Silicone production and environment

1. What are the characteristics of silicone?

Silicones are compounds that contain silicon-carbon (Si-C) bonds, these molecules contain at least one organic group directly linked to a silicon atom. Such compounds usually include other organic or inorganic functional groups linked through elements such as oxygen, sulfur, and nitrogen. The heart of silicone chemistry is siloxane, in which silicon atoms form polymer chains or ring structures with silicon-oxygen bonds (Si-O-Si) as a backbone. Silicone materials have the following distinctive features:

(1) Temperature resistance:

Because of its main chain structure for the stable silicone-oxygen (Si-O) bond, silicone products can be in a wide range of temperatures to maintain stable performance. They can withstand high temperatures without decomposition or degradation and maintain good elasticity at low temperatures.

(2) Weather resistance:

Silicones have good resistance to environmental factors such as ultraviolet light and ozone. They are not easily aged by light, heat, and climatic conditions, so they are commonly used in outdoor applications and situations that require long-term exposure to harsh environments.

(3) Electrical insulation:

Silicone compounds are excellent electrical insulation materials with high dielectric strength, low dielectric loss, and excellent insulation stability, which are suitable for the manufacture of wire and cable insulation, electronic packaging materials, and electrical equipment parts.

(4) Chemical stability:

For many Acids, Alkalis, and Oxidizing agents, silicone shows good chemical inertia, it is not easy to react with most chemicals.

(5) Surface activity:

Silicones have low surface tension and surface energy, which allows them to easily wet a variety of substrates and form a thin and uniform film layer, it has a wide range of applications in the field of coatings, adhesives, lubricants, and defoamers.

(6) Mechanical properties:

Silicone rubber has good elasticity and recovery, it can maintain flexibility in extreme environments, and at the same time with abrasion resistance, tear-resistance, and other characteristics.

(7) Physiological inertia:

Many silicone materials are harmless to human tissue and biocompatible. It is widely used in medical fields such as artificial heart valves, contact lenses, and implant coatings.

(8) Hydrophobicity :

Silicone surfaces usually show strong hydrophobicity, which makes it easy to form a self-cleaning surface and reduce microbial adhesion.

(9) Highly designable:

By changing the side chain structure and crosslinking, different performance characteristics of silicone polymer materials can be synthesized to adapt to a variety of specific application requirements.

In summary, with these unique properties, silicone has extremely important application value in industry, construction, automotive, aerospace, electronics, chemical, pharmaceutical, and other fields.

2. China's Silicone Industry

2.1 China's Silicone Industry Development:

(1) Market size and growth:   

The market size of China's silicone industry continues to expand, and the relevant market is expected to further rise from tens of billions to a higher level by 2025. Global silicone industry downstream application demand is strong, especially in China, due to policy support and the development of emerging areas such as photovoltaic, new energy, ultra-high voltage grid construction, smart wearable devices, etc., silicone market demand has strong growth.

(2) Industrial chain status:

China's silicone industry chain covers a wide range of categories from upstream refining of raw materials (e.g., silica powder) to midstream monomer synthesis and downstream production of various end products, including silicone oil, silicone rubber, silicone resin, and silane coupling agent. Although there is still a dependence on imports in the production of certain high-end products and technological research and development, China has become the center of global silicone production, and local enterprises continue to make breakthroughs in technological progress and industry chain improvement.

(3) Industrial structure and competition pattern:

The competitive pattern in the industry has gradually shifted from competition in upstream production capacity to competition in downstream product development and differentiation. The main production enterprises include Dow and Momentive in the United States and Wacker in Germany. At the same time, a number of competitive local integrated enterprises and leaders have also emerged.

(4) Development prospects and challenges:

With the deepening of the concept of sustainable development and technological advances, the domestic silicone industry is undergoing integration and transformation and upgrading, and entering a more mature and sustainable development stage. Challenges are mainly reflected in how to enhance independent research and development capabilities and reduce dependence on foreign advanced technology and high-end materials. At the same time, it should strengthen the application of environmentally friendly technology and circular economy to achieve green and sustainable development.

China's silicone industry is in an important stage of rapid development and industrial upgrading, which is expected to occupy a more important and dominant position in the global silicone industry chain through technological innovation and market expansion in the future.

2.2 The current situation of China's silicone in the global industry:

(1) Production capacity scale:

As of 2023, China has become the world's largest producer of silicone monomers, with a production capacity of more than 3 million tons/year, and it is still growing. This figure far exceeds that of other countries and regions, showing China's leading position in production capacity in this field.

(2) Industry chain integrity:

China's silicone industry chain is relatively complete, from the upstream silicon metal refining, and monomer synthesis to the downstream deep-processing products such as silicone rubber, silicone oil, silicone resin, and so on, these products have large-scale production capacity, forming a complete industrial chain system.

(3) Market demand and application:

With the development of China's economy and industrial structure upgrading, the demand for silicone materials continues to grow, especially in new energy vehicles, semiconductors, 5G communications, aerospace, construction and building materials, daily chemical products, and other strategic emerging industries that have a wide range of applications.

