solvent

[róng jì]

A liquid that dissolves solids, liquids, or gaseous solutes

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This entry is made by Compilation and application of scientific encyclopedia entries of "Science Popularization China" to examine.

Solvent is a solvent that can be dissolved solid ， liquid Or gas solute Liquid (gas, or solid) (solvent, solute can be solid, liquid Gas ）And then becomes a solution. The most common solvent in daily life is water 。 And the so-called Organic solvent Which contains carbon atoms Organic compound 。 Solvents usually have relatively low boiling points and are easy to volatilize. Or can be determined by distillation To remove, thus leaving the dissolved matter. Therefore, the solvent can not produce chemical reaction on the solute. They must be inert. The solvent can be extracted from the mixture Extraction Soluble The most common example of compounds is the use of hot water to brew coffee or tea. Solvents are usually transparent, colorless liquids, most of which have unique smell.

Chinese name: solvent
Foreign name: Solvent
Features: Melting solid ， liquid Or gas solute Liquid of

Common: water
Smell: Most of them have unique smell
Features: Usually transparent, colorless liquid

catalog

brief introduction

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Solvous concentration Depends on dissolution solution The amount of material in the solvent. Solubility is the maximum amount of substances that can be dissolved by the solvent at a specific temperature. Organic solvents are mainly used for dry cleaning (e.g Tetrachloroethylene ）, for Paint thinner (e.g. toluene, turpentine), used as nail washing water or glue removal (e.g. acetone, Methyl acetate ， Ethyl acetate ）, derusting (e.g. hexane), used as detergent (lemon essence), perfume (alcohol) and chemical synthesis.

It is customary to call gas and solid solute The liquid is called solvent.

Concentration of solution

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The concentration of the solution depends on the amount of substances dissolved in the solvent; dissolution C is the maximum amount of substance that can be dissolved by solvent at a specific temperature. Organic solvents are mainly used for dry cleaning (e.g Tetrachloroethylene ）, as paint thinner (e.g toluene ， turpentine ）, used as nail remover or glue remover (such as acetone, methyl acetate, ethyl acetate), rust remover (such as hexane), detergent (lemon essence), perfume（ alcohol ）It is used for chemical synthesis.

Solvents and solutes can be roughly divided into Polar radical (hydrophilic) and Nonpolar radical (hydrophobic). Polarity can be measured through Dielectric constant or Dipole distance hear.

effect

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introduce

Solvent in an adhesive Plays a very important role in polymerization Medium, so that the reaction is mild and the temperature is easy to control; Some are used to purify monomer and auxiliary ； Some are used to dissolve the base material into a component of the adhesive; Some are used for olefin release adhesive to reach a certain level viscosity , which is conducive to infiltration and coating construction; Some are used to adjust the volatilization speed of adhesive; Some are used for prevent Gels increase storage stability, and some are used as surface cleaning agents before bonding; Some are used to directly bond some Thermoplastic Products; Some can be used to reduce costs and improve efficiency.

Selection of solvents

It is very important to choose the right solvent comprehensive Consider various factors, such as solubility volatilization Speed, safety, economy, source, storage stability, etc. A good solvent must have good solubility, which can be determined by Solubility parameters and hydrogen bond Index judgment. Adhesive Drying rate It is directly related to the volatilization speed of solvent, solvent-thinned adhesives The solvent should be completely volatilized finally. Generally, the adhesive is expected to dry quickly, so the solvent with lower boiling point should be selected. Most organic solvents are easy to burn. When the solvent vapor reaches a certain concentration in the air, it will explode. Pay attention to the safety of the solvent. Most organic solvents have certain toxicity and harm human health , pollution ecological environment , which should be paid enough attention. Solvents account for a large proportion of solvent based adhesives, so it is necessary to consider the cost and try to use cheap and easily available solvents first^[1] 。

classification

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Solvents are divided into Organic solvent And None machine solvent 。

Organic solvent

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introduce

Organic solvents are a large class of organic compounds widely used in life and production, molecular weight Not big, liquid at room temperature. Organic solvents include many kinds of substances, such as alkanes olefin , alcohol aldehyde , amine ester , ether, ketone Aromatic hydrocarbon , hydrogenated hydrocarbon, terpene hydrocarbon Halohydrocarbon , heterocyclic compounds, nitrogen-containing compounds and Sulfur Most compounds are toxic to human body.

