JP2001179712A - Manufacturing method for particle board with composite binder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a particle board with a high strength to density ratio under stable operating conditions. SOLUTION: In the manufacturing process of the particle board, a mixture prepared by mixing ratio of 90 to 30 pts.wt. of MDI to 10 to 70 pts.wt. of an urea-melamine co-condensation resin is used as a binder. The urea-melamine condensation copolymerization resin has a melamine content of 8 to 30% and its pH is 7.5 to 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a particle board, and more particularly to a method of manufacturing a particle board having a high strength-to-density ratio.

[0002]

2. Description of the Related Art Particleboards manufactured from wood chips (wood pieces) have the advantage that uniform long products can be manufactured, and waste materials in the wood industry, such as scraps and veneers derived from plywood factories. Waste materials such as waste, backboards derived from sawmills, low-quality materials,
In addition to wood materials that are of low utility value such as unused wood, fibrous raw materials such as bagasse and flax stalks, and demolition materials for houses,
It is an excellent building material and furniture material that can effectively use railroad sleepers and pine dead wood (insect damage materials), and from the viewpoint of sustainable use of forest resources.

[0003]

However, generally available particle boards are high in specific gravity and heavy, and there is a problem in that workability in handling, processing and installation is inferior. For example, in order to obtain a particle board having a strength exceeding the bending strength of 18 types specified in JIS A 5908, the specific gravity has to be as heavy as 0.7 or more.

[0004] In order to solve such a problem, for example, as disclosed in Japanese Patent Publication No. 58-41192, a chip (woody piece) is coated with a thermoplastic resin, and a thermosetting resin adhesive is further applied thereon. There has been proposed a method of applying heat and pressure after application to suppress the penetration of the adhesive into the chip and increase the peel strength. However, when this prior art is effective in reducing the weight of the board and improving the peel strength,
The bending strength of the particle board was not sufficient.

The present inventors have solved a problem in the prior art, and have disclosed a particle board having a large strength-to-bend strength-to-density ratio and a method for manufacturing the same.
No. 958.

In the above invention, the application amount of the adhesive to the chip is remarkably increased to manufacture a high-performance particle board or a lightweight particle board. In such a particle board manufacturing process, there is a problem that the adhesive force of the chip (raw material) coated with the adhesive increases, which makes it difficult to transport the raw material and also makes it difficult to form uniformly in the forming process. is there.

An object of the present invention is to solve the above-mentioned problems and to provide a method capable of producing a particle board having a large strength-to-density ratio under a stable operating condition.

[0008]

According to a first aspect of the present invention, there is provided a particle board manufacturing process, wherein MDI is added to a urea-melamine co-condensation resin: 10 to 70 parts by weight. The gist is to use a mixture blended at a ratio of 90 parts by weight to 30 parts by weight as a binder.

According to a second aspect of the present invention, the urea-melamine co-condensation resin has a melamine content of 8% to 30%,
The method for producing a particle board using the composite binder according to claim 1, wherein the pH is 7.5 to 9.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on preferred embodiments.

[0011]

Since the present invention is constructed as described above, in the process of manufacturing a particle board having a large strength-to-density ratio using a large amount of adhesive, the adhesive force of a chip (raw material) spray-coated with the adhesive is applied. Eliminates troubles in the raw material transfer process and the forming process caused by the increase, and brings about stable operation in the production of particle board.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, as an adhesive to be sprayed and applied to chips, urea / melamine cocondensation resin: 10 to 70 parts by weight, MDI (diphenylmethane diisocyanate): 90 to 30 parts by weight. Is used as a binder.

When a particle board is manufactured by using only MDI as an adhesive, the chip (raw material) spray-coated with MDI has an extremely small adhesive force, and when forming the raw material, the mat collapses, that is, collapses at the ends of the forming mat. This causes an increase in raw material loss.

For this reason, conventionally, when MDI is added to an amino resin adhesive for the purpose of shortening the hot-press molding time, 1
The addition was limited to a small amount of less than 0%. Or,
MDI was sprayed and applied to the core layer chip, and the upper and lower surface layer chips were used as a hybrid type binder using an amino resin or a phenol resin.

The present invention is directed to a process for producing a particle board having a high strength-to-density ratio, for example, a specific gravity:
In the case of a conventional particle board having a weight of 0.7 to 0.8, the bending strength is 26 N / m, even if the strength is divided.
Particle board of m ^{2 to} 32 N / mm ^2, which is 1.4 to 1.9 times the strength level of conventional products, and lightweight particles having a specific gravity of 0.3 to 0.45, which could not be manufactured conventionally. It is intended for a particle board manufacturing process in which an amino resin adhesive is sprayed and applied to a chip in a much larger amount than conventional levels in order to obtain a board.

