CN110181637B - Method for reducing wood cross grain drying shrinkage - Google Patents
Method for reducing wood cross grain drying shrinkage Download PDFInfo
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- CN110181637B CN110181637B CN201910432491.XA CN201910432491A CN110181637B CN 110181637 B CN110181637 B CN 110181637B CN 201910432491 A CN201910432491 A CN 201910432491A CN 110181637 B CN110181637 B CN 110181637B
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- wood
- reducing
- water content
- drying shrinkage
- fixed pressure
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- 239000002023 wood Substances 0.000 title claims abstract description 89
- 238000001035 drying Methods 0.000 title claims abstract description 28
- 238000000034 method Methods 0.000 title claims abstract description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 28
- 238000010438 heat treatment Methods 0.000 claims abstract description 8
- 230000001105 regulatory effect Effects 0.000 claims abstract description 7
- 238000001816 cooling Methods 0.000 claims abstract description 6
- 230000003044 adaptive effect Effects 0.000 claims abstract description 3
- 230000003750 conditioning effect Effects 0.000 claims description 3
- 238000002791 soaking Methods 0.000 claims description 2
- 230000009467 reduction Effects 0.000 abstract description 7
- 230000009286 beneficial effect Effects 0.000 abstract description 3
- 240000005020 Acaciella glauca Species 0.000 description 7
- 244000166124 Eucalyptus globulus Species 0.000 description 7
- 235000008582 Pinus sylvestris Nutrition 0.000 description 7
- 239000001839 pinus sylvestris Substances 0.000 description 7
- 238000004519 manufacturing process Methods 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 238000007385 chemical modification Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 230000009471 action Effects 0.000 description 2
- 210000002421 cell wall Anatomy 0.000 description 2
- 239000003814 drug Substances 0.000 description 2
- 230000009977 dual effect Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000010875 treated wood Substances 0.000 description 2
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 229920005546 furfural resin Polymers 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- 239000005011 phenolic resin Substances 0.000 description 1
- 229920001568 phenolic resin Polymers 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
Classifications
-
- 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
- B27K5/00—Treating of wood not provided for in groups B27K1/00, B27K3/00
- B27K5/001—Heating
-
- 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
- B27K5/00—Treating of wood not provided for in groups B27K1/00, B27K3/00
- B27K5/0085—Thermal treatments, i.e. involving chemical modification of wood at temperatures well over 100°C
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Forests & Forestry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Chemical And Physical Treatments For Wood And The Like (AREA)
Abstract
The invention discloses a method for reducing the drying shrinkage of wood cross grains, which comprises the following steps: step one, adjusting the water content of the wood to 20% -30%; step two, placing the wood in the step one in a drying kiln, a temperature and humidity regulating box or an oven, and regulating the environment temperature to slowly reduce the water content of the wood in the environment; while reducing the water content, applying a fixed pressure to the wood; step three, reducing the water content of the wood in the step two to be adaptive to the target use condition, and continuously applying fixed pressure; putting the wood in the third step in a vacuum condition for flash type heat treatment, and continuously applying fixed pressure; and step five, cooling the wood treated in the step four, fixing length, width and thickness, and inspecting. The invention realizes the reduction of the wood cross grain drying shrinkage, and has the beneficial effects of controllable and uniform reduction degree.
Description
Technical Field
The invention belongs to the field of physical properties of wood, and particularly relates to a method for reducing the drying shrinkage of wood cross grains.
Background
Desiccation is an inherent property of wood. When the moisture content of wood is below the fiber saturation point, the reduction of the moisture content of wood causes the reduction of the wood size, namely drying shrinkage. When the wood is dried and shrunk, the volume of the wood is lost and the production cost is increased. In addition, wood is an anisotropic material, and the amount of drying shrinkage varies in different directions: the drying shrinkage along the lines is very small and is not more than 0.3 percent; however, the drying shrinkage of the cross grain is large and ranges from 3% to 12%, so that the drying shrinkage of the wood is easy to cause different forms of cracking and warping when the water content is changed. For the engineering wood components, the loosening and the damage of the joints of the components can be caused by the drying shrinkage of the wood caused by the change of the water content. Therefore, the method has important significance for reducing the wood drying shrinkage, particularly the cross grain drying shrinkage, reducing the production cost, improving the wood quality and prolonging the service life of the wood engineering material.
At present, the control mode of the wood drying shrinkage mainly depends on physical or chemical modification. The physical modification is mainly to carry out high-temperature heat treatment on the wood, and to reduce the sensitivity of the wood to moisture by degrading chemical components of the cell wall part of the wood, thereby reducing the wood drying shrinkage. The chemical modification is mainly to impregnate the wood with a medicament, and common medicaments comprise phenolic resin adhesive, furfural resin, polyethylene glycol and the like. When the physical modification mode is adopted to reduce the wood drying shrinkage, chemical components of wood cell walls are degraded to different degrees under the action of long-time high temperature, so that the strength of the wood is lost, and the use of the wood is limited. When the chemical modification mode is adopted to reduce the wood drying shrinkage, the impregnation is uneven, organic matters are volatilized, the production process is complex, and the cost is greatly increased.
