Oriented strand board, preparation method of oriented strand board and application of oriented strand board in container bottom board

Abstract

The invention relates to the technical field of container bottom plates, and discloses an oriented strand board, a preparation method of the oriented strand board and application of the oriented strand board in the container bottom plate. The preparation method of the oriented strand board comprises the following steps: S1, carrying out surface treatment on wood shavings by adopting polytetrahydrofuran-propylene oxide block copolyether glycol and double-end amino modified polytetrahydrofuran ether glycol; and S2, after the wood shavings treated in the step S1 are glued, oriented paving and assembling are conducted, then steam injection and hot press forming are conducted, and the oriented strand board is obtained. According to the oriented strand board manufactured through the method, high mechanical performance can be achieved at low density, and light weight of the container bottom board can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of container bottom plates, and particularly to an oriented strand board, a preparation method thereof, and an application thereof in container bottom plates. Background Art

[0002] The container bottom plate is an important component and main load-bearing fitting of the container. The traditional container bottom plate is mainly a 19-layer wood-based plywood with a thickness of 28 mm made of tropical broad-leaved wood. With the reduction of world tropical broad-leaved wood resources and the increasing environmental protection pressure, the raw material resources for container bottom plates are becoming increasingly scarce. Therefore, developing new alternative materials is an inevitable trend in the development of container bottom plates.

[0003] Currently existing alternative container bottom plates include all-bamboo plywood (such as patent CN114311877A), bamboo-wood composite bottom plates (such as patent CN106393295A). The performance indicators such as density, static bending strength, and elastic modulus of such plates can meet the requirements of plywood for container bottom plates, but the density of the plates is all above 0.85 g / cm 3 above, resulting in relatively large raw material consumption. Moreover, when used as a container bottom plate, it will affect the unit loading capacity of the container and increase the transportation cost. Therefore, reducing its weight (density) while ensuring the mechanical properties of the plate to increase the transportation weight is one of the important topics in the research and development of container bottom plates. Summary of the Invention

[0004] In order to solve the technical problem that the container bottom plate needs to have a relatively high density to meet the mechanical property requirements, the present invention provides an oriented strand board, a preparation method thereof, and an application thereof in container bottom plates. The oriented strand board prepared by the method of the present invention can achieve relatively high mechanical properties at a relatively low density, which helps to realize the lightweight of the container bottom plate.

[0005] The specific technical solution of the present invention is as follows: In the first aspect, the present invention provides a preparation method of an oriented strand board, comprising the following steps: S1: Using polytetrahydrofuran-propylene oxide block copolymer diol and double-ended amino-modified polytetrahydrofuran ether diol to perform surface treatment on the wood strands; S2: After sizing the wood strands treated in step S1, performing oriented mat forming, and then performing steam injection and hot pressing to obtain the oriented strand board.

[0006] In the present invention, the pre-treatment of the wood particles before sizing by the method in step S1 can improve the gluing performance of the wood particles, thereby improving the mechanical properties of the oriented strand board. Among them, a synergistic effect can be generated between polytetrahydrofuran - propylene oxide block copolymer diol (THF - PO) and amino - terminated poly(tetramethylene ether) glycol (NH2 - PTMEG), improving their effect. The specific mechanism is as follows: THF - PO and NH2 - PTMEG can form a heterologous hydrogen bond system on the surface of the wood particles. NH2 - PTMEG contributes high - density hydrogen bond sites, and THF - PO provides steric hindrance protection. The two cooperate with each other, which is conducive to forming a more stable polar interface layer on the surface of the wood particles, and further better improving the gluing performance of the wood particles. Moreover, during the surface treatment of the wood particles, the linear molecular chain of NH2 - PTMEG can insert into the conduit structure of the wood particles to form mechanical anchoring points, and the branched structure in THF - PO can form an elastic sealing ring at the conduit orifice. The combined action of the two enables the subsequent adhesive to produce a "double - effect of anchoring - restraint" during curing, improving the interfacial shear strength. In addition, the polytetrahydrofuran (THF) segments in THF - PO and NH2 - PTMEG are arranged in an oriented manner on cellulose, and the polypropylene oxide (PO) in THF - PO is anchored on lignin. In THF - PO, the crystallization melting temperature (Tm≈40°C) of the THF segment and the glass transition temperature (Tg≈ - 60°C) of the PO segment form a temperature - gradient response, generating a staged plasticization - curing behavior during hot pressing, and improving the penetration depth of the adhesive. By the above method, the pre - treatment of the wood particles before sizing with the cooperation of THF - PO and NH2 - PTMEG can improve the mechanical properties of the oriented strand board to a greater extent. Thus, under the condition of ensuring the mechanical properties of the board, the board density can be reduced to a lower level, realizing the lightweight of the container bottom board.

