JPS59187071A - Adhesive for lateral bonding of raw wood veneer - Google Patents

Abstract

PURPOSE:An adhesive for lateral bonding of raw wood veneer having high finishing ratio of wood veneer depending upon kinds of resins, consisting of an amino precondensate or vinyl acetate polymer, wheat flour, PVA, clay, and triethanolamine as main agents. CONSTITUTION:The desired adhesive consisting of (A) an amino precondensate (preferably urea-formaldehyde precondensate obtained by polymerizing 1mol urea with >=1.95mol formaldehyde sufficiently in alkalinity or acidity) or vinyl acetate polymer (e.g., vinyl acetate-acrylic acid copolymer, etc.), (B) wheat flour and PVA (having preferably 1,400-2,000 polymerization degree and 85-90% saponification degree), (C) clay, and (D) triethanolamine as main agents. Amounts of PVA, wheat flour, and the component C are 10-30phr, 10-20phr, and 10-40phr based on the component A, respectively, and an amount of the component D is preferably 0.05-0.005wt%.

Description

[Detailed description of the invention] The present invention relates to an adhesive for gluing raw veneer.

Plywood is made by cutting continuous strips of veneer made from raw wood and veneer lace into plywood standard dimensions.

Next, three or more veneers are laminated so that the fiber directions are perpendicular to each other.However, the continuous strip-shaped veneer produced from logs is extremely easy to break, so it is difficult to produce veneers whose size does not meet the standard dimensions of plywood. Veneer (below)

A large amount of raw veneer (referred to as small, medium, and medium green veneers) is produced, and conventionally, it was treated as furnace material. However, due to recent circumstances such as the rise in the price of raw wood, it has become necessary to horizontally splice such small raw veneers into veneers of plywood standard size and use them as core boards for plywood.

The present inventor previously invented an adhesive consisting of an amino-based initial condensate and a vinyl acetate polymer as an adhesive for horizontally gluing small raw veneers, and applied for a patent application (Japanese Patent Application No. 66-60 /No.72)
However, this adhesive has a good veneer finish rate when it comes to cross-splitting raw veneers made of the same tree.
Alternatively, the veneer finish height was low for some wood glazes such as Certeis of the Elmaceae family, or for raw veneers made of combinations of different wood species. That is, this adhesive has the disadvantage that the wood species of the veneer must be selected when cross-bonding is performed.

Therefore, the present inventor conducted research to develop an adhesive for raw veneer cross-cutting that does not have such drawbacks and has a high veneer finish rate regardless of the tree species, and as a result, the present invention was completed. did.

The object of the present invention is to invent an adhesive for cross-cutting green veneers that provides a high veneer finish regardless of the wood species.

That is, the present invention relates to an adhesive for cross-cutting green veneer which has the following components A and D as main ingredients.

A Niamino-based initial condensate or vinyl acetate-based polymer B: / Tomato flour and polyvinyl alcohol (hereinafter abbreviated as PVA -F) C: Clay D Nitriethanolamine The present invention will be described in detail below.

The amino yarn initial compound used in the present invention refers to an amino-based condensate having a high degree of mobilization in water or methanol. -L: urea-based condensates such as urea-formaldehyde combination, alcohol-modified urea-formaldehyde condensate, phenol-modified urea-formaldehyde condensate; melamine-formaldehyde combination, alcohol-modified, tymin-formaldehyde condensate; Melamine thread condensation medium for things: urea-melamine co-condensate,
Examples include melamine-benzoguanamine # combination and phenol-melamine-urea cocondensate. Among the above amine condensates, urea 1 mol 2. A urea-formaldehyde condensate prepared by sufficiently polymerizing 7.7 mol or more of formaldehyde, preferably 9'j mol or more in alkaline and acidic conditions, and a 2L co-condensate based on this urea-formaldehyde condensate. Good! L.

stomach. C: Cocondensate (L-1- is a mixture of 1 mol of melamine and Ω mol or more of formaldehyde /!θ~-
2jθ parts by weight of the above urea-formaldehyde combination,
2yo θ ~ 360 weight! Partially polymerized urea-melamine cocondensates can be mentioned which are heat-polymerized at pH/θ or above. Paraform, methylated formalin, etc. that can be reacted can be used.

In carrying out the present invention, the above-mentioned amino-based initial condensate,
It can be used in powder form and in solution in water or alcohol as a solvent.

