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Polyvinyl alcohol (PVA) is an artificial hard white (less often light yellow or cream) polymer that appears as powder, flakes or grains. The crystalline component of the substance can reach up to 68%. Chemical formula polyvinyl alcohol is as follows: [- CH 2 – CH(OH) -] n, where n is the degree of polymerization. The value of n can reach 5000, that is, a polyvinyl alcohol molecule can contain up to 5000 identical units.
This heat-resistant artificial polymer was first obtained by German chemists W. Hermann and W. Gonel through the saponification reaction of polyvinyl ether with potassium hydroxide (KOH).
If most known polymeric substances are obtained by polymerization of monomers, then the process of producing polyvinyl alcohol is fundamentally different: to obtain this substance, a reaction of complete or partial hydrolysis of polyvinyl acetate is necessary, as a result of which the ethyl acetate group is removed.
Modern industrial synthesis of PVA occurs through various variants of the saponification reaction of polyvinyl acetate in an aqueous or alcoholic medium, in the presence of acids or alkalis that play the role of catalysts.
In 2002, a significant event occurred that made it possible to speed up and reduce the cost of the synthesis of polyvinyl alcohol. A team of scientists led by A. A. Kuznetsov discovered and developed a gel-free method for producing PVA.
Properties of polyvinyl alcohol
Pure polyvinyl alcohol is odorless, tasteless and non-toxic. Its only solvent is water. Polyvinyl alcohol does not dissolve in any organic solvent. Particularly resistant to any oils, gasoline, kerosene and other hydrocarbons, as well as diluted alkalis and acids.
PVA is hygroscopic and always contains approximately 5% water, which plasticizes the substance to some extent. But water evaporates easily and quickly. Therefore, ethylene glycol, butylene glycol, phosphoric acid, and glycerin are used as plasticizers for this polymer. The best plasticizer for PVA is glycerin.
Due to its properties, polyvinyl alcohol is widely used in food and pharmaceutical industry , in medicine, in various sectors of the national economy.
Application of polyvinyl alcohol
Since the described substance is physiologically neutral, it is quite understandable wide application polyvinyl alcohol in the food and medical industries. PVA is used as a film-forming agent, moisture-retaining and glazing food additive, which is assigned the international designation E1203. Thanks to the use of PVA, it is possible to retain the required amount of moisture in products subjected to various processing methods. Polyvinyl alcohol is also included in the glaze that coats freshly frozen fish and seafood. E1203 is included in most types of casings used to coat ready-to-eat and semi-finished products. For example, sausages and sausages.
E1203 is officially approved for use in Ukraine and EEC countries. In Russia, this food additive is not officially prohibited, but there is no official permission for the use of polyvinyl alcohol in the manufacture of food products.
The properties of polyvinyl alcohol allow it to be widely used as a material for the production of medical equipment, instruments and devices. In the pharmaceutical industry, PVA is used in the manufacture of coatings and fillers for various tablets. In addition, polyvinyl alcohol is sometimes used for blood transfusions as a plasma substitute. There are often cases when during treatment oncological diseases PVS is used as an embolic agent (in cases where surgery is contraindicated or not necessary). This heat-resistant polymer is also used to produce special fibers that are used to make internal surgical sutures that dissolve over a certain period of time. PVA is also included as a lubricant in liquids for contact lenses and eye drops. This substance is often used in the manufacture of children's and feminine hygiene products and creams.
The use of PVA for the production of polymer films and fibers is widespread. Plasticized polyvinyl alcohol is used to make hoses that are resistant to aggressive liquids.
Some fabric dyeing technologies also require the use of PVA.
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Polyvinyl alcohol is a man-made polymer that easily dissolves in water. It was obtained in 1924 by two chemists - Gonel and Herman - using a saponification reaction.
Polyvinyl alcohol is a white powder with the ability to form a film. This polymer is very strong and flexible, but since these qualities depend on humidity (it absorbs liquid), the tensile strength decreases, and at a certain degree of humidity greater ductility appears. It has hygroscopic properties and easily dissolves (mainly in water). It is not able to dissolve in organic solvents such as fats and oils. When used, this substance does not have a toxic effect, which means it can be considered harmless.
Obtaining alcohol
Polyvinyl alcohol or PVA is obtained from polyvinyl acetate by hydrolysis or alcoholysis and is produced in the form of granules or powder. At receiving PVS A variety of technological methods are used, from simple to quite complex and labor-intensive.
