วันพุธที่ 8 มกราคม พ.ศ. 2557

Ethylene Glycol, เอทิลีนไกลคอล


MONO ETHYLENE GLYCOL, MEG, โมโนเอทิลีนไกลคอล, โมโนเอทธิลีนไกลคอล

ETHYLENE GLYCOL เอทิลีน ไกลคอล, เอทธิลีนไกลคอล

ประโยชน์/การใช้งาน

- ใช้เป็นตัวทำละลายสำหรับ cellulose ester และ ether โดยเฉพาะใน cellophane

- ใช้ในอุตสาหกรรมทำสีฉีดพลาสติก (emulsion paints) ผลิตเส้นใยโปลีเอสเทอร์ หมึกพิมพ์ กาวเครื่องหนัง ยาสูบ เครื่องสำอางบางชนิด

- ใช้เป็น coolant และ antifreeze

- เป็นส่วนประกอบใน brake fluids

- ใช้ในการเตรียม glycol diacatate

ETHYLENE GLYCOL นั้นมีจุดเดือดสูงกว่าน้ำถึงสองเท่าตัว(196 °C) ไม่มีสี ไม่มีกลิ่น ปัจจุบัน ETHYLENE GLYCOL ถูกทำให้จือจางลงใน ANTIFREEZE & COOLANT เพื่อให้เหมาะสมกับการใช้ในรถยนต์ โดยเฉพาะในรถยนต์ใหม่ ๆ ที่ออกมาจากโรงงานนั้น จะมีส่วนผสมของน้ำยานี้อยู่ถึง 50% นั่นหมายถึงถ้าหากว่าหม้อน้ำมีขนาดความจุประมาณ 5 ลิตรก็จะมีน้ำยาผสมมา 2.5 ลิตร โดยเจ้าน้ำยานี้หากผสมกับน้ำในอัตราส่วน 30:70 (ANTIFREEZE & COOLANT 30 %น้ำ 70%) จุดเดือดของน้ำจะเพิ่มขึ้นเป็น 120 องศาเลยทีเดียวอุตสาหกรรมส่วนใหญ่ที่ใช้ อาทิเช่น ใช้สำหรับอุตสาหกรรมสีและหมึกพิมพ์ อุตสาหกรรมน้ำมันเครื่อง ใช้เพื่อลดอุณหภูมิเครื่องจักร/เครื่องชิลเลอร์ ใช้เป็นวัตถุดิบหลักในการผลิต COOLANT(น้ำยาหล่อเย็น) และอื่นๆอีกหลากหลายอุตสาหกรรม

Ethylene glycol (IUPAC name: ethane-1,2-diol) is an organic compound primarily used as a raw material in the manufacture of polyester fibers and fabric industry, and polyethylene terephthalate resins (PET) used in bottling. A small percent is also used in industrial applications like antifreeze formulations and other industrial products. It is an odorless, colorless, syrupy, sweet-tasting liquid. Ethylene glycol is only weakly toxic, but cases of poisonings are not uncommon.

EG is primarily used as a raw material in the manufacture of polyester fibers and fabric industry, and polyethylene terephthalate resins (PET) used in bottling. A small percent is also used in other applications such antifreeze formulations and other products.

Coolant and heat transfer agent[edit]

The major use of ethylene glycol is as a medium for convective heat transfer in, for example, automobiles and liquid cooled computers. Ethylene glycol is also commonly used in chilled water air conditioning systems that place either the chiller or air handlers outside, or systems that must cool below the freezing temperature of water. In geothermal heating/cooling systems, ethylene glycol is the fluid that transports heat through the use of a geothermal heat pump. The ethylene glycol either gains energy from the source (lake, ocean, water well) or dissipates heat to the source, depending if the system is being used for heating or cooling.

Pure ethylene glycol has a specific heat capacity about one half that of water. So, while providing freeze protection and an increased boiling point, ethylene glycol lowers the specific heat capacity of water mixtures relative to pure water. A 50/50 mix by mass has a specific heat capacity of about 3140 J/kg C (0.75 BTU/lb F) three quarters that of pure water, thus requiring increased flow rates in same system comparisons with water. Additionally, the increase in boiling point over pure water inhibits nucleate boiling on heat transfer surfaces thus reducing heat transfer efficiency in some cases, such as gasoline engine cylinder walls. Therefore, pure ethylene glycol should not be used as an engine coolant in most cases.

Antifreeze[edit]

Ethylene glycol disrupts hydrogen bonding when dissolved in water. Pure ethylene glycol freezes at about 12 °C (10.4 °F), but when mixed with water, the mixture does not readily crystallize, and therefore the freezing point of the mixture is depressed. Specifically, a mixture of 60% ethylene glycol and 40% water freezes at 45 °C (49 °F). Diethylene glycol behaves similarly. It is used as a de-icing fluid for windshields and aircraft. The antifreeze capabilities of ethylene glycol have made it a component of vitrification (anticrystallization) mixtures for low-temperature preservation of biological tissues and organs.