It exists in coatings adhesive , paint and cleaner. Frequently use organic solvents, such as, styrene 、 Perchloroethylene 、 Trichloroethylene , Ethylene glycol Ether and Triethanolamine 。

Organic solvent is a kind of organic compound that can dissolve some water-insoluble substances (such as grease, wax, resin, rubber, dye, etc.). It is characterized by being liquid at normal temperature and pressure, with large volatility In the process of dissolution, the properties of solute and solvent remain unchanged.

type

Types of organic solvents: there are many kinds of organic solvents Chemical structure It can be divided into 10 categories: ① Aroma Hydrocarbons : benzene, toluene xylene Etc; ② Fatty hydrocarbons: pentane, hexane, octane, etc.; ③ Alicyclic hydrocarbons: cyclohexane, cyclohexanone, toluene cyclohexanone, etc.; ④ Halogenated hydrocarbons: chlorobenzene, dichlorobenzene dichloromethane Etc.; ⑤ Alcohols: methanol, ethanol, isopropanol, etc.; ⑥ Ethers: ether Propylene oxide Etc.; ⑦ Esters: Methyl acetate 、 Ethyl acetate , propyl acetate, etc.; ⑧ Ketones: acetone, methyl butanone Methyl isobutyl ketone Etc.; ⑨ Glycol derivatives: Ethylene glycol monomethyl ether 、 Ethylene glycol monoethyl ether , ethylene glycol monobutyl ether, etc.; ⑩ Others: acetonitrile, pyridine, phenol, etc.

（1） Acid solvent : Such solvents give proton Its ability to accept protons is stronger than that of formic acid, sulfuric acid, etc.

（2） Alkaline solvent : Solvents with strong ability to accept protons, such as ethylenediamine (NH2CH2CH2NH2), etc.

（3） Amphoteric solvent : Solvents with the same proton receiving capacity are given, such as water, methanol, ethanol, etc.

（4） Inert solvent : Solvents that can neither give nor receive protons, such as benzene, chloroform, etc.

Toxicity prevention

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Toxicity: organic solvents are fat soluble, so they can be quickly absorbed by the complete skin except entering the body through the respiratory tract and digestive tract. After being absorbed into the body, organic solvents will act on the nerves Blood system , as well as the liver and kidney and other substantive organs, and also has certain irritation to the skin and mucosa. Different organic solvents have different main target organs and effects, which depend on the chemical structure, solubility, contact concentration and time of each organic solvent, as well as the sensitivity of the body.

neurotoxicity

With aliphatic hydrocarbon (n-hexane, pentane, gasoline), aromatic hydrocarbon (benzene, styrene, butyl toluene, vinyl toluene), chlorinated hydrocarbon (trichloroethylene dichloromethane ）And carbon disulfide, triocresol phosphate and other fat soluble solvents are common. There are three types of damage to the nervous system caused by organic solvents: the first is poisoning Sexual neurasthenia And autonomic dysfunction. The patient may have dizziness, headache, insomnia, dreaminess, lethargy, weakness, memory loss, anorexia, emaciation, sweating, emotional instability, heart rate acceleration or slowing, blood pressure fluctuations, skin temperature decline or bilateral limb temperature asymmetry, etc; The second is toxic Peripheral neuritis 。 Most of them are sensory type, followed by mixed type. There may be limb numbness, hypoesthesia, tingling, limb weakness Muscular atrophy Equal performance; The third is Toxic encephalopathy , relatively rare, seen in carbon disulfide , benzene, gasoline and other organic solvents.

