JP2851397B2 - Overlay plywood - Google Patents

Description

BACKGROUND OF THE INVENTION <Industrial Application Field> The present invention relates to an overlay plywood having an overlay layer having excellent transparency. More specifically, the present invention relates to an overlay plywood in which an uncured powdered phenolic resin is added, and a paper phenolic resin-containing paper formed by papermaking is pressed and heated on the plywood to form an overlay layer having excellent transparency. This overlay plywood can be used for various uses such as box materials, building materials, furniture, etc., which require aesthetic properties.

<Prior art> Plywood is useful as a material that makes use of the woody feel, or as a base material on which decorative paper is to be provided,
Particularly for the former use, varnish has been applied to the surface for the purpose of improving the aesthetics and protecting the surface. However, the surface of the plywood has a variety of small deformations, so that only a varnish coating film with an uneven surface can be formed, and the plywood is not sufficiently aesthetically pleasing. there were. Further, there is a problem that the varnish coating film has insufficient abrasion resistance since no reinforcing base is added, and thus improvement has been desired.

By the way, a thermosetting resin impregnated paper (Japanese
50-1557464) to form an overlay layer on the surface of a plywood by heating under pressure. According to this method, the cosmetic and abrasion resistance of the surface of the plywood can be improved by the transparency and strength of the phenolic resin of the overlay layer, and it is considered to be useful as an alternative to the varnish coating method. .

However, a method using phenolic resin-impregnated paper (Japanese Unexamined Patent Publication
Japanese Patent No. 50-1557464) discloses a method in which a phenol resin impregnated paper obtained by impregnating a paper with a thermosetting resin, for example, a semi-cured phenol resin, is adhered to the surface of the plywood with an adhesive, and the phenol resin is cured in a short time by heating under pressure. Although it is a method of forming an overlay layer by completion, as far as the present inventors know, phenol resin impregnated paper must be stored refrigerated so as not to cure prematurely, and also dissolve uncured phenol resin. A large amount of solvent vapor evaporates from a large amount of the organic solvent for impregnation such as alcohol, thereby deteriorating the working environment, and the cost of collecting the organic solvent increases the production cost. He also had points. In addition, this method requires an extra difficult operation of applying an adhesive to a non-uniform plywood surface when the phenolic resin-impregnated paper is overlaid on the plywood surface and heated under pressure. He also had points.

In addition, conventional phenol resin-containing paper (Japanese Patent Publication No. 63-2847)
No. 5 is pressurized and heated to form an overlay layer on the surface of the plywood, using a low molecular weight resole resin, the drying temperature (120 ° C) of the papermaking wet sheet encountered during the production of internal paper However, the transparency of the overlay layer was insufficient.

The transparency of the overlay layer has been found by the present inventors to be greatly affected by the fluidity of the phenolic resin and the amount of the phenolic resin added, and even with a low molecular weight resole resin, the fluidity is low. It became clear that the transparency of the overlay layer was insufficient.

Moreover, phenol,
Since a large amount of free monomers such as formalin are contained in the resole resin, when performing continuous papermaking, there is a problem that free monomers may be discharged from white water and pollute rivers and the like. there were.

When a novolak-type phenol resin powder is internally added, a curing agent such as paraformaldehyde and hexamethylenetetramine must be added in advance, but a curing agent suitable for use (for example, hexamethylenetetramine)
Has a problem that it cannot be internally added because it is water-soluble. Even if the water-soluble curing agent can be internally added by fixing the material to the pulp by, for example, adsorbing a water-soluble curing agent on the pulp, ammonia can be removed from the curing agent when the phenol resin is pressed and heated. Such a gas is generated, and a part of the gas remains in the cured phenol resin, thereby causing a problem that transparency of the overlay layer is impaired.

[Summary of the Invention]

<Problems to be Solved by the Invention> The present invention solves the above problems, and provides an overlay plywood in which an overlay layer having excellent transparency is formed by applying pressure and heating to a powdered phenolic resin-containing paper. The purpose is to do so.

<Means for Solving the Problems> In an overlay plywood according to the present invention, an overlay plywood in which an overlay layer is provided on a wooden board is obtained by pressing a powdery phenolic resin-containing paper whose overlay layer is defined as follows. It is characterized by being formed on a wooden board by heating.

(A) A powdery phenolic resin is a hot-melt curable resin obtained by simultaneously performing an addition reaction and a condensation reaction of phenols and formaldehyde in the presence of an excess hydrochloric acid catalyst, and having a methylol group in the molecule. Having a weight average molecular weight of 3500 or more and a gelation time of 3 minutes or more.

