KR20170021386A - A method for bending processing wood improving dimensional stability - Google Patents

Abstract

The present invention relates to a method for manufacturing a bendable wood with improved dimensional stability, and more particularly, to a method for manufacturing a bendable wood, comprising a pretreatment step of softening the timber heated to a temperature below the fiber saturation point, A thermal compression step of thermally compressing the wood at least once with a hot press, a bending step of fixing the thermally compressed wood to a curved surface processing jig of a predetermined shape so that the wood is bent into a predetermined shape, A cooling step of cooling the wood in a combined state for a predetermined period of time to perform a humidification process in a normal state, and a post-treatment drying step of drying the moisture-treated wood in a drying room at a predetermined temperature and for a predetermined period of time.
According to the present invention, since the warp-processed wood is dried in the drying chamber, the latent stress of the compressed processed wood is removed through a post-treatment drying process to improve the dimensional stability of the wood so that the wood is elastically restored to its original shape before bending It is possible to reduce the defective product rate.
In addition, softwood of low specific gravity such as pine wood is also dried by heat compression to produce high-density, dimensionally stabilized processed wood, which makes it possible to utilize not only hardwood but also softwood, thereby increasing the utilization of resources .
In addition, high-density compressed wood with high dimensional stability that utilizes beautiful pattern of natural wood can be manufactured and used in various fields such as building materials, furniture and crafts, architectural civil works, and musical instrument wood.

Description

Technical Field [0001] The present invention relates to a method for manufacturing wood with improved dimensional stability,

The present invention relates to a method for manufacturing a bendable wood having improved dimensional stability, and more particularly, to a method for manufacturing a bendable wood by thermally compressing a general wood material without pretreatment of chemicals such as chemicals, The present invention relates to a method of manufacturing a bend-processed wood with improved dimensional stability, in which the thermally compressed wood is dimensionally restored to its original shape due to moisture absorption and can be stabilized in dimension of the bend-processed wood.

The general wood material has a natural surface texture such as a ring, and has a specific gravity of 0.8 or less and a low hardness, which is weaker than general industrial materials, but has advantages of easy processing. However, since the surface hardness is very weak and it is a porous material, it is excellent in moisture absorptive and desorptive property by moisture, so it is possible to control the humidity by acting as a natural humidifier. However, Due to the swelling and shrinkage of the wooden cell wall, it is accompanied with drawbacks in that the dimensional stability is very poor, such as refraction or distortion.

Particularly, in the case of wooden furniture, the legs of the table and the backboard of the chair often have to be processed into a curved shape. However, due to the inherent characteristics of wood, there is a limitation in forming a single piece of wood into a curved shape. Accordingly, conventionally, a piece of wood is divided into several parts, each of the divided pieces of wood is processed to fit a part of the final curved shape, And then joined or aggregated in such a manner as to bond each other, adhesive bond, or the like to obtain a desired final shape of the curved wood. In such a conventional coupling or aggregation method, a plurality of processes are required to obtain a final curved material, which requires a large amount of labor and a large amount of wood raw materials to be consumed, resulting in low productivity. Moreover, the finishing treatment of the final curved wood is not perfect, The quality of the furniture using the curved wood is lowered.

Accordingly, the wood is subjected to compression and bending processes so that high-density bending-processed wood is utilized as a variety of living materials such as artificial wood materials and building materials.

The method of bending the wood is to fix the wood subjected to the bending process to the bending process fixture and dry it. Since the general wood has a limitation in bending due to its inherent physical characteristics, And heat treatment is applied, or plasticization treatment using ammonia is performed to improve the bending workability of the wood.

Accordingly, in order to improve the bending workability of the wood, water and heat are supplied to the wood to improve the bending workability, or the bending workability is improved through the plasticizing treatment using ammonia.

However, the wood that has been compressed in this way continues to swell and twist as moisture is absorbed in the ground state, and the bending wood is resiliently restored to its original shape by the elastic restoring force, resulting in a high defect ratio, The yield that can be produced is extremely low, resulting in a problem that the productivity is significantly lowered.

Accordingly, the above-described manufacturing method is inferior in manufacturing efficiency, consumes a lot of energy, has a lot of damage in terms of the number of materials, and can not escape from the extremely small-sized domestic handwork.

Therefore, there is a demand for a method for manufacturing a bend-processed wood having high dimensional stability through post-processing so as to overcome the unreasonable point of manufacturing the conventional bend-processed wood so that the thermally compressed wood does not recover its original shape after moisture absorption It is a fact that it is getting higher.

Korean Patent Publication No. 2003-0012322

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a method and apparatus for removing a latent stress of a compressed processed wood through post- .

