[Chemical Knowledge]：The nature, use, upstream and downstream raw materials, storage methods of polymeric MDI, what is polymeric MDI

Polymeric MDI Properties

Polymeric MDI (polymeric diphenylmethane diisocyanate) is an important chemical raw material, usually brown liquid or solid. Its chemical structure contains multiple diisocyanate groups, which makes it have high reactivity. Polymeric MDI is stable at room temperature, but it is easily decomposed at high temperature, releasing toxic cyanate ester gas. It has a density of about 1.2g/cm³ and a boiling point above 200°C. It is insoluble in water, but soluble in many organic solvents such as benzene, toluene and chloroform.

Polymeric MDI Uses

Polymeric MDI is widely used in the polyurethane industry, mainly for the manufacture of rigid foams. These foam materials are widely used in construction, refrigeration equipment, pipeline insulation and other fields because of their excellent thermal insulation performance. Polymeric MDI is also used in the production of elastomers, coatings, adhesives and sealants. Its reactivity allows it to undergo cross-linking reactions with a variety of polyols to form polymeric materials with different properties.

Upstream raw materials

The production of polymeric MDI relies primarily on aniline and formaldehyde. Aniline reacts with phosgene in a phosgenation unit to give chlorinated phenylformyl chloride and then with methylamine to give diphenylmethane diisocyanate (MDI). Solvents such as toluene and benzene are also used in the production process, and the by-products produced in the reaction process need to be separated and treated. Phosgene is a highly toxic gas, and its use and treatment need to be strictly controlled to ensure the safety of the production process.

Downstream Products

The downstream products of polymeric MDI are mainly polyurethane foams. Rigid foam plastics have excellent thermal insulation properties and are widely used in building thermal insulation materials, such as wall thermal insulation boards, roof thermal insulation layers, etc. Flexible foam plastics are used in furniture, mattresses, car seats, etc. Other downstream products include polyurethane elastomers for the manufacture of high-strength materials, polyurethane coatings for surface coatings, and various industrial and civil adhesives and sealants.

Production process

The production process of polymeric MDI includes the phosgenation of aniline, the synthesis of diisocyanates, and the polymerization reaction. The chlorinated phenylformyl chloride is formed by reaction of aniline with phosgene, followed by reaction with methylamine to form the MDI monomer. By controlling the reaction conditions (e. g., temperature, pressure, reaction time), the MDI monomers are polymerized to form polymeric MDI. In the production process, it is necessary to precisely control the reaction parameters to ensure the quality and purity of the products, and at the same time, to deal with the by-products and wastes, and to reduce environmental pollution.

storage method

Polymeric MDI requires high storage conditions and should be stored in a cool, dry, well-ventilated place to avoid direct sunlight and high temperature environments. Its storage container needs to be well sealed, usually using metal or plastic drums for packaging. Because polymeric MDI is toxic and corrosive, operators are required to wear protective equipment such as gloves, goggles and gas masks when exposed. The warehouse needs to be equipped with emergency treatment equipment, such as ventilation equipment and fire extinguishers, to prevent accidental leakage and fire accidents.

market demand

With the rapid development of the global construction industry and the automotive industry, the demand for polyurethane materials is increasing, which in turn is driving the expansion of the polymeric MDI market. In particular, the implementation of green buildings and energy-saving emission reduction policies has led to a strong market demand for high-performance insulation materials. The demand for polyurethane materials in the field of household and electronic appliances is also increasing, which has brought broad market prospects for the polymeric MDI industry.

future development trend

In the future, the polymeric MDI industry will develop in the direction of green, environmental protection and high efficiency. The development of new MDI products with low toxicity and low volatility will become a trend to reduce the harm to the environment and human body. Improving the production process, reducing energy consumption and material consumption, and improving product yield and quality are also important directions for the development of the industry. With the progress of science and technology, the research of bio-based raw materials to replace some petrochemical raw materials is also gradually advancing, and it is expected to achieve a more environmentally friendly mode of production in the future.

Safety and environmental protection

There are certain safety and environmental risks in the production and use of polymeric MDI. Phosgene and aniline used in the production process are toxic substances, and their leakage and discharge need to be strictly controlled. The waste gas, waste liquid and waste residue generated in the production process should be properly treated to avoid environmental pollution. Users should also be careful when using polymeric MDI to avoid skin contact and inhalation of its vapors. Strengthening safety management and environmental protection measures to ensure safety and environmental protection during production and use is an important issue for the development of the industry.

Summary

As an important chemical raw material, polymeric MDI has a wide range of applications and market demand. Its production and use process must be strictly controlled to ensure safety and environmental protection. In the future, with the progress of science and technology and the change of market demand, the polymeric MDI industry will continue to develop in the direction of green, efficient and environmental protection, and open up broader application prospects. By continuously optimizing the production process and product performance, polymeric MDI will bring more convenience and innovation to modern industry and daily life.