WO2008038869A1

WO2008038869A1 - Wood flooring with carbonized solid wood using symmetric structure and process for preparing the same

Info

Publication number: WO2008038869A1
Application number: PCT/KR2007/001024
Authority: WO
Inventors: Seog-Goo Kang; Jee-Woong Kim; Sung-Gyu Lee
Original assignee: Lg Chem, Ltd.
Priority date: 2006-09-26
Filing date: 2007-02-28
Publication date: 2008-04-03
Also published as: KR20080028015A; CN101517177A; KR100970112B1; JP2010504866A; JP5351026B2

Abstract

Provided is wood flooring having a symmetric structure comprising application of carbonized solid wood to top and bottom layers and a process for preparing the same. The wood flooring of the present invention has a symmetric structure by symmetric lamination of high-temperature heat-treated veneers having a thickness of more than 2 mm on top and bottom layers and integration of the layers under given temperature and pressure conditions. Therefore, the wood flooring is capable of maintaining the balance, is capable of completely solving a problem of deformation due to environmental fluctuations, is capable of achieving dimensional stability and high-quality color of product, and is capable of removing surface contamination, thus making it possible to use contaminated lower-grade coniferous lumber as a wood flooring material.

Description

WOOD FLOORING WITH CARBONIZED SOLID WOOD USING SYMMETRIC STRUCTURE AND PROCESS FOR PREPARING THE

SAME

Technical Field

The present invention relates to wood flooring having a symmetric structure comprising application of carbonized solid wood to top and bottom layers and a process for preparing the same. More specifically, the present invention relates to wood flooring having a symmetric structure, which is capable of maintaining the balance and is capable of completely solving a problem of deformation in response to environmental fluctuations by symmetric lamination of high-temperature heat-treated veneers having a thickness of 2 mm or more on both faces of a base layer.

Background Art

In general, wooden floors having a top layer thickness of less than 2 mm are intended for underfloor heating applications and those having a top layer thickness of 2 mm or more are intended for common applications in solid wood floors. Conventional solid wood floors are composed of surface wood having a thickness of more than 2 mm and plywood or strip having a thickness of 5 to 7 mm as a base material. According to the standard specification for the wooden floor, a size of underfloor-heating wood flooring (plywood) is usually confined to a dimension of 75 mm x 92 mm x 900 mm, whereas the solid wood floor is produced in various dimensions of 65 to 210 mm (width) x 360 to 2,525 mm (length). In addition, there are also products impregnated with WPC (Wood Plastic Composite) to improve surface properties.

However, unlike underfloor-heating wood flooring using veneers having a thin thickness, the solid wood flooring using a veneer having a thickness of 2 mm or more suffers from poor dimensional stability and poor warp resistance due to changes in moisture conditions, thereby showing weakness in application thereof to Korean traditional floor heating (Ondol) systems.

Further, commercially available solid wood flooring has a top-bottom asymmetric structure comprising a veneer having a thickness of more than 2 mm on the top and plywood or strip (square lumber having a relatively smaller dimension than a width of the wood flooring is glued perpendicularly relative to the grain direction of the surface wood) on the bottom as a base material, thus resulting in an imbalance of the whole structure and consequently a deterioration in the basic properties of the product as compared to the wood flooring for underfloor heating.

Japanese Unexamined Patent Publication No. 1994-158842 discloses a wooden floor heating panel disposing a heater in the recessed portion of base plywood, which has, however, an asymmetric structure between the upper and lower parts around the base layer.

Japanese Unexamined Patent Publication No. 2005-161624 discloses a wood composite board for the floor panel of the truck. However, this art suffers from poor dimensional stability due to no use of heat-treated wood layers. US Patent Publication No. 2005/0153150 Al discloses a bamboo board for use as container flooring, which also exhibits, however, insufficient poor dimensional stability due to no use of heat-treated wood layers.

Japanese Unexamined Patent Publication No. 2003-251616 discloses a carbonized woody fiber heat insulating material. However, this technique is directed to an insulating material intended for the outer wall or the floor of the building, not to the flooring material.