(B) The fiber base material constituting the powdered phenolic resin-containing paper is substantially made of pulp, and the wood pulp beaten to a freeness of 500 ml to 50 ml is 10 to 50% by volume (total (Based on quantity)

(C) The content of the powder phenol resin in the powder phenol resin internal paper is 50 to 90% by volume (based on the total amount of all the stock).

<Effects of the Invention> According to the present invention, an overlay plywood having an overlay layer having excellent transparency and planar smoothness can be obtained.

[Specific description of the invention]

<Main Requirements of the Present Invention> The present invention consists of several quantitative conditions, in which the unit “vol%” is a percentage based on the volume of a given component excluding air. It is calculated by the volume calculated by weight / true specific gravity.

By the way, the overlay plywood according to the present invention is a pressure-heated powder phenolic resin-containing paper containing a heat-melt-curable type powdery phenolic resin in a volume ratio of 50/50 to 10/90 with respect to a fiber base material made of pulp. Then, an overlay layer is formed on a wooden board.

That is, in the present invention, a hot-melt curable resin obtained by simultaneously performing an addition reaction and a condensation reaction of phenols and formaldehyde in the presence of a large amount of an acid catalyst, and a considerable number of methylols in the molecule. Having a high polymerization degree with a weight average molecular weight of 3500 or more, but having a gelation time of 3
It has been found that an overlay layer having excellent transparency can be formed by adding a large amount of a powdered phenol resin which is at least a minute.

Also, since the powdered phenolic resin has a high degree of polymerization, the amount of free monomers (phenol, formalin) remaining in the resin is extremely small (500 ppm or less). There is no need to consider the volatilization of the monomer, and the working environment can be improved, and the discharge of the monomer from the white water is also eliminated, so that environmental pollution can be prevented.

When paper is made by adding 50% by volume or more of ordinary phenolic resin, most of the increased phenolic resin is released from the pulp sheet in the papermaking process. And causes various problems such as making it impossible to perform stable dehydration by clogging the wire, soiling a blanket for papermaking, and making it difficult to perform stable dehydration from a wet web made of paper. In particular, when paper is made using inorganic or organic fibers in combination, since the phenol resin is hard to settle on the inorganic or organic fibers, the amount of the phenol resin released from the pulp sheet increases accordingly, so the adverse effect is increased. This causes a problem of enlargement.

In addition, in the present invention, the fiber base material has a freeness of 50%.
10 to 50% by volume of fibrillated wood pulp beaten to 0 to 50 ml (representing Canadian standard freeness (beating degree) specified in JIS-P-8121) (total volume of 100% by volume) ) 50- of the powdered phenolic resin
It was able to fix an amount of 90% by volume (the total stock was 100% by volume) and succeeded in obtaining an overlay layer with excellent transparency.

In addition, the whole stock means all the components constituting the internal paper. Therefore, when the internal paper is made of powdered phenolic resin and pulp, it means all of these components and trace components (for example, a fixing agent) added during papermaking. The volume and weight of
Mostly occupied by powdered phenolic resin and pulp. In addition, when synthetic fibers and fillers are added, it refers to those added.

Particularly in papermaking, when a nonionic coagulant is added to a slurry in which a powdered phenolic resin and pulp are dispersed, and then a slurry in which a cationic coagulant is added is formed, the resin is not released from the pulp sheet and is transparent. It has become possible to stably perform continuous papermaking of internal-added paper capable of forming an overlay layer having properties.

<Powdered phenolic resin> The powdered phenolic resin in the present invention is obtained by simultaneously performing an addition reaction and a condensation reaction of phenols and formaldehyde with a molar ratio of phenols / formaldehyde <1 in the presence of an excess hydrochloric acid catalyst. The resulting hot-melt curable resin has a relative number of methylol groups in the molecule, a weight average molecular weight of 3500 or more, and a gelation time of 3 minutes or more.

That is, powdered phenolic resin, under certain conditions,
Since it is obtained by simultaneously performing the addition reaction and the condensation reaction, the ordinary novolak-type and resol-type phenolic resin has a different structure, a resin having a unique physical property that the ordinary phenolic resin does not have Has become. The resin is typically obtained by a reaction between phenol and formaldehyde, but a mixture of phenol and a derivative of phenol may be reacted with formaldehyde.

