JPS5952918B2 - water resistant adhesive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water-resistant adhesive that uses a modified amino resin emulsion that can be cured in alkaline conditions. The purpose of the present invention is to provide a new adhesive that is inexpensive and has excellent water resistance.

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 and the resin is acidified to pH 3 to 6 for curing. 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, an amino resin mainly composed of melamine is used rather than urea, and an amino resin mainly composed of urea cannot provide high water resistance or 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 layer is removed, even those bonded with area resin adhesive will exhibit excellent water resistance and durability.

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

From this point of view, the present inventors have been conducting research on amino resins that harden under alkaline conditions.

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 co-condensing the mixture with 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. 88792/1983). However, by adding a bulking agent such as wheat flour to this modified amino resin liquid,
Furthermore, when wood or the like is bonded using a compounded paste containing an alkaline curing agent such as caustic soda or slaked lime, the adhesive performance varies greatly and a sufficiently stable adhesive strength cannot 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 this can improve and stabilize adhesive performance. Furthermore, as a result of various studies on the emulsification of ketone-modified amino resin liquids, (a) ketone compounds and necessary Depending on the conditions, an aqueous formaldehyde solution was added, or a ketone resin initial condensate obtained by reacting a ketone compound and formaldehyde by a known method was added, and the mixture was heated under alkaline conditions to cause co-condensation. It has been found that the resin liquid can be easily emulsified by subsequently adding an acid 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 among amino compounds such as urea, melamine, thiourea, ethylene urea, acetoguanamine, benzoguanamine, etc., or two or more types of amino compounds. 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. In the condensate, 0.3 to 3 mol of one kind selected from ketone compounds such as acetone, methyl ethyl ketone, methyl isopropyl ketone, acetophenone, cyclohexanone, diacetone acrylamide, diacetone alcohol, etc. per 1 mol of the amino compound is added. Alternatively, the total number of moles of two or more compounds selected from the ketone compounds is added at a ratio of 0.3 to 3 moles per mole of the amino compound, and if necessary, an aqueous formaldehyde solution is added to make alkaline. It can be obtained by co-condensing under heating under conditions, followed by a co-condensation reaction under acidic conditions.

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

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, resulting in the problem that not only is it impossible to obtain a stable emulsion, but also that the production cost becomes significantly high. However, if the ketone compound exceeds 0.3 mol per mol of the amino compound, it will harden under alkaline conditions, and if the ketone compound exceeds 0.3 mol per mol of the amino compound, it will harden under alkaline conditions.
When the amount is in 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 5.
A temperature of 0 to 100°C is desirable. In addition, the pH during cocondensation is such that the cocondensation reaction is first carried out under an alkaline condition with a pH of 8 to 12, and then the cocondensation reaction is subsequently carried out under an acidic condition with a pH of 3 to 6. This is suitable and allows the reaction solution to be easily emulsified.

1. When the resin liquid is completely emulsified, adjust the pH to 5 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 powder, dextrin, gum arabic, sodium alginate, sodium polyacrylate, polyacrylamide, canoleboxymethinoresenolose, It is further enhanced by emulsification in the presence of protective colloidal substances such as polyvinyl alcohol, methylcellulose, phosphorylated starch, cationized starch, or by adding an aqueous solution of these protective colloidal substances to the emulsion. A stable emulsion is obtained.

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

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

The modified amino resin emulsion of the present invention obtained in this way has the characteristic of being hardened by alkalinity, and therefore,
As curing agents, oxides, hydroxides, carbonates, bicarbonates, phosphates, silicates of alkali metals such as lithium, potassium, sodium, etc., and alkaline earth metals such as magnesium, canoresium, strontium, barium, etc. One or more metal compounds exhibiting alkalinity such as acid salts, borates, aluminates, zincates, etc. are used.

Among these, calcium oxides, hydroxides, and basic salts are most preferred as hardening agents because they have a large effect of accelerating hardening and are inexpensive.

Furthermore, these alkaline metal compounds include oxides, hydroxides, hydrochlorides, sulfates, nitrates, phosphates, and silicic acids of polyvalent metals such as copper, aluminum, zinc, iron, chromium, and molybdenum. There is no problem even if salts such as salt are used together.

The third feature of the present invention is that this ketone-modified amino resin emulsion is blended with a powder whose main component is a protein that is insoluble in water at room temperature.

A powder substance whose main component is protein that is insoluble in room temperature water is a powder substance containing protein that becomes solubilized in a short period of time and does not exhibit significant thickening when added to room temperature water. For example, water-insoluble proteins such as high-temperature defatted soybean flour, high-temperature defatted rapeseed meal powder, corn gluten powder, dried blood meal, milk casein, algae protein, bacterial cell protein, etc., which are not normally used as bulking agents, or Powdered materials containing the protein as a main component can be mentioned. Ordinary adhesives use, as fillers, powdered substances whose main component is protein, such as low-temperature defatted soybean flour, egg white powder, and blood albumin, which are easily soluble in room-temperature water.

However, in ketone-modified amino resin emulsion,
When these normally used protein-based powders that are soluble in room-temperature water are added, when an alkali metal or alkaline earth metal oxide, hydroxide, or basic salt is added, an instantaneous increase occurs. It becomes viscous and the mixture turns into a gel.

