JPS604227B2 - glue - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an adhesive that is excellent in water resistance, stability, and various adhesive strengths, and is particularly suitable as an adhesive composition for wood.

Currently, formalin-based condensation resins such as urea resins, phenol resins, and urea-melamine cocondensation resins are mainly used as adhesives for plywood or secondary processing of plywood (see JISK6801, 6802, and 680).
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These are widely used because they are cheap and have good water resistance, but the formaldehyde (hereinafter referred to as formalin) that remains in them may worsen the environment for plywood work, or the plywood using this Formalin has been released from furniture and houses made with this material, and has recently become a major problem in the world. Recently, various attempts have been made to reduce the release of formalin using urea resins, etc., and although considerable results have been reported, it is essentially impossible to eliminate formalin.
Furthermore, during the manufacturing process, variations in the moisture content of the veneer veneer and variations in the heat and pressure conditions often result in incomplete curing of the adhesive, which may cause formalin release from the product.

Therefore, at present, formalin-based condensation resins such as urea resins cannot be said to be safe at all. Furthermore, there are adhesives for plywood that do not contain formalin at all, such as protein-based and vinyl acetate resin-based adhesives, but these are not generally used because of their poor water resistance. Furthermore, various aqueous emulsions are used in various adhesives, but they are not always sufficient in terms of water resistance.

The present invention eliminates these drawbacks, and uses an aqueous emulsion in which a compound having a 1' isocyanate group (hereinafter sometimes simply referred to as isocyanate) is dissolved in a hydrophobic solvent, and a surfactant. and (3' formalin condensation resin).

The adhesive of the present invention does not release formalin and has excellent water resistance, stability, and various adhesive strengths.

By incorporating a surfactant in the present invention, water resistance is improved, changes in water resistance over time are reduced, encapsulation is reduced, viscosity is stabilized, and the solution becomes an emulsion.

Therefore, the usage time of the aqueous emulsion-isocyanate can be significantly extended. As the surfactant to be used, nonionic and anionic surfactants are effective, with anionic surfactants being particularly effective.

Any type of anionic surfactant used here is effective, regardless of its structural components, but examples include carboxylates (fatty acid salts, soap, etc.), sulfate ester salts (higher alcohol ester salts, sulfated oils, sulfated fatty acid esters, sulfated olefins, etc.), sulfonates (alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkyl sulfonates, Ikepon T, Aerosol OT, lignin sulfonates) ) and phosphate ester salts (higher alcohol phosphate ester salts, etc.). The amount of surfactant to be blended is suitably 0.1 to 15% by weight, particularly preferably 2% to 4% by weight, based on the isocyanate.

If the amount is too small, the effect will be poor, and if it is too large, undesirable phenomena such as agglomeration of the emulsion will occur. Although the details of why stability is improved when anionic surfactants are added to aqueous emulsion-isocyanate systems are unknown, the active agents are adsorbed onto the surface of the isocyanate emulsion particles, and the isocyanate and water It is believed that by preventing direct contact of the isocyanate, the decomposition of the isocyanate is delayed and stabilized as an emulsion. Further, in the present invention, a formalin-based condensation resin is blended.

Here, formalin-based condensation resin refers to JISK6801
(Urea resin wood adhesive), K6805 (Melamine/Uria co-condensed resin wood adhesive), and K6802 (phenolic resin wood adhesive).For example, urea-formalin condensed resin, Examples include amino-based condensed resins such as melamine-formalin-based condensed resins, urea-melamine-formalin-based condensed resins, and phenol-formalin-based condensed resins, among which amino-based condensed resins are particularly preferred. Note that these formalin-based condensation resins may be used in powder form, but they can also be used in solution,
In particular, it is preferable to use it as an aqueous solution. The amount of formalin-based condensation resin blended is arbitrary. Furthermore, the compound having an isocyanate group used in the present invention exhibits unique behavior in an aqueous emulsion, and has the effect of imparting water resistance to the composition. For example, tolylene diisocyanate (TD
1, e.g. Bayer Desmodur T), hydrogenated T
D1, trimethylolpropane (TM Yen)-TDI adduct (Desmodm L), triphenylmethane triisocyanate (TTIDesmodurR), methylene bis-diphenyl isocyanate (MDIDesm
odur44), hydrogenated MD1, hexamethylene diisocyanate (DesmodurN), xylene diisocyanate, 4,4 dicyclohexylmethane diisocyanate, and the like are representative ones that can be used.

In addition, as a compound having an isocyanate group, its polymers, such as polyisocyanate, polyol mixed system, ie, hydrous acid group polyester and polyether (Des
Desmodu described above to polyols such as
There is no problem even if a mixture containing an excessive amount of polyisocyanate such as rL is used.

Furthermore, when using a prepolymer method, i.e., an NCO-terminated prepolymer prepolymerized with a polyol and an excess of polyisocyanate, or an OH-terminated prepolymer prepolymerized with an excess of polyol, a polyisocyanate such as Desmodur L mentioned above may be used. There is no problem even if it is used in excess. The blending ratio of isocyanate is 1 to 20% by weight based on the aqueous emulsion (solid content), and when used as a plywood adhesive, it is 10% by weight.
~15% by weight is preferred.

In the present invention, the compound having an isocyanate group is used in a hydrophobic solvent (that is, a solvent that has almost no mutual solubility with water and also has mutual solubility with isocyanate) (
Hereinafter, this solvent will be simply referred to as "solvent."

) and then blended. like this"
By using a solvent, it is possible to uniformly disperse the isocyanate in the aqueous emulsion, and it is also possible to protect the isocyanate group from water by reducing the contact between the isocyanate group and water through an emulsifying effect. Further, by using an isocyanate dissolved in the above-mentioned "solvent", an adhesive composition which is stable and has excellent water resistance can be obtained.

The "solvent" that dissolves the isocyanate means a solvent compound that is normally liquid and has a solubility in water at 20° to 30° and a solubility in water in the solvent of 5 wt % or less.

Typical "solvents" include aliphatic and aromatic hydrocarbons and mixed liquids containing these as main components (e.g. toluene,
xylene, benzene, gasoline, kerosene, ligroin, tetralin, decalin, turpentine, pine oil, liquid paraffin, alkylbenzene, etc.) halogenated hydrocarbons (e.g. methylene chloride, chlorobenzene, chlorotoluene, frombenzene, chlorinated liquid paraffin, etc.),
Ketones (e.g. methyl isobutyl ketone, methyl
-amyl ketone, methyl-n-hexyl ketone, ethyl-n-butyl ketone, di-n-propyl ketone, acetophenone, etc.), ethers (eg, Isof).

esters (e.g., isopropyl acetate, butyl acetate, butyl propionate, citrate, ricinoleate, etc.) as well as various phthalate esters (e.g., dibutyl phthalate, phthalate, etc.). dioctyl acid, butylbenzyl phthalate, etc.), various oleic acid esters, various adipate esters, various azelalic acid esters, various sebacate esters, various stearic acid esters, various benzoic acid esters, various abietic acid esters, various oxalic acid esters, various phosphate ester, etc.)
Other oils containing higher fatty acids as a main component, such as castor oil, can also be used. When dissolving isocyanate in a "solvent", if the "solvent" contains active hydrogen such as a carboxyl group, hydroxyl group, or amine group in its molecule, it will react with the isocyanate compound via the active hydrogen, reducing its effectiveness. It is not appropriate to dilute it.

However, if such a "solvent" does not have active hydrogen, there is no particular dilution limit, so it can be diluted to the limit value that allows the isocyanate solvent system to be uniformly dispersed in water. However, from the viewpoint of water resistance effect and dispersion effect, the amount of isocyanate is 10 to 1000% by weight, preferably 5% by weight based on the "solvent".
It is preferable to add and dissolve 0 to 40% by weight. These "solvents" have various boiling points, and it is desirable to select an appropriate solvent depending on the intended use or usage conditions of the composition.

For example, when used as a synthetic adhesive, it is required to be odorless because heat bonding takes place in an open state when using the adhesive. It is best to use a high boiling point solvent that is difficult to clean.

In this case, the solvent remains in the adhesive layer and acts as a plasticizer. On the other hand, if it is not desirable to leave the "solvent" in the adhesive layer, it is desirable to use a low boiling point solvent.

When a compound having an isocyanate group is dissolved in a "solvent" and then added to an aqueous emulsion, it is preferable to disperse it uniformly by stirring it slightly vigorously.

In the present invention, aqueous emulsions include styrene-butadiene copolymer (SBR) latex, acrylonitrile-butadiene copolymer (NBR) latex, chloroprene (CR) latex, butyl rubber (11R) latex, and polyptadiene (BR) latex. or methyl methacrylate-butadiene copolymer (MBR)
Rubber latex such as latex, polyacrylic acid ester latex, polyvinylidene chloride latex, polyvinyl chloride emulsion, vinyl acetate polymer emulsion such as ethylene-vinyl acetate copolymer emulsion or polyvinyl acetate emulsion, or these. This emulsion is modified with carpoxyl.

