US3738854A - Process for making decorative boards - Google Patents

Abstract

DECORATIVE PANELS ARE OBTAINED BY APPLYING A BASE-COLOR UNDERCOAT, THEN EMBOSSING, PRINTING PATTERN, APPLYING A TRANSPARENT OR SEMITRANSPARENT COAT, HEATING TO OBTAIN ONLY INCOMPLETE DRYING AND TO SHRINK THE CAVITIES PRODUCED IN THE EMBOSSING STEP, APPLYING A SEMI-TRANSPARENT COLOR PAINT WHICH IS INCOMPATIBLE WITH THE COAT PREVIOUSLY APPLIED, FILLING THE CAVITIES WITH A COLORING PAINT AND DRYING.

Description

YUMIO OISHI my) Chou mumaa E0408 June 12, 1973 PROCESS FOR MAKING DECORATIVE BOARDS Filed May 24. 1971 ccccmw ccc v jom $26892 5.28 .58 595 CHOU muozao Ew IE mmjflnzdn Amm jE mDOMDOaQ muZoummEGm United States Patent 3 738 854 rnocnss FOR MAKING bnconA'nvn BOARDS Yumio Gishi, Kanbara-machi, Japan, assignor to Noda Plywood Mfg. Co., Ltd., Shimizu-shi, Shizuoka-ken,

Japan Filed May 24, 1971, Ser. No. 146,246 Claims priority, application Japan, May 27, 1970,

5/45,420 Int. Cl. B44d 1/14, 1/28 U.S. Cl. 117-8 7 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a process for making decorative wooden boards having a stereographic color pattern on the surface thereof.

It is known to form a color pattern with suitable filled cavities on the surface of a wooden board such as plywood, particle board and fiber board. Generally speaking, the conventional process for making such pattern on the surface of a wooden board comprises applying a prime coat and a base-color undercoat on the surface of the wooden board to form a certain color tone on the surface thereof, printing a multi-colored grain pattern on the surface by employing a photogravure offset printing machine, pressing the printed surface with an embossing roll having an aesthetic grain vessel pattern in registry with the printed grain pattern to engrave the grain pattern on the surface and concurrently applying an ink to the embossed pattern cavity. According to this conventional process, a grave in registry with the grain pattern printed on the surface is formed by means of the embossing roll and the bottom portion of the grave is colored with the ink, whereby there can be obtained a decorative board having a stereographic, patterned appearance. However, in the decorative board prepared by such conventional process, the ink is applied only to the bottom portion of the grave whereas the side portion of the grave is left not colored with the ink. Therefore, on the decorative surface, the grain appears small, and according to the conventional process it is impossible to reproduce a vessel pattern of, for instance, chestnut tree, zelko-va tree and oak tree having a grain of 0.2-0.35 mm. or birch tree and Magnolia hypoleuca having a grain of 0.05-02 mm. Further, in the conventional process sufficient pigmentation of cavity interior of various vessel grooves formed by the embossing treatment is not accomplished just in registry with the actual vessel pattern or configuration, and the embossing effect is not fully utilized. On this point, the fatal defect of the conventional process resides.

The primary object of this invention is to provide a process for making decorative boards, which overcomes the above-mentioned defect of the conventional art and which can give decorative boards having a decorative surface having a stereographic appearance is attained by dull finish, by reproducing on the surface of the board a pattern of just the same size and configuration as those of the pattern formed on the surface of an embossing roll.

The above object and other objects can be accomplished by the process of this invention which comprises forming, on the surface of a wooden board on which a prime coat, a base-color undercoat and a patterned print have been optionally applied, cavities of a grain vessel pattern, an

3,738,854 Patented June 12, 1973 abstract pattern or the like by employing an embossing roll, applying on the surface a transparent or semi-transparent upper coat, heating the upper coat in a drying furnace until the upper coat is dried and solidified to the finger-touch sense of dryness, applying on the upper coat a semi transparent coloring paint incompatible with the upper coat paint, immediately filling said paint in embossed cavities on the surface of the wooden board to render the whole surface smooth, and drying and solidifying said upper coat and semi-transparent coloring paint coat.

