JPH10211606A - Manufacture of decorative laminated sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the amount of a formaldehyde in a decorative laminated sheet, which is produced by pasting a decorative sheet to a base board containing a formaldehyde exhalant resin. SOLUTION: An ionizing radiation curing type adhesive 3 under uncured state is interposed between a base board 1 and a decorative sheet 2. Next, by irradiating an ionizing radiation 4 from the rear surface side of the board 1, the adhesive 3 is cured, resulting in pasting the decorative sheet 2 to the board 1. The irradiation of the ionizing radiation from the decorative sheet 2 side may be allowed. During the irradiation of the ionizing radiation 4 for curing the adhesive 3, the formaldehyde in the board 1 is removed through its decomposition or oxidation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a decorative board in which a decorative sheet is adhered to a wood-based material such as wood plywood, particle board, MDF, or a resin-based substrate such as FRP.

[0002]

Taking wood plywood as an example, phenolic resin and urea-formaldehyde resin, which are inexpensive and have high adhesive strength, have been widely used as interlayer adhesives. However, since these adhesive resins emit formaldehyde over time, they have a drawback such as smell of formaldehyde. Therefore, the following attempts have been made to improve this. Adhesives composed of urea / formaldehyde, melamine-based, phenol-based resins, etc.
Change to a resin that does not emit formaldehyde, such as resorcinol resin and epoxy resin. A formaldehyde scavenger is mixed with a formaldehyde-emitting adhesive (for example, Japanese Patent Publication No. 7-110484).
Reference). A formaldehyde scavenger or a resin mixed with a scavenger is applied to the surface of wood plywood (for example, Japanese Patent Publication No.
No. 42164). A paper impregnated with a formaldehyde scavenger, a nonwoven fabric, or the like is attached to the back surface of the decorative board (for example, see JP-A-56-121).
713).

However, in the above-mentioned methods, the cost of the adhesive used is higher than that of urea / formaldehyde-based adhesives and the like, and the temporary adhesiveness (initial adhesive strength) is poor. There is a drawback that the number decreases, and the existing conditions and equipment for bonding are adjusted to the urea-formaldehyde-based adhesives that have been widely used. Need to be done. In addition, the methods (1) to (4) not only increase the cost, but also the method (2) in which the formaldehyde adsorbed and released during the manufacturing process cannot be captured, and the performance of the adhesive changes due to the addition of the formaldehyde capturing agent. In addition, there is a drawback that it is necessary to change the blending amount depending on the grade, so the type of adhesive increases, and it is difficult to treat the end face. However, there is a drawback that the adhesiveness of the plywood may be reduced, and it is difficult to treat the end face. With the method, it is impossible to capture formaldehyde radiating from the surface and the end face of the plywood. It is also conceivable to attach paper or the like impregnated with a formaldehyde scavenger to the surface of the plywood, but when printing on the impregnated substrate, the printability is poor, and two extra layers of extra material are laminated. However, there is a disadvantage that the cost and the process are greatly increased.

[0004] In the case of a so-called melamine resin substrate or an aminoalkyd resin-coated wood board made of a laminate of melamine resin-impregnated paper and phenol resin-impregnated paper, formaldehyde is similarly emitted from the resin component. Therefore, in this case, as a countermeasure, it has been proposed to add a formaldehyde scavenger to the resin itself or an adhesive for laminating the substrate to another substrate. However,
Mixing a formaldehyde scavenger into the adhesive causes problems such as a decrease in adhesive strength, a change in the composition of the adhesive, a change in the bonding conditions, and an increase in cost.Furthermore, the emission of formaldehyde adsorbed on the surface of the substrate must be prevented. There's the problem I said. In addition, when formaldehyde is mixed into the paint, problems such as a decrease in surface properties (hardness, etc.), a change in curing conditions, and a rise in cost occur.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a formaldehyde in a decorative plate obtained by attaching a decorative sheet to a substrate containing a formaldehyde-emitting resin. It is an object of the present invention to provide a method of manufacturing a decorative board effective for reducing the amount.

[0006]

Means for Solving the Problems In order to achieve the above object, the present invention relates to a method for producing a decorative board by attaching a decorative sheet to the surface of a substrate containing a formaldehyde-emitting resin with an adhesive. An ionizing radiation-curable adhesive is used as the adhesive, and this adhesive is interposed between the substrate and the decorative sheet in an uncured state, irradiated with ionizing radiation from the back side of the substrate and cured, and the formaldehyde in the substrate is cured. It is characterized by removing. It is preferable that the decorative sheet is irradiated with ionizing radiation also.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, an ionizing radiation-curable adhesive 3 is interposed between a substrate 1 and a decorative sheet 2 in an uncured state. 1 is irradiated with ionizing radiation 4 from the back side of the adhesive 3
Is cured and the decorative sheet 2 is bonded to the substrate 1. Then, as shown in FIG. 2, it is effective to irradiate ionizing radiation also from the decorative sheet 2 side. In the figures, "x" schematically shows a formaldehyde molecule.

In order for the adhesive 3 to be interposed between the substrate 1 and the decorative sheet 2, the adhesive 3 may be applied to the surface of the substrate 1 in advance, or may be applied to the back of the decorative sheet 2 in advance. Alternatively, it may be applied in advance to both surfaces of the front surface of the substrate 1 and the back surface of the decorative sheet 2. The application amount of the adhesive is about 1 to 100 μm.

[0009] The substrate to be used in the present invention contains a formaldehyde-emitting resin, specifically, a wood plywood (a so-called laminated material) using formaldehyde-emitting resin alone or a formaldehyde-emitting resin as an interlayer adhesive. Particle board or wood fiber board (MDF) using formaldehyde-emitting resin as a binder.
Etc.), and a form obtained by kneading or impregnating a formaldehyde-dispersing resin with a fibrous material to form a composite (FRP in a broad sense). The shape of the substrate is typically a flat plate shape, but may be a curved shape or a molded product having a three-dimensional shape. The thickness of the substrate is usually about 1 to 30 mm.

The formaldehyde-emitting resin includes phenol resin obtained by condensation polymerization of phenol (carbonic acid) and formaldehyde, urea (or urea / formaldehyde) resin obtained by polymerization of urea and formaldehyde, alkyd resin and melamine resin, There are aminoalkyd resins, melamine resins and the like obtained by adding urea resins, guanamine resins and the like. It is believed that the presence of formaldehyde in the resinous material is mainly due to the following reasons. That is, when the resin remains as an unreacted material, when it is left as a resin during a curing reaction (heating and pressurizing), when it remains as a material captured by a material other than resin (wood, paper, and the like), and the like. . In this way, what was present in the resin-based material is gradually released and released.

[0011] The formaldehyde-emitting resin alone is a molded article made of a formaldehyde-emitting resin, and may be in the form of a plate, various three-dimensional shapes, or the like.

Wood used for wood plywood, particle board or wood fiber board includes oak, cedar, pine, zelkova, oak,
Use commonly used ones such as lauan and teak.

Examples of the fibrous material to be kneaded or impregnated with a formaldehyde-emitting resin include high-quality paper, kraft paper, titanium paper, Japanese paper and the like, glass fibers, carbon fibers, inorganic fibers such as asbestos, hemp, cotton, and vinylon. And woven or non-woven fabrics made of organic fibers, and further, short fibers obtained by cutting the inorganic or organic fibers into about 1 to 10 mm. Those obtained by kneading or impregnating the resin with these fibrous materials and curing are so-called FRP, and a melamine resin decorative board is also included in this.

As the decorative sheet, a sheet such as paper, non-woven fabric, synthetic resin sheet or the like, which has been subjected to decorative processing such as painting, picture printing, embossed pattern and the like, is used. Examples of paper used for these sheets include thin paper, high-quality paper, kraft paper, Japanese paper, and latex-impregnated paper. As the nonwoven fabric, one made of organic fibers such as vinylon, polyester, polyolefin, and polyamide is used. As the synthetic resin sheet, a sheet made of polyvinyl chloride, polyolefin, polyester, acrylic, or the like is used.
The thickness of these sheets is appropriately selected according to the application, but is usually about 20 to 200 μm.

