CS239365B1 - A method of treating ligninolulosic raw materials prior to pulping - Google Patents

Abstract

The invention belongs to the field of wood and wood materials processing. It solves a method of treating lignocellulosic raw materials before pulping with urea or a mixture of urea with other plasticizers and swelling agents, or other organic and inorganic compounds, such as solvents, preservatives, flame retardants. The procedure is that urea is added to the raw material in the form of chips, sawdust or shavings in the form of a solution in an amount of 2 to 30% by weight of the dry matter of the lignocellulosic raw material by spraying, soaking or other impregnation, at temperatures of 0 to 200 degrees Celsius, or the solution is added with simultaneous mechanical treatment. It is also possible to proceed in such a way that the addition of the urea solution is carried out in the presence of pressurized steam,

Description

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The present invention relates to the preparation of lignin-cellulosic raw materials prior to pulping. At present, a large number of surface materials based on pulped wood and other lignin cellulose materials are produced. According to the purpose of use, the fibrous matter can be obtained by mechanical, thermo-mechanical or chemical-mechanical means. The energy and technological demands of the process depend on the raw material conditioning stage, and the quality of the product is reflected in the quality and quantity of the product. The most common way to pre-treat lignin-cellulosic material before pulping is by steaming the chopped raw material at a saturated steam pressure of 0.8 to 1.2 MPa. seconds. This treatment results in partial plasticization of the cellulosic raw material and subsequent easier separation and damage of the fibers. In other methods, increased plasticity of the feedstock is achieved by chemical means, for example by treating liquor solutions, alkaline salts, ammonia, and optionally by partial hydrolysis with dilute acid solutions. AO No. 203,568).

Also disclosed is a plasticizing effect of urea, described by Berlin, A.A. 1950, or urea with other plasticizers and agents such as ammonia, di-cyanediamine, dimethylsulfide, ethyl alcohol, and others. Shamojeva et al. Showed a good plasticizing effect of urea on wood products at elevated temperatures and also described the effect of a mixture of urea and phosphoric acid as a flame retardant or use of urea in combination with polyvinyl alcohol as a binder material.

It has been found that the pulping process is facilitated by the treatment of lignin-cellulose materials prior to pulping by the use of urea or urea granules with plasticizers and blowing agents, or other organic and inorganic compounds thereof, such as solvents, preservatives, flame retardants, the essence of which is that in the form of a slurry, chips, sawdust or other shaped feedstock, urea is added in the form of a solution in an amount of 2 to 30% by weight of urea and the dry weight of the lignin-cellulose raw material by spraying, dipping or other impregnation of temperatures of 0 to 200 ° C. One can proceed in such a way that the urea solution is added to the current mechanical treatment or under the presence of pressurized steam. The advantage of the process according to the invention is that the pulping process is considerably improved, namely under the circumstances that pulping is carried out without the use of steam, since the pulping temperature of the pulping apparatus is sufficient to produce a plasticizing effect by grinding the raw material. The effect of urea in the plasticization direction can be compared here with the product of ammonia. The use of urea has more advantages with respect to the use of ammonia.

In addition to improving the working environment, the formation of fibrous material from the smoothness of the subsequent hot pressing and heat treatment, the improvement of the physical and mechanical properties of the materials produced, is more advantageous.

Under the pulping conditions of lignin-lululosic raw materials or compression of fibrous matter, urea is decomposed by hydrolysis to form carbon dioxide oixide and ammonia, while the hydrolysis promotes the presence of acids and bases. Upon heating to the melting point, the urea loses the ammonia molecule to form biuret and heating to a higher temperature loses the ammonia molecule to produce isocyanic acid, which subsequently trimerizes to cyanuric acid. Ammonia, as one of the products of the decomposition reactions mentioned above, has marked plasticizing effects on wood and other decomposition reaction products to improve the physical and mechanical properties of the molded materials. In addition, it is believed that the urea interaction with urea ligand-lignulose component suro-vin. The raw material is processed in the form of chips, chips or sawdust, and urea is added in the form of a solution in an amount of 2 to 30. weight per dry matter of raw material and with additional additions.

The treated lignin-cellulosic feedstock can be pulped through a pressure steam of 0.5 to 1.2 MPa, possibly in a steam-free defibrator without the use of steam. In either case, the energy consumption and wear of the pulping apparatus is lower than that of the pulp after the physical plasticization. As a result of this process, the lignin-cellulosic fiber with a lower amount of damaged fibers is present, which, due to the presence of urea, possibly other substances, it is characterized by reduced flammability, which is the contribution made by subsequent drying and high temperature pressing of the fibrous material, or by the thermal refinement of the leached fibrous material. A further advantage of the inventive process of the present invention is its higher plasticity, which makes it possible to compress the fibrous material at lower pressures and preferably to apply it to the production of shaped moldings. The materials of the present invention with higher urea content are hot-bendable and formable.

Some methods of treating lignin-cellulosic raw materials prior to pulping and making fibreboards are described in more detail in the application examples. Example 1

Beech chips with a moisture content of approx

Claims (2)

P E E D Μ Ε T 1. A method of treating lignin-cellulosic raw materials prior to de-fibrillation of urea or a mixture of urea with other plasticizers and blowing agents or other organic and inorganic compounds, such as solvents, preservatives, flame retardants, characterized in that the raw material in the form of chips, sawdust and chips urea in the form of a solution in amounts of 2 to 30% by weight of urea for addition of shine lignin cellulose raw material by spraying, dipping or otherwise impregnating at temperatures of 0 to 200 ° C or added under simultaneous mechanical treatment. 2. The process for treating lignocellulosic raw materials prior to pulping according to claim 1, characterized in that the urea solution is added in the presence of pressure steam.