JPS5850276B2 - Yakuzai - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an adhesive composition used for joining wet veneer flitches, particularly to a composition with excellent water resistance and curability.

In general, veneer boards are produced by thinly slicing precious wood flitch, and decorative veneer boards have been produced for a long time, and in particular, parquet veneer boards made in the Hakone area of Kanagawa Prefecture have been used domestically as woodworking crafts since the Meiji era. Both are famous, and this is a flitch material that is made by bonding dried wood with glue, sakubi adhesive, etc., and then cutting (slicing) it into thin pieces using a plane, slicer, etc.

Dry flitch materials like this are significantly more difficult to cut than wet materials and require a high degree of skill, but it is impossible to obtain large veneer boards that can be used as building materials, etc.
Only craft-like items of size less than m are produced.

On the other hand, decorative veneer boards used as building materials range from 1 m to 4 m.
Because it is large, about 1.5 ft. in size, it cannot be sliced unless it is wet, but precious wood resources are gradually becoming smaller in diameter, and it is easy to imagine that if they can be joined in advance, it will help improve slicing efficiency.

In addition to resource issues, it is also easy to imagine from the example of box board work that if various types of wet wood can be combined and joined together, beautiful veneer boards can be obtained by slicing them.

However, for many years, bonding wet flitch materials for slicing remained a long-held dream in the industry because no adhesive was known that would adequately bond wet wood without contaminating, discoloring, or damaging the sharp knives of slicers.

Therefore, the method of joining wet wood using an adhesive capable of wet surface bonding and then slicing it is easier to predict than box board work (in other words, anyone who can make such an adhesive should be able to do it). The adhesive for this can be said to be a future issue.

The inventors have already filed a patent application for this kind of industrial dream.
1288, patent application No. 117998, patent application No. 48-3
The present invention relates to an adhesive composition that is a further improvement of the adhesive disclosed in Japanese Patent Application No. 48-34073, which has been gradually realized in Japanese Patent Application No. 48-34073.

The feature of the present invention is that it not only firmly joins wet flitches in a short time, but also has the ability to withstand hot water treatment for softening wood and correcting distortion even after joining.

The adhesive used for joining wet flitches is
34073 (Japanese Unexamined Patent Publication No. 49-118807), in addition to room temperature curability, the following seven conditions have been required.

1. Since flitch materials have been pre-boiled or soaked to improve machinability, they are usually in a moist state, and therefore must be capable of bonding under wet conditions.

2. Since it must be sliced after adhesion, it is necessary to reduce the burden on the blade, and the cured product must not be too hard.

3 The adhesive strength must be strong and the wood layer and adhesive layer must be firmly bonded during cutting.

4. In order to prevent contamination of the material, excessive penetration of the adhesive into the wood layer from the adhesive layer must not occur.

5. It must be compatible with adhesives when applied to plywood.

6. In the case of a baseboard for flooring, etc., it is sometimes desirable to have a facing material with the wood grain directions set at right angles to each other, so it must also be possible to bond the wood grains.

7. It must also be possible to bond dissimilar materials.

The most important feature of this type of wet flitch joint is that it can easily create a so-called mosaic-like veneer board that combines wood of different hues and grains, so it can be used to combine soft materials such as wood, teak, and birch with hard materials. It is possible to arrange a combination of materials, such as zelkova, which is prone to warping and twisting, so as to create a beautiful design.

However, in order to make the flitches easier to cut, these materials require immersion of the joined flitches in high-temperature water for a long period of time, or treatment with wood softening agents in combination with the above-mentioned hot water treatment. Processing such as use is required.

However, the adhesive disclosed in JP-A-49-118807 cannot maintain adhesive strength under such severe processing conditions, and it is difficult to obtain beautiful veneers as described above by bonding wet flitches. Met.

The present inventors have conducted various studies to solve the above-mentioned drawbacks, and as a result, we have found that -NCO in the molecule can be used as an adhesive for wet flitch bonding.
a low molecular weight incyanate compound having two or more groups;
The main component is a urethane prepolymer having a linear or branched long chain skeleton with a molecular weight of several hundred to several thousand, and two or more -NCO groups, and the incyanate compound is combined with the prepolymer. The urethane resin composition, which contains 10 to 20% of the total amount, not only enables wet surface adhesion, but also exhibits stronger adhesion in a shorter time than conventional products, and can be used in hot water after wet flitch bonding. They obtained the surprising result that it was possible to slice the slices without any problems even after the immersion treatment, which led to the present invention.

The urethane prepolymer in the present invention is a polyisocyanate compound such as TDI, MDI, HDI, etc., in contrast to a polyalkylene ether-based or aliphatic polyester-based linear or branched long-chain polyol with a molecular weight of several hundred to several thousand. It can be obtained by blending inocyanate groups in large excess with respect to active hydrogen and reacting in as anhydrous state as possible.

Furthermore, if necessary, the production reaction of the urethane prepolymer may be accelerated or the curing time may be shortened by using an organometallic compound such as dibutyltin dilaurate or an amine such as triethylene diamine as a catalyst.

Next, with regard to low molecular weight incyanate compounds, their combined use dramatically improves the curing speed of urethane prepolymers, the adhesion of wet flitches, the toughness of the adhesive layer after curing, and the resistance to hot water soaking. This can significantly improve the practicality of wet flitch bonding.

In other words, the low-molecular-weight incyanate compound moderately diffuses into the inside of the wet wood surface layer and exerts the so-called anchor effect, greatly improving the adhesive strength and breakage rate to the wet surface, and improving the reliability of the adhesive. In addition, moderately dense crosslinking occurs between the coarse crosslinking of the prepolymer, and the prepolymer alone is
By adding appropriate hardness to the adhesive layer, which is too soft, the overall stiffness can be greatly improved, and by interposing the low molecular weight incyanate compound between the prepolymers, the curing speed can also be greatly increased. It is imagined that it is possible.

As such low molecular weight incyanate compounds,
Those having two or more -NCO groups in the molecule and having a molecular weight of 600 or less are preferable, and those exceeding 600 are not useful for improving the performance of the prepolymer even if used in combination with the prepolymer.

In practical use, for example, tolylene diisocyanate, diphenylmethane diisocyanate, dianisidine diisocyanate, tridene diisocyanate, hexamethylene diisocyanate, metaxylene diisocyanate, knack diisocyanate, polymethylene polyphenylisocyanate, triphenylmethane triisocyanate, transvinylene diisocyanate. , Tris(4-phenylisocyanate thiophosphate), N, N'
(4,4'dimethyl 3,3'-diphenyl diisocyanate) uredione, 4,4',4'-1-dimethyl 3
．． One or more types can be selected from 3','3'-triisocyanate 2,4,6-triphenyl cyanurate, 2,6-diisocyanate methyl caproate, and the like.

Furthermore, the proportion of the incyanate compound having such a low molecular weight is added such that the content of the incyanate compound is 10 to 20% based on the total amount including the prepolymer.

If it is less than 10%, as mentioned above, it is insufficient or impractical in terms of curing speed, adhesive strength, hardness of the cured adhesive layer, and boiling resistance in hot water.

If it exceeds 20%, the adhesive layer becomes hard and brittle, reducing the flexibility of the prepolymer, which is not practical.

Some of the adhesives shown in the above-mentioned JP-A-49-118807 contain small amounts of incyanate compounds similar to those of the present invention. The above-mentioned prepolymers and low-molecular-weight incyanates, which are impractical because the amount of cyanate compounds is too small, contain latent crosslinking agents (such as polyketimine-based ones) that react with water to produce groups having active hydrogen. ) may be blended in advance.

In addition, -NCO such as ketones, esters, aromatic hydrocarbons, etc.
It is best to use an inert solvent that does not react with the group in an anhydrous state to facilitate the reaction and adjust the viscosity. It is preferable to have the main focus on

Furthermore, in the present invention, fillers such as wood flour, cork powder, and wheat flour are used, and chicken tropic agents such as Erosil (manufactured by Nippon Aerosil KK) and bentonite are used to suppress impregnation of resin into the wood. It is also effective to impart chicken-tropic properties to the composition.

