PVA dispersion is a viscous, homogeneous mass of white or yellow color, which is used for gluing materials. From point of view physical characteristics substances, high-quality glue does not contain lumps, specks and other “garbage”.

What types of glue are there?

There are 2 varieties:

• Unplasticized dispersion (grades - D51S, D51V). It differs in that no plasticizer is added to its composition. Thereby this type glue is easily transported in frosty weather (the material can withstand temperatures down to -40C);
• Plasticized dispersion (grades DE51/10S, DF51/15V). It differs from the previous one in that plasticizers are added to it - dibutyl phthalate or EDOS, due to which the glue acquires yellow tint. As for the peculiarities of transportation, this variety “does not tolerate” low temperatures, for it the maximum permissible mark on the thermometer is +5 C.

Specifications

• The substance perfectly glues materials, the connected surfaces stick to each other like a glove;
• PVA dispersion does not pose a threat in terms of fire and explosion hazards;
• It is non-toxic, therefore it is used when working in open and closed spaces;
• The material is resistant to low temperatures;
• Partially soluble in water, acetic acid and other liquids.

Areas of application

“Universal glue” - this phrase perfectly characterizes such a material as PVA dispersion. Buy it for personal use worth it due to the fact that it is indispensable when carrying out work different profiles. For several decades, glue has been successfully used in Russia and abroad in various industries.

• PVA dispersion has proven itself in the furniture industry;
• Successfully used in construction and production of building materials - paints, putties, primers;
• In the printing industry, it has found application in gluing cardboard boxes and other types of products.

Prices

Name of product	Price per kg. in view of VAT Up to 35 thousand rubles	Price per kg. in view of VAT 35-100 thousand rubles.	Price per kg. in view of VAT 100-200 thousand rubles.	Price per kg. in view of VAT > 200 thousand rubles
86,00	84,28	82,50	80,80

PVA dispersion is an indispensable tool in industry, production and household. To have such an assistant as PVA dispersion in your home, it’s easy to buy it. All you need to do is contact us through the form on the website or by phone at any time convenient for you. Moreover, the price at which we sell universal glue is low and profitable when purchasing large quantities of goods. Take more, pay less.

In terms of popularity today, this glue is unlikely to rival the once most famous and widespread silicate glue. And the scope of its application seems to have no boundaries. PVA glue is used to glue paper and fabric, wood and glass, leather and metal.

In addition, PVA is included in many paints and primers, putties and dry construction mixtures.

How do different PVA glues differ from each other, does it matter where to use which glue, and what does a home craftsman need to know in order to competently and the greatest benefit use this truly versatile product of the chemical industry.

How PVA stands for, its composition

But, first of all, how is PVA deciphered? PVA is an abbreviation for polyvinyl acetate. We will not draw chemical formulas, they are unlikely to be of much interest to you, but we will say that the composition of PVA glue includes an emulsion of this very polyvinyl acetate in water with various plasticizers and special additives that enhance certain properties of the glue, making it more prepared for applications in a specific area. We will analyze which PVA glues are used and where they are used in this article, and also give some tips on the unconventional use of this miracle composition.

What are the types of PVA adhesives and their use?

Even a fairly experienced home craftsman does not always know which type of PVA glue will give him best effect in one area or another. Let's try to figure it out together. Classification of PVA adhesives:

1. Household (wallpaper). This is exactly what it was created for; it can withstand 6 cycles of freezing to a temperature of -40°. Of course, it also glues many other things, but we recommend using it for its intended purpose.

2. Stationery (PVA-K). Unlike most of its counterparts, it is not waterproof and frost-resistant. These “weaknesses” must be taken into account, especially when trying to use building mixtures and mortars for additional plasticization. Buy another one.

3. Universal (PVA-MB). It glues everything listed at the beginning of the article; this is the composition most often used for making concrete mixtures, primers and putties. This glue already allows additional plasticization of any building compositions on water based. Frost-resistant, withstands 6 cycles of freezing to a temperature of -20°.

4. Super (PVA-M). In addition to everything that a station wagon glues, this glue is also intended for gluing ceramic tiles, felt-based linoleum, etc. Frost-resistant, withstands 6 cycles of freezing to a temperature of -40°.

5. PVA dispersion is the basis for all adhesive compositions. It is also used in industry not only as an adhesive, but also as a formulation part of multicomponent formulations. There are 2 types:

• unplasticized;
• plasticized.

Additional information about plasticization methods and technical characteristics of PVA dispersions is unlikely to be of interest to the average reader of this article, but many builders prefer to use it to improve the composition of building mixtures. Of course, not in the size of a Euro-cube or barrel, but in smaller packaging, which is available in the assortment of many large hardware stores.