In such a particle board manufacturing process in which a large amount of an amino resin adhesive is sprayed onto a chip, the chip (raw material) spray-coated with the adhesive has an increased adhesive force, and the raw material is formed. Raw materials are sticky in a transporting step or a forming step to a process, causing troubles such as causing a transporting trouble or making uniform forming impossible.

In the present invention, the small adhesive strength of the chip sprayed and coated with MDI is used in reverse, and amino is used as a binder in a particle board manufacturing process in which a large amount of amino resin adhesive is sprayed and coated. A binder in which MDI is mixed with a resin is used. By using a binder containing MDI, in the stage before hot pressing, particle board with the expected physical properties can be obtained by carrying out transport and forming smoothly while suppressing excessive adhesive force and hot pressing. Obtainable.

The mixing ratio of MDI to the amino resin is from 10 parts by weight of urea / melamine co-condensation resin as the amino resin.
MDI: 90 to 30 parts by weight with respect to 70 parts by weight.

If the compounding ratio of MDI is less than 30 parts by weight, the amount of adhesion of the chip (raw material) to which the adhesive is applied becomes excessive, and the smoothness of the raw material in the present invention such as smooth conveyance of the raw material and uniform forming in the forming process is obtained. I can not achieve my purpose.

On the other hand, if the blending ratio of MDI exceeds 90 parts by weight, the end of the forming mat collapses, causing a mat collapse, resulting in an increase in raw material loss (decrease in yield).

The melamine content of the urea / melamine cocondensation resin in the binder used in the particle board production process of the present invention is preferably in the range of 8% to 30%. Further, the pH is preferably 7.5 to 9
Within the range.

When the melamine content in the urea-melamine co-condensation resin is less than 8%, the strength of the particle board obtained by hot pressing is reduced. On the other hand, when the melamine content is 30%, the effect of improving the strength of the particle board is saturated, and when the melamine content exceeds 30%, the production cost of the particle board increases.

The pH of the urea-melamine co-condensation resin is 7.5
If it is less than the above range, the crosslinking / curing reaction of the MDI is suppressed, and the bonding strength between chips in the particle board is reduced. On the other hand, in the alkaline region where the pH exceeds 9, the reaction is too fast and reacts before hot pressing by hot pressing, resulting in a decrease in the strength of the particle board obtained by hot pressing.

The MDI used in the present invention may be either an emulsifying type or a non-emulsifying type. Also, a wax emulsion or an amino resin curing agent such as ammonium chloride can be used in combination.

Example 1 A binder prepared by mixing 60 parts by weight of urea melamine co-condensation resin and 40 parts by weight of MDI with respect to the upper and lower surface chips was 40% (weight ratio of the solid content of the adhesive to the absolute dry amount of the chips). ), And sprayed and mixed using a spray at an adhesive spray ratio of 20% to the core layer chip.

The melamine content in the urea-melamine co-condensation resin was set to 20% and the pH was set to 8. The binder contained a curing agent (ammonium chloride) and a wax emulsion, and the upper and lower surface layers contained an adhesive. On the other hand, it was previously blended so as to be 0.3% by weight and a wax solid content ratio of 2% to the absolute dry amount of the chips, and 2.0% and 0.2% for the core layer.

Next, each of the chips (raw materials) to which the adhesive was applied was mixed with a product having a specific gravity of 0.74 and a product thickness of 28 m.
m, 40% by weight for upper and lower surface layers, 6 for core layer
Weigh at a ratio of 0% by weight, perform forming, 28m
Temperature: 180 ° C., pressure: 3 using a spacer having a thickness of m
Hot-press molding was performed under the conditions of 0 kgf / cm ² and time: 3 minutes and 30 seconds.

The physical property test results of the obtained particle board were as follows: normal bending strength: 32 N / mm ² , 70 ° C. hot water wet bending strength: 22 N / mm ² , peel strength: 1.2 kgf /
cm ² . The physical properties of the particle board
The test was performed based on JIS A 5908.

[0029]

According to the present invention, a particle board having a large strength-to-density ratio can be smoothly transported while suppressing the adhesive force of the raw material, despite the use of a large amount of amino resin adhesive.
It can be manufactured under stable operating conditions such as formation of a uniform forming mat.

According to the second aspect of the present invention, it is possible to produce a particle board having more excellent physical properties under a stable operating condition.

Continued on the front page F-term (reference) 2B260 BA01 BA18 CB01 CD02 CD06 DA02 DA03 DA05 DC15 DD02 EA01 EA05 EB02 EB06 EB11 EB19 EB21

Claims (2)

[Claims] In a particle board manufacturing process, a mixture of urea / melamine cocondensation resin: MDI in a ratio of 90 to 30 parts by weight with respect to 10 to 70 parts by weight of a urea / melamine co-condensation resin is used as a binder. A method for producing a particle board using a composite binder. 2. The method according to claim 1, wherein the urea / melamine co-condensation resin has a melamine content of 8% to 30% and a pH of 7.5 to 9.