DE1276912B - Method and device for the production of wooden bodies - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

B 29 j

German KI .: 39 a7 - 5/04

Number: 1276 912

File number: P 12 76 912.9-15 (W 36573)

Filing date: April 13, 1964

Open date: September 5, 1968

The invention relates to a method for producing wood chip bodies, in particular wood chipboard, from a mass containing wood particles and thermosetting plastic binder, wherein brought the pre-compressed mass between heated press plates, there on the desired end service pressed and treated with superheated steam to harden the plastic binder, and to a device for its implementation.

Such a method is already known in which the chipboard is pressed in a one-step process getting produced. Here, after the loose chipboard has been introduced into a heated one hydraulic press closes the press in 30 seconds, with the wood chip already on their final density and is pressed into a molding 40 mm thick. After that, the overheated Water vapor introduced into the compacted mass. The disadvantage of this method is that the superheated steam cannot evenly distribute in the mass that has already been pressed to the final density, because the flow resistances at some points are much greater than at others. The curing This takes place to different degrees of intensity, which is why ultimately a non-uniform one Density and strength distribution occurs in the cross section of the fitting. The introduced water vapor serves here exclusively to harden the synthetic resin binder. Another disadvantage of this method consists in pressing the mass to its final density before introducing the steam very high pressing pressures are required. As is well known, the pressure resistance of the wood chipboard runs strongly overlinear with increasing density and approaches that of solid bodies. When the density of the To be produced wood chip body goes beyond a certain level, the known method can conventional presses can no longer be carried out. The applicability of the known method is therefore limited to light and thick, low-density wood chips. The result of excessive pressures The limited scope of the known method is therefore a second disadvantage. So stands Finally, the last disadvantage in close connection is that the press closing time increases with desired final density of the workpiece to be produced increases sharply. A long press closing time then leads to the fact that the mass is already on the surfaces facing the hot press plates is hardened by the contact heat while the hardening takes place inside the workpiece only takes place later through the steam. This, too, has a method and apparatus for producing Wood chips

Applicant:

Weyerhaeuser Company, Tacoma, Wash.

(V. St. A.)

Representative:

Dipl.-Ing. A. Grünecker

and Dr.-Ing. H. Kinkeldey, patent attorneys,

8000 Munich 22, Maximilianstr. 43

Named as inventor:

Robert Ligett Corbin, Longview, Wash .;

Joseph Albert Hall, Portland, Oreg. (V. St. A.)

Claimed priority:

V. St. v. America April 22, 1963 (274594)

result in an uneven distribution of hardness and density.

The purpose of the invention is to design the method of the type described above so that a uniform hardening and density of the wood chip body to be produced when using less Compression pressures is achieved. This is achieved according to the invention in that the mass between the Press plates initially pre-pressed to a lower density than the final density without the introduction of steam, then the superheated steam is introduced and finally the mass is pressed to its final density.

In the method according to the invention, the press is initially only over part of its stroke closed. The mass between the press plates is thereby compressed, but to a value that is less than the desired final density of the wood chip body to be produced. So the crowd is significantly looser than in the final state. The overheated mass is now converted into this relatively loose mass Introduced steam. It can be distributed very evenly in it, creating a rapid and on the same curing is achieved at all points of the cross-section. Partial pre-pressing in a first However, this stage is necessary in order to "rinse out" the mass under the action of the superheated steam to avoid. In the process according to the invention, however, the superheated steam does not only have the

809 599/446

3 4

Function, the plastic binder by heating to maintain the overheating release to harden. Rather, it makes the wood degree of the overheated generated in the superheater 2 particles of the mass supple and pliable. Provided steam. The top of the container 6 If, after or during the introduction of the, a pressure relief valve 7 is provided for safety reasons of superheated steam, the press continues up to the 5. The lower end of the container 6 is with a final press plate distance is closed, usual drain pipe 8 and one located therein then the mass plasticized by the steam sets valve 9 provided.