This invention will now be explained.

Any material can be used as substrate in the process of this invention, so far as it has such a property that when it is pressed by an embossing roll or the like, cavities of suitable configurations and depths are formed on the pressed portions and in other portions the surface is kept relatively smooth. In general, however, wooden boards such as plywood, particle board and fiber board are preferably used as substrate. Also assemblies formed by applying paper, synthetic resin sheet or metal foil on the surface of such wooden board may be used similarly.

As paint for a prime coat, a base-color undercoat and a grain or abstract pattern, there may be used the conventional ones used for these purposes. Further, the application of these paints can be conducted by customary methods adopted in the art. More specifically, though the kind of the prime coating varies depending on the kind of the substrate to be used, in the case of an ordinary plywood, a filler coating is applied for prevention of absorption of paints to be laminated on the prime coating, smoothening of the surface and prevention of peeling of laminated coats, and in the case of a hard board, it is preferable to apply a sealer coating with use of a roll coater, a reverse coater or the like. In some cases, a filler coating and a sealer coating are applied in combination.

The base-color undercoat is applied in order to form a uniform color tone on the surface of the substrate wooden board. Generally, the base-color undercoat is formed on the prime coating. However, in case the surface of the wooden board is positively utilized for decoration of the surface, application of the base-color undercoat is omitted.

Printing of a pattern on the surface on which the basecolor undercoat has been applied is effected with use of a photogravure offset printing machine; thus there is printed at grain pattern, an abstract pattern or other optional pattern on the surface of the substrate. It is preferable to make the printed pattern in harmony with a pattern of arrangement of cavities to be formed by means of an embossing roll, whereby the reproduction effect can be greatly heightened.

It is permissible to reproduce a desired pattern only with cavities formed by an embossing roll without printing such pattern by using a printing machine. The printing of such pattern may be effected either before or after forming cavities by the embossing roll.

In accordance with this invention, as explained hereinabove, after a prime coat, a base-color undercoat and a printed pattern have optionally been applied to the substrate surface, a grain vessel pattern, an abstract pattern or other optional pattern is engraved on the surface of the wooden board substrate by pressing the surface with an embossing roll. Formation of pattern cavities may be accomplished by not only an embossing roll but also a mold-pressing plate.

A transparent or semi-transparent upper coat is applied to the surface of the Wooden board on which pattern cavities have been thus formed. Such upper coat is applied for purposes of attaining a good fixation of a semitransparent coloring paint to be applied later, onto the pattern cavities, protecting the decorative surface, pre- 3 venting occurrence of uneven printing and avoiding a color difference brought about by the lot difference.

In accordance with this invention, after such undercoat has been applied on the embossed surface of the wooden board, the paint of the upper coat is allowed to solidify in a drying furnace until the finger-touch sense of dryness is attained in the upper coat paint, and while the upper coat paint is in this state of the finger-touch dryness, a semi-transparent coloring paint incompatible with said upper coating paint is applied on the upper coating-applied surface of the wooden board, and immediately, the semi-transparent coloring paint is filled by a reverse roll into cavities formed by the embossing roll and the upper coating is rendered smooth by the reverse roll, following which the coloring paint and the upper coating paint are dried and hardened, whereby there is obtained on the wooden board a decorative surface having colored cavities.

As is seen from the foregoing explanation, the main structural requirements of this invention are: (l) a semitransparent paint incompatible with the paint of the upper coat is used for coloring interiors of the pattern cavities formed by the embossing roll; (2) the paint to be filled in the interiors of the pattern cavities and color them are filled by means of a reverse roll just after its application on the upper coat-applied surface and the filling of the semi-transparent coloring paint is effected when the paint of the upper coating is in the state of the fingertouch sense of dryness; and (3) the temperature of the upper coat paint in the state of the finger-touch sense of dryness is maintained above room temperature when coating and filling of the semi-transparent coloring paint are effected by the reverse roll.

