DE1234381B - Process and press plates for the production of fiberboard or pellets from lignocellulosic materials - Google Patents

Description

GERMAN Wjfäm PATENT OFFICE German class: 39 a7 - 5/00

EDITORIAL

Number: 1234381

File number: D 357741 c / 39 a7

J 234 381 filing date: March 30, 1961

Opened on: February 16, 1967

The production of hardboard from wood chips or other lignocellulosic materials by defibering and forming a fiber mat from a water suspension of the fiber a sieve, whereby the mat is dewatered to a moisture content of 60 to 64%, is already known. The fiber mat is then formed into one on a screen pad in a hydraulic hot press One-sided smooth plate pressed. This process requires very significant amounts of water, and In addition, a certain amount of soluble organic substances and also short ones get into the sewage Fibers which severely pollute the rivers into which they are drained. It also occurs during manufacture of fiberboard in the "wet process" a significant consumption of water, and the construction of manufacturing plants is therefore tied to watercourses.

In order to enable the production of fiberboard in countries with a lack of water, so-called Dry and semi-dry processes introduced. These enable such preparation of the pulp without excess water that the fibers after defibering (wood chips) from a Air suspension can be promoted and deformed. Depending on the moisture content of the fiber mat you can Plates that are smooth on both sides or smooth on one side can be pressed. In these processes, the actual manufacturing process no harmful waste water, which is compared to the previously used so-called wet process represents a significant improvement.

The panels produced in the dry process have the disadvantage that they have a lower strength and have a higher hygroscopicity than fiberboard produced by the wet process. That's why it was necessary to add binders in the form of synthetic resin to the dry process in order to achieve the same properties to be achieved as with panels from the wet process. This means a certain difficulty of the manufacturing process, on the one hand because an additional Plant for applying this resin must be classified, and on the other hand because synthetic resins are relatively expensive.

There are also known manufacturing processes for fibreboards or compacts made of lignocellulosic material, in which hardboard boards that are smooth on one side are produced without binding agents at higher temperatures and pressures. The wood chips are steamed with high-pressure steam at a pressure of up to 70 atm, using the ligno process and press plates for production
of fibreboard or compacts
Cellulosic materials

Applicant:

Drevärsky vyskumny ustav,
Pressburg (Czechoslovakia)

Representative:

Dipl.-Ing. K. Siebert, patent attorney,
Starnberg, Almeidaweg 12

Named as inventor:
Vojtech Nagy,
Anton Dvorak,
Zdenek Sisler,
Tibor Ferko,
Karol Zembery,

Miloslav Keda, Kosice (Czechoslovakia)

Claimed priority Czechoslovakia from November 19, 1960 (6952)

cellulose-containing material lignin is activated, which is then used for gluing during subsequent pressing the fiber is used. However, when compared with panels from the wet process, these Plates have a significantly lower dynamic strength. In addition, these plates have on the Edges have a lower strength, which can be explained by the fact that during pressing water vapor escapes from the edge parts, which is necessary for the sufficient connection of the wood particles during hot pressing necessary is. This is also noticeable by the lighter color of such panels at the edges. In order to obtain panels with uniform properties, the edges of these panels must be used a relatively wide strip can be cut off.

Furthermore, methods are known in which FormpreßHnge by pressing small wood particles without Binder additive in a hermetically sealed form at temperatures from 125 to 210 ° C and at Pressures of 50 to 300 at can be established.

After a certain reaction time, the compacts are allowed to cool under constant pressure. By

709 E09 / 375

Application of high pressure results in compacts with a high density of 1.35 to 1.4 g / ccm, the is undesirable for fibreboard. The complicated press diagram, especially the cooling the shape in the second stage of the pressing process, requires unusually long pressing cycles (more than 25 minutes), as well as significant consumption of cooling water. The manufacture is particularly with associated significant heat loss, which adversely affects the economy of this.

It has been found that none of the previously known manufacturing processes for fiberboard or compacts made of lignocellulosic material under pressure and at higher temperatures, whether with or without the use of binders resulting from steaming the chopped material for the formation of binders and important for the gluing of the fibers of manufactured panels, water-soluble substances are not used to their full extent. These substances were z. B. at the Manufacture of fiberboard in the wet process during preparation before pressing and during washed out during the first pressing phase.

