First, the purpose and significance of waste rubber recycling and reuse

In the past 50 years, the petrochemical industry has sprung up, and the three synthetic materials such as synthetic resin, synthetic fiber and synthetic rubber have developed rapidly.

Pollution problem

A large number of discarded polymer materials are scattered in the society, forming "white pollution" and "black pollution", which greatly pollute the environment, encroach on useful land and damage human health.

In the past, waste tires were often treated by stacking, burying, and reclamation. Occupy the land, pollute the environment, breed mosquitoes, bacteria, damage the health of residents, and easily cause fires. The pollution caused by burning makes the surrounding grass not live, and the ecological environment causes great harm.

One of the keys to achieving the third-step strategic goal of China’s per capita GNP in the middle of this century to reach the level of moderately developed countries is to ensure

A virtuous circle of ecological environment.

The inevitable requirement of sustainable development

Since the United Nations formulated Agenda 21 in 1992, all countries in the world have taken actions to promote the implementation of sustainable development strategies, and achieving sustainable development has become a common goal pursued by all countries in the world.

In 2003, the Third Plenary Session of the 16th CPC Central Committee put forward the scientific development concept of "people-oriented, comprehensive, coordinated and sustainable development", which marked a major adjustment of China's development strategy and entered a new stage of development.

In order to achieve sustainable development, make full use of resources and protect the environment, developed countries attach great importance to the recycling of waste rubber, and embarked on the legal track earlier, and established a set of recycling management methods in line with the laws of the market economy.

a rubber application country

In 2004, it consumed a total of 4.5 million tons of raw rubber, ranking first in the world.

More than 230 million tires are produced

40-60 million scrap tires, plus hoses, tapes, rubber shoes and other rubber products, nearly 3 million t / year of waste rubber materials.

a country with a shortage of rubber resources

About 45% of annual rubber consumption needs to be imported

Imported rubber was about 2.4 million tons in 2004

There will be no fundamental changes in a short period of time.

According to the inaccurate statistics of various channels, the recycling rate of waste rubber in China is about

65%, compared with Finland, the United States, Japan and other countries, the difference is very large.

The consumption of raw rubber is large, but the recovery rate is low. Therefore, China's rubber industry is still in a serious situation of output-utilization-recycling imbalance.

From the perspective of the supply of petrochemical resources, the world’s petroleum resources are increasingly exhausted.

Proved reserves in the world: 151.1 billion tons

The remaining proved reserves: 137.4 billion tons

According to the current production level, oil resources can only be mined: 40 years

The highest international oil price in 2005 has exceeded: 70 US dollars / barrel

China is a major oil-consuming country and has become a net importer of oil during the Ninth Five-Year Plan period.

The development of synthetic rubber with carbon as the main raw material and the main reinforcing material - carbon black will inevitably be greatly affected by the depletion of petroleum.

In today's relatively scarce energy sources, the recycling of waste rubber is of great significance.

Study the new method of waste rubber utilization, use waste rubber to develop high value-added rubber substitutes, and provide key technical support for creating a resource-saving and environment-friendly harmonious society.

In order to meet the needs of the development of circular economy and society, we must rely on scientific and technological progress, eliminate old technologies in a limited period, develop new technologies, and serialize and standardize the establishment of innovative technology platforms for waste rubber recycling.

Second, the development of waste rubber recycling, regeneration and application technology

Waste rubber recycling method

1. Original and modified use

2, direct combustion, recovery of thermal energy

3, using high temperature cracking technology to recover small molecule chemicals

4. Using physical and chemical regeneration technology, the insoluble and infusible crosslinked rubber is regained plasticity and becomes an elastic material that can be reused.

5, the production of rubber powder as a substitute for polymers, used in rubber and plastics processing industry, construction industry, road traffic and so on.

A. Prototype utilization and refurbishment of tires

Suggest:

1. For tire products, increase the refurbishment rate and then carry out other types of recycling and reuse for the retreaded tire products.

2. For non-tire products, the issue of refurbishment should also be considered. If it cannot be refurbished and cannot be refurbished, other types of recycling and utilization should be carried out;

3. In this way, you can make full use of rubber resources. But be sure to develop downstream recycling technologies.

B. Direct combustion, recovery of heat

The calorific value of waste tires is very high. The waste tires weighing 1kg are equivalent to 11kg of bituminous coal. However, the burning of waste tires does not completely release toxic gases and cause air pollution. Environmental protection measures must be allocated. It is a low-value utilization method.
Incineration: It can solve the problem of possessing land, but it does not make full use of its value, and it will bring serious air pollution!