[0007] In addition to the above effects, the amino group in NH2 - PTMEG and the quinone - type structure in lignin form a charge - transfer complex, which can improve the antifungal performance of the oriented strand board.

[0008] Preferably, in step S1, the wood particles include bamboo wood particles and masson pine wood particles; in step S2, the oriented laying and assembling adopts a five - layer laying method, with two surface layers being bamboo wood particles, and two sub - surface layers and one core layer being masson pine wood particles. The mass ratio between the surface layer, the sub - surface layer and the core layer is 1:0.2 - 0.7:0.7 - 1.7 (more preferably 3:2:5, 4:2:3 or 4:1:4, and even more preferably 3:2:5 or 4:2:3).

[0009] When the mass ratio between the surface layer, the subsurface layer and the core layer is 1:0.2 - 0.7:0.7 - 1.7, the composite structure design of the bamboo particle surface layer, the masson pine particle subsurface layer and the masson pine particle core layer can greatly improve the mechanical properties of the oriented strand board, specifically including the following aspects: (1) There are many longitudinal fibers in the bamboo particles (the proportion of longitudinal fibers > 80%, the anisotropy ratio 8:1), and the fibers in the masson pine particles are distributed in multiple directions (the anisotropy ratio 3:1). By using bamboo particles and masson pine particles in the surface layer and the inner layer respectively, a "hard shell - soft transition" structure can be formed, and when impacted, energy is dissipated through the dislocation and sliding of fibers, improving the energy absorption rate of the oriented strand board; (2) The differential swelling of bamboo (axial CTE 2.5×10 -6 / °C) and masson pine (axial CTE 4.8×10 -6 / °C) forms a self - balancing stress field in the symmetric structure, which can improve the dimensional stability of the board; (3) The surface layer of the bamboo particles has a honeycomb - like closed - cell structure, and the inner layer of the masson pine particles has an open - cell structure. After the two are combined, a "sparse - dense - sparse" penetration gradient can be formed, enabling the adhesive to generate directional capillary flow during hot pressing, thereby improving the bonding strength between the particles; (4) The high elastic modulus of the bamboo particle surface layer and the low elastic modulus of the masson pine particle inner layer produce stress redistribution under cyclic loading, which can extend the fatigue life of the oriented strand board.

[0010] Furthermore, the thickness of the bamboo particles is 0.7 - 1 mm, the length is 120 - 180 mm, and the width is 10 - 50 mm; the thickness of the masson pine particles is 0.4 - 0.6 mm, the length is 130 - 150 mm, and the width is 50 - 60 mm.

[0011] Furthermore, the preparation method of the bamboo particles is as follows: Cut the raw bamboo into sections and process it into a bamboo tube without bamboo knots. After removing the green and yellow parts, perform shaving to obtain bamboo particles.

[0012] Preferably, in step S1, the surface treatment method is: Use a treatment liquid containing poly(tetrahydrofuran - propylene oxide) block copolymer diol and double - end - amino - modified poly(tetrahydrofuran ether) diol to infiltrate or atomize and spray the particles, perform ultrasonic treatment at 40 - 45°C for 0 - 5 min, perform vacuum impregnation at 55 - 65°C for 5 - 15 min, stand at 20 - 30°C for 15 - 20 min, and then dry.

[0013] In the above process, ultrasonic treatment can promote the penetration of the THF chain segment into the cellulose region of the particles, vacuum impregnation helps drive the PO chain segment into the lignin region, and the subsequent standing process at 20 - 30°C helps the amino group to fully combine with the phenolic hydroxyl group in the wood. These three steps of operation help improve the pretreatment effect of the treatment liquid on the particles, and thus improve the mechanical properties of the oriented strand board.

[0014] Further, the time of the ultrasonic treatment is 2 to 5 min.

[0015] Further, in the treatment liquid, the total concentration of polytetrahydrofuran-epoxypropane block copolymer diol and double-ended amino group modified polytetrahydrofuran ether diol is 0.8 to 1.2 wt%; during the infiltration process, the mass ratio of the wood shavings to the treatment liquid is 1:8 to 10; during the atomized spraying process, the spraying amount of the treatment liquid is 0.1 to 0.5 mL / g of wood shavings; the frequency of the ultrasonic treatment is 35 to 45 kHz; the vacuum degree of the vacuum impregnation is -0.1 to -0.5 MPa; the temperature of the drying is 150 to 200 °C and the time is 1 to 3 h.

[0016] Further, the treatment liquid further contains 0.2 to 0.4 wt% of an amino silane coupling agent.

[0017] Preferably, in step S1, the weight average molecular weights of the polytetrahydrofuran-epoxypropane block copolymer diol and the double-ended amino group modified polytetrahydrofuran ether diol are 2000 to 2500 Da and 1500 to 2000 Da respectively, and the mass ratio is 2 to 3:1; in the polytetrahydrofuran-epoxypropane block copolymer diol, the mass ratio of the polytetrahydrofuran chain segment to the epoxypropane chain segment is 1:0.3 to 0.5.

