KR20170021385A

KR20170021385A - A method for compressing wood improving dimensional stability

Info

Publication number: KR20170021385A
Application number: KR1020150115097A
Authority: KR
Inventors: 이원희; 황성욱; 조범근
Original assignee: 경북대학교 산학협력단
Priority date: 2015-08-17
Filing date: 2015-08-17
Publication date: 2017-02-28

Abstract

More particularly, the present invention relates to a method for manufacturing compressed wood, which comprises: 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 thermally compressing step of thermally compressing the wood at least once with a hot press; a cooling step of cooling the thermally compressed wood for a predetermined period of time to humidify the heated wood; And a post-treatment drying step in which the drying step is carried out.
According to the present invention, there is an effect that the dimensional stability of the wood is improved by removing the latent stress of the compressed processed wood through a post-treatment drying process in which the processed wood which is thermocompression-bonded is dried in a drying chamber.
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 is produced and can be used in various fields such as building materials, furniture and crafts, architectural civil engineering materials, and musical instrument materials.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a wood-

More particularly, the present invention relates to a method for producing compressed 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 compression-processed wood with improved dimensional stability, in which the thermally-compressed wood is dimensionally restored to its original shape as moisture is absorbed and the dimension of the compression-processed wood can be stabilized.

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.

These ordinary woods are naturally dried in the shade to remove moisture, but the wood produced by natural drying has a high expansion and contraction ratio, which makes it unsuitable for craft materials and the like.

Accordingly, the wood is compressed and processed at a high density to be utilized as a variety of living materials such as craft materials or building materials.

Such a high-density wood processing method is effective for compressing wood by using a hot press, or for producing a finished product from wood raw materials because the swollen and twisted state caused by the moisture absorption of the compressed wood continues, The yield is extremely low and 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 of manufacturing a compression-treated wood having high dimensional stability through post-processing so that thermally compressed wood is not restored to its original shape due to moisture absorption by overcoming the unreasonable point of such conventional compression- 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 an object of the present invention is to improve the dimensional stability by eliminating latent stress of a processed wood subjected to post-

According to an aspect of the present invention, there is provided a method of manufacturing compressed wood, comprising the steps of pretreating a wood material heated to a temperature below the fiber saturation point by softening the wood material in water vapor for a certain period of time, A heat-compression step of thermally compressing the thermally-compressed wood at least once, a cooling step of cooling the thermally-compressed wood for a predetermined period of time to humidify the heated wood, a step of drying the moisture- Drying step.

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 30% or less.

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, in the thermal compression step, the temperature of the compression pressure is set to 170 to 190 ° C.

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%.

The method for manufacturing compressed wood according to the second embodiment includes a preheating step of hot-rolling a wood material heated to a temperature below the fiber saturation point by using a high-frequency or ultrasonic heat source, a step of heat- A cooling step of cooling the thermally compressed wood for a predetermined period of time to cool and humidify the heated wood, 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.

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, there is an effect that the dimensional stability of the wood is improved by removing the latent stress of the compressed processed wood through a post-treatment drying process in which the processed wood which is thermocompression-bonded is dried in a drying chamber.

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 showing a procedure for manufacturing compressed-processed 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 for manufacturing compressed-processed 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 showing a procedure for manufacturing compressed-processed wood with improved dimensional stability according to a first embodiment of the present invention.

Referring to the drawings, a method for manufacturing compressed wood having improved dimensional stability according to a first embodiment of the present invention includes a preprocessing step S110, a thermal compression step S120, a cooling step S130, ).

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, and then dried to a moisture content of 30% or less.

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. That is, it is preferable that the hot-pressing temperature is 170 to 190 ° 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.

In the cooling-down step (S130), the thermally-compressed wood is cooled to a predetermined thickness to cool the wood in a ground state. This is because, in the thermal compression step of the previous step, the moisture-evaporated wood is humidity-cooled by cooling, thereby moisture-regulating the moisture content to a fiber saturation point (25 to 30%) or less.

In the post-treatment drying step (S140), 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 wood is heat-compressed, .

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 for manufacturing compressed-processed wood with improved dimensional stability according to a second embodiment of the present invention.

Referring to the drawings, a method for manufacturing a compression-treated wood with improved dimensional stability according to a second embodiment of the present invention includes a pretreatment thermal pretreatment step S910, a thermal compression step S920, a cooling step S930, Step S940 is provided.

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

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 cooling step of cooling the thermally compressed wood for a predetermined period of time to perform 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; The method of claim 1,

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 DEG C within 30 minutes to 6 hours and drying the wood so that the moisture content in the wood is 30% or less.

The method according to claim 1,
Wherein the drying temperature in the drying chamber is in the range of 80 to 120 DEG C for 6 to 48 hours in the post-drying process.

The method according to claim 1,
Wherein the thermo-compression temperature in the thermal compression step is set at 170 to 190 ° C.

The method according to claim 1,
Wherein the compression time is 10 to 120 minutes in the thermal compression step, and the compression pressure is 5 to 100 kgf / mm < 2 >.

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 cooling step of cooling the thermally compressed wood for a predetermined period of time to perform 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; The method of claim 1,

8. The method of claim 7,
And the wood is subjected to 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 in the drying chamber is in the range of 80 to 120 DEG C for 6 to 48 hours in the post-drying process.

The method according to claim 1,
Wherein the thermo-compression temperature is set to 180 ° C or lower in the thermal compression step.