In case the semi-transparent coloring paint to be used for coloring interiors of pattern cavities is coated on the whole surface of the wooden board when the upper coat is maintained above room temperature, both the upper coating paint and the semi-transparent paint incompatible therewith and applied thereon are in the very wettable state.

Such wettable state can be attained when the surface tension of the upper coat paint is higher than the interfacial tension between the upper coat paint and the semitransparent paint being filled in cavities. This condition is satisfied only when the upper coat paint has not been completely solidified but still remains in the state of the finger-touch dryness, i.e., in the swollen and half-solidified state and when the temperature of said upper coat paint is higher than room temperature.

The temperature of the upper coating paint in the finger-touch sense of dryness at the time when the semitransparent paint is actually applied differs depending on the kind of the resin contained in the paint, but in order to obtain a uniform coating effect throughout convex and concave portions of the entire surface, it is preferable to maintain the temperature of the upper coat paint at about 40 C. or higher.

When in accordance with this invention the semi-transparent coloring paint is applied while the upper coat paint is in the state of the finger-touch sense of dryness and thus the coloring paint is filled into pattern cavities, a complete bonding is attained between the upper coat paint and the semi-transparent coloring paint.

If a transparent or semi-transparent paint is applied after the upper coat paint has been completely dried and solidified, a good bonding is not obtainable between both paints and the separation of laminated paints is brought about with the lapse of time. This phenomenon is prominent particularly when the paint to be applied on the surface coated with the upper coat paint is incompatible with the upper coat paint.

The reverse roll is useful for attaining sufficient filling of the paints into the pattern cavities and smoothening a finished surface.

The use of the reverse roll is especially useful for smoothening a finished surface in cooperation with use of a paint incompatible with the upper coating paint as the coloring paint to be applied on the surface coated with the upper coating paint and with selection of the specific time for application of the coloring paint, i.e., the time when the upper coat paint is still in the state of the finger-touch sense of dryness.

Further, when the surface of the upper coating paint is smoot-hened by the reverse roll, the upper coat paint is still in the finger-touch dryness and its surface is relatively soft; therefore, when the upper coating paint layer is forcibly smoothened by means of the semi-transparent coloring paint applied thereon by means of the reverse roll, the surface of the upper coat paint is rubbed by an inorganic pigment contained in the semi-transparent coloring paint and fine scars are formed on the surface of the upper coating paint layer, which results in a suitable delustering effect.

By the term the state of the finger-touch sense of dryness used in the present specification is means the state where the coated paint is dried to such an extent that when the coating surface is lightly pressed with a finger, a trace of the finger is left on the surface. In general, if such state is expressed in terms of the drying or solidification degree, the state corresponds with the drying degree of about 30-40%, though it varies to some extent depending on the kind of the resin contained in the paint. In the case of a solvent-type paint, the above state corresponds with the state where about 70-80% of the solvent contained in the paint has evaporated.

Another important requirement of this invention is that a semi-transparent paint incompatible with the upper coat paint is used as the paint to be applied on the upper coating paint-applied surface and filled into the interiors of cavities formed by the embossing roll to color the inner surface of these cavities. Since application of the semi-transparent paint is effected when the upper coating paint is in the state of the finger-touch sense of dryness, if a paint compatible with the upper coating paint is used, when filling of the semi-transparent is carried out by the reverse roll while pressing the surface of the upper coating paint layer by means of the semi-transparent paint coated thereon, the upper coat paint is attacked by the semi-transparent paint, with the result that coating unevenness is brought about and the upper coat is peeled off from the surface of the wooden board. Accordingly, a finish coating composed of a combination of the upper coat paint with the semi-transparent paint to be filled in the interior of the pattern cavities cannot be formed at all and it becomes impossible to color the inner faces of the cavities in a uniform tone. For these reasons, such semi-transparent paint incompatible with the upper coat paint is used for coloring inner faces of the pattern cavities.