Among these, rubber latex, particularly SBR latex or carboxyl-modified SBR latex, is preferred. Further, when the composition of the present invention is used as an adhesive, an extender can be further added.

This extender not only acts as an extender, but also reacts with the other components of the adhesive, particularly the isocyanate, to impart further water resistance and initial adhesion to the adhesive. Usual bulking agents such as wheat flour, starch powder, defatted soybean flour, and blood meal can be used as bulking agents (for example, bulking agents used in urea resins, etc.); It is more preferable because it does not gelatinize in cold water and becomes gelatinized and sticky steel by heating during bonding.

Further, fillers can also be added to the composition of the present invention.

This filler not only acts to prevent excessive penetration of the adhesive into the wood, but also reacts with other adhesive components, particularly isocyanates, to provide the adhesive with additional water resistance and initial adhesion. I will also do this. Inorganic fillers such as clay, kaolin, and talc are used as fillers, but organic fillers such as wood flour and walnut shell powder can also be used.

The blending ratio of these extenders and/or fillers varies depending on the composition, especially the purpose of use of the adhesive, but is 10 to 100% by weight based on the aqueous emulsion, and in particular, 15 to 5% by weight for plywood adhesives. The range is appropriate. Further, these extenders and fillers may be used alone or in combination, but it is most preferable to use the extenders and fillers at the same time. Furthermore, reaction accelerators such as acid, aluminum sulfate, alum, chromium hydroxide, and water glass can be added to the adhesive of the present invention.

When the composition of the present invention is used as an adhesive, it is possible to achieve sufficient adhesion by just adhesion at room temperature (cold pressing), but in order to further improve adhesive strength and water resistance, adhesion by hot pressing is preferable. The composition of the present invention is suitable as an adhesive, particularly for plywood or its secondary processing, but is also suitable for use in woodworking, particle board, corrugated board, metal foil, paper, fabric, etc. adhesives for textile processing, ceramics, inorganic boards {cement-based inorganic boards (asbestos slate boards, pulp cement boards, concrete boards, etc.), mineral inorganic boards (asbestos, rock wool, etc.)
}, it can also be applied to bonding plastic sheets (e.g. PVC tiles, asphalt tiles), glass plates, etc.

In addition, it can be applied as a coating composition for clay coatings and paints. Next, the present invention will be further explained by examples, but the present invention is not limited thereto.

Example 1 To 100% of various commercially available aqueous emulsions (Table 1), 100 parts of urea-formalin condensation resin with a non-volatile content of 50% was added and further added to this was "Nissan Syntrex" (anionic surfactant manufactured by NOF Corporation). and “Nissan Nonion LP20R” (nonionic surfactant manufactured by NOF)
Add 0.4 parts of a 1:1 mixture of 1:1 and mix thoroughly, then add 1 part of a liquid paraffin mixture (75% isocyanate) of isocyanate (Takenate 500, manufactured by Takeda Pharmaceutical), and add 1 part of wheat flour to this. After mixing 5 parts of clay,
The pH was adjusted with ammonium chloride to obtain an adhesive composition.

Using this adhesive, veneer configuration lauan 1.011.01. The plywood was bonded using a coating amount of 25 mm/900, a cold pressure of 10 k9/15 minutes, and a hot pressure of 12 mm/10 k9/m.

The following four types of aqueous emulsions were used. Table 2 shows the results of adhesive force measurement using the JAS method. Table 1 Aqueous emulsion used Table 2 Example 2 10 parts of urea-melamine-formalin cocondensation resin with a non-volatile content of 50% was added to 10 parts of "JSR0692" (SBR latex) manufactured by Japan Synthetic Rubber. After adding 0.2 parts of sodium dodecylbenzenesulfonate to the solution, diheptyl phthalate solutions of various isocyanates (Table 3) were added (
After mixing thoroughly, add 1 part of wood flour and 10 parts of wheat flour, and mix with ammonium chloride.
Plywood bonding was performed in the same manner as in Example 1 using an adhesive adjusted to H5.4.

Table 4 shows the adhesive strength measurement results according to the JIS method. Table 3
Table of isocyanates used 4

Claims (1)

[Claims] 1. An adhesive prepared by blending (1) a compound having an isocyanate group dissolved in a hydrophobic solvent, (2) a surfactant, and (3) a formalin-based condensation resin into an aqueous emulsion.