Production of carbamide-formaldehyde resin by continuous method

Introduction

Carbamide-formaldehyde resins (KFS) are the product of polycondensation of carbamide with formaldehyde. They are non-combustible, non-explosive aqueous suspension.

The generalized scheme of the carbamide resin production process is quite simple. A predetermined amount of raw materials and additives is charged into the stirred reactor. After the catalyst is introduced and the reaction mixture is heated by supplying steam to the built-in coils of the reactor, the condensation process begins. The process is controlled by maintaining the desired temperature and acidity of the reaction mixture.

Formalin and carbamide or KPA (carbamide-formaldehyde concentrate) forcondensate can be used as a raw material. The latter is increasingly used in the production of KFS. KPA is also prepared as formalin, only absorption of formaldehyde-containing gas is carried out with a solution of carbamide, and not with water, as in the case of formalin production.

Carbamide is able to merge, which is due to its good solubility in water. It merges strongly with long-term storage in the package in a hot and wet state (moisture content above 0.5%).

Moisture forms a saturated solution with salt. When the salt cools, its solubility in water decreases, and crystals are released from the saturated solution, which, merging, gradually form a monolithic mass. Reduction of carbamide fusion is achieved by reducing moisture in the finished product and cooling it to a temperature of 50? 60 ° C. Carbamide containing 0.2? 0.25% moisture practically does not merge, crumbles well and disperses.

The issue of ensuring the non-traceability of carbamide during transportation, especially over long distances, is the subject of constant control by the technological personnel of the carbamide manufacturers.

Today, various types of conditioning additives for carbamide are known and have already been tested in the industry. However, the most optimal treatment in the foreseeable future will remain the treatment of formaldehyde carbamide with a component - KPA (KFS).

It is known that the content of formaldehyde in the commercial prilled carbamide in a concentration of more than 0.1% provides the desired degree of crumbling of the granules when transporting the carbamide over medium distances. Today, the consumer wants to see, as a rule, the formaldehyde content in commercial prilled carbamide is already at least 0.25% and even 0.45% for granular carbamide, that is, the relative share of conditioning costs will still be noticeable.

Use of carbamide-formaldehyde resin in construction (CFS)

In industry, carbamide is the starting material for the production of carbamide resins, from which glue used for gluing plywood, varnishes, as well as a large number of various products of technology and everyday life is obtained. Carbamide resins are used to increase the strength of paper, give it transparency, waterproof, as well as in the woodworking industry for impregnating wood for the purpose of making it more resistant, in the leather industry for tanning white leathers, etc.

Carbamide-formaldehyde resins of the HPCG and KFHTP grades, and in rare cases KFMT15 are used for the manufacture of foam by air foaming. KFW and KFMT15 are also used as a binder in the production of chip and fibrous boards.

In the oil industry, it is used for the dewaxing of petroleum products: the extraction from petroleum products (diesel fuels, lubricating oils, etc.) of high-melting higher (starting with C10) aliphatic hydrocarbons. As a result of dewaxing, the operational properties of petroleum products are improved (the freezing temperature decreases).

Carbamide in terms of physicochemical parameters must meet the requirements and standards of GOST 20812010 "Carbamide. Specifications. "

Carbamide formaldehyde resins are indispensable in the production of particle and wood fiber boards, plywood. They are widely used in the production of carbamide foams, glass cloth, find applications in thermal insulation products and in the production of moisture-resistant special grades of paper and cardboard.

Based on aqueous solutions of urea-formaldehyde resins, adhesives used in woodworking and furniture industry are made. Adhesives are able to glue wood with a humidity of 8-15%, they are resistant to microorganisms, water, gasoline and oils and non-combustible substances. The viability of individual grades of adhesives (the time during which the glue is not gelatinized) is from 3 to 6 hours. Their disadvantage is in the gradual release of formaldehyde in the room, which is contained in the glue about 2%.

Along with pure urea-formaldehyde polymers, modified polymers modified with butyl and polyhydric alcohols are produced. These polymers are technically important products and are used for the manufacture of hot air drying varnishes used for impregnation of fabric, paper, cable making, coloring of refrigerators, medical and commercial equipment.

Unmodified and modified urea-formaldehyde resins are widely used to produce press materials that are used to produce parts of telephones, radios and televisions, electric lighting equipment and household items.

Manufacturing difficulties include the fact that mono and dimethylolurea are obtained only when the reaction conditions are accurately met. If these conditions are not met, a precipitate, methylene urea, insoluble in water and other solvents can be obtained. In the preparation of urea-formaldehyde resins, the formation of methylene urea is avoided, as it impairs the quality of the resins. The process must be conducted so that the resin is obtained by condensing a mixture of mono - and dimethylolurea.

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