JPH0437357B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing dry thick veneers used for cosmetic purposes.

So-called thick veneers with a thickness of 0.4 to 0.5 mm used for decorative purposes are manufactured by cutting wet wood fritsch with a high moisture content above the fiber saturation point, in the same way as thin decorative veneers are manufactured. However, if this is applied to a base material such as plywood in a wet state, shrinkage stress will occur as the thick veneer dries, causing warping and cracking, which will prevent the product from becoming a product, so it is usually best to dry it before use. be.

However, when drying a wet thick veneer using a hair dryer, cracks often occur, especially at the end of the wood, and this part has to be cut off before use to avoid a drop in yield. Nakatsuta.

On the other hand, when cutting decorative veneer from the fritches, in order to prevent tears that occur from the ends and sides of the frits during cutting, a moisture-curing urethane adhesive is applied to these surfaces, or a thin web-shaped non-woven fabric is applied to these surfaces. Techniques for pasting such materials have already been proposed and actually used effectively. However, these techniques are only effective in preventing the veneer from breaking during cutting, and cannot prevent the veneer from cracking due to shrinkage of the material during drying as described above.

Therefore, the present inventors have attempted to prevent cracks from occurring at the end of the cut veneer in the drying process of the thick veneer in a wet state obtained by cutting, and to prevent wavy distortion deformation from occurring at the end of the wood. We have conducted a number of intensive studies on ways to achieve this goal. Of course,
As a result of various experiments, thick veneer can be dried by bonding a fiber sheet-like material with specific physical properties, conventionally known as artificial leather, to the end surface of fritchi through an adhesive with specific performance. The present invention was completed based on the discovery that it is possible to reliably prevent the cracking of the butt end that occurs when cutting, and also to prevent the occurrence of waving deformation of the butt end.

That is, in the present invention, at least the end surface of the circumferential side of the fritsch having a moisture content higher than the fiber saturation point,
A tensile sheet made of artificial leather in which a fiber layer with a random three-dimensional structure is impregnated with an elastic polymer material with a continuous microporous structure is made so that it can be bonded on a wet surface and is soft enough to be cut after curing. A decorative dry thick veneer with no cracks from the end surface, characterized in that the frit is cut to a predetermined thickness together with the tensile sheet and then dried. This paper presents a method for manufacturing.

The fritches used in the present invention are generally made from lumber made from logs for cutting with a slicer.
Usually, the material is softened by boiling or soaking in hot water beforehand. Therefore, if the material is a dry plate, it is brought back to a wet state with a moisture content above the fiber saturation point, and the material is softened by boiling before being cut. In addition to being made of a single material, the frits may also be made of laminated materials.

The adhesive used for this lamination is capable of bonding wet wood, does not impede machinability, and can withstand cutting resistance and drying stress that occurs in the wood when it dries after cutting. It goes without saying that it must be powerful.
As such an adhesive, for example, an epoxy adhesive or a hydraulic polyurethane resin adhesive can be suitably used.

The tensile sheet is attached to at least the butt end surface of the fritch during cutting, but it is recommended as a preferred embodiment that it is also attached to other circumferential surfaces of the fritch.

By the way, since the above-mentioned tensile sheet is used to prevent end cracking of a thick veneer cut from a frit, it must have the required tensile strength, especially at least 30 kg. It needs to have a tensile strength of about /cm ² or more, be flexible and cuttable with a slicer, and be highly resistant to hot water and heat.

Considering these required properties, it is generally easy to predict the use of simple nonwoven fabric or paper as the sheet tensile material, but as mentioned above, these materials Although it is possible to prevent cracking, it is not possible to prevent cracking after drying. Compared to these materials, materials conventionally known as artificial leather, i.e. sheet-like materials made by impregnating a fibrous layer with a random three-dimensional structure with an elastic polymer material with a continuous microporous structure, are available. Artificial leather, which is defined as a product, exhibits excellent properties in preventing the occurrence of end cracks, distortion, etc. when drying wet thick veneers.

That is, the occurrence of end cracks during drying is due to the fact that the drying rate of the end part is faster than other parts, so drying stress is generated, and when this is significant, cracks occur from structurally weak parts. On the one hand,
When the tensile stress generated on the surface during drying exceeds the strength of the wood, surface cracking occurs.
Therefore, in order to prevent these problems, it is necessary not only to simply apply an expandable sheet with the required tensile strength to the butt end surface to prevent end cracking, but also to prevent end cracking in response to the shrinkage of the entire veneer. It becomes necessary to adhere an expandable sheet to the butt end surface that allows shrinkage within a certain range and has physical properties that can follow it.

