CA2138429C - Manufacturing method for wood boards - Google Patents
Manufacturing method for wood boards Download PDFInfo
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- CA2138429C CA2138429C CA 2138429 CA2138429A CA2138429C CA 2138429 C CA2138429 C CA 2138429C CA 2138429 CA2138429 CA 2138429 CA 2138429 A CA2138429 A CA 2138429A CA 2138429 C CA2138429 C CA 2138429C
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Abstract
A molding process including the steps of: shaving lumber to produce wooden strands, applying a binder to the wooden strands, and subjecting the wooden strands, to which a binder has been applied, to forming and to thermal compression molding so as to obtain a molded material; and a smoothing process including the steps of: moisturizing the molding material obtained by means of the molding process, and then abrading a surface thereof, are conducted. The plastic deformation remaining within the wood board is caused to become manifest by means of the forcible moisturizing, and thereinafter, the irregularities present in the surface are removed, so that irregularities do not appear in the wood board which is thus produced over along period of time, and surface smoothness can be maintained.
Description
1 ' MANUFACTURING METHOD FOR WOOD BOARDS
Background of the Invention Field of the Invention The present invention relates to a manufacturing method for wood boards, and in particular, relates to a manufacturing method for strand boards which are capable of maintaining superior surface smoothness over a long period of time.
Background Art In recent years, the insufficiency of lumber resources and the protection of the forests have become problems, and it is clear that it will be increasingly difficult to obtain timber from forests. Accordingly, the supply of board materials such as plywood, which are produced using large amounts of raw material lumber, will be uncertain, or will be insufficient, and the cost thereof is also expected to rise greatly. Accordingly, wood boards which can be obtained from the efficient use of wooden strands or ligneous fibers of wooden strands, or the like, which were conventionally regarded as waste materials, have attracted attention, and the application of such wood boards to such various uses has been strongly desired.
Among such wood boards, fiber boards formed from ligneous fibers and strand boards formed from wooden strands are known.
Commonly, in cases in which materials having small dimensions such as ligneous fibers are employed, the wood board which is obtained is uniform, and the surface thereof is smooth; however, the density thereof is high, and the strength and rigidity are insufficient. On the other hand, in the case of strand boards ~8~~9 which employ wooden strands, since strands are employed which are large in comparison with the ligneous fibers, it is possible to provide strength and density which approach those of natural lumber.
Such strand boards are produced by applying binder to wooden strands and subjecting these to forming and thermal compression molding. After molding, the surface of such strand boards has a large degree of irregularity, so that normally, such boards are employed after sanding the surface thereof and bonding a decorative single sheet or the like thereto. This sanding is commonly carried out after storing the strand boards for a period within a range of from a few hours to a few days at room temperature after the thermal compression molding thereof.
However, during the thermal compression molding of the strand boards described above, a high temperature and high pressure are applied under conditions of high humidity caused by the moisture contained in the adhesive, so that irregularities resulting from the cutting of the wooden strands or irregularities present in the wooden strands are subject to plastic deformation, and desiccation is conducted in this state.
After the molding, the wood board is stored at room temperature for a period of a few days, and thus the strand boards were subjected to the sanding process. Accordingly, even though the surface of such strand boards was sanded so as to provide smooth surfaces, nevertheless, the wood board is gradually swelled over a period of time after the sanding by moisture in atmosphere, so that, for example, there were problems in that after finished products were shipped, irregularities appeared on a surface sanded once so as to provide a smooth surface.
. ~8~r9 Furthermore, recently, wood boards have been obtained which have improved surface smoothness as a result of the provision of a layer comprising ligneous fibers at the surface of a strand board produced by thermal compression molding. However, in such a case, while the surface smoothness is improved, this leads to an increase in manufacturing costs of the wood board as a whole, and furthermore, a ligneous fiber layer having poor strength is provided at the surface, and there are thus problems in that the physical characteristics as a flooring material worsen.
Summary of the Invention Accordingly, it is an object of the present invention to provide a method for producing a strand board which is capable of maintaining superior surface smoothness over a long period of time without the provision of a surface-smoothed layer, such as a ligneous fiber layer or the like, at the surface thereof.
This object can be attained by means of a manufacturing method for wood boards which is characterized in comprising: a molding process including the steps of: shaving lumber to produce wooden strands; applying a binder to the wooden strands;
and subjecting the wooden strands, to which a binder has been applied, to forming and to thermal compression molding so as to obtain a molded material; and a smoothing process including the steps of: moisturizing the molding material obtained by means of the molding process;
and then abrading a surface thereof.
In accordance with the manufacturing method of wood boards of the present invention, a process is conducted in which the plastic deformation resulting from the thermal compression 4 ' molding of the wooden strands, which was a cause of the degradation of the surface smoothness of the wood boards, is forcibly manifested in advance by means of forcible moisturizing, and after this, abrading of the surface is conducted and irregularities in the surface are removed.
Accordingly, wood boards produced in accordance with the manufacturing method of the present invention contain no plastic deformation therein, and are capable of maintaining surface smoothness over a long period of time.
Furthermore, in the manufacturing method in accordance with the present invention, it is possible to conduct the molding process and the smoothing process in a continuous manner, or to conduct these processes in a separated manner, so that commercially available strand boards can be used effectively, and it is possible to obtain a wood board having superior durability.
Brief Description of the Drawings Fig. 1 shows an example of a highly suitable apparatus for conducting moisturizing in the smoothing process of the method in accordance with the present invention.
Fig. 2 shows the structure of a steam injection plate which is used in the apparatus shown in Fig. 1.
Fig. 3 is a graph showing the relationship between the water content and the flexural strength of the wood board.
Fig. 4 is a graph showing the relationship between the water content and the flexural Young's modulus of the wood board.
Fig. 5 is a graph showing the relationship between the water content and the wet swelling coefficient of the wood board.
Fig. 6 shows the surface contours, in a wet state, of a wood board produced according to the manufacturing method of the present invention.
Fig. 7 shows the surface contours, in a wet state, of a conventional wood board.
Fig. 8 is a graph showing the relationship between the moisturizing period and the water content of the wood board when the moisturizing conditions are altered.
Fig. 9 is a graph showing the relationship between the moisturizing period and the degree of swelling of the wood board when the moisturizing conditions are changed.
Fig. 10 is a graph showing the change in the degree of swelling of the wood board in cases in which the water content is increased and decreased.
Fig. 11 is a flow chart showing an example of processes in the manufacturing method in accordance with the present invention.
Description of the Preferred Embodiments Hereinbelow, the preferred embodiment of the present invention will be explained in detail with accompanied drawings.
In a preferred embodiment of the manufacturing method for oriented strand boards in accordance with the present invention, first, wooden strands are shaved from lumber as in S1 of Fig.
11. Here, the lumber is not particularly restricted; for example, pulp wood or small diameter trees, or odd ends discarded by sawmills or lumber mills as waste material, of a coniferous or broadleaf type such as Japanese red pine, larch, silver fir, fir, aspen, lodgepole pine, or the like, may be suitably employed. This raw lumber may be dressed, where necessary, and is supplied to a cutting machine such as a shaving machine or the like and is cut, and thus wooden strands are produced. The length, width, thickness and the like of the wooden strands which are produced are not particularly restricted; these dimensions may be appropriately set in accordance with the use of the wood board which is to be produced or the characteristics which are required.
Next, a binder is applied to these wooden strands (S2 in Fig. 11): The method of application is not particularly restricted; however, application by means of a spray method is preferable. For example, a method in which the wooden strands described above.are placed in a rotating drum rotating at low speed, and the binder is applied by means of a spray as the strands tumble within the drum, or a similar method, may be advantageously employed.
The binder which is applied here may comprise a foaming binder, a non-foaming binder, or a mixture thereof; however, in the case in which a decrease in density of the wood board is primarily desired, it is preferable that a foaming binder be used as the main component, while in the case in which an increase in releasability from the thermal compression plate used for molding is primarily desired, it is preferable that a non-foaming binder be the primary component.