Further, in this case, it is desirable to add a water-containing filler such as this powder immediately before use, since water as a hardening agent can be uniformly dispersed and the hardened resin layer can be reinforced.

It may also be colored with a suitable facial dye. Next, examples using the ureene resin adhesive composition of the present invention will be described.

Example 1 First, raw wood for the facing material is sliced so that the slices have a straight grain or board grain to obtain a square or board material, and the surface height is finished horizontally and smoothly.

Next, the wood is soaked in water or boiled to soften it so that it can be easily sliced.

In this case, the moisture content usually reaches 30% to 100% or more.

The material obtained in this way is reacted with various formulations as shown in Table 1, and the resulting prepolymer is treated with TDI.
An adhesive composition prepared such that the content of the low molecular incyanate compound is 10% is uniformly applied.

(It is best to use these appropriately depending on the purpose.

Further, a filler may be added as appropriate. ) In this way, 10 pieces of material each having a width of 30 cm, a length of 180 cL and a thickness of 3 crn were glued together, and then tightened with a 30 cm thick flitch material and a blank turnbuckle to bring the bonded surfaces into close contact and exposed for 24 hours.

In this case, the urethane resin composition of the present invention can be cured in 3 hours at room temperature.

After curing, the turnbuckle was removed and the thickness was 30 cm.
A board with a width of 30 cm and a length of 180 cm was obtained.

In this case, the adhesive layer is completely bonded.

At this time, the cutting methods include joining the sliced materials so that they form a mosaic pattern as in the case of flooring, joining different materials together to give variety to the plywood, and cutting edges. Methods such as joining pieces of wood together or combining planks with straight grains were also possible.

The thus obtained bonded product is boiled in hot water and then sliced into pieces, usually about 0.1 to 4.0 mm, using a slicing device in a conventional manner.

As a result, a covering material of 90 crrL x 180 cfn was obtained.

It can be sliced very easily and the adhesive layer is strongly bonded, and this thin layer has a flexible and strong adhesive layer that can be rolled up and prevents the adhesive from penetrating into the wood. It was very beautiful, with no contamination caused by seepage.

The veneer board obtained in this way is 90 crn x 180 c
B X 1. When it was adhered to Ocm plywood using a vinyl acetate adhesive, it was able to be adhered in the same way as before, and the base plate was superior to conventional products.

Example 2 Using an adhesive composition prepared by adding MDI to a prepolymer obtained by uniformly reacting the various formulations shown in Table 1 so that the content of the low molecular weight isocyanate compound was 15%, Wet pieces of wood were joined to a size of 1 x 6 feet to create a small checkered pattern, pressed in a hydraulic press at room temperature of 20°C for 2 hours, and then sliced to obtain a veneer board with a small checkered pattern. .

The joints of this product were completely joined, and it did not peel off at all during normal handling, and there was no abnormality when it came in contact with plywood.

The adhesive composition without MDI required 12 to 12 hours to cure at room temperature and had poor adhesive properties.

Example 3 A prepolymer obtained by uniformly reacting various formulations shown in Table 1 had a low molecular weight incyanate compound content of 18
Desmodule L [Germany Bayer product name, CO CH3・CH2C (CH20CONHCH3) 3 to 75%
% containing] was used to join wet wood into a 1 x 6 foot size so as to create a small checkerboard pattern, and the mixture was bonded using a hydraulic press at a room temperature of 25°C at a room temperature of 25°C. After 2 hours of pressing and slicing, a veneer with a small checkered pattern was obtained.

This product is a beautiful veneer with no adhesion defects or discoloration or contamination at the joints, and it is a beautiful veneer decorative plywood that is glued to plywood using the usual method.

Claims (1)

[Claims] 1 A urethane prepolymer having a linear or branched long chain skeleton with a molecular weight of several hundred to several thousand and having two or more -NCO groups, and a molecular weight of 600 having two or more -NCO groups in the molecule. The main ingredient is a composition in which the following isocyanate compounds are added such that the content of the isocyanate compounds is 10% (wt%, same hereinafter) or more and 20% or less based on the total amount of the urethane prepolymer. Adhesive composition for wet veneer flitch.