Production process of cold-pressed anti-paralysis edge plywood

Abstract

The cold-pressing anti-paralysis edge plywood production process has the following preparation steps: a. wood is used as the base material of the plywood, and the moisture content of the wood is controlled to be between 8% and 12%; b. the adhesive is prepared according to the following mass parts: phenolic resin, urea-formaldehyde resin, nano-cellulose, flexible polymer and crosslinking agent; c. gluing and grouping: a double-sided gluing method is used to ensure that the adhesive layer uniformly covers the surface of the wood; cross-grouping is used, that is, the wood grain directions of adjacent two layers are perpendicular to each other, so as to improve the stability and anti-deformation ability of the board; d. cold-pressing treatment: the cold-pressing pressure is controlled to be between 1.2 MPa and 1.8 MPa, the pressing time is set to be 12-24 hours, and vibration assistance is implemented during the pressing process; e. pressure relief and taking out. The process effectively reduces the paralysis edge phenomenon. By reasonably controlling the moisture content of the wood and applying micro-vibration during the cold-pressing process, the penetration and dispersion of the adhesive in the wood fibers are promoted.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of cold pressing process of plywood, and particularly relates to a cold pressing anti-sagging edge plywood production process. BACKGROUND

[0002] Plywood cold pressing process is a method of putting coated glue base material and veneer into the press for pressure bonding until the glue layer solidifies into a firm overlay. The characteristics of this process are simple equipment, easy operation, and no need to configure special facilities. However, it also has some limitations, especially the relatively long production cycle, which is more suitable for small batch production. In the cold pressing process, the key process parameters include pressure, time, temperature and the selection of adhesive. Generally, the cold pressing time is determined according to the thickness of the board and the curing speed of the adhesive, usually between 4 to 12 hours. In addition, although the cold pressing process usually does not involve additional heating steps, the environmental temperature also has a certain influence on the curing of the adhesive and the quality of the board. Sagging edge is a common and serious problem in the process of plywood cold pressing production, especially in the cold pressing process. Sagging edge mainly refers to the fact that the edge part of the board fails to achieve the expected hardness and density, leading to the edge being prone to deformation, cracking or warping. This phenomenon has a significant negative impact on the quality and performance of the plywood: first, reducing the strength: sagging edge can significantly reduce the overall strength of the board, making it more prone to damage when subjected to external forces. Second, affecting the appearance: sagging edge usually causes uneven edges of the board, affecting the appearance and texture of the product. Third, reducing the service life: due to the insufficient density and hardness of the sagging edge part, the wear resistance and corrosion resistance of this area are reduced, thus shortening the service life of the plywood. Fourth, safety hazards: in specific applications such as furniture or building structures, sagging edges may cause structural instability and pose safety hazards. In order to avoid quality problems such as sagging edge, strict control of various parameters is required in the cold pressing process. SUMMARY

[0003] The technical problem solved by the present application is to provide a cold pressing anti-sagging edge plywood production process to solve the sagging edge problem in the existing plywood cold pressing process.

[0004] Technical solution: The cold pressing anti-sagging edge plywood production process has the following preparation steps: a. Using wood as the base material of the plywood, the moisture content of the wood is controlled between 8% and 12%; b. Preparing the adhesive according to the following mass parts: phenolic resin 50-60 parts, urea-formaldehyde resin 30-40 parts, nano-cellulose 1-3 parts, flexible polymer 2-5 parts, crosslinking agent 0.5-1.5 parts; c. Gluing and assembling: using double-sided gluing method to ensure that the glue layer uniformly covers the surface of the wood, the amount of glue on each side is controlled between 200-250 g / m 2; the cross-group blank is adopted, i.e. the wood texture directions of two adjacent layers are perpendicular to each other, so as to improve the stability and deformation resistance of the board;d. cold pressing treatment: the cold pressing pressure is controlled between 1.2-1.8 MPa, the pressing time is set to 12-24 hours, the pressing environment temperature is 20-25℃, and the humidity is 45%-55%, and vibration assistance is implemented during the pressing process;e. pressure relief and taking out: after the pressing is completed, the pressure is relieved and the plywood is carefully taken out.