[0018] When the mass ratio between THF-PO and NH2-PTMEG is 2 to 3:1 and the mass ratio of the THF chain segment to the PO chain segment in THF-PO is 1:0.3 to 0.5, better matching effects can be generated between THF-PO and NH2-PTMEG and between the two chain segments in THF-PO, thereby further improving the mechanical properties of the oriented particleboard.

[0019] Preferably, in step S2, during the process of the oriented mat forming, the mat stacking density is 60 to 70 kg / m 3 , the mat orientation rate ≥ 85%, and the matting angle ≤ 15°.

[0020] Preferably, in step S2, the method of sizing is: spraying and sizing the wood shavings with 1 to 10 wt% of an isocyanate adhesive until the sizing amount reaches more than 75%; the conditions of the steam injection are: the steam pressure is 0.8 to 1.2 MPa, the steam temperature is 160 to 180 °C, and the time is 1 to 3 min; the conditions of the hot pressing and forming are: the pressure is 3.5 to 4.0 MPa, the temperature is 160 to 200 °C, and the time is 45 to 60 s / mm.

[0021] Further, the isocyanate adhesive is PMDI.

[0022] In a second aspect, the present invention provides an oriented strand board prepared by using the above preparation method.

[0023] In a third aspect, the present invention provides the application of the above oriented strand board in a container bottom board.

[0024] Compared with the prior art, the present invention has the following advantages: (1) During the pre-treatment of the wood chips before sizing in the present invention, tetrahydrofuran - propylene oxide (THF - PO) and amino - terminated poly(tetramethylene ether) glycol (NH2 - PTMEG) are used. They can cooperate with each other to produce a synergistic effect, and to a greater extent improve the mechanical properties of the oriented strand board.

[0025] (2) During the process of oriented mat forming in the present invention, a composite structure design of a bamboo chip surface layer and a masson pine chip inner layer is adopted, which can improve the mechanical properties of the oriented strand board.

[0026] (3) Through the design of the preparation process in the present invention, the mechanical properties of the oriented strand board are improved, enabling it to achieve a higher strength at a lower density. When used as a container bottom board, it is beneficial to realize the light weight of the container bottom board. Specific Embodiments

[0027] The present invention will be further described below in conjunction with embodiments.

[0028] General Embodiment First, the present invention relates to a method for preparing an oriented strand board, comprising the following steps: S1: Using polytetrahydrofuran - propylene oxide block copolymer diol and amino - terminated poly(tetramethylene ether) glycol to perform surface treatment on the wood chips; S2: After sizing the wood chips treated in step S1, performing oriented mat forming, and then performing steam injection and hot - pressing to obtain the oriented strand board.

[0029] The "amino - terminated poly(tetramethylene ether) glycol" is a product obtained by connecting amino groups to the two terminal hydroxyl groups of poly(tetramethylene ether) glycol. The present invention does not make special limitations on its preparation method, and it can be prepared by conventional methods. For example, through the ring - opening reaction between an epoxy group and an amino group, grafting an epoxy compound containing an amino group at both ends of the molecular chain of poly(tetramethylene ether) glycol. Specifically, the following steps can be adopted: reacting poly(tetramethylene ether) glycol with an epoxy compound containing an amino group at 60 - 70 °C under nitrogen protection and catalyzed by a phase - transfer catalyst for 2 - 4 hours.

[0030] In some specific embodiments, in step S1, the wood shavings include bamboo wood shavings and masson pine wood shavings; in step S2, the oriented mat forming uses a five-layer mat forming method, with two surface layers being bamboo wood shavings, and two sub-surface layers and one core layer being masson pine wood shavings, and the mass ratio between the surface layer, sub-surface layer and core layer is 1:0.2 - 0.7:0.7 - 1.7. Optionally or preferably: The bamboo wood shavings have a thickness of 0.7 - 1 mm, a length of 120 - 180 mm, and a width of 10 - 50 mm; The preparation method of the bamboo wood shavings is: cutting the raw bamboo into sections and processing it into a bamboo tube without bamboo knots, removing the green and yellow parts and then performing planing to obtain the bamboo wood shavings.