However, if the end surface of the veneer is allowed to shrink freely, even if the tensile strength is sufficient, there is a drawback that there is a high risk of wavy distortion occurring at the end of the veneer. do. In other words,
In response to physical property requirements that involve a mutual dilemma: the expandable sheet itself also shrinks and stretches without stopping the shrinkage of the veneer itself to a certain extent, the material called artificial leather has problems with end cracking. It is very effective compared to other materials for the purpose of obtaining a well-balanced product by allowing a certain degree of drying shrinkage of the butt end while preventing the occurrence of drying.

By the way, the fiber layer in the tensile sheet used in this invention is a type of nonwoven fabric that has a random three-dimensional structure with ultrafine synthetic resin zones of about 0.5 to 3.0 mm in thickness. As resins, polyvinyl alcohol, polyamide,
Polyester, acrylic, etc. are used. Furthermore, according to experimental results, it is made of nylon fibers with a diameter of about 0.05 to 0.2 mm, and has a fabric weight of 100 to 500.
Good results were obtained when using a fiber layer fabricated to have a fiber layer of approximately ^1.0 to 3.0 mm in apparent thickness and with a density of approximately 1.0 to 3.0 mm.

The elastic tensile material in the tensile sheet itself has a continuous microporous structure and is uniformly infiltrated into the fiber layer, and polyurethane is generally used.

The adhesive used to attach the above-mentioned tensile sheet to the butt end surface of the frit and, if necessary, other circumferential surfaces, is capable of wet surface adhesion and is soft enough to be cut after curing. Moreover, it needs to have excellent heat resistance. Moreover, the adhesive strength must be such that it does not come off due to impact during cutting, and adhesive strength that exceeds the cutting resistance (approximately 35 kg/cm ² ) is required. Specifically, suitable examples include polyurethane resin adhesives and epoxy resin adhesives having isocyanate groups.

As shown in FIG. 1, by cutting the wet frit 1 with the tensile sheet 3 attached to the butt end surface via the adhesive 2, the desired thickness can be obtained as shown in FIG. A board 1a is obtained, but the tensile sheet 3 cut to that thickness remains adhered to the end surface of this veneer. The veneer immediately after cutting is a wet veneer with a high moisture content, and as described above, it must be dried to an air dry moisture content or lower. This drying method includes natural drying, dryer drying, heat pressure drying, reduced pressure drying, high frequency drying, etc., and the cost, tolerance for drying unevenness, moisture content accuracy, degree of warping of the veneer, degree of occurrence of end cracks, etc. The above-mentioned means are selected or used in combination depending on the degree of demand. Experimentally, heat-pressure drying and high-frequency heating reduced pressure drying were found to be suitable in terms of less occurrence of end cracks.

When drying a wet thick veneer 1a, dry the veneer 1a.
Due to the contraction, a large contraction stress is generated in the width direction as shown by arrow A in FIG. When this shrinkage stress exceeds the cohesive force of the veneer 1a and also exceeds the tensile strength of the tensile sheet 3, the expandable sheet 3 breaks as shown in FIG. There is a possibility that cracks 4 may occur at the end of the thick veneer 1a.

In contrast, in the present invention, since the tensile sheet 3 having the above structure is adhered to the end surface of the veneer 1a, cracking at the end of the veneer can be sufficiently suppressed, and Since the adhesive 2 also impregnates the tensile sheet 3 and reinforces it, the above effects can be achieved even more reliably.

Further, in the present invention, the tensile sheet 3 made of artificial leather itself has a certain degree of elasticity. Therefore, as shown in FIG. 4, as the thick veneer 1a shrinks, the tensile sheet 3 also tends to shrink slightly, and while preventing the sheet from peeling off,
To effectively maintain the above-mentioned effect of preventing wood end cracking, and to reliably prevent significant waving deformation in the wood end portion.

Therefore, according to the present invention, it is possible to obtain a dry thick veneer without cracking or significant deformation at the end of the wood by a relatively simple operation, and the manufacturing yield thereof can be improved.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a state in which a tensile sheet is attached to the end surface of the fritchi, Fig. 2 is a plan view of a thick veneer in a wet state obtained by cutting the fritchi of Fig. 1,
Fig. 3 is a plan view showing the state in which end cracks occur when the tensile strength of the tensile sheet is low, and Fig. 4 is a plan view showing the state of the decorative veneer after drying when the present invention is properly implemented. It is. 1... Fritsch, 1a... Single plate, 2... Adhesive, 3... Tensile sheet.

Claims (1)

[Claims] 1. Made of artificial leather in which a fiber layer with a random three-dimensional structure is impregnated with an elastic polymeric material having a continuous microporous structure, at least on the end surface of the peripheral side of the fritchi, which has a water content higher than the fiber saturation point. After adhering the tensile sheet with a heat-resistant adhesive that can be bonded on a wet surface and is soft enough to be cut after curing, the frits are cut together with the tensile sheet to a predetermined thickness, and then dried. A method for producing a dry thick veneer for decorative use, characterized by: