JPS6054987B2 - Alkali-curing modified amino resin emulsion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a modified amino resin emulsion that can be cured in alkaline conditions. The object of the present invention is to provide excellent new adhesives and reinforcing agents.

Amino resin has traditionally been one of the cheapest plastics, and has therefore been used in large quantities as an adhesive for plywood, particle board, hardboard, laminated wood, etc., and as a reinforcing agent for paper, fiber, etc.

Amino resins are generally subjected to an addition reaction under alkaline conditions,
A condensation reaction is then carried out under acidic conditions.

Therefore, when curing the amino resin, an acidic curing agent is used to make it acidic to pH 3-6. Amino resins provide excellent adhesive strength when bonding wood, paper, etc., but water-resistant adhesive performance and durable adhesive performance vary depending on the amino compound used, and it is important to note that amino resins have excellent adhesive strength when bonding wood, paper, etc. In this case, amino resins mainly composed of melamine are used rather than urea, and amino resins mainly composed of urea cannot provide high water resistance and durability.

The reason why area resins have insufficient water resistance and durability is that the acid in the curing agent used when curing the resin remains in the adhesive layer and acts as a catalyst for the decomposition reaction of methylene bonds. If the acid remaining in the adhesive layer is removed, even products bonded with area resin adhesive will exhibit excellent water resistance and durability.

Therefore, if the amino resin is allowed to cure under alkaline conditions, the water-resistant adhesive performance and durable adhesive performance will be significantly improved.

From this viewpoint, the present inventors have been conducting research on amino resins that harden under alkalinity.

An amino resin obtained by first cocondensing 1.5 to 12 moles of formaldehyde and 0.3 to 3 moles of acetone with respect to 1 mole of the amino compound by heating and condensing the amino compound and formaldehyde by a known method. They discovered that by adding acetone and, if necessary, formaldehyde to the initial condensate and cocondensing the mixture under heating under alkaline conditions, a modified amino resin liquid that hardens under alkalinity could be obtained, and filed a patent application (Japanese Patent Application No. 8879 Wani). however,
When bonding wood, etc. using a compounded paste solution made by adding an extender such as wheat flour to this modified amino resin solution and an alkaline curing agent such as caustic soda or slaked lime, the adhesive performance varies widely and is not sufficiently stable. Adhesive strength could not be obtained.

The reason for this is that the modified amino resin liquid easily penetrates into the wood.
This was due to excessive penetration.

Therefore, the present inventors investigated various ways to prevent excessive penetration of this ketone-modified amino resin liquid into wood, and found that by emulsifying the resin liquid, it suppressed penetration into wood. It has been found that the adhesive performance can be improved and stabilized by this method. Furthermore, as a result of various studies on emulsification of ketone-modified amino resin liquid, we added formaldehyde aqueous solution to the amino compound and reacted it by a known method to obtain an amino resin initial condensate. If necessary, a formaldehyde aqueous solution is added, or a ketone resin initial condensate obtained by reacting a ketone compound and formaldehyde by a known method is added, and the mixture is heated under alkalinity to coexist. It has been found that after condensation, the resin liquid can be easily emulsified by further adding acid 4 and carrying out a co-condensation reaction under acidic conditions.

That is, the modified amino resin emulsion used in the present invention contains 1 mole of one type of amino compound selected from amino compounds such as urea, melamine, thiourea, ethylene urea, acetoguanamine, benzoguanamine, etc., or two or more types of amino compounds selected from among amino compounds such as urea, melamine, thiourea, ethylene urea, acetoguanamine, benzoguanamine, etc. An initial stage of an amino resin obtained by mixing a formaldehyde aqueous solution in an amount corresponding to a ratio of 1.5 to 12 moles of formaldehyde with respect to 1 mole of each mole of the compound, and heating and condensing the mixture by a known method. To the condensate, one selected from ketone compounds such as acetone, methyl ethyl kent, methyl isopropyl ketone, acetophenone, cyclohexanone, diacetone acrylamide, diacetone alcohol, etc. is added at 0.3 to 1 mole of the amino compound. ~3 moles, or the total number of moles of two or more compounds selected from the ketone compounds is the amino compound 1
It can be obtained by adding at a ratio of 0.3 to 3 moles per mole, further adding an aqueous formaldehyde solution as necessary, carrying out heat condensation under alkalinity, and then performing a co-condensation reaction under acidity. .

