CN114536504B - Non-glue fiber plasticizing plate and preparation method thereof - Google Patents

Non-glue fiber plasticizing plate and preparation method thereof Download PDF

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Publication number
CN114536504B
CN114536504B CN202210237040.2A CN202210237040A CN114536504B CN 114536504 B CN114536504 B CN 114536504B CN 202210237040 A CN202210237040 A CN 202210237040A CN 114536504 B CN114536504 B CN 114536504B
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wood
fiber
board
sodium periodate
hot
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CN114536504A (en
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陈媛
李改云
张轶媛
范东斌
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Research Institute of Wood Industry of Chinese Academy of Forestry
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Research Institute of Wood Industry of Chinese Academy of Forestry
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
    • B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
    • B27N3/08—Moulding or pressing
    • B27N3/10—Moulding of mats
    • B27N3/12—Moulding of mats from fibres
    • 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
    • B27K3/04—Impregnating in open tanks
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
    • B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
    • B27N3/08—Moulding or pressing
    • B27N3/10—Moulding of mats
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
    • D21B1/00—Fibrous raw materials or their mechanical treatment
    • D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
    • D21B1/06—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by dry methods
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
    • D21D1/00—Methods of beating or refining; Beaters of the Hollander type
    • D21D1/20—Methods of refining
    • D21D1/30—Disc mills
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/91—Use of waste materials as fillers for mortars or concrete

Abstract

The invention provides a glue-free fiber plasticizing board and a preparation method thereof, wherein wood fibers are prepared by dissociating an S2 layer of a wood secondary wall, dialdehyde modified wood fibers are prepared by directional oxidation of sodium periodate, the dialdehyde modified wood fibers are subjected to hot pressing at a temperature of 75-100 ℃ to form a board after the water content of the dialdehyde modified wood fibers is regulated to 9-15%, and the glue-free fiber plasticizing board with high static bending strength and low water absorption expansion rate is prepared.

Description

Non-glue fiber plasticizing plate and preparation method thereof
Technical Field
The invention relates to a glue-free fiber plasticizing board and a preparation method thereof, in particular to a glue-free fiber plasticizing board based on wood fiber dialdehyde modification and a preparation method thereof.
Background
The non-glue fiber board is an artificial fiber board prepared by hot pressing wood fibers or other plant fibers without adding any adhesive, and the board is realized by virtue of the bonding force of raw materials, such as the chemical action of the fibers, an activating agent, a catalyst and the like in the hot pressing process. The adhesive-free fiber board can avoid the defects caused by the addition of the adhesive because the adhesive is not additionally added.
At present, the adhesives for fiber boards in China still mainly comprise urea-formaldehyde resin adhesives, phenolic resin adhesives, melamine formaldehyde resin adhesives and the like, the usage amount of the adhesives accounts for more than 90% of the total adhesive amount in the fiber board industry, and the fiber board products manufactured by the adhesives can continuously release harmful gases such as formaldehyde and the like, so that the indoor environment is seriously polluted, and the human body is endangered.
In recent years, with increasing importance of environmental protection in China, the limit of formaldehyde pollution to artificial boards is becoming more and more strict, and GB18580-2017 national Standard for limiting the release of formaldehyde in artificial boards and products of interior decoration materials, states that the release of formaldehyde in artificial boards and products of interior decoration materials must be lower than 0.124mg/m 3 (the legal quantity of the climatic chamber is marked as E1). The strict standard puts forward a more stringent requirement on the adhesive for the artificial board, urea formaldehyde and the modification thereofThe sexual glue is difficult to meet the requirement of the fiberboard industry on controlling the formaldehyde release amount of the wood adhesive at the present stage. Accordingly, the research direction in the fiberboard industry has been moving from formaldehyde-based adhesives to non-toxic and harmless green adhesive systems, such as isocyanate adhesives, soy protein adhesives, and the like. However, the non-formaldehyde adhesives have the defects of high cost, unstable performance and the like. For example, soy protein adhesive fiberboard is more environmentally friendly, but has low water resistance, low adhesion, and is not corrosion resistant. Isocyanate adhesives are expensive and are prone to damage to the human body during use and processing.