[0031] In some specific embodiments, in step S1, the surface treatment method is: using a treatment liquid containing poly(tetrahydrofuran - propylene oxide) block copolymer diol and double - terminal amino - modified poly(tetrahydrofuran ether) diol to infiltrate or atomize - spray the wood shavings, performing ultrasonic treatment at 40 - 45 °C for 0 - 5 min, performing vacuum impregnation at 55 - 65 °C for 5 - 15 min, standing at 20 - 30 °C for 15 - 20 min, and then drying. Optionally or preferably: In the treatment liquid, the total concentration of poly(tetrahydrofuran - propylene oxide) block copolymer diol and double - terminal amino - modified poly(tetrahydrofuran ether) diol is 0.8 - 1.2 wt%; during the infiltration process, the mass ratio of the wood shavings to the treatment liquid is 1:8 - 10; during the atomizing spraying process, the spraying amount of the treatment liquid is 0.1 - 0.5 mL / g of wood shavings; The treatment liquid further contains 0.2 - 0.4 wt% of an amino - silane coupling agent.

[0032] The frequency of the ultrasonic treatment is 35 - 45 kHz; the vacuum degree of the vacuum impregnation is - 0.1 - - 0.5 MPa; the drying temperature is 150 - 200 °C, and the time is 1 - 3 h.

[0033] In some specific embodiments, in step S1, the weight - average molecular weights of the poly(tetrahydrofuran - propylene oxide) block copolymer diol and double - terminal amino - modified poly(tetrahydrofuran ether) diol are 2000 - 2500 Da and 1500 - 2000 Da respectively, and the mass ratio is 2 - 3:1; in the poly(tetrahydrofuran - propylene oxide) block copolymer diol, the mass ratio of the poly(tetrahydrofuran) chain segment to the propylene oxide chain segment is 1:0.3 - 0.5.

[0034] In some specific embodiments, in step S2, during the oriented mat forming process, the mat forming bulk density is 60 - 70 kg / m 3 , the mat forming orientation rate ≥ 85%, and the mat forming angle ≤ 15°.

[0035] In some specific embodiments, in step S2, the sizing method is as follows: Spray sizing the wood chips with 1-10 wt% isocyanate adhesive until the sizing amount reaches more than 75%. Optionally or preferably: The isocyanate adhesive is PMDI.

[0036] In some specific embodiments, in step S2, the conditions for steam injection are as follows: steam pressure 0.8-1.2 MPa, steam temperature 160-180 °C, time 1-3 min.

[0037] In some specific embodiments, in step S2, the conditions for hot pressing and forming are as follows: pressure 3.5-4.0 MPa, temperature 160-200 °C, time 45-60 s / mm.

[0038] Second, the present invention relates to an oriented strand board prepared by the above preparation method.

[0039] Third, the present invention relates to the application of the above oriented strand board in the container bottom plate. Specific embodiments The present invention will be described below through specific examples. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. Without departing from the spirit and scope of the inventive concept, changes and advantages that can be conceived by those skilled in the art are included in the present invention, and the appended claims and any equivalents thereof are the scope of protection of the present invention.

[0041] Unless otherwise defined, all technical terms and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the art to which the present disclosure belongs. The raw materials and equipment used in the present invention are conventional raw materials and equipment in the art and can be obtained from conventional commercial channels without special instructions; the methods used in the present invention are conventional methods in the art without special instructions.

[0042] In the following examples and comparative examples, the meanings of the following abbreviations are as follows: THF-PO: Poly(tetrahydrofuran-epoxypropane) block copolymer diol; NH2-PTMEG: Bis(amino)-terminated poly(tetrahydrofuran) ether diol; PEG: Polyethylene glycol.

[0043] Examples 1 to 4 In Examples 1 to 4, an oriented strand board for container bottom plates was prepared according to the following steps: S1: Preparation of bamboo wood chips Cut the raw bamboo into bamboo sections about 2 meters long, then use a bamboo node recognition device to process them into bamboo tubes without bamboo nodes. After removing the green and yellow parts of the bamboo tubes, place them in a planing device for processing to obtain bamboo shavings with a thickness of 0.7 - 1 mm, a length of 120 mm, and a width of 10 - 50 mm.

[0044] S2: Preparation of masson pine shavings Use a drum chipper to process masson pine wood into masson pine shavings with a thickness of 0.4 - 0.6 mm, a length of 150 mm, and a width of 50 - 60 mm.

[0045] S3: Pretreatment of bamboo shavings Add THF - PO (M w = 2500 Da, the mass ratio of the THF segment to the PO segment is 1:0.3), NH2 - PTMEG (M w = 1800 Da) and silane coupling agent KH550 into water to prepare a treatment solution, where the concentration of the silane coupling agent KH550 is 0.3 wt%. The concentrations of THF - PO and NH2 - PTMEG in the treatment solutions of Examples 1 - 4 are shown in Table 1. Mix the bamboo shavings and the treatment solution according to a mass ratio of 1:10, perform ultrasonic treatment at 40 kHz for 3 min at 40°C, then carry out vacuum impregnation at 60°C and -0.1 MPa vacuum for 10 min, and then let it stand at room temperature for 15 min.