Also, 1 mol of formaldehyde per 1 mol of amino compound.
．． When co-condensing 5 to 12 moles of a ketone compound and 0.3 to 3 moles of a ketone compound, the amino compound and formaldehyde and the ketone compound and formaldehyde are heated and condensed separately in advance, and these initial condensates are heated together under alkalinity. After co-condensation, the modified amino resin emulsion used in the present invention can also be obtained by further adding an acid and carrying out the co-condensation reaction under acidic conditions.

In the present invention, when adding a ketone compound to an amino resin initial condensate, when adding an additional formaldehyde aqueous solution, or when adding a ketone resin initial condensate obtained by reacting a ketone compound and formaldehyde in advance, the amino compound 1. formaldehyde per 1 mole.
It is preferable to use an amino resin initial condensate obtained by mixing and reacting at a ratio of 5 to 5 moles. The first feature of the present invention is that the molar ratio of the amino compound to the ketone compound is 0.3 to 3 molar ratios of the ketone compound to 1 mole of the amino compound.
The point is that it is limited to moles.

The ratio of ketone compound to 1 mole of amino compound is 0.
If the amount is less than 3 moles, the amino resin's original properties will be exhibited and it will not harden under alkaline conditions.

On the other hand, if the proportion of the ketone compound is 3.0 moles or more, the viscosity of the resin liquid becomes too low, causing problems in that not only is it impossible to obtain a stable emulsion, but also the production cost becomes significantly high. However, if the ketone compound exceeds 0.3 mole per mole of the amino compound, it will harden under alkaline conditions;
When the amount is within the range of 3 to 3.0 mol, a ketone-modified amino resin emulsion which is suitable for adhesion, impregnation reinforcement, etc. and has excellent stability can be obtained.

The second feature of the present invention is that the amino resin initial condensate and the ketone compound or the ketone resin initial condensate are first co-condensed under alkalinity, and then the co-condensation reaction is continued under acidic conditions. The point is that a ketone-modified amino resin emulsion was easily obtained. The heating temperature when cocondensing a ketone compound or a ketone resin initial condensate with an amino resin initial condensate depends on the boiling point of the ketone compound used, but is generally 50 to 10
A temperature of 0°C is preferred.

In addition, regarding the pH during co-condensation, it is appropriate to first perform the co-condensation reaction under an alkaline condition of PH 8 to 12, and then to perform the co-condensation reaction successively under an acidic condition of PH 3 to 6. The liquid can be easily emulsified.

When the resin liquid becomes completely emulsified, adjust the pH to 5 if necessary.
By adjusting the temperature to ~8 and cooling, an emulsion with excellent storage stability can be obtained. According to this method, a ketone-modified amino resin emulsion can be obtained very easily, but in addition, starch, dextrin, gum arabic, sodium alginate, sodium polyacrylate, polyacrylic acid amide, carboxymethyl cellulose, polyvinyl alcohol, methyl cellulose , emulsify in the presence of protective colloidal substances such as phosphorylated starch, cationized starch, or
Alternatively, a more stable emulsion can be obtained by adding an aqueous solution of these protective colloidal substances to the emulsion.

A stable emulsion can also be obtained by adding an anionic or nonionic surfactant or by using these surfactants in combination with a protective colloidal substance.

Furthermore, the effect of the present invention does not change even if a small amount of one or more compounds that react with formaldehyde, such as phenol, cresol, resorcinol, anorkylresorcinol, etc., is added during the production of the modified amino resin.

The modified amino resin emulsion thus obtained cures under alkaline conditions and exhibits excellent water-resistant adhesive performance.

The third feature of the present invention is that by adding water-based rubber latex to this modified amino resin emulsion,
This feature further improves water-resistant adhesive performance and durable adhesive performance.

The aqueous rubber latex used in the present invention includes natural rubber latex, synthetic rubber latex such as styrene-butadiene rubber, acrylonitrile-butadiene rubber, butyl rubber, isobrene rubber, chloroprene rubber, methacrylic acid-butadiene rubber, etc. Preferably,
Furthermore, derivatives obtained by adding reactive groups such as carboxyl groups, hydroxyl groups, amino groups, and amide groups to these aqueous rubber latexes can also be used.

