular chains and cross-linking points of the vulcanized rubber under the combined effects of plasticizer (softener and activator).

Chinese name: Recycled rubber
Foreign name: reclaimed rubbe

Features: Must be plastic and reusable
Classification: Outer tires, inner tires, rubber shoes

Reclaimed rubber

The softening agent plays the role of swelling and plasticizing. Commonly used are

China is a country with relatively scarce raw rubber resources. About 50% of China's annual consumption of recycled rubber needs to be imported. Finding the source of rubber raw materials and their substitute materials is an endless task for China. Therefore, conscientious and proper disposal of waste rubber is of far-reaching positive and practical significance for making full use of renewable resources, getting rid of the scarcity of natural resources, reducing environmental pollution, and improving people's living environment. Recycled rubber has always been an important raw material for the world rubber industry. On the one hand, it can replace rubber and alleviate

Disposal of waste rubber is one of the serious problems facing people today. In order to meet the ever-increasing material performance requirements, rubber is developing in the direction of high strength, wear resistance, stability and aging resistance, but at the same time it causes the problem that the rubber cannot be naturally degraded for a long time after being discarded. A large amount of waste rubber has caused Pollution (white pollution) is more difficult to handle with black pollution. On the other hand, valuable rubber resources are wasted.

Millions of tons of waste rubber are produced every year around the world, and the amount is so huge that how to effectively treat it has become a problem of general concern in the whole society. For this reason, in addition to incineration of piled waste rubber products as fuel, since 1910, scientists from various countries have studied more effective waste rubber regeneration treatment technology. Recycled rubber refers to waste vulcanized rubber that undergoes physical and chemical processes such as pulverization, heating, and mechanical treatment to change it from an elastic state to a plastic and viscous rubber that can be revulcanized. The essence of the regeneration process is the combination of heat, oxygen, mechanical action, and chemical and physical action of the regenerant to destroy and degrade the vulcanizate network. There are both crosslinks and macromolecules between the crosslinks at the fracture sites. key.

Recycled rubber steam method

1. Oil method

The rubber powder and the regenerant are mixed uniformly, put into an iron pan, sent to a horizontal desulfurization tank, and heated by direct steam. The steam pressure is 7MPa (5 ~ 7kgf / cm2), and the desulfurization time is about 10 hours. The process equipment is simple.

2. Superheated steam method

Mix the rubber powder and the regenerant evenly, put it into a desulfurization tank with an electric heater, pass direct steam, and use an electric heater to increase the temperature to 220 ~ 250 ° C to destroy the fibers in the rubber powder. 4MPa (4kgf / 2).

3 High pressure method

Mix the rubber powder and the regenerant evenly, put it into a closed high-pressure container, and pass 4.9 ~ 69MPa (50-70kgf / cm2) direct steam for desulfurization and regeneration. This method requires high equipment and large investment.

4 Acid method

The rubber powder is first soaked with dilute sulfuric acid to destroy the fibrous material, and then the acid is neutralized and washed with alkali, and then direct steam is passed for desulfurization and regeneration. This method requires corrosion-resistant equipment, consumes a large amount of acid and alkali, has complicated processes and equipment, high costs, and the product is easy to age.

Recycled rubber cooking

1. Water and oil method

The desulfurization equipment of this method is a vertical desulfurization tank with agitation. Steam in the jacket is passed through 0.9 ~ 0.9MPa (9 ~ 10kgf / cm2). Fill the tank with warm water (80 ° C) as the heat transfer medium. During desulfurization, the rubber powder and the regenerant that have been mechanically removed from the fiber are added to the tank, and the stirring time is about 3 hours. Although there are many equipments in this method, the degree of mechanization is high, and the product quality is excellent and stable.

2. Neutral law

The neutral method is basically similar to the water and oil method, the difference is that the neutral method does not remove the fibers in advance, and a zinc chloride solution is added to remove the fibers during the desulfurization process. The effect is not as good as the water and oil method.

3 Alkaline method

Use sodium hydroxide (5-10% concentration) to destroy the fibers in the rubber powder, then neutralize and clean with acid, and then desulfurize and regenerate by direct steam heating. The equipment is easily corroded, the quality of the product is poor, and the method is backward.

