WO2014168588A1

WO2014168588A1 - The process of continuous vacuum/suction veneer impregnation

Info

Publication number: WO2014168588A1
Application number: PCT/SI2013/000070
Authority: WO
Inventors: Renata ČESNIK; Zoran GUŠTIN
Original assignee: Intech-Les, Razvojni Center, D.O.O.
Priority date: 2013-04-11
Filing date: 2013-11-18
Publication date: 2014-10-16
Also published as: SI24340A

Abstract

The invention refers to a process of continuous vacuum/suction veneer impregnation as a way of introducing different liquid substances into the depth of a wooden mass of each veneer sheet separately. The invention is characterized by transporting veneer (1) down the transport device (37) into the formulation applicator (50), where the impregnating formulation is applied onto the open side (la) of the veneer (1), after which it enters impregnation unit (400) in a way that the pressure side (lb) of the veneer faces the vacuum suction nozzles (410), in which case the negative pressure causes suction of the formulation from the open surface (la), and the penetration of the formulation into the depth of a wood veneer (1).

Description

THE PROCESS OF CONTINUOUS VACUUM/SUCTION VENEER IMPREGNATION

Field of the invention

The invention refers to a process of continuous vacuum/suction veneer impregnation as a way of incorporating different liquid substances into the depth of a wooden mass of each veneer sheet separately. Liquid substances can be aqueous solutions of inorganic or organic substances/chemicals or other liquid substances, improving biological sustainability of wood, protecting the wood against fungi, mould, insects and/or provide fire resistance or improve mechanical properties. The invention falls within the branch of wood protection processes and wood modification.

Technical problem:

In order to achieve specific improved characteristics of wood/veneer and products, such as veneered panels, it is necessary to introduce substances and their formulations, i.e. aqueous solutions into the depth of the veneer wooden mass.

Currently known solutions of veneer impregnation with different aqueous/liquid formulations use stationary processes in autoclaves/boilers, which are generally applied for impregnation of the solid wood elements, such as particle boards, beams, planks and furthermore use the vacuum-pressure methods processes with large quantity of formulation, e.g. from 10 to 30 m³. Because of lower temperatures in case of aqueous solutions, where normally larger quantities of 10-30 m3 of water are not heated at high temperatures, the formulations of low concentrations are used, i.e. from 10 to 20%, depending on the type of solutes/formulation/ salt/ chemical .

In case of larger amounts of stacked veneer it is difficult for the formulation to penetrate the wood, because veneer cannot be separated with intermediate particle boards due to its insufficient thickness, as is the case with the solid wood elements. The process of soaking in the basins with liquid formulation is also applied. In the soaking process the formulation quantities may be smaller, usually from 4 to 10 m³; however, it may take a lot of time for the formulation to penetrate the wooden mass, lasting 6 or more hours. A larger quantity of veneer sheets is normally soaked in the pool, usually from 1 to 2 m . Because of larger veneer quantities it may be problematic for the substance to get evenly and uniformly incorporated into the depth of the veneer wooden mass.

This therefore required some improvement in impregnation process by applying a method, which enables uniform and constantly controlled input of substances and formulations into the depth of the veneer wooden mass and also makes it possible to use higher concentration of the formulations and reduces the formulation quantities.

The process of continuous vacuum/suction veneer impregnation according to this invention enables the penetration of different liquid substances into the depth of a wooden mass of each veneer sheet separately with the use of higher concentrations of formulations and thus reduces the formulation quantities.

State of the art

The technical problem, which is not solved in a satisfactory manner, includes using large quantities of formulation with low concentration of active substances and/or long impregnation periods, and massive line-up, spending lots of energy. The patent US 5.512,098 does actually provide the solution of the vacuum veneer impregnation, impregnating each veneer sheet separately, but the process is stationary and the device is in fact a small autoclave.

Description of the invention

The objective of this particular invention is a process, which enables the use of reduced formulation quantities without stocking them and in case of aqueous solutions the use of higher concentration. This is achieved by using a specific device which enables quick and effective deep penetration into a wooden mass of veneer by transporting/feeding the veneer sheet through the device.

Description of the invention

According to this invention, the task was solved with the process of continuous vacuum/suction impregnation by exploiting the wood porosity, particularly thin wood, such as veneer. The process of continuous vacuum/suction veneer impregnation solves the problems of the stationary vacuum-pressure impregnation processes and makes the following aspects possible:

- deposition of the formulation on each veneer sheet separately

- using reduced formulation quantities of aqueous solution chemicals

- using formulations/substances in higher concentrations

The following invention will be described by way of example of the process of vacuum/suction veneer impregnation and figures, which show:

Figure 1 : Flow chart of continuous vacuum/suction veneer impregnation device with a suitable unit of preparing the impregnation formulation

Figure 2: Detailed presentation of veneer 1 in vacuum/suction part of the device of the basic impregnation unit 400.

According to the invention, the process of the vacuum/suction veneer impregnation includes the device, consisting of the following basic units:

- impregnation unit 400, which consists of the suction nozzle 410, lower transport cylinders 420, upper transport cylinders 39,

- a unit to create a suitable vacuum/negative pressure 300, consisting of a vacuum pump 8 for effective suction, container 7 for the formulation surplus,

- a control valve 5 as an interface between the impregnation unit 400 and the unit to create suitable vacuum/negative pressure 300,

- formulation applicator 50 for the application of the formulation on the open side of the la veneer, which may apply the formulation - regarding the type and density of the formulation - onto veneer 1 by splashing, cylinder coating or pouring,

- unit 20 with formulation stock or preparing the impregnation formulation,

- control valve 23 to apply the formulation from unit 20 with the formulation stock into the formulation applicator 50,

- transport unit 37 for veneer transportation through the formulation applicator 50 to the entrance into the impregnation unit 400,

- transport unit 38 on the exit side of the impregnation unit 400.