[0005] The wood is preferably Chinese fir or pine.

[0006] Preferably, the adhesive specifically comprises: phenolic resin 55-58 parts, urea-formaldehyde resin 32-35 parts, nano-cellulose 1.5-2.5 parts, flexible polymer 3-4 parts, and cross-linking agent 0.8-1.2 parts.

[0007] Preferably, the phenolic resin is a thermosetting phenolic resin with a polymerization degree of 500-1000; the urea-formaldehyde resin is an environmentally friendly urea-formaldehyde resin with low formaldehyde release, and the free formaldehyde content is less than 0.3%; the nano-cellulose has a length of 50-100 nanometers and a diameter of 5-20 nanometers; the flexible polymer is a polyether or polyester flexible polymer with a molecular weight of 5000-20000; and the cross-linking agent is a multi-functional epoxy resin or an isocyanate cross-linking agent.

[0008] Preferably, the parameters of the cold pressing treatment are: the pressure is controlled between 1.4-1.6 MPa, the pressing time is set to 16-20 hours, the environment temperature is controlled to 22-24℃, and the humidity is controlled to 48%-52%.

[0009] The specific pressing process is: initial stage: start pressing at a pressure of 0.5-0.8 MPa, and the duration is 20%-30% of the total pressing time; pressure increasing stage: increase the pressure to 1.4-1.5 MPa, and the duration is 40%-50% of the total pressing time; final pressing stage: increase the pressure to 1.6 MPa for the remaining part of the pressing time.

[0010] During the pressure relief, the pressure is relieved at a rate of 0.1-0.2 MPa per minute, and the duration is 10-20 minutes; during the pressure relief process, the pressing environment temperature and humidity are kept stable, the temperature is controlled to 20-25℃, and the humidity is kept at 45%-55%.

[0011] The frequency of the above vibration: during the boosting stage and the final pressure stage, micro-vibration is applied, and the vibration frequency is controlled between 10-50 Hz to promote the penetration and dispersion of the adhesive in the wood fibers; the vibration amplitude: the vibration amplitude of the micro-vibration is controlled between 0.1-0.5 mm to avoid excessive mechanical stress on the board; the vibration time: the micro-vibration is applied in the last 10-15 minutes of each pressing stage to ensure that the adhesive fully penetrates into the wood fibers and forms a good bond.

[0012] Beneficial effects: First, the process significantly improves the bonding strength of the plywood. Through the careful selection of the adhesive formula, including high-performance compounds such as thermosetting phenolic resin, low formaldehyde-releasing urea-formaldehyde resin, and nanocellulose, a strong bond is formed between the layers of the board. This not only enhances the overall structural stability of the board, but also prolongs its service life. Second, the process effectively reduces the edge collapse phenomenon. By reasonably controlling the moisture content of the wood and applying micro-vibration during the cold pressing process, the penetration and dispersion of the adhesive in the wood fibers are promoted. This deep wood fiber bonding method greatly reduces the cracking and shedding of the board edges, thereby improving the appearance quality and practicality of the product. Third, through the detailed cold pressing steps, including the initial stage, the boosting stage, and the final pressure stage, as well as the precise control of pressure, time, and vibration conditions in each stage, it ensures that the adhesive can uniformly and deeply penetrate into the wood. This fine operation not only improves production efficiency, but also guarantees the consistency and reliability of product quality. Finally, through specific data detection, such as bonding strength testing, edge collapse width measurement, and adhesive layer penetration depth detection, the performance of the product can be quantitatively evaluated, providing clear quality control indicators for producers and reliable product quality assurance for consumers. DETAILED DESCRIPTION

[0013] The content of the present application is described in more detail below through examples.

