Methylene chloride

Dichloromethane (CH2Cl2), molecular weight 84.93. Colorless transparent liquid with pungent odor similar to ether. Insoluble in water, soluble in ethanol and ether. Is incombustible low boiling point solvent, commonly used to replace flammable petroleum ether, ether, etc.

On October 27, 2017, the world health organization's international agency for research on cancer released a preliminary list of carcinogens for reference, dichloromethane in the 2A list of carcinogens.

Chinese name

Methylene chloride

The English name

Dichloromethane (Methylene chloride)

Don't say

DCM

Chemical formula

CH2Cl2

The molecular weight

84.93

The CAS login no.

The 75-09-2

EINECS no. Login

200-838-9

Melting point

- 97 ° C

Boiling point

39.75 ℃ at 760 mm Hg

Water soluble

Does not dissolve in water

Dense degree of

1.325 g/mL at 25 °C(lit.)

Outside view

Colorless transparent volatile liquid

Should be used

Industrial raw materials

Security description

Specific target organ toxicity

Hazard description

Prolonged heating gives off poisonous gases

Transport number of dangerous goods

UN 6.1 1593 / PG 3

Hazard class code

Xn, T, F

Safety instructions

S23 - S24/25 - S36/37 - S45 - S16 - S7

Heat of evaporation

28.82 kJ/mol (25℃)

Upper explosion limit %V/V

19

Lower explosion limit %V/V

12

define

Methylene chloride; A brace of chlorine; Methyl chloride; Methylene dichloride; Methylene chloride; Dichloromethane; Dichloromethane; Methylene chloride

DEBLOCKING REAGENT; DEBLOCK REAGENT; DEBLOCK - TCA REAGENT; DETRITYLATING REAGENT; TRICHLOROACETIC ACID/DICHLOROMETHANE; TRICHLOROACETIC ACID IN DICHLOROMETHANE; Aerothene MM; CH2Cl2

The CAS number: 75-09-2

EINECS no. : 200-838-9

Mol file: 75-09-2 Mol

Numbering system

MDL number: MFCD00000881

EINECS no. : 200-838-9

RTECS number: PA8050000

BRN number: 1730800

Physical properties

The physical and chemical constant

1. Properties: colorless and transparent liquid with aromatic smell.

2. Melting point (℃) : -97

3. Boiling point (℃) : 39.8

4. Relative density (water =1) : 1.33

5. Relative vapor density (air =1) : 2.93

6. Saturated vapor pressure (kPa) : 46.5 (20℃)

7. Heat of combustion (kJ/mol) : -604.9

8. Critical temperature (℃) : 237

9. Critical pressure (MPa) : 6.08

10. Octanol/water partition factor: 1.25

11. Flash point (℃) : no, but can form combustible steam/air mixture at more than 100℃

12. Ignition temperature (℃) : 556

13. Upper explosion limit (%) : 23

14. Lower explosion limit (%) : 13

15. Solubility: slightly soluble in water, soluble in ethanol and ether.

16. Viscosity (mPa·s,20 ° C) : 0.425

17. Relative density (25℃, 4℃) : 1.3162

18. Ignition point (° C) : 662

19. Heat of evaporation (KJ/mol,b.p.) : 329.5

20. Melting heat (KJ/mol) : 4.187

Heat of formation (KJ/mol,25 ° C, liquid) : 121.54

Heat of combustion (KJ/kg,25 ° C, liquid) : 558.27

Specific heat capacity (KJ/(kg·K),20 ° C) : 0.992

Conductivity (S/m,25 ° C)