Here, what is meant by a "foaming binder" is a binder which bonds the wooden strands in the wood board to one another and which itself creates foam; it is preferable that the resin ~~~8~~9 component be present solely at the intersection points between wooden strands, which reduces the amount of resin component used by expanding the small spaces between wooden strands with foam cells, and which thus reduces the density of the wood board.
Such a foaming binder may comprise a self-foaming resin, or may comprise a non-foaming resin and a foaming agent. Examples of self-foaming resin include foaming polyurethane resin. Examples of non-foaming resins which are made to foam using a foaming agent include, for example, a polyurethane resin, a polystyrene resin, an epoxy resin, a polyvinyl chloride resin, a phenol resin, a urea resin, or mixtures thereof. Furthermore, examples of the foaming agent include volatile foaming agents, for example, CClgF, CC12F2, CC12F-CC1F2, and the like, or pyrolytic foaming agents, for example, azodicarbon amide, azohexahydrobenzonitrile, 2,2'-azoisobutyronitrile, benzenesulfonohydrazide, N,N'-dimethylterephthalamide, or the like.
Examples of non-foaming binder include, for example, a urea resin, a melamine resin, a phenol resin, or the like.
When foaming binders and non-foaming binders are used in a mixed -fashion, it is preferable that the mixing ratio thereof be within a range of 4:1 - 1:4; however, this is not necessarily so restricted, and this ratio may be appropriately set in consideration of the density or releasability of the wood board which are desired.
Furthermore, it is preferable that the amount of binder which is applied to the wood strands be within a range of 10 -30 parts per weight with respect to 100 parts per weight of the wooden strands.
Next, the wooden strands to which binder has been applied in this manner are subjected to forming (shown in S3 in Fig.
11). In the manufacturing method for wood boards in accordance with the present invention, the use of dry forming, in which, after the wooden strands to which binder has been applied are heated and desiccated, these are dispersed on a thermal compression plate, is preferable. Methods and apparatuses which were conventionally employed may be used in an unchanged manner in this forming. Furthermore, the direction of orientation of the wooden strands is not particularly restricted; however, in order to increase the strength of the wood board, it is preferable that the grain directions of the wooden strands be oriented so as to be essentially in a single direction.
Furthermore, thermal compression is applied to the wooden strands which were subjected to forming, these are molded, and a wood board is formed. It is preferable that the thermal compression conditions be such that the temperature is within a range of 150 - 200°C, and the period is within a range of 5 - 30 minutes; however, these ranges may be appropriately set in accordance with the thickness or density of the wood board.
The above processes will be termed the "molding process" in the present specification as in Fig. 11.
In the manufacturing method for wood boards in accordance with the present invention, a smoothing process which will be discussed hereinbelow is conducted subsequently to the molding process which was described above. In this smoothing process as in Fig. 11, first, the wood board which was obtained by thermal compression molding in the molding process described above is subjected to a moisture ambient so as to be forcibly moisturized ~~8~~9 (shown in S4 in Fig. 11). Concretely, the wood board which was subjected to thermal compression molding is placed in a process apparatus and is subjected to the moisture ambient; in particular, a steam injection method, which a steam is injected into wood boards, is preferable.
In the moisturizing process, moisture is forcibly injected into the molded wood board, as a result, the wood board also forcibly swells prior to the smoothing operation such as sanding. Without the moisturizing process prior to the smoothing operation, the wood board after the smoothing operation gradually swells to arise irregularities on the surface due to moisture of the atmosphere.
Fig. 1 shows an example of a suitable apparatus for processing a wood board by means of such a steam injection method; in the Figure, reference numeral 1 indicates the wood board which is to be moisturized. This wood board 1 is disposed so as to be sandwiched between two steam injection plates 2 having hollows therein. As shown in Fig. 2, in these steam injection plates 2, steam injection apertures 7 are formed in one surface to be opposed to wood boards, and the surface in which these steam injection apertures 7 are formed is disposed so as to be in contact with the wood board 1 which is to be moisturized. Furthermore, the layered unit of these steam injection plates 2 and wood board 1 is compressed by means of two heating plates 3 and thus affixed. Furthermore, piping 11 from a steam generating apparatus 5 is connected to the steam injection plates 2 via a valve 4, and steam is thus supplied to the hollow portions within the steam injection plates 2. In addition, piping 12 is connected to the steam injection plates 2, and by opening the valve 6 provided in this piping 12, steam can be discharged from the hollow portions of the steam injection plates through the steam injection apertures 7.
In this type of moisturizing apparatus, the moisturizing of the wood board 1 is conducted in the following manner. First, in the state in which the valve 6 which is provided in piping 12 is closed, the valve 4 is adjusted, and high pressure steam is supplied to steam injection plates 2 from a steam generating apparatus 5 such as a boiler or the like through piping 11.
When this is done, the steam which is introduced into the hollow portions within the steam injection plates 2 is injected from the injection apertures 7 which are formed in steam injection plates 2 as a result of the pressure thereof. Accordingly, both surfaces of the wood board 1 are moisturized by steam which is injected from injection apertures 7 of the steam injection plates 2 which are disposed at both surfaces thereof.
Here, the steam pressure during moisturizing is within a range of 3 - 10 kg/cm2, and preferably within a range of 5 - 7 kg/cm2, and the steam injection period is set, for example with respect to a wood board having a thickness of 13 mm, to a period within--a range of 5 - 45 seconds, and preferably within a range of 15 - 25 seconds. Furthermore, it is preferable that the temperature of the heating plates be within a range of from room temperature ~ 170°C. However, the steam pressure, the steam injection period, and the temperature of the heating plates can be appropriately set in accordance with conditions such as the thickness or moisture.absorption of the wood board 1 which is to be moisturized, or the number or size of the injection apertures formed in the steam injection plates.
. 2138429 It is preferable that the injection apertures 7 formed in one steam injection plate 2 and the injection apertures 7 formed in the other steam injection plate 2 be formed in such a manner as not to be in mutual opposition when these steam injection plates 2 and 2 are disposed in a mutually opposing manner, that is to say, these apertures are formed so as to be non-symmetrical, and by means of forming the injection apertures 7 in a non-symmetrical manner, the occurrence of irregularities in moisturizing becomes less likely, and it is possible to improve the effectiveness of the moisturizing.
Furthermore, although not shown in the Figure, a mechanism for adjusting temperature, such as, for example, a water cooling mechanism, may be provided on the surfaces of the steam injection plates 2 which are in contact with the heating plates 3, and thus the temperature of the steam injection plates 2 may be adjusted.
Furthermore, a seal material of a shape such as to enclose the wood board 1 and having a thickness which is slightly greater than that of wood board 1 may be disposed between steam injection plates 2 and 2, and the steam may be enclosed during moisturizing in the enclosure of this seal material, and thus the amount of steam employed may be reduced.
High pressure steam is used in the moisturizing by means of the steam injection method described above, so that the steam penetrates forcibly into the interior of the wood board, the moisturizing is conducted efficiently, and it is possible to greatly shorten the moisturizing time.
However, the method for the moisturizing of the wood board in the smoothing process of the method in accordance with the ' 2138429 present invention is not limited to a steam injection method such as that described above; for example, a method in which the wood board is stored in a moisturizing apparatus having a high humidity may be employed. The moisturizing conditions in such a case are such that the temperature is within a range of 60°C -80°C, the humidity is within a range of 800 - 900, and moisturizing is conducted for a period of 4 hours or more, and preferably overnight. In conducting this moisturizing, other methods may be employed, such as methods in which a water spray is applied to the surfaces of the wood board, or the wood board is immersed for a short period of time in a water tank, and is then placed in a heating furnace at a temperature within a range of 30 - 50°C for a period of approximately 10 hours, or the like.
It is preferable that the moisturizing in the present invention be conducted until the water content of the wood board is within a range of 5 - 7%. Furthermore, it is preferable that after the water content of the wood board reaches a level of 130 or more, and preferably a level within a range of 15 - 200, at least once, desiccation be conducted so as to reduce the water content to less than or equal to 120, and preferably to within a range of 5 - 7 0 .