(4) Technological progress and innovation capacity:

Although the technology and market of high-end products were once mainly dominated by developed countries such as Europe, America, and Japan, in recent years, local Chinese enterprises have increased their efforts in technological research and development, constantly breaking through the key technological bottlenecks and enhancing their competitiveness, and import substitution has been realized in some fields.

(5) Industry integration and brand building:

In the market competition, Chinese enterprises have accelerated industrial upgrading through mergers and acquisitions, technological innovation, and other ways, forming leading enterprises with international influence.

Therefore, China's silicone industry is gaining influence globally, not only dominating the total volume but also gradually shortening the gap with advanced countries in terms of quality and technical level, making important contributions to the development of the global silicone industry.

3. What is the silicone industry chain?

3.1 What is the main composition of the silicone industry chain?

(1) Upstream raw materials:

Silicon metal (industrial silicon): As the basic raw material, it is obtained through quartz ore smelting, and after further grinding into silicon powder.

Methylene Chloride: A key raw material for the synthesis of silicone monomer, whose price is affected by the chemical industry such as oil, natural gas, and coal.

(2) Silicone monomer production:

Silicon metal and Methylene Chloride are used as the main raw materials to synthesize silicone monomers, such as Methylchlorosilane (e.g., Dimethylchlorosilane, Trimethylchlorosilane, etc.) through specific chemical reactions.

(3) Silicone intermediates:

A series of silicone intermediates are formed after hydrolysis of monomers, such as Cyclic D4 (Octamethylcyclotetrasiloxane), DMC (Dimethylsiloxane mixed Cyclohexane), and so on.

(4) Midstream deep processing products:

Silicone Resin: It is made from silicone polymers, which can be used in coatings, adhesives, insulating materials, and other fields.

Silicone Oil: Silicone oils of different viscosities and modifications are widely used in a variety of industries such as lubrication, mold release, personal care products, and so on.

Silicone Rubber: Including room-temperature vulcanized silicone rubber and high-temperature vulcanized silicone rubber, it is widely used in seals, wire and cable insulation, medical products, food contact materials, etc.

Silane coupling agent: It plays a key role in composite materials, inorganic filler surface treatment, etc.

Silica: As a reinforcing filler, it is widely used in silicone rubber and other fields.

Others include various functional additives, specialty silanes, etc.

(5) Downstream applications:

Construction and building materials: Building sealants, waterproof materials, etc.

Electronic and electrical appliances: insulation materials, potting adhesive, thermal conductivity materials, etc.

Automotive transportation: vehicle parts, interior materials, tires, etc.

New energy power: Photovoltaic module encapsulation materials, battery pack sealing materials, etc.

Aerospace: High-performance materials, high-temperature resistant parts, etc.

Textiles, daily necessities, transportation, medical, and personal care industries are also widely used.

The entire industrial chain and the links are interrelated, and the technological progress of upstream and downstream enterprises and market supply and demand closely affect the development of the silicone industry.

3.2 What are the main steps in the production of silicone?

(1) Raw material preparation:

Metal silicon powder preparation: Industrial silicon (metal silicon) is processed into silicon powder with uniform particle size through crushing, grinding, and other processes, which is used as the raw material for synthesizing monomers. Preparation of Methylene Chloride (or Chloromethane): Methylene Chloride is usually obtained by a catalytic reaction between methanol and hydrogen under the action of a catalyst.

(2) Silicon monomer synthesis:

Direct method: In the fluidized bed reactor, the chemical reaction between silica powder and Monochloromethane occurs under the effect of a specific catalyst and high-temperature inert atmosphere to produce a series of Methylchlorosilane monomer mixtures, such as Dimethylchlorosilane (DMC), Trimethylchlorosilane (TMCS) and so on.

Indirect method: First through the synthesis of silicone hydride, and then react with silicon powder to generate silicone monomer.

(3) Monomer separation and purification:

The crude monomer mixture from the fluidized bed reactor passes through a cyclone separator to remove dust initially and then enters a scrubbing tower to further remove impurities. After preliminary purification, the crude monomer is subjected to a multi-stage distillation operation in a distillation column system (including several fractionation columns) to extract different types of Methyl Chlorosilane monomers respectively and purify them to the required purity.

(4) Hydrolysis reaction and subsequent treatment:

Various Methyl Chlorosilane monomers obtained from refining are converted into corresponding methyl siloxanes through hydrolysis reaction, for example, D4 (Octamethylcyclotetrasiloxane) can be obtained after hydrolysis of DMC. The hydrolyzed products are subjected to various distillation and distillation processes such as de-low, de-high, binary separation, light component separation, hydrogen-containing separation, etc., in order to obtain siloxane products with different chain lengths and structures.

(5) Deep processing:

According to different needs, these basic organosilicon compounds can be further processed into various downstream products, such as silicone oil, silicone rubber, silicone resin, silane coupling agent, and so on.

(6) End-use applications:

These silicone products are widely used in construction, electrical and electronic, automotive, aerospace, chemical, textile, healthcare, personal care, and other fields.