Vapor pressure (kPa,0 ° C) : 19.3

Vapor pressure (kPa,10 ° C) : 30.6

Vapor pressure (kPa,20 ° C) : 46.5

28. Vapor pressure (kPa,30 ° C) : 68.2

29. Vapor pressure (kPa,35 ° C) : 80.00

30. Volume expansion coefficient (10~40 ° C, liquid) : 0.00137

31. Normal temperature refractive index (n25) : 1.4213

32. Eccentricity factor: 0.192

33. Lennard-jones parameter (A) : 9.951

34. Lennard-jones parameter (K) : 150.5

35. Solubility parameter 0.5:20.378

36. Van der Waals area:

37. Van der Waals volume: 34.710

38. Claimed heat (enthalpy) of the gas phase standard: -95.4

39. Standard gas phase entropy: 270.44

40. Standard free energy of gas phase formation: -68.8

41. Gas phase standard hot melt: 50.88

42. The liquid phase standard claims heat (enthalpy) : -124.26

43. Liquid phase standard entropy: 178.7

44. Liquid phase standard free energy of formation: -70.42

45. Liquid phase standard hot melt: 100.0

Molecular structure data

1. Molar refractive index: 16.38

2. Molar volume (m3/mol) : 67.8

3. Isotonic specific volume (90.2k) : 148.8

4. Surface tension (dyne/cm) : 23.1

5. Polarization rate: 6.49

Chemical properties

The stability of

A compound formed by the substitution of two hydrogen atoms in a molecule of methane with chlorine. Dichloromethane is a colorless, transparent, heavier than water, volatile liquid with an ether-like odor and sweet taste that does not burn, but mixes with a high concentration of oxygen to form an explosive mixture. Dichloromethane is slightly soluble in water, and most commonly used organic solvents, and other chlorine-containing solvents, ether, ethanol can also be miscible in any proportion. Dichloromethane can be quickly dissolved in phenols, aldehydes, ketones, glacial acetic acid, triethyl phosphate, formamide, cyclohexylamine, acetoacetate. Pure methylene chloride without flash point, methylene chloride and gasoline containing such as volume, solvent naphtha or toluene solvent mixtures is non-flammable, however, when the methylene chloride and acetone or methanol liquid to 10:1, mixing ratio, the mixture has a flash point, vapor and air form explosive mixture, explosion limit of 6.2% ~ 15.0% (volume). Dichloromethane is the least toxic methane chloride, and its toxicity is only 0.11% of that of carbon tetrachloride. If it hits the eye directly, it can be painful and corrosive. The vapors of dichloromethane are anesthetic. When there is a serious risk of poisoning, immediately remove from contact and move to fresh air. Some symptoms of poisoning will be relieved or disappear without causing lasting damage.

Toxicological data

Toxicity: transoral toxicity is moderate.

Acute toxicity: LD501600 ~ 2000mg/kg(rats via mouth); LC5056.2 g/m3, 8 h (mouse inhalation); Mice inhaled 67.4 g/m3 ×67 min, resulting in death. 20 ~ 50ml, mild poisoning; 100 ~ 150ml of human oral passage was fatal; People inhaled 2.9 ~ 4.0 g/m3 and became dizzy 20 minutes later.

Subacute and chronic toxicity: rats inhaled 4.69 g/m3, 8 h/d, 75 days, no pathological changes. Exposure time increased with mild hepatic atrophy, steatosis, and cell infiltration.

Mutagenesis: microbe mutagenesis: salmonella typhimurium 5700ppm. DNA inhibition: human fibroblast at 5000ppm/ h (continuous).

Reproductive toxicity: the rats inhaled the lowest toxic concentration (TCL0) of 1250ppm (7 hours, 6-15 days of gestation), causing musculoskeletal dysplasia and abnormal development of the urogenital system.

Carcinogenicity: IARC carcinogenicity review: animal positive, unclear in humans. Animal experimental data and human epidemiological data are insufficient on whether patients should consider dichloromethane as a carcinogen in animals and humans. However, given the current findings in inhalation studies in rats and mice, and the data available after the task force meeting, dichloromethane should be considered as a potential carcinogen to humans.

Environmental behavior

Dangerous properties: high heat in open flame. Decomposition by heat can produce a highly toxic phosgene. In case of high heat, the pressure inside the vessel increases, and there is a risk of cracking and explosion.

Combustion (decomposition) products: carbon monoxide, carbon dioxide, hydrogen chloride, phosgene.

Environmental impacts:

1. Manmade sources of dichloromethane can be put into the atmosphere by the following means: propellant for sprayers, paint remover, metal degreaser.