Disclosure of Invention
The invention aims to solve the technical problems of wood strength loss, non-uniform treatment process, complex production process and high cost in the prior art, and provides a simple and efficient process method, so that the reduction of the transverse grain dry shrinkage of the wood is realized, and the beneficial effects of controllable and uniform reduction degree are achieved. The method is based on the Poisson effect, and applies fixed pressure in the length single direction, or the length and width double directions or the length and thickness double directions of the wood, so as to ensure that the wood is respectively subjected to stretching deformation in the length single direction, or the length and width double directions or the length and thickness double directions. Under the action of fixed pressure, the wood generates a continuous Poisson effect, and the wood is subjected to stretching deformation in a single direction or in the length and width directions or in the length and thickness directions through the flash type vacuum heat treatment, so that the aim of reducing the dry shrinkage is fulfilled.
In order to solve the technical problem, the invention provides a method for reducing the drying shrinkage of wood cross striations, which is characterized by comprising the following steps:
step one, adjusting the water content of the wood to 20% -30%;
step two, placing the wood in the step one in a drying kiln, a temperature and humidity regulating box or an oven, and regulating the environment temperature to slowly reduce the water content of the wood in the environment; while reducing the water content, applying a fixed pressure to the wood;
step three, reducing the water content of the wood in the step two to be adaptive to the target use condition, and continuously applying fixed pressure;
putting the wood in the third step in a vacuum condition for flash type heat treatment, and continuously applying fixed pressure;
and step five, cooling the wood treated in the step four, fixing length, width and thickness, and inspecting.
Preferably, in the first step, the moisture content of the wood is adjusted by soaking in water or by a high humidity conditioning method.
Preferably, the method for high humidity conditioning comprises the following steps: the wood was placed in an environment of 100% humidity for more than 4 weeks.
Preferably, in the second step, the environmental temperature is adjusted to be in a range of 40 ℃ to 70 ℃.
Preferably, in step two, the direction of the applied fixing force is: the length is unidirectional, or the length and width are dual or the length and thickness are dual.
Preferably, in the second step, the value of the applied fixing force is 5% -20% of the elastic ratio limit of the corresponding direction.
Preferably, in the second step, the device for applying the fixing force is a G-shaped carpentry clamp.
Preferably, in the third step, the water content of the wood is reduced to 8% -15%.
Preferably, in the fourth step, the temperature is 160-200 ℃, the time is 2-10 min, and the vacuum degree is 0.01-0.05 MPa in the vacuum condition.
The invention achieves the following beneficial effects:
(1) the wood is continuously applied with fixed pressure based on the Poisson effect, the process is simple and easy to operate, and the uniformity of the drying shrinkage of the treated wood is good;
(2) the applied pressure value is adjustable, so the reduction degree of the drying shrinkage of the treated wood is controllable;
(3) after the treatment by the method, the difference of the drying shrinkage of the transverse grains and the longitudinal grains of the wood is reduced, and the warping and deformation caused by the difference are obviously reduced.
Detailed Description
The invention is further described below. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
Example 1:
step one, adopting eucalyptus wood, and adjusting the water content of the eucalyptus wood to 30%.
Step two, placing the eucalyptus wood obtained in the step one in a drying kiln, adjusting the temperature in the kiln to be 50 ℃, and slowly reducing the water content of the eucalyptus wood in the temperature environment; and (3) applying fixed pressure to the length direction of the eucalyptus wood while reducing the water content, wherein the pressure value is 15% of the elastic proportion limit of the feathering.
And step three, reducing the water content of the eucalyptus wood in the step two to 15%, and continuously applying fixed pressure.
And step four, putting the eucalyptus wood in the step three in a vacuum condition for flash type heat treatment, wherein the temperature is 160 ℃, the time is 10min, the vacuum degree is 0.01MPa, and fixed pressure is continuously applied.
And step five, cooling the wood treated in the step four, fixing length, width and thickness, and inspecting.
Example 2:
step one, adopting fir wood, and adjusting the water content of the fir wood to 20%.
Step two, placing the fir wood in the step one in an oven, adjusting the temperature in a kiln to 70 ℃, and slowly reducing the water content of the fir wood in the temperature environment; and (3) while reducing the water content, applying fixed pressure to the fir in the length direction and the width direction, wherein the pressure value in the length direction is 5% of the elastic proportion limit of the straight line, and the pressure value in the width direction is 10% of the elastic proportion limit of the transverse direction.
And step three, reducing the water content of the fir in the step two to 10%, and continuously applying fixed pressure.
Step four, putting the fir wood in the step three in a vacuum condition for flash heat treatment at 180 ℃ for 5min, wherein the vacuum degree is 0.05MPa, and the fixed pressure is continuously applied;
and step five, cooling the wood treated in the step four, fixing length, width and thickness, and inspecting.
Example 3:
step one, adopting pinus sylvestris wood, and adjusting the water content of the pinus sylvestris wood to 30%.