The term "ionizing radiation" as used in the present invention refers to high-energy ionizing radiation such as electron beams (including beta rays), ultraviolet rays, X-rays and gamma rays. That is, from several mm to several c
It is necessary to have energy capable of penetrating and transmitting through the substrate of m. In the case of a transparent base such as a formaldehyde-emitting resin alone, it is possible to use ultraviolet rays.However, if the base is opaque including a pigment or the like, if the base is opaque such as wood plywood, Electron beam, X
Rays or gamma rays are preferred. The energy of these ionizing radiations is used to remove formaldehyde from the substrate and to cure the adhesive layer by a crosslinking / polymerization reaction. Although the details of the mechanism of formaldehyde removal are unknown, it is presumed that the formaldehyde molecules are probably excited by the energy quanta of ionizing radiation, causing chemical reactions such as oxidation and decomposition and being converted to another substance.

In the case of an electron beam, a high energy type electron beam is used. That is, there is an advantage that the higher the acceleration voltage is, the deeper the penetration depth into the irradiated substrate is. When the thickness of the substrate is 0.1 to 10 mm, an accelerating voltage of 150 keV or more, preferably 1 MeV or more is used. As the irradiation device, various electron beam accelerators such as a Cockloft-Walton type, a Van degraft type, a resonance transformer type, an insulating core transformer type, a linear type, a dynamitron type and a high frequency type are used. Or ⁶⁰ Co (Cobalt 60), ¹⁷⁰
Beta rays emitted from radioactive nuclei such as Tm (thulium 170) may be used. The irradiation energy amount is about 10 to 500 kGy as an absorbed dose.

Since gamma rays basically have higher energy than electron beams, there are basically no restrictions on energy.
The line type is, for example, 1.Co of ⁶⁰ Co (cobalt 60).
Gamma rays 17MeV and 1.33MeV or ²²⁶ R
A (radium 226) 2.2 MeV gamma ray or the like is used.

As an X-ray irradiation device, a betatron,
Those obtained from a linear accelerator or the like can be used. As the ultraviolet light source, an ultraviolet laser such as a low-pressure mercury lamp, a high-pressure mercury lamp, an excimer lamp, or an excimer laser is used.

As the ionizing radiation-curable resin, a prepolymer having a polymerizable unsaturated bond or a cationically polymerizable functional group in the molecule (including a so-called oligomer) and / or a composition curable by ionizing radiation obtained by appropriately mixing a monomer. Is preferably used. Specifically, in the molecule (meta)
It is composed of a radical polymerizable unsaturated group such as an acryloyl group or a (meth) acryloyloxy group, a cationic polymerizable functional group such as an epoxy group, or a monomer having two or more thiol groups, or a prepolymer. These monomers or prepolymers may be used alone or as a mixture of two or more. Here, for example, the (meth) acryloyl group is used in the meaning of an acryloyl group or a methacryloyl group.

Examples of the prepolymer having a radical polymerizable unsaturated group include polyester (meth) acrylate, urethane (meth) acrylate, epoxy (meth)
Acrylate, melamine (meth) acrylate, triazine (meth) acrylate and the like can be used. A molecular weight of about 250 to 100,000 is usually used.

Examples of the prepolymer having a cationically polymerizable functional group include prepolymers such as epoxy resins such as bisphenol epoxy resins and novolak epoxy resins, and vinyl ether resins such as aliphatic vinyl ethers and aromatic vinyl ethers. There is.

Examples of the monofunctional monomer having a radical polymerizable unsaturated group include monofunctional monomers of a (meth) acrylate compound such as methyl (meth) acrylate,
-Ethylhexyl (meth) acrylate, phenoxyethyl (meth) acrylate and the like.

