US3188367A

US3188367A - Process for manufacturing plates from wood shavings and fibers

Info

Publication number: US3188367A
Application number: US141491A
Authority: US
Inventors: Gottschalk Ulrich
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-09-30
Filing date: 1961-09-28
Publication date: 1965-06-08
Anticipated expiration: 1982-06-08
Also published as: DE1161415B; GB923157A; AT242933B; CH390538A

Description

June 8, 1965 u. GOTTSCHALK 3,188,367

PROCESS FOR MANUFACTURING PLATES FROM WOOD SHAVINGS AND FIBERS Filed Sept. 28, 1961 United States Patent 3,188,367 PRQCESS Fill! MANUFAQTURING hLAZiES FREE/I W893) SHAVlNGS AND FEEERS Ulrich Gottschalh, Ludwigstrasse 1A, Jochgrim, Pfalz, Germany Filed Sept. 28, 196i, ar. No.14i,491 Claims priority, application Germany, Sept. 3t), 1966, G 39,614 7 Claims. (El. 264-37) The present invention relates to a process for manufacturing of plates from shavings and/or fibers especially of wood by miXing these particles with a binder and subjecting the mixture then to heat and pressure between the platens of a press.

In known processes of manufacture of plates in this manner, the wood shavings and/ or fibers are first dried to a suitable degree, then mixed with an appropriate binder and this mixture is placed in a substantially uniform layer between the platens of a press or in form of a plurality of layers with sheet metal plates sandwiched therebetween, and then the layer or layers are subjected in the press to appropriate pressure whereby the press platens are preferably heated. The shavings are quite often treated with various chemicals and/or coloring agents before they are subjected to heat and pressure so as to improve the quality of the obtained plates to make the same for instance resistant against humidity, to increase the flame resistance thereof, to make the plates resistant against attacl: by termites or to obtain plates of various colors. Part of the moisture contained in the material to be pressed evaporates during subjection of the material to heat and pressure. The thus created vapor has to escape from the pressed layers during the pressing process to prevent bursting of the formed plates after release of the pressure, if the plates are not subjected to an expensive cooling process while the press remains closed so as to condense the vapors before releasing the pressure. The necessary relatively high temperature for curing the binder will also cause part of the binder and any chemicals mixed with the shavings to evaporate and the odors of such vapors may be disagreeably felt and lead also to an endangering of the health of the press operator. The water vapor and any other vapors forming during the process can escape from the pressed layer or layers only along the edges of the layer or layers since the main surfaces thereof are covered by the press platens or the sandwiched metal sheets between a plurality of layers arranged between the press platens, which detrimentally increases the operating cycle.

During forming of a layer from the mixture of the shavings and binder and any other additions it is also rather difiicult to obtain a uniform distribution of the mixture which will often result that the produced plates will have portions of different specific gravity. This may produce internal stresses in the pressed plates, causing in turn warping of the same; This fact and the limited escape path for the vapors formed during the pressing process, which escape through the edges of the pressed layers, render the production of pressed plates according to the known processes rather difi'icult. This is especially true in the production of pressed plates of a thickness less than 8 millimeters, since with decreasing plate thickness, the specific pressure has to be increased so that the escape of vapors through the edges of the pressed materiallayer is rendered more difiicult and the time thereof is increased, which in turn increases the pressing cycle. The necessary-high specific pressure for the production of plates of small thickness results also some times in adherence of the shaviugs to thepressed plates. Furthermore any non-uniform distribution of the shavings and resulting non-uniform density in the plates will detrimentalddfidfifi? Patented June 8, 1955 1y affect the shape retaining quality of thin plates much more than that of heavier ones. These difiiculties increase especially the manufacturing cost of thin plates.

It is an object of the present invention to overcome these dirficulties encountered in the manufacturing of pressed plates according to known processes.

It is a further object of the present invention to facilitate escape of vapors from the material to be pressed into plates during the pressing process and to reduce thereby the necessary operating cycle for forming such plates.