the pressure a much lower resistance. The container 6 is connected to a line 10

contrary to that which has not yet been treated with steam, in which a valve 11 is arranged. the Dimensions. The line 10 required to achieve the final density has a T-piece 13 to which the re-press pressure is therefore relatively low. That is connected to a branch line 12. the The method according to the invention can therefore be carried out with external ends of the line 10 and the branch line 12 use of conventional presses, especially for wood, are connected to a connection chamber 14, Chip workpieces of high density are applied. which is located above an upper heatable press plate 15 The residence time of the workpiece in the press is 15. The chamber 14 extends along the Because of the short press closing time, the entire circumference of the press plate 15 is far less. long than before. As a result, an undesirable under the heatable press plate 15 is a

tes curing of the surfaces of the workpiece arranged by further heatable press plate 17, the the contacting arm 18 emanating from the press plates, which during pressing avoiding heat. Finally, there is also the ready 20 of a mat 16 between the upper and the lower position and introduction of the superheated steam press plate cooperates with this. Of the easier than with the known method. There arm 18 is attached to a hydraulic (not shown) that is, if the final density of the product is the same, it is sufficient to connect the device with the arm upwards a far lower pressure of the superheated steam and moves down.

fes, which also penetrates the mass much more quickly. heated steam through lines 10 and 12, respectively, into the

In a particularly favorable embodiment, the mat 16 can be pressed in. To the upper press device a steam chamber (not shown in FIG According to the method it is provided that the one shown is connected to the chamber 14 The surface of the press chamber facing the 30 is connected.

Press plate provided with a steam chamber in per se In F i g. 2 and 3 is another embodiment

shown in a known manner by a sintered metal plate with the damping device according to the invention, vapor-permeable pores is formed. The use of this damping device is down to the fact that tion of a sintered metal plate as a vapor press plate with her a different type of connection chamber Verist therefore finds application for the implementation of the invention, that according to FIG. 1 is similar. the According to the method particularly favorable, because the chamber 20 is now in the form of an elongated tube superheated steam through the fine pores of the sintered part, which has a large number of lines metal uniformly and in very fine rays in 21, which the chamber 20 with the indie Chip mass penetrates. A steam press plate 19 is thereby connected to securing devices. the means that the bottom surface of the plate 19 is not yet on its end 40 with several opening leaks brought and therefore relatively loose gene 22 provided, through which the superheated steam in Chip mass is locally »rinsed out«. the mat 16 can be fed. The one in one

Embodiments of a device for the through-bottom plate 28 of the steam press plate 19 demonstration of the method according to the invention are seen in holes 22 are used to spread the shown in the drawings. Therein shows 45 steam and for even distribution of the

F i g. 1 shows a perspective overview of superheated steam throughout the mat 16. Device for pressing pressed wood panels Fig..4 shows a further embodiment of a

according to the invention, steam press plate according to the invention. The steam

F i g. 2 a perspective view of an upper press plate 19 has one with its lower one Press plate, 5 ° surface screwed sintered metal plate 24 on. the

F i g. Fig. 3 is a plan view of the upper press plate with sintered metal plate 24 showing a plurality of fine opening broken away Split to reveal internal details through which the superheated steam passes show and can. As can be seen from Fig. 4, the steam

4 shows a perspective view of a further press plate 19, an upper wall part 26, side embodiment the press plate, with parts of the 55 wall parts 27 and a lower wall part 28 with the Plate broken away to reveal internal details of openings 22. The upper wall part 26 together demonstrate. with the lower wall part 28 and the side wall

The parts in the drawings generally with 1 27 form a chamber 25 through in the designated Dampfpreßvorrichtung has an over-side wall 27 provided openings 23 with the heater 2, which is connected by a pipe 3 with a (not 60 connection chamber 14, shown) steam source is connected. This is the mat 16 between the lower press platen

Superheater 2 consists of the usual heat 17 and the upper steam press plate 19, insulated container and one (not shown) is introduced into the connection chamber 14 Heating device for superheating the steam. A steam in the mat 16 is evenly distributed as the Tube 4 with a valve 5 disposed therein has holes 22 in the lower surface of the bottom plate binds the superheater 2 with a storage container 6. 28 of the chamber 25 are evenly distributed. About that

