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◉ Formaldehyde Introduction
Formaldehyde is an organic chemical substance, the chemical formula is HCHO or CH₂O [1] , the molecular weight is 30.03 [2] , also known as formic. It is a colorless and irritating gas, which is irritating to human eyes and nose. The relative density of gas is 1.067 (air=1), and the density of liquid is 0.815g/cm³ (-20℃). Melting point -92°C, boiling point -19.5°C. Soluble in water and ethanol. The concentration of the aqueous solution can reach up to 55%, generally 35%-40%, usually 37%, called formalin, commonly known as formalin.
It has reducibility, especially in alkaline solution, the reducing ability is stronger. Can burn, steam and air form explosive mixture, the explosion limit is 7%-73% (volume), and the ignition point is about 300 ℃.
It can be obtained by dehydrogenation or oxidation of methanol under the catalysis of metals such as silver and copper, and it can also be separated from the oxidation products of hydrocarbons. It can be used as raw material for phenolic resin, urea-formaldehyde resin, vinylon, urotropine, pentaerythritol, dyes, pesticides and disinfectants. Industrial methanol solution generally contains 37% formaldehyde and 15% methanol as a polymerization inhibitor, with a boiling point of 101 °C.
On October 27, 2017, in the list of carcinogens published by the World Health Organization's International Agency for Research on Cancer, formaldehyde was included in the list of a class of carcinogens. On July 23, 2019, formaldehyde was included in the list of toxic and hazardous water pollutants (the first batch).
◉ Application Field
(1) Chemical raw materials
1) Adhesive
Adhesive is the most important consumption area of formaldehyde in my country, and its consumption accounts for the largest proportion, accounting for about 40% of the total consumption. The main adhesive products produced are urea-formaldehyde resin adhesive, phenolic resin adhesive and melamine-formaldehyde resin adhesive, which are mainly used as treatment agents for wood processing, molding compounds, coatings, textiles and paper. Among them, the adhesive used for wood processing accounts for about 80% of the total adhesive. In 2007 and 2008, the output was 3.135 million tons and 3.448 million tons, and the output continued to grow and the application fields continued to expand. According to incomplete statistics, there are currently more than 3,500 adhesive and sealant manufacturers in my country, but there are less than 100 large-scale enterprises with more than 3,000 varieties and brands. In terms of application, plywood and woodworking use the largest amount of glue, accounting for about 46.97% of the total glue, building material adhesives account for 26.12%, packaging and trademark adhesives account for about 12.14%, shoemaking and leather adhesives account for 6.07%, The usage of other adhesives accounted for 8.7%.
2) POM
The demand for POM (polyoxymethylene) in my country has grown quite rapidly. In 2004, the market demand for polyoxymethylene in China has exceeded the total demand in Western Europe, becoming the world's largest POM-demanding country. Engineering plastics with excellent comprehensive properties will further increase the demand for polyoxymethylene.
3) Paraformaldehyde
Paraformaldehyde is the main raw material for the production of herbicides glyphosate, acetochlor, butachlor, oxacamine, etc. and pesticides such as tricyclazole. In addition, paraformaldehyde also shows great potential in replacing industrial formaldehyde. Some pharmaceutical, paint and resin companies have successfully replaced industrial formaldehyde with low degree of polymerization paraformaldehyde, and have achieved good results. For a long time, due to insufficient domestic paraformaldehyde production technology and unstable product quality, there has been no large-scale production capacity, unable to meet domestic consumer demand, and 60% still rely on imports.
4) MDI
MDI (diphenylmethane diisocyanate) is one of the main raw materials for the production of polyurethane products, and is widely used in the production of PU (polyurethane) rigid foam products. As an essential raw material in leather production, MDI can strengthen leather Because of its softness and good simulation effect, its products have the dual advantages of plastic and rubber, and it has become one of the rapidly developing polymer synthetic materials in the world.
(2) Textile industry
In the production of clothing fabrics, in order to achieve anti-wrinkle, anti-shrinkage, flame retardant and other effects, or to maintain the durability of printing and dyeing, or to improve the hand feel, it is necessary to add formaldehyde to the auxiliaries. The use of formaldehyde printing and dyeing auxiliaries is mostly pure cotton textiles, because pure cotton textiles are prone to wrinkling, and the use of formaldehyde-containing auxiliaries can improve the stiffness of cotton fabrics. Formaldehyde-containing textiles will gradually release free formaldehyde when people wear and use them, causing respiratory inflammation and skin inflammation through human respiratory tract and skin contact, as well as eye irritation. Formaldehyde can cause allergies and cancer. Manufacturers use formaldehyde-containing dyeing auxiliaries, especially some manufacturers use cheap auxiliaries with extremely high formaldehyde content in order to reduce costs, which is very harmful to human body.
(3) Preservative solution
35% to 40% formaldehyde solution, commonly known as formalin, has antiseptic and bactericidal properties, and can be used to soak biological specimens, sterilize seeds, etc., but it is easy to make the specimens brittle due to protein denaturation. The main reason for the antiseptic and bactericidal properties of formaldehyde is that formaldehyde can react with the amino groups that constitute the protein of the organism.
◉ Harm
(1) Acute toxicity
Acute poisoning of formaldehyde is manifested as an irritating effect on the skin and mucous membranes. Inhalation of high concentrations of formaldehyde can cause respiratory irritation symptoms, sneezing, coughing and a burning sensation in the nose and throat; in addition, it can also induce bronchial asthma, pneumonia, and pulmonary edema. A large amount of formaldehyde ingested through the digestive tract at one time can cause symptoms of gastrointestinal and systemic toxicity, corrosive burns in the mouth, throat and digestive tract, abdominal pain, convulsions, and death. Skin contact with formaldehyde can cause allergic dermatitis, pigmentation, skin necrosis and other lesions. Oral ingestion of 10~20ml of formaldehyde solution can cause death.
