DE10232271A1 - Continual production of sheets of wood, e.g. oriented strand board, comprises supplying material onto a continuously moving transport band, heating and pressing - Google Patents

Abstract

A process for the continual production of sheets of wood, especially oriented strand board or other ligno-cellulose containing materials, comprises supplying material onto a continuously moving transport band (13) from a scattering station (12). A process for the continual production of sheets of wood, especially oriented strand board or other ligno-cellulose containing materials, comprises supplying material onto a continuously moving transport band (13) from a scattering station (12). The material and binder pass between a continuously operating press which has two steel bands, and which heats and presses the material. The material scattered consists of strands which are less than 15 mm wide. The lower steel band (4) has an associated endless metal band (15) which passes over deflecting rollers (17). The upper layer of the material is sprayed with water and preheated with steam.

Description

The invention relates to a method for producing wood-based panels, in particular chipboard (OSB) according to the preamble of claim 1 and a system for carrying out the method according to claim 4. Such a method, from which the invention is based, is the subject of the main application DE 101 01 952.1 ,

The main application is the task to provide a process to improve the structural quality on the wood-based panels produced, in particular on OSB panels, a Reduction of wear on the surfaces of the steel strips and a longer one Lifespan for the structuring metal fabric tape can be reached. Should continue the invention made it possible make the process parameters for the wood-based panel to be manufactured between the structure side and the smooth side of the plate so that with it an increased Production performance and product quality in terms of bending strength and bulk density profile can be set and the generation of a structured surface guaranteed reliable is and a facility for implementation to create this procedure.

The solution to this problem is that at least one endless metal fabric belt, which is in contact with one of the steel belts and the pressed material mat, is made of a material with a much higher thermal conductivity but has about the same thermal expansion coefficient as the steel belt, the steel belt and the metal fabric belt run back together through one die Insulating tunnel avoiding heat radiation, but the metal fabric belt is led from the steel belt separate and separate heating tunnel before entering the press area and heated to a higher temperature difference to the steel belt of at least 40 ° Celsius and the specific pressing pressure acting on the material to be pressed during the first 80% –90% of the pressing time in the continuously operating press takes place with a pressure not less than 0.3 N / mm ² .

Although the process and the plant according to the main application can provide satisfactory results, the process and the Plant can still be improved.

In test plants, it has been found that the pressing times are not yet within the specified range for chip boards (OSB). The reason for the long pressing times lies in the low transverse tensile strength of the chip boards to be produced, which can be caused, among other things, by a low use of adhesive. Due to the low transverse pulls, the pressed material mat within the continuously operating press must be completely evaporated to avoid bursting. With thin plates, the evaporation phase is approx. 30 seconds and is therefore longer than the heating phase of the pressed material mat. This problem is even more serious when pressing pulp boards with a density of over 700 kg / m ³ , since they can hardly be vaporized over the narrow surfaces of the mat.

The invention is based on the object Specify the process by which to avoid the evaporation phase is and the performance of the system increases significantly. A Another task is to set up a facility for carrying out the Procedure to switch.

The solution to the procedure is that the spread of the pressed material mat with chips smaller than 15 mm and for one-sided structuring only one on the lower steel band and endless metal fabric tape lying against the pressed material mat runs around gas permeable in the sieve level is so that the pressed material mat during the entire hot pressing is evaporated.

To carry out the procedure there is Plant in that the lower steel belt is a continuous endless Metal mesh tape is assigned, which is gas permeable in the sieve level is.

The desired increase in capacity will achieved because the material to be pressed is very perpendicular to the surface of the board permeable is and thus over the surface can be evaporated in the press. The permeability depends on the schnitzel width. Only if the schnitzel width is less than 15 mm is, is a hot press evaporation over the disk surface and over the gas permeable Screening level possible.

With the method according to the invention, the production of OSB panels with transverse pulls below 0.35 N / mm ^{2 can be carried out} in a continuous press with short pressing times because the mat to be pressed is evaporated through a sieve over the surface of the panel during the entire hot pressing and the beach width is less than 15 mm, preferably 8 mm. This is particularly advantageous for very wide panels with a width of 4 to 10 m. The press plate temperature can be set very high, for example over the entire length of the press 250 ° C.

Because the strainer runs around the bottom the water spray press mat possible and a further reduction in press time the result. But also warming up by means of the steam burst effect with under the mat running sieve and if the width of the chips is smaller this shortens it Time window of the pressing time additionally.

With the method according to the invention, the production of OSB panels or only longitudinally oriented chips panels with densities above 700 kg / m ³ can be carried out in a continuous press with a short pressing time. Sheets produced with this can have a high modulus of elasticity (over 6000 N / mm ² ) and a high flexural strength. According to the method according to the invention, the average Strand width set at 15 mm and the maximum width of the chips is limited to 5% of the mixture. In addition, to achieve the high modulus of elasticity, the fine fraction - i.e. chips with widths less than 3 mm, for example by sieving - must be removed.