[0046] S4: Pretreatment of masson pine shavings Pretreat the masson pine shavings according to the method in step S3. The difference from step S3 is only that: the concentrations of THF - PO and NH2 - PTMEG in the treatment solution are changed (the concentrations of THF - PO and NH2 - PTMEG in the treatment solutions of Examples 1 - 4 are shown in Table 1), and the silane coupling agent KH550 is not added.

[0047] S5: Drying of shavings Place the bamboo shavings and masson pine shavings after the pretreatment in steps S3 and S4 respectively in a rotary drying device and dry them at 150°C for 2 hours.

[0048] S6: Glue application to shavings Take 10 wt% of PMDI adhesive, perform atomized glue spraying on the bamboo shavings and masson pine shavings after drying in step S5, and carry out uniform stirring in a rotary atomizing glue mixer to make the glue content 81% (average value).

[0049] S7: Oriented laying and assembling Put the bamboo shavings and masson pine shavings after sizing in step S5 into a directional former, and pave them into a five-layer structure. The two surface layers are bamboo shavings, and the two sub-surface layers and one core layer are all masson pine shavings. The mass ratio of the surface layer, sub-surface layer and core layer is 3:2:5, and the paving bulk density is 65 kg / m 3 , the paving orientation rate is 85%, and the paving angle is 15° to obtain a board blank.

[0050] S8: Steam injection of the board blank Put the board blank obtained in step S7 into a steam furnace, set the steam pressure to 1.0 MPa, the steam temperature at 170 °C, and steam for 2 minutes.

[0051] S9: Hot pressing and forming Put the board blank after steam injection in step S8 into a hot press, set the pressure to 3.5 MPa, the temperature to 180 °C, and hot press at 60 s / mm to obtain a directional particleboard. The designed thickness of the directional particleboard is 15 mm, and the designed density is 0.75 g / cm 3 .

[0052] Table 1 Concentrations of THF-PO and NH2-PTMEG in the treatment liquid

[0053] Examples 5 to 7 Based on Example 1, Examples 5 to 7 changed the ratio between the two segments in the THF-PO used for shaving pretreatment, and the remaining steps were the same as those in Example 1. Specifically, in Examples 5 to 7, the directional particleboard for container bottom plates was prepared according to the following steps: S1: Preparation of bamboo shavings Cut the raw bamboo into bamboo sections about 2 meters long, then use a bamboo node recognition device to process them into bamboo tubes without bamboo nodes, and then place the bamboo tubes after removing the green and yellow parts in a shaving device for processing to obtain bamboo shavings with a thickness of 0.7 - 1 mm, a length of 120 mm, and a width of 10 - 50 mm.

[0054] S2: Preparation of masson pine shavings Use a drum chipper to process masson pine wood into masson pine shavings with a thickness of 0.4 - 0.6 mm, a length of 150 mm, and a width of 50 - 60 mm.

[0055] S3: Pretreatment of bamboo shavings Put THF-PO (M w = 2500 Da, the mass ratio between the THF segment and the PO segment in the THF-PO used in Examples 5 to 7 is shown in Table 2), NH2-PTMEG (M w(= 1800 Da) and silane coupling agent KH550 were added to water to prepare a treatment solution, where the concentrations of THF-PO, NH2-PTMEG and silane coupling agent KH550 were 0.9 wt%, 0.3 wt% and 0.3 wt% respectively. The bamboo shavings were mixed with the treatment solution at a mass ratio of 1:10, ultrasonically treated at 40 °C for 3 min at a frequency of 40 kHz, then vacuum impregnated at 60 °C and a vacuum degree of -0.1 MPa for 10 min, and then left to stand at room temperature for 15 min.

[0056] S4: Pretreatment of masson pine shavings The masson pine shavings were pretreated according to the method in step S3, and the difference from step S3 was only that: the concentrations of THF-PO and NH2-PTMEG in the treatment solution were changed, and the silane coupling agent KH550 was not added.

[0057] S5: Drying of shavings The bamboo shavings and masson pine shavings after the pretreatment in steps S3 and S4 were respectively placed in a rotary drying equipment and dried at 150 °C for 2 hours.

[0058] S6: Gluing of shavings 10 wt% of PMDI adhesive was taken, and the bamboo shavings and masson pine shavings after drying in step S5 were atomized and glued, and evenly stirred in a rotary atomizing glue mixer to make the glue content 81% (average value).

[0059] S7: Oriented paving and blanking The bamboo shavings and masson pine shavings after gluing in step S5 were placed in an oriented paver and paved into a five-layer structure. The two surface layers were bamboo shavings, and the two sub-surface layers and one core layer were all masson pine shavings. The mass ratio of the surface layer, sub-surface layer and core layer was 3:2:5, the paving bulk density was 65 kg / m 3 , the paving orientation rate was 85%, and the paving angle was 15°, obtaining a board blank.