By the term paint incompatible with the upper coating paint used herein is meant a paint which is hardly melt-blended with the upper coating paint. It is not inevitably necessary that the semi-transparent paint should be incompatible with the ordinary paints, and the degree of incompatibility should not be so high but such incompatibility as will not bring about any trouble in the application of the semi-transparent paint on the upper coating-applied surface and in the reverse roll treatment for filling it into the interiors of cavities is sufficient. In short, it is not required that the semi-transparent paint be completely and absolutely incompatible with the upper coating paint.

The reason why the paint to be filled in cavities must be transparent or semi-transparent is that with use of a semi-transparent paint the color of the inner faces of the pattern cavities can be adjusted to a desired tone. When a paint is filled in the interior of cavities by means of a reverse roll, a thin layer of the paint is formed in smooth portions other than cavities. Accordingly, when an opaque paint is used, the pattern or image printed on the smooth surface portion and the intended aesthetic effect cannot be attained. In the case of a semi-transparent paint, such disadvantage is not brought about. Further, since the content of a pigment is great in the opaque paint, when it is filled in cavities and then dried, the cavities are likely to be completely filled, with the result that it is impossible to retain a fine vessel groove of a width of about 1 mm. on the decorative surface.

As is seen from the foregoing explanation, in this invention a combination of the above requirements of forming cavities on the surface of a wooden board by means of an embossing roll, applying an upper coat on the embossed surface, coating thereon a semi-transparent coloring paint incompatible with the upper coating while the upper coating paint is heated and kept in the state of the finger-touch dryness, and immediately filling the paint in the interiors of the embossed cavities by means of a reverse roll, attains synergetic'effects, whereby the objects of this invention can be fully accomplished.

In accordance with the process of this invention, when a plywood is used as the substrate board, cavities inherently present in the wood surface such as worm-eaten spots or pores, barkholes and knotholes are colored and coated to the interiors thereof, and a pattern is printed on the smooth surface. Accordingly, arrangement of colored cavities gives, together with the pattern printed on the smooth surface, a more beautiful appearance to the decorative surface of the board.

When a semi-transparent paint of a less luster than the upper coat paint is used for coloring inner faces of cavities, there is formed a difference of luster between the smooth surface and the inner faces of the cavities, which further emphasizes the stereographic appearance more distinctly.

Since the upper coating paint is smoothened by means of a reverse roll while it is in the state of the fingertouch dryness, the printed pattern is expressed more beautifully and variations of the configuration of cavities can be made to appear more distinctly. Further, fine scars are formed on the surface of the upper coat when it is pressed via the semi-transparent paint by means of a reverse roll while in the state of the finger-touch sense of dryness, a suitable delustering effect is obtained to form a decorative surface of good depth. Unlike the decorative surface formed by incorporation of a delustering agent in the paint where the entire of the paint layer becomes opaque, the upper coat layer smoothened by a reverse roll has fine scars only on the surface thereof and any influence is not given to the portions beneath said upper coat layer. Accordingly, the printed pattern beneath the upper coat layer looks embossing from the interior while suitably delustered, which results in a great aesthetic effect. Further, although in the conventional process color painting of interiors of grain grooves is conducted by one separate step, in the process of this invention this can be accomplished coincidentally by the treatment with a reverse roll. Accordingly, the manufacturing process can be made simple and an effect of labour-saving is attained in this invention.

For better illustration, this invention will now be explained by referring to accompanying drawings.

The rfigureis a diagram illustrating an apparatus for practising the process of this invention using a lauan plywood.

Referring to the figure, plywood P is automatically forwarded and the surface is ground by means of a wide belt sander constructed with a series of two connected grinding drums. A sand paper of a #240 grit grind cloth is coated on first grinding drum 1 of the wide belt sander and a sand paper of a #400 grint grind cloth is coated on second grinding drum 2. By grinding the surface of the lauan plywood, wood fiber fluifs which would other- 6 wise raise during the coating step can be removed from the surface.

