JP2005238806A - Bark board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a board which consists of the bark of a Japanese cedar or that of a Japanese cypress, which makes the quantity of emitted formaldehyde small, which has proper strength performance, and which is excellent in antifungal properties. <P>SOLUTION: The bark of the Japanese cedar or that of Japanese cypress occupies at least 20 wt% of a lignocellulose substance; an adhesive is produced by making grass lignin react with phenols and aldehydes in the presence of an alkaline catalyst or an acid catalyst; and the 0.2-30 wt% adhesive is added to the lignocellulose substance, heated and pressurized, so that the board can be formed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a board such as a particle board or a fiber board using an adhesive using a gramineous plant lignin.

[Background technology]
Boards such as particle boards and fiber boards are generally formed by adding an adhesive to a lignocellulosic material chip, fiber or the like and heating and pressing them.

  Conventionally, adhesives such as urea resins, urea melamine resins, and phenol resins have been used as adhesives for these boards. In recent years, formaldehyde has been released from boards that use these adhesives, and this is the human body. It has become a problem to adversely affect the environment.

  Some of the inventors have previously invented boards with very low formaldehyde generation and good strength characteristics using an adhesive mainly composed of gramineous lignin. (Patent No. 336189)

  However, while the presence of formaldehyde in the conventional board is harmful to the human body, it plays an antibacterial role. Therefore, the board of the previous patent No. 336189 has the disadvantage of low antibacterial properties instead of being harmless to the human body.

A natural or synthetic antibacterial agent can be easily added to provide antibacterial properties. However, when using an adhesive that uses a grass lignin, the combination of the antibacterial agent causes hardening inhibition and good strength. A board with performance cannot be obtained.
[Disclosure of the Invention]

[Problems to be solved by the invention]
An object of the present invention is to provide a board having a very small amount of formaldehyde released, a good strength performance, and an excellent antibacterial property.

[Means for solving problems]
As a result of intensive research, the inventors have used cedar or cypress bark as a lignocellulosic material, thereby using an adhesive with a very low release amount of formaldehyde mainly composed of a grass family lignin. A board with performance and excellent antibacterial properties was obtained.

  That is, the board of the present invention is a board obtained by adding 0.2 to 30% by weight of an adhesive to a lignocellulosic material and heating and pressurizing, and 20% by weight or more of the lignocellulosic material is cedar or cypress. And the adhesive is obtained by reacting gramineous plant lignin with phenols and aldehydes in the presence of an alkali catalyst or an acidic catalyst.

  The board in the present invention is a board formed by mixing a small piece of lignocellulosic material such as wood, pulp, and herbaceous materials, such as particle board and fiber board, with an adhesive and heating and pressing.

  In the present invention, at least 20% by weight, preferably 30 to 80% by weight of the lignocellulosic material is cedar or cypress bark. When the amount of cedar or cypress bark used is less than 20% by weight, sufficient antibacterial properties of the board are not exhibited.

  The adhesive used in the present invention is obtained by reacting gramineous plant lignin with phenols and aldehydes in the presence of an alkali catalyst or an acidic catalyst.

  In such an adhesive, the weight of the gramineous lignin used is preferably 30% by weight or more, and preferably 50 to 80% by weight of the solid content of the adhesive obtained by the reaction.

  Such an adhesive is used in an amount of 0.2 to 30% by weight, preferably 0.5 to 20% by weight, based on the lignocellulosic material.

  Gramineous plant lignins used in such adhesives include lignins of all gramineous plants such as rice, wheat, bamboo, sugarcane, reeds, and cucumbers.

  Such gramineous lignin may of course be extracted directly from gramineous plants, but it is industrially advantageous to be extracted from pulp waste liquor. When using lignin extracted from pulp waste liquor, the type of cooking method is any of so-called chemical pulping methods such as kraft method, sulfite method, soda method, semi-chemical method, thermomechanical pulping method, organic solvent method, etc. Things can also be used.

  As phenols used in the adhesive used in the present invention, all phenols such as phenol, cresol, xylenol, bisphenol A, bisphenol F, resorcinol can be used. It is particularly preferred to use The amount used is preferably 100% by weight or less, particularly preferably 5 to 60% by weight, based on the grass lignin. The amount used may exceed 100% by weight, but the cost is high and the improvement of physical properties cannot be expected.

