JPH10139903A - Substrate processing method - Google Patents

Abstract

(57) [Problem] To provide an effective method for treating a substrate containing a formaldehyde-emitting resin and reduce the amount of formaldehyde emitted from the substrate. SOLUTION: Formaldehyde in the substrate is reduced by bringing the surface of the substrate into contact with plasma. It is preferable that the surface of the substrate be brought into contact with plasma under a heated state. When the substrate is further heated, the substrate 1 is heated only from the lower surface A side, and the substrate 1 is heated with a temperature gradient such that the lower surface A is high temperature and the upper surface B is low temperature. Is transferred from the lower surface A to the upper surface B with heat diffusion and is released from the upper surface B. Therefore, it is more effective to bring the upper surface B of the substrate 1 into contact with the plasma particles 3 while performing the temperature gradient heating. It is.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wood plywood, a particle board, a wood substrate such as MDF, a resin substrate such as FRP, a decorative plate on which a decorative sheet is adhered, and the like. The present invention relates to a method for processing a substrate including:

[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 (formalin) over time, they have a drawback such as smell of formalin. Therefore, the following attempts have been made to improve this. Urea / formalin-based, melamine-based, phenol-based adhesives are changed to those that do not emit formaldehyde, such as vinyl acetate emulsions, resorcinol resins, and epoxy resins. A formaldehyde scavenger is mixed with the formaldehyde-emitting adhesive (for example, Japanese Patent Publication No. 7-1104).
No. 84). A formaldehyde scavenger or a resin mixed with a scavenger is applied to the surface of a wooden material (for example,
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 / formalin-based adhesives and the like, and the temporary adhesiveness is poor, and the number of non-defective products at the time of production is reduced. There are disadvantages, and it is necessary to change the processing conditions for each adhesive. In addition, all of the methods (1) to (4) increase the cost, and the methods (2) and (3) require that the amount of formaldehyde adsorbed and released during the manufacturing process cannot be captured, and that the amount of the adhesive must be changed depending on the grade. There are drawbacks that the number of types increases and that the end face treatment is difficult.In the method, it is necessary to consider the adhesion with the decorative sheet to be attached to the surface, and there is a disadvantage that the end face treatment is difficult. However, when printing on an impregnated substrate, there is a drawback that printability is poor.

[0004] In the case of a so-called decorative melamine resin board or a wood board coated with an amino alkyd resin, which is a laminate of a melamine resin impregnated paper and a phenol resin impregnated paper, formaldehyde is also 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 decorative board to another substrate. However, if formaldehyde is mixed into the adhesive, 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 will occur, and furthermore, if formaldehyde adsorbed on the surface of the decorative plate cannot be prevented from being emitted, it cannot 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 problems, and an object of the present invention is to treat a substrate containing a formaldehyde-emitting resin in an amount effective for reducing the amount of formaldehyde in the substrate. It is to provide a method.

[0006]

In order to achieve the above object, the present invention provides a processing method for reducing the amount of formaldehyde on a substrate containing a formaldehyde-emitting resin, wherein the surface of the substrate is brought into contact with plasma. It is characterized by:

It is preferable that the surface of the substrate is brought into contact with the plasma under the heating condition. In this case, it is more effective to heat the substrate with a temperature gradient so that the lower surface is at a high temperature and the upper surface is at a low temperature, and to bring the upper surface into contact with plasma.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The substrate targeted in the present invention contains a formaldehyde-emitting resin.
Formaldehyde-dispersing resin alone, wood plywood (including so-called glued laminated material) using formaldehyde-dissipating resin as an interlayer adhesive, particle board or wood fiber board using formaldehyde-dissipating resin as binder
DF, etc.), kneaded or impregnated with a fibrous material and compounded with formaldehyde-emitting resin (FRP in a broad sense),
The decorative plate may be in any form of a decorative plate in which various decorative sheets are attached to various base materials via an adhesive layer containing a formaldehyde-emitting resin as a component. The shape of the substrate is typically a flat plate or a sheet, but may be a curved plate or a molded product having irregularities or a three-dimensional shape on the surface.

Examples of the formaldehyde-emitting resin include a phenol resin obtained by condensation polymerization of phenol (carbonic acid) and formaldehyde, a urea (or urea-formaldehyde) resin obtained by polymerization of urea and formalin,
There are aminoalkyd resins, melamine resins, and the like obtained by adding melamine resins, urea resins, guanamine resins, and the like to alkyd resins. 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.

[0010] The formaldehyde-emitting resin alone is a molded article made of a formaldehyde-emitting resin, and may be in the form of a plate, a sheet, or various three-dimensional shapes. 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, paper such as kraft paper, titanium paper and Japanese paper, inorganic fibers such as glass fiber, carbon fiber and 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.

In a decorative board in which various base materials and various decorative sheets are adhered with an adhesive layer interposed therebetween, the various base materials may be a wooden board (single board, or the above-mentioned wood plywood, particle board, wood fiber, etc.). Plate, a metal plate, a cement plate, a calcium silicate plate, a ceramic plate and the like. As the various decorative sheets, sheets obtained by subjecting sheets such as paper, nonwoven fabric, and synthetic resin sheets to decorative treatments such as painting, picture printing, and embossing of uneven patterns are used.

Plasma is a group of particles containing positively and negatively charged particles, which are substantially electrically neutral as a whole. Solid plasma and liquid plasma also exist, but gas plasma is used here. In this plasma, electrons,
There are emitted photons such as charged particles such as positive ions and negative ions, neutral atoms and molecules, and radicals. The plasma is chemically active due to the presence of these particles,
When formaldehyde comes into contact with plasma, it is decomposed into formic acid or further H ₂ O or CO ₂ .

The plasma that can be used is a so-called “low-temperature plasma” from the viewpoints of easy control of the plasma, easy generation of the plasma, suitability of the temperature and energy of the plasma, and the like.
Is used. Among the low-temperature plasmas, a low-temperature plasma by discharge excitation is particularly preferable. There are the following methods for generating low-temperature plasma. Surface creeping method An electrode having a planar electrode formed on one of the front and back surfaces of the dielectric and a string electrode formed on the other is prepared, and a voltage of 1 kV to 1 is applied between the electrodes.
An alternating voltage having a frequency of about 00 kV and a frequency of about 1 kHz to 100 kHz is applied, and a creeping streamer discharge is performed along the dielectric surface to excite a gas to form a plasma. The dielectric is preferably made of ceramics. Pulse corona discharge method wire-cylinder method, wire-plat
The e method is a typical example. Voltage 1kV-100 between electrodes
About kV, rise time 10 to 50 ns, pulse half width 50
A pulse voltage of ~ 500 nS is applied to cause streamer corona discharge to excite the gas. Packed bed reactor method After filling ferroelectric pellets between electrodes, voltage 1
About kV-100kV, frequency 50kHz-100kHz
An AC voltage of about z is applied, and a discharge is excited by a local and pulsed strong electric field generated in the vicinity of the pellets, thereby exciting a gas to form a plasma. Silent discharge method After inserting a dielectric between the electrodes, a voltage of 1 kV to 100 k
An AC voltage having a voltage of about V and a frequency of about 50 kHz to 100 kHz is applied to discharge to excite a gas to form a plasma. Other methods DC corona discharge method, combined use of surface discharge method and silent discharge method, combined use of packed bed reactor method and pulse corona discharge method, etc.

Among them, the creeping discharge method has good reaction efficiency irrespective of the type of plasma gas. O ₂ (oxygen), N _2
2 (nitrogen), H ₂ O (water vapor), argon, air, or a mixed gas thereof is used. The pressure of these gases is about atmospheric pressure (about 760 mmHg) to about 1 mmHg, and is usually used at about atmospheric pressure. O, O in the excited state of these gases in low-temperature plasma
₃ (ozone), N, N ₂ , OH, etc. react with formaldehyde to carry out the above decomposition or oxidation.
The processing by the low-temperature plasma is performed in a state where the substrate is sealed in a closed chamber together with the plasma raw material gas. However, when performing low-temperature plasma processing in air at atmospheric pressure, it is also possible to perform processing in an open state.