In contrast, the non-adhesive fiberboard can avoid the defects caused by the addition of the adhesive, and the development of the self-adhesive fiberboard without the synthetic adhesive, particularly without the addition of the conventional synthetic adhesive, has become an important research direction in the field of artificial boards.
At present, when the non-glue fiber board is prepared, the surface degradation of wood fiber is mostly realized by adopting a pretreatment method, and degradation products act as an adhesive in the hot pressing process, but the performance of the non-glue fiber board is not ideal compared with that of an aldehyde fiber board. The wood surface contains a large amount of hydroxyl groups, such as hydroxyl groups at C2, C3 and C6 in a cellulose structural unit, the hydroxyl groups have low activity, and the self-crosslinking formed hydrogen bonds have high strength but are easy to break after water absorption.
In contrast, patent application CN106476108A discloses a method for preparing formaldehyde-free fiber board by using dialdehyde cellulose, which adopts a two-step method strategy, firstly, conifer pulp is oxidized into dialdehyde cellulose, then is mixed with straw particles, and free hydroxyl groups on the surface of straw fibers and aldehyde groups on the dialdehyde cellulose undergo aldol condensation reaction. But the aldehyde group of the method is obviously lower, the accessibility of the hydroxyl group on the surface of the straw is lower, and the formed glue-free fiber board has lower static bending strength and high water absorption expansion rate.
Disclosure of Invention
The present invention has been developed in view of the above problems, and an object of the present invention is to provide a glue-free fiber plasticized plate having a high static bending strength and a low water swelling rate, and a method for producing the same.
According to the first scheme of the invention, a preparation method of a glue-free fiber plasticizing board is provided, wood fibers are prepared by dissociating an S2 layer of a wood secondary wall, dialdehyde modified wood fibers are prepared by directional oxidation of sodium periodate, the water content of the dialdehyde modified wood fibers is regulated to 9% -15%, and then the dialdehyde modified wood fibers are hot-pressed at the temperature of 75-100 ℃ to form the board.
Preferably, the water content of the dialdehyde modified wood fiber is regulated to be 10% -15%.
Preferably, the board is hot pressed at a temperature of 80-90 ℃.
Preferably, the wood fibers are produced by dissociating the wood secondary wall S2 layer by pulping papermaking chemistry.
Preferably, the plate is hot-pressed under the hot-pressing pressure of 15-20 MPa and the pressure is maintained for 3-5 minutes.
Preferably, preparing the dialdehyde modified wood fiber by directionally oxidizing the wood fiber with sodium periodate comprises:
after adding water and wood fiber into a container, adding sodium periodate and isopropanol, stirring at room temperature in a dark place, filtering and washing to be neutral to remove unreacted sodium periodate and isopropanol, and performing drying and balancing.
Preferably, the mass ratio of the wood fiber to the sodium periodate is 1:0.8-1:2.5.
Preferably, the wood is selected from dried wood and/or branch wood of poplar, eucalyptus, fir or masson pine.
According to a second aspect of the present invention there is provided a glue-free fibre plasticised board made by the method of preparation as described in any of the above.
According to the invention, compared with the prior art, the high-strength degradable plasticizing plate has the advantages of high static bending strength and extremely low water expansion rate, and is novel.
Drawings
FIG. 1 is a schematic diagram showing aldol condensation reaction during hot pressing of a fiberboard.
FIG. 2 is a cross-sectional electron microscopic view showing a plasticized sheet having a high water content of 15%.
FIG. 3 is a cross-sectional electron microscope image showing that a non-adhesive fiberboard was prepared with a low water content of 3%.