2. Air circulation: dichloromethane enters the atmosphere and reacts with hydroxyl radicals to decompose, with a half-life of several months.

3. Biological decomposability: methylene chloride in the case of sufficient oxygen, and the sludge of Sewage (seed) or activated sludge reaction, between 6 hours to 7 days will be completely biodegradable.

4. Although there is no experimental data on bioconcentration, it can be inferred that there is no bioconcentration of dichloromethane due to its low octanol and water distribution coefficient.

5. The Henry's law constant for volatile dichloromethane from water/soil is high, and it evaporates rapidly and steadily from water, with a half-life time of 3-5.6 hours.

The stability of

1. The toxicity is very small, and the recovery after poisoning is fast, so it can be used as anesthetic. Irritant to skin and mucous membrane. Transoral LD50:1.6mL/kg in young adult rats. Maximum permissible air concentration of 500×10-6. The operation should wear gas masks, found poisoning immediately after leaving the scene, symptomatic treatment. The smallest of the chlorides of methane. The anesthesitic sex of steam is strong, inhale can cause acute poisoning in large quantities, appear the symptom such as nasal ache, headache, vomiting. Chronic poisoning can cause dizziness, fatigue, loss of appetite, impaired hematopoietic function, reduced red blood cells. Liquid dichloromethane causes dermatitis in contact with the skin. The rats died after inhaling 90.5g/m3 of vapor for 90 minutes. The olfactory threshold concentration was 522mg/m3, and the maximum permissible workplace concentration was 1740mg/m3.

2. Stability: stability.

3. Forbidden substances: alkali metal, aluminum.

4. Conditions to avoid contact: light, moist air.

5. Polymerization hazard: no polymerization.

6. Decomposition products: hydrogen chloride, phosgene.

Pyrolysis produces HCl and trace phosphorescence, which are heated with water for a long time to form formaldehyde and HCl. Further chlorination leads to CHCl3 and CCl4. Colorless volatile liquid that burns. Methylene chloride reacts with sodium hydroxide at high temperature to form formaldehyde. In industry, dichloromethane is prepared by reaction of natural gas and chlorine gas, and obtained by rectification. It is an excellent organic solvent, commonly used to replace flammable petroleum ether, ether, etc., and can be used as dental local anesthetic, refrigerant and extinguishing agent, etc. The irritation to the skin and mucous membrane is slightly stronger than chloroform.

Stability: under normal temperature (normal temperature) without moisture, dichloromethane than its peers (chloroform and carbon tetrachloride) stable.

Hazard decomposition: long-term contact with water will slowly decompose to produce hydrogen chloride.

Aggregation of hazards: does not occur.

Reactivity and incompatibility:

1. Common metals: allow a little decomposition at room temperature. Alkaline earth metals, zinc and their compounds do not form grigard reagent at low temperature, but they are easy to form carbin reagent at high temperature.

2. The mixture of dichloromethane and nitrous oxide is explosive when shaken by the equivalent of 25 grams of dynamite or less.

3. Mixed with lithium debris, it is sensitive to shocks and can explode, sometimes quite violently.

4. Explosive mixtures are formed in a variety of conditions where oxygen is present in high concentrations in the air, in liquid oxygen, and in potassium, sodium, and potassium-sodium alloys in nitrogen tetroxide.

5. Nitric acid: formation of explosive products.

6. Strong oxidant: may react explosively.

7. Strong acid: may react explosively.

8. Iron, some stainless steels, copper and nickel: corrosion of these metals at high temperatures and in the presence of water.

9. Aluminum powder: at the right pressure, 95℃ will produce an uncontrollable exothermic reaction.

10. Amines: exothermic reactions.

11. React violently with the following compounds: amines, lithium, nitric acid, sodium potassium.

12. The top layers of plastic, rubber, and some paint break down.

13. It is possible to accumulate electrostatic charges and cause a steam explosion.

use

Dichloromethane has the advantages of strong solubility and low toxicity. It is widely used in the manufacture of safe film film and polycarbonate, and the rest is used as paint solvent, metal degreaser, gas smoke spray agent, polyurethane foaming agent, mold release agent and paint removal agent.

