JPH0440163B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a laminated veneer of stable quality that can be widely used for building walls, furniture, cabinet floors, etc. In the conventional manufacturing method of laminated veneer, multiple laminators of the same or different types are used, which are made from high-quality hardwood or coniferous wood, their offcuts, or raw lumber from small-diameter trees. Because there is a large variation in the number of logs and multiple laminators are glued together in an unstable state, if you boil them in the same way as regular logs and fritches,
There was a problem in that the assembled laminars were subject to rapid expansion and contraction, resulting in damage to the adhesive layer. Therefore, the laminated veneer obtained by cutting has poor dimensional stability.
Furthermore, the adhesiveness was poor and the quality was not stable. Incidentally, recently, water-based vinyl urethane adhesives defined below have been developed as adhesives for woodworking, particularly for laminated wood and composite materials. However, as far as the present inventors know, there is no example yet of creating a laminated fritch using this adhesive and producing a laminated veneer by cutting or the like. It has been confirmed from the results of various experiments that water-based vinyl urethane adhesives have adhesive strength equivalent to or superior to conventional resorcinol resin adhesives and the like. However, water-based vinyl urethane adhesives are preferably applied to dry wood surfaces because a significant amount of water in the adhesive must be lost in order to completely cure. If applied to a wood surface with a moisture content significantly higher than the fiber saturation point, the curing process of the adhesive will be significantly delayed, leading to poor adhesion. On the other hand, Yuzo Handa, Complete Book of Practical Wood Processing 3, Wood Adhesion and Adhesives,
Morikita Publishing Co., Ltd., published October 1960, No. 20-21
As described in the paper, it is generally said that the highest adhesive strength is obtained when wood is dried to a moisture content of 8 to 12%. Therefore, even in the case of water-based vinyl urethane adhesives, it is considered desirable to apply them to wood whose moisture content has been adjusted to be as low as possible, especially within the above range, and this is somewhat difficult for those skilled in the art. It had become common sense. Furthermore, water-based vinyl urethane adhesives usually contain a crosslinking agent to accelerate curing. When the proportion of the crosslinking agent is increased sequentially from 5, 10, 15, and 20%, the adhesive strength of the adhesive also increases, but the amount of increase gradually becomes smaller, and when it exceeds 20%, it becomes almost saturated. reach the area. This fact shows that the wood industry
Volume 34, June, Volume 387, 1979, pages 14-18, Adhesive
June 1979, pages 244-249, and adhesive 1976
This can be easily confirmed from the description in publications such as October, pages 352 to 362. Therefore, it has been thought that a water-based vinyl urethane adhesive containing 15 to 20 parts of a crosslinking agent is appropriate. However, even when water-based vinyl urethane adhesives are applied under the above-mentioned desirable conditions, the resulting laminated veneer is a product of considerably inferior quality, or even close to optimal quality. Even if a laminated veneer could be obtained, the problem was that the productivity was very low, making it extremely disadvantageous for actual mass production. The present inventor confirmed this fact in the course of his own research. The present invention was made to solve the above-mentioned problems, and an object of the present invention is to provide a method capable of manufacturing a laminated veneer of optimum quality with high productivity. After further research and testing, the inventor discovered that the surface of the laminar for lamination was completely unexpected.
The moisture content is adjusted to a range of 15 to 18%, which is drying from the inside but wetter than the optimal conditions, and for adhesion of the lamina,
A water-based vinyl urethane adhesive containing a very large amount of crosslinking agent (30 to 50 parts in winter, 20 to 40 parts in spring/autumn, and 18 to 30 parts in summer) is applied, and the assembled fritsch thus prepared is exposed to air under specific conditions. The present invention was completed based on the discovery that by curing and then curing in water, a laminated veneer of optimal quality with excellent dimensional stability, surface properties, etc. can be obtained with high productivity. That is, the method for producing a laminated veneer according to the present invention involves smoothing the surface to be bonded, and then drying the surface so that the moisture content is 15 to 18% than the inside, so that the surface moisture is adjusted. prepare a laminar for use, then arrange the laminar in desired dimensions and shape,
Next, a water-soluble polymer and/or an aqueous polymer dispersion is used as a main ingredient, and a crosslinking agent mainly composed of an isocyanate-based compound is added as an essential ingredient to the above-mentioned main ingredient.