It is an additional object of the present invention to facilitate the manufacture of such pressed plates of substantially uniform specific weight so as to improve the quality of the obtained plates and so as to make especially production of thin plates to a thickness of a minimum'of 2 mm. commercially possible.

With these objects in view the process of manufacturing of plates from shavings and fibers, especially of wood, comprises essentially the step of mixing shavings and fibers of wood with a binder, forming at least one layer of the binder treated material, superimposing upon said binder treated material a second layer of moisture and vapor absorbing material, and applying heat and pressure to said superimposed layers to form a plate from said binder treated material, whereby moisture contained in said first mentioned layer and vapors forming during the process will be at least in part absorbed by the second layer. In other words, in the process according to the present invention moisture contained in the binder treated material and vapors forming during the process cannot only escape through the edges of the layer of binder treated material, but such moisture and vapors may escape through one main surface of the binder treated material into the second layer adjacent thereto and in contact with this main surface so that the pressing cycle can be considerably reduced.

Preferably a pair of layers from said binder treated material with a third layer of moisture and vapor absorbing material sandwiched between the pair of layers is arranged between the press platens so that two plates can be simultaneously formed while moisture and vapors forming during the process may escape from the outer layers of binder treatedma-terial into the central layer of moisture and vapor absorbing material.

Sincemost of the vapors produced during the process will be absorbed by the central layer the escape of such vapors in the surrounding atmosphere is substantially prevented and any health damage produced by such vapors is thereby considerably reduced.

The central layer, according to the present invention is preferably formed from resilient material so that with an uneven distribution of the material in the binder treated layers portions of the central layer may be compressed to a greater or lesser degree during the pressing which will result in an uneven surface of the finished 7 plates in contact withthe thirdlayer, while the finished The resilient intermediate layers can be formed frorn' various materials and the layer may be formed from continuous material or from loose particles. Especially in the first case it is preferred to treat the surfaces of the intermediate layer which come in contact with the binder treated material layers with material which is re;

pellent to the binder, or which at least will not adhere thereto, so that an easy separation of the finished plates i from the intermediate layer can be obtained. "Thus the surfaces of the intermediate layer which come in con- 3 tact with the binder treated material layers may be dusted with powdery material, or fabrics may be placed on the surfaces of the intermediate layer which come in contact with the binder treated material to prevent penetration of the binder into the intermediate layer during the pressing process.

According to the present invention the intermediate layer may also be formed from wood shavings and fibers as are used for the outer layers from which during the pressing process the plates are formed, but the wood shavings and fibers for the intermediate layer are not mixed with a binder. The shavings and fibers which have served during the first operating cycle as intermediate layer and which have absorbed the moisture and vapors from the outer layers during the pressing process, are then mixed with a binder and used in the next press cycle for forming at least part of the outer lay-. ers from which the plates are to be formed. By properly choosing the volume of the intermediate layer it is possible to obtain in the intermediate layer during the pressing process and during transfer of the moisture content from the outer layers into the intermediate layer, a moisture content in the. intermediate layer best suitable for mixing the material of the intermediate layer with the binder and for subsequent pressing of the thus obtained mixture into plates.

When the material of the intermediate layer is formed from wood shavings and fibers which are subsequently used for forming part of the outer layers from which the plates are to be formed, it is also possible to mix the shavings and fibers to be used as an intermediate layer, before they are introduced between the press platens with color additives, with material to improve the flame resistance thereof, or other chemicals as mentioned above and such materials will penetrate into the shavings and/or fibers during the limited heating of the intermediate layer during the pressing process, substantially without evaporating. This may also increase the absorption capability of the surfaces of the wood shavings fibers for the binder material to be mixed subsequent with these shavings and the chemicals which have been absorbed by the shavings and fibers of the intermediate layer will be rendered less volatile during the subsequent pressing process.