Ethylene glycol freezing point vs. concentration in water

Weight percent EG (%)     Freezing point (°F)              Freezing point (°C)

0              32           0

10           25           4

20           20           7

30           5              15

40           10        23

50           30        34

60           55        48

70           60        51

80           50        45

90           20        29

100         10           12

However, the boiling point for aqueous ethylene glycol increases monotonically with increasing ethylene glycol percentage. Thus, the use of ethylene glycol not only depresses the freezing point, but also elevates the boiling point such that the operating range for the heat transfer fluid is broadened on both ends of the temperature scale. The increase in boiling temperature is due to pure ethylene glycol having a much higher boiling point and lower vapor pressure than pure water; there is no chemical stabilization against boiling of the liquid phase at intermediate compositions, as there is against freezing.

Ethylene glycol boiling point vs. concentration in water

Weight Percent EG (%)     Boiling Point (°F) Boiling Point (°C)

0              212         100

10           215         102

20           215         102

30           220         104

40           220         104

50           225         107

60           230         110

70           240         116

80           255         124

90           285         140

100         387         197

Monoethylene Glycol


Monoethylene glycol (MEG) is an important raw material for industrial applications. A primary use of MEG is in the manufacture of polyester (PET) resins, films and fibers. In addition, MEG is important in the production of antifreezes, coolants, aircraft anti-icer and deicers and solvents.


Applications for Monoethylene Glycol, Ethylene Glycol:

Polyester Resins

Antifreeze and Coolants

Gas Dehydration and Treating

Chemical Intermediates

Heat Transfer Fluids

Solvents

Other Applications

Polyester Resins

Ethylene glycols are used as a reactant in the manufacture of polyester resins. Dow produces ethylene glycols for use in polyester fiber, films and polyethylene terephthalate (PET) resin production, as well as alkyd resins used in paints. The uses for polyester resins are extremely varied, and include boat and marine, construction materials, automotive and aircraft bodies, luggage, furnishings, appliances, textiles and packaging.Polyester fibers are commonly found in textile applications including clothing and carpets.Polyester films are frequently used in packaging and wraps for consumer goods, as well as video, audio and computer tapes. PET is widely used in the manufacturing of beverage bottles and containers, and other consumer goods packaging.

Antifreeze and Coolants

Ethylene glycols remain viscous at low temperatures; they have a low freezing point and high boiling point. Ethylene glycols are frequently used to make automobile antifreeze and coolants, aircraft anti-icing and deicing materials.

Gas Dehydration & Treating

Ethylene glycols are commonly used in natural gas hydration and treating applications to remove water and impurities. Diethylene glycol (DEG), Triethylene glycol (TEG) and Tetraethylene glycol (TETRA EG) have excellent hygroscopicity and low volatility. Because of these characteristics, DEG, TEG and TETRA EG are in high demand in the natural gas drying market.

Chemical Intermediates

Ethylene glycols including monoethylene glycol (MEG), diethylene glycol (DEG), triethylene glycol (TEG) and tetraethylene glycol (TETRA EG), are versatile chemical intermediates used to produce a variety of products for commercial and industrial use:

Adhesives and coatings

Emulsifiers

Lubricants

Plasticizers

Polyurethane foams

Solvents

Silicone compounds

Thermoplastics

Unsaturated polyester resins

Heat Transfer Fluids

Monoethylene glycol (MEG), diethleyene glycol (DEG), triethylene glycol (TEG) and tetraethylene glycol (TETRA EG), due to their low freezing point, freezing point depressant and high boiling point are predominantly used in heat transfer fluids.

Solvents

Diethylene glycol (DEG), triethylene glycol (TEG) and tetraethylene glycol (TETRA EG) have excellent solvent properties. TEG and TETRA EG are used as solvents in several applications:

Aromatic and paraffinic hydrocarbons separations

Cleaning compounds

Cyanoacrylate and polyacrylonitrile

Polyethylene terephthalate (PET) production equipment cleaning

Steam-set printing inks

Other Applications

Triethylene glycol (TEG) and tetraethylene glycol (TETRA EG) may be used directly as a plasticizer or modified by esterification. As a plasticizer, TEG and TETRA EG are used in the manufacture of:

Safety glass

Separation membranes (silicone rubber, polyvinyl acetate, cellulose triacetate)

Ceramic materials (resistant refractory plastics, molded ceramics)

Demand for tetraethylene glycol is strong in the area of BTX (benzene, toluene, xylene) extraction to separate aromatic hydrocarbons from non-aromatic hydrocarbons.

Monoethylene glycol (MEG), diethylene glycol (DEG) are often used in water-based paints, dry-wall compounds, glass cleaners, dyes, waxes and adhesives as a freezing point depressor to avoid damage by low-temperature extremes.

In addition, monethylene glycol and diethylene glycol are also used as binders for foundry sand molding, and a lubricant for glass- and cement-grinding. In addition, both homologs are also used as humectants in textile fiber, paper, leather, adhesive and glue applications.

 

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