According to an aspect of the present invention, there is provided a method for manufacturing a bendable wood, comprising: a pretreatment step of softening the timber heated to a temperature below the fiber saturation point by steam for a certain period of time in water vapor; A heat compression step of thermally compressing the thermally compressed wood at least once, a bending step of fixing the thermally compressed wood to a curved surface processing jig of a predetermined shape so that the wood is bent into a predetermined shape, Cooling the wood for a certain period of time and humidifying the wood in a pre-heated state, and drying the moisture-treated wood in a drying chamber at a predetermined temperature and for a predetermined period of time.

Here, in the pretreatment step, the wood is steamed at a temperature of 50 to 150 ° C. within 30 minutes to 6 hours, and the wood is dried to have a water content of 13 to 20%.

Also, in the post-treatment drying step, the inside temperature of the drying chamber is 80 to 120 ° C and the drying treatment is performed for 6 to 48 hours.

In addition, the hot-pressing temperature in the thermal compression step is set at 180 ° C or less.

In the thermal compression step, the pressing time is set to 10 to 120 minutes, and the pressing pressure is set to 5 to 100 kgf / mm < 2 >.

Further, in the thermal compression step, the hot press is operated so that the thickness of the wood is compressed to 50% or less.

The method of manufacturing a bendable wood according to the second embodiment includes a preheating step of hot-rolling a wood material heated to a temperature below a fiber saturation point by using a high-frequency or ultrasonic heat source, a step of heat- A bending process step of fixing the thermally compressed wood to a curved machining jig of a certain shape so that the wood is bent into a predetermined shape, a step of cooling the wood in a state of being coupled to the curved machining jig for a predetermined time, And a post-treatment drying step of drying the moisture-treated wood in a drying chamber at a predetermined temperature and for a predetermined period of time.

In addition, in the step of preheating and drying the wood, the wood is softened for 5 minutes to 60 minutes.

Also, in the post-treatment drying step, the inside temperature of the drying chamber is 80 to 120 ° C and the drying treatment is performed for 6 to 48 hours.

In addition, the hot-pressing temperature in the thermal compression step is set at 180 ° C or less.

In the thermal compression step, the pressing time is set to 10 to 120 minutes, and the pressing pressure is set to 5 to 100 kgf / mm < 2 >.

Further, in the thermal compression step, the hot press is operated so that the thickness of the wood is compressed to 50% or less.

According to the present invention, since the warp-processed wood is dried in the drying chamber, the latent stress of the compressed processed wood is removed through a post-treatment drying process to improve the dimensional stability of the wood so that the wood is elastically restored to its original shape before bending It is possible to reduce the defective product rate.

The effect of preventing the wood from being restored to its original shape again and improving the dimensional stability of the wood.

In addition, softwood of low specific gravity such as pine wood is also dried by heat compression to produce high-density, dimensionally stabilized processed wood, which makes it possible to utilize not only hardwood but also softwood, thereby increasing the utilization of resources .

In addition, high-density compressed wood with high dimensional stability that utilizes beautiful pattern of natural wood can be manufactured and used in various fields such as building materials, furniture and crafts, architectural civil works, and musical instrument wood.

FIG. 1 is a flowchart illustrating a manufacturing procedure of a bendable wood with improved dimensional stability according to a first embodiment of the present invention.
Fig. 2 is a table showing changes in the specific gravity of each species depending on the degree of thermal compaction.
3 is a graph showing changes in the internal density distribution of the wood according to the degree of thermal compaction.
4 is a graph showing the change in the compressive strength of the wood species according to the degree of thermal compaction.
5 is a graph showing changes in the bending strength of wood according to the degree of thermal compaction.
FIG. 6 is a graph showing the change in the surface hardness of wood according to the degree of thermal compaction.
Fig. 7 is a table showing changes in surface hardness according to a hot-pressure temperature and a hot-pressure time.
FIG. 8 is a graph showing the change in dimensional stability according to the temperature and pressure.
FIG. 9 is a flowchart showing a procedure of manufacturing a bendable wood with improved dimensional stability according to a second embodiment of the present invention.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a flowchart illustrating a manufacturing procedure of a bendable wood with improved dimensional stability according to a first embodiment of the present invention.

Referring to the drawings, a method for manufacturing a bendable wood having improved dimensional stability according to a first embodiment of the present invention includes a pretreatment step S110, a thermal compression step S120, a bending step S130, a cooling step S140, And a post-treatment drying step (S150).

In the pretreatment step (S110), the interior of the wood is softened so as to facilitate the compression of the wood. In the present invention, the wood having moisture content less than the fiber saturation point (25 ~ 30% To be softened.