As a colorless liquid, dichloromethane is used as a reaction medium in the pharmaceutical industry to prepare ampicillin, oxybenzacillin and pioneer mycin. It is also used as solvent for film production, solvent for petroleum dewaxing, aerosol propellant, organic synthetic extraction agent, foaming agent and metal cleaning agent for polyurethane and other foams.

Dichloromethane is mainly used in film production and medicine in China. Among them, the consumption of film production accounts for 50% of the total consumption, 20% of the total consumption of medicine, 20% of the total consumption of cleaning agents and chemical industry, and 10% of the other aspects. Dichloromethane is also used as a refrigerant in industrial refrigeration systems, but can be very harmful, producing a highly toxic phosphorescent when in contact with open fires or hot objects. When wet air hydrolyze to produce trace hydrogen chloride, light can also promote hydrolysis and enhance the corrosion of metal.

Used for grain fumigation and refrigeration of low pressure refrigerator and air conditioner. It is used as an auxiliary foaming agent in the production of polyether urethane foams and as a foaming agent for extruding polysulfone foams.

Dichloromethane is also used to make decaffeinated coffee. The coffee is steamed so that the caffeine dissolves and floats to the surface. Dichloromethane is then used to remove the caffeine.

The preparation of

Method: 1. Natural gas reaction with chlorine gas, after hydrogen chloride by-product hydrochloric acid is absorbed by water, residual trace hydrogen chloride is removed with alkali solution, and then dried, compressed, condensed and distilled to obtain the finished product, in which chlorine gas is 100% 4000, natural gas (under standard conditions), methane content 97% 1000m3/t, liquid alkali 100% 274.

2. Chlorinated methane reacts with chlorine gas under 4000kW light to produce dichloromethane, which is washed by alkali, spoiled, condensed, dried and rectified. The main by-product is trichloromethane. Chloromethane ≥98% 746, liquid chlorine ≥99.5% 854, caustic soda 30% 221.

Industry is generally synthesized by chlorination of methane. Chlorination of methane produces a mixture that includes four chloromethane compounds, but because the boiling points are separated at large distances, they can be easily separated and purified by ordinary fractionation techniques.

Matters needing attention

Environmental hazards

The substance may be harmful to the environment and accumulate in groundwater. Particular attention should be paid to aquatic life. Attention should also be paid to the pollution of the atmosphere.

Health hazard

Invasion: inhalation, ingestion, percutaneous absorption.

Health hazard: this product has the anesthetic effect, mainly damages the central nervous system and the respiratory system. The main route of human contact is inhalation. It has been measured that high concentrations of dichloromethane exist in indoor production environments when dichloromethane is used as paint remover. The general population is exposed to much lower doses through ambient air, drinking water and food. It is estimated that about 80% of the world's production of dichloromethane is released into the atmosphere, but the compound's rapid rate of photolysis makes it impossible for it to accumulate in the atmosphere. The initial degradation products are phosgene and carbon monoxide, which are converted into carbon dioxide and hydrochloric acid. When dichloromethane is present in surface water, much of it evaporates. In the presence of oxygen, it tends to biodegrade, so bioaccumulation seems unlikely. But its behavior in the soil still needs to be determined.

Health hazard effects:

Acute: 1. Slight irritation of the nose and throat.

2. 1 ~ 2 hours of 500 ~ 1,000 PPM may result in mild suppression of the central nervous system, such as dizziness, dizziness, nausea, numbness of hands and feet, fatigue, inability to concentrate and reduced coordination.

3. Very high exposure can cause loss of consciousness and death.

Skin: 1. Fluids irritate the skin.

2. Serious irritation may occur if it flows into gloves, shoes or tight clothing.

Eyes: 1. Fluid and high concentration of vapor may cause irritation.

2. Fluid may cause temporary irritation of the cornea.

Ingestion: 1. In animal studies, dichloromethane is rapidly absorbed into the body causing moderate toxicity with symptoms such as inhalation.

Chronic: 1. Inhalation: liver and kidney damage at very high concentrations. Repeated exposure to 500 to 3,600 PPM has also been reported to cause brain damage.