According to known processes it is preferred to compress the binder treated material in a third or quarter of the total press cycle with the maximum pressure to the desired finished plate thickness and to reduce thereafter the pressure in steps or gradually up to the end of the pressing cycle. Contrary to this usually used pressure cycle it is preferred according to the present invention to gradually increase the pressure from the start to the end of the pressing cycle or to gradually increase the pressure upto the maximum pressure necessaryto obtain the desired plate thickness at the start of the pressing cycle and to maintain the maximum pressure then up to the end of the pressing cycle.

If spacer means are used in a known manner to limit the approach of the press platens to each other to a predetermined degree, it is preferred according to the present invention to increase the pressure on the press platens gradually so that the press platens will abut against the spacer means only at the end of the operating cycle.

The novel features which are considered as characteristic for the invention are set forth in particular in the appendedclaims. The invention itself, together with additional objects and advantages thereof, will be best understood from the following description of a specific method when read in connection with the accompanying drawing which schematically illustrates an arrangement for carrying out the method of the present invention.

The drawing schematically illustrates a novel arrangement of known apparatus and machine elements with l respect to each other and no attempt has been made to illustrate the specific construction of the various apparatus used, since such apparatus are well known in the art and the specific construction thereof does not form part of the present invention.

According to the arrangement shown wood in the form of blocks or logs is fed into a shaver or comminuting means 1 to be comminuted therein into wood shav ings and/or fibers and the wood particles produced in the comminuting means 1 have to be made the smaller the thinner the thickness of the produced plate is to be. If the thickness of the produced plate is to be smaller than 5 mm., it is preferred to comminute at least part of the wood into fibers and the percentage of wood fibers to wood shavings, has to be increased the thinner the produced plate is to be. The shavings and/ or fibers produced in the comminuting means 1 are then transported by transporting means, schematically illustrated by the arrow, into a drier 2 in which during the first operating cycle part of the material is dried to a lesser and another part is dried to a higher degree. The lesser dried fibers and/or shavings are then transported over the path a by transporting means of known constructions into mixing means 3 of known construction in which the shavings and/ or fibers are mixed with a binder. The binder treated material is fed by third transporting means, schematically shown in the drawing, between the platens 7 of a press 6 while the portion of the shavings and/or fibers dried to a higher degree in the dryer 2 is fed over thepath b by a fourth transporting means between the press platens 7 to form an intermediate layer 5 between the layers 4 formed by the binder treated material. The press platens 7 are preferably heated and the superimposed layers 4, 5, 4 are then subjected to pressure by moving the press platens 7 toward each other. During application of heat and pressure to the superimposed layers the binder material is cured whereby moisture and vapor emanating from the material of the layers 4 will be substantially absorbed by the shavings and/or fibers of the intermediate layer 5. The pair of plates 4, 4' produced from the layers 4 are separated at the end of the press cycle from the intermediate layer 5 and subsequently transported over the path 0 by transporting means of any well known construction into a brushing apparatus 8 which has a pair of brush rollers 8, 8" for brushing any shavings and/or fibers of the intermediate layer 5, adhering to the finished plates, therefrom. The brush rollers 8' and 8" are preferably shiftable in vertical direction so that only the surface of the respective plate 4 which was during the pressing process in contact with the intermediate layer 5 will be brushed off during the passage of the respective plate through the brushing means 8. Preferably, the plates 4', 4 are subsequently passed through a planer 9 which has a pair of rotating planers 9', 9", which are also preferably shiftable in vertical direction so that during passage of the respective plates 4' through the planer 9 only such surfaces of the plates will be machined which have been during the pressing operation in contact with the intermediate layer 5.