For this purpose, in the present invention, the wood is heated to a temperature of 50 to 150 ° C. for about 30 minutes to 6 hours. In general, the wood is dried to have a water content of 30% or less. In the present invention, To 20%.

If the water content in the wood is less than 13%, the wood easily breaks during the bending process. If the moisture content in the wood is more than 20%, the wood surface will be broken during the bending process.

The thermal compression step (S120) is a process for compressing and compressing wood at a high temperature using a hot press to remove intracellular lumens, thereby increasing the density of the wood and improving the strength and elastic modulus.

In this thermal compression step (S120), the hot press is compressed at least once several times until the thickness of the wood is formed to a certain thickness. This is because when the wood is compressed to a certain thickness by applying a lot of pressure to the wood at one time, the wood breakage phenomenon occurs and the steam is gradually discharged from the wood several times, so that the wood thickness is gradually compressed by the hot press do.

Particularly, the setting of the compression ratio of the thickness of the wood will be described in detail through the experimental results of FIGS. 2 to 6.

FIG. 2 is a table showing the change in the specific gravity of each species according to the degree of thermo-compaction. As the comparative wood, pine trees, pine trees and pine trees were selected as experiment subjects, . Experimental results show that the specific gravity increases with the compression ratio from 10% to the higher compression ratio. In the case of 50%, the specific gravity is highest in each species.

In addition, when the thickness of the wood is 50% or more, the structure is broken and the wood thickness is not compressed to 50% or more.

FIG. 3 is a graph showing changes in the internal density distribution of the wood according to the degree of thermo-compaction. FIG. 3 (a) shows the internal density of the wood before compression and has an average density of 464 kg / The density waveform is not uniform. In the graph (b), the thickness of wood is compressed by 10%, and the density is 27 mm thick. The average density is 483 kg / ㎤. The graph (c) shows that the average density value is increased to 636 kg / cm 3 when the wood is compressed to have a thickness of 30%. In the graph (d), the internal density is measured by compressing the wood thickness to 50%, and the wood thickness is compressed to 15 mm. As the compression ratio is increased, the internal density is higher and the internal density waveform is uniformized. .

FIG. 4 is a graph showing the change in the compressive strength of the wood according to the degree of thermal compaction, FIG. 5 is a graph showing the change in the bending strength of the wood according to the degree of thermal compaction, and FIG. Fig.

4 and 6 are graphs showing changes in longitudinal compressive strength, bending strength and surface hardness of various species of Pinus koraiensis, Pinus densiflora and Larix kaempferi according to the degree of thermo-compaction, , And that the higher the thermal compaction, the higher the compressive strength, the flexural strength, and the surface hardness.

As a result of comparing the specific gravity, density, compression strength, bending strength and surface hardness according to the degree of wood thermal compaction, the highest experimental results are obtained when the wood thickness is compressed to 50%. Accordingly, During the compression step, the thermo-press is pressed several times to the wood so that the thickness of the wood is reduced to 50%.

FIG. 7 is a table showing changes in surface hardness according to a hot-pressing temperature and a hot-pressing time, and FIG. 8 is a graph showing a change in dimensional stability according to a hot-pressing temperature.

Referring to FIG. 7, it can be seen that the surface hardness is increased while the temperature of the hot-pressing is increased from 140 ° C to 180 ° C. This shows that the density increases and the internal moisture content of the wood decreases to increase the surface hardness. The surface hardness is reduced by the surface heat deterioration due to the high heat at 200 캜. That is, it is understood that the surface hardness is lowered at 180 ° C or higher.

FIG. 8 shows the dimensional change recovery rate of the wood by a 24-hour absorption test at a constant hot-pressing temperature and a hot-pressing time of 50%. The dimensional change recovery rate is 0.35% at 220 ° C.

Accordingly, in order to maximize the dimensional stability of the wood, when the temperature of the hot pressing is set to 220 캜 in the thermal compression step, the surface of the wood is deteriorated due to the high temperature, and the mechanical performance is deteriorated.

Accordingly, in the present invention, a separate post-wood drying step is carried out in order to maintain dimensional stability at a temperature of not more than 180 ° C.

In addition, the pressing time in the thermal compression step is about 10 to 120 minutes depending on the species and thickness of the wood, and the pressing pressure is preferably 5 to 100 kgf / mm 2.

Bending process step ( S130) fix the thermally compressed wood to a curved surface processing jig of a certain shape so that the wood is bent into a certain shape. Such a curved surface machining jig combines curved machining jigs having a curved surface shape on both side surfaces of a wood by a pressing device of a curved surface to which wood adheres, or by a manual operation, and bolts the wood to press the wood so that the wood is bent into a certain shape.

