FR2590833A1 - PROCESS FOR MANUFACTURING PARTICLE BOARDS - Google Patents

Abstract

A method of making water resistant particle boards by molding and bonding together with an adhesive wood chips or flakes or other fibrous plant material. Before the chips or flakes are adhered together, they are heated to a temperature of 100 degrees C to 200 degrees C for at least one hour in an atmosphere containing 95% or more non-combustible gas, while rotating, so that water and sap can thus be completely removed. Field of application: Industries processing wood products. (CF DRAWING IN BOPI)

Description

The present invention relates to a manufacturing process

  cation of water-resistant particle boards.

  Particle boards consist of chips or flakes of wood or other vegetable fibers which are molded to the desired shape for the board and adhered together with an adhesive material

  any appropriate. These particle boards do not pre-

  Feel noticeably no anisotropy, nor the knots, sails, etc., which are found in conventional wood products. Particle boards may be molded so as to have sufficient mechanical strength in practice and desired dimensions from valuable wood materials, including

  sections of small diameter. Particle board can

  can be produced in increased yields. For these reasons

  sound, particle board is commonly used as furniture materials, building materials,

and others.

  However, chips or flakes that make up particle board absorb water or moisture like conventional wood products. When

  particle board is exposed to water or moisture

  As a result, they can swell and change dimensions, for example, thickness, width and length. In addition,

  moisture or water that has entered the chips or pail-

  leaves do not evaporate easily. Thus, the inflated particle boards can hardly be reduced to their

  initial shape and their mechanical strength is reduced.

  These phenomena pose problems in the manufacture and

  the work of products made with particle board.

  Various proposals have been made to remedy these

  disadvantages, such as improving the adhesive

  to join together the chips or flakes of

  wood, or to resinify the chips or flakes of wood.

  However, no proposal has yet been made for

  to obtain a particle board with perfect resistance

water and moisture.

  An object of the present invention is therefore

  to provide a method for producing party panels

  by molding chips or flakes of wood or

  plant fiber materials to the desired configuration for a panel and adhering together

  skins or glitter with an adhesive, perfect it

  wherein said chips or flakes are heated at a temperature of 100 ° C. to 200 ° C. for at least one hour while rotating them in an atmosphere containing 90% or more of incombustible gas in order to completely eliminate the moisture and sap of said chips or flakes, this step taking place before the step

  said chips or flakes are adhered together.

  Since the dried chips or flakes contain only fibers without water or sap, the adhesive can penetrate sufficiently into the fabric of the chips or flakes to adhere or stick together in

  producing increased mechanical strength. When a

  particles are made of such chips or pail-

  sticky or adhered, it can not swell even if it is subjected to water or moisture. Thus, the method according to the present invention provides a particle board whose

  resistance to water and moisture and mechanical resistance

are improved.

  The present invention will be described in more detail

  by the following description and with reference to the attached drawing

  in which: the single figure is a graph showing the results of tests carried out on particle board manufactured according to the method of the present invention and on

  samples manufactured according to the prior art.

  In accordance with the present invention, an adhesive is first applied to chips or flakes of any material of wood or other suitable vegetable fiber. The chips or flakes are then molded to the desired shape for the panel. The novel and essential feature of the present invention lies in the fact

  chips or flakes are treated in such a way as to

  resistance to water prior to the application stage.

  application of the adhesive to chips or flakes.

  The wood materials used to produce chips or flakes in the present invention are not limited to a particular type of wood material. For example, any way used to produce conventional particle boards can be used. of the

  wood containing more water and sap may

  can also be used in the process of the present invention since they can be dried to eliminate

complete with water and sap.

  The blocks of wood are then cut or

  formed into chips or flakes in any suitable manner as in conventional methods. Shape and dimension

  chips or flakes are determined in an appro-

  requested according to the quality and class of the

  which it is desired to produce, as in conventional methods. Chips or flakes can be obtained by breaking or cutting undried woods with a high water content. If wood materials with a water content of approximately 6% are used, the duration requested by the

  The method of the present invention can be shortened.

  The chips or flakes thus produced are

  arranged in a drying container or autoclave

  which can be classic. Then the air is extracted from the

  container interior or drying autoclave. Incomplete gas

  selected from among the inert gases such as argon, helium and krypton, carbon dioxide, ammonia, sulfur dioxide and nitrogen, is then introduced into the drying container or autoclave to constitute

  an atmosphere containing 95% or more of incombustible gas.

  The incombustible gas to be introduced can be

  25 of an association of two or more incombustible gases

  mentioned above. In short, it is desirable that the atmosphere of the drying vessel contains very little or no oxygen. If the drying container contains more oxygen, chips or flakes may burn or char, which reduces their mechanical strength when heated to a temperature of

  high erase as will be described.