Hematotoxicity

Aromatic hydrocarbons, especially benzene, are the most common. When benzene reaches a certain dose, it can inhibit the hematopoietic function of bone marrow. Usually, white blood cells decrease first, then platelets decrease, and finally red blood cells decrease Pancytopenia 。 Individuals who are sensitive to benzene may develop leukemia.

Hepatorenal toxicity

It is mainly found in chlorinated hydrocarbon organic solvents, such as chloroform carbon tetrachloride 、 Trichloroethylene 、 Tetrachloroethylene 、 Trichloropropane 、 Dichloroethane Etc. Toxic hepatitis The main pathological changes were fatty liver and hepatocyte necrosis. Clinically, there may be liver pain, loss of appetite, weakness, emaciation Hepatosplenomegaly 、 Abnormal liver function Etc. The renal damage caused by organic solvents is mostly tubular, resulting in proteinuria and progressive decline of renal function.

Skin mucous membrane irritation

Most organic solvents have varying degrees Skin mucosa Stimulation, but mainly ketones and esters. May cause Respiratory inflammation , bronchial asthma, contact and allergic dermatitis, eczema, conjunctivitis, etc.

prevention and cure

When producing and using organic solvents, it is necessary to strengthen sealing and ventilation to reduce the dissipation and evaporation of organic solvents. Automatic and mechanized operation shall be adopted to reduce the chance of direct contact of operators. Personal protective equipment, such as gas mask or protective gloves, shall be used. When the skin mucous membrane is polluted, it should be washed clean in time. Do not eat or smoke with contaminated hands. Wash hands, bathe and change clothes frequently. Health examination shall be carried out regularly, and corresponding treatment and strict dynamic observation shall be carried out when signs of poisoning are found early.

influence

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Influence of absorption band position

The influence of solvent on the absorption band is related to the solvent, solute and the type of transition band. According to the properties of both solute and solvent, different effects are produced. If the intermolecular effect on the stability of the excited state is stronger than that of the ground state, the absorption band of the relevant transition moves towards red. On the contrary, those that make the ground state more stable move to the blue. When the solute is a non-polar molecule Non-polar solvent The interaction between them is only a weak dispersion. The influence of solvent on solute is often very small, and the spectrum of solution is close to that of gas. If the excited state of the solute has a dipole or is accompanied by charge transfer, the wavelength of the absorption band will shift to red with the increase of the dielectric constant or refractive index of the solvent.

Influence of ultraviolet absorption spectrum

When a pure compound is measured in a series of different solvents, the data obtained, including the intensity and the wavelength position of the absorption band, often vary with the solvent. According to the properties of solute and solvent, sometimes chemical reaction may occur between them, or complex may be formed. The dissociation constant and tautomeric equilibrium of solute are also related to the solvent, so that different solvents can produce very different spectra. Therefore, when comparing or checking the spectra of compounds, it is better to use the same solvent. If the solvents used are different, the influence of solvents should be taken into account when analyzing the spectra. In addition, it is sometimes possible to infer the transition type of an absorption band from the difference in different solvents.

The physical interactions between solvent and solute are static electricity Interaction, dispersion, hydrogen bonding, charge transfer and Electric charges repel each other Function, etc. Such intermolecular interactions have different effects on molecular energy levels, resulting in different spectra.

Food safety issues

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Why every time Food safety incidents Are they all caused by ink? It turns out that the main culprit of ink pollution is the solvent it contains. The solvent in the ink plays a "intermediary" role in binding pigments and adhesives to printed articles. The working principle is to mix the pigment and solvent first, and then dissolve them into a liquid that can flow. The liquid solvent volatilizes and then becomes a solid, so as to transfer and attach the pigment to the printed matter. Volatility of solvent is an important source of pollution, which not only pollutes the air and endangers the health of workshop workers, but also can cause secondary pollution when consumers use it if they stack it immediately after printing. The above mentioned behavior of putting potato chips on the patterned pad paper is a wrong operation method that leads to secondary pollution.

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