The entire silicone production process involves complex chemical reactions and fine physical separation technology, which requires high equipment requirements and strict quality control.

3.3 What are the types of chemical reactions in the silicone industry chain?

(1) Monomer synthesis:

Under the action of a catalyst, gas-solid phase reaction Metal silicon (Si) and Chloromethane (CH3Cl) to generate Methylchlorosilane in a high-temperature, such as Dimethylchlorosilane (Me2SiCl2), Trimethylchlorosilane (Me3SiCl) and so on.

Si + 3CH3Cl Me3SiCl + 2HCl

Si + 3 CH3Cl (CH3)3SiCl

(2) Hydrolysis reaction:

Methylchlorosilane is hydrolyzed to produce the corresponding Methylsiloxane. For example, Dimethyl dichlorosilane (DMDM) is hydrolyzed to obtainOoctamethylcyclotetrasiloxane (D4).

(CH3)2SiCl2 + 2H2O (CH3)2Si(OH)2 + 2HCl

(CH3)2Si(OH)2 can be further condensed to form cyclic siloxanes such as D4.

(3) Cracking and rearrangement reactions:

Hydrolysis products are converted into silicone compounds with different chain lengths and structures by thermal or catalytic cleavage.

(4) Hydrosilylation:

Silicone compounds containing silicone hydrogen bonds (Si-H) and organic compounds containing unsaturated bonds (such as C=C, CC, C=O, etc.) undergo an addition reaction, which is used to prepare a variety of functional silicone oils, silicone resins, and silicone rubber prepolymers.

RSiH3 + CH2=CH-R' RSiR'R + H2

(5) Cross-linking reaction:

In the production process of silicone rubber, adding appropriate cross-linking agents (such as platinum complexes, peroxides, etc.), so that the linear or branched-chain silicone molecules cross-linking reaction occurs between the formation of a three-dimensional network structure of the elastomer.

(6) Condensation reaction:

In the preparation of certain high molecular weight silicone resins, the siloxane main chain and side chain structure are formed by dehydration condensation between silanols.

(7) Functional group transformation reaction:

Functionalization of existing silicone compounds, e.g., conversion of the Silylhydrazine group to other reactive functional groups (e.g., Methoxy, Amino, epoxy, Carboxyl, etc.) to suit specific applications.

(8) Use of silane coupling agents:

Silane coupling agents are able to react simultaneously with the hydroxyl groups on the surface of inorganic materials and organic polymer molecules to improve the interfacial bonding between the two.

These chemical reactions constitute a complete chain of silicones from basic raw materials to final products, according to different applications and product characteristics, the need for targeted selection, and the design of the corresponding chemical process.

4. Why need deep processing in the silicone industry chain?

4.1 Improve added value:

Silicone monomers such as Methyl Chlorosilane after hydrolysis, Polymerization, and other reactions to get the initial processing products (such as silicone oil, silicone rubber, etc.) which are relatively low added value. Through further processing, these basic raw materials can be transformed into end products with better performance, more specialized uses, and higher technological content, such as special silicone rubber products, high-performance silicone resin coatings, silane coupling agents for the electronic and mechanical industries, thereby greatly increasing the economic value of the product.

4.2 Meet the diversity of market demand:

Different applications have specific needs for silicone materials, such as high-temperature resistance, low-temperature resistance, insulation, hydrophobicity, elasticity, adhesion, and other characteristics of different requirements. Deep processing can customize the production of products that meet the needs of different industries and users, and broaden the scope of application, such as the wide range of applications in the medical, automotive, aerospace, new energy, electronics and electrical appliances, construction, and other industries.

4.3 Industry chain integration and competitiveness enhancement: 

Deep processing helps enterprises realize upstream and downstream integration of the industrial chain, reduce dependence on external markets, and enhance market competitiveness. By extending to the downstream, enterprises can not only obtain higher profits, but also better resist the risks brought about by fluctuations in raw material prices, and occupy market share through continuous innovation and development of new products.

4.4 Efficient utilization of resources:

Through deep processing, enterprises can make fuller use of silicone raw materials, improve the output value of the final products produced by the unit weight or volume of silicone monomer, promote the effective use of resources, and maximize economic benefits.

4.5 Environmental protection and sustainable development:

Highly developed deep processing technology can reduce the generation of waste and improve the waste recycling rate, which is conducive to the realization of green production and circular economy, responding to the industrial policy of sustainable development and social responsibility.

In summary, deep processing is an important way for the silicone industry to enhance its competitiveness, and adapt to changes in market demand and technological progress.

5. What is the deep processing of silicone?

5.1 What is the main direction of deep processing of silicone?

(1) Silicone oil and its modified products:

Silicone oil is an important branch of silicone deep processing, including different viscosity grades of linear or cyclic silicone oil, as well as special modifications to adapt to a variety of uses, such as for cosmetics and personal care products, textile finishing agents, lubricants, mold release agents, defoamers and so on.