A number of cement plants, power plants, paper mills, and steel plants in the United States, Japan, and Western Europe use waste tires as fuel. According to statistics, the use of waste tires accounts for about 50% of total tires. This recycling method does not allow waste rubber products to benefit in the field of polymer material recycling, and ultimately only consumes valuable non-renewable resources.

China has not yet seen reports of industrialization. If it is necessary to establish a related enterprise, there must be systematic environmental protection projects, and the investment is not small.

C. Pyrolysis, recovery of small molecule chemicals

Using high temperature cracking technology, the waste rubber is cracked into small molecule chemicals, such as fuel oil, carbon black, and a large amount of steel wire can be recovered at the same time.

The existing problems: the current problems at home and abroad are the high cost of the waste rubber cracking equipment, the separation and purification process of cracking products such as heavy oil is difficult to control, and the quality of the obtained crude carbon black is poor, and further processing and improvement is needed, so the current effect Not obvious.

There are also manufacturers in China (such as China's Zhejiang Lishui Wanbao Waste Tire Processing Factory, Taipei Rongji Industrial Co., Ltd.), but the processing capacity is not large.

The great development of roads and transportation has promoted the development of the tire industry. High-speed, safe, high-wearing high-performance tires have become the mainstream of demand. According to statistics, in 2004 the world's tire production has reached 3 billion, and is growing at a rate of several hundred million.

D. Waste rubber production reclaimed rubber

The use of waste rubber to produce recycled rubber is a traditional waste rubber recycling method.

Status of recycled rubber:

In 2004, China's production of reclaimed rubber was 300,000 tons, which could create an output value of 1.2 billion for the country every year. Recycled rubber has always been an important raw material for the rubber industry. In principle, the network-like rubber macromolecules are dissociated into linear macromolecules. Reusing it as a rubber material is an ideal way to recycle and reuse. It has many advantages.

The methods currently used in China are mainly oil method and high temperature dynamic desulfurization technology, but there is still some pollution.

Due to the plastic formability of reclaimed rubber and low price,
The short-term still can not be completely replaced, the market demand is still relatively large.

Researching new types of pollution-free regeneration technology is the basic condition for making reclaimed rubber better as a member of a circular economy.

The traditional oil method and water oil method are currently basically not produced in developed countries. The current methods used in China are mainly high-temperature dynamic desulfurization technology, but there is still some pollution.

Shear flow field reaction control technology:

The chemical reacted with the sulfur cross-linking bond is mixed with the rubber powder in a normal temperature and high-speed shear field, and the in-situ reaction is carried out to form a flowable reclaimed rubber.

☆ With orange peel, allicin, durian shell and other extracts, the waste plastics can be exchanged for flow field reaction control regeneration.

☆Indian two doctors prepared Delink regenerant from plant extracts, which can be used for directional desulfurization regeneration of waste rubber by shear flow field reaction control technology through shear flow field reaction control technology. It also received good results. .

Targeted desulfurization regeneration:

Microwave regeneration:

The microwave desulfurization method is a non-chemical, non-mechanical one-step desulfurization regeneration method. It uses the action of microwave energy to break the S-S and S-C bonds in the rubber powder.

Microwave field: f=2450 or 915MHz, the polar group-containing rubber oscillates with the electromagnetic wave under the action of high-strength cross-frequency electromagnetic field, due to the thermal dynamics of the molecule itself and the interaction of adjacent molecules, in the polar group and molecule There is tremendous energy between them. The weak bond in the rubber powder is broken.

The microwave desulfurization method was first studied by Nortety et al. in the United States, and has been put into industrial application in the United States. The Japanese patent also has an introduction to the microwave desulfurization process.

The regeneration effect of microwave on white carbon black reinforcing glue is better than that of carbon black reinforcing glue.

Effect of microwave heating method on properties of vulcanizate

Effect of microwave heating method on properties of vulcanizate

Ultrasonic regeneration:

1. Acronym University invented the ultrasonic desulfurization method in 1993. This method utilizes a high-density energy field to break the cross-linking bond and retain the molecular backbone to achieve the purpose of regeneration.

