Some ester alkyl and aryl phosphate compounds still have delayed neurotoxicity, because organophosphorus pesticides inhibit the target esterase (neurotoxic esterase) in vivo and make it "aging", thus causing delayed neuropathy. This toxic effect has nothing to do with cholinesterase activity.
The sustained release of organophosphorus pesticides in microcapsule form can last for a long time.
Organophosphorus and carbamate are the main causes of acute pesticide poisoning, and are also the key detection varieties of pesticide residues in vegetables at present. Enzyme inhibition method is a detection method based on its toxicological mechanism to insects. The toxicological mechanism of organophosphorus and carbamate insecticides is the same, both of which inhibit the activities of acetylcholinesterase (Ache) and carboxylesterase, leading to the accumulation of acetylcholine (Ach) and carboxylate, affecting the normal nerve conduction of insects and leading to death.
Arsenic and its compounds can be absorbed by respiratory tract, digestive tract and panel and enter human body. 95%-99% arsenic in blood binds to globin in red blood cells. Arsenic in tissues is mainly distributed in liver, kidney, gastrointestinal wall, muscle and so on. Panels, hair, nails and bones can all be used as solid reservoirs of arsenic. Arsenic in the body is mainly excreted from the kidneys and digestive tract, and some from the face plate, hair and nails. The toxic effect of arsenic is that arsenic ions combine with sulfhydryl groups and hydroxyl groups in the molecular structure of enzyme protein in vivo, which makes the enzyme lose its activity. When pyruvate oxidase, choline oxidase, transaminase, α -glycerophosphate dehydrogenase, 6- phosphoglucose dehydrogenase or cytochrome oxidase are inhibited, they interfere with the normal metabolism of cells, affect the process of respiration and oxidation, make cells pathological, and inhibit cell division and proliferation. In addition, arsenious acid and arsenious acid can replace phosphoric acid in many biochemical processes, thus decoupling the process of oxidizing phosphoric acid and reducing the formation of high-energy phosphate bonds, thus interfering with cell energy metabolism. Metabolic disorder can first harm nerve cells, causing toxic neurasthenia and polyneuritis. Arsenic can also directly damage arterioles and capillary walls, and can also act on the vasomotor center of blood vessels, paralyzing smooth muscle of blood vessel walls, increasing permeability, reducing blood volume and aggravating organ damage. Arsenic sulfide, such as realgar and orpiment, is insoluble in water and has low toxicity. Arsenic trioxide has high water solubility and the strongest toxicity. Arsenic trioxide and arsenic trichloride have * * * effects on eyes, upper respiratory tract and face plate. The mechanism of hydrogen arsenide poisoning is completely different: inhibition of glutathione peroxidase leads to peroxide formation and hemolysis; It may also be that arsenic combines with sulfhydryl group, which damages the sodium and potassium pump function of erythrocyte membrane. Acute renal failure often occurs after massive intravascular hemolysis. The dose of arsenic poisoning is 5 ~ 50mg, and the lethal dose is 60 ~ 200mg.
Mercury vapor can easily penetrate the lipid-containing cell membrane of alveolar wall, combine with lipids in blood, and quickly distribute to all tissues of the body. Mercury is oxidized to Hg ~ (2+) in red blood cells and other tissues, and it is difficult to be released after being combined with protein. Metal mercury is hardly absorbed in the gastrointestinal tract, accounting for only about one tenth of food intake, and the absorption of mercury salt in the digestive tract is about 10%. Mercury is excreted mainly through urine and feces, with a small amount of saliva, milk and sweat, and little distribution in the lungs. The half-life of mercury in the body is 60 days, and the mercury salt is about 40 days, and the excretion in the first 4 days is large.
Mercury ion is easy to combine with sulfhydryl group, which inactivates cytochrome oxidase, pyruvate kinase and succinate dehydrogenase related to sulfhydryl group. Mercury also combines with amino groups, carboxyl groups and phosphoryl groups, affecting the activity of functional groups. Because the activities of these enzymes and functional groups are affected, the biological activity and normal metabolism of cells are hindered, which eventually leads to cell degeneration and necrosis. In recent years, it has been found that the damage of mercury to kidney is mainly caused by epithelial cells of renal proximal convoluted tubule. Mercury can also cause immune dysfunction, produce autoantibodies, and lead to nephrotic syndrome or glomerulonephritis.
