WO2003085059A1 - Adhesive composition for processed wood product, and processed wood product produced by use of said adhesive composition - Google Patents

Abstract

An adhesive composition for a processed wood product utilizing a natural resource, which has an excellent adhesion strength being the same as or higher than that of a conventional synthetic adhesive for a processed wood product, generates no volatile substance harmful to a human body after application, and exhibits excellent natural circulation property and environmental compatibility; and a processed wood product which is produced by the use of the adhesive composition for a processed wood product and is excellent in natural circulation property and environmental compatibility.

Description

 Description Adhesive composition for processed wood products, and processed wood products manufactured using the adhesive composition

 The present invention relates to an adhesive composition for a processed wood product containing an acidic aqueous solution of chitosan, and a processed wood product manufactured using the adhesive composition.

Background art

 Conventionally, in the manufacture of processed products (wood products) made from wood, natural adhesives such as pine resin, persimmon juice, and glue have been used as adhesives. However, all of these natural adhesives have low adhesive strength, and more unfortunately, these raw materials are now becoming expensive.

 Instead of the natural adhesive, synthetic adhesives such as urea resin, melamine resin, phenol resin and polyacetate resin are also used. Synthetic adhesives have excellent adhesive strength and are inexpensive.

 In recent years, the generation of volatile substances harmful to the human body has been a problem from wood products such as furniture and building interior materials using synthetic adhesives. Of particular interest as harmful volatiles is formaldehyde, which is an effective disinfectant, disinfectant, preservative, and preservative in the synthetic adhesives, generally as a raw material, or optionally. It is formulated as an antibacterial or insect repellent. However, formaldehyde is also a volatile chemical designated by the Ministry of Health as a deleterious substance. Formaldehyde from furniture and interior materials manufactured using such synthetic adhesives continues to evaporate into the atmosphere for a long time. If the concentration exceeds a certain level, the user or occupant may develop a type of allergic syndrome called sick house syndrome.

Further, wood products using such a synthetic adhesive also have a problem that, when used or applied, when discarded or reused, natural circulation and environmental compatibility are low. Therefore, the development of a new type of adhesive for processed wood products that does not contain volatile substances harmful to the human body and has excellent natural circulation and environmental compatibility is urgently needed.

Disclosure of the invention

 (Technical problems to be solved by the invention)

 Accordingly, an object of the present invention was to provide an adhesive composition for a processed wood product, which solved the above-mentioned problems, and a processed wood product manufactured using the adhesive composition.

 (How to solve it)

 Chitin and chitosan are polysaccharides contained in the crustacean of Kaedebi, the hull of insects, the organs of mollusks such as squid and shellfish, and the cell walls of fungi and the cells of filamentous fungi. Both chitin and chitosan have repeating units of darcosamine and N-acetyl darcosamine of the following formula. In general, those having a degree of deacetylation of an N-acetylamino group of 50% or less in the following formula (that is, those having a y / (x + y) ratio of 0.5 or less) are called chitin, which is referred to as chitin. Deacetylation degree by hydrolysis 50% or more

(y Z (x + yb O, 5 or more)) and those that dissolve in acid are called chitosan, where chitin is dissolved only in special solvents such as formic acid, but chitosan is weak acid It is known to dissolve in acidic aqueous solutions containing

 [Formula 1]

 Chitin and chitosan are natural resources and harmless to the human body, and in recent years have attracted attention for their excellent antibacterial activity and environmental purification. Therefore, it is expected to be used as a water purification material, and also in many fields such as food, agriculture, fisheries and livestock, and medical care.

Furthermore, as shown in the above formula, chitin and chitosan have a similar molecular structure to cellulose contained in wood, paper, and the like. Is also considered excellent.

 Therefore, when an acidic aqueous solution of chitosan was used as an adhesive for wood products, it was found that the adhesive strength was equal to or higher than that of the synthetic adhesive. Further, the present inventors have confirmed that a wood product bonded using an acidic aqueous solution of chitosan exhibits high adhesiveness even after being immersed in water, that is, exhibits excellent water resistance. It was completed.

 Accordingly, the present invention provides an adhesive composition for wood products containing an acidic aqueous solution of chitosan, and a wood product manufactured using the adhesive composition.

BEST MODE FOR CARRYING OUT THE INVENTION

Adhesive composition

 A first aspect of the present invention is an adhesive composition for a processed wood product, comprising an acidic aqueous solution of chitosan.

 The chitosan preferably used in the present invention is sufficiently soluble in an aqueous solution containing a weak acid. In particular, the degree of deacetylation of the N-acetylamino group in the above formula is 50% or more (in the above formula, y / (x + y) ratio of 0.5 or more). In the present invention, most preferably, chitosan having a degree of deacetylation of the N-acetylamino group in the above formula of 70 to 92% is used.

