Formaldehyde

• Methanal
• Methylaldehyd
• Oxomethan
• Formylhydrat
• Ameisensäurealdehyd
• Ameisenaldehyd
• Formalin / formaldehyde ( 35 - to 37 - percent solution of formaldehyde with methanol as an anti- Polymerisationszusatz )

A colorless, pungent -smelling gas penetrating

Gaseous

0.82 g · cm -3 ( -20 ° C)

-117 ° C

-19 ° C

From 0.43 to 0.44 MPa ( 20 ° C)

Slightly soluble in water

Risk

0.3 ml · m -3; 0.37 mg · m-3

• 42 mg · kg -1 ( LD50, mouse, oral)
• 100 mg · kg -1 ( LD50, rat, oral)

-108.6 KJ / mol

Template: Infobox chemical / molecular formula search available

Formaldehyde [ fɔrm | aldehydes ː t even ... hy ː t ] is the common name for the chemical compound methanal, the simplest aldehyde. The IUPAC name methanal is derived from methane by appending the suffix - al for aldehydes from. The trivial name is derived from formaldehyde " formica " from the Latin word for ant, as methanal can be converted by oxidation into formic acid ( formic acid ). A polymer of formaldehyde is paraformaldehyde, which is used, inter alia, in cell biology.

History

The formaldehyde was discovered by Alexander Mikhailovich Butlerov 1855. The first technical presentation by dehydrogenation of methanol was realized by AW von Hofmann in 1867. With the discovery of urea resins and phenolic resins, the need for formaldehyde increased strongly from the beginning of the 20th century.

Occurrence

Formaldehyde is in the nature, for example in mammalian cells during normal metabolism as intermediate steps: In humans, about 50 grams per day in this way is formed and reduced. People breathe from about 0.001 to 0.01 mg/m3 formaldehyde, there is no significant difference in smokers or non-smokers. The blood of mammals constantly contains two to three milligrams of formaldehyde per liter. Further also formaldehyde created in the photo- oxidation in the atmosphere. Also found in fruits such as apples or grapes comes before formaldehyde naturally. Also comes before formaldehyde in wood and diffused in small quantities to the outside world.

Formaldehyde also develops in virtually all incomplete burns and other oxidation processes of longer- organic substances. In the tropical atmosphere, the mixing ratio of formaldehyde about 1 ppb, a major source is here the oxidation of methane.

Formaldehyde is also one of those compounds that could be detected by radio astronomy in space.

Formaldehyde is a starting material for the production of various plastics, such as DPN and POM. In the combustion of POM, it is released as a product of combustion again.

Production and representation

Technically formaldehyde is obtained by catalytic oxidation of methanol:

Two processes have prevailed in essence, that differ essentially in the nature of the catalyst:

• Metalloxidverfahren: Certain metal oxides are used as catalyst.

Both methods have different advantages and disadvantages. Thus a change of the catalyst, for example, much more frequently necessary in the silver process, on the other hand, it can be relatively easily reactivated by the plant operator. Metalloxidverfahren with the production of urea -formaldehyde concentrate ( UFC) is easier possible and the aqueous formaldehyde solution in the silver method is of higher quality ( lower content of formic acid).

The reaction is exothermic - that is, the corresponding hot gas mixture has to be cooled quickly in order to avoid side reactions, so that the heat of reaction can be used for the generation of superheated steam.

The resulting formaldehyde gas was then extracted in " scrubbers " means water, or a urea solution, wherein an aqueous formaldehyde solution or a urea -formaldehyde concentrate is produced. The resulting solutions contain in addition to unreacted methanol and small amounts ( about 100-300 ppm ) of formic acid ( HCOOH ).

The annual world production of formaldehyde was t in 2007 about 21 million; of which about 4 million tonnes produced in the EU alone.

Properties

Physical Properties

Formaldehyde is a colorless, pungent -smelling substance which is gaseous at room temperature. As gas its odor is perceptible at concentrations of 0.05-1 ml/m3.

Chemical Properties

Formaldehyde is very soluble in water. In aqueous solution, an aldehyde hydrate ( Methandiol ), wherein the equilibrium of this reaction - almost 100% on the side of the hydrate - unlike eg ethanal. The hydrate is slightly acidic ( pKa 13.3 ).

Safety characteristics

Formaldehyde forms with air over a wide concentration range explosive mixtures. The explosive range is between 7 % by volume (87 g/m3) as the lower explosive limit ( LEL) and 73 vol% (910 g/m3) as the upper explosive limit ( UEL).

Toxic properties

Acute toxicity

Formaldehyde can cause allergies, skin, respiratory and eye irritation if used improperly. Acute life-threatening ( toxic pulmonary edema, pneumonia) is from a concentration of 30 ml / m³. In chronic exposure is carcinogenic and also affects memory, concentration and sleep.

Most poisonings do not occur by direct contact with formaldehyde on, but by drinking methanol in low-quality alcohol drinks. Here, the methanol in the body first converts to formaldehyde by alcohol, then quickly by aldehyde dehydrogenases in formic acid to. This is metabolized slowly and can lead to acidosis. Formaldehyde denatured even particularly easy retinal proteins, which can lead to blindness.

The therapeutic measures in a Formaldehydintoxikation are varied. When ingested (but not milk, which increases the rate of absorption! ) The administration of activated charcoal is appropriate. The treatment of acidosis occurs by a sodium bicarbonate infusion. A more detailed treatment can be carried out by administration of Hustensedativa, inhaled β -agonists, or inhaled glucocorticoids. By the action of formalin fumes ammonia to form hexamethylenetetramine is canceled.

Carcinogenic risk

Legally binding formaldehyde is classified in Annex VI to Regulation 2008/1272/EG on classification, labeling and packaging of substances and mixtures in Category 2: " suspected human carcinogens ." Formaldehyde has been shown shown carcinogenic effects in animal experiments with rats, but only at high concentrations from 6 ml/m3. In 2004, amended the International Agency for Research on Cancer ( IARC ) of the World Health Organization since 1995 the existing classification of formaldehyde from " suspected carcinogenic effects " to " carcinogenic to humans ". Carcinogenic, mutagenic or toxic for reproduction substances classified ( " CMR " ) are considered particularly dangerous and must be replaced by less dangerous substances. Background of the WHO classification is an epidemiological study that has demonstrated an increased mortality due to tumors of the nasopharynx in workers who were exposed to several years in the industry formaldehyde.

Through the WHO study, the Federal Institute for Risk Assessment (BfR ) felt compelled to assess the carcinogenic risks linked to formaldehyde. Since 2006, the BfR for the carcinogenicity of formaldehyde absorbed through the respiratory air provides the basis of the results of their own study is considered adequate. The effect was concentration-dependent: " at indoor air levels at or below 124 micrograms of formaldehyde per cubic meter is practically no carcinogenic effect is expected. Repeated, clear this value is exceeded health risks may exist. " A legally binding classification of formaldehyde as a carcinogen need not already done by the European Chemicals Agency.

In the U.S., formaldehyde in 1981 was initially classified in the second report on carcinogens with the suspicion of carcinogenicity in humans. Since June 2011, the U.S. Department of Health classifies formaldehyde as carcinogenic to humans, as the present studies, sufficiently prove this.

Limits

In the field of textiles ( clothing ) applies to voluntary testing for harmful substances in the context of a check seal (about Toxproof or Oeko-Tex 100) has a detection limit of 16 mg / kg (16 ppm). This is also the limit for baby clothing. For clothing worn close to 75 mg / kg for other textiles are 300 mg / kg. The allowable " limit " in Germany is 1500 mg / kg (1500 ppm). This is not a real limit, as only the following declaration must be stated (quote BedGgstV ( Bedarfsgegenständeverordnung ) ): Textiles with a matter content of more than 0.15 percent of free formaldehyde that come with the intended use with skin contact and with are provided an equipment must be marked: " Contains formaldehyde. It is recommended that you wash the garment for better skin compatibility before you wear it. "

1977 recommended the Federal Health Office a benchmark for the indoor air of a maximum of 0.1 ppm formaldehyde. The Federal Institute for Risk Assessment ( BfR) has held in 2006 on the basis of his study on cancer -producing effect no change in the threshold necessary. Members of the Indoor Air Hygiene Commission of the Federal Environment Agency and representatives of the Association of supreme state health authorities said 2006 to BfR in the retention of the limit.

The legally binding occupational exposure limit of 0.62 mg/m3 of the Technical Rule 900 or 0.5 ml/m3 was suspended in 2006 following the revision of the Technical Rule for adaptation to the new Ordinance on Hazardous Substances. Transition, the value for the maximum allowable concentration of 0.3 ml/m3 is accordingly called 0.37 mg/m3 in safety data sheets, which is not legally binding and by the German Research Foundation (DFG) is recommended. Its application also recommends the BG Institute for Occupational Safety and Health ( IFA ). The work program 2009-2012 of the Committee for Hazardous Substances of the German Federal Institute for Occupational Safety and Health ( BAuA) the legally binding occupational exposure limit of Technical Rule 900 is still for processing (as of: November 11, 2012). Editing is done in the Subcommittee III " hazardous material review" chaired by Dr. Gisela strop (Bayer Schering Pharma AG, since 2011 Bayer HealthCare Pharmaceuticals ).

Use

Formaldehyde is one of the most important organic raw materials in the chemical industry and serves as the starting material for many other chemical compounds. BASF alone has an annual production capacity of about 500,000 tonnes of formaldehyde; in the EU, around 4 million tonnes in 2007, about 21 million tonnes were produced worldwide.

In the laboratory, formaldehyde is used, among others, in the context of the Mannich reaction and the Blanc reaction. Since formaldehyde as all aldehydes is a strong reducing agent, it was formerly used for destroying germs ( Formalintabletten ). Formaldehyde is among other things used in the production of dyes, pharmaceuticals and textile finishing ( " wrinkle-free "). In the early 1960s, the proportion of free formaldehyde ( from amino ) over two percent of the textile goods weight and reached its maximum value at this time. Today must textiles that come with the intended use in contact with skin and contain more than 0.15 percent free formaldehyde and are marked as follows: " Contains formaldehyde. It is recommended that you wash the garment for better skin compatibility before you wear it. ". However, compliance with this requirement in the responsibility of the consumer is.

In cosmetics, formaldehyde is used as a preservative, which is considered problematic because of the skin irritation potential of the substance. In Germany, about twelve percent of the cosmetics are preserved with formaldehyde donors currently. As in the EC formaldehyde must be declared by the manufacturers of cosmetics or hair washing and the fabric has a bad reputation, is increasingly being waived.

Formaldehyde is used as an adjuvant in vaccines, such as in Havrix 1440 against hepatitis A.

Polymerized as Thermoplastic polyoxymethylene (POM -H).

Together with Phenol formaldehyde condenses to a phenol resin, such as bakelite.

Formaldehyde reacts with urea to form urea -formaldehyde resins (UF - resins), melamine to melamine -formaldehyde resins (MF- resins), both of which belong to the aminoplast.

As 4-8 % formaldehyde solution (formalin), it is used as a common fixative in Histology. It is a protein cross-linking, an additive Fixans. It stops autolysis and putrefaction of ( medical ) tissue samples and makes it durable. The penetration rate is specified at 1 mm / h (rule of thumb ). The rate of crosslinking is significantly slower than the primary attachment of formaldehyde (at least 2-3 days for adequate fixation ). It methylene bridges and bridges are in this case formed by Schiff bases. The attachment may be by (long ) washing in water or exposed to hot buffer solutions of different pH values ​​be reversed ( antigen retrieval ). Methylene bridges to be stable.

Furthermore, such a formaldehyde solution is used for body preservation, as well as for the preservation of anatomical and biological preparations, such as insects ( proposed in 1893 by Isaac Blum). As such pickled material is durable for years, it can easily be used as reference material or of intuition in medicine and biology for research and educational purposes. Also for artistic purposes it is employed. Preserved British artist Damien Hirst a shark in formaldehyde. Because of the health hazards posed by formaldehyde but now often resort to other preservatives such as ethanol or isopropyl alcohol.