The mixing derivatives of phenol, o-, m- or p- cresol, bisphenol A, o-, m- or p-C ₂ ~C ₄ alkyl phenol, p- phenylphenol, xylenol, a resorcinol, and the like.

The powdered phenolic resin itself obtained by simultaneously proceeding the addition reaction and the condensation reaction from phenols and formaldehyde is known (JP-A-57-177011, JP-A-58-17114, JP-A-58-17114, 58-111822,),
It is known that powdered phenolic resins having various different physical properties can be obtained. However, it has been found in the present invention that the obtained internal paper has moldability and the molded overlay layer also has excellent transparency.

"Weight average molecular weight" is measured by gel permeation chromatography after dissolving in methanol.

The particle size is from 1 to 150 μm, preferably from 1 to 150 μm.

 The gel time is 3 minutes or more, preferably 5 minutes or more.

<Fiber Substrate Substantially Made of Pulp> The paper internally containing a powdered phenolic resin according to the present invention is obtained by papermaking a slurry in which a powdered phenolic resin and a fiber base substantially consisting of pulp are dispersed in water. Here, "substrate substantially composed of pulp" means that pulp may contain synthetic fibers (inorganic fibers, organic fibers). That is, the overlay layer according to the present invention improves abrasion resistance and dimensional stability and increases heat resistance and the like without impairing excellent transparency by adding a synthetic fiber.

The pulp used in the present invention is typically wood pulp, but it may be one made from plants other than wood,
Both can be used in combination. There are various types of wood pulp classified according to the pulping process (mechanical treatment, chemical treatment, or a combination of both). These may be used alone or in combination. In addition, 500 ml with a freeness of 50 ml or more
Hereinafter, fibrillated wood pulp beaten to preferably 200 to 480 ml is contained in the whole stock in a ratio of 10 to 50% by volume (based on the total amount of the whole stock). The volume of the fibrillated wood pulp is preferably at least 1/3 of the volume of the powdered phenol resin.

As pulp, LBKP, LUKP, NUKP, NBKP, GP, RG
P and CGP are preferred.

<Synthetic Fibers and Fillers> Synthetic fibers that can be added to the pulp include, in the present invention, semi-synthetic fibers (for example, cellulose acetate fibers), and other than these fibers which are usually organic. And inorganic fibers. Both can be used together. Synthetic fibers are
20% by volume or less (total amount of all stock is 100% by volume),
Preferably, it can be added in an amount of 15% by volume or less. With that amount, the fixation of the powdered phenol resin to the pulp is not impaired, and the transparency of the overlay layer is not impaired. In addition, the wear resistance and dimensional stability of the overlay layer can be improved, and the heat resistance and the like can be increased. Also, from the point of mixing with pulp fiber,
It is preferable to use synthetic fibers having an aspect ratio (fiber length / fiber diameter) of 1000 or less.

Specific examples of the organic fiber include the following.

Polyester fiber, acrylic fiber, aramid fiber, phenol fiber, rayon fiber, vinylon fiber, etc. These organic fibers contribute to increasing the dimensional stability of the overlay layer.

Specific examples of the inorganic fiber include the following.

Glass fiber, alumina silica fiber, alumina fiber, carbon fiber, etc. These improve the wear resistance of the overlay layer,
It contributes to an increase in heat resistance and dimensional stability.

The powdered phenolic resin-containing paper according to the present invention may be a paper containing a filler, corresponding to the fact that the paper is paper. The filler is commonly used in the papermaking industry and generally comprises a powdered inorganic substance. In the present invention, a proper one is selected from these, and an inherent or specific effect can be expected. For example, a silica powder is used to impart abrasion resistance to the overlay layer, an aluminum hydroxide powder is used to impart flame retardancy, and an indium oxide powder or tin oxide powder or surface is used to impart conductivity. Titanium oxide powder having conductivity can be added.

Such a filler is desirably added in a range that does not impair the surface smoothness of the overlay layer and the like.
Suitably, it is 30% by volume (based on the total amount of all stocks), preferably 15 to 20% by volume. It is to be noted that the case where the filler is not used is the one that maximizes the aesthetics of the plywood having the transparency and the smooth surface.