Some manufacturers of PVA-based adhesives slightly expand their classification to attract customers. This is how PVA construction glue appeared, which is positioned as a composition that exceeds the universal one in its properties. Sometimes the names of several types of adhesives are used simultaneously. In such cases, before using glue, you need to read what materials it is intended for gluing - here the manufacturer will be more careful and will not write that this particular glue can be used to glue ceramic tiles, if it is intended for paper.

It remains to add that some types of PVA adhesives are directly manufactured for narrow applications. This does not mean that they cannot glue the same paper or cardboard, they just contain additives for best adhesion specific materials.

PVA and dry construction mixtures

In fact, dry mortars became widely possible because the PVA dispersion was dried and made available in powder form.

Any building mixture consists of:

• filler, which is most often quartz sand, but it can also be chalk, expanded clay, etc.;
• binder, which is cement, lime, gypsum;
• chemical additives, which are often based on PVAD-based dispersion powder.

Of course, in addition to this powder, there are other chemical additives, but their composition and quantity in different mixtures is different. We mention this in general so that a thrifty owner can, in some cases, save money by understanding the essence.

Namely. All chemicals in building mixtures account for from 2 to 5%, everything else is filler and binder. When buying a cement building mixture, you often buy cement and sand at an expensive price. And drying the PVA dispersion adds a fair amount of cost, so that you end up diluting it with water and getting the same PVA. And for the rest of the chemistry, for most not very special mixtures, some kind of liquid soap or even washing powder in an amount of 2 - 3% of the amount of binder. At worst, even shavings from laundry soap will do.

PVA glue for replacing building compounds

Now that the essence of obtaining fashionable compositions has become clearer, we can detail some of them a little more.

Let's start with the simplest thing.

1. Almost any type finishing works preceded by priming the surface. Most manufacturers recommend doing this only with their primer, that's all. deepest penetration. But a 10% solution of PVA glue (preferably dispersed) will penetrate just as well and ensure excellent adhesion of the material. Try it and see for yourself. And if you add some dye to this composition for water-based paints, you will get an excellent impregnation paint for concrete, allowing you to create wonderful illusions natural stone, brick. You just need to coat it with varnish.

2. Cheapest finishing putty it will work if you mix chalk with PVA until it becomes thick like sour cream, although for deep cracks you can make it thicker. It is clear that the composition can be adjusted within a wide range by a certain amount of water. There are 2 disadvantages that you just need to consider:

• long drying time;
• difficulties in machine processing of the finished surface due to high temperatures in the processing area due to the friction of the working tool.

3. Gypsum putty, like an analogue of plasterboard glue, is obtained by mixing 1 part gypsum, 2 parts chalk and the same PVA glue. But with a little experimentation with the ratios, you can get the perfect product, tailored to your style and work rhythm. The same gypsum or cement mixed with PVA will become an excellent putty for a concrete floor; sometimes it will be useful to add fine sand to this composition. Oh, no matter what ratio you cook it in cement-sand mixture, depending on the brand and quality of cement, fraction and quality of sand, if you add a glass of dispersed or even universal PVA to a bucket and detergent, as described above, you will successfully replace most of the super-fashionable mixtures.

4. Most people consider PVA glue to be the best for gluing wood. And although modern polyurethane adhesives have begun to push PVA out of this area in some places, their relative high cost cannot do this everywhere.

And there is nothing to say about home use - here PVA will not have competitors for a long time.

But wood is a fairly soft material that often suffers serious damage even with minor carelessness in handling. And here PVA can become an indispensable assistant. If it is mixed with wood dust, which can be freely found on any wood production, then we get a putty called “ liquid tree" By varying its consistency, you can obtain a composition that can cope with the deepest wounds on wooden surfaces, as well as products made from fiberboard, chipboard and MDF.

5. It remains to add that, given the presence of PVA in the form of a redispersible powder in many building compositions (which can be read on the packaging), we can successfully increase the degree of plasticization of these same compositions by introducing an additional amount of PVA into the finished mixture.

So, when applying a bark beetle mixture using a Hopper plaster gun for exterior finishing of buildings, we recommend adding dispersed PVA at the rate of 1 liter per 25 kg of mixture. This will make the solution more plastic and subsequently even more resistant to external influences.

At the same time, you can safely add dye there; PVA will help them combine into a magnificent mixture.

Dear readers, if you have any questions, please ask them using the form below. We will be glad to communicate with you;)

Comments11 comments

Bravo! I 100% support your point of view on fashionable mixtures.

