JPS5841164B2 - Shitsujiyunmokuzaino Setsugohouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for joining wet wood, and more particularly to a method for joining wet wood using a urethane resin composition containing a urethane resin prepolymer and an incyanate compound as main components.

Regarding the bonding of wet wood, in the past many methods have been proposed and put into practical use by heating and compressing wet veneers with a press, but there are few examples of room-temperature bonding of wet wood, and only recently. Forest production
ct journal vol 21, A6.8('
71), JP-A-48-82008, JP-A-49133
11, Japanese Patent Publication No. 49-30510. Japanese Patent Publication No. 49-3051
1. Japanese Patent Publication No. 49-55805, Japanese Patent Application Publication No. 49-55806
, JP-A-49-55807, JP-A-49-71115,
Many proposals regarding the joining of wet wood have been made in Japanese Patent Laid-Open Publication No. 109507, etc., and have come to be put to practical use.

To summarize these in relation to the present invention, the method of using a resorcinol resin adhesive has problems with adhesion when the bonding surface has a high moisture content, and only the bonding surface must be dried to 18% or less. In addition, there are problems with contamination due to the adhesive itself being colored dark red, damage to knife blades during processing due to its excessive hardness, and cracking of joints due to morosa during cutting with slicers, rotary laces, etc. There is a hat theme.

Epoxy resin adhesives with specific formulations can bond wet surfaces as they are, but they may cause oil stain-like contamination due to excessive penetration of the epoxy resin into the material, or excessive penetration of the basic curing agent. There are problems such as discoloration and contamination of the material, troublesome formulation because it is a two-component type, restrictions on pot life, and irritating irritation to human skin.

In addition, by selecting various formulations of epoxy resin adhesives,
Although the hardness and flexibility can be improved, since it does not have sufficient rubber-like elasticity, the joints are brittle and easily come apart when cutting with a slicer, rotary lace, etc.

As described above, the inventors have developed a one-component fast-curing adhesive composition that causes very little contamination of wood and has excellent rubber elasticity as a room-temperature curing type adhesive composition for wet wood, and a one-component fast-curing adhesive composition for wet wood using the same. This is a completed method of joining.

First, the purpose of the present invention must be achieved by satisfying the following conditions.

(L) In general, it is very rare that wet wood does not undergo any cutting after being joined, and in most cases some kind of cutting is required.

Therefore, it must not only be possible to bond the wet surfaces of wood, but also provide a flexible joint that will not damage or cause excessive wear on the sharp edges of various woodworking machines.

(2) If the wet wood is veneer flitch material and especially in hard water,
Since it is necessary to boil the flitch material for a long time after bonding and prior to slicing, the adhesive layer must have excellent water resistance and hot water resistance.

(3) The adhesive strength must be strong and the wood must be firmly joined.

In particular, when vertically joining raw wood scraps for plywood or lumber, the cut surfaces of the wood fibers must be joined together.
Alternatively, in the case of joining veneer flitch materials, it is possible to combine the wood grain directions at right angles to each other, so joining in all directions must be possible.

In addition, if the stopper is made of cherry blossom or rosewood, it must also be possible to join different materials such as teak or towel nut.

Furthermore, the adhesive strength must not decrease or peel off not only when the wood is wet but also after drying.

In addition, when cutting small-diameter wood by joining the sides of the peeled rotary lace core material and cutting with the rotary lace, or when cutting with the rotary lace after injecting adhesive into the cracks of the raw wood and joining, there is a strong impact on the joint. Strong adhesive strength is required because force is applied.

(4) Contamination of the material is undesirable in cases where the material itself is colored, such as in the case of resorcinol resins, since coloration of the adhesive layer is unavoidable.

In addition, contamination caused by oily matter such as epoxy resin, discoloration, and discoloration caused by ultraviolet rays after application are also impractical when adhering cosmetic materials.

(5) Regarding the workability of adhesion, it is better to use resorcinol-based resin adhesives and epoxy-based resin adhesives (one-component type urethane adhesives that are cured by the moisture content of wet wood, rather than types that mix the main ingredient and curing agent in specified proportions). Resins have better workability and do not have pot life restrictions like the resorcinol or epoxy resins.

In particular, conventional two-component adhesives have a short pot life if you try to shorten the curing time at room temperature.It goes without saying that fast-curing adhesives that do not have to worry about pot life at room temperature are preferable. .

The present invention is an industrially useful method that uses a moisture-curable urethane resin adhesive composition having a special formulation described below as satisfying the above requirements.

That is, it is inappropriate for the urethane prepolymer used as the first component of the urethane resin composition used in the present invention to be hard and brittle. It is preferable that 1,000 polyether chains or polyester chains form a somewhat coarse network bond and exhibit strong rubber elasticity.