2. The ultrasonic field can generate high-frequency stretching stress in a variety of media, and high-amplitude oscillating waves can cause solid fragmentation and liquid cavitation. The sonic cavitation causes the energy of the ultrasonic waves to concentrate on the local position of the molecular bonds, causing the ultrasonic field of lower energy density to transform into a high energy density at the destruction of the holes.

3. According to reports, Isayev A.Ier.a1. After ultrasonic regeneration with GRT (waste tire rubber powder), the physical and mechanical properties of the vulcanizate were measured as follows: tensile strength of about 9 MPa and elongation at break of 270%. This performance is higher than ordinary reclaimed rubber.

4. Isayev AI et al. also mathematically described the process of ultrasonic desulfurization and established a topology model. Ultrasonic desulfurization is the real regeneration of waste rubber, but the method has not removed the cost and technical barriers of commercial production, and commercial production will take some time.

Right angle head ultrasonic desulfurization device schematic

Schematic diagram of coaxial head ultrasonic desulfurization device

Electron beam regeneration:

Adjusting the electron beam energy selectively destroys the crosslinks and retains the molecular backbone, so that the vulcanized rubber achieves the purpose of regeneration.

Microbial regeneration:

Microbial regeneration is a new regeneration technology in recent years, in line with the direction of sustainable social development.

Fliermans et al. used some thermophilic microorganisms to treat the vulcanizate at 65 ° C, selectively breaking the chemical bonds of the vulcanizate, and gradually removing sulfur from the surface of the rubber particles to obtain a loose crosslinked network. .

Lions et al. use sulfur bacteria to separate elemental sulfur and sulfuric acid from waste rubber, and can obtain reclaimed rubber and sulfur in a simple manner.

Straube puts the waste rubber powder into a solution containing thiobacteria to carry out a biochemical reaction in the air. The sulphur-dissolving bacteria breaks the sulfur bond of a few μm thick on the surface of the rubber particle, exhibiting reclaimed rubber properties. At this time, sulfur is released from the surface layer or reacted to form sulfuric acid.

Romine et al. place the waste rubber powder in a reaction containing desulfurized bacteria or an enzyme produced by the bacteria. Bacteria or enzymes convert S in S-S and S-C in the vulcanizate to sulfoxide or sulfone.

Bredbreg et al. treated the surface of the frozen comminuted tire rubber powder using Thiobacillus ferrooxidans.

Arenskotter et al. believe that several commonly used microorganisms that degrade rubber are actinomycetes, mycobacteria, and soil filamentous bacteria.

In recent years, our research group, under the auspices of the National Fund and the 863 Project, is studying the cultivation and desulfurization process of microbial regenerative bacteria, and has obtained some obvious results.

A new type of microbial agent and Thiobacillus ferrooxidans have been cultivated.

The process and effect of microbial inoculant and Thiobacillus ferrooxidans on desulfurization of rubber powder were studied, and meaningful basic data were obtained.

Cultured organisms:

E. Waste rubber pulverization to prepare rubber powder

The preparation of waste rubber into rubber powder is a new recycling method in recent years. The waste rubber powder is prepared by freezing or mechanical shearing and then used as a substitute for polymer materials.

Scrap rubber is smashed at room temperature:

The waste rubber can be pulverized to a fineness of about 40 to 60 mesh by using a breaker, an open mill, and a disc grinder. The price is cheaper.

Waste rubber freeze smash:

First, the liquid nitrogen freeze-pulverized the waste rubber, and can be pulverized to a fineness of 200 mesh or more. Recycle steel cords. 0.5 liters of liquid nitrogen/kg of rubber powder.

Second, the turbine freeze-pulverized waste rubber can be pulverized to a fineness of 80-100 mesh or more. Recycle steel cords. High power consumption.

During the “Eight Five-Year Plan” period, the Ministry of Science and Technology of the People's Republic of China established a joint project to crack down on the crushing technology and surface activation technology of waste rubber.

Through the efforts of many domestic research institutes, we have designed a normal temperature mechanical pulverizer and a turbo refrigeration pulverizer, and established a number of rubber powder and activated rubber powder production lines with an annual production capacity of nearly 10,000 tons.

At present, the production enterprises of rubber powder are blooming everywhere, forming a large-scale production.

Various color powder:

The production and application of rubber powder is one of the most promising ways to recycle and recycle waste rubber.

The production and application of rubber powder is called “Chaoyang” industry in foreign countries. It is the second change in the comprehensive utilization of waste rubber, bringing new vitality and vitality to the comprehensive utilization of waste rubber.