Moreover, for more than 40 years I have been using a mixture of creamy cement mortar (without sand) and good (imported) PVA, about 1 tbsp. spoon per liter of solution (more or less is determined experimentally depending on the purpose of the solution).
As an example from my own experience, I can say the following:
1. The tile is firmly glued to any surface. I glued 10 mm of plywood to a sheet to cover the pipes in the toilet, so after drying, when trying to straighten the slightly bent sheet (it was necessary to bend it slightly in the opposite position at the beginning), several tiles simply burst in the center of the sheet, but none of them came off and are holding on dead for about 40 years now. The only peculiarity is that before gluing, the tile must be moistened with a 10% solution of the same PVA so that the solution adheres to the base of the tile, and not just to the chalk layer, which is what usually causes the tile to peel off from the surface. This solution is also indispensable when gluing tiles to walls covered with oil paint and when repairing peeling tiles.
2. As a wood putty, it can be used to initially seal cracks or flaws in furniture and wooden structures of any depth with virtually no shrinkage.
3. Also used when connecting cast iron plumbing pipes instead of minting. The result is such a dead connection that it eliminates the possibility of further disassembly if necessary! At least I just had to break one of the connected pipes

That is, it turns out cheap and cheerful and without any bells and whistles and fashionable mixtures!

What does the word pva mean?

PVA is polyvinyl acetate

Hello! Please tell me which PVA can be used to repair hunting skis (cracks and peeling)? Thank you.

You can use any of the PVA glues, except for purely office glue, which has too low a concentration. We recommend taking either dispersed (it says so on it) or construction - they are more expensive, but also of higher concentration. In your case, an important role will be played not so much by the adhesive composition, but by good pressure on the peeled layer after applying the glue. To do this, you can pour a small amount of sand into a durable plastic bag, put it on the glued layer and tighten the ski with clamps through the board(s). After drying, the polyethylene will easily come off from the exposed glue. The excess can be removed using sandpaper and the surface can be varnished. If there are deep chips, then repair them using the method described in the article, preparing the so-called. "liquid tree" It is important to take your time here and let the glue fully polymerize.

After repairing the tiles, there was some PVA construction glue left, can it be used for gluing wood?

Of course you can

You can make your own high-quality wood putty from PVA glue. To do this, you need to mix the glue with small sawdust to the consistency of thick sour cream. This putty can be used on any wooden surfaces. It has excellent adhesion, does not shrink when dried, and adheres firmly to the surface. This putty interacts well with various varnishes and paints and is universal remedy for home craftsmen.

Hello everyone. I have a question for the experts and just knowledgeable people. When building a private house, I used OSB boards for exterior finishing. So the question is this: because. The façade paint does not stick to OSB, I decided to cover the OSB with fiberglass (gossamer) using PVA. How correct is my idea? Can PVA be used for outdoor work? Is it possible to paint walls over PVA and if so, then with what?

Good afternoon.
We are engaged in the production of gypsum artificial decorative stone (tiles)
I saw information in the article about the possibility of using PVA.
PLEASE give more specific recommendations for use.

Hello! I really liked your article! I'm not an expert, but I like to do a lot of things on my own. And of course savings!!! But I'm a little confused. Can you help me? I have four jobs to do: 1) gluing a fabric-based film onto a putty wall, 2) installing a ceiling foam plinth (PVA is needed to add finishing putty), 3) gluing the ceiling with decorative crumpled paper, such as thin parchment ON already pasted ceiling tiles! And 4) try to do an “acrylic fill”, it’s something like modern painting abstract. Can also make an economical primer. My question is this: which PVA glue do I need, or do I still need several, such as household/wallpaper PVA, PVA-MB...? Please can you answer my email?

Coarse polyvinyl acetate homopolymer dispersion (PVAD)

Polyvinyl acetate dispersion (GOST 18992-80) is a viscous white homogeneous liquid with a specific gravity of 1.1 g/cm3, which is a product of polymerization of vinyl acetate in an aqueous medium in the presence of an emulsifier and a polymerization reaction initiator, mixed with or without a plasticizer.

PVAD is produced in different viscosity grades, in which the monomer content is standardized within 0.8%, dry residue content at least 50%, pH within 4.5-6.0, dispersion viscosity depending on the brand from 10 to 120c according to BMC, amount of plasticizer from 5 to 15%.
Plasticized PVAD is not frost-resistant, freezes at 0C and does not return to its original state after thawing. The unplasticized dispersion can withstand at least four freeze-thaw cycles and is mixed with a plasticizer immediately before use.

Polyvinyl acetate (PVA) dispersions are products with wide range of applications in a wide variety of fields. Due to their universal adhesive and binding properties, resistance to aging, high adhesive ability and environmental friendliness, polyvinyl acetate dispersions are widely used in industry, construction and everyday life. It is not for nothing that this unique product is called the material of “a thousand possibilities.”

• PVAD is widely used in the manufacture of water-based paints, adhesives, putties, mastics, primers, as a binder in polymerization compositions, fiberglass, leather, and non-woven materials.
• PVA dispersions are also widely used in the printing and woodworking industries, in the production of corrugated cardboard and cardboard packaging, plasterboard and furniture, heat-insulating and fire-resistant mineral wool slabs, nonwovens such as synthetic winterizer and in many other technological processes.
• Polyvinyl acetate adhesives non-waterproof, soluble in butyl acetate, perchlorethylene and other solvents, i.e. they are not completely irreversible. This serves as the basis for their use in restoration work.