Detailed Description
It should be noted that the process of the present invention will be described with respect to values related to temperature or pressure, rate of change of the process, etc., for example, as temperature is an example, it should be understood by those skilled in the art that when referring to the actual meaning of carrying out the reaction at a certain temperature, the control of the temperature is not an absolute constant temperature, but may even tend to exhibit some float which may in some cases exceed a degree or more, as long as the purpose of implementation is achieved. The magnitude of the temperature change and the accuracy of the temperature control are based on the scope of the understanding of those skilled in the art.
In addition, the temperature defined herein may be an input to temperature control on the equipment used, the temperature at some point in the actual process depending on the specifics of the machine equipment and the conditions at the time of the reaction. The defined temperature may also be the target of operator instructions, which in actual control may involve a time of temperature change, even including a process of repeatedly floating up and down, for example heating the reactor when a temperature below the defined temperature is detected, and cooling the reactor above the defined temperature, thereby maintaining the commanded temperature as a whole.
When referring to the concept of room temperature or room temperature, it is usually 22 to 25 ℃, and may be 20 to 28 ℃ depending on the process, and the room temperature or room temperature is understood differently in different fields in the actual industry, but the application of the patent law should be interpreted as limiting the purpose of the invention, and not as limiting the scope of experience in a narrow sense in a certain field.
In the present invention, if temperature or room temperature limitation is not mentioned, it is generally considered that the process is performed at normal temperature or room temperature, and the person skilled in the art can control the conditions of the process without special knowledge, unless specifically indicated or understood by the person skilled in the art.
Chemical implementations have some non-replicability in engineering errors, but should have replicability in the technical results sought, and an understanding of the full disclosure of the invention and the scope of protection in the patent laws should be based on the basic principles set forth above.
In the present invention, unless otherwise specified, the numerical ranges "a to B" mean a or more (a or more) and B or less (B or less).
The present application is described in further detail below with reference to examples.
It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. The invention may be variously modified within the scope defined by the claims. New variations and the like, obtained by combinations of different implementations or embodiments, and common technical means, are also considered to be included in the scope of the present invention.
In the present invention, the specific technology or conditions are not specified in the examples, and the specific technology or conditions are described in the literature in the field or are carried out in accordance with the product specifications. The equipment used is not pointed out by manufacturers, and is a conventional product which can be purchased by a regular channel manufacturer. The chemical raw materials used in the invention can be conveniently purchased in the domestic chemical product market.
The embodiment provides a preparation method of a glue-free fiber plasticizing board, which is to prepare wood fiber by dissociating an S2 layer of a secondary wall of wood, prepare dialdehyde modified wood fiber by directional oxidation of sodium periodate, regulate the water content of the dialdehyde modified wood fiber to 9% -15%, and then heat-press the dialdehyde modified wood fiber at 75-100 ℃ to form the board.
The non-glue fiber board is an artificial fiber board prepared by hot pressing wood fibers or other plant fibers without adding any adhesive, and the board is realized by the self-binding force of the raw materials in the hot pressing process. The non-glue fiber plasticizing board refers to the fiber which is partially or completely plasticized in the preparation of the non-glue fiber board.
The term "wood fiber" or "other plant fiber" is used herein to mean naturally occurring fibrous biomass of woody or other plant species, and includes fibrous materials obtained by subjecting them to a certain physical or chemical process such as crushing or dissociation. Wood fibers refer to wood-like natural resources or processed logs in the above definition.
The plant fiber obtained in nature mainly comprises cellulose, hemicellulose and lignin, the existence and the storage quantity of the three components can be changed through certain processing, and the wood fiber prepared by dissociating the S2 layer of the secondary wall of the wood is adopted as a raw material in the preparation method.
Since wood fibers mainly include cellulose, hemicellulose, and lignin, the wood fiber components may be chemically modified to change their own properties. In the method, the sodium periodate is used for carrying out directional oxidation on the wood fiber, so that the dialdehyde modified wood fiber is prepared.