[0060] S8: Steam spraying of board blank The board blank obtained in step S7 was put into a steam furnace, the steam pressure was set at 1.0 MPa, the steam temperature was 170 °C, and steam spraying was carried out for 2 minutes.

[0061] S9: Hot pressing and forming The board blank after steam spraying in step S8 was put into a hot press, the pressure was set at 3.5 MPa, the temperature was 180 °C, and hot pressing was carried out at 60 s / mm, obtaining an oriented particleboard. The designed thickness of the oriented particleboard was 15 mm, and the designed density was 0.75 g / cm 3 .

[0062] Table 2 Ratio between two chain segments in THF-PO Mass ratio of THF segment to PO segment Example 1 1:0.3 Example 5 1:0.5 Example 6 1:0.1 Example 7 1:1

[0063] Comparative Examples 1 to 3 Based on Example 1, Comparative Examples 1 to 3 changed the type of pretreatment agent used for the particle pretreatment, and the remaining steps were the same as those in Example 1. Specifically, in Comparative Examples 1 to 3, the oriented strand board for container bottom plates was prepared according to the following steps: S1: Preparation of bamboo particles The raw bamboo was cut into bamboo sections about 2 meters long, and then processed into bamboo tubes without bamboo knots using a bamboo knot recognition device. After removing the green and yellow parts of the bamboo tubes, they were placed in a planing device for processing to obtain bamboo particles with a thickness of 0.7 - 1 mm, a length of 120 mm, and a width of 10 - 50 mm.

[0064] S2: Preparation of masson pine particles The masson pine wood was processed into masson pine particles with a thickness of 0.4 - 0.6 mm, a length of 150 mm, and a width of 50 - 60 mm using a drum chipper.

[0065] S3: Pretreatment of bamboo particles The pretreatment agent and silane coupling agent KH550 were added to water to prepare a treatment solution, where the concentration of silane coupling agent KH550 was 0.3 wt%. The pretreatment agents used in Comparative Examples 1 to 3 and their concentrations in the treatment solution are shown in Table 3. The bamboo particles were mixed with the treatment solution at a mass ratio of 1:10, subjected to ultrasonic treatment at 40 kHz for 3 min at 40°C, then vacuum impregnated at 60°C and a vacuum degree of -0.1 MPa for 10 min, and then left to stand at room temperature for 15 min.

[0066] S4: Pretreatment of masson pine particles The masson pine particles were pretreated according to the method in step S3, and the difference from step S3 was only that: the concentration of the pretreatment agent in the treatment solution was changed (the pretreatment agents used in Comparative Examples 1 to 3 and their concentrations in the treatment solution are shown in Table 3), and silane coupling agent KH550 was not added.

[0067] S5: Drying of particles The bamboo particles and masson pine particles after the pretreatment in steps S3 and S4 were respectively placed in a rotary drying device and dried at 150°C for 2 hours.

[0068] S6: Glue application to particles 10 wt% of PMDI adhesive was taken, and the bamboo particles and masson pine particles after drying in step S5 were subjected to atomized glue spraying and uniformly stirred in a rotary atomizing glue mixer to make the glue content 81% (average value).

[0069] S7: Oriented paving and blank assembly Place the bamboo shavings and masson pine shavings after sizing in step S5 in a directional former, and lay them into a five-layer structure. The two surface layers are bamboo shavings, and the two sub-surface layers and one core layer are all masson pine shavings. The mass ratio of the surface layer, sub-surface layer, and core layer is 3:2:5, and the laying bulk density is 65 kg / m 3 , the laying orientation rate is 85%, and the laying angle is 15° to obtain a green board.

[0070] S8: Steam injection of the green board Put the green board obtained in step S7 into a steam furnace, set the steam pressure to 1.0 MPa, the steam temperature at 170 °C, and inject steam for 2 minutes.

[0071] S9: Hot pressing and forming Put the green board after steam injection in step S8 into a hot press, set the pressure to 3.5 MPa, the temperature to 180 °C, and hot press at 60 s / mm to obtain a directional particleboard. The designed thickness of the directional particleboard is 15 mm, and the designed density is 0.75 g / cm 3 .

[0072] Table 3 Pretreatment agents and their concentrations in the treatment liquid

[0073] Comparative example 4 Based on Example 1, Comparative example 4 changed the mass ratio between layers during the directional laying and assembling process, and the remaining steps were the same as those in Example 1. Specifically, in Comparative example 4, a directional particleboard for container bottom plates was prepared according to the following steps: S1: Preparation of bamboo shavings Cut the raw bamboo into bamboo sections about 2 meters long, then use a bamboo node recognition device to process them into bamboo tubes without bamboo nodes, and then place the bamboo tubes after removing the green and yellow parts in a planing device for processing to obtain bamboo shavings with a thickness of 0.7 - 1 mm, a length of 120 mm, and a width of 10 - 50 mm.

