Environmental protection and sustainable development of rubber industry

1. Environmental protection of raw materials of rubber products

It is required that the rubber products produced do not contain harmful substances exceeding the limit value, and do not use prohibited dangerous substances, so as not to endanger human health, especially carcinogens.

Synthetic rubber raw materials in the production of heavy metals, processing oil, vulcanization agents, accelerators in the production process will cause some harm to the environment and the human body, we will be further elaborated in the following rubber products material impact on the environment.

1.1 Heavy Metals

The type and grade of raw materials of rubber products will affect the content of heavy metals. Therefore, care should be taken to avoid or reduce the use of raw materials containing chromium and nickel. The chrome plating layer of the mold and skeleton will also bring chromium elements to the rubber, so it is necessary to develop new chromium plating technology. The rubber shoe industry should pay attention to the limit value of heavy metals in textile and leather dyes, and limit the use of metal complex dyes containing copper, chromium and nickel. The content of heavy metals in rubber products does not only come from one or two key raw materials, but is the sum of all raw materials (including raw rubber) heavy metal content. Although some raw materials contain very small amounts of heavy metals, it is also necessary to pay attention to "a little adds up".

1.2 Processing oil

Rubber processing oil includes aromatic oil, paraffin oil and naphthenic oil. Aromatic oil can not be used for rubber products with environmental protection requirements because it contains a large number of polycyclic aromatic hydrocarbons, which also limits the application of oil-filled rubber with high aromatic oil. Although we have developed oil-filled rubbers with lower PAHs content, the types and amounts of PAHs they contain have not been reported, and it is unclear whether they will meet EU environmental requirements. In paraffin oil and naphthenic oil, the content of polycyclic aromatic hydrocarbons is also very different due to the different origin and processing technology. In addition, when processing oil-filled synthetic rubber, a lot of oil and gas will be emitted, and the pumping and exhaust devices should be set up in the relevant places.

1.3 vulcanization agent

Sulfur carrier type vulcanizing agent is often used for sulfur free coordination, typical examples are TMTD, DTDM. Organic peroxide vulcanizing agent is mainly used in heat-resistant formulations, its key is not toxic but explosive, so the protection level is included in class B, must be stored in a cool place <30°C, and it is customary to mix with inert fillers to reduce its activity. It is easy to emit smoke during processing, so it is necessary to strengthen ventilation and exhaust, and the concentration in the air should be limited to 1 mg/m3.

1.4 Accelerators

Sulfenamide, thiuram and dithiocarbamate are several kinds of accelerators that are used more at present, and they all produce carcinogens (nitroso compounds) in vulcanization. The promoters involved include TMTD, NOBS, BZ, EZ and DTDM. German industrial standards stipulate that the mass concentration of nitrosamines per square meter in the working environment of rubber enterprises shall not exceed 11,000 mg, and another type of carcinogenic accelerator is NA-22 commonly used in non-sulfur modified neoprene rubber.

2. Prevention of public hazards in rubber industry

2.1 Sources of public hazards

Flue gas: This is the main form of air pollution in rubber processing, which will be produced in the process of rubber mixing, return refining, calendering, extrusion, vulcanization and so on, of which the vulcanization is the most concentrated. The carbon black plant has more flue gas formation. Measures to control black carbon smoke include improving the collection system so that the concentration of black carbon dust in the exhaust gas is less than 18 mg/m3. Make full use of the heat energy of the tail gas, reduce the pollution of harmful combustible gas to the atmosphere, and purify the sulfur dioxide in the discharged gas. In addition, it is necessary to improve the wet granulation system of carbon black, so that the dust concentration of the workshop is less than 6 mg/m3.

Dust: It is a common form of public hazard in rubber factories, generated in rubber mixing powder and spraying spacer. Since most of the auxiliaries are powders, and the particle size is developing to a finer degree, the degree of flying is increased. The TLV of inorganic fillers in foreign countries is prescribed to be 10mg/m3, but it is actually much lower than this, and it is customary to control it below 2.5 mg/m3. The above is for grade A, and for powder materials with grade B toxicity, the oral dose LD50 is used to control. The harm of dust to the human body is mainly inhaled in the body, which leads to silicosis after long-term accumulation.

Solvents: The public hazards of solvents are mainly manifested in two aspects: (1) lead to occupational diseases. Concentrated in the glue manufacturing and brushing two processes, of which the most representative is chloroprene glue, a wide range of applications, China's shoe adhesive annual output of up to 200,000 t, and the use of aromatic hydrocarbon solvents or chlorinated solvents. The former such as benzene, toluene, xylene; the latter such as dichloroethane. These two types of solvents are more toxic, workers are prone to chronic diseases after long-term exposure, the most serious will suffer from cancer, leukemia and damage to the nervous system. The aromatic hydrocarbon solvent is benzene, toluene, xylene in order of toxicity, and people will feel fatigue, headache, lethargy and other chronic symptoms after long-term contact with them.