The storage container 6 is with the usual (the steam does not have to go through the sintered metal plate thermal insulation means and heating device 24 shown flow, leading to an even finer spread

5 6

of the steam and its even distribution 70.4 kg / cm ² . When the mat 16 is pressed

serves throughout the mat 16. the lower press plate 17 through the resistor

The compressed wood panel 16 thus obtained has one of the mat 16 smoother before obtaining the desired thickness Surface on as if it were kept without sintering. When the mat 16 the pressure of the lower plate 24 would be made. 5 press plate 17 is exposed, the valve 11

^{Various comminuted or powdery pressures of about 3.52 to 10.56 kg / cm 2} and, for example, lignocellulose-containing particles can be used as starting materials for producing the mat 16, and superheated steam flows under one. 27.8 to 250 ° C overheating temperature by the There are z. B. sawdust, sawdust, flakes of small holes 22 in the bottom plate 28 of the steam or wood flour and various on chemical io press plate 19. When flowing the overheated path, wood pulp can be used, but steam through the mat 16 is plasticized, shredded wood is preferably used. This then continues the closing movement of the lower press plate 17 can be obtained from any suitable materials and compacts the, such. B. sugar cane, straw, tree bark mat 16 to the desired thickness. The overheated steam or the like, but preferably directly from the wood 15, flows into the mat for 1 to 30 seconds, whereupon the various tree species. Valve 11 is closed. After a total of approximately

The resin binder for the wood particles can take 15 to 300 seconds. The mat 16 is removed from the lower press plate of any thermosetting resin and is a fully hardened and preferably made of urea formaldehyde or hardened and solidified hardboard. The combined phenol formaldehyde resin. The superheated steam required in the container 6 is replaced by the binding agent to be used in each case, depending on the new steam that is supplied to the container by the superheater 2 due to the strength, hardness and surface properties, etc. opening the valve 5,
selected, which have the finished Preßholzplatte It must be pointed out that the Übersoll, heated steam, which the perforated plate from the

In general, the press chamber 14 according to the invention is fed into the mat

wooden panel is manufactured according to the following guidelines and can escape from its edges. When arriving

where the starting material is, for example, wood: this process is used in the press

1st step: Preparation of a wood powder mass, plates above normal temperatures and in steam from mechanical or chemical pulp, maintain a high level of overheating. Wood shavings, sawdust or finished wood flakes. 30 A very good pressed wood panel can be combined with a short

Step 2: Machining the natural wood steam introduction period to be established. Darzellpulpulstoff by further mechanical or marriage is beyond the in connection with mix operations, sorting and drying. the conventional methods used high

3rd step: Mixing in the selected hot hardening temperatures of the press plates resulting in damage Resin or resins to bind the particles. 35 lent effect as a result of the present Ver-This Operation can be multiplied in any of the short pressing times achieved by driving Steps of the procedure take place. avoided. Since a high degree of overheating occurs

4th step: Production of a thick felt mat with low density that is kept from the particles and the temperatures of the presses. plates are high, the steam in the mat

5th step: Pre-compress the mat to make it easier - does not condense and therefore does not leave any tion of their handling. Moisture that would have to be removed afterwards.

If you now want a finished mat from the mat 16, the internal temperature of the mat is determined by a heat-pressed wood panel to obtain, proceed as follows: release of the superheated steam to the wood particles

The superheater 2 is operated with a suitable (not increased rapidly. The high temperatures of the presses shown) Plating the steam source by means of the pipe 3 serves to maintain this temperature level. The steam is maintained in the required manner so that additional damping is unnecessary. overheated and passed through pipe 4 and valve 5 to the explanation of the present treachery 6 forwarded. The overheating effect achieved one has to look at the process can be between 44 and 250 ° C. Then think of it as a line heat transfer. Of the If a (not shown) located in the container 6 50 superheated steam does not condense, there will be none Heating device actuated to adjust the temperature of the heat used in the vaporization and the steam Container 6 of stored, superheated steam flows through the mat from the center in Richder To keep the height in the superheater 2 received tion on their edges and heated the mat elements became. only by convection.