The plasticized dispersion is ready for use, has practically unlimited viability, is non-toxic, is characterized by elasticity and stability of the adhesive joint, light and fungal resistance.

The glue is non-contact, it does not set immediately, so during the gluing process it is necessary to apply significant pressure, the amount of which depends on the shape of the part, the wood species, the condition of the surface to be glued, the room temperature and other factors.

The gluing process (polymerization) can be affected by acid dyes and mordants used for dyeing veneer, so PVAD should not be used for cladding and mosaic work.

The film formed when the dispersion dries has a number of valuable properties: exceptional light fastness, strength, transparency, good adhesion to hydrophilic substances, airtightness.

Polyvinyl acetate dispersion DD50/10С
TU 2241-001-25031183-06

• Polymer emulsion for the production of water-dispersed materials: PVA adhesives, putties, mastics, VD-VA primers, water-dispersed paints.
• Adhesive for production plasterboard sheets and slabs.
• Binder for the production of mineral wool insulation.

Not frost-resistant

Polyvinyl acetate dispersion DD50/15V (High viscosity)
TU 2241-001-25031183-06
Homopolymer, coarse, polyvinyl acetate dispersion, plasticized - plasticizer "EDOS", stabilized with polyvinyl alcohol.

• Glue for gluing wood (joining and pressing technologies).
• Adhesive for gluing paper, cardboard and corrugated cardboard packaging.
• Polymer dispersion for printing production (binding and stitching works).

Not frost-resistant

Shipment is carried out both in the buyer's container and in the seller's container.

Find out the price PVA dispersion is an adhesive obtained as a result of the polymerization of vinyl acetate in an aqueous solution of polyvinyl alcohol colloid in full compliance with the requirements of GOST 18992-80. The polymers present in the glue differ high performance gluing, so PVA dispersion is often used to create printed and packaging products. Externally, the dispersion looks like a creamy viscous substance, which becomes transparent during polymerization during the sizing process. PVA glue for printing can be unplasticized (grades D51S; D51V) and with plasticizer EDOS (DE51/10S) or Dibutyl phtholate (DF51/15V). The unplasticized dispersion has a pure White color

, and the plasticized one is distinguished by a faint shade of yellow. The polymers present in PVA glue create a film that protects the surfaces being glued from fat, mechanical stress and increases resistance to UV radiation.

Technical characteristics of PVA glue The Concord company sells dispersion PVA, price

• which is acceptable and meets all the requirements of a high-viscosity plasticized dispersion:
• Stabilization with polyvinyl alcohol.
• Viscosity 90-120 C
• Dry residue above 54%.
• Mass fraction of residual monomer is not higher than 0.48%
• pH value within 4.5-6.0
• Suspended particle size 1-3 microns
• Conditional viscosity according to art. Navy mug from 41 to 120.
• The sedimentation of suspended matter is not higher than 5%.
• Density 1-1.2 grams per centimeter at a temperature of 200
• The glue is non-toxic, non-flammable and environmentally friendly

The glue base is an aqueous solution, so it freezes easily if stored incorrectly and can retain its properties only for up to 4 thawing/freezing cycles, and already polymerized adhesive compounds are frost-resistant. It is very important that, for example, plasticized PVA dispersion DV51/15V was stored and transported at an air temperature of at least 5 degrees Celsius, otherwise after thawing it will lose its adhesive properties. At the Concord company buy PVA glue It is possible at any time of the year, but in winter frosts only unplasticized dispersion is delivered to the customer, and the plasticizer is added separately in heated rooms. For different technological processes, glue can be diluted with water in different proportions and thereby reduce viscosity. Subject to all technical specifications PVA dispersion will be the ideal adhesive composition, which is easy and convenient to work with to achieve ideal results.

The guaranteed shelf life of PVA glue according to technical specifications is six months.

The Concord company offers high-quality PVA glue, which you can buy in 50-kilogram barrels.