2. B. carcinogenicity: a third study found no increase in cancer in chronically exposed workers, but the IARC has labeled it a possible carcinogen.

Environmental standards

National occupational health standard of the People's Republic of China gbz2.1-2007 occupational exposure limits for hazardous chemical factors in the workplace

The time-weighted average permissible concentration of dichloromethane was pc-twa 200mg/m3.

Monitoring method

Portable gas chromatography; Water quality testing pipe method; Gas detection tube method

Gas tachometer tube (German delger products)

Laboratory monitoring methods:

Source categories of monitoring methods

Gas chromatography methods for determination of hazardous substances in air (second edition), hangzhou shiping edits air

Purge, trap and gas chromatography for water quality at China environmental monitoring station

Gas chromatography solid waste test and analysis evaluation manual, China environmental monitoring station

Analysis of organic compounds in urban and industrial wastewater by gas chromatography

EPA524.2 method for water quality

Environmental standards

The maximum permissible concentration of hazardous substances in the air of workshops in the former Soviet union is 50mg/m3

The maximum permissible concentration of hazardous substances in drinking water sources in China (to be promulgated) is 0.02mg/L

China's surface water environment quality standard (GHZB1-1999) (I), Ⅱ, Ⅲ waters 0.005 mg/L

Former Soviet union (1975) maximum permissible concentration of harmful substances in water is 7.5mg/L

Japan (1993) environmental standard (mg/L) surface water: 0.002

Waste water: 0.02

Soil leaching liquid: 0.002

Threshold olfactory concentration: 150ppm

The disposal method

Emergency treatment of leakage

Quickly evacuate the leakage contaminated area personnel to the safety zone, and isolation, strict access restrictions. Cut off the fire. It is recommended that emergency personnel wear self - contained positive pressure air breathing apparatus. And the use of sewers, drainage ditch and other restrictive space. Small leakage: adsorption or absorption by sand or other non-combustible materials. Large leakage: build a dike or pit.

Waste disposal method: incineration method is recommended. Waste mixed with other fuels to incinerate, combustion should be sufficient to prevent the formation of phosgene. Nitrogen oxides from the incinerator exhaust are removed by an acid scrubber.

Ii. Protective measures

Respiratory protection: direct gas mask (half mask) should be worn when the concentration in the air exceeds the limit. Wear an air breathing apparatus during emergency rescue or evacuation.

Eye protection: wear chemical safety glasses when necessary.

Body protection: wear protective clothing.

Hand protection: wear chemical-resistant gloves.

Others: smoking, eating and drinking are not allowed at work. Wash and change after work. Store contaminated clothes separately and wash them for later use. Pay attention to personal hygiene.

First aid measures

Skin contact: remove contaminated clothing and rinse thoroughly with soap and water.

Eye contact: lift eyelid and rinse with flowing water or normal saline. Go to a doctor.

Inhalation: quickly remove from site to fresh air. Keep respiratory tract open. If breathing becomes difficult, administer oxygen. If breathing stops, give artificial respiration immediately. Go to a doctor.

Ingestion: 1. Do not feed anything through the mouth if the patient is about to lose consciousness, has lost consciousness or has convulsion.

2. Do not induce vomiting.

3. Patients were given 250 ml of water to dilute their stomach contents.

4. If the patient vomits spontaneously, lean forward to reduce the risk of inhalation and repeatedly feed.

5. If breathing stops, the trained person is given artificial respiration and the heart stops performing CPR.

6. Get the patient to an emergency medical unit quickly. Drink plenty of warm water, induce vomiting and seek medical advice.

Most important symptoms and harmful effects: very high exposure may lead to loss of consciousness and death.

Protection for emergency personnel: when patients inhale and swallow toxic substances, do not directly use mouth-to-mouth resuscitation, but use one-way air feeding pocket mask and other medical equipment to perform artificial respiration. Wear grade C protective equipment to perform first aid in the safety zone.