Step two, placing the pinus sylvestris in the step one in a constant temperature and humidity box, adjusting the temperature in the kiln to 40 ℃, and slowly reducing the water content of the pinus sylvestris in the temperature environment; when the water content is reduced, fixed pressure is applied to the length direction and the thickness direction of the pinus sylvestris, the pressure value in the length direction is 10% of the elastic proportion limit of the grain, and the pressure value in the thickness direction is 10% of the elastic proportion limit of the transverse direction.
And step three, reducing the water content of the pinus sylvestris in the step two to 8%, and continuously applying fixed pressure.
Fourthly, putting the pinus sylvestris in the third step into vacuum for flash heat treatment, wherein the temperature is 200 ℃, the time is 10min, the vacuum degree is 0.05MPa, and fixed pressure is continuously applied;
and step five, cooling the wood treated in the step four, fixing length, width and thickness, and inspecting.
The standard test pieces according to the above three examples and comparative examples (ordinary wood without any treatment) were subjected to the test, and the test results are shown in the following table 1.
TABLE 1 index of wood grain shrinkage
When the wood treated by the method of the invention is compared with the common wood, the cross grain dry shrinkage is obviously reduced by combining the analysis of the table 1.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (4)
1. A method for reducing the drying shrinkage of wood cross striations is characterized by comprising the following steps:
step one, adjusting the water content of the wood to 20% -30%;
placing the wood in the step one in a drying kiln, a temperature and humidity regulating box or an oven, and regulating the environment temperature, wherein the environment temperature is regulated to be 40-70 ℃, so that the moisture content of the wood is slowly reduced in the environment; while reducing the moisture content, exert the fixed pressure to the timber, the direction of the said fixed force of exerting is: the length is in a single direction, or the length and the width are in double directions, or the length and the thickness are in double directions, and the value of the applied fixing force is 5% -20% of the elastic ratio limit of the corresponding direction;
step three, reducing the water content of the wood in the step two to be adaptive to target use conditions, reducing the water content of the wood to 8% -15%, and continuously applying fixed pressure;
putting the wood in the third step into a vacuum condition for carrying out flash type heat treatment, wherein in the vacuum condition, the temperature is 160-200 ℃, the time is 2-10 min, the vacuum degree is 0.01-0.05 MPa, and the fixed pressure is continuously applied;
and step five, cooling the wood treated in the step four, fixing length, width and thickness, and inspecting.
2. The method for reducing the drying shrinkage of the wood wales according to claim 1, wherein in the first step, the moisture content of the wood is adjusted by soaking in water or humidifying with high humidity.
3. The method for reducing the drying shrinkage of wood cross striations as claimed in claim 2, wherein the method for high humidity conditioning comprises: the wood was placed in an environment of 100% humidity for more than 4 weeks.
4. The method as claimed in claim 1, wherein in the second step, the device for applying the fixing force is a G-type carpentry clamp.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910432491.XA CN110181637B (en) | 2019-05-23 | 2019-05-23 | Method for reducing wood cross grain drying shrinkage |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910432491.XA CN110181637B (en) | 2019-05-23 | 2019-05-23 | Method for reducing wood cross grain drying shrinkage |
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| CN110181637A CN110181637A (en) | 2019-08-30 |
| CN110181637B true CN110181637B (en) | 2020-11-10 |
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| CN201910432491.XA Active CN110181637B (en) | 2019-05-23 | 2019-05-23 | Method for reducing wood cross grain drying shrinkage |
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| CN113352418B (en) * | 2021-05-08 | 2022-06-17 | 南京林业大学 | Method for enhancing longitudinal mechanical property of wood |
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| JP3881643B2 (en) * | 2003-03-26 | 2007-02-14 | 株式会社加来野製作所 | Wood dryer and drying method using the same |
| GB0819436D0 (en) * | 2008-10-23 | 2008-12-03 | Kurawood Plc | Lignocellulosic material and modification of lignocellosic material |
| CN106272841A (en) * | 2016-10-18 | 2017-01-04 | 南京林业大学 | A kind of manufacture method of special-shaped bamboo trunk |
| CN107234693A (en) * | 2017-05-18 | 2017-10-10 | 朱贝康 | A kind of method of drying of wood processing |
| CN108081415A (en) * | 2017-12-25 | 2018-05-29 | 广西南宁侨盛木业有限责任公司 | A kind of drying means of artificial forest speed Feng An sawn timbers |
| CN108705642A (en) * | 2018-05-21 | 2018-10-26 | 韩立根 | A kind of environmental protection bamboo wood bar component manufacturing method |
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Effective date of registration: 20231222 Address after: 223700 No.139, Fazhan Avenue, high tech Industrial Development Zone, Siyang County, Suqian City, Jiangsu Province Patentee after: Jiangsu nature smart home Co.,Ltd. Address before: Longpan road Xuanwu District of Nanjing city of Jiangsu Province, No. 159 210037 Patentee before: NANJING FORESTRY University |