| 25.11.2015

Homopolymer coarse PVADs

This type of dispersion with particle sizes up to 1-3 microns is produced by the domestic industry on a large scale. Coarsely dispersed PVADs have exceptionally high resistance to various factors: they can withstand repeated freezing and thawing, heating to almost 100°C, and the introduction of various fillers, including electrolytes. The disadvantage of these dispersions is the relatively low water resistance of the coatings they form, their low transparency, and lack of gloss. Homopolymer coarse PVADs are produced by emulsion polymerization of VA in the presence of a protective colloid - PVA and a redox initiating system H2O2 - FeSO4 at a pH of 2.8-3.2 using a periodic or continuous method. The choice of a specific formulation depends on the characteristics of the brand of the resulting dispersion (viscosity, solids content), as well as on the quality of the feedstock (MM PVA, sodium acetate content in it, monomer activity, etc.). Emulsion polymerization of VA is carried out by a periodic method in reactor 4 made of chromium-nickel steel with a capacity of 4-16 m3, equipped with an anchor or anchor-blade mixer, a jacket for heating and cooling, as well as a system of two series-connected refrigerators, one of which is cooled by circulating water, the other - water with a temperature not higher than 5°C or brine. From the apparatus for preparing the aqueous phase, a solution of PVA and formic acid is loaded into the polymerizer through a measuring cup. An aqueous solution of FeSO4 is introduced directly into the polymerizer. The heat of reaction is removed mainly due to the evaporation of the azeotropic mixture of VA and water, condensing in reflux condensers 5 and 6; 20% of the heat is removed through the jacket of the device. To facilitate the operating conditions of the heat removal system, VA and hydrogen peroxide are supplied in 3-5 doses. The polymerization temperature is initially determined by the boiling point of the azeotropic mixture VA - water (65-68 °C); as the reaction proceeds and the monomer content decreases, the temperature of the reaction mixture rises to 70-75 °C, and it should not exceed 92 °C. Upon completion of the polymerization of the last portion of VA, the reaction mass is cooled to a temperature of no more than 60 ° C and pressed under compressed nitrogen into standardizer 7 with a capacity of 6 - 40 m3. If the content of residual VA in the dispersion exceeds 0.5% (wt), the monomer is distilled off from the polymerizer or standardizer at 75-85 °C and residual pressure 200-266 hPa. In the standardizer, the dispersion is neutralized with an aqueous solution of ammonia to pH 4.5-6 in order to prevent corrosion of equipment during its subsequent processing. To prevent dilution of a dispersion containing low values pH, it is advisable to neutralize PVAD with powdered calcium oxide or hydroxide. Due to comparatively high temperature After glass transition of PVA (28 °C), when HSAD dries, brittle films are formed, which does not allow the dispersion to be used for coatings, and in many cases, as an adhesive. To reduce the glass transition temperature of the polymer, the dispersion is plasticized with DBP. If PVAD is used for the manufacture of containers and other purposes in the food industry, as a plasticizer. Torah use less toxic dibutyl sebacate. The operation of plasticizing the dispersion is carried out in a standardizer by uniformly introducing the plasticizer into the PVAD with stirring for 2.5-3.5 hours, the temperature of the dispersion should not exceed 50 °C. Mixing of the dispersion continues for another 5-12 hours until the polymer is finally combined with the plasticizer. The plasticization process is usually accompanied by an increase in the viscosity of PVAD, the greater the higher the plasticization temperature. The plasticized dispersion is not frost-resistant, therefore winter period PVAD and plasticizer are transported and stored separately, which increases transportation costs and requires the use of special equipment to plasticize the dispersion before use. The introduction of 0.2-0.5% (wt.) maleic anhydride into the dispersion, followed by heating the composition for 2 hours at 68-72 °C makes it possible to obtain frost-resistant plasticized PVAD. The dispersion's resistance to freezing is determined by the formation of an acidic ester of PVA and maleic acid, which improves the surface-active properties of the protective colloid. Heating the composition to a higher temperature is accompanied by an increase in the viscosity of PVAD, up to its transition to a paste-like state. Shipment finished products carried out in barrels, railway tanks or in other containers provided for by GOST 18992-80. The container is made of aluminum, of stainless steel or lined with polyethylene. The containers are filled by pressing the PVAD with compressed nitrogen from standardizers or storage facilities through a mechanical screw classifier. The dispersion is pressed through the classifier mesh, and pieces and films of polymer are unloaded by a screw and sent for waste destruction. A method has been developed for optimizing the emulsion polymerization process of VA, based on the joint solution of model equations that determine the dependence of the quality indicators of PVAD on the formulation and polymerization mode. It allows you to choose optimal conditions for the production of any brand of PVAD, 'ensuring high quality of the product: minimum content of insoluble part, residual VA, resistance to dilution, etc. Polymerization of VA by a continuous method is carried out in a unit consisting of stepwise polymerizing reactors with a capacity of 0.8-2, 5 m3, connected to each other by overflow pipes (flows). The reaction mass flows along them from the upper part of the previous reactor into bottom part subsequent. The optimal number of polymerization reactors, determined by mathematical modeling taking into account the features of emulsion polymerization of VA in the presence of PVA (complete segregation of particles), turned out to be five. After polymerization is completed, the dispersion is cooled in coolers 10 and enters a standardizer, from which, under a vacuum created by a vacuum pump, unreacted monomer is removed. The remaining operations are practically no different from those described for the periodic method. Installation continuous action automated, its productivity is 700-4000 kg/h PVAD, depending on the capacity of the polymerizers.