The mechanism of the hydroformylation modification of cellulose is shown in the following formula 1, and sodium periodate is capable of selectively oxidizing secondary hydroxyl groups at the C2 and C3 positions of cellulose to aldehyde groups to give dialdehyde cellulose (Dialdehyde Cellulose, DAC).
[ 1 ]
The invention utilizes the hydroformylation modification mechanism of the cellulose, and the secondary hydroxyl groups on the C2 and C3 positions of the cellulose in the wood fiber are selectively oxidized into aldehyde groups by sodium periodate, so that the dialdehyde modified wood fiber is obtained.
Oxidation of wood fibers with sodium periodate is a well established technique in this example embodiment: adding a certain volume of distilled water into a beaker, adding a certain amount of wood fiber, quickly adding sodium periodate and isopropanol, stirring for a certain time at room temperature in a dark place, performing suction filtration to neutrality, removing unreacted sodium periodate and isopropanol, and drying and balancing to obtain the dialdehyde modified wood fiber.
The method adopts wood fiber prepared by dissociating the S2 layer of the wood secondary wall as a raw material. The wood is selected from needle wood such as poplar, eucalyptus, fir, masson pine, etc., and broad-leaved wood such as artificial forest wood, and branch wood. Specifically, the secondary wall dissociated wood fiber can be obtained by adopting a pulping and papermaking process chemical method. The length of the wood fiber is 0.2-5 mm, the width is 10-30 mu m, and the thickness is 3-10 mu m.
The traditional artificial board technology adopts a thermal grinding method to prepare wood fibers, is mainly dissociated from the intercellular layer of the cell wall, takes lignin as the main material on the surface, is unfavorable for the directional oxidation of sodium periodate to form aldehyde groups, and is favorable for further oxidation modification due to the fact that pulping and papermaking chemical pulp is mainly dissociated from the secondary wall, cellulose on the surface of the wood fibers is exposed, and the accessible hydroxyl content on the surface is high.
In the molecular structure of wood fiber, lignin and hemicellulose are connected through hydrogen bonds and ester bonds, and the cellulose is wrapped in the molecular structure to form a closed three-dimensional network structure. The cell wall of the plant fiber is composed of primary wall (P) and secondary walls (S1, S2, S3), wherein the secondary wall S2 layer has the highest cellulose content, but is surrounded by other cell walls to form a compact tissue structure.
As a method of dissociating the fiber secondary wall S2 layer, a method disclosed in patent application CN112941947a can be specifically exemplified. By breaking the resistance of the molecular structure of the plant fiber, the barrier of the tissue structure can be overcome, the dissociated plant fiber of the secondary wall S2 layer can be obtained, and the dissociated plant fiber surface can be subjected to efficient chemical modification due to the increased cellulose content.
The cellulose with high content in the prepared dialdehyde modified wood fiber is modified by dialdehyde, and in the further hot pressing process of the fiber board, as shown in figure 1, free hydroxyl groups on the surface of the wood fiber and modified aldehyde groups undergo aldol condensation reaction, and the wood fiber is connected through the aldehyde wood fiber, so that the non-glued bonded fiber board is formed.
The adhesive-free fiberboard manufactured in this way does not need to be added with an adhesive in the production process, so that the defects caused by the addition of the adhesive are avoided: for example, the pollution limit of aldehyde adhesives, the high cost of non-formaldehyde adhesives, the unstable performance and the like.
However, the fiber itself also has hydroxyl hydrogen bonding during the hot pressing process, and the hydrogen bonding is easily broken under the action of water molecules, thus exhibiting higher water absorption. In the method, the dialdehyde modified wood fiber is further subjected to hot pressing to form a board after the water content is regulated to 9% -15%.