The vinyl acetate polymer used in the present invention includes:
Vinyl acetate polymer: vinyl acetate, acrylic acid, maleic acid, fumaric acid, itaconic acid or their esters and C copolymer; vinyl acetate-acrylamide copolymer;
Vinyl acetate-N-methylol acrylamide copolymer: vinyl acetate-trialyl isocyanurate copolymer;
Vinyl acetate-trialyl cyanurate copolymer: Vinyl acetate and α-olefin copolymer such as ethylene, propylene; Vinyl acetate-vinyl chloride copolymer; Vinyl acetate-diethyl fumarate-acrylic acid copolymer; Acetic acid Vinyl-ethylene-maleic acid (also it[water-maleic acid:/[) copolymer: vinyl acetate-ethylene-crotonic acid copolymer;
Vinyl acetate-ethylene-trialyl in cyanurate copolymer; Vinyl acetate-ethylene-N-methylolacrylamide copolymer; Acetic acid and nyl-ethylene-methacrylic acid copolymer; Vinyl acetate-ethylene-vinyl chloride copolymer etc. can be enjoyed. These vinyl acetate polymers can be produced by radical polymerization using emulsion polymerization, solution polymerization, bulk polymerization, etc., and the adhesive of the present invention can be produced by employing emulsion polymerization. The amino-based initial condensate and vinyl acetate-based polymers of the present invention, which can be easily produced, can be used alone or in combination.

Examples of the PVA used in the present invention include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, and various citrus-modified polyvinyl alcohols such as urethanized polyvinyl alcohol. Degree♂! There are commercially available products with ~ri0'X.

Good o [〈Used.

The reason why PVA is added in the present invention is to reinforce the adhesive force and to prevent the adhesive from flowing (so-called sagging) when applying the adhesive.

Usually, PVA glue is 10% of the A component of the adhesive of the present invention.
It is added at a ratio of ~3θ outer multiplying percentage (phr).

If the proportion of PV'A added is more than 30 phr, the solution viscosity of the adhesive becomes too high, making it difficult to handle. In addition, in a temporarily bonded state in which adhesive is applied and bonded to the end surfaces of green veneers, when the adhesive is deposited for several hours to a day and night, blocking of the green veneers that have protruded sideways tends to occur. -10,000% If the addition ratio of PVA is less than /θphr, the temporary bonding force will be weak and peeling will occur frequently before heat curing.The reason why wheat flour is added in the present invention is to impart thixotropic properties to the adhesive. It is for this purpose. The adhesive has thixotropic properties, so there is little sagging or seepage into the veneer during application, and the amount of adhesive applied is maintained. , Usually, wheat flour has /θ~, for the A component of the present invention.
! If the addition ratio of flour is more than 1 theta phr, the viscosity of the adhesive solution will be too high and it will be difficult to handle. Moreover, the temporary adhesive strength becomes weaker. on the other hand,
If the addition ratio of wheat flour is less than /Ophr, blocking tends to occur.

For unknown reasons, by adding both PVA and flour, the adhesive has sufficient adhesive strength and a very high veneer finish, regardless of the wood glaze on the veneer. If one or both of the adhesives are missing, depending on the tree species, adhesive strength may not be developed, and the finished veneer will have a poor quality.

In the present invention, the reason why clay is added is to prevent curing shrinkage during curing of the amino-based condensate (C) in addition to acting as a filler, and to reinforce the adhesive force and to increase the pf of the adhesive.
(This is to make it from neutral to weakly alkaline with 'f7~. Clay is added at a ratio of 10 to ¥ Ophr per component A of the present invention. If the addition ratio of clay is more than Ophr, the adhesive The viscosity of the solution becomes too high, resulting in internal pressure when handled.Also, the temporary adhesive strength is greatly reduced, making it easy to peel off during heat curing.On the other hand, when the proportion of clay added is /Oph
If it is less than 2 r, the yellow color will be insufficient to suppress curing shrinkage.

The reason why triethanolamine is added in the present invention is to improve the storage stability of the #adhesive by utilizing its buffering effect. The amine-based initial condensation material tends to condense and shift the pH of the adhesive to the acidic side, and as the pH of the adhesive becomes acidic, the initial condensation material of the amine yarn tends to condense. As a result, the viscosity of the adhesive system increases [1, making it unusable. That is, by adding triethanolamine, changes in the pH of the adhesive are buffered, the rate of increase in viscosity of the adhesive is suppressed, and storage stability is extended. As a result of measuring the storage stability of the adhesive, it was found that the adhesive with added triethanolamine lasted about 30 days at /j'c:, and about 75 days at 30°C, whereas the adhesive without the addition of triethanolamine lasted about 30 days at 30°C. /-t°C for about 7j days and at 30°C for about 2 days, and the application effect is great. In order to suppress the combinatorial reaction, triethanolamine is added to adjust the pH of the final adhesive to 2 to J', but the addition ratio is usually 1:0. O! ~O9θoswt'') 6. If the pH of the adhesive is basic (pH 2 or higher) when triethanolamine is added, the curing speed of the adhesive will be slow and the processing time in the heat drying process will be long. Conversely, even if triethanolamine is added, if the adhesive has an acidic pH of 2 or less, the storage stability will be very poor.