A wood board which is moisturized in this manner swells prior to the smoothing operation such as sanding, i.e., irregularities to be caused by moisture in atmosphere appears on the surface prior to the smoothing operation.
Next, the surface of the wood board which has been forcibly moisturized as described above is smoothed, and the irregularities therein are removed (shown in SS in Fig. 11).
. 2138429 Therefore, thickness swelling of the wood board to be generated by moisture in atmosphere is reduced. This removal of the surface irregularities may be conducted by means of a conventionally employed method such as sanding or the like, and a sanding apparatus such as, for example, a drum sander, a wide belt sander, or the like, may be employed.
The smoothing process which was explained in detail above may be conducted in a continuous manner after the molding process, or may be conducted separately from the molding process.
Here, what is meant by "conducting these processes in a continuous manner" is that the molding process and the smoothing process are conducted continuously as a single operation, so that the time gap between these two processes is at the longest 1 week or less, and is normally 3 days or less.
In addition, what is meant by "conducting these processes separately" is that the molding process and the smoothing process are conducted at different places or are conducted so as to be independent of one another in time; the time gap between these two processes is not strictly limited, but is preferably 1 week or more, and more preferably 1 month or more. Accordingly, cases in which boards manufactured by a different process or method at a different site are obtained, such as the purchase of commercially-available wooden boards, and these are subjected to the smoothing process, are also included in the meaning of "processes separately carried out".
In the manufacturing method for wooden boards in accordance with the present invention, it is preferable that a decorative veneer or the like be bonded to the surface of the wood board, the irregularities of the surface of which have been removed and the surface of which has been smoothed, or that various coatings be executed thereon. An oak veneer having a conventionally employed thickness within a range of 0.2 - 0.8 mm or the like may be suitably employed as the decorative veneer.
The above explanation discussed only one example of the manufacturing method for wood boards in accordance with the present invention; a variety of applications are possible. For example, a wood board in which layers comprising wooden strands of different dimensions are laminated together may be employed as the wood board which is produced by means of the manufacturing method of the present invention, in addition to strand boards comprising only one layer. In such a case, after shaving the wooden strands, an operation in which the wooden strands are separated in accordance with the dimensions thereof such as the thickness, length, width, or the like, or an operation in which a binder is applied to the separated wooden strands, may be provided.
Furthermore, it is preferable that an operation in which the wooden strands are acetylated after being shaved be provided. In the case in which the wooden strands are acetylated, it is preferable that after desiccating the wooden strands so as to reduce the water content to 30 or less, and preferably to 10 or less, the wooden strands be brought into contact with a vapor of acetic acid, acetic anhydride, chloroacetic acid, or the like, in the gas phase, and acetylation be carried out until an acetylation degree within a range of 12 - 20% is achieved.
Furthermore, a variety of operations may be included, where ' 15 ' necessary, in the manufacturing method in accordance with the present invention, such as, for example, an operation in which the shaved wooden strands are stored, an operation in which, in the case in which the water content has become excessive as a result of the forced moisturizing, heating is conducted and adjustment to an appropriate water content is carried out, or the like.
As explained above, in the wood board produced in accordance with the manufacturing method of the present invention, the thickness swelling is reduced by forcible moisturizing, and thereinafter, the irregularities in the surface of the wood board are removed prior to a smoothing operation, so that surface smoothness can be maintained over a long period of time.
Furthermore, in the manufacturing method in accordance with the present invention, the moisturizing temperature is set to a high level, and thereby it is possible to shorten the moisturizing period; after raising the water content at least once, the water content is reduced to a predetermined value, and thereby, it is possible to effectively remove the plastic deformation present in the interior of the wood board.
Hereinbelow, the present invention will be explained on the basis of examples for the purposes of clarity.
(Example 1) Wood strands having a thickness within a range of 0.1 - 0.8 mm, a length within a range of 75 - 80 mm, and a width within a range of 5 - 50 mm were produced using a shaving machine (produced by Iwakura Corporation). These wooden strands were ~~~4g desiccated so as to have a water content of 50.
parts per weight of a mixture of foaming urethane resin (crude MDI, produced by Sumitomo Bayer Urethane Co., Ltd.) and aqueous phenol resin in a weight ratio of 2:1 were prepared, 100 parts per weight of the wooden strands described above were placed in a rotating drum rotating at low speed, and the binder was applied to the wooden strands by means of dispersion using a spray as the wooden strands tumbled within the drum.
After the wooden strands to which the binder had been applied were desiccated, these were dispersed on a thermal compression plate so that the grain directions of the wooden strands were arranged so as to be essentially identical, and thus a forming member having a thickness of 250 mm was obtained.
This forming member was subjected to thermal compression molding for a period of 4 hours at a temperature of 210°C and at a pressure of 2 MPa. The thickness of the wood board which was obtained was 12 mm, and the density thereof was 0.58 g/cm3.
Next; this thermal compression molded wood board was placed in a moisturizing apparatus in a continuous manner, and was moisturized for a period of 12 hours at a temperature of 70°C
and at--a humidity of 90 0 .
This forcibly moisturized wood board was placed in a drum sander, and the surface irregularities therein were removed by sanding.
A decorative veneer comprising an oak veneer having a thickness of 0.3 mm was bonded to one surface of this wood board using an aqueous polymeric isocyanate-type adhesive (produced by Koyo Sangyo, KR7800) for a period of 3 minutes at a temperature of 110°C and at a pressure of 1.0 MPa. The surface of the wood ~~38429 board was smooth, so that the decorative veneer bonded satisfactorily. Furthermore, after the surface thereof was sanded, a urethane coating having a thickness of approximately 50 elm was executed thereon. The appearance of the wood board thus obtained was smooth and favorable. Furthermore, even when this wood board was subjected to an accelerating test corresponding to the passage of 3 years at normal temperatures, irregularities did not develop in the surface thereof, and the smoothness was maintained.
(Example 2) As in Example 1, wooden strands having a thickness of 0.5 mm, a length within a range of 20 - 100 mm, and a width within a range of 3 - 50 mm were shaved, and after these wooden strands were acetylated, an aqueous phenol resin (a resin component of 30) was applied thereto. After these wooden strands to which a binder had been applied were desiccated, they were divided into three parts, and were dispersed on a thermal compression plate so as to form a three-layered forming member in which the grain directions of the wooden strands in each layer were essentially identical, and the directions of orientation of adjoining layers were mutually perpendicular. This three-layered forming member was subjected to thermal compression molding for a period of 200 seconds at a temperature of 200°C. The wood board which was obtained had a thickness of 13 mm.
Next, this thermal compression molded wood board was placed in a continuous manner in a moisturizing apparatus, and the interior of this moisturizing apparatus was adjusted so as to attain a temperature of 35°C and a humidity of 950 (an equilibrium moisture content of 220). Here, what is meant by the "equilibrium moisture content" is a value indicating the moisture content of the wood board when the wood board is placed in such an environment and reaches a state of equilibrium.
After the passage of an appropriate amount of time, this wood board was removed from the moisturizing apparatus, and the water content, the flexural strength, the flexural Young's modulus, and the thickness swelling thereof were measured. The relationship between the water content and each of these values is shown in Figs. 3 to 5.
It can be seen from Figs. 3 to 5 that as the water content of the wood board increases, the flexural strength, flexural Young's modulus, and thickness swelling thereof decline.
Judging from these results, if the water content is 70 or less, a wood board can be obtained which has a flexural strength of approximately 40 MPa or more, and a flexural Young's modulus of approximately 45 x 102 MPa, and if the water content is 50 or more, it is possible to limit the thickness swelling to approximately 5.50 or less.
Next, a wood board which was moisturized so as to have a water content within a range of 5 - 7o was placed in a drum sander, and the surface thereof was smoothed by means of sanding. Furthermore, after this smoothed wood board was immersed in water for a period of 12 hours, a sample having a length of 150 mm and a width of 150 mm was cut therefrom, and the surface contour thereof was measured using a universal surface contour measuring apparatus (SE-3AK, produced by Kosaka Laboratory, KK). The results of the measurements are shown in Fig. 6. In Fig. 6, the horizontal axis indicates the ~~~8~2~
longitudinal direction of the measurement sample, and the vertical axis indicates the irregularity present in the surface;
measurement was conducted over a length of 10 cm at 20 locations at 5 mm intervals, and the results thereof are shown.
(Comparative Example 1) A wood board which was molded in a manner identical to that of Example 2 was subjected to sanding identical to that of Example 2 without being moisturized. After immersing this wood board in water for a period of 12 hours, the surface contour thereof was measured in a manner identical to that of Example.2.
However, measurement was conducted at 15 locations. The results thereof are shown in Fig. 7.
When these results are compared, it can be seen that in the wood board in accordance with Example 2 in which sanding was conducted after moisturizing, the largest irregularity present in the surface was approximately on the level of 0.3 mm, and little irregularity was present overall; however, in the wood board in accordance with Comparative Example 1, which was not subjected to moisturizing, the irregularity present in the surface was maximally on the level of approximately 0.6 mm, and a large amount of irregularity was present overall.
(Example 3) Commercially available strand boards were placed in a moisturizing apparatus, and were moisturized in accordance with the three sets of conditions (A, B, C) shown below. The relationship between the moisturizing period and the water content and swelling of these strand boards are shown in Figs. 8 ~~~8429 ' 20 and 9.
Conditions A: temperature 80°C, humidity 90% (equilibrium water content 150) Conditions B: temperature 60°C, humidity 900 (equilibrium water content 170) Conditions C: temperature 35°C, humidity 950 (equilibrium water content 230) From the results shown in Fig. 8, it can be seen that using conditions C, even though the humidity was the highest, the rate of increase in water content was the slowest, and comparing conditions A and B, the amount of time required until a water content of 7o was achieved was essentially identical at approximately 4 hours; however, thereinafter, the water content stabilized at 12 - 13o when conditions A were employed, while the water content increased slowly when conditions B were employed. Furthermore, while it took a period of 20 hours to reach a water content of, for example, 12o using conditions A, a period of approximately 50 hours was required when conditions B
were employed. A similar trend can also be observed in Fig. 9;
when conditions A were employed, the swelling reached a level of approximately 2o at a point in time 20 hours after the initiation of moisturizing, and stabilized thereafter, while when conditions B were employed, a period of approximately 70 hours was required; and when conditions C were employed, a swelling of 2o was not achieved even after a period of 120 hours. That is to say, it can be seen that when conditions A
were employed, recovery from the plastic deformation which was present in the strand board was achieved as a result of the moisturizing and swelling occurred.
' 21 (Example 4y A commercially-available strand board was placed in a moisturizing apparatus, and this was moisturized under conditions such that the temperature thereof was 60°C and the humidity was 900, so as to achieve a water content of approximately 150, and thereinafter, the interior of the moisturizing apparatus was set so that the temperature thereof was 35°C and the humidity thereof was 200, and the water content was reduced. The relationship between water content and thickness at this time is shown in Fig. 10.
In accordance with Fig. 10, when, for example, a water content of 7o was attained, the case in which the water content was first raised to a level of approximately 15o and then was reduced to 7o exhibits. greater swelling than the case in which moisturizing to a water content of 7o was conducted from a desiccated state. Accordingly, it can be seen that by first raising the water content at least once and then lowering the water content to a predetermined value, the effect of recovery from the internal plastic deformation is greater.
(Example 5) A wood board having a thickness of 13 mm was produced by thermal compression molding in a manner identical to that of Example 2.
Next, this thermal compression molded wood board was placed in a continuous manner in a moisturizing apparatus such as that shown in Fig. 1. A valve provided on piping coupled to a steam generation apparatus and the steam injection plates was ' 22 adjusted, and high pressure steam having a pressure of 6 kg/cm2 was injected for a period of 20 seconds from the steam injection apertures, and moisturizing was conducted. The heating plate temperature was the temperature of the chamber (30°C).
As a result, it was determined that whereas the water content of the wood board prior to moisturizing was within a range of 1 - 30, the water content of the wood board after moisturizing was within a range of 17 - 20%, and thus, sufficient moisturizing was conducted by processing for 20 seconds.
Next, the wood board was removed from the moisturizing apparatus, and was stored under conditions such that the temperature was within a range of 25 - 30°C and t he humidity was within a range of 60 - 70%, and was thus desiccated, and the water content thereof declined to a level within a range of 10 -120. When the flexural strength, flexural Young's modulus, and wet swelling coefficient of the desiccated wood board were measured, it was determined that these physical values were essentially identical to the values of the wood board of Example 2, and-a decline therein was not observed.
Next, the wood board, the water content of which had been reduced to a level within a range of 10 - 120, was placed in a drum sander, and the surface thereof was smoothed by sanding.
Furthermore, after this smoothed wood board was immersed in water for a period of 12 hours, a sample having a length of 150 mm and a width of 150 mm was cut therefrom, and the surface contour thereof was measured using a universal surface contour measurement apparatus (SE-3AK, produced by Kosaka Laboratory, KK). As a result, it was determined that the irregularity in .. ~ ~~~~~5 the surface had a maximum level of 0.3 mm, and thus surface smoothness equivalent to that of the wood board in accordance with Example 2 was maintained.
Although the invention has been described in detail herein with reference to its preferred embodiments and certain described alternatives, it is to be-understood that this description is by way of example only, and is not to be construed in a limiting sense. For example, preferred embodiment is explained along with an oriented strand board, it shall not be so limited. It is further understood that numerous modifications in the details of the embodiments of the invention and additional embodiments of the invention will be apparent, and will be made by, persons of ordinary skill in the art having reference to this description. It is contemplated that all such changes and additional embodiments are within the spirit and true scope of the invention as claimed below.
Background of the Invention Field of the Invention The present invention relates to a manufacturing method for wood boards, and in particular, relates to a manufacturing method for strand boards which are capable of maintaining superior surface smoothness over a long period of time.
Background Art In recent years, the insufficiency of lumber resources and the protection of the forests have become problems, and it is clear that it will be increasingly difficult to obtain timber from forests. Accordingly, the supply of board materials such as plywood, which are produced using large amounts of raw material lumber, will be uncertain, or will be insufficient, and the cost thereof is also expected to rise greatly. Accordingly, wood boards which can be obtained from the efficient use of wooden strands or ligneous fibers of wooden strands, or the like, which were conventionally regarded as waste materials, have attracted attention, and the application of such wood boards to such various uses has been strongly desired.
Among such wood boards, fiber boards formed from ligneous fibers and strand boards formed from wooden strands are known.
Commonly, in cases in which materials having small dimensions such as ligneous fibers are employed, the wood board which is obtained is uniform, and the surface thereof is smooth; however, the density thereof is high, and the strength and rigidity are insufficient. On the other hand, in the case of strand boards ~8~~9 which employ wooden strands, since strands are employed which are large in comparison with the ligneous fibers, it is possible to provide strength and density which approach those of natural lumber.
Such strand boards are produced by applying binder to wooden strands and subjecting these to forming and thermal compression molding. After molding, the surface of such strand boards has a large degree of irregularity, so that normally, such boards are employed after sanding the surface thereof and bonding a decorative single sheet or the like thereto. This sanding is commonly carried out after storing the strand boards for a period within a range of from a few hours to a few days at room temperature after the thermal compression molding thereof.
However, during the thermal compression molding of the strand boards described above, a high temperature and high pressure are applied under conditions of high humidity caused by the moisture contained in the adhesive, so that irregularities resulting from the cutting of the wooden strands or irregularities present in the wooden strands are subject to plastic deformation, and desiccation is conducted in this state.