Then, an aqueous filler is applied on the surface of the plywood by means of a coating roll 3 of a first reverse coater, whereby vessel grooves, cracks, scars and other pores on the surface of the plywood are filled with the filler by reverse roll 4 rotating in the direction reverse to the forward direction of the pywood. The superfluous filler left on the flat portion is scraped and wiped off by means of blade 5 close to the surface of reverse roll 4.

The amount applied of the aqueous filler is controlled by adjusting the distance between coating roller 3 and roller 6. Reverse roll 4 is so provided as to rotate in the direction reverse to the rotation direction of coating roll 4 and feeding rolls 7 and 8, and its peripheral speed is made different from that of these rollers.

The aqueous filler applied on the surface of the plywood is pressed and intruded in the vessel grooves open to the surface by means of reverse roll 4 while it is not dried, and the excess of the aqueous filler is removed of blade 5. Thus, the aqueous filler is left only in cavities of vessel grooves and other pores to form a fiat level on the surface of the plywood.

Then, the plywood is forwarded into drying furnace 9 Where hot air is circulated, and while it is passing through the drying furnace, water contained in the aqueous filler a is allowed to evaporate and the aqueous filler is dried and solidified, and the volume thereof is reduced. Thus, there are formed slightly concave portions a at points of vessel grooves and cracks. Then, a filler of a lacquer type is coated by means of coating roll 10 while the amount applied is adjusted by doctor roller 11 of a second reverse coater, and the filler is immediately presstfilled into slightly concave portions a of the aqueous filler by means of reverse roll 12 rotating in the direction reverse to the forwarding direction. Excess of the lacquer t'ype filler is removed by means of doctor blade 13.

After the lacquer type filler has been filled into slightly concave portions a, the plywood is passed through infrared drying furnace 14, whereby the solvent of the lacquer type filler is allowed to evaporate and the filler is dried and solidified to render the plywood surface smooth. Since vessel grooves are present as cavities throughout the surface of the lauan plywood, in order to produce a desired grain pattern on the plywood surface, it is necessary to render the surface fiat.

The frequency of the treatment with an aqueous filler may be varied depending on the kind of the desired appearance, and in the above sealing treatment, the plywood surface can be made smoother by increasing the frequency of the treatment with the aqueous filler.

After the lacquer type filler has been dried, the plywood is inserted in second wide belt sander 15 and the surface is ground by a sand paper of a 380 grit grind cloth to render the surface smooth and flat. Thus, filler 6 is completely filled in cavities, and the original appearance of the lauan plywood is lost. Thus, a desired pattern can be formed freely on the surface of the plywood.

In the sealing treatment with aqueous and lacquer type filler, if the sander grinding is effected after the lacquer type filler has been dried and solidified, clogging of meshes of the sand paper can be reduced as compared with the case where the sealing treatment is conducted with use of the aqueous filler alone, whereby the operability of the the process can be improved. In the case of the aqueous filler, there is a tendency that the resin component is softened during the grinding treatment, and it is likely to be filled in meshes of the sand paper, with the consequence that the grinding ability of the sand paper is lost. In the above sealing treatment, a reverse coater is an appropriate device to be used conveniently for attaining the filling effect sufficiently in lauan plywood which has pores and cavities having openings of large sizes.

A base-color under coat of a desired pattern is applied to the so sealed surface of the plywood by means of coating roll 17 while the amount applied is adjusted by doctor roll 16 of a roller coater. The solvent contained in the coating paint is vaporized by means of drying furnace 18 and thus there is formed a base-color under coat layer It is necessary to change the color tone of the base-color undercoat layer (0) depending on the desired pattern. The coating of the base-color paint may be accomplished also by employing an automatic spray coater, a curtain flow coater or other customary coating device.

Just after the base-color under coat layer has been formed by passage through drying furnace 18, an embossing roll 19 having on the barrel surface projections 20 the vessel grooves of desired grain pattern is impressed on the base-color undercoat applied surface of the plywood, whereby cavities (d) of a pattern closely resembling the desired grain pattern of vessel grooves are formed. Said cavities (d) exhibit a stereographic appearance of the desired grain pattern, and the cavities as a whole form throughout the plywood surface a grain pattern closely resembling the desired grain pattern.

The embossed pattern (a) comprises numerous cavities varying in the size, the depth and the configuration depending on the desired grain pattern, and these cavities are extended to the base-color undercoat, the prime coat filler or the base tissue of the plywood.

In the decorative board prepared in accordance with the process of this invention, an appearance resembling the appearance of a valuable broad-leaved tree such as rose wood, walnut and teak wood is formed on the surface of substrate lauan plywood.

On the surface of a valuable broad-leaved tree, vessel grooves are present as cavities, and rubbery material or tylosis is deposited in the cavities and acts as coloring matter. Thus, the cavities are densely colored, and as a whole there is formed a pattern of vessel grooves and a grain pattern inherent to natural wood is formed by deposition of coloring matters. Accordingly, in order to obtain a decorative surface having an appearance closely resembling the appearance of a natural broad-leaved tree, it is necessary to form a pattern of vessel grooves corresponding with a pattern of said concave vessel grooves, and to produce a color shade corresponding with that appearing in vessel grooves of the natural tree and a grain pattern inherent to the natural wood.

Then, a printing ink is applied to the embossed surface of the plywood. The ink is transferred onto offset roller 22 from cylinder 21 of a photogravure printing machine and then coated on the base-color undercoat-applied surface (c) having cavities (d) to thereby form a pattern (e) corresponding with a desired grain pattern.

The pattern (e) and cavities (d) are in registry with each other so that the desired grain pattern will be formed on the surface. The pattern (e) may be multicolor printed by conducting a plurality of photogravure offset printing steps. Then, a transparent upper coat paint is applied on the surface by means of coating roller 24 while the amount applied is adjusted by doctor roller 23 of a roller coater. Then, the plywood is passed through drying furnace 25 in a short of time, and while the transparent upper coat paint is half dried to such an extent that when a finger is lightly placed on the coat surface, a trace of the finger is left thereon, a semi-transparent coloring paint is applied on the upper coat paint layer (1) by means of coating roller 27 while the amount applied is adjusted by means of doctor roller 26 of a third reverse coater. Immediately, the coated surface is pressed by reverse roll 28 rotating in the direction reverse to the forward direction, and the semi-transparent coloring paint is pressed and led into cavities (j). Excessive semi-transparent coloring paint left on the fiat face portion is transferred to the reverse roller surface and scraped and removed by blade 29. Then, the plywood is passed through drying furnace 30, whereby the upper coat paint layer (1) which has been in the state of the finger-touch dryness and the semi-transparent color ing paint (i) embedded in cavities j) are dried and sol1d1- fied to form an upper coat (h).

EXAMPLE 1 The surface of lauan plywood of 5 mm. thickness is subjected to the grinding treatment with a wide belt sander provided with a combination of 240 grit grind cloth and a 400 grit grind cloth, and an aqueous filler is applied on the entire of the plywood surface by means of coating roll 3 while the amount applied of the filler is adjusted by doctor roll 6 of a first reverse coater. The amount applied of the filler is 70-90 g./m. The aqueous filler comprises 40 parts by weight of vinyl acetate emulsion, 7 parts by weight of titanium white, 13 parts by weight of clay, 20 parts by weight of Zinc flower, 10 parts by weight of 5% sodium secondary phosphate and 10 parts by weight of water. The reverse rotation rate of reverse roll 4 of the first reverse coater is reduced by 20% as compared with the rotation rate of coating roll 3. In this manner, the aqueous filler is efficiently filled into vessel grooves open to the plywood surface while it is being rubbed thereinto by reverse roll 4. Excessive filler is transferred onto the surface of reverse roll 4 and wiped off. The pressure of compressed air of reverse roll 4 is fixed to 7 kg./cm.

Then, the lauan plywood is passed over a period of 10 minutes through drying furnace 9 where hot air maintained at C. is circulated, and the plywood is coated with 40-50 g./m. of a lacquer type filler by means of coating roll 10, while the amount applied of the filler is adjusted by doctor roll 11 of a second reverse roller. The lacquer type filler comprises 5.0 parts by weight of /2 see-grade nitrocellulose, 9.0 parts by weight of modified maleic acid resin, 26.0 parts by weight of zinc flower, 23.0 parts by Weight of china clay, 2.5 parts by weight of modified alcohol, 4.5 parts by weight of ethyl acetate, 7.0 parts by weight of amyl acetate and 23.0 parts by weight of Ruol.

Reverse roll 12 of the second reverse coater is reversely rotated at the same rate as coating roll 10, and the pressure of compressed air of the reverse roll is fixed to 5 kg./cm. The lacquer type filler filled in cavities (a) and thinly coated on the entire of the plywood surface is heated for 5 minutes in infra-red ray drying furnace 14, and thus dried and solidified.

After passage of infra-red ray drying furnace plywood furnace is ground by a 380 grit grind cloth of second wide belt sander 15, whereby the surface is rendered smooth and flat, and fluffs and other projections are removed. A base-color paint prepared so as to exhibit a color tone of rose wood to be simulated is applied on the plywood surface in an amount of 40 g./m. by means of coating roll 17 while the amount applied of the base-color paint is adjusted by doctor roll 16 of a roller coater. The basecolor paint comprises 4.0 parts by weight of /2 sec.- grade nitrocellulose, 12.0 parts by weight of modified maleic acid resin, 25 parts by weight of zinc flower, 10 parts by weight of titanium white, 5 parts by weight of yellow iron oxide, 3 parts by weight of red iron oxide and 1.0 part by weight of carbon black. The plywood is then passed over a period of 6 minutes through drying furnace 18 where hot air maintained at 60-l00 C. is circulated, whereby a base-color coat layer (0) is formed. Embossing roll having on the barrel surface protrusions of 0.5 mm. height and 1-2 mm. diameter forming a pattern corresponding with a desired pattern of vessel grooves of rose wood is pressed on the base-color coat layer (0) to form vessel grooves (d) thereon. The pressing of embossing roll 19 is effected under a pressure of about 20 kg./cm. The grain vessel groove cavities (d) exhibit a configuration and an arrangement pattern resembling those of rose wood to be simulated.

In a photogravure offset printing machine, a printing ink is filled by a doctor roll into photogravure cylinder 21 engraved with small concave points exhibiting a pattern corresponding with the grain pattern of rose wood, and the ink pattern is transferred onto the surface of offset roll 22 and then printed on the surface of the basecolor coat layer to form a grain pattern (e) of rose wood.

A transparent, oil-modified aminoalkyd resin upper coat paint comprising 30 parts by weight of soy bean oil-modified alkyd resin, 40 parts by weight of butylated ureamelamine copolycondensate resin, 15 parts by weight of modified alcohol, 12 parts by weight of xylol and 3 parts by weight of a curing agent (para-toluene sulfonic acid) is coated in an amount of 45 g./m. on the plywood surface, and it is dried for 32 seconds in a drying furnace Where hot air maintained at 50-100 C. is circulated at a rate 2 m./min. At this point, the coat temperature is about 65 C. and the coat surface is in the state of the finger-touch dryness. This upper coat layer (1) is coated with an aqueous acrylic resin paint in an amount of 40- 50 g./m. by means of coating roll 27 while the amount applied is adjusted by doctor roll 26 of a third reverse coater. The aqueous acrylic resin paint comprises 88 parts by weight of acryl ester emulsion, parts by weight of water, 1.2 parts by weight of carbon black, 0.5 part by weight of Benzidine Yellow and 0.3 part by weight of red iron oxide. Just after the coating of the aqueous acrylic resin paint, it is filled into cavities of a rose wood pattern formed by the embossing roll, by means of reverse roll rotating in the direction reverse to the forward direction. Excessive aqueous acrylic resin paint coated on partions other than said cavities is transferred onto the surface of reverse roll 25 and scraped and removed by doctor blade 29 close to the surface of reverse roll 25. Then, the plywood is passed over a period of minutes through drying furnace 30 where hot air maintained at 60l10 C. is circulated at a rate of 2-5 mm./min. whereby the upper coat paint layer (f) and the aqueous acrylic resin paint are dried and solidified to form a transparent upper coat (h) and a coating (i) of the aqueous acrylic resin filled in the cavities.