(2) Silicone rubber:

Deep processing of silicone rubber includes room-temperature vulcanized silicone rubber (RTV) and high-temperature vulcanized silicone rubber (HTV), which are used in many fields such as wire and cable insulations, automotive parts, building seals, medical products, kitchenware, and so on. Through the formula design and processing technology improvement, it can develop heat-resistant, cold-resistant, aging-resistant, weather-resistant, and electrical insulation properties of special silicone rubber products.

(3) Silicone resin:

Silicone resin deep processing involves a variety of crosslinking cured coatings, potting adhesive, insulating varnish, and high-temperature resistant materials. These products are widely used in the electrical and electronic industry, aviation and cosmic materials, anti-corrosion coatings, and other fields.

(4) Silane coupling agent:

As a key additive to improve the interfacial bonding between inorganic and organic materials, silane coupling agent has important applications in composites, coatings, adhesives, filler treatment, and so on.

(5) Functional silanes and other intermediates:

Functional silanes include a series of compounds that can enhance the performance of materials, such as waterproof and moisture-proof agents, surfactants, viscosity enhancers, and so on. In addition, there are a series of silicone intermediates synthesized for specific applications.

(6) High-performance thermal management materials:

With the growth in demand for heat dissipation in new energy vehicles, electronic devices, and other fields, the development and production of silicone thermal management materials has become a major direction, such as thermally conductive silicone grease, thermally conductive gaskets, phase change materials and so on.

(7) Biomedical materials.

In the field of biomedicine, silicone is used in the manufacture of medical implants, drug carriers, tissue engineering scaffolds, etc. due to its good biocompatibility and stability.

(8) Environmentally friendly silicone products:

For the increasingly stringent environmental regulations, research, and development of low VOC emissions, easy-to-recycle, biodegradable green silicone products have become an important development direction.

In short, the deep processing of silicone is committed to improving the technological content and added value of products, expanding new areas of application, and the continuous pursuit of lower environmental impact of the production process and technological innovation.

5.2 What is the common equipment for deep processing of silicone?

(1) Precision mixing equipment:

As silicone materials in the deep processing process require precise control of raw material ratios and mixing uniformity, it requires the use of efficient and precise mixing machines, such as high shear dispersers, powerful dispersers, double planetary mixers, and so on.

(2) Reactor and reactor:

According to different synthesis routes and reaction conditions, reaction kettles of different volumes, and materials and with heating and cooling functions capable of withstanding high-pressure or vacuum operation may be required. For continuous production processes, a continuous reactor system may also be involved.

(3) Distillation columns and separation devices:

In the purification of silicone monomers and a variety of intermediates, the preparation of finished products, a distillation tower is used to achieve effective separation and purification of compounds, to ensure that product quality meets the requirements of specific indicators.

(4) Grinding and crushing equipment:

For composite materials containing fillers or pigments, high-speed dispersers, sand mills, and other equipment are needed for grinding and crushing processing, so that the material to achieve the ideal particle size distribution and dispersion state.

(5) Vulcanization and curing equipment:

For silicone rubber products, it is necessary to equip the corresponding vulcanization equipment (such as a plate vulcanizing machine, injection vulcanizing machine, etc.) to achieve the crosslinking reaction and molding of silicone rubber materials.

(6) Potting and encapsulation equipment:

For the potting and sealing protection of electronic components, it is necessary to use an automated potting and sealing machine for accurate and fast potting and sealing operations.

(7) Testing and quality control equipment:

Including a viscometer, hardness tester, electrical properties tester, thermal analyzer (such as DSC, TGA), etc., which are used for real-time monitoring and final inspection of the physical properties of the product, chemical properties thermal stability, and other indicators.

(8) Environmental treatment facilities:

Environmentally friendly production facilities include exhaust gas purification equipment (e.g. RTO/RCO), wastewater treatment facilities, and solid waste collection and disposal systems to ensure that the entire production process complies with strict environmental regulations and standards.

(9) Automated control system:

Highly automated control systems can ensure that the production process of temperature, pressure, mixing speed, and other parameters are stable and controllable, and also improve production efficiency, and reduce product quality problems caused by human factors.

In short, silicone deep processing equipment not only requires a high degree of professionalism and technical adaptability but also needs to strictly comply with the relevant provisions of production safety and environmental protection, while focusing on the reliability and durability of the equipment to ensure the continued stability of production and economic benefits.

5.3 Chinese market prospects for silicone deep-processed products.

(1) Favorable policies:

The states encourage and introduce the development of new silicone deep-processing products while restricting and eliminating backward silicone upstream monomer production capacity, China's silicone industry outlook is promising.

(2) Application expansion:

Silicone deep-processing applications, especially the application of high-tech products continue to expand, 5G communications, new energy, consumer electronics, and other emerging industries show a booming development trend. The rapid popularization and replacement of end-user products and supporting infrastructure have greatly driven the upstream of the industrial chain silicone product demand growth.

(3) Consumption upgrading:

Along with the improvement of national income level and the generalization of consumption upgrading, consumer demand for daily necessities is more diversified, especially the pursuit of higher-quality products and services for female consumers, with "her economy" as the main market cosmetic enterprises continue to innovate their products and consumption concepts. It continuously stimulated the growth of demand for female cosmetic products and also brought the increment of silicone products in the upper reaches of the industry chain.