Fire extinguishing method: mist water, sand, foam, carbon dioxide. Suitable fire extinguishing agent: chemical powder, foam, carbon dioxide, water mist

Special hazards that may be encountered when extinguishing a fire: 1. 2. Toxic gases can be broken down in a fire and are dangerous.

Special fire extinguishing procedures: 1. Spray water to cool the containers exposed to the fire, and spray water to flush the leakage away from the exposed area.

2. When such matter catches fire or is caught in fire: do not put out the fire unless you can stop its dispersal. If the fire is out of control or the container is exposed, an area within 2,500 feet must be evacuated.

3. cool the container with a large amount of water until the fire is extinguished. (erg2002)

4. Do not flush the spilled material directly, as splashes may occur (erg2002)

1. Post-combustion toxic products: post-combustion products include toxic gases and vapors (e.g. hydrogen chloride, phosphorescence and carbon monoxide).

2. The vapor of dichloromethane is heavier than air and can travel a considerable distance to reach the ignition source and burn back.

storage

Precautions for operation and storage

1. Avoid droplet formation during operation and wear appropriate personal protective equipment.

2. Avoid letting the released steam and fog droplets into the air of the work area.

3. Operate in a well ventilated area and minimize usage.

4. Emergency response equipment should be available at all times for extinguishing fires and dealing with spills.

5. Hazardous residues may remain in empty storage containers.

6. Do not operate near welds, flames or hot surfaces.

7. Store in a cool, dry, well-ventilated place without direct sunlight.

8. Storage should be away from heat source, flame and incompatible substances, such as strong oxidant, strong acid, nitric acid.

9. Store in properly labeled containers.

10. Unused containers and empty drums should be tightly covered.

11. Avoid damage to containers and check drums regularly for defects such as breakage or overflow.

12. Containers are galvanized or lined with Phenolic resins to reduce the likelihood of decomposition of dichloromethane.

13. Limited storage.

14. Post warning signs where appropriate.

15. The storage area should be separated from the working area with intensive staff, and the access to the area should be restricted.

16. Use plastic water pipes that are prescribed for substances to discharge poisons. (hazardtext)

17. The material may accumulate static electricity which may cause combustion. (hazardtext) 7. Store in a cool, dry, well ventilated and sunshine can't direct.

Packing storage and transportation: sealed packing with galvanized iron drum, 250kg per barrel, can be transported by train tanker or automobile. It should be stored in a cool, dark and dry place with good ventilation.

Products indicators

Leakage treatment method

Personal precautions: 1. Limit access to contaminated areas before they are completely cleaned.

2. Make sure the cleanup is carried out by trained personnel.

3. Wear appropriate personal protective equipment.

4. Ventilate the area.

5. Extinguish or remove all sources of ignition.

6. Report to government safety, health and environmental protection related units.

Environmental considerations:

1. In case of leakage, immediately isolate non-related personnel at least 25~50 feet away [erg2002]

2. In case of large leakage, people should be evacuated to the headwind 100 meters away. (erg2002)

2. Evacuate persons 800 meters away when fire breaks out [erg2002]

1. Don't touch the leakage.

2. Avoid leakage into sewers, drains or confined Spaces.

3. Try to prevent or reduce spills as safety permits.

4. Containment of the leaking material with sand, soil, or other absorbent material that does not react with the leaking material.

5. Small leakage: absorption by absorbing substances that do not react with exudates. Contaminated absorption and leakage of substances have the same hazards, must be placed in the appropriate containers covered and marked, with water to flush the overflow area. Small spills can be diluted with large amounts of water.

6. Large leakage: build a dike or dig a pit. Cover with foam to reduce vapor hazard. Transfer by pump to tanker or special collector, recycling or transport to waste disposal site for disposal.

7. Environmental considerations:

A. in the soil:

1. Dig a hole, pond, or lagoon to contain a liquid or solid substance.

2. Use polyurethane, sandbags and soil to cover the surface.

3. Dust the sky to absorb large quantities of liquid matter into powder. (HSDB)

B. the water:

1. Use natural barriers or oils to control the extent of contamination.

2. Then use water pipes to absorb the controlled substances.

3. Use mechanical excavators to remove areas beyond your control. (HSDB)