Why is nonmetallic arsenic one of the five poisons of heavy metals? Arsenic is amphipathic, and nonmetallic mercury (Hg), cadmium (Cd), lead (Pb), chromium (Cr) and arsenic (As) have metallic properties, commonly known as "five poisons". These five elements are all heavy metals.
These toxic elements will not be degraded by microorganisms in water, but will continue to spread, transfer, disperse and enrich. Enriched heavy metals have greater toxicity in human body, which is called "toxicity amplification" in chemistry.
In the early 1950s, in Minamata Prefecture, Japan, some cats were found jumping into the river for no reason. Later, some women suddenly became numb and insane, fell asleep for a while, became excited for a while, screamed in pain, and finally died. This unknown disease was later called "Minamata disease". Through the research of environmental workers, it is found that the root cause of this disease is mercury pollution. Due to the mercury-containing wastewater discharged from petrochemical plants, people eat aquatic organisms such as fish, shrimp and shellfish which are polluted by mercury and rich in methylmercury, resulting in a large number of central nervous system poisoning of consumers. In this poisoning incident, 283 people were poisoned by mercury, and more than 60 of them died. In natural water, if there is 0.0 1 mg of mercury per1liter of water, it will have strong toxicity to human body and can be amplified in the body through the food chain. Once mercury enters the human body in the form of organic mercury or methylmercury, it immediately reacts with enzymes in the human body, decomposes enzymes and inactivates them, and can also invade the blood supply tissues of the brain and placenta, which not only harms the human brain, but also can be passed on to the fetus.
After long-term accumulation of cadmium in human body, it will cause hypertension and lead to cardiovascular diseases. For example, the "bone pain disease" discovered in Japan is due to excessive accumulation of cadmium, which will cause renal insufficiency. If calcium in bones is replaced by cadmium, bones will soften, and the incubation period of this disease can be as long as 10-30 years.
Since these "five poisons" have such bad toxic effects, can human beings completely isolate these substances without them? No, trace metal elements are necessary for animals, plants and human bodies. For example, a proper amount of chromium can transform excess sugar in human blood and prevent diabetes. If the chromium in human tissues is reduced, it will seriously reduce people's appetite.
In addition, these metals are also essential elements in industry. Mercury is the most toxic of the five poisons, which is widely used in industry, such as thermometers, pressure gauges, high current switches in electrical equipment control instruments and so on. It is also widely used as a fungicide in agriculture to prevent wood rot. Cadmium is widely used in paints, batteries and photography.
Its ions are highly oxidizing and can denature animal protein cells. Although it is not metal, it is at the boundary between metal and nonmetal in the periodic table of elements. Simple substance has metallic luster and looks like metal, but its appearance can't explain anything. The key is that its properties have metal characteristics.
How do you say polyurethane in English?
English pronunciation:/,p? Livzon? ，θein/
American sound:/,pɑl? jur？ ，θen/
The degree of amino group in carbamate and the reaction of isocyanate. The condensation of aniline and formaldehyde under acidic conditions is a fully mature technical route for MDI production abroad. The reactants were neutralized with alkali and then distilled to obtain diphenylmethane diamine (MDA). After MDA is dissolved in solvent, it is phosgenated to produce 4.4-MDI 2.4-MDI 2.2-MDI or mixed PMDI, and then purified by distillation to obtain pure MDI. The reaction of free amine with phosgene is the most important method of MDI. Before the reaction, amine was dissolved in an inert solvent, and excess phosgene of the same solvent was continuously added at low temperature to form carbamoyl chloride and amine hydrochloride slurry, then heated to high temperature, and excess phosgene was introduced until a clear solution was obtained. The reaction is carried out in about 20% solution. In order to reduce side reactions, phosgene must be above 50%. Phosgene is toxic and fatal to human body, so the central government strictly controls it. Moreover, the phosgene production investment is large, and transportation and storage are inconvenient. The generated hydrogen chloride has serious corrosion to equipment, demanding production requirements, high operational risk and difficult equipment maintenance. Nowadays, people are actively developing methods to replace phosgene.
Monsanto has issued a patent. TDI and MDI are produced by non-phosgene methods, such as amine method, carbon dioxide method and dehydrating agent method. The reaction produces carbamate at almost normal pressure and low pressure, and then dehydrates with phosphorus pentoxide and triethylamine as dehydrating agents to produce isocyanate. From the whole reaction, the dominant direction in the future is to catalyze carbonyl group to synthesize carbamate, and then pyrolyze it into MDI. It is reported that BASF has established industrial production facilities for carbamate process in Belgium and the United States. According to the data reported by Asahi Glass Company, the production cost of non-phosgene method is 20% lower than that of phosgene method.
The carbamate method is that aniline and carbamate are first made into aniline carbamate, then mixed with nitrobenzene in the presence of sulfuric acid to form MDI mixture, and then distilled to get the finished product.
Aniline first reacts with carbon monoxide, ethanol and oxygen to produce ethyl aniline formate (EPC). Then EPC and formaldehyde solution were concentrated to produce binuclear methylene diphenyl carbamate (MDV), and the product was pyrolyzed to produce MDI and ethanol, and the product was recycled for carbonylation.
In the reaction process, the presence of aniline can reduce the carbonylation of nitrobenzene and improve the yield of carbamate. In order to make the reaction go smoothly. Methanol is usually in excess. The feed ratio of raw materials is methanol: aniline: nitrobenzene: catalyst13.5:1.0:1.0: 0.002, and the reaction is carried out at CO pressure of 6.87Mpa and 160℃ for 3.5h to generate EPC. The catalyst used is a new carbonyl compound, and the reaction liquid is quickly discharged and sent to the lower tank.
Excess carbon monoxide and by-product carbon dioxide are sent to a stirred reactor to promote the mixing of the solution and organic substances. The reaction is heated by induction coil and reacts at the interface of formaldehyde solution/sulfuric acid layer and EPC/ organic layer. The reaction temperature is controlled at 75℃, and the intermediate product MDV/PMDV is generated under normal pressure.
Then the reactants enter the organic matter/solution separator, and most of the H2SO4 catalyst is separated for recycling. The organic layer was washed with water to remove residual sulfuric acid and unreacted formaldehyde.
The reaction mixture contains unreacted EPC, MCV/PMDV, organic solvent and reaction intermediate, effluent from organic/solution separator and liquid accelerator, which is converted into MDV/PMDV at 75℃ and atmospheric pressure for about 20min minutes.
After purification, the generated MDV/PMDV enters the degradation device. In the presence of inert solvent, the reaction humidity is controlled at 250℃, the pressure is controlled at 20Pa, and the residence time is 65438±0h h.. Nitrogen was continuously introduced to remove excess methanol from the reactor. The bottom product is sent to MDI extraction tower to separate MDI and by-product polyisocyanate.
Is polyurethane fiber (spandex) a polyester fiber? Spandex belongs to polyurethane fiber, not polyester fiber.
Polyurethane fiber and polyester fiber are two different kinds of synthetic fibers.
Just as Belarus does not belong to Russia, just as red pandas and giant pandas are two species.
Polyester is polyester fiber! See synthetic fiber classification:
Polyamide fiber, nylon, polyamide fiber, nylon, nylon, polyamide.
Polyester fiber, polyester fiber, polyester, polyester, polyethersulfone, polyethylene terephthalate, polyester.
Polyacrylonitrile fiber, acrylic fiber, acrylic fiber, PVN.
Polyvinyl alcohol fiber, vinylon, vinylon, polyvinyl alcohol fiber, polyvinyl alcohol.
Polypropylene fiber, polypropylene fiber, polypropylene fiber, polypropylene
PVC fiber, PVC fiber, chlorine fiber, PVC
PVDC polyvinylidene chloride fiber
Polyethylene fiber, ethylene fiber, polyethylene fiber, polyethylene
Polyurethane fiber, spandex, polyurethane elastic fiber, spandex, op.
No, that's spandex, commonly known as lycra, which is a kind of high elastic fiber. Nowadays, many sportswear are made of Lycra, especially swimsuits. The full name of polyester fiber is polyethylene terephthalate, commonly known as polyester. Good rigidity and wrinkle resistance, but no elasticity, not suitable for sportswear.
Is PU polyurethane or polyurethane? What is its general formula? Polyurethane, English name polyurethane, abbreviation PU, abbreviation of polyurethane, I don't have the software for drawing chemical molecular formula, so I can't write the general formula for you. It is a polymer with repeated structural units containing-nhcoo-groups in the main chain of macromolecules. It shouldn't be difficult for you to write by name.
What is the UN number of TPU colloidal particles/polyurethane? The supplier of TPU raw materials reminds you that the UN number of TPU rubber particles/polyurethane is compiled by the factory itself, which means that only the manufacturer knows it.