Disclosure of Invention Technical Problem

Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide wood flooring which is capable of improving dimensional stability owing to a superior rate of change in response to moisture and heat via the use of carbonized solid wood in the top and bottom layers, as compared to that of conventional solid wood flooring, is capable of solving a problem of distortion associated with heat and humidity owing to finishing of the top and bottom layers with the same material, and is designed to be suitable for Korean traditional floor heating (Ondol) systems by imparting the stability of symmetric structure. It is another object of the present invention to provide wood flooring which is capable of improving consumer's emotional image of the product by achieving high-quality color of wood flooring via the heat treatment.

Technical Solution

In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of wood flooring comprising a base layer and carbonized solid wood layers symmetrically laminated on both faces of the base layer.

The present invention is characterized by achieving remarkably improved dimensional stability via the symmetric configuration of the carbonized solid wood layers laminated on both faces of the base layer, simultaneously with a high-quality color of the wood flooring via the heat treatment. The carbonized solid wood layer in the present invention is preferably a veneer which is heat-treated at a temperature of 150 ^°C to 230 ^°C .

Chemical components constituting the wood may be broadly classified into cellulose, hemicellulose, lignin, and other extracts.

Among those chemical components, hemicellulose undergoes thermal decomposition at a temperature above 150^°C , thus causing changes in the physicochemical properties of the wood. In addition, the thermal decomposition of cellulose takes place at a temperature of 240 ^°C to 350 ^°C, which will lead to a severe decrease in the strength of the wood.

Decreases in water adsorption sites during such a heat treatment process lead to stable maintenance of shrinkage and expansion rates, improved biological durability, deepening of wood color, migration of extracts in the wood, reduction in weight of the wood, decreases in an equilibrium moisture content and increases in heat-insulating performance.

The preferred form of the wood flooring to be applied in the present invention is solid wood flooring in which the upper carbonized solid wood layer has a thickness of 2 mm or more.

In the present invention, the base layer may be composed of at least one wood-based board selected from raw wood, water-resistant plywood, medium density fiberboards (MDFs), high density fiberboards (HDFs), particle boards (PBs), and resin-wood meal mixed boards. The wood flooring of the present invention may be comprised of a surface-treated layer, a carbonized solid wood layer, a base layer and a carbonized solid wood layer, in the direction from the top to the bottom.

In order to impart various functionalities to the wood flooring of the present invention, at least one layer of the surface-treated layer, carbonized solid wood layer and base layer may contain at least one functional material selected from charcoal, loess, silver, Maekbanseok (Elvan), germanium, magnetite, jade, an antibacterial agent and an insect repellent; at least one cured resin selected from epoxy, phenol, acrylic, melamine, polyurethane, unsaturated polyester and diallylphthalate; at least one filler selected from calcium carbonate, talc, titanium oxide, silica, glass powder and silicon dioxide; and/or at least one flame retardant selected from phosphoric ester, halogeno hydrocarbon, antimony oxide, aluminum hydroxide, phosphate compound and dicyandiamide.

Description of Drawings

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawing, in which: FIG. 1 is a cross-sectional view of wood flooring having a symmetric structure according to the present invention.

Best Mode

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view of wood flooring having a symmetric structure according to the present invention, which comprises a surface-treated layer 10, a carbonized solid wood layer 20, a base layer 30 and a carbonized solid wood layer 20, in the direction from the top to the bottom.

The surface-treated layer 10 may be composed of a conventional UV- curable or heat-curable surface-treated layer.

The carbonized solid wood layer 20 is a wood layer which is heat-treated at a high temperature to induce dimensional stabilization. Heat treatment of the wood leads to a decrease in a water content of the wood, thereby improving dimensional stability, and also leads to color changes of the wood into black and deep color tones, thereby providing a high-quality feel.

Preferably, the carbonized solid wood layer 20 is composed of a veneer having a thickness of 2 mm or more, which is heat-treated at a temperature of 150 to 230 "C. In order to achieve a complete symmetric structure, the top and bottom layers are preferably composed of the same material with the same thickness. As the veneer, common wood may be used.

The base layer 30 is composed of a wood-based board, such as raw wood, water-resistant plywood, MDF, HDF, particle board (PB), resin-wood meal mixed board or the like.