In this case, by using hydrophilic polyether chains or polyester chains as the main component, it not only exhibits strong rubber elasticity, but also has moderate hydrophilicity, which allows for good compatibility with the wet wood surface, and also allows for good compatibility with the wet wood surface. It also makes it easier for water to spread,
Even if it is cured with S while water is dispersed in the adhesive layer, the physical properties will hardly deteriorate, allowing ideal wet surface adhesion.

It is understood that the urethane prepolymer, which is the first component of the present urethane resin composition, can be produced by any manufacturing method and used in the same manner as long as it satisfies the above requirements. An example of the manufacturing method is as follows to make it easier.

For polyalkylene ether-based or aliphatic polyester-based long-chain or branched long-chain polyols with a molecular weight of several hundred to several thousand, polyisocyanate compounds such as MDI, MDI, HDl, etc. are added with excess incyanate groups relative to active hydrogen. and reacted in as anhydrous state as possible, with -
A polyurethane prepolymer containing two or more NCO groups is obtained.

If necessary, the bleed polymer formation reaction or curing time may be accelerated by using an organometallic compound such as dibutyltin dilaurate or an amine such as triethylene diamine as a catalyst.

Next, regarding the low molecular weight incyanate compound, which is the second component of the urethane resin composition of the present invention, by using it in combination, the curing speed of the urethane prepolymer, the adhesion to wet surfaces, and the This dramatically improves the adhesion to the resin layer and the toughness of the cured resin layer, and can significantly improve practicality.

In other words, the low molecular weight isocyanate compound moderately diffuses into the wet wood surface layer and exerts a so-called anchoring effect, greatly improving the adhesive strength and breaking rate to the wet surface, increasing the reliability of adhesion, and Appropriately dense crosslinking occurs between the coarse crosslinking of the prepolymer, and by adding appropriate hardness to an adhesive layer that would otherwise be too soft using the prepolymer alone, the overall toughness can be greatly improved. It is assumed that the curing speed can be greatly increased by interposing a molecular weight isocyanate compound between the prepolymers.

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.

Practically, for example, tolylene diisocyanate, diphenylmethane diisocyanate, dianisidine diisocyanate, tridene diisocyanate, hexamethylene diisocyanate, metaxylene diisocyanate, naphthalene diisocyanate, polymethylene polyphenylisocyanate, triphenylmethane triisocyanate, transvinylene diisocyanate, tris(4- phenyl isocyanate thiophosphate), N-N'(4
・4'-dimethyl 3,3'-diphenyl diisocyanate) uredione, 4,4',4"-trimethyl 3,3'
- One or more types can be selected from 3" triisocyanate 2,4,6-triphenyl cyanurate, 2,6-dicyanate methyl caproate, etc.

The content of the urethane prepolymer of the present invention in the adhesive composition of the present invention is required to be 20% or more, since if it is less than 20%, the adhesive strength will be insufficient and it will be impractical.

Particularly when adhesive strength is required, for example, when the end surfaces of end cuts of plywood raw wood are joined, cut with a rotary lace to obtain a veneer, and dried with a dryer to obtain a dry veneer.5
High contents of 0-75% or more are preferred.

When filling and bonding small-scale racks of wet logs for plywood, a content of 20 to 30% or more is sufficient.

When wet flitch material is sliced after joining the wood fibers parallel to each other, it is possible to cut the wood at a rate of 30 to 40% or more, but when the fibers are joined at right angles and sliced after boiling, it is possible to cut the wood at a rate of 70% or more. The content is preferred.

Next, if the proportion of the low molecular weight incyanate compound in the adhesive composition is less than 3%, almost no effect will be seen, so the proportion of the incyanate compound should be 3% or more.

Moreover, if it exceeds 20%, the adhesive layer becomes hard and brittle (the flexibility of the prepolymer is reduced), which is not acceptable.

Next, in addition to the urethane resin composition of the present invention comprising the above prepolymer and low molecular weight isocyanate, a latent crosslinking agent (
For example, polyketimine-based adhesives, etc.) may be blended in advance into the adhesive composition of the present invention.

In addition, in the adhesive composition of the present invention, an inert solvent that does not react with -NCO groups such as ketones, esters, aromatic hydrocarbons, etc. may be appropriately used in an anhydrous state to facilitate the smooth progress of the reaction and reduce the viscosity. However, for the purpose of the present invention, it is preferable to use a hydrophilic solvent as the main solvent.

Furthermore, in the adhesive composition of the present invention, wood flour, cork powder,
Add a filler such as wheat flour, or use a thixotropic agent such as Erosil (Nippon Aerosil) or bentonite to suppress the impregnation of the resin into the wood. It may also be modified with a thermosetting resin containing active hydrogen, such as epoxy resin, amino resin, or phenol resin.

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. Note that the low-molecular incyanate compound as a component of the resin composition of the present invention is extremely reactive and easily reacts with moisture in the air and decreases, so it is necessary to compensate for such decrease during the reaction. Inorganic or organic fillers commonly used in adhesive compositions contain a considerable amount of water and reactive groups, and by mixing them, low-molecular-weight isocyanate compounds can be Since the weight loss is significant, it is necessary to consider complementary signals for such weight loss.