In the cooling-down step (S140), the wood in the state of being coupled to the curved surface machining jig is allowed to cool and is subjected to a humidification process. This means that the wood in which the moisture has evaporated in the previous compression step, which is the heat step in the previous step, is humidified by cooling and moisture is kept at a water saturation point (25 to 30%) or less.

In the post-treatment drying step (S150), the moisture-treated wood as described above is dried in the drying chamber for a predetermined temperature and time. In this case, the inside temperature of the drying chamber is 80 to 120 ° C., the drying time is 6 to 48 hours, the drying is performed in the range of 6 to 48 hours, the heat is compressed and the thickness is changed, The wood in the state of being attached to the jig is allowed to dry as it is.

In this post-treatment drying step, the residual stress caused by the wood processing is removed so that the thermally compressed wood having a thickness of 50% at a temperature of 180 ° C. is not restored to its original state due to the resilience of the dimension.

FIG. 9 is a flowchart showing a procedure of manufacturing a bendable wood with improved dimensional stability according to a second embodiment of the present invention.

Referring to the drawings, a method for manufacturing a bendable wood with improved dimensional stability according to a second embodiment of the present invention includes a pretreatment preheating step S910, a thermal compression step S920, a bending step S930, (S940) and post-treatment drying step (S950).

In the second embodiment of the present invention, unlike in the first embodiment, the wood that has been moistened in a moisture content of 25% to 30% or less of the saturation point of the wood is subjected to heat treatment using high frequency or ultrasonic heat source, .

However, since the pretreatment process takes about 5 to 60 minutes, the pretreatment process is performed faster than the enhancement treatment process of the first embodiment, The production amount can be increased, and the softening degree can be controlled by an appropriate amount by the heating method.

In the second embodiment, the subsequent manufacturing process other than the preprocessing step is performed in the same manner as in the first embodiment.

Although the present invention has been described in connection with the above-mentioned preferred embodiments, it is possible to make various modifications and variations without departing from the spirit and scope of the invention. Accordingly, the scope of the appended claims should include all such modifications and changes as fall within the scope of the present invention.

Claims (12)

A pretreatment step of softening the timber heated to a temperature below the fiber saturation point by steam for a certain period of time,
A thermal compression step of thermally compressing the wood at least once by a hot press;
A bending process step of fixing the thermally compressed wood to a curved surface processing jig of a certain shape so that the wood is bent into a predetermined shape;
A cooling step of cooling the wood in a state of being coupled to the curved machining jig for a predetermined period of time and performing a humidification process in an established state;
Drying the moisture-treated wood in a drying chamber at a predetermined temperature for a predetermined period of time; Wherein the method comprises the steps of:
The method according to claim 1,
Wherein the pretreating step is carried out by increasing the wood at a steam temperature of 50 to 150 ° C. within 30 minutes to 6 hours and drying the wood so that the water content in the wood reaches 13 to 20% .
The method according to claim 1,
Wherein the drying temperature of the drying chamber is 80 to 120 ° C for 6 to 48 hours in the post-treatment drying step.
The method according to claim 1,
Wherein the thermo-compression temperature is set to 180 ° C or lower in the thermal compression step.
The method according to claim 1,
Wherein the compression time is 10 to 120 minutes and the compression pressure is 5 to 100 kgf / mm < 2 > in the thermal compression step.
The method according to claim 1,
Wherein the thermo-compression press is operated so that the thickness of the wood is reduced to 50% or less in the thermal compression step.
A preheating step of heat-treating the wood heated to a temperature below the fiber saturation point using a high-frequency or ultrasonic heat source;
A thermal compression step of thermally compressing the wood at least once by a hot press;
A bending process step of fixing the thermally compressed wood to a curved surface processing jig of a certain shape so that the wood is bent into a predetermined shape;
A cooling step of cooling the wood in a state of being coupled to the curved machining jig for a predetermined period of time and performing a humidification process in an established state;
Drying the moisture-treated wood in a drying chamber at a predetermined temperature for a predetermined period of time; Wherein the method comprises the steps of:
8. The method of claim 7,
Wherein the wood is subjected to a softening treatment for 5 to 60 minutes in the step of preheating and drying the hot-rolled steel.
8. The method of claim 7,
Wherein the drying temperature of the drying chamber is 80 to 120 ° C for 6 to 48 hours in the post-treatment drying step.
The method according to claim 1,
Wherein the thermo-compression temperature is set to 180 ° C or lower in the thermal compression step.
The method according to claim 1,
Wherein the compression time is 10 to 120 minutes and the compression pressure is 5 to 100 kgf / mm < 2 > in the thermal compression step.
The method according to claim 1,
Wherein the thermo-compression press is operated so that the thickness of the wood is reduced to 50% or less in the thermal compression step.

Images