The water content herein refers to the percentage of the weight of water contained in the wood to the weight of the wood after absolute drying. The method for regulating the water content can be selected according to actual conditions, for example, the dialdehyde modified wood fiber is laid in a constant temperature and humidity box in a flat manner, and the required water content is obtained by a weight method.
The dialdehyde modified wood fiber is hot-pressed under the high water content of 9% -15%, and water molecules can destroy the hydrogen bond combination of cellulose in the wood fiber, are favorable for releasing hydroxyl sites, and have more aldol condensation reaction with the modified cellulose aldehyde group, so that the water absorption expansion rate is greatly reduced.
Further, the dialdehyde modified wood fiber with the water content of 9-15% is hot pressed into a board at the temperature of 75-100 ℃.
The water molecules reduce the glass transition temperature of lignin in wood fibers, so that the lignin is melted at about 80 ℃, and the coated cellulose plays a hydrophobic role.
In addition, the hemicellulose which is most easy to absorb moisture in the wood fiber is partially degraded at low temperature and high humidity, so that small molecular saccharides can be formed to serve as an adhesive to play a role in enhancing, and the water absorption capacity of the hemicellulose can be reduced.
Therefore, the binding force of glue-free bonding is accelerated when the water molecules plasticize the fiber, and in the hot pressing process, the water molecules migrate out, and hemicellulose, lignin and cellulose form a stable state again, so that the fiber plasticization board with high internal bonding strength, good uniformity and low water absorption expansion rate is formed.
Therefore, the method selects a low-temperature and high-humidity environment to carry out hot pressing to form a board on the basis of dialdehyde modification of wood fibers, thereby obtaining the artificial board with static bending strength reaching more than 75Mpa, elastic modulus reaching more than 80GPa and water absorption expansion rate lower than 3 percent, which is obviously superior to the common fiber board.
In addition, the method also carries out research on the combination of the quality state layer of the material and the hot pressing temperature. On one hand, after the fiber is subjected to dialdehyde modification, the pyrolysis temperature is obviously reduced from the original temperature higher than 300 ℃ to 180 ℃, and the carbonization and degradation of the fiber board are easily caused by the overhigh temperature. On the other hand, the higher the humidity is, the lower the glass transition temperature of lignin is, the humidity which is obviously higher than that of the lignin prepared by a common fiber board is adopted, and the lignin is softened and even vitrified converted at about 80 ℃ under the action of a high-pressure double layer, on the other hand, hemicellulose is partially degraded, can be paved on the surface of the fiber in the hot pressing process, acts as a part of adhesive, assists in aldol condensation reaction, and enhances the internal binding force of the fiber. If the hot pressing temperature is too high, lignin carbonization and full degradation of hemicellulose can occur, and modified cellulose can also be degraded to form a plate with excessive carbonization.
Thus, according to the present embodiment, a novel plasticized sheet can be produced, which is advantageous in terms of workability, high-strength, and capable of substituting for part of plastic, and has degradability, which is different from conventional fiberboard in terms of quality and structure, and the conventional fiberboard is thermosetting.
Regarding the formation of plasticization, water is a plasticizer, which in this application has a significant plasticizing effect with a high water content. On the other hand, after the cellulose on the surface of the fiber is dialdehyde, the original annular molecular structure is opened to form a chain structure, which is favorable for the flexible development of the cellulose, and the plasticizing effect of water is added to form a plate with certain plasticity, thus the plate has the characteristic of plastics and can replace part of plastics. Thus, according to the application, a novel degradable environment-friendly plastic material can be obtained.
The invention thus also provides structural embodiments which are novel glue-free fibre plasticized panels produced according to the above production method, which have a great static bending strength and an extremely low water expansion compared with existing fibre panels, and which in fact result in a novel degradable environment-friendly plastics material.
Hereinafter, specific processes and comparative examples for the preparation of the non-adhesive fiber plasticized sheet are described. The details of the foregoing are not repeated.
Spare material
This embodiment is itself an example of a pulping and papermaking process chemistry.