When using the dry process, the base material was below 8 ° / o or less Moisture dried up, so that it was impossible to use the water-soluble substances here too, because the moisture required for the reaction was missing.

In the semi-dry process, the humidity was kept within the limits of 25 to 36%, but this evaporated immediately at the beginning of the pressing and was responsible for the reaction and thus for the formation binders can no longer be used. With the dry and also with the semi-dry process the ability to plastify is therefore lost at the first moment of pressing.

According to this invention, hardboard is obtained from, similarly to panels from the wet process high dynamic strength when regulated during the attenuation of the lignocellulosic material and between the limits of 2 to 30% obtained water-soluble matter content and the Moisture of the frayed, 2 to 30% predried material in the predetermined, used lignocellulosic material dependent ratio is chosen, according to the after Reaction of the formation of binding agents of the water-soluble substances, the continuous or interrupted discharge the amount of vapor gas mixture from the closed press space during the pressing of the material timed at a temperature of 180 to 260 ° C and a pressure of 25 to 70 kg / sqcm will.

In the drawing is an embodiment of the pressing of lignocellulosic material in the Process according to this invention used press plates are shown schematically.

According to the invention one proceeds so that wood or other lignocellulosic material in known Way chopped and then a short steaming at medium or low Pressure between 1.5 and 20 at. The steaming time and the temperature or pressure value is depends on the type of raw material and is controlled with the help of the degree of degradation of the lignocellulosic Materials determined by analyzing the amount of water-soluble matter what happens in this Procedure is very important. For the production of

Fiberboard with a sufficiently high dynamic strength, which is similar to that of the wet process, it is necessary to to keep the content of water-soluble substances between 2 and 30%. When preparing the Fibers can have catalytically active chemicals, such as some alkaline or acidic compounds, such as B. caustic soda, sodium carbonate, sulfuric acid or zinc chloride or the like. Used will.

The damped material is then applied in a known manner e.g. B. frayed by grinding disks and then overdried to a humidity of 2 to 30% as needed. The moisture content depends on the type of raw material used and the content of water-soluble substances and is therefore controlled. During the drying process, which is carried out in an air stream, coarse fractions can be sorted out that are re-ground on a special mill, and fiber particles (fiber particles) can be fractionated according to size.

During the drying process, the heat accumulated in the material during its preparation is advantageously used. Individual fiber fractions are pneumatically conveyed into one or more molding chambers these the fibers are applied evenly to an endless belt, in such a way that the fine fractions on the surfaces, but the coarse parts are layered in the middle of the formed fiber mat will. This belt conveys the fiber mat into a continuously operating roller pre-press, where the Mat is compacted in a known manner.

It is compacted in the cold process (without increased temperatures) or by heating the mat over 100 ° C, which on the one hand results in a stronger compaction of the mat (which is also due to low Makes noticeable suspension after the prepress) and on the other hand a better cohesion is achieved, which allows the mat to be trimmed to sharp edges and safe handling when conveying it further enables. This shortens the pressing time in the hydraulic hot press.

Before entering the hydraulic hot press, the mat can be washed with water or with Solutions containing active substances to protect the finished panels from plant and animal pests contain, or with fire retardant or with solutions that increase the resistance to moisture raise, be sprinkled. These funds can of course also be found elsewhere in the Production line, such as B. in steaming or in the defibering, can be added.

The pressing of lignocellulosic material has so far been carried out in a closed room in such a way that that the pressed fabric itself forms a hermetic seal. The formation of the breech through the fabric itself can be achieved so that a thicker one at the edges of the pressed material Layer is applied and the closure is created by pressing the material together. A The disadvantage of the method mentioned is the significant loss of material.