Homopolymer ton-disperse PVADs

Finely dispersed homopolymer PVADs with a particle diameter of up to 0.5 μm are obtained by emulsion polymerization of VA in the presence of an emulsifier and initiator ammonium persulfate at pH 8-10, providing maximum speed initiator decomposition. This type of dispersion, unlike coarse PVADs, forms a shiny, water-resistant coating upon drying and is used primarily in the production of high-quality water-based paints. To obtain finely dispersed PVAD, the following installation can be used: a solution of ammonium persulfate and VA is introduced into the polymerizer in five equal portions, with each subsequent portion being fed after the completion of polymerization of the previous one, as in the periodic process of obtaining coarse PVAD. After polymerization is completed, the dispersion is cooled to 20-40 °C and, using compressed nitrogen, is pressed into a standardizer, where plasticization is performed. The finished PVAD is poured into containers for shipment to the consumer. The finely dispersed PVAD obtained in this way is not frost-resistant, so it can be transported and stored only at a temperature not lower than 5 °C. To impart frost resistance to the dispersion, 3 parts (wt.) of MBM are added to VA at the polymerization stage. After polymerization is completed, the dispersion is neutralized to pH 6.5-7.5 with diluted ammonia water with a concentration of no more than 12% (wt).

Vinyl acetate copolymer dispersions

The method of plasticizing dispersions with external plasticizers has a number of disadvantages, including the possibility of migration of the plasticizer from the polymer, its volatilization, and the increased toxicity of most plasticizers. All of these disadvantages are devoid of another method of plasticizing PVA - copolymerization of VA with monomers that impart increased elasticity to the copolymer. The most widely used comonomers for the preparation of copolymer dispersions based on VA are esters of maleic and acrylic acids and ethylene. Dispersions of copolymers of vinyl acetate with dibutyl maleate are produced in the form of both medium-dispersed products with a particle size of 0.8-1.5 microns, the synthesis of which uses high-molecular-weight surfactants (incompletely hydrolyzed PVA), hydroxyethylcellulose or mixtures of these polymers with low-molecular-weight surfactants, and finely dispersed ones based on an emulsifier S-10. A dispersion of copolymer VA with DBM, obtained in the presence of a mixture of hydroxyethylcellulose and the nonionic emulsifier proxanol-168, has increased frost resistance. Dispersions of vinyl acetate copolymers with acrylic acid esters are prepared using 2-ethylhexyl acrylate (2-EHA), butyl acrylate, and acrylic acid as comonomers. When copolymerizing VA with 2-EHA in an emulsion, PVA in combination with proxanol-168 is used as a protective colloid, and the H2O2-FeSO4 redox system is used as an initiator. The copolymerization process proceeds in the same way as in the production of homopolymer PVAD, in an acidic environment at a pH of the aqueous phase of 2.8-3.2, achieved by the introduction of formic acid. Due to the higher activity of 2-EHA compared to VA, to obtain a compositionally homogeneous copolymer, a compensatory copolymerization method is used, first introducing all of VA and only 2.5% (wt.) of the calculated amount of 2-EHA, and then gradually throughout the entire copolymerization process load the remaining amount of 2-ethylhexyl acrylate. Dispersions of ternary copolymers of VA with butyl acrylate and acrylic acid are obtained by emulsion copolymerization of these monomers using C-10 as an emulsifier mixed with sulfanol. Dispersions of VA copolymers with acrylic and maleic acids, neutralized with ammonia, form highly viscous aqueous solutions. Dispersions of copolymers of vinyl acetate with ethylene (SVED) have the ability to form films even at low temperatures, and films based on them are water-, light- and weather-resistant, and are also relatively resistant to alkaline hydrolysis. In addition, the advantage of SVEDs is their lower cost not only compared to other copolymer, but also homopolymer dispersions due to the use of cheap ethylene as a comonomer. SVED is obtained by copolymerizing VA with ethylene in autoclave reactors at pressures up to 5 MPa by batch and continuous methods. To synthesize coarse grades of SVED, a protective colloid (PVA) and a redox initiating system H2O2-FeSO4 are used. Finely dispersed SVEDs are obtained in the presence of an emulsifier S-10 or OP-10 and an initiator - potassium or ammonium persulfate. The pressure at which the process is carried out is higher, the more ethylene units that must be introduced into the copolymer macromolecule. In addition to ethylene, vinyl chloride can be introduced into the copolymer, which helps to increase the strength, water and alkali resistance of films and coatings obtained from dispersions. The preparation of the aqueous phase is carried out in devices with a capacity of up to 60 m3, equipped with a jacket and a stirrer. When producing SVED, approximately the same ratio of components of the aqueous phase is used as in the production of PVAD. The copolymerization reaction takes place in a batch polymerizer-autoclave with a capacity of 20 m3 with a heat exchange mixing device tubular type and a multi-zone jacket that serves to remove the heat of polymerization (- 1880 kJ/kg of copolymer). The aqueous phase is pumped into the polymerizer by pump 2, after which the apparatus is filled with ethylene to a pressure of 2.6 MPa in the production of coarse SVED grades or 5 MPa in the case of synthesis of fine SVED grades. VA in apparatus 6 is saturated with ethylene, which compensates for the loss of ethylene included in the copolymer. In addition, due