A water-based adhesive that cures at room temperature (hereinafter referred to as water-based vinyl urethane adhesive) containing 30 to 50 parts for winter, 20 to 40 parts for spring/autumn, and 18 to 30 parts for summer per 100 parts is applied to the laminar and crimped. After that, the assembled fritchi is cured for 24 to 40 hours under conditions of a temperature of 25 to 40°C and a relative humidity of 40 to 70%, and then cured in water in a water pot at 30°C or less, The method is characterized in that the moisture content of each assembled laminar is averaged, then it is boiled, and then it is cut. The laminated laminar to be bonded is manufactured using the following process. First, domestically produced materials such as broad-leaved trees and coniferous trees such as red duck, yellowfin, zelkova, oak, shioji, tabunoki, horse chestnut, black oyster, etc., as well as abodeira, walnut, ebony, satinwood, rosewood, zebrawood, dao, teak, Brazilian rose, mahogany, etc. Imported high-grade wood, its offcuts, or small-diameter raw wood are sawn to the desired size using a sawmill, and then processed to smooth the surface to be adhered to the desired finished size using a hand plane, automatic plane, etc. I do. In order to remove moisture from the surface of the finished laminar (drying), the laminar is piled up and usually dried at a room temperature of 25°C or higher. Drying is performed until the surface moisture content of the wood reaches 15 to 18% at a depth of 0.3 to 0.5 mm from the surface, for example. That is, one feature of the present invention is that the moisture content of the smooth finished laminar surface is 15 to 18%.
Adjust the surface moisture so that it dries more strongly than the inside. If you apply a water-based vinyl urethane adhesive without drying the surface and keeping the water content on the surface of the laminar as high as the inside, the curing time of the adhesive will be significantly longer and the Since adhesion failures frequently occur during manufacturing days, it is difficult to apply the above-mentioned adhesive.
By limiting the moisture content of the lamina surface to the above range, satisfactory initial adhesive strength and equilibrium adhesive strength can be obtained for the water-based vinyl urethane adhesive, and the wood breakage rate can also be improved. However, the internal moisture content of laminar is generally
Since the adhesive is as high as 30 to 50%, if the curing of the adhesive is not completed early, there is a risk that internal moisture will seep out to the surface, resulting in poor curing. Therefore, in the present invention, a water-based vinyl urethane adhesive containing a crosslinking agent in an extremely higher proportion than usual is used to enable the adhesive to cure in a short period of time. This point is the second feature of the present invention. In addition, from the viewpoint of adhesive strength, the moisture content of the laminar surface should be adjusted to less than 15%, especially from 8 to 8%.
It is preferable to do this so that the ratio is 12%. However, in order to dry wood to a moisture content of 8 to 12%, it is necessary to dry the wood sufficiently by natural drying and then further perform artificial drying. Normally, natural drying requires about 3
It takes 15 to 30 days for a cm board, and 10 to 20 days for an approximately 1 inch board for artificial drying (Takamaro Mitsuhisa, Wood Drying, published by Morikita Publishing Co. , pp. 192-194). Therefore, e.g. width
When oak wood with dimensions of 25 to 80 mm x height 80 mm x length 300 to 1000 mm is used for laminar laminar, it takes 40 to 80 days for natural drying for general wood species.
15 to 30 days for artificial drying. Furthermore, artificial drying is economically disadvantageous since it usually costs about 20 times more than natural drying. Therefore, the method of adjusting the moisture content of the laminar surface to a moisture content of 8 to 12% is not adopted in actual mass production because the addition of an artificial drying process causes a significant decrease in productivity and a significant increase in manufacturing costs. I can't. The laminar for lamination obtained through the above process is first cut to the desired length so that it can correspond to the color pattern and dimensions of the desired product laminated veneer, and then the laminar for lamination with the determined length is While arranging the wood grain in a well-balanced manner in the cutting direction,
Combine into shapes. A water-based vinyl urethane adhesive is then applied to the surface of each combined laminar assembly to be bonded using a sprayer or brush. In water-based vinyl urethane adhesives, the isocyanate group of the isocyanate compound, which is the crosslinking component, reacts with the active groups of the main ingredient polyvinyl alcohol, other water-soluble polymers, and aqueous polymer dispersion at room temperature, creating urethane bonds and crosslinking. By doing so,
It has strong adhesive strength (JAS standard type or higher), has elasticity in the adhesive layer, and can withstand boiling at high temperatures. By using a room temperature curable adhesive, the adhesive performance is stable and the workability of the blade is good (the blade does not spill), so it is suitable for the method of the present invention. Such characteristics cannot be obtained with thermosetting adhesives or moisture-curing urethane adhesives. Normally, water-based vinyl urethane adhesives are used in a blending ratio of the main component, the main component, and the crosslinking component, in the range of 5 to 15 parts of the crosslinking agent to 100 parts of the main component, but in the case of the present invention These blending ratios are not appropriate. That is, in the present invention, the bonded laminar is subjected to long-term underwater treatment and hot to hot water treatment before cutting, so if a normal compounding ratio is used, the adhesive layer will lift or peel, making cutting impossible. The blending ratio of the aqueous vinyl urethane adhesive used in the present invention is 30 to 50 parts of the crosslinking agent in winter to 100 parts of the main agent.
A range of 20-40 parts in spring and autumn and 18-30 parts in summer is suitable. In each season, if the blending ratio of the crosslinking agent is less than the limit value, the hot water resistance of the adhesive layer will be insufficient, and if it exceeds the upper limit value,
The potable life of the blended adhesive liquid is short, and the adhesive layer has no elasticity and becomes hard and brittle, making it unusable. Note that the amount of adhesive applied is appropriately determined so as to maximize the adhesive effect. Next, each laminar assembly coated with adhesive is arranged again in the desired size and shape and bonded under pressure using a cold press machine. After compaction, it is cured indoors under atmospheric conditions, preferably at a room temperature of 25 to 40°C and a humidity of 40 to 70%. The reason for limiting the room temperature and humidity is to prevent the wood from expanding and contracting. The curing time varies depending on the temperature and humidity, but 24 to 40 hours is usually preferred in consideration of the adhesive curing speed. Then, the assembled fritsch made of the above-mentioned laminar laminated together and bonded together is cured in water in a water pot. The purpose of this underwater curing is that since multiple laminars of the same or different types are used, the moisture content inside each laminar varies widely, and the laminar is bonded in an unstable state. When boiling is performed in the same way as for logs and fritches, the expansion and contraction between each lamina is rapid, and in order to prevent damage to the adhesive layer, the moisture content of each lamina that makes up the assembled fritchi is averaged to stabilize the quality. There is a particular thing. This underwater curing is carried out for 10 to 20 days using ordinary wood in a water pot at a water temperature of 30°C or less, with the aim of preventing rapid expansion of the assembled fritsch. Next, the assembled fritsch that has been stabilized by curing in water is boiled. Boiling is done for the purpose of softening the laminated fritsch, and in order to prevent damage to the adhesive layer, avoid sudden temperature increases. Temperature is 60-70
Continue until the temperature reaches ℃. After boiling, cutting to a desired thickness using a slicing machine or the like will yield a laminated veneer of good quality. As mentioned above, the third feature of the present invention is to perform atmospheric curing followed by underwater curing under specific conditions. Hereinafter, one embodiment of the present invention will be described based on the drawings. Zelkova, oak thickness 75mm, width 30mm, length 300
The wood was sawn to a size of 1 mm or more, and the surface was finished using a hand plane or an automatic plane to a finished size of 70 mm in thickness, 25 mm in width, and 600 mm in length to obtain laminar for lamination. Next, multiple laminars for lamination were piled up and dried at room temperature of 25°C or higher until the moisture content of the wood was 15-18% at a surface depth of 0.3-0.5 mm. Detection of moisture content is
Measured using an electrical resistance moisture meter (Kett moisture meter). However, the detection part at the tip of the measuring instrument shall be a net one to measure the moisture content of the wood surface. Each laminated laminar was then finished and cut into lengths of 250 to 600 mm using a cross-cutting machine. The laminar for lamination having a determined length is arranged in a well-balanced manner, for example, as shown in the figure, in terms of color pattern and cutting method, so as to obtain a desired laminated veneer. In Figure 1, the assembled laminar 1 is numbered, and water-based vinyl urethane adhesive (manufactured by Koyo Sangyo KK, KR-120 (main agent) 100
parts, 20 parts of AD (crosslinking agent) are evenly mixed)
275 g/m ^{2 of} the adhesive was applied to the adhesive surface of the laminar laminar 1 using a sprayer or a brush. Then, they were stacked and arranged in numerical order again, and the adhesive surfaces were fixed by pressing with a cold press machine. pressure is 10~12
When the temperature reaches Kg/cm ² , clamp it and remove it from the cold press at a room temperature of 25-40℃ and a humidity of 40-70℃.
% was cured indoors for 24 to 40 hours. By curing, a composite fritch 2 (see FIG. 1) in which a plurality of laminars 1 were integrated was obtained. After curing, the clamp of the assembled fritsch 2 was removed and the pressure was released. Next, put the assembled Fritsch 2 into a water pot at 30℃ or less for 12 hours.
