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Heat pressing novel method for manufacturing wood veneer/laminated veneer lumber

A technology of laminated veneer lumber and a new method, which is applied to the joining of wooden veneers, manufacturing tools, and wood processing appliances, etc. It can improve the economic efficiency of the factory, reduce the thickness of the rotary cutting, and shorten the hot pressing time.

Inactive Publication Date: 2009-02-18
NANJING FORESTRY UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

When using this conventional hot-pressing method to press plywood and other products, the length of hot-pressing time mainly depends on the speed at which the center layer of the slab heats up to the curing temperature of the glue, and the optimal hot-pressing pressure mainly depends on the tree species, board thickness, veneer density and water content. Therefore, the conventional hot pressing method not only takes a long time for hot pressing, but also has problems such as uneven board thickness, excessive compression of the board or significant loss of thickness, and easy bubbling of the product, which is very important for effectively improving wood utilization and factory economic benefits. extremely unfavorable

Method used

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  • Heat pressing novel method for manufacturing wood veneer/laminated veneer lumber
  • Heat pressing novel method for manufacturing wood veneer/laminated veneer lumber
  • Heat pressing novel method for manufacturing wood veneer/laminated veneer lumber

Examples

Experimental program
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Effect test

example 1

[0015] Example 1: The length and width are 83.8cm×61.0cm twisted leaf pine five-layer plywood, and the nominal thickness is 15.5mm;

[0016] ●Preparation of veneer: peeling thickness: 3.175mm; average moisture content 3.5%, 5.5%;

[0017] ●Glue type and sizing amount: phenolic resin glue (PF), single-sided sizing amount 157g / m 2 ;

[0018] ●Press: The width is 91cm×91cm single-layer hot press;

[0019] ◆Conventional process (hot-pressing control curve is similar to attached figure 2 ): hot pressing pressure 1.31MPa; hot pressing temperature 155℃;

[0020] ◆New process (hot-pressing control curve is similar to attached image 3 shown): the hot-pressing pressure is 0.3-0.8MPa higher than the conventional hot-pressing according to the moisture content of the veneer; the hot-pressing temperature is 155°C;

[0021] For the two processes, when the temperature of the most central adhesive layer in the thickness direction of the sheet is 110 °C, the pressure relief begins, and t...

example 2

[0025] Example 2: The length and width are 83.8cm×61.0cm, thirteen layers of twisted leaf pine veneer laminated timber, the thickness of the board is 37.7 or 38.0mm;

[0026] ●Preparation of veneer: peeling thickness: 3.175mm; average moisture content 3.5%, 5.5%, 9.0%;

[0027] Glue type and sizing amount: phenolic resin glue (PF), single-sided sizing amount 171g / m 2 ;

[0028] ●Press: The width is 91cm×91cm single-layer hot press;

[0029] ◆Conventional process (hot-pressing control curve is similar to attached figure 2 ): hot pressing pressure 1.31MPa; hot pressing temperature 155℃;

[0030] ◆New process (hot-pressing control curve is similar to attached image 3 ): The hot pressing pressure is 0.3-0.8MPa higher than the conventional hot pressing according to the moisture content of the veneer; the hot pressing temperature is 155℃;

[0031] For both processes, the pressure relief starts when the temperature of the most central adhesive layer in the thickness direction ...

example 3

[0035] Example 3: The length and width are 1220mm×2440mm five-layer plywood, and the nominal thickness is 15.5mm;

[0036] ●Veneer preparation: 3.338mm thick Douglas fir veneer; moisture content is 3%;

[0037] ●Glue type and sizing amount: phenolic resin glue (PF), single-sided sizing amount 157g / m 2 ;

[0038] ●Preload: 3 minutes

[0039] ●Press: 40-layer periodic hot press;

[0040] ◆Conventional process (hot-pressing control curve is similar to attached figure 2 ): A total of 40 sheets were pressed, and the process was: hot-pressing pressure 1.31MPa; hot-pressing time 285 seconds; hot-pressing temperature 140.5°C;

[0041] ◆New process (plate compression control unit is installed on the press): a total of 40 sheets are pressed, and the process is: hot pressing pressure 1.45MPa (limited by the hydraulic system of the factory press, the pressure is only 0.14MPa higher than the conventional hot pressing); The constant pressure holding time is 240 seconds; the total hot ...

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Abstract

The invention provides a novel hot pressing method for producing a veneer / laminated veneer lumber so as to solve the problems of long period, low wood utilization rate, uneven thickness of products, great compression loss, easy bubbling, variation of heat-pressing process along with tree species, veneer density and water ratio and the like, existing in the prior hot pressing process. In the method, pressure control and position control simultaneously act on a hot pressing period, and the first phase of hot pressing is controlled by constant pressure which is 0.1 to 1.0Mpa higher than the prior hot pressing pressure so as to accelerate heat transfer and plate blank compression; when the plate achieves the target thickness, the system automatically enters the second phase, namely the position control phase, herein the thickness of the plate does not change, but the pressure automatically drops; and when a glue film in the center of the plate reaches the temperature of solidification, the system enters pressure relief phase. The method can effectively improve the evenness of the plate thickness and the utilization rate of wood, shorten hot pressing period, improve the production efficiency of a hot press, ensure product quality, simplify the operation of the hot press, and improve the stability of hot pressing process.

Description

technical field [0001] The invention relates to a new hot pressing method for manufacturing plywood and laminated veneer lumber (LVL), belonging to the field of man-made panel manufacturing and automation. Background technique [0002] Hot pressing is one of the most important and expensive steps in the production of wood-based panels. At present, non-veneer composite materials such as oriented strand board (OSB) and medium density fiberboard (MDF) generally use a thickness (or position) controlled hot pressing process; while veneer composite materials such as plywood and laminated veneer (LVL) Conventional hot pressing usually employs a relatively low constant pressure controlled hot pressing process. When using this conventional hot-pressing method to press plywood and other products, the length of hot-pressing time mainly depends on how fast the center layer of the slab heats up to the curing temperature of the glue, and the optimal hot-pressing pressure mainly depends o...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B27D1/04
Inventor 王建和金菊婉赵茂程
Owner NANJING FORESTRY UNIV
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