 Chitosan having the above-mentioned characteristics is, as disclosed in Chitin, Chitosan Handbook (edited by Chitin and Chitosan Study Group, Gihodo Shuppan, 1995), chitin (for example, Koyo Chemical Co., Ltd., trade name SEC), It can be prepared by hydrolysis using an alkaline solution such as sodium hydroxide (40%) at 100 to 130 ° C. for 2 to 8 hours.

 Alternatively, as long as it has the above characteristics, industrially commercially available chitosan may be used as it is (for example, trade name S K-10, S K-50, etc., manufactured by Koyo Chemical Canole Co., Ltd.).

 By dissolving the thus obtained chitosan in an acidic aqueous solution, the adhesive composition of the present invention is prepared.

The acidic aqueous solution for dissolving chitosan is an aqueous solution containing a weak acid. Weak acids include inorganic acids such as phosphoric acid, diluted hydrochloric acid, boric acid, diluted sulfuric acid, and diluted nitric acid, and carbon atoms in the molecule. Includes organic mono-, di- and tri-carboxylic acids of 1 to 7 numbers. Examples of organic mono-, di- and tri-carboxylic acids include formic acid, acetic acid, propionic acid, glyconoleic acid, lactic acid, cunic acid, malonic acid, oxalic acid, succinic acid, daltaric acid, adipic acid, benzoic acid , Malic acid, atarilic acid, methacrylic acid, chromanic acid, dalconic acid, maleic acid, fumaric acid, phthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, and the like. Organic sulfonic acids such as methanesulfonic acid and paratoluenesulfonic acid may also be used as the weak acid.

 The concentration of the acidic aqueous solution is preferably in the range of 1 to 20%, particularly preferably 5 to 10%.

 Most preferably, the acidic aqueous solution is an aqueous solution of acetic acid of 3 to 0% containing acetic acid of equal weight to the dissolved chitosan.

 The chitosan is contained in the range of 0.5 to 15% by weight, particularly preferably 2 to 10% by weight based on the total weight of the adhesive composition of the present invention, whereby good adhesion to wood is obtained. Strength can be imparted.

 Further, the adhesive composition of the present invention may contain, as necessary, various additives usually contained in the art. Additives include methanol, ethanol, urea, silica-alumina, calcium carbonate and talc.

 The total weight of said additives may range from 1 to 10% by weight relative to the total weight of the adhesive composition.

 The additives may be added simultaneously with dissolving the chitosan in the acidic aqueous solution or after dissolving the chitosan, depending on the type and function.

 Since the adhesive composition of the present invention is prepared in a solution state, it can be uniformly applied to an object to be coated.

The adhesive composition of the present invention, the surface of the object to be coated to be cane adhesive, preferably 0. from 005 to 0. L, more preferably GZcm ² applied at 0.01 to 0.05 coating fabric of GZcm ² Thereby, an excellent tensile adhesive strength of about ΙδΝΖπιπι ² is achieved.

Wood products

The present invention also provides, as a second aspect, a wooden product manufactured using the adhesive composition of the present invention. Applicable wood products are not only wood itself, but also It may be a board and a laminated wood. Accordingly, the wood products provided by the present invention include processed and molded wood plywood or glulam, and combinations thereof, and include, for example, building exteriors such as beams, walls and floors. Examples include interior materials, furniture such as desks, wooden toys, musical instruments, decorative ornaments, and their components.

 The processed wood product of the present invention is excellent in the ability to be manufactured using the adhesive composition of the present invention containing chitosan, which is a natural resource, as well as excellent in natural circulation and environmental compatibility. The invention's effect

 The adhesive thread composition of the present invention is a natural resource and contains chitosan that is harmless to the human body. By applying the adhesive composition of the present invention, in the bonding between woods, the bonding strength is equal to or higher than that of a conventionally known synthetic adhesive, specifically, the coating amount is 0.

Excellent tensile bond strengths on the order of 1-5 NZmm ² can be achieved when applied at 0.05-0.1 g Z cm ² .

 It is also known that chitosan contained in the adhesive composition of the present invention has an antibacterial property and an environmental purification action. Therefore, when the adhesive composition of the present invention is used in the manufacture of exterior and interior materials, furniture, and processed wood products such as toys and educational materials in schools and medical facilities, the present invention can be used. Wood products can also be expected to have excellent natural circulation and environmental compatibility, as well as antibacterial properties and environmental purification.

 Wood processed products bonded using the adhesive composition of the present invention can be applied to applications requiring water resistance because the adhesiveness of the processed wood products is not reduced by adhesion or immersion of water.

Example

Preparation Example 1: Preparation of adhesive composition

 The adhesive of the present invention is obtained by dissolving chitosan fine particles (size 80 mesh or more, deacetylation degree 87%) obtained by mechanically pulverizing chitosan SK-50 manufactured by Koyo Chemical in an acetic acid aqueous solution. A composition was prepared. The chitosan content in the obtained adhesive composition was 8% by weight based on the total weight of the composition. /. Met.