Recycled Rubber Machinery

1. Mixer method

The internal mixer used is a super-strength structure, and the surface of the rotor is plated with hard chromium or surfacing wear-resistant alloy. The rotation speed is 60 80r / min, the pressure of the upper plug is 1.24MPa (12.6kgf / cm2), the operating temperature is controlled at 230 280 , and the time is 7 15 minutes. This method has short production cycle and high efficiency.

2. Screw extrusion

The main machine is a screw extruder (similar to a rubber extruder), with screw diameters of 6, 8, 12in. There is a jacket in the casing, and the temperature is controlled by steam or oil (about 200 ° C). During operation, the rubber powder and the regenerant are mixed and fed into the machine in advance. The rubber compound can be discharged from the discharge port after 3 to 6 minutes under the action of the shearing and extruding of the screw. This method is continuous production, short cycle, high efficiency, and good product quality, but due to the large wear of the screw and the inner sleeve, the material requirements of the equipment are higher.

3 Rapid desulfurization

The main machine is a mixer with a special structure (similar to a plasticizer). There is a material blocking device in the tank. The stirring speed is adjustable and driven by a DC motor. The speed is divided into two gears. The low speed is controlled at 720 r / min and the high speed is 1440 r / min. After stirring for 10 minutes, the air is gradually cooled and the cooling is performed in a cooler. This method has a short production cycle, fast mixing speed, difficult to control process, and insufficient product quality, which is more suitable for recycling waste synthetic rubber.

4 Rotational dynamics

After mixing the rubber powder and the regenerant evenly, put it into the equipment with a pair of hollow screws, heat it with an oil bath, and control the temperature at 240-260 ° C for continuous desulfurization. The rubber material can be desulfurized and regenerated after 15 minutes. .

Recycled rubber chemistry

1. Dissolution method

Put the rubber powder and softener into an electrically heated mixing tank, add 40-50% softener (100% rubber powder), generally using heavy oil or residual oil. The temperature is controlled at 200-220 ° C and stirred for 2 to 3 hours. The product after the reaction was a semi-liquid viscous substance. The product can be directly used in rubber products, instead of some softeners, and can also be used as waterproof and anticorrosive materials in the construction industry.

2. Grafting

In the process of rubber and sulfur, some monomers with special properties (such as styrene, acrylate, etc.) are added, and the monomers are reacted with the rubber at a high temperature of 200 to 230 ° C. Recycled rubber with properties of this monomer polymer (such as abrasion resistance, oil resistance, etc.). The reaction process of this method is difficult to control.

3 Dispersion method

Add rubber powder and emulsifier, softener, activator, etc. to the kneader, mix and press, and then slowly add the dilute alkali solution to make the rubber powder into a paste, then dilute it with water, and scrape it off Add 1% acetic acid to make it solidify. Finally, it is dried and compressed to obtain the finished product. The equipment of this method is simple, the process operation is not easy to control, and it is batch production.

4 Low temperature plasticizing

Mix the rubber powder with organic amines or low-molecular polyamides, metal naphthenates, aliphatic acids and softeners, activators, etc., and place them at a temperature of 80 to 100 ° C for a certain period of time. The oxidation-reduction reaction achieves the purpose of regeneration. This method saves energy, the equipment is simple, but the product has low plasticity.

Recycled Rubber Physics

The high-temperature continuous desulfurization method mixes the rubber powder and the regenerant as required, and then sends it into a horizontal multi-layer screw conveyor. The conveyor has a jacket and a far-infrared heating device. The rubber is subjected to far-infrared during the transportation process. The uniform heating can achieve the purpose of regeneration. This method is continuous production, with shorter cycle, better quality, and less complicated equipment. It is a new method being explored.

Microwave method

Crush the polar waste vulcanizate to 9.5mm size rubber particles, add a certain amount of dispersant, and transfer it to a pipe made of glass or ceramics to make the rubber particles advance at a certain speed and receive the energy from the microwave generator . The energy of the microwave generator is adjusted to cause the C-S and S-S bonds in the rubber powder molecules to be broken to achieve the purpose of regeneration.