(4) Increase in industrial concentration:

In recent years, with the guidance of the national industrial policy, environmental protection policies, and the tightening of the market competition over the years, China's silicone industry becomes more and more concentrated. The industry's large-scale enterprises obtaining a larger and larger market share, while a number of small and medium-sized enterprises that raw materials and high energy consumption, environmental protection investment is not enough, serious pollution and the backward production capacity is gradually eliminated, the entire industrial structure of the silicone industry has been significantly improved and optimized.

5.4 What are the common silicone deep-processing products?

(1) Silicone rubber: It is mainly used in the production of seals, insulating materials, buttons, protective gear, etc..

(2) Silicone oil: It is used to make lubricants, defoamers, mold release agents, cosmetics and so on.

(3) Silicone resin: It is used to make insulating paints, coatings, adhesives, encapsulation materials, and so on.

(4) Silane coupling agent: It is used to improve the adhesion, water resistance, and heat resistance of materials.

(5) Silane cross-linking agent: It is used to improve the heat resistance, mechanical properties, and electrical properties of materials.

(6) Silane gas: It is used in chip manufacturing, solar cell production, LED encapsulation, etc.

(7) Silane flame retardant: It is used to improve the flame retardant properties of materials.

(8) Silane antioxidants: It is used to improve the antioxidant properties of materials.

(9) Silane biocides: It is used for sterilization and disinfection.

(10) Silane light stabilizer: It is used to improve the light stability of the material.

With the continuous development of science and technology, the types of silicone deep-processing products will continue to increase.

5.5 How about the trend of high performance of silicone deep processing products?

(1) High-temperature performance enhancement: By improving the molecular structure and adding additives, etc., to improve the stability and reliability of silicone products in high-temperature environments.

(2) Enhanced weather resistance: Using special additives and protective measures so that silicone products can better resist the effects of ultraviolet rays, oxidation, and other factors to extend the service life.

(3) Optimization of mechanical properties: Enhancing the hardness, strength, elasticity, and other mechanical properties of silicone products to meet the needs of more demanding applications.

(4) Improvement of electrical properties: To improve the insulating properties of silicone products, electrical conductivity, and other electrical properties for adapting to the development of electronics, electrical and other fields.

(5) Optical performance improvement: Improving the transparency of silicone products, refractive index, and other optical indicators to meet the requirements of optical devices, display technology, and other fields.

(6) Improvement of biocompatibility: Making silicone products safer and more affinity for human tissue, applied to the field of biomedical science, such as medical devices, implant materials, etc.

(7) Optimization of environmental performance: Developing more environmentally friendly silicone products to reduce the impact on the environment, in line with the requirements of green development.

(8) Multi-functional integration: The integration of a variety of properties into a silicone product can achieve a multi-purpose material, and improve the added value of the product.

(9) Intelligent development: Combined with sensors, intelligent materials, and other technologies, silicone products have self-diagnosis, self-repair, and other intelligent functions.

(10) Customized production: According to the specific needs of customers, providing personalized silicone deep-processing products to meet special applications in different areas.

These trends reflect the market demand for high-performance silicone deep-processing products, companies need to continue to innovate research and development to meet the changing market demand. With the progress of science and technology and the expansion of application areas, the trend of high performance of silicone deep-processed products will also continue to develop and evolve.

5.6 The impact of the high performance of silicone deep processing products on the market competition pattern:

(1) Product differentiation:

High-performance products to meet customer demand for special performance, so that enterprises can launch differentiated products differentiated from competitors to increase market competitiveness.

(2) Increase value-added:

High-performance silicone deep-processing products usually have higher added value, which helps enterprises improve profit levels, thereby gaining a greater advantage in market competition.

(3) Expand application areas:

With the improvement of product performance, its application areas may be further expanded, bringing new market opportunities for enterprises.

(4) Increased technical barriers:

High-performance requires companies to have more advanced technology and R&D capabilities, which will increase the technical barriers for new entrants, and help existing companies to maintain a competitive advantage.

(5) Competition for market share:


Customers are usually more inclined to choose products with better performance, so high-performance products are likely to help companies compete for market share and change the pattern of market competition.

(6) Driving innovation and R&D:

In order to stand out in the competition of high performance, enterprises need to continuously increase R&D investment and promote technological innovation, thus enhancing the technological level of the whole industry.

(7) Cooperation and alliance:

Enterprises may need to cooperate with universities, research institutions, etc., to conduct joint R&D and technological innovation to meet market demand for high-performance products.

(8) Accelerating industry integration:

High performance may lead to increased market competition, and some enterprises with weaker technical strength may be eliminated or acquired, thus accelerating the process of industry integration.

Changes in the pattern of market competition are affected by a variety of factors, including market demand, price, brand, and marketing strategy. Enterprises need to consider these factors comprehensively and continuously improve their strengths to adapt to market changes and succeed in competition. The government and industry organizations should also provide a good innovation environment to promote the healthy development of the silicone deep processing industry.