<Inner paper> The internal paper of the powdered phenolic resin according to the present invention is usually produced as follows. That is, powder phenolic resin 50-90% by volume (based on the total amount of all stock),
A slurry composed of at least 10% by volume (based on the total amount of the stock) of fibrillated wood pulp beaten to a freeness of 500 ml or less, a fiber base material and water is prepared to fix the powdered phenolic resin to the pulp fibers. . The concentration of the slurry is 0.1-1% by weight, preferably 0.05-0.1% by weight. Thereafter, the slurry is subjected to papermaking in a papermaking process in a papermaking process to obtain a dry phenolic resin-containing paper in a dry state. As the paper machine, a round paper machine, a fourdrinier paper machine, or an inclined wire mesh paper machine is typically used. The fixing of the powdered phenol resin is effectively performed by adding a nonionic coagulant and a cationic coagulant to the slurry. As the flocculant, a nonionic flocculant is first added to the slurry in which the powdered phenolic resin and pulp are dispersed, and then (preferably immediately before the paper machine), a cationic flocculant is added to the slurry to remove the powdered phenolic resin. Fix it. The addition amount of the nonionic coagulant is 0.05 to 0.5% by weight (based on the total amount of all stocks), preferably 0.1 to 0.3% by weight, and the addition amount of the cationic coagulant is 0.05 to 0.5% by weight ( (Based on the total amount of all stocks), preferably 0.1 to 0.3% by weight.
Specific examples of the nonionic coagulant include, for example, the following.

 Polyethylene oxide, polyacrylamide, etc.

Specific examples of the cationic flocculant include the following.

Polyethylene imide, polyamide polyamine, cation-modified polyacrylamide, cationized starch and the like.

When adding powdered inorganic materials and / or synthetic fibers, it is common to add these flocculants to the slurry.

The resulting dry phenolic resin-filled paper in a dry state is easy to print on the surface. Typical printing methods include offset printing and screen printing.

<Wood board> The overlay plywood in the present invention is obtained by forming an overlay layer on a wood board. Here, "wood board"
Plywood obtained by gluing wood veneers with an adhesive, glued wood chips or pulverized wood flour into a board by pressing with resin, and a single piece of wood or thin leaf pasted on it, and usually And wooden boards. Also,
This "wood board" includes, in addition to the above, those having decorative paper adhered thereto. Such a wood board is a fire-retardant or antiseptic one,
It goes without saying that this may be the case.

In addition, even if it says a wooden board, the magnitude | size of length x width with respect to the thickness is arbitrary.

<Formation of Overlay Layer> The overlay layer according to the present invention is formed by pressurizing and heating the internal paper laminated on the wooden board to melt-harden the powdered phenolic resin and to melt-adhere to the surface of the wooden board. The pressurizing and heating device is not particularly limited, and for example, a hot press or the like can be used.

The heating is carried out at a temperature of from 120 to 180 ° C., particularly preferably from 140 to 170 ° C., necessary for hot-melting and subsequently curing the powdered phenolic resin.

Pressurization, hot melt powder phenol resin fills the space (gap) of the pulp fibers, and 5~70kg / cm ² to obtain the adhesion between the wood plate, preferably 10 to 50 kg / cm ^2, particularly preferably 30-40 kg / cm ² . The heating and pressurizing can be performed in a short time, preferably about 5 to 10 minutes.

The resulting overlay layer has excellent transparency, so that the overlay layer alone can impart aesthetics to the overlay plywood, but between the overlay layer and the wood board, If a printed layer is formed on the wooden board side and / or on the wooden board, the printed layer can be visually recognized through the overlay layer, so that the surface of the plywood can be given an aesthetic appearance.

<Experimental Example> The following experimental example illustrates the present invention more specifically. The present invention is not limited by these experimental examples. Tables 1 and 2 summarize the following experimental examples.

Example 1 Wood pulp (LBKP) is beaten to a freeness of 400 ml with a refiner after defibration at a concentration of 1%. Then, a slurry having a concentration of 0.25% by weight was dispersed in water at a ratio of 50% by volume of a powdered phenol resin (trade name: Bellpearl S-890, manufactured by Kanebo Co., Ltd.) to 50% by volume of a fiber base material made of wood pulp. Was prepared. After dispersion, a nonionic polymer coagulant (trade name: N-210M, manufactured by Showa Denko KK) was added to the slurry at a ratio of 0.3% by weight of the total paper amount to fix the powdered phenol resin to the wood pulp. After that, a cationic flocculant (trade name: Crifix CP-633,
Kurita Kogyo Co., Ltd.) was added to the slurry at a ratio of 0.2% by weight, and papermaking was performed at 60 g / m ² per square meter using a round paper machine. By overlaying the paper-made internal paper on plywood and pressing it at 150 ° C, 40 kg / cm ² for 7 minutes, the surface of the plywood itself is clearly projected, and an overlay layer with excellent transparency is laminated on the surface. Plywood was obtained.