In order to impart various functionalities to the wood flooring of the present invention, at least one layer of the surface-treated layer 10, carbonized solid wood layer 20 and base layer 30 may contain functional materials such as charcoal, loess, silver, Maekbanseok (Elvan), germanium, magnetite, jade, an antibacterial agent and an insect repellent, thereby providing various beneficial effects for health, such as far-infrared radiation, emission of anions, antibacterial action, insect-repelling action, and the like. In addition, physical properties of the product, such as durability, abrasion resistance and water resistance, may be improved by an addition of cured resins such as epoxy, phenol, acrylic, melamine, polyurethane, unsaturated polyester and diallylphthalate. Further, fillers, such as calcium carbonate, talc, titanium oxide, silica, glass powder and silicon dioxide, may be added to provide various functions such as effects of a hypocaust (Korean Ondol) heating system, improvement of thermal conductivity, and the like. Further, flame retardancy may be imparted to the product by the addition of flame retardants such as phosphoric ester, halogeno hydrocarbon, antimony oxide, aluminum hydroxide, phosphate compound and dicyandiamide.

For preparation of the wood flooring including the carbonized solid wood layer, raw materials for heat treatment are prepared by cutting wood in the form of square lumber having a thickness capable of obtaining large amounts of veneers after lumber sawing.

Examples of broadleaf trees that can be used in the carbonized solid wood layer may include oak, birch, walnut, cherry and ash, and examples of domestic coniferous trees may include larch. These wood materials may be used with a water content of 5 to 10%. Green timber may be directly used in heat treatment, or otherwise may be previously dried, if necessary. Further, the four sides of the square lumber may be finished smooth with a plane, followed by heat treatment to achieve a high- quality surface. The heat treatment process may take 12 to 24 hours, depending upon various conditions.

The heat treatment process may be broadly divided into three steps: drying, high-temperature treatment and cooling. As the first step, drying, also called high-temperature drying, is a process of reducing the water content in the lumber to almost zero %. Maximum care should be taken to avoid the occurrence of internal checks or honeycombs. Drying conditions may vary depending upon the initial water content, species of trees and a thickness of lumber.

For high-temperature treatment as the second step, the treatment temperature is elevated to a predetermined range of 150 to 230 "C and then the optimum temperature is maintained for a given period of time. For this purpose, steam is used to prevent the likelihood of a fire and to control chemical changes in the lumber.

As the final step, the cooling process is carried out while taking care to prevent cracking or splitting of the lumber which may occur due to high temperature differences between the heat-treated lumber and the surrounding air. Herein, the water content of the heat-treated lumber is necessary to be adjusted to a desired level suitable for final applications. Typically, a final water content is in a range of 5 to 7%, and cooling is carried out for 5 to 15 hours depending upon the heat treatment temperatures.

Depending upon species of trees (broadleaf trees and coniferous trees) used during the heat treatment process, each condition factor (a maximum heat treatment temperature, amounts of steam to be used, operation time for each step, and the like) can be optimized. The thus-heat treated lumber is cut and finished to meet standard requirements for the wood flooring and is then used as top and bottom layers. Individual layers in conjunction with a base layer are integrated under given temperature and pressure conditions to thereby form wood flooring.

EXAMPLES Now, the present invention will be described in more detail with reference to the following examples. These examples are provided only for illustrating the present invention and should not be construed as limiting the scope and spirit of the present invention.

Example 1

A carbonized solid wood layer 20, a base layer 30 and a carbonized solid wood layer 20 in the top-to-bottom direction were integrated into a symmetric structure by pressing. Then, a surface-treated layer 10 was formed thereon. The resulting structure was cut in the form of tongue and groove to prepare a symmetric structure of wood flooring having the carbonized solid wood layers.

As the carbonized solid wood layer 20 applied to the top and bottom layer of the base layer, a wood layer having a thickness of about 3.0 mm and a water content of 5 to 7% was used which was heat-treated at a temperature of 180 to 200 ^°C . As the base layer 30, Finnish Birch plywood having a thickness of 4.0 mm and a water content of 5% was used. As an adhesive, an aqueous emulsion containing vinyl urethane as a main component was mixed with a 10% curing agent. A room temperature-compressible and room temperature-curable resin was used. Hereinafter, the manufacturing process of wood flooring will be specifically described.