6. How to make the silicone industry more environmentally friendly?

6.1 What are the environmental impacts of the silicone production process? 

(1) Air pollution:

The synthesis process of silicone production produces a large number of organic waste gases, including unreacted raw materials, by-products, and high-temperature cracking of hydrogen chloride and other harmful gases. If not effectively treated exhaust gas directly discharged into the atmosphere, will cause serious pollution of air quality and may be harmful to human health and the surrounding ecological environment.

(2) Water pollution:

During the preparation of siliconE monomers (such as Methyl Chlorosilane) and the processing of subsequent products, wastewater containing organic and inorganic substances will be generated. Pollutants in the wastewater include salts, silicates, organosilicon compounds, catalyst residues, etc. If discharged directly without proper treatment, it will pose a threat to surface water, groundwater, and aquatic ecosystems.

(3) Solid waste:

The silicone production process will produce a certain amount of solid waste, including dust, waste residue, waste catalysts, and so on. If not reasonably disposed of solid wastes, not only occupy land resources but may also lead to soil quality degradation and the accumulation of heavy metals and other harmful substances.

(4) Occupational health risks:

People working in silicone production workshops for a long time may suffer from occupational diseases such as silicosis due to inhalation of silica dust or contact with harmful chemical substances.

(5) Ecological impact:

Some organosilicon products and their degradation products may have toxic effects on sensitive aquatic populations, affecting the aquatic ecological balance.

In order to mitigate the negative impact of the silicone industry on the environment, enterprises are usually required to adopt advanced clean production and environmental protection technologies, strictly comply with relevant environmental regulations, ensure that exhaust gas, wastewater, and solid waste are properly treated and recycled, and improve the environmental performance of the entire industrial chain through the continuous research and development of low-toxicity, easy-to-degradable and environmentally friendly silicone materials. At the same time, the state and local authorities have also formulated a series of strict environmental standards and emission control requirements to regulate the environmental behavior of the organosilicon industry.

6.2 What are the main pollutants in the wastewater of the silicone industry chain?

(1) Organic substances:

Including Benzene, Toluene, Xylene, Ethanol, Butanol, Chlorosilanes, etc. These are organic solvents and by-products produced during the synthesis of silicone monomers and the subsequent production of resins, rubbers, and other products.

(2) Polymers:

Such as silicone oil, silicone rubber, silicone resin, silicone intermediates, etc. These are the main components of silicone materials and may enter the wastewater during the cleaning reaction equipment or product processing stage.

(3) Inorganic substances:

Including hydrochloric acid, sulfuric acid, sodium hydroxide, and other strong acids and strong bases, which are used as a reaction medium or neutralizer residue in the wastewater.

(4) Heavy metal ions:

Certain processes may involve heavy metal catalysts or other heavy metal-containing raw materials, and their residues in wastewater will increase the toxicity of wastewater.

(5) Chlorides and other salts:

Since silicone compounds usually contain chlorine elements, the wastewater contains high salt content, mainly chloride salts.

(6) Surfactants and additives:

All kinds of surfactants and other auxiliary additives used in the production process of silicone products may also be present in the wastewater.

(7) COD (Chemical Oxygen Demand):

Silicone wastewater has high COD characteristics, meaning that the wastewater can be oxidized and decomposed by the extremely high content of organic substances, causing serious pollution of the water environment.

(8) pH instability:

Silicone wastewater is often acidic and needs to be neutralized in order to meet the discharge standards.

(9) Suspended solids (SS):

Including particulate silica powder, raw materials that are not fully reacted, and sludge produced in the flocculation and precipitation process.

Silicone wastewater treatment poses a challenge to wastewater treatment because it contains complex and difficult-to-degrade silicone compounds. The following are some common methods for silicone wastewater treatment:

(1) Physical method:

Mixing and flocculation precipitation: By adding flocculants (such as polymerized aluminum chloride, polyacrylamide, etc.) to make the particles in the wastewater aggregate and sediment.  Filtration: including deep filtration, membrane filtration, and other ways to remove suspended and partially dissolved substances. Solid-liquid separation: such as filter-pressing technology to dewater the sludge after flocculation.

(2) Chemical method:

Iron and carbon micro-electrolysis: using iron and carbon fillers to form a primary cell under acidic conditions, generating Fe2+ ions to catalyze the oxidation of organic pollutants. Fenton reagent oxidation: the use of H2O2 in the Fe2+ catalyzed by the generation of hydroxyl radicals, advanced oxidation of silicone compounds in wastewater. Chemical coagulation: add specific chemicals to promote the wastewater organosilicon substances to form flocs that are easy to precipitate.

(3) Biological method:

Anaerobic biological treatment: anaerobic bacteria decompose part of the organic matter to improve the biochemistry of wastewater. Aerobic biological treatment: using activated sludge or biofilm process, utilizing microorganisms to degrade the biodegradable components in organosilicon wastewater.  Two-stage or multi-stage biochemical treatment: through multi-stage aerobic and anaerobic reaction to gradually degrade organic matter.