Example 2 The mixing ratio was 10% by volume of high beaten pulp (freeness = 50 ml), 90% by volume of powdered phenolic resin (trade name: Bellpearl S-890, manufactured by Kanebo Co., Ltd.) (the total amount of both was 100% by volume). Papermaking was performed in the same manner as in Example 1 except that the papermaking was performed, but continuous papermaking was possible. The internally added paper obtained after the papermaking was heated and pressed in the same manner as in Example 1 to obtain an overlay plywood having an overlay layer having excellent transparency laminated on the surface.

Example 3 The mixing ratio was 50% by volume of powdered phenolic resin, 30% by volume of pulp (freeness = 400 ml), and glass fiber (trade name: UPG1 / 4ZA50).
8, papermaking was performed in the same manner as in Example 1 except that the volume was 20% by volume (a total amount was 100% by volume) manufactured by Unitika UM Glass Co., Ltd. After the papermaking, the resultant was hot-pressed in the same manner as in Example 1 to obtain an overlay plywood having a transparent overlay layer. The overlay plywood was subjected to a head abrasion test according to the test method of ASTM D673-70, and the wear resistance was evaluated from the surface roughness, and compared with the overlay plywood of Example 1. The overlay plywood of this example in which the inorganic fibers were blended was improved in terms of abrasion resistance as compared with the overlay plywood of Example 1.

Example 4 The mixing ratio was 50% by volume of powdered phenol resin, 30% by volume of pulp (freeness = 400 ml) and rayon fiber (1.5d × 5 mm,
Papermaking was performed in the same manner as in Example 1 except that the volume was 20% by volume (manufactured by Daiwabo Co., Ltd.) (total amount is 100% by volume). After the papermaking, an overlay plywood having a transparent overlay layer was obtained by hot pressing in the same manner as in Example 1.

Example 5 The mixing ratio was 50% by volume of powdered phenolic resin, 20% by volume of indium oxide (In ₂ O ₃ ), 20% by volume of pulp (freeness = 400 ml), and 10% by volume of highly beaten pulp (freeness = 50 ml). Papermaking was carried out in the same manner as in Example 1 except that the total amount was 100% by volume. After the papermaking, the resultant was hot-pressed in the same manner as in Example 1 to obtain an overlay plywood having a transparent overlay layer. The surface resistance of this overlay plywood was 1 kOhm / □.

Example 6 The mixing ratio was 50% by volume of powdered phenol resin, 20% by volume of aluminum hydroxide (Al ₂ (OH) ₃ ), and pulp (freeness = 400).
The papermaking was performed in the same manner as in Example 1 except that 20% by volume) and 10% by volume (the total amount was 100% by volume) of a fiber base material (freeness = 50 ml) composed of highly beaten pulp. . After the papermaking, it was heated and pressed in the same manner as in Example 1 to obtain an overlay plywood having an overlay layer having heat resistance.

Example 7 After offset printing was performed on the internal paper obtained in Example 1 with an acrylic / urethane resin-based printing ink, the internal paper and the plywood were laminated so that the printing surface was in contact with the plywood. By heating and pressing under the same conditions as in Example 1, an overlay plywood projecting the print layer was obtained.

Example 8 Screen printing was performed on the plywood with an acrylic / urethane resin-based printing ink, and the internal paper obtained in Example 1 was laminated thereon, followed by heat-pressing under the same conditions as in Example 1 to obtain a plywood. An overlay plywood in which the printing layer was transferred to the surface was obtained.

Comparative Example 1 Papermaking was performed in the same manner as in Example 1 except that the mixing ratio was changed to 45% by volume of the powdered phenol resin and 55% by volume of pulp (freeness = 400 ml) (the total amount of both was 100% by volume). . Although continuous papermaking was possible with this composition, the resulting internally-added paper was hot-pressed in the same manner as in Example 1. As a result, the powdery phenolic resin could not fill the space of the paper fibers. Due to whitening, sufficient transparency was not obtained.

Comparative Example 2 Papermaking was carried out in the same manner as in Example 1 except that the mixing ratio was 95% by volume of the powdered phenolic resin and 5% by volume (freeness = 50 ml) of 5% by volume (the total amount of both was 100% by volume). Was. In the case of this ratio, the powder phenol resin did not settle on the pulp fiber because the amount of fibers in the fiber base made of pulp was insufficient, and continuous papermaking was impossible.