Therefore, the content in the claims of the present invention refers not to the blending ratio at the time of manufacturing the adhesive composition, but to the ratio after the adhesive composition is manufactured, that is, after the low molecular incyanate compound is reduced during storage.

As described above, the present invention uses an adhesive composition containing 20 to 97% and 3 to 20% of a urethane prepolymer and a low molecular weight isocyanate compound, respectively.
This is an industrially useful method that allows wet wood of various types to be joined together in a short time without any contamination, does not damage sharp knives after joining, and provides a joint with good heat resistance.

Next, examples will be described.

Example 1 Prepolymer 802, methyl ethyl ketone, obtained by reacting 1 mole of polypropylene glycol (molecular weight 450), 2 moles of triol polyether (trimethylolpropane with ethylene oxide added, molecular weight 500) and 3.5 moles of tolylene diisocyanate 10g, powdered PVC 30? and tolylene diisocyanate) 2C1 were mixed.

The tolylene diisocyanate content of the adhesive composition (4) was determined to be about 10% by a distillation method after 7 days.

When birch wood and beech wood with a moisture content of 50 to 100% were bonded using the composition (A) so that the fiber directions were perpendicular to each other, the bonding was possible in 2 hours at room temperature, but it Adhesive composition with an isocyanate content of 1% (B
) required 12 hours under the same conditions.

The wet material bonded using the composition (N) could be easily cut with a slicer, and the resulting veneer had no abnormalities in the bonded area even after forced drying.

After finishing the end surfaces of two lauan logs with a diameter of 60 cTL horizontally with a planer, 301' of composition (4) was applied to the end surfaces, and the end surfaces were pressed together at a pressure of 3 kg/crA for about 2 hours. Obtained a unified log.

The raw wood could be easily cut into a veneer by a conventional method using a rotary lace, and the veneer showed no abnormality even after being dried in a dryer.

Example 2 Prepolymer 10 (1, 20 g of methyl ethyl ketone, 20 g of methyl ethyl ketone,
Powdered vinyl acetate/ethylene copolymer 3 (l and tolylene diisocyanate) 30? were mixed uniformly to obtain an adhesive composition (q).

Using the adhesive composition (C), a plug material with a moisture content of 30 to 90% (vertical 15 crfL, horizontal 3.7 cr/L1 height 2
0cr/L) joined in a small checkered pattern and 30X180 height 2
o block flitch was obtained.

The flitch was cut with a slicer to obtain a sliced veneer with a small checkered pattern of 0.3 mm.

There were no abnormalities in the joints during slicing, handling, or joining to plywood.

In addition, the adhesive composition (C) was applied to the side surface parallel to the fiber direction of a 25 mm thick lauan veneer with a water content of 70%, and the adhesive composition (C) was applied one after another in a crisscross pattern at 40°C for 25 minutes. A veneer was obtained which was left to stand and was pieced together into one piece.

The veneer showed no abnormality even after being dried for 35 minutes in a dryer at 175°C, and there were no problems in normal plywood manufacturing.

Example 3 Prepolymer 1.00 ? , methyl ethyl ketone 15
y', treated wood flour (commercially available wood flour 100 ml was uniformly sprayed with 20 ml of tolylene diisocyanate to reduce the moisture and active hydrogen contained in the wood flour).

It is necessary to use pre-treated wood flour because if untreated wood flour is blended as is, the composition may gel within a few days.

In addition, even when blending inorganic powders that do not have active hydrogen, they always contain water, so unless they are pretreated with a low-molecular incyanate compound, the shelf life of the adhesive composition may be compromised. ) 4C1 and tolylene diisocyanate 20'? were mixed uniformly to obtain adhesive composition p).

Cut each side of four pieces of peeled core material from logs for lauan plywood (wet core material remaining after rotary cutting with a rotary lace; in this example, diameter 25c/rL was used). Two surfaces forming an angle were provided, and after applying the composition (D) to the flat surfaces, the four pieces of wood were assembled into a bundle so that their flat parts were aligned, and they were tightened with a steel band for packing and left to stand for 2 hours. The steel band was removed and a veneer was obtained by cutting with a rotary lace.

The joints of the veneers showed no abnormalities during cutting with a rotary lace or after drying with a dryer (170° C.), and could be used as ordinary veneers for plywood.

Claims (1)

[Claims] 1. In a method of bonding and integrating wet wood with a urethane resin adhesive composition, the urethane resin composition (1) has a long chain or branched long chain skeleton with a molecular weight of 100 or more, and -NCO The adhesive composition contains a urethane prepolymer having two or more groups and (2) an incyanate compound having two or more -NGO groups in the molecule and having a molecular weight of 600 or less as the main constituents, and the content of 1) is 20 to 20% in the adhesive composition. 97% (2)
A method for joining wet wood, characterized in that the content of the composition is 3 to 20%.