Each layer was stacked and then integrated by a press. The integration process of the individual layers was carried out at an ambient temperature for 60 minutes under a pressure of 12 kgf/cm . The integrated surface layer was polished with sandpaper. After primer coating and intermediate coating were sequentially carried out, the resulting structure was cut into a real-size of the product having 70 mm (width) x 590 mm (length) using a tenoner. Sides of the structure were subjected to T&G processing and finally surface top coating was carried out, followed by packaging to prepare a finished product.

Example 2

Wood flooring was prepared in the same manner as in Example 1 , except that a core board made of Myanmar teak was stacked on the base layer 30 of Example 1. Comparative Example 1

Non-heat treated wood flooring having the same structure as Example 1.

Comparative Example 2 Commercially available conventional wood flooring.

Experimental Example 1

Physical properties of the wood flooring having a symmetric structure by application of carbonized solid wood layers to the top and bottom of a base layer, which was prepared in Example of the present invention, were compared with those of non-treated wood flooring having the same structure and conventional commercially available wood flooring. The results thus obtained are given in

Table 1 below. As can be confirmed, the wood flooring prepared in Example 1 exhibited superior dimensional stability and warp resistance, as compared to the wood flooring of Comparative Examples 1 and 2.

For a test under high-temperature conditions, the product samples were dried for 6 hours in a drying machine at 80 ^°C . For a soaking treatment test, the samples were immersed in room-temperature water for 6 hours. Thereafter, the dimension of the samples in width and length directions and a degree of warping were measured using Vernier calipers and a thickness gauge, respectively. [Table 1]

Industrial Applicability As apparent from the above description, wood flooring according to the present invention is capable of solving the deformation problem of the product due to environmental changes via application of a triple-layer structure comprising a base layer and veneers having the same thickness applied to the top and bottom of the base layer, wherein the intermediate base layer is composed of a wood-based board, such as raw wood, water-resistant plywood, MDF, HDF, particle board (PB), resin-wood meal mixed board or the like. For this purpose, three layers of the wood flooring are stacked to have a balanced top-bottom symmetric structure and integrated together under given temperature and pressure conditions.

Further, the present invention provides Korean-type wood flooring which is capable of being used under any environment by completely solving problems of deformation due to heat and humidity via the application of high-temperature heat-treated veneers having a thickness of 2 mm or more to top and bottom layers, and is designed to meet requirements suitable for floor heating (Ondol) systems by solving problems of height differences between products due to unevenness, indentation and bending of the floor via T&G processing.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

1. Wood flooring comprising a base layer and a carbonized solid wood layer laminated on at least one of both faces of the base layer.

2. The wood flooring according to claim 1, wherein the carbonized solid wood layers are laminated to have a symmetric structure on both faces of the base layer.

3. The wood flooring according to claim 1, wherein each of the carbonized solid wood layers is a veneer which is heat-treated at a temperature of 150 to 230 ^°C .

4. The wood flooring according to claim 1, wherein the upper carbonized solid wood layer has a thickness of 2 mm or more.

5. The wood flooring according to claim 1, wherein the base layer is composed of at least one wood-based board selected from raw wood, water- resistant plywood, medium density fiberboard (MDF), high density fϊberboard (HDF), particle board (PB), and resin-wood meal mixed board.

6. The wood flooring according to claim 1, wherein the wood flooring includes a surface-treated layer, a carbonized solid wood layer, a base layer and a carbonized solid wood layer, in the direction from the top to the bottom.

7. The wood flooring according to claim 6, wherein at least one of the surface-treated layer, the carbonized solid wood layers and the base layer contains at least one functional material selected from charcoal, loess, silver, Elvan, germanium, magnetite, jade, antibacterial agents and insect repellents.

8. The wood flooring according to claim 6, wherein at least one of the surface-treated layer, the carbonized solid wood layers and the base layer contains at least one cured resin selected from epoxy, phenol, acrylic, melamine, polyurethane, unsaturated polyester and diallylphthalate.

9. The wood flooring according to claim 6, wherein at least one of the surface-treated layer, the carbonized solid wood layers and the base layer contains at least one filler selected from calcium carbonate, talc, titanium oxide, silica, glass powder and silicon dioxide.

10. The wood flooring according to claim 6, wherein at least one of the surface-treated layer, the carbonized solid wood layers and the base layer contains at least one flame retardant selected from phosphoric ester, halogeno hydrocarbon, antimony oxide, aluminum hydroxide, phosphate compound and dicyandiamide.