ДИМЕТИЛТЕРЕФТАЛАТ

Описание

Dimethyl terephthalate (DMT) is an organic compound with the formula C₆H₄(CO₂CH₃)₂. It is the diester formed from terephthalic acid and methanol. It is a white solid that melts to give a distillable colourless liquid.

Химические свойства

The empirical formula of dimethyl terephthalate (DMT) is C10H10O4. Its structural formula is 1,4-(COOCH3)2C6H4. At room temperature, exists as colorless crystals. DMT is soluble in ether and chloroform, slightly soluble in ethanol, and fairly insoluble in water (<1 g/L at 13℃).

Использование

Dimethyl terephthalate is used in the production of polyesters, including polyethylene terephthalate (PET) and poly trimethylene terephthalate. It consists of benzene substituted with carboxy methyl groups (CO₂CH₃) at the 1 and 4 positions. Because DMT is volatile, it is an intermediate in some schemes for the recyclic of PET, e.g. from plastic bottles.
Hydrogenation of DMT affords the diol cyclohexanedimethanol, which is a useful monomer.

Определение

ChEBI: Dimethyl terephthalate is a diester resulting from the formal condensation of the carboxy groups of terephthalic acid with methanol. It is a primary ingredient widely used in the manufacture of polyesters and industrial plastics. It is a methyl ester, a diester and a phthalate ester. It derives from a terephthalic acid.

Подготовка

Several processes have been developed for the preparation of dimethyl terephthalate from p-xylene, but the most important proceeds as follows:

The oxidation steps are carried out in the liquid phase at about 170??C and 1.5 MPa (15 atmospheres) in the presence of a cobalt acetate or naphthenate catalyst whilst the esterifications are conducted at about 150??C. Dimethyl terephthalate may also be produced by esterification of terephthalic acid.

Методы производства

Dimethyl terephthalate (DMT) has been produced in a number of ways. Conventionally and still of commercial value is the direct esterification of terephthalic acid. Alternatively, it can be prepared by alternating oxidation and methyl-esterification steps from p-xylene via methyl-p-toluate.

Общее описание

Dimethyl terephthalate appears as white solid or heated colorless liquid. Has no odor. Liquid solidifies in cool water. Solid and liquid sink in water. (USCG, 1999)

Реакции воздуха и воды

When mixed with air, the vapor or dust forms very hazardous and highly reactive mixtures. . Insoluble in water.

Профиль реактивности

DIMETHYL TEREPHTHALATE is an ester. Esters react with acids to liberate heat along with alcohols and acids. Strong oxidizing acids may cause a vigorous reaction that is sufficiently exothermic to ignite the reaction products. Heat is also generated by the interaction of esters with caustic solutions. Flammable hydrogen is generated by mixing esters with alkali metals and hydrides. Can generate electrostatic charges. [Handling Chemicals Safely 1980. p. 250]. DIMETHYL TEREPHTHALATE is sensitive to heat. The molten material reacts with water due to the temperature. DIMETHYL TEREPHTHALATE is incompatible with strong oxidizers, strong acids and strong bases.

Угроза здоровью

Molten DMT will cause severe burns of skin on contact.

Пожароопасность

DIMETHYL TEREPHTHALATE is combustible.

Профиль безопасности

Moderately toxic by intraperitoneal route. Mdly toxic by ingestion. An eye irritant. Mutation data reported. When heated to decomposition it emits acrid smoke and irritating fumes

Канцерогенность

In a study conducted by the NCI, DMT was not considered to be carcinogenic in rats or mice ingesting 2500 or 5000 ppm in the diet for 103 weeks.

Источник

Dimethyl terephthalate is a natural product found in Hypotrachyna nepalensis, Uncaria elliptica, and other organisms with data available.

Методы очистки

Purify it by recrystallisation from aqueous EtOH, MeOH or CCl4; or by zone melting. [Beilstein 6 H 843, 6 III 4250, 6 IV 3303.] .