The shavings and/or fibers of the intermediatelayer 5, the humidity content of which has been increased during the preceding pressing process to a degree suitable for the subsequent application of a binder and press forming the material into plates, are transported after the first pressing cycle over the path d, by transport ing means of any well known construction, into the mixing means 3 in which this material is mixed with a binder, so that the mixture may be subsequently used for forming at least part of the layers 4 between the press platens, to be formed during the next pressing cycle into plates 4. Before feeding the material of the intermediate layer 5 into the mixing means 3, the compressed shavings and/or fibers may be loosened up by any means is known in the art. The shavings and/or fibers removed from the finished plates 4' in the apparatus 8 and the shavings produced during machining of the finished plates 4' in the apparatus 9 are preferably also fed together with the material of the intermediate layer into the mixing means 3 to be mixed with the binder so that any waste of material is avoided.

By properly selecting the volume of the shavings and/or fibers of the layers 4 and the intermediate layer 5 it is possible, after the first molding cycle, to use the material of the intermediate layer 5 to form therefrom part or all of the outer layers 4 from which the plates are to be formed so as to omit feeding of lesser dried shavings and/or fibers from the dryer 2 over the path a into the mixing means 3, or to considerably reduce the amount of shavings and/or fibers fed over this path. In other words, during the second and following pressing cycles, the material used in the preceding pressing cycle to form the intermediate layer 5, is mixed with a binder and the thus obtained mixture is then used for forming the layers which are subsequently formed into the plates 4'.

If the plates to be produced are to be provided with special additives, such as paraifin and mineral waxes to increase the moisture resistance of the finished plates, or ammonium phosphate or boric acid as flame resisting agents, pentachlorophenol to prevent attack of the finished plates by termites, or any color additives, then such additives or chemicals are preferably mixed in an additional mixer to the shavings and/or fibers which are first used for forming the intermediate layer 5. In this way such additives or chemicals will penetrate the shavings and/or fibers forming the intermediate layer 5 during the pressing process, whereby better action of these chemicals and additives on the material is obtained.

If the intermediate layer 5 is not formed from loose shavings and/or fibers, but from continuous but resilient material, then it is preferred to cover the surfaces of the intermediate layer 5 in contact with the outer layers 4 with powdery material which will substantially prevent penetration of the binder material of the layers into the intermediate layer 5 so as to facilitate separation of the intermediate layer from the plates 4' formed from the outer layers 4. For the same purpose the surfaces of the intermediate layer 5 in contact with the outer layers 4 may also be covered with netlike material or fabric permeable by moisture and vapor.

The pressure on the plates 7 of the press is preferably controlled as mentioned above, that is, the pressure is either increased gradually from the beginning up to the end of the press cycle, or the pressure is increased during the beginning of the press cycle to the necessary maximum, to obtain the desired plate thickness and then maintained at this maximum up to the end of the pressing cycle. If spacer means are used between the press platens to limit the extent of approach thereof to each other, then the pressure is controlled in such a manner that the press platens will contact the spacer means only at the end of the press cycle.

It is understood that the process of the present invention can be carried out with more than three layers and in this case an intermediate layer 5 formed from material as mentioned above is always placed between two subsequent layers 4 from which the finished plates 4' are to be formed.

While the invention has been illustrated and described as embodied in a process for manufacturing of pressed plates, it is not intended to be limited to the details shown, since various modifications many be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can ous applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A process of manufacturing plates from wood shavings and fibers comprising the steps of mixing wood shavings and fibers with a binder; forming a pair of layers from said binder treated material with a third layer of Wood shavings and fibers without a binder sandwiched therebetween; applying heat and pressure to said superimposed layers to form a pair of plates from said layers of binder treated material, whereby moisture contained in said pair of layers and vapors forming during the proc ess will be at least in part absorbed by said third layer; separating said plates from said third layer; mixing the material of said third layer with a binder; and using the thus obtained mixture for forming at least part of a pair of layers for forming plates therefrom during the next operating cycle.

2. A method as defined in claim 1 in which said wood shavings and fibers for forming the third layers are mixed with material for increasing the moisture resistance thereof.