Comparative Example 3 The mixing ratio was 60% by volume of powdered phenolic resin, 10% by volume of pulp (freeness = 400 ml) and glass fiber (trade name: UPG1 / 4Z)
Example 1 except that A508, manufactured by Unitika Yuemgram Co., Ltd.) was 30% by volume (the total amount is 100% by volume).
Paper-making was performed in the same manner as described above. Although continuous papermaking was possible with this composition, the hot pressing was performed in the same manner as in Example 1. However, since the powdered phenolic resin could not fill the space of the paper fibers, the phenolic resin layer was whitened, which was insufficient. No transparency was obtained.

Comparative Example 4 The mixing ratio was 50% by volume of powdered phenol resin and 50% by volume of pulp (freeness = 550 ml) (the total amount of both was 100% by volume).
Papermaking was carried out in the same manner as in Example 1 except that the above conditions were used.
Although continuous papermaking was possible with this composition, the hot press was performed in the same manner as in Example 1. However, since the powdered phenolic resin could not fill the space of the paper fibers, the overlay layer was whitened and was insufficient. No transparency was obtained.

Claims (4)

(57) [Claims] In an overlay plywood comprising an overlay layer provided on a wooden board, the overlay layer pressurizes and heats a powdered phenolic resin-containing paper as defined in the following (a) to (c). An overlay plywood, characterized in that it is formed on a board. (A) A powdery phenolic resin is a hot-melt-curable resin obtained by simultaneously performing an addition reaction and a condensation reaction of phenols and formaldehyde in the presence of an excess hydrochloric acid catalyst, and having a methylol group in the molecule. Having a weight average molecular weight of 3500 or more and a gelation time of 3 minutes or more. (B) The fiber base material constituting the powdered phenolic resin-containing paper is substantially made of pulp and has a freeness of 500 to 50 ml.
The wood pulp that has been beaten must contain 10 to 50% by volume (based on the total amount of all stock). (C) The content of the powder phenol resin in the powder phenol resin internal paper is 50 to 90% by volume (based on the total amount of all the stock). 2. In an overlay plywood having an overlay layer provided on a wooden board, the overlay layer pressurizes and heats a powdered phenolic resin-containing paper as defined in the following (a) to (d). An overlay plywood, characterized in that it is formed on a board. (A) A powdery phenolic resin is a hot-melt-curable resin obtained by simultaneously performing an addition reaction and a condensation reaction of phenols and formaldehyde in the presence of an excess hydrochloric acid catalyst, and having a methylol group in the molecule. Having a weight average molecular weight of 3500 or more and a gelation time of 3 minutes or more. (B) The fiber base material constituting the powdered phenolic resin-containing paper is substantially made of pulp and has a freeness of 500 to 50 ml.
8 to 50% by volume (based on the total amount of all stock) of wood pulp that has been beaten. (C) The content of the powdered phenolic resin in the paper containing the powdered phenolic resin is 40 to 90% by volume (based on the total amount of all the stocks). (D) Synthetic fibers are contained in the range of 0 to 20% by volume (based on the total amount of all stocks). 3. An overlay plywood in which an overlay layer is provided on a wooden board, the overlay layer pressurizing and heating a powdered phenolic resin-containing paper defined as (A) to (E) below. An overlay plywood, characterized in that it is formed on a board. (A) A powdery phenolic resin is a hot-melt-curable resin obtained by simultaneously performing an addition reaction and a condensation reaction of phenols and formaldehyde in the presence of an excess hydrochloric acid catalyst, and having a methylol group in the molecule. Having a weight average molecular weight of 3500 or more and a gelation time of 3 minutes or more. (B) The fiber base material constituting the powdered phenolic resin-containing paper is substantially made of pulp and has a freeness of 500 to 50 ml.
5 to 45% by volume of wood pulp (based on the total amount of all stock). (C) The content of the powdered phenolic resin in the paper containing the powdered phenolic resin is 25 to 81% by volume (based on the total amount of all paper stocks). (D) Synthetic fibers are contained in the range of 0 to 20% by volume (based on the total amount of all stocks). (E) The powdered inorganic substance is contained in the range of 10 to 30% by volume (based on the total amount of all stocks). 4. A printed layer provided on one or both of the wooden board and the overlay layer between the wooden board and the overlay layer, wherein the printed layer can be visually recognized through the overlay layer. An overlay plywood according to any one of the preceding claims.