EXAMPLE 2 A prime sealing coat and a base-color coat are applied on the surface of a plywood of 5 mm. thickness. After drying, cavities of 0.5 mm. depth and 1-2 mm. diameter are formed to simulate the configuration and arrangement of vessel grooves of rose wood, by means of an embossing roll. Then, a grain pattern of rose wood is printed on the embossed surface by means of a photogravure offset printing machine, and a transparent, oil-modified alkyd resin paint is coated thereon in an amount of 45 g./m. by means of a roller coater. The plywood is dried for 32 seconds in -a drying furnace where hot air maintained at 50-100" C. is circulated at a rate of 2 m./min. While the coat temperature is at about 65 C. and the coat is in the state of the finger-touch dryness, and aqueous acrylic resin incorporated with 1.2 weight percent of carbon black, 0.5 weight percent of Benzidine Yellow and 0.3 weight percent of red iron oxide is coated on the surface of the plywood by means of a reverse coater, and the resin is filled into the cavities of the plywood surface by means of a reverse roll, following which drying and solidification of coated paints are effected. Thus, there is obtained a decorative board having a wood-tactile appearance having a printed pattern resembling the rose wood grain pattern and colored cavities exhibiting a configuration and a pattern resembling those of rose wood.

What is claimed is:

1. A process for reproducing decorative boards having a natural grain design of wood on a panel of wood or like lignocellulose material which comprises the steps of:

(a) applying a base-color undercoat to said panel to mask completely the color of said material,

(b) embossing said panel to impress in said undercoat layer first cavities of grain vessel pattern,

(c) printing a patterned print on the surface of said panel,

((1) applying a transparent or semi-transparent finishing coat on the printed and embossed surface of said panel,

(e) heating the coated panel until the finished coat is dried to finger-touch dryness, whereby the upper coat shrinks and smaller second cavities of grain vessel pattern are reproduced in said upper coat in the positions of the first cavities of the undercoat,

(f) applying on the upper coat a semi-transparent coloring paint which is incompatible with the upper coat,

(g) immediately filling the second cavities with the applied coloring paint,

(h) and drying said upper coat and semi-transparent coloring paint.

2. The process according to claim 1 wherein a prime coat is applied prior to said undercoat to fill the indentations.

3. The process according to claim 1 wherein a sealer is applied prior to said undercoat.

4. The process according to claim 1 wherein said finger touch dryness is achieved by heating until about of the solvent type paint have evaporated.

5. The process according to claim 1 wherein the upper coat is maintained at a temperature above room temperature during the step when the cavities are filled with coloring paint. 7

6. The process according to claim 1 wherein a semitransparent paint is applied in step (f) with a luster lower than the luster of the upper coat in step (e).

7. The process according to claim 1 wherein said printed pattern in step (c) is multicolored.

References Cited UNITED STATES PATENTS 3,486,919 12/ 1969 Dreazy et al. 117---8 2,032,405 3/1936 Fischer et al 117--8 3,247,047 4/1966 Buckley 161-123 WILLIAM D. MARTIN, Primary Examiner T. G. DAVIS, Assistant Examiner US. Cl. X.R. 117-85, 12, 147

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