If the surface of the substrate is heated simultaneously with the contact with the plasma, formaldehyde can be released more efficiently. The substrate may be heated by means such as infrared radiation or dielectric heating. The substrate heating temperature is usually 30
About 150 ° C. However, the material of the substrate is limited to a range that does not cause deterioration, alteration, or damage such as melting, ignition and combustion, decomposition, chemical reaction, and crystal transformation. For ordinary woody materials, 30 to 100 ° C is preferable.

When the substrate is heated, for example, when far infrared rays are irradiated only from the lower surface of the substrate 1 as shown in FIG. 1 (a), a temperature gradient is set so that the lower surface A becomes higher and the upper surface B becomes lower. As a result, as shown in FIG. 1B, the formaldehyde molecules 2 move from the high temperature side to the low temperature side, that is, move from the lower surface A to the upper surface B with the thermal diffusion, and are released from the upper surface B. It is preferable to combine such a heating method with plasma irradiation. Specifically, if an irradiation device is placed on the upper surface B side where formaldehyde molecules 2 are emitted at a high concentration to bring the plasma particles 3 into contact with the substrate, the efficiency of decomposing the released formaldehyde 2 is increased. good. Of course, it is also possible to make the lower surface A side of the high temperature of the substrate 1 having a temperature gradient come into contact with the plasma, or to make both surfaces of the upper surface B and the lower surface A come into contact with the plasma at the same time.

The processing method of the present invention is also effective for removing organic gases other than formaldehyde emitted from the substrate. Examples of the organic gas that can be removed include benzene, toluene, xylene, methyl chloride, trichlorethylene, hexane, and ethylene chloride.

[0019]

EXAMPLES (Example) Rawan veneer veneers were bonded with a urea resin adhesive and hot pressed to produce a 10 mm thick formaldehyde-emitting woody plywood composed of five veneers. The plywood was sealed in a sealed chamber, and the chamber was filled with air having an air pressure of 760 mmHg. Next, infrared rays were applied only from below the plywood using a high-pressure mercury lamp provided in the lower part of the chamber, and the plywood was heated so that the lower surface temperature was 80 ° C and the upper surface temperature was 70 ° C. In this heating state, the ceramic plate provided on the top of the plywood was used as a dielectric, and a voltage of 20 kV and a frequency of 50 kHz were applied between the planar electrodes and the string electrodes provided on the front and back sides.
By applying an AC voltage of z and performing surface discharge, air molecules were excited to generate low-temperature plasma. After the plasma was brought into contact with the upper surface of the plywood and left for 1 hour in this state, the discharge was stopped and the plywood was cooled to 20 ° C. and then taken out of the chamber.

(Comparative Example) A wood plywood similar to that used in Example 1 was prepared, and was left in the air at 20 ° C. for 1 hour without plasma treatment.

The treated sample of the above example and the untreated sample of the comparative example were subjected to a formaldehyde emission test specified in JISA-5908. as a result,
Treated samples have a formaldehyde emission of 0.1
20 mg / l for the untreated sample versus mg / l.

[0022]

As described above, according to the substrate processing method of the present invention, formaldehyde present in the substrate can be easily and efficiently reduced, and the emission of formaldehyde over time can be sufficiently reduced. be able to. Also,
Only the plasma needs to be generated and no extra additives to the substrate itself are required. Therefore, the performance of the substrate itself is not affected, and the suitability of manufacturing and post-processing the substrate is not affected.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram in which plasma is brought into contact with a substrate subjected to temperature gradient heating.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Formaldehyde molecule 3 Plasma particle A Lower surface B Upper surface

Claims (3)

[Claims] 1. A processing method for reducing the amount of formaldehyde on a substrate containing a formaldehyde-emitting resin, the method comprising: bringing the surface of the substrate into contact with plasma. 2. The method for processing a substrate according to claim 1, wherein the surface of the substrate is brought into contact with plasma under a heating state. 3. The method for processing a substrate according to claim 2, wherein the substrate is heated with a temperature gradient such that the lower surface is at a high temperature and the upper surface is at a low temperature, and the upper surface is brought into contact with plasma. A method for processing a substrate, comprising: