CN113334514A - Preparation method of oil-heated single-surface-layer compressed and densified wood - Google Patents
Preparation method of oil-heated single-surface-layer compressed and densified wood Download PDFInfo
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- CN113334514A CN113334514A CN202110750702.1A CN202110750702A CN113334514A CN 113334514 A CN113334514 A CN 113334514A CN 202110750702 A CN202110750702 A CN 202110750702A CN 113334514 A CN113334514 A CN 113334514A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
- B27K3/00—Impregnating wood, e.g. impregnation pretreatment, for example puncturing; Wood impregnation aids not directly involved in the impregnation process
- B27K3/02—Processes; Apparatus
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
- B27K3/00—Impregnating wood, e.g. impregnation pretreatment, for example puncturing; Wood impregnation aids not directly involved in the impregnation process
- B27K3/34—Organic impregnating agents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27M—WORKING OF WOOD NOT PROVIDED FOR IN SUBCLASSES B27B - B27L; MANUFACTURE OF SPECIFIC WOODEN ARTICLES
- B27M1/00—Working of wood not provided for in subclasses B27B - B27L, e.g. by stretching
- B27M1/02—Working of wood not provided for in subclasses B27B - B27L, e.g. by stretching by compressing
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- Wood Science & Technology (AREA)
- Forests & Forestry (AREA)
- Mechanical Engineering (AREA)
- Chemical And Physical Treatments For Wood And The Like (AREA)
Abstract
The invention provides a preparation method of oil-heated single-side surface layer compressed and densified wood, which comprises the following steps: immersing the lower surface layer of the wood into dimethyl silicon oil preheated to 160-180 ℃ for 8-12min, taking out, placing in a hot press with an upper press plate not heated and a lower press plate preheated to 160-180 ℃, placing the oil-immersed surface of the wood on the lower press plate, hot-pressing for 10-15min, and gradually compressing the wood to the required thickness; raising the temperature of the lower pressing plate to 240 ℃ at 220-; stopping heating the lower pressing plate, cooling the lower pressing plate by using a cooling medium to ensure that the temperature of the lower pressing plate is rapidly reduced to 60-100 ℃, and then taking out the wood from the hot pressing machine. The prepared wood has obviously improved surface strength, particularly hardness, low rebound rate, small deformation and stable size.
Description
Technical Field
The invention relates to a method for densifying wood.
Background
Most fast-growing wood has the problems of small diameter grade, low density, uneven wood color and the like, so that the application of the fast-growing wood in the fields of furniture, buildings and the like is limited. The wood is a viscoelastic natural high molecular polymer material, can generate elastic-plastic deformation under the synergistic action of moisture-heat-force, and provides favorable conditions for the preparation of compressed wood. At present, the wood compression mainly adopts a wet-heat compression method, namely, the wood is subjected to steam treatment, softening pretreatment is carried out by improving the temperature and the water content of the wood, then the whole compression densification is carried out on the wood under the action of certain external force, although the physical and mechanical properties of the fast-growing wood can be obviously improved, the compression ratio is large, and the volume loss of the wood is large. In addition, the phenomena of high thickness resilience, uneven wood surface and the like caused by stress and self moisture absorption characteristics of the compressed wood are serious, secondary processing treatment such as heat treatment is generally needed to fix the early compression effect, and the problems of complicated process and equipment and the like are prominent.
For example, the prior art CN10266941B discloses a surface enhanced manufacturing method of fast growing wood, which is prepared by the following steps:
(1) drying, namely drying the fast growing wood until the water content is 5-12%;
(2) carbonizing, namely carbonizing the dried fast-growing wood for 2 to 4 hours at the temperature of 175 to 200 ℃ in carbonizing equipment;
(3) a surface reinforcing step, namely placing the fast growing wood on a hot press for hot pressing, closing a hot pressing plate of the hot press, and keeping the temperature difference between the upper surface and the lower surface of the pressed wood more than 100 ℃ for more than 5 seconds to carry out compression reinforcing treatment;
(4) and (3) a heat treatment fixing step, namely, orderly stacking fast growing wood obtained by surface reinforcement, pressing a pressed block in a wood pile, then putting the wood into a wood heat treatment device, quickly heating and humidifying, keeping the temperature difference of a dry bulb and a wet bulb between 40 ℃ and 50 ℃ in the heating and humidifying processes until the temperature of the wet bulb reaches 100 ℃, directly heating to 180-220 ℃ to carry out heat treatment on the wood for 2-4 hours, stopping heating and atomized water to finish the heat treatment when the temperature of the wood is quickly reduced to be less than 120 ℃ in the heat treatment device by adopting a continuous atomized water spraying method, and taking out the wood after the temperature in the natural cooling heat treatment device is reduced to 60 ℃.
Compared with the present patent, CN10266941B has the following disadvantages: besides the hot press, the wood needs to be matched with carbonization heat treatment equipment, the process flow is complex, the wood needs to be subjected to temperature rise and temperature reduction repeatedly, the energy consumption is high, particularly, the wood is softened through the carbonization step to be beneficial to surface enhancement, after the hot-pressing compression is finished, the heat treatment fixation needs to be carried out, and the heat treatment fixation can be basically equal to the carbonization step again.
Disclosure of Invention
The invention aims to provide a preparation method of oil-heated single-side surface layer compressed and densified wood, which is remarkably improved in surface strength, particularly hardness, of one side of the wood prepared by the method, low in rebound rate, small in deformation and stable in size.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of oil-heated single-surface-layer compressed and densified wood is characterized by comprising the following steps: the method comprises the following steps:
a. dipping high-temperature oil: immersing the lower surface layer of the wood into dimethyl silicone oil preheated to 160-180 ℃ for 8-12min and taking out;
b. hot pressing: placing the wood impregnated with hot oil in a hot press with an unheated upper press plate and a preheated lower press plate at 180 ℃ of 160-;
c. heat setting: raising the temperature of the lower pressing plate to 240 ℃ at 220-;
d. and (3) cooling: stopping heating the lower pressing plate, cooling the lower pressing plate by using a cooling medium to ensure that the temperature of the lower pressing plate is rapidly reduced to 60-100 ℃, and then taking out the wood from the hot pressing machine.
The invention has the beneficial effects that:
in the step a, the thickness of the lower surface layer of the wood impregnated with the high-temperature oil is 20-35% of the total thickness of the wood; in the step b, the thickness of the compressed wood is 75-80% of the original thickness of the wood. The thickness of the lower surface layer of the wood impregnated with the high-temperature oil determines the actual compression area and the surface reinforcing effect of the wood to a great extent, the interior of the wood with small surface reinforcing effect is compressed to a certain extent due to the overlarge impregnation thickness, and the degree of surface compression is reduced under the condition that the overall compression rate is not changed, so that the final surface reinforcing effect is reduced. Increasing the compression ratio, i.e. decreasing the ratio of the thickness of the compressed wood to the original thickness of the wood, can certainly improve the wood modification effect, but also decrease the wood yield, increase the material cost, and put forward a high requirement on the performance requirement of the compression capability (maximum force) of the hot press, while if the thickness or compression ratio of the lower surface of the wood impregnated with high temperature oil is too small, the compression enhancement effect cannot meet the expected requirement. The main innovation point of the invention is that a high-temperature oil impregnation pretreatment method is introduced to directionally soften the surface area which has the main effect on the later-stage use performance of the wood, so that the compression change in the hot pressing process is mainly generated on the surface layer of the wood, the use performance of the wood, especially the surface layer, is improved on the premise of not increasing the integral compression rate of the wood and keeping a certain outturn rate, and the added value of the fast-growing and low-quality wood is improved.
The preparation method of the oil-heated single-surface-layer compressed and densified wood is fast-growing wood, such as poplar or spruce.
Detailed Description
The invention provides a method for preparing compressed and densified wood by impregnating a single-side surface layer of wood with dimethyl silicone oil and then integrating hot-pressing compression and heat setting. Firstly, dimethyl silicon oil is preheated to 160-180 ℃, a storage rack with a certain thickness (the height of the storage rack can be adjusted) is placed in a device filled with oil, the height difference between the height of the storage rack and the oil surface is the surface layer impregnation thickness of the wood, the conventional kiln dried wood is placed on the storage rack filled with high-temperature hot oil, and the wood is immersed in oil for 10min in a frying way, at the moment, because the boiling point of water is far lower than the temperature of the hot oil, the water content in the wood is evaporated at high temperature, the water content is reduced, a large number of small holes are formed in the wood, then the capillary siphon phenomenon occurs, the oil is quickly sucked into pores on the surface layer of the wood, and the oil occupies cell cavities and cell gaps of the wood; the hot oil impregnated wood was then placed in a preheated hot press, wherein: the upper pressing plate is not heated to keep room temperature, and the lower pressing plate is heated to the specified temperature of 160 ℃ and 180 ℃. The oil-impregnated surface of the wood is placed on a lower heating plate, the hot pressing temperature is 160-. At the moment, oil enters the surface layer and the sub-surface layer of the wood at the later stage of the 'frying' dipping process, so that the mechanical strength of the area is favorably reduced (similar to the classic wood theory of 'increasing of water content and reducing of mechanical strength'), and the wood is conveniently compressed and compacted. The wood core layer loses water at high temperature in the 'frying' dipping process, the water content is reduced, the compressive strength is increased, so under the condition that the unit pressure is the same as that of the surface layer area, the condition that the compression amplitude of the core layer is reduced or even not compressed can be realized, and a density gradient is created between the surface layer and the core layer of the board, namely, the surface strength, particularly the hardness of the board is obviously improved under the condition that the volume loss rate of the board is reduced as much as possible; and (4) entering a heat setting stage after the hot pressing stage is finished, raising the temperature of the lower pressing plate to 240 ℃, reducing the pressure to 0.05-0.1Mpa, and keeping the temperature for 30-50 min. At the moment, the internal stress generated by hot pressing in the compression process can be released as soon as possible when the press is about to open by reducing the pressure, and the thickness expansion caused by the release of the internal stress in the subsequent processing process is reduced; in addition, high temperature can lead to cellulose, hemicellulose, lignin in the timber all to take place the degradation of different degree, and the hydroscopicity hydroxyl reduces, and the hygroscopicity reduces, can effectively reduce because timber kick-backs because of the thickness that the moisture absorption leads to in the later stage use, and both synergistic effect play the positive role to the thickness of restraining compression timber kick-backs. The oil overflows from the periphery of the wood in the early hot pressing process, and the overflowing oil can form a protective layer for isolating oxygen on the outer surface of the wood in the heat setting stage, so that the problems of excessive thermal oxidation, reduced mechanical strength and the like of the wood in long-time high-temperature hot setting on a press are prevented. Meanwhile, the hot pressing temperature is increased, the rigidity of the wood is reduced to a certain extent, and the release of internal stress is facilitated, the time of the stage is set to be longer than that of the compression stage, mainly because the recoverable visco-elastic deformation formed in the compression process of the wood can be converted into the plastic deformation which is not easy to recover under the action of longer heat setting, and when the high-temperature long-time treatment is carried out, the molecular motion of the wood is violent, the motion of a molecular chain segment or the whole molecular chain is excited, the relatively stable motion of the molecular chain is generated, the internal stress accumulated in the hot pressing stage is converted into energy in other forms, and the internal stress of the system is reduced, so that the compressed wood obtains excellent dimensional stability; and finally, introducing cooling water into the lower pressing plate, rapidly reducing the temperature of the lower pressing plate to 60-100 ℃, and taking out the wood from the hot press. Example 1:
immersing the lower surface layer of the poplar wood with the thickness of 24mm into dimethyl silicone oil preheated to 180 ℃ for 8min, and taking out; placing the poplar wood soaked with hot oil in a hot press with an unheated upper press plate and a preheated lower press plate to 180 ℃, placing the wood oil-soaked surface on the lower press plate, hot-pressing at 180 ℃ for 10min, and compressing the wood to a thickness of 19mm (the compression ratio is 20.8%); after the hot pressing stage is finished, the temperature of the lower pressing plate is raised to 220 ℃, the hot pressing pressure is reduced to 0.05-0.1Mpa, the lower pressing plate is insulated for 50min, then cooling medium is introduced into the lower pressing plate to rapidly reduce the temperature to 60 ℃, then the wood is taken out from the hot pressing machine, is placed in an environment with the temperature of 35 ℃ and the humidity of 65% for humidifying treatment, is taken out and planed (the planing quantity is 1-1.5mm) after being balanced, and the mechanical property is measured. And then, putting the wood in an oven with the temperature of 103 ℃ in sequence to be dried in an oven to be in an oven-dry state, the temperature of 50 ℃ and the humidity of 95% in sequence to be balanced in a stable state, putting the wood in the oven with the temperature of 103 ℃ in sequence to be dried in an oven-dry state again, measuring the thickness dimension in the oven-dry state for 2 times in sequence, and calculating the irreversible thickness rebound rate caused by the high-humidity environment.
Note: for poplar compressed wood, surface hardness refers to the oil-impregnated surface hardness.
Example 2:
immersing the lower surface layer of the fir wood with the thickness of 35mm into dimethyl silicone oil preheated to 170 ℃ for 10min, and taking out; putting the fir wood soaked with hot oil into a hot press with an unheated upper press plate and a preheated lower press plate to 170 ℃, putting the oil-soaked surface of the wood on the lower press plate, hot-pressing at the temperature of 170 ℃ for 15min, and compressing the wood to the thickness of 26.5mm (the compression rate is 24.2%); after the hot pressing stage is finished, the temperature of the lower pressing plate is increased to 240 ℃, the hot pressing pressure is reduced to 0.05-0.1Mpa, the lower pressing plate is insulated for 50min, then a cooling medium is introduced into the lower pressing plate for cooling so as to rapidly reduce the temperature to 80 ℃, then the wood is taken out from the hot pressing machine, is placed in an environment with the temperature of 35 ℃ and the humidity of 65% for humidifying treatment, is taken out and planed (the planing quantity is 1-1.5mm) after being balanced, and the mechanical property is measured. And then, putting the wood in an oven with the temperature of 103 ℃ in sequence to be dried in an oven to be in an oven-dry state, the temperature of 50 ℃ and the humidity of 95% in sequence to be balanced in a stable state, putting the wood in the oven with the temperature of 103 ℃ in sequence to be dried in an oven-dry state again, measuring the thickness dimension in the oven-dry state for 2 times in sequence, and calculating the irreversible thickness rebound rate caused by the high-humidity environment.
Note: for fir compressed wood, surface hardness refers to the oil impregnated surface hardness.
Claims (5)
1. A preparation method of oil-heated single-surface-layer compressed and densified wood is characterized by comprising the following steps: the method comprises the following steps:
a. dipping high-temperature oil: immersing the lower surface layer of the wood into dimethyl silicone oil preheated to 160-180 ℃ for 8-12min and taking out;
b. hot pressing: placing the wood impregnated with hot oil in a hot press with an unheated upper press plate and a preheated lower press plate at 180 ℃ of 160-;
c. heat setting: raising the temperature of the lower pressing plate to 240 ℃ at 220-;
d. and (3) cooling: stopping heating the lower pressing plate, cooling the lower pressing plate by using a cooling medium to ensure that the temperature of the lower pressing plate is rapidly reduced to 60-100 ℃, and then taking out the wood from the hot pressing machine.
2. The process for preparing oil-heated single-surface-layer compressed densified wood according to claim 1, characterized by comprising: in the step a, the thickness of the lower surface layer of the wood impregnated with the high-temperature oil is 20-35% of the total thickness of the wood.
3. The process for preparing oil-heated single-surface-layer compressed densified wood according to claim 1, characterized by comprising: in the step b, the thickness of the compressed wood is 75-80% of the original thickness of the wood.
4. The process for preparing oil-heated single-surface-layer compressed densified wood according to claim 1, characterized by comprising: the wood is fast-growing wood.
5. The method for preparing oil-heated single-surface-layer compressed and densified wood according to claim 4, characterized by comprising the following steps: the wood is fast-growing wood with low density and soft hardness, and comprises poplar or pine and fir.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202110750702.1A CN113334514A (en) | 2021-07-01 | 2021-07-01 | Preparation method of oil-heated single-surface-layer compressed and densified wood |
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| CN202110750702.1A CN113334514A (en) | 2021-07-01 | 2021-07-01 | Preparation method of oil-heated single-surface-layer compressed and densified wood |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116533339A (en) * | 2023-02-28 | 2023-08-04 | 西昌学院 | Preparation method and application of single-side compression layer positioning quantitative compressed wood |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103978532A (en) * | 2014-06-05 | 2014-08-13 | 南京林业大学 | Modified treatment method of wood and bamboo, modified wood, modified bamboo and floor |
| CN106863512A (en) * | 2017-02-07 | 2017-06-20 | 南京林业大学 | The preparation method of outdoor timber recombinant material |
| CN108582378A (en) * | 2018-03-29 | 2018-09-28 | 华南农业大学 | A kind of unilateral side surface layer compressed wood and preparation method thereof |
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2021
- 2021-07-01 CN CN202110750702.1A patent/CN113334514A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103978532A (en) * | 2014-06-05 | 2014-08-13 | 南京林业大学 | Modified treatment method of wood and bamboo, modified wood, modified bamboo and floor |
| CN106863512A (en) * | 2017-02-07 | 2017-06-20 | 南京林业大学 | The preparation method of outdoor timber recombinant material |
| CN108582378A (en) * | 2018-03-29 | 2018-09-28 | 华南农业大学 | A kind of unilateral side surface layer compressed wood and preparation method thereof |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116533339A (en) * | 2023-02-28 | 2023-08-04 | 西昌学院 | Preparation method and application of single-side compression layer positioning quantitative compressed wood |
| CN116533339B (en) * | 2023-02-28 | 2024-08-09 | 西昌学院 | Preparation method and application of single-side compression layer positioning quantitative compressed wood |
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