to the partial dissolution of ethylene in VA, the homogenization of comonomers improves and the ethylene content in the copolymer increases. The dosage of ethylene-saturated VA and the initiator into the polymerizer is carried out for approximately 10 hours at 60-70 °C. Isolation of polymers from dispersions As a rule, PVADs are used in various industries National economy in the form of water-dispersed products. But in cases where the cost of transporting water is too high or it is necessary to obtain dry compositions based on PVA, VA homo- and copolymers are isolated from dispersions in the form of powders. After mixing in water, these powders again form stable dispersions, which is why they are called redispersible. Redispersible PVA and VA copolymers are obtained by drying the corresponding dispersions with a concentration of 20-25% (wt.) in dryers from Anhydro or Niro Atomizer (Denmark). The dispersion is sprayed using a special nozzle or a rapidly rotating disk; hot nitrogen or air is supplied to the dryer from the side of the spray device. The gas temperature at the inlet to the dryer is 80-85 °C, at the outlet 35-40 °C. The dry powder is separated in a cyclone and the air is released into the atmosphere; when nitrogen is used, closed loop. The finished redispersible powder has a moisture content of no more than 2% (mass). The redispersing effect can only be obtained in the case of dehydration of coarse products obtained in the presence of protective colloids, usually PVA. To prevent the powder from sticking to the walls of the dryer and clumping, 0.5-10% of aerosil by weight of the polymer is added to the dispersion. Dispersions modified with thermosetting resins One of the main disadvantages of PVADs when used as coatings and adhesives is the low water resistance of the resulting materials, which is due to the presence of hydrophilic protective colloids or emulsifiers in the dispersions, as well as the high polarity of the molecules of the PVAD itself. There are many ways to modify PVLD in order to increase the water resistance of the films, coatings and adhesive joints. One of the most technologically advanced methods for modifying coarse homo- and copolymer dispersions is the preparation of PVAD compositions with thermosetting oligomers. The production of such compositions is possible at dispersion manufacturing plants. Epoxy resins of the ED-20 and UP-160 grades or resol phenol-formaldehyde resin in the form of an alcohol solution—bakelite varnish LBS-1—are used as thermosetting oligomers for modifying PVAD. Combination of PVAD with epoxy resin produced in devices equipped with a stirrer, at room temperature. The dispersion is loaded into the apparatus and, with constant stirring, equal amounts of epoxy resin (up to 30% by weight of PVA) and demineralized water are gradually added to it over 2-4 hours. Mixing after loading of resin and water is completed until the dispersion is completely combined with the resin, determined visually. Modification of PVAD with bakelite varnish is carried out under similar conditions. Bakelite varnish, previously diluted with ethyl acetate in an amount of 10% of the varnish weight, is added to PVAD gradually over 5-6 hours, after which the composition is mixed for another 2-3 hours. The ratio of PVAD and bakelite varnish is from 100:40 to 100:50 mass. The introduction of ethyl acetate into the composition prevents the precipitation of phenolic resin from the solution when mixing the varnish with an aqueous dispersion. As a result of mixing PVAD with resins, water-dispersion compositions are obtained, which are multicomponent systems in which the combination of ingredients occurs during the process of film formation as water is removed. For complete curing of films (formation of polymers with a three-dimensional structure), the introduction of hardeners is required, which is usually polyethylene polyamine for epoxy resin, and acids, such as phosphoric or oxalic, for phenol-formaldehyde resins. When curing films obtained from a composition of PVAD with epoxy resin (PVAD), heat treatment at 110 °C for 3-4 hours is always necessary. Curing of films made from a composition of PVAD with phenol-formaldehyde resin (PVADF) can occur both in the cold (with the introduction of acid catalysts into the composition) and at 100-120°C without hardeners. PVAED and PVADF make it possible to obtain products with increased water resistance and mechanical strength in comparison with materials based on the original PVAD. However, a comparison of the properties of these two compositions shows that films made from PVAED are highly resistant to organic solvents, in contrast to films made from PVADF, but the latter have higher water resistance. This is explained by the fact that if, when curing PVAED, structuring occurs throughout the entire volume of the polymer composition, then when curing PVADF, an increase in water resistance is a consequence chemical interaction hydroxyl groups of the protective colloid (PVA) with methylol groups of phenol-formaldehyde resin. The water resistance of coatings and adhesive compounds made from coarse PVAD can also be increased by modifying the dispersions with urea resins, tetraethoxysilane and its hydrolysis products, isocyanates and other compounds that interact with the hydroxyl groups of PVA. The structuring of finely dispersed PVADs is carried out using “cross-linking” agents that react directly with the functional groups of VA srpolymers. For example, compositions from dispersions of copolymers containing units of acrylic or maleic acid and diglycidyl ethers of mono-, di- or triethylene glycol form coatings and films that acquire a three-dimensional structure when heated to 110-115 ° C. These structuring agents simultaneously act as dispersion plasticizers.

