Current use status of dimethyl phthalate

Introduction to dimethyl phthalate

Dimethyl phthalate (DMP) is a colorless, transparent and slightly yellow oily liquid with a slightly aromatic odor. Boiling point: 283.7°C. It is miscible with general organic solvents such as ethanol and ether, and is insoluble in water and petroleum ether. Dimethyl phthalate (PAEs), as an important chemical raw material, is widely used in industrial production such as plastics and rubber. Such substances have stable chemical properties, are persistent, accumulative, and difficult to degrade naturally.

Source of dimethyl phthalate

Dimethyl phthalate exists in in air, water and soil. Dimethyl phthalate in air, water and soil mainly comes from human production activities.

Phthalates in the air Dimethyl ester mainly comes from spray coatings, incineration of waste plastics, volatilization of plasticizers in various plastic products (such as agricultural films), production waste gas emissions, and combustion of domestic heating fuels. Wang Lixin et al.’s research on indoor phthalates in my country shows that: my country’s indoor dimethyl phthalate (DMP), diethyl phthalate (DEP) and di(2-ethylhexyl phthalate) ) ester (DEHP) concentration (gas phase, particle phase and dust fall) is significantly higher than that in developed countries. DMP content in winter is greater than in summer, and DMP mainly comes from coal burning. Many similar studies in other regions of the country and different regions abroad have also obtained similar results, indicating that DMP is ubiquitous in the air and is a very common air pollutant.

Dimethyl phthalate in soil mainly comes from agricultural chemicals (agricultural mulch films, fertilizers and agricultural urban sludge, etc.) and irrigation water. According to reports, the annual consumption of plastic films nationwide It exceeds 1.1 million tons, and the amount of agricultural film residue in farmland soil can reach up to 43.9kg hm. The soil agricultural film residue not only causes the degradation of soil physical and chemical functions, but also releases a large amount of phthalate esters, causing the soil to be contaminated by phthalate esters. Some farmland soils in my country have been contaminated by DMP to a certain extent, and the content is mostly in the order of mg kg^-1.

Dimethyl phthalate in water bodies mainly comes from surface water and groundwater (Especially the collection of industrial wastewater, solid waste accumulation, rainwater leaching and slow leaching release of PVC plastics are the main sources of PAES in the water environment. Gao Xu et al. studied the changes in PAEs in conventional drinking water. The contents of dimethyl phthalate, diethyl phthalate, diisobutyl phthalate, and dioctyl phthalate in the source water were respectively 3.78, 5.48, 218.55, 130.72ng·L-1, while their contents in the factory water are 2.47, 3.69, 139.20, 108.25ng·L^-1 respectively. Due to the low vapor pressure of phthalate esters (PAEs), their volatilization loss in water is very small, and DMP entering the water environment is difficult to migrate and transform into the atmospheric environment.

phthalateApplication of dimethyl ester

Dimethyl phthalate is extremely widely used. It is a plasticizer with strong solubility for a variety of resins. It is compatible with a variety of cellulose resins, rubber, and vinyl resins, and has good properties. Membrane, adhesive and waterproof. It is often used in conjunction with diethyl phthalate (DEP) in the production of cellulose acetate films, varnishes, transparent papers and molding powders. A small amount is used in the production of nitrocellulose. It can also be used as a plasticizer for nitrile rubber. Adding it to polymers that require plasticization can increase the plasticity of the polymer. Usually they do not react chemically with polymers, and their interaction with polymers is mainly swelling at elevated temperatures, forming a solid solution with the polymers. The main function of plasticizer is to weaken the secondary bonds between polymer molecules, that is, van der Waals forces, thereby increasing the mobility of the polymer molecular chain and reducing the crystallinity of the polymer molecular chain, that is, increasing the plasticity of the polymer. , manifested as a decrease in the hardness, modulus, softening temperature and brittleness temperature of the polymer, while an increase in elongation, flexibility and flexibility.

Dimethyl phthalate Current status of the use of esters

Plasticizers are the most commonly used additives in plastics, among which dimethyl phthalate is currently the most widely used. Plasticizers account for about 70% of all plasticizer consumption, and the annual consumption in China alone is nearly one million tons. Although dimethyl phthalate is not the most commonly used plasticizer among phthalate esters (PAEs), the raw material for the production of dimethyl phthalate (phthalic anhydride) is very cheap and Easy to obtain. Therefore, the use of dimethyl phthalate in my country is still very large.