(4) Advanced oxidation technology: Ozone-catalyzed oxidation: Using ozone combined with catalyst to enhance oxidation capacity and destroy the molecular structure of organosilicon. Electrochemical oxidation: direct or indirect oxidation of silicone pollutants in wastewater on the electrode surface.

(5) Evaporation and condensation recovery method:

Evaporation and concentration: evaporation of water in the wastewater by heating, leaving a high concentration of silicone components for subsequent treatment or resource recovery. Evaporation condenser: makes the volatile pollutants and salts in the wastewater can be separated while improving the biochemistry of wastewater.


(6) Other combined processes:

According to the characteristics of wastewater, the design of pretreatment, main treatment, and deep treatment combined with a comprehensive treatment program, such as physical and chemical pretreatment to reduce toxicity, and then biochemical treatment, and finally supplemented by advanced oxidation technology to further reduce COD.

These methods can be used individually, or flexibly combined into a variety of processes according to the characteristics of wastewater and emission standards, in order to achieve effective treatment of organosilicon wastewater and discharge standards and to recover valuable resources as far as possible.

6.3 What about the main treatment difficulties of silicone wastewater?

(1) Difficult to degrade:

Silicone compounds are mainly based on silicon-oxygen bonding as the main chain structure, this stable covalent bond makes organosilicon molecules have strong chemical stability, and are not easily decomposed by the general biological or chemical oxidation process.

(2) High concentration of organic matter:

Silicone production wastewater contains a large number of silicone intermediates, Alcohols (such as Methanol, and Ethanol), silicone resins, silicone oil, and other components, resulting in its COD (Chemical Oxygen Demand) and BOD (Biochemical Oxygen Demand) usually high, far exceeding the design capacity of conventional wastewater treatment plants.

(3) Toxicity and inhibition:

Some of the silicone substances may have toxic or inhibitory effects on microorganisms, reducing the activity of the biochemical treatment system and affecting the efficiency of the anaerobic and aerobic biological treatment processes.

(4) Existence of heavy metal ions:

The wastewater generated from the monomer synthesis process may contain heavy metal ions such as copper, zinc, etc. These heavy metals are not only harmful to the environment but also may form complexes that are difficult to precipitate and separate during the treatment process, which increases the complexity of wastewater treatment.

(5) Strong acidity and alkalinity:

Silicone wastewater often shows strong acidity or alkalinity, which needs to be neutralized and pre-treated in order to meet the requirements of the subsequent treatment process.

(6) Large sludge production and processing difficulties:

Chemical precipitation, iron and carbon microelectrolysis, and other methods will produce a large number of sludge containing heavy metals or other hazardous substances, this part of the sludge is hazardous waste, with high treatment costs and strict environmental requirements.

(7) Low resource recovery rate:

Due to the complex composition of silicone wastewater, and the current technical means to achieve an effective removal of pollutants at the same time, it is often difficult to efficiently recover the valuable components.

In summary, in the treatment of silicone wastewater, high technical requirements, complex treatment processes, and high operating costs, and for the existing treatment facilities and technologies, achieving high standards of discharge requirements is a challenge. Therefore, the development of new treatment technologies and processes that are efficient, economical, and environmentally friendly has become an important research direction in this field.

6.4 What are the waste gas pollutants in silicone production?

(1) Hydrogen chloride (HCl):

In the silicone monomer production process, metal silicon and Methylene Chloride reactions to generate Methyl Chlorosilane will produce a large amount of hydrogen chloride exhaust gas.

(2) Chlorosilanes:

Including various Methyl Chlorosilanes, chloromethane, and other chlorine-containing silicon compounds, etc., which may be volatilized or leaked into the atmosphere during the synthesis and treatment process.

(3) Dust:

Silica dust is generated by unorganized emissions of silica dust during processing and conveying, as well as other solid particulate matter.

(4) Acid gases:

In addition to hydrogen chloride, this may contain other acid gases such as hydrogen fluoride (HF) and sulfur dioxide (SO2).

(5) Volatile organic compounds (VOCs):

For example, organic solvents such as methanol, ethanol, xylene, and some low molecular weight organosilicon compounds, may escape in the form of vapors in the high-temperature reaction or post-treatment stage.

(6) Flammable and explosive gases:

Such as methyl dichlorosilane, methyl trichlorosilane, etc. These compounds are not only harmful to the environment but also have a high risk of fire and explosion.

(7) Nitrogen oxides (NOx):

Nitrogen oxide emissions may occur in certain high-temperature process segments.

In order to reduce the impact of these pollutants on the environment, silicone producers usually use high-efficiency exhaust gas collection systems with corresponding purification facilities for treatment, such as condensation, absorption and neutralization, adsorption, combustion (RTO/RCO), and other technologies to remove the harmful components of the exhaust gas.