If the adhesive of the present invention has a pH ≠ 7) and the dryer temperature is low, a curing catalyst may be used to speed up the curing rate. As curing catalysts, typical inorganic and organic acids, ammonium salts such as acidic sodium sulfate, and a group of curing agents conventionally known as latent curing agents may be used as appropriate. .

In order to make the glue easier to handle when applying the glue to the edge of a veneer, the adhesive of the present invention has the advantage that Aerosil is added to the adhesive to impart thixotropic properties to the glue. You can do that too.

! In order to further accelerate the curing of the adhesive of the present invention and obtain good adhesive performance, polyamine, polyaldehyde, polyoxide, borianno hydride, chromium nitrate,
A crosslinking agent such as aluminum chloride may be added, and an antifoaming agent such as metal soap, silicone oil, fatty acid ester, etc. may also be added to prevent excessive foaming during curing.

Thickeners such as oxidized starch, dialdehyde starch, acrylamide, methylcellulose, carboxymethylcellulose, sodium alginate, vegetable gum, and cellulose powder can also be used in combination with the adhesive of the present invention.

The adhesive of the present invention may also contain fillers such as silica, silica, silicic acid groups, cellulose, wood flour, coconut shells, and calcium carbonate.

In addition, if you want to color the adhesive part, malachite green,
A water-soluble dye such as methylene blue or the like may be appropriately added to the adhesive of the present invention.

A bullock cart whose end faces are bonded using the adhesive of the present invention is prepared by solidifying the threads on the front or back side with a hot melt adhesive as necessary, and then drying it at 770 to 200°C.
When manufacturing the adhesive of the present invention, the adhesive can be cured by heating and drying.
y, water, and various additives as necessary are manufactured. At that time, if you carry out the matters described below (e) (depending on +-, the viscosity will increase from θθ to -00θ voids//J- Adhesives can be easily produced at ~30°C.

(1) Vinyl acetate polymers are manufactured using emulsion polymerization method.
gh,...,z, those in the form of powder or emulsion are used.

(2) Saponified polyvinyl alcohol is used by dissolving it in a portion of the water used in the entire pre-sealing adhesive system. For example, it is used as a =2s wt% aqueous solution.

(3) When preparing, add triethanolamine last, and the adhesive has a preferred pH of 7 to L! Adjust to ″.

The adhesive of the present invention can be used for horizontal stripping with a laminated finish commonly used for plywood.

In order to clearly explain the present invention in detail, examples and reference examples are given below, but the present invention is limited by the following examples and reference examples. isn't it.

After the dehyde condensate, vinyl acetate copolymer emulsion, vinyl acetate-acrylic acid copolymer, and partially saponified polyvinyl alcohol were uniformly combined in primary iM, flour, clay, triethanolamine, silicone oil, and water were added to the water. By uniformly polymerizing again, an adhesive having a viscosity of j coθboids/, 2j°C was obtained. The following A and C test pieces were prepared using the adhesive, and the bending strength and veneer finish rate were measured. The results are shown in Tables 1 and 2.

(Creation of test piece) Thickness ζ 3.2 mm, rl] 3 mm, and length/ri θ
Raw veneer of war (moisture content country: 33'). ), and the adhesive was applied to the 2 pieces (α sheet) in 3 places as shown in (6) in Figure 1.The adhesive was dried with hot air at Q'C to harden the adhesive. At this time, the number of horizontally laid veneers (β sheets) where the number of peeled points was / or less among the three bonding points with C'' points was measured. When bending a horizontally laid veneer, the bending strength test was carried out using Tensilon (manufactured by Toyo Holdwin), and also 11 times. The span width was set to 2 crn, and a test piece was set up so that the upper anti-folding rod and the glancing-glued y-base part were parallel, and the maximum load at the time of failure was measured as the bending contact and sliding strength. 2) Measured values when creating veneer finished vehicle sleeping test pieces: α and 2β.

The veneer finish rate was calculated using the following formula.

Example-32%Ho/l/-qsu7/3? ? (/, 96 mol)'
f.

/θ%-Adjust the pH to 9.0 with an aqueous sodium hydroxide solution, further add urea 602 (7 mol), heat at or-1, react at 70°C for 30 minutes, and then add -0%-formic acid. pH
u, Y and after 3θ minute reaction.

A urea resin was produced by neutralizing it to pH 7.0 with a 10% aqueous sodium hydroxide solution. In addition to this, formalin/res
Add y (19 mol) and melamine/262 (1 mol) f, and adjust the pH to 3.0 with 30% aqueous sodium hydroxide solution.
After binding, the reaction was carried out at s°C/unexamined patent publication. Then, the pH was adjusted to θ with formic acid to 120° C. to obtain a urea-melamine common compound with a viscosity of coboide (2 s° C.) and a solid content of 57+X.