According to the invention, the reaction equilibrium of the formation of binding agents is maintained by that the content of water-soluble substances and the moisture of the defibrated material can be selected in a predetermined ratio, according to which then during the pressing the drainage of the steam gas mixture (which during the

Claims (7)

Pressing occurs) is regulated in time. For this purpose, the steam gas mixture is then released continuously or discontinuously in a regulated manner. It is advantageous to use the closure formed by the fabric itself, namely that press plates are used as shown in the drawing to meet this requirement. A sheet of these is provided over the entire circumference with a coherent raised edge, flange or frame 2 or with a similar wedge-shaped border. The material 3 to be pressed is applied at a uniform height to the entire sheet 1, usually to a sheet without an edge 2, and the sheet 1 'provided with the edge 2 and having the outline of the desired compact is placed on the mat thus formed . The height of the edge or flange 2 can reach the thickness of the compact or be higher. In this case, the counter plate is provided with appropriate notches. At the points where the edge or flare is located, the material is compressed faster and more, and so the seal 4 is created with a greater density. This seal then forms the closure of this space. After pressing, the material compressed under the edge is the separating boundary between the quality pressed part and the edge. The pressed groove marked by the edge is used for easy separation or direct format cutting of the compact. An advantage of the proposed design of the press plates is in particular the possibility of forming compacts with the desired shape, increasing the quality of the product and reducing the amount of waste. The application of edges to the pressing plates does not require significant costs and can be carried out on all existing plates. The invention can not only be used for pressing large formats, but can also be used advantageously when pressing smaller compacts and patterns on plates, e.g. B. tile pattern can be used. During the pressing, the excess of the steam gas mixture is released in a regulated manner, intermittently or continuously. When the steam gas mixture is released in a regulated, step-by-step manner, this mixture can either be released at certain time intervals or gradually so that the equilibrium of the chemical reaction of the formation of the binding agent is maintained. After pressing, which takes 1 to 10 minutes depending on the plate thickness, the plate is removed from the press while it is hot, i.e. without cooling under pressure. After pressing, the panels are trimmed or post-cured and air-conditioned in a known manner. The pressing conditions can vary depending on the desired plate quality, namely the temperature between 180 and 260 ° C and 4 pressure between 25 and 70 kg / cm 2. This process is used to produce panels that are smooth on both sides; however, plates that are smooth on one side can also be produced. Almost all types of wood, i.e. coniferous and hardwoods, as well as other lignocellulose-containing materials, all types of wood can be used as raw material, since in this process not only the length of the elementary fiber is decisive, but also the amount and character of active substances that arise in the hydrothermal treatment of wood during steaming, defibering, preheating and pressing. Patent claims: 1. Process for the production of fiberboard or compacts with one or both sides smooth Surface made of lignocellulosic materials under pressure and at elevated temperatures in closed press room, the material being steamed at medium or low pressures is prepared, characterized in that the during the damping of the material regulated water-soluble content obtained between the limits of 2 to 30% Substances and the moisture of the defibrated, to 2 to 30% predried material in the predetermined, depending on the used lignocellulose-containing material ratio is chosen, according to the reaction after the reaction the formation of binding agents in the water-soluble substances, the continuous or interrupted discharge the amount of vapor gas mixture from the closed press space during the pressing of the Materials at a temperature of 180 to 260 ° C and a pressure of 25 to 70 kg / sqcm is timed. 2. The method according to claim 1, characterized in that when sorting out coarser Share in the air flow the heat accumulated in the material for simultaneous drying of the defibrated material is exploited. 3. The method according to claim 1 and 2, characterized in that the chopped material under Addition of catalytically active chemicals - alkaline or acidic compounds - such as sodium hydroxide, sodium carbonate, sulfuric acid, zinc chloride or the like. Is steamed. 4. The method according to claim 1 to 3, characterized in that the intended for pressing Fiber mass is pre-pressed at an elevated temperature above 100 ° C. 5. Press plates for carrying out the method according to claim 1 to 4, characterized in that one of the plates (1 ') on the entire circumference with a contiguous edge, border or frame (2) od. The like. Is provided, which simultaneously has the format of Product forms. 6. Press plates according to claim 5, characterized in that the height of the edge or flange (2) corresponds to the thickness of the compact. 7. Press plate according to claim 5 and 6, characterized in that one of the plates (1 ') is provided with a raised edge or flange (2) which is higher than the thickness of the compact, and the other plate (1) corresponding opposite Has notches. Considered publications:
German Auslegeschrift No. 1050 991;
Austrian patent specification No. 185 227. 1 sheet of drawings 709 509/378 2.67 © Bundesdruckerei Berlin