Polyvinyl alcohol - application
PVA is used quite widely today. It can act as a thickener in the manufacture of glue and shampoos, and is used to produce latex material. It is successfully used by restorers to restore artistic paintings. Due to its hygroscopicity, it has found wide application in the creation of hygiene products. All kinds of diapers, tampons and pads are made using PVA. Manufacturers have not forgotten polyvinyl alcohol food products. It is used as an emulsifier in the production of mayonnaise, sauces, ketchups and other food products, and is also used as confectionery.
Modern medicine has also adopted some of the properties of PVA. It is used in the production of some medicines, after being thoroughly purified from impurities. Ophthalmologists use polyvinyl alcohol for preparation and as a lubricant for contact lenses. Even oncologists have found the use of PVS in the treatment of cancer. In particular, it is necessary to perform the non-surgical embolization procedure. And this is not the entire range of uses of polyvinyl alcohol in medicine.
In the textile industry, PVA is used for stripping, and in the paper industry - for stripping. In addition, it is an indispensable component in the production of cellulose. Polyvinyl alcohol is necessary for builders and metallurgists, tanners and manufacturers of paint and varnish products. All factories that produce artificial fibers use PVA to make them, which gives them strength through the process of sizing the threads.
Even such a science as microbiology began to use PVA in the process of cells. Polyvinyl alcohol has also found application in printing, in particular in silk-screen printing. In this area, it is used as a polymer layer for the copying process. It can also be used as a packaging or protective material in production to cover parts, due to the fact that the PVA layer is easily removed.
Enterprises that manufacture and use molds also successfully use this polymer. Today, PVA is becoming increasingly widespread in the national economy. It is affordable, easy to transport (usually in plastic bags, packed in paper bags) in closed transport to avoid getting wet. Since polyvinyl alcohol is flammable, care must be taken when storing and handling it.
The chemical formula of polyvinyl alcohol is (C2H4O)x, where x is responsible for the degree of polymerization. This substance is presented in the form of a white or light cream powder.
Polyvinyl alcohol does not have a specific smell or taste. It is considered a thermoplastic polymer, so it dissolves well in various liquids: glycerin, water, urea, dimethyl formaldehyde. PVA boils at a temperature of 228°C, but begins to melt already at 200°C.
Polyvinyl alcohol is not affected by aggressive substances:
- . oils,
- . petrol,
- . alkali solutions,
- . kerosene, etc.
In addition, this substance does not release toxins. This powder always contains about 5% water. This component makes alcohol more plastic. Also, to increase the plasticizing properties, the following is added to the composition of polyvinyl alcohol:
- . glycerol,
- . butylene glycol,
- . phosphoric acid.
On an industrial scale, this powder is obtained as a result of polymer-analogous reactions. They involve both simple and complex compounds of polyvinyl ethers. In practice, this process occurs due to the saponification of polyvinyl acetate in an alcoholic environment. PVA can also react with bases and acids that are in water.
There are several brands of polyvinyl alcohol, they are divided into: fully hydrolyzed and partially hydrolyzed. One of the most popular brands in the textile industry is considered to be 16th grade. Polyvinyl alcohol 16 has White color, produced in the form of granules. It is used during the processing of fabrics and leather.
Properties of PVA
The properties of polyvinyl chloride are quite varied, since it can be greatly influenced by air humidity. With increased humidity, it begins to lose density. Under normal climatic conditions, this substance has high elasticity and strength. This alcohol is capable of imparting adhesive properties to raw materials.
PVA also has film-forming properties, but at the same time, it is not capable of dissolving in acids, alkalis and solvents. If water gets on dry PVA powder, this material will completely dissolve in it.
Polyvinyl alcohol-based adhesive has high density and viscosity. It is used in the production of containers and tailoring. It is resistant to gasoline, oils and acids.
Application of PVA
This powder is involved in the manufacturing process of other polymer compounds. With its help you get:
- . polyvinyl nitrate,
- . polyvinyl acetal,
- . polyvinyl acetate dispersions.
In Asian countries, PVA is involved in the production of textile fibers and fabrics. If we consider this material from the point of view of universality, then it is used in almost all spheres of human activity.
In the agricultural sector, it is added to synthetic fertilizer formulations; they qualitatively improve the composition of the soil.
In the metallurgical field, PVA is used for hardening steel metal.
Polyvinyl alcohol is an indispensable component in the production process building materials. It helps protect the finish of many materials.
This material can be found in the compositions of perfumes and cosmetics.