  As the aldehydes, formaldehyde, acetaldehyde, furfural, benzaldehyde, glyoxal, and the like can be used, but it is particularly preferable to use formaldehyde or furfural from the viewpoint of performance and cost. These may be used alone or in combination of two or more. The amount used is preferably in the range of 0.2 to 5.0 in terms of the molar ratio of formyl group to phenol monomer.

  As formaldehyde, all formaldehydes such as formalin, paraformaldehyde and polyoxymethylene can be used. The amount used is preferably in the range of 1.2 to 5.0, more preferably in the range of 1.8 to 3.5 in terms of molar ratio to the phenol monomer. Formaldehyde exhibits excellent strength performance when used in small amounts.

  The adhesive of the present invention is preferably obtained by reacting the above gramineous plant lignin with phenols and aldehydes under alkaline conditions of pH 9 or more, particularly pH 10 or more. As the catalyst, any alkali catalyst that satisfies such pH conditions, including oxides or hydroxides of alkali metals and alkaline earth metals, can be used.

  The reaction of lignin with phenols and aldehydes is the reaction of lignin with phenols followed by the reaction of aldehydes, the reaction of lignin with phenols and aldehydes at the same time, the reaction of phenols and aldehydes. Examples of the method of reacting lignin with a reaction product of phenols and aldehydes are preferred.

  Such a board of the present invention has the same strength performance as the board product using the adhesive mainly composed of the previous gramineous plant lignin, has the same low formaldehyde emission amount, and far superior antibacterial properties. Have Such strength performance includes mechanical strength and water absorption thickness expansion coefficient.

  The formaldehyde emission amount of the board of the present invention varies depending on the amount of adhesive used and the material of the lignocellulosic material, but is a measurement method defined in JIS A 5908 5.11, and is usually 0.0 to 0.5 mg / l, preferably Is 0.0 to 0.3 mg / l.

Further, the strength performance of the board of the present invention varies depending on the amount of adhesive used and the density of the target board, but the bending strength is 3 N / mm ² or more as the mechanical strength, preferably 8 N / mm ^{2 to} 25 N / a mm ^2, water thickness expansion rate of 20% or less in the measurement method defined in JIS a 5908 5.10, preferably not more than 12%.

  In addition, the antibacterial properties of the board of the present invention cannot be specified unconditionally due to various natural conditions, but usually 30 days or more, preferably 50 days or more in an environment of 90% or higher humidity with sufficient water contained. Mold does not occur even if left unattended.

The reason why the board of the present invention has good strength performance and excellent antibacterial properties can be considered as follows.
The bark of cedar and cypress has an antibacterial component called ferguinol. Ferguinol is evenly contained in the bark of cedar or cypress, and the amount of ferguinol present in the vicinity of the bonding surface between the chips on the board is very small, and therefore does not inhibit the curing of the adhesive. Therefore, the strength performance of the board is kept good.
On the other hand, since the amount of ferguinol present outside the vicinity of the bonding surface between the chips of the board is large, it stays inside the board after the board is molded and exhibits antibacterial properties.

[The invention's effect]
The present invention has the following effects.
(1) The board of the present invention has excellent antibacterial properties.
(2) The board of the present invention has excellent mechanical strength.
(3) The board of the present invention has excellent water resistance.
(4) The board of the present invention solves the problem of environmental pollution caused by pulp waste liquid.
(5) The board of the present invention can effectively use unused resources of cypress and cedar skin.
(6) The board of the present invention is economically advantageous because a lignocellulosic board can be produced at a low raw material cost.
(7) The board of the present invention is extremely safe for the human body because the amount of formaldehyde generated is extremely small compared to the conventional wooden board.

[Best Mode for Carrying Out the Invention / Example]
EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited by this.

  In the examples, the adhesive was produced by the following method. That is, as a gramineous plant lignin, a lignin powder extracted from a wheat straw pulp waste liquid by a soda cooking method was used. Further, in a reaction vessel equipped with a cooler and a stirrer, formalin corresponding to a molar ratio of 3 with respect to phenol and phenol, and sodium hydroxide with a molar ratio of 0.33 with respect to phenol were reacted at 50 ° C. for 40 minutes, Formaldehyde reaction product X was prepared. Next, the reaction product X is added to the grass lignin so that the proportion of phenol in the reaction product X is 20% by weight with respect to the grass lignin, and the concentration further becomes 40% by weight. Thus, water was added and reacted at 80 ° C. for 90 minutes to produce an adhesive.