PRODUCTION OF POLYVINYL ACETATE BY SUSPENSION METHOD

To polymerize VA in suspension, you can use the same polymerizers as for producing PVAD by the batch method. The size of PVA granules depends mainly on the rotation speed of the mixer, which should be at least 90 rpm depending on the capacity of the reactor. The aqueous phase (a solution of incompletely saponified PVA) is loaded into the polymerizer, it is heated to 60^62°C, and VA with BP dissolved in it is fed. As the VA conversion increases, the temperature of the reaction mass is gradually raised to 65-67 C, and at the end of the process. During polymerization, the suspension is kept for 2 hours at 90-95 °C. The total duration of polymerization reaches 7-9 hours. The duration of this operation can be significantly reduced if, before conversion, 30-70% of VA is polymerized in bulk, and then the reaction mixture is dispersed in an aqueous solution of a stabilizer and the polymerization of VA is completed in suspension. The cooled suspension is centrifuged, the PVA granules are washed with water, and the polymer is dried in a rotating horizontal cylindrical dryer with air circulation. In the same way, suspension copolymers of VA with Dibutyl maleate and ethylene are obtained. In the latter case, copolymerization is carried out in a polymerizer-autoclave under pressure up to 2 MPa.

STRUCTURE AND PROPERTIES OF POLYVINYL ACETATE

Polyvinyl acetate is an amorphous, colorless, tasteless and odorless thermoplastic polymer. PVA produced in industrial plants has saponified and unsaponifiable branches formed as a result of chain transfer reactions to the polymer and monomer. The terminal groups of the PVA macrochain can be fragments of initiator molecules, as well as solvents and impurities present in the reaction mixture. The content of head-to-head structures in industrial samples is 1-2.5% (mol.).

PHYSICAL-MECHANICAL AND ELECTRICAL PROPERTIES OF POLYVINYL ACETATE

The physical and mechanical properties of PVA largely depend on the molecular weight and degree of branching of the polymer. The elastic modulus and elongation at break of linear PVA are significantly higher than that of branched PVA. At the same time, branched PVA has higher heat resistance compared to a linear polymer of the same molecular weight due to a higher concentration of structural network nodes, overlaps and interweaving of macromolecules. Dielectric loss tangent and the dielectric constant PVAs change with temperature, frequency, and moisture content of the polymer. Thus, at 20 °C tg b has a maximum value at 107-108 Hz, but with decreasing temperature* the maximum tg b shifts to the region of lower frequencies. With a decrease in current frequency to 60 Hz, the dielectric constant increases to 6.1, and after exposure to PVA at 100% relative humidity- up to 10. Being a polar polymer, PVA is highly soluble in chlorinated hydrocarbons, esters, ketones, acetic acid, dioxane, aromatic hydrocarbons, methanol, 95% ethanol; swells strongly in higher alcohols. Addition to propyl and isopropyl alcohols small quantities water makes them PVA solvents. PVA is insoluble in water, aliphatic hydrocarbons, gasoline, kerosene, mineral oils, turpentine, carbon disulfide, glycol, glycerin. The molecular weight of PVA, depending on the conditions for obtaining the polymer, varies from 10,000 to 2,000,000. The limiting viscosity number depends on the degree of branching of PVA. At the same MM, branched PVA is lower than linear one. Below are the values ​​of K a a for industrial samples of PVA obtained various methods and differing in the degree of branching were measured in an acetone solution at 20 °C; The MW of PVA was determined by sedimentation in an ultracentrifuge. In a methanol solution until complete conversion. In a methanol solution until conversion is 50-60%. The plasticizing effect of various comonomers can be assessed by the reduction in Tc of VA copolymers. Ethylene is the most effective “internal” plasticizer, and also the cheapest comonomer. At a content of 40 wt% ethylene, the relative elongation reaches 2000%, while the tensile breaking stress of the films decreases to 2 MPa. Copolymers of this composition resemble rubber in properties. The introduction of vinyl chloride units into the copolymer, on the contrary, increases its rigidity. By varying the content of VA, ethylene and vinyl chloride units in the ternary copolymer, a sufficiently elastic and durable material can be obtained.