In surface disinfectants, formaldehyde is still one of the most effective ingredients.

It is also used for the production of:

Sweeteners, binders, adhesives, textile auxiliaries, fertilizers, preservatives, foundry sand binders, ion exchange resins, casting resins, tannins, hardness additives, Vulkanisationszusatz, filling agents, fungicides, explosives, situ foams, self.

A television documentary reported 2012 on the smuggling of poultry meat made ​​in Europe to Nigeria in 2010; for the illegal transport this meat was prepared, regardless of the health risks with formalin, reported in an employee of the Church Development Service.

Emission sources

Certain formaldehyde-containing materials (among other wood materials, floor coverings, furniture and textiles) can cause in closed rooms by outgassing contamination of the air we breathe. In the eighties, in this context, particle board and plywood, for their manufacture amino resins were used as binders come under suspicion. However, there are the many today formaldehyde bonded wood materials and furniture are commercially available. On the other hand, the emissions were significantly reduced in the formaldehyde-based wood materials. Nevertheless, it still comes to exceedances in cots. The contaminant remediation formaldehyde- contaminated buildings but especially in older wooden prefabricated houses to be a big issue.

Another important source for the emission of formaldehyde are incomplete combustion processes running. These can be found for example in internal combustion engines of motor vehicles, in foundries and in the manufacture of plastic articles. Even when smoking occurs in this manner formaldehyde, which is not insignificant contribution to air pollution. In total smoke a single cigarette, there are about 0.02-0.1 mg formaldehyde.

The combustion of biogas, sewage and landfill gas in gas engines high formaldehyde concentrations are frequently measured. Thus, the emission levels meet the statutory limits, a post-treatment of the exhaust gas is usually required.

Another problem is the burning of wood in small furnaces, since the combustion occurs often incomplete due to irregular feeding or wet wood. In the end, these installations used in house operation formaldehyde concentrations of 50-100 mg · m- 3, which in the old federal states to a total emission of about 1000 tonnes per year added ( estimate for 1980). By comparison, the much more economical and cleaner working large industrial combustion plants for fuel gas, oil and coal in 1980 had a total emission of 50 tons per year.

An important natural source of emissions is the atmospheric oxidation of methane.

Proof

Proof of free or labile formaldehyde is possible with chromotropic by the chromotropic acid reaction. In addition, a detection with Methylbenzothiazolonhydrazon or fuchsin acid ( Schiff's reagent) is possible. Gaseous formaldehyde is also detected through its absorption spectroscopy in the near ultraviolet and in the infrared spectral range.

The European Pharmacopoeia leaves in the limit test for formaldehyde acetylacetone admit and compare the depth of the resulting staining with a reference.

For wood materials, there are different methods and standards for the quantitative determination of parameters, which ultimately can infer the emission potential or the "real " emission behavior:

• " Perforator method": Value in mg formaldehyde per 100 g of sample, see perforator (chemistry)
• Desiccator method: " Small " sample pieces give off formaldehyde in water, reported in mg / l
• " Chamber - methods ": Large plate samples are examined for their formaldehyde emission in a test chamber over a longer period, giving the pararosaniline: ppm 0.01 ppm = 0.0124 mg formaldehyde / m³ air = 12.4 ug formaldehyde / m³ room air, limit of 0.01 ppm

The determination is made in accordance with DIN EN ISO 14184-1:2011-12 (replacement for DIN 54260:1988-029 ), § 64 LFGB (former § 35 LMBG ) B 82.02-1 (free and releasable formaldehyde ) and DIN EN 717 - 1 ( wood materials, formaldehyde emission by the chamber method ), or in accordance with DIN EN 120 ( wood-based panels - Determination of formaldehyde content according to the perforator method ).

Disposal

The disposal as solvent with the waste code 070704 " other organic solvents, washing liquids and mother liquors " in tightly closed containers.

Trivia

Formaldehyde has 50-00-0 with the first and lowest in 1965 assigned CAS number.