Urea-formaldehyde resins: production, use and properties

Urea-formaldehyde resins are widely used in construction, wood processing and some other branches of the national economy. The industrial way to produce them was first launched in the United States in 1927. According to the water resistance and strength of polyester and epoxy materials, such resins are somewhat inferior. But their production is much cheaper.

How to produce

KPS resin is obtained, as already can be judged by the name, by polycondensation of formaldehyde with urea. They represent a non-flammable aqueous suspension, the degree of viscosity and color may vary depending on the brand. The production of urea-formaldehyde resins usually involves the use of special apparatus equipped with a jacket and a special stirring device. In total, the process of manufacturing such products includes three main stages:

• Polycondensation;

• Acid condensation;

• Drying.

Polycondensation of the resin is carried out in an alkaline medium at a pH of the reaction solution of 7.5-8. During the manufacturing process, the molar ratio of carbamide to formaldehyde is 1: 1.6-1.9.

Acid condensation is carried out in a medium with pH = 4.5-4.8. At this stage, in connection with the increase in the molecular mass, the viscosity of the solution begins to increase sharply. еще одну порцию карбамида. At the end of the acid condensation reaction, another portion of carbamide is added to the resin . The required amount of this substance is calculated in such a way that the molar ratio of the components in the finished solution is 1: 1.3-1.4. At the drying stage, the resin is adjusted to the desired values of the conventional viscosity. продукт охлаждают и модифицируют с целью снижения его токсичности. At the final stage, the product is cooled and modified to reduce its toxicity.

Scope of use

Use urea formaldehyde resin (formula N = CH2 C = O and NH2 HOCH2NH C = O NH2) can be produced:

• Fiberboard and chipboard;

• Plywood;

• Fillings, varnishes and paints;

• Moisture-proof paper and cardboard (impregnation);

• Foam.

карбамидоформальдегидная (КФ-МХ2) в бурении . Also very often the resin is carbamide-formaldehyde (CF-MX2) in drilling . In this case, it is used as the basis of oil wells. The latter, in turn, are viscous mixtures capable of rapidly solidifying in air. Tamponage solutions are used mainly to fasten casing strings and to protect them from corrosion.

Glue based on CFS

At enterprises of the woodworking industry in its pure form, CFS is rarely used. Much more often serves as the main element in the carbamide-formaldehyde resin glue used in the carpenter's business. The main varieties of such tools, produced on the basis of CFS, there are five:

• KF-B - quick-setting glue;

• КФ-О - general purpose (the content of formaldehyde is not higher than 0.25%);

• КФ-МТ - low-toxic, used for the production of fiberboard and chipboard;

• KF-F - with increased viability;

• KF-BZH - combining the advantages of brands KF-B and KF-G.

Fast-hardening adhesives KF-B at the enterprises of the woodworking industry are used mainly for the production of plywood and for the lining of furniture boards on single-span presses. The small-oxide product KF-O is used, for the most part, only for gluing paper. Also, such glue can be used in the production of plywood. Particleboard and fiberboard with its use are not manufactured. For the production of plates based on chips or fiber, the product of the brand KF-MT is used.

Glue with increased viability is great for connecting all kinds of furniture parts. In construction, in some cases, it can also be used to strengthen weak soils. Universal adhesives KF-BZH are most often used in the manufacture of plywood and furniture. They can also be used in the manufacture of various types of joinery products. Depending on the type of hardener, all adhesives based on CFS can be used for both hot and cold gluing.

Sometimes in the construction, woodworking, etc., special glues with various kinds of modification additives are used.

Properties of KF-MT Resin

The technical characteristics of urea-formaldehyde resins, depending on the field of application, can be different. From the table below, you can get information about the properties of the most popular resin KF-MT used in the production of fiberboard and chipboard.

From other brands of KF-resins, KF-MT differs primarily in reduced viscosity with a relatively high dry residue. Such characteristics allow it to be introduced into mixers with airless spraying. The use of such equipment, in turn, makes it possible to significantly reduce the humidity of the resin-treated wood particles and, consequently, to reduce the pressing time of the plates.

Impregnating resins (GFP)

This type of CFS is used in the manufacture of moisture-resistant cardboard and paper. Sometimes it is also used for impregnating decorative roll films, chipboard plywood and fiberboard. The characteristics of this product are shown in the table below.

Characteristics of the resin used for the production of coatings

For this purpose, the product of grade K-421-02 is usually used. It is a clear melamine melamine-formaldehyde resin and has the following properties:

Properties of KF-MX2

Urea-formaldehyde resins used for the production of grouting mortars must also fully comply with GOST.