The mat 16 is then placed on the lower press 55 The method according to the invention can also be applied to

plate 17 placed. The hydraulic ram arm 18 hand of the example below explained in more detail

will be through the hydraulic (not shown).

Motor moves up and brings the mat into Douglas fir particles were made with a urine

the vicinity of the upper steam press plate 15 or 19.

It can be seen that both the upper heated 60 box is given. The particles were obtained

Press plate 15 or 19 as well as the lower heated mat to be treated is cold-pressed. Of the

Press plate 17 can be heated with steam. The moisture content of the mat was 8% at hers

upper and lower press plates 15 and 17, respectively, inserted into the molding press. The press plates

can be heated to a temperature up to 204 ° C were heated to 204.4 ° C. The steam press plate

will. 65 contained 2.38-mm holes that were spaced apart

The lower press platen 17 is then lifted 50.80 mm apart. At

and presses the mat 16 for about 1 to 60 seconds. The steam press plate was a steam line of

connected at a pressure between about 3.52 and about one superheater. The mat was

pressed at a pressure of 21.12 kg / cm ² for 30 seconds. The valve 11 was then opened and ^{superheated steam at a pressure of 3.52 kg / cm 2} at 148.85 ° C. flowed through the small openings 22 of the steam press plate and into S the mat. After 5 seconds the valve was closed. The internal temperature of the mat rose from 21 to 165.5 ° C in 2 seconds, whereupon the press was closed further. The heating or heat treatment took place without increasing the weight of the mat. After a total time of 120 seconds, a 19.05 mm thick, 0.637 kg / dm ³ dense hardboard was removed from the press, which was completely cured and solidified.

It can be seen that according to the invention dry steam for the convection transfer of heat in the mat 16 is used. Only heat is used to solidify the mat through To promote plasticization of the lignocellulosic material and the binders that harden when used to harden. Steam and displaced air escape from the edges of the mat as a result of the Using high vapor injection pressures, a pressure differential is established for short periods of time. By rapidly increasing the internal temperature of the mat as mentioned above, the lignocellulosic Material plasticized by the heat of the superheated steam and then faster and more evenly pressed than was possible with the conventional methods, which are more common Steam was used.

It will be seen that the preferred embodiment of the invention is within the spirit of the invention, the details of which are described above can be changed, e.g. B. by using fluted steam press plates.

Claims (7)

Patent claims: 1. A method for producing wood chips, in particular chipboard, from a Mass containing wood particles and thermosetting plastic binder, the precompacted Put mass between heated press plates, there pressed to the desired final density and to cure the plastic binder is treated with superheated steam, characterized in that the mass between the press plates initially Pre-pressed to a lower than the final density without the introduction of steam, then the superheated Steam introduced and finally the mass is pressed to the final density. 2. The method according to claim 1, characterized in that the mass is under a pressure of about 3.5 to 70 kg / cm ² when the superheated steam is introduced. 3. The method according to claims 1 and 2, characterized in that the mass is ^{exposed to the pressure of about 3.5 to 70 kg / cm 2} for about 1 to 60 seconds before the introduction of the superheated steam. 4. The method according to at least one of claims 1 to 3, characterized in that the superheated steam is under a pressure of about 0.35 to 10.5 kg / cm ² when it is introduced into the mass. 5. The method according to at least one of claims 1 to 4, characterized in that the Superheated steam is introduced into the mass for 1 to 30 seconds. 6. The method at least according to claim 1, characterized in that the mass according to the Introducing the heated steam in about 15 to 300 seconds. Pressed to the final density. 7. Apparatus for performing the method according to claims 1 to 6, with a a pair of press having heatable press plates and a steam chamber at least one of the press plates, which is connected to the press space via steam passage openings in the press plate is in communication and can be connected to a device for generating superheated steam is, characterized in that the press chamber facing surface of the press plate provided with the steam chamber in is formed in a manner known per se by a sintered metal plate with vapor-permeable pores. Considered publications:
German interpretative document No. 1056 358. 1 sheet of drawings 809 599/446 8.68 © Bundesdruckerei Berlin