However, as in the present invention, when a powder mainly composed of proteins insoluble in room temperature water, which is not normally used as a bulking agent, is added, alkali metal or alkaline earth metal oxides, hydroxides, or Even when a basic salt is added, no rapid increase in viscosity is observed, and the viscosity increases gradually to obtain an adhesive rich in 1f-viscosity.

In addition, many powdered materials whose main component is protein that is insoluble in room-temperature water are relatively inexpensive, so they not only have the economical effect of reducing the cost of adhesives, but also have the advantage that ketone-modified amino resin emulsions can be coated with Since it prevents excessive penetration into the material, it has a remarkable effect on improving temporary adhesion and normal and water-resistant adhesion performance.

The adhesive of the first aspect of the present invention includes (a) a ketone-modified amino resin emulsion, (b) a powder whose main component is a protein insoluble in water at room temperature, and (c) an alkali metal or alkaline earth metal-based adhesive. It has three essential components: one or a mixture of two or more selected from oxides, hydroxides, and basic salts, and the blending ratio is 100 parts by weight of the ketone-modified amino resin emulsion. For,
Powdered material whose main component is protein that is insoluble in room temperature water 5 to 200
Preferably, the amount of the alkali metal or alkaline earth metal oxide, hydroxide or basic salt is 0.5 to 50 parts by weight.

At this time, if the amount of powdered material whose main component is protein that is insoluble in water at room temperature exceeds 200 parts by weight, the water-resistant adhesive performance will decrease, and the oxides of alkali metals or alkaline earth metals, The amount of hydroxide or basic salt is 50
If the amount exceeds 1 part by weight, the usable life of the adhesive will be significantly shortened, causing a practical problem.

The adhesive of the second aspect of the present invention is a water-resistant adhesive characterized in that the three components of the first aspect are blended with water-based rubber lattetus as a fourth component.

The aqueous rubber latex used in the present invention includes natural rubber latex, styrene-butadiene rubber, acrylonitrile-butadiene rubber, butyl rubber,
Synthetic rubber latexes such as isoprene rubber, chloroprene rubber, methacrylic acid-butadiene rubber, etc. are preferable, and these aqueous rubber latexes further contain carboxyl groups, hydroxyl groups, amino groups, amide groups, etc.
Derivatives with reactive groups such as groups can also be used.

Although the blending ratio of the aqueous rubber latex is not necessarily limited, it is possible to
It is preferable to mix within the range of 5 to 200 parts by weight with respect to 0 parts by weight. (If the amount of water-based rubber latex added is less than 5 parts by weight, the effect of improving adhesion performance by adding the latex will be sufficient. If it is more than 100 parts by weight, the product cost will increase and the practicality will decrease. Whether the aqueous rubber latex is blended in advance or at the time of use, the effect of improving adhesive performance remains the same.

The water-based rubber latex used in the present invention has the effect of significantly improving the adhesive performance of water-resistant adhesives.

That is, the addition of water-based rubber latex further improves the adhesive strength in normal state and in water resistance. When used, the water-resistant adhesive of the present invention can be used with a filler based on starch such as wheat flour, barley flour, rice flour, corn starch, tapioca starch, etc., or with fillers such as gypsum, diatomaceous earth, clay, zeolite, talc, asbestos, etc. Addition of inorganic fillers or organic fillers such as walnut flour, corn flour, wood flour, etc. does not affect the effectiveness of the present invention. Furthermore, a thermoplastic resin emulsion such as vinyl acetate resin, ethylene acetate copolymer resin, acrylic acid ester resin, etc. may be added.

The water-resistant adhesive of the present invention can be applied to plywood, laminated veneer wood, laminated wood,
Suitable for bonding wood materials such as particle boards, hardboards, wood panels, etc., as well as asbestos slate boards, calcium silicate boards, magnesium carbonate boards, rock wool boards, valve cement boards, gypsum boards, and wood wool cement. board,
It can also be used to bond inorganic molded materials such as foamed concrete plates and glass fibers, and exhibits excellent water-resistant adhesive performance that can withstand strong immersion in boiling water. Next, examples of the present invention will be given.

Example 1 202 g of formalin with a concentration of 37% and 60 g of urea were added in a volume of 5
The mixture was weighed into a 00ml Mitsuro flask, and dibasic sodium phosphate was added thereto to adjust the pH to 9.6, and the temperature was raised to 90°C while stirring.

After reacting at 90° C. for 30 minutes, 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 g of acetone and 1.2 g of polyvinyl alcohol CKK Kuraray Co., Ltd., #205) were added and reacted for 20 minutes, then heated to 80° C. and reacted for 30 minutes.

Then, 20% formic acid aqueous solution was added to adjust the pH of the reaction solution to 4.
I dropped it to 0 and continued the reaction.

After about 40 minutes, the reaction solution started to become milky and 60 minutes after the acid addition.
After several minutes, when the mixture was completely emulsified, tribasic sodium phosphate was added to adjust the pH of the reaction mixture to 7.5, and the mixture was cooled.

Claims (1)

[Scope of Claims] 1 (a) Ketone-modified amino resin emulsion, (b)
Powder material whose main component is protein that is insoluble in room temperature water, and (
c) A water-resistant adhesive mainly consisting of oxide hydroxides or basic salts of alkali metals or alkaline earth metals. 2 (a) Ketone-modified amino resin emulsion, (b)
Powder material whose main component is protein that is insoluble in water at room temperature, (c) oxides, hydroxides, or basic salts of alkali metals or alkaline earth metals, and (d) aqueous rubber latex.
A water-resistant adhesive consisting mainly of