Urea-formaldehyde foam: scope of use

This product is used mainly in construction as a thermal insulation material. It can be used for insulation from cold:

• Walls;

• Under-roof space;

• Interfloor ceilings and ceilings.

In comparison with conventional expanded polystyrene, FPP foam has one important advantage. This material is completely incombustible. Urea-formaldehyde resins Belong to the group of thermoactive substances. That is, reverse reactions in them can not happen by definition. Accordingly, CFS-foam during the fire does not form a melt. The only thing - under the influence of high temperatures, it loses a little in mass, allocating nitrogen and carbon dioxide that are not harmful to human health. The service life of this type of foam is about the same as that of extruded polystyrene - about 80 years. This material can be used both in the form of slabs and in a liquid state. In the latter case, the mass is simply poured into the cavities of various types of building structures.

How to make polystyrene foam

For the first time this interesting material appeared in the late 30's in Germany. In Europe, when building buildings and structures it is used very widely. In 30% of cases with the insulation of various kinds of enclosing structures this material is used. Recently, more and more popular CFS foam has become in Russia.

The technology of manufacturing this heater is relatively simple. On sale even there is a special, relatively inexpensive equipment, which, in principle, anyone can buy. Such settings work as follows:

• In one of the tanks is poured a water solution of orthophosphoric acid and a foaming agent;

• In fact, the urea-formaldehyde resin itself is placed in another container;

• The cocks open in a barrel.

A powerful pump is used to mix the material components. Carbamide-formaldehyde resin and foam stream are distilled into a special mixer. The mass obtained in this container is poured into the cavity of the building structures through a hose with a nozzle.

Properties of the resin used for the production of expanded polystyrene

For this purpose, the product of the brand KFZH-PV is usually used in construction. This liquid resin is white or light brown in color, the technical characteristics of which must exactly meet the requirements of GOST.

How to label KF-resins

Thus, the application of urea-formaldehyde resin, which is very wide in industry and in the field of construction, has found. This product is marked according to the requirements of GOST-14192. On the label of the container with CFS or in the delivery note there should be:

• The name of the manufacturer with its trademark;

• Net weight;

• Brand of resin;

• Date of manufacture;

• Batch number;

• The designation of the standard itself.

How the resin should be packed

Large woodworking and construction companies purchase this product usually in very large quantities. In this case, the urea-formaldehyde KF resin is delivered to the destination in railroad tank cars. The product lots are less spilled into steel drums. The latter before use, according to GOST-13950, must be thoroughly washed. Standards allow resin pouring, including in multi-turn drums with small external defects.

Test methods

Carbamide-formaldehyde resins are used in factories in batches (with the same characteristics and mass of not more than 200 tons). To test the quality of the product, tests are carried out. At the first stage they produce:

• Sampling of point samples by a metal tube;

• Connection of all samples with placement in a glass jar;

• Sticking of labels with the date and place of sampling.

Actually, the tests themselves can include a visual inspection, as well as a determination in the laboratory:

• The mass of the dry residue of each sample;

• Mass fraction of free formaldehyde;

• Concentration of hydrogen ions;

• Gelatinization time;

• Miscibility with water;

• Tensile strength.

How to transport and store correctly

Transport resin urea-formaldehyde (the class of danger of this substance - II) can be on all modes of transport. At temperatures below 0 ° C, only tanks with heat exchangers or thermal insulation coatings may be used. In the latter case, the heating is carried out by feeding hot water into the tank casing. The temperature of the CFC after this procedure should not exceed 25 ^° C. Do not preheat the product with steam.

In summer, at t air of 25 ^о С, the resin can be transported no longer than for 10 days. Store the product at a temperature of not less than 5 ° C and not more than 20 ° C in a tightly closed container. It is not allowed to keep barrels or tanks with tar under direct sunlight. Also, GOST prescribes to store containers with this product under a canopy, not allowing the impact of atmospheric precipitation on it.

Urea-formaldehyde resin: manufacturers and brands

For today in Russia it is made about 500 thousand tons of CFS per year. The largest domestic companies involved in the production of this product are:

• Yugorsky lespromholding;

• Shatura;

• Cherepovets and Povolzhsky plywood and furniture plants;

Also, we are engaged in the manufacture of such products as carbamide-formaldehyde resin, Russian-Finnish producers in our country. Specialized in the production of this material, for example, CJSC "Metadineya" and the company Kronostar-Vostok, part of the European concern Swiss Krono Group. In addition, CFS is one of the varieties of products produced by such giants of the chemical industry as Acron and Metafax.