  In addition, in order to examine the bending strength, water resistance, formaldehyde emission amount and antibacterial properties of the board of the present invention, a particle board using the resin composition of the present invention as an adhesive was produced.

The particle board is a demolition material or cedar bark as a lignocellulosic material, or an absolutely dry flake obtained by cutting a cypress bark using a knife ring flaker (Pallman) with a blade size of 0.6 mm, After applying 10% by weight of adhesive as a non-volatile component to 340 g of the flakes with a spray gun, the mat was formed in a 22 cm square forming box using a 1 cm size spacer (target specific gravity 0.7 g / cm ³ ) and a pressure of 50 kgf / cm ² and heating at a temperature of 210 ° C. for 15 minutes.

  Further, the bending strength was measured for examining the strength performance of the board, and the water absorption thickness expansion coefficient was measured for examining the water resistance. The bending strength was determined by an average value of measured values of three test pieces cut to a size of 50 × 200 mm in accordance with JIS A 5908 5.5. The water absorption thickness expansion coefficient was determined by an average value of measured values of three test pieces cut to a size of 50 × 50 mm in accordance with JIS A 5908 5.10. The amount of formaldehyde released was determined according to JIS A 5908 5.11.

In order to examine the antibacterial property of the board, the test was conducted by the following method.
That is, three test pieces cut to a size of 50 × 50 mm were immersed in water for 2 hours, and then left in a room with a humidity of 90% or more and a temperature of 25 ± 5 ° C. The presence or absence of mold was examined over time.

Comparative Example 1
A particle board was manufactured using the flakes of the building demolition material and the adhesive. The particle board had a bending strength of 21 N / cm ² , a water absorption thickness expansion rate of 9%, and a formaldehyde emission of 0.1 mg / l. In the antibacterial test, mold was generated after 15 days.

Example 1
A particle board was produced in the same manner as in Comparative Example 1 except that the flakes were cedar bark. The particle board had a bending strength of 19 N / cm ² , a water absorption thickness expansion coefficient of 8%, and a formaldehyde emission amount of 0.1 mg / l. In the antibacterial test, mold did not occur even after 100 days.

Example 2
A particle board was produced in the same manner as in Comparative Example 1 except that the flakes were cypress bark. The particle board had a bending strength of 18 N / cm ² , a water absorption thickness expansion rate of 7%, and a formaldehyde emission of 0.1 mg / l. In the antibacterial test, mold did not occur even after 100 days.

Example 3
A particle board was produced by the same method as Comparative Example 1 except that the weight ratio of the building demolition material and the cedar bark was 1: 1. The particle board had a bending strength of 21 N / cm ² , a water absorption thickness expansion rate of 8%, and a formaldehyde emission of 0.1 mg / l. In the antibacterial test, mold did not occur even after 100 days.

Comparative Example 2
A particle board was produced in the same manner as in Comparative Example 1 except that a commercially available urea melamine resin adhesive was used. The particle board had a bending strength of 21 N / cm ² , a water absorption thickness expansion rate of 10%, and a formaldehyde emission of 1.2 mg / l. In the antibacterial test, mold did not occur even after 100 days had passed.

Comparative Example 3
A particle board was produced in the same manner as in Comparative Example 1 except that a commercially available phenol resin adhesive was used. The particle board had a bending strength of 20 N / cm ² , a water absorption thickness expansion rate of 9%, and a formaldehyde emission of 0.9 mg / l. In the antibacterial test, mold was generated after 60 days.

Claims (4)

  A board obtained by adding 0.2 to 30% by weight of an adhesive to a lignocellulosic material and heating and pressing to form a board, wherein 20% by weight or more of the lignocellulosic material is cedar or cypress bark, and the bonding The board | substrate characterized by the agent reacting gramineous plant lignin, phenols, and aldehydes in presence of an alkali catalyst or an acidic catalyst.   The board according to claim 1, which is formed by heating and pressing at a temperature of 180 to 250 ° C.   The board according to claim 1 or 2, wherein the adhesive is a reaction product of lignin, phenols and aldehydes under alkaline conditions of pH 9 or higher.   The board according to claim 3, wherein the adhesive uses formaldehyde as an aldehyde, and the molar ratio of formaldehyde to phenol monomer is 1.2 to 5.0.