The mixing ratio of the aqueous rubber latex and the modified amino resin emulsion is not necessarily limited, but it is within the range of 5 to 100 parts by weight of the aqueous rubber latex to 10 parts by weight of the modified amino resin emulsion. It is preferable to do so.

If the amount of water-based rubber latex mixed is less than 5 parts by weight, the adhesion performance will not be improved much by adding the latex.
Moreover, if it exceeds 100 parts by weight, the product cost increases and practicality decreases.

Furthermore, water-based rubber latex and modified aluminum. Even if it is mixed with the resin emulsion in advance or mixed at the time of use, the improvement in adhesive performance remains the same.

The modified amino resin emulsion of the present invention has the characteristic of curing in alkaline conditions, and therefore, as a curing agent, alkali metals such as lithium, potassium, sodium, etc., and alkaline earths such as magnesium, calcium, strontium, barium, etc. 1 selected from alkaline metal compounds such as metal oxides, hydroxides, carbonates, bicarbonates, phosphates, silicates, borates, aluminates, zincates, etc. One species or two or more species may be used.

In addition, these metal compounds exhibiting alkalinity include subacids, hydroxides, hydrochlorides, sulfates, slaked salts, etc. of polyvalent metals such as copper, aluminum, zinc, iron, chromium, molybdenum, etc. Salts such as phosphates and silicates may be used in combination. Furthermore, when used, wheat flour, barley flour, rice flour, or cornstarch may be added to the mixed solution of the modified amino resin emulsion of the present invention and a curing agent as necessary. , starch-based fillers such as tapioca starch, inorganic fillers such as gypsum, diatomaceous earth, bentonite, clay, zeolite, talc, asbestos, etc., or walnut shell powder, coconut shell powder, wood flour, etc. Organic fillers such as organic fillers can also be added.

The emulsion formulation of the present invention thus obtained is
Suitable for bonding wood materials such as plywood, laminated veneer, laminated wood, particle board, hardboard, wood panels, etc., as well as asbestos slate board, calcium silicate board, gypsum board, wood wool cement board, and foam. It can also be used to bond inorganic molded materials such as concrete plates, and exhibits excellent water-resistant adhesive performance that can withstand immersion in boiling water. It also exhibits excellent characteristics as a reinforcing agent for paper, fibers, etc.

Next, examples of the present invention will be shown. Example 1 2.02f of formalin at a concentration of 37% and 60fI of urea were weighed into a Mitsuro flask with a capacity of -500TtLt, and tribasic sodium phosphate was added to adjust the pH to 9.6, and the pH was adjusted to 90% while stirring.
The temperature was raised to ℃.

After reacting at 900C for 3 days, a 20% aqueous formic acid solution was added to adjust the pH of the reaction solution to 5.0, and the condensation reaction was continued.

The reaction solution was cooled to 10°C, and when it became cloudy, tribasic sodium phosphate was added to adjust the pH of the reaction solution to 9.0, and at the same time the temperature of the reaction solution was cooled to 50°C.
Next, 32 y of acetone and 1.2 y of polyvinyl alcohol (manufactured by KK Kuraray, #205) were added, and after a two-powder reaction, 8
The temperature was raised to 0'C and the reaction was carried out for 30 minutes. After that, 20%
A formic acid aqueous solution was added to lower the pH of the reaction solution to 44.0, and the reaction was continued.

After about 4 powders, the reaction solution started to become emulsified, and when it became completely emulsified 6 millimeters after the addition of the acid, tribasic sodium phosphate was added to bring the pH of the reaction solution to 7.5, and the reaction solution was cooled.

To 10 parts of the acetone-modified area resin emulsion thus obtained, SBR latex (Japan Synthetic Rubber KK
Co., Ltd., #0668) was added and mixed to prepare the alkali-curable modified amino resin emulsion of the present invention.
In addition, this is mixed with wheat flour Tasei Seifun K. Made in K, Akahana) W part,
A sizing solution was prepared by adding and mixing 15 parts of slaked lime. Apply this glue to a thickness of 2. ", Apply 150v/Wt to the front and back surfaces of lauan veneer with a moisture content of 7 to 8%, and stack lauan veneers of the same thickness so that the fiber directions are perpendicular to each other. 10k9/C! After 1 preliminary compaction at 1 pressure, 2. Plywood was produced by heating and pressing the powder. The tensile adhesive strength of the obtained plywood was measured according to the JAS Type 1 plywood standard.