6.5 What are the solid wastes generated by silicone and how to treat?

(1) By-products and residues:

A certain amount of solid by-products, such as reaction residues and filtration residues, may be generated during the production of organosilicon. These residues usually contain raw materials that have not been fully reacted, catalysts, and useless by-products generated by the reaction, and can be treated by the methods described in the patent, such as extracting valuable components such as silica powder and copper powder from them by acid solubilization.

(2) Waste catalyst:

Certain catalysts used in the silicone synthesis process become spent catalysts after use and need to be recycled or safely disposed of through specific technologies.

(3) Wastewater treatment sludge:

Sludge generated after the wastewater treatment process (e.g., physical and chemical pretreatment, biochemical treatment, etc.) may contain heavy metals, organic matter, and other hazardous substances, which need to be dewatered and stabilized and selected for landfill, incineration or resource utilization according to its nature.

(4) Equipment cleaning waste:

Waste generated during the cleaning and maintenance of production equipment may contain silicone oils, solvents, and other mixed pollutants, which need to be collected and targeted for purification and treatment.

(5) Waste packaging materials:

Including containers with raw materials or finished products, should follow the principle of circular economy, as far as possible, classification and recycling, and reuse.

Comprehensive treatment of silicone solid waste methods and technologies may include:

(1) Resource utilization: as mentioned above, silicon powder and metal are extracted from the waste residue and converted into marketable products.

(2) Thermal treatment: For the parts that are not suitable for recycling, they can be reduced by high-temperature incineration, and part of the incineration process can achieve energy recovery.

(3) Curing/stabilization: Wastes containing strong toxicity and easy to migrate are cured to reduce their environmental risks.

(4) Safe landfill: For residual solid waste that cannot be effectively resourced or treated, it must be disposed of in a safe landfill that meets the standards in accordance with the requirements of relevant environmental regulations.

(5) regeneration process: the development of new regeneration technologies and processes, solid waste into raw materials or energy that can re-enter the industrial chain cycle.

Overall, the solid waste treatment in the silicone industry chain emphasizes the principles of minimization, resource utilization, and harmlessness, and strives to improve economic efficiency while protecting the environment.

6.6 Silicone enterprises need to be equipped with environmental protection equipment:

(1) Waste gas treatment equipment:

 Exhaust gas scrubbing tower: It is used to remove hydrogen chloride, acidic gases, organic volatile organic compounds (VOCs), and other harmful gases generated during the production process.

Activated carbon adsorption device: To adsorb toxic and harmful substances in organic waste gas.

RTO/RCO (Regenerative Thermal Oxidizer/Catalytic Combustion Device): Highly efficient thermal decomposition of high-concentration organic waste gas.

 Dust collector: Such as a bag filter or electric dust collector to capture the dust in the production process.

(2) Wastewater treatment facilities:

 Pre-treatment system: Including grills, sedimentation tanks, conditioning tanks, etc., to preliminarily separate suspended matter and large particles of impurities in the wastewater.

 Chemical reaction tank: It is used to neutralize the acidity and alkalinity of wastewater, as well as flocculation, coagulation, and precipitation treatment of wastewater containing organic matter and heavy metal ions.

 Biological treatment unit: Such as activated sludge method, biofilm method, and other biochemical treatment facilities, using microorganisms to degrade organic pollutants in wastewater.

 Deep treatment systems: Such as advanced oxidation technology (AOP), reverse osmosis (RO), electrodialysis (ED), ultrafiltration (UF), and other processes, to further reduce the concentration of hazardous substances in wastewater to the discharge standard.

 Water Reuse Facilities: After multi-stage treatment and purification, part of the wastewater will be recycled and reused in the production process or other non-drinking water uses.

(3) Solid waste disposal facilities:

 Solid Waste Collection and Classification System: Including temporary storage areas and classification facilities for solid waste.

 Hazardous Waste Incinerator: For solid wastes that contain toxic and hazardous components and cannot be resourced, incineration technology is used for harmless treatment.

 Curing/stabilization unit: Stabilization of specific hazardous wastes to reduce their mobility and toxicity.

 Waste catalyst regeneration or safe landfill facilities: For special solid wastes such as waste catalysts, appropriate means are adopted for regeneration and utilization or safe landfill in accordance with regulations.

(4) Noise control facilities:

Soundproof enclosure or silencer: Installed on the production equipment that generates large noise to reduce noise pollution.

(5) Environmental monitoring system:

 Online monitoring equipment: Real-time monitoring of pollutant concentrations at the waste gas and wastewater discharge outlets to ensure that emissions meet standards.

 Laboratory analyzing instruments: Regularly take samples to test the content of various pollutants in wastewater, waste gas, and solid waste to meet the requirements of environmental protection supervision.

(6) Energy saving and emission reduction equipment:

Waste heat recovery system: Utilize the waste heat generated during the production process to improve energy utilization and reduce greenhouse gas emissions.

Silicone industry chain enterprises must be based on their own production process characteristics and environmental policy requirements, a reasonable allocation of various types of environmental protection facilities, to ensure that the entire production process achieves the "three wastes" (waste gas, wastewater, solid waste) effective management and compliance emissions. Also need to actively implement cleaner production and circular economy concepts, and improve resource utilization, and environmental management