To this urea-melamine cocondensate, a 9-part aqueous vinyl alcohol solution was added, and then wheat flour, clay, silicone oil, and triethanolamine were added to give a viscosity of 7-t0 boids/2! °C adhesive was obtained.

The composition of the ingredients used (composition number) is shown in Table 7. The bending adhesive strength test 1. of the adhesive and the measurement of the veneer finish rate were carried out in accordance with Example 1, and the respective results were are shown in Tables 1 and 2.

Example 3~! Amino yarn initial condensate, vinyl acetate polymer, polyvinyl alcohol 5-partly saponified with water,
Wheat flour, clay, triethanolamine, and silicone oil were blended, and as shown in the notes, a mixture was prepared according to Example 1 and Example 2, and The song was adhesive strength test, veneer finish 1 [Measurements were carried out according to Example/and Example 2, and the results are shown in Tables 1 and 2.

Reference examples/Examples/And Examples! In contrast, adhesives to which partially saponified polyvinyl alcohol, J1i&, clay, and triethanolamine were not added were listed as reference examples.

A urea-formaldehyde condensate, a vinyl acetate polymer emulsion, and water were mixed to obtain a liquid viscous water sealant. The amounts of the ingredients used are shown in Table 1. Bending adhesion strength test and veneer finish shrinkage measurement were conducted in accordance with Example/.
The respective results are shown in Tables 1 and 2.

Reference example/Example/and Example sy (for partial saponification point 37 w
t% formalin/6r? (/, 93 mol), 10w
t96 Adjust the pH to 9.0 with aqueous sodium hydroxide, add urea toy (1 mol), and heat to 0°C.
After reacting for 30 minutes at O'C, the pH was adjusted to -0W'' with 96 formic acid. was prepared.

Further, formalin/93f (2.4°C mol) and melamine/5ty (1 mol) were added to this, and the pH was adjusted to 3. θ and [compound (viscosity cobois (26'C), solid content -t7%) were obtained. Powdered polyvinyl acetate and water were added to this urea-melamine co-combination and mixed for 10 minutes (with knee stirring, the viscosity was 4trθ).
Poise (!℃) adhesive was obtained. Bending adhesive strength test,
The finished height of the veneer was measured according to Example 7, and the results are shown in Tables 1 and 2.

Reference Example 3 to Example 7% Example and Example! Adhesives to which wheat flour, clay, and triethanolamine were not added were used as Reference Examples 3 and 3.

The amino-based primary M condensate used, vinyl acetate polymer, water, and partially saponified polyvinyl alcohol.

The amount of silicone oil blended is shown in Table 1, and adhesives were prepared according to Examples/--3 and Reference Example/. The bending adhesive strength test and the veneer finish rate measurement were carried out according to the 1-length example, and the results are shown in Tables 1 and 2.

Note 1) + All the same as those made in Example - (Mukoya Koboiz (〕sr), ), resin solid content j 2%) 2) Swinbond 760 (B-';#θ) (Nippon Kasei Co., Ltd. Swinbond is a registered trademark of Nippon Kasei Co., Ltd., resin solid content 7%, viscosity #, 2θ voids/-! °C 3) + Same as that used in Example/(viscosity/θO voids (ko! °C), main component concentration 50% by weight) 4) Movinyl powder Ml; Part name (manufactured by Hoechst Synthesis Co., Ltd.) 5 ) Mobile 6! θ; Product name (manufactured by Hoechst Synthesis Co., Ltd.), vinyl h acid/acrylic acid-2θ/3θ (weight ratio), viscosity 3θ0 voids (2-t°C)% main component concentration! θ
Judo% degree j! Weight %, trade name Monibir/Za/E (manufactured by Hoechst Gosei Co., Ltd.) 7) Poval J/7-8; trade name (manufactured by Rirare Co., Ltd.), degree of saponification, rtr mol%, degree of polymerization/700 8) Product name; KS, <t (manufactured by Shin-Etsu Chemical Co., Ltd.) As is clear from the above table/table and Table 1, the adhesive of the present invention is -, -1° Regardless of the resin, especially As a result, it has a wide range of compatibility with different wood glaze combinations.

Provides high wetting strength and veneer finish rate. Therefore, the adhesive of the present invention is a suitable adhesive for traversing oxcarts.

[Brief explanation of the drawing]

Figure 1 is a perspective view to show how to cross the raw veneer◎ / and /'... Raw NL&, - and 2'...
...End face, 3.3' and 3"...Illumination coating L
ltφ bay agent applicant: Nippon Kasei Co., Ltd. agent Patent attorney Hase - Others/names

Claims (1)

[Claims] (1) An adhesive for cross-cutting green veneer, which contains the following components A and D as main ingredients. A Niamino-based initial condensate or vinyl acetate polymer B: Wheat flour and polyvinyl alcohol C: Clay D Nitriethanolamine