[0074] S2: Preparation of masson pine shavings Use a drum chipper to process masson pine wood into masson pine shavings with a thickness of 0.4 - 0.6 mm, a length of 150 mm, and a width of 50 - 60 mm.

[0075] S3: Pretreatment of bamboo shavings Place THF-PO (M w = 2500 Da, the mass ratio of the THF segment to the PO segment is 1:0.3), NH2-PTMEG (M w(with a molecular weight of 1800 Da) and silane coupling agent KH550 were added to water to prepare a treatment solution, where the concentrations of THF-PO, NH2-PTMEG, and silane coupling agent KH550 were 0.9 wt%, 0.3 wt%, and 0.3 wt%, respectively. The bamboo shavings were mixed with the treatment solution at a mass ratio of 1:10, sonicated at 40 kHz for 3 min at 40 °C, then subjected to vacuum impregnation at 60 °C and a vacuum degree of -0.1 MPa for 10 min, and then left to stand at room temperature for 15 min.

[0076] S4: Pretreatment of masson pine shavings The masson pine shavings were pretreated according to the method in step S3, with the difference from step S3 being only that the concentrations of THF-PO and NH2-PTMEG in the treatment solution were changed, and the silane coupling agent KH550 was not added.

[0077] S5: Drying of shavings The bamboo shavings and masson pine shavings after the pretreatment in steps S3 and S4 were respectively placed in a rotary drying device and dried at 150 °C for 2 hours.

[0078] S6: Gluing of shavings 10 wt% of PMDI adhesive was taken, and the bamboo shavings and masson pine shavings after drying in step S5 were atomized and glued, and evenly stirred in a rotary atomizing glue mixer to make the glue content 81% (average value).

[0079] S7: Oriented laying and assembling The bamboo shavings and masson pine shavings after gluing in step S5 were placed in an oriented laying machine and laid into a five-layer structure, with two surface layers being bamboo shavings, and two sub-surface layers and one core layer being masson pine shavings. The mass ratio of the surface layer, sub-surface layer, and core layer was 1:1:1, the laying bulk density was 65 kg / m 3 , the laying orientation rate was 85%, and the laying angle was 15°, obtaining a board blank.

[0080] S8: Steam spraying of board blank The board blank obtained in step S7 was put into a steam furnace, the steam pressure was set to 1.0 MPa, the steam temperature was 170 °C, and steam spraying was carried out for 2 minutes.

[0081] S9: Hot pressing and forming The board blank after steam spraying in step S8 was put into a hot press, the pressure was set to 3.5 MPa, the temperature was 180 °C, and hot pressing was carried out at 60 s / mm to obtain an oriented particleboard. The designed thickness of the oriented particleboard was 15 mm, and the designed density was 0.75 g / cm 3 .

[0082] Test example The oriented strand boards prepared in each example and comparative example were subjected to mechanical property tests, and the results are shown in Table 2.

[0083] Table 4 Mechanical property test results

[0084] As can be seen from Table 4: (1) Compared with Comparative Examples 1 to 3, the oriented strand boards prepared in Examples 1 to 4 have better mechanical properties. This indicates that compared with PEG, the pre-treatment of strands with THF-PO and NH2-PTMEG before sizing can improve the mechanical properties of the oriented strand board; and there is a synergistic effect between THF-PO and NH2-PTMEG, making the effect of compound use better than that of using THF-PO and NH2-PTMEG alone.

[0085] The reason for the above effect is analyzed as follows: THF-PO and NH2-PTMEG can form a hetero-hydrogen bond system on the surface of the strands. NH2-PTMEG contributes high-density hydrogen bond sites, and THF-PO provides steric hindrance protection. The two cooperate with each other, which is beneficial to form a more stable polar interfacial layer on the surface of the strands, thereby better improving the bonding performance of the strands; and during the surface treatment of the strands, the linear molecular chain of NH2-PTMEG can insert into the strand conduit structure to form mechanical anchoring points, and the branched structure in THF-PO can form an elastic sealing ring at the conduit orifice. The combined action of the two causes a "anchoring-constraint" dual effect during the curing of the subsequent adhesive, improving the interfacial shear strength.

[0086] (2) The mechanical properties of the oriented strand boards prepared in Examples 1 and 2 are better than those in Examples 3 and 4. This indicates that the ratio between THF-PO and NH2-PTMEG will affect the mechanical properties of the oriented strand board. When their mass ratio is 2-3:1, the two can cooperate better, improve the pre-treatment effect before sizing, and thus endow the oriented strand board with better mechanical properties.