Preparation Example 2: Adhesion and composition Chitosan SK-10 manufactured by Koyo Chemical Co., Ltd. What is Preparation Example 1 by dissolving chitosan microparticles (size: 80 mesh or more, deacetylation degree: 71%) obtained by mechanically pulverizing in an acetic acid aqueous solution. Another adhesive composition of the present invention was prepared. The concentration of chitosan in this adhesive composition was 8% by weight based on the total weight of the composition.

Control adhesive

 Aqueous polymer-isocyanate two-pack type synthetic adhesive manufactured by Aikiri Kogyo Co., Ltd., trade name Aibon-I AUH_1 was used as a control adhesive.

Example

 The following tests (1) and (2) were performed to examine the adhesiveness of each of the adhesive compositions obtained in Preparation Examples 1 and 2 and the control adhesive to wood. (1) Tensile bond strength test-Preparation of two test pieces:

The cedar pieces were processed as shown in Fig. 1 in accordance with JISK 6851 to form a two-ply plywood, which was then placed with the bonding surfaces facing each other. On one of opposite faces, it was uniformly applied each adhesive composition obtained in Preparation Example 1 and 2 and the control adhesive at each coating weight of about 0. 0 1 2 g Z cm 2, the other One of the cedar pieces was stuck together and subjected to 1B free pressure bonding at room temperature under the conditions of ^{20 to} 5 O kg / cm ² to produce a test piece of two pieces.

 Cypress wood, cedar and cypress thinned wood of the same dimensions were used in place of cedar wood, and according to the same procedure, two test pieces of cypress wood, cedar and cypress thinned wood were prepared.

Preparation of triplicate test strips:

 Two pieces of plywood prepared by laying the same cedar wood sideways between two pieces of cedar wood were prepared, and these were used as substitutes for the plywood of the two pieces. Except that the test pieces were used, three test pieces were prepared according to JISK 6851 (see Fig. 2).

 Cypress wood, cedar and cypress thinned wood of the same dimensions were used in place of the cedar wood pieces, and according to the same procedure, three test pieces of cypress wood, cedar and cypress thinned wood were prepared.

Test method:

The two-piece or three-piece test pieces obtained above were respectively subjected to 25 ° C and 60% According to JIS K6851 under the standard condition of RH, the maximum point load (N) when the adhesion between the pieces of wood was broken was measured at a distance between the chucks of 10 mm and a pulling speed of 5 mm, min. The obtained maximum point load (N) was divided by the adhesive area of the test piece (331.5 Omm ² ) to calculate the tensile adhesive strength. All results are shown in Tables 1 and 2 below.

 (2) Water resistance test

 A two-piece test piece made of the cedar material of Example 2 was immersed in water at room temperature for 24 hours. Then, after taking out and drying, the tensile adhesive strength was tested in the same manner as in the above (1). Table 1 shows the results.

 【table 1】

 *: The adhesive composition of the present invention (an aqueous acetic acid solution containing 8% by weight of chitosan (SK-50) having a degree of deacetylation of 87%)

 **: Adhesive composition of the present invention (aqueous acid solution containing 8% by weight of chitosan (SK-10) having a degree of deacetylation of 71./.)

 ***: Ai Riki Kogyo's 7-functional polymer-isocyanate-based two-pack synthetic adhesive, trade name Aibon-AUH-1

The results in Table 1 indicate that the adhesive composition of the present invention (Preparation Examples 1 and 2) has excellent tensile strength equal to or higher than that of a commercially available synthetic adhesive (Comparative Preparation Example) regardless of the type of wood to be applied. It can be seen that the adhesive strength is high. In this regard, from the photograph of FIG. 3 showing the appearance of the test piece to which the adhesive composition of the present invention of Preparation Example 1 was applied after the test, it was found that the wood in the fractured part of the test piece was not in the adhesive layer but in the wood. It can be confirmed that it is generated from the vicinity of the adhesive applied portion of the piece. This also indicates that the adhesive composition of the present invention has such a high adhesive strength as to cause cohesive failure.

 From the results shown in Table 2, it can be seen that the adhesive thread and the composition of the present invention (Preparation Example 2) also exhibits excellent adhesive strength in bonding thinned timber, which is equivalent to ordinary wood.

 Further, Table 1 also shows the results of the test pieces using the adhesive composition of the present invention (Preparation Example 2) after the water resistance test. Since this is equivalent to the value before the water resistance test, it was also found that the adhesive composition of the present invention had excellent water resistance.

BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a top view and a side view showing the shape and dimensions of a two-piece test piece according to JIS 6849.

 FIG. 2 is a top view and a side view showing the shape and dimensions of a three-piece test piece conforming to JIS K 649.

 FIG. 3 is a photograph showing two and three test pieces of cedar wood to which the adhesive composition of the present invention (Preparation Example 1), which was broken after the tensile adhesion test, was applied.

Claims

The scope of the claims

1. Adhesive for processed wood products containing acidic aqueous solution of chitosan.

 2. Processed wood products manufactured using glue for processed wood products containing an acidic aqueous solution of chitosan.