VOC Control In The Rubber Industry

VOC control in the rubber industry

--emission standards lead green change

VOCs in the rubber industry are generated in multiple production links. In the raw material processing stage, the low-molecular organic components contained in natural rubber and the monomer substances remaining in the production of synthetic rubber have begun to volatilize. In the mixing stage, some organic components of rubber softeners, accelerators, antioxidants and other additives escape under the action of high temperature. For example, the commonly used aromatic oil softener will release volatile substances during mixing. In the vulcanization process, the low-molecular organic by-products produced by the reaction of cross-linking agents and vulcanization accelerators are also an important source of VOCs. For example, the sulfur vulcanization system will produce sulfur-containing organic compound volatiles. These volatiles contain a variety of substances, the most common of which are aromatic hydrocarbons such as benzene, toluene, and xylene. They are typical representatives of VOCs in the rubber industry.

1. What is VOC, VOC in the rubber industry?

VOC (volatile organic compounds) in the rubber industry refers to organic compounds that are volatilized from raw materials, additives and production processes during the rubber production process. These compounds are volatile and have a high vapor pressure at room temperature. For example, organic solvents used in rubber processing, aromatic hydrocarbons such as benzene, toluene, and xylene, as well as organic components contained in some rubber softeners and plasticizers, all fall into the category of VOC.

2. Where do VOCs in the rubber industry come from?

Raw materials: Natural rubber itself contains some low-molecular organic components, which will volatilize during the processing. In the production process of synthetic rubber, monomer and additive residues will also become the source of VOC. For example, incompletely reacted styrene monomer in the production of styrene-butadiene rubber.

Processing aids: A large number of additives are used in rubber mixing, vulcanization and other processing processes, such as rubber softeners (such as aromatic oils), accelerators, antioxidants, etc. Under high-temperature processing conditions, some of these additives will volatilize to form VOCs. For example, during the mixing process of aromatic oil, due to the increase in temperature, the volatile components in it will be emitted into the air.

Vulcanization process: Vulcanization is a key step in rubber processing. During the vulcanization process, crosslinking agents and vulcanization accelerators in rubber will undergo chemical reactions. This process will produce some low-molecular organic by-products, which will be released in the form of VOCs. For example, when using a sulfur vulcanization system, sulfur-containing organic compound volatiles will be produced.

3. What are the hazards of VOC in the rubber industry ?

• Hazards to human health

Benzene series (such as benzene, toluene, and xylene) in the rubber industry VOC are toxic and harmful substances. Long-term exposure to benzene can lead to abnormal hematopoietic function and cause serious diseases such as leukemia. Toluene and xylene can stimulate the central nervous system and cause symptoms such as dizziness, headache, nausea, and vomiting.

Some chlorine-containing VOCs (such as chlorinated hydrocarbons that may be produced during the processing of chloroprene rubber) can cause damage to organs such as the liver and kidneys after entering the human body.

• Environmental hazards

VOCs participate in photochemical reactions in the atmosphere to produce ozone (O₃) and secondary organic aerosols (SOA). Ozone is a strong oxidant that can damage plants, such as causing crop leaves to turn yellow and growth to be stunted. At the same time, high concentrations of ozone can also irritate the human respiratory tract and cause respiratory diseases.

Secondary organic aerosols can reduce atmospheric visibility, leading to the formation of haze weather, affecting air quality and climate change.

4. What are the emission standards and control measures ?

Emission standards

In China, the Rubber Products Industry Pollutant Emission Standard (GB 27632 - 2011) has made provisions for VOC emissions in the rubber industry. For example, there are clear requirements for the emission limits of non-methane total hydrocarbons from rubber refining units and vulcanization units. The emission limit of non-methane total hydrocarbons from rubber refining units is 10mg/m³ (organized emissions).

• USA

National emission standards : The U.S. Environmental Protection Agency (EPA) has established relevant emission standards. For example, in November 2023, EPA issued a proposal to revise the national emission standards for hazardous air pollutants in the rubber tire manufacturing industry, proposing to establish a maximum achievable control technology (MACT) limit for total hydrocarbons (THC) for the rubber processing subcategory.