[0087] (3) The mechanical properties of the oriented strand boards prepared in Examples 1 and 5 are better than those in Examples 6 and 7. This indicates that during the pre-treatment of the strands before sizing, the ratio between the two chain segments in the THF-PO used will affect the mechanical properties of the oriented strand board. When the mass ratio between the THF chain segment and the PO chain segment is 1:0.3-0.5, it can endow the oriented strand board with better mechanical properties.

[0088] The reason for the above effect is as follows: The THF segments are arranged in an oriented manner on cellulose, and the PO is anchored on lignin. The crystallization melting temperature of the THF segments (Tm≈40 °C) and the glass transition temperature of the PO segments (Tg≈-60 °C) form a temperature gradient response, generating a staged plasticization-curing behavior during hot pressing, which can increase the penetration depth of the adhesive. If the proportion of the THF segments in THF-PO is too high or too low, the above effects will decline, thereby affecting the mechanical properties of the finally produced oriented strand board.

[0089] Unless otherwise specified, the raw materials and equipment used in the present invention are all common raw materials and equipment in the art; unless otherwise specified, the methods used in the present invention are all conventional methods in the art.

[0090] The above are only the preferred embodiments of the present invention, and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent transformations made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing oriented strand board, characterized in that, It includes the following steps: S1: Use poly(tetrahydrofuran - propylene oxide) block copolymer diol and double - ended amino - modified poly(tetrahydrofuran ether) diol to conduct surface treatment on wood chips. S2: After sizing the wood chips treated in step S1, conduct oriented paving and forming of a blank, and then perform steam injection and hot - pressing to obtain an oriented strand board.

2. The preparation method according to claim 1, characterized in that, In step S1, the wood chips include bamboo wood chips and masson pine wood chips; in step S2, the oriented paving and forming of a blank adopt a five - layer paving method, with two surface layers being bamboo wood chips, and two sub - surface layers and one core layer being masson pine wood chips. The mass ratio between the surface layer, sub - surface layer, and core layer is 1:0.2 - 0.7:0.7 - 1.

7.

3. The preparation method according to claim 1, characterized in that, In step S1, the method of surface treatment is as follows: Use a treatment liquid containing poly(tetrahydrofuran - propylene oxide) block copolymer diol and double - ended amino - modified poly(tetrahydrofuran ether) diol to infiltrate or atomize and spray the wood chips, conduct ultrasonic treatment at 40 - 45 °C for 0 - 5 min, conduct vacuum impregnation at 55 - 65 °C for 5 - 15 min, stand at 20 - 30 °C for 15 - 20 min, and then dry.

4. The preparation method according to claim 3, characterized in that, In the treatment liquid, the total concentration of poly(tetrahydrofuran - propylene oxide) block copolymer diol and double - ended amino - modified poly(tetrahydrofuran ether) diol is 0.8 - 1.2 wt%; during the infiltration process, the mass ratio of wood chips to the treatment liquid is 1:8 - 10; during the atomization and spraying process, the spraying amount of the treatment liquid is 0.1 - 0.5 mL / g of wood chips; the frequency of ultrasonic treatment is 35 - 45 kHz; the vacuum degree of vacuum impregnation is - 0.1 - - 0.5 MPa; the drying temperature is 150 - 200 °C, and the time is 1 - 3 h.

5. The preparation method according to claim 3, characterized in that, The treatment liquid also contains 0.2 - 0.4 wt% of an amino - silane coupling agent.

6. The preparation method according to claim 1 or 3, characterized in that In step S1, the weight - average molecular weights of poly(tetrahydrofuran - propylene oxide) block copolymer diol and double - ended amino - modified poly(tetrahydrofuran ether) diol are 2000 - 2500 Da and 1500 - 2000 Da respectively, and the mass ratio is 2 - 3:1; in poly(tetrahydrofuran - propylene oxide) block copolymer diol, the mass ratio of the poly(tetrahydrofuran) chain segment to the propylene oxide chain segment is 1:0.3 - 0.

5.

7. The preparation method according to claim 1 or 2, characterized in that, In step S2, during the process of oriented paving and blank forming, the paving bulk density is 60 - 70 kg / m 3 , the paving orientation rate ≥ 85%, and the paving angle ≤ 15°.

8. The preparation method according to claim 1, characterized in that, In step S2, the method of sizing is as follows: Use 1 - 10 wt% of an isocyanate - type adhesive to conduct spray sizing on the wood chips until the glue content reaches more than 75%; the conditions for steam injection are: steam pressure 0.8 - 1.2 MPa, steam temperature 160 - 180 °C, time 1 - 3 min; the conditions for hot - pressing are: pressure 3.5 - 4.0 MPa, temperature 160 - 200 °C, time 45 - 60 s / mm.

9. An oriented strand board prepared by using the preparation method according to any one of claims 1 - 8.

10. Application of the oriented strand board according to claim 9 in a container bottom board.

Images