The results are shown in the table below. As a control example, the adhesive strength of plywood manufactured in the same manner using an acetone-modified area resin emulsion without the addition of SBR latex was also shown. Example 2 Methyl ethyl ester 44f1 baraform (formaldehyde content 81%) 148V137% formalin 162
Weigh out f into a four-sided flask with a capacity of 2e, and add 2% aqueous sodium hydroxide solution dropwise little by little while stirring to adjust the pH of the reaction solution.
was adjusted within the range of 8.4 to 9.6 (TlB test paper).

Next, keep the temperature around 7 (s) and continue stirring until 2%
After adding a caustic soda aqueous solution and continuing the reaction for 3 hours while keeping the pH within the range of 8.4 to 9.6, the mixture was cooled to obtain a ketone resin initial condensate. A commercially available area resin liquid (manufactured by Honen Oil Co., Ltd., 1-002) and a melamine resin liquid (manufactured by Honnen Oil Co., Ltd., ML-044) were mixed with this ketone resin initial condensate in a weight ratio of 2:1:1. The pH was adjusted to 9.0 by adding tribasic sodium phosphate, and a three-powder cocondensation reaction was carried out at 80°C.

Then, 20% formic acid aqueous solution was added to adjust the pH of the reaction solution to 5.
I dropped it to 0 and continued the reaction for 6 more times.

After 30 to 4 minutes of acid addition, the reaction solution begins to become milky and becomes 6.
After the war, it became completely emulsified. When emulsification was completed, tribasic sodium phosphate was added, the pH of the reaction solution was adjusted to 7.5, and the mixture was cooled.

NBR latex (manufactured by Nippon Zeon ■, Nipole #156) was added to 100 parts by weight of the emulsion thus obtained.
2) After adding and mixing 5 parts by weight to prepare the alkali-curing modified amino resin emulsion of the present invention, further add 1 part by weight of wheat flour (Akahana manufactured by Nisshin Seifun K.K.) and 15 parts by weight of slaked lime. Parts by weight were added and mixed to prepare a paste solution. This size solution was applied to the front and back surfaces of a lauan veneer with a thickness of 2.0 m and a moisture content of 7 to 8% at a rate of 150 y/bo, respectively, and the lauan veneers of the same thickness were placed so that the fiber directions were perpendicular to each other. Plywood was manufactured by overlapping and temporarily pressing at a pressure of 10k9/Cri, followed by heating and pressing at a temperature of 12CfC1 and a pressure of 10kg/(i).The tensile adhesive strength of this plywood was measured according to the JAS Class 1 plywood test method.

The result is a uniform adhesive strength of 15.2k9/Crll in normal condition.
The average adhesive strength after repeated boiling was 14.1k9/Clll. As a control example, the adhesive strength of plywood similarly manufactured using a ketone-modified amino resin emulsion without the addition of NBR latex was 13.5k9/Cltl, an average adhesive strength of 13.5k9/Cltl after repeated boiling. 1
It was 2.3 kg/d.

As clearly recognized from the above results, the alkali-curable modified amino resin emulsion of the present invention has excellent adhesive performance.
In particular, the water-resistant adhesive performance is even more excellent.

Claims (1)

[Claims] 1 formaldehyde for 1 mole of amino compound.
When co-condensing at a ratio of 5 to 12 moles and 0.3 to 3 moles of the ketone compound, (a) the ketone compound is added to the amino resin initial condensate obtained by mixing formaldehyde with the amino compound and heating and condensing the mixture. If necessary, an aqueous formaldehyde solution is added, or (b) an amino compound and formaldehyde or a ketone compound and formaldehyde are heated and condensed separately, and these initial condensates are mixed together under alkaline conditions. An alkali-curable modified amino resin emulsion consisting of a modified amino resin emulsion obtained by heating co-condensation and then adding an acid to perform a co-condensation reaction under acidic conditions to form an emulsion, and an aqueous rubber latex.