The respective dissociated secondary wall S2 layer fiber raw materials were prepared as plant samples from the respective commercially available poplar, fir, and pinus massoniana for each of the examples and comparative examples hereinafter.
Will contain waterCrushing plant samples with the weight of 20-30% by using a crusher, soaking, filtering, transferring into a double-screw extruder, fluffing for 10-15 min, and crushing plant wood chips; mixing the obtained plant sample with alkaline hydrogen peroxide solution, wherein the alkaline hydrogen peroxide solution is 10-25% of NaOH solution and 10-16% of H solution based on the dry weight of the plant sample 2 O 2 1.5-3% Na of solution and plant sample dry weight 2 SiO 3 ·9H 2 The O solution and the diethylenetriamine pentaacetic acid serving as a chelating agent accounting for 0.2% -0.5% of the dry weight of the plant sample are uniformly mixed to prepare the plant sample, and the plant sample and the alkaline hydrogen peroxide solution are mixed according to a solid-liquid ratio of 1:5, uniformly mixing and stirring, and then placing the mixture into a disc mill with the rotating speed of 3000r/min and the disc milling interval of 0.5mm for disc milling; then placing the plant sample in an oven with the temperature of 95-105 ℃ for reaction for 1-1.5 hours, washing, dehydrating and submerging the obtained plant sample, removing fiber bundles by using a vibrating screen, and finally obtaining the plant fiber with dissociated secondary wall S2 layer.
Example 1
Step 1): 800mL of distilled water was added to a 1.5L beaker, 50g of poplar fiber was weighed into the beaker, 40g of sodium periodate and 5g of isopropyl alcohol were rapidly added, and stirred at room temperature in the absence of light for 4 hours. Filtering and washing to neutrality to remove unreacted sodium periodate and isopropanol, and drying and balancing to obtain the dialdehyde modified wood fiber.
Step 2): 40g of dry dialdehyde modified wood fiber is weighed and laid in a constant temperature and humidity box, the moisture content reaches 9% by a weight method, and the wood fiber with the moisture content of 9% is uniformly dispersed for standby by a crushing and dispersing machine.
Step 3): and (3) placing the uniformly dispersed wood fibers into a 10cm multiplied by 10cm pre-pressing frame for preliminary pre-pressing, placing a thickness gauge with the thickness of 3mm between two steel plates, performing hot-pressing forming at the temperature of 75 ℃, maintaining the hot-pressing pressure at 15MPa for 5 minutes, and then releasing pressure, cooling and trimming to obtain the glue-free fiber plasticizing plate.
The prepared glue-free fiber plasticizing board is detected:
static bending strength: 58MPa
Modulus of elasticity: 72GPa
Moisture absorption expansion rate for 24 hours: 7%
Example 2
Step 1): 800mL of distilled water was added to a 1.5L beaker, 50g of poplar fiber was weighed into the beaker, 50g of sodium periodate and 5g of isopropyl alcohol were rapidly added, and stirred at room temperature for 6 hours in the absence of light. Filtering and washing to neutrality to remove unreacted sodium periodate and isopropanol, and drying and balancing to obtain the dialdehyde modified wood fiber.
Step 2): 40g of dried aldehyde wood fiber is weighed and laid in a constant temperature and humidity box, the water content reaches 10% by a weight method, and the wood fiber with the water content of 10% is uniformly dispersed by a crushing and dispersing machine for standby.
Step 3): and (3) placing uniformly dispersed wood fibers into a 10cm multiplied by 10cm pre-pressing frame for preliminary pre-pressing, then placing a thickness gauge with the thickness of 3mm between two steel plates, performing hot-pressing forming at the temperature of 100 ℃, maintaining the hot-pressing pressure at 20MPa for 3 minutes, and then releasing pressure, cooling and trimming to obtain the glue-free fiber plasticizing plate.