[0014] Example 1

[0015] Select Chinese fir as the base material, control its moisture content to be 10%. Prepare the adhesive, phenolic resin (thermosetting, degree of polymerization 700): 55 parts; urea-formaldehyde resin (low formaldehyde release, free formaldehyde content 0.25%): 35 parts; nanocellulose (length 70 nanometers, diameter 15 nanometers): 2 parts; flexible polymer (polyether, molecular weight 15000): 4 parts; crosslinking agent (multi-functional epoxy resin): 1 part. Adopt double-sided gluing, and the gluing amount of each side is 220 g / m 2The cold pressing parameters were: pressure 1.5 MPa, pressing time 18 hours, ambient temperature 23°C, humidity 50%, micro-vibration applied during the ramping and final pressure phases, vibration frequency 30 Hz, vibration amplitude 0.3 mm. Initial phase: the pressing started at a pressure of 0.6 MPa, for a duration of 25% of the total pressing time (18 hours), i.e. 4.5 hours. No vibration was applied during this phase. Ramping phase: the pressure was gradually increased to 1.5 MPa, for a duration of 45% of the total pressing time, i.e. 8.1 hours. Micro-vibration was applied during this phase, with a vibration frequency of 30 Hz and a vibration amplitude of 0.3 mm, for 5 minutes every 30 minutes. Final pressure phase: the pressure was increased to 1.6 MPa for the remaining part of the pressing time (5.4 hours). Micro-vibration was continued, with the same parameters as during the ramping phase. The pressure was then released at a rate of 0.15 MPa per minute for 15 minutes, while maintaining the ambient temperature at 23°C and the humidity at 50%.

[0016] Detection

[0017] Bond strength test, procedure: sample preparation: test specimens were cut from the plywood panels to the standard dimensions (100 mm x 25 mm x actual thickness). Conditioning: the test specimens were conditioned to ensure that they were at equilibrium before testing, avoiding excessive moisture or excessive dryness. Clamping the test specimen: the test specimen was clamped at both ends in the grips of the testing machine, ensuring that the centre of the test specimen was aligned with the axis of the grips. Loading and testing: the test specimen was subjected to a tensile force at a constant rate (10 MPa / min) until the test specimen failed. Recording the data: the maximum failure load was recorded and the bond strength was calculated from the dimensions of the test specimen 12.5 MPa.

[0018] Bond strength calculation formula: bond strength = maximum failure load / (test specimen width x length of test specimen shear plane)

[0019] Flange width measurement procedure: sample preparation: representative samples of the plywood panels were selected. Observation and marking: the edge of the plywood panel was observed and the extent of the flange was marked. Measurement: a precise calliper or measuring instrument was used to measure the maximum width of the flange. Recording the data: the measured width of the flange was recorded 0.2 mm.

[0020] Glue line penetration depth detection procedure: sample preparation: small test specimens were cut from the plywood panels, ensuring that they contained a complete glue line. Mounting and grinding: the test specimens were mounted in resin and then ground until the interface between the glue line and the wood was clearly visible. Observation and measurement: the interface between the glue line and the wood was observed under a microscope and the depth of penetration of the glue line into the wood was measured. Recording the data: the maximum depth of penetration of the glue line was recorded 120 μm.

[0021] Example 2

[0022] The procedure is the same as Example 1, but the vibration frequency is changed to 10 Hz. The effect test data: bonding strength (MPa): 9.8; edge drop width (mm): 0.4; glue layer penetration depth (μm): 100; the plywood bonding strength is high, there is slight edge drop, the vibration frequency is low, and the adhesive penetration effect is general.

[0023] Example 3

[0024] The procedure is the same as Example 1, but no vibration is applied. The effect test data: bonding strength (MPa): 9.0; edge drop width (mm): 0.7; glue layer penetration depth (μm): 80; the effect: the plywood bonding strength is general, there is obvious edge drop phenomenon, and no vibration assistance, the adhesive penetration effect is poor.

[0025] Example 4

[0026] The procedure is the same as Example 1, but the cold pressing time is changed to 12 hours. The effect: due to the short pressing time, the plywood bonding strength is relatively low 7.0 MPa, there is edge drop phenomenon 1.0 mm, and although there is vibration assistance, the time is insufficient to cause incomplete penetration of the adhesive 85 μm.