Examples of the polyfunctional monomer having a radical polymerizable unsaturated group include diethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, and trimethylolpropane ethylene oxide. There are tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate and the like.

Examples of the monomer having a thiol group include:
There are trimethylolpropane trithioglycolate, dipentaerythritol tetrathioglycolate and the like.

For curing with ultraviolet rays, a photopolymerization initiator is added to the ionizing radiation-curable resin. In the case of a resin having a radically polymerizable unsaturated group, acetophenones, benzophenones, thioxanthones, benzoin, benzoin methyl ether and the like can be used alone or in combination as a photopolymerization initiator. In the case of a resin system having a cationically polymerizable functional group, an aromatic diazonium salt, an aromatic sulfonium salt, an aromatic iodonium salt, a metaceron compound, a benzoinsulfonic acid ester, or the like is used alone or as a mixture as a photoinitiator. be able to. The amount of addition of these photopolymerization initiators is 0.1 to 100% by weight of the ionizing radiation-curable resin.
It is about 1 to 10% by weight.

Various additives are further added to the ionizing radiation-curable resin as required. As these additives, for example, extender composed of fine powders such as vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, thermoplastic resin such as acrylic resin and cellulose resin, calcium carbonate, barium sulfate, silica and alumina (Filler), coloring agents such as dyes and pigments.

Irradiation with ionizing radiation can be performed in air (atmospheric pressure or reduced pressure), in an inert gas such as nitrogen, or in vacuum. The ambient temperature and the substrate temperature at the time of irradiation may be room temperature, but within a range that does not cause thermal deterioration of the substrate or the decorative sheet, it is preferable to heat either the atmosphere or the substrate or both to promote removal of formaldehyde. . The heating temperature is usually about 40 to 100 ° C. Heating uses means such as infrared irradiation, dielectric heating, and hot air blowing. Irradiation may be performed from only one direction on the back side of the substrate, or may be performed simultaneously or sequentially from both sides of the substrate. In particular, irradiation from both the front and back surfaces is preferable when the penetrating power of ionizing radiation is weak, when the substrate to be irradiated is thick, or when a decorative sheet that is easily deteriorated by ionizing radiation is laminated on the surface of the substrate. That is, since the intensity of ionizing radiation is attenuated by an exponential function of the penetration distance (depth), when irradiated from both front and back surfaces, the intensity near the substrate surface (absorbed dose) does not extremely increase and the intensity at the central portion inside the substrate is reduced. The intensity (absorbed dose) is prevented from attenuating, and uniform and good formaldehyde removal is possible over the entire thickness inside the substrate. Further, when the ionizing radiation is irradiated from only one direction of the substrate, it is preferable to perform the irradiation from the back side for the following reason. That is, since the thickness of the base material is thicker than the thickness of the decorative sheet and the adhesive layer, the intensity of ionizing radiation at the stage when the light is transmitted to the vicinity of the surface opposite to the irradiation side of the substrate is attenuated. Therefore, if the irradiation is performed only from the decorative sheet side, if it is transmitted to the surface opposite to the irradiation surface of the substrate and further irradiated with an absorbed dose sufficient to remove formaldehyde in the vicinity, the irradiated surface side will have an excessive absorbed dose. become. In this case, changes that directly affect the performance such as discoloration, changes in surface physical properties, and decrease in adhesive strength appear in the decorative sheet and the adhesive layer. Therefore, irradiation from the decorative sheet side is not preferable in the present invention. On the other hand, the surface of the substrate on which the decorative sheet is not adhered has little practical effect due to discoloration or change in physical properties. Therefore, irradiation is performed from the non-adhered surface (back surface) of the decorative sheet.

The manufactured decorative board is further cut into various dimensions and shapes as necessary, and then subjected to processing such as cutting and V-cut, and lamination with various materials, and then to the construction of ceilings, floors, walls and the like. It is used for interior materials, cabinets, furniture such as desks, cabinets for light electrical equipment such as television receivers, containers such as boxes, interior materials for vehicles such as automobiles and trains, interior materials for aircraft, and interior materials for ships.