Application 1: Waste rubber powder modified asphalt as paving material Beijing Road Administration Bureau March 2007 Rubber Powder Asphalt and Mixture Design and Construction Guide This year, the city's road overhaul will promote the use of rubber powder modified asphalt.

On a 3-inch deep, two-lane road, 16,000 used tires per mile.

Countries such as Europe and the United States have used waste rubber powder to modify asphalt technology for more than 20 years.

There are already 11,000 km of highways in the United States paved with rubber powder modified asphalt materials.

The United States stipulates on page 1038(d) of the ISTEA (Interstate Road Transport Effectiveness Act) that states use recycled tires for asphalt paving.

Performance of waste rubber powder waste rubber / asphalt high grade road material:

Rubber powder modified asphalt can significantly improve the high and low temperature resistance of asphalt (70 °C does not flow, -35 °C is not brittle), increase the friction coefficient of asphalt pavement, reduce light reflection, safety, driving comfort, and extend the use of roads. life. In particular, the noise reduction effect is remarkable, which is equivalent to a 30% reduction in traffic flow.

China has added 50,000 kilometers of expressways every year, and needs to lay 8 million tons of asphalt every year. 8 million tons of asphalt was laid. If 10 to 15% of rubber powder is used to modify the asphalt, the annual demand for rubber powder is 800,000 to 1.2 million tons, which can create an output value of 40 billion yuan.

Preparation technology and industrialization of rubber powder/asphalt road materials:

The main problems of rubber powder modified asphalt:

First, when the waste rubber powder is added, the waste rubber powder is added to the asphalt of 160 to 165 ° C to modify it, the viscosity of the system suddenly increases, and the fluidity deteriorates, making the stirring operation difficult, and the stirring temperature is increased, although Reduce the viscosity of the system, but both rubber powder and asphalt produce a certain degree of aging, which seriously affects the quality of the modified asphalt;

Secondly, the interface of rubber powder/asphalt is not well combined, and the phase stability is poor. When the modified asphalt is evenly stirred and has not been mixed with the pavement stone, the modified asphalt will precipitate and isolate, making the construction quality difficult to control. .

Beijing University of Chemical Technology, together with Beijing Road New Modified Asphalt Co., Ltd. and Beijing Highway Research and Design Institute, created a “low temperature and high shear in-situ modification method” to prepare high performance rubber powder modified asphalt.

The research is underway and it is expected to make an important contribution to the rubber powder modified asphalt industry in China.

Application 2 Preparation of activated rubber powder as a substitute for rubber

The United States, Japan, Russia and other countries use rubber powder to produce various rubber products, such as soles, rubber sheets, waterproof building materials, conveyor belts, sound-absorbing panels, etc., which are also widely used in tire treads, which can significantly improve the performance of tread rubber. It also reduces costs.
Progress in China's waste rubber powder industry:

Inspired by the developed countries, during the "Eighth Five-Year Plan" period, the Ministry of Science and Technology of the People's Republic of China initiated a joint research on the crushing technology and surface activation technology of waste rubber.

Through the efforts of many domestic research institutes, we have designed a normal temperature mechanical pulverizer and established an activated rubber powder production line with an annual production capacity of nearly 10,000 tons.

The use of 15-20% activated rubber powder in car and truck tire tread rubber has received significant social and economic benefits.

After the “Eighth Five-Year Plan”, the production enterprises of rubber powder bloomed everywhere and formed a certain scale.
Application of 3 rubber powder and plastic blending to prepare thermoplastic elastomer materials Production of high value-added irrigation pipes, seals, damping plates, waterproof membranes, etc.

Preparation technology and industrialization of waste rubber powder thermoplastic elastomer

Beijing University of Chemical Technology and Beijing Oriental Yuhong Waterproof Material Co., Ltd. have developed a new generation of WRP/WRP/resin resin TPV low-cost waterproofing membrane.
Application 4 "High temperature and high pressure sintering forming high temperature and high pressure sintering forming" to prepare hard and tough rubber products Application 5 Preparation of rubber floor tiles

Prospects The use of targeted desulfurization technology to produce reclaimed rubber, waste rubber to prepare rubber powder and activated rubber powder, crack recovery of small molecular oils and carbon black, etc., is the main way and method of environmentally friendly waste rubber recycling. The virtuous recycling of a large number of waste tires will definitely make our social environment better.