It was cured in water for a day. After curing in water, it was boiled for 5 days at a temperature increase of 10°C per day until the maximum temperature reached 70°C. When the laminated fritsch 2 after boiling is cut in the direction of arrow A in FIG. A stable laminated veneer was obtained. In addition, a water-based vinyl urethane adhesive with a different formulation (manufactured by Koyo Sangyo KK, KR-132 (base agent) 100 parts AJ-1
(Crosslinking agent) When a uniform mixture of 45 parts was used, the same good results as in the above example were obtained. Next, examples of comparative tests with different water contents and crosslinking agent ratios will be described. The test procedure is as follows. (1) Sample and adhesive type Oak tree, width 25mm x height 80mm x length 900mm
Samples were laminars having the dimensions of , and five sets were prepared for each number required for the fritches. Sample No.1
I decided to call it No.5. A water-based vinyl urethane adhesive (KR-7700, manufactured by Koyo Sangyo Co., Ltd.) was used as the adhesive. (2) Single veneer production procedure Basically, laminated veneers were produced respectively according to the procedure described in the explanation of the above examples. The moisture content of the laminar surface to be adjusted and the crosslinking agent contained in the adhesive were varied for each sample as follows. Sample Laminar surface moisture content Crosslinking agent ratio No. 1 15-18% 30 parts No. 2 15-18% 40 parts No. 3 20-30% 60 parts No. 4 20-30% 15 parts No. 5 10- 12% 15 parts For each sample, after prescribed curing, laminated veneers with a thickness of 0.2 mm and a thickness of 0.4 mm were obtained by cutting. (3) Testing and evaluation Regarding the following items, measurement tests were conducted as necessary for the laminated veneers etc. produced from each sample, and the quality of the evaluation was determined. (a) Adhesive strength In addition to laminated veneer panels, we also evaluated the adhesive strength of laminated fritches. The evaluation criteria are as follows. A...Good B...Slightly poor C...Poor (b) Exposure of adhesive layer Whether the white adhesive layer seeped out on the surface of the veneer was observed and evaluated in the longitudinal direction and on the holo surface. (c) Surface smoothness The smoothness of the veneer surface was observed, particularly whether so-called rough skin occurred due to excessive drying. (d) Occurrence of curls and fringes The laminated veneer was further dried to examine whether curls (curvature) and fringes (wavy deformation) would occur. (e) Dimensional stability Dimensional stability was evaluated by measuring the expansion rate when boiled at 50°C for 168 hours, and the contraction rate when air-dried (12%) and completely dried. (f) Total number of manufacturing days The total number of days required from adjusting the moisture content of the laminar to finishing it into a laminated veneer by cutting the laminated fritsch was calculated. (g) Economical efficiency The economical efficiency was evaluated based on the cost incurred in producing the laminated veneer. The evaluation criteria are as follows. a...cheap b...relatively expensive c...extremely expensive or needs to be profitable in appearance In fact, the production cost of sample No. 5 is the same as that of samples No. 1 and No. 2.
It was 5 to 20 times the cost. (4) Results The results of the above evaluation are summarized in Table 1 below. Further, the expansion and contraction rates in terms of dimensional stability are illustrated in FIGS. 2A and 2B.

[Table] * Rough skin defects occurred.
** After adjusting the moisture content to nearly 20% by natural drying, artificial drying was further performed for the required number of days.
Incidentally, samples No. 1 to No. 4 could be sufficiently treated by natural drying alone.
From these results, sample No. by the method of the present invention.
It can be seen that the cases of No. 1 and No. 2 are excellent in all aspects such as adhesive strength, surface properties, and dimensional stability, and are also very advantageous in terms of productivity and economy. On the other hand, it can be seen that samples No. 3 and No. 4 have significantly poor dimensional stability. Furthermore, sample No. 3
It can be understood that in the case of sample No. 4, oozing of the adhesive onto the surface of the veneer becomes a problem, and in the case of sample No. 4, a decrease in adhesive strength especially at low temperatures becomes a problem. Further, in the case of sample No. 5, not only did the surface of the veneer have poor smoothness due to excessive drying, but it was also extremely disadvantageous in terms of productivity and economy, and therefore was not suitable for actual mass production. According to the method of the present invention as explained above, the dimensional stability is particularly good, there is little elasticity peculiar to wood,
It is possible to obtain a laminated veneer of stable quality that can fully meet desired color patterns and dimensions. The applications of the laminated veneer obtained by the method of the present invention are wide, such as building walls, furniture, cabinets, floors, etc.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the state in which the assembled fritches are cut, and FIGS. 2A and 2B are graphs showing the expansion and contraction rates of each sample of the assembled veneer. In the figure, 1... Laminar for lamination, 2... Fritsch for lamination.

Claims (1)

[Claims] 1. Finishing the surface to be adhered smooth and then drying the surface so that the moisture content is 15 to 18% than the inside to produce a laminar laminar with controlled surface moisture; Next, arrange the laminar in the desired size and shape,
Next, a water-soluble polymer and/or an aqueous polymer dispersion is used as a main ingredient, and a crosslinking agent mainly composed of an isocyanate-based compound is added as an essential ingredient to the above-mentioned main ingredient.
100 copies: 30-50 copies in winter, 20-40 copies in spring/autumn,
A room-temperature curing water-based adhesive containing 18 to 30 parts of summer is applied to the laminar and pressed to produce a composite frit, and then the composite frit is applied under conditions of a temperature of 25 to 40°C and a relative humidity of 40 to 70%. After curing for 24 to 40 hours in a water pot at 30°C or lower, the laminar is cured in water to average the moisture content of each laminar, then boiled, and then cut. Method of manufacturing the board.