After the molding, the wood board is stored at room temperature for a period of a few days, and thus the strand boards were subjected to the sanding process. Accordingly, even though the surface of such strand boards was sanded so as to provide smooth surfaces, nevertheless, the wood board is gradually swelled over a period of time after the sanding by moisture in atmosphere, so that, for example, there were problems in that after finished products were shipped, irregularities appeared on a surface sanded once so as to provide a smooth surface.
. ~8~r9 Furthermore, recently, wood boards have been obtained which have improved surface smoothness as a result of the provision of a layer comprising ligneous fibers at the surface of a strand board produced by thermal compression molding. However, in such a case, while the surface smoothness is improved, this leads to an increase in manufacturing costs of the wood board as a whole, and furthermore, a ligneous fiber layer having poor strength is provided at the surface, and there are thus problems in that the physical characteristics as a flooring material worsen.
Summary of the Invention Accordingly, it is an object of the present invention to provide a method for producing a strand board which is capable of maintaining superior surface smoothness over a long period of time without the provision of a surface-smoothed layer, such as a ligneous fiber layer or the like, at the surface thereof.
This object can be attained by means of a manufacturing method for wood boards which is characterized in comprising: a molding process including the steps of: shaving lumber to produce wooden strands; applying a binder to the wooden strands;
and subjecting the wooden strands, to which a binder has been applied, to forming and to thermal compression molding so as to obtain a molded material; and a smoothing process including the steps of: moisturizing the molding material obtained by means of the molding process;
and then abrading a surface thereof.
In accordance with the manufacturing method of wood boards of the present invention, a process is conducted in which the plastic deformation resulting from the thermal compression 4 ' molding of the wooden strands, which was a cause of the degradation of the surface smoothness of the wood boards, is forcibly manifested in advance by means of forcible moisturizing, and after this, abrading of the surface is conducted and irregularities in the surface are removed.
Accordingly, wood boards produced in accordance with the manufacturing method of the present invention contain no plastic deformation therein, and are capable of maintaining surface smoothness over a long period of time.
Furthermore, in the manufacturing method in accordance with the present invention, it is possible to conduct the molding process and the smoothing process in a continuous manner, or to conduct these processes in a separated manner, so that commercially available strand boards can be used effectively, and it is possible to obtain a wood board having superior durability.
Brief Description of the Drawings Fig. 1 shows an example of a highly suitable apparatus for conducting moisturizing in the smoothing process of the method in accordance with the present invention.
Fig. 2 shows the structure of a steam injection plate which is used in the apparatus shown in Fig. 1.
Fig. 3 is a graph showing the relationship between the water content and the flexural strength of the wood board.
Fig. 4 is a graph showing the relationship between the water content and the flexural Young's modulus of the wood board.
Fig. 5 is a graph showing the relationship between the water content and the wet swelling coefficient of the wood board.
Fig. 6 shows the surface contours, in a wet state, of a wood board produced according to the manufacturing method of the present invention.
Fig. 7 shows the surface contours, in a wet state, of a conventional wood board.
Fig. 8 is a graph showing the relationship between the moisturizing period and the water content of the wood board when the moisturizing conditions are altered.
Fig. 9 is a graph showing the relationship between the moisturizing period and the degree of swelling of the wood board when the moisturizing conditions are changed.
Fig. 10 is a graph showing the change in the degree of swelling of the wood board in cases in which the water content is increased and decreased.
Fig. 11 is a flow chart showing an example of processes in the manufacturing method in accordance with the present invention.
Description of the Preferred Embodiments Hereinbelow, the preferred embodiment of the present invention will be explained in detail with accompanied drawings.
In a preferred embodiment of the manufacturing method for oriented strand boards in accordance with the present invention, first, wooden strands are shaved from lumber as in S1 of Fig.
11. Here, the lumber is not particularly restricted; for example, pulp wood or small diameter trees, or odd ends discarded by sawmills or lumber mills as waste material, of a coniferous or broadleaf type such as Japanese red pine, larch, silver fir, fir, aspen, lodgepole pine, or the like, may be suitably employed. This raw lumber may be dressed, where necessary, and is supplied to a cutting machine such as a shaving machine or the like and is cut, and thus wooden strands are produced. The length, width, thickness and the like of the wooden strands which are produced are not particularly restricted; these dimensions may be appropriately set in accordance with the use of the wood board which is to be produced or the characteristics which are required.
Next, a binder is applied to these wooden strands (S2 in Fig. 11): The method of application is not particularly restricted; however, application by means of a spray method is preferable. For example, a method in which the wooden strands described above.are placed in a rotating drum rotating at low speed, and the binder is applied by means of a spray as the strands tumble within the drum, or a similar method, may be advantageously employed.
The binder which is applied here may comprise a foaming binder, a non-foaming binder, or a mixture thereof; however, in the case in which a decrease in density of the wood board is primarily desired, it is preferable that a foaming binder be used as the main component, while in the case in which an increase in releasability from the thermal compression plate used for molding is primarily desired, it is preferable that a non-foaming binder be the primary component.
Here, what is meant by a "foaming binder" is a binder which bonds the wooden strands in the wood board to one another and which itself creates foam; it is preferable that the resin ~~~8~~9 component be present solely at the intersection points between wooden strands, which reduces the amount of resin component used by expanding the small spaces between wooden strands with foam cells, and which thus reduces the density of the wood board.
Such a foaming binder may comprise a self-foaming resin, or may comprise a non-foaming resin and a foaming agent. Examples of self-foaming resin include foaming polyurethane resin. Examples of non-foaming resins which are made to foam using a foaming agent include, for example, a polyurethane resin, a polystyrene resin, an epoxy resin, a polyvinyl chloride resin, a phenol resin, a urea resin, or mixtures thereof. Furthermore, examples of the foaming agent include volatile foaming agents, for example, CClgF, CC12F2, CC12F-CC1F2, and the like, or pyrolytic foaming agents, for example, azodicarbon amide, azohexahydrobenzonitrile, 2,2'-azoisobutyronitrile, benzenesulfonohydrazide, N,N'-dimethylterephthalamide, or the like.
Examples of non-foaming binder include, for example, a urea resin, a melamine resin, a phenol resin, or the like.
When foaming binders and non-foaming binders are used in a mixed -fashion, it is preferable that the mixing ratio thereof be within a range of 4:1 - 1:4; however, this is not necessarily so restricted, and this ratio may be appropriately set in consideration of the density or releasability of the wood board which are desired.
Furthermore, it is preferable that the amount of binder which is applied to the wood strands be within a range of 10 -30 parts per weight with respect to 100 parts per weight of the wooden strands.
Next, the wooden strands to which binder has been applied in this manner are subjected to forming (shown in S3 in Fig.
11). In the manufacturing method for wood boards in accordance with the present invention, the use of dry forming, in which, after the wooden strands to which binder has been applied are heated and desiccated, these are dispersed on a thermal compression plate, is preferable. Methods and apparatuses which were conventionally employed may be used in an unchanged manner in this forming. Furthermore, the direction of orientation of the wooden strands is not particularly restricted; however, in order to increase the strength of the wood board, it is preferable that the grain directions of the wooden strands be oriented so as to be essentially in a single direction.
Furthermore, thermal compression is applied to the wooden strands which were subjected to forming, these are molded, and a wood board is formed. It is preferable that the thermal compression conditions be such that the temperature is within a range of 150 - 200°C, and the period is within a range of 5 - 30 minutes; however, these ranges may be appropriately set in accordance with the thickness or density of the wood board.
The above processes will be termed the "molding process" in the present specification as in Fig. 11.
In the manufacturing method for wood boards in accordance with the present invention, a smoothing process which will be discussed hereinbelow is conducted subsequently to the molding process which was described above. In this smoothing process as in Fig. 11, first, the wood board which was obtained by thermal compression molding in the molding process described above is subjected to a moisture ambient so as to be forcibly moisturized ~~8~~9 (shown in S4 in Fig. 11). Concretely, the wood board which was subjected to thermal compression molding is placed in a process apparatus and is subjected to the moisture ambient; in particular, a steam injection method, which a steam is injected into wood boards, is preferable.