Other advantageous measures and refinements of the subject matter of the invention result from the dependent claims and the following description with drawings.

From the drawing, the system shown in a schematic representation can be seen, with which the pressed material mat 10 Made of oriented or unoriented long chips less than 15 mm wide on a conveyor belt 13 from the spreading station 12 is sprinkled. According to the main patent, the conveyor belt serves 13 thereby to continue the pressing mat 10 by a spray device 23 and a preheater 22 in the continuously working press 1 , The endless conveyor belt 13 is over pulleys 14 guided. As a continuously working press 1 can serve a so-called double belt press, which in its main parts consists of a movable upper frame upper part 3 and from a solid frame base 2 consists of the adjustable press nip 11 form. Upper frame 3 and lower frame 2 are driven by drums 8th and deflection drums 9 of steel strips 4 and 5 circulate. At the press nip 11 facing sides of frame top 3 and lower frame 2 are the heatable and coolable press plates 6 and 7 appropriate. The one from the continuous working press 1 Extending finished wood-based panel is included 19 designated.

According to the invention is the lower steel strip 4 a surrounding metal mesh tape 15 associated with gas-permeable training in the sieve level, which according to the main patent from a material of higher thermal conductivity than the steel belt 4 or 5 there is, the steel band 4 or 5 and the metal cloth tape 15 are routed through an isolating tunnel in the return to prevent heat radiation and to save energy, as well as the metal fabric tape 15 before entering the press nip 11 in a heating tunnel 18 to a much higher temperature than the associated steel strip 4 or 5 in the inlet to the press nip 11 has. In the heating tunnel 18 becomes the metal cloth tape 15 via a lower heating plate 21 led, possibly also an upper heating plate 21 can be assigned. The preheating of the metal fabric tape 15 can also, or additionally, by means of a heating roller 20 be carried out, preferably the last pulley 17 in front of the inlet gap as a heating roller 20 is executed.

1.

continuous working press

Second

Frame bottom

Third

Upper frame

4th

steel strip below

5th

steel strip above

6th

press plate below

7th

press plate above

8th.

driving drum

9th

Umlenktrommel

10th

press material mat

11th

press nip

12th

spreading station

13th

conveyor belt

14th

guide rollers

15th

Metal fabric tape

16th

Isoliertunnel

17th

guide rollers

18th

Aufheiztunnel

19th

Wood panel

20th

Aufheizrolle

21st

Hot Plates

22nd

preheater

23rd

spraying

Claims (8)

Process for the continuous production of wood-based panels, in particular of wood chips or other lignocellulosic materials, in which a spreading station on a continuously moving conveyor belt is used to form a press material mat with binding agent, which after insertion is inserted between the upper and lower frame parts circumferentially guided steel strips of a continuously operating press using pressure and heat to a sheet strand or an endless wood-based panel is cured DE 101 01 952.1 , characterized in that the spreading of the pressed material mat takes place with chips smaller than 15 mm in width and, for a one-sided structuring, only one endless metal fabric belt lying against the lower steel belt and on the pressed material mat, which is gas-permeable in the sieve plane, so that the pressed material mat during the entire hot pressing is evaporated. A method according to claim 1, characterized in that the Scattering of the pressed material mat with chips with an average width of 15 mm, the proportion of chips with a greater width than 15 mm, however, does not exceed 5% of the total mixture. A method according to claim 1 and 2, characterized in that the scattering of the pressed material mat with Shavings less than 3 mm wide are prevented by placing them in front the scattering station. A method according to claim 1, characterized in that the Scatter the pressed material mat with an average cutlet Width between 6 and 10 mm A method according to claim 1, characterized in that the upper cover layer of the pressed material mat is enriched with spray water. Process according to the claims 1 and 2 and 5, characterized in that both cover layers the material to be pressed is preheated using steam. Process according to the claims 1 to 6, characterized in that the entire mat to be pressed preheated by steam becomes. System for the continuous production of wood-based panels, in particular of wood chips or OSB, from wood or other lignocellulosic materials with a surface structured on one side, comprising a spreading station, a conveyor belt which is continuously moving under the spreading station and a continuously operating press, a mixture of the spreading station Long chips and binders can be scattered unoriented or oriented to form a pressed material mat, the continuously operating press consists of an upper frame part and a lower frame part and attached heatable and coolable press plates as well as two endless steel belts which transfer the pressing pressure and pull the pressing material through the continuously working press, whereby the steel belts are guided around the upper frame and lower frame via drive and deflection drums and are supported according to DE 101 01 952.1 , to carry out the method according to claims 1 to 4, characterized in that the lower steel strip ( 4 ) an all-round endless metal fabric tape ( 15 ) is assigned, which is gas-permeable in the sieve level.