Industry emission standards : Different state governments can formulate stricter VOCs emission control standards based on their own conditions, provided that they comply with federal standards. For example, some states have more detailed regulations on equipment leakage and storage tank breathing emissions of rubber manufacturers.

Specific controlled substances and limits : Strict emission concentration and emission limits are set for harmful substances such as benzene, toluene, and xylene. Enterprises must strictly comply with them, otherwise they will be punished according to law. 2.

• European Union

EN ISO 10580:2012 : specifies the emission requirements of volatile organic compounds (VOC) for elastic fabrics and laminate floor coverings. If rubber products are used in the production of such products, they must meet the VOC emission limit requirements in this standard3.

Integrated Pollution Prevention and Control Directive (IPPC) : requires industrial enterprises to take comprehensive measures to prevent and control pollution, and regulates the production process, equipment maintenance, and waste gas treatment of the rubber industry to reduce the emission of pollutants such as VOCs. Enterprises need to achieve the corresponding environmental performance standards by adopting the best available technology (BAT), which clarifies the technical and management measures for VOC emission reduction in various rubber production processes.

• Japan

JIS A 1903:2008 and JIS A 1903:2015 : These two standards specify the determination method of volatile organic compound (VOC) emissions from building products. They use a passive method to detect and evaluate VOC emissions from rubber products and other building-related materials, providing a basis for controlling VOC emissions from rubber products used in the construction field.

5. What control measures will be taken? (Source control, process control, end-of-pipe control)

Control measures

- **Source control**: Select raw materials and additives with low VOC content. For example, use environmentally friendly rubber softeners to replace traditional aromatic oils to reduce VOC generation. In the production of synthetic rubber, optimize the polymerization process, increase the monomer conversion rate, and reduce the residual monomer content.

- **Process control**: Strengthen the ventilation system during the production process. Install efficient gas collection hoods and ventilation ducts in the rubber mixing workshop and vulcanization workshop to collect the generated VOCs and then treat them. At the same time, optimize the vulcanization process parameters such as temperature and time to reduce VOCs generated by excessive vulcanization.

- **End-of-pipe treatment**: Use a variety of VOC treatment technologies, such as adsorption, catalytic combustion, and biological treatment. The adsorption method uses adsorbents such as activated carbon to adsorb VOC, and the purified gas meets the emission standards. The catalytic combustion method is to burn and decompose VOC into carbon dioxide and water at a lower temperature under the action of a catalyst. The treatment efficiency is high, but attention should be paid to the selection and maintenance of the catalyst. The biological treatment method uses the metabolism of microorganisms to decompose VOC. It has the advantages of low cost and no secondary pollution, but the treatment efficiency is relatively low and is suitable for the treatment of low-concentration VOC.

• With the increasing awareness of environmental protection and the urgency of environmental governance, emission standards for the rubber industry have emerged. Driven by the environmental protection situation at home and abroad, relevant policy orientations have prompted the release of the "Emission Standards for Pollutants in the Rubber Products Industry" (GB 27632 - 2011). This standard has strict and detailed regulations on VOC emissions in the rubber industry . In terms of the emission limit of non-methane total hydrocarbons, the organized emission limit of the rubber refining unit is 10mg/m³, and the vulcanization unit also has corresponding clear limit requirements.

• For unorganized emissions, the concentration limit of the monitoring point within the factory boundary is also stipulated. In addition, the standard puts forward systematic requirements for enterprise monitoring and supervision. Enterprises need to monitor at specific monitoring points at the prescribed frequency, and install automatic monitoring equipment for pollutant emissions to connect to the environmental protection department to ensure that the emission data is transparent and traceable, and fully regulate the VOC emission behavior of rubber enterprises.

While ensuring that we provide sealing solutions to our users, we(Lindepolymer) also strictly implement national and international environmental standards.