The prepared glue-free fiber plasticizing board is detected:
static bending strength: 65MPa of
Modulus of elasticity: 78GPa
Moisture absorption expansion rate for 24 hours: 5%
Example 3
Step 1): 800mL of distilled water was added to a 1.5L beaker, 50g of fir fiber was weighed and added to the beaker, 50g of sodium periodate and 5g of isopropyl alcohol were rapidly added, and stirred at room temperature in the absence of light for 8 hours. Filtering and washing to neutrality to remove unreacted sodium periodate and isopropanol, and drying and balancing to obtain the dialdehyde modified wood fiber.
Step 2): 40g of dried aldehyde wood fiber is weighed and laid in a constant temperature and humidity box, the water content reaches 12% by a weight method, and the wood fiber with the water content of 12% is uniformly dispersed for standby by a crushing and dispersing machine.
Step 3): and (3) placing uniformly dispersed wood fibers into a 10cm multiplied by 10cm pre-pressing frame for preliminary pre-pressing, placing a thickness gauge with the thickness of 3mm between two steel plates, performing hot-pressing forming at the temperature of 80 ℃, maintaining the hot-pressing pressure at 15MPa for 5 minutes, and then releasing pressure, cooling and trimming to obtain the glue-free fiber plasticizing plate.
The prepared glue-free fiber plasticizing board is detected:
static bending strength: 68MPa of
Modulus of elasticity: 74GPa
Moisture absorption expansion rate for 24 hours: 5%
Example 4
Step 1): 800mL of distilled water was added to a 1.5L beaker, 50g of Pinus massoniana wood fiber was weighed and added to the beaker, 100g of sodium periodate and 5g of isopropyl alcohol were rapidly added, and the mixture was stirred at room temperature for 4 hours in a dark place. Filtering and washing to neutrality to remove unreacted sodium periodate and isopropanol, and drying and balancing to obtain the dialdehyde modified wood fiber.
Step 2): 40g of dried aldehyde wood fiber is weighed and laid in a constant temperature and humidity box, the water content reaches 15% by a weight method, and the wood fiber with 15% water content is uniformly dispersed for standby by a crushing and dispersing machine.
Step 3): and (3) placing uniformly dispersed wood fibers into a 10cm multiplied by 10cm pre-pressing frame for preliminary pre-pressing, placing a thickness gauge with the thickness of 3mm between two steel plates, performing hot press forming at the temperature of 85 ℃, maintaining the hot press pressure at 18MPa for 5 minutes, and then releasing pressure, cooling and trimming to obtain the glue-free fiber plasticizing plate.
The prepared glue-free fiber plasticizing board is detected:
static bending strength: 72MPa of
Modulus of elasticity: 80GPa (gigabit)
Moisture absorption expansion rate for 24 hours: 3%
Comparative example 1
Fiberboard was prepared by the same method as in example 1 using poplar fiber not modified by dialdehyde, and the detection result was:
static bending strength: 16MPa (MPa)
Modulus of elasticity: 4GPa (GPa)
Moisture absorption expansion rate for 24 hours: 95% of
Comparative example2
A fiberboard was produced in the same manner as in example 1, except that the hot pressing temperature was set at 120 ℃.
Implementation results: the plate bubbling has carbonized scorched smell and is easy to be crisp.
Comparative example 3
Fiber boards were prepared by using the dialdehyde modified poplar fiber in the same hot pressing method as in example 1, but with a water content of 3%, and the detection results were:
static bending strength: 32MPa of
Modulus of elasticity: 25GPa
Moisture absorption expansion rate for 24 hours: 36%
The detection results of the above examples and comparative examples were measured by the following detection examples.
Detection example 1:
and (3) detecting static bending strength:
cutting a test piece into the sizes of 5mm multiplied by 4mm multiplied by 60mm, adjusting the support span of the mechanical detector to be at least 20 times the thickness of the test piece, placing the test piece on the support, enabling the long axis of the test piece to be perpendicular to the supporting roller, enabling the center point of the test piece to be below the loading roller, loading the test piece at a constant speed, adjusting the loading speed, achieving the maximum load within 1min, recording the maximum load, and taking the average value of 5 parallel detection.