In the moisturizing process, moisture is forcibly injected into the molded wood board, as a result, the wood board also forcibly swells prior to the smoothing operation such as sanding. Without the moisturizing process prior to the smoothing operation, the wood board after the smoothing operation gradually swells to arise irregularities on the surface due to moisture of the atmosphere.
Fig. 1 shows an example of a suitable apparatus for processing a wood board by means of such a steam injection method; in the Figure, reference numeral 1 indicates the wood board which is to be moisturized. This wood board 1 is disposed so as to be sandwiched between two steam injection plates 2 having hollows therein. As shown in Fig. 2, in these steam injection plates 2, steam injection apertures 7 are formed in one surface to be opposed to wood boards, and the surface in which these steam injection apertures 7 are formed is disposed so as to be in contact with the wood board 1 which is to be moisturized. Furthermore, the layered unit of these steam injection plates 2 and wood board 1 is compressed by means of two heating plates 3 and thus affixed. Furthermore, piping 11 from a steam generating apparatus 5 is connected to the steam injection plates 2 via a valve 4, and steam is thus supplied to the hollow portions within the steam injection plates 2. In addition, piping 12 is connected to the steam injection plates 2, and by opening the valve 6 provided in this piping 12, steam can be discharged from the hollow portions of the steam injection plates through the steam injection apertures 7.
In this type of moisturizing apparatus, the moisturizing of the wood board 1 is conducted in the following manner. First, in the state in which the valve 6 which is provided in piping 12 is closed, the valve 4 is adjusted, and high pressure steam is supplied to steam injection plates 2 from a steam generating apparatus 5 such as a boiler or the like through piping 11.
When this is done, the steam which is introduced into the hollow portions within the steam injection plates 2 is injected from the injection apertures 7 which are formed in steam injection plates 2 as a result of the pressure thereof. Accordingly, both surfaces of the wood board 1 are moisturized by steam which is injected from injection apertures 7 of the steam injection plates 2 which are disposed at both surfaces thereof.
Here, the steam pressure during moisturizing is within a range of 3 - 10 kg/cm2, and preferably within a range of 5 - 7 kg/cm2, and the steam injection period is set, for example with respect to a wood board having a thickness of 13 mm, to a period within--a range of 5 - 45 seconds, and preferably within a range of 15 - 25 seconds. Furthermore, it is preferable that the temperature of the heating plates be within a range of from room temperature ~ 170°C. However, the steam pressure, the steam injection period, and the temperature of the heating plates can be appropriately set in accordance with conditions such as the thickness or moisture.absorption of the wood board 1 which is to be moisturized, or the number or size of the injection apertures formed in the steam injection plates.
. 2138429 It is preferable that the injection apertures 7 formed in one steam injection plate 2 and the injection apertures 7 formed in the other steam injection plate 2 be formed in such a manner as not to be in mutual opposition when these steam injection plates 2 and 2 are disposed in a mutually opposing manner, that is to say, these apertures are formed so as to be non-symmetrical, and by means of forming the injection apertures 7 in a non-symmetrical manner, the occurrence of irregularities in moisturizing becomes less likely, and it is possible to improve the effectiveness of the moisturizing.
Furthermore, although not shown in the Figure, a mechanism for adjusting temperature, such as, for example, a water cooling mechanism, may be provided on the surfaces of the steam injection plates 2 which are in contact with the heating plates 3, and thus the temperature of the steam injection plates 2 may be adjusted.
Furthermore, a seal material of a shape such as to enclose the wood board 1 and having a thickness which is slightly greater than that of wood board 1 may be disposed between steam injection plates 2 and 2, and the steam may be enclosed during moisturizing in the enclosure of this seal material, and thus the amount of steam employed may be reduced.
High pressure steam is used in the moisturizing by means of the steam injection method described above, so that the steam penetrates forcibly into the interior of the wood board, the moisturizing is conducted efficiently, and it is possible to greatly shorten the moisturizing time.
However, the method for the moisturizing of the wood board in the smoothing process of the method in accordance with the ' 2138429 present invention is not limited to a steam injection method such as that described above; for example, a method in which the wood board is stored in a moisturizing apparatus having a high humidity may be employed. The moisturizing conditions in such a case are such that the temperature is within a range of 60°C -80°C, the humidity is within a range of 800 - 900, and moisturizing is conducted for a period of 4 hours or more, and preferably overnight. In conducting this moisturizing, other methods may be employed, such as methods in which a water spray is applied to the surfaces of the wood board, or the wood board is immersed for a short period of time in a water tank, and is then placed in a heating furnace at a temperature within a range of 30 - 50°C for a period of approximately 10 hours, or the like.
It is preferable that the moisturizing in the present invention be conducted until the water content of the wood board is within a range of 5 - 7%. Furthermore, it is preferable that after the water content of the wood board reaches a level of 130 or more, and preferably a level within a range of 15 - 200, at least once, desiccation be conducted so as to reduce the water content to less than or equal to 120, and preferably to within a range of 5 - 7 0 .
A wood board which is moisturized in this manner swells prior to the smoothing operation such as sanding, i.e., irregularities to be caused by moisture in atmosphere appears on the surface prior to the smoothing operation.
Next, the surface of the wood board which has been forcibly moisturized as described above is smoothed, and the irregularities therein are removed (shown in SS in Fig. 11).
. 2138429 Therefore, thickness swelling of the wood board to be generated by moisture in atmosphere is reduced. This removal of the surface irregularities may be conducted by means of a conventionally employed method such as sanding or the like, and a sanding apparatus such as, for example, a drum sander, a wide belt sander, or the like, may be employed.
The smoothing process which was explained in detail above may be conducted in a continuous manner after the molding process, or may be conducted separately from the molding process.
Here, what is meant by "conducting these processes in a continuous manner" is that the molding process and the smoothing process are conducted continuously as a single operation, so that the time gap between these two processes is at the longest 1 week or less, and is normally 3 days or less.
In addition, what is meant by "conducting these processes separately" is that the molding process and the smoothing process are conducted at different places or are conducted so as to be independent of one another in time; the time gap between these two processes is not strictly limited, but is preferably 1 week or more, and more preferably 1 month or more. Accordingly, cases in which boards manufactured by a different process or method at a different site are obtained, such as the purchase of commercially-available wooden boards, and these are subjected to the smoothing process, are also included in the meaning of "processes separately carried out".
In the manufacturing method for wooden boards in accordance with the present invention, it is preferable that a decorative veneer or the like be bonded to the surface of the wood board, the irregularities of the surface of which have been removed and the surface of which has been smoothed, or that various coatings be executed thereon. An oak veneer having a conventionally employed thickness within a range of 0.2 - 0.8 mm or the like may be suitably employed as the decorative veneer.
The above explanation discussed only one example of the manufacturing method for wood boards in accordance with the present invention; a variety of applications are possible. For example, a wood board in which layers comprising wooden strands of different dimensions are laminated together may be employed as the wood board which is produced by means of the manufacturing method of the present invention, in addition to strand boards comprising only one layer. In such a case, after shaving the wooden strands, an operation in which the wooden strands are separated in accordance with the dimensions thereof such as the thickness, length, width, or the like, or an operation in which a binder is applied to the separated wooden strands, may be provided.
Furthermore, it is preferable that an operation in which the wooden strands are acetylated after being shaved be provided. In the case in which the wooden strands are acetylated, it is preferable that after desiccating the wooden strands so as to reduce the water content to 30 or less, and preferably to 10 or less, the wooden strands be brought into contact with a vapor of acetic acid, acetic anhydride, chloroacetic acid, or the like, in the gas phase, and acetylation be carried out until an acetylation degree within a range of 12 - 20% is achieved.
Furthermore, a variety of operations may be included, where ' 15 ' necessary, in the manufacturing method in accordance with the present invention, such as, for example, an operation in which the shaved wooden strands are stored, an operation in which, in the case in which the water content has become excessive as a result of the forced moisturizing, heating is conducted and adjustment to an appropriate water content is carried out, or the like.
As explained above, in the wood board produced in accordance with the manufacturing method of the present invention, the thickness swelling is reduced by forcible moisturizing, and thereinafter, the irregularities in the surface of the wood board are removed prior to a smoothing operation, so that surface smoothness can be maintained over a long period of time.
Furthermore, in the manufacturing method in accordance with the present invention, the moisturizing temperature is set to a high level, and thereby it is possible to shorten the moisturizing period; after raising the water content at least once, the water content is reduced to a predetermined value, and thereby, it is possible to effectively remove the plastic deformation present in the interior of the wood board.
Hereinbelow, the present invention will be explained on the basis of examples for the purposes of clarity.
(Example 1) Wood strands having a thickness within a range of 0.1 - 0.8 mm, a length within a range of 75 - 80 mm, and a width within a range of 5 - 50 mm were produced using a shaving machine (produced by Iwakura Corporation). These wooden strands were ~~~4g desiccated so as to have a water content of 50.
parts per weight of a mixture of foaming urethane resin (crude MDI, produced by Sumitomo Bayer Urethane Co., Ltd.) and aqueous phenol resin in a weight ratio of 2:1 were prepared, 100 parts per weight of the wooden strands described above were placed in a rotating drum rotating at low speed, and the binder was applied to the wooden strands by means of dispersion using a spray as the wooden strands tumbled within the drum.
After the wooden strands to which the binder had been applied were desiccated, these were dispersed on a thermal compression plate so that the grain directions of the wooden strands were arranged so as to be essentially identical, and thus a forming member having a thickness of 250 mm was obtained.
This forming member was subjected to thermal compression molding for a period of 4 hours at a temperature of 210°C and at a pressure of 2 MPa. The thickness of the wood board which was obtained was 12 mm, and the density thereof was 0.58 g/cm3.
Next; this thermal compression molded wood board was placed in a moisturizing apparatus in a continuous manner, and was moisturized for a period of 12 hours at a temperature of 70°C
and at--a humidity of 90 0 .
This forcibly moisturized wood board was placed in a drum sander, and the surface irregularities therein were removed by sanding.
A decorative veneer comprising an oak veneer having a thickness of 0.3 mm was bonded to one surface of this wood board using an aqueous polymeric isocyanate-type adhesive (produced by Koyo Sangyo, KR7800) for a period of 3 minutes at a temperature of 110°C and at a pressure of 1.0 MPa. The surface of the wood ~~38429 board was smooth, so that the decorative veneer bonded satisfactorily. Furthermore, after the surface thereof was sanded, a urethane coating having a thickness of approximately 50 elm was executed thereon. The appearance of the wood board thus obtained was smooth and favorable. Furthermore, even when this wood board was subjected to an accelerating test corresponding to the passage of 3 years at normal temperatures, irregularities did not develop in the surface thereof, and the smoothness was maintained.
(Example 2) As in Example 1, wooden strands having a thickness of 0.5 mm, a length within a range of 20 - 100 mm, and a width within a range of 3 - 50 mm were shaved, and after these wooden strands were acetylated, an aqueous phenol resin (a resin component of 30) was applied thereto. After these wooden strands to which a binder had been applied were desiccated, they were divided into three parts, and were dispersed on a thermal compression plate so as to form a three-layered forming member in which the grain directions of the wooden strands in each layer were essentially identical, and the directions of orientation of adjoining layers were mutually perpendicular. This three-layered forming member was subjected to thermal compression molding for a period of 200 seconds at a temperature of 200°C. The wood board which was obtained had a thickness of 13 mm.
Next, this thermal compression molded wood board was placed in a continuous manner in a moisturizing apparatus, and the interior of this moisturizing apparatus was adjusted so as to attain a temperature of 35°C and a humidity of 950 (an equilibrium moisture content of 220). Here, what is meant by the "equilibrium moisture content" is a value indicating the moisture content of the wood board when the wood board is placed in such an environment and reaches a state of equilibrium.
After the passage of an appropriate amount of time, this wood board was removed from the moisturizing apparatus, and the water content, the flexural strength, the flexural Young's modulus, and the thickness swelling thereof were measured. The relationship between the water content and each of these values is shown in Figs. 3 to 5.
It can be seen from Figs. 3 to 5 that as the water content of the wood board increases, the flexural strength, flexural Young's modulus, and thickness swelling thereof decline.
Judging from these results, if the water content is 70 or less, a wood board can be obtained which has a flexural strength of approximately 40 MPa or more, and a flexural Young's modulus of approximately 45 x 102 MPa, and if the water content is 50 or more, it is possible to limit the thickness swelling to approximately 5.50 or less.
Next, a wood board which was moisturized so as to have a water content within a range of 5 - 7o was placed in a drum sander, and the surface thereof was smoothed by means of sanding. Furthermore, after this smoothed wood board was immersed in water for a period of 12 hours, a sample having a length of 150 mm and a width of 150 mm was cut therefrom, and the surface contour thereof was measured using a universal surface contour measuring apparatus (SE-3AK, produced by Kosaka Laboratory, KK). The results of the measurements are shown in Fig. 6. In Fig. 6, the horizontal axis indicates the ~~~8~2~
longitudinal direction of the measurement sample, and the vertical axis indicates the irregularity present in the surface;
measurement was conducted over a length of 10 cm at 20 locations at 5 mm intervals, and the results thereof are shown.
(Comparative Example 1) A wood board which was molded in a manner identical to that of Example 2 was subjected to sanding identical to that of Example 2 without being moisturized. After immersing this wood board in water for a period of 12 hours, the surface contour thereof was measured in a manner identical to that of Example.2.
However, measurement was conducted at 15 locations. The results thereof are shown in Fig. 7.
When these results are compared, it can be seen that in the wood board in accordance with Example 2 in which sanding was conducted after moisturizing, the largest irregularity present in the surface was approximately on the level of 0.3 mm, and little irregularity was present overall; however, in the wood board in accordance with Comparative Example 1, which was not subjected to moisturizing, the irregularity present in the surface was maximally on the level of approximately 0.6 mm, and a large amount of irregularity was present overall.
(Example 3) Commercially available strand boards were placed in a moisturizing apparatus, and were moisturized in accordance with the three sets of conditions (A, B, C) shown below. The relationship between the moisturizing period and the water content and swelling of these strand boards are shown in Figs. 8 ~~~8429 ' 20 and 9.
Conditions A: temperature 80°C, humidity 90% (equilibrium water content 150) Conditions B: temperature 60°C, humidity 900 (equilibrium water content 170) Conditions C: temperature 35°C, humidity 950 (equilibrium water content 230) From the results shown in Fig. 8, it can be seen that using conditions C, even though the humidity was the highest, the rate of increase in water content was the slowest, and comparing conditions A and B, the amount of time required until a water content of 7o was achieved was essentially identical at approximately 4 hours; however, thereinafter, the water content stabilized at 12 - 13o when conditions A were employed, while the water content increased slowly when conditions B were employed. Furthermore, while it took a period of 20 hours to reach a water content of, for example, 12o using conditions A, a period of approximately 50 hours was required when conditions B
were employed. A similar trend can also be observed in Fig. 9;
when conditions A were employed, the swelling reached a level of approximately 2o at a point in time 20 hours after the initiation of moisturizing, and stabilized thereafter, while when conditions B were employed, a period of approximately 70 hours was required; and when conditions C were employed, a swelling of 2o was not achieved even after a period of 120 hours. That is to say, it can be seen that when conditions A
were employed, recovery from the plastic deformation which was present in the strand board was achieved as a result of the moisturizing and swelling occurred.
' 21 (Example 4y A commercially-available strand board was placed in a moisturizing apparatus, and this was moisturized under conditions such that the temperature thereof was 60°C and the humidity was 900, so as to achieve a water content of approximately 150, and thereinafter, the interior of the moisturizing apparatus was set so that the temperature thereof was 35°C and the humidity thereof was 200, and the water content was reduced. The relationship between water content and thickness at this time is shown in Fig. 10.
In accordance with Fig. 10, when, for example, a water content of 7o was attained, the case in which the water content was first raised to a level of approximately 15o and then was reduced to 7o exhibits. greater swelling than the case in which moisturizing to a water content of 7o was conducted from a desiccated state. Accordingly, it can be seen that by first raising the water content at least once and then lowering the water content to a predetermined value, the effect of recovery from the internal plastic deformation is greater.
(Example 5) A wood board having a thickness of 13 mm was produced by thermal compression molding in a manner identical to that of Example 2.
Next, this thermal compression molded wood board was placed in a continuous manner in a moisturizing apparatus such as that shown in Fig. 1. A valve provided on piping coupled to a steam generation apparatus and the steam injection plates was ' 22 adjusted, and high pressure steam having a pressure of 6 kg/cm2 was injected for a period of 20 seconds from the steam injection apertures, and moisturizing was conducted. The heating plate temperature was the temperature of the chamber (30°C).
As a result, it was determined that whereas the water content of the wood board prior to moisturizing was within a range of 1 - 30, the water content of the wood board after moisturizing was within a range of 17 - 20%, and thus, sufficient moisturizing was conducted by processing for 20 seconds.
Next, the wood board was removed from the moisturizing apparatus, and was stored under conditions such that the temperature was within a range of 25 - 30°C and t he humidity was within a range of 60 - 70%, and was thus desiccated, and the water content thereof declined to a level within a range of 10 -120. When the flexural strength, flexural Young's modulus, and wet swelling coefficient of the desiccated wood board were measured, it was determined that these physical values were essentially identical to the values of the wood board of Example 2, and-a decline therein was not observed.
Next, the wood board, the water content of which had been reduced to a level within a range of 10 - 120, was placed in a drum sander, and the surface thereof was smoothed by sanding.
Furthermore, after this smoothed wood board was immersed in water for a period of 12 hours, a sample having a length of 150 mm and a width of 150 mm was cut therefrom, and the surface contour thereof was measured using a universal surface contour measurement apparatus (SE-3AK, produced by Kosaka Laboratory, KK). As a result, it was determined that the irregularity in .. ~ ~~~~~5 the surface had a maximum level of 0.3 mm, and thus surface smoothness equivalent to that of the wood board in accordance with Example 2 was maintained.
Although the invention has been described in detail herein with reference to its preferred embodiments and certain described alternatives, it is to be-understood that this description is by way of example only, and is not to be construed in a limiting sense. For example, preferred embodiment is explained along with an oriented strand board, it shall not be so limited. It is further understood that numerous modifications in the details of the embodiments of the invention and additional embodiments of the invention will be apparent, and will be made by, persons of ordinary skill in the art having reference to this description. It is contemplated that all such changes and additional embodiments are within the spirit and true scope of the invention as claimed below.
Claims (11)
1. A manufacturing method for wood boards comprising:
a molding process including the steps of: shaving lumber to produce wooden strands; applying a binder to said wooden strands; and subjecting said wooden strands, to which a binder has been applied, to forming and to thermal compression molding so as to obtain a molded material; and a smoothing process including the steps of: moisturizing said molded material obtained by means of said molding process;
and then abrading a surface thereof.
a molding process including the steps of: shaving lumber to produce wooden strands; applying a binder to said wooden strands; and subjecting said wooden strands, to which a binder has been applied, to forming and to thermal compression molding so as to obtain a molded material; and a smoothing process including the steps of: moisturizing said molded material obtained by means of said molding process;
and then abrading a surface thereof.
2. A manufacturing method for wood boards comprising:
a molding process including the steps of: shaving lumber to produce wooden strands; applying a binder to said wooden strands; subjecting said wooden strands, to which a binder has been applied, to forming and to thermal compression molding so as to obtain a molded material; and a smoothing process including the steps of: moisturizing said molded material obtained by means of said molding process so as to increase a water content thereof; desiccating said molded material so as to decrease a water content thereof; and then abrading a surface thereof.
a molding process including the steps of: shaving lumber to produce wooden strands; applying a binder to said wooden strands; subjecting said wooden strands, to which a binder has been applied, to forming and to thermal compression molding so as to obtain a molded material; and a smoothing process including the steps of: moisturizing said molded material obtained by means of said molding process so as to increase a water content thereof; desiccating said molded material so as to decrease a water content thereof; and then abrading a surface thereof.
3. A manufacturing method for wood boards in accordance with claim 1 or 2, wherein said smoothing process is conducted in a continuous manner with said molding process.
4. A manufacturing method for wood boards in accordance with claim 1 or 2, wherein said smoothing process is conducted in such a manner as to be separate from said molding process.
5. A manufacturing method for wood boards in accordance with claim 1 or 2, wherein said step of moisturizing is conducted by means of a steam injection method.
6. A method of manufacturing a oriented strand board comprising the steps of:
(a) Providing wood strands;
(b) molding the wood strands with binding material to form a molded oriented strand board;
(c) after the molding step (b), moisturizing the oriented strand board to cause irregularities on a surface of the oriented strand board; and (d) after the moisturizing step(c), removing the irregularities from the surface of the oriented strand board.
(a) Providing wood strands;
(b) molding the wood strands with binding material to form a molded oriented strand board;
(c) after the molding step (b), moisturizing the oriented strand board to cause irregularities on a surface of the oriented strand board; and (d) after the moisturizing step(c), removing the irregularities from the surface of the oriented strand board.
7. A method according to claim 6, wherein the step (c), the moisturizing step is performed by injecting moisture into the oriented strand board.
8. A method according to claim 6, wherein the step (d), the removing step is performed by a sanding.
9. A method according to claim 6; wherein the step (b) the binding material comprises a material selected from a group consisting of polyurethane resin, polystyrene resin, epoxy resin, polyvinyl chloride resin, phenol resin, urea resin and mixtures thereof.
10. A method according to claim 6, wherein the step (b), the binding material further comprises the foaming agent.
11. A method according to claim 10, wherein the foaming agent comprises a material selected from a group consisting of CC13F, CC12F2, CC12F-CC1F2, azodicarbon amide, azohexahydrobenzonitrile, 2,2'-azoisobutyronitrile, benzenesulfonohydrazide, and N,N'-dimethylterephthalamide.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP33861693 | 1993-12-28 | ||
| JP5-338616 | 1993-12-28 | ||
| JP23820194A JP3368689B2 (en) | 1993-12-28 | 1994-09-30 | Wood board manufacturing method |
| JP6-238201 | 1994-09-30 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2138429A1 CA2138429A1 (en) | 1995-06-29 |
| CA2138429C true CA2138429C (en) | 2001-02-20 |
Family
ID=26533574
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2138429 Expired - Lifetime CA2138429C (en) | 1993-12-28 | 1994-12-19 | Manufacturing method for wood boards |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JP3368689B2 (en) |
| CA (1) | CA2138429C (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3050156B2 (en) * | 1996-05-31 | 2000-06-12 | ヤマハ株式会社 | Wood board manufacturing method |
| WO2016056207A1 (en) * | 2014-10-08 | 2016-04-14 | パナソニックＩｐマネジメント株式会社 | Plant-based board production method and plant-based board |
| PL3774241T3 (en) * | 2018-04-13 | 2023-10-23 | Tricoya Technologies Ltd | Acetylated wood and method of making same |
| CN112976204A (en) * | 2021-04-07 | 2021-06-18 | 济南银鑫建材有限公司 | Board flatting mill that can high-efficient pressurization humidification |
-
1994
- 1994-09-30 JP JP23820194A patent/JP3368689B2/en not_active Expired - Lifetime
- 1994-12-19 CA CA 2138429 patent/CA2138429C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| CA2138429A1 (en) | 1995-06-29 |
| JPH07232309A (en) | 1995-09-05 |
| JP3368689B2 (en) | 2003-01-20 |
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| EEER | Examination request | ||
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Effective date: 20141219 |