A solution of polyvinyl alcohol in the adhesive helps to glue various fabrics, leather, paper and other materials. It is used to glue tags and labels.
IN Western countries this substance has even found its use in the field of painting. With its help, the conservation of iconic ancient exhibits is carried out.
The production of polyvinyl alcohol helps doctors perform blood transfusions and make fixations when collecting samples.
Low molecular weight PVA is used in the food production process. It is introduced into product formulations as a glazing agent. They process fish, seafood, and sausages.
It is also worth noting that this powder is added to the following formulations:
- . eye drops,
- . contact lens removers,
- . construction fittings,
- . water-soluble packaging materials,
- . shampoos, gels and balms.
Some online resources claim that previously polyvinyl alcohol could be found in any pharmacy. At the moment, this polymer is prohibited for use in the food industry in the territory Russian Federation. In the world they can label E1203 as a food additive.
Manufacturers and cost
The main world producers of polyvinyl alcohol are the following countries:
- . China,
- . Korea,
- . USA.
- . Japan,
- . Spain.
In the Russian Federation, this material is produced by companies:
- . OdiHim LLC,
- . LLC VitaHim,
- . LLC Ekonomemikal,
- . LLC Status.
The average price for polyvinyl alcohol is $2.5-3.5. PVA is packaged in bags weighing from 20 kg. This material must be stored in dry and well-ventilated areas. The air temperature should be room temperature.
In warehouses with PVS it is strictly prohibited high humidity air. Polyvinyl alcohol can be stored in a stacking manner. If all storage requirements for this material are met, it can retain its properties indefinitely.
PVOH, polyvinyl alcohol.
Chemical properties
Water-soluble artificial thermoplastic polymer. The substance is obtained from polyvinyl acetate using an alkaline hydrolysis reaction or alcoholism . The chemical compound was first prepared in 1924. This is a slightly branched polymer, the degree of polymerization is about 500-2500. The substance is quite tensile strength, flexible, and has the ability to form films. The average melting point is 230 degrees, glass transition temperature = 85 degrees Celsius. Alcohol is stable against oils, fats and organic solvents. Specific heat capacity of Polyvinyl Alcohol = 1.26 kJ per kg per 1 degree. On the territory of the Russian Federation, the substance is released in accordance with GOST 10779 78.
Applications of Polyvinyl Alcohol:
- as an adhesive material and thickener in glue, shampoo, latex products;
- in the production of artificial fibers, cosmetics for child care;
- as an emulsifier in the food industry;
- when conducting research in microbiology for the immobilization of enzymes and cells;
- to provide a barrier layer for carbon dioxide in bottles from polyethylene terephthalate ;
- in the production of polyvinyl acetals;
- in medicine as part of eye drops and solutions for storing contact lenses, in some medicines, as an embolic agent in the treatment of oncological diseases.
pharmachologic effect
Keratoprotective, moisture retaining.
Pharmacodynamics and pharmacokinetics
The substance protects the skin and mucous membranes of the eye, the cornea from exposure external factors. Polyvinyl alcohol softens and moisturizes the surface of the eye and increases the stability of the tear film during intense evaporation of fluid. The product exhibits properties similar to the natural product of the conjunctival glands - mucin . When used topically, the medicine does not enter the bloodstream.
Indications for use
The product is used in combination with other substances:
- to eliminate the feeling of discomfort and burning, dry eyes;
- at ;
- as a tear substitute when the intensity of tear fluid production decreases;
- for the treatment of chronic purulent otitis , varicose and trophic ulcers;
- for purulent surgical diseases, chemical and thermal burns .
Contraindications
The substance must not be used for.
Side effects
Polyvinyl alcohol rarely causes adverse reactions. Sometimes they appear allergic reactions .
Instructions for use (Method and dosage)
The dosage and method of use of the drug depends on the dosage form, the disease and the purpose of using alcohol.
Medicines are used topically, washed in the nasopharynx or instilled into the conjunctival sac.
Overdose
There are no data on cases of drug overdose.
Interaction
The substance is incompatible with phosphates , sulfates and other organic salts, a precipitate may form.
The compound is destroyed when exposed to strong acids and weak alkalis.
In the presence of borax, the substance can turn into a gel.
Terms of sale
Res prescription.
special instructions
The tool cannot be used if it is changed appearance, turbidity, precipitation.
Drugs containing (Analogs)
The substance is contained in the preparations:, Oftolik BC , Sicaprotect . Including products for non-medical use, they are produced under the following brands: Alcotex, Gelvatol, Polyviol, Kartonol and so on.