[0029]

【Example】

(Example 1) Raw material is used as the material type, and the total thickness is 5.5 m.
m was laminated by a hot press to produce a plywood. The number of laminated veneers was three, and a urea / formaldehyde resin was used as an interlayer adhesive. On the other hand, thickness 0.15m
m, printed on a vinyl chloride resin sheet having a plasticizer content of 100 parts by weight of resin and 23 parts by weight of DOP with an ink comprising a mixture of a binder and a pigment in a 1: 1 weight ratio of acrylic and vinyl chloride vinyl acetate copolymer. Was prepared. Then, an electron beam curable adhesive composed of a radical polymerization type polyfunctional urethane acrylate prepolymer is applied to the surface of the plywood at a flow rate of 14 g / m ² (at the time of drying) by a flow coating method, and a cosmetic is applied on the adhesive. After laminating the sheet, an electron beam was irradiated from the back side of the plywood in an air atmosphere to obtain a decorative plate on which a decorative sheet was stuck. The irradiation conditions of the electron beam are as follows.

Ionizing radiation type: electron beam Irradiation device: Cockcroft-Walton electron accelerator Acceleration voltage: 2 MeV Irradiation dose: 15 kGy

(Example 2) After a decorative sheet was laminated on a plywood in the same manner as in Example 1, the decorative sheet was adhered by simultaneously irradiating electron beams in the air atmosphere from the back side of the plywood and the decorative sheet side. A decorative plate was obtained. The irradiation conditions of the electron beam are as follows.

<Cosmetic sheet side> Ionizing radiation type: electron beam irradiation device: Cockcroft-Walton type electron accelerator Acceleration voltage: 200 keV Irradiation dose: 10 kGy <Back side> Ionizing radiation type: electron beam irradiation device: Cockcroft-Walton type electron accelerator Acceleration voltage : 1MeV Irradiation dose: 10kGy

Comparative Example Using the same plywood and decorative sheet as in Example 1, a decorative sheet was produced using a vinyl acetate resin-based adhesive. The coating amount of the adhesive was 14 g / m ² (at the time of drying), and after lamination, curing was performed at 40 ° C. for 30 minutes.

<Evaluation of the amount of formaldehyde>
JIS-A-5908 for the decorative board obtained in Comparative Example 2 and Comparative Example
Quantitative evaluation was performed according to the “formaldehyde emission test” described in JAS special plywood, and the results shown in Table 1 were obtained. From this result, it can be seen that the amount of formaldehyde is reduced in the case of using an ionizing radiation-curable adhesive as the adhesive and passing the ionizing radiation irradiation step. In the decorative plates of Examples 1 and 2, the decorative sheets were firmly adhered.

[0035]

[Table 1]

[0036]

As described above, according to the manufacturing method of the present invention, it is possible to reduce the amount of formaldehyde present in the substrate when the substrate is irradiated with ionizing radiation for curing the adhesive for attaching the decorative sheet to the substrate. Thus, the emission of formaldehyde over time can be sufficiently reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining a manufacturing method of the present invention.

FIG. 2 is an explanatory view showing a state in which ionizing radiation is also applied from the decorative sheet side.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 decorative sheet 3 ionizing radiation-curable adhesive 4 ionizing radiation

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // C08J 7/00 302 C08J 7/00 302

Claims (2)

[Claims] 1. A method of manufacturing a decorative board by attaching a decorative sheet to the surface of a substrate containing a formaldehyde-emitting resin by using an adhesive, wherein an ionizing radiation-curable adhesive is used as the adhesive. Characterized in that an uncured state is interposed between the substrate and the decorative sheet, the substrate is cured by irradiating it with ionizing radiation from the back side of the substrate, and formaldehyde in the substrate is removed. 2. The method according to claim 1, wherein the decorative sheet is irradiated with ionizing radiation also.