Static bending strength formula:
sigma: static bending strength of the test piece and MPa;
F max : maximum load and N when the test piece is damaged;
l: the distance between the two supports is mm;
b: test piece width, mm;
t: test piece thickness, mm.
Detection example 2:
and (3) detecting the elastic modulus:
the elastic modulus test method and the static bending strength are the same.
Elastic modulus formula：
E b : elastic modulus of test piece, MPa;
l: the distance between the two supports is mm;
b: test piece width, mm;
t: the thickness of the test piece is mm;
F 2 -F 1 : the increment of the load in the straight line segment of the load-deflection curve, N;
a 2 -a 1 : the increase in deformation in the middle of the test piece, i.e. in force F 2 ～F 1 Deformation of the test piece in the interval is mm.
Detection example 3:
and (3) detecting the water absorption expansion rate:
cutting the test piece into pieces with the size of 20mm multiplied by 20mm, immersing the test piece in a water tank with the pH value of 7+/-1 and the temperature of (20+/-1) DEG C, wherein the upper part of the test piece is lower than the water surface (25+/-5) mm, immersing for 24 hours, taking out the test piece after immersing, wiping off the surface attached water, measuring the thickness of the test piece at the original measuring point, and ensuring that the water absorption expansion rate is the ratio of the thickness increment after water absorption to the thickness before water absorption.
The formula of the water expansion rate:
t: water absorption thickness expansion rate,%;
t 1 : the thickness of the test piece before soaking is mm;
t 2 : test piece thickness after soaking, mm.
Detection example 4
The plates obtained in example 4 and comparative example 3 were observed under an electron microscope to obtain sectional electron microscopic images of fig. 2 and 3.
As can be seen from fig. 2, the fiber morphology was substantially absent at a high water content of 15%.
As shown in fig. 3, the fiber morphology was seen in the case of 3% low water content.

Claims (6)

1. A method for preparing a glue-free fiber plasticizing plate is characterized in that wood fibers are prepared by dissociating an S2 layer of a wood secondary wall, dialdehyde modified wood fibers are prepared by directional oxidation of sodium periodate, the dialdehyde modified wood fibers are hot-pressed into a plate at a temperature of 75-100 ℃ after the water content of the dialdehyde modified wood fibers is regulated to 9-15%, wherein the hot-pressed plate is hot-pressed at a hot-pressing pressure of 15-20 MPa for 3-5 minutes under a pressure maintaining condition, the mass ratio of the wood fibers to the sodium periodate is 1:0.8-1:2.5,
wherein, the preparing of the dialdehyde modified wood fiber by directionally oxidizing the wood fiber by sodium periodate comprises the following steps:
after adding water and wood fiber to the vessel, sodium periodate and isopropyl alcohol were added, stirred at room temperature in the dark for 4 hours, suction-filtered to neutrality to remove unreacted sodium periodate and isopropyl alcohol, and dried and equilibrated.
2. The process according to claim 1, wherein,
the water content of the dialdehyde modified wood fiber is regulated to be 10 to 15 percent.
3. The process according to claim 1, wherein,
hot pressing at 80-90 deg.c to form board.
4. The process according to claim 1, wherein,
the wood fiber is prepared by dissociating the S2 layer of the wood secondary wall by pulping and papermaking chemical method.
5. The process according to claim 1, wherein,
the wood is selected from dried wood and/or branch wood of poplar, eucalyptus, fir or masson pine.
6. A glue-free fibre plasticized board, characterized in that it is produced by the production method according to any one of claims 1 to 5.
CN202210237040.2A 2022-03-10 2022-03-10 Non-glue fiber plasticizing plate and preparation method thereof Active CN114536504B (en)

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