In animal experiments, the LD50 of formaldehyde ingested orally in rats is 800 mg/kg, the LD50 of formaldehyde absorbed by rabbits through skin is 2700 mg/kg, and the LD50 of formaldehyde inhaled by rats through respiratory tract is 590 mg/m3.
(2) Chronic toxicity
Long-term exposure to formaldehyde can reduce the body's respiratory function, the information integration function of the nervous system, and affect the body's immune response. It also has toxic effects on the cardiovascular system, endocrine system, digestive system, reproductive system, and kidneys. Systemic symptoms include headache, fatigue, anorexia, palpitations, insomnia, weight loss, and autonomic disorders. Animal experiments also confirmed the pathological changes of the above-mentioned related systems.
(3) Mutagenicity
Formaldehyde can mutate Salmonella typhimurium and Escherichia coli with or without the presence of a metabolic activation system. The micronucleus rate of bone marrow polychromatic erythrocytes was significantly increased when mice were continuously and dynamically exposed to formaldehyde at concentrations of 0.5 mg/m3, 1.0 mg/m3 and 3.0 mg/m3 for 72 hours.
(4) Carcinogenicity
On October 27, 2017, in the list of carcinogens published by the World Health Organization's International Agency for Research on Cancer, formaldehyde was included in the list of a class of carcinogens.
Research animals have found that rats exposed to 15 μg of formaldehyde per cubic meter for 11 months can cause nasal cancer. A new study published by the National Cancer Institute on May 12, 2009 shows that chemical factory workers who are frequently exposed to formaldehyde are much more likely to die from cancers such as blood cancer and lymphoma than those who are less exposed to formaldehyde. In 2010, it was found that formaldehyde can cause gene mutation and chromosomal damage in mammalian cell nucleus. Formaldehyde has a combined effect with other polycyclic aromatic hydrocarbons, such as the combined effect of benzopyrene, which will increase the toxicity.
◉ Formaldehyde Testing
Formaldehyde testing refers to the quantitative detection of formaldehyde contained in air, water, food, clothing, board, leather, etc. by specific methods or instruments. White or non-iron clothes, especially some jeans, 100% wrinkle-proof and shrink-resistant clothes, or cotton non-iron shirts are shaped with glyoxal resin, which contain formaldehyde.
◉ Detection Method
The main detection methods of formaldehyde in living room, textile and food at home and abroad are: spectrophotometry, electrochemical detection method, gas chromatography, liquid chromatography, sensor method, etc.
(1) Spectrophotometry
Spectrophotometry is a qualitative and quantitative analysis method based on the selective absorption of electromagnetic radiation by substances with different molecular structures. It involves ethylene acetone method, phenol reagent method, AHMT method, magenta-sulfurous acid method, chromotropic acid method, phloroglucinol method, catalytic spectrophotometry, etc. Its advantages and certain limitations.
(2) Electrochemical method
Electrochemical analysis is a method for quantitative analysis of the concentration of analytes in the reaction system based on the changes in current (voltammetry), electricity (coulomb method), and potential (potentiometric method) generated in chemical reactions, and is used for formaldehyde detection. There are two kinds of polarography and potentiometric method.
(3) Chromatography
Chromatography has strong separation efficiency, is not easily interfered by the color of sample matrix and reagents, and is sensitive and accurate for the detection of complex samples, and can be directly used for the analysis and detection of formaldehyde in rooms, textiles, and food. The formaldehyde in the sample can also be derivatized and then measured. The sample components in the room, textiles, and food are generally complex, with many interfering components and low formaldehyde content. In conventional detection methods, it takes a lot of time and energy to perform pretreatment such as separation and concentration before detection. The chromatographic method has high sensitivity, accurate quantification and strong anti-interference, and can be directly used for the detection of formaldehyde in rooms, textiles and food. However, chromatography requires high equipment, long derivatization time, and cumbersome extraction and other steps and operations.
(4) Sensor method
Sensors used to detect formaldehyde include electrochemical sensors, optical sensors, and photobiochemical sensors. The electrochemical sensor is relatively simple in structure and low in cost, among which high-quality products have stable performance, and the measurement range and resolution can basically meet the requirements of indoor environmental detection. But the disadvantage is that there are many interfering substances, and the electrolyte is consumed by irreversible chemical reaction with the measured formaldehyde gas, so its working life is generally short. Optical sensors are expensive and bulky, and are not suitable for online real-time analysis, which limits their widespread use. Although the photobiochemical sensor improves the selectivity, the sensor is unstable due to the activity of the enzyme and other factors, and lacks practicability. Moreover, the price of the general formaldehyde gas sensor is too high and it is difficult to popularize.
◉ Compliance Services
As a professional third-party testing and certification service organization, Jiayu Testing has qualifications such as CMA, CNAS, CBTL, CPSC, and has obtained laboratory accreditation from multiple authoritative certification agencies at home and abroad. The laboratory is strictly built and managed according to standards, equipped with advanced instruments and equipment, and has a skilled professional technical team with rich industry service experience and strong testing technology capabilities. It is proficient in various regulatory standards and provides formaldehyde testing services to assist enterprises in actively responding to regulatory requirements and effectively improving product compliance. Welcome to contact us at 400-9269-886!
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