The process on the continuous vacuum/suction veneer impregnation device runs as follows: Veneer 1 is transported along the transport device 37, which can either be a conveyor belt or mesh conveyor belt with upper transport cylinders 40, which additionally guide/run veneer sheet 1 into the formulation applicator 50.

Sensor 60, which can be a photocell and is placed at the beginning of the transport device 37, turns on/opens the applicators 50 in a programmed time-lag; the applicators apply the impregnation formulation in suitable quantity on the open side of the la veneer, i.e. the side of veneer 1, which is acquired by peeling or cutting on the side of the knife, which peels off or cuts veneer. Prior the continuous vacuum/suction impregnation process veneer normally contains water below the fibre saturation point (FSP), which amounts on average to about 30% of the moisture content; however, in individual species and individual pieces of wood that value may vary by several percentage points.

After applying suitable quantity of impregnation formulation onto the 1 a veneer surface, the veneer sheet 1 enters the basic impregnation unit 400.

Individual veneer sheet 1 with pressure side lb, i.e. the side of pressure particle board in manufacturing, cutting and peeling, is rotated into the vacuum suction nozzles 410, where the negative pressure is created with vacuum pump 8, causing the suction of formulation, placed on the la open side of the veneer 1 and pours deeply into the veneer depth because of the negative pressure. Vacuum suction nozzles 410 spread over the entire width of the basic impregnation unit 400. The number of nozzles depends on the type of wood, veneer thickness and impregnating agent.

The vacuum suction impregnation effect is ensured by unit 300, which creates suitable vacuum/negative pressure with vacuum pump 8 to achieve effective suction of the impregnating agent into the depth of wood veneer 1. The vacuum efficiency is regulated by the control valve 5 as an interface between the impregnation unit 400 and the unit, which creates suitable vacuum/negative pressure 300 through intermediate measuring control device 440, which regulates the suction by opening and closing, regarding the value of the previously set negative pressure/vacuum.

Through the transporting device - conveyor belt 38 with impact transport cylinders 41 - the veneer sheet 1 leaves the impregnation unit 400.

Unit 20 is optional: through control valve 23 for formulation application, the IBC container, for example, with previously prepared substances can be connected to the device 400. Unit 20 for preparing the impregnation formulation can be used in case of preliminary preparation of the impregnating agent, for example by dilution with water or other solvents. The solvent enters through valve 1 1 and if necessary, it is processed adequately in unit 15, e.g. by being heated to a higher temperature level; this increases the pressure in pressure unit 14 because of the improved mixing in mixing unit 13. In the stock unit 19 there is a powder form of impregnating agent, which is applied into the mixing unit 13 through the dosage unit 16. The prepared impregnation formulation is stored in the container 18. Through control valve 23 the formulation is applied onto the veneer through the applicator 50.

According to the invention, it is possible to prepare the impregnation formulation promptly in smaller quantities. In case of aqueous solutions it is possible to warm the impregnation formulation by applying higher temperature, because of heating smaller amounts of water; the temperature, however, must not exceed the boiling point, which affects the process of achieving higher formulation concentrations. According to this invention higher concentrations may be just below the saturation limit. It is well known that the saturation limit increases with the temperature of the solvent/water, so the limit between the temperature and concentration must be defined for every formulation.

Claims

1. The process of continuous vacuum/suction veneer impregnation as a way of introduction different liquid substances into the depth of a wooden mass of each veneer sheet separately, where liquid substances can either be aqueous solutions of inorganic or organic substances/chemicals or other liquid substances, improving biological sustainability of wood, protecting the wood against fungi, mould, insects and/or provide fire resistance or improve mechanical properties, characterized in that the veneer (1) is transported along the transportation device (37) into the formulation applicator (50), where the impregnating formulation is applied onto the open side (la) of veneer (1), which then enters the impregnation unit (400) in a way that the pressure side (lb) of the veneer faces the vacuum suction nozzles (410), whereby the negative pressure causes the suction of the formulation from the open surface (la), and the penetration of the formulation into the depth of a wood veneer (1).

2. The process according to claim 1, characterized in that the formulation applicator (50) applies the formulation onto veneer by splashing, cylinder coating or pouring.

3. The device for performing the process according to claim 1, characterized in that it consists of a transport device (37), which transports the veneer sheet (1) into the applicator (50), whereby the sensor (60), located at the beginning of the transport device (37), with a programmed time-lag, turns on/opens the nozzles of the applicator (50) and after the application of impregnating formulation the veneer sheet (1) enters the impregnation unit (400) with vacuum suction nozzles (410), wherein a negative pressure is created with a vacuum pump (8) and whereby the vacuum suction nozzles (410) are spread over the entire width of the impregnation unit (400).

4. The process according to claim 1, characterized in that the preparation of the impregnating formulation is continuous in smaller quantities, and in case of aqueous solutions heated to higher temperatures without exceeding the boiling point, in higher concentrations, and whereby the higher concentrations are preferably just below the saturation limit.