3. A method as defined in claim 1 in which said wood shavings and fibers for forming the third layers are mixed with material for increasing the flame resistance thereof.

4. A method as definedin claim 1 in which said wood shavings and fibers for forming the third layers are mixed with material for preventingattack of the finished plates by termites.

5. A method as defined in claim 1 in which said wood thus obtained material to reduce the moisture contents thereof to a predetermined degree suitable for mixing the material with a binder; drying another portion of said comminuted wood material to a greater degree than said first mentioned portion; mixing said first mentioned portion of said dried material with a binder; forming from said binder treated material a pair of layers and from said second mentioned portion a third layer sandwiched between said pair of layers; subjecting said superimposed layers to heat and pressure to form a pair of plates from said binder treated layers, whereby moisture contained in said pair of layers and vapors forming during the process will be at least in part absorbed by said third layer and said third layer being made of such a thickness that the moisture transferred thereinto will moisten the material of said third layer to contain a degree of moisture substantially equal to said predetermined degree; separating said plates from said third layer; mixingthe material of said third layer with the binder; and using the thus obtained mixture for forming at least part of a pair of layers for forming plates therefrom during the next operating cycle. i

7. A process of manufacturing plates from wood shavings and fibers, comprising the steps of mixing said shavings and fibers with a binder; forming -a pair of layers from said binder treated material with a third resilient layer of particulated moisture and vapor absorbing material without a binder sandwiched between said pair of layers; applying heat and pressure to said-superimposed layers to form a pair of plates from said binder'treated material, whereby moisture contained in said pair of layers and vapors forming during the process will be at least in part absorbed by said third layer; separating said plates from said third layer; brushing any particles of "1 8 ing said plates after separation at surfaces thereof which 2,431,720 12/47 Willey. had been directed toward said third layer; mixing said 2,587,171 2/52 Knewstubb et a1 156-254 brushed-01f particles, the shavings obtained in the plan- 2,642,371 6/53 Fahrni 15632 ing operation and the material of said third layer with 2,745,779 5/56 Ritter et al. 154-45.9 a binder; and using the thus obtained mixture for form- 5 2,322,028 2/58 flimmelheber et 1 156 36 ing at least part of a pair of layers for forming plates 3 057,022 10 2 Bar et 1 2 4 113 th f d th t t' r l ere r0111 uring e nex opera ing (:36 e FOREIGN PATENTS References Cited by the Examine-1' 401,553 11/33 Great Britain UNITED STATES PATENTS 10 v T 5 5 7 /02 Edison ALEXABDER ODMERKEL, Przmary Examiner.

1,098,967 6/14 Peterson 156-323 EARL M. BERGERT, Examiner.

Claims

1. A PROCESS OF MANUFACTURING PLATES FROM WOOD SHAVINGS AND FIBERS COMPRISING THE STEPS OF MIXING WOOD SHAVINGS AND FIBERS WITH A BINDER; FORMING A PAIR OF LAYERS FROM SAID BINDER TREATED MATERIAL WITH A THIRD LAYER OF WOOD SHAVINGS AND FIBERS WITHOUT A BINDER SANDWICHED THEREBETWEEN; APPLYING HEAT AND PRESSURE TO SAID SUPERIMPOSED LAYERS TO FORM A PAIR OF PLATES FROM SAID LAYERS OF BINDER TREATED MATERIAL, WHEREBY MOISTURE CONTAINED IN SAID PAIR OF LAYERS AND VAPORS FORMING DURING THE PROCESS WILL BE AT LEAST IN PART ABSORBED BY SAID THIRD LAYER; SEPARATING SAID PLATES FROM SAID THIRD LAYER; MIXING THE MATERIAL OF SAID THIRD LAYER WITH A BINDER; AND USING THE THUS OBTAINED MIXTURE FOR FORMING AT LEAST PART OF A PAIR OF LAYERS FOR FORMING PLATES THEREFROM DURING THE NEXT OPERATING CYCLE.