  The temperature of the drying container or autoclave

  is then raised in the range from 100 to 200 C. This time

  The temperature can be selected appropriately depending on

  the quality of the chips or flakes placed in the container

  drying. In most cases, it is desirable

  to heat the chips or flakes at a temperature of 200 ° C., since they can be dried to the most advantageous state as to the principle of the present invention, in which state the water and the sap are completely removed from the chips or glitter. If chips or flakes are heated to a temperature of 100 C or less, water and sap are insufficiently removed. On the contrary, if chips or flakes are heated to a temperature

  above 2000C, they may burn or carbonate

  to become unsuitable as panel material

of particles.

  Preferably, these atmosphere and temperature conditions are maintained for at least one hour at

  normal pressure. At the same time, chips or pail-

  The articles are rotated, for example by rolling the container or drying autoclave. Water and

  sap are therefore better removed chips or glitter.

  The duration during which chips or flakes are

  heated to a chosen temperature is determined

  quality, size and other factors related to chips or flakes. In all cases,

  the duration must be at least one hour for the purpose

  ket. Normally, chips or flakes are heated

  at a selected temperature for four to eight hours.

  When chips or flakes have been heated

  At a selected temperature for a selected time, water and sap are completely removed from the chips.

  or glitter, only the fibers remaining in their tissues.

  The weight of chips or flakes so treated is inferred

  with the chips or flakes used for

  from conventional particle boards. The chips or flakes so treated are not burned or charred as they are heated in the aforementioned gas atmosphere

  incombustible. In addition, chips or flakes are uni-

  formally treated because they are rotated during the heating

  wise. A synthetic resin adhesive, for example a urea resin adhesive, is applied to the dried chips or flakes in the conventional manner. Quality and

  the amount of the synthetic resin adhesive are similar

  to those of the synthetic resin adhesive used

  in the conventional method. In other words, they are

  mine in an appropriate margin according to the various

  required for finished products, eg quality, class, workability, cost of manufacture,

  and others. In this step, the adhesive can penetrate

  inside each of the chips or flakes,

  because these contain only fibers without water or sap.

  Then, the chips or flakes are molded into the shape

  the panel and are also adhered together using a conventional molding apparatus. The molded panel is then subjected to conventional processing steps such as hot pressing, dimensional finishing, surface abrasion, etc. to obtain a

final product.

  The particle board thus obtained does not swell when subjected to water or moisture, as it consists of water-resistant chips or flakes that are glued together. Particleboard has a higher mechanical strength and a lower weight because the chips or glitter it contains are more firmly

  glued together. The formability of the panel of

  is similar to that of the classical particleboard

  if that. Particle board can resist rotting

  ture and insects because the water and the sap are totally

eliminated.

  The following non-limiting example illustrates the

this invention.

Example

  Chips are first placed in an auto-

  clave. The air contained in the autoclave is replaced by an atmosphere containing 95% or more of inert gas. The chips contained in the autoclave are heated at a temperature of C to 200 C for a time ranging from one hour to two hours. The water content is then adjusted to a maximum of 4%.

  Dried chips are applied to a conventional adhesive

  and a water-repellent material. Then we give the chips

  the desired configuration for the panel, in a standard way

  without any additional equipment or tools

  ticular. The formed panels are hot pressed under a

  pressure of 2.0 MPa, at a temperature of 170 to 180 C

  five minutes. The resulting particle board meets the requirements of Quality Standard JIS 5908 that a particle board must have a

  density of 0.72-0.75, water content of 5-8%, resistance

  bending strength of 18.0 MPa or greater, a pull-out strength of 0.3 MPa, a wood screw retention force of 5.0 MPa or more, and a formaldehyde release of 5 or less mg / l, etc.

  Particleboard resistant to water

  in accordance with the process of the present invention and

  Particle board batches produced according to the prior art processes have been subjected to expansion tests on the basis of JIS 5908. The results are shown in the accompanying drawing in which the letters

  A and B denote the particle boards of the prior art

  while the letter C designates the panels of parti-

  of the present invention. It is apparent from this graph that the expandability of water-resistant particle boards in accordance with the present invention is less than

  that of the panels of the prior art.

Claims (4)

  1. Process for manufacturing party panels   water resistant by molding and adhering chips or flakes of wood or other vegetable fibrous material together by the use of an adhesive, characterized in that it comprises, before the step o said flakes or flakes are bonded together, a step in which said chips or flakes are heated at a temperature of 100 ° C to 200 ° C for at least one hour in an atmosphere containing 95% or more of incombustible gas while making turn the chips or glitter, so that the water and sap contained   in said chips or flakes can be complete- eliminated.   2. Method according to claim 1, characterized in that said chips or flakes are heated in a rotary autoclave.   3. Method according to claim 1, characterized in that it further comprises a step where one presses at   hot the resulting particle board.   4. Method according to claim 1, characterized.   in that the incombustible gas is selected from among inert gases including argon, helium, krypton and others, carbon dioxide, ammonia, sulfur dioxide,   nitrogen or a combination of two or more of these gases.