[0027] Example 5

[0028] The procedure is the same as Example 1, but the wood moisture content is controlled to 15%, which exceeds the specified range. The effect: the plywood bonding strength is low 5.0 MPa, the edge drop phenomenon is serious 2.0 mm, and the high wood moisture content affects the adhesive bonding effect, which is difficult to improve even with vibration assistance.

[0029] Effect Comparison

[0030] By comparing the above five examples, it can be seen that the effect of Example 1 is the best. The reasonable vibration frequency and time significantly improve the penetration and dispersion effect of the adhesive in the wood fibers, thereby enhancing the bonding strength of the plywood and reducing the edge drop phenomenon. The effect of Example 2 is second due to the low vibration frequency. The effect of Example 3 is further reduced due to the absence of vibration. The pressing time of Example 4 is too short, which affects the penetration effect of the adhesive. The wood moisture content of Example 5 is too high, which seriously affects the quality of the plywood. Therefore, in the cold pressing anti-edge drop plywood production process, reasonable control of vibration parameters, pressing time and wood moisture content is a key factor.

[0031] The above examples are only used to illustrate the content of the present application, and are not limiting, therefore any change within the meaning and scope equivalent to the claims of the present application should be considered as included in the scope of the claims.

Claims

1. A process for the production of cold-pressed paralytic edge plywood, characterized by, The preparation steps are: a. taking wood as the base material of plywood, and controlling the moisture content of the wood between 8%-12%; b. preparing the adhesive according to the following mass parts: phenolic resin 55-58 parts, urea-formaldehyde resin 32-35 parts, nano-cellulose 1.5-2.5 parts, flexible polymer 3-4 parts, crosslinking agent 0.8-1.2 parts; the phenolic resin is a thermosetting phenolic resin with a degree of polymerization between 500-1000; the urea-formaldehyde resin is an environmentally friendly urea-formaldehyde resin with low formaldehyde release, and the free formaldehyde content is less than 0.3%; the nano-cellulose has a length of 50-100 nanometers and a diameter of 5-20 nanometers; the flexible polymer is a polyether or polyester flexible polymer with a molecular weight between 5000-20000; the crosslinking agent is a multi-functional epoxy resin or an isocyanate crosslinking agent; c. gluing and assembling: using a double-sided gluing method to ensure that the adhesive layer uniformly covers the surface of the wood, and the amount of adhesive on each side is controlled between 200-250g / m²; using cross-assembly, i.e. the grain direction of adjacent two layers of wood is perpendicular to each other, to improve the stability and deformation resistance of the board; d. cold pressing treatment: the cold pressing pressure is controlled between 1.4-1.6MPa, the pressing time is set to 16-20 hours, the pressing environment temperature is between 22-24℃, and the humidity is between 48%-52%, and vibration assistance is implemented during the pressing process; initial stage: start pressing at a pressure of 0.5-0.8MPa, and the duration is 20%-30% of the total pressing time; pressure increasing stage: increase the pressure to 1.4-1.5MPa, and the duration is 40%-50% of the total pressing time; final pressing stage: increase the pressure to 1.6MPa in the remaining part of the pressing time; the vibration frequency: micro-vibration is applied in the pressure increasing stage and the final pressing stage, and the vibration frequency is controlled between 10-50Hz; vibration amplitude: the vibration amplitude of micro-vibration is controlled between 0.1-0.5mm; vibration time: micro-vibration is applied in the last 10-15 minutes of each pressing stage; e. pressure relief and removal: after the pressing is completed, the pressure is relieved and the plywood is removed, and the pressure is relieved at a rate of 0.1-0.2MPa per minute for 10-20 minutes; during the pressure relief process, the pressing environment temperature and humidity are kept stable, the temperature is controlled between 20-25℃, and the humidity is kept between 45%-55%.

2. The process for producing cold-pressed paralytics-preventing edge-bonded plywood according to claim 1, characterized in that, The wood is Chinese fir or pine.